Design and modeling of a passive magnetic vibration absorber for robotic polishing process

Abstract

Due to the low stiffness of workpieces, chattering easily occurs during robotic polishing operations and leads to poor surface quality and reduced machining accuracy. In this work, in order to reduce vibration during robotic polishing, a passive vibration absorber was designed by the principles of homopolar repulsion and electromagnetic induction. The passive vibration absorber included an upper platform, a damping block, and a lower platform. The flange of the robot was connected to the end polishing effector through the top platform, and its base platform and damping block were movable along the guiding shafts. In addition, permanent magnets were attached to the top and lower platforms and the damping block. During the polishing process, a repulsive force was generated between the homo-polar permanent magnets existing on the upper plate and the damping block. Similarly, a repulsive force was also generated between the bottom platform and the damping block. Due to the magnetic field generated by the eddy current, the magnetic field of the permanent magnets was time-varying and opposite to the external magnetic field of the moving damping block, which generated a repulsive force to compensate for vibration during the polishing process. As the workpiece had multiple modes involved in vibration and its dynamic characteristics varied with the position of the grinding tool, the repulsive force and the damping force effectively reduced vibration and dissipated the energy of the oscillating system. The modeling and dynamic analysis of the proposed vibration absorber were performed to achieve an optimal design. Finally, experimental studies were carried out to evaluate the effects of this vibration absorber. The experimental results demonstrated that the absorber could effectively limit the fluctuation of the polishing force, suppress the vibration of the spindle, and enhance the surface quality of the polished workpiece.