The Research Of Vehicle Speed Calculation By Momentum In Traffic Accident Based On Laser Point Cloud

For the rapidly increasing of car population, imperfect transport facilities and road planning, lack of security awareness etc., the transport accidents arise more frequently in our nation, which has attracted more and more people’s attention at the same time. The reconstruction research of the accident is conducive to figure out the accident cause, develop effective preventive measures, and provide scientific basis for judicial accountability identified. The accident reconstruction is classified into two parts:field data collection and the calculation of vehicle motion. For the irretrievable the spot affected, data collection has the greatest impact on the final result. With the development of 3D laser measurement technology, people began to apply it to the data acquisition of the spot affected, and has gained some achievements, but rarely calculation methods of vehicle motion state applying to laser measurement data are proposed. Therefore, a new vehicle speed reverse algorithm based on the field measurement data associated with 3D laser measurement technology is proposed in this paper. The concrete research contents are:(1) In order to obtain the cloud data of spot to the accident processing efficiently, reasonable 3D laser scanning program is developed in this paper to obtain the cloud data, which concludes on-site viewing, coordinated drawing, the selection of scanning site, scanner arrangement and field scanning etc. In order to solve the problems by the transparent or black objects, image the spraying agent to improve the effect of scanning.(2) For the high noise, low resolution and data redundancy of original point cloud data don’t suit for the accident analysis directly, so it is necessary to pretreat the primitive point cloud. Use ICP algorithm, k-tree and vertex triangle method to improve the quality of point cloud data.(3) The paper proposes vehicle speed reverse algorithm based on the function direction of collision momentum according to the three dimensional laser scanner which can measure the vehicle’s deformation angle. The momentum value is calculated by the theorem of momentum, collision deformation energy, two-dimensional collision dynamics matrix of the vehicle and collision momentum angle, and the vehicle motion state before and after the collision is calculated at the same time. For the vehicle slid path is not applied to the calculation, the calculation error is smaller than the computing method which is based on the vehicle speed, and has a wider range of application.(4) In order to figure out the relationship between the deformation angular of vehicle collision and the function direction of collision momentum, the LS-DYNA finite element technology is applied to build the vehicle collision model to simulate the collision accident under different angular to obtain the deformation angular-data of the momentum function direction, and establish the sample library. What’s more, the momentum function direction is calculated by seven elements regression equation based on analogy method. The tolerance analysis is finished in this paper to verify the validity of the transformation equation.(5) Verify the momentum reverse speed method in actual application. Reverse the vehicle speed in traffic accident by 3D laser data. The result shows that the momentum reverse speed method is proved by handling a traffic accident without glide path. Finally, based on the complicated mathematical calculation step in momentum reverse speed method, compile a tool for automatic calculation.