Research Of Fast Tool Servo Systembased On PZT

With the development of science and technology, aspheric optical parts is used more and more widely in military, aerospace, medical and other fields, which is closely related to people’s life. Due to the traditional machining method is difficult to meet accuracy requirement, some microstructure surface manufacturing technology developed recently also has limitation. However, ultra-precision turning has many advantages to process microstructure compared with the methods above, such as machining asymmetric spherical and the surface roughness of part can reach nanoscale, etc. Therefore, single point diamond turning is more and more important to process micro-structure.The control technology of Fast-Tool-Servo(FTS) has been researched in this article, as well as improving the trajectory planning algorithm of the microstructure surface. The fast tool is the key to process microstructure surface. It determines the complexity of the microstructure surface which can be processed. The process precision of the surface is also influenced by the fast tool. Therefore, the FTS must be able to achieve high frequency and high precision of feed. Because of the hysteresis of PZT, which is the core components of the tool holder, the FTS error increase greatly. So this article developed piezoelectric ceramics Preisach model and its inverse model. A compound model with PID feedback control is established based the Preisach model. The precise control of FTS has been realized by writing the bottom servo control algorithm of UMAC.The microstructure surfaces can be divided into two categories, one can be described by a unified functional expression, and the others are not. The micro structure surface path planning algorithm for the processing quadrilateral and hexagonal arrays has been designed in this article, and the simulation and experiment are carried out to confirm the validity of the algorithm.Traditionally, off-line calculation is adopted to obtain the cutter location when planning microstructure surface path. Then the data of the tool will be downloaded to the UMAC. However, in order to make the surface more precise, more cutter site data is needed, which is often limited by the memory capacity of UMAC. In order to save the memory space of UMAC, this paper studies the algorithm of on-line tool site calculation and compensation. In order to speed up the calculation speed of the coordinate of the cutter in the on-line compensation, the method of Hermite interpolation is designed, and the influence of the external parameters is analyzed. The results show that the method has good stability and high accuracy.When processing microstructure surface, the selection of speed for each axis will be affected by some special restrictions. The related constraints are analyzed, and the flow of determining the rate of each axis is given.In addition, the numerical control system for processing microstructure surface is developed, which integrates trajectory planning, the calculation of tool parameters, the calculation of processing parameters and the monitoring of the lathe.Finally, experiments for machining non-rotate symmetrical surface are performed to confirm all the algorithm developed.