An equivalent-input-disturbance approach for current sensor faults estimation and rejection in permanent magnet synchronous motor drives

Abstract

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.

An improved sliding-mode observer-based equivalent-input-disturbance approach for permanent magnet synchronous motor drives with faults in current measurement circuits

“…The maximum steady-error between the estimate and its reference was 0.175 A. (b) In the case of the SMO-EID method in Huang et al (2020) (see Figure 8(b)): the maximum value of the surge of the estimate was about 79.8 A at t = 0:005 s, and the estimate reached its reference at about t = 0:012 s. When the fault occurred at t = 0:4 s, there was still a surge and its maximum value was about 22.2 A. The estimate reached its reference at about t = 0:4016 s again.…”

“…The gain of the improved SMO was chosen to be We compared with the SMO-based EID (SMO-EID) method in Huang et al (2020) and the conventional EID one to validate the effectiveness of the designed improved SMO- Figure 4 shows the actual speed and its reference. The actual speed reached steady state at about 0.02 s. There was a small surge when the load torque suddenly changed from 0 Nm to 5 Nm at t = 0:2 s, and reached steady state at about 0.22 s again.…”

“…Through the comparison of the above results, we find that the main drawback of the SMO-EID approach in Huang et al (2020) is that the tracking accuracy was not high and the surge and fluctuation were big because it did not consider the influence of speed on the dynamic estimation error. Furthermore, the designed ISMO-EID method had faster response-speed and higher tracking accuracy than those of the conventional EID approach.…”

“…The EID method is effective in rejecting disturbances from control input channels and does not need to know the inverse model of a system (Cai et al, 2019;Wu et al, 2020). The basic idea of the EID is shown in our previous works presented in Huang et al (2019Huang et al ( , 2020 for the rejection of disturbance or a current sensor fault in PMSM drives. In this paper, an improved SMObased EID is investigated aimed mainly at high-precision and robust estimation and rejection of faults in current measurement circuits for a PMSM drive.…”

“…That is, the structure of an original system is not changed and the risk of system instability is decreased. (b) Unlike other works (Huang et al, 2019(Huang et al, , 2020, a system-error-dynamics matrix is decomposed into speed-dependent and speed-independent parts. A decoupling term based on the speed-dependent part is introduced to eliminate the effect of motor speed on the estimation accuracy of improved SMO.…”