结构振动的滑模变结构半主动控制

研究应用磁流变阻尼器(MRD)对结构振动半主动控制的算法和原理。研制并对磁流变阻尼器进行了阻尼特性实验，采用非线性滞回双粘性模型描述磁流变阻尼器的阻尼特性，模型结果与实验结果非常一致。采用滑模控制算法和趋近律方法设计了半主动控制器。利用滑模控制方法所建立的控制器，本文给出了地震激励下结构振动半主动控制算例。计算分析表明，半主动滑模控制具有控制效果明显、鲁棒性好等优点，是一种非常有发展前途的控制方法。     

建筑结构的SMA被动振动控制方法

文章根据Robery K等研制的SMA中心牵引型耗能器的基本原理，设计出一种具有自我保护能力的新型耗能器，并建立了对应的力学模型。在此基础上，利用Brinson相变发展的本构模型从热力学第一定律出发建立了耗能器的热力学平衡方程式，为了探讨耗能器在结构中的被动控制效果，文章以三层单跨框架结构为例建立了结构在耗能器作用下的动力学方程式。最后，文章分别对耗能器与框架结构进行了数值仿真计算。结果表明，耗能器的耗能能力随温度的升高而下降，通过温控器的调节或改变相变温度点，可以使耗能器处于最佳耗能状态；SMA耗能丝材愈短，在相同的耗能器行程下，丝材应变愈大，相变发展愈充分，耗能量愈大，但最大应变不能超过材料的最大可恢复应变；SMA耗能器对结构在地震作用下的动力响应具有较显著的抑制作用，位移的峰值衰减率约50％一70％。     

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.     

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     

A novel scheme for nonlinear displacement-dependent dampers

In this paper, a novel scheme for nonlinear displacement-dependent (NDD) damper is introduced. The damper is attached to a simple mass-spring-damper vibration system. The vibration system equipped with a NDD damper is mathematically modeled and the nonlinear governing differential equation of the system is derived. To obtain the displacement of the system, the approximate analytical solution of the governing equation is elaborated using the multiple scales method. The advised approximate analytical algorithm is performed for several case studies and is also verified by the numerical fourth-order Runge?CKutta method. In addition, the performance of the NDD damper is analyzed and compared with the performance of the traditional linear damper. It is found that the proposed NDD damper scheme along with the multiple scales method is not only feasible for vibration reduction but also yields satisfactory response performance rather than the existing traditional linear damper.     

磁流体特性对磁流变火炮后坐阻尼器性能的影响

针对火炮后坐磁流变阻尼器的特点,以某单管25 mm火炮实验用磁流变阻尼器为研究对象,基于Herschel-Bulkley本构模型,建立了该炮磁流变后坐阻尼器的轴对称一维层流模型,获得了不同磁场作用下阻尼力随活塞速度的变化规律。运用火炮的后坐运动方程,计算了不同磁流体特性指数下,火炮的后坐位移和后坐速度。计算结果表明,磁流体特性指数的变化对磁流变后坐阻尼器的性能影响显著。     

Performance evaluation of electronic control suspension featuring vehicle ER dampers

This paper presents ride comfort and driving stability performances of electronic control suspension (ECS) equipped with controllable electrorheological (ER) damper and appropriate control strategy. In order to achieve this goal, a cylindrical type ER damper which is applicable to Macpherson strut type suspension of a mid-sized passenger vehicle is designed and manufactured on the basis of the required damping force level of an existing passenger vehicle. After experimentally evaluating the field-dependent damping force and dynamic characteristics of the controllable ER damper, ECS consisting of sprung mass, spring, tire and controller is established in order to investigate the ride comfort and driving stability performances. On the basis of the governing equation of motion of the suspension system, five control strategies (soft, hard, comfort, sports and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in both time and frequency domains under various road conditions. In addition, a comparative work is undertaken to investigate inherent control characteristics of each control strategy.     

不同耗能器安装方式下的结构振动控制效果分析

在斜支撑和Ⅴ形支撑的基础上，提出了安装阻尼器的三种新型附加联动机构支撑形式；并对这三种支撑形式下的阻尼器行程和控制力的计算进行了分析，采用放大系数的形式使计算公式得以简化；以SMA耗能阻尼器为对象，利用笔者编写的计算机程序，对包括斜支撑和Ⅴ形支撑在内的五种阻尼器安装方式进行了仿真计算。结果表明：(1)不同安装方式的振动控制效果各不相同，上肢联动机构的放大作用最大；(2)SMA耗能阻尼器的控制效果受SMA丝材长度的影响较大；(3)对不同的结构和不同的阻尼器应选择不同的阻尼器安装方式，才能使整体控制效果达到最佳。     

Suppression of multiple modal resonances of a cantilever beam by an impact damper

Impact dampers are usually used to suppress single mode resonance. The goal of this paper is to clarify the difference when the impact damper suppresses the resonances of different modes. A cantilever beam equipped with the impact damper is modeled. The elastic contact of the ball and the cantilever beam is described by using the Hertz contact model. The viscous damper between the ball and the cantilever beam is modeled to consume the vibrational energy of the cantilever beam. A piecewise ordinary differential-partial differential equation of the cantilever beam is established, including equations with and without the impact damper. The vibration responses of the cantilever beam with and without the impact damper are numerically calculated. The effects of the impact absorber parameters on the vibration reduction are examined. The results show that multiple resonance peaks of the cantilever beam can be effectively suppressed by the impact damper. Specifically, all resonance amplitudes can be reduced by a larger weight ball. Moreover, the impacting gap is very effective in suppressing the vibration of the cantilever beam. More importantly, there is an optimal impacting gap for each resonance mode of the cantilever beam, but the optimal gap for each mode is different.     

