引力波及引力波的探测

引力波也叫引力辐射,是爱因斯坦广义相对论中的一项重要预言,是基础物理和天文学中一个重要的内容。人类为探索引力波付出了几十年的努力,从早期的棒状探测器到后来的激光干涉引力波探测器,各国学术机构和科学家们不断采用最先进的技术寻找引力波源,探测器的探测范围和灵敏度也不断提高。在探测引力波的过程中,形成了一门引力波天文学的新兴学科,使人们逐渐了解宇宙的奥秘,寻找宇宙中天体的运行规律,而引力波也成为了当今科学界学术重点和热门课题。     

压缩态光场在激光干涉仪引力波探测器中的应用

激光干涉仪在引力波发现中起着关键作用,标准量子极限是干涉仪灵敏度进一步提高的主要障碍,压缩态光场注入是超越标准量子极限的重要手段。分析了压缩态光场的主要特点,讨论了压缩态光场的产生机制,介绍了压缩态光场技术在超越标准量子极限中的应用。     

激光干涉仪引力波探测器的基本光学结构

引力波是爱因斯坦广义相对论的重要预言,引力波探测是当代物理学最重要的前沿领域之一。以引力波探测为基础的引力波天文学是一门新兴的交叉科学,是对传统电磁辐射天文学的巨大拓展与补充。作为一种大型的精密光学仪器并作为引力波天文学研究的关键设备,激光干涉仪引力波探测器已在世界各地蓬勃发展起来,开辟了引力波探测的新时代。给出了激光干涉仪引力波探侧器的工作原理和基本光学结构,讨论了主要的性能参数,分析了光学镜的结构特点及测量方法。     

光量子噪声对激光干涉仪引力波探测器灵敏度的影响

激光干涉仪在引力波发现中起着关键作用,光量子噪声是干涉仪灵敏度进一步提高的主要障碍。详细分析了光量子噪声中霰弹噪声和辐射压力噪声产生的机制和主要特点,讨论了标准量子极限,扼要介绍了信号循环、压缩光场等标准量子极限突破技术。     

基于并联RSO优化自抗扰的PMSM速度控制

为提高永磁同步电机调速系统的速度精度及抗干扰能力,提出一种并联降阶状态观测器优化线性自抗扰控制的方法。对传统线性扩张状态观测器进行改进,设计了降阶状态观测器。为了提升控制器在有限带宽内的抗扰动能力,设计并联型的降阶状态观测器。仿真结果表明,控制系统的速度精度和鲁棒性得到明显的提升。     

开启引力波天文物理高级探测器新纪元

激光干涉引力波观察台(LIGO)是世界卓越的干涉型引力波探测设备。最初的LIGO探测器已经超出了设计的灵敏度,能够用来探测相距大约40 Mpc的双中子星的合并信号,探测信噪比等于8。当探测器还没被建造时,LIGO科研团队主要和Virgo团队合作,探究了大量天体物理学方面的上限。LIGO目前已经步入了先进探测的新领域,拥有升级版的先进LIGO干涉型探测器。LIGO实验室也和众多印度研究中心合作,在印度建立了一个先进的LIGO干涉仪。从而LIGO探测网络扩展了,拥有3个远距分散的干涉仪在单一网络中运行。     

板带轧机主传动系统的鲁棒故障检测与重构

考虑模型的非线性摩擦阻尼和主传动系统在轧制过程中受到外部干扰的情况,建立了板带轧机主传动系统的数学模型。针对该系统,设计了一种非线性未知输入观测器(unknown input observer,简称UIO)并用于轧机主传动系统的故障检测和故障重构。为了增强残差对故障信号的灵敏度,提高观测器故障检测精度,构建未知输入观测器,将外部干扰从残差中解耦。利用H_∞性能指标提高观测器对故障重构的鲁棒性,采用Lyapunov稳定性理论进行误差动态系统的收敛性分析。为了改进观测器的设计过程,把增益矩阵求解问题转化为受线性矩阵不等式(linear matrix inequality,简称LMI)约束的优化问题。将产生的残差与设定的阈值进行对比,实现故障的检测并完成故障重构。通过对2 030 mm冷连轧机F4号机架主传动系统的仿真研究,验证了该观测器可以准确地对系统状态进行跟踪,并能够检测和估计出主传动系统的故障。     

基于离散型扰动观测器的直线电动机控制研究

针对推力波动、摩擦力等因素对直线电动机控制性能的影响,设计了一种基于扰动观测器的高速高精度位置伺服系统。采用离散时间的扰动观测器设计方法,对考虑与忽略时间延迟环节时,扰动观测器的品质进行比较。仿真分析与试验研究表明：在高速高精度的直线电动机运动控制中,引入带有时间延迟的扰动观测器,能够消除直线电动机速度响应曲线中的微小振荡,减小位置响应曲线中的超调和稳定时间。     

基于DOB的永磁同步电机蚁群优化鲁棒控制

针对永磁同步电机参数测量不准或摄动的问题,设计了一种经蚁群算法优化的H∞混合灵敏度鲁棒控制器,从而获得良好鲁棒性。为使系统兼顾鲁棒跟踪性能和抗扰性,引入扰动观测器并对控制器参数和扰动观测器参数进行组合寻优。在Matlab/Simulink搭建仿真模型仿真后结果表明,该控制系统在参数摄动时仍保持良好的动稳态跟踪性能,具有很强的鲁棒性和抗扰性,在复杂未知的实际工况中应用前景广阔。     

全数字BLDCM调速系统中基于SPI技术的变量观测器

文章介绍了利用SPI技术设计并实现了全数字BLDCM调速系统中的变量观测器，以及该观测器在BLDCM调速系统中的实际应用。     

Thermal effects in the Input Optics of the Enhanced Laser Interferometer Gravitational-Wave Observatory interferometers

We present the design and performance of the LIGO Input Optics subsystem as implemented for the sixth science run of the LIGO interferometers. The Initial LIGO Input Optics experienced thermal side effects when operating with 7 W input power. We designed, built, and implemented improved versions of the Input Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO interferometers, designed to run with 30 W input power. At four times the power of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved performance including better optical isolation, less thermal drift, minimal thermal lensing, and higher optical efficiency. The success of the Input Optics design fosters confidence for its ability to perform well in Advanced LIGO.     

