Robust Sliding Mode Control Strategy for Variable-Gear-Ratio Magnetic-Geared Machines

Variable-gear-ratio magnetic-geared machines (VGRMGMs) which could achieve adjustable gear ratios, shows substantial application prospects in driving systems. However, the VGRMGMs suffer from dynamic performance deficiencies such as slow dynamic responses and excessive speed overshoots. A robust sliding mode control (RSMC) strategy based on a load torque observer is proposed in this paper in order to improve the dynamic performance of the VGRMGM. A sliding mode speed controller and a torque observer for feedforward compensation in the current loop, is employed to improve the robustness and dynamic performance of the VGRMGM. Under speed-regulation conditions, the RSMC strategy achieves a 6% reduction in overshoot and a 25.4% improvement in response speed compared with conventional PI control. For load-variation conditions, the overshoot is reduced by 5%, and the response speed is improved by 32.1%, highlighting the VGRMGM superior transient performance. Experimental evaluations on a purpose-built test rig validate the enhancement of the RSMC strategy in terms of improved dynamic performance.