Research On The Design-Oriented Dynamic Assembly Of Transmission In Virtual Environment

Transmission of military armored vehicle has complicated structure,compact space and high requirement for assembly process.It is expensive that the physical prototype is used to assembly and assembly training.Virtual reality is widely researched as emerging technology in recent years.The application of virtual reality technology to assembly design and assembly training can not only make the assembler fully understand and experience the product structure,but also find the problem of structural design,and improve the assembly and maintainability of the product.Traditional virtual assembly softwares,such as CAD software Pro/E and Catia,use predefined assembly objects and assembly constraints to solve pose matrix by constraints,so that the parts is transformed from the initial pose to the final pose.It is called as “one touch” assembly,which has disadvantages,(1)no assembly path,(2)interpenetration of parts,(3)reasonableness of structural design cannot be tested,(4)simple assembly interaction and lack of natural human computer interaction.The dynamic assembly theory is put forward,where assembly feature collision detection and feature parameters are used to realize constraint automatic recognition and the motion of parts is characterized by degree of freedom reduction of pose change.The dynamic assembly platform is developed by Unity3 D in virtual reality.The theory and methods are validated by shaft of some transmission.The main contents are as follows.The research of dynamic assembly theory is carried out with the function of geometric feature recognition and constraint real-time updating,and the data structure of part model for dynamic assembly in virtual environment is defined.In the development environment of Visual Studio,a plug-in program is written using the secondary development tools of Pro/Toolkit for extracting the information of the original parts,and the visual editing and management of parts is written by using the QT interface editor library.The mathematical description and derivation of assembly constraint and part motion in dynamic assembly theory are carried out.The geometric features of parts are located by collision detection method,and the constraint types are identified by parameter matching method.The degree of freedom reduction method is used to determine the motion law of parts under multiple constraints,and the constraint tree is used to store and manage the constraint relations among the parts in the virtual environment.Based on the Unity3 D rendering engine,the virtual environment is constructed,The dynamic assembly theory,the HUD technology and the Leap Motion gesture capture device are used to build the visual human-computer interaction assembly platform.The virtual assembly function test is carried out with a transmission shaft system as an example,and the feasibility of the theory is verified.From the aspects of motion description,constraint expression,constraint solving and constraint establishment under the constraint conditions,this paper puts forward the assembly feature as the constraint recognition base element,and triggers the assembly constraint mapping algorithm by collision detection to realize the dynamic assembly of the parts,and provides the software platform with functions of human-computer interaction,tooling usage,assembly operation,structural design error detection and assembly process optimization,etc.