Final Report Summary - SWARMITFIX (Self reconfigurable intelligent swarm fixtures)
Executive summary:
Today's smartest adaptable fixtures have limited adjustment capability, are mostly operated manually, are usually setup off-line with help of external measuring equipment, e.g. laser. Significant increase in effectiveness and decrease in cost may come from on-line fully actuated configuration/ reconfiguration, large adaptability to different shapes and the capability to dynamically concentrate the support in the region where manufacturing is actually performed, doing that on-line and without moving/ removing the part from the fixture. SWARMITFIX develops the new concept of self adaptable swarm fixtures composed of mobile agents that can freely move on a bench and reposition below the supported part behaving as a swarm, all without moving/ removing the part from the fixture.
Each fixture agent is composed of:
-a mobile platform,
-a parallel robot fixed to the mobile platform,
-an adaptable head with phase-change fluid and an adhesion arrangement, to sustain/ clamp the supported part perfectly adapting to the part local geometry.
The objectives of the project are to:
-rethink the fixtures as a multiagent swarm system, achieving high online adaptability and reconfigurability with the minimum necessary number of support units.
-The use of swarm single agents, designed as parallel robots (for high stiffness and position accuracy) on a mobile base, being able to freely move on the fixture bench to reach desired support locations, anchor to the bench, accurately position and orient their support heads.
-Introducing the concept of phase-change fluid in the head of each swarm agent in order to get a perfect geometrical adaptation to the local shape of the supported part and at the same time to realize stiff support and clamping.
-Developing an offline simulator to program/ check the fixture configuration for specific CAD sheet geometries and manufacturing cycles.
-Developing an intelligent control system relying on high level intelligent organization and control, and low level behaviors of the agents.
-Developing a virtual environment for the design and digital mock-up of new SWARMITFIX fixtures addressing modularity and standardization issues.
Project Context and Objectives:
The project aims at developing intelligent fixture technology for the manufacturing of components made of thin sheets with 3D geometries processed by different methods and connected together.
While the use of such components is growing in quantity due to current trends towards life cycle design and sustainable production, and in geometrical complexity due to aesthetic and quality issues, the manufacturing equipment is not growing in flexibility in parallel with the same trends.
Minimum use of material, aesthetic and quality issues also have an influence on the manufacturing requirements and processes adopted:
-Continuous welding is replacing spot welding;
-Round holes at precise locations are preferred to slotted holes traditionally used for relative adjustment in assemblies;
-Execution of accurate grooving and windowing operations is increasing;
-Complex surface geometries are adopted to satisfy stiffness requirements as with thicker material.
The demand for flexibility is pushed by short time-to-market, production in small and variable batch and mass customization for some products.
The sheets are first formed, normally by pressing or other forming technologies, and then further processed (deburred, milled, holed, contoured etc.). Fixtures to support and keep the sheets in form are required for the execution of almost all of these secondary manufacturing operations.
Significant increase in effectiveness and decrease in cost may come from on-line fully actuated configuration/reconfiguration, large adaptability to different shapes of the part to support and the capability to dynamically concentrate the support in the region where manufacturing is currently performed, without moving/removing the part from the fixture.
With these aims, we develop the new concept of self adaptable swarm fixtures composed of mobile agents that can freely move on a bench and reposition below the supported part as required, behaving as a swarm, all without moving/removing the part from the fixture. In this view, each swarm agent is composed of:
-A mobile base,
-A parallel robot fixed to the mobile base with at least three degrees of freedom;
-An adaptable head with an adhesion arrangement that comes in contact and sustains the supported part perfectly adapting to the part local geometry.
Once reached the assigned location, the agent anchors to the bench and then adjusts position and shape of the head to the supported part.
Adjustment is carried out at two levels:
-The parallel robot provides fine tuning of the position of the head with resolution higher than that of the mobile platform;
-The head has a fluidly conformable shape and contains a material whose physical phase can be switched from fluid to solid, e.g. electro or magneto-rheological fluid; first the material in the head is fluid to adhere and adapt exactly to the local shape of the part to support; then the material phase switches to solid realizing a stiff support with an adhesion system that locks the part to the head.
The project main objectives are:
1. Rethinking the fixture as a multiagent swarm system to achieve high online adaptability and reconfigurability with minimum number of support units.
This is the main objective of the project. It will be achieved through the realization of a physical prototype that will demonstrate the concept soundness and functionalities with reference to the active support of the workpiece during the specified manufacturing operations (mainly drilling and milling). The validation tests will be performed within the Piaggio Aero premises.
2. Using swarm single agents, designed as parallel robots (for high stiffness and position accuracy) on a mobile base, able to freely move on the fixture bench to reach desired support locations, anchor to the bench, accurately position and orient their support heads.
The swarm unit is conceived and designed as an intelligent agent able to work by itself and able to collaborate and co-operate with other similar units.
This will involve:
-The application of advanced methods for the synthesis and optimization of task-oriented parallel robots under workspace, stiffness and accuracy constraints;
-The adoption of design criteria for cost effectiveness, robustness and reliability;
-The selection and development of suitable power transmission between agents and fixture bench and data communication from/to the agents.
3. Introducing the concept of phase-change fluid in the head of each swarm agent in order to get a perfect geometrical adaptation to the local shape of the supported part and at the same time to realize stiff support and clamping.
This objective is crucial as it addresses the realization of new supporting/clamping tools that gently adapt to the surface of the thin sheet part and firmly keep it blocked during the operation. It includes the application of know-how in the field of smart materials and their use in robotic systems for the development of the phase-change head, including analysis of local distributions of contact and reshaping pressures at the head-part interface and related influence on the local geometry of the part and on the holding forces during manufacturing.
4. Developing an offline simulator to program/check the fixture configuration for specific CAD sheet geometries and manufacturing cycles.
This will address the generation of the map of support locations by the supervisory controller based on CAD data of the supported sheet and manufacturing process information (NC file of the parts to be supported). The controller will use an internal simulator to determine the minimum of supports and clamps assuring correct overall position and shape of the sheet and will derive and manage in an optimal way the concentration of support agents in the regions under manufacturing. The setup of traditional fixtures is static; the swarm fixture concept implies dynamic setup because number and locations of the supports change during the execution of the manufacturing operations on the workpiece (the fixture continuously adapts to the progression of the manufacturing). The programming interface will make I/O and process easily understandable to the user and will manage the interfacing of the swarm fixture to the manufacturing system.
5. Developing an intelligent control system relying on high level intelligent organization control and low level behaviors of the agents.
A two tiers control system will be employed. One tier will be responsible for finding the optimal distribution of the support points and the other tier will be responsible for moving the robots to their destinations. The latter will be behavior based, thus each robot will be treated as an autonomous agent moving to its destination point, however avoiding collisions on its way. This objective will be achieved by steps. At the first step each robot of the swarm will be behavior based controlled, while the goal (i.e. the location) to reach will be produced by a high level planner. At the second step the complex high-level planning capabilities including all algorithms and methods will be implemented and setup to realize the targeted shape multipoint support.
Measurable and verifiable fixture performance objectives
-Orthogonal stiffness higher than 1 N/um (higher than in best today's Modular Flexible Fixture Systems MFFS)
-Absolute accuracy in all directions at each supporting point lower than 2100um and local deformation caused by head and head-part adhesion system lower than 100 um in all directions (with no external load applied) Repositioning time for each single agent lower than 60 s
-Design of the single support agents to concentrate more than 3 heads in a 200mm side square (estimated feasible for high-speed holing, riveting, etc.)
-Set-up time to reconfigure the fixture to a new part lower than 5 minutes (many hours for traditional aeronautics/ automotive fixtures and comparable to best MFFS and Robotic Fixtureless Assembly RFA)
-Outstanding adaptability compared to the more adaptable fixtures available for 3D thin sheet parts (estimated higher than 70%)
Project Results:
Once the requirements for the system, fundamental ideas and working principles were established and accepted by all the partners, several Scientific and Technical specific results were determined by the consortium. These not only had become the cornerstones for the project objectives to be fulfilled, but represent the way for further exploitation of the results as separate units or as whole. At the same time, these foregrounds represent a clear path to achieve the desired results and to comply with the fixed objectives, which in turn will lead to the innovative fixture system envisioned.
The specific Science and Technology (S & T) foregrounds results selected by consortium and that have a bigger possibility of exploitation are the following:
1.Single support parallel robot module
2.Adaptable head module: sand head
3.Locker module 138 special
4.Powered bench
5.Swarm control and planning system HMI
6.Integrated SWARMITFIX
7.Adaptable head module 2: MRF
8.Exechon analytical kinematics and singularity/workspace analysis.
An explanation of the aforementioned Science and Technology (S & T) results achieved is given in this section.
1. Single support parallel robot module
The research within Machine Tools has always been driven to combine the flexibility and envelope of the robots with the accuracy and stiffness of traditional Machine Tools. In the last 20 years the focus of this development has been Parallel Kinematics Machines so called PKM. This technology means that the motions in X, Y and Z are performed by three or more parallel axis's that gives an outstanding stiffness and accuracy with a maintained flexibility and envelope. The first machine that actually proved this technology was the Tricept, a PKM machine, developed by Karl-Erik Neumann, that already 1994 performed real work in the industry (taken from http://www.exechon.com online).
Regarding the ranking among the market of this type of machine, we can summarize the following:
-Articulate Arm Robots: The first electrical robots was developed in the beginning of 1970 as a technology that should replace human workers in fields of hard monotone and hazardous work like spot welding, arc welding and handling etc. The target was to build a robot with a large work envelope and a great flexibility without any requirement of high accuracy and stability which wasn't required for the applications in question. To achieve these goals the technology used is a so called serial linkage technology meaning that every additional axis is mounted on the previous one. This technology has the advantage of being able to move the mechanics in all directions giving the required flexibility and envelope however without accuracy and stiffness.
-Traditional Machine Tools: It's well known in the industry that all CNC Machine Tools has a very high requirement of accuracy and stiffness to be able to manufacture parts for an industry that requires microns of accuracy in combination with a high chip removal capacity. However, what people normally don't realize is that all traditionally Machine Tools on the market are also based on a serial linkage technology, like the robots, with all the disadvantages in the areas of accuracy and stiffness that comes with it. So, to compensate for this 'bad' technology the Machine Tool manufacturers have to design the machines with massive structures and wide beds to make sure that the serial linkage system maintain the accuracy and stiffness also in the end of the last linkage. However, these massive structures and wide beds totally eliminate the flexibility that is significant for robots.
-Parallel Kinematics Machines: The dream of all developer within Machine Tools has always been to combine the flexibility and envelope of the robots with the accuracy and stiffness of traditional Machine Tools. In the last 20 years the focus of this development has been Parallel Kinematics Machines so called PKM. This technology means that the motions in X, Y and Z are performed by three or more parallel axis's that gives an outstanding stiffness and accuracy with a maintained flexibility and envelope.
-XMIN: The X150developed within SWARMITFIX has managed to combine all above features a package those in a small handle size with a unique performance.
In terms of the competitors it is possible to summarize the following:
-Existing Parallel Kinematics Machines: Parallel Kinematics, as an occurrence, is a number of parallel 'arms' connected to each other in one end and to a base in the other end and by default this design requires joints with multiple Inactive Degrees Of Freedom (IDOF). The number of parallel arms in a Parallel Kinematics Machine (PKM) depends on the design and can vary from three arms up to eight arms but in all cases the target of the design is to combine flexibility and stiffness. Significant for all PKM machines is the problem of the joints, which are complex and difficult to manufacture with high stiffness and backlash free to the right cost. This technology issue limits the number of PKM machines on the market and is also the reason why the most successful designs are the PKMs with less number of joints and IDOFs. The Tricept is today the PKM with fewest number of joints and IDOFs and that's why the Tricept has 70% of the market of PKMs today.
-X150: The new Exechon Concept takes care of all previously described known PKM problems and features all goals for PKM machines such as, high stiffness in combination with extreme flexibility and dynamics. The new Exechon Concept is based on the use of fewer joints with no more than one Degree Of Freedom (1-DOF) and the use of actuators with two Degrees Of Stiffness (2-DOS), linear and bending in one direction. This design forms a solid structure that completely takes care of the bending and torsion forces applied to the machine in all directions.
2. Adaptable head module: sand head
The adaptable head modules developed in this project were separated depending on the working principle of the head. This is, depending on the applications and specially for addressing different industrial interests. This section is devoted to the Sand head module were DIMEC is the lead developer.
