Detection of faults in flight control actuators with hard saturation and friction non‐linearity

Expeditious diagnosis and prognosis in mission critical flight control actuation system is essential to prevent loss of aerospace vehicles on impending failures. This paper presents the application of the additive form of the Unscented Kalman Filter (UKF‐A) estimator for detecting faults in actuators with significant saturation and friction nonlinearity. An electromechanical flight actuator based on a DC torque motor is considered. The complete dynamics of the actuator including mounting structure stiffness, load dynamics, compensators, power amplifier with current loop and saturation nonlinearity, along with friction nonlinearity is considered. Capability of the method for detecting faults like changes in motor coil resistance and inductance, torque constant and viscous friction coefficient in the actuator under realistic input conditions is demonstrated. The method presented is attractive for real time implementation as only a single estimator is used for fault diagnosis. Robustness of the scheme to sensor noise and external disturbances is also presented.