Final Report Summary - STAMAS (Smart technology for artificial muscle applications in space)
Executive Summary:
The STAMAS has been a great and successful conducted effort focused on joining several incipient and promising terrestrial technologies to pose and demonstrate its suitability and accuracy in the space domain. Due the expertise of the participants in the project, the project has been focused in enhancing the life in space by improving the performance of the space suits and diminishing the health effects of the gravity absence.
In a 36 month duration project, two different technologies have been put in the spotlight: SMA (Shape Memory Alloys) and EAP (Electroactive Polymers). Thanks to the efforts devoted, these two present terrestrial applications have been handled to research in new concepts of artificial muscle systems for biofeedback suits for astronauts, as an alternative to currently used technologies. To this end, the project team has proposed to focus on designing, developing and testing both a lower and an upper limb biofeedback suit demonstrator. The lower limb demonstrator incorporate different types of artificial muscles subsystems in complementary configuration in order to attack the different pathologies originated due to microgravity (muscle atrophy, bone loss, and shifting of blood distribution). The upper limb demonstrator provides actuating systems for the assistance of astronauts while wearing space gloves during Extra-Vehicular Activities (EVA). In practical terms, biofeedback leg and hand suits have been developed. These parts of the human body have been selected for being the most critical and representative – in terms of engineering complexity and as key elements that require particular solutions to known problems of human space flights. In other words, a successful demonstrator of those devices for sure represents an important achievement for the design and development of a whole smart suit. The results have been very promising, being materialised in two functional prototypes, which have been validated in operational simulated conditions (TRL 4) opening a promising R&D landscape and awakening the interests of several key stakeholders with whom there has been a continuous feedback.
Project Context and Objectives:
STAMAS is an European Project developed by Arquimea Ingeniería, DLR, ETH Zürich, Sensodrive, Universidad Carlos III de Madrid and Universitá di Pisa.
The main goal of the project is to create innovative exo-robotic hands and legs, using Shape Memory Alloys (SMA) and Electro-Active Polymers (EAP) actuators which aim is to support astronauts exercising to mitigate the effects of microgravity on the body and to assist the astronaut’s fingers movements during Extra Vehicular Activities (EVAs).
General Objectives
• To generate the scientific basis to provide a smart suit for on-board spacecraft use which is able to control, mitigate and even treat the health problems that could arise owed to microgravity and lack of mobility, as well as to the stiffness of the space suit during EVAs.
• To bring experience on SMA/EAP technologies in the space domain, adapting the existing terrestrial technologies to space domain contributing to the substitution of conventional actuators.
• To adapt different biometric sensors to the on-board space requirements to promote their applicability as an integral part of the astronaut’s equipment, improving its functionality and safety.
• To adapt and develop sensors to be embedded in the suit for the control of the mechanical behaviour of the suit and its actuators.
• To develop a control architecture able to process and interpret the information of the biological parameters of the astronaut, his/her movement intentions and the status of the suit and the actuators in order to provide the corresponding orders to the suit subsystems and feedback to the user.
• To develop a functional prototype of bio-feedback leg and hand which can be set over the astronaut’s space suit, and react to his/her actions.
• To create a demonstration prototype of a light weight, flexible exoskeleton robotic system based on SMA and EAP actuating technologies, to be test on human beings.
• To obtain a significant technological demonstrator that will enable partners to show their technological capabilities, which will represent an important advantage at commercial level.
• To enlarge the scope of the project to applications other than space specific, such as healthcare or rehabilitation robotics.
Introduction – Problem description
When astronauts return to Earth after a long period in space, their organism shows several signs after living in microgravity, such as loss of muscles mass and bones density, increase of body length, blood distribution problems, heart dysfunction and orthostatic intolerance. Other functions such as proprioception or the capability to react quickly to recover body stability are also degraded by the effect of microgravity.
Currently, on the International Space Station (ISS), countermeasures are taken in the form of exercise plans to prevent the severity of the symptoms. These plans include three phases comprising pre-flight, in-flight and post-flight exercise programs in order to prepare, maintain and adapt the astronaut’s physical condition during the whole length of the mission. A leg exoskeleton has been developed in this project for the exercising during in-flight phase.
A further problem encountered by astronauts on the ISS occurs during EVAs. EVAs performed by astronauts are limited by several factors. One of these limitations is the duration of the space walks due to the hand fatigue that astronauts suffer when performing manual tasks. This fatigue is mainly caused by the stiffness of the spacesuit gloves. The gloves are internally pressurized, as the rest of the spacesuit, to protect the astronaut from the vacuum of Space. The pressure inside the gloves increases the stiffness of each joint of the glove, making the astronaut to exert great forces to overcome this stiffness and mobilize the fingers.
In addition, the astronaut has to operate tools or other installations which have to be carefully designed to be gripped or handled in special ways. The resistance force of the glove due to air pressure and stiff materials and the additional space and distance between the fingers and the grasped object translates in loss of touch feeling and dexterity. Thus, the astronaut has to fight against high forces when performing manipulation tasks during spacewalks. These forces disturb the intended tasks thus reducing efficiency, and causing dramatic fatigue of the astronauts’ hands and fingers. A hand exo - muscular system demonstrator has been developed with the aim of assisting the astronauts in these manual tasks, reducing the extra amount of force required to move their hands.
LEG DEMONSTRATOR
One of the main objectives of the STAMAS project is to design an actuated device for the lower limb – the leg demonstrator – to be used for exercising inside the ISS, to address the problem of weightlessness that results in a loss of bone density and of muscular mass. The objectives of these measurements are to improve the exercising in orbit, to explore new countermeasures and to develop exercising devices that can be worn for long periods of time in order to exercise the legs during normal life in the ISS as well as provide a complement to current exercising devices. The leg device imposes several difficulties to the astronaut’s movement and performs oppression and release forces over the user’s thigh in order to modify the blood distribution. The leg demonstrator is divided into three different actuating subsystems, each one designed to tackle different problems associated with prolonged stays in a microgravity environment. These subsystems are:
• Ankle Lateral Actuating System · ALAS
It exerts lateral forces over the ankle, in order to generate sudden little deviations on the ankle position. The user has to use his proprioceptive abilities to keep his/her own balance.
This help to maintain the good state of all the secondary muscles, which usually support the main muscles. The lateral forces generated by this system are created by a set of actuated SMA wires.
• Smart Elastic Bands System · SEBS
It is intended for generating a resistance to the knee movement. This device can vary the degree of resistance and the point of the leg that has to perform a greater effort on the flexion-extension movement. The resistance force is generated by a device formed by thermally controlled SMA superelastic bands.
• Electro-Active Polymer Bands · EAPB
They are placed surrounding the lower limbs. Their function is to generate alternative compressions, thus improving the blood flow in the lower limbs, replying the effect of pumping muscles. This way the blood flow might be improved in the lower limbs, mitigating the muscular volume loss in microgravity.
HAND DEMONSTRATOR
The Hand Demonstrator is driven by the Hand Exo-Muscular System (HEMS), which is an actuated device used to compensate the stiffness of the space suit by counteracting the force exerted by the pressurized glove, in such way that the force demanded to the astronaut to flex the fingers is reduced. These forces are generated by aims of several SMA linear actuators, which are connected to the gloves by thin tendons connected to the actuators. Several thin rings are placed over the glove in order to guide and fix these elements. The actuated system is called Hand Exo-Muscular System (HEMS) and the proposed solution is based on a bio-inspired principle formed by flexible muscle-like systems as an alternative to state-of-the-art rigid exo-skeletons.
The device detects the movement of each of the user’s fingers and acts over the glove helping the user to flex them, so that the apparent stiffness of the glove is reduced and the astronaut’s dexterity is improved. An important fact to be taken into account is that the demonstrator is intended to be integrated within an EVA glove. The device is light and low volume. The SMA wires are the basis of the actuating system, thanks to their high force to volume rate characteristics and thus, providing a biomimetic design.
PROJECT TEAM
ARQUIMEA, leader of the project, is an engineering company specialized in the development of customised sensors, actuators and microsystems. The company was founded as a Spin Off of the “Departamento de Ingeniería de Sistemas y Automática” of the Universidad Carlos III de Madrid. ARQUIMEA`s design department is currently composed of 24 engineers, with demonstrated experience in aerospace and electronics (such as EADS Astrium, Analog Devices, Bell laboratories and Motorola, among others).
The most relevant business area of ARQUIMEA strategy is related to the development of SMA based actuators. In fact, the origin of the company six years ago was the development of SMA actuators for artificial muscles; project called EURISMA. This project consists in the application of a SMA based actuator to control the urethra in cases of incontinency.
Key personnel: Mr. Marcelo Collado has degree in Telecommunications Engineering by the UC3M (Madrid) and Master in Space and Satellite Technologies by the UPM (Madrid). He has been working for years in the development of SMA applications in the aerospace, automotive and biomedical industry. He has a wide knowledge of the field, supported by many publications in specialized journals as well as communications in scientific congresses.
DLR (Deutsches Zentrum Für Luft Und Raumfahrte), is an Aerospace Research Center as well as the German Space Agency. It is one of the biggest and most acknowledged Institutes in the field worldwide. The institute contributes to several international projects in FP6/FP7 (IP, STREP) as well as space projects and many national research projects. To mention in relation to STAMAS are the FP6 IP SKILLS Multimodal Interfaces for Capturing and Transfer of skills, FP7 IP DEXMART DEXterous and autonomous dualarm/ hand robotic manipulation with smart sensory-motor skills and FP7 STREP GeRT Generalizing Robot Manipulation Tasks. DLR provides its high-competence in designing, building and controlling robots, that sustains the hard conditions of space flight to STAMAS project. Besides that DLR has made use of its experience in the control of haptic human machine interfaces.
Key personnel: Mr. Thomas Hulin received his degree as electrical engineer from the Technical University of Munich, Germany, in Sep. 2003. Since 2003 he is scientist at the German Aerospace Center, Institute of Robotics and Mechatronics. His research interests, in which he has (co-)authoredmore than 30 publications, include control theory for haptic rendering, haptic rendering algorithms, multimodal human machine interfaces, skill transfer, and virtual reality.
ETH (Eidegenössissche Technische Hochschule Zürich). Founded in 1855, ETH Zurich has come to symbolize excellent education, groundbreaking basic research and applied results that are beneficial for society as a whole. Nowadays, it offers researchers an inspiring environment and students a comprehensive education as one of the leading international universities for technology and the natural sciences. ETH Zurich has more than 16,000 students from approximately 80 countries, 3.500 of whom are doctoral candidates. More than 400 professors teach and conduct research in the areas of engineering, architecture, mathematics, natural sciences, system-oriented sciences, and management and social sciences. One of ETH Zurich’s primary concerns is transferring its knowledge to the private sector and society at large. It has succeeded in this, as borne out by the 80 new patent applications each year and the 215 spin-off companies that were created out of the institute between 1996 and 2010. ETH Zurich is a leading global natural science and engineering university, and plays an important role in the Swiss economy. ETH transfer supports collaborations with ETH Zürich, licensing of ETH technologies, contacts to ETH Zurich Spin-off companies and innovation and start-up support programs, among others.
Key personnel: Robert Riener, leader of the Sensory-Motor Systems (SMS) Laboratory, holds a “Double-
Professorship” affiliated to the Mechanical Engineering Department of the ETH Zurich andthe Spinal Cord Injury Center, University Hospital Balgrist, University Zurich. The SMS Lab has broad experience in several areas that are relevant for the development and dissemination plans of STAMAS. The innovative control strategies allow a rehabilitation robot for the first time to “cooperate” with the patient. From 1998 till 2004, Riener did participate in the EU funded projects “Neuros” and “NeuralPRO”. Riener was the leader of the German network project “VOR”. Currently, he is subproject-leader within the Swiss National Science Foundation project “NCCR Neuro”. Prof. Riener did successfully coordinate the EU-Project MIMCS.
