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Advanced Load Sensing technology for Aerospace Application

Periodic Reporting for period 1 - TecALSens (Advanced Load Sensing technology for Aerospace Application)

Reporting period: 2018-11-01 to 2019-10-31

Future aircraft architectures like more and all-electric aircraft, foresee the use of electrical actuators and more in general a higher level of loads monitoring for primary and secondary flight control and landing gears.
Current load sensors are mostly based on bonded strain gauge and LVDT (Linear Variable Differential Transformer) technologies. More innovative and “smart” components require more reliable and stable load sensors, which overcome the drawbacks of bonded strain gauge technology and, at the same time, enable a smooth integration with on-board electronics. The scope of the TecALSens project is to develop and deliver a load sensor able to enhance current load sensor technology and to provide the aeronautic industry a new class of products ready for experimental validation at on-ground platform level. Air traffic contributes to overall well-being but also to the impact on air quality. Within the Systems ITD Platform new aircraft architecture are being analysed for accomplishing with the environmental objectives set by ACARE: Reduction of CO2 emissions by 50% per passenger kilometre, reduction of NOx emissions by 80%; reduction of perceived noise by 50%.
The more- and all-electric aircraft configurations represent a new approach to overall aircraft architecture: Replacement of hydraulic and pneumatic systems by means of electro-mechanical actuators (EMA) contributes to more efficient fuel burning, to an optimised energy management and therefore to a reduction of pollutant emission.
The implementation of Electro-Mechanical Actuators (EMA) requires the insertion of load sensors for monitoring and controlling actuator’s performance. The TecALSens project addresses all these challenges and focuses on the development of a load sensor able to satisfy this request and suitable for the integration. Main objective of the TecALSens project is the development of a new load sensor based on a sensor technology able to overcome the drawbacks of current load sensors technology like, for instance, bonded strain gauges. The new load sensor must be able fulfil the stringent requirements of an aeronautic device for integration in primary and secondary flight control systems. At the end, the load sensor will be developed up to TRL 5-6.
TecALSens activities have started by collecting and discussing the requirements. The frame for force sensor development has been defined considering electronics development, mechanical design, on-board interfaces and integration of the device in the aircraft.
Four different application have been considered: Load Sensing Drive Strut – LSDS; Electro-Mechanical Actuator – EMA; Landing gear: Pintle Pin; Landing gear: Wheel axle.
All these application have been analysed considering overall feasibility from the point of view of force measurement, accuracy of force measurement , integration of the device and of the electronics.
A general layout of the electronics has been defined and discussed with TM’s team.
RTCA DO160G specifications has been considered for testing sensor performances; A detailed test plan has been prepared and submitted to the TM.
Further, each application has been thoroughly analysed by means of numerical simulations for identifying the most promising position for the sensing element. Mechanical layout and integration of electronics and cables have been considered for design issues.
Regarding the choice of the sensing element, an analysis of currents state of the art force sensor applications in aeronautics and of future insertion of this device has been conducted. Resistive-effect-based load sensor (especially strain gauges and thin-film sensors) are those that better fit to general project requirements considering force range, maturity level reached, applications suggested and expected stability and accuracy. Thin-film based load sensor elements have shown better properties and have been selected as promising technology for the purposes of the project. For this project load sensor will be developed for measuring forces in Z and X directions. The complete load sensor will be tested already at first batch and not a dummy version of it. Design of the whole load sensor – overall layout and mechanical parts, electronics, electrical and mechanical interfaces, has been conducted and finalised.
Sensor body inner geometry has been refined for hosting two thin-film sensors as sensing elements (considering force measurement in two perpendicular directions X and Z). Finite-element simulation have been run for determining load sensor stiffness and sensing element signal amplitude. Sensor inner geometry has been adapted for accommodating two independent electronic units, the cover necessary for protecting the electronics and for the connection to the on-board electronics. Outer geometry of the sensor has been defined for fitting to the inner geometry of the wheel axle. Technical drawings of all components have been completed and CAD-models have been prepared manufacturing. Both electronics PCBs have been manufactured. First article inspection (FAI) has been conducted at tecsis: first results show outstanding results and appear very promising for further tests. Analysis of the solutions has been summarised in a new document. Tolerance analysis of electronics has been prepared; the document is currently under verification at tecsis. Compliance and verification matrices for testing activities, have been prepared and shared with TM.
Project status shows a sound development of the load sensor: Electronics layout, mechanical components and interfaces design are currently mature enough for promising and successful further steps.
Load sensors currently applied on civil aircraft are few and restricted mostly to strain gauge and LVDT technologies. Future trends of aircraft architecture, like for instance more and all-electric configuration, show the need for wider insertion of these devices. The load sensor developed in this project build the basis for a new technology, which is so far not yet available on the market. A load sensor based on the thin-film technology offers several advantages with respect to strain gauges and LVDT: precise and punctual measurement of forces, long-term stability of connection to the hosting structure, very small dimensions, high accuracy, and possibility of a redundant sensor for even higher accuracy, automation of production processes for high quality and repeatability of results.
At the end of the TecALSens project, a new class of load sensors based on the thin-film technology will be available at a high maturation level (TRL 5-6). This opens new possibilities for the introduction of this type of device in the future electro-mechanical and electro-hydraulic actuators for measuring load in landing gears and in other components of an aircraft. More and all-electric aircraft architectures will take advantage of this new product.
Considering societal and environmental challenges more and all-electric aircraft architectures generates a direct effect on the environmental impact of air transport by reducing fuel consumption and the amount of pollutant (less weight, more efficient on-board energy management).
These technologies strengthen European position in a strategic sector like aeronautics by increasing its competitiveness. This supports the innovation of tecsis as an SME by delivering high technical results and enabling the generation and growth of new competences and qualified jobs.
3D CAD overview of wheel axle and load sensor
Printed Circuit Board of load sensor electronics