斜拉索振动被动控制中电/磁流变阻尼器的最优阻尼器能量输入

研究了电／磁流变（ER／MR）阻尼器在恶劣条件下作为被动阻尼器使用时斜拉索的振动问题。对斜拉索和阻尼器的振动特性进行研究，采用Halmiton原理和模型识别技术建立斜拉索-阻尼器的非线性数学模型；采用随机噪声作为激励，通过不断调整阻尼器的能量输入，进行斜拉索-ER／MR阻尼器系统的振动被动控制试验。试验结果表明，存在一个最优的阻尼器能量输入，在该输入下能够有效地抑制斜拉索振动。根据所建立的非线性动力计算模型得到的计算结果与振动控制试验结果吻合良好。考虑到系统的非线性，研究了荷载大小和阻尼器安装位置对最优阻尼器能量输入的影响。研究结果为在恶劣条件下利用ER／MR阻尼器进行斜拉索振动被动控制时的阻尼器设计提供了依据。     

阻尼器对频率法拉索索力测量的影响

振动频率法应用于索-阻尼器体系的索力计算会产生较大误差.为了考察阻尼器对频率法拉索-阻尼器体系索力测量精度的影响,采用有限元仿真分析方法,分别研究了阻尼器阻尼系数、安装高度及其刚度等因素对体系频率和索力测量的影响.研究发现,阻尼系数和安装高度对高阶频率影响显著,阻尼器刚度对低阶频率影响显著.在阻尼系数和刚度都大于其对应临界值时,拉索在阻尼器位置处近似铰支,采用修改索长方法可在一定程度上提高索力测量精度.此外,采用拉索的二阶频率可以消除垂度影响,从而改进索力测量精度.     

PVDF传感器实现斜拉桥桥索张力在线监测

斜拉索是斜拉桥的主要承载部件，斜拉桥桥跨结构的重量和桥上活载绝大部分或全部通过斜拉索传递到索塔上，实时监测分布于大桥上的桥索张力变化，对于了解斜拉桥的健康状态，确保斜拉桥的安全是至关重要的。采用聚偏二氟乙烯（Polyvinylidene Fluoride）通过监测应变得到拉索的振动信号，计算出拉索的张力，实现斜拉索张力的在线测量。     

超长斜拉索张力振动测量的传递矩阵法

振动法测量拉索张力需要准确描述索力与自振频率的关系,为反映超长斜拉索的真实构形及垂度效应,满足超大跨斜拉桥对测试精度的要求,考虑超长斜拉索垂度、倾角、自重及切向张力沿拉索变化的影响,在静力分析推导出斜拉索静态构形的悬链线方程基础上建立超长斜拉索振动的离散模型,应用多体系统传递矩阵法计算拉索固有频率,通过求解特征方程建立索力与振动频率的关系,提高了超长斜拉索张力的振动测量精度,完善了索力振动测量方法。通过对实际工程的测试结果分析表明,该方法具有准确、实用和易编程的特点,完全能满足工程应用要求。     

钟摆式阻尼器在塔器防振中的应用研究

以风阻尼器为基本模型,设计了适合塔器应用的钟摆式阻尼器,确定钟摆阻尼器尺寸与其频率的关系式,以此为基础设计钟摆式阻尼器。采用适当的几何相似系数,建立实验室小试模型,通过自由振动法测量系统的阻尼比,验证阻尼器效果。以此作为参考标准,对比分析了各阻尼器安装在不同位置处的效果,研究了质量比与安装位置对阻尼器效果的影响。通过瞬态动力学分析与实验结果进行对比验证,并分析阻尼器数量对阻尼器防振效果的影响。研究工作为塔器防振中阻尼器的设计与应用提供了参考依据。     

考虑柔索垂度影响的索牵引并联机器人跟踪控制

为考虑柔索垂度影响采用抛物线方程来描述大跨度柔索的构形,推导出索端张力与索端位移和索长变化之间的关系。基于柔索力学方程建立索牵引机器人的动力学模型,模型中作用在末端执行器上的柔索合力与柔索长度和末端执行器的位姿直接相关。为便于在控制设计中引入力学模型,对动力学方程进行线性展开,得到作用在末端执行器上的柔索合力增量与索长变化和末端执行器位移之间的关系。作用在末端执行器上的柔索合力可以表示为其期望值与相应的增量之和,该增量是由索长误差及末端执行器位姿误差引起的。控制设计时首先采用李雅普诺夫法针对柔索合力设计反馈控制器,然后利用前述的增量关系构造出基于末端执行器位姿反馈,以索长调整量为控制输出的非线性控制器。该控制器在本质上为一带补偿项的非线性PD控制,控制器参数可随系统状态的变化而自动调整。数值算例证明了控制算法的有效性。     

