Study On Key Technologies Of Ultra-precision Turning Based On A Long Range FTS

There are many outstanding advantages of optical freeform surfaces in improving optical performance,simplifying the system structure,improving imaging quality,reducing component count and weight,improving product design,etc.With the development of the photoelectric science and technology,optical freeform surfaces are starting to be widely used and have good prospects in lots of applications,such as aerospace,civil,defense and military fields.Compared with conventional rotational symmetrical optical surfaces,it is difficult to achieve the efficient and ultra-precision mancufacturing of the optical freefrom surfaces,which have the complex structure of non-rotational symmetry.It becomes the major bottleneck restricting the extensive development and application of the optical freeform surface.With the development of machine tool technology,ultra-precision machining technology which is a manufacturing technique for optical freeform surfaces has many advantages over the other traditional methods.Optical freeform surface machining based on a fast tool servo is a very popular freeform surface ultra-precision machining technology.Nowadays,in Europe and America,Japan and other industrialized countries,the ultra-precision machine tool used to manufacture optical freeform surfaces has stepped into the stage of industry application and commercial backgrounds,in the meanwhile,the emergence of new technological advances.The processed high precision optical freeform surface parts have a large number of applications in various fields.In recent years,many domestic units have carryied out a study of Fast Tool Servo machining technology.There have been many progresses in device design,motion control algorithm and processing experiment,etc.But due to a late start,there are still many key basic technologies to be researched.Based on the above reasons,this paper studies the key technologies of ultra-precision machining of optical freeform surface based on a long rang FTS.This paper is mainly composed of the following contents:1.In this paper,a long range fast tool servo system has been developed.Bsed on the analysis of the open loop characteristic test of FTS system,the mathematical model of the system has been established.In order to improve the accuracy of motion control,this paper proposes an adaptive feedforward cancellation control algorithm,which uses an internal model PID control algorithm.The system using the internal model PID controller can achieve higher robust stability,faster response speed,larger bandwidth,which make the performance of the whole control system improved.The simulated experimental cerification has been carried out.2.Based on the developed long range FTS system,ultra-precision machining system of freeform surface is developed.Combined with dynamic analysis theory,by means of the finite element analysis method,the inherent characteristics and dynamic response of the ultra-precision machining system have been analyzed.It provides the reliable guarantee for the machining quality of the optical freeform surface.3.The tool path planning of ultra-precison fast tool sevo machining and the simulation and prediction of there-dimensional surface topography of the machining of freeform surface have been studied.According to the principle of fast tool servo machining,the FTS processing model driven by helical projection has been established.The two kinds of tool path generation method and tool radius compensation strategy have been analyzed.Based on considering the tool-workpiece vibration in the cutting direction and feeding direction,the rotation matrix is introduced,the simulation and prediction model of ultra-precision machining three-dimensional surface topography has been established.By using this simulation model,the machining parameters can be optimized and the three-dimensional surface topography of freeform ultra-precision machining surface can be predicted,which provides the guidance for further experimental research.4.The related machining experiments are carried out on the ultra-precision machine tool platform using the developed long range FTS system.Through a series of machining experiments of freeform optics,including lens array and vehicle rear-view mirror surface,the feasibility and practicability of the developed FTS system used to machining the freeform surface have been verified.A good foundation for further manufacturing application of ultra-precision fast tool servo machining of the optical freeform surface is built.