船舶机械磁悬浮气囊混合隔振技术

有源无源混合隔振是控制船舶低频线谱噪声的重要技术,但工程应用的实例还非常少见。在磁悬浮-气囊混合隔振理论和原理样机研究的基础上,针对船用机械低频线谱的隔振需求,进一步突破了体积小、输出力大、功耗低、频响平直、波形失真度低等磁悬浮作动器工程化设计技术;解决了混合隔振器的稳定性和冲击、摇摆适应性等技术难题;研究了工程实用的控制算法,采用非线性逆模型补偿使控制系统线性化,并提出了窄带Fx-Newton时域算法,可在机械设备运行时的多线谱、多通道耦合、线谱振幅非稳态等情况下实现快速稳定控制;研制了船用200 kW柴发机组混合隔振装置,实验结果表明该技术具有优良的宽频隔振效果和低频线谱控制能力,性能可满足工程实用要求。     

船舶机械磁悬浮气囊混合隔振技术

有源无源混合隔振是控制船舶低频线谱噪声的重要技术,但工程应用的实例还非常少见。在磁悬浮-气囊混合隔振理论和原理样机研究的基础上,针对船用机械低频线谱的隔振需求,进一步突破了体积小、输出力大、功耗低、频响平直、波形失真度低等磁悬浮作动器工程化设计技术;解决了混合隔振器的稳定性和冲击、摇摆适应性等技术难题;研究了工程实用的控制算法,采用非线性逆模型补偿使控制系统线性化,并提出了窄带Fx-Newton时域算法,可在机械设备运行时的多线谱、多通道耦合、线谱振幅非稳态等情况下实现快速稳定控制;研制了船用200 kW柴发机组混合隔振装置,实验结果表明该技术具有优良的宽频隔振效果和低频线谱控制能力,性能可满足工程实用要求。      

基于磁悬浮作动器的自适应有源振动控制研究

针对周期扰动提出一种基于磁悬浮作动器的非线性前馈自适应有源振动控制算法。算法中将磁悬浮作动器视为具有时变非线性的单输入输出系统,并使用径向基函数神经网络进行控制,分别采用聚类算法和随机梯度算法对其隐层中心点和输出层权值进行自适应调整。该算法摆脱了传统磁悬浮控制对模型的依赖,在正常工作条件下不需对作动器建模。仿真和实验结果表明:在单自由度主动隔振系统中,非线性自适应算法可以显著降低周期振动的能量,同时能对磁悬浮作动器的时变非线性进行有效的补偿。      

空气弹簧隔振台特性试验及信号处理算法研究

超精密测量对环境振动要求非常严格,其仪器设备中多安装隔振装置。为评估某重点实验室圆度仪中使用的仪用小型空气弹簧隔振台的隔振性能,利用压电式加速度传感器设计振动测试试验。根据振动测试中信号的实际情况,设计信号处理算法,对采集到的加速度信号进行预处理、积分运算、频谱分析,消除信号中低频趋势项和干扰噪声,还原实际振动状况,准确获取隔振系统振动位移曲线及其固有频率。试验表明,该空气弹簧隔振系统各项指标满足隔振要求。信号处理算法对振动测试中的加速度信号处理具有一定指导意义,也可作为故障诊断中加速度信号处理的参考。     

弹性基础隔振系统的简化性能指标和有源控制力

系统研究了基础弹性对单层隔振系统、双层隔振系统及浮筏隔振系统隔振性能的影响。分析了不同隔振系统与不同弹性基础间的振动耦合特性,讨论了不同隔振系统的振级落差和力传递率特性,给出了振级落差和力传递率的简化计算方法。针对不同隔振系统的有源隔振问题,比较了不同作动器安装方式所需的控制力。研究表明,对于所有隔振系统,增加基础的刚度和阻尼有利于提高振级落差和力传递率;对于浮筏隔振系统,增加筏架的刚度和阻尼有利于提高隔振性能和减少有源隔振所需的控制力。      

