An end-effector for polishing based on a parallel mechanism with 3-PSS + PS′

To enable a polishing tool to automatically adjust its posture and adapt to the surface of the workpiece, an end-effector based on a parallel mechanism with 3-PSS + PS′ (prismatic–spherical–spherical + prismatic–sphere–pin) was designed by using the reverse adaptive working principle. Based on the spiral theory, the degrees of freedom (DOF) of the mobile platform in the parallel mechanism are analyzed, and its DOF are verified according to the modified Grübler–Kutzbach formula. According to the kinematic analysis, the relationship between the plunger movement distance and the grinding wheel spatial pose is determined. The polishing force function between the grinding wheel and workpiece is obtained according to the analysis of the spatial pose of the grinding wheel. The main structural dimensions of the model were determined, and the physical model was given. The simulation analysis of the designed structure is carried out; the results show that the end-effector can realize 3-DOF motion. The maximum rotation angle of the grinding wheel around the x-axis and y-axis is 7.68° and 6.68°, respectively, which meets the design requirements. Within the working range, without controlling the end of a manipulator, the grinding wheel can adaptively compensate the trajectory error, and for different materials 45 steel, HT-200, 6061, the polishing force fluctuation is within 2.56% after stable polishing, which is basically constant.