Global optimization of distributed output feedback controllers

When the frequency range over which a reduction in vibration is desired is limited to a particular structural mode of vibration, for example, it is shown that a centralized velocity feedback controller can perform better than a decentralized controller for a given level of control effort. The decentralized controller, however, has the desirable properties of scalability and ease of implementation. A number of strategies for clustering the control locations have been proposed to exploit both the performance of the centralized controller and the scalability of decentralized controllers but these have previously been only locally optimal. This paper describes methods by which these distributed controllers may be designed to be globally optimal and gives examples of simulated results of these optimal distributed controllers.     

Information-theoretic approach to the study of control systems

We propose an information-theoretic framework for analyzing control systems based on the close relationship of controllers to communication channels. A communication channel takes an input state and transforms it into an output state. A controller, similarly, takes the initial state of a system to be controlled and transforms it into a target state. In this sense, a controller can be thought of as an actuation channel that acts on inputs to produce desired outputs. In this transformation process, two different control strategies can be adopted: (i) the controller applies an actuation dynamics that is independent of the state of the system to be controlled (open-loop control); or (ii) the controller enacts an actuation dynamics that is based on some information about the state of the controlled system (closed-loop control). Using this communication channel model of control, we provide necessary and sufficient conditions for a system to be perfectly controllable and perfectly observable in terms of information and entropy. In addition, we derive a quantitative trade-off between the amount of information gathered by a closed-loop controller and its relative performance advantage over an open-loop controller in stabilizing a system. This work supplements earlier results (Phys. Rev. Lett. 84 (2000) 1156) by providing new derivations of the advantage afforded by closed-loop control and by proposing an information-based optimality criterion for control systems. New applications of this approach pertaining to proportional controllers, and the control of chaotic maps are also presented.     

Robust SMES controller design for stabilization of inter-area oscillation considering coil size and system uncertainties

It is well known that the superconducting magnetic energy storage (SMES) is able to quickly exchange active and reactive power with the power system. The SMES is expected to be the smart storage device for power system stabilization. Although the stabilizing effect of SMES is significant, the SMES is quite costly. Particularly, the superconducting magnetic coil size which is the essence of the SMES, must be carefully selected. On the other hand, various generation and load changes, unpredictable network structure, etc., cause system uncertainties. The power controller of SMES which is designed without considering such uncertainties, may not tolerate and loses stabilizing effect. To overcome these problems, this paper proposes the new design of robust SMES controller taking coil size and system uncertainties into account. The structure of the active and reactive power controllers is the 1st-order lead-lag compensator. No need for the exact mathematical representation, system uncertainties are modeled by the inverse input multiplicative perturbation. Without the difficulty of the trade-off of damping performance and robustness, the optimization problem of control parameters is formulated. The particle swarm optimization is used for solving the optimal parameters at each coil size automatically. Based on the normalized integral square error index and the consideration of coil current constraint, the robust SMES with the smallest coil size which still provides the satisfactory stabilizing effect, can be achieved. Simulation studies in the two-area four-machine interconnected power system show the superior robustness of the proposed robust SMES with the smallest coil size under various operating conditions over the non-robust SMES with large coil size.     

低杂波电流驱动阴极高压电源系统的优化与实现

4.6 GHz 低杂波电流驱动（LHCD）是EAST托卡马克装置辅助加热系统的重要组成部分。其阴极高压直流电源基于脉冲阶梯调制（PSM）技术,采用64个直流模块串联输出50 kV直流电压。单模块的调制频率设计为50 Hz,故而系统调节速度有限,面对实际运行中网侧电压波动引起的干扰时,电源无法做出更快速的响应与反馈调节,从而导致输出电压产生大幅波动,影响输出性能。为提高电源调节速度和抗干扰能力,设计了具有1 kHz调制能力的高频整流模块以替代部分原低频模块,利用高频模块的快速调节能力抑制输出电压的波动。实验结果表明,升级后的电源输出电压波动减小了50%,更好地满足速调管对于电压精度和稳定度的控制要求,保障了系统运行的可靠性。     

Vibration control of a structure with ATMD against earthquake using fuzzy logic controllers

