Research On Hierarchical Target Decomposition Of Vehicle Handling And Stability

With the continuous innovation of driverless and new energy technology,vehicle intelligence has ushered in great strides.At the same time,people’s requirements for vehicle performance have gradually increased,which puts forward higher requirements for vehicle handling and stability.The handling and stability performance of the vehicle depends on the mutual cooperation of various systems of the vehicle.Even small changes in the installation position of parts will have a great impact on the handling and stability of the vehicle.Then how to systematically decompose the handling and stability index of the vehicle into various subsystems and parts,and how to efficiently match and optimize the parameters of subsystems and parts,These two have become the key to the development and improvement of vehicle handling and stability.In view of the above problems,this paper establishes a decomposition system for the development of vehicle handling and stability,combines the generalized backstepping theory and NSGA-Ⅱ genetic algorithm to form an interval optimization method,and realizes the optimization of multiple indexes of vehicle handling and stability with the help of the joint simulation technology of MATLAB and multi-body dynamics software motion,and improves the scores of various handling and stability tests.Among them,the "short board item" in the handling and stability performance score of the object vehicle is analyzed,and the optimization effect of steady-state rotation test and steering alignment performance test is particularly significant.They have increased from 76 and 67 to 89 and 80 respectively,which further verifies the effectiveness of the method proposed in the paper.The specific research contents are as follows:(1)Combined with the theory of vehicle system dynamics and the evaluation method of vehicle handling and stability,this paper defines the influence relationship between the evaluation index of vehicle handling and stability and various systems and parts of the vehicle body,introduces the evaluation scoring criteria in the national standard of handling and stability to quantify it,and further combines the theoretical decomposition framework of the whole vehicle handling and stability performance with the objective evaluation system,So as to establish a set of tree decomposition diagram.(2)By establishing the vehicle multi-body dynamics model used to study the vehicle handling and stability performance,and on the basis of confirming the confidence of the vehicle model simulation results,a number of handling and stability performance simulation tests are carried out item by item according to GB / T 6323-2014 vehicle handling and stability performance test methods.Then,according to GB / T 6323-2014 test method for vehicle handling and stability,the test scores are calculated respectively,and the handling and stability scores before and after optimization are compared and analyzed.(3)The established decomposition tree chart of vehicle handling and stability covers 5 tests,a total of 13 evaluation indexes,and a total of 22 influence parameters,which brings great workload to the subsequent optimization design.Therefore,the paper adopts the sensitivity analysis and calculation method of introducing adjoint variables to select the parameters(significant influence factors)that have a significant impact on the evaluation indexes of each test,which not only improves the efficiency of the optimization process,but also avoids the problems of non convergence and low accuracy of the optimization results caused by too many influence factors.(4)Combined with previous studies,it can be seen that it is impossible to find a reasonable value of common impact factors to optimize all indicators.Therefore,this paper adopts the idea of solving the optimal interval of design variables in the generalized backstepping method to convert the optimal value of solving the common influence factor into the optimal interval of solving the common influence factor,so as to convert the optimal numerical score of the optimized handling and stability performance into the optimal score interval,and obtain better optimization results.