Vibration Of Car Body Research Articles

Ride performance of a high speed rail vehicle using controlled semi active suspension system

The rail–wheel interaction in a rail vehicle running at high speed results in large amplitude vibration of carbody that deteriorates the ride comfort of travellers. The role of suspension system is crucial to provide an acceptable level of ride performance. In this context, an existing rail vehicle is modelled in vertical, pitch and roll motions of carbody and bogies. Additionally, nonlinear stiffness and damping parameters of passive suspension system are defined based on experimental data. In the secondary vertical suspension system, a magneto-rheological (MR) damper is included to improve the ride quality and comfort. The parameters of MR damper depend on the current, amplitude and frequency of excitations. At different running speeds, three semi-active suspension strategies with MR damper are analysed for periodic track irregularity and the resulting performance indices are juxtaposed with the nonlinear passive suspension system. The disturbance rejection and force tracking damper controller algorithms are applied to control the desired force of MR damper. This study reveals that the vertical vibrations of a vehicle can be reduced significantly by using the proposed semi-active suspension strategies. Moreover, it naturally results in improved ride quality and passenger’s comfort in comparison to the existing passive system.

Carbody elastic vibrations of high-speed vehicles caused by bogie hunting instability

ABSTRACTIn particular locations of the high-speed track, the worn wheel profile matched up with the worn rail profile will lead to an extremely high-conicity wheel–rail contact. Consequently, the bogie hunting instability arises, which further results in the so-called carbody shaking phenomenon. In this paper, the carbody elastic vibrations of a high-speed vehicle in service are firstly introduced. Modal tests are conducted to identity the elastic modes of the carbody. The ride comfort and running safety indices for the tested vehicle are evaluated. The rigid–flexible coupling dynamic model for the high-speed passenger car is then developed by using the FE and MBS coupling approach. The rail profiles in those particular locations are measured and further integrated into the simulation model to reproduce the bogie hunting and carbody elastic vibrations. The effects of wheel and rail wear on the vehicle system response, e.g. wheelset bifurcation graph and carbody vibrations, are studied. Two improvement measures, including the wheel profile modification and rail grinding, are proposed to provide possible solutions. It is found that the wheel–rail contact conicity can be lowered by decreasing wheel flange thickness or grinding rail corner, which is expected to improve the bogie hunting stability under worn rail and worn wheel conditions. The carbody elastic vibrations caused by bogie hunting instability can be further restrained.

Experimental investigations on the damping effect due to passengers on flexural vibrations of railway vehicle carbody and basic studies on the mimicry of the effect with simple substitutions

ABSTRACTThe effect of passengers on a railway vehicle is usually considered as additional mass in designing a carbody. However, previous studies by means of stationary excitation tests or running tests using actual vehicles indicate that passengers behave not as mass but as damping. In this paper, the authors examined the passengers' damping effect under controlled excitation conditions on a roller rig through a series of excitation tests using a commuter-type vehicle. Large and multi-modal reductions of flexural vibrations of the carbody were observed when passengers existed. Influences of the number of passengers, distributions and postures of passengers were investigated. The authors also tried to mimic the damping effect by passengers using flexible tanks filled with fluids. Three kinds of fluids which have different viscosities have been tested. As a result of the excitation tests, good vibration reduction effects were observed by applying those tanks, and it has been found that the flexible tanks filled with fluids bring about vibration reduction effect (including multi-modal reduction) which is equal to or rather better than the case of similar mass of passengers in the carbody; the difference of viscosity gave little affect on the damping abilities. From these measurement results, a possibility of realising effective damping devices against flexural vibrations of railway vehicle carbodies representing passengers damping effect, in a simple, economical and environmental friendly way, has been demonstrated.

Passive control of railway vehicle car body flexural vibration by means of underframe dampers

To suppress vertical flexural vibration of a railway vehicle car body, a new passive control method by mounting dampers on the longitudinal beams of the car body underframe is proposed. The method is firstly studied by an Euler-Bernoulli beam model using Green’s functions, then it is further verified by a nonlinear dynamic model of the vehicle. Results show that the car body flexural vibration can be noticeably reduced by this method. It is better to mount the damper near the car body centre. The higher damping coefficient of the damper, the more effective in decreasing the car body first vertical bending vibration. The higher the rigidity of the damper bracket and rubber bush, the better performance of the damper. It is found that when mounting six dampers at proper positions, the damping coefficient of each damper is 1.33×107 N·s/m, even if the first vertical bending frequency of the studied car body is only 7.2 Hz, a very good ride quality will be achieved when the vehicle runs at 250 km/h.

