Current sensor is commonly used in a permanent magnet synchronous motor (PMSM) drive system. Occurrence of unexpected current sensor faults may cause feedback currents deviation and system degradation, which can be extremely detrimental to the safety of the industrial system with PMSM. This paper presents an estimation and rejection strategy of current sensor faults for a PMSM drive system. Sensor faults in current measurement circuits are treated as system disturbances by constructing a new system plant. A sliding mode observer and an improved equivalent-input-disturbance (EID) estimator are designed for the plant based on the EID theory. Accurate estimates of the current sensor equivalent-input-faults are thus obtained readily. Faults rejection is performed by subtracting the equivalent-input-faults from the control input. This allows an existing controller in a PMSM system to continue to function normally even a current sensor fault occurs. An existence analysis and stability proof are also discussed in detail for the system. Finally, different faults examples and a hardware-in-the-loop experiment are given to demonstrate the efficiency of the method.

The reliability of permanent magnet synchronous motor (PMSM) systems is very important in high-precision industrial drives. However, disturbance or sensor fault may cause the performance degradation of the system. This paper presents an improved sliding-mode-observer (SMO)-based equivalent-input-disturbance (EID) approach for the rejection of faults in current measurement circuits of a PMSM drive. A system model, which contains faults in current measurement circuits, is first constructed by using EIDs in control input circuits. Then, an improved SMO is designed to estimate the equivalent-input-faults. The effect of the faults on the system is rejected based on the EID theory. Moreover, the global stability and convergence analysis is also provided. Experiments and comparisons demonstrate the effectiveness of the method.