Modelling and vibration control of magnetorheological-based polishing tool for robotic polishing process

The instability of the polishing force in the robot polishing process causes vibration of the polishing tool and degrades surface quality. Controlling vibration is essential for enhancing machining quality during high-precision polishing. This paper presents a magnetorheological (MR)-based polishing tool and vibration control method for improving the stability and reducing the vibration during machining. Firstly, a polishing end-effector with MR-based damper and magnetic spring mechanism is designed, the damping and stiffness model are built, the vibration dynamic model is established, and the vibration characteristics are theoretically analyzed. Multi-objective optimization is carried out to minimize the maximum frequency response value of polishing system. Then, a disturbance observer is designed to estimate the nonlinear cutting force and the stability is proved. To maintain normal contact force and reduce polishing tool vibration, a vibration controller based on polishing force with gravity compensation is proposed. The measured vibration amplitude and estimated cutting force are used as feedback in the controller to maintain the desired contact force. Finally, the polishing experiments are carried out to verify the feasibility of proposed strategy. The results show that the proposed method suppress the fluctuation of the polishing force and reduce vibration, the maximum vibration amplitude is reduced by 45% and the surface roughness is improved up 57.9%.