Research Of Macro-micro Driven Ultra-precision Positioning Stage And Application On Grinder

The positioning accuracy of the precision stage is one of the key factors constraining the machining accuracy. The macro-micro driven ultra-precision positioning stage divides the system into two parts, macro positioning stage and micro positioning one. The macro positioning stage completes the movement with high-speed, large travel, low resolution. The micro positioning stage compensates macro positioning error, and restrains vibration suppression, so the entire system has so many advantages, such as large travel, high-speed, high-resolution, high frequency response. The macro-micro driven ultra-precision positioning stage is the new way to resolve the contradiction of the positioning of machine system between long travel and high resolution.Based on the analysis of the macro-micro driven technology and the application background of the Shanghai scientific and technological project 'piezoelectric-actuated ultra-precision feeding system applied to grinding', this paper develops the macro positioning stage by the servo motor and ball screw, and the micro one by piezoelectric ceramic, to obtain higher resolution and faster response speed. The positioning system uses precise detecting system as the feedback element of the closed-loop system to ensure global precision. Some researches have been done including:1. Based on the work character of piezoelectric actuator, and the lever principle of the support-oriented mechanism, this paper designs a support-oriented institution by a flexible hinge group, and uses the finite element method to analyze the structure to meet the requirements of intensity and stiffness. Based on the basic theory of the structure fatigue life analysis and the finite element method, the flexible hinge structure fatigue life is analyzed, which meets use requirements of high-cycle fatigue life.2. This paper analyzes the dynamic model on the basis of analysis of the mathematical models of the micro positioning stage and macro-micro ultra-precision positioning stage, and does a thorough research work about the key techniques in the macro-micro ultra-precision positioning stage, which builds the basis for the design of the control system.3. This paper establishes the feedforward control model of piezoelectric actuator by polynomial fit algorithm, and designs the closed-loop control system. According to the character and demands of grinding, this paper designs the working flow of the control system on grinder, and builds the communications between the CNC system and the micro feeding control system to solve the integration problems.4. The experimental results presented in the paper demonstrate feasibility and advantages of macro-micro dual driven positioning. Micro positioning system has a positioning accuracy of±0.03μm, the minimum feeding accuracy of the precision grinder is 0.1±0.02 urn. According to many machining experiment, it gets a good result. It is believed that experiences acquired in the research work will pave good basis for the following studies.