Backstepping sliding mode controller for a co-ordinated links (COOL) robot arm

In this paper, a backstepping sliding mode controller is proposed for trajectory tracking of a robotic arm. The controller gain is adaptively tuned to tackle unknown uncertainties and a dynamic surface controller logic is used in the final stage to get rid of the explosion of terms problem inherent in backstepping design. Also, the relative degree of the system is increased by one so that the control law is finally obtained as an integral of a discontinuous signal thereby reducing the chattering prevalent in the sliding mode. The combination of the backstepping and sliding mode control methods makes the controller robust against both matched and mismatched uncertainties. Simulation studies conducted on a 3 degrees of freedom co-ordinated links (COOL) robot arm shows effectiveness of the proposed controller.