Compressive Measurement Identification of Linear Time-Invariant System Application in DC Motor

In traditional system identification (SI), actual values of system parameters are concealed in the input and output data;hence, it is necessary to apply estimation methods to determine the parameters. In signal processing, a signal with N elements must be sampled at least N times. Thus, most SI methods use N or more sample data to identify a model with N parameters;however, this can be improved by a new sampling theory called compressive sensing (CS). Based on CS, an SI method called compressive measurement identification (CMI) is proposed for reducing the data needed for estimation, by measuring the parameters using a series of linear measurements, rather than the measurements in sequence. In addition, the accuracy of the measurement process is guaranteed by a criterion called the restrict isometric principle. Simulations demonstrate the accuracy and robustness of CMI in an underdetermined case. Further, the dynamic process of a DC motor is identified experimentally, establishing that CMI can shorten the identification process and increase the prediction accuracy.

Perturbation Analysis of Continuous-Time Linear Time-Invariant Systems

In this paper, we consider the perturbation analysis of linear time-invariant systems, which arise from the linear optimal control in continuous-time. We provide a method to compute condition numbers of continuous-time linear time-invariant systems. It solves the perturbed linear time-invariant systems via Riccati differential equations and continuous-time algebraic Riccati equations in finite and infinite time horizons. We derive the explicit expressions of measuring the perturbation bounds of condition numbers with respect to the solution of the linear time-invariant systems. Furthermore, condition numbers and their upper bounds of Riccati differential equations and continuous-time algebraic Riccati equations are also discussed. Numerical simulations show the sharpness of the perturbation bounds computed via the proposed methods.

Isolated Area Load Forecasting using Linear Regression Analysis: Practical Approach

This paper presents an analysis to forecast the loads of an isolated area where the history of load is not available or the history may not represent the realistic demand of electricity. The analysis is done through linear regression and based on the identification of factors on which electrical load growth depends. To determine the identification factors, areas are selected whose histories of load growth rate known and the load growth deciding factors are similar to those of the isolated area. The proposed analysis is applied to an isolated area of Bangladesh, called Swandip where a past history of electrical load demand is not available and also there is no possibility of connecting the area with the main land grid system.

A Piecewise Linear Isotropic-Kinematic Hardening Model with Semi-Implicit Rules for Cyclic Loading and Its Parameter Identification

A simple constitutive model,called semi-implicit model,for cyclic loading is proposed for steel materials used for structures such as building frames in civil engineering.The constitutive model is implemented in the E-Simulator,which is a software package for large-scale seismic response analysis.The constitutive relation is defined in an algorithmic manner based on the piecewise linear combined isotropic-kinematic hardening.Different rules are used for the first and subsequent loading states to incorporate characteristics such as yield plateau and Bauschinger effect of rolled mild steel materials.An optimization method is also presented for parameter identification from the results of cyclic and monotonic loading tests.Therefore,the proposed model is readily applicable to practical elastoplastic analysis of building frames.Accuracy of the model is demonstrated in an example of a cantilever subjected to various types of cyclic loading.

Load Frequency Control of Small Hydropower Plants Using One-Input Fuzzy PI Controller with Linear and Non-Linear Plant Model

This study presents an intelligent approach for load frequency control (LFC) of small hydropower plants (SHPs). The approach which is based on fuzzy logic (FL), takes into account the non-linearity of SHPs—something which is not possible using traditional controllers. Most intelligent methods use two- input fuzzy controllers, but because such controllers are expensive, there is economic interest in the relatively cheaper single-input controllers. A non- linear control model based on one-input fuzzy logic PI (FLPI) controller was developed and applied to control the non-linear SHP. Using MATLAB/Si- mulink SimScape, the SHP was simulated with linear and non-linear plant models. The performance of the FLPI controller was investigated and compared with that of the conventional PI/PID controller. Results show that the settling time for the FLPI controller is about 8 times shorter;while the overshoot is about 15 times smaller compared to the conventional PI/PID controller. Therefore, the FLPI controller performs better than the conventional PI/PID controller not only in meeting the LFC control objective but also in ensuring increased dynamic stability of SHPs.

