Simple Fault-Tolerant Control of a Permanent Magnet Synchronous Motor with Faulty Position Sensor

In speed control of permanent magnet synchronous motors, the measured position signal is usually used for motor commutation and speed calculation. Since the position and speed signals are fed back to the controller, a sensor fault during operation is a severe problem. This contribution proposes a simple linear estimation method that reconstructs rotor position and speed. A comparison between measured signals and estimates allows to detect faults during operation. Furthermore, the estimated signals are used for reconfiguration after the occurrence of a fault. The fault detection logic is based on an adaptive threshold facilitating an operating point-dependent compromise between robustness against uncertainties and sensitivity to faults. Measurement results show that no faults are detected during fault-free operation, whereas the proposed algorithm instantly recognizes the sudden supply voltage outage of the used in-cremental encoder. The investigated reconfiguration mechanism allows for the control of the motor at medium and high speeds after the detection of a fault. This can be used to decelerate the motor in a controlled manner.