A novel control strategy for reproducing the floor motions of high-rise buildings by earthquake-simulating shake tables

To enable the experimental assessment of the seismic performance of full-scale nonstructural elements with multiple engineering parameters(EDPs),a three-layer testbed named Nonstructural Element Simulator on Shake Table(NEST)has been developed.The testbed consists of three consecutive floors of steel structure.The bottom two floors provide a space to accommodate a full-scale room.To fully explore the flexibility of NEST,we propose a novel control strategy to generate the required shake table input time histories for the testbed to track the target floor motions of the buildings of interest with high accuracy.The control strategy contains two parts:an inverse dynamic compensation via simulation of feedback control systems(IDCS)algorithm and an offline iteration procedure based on a refined nonlinear numerical model of the testbed.The key aspects of the control strategy were introduced in this paper.Experimental tests were conducted to simulate the seismic responses of a full-scale office room on the 21^(st)floor of a 42-story high-rise building.The test results show that the proposed control strategy can reproduce the target floor motions of the building of interest with less than 20%errors within the specified frequency range.

Dispersion compensation in an open-loop all-optical chaotic communication system

The optical chaotic communication system using open-loop fiber transmission is studied under strong injection conditions. The optical chaotic communication system with open-loop configuration is studied using fiber transmission under strong injection conditions. The performances of fiber links composed of two types of fiber segments in different dispersion compensation maps are compared by testing the quality of the recovered message with different bit rates and encrypted by chaotic modulation （CM） or chaotic shift keying （CSK）. The result indicates that the performance of the pre-compensation map is always worst. Two types of symmetrical maps are identical whatever the encryption method and bit-rate of message are. For the transmitting and the recovering of message of lower bit rate （1 Gb/s）, the post-compensation map is the best scheme. However, for the message of higher bit rate （2.5 Gb/s）, the parameters in communication system need to be modified properly in order to adapt to the high-speed application. Meanwhile, two types of symmetrical maps are the best scheme. In addition, the CM method is superior to the CSK method for high-speed applications. It is in accordance with the result in a back-to-back configuration system.

ATM Open-Loop Shuffleout网络丢失率新的计算方法

文献 [1]提出了Open LoopShuffleout的ATM交换结构 .它是基于多级自路由、输出排队的Banyan结构 .文献[9]在文献 [1]的基础上构造了多递ATMShuffleout交换结构 .这种Open LoopShuffleout的ATM交换结构的信元丢失率包括三部分 ,其中之一就是网络丢失率πn.文献 [1]计算网络丢失率是在假设任意一级交换单元中每一输出端口的负载相同的前提下进行的 .本文考虑了更一般的情况 ,给出了精确计算网络丢失率的分析模型 ,不仅能够处理随机业务 ,而且还能处理热点业务 .模型分析和仿真的数字结果显示了在热点业务下一些有益的结论 .

Instability of cylinder wake under open-loop active control

Instability of a wake controlled by a streamwise Lorentz force is investigated through a Floquet stability analysis. The streamwise Lorentz force, which is a two-dimensional control input created by an electromagnetic actuator located on the cylinder surface,adjusts the base flow to affect the three-dimensional wake instability and achieve wake stabilization and transition delay. The instability mode at a Reynolds number Re = 300 can be transformed from B to A with N = 1.0, where N is an interaction number representing the strength of the Lorentz force relative to the inertial force in the fluid. The wake flow is Floquet stable when N increases to 1.3. The spanwise perturbation wavelengths are 3.926 D and 0.822 D in the modes A and B, respectively, where D is the cylinder diameter. In addition, the oscillating amplitudes of drag and lift are reduced with the increase in the interaction number. Particle tracing is used to explore the essential physical mechanism for mode transformation. The path lines show that suppression of flow separation hinders the fluid deformation and rotation, leading to the decrease in elliptic and hyperbolic instability regions, which is the material cause of mode transformation.All of the results indicate that wake stabilization and transition delay can be achieved under open-loop active control via the streamwise Lorentz force.