UNIPI (University Of Pisa). The Interdepartmental Research Center "E. Piaggio" is an institute of the University of Pisa devoted to multidisciplinary research in the fields of Bioengineering and Robotics, and to
training of research personnel. In this project, the Center was represented by the Bioengineering Group which has a longstanding and internationally recognized expertise in the field of Electroactive Polymer (EAPs)
as smart materials for electromechanical transducers. In this field, the Group is an international reference and coordinates the “European Scientific Network for Artificial Muscles”, entirely focused on EAPs (www.esnam.eu). In this project, the Group performed the following activities: design and manufacturing of new kinds of electroactive polymer actuators based on dielectric elastomers; mechanical, electrical and electromechanical characterization of materials and testing of the actuators; cooperation to the design, development and demonstration of the intended application.
Key personnel: Dr. Federico Carpi (Ph.D. degree in Bioengineering at University of Pisa). Currently is Postdoc researcher at this University. Coordinator of the “European Scientific Network for Artificial Muscles (ESNAM)”. His main research activities concern the development of novel materials and actuators for electroactive polymer-based artificial muscles and their applications.
SD (SENSODRIVE GmbH) is a spin-off company from the German Aerospace Centre DLR. SD main goal is to bring the latest drive, sensor, and control technology into the industry. Customers from the air- and space-industry, medical technology, simulator manufacturers, as well as the automotive branch rely on SENSODRIVE technology. The special mechatronic know-how enables the SD engineers to develop
customer specific products as well as own products with unique features. Therefore, the company counts with a wide range of products among which sensor actuators, motion controllers and special actuators can be identified. All products are designed with the latest concurrent engineering methods; being the integration of mechanics, electronics, sensor technology, and advanced controllers the company’s specialty.
SENSODRIVE servo actuators are based on the ideas of the DLR light-weight robot. The unique compactness and performance are achieved by optimizing each individual component.
Key personnel: Norbert Sporer studied electronics at the Fachhochschule München. He got a degree from the technical University of Munich. Besides his studies in Automation and Control” Mr. Sporer worked as development engineer at the Institute of Automatic Control Engineering. He is currently working in the Institute of Robotics and Mechatronics at the DLR as project manager for the light-weight robot. With the light-weight robot development the team has been able to set new benchmarks in robotics. As requested by the head of the Institute, Mr. Sporer is still in charge of the light-weight robot project.
UC3M (Universidad Carlos III De Madrid). Founded in 1989, the Carlos III University of Madrid (UC3M) is a public university whose main goal is to provide specialised training in Law and Social Sciences and Engineering, as well as to become a prime European research centre. UC3M has strived to make research one of the fundamental pillars of its activity, both for the enhancement of its teaching and for the new knowledge and new areas of research. ROBOTICSLAB was founded in 1981 when participated in the development of one of the first robots in Spain, the DISAM-0. This centre has evolved and become one of the most representative robotics research group in Spain
Key personnel: Dr. Luis Moreno (Degree in Automation and Electronics Engineering in 1984; Ph.D. in 1988
from the Universidad Politécnica de Madrid). From 1988 to 1994, he was an associate professor at the Universidad Politécnica de Madrid. In 1994 he joined UC3M, from 2007 is the head of the Departament of Systems Engineering and Automation. He has been involved in several mobile robotics projects in Robotics Lab of the UC3M. His research interests are in the areas of mobile robotics, mobile manipulators, environment modelling, path planning, learning problems in robotics and mobile robot global localization problems.
Project Results:
HAND SUIT
• Extra Vehicular Activities (EVA) performed by astronauts are limited by several factors. The gloves are internally pressurized to protect the astronaut from the vacuum of Space. The internal pressure increases the stiffness of each joint of the glove, making the astronaut to exert great forces to overcome this stiffness. The stiffness also leads to other problems, such as premature hand fatigue, damages in the nails, difficulties to move with dexterity and lack of control about the applied strength on the objects.
• The objective of the hand demonstrator o is to reduce the effect of the stiffness of the glove by counteracting the force exerted by the pressurized glove. These forces are generated by aims of several linear actuators connected to the gloves.
• The device predicts the user’s movement intention and acts over the glove to reduce the stiffness.
It is composed by the following modules:
- Hand Exo-Muscular System (HEMS) – actuating system that reduces the stiffness of the spacesuit glove. 6 SMA flexible actuators connected to the fingers (1 for each finger and 2 for the thumb).
- Finger Sensors (FS) – 6 force sensors located on the fingertips (2 for the thumb)
- Central Control Unit (CCU) / GUIs – overall behaviour of device, monitor of parameters, security and safety.
- Sensor Module (SM) – transmitting information from sensors to other components.
General description:
- The FS register force information to detect the movement intention of the user. This information is sent to the CCU through the SM FS to monitor the user movement intention to decide the adequate actions (sending control signals to the actuating system) when using the device.
- The sensors of the HEMS measure information about position and force. All this information should be transmitted to the CCU to check the status of the actuating system and to send the required control actions.
- The SMs are responsible of coordinating the data acquisition and transferring sensor signals to the upper control layers.
- The CCU sends command signals to the actuating system via the Microcontroller and Driver block. The required control actions are also sent to the actuating system module (HEMS) using the SMs.
- The Platform is formed by the Power Unit and the Suit Structure. A Power Unit is required to feed each module of the device in a direct or indirect way. The suit structure gives mechanical support to the demonstrator, providing a suit demonstrator for the hand. It contains fixations for the different subsystems and blocks and connections for the transmission of forces to the user.
HAND EXO-MUSCULAR SYSTTEM
- Shape memory effect to perform the required actuation. When heated, the SMA wires contract, thus causing the flexion of the fingers. Upon cooling, the wires gradually return to their initial length thanks to the opposition force produced by the stiffness of the EVA glove, which also cause the extension of the user’s fingers.
- Force applied on the fingers, allowing a more comfortable flexion while wearing a stiff glove. The amount of force is controlled by the user by changing the pressure applied in the fingertips.
- Mechanical structure – glove with a series of tendons attached to the fingertips and tendons routed through the underside of the fingers and the palm of the hand.
- The index, middle, ring and little fingers have only one tendon each, while the thumb has two tendons.
- Tendon system attached to the output of the HEMS actuators through an interface consisting of a series of pulleys to multiply the linear displacement of the actuators.
- Rigid tendons allows to flex the wrist without affecting the actuators performance.
- HEMS actuating system fixed end in the shoulder, where it is linked to Bending Beams force sensors.
- Sensors: fingertip sensors (FlexiForce #A201), force sensors (Bending Beam), and position sensors (Rolin linear).
HEMS Specifications
Linear stroke 25 mm
Maximum force 35 N
Technology SMA actuator
Max. Frequency of complete cycle 0.125 Hz
Lifetime 50,000 actuating cycles
Aggregated mass < 1500 g
Power consumption 300 W
HEMS Controller Performances Control of fingers
Resolution > 0.025 Nm
Freq. 1 kHz
Position Sensor Range 0-40 mm
min. res. 1 μm to 250 μm
Freq. > 100 Hz
Force Sensor Range > 50 N
min. res. > 0.5 N
Freq. 1 kHz
FINGER SENSORS
- The FS are formed by six force sensors located on the fingertips.
- One sensor is placed on each finger except in the thumb, which has two of them because two degrees of freedom have been analysed/controlled.
- Each sensor is a force sensing resistor (FlexiForce #A201 capacity sensor) that obtains analogic signals.
- These sensors are connected to the SM FS.
FS Specifications
Range Sensitivity towards 20N able to withstand 110 N
Power Consumption 0.1-0.5 V
2.5 mA max
Resolution 12 bit
Output signal Digital over Sensor Module
CENTRAL CONTROL UNIT - GUIS
- Overall control of hand demonstrator: upper control hierarchies, and two GUIs, one for the astronaut, and the other one for an expert or engineer.
- Monitors user parameters measured by the FS and information from actuating system.
- In case of an error, safety strategy that deactivates the device.
- Checks with regard to: timeout (delay between device and controller), status (actuating system), plausibility (sensor data), and range (control commands).
- Setting the required force to support the astronaut in manipulation tasks.
- Expert GUI: visualization of commanded and measured data, input and control of control parameter values, and data logging.
- Astronaut GUI: intuitive and easy-to-use interface that offers the astronaut access to the selected parameters and that displays information on the device state.
PLATFORM
- The Power Unit and the Suit Structure are included in the Platform.
- The Power Unit feeds each module of the device in a direct or indirect way. It feeds directly the CCU, the Microcontroller and Driver and the SMs.
- The Suit Structure gives mechanical support to the demonstrator, providing a suit demonstrator for the hand. It contains fixations for the different subsystems and blocks and connections for the transmission of forces to the user. It also provides protection to the user.
- The Bending Beam is attached to a mechanical interface that is used as its structure. This interface provides an easy system for attaching and detaching the HEMS actuators to the shoulder structures when putting on and off the suit.
Platform – Power Supply Specifications of each module
CCU European electrical standard, 230 V, 50 Hz
Microcontroller Micro-USB to USB A
Drivers 0-40 V, 0-20 A (banana connectors)
SM 12 V, 0-0.5 A (banana connectors)
HEMS actuators Molex 22-27-2021 with two pins
FS 0.1-0.5 V, 2.5 mA
SENSOR MODULES
- There are different types of sensors in the actuating systems of the hand demonstrator. The SMs have been designed to coordinate the data acquisition and to transfer signals to the upper layers.
- The SM board is able to read all the sensors and is connectible with the SMA Controller.
- A CAN Bus system is used to coordinate the information provided by the set of SMs because of the quantity of sensors and the spatial distribution.
LEG
• The effect of microgravity during prolonged stays in space causes different problems. Astronauts suffer from several health problems, such as bone loss, muscle atrophy or a change of blood circulation and distribution.
• The leg demonstrator is an an advanced exercising device that can be used individually or complementing the existing exercising devices on board.
• It imposes several difficulties to the astronaut’s movement and performs oppression and release forces over the user’s thigh to modify the blood distribution.
• The main objective of the actuating systems is to mitigate the consequences caused by microgravity in space.
• The leg suit contains three different actuating systems (ALAS, SEBS and EAPB) based on different technologies that rely on smart materials: Shape Memory Alloys (SMA) and ElectroActive Polymers (EAP).
It is composed by the following modules:
- Ankle Lateral Actuating System (ALAS) - lateral forces over the ankle joint to exercise the ankle’s lateral muscle.
- Smart Elastic Bands System (SEBS) - variable resistance to the knee movement in flexion-extension movement.
- ElectroActive Polymer Bands (EAPB) - alternative compressions, improving the blood flow in the lower limbs, replying the effect of pumping muscles.
- Body Sensors (BS) – information about blood pressure and heart rate.
- Central Control Unit (CCU) / GUIs – overall behaviour of device, monitor of parameters, security.
- Sensor Module (SM) – transmitting information from sensors to other components.
General description:
- The BS measures blood pressure and heart rate. This information is sent to the CCU to monitor the user parameters to decide the adequate actions (sending control signals to the actuating systems) when exercising.
- The SEBS and ALAS sensors measure information about position, force, and temperature. This information is transmitted to the CCU to check the status of the actuating systems and to send the required control actions.
- The SMs are responsible of coordinating the data acquisition and transferring sensor signals to the upper control layers.
- The CCU sends command signals to the actuating systems. The required control actions are also sent to the actuating system modules (SEBS and ALAS) using the SMs.
- The EAPB module has its own driver electronics, which feeds the EAP with the high-voltage signal required for its actuation. This driver is directly connected to the CCU, performing an ON/OFF control of the device.
- The Platform is formed by the Power Unit and the Suit Structure. A Power Unit is required to feed each module of the device in a direct or indirect way. The Suit Structure gives mechanical support to the demonstrator, providing a suit demonstrator for the leg. It contains fixations for the different subsystems and blocks and connections for the transmission of forces to the user.
ANKLE LATERAL ACTUATING SYSTEM
- Lateral forces over the ankle joint to exercise the ankle’s lateral muscles.
- Options:
- Maintained forces with low variation rate to perform a passive-active exercising of the user’s ankle.
- Fast sudden impulses to emulate the loads appeared when a person changes its direction or the ground is tilted.
- Two symmetrical devices linked by straps, internal and external ALAS, in charge of exerting inversion and eversion forces, respectively.
- Lateral forces created by a set of actuated SMA wires.
