Research On Error Analysis And Compensation Of Ultra-precision Air-floating Turntable

Ultra-precision Machine Tool is a kind of equipment used to process high additional value products and parts. As the core component of Ultra-precision Machine Tool, the reliability and precision of the machine tool are determined by the performance of the airfloating turntable, which could influence the precision of the products. In many high technology fields, the geometric surface of many high additional value products and parts which meet the precision of nanometer are very complex.So, in order to improve the nano manufacturing precision, the air- floating turntable system with higher precision is needed. However, shafting errors and cogging torque would affect angular displacement precision of the air- floating turntable, and the decrease of the error is limited by technological level conditions. Therefore, it is necessary to build a software compensation system. This method not only can reduce the error(Sometimes, it can eliminate the error), but also responds quickly.And, it is easy to integrated turntable system. It is of great significance when we develop an air- floating turntable with simple structure and excellent performance.Aiming at the precision of the air- floating turntable, this paper analyzes the principal factor: shafting errors of the motion system and cogging torque of the motor, which affect angular displacement precision of the air- floating turntable. Common axis errors of the motion system include offset error and tilt error. In this paper, the influence of the offset error on the motion trajectory and the angular displacement precision of the air- floating turntable, the influence of the tilt error on the motion precision and the measuring surface roundness of air- floating turntable are given. This paper analyzes the influence of shafting errors on the circular grating angle measuring system. The offset of circular grating will lead to that the number of the light and shade transformation of Moire fringe would periodically change. The tilt of the circular grating will not only change the distance of the Moire fringe, but also will lead to that the number of the light and shade transformation of Moire fringe would periodically change. This paper analyzes the external rotor motor of the air- floating turntable. This paper obtains the cogging torque curve by Maxwell 2D simulation model, and it is consistent with the measured curve. The paper have optimized the pole arc coefficient and slot width to weaken cogging torque of the external rotor motor, and the simulation results show that the optimization method is effective. In order to analyze the influence of the error on the turntable, this paper builds the test system based on spindle measurement, and we can test the precision of the turntable by using this test system. Test data show that the position precision and repeated position precision of the turntable axis is far below the requirements. In order to reduce the effect of error on the turntable, according to the test data, the position error curve is given in this paper. Then, the error is compensated by using the compensation system of Soloist software. The compensation results show that the position precision and repeated position precision of the axis turntable fulfill the requirement, and the method of compensating position error of the turntable by using Soloist software is feasible.