Investigation on the flow control of micro-vanes on a supersonic spinning projectile

Studies have shown that micro-wedge vortex generators(MVG)can effectively control the flow separation of supersonic boundary layer.In order to improve the flight stability of spinning projectile,the original standard 155 mm projectile was taken as an example,and the micro-vanes were mounted at the projectile shoulder to investigate the separation control on the aerodynamic characteristics of projectile.Numerical simulations were performed with the use of DES method for the flow fields of projectiles with and without micro-vanes,and the characteristics of the boundary layer structures and aerodynamic data were compared and discussed.Numerical results show that the micro-vanes can be used to inhibit separation of fluid on projectile surface,and improve the flight stability and firing dispersion of projectile.

Optimal Control Model for the Transmission of Novel COVID-19

As the corona virus(COVID-19)pandemic ravages socio-economic activities in addition to devastating infectious and fatal consequences,optimal control strategy is an effectivemeasure that neutralizes the scourge to its lowest ebb.In this paper,we present a mathematical model for the dynamics of COVID-19,and then we added an optimal control function to the model in order to effectively control the outbreak.We incorporate three main control efforts(isolation,quarantine and hospitalization)into the model aimed at controlling the spread of the pandemic.These efforts are further subdivided into five functions;u1(t)(isolation of the susceptible communities),u2(t)(contact track measure by which susceptible individuals with contact history are quarantined),u3(t)(contact track measure by which infected individualsare quarantined),u4(t)(control effort of hospitalizing the infected I1)and u5(t)(control effort of hospitalizing the infected I2).We establish the existence of the optimal control and also its characterization by applying Pontryaging maximum principle.The disease free equilibrium solution(DFE)is found to be locally asymptotically stable and subsequently we used it to obtain the key parameter;basic reproduction number.We constructed Lyapunov function to which global stability of the solutions is established.Numerical simulations show how adopting the available control measures optimally,will drastically reduce the infectious populations.

Modelling the Optimal Control of Transmission Dynamics of <i>Mycobacterium ulceran</i>Infection

This paper examines optimal control of transmission dynamics of Mycobacterium ulceran (MU) infection. A nonlinear mathematical model for the problem is proposed and analysed qualitatively using the stability theory of the differential equations, optimal control and computer simulation. The basic reproduction number of the reduced model system is obtained by using the next generation operator method. It is found that by using Ruth Hurwitz criteria, the disease free equilibrium point is locally asymptotically stable and using centre manifold theory, the model shows the transcritical (forward) bifurcation. Optimal control is applied to the model seeking to minimize the transmission dynamics of MU infection on human and water-bugs. Pontryagin’s maximum principle is used to characterize the optimal levels of the controls. The results of optimality are solved numerically using MATLAB software and the results show that optimal combination of two controls (environmental and health education for prevention) and (water and environmental purification) minimizes the MU infection in the population.

Receding horizon H_∞ control for discrete-time Markovian jump linear systems

Receding horizon H∞ control scheme which can deal with both the H∞ disturbance attenuation and mean square stability is proposed for a class of discrete-time Markovian jump linear systems when minimizing a given quadratic performance criteria. First, a control law is established for jump systems based on pontryagin’s minimum principle and it can be constructed through numerical solution of iterative equations. The aim of this control strategy is to obtain an optimal control which can minimize the cost function under the worst disturbance at every sampling time. Due to the difficulty of the assurance of stability, then the above mentioned approach is improved by determining terminal weighting matrix which satisfies cost monotonicity condition. The control move which is calculated by using this type of terminal weighting matrix as boundary condition naturally guarantees the mean square stability of the closed-loop system. A sufficient condition for the existence of the terminal weighting matrix is presented in linear matrix inequality （LMI） form which can be solved efficiently by available software toolbox. Finally, a numerical example is given to illustrate the feasibility and effectiveness of the proposed method.

