Signal Processing And Error Analysis Of Planar Two-Dimensional Time-grating Displacement Sensor

Precision displacement measurement technology is an important symbol to measure the level of a country’s manufacturing industry.With the development of the third industrial revolution,the demand for precision measurement instruments in manufacturing industry is more and more extensive,and the demand for errors is also higher.In displacement measurement,linear plane displacement is the most typical application.In recent years,a time grating linear displacement sensor based on clock pulse has been developed in China.It does not depend on space precise marking,and can achieve high resolution and high precision displacement measurement.In plane displacement measurement,if two sensors are installed at the same time,this method saves the cost and simplifies the method,but at the same time,it also brings about the difficulty of ensuring consistency,which will lead to larger measurement errors.At present,based on the development of one-dimensional time-grating linear displacement sensor,the research work of two-dimensional time-grating linear displacement sensor is carried out.As an integrated two-dimensional linear sensor,it can simplify the installation structure and obtain higher measurement accuracy of two-dimensional plane displacement.Aiming at the particularity of the planar two-dimensional time grating displacement sensor,the signal processing circuit of the sensor is designed,and the sensor error is analyzed from many aspects to realize the error correction of the sensor.Based on this,the signal processing and error analysis of planar two-dimensional time grating displacement sensor are studied in this paper.The main research contents are as follows:(1)By introducing the theory of one-dimensional time-grating displacement sensor,the working mechanism of two-dimensional time-grating displacement sensor is studied,the signal transmission path and processing method in the measurement process are deeply analyzed,and the signal processing circuit based on STM32F407 VGT chip is proposed and designed.The harmonic error correction method with equal spacing is proposed to correct the error of measurement data,which improves the measurement accuracy.(2)Modularized and highly integrated hardware circuit design is adopted to ensure the stability of the electrical system.In order to reduce the interaction between the two induction signals,the excitation signals with frequencies of 10 KHz and 20 KHz are adopted.The hardware circuit system designed in this paper integrates the excitation signal generation module,signal induction module,induction signal conditioning module,time difference measurement module and so on.TDC-GP2 combined with clock pulse interpolation is used in time difference measurement,which effectively solves the problems of small measurement range and low resolution of clock pulse in TDC-GP2 measurement.(3)According to the transmission mechanism of time grating signal,the error sources are found.The main error sources are non-orthogonal phase of two-phase excitation signal,unequal amplitude,square wave signal fluctuation,zero-level fluctuation and amplitude fluctuation in induction signal processing.Aiming at the errors caused by these problems,an equally spaced harmonic error correction algorithm based on FFT(Fourier transform)is proposed.The software is designed.(4)Using laboratory environment to build experimental verification platform.The stability of excitation signal,induction signal and square wave signal is verified by experiment.The error correction algorithm proposed in this paper can achieve high measurement accuracy.The displacement measurement resolution in X and Y directions within a pitch can reach 4.4nm.In summary,the signal processing circuit designed in this paper and the error correction algorithm proposed in this paper improve the high precision measurement of two-dimensional displacement,and promote the research and development of two-dimensional time grating displacement sensor and the process of marketization.