Sliding Mode Speed Control for Predictive Torque Control-Based Induction Machine Drives Based on Adaptive Variable Rate Reaching Law and Disturbance Extended Sliding Mode Observer

For the predictive-torque-control (PTC) based induction-machine (IM) drives, to promote the speed tracking performance as well as the robustness against various unknown disturbances, such as friction, external load disturbance and parameter mismatch. A sliding-mode control with adaptive-variable-rate reaching law (SMC-AVRRL) and a disturbance-extended sliding-mode observer (DESMO) is proposed. First, the speed loop of PTC which utilizes the classical PI control is analyzed. It indicates that the control performance of the PI controller degrades apparently under sudden load disturbances and induction-machine parameters mismatch. Then the sliding-mode control with adaptive-variable-rate reaching law is proposed. Taking the typical reaching law, namely exponential reaching law (ERL), as a comparison object, the AVRRL method can reduce the chattering and convergence time simultaneously. The stability of the proposed SMC-AVRRL is analyzed by the Lyapunov stability theory. Moreover, to further enhance the anti-disturbance capacity, the proposed SMC-AVRRL is then combined with a disturbance-extended sliding-mode observer (DESMO), named the SMC-AVRRL + DESMO method. The experimental results show that the proposed SMC-AVRRL + DESMO method can not only achieve high speed tracking accuracy, but also achieves better robustness.