Effect Of Target Properties On The Non-cooperative Laser Ranging System

Non-cooperative target large-scale spherical coordinate measurement system based on FMCW laser ranging technology does not need to cooperative target.The advantage of this system is safe,efficient,wide measurement range and high accuracy.It can meet the current growing demand for large space precision measurements.However,compared with the cooperation target laser ranging system,the uncertainty of measured target surface results that laser backscattering mechanism is very complex,so that the accuracy and measurement range of non-cooperative target laser ranging system are severly affected.Therefore,for this problem,this thesis launches a series of surface measurement characteristics and its effects on distance,it is the key research content to improve the overall accuracy and range of the measurement system.The main work profiles are as follows:Firstly,this thesis proposes a test method for manufacturing surface roughness on the performance of laser measuring based on the study on the rough surface scattering characteristics.And we develop a test device.Diffuse scattering properties of standard white board and standard roughness specimen in the infrared laser irradiation are tested and analyzed.This study reinforces the test support and engineering application interpretation for the interaction mechanism between laser and material.It is also provides a theoretical and experimental basis for non-cooperation target issue in laser radar.Secondly,the approximate analytical methods of rough surface backscattering coefficient are derivated.They include integral equation methods,Kirchhoff approximation method and perturbation method.The numerical results of the backscattering coefficient of random Gaussian rough surface are calculated.Then,experimental studies of scattering properties to the actual machining surface are conducted.The influence of incident azimuth,angle of incidence,the polarization direction of the incident light and the surface morphology on the scattering characteristics of the actual machining surface is analyzed.Thirdly,the backscattering properties of real machined surface are measured and analyzed.On this basis,the network model of backscattering of machined surface is established based on artificial neural networks.Then,the machined surface dimensional parameters inversion model based on genetic algorithm is constructed.This model can greatly improve the measurement range.Fourthly,the mathematical model of effect of rough surface to the laser radar measurement signal is established.The ideal signal,the ramp signal,the mutation signal and random rough surface signal are simulated.The effect of surface roughness and correlation length on the measurement signal is analyzed.Finally,the FMCW laser radar theoretical model of ranging accuracy is derivated.The factors affecting the accuracy of laser radar is analyzed,focusing on the influence of surface properties to the ranging accuracy.Then,a large ranging experiment is designed and theoretical analysis is verified.In addition,for this type of surface morphology,this thesis proposes a method to reduce the measurement uncertainty and this method weakened the influence of rough surface.