Vehicle Vibration Environment Research Articles

Model Predictive Control of a Semi-Active Vehicle-Mounted Vibration Isolation Platform.

When conventional delivery vehicles are driven over complex terrain, large vibrations can seriously affect vehicle-loaded equipment and cargo. Semi-active vehicle-mounted vibration isolation control based on road preview can improve the stability of loaded cargo and instruments by enabling them to have lower vertical acceleration. A combined dynamic model including a vehicle and platform is developed first. In order to obtain a non-linear relationship between damping force and input current, a continuous damping control damper model is developed, and the corresponding external characteristic tests are carried out. Because some conventional control algorithms cannot handle complex constraints and preview information, a model predictive control algorithm based on forward road preview and input constraints is designed. Finally, simulations and real tests of the whole vehicle vibration environment are carried out. The results show that the proposed model predictive control based on road preview can effectively improve vibration isolation performance of the vehicle-mounted platform.

Dynamic modeling of a metro vehicle considering the motor–gearbox transmission system under traction conditions

Abstract. As a vital means of transportation to alleviate urban traffic congestion, the metro vehicle has been developing rapidly in China during recent years. For the violent vibration and shock under the frequent switches between traction and braking conditions, higher requirements are put forward in the drive system. The dynamic performance of the traction motor and gearbox, which are the key elements in the drive system of the metro vehicle, is worthy of attention. Based on the classical vehicle–track coupled dynamics and the gear dynamics theory, a vertical–longitudinal dynamics model for a metro vehicle with frame-hung motors and gearboxes is developed in this paper. This model enables the consideration of some complicated excitations, such as external excitations (the track vertical irregularity) and internal excitations (the mesh stiffness and the dynamic transmission error). The established dynamics model is then validated by comparing the simulated results with the field test results in both time domain and time–frequency domain under traction conditions. Consequently, the established dynamics model is demonstrated to be capable of revealing the dynamic performance of the metro vehicle effectively, especially for the traction and transmission system in the entire vehicle vibration environment of a metro. In turn, the results indicate that the gear transmission has a great and lasting effect on the force state of the traction motors and gearboxes compared to its effect on the axle load transfer.

Performance of liquid cooling battery thermal management system in vibration environment

Battery thermal management system (BTMS) is an important component to the safety of electric vehicles, but few studies have considered the impact of vehicle vibration environment on the performance of thermal management systems. In this context, the performance of liquid cooling BTMS in vibration environment is discussed. To make better use of vibration, a novel structure based on the classical serpentine channel is proposed. Compared with the original structure, the cooling performance of the novel one under vibration is obviously improved. For novel structures with different design parameters, vibration reduces the average temperature of the channel wall by 1.8 K and increases the wall-averaged Nusselt number to at least 17, twice that of original structure, while the increase in pressure drop is insignificant. The mechanism and influencing factors are also preliminarily discussed. The work analyzed BTMS under actual working condition and provided a new direction for the design of high-performance BTMS.

Effect of track irregularities of high-speed railways on the thermal characteristics of the traction motor bearing

The operating temperature plays a key role in the service reliability of ball bearings used in the traction motor of high-speed trains. Studies on the heat generation and temperature distributions of the bearing under the vehicle vibration environment are critical for designing the high-speed train traction motor bearing and to monitor its operation. In this paper, an SKF friction torque model that considers the inlet shear heating reduction and kinematic replenishment/starvation reduction was used to calculate the power loss of the bearing operating in a high-speed train. A thermal analysis model of the bearing, which takes into account the vehicle vibration due to track irregularities, was developed to study the thermal characteristics of the bearing operating in a high-speed train. Experiments were conducted on a service high-speed train (i.e. CRH380B) to validate the proposed bearing thermal analysis model. The thermal characteristics of the bearing and the influence of key factors on the operating temperature of the bearing under vehicle vibration due to track irregularities were studied with the proposed bearing thermal analysis model. The results show that the thermal failure of the bearing subassemblies most likely occurs at the balls region owing to the highest temperature in that region, compared to the inner and outer raceway of the bearing. The method of applying grease with appropriate kinematic viscosity should be adopted to reduce the power loss of bearing while meeting the lubrication requirement. The vehicle vibration due to track irregularities significantly influences the thermal characteristics of high-speed train motor bearings, which cannot be ignored in the thermal analysis of bearings operating in a high-speed train.

