Multi-objective Optimization Of Bus Body Frame Based On Agent Model

The optimization design of the bus body can not only reduce the raw materials required for manufacturing,but also reduce the quality of the bus body,improve the performance and reduce emissions,so it is imperative to optimize the bus body.In this paper,based on the agent model method,a 12-meter long bus body frame is used as the research object,based on 15 design variables,the objective and constraint functions of the body are fitted by Lagrange method based on dimensionality reduction to optimize the body frame.The major studies and findings are as follows:1.According to the three-dimensional geometric model of bus frame,the body frame structure is meshed.Aiming at the loading and constraint conditions of horizontal bending,ultimate torsion,sharp turning and emergency braking,the static strength under different working conditions was analyzed in the finite element software.The results show that the body structure can meet the strength requirements in any working conditions.2.The modal analysis of the body frame is carried out,and the frequency values and the first 10 modes of the body frame are listed.The analysis results show that the body structure does not resonate with the external excitation source.3.15 parts were selected by sensitivity to participate in the lightweight design.The minimum quality of body frame as the goal,The thickness of the screened parts is taken as the design variable,with body structure under four conditions of stress values are less than the allowable stress of material as constraints,the mathematical expressions of the mass and the constraint stress of the bus body frame are fitted based on the Lagrange method based on dimensionality reduction,and the mathematical model of the body frame lightweighting is established.Finally,the mathematical model of lightweighting is solved by the sequential quadratic programming method,which reduces the body frame by 177.4kg,accounting for6.58% of the total mass of the body frame.4.The aim is to minimize the mass of body frame and maximize the stiffness of body,with body structure under four conditions of stress values are less than the allowable stress of material and the first free modal frequencies is smaller than the original order modal frequency as constraints,The mathematical expressions of mass,body rigidity,stress and modal frequency are fitted based on the Lagrange method based on dimensionality reduction,and the Pareto solution set containing 60 sets of solutions is solved by using the multi-objective genetic algorithm,and the superiority and inferiority indexes of each set of solutions are calculated and the optimal solution is selected.