Research On Motorcycle Vibration Under Test Load

With the progress and development of society,motorcycle,as an important tool for people’s production and life,pay more and more attention to their use and experience,especially vibration comfort.The vibration comfort level of motorcycles also directly reflects the development and design level of manufacturing companies.Therefore,studying the vibration comfort of motorcycles has very important engineering value for meeting the needs of people and improving the level of enterprise design and manufacturing.This article takes a company motorcycle as the research object and conducts vibration comfort test evaluation on it.The combination of experiment and simulation is used to analyze the vibration transfer path of the excitation under test conditions.By improving the suspension structure in the main path,the goal of improving the vibration comfort of the motorcycle is finally achieved.First,the study found that the first-order natural frequency of the motorcycle frame is 94.53 Hz,which is in the range of 41.67 Hz to 133.33 Hz of the engine’s first-order reciprocating inertial force frequency.Considering that the vibration caused by the engine is transmitted to the driver through the handle,cushion and pedals,which affects the vibration comfort,the vibration comfort test evaluation is carried out on these parts.It was found that the handle vibration comfort was poor when the engine speed was 6500r/min and 7300r/min,which did not meet the requirements of the enterprise.For this reason,the transfer path of the car is analyzed to find the main path that affects the vibration of the handle.Secondly,the transfer function of the transfer path model and the method of obtaining the test load are analyzed.Combined with the structural characteristics and test conditions of the motorcycle,a vibration transfer path analysis model was established with the passive end of the engine mount as the path input point and the handlebar as the response(output)point.The finite element model of the vehicle including the frame,the handle assembly,the front and rear shock absorber assembly,the rear flat fork assembly,the front and rear pedal assembly and other components is used to calculate the transfer function of the path.Compare the characteristics of three different methods: the direct method of load identification,the suspension dynamic stiffness method and the inverse matrix method,and determine the application of the inverse matrix method.Using the engine operating condition data obtained from the bench test,the working load at the path input point was identified.Then,compare the response results of the handle obtained by the simulation of the transfer path with the test data.The results show that the maximum peak frequency accords with and the amplitude is close,which proves the feasibility of the simulation model.The path leading to poor vibration comfort of the handlebar is analyzed by considering the amplitude and phase of the contribution,and the main paths that affect the handlebar vibration are found to be the left rear lower suspension z direction and the right rear lower suspension x direction.The vibration transmission path characteristics of the main path are analyzed,and it is determined that the reason for the poor vibration comfort of the handle is the large test load at the path point and the poor structure transfer function.Finally,a single-degree-of-freedom system model is established,and the influence of stiffness,mass,and damping changes on the transfer function is obtained.Through the analysis of the influencing factors of the transfer function,the structure of the input end of the main transfer path is improved,that is,the improved method of weakening the stiffness of the left and right rear and lower suspensions.The transfer function before and after the suspension improvement is compared and analyzed,and the improvement effect is predicted through simulation.Carry out strength analysis of the improved suspension structure to determine whether it meets the requirements.The improved simulation results show that the vibration comfort of the handlebars,cushions and pedals all meet the requirements of the enterprise.