主动控制用大输出力电磁作动器优化设计

采用将电磁作动器集成至气囊隔振器内部的方式能够很好地实现宽频隔振与线谱控制,但由于气囊内的空间有限,作动器在有限的空间内其体积要尽可能小的同时,还要输出足够大的主动控制力,这对主动控制用大输出力电磁作动器的优化设计提出了更高的要求。建立了电磁作动器的理论模型与漏磁模型;采用ANSYS有限元软件中的优化模块对电磁作动器进行了优化设计,并获得了符合结构尺寸与主动控制输出力要求的作动器;分析了电磁作动器的可控输出力与最大磁饱和密度随电流变化的关系。仿真结果表明,设计的电磁作动器在满足空间尺寸的前提下,通入6A交变电流时其输出的主动控制力能够达到646N,满足设计指标,有助于作动器的研制。     

自适应主动共振吸振器的设计和减振性能研究

为了扩大吸振器的工作频带,减小吸振器的阻尼,最终提高吸振器的减振效果,本文设计了一种自适应主动共振吸振器。文中对几种不同种类吸振器的减振原理、动力学特性等进行了理论分析和比较,集成自调谐吸振器和主动吸振器的优点,完成了一种自适应主动共振吸振器的设计,并提出了一种变步长、双寻优的控制算法。在振动台上测试了吸振器的动力学特性并理论分析了吸振器的移频特性和阻尼特性。在两端固支梁上对吸振器的减振效果进行了实验评估。实验结果显示,相比自调谐吸振器,加入主动力控制后,自适应主动共振吸振器的阻尼比从0.04减小至0.02,减振效果得到了显著的提高。     

电磁约束阻尼层结构振动主动控制研究

基于弹性、粘弹性、电磁学理论,应用Hamilton原理,导出了覆盖电磁约束层阻尼(EMCLD)主动控制方式的梁的控制方程,并针对覆盖EMCLD的悬臂梁,进行了主动控制仿真模拟,得到了较好的控制效果,分析了控制电流和阻尼层厚度对控制效果的影响.结果表明电磁约束阻尼技术具有结构简单、作动方式合理、耗能低的优点,是一种有效的振动主动控制方式.     

浮筏多通道协调振动主动控制实验研究

在浮筏上引入主动吸振器可以有效地改善其低频减振性能.建立了带有4个主动吸振器的浮筏振动主动控制实验系统;以提高系统低频减振性能为目标,研究了4个主动吸振器的协调控制问题.首先,通过实验建模获得系统的时域脉冲序列模型;在此基础上设计了基于多通道滤波x-最小均方(Least Mean Square,LMS)算法的自适应前馈控制律;最后,在实验系统上进行了4个目标点的多通道协调主动吸振控制实验,在15～25Hz频段内基本上都取得了15dB以上的主动减振效果.实验结果证明了多吸振器协调主动控制对提高浮筏低频减振能力的有效性.     

浮筏的主动吸振控制实验研究

浮筏在低频减振方面存在较大不足,而这恰是主动减振的优势.将两者相结合,研究了浮筏的主动吸振控制问题.研制了一种主动吸振器,建立了以DSP F2812为核心的控制系统;提出了符号LMS算法,与广泛使用的滤波x-LMS等算法相比,该算法不需要精确的模型信息;在此基础上设计了自适应前馈主动吸振控制律,并在浮筏实验平台上进行主动吸振控制实验.实验结果表明,通过主动吸振控制,浮筏的低频减振能力得到了显著的改善.     

风力机叶片压电振动的主动控制研究

提出了将智能材料粘贴在叶片表面或嵌入叶片内部形成新结构的概念。本文将智能材料作为传感器和作动器,通过机电耦合抑制叶片的振动;利用有限元软件 Algor 分析在气动力作用下叶片的应力、应变;基于压电陶瓷第一压电方程,将风电叶片简化成柔性悬臂梁,建立了压电智能悬臂梁状态空间的动力学模型;针对此系统利用最优控制理论进行主动振动控制,设计了在系统低阶模态空间的振动控制器。最后通过计算机仿真得出：系统振动幅度缩小了约20%,振动时间减少了约80%,从而说明了此主动振动控制方法的有效性和可行性,对防止叶片这一弹性体发生颤振也起到一定的作用。     

磁流变弹性体自调谐式吸振器及其优化控制

本文研制了一种基于磁流变弹性体的自调谐式吸振器,它利用磁流变弹性体这种新型智能材料作为吸振器的弹性元件和阻尼元件,通过外加磁场控制磁流变弹性体的剪切模量来改变吸振器的固有频率,实现吸振器的移频.并将遗传算法改进移植到吸振器,对其进行优化控制.实验结果表明,这种遗传算法具有全局搜索和快速收敛的特点,它能使吸振器快速找到吸振器减振效果最佳点,并且经过优化控制的磁流变弹性体自调谐式吸振器在移频范围内具有很好的减振效果,减振效果最高可达25dB.     

