Abstract:

In view of the underwater manipulator system with more uncertainty and random interference, the effect of the underwater environment on the dynamic model and impedance controller is analyzed, and an impedance controller based on environmental parameter identification is constructed to solve the force tracking problem of underwater compliant grasping. The environmental stiffness is identified online by recursive least squares with the introduction of a forgetting factor, so as to correct the reference position. The steady-state error of the contact force is reduced, and real-time and accurate force tracking is achieved. Simulation with the MATLAB/Simulink are carried out. It is shown that the controller can quickly achieve tracking of the desired force and real-time estimation of contact stiffness under the introduction of continuous external interference force and desired force adjustment, and has good robustness. Finally, experiments prove that the controller has fast and stable force tracking performance in real underwater compliant grasping tasks. Furthermore, the average steady-state force tracking deviation is about 0.014 N, and the maximum force tracking deviation is about 0.138 N.

Key words: underwater gripper, compliant grasping, impedance control, parameter identification, recursive least squares method, forgetting factor, random interference, force tracking