Research On Modeling Of Vehicle Suspension System Characteristics

The product development using vehicle virtual prototype technology is the trend of full-vehicle development in the future. Vehicle virtual prototype dynamic simulation takes the place of real vehicle test, which both shortens vehicle development time and lowers the cost, and reduces the risk of extreme conditions. The full-vehicle development with virtual prototype technology brings revolutionary progress to the car industry.However, the virtual prototype technology's wide application depends on the fidelity of vehicle dynamics model in the automobile products R&D, which makes modeling accurately more and more important. Vehicle dynamics model can be summarized as the model based on assembly structure and the model based on assembly characteristics. In the early stages of vehicle design and development can't be informed of the specific structural parameters of the vehicle, the assembly can only define the assembly characteristics to the vehicle development; And for component manufacturers, vehicle manufacturers can't get spare parts from the specific structural parameters, only through the external characteristics of components to guide product development and design, so the model based on assembly characteristics are important to the vehicle development. Now vehicle dynamics model's simulation in the handling and stability properties is mostly good, but the quality of vehicle dynamic:friction, hysteresis, and high frequency link is considered less, the vehicle dynamics model must to be perfected continually to make it more accurate and truly reflect the car's quality characteristics, thereby to make virtual prototype technology function properly.This paper does research on the modeling method of the suspension system's characteristics, which includes two aspects:the modeling method of the load-supporting characteristic and the orientation characteristic. As elastic components are widely used and various components'coupling effect, the suspension system's characteristics as a whole show remarkable non-linear hysteresis characteristic and compliance changes. At present, the model of suspension load-supporting characteristic just builds linear or nonlinear stiffness characteristics about elastic components, but Most of the vehicle suspension system is the coupling of elastic components and damping components. So suspension system's internal friction leads to friction existing in suspension system, and namely load-bearing characteristic presents non-linear hysteresis. Though suspension oriented characteristics in the oriented force model based on the roll center theoretical modeling has been perfect, it is less into consideration in K&C characteristic parameter model. And many suspension K&C characteristic parameters'selecting and parameters processing are very complex. In view of the above problems, the suspension load-supporting characteristic and oriented characteristic's modeling method is studied separately in order to improve the suspension model's accuracy and make it more in line with the test data of the suspension system's characteristics, then more accurately and fully reflect the vehicle working performance and quality characteristics. And the model parameters identification method and the test data processing are studied.Firstly, the progress of the vehicle suspension system dynamics model and suspension K&C characteristic test research is investigated in the paper, and the actual suspension system's characteristics and the shortages of the model are analyzed. Then the research's purpose and technology exploring route is put forward, determining the research's content and structure arrangement of this paper.Then, the suspension load-supporting modeling method is studied. The modified ideas about the Fancher model are put forward on the base of researching and summarizing several mechanic system hysteretic models and hysteresis problems of the current vehicle suspension load-supporting characteristics modeling. And the correction algorithm for the unloading lower envelopes and the transition envelopes is given respectively, realizing that the unloading lower envelopes and the transition envelopes of the suspension system load-supporting characteristic curve are inconsistent. Through contrasting and analyzing the simulation results and test data, the validity of the Fancher model is verified.The third part is the research on the suspension oriented characteristic modeling method, expatiating two aspects of the suspension oriented characteristic:the oriented force model based on roll center and the K&C characteristic parameters. And this part mainly studies the K&C characteristic parameters of the suspension oriented characteristic, summarizes the characteristic parameters affecting the suspension K&C characteristic, analyses its influence on vehicle performance, at the same time surveys and summarizes main K&C characteristic parameters in the world, and the ASCL suspension K&C characteristic parameters and corrected method is obtained on the base of analyzing the characteristic parameters. Meanwhile the oriented force model based on the roll center theory is introduced in order to establish a complete suspension model.Finally the model parameters are identified and test data are processed. According to the complete suspension system's characteristics model established above, the methods to identify the load-supporting characteristic and oriented K&C characteristic parameters is studied respectively. And the parameters are extracted from ABD suspension K&C test data. In the end, the test data processing software is achieved by establishing MATLAB/GUI.