Reducing the chattering using the generalized variable structure control applied to a manipulator arm

The authors present experimental results, in step response, of the generalized (GVS) and the classical (CVS) variable structure control law for control of a manipulator. The methodology of synthesis has been given for the implementation of this new control law GVS. Experimental results have been presented for the three axes of robot. A comparison of performances of the CVS and GVS algorithms is been undertaken for parameter variations of the plant and for external disturbances. Obtained results show that the two controls are robust to parameter variations of the plant (payload variation) and insensitive to external disturbances, since the dynamics of system is fixed by the sliding surface. In sliding mode, the system evolves as a system of first order. The rapidity of the two control laws is comparable (the time response is practically the same). The chattering due to the discontinuity of control has been reduced by the GVS control in comparison to the CVS control. Finally, obtained results from implementation show advantages of this new technique of GVS control of viewpoint of the chattering, as well as the robustness of the two algorithms of variable structure control to errors of modelization and to external disturbances; this despite the linear approximation made on the dynamic model of robot. Therefore, the variable structure controllers present a solution to problems of the control of nonlinear systems and especially in the domain of robotics