Research On The Lightweight Method Of Urban Bus Skeleton Based On Combined Approximate Model

The purpose of this paper is to find a lightweight design method for urban bus body skeletons that has high computational efficiency,shortens the development cycle and guarantees the global optimal solution.Taking a hybrid bus frame as the research object,a series of researches are carried out in combination with finite element,DOE test design,approximate model,deterministic and robust size optimization,and game theory combination weighting.The finite element static performance analysis of the body frame.The static analysis of the car body skeleton finite element model is carried out under five typical operating conditions of full load bending conditions,acceleration conditions,emergency braking conditions,sharp turning conditions and extreme torsion conditions of urban buses.The results show that the safety factor of each working condition is greater than 1.5,so the material performance has not been fully utilized,and the body frame has the potential for lightweight design.Construction of the approximate model of the body frame combination.In order to solve the problem that various single approximate model methods have different prediction capabilities for different state variables,compare the constructed radial basis neural network(RBF),response surface(RSM),particle swarm support vector machine(PSOSVM)And Kriging(Kriging)approximation model to fit the accuracy of the body frame performance response,and use the method of minimizing the mean square error to calculate the weight coefficients of each single approximate model,and then establish a combined approximate model of the urban bus body frame performance response,It has laid the foundation for the lightweight research of the body frame under various working conditions.Dimensional optimization considering determinism and 6? robustness.Deterministic optimization of five typical working conditions of passenger cars based on combined approximate model.The optimized total mass of fully loaded bending,acceleration,emergency braking,sharp cornering and extreme torsion conditions was reduced by 16.4%,14.5%,21.3%,17.98%,and 10.9%,respectively,relative to the original weight.The quality level analysis of the deterministic optimization results shows that the output response of the full-load bending condition and the ultimate torsion condition does not meet the design requirement of 6? quality level.Furthermore,based on the 6? robust design of the combined approximation model,the total mass of the body frame under full-load bending conditions and ultimate torsion conditions was reduced by 11.2% and 8.6%,respectively,relative to the original weight.Based on the game theory combined weight method to determine the weight of the passenger car's working conditions.Aiming at the problem of insufficient accuracy and rationality in determining the weight of passenger car operating conditions by traditional weight calculation methods,a combination weighting method based on game theory is used to determine the subjective weights determined by the analytic hierarchy process improved by the gray correlation model and the objective weights determined by the entropy weights.Combined,the weight of the city bus under five typical working conditions is: 35.4%,18.9%,21.1%,14.7% and 9.9%;the total mass of the body frame is reduced from the original 2472 kg to 2087.34 kg,relative to The original weight was reduced by 15.6%,achieving the purpose of light weight.The basic performance of the optimized body frame and the quality level of the response were checked and analyzed,and the results met the design requirements.In summary,this topic addresses the limitations of a single approximate model method,deterministic optimization is prone to fall into local optimality,and the unreasonable distribution of multi-operating weight coefficients,etc.,a lightweight design is proposed for the body frame based on a combined approximate model method The optimization results show that the method proposed in this paper has a certain reference value in the realization of lightweight design of passenger cars.