Instrument fault detection and compensation scheme for direct torque controlled induction motor drives

The effects of instrument faults in direct-torque-control-based induction motor drives are analysed and an instrument fault detection isolation scheme (IFDIS) for the drives is proposed. The IFDIS detects and isolates the incipient fault(s) of a speed sensor and current sensors in real-time. The scheme consists of an adaptive gain scheduling observer as a residual generator and a special sequential test logic unit. Although the IFDIS is a single observer scheme, it has the function of fault isolation that normally only a multiple-estimator-based IFDIS possesses. Simulation results show the detection and isolation performance of the IFDIS and the applicability of the scheme to fault tolerant control system design.