基于分段-模糊PID策略的化工企业低成本自控系统

针对当前中小型化工企业自动化水平低、安全联锁不完善等现状,提出一种符合化工行业特点的低成本自动控制策略,采用传统控制与智能控制相结合的方式实现温度及流量闭环控制。该控制策略能有效满足生产自动化需求、改善温度闭环的控制效果,提高产品质量与生产效率。     

Competition in Regulated Markets with Sluggish Beliefs about Quality

We investigate the effect of competition on quality in regulated markets (e.g., health care, higher education, public utilities), using a Hotelling framework, in the presence of sluggish beliefs about quality. We take a differential‐game approach, and derive the open‐loop solution (providers choose the optimal quality investment plan based on demand at the initial period) and the feedback closed‐loop solution (providers observe demand in each period and choose quality in response to current demand). If variable costs are strictly convex, and the degree of cost complementarity between quality and output is not too strong, the steady‐state quality is higher under the open‐loop solution than under the feedback solution. In both solutions, quality and demand move in opposite directions over time on the equilibrium path to the steady‐state. While lower transportation costs or less sluggish beliefs lead to higher quality in both solutions, the quality response is weaker when players use feedback strategies.     

控制回路断线的处理

断路器控制回路是变电站二次回路的重要部分,该回路正常与否直接影响到断路器的正常分合闸。文章主要分析了控制回路的闭锁特点,对控制回路断线的处理方法进行了探讨,最后通过两个实例分析和证明本文的论点。     

PLC在变频闭环调速系统中的应用

本文以西门子s7-200PLC、变频器和旋转编码器组成的交流变频闭环调速系统为例,介绍了基于PLC的变频闭环调速系统的工作原理、设计与实施方法,阐述了PLC在变频闭环调速控制系统中应用和实施过程的关键技术,并指出了系统在设计与实施过程中中应注意的问题。     

基于稳定域的网络控制系统分析

网络控制系统是通过网络将分布于不同地理位置的传感器、控制器和执行机构连接起来,形成的一种全分布实时反馈闭环控制系统。文章以控制网络的服务质量为基础,围绕着网络系统的稳定性等性能指标,研究了网络控制系统的稳定域分析方法。     

基于稳定域的网络控制系统分析

网络控制系统是通过网络将分布于不同地理位置的传感器、控制器和执行机构连接起来,形成的一种全分布实时反馈闭环控制系统。文章以控制网络的服务质量为基础,围绕着网络系统的稳定性等性能指标,研究了网络控制系统的稳定域分析方法。     

柔性直流输电阀短路故障分析及其保护策略探讨

柔性直流输电技术(HVDCFlexible)采用电压源型换流器(VSC)以及PWM技术,其中全控型IGBT换流阀是VSC换流站的核心器件。本文主要根据柔性直流输电换流桥阀的工作过程,分析了VSC换流站整流侧发生阀短路故障时系统交直流侧的故障特征。总结故障特征并与传统HVDC系统发生类似故障时的故障特征进行比较,分析传统HVDC的保护策略应用于柔性直流输电的可行性。     

On the generalized principal-agent problem: Decomposition and existence results

This paper addresses the class of generalized agency problems: situations in which adverse selection and moral hazard are jointly present. We present a decomposition of the principal's optimization problem under the first-order approach that sheds light on the interactions between the two types of private information, and also significantly improves tractability. We use the decomposition to (1) provide examples of closed form solutions of the optimal contract, and (2) analyze the existence of optimal contracts. We also show that the first-order approach is valid in generalized agency problems if the production technology satisfies the linear distribution function condition (LDFC) in actions and types. For more general production technologies the Mirrlees-Rogerson sufficient conditions need to be extended to include restrictions on the form of the optimal contract. Received: 11 August 1997 / 26 September 1999     

基于PLC的汽车输送主副线速同步控制系统的设计

本文基于PLC、变频器、编码器组成汽车输送主、副线主从控制的双闭环随动控制系统，采用主输送线的实际运行速度作为副输送线的设定值，实现汽车输送主副线的传动速度同步、高精度稳速控制；该系统可有效抑制外部干扰，消除速度偏差，稳定程度高；实际应用效果达到设计要求。     