基于神经网络的磁流变阻尼器逆控制研究

为了解决阻尼器的非线性问题,设计了一种纯剪切型磁流变阻尼器,并针对其非线性特性,提出了利用径向基函数（RBF）神经网络的非线性映射能力,以建立磁流变阻尼器的逆模型。由已训练的磁流变（MR）阻尼器的逆向神经网络模型和MR阻尼器组成的控制单元,在给定所需控制力的情况下,使MR阻尼器产生相应的阻尼力,实现了MR阻尼器提供连续可调输出力的目的,也使得纯剪切型MR阻尼器在一些需要精确控制的场合能够方便使用。仿真结果表明,神经网络逆控制的方法是有效的、可行的。     

阵风载荷作用下高耸结构利用TLCD的减振性能研究

设计制作了一个具有动力等效的高耸结构缩比模型（TLCD减振模型）,并采用位移张弛激励方式来模拟阵风载荷对高耸结构进行失稳加载,应用LMSTest．1ab振动噪声集成试验系统的动力测试平台,进行一系列测试试验,查看TLCD阻尼器的结构减振性能效果,并对TLCD阻尼器减振效果的主要影响因素进行了研究。结果表明,TLCD液体质量和液体有效长度对TLCD阻尼器减振效果有较大影响。     

具有调谐惯容阻尼器的建筑结构减震设计

为提升传统调谐质量阻尼器(tuned mass damper,简称TMD)应用的方便性,提出利用调谐惯容阻尼器(tuned inerter damper,简称TID)对结构进行减震控制,推导了基底白噪声激励下建筑结构的TID最优阻尼参数和最优刚度参数的解析式以及无阻尼的位移方差解析式。分析表明,TID最优参数与其安装的相邻楼层振型坐标差的平方有关,该值越大,控制效果越好。通过3个均匀结构和1个12层的非均匀结构模型分析表明:TID对中低层结构的控制效果较好,且对高阶振型控制优势明显;TID-TMD混合控制方案在地震作用下的控制效果更明显,优于TID,且总体上与多重TMD控制效果相近;TID-TMD仅需在顶层安装TMD,其余楼层安装TID,减少了多重TMD控制高阶振型带来的空间占据、安装不便、质量过大等问题。     

MR阻尼器控制与滞环特性相分离的F-v模型

提出了一种基于对称和不对称Sigmoid函数,描述半主动可控磁流变液(MR)阻尼器阻尼力—相对速度(F-v)数学模型。该模型准确地描述了MR阻尼器非线性饱和的直流电流控制和对称滞环F-v的工作特性,以及激励频率和幅度对阻尼力的强影响特性,具有精度高和电流控制增益与滞环算子相分离的特点。将该模型与车辆悬架动力学模型结合分析,仿真结果表明MR阻尼器对实现新一代智能车辆悬架系统设计有潜在的意义,所提出的模型对进一步推动车辆悬架减振控制器设计研究有重要作用。     

Neuro-fuzzy control strategy for an offshore steel jacket platform subjected to wave-induced forces using magnetorheological dampers

Magnetorheological (MR) damper is a prominent semi-active control device to vibrate mitigation of structures. Due to the inherent non-linear nature of MR damper, an intelligent non-linear neuro-fuzzy control strategy is designed to control wave-induced vibration of an offshore steel jacket platform equipped with MR dampers. In the proposed control system, a dynamic-feedback neural network is adapted to model non-linear dynamic system, and the fuzzy logic controller is used to determine the control forces of MR dampers. By use of two feedforward neural networks required voltages and actual MR damper forces are obtained, in which the first neural network and the second one acts as the inverse dynamics model, and the forward dynamics model of the MR dampers, respectively. The most important characteristic of the proposed intelligent control strategy is its inherent robustness and its ability to handle the non-linear behavior of the system. Besides, no mathematical model needed to calculate forces produced by MR dampers. According to linearized Morison equation, wave-induced forces are determined. The performance of the proposed neuro-fuzzy control system is compared with that of a traditional semi-active control strategy, i.e., clipped optimal control system with LQG-target controller, through computer simulations, while the uncontrolled system response is used as the baseline. It is demonstrated that the design of proposed control system framework is more effective than that of the clipped optimal control scheme with LQG-target controller to reduce the vibration of offshore structure. Furthermore, the control strategy is very important for semi-active control.     

采用半主动TMD的建筑结构振动控制研究

为了改善在建筑结构中采用调频质量阻尼器（简称TMD）进行抗震时抗震效果不稳定和抑制频带窄等缺点，研究了变阻尼半主动调频质量阻尼器（简称STMD）。为了使阻尼变化容易实现，在设计激励力时采用了阶跃函数方式；同时还考虑到变动阻尼应在一定范围内进行的特点，提出了含约束的结构振动半主动控制方案；在控制策略方面，考虑到地震的随机性，引入了广义预测控制方法。从实例分析可知，采用STMD可以使设计质量、刚度和阻尼值分别下降约30％，90％，90％。计算仿真结果表明，采用STMD的抗震效果比TMD要好得多。     

Modeling the fine particle impact damper

The fine particle impact dampers (FPIDs) using plastic deformation of fine particles as irreversible energy sink can exhaust much more vibration energy than single mass impact dampers (SMIDs) and thus can work well in low frequency domain. A numerical model is set up in this paper to capture the complex physics involved in the FPID. Experimental results on a cantilever beam with FPID showed good agreement with the model predictions. We show that in all cases the damping performances of the FPID are much better than that of the SMID, and fine particles enrolled in the FPID play a key role in vibration energy dissipation. The damper clearance and the mass ratio are two important parameters for the damping ability of the FPID, for which an optimal combination of them exists targeting the largest damping ability.     

