Stability analysis of a noise control system in a duct by using delay differential equation

The paper deals with the criteria for the closed- loop stability of a noise control system in a duct. To study the stability of the system, the model of delay differential equation is derived from the propagation of acoustic wave governed by a partial differential equation of hyperbolic type. Then, a simple feedback controller is designed, and its closed- loop stability is analyzed on the basis of the derived model of delay differential equation. The obtained criteria reveal the influence of the controller gain and the positions of a sensor and an actuator on the closed-loop stability. Finally, numerical simulations are presented to support the theoretical results.

对称故障下变流器控制对差动保护影响及优化策略

变流器输出故障特征的强可控性给交流系统继电保护带来了严峻挑战。该文分析并网线路发生对称故障时跟网型变流器的控制响应过程,从故障期间变流器电流控制目标不能自动匹配故障回路功率需求的角度,分析推导变流器网侧电压相位发生跳变并不断旋转的变化特征。受故障回路阻抗约束,变流器输出短路电流相位与网侧电压相位同步变化,造成并网线路差动保护性能严重下降。基于变流器网侧电压相位变化机理,从电流控制目标与锁相环控制两个维度,提出兼顾保护需求和供电需求的变流器控制优化策略。仿真结果表明,并网线路对称故障时所提策略能有效抑制两侧电流相位差,显著提升了差动保护动作性能。

复杂干扰下的管沟机器人内外环滑模自抗扰控制

管沟机器人是一种运行在排水管道,公路排水渠的欠驱动差分移动机器人,针对管沟机器人在实际环境中受到的复杂环境干扰,为了使管沟机器人具有更好的运动控制性能,提出了一种内外环的滑模自抗扰控制方法;首先对管沟受到的复杂环境干扰进行分析,将管沟机器人受到的复杂环境干扰解耦成横向和纵向干扰,建立出在干扰情况下的运动学模型;依据理想运动学模型建立出外环的滑模控制器,得出理想控制律,依据干扰运动学模型建立扩张状态观测器,观测出环境干扰数值,从而建立内环的滑模控制器,利用观测值修正外环的理想控制律;同时利用Lyapunov稳定性原理对系统进行分析,最后搭建了Matlab的Simulink模型进行仿真验证,最终证明了所提出的方法具有较强的鲁棒性和运动控制性能。

一种喷口控制的多目标约束设计方法

为克服试凑法在控制回路参数优化中的局限性,针对涡扇发动机在加力状态易出现喷口摆动的不协调现象,考虑喷口双环控制结构工作特点,采用按需正向设计策略,按照控制系统时域、频域性能指标设计要求,制定兼顾频域、时域性能要求的内、外环协调控制的设计目标准则,提出一种喷口控制的多目标约束的差分进化内外环控制参数自整定优化设计方法,在双转子涡扇发动机非线性模型上进行闭环控制系统仿真验证。结果表明:在飞行高度从0增加到10 km、飞行马赫数从0加速到0.9的起飞和爬升状态进入加力过程以及平飞中保持飞行马赫数不变的关断加力过程中,发动机未出现喷口摆动等现象,涡轮落压比最大相对误差不大于1.5%,喷口闭环控制系统具有期望的伺服跟踪和抗飞行条件变化干扰能力。

基于硬件在环的双挂汽车列车高速横向稳定性控制研究

针对双挂汽车列车在高速超车工况的横向失稳、挂车折叠和甩尾等危险情况,提出了一种基于模糊比例、积分、微分(Proportion、Integral、Differential,PID)控制的直接横摆力矩差动制动控制策略,分别以双挂汽车列车TruckSim非线性模型与四自由度线性模型的质心侧偏角、横摆角速度的偏差及其偏差变化率为目标,设计了2种差动制动的横向稳定性控制策略,分别为仅牵引车控制的单控模式和牵引车加挂车都控制的多控模式,通过MATLAB/Simulink软件和TruckSim软件联合仿真以及硬件在环(Hardware-in-the-Loop,HIL)平台对控制策略的有效性进行仿真验证。结果表明:在高速超车工况下,相较于无控制车辆和单控模式车辆,多控模式车辆的横向稳定性控制系统更能降低车辆的质心侧偏角、横摆角速度、铰接角和车辆后部放大(Rearward Amplification,RWA)系数,在改善双挂汽车列车横向稳定性方面优势明显。

