Realization of the Linear Tree that Corresponds to a Fundamental Loop Matrix

Graph realization from a matrix is an important topic in network topology. This paper presents an algorithm for the realization of a linear tree based on the study of the properties of the number of the single-link loops that are incident to each tree branch in the fundamental loop matrix Bf. The proposed method judges the pendent properties of the tree branches, determines their order one by one and then achieves the realization of the linear tree. The graph that corresponds to Bf is eventually constructed by adding links to the obtained linear tree. The proposed method can be extended for the realization of a general tree.

Analytical solution for a class of linear quadratic open-loop Nash game with multiple players

In this paper, the Nash equilibria for differential games with multiple players is studied. A method for solving the Riccati-type matrix differential equations for open-loop Nash strategy in linear quadratic game with multiple players is presented and analytical solution is given for a type of differential games in which the system matrixcan be diagonalizable. As the special cases, the Nash equilibria for some type of differential games with particular structure is studied also, and some results in previous literatures are extended. Finally, a numerical example is given to illustrate the effectiveness of the solution procedure.

Nonlinear instability suppression of closed-loop pilot-vehicle system with rate-limiting actuator based on anti-windup compensation

To solve the flight safety problem caused by nonlinear instabilities（category II pilot induced oscillations, PIOs） of the closed-loop pilot-vehicle system with rate-limiting actuator, the antiwindup（AW） compensation method to avoid category II PIOs is investigated. Firstly, the AW compensation method originally used for controlling input magnitude limited system is introduced, then this method is extended for controlling input rate-limiting system through a circle criterion theorem. Secondly, the establishment of the AW compensator is transformed into the solving of linear matrix inequalities. Finally, an AW compensator establishment algorithm for the closed-loop pilot-vehicle system with the rate-limiting actuator is obtained. The effectiveness of the AW compensation method to avoid category II PIOs is validated by time-domain simulations,and compared with rate-limited feedback（RLF） command rate compensation method. The results show that the AW compensation method can effectively suppress category II PIOs and maintain the nominal performance when the closed-loop pilot-vehicle system is normal. Unlike the command rate compensator which works upon system uninterruptedly, the AW compensation method affects the closed-loop pilot-vehicle system only when the rate-limiting of actuator is activated, so it is a novel PIO avoidance method.

基于改进Loop细分的二维图像矢量化方法

现有的矢量化方法得到的矢量图缩放不方便,为此,用改进的Loop细分方法实现二维图像矢量化。首先用Douglas-Peucker算法提取图像边界,然后用Delaunay三角剖分算法得到三角网格,最后用改进的Loop细分算法细分三角网格得到矢量图。细分时,对三角网格顶点进行线性细分,对顶点的像素值进行Loop细分,同时,在原有Loop细分规则的基础上,修改网格边界上的三角形内部新点生成规则。实验结果表明:提出的矢量化方法得到的矢量图缩放较为方便。

Stochastic Resonance in a Bistable System with Time-Delayed Feedback Loops

The phenomenon of stochastic resonance of a bistable system subjected to linear time-delayed feedback loops driven by multiplieative Gaussian coloured noise and additive Gaussian white noise is investigated. Firstly, the analytic expression of the quasi-steady distribution function Ps （x, t） is derived by applying the unified coloured noise approximation and the Novikov Theorem; Secondly, the expression of the signal-to-noise ratio （SNR） is obtained in the adiabatic limit to quantify the stochastic resonance. Finally, tile effects of the linear coefficient a, the nonlinear coefficient b, the linear time-delayed feedback coefficient c and the delay time r on Ps（x,t） and SNR^± are discussed. It is found that the effects of the linear coefficient and the nonlinear coefficient, the positive linear time-delayed feedback coefficient and the negative linear time-delayed feedback coefficient, the positive delayed time and the negative delayed time on Ps（x,t） and SNR^± are different, respectively. This discussion would be helpful to the study of the system reliability and controlling stochastic resonance.

High-FM-linearity wideband chirp generator

An S-band wideband chirp generator using specially designed fast lock phase lock loop（FL-PLL） was demonstrated.To realize high linearity,structure of direct digital synthesizer（DDS） plus FL-PLL was used.DDS gives ideal linearity while FL-PLL retains the linearity and provides radio frequency.The system block diagrams were showed and the timing relationships of the components were provided.Two important considerations of the system,wideband loop and wideband voltage control oscillator（VCO）,were discussed;meanwhile,after analyzing the considerations,corresponding solutions were presented.Measurement results show that the generated 2560MHz to 2960MHz chirp reaches a high FM linearity of 0.003%.

弱电网下光伏并网系统锁相环参数自适应控制

针对弱电网下PLL(phase-looked loop,PLL)会使并网逆变器的稳定性下降问题,提出一种锁相环带宽自适应控制策略来实现锁相环参数依据电网实时阻抗值来获得最优的控制参数,保证系统最佳控制性能和稳定运行,从而提升跟网型逆变器在弱电网下的对电网阻抗的适应能力。利用PSCAD/EMTDC进行仿真验证,仿真结果证明自适应控制策略正确、有效。

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.