Damping of vibrations at resonant frequencies of electrical systems

Attention focuses on reducing the vibration of energy-intensive electrical systems, such as the power units of autonomous vehicles. The amplitude–frequency spectra of input and output vibrational signals for hydraulic vibrational bearings and cable vibrational dampers are investigated. Cable vibrational dampers are more effective in quenching impact loads, while hydraulic vibrational bearings are better at suppressing long-term vibration.     

模糊控制磁流变阻尼器与磁悬浮装置并联减振研究

针对磁悬浮装置参振质量大、刚度和阻尼低、振动幅值大时抑制振动效果差的问题,提出一种磁流变阻尼器与磁悬浮装置并联减振的方法。由于磁流变阻尼器具有非线性和滞回特性,目前的力学模型还不够精确,为此提出采用模糊控制方法对磁流变阻尼器进行控制,建立了基于TMS320LF2407A DSP的模糊控制磁流变阻尼器与磁悬浮并联减振系统。理论分析与实验结果证明,采用模糊控制磁流变阻尼器与磁悬浮装置并联减振,可以达到理想的减振效果,振动幅值可由0.48mm减小到0.16mm。     

Semi-active vibration control of an eleven degrees of freedom suspension system using neuro inverse model of magnetorheological dampers

A semi-active controller-based neural network for a suspension system with magnetorheological (MR) dampers is presented and evaluated. An inverse neural network model (NIMR) is constructed to replicate the inverse dynamics of the MR damper. The typical control strategies are linear quadratic regulator (LQR) and linear quadratic gaussian (LQG) controllers with a clipped optimal control algorithm, while inherent time-delay and non-linear properties of MR damper lie in these strategies. LQR part of LQG controller is also designed to produce the optimal control force. The LQG controller and the NIMR models are linked to control the system. The effectiveness of the NIMR is illustrated and verified using simulated responses of a full-car model. The results demonstrate that by using the NIMR model, the MR damper force can be commanded to follow closely the desirable optimal control force. The results also show that the control system is effective and achieves better performance and less control effort than the optimal in improving the service life of the suspension system and the ride comfort of a car.     

磁流变液阻尼器-柔性转子系统振动特性与控制的再研究

对先前提出的理论分析模型进行适当改进，用新模型对支承在磁流变液阻尼器上的单盘悬臂柔性转子系统的振动特性和控制技术进行再研究。研究表明，随着磁流变液阻尼器的库仑阻尼力的增大，系统在无阻尼临界转速处振幅明显下降，但在两阶临界转速之间的一定转速区振幅增加；同时，随着库仑阻尼力的增加，阻尼器轴承处的振幅在几乎所有转速时都被减小，甚至在某些转速区间该轴承被“锁住”，而且轴承能够振动的区间越来越窄。这说明转子系统从一个弹性支承系统逐步转化为一个准刚性支承系统，阻尼器支承的有效刚度越来越大，使得一阶有阻尼临界转速逐渐提高，并逐渐接近刚支临界转速。根据这些特性，提出通过开关控制抑止转子通过两阶临界转速过程中的振动，并使转子振幅在全转速区达到最小。仿真结果表明，系统能平稳通过两阶临界转速。     

Finite Difference Solution of Response Time Delay of Magneto-rhelological Damper

Magneto-rhelological(MR) dampers are devices that employ rheological fluids to modify their mechanical properties. Their mechanical simplicity, high dynamic range, lower power requirements, large force capacity, robustness and safe manner of operation in cases of failure have made them attractive devices for semi-active real-time control in civil, aerospace and automotive applications. Time response characteristic is one of the most important technical performances of MR dampers, and response time directly affects the control frequency, application range and the actual effect of MR dampers. In this study, one kind of finite difference solution for predicting the response time of magneto-rheological dampers from "off-state" to "on-state" is put forward. A laminar flow model is used to describe the flow in the MR valve, and a bi-viscous fluid flow model is utilized to describe the relationship of shear stress and shear rate of MR fluid. An explicit difference format is used to discretize the Novior-Stoks equation, and stability condition of this algorithm is built by Von-Neumann stability criterion. The pressure gradient along the flow duct is solved by a dichotomy algorithm with iteration, and the changing curve of the damping force versus time of MR damper is obtained as well. According to the abovementioned numerical algorithm, the damping forces versus time curves from "off-state" to "on-state" of a cylindrical piston type MR damper are computed. Moreover, the MR damper is installed in a material test system(MTS), the magnetic field in the wire circles of the MR damper is "triggered" when the MR damper is imposed to do a constant speed motion, and the damping force curves are recorded. The comparison between numerical results and experimental results indicates that this finite difference algorithm can be used to estimate the response time delay of MR dampers.