Trajectory tracking control of characteristic model for nonplanar hex-rotor UAV

The nonplanar hex-rotor unmanned aerial vehicle(UAV)has much higher driving property,greater payload capacity and damage tolerance than quad-rotor UAV.It is difficult to design a highperformance controller of easy engineering implementation for strongly coupled nonlinear hex-rotorUAV system.In response to this practical problem,an adaptive trajectory tracking control based oncharacteristic model for nonplanar hex-rotor is studied.Firstly,the dynamic model for the hex-rotorUAV is devised.Secondly,according to dynamic characteristics,environmental characteristics andcontrol performance requirements,the characteristic model of the hex-rotor UAV is constructed.Then,based on the characteristic model,a golden section adaptive controller is designed to realizetrajectory tracking.Furthermore,the stability analysis of the closed loop hex-rotor system is given.Finally,the validity of the proposed trajectory tracking control method adopted in the nonplanar hex-rotor UAV is demonstrated via numerical simulations and hex-rotor prototype experiments.

Study on Quality Control of Drilling Fluid

Drilling fluid is an important construction technique in the drilling engineering.However,because of the influence of present situation of domestic drilling geological,drilling fluid has not yet been paid sufficient attention.During the construction process,there is not enough professional personnel and apparatus,the fluid recipes are in mess,and they can’t meet different kinds of formations,which cause that the efficiency of the drilling work is low and accidents in the hole happens frequently.This passage which is based on the characteristics and principles of quality control in each section of drilling fluid studies on the quality control,the system composition and how to ensure quality in details.It is also hoped to have the certain value and significance for the future quality control of drilling fluid.

Applying Linear Controls to Chaotic Continuous Dynamical Systems

In this case-study, we examine the effects of linear control on continuous dynamical systems that exhibit chaotic behavior using the symbolic computer algebra system Mathematica. Stabilizing (or controlling) higher-dimensional chaotic dynamical systems is generally a difficult problem, Musielak and Musielak, [1]. We numerically illustrate that sometimes elementary approaches can yield the desired numerical results with two different continuous higher order dynamical systems that exhibit chaotic behavior, the Lorenz equations and the Rössler attractor.

基于CNN和LSTM混合网络的直流充电桩功率模块优化

直流充电桩内部功率变化动态性过强,不易捕捉及计算误差过大,提出基于CNN和LSTM混合网络的功率模块优化方法。根据充电桩电路工作原理,得到电路内部各项参数间存在的直接关联,根据该点采用三相电网平衡原理设计电力稳定控制函数,计算满足电压、电流以及功率最稳的调节比例系数,并作为调节点,建立CNN和LSTM混合网络多层次模型,计算有序、无序充放电过程的电力负荷变化,利用调节比例系数按照充电、放电所需功率需求完成优化。实验结果表明,所提方法的充电桩功率稳定,对充电桩的电压偏移量实现有效改善。

构网型变流器:物理本质与特征

全球能源产业变革促进了电力系统电力电子化转型,以新能源为主体的电力电子化电力系统中同步机占比低,系统呈现低惯量、弱阻尼特征,引发了一系列运行问题。构网型变流器本质为电压源,能够主动构建电压频率,为系统提供惯量支撑,有利于改善系统稳定性,是提高新能源主动支撑能力的有效手段,近年来成为研究热点。该文从电力电子化电力系统的运行问题出发,梳理了下垂控制、虚拟同步机控制等典型构网型控制策略的实现原理及内在联系,建立构网型控制策略的统一数学模型;通过类比稳态条件下同步机与构网型变流器的电压频率构建原理,揭示了构网型变流器的物理本质,从电压频率构建、惯量阻尼支撑、同步机制等角度解释了构网型变流器的内涵与特性,可为构网型变流器的稳定与控制提供理论参考。

自动控制原理课程案例式教学研究——以闭环直流调速案例为例

针对自动控制原理课程理论性强、教学内容抽象等问题,以“闭环直流调速案例”为例,探讨了在自动控制原理课程中“案例式教学”的具体实施策略,并给出了案例背景介绍、提出问题、小组讨论、引导答疑以及总结结论等环节的实施过程。与传统教学模式相比,“案例式教学”方法可以帮助学生更好地理解抽象的知识点,提高学生分析和解决问题的能力。