带执行机构的恒压差控制系统稳定性研究

基于某型航空发动机加力燃油调节器的恒压差控制系统,推导出带执行机构的恒压差控制装置的动态数学模型(状态空间形式),得到其传递函数,并利用Simulink建立仿真模型,根据模型求取闭环零极点图,提取了影响压差控制系统稳定性的6个参数,包括节流嘴直径、压差控制活门和压差执行活门节流孔面积梯度、压差控制活门和压差执行活门阀芯面积,并研究了其对系统稳定性的影响。通过合理的元件试验方案进行试验验证,最终确定此恒压差控制装置的数学模型仿真结果可以作为恒压差控制装置动态稳定性分析以及设计的依据。

闭环变风量控制系统在实验室通风系统中的应用

变风量控制系统在实验室建设中被广泛应用,有助于提升实验室的安全性和实现节能减排的目标。但由于排风柜面风速、实验室静压差、管道静压测量易受传感器安装位置、安装方式、气流扰动等因素的影响,给基于闭环控制方式的实验室变风量控制系统的设计与应用带来了挑战。文章从系统控制原理、性能影响因素出发,以变风量控制系统在某化学实验室中的应用为研究对象,采用数值模拟方法对实验室压力分布、速度分布、空气龄等核心参数进行验证。结果表明,基于性能影响对策优化后的化学实验室气流组织良好,满足排风柜设计使用和实验室化学暴露控制要求。

State Feedback Control for a Class of Fractional Order Nonlinear Systems

Using the Lyapunov function method, this paper investigates the design of state feedback stabilization controllers for fractional order nonlinear systems in triangular form, and presents a number of new results. First, some new properties of Caputo fractional derivative are presented, and a sufficient condition of asymptotical stability for fractional order nonlinear systems is obtained based on the new properties. Then, by introducing appropriate transformations of coordinates, the problem of controller design is converted into the problem of finding some parameters, which can be certainly obtained by solving the Lyapunov equation and relevant matrix inequalities. Finally, based on the Lyapunov function method, state feedback stabilization controllers making the closed-loop system asymptotically stable are explicitly constructed. A simulation example is given to demonstrate the effectiveness of the proposed design procedure. © 2014 Chinese Association of Automation.

