Study On Vehicle Suspension System And Vehicle Ride Comfort

Due to the pursuit of higher speed and comfort,the vehicle's ride comfort has become an increasingly hot research topic in the process of rapid development of the auto industry.With the rapid development of science and technology,a variety of software have been applied to the automotive industry,which used to guide the research and development of automobile.Therefore,the dynamic analysis and the ride comfort prediction of vehicle by appropriate theories and software are important measures in vehicle design stage,which contribute to improve quality and shorten the cycle.This paper receives the funding by Major National Science and Technology Projects as well as Natural Science Basic Research Program of Shaanxi Province.This subject will take a certain type of domestic car as the research target,the main research contents are as follows.1)The dynamic analysis of vehicle suspension system.Firstly,the vibration model of the automobile suspension system is established,the complex frequency-response functions are derived.Secondly,the amplitude-frequency characteristic curves of vehicle body acceleration,suspension dynamic deflection and dynamic tire load are studied.Thirdly,root mean square(RMS)value of each vibration response is calculated by MATLAB.They are 1.3609m/s2,0.0086 m and 688.5651 N when the car is running at speed of 50km/h on C random road.In addition,the effect of suspension stiffness and damping coefficient on vibration response is studied respectively.Lastly,the influence rule of each parameter of suspension on the vehicle ride comfort is obtained.2)Study on stochastic road surface excitation model.Single-wheel road surface model is established based on filtered white noise method.The spatial correlation of vehicle' left and right wheels track,as well as the temporal correlation of front and rear wheels track,are analyzed theoretically.Then the four-wheel road surface model is built.The MATLAB/SIMULINK software is used to simulate the excitation signal of the C level random road surface,which elevation changes within the range from-0.05 to 0.05 m.The RMS value of its elevation is 16.44 mm,which is close to the C standard's 15.23 mm.Finally,a check of the power spectral density(PSD)curve proved that the generated random road excitation can meet the actual road surface.3)Study on dynamics model of vehicle system.A full-loaded vehicle mechanics model with 12 degrees of freedom(DOF)is established,which can take into account the feelings of passengers in different positions.The vibration differential equations of system are derived by Darren Bell's principle,and then the natural frequencies and the corresponding principal modes are calculated by using MATLAB.4)Study on vehicle ride comfort simulation.The road-vehicle-human system's simulation model is established by using SIMULINK.When the vehicle is traveling at different speeds,the vibrations of human bodies at different positions are simulated and time domain curves are obtained.And then,this paper calculates the total weighted acceleration RMS values of passengers while vehicle speed ranging from 40 to 70km/h.When the vehicle speed is 50km/h,the values are 0.3583,0.4232,0.4327,0.5048 and 0.5888m/s2.With the increase of speed,RMS increases monotonously.Next,based on the summary of the international standards and domestic standards,this paper analyzes the ride comfort of the car.In the end,the correctness of the simulation process is verified according to the test results.