基于声辐射模态的有源控制解耦

在声辐射模态有源噪声控制策略框架下,选择压电陶瓷片作为控制作动器。根据前四阶声辐射模态形状特点提出了四种压电作动器位置布置方法。理论分析及数值计算表明,以这种方式布放的压电作动器不仅能有效地降低结构辐射的声功率,而且控制过程中这四组作动器分工明确,从而将控制方程解耦。在控制前几阶声辐射模态声功率时可以将复杂的多输入/多输出控制系统转变为几个简单的、互相独立的单输入/单输出控制系统。     

基于声辐射模态的有源控制解耦在固定支承板上的研究

基于声辐射模态的主动控制理论,以固定支承板为例,通过四组作动器在固定支承板上的布放,使其能分别控制不同阶声辐射模态辐射的声功率,来使控制方程解耦,从而设计了比较简单与稳定的单输入/单输出控制系统,模拟计算取得了较好的控制效果。同时本文对控制过程中的溢出等问题进行了一定的探讨。     

通过声辐射模态研究结构声辐射的有源控制

以简支平板为例,通过声辐射模态建立了弹性结构声辐射的有源主动控制策略。并分析了声辐射模态的数学和物理意义。研究发现在中、低频时,声辐射模态对应的辐射效率随着模态阶数的增加而迅速降低。在此基础上,本文提出了一种新的控制策略,即抵消前k阶声辐射模态的伴随系数,使得前k阶声辐射模态的声功率为零。本文以点力作动器作为控制力源进行了数值计算研究。     

结构声辐射的振动模态分析和声辐射模态分析研究

基于辐射声功率的二次型表达式,采用有限元法、Rayleigh积分和边界元法对结构声辐射进行了振动模态分析和声辐射模态分析研究。振动模态间的耦合对辐射声功率影响的研究表明:结构各阶振动模态自身对结构辐射声功率的贡献是增大结构的辐射声功率,而振动模态间的耦合可能会增大结构辐射声功率,也可能会减小结构辐射声功率,或对辐射声功率没有影响。而且,当振动模态间的耦合作用对辐射声功率的影响不大时,采用振动模态控制可取得较好的减振降噪双重控制效果。将混合的Helmholtz积分方程方法用广义逆引入到三维复杂结构声辐射分析的声辐射模态公式中,解决了特征频率下解不唯一问题。还研究了正方形封闭空间结构声辐射模态的辐射效率和形状,并对结构声辐射的振动模态控制和声辐射模态控制进行了讨论。     

结构振动模态和声辐射模态之间的对应关系及其应用

声辐射模态和结构振动模态之间的内在关系一直缺乏有效的证明。该文证明并揭示了结构振动模态和声辐射模态之间的对应关系,而且对该关系的有效性和实用性进行了验证。首先从声辐射模态和振动模态的概念出发,利用结构振速的模态叠加特性,建立了两种模态之间的联系方程式;在此基础上根据各种模态形状的对称或反对称性推导出两种模态之间的对应关系;然后对其进行了数值仿真验证。研究表明:对于简支矩形平板而言,在低频范围内,奇-奇振动模态对应的主导声辐射模态是第1阶;偶-奇模态对应第2阶;奇-偶模态对应第3阶;偶-偶模态对应第4阶。最后将这种对应关系应用于结构声辐射有源控制中,通过对主导声辐射模态进行抵消,取得了很好的控制效果。     

The relationship between acoustic radiation modes and structural modes and its applications

Both acoustic radiation modes and structural modes play an important role in the field of structure-borne sound, however, little work has been done for inherent relations between these two kinds of modes. This paper is focused on the relationship between the radiation modes and structural modes and its physical mechanisms. First, a governing equation for relating the radiation mode and structural mode is given based on the characteristics of the modes. Then, using the symmetric or anti-symmetric properties of two kinds of modes, the corresponding relations are presented. And then, numerical examples are given to verify the theoretical investigations, and it has been shown that, for a simply supported rectangular panel vibrating at low frequencies, the first radiation mode is dominant corresponding to (odd, odd) structural modes; the following radiation modes are respectively dominant corresponding to (even, odd), (odd, even), and (even, even) structural modes. Finally, such relations are applied to active acoustic structural control and provide a direct help for the design of active control strategy and arrangement of the secondary forces.     

