Fault detection of networked control systems with uncertain time-varying delay and quantization error

Problems related to fault detection of networked control systems (NCSs) with both uncertain timevarying delay and quantization error are studied in this paper. A novel model with the form of polytopic uncertainty is given to represent the influences of both the time-varying delay and the quantization error, and then the reference model based method is used to design the residual generator that is robust to both unknown network-induced delay and unknown inputs. A numerical example is also given to illustrate the merits of the presented method. The proposed method can be regarded as an extension of the authors’ former work, which can only deal with time-varying delay.     

An improved frame-layer bit allocation scheme for H.264/AVC rate control

In this paper, we aim at improving the video quality degradation due to high motions or scene changes. An improved frame-layer bit allocation scheme for H.264/AVC rate control is proposed. First, current frame is pre-encoded in 16×16 modes with a fixed quantization parameter (QP). The frame coding complexity is then measured based on the resulting bits and peak signal-to-ratio (PSNR) in the pre-coding stage. Finally, a bit budgetis calculated for current frame according to its coding complexity and inter-frame PSNR fluctuation, combined with the buffer status. Simulation results show that, in comparison with the H.264 adopted rate control scheme, our method is more efficient to suppress the sharp PSNR drops caused by high motions and scene changes. The visual quality variations in a sequence are also relieved.     

Adaptive path following controller of underactuated ships using serret-frenet frame

This paper presents an adaptive path following control law to steer underactuated ships along a predefined path at a constant forward speed with uncertain parameters due to changes of added mass matrices. The proposed controller is based on analytic model predictive control and model reference adaptive control. The Serret-Frenet frame is used to describe the ship dynamics. The analytic model predictive control provides a systematic method rather than try-and-error method to get appropriate control parameters to guarantee the stability of the closed-loop system, and the well-defined relative degree is guaranteed by introducing output-redefinition. An identification algorithm based on model reference adaptive control is used to identify the uncertain parameters. Numerical simulations are provided to demonstrate the validity of the proposed control law.     

基于MIDAS的大跨度连续刚构桥振动特性分析

自振频率是桥梁结构动力特性的模态参数,也是评价桥梁动力性能的重要依据．本文以某大跨度连续刚构为例,采用大型专业结构分析软件MIDAS建立该桥的有限元计算模型进行模态分析,得出相关模态参数,为桥梁检测等提供参考．     

轨道交通拥挤传播速率量化模型研究

轨道交通作为综合客运交通系统的骨干,影响着城市客运交通乃至社会经济的正常运转,对其大客流拥挤传播规律的研究有助于提高轨道交通系统的运输安全和效率.以往学者研究的大客流传播模型中往往参数量化缺失或者缺乏实际意义,因此,本文着眼于量化大客流传播模型中的参数,旨在构建客流影响下的拥挤传播模型.首先,分析大客流传播模型中参数及其影响因素,阐述现有传播速率量化模型;其次,以客流的不确定性作为研究对象,分析客流传播特征;再次,通过轨道交通客流数据量化模型参数相关的客流和列车剩余载客能力,界定大客流影响阈值;然后,构建考虑客流因素的传染病模型,量化拥挤传播速率,据此分析客流对轨道交通拥挤传播的影响;最后,以北京地铁13号线为例,比较不同时段、不同换乘情况下其大客流拥挤传播影响范围的差异,分析其原因,从而为优化轨道交通系统的服务水平及大客流事件应急处置提供参考和借鉴.     

