Research Of Self-propelled Agricultural Machinery Virtual Experiment Method Based On Virtual Reality

In order to shorten the product development cycle, maintain costs reduction, and improve design quality and products competitiveness, a virtual experiment system based on virtual reality for self-propelled agricultural machinery combining with the physics engine was established by means of modern computer graphics, computer simulation technology, information processing technology, and real-time interactive technology. The virtual experiment system has real-time characteristics, interactivity and physics properties which follow the objective movement law of the objects. To design the self-propelled agricultural machinery virtual experiment system, the key problems and methods of the system were studied.According to the demands of self-propelled agricultural machinery virtual experiment, and from the aspects of modeling method, key modeling technology, model structure optimization etc, the scene model and agricultural machinery geometric model of virtual reality systems were created combining with particle effects and shadows in the vega prime application module.Aiming at the performance testing characteristics of rice and wheat combine harvester, dynamics and kinematics analysis were carried out on the harvester. The mathematical models of harvester engine, steering system, longitudinal traction performance and vertical ride performance were created. The longitudinal and lateral characteristics of the tire were simulated using neural network technology, and we created the mathematical formulas of vertical stiffness and damping resistance of the tire based on experimental data and least-squares fitting, which provided a mathematics theoretical basis for harvester performance virtual test.The dynamic mathematical model is converted into C code used by the RTW (Real-Time Workshop) technology. Combining physics engine with harvester geometric model, physical behavior model and virtual reality experiment system were built which follow the objective physical laws. A virtual reality experiment method to co-simulate RTW technology with physics engine in virtual reality system was put forward.According to the characteristics of soil pressure model and aiming at soft road surface subsidence phenomenon after agricultural vehicle passing, an implementation method of dynamic terrain real-time visualization was described. Combining with dynamic mathematical model of harvester, the harvester performance test and test result were shown by visual interface of virtual test scenarios. At last, the virtual experiment performance of harvester was evaluated according to simulation data.The vertical acceleration signal obtained by actual measurement was filtered in Labview software. According to the least-squares method to remove the trend item of the signal, the acceleration signal is converted to a displacement signal. And then, comparing the signal with that obtained in virtual experiment at the same conditions to verify the effectiveness and accuracy of the virtual experiment system and vertical mathematical model. Based on the virtual experiment simulation data, evaluation indicators of dynamic traction performance were calculated by the probability statistical average method, then the effectiveness and accuracy of the virtual experiment system and longitudinal mathematical model of harvester can be evaluated.Driving simulator is connected to the virtual agricultural machinery and the virtual experiment system using man-machine interface technology. To control the movement state of virtual agricultural machinery by the information inputted from driving simulator, and then, the dynamic effect and movement form which obey the objective movement law real-time output to the projection screen, Therefore, real-time interactions of the self-propelled agricultural machinery virtual experiment were implemented.