Radiation clusters and the active control of sound transmission into a symmetric enclosure

Radiation cluster control is proposed for the purpose of attenuating harmonic sound transmission into a symmetric enclosure using error signals derived from structural vibration sensors. The approach falls into a category of middle authority control, which is between LAC (low authority control: structural modal control) and HAC (high authority control: radiation modal control), possessing the benefit of practicality over LAC, while providing high control performance and some flexibility of control gain assignment similar to HAC. The structure of a radiation cluster control system is outlined, showing that it is possible to control a target cluster without affecting the other clusters. A design procedure for the radiation cluster control system is then proposed. Numerical results are also presented.     

The design of synthesized structural acoustic sensors for active control of interior noise with experimental validation

In this paper, the feasibility of using synthesized structural acoustic sensors (SSAS) for active noise control inside irregularly shaped enclosures is investigated. A SSAS consists of a cluster of inter-connected discrete PVDF elements, located on the surface of a vibrating structure enclosing a sound field. An optimal design ensures the sensor output to be directly related to the acoustical potential energy inside the enclosure. Hence, synthesized structural acoustic sensors can provide error signals for an active noise control system, and the use of microphones inside the enclosure can be avoided. A cylindrical shell with a floor partition, which can be used to model an aircraft cabin, is used as a test case. PZT actuators are used as control actuators. Both SISO (single input and single output) and MIMO (multi-input and multi-output) control systems are optimally designed using Genetic Algorithms and implemented with a Filtered-X Feedforward LMS (least-mean-square) controller. Their control performances are evaluated with different types of disturbances. To show the effectiveness of the optimal design approach, some non-optimal control systems are also tested and compared with the optimal one. It is shown that with optimally designed SSAS, an active structural acoustic control system can effectively reduce noise inside the enclosures without using any acoustic transducers.     

Active-passive vibration absorber of beam-cart-seesaw system with piezoelectric transducers

In contrast with fully controllable systems, a super articulated mechanical system (SAMS) is a controlled underactuated mechanical system in which the dimensions of the configuration space exceed the dimensions of the control input space. The objectives of the research are to develop a novel SAMS model which is called beam-cart-seesaw system, and renovate a novel approach for achieving a high performance active-passive piezoelectric vibration absorber for such system. The system consists of two mobile carts, which are coupled via rack and pinion mechanics to two parallel tracks mounted on pneumatic rodless cylinders. One cart carries an elastic beam, and the other cart acts as a counterbalance. One adjustable counterweight mass is also installed underneath the seesaw to serve as a passive damping mechanism to absorb impact and shock energy. The motion and control of a Bernoulli-Euler beam subjected to the modified cart/seesaw system are analyzed first. Moreover, gray relational grade is utilized to investigate the sensitivity of tuning the active proportional-integral-derivative (PID) controller to achieve desired vibration suppression performance. Consequently, it is shown that the active-passive vibration absorber can not only provide passive damping, but can also enhance the active action authority. The proposed software/hardware platform can also be profitable for the standardization of laboratory equipment, as well as for the development of entertainment tools.     

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介绍了J-TEXT装置上将用于辅助加热研究的一套100kV/60A高压电源。这套高压电源基于PSM技术设计,由144个开关电源模块构成。为了满足隔离、控制和保护的要求,采用PXI和FPGA技术设计了符合CODAC规范的PSM电源控制系统,并提出改进的PSM控制策略实现对高压电源的控制。为验证控制系统的性能,在由8个模块组成的高压电源模型样机上对控制系统进行了测试,测试结果表明,系统各项性能良好,可以满足100kV/60A高压电源的控制要求。     

不确定混沌系统的多项式函数模型补偿控制

针对不确定混沌系统控制问题, 研究了一种基于共轭梯度法(conjugate gradient algorithm, CGA)的多项式函数模型 (polynomial-basis-functions model, PBFM)的补偿控制方法. 该方法首先用PBFM对混沌系统的动力学特性进行拟合, 然后用拟合好的PBFM模型对不确定混沌系统进行前馈补偿控制. 该方法的特点是不需要被控混沌系统的数学模型, 可以快速跟踪任意给定的参考信号. 数值仿真试验表明了该方法不仅具有响应速度快、控制精度高, 而且具有较强的抑制混沌系统参数摄动能力和抗干扰能力. 关键词： 混沌控制 多项式函数模型 共轭梯度法     

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.     

