Chattering Attenuation Disturbance Observer for Sliding Mode Control: Application to Permanent Magnet Synchronous Motors

In existing sliding mode control (SMC) methods, a disturbance observer (DOB) is employed to achieve disturbance rejection and reduce chattering, which is a major disadvantage associated with SMC and increases with increasing switching gain. However, the disturbance in a DOB associated with SMC is typically estimated using a control input that exhibits chattering. Although the existing methods can reduce chattering using SMCs with DOBs, the estimated disturbance comprises undesirable high-frequency components caused by the control input. In this article, a chattering attenuation disturbance observer (CADOB) is proposed to achieve chattering reduction in the SMC. A frequency spectrum analysis is performed for the control input, estimated disturbance, and controlled state to elucidate the effect of chattering in the control input on the estimated disturbance and controlled state obtained using existing methods. The proposed CADOB is designed to estimate the disturbance with a reduction in undesirable high-frequency components. The frequency response results demonstrate that the effect of chattering in the control input on the estimated disturbance can be reduced by using CADOB, while maintaining the disturbance estimation performance. Moreover, the performance of the CADOB is experimentally validated using SMC in permanent-magnet synchronous motors.