Yaw Damper Research Articles

Bifurcation and stability analysis of a high-speed rail vehicle with active yaw dampers

Active yaw dampers (AYDs) show promise in addressing the carbody and bogie hunting issues of high-speed rail vehicles. However, the bifurcation behaviour under active control and the control law for hunting instability still require investigation. This study presents a comprehensive description of the linear control law, which can be simplified to various schemes, including skyhook damping, groundhook stiffness, modal, and blended schemes. The bifurcation behaviour under active control was analysed using a simplified lateral-dynamics-intended seven DOFs vehicle model and verified using a 3D full DOFs model in SIMPACK. Besides the well-known Hopf bifurcation, results also revealed a branching point (BP) and two new stable asymmetric equilibria. Although the asymmetric equilibria born through BP are stable, BP bifurcation should still be avoided for wheel flange contact and derailment concerns. Possible control laws are explored for two hunting scenarios: carbody hunting and bogie hunting. For carbody hunting cases, the control force can be either a linear function of bogie yaw displacement or a linear weighting function of bogie lateral and carbody roll velocity. The dominant frequency of the actuated force falls below 2 Hz, with a peak of 1.6 kN, and the allowable time delay is 70 ms. For bogie hunting cases, the control force can be a linear function of either bogie yaw displacement or velocity. In other words, both the groundhook stiffness and damping strategy are applicable. However, the actuated force contains several relatively high-frequency components (6∼13 Hz), which poses challenges to the control system and actuators, and the allowable time delay is relatively small.

Experimental and numerical research on the bogie hunting of a high-speed train caused by the empty stroke of yaw damper

The yaw damper serves as a hydraulic system connecting the bogie frame with the carbody and is the most critical component to prevent unstable oscillations of high-speed vehicles. Accidently, some unexpected factors can cause the yaw damper to fail, resulting in vehicle hunting instability. In this paper, a severe bogie-hunting phenomenon was monitored during the operation of a Chinese high-speed train. Specific research on the cause and solutions was performed by experimental and numerical methods. The wheel-rail contact relationship and the dynamic performance of the yaw damper were measured and analysed to identify the primary contributor to violent bogie hunting. The results indicated that the abnormal dynamic stiffness and damping of the yaw damper caused by the compression empty stokes serve as the primary origin of this abnormal vibration. The multi-body dynamics model of the high-speed train was established by integrating the field-tested parameters. The bogie hunting phenomenon was reproduced successfully, and the influences of yaw damper parameters on bogie hunting stability were analysed to propose the optimisation scheme. Finally, two solutions were adopted to suppress the empty compression strokes of the yaw damper and verified by the roller rig test.

Modelling and simulation of nonlinear dynamic characteristics of yaw dampers subjected to variable temperature operation condition of high-speed trains

Modelling and simulation of nonlinear dynamic characteristics of yaw dampers subjected to variable temperature operation condition of high-speed trains

Hunting motion of high-speed emu during cross-line operation: Mechanism and countermeasures

During the operation of the Chinese 250 km/h-level EMU, hunting occurs when the EMU crosses from Line B to Line A. Numerous tests and simulations have been conducted to investigate the mechanism of this phenomenon. Comparisons of the measured rail profiles of the two lines indicate that the left rail in Line A is higher than that in Line B at the inner rail shoulder. In addition, the top position of the right rail in Line A is approximately 2–3 mm closer to the inside than that of the right rail in Line B, with the right rail in Line A being higher than that in Line B at the inner rail shoulder. These differences cause a significant increase in the wheel–rail equivalent conicity when the EMU crosses from Line B to Line A and further cause the hunting phenomenon. Moreover, simulations and experiments are conducted to investigate the countermeasures for EMU cross-line hunting. Field test results show that both increasing the damping of the yaw damper and wheel reprofiling can improve the stability during EMU cross-line operation; however, the effect of increasing the damping of the yaw damper is limited under particularly poor wheel–rail relationship. Simulation results reveal that rail grinding of Line A referring to the Chinese 60N rail profile can also improve the stability of the EMU during cross-line operation.