- On its top end, ALAS mechanically attached to the SEBS system. On the bottom end, linked to the astronaut’s foot by a semi-rigid element.
- Sensors: force (Sensodrive Bending Beam) and position (RM08 Rolin). All sensors needed twice (internal and external).
ALAS Specifications
Linear stroke 15 mm
Maximum torque 1.5 Nm
Maximum force 50 N
Technology SMA actuator
Max. Frequency of complete cycle 0.25 Hz
Lifetime 50,000 actuating cycles
Aggregated mass < 500 g
Power consumption 100 W
ALAS Controller Performances Control of load to the ankle
Resolution > 0.025 Nm
Freq. 1 kHz
Position Sensor Range 0-360°
min. res. > 0.5°
Freq. > 1kHz
Force Sensor Range > 50 N
min. res. > 0.25 N
Freq. > 1kHz
SMART ELASTIC BANDS SYSTEM
- Produces a resistive force to the knee movement, able to change the degree of resistance on the flexion-extension movement.
- Two SEBS devices united by straps (SEBS front and SEBS back). Each actuating system is in charge of exerting the flexion and extension forces, respectively.
- Mechanical interface to the suit structure, ensuring structural integrity and a proper force transmission from the actuator to the leg.
- Structure connected to the user hip, user leg guided through his knee and the rest of the suit properly to ensure the force transmission. It allows the user to make his/her whole range of movements of the knee.
- On its top end, the SEBS device is mechanically attached to the hip. On the bottom end, the device is connected to the ALAS device.
- Opposing force produced by a set of SMA sheets working on the superelastic region. The stiffness is modified by adjusting the temperature of the SMA elements using heaters.
- By varying the amount of resistance produced by the SEBS, it is possible to train a wide range of the leg’s muscles, allowing the user to prevent the loss of muscle weight.
- Sensors: force (K100), position (Rolin magnetic encoder), and 16 temperature (16 PT1000) in each SEBS device.
SEBS Specifications
Max. Deformation > 60 mm
Max. Force > 300 N
Total load applied [40%,60%] muscle load
Technology SMA – Superelastic elements
Lifetime 50,000 actuating cycles
Aggregated mass < 400 g
Power Consumption < 160 W
SEBS Controller Performances Adjustment of elastic behaviour (resistive load)
Freq. > 50Hz
Temperature Sensor Range -50°C to 150°C
Resolution 12 bit
Position Sensor Range [0,60] mm
Resolution 1 μm to 250 μm
Force Sensor Range [0,1000] N
Resolution > 5 N
ELECTROACTIVE POLYMER BANDS
• Generation of alternative compressions, improving the blood flow in the lower limbs, replying the effect of pumping muscles. Surrounding the lower limbs.
• Three hardware components: EAP band, mock up limb simulator and high voltage power unit.
- EAP band: multilayer stack of several dielectric elastomer films coated with compliant electrodes. The stack is coupled to soft passive elastomeric layers, which represent a suitable mechanical interface with the limb and, at the same time, ensure proper electrical insulation of the user and protection of the device.
- Electrical connections by means of metal stripes, one end connected to the band’s electrode and the other one to a voltage lead.
- Mock-up limb simulator: soft tubular structure pressurized by air. A pressure gauge allows for reading the variation of pressure inside the air chamber.
- High voltage unit: electrical interface consisting on a High-voltage step-up converter driven at low voltages (0-5 V) via a buffer (simple operational amplifier in voltage follower configuration).
EAPB Specifications
Lifetime 100,000 actuating cycles
Pressure Range [0,33] kPa
Max. Compression Freq. 0.5 Hz
Compression duration Range [1,300] s
Band dimensions 270x140x6 mm
Radious (limb simulator) 40 mm
Longitudinal length of air chamber (limb simulator) 180 mm
Power supply 0-5 V
High voltage unit power supply 0-10 kV
Safe limit (high voltage unit) 7 kV
BODY SENSORS
- CNAP monitor (two air cuffs): first one applied to the upper arm of the user, and second one to their index and middle fingers. An external device controls the pressure of these cuffs, and calculates blood pressure and heart rate.
- Hand where the finger cuffs are placed should be at the level of the heart.
- Arm movements avoided.
- Strain gauge: elastic tube that changes electrical resistance based on its elongation. Wrapped around the leg to monitor changes of leg diameter due to changes of blood volume.
- Requirement: no occlusions to blood flow.
BS Specifications
BLOOD PRESSURE Range [4, 33.3] kPa ±0.6 kPa
Power Consumption 18 VDC
3 A Imax
BLOOD VOLUME Range [0; 10] mm ±0.001 mm
Weight < 500 g
Power Consumption 15 VDC
3 A Imax
CENTRAL CONTROL UNIT – GUIS
- Overall control of leg demonstrator: upper control hierarchies, and two GUIs, one for the astronaut, and the other one for an expert or engineer.
- Monitors user parameters measured by the BS and information from actuating systems.
- In case of an error, safety strategy that deactivates the device.
- Checks with regard to: timeout (delay between device and controller), status (actuating systems), plausibility (sensor data), and range (control commands).
- Setting the training intensity of the astronaut.
- Expert GUI: visualization of commanded and measured data, input and control of control parameter values, and data logging.
- Astronaut GUI: intuitive and easy-to-use interface that offers the astronaut access to the selected parameters and that displays information on the device state.
PLATFORM
- Power Unit and the Suit Structure included in the Platform.
- The Power Unit feeds each module of the device in a direct or indirect way. It feeds directly the CCU, the Microcontroller and Driver (which feeds the SEBS and ALAS SMA actuators), the EAPB, and the SMs.
- The Suit Structure gives mechanical support to the demonstrator, providing a suit demonstrator for the leg. It contains fixations for the different subsystems and blocks and connections for the transmission of forces to the user. It also provides protection to the user.
Platform – Power Supply Specifications of each module
CCU European electrical standard, 230 V, 50 Hz
Microcontroller Micro-USB to USB A
Drivers 0-40 V, 0-20 A (banana connectors)
SM 12 V, 0-0.5 A (banana connectors)
SEBS and ALAS actuators Molex 22-27-2021 with two pins
EAPB Europeanelectrical standard, 230 V, 50 Hz
BS (amplifier of strain gauge) ±5 V, 50 mA
BS (strain gauge) 10 V, 100 mA
SENSOR MODULES
- There are different types of sensors in the actuating systems of the leg demonstrator. The SMs have been designed to coordinate the data acquisition and to transfer signals to the upper layers.
- The SM board is able to read all the sensors and is connectible with the SMA Controller.
- A CAN Bus system is used to coordinate the information provided by the set of SMs because of the quantity of sensors and the spatial distribution.
Potential Impact:
SOCIOECONOMIC IMPACT, DISSEMINATION AND EXPLOITATION
Potentially exploitable products and technologies
The main challenge of this project is the adaptation of mature SMA and EAP based technologies to develop new concepts of feasible artificial muscles integrated in a biofeedback suit for astronauts. The main system to be developed is formed by two subsystems: biosensor subsystem and artificial muscle subsystem. From both the overall system and the subsystems, project developers have taken the necessary heritage and knowledge in order to develop new potentially exploitable products and technologies:
Biosensor subsystem
The set of sensors is a key part of the biofeedback suit. This provides constant feedback to the control system, which connect or disconnect the SMA/EAP actuators. The set of sensors consists of:
- O2 saturation (reflective pulsoxymetry) two channels ECG, temperature.
- Blood pressure meter based on the oscillometric method.
- Volume sensors for big groups of muscles (i.e. legs, chest, abdomen).
Apart from its use in space, potential terrestrial applications of the proposed biosensor system are very clear, especially in the field of medicine. It is possible to implement an innovative customizable sensing system for patients’ online monitoring. Thanks to the possibility of setting custom configurations, users could monitor different parameters according to their needs.
For this project, no new sensors have been developed. However, ARQUIMEA experience in microelectronics design for space has been used within the project to assess the possibility to integrate the overall sensor acquisition electronics in a single chip, enabling smooth integration into the biofeedback suit, as well as lower consumption in the overall biofeedback sensor subsystem. The implementation of this chip in a further project continuation would be beneficial for optimizing both the space and terrestrial applications of the proposed sensing system.
Mechanical sensors subsystem
A set of sensors was included in the active biofeedback suit for the measurement of the status of actuators and mechanical parts of the suit. The signals obtained from these sensors are used by the different controllers to handle the actuation of the artificial muscles and to take decisions from the status of the user joints. These sensors include:
- Position sensors for the actuators (artificial muscles).
- Force sensors for the actuators (artificial muscles).
- Torque/position sensors to obtain the state of the joints
- Temperature sensors for controlling the temperature of actuators.
Apart from its use in the propose application, potential terrestrial applications of these sensors can be found in different sectors, such as industrial, robotics…
Artificial muscle subsystem
The active biofeedback suit is able to exert resistance stress in order to force human body to exercise and train. The forces to be applied at the legs target two levels: resistance forces in order to induce the skeletal muscle operation, simulating gravity forces and massage forces in order to stimulate the lower limb and induce the blood circulation from upper to lower limb. For the resistance forces an artificial muscle with high power/mass ratio, high resilience, low relative deformation (muscles are very large) and low speed is sought. To this end, according to the preliminary technology trade-off, SMA fibers are considered the best candidate.
For the massage forces, the most suited technology is EAP, since large relative deformation and low forces are required. The stockings must apply annular forces around the thigh, small forces (massage force requirements are very low). Recent developments based on dielectric elastomer bands for active bandage have shown feasibility of this approach.
The SMA/EAP technology validated in the frame of the project boosted a further development of actuating systems for both space and terrestrial applications. In the space field, besides the proposed artificial muscle applications, STAMAS has eased the improvement on the performance of already existing SMA based actuators, such as hold-down and release mechanisms, pin pullers or rotary and linear actuators. Specifically, the knowledge acquired by ARQUIMEA in SMA manufacturing, characterization and control allowed the company to use these materials for a more efficient actuation of its low-shock, low-weight, non-explosive space devices. Such characteristics are also very positive for other terrestrial applications, such as medicine (smart implants, artificial muscles…) or nuclear (radiation immune tools and devices for remote handling…).
Section 6 of the present document describes the expected potential products and the exploitation strategy to be implemented per each partner of the STAMAS consortium with regard to its own particular foreground to be obtained.
EAP dynamic limb compression bandage
The innovative EAP compression bandage developed in this project is expected to lead to potentially exploitable products and technologies not only suitable for space suits but also for different applications. In particular, the EAP-based compression bandage might find applications in the following specific examples of products:
1) Massage devices for patients suffering of malfunctioning of the lower limbs circulatory system: pathological or gravity-induced malfunctioning of the lower limbs circulatory system are currently addressed with both static or dynamic compression systems such as compression stockings and pneumatic compression sleeves. In particular, such compression systems are utilized as a treatment for the prevention of deep vein thrombosis, orthostatic hypotension and other venous-return related problems. However, the static compression offered by compression stockings was proved to be less effective than the time-dependent one provided by intermittent pneumatic compression systems. On the other hand, the latter require the use of bulky pneumatic cuffs and a pumping box, resulting impractical in many conditions.
The developed EAP compression bandage overcomes the shortcomings of both compression stockings and pneumatic compression systems, allowing for the development of conformable, light-in-weight, low-power consuming, and noise and heat free wearable systems or garments able to provide dynamic compression actions distributed over different body portions.
2) Haptic devices for man-machine interfaces (e.g. for virtual reality systems): in this case, evolutions of the devices might be used to develop soft, conformable, light-in-weight, low-power consuming, and noise and heat free wearable systems aimed at providing man-machine interfaces with actuating functions, either at low or at high frequencies. Virtual reality systems are just an examples of possible systems that might benefit of these new technologies.
3) Safety systems for drivers or other operators (e.g. use of vibrations as an alarm integrated within wearable systems): in this case, evolutions of the devices might be used to develop soft, conformable, light-in-weight, low-power consuming, and noise and heat free wearable systems aimed at allowing different kinds of operators to perform tasks more safely. A specific example is represented by drivers of vehicles. Here, the driver’s suit/garment or gloves might be fitted with conformable alarm systems alerting the driver with vibrations in case of need or danger (e.g. warning systems in case of incipient sleeping detected by external sensors).
