Modified sliding mode speed controller for vector controlled induction motor drive

Sliding mode controller with boundary layer (SLMB) had been proposed by Slotine to overcome the chattering problem associated with conventional sliding mode controller (CSLM). However, if the boundary layer chosen is large then the dynamic response of the SLMB controller becomes slow and therefore degrades the performance of the controller. In order to overcome this problem, in this paper we propose a modified sliding mode controller with boundary layer (MSLMB). The MSLMB uses an additional continuous control term, which measures the distance of the state trajectory from the switching surface. The inclusion of this additional continuous control term makes the control action strong and therefore provides improved transient performance while retaining all the attractive properties of conventional SLMB. The performance of the MSLMB controller is examined through simulation and experimental studies by applying it to control the speed of a vector controlled induction motor drive system. Test results obtained experimentally show improvements in transient performance over conventional SLMB and therefore demonstrates the validity of the proposed MSLMB speed controller.