In this paper, fuzzy logic and PD controllers are designed for a multi-degree-of freedom structure with active tuned mass damper (ATMD) to suppress earthquake-induced vibrations. Fuzzy logic controller (FLC) is preferred because of its robust character, superior performance and heuristic knowledge use effectively and easily in active control. A fifteen-degree-of-freedom structural system is modeled with two types of actuators. These actuators are installed on the first storey and fifteenth storey which has ATMD. The system is then subjected to Kocaeli Earthquake vibrations, which are treated as disturbances. In control, linear motors are used as the active isolators. At the end of the study, the time history of the storey displacements and accelerations, ATMD displacements, control voltages, frequency responses of the both uncontrolled and the controlled structures are presented. Performance of the designed FLC has been shown for the different loads and disturbances using ground motion of the Kobe Earthquake. The results of the simulations show a good performance by the fuzzy logic controllers for different loads and the earthquakes.     

Fixed time integral sliding mode controller and its application to the suppression of chaotic oscillation in power system

Chattering phenomenon and singularity are still the main problems that hinder the practical application of sliding mode control. In this paper, a fixed time integral sliding mode controller is designed based on fixed time stability theory,which ensures precise convergence of the state variables of controlled system, and overcomes the drawback of convergence time growing unboundedly as the initial value increases in finite time controller. It makes the controlled system converge to the control objective within a fixed time bounded by a constant as the initial value grows, and convergence time can be changed by adjusting parameters of controllers properly. Compared with other fixed time controllers, the fixed time integral sliding mode controller proposed in this paper achieves chattering-free control, and integral expression is used to avoid singularity generated by derivation. Finally, the controller is used to stabilize four-order chaotic power system. The results demonstrate that the controller realizes the non-singular chattering-free control of chaotic oscillation in the power system and guarantees the fixed time convergence of state variables, which shows its higher superiority than other finite time controllers.     

Fractional-order optimal fuzzy control for network delay

Fuzzy logic control has been used frequently in tuning network control system (NCS) due to its on-line dynamic static non-linear match and several remarkable fractional-order controllers have achieved satisfactory control performance when applied to NCS in present years, therefore, in this paper, a novel fractional fuzzy logic controller which combined the fractional algorithm and fuzzy logic control together has been proposed to deal with fixed and random network induced delays in closed-loop feedback systems. The comparisons of set-point tracking performances of fractional fuzzy logic PID controller (FFuzzyPID), conventional fuzzy logic PID controller(FuzzyPID), fractional optimal PID controller (FOPID), and optimal PID controller(OPID) on a representative plant with fixed and random network delays have been shown with simulations. The simulation results indicate that fractional fuzzy logic controller has higher capability to handle network delays compared with other controllers in most cases.     

Chaos detection and control in a typical power system

In this paper, a new chaotic system is introduced. The proposed system is a conventional power network that demonstrates a chaotic behavior under special operating conditions. Some features such as Lyapunov exponents and a strange attractor show the chaotic behavior of the system, which decreases the system performance. Two different controllers are proposed to control the chaotic system. The first one is a nonlinear conventional controller that is simple and easy to construct, but the second one is developed based on the finite time control theory and optimized for faster control. A MATLAB-based simulation verifies the results.     

Critical points and transitions in an electric power transmission model for cascading failure blackouts

Cascading failures in large-scale electric power transmission systems are an important cause of blackouts. Analysis of North American blackout data has revealed power law (algebraic) tails in the blackout size probability distribution which suggests a dynamical origin. With this observation as motivation, we examine cascading failure in a simplified transmission system model as load power demand is increased. The model represents generators, loads, the transmission line network, and the operating limits on these components. Two types of critical points are identified and are characterized by transmission line flow limits and generator capability limits, respectively. Results are obtained for tree networks of a regular form and a more realistic 118-node network. It is found that operation near critical points can produce power law tails in the blackout size probability distribution similar to those observed. The complex nature of the solution space due to the interaction of the two critical points is examined.(c) 2002 American Institute of Physics.     

