Research On Calibration Technology Of Pavement Topography Structured Light Measurement System

With the development and application of autonomous and advanced assisted driving system,dynamic environment perception technology came into being.Currently,the main way to obtain obstacles and road marking information on structured roads uses laser radar and camera combined with ultrasonic radar.But for unstructured roads,especially for the topography of bumpy soil,sand and gravel roads,using structured light to measure the road surface is more effective.For ensuring the accuracy of the measurement system,the structured light system needs to be calibrated to solve the problem of obtaining the three-dimensional geometric contour of the road to be measured.Because of the self-reliant of the light plane or camera inherited parameters in the traditional method,bringing out the diffuse error of the equipment itself easily leads to the low accuracy of the overall system calibration.Thus,this paper study a direct calibration method for us structured light systems,which integrates the camera and the laser calibration process.According to the characteristics of pavement topography,this study firstly determined the type of the optical equipments.Then came up with a road surface morphology measurement system with lattice structured light to measure the three-dimensional coordinate of the pavement topography.The paper analyzed the triangulation measurement principle and the projection mapping of the industrial camera,and realized the derivation and transition of the lattice-laser structured light system.For the feature of complicated calibration process which is easily to introduce errors,we carried out the integrated calibration of the measuring system to simplify the model.Based on projection mapping we established a mathematical model of the direct method.In order to majorization the model structure,subsequently.we took the least absolute shrinkage to selecte operator parameters.Hereafter study used least angle regression to run features spankingly,used cross-validation and made error analysis of the regression and the test results.After analysis,by Calibrating the entire visual system not camera and structure device position separately,avoiding various structural parameters,but with lack of global applicability on object-image map.We present a regional calibration method based on the distoration migration vector.The sub-region template is established according to the distortion distribution law of the lens.System integration and direct calibration are performed in the sub-intervals to obtain the object image mapping function of the entire measurement system.For obtaining the laser characteristics in images,we studied the technology of spot image extraction and and centroid coordinate positioning,completing the collection of the structured light feature point by obtaining the sub-pixel centroid of the lattice in the image plane.The paper builds a calibration platform for the pavement topography based on structured light measurement system,using for prophase calibration and later testing.The experimental results shows,the bias of the test data from the calibration method above within 3 millimeters,which can effectively use the structured light to assist the monocular vision implements to output the depth data of the wavy road from the image sequence.It has been verified that this calibration method of this structured light measurement system has some outstanding advantages,such like the simpler construct,not only high accuracy but reliability.Above all,meeting the detection requirements of the ground unmanned vehicles.