Study On Rapid Design Of Beam-like Cross-section Of Automobile Body Based On P1N1Plant Growth Algorithm In The Conceptual Design Phase

With the development of the automotive industry as well as the increasingly fiercecompetition in the automotive market, the automobile performance of strength, stiffness andsecurity are required to be better. Conceptual design phase has played a pivotal role in thevehicle development process. At this stage the body structure design plays an important roleto reduce the development cost of the vehicle and shorten the production cycle. As thecross-section of the body has a direct impact on the stiffness, strength, and safety performanceof the car, so a reasonable and effective design of automotive body key section at theconceptual design stage is very important in the entire development process of the car body.In order to efficiently design the key section of the body in the conceptual design phrase,this paper presents a fast optimization method of cross section based on P1N1plant growthalgorithm. Firstly, this paper establishes a simplified model of body frame beam section withthe the database of key section and makes comparative analysis of the error. Secondly,asymmetric optimization design of beam section with a simplified model is made through amulti-constraint condition. In the end simultaneous optimization of the shape and thicknessare completed with P1N1plant growth algorithm and it is realized that rapid optimization ofkey cross-section of the automobile body in the conceptual design phase. The main aspects ofthe study are as follows:(1) A simplified model of body frame beam section with the database of key section isestablished and comparative analysis of the error is made with constraints of torsional modes,the bending stiffness condition and torsional stiffness condition, which provides effectiveguidance for the next detailed design of the cross section.(2) Set the thickness of the two adjacent sides of rectangular beam cross-section todifferent variables with the simplified model and make asymmetric optimization design ofbeam section. It avoids the shortcomings of the simplified cross section of equal thickness—master of inertia is zero—when seeking cross-section mechanical parameters before. Thethickness of the adjacent edges of the rectangle are set as two variables(the remaining twosides as a fixed value). It is four parameters with the length and width of a rectangle in everybeam. With constraints of six simplified conditions—torsional modes, the bending stiffnesscondition, torsional stiffness condition, frontal crash streamline state, side impact streamlinestate and offset collision streamline state, the optimized value of the key mechanicalparameters of the beam cross-section are obtained ultimately, which provided criticalguidance for the next detailed design. (3) Describe the development process and the application of plant growth simulationalgorithm. By improving plant growth simulation algorithm P1N1plant growth algorithm wasproposed for the cross-section optimization. By extracting the node coordinates and theperformance parameters of the cross section, the node coordinates of beam cross-section wereimported into P1N1plant growth algorithm as design variables to optimize, therebycontrolling the beam cross-sectional shape and thickness. Based on P1N1plant growthalgorithm, a mathematical model and corresponding program were established. Anapplication has proved that this method is effective.This study shows that: a fast optimization method of the beam cross-section design of carbody in the conceptual design phase which is based on P1N1plant growth algorithm has beenused to effectively solve the problem that the beam cross-sections are blindly designed in theabsence of various detailed parameters in the early design phase. This played a certain role inthe design of key section of the body in the conceptual design phase with a strong theoreticalvalue and engineering value.