Multi-region Coordination And Process Optimization Design Of Car Door Fitting Accuracy

The car door fitting lies at the downstream of the body assembly process.The fitting condition has direct effect on wind noise,leaking,closing force and other functional requirements,so it is an important part of car perceived quality.The fitting range between door and side-body is large,with high quality requirement.Also,the fitting accuracy has a significant multi-region attribute,which makes consistency control in batch production difficult for car manufacturers.Therefore,the studying on multi-region coordination and locating optimization is beneficial for reducing the effect of input deviation on the accuracy of car door fitting and allocating upstream deviation to multiple regions,the consistency of door fitting in batch production shall be improved,so that the workload of rework is reduced.Aiming at the above problems,this thesis firstly introduces the door structure,welding and door fitting process;secondly,based on deterministic locating model,the assembly deviation model of door profile feature is deduced;next,the numerical evaluation method of car door fitting accuracy is proposed on the basis of line segment Hausdorff distance,as well as analyzing the strong correlation between the accuracy of the door fitting and the evaluation method;then,the objective function of the vehicle door locating optimization is established on the foundation of profile feature assembly deviation model and line segment Hausdorff distance,and the optimal locating scheme shall be got based on differential evolution algorithm;finally,by simulation analysis and the test of a trial car fitting,the feasibility of the proposed method is verified.The major research contents are as follows:(1)Door welding,fitting processFirstly,according to the structure and production process,this thesis introduces the common types and characteristics of the door,then the welding process flow and the quality inspection and evaluation method of door assembly are analyzed;at last,a discussion is made on the fitting process and existing problems in detail.(2)Assembly deviation model of door profile feature based on deterministic locatingBased on the locating stability parameter,the model transforms the multi-constraint condition of car door into deterministic locating mode.Then,based on deterministic locating model and considering locating and manufacturing deviation,the assembly deviation model of door profile feature is deduced.(3)Multi-region coordination and locating optimization modelThis thesis analyzes the characteristics and problems of the existing fitting quality measurement methods,and proposes The numerical evaluation method of car door fitting accuracy based on line segment Hausdorff distance.The optimization objective function of single-door locating optimization and multi-region coordination locating optimization are respectively established on the foundation of the existing profile feature point set and its deviation information.Moreover,a locating optimization model is established based on differential evolution algorithm.(4)Application verification of multi-region coordination and locating optimization for car door fittingCombine with the case of door fitting,the locating optimization is conducted.To start with,the locating optimization function of front door and rear door is established,by comparing Gap Parallelism before and after optimization,the validity of the method is verified.Then,with the establishment of the locating optimization function of the multi-region coordination,the research analyzes and compares the gap parallelism of the two models,which indicates that multi-region coordinated locating optimization can improve the consistency of door fitting.