The sand head is the name employed to refer to the head module which uses granular material to adapt to the shape of the workpiece. The motivation of developing a support interface between agents and workpiece different from a commercial vacuum cup is; because the simple use of suction vacuum cups do not allow an adequate clamping of the metal sheet during the execution of manufacturing, it was thought then, to combine the action of a suction cup (reproduced in the form of an outer lip) with the action of a membrane containing granular material to increase the contact surface between the head and the sheet.
The principle idea, in which the scientific research and thus, expected results, were driven; was to create a vacuum head based on the principle of hydrostatic segregation and clustering of an incoherent mix of particles: suction of air from the inter-particular space is used to compact the material into a hard state. In a granular material the grains are arranged in space depending by external actions: when submitted to small mean stress the shear strength is very small and the granular material can flow almost like a liquid (i.e. silos); when the mean stress is high the granular material will be able to bear high loading such as in the case of infrastructures.
The final design of the sand head prototype was thought to optimize the operating conditions and reduce the dimensions of the module. It is conceived as a cup, covered by an outer lip that gives the necessary sealing for the vacuum to be produced. The powder is packaged in the center of the cup, held in place at the bottom side by a ring of silencers that conform the filter. At the top side the sand is packaged by a deformable membrane with a lens-like shape so to take advantage from the distribution of the material's stress and increase the stiffness with vacuum. On the bottom side of the cup, after the silencer a second membrane manufactured in rubber is encountered. The rubber membrane permits the repositioning of the powder into the chamber during the positioning of the head under the workpiece (introducing compressed air at the base of the membrane, it expands relocating the powder and filling the whole space of the chamber). The vacuum is given by 4 push-in fittings located at the bottom of the cup.
The prototype is manufactured with 4 plates; forming the powder chamber. In the following each plate is described briefly:
Lower plate: Contains a total of five holes in which 4 push-in fittings are housed to deliver vacuum to the head, 1 more push-in fitting used to pressurize the deformable rubber membrane and a groove which permits the passage of air.
-Collar: This component houses the ring of silences and is the main component if the powder chamber.
-Silencers ring: It is designed with an inclined face that is necessary to create the lens-like shape arc. Each silencer is mounted in a purposely designed hole distributed around it.
-Top flange: It is designed to mechanically lock the external membrane holding the powder at the top side of the module.
3. Mobile base and locker module VERO-S NSE plus 138 special
The purpose of this subsystem is to realize the motion of the agents on the bench. In principle, translational horizontal displacements realized only with motions in two perpendicular directions (x and y motions) is sufficient. However, it is increasingly desirable to have less strict non-holonomic constraints, i.e. to have the ability for the agent base to move in one or more diagonal directions. The main reason is the need for fast repositioning during milling, which may be impossible if the required displacement must be realized by two separate motions with a necessary full stop between them.
During the initial steps of the research carried out to define the best and more reliable motion operation of the mobile base, several locomotion principles were developed and studied to finally choose the one with the best performance. The various studied principles are: sliding, rolling in grooves, rolling with tracks, rolling directly on the bench, and swinging around a vertical axis. The later, the swing locomotion principle was selected in order to realize the mobile base. The mobile base or platform gives the first position tuning of the system, using the swing locomotion method and a 3 legged base with modified commercial Schunk lockers for the docking mechanism. The three legs are inserted alternatively in the bench. The base rotates about one inserted leg while the other two are pulled up; it then rotates at an angle and stops with the unused legs above free bench pins. Then, one of the latter legs slides in, while the former is pulled out keeping the third leg pulled up. The presence of one leg always inserted in the bench guarantees the equilibrium of the agent; and the special gear transmission provides the necessary torque for the agent to rotate orienting at the same time the retracted legs thanks to the two spur gears in each leg. Furthermore, the legs are equipped with the electrical female connectors providing electric power to the whole agent and the capability to transmit air from the bench to the on-board tank. Since the rotation is about a single leg the locking force has to be greater than 10 kN. This force is provided by the Schunk components that together provide:
- holding force of 75kN;
-draw in force of 18kN;
-repeated accuracy less than 0.005mm.
The following is the description of said modifications:
-Air supply: In order to let the air supply be carried from the work bench to the whole agent, the locker had to be able to let the air pass through it. A special component was introduced. A small whole to house a coupling was introduced. Couplings are used to prevent leakage when transmitting liquid or gaseous mediums. The coupling elements are special mounting parts, which are built directly into accommodation housing. The system seal (axial seal) between coupling mechanism and coupling nipple acts axially and is placed in the coupling mechanism. The coupling nipple is located in the bench and when interfaced with the coupling mechanism inserted in the locker the air is permitted to free pass through. This modification is of the out-most importance given that without it a pipe less functioning of the agents would not be possible.
-Anti-rotation pin: Also in the circumference generated by the mounting screws an 8 mm diameter whole was introduced, this is to permit the anti rotation pin located in the bench to be inserted. At the same time this pin gives the orientation of the locker in the bench. The whole is made with H7 tolerance and it is the principle centering component on the locker. If this pin is not correctly aligned with the respective whole introduced in the locker the locker can not be clamped. At the same time, this pin lets the agent rotate about the clamped leg.
-Central removable plug: The central removable plug located in the locker is a standard feature of the component; however in this project the use has been little modified. The whole is envisioned to provide a blow-out function which in some way is used. However the major interest of having through whole in the middle of the locker was to provide a place in which electrical connectors could be placed and at the same time use the blow-out function to blow compressed air as part as the cleaning system describe before. The electrical connectors embedded then in the locker permit the agent to take the necessary electricity directly from the bench. The same way as for the air supply, this lets the agent to work wireless, thus without introducing constrains in its operation due to wires hanging around the mobile base.
-Clamping Schunk pin: This is a necessary accessory also from Schunk in order to use the locker; this will be addressed in the section Powered bench.
4. Powered bench
The work bench is one of the most important results obtained during the project, without disregarding the importance of the whole project of course. However without the working bench the locomotion and hence the functioning of the agents would be impossible. Furthermore, the bench can be on its own and important commercial component for every system using the quick change pallet system from Schunk and in need of pneumatic and power supply. As already established, we have used commercial docks provided by the Schunk comprising a female and a male unit. One of the two units is a simple and passive mechanical interface while the unit with opposite gender is equipped with the mechanisms for the generation of the locking force. The units in the bench, which are numerous, are the passive ones while the units in the agent are the ones equipped with the locking equipment in order to minimize the cost of the system.
Initially research was made considering a type of unit with simple female and male unit with locking mechanisms. A design of the agent has been completed with these units and static and structural analyses have been carried out on the mock-up of the system. The locomotion of the agent on walls and upside-down was possible with limitations in the load and velocity of repositioning so a decision was made to change to a different model of locker with passive male and higher load capacity and stiffness. This final locking system comprises equipment for the feeding of compressed air to the agent, electrical power to the agent and equipment for blowing out the swarf and cleaning the surface before locking.
The cleaning system is divided in two parts:
-Cleaning system in the bench by blowing air directly from the pin modules;
-Cleaning system on-board the mobile base, blowing air to the bench surface.
With the selected design the swarf is blown purposely in the correct direction away from the module's surface and directly to the base legs surface assuring a proper contact between the two. In the bottom part of the workbench electrical and pneumatic connections are housed, the rows of clamping modules are supplied by rows of connections forming a fork like system underneath the bench. The pneumatic and electrical components rows of the fork like housing system utilized, are intercalated between them, making easy to recognize which is row is for electrical components and which one is for pneumatic components. To level the bench, protect the connections and fix it a frame was created. It also gives the capability for the bench and hence the whole system to be mounted in different positions increasing the modularity and customization of the fixture system.
The work bench represents innovation in the form of a unique modular bench supporting continuous reconfiguration in presence of large amount of swarf, guaranteeing accuracies comparable to manual reconfigurable benches. Its robustness contributes to a continuously increasing accuracy needed in the manufacturing industry. Once the technology is proven different sizes can be created depending on the specific end user application.
5. Swarm control and planning system HMI
The control system has been designed following a formal approach based on the definition of the system structure in terms of agents and transition function definition of its behavior. Thus, a modular system has resulted enabling software parametrization. This facilitated introduction of changes is brought about by testing different variants of the mechanical structure of the system. A novel approach to task planning for a self adaptable and reconfigurable fixture system has been developed as well. The solution for task planning is based on constraint satisfaction problem approach. The planner takes into account physical, geometrical, and time-related constraints.
An off-line program, on the basis of CAD geometric data about the panel, representing its state before and after machining, generates the plan of relocation of the mobile supports and the parallel manipulators. Some optimization techniques will be used for that purpose. The panels will be subjected to the following machining operations:
-Drilling: in this case the support locations depend on the form of the material. One static configuration of several manipulators will serve the drilling of a number of holes,
-Milling: which is a continuous process requires the manipulators to relocate during milling. This has to be done fast enough so that the current milling speed will not be affected
6. Integrated SWARMITFIX
With the SWARMITFIX fixture an RFA (robotic fixturless assembly) system has been developed at a higher level of modularity and flexibility. It merges the advantages of RFAs with those of MFFSs (modular flexible fixture systems), namely: the ability to distribute the support action; adaptability to workpiece shapes in a larger range; and stiffness of the provided support.
The swarm fixture agents have to satisfy requirements analogous to the ones of multi-posts fixtures in terms of adaptability of workspace of positioning of the heads, head adaptability, force of adhesion and stiffness.
A critical characteristic of the fixturing system is the size of an individual agent. It is higher than post units due to the embedded actuators, sensors and docking-locking devices. This gives some limitations in the number of agents that can concentrate in a region and has influenced the choice of the degrees of freedom of the head positioning mechanism.
The prototype was completely integrated for the first time in Piaggio Aero and consists of:
-Fully functional workbench, air and electric supply embedded.
-2 fully functional agents consisting of mobile base, pkm and MRF head
-4 passive supports with adjustable height to hold the workpiece in place on the periphery with vacuum cups and dismountable joints for precise location of the workpiece.
The SWARMITFIX project has always been intended to be a solution for the manufacturing of large thin metal aluminum panels; this means that the focal point of interest within the industry is that of the aerospace, however, also automotive industry in particular bus and truck manufacturers as well as train industry can benefit from the system. In particular the final customer of the system can be benefited from an unachieved flexibility so far, constant accuracy over any extension and full compatibility with the manufacturing environment in presence of swarf and cooling liquids.
From this point forward, in order to arrive to a fully commercial product investment is needed, however it is difficult to establish the amount, this is because it depends on how well accepted within the industry the system is. An important point is that after the first developed prototype an approximate price can be speculated rounding the 1 M Euros for a system comprising 4 intelligent fixture agents, a 10m x 5m bench and a set of passive auxiliary supports to hold the workpiece in the periphery. Furthermore, again stating from a good acceptance pf the system and the new trend being developed for the manufacture industry the market size over a single year can be estimated to be around the 10 M Euros.
The acceptance and thus the market opportunity comes as well form the fact that at this moment the system cost is proportional to the scale and constant performance, competing with other products for similar use on large sizes and with high flexibility needed. Furthermore there is no direct competitor that can provide the same characteristics embedded in a single product, the closer competitors are producers of reconfigurable fixtures and rigs with partial adaptability embedded, multipoint adaptable fixtures and at some extent manual reconfigurable fixtures producers. The growth of swarm fixture in the market is based at least for the first years on improvements of in use technology.
7. Adaptable head module 2: MRF Head
As already mentioned, two adaptable head modules were developed during the SWARMITFIX project. The MRF head module utilizes special material to conform to the wide range of panels having different surface curvatures. In simpler words, the head needs to adapt and adhere to the local geometry of the surface were the machining operation is been carried out. Following this particular characteristics the MRF head module was designed to comply with the following requirements:
-Enough yield stiffness to hold the panel and withstand the machining forces
-Rigid adhesion to the sheet keeping constant contact during milling and drilling operations
-Self adaptability to the workpiece
-Fast operation time
-Insensible to thermal changes
-Triangular base: It is the lower part of the triangular head and is made of T 300 Series Stainless Steel austenitic. The material was chosen to guarantee the effect of the magnetic field on the MR fluid. Presents the channels in which the magneto-rheological fluid is introduced. Each channel is designed to lead the MR fluid from the central collector to two of the holes of the guidance, whereas the channels at the edge of the triangle lead the fluid to three holes. All the channels are connected to the central collector, so all the 27 holes of the guidance are in order to allow all the movements needed by the pistons to adapt correctly to the surface of the workpiece. It also presents the necessary holes to insert the vacuum connector and the proximity sensor.