多通道窄带Fx-Newton时频算法及动力机械有源隔振实验

提出了一种多通道窄带Fx-Newton算法,用多个控制器并联控制各窄带带通滤波器提取的多根线谱。离线辨识次级通道频响矩阵并求逆后,只需L×L个(通道数为L)2阶滤波器即可实现次级通道逆模型滤波,从而使控制器系数向最优值迅速收敛。还提出了窄带滤波相位差的自适应补偿算法,可提高线谱频率波动时的控制鲁棒性。在200 kW实船柴油发电机有源无源隔振装置上进行了实验,结果表明该算法可同时控制10~11根线谱,使每根线谱衰减10~35 dB。该算法运算量小,在保证收敛稳定性的同时、收敛速度大于FxLMS算法(尤其在次级通道矩阵特征值分散度大的情况)。     

多通道窄带Fx-Newton时频算法及动力机械有源隔振实验

提出了一种多通道窄带Fx—Newton算法,用多个控制器并联控制各窄带带通滤波器提取的多根线谱。离线辨识次级通道频响矩阵并求逆后,只需L×L个(通道数为L)2阶滤波器即可实现次级通道逆模型滤波,从而使控制器系数向最优值迅速收敛。还提出了窄带滤波相位差的自适应补偿算法,可提高线谱频率波动时的控制鲁棒性。在200kw实船柴油发电机有源无源隔振装置上进行了实验,结果表明该算法可同时控制10~11根线谱,使每根线谱衰减10~35dB。该算法运算量小,在保证收敛稳定性的同时、收敛速度大于FxLMS算法(尤其在次级通道矩阵特征值分散度大的情况)。      

一种用于主动降噪耳机的权重滤波误差信号滤波-x最小均方算法*

针对传统FxLMS算法前馈自适应主动降噪耳机系统因果性条件不足时在宽带噪声环境中产生的高频噪声抬升问题,该文引入权重滤波误差信号FxLMS算法用于抑制高频噪声的抬升,但该算法带来了低频降噪量不足问题。因此,进一步提出将固定系数混合控制器与权重滤波误差信号FxLMS算法结合,在解决高频噪声抬升问题的同时,保证了良好的低频降噪量。基于DSP平台实现了提出的主动降噪耳机方案。实验证明,该方案针对宽带和单频等噪声都取得了较好的降噪效果。     

舰船隔振装置技术及其进展

隔振装置是降低舰船机械噪声最重要的技术之一,目前已有大量文献对舰船隔振装置技术进行了研究,但系统、全面地论述其技术特点、应用和进展,尤其是我国在该领域进展的文献相当缺乏。针对已应用并取得成效的舰船隔振装置技术,首先概述了其发展历程,分析了单层隔振装置、双层隔振装置、浮筏双层隔振装置和气囊隔振装置的技术特点;然后介绍了近年来该领域的进展,包括智能气囊隔振装置、推进动力系统新型隔振装置、主被动混合隔振装置、推力轴承隔振装置等;最后对隔振装置技术的未来发展趋势进行了展望。通过系统地总结梳理,较完整地呈现了舰船隔振装置技术发展概况,可供舰船减振降噪研究和工程设计人员参考。      

多级复合抑振系统的设计与研究

研究了多级复合抑振系统的动力学特性,以多级抑振系统刚体空间一般运动的坐标变换,系统的动能、势能和阻尼耗散函数,系统的拉格朗日方程为理论基础, 得出适用于质量块之间或质量块与平台之间具有多个相对运动自由度的多级隔振系统的运动微分方程组.分析了主动控制力与抑振器参数之间的关系.结果表明：对于多级复合抑振系统,抑制中高低频振动时,抑振作动器置于抑振对象与刚体之间的抑振性能较好,所需的主动抑振控制力也不大,并且易于实现各种先进的抑振控制.     

