Multi-objective Optimization For Rollover Safety Of A Fully Integral Bus Based On Rsm

To enhance the safety of buses, there are some regulations concerning the bus rollover both domestic and overseas, such as the European regulation ECE R66 and the GB T17578. They demand that no part of the vehicle shall intrude into the residual space during the rollover. However, another requisite in rollover safety optimization is the energy absorbed by structures of the vehicle during the first collision between the vehicle and the floor. So in the process of multi-objective optimization, the minimum distance between the structures and the residual space is considered as the restriction, while the energy absorbed by the structures and the mass of the vehicle are considered as objectives, as the thickness of key structures considered as variables.Vehicle structures are complex, thus the function of objectives and variables is implicit. So, the rollover safety of buses cannot be optimized directly. The Response Surface Method (RSM) is suitable for this question. The main idea of RSM is to replace the real function between the objectives and variables with a explicit approximate model.Firstly, a finite elements model is constructed, including the frame structures, windscreens and skin panels. According to the calculation result, it is found that the window pillar intrudes into the residual space, and this result cannot meet the requirement of regulation ECE R66. Then, the 10 key parts among the superstructures are selected using the regression method. In succession, the response surfaces are constructed, including the energy absorbed by key structures, the mass of the vehicle and the minimum distance between structures and residual space. Based on these response surface models, a multi-objective optimization is performed. The solution indicates that the strength of optimized superstructures can meet the requirement of regulation ECE R66, the energy absorbed by the superstructures is much more, that is to say the rollover safety of the vehicle is enhanced. Meanwhile, the mass of the vehicle is much lighter, the lightweight is achieved.