An Improved Frequency Synchronizer for Mobile OFDMSystems

1IntroductionOrthogonal Frequency Division Multiplexing(OFDM) hasgained strong position in the next generation widebandwireless systems for its advantages over frequency-selec-tive fading channels . The principal weakness of OFDMis its sensitivity to Carrier Frequency Offset ( CFO)caused by Doppler drifts and/or oscillator instabili-ties[1 ~3]. Many frequency synchronization algorithmsfor OFDM have been proposed, which can be dividedinto three main categories .First groupis based on s…     

Optimal trajectory planning for robots under the consideration of stochastic parameters and disturbances

Efficient control strategies of robots should cause only low on-line correction expenses. Hence, the mostly available statistical and a priori informations about the random parameters and disturbances of the underlying mechanical system and its environment should be considered already for off-line programming of robots. Measuring the violations of the basic mechanical conditions by means of expected penalty costs, a stochastic optimization problem is obtained for the computation of an optimal open-loop control. The stochastic optimization problem can be solved — after discretization — by parameter optimization.     

用单片机控制多路萃取试剂流量

提出了一种由单片机控制的萃取试剂流量控制系统。该系统采用定容式计量腔,以时间作为控制变量,具有结构简单、制作要求不高、易满足耐腐蚀要求、不需机械动力和停电自动阻断试剂的特点。     

两相混合式步进电动机开环矢量细分控制系统

该文构建了两相混合式步进电动机的开环矢量细分驱动控制系统,运用DSP芯片从软件角度实现所有算法,产生脉宽调制波来控制两相H桥的开通,以此来控制两相绕组中的电流,根据DSP产生PWM的原理,对其进行了死区补偿。文中详细阐述了系统的原理、组成构架和实现方案,实验结果表明,该系统具有运行稳定、控制简单等特点。     

用于索承结构中斜拉索开环振动控制的磁流变阻尼器设计

斜拉索被广泛应用于索承结构,如大跨度桥梁或屋盖结构等.由于极低的内在阻尼,斜拉索易发生因其支承的运动或天气状况影响而引起的大幅值的振动.这些振动可以危及斜拉索本身以及整个索承结构的安全与寿命,甚至引起人们对该类结构信心的降低.在斜拉索减振的诸多方法中,采用磁流变阻尼器的智能阻尼技术近来引起了人们的研究兴趣.该阻尼器的阻尼特性可以通过调节(控制)磁场的输入电流/电压而改变,从而实现在不同振动(频率及幅值)情况下的最优或次优减振效果.本文发展了一个数学模型用于评价在开环控制状态下斜拉索-阻尼器系统的阻尼比.该模型考虑了阻尼器的安装高度、阻尼系数、刚度、质量、支撑刚度、磁变阻尼力以及斜拉索的垂度与倾角等因素,推导出了一个‘广义的通用公式’用于阻尼器参数的设计与优化,即寻求可提供系统最大阻尼比的最佳阻尼器参数.本文以目前世界最长斜拉桥——苏通大桥的最长斜拉索为例,确定了能够提供足够的阻尼以抑制风雨振的阻尼器安装高度以及相应的阻尼器参数.     

TCP/IP拥塞控制算法研究

TCP/IP拥塞控制的研究是计算机网络最活跃的领域之一,其目的是解决TCP/IP拥塞控制所面临的自相似性问题、效率问题、公平性问题。文中从控制理论角度对开环与闭环控制拥塞模式进行了阐述,从造成TCP/IP拥塞原因入手,并对其相应的策略做出改进,此外还对闭环拥塞控制的基本策略：许可控制、依赖路由选择、隐式拥塞信令、显式拥塞信令及抑制包策略进行了分析并提出了相应的抑制包策略改进方法,并取得了很好的成效。     

Real-time edge-enhanced dynamic correlation and predictive open-loop car-following control for robust tracking

We present a robust framework for a real-time visual tracking system, based on a BPNN-controlled fast normalized correlation (BCFNC) algorithm and a predictive open-loop car-following control (POL-CFC) strategy. The search for the target is carried out in a dynamically generated resizable search-window. In order to achieve the robustness, we use some edge-enhancement operations before the correlation operation, and introduce an adaptive template-updating scheme. The proposed tracking algorithm is compared with various correlation-based techniques and (in some cases) with the mean-shift and the condensation trackers on real-world scenarios. A significant improvement in efficiency and robustness is reported. The POL-CFC algorithm approximates the current velocity of an open-loop pan-tilt unit, computes the predicted relative-velocity of the object using Kalman filter, and generates the precise control signals to move the camera accurately towards the maneuvering target regardless of its changing velocity. The proposed system works in real-time at the speed of 25–200 frames/ second depending on the template size, and it can persistently track a distant or near object even in the presence of object fading, low-contrast imagery, noise, short-lived background clutter, object-scaling, changing object-velocity, varying illumination, object maneuvering, multiple objects, obscuration, and sudden occlusion.     

力矩受限圆轨二级倒立摆系统非线性摆起过程控制

目的研究了力矩受限时圆轨二级倒立摆摆起控制量确定的最优化算法，实现圆轨二级倒立摆非线性系统摆起过程有效控制．方法对于设定的摆起时间，进行时间分段．以每个时间段上控制量为设计变量，以与设计变量相关的终点约束条件为目标函数．将控制量受限条件构造在复杂嵌套的目标函数中，建立了摆起过程控制量计算的最优化方法．结果编制出力矩受限时圆轨二级倒立摆摆起的开环控制量程序与控制量确定．采用计算出控制量实现了摆起过程仿真控制，并成功地实现了圆轨二级倒立摆摆起的实物摆起控制．结论通过力矩受限时倒立摆摆起控制量分析与实物摆起控制实现，表明所提出方法有效性和可行性，为复杂强非线性系统的过程控制提出依据．     

步进电机控制系统建模及运行曲线仿真

为了优化开环情况下步进电机的控制,研究运行曲线和传动刚度对步进电机开环控制系统运动情况的影响.依据步进电机运行原理和系统动力学特性,建立控制系统数学模型.设计一种基于正矢函数,高阶平滑的加减速曲线,并与常见的匀加减速曲线和指数型加减速曲线进行了比较仿真.仿真结果表明正矢型加减速曲线能够更好地抑制运动过程中的冲击,减小终...     

负反馈放大器增益的拆环计算

基于理想方块图，应用拆环法导出了电压并联负反馈放大器的源增益、增益的计算式，全面描述了影响源增益、增益的电路参数。