Research On Motion Planning Of End Effector In Large-Scale Space Mobile Measurement System

In the past ten years,mobile measurement systems with high precision and wide range have been in great demand in the railway transportation,aerospace,automobile manufacturing and other industries.The user's requirements on the quality of product manufacturing are constantly improving with the development of large-scale equipment manufacturing industry.The design and manufacturing technology of industrial products has been constantly updated,and the measurement of industrial site size has gradually emerged the features of diversified measurement objects,complicated measurement environment,and automatic measurement process,etc.The existing industrial size measurement system has been unable to meet the increasing demand for automation and high efficiency of large-scale spatial coordinate measurement.Therefore,a graphical user interface with a function of automatic planning of measurement equipment motion needs to be developed urgently.This paper takes the exterior surface of the EMU driver's cab as the research object,and focuses on the method that can realize the motion planning automation and the graphical user interface with visualization function.Firstly,the existing measurement equipment point distribution strategy is studied and a new measurement point distribution method is proposed.The known CAD model is converted to the STL format,and the triangle is used to approximate the surface of the workpiece to be tested.The parameters of the scanner and the curvature of the surface are used to discretize the surface of the CAD model into point cloud data.The mathematical model is constructed by interpolating the point cloud data with the cubic uniform B-spline.At the same time,a mathematical model of the working field of the measurement equipment is established.An algorithm with automatic point distribution function is designed based on the above mathematical modelsSecondly,a path planning method of measurement equipment is studied and an obstacle avoidance path generation strategy is proposed.The surface is segmented according to the working range of a visual tracking system and the working space of the robot,and the ant colony algorithm is used to obtain the shortest path passing through all the measurement points in each region.According to the reference distance of the visual measurement system,the equidistant surface of the CAD model to be tested is obtained,and the triangle patch closest to the coordinate point of each measurement equipment is obtained and projected,and the "shortest distance between two adjacent points on a polyhedron" algorithm is used to obtain the coordinates of the intermediate points of the adjacent projection points.The endpoint and the intermediate point are interpolated by using the cubic uniform B-spline to obtain a collision-free path for the manipulator end effector.Finally,the trajectory of the manipulator is planned in the Cartesian space,and a method of visualizing the measurement process is proposed and a graphical user interface for motion planning is designed.The acceleration curve of the traditional trapezoidal velocity curve is discontinuous,which will cause the vibration and impact of the robot arm,thus seriously affecting the service life of the robot.According to the length of the point-to-point motion path,the traditional S-type velocity planning is divided into four modes,and the effectiveness of the method is verified by MATLAB.A mathematical model of the working field of the measurement equipment is established to find and dye the common area of the quadrangular prism and the surface in each pose.It can be judged whether there is an unmeasured area on the surface by observing the color change of the surface.