HYBRID CONTROL WITH SLIDING-MODE PLUS SELF-TUNING PI FOR ELECTRICAL MACHINES
Ziqian Liu - Qunjing Wang
This paper presents an approach toward the design of a hybrid speed control with sliding-mode plus self-tuning PI for induction motors. As the variations of both control system parameters and operating conditions occur, the conventional control methods may not be satisfied further. Sliding-mode control is robust with respect to both induction motor parameter variations and external disturbances. By embedding a self-tuning PI control into the sliding-mode control, the chattering problem, which is the main disadvantage in sliding-mode control, can be suppressed. Meanwhile, PI parameters are derived by applying the method of gradient descent optimization to the parameter space to achieve self-tuning online. This makes the PI control robust to changes in the induction motor drive. In addition, a low-pass filter is put after speed controller to smooth discontinuous control signal in order to achieve a smooth torque control. Simulation results show that good transient and steady state responses can be obtained by applying the proposed control, ie, the system achieves fast response, overshoot suppression, zero steady-state error, and strong robustness..
Keywords: sliding-mode control, self-tuning PI control, gradient descent optimization, hybrid speed control, indirect vector control, induction motor