A Video Game Based on Optimal Control and Elementary Statistics

The video game presented in this paper is a prey-predator game where two preys (human players) must avoid three predators (automated players) and must reach a location in the game field (the computer screen) called preys’ home. The game is a sequence of matches and the human players (preys) must cooperate in order to achieve the best perform- ance against their opponents (predators). The goal of the predators is to capture the preys, which are the predators try to have a “rendez vous” with the preys, using a small amount of the “resources” available to them. The score of the game is assigned following a set of rules to the prey team, not to the individual prey. In some situations the rules imply that to achieve the best score it is convenient for the prey team to sacrifice one of his components. The video game pursues two main purposes. The first one is to show how the closed loop solution of an optimal control problem and elementary sta- tistics can be used to generate (game) actors whose movements satisfy the laws of classical mechanics and whose be- haviour simulates a simple form of intelligence. The second one is “educational”, in fact the human players in order to be successful in the game must understand the restrictions to their movements posed by the laws of classical mechanics and must cooperate between themselves. The video game has been developed having in mind as players for children aged between five and thirteen years. These children playing the video game acquire an intuitive understanding of the basic laws of classical mechanics (Newton’s dynamical principle) and enjoy cooperating with their teammate. The video game has been experimented on a sample of a few dozen children. The children aged between five and eight years find the game amusing and after playing a few matches develop an intuitive understanding of the laws of classical me- chanics. They are able to cooperate in making fruitful decisions based on the positions of the preys (themselves), of the predators (their opponents) and on the physical limitations to the movements of the game actors. The interest in the game decreases when the age of the players increases. The game is too simple to interest a teenager. The game engine consists in the solution of an assignment problem, in the closed loop solution of an optimal control problem and in the adaptive choice of some parameters. At the beginning of each match, and when necessary during a match, an assign- ment problem is solved, that is the game engine chooses how to assign to the predators the preys to chase. The resulting assignment implies some cooperation among the predators and defines the optimal control problem used to compute the strategies of the predators during the match that follows. These strategies are determined as the closed loop solution of the optimal control problem considered and can be thought as a (first) form of artificial intelligence (AI) of the preda- tors. In the optimal control problem the preys and the predators are represented as point masses moving according to Newton’s dynamical principle under the action of friction forces and of active forces. The equations of motion of these point masses are the constraints of the control problem and are expressed through differential equations. The formula- tion of the decision process through optimal control and Newton’s dynamical principle allows us to develop a game where the effectiveness and the goals of the automated players can be changed during the game in an intuitive way sim- ply modifying the values of some parameters (i.e. mass, friction coefficient, ...). In a sequence of game matches the predators (automated players) have “personalities” that try to simulate human behaviour. The predator personalities are determined making an elementary statistical analysis of the points scored by the preys in the game matches played and consist in the adaptive choice of the value of a parameter (the mass) that appears in the differential equations that define the movements of the predators. The values taken by this parameter determine the behaviour of the predators and their effectiveness in chasing the preys. The predators personalities are a (second) form of AI based on elementary statistics that goes beyond the intelligence used to chase the preys in a match. In a sequence of matches the predators using this second form of AI adapt their behaviour to the preys’ behaviour. The video game can be downloaded from the website: http://www.ceri.uniroma1.it/ceri/zirilli/w10/.

基于非线性PID的微电网虚拟同步发电机控制

为解决传统虚拟同步发电机(VSG:Virtual Synchronous Generator)电压电流双闭环控制的抗扰动性能差,受系统参数变化及各种不确定影响较大等问题,在建立微电网VSG转动惯量自适应控制模型的基础上,采用一种基于跟踪微分器的非线性PID(Proportion Integration Differentiation)实现电压外环和电流内环的控制,并根据输出信号的反馈值实时调节系统动态响应,从而达到稳定输出的效果。通过仿真验证了基于非线性PID的微电网虚拟同步发电机双闭环控制的正确性和有效性。

基于自适应步长双闭环模型预测控制的主动配电网优化调度

为应对不确定性分布式可再生能源大量接入对主动配电网优化调度带来的挑战,提出一种基于自适应步长双闭环模型预测控制的主动配电网优化调度策略。首先,在常规模型预测控制的基础上建立双闭环反馈机制,通过充分利用主动配电网中各可控资源实时反馈信息,提升系统优化调度的可靠性;其次,在优化调度中动态调整模型预测控制的域参数,设计变步长决策指标以自适应改变时间步长,从而协调优化精度与计算时间的矛盾;然后,基于上述理论建立调度模型,并采用复合微分进化算法进行求解,使系统的运行效益达到最佳。最后通过算例分析,证明了所提策略的可行性和优越性。

基于自抗扰控制技术的起重机位置控制系统研究

在起重机的起吊工作过程中,由于起吊重物的摆动、变幅臂弹性变形等因素引起的未知负载干扰,会导致起重机的位置控制系统稳定性降低。针对这一问题,提出了一种基于自抗扰控制算法的泵阀协同位置控制系统。首先,介绍了液压起重机泵阀协同位置控制系统的组成和原理,建立了系统的数学模型,提出了变幅机构的位置控制策略和具体的控制方法,并设计了一种自抗扰控制器;然后,建立了起重机变幅系统位置控制系统的元件仿真模型,并进行了元件试验,对仿真模型的准确性进行了验证;最后,建立了AMESim和MATLAB联合仿真模型,对自抗扰控制器的位置控制性能和系统稳定性进行了研究。研究结果表明:与传统的PID控制器相比,所设计的自抗扰控制器(基于自抗扰控制算法的泵阀协同位置控制系统)对S型曲线位置跟踪误差减小了1.2 mm;同时,所设计的自抗扰控制器比传统的PID控制器具有更高的稳定性。