基于叠加原理和前推回代法的10kV配电网合环潮流计算

目前,10kV配电网大部分为环网结构,开环运行。当某一段线路需要检修时,配电网一般采用停电倒负荷方式。其缺点：一是损失供电量;二是要提前通知相关用户停电,比较麻烦。文章分析了配电网的结构特点和配电网潮流算法（前推回代法是配电网潮流计算的有效算法,但该算法只适用于辐射状配网）,在此基础上,提出了一种基于叠加原理和前推回代法的配网合环潮流改进算法。先用前推回代法计算合环前的配网潮流．然后在开口处加反向电压求潮流,二者叠加就是合环后的配网潮流。计算合环潮流的作用,就是要改变检修方式的操作,实现先合环后带电倒负荷。计算合环潮流的目的是确定合环潮流不会使线路保护误动。以保证合环操作带电倒负荷的可靠性。     

基于SVPWM的轻型直流输电控制策略研究

文章针对VSC采用SVPWM的控制方式，分析研究了SVPWM的等效三角载波PWM。以VSC的稳态模型为基础，通过坐标变换推导出VSC功率传输方程的直角坐标形式，并且求得控制量同功率值之间的解析关系式。采用逆系统方法设计了VSC的功率传榆控制系统，以及基于有功、无功独立调节的VSC—HVDC控制系统。仿真结果表明，建立的VSC—HVDC系统能较好地向无源网络供电，实现了VSC传输功率的独立、灵活调节。     

直流电机双闭环调速系统分析及仿真研究

直流调速是现代电力拖动自动控制系统中发展较早的技术,直流电动机调速系统以其优良的调速性能具有广阔的市场。在详细讨论了直流电机调速系统的转速电流双闭环调速系统的基础上,利用Matlab-Simulink进行了仿真实验,仿真结果验证了双闭环控制方案的合理性,为不同场合的直流调速系统的应用选择提供了依据。     

MANAGERIAL ISSUES IN CLOSING THE LOOP

The consequences for corporations striving to meet the new requirements of ‘closing the loop’ are investigated. An integrated managerial framework is developed to manage products over their complete life cycle. Effectively managing systems for ‘closing the loop’ requires a careful examination of the complex web of markets, government regulations, consumer behavior, supplier relationships and their impact on the value chain of an individual corporation. The underlying assumption is that developing a systematic framework of managerial issues for managing products over their complete life cycle is necessary to cope with the increased complexity caused by the tools related to ‘closing the loop’. Although managerial issues are the focus in this paper, this does not imply that changing consumer behavior or a more incentive and innovation oriented regulatory approach are not of importance. Without such an approach only a few pioneers will follow a closed loop system.     

闭环物流系统的成本因素分析

根据定位-配给。运输车辆安排，定位运输，定位-路径-库存等问题概念给出了此类问题的国内外研究现状，并结合闭环物流系统特征，给出闭环物流系统中关于选址-路径-库存问题的研究思路及成本因素分析。     

基于视觉检测的邮件分拣机包件检测系统方案设计

针对现有邮件分拣系统的不足,提出了一种基于计算机视觉的邮件检测方案,包括检测系统的硬件结构和软件设计流程,使分拣控制系统由开环变为闭环,从而提高分拣的准确率。     

仿真PLC开发和应用研究

文章介绍一种基于VB的仿真PLC软件,对软件的特色功能及软件实现的关键技术作了论述,并简要介绍了软件的使用方法和注意事项。     

PLC和变频器在螺杆式空压机节能改造中的应用

文章介绍了螺杆式空压机的工作原理,并分析了传统空压机供气系统中存在的缺点,提出由变频器、PLC和触摸屏组成的闭环自动恒压供气节能改造方案。     

PLC和变频器在螺杆式空压机节能改造中的应用

文章介绍了螺杆式空压机的工作原理，并分析了传统空压机供气系统中存在的缺点，提出由变频器、PLC和触摸屏组成的闭环自动恒压供气节能改造方案。     

关于医院后勤仓库库存控制的研究

分析了医院后勤仓库库存存在的问题,提出了解决方案并进行了定量计算,最后给出了更优的对策措施。     

A Turnpike Theorem in the Closed Dynamic Leontief Model with a Singular Matrix of Capital Coefficients

The paper refers to the well-known Tsukui turnpike theorem on convergence of optimal growth trajectories in the closed dynamic Leontief model to the maximum balanced growth trajectory, called turnpike. In the original proof of this theorem, the assumption that the matrix B of capital coefficients is non-singular plays an essential role. For many reasons this assumption, very convenient for theoretical analysis, is not always satisfied in input-output systems built for empirical purposes. This paper fills the gap between theory and empirical studies, presenting a proof that convergence of optimal trajectories towards the turnpike is also a characteristic feature of the closed Leontief model in the case when matrix B is singular. The general idea of the proof is based on the approximation of a singular matrix B by an infinite sequence of non-singular matrices.