Time delay in a semi-active damper: modelling the bypass valve

Ride comfort and handling of off-road vehicles can be significantly improved by replacing the normal passive dampers in the vehicle suspension system with controllable, two-state, semi-active dampers. The hydraulic valve, which enables the semi-active damper characteristics to be controlled, is a critical component of a semi-active damper and has a marked influence on suspension performance. Models of the dynamics of a hydraulic bypass valve used on semi-active suspension systems for heavy vehicles were investigated. It is envisaged that similar models will eventually be incorporated into a full vehicle, three-dimensional simulation study. Valve response time (or time delay) is used as a measure of model accuracy because it is an important parameter in the performance of a semi-active damper. Models were created with AMESim, a commercial fluid power simulation environment, and MATLAB. AMESim was found to be capable of dealing with detailed and complex fluid power models. Attempts to solve models of similar complexity in the MATLAB environment were unsuccessful due to numerical stiffness. Experimental work was conducted to obtain dynamic performance data with which to validate model integrity. Several external factors influenced the valve behaviour during experiments. Test bench dynamics significantly influences results and obscures the absolute accuracy of the models and the experimental data. The investigation demonstrated an approach to creating fluid power models for this application that can be used in simulation, but also indicated that substantial effort is required in the process. The accuracy of the current model is not sufficient for design purposes.     

Development and experimental evaluation of translational semi-active dampers on a high mobility off-road vehicle

This paper describes the further development and experimental evaluation of two-state semi-active translational dampers on a 6×6 high mobility off-road vehicle. As only ride comfort was enhanced during previous work, the low-speed damping characteristics on the semi-active damper was increased in order to improve vehicle handling. The existing passive dampers, as normally fitted to the test vehicle, were modified to the semi-active configuration by adding a bypass assembly and a controllable valve. Experimental work included driving over various repeatable surfaces at different speeds and executing severe lane change manoeuvres. Results indicated that both handling and ride comfort were improved when selecting the semi-active configuration.     

Semi-active hydropneumatic spring and damper system

This paper is concerned with the development of a semi-active hydropneumatic spring and damper system, comprising of a two state hydropneumatic spring and a two state hydraulic damper. The system was specifically developed to improve the ride comfort and handling of large off-road vehicles. The suspension requirements for good ride comfort and handling for heavy off-road vehicles are discussed with special reference to the advantages of semi-active hydropneumatic springs and semi-active dampers. The layout and functioning of an experimental spring and damper unit used for laboratory tests are discussed. Spring and damper characteristics, as well as valve response times for both the semi-active spring and semi-active damper were determined. A single degree of freedom test rig with a sprung mass of 3 tons was used to perform first order ride comfort tests. Tests include step response and random input response. The test rig was also used to evaluate semi-active control strategies for both spring and damper as well as a control strategy for implementing ride height adjustment without using an external hydraulic pump.     

高速铁路连续箱型梁桥的动力响应与减振分析

根据列车具体的轴距和轴重,建立了和谐号动车组CRH380AL型列车简化模型;对高速铁路两跨连续梁桥采用多自由度欧拉伯努利梁单元进行主梁的模拟,并将液体黏滞阻尼器模拟为有限元阻尼单元;采用Newmark直接积分方法求解了高速列车作用下的连续梁桥运动方程,数值分析了列车车速以及液体黏滞阻尼器的阻尼系数对于高速铁路连续梁桥振动响应的影响。结果表明:黏滞阻尼器对于桥梁具有明显的减振效果,阻尼力不仅与阻尼系数有关还与列车时速有关;同一黏滞阻尼器条件下,桥梁的最大加速度并不随列车速度的增加而单调增加,而是在某些特定列车车速下桥梁的最大加速度出现了峰值,且随着黏滞阻尼器的阻尼系数增大,桥梁振动响应峰值处的最大加速度减幅不同;同一列车时速的条件下,桥梁的减振效果并不是随着阻尼系数的递增呈正比递增,而是随着阻尼系数的增大,阻尼器的减振效果增幅在减小。     

Nonlinear Stiffness of a Magneto-Rheological Damper

The last decade has witnessed an important role of magneto-rheological dampers in the semi-active vibration control on the basis of empirical models. Those models established by fitting experimental data, however, do not offer any explicit expressions for the stiffness and the damping of magneto-rheological dampers. Hence, it is not easy for engineers to get any intuitive information about the effects of stiffness and damping of a magneto-rheological damper on the dynamic performance of a controlled system. To manifest the nonlinear properties of a magneto-rheological damper, this paper presents the hysteretic phenomena and the additional nonlinear stiffness of a typical magneto-rheological damper in terms of equivalent linear stiffness and equivalent linear damping. Then, it gives a brief discussion about the effect of nonlinear stiffness on the vibration control through the numerical simulations and an experiment for the semi-active suspension of a quarter car model with a magneto-rheological damper installed. Both numerical simulations and experimental results show that the additional nonlinear stiffness in the magneto-rheological damper is remarkable, and should be taken into consideration in the design of vibration control.     

