Uncertainty analysis of ship model vertical center of gravity and transverse moment of inertia test

The usability of test results of ship model vertical center of gravity and transverse moment of inertia is generally depends on its uncertainty. Referring to the guidelines for uncertainty analysis in examination of liquid dynamic recommended by International Towing Tank Conference （ ITTC）, the results were analyzed, bias limits and precision limits were calculated and total uncertainty was estimated. The total uncertainty of six tests on ship model vertical center of gravity is is 0. 16% of the mean value, and the total uncertainty of six tests on ship model transverse moment of inertia is 5.66% of the mean value. The test results show that the total uncertainty of both the multiple tests and the single test is from the precision limits of ship model vertical center of gravity and transverse moment of inertia tests. Thus, the improved measurement system stability can enormously decrease the total uncertainty of multiple tests and the single test.

Estimation Method of Center of Inertia Frequency Based on Phasor Measurement Data

In the world, recent increased disturbances, congestion management problems, and increases of complexity in operating power systems have brought the need for integrations and improvements of power systems. Advanced applications in WAMPAC （wide area monitoring, protection, and control） systems provide a cost effective solution to improve system planning, operation, maintenance, and energy trading. Synchronized measurement technology and the application are an important element of WAMPAC. In addition, PMUs （phasor measurement units） are the most accurate and advanced time-synchronized technology available for WAMPAC application. Therefore, the original measurement system of PMUs has been constructed in Japan. This paper describes the estimation method of a center of inertia frequency by applying actual measurement data. The application of this method enables us to extract power system oscillations from measurement data appropriately. Moreover, this proposed method will help to the clarification of power system dynamics and this application will make it possible to realize the monitoring of power system oscillations associated with the power system stability.

圆环筒贮箱液体绕横轴的有效转动惯量

航天器贮箱内液体绕横轴和纵轴的有效转动惯量参数是飞行控制系统仿真分析的重要基础,本文分析整理了航天器圆环筒形平底贮箱内液体的有效转动惯量计算方法,依据自由液面平底圆环筒贮箱平动和绕质心横向转动激励下的液体晃动力与力矩的解析表达式,推导了激励频率趋于无限大时,液体平动晃动合力作用点所在位置和绕质心的有效转动惯量表达式,并在平底圆筒条件下利用移轴定理,验证了与液体惯性中心所在位置和绕惯性中心有效转动惯量的一致性。分析了贮箱深度和内、外径比对液体转动惯量的影响规律,补充完善了液体转动晃动特性的理论分析成果。

跟踪COI思想应用于多机系统励磁控制

针对多机电力系统,提出了发电机功角和频率以动态跟踪系统惯量中心(COI)为目标的励磁控制思想。在该思想下,各发电机的功角按一定距离动态追踪系统COI功角的变化,而各发电机的频率则动态追踪系统COI频率的变化。相比于当前绝大多数以原运行点为发电机调节目标的控制思想而言,文中所提出的思想的主要特点在于它是利用系统的动态COI信号来将各发电机拉向同步,系统将根据实际情况稳定于某一可接受的频率,而不是局限于工频。在相同的发电机模型基础上,建立了2种不同思想下的控制系统模型,并给出了采用相同方法设计的鲁棒控制器。最后采用2区4机系统进行了动态仿真,以比较这2种鲁棒控制器以及自动电压调节器+电力系统稳定器(AVR+PSS)励磁系统在提高电力系统暂态稳定性方面的控制功效。

弹射过程人椅系统动态质量特性的建模与分析

人椅系统的质量特性是弹射座椅轨迹和姿态控制精度的重要影响因素。由于缺乏动态质量特性仿真模型,现阶段采用静态参数设计的弹射座椅控制规律可能在实际应用中出现偏差。本文在弹射座椅六自由度运动模型的基础上,考虑火箭包工作质量变化、人体脊柱压缩、座椅座垫压缩和人体头颈部转动等影响因素,建立了弹射过程人椅系统动态质量特性的计算模型。通过对三个典型工况计算结果的分析,说明了计算模型的合理性;最后分别采用动态、静态质量特性模型对弹射过程轨迹姿态进行仿真,并分析了两模型在救生效果上的差异性。本文建立的模型可以为后续弹射座椅控制规律的精细化设计提供借鉴。

刚体的转动惯性旋心

转动惯量是刚体转动惯性的度量,转动惯性旋心是刚体的特殊转动中心,刚体对旋心的转动惯量张量是一个二阶球形张量,刚体对过旋心的任意轴的转动惯量都相等,过旋心的任意轴都是刚体的惯量主轴.提出并证明了转动惯性旋心定理:当刚体对质心的三个主转动惯量均相等时,质心是刚体唯一的旋心;当刚体对质心的三个主转动惯量当中仅较小的两个主转动惯量相等时,刚体有且仅有两个旋心,均在主转动惯量较大的中心惯量主轴上且关于质心对称分布,两个旋心到质心的距离均等于刚体对质心的较大与较小主转动惯量差值与刚体质量比值的平方根;当刚体对质心的三个主转动惯量互不相等或者仅其中较大的两个主转动惯量相等时,刚体不存在转动惯性旋心.

