| With the improvement of the modern precision instrument industry’s requirements for measurement accuracy,the dual-frequency laser interferometer measurement system,which is widely used in CNC machining and coordinate measurement equipment,has become more and more important.Generally,the factors that affect the accuracy of the dual-frequency laser interferometer measurement system mainly include frequency stabilization accuracy,nonlinearity and signal processing system.In the past,many studies have been done on the first two,and they are fruitful.In order to shorten the gap,this article focuses on the design of the signal processing system of the dual-frequency laser interferometer.In view of the existing dual-frequency laser interferometer signal processing system,there are generally problems that the measurement resolution is not high,the measurement speed is not fast,and the system integration is not high enough to meet the requirements of high-precision measurement environment.This paper studies and designs a set that can be applied at the same time.It is a high-resolution signal processing system for the Zeeman effect type and double-longitudinal model dual-frequency laser interferometer.First of all,by designing the pre-processing circuit of the Zeeman effect type and dual-longitudinal model dual-frequency laser interferometer,the photoelectric receiving device with high signal-to-noise ratio and the high-reliability high-frequency amplifier circuit are selected to realize the high performance of the dual-frequency laser interferometer Measure the speed target.The frequency reduction circuit composed of power divider,mixer and oscillator is used to effectively reduce the frequency of the dual longitudinal model dual-frequency laser interferometer to about 5MHz,which solves the problem that the signal after the original mixing measures is actually a quasi-DC Signals can only be amplified by low magnification DC in the follow-up,which is prone to DC drift problems,so that the signal processing system has the signal processing capability of the Zeeman effect type and dual longitudinal model dual frequency laser interferometer at the same time.Secondly,this article uses the "direct phase comparison method" circuit with the high-frequency signal vector measurement integrated device AD8302 as the core to realize the subdivision measurement of the system’s non-full-period phase difference.Aiming at the problem that AD8302 cannot judge the phase polarity during the phase difference measurement process,through research and comparison,a phase polarity judgment circuit composed of Schmitt trigger and D trigger is designed,which solves the existing dual-frequency laser interferometry.The system generally has the problem of insufficient electronic subdivision of the measurement signal to achieve high resolution.Furthermore,this article also designed a micro-division counting integrated circuit based on programmable logic device CPLD and microcontroller ARM,which realized the counting processing of the phase difference of the whole cycle,and significantly improved the integration and anti-interference ability of the dual-frequency interferometry system.Finally,this article briefly analyzes the errors that affect the overall measurement accuracy of the dual-frequency laser measurement system,explains the sources and effects of various errors,and proposes measures to reduce the errors.In order to verify whether the system design meets the requirements of high resolution and high speed measurement,this paper has done some verification experiments,mainly including resolution verification experiments and high speed measurement verification experiments.The resolution and high-speed verification test methods used in this article are introduced in detail,and the experimental results show that the overall resolution of the dual-frequency laser interferometer signal processing system is better than 0.6nm,and the maximum allowable measurement speed of the system is 1300mm/s. |
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