-Guidance: The upper part is made by aluminum, to prevent the magnetization of the sheet during processing. Since the part is the guidance for the 27 small pistons necessary to support the workpiece, to minimize corrosion and wear of the guide holes it was chosen as material Al 6082, a medium strength alloy with excellent corrosion resistance.
-Pistons and O-rings: The small pistons are 25 mm long and have a diameter of 6 mm. To guarantee the contact with the surface, the pistons have a circular head. In order to reduce the friction between the pistons and the guidance the selected material for the final prototype is Delrin. To prevent the loss of magneto-rheological fluid the pins present two seats for o-rings, endless round sealing rings of circular sections. An O-Ring seal is a means for closing passageway preventing an unwanted escape or loss of fluid.
-Rubber cover: It is located at the top of the guidance and glued to a purposely designed protrusion. The material used is a vulcanizable at room temperature silicon by means of a polyaddition reaction.
The triangular head of the MRF module is the core of the development attempting to introduce a new kind of adaptable fixture that can replace the vacuum cups or commonly used grippers. However, a means for activating the phase-change material is needed as well as an actuator to rotate to the proper orientation the head. These can be seen as the core body of the module and are the pneumatic cylinder, servomotor and bracket used to connect the head module to the PKM.
-Pneumatic cylinder: The pneumatic cylinder is needed only to move the neodymium magnet located inside it to supply the magnetic field needed to increase the viscosity of the magneto-rheological fluid. In this way once the small pistons have adapted to the workpiece shape, the cylinder is actuated sending the magnet close to the fluid collector and solidifying it. The cylinder is divided in two parts, the upper part holds the magnet while the lower one is connected to the air supply and holds the necessary seals to prevent air flowing away from it. On the outside part of the lower section of the cylinder, two bearings are located interfacing the bracket; these are needed to let the module rotate in order to achieve proper orientation. At the bottom of the lower section a cap is screwed to hold the servomotor.
-Servo motor: The selected actuator is a Harmonic Drive hollow shaft servo motor capable of rotating the head module to the desired orientation according to the workpiece shape.
-Bracket: The bracket is used to interface the module to the PKM and locate the necessary bearing that will let the module to rotate achieving the orientation needed. The cylinder is inserted in the bracket and secured by screwing the motor to it as well. On the other hand, the bracket is also screwed to the extension arm that comes from the PKM 6 dof flange. This, although decrease the stiffness of the parallel machine, is needed to let the plan calculate feasible locations of the heads.
8. Exechon analytical kinematics and singularity/workspace analysis
The equations used to describe the kinimatics of the PKM are better seen in the attached PDF which presents a synthesis of the whole development of the kinematic analysis reported in the scientific article (Zoppi, M.; Zlatanov, D.; Molfino, R. 'Kinematics analysis of the Exechon tripod'. Proceedings of the ASME 2010 International Design Engineering Technical Conferences and Computers, August 18th 2010.)
For the single support parallel robot module (Exechon X150 PKM, described in section 3.1) to be controlled, the kinematic analysis was needed. It is common to solve this paradigm numerically; however strong computational capabilities are needed and the operation time is increased not to mention the needed space to install a robust enough computer on board the agent. In order to optimize the performance of the system, in both operation time and space, the analytical analysis and solution was developed.
Inverse position kinematics
In practice the PM is used as a regional manipulator, a 3-dof positioning device, with a typically spherical wrist attached to the end-effector at point S. This results in a combined hybrid manipulator, like the 5-dof Exechon PKM and the 6-dof fixture agent X 150. The end-effector of this hybrid chain is denoted by ee.
We have assumed that we have a 6-dof mechanism with a spherical wrist, centered at S. When solving the inverse kinematics of the hybrid tripod the first (easy) step is to obtain the coordinates of point S, which is a known point in the body ee whose location is given.
From this, one proceeds to solve the inverse kinematics of the 3-dof parallel tripod, from a given point S of the 3-dof platform. The result is the three input parameters, for example, the joint variables of the prismatic joints. To complete the inverse kinematics of the 6-dof hybrid manipulator, it remains to obtain the joint variables of the three actuated joints in the serial spherical wrist. This is obtained from the relative orientation of the hybrid chain end-effector, ee, and the PM platform, e, by means of a standard Euler-angle calculation.
The overall process for obtaining the inverse kinematics will not reported in these lines, due to the large amount of equations.
This analytical solution of the inverse kinematics of the PKM is used by the control system to move to the desired position the PKM. It basically solves analytically the configuration and returns the necessary Euler angles of each joint. The controller user interface is capable of exporting the current configuration Euler angles into a separate file and thus create a manual plan from them. On the other hand, if one wants to drive the PKM to a desired location and knows the Euler angle of such location, it is possible for the user to import these angles as XML to the interface and execute the motion.
Potential Impact:
Being the goal of the SWARMITFIX project to create and original autonomously reconfigurable fixture system; there is a lack of familiarity surrounding the novelty of the concept and technology in both industry and research centers. At the same time the novelty of the concept and system developed give place, according to the consortium, to an important economical impact especially in the fixture and manufacture industries.
The impact on 'New generation of products helping European instrument manufacturers and machine builders to stay ahead of the competition' is achieved through the following recalled objectives. These intelligent devices solve a problem of growing importance for aircraft and automotive industries where the amount of material is reduced for costs and life cycle Eco-consistency reasons. These sectors represent in Europe more than 450 billion Euros (ACEA 2001 and EADS 2007 data). Near future applications are also foreseen in the railway, metal construction and furniture, white industry and ship building sectors.
Potential expected impact
The SWARMITFIX project specific objectives have been outlined in a way that obtaining such results the impact in both industrial and socioeconomic level will be maximized. According to each attained objective expected potential impact can be achieved. A relationship between the expected impact and the specific objective that will help to achieve the said impact is given as follows:
Adaptive production systems
The project will contribute to the development of new manufacturing systems that adapt to flexible, small or even single batch oriented production. Today, adaptability of production systems relies on available robotics and it is limited by the devices that interface directly the pieces to be manufactured like fixtures and grippers. The problem of modular and adaptive fixtures has been considered by different research actors but no solution till now satisfies completely the requirements on agility and adaptability addressed by the work programme.
Rapidly configurable machines, self-adaptive machine structures, self-optimization. reduction of time needed for reconfiguration and maintenance
The swarm fixture developed, with simple robots reconfiguring in real time to adapt to different thin sheet shapes, will substitute sets of complex specific devices purposely designed for a very limited range of pieces. This results in savings in cost and reduction in fixturing and set up time. Modularity of the homogeneous robots swarm guarantees fast maintenance and scalability. Furthermore the new hybrid control approach will optimize reconfigurability against every operation phase in the manufacturing cycle. In this way the new fixturing system impacts perfectly the work programme issues. Impact will be both at manufacturing shop floor level up to production planning and logistics levels with improved productivity along all the chain.
Control system architectures for mechatronic knowledge-based systems
The new generation of fixtures adopts a set of behavior based mechatronic agents. The control architecture relies both on implicit, stigmergy based, and explicit communication. This innovative architecture together with the intrinsic high stability of the agent mechatronic design produces robustness and stiffness to the overall system. Reconfiguration planning goal and logic's are based on the knowledge of the behaviors of single and multiple cooperating agents that adapt in real time to the specific manufacturing task. The swarm fixture concept involves problems of seamless connectivity and inter-working of scalable embedded systems in the manufacturing domain. The fixture agents cooperate in spatial proximity to jointly realize the common workpiece support task and together represent a small-scale complex distributed system expressing a reactive, but also efficient, robust, predictable, safe behavior.
More efficient, flexible, secure, easier to maintain and more productive (large infrastructure) manufacturing plants
The new fixture is a distributed system that requires a new engineering approach ensuring efficient, adaptable, safe and secure behavior for the manufacturing process. The self adaptability of the fixture improves the flexibility towards customized production, reduces human presence and work in the production environment rising safety and security, avoids re-fixturing tasks, and reduces fixturing setup time improving plant productivity. The modular distributed system makes maintenance interventions easier and faster. While the fixture can be considered a 'small scale' distributed system, the control methodology developed for the dynamic fast reconfiguring architecture can be applied to more complex, large scale distributed systems.
Quantification of economical impact
The new generation of fixtures will open significant gain perspectives to their builders and suppliers and will allow to their users, mainly to manufacturers in aerospace and automotive sectors but not limited to, to produce their products at shorter time to market, improved quality, lower cost and reduced resources consumption, thus allowing them to stay ahead of the global competition. Using as few as only two intelligent advanced Exechon PKM Agents to machine a complete panel will not only reduce the cost of the fixture dramatically, but also increase the accessibility and the up-time in production, and the same Agents can be moved between several flat tables and reduce the need of dedicated fixtures substantially.
A rough but conservative estimation of the quantification of these impacts follows:
Fixture storage and management costs are reduced of more than 400% with no need to store, maintain and manage trimming tools. Furthermore the high re-configurability allows the machining of left and right part kits in the same space. It also allows older parts to be machined without storing conventional tools for years.
If compared to traditional methods adopted for limp sheet manufacturing the adoption of the new highly reconfigurable fixtures, whose set-up time is in the range of minutes and may be performed in hidden time, will allow to cut the re-tooling times, which for complex and delicate thin sheets are in the range of hours. For thin sheet manufacturing cycle of about 10 operations the expected reduction of the producing time is 90%.
Re-fixturing operations require an attentive and very accurate manual re-positioning of the thin sheet on the fixture for next operation; the re-positioning errors are the main cause of defects. The use of the new fixture will avoid many manual re-positioning steps because it is the fixture itself that is programmed to adapt the supporting points to the different sequential operations and the re-positioning program, before the actuation, is checked through simulation.
An estimate of main savings offered by one SWARMITFIX installation in the aerospace manufacturing sector as perceived by end-users themselves as follows:
Taking the conventional fixtures costs of manufacture and re-tooling, the use of the SWARMITFIX system in which only one time investment and no re-tooling is needed the savings can sum up to 2M Euros, this is mainly, because with conventional fixtures there is one purposely fixture for each manufactured part and the cost of each fixtures is very elevated. On the other hand, for any minor redesign of the part, relevant changes in the fixture are in order (re-tooling); finally if the redesign is big, a completely new fixture maybe needed increasing even more the costs. Again, with to store several dedicated fixtures the maintenance and storage savings are expected to be of around 100 k Euros / year X 5 years. Given the high adaptability, re-configurability and autonomy of the system the set-up time can be reduced by 95% meaning a saving of nearly 720 k Euros / year X 5 years. The set up time reduction and the characteristics of the system represent a lower time cycles for manufacturing the workpieces, in terms of time cycle it is considered to be a reduction of 975 h / year of manufacturing operation that equals to an approximate of 78 k Euros / year X 5 years. Finally the estimated expected savings during the first 5 years, considering the above mentioned aspects can amount to 6,490,000 Euros.
However estimated savings can be approximated as follows:
In the automotive sector the replacement of conventional fixtures cannot be completely done, this means the system cannot be used for all the parts comprised in an automobile given the size of them. However, the replacement of the fixtures when possible means an estimated saving of 840 k Euros. At the same the storage and management of fixtures is decreased even more than for the aerospace, this is because in this sector more dedicated fixtures are used meaning that when replacing them with the SWARMITFIX system more fixtures disappear form storage, this can amount to 115 k Euros / year X 5 years. The set-up time reduction is less given the lower amount of fixtures that can b replace, in any case the reduction is expected to be of 75% meaning a saving of 600 k Euros / year X 5 years. In terms of time cycle reduction, in the automotive sector it is foreseen that using the SWARMITFIX system less repositioning of parts are possible, less manufacturing operations to adapt the support device to the part local shape are achieved, it is important to stress these manufacturing operations are of no added value to the final product and only increase the total manufacturing costs. The total time saved is considered to sum up to 1200 h / year and giving an estimated saving of 98.500 k Euros / year X 5 years. Finally the estimated expected savings during the first 5 years, considering the above mentioned aspects in the automotive sector can amount to 4,907,500 Euros.
Scope of the dissemination activities
Several dissemination activities have been done during the life of the project, others are still ongoing or will be done to further exploit the results and bring to the industry the development done.