Open-loop frequency response for a chaotic masking system

In this paper, a new numerical simulation approach is proposed for the study of open-loop frequency response of a chaotic masking system. Using Chua＇s circuit and the Lorenz system as illustrative examples, we have shown that one can employ chaos synchronization to separate the feedback network from a chaotic masking system, and then use numerical simulation to obtain the open-loop synchronization response, the phase response, and the amplitude response of a chaotic masking system. Based on the analysis of the frequency response, we have also proved that changing the amplitude of the exciting （input） signal within normal working domain does not influence the frequency response of the chaotic masking system. The new numerical simulation method developed in this paper can be extended to consider the open-loop frequency response of other systems described by differential or difference equations.

Analytical solution for a class of linear quadratic open-loop Nash game with multiple players

In this paper, the Nash equilibria for differential games with multiple players is studied. A method for solving the Riccati-type matrix differential equations for open-loop Nash strategy in linear quadratic game with multiple players is presented and analytical solution is given for a type of differential games in which the system matrixcan be diagonalizable. As the special cases, the Nash equilibria for some type of differential games with particular structure is studied also, and some results in previous literatures are extended. Finally, a numerical example is given to illustrate the effectiveness of the solution procedure.

PERFORMANCE OF A NEW DECODING METHOD USED IN OPEN-LOOP ALL-OPTICAL CHAOTIC COMMUNICATION SYSTEM

A new decoding method with decoder is used in open-loop all-optical chaotic communication system under strong injection condition.The performance of the new decoding method is numerically investigated by comparing it with the common decoding method without decoder.For new decoding method,two cases are analyzed,including whether or not the output of the decoder is adjusted by its input to receiver.The results indicate the decoding quality can be improved by adjusting for the new decoding method.Meanwhile,the injection strength of decoder can be restricted in a certain range.The adjusted new decoding method with decoder can achieve better decoding quality than decoding method without decoder when the bit rate of message is under 5 Gb/s.However,a stronger injection for receiver is needed.Moreover,the new decoding method can broaden the range of injection strength acceptable for good decoding quality.Different message encryption techniques are tested,and the result is similar to that of the common decoding method,indicative of the fact that the message encoded by using Chaotic Modulation(CM) can be best recovered by the new decoding method owning to the essence of this encryption technique.

Chaos Correlation in Open-loop Semiconductor Lasers Scheme Effected by Variable Feedback Time

The effect of optical feedback time （depend on the distance between the front facet of the laser and the external mirror） on the chaos synchronization in open-loop communication system have been investigated. In this system, the dynamics of semiconductor lasers with both the optical feedback and optical injection are coherently coupled with the internal laser field. The synchronization map becomes a cloud of points for some parameters values （no correlation between Master laser ML and Slave laser SL outputs）. It means that the two lasers are decoupled. It can be clearly seen when kf = 0.2, kinj = 0.4 and τ = 1 the correlation between these two laser outputs are in a diagonal line, which implies the excellent correlation between them and verifies their synchronization. It is evident that the synchronization quality of open-loop scheme improves for this value is better than that of the other amounts. Value is better than that of the other amounts.

Residue Based Open-Loop Modal Analysis Method for Detecting LFMR of PMSG-WFs Penetrated Power Systems

This paper proposes a residue based open-loop modal analysis method to detect low frequency modal resonance(LFMR),including asymmetric low frequency modal attraction(ALFMA)and asymmetric low frequency modal repulsion(ALFMR),of permanent magnetic synchronous generator based wind farms(PMSG-WFs)penetrated power systems.The formation of ALFMA and ALFMR caused by two open-loop low frequency oscillation(LFO)modes moving close and apart is analyzed in detail.Via predicting the trajectories of closed-loop LFO modes based on calculation of residue of open-loop LFO modes,both ALFMA and ALFMR can be detected.The proposed method can select LFO modes which move to the right half complex plane as control parameters vary.Simulation studies are carried out on a three-machine power system and a four-machine 11-bus power system to verify the properties of the proposed method.