Experimental evaluation of an unsophisticated two state semi-active damper

This paper describes the experimental evaluation of a two-state damper, used as the variable force element in a semi-active suspension. The study was necessary to establish the influence of non-ideal operating conditions when existing control strategies were evaluated in a practical environment. Three existing control strategies, each derived by using a different approach, were chosen for evaluation purposes and to experimentally determine the feasibility of semi-active suspensions. The control valve used to switch between states consisted of a pressure-dependent logic element and a directional spool valve. Characterization of the valve revealed a highly non-linear behaviour when switching between states. Experimental results indicated that two state semi-active dampers, which should offer a substantial cost saving over continuous variable dampers, especially in heavy wheeled vehicle applications, provide significant ride improvement potential. Furthermore, it was established that more complex phenomena existed than those normally taken into account during the usual theoretical evaluation of semi-active dampers.     

MR阻尼器的半主动控制研究

MR阻尼器能提供可以调节的阻尼力,适合用作减少结构地震响应的半主动控制器。本文对MR阻尼器的半主动控制进行研究,提出了状态跳跃算法,根据结构响应的大小实现MR阻尼器的状态切换,使结构响应得到有效的控制。这种控制策略简便,不需要在线计算,便于实施。由于速度响应直接影响MR阻尼器的阻尼力,建议用速度响应作为MR阻尼器进行状态切换的变量。文中给出了两个算例,进行了计算分析和比较,说明了状态跳跃控制算法的特点。     

Non-linear parametric modelling of a high-speed rail hydraulic yaw damper with series clearance and stiffness

At high operational speeds, the train system becomes very sensitive to parameter variations of components. Therefore, it is imperative to incorporate more accurate component models in the vehicle dynamics studies. This study addresses a more subtle and comprehensive non-linear parametric model of a high-speed rail hydraulic yaw damper. A new concept of a hydraulic yaw damper model is suggested, in which the small mounting clearance, the series stiffness, and the viscous damping are built in. The series stiffness is the tandem result of the dynamic oil stiffness, the rubber attachment stiffness, and the mounting seat stiffness. A dynamic oil property model is established and coupled to the entire modelling process, in which the density, the dynamic viscosity, the volumetric elastic modulus, and the stiffness of the oil are all changeable in terms of the instantaneous working pressure, the oil temperature, and the entrapped air ratio of the oil. The dynamic flow loss and the valve system dynamics are also incorporated. Experiments validated that the established non-linear parametric model is accurate and robust in predicting the damping characteristics within an extremely wide speed range. The validated damper model was then successfully applied to a thorough parameter sensitivity analysis and damping nature prediction under practical, in-service conditions. The established damper model couples all the main influential factors that are not or are insufficiently considered in normal-speed problems; thus, it will be more accurate and appropriate for furthering high-speed problem studies.     

三种电流变阻尼器阻尼特性的对比分析

首先简要地介绍了电流变体材料以及电流变阻尼器的基本概念,进而阐明了剪切模式电流变阻尼器、流动模式电流变阻尼器和复合模式电流变阻尼器的工作原理。最后,应用非牛顿流体力学理论给出了它们的阻尼力模型,并对其各自的阻尼特性进行了一些理论分析和探讨。     

汽车液压阻尼器的四段线性化模型

通过对现有某车用液压阻尼器的实验研究和车辆悬架系统动力学仿真研究，发现这种阻尼器的动力学特性存在复杂的非线性行为。为准确描述这类阻尼器的动力学特性和进行汽车悬架系统的动力学仿真研究，本文根据阻尼器的实验数据，提出一种新型四段线性化阻尼器模型，并建立其相应的数学模型。通过汽车悬架系统的动力学仿真研究表明，采用四段线性化阻尼器模型，汽车悬架系统簧载质量在不同路面不平度函数作用下的加速度响应和均方根加速度响应随频率变化不会出现大的波动。与等效线性化阻尼器模型相比，四段线性化阻尼器模型，能较好降低汽车悬架系统簧载质量的加速度响应和均方根加速度响应，有利于提高汽车乘坐舒适性和行驶稳定性，并为新型阻尼器设计提供一个新的思路。     

