Intelligent active vibration control in an isolation platform

This paper presents the study on the vibration attenuation in an isolated platform by combining multi-layer perception (MLP) neural network, radial basis function (RBF) neural network, cerebella model articulation controller (CMAC) neural network and fuzzy neural networks (FNN) with error back propagation algorithm to control voice coil actuator. Usually, the methods in past time to control vibration were mainly designed by using mathematical models, which must be nearly close to the actual plant models. As regards to these utilized control methods, the most important advantage of them are that they have capability of self tuning the parameters of controllers and could adapt the changes of the environments. The performance of attenuation and control effectiveness can be evaluated by placing the accelerator to measure the amplitude at the center of the isolated platform. The experimental results in this study show that the control methods as adopted could greatly attenuate the vibration of resonance and external disturbance in an isolation platform.     

车载光学平台双层隔振系统设计与试验研究

分析了冲击、振动对车载精密光学系统的影响,指出了光学平台的变形和振动是影响车载精密光学系统精度和稳定性的主要因素,提出了车载光学平台双层隔振系统的设计方案。采用ANSYS有限元方法分析了光学平台隔振系统的振动模态和减振比,完成了车载状况下的光学平台振动测试。分析与测试结果表明,车载光学平台的双层隔振结构具有良好的稳定性,且对环境强振动有很好的衰减作用。该双层隔振技术方案及其分析测试方法,对于各种车载精密光学系统和设备具有重要的工程应用价值。     

车载光学平台双层隔振系统设计与试验研究

 分析了冲击、振动对车载精密光学系统的影响,指出了光学平台的变形和振动是影响车载精密光学系统精度和稳定性的主要因素,提出了车载光学平台双层隔振系统的设计方案。采用ANSYS有限元方法分析了光学平台隔振系统的振动模态和减振比,完成了车载状况下的光学平台振动测试。分析与测试结果表明,车载光学平台的双层隔振结构具有良好的稳定性,且对环境强振动有很好的衰减作用。该双层隔振技术方案及其分析测试方法,对于各种车载精密光学系统和设备具有重要的工程应用价值。     

Design and analysis of an intelligent vibration isolation platform for reaction/momentum wheel assemblies

This study focuses on design and analysis of an intelligent vibration isolation platform for reaction wheel assemblies (RWAs) and momentum wheel assemblies (MWAs). A passive platform consisting of four folded beams is designed and analysed for MWAs. A simple and effective mathematical model is developed for the system consisting of the platform and MWAs, and this model is used to investigate the passive vibration isolation performance. Further development is performed to produce an intelligent platform for RWAs, with piezoelectric sensors and actuators bonded to the vertical beams. The flywheel imbalance and impulse load are assumed to be input disturbances for the investigation of the active vibration isolation performance by the finite element method (FEM). The simulation results show that the passive vibration isolation platform is particularly effective for the suppression of a high frequency range vibration for MWAs, and the intelligent platform using velocity feedback control effectively attenuates the dynamic amplification of amplitude at resonance for RWAs. Thus, it is concluded that the passive platform can be used as a vibration isolation platform for MWAs and that the intelligent one can be used for RWAs.     

Passive vibration isolation of reaction wheel disturbances using a low frequency flexible space platform

Reaction wheel assemblies (RWAs) are momentum exchange devices used in fine pointing control of spacecrafts. Even though the spinning rotor of the reaction wheel is precisely balanced to minimize emitted vibration due to static and dynamic imbalances, precision instrument payloads placed in the neighborhood can always be severely impacted by residual vibration forces emitted by reaction wheel assemblies. The reduction of the vibration level at sensitive payloads can be achieved by placing the RWA on appropriate mountings. A low frequency flexible space platform consisting of folded continuous beams has been designed to serve as a mount for isolating a disturbance source in precision payloads equipped spacecrafts.Analytical and experimental investigations have been carried out to test the usefulness of the low frequency flexible platform as a vibration isolator for RWAs. Measurements and tests have been conducted at varying wheel speeds, to quantify and characterize the amount of isolation obtained from the reaction wheel generated vibration. These tests are further extended to other variants of similar design in order to bring out the best isolation for given disturbance loads. Both time and frequency domain analysis of test data show that the flexible beam platform as a mount for reaction wheels is quite effective and can be used in spacecrafts for passive vibration control.     