Participation factors of wind turbine structures under rotor blade wind loads

A participation factor formulation is developed to determine the importance of each natural frequency due to rotor blades induced forces and moments. This factor can be used to realize the quantitative influence of a mode due to rotor-induced responses and know which active degree of freedom of that mode at the tower top. For jacket support structures, the participation factor of the first torsional mode is often large, so the multiple of the 3P frequency (nF3p) approaching the first torsional mode will cause serious resonance conditions. Thus, appropriate small yaw stiffness and large yaw damping are suggested to avoid resonance and reduce high-frequency fatigue damage. The participation factors of the second and third bending rotational natural frequencies often between 10% and 30% are not concentrated compared to the first torsional natural frequency. The resonance of this mode with nF3p may not be severe for fatigue issues, but it is still necessary to avoid it. The tuned mass damping can be used to reduce the rotor-induced forces and moments, while the proposed participation factor is useful to know which mode and location should be first reduced.

Experimental study of bogie instability monitoring and suppression measures for high-speed EMUs

As the key part of the rail vehicle, the bogie’s dynamic performance directly affects the vehicle’s operating performance. A large number of bogie instability phenomena occur during the operation of high-speed Electric Multiple Units (EMUs), which has an important impact on the safety and passenger comfort of the high-speed EMUs. In this paper, through a combination of line tests and simulations to study bogie hunting, line tests are first conducted to test the vibration data and wheel wear evolution of the high-speed EMUs. The data was analyzed to find out the evolution of the bogie instability law of the high-speed EMUs. Then the vehicle dynamic model is established to find out the mechanism of the bogie instability, and finally bogie instability suppression measures are proposed. The results of the test data showed that the wheel wear, the frequency and the amplitude of bogie instability of motor car is greater than that of the trailer car, and the ride index is poorer. The ride indexes at the early and late stages after wheel re-profiling do not exceed 2.5. The equivalent conicity increase is the main cause of bogie instability, and the bogie instability can be effectively suppressed by wheel re-profiling, replacing the yaw damper, and the rail grinding.

An abnormal carbody swaying of intercity EMU train caused by low wheel–rail equivalent conicity and damping force unloading of yaw damper

AbstractLow-frequency carbody swaying phenomenon often occurs to railway vehicles due to hunting instability, which seriously deteriorates the ride comfort of passengers. This paper investigates low-frequency carbody swaying through experimental analysis and numerical simulation. In the tests, the carbody acceleration, the wheel–rail profiles, and the dynamic characteristics of dampers were measured to understand the characteristics of the abnormal carbody vibration and to find out its primary contributor. Linear and nonlinear numerical simulations on the mechanism and optimization measures were carried out to solve this carbody swaying issue. The results showed that the carbody swaying is the manifest of carbody hunting instability. The low equivalent conicity and the decrease of dynamic damping of the yaw damper are probably the cause of this phenomenon. The optimization measures to increase the equivalent conicity and dynamic damping of the yaw damper were put forward and verified by on-track tests. The results of this study could enrich the knowledge of carbody hunting and provide a reference for solving abnormal carbody vibrations.

Influence of clearance and structural coupling parameters on shimmy stability of landing gear

AbstractThere are many factors causing the shimmy of the aircraft landing gear and structural clearance of landing gear is a typical factor. Some aircraft in service or operation did not shimmy before, but suddenly appeared after a period of use. To solve the problem of clearance shimmy during the service of a certain aircraft, we established a dynamic model of rotating gear with clearance based on the flexible multi-body dynamics model of landing gear and L-N contact theory. We defined different types of clearance and established a mechanical model of aircraft pendulum vibration considering the clearance of landing gear structure for dynamic simulation, and studied the effects of different clearance types, clearance size of motion pair and different clearance positions on the stability of pendulum. The results show that the axial clearance has little effect on the shimmy performance of landing gear; the radial clearance has a certain effect on the shimmy performance of medium speed running, which slightly improves the shimmy damping required by medium speed running; the rotational clearance affects the shimmy performance of the nose landing gear by affecting the force transmission of structural components. The required shimmy damping coefficient increases at low speed and decreases at high speed. The main reason for the return clearance is that during the return, the shimmy damper does not work, which leads to the decrease of the shimmy damping performance and the increase of the required shimmy damping coefficient in the whole speed range. Meanwhile, the structural clearance will increase the shimmy frequency of the nose landing gear. By analysing the yaw angle of the nose landing gear and the time domain curve of the yaw angle of the yaw damper, we can determine which structure of the landing gear and which type of clearance is the cause of the yaw. Finally, the coupling effect caused by the main structural parameters of the landing gear in “gap shimmy” was analysed according to different mechanical stability distances and strut stiffness of the nose landing gear, providing reference for aircraft anti-shimmy design, nose landing gear fault diagnosis and nose landing gear maintenance support.

