Alleviation of chattering in variable structure control signal for flexible one-link manipulator

A variable structure controller design for the tip position control of a flexible one-link manipulator was presented by Thomas et al. (1997). The control torque obtained using this design methodology was subjected to high frequency chattering. This makes it impossible to implement the controller in practice. The absence of a sign(S) function in the control law makes it impossible to implement the boundary layer technique of chatter reduction where the sign(S) function is replaced by a saturation type function to yield a continuous control signal approximation that confines the system trajectory to a small band neighboring the switching surface. This paper presents a new switching law which not only alleviates chattering in the control signal but also ensures ideal sliding mode motion. Simulation results are presented to verify the claims attributed to the proposed method.