逆变器双闭环入网低电流控制方法仿真

为了提高低输入电压逆变器的稳定性以及电能质量,研究双闭环入网电流控制方法。构建低输入电压逆变器数学模型与电压电流微分方程,采用阻抗分析方法分析低输入电压逆变器的稳定性,设定低输入电压逆变器稳定条件;根据分析结果将LCL型滤波器引入电流控制中,设计LCL型滤波器的电感、谐波电容、谐振频率、谐波衰减以及阻尼电阻,通过LCL型滤波器完成低电流控制。仿真结果表明,所提方法的电流跟踪精度高、鲁棒性高、抗谐波能力强,验证了该方法的有效性。

一种低噪声全差分电荷泵型锁相环的实现

采用HHGrace 180 nm CMOS工艺实现了一款低噪声全差分电荷泵型锁相环,可为物理层芯片提供精确且稳定的时钟信号。鉴频鉴相器和分频器采用电流模逻辑电路构成基本单元,提高了锁相环的工作速度;设计了一种改进型差分电荷泵,引入共模反馈使电荷泵输出电压的静态工作点更加稳定,提高了锁相环的相位噪声性能。测试结果表明,该锁相环功耗小于24 mW,芯片面积为510μm×620μm,锁定时间小于2.5μs,相位噪声为-108 dBc/Hz@100 kHz、-113 dBc/Hz@1 MHz。

乙烯裂解炉投退料过程控制回路自愈研究

乙烯裂解反应在投退料过程中,相关控制回路处于非平稳过程。由于非平稳操作过程工艺参数波动较大,并且整个过程需要密切关注每个炉管的出口温度以及进料流量偏差等参数,因此对基础回路的控制性能要求较高。提出了一种控制性能评估方法对投退料过程控制回路在线实时监控,并针对控制性能不良的控制回路在线调整控制器参数,实现了投退料过程控制回路性能自愈,为实现乙烯裂解炉投退料非平稳操作过程自动控制奠定了基础。

窄频差硅基环形陀螺检测闭环控制系统设计

针对窄频差硅基环形波动陀螺动态性能差的问题,提出了一种基于比例积分微分-惯性环节(proportion integral differential-inertial element,PID-IE)的串联式相位校正检测闭环系统控制器。以硅微机械陀螺仪结构运动方程为基础建立了理想的窄频差U形弹性梁硅基环形波动陀螺仪的系统模型。通过对环形陀螺开环工作状态下的系统模型及其外围电路的传递函数和波特图分析,设计了一种基于PID-IE的检测闭环系统控制器。通过对其系统模型及外围电路时域仿真,验证了该检测闭环控制系统的可行性,通过仿真发现,加入该控制器后的陀螺输出稳定时间减少了50%,陀螺检测位移输出减小了2个数量级,基本实现了该陀螺的检测位移抑制。在模拟电路中实现了该检测闭环控制系统后,通过实验测试了陀螺检测闭环控制前后的各项性能指标。通过实验测试发现,实现闭环控制后,陀螺输出稳定时间约为0.15 s,陀螺检测位移在闭环工作状态下比开环工作状态减小了97%,陀螺的标度因数比检测开环提高了10倍,零偏及零偏不稳定性与检测开环相比分别提升了3倍和8倍,且闭环控制系统的工作带宽比开环工作带宽提高了30倍。

Flatness-Based Control in Successive Loops for Unmanned Aerial Vehicles and Micro-Satellites