Hydrodynamic Analysis of C-start in Crucian Carp

The kinematics of turning maneuvers of startled Crucian Carp (Carassius auratus) are presented. All escape responses observed are C-type fast-starts. The position of the center of mass and the moment of inertia of the fish are calculated. The results show that the position of the center of mass is always at 35% of the length of the fish from the head and the position of the center of mass and moment of inertia can be considered unchanged during C-start of Crucian Carp. Hydrodynamic analysis of the C-start is given based on the kinematics data from our experiments. The C-start consists of three stages. In stage 1, the tail fin of fish rapidly flaps in one direction, and a large moment acts on the fish′s body, which rotates around the center of mass with an angular acceleration. In stage 2, the tail fin flaps more slowly in the opposite direction at slower speed, the fish′s body rotates around the center of mass with angular deceleration and the center of mass of the fish moves along an arc. In stage 3, the moment approximately equals zero, the fish′s body stops rotating and the center of mass the moves along a straight line.

面向新能源电力系统频率时空动态的节点等效惯量指标及其应用

大规模新能源接入电力系统导致系统频率动态过程发生了根本改变,一方面,惯量在系统中空间分布不均匀,系统频率动态呈现出空间分布差异,另一方面,新能源将采用附加控制手段为系统提供虚拟惯量,影响系统惯量响应过程,而传统同步机系统惯性中心视角下的系统总惯量指标无法计及上述因素。该文分析新能源电力系统频率时空动态过程,类比同步机系统总惯量,从扰动不平衡功率与节点频率下降速率之间的关系出发定义节点等效惯量指标,能够合理计及频率空间分布以及新能源虚拟惯量。结合扰动瞬间有功-发电机转速动态过程和系统频率空间相关性推导节点等效惯量指标的表达式。接着,从计及节点等效惯量指标的机组组合和面向在线监测与实时控制的频率动态分区2个角度给出了指标应用示例。最后,以改进的IEEE 39节点系统为例,验证所提指标的有效性和计算方法的正确性。提出的节点等效惯量指标能够弥补新能源电力系统频率时空动态过程分析及刻画的不足,具备现场应用潜力。

Power System Transient Stability Analysis with Integration of DFIGs Based on Center of Inertia

As power systems experience increased wind penetration,an effective analysis and assessment of the influence of wind energy on power system transient stability is required.This paper presents a novel center of inertia(COI)approach to understand how integrated doubly fed induction generators(DFIGs)affect the transient dynamics of a power system.Under the COI coordinate,the influence of integrated DFIGs is separated into the COI related and individual synchronous generator related parts.Key factors that affect the COI’s dynamic motion as well as the rotor dynamics of each individual synchronous generator with respect to the DFIG integration are investigated.To further validate the analysis,comparative simulations of three different scenarios with varying DFIG capacities,access locations,and the replacement of synchronous generators are conducted.The results show that the dynamics of the COI and the individual generators are affected by the integrated DFIGs via different mechanisms,and are sensitive to different variables in the DFIG’s integration condition.

非对称薄壁箱形截面的扭转几何特性研究

为了揭示顶板单向横坡对薄壁箱形截面扭转几何特性的影响,推导了顶板为倾斜布置的非对称薄壁箱形截面扭转中心位置、主扇性坐标及主扇性惯性矩的实用计算公式。运用推导的实用公式并结合数值算例,比较顶板倾斜布置和水平布置对截面扭转几何特性的影响,并分析了顶板横坡、箱室高宽比及悬臂板宽度变化对扭转几何特性的影响规律。研究表明,本文计算值与有限元软件ANSYS中截面特性计算结果吻合很好;当不考虑顶板横坡时,对扭转中心横向位置及高腹板与底板交点处的主扇性坐标影响显著;当箱室高宽比小于0.65时,其变化对扭转中心的横向位置有显著影响;主扇性惯性矩随顶板横坡的增大而减小,随悬臂板宽度及箱室高宽比的增大而增大。

利用本地频率线性分量的电力系统功率缺额估计方法

针对现有功率缺额估计方法可靠性低、耗时长等缺点,提出了一种基于本地频率信息的快速功率缺额估计方法。首先,通过求解常微分方程初值问题,证明了在系统受扰初期,本地频率变化量可以表示为一个线性分量与n-1个机电模式的线性组合,且本地频率的线性分量与系统惯量中心频率变化量相等。基于这一特性,提出了一种无需远程通信的系统功率缺额快速估算方法。该方法基于最小二乘拟合提取本地频率的线性分量来估计系统惯量中心频率,并结合惯量水平估算系统的功率缺额。最后,在PSCAD/EMTDC中搭建了新英格兰39节点系统,验证了所发现性质的正确性和所提功率缺额估计方法的有效性。

局部频率测量数据驱动的电力系统功率缺额在线评估方法

随着新能源并网比例的不断提高,新型电力系统的惯量及频率支撑能力不断降低,导致系统在遭受扰动时易出现频率崩溃,因此需要对扰动后系统功率缺额进行快速准确评估以用于功率缺额的快速填补.提出了一种局部频率测量数据驱动的基于深度卷积和长短期记忆复合神经网络的系统功率缺额在线评估方法.首先,由于同步测量获取实际惯量中心(COI)频率无法适应在线评估的快速性,所以利用局部测量频率估算得到COI频率,避免了复杂通信造成的延时效应;然后设计了一种深度复合神经网络,挖掘海量频率数据和功率缺额间的关联信息;最后搭建39节点系统进行仿真验证,结果显示了所提方法的有效性和快速性.