A NEW STOCHASTIC OPTIMAL CONTROL STRATEGY FOR HYSTERETIC MR DAMPERS

I. INTRODUCTION Magneto-rheological (MR) ?uid as a smart material possesses fairly good essential characteristics suchas reversible change between liquid and semi-solid in milliseconds with a controllable yield strengthwhen exposed to a magnetic ?eld. A…     

履带车辆磁流变减振器响应时间研究

磁流变减振器是应用磁流变液在强磁场下的快速可逆变特性而制造的一种新型振动控制装置,是履带车辆主动悬挂系统的核心部分。本文从理论上分析磁流变减振器响应时间的组成,在磁流变液的Bingham模型和流体力学的基础上,分析了流体流变响应时间的影响因素,提出了近似算法,并在磁流变减振器的实验基础上,作出阻尼力与位移的曲线图,求出阻尼力突变并达到稳定的响应时间。     

阻尼耗能减振框架结构地震作用振动方程求解及地震反应分析Calculation of vibration equation and analysis of seismic response for damping energy dissipation frame structure

研究了设置耗能阻尼器框架的地震作用振动方程求解及该结构的地震反应。框架结构设置耗能阻尼器后,振动方程的阻尼矩阵不再对振型具有正交性,本文对该振动方程给出了状态方程直接积分法,并与传统强制解耦法进行了比较分析,结果表明强制解耦法对结构第一阶振动反应求解偏差较小,而对于高阶振动反应差别较大,并且强制解耦法高估了阻尼器的减震效果。继而采用状态方程直接积分法对设置有粘滞阻尼器的框架结构进行了地震反应分析,探讨了阻尼器位置对框架结构地震反应的影响,结果表明设置有阻尼器的楼层减振效果明显,未设置阻尼器的楼层减振效果差别较大,甚至有可能出现楼层层间侧移增大的现象,由此提出耗能阻尼器应在结构中合理设置。     

Fluid formulae for damping changeability conceptual design of railway semi-active hydraulic dampers

Damping changeability design and evaluation is the most fundamental issue at the beginning of any new railway semi-active hydraulic damper development. Therefore, physical fluid mechanics for the calculation of basic structure and resistance parameters of the damper should be carefully studied in the conceptual phase. Fluid formulae for changeable damping performance evaluation of two commercial railway semi-active hydraulic dampers are established. Simulation results show that the damper switched by high-speed solenoid valves obtains a wide range of changeable damping coefficients, which guarantees the absorption of a wide spectrum of vibrations; however, a different low cost damper regulated with an inversely proportional relief valve, whose Force-velocity characteristics share the same rising curve, is relatively limited in damping ability. In order to overcome the drawback of the latter one with no obvious cost increase, a new semi-active hydraulic damper which is regulated by a simple proportional throttle valve is proposed. Continued fluid formulation and simulation suggests that the damper can change its damping force rising curves or “effective” damping coefficients continuously, within a considerably wide range. Thus, fluid formulae explicitly established in this study are of significance in the damping changeability conceptual design, further refinement and control design for the three semi-active hydraulic dampers. The proposed new damper, which has both a simple configuration and an easy-to-control ability, might be feasible for industry applications.     

Homoclinic bifurcation and chaos attractor in elastic two-bar truss

In this paper, we present a dynamic bifurcation analysis of the non-linear Duffing's equation on a simple elastic structure. The structure is a two-bar elastic truss with a damper, and possesses geometrical non-linear stiffness. We consider the dynamic instability of its structure based on Duffing's oscillation, which shows bifurcation behavior of the homoclinic orbit. We could numerically forecast the trajectory near the invariant saddle point of homoclinic bifurcation on this model, and we found that it is possible to solve dynamic bifurcation and strange attractors (chaos) on this non-linear structure. On this truss, we could investigate the dynamic stability of the strange attractor using Lyapunov exponents under the frequency and/or the amplitude parameter of periodic load.     