An alternative control strategy for semi-active dampers on off road vehicles

A control strategy is developed that takes into account the pitch and roll degrees of freedom on an off road wheeled vehicle in order to control discrete adjustable semi-active dampers more effectively. From the literature it was concluded that some existing semi-active control strategies were derived by employing models with either one or two degrees of freedom. If these strategies are applied to control semi-active dampers on a vehicle, each wheel station is controlled separately. The other degrees of freedom of the sprung mass, such as roll and pitch, are therefore not explicitly taken into account. The alternative control strategy determines that combination of damper states that will provide the highest acceleration opposing the movement of the sprung mass (deceleration), or the lowest acceleration in the direction of movement of the sprung mass. Simulation and experimental results indicated that the strategy that minimises the highest absolute value of the roll or the pitch acceleration performed significantly better than an existing semi-active control strategy (based on the absolute and relative damper velocities), especially when ride comfort under off-road conditions was taken into account. Four conventional dampers were modified, adding a by-pass assembly and controllable valve. The effect of using semi-active dampers on an off-road vehicle was evaluated during an extensive experimental programme, using ride comfort as basis. Results showed that the control strategy, as developed in this study, provided better responses in comparison to the passive configuration and an existing control strategy.     

Design method for fluid viscous dampers

A basic design method of doubly acting fluid viscous dampers with double guide bars is presented. The flow of the viscoelastic fluid between two parallel plates, one of which is started suddenly and the other of which is still, is analyzed. According to this solution, the velocity and the shear stress of the fluid at the fringe of the piston are solved approximately. A mathematical model of viscous dampers is derived, and the shock test is carried out. From experimental results, the parameters of the mathematical model are determined. Consequently, a semi-empirical design equation is obtained. Applying this equation to a certain practical damper, the damping material is chosen and the physical dimensions of the damper are determined. Shock tests using this damper are performed. Theoretical results are in good agreement with experimental results, which validates the reliability of the calculated physical dimensions of the specimen damper and the validity of the basic design equation. An erratum to this article can be found at     

Semi-active rotary damper for a heavy off-road wheeled vehicle

The development, simulation and laboratory testing of two-state discrete adjustable semi-active rotary dampers for heavy off-road wheeled vehicles, which is a joint venture between the South African based company Reumech Ermetek and Horstman Defence Systems from the UK, is described. A brief history of semi-active damping and rotary dampers is given, after which the working principle and features of combining the two technologies is outlined. Three dimensional simulation is used to determine the ride comfort gains achievable with semi-active rotary dampers compared to the conventional translational dampers currently used on the vehicle under consideration. Simulations are performed over different terrains, including the APG track and discrete obstacles. Semi-active rotary dampers were integrated on the 6×6 GV6 Self-propelled Gun Howitzer in order to quantify the improvements in ride comfort, transient response and handling of the vehicle as indicated by the simulation results. The control system, control strategies and characterisation tests, which includes determination of on and off characteristics as well as valve response times, are discussed.     

基于分数阶磁流变液阻尼器模型的车辆悬架组合控制

磁流变液阻尼器的分数阶Bingham模型结构形式简单, 而且可以更好地描述系统的滞回特性. 建立了含有分数阶Bingham模型的单自由度1/4车辆悬架系统模型, 利用磁流变液阻尼器对在路面简谐激励下的非线性车辆悬架系统进行振动控制. 研究了含有分数阶Bingham模型的悬架系统在天棚阻尼半主动控制下的主共振响应, 利用平均法得到了系统的近似解析解. 求解了系统定常解的幅频响应方程, 并根据李雅普诺夫稳定性理论得到了悬架系统的稳定性条件. 通过绘制数值解和解析解的幅频响应曲线对比图, 验证了近似解析解的正确性. 利用簧载质量垂直方向的加速度均方根值分析了半主动控制对车辆乘坐舒适性的影响, 发现天棚阻尼半主动控制策略在低频激励区域反而会降低车辆的乘坐舒适性. 因此提出了一种被动控制与半主动控制相结合的组合控制策略, 并分析了半主动控制参数对振动控制效果的影响. 分析结果表明, 该组合控制策略不但能够提高车辆的乘坐舒适性, 而且能有效抑制悬架系统的主共振振动幅值.      

质量阻尼器的发展

广泛评述了调谐质量阻尼器(TMD)、多重调谐质量阻尼器(MTMD)、主动质量阻尼器(AMD)、半主动 TMD(SATMD)、主动调谐/主被动调谐/混合质量阻尼器(ATMD/APTMD/HMD)的研究现状.TMD, MTMD, AMD, SATMD, ATMD/APTMD/HMD能够有效地减小结构的风振与地震反应.指出强震下结构设置TMD, MTMD, AMD, SATMD, ATMD/APTMD/HMD的主要目的是限制结构屈服的进一步发展.因此,基于非线性结构模型的TMD, MTMD, AMD, SATMD, ATMD/APTMD/HMD研究具有重要意义.指出了TMD, MTMD, AMD, SATMD, ATMD/APTMD/HMD 有待于进一步研究的若干问题.提出了结构主动多重调谐质量阻尼器(AMTMD)和多重主被动调谐质量阻尼器(MAPTMD)的新控制策略.介绍了AMTMD和MAPTMD的研究进展并指出了进一步研究的发展方向.      

