Tracking Control of Manipulator Based on High-Order Disturbance Observer

This paper develops a composite tracking controller for a two-link manipulator. Because a completely accurate dynamic model for a manipulator is unavailable in practice and because a manipulator generally suffers from all types of unknown external disturbances from its working environment, a high-order disturbance observer (HODO) is introduced. Both the internal and external disturbances are regarded as a total compound disturbance to be estimated by the HODO. To achieve excellent tracking performance of a self-designed manipulator platform for any bounded initial state, a sliding-mode controller is proposed with disturbance estimation compensation. The bounded stability of the closed-loop control system is analyzed with the Lyapunov method. Finally, simulation results and experimental results are provided to demonstrate the effectiveness of the proposed tracking controller.