Self-powered active vibration control using a single electric actuator

The authors have proposed self-powered active vibration control systems that achieve active vibration control using regenerated vibration energy. Such systems do not require external energy to produce a control force. This paper presents a self-powered system in which a single actuator realizes active control and energy regeneration.The system proposed needs to regenerate more energy than it consumes. To discuss the feasibility of this system, the authors proposed a method to calculate the balance between regenerated and consumed energies, using the dynamical property of the system, the feedback gain of the active controller, the specifications of the actuator, and the power spectral density of disturbance. A trade-off was found between the performance of the active controller and the energy balance. The feedback gain of the active controller is designed to have good suppression performance under conditions where regenerated energy exceeds consumed energy.A practical system to achieve self-powered active vibration control is proposed. In the system, the actuator is connected to the condenser through relay switches, which decide the direction of the electric current, and a variable resistor, which controls the amount of the electric current. Performance of the self-powered active vibration was examined in experiments; the results showed that the proposed system can produce the desired control force with regenerated energy, and that it had a suppression performance similar to that of an active control system using external energy. It was found that self-powered active control is attainable under conditions obtained through energy balance analysis.     

Adaptive-passive vibration isolation between nonrigid machines and nonrigid foundations using a dual-beam periodic structure with shape memory alloy transverse connection

This paper examines the problem of broadband vibration control of nonrigid systems employing periodic structures with tunable parameters. It investigates this by using a semi-two-dimensional model that applies a dual-beam periodic structure with transverse branches as a parameter-tunable isolator. Conventional study of vibration control problems, including the problem of vibration control by periodic structures, usually reduces systems to equivalent single- or multi-mount models with only a unidirectional translation at a mounting point. This assumption of decoupling leads to the erroneous prediction of vibratory power transmission when designing an isolator for a nonrigid system. Such a periodic structure involves the coupling of vibrations between different mounting points and different directions of motion and is therefore a reasonable simulation of the real-life problem. However, its application as a periodic isolator has not been proposed previously. The configuration of shape memory alloy (SMA) branches and non-SMA dual beams is proposed in order that this structure can effectively exploit the advantages of SMA materials, namely their significantly varying Young?s moduli which can be tuned to adjust and widen the stop bands, and can prevent the associated limitation of hysteresis. Equations are derived governing the vibration transmitted through any number of periodic mounts between nonrigid machines and foundations. Based on the derived results, two methodologies are developed to determine the proper Young?s moduli of the SMA branches and minimize the transmitted power. The numerical results demonstrate that the adaptive SMA branches at the proper temperatures are able to attenuate broadband vibration by adjusting the locations and broadening the widths of stop bands. With the application of a semi-two-dimensional periodic structure to broadband vibration isolation, this paper provides an approach and supporting methodologies for broadband vibration control using periodic structures.     

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.     

Stability and performance limits for active vibration isolation using blended velocity feedback

This paper presents a theoretical study of active vibration isolation on a two degree of freedom system. The system consists of two lumped masses connected by a coupling spring. Both masses are also attached to a firm reference base by a mounting spring. The lower mass is excited by a point force. A reactive control force actuator is used between the two masses in parallel with the coupling spring. Both masses are equipped with an absolute velocity sensor. The two sensors and the actuator are used to implement velocity feedback control loops to actively isolate the upper mass from the vibrations of the lower mass over a broad range of frequencies. The primary concern of the study is to determine what type of velocity feedback configuration is suitable with respect to the five parameters that characterise the system (the three spring stiffnesses and the two masses). It is shown analytically that if the ratio of the lower mounting spring stiffness to the lower mass is larger than the ratio of the upper mounting spring stiffness to the upper mass (supercritical system), feeding back the absolute upper mass velocity to the reactive force actuator results in an unconditionally stable feedback loop and the vibration isolation objective can be fully achieved without an overshot at higher frequencies. In contrast, if the ratio of the lower mounting spring stiffness to the lower mass is smaller than the ratio of the upper mounting spring stiffness to the upper mass (subcritical system), the upper mass velocity feedback is conditionally stable and the vibration isolation objective cannot be accomplished in a broad frequency band. For subcritical systems a blended velocity feedback is proposed to stabilise the loop and to improve the broad-band vibration isolation effect. A simple inequality is introduced to derive the combinations between the two error velocities that guarantee unconditionally stable feedback loops.     