冠状动脉系统高阶滑模自适应混沌同步设计

针对冠状动脉系统混沌同步问题, 系统模型受到有界但未知的不确定干扰条件下, 利用几何齐次性理论和积分滑模面设计高阶滑模自适应控制器, 使响应系统在有限时间内跟踪驱动系统, 该方法无需提前预知扰动边界. 采用Lyapunov理论对闭环系统进行分析并证明该控制器保证该系统能够在有限时间内镇定, 从仿真实验结果可以看出所设计的控制器在不确定干扰的情况下系统具有良好鲁棒性和未知参数的自适应性, 为能够有效治疗心肌梗死等冠状动脉疾病提供了一定的理论依据.     

Acoustic cluster control of noise radiated from a planar structure

Acoustic cluster control is proposed for the purpose of achieving global sound attenuation of a planar structure. First, acoustic cluster filtering using a point sensor array is presented, which enables the grouping of sound radiated from a target object into a set of clusters, such that each cluster possesses the same common characteristics. This allows the possibility of extracting the cluster of interest without causing observation spillover. Based on the principle of reciprocity, cluster actuation using a point source array is then presented. Driving the source array in accordance with a proposed control law, the excitation of the designated cluster is performed without causing control spillover. Moreover, by combining both acoustic cluster filtering and acoustic cluster actuation, acoustic cluster control may be performed. In implementing acoustic cluster control, the necessary and sufficient condition for the acoustic cluster control is illustrated. It is also shown that the sound radiated from a planar structure may be captured in appropriate acoustic cluster filtering so that acoustic cluster control may be implemented. Experiment was conducted demonstrating the capability as well as the validity of the acoustic cluster filtering, actuation, and control for suppressing the noise radiated from a rectangular panel.     

单向耦合网络连接的Lorenz系统的追踪控制

基于Lyapunov稳定性理论，将单个Lorenz系统的一种追踪控制方案用于单向耦合网络连接的Lorenz系统. 只对网络系统的一个节点加入控制器，就实现了单向耦合网络连接的Lorenz系统的单个输出变量对任意给定参考信号的追踪. 数值仿真表明，当网络的耦合强度足够大时，可以实现包括同结构和异结构系统信号之间的有效追踪. 关键词： Lorenz混沌系统 复杂动态网络 追踪控制 单向耦合     

Analytical results for the cluster size distribution in controlled deposition processes

This paper proposes a controlled particle deposition model for cluster growth on the substrate surface and then presents exact results for the cluster (island) size distribution. In the system, at every time step a fixed number of particles are injected into the system and immediately deposited onto the substrate surface. It investigates the cluster size distribution by employing the generalized rate equation approach. The results exhibit that the evolution behaviour of the system depends crucially on the details of the adsorption rate kernel. The cluster size distribution can take the Poisson distribution or the conventional scaling form in some cases, while it is of a quite complex form in other cases.     

Extremum of the percolation cluster surface

The internal and external surfaces of a percolation cluster, as well as the total surface of the entire percolation system, are investigated numerically and analytically. Numerical simulation is carried out using the Monte Carlo method for problems of percolation over lattice sites and bonds on square and simple cubic lattices. Analytic expressions derived by using the probabilistic approach describe the behavior of such surfaces to a high degree of accuracy. It is shown that both the external and total surface areas of a percolation cluster, as well as the total area of the surface of the entire percolation system, have a peak for a certain (different in the general case) fraction of occupied sites (in the site problem) or bonds (in the bond problem). Two examples of technological processes (current generation in a fuel cell and self-propagating high-temperature synthesis in heterogeneous condensed systems) in which the surface of a percolation cluster plays a significant role are discussed.     

高精密运动工作台控制系统的设计与研究

设计并研制了用于母盘刻录机的高精密运动工作台及其控制系统。工作台控制系统采用线光栅作为工作台位移检测工具。采用数字位置环和模拟电流环组成双闭环随动系统,其中位置控制器是带有速度前馈和加速度前馈的数字PID伺服滤波器。实验结果表明,该系统可以满足母盘刻录机的要求。     

CSNS反角白光中子源束线控制系统研制

中国散裂中子源(CSNS)反角白光中子源束线主要由中子束窗、中子开关、中子准直器和真空管道等组成。为了保证CSNS反角白光中子源束线安全、稳定、可靠地运行,研制了基于EPICS(Experimental Physics and Industrial Control System)软件架构的控制系统。该系统主要由中子束窗、中子开关及中子准直器的运动控制系统、真空控制系统和控制室三部分组成,实现了对反角白光中子源束线主要设备的远程监测和控制。测试结果表明,该系统具有稳定可靠性高、人机交互友好的特点,很好地满足了反角白光中子源束线运行的需要。     