Active noise cancellation in a suspended interferometer

We demonstrate feed-forward vibration isolation on a suspended Fabry-Perot interferometer using Wiener filtering and a variant of the common least mean square adaptive filter algorithm. We compare the experimental results with theoretical estimates of the cancellation efficiency. Using data from the recent Laser Interferometer Gravitational Wave Observatory (LIGO) Science Run, we also estimate the impact of this technique on full scale gravitational wave interferometers. In the future, we expect to use this technique also to remove acoustic, magnetic, and gravitational noise perturbations from the LIGO interferometers. This noise cancellation technique is simple enough to implement in standard laboratory environments and can be used to improve signal-to-noise ratio for a variety of high precision experiments.     

Developing an optical chopper-modulated capacitive probe for measuring surface charge

Gravitational-wave observatories such as Laser Interferometer Gravitational-Wave Observatory (LIGO) use suspended optics in a Michelson interferometer configuration to measure strains in space between 10 Hz and 3 kHz. One potential noise source in this frequency range is the buildup and motion of surface charge on the optics, which can generate fluctuating electric fields, interfere with position control, and reduce reflectance by attracting dust to the optical surface. We have developed a capacitive probe to measure the magnitude and relaxation time of surface charge deposited on smaller test optics in high vacuum ( approximately 10(-5) Torr). Our device modulates capacitance with a tuning-fork optical chopper between probe and sample, chosen for vacuum compatibility and minimal cost. We have found that the probe has a resolution of (3.5+/-0.5)x10(5) e(-)cm(2) in air, on the order of charging levels that could contribute noise to Advanced LIGO, and sufficient for measuring relaxation times on test optics.     

Tip-tilt mirror suspension: beam steering for advanced laser interferometer gravitational wave observatory sensing and control signals

We describe the design of a small optic suspension system, referred to as the tip-tilt mirror suspension, used to isolate selected small optics for the interferometer sensing and control beams in the advanced LIGO gravitational wave detectors. The suspended optics are isolated in all 6 degrees of freedom, with eigenmode frequencies between 1.3 Hz and 10 Hz. The suspended optic has voice-coil actuators which provide an angular range of ±4 mrad in the pitch and yaw degrees of freedom.     

Damping and local control of mirror suspensions for laser interferometric gravitational wave detectors

The mirrors of laser interferometric gravitational wave detectors hang from multi-stage suspensions. These support the optics against gravity while isolating them from external vibration. Thermal noise must be kept small so mechanical loss must be minimized and the resulting structure has high-Q resonances rigid-body modes, typically in the frequency range between about 0.3 Hz and 20 Hz. Operation of the interferometer requires these resonances to be damped. Active damping provides the design flexibility required to achieve rapid settling with low noise. In practice there is a compromise between sensor performance, and hence cost and complexity, and sophistication of the control algorithm. We introduce a novel approach which combines the new technique of modal damping with methods developed from those applied in GEO 600. This approach is predicted to meet the goals for damping and for noise performance set by the Advanced LIGO project.     

Invited article: CO2 laser production of fused silica fibers for use in interferometric gravitational wave detector mirror suspensions

In 2000 the first mirror suspensions to use a quasi-monolithic final stage were installed at the GEO600 detector site outside Hannover, pioneering the use of fused silica suspension fibers in long baseline interferometric detectors to reduce suspension thermal noise. Since that time, development of the production methods of fused silica fibers has continued. We present here a review of a novel CO(2) laser-based fiber pulling machine developed for the production of fused silica suspensions for the next generation of interferometric gravitational wave detectors and for use in experiments requiring low thermal noise suspensions. We discuss tolerances, strengths, and thermal noise performance requirements for the next generation of gravitational wave detectors. Measurements made on fibers produced using this machine show a 0.8% variation in vertical stiffness and 0.05% tolerance on length, with average strengths exceeding 4 GPa, and mechanical dissipation which meets the requirements for Advanced LIGO thermal noise performance.     

结构响应敏度计算的非协调元法

提出非协调元求解结构响应敏度的一般算法。介绍了非协调函数的一般生成方法和满足分片检验条件的一非协调元，建立了使用非协调元进行响应敏度计算的一般公式。最后，文中算例使用非协调元和协调等参元计算了结构响应的敏度值，并对二者的计算结果进行比较。数值验证表明，使用非协调元求得的敏度值比使用等参元的结果更好，非协调元更适合敏度分析。     

敏感度分析技术在微波结构设计中的应用

文中简介了Pro/E行为建模技术,行为建模技术包括敏感度分析、可行性优化分析和多目标设计研究.文中最后用一个实例说明了Pro/E行为建模技术中的敏感度分析在微波结构设计中的应用.结果表明,敏感度分析技术可以提高设计效率和设计质量,在实际工程应用中具有参考价值.     

循环流化床上ECT传感器灵敏场的有限元分析

电容层析成像传感器的敏感场受多相流介质分布的影响,软场特性给图像重建带来很大困难,为了提高重建图像质量,对敏感场分布进行分析是非常必要的.该文以12电极方形电容传感器为基础,对电容层析成像技术应用于循环流化床研究做了简单阐述,着重研究了用有限元法对方形电容传感器敏感场分布的计算机仿真,讨论了负敏感场的处理方法.