阻尼吸振器与无阻尼吸振器吸振性能的比较

本文对阻尼吸振器及无阻尼吸振器的吸振性能作了分析与比较．同时，探讨了吸振器类型及其参数的选择方法．     

磁流变弹性体自调谐式吸振器及其优化控制

本文研制了一种基于磁流变弹性体的自调谐式吸振器，它利用磁流变弹性体这种新型智能材料作为吸振器的弹性元件和阻尼元件，通过外加磁场控制磁流变弹性体的剪切模量来改变吸振器的固有频率，实现吸振器的移频。并将遗传算法改进移植到吸振器，对其进行优化控制。实验结果表明，这种遗传算法具有全局搜索和快速收敛的特点，它能使吸振器快速找到吸振器减振效果最佳点，并且经过优化控制的磁流变弹性体自调谐式吸振器在移频范围内具有很好的减振效果，减振效果最高可达25dB。     

层叠式PVDF压电作动器及圆柱壳的振动主动控制

设计了一个层叠式PVDF压电作动器用于壳结构的振动控制。考虑压电层、粘接层、壳体耦合关系,推导了表面局部粘贴层叠式PVDF压电作动器的圆柱壳的振动控制方程,给出了作动力与压电层和粘接层层数、厚度之间的关系以及作动力与作动器粘贴位置之间的关系。针对一端固定、另一端自由的圆柱壳,进行了振动控制仿真。结果表明层叠式PVDF压电作动器作动力与作动器层数近似成线性关系,增大作动器层数能有效增大作动力,在低控制电压下能显著抑制圆柱壳振动,作动器周向不完全粘贴时,在径向产生的径向作动力对壳体横向振动控制非常有利。说明了层叠式PVDF压电作动器是一种可用于壳体结构振动并具有良好作动效果的作动器。     

Imposing nodes for linear structures during harmonic excitations using SMURF method

Vibration absorbers are usually designed using the finite element (FE) model of structures. It is generally believed that the modal models are more accurate than FE models, because in modal testing the model is built by direct measurement of the test structure. In this paper, a method is proposed to design a translational vibration absorber using the measured frequency response functions of a primary structure. The designed vibration absorber imposes a node on the structure when it is excited by a harmonic force. The method is based on the structural modification using experimental frequency response functions technique and determines the required receptance of the absorber at the excitation frequency. Moreover, a procedure is developed to suppress the vibration amplitude of two arbitrary points on a linear structure subjected to harmonic excitations by attaching two sprung mass absorbers. A cantilever beam is considered for the numerical case study, and the sprung masses are designed to suppress the vibration amplitude of the beam at the selected arbitrary points. A U-shape plate was considered for the experimental validation of the method for imposing a node using one absorber. Also, a beam was tested to demonstrate the effectiveness of method for imposing two nodes on the structures. The experimental results show that the designed absorbers can considerably suppress the vibration amplitude at the selected points on the structure.     

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.     

扁壳结构弯曲与扭转振动控制试验研究

扁壳结构的弯曲与扭转振动控制对该类结构的应用具有重要意义。本文采用不影响壳体结构的粗压电纤维复合材料(MFC)作动器对其弯曲与扭转振动进行主动控制。建立局部表面粘贴MFC作动器的开口圆柱扁壳的动力学解析模型,得到了作动力和作动力矩的解析表达式,分析了扁壳结构上MFC作动器在弯曲与扭转振动控制中的作动机理。针对一开口碳纤维圆柱扁壳,设计了模糊PD控制器,开展了定频与随机激励下壳体弯曲与扭转振动控制试验,并与传统PD控制试验效果进行了对比。结果表明:MFC作动器在壳体弯曲和扭转振动控制方面作动能力突出;模糊PD控制器的控制效果优于传统PD控制器的控制效果。     

主动移频式动力吸振器及其动力特性的研究

动力吸振器是振动控制中比较有效的减振装置,只要吸振器(子系统)的振动固有频率与振动物体(主系统)的振动频率相同,即可有效地消除主系统的振动。但传统动力吸振器的控制频率带宽较窄,限制了其稳定性和减振效果的提高。本文通过独特的机械设计,研制了一种可以通过调节自身的几何参数,使得其固有频率随几何参数线性变化的主动移频的新型动力吸振器,并初步设定了相应的控制方法。文中还对其动力学特性进行了理论分析和实验测试,分析了它的机理,评估了它的实际减振效果。研究结果表明该吸振器可以大范围调节自身固有频率,有效拓宽吸振频带,具有良好的减振性能和稳定性。     