构网型变流器功率同步控制稳定性机理分析

构网型变流器具有“主动构网”能力,可以为电网提供阻尼和频率支撑,但在低阻抗电网下存在稳定性问题。为了研究低阻抗下构网型变流器功率同步控制稳定性机理,首先,建立了体现功率同步动态特性的构网型变流器接入交流电网小信号模型。然后,以功率同步控制为主体,在牛顿动力学体系框架内,建立了构网型变流器接入低阻抗电网的动力学模型,将功率的偏移量分解为同步分量和阻尼分量,用以表征功率同步控制的稳定性。接着,结合模态分析和动力学特性分析,通过研究特征根轨迹和参与因子曲线,以及阻尼分量和同步分量的变化,分析了电网强度和控制参数等对功率同步控制的影响规律,揭示其内在机理。最后,通过构网型变流器接入电网的仿真模型验证了结论的正确性。

基于安全强化学习的电网稳控策略智能生成方法

新型电力系统的“双高”趋势改变了电力系统经典稳定特性,导致稳定机理更复杂,系统稳定模式更多样,因此基于典型运行方式的在线稳定控制策略面临挑战。为解决新型电力系统的功角稳定问题,提出了基于安全强化学习的稳控策略智能生成方法。首先,建立了电力系统稳控问题的含约束马尔可夫模型,归纳并提出了紧急控制切机动作涉及的安全约束。其次,为了提高对于电网暂态响应的时空特征提取能力,构建了基于图卷积层和长短期记忆单元的特征感知网络。然后,为了提高稳控策略智能体的训练效率,提出了基于内嵌领域知识约束的近端策略优化算法稳控策略训练框架。最后,在IEEE 39节点系统和某实际电网中进行测试验证。结果表明,所提方法能够根据系统运行状态和故障响应自适应生成切机稳控策略,其决策效果和效率均优于现有的稳控策略。

弹光调制器相频特性分析与稳定控制技术

针对弹光调制器(Photoelastic Modulator,PEM)在高压驱动下的谐振频率漂移问题,研究了一种基于PEM谐振相位跟踪的稳定控制技术。建立了PEM与其谐振匹配回路的等效电路模型,推导了PEM驱动电压的幅频、相频关系,以及PEM谐振频率与驱动电压谐振相位的关系。搭建了PEM控制系统,以初始谐振频率的反馈电压相位为零相位基准,调节驱动电压将反馈电压相位稳定在相位基准值附近,并随谐振频率的变化修正相位基准值,从而使驱动电压频率始终稳定于PEM谐振频率附近。以1/4波、半波的PEM的相位延迟幅值为例,分别进行了时长60 min稳定控制测试,实验结果表明:(1)PEM工作在1/4波状态时,相位延迟幅值δ0标准偏差σδq=0.0014 rad,最大相对偏差为0.58%;(2)PEM工作在半波状态时,标准偏差σδh=0.0013 rad,最大相对偏差为0.32%。

具有疫苗接种和潜伏期的传染病模型的最优控制分析

建立了具有疫苗接种和潜伏期的传染病最优控制模型,得到了基本再生数R_(0),构造了Lyapunov函数.当R_(0)<1时,无病平衡点是全局渐近稳定的;当R_(0)>1时,地方病平衡点是全局渐近稳定的.利用最优控制理论和Pontryagin原理分析了最优控制策略,使得疾病控制过程中的成本最低.用数值模拟验证了理论结果的正确性.

二十辊轧机辊系耦合振动特性及振动控制

精密极薄带因具备高精度、耐腐蚀、优异表面光洁度等性能,被广泛应用于微制造、微电子等高技术领域。二十辊轧机辊系的耦合振动对极薄带的生产有着重要的影响。考虑到轧制工艺和润滑状态等变化形成非线性轧制界面,建立了一种二十辊轧机辊系耦合动力学模型。应用多尺度法求解主共振和内共振的幅频特性方程,分析了不同参数对幅频特性曲线的影响。基于奇异性理论探究了不同参数与系统分岔的关系。同时,根据李雅普诺夫一次近似稳定性判据,结合系统动相平面相轨迹图,对系统稳定性进行判断分析。然后,基于Washout filter控制器原理设计了一种状态反馈控制器,通过对系统进行状态空间表达式变换,分析了控制增益对幅频特性的影响。利用时域图、相位图、频谱图以及Poincaré截面图进行仿真对比,验证了所设计控制器的可行性和有效性,为二十辊轧机振动及其控制的研究提供了一定的理论指导。

