Real-time fault detection and accommodation for COTS resolver position sensors

Resolver sensors are utilized as absolute position transducers to control the position and speed of actuators in many flight critical applications where robustness, accuracy and ability to operate in extreme environmental conditions are required. To ensure these requirements, several designs for self-diagnosing sensors were proposed in the past. However, such designs require additional instrumentation leading to further development and certification costs. To mitigate such costs, a methodology was sought to achieve similar self-diagnosis capabilities that can be retrofitted to already existing commercial off-the-shelf (COTS) resolver sensors. To achieve this goal, this paper proposes a new approach for real-time tracking of resolver faults with the ability to perform real-time fault detection. However, the additional benefit of this approach is the ability to accommodate faults in real-time once a fault is detected. The primary fault studied in this paper is resolver channel mismatch. A formulation based on the physical operating principles for a resolver sensor is provided. Diagnostic measures are identified for use in statistical-based fault-detection routines. Then, estimates for the resolver mismatch are tracked using a time-varying Kalman filter. Fault accommodation is achieved by applying the tracked estimates to adjust for the resolver mismatch. Finally, the fault detection and accommodation routines are evaluated in Simulink for an electro-mechanical actuator (EMA).