Semi-Active Predictive Control of Isolated Bridge Based on Magnetorheological Elastomer Bearing

Time-delay of magnetorheological elastomer bearing(MRB) can bring structural response menace to bridges. This paper investigates a bridge pier-bearing semi-active-coupling control method based on model predictive control(MPC). The presented strategy takes the structure prediction model to predict the state responses of the controlled plant in a period of future time. Then, the control law can be determined by solving a finite horizon optimization problem. The peak shearing force of pier top, the displacement and the acceleration of beam are chosen as control goals, and the vibration isolation rate is applied to characterize the vibration isolation effect.It is noted that MPC method naturally takes the time-delay and uncertain interference into consideration, and significantly improves the control performance of the system. Finally, the numerical example is described and the seismic response of isolated bridge based on MRB is analyzed. The simulation results show that predictive control can be used to control the time-delay of bridge system in different degrees. The best control performance is at0.4 s. Even if the time-delay reaches 2 s, it is still good. Therefore, the control method significantly reduces the adverse effects of time-delay on the system, and has a good vibration isolation performance.     

大跨径预应力连续刚构桥施工控制的理论与方法

运用工程控制论的思想, 将预应力连续刚构桥的施工控制视为一随机最优控制问题, 建立相应的数学模型、目标函数及物理模型, 采用卡尔曼最优一步预测, 按确定性的最优控制规律构成闭环状态反馈系统． 同时, 在现场建立计算机工作站, 使计算机对各施工阶段进行调整控制,达到控制的目的． 其成果已在重庆黄花园嘉陵江大桥的施工控制中得到了应用．     

改进MOG-LRMF 的铁轨动态异物检测

针对复杂铁路环境下动态入侵异物检测精度低和抗扰能力差等问题,提出一种基于改进MOG-LRMF算法的铁路轨道异物入侵实时检测方法. 引入仿射变换,对视频序列可能出现的抖动进行预校正处理;分析MOG-LRMF模型特点,利用MOG模型对视频帧中的背景进行建模,用前一帧背景中学习到的知识对当前帧背景进行预测,优化MOG-LRMF参数求解模型;利用EM算法对改进MOG-LRMF模型进行参数求解,实现背景在线实时更新. 实验结果表明,改进的MOG-LRMF算法在光照充足、光线较弱、相机存在抖动、背景复杂及存在多个目标情形下都能提高目标检测精度,具有较好的抗干扰性、鲁棒性和快速性.     

基于货物运到期限的编组站动态配流优化研究

运到期限是铁路货物运输组织的关键问题,保障运到期限,对提升铁路货物运输质量与竞争力有重要意义.本文以编组站动态配流为研究对象,考虑不同货物对运输时效性要求的不同,以车流在站停留时间加权值总和最小为优化目标;采用均值比例分配法将运到期限分配到货物运输编组站作业环节,成为车流最大在站停留时间约束,同时考虑编组去向等约束,建立基于运到期限的编组站调机运用计划与配流计划综合优化模型,设计模拟退火算法对模型进行求解.最后通过算例分析表明,本文的模型和算法能够有效地解决编组站动态配流问题,同时满足车流的运到期限要求.     

OV 模型交通流阻尼特性研究

对交通流跟驰模型施以拉氏变换（或z 变换）,转换为控制系统传递函数形式, 进而通过分析传递函数来探讨交通流系统稳定性及控制方法,这是交通流稳定性理论研 究重要方向之一.为进一步挖掘分析稳定交通流系统在稳定状态下动态特性,基于最优速 度跟驰模型,以控制理论时域分析方法,研究了交通流系统在欠阻尼和过阻尼两种情况 下阶跃响应动态特性,并以仿真算例验证了理论正确性.过阻尼较欠阻尼交通流系统稳定 性好,但调节时间更长,若将交通事件抽象为阶跃响应,通过分析交通流系统调节时间、 超调量等参数,可为计算交通事件持续时间作参考,进而制定合理有效的交通管理措施.     

基于音频内容的DCT域脆弱水印算法

为了实现音频文件的完整性认证,提出了一种基于内容的脆弱水印算法.对于一维序列,改变其离散余弦变换(DCT)域交流系数不会改变该序列的幅值和.基于这一性质,在音频分帧后,再对每帧分组,计算每组采样点和的绝对值,相加后得到该帧的和,将其作为该帧音频的特征,量化后转换为二进制作为水印;然后,用量化索引调制方法,通过调整每组DCT域的低频系数嵌入水印.实验表明:该算法具有很好的不可感知性;得到的含水印音频的信噪比约为80 dB;算法对添加噪声、重量化、重采样、低通滤波、MP3压缩等操作具有很强的敏感性,并且能够确定替换等恶意篡改的位置.     

