Riding Comfort Analysis And Optimization Of Rigid-Flexible Coupling Motorcycle Model Based On Flexible Rear Fork

The rear fork is an important part of the rear suspension system of the motorcycle.It is directly connected to the frame and the rear wheel.It mainly bears the vertical load and transmits the driving torque of the motorcycle.The rear fork usually adopts cantilever a structure,and its flexibility is obvious in the process of movement.Compared with the traditional research method based on rigid rear fork motorcycle ride comfort,the simulation optimization results are far from the experimental verification.Therefore,it is necessary to study the influence of a rigid-flexible coupling model based on a flexible rear fork on motorcycle ride comfort.In this paper,a 400 cc large displacement motorcycle is taken as the research object.The flexible fork is processed,and the rigid-flexible coupling multi-body dynamics model of a motorcycle based on the flexible fork is established.The ride comfort simulation analysis and optimization design are carried out,and the optimization scheme is verified by a real motorcycle test.The specific research work is as follows:(1)The finite element analysis model of the rear fork is established.According to the principle of modal analysis,the natural frequency and modal shape of the rear fork are obtained by using the computational modal method.By comparing the calculated modal with the experimental modal,the results show that the natural frequency and modal shape of each order of the rear fork are in good agreement,which verifies the correctness of the finite element model of the rear fork.(2)Based on the basic theory of multi-body dynamics,the relevant parameters of real motorcycle parts are obtained through three-dimensional numerical simulation and bench test.The multi-rigid-body dynamics model and the rigid-flexible coupling model based on a flexible rear fork are established in VI-Motorcycle software for simulation analysis.Compared with the real motorcycle test data,it is verified that the rigid-flexible coupling motorcycle model is more in line with the real motorcycle driving situation.(3)Referring to the motorcycle ride comfort test method,the model of the deceleration zone pulse road and the C-level random road are established in the VI-Road module,and the influence of the pulse road and the random road on the ride comfort of the motorcycle is analyzed.Aiming at the problem of pitch vibration and vertical vibration of a motorcycle,the sensitivity analysis of suspension system parameters is carried out by using Isight integrated VI-Motorcycle and MATLAB software.Five design variables are determined,and multi-objective optimization is completed by using NSGA-II genetic algorithm.The optimized model is simulated again,and the results show that the ride comfort of the motorcycle is significantly improved.(4)Based on the multi-objective optimization results,the real motorcycle is reformed.The comparison of the real motorcycle test data before and after the reform shows that under different motorcycle speeds,the peak value of the absolute value of the pitch angle acceleration and the peak value of the absolute value of the vertical acceleration of the motorcycle mass center under the pulse road condition are reduced by14.80 % and 17.47 % respectively.Under the random road condition,the root mean square value of motorcycle pitch angle acceleration and the root mean square value of motorcycle centroid vertical weighted acceleration decreased by 16.72 % and 16.06 %respectively.The real motorcycle optimization effect is good,which proves the feasibility and effectiveness of the scheme.