Stability Augmentation in Lateral Directional Dynamics: A Multivariable Approach

This paper delves into the concept of stability augmentation in lateral-directional dynamics, focusing on a multivariable approach. In aircraft control systems, ensuring lateral-directional stability is crucial for safe and efficient flight. The primary objective is to examine the feedback control system's role in enhancing stability and how it interacts with the aircraft's inherent dynamics. We begin by exploring the basic augmentation system for lateraldirectional dynamics, which includes the feedback of body-axis roll rate to ailerons and yaw rate to the rudder, commonly referred to as the yaw damper. One of the key challenges addressed in this paper is the need to overcome the interference caused by the yaw damper when coordinating turns. This interference results from the constant nonzero yaw rate present during coordinated turns. To address this issue, the concept of "transient rate feedback" is introduced, which uses a washout filter to differentiate the feedback signal and minimize its effect during steady-state conditions. The paper presents mathematical models and transfer functions that describe the behavior of the lateral-directional augmentation system. It discusses the impact of different parameters, such as the time constants of actuators and washout filters, on the system's performance. The design of the feedback loops for roll and yaw control is elaborated upon, emphasizing the trade-offs between roll response, dutch roll damping, and roll-yaw coupling. Simulation results are used to evaluate the effectiveness of the stability augmentation system in improving the aircraft's roll response and dutch roll damping under varying flight conditions. The paper concludes with insights into the challenges and benefits of multivariable control system design for lateral-directional stability augmentation in aircraf

The effect of the installation angle of a high speed train yaw damper on wheel wear

The yaw damper is of great significance to the dynamic performance of high-speed trains. In this work, the influence of different installation angles of yaw dampers on dynamic responses and wheel wear is investigated. Firstly, the detailed dynamic model of a high-speed train is developed, which includes all kinds of nonlinear factors, such as wheel/rail contact relationship and nonlinear characteristics of various damping, and the influence of the installation angle of the yaw damper on dynamic performances of railway vehicles is investigated. Then the wheel wear prediction procedure is also proposed to obtain the effect of the installation angle of the yaw dampers on wheel wear evolution. The results show that the nonlinear critical speed of railway vehicles gradually increases with the increasing lateral distance of the yaw damper at the frame side. While critical velocity gradually decreases with increasing vertical installation distance of the yaw damper at the car body side. The maximum wheel wear depth will also gradually increase with increasing vertical distance at the car body side and increasing lateral distance of the yaw damper at the frame side when the vehicle runs on the tangent track. Moreover, it is also noticed that the wear depth of the wheel on both sides will gradually increase with the increasing vertical installation distance of the yaw damper at the car body side when the vehicle runs on a curved track. When the lateral installation angle of the yaw damper is less than 0°, the wheel wear rate remains constant and the wear sensitivity of the wheel to lateral installation angle is low, if the lateral installation angle of the yaw damper is greater than 0°, wheel wear rate increases significantly with increasing lateral installation angle of the yaw damper.

Influence of yaw dampers on vertical vibration of railway car body induced by wheels rotation and its countermeasures

Influence of yaw dampers on vertical vibration of railway car body induced by wheels rotation and its countermeasures

Application of yaw dampers with frequency-selective damping to improve the locomotive adaptability to low/high conicity stability

High-speed locomotives are prone to the carbody or bogie hunting under extreme wheel-rail contact conditions, which can cause negative impacts on vehicle dynamics performance. The influence of key suspension parameters on the carbody lateral ride comfort and bogie lateral acceleration is investigated by the multi-objective optimization and Sobol global sensitivity analysis methods, which is based on the Radial Basis Function Neutral Network surrogate model. The results illustrate that the yaw damper damping is sensitive to the two hunting stabilities, but conventional yaw dampers with fixed damping fail to satisfy both the stability demands simultaneously. Therefore, this paper presents a damping-adjustable yaw damper integrating an FSD (frequency-selective damping) valve to guarantee the lateral stability especially in abnormal wheel-rail contact states, and the application effects of the FSD yaw damper for the locomotive are researched by dynamics simulations. The results show that the FSD yaw damper can improve the adaptability of the locomotive to both the low and high wheel-rail contact conicity service conditions compared with the conventional yaw dampers.