The control problem for the multivariable and nonlinear dynamics of unmanned aerial vehicles and micro-satellites is solved with the use of a flatness-based control approach which is implemented in successive loops.The state-space model of(i)unmanned aerial vehicles and(ii)micro-satellites is separated into two subsystems,which are connected between them in cascading loops.Each one of these subsystems can be viewed independently as a differentially flat system and control about it can be performed with inversion of its dynamics as in the case of input–output linearized flat systems.The state variables of the second subsystem become virtual control inputs for the first subsystem.In turn,exogenous control inputs are applied to the first subsystem.The whole control method is implemented in two successive loops and its global stability properties are also proven through Lyapunov stability analysis.The validity of the control method is confirmed in two case studies:(a)control and trajectories tracking for the autonomous octocopter,(ii)control of the attitude dynamics of micro-satellites.

基于二自由度PID的三相PWM整流器调压改进策略

基于前端电压源型整流器(voltage source rectifier,VSR)与后端电压源型逆变器(voltage source inverter,VSI)级联的VSR-VSI双三相脉冲宽度调制(pulse width modulation,PWM)变换器已在电梯能量回馈系统中得到广泛应用,但前端三相VSR采用传统比例积分(proportional integral,PI)双闭环控制结构通常存在中端直流母线电压无法兼顾抗干扰性和跟踪性的问题。为此,文中提出一种基于二自由度比例积分微分(proportional integral differential,PID)的三相PWM整流器调压改进策略。首先,阐述基于VSR-VSI双三相PWM变换器级联系统的结构和工作原理,并给出前端三相VSR的传统PI双闭环控制方案及其参数设计过程,分析该方案不能兼具良好的抗干扰性与跟踪性的原因。在此基础上,给出基于二自由度PID的前端三相VSR直流调压优化策略及其参数设计方法。最后,利用软件仿真与实验测试对比结果共同验证了所述三相PWM-VSR直流调压改进策略的有效性与优越性。

新型二阶磁控忆阻器简化模型的设计与验证

忆阻理论的提出极大地推进了混沌系统的发展,丰富了混沌电路的动力学行为。运算放大器因其强大的信号处理能力,成为忆阻器电路模型的重要组成部分。本文基于低功耗差分对构建了一种极简化的运算放大器,该运算放大器将所需晶体管数目减少至2个;以此运算放大器为基础,设计了新型二阶磁控忆阻器的模拟等效电路模型和硬件实验电路。结果表明:激励信号频率增加,斜“8”字形紧磁滞回线的旁瓣面积减小;激励信号幅度增加,斜“8”字形紧磁滞回线的旁瓣面积增加。电路仿真结果与硬件电路实验结果验证了新型磁控忆阻器模型的有效性与设计方法的正确性。

Online differential pressure reset method with adaptive adjustment algorithm for variable chilled water flow control in central air-conditioning systems

Central air-conditioning systems predominantly operate under partial load conditions.The optimization of a differential pressure setpoint in the chilled water system of a central air-conditioning system leads to a more energy-efficient operation.Determining the differential pressure adjustment value based on the terminal user's real-time demand is one of the critical issues to be addressed during the optimal control process.Furthermore,the online application of the differential pressure setpoint optimization method needs to be considered,along with the stability of the system.This paper proposes a variable differential pressure reset method with an adaptive adjustment algorithm based on the Mamdani fuzzy model.The proposed method was compared with differential pressure reset methods with reference to the chilled water differential temperature,outdoor temperature,and linear model based on the adjustment algorithm.The energy-saving potential,temperature control effect,and avoidance of the most unfavorable thermodynamic loop effects of the four methods were investigated experimentally.The results indicated that,while satisfying the terminal user's energy supply demand and ensuring the avoidance of the most unfavorable thermodynamic loop,the proposed adaptive adjustment algorithm also decreased the differential pressure setpoint value by 25.1%—59.1%and achieved energy savings of 10.6%-45.0%.By monitoring the valve position and supply air temperature of each terminal user,the proposed method exhibited suitable online adaptability and could be flexibly applied to buildings with random load changes.