Disambiguation of Uniform Demagnetization Fault From Position Sensor Fault in FOC PMSM Applications

Electrification of higher torque density applications in the transportation sector and robotics sector are primarily met with permanent magnet synchronous machines (PMSMs), attributing to their unique properties. However, wide operating temperatures, field weakening controls, and low-quality magnets, lead to uniform demagnetization of rotor magnets. Demagnetization in torque control applications reduce the effective output torque as the output torque is proportional to rotor flux level. Detection of such rotor demagnetization is essential and only second to few key faults from the system perspective. However, static position sensor offset error (SPSOE) is a fault mode that may mask itself as a demagnetization fault. Though the demagnetization fault is irreversible, the SPSOE is remediable avoiding sustained-severe degradation of system performance. The false positive nature of demagnetization detection and the SPSOE are discussed in detail in the paper, and a disambiguation strategy is proposed and successfully implemented. Simulation and experimental results are presented to validate the effectiveness of the proposed strategy.