Smoothing out the adaptive variable structure control law for induction motors

This paper presents a new variable structure control law that improves the performance of the control law presented in our previous work [2]. The new smoothed control law reduces the chattering phenomenon of the previous one, and therefore implies less activity control and diminish the mechanical fatigue of the system. The proposed design employs the so called vector (or field oriented) control theory for the induction motor drives and the designed control law is based on sliding-mode algorithm that overcomes the system uncertainties. The proposed sliding-mode control law incorporates an adaptive switching gain to avoid calculating an upper limit of the system uncertainties. The stability analysis of the proposed controller under parameter uncertainties and load disturbances is provided using the Lyapunov stability theory. Finally simulated results show the improvements of the new smoothed control law.