Complementary sliding mode control with adaptive switching gain for PMSM

Since the control system in a permanent magnet synchronous motor (PMSM) has uncertainties and disturbances, the switching gain is a key factor in effecting chattering in sliding mode control. An adaptive switching gain is proposed for complementary sliding mode control (CSMC) to regulate the PMSM velocity. The proposed switching gain is designed according to system uncertainties. When the value of the sliding modulus is outside the boundary layer, it is positive, resulting in an increase in the switching gain. Conversely, when it is negative, the gain is decreasing. Further, the proposed law considers an arbitrary small vicinity of the sliding manifold, in which the derivatives of the adaptive switching gains are inversely proportional to the sliding modulus to speed up the gain adjustment process. The proposed gain for complementary sliding mode control is applied to regulate the PMSM velocity; comparisons of experimental results show that the proposed gain has a faster gain adjustment process than CSMC and alleviates chattering, resulting in a greater velocity accuracy.