Actuator Remaining Life Estimation Under Fault Tolerant Operation

Recently, a consistent push towards a “more electrical” approach for drive systems in the aerospace and automotive industries has fueled interest in condition monitoring and prediction of impending electronic system failures and remaining useful life (RUL) of critical components. The ever-expanding use of the electrical actuator and power drives significantly increases the possibilities of applying reconfiguration techniques under fault condition for extended operation of electric machinery, including electrical actuators. Consequently, operation in the fault tolerant mode has a growing interest and potential wide-spread application. The modern actuator mainly consists of a brushless DC motor (BLDC) that is composed of stator winding, a permanent magnet rotor and Hall Effect sensors. The temperature in the actuator winding, estimated using a thermal model of the system, presents a simplified process that accounts for precise actuator losses using the measurement of the phase current and one external temperature. The remaining useful life estimation is based on a segmented-modified Arrhenius model with variable coefficient depending on the level of stress the actuator is exposed to, corresponding to the fault tolerant technique applied. The methodology developed here is intended for a standalone system but is fast enough so that, if required, can be embedded in the actuator microcontroller providing vital information about the sustainability and duration of the fault tolerant technique applied in real time. The fault tolerant strategies included in this paper are system operation under transistor and winding suppression and its effects are analyzed to the actuator winding, permanent magnet rotor and the three embedded Hall Effect sensors. Other methods such as the Power law are also examined. The implementation of the technique applied is shown in an open source controller and actuator test bench.