车身顶棚振动独立模态控制研究

针对乘用车结构振动和噪声问题,对嵌入压电传感器和致动器的汽车顶棚进行了振动主动控制研究;对压电平板进行数学建模,通过有限元分析某国产乘用车车身顶棚模态振型,合理选择传感器和致动器增益,作为最小化振动响应这一目标函数的参数;控制器的设计应用了独立模态空间控制法,将压电传感器和致动器及独立模态空间控制法(IMSC)组成的控制系统应用于汽车顶棚振动主动控制,实验结果表明,即使当控制回路被电磁噪声干扰时,控制前后系统的振级相差可达到30%左右,取得了有效的振动抑制效果。     

四激励二维正交复合夹心式压电超声换能器的设计

提出了一种四激励二维正交复合夹心式压电超声换能器,换能器由四组纵向极化压电陶瓷晶堆、一个中心耦合金属块和四个外部金属圆锥组成。基于二维耦合振动机理和机电类比原理,建立了换能器的等效电路模型并推导了其谐振频率方程。利用有限元软件仿真分析了四激励正交复合换能器的频响特性和振动特性,并与其单独一个方向振子的振动特性进行了对比。加工了反相和同相模态的换能器,利用阻抗分析仪和激光测振仪测试了其频率响应和二维四向纵振动输出特性,并进行了大功率二维四向超声乳化实验测试。理论、仿真和实验结果表明:换能器具有反相和同相两个纵向正交共振模态,在这两种共振模态下均可实现二维四向纵振动输出,且换能器两个正交方向振子的纵向振动具有相互耦合加强的作用;等效电路法和有限元法所得换能器的共振频率和有效机电耦合系数与实验测试结果吻合,通过与单激励正交复合夹心式压电超声换能器的有效机电耦合系数对比,发现该换能器具有更高的有效机电耦合系数。     

基于蚁群算法的车身振动主动控制研究

针对乘用车车身结构振动抑制问题,采用基于蚁群算法的参数自适应PID控制器,以压电元件为测量和控制元件,进行了振动主动控制仿真和实验研究;首先对白车身结构进行实验模态分析,确定了压电元件的布片位置并确定压电控制的传递关系,然后设计基于蚁群算法的PID参数自适应控制器,制定了控制方案,进行了模拟仿真分析,最后搭建试验平台,以某国产乘用车白车身为被控结构,进行了车身振动主动控制实验;系统仿真和实验结果表明,施加控制时车身的振动幅值较未施加控制时大幅减小,在振动幅值较大的低频区域,其振动幅值明显降低;从而验证了应用基于蚁群算法的参数自适应PID控制技术,不仅可以有效降低车身的振动幅度,而且对传统控制方法控制效果不佳的振动低频区域,控制效果明显。     

汽车车内噪声主动控制系统仿真

摘要：降低汽车空腔的振动,是抑制汽车车内噪声的有效途径之一。以激振器、作动器和控制器等为主要部件,搭建了简化的汽车车内噪声主动控制系统,该系统通过将汽车空腔模型简化为板件,以减弱板件振动为目标,实现了汽车车内噪声主动控制。采用简谐正弦及余弦信号作为激振器发出的激励,用于模拟板件的初始振动,控制器通过采用模糊控制算法直接控制压电陶瓷作动器的振动,压电陶瓷作动器的振动用于抑制板件的振动,完成了汽车车内噪声主动控制系统仿真。仿真结果表明,研究采用的汽车车内噪声主动控制系统,使汽车空腔振动降低23%,为解决由汽车发动机和动力总成的振动所引发的汽车车内噪声问题提供了一个有效途径。     

基于最小关节力矩优化的自由浮动空间刚柔耦合机械臂混沌动力学建模与控制

采用拉格朗日法、假设模态法和系统动量守恒原理,推导了一种平面内三连杆的自由浮动刚柔耦合冗余度空间机械臂的动力学模型.基于最小关节驱动力矩优化,建立了自由浮动刚柔耦合冗余度空间机械臂的混沌运动状态方程,采用混沌数值方法分析机械臂运动中的混沌现象,分别在工作空间、关节空间和模态空间,设计鲁棒Proportional-Derivtive(PD)补偿控制、延迟反馈控制和模态力最优控制,实现了轨迹跟踪、混沌运动抑制和振动控制.通过数值仿真验证了建模与控制方法的有效性.     