流体阻尼器中粘性发热的反馈作用与热平衡研究

主要针对长阻尼孔形式下的流体阻尼器进行分析,在三参数模型的基础上研究了流体粘性发热对流体阻尼力的反馈作用,从而建立了含热能转换与热交换的阻尼器的动力学模型,同时对系统的热平衡状态进行了分析。最后通过数值分析对该时变系统从时域和频域上讨论了粘性发热对隔振效果的影响,发现温度变化对共振频率的漂移及幅值大小的影响较大。     

Study on the force transmissibility of vibration isolators with geometric nonlinear damping

By a special layout of the damper in a vibration isolation system, the velocity-nth power damping of the damper can be transformed into the velocity-displacement dependent damping in the moving direction due to geometric nonlinearity. This study is mainly concerned with the mechanism of this geometric nonlinear damping and tries to find some guidelines for designing isolators with high performance, regardless of the isolator is passive or active. The model used in this study is an unconstrained two-degree-of-freedom isolation system, which is suitable for investigating vibration isolation in space vehicles. The motion equation is solved by the averaging method to obtain the amplitude–frequency equation. The influence of damping coefficients on the force transmissibility is analyzed. Results show that this kind of damping has some advantages in improving isolation performance at both the resonance and higher frequencies. Meanwhile, it can also degrade the isolation performance if unreasonable parameters are chosen.     

A direct experimental–numerical method for investigations of a laboratory under-platform damper behavior

Under-platform dampers are commonly adopted in order to mitigate resonant vibration of turbine blades. The need for reliable models for the design of under-platform dampers has led to a considerable amount of technical literature on under-platform damper modeling in the last three decades.Although much effort has been devoted to the under-platform damper modeling in order to avail of a predictive tool for new damper designs, experimental validation of the modeling is still necessary. This is due to the complexity caused by the interaction of the contacts at the two damper-platform interfaces with the additional complication of the variablity of physical contact parameters (in particularly friction) and their nonlinearity. The traditional experimental configuration for evaluating under-platform damper behavior is measuring the blade tip response by incorporating the damper between two adjacent blades (representing a cyclic segment of the bladed disk) under controlled excitation. The effectiveness of the damper is revealed by the difference in blade tip response depending on whether the damper is applied or not. With this approach one cannot investigate the damper behavior directly and no measurements of the contact parameters can be undertake. Consequently, tentative values for the contact parameters are assigned from previous experience and then case-by-case finely tuned until the numerical predictions are consistent with the experimental evidence. In this method the physical determination of the contact parameters is obtained using test rigs designed to produce single contact tests which simulate the local damper-platfom contact geometry. However, the significant limitation of single contact test results is that they do not reveal the dependence of contact parameters on the real damper contact conditions. The method proposed in this paper overcomes this problem.In this new approach a purposely developed test rig allows the in-plane forces transferred through the damper between the two simulated platforms to be measured, while at the same time monitoring in-plane relative displacements of the platforms. The in-plane damper kinematics are reconstructed from the experimental data using the contact constraints and two damper motion measurements, one translational and one rotational. The measurement procedures provide reliable results, which allow very fine details of contact kinematics to be revealed. It is demonstrated that the highly satisfactory performance of the test rig and the related procedures allows fine tuning of the contact parameters (local friction coefficients and contact stiffness), which can be safely fed into a direct time integration numerical model.The numerical model is, in turn, cross-checked against the experimental results, and then used to acquire deeper understanding of the damper behavior (e.g. contact state, slipping and sticking displacement at all contact points), giving an insight into those features which the measurements alone are not capable of producing. The numerical model of the system is based on one key assumption: the contact model does not take into account the microslip effect that exists in the experiments.Although there is room for improvement of both experimental configuration and numerical modeling, which future work will consider, the results obtained with this approach demonstrate that the optimization of dampers can be less a matter of trial and error development and more a matter of knowledge of damper dynamics.     

基于Abaqus的剪切型阻尼器单元开发与应用

基于Abaqus软件平台,利用FORTRAN语言二次开发了一种剪切型金属阻尼器用户子单元(UEL)。通过与Abaqus软件库中用于近似模拟阻尼器的单元进行比较,验证了该用户子单元的正确性,为Abaqus软件二次开发提供了参考。与软件库自带的单元相比,该用户子单元参数输入简单,无需试算,动力分析下的滞回性能更明显。同时,本文对软件中的不同单元进行了探讨,为剪切型金属阻尼器的模拟提供了新的思路。     

Testing and modeling of a CLEMR damper and its application in structural vibration reduction

In this paper, a new kind of combined lead extrusion magnetorheological (CLEMR) damper is proposed. First, tests on CLEMR damper at different currents, excitation amplitudes, and frequencies are carried out. Experimental results show that even when power fails, CLEMR damper can still absorb and dissipate vibration energy of the structure effectively, and its damping force can also be well adjusted in a large range of damping force. Then a mathematical model employing the current, excitation amplitude, and frequency as inputs is proposed and verified by comparing experimental and numerical results. Comparison results show that the proposed model can describe the effects of current, amplitude, and frequency on properties of CLEMR damper. Finally, elastic-plastic dynamic time-history analyses on frame structure with and without CLEMR damper are carried out to evaluate the effectiveness of CLEMR damper in reducing seismic responses of the structures; dynamic responses of the uncontrolled and the controlled structures are then compared. Comparison results show that the displacement responses of each floor of the controlled structure, as well as the number of the cracking point and yielding point of the member, reduce significantly, which implies that the proposed CLEMR damper holds promise in reducing and suppressing the vibration responses of the civil structures.     

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。