PD output feedback control design for industrial robotic manipulators

This paper presents an output feedback PD-type controller for the trajectory tracking control of robotic manipulators. A linear observer is used to estimate the unknown velocity signals of the nonlinear manipulator. In the first part of this paper, we propose a PD-like output-feedback control law. The Lyapunov method is used to characterize the asymptotic property of all the signals in the closed-loop error model dynamics. This property sets the bound on the tracking error trajectory of the closed-loop system. In the second part, we remove the nominal model dynamics from the control design to formulate a model-independent PD-type output feedback approach. Using an asymptotic analysis for the singularly perturbed closed-loop model, we guarantee that all the signals under the proposed PD output feedback design are bounded and their bounds can be made arbitrarily small by using observer-controller gains. Implementation results demonstrate the potential application of the proposed method on real systems.