电磁耦合实验平台系统线缆束的电磁拓扑分析

复杂线缆束系统的电磁耦合分析,随着电磁环境的日趋复杂化,显得越来越困难。而高功率电磁辐射技术的发展,对具有复杂电缆束网络和电子设备的系统,带来了严重的电磁威胁。这从电磁攻击与电磁防护两方面,对复杂线缆束的电磁耦合分析,都提出了更加迫切的需求。由于复杂线缆束网络所涉及的几何空间的边界条件十分复杂,所以很难用时域有限差分(FDTD)或频域有限差分(FDFD)方法求解复杂线缆束网络系统的电磁耦合问题。我们在基于传输线理论,采用拓扑学中将空间按照拓扑结构进行分解的思想,建立了线缆束网络电磁耦合的拓扑模型,得出了计算复杂线缆束网络系统终端耦合电压与电流的计算方法,并给出了仿真计算实例用以验证电磁拓扑法处理线缆网络电磁耦合效应的有效性。     

电磁耦合实验平台系统线缆束的电磁拓扑分析

复杂线缆束系统的电磁耦合分析,随着电磁环境的日趋复杂化,显得越来越困难。而高功率电磁辐射技术的发展,对具有复杂电缆束网络和电子设备的系统,带来了严重的电磁威胁。这从电磁攻击与电磁防护两方面,对复杂线缆束的电磁耦合分析,都提出了更加迫切的需求。由于复杂线缆束网络所涉及的几何空间的边界条件十分复杂,所以很难用时域有限差分(FDTD)或频域有限差分(FDFD)方法求解复杂线缆束网络系统的电磁耦合问题。我们在基于传输线理论,采用拓扑学中将空间按照拓扑结构进行分解的思想,建立了线缆束网络电磁耦合的拓扑模型,得出了计算复杂线缆束网络系统终端耦合电压与电流的计算方法,并给出了仿真计算实例用以验证电磁拓扑法处理线缆网络电磁耦合效应的有效性。     

双稳态结构中的1/2次谐波共振及其对隔振特性的影响

以典型的双稳态系统——屈曲梁结构为例,基于等效模型,结合解析、数值和实验手段,研究了双稳态结构中的1/2次谐波共振特性、演化过程、参数调节规律及其对隔振特性的影响.研究发现,当非线性刚度系数或激励幅值增加到一定程度时,系统会在一定带宽下产生显著的1/2次谐波共振;随着激励幅值增加,阻尼系统的1/2次谐波遵循“产生-增强-衰退-消失”的过程,该过程对峰值频率和峰值传递率有重要影响;适当提高非线性强度能有效改善双稳态结构隔振特性.针对双稳态屈曲梁结构开展的实验验证了1/2次谐波特性和隔振特性变化规律.     

Control algorithms for active vibration isolation systems subject to random disturbances

Isolation from disturbances, particularly from foundations of high precision instruments, is achieved through either passive or active vibration control systems. Although a passive isolation system offers a simple and reliable means of protecting precision equipment from a vibration environment, it has performance limitations since its controllable frequency range is limited. An effective method for reducing an oscillation is by using an active vibration isolation system, which allows control of the dynamic rigidity of shock absorbers. In this paper, by considering the characteristics of the disturbing influences acting upon vibro-isolated objects, the dynamic characteristics of the AVIS device and control restriction, new optimal and quasi-optimal control algorithms are proposed. The characteristics of the new quasi-optimal active vibration isolation system proposed in the paper are investigated via experiments. It is shown that the adopted quasi-optimal active vibration isolation system can improve performance using in situ measurements.     

A long-period conical pendulum for vibration isolation

A practical design for a long-period conical pendulum based on the Scott-Russel linkage is presented together with proof-of-concept measurements on a simple prototype showing good stability for periods in excess of 20 seconds. The design is intended as a vibration isolation component for gravitational wave detection.     

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.     

Fast filtering algorithm based on vibration systems and neural information exchange and its application to micro motion robot

This paper develops a fast filtering algorithm based on vibration systems theory and neural information exchange approach. The characters, including the derivation process and parameter analysis, are discussed and the feasibility and the effectiveness are testified by the filtering performance compared with various filtering methods, such as the fast wavelet transform algorithm, the particle filtering method and our previously developed single degree of freedom vibration system filtering algorithm, according to simulation and practical approaches. Meanwhile, the comparisons indicate that a significant advantage of the proposed fast filtering algorithm is its extremely fast filtering speed with good filtering performance. Further, the developed fast filtering algorithm is applied to the navigation and positioning system of the micro motion robot, which is a high real-time requirement for the signals preprocessing. Then, the preprocessing data is used to estimate the heading angle error and the attitude angle error of the micro motion robot. The estimation experiments illustrate the high practicality of the proposed fast filtering algorithm.     

载人航天器电测自动化程序设计及应用

针对现有载人航天器电测过程不能流程化、自动化程控,消耗了相当多的人力资源和时间成本的问题,设计了载人航天器自动化测试程序。通过对自动化测试程序的格式、功能、处理流程进行分析和设计,为航天器电测提供基础数据资源,实现了航天器电测全周期自动化、流程化,能够适应不同系列载人航天器电测,有效减少测试人员的手动操作及岗位人员数量,提高了测试效率,满足高强度的地面测试,高效完成高密度的载人航天器发射任务。     