柳赞油田多层砂岩优势渗流通道特征及喉道体积

陆相油藏储集层非均质性强,长期注水开发容易形成优势渗流通道,导致油井快速水淹,驱油效率降低,开发效果变差。以柳赞油田古近系渐新统沙河街组为例,综合分析测井岩电响应、储集层非均质性、注采特征、储集层孔隙特征等,描述柳赞油田多层砂岩优势渗流通道特征,确定了该区优势渗流通道形成条件,通过建立优势渗流通道喉道体积的计算方法,明确了油藏下一步调驱剂用量,达到了有效封堵优势渗流通道的目的,研究成果可为油田下一步稳油控水提供技术支撑。

光栅MOEMS加速度计温度特性

由于硅微机械加速度计受温度影响,导致硅弹性模量和热膨胀系数发生变化,造成微光机电系统(MOEMS)加速度计标度因数漂移、测量稳定性下降等问题。首先,采用COMSOL软件对光栅MOEMS加速度计微机械结构部分进行了温度特性仿真,分析了硅弹性模量温度系数和热膨胀系数对光栅MOEMS加速度计微机械结构标度因数和零位的影响。其次,设计了温控精度达0.1℃的温度控制系统,并利用该系统对加速度计进行温度控制。最后,对光栅泰伯效应MOEMS加速度计温度特性展开测试,结果表明,加速度计的标度因数随温度升高而增大,零偏稳定性随温度的升高而降低,加速度计标度因数温度系数为0.30 V·g^(-1)·℃^(-1),零偏稳定性温度系数为-7.78μg/℃,其变化趋势与仿真结果一致。这为实现全温范围下高精度MOEMS加速度计奠定了基础。

水平井AICD控水阀油水过流特性仿真研究

水平井石油开采过程中容易出现底水突进现象,导致含水率迅速上升,开采周期缩短,严重影响油田采收率。针对一种新型的流道式自动流入控水装置(简称FD-AICD),借助于计算流体力学方法对装置的阻水过油流动行为进行研究,通过多参数影响分析定量评估阀对水平井稳油控水的作用效果。通过实验和数值仿真得到FD-AICD装置对于不同粘性过流液的压降-流量关系,验证数值仿真模型的可靠性。由数值模拟分析内部流道的流动机理,获得水和过油的过流流场特性,通过流体敏感性分析,总结结构参数对FD-AICD控水性能的影响。结果表明:过流压降随流量的增加而增加,过水压降高于过油压降;水相主要通过切向主流道流入环形腔室做高速旋转流动,油相则主要通过径向分支流道流入环形腔室,不经旋转直接流向出口;流量、粘度对压降的影响程度要高于密度;流场深度、出口直径对过流压降有显著影响,而内外圆环挡板角度差的影响不明显。

多次采掘扰动下小煤柱失稳特征及控制技术研究

以某矿7 m小煤柱为研究对象,通过理论分析、相似材料模拟、数值模拟和现场实测等方法发现,一次掘进扰动后,煤柱破坏区宽度为2 m,二次掘进扰动后,煤柱破坏区宽度为2.2 m,一次回采扰动后,煤柱基本已发生完全破坏,二次回采扰动后,破坏程度进一步加剧,提出基于“树形骨架结构”围岩改性的区段小煤柱稳定性控制技术,通过现场试验发现,围岩改性后,顶底板移近量从60 mm/月降低至24 mm/月,且围岩完整性有明显提高,证明可以有效提高小煤柱稳定性。

汽油发动机电控元件检修浅析

汽油发动机电控元件包含传感器、执行器及ECM等。文章详细介绍碳罐电磁阀及节流阀体的工作原理和技术特性,针对常见问题给出故障诊断的相关检修建议,为售后故障分析判断提供帮助。