AN ANALYSIS oF THE SHEAR FAILURE OF RIGID-LINEAR HARDENING BEAMS UNDER IMPULSIVE LOADING

A theoretical rigid-plastic analysis for the dynamic shear failure of beams under impulsive loading is presented when using a travelling plastic shear hinge model which tabes into account material strain hardening. The maximum dynamic shear strain and shear strain-rate can be predicted in addition to the permanent transverse deflections and other parameters. The conditions for the three modes of shear failure, i.e., excess deflection failure, excess shear strain failure and adiabatic shear failure are analyzed. The special case of an infinitesimally small plastic zone is discussed and compared with Nonaka's solution for a rigid, perfectly plastic material. The results can also be generalized to examine the dynamic response of fibre-reinforced beams.

NON-LINEAR DYNAMIC BEHAVIOR OF THERMOELASTIC CIRCULAR PLATE WITH VARYING THICKNESS SUBJECTED TO NONCONSERVATIVE LOADING

The non-linear dynamic behaviors of thermoelastic circular plate with varying thickness subjected to radially uniformly distributed follower forces are considered. Two coupled non-linear differential equations of motion for this problem are derived in terms of the transverse deflection and radial displacement component of the mid-plane of the plate. Using the Kantorovich averaging method, the differential equation of mode shape of the plate is derived, and the eigenvalue problem is solved by using shooting method. The eigencurves for frequencies and critical loads of the circular plate with unmovable simply supported edge and clamped edge are obtained. The effects of the variation of thickness and temperature on the frequencies and critical loads of the thermoelastic circular plate subjected to radially uniformly distributed follower forces are then discussed.

Modified Single Phase SRF d-q Theory Based Controller for DVR Mitigating Voltage Sag in Case of Nonlinear Load

This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag particularly for nonlinear load. In case of single phase distribution line with nonlinear load, the complexity of controller’s design becomes more serious issue. The present single phase and/or three phase theories applicable to DVR shows poor response to restore voltage sag in case of nonlinear load due to presence of harmonics. Hence restoration of voltage sag in single phase nonlinear load connected system has been a serious concern. Therefore, new controller for DVR has been proposed incorporating effective design concept for fundamental component extraction in case of nonlinear load. The single phase SRFT based main controller for DVR works on two separate closed path viz. feed forward path for quick transient response and feedback path for reducing the steady state error. Moreover, pre-sag mitigation strategy of DVR has been adapted through these two aforementioned paths. Complete design of proposed controller is based on phasor analysis. It also consist of proportional integral (PI) controller to reduce the error in the DC-link voltage during compensation time. The controller performance has been verified in MATLAB Simulink for both types (linear and nonlinear) of load. The results obtained indicates that the proposed controller is effective in its performance.

考虑加载历史的小半径曲线桥梁梁轨相互作用分析

目前,大部分考虑加载历史的梁轨相互作用研究都集中在直线桥梁上,针对曲线桥梁,尤其是小半径曲线桥梁,梁轨相互作用的研究相对较少。采用理想弹塑性滞回阻力模型模拟扣件纵向阻力,运用有限元软件,建立以城东特大桥为研究对象的钢轨-桥梁-墩台三维有限元空间力学计算模型,研究曲线半径对于梁轨相互作用的影响,探究了多荷载耦合作用、往复荷载作用以及循环荷载作用下考虑加载历史效应的曲线桥梁梁轨相互作用情况,并提出“拉力百分比”以及“压力百分比”的概念以便分析曲线半径对传统线性叠加法误差的影响。结果表明,曲线桥梁中梁轨纵、横向相互作用分别与曲线半径成正、反比,相关数据改变幅度与曲线半径成反比且当曲线半径超过800 m时基本收敛,此时可采用“以直代曲”的简化算法;曲线半径对于横向梁轨相互作用影响程度大于纵向,相较于挠曲、制动工况,伸缩工况受曲线半径影响更加显著;多荷载耦合作用下,采用传统线性叠加法相较于考虑加载历史更为保守且温度荷载起主要贡献;考虑加载历史时钢轨在往复荷载作用下会产生不可忽视的残余内力,且在循环荷载作用下将会产生收敛于第1次往复荷载下的残余内力,这是扣件纵向阻力的弹塑性滞回特性决定的;线性叠加法误差与曲线半径具有相关性,相较于挠曲、制动工况,伸缩工况下对其更为敏感。研究结果可为考虑加载历史下曲线桥梁结构设计提供参考。