Connections Between Induction Generator Effect and Open-loop Modal Proximity to Cause Sub-synchronous Oscillations in Series-compensated Power System

The induction generator effect(IGE)and the openloop modal proximity(OLMP)are two different reasons why subsynchronous oscillations(SSOs)in a series-compensated power system(SCPS)may occur.The IGE attributes the growing SSOs to negative resistance,while the OLMP explains the SSO mechanism from the standpoint of modal conditions.In this paper,we investigate the connections between the IGE and the OLMP through equivalent RLC circuit and open-loop modal analysis.Our investigation is conducted for two types of seriescompensated power systems where either a synchronous generator or a DFIG is connected at the sending end.The investigation reveals the conditions,in which the IGE and the OLMP may jointly cause the growing SSOs,i.e.,both the IGE and the OLMP can explain why the growing SSOs occur.Furthermore,the investigation indicates that the IGE and the OLMP may be totally irrelevant and lead to growing SSOs separately.This implies that it is possible that in a SCPS,the growing SSOs are only due to the IGE,and the OLMP is non-existent,and vice versa.Hence,when the growing SSOs occurs in a SCPS,examination based on both the IGE and the OLMP should be carefully conducted in order to find if the oscillatory instability is due to the IGE,or the OLMP,or both of them.

Implicit Function Based Open-loop Analysis Method for Detecting the SSR Using Identified System Parameters

This paper proposes an implicit function based open-loop analysis method to detect the subsynchronous resonance(SSR),including asymmetric subsynchronous modal attraction(ASSMA)and asymmetric subsynchronous modal repulsion(ASSMR),of doubly-fed induction generator based wind farms(DFIG-WFs)penetrated power systems.As some important parameters of DFIG-WF are difficult to obtain,reinforcement learning and least squares method are applied to identify those important parameters.By predicting the location of closed-loop subsynchronous oscillation(SSO)modes based on the calculation of partial differentials of characteristic equation,both ASSMA and ASSMR can be found.The proposed method in this paper can select SSO modes which move to the right half complex planes as control parameters change.Besides,the proposed open-loop analysis method is adaptive to parameter uncertainty.Simulation studies are carried out on the 4-machine 11-bus power system to verify properties of the proposed method.

基于干扰和功率控制的多小区分布式波束成形

在多小区干扰信道中,基于分布式竞争设计,提出两种优化基站发射波束成形矩阵的设计,使每个小区的最差信干噪比最大.一种是基于干扰控制的设计,利用差异化的干扰系数,抑制小区间的干扰,提高系统性能.另一种是基于功率控制的设计,通过调整各基站的发射功率,提高系统性能.这两种设计,都能保持算法的分布式特性,又能有效地提高用户信干噪比.仿真分析表明,基于功率控制的设计在功率大的情况下,性能优于基于干扰控制的设计.

天线校准误差建模及对开环波束赋形技术的影响

时分双工系统中上下行无线信道具有互易性,使得基站可以利用获得的上行信道信息实施开环波束赋形技术。但是基站天线口与基带处理模块之间的射频通道并不对称,在进行校准后由于硬件精度所限会有天线校准误差。为此,根据实测数据对天线校准误差进行建模,通过仿真得出,射频通道校准幅度误差标准差在1dB、角度误差在20°以内时,开环波束赋形技术在误码率为10-5时性能损失小于1dB。并由此给出了对天线校准误差的要求。

互耦效应对DOA估计的影响

在均匀线性阵列模型下,结合常规波束形成算法、Capon最小方差无失真响应(MVDR)波束形成算法、MUSIC算法、ESPRIT算法和Root-MUSIC算法等几种主要到达角(DOA)估计算法的原理,分析了互耦效应影响这些算法的作用机理,并利用MATLAB进行了数值仿真。理论分析和仿真结果表明,互耦效应带来的误差增大了DOA估计算法的估计误差,降低了估计成功概率,严重影响了算法的性能。