Laser pulse control of ultrafast electron transfer reactions

The optimal control (OC) scheme for molecular dynamics is applied to the study of ultrafast bridge mediated electron transfer (ET). Utilizing the methods of dissipative quantum dynamics in combination with the OC approach the guided charge motion in a donor-bridge-acceptor system including a single active vibrational coordinate is studied. The control field drives the optical transition from the electronic ground-state of the ET system into the donor-level and can be used to prepare special electronic and vibrational states. In particular, it is demonstrated that charge localization becomes possible at the acceptor or bridge molecule as well as in the electronic ground-state of the ET system. Received 30 August 2000 and Received in final form 25 October 2000     

基于DSP的激光陀螺稳频回路设计及其参数整定

针对某小型化激光陀螺,对基于TMS320F2810数字信号处理芯片（DSP）的激光陀螺交流抖动稳频回路设计及其参数整定进行了理论分析、Matlab数值仿真和实验研究。TMS320F2810这款芯片具有集成度高、处理速度快、功耗低和性价比高等突出优点,有利于实现激光陀螺控制系统的小型化。基于这款DSP芯片实现了某小型化激光陀螺的交流抖动稳频回路的软、硬件设计,使用衰减曲线法得到了该型激光陀螺经优化后的PID控制参数（Kp=0.048,Ki=0.059,Kd=0.013）,并根据国军标对稳频回路进行了实验验证。实验结果表明,稳频控制回路经过PID参数整定后,该小型化激光陀螺的零偏稳定性从0.025/h降到0.014/h,该稳频控制回路在目标型号激光陀螺上满足预期的性能指标要求。     

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介绍了HL-2A等离子体密度反馈控制系统的设计和实现。从密度反馈控制系统的设计原理、硬件设计和软件设计几方面,论述了等离子体密度反馈系统在HL-2A装置上的实现。实验证明,该系统实现了维持稳定可靠的密度波形的要求。     

Molecular dipole static polarisabilities and hyperpolarisabilities of conjugated oligomer chains calculated with the local π-electron coupled cluster theory

A new semi-empirical π-electron local coupled cluster theory has been developed to calculate static dipole polarisabilities and hyperpolarisabilities of extended π-conjugated systems. The key idea of the approach is the use of the ethylene molecular orbitals as the orbital basis set for π-conjugated compounds (the method is termed the Covalent Unbonded Molecules of Ethylene method, cue). Test calculations of some small model organic conjugated compounds demonstrate high accuracy of the version of the cue local coupled cluster theory developed in this work in comparison with the π-electron full configuration interaction (FCI) method. Calculations of different conjugated carbon-based oligomer chains (polyenes, polyynes, polyacenes, polybenzocyclobutadiene, etc.) demonstrate fast convergence (per π-electron) of the polarisability and hyperpolarisability values in the calculations when more classes of orbital excitations are included in the coupled cluster single and double (CCSD) excitation operator. The results show qualitatively correct dependence on the system size.     

Predictive control of a chaotic permanent magnet synchronous generator in a wind turbine system

This paper investigates how to address the chaos problem in a permanent magnet synchronous generator(PMSG)in a wind turbine system.Predictive control approach is proposed to suppress chaotic behavior and make operating stable;the advantage of this method is that it can only be applied to one state of the wind turbine system.The use of the genetic algorithms to estimate the optimal parameter values of the wind turbine leads to maximization of the power generation.Moreover,some simulation results are included to visualize the effectiveness and robustness of the proposed method.     

Sinusoidal reference strategy for adaptive feedforward vibration control: numerical simulation and experimental study

A new control approach named Sinusoidal Reference Strategy is developed for adaptive feedforward structural control. In this approach, the recursive-least-squares algorithm is used and a higher frequency sinusoidal signal is utilized as the reference signal. The present approach is able to overcome some of the shortcomings of the conventional adaptive feedforward control. Numerical simulations are then conducted on reducing wind-induced vibrations of the JIN MAO Building in Shanghai, China, with a height of 420 m. A multiple-degree-of-freedom (m.d.o.f.) aeroelastic model of a general super-tall building and an active mass damper (AMD) actuator are designed and manufactured. Wind tunnel tests are carried out to investigate further the control efficiency and robustness of the present approach. Both the simulation and experimental results show that the approach can reduce vibration of super-tall buildings remarkably, and can adapt to dynamic uncertainties and modelling errors of the buildings.     

Autoimmune control of lesion growth in CNS with minimal damage

Lesions in central nervous system (CNS) and their growth leads to debilitating diseases like Multiple Sclerosis (MS), Alzheimer’s etc. We developed a model earlier [1, 2] which shows how the lesion growth can be arrested through a beneficial auto-immune mechanism. We compared some of the dynamical patterns in the model with different facets of MS. The success of the approach depends on a set of control parameters and their phase space was shown to have a smooth manifold separating the uncontrolled lesion growth region from the controlled. Here we show that an optimal set of parameter values exist in the model which minimizes system damage while, at once, achieving control of lesion growth.