Antidisturbance Speed Control for Induction Machine Drives Using High-Order Fast Terminal Sliding-Mode Load Torque Observer

Speed loop is the key factor affecting the performance of induction machine (IM) drives. Conventionally, the proportional integral (PI) controller is applied for its simple implementation and static-errorless; however, its performance degrades apparently under sudden external load torque changes. To address this problem, this paper presents a nonlinear control strategy, combining the conventional PI control with a high-order fast terminal sliding-mode (HOFTSM) load torque observer. The external load torque is estimated online by the proposed HOFTSM observer, and then the estimated torque is used as feed-forward compensation for the PI controller. Moreover, the designed HOFTSM observer shows superiorities in fast convergence rate and chattering elimination. Comparison experiments show that the load torque rejection of the IM speed loop is significantly enhanced by using the proposed approach.