Linear stability analysis of a high-speed rail vehicle concerning suspension parameters variation and active control

An Eigen root analysis is fulfilled for a high-speed rail vehicle concerning suspension parameters variation and active control using a simplified lateral-dynamics-intended model. The model is verified to be capable of reflecting the modal features of both carbody suspension modes and hunting modes. Subsequently, the effects of suspension parameters and the active yaw damper (AYD) on the vehicle modes are examined with various wheel/rail conicities. It shows that the frequency of hunting motion does not linearly increase with the vehicle speed but saturates to a value over 300 km/h. The crucial influential suspension parameters of the vehicle modes include the series stiffness and damping coefficient of the yaw damper, the longitude positioning stiffness on the wheelset, the series damping of the lateral damper, and the lateral stiffness of air springs. Sky-hook damping/stiffness control of AYD helps to increase the modal damping for bogie hunting concerns. For a large conicity of 0.37 case, a minimum of 400 kN·s/m is suggested for the damping control and 10 MN/m for stiffness control. Moreover, the damping control would adequately relieve the carbody hunting with a conicity of 0.11, and the stiffness control still works fine even with an extremely small conicity of 0.07.

Innovative passive yaw damper to increase the stability and curve-taking performance of high-speed railway vehicles

Yaw dampers are implemented on high-speed trains to reduce their tendency towards unstable movement (hunting) while running at high-speed. Although they have a positive influence on the vehicle’s stability, these devices impose a steering resistance action on the bogies while negotiating tight curves at low speed, and so standard passive devices must be designed taking conflicting objective functions into account. This paper presents an innovative yaw damper able to overcome this trade-off by introducing a passive solution able to modify this component’s working behaviour during different vehicle operating conditions. To quantify the efficacy of this solution, numerical models of innovative and standard dampers were developed and validated by means of experimental tests. Then, they were co-simulated with a multibody model of a real test case vehicle running under different operating conditions.

Increasing the fatigue life of offshore wind turbine jacket structures using yaw stiffness and damping

In this study, an appropriate proportion of yaw stiffness and damping is proposed to greatly improve the fatigue life at the tubular joints of offshore wind turbine (OWT) jacket support structures. The fatigue analyses using the DTU 10-MW OWT jacket support structure under 1148 IEC-61400-3 loads indicated that the torsion of rotor blades under turbulent wind conditions is the most important load leading to fatigue damage to tubular joints. Other loads, such as the moments generated from rotor blades and wave loads, are less important than the torsion. A Guyan reduction two-degrees-of-freedom model and eleven full finite element models indicated that low stiffness and large damping of the yaw system can significantly increase the fatigue life of tubular joints, and the yaw angular velocity will not increase. However, it is necessary to address the restrictions in the yaw rotation and to avoid Fn3P resonance (Integer multiples of 3P) with the first natural frequency of the structural vertical rotation.

Suspension parameters design for robust and adaptive lateral stability of high-speed train

An adequate hunting stability margin is required through the optimisation and matching of bogie suspension parameters for high-speed trains. Moreover, the dynamics design is particularly important for the robust lateral stability to adapt to wheel–rail wear and track deformation. The hunting stability margin of vehicles, as well as the wheel–rail contact state adaptability should be taken into account. In this regard, the robust hunting stability Pareto optimisation of bogie suspension parameters for different wheel–rail wear stages is executed. A method for the centralised optimisation of key bogie suspension parameters based on vehicle lateral robust stability is presented, and the principle of two typical parameters matching for high-speed vehicles is summarised. In addition, in order to make the vehicle automatically adapt to different wheel–rail geometry contact states without any sensors and control systems, a new idea of frequency-dependent stiffness (SDF) of yaw damper is proposed to ensure the lateral stability margin especially in extreme wheel–rail contact states, which is verified through the vehicle linear system stability and ride comfort comparative analysis. Finally, the adaptive stabilisation mechanism of the vehicle with the frequency-dependent stiffness of yaw damper is clarified.

