Enhancement of sliding mode controller by fuzzy logic with application to robotic manipulators

It is well known that sliding mode control algorithm can give good transient performance and system robustness. However, due to the sensitivity of the sliding mode controller before reaching the sliding surface and the presence of chattering may introduce problems to motion tracking control of robot manipulators. In this paper, a proposed technique to adaptively tune the sliding mode controller gain has been presented. The proposed technique, incorporating a fuzzy logic system as adaptation mechanism of the sliding mode controller with a proposed chattering index, provides a fuzzy logic adaptive sliding mode controller. The proposed controller has been applied to a motion trajectory tracking of a two-degree of freedom polar manipulator. Simulation study has been carried out to evaluate the performance of the proposed controller and to compare its performance with a recent conventional sliding mode controller performance. The simulation results showed that the proposed controller has impressively achieved a highly performance with minimum reaching time and smooth control actions. In addition the results have proven the effectiveness and robustness of the proposed controller to achieve considerable enhancement of the motion tracking of robotics characterized by disturbances and parameter uncertainties.