トーラス形弾性体による鉄道車両の車体弾性振動低減手法の提案とその振動設計

This paper presents a basic study to develop a new damping device against flexural vibration of railway vehicle carbody utilizing elastic deformation of an elastic body as a dynamic vibration absorber (DVA). A donut-shaped elastic body (called ”elastic torus” in this study) is proposed considering practical application to rail vehicles. Vibration measurement tests using some existing elastic tori are carried out to examine the effect by their size and infill upon natural frequency. In addition, excitation tests for a 1:5 scale model of a Shinkansen vehicle carbody are conducted, and the DVA effect by applying such elastic torus against the first mode of flexural vibration of the carbody is demonstrated. Then, numerical studies using finite element (FE) analysis are carried out and it has been found that the shape and the size of an elastic torus having desired natural frequency can be determined by the numerical model. Finally, an elastic torus dedicated as a DVA for rail vehicles made of rubber filled with water is designed using the FE model and manufactured actually.

Influence of Wheel Eccentricity on Vertical Vibration of Suspended Monorail Vehicle: Experiment and Simulation

This paper investigates the influence of wheel eccentricity on vertical vibration of suspended monorail vehicle based on experiment and simulation. Two sets of tests are conducted in the first Chinese suspended monorail, and the tested acceleration is analyzed and exhibited. A multibody dynamic model of the suspended monorail vehicle is established to simulate the vertical vibration of car body excited by wheel eccentricity. The results show that there are three factors which may cause an abnormal vibration considering the track and the vehicle system. The influence of wheel eccentricity on the car body vibration was firstly analyzed. Simulated acceleration of car body has a great accordance with test. The wheel eccentricity could excite the resonance of car body at the speed of 21 km/h, and the vertical acceleration would increase considerably. Decreasing the secondary stiffness can effectively reduce the vertical vibration caused by wheel eccentricity, especially at the resonant speed. In the secondary test, the peak of car body acceleration at speed of 20 km/h is not appearing when only renewing the wheels, and the acceleration is decreasing obviously at the domain frequency. It is further determined that the abnormal vibration is mainly caused by the wheel eccentricity.

弾性トーラスによる鉄道車両の車体弾性振動低減効果（実車を用いた制振効果の確認と制振メカニズムの数値的検討）

弾性トーラスによる鉄道車両の車体弾性振動低減効果（実車を用いた制振効果の確認と制振メカニズムの数値的検討）

Influence of yaw dampers on vertical vibration of railway vehicle carbody and verification of effect by the new mounting structure of yaw damper

Influence of yaw dampers on vertical vibration of railway vehicle carbody and verification of effect by the new mounting structure of yaw damper

鉄道車両の車体振動低減のための新たなヨーダンパ取付け構造の開発

It is pointed out that the yaw dampers, which are often installed in between carbody and bogie frame of a high-speed railway vehicle, have such unfavorable points that the damping force is generated not only in the yawing direction but also in other direction. As a result the damping force is generated also to the longitudinal or pitching vibration of a bogie, and the excitation force acts in the longitudinal direction of the carbody resulting in the increase of the carbody vibration of the longitudinal or vertical direction. In this research, to enable the reduction of the excitation of the carbody vibration while maintaining the original function of yaw dampers to prevent bogie hunting motion, a new mounting structure of yaw dampers on railway vehicles has been developed. The new mounting structure enables to reduce the excitation force transmitted from a bogie frame to a carbody through yaw dampers. In this paper, the effect of yaw dampers on the carbody vertical vibration is firstly shown based on the results of an excitation test of a full-scale vehicle, then the outline of the new mounting structure for yaw dampers and the design and manufacture of the prototype device are presented. The vehicle dynamics model based on multi body dynamics was constructed and the suppression effect of the yaw damper force generated to movement in the direction other than the yawing direction of a bogie was verified by the numerical simulation. Moreover, the prototype device was installed on a full-scale test vehicle and a bogie hunting motion test was carried out to verify the running stability.