The scope of the project cannot be addressed at a national level. First of all, the competence centers and research institutions in the various disciplines involved (end-users profiling, mechatronic design methodologies, information technology) are spread in different countries. Then, in relation to manufacturers of products made of thin sheets, even though some European countries (such as Germany, Italy, France, UK, Sweden) exhibit the highest concentration of big companies, smaller producers are based in almost every European nation. Hence a project like SWARMITFIX aiming at a general solution of a manufacturing problem common to different manufacturing sectors can only be conceived at a European level. This is also true when one considers the need of gathering around such an important objective the necessary critical mass in terms of transectorial know how and financial resources to sustain the research. It was then deemed impossible to initiate such a wide scope and ambitious research at private or national level. The project is an opportunity for the partners to establish a transnational cooperation. The complementary expertise will guarantee effective problem solving and accurate definition of application requirements. Impact will be greater and cost-effective higher than that which would come from several smaller national projects as a large market platform will push and support SWARMITFIX.
Promotional, dissemination and marketing activities
Dissemination activities have been done during the project and will continue in order to share the knowledge to the industry. This, as envisioned by the consortium is needed in order to obtain not only the necessary feedback by the end-users that drove the research done, but to obtain at the end a real commercial product that will be of interest to the same end-users.
The biggest challenge for putting a new product on the market is to find an established channel of distribution. This challenge is even bigger when the product in question has a high level of innovation in it. Through the network of Exechon we have now found what we consider a perfect partner for the first real market introduction, Delfoi in Sweden. Delfoi's business idea is to deliver a super modular manual fixturing for the Aerospace and Automotive industry using a flexible box system combining various modular profiles with manual adjustable parallel kinematics holders. This solution is perfect for one-off prototype manufacturing but in combination with SWARMITFIX Agents it would also attract the volume manufacturing industry. Exechon, Delfoi and Airbus are currently discussing a live project in this direction. During 2010 extensive discussion has taken place between Airbus, Delfoi, and Exechon regarding the use of SWARMITFIX Agents in combination with the Delfoi Boxjoint system to be able to supply Airbus with a semi automated and flexible fixturing system.
Involvement in robotics associations
Dissemination and innovation promotion in the field is greatly facilitated by the help of robotics industrial and academic associations. These organizations have strong ties with their national and regional industries and research communities.
The following institutions were involved:
-SIRI, The Italian Association of Robotics and Automation, http://www.robosiri.it
-VDMA Robotics + Automation in Germany, http://www.vdma.org
-EURON EUropean RObotics research Network, http://www.euron.org
-UCIMU-SISTEMI PER PRODURRE, http://www.ucimu.it
After gathering the results form the system trials, different associations will be involved.
Website
The website of the project has been designed and activated: http://www.SWARMITFIX.eu
It is used by the partners both as a repository of documents and to disseminate knowledge to relevant target manufacturing sectors: automotive, aeronautics, trains, shipbuilding. Links to MANU-FUTURE and EUROP are included and new links will be added upon request from the interested institutions. It was decided that each WP leader will have full access to the relevant area and will be responsible for the related content within the website. PMARlab-DIMEC will be responsible for the overall administration of the website, and will oversee and maintain the contents. A 'restricted area' for the exchange of confidential material and material under development has been created and has proven to be a useful tool for the exchange of ideas between partners.
Poster presentation and flyer distribution
Information about SWARMITFIX has features prominently on the PMARlab-DIMEC poster created in 2008. The poster and the project have been presented at multiple meetings and events:
The SWARMITFIX concept was presented at the following meetings and conventions:
-ISICT course on Robotics, Genoa 31 January 2009-10-02
-ISR 2009, Barcelona 10-12 March 2009
-IFR meeting Barcelona, 13 March 2009
-IMB 2009, Köln, 21-24 April 2009
-Alumotive 2009, Montichiari, 2-3 April 2009
-EWF, EUROJOIN 7 / GNS5, Venice, 21-22 May 2009
-Training Course SIRI, Comau, June 21 2009
-Strategic Research Agenda for robotics in Europe, Brussels, 7 July 2009
-Summer Schools on Screws Theory, Genoa 22-30 August 2009
-CLAWAR'09, Istanbul, 9-11 September 2009
-ATA Conference on Vehicles architectures, Florence 25 September 2009International Conference on Reconfigurable Mechanisms and Robots, REMAR'09, held in London, 22-24 June, 2009
-Manufacture 2009 Conference - Implementation of a sustainable European Manufacturing Industry, Gothenburg, 30 November - 1 December 2009
-Reconfigurable Exechon Parallel Kinematics, Simplified Machining and Assembly, Karl-Erik Neumann, Al Bolen, Exechon AB - Aero Tech Congress and Exhibition, Seattle, WA, USA, 10-12 November 2009.
-Presentation by Karl-Erik Neumann, 1st Advanced Manufacturing Technology Forum, Filton, UK, 20-22 October 2009, Aero Tech, Seattle, USA, November 10-12 2009.
-Presentation by Karl-Erik Neumann, Manufuture 2009, the European Manufacturing Conference, 30 November - 1 December 2009, Gothenburg, Sweden.
-SWARMITFIX presentation, Ladislav Vargovcik, EURON-EUROP Annual Meeting, 10-12 March, 2010, San Sebastian, Spain.
-ALUMOTIVE, Montichiari, 2-4 Aprile 2009
-R. M. Molfino, Swarm Fixturing of Aircraft Body Components and Fixturing of car Body Assemblies, Automate 2011, Chicago, March 21-24, CD Conference Proceedings.
Publications
A list of publications regarding the achievements of the project is given below; it is important to stress these publications let the scientific and industrial community to understand not only the importance of the system but the details of design, manufacture and specific characteristics achieved.
Newspaper articles on the project appeared in the Mediaplanet Automation supplement of the Italian national daily business newspaper Il Sole 24 Ore, as well as in the daily Italia Oggi.
-SWARMITFIX un'attrezzatura intelligente, Rezia Molfino, Matteo Zoppi, MEDIA-PLANET AUTOMATION, Il sole 24 ore, 17 November 2009 200.000 copies
-The same on Italia Oggi, 16 November 2009 100.000 copies
Research papers on different components developed within the project have been accepted for publication in the proceedings of several conferences: ISR-Robotic, the Joint 41st International Symposium on Robotics and 6th German Conference on Robotics, 7-9 June 2010, CCMMS, the Chinese Conference on Mechanism and Machine Science, 20-25 July, 2010, Shanghai, China, the ASME 2010 International Design Engineering Technical Conferences (IDETC), 15-18 August, Montreal, Canada. Two papers have been submitted for presentation at the 11th Polish National Robotics Conference, 9-12 September, Karpacz, Poland and one to Frontiers of Mechanical Engineering in China.
-R. Molfino, M. Zoppi, and D. Zlatanov. Reconfigurable swarm fixtures. In Reconfigurable Mechanisms and Robots Proc. of the Int. Conf. REMAR 2009, volume IEEEcn:CFP0943G-PRT, pages 696-701. KC, London, UK, Jul. 22-24 2009.
-R. Molfino, M. Zoppi, Attrezzature robotiche per manipolazione e supporto di stampati, ALUMOTIVE, Montichiari, 2-4 Aprile 2009
-Xiong Li, Aamir Khan, Roberto Avventenente, Matteo Zoppi, Dimilter Zalanov, Rezia Molfino, Development and Analysis of Shape Conformable Support of Self-reconfigurable Intelligent Swarm Fixture, ISR 2010, Munich, June 7-9, 2010
-C. Zielinski, T. Winiarski, P. Trojanek, T. Kornuta: 'Multi-agent control system specification of a robot based reconfigurable fixture', 11th National Robotics Conference, Karpacz, Poland, 9 - 12 September 2010.
-W. Szynkiewicz, W. Kasprzak, T. Zielinska, D. Zlatanov: 'Planowanie rozmieszczenia ruchomych podpór przy obróbce przedmiotów o duzych rozmiarach' (Planning of the distribution of mobile supports for large objects subjected to machinning), 11th National Robotics Conference, Karpacz, Poland, 9 - 12 September 2010.
-W. Szynkiewicz, T. Zielinska, W. Kasprzak: 'Robotized machining of big work pieces: localization of supporting heads', Frontiers of Mechanical Engineering in China.
-Summary of the project in Institute of Control and Computation Engineering 2009 Annual Report, pg.60 also: http://www.ia.pw.edu.pl/download/Annual09.pdf
-Robot Control and Pattern Recognition Group's web page mentions the project at: http://robotics.ia.pw.edu.pl/twiki/bin/view/Grants/GSWARMITFIXFP7-214678
-R. Molfino, M. Zoppi. ''SWARMITFIX un'attrezzatura intelligente'', Italia Oggi, Class Editori. R. Molfino, M. Zoppi. ''SWARMITFIX un'attrezzatura intelligente'', Media-Planet Automation, Il Sole 24 ore.
-Zoppi, M.; Zlatanov, D.; Molfino, R. ''Kinematics analysis of the Exechon tripod''. Proceedings of the ASME 2010 International Design Engineering Technical Conferences and Computers, August 18th 2010.
-Zielinski C., Kornuta T., Trojanek P., Winiarski T., Walecki M. ''Specification of a Multi-Agent Robot-Based Reconfigurable Fixture Control System''. 8th International Workshop on Robot Motion and Control, RoMoCo'11.
-Zielinski C., Kornuta T. ''Generation of Linear Cartesian Trajectories for Robots Using Industrial Motion-Controllers'', 16th International Conference on Methods and Models in Automation and Robotics, MMAR'2011.
-Molfino, Rezia; Zoppi, Matteo, ''The robotic swarm concept in fixtures for transport industry''. The 7th International ASME/IEEE Conference on Mechatronics and Embedded Systems and Applications.
-L. Xiong, M. Zoppi, R. Molfino, Reducing Computation Time In Optimization Procedure For Fixture Layout Based On SWARMITFIX, 5th International Conference on Integrated Modeling and Analysis in Applied Control and Automation IMAACA 2011, Rome, 12-14 September 2011, CD Proceedings
-Li, X.; Zoppi, M.; Molfino, R.; de Leonardo, L. ''Design of a mobile base for a self-reconfigurable intelligent swarm fixture system. The 14th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2011.
-de Leonardo, L.; Zoppi, M.; Li, X.; Gagliardi, S.; Molfino, R. ''Developing a new concept of Self Reconfigurable Intelligent Swarm Fixtures''. Proc. of the Int. Conf In Reconfigurable Mechanisms and Robots. REMAR 2012
Educational activities
Two Ph.D candidates, at the University of Genoa and the Warsaw University of Technology, are basing their research on the project. Students in the EMARO (European Master in Robotics) Erasmus Mundus programme have been exposed and have contributed to aspects of SWARMITFIX.
Ph. D research theses:
-Li Xiong- Universita di Genova (DIMEC)
-Piotr Trojanek - WUT - work on his Ph.D. on multi-robot coordination.
M. Sc Thesis
-Serena Gagliardi - Universita di Genova (DIMEC)
-Luis de Leonardo (EMARO) - Universita di Genova (DIMEC) Laboratory work
Laboratory work
-Flexible Automation students - Universita di Genova
-Robot mechanics students - Universita di Genova
-EMARO (European Master on Advanced Robotics) students - DIMEC-UNIGE, WUT
The following courses will include materials and offer projects related to SWARMITFIX:
-Robot Mechanics
-Flexible Automation
-Control of Mechatronic Systems
-Industrial and Service Robotics
-Robot Programming Methods
-Mechanical Design Methods in Robotics
-Mobile Robots
Direct contact with potential users
In the course of their business contacts the SWARMITFIX participants are familiarizing their partners with its concepts and emerging technology. The following major companies have been contacted and had been exposed to the ideas and results of the project:
-A branch of Kuka working on aerospace manufacturing systems. The SWARMITFIX concept has been introduced in discussions with DIMEC and PAI.
-AMS, Ace Manufacturing Systems, India. The company is an Exechon licensee. SWARMITFIX was introduced by Exechon, further presentations are planned.
-TAL Manufacturing Solutions, India, the makers of the TATA car. The company is an Exechon licensee. SWARMITFIX was introduced by Exechon CEO Kalle Neumann; follow-up presentations are planned. (See Appendix C.)
-BFW, Bharat Fritz Werner, India. The company is an Exechon licensee. SWARMITFIX was introduced by Exechon CEO Kalle Neumann; follow-up presentations are planned.
-Premier, India. The company is an Exechon licensee. SWARMITFIX was introduced by Exechon CEO Kalle Neumann; follow-up presentations are planned.
-Shanghai Jiaotong University, Shanghai, China, September 2009. Swarm fixturing technology was presented to invited participants to a special event purposely organized.