不同类型水平弹簧组合刚度非线性吸振器的性能分析及稳定性研究

动力吸振器作为一种振动控制单元被广泛运用于各种工程场合,但传统的线性吸振器只能实现窄带振动控制.文章在线性吸振器的基础上引入对称水平弹簧构建线性刚度与非线性刚度相结合的组合刚度非线性吸振器,以提升吸振器的吸振性能.考虑实际工程中可能的安装方式,分别建立水平弹簧接地安装和不接地安装的组合刚度非线性吸振器模型,利用谐波平衡法结合弧长延拓法解析求解动力学响应,并与数值结果相互验证,证明了求解结果的准确性.随后分析比较两种组合刚度非线性吸振器与线性吸振器以及非线性能量阱之间的吸振性能,发现水平弹簧接地安装类型的组合刚度非线性吸振器在保留线性吸振器优势的同时又改善其吸振频带窄的缺点,且与非线性能量阱相比在主共振频率附近的较宽频内吸振性能更优.在此基础上,讨论了水平弹簧参数以及吸振器阻尼对主结构振动幅频响应和稳定性的影响,最后观察分析主结构幅频响应曲线不稳定区内的复杂动力学行为.研究结果表明合适的设计参数能够使得主结构振动峰值较低的同时,频响曲线不稳定运动区域的范围也较小.     

Design of a tuned vibration absorber for a slender hollow cylindrical structure

Abstract

In this paper, details of the design work for a tuned vibration absorber to be used on a hollow cylindrical structure is presented. The vibration problem is of resonant type and the tuned vibration absorber is designed to suppress the displacement vibration response of the free end of the slender hollow structure dominated by the contribution of its lowest transverse vibration modes. The structure is modeled using a commercial finite element software. Finite element model of the structure is verified using experimentally obtained frequency response functions and modal parameters. Effective parameters of the tuned vibration absorber design are then determined based on finite element analysis simulations of the vibration suppression performance of the tuned vibration absorber as it is used on the structure. Details of the tuned vibration absorber design are determined and a prototype is fabricated. Prototype tuned vibration absorber is then characterized experimentally both as a standalone system and also as it is used on the main structure. Vibration reduction performance of the physical prototype of the tuned vibration absorber is also compared with its vibration reduction performance estimated from finite element analysis simulations so that the analysis based design process can be validated.

Communicated by Dumitru Caruntu.     

Amplitude reduction of primary resonance of nonlinear oscillator by a dynamic vibration absorber using nonlinear coupling

The paper presents the characteristics of a new type of nonlinear dynamic vibration absorber for a main system subjected to a nonlinear restoring force under primary resonance. The absorber is connected to the main system by a link in order to be excited with twice the frequency of the motion of the main system. The natural frequency of the absorber is tuned to be twice the natural frequency of the main system, in contrast to autoparametric vibration absorber, whose natural frequency is tuned to be one-half the natural frequency of the main system. The presented absorber is not excited through the autoparametric resonance, i.e., no trivial equilibrium state exists. Therefore, the absorber always oscillates because of the motion of the main system and cannot be trapped by Coulomb friction acting on the absorber, in contrast to the autoparametric vibration absorber. Under small excitation amplitude, this absorber does not produce an overhang in the frequency response curve, which occurs because of the use of the conventional autoparametric vibration absorber; the overhang renders the response amplitude larger than that in the case without an absorber. In addition, the absorber removes the hysteresis in the frequency response curve caused by the nonlinearity of the restoring force acting on the main system. Regarding large excitation amplitude, the response amplitude in the main system can be decreased by increasing the damping of the absorber, but that decrease is limited by the nonlinearity in the restoring force acting on the main system. This paper also describes experimental validation of the absorber under small excitation amplitude using a simple apparatus.     

Nonlinear equivalent model and its identification for a delayed absorber with magnetic action using distorted measurement

For an absorber with the magnetic action and the delayed feedback, the equivalent strongly nonlinear model of the magnet force is proposed. We develop an identification algorithm with correcting distorted output measurement to identify and estimate the relevant parameters of the equivalently nonlinear model and the time delay in the feedback loop. The detailed steps of the algorithm are given analytically. We configure an experimental device of a delayed electromechanical absorber with action of the nonlinear magnetic force. The new algorithm is employed to identify the relative parameters of the device, such as time delay, damping and nonlinear stiffness, based on data of the output measurement with distortion. The results show that it is reasonable that the magnet action may be equivalent to the cubic nonlinear force. One may also see that the new algorithm may treat the experimental distorting measurement and correct it as long as the measurement still keeps periodicity. As an important result, values of the identified parameters with the correcting distortion are closer to those of the original measurement than those without the no correcting distortion for some excitation frequencies. It means that the algorithm may correct the polluted measurement, so that the quality of the identification is greatly improved. The new algorithm may be useful for design of nonlinear electromechanical absorber with time-delayed feedback.