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IMPROVED TORQUE STABILITY OF REACTION WHEELS VIA EMBEDDED DIGITAL WHEEL SPEED CONTROL (ARTES AT 4C.041)

ESA Open Invitation To Tender AO8667
Open Date: 08/07/2016
Closing Date: 14/10/2016 13:00:00


Status: ISSUED
Reference Nr.: 16.1TT.14
Prog. Ref.: ARTES 5 Sub-El. 5.1
Budget Ref.: E/0505-01B - ARTES 5 Sub-El. 5.1
Special Prov.: BE+DK+FR+DE+IT+NL+ES+SE+CH+GB+IE+AT+NO+FI+PT+LU+CZ+RO+CA
Tender Type: C
Price Range: > 500 KEURO
Products: Satellites & Probes / AOCS & GNC / Actuators / Wheels (Momentum, Reaction)
Technology Domains: Space System Control / AOCS/GNC Sensors and Actuators / AOCS/GNC Inertial and Magnetic Actuators
Establishment: ESTEC
Directorate: Directorate Telecom & Integrated Applica
Department: Telecom Technologies, Product& Systems Department
Division: Technologies and Product Division
Contract Officer: Rinaudo, Nicole
Industrial Policy Measure: N/A - Not apply
Last Update Date: 08/07/2016
Update Reason: Tender issue

Objective: The objective of this activity is to improve reaction wheel torque stability and repeatability via the application of an internal wheel speed control loop, and to demonstrate the feasibility and effectiveness by test at Breadboard level. A secondary objective is to assess the possibility of achieving a cost reduction for the electronics via the wholesale migration towards a digital wheel drive electronics. Targeted Improvements: Improved pointing performances, lower mass and lower overall cost solution at spacecraft level. The reaction wheel electronics cost, mass and volume is targeted to be reduced by 25%.A reaction wheel digital signal interface is expected to further reduce costs at system level. Description: All conventional reaction wheels have to face bearing lubrication related phenomena that result in torque instabilities. These, together with any variation/deviation in the reaction torque realisation profile, have an impact on S/C pointing performance. Currently, all reaction wheels for GEO telecom applications are based on heritage designs relying on analogue discrete wheel drive electronics. These are bulky and costly to assemble and test. Further, they impact significantly the system AIT process and are not readily interchangeable with similar wheels from other manufacturers creating potential supply chain issues. The choice of analogue interfaces is driven by current equipment availability and potential re-use. Digital motor controllers and embedded motor speed control are used extensively in other applications and have also been demonstrated on some small wheels. Such approaches have the potential to react quickly to (erratic) changes in the friction torque by rapid local detection of wheel speed changes while simultaneously allowing the integration of several functions in a single component and shrinking the overall electronics. Such an implementation naturally leads itself also to digital interfaces, which open the way for more exchangeability between units. Other approaches also exist (e.g. external to the reaction wheel equipment), but these are likely to lead to higher cost and mass than current products and so are not considered here. The increasing demand for high pointing stability, for e.g. multi-spot missions and optical inter-satellite links, shows a clear need for improving the reaction wheel torque stability. And the digital speed control embedded in the wheel is the most promising way to improve torque stability without large scale bearing technology changes, and potentially leads to important system budget savings at satellite attitude control level. The proposed work logic is the following:­ Define gather requirements (including interface, commanding, mass, cost and performance requirements) - in close collaboration with primes operators covering 20 to 100Nmswheels.­ Propose and study wheel speed control loop algorithms, for the full wheel speed range, enabling the improvement of the performances (in particular torque stability and torque realisation repeatability) as well as the required wheel speed measurement techniques needed to ensure sufficient accuracy over the full wheel speed range. This study shall consider both compatibility with existing Reaction Wheel Assembly (RWA) designs and their wheel speed measurement hardware as well as produce proposals for improved wheel speed measurement solutions. It is expected that different techniques are required for different wheel speed ranges in order to ensure the maximum performance. The algorithms shall also ensure that they are designed such as to not have any adverse reactions with AOCS measurement and control loops (e.g. shall be sufficiently high bandwidth as to fall well outside of the AOCS measurement and control domain). Propose a new electrical design embedding not only the wheel speed loop, but also as many of the required wheel drive electronic functions (motor controller, external interface, housekeeping etc.) in a single component (i.e. FPGAA or ASIC) with the goal of reaching a new WDE design with reduced footprint, assembly/test effort and cost.­ Design, build test this solution at breadboard level and demonstrate the performances achievable with an existing RWA hardware and from there extrapolate what could be achieved with updated RWA hardware and also to determine how much degradation bearing/lubrication or other (e.g. cogging torque) induced torque instabilities could be potentially removed by such methods.­ Propose a roadmap (with associated cost) to reach a recurring fully qualified product based on the concepts demonstrated.

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