基于自动车牌识别数据的混合交通流饱和流率实时估计

为解决混合交通流饱和流率测算的实时性和时变性问题,实时获得混合交通流的饱和流率用以信号配时,本文提出基于自动车牌识别数据(Automatic License Plate Recognition,ALPR)的混合交通流饱和流率实时自动估计方法。首先,分信号周期提取车头时距数据,在当前车和后车车辆类型确定时车头时距满足同一正态分布的假设基础上,构建车头时距的高斯混合模型并应用 EM(Expectation Maximization) 算 法 求 解 ;其 次 ,基 于 赤 池 信 息 准 则 (Akaike Information Criterion,AIC)选取高斯混合模型的最优个数,拟合数据得到高斯混合模型参数;最后,根据车头时距的高斯混合模型推算出混合交通流饱和流率。以杭州城市道路3条路段的ALPR数据为例,分析基于 ALPR 数据获取车头时距的采样误差,对模型进行验证,并与传统的 HCM(Highway Capacity Manual)方法进行对比。结果表明：基于ALPR数据的车头时距采样误差满足精度要求; 与HCM的实测法相比,模型所得的混合饱和交通流率相对误差小,结果准确;该方法与传统的标准车流饱和流率折算法效果相近,并考虑混合交通流时变特性,能自动部署实时计算,鲁棒性良好,有实际应用意义。     

Spatter rate estimation of GMAW-S based on partial least square regression

This paper analyzes the drop transfer process in gas metal arc welding in short-circuit transfer mode （GMAW-S） in order to develop an optimized spatter rate model that can be used on line. According to thermodynamic characters and practical behavior, a complete arcing process is divided into three sub-processes： arc re-ignition, energy output and shorting preparation. Shorting process is then divided as drop spread, bridge sustention and bridge destabilization. Nine process variables and their distribution are analyzed based on welding experiments with high-speed photos and synchronous current and voltage signals. Method of variation coefficient is used to reflect process consistency and to design characteristic parameters. Partial least square regression （PLSR） is utilized to set up spatter rate model because of severe correlativity among the above characteristic parameters. PLSR is a new multivariate statistical analysis method, in which regression modeling, data simplification and relativity analysis are included in a single algorithm. Experiment results show that the regression equation based on PLSR is effective for on-line predicting spatter rate of its corresponding welding condition.     

A rate-distortion based quantization level adjustment algorithm in block-based video compression

In this paper, a rate-distortion based quantization level adjustment (RDQLA) algorithm is presented. Based on the rate-distortion criterion, the quantization level adjustment algorithm effectively improves coding efficiency by adaptively optimizing quantization levels of the signals near the boundaries of quantization cells and adjusting quantization levels per block. In addition, it has no overhead and is fully compatible with the existing compression standards. The proposed algorithm can be applied in any block based image and video coding method. In particular, the algorithm has been verified on the platform of H.264. Experimental results show that the proposed algorithm improves objective and subjective performances substantially. It is shown that the proposed algorithm has a gain of several dB comparing with the newest H.264 standard for high bit rates. Foundation item: the Special Foundation of Outstanding Young Teacher of Shanghai     

车联网中驾驶员反应时间实时估计方法

结合车辆非线性分段制动特性和车辆状态数据对驾驶员反应时间进行实时估 计,采用特征数据拟合出初速度与减速度上升时间关系模型,通过BP神经网络推算减速 度上升过程中减速度随时间非线性变化关键参数,并在此基础上基于车辆动力学运动规 律求解车辆分段制动位移,通过实际位移与理论位移等价关系实现驾驶员反应时间实时 估计,最后利用Newell 跟驰模型场景对本文提出方法进行仿真验证.结果表明：不同初速 度条件下,反应时间估计值平均误差不超过0.022 s;不同反应时间条件下,反应时间估计 值平均误差不超过0.013 s.本文提出的反应时间估计方法不用增加通信负担和额外设备, 能够达到较高精度,具备更优的适应性、可用性及工程价值.     

