Study On Optimal Path Planning For Automated Dimensional Inspection Of Complex Free-form Surfaces’ Features On The Auto Body

The measurement of body structure size,form and position is the basis of quality evaluation,process monitoring and diagnosis control in manufacturing process.In the detection equipment of auto body precision,CMM is the first choice for body deviation data collection because of its high precision,flexibility and programmable development.The results of CMM are often used as the standard for other calibration processes.However,due to the complexity of the body structure and detection characteristics,the detection planning of the body in engineering practice relies heavily on the engineering experience.Meanwhile,there are still some problems in the planning process,such as low efficiency,poor repeatability and non-excellent detection scheme,which seriously affect the development cycle of the body size engineering.This paper makes a systematic research on the accessibility analysis of detection feature,collision detection algorithm,obstacle avoidance strategy and measurement path planning,and carries out engineering application verification.An intelligent CMM path planning method is proposed for the complex characteristics of vehicle body.On the one hand,the efficiency of automatic path planning is improved by studying the process and method of path planning.On the other hand,the intelligent optimization algorithm is used to obtain the detection path that traverses all features,has no collision with the environment and has the shortest detection time.The main research contents of this paper are as follows:(1)Accessibility analysis of detection characteristics based on static collision detectionAccording to the measurement requirements of various features,the method of selecting parameters of measuring equipment,such as the connection mode of connecting rod and measuring angle,is studied.Under the condition of accurate detection of each dimension feature,the measurement Angle and tolerance range conforming to the detection standard are extracted.Then,based on the static collision detection algorithm,the collision-free connection mode and measurement angle are selected.Finally,the minimum set of connecting rod and measuring angle combination under the condition of characteristic accessibility is studied.(2)Research on local path planning based on dynamic collision detection and automatic obstacle avoidance strategyAiming at the shortcomings of the traditional hierarchical bounding box method in the application of auto body collision detection,this paper proposed a " Dynamic searching volume " collision detection method based on spatial geometry operation.Firstly,the search space is constructed according to the starting and ending positions of the probe motion,and the interference inspection of the structural point cloud of the auto body and the scanning space of the measuring machine is studied.For paths with collision,an automatic obstacle avoidance strategy based on "effective vector sum" in multiple scenarios is proposed to complete collision free planning of local paths.(3)Research on intelligent planning and optimization of global detection pathIn this paper,a path planning algorithm based on simulated annealing is proposed to improve the detection efficiency of body in white.Firstly,the time estimation method of probe motion process is studied,and the detection time matrix and the optimization model of path planning are constructed.Then,the iterative optimization method of detection order based on simulated annealing is studied to obtain the global detection path which traverses all features,has no collision and has the shortest time.(4)Engineering applicationBased on the above theoretical research,combined with the engineering project to carry out the application verification of the auto body path planning,and realize the automatic and efficient detection path planning of a large number of features on the body structure.In addition,combined with DMIS language,the results of the planning are automatically compiled into a computer identifiable program,which provides an effective tool for the engineering practice of auto body detection planning.Accessibility analysis of features,collision detection and obstacle avoidance strategy,global path optimization algorithm and so on will provide effective reference and basis for the detection path planning of complex thin plate products such as aircraft fuselage and train body.