List of Websites:
http://www.swarmitfix.eu
http://www.youtube.com/user/LMdeLeonardo?feature=mhee
Today's smartest adaptable fixtures have limited adjustment capability, are mostly operated manually, are usually setup off-line with help of external measuring equipment, e.g. laser. Significant increase in effectiveness and decrease in cost may come from on-line fully actuated configuration/ reconfiguration, large adaptability to different shapes and the capability to dynamically concentrate the support in the region where manufacturing is actually performed, doing that on-line and without moving/ removing the part from the fixture. SWARMITFIX develops the new concept of self adaptable swarm fixtures composed of mobile agents that can freely move on a bench and reposition below the supported part behaving as a swarm, all without moving/ removing the part from the fixture.
Each fixture agent is composed of:
-a mobile platform,
-a parallel robot fixed to the mobile platform,
-an adaptable head with phase-change fluid and an adhesion arrangement, to sustain/ clamp the supported part perfectly adapting to the part local geometry.
The objectives of the project are to:
-rethink the fixtures as a multiagent swarm system, achieving high online adaptability and reconfigurability with the minimum necessary number of support units.
-The use of swarm single agents, designed as parallel robots (for high stiffness and position accuracy) on a mobile base, being able to freely move on the fixture bench to reach desired support locations, anchor to the bench, accurately position and orient their support heads.
-Introducing the concept of phase-change fluid in the head of each swarm agent in order to get a perfect geometrical adaptation to the local shape of the supported part and at the same time to realize stiff support and clamping.
-Developing an offline simulator to program/ check the fixture configuration for specific CAD sheet geometries and manufacturing cycles.
-Developing an intelligent control system relying on high level intelligent organization and control, and low level behaviors of the agents.
-Developing a virtual environment for the design and digital mock-up of new SWARMITFIX fixtures addressing modularity and standardization issues.
Project Context and Objectives:
The project aims at developing intelligent fixture technology for the manufacturing of components made of thin sheets with 3D geometries processed by different methods and connected together.
While the use of such components is growing in quantity due to current trends towards life cycle design and sustainable production, and in geometrical complexity due to aesthetic and quality issues, the manufacturing equipment is not growing in flexibility in parallel with the same trends.
Minimum use of material, aesthetic and quality issues also have an influence on the manufacturing requirements and processes adopted:
-Continuous welding is replacing spot welding;
-Round holes at precise locations are preferred to slotted holes traditionally used for relative adjustment in assemblies;
-Execution of accurate grooving and windowing operations is increasing;
-Complex surface geometries are adopted to satisfy stiffness requirements as with thicker material.
The demand for flexibility is pushed by short time-to-market, production in small and variable batch and mass customization for some products.
The sheets are first formed, normally by pressing or other forming technologies, and then further processed (deburred, milled, holed, contoured etc.). Fixtures to support and keep the sheets in form are required for the execution of almost all of these secondary manufacturing operations.
Significant increase in effectiveness and decrease in cost may come from on-line fully actuated configuration/reconfiguration, large adaptability to different shapes of the part to support and the capability to dynamically concentrate the support in the region where manufacturing is currently performed, without moving/removing the part from the fixture.
With these aims, we develop the new concept of self adaptable swarm fixtures composed of mobile agents that can freely move on a bench and reposition below the supported part as required, behaving as a swarm, all without moving/removing the part from the fixture. In this view, each swarm agent is composed of:
-A mobile base,
-A parallel robot fixed to the mobile base with at least three degrees of freedom;
-An adaptable head with an adhesion arrangement that comes in contact and sustains the supported part perfectly adapting to the part local geometry.
Once reached the assigned location, the agent anchors to the bench and then adjusts position and shape of the head to the supported part.
Adjustment is carried out at two levels:
-The parallel robot provides fine tuning of the position of the head with resolution higher than that of the mobile platform;
-The head has a fluidly conformable shape and contains a material whose physical phase can be switched from fluid to solid, e.g. electro or magneto-rheological fluid; first the material in the head is fluid to adhere and adapt exactly to the local shape of the part to support; then the material phase switches to solid realizing a stiff support with an adhesion system that locks the part to the head.
The project main objectives are:
1. Rethinking the fixture as a multiagent swarm system to achieve high online adaptability and reconfigurability with minimum number of support units.
This is the main objective of the project. It will be achieved through the realization of a physical prototype that will demonstrate the concept soundness and functionalities with reference to the active support of the workpiece during the specified manufacturing operations (mainly drilling and milling). The validation tests will be performed within the Piaggio Aero premises.
2. Using swarm single agents, designed as parallel robots (for high stiffness and position accuracy) on a mobile base, able to freely move on the fixture bench to reach desired support locations, anchor to the bench, accurately position and orient their support heads.
The swarm unit is conceived and designed as an intelligent agent able to work by itself and able to collaborate and co-operate with other similar units.
This will involve:
-The application of advanced methods for the synthesis and optimization of task-oriented parallel robots under workspace, stiffness and accuracy constraints;
-The adoption of design criteria for cost effectiveness, robustness and reliability;
-The selection and development of suitable power transmission between agents and fixture bench and data communication from/to the agents.
3. Introducing the concept of phase-change fluid in the head of each swarm agent in order to get a perfect geometrical adaptation to the local shape of the supported part and at the same time to realize stiff support and clamping.
This objective is crucial as it addresses the realization of new supporting/clamping tools that gently adapt to the surface of the thin sheet part and firmly keep it blocked during the operation. It includes the application of know-how in the field of smart materials and their use in robotic systems for the development of the phase-change head, including analysis of local distributions of contact and reshaping pressures at the head-part interface and related influence on the local geometry of the part and on the holding forces during manufacturing.
4. Developing an offline simulator to program/check the fixture configuration for specific CAD sheet geometries and manufacturing cycles.
This will address the generation of the map of support locations by the supervisory controller based on CAD data of the supported sheet and manufacturing process information (NC file of the parts to be supported). The controller will use an internal simulator to determine the minimum of supports and clamps assuring correct overall position and shape of the sheet and will derive and manage in an optimal way the concentration of support agents in the regions under manufacturing. The setup of traditional fixtures is static; the swarm fixture concept implies dynamic setup because number and locations of the supports change during the execution of the manufacturing operations on the workpiece (the fixture continuously adapts to the progression of the manufacturing). The programming interface will make I/O and process easily understandable to the user and will manage the interfacing of the swarm fixture to the manufacturing system.
5. Developing an intelligent control system relying on high level intelligent organization control and low level behaviors of the agents.
A two tiers control system will be employed. One tier will be responsible for finding the optimal distribution of the support points and the other tier will be responsible for moving the robots to their destinations. The latter will be behavior based, thus each robot will be treated as an autonomous agent moving to its destination point, however avoiding collisions on its way. This objective will be achieved by steps. At the first step each robot of the swarm will be behavior based controlled, while the goal (i.e. the location) to reach will be produced by a high level planner. At the second step the complex high-level planning capabilities including all algorithms and methods will be implemented and setup to realize the targeted shape multipoint support.
Measurable and verifiable fixture performance objectives
-Orthogonal stiffness higher than 1 N/um (higher than in best today's Modular Flexible Fixture Systems MFFS)
-Absolute accuracy in all directions at each supporting point lower than 2100um and local deformation caused by head and head-part adhesion system lower than 100 um in all directions (with no external load applied) Repositioning time for each single agent lower than 60 s
-Design of the single support agents to concentrate more than 3 heads in a 200mm side square (estimated feasible for high-speed holing, riveting, etc.)
-Set-up time to reconfigure the fixture to a new part lower than 5 minutes (many hours for traditional aeronautics/ automotive fixtures and comparable to best MFFS and Robotic Fixtureless Assembly RFA)
-Outstanding adaptability compared to the more adaptable fixtures available for 3D thin sheet parts (estimated higher than 70%)
Project Results:
Once the requirements for the system, fundamental ideas and working principles were established and accepted by all the partners, several Scientific and Technical specific results were determined by the consortium. These not only had become the cornerstones for the project objectives to be fulfilled, but represent the way for further exploitation of the results as separate units or as whole. At the same time, these foregrounds represent a clear path to achieve the desired results and to comply with the fixed objectives, which in turn will lead to the innovative fixture system envisioned.
The specific Science and Technology (S & T) foregrounds results selected by consortium and that have a bigger possibility of exploitation are the following:
1.Single support parallel robot module
2.Adaptable head module: sand head
3.Locker module 138 special
4.Powered bench
5.Swarm control and planning system HMI
6.Integrated SWARMITFIX
7.Adaptable head module 2: MRF
8.Exechon analytical kinematics and singularity/workspace analysis.
An explanation of the aforementioned Science and Technology (S & T) results achieved is given in this section.
1. Single support parallel robot module
The research within Machine Tools has always been driven to combine the flexibility and envelope of the robots with the accuracy and stiffness of traditional Machine Tools. In the last 20 years the focus of this development has been Parallel Kinematics Machines so called PKM. This technology means that the motions in X, Y and Z are performed by three or more parallel axis's that gives an outstanding stiffness and accuracy with a maintained flexibility and envelope. The first machine that actually proved this technology was the Tricept, a PKM machine, developed by Karl-Erik Neumann, that already 1994 performed real work in the industry (taken from http://www.exechon.com online).
Regarding the ranking among the market of this type of machine, we can summarize the following:
-Articulate Arm Robots: The first electrical robots was developed in the beginning of 1970 as a technology that should replace human workers in fields of hard monotone and hazardous work like spot welding, arc welding and handling etc. The target was to build a robot with a large work envelope and a great flexibility without any requirement of high accuracy and stability which wasn't required for the applications in question. To achieve these goals the technology used is a so called serial linkage technology meaning that every additional axis is mounted on the previous one. This technology has the advantage of being able to move the mechanics in all directions giving the required flexibility and envelope however without accuracy and stiffness.
-Traditional Machine Tools: It's well known in the industry that all CNC Machine Tools has a very high requirement of accuracy and stiffness to be able to manufacture parts for an industry that requires microns of accuracy in combination with a high chip removal capacity. However, what people normally don't realize is that all traditionally Machine Tools on the market are also based on a serial linkage technology, like the robots, with all the disadvantages in the areas of accuracy and stiffness that comes with it. So, to compensate for this 'bad' technology the Machine Tool manufacturers have to design the machines with massive structures and wide beds to make sure that the serial linkage system maintain the accuracy and stiffness also in the end of the last linkage. However, these massive structures and wide beds totally eliminate the flexibility that is significant for robots.
-Parallel Kinematics Machines: The dream of all developer within Machine Tools has always been to combine the flexibility and envelope of the robots with the accuracy and stiffness of traditional Machine Tools. In the last 20 years the focus of this development has been Parallel Kinematics Machines so called PKM. This technology means that the motions in X, Y and Z are performed by three or more parallel axis's that gives an outstanding stiffness and accuracy with a maintained flexibility and envelope.
-XMIN: The X150developed within SWARMITFIX has managed to combine all above features a package those in a small handle size with a unique performance.
In terms of the competitors it is possible to summarize the following:
-Existing Parallel Kinematics Machines: Parallel Kinematics, as an occurrence, is a number of parallel 'arms' connected to each other in one end and to a base in the other end and by default this design requires joints with multiple Inactive Degrees Of Freedom (IDOF). The number of parallel arms in a Parallel Kinematics Machine (PKM) depends on the design and can vary from three arms up to eight arms but in all cases the target of the design is to combine flexibility and stiffness. Significant for all PKM machines is the problem of the joints, which are complex and difficult to manufacture with high stiffness and backlash free to the right cost. This technology issue limits the number of PKM machines on the market and is also the reason why the most successful designs are the PKMs with less number of joints and IDOFs. The Tricept is today the PKM with fewest number of joints and IDOFs and that's why the Tricept has 70% of the market of PKMs today.
-X150: The new Exechon Concept takes care of all previously described known PKM problems and features all goals for PKM machines such as, high stiffness in combination with extreme flexibility and dynamics. The new Exechon Concept is based on the use of fewer joints with no more than one Degree Of Freedom (1-DOF) and the use of actuators with two Degrees Of Stiffness (2-DOS), linear and bending in one direction. This design forms a solid structure that completely takes care of the bending and torsion forces applied to the machine in all directions.
2. Adaptable head module: sand head
The adaptable head modules developed in this project were separated depending on the working principle of the head. This is, depending on the applications and specially for addressing different industrial interests. This section is devoted to the Sand head module were DIMEC is the lead developer.
