Design And System Development Of Precision Two-Dimensional Motion Platform

Precision positioning platform plays an important role in many areas,such as microelectronics,medical treatment,aviation,space flight,etc.Each development and application of precision positioning platform technology will strongly promote the development of science and technology.Therefore,research on precision positioning platform technology has extremely important theoretical and practical significance.Aiming at image scan of large-format image stitching carried out by digital microscope,mechanical structure and control system of a two-dimensional numerical control stage was designed in this paper.Main research contents are as follows:(1)According to design specification of the movable platform,some components,such as ball screw,and cross ball guide,were selected.The two-dimensional stacked coplanar structure was used to reduce the Abbe error,which improved integration of mechanical system of the platform,enabling it to become more compact and flat.In addition,finite element analysis on the mechanical structure was conducted and results showed that deformation of the structure was 0.2295 ?m under the load of 10 KG.(2)Controlled by STC89C516RD+ MCU,a closed-loop displacement control system of the two-dimensional numerical control stage based on the combination of grating scale feedback with high-precision and PID precision motion control was designed,which could achieve motion control of the two-dimensional movable stage in the directions of both X and Y.Differential signal of grating scale was received by DS26C32 chip,and direction identification and counting for the differential signal were carried out by HCTL-2032 chip.Then,incremental PID control algorithm was used,and Z-N critical proportioning tuning formula was used for parameters tuning of the PID control algorithm.(3)For human-computer interaction system,joystick was operated by hand for fast positioning of the platform,and then precisely positioning was achieved by parameters input through matrix keyboard.Meanwhile,LCD1602 was used to display the present operation state of the system.Analog signal of joystick was transformed to digital signal by ADC0832 chip,which was easily read by MCU.In order to save I/O ports of the MCU,matrix keyboard was connected with MCU through extended I/O ports of PCF8575 chip.(4)Interpolation program of straight line,clockwise and anticlockwise arc was written based on point-by-point comparison,and interpolation program of sine and cosine was written based on tiny straight segment fitting,so that,the platform can achieve straight-line,clockwise and anticlockwise arc,sine and cosine movement.Proteus software was used to conduct circuit simulation of the control system.(5)Error sources of the platform were analyzed.Dual-frequency laser interferometer was used to calibrate the designed numerical control two-dimensional stage and compensation model of motion control error in the directions of both X and Y was established.Therefore,motion precision of the system improved.All in all,on the basis of the design specification,hardware and software system design of the platform were completed in this paper.Results indicate that the designed platform can achieve rapid response and stable control,and its performance index can meet the requirements of the design specification.After compensation,repetitive positioning accuracy was better than ±5um in the travel range of 100×100mm.