流固耦合声子晶体管路冲击振动特性研究

流固耦合管路系统广泛应用于各种装备中,通常用来传递物质和能量或者动量.由于流固耦合效应,管壁在流体作用下易产生强烈的振动与噪声,对装备安全性、隐蔽性产生严重影响,甚至造成严重破坏.流固耦合管路振动抑制需求迫切,意义重大.声子晶体可以利用其带隙特性抑制特定频率范围内弹性波的传播,在减振降噪领域具有广泛的应用前景.本文基于声子晶体理论,研究了流固耦合条件下的布拉格声子晶体管路冲击振动传递特性.将传递矩阵法和有限元法相结合,计算了能带结构与带隙特性,重点考虑了流固耦合效应下,不同冲击激励条件下声子晶体管路振动特性,分析了流固耦合对声子晶体管路振动传递特性的影响.研究结果为流固耦合条件下管路系统的振动控制提供了技术参考.     

复杂网络可控性研究现状综述

控制复杂系统是人们对复杂系统模型结构及相关动力学进行研究的最终目标, 反映人们对复杂系统的认识能力. 近年来, 通过控制理论和复杂性科学相结合,复杂网络可控性的研究引起了人们的广泛关注. 在过去的几年内, 来自国内外不同领域的研究人员从不同的角度对复杂网络可控性进行了深入的分析研究, 取得了丰硕的成果. 本文重点讨论了复杂网络的结构可控性研究进展, 详细介绍了基于最大匹配方法的复杂网络结构可控性分析框架, 综述了自2011年以来复杂网络可控性的相关研究成果, 具体论述了不同类型的可控性、可控性与网络拓扑结构统计特征的关联、基于可控性的网络及节点度量、控制的鲁棒性和可控性的相关优化方法. 最后, 对网络可控性未来的研究动态进行了展望, 有助于国内同行开展网络可控性的相关研究.     

光电经纬仪机电一体化耦合特性

区别于传统刚体控制模型,将结构动态设计方法与控制理论相结合,构建了光电经纬仪的柔性机电耦合控制模型,分析了该模型的结构基频、阻尼比等机械因素与控制带宽的耦合关系,并提出了光电经纬仪动态量化设计准则.实验表明:光电经纬仪结构谐振频率ω_n应尽可能地远大于系统谐振频率ω_r,至少满足ω_n≥3ω_r.该方法有效可行,可解决高精度大型经纬仪机电谐振问题,为设计快速响应、高跟踪精度的光电经纬仪提供了工程依据.     

基于2-2型压电复合材料的新型宽频带径向振动超声换能器

本文提出了一种基于2-2型压电复合材料的新型宽频带径向振动超声换能器,它主要由内金属圆环和外压电陶瓷复合材料圆环组成.首先利用Newnham串并联理论和均匀场理论推导了2-2型压电复合材料的等效参数;其次利用解析法得到了金属圆环和径向极化压电复合陶瓷圆环径向振动的机电等效电路;最后得到了换能器的六端机电等效电路,从而得到了换能器的频率方程.接着分析了换能器共振频率和反共振频率以及有效机电耦合系数与几何尺寸、两相体积占比的关系,采用仿真软件对新型换能器的径向振动进行了数值模拟.结果表明,利用解析法得到的共振频率和反共振频率与数值模拟结果吻合较好.此外,对换能器在水下的辐射声场进行了仿真研究,结果表明新型复合材料径向换能器相比传统纯陶瓷径向换能器,发射电压响应幅值更大,工作带宽提高接近一倍,声匹配更佳.     

压电管堆式宽带换能器*

研究了一种具有管状叠堆结构的圆管换能器,其敏感元件是由纵向极化压电陶瓷单元组成的薄壁管状压电叠堆,探讨利用管状叠堆纵向和径向振动耦合实现宽带发射。利用压电柱壳振动理论推导了管堆的频率方程,分析了换能器的纵向和径向模态的振动耦合特性。在理论分析的基础上利用有限元方法对换能器的带宽和发射电压响应进行优化并研制换能器样机。测试结果表明,纵向极化的管状压电叠堆结构具有良好的发射电压响应和宽带特性,与理论及仿真结果相符。     

Experimental verification of the optimal tuning of a tunable vibration neutralizer for global vibration control

A theoretical method has been previously proposed by the authors to optimize a tunable vibration neutralizer for global vibration control. However, experimental verification of the tuning method has yet to be presented. This paper aims to do this. It is shown that by using the proposed optimization method, the tunable vibration neutralizer can be as effective as an active control device in reducing global vibration of a structure. One particularly interesting finding is that although the vibration neutralizer is a passive device which is incapable of supplying energy to a system, it appears to be as effective as active control in reducing the global vibration of a structure, even in the frequency range where the control device is required to supply energy.     