Adaptive stability mechanism of high-speed train employing parallel inerter yaw damper

The aim of the study is to design a secondary yaw suspension that will control both low-frequency body motion and bogie hunting under different wheel–rail equivalent conicities. In order to enable the high-speed train to adaptively adjust to different wheel tread wear stages and improve the lateral dynamic performance of the vehicle in extreme wheel–rail contact states without any sensors and control systems, the eddy current damper with the parallel inerter as the yaw damper is proposed, and the in-depth research on its working mechanism is conducted. By establishing the theoretical analysis model of the lateral dynamics of high-speed train, and the multi-objective optimisation of the vehicle performances is carried out. The optimal parameters of the yaw damper under different wheel–rail contact conditions are analysed and the importance of frequency-dependent stiffness of yaw damper is obtained. Based on the characteristics of high-frequency transmissibility of inerter, the parallel inerter is applied to solve the limitation of insufficient dynamic stiffness of the traditional hydraulic yaw damper. The parameter configuration of the yaw damper with small series stiffness and large parallel inerter is proposed, and the stable operation of trains in major wheel–rail contact equivalent conicity is realised by using its frequency-dependent stiffness characteristics. In addition, the optimal energy dissipation and negative stiffness conditions of the parallel inerter yaw damper are analysed in this paper.

Double-parameter Hopf bifurcation analysis of a high-speed rail vehicle with an alternative wheel/rail contact approximation

This investigation integrates an alternative fully-parameterized approximation of nonlinear wheel/rail interaction into a simplified vehicle model, and a two-parameter Hopf bifurcation analysis is conducted to reveal the influence of the wheel/rail contact geometry and secondary suspension parameters for high-speed rail vehicles. The bifurcation diagram is compared among the 6 DOFs bogie model, linear and nonlinear 7 DOFs vehicle model, nonlinear 17 DOFs vehicle model, and 3D full DOFs vehicle model. It shows that the nonlinear 7 DOFs vehicle model can meet the requirement of both carbody hunting and bogie hunting simulations. 6 DOFs bogie model can only be used in bogie hunting bifurcation analysis. Linear vehicle model would bring errors in either critical speed or limit circle magnitude. The divergences in the linear terms of rolling radius and contact angle polynomials are significant enough in field operation to cause a noticeable difference in Hopf bifurcation speed. Attention shall be paid to the shape of equivalent conicity and contact angle curve. The crucial parameters to the Hopf bifurcation include the series stiffness and damping coefficient of the yaw damper and the lateral damper damping. However, the requirement of suspension parameters for stability can conflict in carbody hunting and bogie hunting cases.

Roll–Yaw Lock: Aerodynamic Motion Instabilities of Floating Offshore Wind Turbines

Abstract This article presents an investigation of a newly discovered motion instability phenomenon for floating wind turbines, first observed in numerical aero-hydro-servo-elastic simulations. The source of instability is identified as antisymmetric aerodynamic stiffness coupling terms in roll and yaw caused by the turbine thrust force. Analytical expressions for the roll–yaw and yaw–roll stiffness coupling terms are derived, using the actuator disk analogy of the rotor plane. It is demonstrated that a two degrees-of-freedom linear equation of motion without explicit external forcing qualitatively captures the instability. Based on this model, an analytical stability criteria is derived. An intuitive physical explanation of the phenomena is provided, considering the energy flow of the system. An important finding is that dissipative forces, in the form of aerodynamic and hydrodynamic damping, are needed to fully explain the observed instability. It is demonstrated, counterintuitively, that increased damping in yaw reduces the stability margin. This is explained by the fact that dissipative forces result in a phase difference between the harmonic roll and yaw motion in the coupled roll–yaw modes.

Performance Degradation Estimation of High-Speed Train Bogie Based on 1D-ConvLSTM Time-Distributed Convolutional Neural Network.

High-speed train bogies are essential for the safety and comfort of train operation. The performance of the bogie usually degrades before it fails, so it is necessary to detect the performance degradation of a high-speed train bogie in advance. In this paper, with two key dampers on the bogie taken as experimental objects (lateral damper and yaw damper), a novel 1D-ConvLSTM time-distributed convolutional neural network (CLTD-CNN) is proposed to estimate the performance degradation of a high-speed train bogie. The proposed CLTD-CNN is an encoder-decoder structure. Specifically, the encoder part of the proposed structure consists of a time-distributed 1D-CNN module and a 1D-ConvLSTM. The decoder part consists of a 1D-ConvLSTM and a simple time-CNN with residual connections. In addition, an auxiliary training part is introduced into the structure to support CLTD-CNN in learning the performance degradation trend characteristic, and a special input format is designed for this structure. The whole structure is end-to-end and does not require expert knowledge or engineering experience. The effectiveness of the proposed CLTD-CNN is tested by the high-speed train CRH380A under different performance states. The experimental results demonstrate the superiority of CLTD-CNN. Compared to other methods, the estimation error of CLTD-CNN is the smallest.