Barrier Lyapunov Function Based Output Control and Extended State Observer for a Manipulator with Time-Varying Output Constraints and Uncertainties

In this paper, an adaptive output feedback controller is proposed for an n-degrees of freedom (DOF) manipulator with the time-varying output constraints, the unmeasured variables, and the external disturbances. An extended state observer (ESO) is employed for estimating not only the external disturbance but also the unmeasured states in order to improve the accuracy of the closed-loop system. When the barrier Lyapunov function is used to develop the proposed control with the ESO, the output constraints of the robotic manipulator are overcome. Finally, some simulations of the proposed control are conducted on a 3-DOF manipulator to verify the effectiveness of the proposed control with the presence of unknown frictions, external disturbance, and the time-varying output constraints.