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.

Open-plus-closed-loop control for chaotic motion of 3D rigid pendulum

An open-plus-closed-loop （OPCL） control problem for the chaotic motion of a 3D rigid pendulum subjected to a constant gravitationM force is studied. The 3D rigid pendulum is assumed to be consist of a rigid body supported by a fixed and frictionless pivot with three rotational degrees. In order to avoid the singular phenomenon of Euler＇s angular velocity equation, the quaternion kinematic equation is used to describe the motion of the 3D rigid pendulum. An OPCL controller for chaotic motion of a 3D rigid pendulum at equilibrium position is designed. This OPCL controller contains two parts： the open-loop part to construct an ideal trajectory and the closed-loop part to stabilize the 3D rigid pendulum. Simulation results show that the controller is effective and efficient.

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.

船用柴油机SCR系统控制策略试验研究

为降低船用柴油机NO_(x)排放,分析柴油机选择性催化还原(selective catalytic reduction,SCR)后处理系统的开环、闭环控制策略,对不同策略及工况下NO_(x)转化率及NH3泄露进行试验对比。结果表明:采用开环策略,柴油机功率与额定功率的比为75%以上时,NO_(x)转化效率可达到83%,但不同工况下NO_(x)转化率波动超过20%;采用闭环控制策略,不同工况下NO_(x)转化率稳定在85%左右,尾气中NH_(3)的体积分数低于20×10^(-6);闭环控制策略下NO_(x)转化率具有自调整、高稳定性、响应速度快等优势,可降低NO_(x)排放且尾气中NH3的体积分数在规定范围内。

海上换流站的控制方法研究

柔性直流输电工程所含元器件较多,控制方式比较复杂,在运行中易发生高频震荡等问题。为了防止高频震荡导致风电解列和系统崩溃,本文分析讨论了海上柔直工程采用的开、闭环转换策略和开、闭环转换的时机。实践表明,采用阻尼振荡高频谐振抑制策略使得系统在开、闭环转换过程中不会发生高频谐振,增强了系统的稳定性。

有源电力滤波器补偿的PI解耦控制技术研究

电网中电压和电流波形的失真会产生谐波,导致电网功率因数降低,并影响电力系统的稳定性和可靠性。为了确保电力系统的正常工作,研究了基于有源电力滤波器补偿的比例积分(PI)解耦控制技术。设计了基于二极管钳位式的有源电力滤波器模型。结合基尔霍博电压法,降低控制谐波和解除部分变量耦合。针对设备非线性产生的谐波,分析有源电力滤波器的可逆性,获得输入雅可比矩阵,以实现滤波器旋转坐标的线性化。利用变换矩阵转换转动角速向量,输入谐波的幅度,输出电流取样延迟,完成无差PI解耦控制。试验结果表明,所提技术能够有效解耦滤波器的谐波电流成分,从而补偿电网中的失真电流。该技术可以减少谐波对电力系统的整体影响,保证设备的正常运行。

光伏场经柔直并网振荡稳定性分析与抑制方法研究

光伏场经柔直送出是未来电力系统发展的一个重要趋势,但是光伏与柔直系统之间的相互作用存在引发系统振荡失稳的风险。为此,文中建立光伏场经柔直并网的开环和闭环互联模型,基于开环模式谐振理论,分析光伏场子系统与柔直子系统之间的动态交互作用。当二者发生强交互作用时,可能会使相应的闭环振荡模式进入复平面右侧,进而引发系统振荡失稳。针对光伏场子系统与柔直子系统之间的交互失稳风险,可以通过调整主导环节的控制参数进行抑制;当控制参数无法调整时,文中提出一种对光伏单元附加阻尼控制器的抑制措施,调整光伏场子系统的开环振荡模式,使其在复平面远离柔直子系统的开环振荡模式,从而破坏模式谐振,使闭环系统稳定。文中通过仿真算例,验证了上述理论分析结果的正确性以及所提阻尼控制器的有效性。

断路器分合闸线圈烧毁的原因分析及改进方法研究

针对断路器分合闸操作过程中线圈烧毁现象,从断路器操作机构以及控制回路工作原理着手,分析得出分合闸线圈烧毁的根本原因为线圈长时间带电。对此提出了多种改进方法,经过比对确定非接触测量为最优方法。该方法可以在不拆卸操作机构器件、不更改控制回路的条件下完成对分合闸线圈运行情况的监测与评估,实现实时保护及提前预测。

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.

Energy-Efficient Optimal Guaranteed Cost Intermittent-Switch Control of a Direct Expansion Air Conditioning System

To improve the energy efficiency of a direct expansion air conditioning(DX A/C) system while guaranteeing occupancy comfort, a hierarchical controller for a DX A/C system with uncertain parameters is proposed. The control strategy consists of an open loop optimization controller and a closed-loop guaranteed cost periodically intermittent-switch controller(GCPISC). The error dynamics system of the closed-loop control is modelled based on the GCPISC principle. The difference,compared to the previous DX A/C system control methods, is that the controller designed in this paper performs control at discrete times. For the ease of designing the controller, a series of matrix inequalities are derived to be the sufficient conditions of the lower-layer closed-loop GCPISC controller. In this way, the DX A/C system output is derived to follow the optimal references obtained through the upper-layer open loop controller in exponential time, and the energy efficiency of the system is improved. Moreover, a static optimization problem is addressed for obtaining an optimal GCPISC law to ensure a minimum upper bound on the DX A/C system performance considering energy efficiency and output tracking error. The advantages of the designed hierarchical controller for a DX A/C system with uncertain parameters are demonstrated through some simulation results.