基于声辐射模态的有源结构声传入及其辐射控制

从辐射模态的概念和角度研究利用结构误差传感方法对弹性封闭空间结构声辐射进行传感和有源控制。首先分析了辐射模态的数学和物理意义并揭示了辐射模态与声腔模态之间的内在耦合关系。通过声辐射模态建立了弹性封闭空间结构声辐射传感和有源控制模型,并提出了通过传感器阵列测量结构表面有限点的振速分布和设计特定的辐射模态空间滤波器来获得控制所需的误差信号。在此基础上对封闭空间结构声辐射有源控制和误差传感策略进行了深入的理论和数值仿真分析,重点讨论了传感器的数量和布放对辐射模态传感及其有源控制效果的影响。结果表明:辐射模态与声腔模态的耦合具有严格的选择性,各阶辐射模态的形状和与相耦合的主导声模态在耦合面上的形状非常相似;利用结构传感技术传感封闭空间的辐射模态时测点不足或空间采样不足将可能产生较严重的模态泄漏问题,使得不希望的结构模态泄露进所测的辐射模态当中来。在低频范围内,一般只需传感并最小化前三阶有效辐射模态声势能,在更低频和空间声模态频率附近,只需最小化前一阶最有效辐射模态声势能,便能和总声势能最小化策略控制效果基本一样。     

基于分布式体积速度传感的结构声辐射有源控制实验研究

以简支矩形薄板为研究对象,首先在波数域内对结构振动体积速度与辐射声功率的关系进行分析,推导出反映结构模态对体积速度贡献规律的数学表达式。在此基础上,结合PVDF (Polyvinylidene Fluoride)压电薄膜的电荷输出方程,利用三角函数的正交性,给出一种方法来设计体积速度传感器,并针对具体模型进行了结构体积速度测量实验。结果表明,所设计的分布式体积速度传感器具有较好的传感精度。在此基础上,利用所设计的传感器进行了结构声辐射有源控制实验研究,分别针对单频和带宽信号激励情况下的有源控制实验取得了满意的控制效果,从而验证了本文PVDF体积速度传感器设计方法的正确性以及通过PVDF膜传感结构声辐射并作为误差传感器进行有源控制的有效性。     

Broadband radiation modes: estimation and active control

In this paper we give a formulation of the most efficiently radiating vibration patterns of a vibrating body, the radiation modes, in the time domain. The radiation modes can be used to arrive at efficient weighting schemes for an array of sensors in order to reduce the controller dimensionality. Because these particular radiation modes are optimum in a broadband sense, they are termed broadband radiation modes. Methods are given to obtain these modes from measured data. The broadband radiation modes are used for the design of an actuator array in a feedback control system to reduce the sound power radiated from a plate. Three methods for the design of the actuator are compared, taking into account the reduction of radiated sound power in the controlled frequency range, but also the possible increase of radiated sound power in the uncontrolled frequency range.     

复杂结构声辐射模态的计算

结构辐射阻矩阵的特征向量就是其声辐射模态,复杂结构的辐射阻矩阵获取困难阻碍了声辐射模态理论的进一步应用。为此提出一种基于等效源方法的复杂结构辐射阻矩阵计算方法,由此形成了一套完整的计算复杂结构声辐射模态方法。最后通过仿真算例对影响结构辐射阻矩阵计算精度的因素进行了分析,给出了复杂结构辐射阻矩阵构造的一般原则。理论推导和数值仿真算例表明所提出的复杂结构声辐射模态计算方法是有效的。该方法简化了复杂结构声辐射模态的计算,计算效率较高。     

A piezo-based bearing for the active structural acoustic control of rotating machinery

This paper presents an active bearing for reducing the radiated structure borne noise of rotating machinery. This modular bearing uses piezostacks to generate secondary forces in the vibration transmission path of the controlled structure. The bearing is tested on an experimental test bed comprising a rotating shaft, which is mounted in a frame. Noise is radiated by a plate that is attached to the frame. To evaluate different control approaches, a simplified model of the set-up was made. Based on the simulation results, a combination of feedback and repetitive control is implemented, using a force and acceleration measurement. This way, a noise reduction of more than 10 dB is achieved at the most important resonance frequencies of the system below 1 kHz.     

Radiation modal expansion: application to active structural acoustic control

This paper demonstrates active structural acoustic control using multiple input/output adaptive sensoriactuators combined with radiation filters and a feedback control paradigm. A new method of reduced order modeling/design of radiation filters termed radiation modal expansion (RME) is presented. For the experiments detailed in this paper, the RME technique reduced the modeling of the radiation matrix from 400 transfer functions to 6 transfer functions (multiplied by a constant transformation matrix). Experimental results demonstrate reductions of radiated sound power on the order of 5 dB over the bandwidth of 0-800 Hz.     

Ventilation duct with concurrent acoustic feed-forward and decentralised structural feedback active control

This paper presents theoretical and experimental work on concurrent active noise and vibration control for a ventilation duct. The active noise control system is used to reduce the air-borne noise radiated via the duct outlet whereas the active vibration control system is used to both reduce the structure-borne noise radiated by the duct wall and to minimise the structural feed-through effect that reduces the effectiveness of the active noise control system. An elemental model based on structural mobility functions and acoustic impedance functions has been developed to investigate the principal effects and limitations of feed-forward active noise control and decentralised velocity feedback vibration control. The principal simulation results have been contrasted and validated with measurements taken on a laboratory duct set-up, equipped with an active noise control system and a decentralised vibration control system. Both simulations and experimental results show that the air-borne noise radiated from the duct outlet can be significantly attenuated using the feed-forward active noise control. In the presence of structure-borne noise the performance of the active noise control system is impaired by a structure-borne feed-through effect. Also the sound radiation from the duct wall is increased. In this case, if the active noise control is combined with a concurrent active vibration control system, the sound radiation by the duct outlet is further reduced and the sound radiation from the duct wall at low frequencies reduces noticeably.     

