A Differential Micro-feed System Based On Adaptive Compensation

The increasing demand in the machining accuracy of precision machine tools in the micro electronic technique, communication, spaceflight and biotechnology fields have stimulated the development of long-range ultra-precision positioning table. Currently there are a variety of different types of ultra-precision positioning tables. However, major challenge still exists: how to achieve the critical characteristics of long-range, highresolution, high-speed and low-cost simultaneously. The studying aims of this paper are to develop an experiment table system using differential structure including its hardware and software systems. Three dimensional modeling and motion simulating according with the table’s actual sizes. Studying some key points in positioning technique, such as achieving system positioning errors detection and calibration experiments, analyzing error compensation method based on sampling dual-loop, realizing error dynamic compensation based on adaptive compensation using error modeling and differential control method.This paper firstly summarizes the micro-feed system research status in China and abroad and discusses current various micro-feed system characteristics and development tendency. The design scheme is consisted of motion cotroller, AC servo motor and NC tables with differential structure after comprehensive comparing current various micro-feed systems and according to the principle of low-cost and high-speed. The system is integrated with a PC as host computer and linear gratings as position feedback system. A user-friendly human-computer interface is exploited using Visual Basic 2010. Secondly, ball screw characteristics and error distribution law are expounded. The mechanical characteristic and dynamic and static characteristic of servo-feed system are analyzed. Micro feed system mathematical model is set up and a 3D model is built using Solidworks software according with the table’s actual sizes. Then the model motion simulation is achieved under friction factor using Adams software. Thirdly, system position error sources, influencing factors and compensation methods are discussed and the sampling dual-loop compensation method is used in the experiment. The method improves the position accuracy effectively. The last and most important step is the research of error dynamic compensation. The error dynamic compensation principle and methods are discussed and a adaptive compensation method using error modeling and differential control is presented. System errors and random errors are treated as a whole in grey model GM(1,1) in the dynamic errors modeling. The character of dynamics errors is explained in way of energy change by GM(1,1). The model has the merits of little modeling data, little computing time and fast errors compensating speed. So it is an effeetive method for dynamic errors compensation. System effective path is fitted and predicted and the tables’ micro-feed according to the path using differential control realized in the program at proper speed scope of servo motors.Through theoretical research and practical application, error dynamic compensation is achieved based on adaptive compensation method using error modeling and differential theory. The device possesses the advantages of long-range, high-resolution, high-speed and low-cost, which provides a new way for the design of micro-displacement mechanism. Long-range and high resolution can be satisfied using a novel structure and proper compensation method under the limited conditions without complex mathematic model.