Research And Development Of Interactive Virtual Assembly Platform For Large Agricultural Machinery

In recent years,the development of agricultural mechanization in China has increased rapidly,and the status of agricultural machinery products in agricultural development has gradually increased.The tractor gearbox directly affects the workload,power and stability of the whole machine,Because of its complicated structure and strict assembly requirements.At the same time,the traditional assembly training and design which is directly to the real machine operation for tractor gearbox has the problems such as high design cost,long assembly training period,and large safety hazards.Therefore,improving the assembly design level of the transmission has an important significance in the development of the agricultural machinery industry.A virtual reality technology-based interactive virtual assembly platform for large-scale agricultural machinery gearbox has been developed,which mainly includes virtual assembly scene,component assembly positioning,assembly effect evaluation,dynamic motion simulation,human-computer interaction interface and other modules.The experiments have proved that the platform can perform active virtual assembly,interference detection,learning assembly knowledge,program design,and prompt assembly errors according to user requirements.The main research work and innovations are as follows:(1)For the traditional system design methods has the problems of complicated configuration and difficult to respond to change of demand.This paper has combined with the advantages of multi-Agent system,each virtual part is set as an agent,and a situational assembly model of the human-computer interaction system for multi-Agent-based complex gearbox has been proposed.A bottom-up multi-Agent interactive assembly platform framework has been built.The large complex gearbox assembly platform has been decomposed into a small,easy-to-manage spatial network relationship between the main agent and the sub-Agent,which simplifies the structure of the system and makes the platform easy to manage and control.(2)By comparing the advantages and disadvantages of several common colliders,the design of the OBB collider has been improved,and a multi-Mesh Collider method has been proposed,which can draw the collision box suitable for complex gearbox parts with relatively high precision,the face of the collision box can be reduced according to the application scene to achieve the purpose of improving system fluency.Simulating the collision of gears in the real world by combined with the physics engine that comes with Unity3 D to evaluate the feasibility of assembly.The experiments show that the time consumed by each frame of the platform is about 10 ms,which can ensure the smoothness and real-time interaction of the simulation system.(3)For the traditional animation assembly has the problems of the insufficient human-computer interaction and the single assembly method.This paper has developed the disassembly and assembly method based on state machine,the assembly positioning method based on circular detection,the assembly positioning method based on geometric constraint,A assembly and disassembly training method suitable for users at different stages has been designed by comparing the three assembly and disassembly methods with experiments from human-computer interaction,assembly speed,learning training efficiency,assembly tolerance and other aspects.At the same time,a relatively simple gear assembly and disassembly sequence method has been introduced.Finally,the feasibility of three assembly methods has been proved by several different part assembly experiments.(4)A software framework of the virtual assembly platform for complex gearbox has been built.The Solid Works software is used to model the gearbox components from a group of large tractor 1200 series gearboxes,and the model format conversion tool is used to convert these models into.fbx format which can support by Unity3 D.In order to provide a more comfortable operating experience,the platform also built other modules such as virtual scene change and roaming mode setting,so that users can interact with the platform more comfortably.Finally,the platform has been multiple operated and functional tested to improve its feasibility,integrity and practicability.