SMA actuators
SENSODRIVE has gained knowledge on the application of SMA actuators in force/torque controlled systems including the sensors needed for those applications. The combination of SMA actuators with existing control know-how enables SENSODRIVE to offer engineering services in a wide range of potential applications and possibly enter new markets.
Furthermore, SENSODRIVE developed bending beams with a digital electronic interface (SPI) that can be used in upcoming projects.
A miniature PCB to amplify and digitize the low-voltage signals from the bending beam was developed. It was used in the STAMAS-Project to connect the bending beams to the sensor module and to the controller. SENSODRIVE will use this PCB in other projects and will continue to do so.
The sensor module, a PCB connecting various sensors (temperature, bending beam, incremental encoder, etc.), with diverse interfaces (analog, SPI, RS485) to the controller via CAN will be used in other projects where distributed sensing and digitizing is required.
Potential users of the technology
As stated before, STAMAS project pretends to extend the use of some fairly mature terrestrial actuation technologies into new innovative space applications. Nevertheless, project foreground also shows attractive potential non-space usage. In this section, both markets – space and non-space – are discussed identifying potential users and advantages provided by the technology. Apart from the specific applications described below, STAMAS works have provided a deep knowledge in new configurations and control of SMA materials in force and position. This allows a wide bunch of new potential uses for these materials for both space and terrestrial, such as more accurate devices, flexible actuators, “snake” robotics, super elastic elements with variable and controllable elasticity, etc.
Space applications
The main project result is the technology necessary to develop a future astronauts’ suit, a “smart-suit” using SMA and EAP, to mitigate the effects of weightlessness and motor inactivity on astronauts during the space missions. Therefore, the use case of STAMAS in space is restricted either to long manned missions (i.e. long stays at the ISS and future missions to Mars and similar) or for training and preparation on Earth. In addition, in most of the cases one single device will be used by several astronauts, so no high amounts of units per customer or mission are expected to be sold.
The following table lists the target groups that are potential buyers or stakeholders of STAMAS technology and thus, at which the exploitation activities will be addressed:
TARGET GROUP REASON FOR DISSEMINATION EXPLOITATION OFFERED BENEFITS
Policy and decision makers
(government agencies engaged in activities related to outer space and space exploration) Awareness
Understanding Suggestions for new legislation and barriers to development
Space research community Involvement Research topics. Take up of innovations and adaptations
European Space Industry Involvement
Action Information and solutions that can adapt terrestrial products and services for space applications
New ways of working and collaborating
Efficiency and innovation
End users: worldwide space agencies Awareness
Action Driving innovation for space missions through technical competence and a strong customer focus
Other stakeholders Involvement
Action Information and solutions that can improve products and services.
New ways of working and collaborating
Efficiency and innovation
Media Awareness Further dissemination
Public sector actors such as Space Agencies and Policy Makers are considered as a priority, due to the applicability that STAMAS results may have in their programs and future actuations. Other interesting target of the exploitation activities will be the mass media, thanks to their potential to spread the results.
Non-space applications
SMA/EAP based actuation systems are quite extended in different terrestrial sectors, such as: automotive actuators (low-weight actuators for opening the trunk, adjusting the rear view mirror, etc.), robotics (such as robotic fingers and hands), aeronautics (morphing flaps and engine parts) or instrumental, stents and implants in medical field. All those sectors are also potential stakeholders, so the developed technologies will be also disseminated and exploited with them.
More specifically, within the STAMAS project two devices have been developed so far – hand and ankle – that can be commercialized as standalone products mainly for medical purposes:
physiotherapy/rehabilitation and support to elderly or people with reduced mobility are the most promising applications. Another one is the use of the technology for elite sport training; here we can find a twofold application: to get recovered from an injury in hands or ankles, or to train and strengthen those parts.
The following table shows some of the main players to be reached in order to tackle this potential market:
TARGET GROUP REASON FOR DISSEMINATION EXPLOITATION OFFERED BENEFITS
Governmental decision makers Awareness
Understanding Approval of the devices for medical use
Hospitals, specialized clinics and rehabilitation centers Awareness
Understanding New devices for more effective treatment
Nursing homes Awareness
Understanding Technology to ease the life of the elderly
Sport centers and sport clubs Awareness
Understanding New training and injuries recovering systems
Medical laboratories Involvement New potential products to be commercialized
The fact of involving specialized medical companies as commercial partners is mainly due to the complex and costly process required to validate a new technology for medical human applications. Furthermore, a strategic commercial partner will certainly ease accessing hospitals, clinics, distributors and end users.
In the industrial sector, SMA actuators could, for instance, be used as valve actuators. Another field is augmented reality where force feedback solutions with miniaturized actuators are required. The actuators could also be used for training or supportive systems in health care.
For controlling these systems knowing the sensor signals are mandatory. With the help of Sensor Module, signals of various sensors can be read and digitalized locally and sent to the control. The system is less sensitive and can be used in areas with high electric magnetic field disturbance. (i.e. plant engineering and construction). Another advantage is the reduction of harness due to a bus system leaving space for other possibilities.
Socioeconomic impact of the project
The entire foreground involved in the execution of this project is in line with the premises and objectives detailed in the European 2020 Strategy and in the last published European Space Policy “Towards a Space Strategy for the European Union that Benefits its Citizens”. According to these objectives, it is crucial to build a competitive European Community and contribute to the smart, sustainable and inclusive growth of Europe, taking the premise of knowledge and innovation as a starting point; STAMAS perfectly fits in this target. One of the essential initiatives included within these strategic objectives for European Community is to develop an effective space policy to provide the tools to address some of the key global challenges. Hence, the STAMAS project is expected to directly or indirectly provide part of the necessary technology to improve space initiatives and innovations and place Europe in a better competitive standing.
The European Space Policy basically considers a few priority actions conceived for giving response to three type of needs: social (combating climate change, civil security, humanitarian and development aid, transport and information, etc.), economic (generating space knowledge and products, promoting innovation, competitiveness, growth and job creation), strategic (cementing the EU’s position as a major player on the international stage and contributing to the Union’s economic and political independence).
According to this Policy, the improvement of the European Space Industry Competitiveness will significantly contribute to the overall European Competitiveness. Space is a key sector for supplying independence to the economy in Europe. A plausible deficiency of this sector is the low concentration of SMEs. One of the main objectives of this sector is the steady, balanced development of the industrial base as a whole, including SMEs, greater competitiveness on the world stage, non-dependence for strategic subsectors such as launching, which require special attention, and the development of the market for space products and services. On the other hand, this Space Policy requires also a solid technological base and competitive space industry. This Policy also points out the need for developing key generic technologies. So that, according to this, the STAMAS project contributes to the fulfillment of the strategic objectives of the European Space Policy, providing disruptive and innovative research into the space domain and increasing the number of competitive SMEs operating in the space sector.
With regard to its contribution to the European Space Work Programme 2012, STAMAS primarily helps reaching goals set within the Theme 9 (Activity 9.3) as the development proposed in STAMAS contributes to translate terrestrial technologies into the space domain. Specifically, STAMAS project has adapted SMA and EAP actuators based technologies for its utilization in a smart space suit. As explained before, these actuation technologies are commonly used in the last few years in numerous of industrial, non-industrial and medical applications.
The STAMAS project is also considered as high-impact research due to the very innovative character of the developments involved. Artificial muscles have never been considered for its utilization in space environment and consequently, several technical risks are associated, however, the background expertise and commitment of the partners involved has contributed to the success of the project.
Additionally, the targets of the STAMAS project are in line with the Europe 2020 Strategy. This policy puts forward three main priorities: an economy based on knowledge and innovation; promotion of an efficient, greener and more competitive economy; and fostering a high-employment economy. Among these general targets, special attention is paid to strengthen knowledge and innovation. Currently, R&D spending in Europe is below 2%, compared to 2.6% in the US and 3.4% in Japan, mainly as a result of lower levels of private investment. The fostering of private investment in R&D is essential to cover this gap and make Europe a more competitive area. Under this target, numerous initiatives have been proposed in the Europe 2020 Strategy.
On the other hand, building a sustainable and competitive economy through developing new processes and technologies, including green technologies, are key actions that contribute to the improvement of the competitiveness of Europe. Under this general target, various initiatives have also been proposed, standing out in the frame of this project “the development of an effective space policy to provide the tools to address some of the key global challenges”.
STAMAS indirectly contributes to the achievement of objectives within the 2020 Strategy. It mainly helps increasing the percentage of private investment in R&D, especially by SMEs with the participation of ARQUIMEA and SENSODRIVE. Furthermore, STAMAS is a challenging project studying the utilization of efficient and innovative technologies in the space domain. Therefore, STAMAS project provides technological tools for improving European space competitiveness as it is claimed in the Europe 2020 Strategy.
So that, STAMAS project is part of the private investment on R&D coming from SMEs that will partially mitigate some fundamental weaknesses of the actual European economy. STAMAS project gives evidence of the new business conscience implanted in the SMEs business structure focused in increasing R&D and innovation investment as an effective measure for fighting actual crisis.
Finally, STAMAS project has also contributed to the generation of high-skilled personnel across scientific and technical disciplines that will contribute to the aerospace field. The personnel employed on this project has received from their respective employers and the rest of consortium member’s world-class technological training that enable them to compete on an international stage when the project reaches its conclusion. Therefore, the European Union has gained a highly skill and well-trained workforce of personnel specialized in aerospace, microelectronics, systems engineering, automation, etc. An increase in employment in related areas is expected if project achieve successfully the objectives that have been established.
The STAMAS consortium considers this project as an important step necessary to bring SMA and EAP based actuation technologies into the space market. The nature and main features of this type of technology makes these actuators appropriate for space applications.
After the project, partners are expected to continue working on further fundamental knowledge and optimization of artificial muscles to create a more feasible, high performance and more durable technology with more applicability in the space domain. The industry partners are large and well established companies with the required capacity to drive this towards full commercialization, while R&D partners will continue the more basic and fundamental research.
Socioeconomic impact: terrestrial applications
Out of space, the terrestrial applications identified for STAMAS foreground will mainly have a positive socioeconomic impact in the healthcare and wellbeing areas. The use of SMA- and EAP-based artificial muscles in physiotherapy, prosthetics, injuries recovering and assistance to impaired people allows the implementation of new treatments and solutions that will improve the currently available technics, in terms of performance and recovery time. This will not only have a significant social impact in the life quality of the users, but also economic, thanks to the expected cost reduction due to shorter-time treatments and the use of more efficient technologies.
Regular training with the STAMAS suit will improve the astronaut’s health condition in orbit by reducing (or avoiding) amyotrophia and bone antrophy. On earth, the results of the STAMAS-project can be used to support elderly and impaired people by reducing bone abrasion and avoiding injuries. In medical institutes training capabilities for people who are in recovery after a stroke might be improved using the results of the STAMAS-project.
Furthermore terrestrial exo-skeletons enable people to take part on life in an active way, while reducing stress in people’s occupational activities so that they are able to stay longer in their profession and gain a high recreational value.
On the other hand, the wide expertise acquired in STAMAS with regards to the control of the SMA materials in force and position also supposes a clear breakthrough that will help boosting the use of this technology in general for terrestrial applications to replace less effective technologies. New configurations of SMA based devices will be possible. The main advantages of these materials (memory effect and super elasticity) can be better exploited, not only for medical, but also for general applications, such as industrial, automotive or avionics. Altogether represents a clear economic impact.
List of Websites:
www.stamas.eu
ARQUIMEA (Project Coordinator)
Mr. Marcelo Collado: mcollado@arquimea.com
DLR (Deutsches Zentrum Für Luft Und Raumfahrte
Mr. Thomas Hulin: Thomas.Hulin@dlr.de
ETH (Eidegenössissche Technische Hochschule Zürich)
Mr. Robert Riener: robert.riener@hest.ethz.ch
UNIPI (University Of Pisa)
Dr. Federico Carpi: f.carpi@qmul.ac.uk
SD (SENSODRIVE GmbH)
Mr. Norbert Sporer: norbert.sporer@sensodrive.de
UC3M (Universidad Carlos III De Madrid)
Dr. Luis Moreno: moreno@ing.uc3m.es
The STAMAS has been a great and successful conducted effort focused on joining several incipient and promising terrestrial technologies to pose and demonstrate its suitability and accuracy in the space domain. Due the expertise of the participants in the project, the project has been focused in enhancing the life in space by improving the performance of the space suits and diminishing the health effects of the gravity absence.
