Research On The Motion Track Of Aspheric Optical Parts Processing Based On Tangent Rotary Method

Aspheric optical part processing is a well known difficult problem around the world. At present, although small amount high precision aspheric optical parts can be produced through NC turning and grinding technology, however, it takes a long time to get high precision surface, which cause low efficiency. In addition, it creates surface ripple error and is difficult to ensure local surface precision by using existing NC trajectory shaping method for aspheric part machining. This kind surface ripple error will have a strong impact on optical property of precision optical system. To solve these problems, trajectory shaping controlling on processing high order aspheric with NC rotary tangent method is the main research issue in this paper.Put forward the trajectory shaping controlling theory of processing high order aspheric optical parts with NC rotary tangent method and established mathematical model through analyzing trajectory shaping controlling method and the aspheric surface characteristics the existing NC machining. Based on demands of process technology and performance index, PC+NC step-up structure based on UMAC is chosen as design scheme in this control system, automatic control frequency conversion synchronous motor servo system made up of zero-drive technology and analogue linear amplifier is adopted, so as to realize tri-axial linking control. Controlling soft ware design scheme is composed of upper monitor and slave computer. Upper monitor soft ware uses Microsoft Visual C++ 6.0 development environment to mainly complete human-computer interaction module designing, preprocessing, motion programming and communication between upper monitor and slave computer. And motion procedure is achieved through PVT interpolation algorithm and electronic cam algorithm of UMAC.Taking the real high order aspheric optical part as an example, simulated and calculated on its trajectory shaping control, obtained concrete values of geometric parameters and control parameters in the course of the trajectory shaping. According to movement control strategy and control method, observed changing law of these values, respectively analyzed approach relations between control trajectory, synthesized by trajectories on x axis, and y axis and ideal trajectory. The solution of decreasing or erasing controlling system error is put forward through error analysis of the constructed control system.The results show that under the same interpolation step length, approximation error caused by conic subsection approaching ideal trajectory is relatively small, then improve aspheric machining accuracy. In terms of theory using trajectory shaping with rotary tangent method can decrease or eliminate ripple error caused by NC interpolation, so guarantee continuous and smooth of the surface of work piece in machining.