Noise decomposition algorithm and propagation mechanism in feed-forward gene transcriptional regulatory loop

Feed-forward gene transcriptional regulatory networks, as a set of common signal motifs, are widely distributed in the biological systems. In this paper, the noise characteristics and propagation mechanism of various feed-forward gene transcriptional regulatory loops are investigated, including （i） coherent feed-forward loops with AND-gate, （ii） coherent feed-forward loops with OR-gate logic, and （iii） incoherent feed-forward loops with AND-gate logic. By introducing logarithmic gain coefficient and using linear noise approximation, the theoretical formulas of noise decomposition are derived and the theoretical results are verified by Gillespie simulation. From the theoretical and numerical results of noise decomposition algorithm, three general characteristics about noise transmission in these different kinds of feed-forward loops are observed, i） The two-step noise propagation of upstream factor is negative in the incoherent feed-forward loops with AND-gate logic, that is, upstream factor can indirectly suppress the noise of downstream factors, ii） The one-step propagation noise of upstream factor is non-monotonic in the coherent feed-forward loops with OR-gate logic, iii） When the branch of the feed-forward loop is negatively controlled, the total noise of the downstream factor monotonically increases for each of all feed-forward loops. These findings are robust to variations of model parameters. These observations reveal the universal rules of noise propagation in the feed-forward loops, and may contribute to our understanding of design principle of gene circuits.

单分支线性约束循环程序的终止性分析

秩函数法是循环终止性分析的主要方法,秩函数的存在表明了循环程序是可终止的.针对单分支线性约束循环程序,提出一种方法对此类循环的终止性进行分析.基于增函数法向空间的计算,该方法将原程序空间上的秩函数计算问题归结为其子空间上的秩函数计算问题.实验结果表明,该方法能有效验证现有文献中大部分循环程序的终止性.

集成式电液制动系统自适应压力控制

针对集成式电液制动系统(integrated electro-hydraulic brake system,IEHB)存在的复杂液压非线性特性和时变摩擦干扰,提出一种自适应压力控制策略。外环压力控制器引入液压特性的动态线性化模型并基于滑模观测器对模型参数实时辨识实现对非线性液压特性的自适应。内环伺服控制器采用基于压力的连续摩擦补偿和反步动态面控制应对传动机构摩擦阻碍。硬件在环实验结果表明,与现有的先进级联压力控制相比,设计的压力控制策略在多种工况下均表现出更高的控制精度和鲁棒性,并显著提升了IEHB在不同液压回路结构下的压力控制效果。

采用双二阶广义积分器锁相环的MMC多谐波线性化阻抗建模与分析

与传统单同步坐标系锁相环相比,双二阶广义积分器锁相环(dual ge neralized integrator phase-locked loop,D SOGIPLL)能够在三相电压不平衡、畸变和谐波复杂情况下快速、准确锁相。然而,目前鲜有关于采用DSOGI-PLL的模块化多电平换流器(modular multilevel converters,MMC)阻抗模型。基于多谐波线性化法建立了采用DSOGI-PLL的MMC阻抗模型,并验证了所建立模型的准确性。基于此模型,分析了控制参数对MMC阻抗特性的影响,并对比分析了接入不同强度电网时的系统稳定性。结果表明,与传统锁相环相比,DSOGI-PLL特有的阻尼系数会对MMC阻抗特性产生影响,阻尼系数的减小有利于提高系统稳定性,在其他控制器参数变化或电网强度变化导致并网MMC不稳定时,可通过减小阻尼系数使系统达到稳定状态。

Robust H_∞ Stabilization of Uncertain Linear Time-Delay System with Delayed/Undelayed State Feedback Controllers

This paper focuses on the H∞ controller design for linear systems with time-varying delays and norm-bounded parameter perturbations in the system state and control/disturbance. On the existence of delayed/undelayed full state feedback controllers, we present a sufficient condition and give a design method in the form of Riccati equation. The controller can not only stabilize the time-delay system, but also make the H∞ norm of the closed-loop system be less than a given bound. This result practically generalizes the related results in current literature.