In a 36 month duration project, two different technologies have been put in the spotlight: SMA (Shape Memory Alloys) and EAP (Electroactive Polymers). Thanks to the efforts devoted, these two present terrestrial applications have been handled to research in new concepts of artificial muscle systems for biofeedback suits for astronauts, as an alternative to currently used technologies. To this end, the project team has proposed to focus on designing, developing and testing both a lower and an upper limb biofeedback suit demonstrator. The lower limb demonstrator incorporate different types of artificial muscles subsystems in complementary configuration in order to attack the different pathologies originated due to microgravity (muscle atrophy, bone loss, and shifting of blood distribution). The upper limb demonstrator provides actuating systems for the assistance of astronauts while wearing space gloves during Extra-Vehicular Activities (EVA). In practical terms, biofeedback leg and hand suits have been developed. These parts of the human body have been selected for being the most critical and representative – in terms of engineering complexity and as key elements that require particular solutions to known problems of human space flights. In other words, a successful demonstrator of those devices for sure represents an important achievement for the design and development of a whole smart suit. The results have been very promising, being materialised in two functional prototypes, which have been validated in operational simulated conditions (TRL 4) opening a promising R&D landscape and awakening the interests of several key stakeholders with whom there has been a continuous feedback.
Project Context and Objectives:
STAMAS is an European Project developed by Arquimea Ingeniería, DLR, ETH Zürich, Sensodrive, Universidad Carlos III de Madrid and Universitá di Pisa.
The main goal of the project is to create innovative exo-robotic hands and legs, using Shape Memory Alloys (SMA) and Electro-Active Polymers (EAP) actuators which aim is to support astronauts exercising to mitigate the effects of microgravity on the body and to assist the astronaut’s fingers movements during Extra Vehicular Activities (EVAs).
General Objectives
• To generate the scientific basis to provide a smart suit for on-board spacecraft use which is able to control, mitigate and even treat the health problems that could arise owed to microgravity and lack of mobility, as well as to the stiffness of the space suit during EVAs.
• To bring experience on SMA/EAP technologies in the space domain, adapting the existing terrestrial technologies to space domain contributing to the substitution of conventional actuators.
• To adapt different biometric sensors to the on-board space requirements to promote their applicability as an integral part of the astronaut’s equipment, improving its functionality and safety.
• To adapt and develop sensors to be embedded in the suit for the control of the mechanical behaviour of the suit and its actuators.
• To develop a control architecture able to process and interpret the information of the biological parameters of the astronaut, his/her movement intentions and the status of the suit and the actuators in order to provide the corresponding orders to the suit subsystems and feedback to the user.
• To develop a functional prototype of bio-feedback leg and hand which can be set over the astronaut’s space suit, and react to his/her actions.
• To create a demonstration prototype of a light weight, flexible exoskeleton robotic system based on SMA and EAP actuating technologies, to be test on human beings.
• To obtain a significant technological demonstrator that will enable partners to show their technological capabilities, which will represent an important advantage at commercial level.
• To enlarge the scope of the project to applications other than space specific, such as healthcare or rehabilitation robotics.
Introduction – Problem description
When astronauts return to Earth after a long period in space, their organism shows several signs after living in microgravity, such as loss of muscles mass and bones density, increase of body length, blood distribution problems, heart dysfunction and orthostatic intolerance. Other functions such as proprioception or the capability to react quickly to recover body stability are also degraded by the effect of microgravity.
Currently, on the International Space Station (ISS), countermeasures are taken in the form of exercise plans to prevent the severity of the symptoms. These plans include three phases comprising pre-flight, in-flight and post-flight exercise programs in order to prepare, maintain and adapt the astronaut’s physical condition during the whole length of the mission. A leg exoskeleton has been developed in this project for the exercising during in-flight phase.
A further problem encountered by astronauts on the ISS occurs during EVAs. EVAs performed by astronauts are limited by several factors. One of these limitations is the duration of the space walks due to the hand fatigue that astronauts suffer when performing manual tasks. This fatigue is mainly caused by the stiffness of the spacesuit gloves. The gloves are internally pressurized, as the rest of the spacesuit, to protect the astronaut from the vacuum of Space. The pressure inside the gloves increases the stiffness of each joint of the glove, making the astronaut to exert great forces to overcome this stiffness and mobilize the fingers.
In addition, the astronaut has to operate tools or other installations which have to be carefully designed to be gripped or handled in special ways. The resistance force of the glove due to air pressure and stiff materials and the additional space and distance between the fingers and the grasped object translates in loss of touch feeling and dexterity. Thus, the astronaut has to fight against high forces when performing manipulation tasks during spacewalks. These forces disturb the intended tasks thus reducing efficiency, and causing dramatic fatigue of the astronauts’ hands and fingers. A hand exo - muscular system demonstrator has been developed with the aim of assisting the astronauts in these manual tasks, reducing the extra amount of force required to move their hands.
LEG DEMONSTRATOR
One of the main objectives of the STAMAS project is to design an actuated device for the lower limb – the leg demonstrator – to be used for exercising inside the ISS, to address the problem of weightlessness that results in a loss of bone density and of muscular mass. The objectives of these measurements are to improve the exercising in orbit, to explore new countermeasures and to develop exercising devices that can be worn for long periods of time in order to exercise the legs during normal life in the ISS as well as provide a complement to current exercising devices. The leg device imposes several difficulties to the astronaut’s movement and performs oppression and release forces over the user’s thigh in order to modify the blood distribution. The leg demonstrator is divided into three different actuating subsystems, each one designed to tackle different problems associated with prolonged stays in a microgravity environment. These subsystems are:
• Ankle Lateral Actuating System · ALAS
It exerts lateral forces over the ankle, in order to generate sudden little deviations on the ankle position. The user has to use his proprioceptive abilities to keep his/her own balance.
This help to maintain the good state of all the secondary muscles, which usually support the main muscles. The lateral forces generated by this system are created by a set of actuated SMA wires.
• Smart Elastic Bands System · SEBS
It is intended for generating a resistance to the knee movement. This device can vary the degree of resistance and the point of the leg that has to perform a greater effort on the flexion-extension movement. The resistance force is generated by a device formed by thermally controlled SMA superelastic bands.
• Electro-Active Polymer Bands · EAPB
They are placed surrounding the lower limbs. Their function is to generate alternative compressions, thus improving the blood flow in the lower limbs, replying the effect of pumping muscles. This way the blood flow might be improved in the lower limbs, mitigating the muscular volume loss in microgravity.
HAND DEMONSTRATOR
The Hand Demonstrator is driven by the Hand Exo-Muscular System (HEMS), which is an actuated device used to compensate the stiffness of the space suit by counteracting the force exerted by the pressurized glove, in such way that the force demanded to the astronaut to flex the fingers is reduced. These forces are generated by aims of several SMA linear actuators, which are connected to the gloves by thin tendons connected to the actuators. Several thin rings are placed over the glove in order to guide and fix these elements. The actuated system is called Hand Exo-Muscular System (HEMS) and the proposed solution is based on a bio-inspired principle formed by flexible muscle-like systems as an alternative to state-of-the-art rigid exo-skeletons.
The device detects the movement of each of the user’s fingers and acts over the glove helping the user to flex them, so that the apparent stiffness of the glove is reduced and the astronaut’s dexterity is improved. An important fact to be taken into account is that the demonstrator is intended to be integrated within an EVA glove. The device is light and low volume. The SMA wires are the basis of the actuating system, thanks to their high force to volume rate characteristics and thus, providing a biomimetic design.
PROJECT TEAM
ARQUIMEA, leader of the project, is an engineering company specialized in the development of customised sensors, actuators and microsystems. The company was founded as a Spin Off of the “Departamento de Ingeniería de Sistemas y Automática” of the Universidad Carlos III de Madrid. ARQUIMEA`s design department is currently composed of 24 engineers, with demonstrated experience in aerospace and electronics (such as EADS Astrium, Analog Devices, Bell laboratories and Motorola, among others).
The most relevant business area of ARQUIMEA strategy is related to the development of SMA based actuators. In fact, the origin of the company six years ago was the development of SMA actuators for artificial muscles; project called EURISMA. This project consists in the application of a SMA based actuator to control the urethra in cases of incontinency.
Key personnel: Mr. Marcelo Collado has degree in Telecommunications Engineering by the UC3M (Madrid) and Master in Space and Satellite Technologies by the UPM (Madrid). He has been working for years in the development of SMA applications in the aerospace, automotive and biomedical industry. He has a wide knowledge of the field, supported by many publications in specialized journals as well as communications in scientific congresses.
DLR (Deutsches Zentrum Für Luft Und Raumfahrte), is an Aerospace Research Center as well as the German Space Agency. It is one of the biggest and most acknowledged Institutes in the field worldwide. The institute contributes to several international projects in FP6/FP7 (IP, STREP) as well as space projects and many national research projects. To mention in relation to STAMAS are the FP6 IP SKILLS Multimodal Interfaces for Capturing and Transfer of skills, FP7 IP DEXMART DEXterous and autonomous dualarm/ hand robotic manipulation with smart sensory-motor skills and FP7 STREP GeRT Generalizing Robot Manipulation Tasks. DLR provides its high-competence in designing, building and controlling robots, that sustains the hard conditions of space flight to STAMAS project. Besides that DLR has made use of its experience in the control of haptic human machine interfaces.
Key personnel: Mr. Thomas Hulin received his degree as electrical engineer from the Technical University of Munich, Germany, in Sep. 2003. Since 2003 he is scientist at the German Aerospace Center, Institute of Robotics and Mechatronics. His research interests, in which he has (co-)authoredmore than 30 publications, include control theory for haptic rendering, haptic rendering algorithms, multimodal human machine interfaces, skill transfer, and virtual reality.
ETH (Eidegenössissche Technische Hochschule Zürich). Founded in 1855, ETH Zurich has come to symbolize excellent education, groundbreaking basic research and applied results that are beneficial for society as a whole. Nowadays, it offers researchers an inspiring environment and students a comprehensive education as one of the leading international universities for technology and the natural sciences. ETH Zurich has more than 16,000 students from approximately 80 countries, 3.500 of whom are doctoral candidates. More than 400 professors teach and conduct research in the areas of engineering, architecture, mathematics, natural sciences, system-oriented sciences, and management and social sciences. One of ETH Zurich’s primary concerns is transferring its knowledge to the private sector and society at large. It has succeeded in this, as borne out by the 80 new patent applications each year and the 215 spin-off companies that were created out of the institute between 1996 and 2010. ETH Zurich is a leading global natural science and engineering university, and plays an important role in the Swiss economy. ETH transfer supports collaborations with ETH Zürich, licensing of ETH technologies, contacts to ETH Zurich Spin-off companies and innovation and start-up support programs, among others.
Key personnel: Robert Riener, leader of the Sensory-Motor Systems (SMS) Laboratory, holds a “Double-
Professorship” affiliated to the Mechanical Engineering Department of the ETH Zurich andthe Spinal Cord Injury Center, University Hospital Balgrist, University Zurich. The SMS Lab has broad experience in several areas that are relevant for the development and dissemination plans of STAMAS. The innovative control strategies allow a rehabilitation robot for the first time to “cooperate” with the patient. From 1998 till 2004, Riener did participate in the EU funded projects “Neuros” and “NeuralPRO”. Riener was the leader of the German network project “VOR”. Currently, he is subproject-leader within the Swiss National Science Foundation project “NCCR Neuro”. Prof. Riener did successfully coordinate the EU-Project MIMCS.
