Trajectory tracking control of a 6-DOF hydraulic parallel robot manipulator with uncertain load disturbances

This study addresses the trajectory tracking control of a 6-DOF (degrees of freedom) hydraulic parallel robot manipulator with uncertain load disturbances. As load disturbances are the main external disturbances of the parallel robot manipulators and have a significant impact on system tracking performance, many researchers have been devoted to synthesize advanced control methods for improving the system robustness under the assumption that load disturbances are bounded. However, load disturbances are uncertain and vary in a large range in real situation happening in most hydraulic parallel robot manipulators, which is opposed to the assumption. In this paper, the load disturbances are directly measured by force sensors. Then a sliding mode control with discontinuous projection-based adaptation laws is proposed to improve the tracking performance of the parallel robot manipulator. Simulations and experiments with typical desired trajectory are presented, and the results show that good tracking performance is achieved in the presence of uncertain load disturbances.

Research Highlights
► The trajectory tracking control of a 6-DOF hydraulic parallel robot manipulator with uncertain load disturbances.
► The load disturbances are directly measured by force sensors.
► Good tracking performance is achieved in the presence of uncertain load disturbances