Wheel wear analysis of motor and unpowered car of a high-speed train

The wheel-wear characteristics of the motor and unpowered car of a high-speed train were investigated, for the first time, by a wheel-wear prediction model comprising a wheel-wear sub-model, an unpowered car dynamics sub-model, and a novel motor-car dynamics sub-model. The motor-car dynamics model considers the detailed structural characteristics and working mechanics of the traction transmission system. Assuming the real track parameters and track irregularities, it handles the nonlinear factors such as the traction characteristics, gear backlash, time-varying mesh stiffness, gear friction and wheel–rail contact. This study assessed the wheel-wear characteristics of a high-speed train by suitable performance indices (wheel-wear depth and contact patch energy). Finally, the model was validated by comparing the simulation results with those of field tests. The predicted and measured wheel wear were in good agreement. Both the wheel wear depth and contact energy were higher for the motor car than the unpowered car, because the traction torque on the wheelsets of the motor car increased the longitudinal creepage. During one re-profiling cycle, the transmission stability of the gear transmission system worsened with continuous wheel-wear. Furthermore, the proposed methods can assess the wheel wear and working status of the traction transmission system in the vehicle vibration environment of any rail vehicle.

Torsional vibration analysis of the gear transmission system of high-speed trains with wheel defects

The gear transmission system of a high-speed train is the key component, which delivers the traction torque from the motor to the wheelset. It couples with the vehicle system via the suspension system, gear meshing and the wheel–rail interface. The dynamic performance of the transmission system directly affects the operational reliability or even the running safety of high-speed trains. In this study, the effects of wheel polygonalisation and wheel flat on the dynamic responses of the transmission system are investigated through simulations of a novel vehicle dynamics model. This model integrates the flexible gearbox housing, the time-varying mesh stiffness and the nonlinear gear tooth backlash, and the track irregularities to obtain more realistic responses of the traction transmission systems in a vehicle vibration environment, from motors to wheelsets, under the effects of the wheel flat and polygonal wear. The field experimental tests are implemented for a vehicle running along a main high-speed railway line in China. Subsequently, the developed dynamics model is validated with good agreement between the experimental and the theoretical results. The calculated results revealed that wheel flat and wheel polygonal wear caused a high-frequency fluctuation of both the longitudinal creep force and the gear mesh force, causing a violent and complex torsional vibration of the gear transmission system. Moreover, the flexible deformation of the gearbox housing, especially its resonance due to the wheel polygonal wear, contributed to the torsional vibration of the gear transmission system.

Effect of the drive system on locomotive dynamic characteristics using different dynamics models

Based on the theory of vehicle-track coupled dynamics and gear system dynamics, a locomotive-track coupled spatial dynamics model is established by considering the dynamic effects of the gear transmission system. The vibration responses of a locomotive’s major components are then simulated using three locomotive-track models, namely the proposed dynamics model with the gear transmissions, a locomotive-track coupled dynamics model that considers the traction motor, and the classical Zhai’s model. The locomotive dynamic responses of the three models are extracted and compared to reveal discrepancies between them so as to explore the dynamic effects of the power transmission system and clarify potential applications of these models. The results indicate that the dynamic effects of the gear transmissions have a negligible influence on the lateral vibrations of the locomotive components. However, they have obvious effects on the vertical and longitudinal vibrations of the wheelset and the traction motor. Another advantage of the locomotive dynamics model that considers the dynamic effects of the gear transmissions is that the dynamic performance of the drive system can be assessed in the vehicle vibration environment. This study provides theoretical references that can assist researchers in choosing the most appropriate locomotive dynamics model according to their specific research purpose.

Establishment and validation of a locomotive–track coupled spatial dynamics model considering dynamic effect of gear transmissions

Abstract Gear transmission is a key element in a locomotive for delivery of traction power from the electric motor to the wheelset. Its dynamic performance has a direct effect on the operational reliability or even safety of the locomotive or the train. In this paper, based on the classical vehicle–track coupled dynamics theory and the gear dynamics theory, a locomotive-track coupled spatial dynamics model is established where the dynamic effects from the gear transmissions are considered. In this model, the gear transmission system and the classical locomotive–track system are coupled with each other via wheel–rail contact interface and the gear mesh interface. The dynamic interactions between the rotational motions of the power transmission system, the vertical, lateral, longitudinal, roll, yaw and pitch motions of the components in a locomotive are fully included. This more comprehensive dynamics model of the locomotive–track system enables detailed investigations on the system dynamic performance under the complicated excitations from both the track geometrical irregularity and the internal mesh process of gear pairs (e.g. time-varying mesh stiffness, gear errors), especially the dynamic responses of the gear transmission in the complete vehicle vibration environment. This model is finally validated by comparisons with the field test data in the time- and time-frequency domains. And it is capable of being used for dynamics related assessment, such as vibration, fatigue and damage of the powered railway vehicles considering gear transmissions, especially for traction and/or braking conditions.