The sand head is the name employed to refer to the head module which uses granular material to adapt to the shape of the workpiece. The motivation of developing a support interface between agents and workpiece different from a commercial vacuum cup is; because the simple use of suction vacuum cups do not allow an adequate clamping of the metal sheet during the execution of manufacturing, it was thought then, to combine the action of a suction cup (reproduced in the form of an outer lip) with the action of a membrane containing granular material to increase the contact surface between the head and the sheet.
The principle idea, in which the scientific research and thus, expected results, were driven; was to create a vacuum head based on the principle of hydrostatic segregation and clustering of an incoherent mix of particles: suction of air from the inter-particular space is used to compact the material into a hard state. In a granular material the grains are arranged in space depending by external actions: when submitted to small mean stress the shear strength is very small and the granular material can flow almost like a liquid (i.e. silos); when the mean stress is high the granular material will be able to bear high loading such as in the case of infrastructures.
The final design of the sand head prototype was thought to optimize the operating conditions and reduce the dimensions of the module. It is conceived as a cup, covered by an outer lip that gives the necessary sealing for the vacuum to be produced. The powder is packaged in the center of the cup, held in place at the bottom side by a ring of silencers that conform the filter. At the top side the sand is packaged by a deformable membrane with a lens-like shape so to take advantage from the distribution of the material's stress and increase the stiffness with vacuum. On the bottom side of the cup, after the silencer a second membrane manufactured in rubber is encountered. The rubber membrane permits the repositioning of the powder into the chamber during the positioning of the head under the workpiece (introducing compressed air at the base of the membrane, it expands relocating the powder and filling the whole space of the chamber). The vacuum is given by 4 push-in fittings located at the bottom of the cup.
The prototype is manufactured with 4 plates; forming the powder chamber. In the following each plate is described briefly:
Lower plate: Contains a total of five holes in which 4 push-in fittings are housed to deliver vacuum to the head, 1 more push-in fitting used to pressurize the deformable rubber membrane and a groove which permits the passage of air.
-Collar: This component houses the ring of silences and is the main component if the powder chamber.
-Silencers ring: It is designed with an inclined face that is necessary to create the lens-like shape arc. Each silencer is mounted in a purposely designed hole distributed around it.
-Top flange: It is designed to mechanically lock the external membrane holding the powder at the top side of the module.
3. Mobile base and locker module VERO-S NSE plus 138 special
The purpose of this subsystem is to realize the motion of the agents on the bench. In principle, translational horizontal displacements realized only with motions in two perpendicular directions (x and y motions) is sufficient. However, it is increasingly desirable to have less strict non-holonomic constraints, i.e. to have the ability for the agent base to move in one or more diagonal directions. The main reason is the need for fast repositioning during milling, which may be impossible if the required displacement must be realized by two separate motions with a necessary full stop between them.
During the initial steps of the research carried out to define the best and more reliable motion operation of the mobile base, several locomotion principles were developed and studied to finally choose the one with the best performance. The various studied principles are: sliding, rolling in grooves, rolling with tracks, rolling directly on the bench, and swinging around a vertical axis. The later, the swing locomotion principle was selected in order to realize the mobile base. The mobile base or platform gives the first position tuning of the system, using the swing locomotion method and a 3 legged base with modified commercial Schunk lockers for the docking mechanism. The three legs are inserted alternatively in the bench. The base rotates about one inserted leg while the other two are pulled up; it then rotates at an angle and stops with the unused legs above free bench pins. Then, one of the latter legs slides in, while the former is pulled out keeping the third leg pulled up. The presence of one leg always inserted in the bench guarantees the equilibrium of the agent; and the special gear transmission provides the necessary torque for the agent to rotate orienting at the same time the retracted legs thanks to the two spur gears in each leg. Furthermore, the legs are equipped with the electrical female connectors providing electric power to the whole agent and the capability to transmit air from the bench to the on-board tank. Since the rotation is about a single leg the locking force has to be greater than 10 kN. This force is provided by the Schunk components that together provide:
- holding force of 75kN;
-draw in force of 18kN;
-repeated accuracy less than 0.005mm.
The following is the description of said modifications:
-Air supply: In order to let the air supply be carried from the work bench to the whole agent, the locker had to be able to let the air pass through it. A special component was introduced. A small whole to house a coupling was introduced. Couplings are used to prevent leakage when transmitting liquid or gaseous mediums. The coupling elements are special mounting parts, which are built directly into accommodation housing. The system seal (axial seal) between coupling mechanism and coupling nipple acts axially and is placed in the coupling mechanism. The coupling nipple is located in the bench and when interfaced with the coupling mechanism inserted in the locker the air is permitted to free pass through. This modification is of the out-most importance given that without it a pipe less functioning of the agents would not be possible.
-Anti-rotation pin: Also in the circumference generated by the mounting screws an 8 mm diameter whole was introduced, this is to permit the anti rotation pin located in the bench to be inserted. At the same time this pin gives the orientation of the locker in the bench. The whole is made with H7 tolerance and it is the principle centering component on the locker. If this pin is not correctly aligned with the respective whole introduced in the locker the locker can not be clamped. At the same time, this pin lets the agent rotate about the clamped leg.
-Central removable plug: The central removable plug located in the locker is a standard feature of the component; however in this project the use has been little modified. The whole is envisioned to provide a blow-out function which in some way is used. However the major interest of having through whole in the middle of the locker was to provide a place in which electrical connectors could be placed and at the same time use the blow-out function to blow compressed air as part as the cleaning system describe before. The electrical connectors embedded then in the locker permit the agent to take the necessary electricity directly from the bench. The same way as for the air supply, this lets the agent to work wireless, thus without introducing constrains in its operation due to wires hanging around the mobile base.
-Clamping Schunk pin: This is a necessary accessory also from Schunk in order to use the locker; this will be addressed in the section Powered bench.
4. Powered bench
The work bench is one of the most important results obtained during the project, without disregarding the importance of the whole project of course. However without the working bench the locomotion and hence the functioning of the agents would be impossible. Furthermore, the bench can be on its own and important commercial component for every system using the quick change pallet system from Schunk and in need of pneumatic and power supply. As already established, we have used commercial docks provided by the Schunk comprising a female and a male unit. One of the two units is a simple and passive mechanical interface while the unit with opposite gender is equipped with the mechanisms for the generation of the locking force. The units in the bench, which are numerous, are the passive ones while the units in the agent are the ones equipped with the locking equipment in order to minimize the cost of the system.
Initially research was made considering a type of unit with simple female and male unit with locking mechanisms. A design of the agent has been completed with these units and static and structural analyses have been carried out on the mock-up of the system. The locomotion of the agent on walls and upside-down was possible with limitations in the load and velocity of repositioning so a decision was made to change to a different model of locker with passive male and higher load capacity and stiffness. This final locking system comprises equipment for the feeding of compressed air to the agent, electrical power to the agent and equipment for blowing out the swarf and cleaning the surface before locking.
The cleaning system is divided in two parts:
-Cleaning system in the bench by blowing air directly from the pin modules;
-Cleaning system on-board the mobile base, blowing air to the bench surface.
With the selected design the swarf is blown purposely in the correct direction away from the module's surface and directly to the base legs surface assuring a proper contact between the two. In the bottom part of the workbench electrical and pneumatic connections are housed, the rows of clamping modules are supplied by rows of connections forming a fork like system underneath the bench. The pneumatic and electrical components rows of the fork like housing system utilized, are intercalated between them, making easy to recognize which is row is for electrical components and which one is for pneumatic components. To level the bench, protect the connections and fix it a frame was created. It also gives the capability for the bench and hence the whole system to be mounted in different positions increasing the modularity and customization of the fixture system.
The work bench represents innovation in the form of a unique modular bench supporting continuous reconfiguration in presence of large amount of swarf, guaranteeing accuracies comparable to manual reconfigurable benches. Its robustness contributes to a continuously increasing accuracy needed in the manufacturing industry. Once the technology is proven different sizes can be created depending on the specific end user application.
5. Swarm control and planning system HMI
The control system has been designed following a formal approach based on the definition of the system structure in terms of agents and transition function definition of its behavior. Thus, a modular system has resulted enabling software parametrization. This facilitated introduction of changes is brought about by testing different variants of the mechanical structure of the system. A novel approach to task planning for a self adaptable and reconfigurable fixture system has been developed as well. The solution for task planning is based on constraint satisfaction problem approach. The planner takes into account physical, geometrical, and time-related constraints.
An off-line program, on the basis of CAD geometric data about the panel, representing its state before and after machining, generates the plan of relocation of the mobile supports and the parallel manipulators. Some optimization techniques will be used for that purpose. The panels will be subjected to the following machining operations:
-Drilling: in this case the support locations depend on the form of the material. One static configuration of several manipulators will serve the drilling of a number of holes,
-Milling: which is a continuous process requires the manipulators to relocate during milling. This has to be done fast enough so that the current milling speed will not be affected
6. Integrated SWARMITFIX
With the SWARMITFIX fixture an RFA (robotic fixturless assembly) system has been developed at a higher level of modularity and flexibility. It merges the advantages of RFAs with those of MFFSs (modular flexible fixture systems), namely: the ability to distribute the support action; adaptability to workpiece shapes in a larger range; and stiffness of the provided support.
The swarm fixture agents have to satisfy requirements analogous to the ones of multi-posts fixtures in terms of adaptability of workspace of positioning of the heads, head adaptability, force of adhesion and stiffness.
A critical characteristic of the fixturing system is the size of an individual agent. It is higher than post units due to the embedded actuators, sensors and docking-locking devices. This gives some limitations in the number of agents that can concentrate in a region and has influenced the choice of the degrees of freedom of the head positioning mechanism.
The prototype was completely integrated for the first time in Piaggio Aero and consists of:
-Fully functional workbench, air and electric supply embedded.
-2 fully functional agents consisting of mobile base, pkm and MRF head
-4 passive supports with adjustable height to hold the workpiece in place on the periphery with vacuum cups and dismountable joints for precise location of the workpiece.
The SWARMITFIX project has always been intended to be a solution for the manufacturing of large thin metal aluminum panels; this means that the focal point of interest within the industry is that of the aerospace, however, also automotive industry in particular bus and truck manufacturers as well as train industry can benefit from the system. In particular the final customer of the system can be benefited from an unachieved flexibility so far, constant accuracy over any extension and full compatibility with the manufacturing environment in presence of swarf and cooling liquids.
From this point forward, in order to arrive to a fully commercial product investment is needed, however it is difficult to establish the amount, this is because it depends on how well accepted within the industry the system is. An important point is that after the first developed prototype an approximate price can be speculated rounding the 1 M Euros for a system comprising 4 intelligent fixture agents, a 10m x 5m bench and a set of passive auxiliary supports to hold the workpiece in the periphery. Furthermore, again stating from a good acceptance pf the system and the new trend being developed for the manufacture industry the market size over a single year can be estimated to be around the 10 M Euros.
The acceptance and thus the market opportunity comes as well form the fact that at this moment the system cost is proportional to the scale and constant performance, competing with other products for similar use on large sizes and with high flexibility needed. Furthermore there is no direct competitor that can provide the same characteristics embedded in a single product, the closer competitors are producers of reconfigurable fixtures and rigs with partial adaptability embedded, multipoint adaptable fixtures and at some extent manual reconfigurable fixtures producers. The growth of swarm fixture in the market is based at least for the first years on improvements of in use technology.
7. Adaptable head module 2: MRF Head
As already mentioned, two adaptable head modules were developed during the SWARMITFIX project. The MRF head module utilizes special material to conform to the wide range of panels having different surface curvatures. In simpler words, the head needs to adapt and adhere to the local geometry of the surface were the machining operation is been carried out. Following this particular characteristics the MRF head module was designed to comply with the following requirements:
-Enough yield stiffness to hold the panel and withstand the machining forces
-Rigid adhesion to the sheet keeping constant contact during milling and drilling operations
-Self adaptability to the workpiece
-Fast operation time
-Insensible to thermal changes
-Triangular base: It is the lower part of the triangular head and is made of T 300 Series Stainless Steel austenitic. The material was chosen to guarantee the effect of the magnetic field on the MR fluid. Presents the channels in which the magneto-rheological fluid is introduced. Each channel is designed to lead the MR fluid from the central collector to two of the holes of the guidance, whereas the channels at the edge of the triangle lead the fluid to three holes. All the channels are connected to the central collector, so all the 27 holes of the guidance are in order to allow all the movements needed by the pistons to adapt correctly to the surface of the workpiece. It also presents the necessary holes to insert the vacuum connector and the proximity sensor.
