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Position Control of Induction Motor with a Modified VSC

It has been known that variable structure control(VSC) has theoretically powerful control technique of providing fast response, no overshoot, and very robust control with respect to system parameter variations and disturbances. However, the technique has not become more widely extended in the industrial circles because chattering phenomenon which may excite high-frequency unmodelled plant dynamics and damage to system components exists. In this paper, a modified variable structure control(MVSC) is developed to alleviate these problems, full-order flux observer os to estimate rotor flux without influences for the parameter variations of the motor. and which are applied to the position control of induction motor. While the conventional VSC makes the structure of the system change with high-frequency switching on the center of the one switching surface, in the MVSC two switching surfaces are used to establish a sliding sector. The structure of the system with low-frequency swiching. Therefore, the proposed algorithm has the properties of reducing chattering, reducing the benefits achieved in the conventional VSC, and working even under the influences of parameter variations. Experimental results show the effectiveness of the control strategy proposed here for the position control of induction motor.