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This paper proposes a method of quality for the uneven removal caused by the change of the radius of curvature in the aspheric surface polishing and finishing. This method uses a polishing disk and a bonnet as polishing devices, two kinds of aspheric parts as workpieces with a concave surface and a convex surface respectively. By deriving the model of pressure and velocity at different positions, the equation between dwell time and curvature radius on the elliptical generatrix of aspheric workpiece could be obtained from the famous Preston equation on polishing material removal. According to the dwell time on the different path points, the movement of the robot could be controlled. In this way, only the dwell time of the path points on the elliptical generatrix needs to be calculated, rather than the entire aspheric surface. By measuring the values of surface roughness in the polishing of concave and convex aspheric surfaces, the experimental results verify that the method could improve the processing efficiency. [ABSTRACT FROM AUTHOR]

In the process of curved surface polishing and buffing, the tools have to be compressed on the workpiece and moved to wear the surface, so the normal force and tangential feed movements should be provided and controlled synchronously. It is a typical kind of compliant control, which would most likely be done under the hybrid motion/force control policy. Although its related theory is already almost perfect, this method could seldom be used in the process of curved surface polishing and buffing, if ever, for it is always not easy to orthogonalize force control space from movement control space. In this paper, a force control subsystem is developed and fixed on a computer numerical control (CNC) lathe to control the normal force independently, and the normal force control space is orthogonalized from the feed movement control space by geometry defining for aspheric surface polishing. Furthermore, the orthogonalization in the domain of time is taken to make the force control not to interpolate with the displacement control of the feed movements. Experiments in controlling and polishing the normal force show that the hybrid motion/force control policy could be used in the process of aspheric surface polishing and buffing by keeping the normal force control and feed movement control independently in both domains of space and time. [ABSTRACT FROM AUTHOR]

In this paper, a method of maintaining a constant polishing pressure is proposed for a NC polishing system by controlling the polishing force during the polishing process. First, the NC polishing system is developed to resolve the force-position coupling problem encountered in common polishing processes. It mainly consists of a force control subsystem based on a magnetorheological torque servo to provide a controllable torque to polishing tool to generate the polishing force and a position control subsystem based on a general CNC lathe to control the position of the polishing tool. Second, a constant polishing pressure model is established by controlling the polishing force according to the variation of the curvature of the aspheric surfaces, and the polishing parameters for model are planned. Then, the control model of the polishing system is proposed, and a PID controller is designed for torque tracking with the actual torque feedback from a torque sensor. Finally, polishing experiments are conducted with constant force and constant pressure, respectively. Experimental results show that the surface roughness is greatly improved, the aspheric surfaces can be polished more uniformly with constant pressure than with constant force, and the PID controller can meet the requirements for the polishing force control. [ABSTRACT FROM AUTHOR]