-Guidance: The upper part is made by aluminum, to prevent the magnetization of the sheet during processing. Since the part is the guidance for the 27 small pistons necessary to support the workpiece, to minimize corrosion and wear of the guide holes it was chosen as material Al 6082, a medium strength alloy with excellent corrosion resistance.
-Pistons and O-rings: The small pistons are 25 mm long and have a diameter of 6 mm. To guarantee the contact with the surface, the pistons have a circular head. In order to reduce the friction between the pistons and the guidance the selected material for the final prototype is Delrin. To prevent the loss of magneto-rheological fluid the pins present two seats for o-rings, endless round sealing rings of circular sections. An O-Ring seal is a means for closing passageway preventing an unwanted escape or loss of fluid.
-Rubber cover: It is located at the top of the guidance and glued to a purposely designed protrusion. The material used is a vulcanizable at room temperature silicon by means of a polyaddition reaction.
The triangular head of the MRF module is the core of the development attempting to introduce a new kind of adaptable fixture that can replace the vacuum cups or commonly used grippers. However, a means for activating the phase-change material is needed as well as an actuator to rotate to the proper orientation the head. These can be seen as the core body of the module and are the pneumatic cylinder, servomotor and bracket used to connect the head module to the PKM.
-Pneumatic cylinder: The pneumatic cylinder is needed only to move the neodymium magnet located inside it to supply the magnetic field needed to increase the viscosity of the magneto-rheological fluid. In this way once the small pistons have adapted to the workpiece shape, the cylinder is actuated sending the magnet close to the fluid collector and solidifying it. The cylinder is divided in two parts, the upper part holds the magnet while the lower one is connected to the air supply and holds the necessary seals to prevent air flowing away from it. On the outside part of the lower section of the cylinder, two bearings are located interfacing the bracket; these are needed to let the module rotate in order to achieve proper orientation. At the bottom of the lower section a cap is screwed to hold the servomotor.
-Servo motor: The selected actuator is a Harmonic Drive hollow shaft servo motor capable of rotating the head module to the desired orientation according to the workpiece shape.
-Bracket: The bracket is used to interface the module to the PKM and locate the necessary bearing that will let the module to rotate achieving the orientation needed. The cylinder is inserted in the bracket and secured by screwing the motor to it as well. On the other hand, the bracket is also screwed to the extension arm that comes from the PKM 6 dof flange. This, although decrease the stiffness of the parallel machine, is needed to let the plan calculate feasible locations of the heads.
8. Exechon analytical kinematics and singularity/workspace analysis
The equations used to describe the kinimatics of the PKM are better seen in the attached PDF which presents a synthesis of the whole development of the kinematic analysis reported in the scientific article (Zoppi, M.; Zlatanov, D.; Molfino, R. 'Kinematics analysis of the Exechon tripod'. Proceedings of the ASME 2010 International Design Engineering Technical Conferences and Computers, August 18th 2010.)
For the single support parallel robot module (Exechon X150 PKM, described in section 3.1) to be controlled, the kinematic analysis was needed. It is common to solve this paradigm numerically; however strong computational capabilities are needed and the operation time is increased not to mention the needed space to install a robust enough computer on board the agent. In order to optimize the performance of the system, in both operation time and space, the analytical analysis and solution was developed.
Inverse position kinematics
In practice the PM is used as a regional manipulator, a 3-dof positioning device, with a typically spherical wrist attached to the end-effector at point S. This results in a combined hybrid manipulator, like the 5-dof Exechon PKM and the 6-dof fixture agent X 150. The end-effector of this hybrid chain is denoted by ee.
We have assumed that we have a 6-dof mechanism with a spherical wrist, centered at S. When solving the inverse kinematics of the hybrid tripod the first (easy) step is to obtain the coordinates of point S, which is a known point in the body ee whose location is given.
From this, one proceeds to solve the inverse kinematics of the 3-dof parallel tripod, from a given point S of the 3-dof platform. The result is the three input parameters, for example, the joint variables of the prismatic joints. To complete the inverse kinematics of the 6-dof hybrid manipulator, it remains to obtain the joint variables of the three actuated joints in the serial spherical wrist. This is obtained from the relative orientation of the hybrid chain end-effector, ee, and the PM platform, e, by means of a standard Euler-angle calculation.
The overall process for obtaining the inverse kinematics will not reported in these lines, due to the large amount of equations.
This analytical solution of the inverse kinematics of the PKM is used by the control system to move to the desired position the PKM. It basically solves analytically the configuration and returns the necessary Euler angles of each joint. The controller user interface is capable of exporting the current configuration Euler angles into a separate file and thus create a manual plan from them. On the other hand, if one wants to drive the PKM to a desired location and knows the Euler angle of such location, it is possible for the user to import these angles as XML to the interface and execute the motion.
Potential Impact:
Being the goal of the SWARMITFIX project to create and original autonomously reconfigurable fixture system; there is a lack of familiarity surrounding the novelty of the concept and technology in both industry and research centers. At the same time the novelty of the concept and system developed give place, according to the consortium, to an important economical impact especially in the fixture and manufacture industries.
The impact on 'New generation of products helping European instrument manufacturers and machine builders to stay ahead of the competition' is achieved through the following recalled objectives. These intelligent devices solve a problem of growing importance for aircraft and automotive industries where the amount of material is reduced for costs and life cycle Eco-consistency reasons. These sectors represent in Europe more than 450 billion Euros (ACEA 2001 and EADS 2007 data). Near future applications are also foreseen in the railway, metal construction and furniture, white industry and ship building sectors.
Potential expected impact
The SWARMITFIX project specific objectives have been outlined in a way that obtaining such results the impact in both industrial and socioeconomic level will be maximized. According to each attained objective expected potential impact can be achieved. A relationship between the expected impact and the specific objective that will help to achieve the said impact is given as follows:
Adaptive production systems
The project will contribute to the development of new manufacturing systems that adapt to flexible, small or even single batch oriented production. Today, adaptability of production systems relies on available robotics and it is limited by the devices that interface directly the pieces to be manufactured like fixtures and grippers. The problem of modular and adaptive fixtures has been considered by different research actors but no solution till now satisfies completely the requirements on agility and adaptability addressed by the work programme.
Rapidly configurable machines, self-adaptive machine structures, self-optimization. reduction of time needed for reconfiguration and maintenance
The swarm fixture developed, with simple robots reconfiguring in real time to adapt to different thin sheet shapes, will substitute sets of complex specific devices purposely designed for a very limited range of pieces. This results in savings in cost and reduction in fixturing and set up time. Modularity of the homogeneous robots swarm guarantees fast maintenance and scalability. Furthermore the new hybrid control approach will optimize reconfigurability against every operation phase in the manufacturing cycle. In this way the new fixturing system impacts perfectly the work programme issues. Impact will be both at manufacturing shop floor level up to production planning and logistics levels with improved productivity along all the chain.
Control system architectures for mechatronic knowledge-based systems
The new generation of fixtures adopts a set of behavior based mechatronic agents. The control architecture relies both on implicit, stigmergy based, and explicit communication. This innovative architecture together with the intrinsic high stability of the agent mechatronic design produces robustness and stiffness to the overall system. Reconfiguration planning goal and logic's are based on the knowledge of the behaviors of single and multiple cooperating agents that adapt in real time to the specific manufacturing task. The swarm fixture concept involves problems of seamless connectivity and inter-working of scalable embedded systems in the manufacturing domain. The fixture agents cooperate in spatial proximity to jointly realize the common workpiece support task and together represent a small-scale complex distributed system expressing a reactive, but also efficient, robust, predictable, safe behavior.
More efficient, flexible, secure, easier to maintain and more productive (large infrastructure) manufacturing plants
The new fixture is a distributed system that requires a new engineering approach ensuring efficient, adaptable, safe and secure behavior for the manufacturing process. The self adaptability of the fixture improves the flexibility towards customized production, reduces human presence and work in the production environment rising safety and security, avoids re-fixturing tasks, and reduces fixturing setup time improving plant productivity. The modular distributed system makes maintenance interventions easier and faster. While the fixture can be considered a 'small scale' distributed system, the control methodology developed for the dynamic fast reconfiguring architecture can be applied to more complex, large scale distributed systems.
Quantification of economical impact
The new generation of fixtures will open significant gain perspectives to their builders and suppliers and will allow to their users, mainly to manufacturers in aerospace and automotive sectors but not limited to, to produce their products at shorter time to market, improved quality, lower cost and reduced resources consumption, thus allowing them to stay ahead of the global competition. Using as few as only two intelligent advanced Exechon PKM Agents to machine a complete panel will not only reduce the cost of the fixture dramatically, but also increase the accessibility and the up-time in production, and the same Agents can be moved between several flat tables and reduce the need of dedicated fixtures substantially.
A rough but conservative estimation of the quantification of these impacts follows:
Fixture storage and management costs are reduced of more than 400% with no need to store, maintain and manage trimming tools. Furthermore the high re-configurability allows the machining of left and right part kits in the same space. It also allows older parts to be machined without storing conventional tools for years.
If compared to traditional methods adopted for limp sheet manufacturing the adoption of the new highly reconfigurable fixtures, whose set-up time is in the range of minutes and may be performed in hidden time, will allow to cut the re-tooling times, which for complex and delicate thin sheets are in the range of hours. For thin sheet manufacturing cycle of about 10 operations the expected reduction of the producing time is 90%.
Re-fixturing operations require an attentive and very accurate manual re-positioning of the thin sheet on the fixture for next operation; the re-positioning errors are the main cause of defects. The use of the new fixture will avoid many manual re-positioning steps because it is the fixture itself that is programmed to adapt the supporting points to the different sequential operations and the re-positioning program, before the actuation, is checked through simulation.
An estimate of main savings offered by one SWARMITFIX installation in the aerospace manufacturing sector as perceived by end-users themselves as follows:
Taking the conventional fixtures costs of manufacture and re-tooling, the use of the SWARMITFIX system in which only one time investment and no re-tooling is needed the savings can sum up to 2M Euros, this is mainly, because with conventional fixtures there is one purposely fixture for each manufactured part and the cost of each fixtures is very elevated. On the other hand, for any minor redesign of the part, relevant changes in the fixture are in order (re-tooling); finally if the redesign is big, a completely new fixture maybe needed increasing even more the costs. Again, with to store several dedicated fixtures the maintenance and storage savings are expected to be of around 100 k Euros / year X 5 years. Given the high adaptability, re-configurability and autonomy of the system the set-up time can be reduced by 95% meaning a saving of nearly 720 k Euros / year X 5 years. The set up time reduction and the characteristics of the system represent a lower time cycles for manufacturing the workpieces, in terms of time cycle it is considered to be a reduction of 975 h / year of manufacturing operation that equals to an approximate of 78 k Euros / year X 5 years. Finally the estimated expected savings during the first 5 years, considering the above mentioned aspects can amount to 6,490,000 Euros.
However estimated savings can be approximated as follows:
In the automotive sector the replacement of conventional fixtures cannot be completely done, this means the system cannot be used for all the parts comprised in an automobile given the size of them. However, the replacement of the fixtures when possible means an estimated saving of 840 k Euros. At the same the storage and management of fixtures is decreased even more than for the aerospace, this is because in this sector more dedicated fixtures are used meaning that when replacing them with the SWARMITFIX system more fixtures disappear form storage, this can amount to 115 k Euros / year X 5 years. The set-up time reduction is less given the lower amount of fixtures that can b replace, in any case the reduction is expected to be of 75% meaning a saving of 600 k Euros / year X 5 years. In terms of time cycle reduction, in the automotive sector it is foreseen that using the SWARMITFIX system less repositioning of parts are possible, less manufacturing operations to adapt the support device to the part local shape are achieved, it is important to stress these manufacturing operations are of no added value to the final product and only increase the total manufacturing costs. The total time saved is considered to sum up to 1200 h / year and giving an estimated saving of 98.500 k Euros / year X 5 years. Finally the estimated expected savings during the first 5 years, considering the above mentioned aspects in the automotive sector can amount to 4,907,500 Euros.
Scope of the dissemination activities
Several dissemination activities have been done during the life of the project, others are still ongoing or will be done to further exploit the results and bring to the industry the development done.