Effect of vehicle vibration environment of high-speed train on dynamic performance of axle box bearing

ABSTRACTIn this study, we developed a comprehensive three-dimensional vehicle–track coupled dynamics model considering the traction drive system and axle box bearing. In this model, dynamic interactions between the axle box bearing and other components, such as the wheelset and bogie frame, are considered based on a detailed analysis of the structural properties and working mechanism of the axle box bearing. A few complicated dynamic excitations, such as the time-varying mesh stiffness of gears, time-varying stiffness of bearing, bearing gaps and track irregularities, are considered. Then, the dynamic responses of the vehicle–track system are demonstrated via numerical simulations based on the established dynamics model. The results indicate that the traction drive system and track irregularities can significantly influence the dynamic interactions of the axle box bearing. The necessity of considering the excitation caused by gear meshing and track irregularities when assessing the dynamic performance of the axle box bearing is demonstrated.

Vibration Levels in Vans as a Function of Payload and Leaf Spring Sheet Number

Abstract Measuring the vehicle vibration environment is essential to understanding and simulating the adequacy of a packaged-product system and its ability to ensure protection from transportation hazards. In the transportation industry, various vehicles are used to perform shipping tasks, including light commercial vehicles that became the most popular vehicles in single unit and lightweight package transportation. In this study, the transport vibration levels in vans were measured as a function of payload and number of leaf spring sheets used. The vans consisted of one with a 20 % payload of total capacity and another with an 80 % payload. The vans were divided into two groups: those with a single leaf spring and those with a double leaf spring. The measurement conditions were the motorway and speed between 110 and 130 km/h. The results revealed that transport vibration levels are affected by payload and the number of spring sheets. A low payload and single leaf spring contributed to the highest transport vibration levels. The power density level peaks were between 1.5 and 3.5 Hz, then around 15 Hz.

Methodology of Developing a Combined Environmental Stress Schedule for Reliability Growth Testing: Part II. The Tracked Vehicle Vibration Environment

This three-part series describes how to develop an environmental test schedule for military ground-mobile equipment installed on a tracked vehicle based on the user's mission profile. The test schedules combine both operational and storage environmental stresses. Part I describes the equipment to be tested, provides a general overview of its mission profiles, and identifies appropriate climatic conditions. Part II discusses the complexities of the tracked-vehicle vibration environment, including research conducted in the Arizona desert and the Alaskan aretic. Part III compares test profiles based on excluding benign environmental phases with profiles that include benign stress conditions.

Notes on springs

Gear transmission is a key element in a locomotive for delivery of traction power from the electric motor to the wheelset. Its dynamic performance has a direct effect on the operational reliability or even safety of the locomotive or the train. In this paper, based on the classical vehicle–track coupled dynamics theory and the gear dynamics theory, a locomotive-track coupled spatial dynamics model is established where the dynamic effects from the gear transmissions are considered. In this model, the gear transmission system and the classical locomotive–track system are coupled with each other via wheel–rail contact interface and the gear mesh interface. The dynamic interactions between the rotational motions of the power transmission system, the vertical, lateral, longitudinal, roll, yaw and pitch motions of the components in a locomotive are fully included. This more comprehensive dynamics model of the locomotive–track system enables detailed investigations on the system dynamic performance under the complicated excitations from both the track geometrical irregularity and the internal mesh process of gear pairs (e.g. time-varying mesh stiffness, gear errors), especially the dynamic responses of the gear transmission in the complete vehicle vibration environment. This model is finally validated by comparisons with the field test data in the time- and time-frequency domains. And it is capable of being used for dynamics related assessment, such as vibration, fatigue and damage of the powered railway vehicles considering gear transmissions, especially for traction and/or braking conditions.