The Research On Tracking Control Of Fast Tool Servo Device

Non-Rotationally Symmetric Surfaces(NRS) is no axis of symmetry of the optical surface,which has great advantage and is concerned by lots of people in the world. With the development of photonics technology, NRS surface not only in the military field, but also in consuming industries is widely used.There are mang disadvantages in traditional manufacturing technology,so developing an advanced manufacturing technology is key whether can NRS surface be widely used.In present,diamond turning which is based on fast tool servo is considered as the most advanced technology which is most promising, high-performance, precision, low-cost .It is key for diamond turning based on fast tool servo that designing fast tool servo devices and designing effective control methods. The concern of this paper is with the control of novel and multi-band fast tool servo.This device contain two parts:long-strike,low-frequency fast tool servo which is drived by voice coil actuator and short-strike, high-frequency fast tool servo which is drived by piezoelectric actuator.In this paper, contents discussed as following:(1)Modelling fast tool servo.Investigating the characteristics of transfer function by analyzing Electromechanical coupling model.(2)After decompositing the Non-Rotationally Symmetric Surfaces which is to be processed, we can conclude that the tool has smalle horizontal feed in X, the adjacent tracks of tool is similar cycle and the frequency of tracks is closed to the frequency of spindle rotation.so, we can know that the input signal could be considered as repetitive signal periodic.Repetitive control can track this type signal effectively. According to the characteristics of the input signal,we will discuss the adaptive feedforward control in order to enhance the ability of trajectory tracking.(3)Because there are electromagnetic inertia and mechanical inertia in fast tool servo system,the system exisits periodic lag.In order to reduce tracking error which is caused by periodic lag,this paper tried to introduce zero phase error tracking control.(4)To study advantage and disadvantage of the control system which is used AFC or ZPETC respectively.There are some inevitable disadvantages when adopt AFCor ZPETC independently. In this paper,AFC and ZPETC are used together to enhance control system's performance.We can learn that AFC+ZPETC method can play a great role and restrain disadvantage of these method respectively by system simulation.We can get some conclutions through this article:(1)By analyzing the model of FTS,we can learn that the electromechanical coupled system of FTS which is drived by voilce coil actuator is a typical second order system,and so is the FTS drived by PZT. So we can adopt detas in paper[31] to carry on simulation.(2)Using AFC for the system alone,the results of the simulation show that this method has great overshoot and it needs five cycles to restrain error in ideal range and it also has great advantages such as slight steady-state tracking error and high performance in restraining perturbance.(3)Using ZPETC for the system alone,the results of the simulation show that this method has large steady-state tracking error and the tracking accuracy of system is affected by external disturbance significantly and ZPETC controller has a fast response,and can restrain perturbance at beginning.(4)Considering the characteristics of AFC and ZPETC ,AFC+ZPETC integrated controller is used in this paper. In integrated controller, AFC can play a role in reducing steady-state tracking error and enhancing robustness of system. At the same time, adding ZPETC in controller can make system respose faster. Compared with method mentioned in literature[31],It has smaller tracking error and stronger robust.