Sliding mode control design with adaptable gains for robotic manipulators

Uncertainty in manipulators is rooted in two factors: error of measurement and parameters uncertainty of dynamics; Hence it is necessary to include it in control design. Sliding mode control (SMC) is a proper approach for controlling uncertain systems. SMC regulates system´s states to a desired dynamics, defined by sliding surface. Gains of control law determine the rate of movement towards sliding surface or maintaining on it. Low value of gains make error and high value of that results in chattering effect. In this paper, a general method is introduced to provide an adaptive gain for the SMC controller based on dynamics of model including its uncertainty in the structure for multi-input-multi-output (MIMO) systems. The structure is expressed for two types of corrective functions: sign and inverse tangent functions. The application of the adaptive SMC is implemented on manipulators in a general manner. An SCARA robot is selected for simulation study showed significant improvement in comparison with conventional SMC.