Research And Implementation On Virtual Assembly Technology Of Automobile Main Reducer

Automotive main reducer is an important part of the automotive transmission system,which has a wide variety of components and complex assembly process.The traditional product design methods cannot find and solve the problems that may occur during the main reducer assembly process in advance,which often cause the repeated production of R＆D samples.The transparency and intelligence of product R＆D and assembly sequence planning can be realized by using virtual assembly technology.R＆D personnel can identify and improve the design defects of the main reducer without producing product samples,which not only can reduce the product design cost,but also can shorten the product development cycle.So,this thesis takes the automobile main reducer as the research object,the key technologies such as assembly sequence planning,collision detection and virtual assembly simulation in the main reducer virtual assembly were studied.At the same time,based on this,a set of main reducer virtual assembly system in augmented reality environment was developed.And the system was applied to the enterprise product R＆D and teaching training.The specific research contents are:Firstly,the assembly sequence planning of the main reducer was studied based on the disassembly method and the genetic algorithm.The main reducer interference matrix was built according to the geometric constraint relationships between components.The changing times of disassembly direction,disassembly tool and disassembly fixture were selected as the objective function of the disassembly efficiency optimization,so the main reducer disassembly sequence evaluation method was constructed and the fitness function was established based on the evaluation method.The genetic algorithm was improved by considering the addition of assembly basis part when establishing the fitness function,which makes the planned assembly sequence closer to the actual assembly process and improves the assembly sequence generation efficiency.The genetic algorithm flow was designed by using interference matrix as the criterion of disassembling sequence feasibility and combining with fitness functions,genetic operators and other basic elements.And the optimal assembly sequence of the main reducer was solved by programming operation.Secondly,the collision detection in the virtual assembly process of the main reducer was implemented based on the AABB hierarchical bounding box algorithm and mesh collider.In order to ensure the smooth operation of the system and improve the accuracy of collision detection,the mesh collider was added to the fixture used for the assembly,the AABB hierarchical bounding box were built by recursive method to the main reducer components and the created bounding box was updated in real time by using rotation control based on quaternion.In the implementation of collision detection,the collision detection between the main reducer components was realized by the intersection detection between the AABB hierarchical bounding boxes and the triangular face intersection detection of the component models,the collision detection between the main reducer components and the fixture used for assembly was performed with the box collider as an intermediary.Finally,the virtual assembly system of the main reducer in augmented reality environment was designed by using C# programming language.Using UG to build the3 D models of the main reducer assembly and the fixture used for assembly and import them into Unity3 D.At the same time,the model face optimization,texture and rendering were completed to improve the fluency and authenticity of the system.The system human-computer interaction mechanism combining gesture interaction and speech recognition was built based on the gaze ray collision detection technology.The virtual assembly system was developed in combination with human-computer interaction mechanism,collision detection algorithm,user interface design and spatial mapping technique in Unity3 D.The system was published to Holo Lens for 3D visualization simulation of the main reducer assembly process,and on this basis,the feasibility of the assembly sequence planning results of the main reducer was verified.