基于频率变化率的被动式孤岛检测方法

为解决目前传统被动式孤岛检测方法精度低、检测盲区较大的问题,通过分析孤岛前后公共耦合点频率变化规律,提出了一种基于频率变化率的新型孤岛检测方法。锁频环控制通过无功功率负反馈实现对电网频率的跟踪,采用局部加权线性拟合算法对频率变化曲线进行拟合,求取频率拟合曲线斜率后,利用斜率曲线的波动变化来检测出孤岛的发生。Matlab/Simulink仿真结果表明,该方法能够在各种情况下准确地检测孤岛效应,消除检测盲区,且适用性强。

基于改进一阶LADRC光伏逆变器母线电压控制

两级式光伏逆变器的中间直流母线电压的稳定性是光伏逆变器良好的发电质量和长期运行的关键。光伏逆变器的发电功率易受到光照强度、温度等环境因素的影响,该功率波动会在直流母线电压上产生较大扰动。为了提升直流母线电压的抗扰性,改善逆变器的控制性能,提出了一种基于改进一阶线性自抗扰控制(LADRC)的光伏逆变器母线电压控制策略。采用改进一阶LADRC对逆变器双环控制中的电压外环控制器进行设计。在传统LADRC的线性扩张状态观测器的基础上,将状态变量表达式中系统控制量的分量去除,使得状态变量的观测误差方程中只含有与系统输入量相关的误差分量,减小了状态变量的观测误差。新增状态变量并引入前一控制周期的系统控制量,根据总和扰动表达式对总和扰动重新进行估计并补偿。在频域上对改进LADRC的控制性能进行分析,相较传统LADRC而言,改进LADRC的系统带宽增大,动态跟踪能力增强,在中低频段具有更小的扰动增益。仿真和试验表明改进LADRC具有更短的调节时间,系统动态性能具有较好的提升,直流母线电压的抗扰性增强。

中型无人直升机内环控制器的设计与实现

针对某中型无人直升机对内环控制的特殊需求,考虑模型参数不确定以及各种扰动对无人直升机控制的影响,设计一种基于线性自抗扰的内环控制系统,实现无人直升机控制系统对不确定扰动的抑制。介绍无人直升机动力学建模、稳定性分析、内环控制器设计与仿真验证的一整套设计流程。结果表明:所设计的内环控制器能够满足技术需求,有很好的抗扰效果,达到了预期的研究目标。

基于Kent映射的数字集群动态负载均衡算法研究

由于动态负载均衡是保证数字集群系统正常运行中不可缺少的环节,但其在控制过程中存在易受通信故障等因素的干扰问题,为此提出基于Kent映射的数字集群动态负载均衡算法。通过基于云平台的虚拟机系统采集数字集群的节点连接数、响应时间、动态负载等信息,分析数字集群系统的负载情况。其次构建数字集群资源利用率模型,通过基于Kent映射的灰狼算法对模型求解得到数字集群的资源利用率。最后将资源利用率输入LQR(Linear Quadratic Regulator)控制回路器中,通过控制服务器的迁移实现数字集群的动态负载均衡。实验结果表明,所提算法处理后的数字集群响应时间短、适应度值大、容错能力强。

一种基于双环LADRC的混合储能变换器控制方法

混合储能变换器可以帮助提升光伏发电系统的动态响应能力和稳定性,但传统线性控制器在执行双向DC-DC变换器控制时表现不足。针对直流母线电压易受变换器非线性噪声、光伏输出功率和负载扰动影响的问题,设计了一种基于双环LADRC的混合储能变换器控制策略。通过分析混合储能变换器主电路的工作原理,建立了主电路的扰动模型。基于扰动模型完成了对电压-电流双环LADRC控制器的设计,并结合功率分频实现了混合储能变换器的整体控制策略。仿真结果表明,与传统比例积分控制器相比,基于双环LADRC的混合储能变换器控制策略使母线电压幅值波动减小了39.4%,调节时间减少了25.0%,在功率响应和直流母线电压支撑方面表现出优越的动态响应和抗扰能力。

基于线性自抗扰的伺服电缸反向间隙控制

针对伺服电缸加载过程中出现的反向间隙问题,提出了线性自抗扰控制器(LADRC)的解决方案。搭建全闭环伺服电缸控制系统试验平台,完成位置环PID控制器控制下,反向间隙的测量;以伺服电缸控制系统位置环为控制对象,通过MATLAB/Simulink仿真和试验分析,将线性自抗扰控制器与位置环PID控制器进行对比。研究表明,相比较PID控制器,线性自抗扰控制器在阶跃信号和正弦信号作用下,调节时间短、超调量小,动态跟踪误差下降明显。针对伺服电缸存在的反向间隙造成的输出滞后问题,线性自抗扰控制器性能优于PID控制器,更加满足压装工艺的需求。

基于模糊控制的PWM整流器电压调速策略

针对三相脉宽调制(pulse width modulation,PWM)整流器控制系统的直流侧电压响应速率问题,提出一种基于模糊控制的电压快速响应控制策略.建立PWM整流器在qd坐标系下的数学模型,并进行欠驱动特性分析和控制策略研究,设计级联双闭环控制结构.利用部分反馈线性化策略,设计电流内环控制器,为提升直流侧电压响应速度,提出电压外环模糊控制策略.所提控制策略能够在0.05 s实现稳定,功率因数达到了0.99,提升了系统抗扰动能力,仿真结果证明了所设计控制方案的有效性.