Modeling And Simulation For Rail Vehicle Ride Quality In Frequency Domain

With the development of the economy and society, the total quantity of rail transport has continuously been increasing. Railway department has to meet the needs of passenger and goods transport by means of high speed and heavy load, however, a series of dynamic problems occurred, and vibration problem of vehicle is critical. The vibration of vehicle will worsen ride quality and increase the additional dynamic load which rail structure can withstand. The repeating effect will inevitably cause rail structure exhausted, damaged as well as a low reliability, which will aggravate the vehicle vibration in reversal and result in a bad travel comfort.Achieving "safe, fast, comfortable and economic" transportation is a design ideal for transportation tools, so is rail transportation. How to keep the top ride quality of train at the premise of the enhancement of running speed has always aroused many researchers'great interest.A lot of document on vehicle random vibration field of research has been consulted before writing this paper. The induction and summary of the research on application of random vibration theory to vehicle dynamics, power spectral density (PSD), the vehicles dynamics system modeling, output calculating and so on, has been made.Based on the concept of vehicle dynamics, the study of a system includes three aspects, input, System Property and output. In the research of rail vehicle ride quality, the input of the system should be firstly engaged in. As to the rail vehicles vibration system, the main input is track irregularities. Foreign have done plenty of test and statistic analysis work on track irregularities which is considered to be the vibration system random exciter, and have established the PSD expressions which reflects the characteristic of track random irregularities. But the PSD expressions are different from each other. Chinese railway researchers also did a research in this field. However, due to limited conditions, currently, there is no unified PSD expression which can reflect the actual situation of the track irregularity. To solve this problem, this paper unified Chinese main track irregularities PSD expression and several overseas typical track irregularities expressions. In order to make sure the difference between Chinese main track irregularities PSD expression and several overseas typical track irregularities expression, this paper plotted and compared function images.Ever since a long time ago, diverse mechanical models have been established with diverse suppositions to solve different problems. To study and analyze a specific problem in an easier and faster way, a proper and rational mechanical model should be chosen. This paper mainly research on how ride quality changes when vehicle runs at different speed under different PSD, and this research is carried on in the low frequency field. Therefore, this paper selected 1/2 plane 10 DOFS vehicle model as the research object. Only vertical and nod vibration was considered in this paper.The differential equation of 1/2 plane 10 DOFS vehicle model was deduced according to Lagrange's equation. The system frequency response function was deduced according to frequency-domain analysis method. Wheel-rail interaction and dynamic deflection calculate formulas are particularly deduced according to the automobile ride comfort research method. Programs are developed by MATLAB to realize the method as shown above.For passenger car, at the condition of same speed and same PSD input, the body and steering bogie accelerations, the first suspension dynamic deflection of front steering bogie and the first wheels wheel-rail interaction of CRC(Changchun Railway vehicle Co., Ltd) high-speed passenger car, SFLRC(SiFang Locomotive and Rolling Stock Co., Ltd) quasi-high speed passenger car, SY97846 passenger car for test, typical high-speed passenger car are calculated. This paper separately calculated the outputs of CRC high-speed passenger car with different PSD input effect and at different speed, and calculated the dynamic deflection of first and second suspension of front steering bogie. For freight car, this paper calculated the outputs of C62A freight car with different PSD input effect and at different speed, and calculated the dynamic deflection of first and second suspension of front steering bogie. The Sperling ride index has been widely used in China ever since. In this paper the Sperling ride index of 5 different types of vehicles output under different input PSD has been calculated, and this shows the distinction among the conclusions of different vehicles ride quality under different input PSD in a further way.Dynamic calculation results show that the body acceleration power spectral response mainly concentrated in the low frequency range. The output of steering is larger than body's because of buffering and vibration decreasing effect of all levels components, and the output of first suspension is larger than second suspension's; With vehicle speed increasing, the responses of acceleration, dynamic deflection, wheel-rail interaction become larger and larger, ride quality become badly, and the'empty'frequency moves to high frequency range; Different tracks spectrum analysis shows that the outputs of German high interference spectrum and USA sixth band spectrum are very similar, and the amount is very small. England track irregularities are worst, and its output amount is largest. China track irregularities are similar with USA fourth band track irregularities, and ride quality is worse than USA sixth band spectrum and German high interference spectrum.