| Vehicle dynamic simulation technique is a powerful tool for auto design and production. As a general technique to increase national competition, it's the international research focus for decades. The simulation technique key part is that vehicle dynamic model has RTS (real time simulation) and high fidelity. Now, there are two important theories in vehicle system dynamics. One is Roll-Center theory. The other is multi-body dynamic theory. The vehicle model based on Roll-Center theory use a set of complex parameters obtained from vehicle examination to describe the complex character of kinematics, dynamics and elasticity .This method avoids solving the complicated kinematics and dynamic equation group, so it has the faster solving velocity and the better real-time characteristic. It has been proved that this model has preferable fidelity. The vehicle model based on multi-body dynamic theory can build the more complicated and more elaborate model. There are lots of commercial soft wares like ADAMS, DADS. But multi-body programs employ nonlinear differential algebraic equations that require iterative solution methods that run slowly and with variable time steps. It usually wastes some weeks to solve one condition. So this kind model is not suitable for full vehicle dynamic design and optimization. Now the vehicle dynamic model working on the first large-scale automobile driving simulator of China is developed in 2000.This model has the fidelity that better than eighty percent. But the model has some deficiencies such as it can not simulate the non-level road condition and the static friction condition veritably. The dissertation tries to do some reasonable improvement for China First Driver-Simulator. The new model has the attribute of facing to real-time simulation and facing to non-level road condition. Based on the research of vehicle system dynamics in The State Key Laboratory of Automobile Dynamic Simulation, we do many works to build a model suited for driver simulator. There are four parts in the dissertation. In chapter one, the history of vehicle dynamic model and distinctness are discussed, based on the need of update for driver simulator of our laboratory, the contents of the dissertation are put forward. In chapter two, we build the vehicle dynamic model suited for the driver simulator. Because the vehicle model has separated the car-body system, the suspension system and the car-wheel system, it can reduce the coupling degree. Considering the condition of my lab, we suppose the mass of suspension poles can be neglected, a proper suspension model is built based on Roll-Center theory. Compare with the multi-body model, it can avoid solving the complex rigidity differential-algebra equation, improve the solving speed greatly. In chapter three, the tire model including mass of contact patch and elastics carcass is built based on Unitire model and Swift model. Try to calculate transient slip rate and slip velocity through the contact patch dynamic formulas. On the static friction condition such as parking, the carcass is treated as "directional sensor"to estimate the relation of tire and ground, so the vehicle can simulate the static friction condition steadily. Based on ground vertical vector and carcass turn angle, the tire force coordinate is defined that is suitable for non-level road condition. In chapter four, the dissertation discusses the algorithm for vehicle dynamic real time simulation. The increment algorithm of Euler angle transfer are used to insure that the vehicle dynamic model can get right simulation result on complex conditions. The... |