UNIPI (University Of Pisa). The Interdepartmental Research Center "E. Piaggio" is an institute of the University of Pisa devoted to multidisciplinary research in the fields of Bioengineering and Robotics, and to
training of research personnel. In this project, the Center was represented by the Bioengineering Group which has a longstanding and internationally recognized expertise in the field of Electroactive Polymer (EAPs)
as smart materials for electromechanical transducers. In this field, the Group is an international reference and coordinates the “European Scientific Network for Artificial Muscles”, entirely focused on EAPs (www.esnam.eu). In this project, the Group performed the following activities: design and manufacturing of new kinds of electroactive polymer actuators based on dielectric elastomers; mechanical, electrical and electromechanical characterization of materials and testing of the actuators; cooperation to the design, development and demonstration of the intended application.
Key personnel: Dr. Federico Carpi (Ph.D. degree in Bioengineering at University of Pisa). Currently is Postdoc researcher at this University. Coordinator of the “European Scientific Network for Artificial Muscles (ESNAM)”. His main research activities concern the development of novel materials and actuators for electroactive polymer-based artificial muscles and their applications.
SD (SENSODRIVE GmbH) is a spin-off company from the German Aerospace Centre DLR. SD main goal is to bring the latest drive, sensor, and control technology into the industry. Customers from the air- and space-industry, medical technology, simulator manufacturers, as well as the automotive branch rely on SENSODRIVE technology. The special mechatronic know-how enables the SD engineers to develop
customer specific products as well as own products with unique features. Therefore, the company counts with a wide range of products among which sensor actuators, motion controllers and special actuators can be identified. All products are designed with the latest concurrent engineering methods; being the integration of mechanics, electronics, sensor technology, and advanced controllers the company’s specialty.
SENSODRIVE servo actuators are based on the ideas of the DLR light-weight robot. The unique compactness and performance are achieved by optimizing each individual component.
Key personnel: Norbert Sporer studied electronics at the Fachhochschule München. He got a degree from the technical University of Munich. Besides his studies in Automation and Control” Mr. Sporer worked as development engineer at the Institute of Automatic Control Engineering. He is currently working in the Institute of Robotics and Mechatronics at the DLR as project manager for the light-weight robot. With the light-weight robot development the team has been able to set new benchmarks in robotics. As requested by the head of the Institute, Mr. Sporer is still in charge of the light-weight robot project.
UC3M (Universidad Carlos III De Madrid). Founded in 1989, the Carlos III University of Madrid (UC3M) is a public university whose main goal is to provide specialised training in Law and Social Sciences and Engineering, as well as to become a prime European research centre. UC3M has strived to make research one of the fundamental pillars of its activity, both for the enhancement of its teaching and for the new knowledge and new areas of research. ROBOTICSLAB was founded in 1981 when participated in the development of one of the first robots in Spain, the DISAM-0. This centre has evolved and become one of the most representative robotics research group in Spain
Key personnel: Dr. Luis Moreno (Degree in Automation and Electronics Engineering in 1984; Ph.D. in 1988
from the Universidad Politécnica de Madrid). From 1988 to 1994, he was an associate professor at the Universidad Politécnica de Madrid. In 1994 he joined UC3M, from 2007 is the head of the Departament of Systems Engineering and Automation. He has been involved in several mobile robotics projects in Robotics Lab of the UC3M. His research interests are in the areas of mobile robotics, mobile manipulators, environment modelling, path planning, learning problems in robotics and mobile robot global localization problems.
Project Results:
HAND SUIT
• Extra Vehicular Activities (EVA) performed by astronauts are limited by several factors. The gloves are internally pressurized to protect the astronaut from the vacuum of Space. The internal pressure increases the stiffness of each joint of the glove, making the astronaut to exert great forces to overcome this stiffness. The stiffness also leads to other problems, such as premature hand fatigue, damages in the nails, difficulties to move with dexterity and lack of control about the applied strength on the objects.
• The objective of the hand demonstrator o is to reduce the effect of the stiffness of the glove by counteracting the force exerted by the pressurized glove. These forces are generated by aims of several linear actuators connected to the gloves.
• The device predicts the user’s movement intention and acts over the glove to reduce the stiffness.
It is composed by the following modules:
- Hand Exo-Muscular System (HEMS) – actuating system that reduces the stiffness of the spacesuit glove. 6 SMA flexible actuators connected to the fingers (1 for each finger and 2 for the thumb).
- Finger Sensors (FS) – 6 force sensors located on the fingertips (2 for the thumb)
- Central Control Unit (CCU) / GUIs – overall behaviour of device, monitor of parameters, security and safety.
- Sensor Module (SM) – transmitting information from sensors to other components.
General description:
- The FS register force information to detect the movement intention of the user. This information is sent to the CCU through the SM FS to monitor the user movement intention to decide the adequate actions (sending control signals to the actuating system) when using the device.
- The sensors of the HEMS measure information about position and force. All this information should be transmitted to the CCU to check the status of the actuating system and to send the required control actions.
- The SMs are responsible of coordinating the data acquisition and transferring sensor signals to the upper control layers.
- The CCU sends command signals to the actuating system via the Microcontroller and Driver block. The required control actions are also sent to the actuating system module (HEMS) using the SMs.
- The Platform is formed by the Power Unit and the Suit Structure. A Power Unit is required to feed each module of the device in a direct or indirect way. The suit structure gives mechanical support to the demonstrator, providing a suit demonstrator for the hand. It contains fixations for the different subsystems and blocks and connections for the transmission of forces to the user.
HAND EXO-MUSCULAR SYSTTEM
- Shape memory effect to perform the required actuation. When heated, the SMA wires contract, thus causing the flexion of the fingers. Upon cooling, the wires gradually return to their initial length thanks to the opposition force produced by the stiffness of the EVA glove, which also cause the extension of the user’s fingers.
- Force applied on the fingers, allowing a more comfortable flexion while wearing a stiff glove. The amount of force is controlled by the user by changing the pressure applied in the fingertips.
- Mechanical structure – glove with a series of tendons attached to the fingertips and tendons routed through the underside of the fingers and the palm of the hand.
- The index, middle, ring and little fingers have only one tendon each, while the thumb has two tendons.
- Tendon system attached to the output of the HEMS actuators through an interface consisting of a series of pulleys to multiply the linear displacement of the actuators.
- Rigid tendons allows to flex the wrist without affecting the actuators performance.
- HEMS actuating system fixed end in the shoulder, where it is linked to Bending Beams force sensors.
- Sensors: fingertip sensors (FlexiForce #A201), force sensors (Bending Beam), and position sensors (Rolin linear).
HEMS Specifications
Linear stroke 25 mm
Maximum force 35 N
Technology SMA actuator
Max. Frequency of complete cycle 0.125 Hz
Lifetime 50,000 actuating cycles
Aggregated mass < 1500 g
Power consumption 300 W
HEMS Controller Performances Control of fingers
Resolution > 0.025 Nm
Freq. 1 kHz
Position Sensor Range 0-40 mm
min. res. 1 μm to 250 μm
Freq. > 100 Hz
Force Sensor Range > 50 N
min. res. > 0.5 N
Freq. 1 kHz
FINGER SENSORS
- The FS are formed by six force sensors located on the fingertips.
- One sensor is placed on each finger except in the thumb, which has two of them because two degrees of freedom have been analysed/controlled.
- Each sensor is a force sensing resistor (FlexiForce #A201 capacity sensor) that obtains analogic signals.
- These sensors are connected to the SM FS.
FS Specifications
Range Sensitivity towards 20N able to withstand 110 N
Power Consumption 0.1-0.5 V
2.5 mA max
Resolution 12 bit
Output signal Digital over Sensor Module
CENTRAL CONTROL UNIT - GUIS
- Overall control of hand demonstrator: upper control hierarchies, and two GUIs, one for the astronaut, and the other one for an expert or engineer.
- Monitors user parameters measured by the FS and information from actuating system.
- In case of an error, safety strategy that deactivates the device.
- Checks with regard to: timeout (delay between device and controller), status (actuating system), plausibility (sensor data), and range (control commands).
- Setting the required force to support the astronaut in manipulation tasks.
- Expert GUI: visualization of commanded and measured data, input and control of control parameter values, and data logging.
- Astronaut GUI: intuitive and easy-to-use interface that offers the astronaut access to the selected parameters and that displays information on the device state.
PLATFORM
- The Power Unit and the Suit Structure are included in the Platform.
- The Power Unit feeds each module of the device in a direct or indirect way. It feeds directly the CCU, the Microcontroller and Driver and the SMs.
- The Suit Structure gives mechanical support to the demonstrator, providing a suit demonstrator for the hand. It contains fixations for the different subsystems and blocks and connections for the transmission of forces to the user. It also provides protection to the user.
- The Bending Beam is attached to a mechanical interface that is used as its structure. This interface provides an easy system for attaching and detaching the HEMS actuators to the shoulder structures when putting on and off the suit.
Platform – Power Supply Specifications of each module
CCU European electrical standard, 230 V, 50 Hz
Microcontroller Micro-USB to USB A
Drivers 0-40 V, 0-20 A (banana connectors)
SM 12 V, 0-0.5 A (banana connectors)
HEMS actuators Molex 22-27-2021 with two pins
FS 0.1-0.5 V, 2.5 mA
SENSOR MODULES
- There are different types of sensors in the actuating systems of the hand demonstrator. The SMs have been designed to coordinate the data acquisition and to transfer signals to the upper layers.
- The SM board is able to read all the sensors and is connectible with the SMA Controller.
- A CAN Bus system is used to coordinate the information provided by the set of SMs because of the quantity of sensors and the spatial distribution.
LEG
• The effect of microgravity during prolonged stays in space causes different problems. Astronauts suffer from several health problems, such as bone loss, muscle atrophy or a change of blood circulation and distribution.
• The leg demonstrator is an an advanced exercising device that can be used individually or complementing the existing exercising devices on board.
• It imposes several difficulties to the astronaut’s movement and performs oppression and release forces over the user’s thigh to modify the blood distribution.
• The main objective of the actuating systems is to mitigate the consequences caused by microgravity in space.
• The leg suit contains three different actuating systems (ALAS, SEBS and EAPB) based on different technologies that rely on smart materials: Shape Memory Alloys (SMA) and ElectroActive Polymers (EAP).
It is composed by the following modules:
- Ankle Lateral Actuating System (ALAS) - lateral forces over the ankle joint to exercise the ankle’s lateral muscle.
- Smart Elastic Bands System (SEBS) - variable resistance to the knee movement in flexion-extension movement.
- ElectroActive Polymer Bands (EAPB) - alternative compressions, improving the blood flow in the lower limbs, replying the effect of pumping muscles.
- Body Sensors (BS) – information about blood pressure and heart rate.
- Central Control Unit (CCU) / GUIs – overall behaviour of device, monitor of parameters, security.
- Sensor Module (SM) – transmitting information from sensors to other components.
General description:
- The BS measures blood pressure and heart rate. This information is sent to the CCU to monitor the user parameters to decide the adequate actions (sending control signals to the actuating systems) when exercising.
- The SEBS and ALAS sensors measure information about position, force, and temperature. This information is transmitted to the CCU to check the status of the actuating systems and to send the required control actions.
- The SMs are responsible of coordinating the data acquisition and transferring sensor signals to the upper control layers.
- The CCU sends command signals to the actuating systems. The required control actions are also sent to the actuating system modules (SEBS and ALAS) using the SMs.
- The EAPB module has its own driver electronics, which feeds the EAP with the high-voltage signal required for its actuation. This driver is directly connected to the CCU, performing an ON/OFF control of the device.
- The Platform is formed by the Power Unit and the Suit Structure. A Power Unit is required to feed each module of the device in a direct or indirect way. The Suit Structure gives mechanical support to the demonstrator, providing a suit demonstrator for the leg. It contains fixations for the different subsystems and blocks and connections for the transmission of forces to the user.
ANKLE LATERAL ACTUATING SYSTEM
- Lateral forces over the ankle joint to exercise the ankle’s lateral muscles.
- Options:
- Maintained forces with low variation rate to perform a passive-active exercising of the user’s ankle.
- Fast sudden impulses to emulate the loads appeared when a person changes its direction or the ground is tilted.
- Two symmetrical devices linked by straps, internal and external ALAS, in charge of exerting inversion and eversion forces, respectively.
- Lateral forces created by a set of actuated SMA wires.
- On its top end, ALAS mechanically attached to the SEBS system. On the bottom end, linked to the astronaut’s foot by a semi-rigid element.
