Position Sensor Fault-Tolerant Control of IPMSM Drives Using Hybrid Sensorless Estimation Over the Full Speed Range

This study proposes a new hybrid sensorless control estimation structure that provides a fault tolerant control (FTC) when a position sensor fault occurs in permanent magnet synchronous motor (PMSM). The proposed hybrid estimator combines two techniques with using speed dependent weighting transition. High frequency signal injection is applied at standstill and low speeds, while at higher speeds, an extended Back-EMF observer takes over. Within the transition band, the two estimators are combined by a vectorial cross-fade, resulting in a continuous position estimate. The sensor fault is detected by monitoring the angular difference between the sensor output and the complementary sensorless estimation. The residual threshold is adjusted dynamically so that false triggers and missing triggers are avoided during acceleration and deceleration. Additionally, a decision making delay is added to prevent noise induced false alarms. When the fault is detected, the position feedback is smoothly switched to sensorless operation without interruption. The proposed strategy is tested across the full speed range of the PMSM via simulation, including steady-state, transient, and sensor failure scenarios. As a result of these scenarios, a new hybrid sensorless estimation structure capable of handling low-amplitude sensor biases in the position sensor across the full speed range has been designed. Also, the Back-EMF estimation was compared with the Extended Kalman Filter at medium and high speeds, demonstrating a lower error detection threshold, quicker response, and reduced computational load.