Vibro-acoustic control with a distributed sensor network

The purpose of this work is to demonstrate the ability of a distributed control system, based on a smart sensor network, to reduce acoustic radiation from a vibrating structure. The platform from which control is effected consists of a network of smart sensors, each referred to as a node. Each node possesses its own computational capability, sensor, actuator and the ability to communicate with other nodes via a wired or wireless network. The primary focus of this work is to employ existing group management middleware concepts to enable vibro-acoustic control with such a distributed network. Group management middleware is distributed software that provides for the establishment and maintenance of groups of distributed nodes and that provides for the network communication among such groups. The control objective is met by designing distributed feedback compensators that take advantage of node groups in order to effect their control. The node groups are formed based on physical proximity. The global control objective is to minimize the radiated sound power from a rectangular plate. Results of this investigation demonstrate that such a distributed control system can achieve attenuations comparable to those achieved by a centralized controller.     

风力发电统一变桨距的双模糊控制策略研究

风电机组输出功率有两个主要影响因素,一个是风速的波动性,另一个是不可控性,对该目标的实现带来了困扰,使得传统控制策略在其稳定性控制方面效果并不理想。针对这一缺陷,提出了统一变桨距的双模糊控制策略。该双模糊控制系统的主体部分由模糊PID控制器和模糊前馈补偿器两部分组成。与传统控制策略相比,双模糊控制策略减小了风电机组输出功率的波动范围,降低了控制器参数的调整频率。仿真结果证明了该控制策略的有效性。     

中性束注入器离子源测试台可编程逻辑控制系统

 为实现对离子源测试台系统现场设备的实时监控,设计了一套基于现场总线（Profibus）通讯协议的可编程逻辑控制器（PLC）系统。根据综合测试台测控要求确定PLC系统硬件配置,组建单主站Profibus-DP网络实现高速分布式I/O系统。该系统实时监测现场设备状态并与中性束注入总控实时交换数据,协调控制现场设备按序稳定运行。全图形化的人机操作界面实现了系统运行的可视化操作,数据的实时存储和显示为物理操作人员提供了实验分析依据。整个系统控制稳定可靠,重复性好,兼容性及扩展能力强。     

基于实时Linux的极向场电源主控制系统的设计

为了满足极向场电源控制系统严苛的实时响应的要求,选择实时Linux系统作为系统平台,采用一个开放源代码的、基于C/C++的Eclipse可扩展的开发平台作为开发工具,完成极向场电源主控制系统的设计,实现了在一个控制周期内(1ms)对极向场电源系统的12套本地控制器的实时通信和实时控制。对极向场电源主控制系统的高速通信和实时控制、稳定可靠等关键问题给出了可行的实践性的解决方法。经实验测试,该设计运行稳定,能满足极向场电源控制系统的实时需求。     

面向多蒸发器制冷系统的高效能控制器设计

针对多蒸发器制冷系统的高效控制问题提出了基于模型预测控制的精确控制方法。利用在多蒸发器上分布式部署单个控制器以实现对整个制冷系统的制冷能力和蒸发过热等指标的控制能力。对多蒸发器压缩器制冷循环过程进行了建模分析,给出了其工作过程中详细的关系式,在此基础上设计了基于模型预测的控制器,并进行实验仿真,结果表明控制器的响应动作与实际的制冷需求基本一致。     

直膨式空调人工神经网络在线自适应控制器应用研究

直接膨胀式空调系统人工神经网络控制器已经有了一些研究成果,为了解决控制器控制范围和精度的问题,引入在线自适应控制系统。该控制器的控制能力测试采用直接膨胀式空调系统实验装置进行。试验结果表明,基于人工神经网络动态模型的在线自适应控制器进行训练的前提下,该控制器能够将室内空气的干球和湿球温度控制在一定范围内,具有较高的控制精度。     

Feedback control of acoustic musical instruments: collocated control using physical analogs

Traditionally, the average professional musician has owned numerous acoustic musical instruments, many of them having distinctive acoustic qualities. However, a modern musician could prefer to have a single musical instrument whose acoustics are programmable by feedback control, where acoustic variables are estimated from sensor measurements in real time and then fed back in order to influence the controlled variables. In this paper, theory is presented that describes stable feedback control of an acoustic musical instrument. The presentation should be accessible to members of the musical acoustics community who may have limited or no experience with feedback control. First, the only control strategy guaranteed to be stable subject to any musical instrument mobility is described: the sensors and actuators must be collocated, and the controller must emulate a physical analog system. Next, the most fundamental feedback controllers and the corresponding physical analog systems are presented. The effects that these controllers have on acoustic musical instruments are described. Finally, practical design challenges are discussed. A proof explains why changing the resonance frequency of a musical resonance requires much more control power than changing the decay time of the resonance.     