- Sensors: force (Sensodrive Bending Beam) and position (RM08 Rolin). All sensors needed twice (internal and external).
ALAS Specifications
Linear stroke 15 mm
Maximum torque 1.5 Nm
Maximum force 50 N
Technology SMA actuator
Max. Frequency of complete cycle 0.25 Hz
Lifetime 50,000 actuating cycles
Aggregated mass < 500 g
Power consumption 100 W
ALAS Controller Performances Control of load to the ankle
Resolution > 0.025 Nm
Freq. 1 kHz
Position Sensor Range 0-360°
min. res. > 0.5°
Freq. > 1kHz
Force Sensor Range > 50 N
min. res. > 0.25 N
Freq. > 1kHz
SMART ELASTIC BANDS SYSTEM
- Produces a resistive force to the knee movement, able to change the degree of resistance on the flexion-extension movement.
- Two SEBS devices united by straps (SEBS front and SEBS back). Each actuating system is in charge of exerting the flexion and extension forces, respectively.
- Mechanical interface to the suit structure, ensuring structural integrity and a proper force transmission from the actuator to the leg.
- Structure connected to the user hip, user leg guided through his knee and the rest of the suit properly to ensure the force transmission. It allows the user to make his/her whole range of movements of the knee.
- On its top end, the SEBS device is mechanically attached to the hip. On the bottom end, the device is connected to the ALAS device.
- Opposing force produced by a set of SMA sheets working on the superelastic region. The stiffness is modified by adjusting the temperature of the SMA elements using heaters.
- By varying the amount of resistance produced by the SEBS, it is possible to train a wide range of the leg’s muscles, allowing the user to prevent the loss of muscle weight.
- Sensors: force (K100), position (Rolin magnetic encoder), and 16 temperature (16 PT1000) in each SEBS device.
SEBS Specifications
Max. Deformation > 60 mm
Max. Force > 300 N
Total load applied [40%,60%] muscle load
Technology SMA – Superelastic elements
Lifetime 50,000 actuating cycles
Aggregated mass < 400 g
Power Consumption < 160 W
SEBS Controller Performances Adjustment of elastic behaviour (resistive load)
Freq. > 50Hz
Temperature Sensor Range -50°C to 150°C
Resolution 12 bit
Position Sensor Range [0,60] mm
Resolution 1 μm to 250 μm
Force Sensor Range [0,1000] N
Resolution > 5 N
ELECTROACTIVE POLYMER BANDS
• Generation of alternative compressions, improving the blood flow in the lower limbs, replying the effect of pumping muscles. Surrounding the lower limbs.
• Three hardware components: EAP band, mock up limb simulator and high voltage power unit.
- EAP band: multilayer stack of several dielectric elastomer films coated with compliant electrodes. The stack is coupled to soft passive elastomeric layers, which represent a suitable mechanical interface with the limb and, at the same time, ensure proper electrical insulation of the user and protection of the device.
- Electrical connections by means of metal stripes, one end connected to the band’s electrode and the other one to a voltage lead.
- Mock-up limb simulator: soft tubular structure pressurized by air. A pressure gauge allows for reading the variation of pressure inside the air chamber.
- High voltage unit: electrical interface consisting on a High-voltage step-up converter driven at low voltages (0-5 V) via a buffer (simple operational amplifier in voltage follower configuration).
EAPB Specifications
Lifetime 100,000 actuating cycles
Pressure Range [0,33] kPa
Max. Compression Freq. 0.5 Hz
Compression duration Range [1,300] s
Band dimensions 270x140x6 mm
Radious (limb simulator) 40 mm
Longitudinal length of air chamber (limb simulator) 180 mm
Power supply 0-5 V
High voltage unit power supply 0-10 kV
Safe limit (high voltage unit) 7 kV
BODY SENSORS
- CNAP monitor (two air cuffs): first one applied to the upper arm of the user, and second one to their index and middle fingers. An external device controls the pressure of these cuffs, and calculates blood pressure and heart rate.
- Hand where the finger cuffs are placed should be at the level of the heart.
- Arm movements avoided.
- Strain gauge: elastic tube that changes electrical resistance based on its elongation. Wrapped around the leg to monitor changes of leg diameter due to changes of blood volume.
- Requirement: no occlusions to blood flow.
BS Specifications
BLOOD PRESSURE Range [4, 33.3] kPa ±0.6 kPa
Power Consumption 18 VDC
3 A Imax
BLOOD VOLUME Range [0; 10] mm ±0.001 mm
Weight < 500 g
Power Consumption 15 VDC
3 A Imax
CENTRAL CONTROL UNIT – GUIS
- Overall control of leg demonstrator: upper control hierarchies, and two GUIs, one for the astronaut, and the other one for an expert or engineer.
- Monitors user parameters measured by the BS and information from actuating systems.
- In case of an error, safety strategy that deactivates the device.
- Checks with regard to: timeout (delay between device and controller), status (actuating systems), plausibility (sensor data), and range (control commands).
- Setting the training intensity of the astronaut.
- Expert GUI: visualization of commanded and measured data, input and control of control parameter values, and data logging.
- Astronaut GUI: intuitive and easy-to-use interface that offers the astronaut access to the selected parameters and that displays information on the device state.
PLATFORM
- Power Unit and the Suit Structure included in the Platform.
- The Power Unit feeds each module of the device in a direct or indirect way. It feeds directly the CCU, the Microcontroller and Driver (which feeds the SEBS and ALAS SMA actuators), the EAPB, and the SMs.
- The Suit Structure gives mechanical support to the demonstrator, providing a suit demonstrator for the leg. It contains fixations for the different subsystems and blocks and connections for the transmission of forces to the user. It also provides protection to the user.
Platform – Power Supply Specifications of each module
CCU European electrical standard, 230 V, 50 Hz
Microcontroller Micro-USB to USB A
Drivers 0-40 V, 0-20 A (banana connectors)
SM 12 V, 0-0.5 A (banana connectors)
SEBS and ALAS actuators Molex 22-27-2021 with two pins
EAPB Europeanelectrical standard, 230 V, 50 Hz
BS (amplifier of strain gauge) ±5 V, 50 mA
BS (strain gauge) 10 V, 100 mA
SENSOR MODULES
- There are different types of sensors in the actuating systems of the leg demonstrator. The SMs have been designed to coordinate the data acquisition and to transfer signals to the upper layers.
- The SM board is able to read all the sensors and is connectible with the SMA Controller.
- A CAN Bus system is used to coordinate the information provided by the set of SMs because of the quantity of sensors and the spatial distribution.
Potential Impact:
SOCIOECONOMIC IMPACT, DISSEMINATION AND EXPLOITATION
Potentially exploitable products and technologies
The main challenge of this project is the adaptation of mature SMA and EAP based technologies to develop new concepts of feasible artificial muscles integrated in a biofeedback suit for astronauts. The main system to be developed is formed by two subsystems: biosensor subsystem and artificial muscle subsystem. From both the overall system and the subsystems, project developers have taken the necessary heritage and knowledge in order to develop new potentially exploitable products and technologies:
Biosensor subsystem
The set of sensors is a key part of the biofeedback suit. This provides constant feedback to the control system, which connect or disconnect the SMA/EAP actuators. The set of sensors consists of:
- O2 saturation (reflective pulsoxymetry) two channels ECG, temperature.
- Blood pressure meter based on the oscillometric method.
- Volume sensors for big groups of muscles (i.e. legs, chest, abdomen).
Apart from its use in space, potential terrestrial applications of the proposed biosensor system are very clear, especially in the field of medicine. It is possible to implement an innovative customizable sensing system for patients’ online monitoring. Thanks to the possibility of setting custom configurations, users could monitor different parameters according to their needs.
For this project, no new sensors have been developed. However, ARQUIMEA experience in microelectronics design for space has been used within the project to assess the possibility to integrate the overall sensor acquisition electronics in a single chip, enabling smooth integration into the biofeedback suit, as well as lower consumption in the overall biofeedback sensor subsystem. The implementation of this chip in a further project continuation would be beneficial for optimizing both the space and terrestrial applications of the proposed sensing system.
Mechanical sensors subsystem
A set of sensors was included in the active biofeedback suit for the measurement of the status of actuators and mechanical parts of the suit. The signals obtained from these sensors are used by the different controllers to handle the actuation of the artificial muscles and to take decisions from the status of the user joints. These sensors include:
- Position sensors for the actuators (artificial muscles).
- Force sensors for the actuators (artificial muscles).
- Torque/position sensors to obtain the state of the joints
- Temperature sensors for controlling the temperature of actuators.
Apart from its use in the propose application, potential terrestrial applications of these sensors can be found in different sectors, such as industrial, robotics…
Artificial muscle subsystem
The active biofeedback suit is able to exert resistance stress in order to force human body to exercise and train. The forces to be applied at the legs target two levels: resistance forces in order to induce the skeletal muscle operation, simulating gravity forces and massage forces in order to stimulate the lower limb and induce the blood circulation from upper to lower limb. For the resistance forces an artificial muscle with high power/mass ratio, high resilience, low relative deformation (muscles are very large) and low speed is sought. To this end, according to the preliminary technology trade-off, SMA fibers are considered the best candidate.
For the massage forces, the most suited technology is EAP, since large relative deformation and low forces are required. The stockings must apply annular forces around the thigh, small forces (massage force requirements are very low). Recent developments based on dielectric elastomer bands for active bandage have shown feasibility of this approach.
The SMA/EAP technology validated in the frame of the project boosted a further development of actuating systems for both space and terrestrial applications. In the space field, besides the proposed artificial muscle applications, STAMAS has eased the improvement on the performance of already existing SMA based actuators, such as hold-down and release mechanisms, pin pullers or rotary and linear actuators. Specifically, the knowledge acquired by ARQUIMEA in SMA manufacturing, characterization and control allowed the company to use these materials for a more efficient actuation of its low-shock, low-weight, non-explosive space devices. Such characteristics are also very positive for other terrestrial applications, such as medicine (smart implants, artificial muscles…) or nuclear (radiation immune tools and devices for remote handling…).
Section 6 of the present document describes the expected potential products and the exploitation strategy to be implemented per each partner of the STAMAS consortium with regard to its own particular foreground to be obtained.
EAP dynamic limb compression bandage
The innovative EAP compression bandage developed in this project is expected to lead to potentially exploitable products and technologies not only suitable for space suits but also for different applications. In particular, the EAP-based compression bandage might find applications in the following specific examples of products:
1) Massage devices for patients suffering of malfunctioning of the lower limbs circulatory system: pathological or gravity-induced malfunctioning of the lower limbs circulatory system are currently addressed with both static or dynamic compression systems such as compression stockings and pneumatic compression sleeves. In particular, such compression systems are utilized as a treatment for the prevention of deep vein thrombosis, orthostatic hypotension and other venous-return related problems. However, the static compression offered by compression stockings was proved to be less effective than the time-dependent one provided by intermittent pneumatic compression systems. On the other hand, the latter require the use of bulky pneumatic cuffs and a pumping box, resulting impractical in many conditions.
The developed EAP compression bandage overcomes the shortcomings of both compression stockings and pneumatic compression systems, allowing for the development of conformable, light-in-weight, low-power consuming, and noise and heat free wearable systems or garments able to provide dynamic compression actions distributed over different body portions.
2) Haptic devices for man-machine interfaces (e.g. for virtual reality systems): in this case, evolutions of the devices might be used to develop soft, conformable, light-in-weight, low-power consuming, and noise and heat free wearable systems aimed at providing man-machine interfaces with actuating functions, either at low or at high frequencies. Virtual reality systems are just an examples of possible systems that might benefit of these new technologies.
3) Safety systems for drivers or other operators (e.g. use of vibrations as an alarm integrated within wearable systems): in this case, evolutions of the devices might be used to develop soft, conformable, light-in-weight, low-power consuming, and noise and heat free wearable systems aimed at allowing different kinds of operators to perform tasks more safely. A specific example is represented by drivers of vehicles. Here, the driver’s suit/garment or gloves might be fitted with conformable alarm systems alerting the driver with vibrations in case of need or danger (e.g. warning systems in case of incipient sleeping detected by external sensors).
