Analysis And Optimization Of Handling Stability Of A Rigid-Flexible Coupling Motorcycle With Front Suspension

At present,most of the research on the handling stability of motorcycles adopts the multi-rigid-body method,which leads to a great difference between the handling stability of the whole vehicle and the actual situation.To solve this problem,a rigid-flexible coupling dynamic model of a 400 CC motorcycle based on flexible front damping is established.The simulation analysis and optimization design of handling stability are carried out,and the optimization scheme is verified by a real vehicle test.The main research contents are as follows:(1)The finite element model of the front damping is constructed,and the natural frequency and vibration mode are analyzed by the computational modal method.The correctness of the simulation model is verified by the experimental modal method,and the MNF file is generated.Then,according to the obtained parameters,the rigid-flexible coupling dynamic model and multi-rigid body model of the motorcycle based on flexible front damping are constructed respectively.The accuracy of the two models is verified by the real vehicle test.The results show that the two models are accurate and reliable,and can be used for handling stability research.However,the error of the rigid-flexible coupling model is smaller and more consistent with the real vehicle situation.(2)The influence of flexible front suspension on the handling and stability of the vehicle model is explored.The VI-Motorcycle is used to simulate the dynamic characteristics of the vehicle under slalom condition,U-turn condition,steady turning condition and lane change condition,and the handling and stability evaluation index is introduced to analyze it.The results show that the flexibility of the front damping has little effect on the handling and stability performance of the vehicle under the slalom condition and the U-turn condition,and has a relatively large effect on the steady turning condition and the lane change condition.Therefore,it is optimized under the steady turning condition and lane change condition,and the optimization results are verified by the slalom condition and U-turn condition.(3)Through the sensitivity analysis of the suspension system parameters of the rigid-flexible coupling motorcycle model,the optimization variables are determined,and the NSGA-Ⅱ genetic algorithm is selected to perform multi-objective optimization under steady turning condition and lane change condition to improve the handling stability of the rigid-flexible coupling motorcycle model.In order to verify the effectiveness of the optimization scheme,the handling stability indexes before and after the optimization of the slalom condition and the U-turn condition are compared.The results show that the effectiveness of the scheme is verified and the handling and stability performance of the vehicle under other conditions is improved.(4)The optimized design variables are used for real vehicle trial production,and the real vehicle test is carried out with the help of equipment to further verify the correctness of the optimization scheme.The results show that the roll transfer function,roll rate and yaw rate of the real vehicle test under the slalom condition are 0.552,112.10deg/s and 85.48deg/s,respectively,and the optimized simulation errors are 5.25%,4.84% and 4.46%,respectively.The Koch index,roll rate and yaw rate of the real vehicle test under U-turn condition are 0.0235,31.08deg/s and 56.24deg/s,respectively,and the optimized simulation errors are 5.11%,6.69% and 5.74%,respectively,which proves the feasibility of the optimization scheme.