Controlling Chaotic Cscillations with Input-Output Linearization

In this paper, the nonlinear control of chaotic oscillations was investigated by using the input output linearization control method. The chaotic attitude of a kind of spacecraft was discussed. It is demonstrated that the input output linearization control law is the nonlinear version of the parametric open plus closed loop control law.

单片机稳恒控制半导体激光器功率研究

为了提高半导体激光器的整体性能,需要对其功率稳定性控制方法展开研究,提出一种利用单片机实现半导体激光器功率稳恒控制的方法,该方法设计了定功率闭环控制电路和定电压开环控制电路,在半导体激光器运行过程中利用上述电路实现闭、开环控制,通过脉冲电源控制半导体激光器中的脉冲电流,在此基础上利用ATmega16单片机调整电路电流,划分半导体激光器的输出功率区域,在不同区域中利用PID控制器展开功率稳恒控制。实验结果表明,所提方法的激光功率稳定度高、抗干扰性强、功率控制效果好。

A Design of a PID Self-Tuning Controller Using LabVIEW

In this paper a trial has been made to design a simple self-tuning LabVIEW-based PID controller. The controller uses an open-loop relay test, calculates the tuned parameters in an open loop mode of operation before it updates controller parameters and runs the process as a closed-loop system. The controller reacts on a persistent offset error value as a result of load disturbance or a set point change. Practical results show that such a controller may be recommended to control a variety of industrial processes. A GUI was developed to facilitate control-mode selection, the setting of controller parameters, and the display of control system variables. GUI makes it possible to put the controller in manual or self-tuning mode.

虚拟现实在实验动物行为分析中的应用进展

虚拟现实(virtual reality,VR)是一种通过计算机进行场景模拟的新兴技术,近年来已经成为动物行为分析的可靠工具。动物行为对动物生存至关重要。动物行为分析为遗传学、生态学、神经科学、经济学以及机器人科学等领域的科技进步提供了有用信息。动物行为分析可分为刺激独立于动物对刺激的反应的开环研究,以及刺激根据动物的实时运动进行调整的闭环研究。本文首先梳理了动物行为分析的起源、概念和应用领域,回顾了传统技术条件下以视觉刺激为代表的动物行为开环研究的不足;然后以视觉、嗅觉、触觉、听觉刺激为例,分析了虚拟现实技术条件下的动物行为分析系统能够将精确的实验控制与复杂的实验动物行为相结合的可行性,完成了真实物理世界的实验方法无法实现的闭环研究;最后对虚拟现实发展为高级模拟及虚拟动物的前景进行了展望。

基于Arduino的数控机床改造控制系统设计

为实现对现有设备的循环利用,基于Arduino平台完成了开环控制器的研究与开发,对现有数控机床执行简单的改造。以Objet Quadra Tempo 3D打印机为数控机床改造对象,通过现有的低成本组件及开源软件,对因维护成本高而被视为过时的设备进行改装,以降低电子及工业废物数量。采用ArduinoMega 2560单片机对步进电动机驱动器进行控制。Arduino微控制器可通过简单的方式控制模拟和数字设备。改造过程中,安装了用于加工木材和聚碳酸酯材料的电主轴,实现了通过低成本部件将3D打印机改造为可加工木材及聚碳酸酯等材料的数控铣床。

一种减小城轨列车EMB制动冲击的控制方法

在轨道交通行业,电子机械制动(Electromechanical Brake,EMB)系统是一种通过电机驱动机械传动机构输出可控制动力的制动系统。在传统控制方案下,制动夹钳使用寿命较短,且制动响应时长不理想,根本原因是系统通信时间间隔较大、制动冲击未得到有效控制等。针对上述问题,提出一种开环控制方案,采用精简指令实现在规定响应时长内减小冲击的目标,并利用MATLAB/Simulink对制动过程进行建模与仿真。通过比较不同控制方案下的仿真结果,探讨开环控制方案对减小制动冲击的可行性。

具有丢包补偿的GORC-PID算法无线温度控制系统

对于工业过程控制中有线控制存在的布线困难、可拓展性差、维护成本高等问题,本文设计并开发了具有丢包补偿GORC-PID(generalized open-loop response control-PID)算法的无线温度控制系统。以工业上通用的WirelessHART为标准协议,使用无线硬件设备搭建无线通信网络,替代有线通信方式,并以监视与控制通用系统(monitor and control generated system, MCGS)组态软件为控制平台,采用改进的广义开环响应控制(generalized open-loop response control, GORC)与PID控制相结合的控制算法,通过构建的具有丢包补偿的Smith预估器对丢包数据进行估计,得出补偿的估计值,并参与GORC滚动优化中,来实现对温度的实时监测与控制。以高温炉作为研究对象进行实验,结果表明所设计的无线温度控制系统不仅可以有效解决有线过程控制中存在的问题,而且可以解决无线通信过程中的丢包、迟滞等问题,具有良好的工业价值。

基于线性遗传规划的航空发动机NO_(x)排放开环控制

传统航空发动机减排方法主要优化发动机空间结构,这使得其结构变得很复杂,且面临回火、燃烧不稳定、宽范围适应性差等诸多问题。本文使用基于线性遗传规划在时域上调制燃料流量的方法来实现NO_(x)排放控制。实验基于双旋流的单头部燃烧室,搭建了开环控制实验系统;使用线性遗传规划算法对中心燃料控制律进行迭代优化;最后结合机器学习,分析了控制律的优化过程。结果表明:线性遗传规划算法通过对重要搜索路径的选取来获得最优控制律,在最优控制律下,NO_(x)排放量相较于无控制状态有效下降了43.1%。