Model-based Control of the Hydraulic Manipulator for the High-precision Trajectory Tracking

The hydraulic manipulator has high non-linear dynamic characteristics, causing large errors of end-effector trajectory tracking. A model-based control algorithm (Model-based control, MBC) with dynamic parameters identification was proposed for high-precision end-effector trajectory tracking of the hydraulic manipulator. The control algorithm was composed of three output parts: the hydraulic cylinder position feedback controller of the outer loop, the force controller of the inner loop and the feedforward flow compensation controller. The force controller fully considered the dynamics model of the hydraulic manipulator and compensated for the influence of inertial force, gravity force, and friction force on the control accuracy. The position controller is used to eliminate the force deviation caused by hydraulic actuators. The feedforward flow compensator calculates the flow compensation amount according to the dynamic model of the hydraulic actuator to improve the control response and accuracy. The least-square parameter identification method was adopted to solve the problem of inaccurate parameters in the dynamics model, and the accurate dynamic parameters of the hydraulic manipulator were captured under the excitation trajectory. The experimental results show that the proposed MBC control algorithm for identifying dynamic parameters improves the tracking accuracy of motion position in free space by 39.24% compared with the MBC control with 3D model parameters, and increases the tracking accuracy by 93% compared with the traditional PID control, which significantly improves the trajectory tracking accuracy. © 2023 Chinese Mechanical Engineering Society. All rights reserved.