Studies On The Design Optimization Method Of Suspension KnC Of C- Class Vehicle

The design of suspension system is a crucial part of chassis research and development, the kinematics and compliance characteristics of the suspension system is the heart of the chassis development. How to optimize suspension KnC in the term of the vehicle performance is the key point of chassis development.Associated with the project of a C-Class vehicle development, this dissertation focuses on the problem that how to optimize the suspension properties in the vehicle research and development.In order to match the suspension system with full vehicle performance, the following problems must be solved:●How to choose the perfect suspension KnC in the perspective of the overall vehicle performance?●How to design the structure of the suspension system to achieve the expected suspension KnC in the light of the suspension structure?This dissertation studies mainly about these above two problems.Firstly, review the history and literature about the suspension optimization method, additionally address the background and application of the study, and thereafter describe the main content of the dissertation.Secondly, overview the suspension KnC, and analyze the cause of the main suspension KnC. In the mean while, introduce the influence of the suspension KriC on full vehicle performance as well as the suspension KnC test facilities.Furthermore, according to the experimental data of the benchmarking vehicle, the structure-based suspension model and property-based whole vehicle model have been established individually. By the test data of suspension KnC as well as full vehicle handling stability and ride performance, the suspension and overall vehicle model have been validated, preparing for the following suspension KnC optimization.In order to optimize the property of the suspension system, the essential step is to establish the approach of objective evaluation for the vehicle performance. Thus, in the following work, this dissertation mainly focuses on the handling stability and ride comfort. As for ride comfort, the method recommended by ISO2631 has been used widely, so as in this dissertation. According to the practical problem, consider the RMS of the vertical vibration acceleration of the sprung mass, the suspension deflection and the tire dynamical load. As for handling stability, there is no unified standard, so that this dissertation mainly focuses on this point. On the basis of the former work of the research group, this dissertation takes ISO Lane,Slalom and On Center as the evaluation experiment; and employs the indexes presented by Prof. Guo and indexes which presents the performance of the On Center handling. The input and output data used for establishing objective handling evaluation are obtained from lots of experiments, then exploits SVM which is based on the statistical learning theory to establish the evaluation approach, considering the correlation of subjective and objective evaluation. According to the results, it shows that the method fits the experimental data points well and has better prediction ability, and it satisfies the requirement of the suspension optimization in the vehicle development.To optimize the suspension properties, the vehicle-system-structure decomposition method was used. In the first place, take the handling and ride of the vehicle as the objective, optimize the suspension properties; then, take suspension properties as the objective, optimize the suspension hard points and bushing stiffness to determine the key parameters' design of suspension system in the vehicle development.To optimize the properties of the suspension, take advantage of the CarSim and iSIGHT as the main method. How to choose the initial values of the optimization problem is very vital, this dissertation addresses the method for choosing initial values closed to the optimal solution, so that the optimization method is more suitable for practical chassis development. The response surface methodology and Kriging method for model approximation are also researched; finally, use multi-objective optimization method to get Pareto solution.As for the optimization of the hard points and bushing stiffness, ADAMS and iSIGHT co-simulation method is exploited, with multi-objective method to optimize the hard points and bushing stiffness.Major Innovations of the Dissertation:(1) Establish the vehicle handling objective evaluation system with SVM;(2) In the vehicle development, optimize the suspension properties, especially suspension KnC, considering the handling and ride;. (3) Research the hard points and bushing stiffness optimal designing method, as a reference for the engineering application.