Parameters Sensitivity Analysis And Optimization For The Performance Of Vehicle Handling And Stability

Vehicle handling and stability performance is an important part of the automobile theory. It includes two parts that link to each other closely and the tow parts are handling performance and stability performance. Vehicle handling and stability performance not only influences convenience of steering but also determines the security of the high-speed automobile. With the improvement of the road condition and the boost of the speed, vehicle handling and stability performance is paid more and more attention, so it becomes an important direction of development.Vehicle handling and stability performance is usually studied with tow methods which are simulation and experiment. The methods of simulation analysis build a model that are simplified to some extent using computer, and the maneuver signals of the driver are regarded as the input of the model. Then the vehicle handling and stability performance is expressed by solving the response of the system. Simulation analysis spends less time and expense and it is repeatable. The more important is that the design layout can be optimized quickly and it can realize the utmost condition which can not test. So simulation analysis increasingly becomes important.Suspensions are the important components to determine the ride and handling performances of a vehicle, as well as reduce shock and vibration transferred from the road to the body. In the initial layout design, the hard points need to be determined to obtain handling and stability performance close to the desired targets. However, it is difficult to use analytic methods in suspension design, and in fact layout design is dependent on the experience and know-how of the chassis designers. If the handling and stability performance is optimized with respect to the hard points, even junior designers can easily develop suspension with the desired handling and stability performance. Hence an optimized technique that achieves a design within the desired handling and stability performance are required.This paper creates a virtual prototype of a full car using ADAMS. In this paper, the sensitivity of the coordinates of the hard points in suspensions and the parameters of sprung-mass are calculated. Based on the result of the sensitivity analysis, the coordinates of hard points and the parameters of sprung-mass are optimized respectively. After the optimization of the coordinates of hard points,the other parameters of suspensions are optimized too. In the end, the inertia of steering wheel and the ratio between the pinion and the rack which in steering system are optimized. The work of this paper goes as follows:Firstly, a dynamic model of a full car is created using ADAMS/Car. During modeling, the interface between ADAMS/Car and other modules in ADAMS is full used. So the function of the ADAMS/Car is greatly extended. For example, the viscous friction in steering system is modeled using control tool box. After creating the model, performing several type of test simulation such as slalom, double lane change, center steering etc, comparing the results of simulations and experiments, so the validity of the model can be verified.Secondly, the comprehensive evaluated function is linked into the model using the several type data in ADAMS/Car and this function is regarded as objective function used during sensitivity analyzing and optimizing. The communicators are used to exchange data between templates when the creating the objective function. Thirdly, the sensitivity of the coordinates of the hard points in front suspension is calculated. Based on the result of sensitivity of the coordinates of the hard points in front suspension, the six coordinates which have more influence on the vehicle handling and stability performance are optimized. And then, toe angle, camber angle, the stiffness of coil spring and the damp of damper in front suspension are optimized. After optimization, the value of objective function reduces from 3.4062 to 3.029.Fourthly, the sensitivity of the coordinates of the hard points in rear suspension is calculated. Based on the result of sensitivity of the coordinates of the hard points in rear suspension, the four coordinates which have more influence on the vehicle handling and stability performance are optimized. And then, toe angle, camber angle, the stiffness of coil spring and the damp of damper in rear suspension are optimized. After optimization, the value of objective function reduces from 3.4062 to 3.0762.Fifth, the sensitivity of the parameters of the sprung-mass is calculated. Just as the results show, the inertia of x axis has more influence than the inertia of y, z axis.