Modeling And Simulation For The Ride Comfort Of Minibus And Research On Its Parameter Matching

With the gradually elimination influence of the 2008 financial crisis,China automobile market grown up steadily and fast,the production and sales climbed year after year,and leapt world first in 2009. As a special vehicles,minibus is remarkable for its high cost performance and wide applications, and it has developed fast in recent years. In 2009,minibus production and sales had blockbuster expansion,the year-on-year growth rate reached over eighty percent,far beyond the production increase of the whole automobile market at the same period. However,the research for minibus is still very little,its ride comfort research is even less. Therefore,modeling and simulation for the ride comfort of minibus have gradually become a matter of concern.Scholars at home and abroad have researched on minibus ride comfort through Multi-body parametric method. They didn't concern the difference between minibus and mini-car when establishing the full vehicle model. In addition,it is difficult to get the body structure parameters in advance when use this method. In this paper,the minibus is considered as particular vehicle,the centralized parameter method is used to establish the minibus vibration model,and its ride comfort is studied. First,seven degree-of-freedom vibration model is established for the minibus. Second,the description of the road stochastic excitation in frequency domain is summarized. The road stochastic excitation model in time domain is constructed by using filter white noise method,its algorithm is developed,and road excitation is obtained and its accuracy validated. Third,the ride comfort of the minibus is studied systematically and the suspension parameters matching with the ride comfort of the minibus are finished.Main research content of this paper is as follows:(1)The vibration modeling of minibus with seven degree of freedom in plane area Combined the research focus of the paper,the vibration model of minibus with seven degree-of-freedom in plane area is established according to the real arrangement of the minibus. The mathematical model is deduced according to Lagrange equation. The expressions of the wheel static load and suspension dynamic deflection are derived and lay model foundation for ride comfort simulation in time and frequency area.(2)Road stochastic excitation model simulation in frequency domain and time domain The road stochastic excitation models are described in frequency domain,including description both spatial frequency domain and time frequency domain by using power spectral density,and the improved measures are put forward. The theory about standard white noise is summarized. The road stochastic model is deduced by using filter white noise model based on relationship between excitation and response of single-degree-freedom linear system. The road stochastic excitation in time domain is obtained by the developed algorithm. Fourier transform is used to get the power spectral density to prove the road stochastic excitation accuracy. It can be conclude that filter white noise method used in ride comfort simulation is accurate and possible.(3)Ride comfort simulation of the minibus and research on its parameter matching Based on the latest standard of GB/T4970-2009,triangle convex block is used to describe the road pulse excitation. The road pulse excitation model is constructed in time domain,the simulation of the minibus ride comfort is carried out by using the road pulse excitation,and speed characteristic curves of three seats are drawn.The road stochastic model is constructed by using filter white noise model,and is used in minibus ride comfort simulation. The vibration response quantities are obtained in time domain, and how the speed and road level influence the ride comfort of the minibus is analyzed.Ride comfort of the minibus is studied in frequency domain,and the power spectral density of the vibration response quantity is obtained. The influence about the change of the load is discussed. The result indicate that the ride comfort of the minibus is quite well,and the change of the load has influence only on the seat acceleration,the influence on the wheel static load and suspension dynamic deflection can be ignored.The power spectral density of the vibration response quantity is obtained in time domain by using Welch method and compared with the result from frequency method. The result prove that it is valid and practicable to construct road stochastic model using filter white noise method and put it in use in the simulation of the ride comfort.With the orthogonal experiment method,the stiffness and damper of the suspension are taken as the factors in concern and three seats of the minibus weighted acceleration RMS value as the test index in concern to study how each factor influence the minibus ride comfort. Under given three levels, the optimal parameter combination is obtained. With the optimal parameter combination,the ride comfort has improved 10 percent in frequency simulation by before optimization. For the road pulse excitation simulation,seats acceleration converged faster. All this result prove that the suspension parameters are optimized by using the orthogonal experiment method,and the ride comfort of the minibus are be improved.