SMA actuators
SENSODRIVE has gained knowledge on the application of SMA actuators in force/torque controlled systems including the sensors needed for those applications. The combination of SMA actuators with existing control know-how enables SENSODRIVE to offer engineering services in a wide range of potential applications and possibly enter new markets.
Furthermore, SENSODRIVE developed bending beams with a digital electronic interface (SPI) that can be used in upcoming projects.
A miniature PCB to amplify and digitize the low-voltage signals from the bending beam was developed. It was used in the STAMAS-Project to connect the bending beams to the sensor module and to the controller. SENSODRIVE will use this PCB in other projects and will continue to do so.
The sensor module, a PCB connecting various sensors (temperature, bending beam, incremental encoder, etc.), with diverse interfaces (analog, SPI, RS485) to the controller via CAN will be used in other projects where distributed sensing and digitizing is required.
Potential users of the technology
As stated before, STAMAS project pretends to extend the use of some fairly mature terrestrial actuation technologies into new innovative space applications. Nevertheless, project foreground also shows attractive potential non-space usage. In this section, both markets – space and non-space – are discussed identifying potential users and advantages provided by the technology. Apart from the specific applications described below, STAMAS works have provided a deep knowledge in new configurations and control of SMA materials in force and position. This allows a wide bunch of new potential uses for these materials for both space and terrestrial, such as more accurate devices, flexible actuators, “snake” robotics, super elastic elements with variable and controllable elasticity, etc.
Space applications
The main project result is the technology necessary to develop a future astronauts’ suit, a “smart-suit” using SMA and EAP, to mitigate the effects of weightlessness and motor inactivity on astronauts during the space missions. Therefore, the use case of STAMAS in space is restricted either to long manned missions (i.e. long stays at the ISS and future missions to Mars and similar) or for training and preparation on Earth. In addition, in most of the cases one single device will be used by several astronauts, so no high amounts of units per customer or mission are expected to be sold.
The following table lists the target groups that are potential buyers or stakeholders of STAMAS technology and thus, at which the exploitation activities will be addressed:
TARGET GROUP REASON FOR DISSEMINATION EXPLOITATION OFFERED BENEFITS
Policy and decision makers
(government agencies engaged in activities related to outer space and space exploration) Awareness
Understanding Suggestions for new legislation and barriers to development
Space research community Involvement Research topics. Take up of innovations and adaptations
European Space Industry Involvement
Action Information and solutions that can adapt terrestrial products and services for space applications
New ways of working and collaborating
Efficiency and innovation
End users: worldwide space agencies Awareness
Action Driving innovation for space missions through technical competence and a strong customer focus
Other stakeholders Involvement
Action Information and solutions that can improve products and services.
New ways of working and collaborating
Efficiency and innovation
Media Awareness Further dissemination
Public sector actors such as Space Agencies and Policy Makers are considered as a priority, due to the applicability that STAMAS results may have in their programs and future actuations. Other interesting target of the exploitation activities will be the mass media, thanks to their potential to spread the results.
Non-space applications
SMA/EAP based actuation systems are quite extended in different terrestrial sectors, such as: automotive actuators (low-weight actuators for opening the trunk, adjusting the rear view mirror, etc.), robotics (such as robotic fingers and hands), aeronautics (morphing flaps and engine parts) or instrumental, stents and implants in medical field. All those sectors are also potential stakeholders, so the developed technologies will be also disseminated and exploited with them.
More specifically, within the STAMAS project two devices have been developed so far – hand and ankle – that can be commercialized as standalone products mainly for medical purposes:
physiotherapy/rehabilitation and support to elderly or people with reduced mobility are the most promising applications. Another one is the use of the technology for elite sport training; here we can find a twofold application: to get recovered from an injury in hands or ankles, or to train and strengthen those parts.
The following table shows some of the main players to be reached in order to tackle this potential market:
TARGET GROUP REASON FOR DISSEMINATION EXPLOITATION OFFERED BENEFITS
Governmental decision makers Awareness
Understanding Approval of the devices for medical use
Hospitals, specialized clinics and rehabilitation centers Awareness
Understanding New devices for more effective treatment
Nursing homes Awareness
Understanding Technology to ease the life of the elderly
Sport centers and sport clubs Awareness
Understanding New training and injuries recovering systems
Medical laboratories Involvement New potential products to be commercialized
The fact of involving specialized medical companies as commercial partners is mainly due to the complex and costly process required to validate a new technology for medical human applications. Furthermore, a strategic commercial partner will certainly ease accessing hospitals, clinics, distributors and end users.
In the industrial sector, SMA actuators could, for instance, be used as valve actuators. Another field is augmented reality where force feedback solutions with miniaturized actuators are required. The actuators could also be used for training or supportive systems in health care.
For controlling these systems knowing the sensor signals are mandatory. With the help of Sensor Module, signals of various sensors can be read and digitalized locally and sent to the control. The system is less sensitive and can be used in areas with high electric magnetic field disturbance. (i.e. plant engineering and construction). Another advantage is the reduction of harness due to a bus system leaving space for other possibilities.
Socioeconomic impact of the project
The entire foreground involved in the execution of this project is in line with the premises and objectives detailed in the European 2020 Strategy and in the last published European Space Policy “Towards a Space Strategy for the European Union that Benefits its Citizens”. According to these objectives, it is crucial to build a competitive European Community and contribute to the smart, sustainable and inclusive growth of Europe, taking the premise of knowledge and innovation as a starting point; STAMAS perfectly fits in this target. One of the essential initiatives included within these strategic objectives for European Community is to develop an effective space policy to provide the tools to address some of the key global challenges. Hence, the STAMAS project is expected to directly or indirectly provide part of the necessary technology to improve space initiatives and innovations and place Europe in a better competitive standing.
The European Space Policy basically considers a few priority actions conceived for giving response to three type of needs: social (combating climate change, civil security, humanitarian and development aid, transport and information, etc.), economic (generating space knowledge and products, promoting innovation, competitiveness, growth and job creation), strategic (cementing the EU’s position as a major player on the international stage and contributing to the Union’s economic and political independence).
According to this Policy, the improvement of the European Space Industry Competitiveness will significantly contribute to the overall European Competitiveness. Space is a key sector for supplying independence to the economy in Europe. A plausible deficiency of this sector is the low concentration of SMEs. One of the main objectives of this sector is the steady, balanced development of the industrial base as a whole, including SMEs, greater competitiveness on the world stage, non-dependence for strategic subsectors such as launching, which require special attention, and the development of the market for space products and services. On the other hand, this Space Policy requires also a solid technological base and competitive space industry. This Policy also points out the need for developing key generic technologies. So that, according to this, the STAMAS project contributes to the fulfillment of the strategic objectives of the European Space Policy, providing disruptive and innovative research into the space domain and increasing the number of competitive SMEs operating in the space sector.
With regard to its contribution to the European Space Work Programme 2012, STAMAS primarily helps reaching goals set within the Theme 9 (Activity 9.3) as the development proposed in STAMAS contributes to translate terrestrial technologies into the space domain. Specifically, STAMAS project has adapted SMA and EAP actuators based technologies for its utilization in a smart space suit. As explained before, these actuation technologies are commonly used in the last few years in numerous of industrial, non-industrial and medical applications.
The STAMAS project is also considered as high-impact research due to the very innovative character of the developments involved. Artificial muscles have never been considered for its utilization in space environment and consequently, several technical risks are associated, however, the background expertise and commitment of the partners involved has contributed to the success of the project.
Additionally, the targets of the STAMAS project are in line with the Europe 2020 Strategy. This policy puts forward three main priorities: an economy based on knowledge and innovation; promotion of an efficient, greener and more competitive economy; and fostering a high-employment economy. Among these general targets, special attention is paid to strengthen knowledge and innovation. Currently, R&D spending in Europe is below 2%, compared to 2.6% in the US and 3.4% in Japan, mainly as a result of lower levels of private investment. The fostering of private investment in R&D is essential to cover this gap and make Europe a more competitive area. Under this target, numerous initiatives have been proposed in the Europe 2020 Strategy.
On the other hand, building a sustainable and competitive economy through developing new processes and technologies, including green technologies, are key actions that contribute to the improvement of the competitiveness of Europe. Under this general target, various initiatives have also been proposed, standing out in the frame of this project “the development of an effective space policy to provide the tools to address some of the key global challenges”.
STAMAS indirectly contributes to the achievement of objectives within the 2020 Strategy. It mainly helps increasing the percentage of private investment in R&D, especially by SMEs with the participation of ARQUIMEA and SENSODRIVE. Furthermore, STAMAS is a challenging project studying the utilization of efficient and innovative technologies in the space domain. Therefore, STAMAS project provides technological tools for improving European space competitiveness as it is claimed in the Europe 2020 Strategy.
So that, STAMAS project is part of the private investment on R&D coming from SMEs that will partially mitigate some fundamental weaknesses of the actual European economy. STAMAS project gives evidence of the new business conscience implanted in the SMEs business structure focused in increasing R&D and innovation investment as an effective measure for fighting actual crisis.
Finally, STAMAS project has also contributed to the generation of high-skilled personnel across scientific and technical disciplines that will contribute to the aerospace field. The personnel employed on this project has received from their respective employers and the rest of consortium member’s world-class technological training that enable them to compete on an international stage when the project reaches its conclusion. Therefore, the European Union has gained a highly skill and well-trained workforce of personnel specialized in aerospace, microelectronics, systems engineering, automation, etc. An increase in employment in related areas is expected if project achieve successfully the objectives that have been established.
The STAMAS consortium considers this project as an important step necessary to bring SMA and EAP based actuation technologies into the space market. The nature and main features of this type of technology makes these actuators appropriate for space applications.
After the project, partners are expected to continue working on further fundamental knowledge and optimization of artificial muscles to create a more feasible, high performance and more durable technology with more applicability in the space domain. The industry partners are large and well established companies with the required capacity to drive this towards full commercialization, while R&D partners will continue the more basic and fundamental research.
Socioeconomic impact: terrestrial applications
Out of space, the terrestrial applications identified for STAMAS foreground will mainly have a positive socioeconomic impact in the healthcare and wellbeing areas. The use of SMA- and EAP-based artificial muscles in physiotherapy, prosthetics, injuries recovering and assistance to impaired people allows the implementation of new treatments and solutions that will improve the currently available technics, in terms of performance and recovery time. This will not only have a significant social impact in the life quality of the users, but also economic, thanks to the expected cost reduction due to shorter-time treatments and the use of more efficient technologies.
Regular training with the STAMAS suit will improve the astronaut’s health condition in orbit by reducing (or avoiding) amyotrophia and bone antrophy. On earth, the results of the STAMAS-project can be used to support elderly and impaired people by reducing bone abrasion and avoiding injuries. In medical institutes training capabilities for people who are in recovery after a stroke might be improved using the results of the STAMAS-project.
Furthermore terrestrial exo-skeletons enable people to take part on life in an active way, while reducing stress in people’s occupational activities so that they are able to stay longer in their profession and gain a high recreational value.
On the other hand, the wide expertise acquired in STAMAS with regards to the control of the SMA materials in force and position also supposes a clear breakthrough that will help boosting the use of this technology in general for terrestrial applications to replace less effective technologies. New configurations of SMA based devices will be possible. The main advantages of these materials (memory effect and super elasticity) can be better exploited, not only for medical, but also for general applications, such as industrial, automotive or avionics. Altogether represents a clear economic impact.
List of Websites:
www.stamas.eu
ARQUIMEA (Project Coordinator)
Mr. Marcelo Collado: mcollado@arquimea.com
DLR (Deutsches Zentrum Für Luft Und Raumfahrte
Mr. Thomas Hulin: Thomas.Hulin@dlr.de
ETH (Eidegenössissche Technische Hochschule Zürich)
Mr. Robert Riener: robert.riener@hest.ethz.ch
UNIPI (University Of Pisa)
Dr. Federico Carpi: f.carpi@qmul.ac.uk
SD (SENSODRIVE GmbH)
Mr. Norbert Sporer: norbert.sporer@sensodrive.de
UC3M (Universidad Carlos III De Madrid)
Dr. Luis Moreno: moreno@ing.uc3m.es