The scope of the project cannot be addressed at a national level. First of all, the competence centers and research institutions in the various disciplines involved (end-users profiling, mechatronic design methodologies, information technology) are spread in different countries. Then, in relation to manufacturers of products made of thin sheets, even though some European countries (such as Germany, Italy, France, UK, Sweden) exhibit the highest concentration of big companies, smaller producers are based in almost every European nation. Hence a project like SWARMITFIX aiming at a general solution of a manufacturing problem common to different manufacturing sectors can only be conceived at a European level. This is also true when one considers the need of gathering around such an important objective the necessary critical mass in terms of transectorial know how and financial resources to sustain the research. It was then deemed impossible to initiate such a wide scope and ambitious research at private or national level. The project is an opportunity for the partners to establish a transnational cooperation. The complementary expertise will guarantee effective problem solving and accurate definition of application requirements. Impact will be greater and cost-effective higher than that which would come from several smaller national projects as a large market platform will push and support SWARMITFIX.
Promotional, dissemination and marketing activities
Dissemination activities have been done during the project and will continue in order to share the knowledge to the industry. This, as envisioned by the consortium is needed in order to obtain not only the necessary feedback by the end-users that drove the research done, but to obtain at the end a real commercial product that will be of interest to the same end-users.
The biggest challenge for putting a new product on the market is to find an established channel of distribution. This challenge is even bigger when the product in question has a high level of innovation in it. Through the network of Exechon we have now found what we consider a perfect partner for the first real market introduction, Delfoi in Sweden. Delfoi's business idea is to deliver a super modular manual fixturing for the Aerospace and Automotive industry using a flexible box system combining various modular profiles with manual adjustable parallel kinematics holders. This solution is perfect for one-off prototype manufacturing but in combination with SWARMITFIX Agents it would also attract the volume manufacturing industry. Exechon, Delfoi and Airbus are currently discussing a live project in this direction. During 2010 extensive discussion has taken place between Airbus, Delfoi, and Exechon regarding the use of SWARMITFIX Agents in combination with the Delfoi Boxjoint system to be able to supply Airbus with a semi automated and flexible fixturing system.
Involvement in robotics associations
Dissemination and innovation promotion in the field is greatly facilitated by the help of robotics industrial and academic associations. These organizations have strong ties with their national and regional industries and research communities.
The following institutions were involved:
-SIRI, The Italian Association of Robotics and Automation, http://www.robosiri.it
-VDMA Robotics + Automation in Germany, http://www.vdma.org
-EURON EUropean RObotics research Network, http://www.euron.org
-UCIMU-SISTEMI PER PRODURRE, http://www.ucimu.it
After gathering the results form the system trials, different associations will be involved.
Website
The website of the project has been designed and activated: http://www.SWARMITFIX.eu
It is used by the partners both as a repository of documents and to disseminate knowledge to relevant target manufacturing sectors: automotive, aeronautics, trains, shipbuilding. Links to MANU-FUTURE and EUROP are included and new links will be added upon request from the interested institutions. It was decided that each WP leader will have full access to the relevant area and will be responsible for the related content within the website. PMARlab-DIMEC will be responsible for the overall administration of the website, and will oversee and maintain the contents. A 'restricted area' for the exchange of confidential material and material under development has been created and has proven to be a useful tool for the exchange of ideas between partners.
Poster presentation and flyer distribution
Information about SWARMITFIX has features prominently on the PMARlab-DIMEC poster created in 2008. The poster and the project have been presented at multiple meetings and events:
The SWARMITFIX concept was presented at the following meetings and conventions:
-ISICT course on Robotics, Genoa 31 January 2009-10-02
-ISR 2009, Barcelona 10-12 March 2009
-IFR meeting Barcelona, 13 March 2009
-IMB 2009, Köln, 21-24 April 2009
-Alumotive 2009, Montichiari, 2-3 April 2009
-EWF, EUROJOIN 7 / GNS5, Venice, 21-22 May 2009
-Training Course SIRI, Comau, June 21 2009
-Strategic Research Agenda for robotics in Europe, Brussels, 7 July 2009
-Summer Schools on Screws Theory, Genoa 22-30 August 2009
-CLAWAR'09, Istanbul, 9-11 September 2009
-ATA Conference on Vehicles architectures, Florence 25 September 2009International Conference on Reconfigurable Mechanisms and Robots, REMAR'09, held in London, 22-24 June, 2009
-Manufacture 2009 Conference - Implementation of a sustainable European Manufacturing Industry, Gothenburg, 30 November - 1 December 2009
-Reconfigurable Exechon Parallel Kinematics, Simplified Machining and Assembly, Karl-Erik Neumann, Al Bolen, Exechon AB - Aero Tech Congress and Exhibition, Seattle, WA, USA, 10-12 November 2009.
-Presentation by Karl-Erik Neumann, 1st Advanced Manufacturing Technology Forum, Filton, UK, 20-22 October 2009, Aero Tech, Seattle, USA, November 10-12 2009.
-Presentation by Karl-Erik Neumann, Manufuture 2009, the European Manufacturing Conference, 30 November - 1 December 2009, Gothenburg, Sweden.
-SWARMITFIX presentation, Ladislav Vargovcik, EURON-EUROP Annual Meeting, 10-12 March, 2010, San Sebastian, Spain.
-ALUMOTIVE, Montichiari, 2-4 Aprile 2009
-R. M. Molfino, Swarm Fixturing of Aircraft Body Components and Fixturing of car Body Assemblies, Automate 2011, Chicago, March 21-24, CD Conference Proceedings.
Publications
A list of publications regarding the achievements of the project is given below; it is important to stress these publications let the scientific and industrial community to understand not only the importance of the system but the details of design, manufacture and specific characteristics achieved.
Newspaper articles on the project appeared in the Mediaplanet Automation supplement of the Italian national daily business newspaper Il Sole 24 Ore, as well as in the daily Italia Oggi.
-SWARMITFIX un'attrezzatura intelligente, Rezia Molfino, Matteo Zoppi, MEDIA-PLANET AUTOMATION, Il sole 24 ore, 17 November 2009 200.000 copies
-The same on Italia Oggi, 16 November 2009 100.000 copies
Research papers on different components developed within the project have been accepted for publication in the proceedings of several conferences: ISR-Robotic, the Joint 41st International Symposium on Robotics and 6th German Conference on Robotics, 7-9 June 2010, CCMMS, the Chinese Conference on Mechanism and Machine Science, 20-25 July, 2010, Shanghai, China, the ASME 2010 International Design Engineering Technical Conferences (IDETC), 15-18 August, Montreal, Canada. Two papers have been submitted for presentation at the 11th Polish National Robotics Conference, 9-12 September, Karpacz, Poland and one to Frontiers of Mechanical Engineering in China.
-R. Molfino, M. Zoppi, and D. Zlatanov. Reconfigurable swarm fixtures. In Reconfigurable Mechanisms and Robots Proc. of the Int. Conf. REMAR 2009, volume IEEEcn:CFP0943G-PRT, pages 696-701. KC, London, UK, Jul. 22-24 2009.
-R. Molfino, M. Zoppi, Attrezzature robotiche per manipolazione e supporto di stampati, ALUMOTIVE, Montichiari, 2-4 Aprile 2009
-Xiong Li, Aamir Khan, Roberto Avventenente, Matteo Zoppi, Dimilter Zalanov, Rezia Molfino, Development and Analysis of Shape Conformable Support of Self-reconfigurable Intelligent Swarm Fixture, ISR 2010, Munich, June 7-9, 2010
-C. Zielinski, T. Winiarski, P. Trojanek, T. Kornuta: 'Multi-agent control system specification of a robot based reconfigurable fixture', 11th National Robotics Conference, Karpacz, Poland, 9 - 12 September 2010.
-W. Szynkiewicz, W. Kasprzak, T. Zielinska, D. Zlatanov: 'Planowanie rozmieszczenia ruchomych podpór przy obróbce przedmiotów o duzych rozmiarach' (Planning of the distribution of mobile supports for large objects subjected to machinning), 11th National Robotics Conference, Karpacz, Poland, 9 - 12 September 2010.
-W. Szynkiewicz, T. Zielinska, W. Kasprzak: 'Robotized machining of big work pieces: localization of supporting heads', Frontiers of Mechanical Engineering in China.
-Summary of the project in Institute of Control and Computation Engineering 2009 Annual Report, pg.60 also: http://www.ia.pw.edu.pl/download/Annual09.pdf
-Robot Control and Pattern Recognition Group's web page mentions the project at: http://robotics.ia.pw.edu.pl/twiki/bin/view/Grants/GSWARMITFIXFP7-214678
-R. Molfino, M. Zoppi. ''SWARMITFIX un'attrezzatura intelligente'', Italia Oggi, Class Editori. R. Molfino, M. Zoppi. ''SWARMITFIX un'attrezzatura intelligente'', Media-Planet Automation, Il Sole 24 ore.
-Zoppi, M.; Zlatanov, D.; Molfino, R. ''Kinematics analysis of the Exechon tripod''. Proceedings of the ASME 2010 International Design Engineering Technical Conferences and Computers, August 18th 2010.
-Zielinski C., Kornuta T., Trojanek P., Winiarski T., Walecki M. ''Specification of a Multi-Agent Robot-Based Reconfigurable Fixture Control System''. 8th International Workshop on Robot Motion and Control, RoMoCo'11.
-Zielinski C., Kornuta T. ''Generation of Linear Cartesian Trajectories for Robots Using Industrial Motion-Controllers'', 16th International Conference on Methods and Models in Automation and Robotics, MMAR'2011.
-Molfino, Rezia; Zoppi, Matteo, ''The robotic swarm concept in fixtures for transport industry''. The 7th International ASME/IEEE Conference on Mechatronics and Embedded Systems and Applications.
-L. Xiong, M. Zoppi, R. Molfino, Reducing Computation Time In Optimization Procedure For Fixture Layout Based On SWARMITFIX, 5th International Conference on Integrated Modeling and Analysis in Applied Control and Automation IMAACA 2011, Rome, 12-14 September 2011, CD Proceedings
-Li, X.; Zoppi, M.; Molfino, R.; de Leonardo, L. ''Design of a mobile base for a self-reconfigurable intelligent swarm fixture system. The 14th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2011.
-de Leonardo, L.; Zoppi, M.; Li, X.; Gagliardi, S.; Molfino, R. ''Developing a new concept of Self Reconfigurable Intelligent Swarm Fixtures''. Proc. of the Int. Conf In Reconfigurable Mechanisms and Robots. REMAR 2012
Educational activities
Two Ph.D candidates, at the University of Genoa and the Warsaw University of Technology, are basing their research on the project. Students in the EMARO (European Master in Robotics) Erasmus Mundus programme have been exposed and have contributed to aspects of SWARMITFIX.
Ph. D research theses:
-Li Xiong- Universita di Genova (DIMEC)
-Piotr Trojanek - WUT - work on his Ph.D. on multi-robot coordination.
M. Sc Thesis
-Serena Gagliardi - Universita di Genova (DIMEC)
-Luis de Leonardo (EMARO) - Universita di Genova (DIMEC) Laboratory work
Laboratory work
-Flexible Automation students - Universita di Genova
-Robot mechanics students - Universita di Genova
-EMARO (European Master on Advanced Robotics) students - DIMEC-UNIGE, WUT
The following courses will include materials and offer projects related to SWARMITFIX:
-Robot Mechanics
-Flexible Automation
-Control of Mechatronic Systems
-Industrial and Service Robotics
-Robot Programming Methods
-Mechanical Design Methods in Robotics
-Mobile Robots
Direct contact with potential users
In the course of their business contacts the SWARMITFIX participants are familiarizing their partners with its concepts and emerging technology. The following major companies have been contacted and had been exposed to the ideas and results of the project:
-A branch of Kuka working on aerospace manufacturing systems. The SWARMITFIX concept has been introduced in discussions with DIMEC and PAI.
-AMS, Ace Manufacturing Systems, India. The company is an Exechon licensee. SWARMITFIX was introduced by Exechon, further presentations are planned.
-TAL Manufacturing Solutions, India, the makers of the TATA car. The company is an Exechon licensee. SWARMITFIX was introduced by Exechon CEO Kalle Neumann; follow-up presentations are planned. (See Appendix C.)
-BFW, Bharat Fritz Werner, India. The company is an Exechon licensee. SWARMITFIX was introduced by Exechon CEO Kalle Neumann; follow-up presentations are planned.
-Premier, India. The company is an Exechon licensee. SWARMITFIX was introduced by Exechon CEO Kalle Neumann; follow-up presentations are planned.
-Shanghai Jiaotong University, Shanghai, China, September 2009. Swarm fixturing technology was presented to invited participants to a special event purposely organized.
List of Websites:
http://www.swarmitfix.eu
http://www.youtube.com/user/LMdeLeonardo?feature=mhee