Vibration isolation via a scissor-like structured platform

More and more attentions are attracted to the analysis and design of nonlinear vibration control/isolation systems for better isolation performance. In this study, an isolation platform with n-layer scissor-like truss structure is investigated to explore novel design of passive/semi-active/active vibration control/isolation systems and to exploit potential nonlinear benefits in vibration suppression. Due to the special scissor-like structure, the dynamic response of the platform has inherent nonlinearities both in equivalent damping and stiffness characteristics (although only linear components are applied), and demonstrates good loading capacity and excellent equilibrium stability. With the mathematical modeling and analysis of the equivalent stiffness and damping of the system, it is shown that: (a) the structural nonlinearity in the system is very helpful in vibration isolation, (b) both equivalent stiffness and damping characteristics are nonlinear and could be designed/adjusted to a desired nonlinearity by tuning structural parameters, and (c) superior vibration isolation performances (e.g., quasi-zero stiffness characteristics etc.) can be achieved with different structural parameters. This scissor-like truss structure can potentially be employed in different engineering practices for much better vibration isolation or control.     

Efficient modal control strategies for active control of vibrations

Some efficient strategies for the active control of vibrations of a beam structure using piezoelectric materials are described. The control algorithms have been implemented for a cantilever beam model developed using finite element formulation. The vibration response of the beam to an impulse excitation has been calculated numerically for the uncontrolled and the controlled cases. The essence of the method proposed is that a feedback force in different modes be applied according to the vibration amplitude in the respective modes i.e., modes having lesser vibration may receive lesser feedback. This weighting may be done on the basis of either displacement or energy present in different modes. This method is compared with existing methods of modal space control, namely the independent modal space control (IMSC), and modified independent modal space control (MIMSC). The method is in fact an extension of the modified independent space control with the addition that it proposes to use the sum of weighted multiple modal forces for control. The proposed method results in a simpler feedback, which is easy to implement on a controller. The procedure is illustrated for vibration control of a cantilever beam. The analytical results show that the maximum feedback control voltage required in the proposed method is further reduced as compared to existing methods of IMSC and MIMSC for similar vibration control. The limitations of the proposed method are discussed.     

Passive and active interior noise control of box structures using the structural intensity method

This paper presents passive and active vibro-acoustic noise control methods for attenuating the interior noise level in box structures which can be an analogy of cabins of vehicle and aircraft. The structural intensity (SI) approach is adopted to identify the predominant vibration panels and interior noise sources for box structures. In the study, the finite element method is used to determine the structural vibration and structural intensity in the box surfaces. According to structural intensity vectors plot and structural intensity stream lines presentation, the possible effective control positions where the dampers may be attached and the active control forces may act to reduce vibration and interior noise, are identified. From the study, it can be demonstrated that the structural intensity approach and stream line presentation are possible methods for identifying the vibro-acoustic interior noise source and predominant panels which may be modified to reduce the interior noise level. The structural intensity methodology, passive and active noise control results can be extended to the further study of the vibration and interior noise control of actual cabins of vehicles and aircraft.     

Layout optimization methodology of piezoelectric transducers in energy-recycling semi-active vibration control systems

An optimization methodology is proposed for the piezoelectric transducer (PZT) layout of an energy-recycling semi-active vibration control (ERSAVC) system for a space structure composed of trusses. Based on numerical optimization techniques, we intend to generate optimal location of PZTs under the constraint for the total length of PZTs. The design variables are set as the length of the PZT on each truss based on the concept of the ground structure approach. The transient problems of the mechanical and electrical vibrations based on the ERSAVC theory are considered as the equations of state. The objective is to minimize the integration of the square of all displacement over the whole analysis time domain. The sensitivity of the objective function is derived based on the adjoint variable method. Based on these formulations, an optimization algorithm is constructed using the fourth-order Runge–Kutta method and the method of moving asymptotes. Numerical examples are provided to illustrate the validity and utility of the proposed methodology. Using the proposed methodology, the optimal location of PZTs for the vibration suppression for multi-modal vibration is studied, which can be benchmark results of further study in the context of ERSAVC systems.     

