Dynamics Analysis And Structure Optimization Design Of Key Components For 4WD Vehicle Power Distribution

With the development of automotive technology, four-wheel drive vehicle is increasingly getting popular among customers and many car manufacturers have also introduced various kinds of four-wheel drive (4WD) vehicles. However, the research on transfer case, which is the key component of four-wheel drive vehicle for power distribution is rare and no excellent theoretical system is formed. Therefore, it is of great theory significance and application value to carry out the theoretical research for four-wheel drive vehicles of different types.In this paper, based on the summary of analysis on the key components for power distribution of All Wheel Drive (AWD), Part-time 4WD and Real-time 4WD vehicles, a research method combined with theoretical analysis, numerical simulation and experiments is adopted for an in depth study on mechanical transfer case, intelligent torque distribution transfer case and the inter wheel differential. The main research procedures and results are summarized as follows:(1) A transfer case adaptive reconfiguration design system is built based on adaptive reconfiguration design theory, including modules like design plan, component adaptive design and intelligent assembly, and so on, which introduces a new method for the design of transfer case assembly components; on this basis, a transfer case adaptive reconfiguration design software is developed with Visual C#.net and Sql Server.(2) With the structural characteristics of the 3 common kinds of transfer case for 4WD vehicles, the power transmission characteristics of various transfer cases and mechanical formulas of transfer case under limit condition are figured out; taking the transfer case of a real-time 4WD vehicle as an example, the modal experiment and finite element modal analysis, static analysis, fatigue life analysis and topology optimization design are conducted to provided a reference for the mechanical analysis of transfer case.(3) Transfer case dynamic mesh and two-phase flow model are established based on the fluid-solid coupling theory. Besides, through comparison between experiment and computer numerical simulation, the accuracy of the model established is verified; on this basis, the flow characteristics of the flow field within the enclosed transfer case was acquired; and through the two-phase flow simulation analysis with different oil-soaked height, the optimized model of transfer case lubricating oil amount based on response surface methodology is built to obtain the optimal amount of lubricating oil, which provides a theoretical method for the design of amount of lubricating oil for transfer case.(4) Multi-disciplinary collaborative optimization for transfer case based on the satisfaction evaluation method is proposed to built the transfer case optimized model with the volume, maximum grade ability and fuel economy as evaluation indicators. The combinatorial optimization methods of DOE-ASA algorithm is adopted to optimize the design which obtains satisfactory results. The fuel consumption and the volume of transfer case decreased significantly after optimization.(5) Considering the structural characteristics of the differential between the wheel assembly and the characteristics of casting brittleness, based on the Particle Swarm algorithm, parametric modeling method is carried out to optimize the design of differential structure. The difference between mechanical properties of the differential before and after optimization verified the optimization results.(6) According to the research on the impact of power distribution between right and left wheels or between front and rear axles on the vehicle performances like power, fuel economy, braking and driving safety, the following conclusion can be drawn:with different road adhesion coefficient and different speed, torque distribution between the axis significantly affect power indicators and fuel economy indicators; and torque distribution between the axis has little impact on the braking performance; When the car steers, power transfer of the front and rear axles has a significant effect on sideslip angle and yaw rate of the whole car. When the power is transferred from the rear axial to the front axle, the vehicle safety has improved significantly; When the car steers, increasing torque distribution of the inside wheels would help the car’s steering driving state; compared with the torque distribution between the axles, torque distribution between the wheels is superior for improving driving safety.(7) The method to improve the safety performance of cars by the power distribution is proposed and formula of effects of power distribution on driving safety is figured out; dynamic torque control algorithm research based on neural network PID algorithm is conducted. On this base, a power distribution control device in the ring platform based on NI device is established, and the validation of the control method is verified by collecting real vehicle test data.