Adaptive population-based multi-objective optimization in SDN controllers for cost optimization

In Wireless Sensor Networks, Software Defined Networks (SDN) provide a logically centralized control plane as a potential means of streamlining network management (WSNs). The employment of several SDN controllers to build a physically distributed SDN is a common tactic to boost speed, expand scalability, and offer fault tolerance. However, the deployment of many controllers results in increased synchronization and deployment expenses. Therefore, selecting the optimal location for SDN controllers to improve WSN performance is a research issue. In this paper, the multi-objective optimization problem known as the controller placement problem (CPP) is initially formulated. Cost, time, and reliability are just a few of the restraints that are taken into consideration in this regard. In addition, a new Adaptive Population-Based Cuckoo Optimization (APB-CO) for optimal controller placement is implemented. In the end, APB-CO performs experiments to validate the efficacy by analyzing Sync (7.5), Coverage (47), Controller Cost (4.8), and Fitness (0.6983) for the 100th node variation at network 1. The proposed model obtained the controller cost as 34.4, compared to the existing method such as Simulated Annealing (44.3) and Greedy Approach (42.6).     

Power control of optical CDMA star networks

In this paper, we apply the power control concept to optical CDMA star networks. Two approaches are considered, namely, centralized and distributed power control. Both approaches are used to optimize the optical transmit power and to maximize network capacity in terms of the number of users satisfying a target signal to interference (SIR) ratio. Centralized algorithms result in the optimum power vector while distributed algorithms are more suitable for practical system implementation and eliminate the need for a centralized control node. Both analytical and simulation results show significant improvement in the performance of the power controlled optical CDMA system. For instance, in a network of 31 nodes, a doubling of the capacity as compared to the non power control case is obtained. Furthermore, we show in the interference-limited case that the network performance is upper bounded by the number of nodes and the correlation properties of the employed code rather than network attenuation and optical fiber lengths. The concept of network partitioning is then introduced to simplify optimum power calculations. Using network partitioning, we find in the interference-limited case that the optical fibers after the star coupler are irrelevant to the optimum power evaluation.     

Power oscillation suppression by robust SMES in power system with large wind power penetration

The large penetration of wind farm into interconnected power systems may cause the severe problem of tie-line power oscillations. To suppress power oscillations, the superconducting magnetic energy storage (SMES) which is able to control active and reactive powers simultaneously, can be applied. On the other hand, several generating and loading conditions, variation of system parameters, etc., cause uncertainties in the system. The SMES controller designed without considering system uncertainties may fail to suppress power oscillations. To enhance the robustness of SMES controller against system uncertainties, this paper proposes a robust control design of SMES by taking system uncertainties into account. The inverse additive perturbation is applied to represent the unstructured system uncertainties and included in power system modeling. The configuration of active and reactive power controllers is the first-order lead–lag compensator with single input feedback. To tune the controller parameters, the optimization problem is formulated based on the enhancement of robust stability margin. The particle swarm optimization is used to solve the problem and achieve the controller parameters. Simulation studies in the six-area interconnected power system with wind farms confirm the robustness of the proposed SMES under various operating conditions.     

Polarization controlled multiwavelength switchable erbium-doped fiber laser based on high birefringence few-mode fiber loop mirror

A multiwavelength switchable erbium-doped fiber laser with linear cavity is proposed and experimentally demonstrated. It is based on a fiber loop mirror incorporating a piece of high birefringence few-mode fiber and polarization controller. Due to dependence of its reflection properties on the polarization controllers, the fiber laser can operate in the random combination of three wavelengths by only adjusting the polarization controllers in the linear cavity. The wavelengths involved in the switching operation are determined by the merged Sagnac and intermodal interferences elicited in the fiber loop mirror. The optical signal to noise extinction ratio of every oscillation line is higher than 40 dB and power fluctuation less than 0.5 dB.