A class of fuzzy output feedback tracking controllers for robot manipulators with bounded torque inputs

To deal with the problem of the output feedback tracking (OFT) control with bounded torque inputs of robot manipulators, we propose a generalized fuzzy OFT controller based on a class of saturation functions. First, considering the fact that the output toque of joint actuators is limited, a general expression for a class of saturation functions is given. Taking it as template, different kinds of specific saturation functions can be created to be applied in the saturated control law. Second, to carry out the whole closed-loop control with only position measurements, a linear filter is involved to generate a pseudo velocity error signal. As a third contribution, a fuzzy self-tuning regulator is added to obtain an adaptive performance in tackling the disturbances during the tracking control. Moreover, an explicit stability proof of the control systems based on the theory of singularly perturbed systems is presented. Finally, numerical simulations on a sample controller are implemented to verify the effectiveness of the proposed approach.