交联聚丙烯压电驻极体的压电性能及振动能量采集研究

以电子束辐照交联聚丙烯(IXPP)泡沫薄板为原材料, 首先利用热压工艺对微观结构进行改性, 然后采用电晕充电方法对样品实施极化处理, 使之具有压电效应, 成为压电驻极体. 通过准静态和动态压电系数d₃₃、复电容谱, 以及等温衰减的测量, 研究了IXPP压电驻极体膜的机电耦合性能; 同时考察了基于IXPP压电驻极体膜的振动能量采集器在{3-3}模式下对环境振动能的俘获. 结果表明, IXPP压电驻极体的准静态压电系数d₃₃可高达620 pC/N; 厚度方向的杨氏模量和品质因数(FOM, d₃₃·g₃₃)分别是0.7 MPa和11.2 GPa^-1; 在50, 70和90℃下进行等温老化, 经过24 h后, IXPP压电驻极体膜的准静态压电系数d₃₃分别降低到初始值的54%, 43%和29%; 采用面积为3.14 cm²的IXPP压电驻极体膜为换能元件, 当振子质量为25.6 g, 振动频率为820 Hz时, 振动能量采集器在匹配负载附近可以输出高达65 μW/g²的功率.     

A technique for removing platform vibration noise from a pulsed ladar vibration sensor

A technique has been developed for removing platform-induced vibration noise from a pulsed ladar vibration sensor. Deriving the vibrational characteristics of the platform is accomplished by simulating ambient atmospheric aerosols as a stationary reference target. Using a pulsed coherent detection ladar, the instantaneous Doppler frequency shifts from both aerosols and a distant hard target are measured and recorded, while the data acquisition is range gated so that both Doppler measurements are made from a single pulse. Periodic measurements are then made to develop a time history of the fluctuations in the Doppler signals, after which two vibration spectra are derived by Fourier transforming the time histories of the instantaneous Doppler shifts. The first spectrum contains information regarding the relative motion between the target and platform, while the second spectrum contains information regarding the relative motion between the platform and the stationary aerosols. When the second spectrum is subtracted from the first, the resulting spectrum is the true vibrational signature of the target. The advantages of this new technique over conventional continuous wave ladar vibration sensors are: target range information is obtainable; the average power required from the laser is significantly reduced; and additional sensing equipment is not needed to derive the platform-induced noise spectrum. The principles of this technique are experimentally verified using a 2 μm pulsed ladar.     

Research on performance indices of vibration isolation system

Power flow transmissibility is proposed as a performance index to evaluate the performance of isolation system. It is defined as the ratio of the power flow input into the equipment and the power flow transmitted into the receiver. Based on a simple vibration isolation system, its relationship with other performance indices is given by theoretical and numerical analysis. The results show that power flow transmissibility can reflect the response characteristics of the whole isolation system effectively. In addition, power flow transmissibility can be estimated easily according to vibration acceleration level difference and does not involve the measurement of power flow. Furthermore, the influences of several parameters such as the damping, loss factor and stiffness of isolator on power flow transmissibility are analyzed.     

FEM dynamic model for active vibration control of flexible linkages and its application to a planar parallel manipulator

Development of dynamic models of flexible linkages, with flexible motion caused by rigid body motion and electromechanical coupling of transduction devices and the host linkage, is very important for the design of active vibration control laws for flexible-link mechanisms. In the first part of this paper, the Lagrange finite element (FE) formulation is used to derive such a dynamic model for a flexible planar linkage with two translational and one rotational degrees of freedom. Linear electromechanical coupling of surface-bonded lead zirconate titanate (PZT) patches with the host linkage is incorporated into the model. In the second part of this paper, this dynamic model is applied to a flexible-link planar parallel manipulator. Based on standard kineto-elastodynamic assumptions, the linkage dynamic model is simplified and simulation of strain rate feedback control using PZT sensors and actuators is performed. Numerical results show that PZT actuators effectively damp vibration of the flexible linkages.     

The identity between the Rayleigh-Kohn and Newton-Raphson procedures and its application to the vibration analysis of single-junction branched systems

This paper presents an iterative procedure for determining the natural frequencies and mode shapes of vibration of single-junction branched systems that enables large order systems of this class to be solved. The method is based on the Holzer table but with the modification that the junction rotor is considered as the residual torque rotor, and the vibration amplitude of the residual rotor is always normalized to unity. A consequence of this form of normalization is that the Rayleigh-Kohn and Newton-Raphson iterative techniques become identical, and this identification enables the natural frequencies of the system to be determined in any order by a simple iterative formula. The method is illustrated by application to a typical marine system.     

Perception,comfort and performance criteria for human beings exposed to whole body pure yaw vibration and vibration containing yaw and translational components

Human perception thresholds, in both the presence and the absence of visual cues, and equal sensation contours for low frequency whole body pure yaw vibration were investigated. The results from these and other laboratory tests were combined with field test data for the human response to predominantly yaw vibration, caused by rotational oscillations of civil structures about a vertical axis of the human subjects, to provide guidelines for probable human response to pure yaw vibration at different levels in a variety of circumstances. Relationships have also been derived to allow assessment of the probable responses of occupants of fixed structures to motion which exposes them to the more common case of simultaneous yaw and horizontal translational components of vibration.