Sensitivity Analysis On The Kinematic Accuracy Of Automotive Steering Mechanism And Optimization Design

The kinematic accuracy analysis and optimization dedign theory of automobile steering mechanism is a subject worthy of further study and has important theoretical and practical significance.The Sobol' method is used as the basic mathematical tools for the global sensitivity analysis on the kinematic precision.In order to put forward some new design methods and to obtain some valuable conclusions,the kinematic precision of the steering mechanism is studied.The existing sensitivity analysis methods are briefly introduced,and then the basic principle of Sobol' global sensitivity analysis method,the definition of sensitivity index and the Monte Carlo method of sensitivity index calculation are emphatically introduced.A global sensitivity analysis program is designed in Matlab language.Taking the sensitivity analysis of Ishigami function and Sobol' g-Function function as two examination questions,the designed program is checked and verified.The Sobol' global sensitivity analysis of these two examination functions is carried out by using the designed program,and the analytical results agree well with the known analytical solutions.The results show that the sensitivity analysis program is correct and reliable,and the calculation accuracy is enough to meet the needs of engineering design and analysis.The sensitivity of kinematic accuracy of the integral steering trapezium mechanism is analyzed by using the designed Sobol' global sensitivity analysis program.The mathematical model of kinematic accuracy of the mechanism is established by taking into account the influence of the manufacturing error of the rod length and the clearance of the kinematic pairs.The sensitivity analysis results show that the four kinematic pairs with clearance in the rear steering trapezoid mechanism are important factors affecting the kinematic accuracy of the mechanism,and the two main pins with clearance are the key factors.Taking the steering mechanism matched with the rack-and-pinion steering gear as an example,the sensitivity analysis of the divided steering trapezium mechanism is studied.Considering the stochastic manufacturing error of the rod and no effect of the clearance in the kinematic pair,Sobol' global sensitivity analysis results show that the length of the steering tie-rod with stochastic manufacturing error is the key factor affecting the kinematic precision of the steering mechanism.Based on the Sobol' global sensitivity analysis,two optimal design methods areproposed.One is the optimal design method based on the additional target of Sobol'total sensitivity.Based on the original design optimization model,the maximum total sensitivity of all design variables is used as an additional objective function.The new optimization design model with double objective functions is established.The double objective functions are the original objective function and the additional objective function.The other is a direct optimization method based on sensitivity analysis.For this method,Sobol' global sensitivity analysis on the existing design scheme is carried out firstly,and then the important factors and the key factors affecting the objective function are found out.With these important factors and especially the key factors improved,the existing design scheme can be further optimized.Two optimaitation design examples are given to examine the validity of the proposed optimization design methods.