Adaptive gait planning for quadruped robot based on center of inertia over rough terrain

Controlling the quadruped robot for walking on a rough terrain without any visual perception is a great challenge. In the present study, a simple measuring method is proposed for obtaining the total force applied on the center of inertia of the quadruped robot with force sensing information in the static gait. Based on the zero moment point stable criterion, an extended criterion on the virtual supporting plane is presented to guarantee the stable walking of the quadruped robot. Moreover, an adaptive omnidirectional gait planning is developed for the quadruped robot applying the extended zero moment point on the center of inertia to obtain the stable criterion over rough terrain. It is found that when the proposed gait planning is applied on the quadruped robot, unknown surroundings successfully adapted without establishing the huge height map. Experiments are carried out to investigate walking of the quadruped robot at three different conditions, including the flat, rough terrain, and rough slope. It is concluded that the proposed method has reasonable performance in the studies case.

基于广域测量信息的HVDC鲁棒控制器设计

高压直流输电(high voltage direct current,HVDC)附加控制可以提高交直流系统的稳定性,但由直流简化模型引起的误差、信号时滞及各种干扰给附加控制器的设计增加了需要考虑的不确定因素。为克服不确定因素的影响以提高交直流系统的稳定性水平,提出一种HVDC广域鲁棒控制器(wide area robust controller,WARC)设计方法。首先根据区域惯量中心的运动方程和滑模控制设计方法确定滑模切换面,然后利用李雅普诺夫稳定性定理保证系统在不确定因素存在的情况下渐近稳定。分别以交直流并联系统和多馈入系统为例,通过PSCAD/EMTDC的时域仿真将WARC与传统极点配置及PID控制方法相比较,时域仿真结果和区间振荡模式分析均表明所提WARC能有效提高系统稳定性,且比传统控制方法性能优越。

基于惯量中心动态信号的交直流互联系统稳定控制

针对交直流互联电力系统的稳定控制问题,提出了基于系统惯量中心(center of inertia,COI)动态信号的发电机励fr磁和直流功率调制综合控制方案。该方案中各发电机功角和频率动态跟踪由广域测量系统提供的系统COI动态功角和频率轨迹。直流输电线路功率调制的目标是阻尼区域COI功角和频率间的相互振荡。考虑到模型误差和外部干扰因素,采用反步法设计了非线性鲁棒控制器。对某4机2区域系统进行仿真实验,结果表明该控制方案和控制器突破了系统只能稳定于工频下的局限,增大了系统的稳定域,显著改善了系统的功角稳定性。

复摆法弹药静态多参数测试仪器研究

基于复摆原理研制了弹药静态参数多功能测试样机。可以用来测量质心位置、质偏、转动惯量、惯性积、动不平衡度等多种参数,同时推导了相应的计算公式,并利用样机进行了实际测量,测量结果表明该方法是有效和可行的,且具有快速、高效、高精度等特点。

基于广域量测数据的电力系统动态频率分析方法

提出了一种基于广域量测数据的电力系统动态频率求取方法。该方法对系统进行线性化处理,利用扰动后瞬间系统广域量测数据,形成雅可比矩阵,进一步求解系统的状态方程,从而直接计算出系统各发电机频率曲线的时域函数表达式。该算法考虑了调速器的动态特性、网损及负荷变化对系统惯性中心频率的影响,且不需要进行逐步积分。仿真结果表明,该算法求出的惯性中心频率函数能够较好地描述系统惯性中心的频率动态特性,具有较高的精度。

基于部分惯量中心等值的多机系统特征根计算

根据不同频率振荡模式的正交性质，针对每一振荡模式将系统机组分成两群，利用部分惯量中心（ＰＣＯＩ）将两个机群分别等值成两台发电机，在等值两机系统上进行特征根的计算。给出了１０机新英格兰系统的计算结果，证明了该方法的有效性。最后分析了误差原因，并提出了进一步提高计算精度的一些方法。

头盔质量特性高精度测试仪研究

头盔的质量特性是评价和改善其工效性的重要依据。围绕质量和质心的精确测试,设计了头盔定位机构和标准头模;针对转动惯量的高精度测试,构造了基于磁悬浮轴承的扭摆测试台;结合测试机构讨论了头盔质量、质心及转动惯量精确测试的原理与方法。通过PC测控系统的抗干扰设计实现了测试仪可靠控制和高精度数据采集。系统实验与生产应用表明,该测试仪操作简单、易于维护,其常规测试精度分别达到质量0.05%、质心0.1%和转动惯量0.5%,验证了设计的有效性。