Research On The Simulation And Analysis Of 22 DOFs Vehicle Dynamic Model

Vehicle virtual prototype technology is the core technology which can shorten product design cycle, save R&D expenses and reduce the risk of development. The key to apply virtual prototype technology in vehicle R&D process depends on the fidelity, real-time simulation and simulation condition applicability of vehicle dynamics model. At present, the major domestic carmakers have started to design using the internationally popular vehicle dynamics simulation software such as MSC. Adams, Carsim, etc in the product design process. But there are many difficulties in the vehicle design, road test and debugging phase because the designers can't grasp the core of the software theory. Therefore, based on the analysis of multi-body system dynamics modeling method, this paper is committed to build a vehicle dynamics simulation model on the basis of assembly features and study the factors which have impact on vehicle handling stability.First of all, in order to facilitate the research, the structure and the degree of freedom of the vehicle have been simplified appropriately; four different sets of coordinate systems and wheel unit vectors are established to describe the relative position, attitude angle and force transitive relation between the rigid bodies. One coordinate system can be converted to another by means of the direction cosine matrix. Then, PAC2002 Magic Formula tire model is established to compute the force and torque generated between the tire and the ground. And introduce the first-order relaxation length to describe the transient characteristics of tire force. The suspension K&C characteristic correction model is to correct the wheel alignment parameters. The suspension model is established based on the roll center theory. Use multi-body system dynamics knowledge to analyze the movement state relations between wheels, suspension and body and conduct force, kinematic and dynamic analysis of various rigid bodies. At last, establish the vehicle 22 kinetic equations under the body coordinate system.Adopt Adams-Bashforth linear multi-step method to do numerical integration, write vehicle multi-body simulation procedures in MATLAB, and conduct simulations including the vehicle linear acceleration, deceleration, steering wheel angle step input and steady rotation. Compared with Adams and Carsim model simulation results, the established model has high calculation precision and efficiency to meet the requirements of real-time computing. The analysis of factors on vehicle handling stability is conducted combined with the vehicle dynamics simulation model and fuzzy grey correlation analysis model. The established model is an effective tool to study the vehicle dynamics. It can provide theoretical guidance in chassis system design and development and assembly debugging for the engineering staff, and a platform to develop various electronic control systems.