Research On Control System Of FMCW Laser Interference Displacement Motion Platform

Precision positioning is a high-precision positioning technology at the nanometer level,occupying a very important position in the high-technology field,especially in the production of semiconductor chips.Therefore,precision positioning technology has become the focus of research in various countries around the world,while domestic research on this technology started relatively late.Improving positioning accuracy and measurement accuracy has been a difficult point in this research direction.In order to solve this problem,this article uses the advanced Frequency Modulated Continuous Wave(FMCW)measurement technology for the first time.Based on a piezoelectric driven precision displacement platform,a nanoscale precision displacement platform and its control system are designed to achieve nanoscale high-precision positioning.Firstly,the principle of FMCW laser interferometry measurement was studied and analyzed.Based on the Soreb Nano Max piezoelectric displacement platform,a piezoelectric precision displacement platform and its control system were designed and constructed.The control system includes a piezoelectric driven displacement table,FMCW laser interference displacement sensor,optical interference measurement structure,and control end software.Secondly,control software was designed and written using Qt platform and C++language.The software includes functions such as driving control of piezoelectric controllers,data reception and analysis of FMCW displacement sensors,interface design,drawing,data display,file saving,and control mode selection.Then,an analysis was conducted on the disturbance of the environment and the hysteresis and creep characteristics of piezoelectric ceramic materials themselves.This paper selected open loop,closed-loop,and PID control methods.This paper wrote algorithm programs under three control methods,and adjusted the parameters of PID control.This article conducts comparative experiments on three control methods under the same experimental conditions.The experimental results show that the open loop control can not eliminate the non-linearity of piezoelectric ceramics,and the system has a large difference from the set value when it is stable;Closed loop control can eliminate errors caused by non-linearity,but there are significant overshoots and oscillations in the system during adjustment;PID control has fast positioning time and good system stability.Finally,through experiments under PID control,the results showed that the positioning stroke of the system was 30μm,the positioning standard deviation was about 3.53 nm,and the average positioning time was about 0.87 s.The precision displacement platform designed in this project can achieve nanmeter level displacement control,and has great application prospects in high-end lithography machines.