一种空间热控箱及其在运行轨道中的热分析

本文详细介绍了一种用于国际空间站的空间热控箱,在此空间热控箱内部采用主动式环路热管的工作原理,文章对热控箱进行了在运行轨道上冷、热两种极限工况以及当系统突然断电情况下的热分析。通过数值模拟的计算结果表明,由支架传入或散失的热量是不可以忽视的,因此为了保证系统正常运行,必须要采取必要的措施对整个系统进行热量补偿。     

空间大口径望远镜稳像系统发展现状及趋势

介绍了目前国际上已发射及正在论证的大型空间望远镜的稳像控制系统,主要包括自由飞行模式的HUBBLE、JWST、ATLAST-8m和ATLAST-9.2m,载体搭载模式的SOFIA和OPTⅡX。详细论述了这些空间望远镜稳像系统的组成、工作原理、主要元件、性能指标和控制算法,并对基于磁悬浮技术的无扰动载荷设计概念和机械臂直接驱动空间相机的设计思想进行了介绍。分析表明,基于机械臂和磁悬浮技术的精密稳像及主动振动抑制系统是未来的发展趋势。     

A multi-input multi-output adaptive feed-forward controller for vibration alleviation on a large blended wing body airliner

Turbulent atmosphere, gusts, and manoeuvres significantly excite aircraft rigid body motions and structural vibrations, which leads to reduced ride comfort and increased structural loads. In particular BWB (Blended Wing Body) aircraft configurations, while promising a significant fuel efficiency improvement compared to wing-tube configurations, exhibit severe sensitivity to gusts. In general, a flexible aircraft represents a lightly damped structure involving a large variety of uncertainties due to fuel mass variations during flight, control system nonlinearities, aerodynamic nonlinearities, and structural nonlinearities, to name just a few. Especially at the beginning of flight testing of a newly developed aircraft type, plant models generally require a lot of verification and adjustment based on obtained flight test data, before they can be used reliably for control law design. Adaptive control already is a well-established method for many active noise and vibration control problems, and thus is proposed here for application to the problem of gust load alleviation. However, safety requirements are significantly higher for gust load alleviation systems than for most noise and vibration control systems. This paper proposes a MIMO (Multi-Input Multi-Output) adaptive feed-forward controller for the alleviation of turbulence-induced rigid body motions and structural vibrations on aircraft. The major contribution to the research field of active noise and vibration control is the presentation of a detailed stability analysis of the MIMO adaptive algorithm in order to support potential certification of this method for a safety-critical application. Finally, the proposed MIMO adaptive feed-forward vibration controller is applied to a longitudinal flight dynamics model of a large flexible BWB airliner in order to verify the derived vibration controller on a challenging control problem.     

Experimental application of orthogonal eigenstructure control for structural vibration cancellation

Orthogonal eigenstructure control (OEC) is a novel feedback control that is applicable to linear systems. Orthogonal eigenstructure control can minimizes the trial and error by the controller designer. It finds orthogonal vectors to some targeted modes of the structure within the achievable eigenvector set. When the targeted modes are replaced with the orthogonal vectors, it results in a decoupled system or structure that leads to vibration isolation. In this article, experimental application of this control method for active vibration cancellation of a plate is presented. Piezoelectric actuators are used as control actuators and accelerometers are used as feedback sensors. Vibration cancellation in a plate due to 150 Hz sinusoidal disturbance and a wideband disturbance within the range 200-300 Hz are experimentally studied. Since OEC is a model-based control method, system identification techniques are used for estimating the state-space realization of the system model. The effect of tuning the control gain is studied to compensate for the inaccurate system identification or factors that cannot be identified easily but play a major role in vibration of a structure. A finite element model of a plate is considered and the effects of scaling the control gains are investigated. It is shown that there is an allowable region for tuning the control gain without loosing the stability. The result of this analysis is used in the experiment for adjusting the control gains.