Subsection Nonsingular Terminal Sliding Mode Control for Single Winding Broken Fault of In-Wheel-motor of Electric Vehicle

The brushless DC motor (BLDCM) is mostly used as the In-Wheel-motor of distributed-driven electric vehicles. Due to operating environment harsh, the BLDCM-EV frequently is in the trouble of single-winding-broken-fault (SWBF). Once the SWBF occurs, it would result in the BLDCM-EV torque huge fluctuation and even the EV is out of control. In this paper, the fluctuation mechanism of electromagnetic torque of BLDCM-EV is studied at both the normal operating mode and the fault operating mode. According to the study, the three phase currents of BLDCM-EV become asymmetrical and unbalance in SWBF, which leads to huge fluctuation of electromagnetic torque. For this reason, a novel fault tolerant control strategy of the two-phase-four-state operation mode is proposed which is based on an inverter topology of three-phase-four-leg. In the normal operation mode, the inverter works at the three-phase-six-state operation mode, whereas in the SWBF mode, the inverter works at the two-phase-four-state operation mode. In addition, the key of the strategy is a proposed new current control algorithm of subsection nonsingular terminal sliding mode control (SNSMC), which can be designed according to the different time segments of motor currents. By the control algorithm, the average output torque of BLDCM-EV can be improved and maintained a constant with a few little ripples; thus, the vibration and the power loss of the electric vehicle are avoided.