基于装卸顺序的中型机多航段协同配载优化

多航段、多经停的航空货运航班,飞行过程中需要合理控制飞机的重心(CG)位置,保持平衡状态,中转站装卸操作过程中需要避免额外装卸操作,减少时间和劳力浪费,因此,研究多航段航班的协同配载问题具有重要现实意义。根据航空器自身特点与集装器(ULD)装卸顺序,结合各航段飞机装载平衡与过站机场ULD装卸操作要求,通过协调分配各航段ULD和散货位置,建立了中型机联程航班多目标整数线性规划模型。模型考虑了ULD和散货的质量、体积及与舱位的匹配限制,航空器限重、舱位限重、舱位及区域累积限重、上下舱联合限重和CG位置的平衡限制,以及前后航段ULD和散货的连接性约束。根据造成中间机场额外装卸操作的2种原因,基于装卸顺序,提出装卸优化模型,通过ULD的舱内平移,优化了CG,减少了装卸次数。以B757-200F机型为例,在两装一卸、一装两卸和两装两卸3种场景下,采用商用求解器Gurobi,分别针对3种不同目标函数组合进行求解和分析对比。实验表明:所提模型可以有效协调过站货物的额外装卸次数,优化前后两航段的CG位置。

含循环换电负荷及充电站的微电网多目标优化调度

电动换电重卡由于具有充电功率高、周期性强的循环换电负荷特性,一旦短时大量接入微电网中,将带来经济性和安全性的挑战。首先讨论电动汽车充电、循环换电负荷的不同特性,建立含循环换电负荷及充电站的微电网模型;提出一种综合考虑微电网经济性及联络线功率波动性的多目标调度优化方法;采用线性加权方法将多目标问题转化为单目标问题;最后利用CPLEX工具对仿真算例进行求解,仿真算例表明,所提优化方案可有效求解综合考虑不同权重下微电网净利润、联络线交换功率及换电站内电池最优调度问题,能在尽可能减小微电网与上级电网交换功率波动性的同时,使得微电网获得最大净利润。

游离氧化铁对崩岗不同土层土壤胀缩特性的影响

【目的】研究游离氧化铁对崩岗不同土层土壤胀缩特性的影响。【方法】利用无荷膨胀试验、线性收缩试验和计算土壤胶体扩散双电层中滑动层厚度,分析游离氧化铁对崩岗不同土层土壤胀缩特性的影响。【结果】游离氧化铁含量与崩岗土壤无荷膨胀率呈线性递增关系(P<0.01),与土壤线性收缩率呈线性递减关系(P<0.05);在电解质浓度相同的条件下,崩岗土壤滑动层厚度随着游离氧化铁含量的提高而增大;游离氧化铁含量不同的红土层、砂土层的土壤滑动层厚度与无荷膨胀率均呈显著正相关(P<0.05),与线性收缩率呈显著负相关(P<0.05)。【结论】游离氧化铁含量影响土壤滑动层厚度,进而影响土壤的胀缩性能。

基于回归模型的中央监控平台设计与实现

中央监控平台是一个以数据为中心的服务器保护平台。该平台通过组合服务器上的哨兵来防止数据免受泄露和攻击,同时对系统的运行状态进行全面的监测。通过数据分析,并运用数理统计的方法,在可提供的计算力与系统资源利用率之间建立线性回归模型。该模型解释了在某一资源消耗状态下,系统可提供的计算力估算值,在可允许误差为0.1的情况下,其准确率可以达到97%以上,为当前系统运行状态做出精准的评估。

