Switching on the derivative of control to reduce chatter

When applying a classical sliding-mode control based on variable structure systems, a high-frequency chatter appears. This phenomenon, caused by disco ntinuous control, is usually undesirable for most practical applications. T he paper proposes a robust control law for decreasing the chatter, based on a generalised sliding-mode control that switches on the derivative of cont rol instead of the central input itself. This new robust control algorithm will be applied an a SCARA type manipulator arm with three degrees of freed om, in the case of trajectory tracking mode, to show the reduced chatter an d its robustness against manipulated payload variation and external disturb ance. Experimental results demonstrating the advantages and superiority of the generalised variable structure controller over the classical variable s tructure controller are presented.