Research On Key Technology Of Virtual Massive Production Tuning Of Automotive Chassis Functional Components

The core technical elements of automotive products in market competition mainly include reliability,steady-state performance,transient dynamic performance,product consistency of the above performance in massive production process,and attenuation of the above performance after a period of use(persistence).After decades of development,China has fully mastered the technology of reliability and steady-state performance,and the related performance indicators of independent automobile brands have reached the international first-class level.There is an urgent need to improve the dynamic performance,massive production consistency and performance durability of China's own brand automobiles.At present,the dynamic performance of products under transient conditions can only be developed by subjective evaluation of actual vehicle field test.In order to ensure the consistency of dynamic performance in mass production,when the supporting assembly changes or the production process changes,the performance tuning process needs to be repeated several times.This kind of massive production performance tuning is essentially a classic iterative development of physical sample car,without the use of simulation technology for virtual adjustment,which has long development cycle,high cost and high product risk.The main reasons for restricting the realization of virtual massive production tuning are as follows: first,the models of suspension,bushings,shock absorbers,buffer blocks and tires,which are often replaced in the dynamic performance adjustment based on subjective evaluation,are inaccurate in determining the dynamic quality of automobiles;Second,after the variable range of dynamic performance required by the consistency of yield and the persistence of performance is determined,there is no quick solution to the variable range of the above functional components.Aiming at the above two problems,the frictional hysteresis effect is introduced into the existing functional component model,a higher precision functional component model is established,the experimental identification technology of the newly established semi-empirical model is researched,the interval mathematics method and the generalized least square method is adopted in this paper.This paper researched a fast decomposition method from the variable range of dynamic performance to the variable range of functional component characteristics,so as to realize the virtual tuning of massive production.In order to complete the research idea,based on a large number of domestic and foreign literatures,this paper takes the vehicle handling and stability as the entry point and makes relevant innovative research in the following aspects:1)Functional component modeling taking into account frictional hysteresis characteristics: Current business dynamics software features used in the model,only consider the linear stiffness and damping,without considering the friction,which makes the model of the road or artificial tiny disturbance as well as the vehicle itself occurring in the process of manufacturing deviation is too sensitive,cannot reflect the inclusiveness of the car itself,the stability and robustness,do not tally with the real vehicle performance.After many years of exploration,the quality dynamics model is established and the transient performance of vehicles can be simulated and analyzed by computer.Based on the previous experience of the research group,this paper focuses on the functional component model,establishes the functional component model considering the friction hysteresis and dynamic and static friction switch,and applies it to the dynamics model based on parts.It can more accurately simulate the central area(anti-human interference),the stability of straight line driving on uneven road surface(anti-road interference),straight line running deviation(hard point deviation or positioning deviation),rear wheel follow-up steering and other conditions.2)One-step identification method of parameters of rubber functional parts:Because the friction hysteresis characteristics and dynamic and static friction switch are considered in the model of rubber functional parts,it is difficult to identify parameters through experimental data.In order to solve this problem,a one-step identification method is proposed in this paper,that is,it is not necessary to separate the dynamic and static test results,but to identify all the parameters of the model step by step according to the dynamic test results using simulated annealing particle swarm optimization method.This identification method effectively solves the problem of noise sensitivity caused by the stepwise identification method in the previous model,which separates the speed-related components and the independent components in the test data,and the problem that the commonly used optimization method is easy to fall into the local minimum solution.3)Rapid solution of variable range of functional component characteristics:The current industry uses the DOE method for mass production adjustment of real cars,which requires repeated iterative experiments on real cars,takes a long time and costs a lot;The virtual DOE experiment is carried out on the computer,and the cost is reduced and the efficiency is improved compared with the real car adjustment.However,it also takes a long time to complete an analysis because of repeated iterations on the computer.This paper tries to find a method to reduce the number of DOE and quickly solve the variable range of the feature of a functional component.Firstly,DOE analysis was used to obtain functional component characteristics sensitive to vehicle performance indicators.Then,the change gradient between those highly sensitive functional component characteristics and vehicle performance index is obtained by DOE analysis,and Jacobi matrix is established according to these change gradient.Finally,interval mathematics and least square method are used to solve the generalized inverse matrix of the Jacobi matrix,and the variable range of the feature of the functional component is obtained.Based on the data of M8 x model,a vehicle dynamics model considering friction hysteresis is established.The influence of friction characteristics of functional components on K&C analysis results was verified by dynamic K&C analysis of models with and without considering friction characteristics of functional components.Finally,taking the steering wheel Angle step condition as an example,the design parameters with high performance sensitivity were found through the sensitivity analysis between the design parameters of each system and the vehicle performance,and the consistency of the vehicle handling performance was simulated and verified by the fast solution method of the variable range of functional components.According to the analysis results,the allowable deviation range of the functional components is corrected.The results show that the dynamic model established in this paper and the fast solution method can effectively realize the decomposition from the vehicle performance tolerance to the variable range of functional component parameters in the conceptual design stage,and provide technical guidance for the tolerance design of functional components and subsequent production tuning.