Continous sliding mode control of DD robot mechanism

Abstract

In this paper, a nonmodel-based discrete-time chattering-free sliding mode control scheme is applied. The distinctive feature of the scheme is its robustness to different initial condition values and to parameter mismatch. Nonlinear control principles are used, namely the combined feedforward and the robust negative feedback part based on the VSS controllers. In the discrete-time expression the discontinuous operation of controllers in the sliding mode has been replaced by the continous one. In this way, the chattering of control input has been eliminated and the excitation of the dynamic system without high frequency oscillations has been achieved. The proposed control solution is near an ideal control function in the sliding mode. Unlike other algorithms intended to avoid chattering, this nonmodel based approach uses only the information about the distance from the sliding mode manifold to derive the control. The advantage of the proposed control scheme prevails over the conventional model-based control scheme since no precise knowledge of mathematical model is necessary. In order to implement the control, only the structure of input matrix and the mean values of its parameters must be known. The parameters of the control depend only on the plant's gain matrix and the gradient of the sliding mode manifold. The proposed control scheme is applied on a mininal cofiguration direct drive robot mechanism.