一种改进的宽带波束形成方法

宽带信号具有目标回波携带的信息量大及混响背景相关性弱等特点,在声纳系统中应用越来越广泛。为了减小FIR滤波器的幅度和相位误差对宽带波束形成器性能的影响,采用线性约束最小方差自适应算法保证FIR数字滤波器的相位特性严格线性;采用基于幅度误差函数的代价因子自适应迭代算法使FIR数字滤波器通带内近似满足等纹波的幅度特性,达到FIR数字滤波器与设计指标要求最佳匹配的目的。对10阵元等间隔线阵的分析仿真结果表明该方法是有效的,并适用于其它阵型,对于声纳系统具有显著的应用价值。

基于软件无线电的智能天线

智能天线是在软件无线电基础上提出的天线设计概念,是数字波束形成(DBF)技术与软件无线电完美结合的产物。本文主要介绍了智能天线基本组成,讨论了智能天线波束形成算法的分类,以及工程实现中的关键技术。

一种开环流水线A/D转换器的系统仿真

介绍了一种开环(Open-Loop)流水线结构的A/D转换器的行为级仿真.通过对系统结构的分析,对影响系统性能的主要参数以及非线性因素进行了深入研究,提出了对系统的主要模块进行数学建模和仿真方法.搭建了测试平台,对一个8位、250MHz采样频率的开环流水线结构A/D转换器进行了理想情况仿真,验证了系统结构,并通过对加入非理想因素后的系统仿真,得出一组满足实际系统设计要求的性能指标.

存在误差情况下的QSP波束成形器性能分析

在移动通信中,由于移动而导致信号波达方向不断变化,同时天线阵导向矢量扰动误差和采样协方差矩阵估计误差的存在,使得传统波束成形器产生波束畸变和明显的输出信干噪比下降.QSP波束成形器作为一种新的鲁棒性波束成形器,在上述应用场景,具有很好的性能.本文分析了QSP波束成形器的性能,并通过仿真比较验证了QSP波束成形器的有效性.分析和实验表明,在上述应用环境中,通过适当调整影响因子,QSP波束成形器较传统波束成形器有更稳定的输出性能.

Open loop control of vortex-induced vibration of a circular cylinder

In this paper both numerical and experimental investigations have been carried out to suppress the vortex-induced vibration （VIV） of a circular cylinder in an electrically low-conducting fluid. The electromagnetic forces （Lorentz forces） in the azimuthal direction were generated through the mounted electrodes and magnets locally on the surface of the cylinder, which have been proved having an accelerating effect to the fluid on the surface of the cylinder. Results of computations are presented for synchronous vibration phenomenon of a cylinder at Re = 200, which are in good agreement with previous computational results. With the Lorentz forces loaded, the VIV of the cylinder has been suppressed successfully. Experimental results have also shown the same tendency and are in reasonable agreement with the numerical results.

Adaptive adjustment of iterative learning control gain matrix in harsh noise environment

For the robustness problem of open-loop P-type iterative learning control under the influence of measurement noise which is inevitable in actual systems, an adaptive adjustment algorithm of iterative learning nonlinear gain matrix based on error amplitude is proposed and two nonlinear gain functions are given. Then with the help of Bellman-Gronwall lemma, the robustness proof is derived. At last, an example is simulated and analyzed. The results show that when there exists measurement noise, the proposed learning law adjusts the learning gain matrix on line based on error amplitude, thus can make a compromise between learning convergence rate and convergence accuracy to some extent： the fast convergence rate is achieved with high gain in initial learning stage, the strong robustness and high convergence accuracy are achieved at the same time with small gain in the end learning stage, thus better learning results are obtained.