Digital Target Location And Tracking System Based On PSD

Position sensitive detector(PSD)is an optical energy/position conversion device with many advantages such as fast response,high resolution and lowcost,which has been widely used in the field of target localization tracking.However,the proportion of analog circuits in the traditional PSD application in the target location tracking system is too high,resulting in insufficient tracking accuracy and anti-interference capability of thesystem.For this problem,this paper develops a PSD-based digital target location tracking system using digital signal processing circuits andtracking servo control modules in the context of the application of optoelectronic follow-up systems in a simulated battlefield environment.The main research contents are as follows:(1)This paper analyzes the performance index,error influencing factors and solutions of PSD,establishes the mathematical model of the spot position detection of PSD,and studies the measurement error caused by the background light and the system modulation and demodulation technology.In order to solve the problem of nonlinear distortion error in PSD measurement,a cubic spline interpolation algorithm is proposed.In order to avoid the influence of environmental noise and background light on the laser output,sinusoidal modulation and demodulation method is used to process the laser output.(2)This paper completed the system overall structure design,including the selection of laser module,PSD signal processing module design,single-chip processor module design,the actual servo control system module,encoder module design.The system first converts the output current of PSD into voltage signal which is convenient for acquisition,then collects the multi-channel ADC signal by DMA method for processing,and then gets the spectrum information of the signal by FFT transform,based on the spectrum information,the time domain signal of the frequency is recovered,and the PSD position detector deviation signal is used as feedback.combined with the angle information of the tracking turntable encoder,an integral separate PID control algorithm is used to control the servo motor driving the rotating mirror to track the target ball.(3)This paper completed the PSD output performance test,spot position solution test,and two-dimensional tracking mirror angle test.The cubic spline interpolation algorithm is used to correct the nonlinear error of PSD.After the correction,the angle error is controlled within0.4’,and the error is reduced about 5%.It shows that the algorithm can realize the nonlinear distortion correction of PSD well.Theoretical analysis and modeling simulation of the tracking servo control system were carried out.MATLAB/Simulink was used to establish the mathematical model of the current-speed-position three-loop control system for simulation.Through the simulation analysis,the overshoot of step signal response curve of three closed-loop servo control system is δ about 20%,After adding the interference,the steady-state error does not exceed 0.2% of the system reference input,which has good steady-state performance and tracking performance.(4)This paper build a hardware platform to test the tracking capability of the system.It is verified by experiments that when the azimuth pitching velocity of the tracking servo control system is less than 15°/s in the range of 2m~2.5m,and the azimuth pitching acceleration is about 50°/s2.The system can accurately track the movement of the target ball in the range of1m~35m.At 10 m,the tracking accuracy is 0.44 ’,and the maximum tracking angular velocity is1.93°/s.At 35 m,the dynamic tracking accuracy is 0.13 ’,the maximum working angular speed is very small,only 0.56°/s.The system has a good tracking performance.It can meet the requirements of system design.