基于RLLE算法的脑力负荷分类

近年来,随着人工智能领域技术的不断发展,脑机接口(brain-computer interface,BCI)吸引了更多学者的关注。实时监测高强度脑力工作者的脑力负荷水平并根据其任务做出动态调整是保护国家财产和操作人员安全的重要手段。研究表明由脑电图(electroencephalogram,EEG)提取的特征功率谱密度对于脑力负荷的变化比较敏感,但由于其维数过高,容易造成数据灾难。传统的主成分分析降维(principal component analysis,PCA)算法会损失数据的部分非线性特征。局部线性嵌入(locally linear embedding,LLE)是常用的非线性降维算法,但该算法对噪声的敏感性高,降维结果受参数影响较大。稳健局部线性嵌入算法RLLE(robust locally linear embedding),在LLE优化权重矩阵时添加了正则项优化,不仅增强了模型的抗噪能力,也解决了解模型过程中可能会出现的矩阵病态和奇异性问题。实验结果表明,经过RLLE降维后的数据使用支持向量机(support vector machine,SVM)分类精度普遍高于经过PCA和LLE的降维方式,具有更强的抗干扰能力。

基于希尔伯特变换的电网络约束关系研究

为了研究电压波动条件下的电网络约束关系,文章基于希尔伯特变换,构建了供电电压存在波动下线性时不变负载上电压、电流的解析信号模型,推导出了以解析信号表征线性时不变电网络的拓扑约束和元件约束关系,将相量法思想拓展至对供电电压波动下线性时不变电网络响应特性的分析与求解。仿真验证结果表明,供电电压存在波动条件下,文中所建立的基于希尔伯特变换的电网络约束关系,不仅物理意义清晰、表征简明,而且正确、好用。文章所建立的电网络约束关系,能够为供电电压波动条件下电网络中线性时不变负载上电压电流关系的建模、仿真分析与计算提供指导。

一种高载荷燃气轮机高压透平可控扩散叶型开发

文章针对某燃气轮机高压透平,开发了一种高载荷叶型,其叶型Zweifel载荷系数达到1.2,对该叶型在典型的燃机叶片运行压比下进行平面叶栅吹风试验验证,试验结果显示气动载荷分布与设计值匹配较好,在设计工况下叶型能量损失系数为1.4%;在1.1到1.7的压比之间叶型损失系数都小于1.7%,出口气流角的变化在1°以内;在-10°到20°的攻角变化范围内表现出优异的气动性能;不同的安装角下叶型损失系数都在1.5%以内。

基于标幺化三阈值事件检测与LDA分类器的工商业负荷辨识方法

非侵入式负荷辨识技术能够低成本的获取用户各类设备使用情况,实现电力负荷的在线监测与分析,对支撑负荷预测、需求响应等应用开展有着重要意义。针对一般工商业用户类型多样、负荷种类繁多、设备运行特性复杂的特点,提出了一种基于标幺化三阈值事件检测与LDA分类器的工商业负荷辨识方案。首先针对不同能耗级别、不同启停特性的设备设计了参数可调的统一负荷事件检测框架,提升了缓变型、分段型、震荡型负荷事件的检出准确度。随后提出了基于多元特征与LDA线性判别的设备类型判断算法,在兼顾边缘端计算效率的同时取得了与随机森林等非线性分类器相同的辨识性能。

基于Kent映射的数字集群动态负载均衡算法研究

由于动态负载均衡是保证数字集群系统正常运行中不可缺少的环节,但其在控制过程中存在易受通信故障等因素的干扰问题,为此提出基于Kent映射的数字集群动态负载均衡算法。通过基于云平台的虚拟机系统采集数字集群的节点连接数、响应时间、动态负载等信息,分析数字集群系统的负载情况。其次构建数字集群资源利用率模型,通过基于Kent映射的灰狼算法对模型求解得到数字集群的资源利用率。最后将资源利用率输入LQR(Linear Quadratic Regulator)控制回路器中,通过控制服务器的迁移实现数字集群的动态负载均衡。实验结果表明,所提算法处理后的数字集群响应时间短、适应度值大、容错能力强。