Coupling analysis of a matched piezoelectric sensor and actuator pair for vibration control of a smart beam

This paper presents a theoretical and experimental study of the in-plane and out-of-plane coupling of a matched piezoelectric sensor/actuator pair bonded on a beam. Both the sensor and actuator are triangularly shaped polyvinylidene fluoride (PVDF) transducers and are intended to provide a compact sensor/actuator system for beam vibration control. The measured sensor-actuator frequency response function has shown an unpredicted increase in magnitude with frequency, which was found, to be due to in-plane vibration coupling. An analytical model has been developed to decompose the sensor-actuator response function into an in-plane contribution and an out-of-plane contribution. This in-plane coupling can limit the feedback control gains when a direct velocity feedback control is applied. A method called the j omega s compensation method is proposed to identify the effect of the in-plane vibration coupling at low frequencies. Even after this compensation, however, there was unexpected strong out-of-plane coupling at even modes, which may have been caused by a lack of accuracy in the shaping of the PVDF sensor and actuator. Numerical simulations have confirmed the sensitivity of the matched sensor/actuator pair with shaping errors.     

Design and Optimization of the Electromagnetic Actuator in Active-Passive Hybrid Vibration Isolator

The design and optimization of actuators are difficult and critical for the active-passive hybrid vibration control system. In this paper, an electromagnetic actuator model is established based on Ohm’s Law for magnetic circuit considering the leakage flux. The 600N electromagnetic actuators are designed and optimized based on ANSYS simulation according to the engineering request. Its transient characteristics are studied. The effects of different structural parameters on its output force are analyzed. The experimental results show that the structure parameters and output force characteristics of the designed electromagnetic actuators satisfy the practical requirement.     

Hybrid vibration absorber with virtual passive devices

A vibration control scheme integrating a passive mass–spring resonator and a linear actuator is developed. A control algorithm is devised to convert the actuator into an additional set of virtual mass–spring structure of programmable characteristic frequency. The relative motion between the primary body and the reaction mass is measured, as well as the acceleration of the reaction mass. This hybrid dynamic vibration absorber is capable of neutralizing a harmonic disturbance regardless of the detailed dynamics of the primary structure and other passive elements. Stability analysis leads to a simple, explicit stability criterion. Distribution of the counter-disturbance force between the active and passive devices is analyzed, and the transient performance is also investigated. Real-time experiments as well as numerical simulations are conducted to confirm the effectiveness of the proposed scheme.     

Active isolation of a flexible structure from base vibration

This paper presents a theoretical and experimental investigation into an active vibration isolation system. Electromagnetic actuators are installed in parallel with each of four passive mounts, which are placed between a flexible equipment structure and a base structure which is either flexible or rigid. Isolation of low-frequency vibration is studied, so that the passive mounts can be modelled as lumped parameter springs and dampers. Decentralized velocity feedback control is employed, where each actuator is operated independently by feeding back the absolute equipment velocity at the same location. Good control and robust stability have been obtained both theoretically and experimentally for the multichannel control systems. This is to be expected if the base structure is rigid, in which case the actuator and sensor are, in principle, collocated and the control system implements a skyhook damper. With a flexible base structure, however, collocation is lost due to the reactive actuator force acting on the base structure, but the control system is still found to be robustly stable and to perform well. Attenuations of 20 dB are obtained in the sum of squared velocities on the equipment structure at the rigid-body mounted resonance frequencies. In addition, attenuations of up to 15 dB are obtained at the resonance frequencies of both the low order flexible modes of the base structure and the equipment structure.