Fuzzy boundary layer tuning as applied to the control of a direct drive robot

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Chattering in the control signal is a significant problem in sliding mode control applications. The boundary layer approach is one of the many modifications proposed in the literature to avoid the chattering. In this approach, instead of the discontinuous sliding mode control, a high gain feedback control law is employed. The thickness of the boundary layer is an important design parameter. This paper proposes a fuzzy on-line tuning method to adjust the boundary layer thickness for the best system performance without chattering. The method features the measurement of the chattering in the control signal. Experimental results with a two degrees of freedom direct drive robot arm are presented.