Vibration modeling and position-dependent analysis of spatial trajectory roller coaster

A vibration quarter-carbody model of a roller coaster running on a spatial trajectory is derived based upon the motion parameters, vertical acceleration, angular velocity, angular attitude, and transient position. These motion parameters are acquired from an ADAMS virtual prototype. The vibration response of the carbody is obtained by solving the differential equations with variable coefficients. Besides, the validity of both the ADAMS virtual prototype and the vibration model is verified by the simulated results versus the actually measured ones. Furthermore, a method, called as space frequency characteristics, is proposed to investigate the relation between the carbody vibration and the motion parameter of roller coaster, which reveals that the carbody vibration is related to its transient position and the influence of the randomness of the motion parameters on the vibration is eliminated. This research is supposed to be helpful for the fault diagnosis of roller coaster by considering both the vibration and motion signals.

Study on the Influence of the Center of Gravity of an Under-Chassis Equipment on the Dynamic Performance of High Speed EMU Trains

In order to consider the influence of the center of gravity of an under-chassis equipment on the dynamic performance of high speed EMU trains, the equipment is considered as a rigid body with six degrees of freedom, the vibration of six degrees of freedom of the vehicle equipment is decoupled by using the energy decoupling theory. Based on the platform of Matlab software, the software for the optimal design of the suspension parameters of the under-chassis equipment is developed. Results show that the developed software can complete the function set. Each order of the rigid vibration mode of the equipment can be decoupled well. The reduction effect of the designed suspension system is remarkable, and the carbody vibration condition has been effectively improved.

Multibody dynamics analysis for the coupled vibrations of a power split hybrid electric vehicle during the engine start transition

Minimizing working time of the internal combustion engine is an important method for hybrid electric vehicles to save energy and reduce emissions. However, vibrations caused by frequent engine starts and stops deteriorate driveability and ride comfort. Especially in power split hybrid vehicles, there is no kinematically decoupled device between the engine and transmission, so that vibrations transfer from the powertrain to the car body through not only engine mounts but also the driveline system. Hardware test results show that the longitudinal vibration of seat track is the most severe with a maximum peak-to-peak acceleration of 1.8 m/s2. In this study, dynamic models of the driveline system and the powertrain mounting system are respectively established in detail. The natural characteristic analyses of the two dynamic models reveal that engine order vibrations can stimulate a series of low-frequency resonances during the engine starts, which is finally embodied in the car body vibrations. Then, two dynamic models are coupled together to analyze the transient dynamic characteristics associated with engine starts. It is evident by simulations that the longitudinal vibration of car body is mainly transferred by the driveline, whereas the vertical vibration of car body is mainly transferred by the powertrain mounting system. Besides, the initial crankshaft position of the gasoline engine has an obvious effect on the engine order vibration, and further results in different transient responses of the full vehicle system.

Experimental investigation on the dissipative and elastic characteristics of a yaw colloidal damper destined to carbody suspension of a bullet train

Yaw damper represents a major source of excitation for flexural vibration of the railway carbody. In order to reduce transmissibility of such undesired excitation, yaw damper should allow for large force transmission at low working frequencies, but should behave as vibration isolator at high working frequencies. Unfortunately, the yaw oil damper (OD), which is nowadays in service, has poor intrinsic elastic capabilities and provides damping forces varying as a power function versus the piston speed. Since colloidal damper (CD) has intrinsic elastic capabilities and larger damping forces at lower excitation frequencies, it occurs as an attractive alternative solution to traditional yaw dampers. In this work, a yaw CD destined to carbody suspension of a bullet train was designed and manufactured; then, its dynamic characteristics, produced by both the frictional and colloidal effects, were evaluated from the experimental results, obtained during horizontal vibration tests, performed on a ball-screw shaker. Compared to the corresponding classical yaw OD, the trial yaw CD allowed for: weight reduction of 31.6%; large damping force, dissipated energy and spring constant at long piston stroke under low excitation frequency; low damping force, dissipated energy and spring constant at short piston stroke under high excitation frequency. Elastic properties were justified by introducing a model for the spring constant that included the effect of pore size distribution.

