Decoupled disturbance compensation under control saturation with discrete-time variable structure control method in industrial servo systems

This paper presents a new decoupled disturbance compensation scheme with discrete-time variable structure control, to provide asymptotic convergence property even when the control input is driven beyond saturation limits. Discrete-time variable structure control (DVSC) method with a decoupled disturbance compensator (DDC) has been widely used in many applications, attributed to the robust properties in the presence of external disturbances and parametric uncertainties. However, when the control input is driven beyond saturation limits, the DVSC method with DDC cannot provide robust performance. This paper develops a disturbance estimation scheme that can maintain the asymptotic convergence property of the disturbance estimation error dynamics in the presence of control saturation. Experiments are performed on a servo system, and experimental results show that the developed method performs well in the presence of control input saturation.