基于声辐射模态讨论声能量辐射与传递

声辐射模态表示了振动声源表面的辐射模式。基于声辐射模态讨论了振动声源表面声能量辐射和声场中声能量传递的性质,给出声能量辐射和传递的模式。采用表面声强描述振动声源表面的声能量辐射,采用声强描述声能量在声场中的传递。表面声强和声强可分解成两部分,一部分将辐射的声能量传递到远场;另一部分表现为振动声源与声场之间的能量交换。针对矩形板分析了声能量辐射和传递,数值计算结果与理论结果一致。结果表明基于声辐射模态讨论声能量辐射与传递是可行的和有效的。     

利用声辐射模态对声场进行重构

声辐射模态是定义在振动表面上的一组互相独立的基函数,描绘了振动表面的多极子辐射模式。本文利用声辐射模态对平板辐射的声场进行重构，并同时就频率和模态数对误差的影响进行了分析。针对复杂振动表面幅射的声场，重构时需正则化处理。数值计算结果和对应的理论值达到很好的吻合。     

The design of synthesized structural acoustic sensors for active control of interior noise with experimental validation

In this paper, the feasibility of using synthesized structural acoustic sensors (SSAS) for active noise control inside irregularly shaped enclosures is investigated. A SSAS consists of a cluster of inter-connected discrete PVDF elements, located on the surface of a vibrating structure enclosing a sound field. An optimal design ensures the sensor output to be directly related to the acoustical potential energy inside the enclosure. Hence, synthesized structural acoustic sensors can provide error signals for an active noise control system, and the use of microphones inside the enclosure can be avoided. A cylindrical shell with a floor partition, which can be used to model an aircraft cabin, is used as a test case. PZT actuators are used as control actuators. Both SISO (single input and single output) and MIMO (multi-input and multi-output) control systems are optimally designed using Genetic Algorithms and implemented with a Filtered-X Feedforward LMS (least-mean-square) controller. Their control performances are evaluated with different types of disturbances. To show the effectiveness of the optimal design approach, some non-optimal control systems are also tested and compared with the optimal one. It is shown that with optimally designed SSAS, an active structural acoustic control system can effectively reduce noise inside the enclosures without using any acoustic transducers.     

Real-time active suppression of scattered acoustic radiation

Active noise control usually aims at reducing the total acoustic pressure due to a noise source; it may also be used in principle to reduce the scattered acoustic radiation from a reflecting body in order to render it invisible to incident acoustic waves. In this paper, a real-time control strategy is introduced to achieve, with ordinary noise sources and sensors, the effective suppression of the noise scattered by a 3-D surface. Numerical simulations of 2-D and 3-D control are used to illustrate the potential of this control strategy. Preliminary experimental results are also given for the 1-D case of a rigid body inserted into a duct.     

利用声激励控制颤振的实验研究

继声控制颤振的理论研究之后,本文又进行了成功的风洞实验,验证了文献1中所提出的理论,给出了较有价值的实验结果,预示了这一新技术、新思想应用于流致振动领域的前景.     

主动噪声控制声学通道的实验辨识

传统的自适应滤波器不能直接用于主动噪声控制，因为扬声器和误差传声器之间的声学通道可能使系统不稳定。本文根据声学通道的相应特性，建立补偿滤波器，提出了用实验方法辨识声学通道传输特性。在房间实验中研究了单通道相位因子的变化特性，并进一步用于飞机人多通道主动噪声控制，给出了相应的实验结果。     

Multi-harmonic active structural acoustic control of a helicopter main transmission noise using the principal component analysis

This paper evaluates the feasibility and effectiveness, under controlled conditions, of active structural acoustic control of a helicopter main transmission in order to attenuate the vibration of the receiving roof panel and its sound radiation into the cabin. The vibroacoustic analysis of a typical helicopter drive train is conducted to extract the dominant tones generated by the various transmission stages. A finite element model of a Bell 407 transmission and simplified roof structure is developed in order to investigate various active control arrangements using piezoceramic actuators to control wave propagation in the gearbox supporting struts or receiving panel. The principal component analysis is used to extract the most significant control paths and reduce the control effort. A multiple frequency principal component least mean square (PC-LMS) algorithm is implemented on a laboratory setup and is used to successfully reduce up to seven gearbox tones simultaneously.