Influence of under-chassis-suspended equipment on high-speed EMU trains and the design of suspension parameters

A numerical method for the calculation of the frequencies of vibration of a car body on a high-speed electric multiple unit train with under-chassis-suspended equipment is proposed. In addition, the design of the parameters of the suspension system for the equipment is presented; it is based on the principles of mode matching, transmissibility matching, and consideration of the optimal vibration of both car body and equipment. It is shown that by tuning the suspension stiffness, the first vertical bending frequency of the car body displays a frequency-hopping phenomenon. The first vertical bending frequency of the car body can be enhanced by optimizing the suspension parameters, so as to suppress the vibrations of both the car body and the suspended equipment.

Adaptive neural network control for active suspension system with actuator saturation

This study investigates adaptive neural network (NN) state feedback control and robust observation for an active suspension system that considers parametric uncertainties, road disturbances and actuator saturation. An adaptive radial basis function neural network is adopted to approximate uncertain non-linear functions in the dynamic system. An auxiliary system is designed and presented to deal with the effects of actuator saturation. In addition, since it is difficult to obtain accurate states in practice, an NN observer is developed to provide state estimation using the measured input and output data of the system. The state observer-based feedback control parameters with saturated inputs are optimised by the particle swarm optimisation scheme. Furthermore, the uniformly ultimately boundedness of all the closed-loop signals is guaranteed through rigorous Lyapunov analysis. The simulation results further demonstrate that the proposed controller can effectively suppress car body vibrations and offers superior control performance despite the existence of non-linear dynamics and control input constraints.

床下機器の高減衰弾性支持による鉄道車両の車体弾性振動低減

床下機器の高減衰弾性支持による鉄道車両の車体弾性振動低減

Flexible vibration analysis for car body of high-speed EMU

The resonance of the flexible vibration of car body, which has not been detected before on a passenger coach, occurred recently on a high-speed Electric multi units (EMU) when the train was running at 300 km/h on Beijing-Shanghai line. In this investigation, the force transmission from track to car body via suspensions is elaborated first with possibly induced factors briefly discussed. Both the measurements and experiments in field and in laboratory were conducted to evaluate the resonances and the excitation as well as transmission. Moreover, a three-dimensional railroad vehicle model was built in a computational non-linear Multibody system (MBS) framework, in which the car body flexibility was modeled using Finite element (FE) method. The model was validated and shows good agreements with measurements. Furthermore, the measured wheel and rail profiles were used to analyze the wheel/rail interaction for both new and worn states. The effects of the wheel-rail contact conditions on stabilities, dynamics and riding comforts were also examined. Feasible solutions were promoted to avoid the resonance and following by validating tests. It shows that the high frequency excitation arises from the hunting motion of bogie that closes to the modals of the car body, leads to the resonance of the structure of the car.

鉄道車両の車内騒音低減のための吊り床構造の提案

This work presents a study to reduce interior noise of railway vehicle by suspending floor plate from side wall of carbody. Recently speedup and weight reduction of railway vehicle were achieved, interior noise can be higher because of rail noise and vibration transfer from bogie, which is transferred through traction link, floor of carbody, and joists to floor plate. The frequency of these structure borne noise is from tens to hundreds of Hz, and is considered difficult to reduce these low-frequency noise. Then lower vibration of side wall is noted by measuring carbody vibration, and suspended floor is proposed to reduce vibration transfer from carbody to floor plate. Two stationary vibration tests are conducted to by applying suspended floor to Shinkansen-type test vehicle. In the tests floor plate is suspended by band plate, wire, or plate from rack or skirt and rail noise is adopted by actuator, or by running on roller. Finally, vibration and interior noise reduction is achieved successfully.

車体振動低減のための新たなヨーダンパ取付構造の開発

車体振動低減のための新たなヨーダンパ取付構造の開発

Delay Scheduling for Delayed Resonator Applications

This paper is on suppression of carbody vibrations utilizing multiple-delay Delayed Resonator (DR) with combination of speed and position feedback. The resonance frequency of DR under varying excitation frequency is tuned by delay scheduling concept. Characteristic Treatment of Characteristic Roots (CTCR) method with Extended Kronecker Summation is used to assess both the operation frequency of DR and overall stability of the system. An experimental study is included to present the effectiveness of the method.