Nonlinear modeling and experimental characterization of hydraulic dampers: effects of shim stack and orifice parameters on damper performance

A nonlinear model of monotube hydraulic dampers is presented with an emphasis on the shim stack properties and their effects on the overall damper performance. There has been no published detailed analysis of the effects of shim stack design in a hydraulic damper to date. Other damper models have used simplifying assumptions for the shim stack deflection and effects of the shim stack have not been completely studied. Various parameters affecting the nonlinear characteristics of monotube dampers such as the hysteresis region are studied. The model presented in this paper can be used for design purposes and helps in developing controllable valvings based on shim stacks. It can also be used to design controllable bypasses in hydraulic dampers. The mathematical model is validated by comparison against experimental test results carried out on an OHLINS CCJ 23/8 monotube damper, in CVeSS test facilities.     

Behavior explanation and a new model for nonlinear viscous fluid dampers with a simple annular orifice

Viscous fluid dampers have been used in many building and bridge construction projects for earthquake damage mitigation. Previous study has shown that silicone oil properties, such as the fluid shear-thinning and relaxation effects, play important roles for the annular-orificed fluid damper behavior, and the Navier-Stokes equations based on these mechanisms were developed. In the current study, attempts are made to explain the effects of frequency, damper dimensions, and viscosity of silicone oil on the damper stiffness behavior using the developed equations. It is found that the developed equations successfully explain the observed phenomena. To avoid the complicated fluid dynamics analyses for damper parameters, such as the damping factor and the velocity power exponent, a new four-parameter equation considering both the fluid shear-thinning and stiffness effects, with a form similar to the widely used two- or three-parameter equation is proposed. The results of the new model successfully capture the damper behavior both at low and high frequencies and show an advantage that better consistent results can be obtained in the velocity range for the building and bridge applications.     

架空输电线防振锤阻尼特性实验研究

本文利用梁的振动理论对防振锤的阻尼特性进行研究。通过正弦激励下的共振驻留法,分别对不同型号以及同种型号不同锤头质量的防振锤进行振动实验,应用能量平衡原理得到了防振锤的阻尼特性曲线,分析了不同模态响应在阻尼耗能中的贡献。考虑不同类型阻尼对于减振性能的作用,在Lazan阻尼假设的基础上,利用经验公式推导了阻尼系数计算公式。结果表明,钢绞线变形大小直接影响防振锤的阻尼值大小;阻尼对减小共振频率附近的受迫振动幅值作用明显,验证了防振锤的减振性能;同时锤头质量的变化可以影响阻尼曲线的变化。以上结论可为防振锤的防振设计和应用提供参考。     

An analytical approach to optimally design of electrorheological fluid damper for vehicle suspension system

This work develops an analytical approach to optimally design electrorheological (ER) dampers, especially for vehicle suspension system. The optimal design considers both stability and ride comfort of vehicle application. After describing the schematic configuration and operating principle of the ER damper, a quasi-static model is derived on the basis of Bingham rheological laws of ER fluid. Based on the quasi-static model, the optimization problem for the ER damper is built. The optimization problem is to find optimal value of significant geometric dimensions of the ER damper, such as the ER duct length, ER duct radius, ER duct gap and the piston shaft radius, that maximize damping force of the ER damper. The two constrained conditions for the optimization problem are: the damping ratio of the damper in the absence of the electric field is small enough for ride comfort and the buckling condition of the piston shaft is satisfied. From the proposed optimal design, the optimal solution of the ER damper constrained in a specific volume is obtained. In order to evaluate performance of the optimized ER damper, simulation result of a quarter-car suspension system installed with the optimized ER damper is presented and compared with that of the non-optimized ER damper suspension system. Finally, the optimal results of the ER damper constrained in different volumes are obtained and presented in order to figure out the effect of constrained volume on the optimal design of ER damper.     

Dynamic properties of automotive damper modules

This paper addresses the dynamic properties of automotive shock absorber modules. Analyzing an equivalent linear system, a set of characteristic dimensionless numbers are introduced in order to qualify the dynamic performance of the damper and the damper module. The dependency of these numbers on the main parameters of the module like the damping constant, the spring stiffness of the damper, the top mount stiffness and the piston rod mass is shown. These numbers may also serve as similarity coefficients for quite different dampers regarding their dynamic behavior. Furthermore, they can be used to adjust the stiffness of the different force elements of the damper module to achieve an optimal damping quality.