A flow-limited rate control scheme for the master-slave hydraulic manipulator

Rate control is the most used operation method for master-slave hydraulic manipulators. However, the trajectory from the master controlled by the operator cannot completely meet the dynamic limitations and flow restriction of the hydraulic manipulator. Continuous large errors and oscillation will occur due to flow restrictions and high-order dynamics beyond the dynamic boundaries. That significantly limits the velocity tracking performance of a hydraulic manipulator. This paper proposes a flow-limited rate control scheme for the master-slave hydraulic manipulators. The variable velocity mapping is developed, adjusting the velocities to meet the pump and valves flow limits. An adaptive robust rate controller of hydraulic manipulators is designed. An adaptive boundary estimator is introduced to estimate the hydraulic manipulator acceleration boundaries, and a variable structure controller is used to plan the velocities to meet dynamic limits. The proposed control scheme was tested on a hydraulic manipulator. The results showed that the control scheme reduced velocity error and avoided the manipulator vibration, so the performance is improved for the hydraulic manipulator.