道路拥堵概率估计方法及其在城市交通运行评价中的应用

首先提出能够统一描述不同交通负荷下路段内车流离散性进的出行时间指数 （TTI）概率分布模型,并建立该分布模型参数随路段速度变化的模型.进而给出一种新的 拥堵概率估计方法.其根据路段速度获得路段内车辆TTI 的概率分布参数,进而获得隐含 的车辆TTI 概率分布及路段处于不同拥堵状态的概率.应用于交通运行评价,解决了现有 方法评价结果受路段长度影响,以及微观评价波动性大的缺陷.给出的理论方法在交通运 行分析、仿真及控制领域具有广泛的应用前景.     

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本文根据UTCS与UTFGS子系统功能独立及功能整合和互补的特征，基于递阶优化思想对UTCS与UTFGS进行协同优化建模，在模型求解过程中，本文提出以相邻两个控制周期作为一个诱导周期，利用后一个控制周期的控制参数作为计算下一个诱导周期诱导策略的输入参数，进行跟进计算，这种计算思路既能保证交通控制与诱导和实时交通流的紧密相随和动态性，又能保证诱导策略的连续性和继起性，实现了交通控制与诱导的动态协同。并通过仿真分析说明算法的有效性。本文研究为UTCS与UTFGS协同的最终实现提供理论指导和方法依据。     

城市信号交叉口交通运行评价参数视频检测

针对交叉口排队长度和延误等交通运行评价参数很难直接被检测到的问 题,本文提出了一种基于视频处理的交叉口运行评价参数的综合检测方法.该方法首先 将选择性背景更新机制引入块级背景差分,并结合块级帧间差分实现快速的排队车辆 检测.然后,利用虚拟平行线定位每车道排队车辆首尾端,并结合排队首尾车的跟踪与停 车线处虚拟线圈的计数来检测排队车辆数,进而获得延误、停车次数等其它交通运行评 价参数.实际测试结果表明,该方法能有效实现多参数的同时检测,并且能有效提高检测 的准确率.与实际值比较,参数检测值平均误差小于5%,能较好地满足交叉口运行性能 评价需要.     

一种通用的异步电动机仿真模型

从异步电动机动态数学模型出发，建立了异步电动机在任意同步旋转坐标下的仿真模型，该模型具有精度高、稳定性强，且与电机参数无关；仿真过程中，电机内部状态变量的初始值可以任意设定，并能够计算出几乎所有的电机物理量及其动态变化过程。因此，该模型可以方便地用于对变流装置、电动机及交流传动系统的稳态、动态过程研究。     

基于集群效应的独立式冷却模块气动特性研究

为了研究独立式冷却模块中多热交换器气动特性之间的集群效应,以典型双热交换器工程机械独立式冷却模块为例进行试验与数值仿真研究. 采用多孔介质模型模拟热交换器,利用多重参考坐标系方法模拟风扇性能,建立4种不同热交换器布置方案下的独立式冷却模块数值模型,对比分析气动特性,并进行冷却模块气动性能试验;通过改变热交换器间面积比与厚度比,完成独立式冷却模块气动特性主动控制方法的数值仿真研究. 研究结果表明:独立式冷却模块气动特性上具有独特的集群效应,即当热交换器呈对置方式布置时,不论两者的倾斜角度如何,气动阻力都相等;数值仿真发现相比于面积比控制,当采用厚度比控制的主动控制策略时,改变独立式冷却模块热交换器之间的厚度比,流量比变化更为平缓,且受风扇转速的影响更小,并据此得到两热交换器之间冷却风量、气动阻力与结构参数之间的试验关联式.