基于Profinet的双主轴数控磨床控制系统的设计与实现北大核心

在设计双主轴数控外圆磨床控制系统方案时,两个砂轮主轴电机转速采用模拟量模块控制,但数控系统只能支持一个模拟主轴的控制。为解决此问题,通过808D AD数控系统的Profinet总线通信接口连接S7⁃1200 PLC扩展第二模拟主轴。对第二模拟主轴进行数控编程时用R参数代替S转速指令,使用GET指令、S7通信协议将转速指令发送至远程PLC端,再从PLC的模拟量模块中输出;第二模拟主轴的编码器连接至PLC的高速计数器输入口,使用PUT指令将实际转速传输至数控系统侧;针对双主轴磨削工艺设计制作808D AD的用户自定义界面,可显示2个主轴的指令转速、实际转速。结果表明:采用总线通信,系统抗干扰能力强,第二模拟主轴的转速误差可以控制在10%以内,对主轴转速控制或非联动位移轴控制具有一定的参考价值。     

章水大余县骨干水库防洪调度分析及思考

闸门的正确启闭是水库运行管理工作中需要重点关注的问题,而闸门的启闭控制则主要利用闸门启闭机来实现。本文所述水库闸门采用了先进的SIMATIC S7-1200控制装置,并利用计算机技术对水库闸门运行情况进行远程自动监视和控制。通过近两年的运行,闸门监控系统操作灵活、维护方便,实现了水库管理“现场测站无人值守、中心站少人值班”的控制模式,提高了水库的运行管理能力。     

基于S7-1200 PLC的变频调速恒压供水系统

针对现代社会对恒压供水的需求,设计恒压供水系统。系统采用西门子最新面向市场的S7-1200 PLC进行逻辑控制,利用西门子变频器MM440进行压力调节。变频器和PLC作为系统控制的核心部件,时刻跟踪管网压力与给定压力的偏差变化,经变频器内部PID运算,通过S7-1200 PLC控制变频与工频切换,自动控制水泵投入的台数和电机转速,实现闭环自动调节恒压变量供水,在保持恒压下达到控制流量的目的。运行结果表明,该系统具有压力稳定、结构简单、工作可靠等特点,基本满足设计要求。     

带启动时间的二次可选服务的多重休假M/G/1排队

本文研究带启动时间的二次可选服务的多重休假M/G/1排队模型.应用嵌入马尔可夫链以及广义服务时间的方法,给出了稳态队长的母函数、等待时间的LST及其随机分解结果,同时也给出模型的两个特例.最后通过数值例子说明该模型可以较好地模拟一些实际问题.     

用方面化特征模块开发OpenRISC1200软核

对OpenCores上的OpenRISC1200项目(简称OR1200)的统计发现,条件编译指令的使用高达714次,嵌入在条件编译指令间的代码占代码总量的61.60%。条件编译在硬件开发中被大量使用,但在软件开发时却并不提倡。因此,本文提出用方面化特征模块(AFM)开发硬件系统,以避免条件编译指令的使用。作为案例,本文给出用AFM重新开发OR1200项目的过程,它使得OR1200各features的开发从同时开发变为顺序开发,使得服务于各feature的代码从纠缠在一起变为相互独立,有利于OR1200的维护和调试。最后,基于OR1200的开发过程,本文建立了一套AFM开发方法下的硬件系统的形式化模型,它是进一步的形式化验证工作的基础。     

A stochastic programming model for the thermal optimal day-ahead bid problem with physical futures contracts

The reorganization of the electricity industry in Spain completed a new step with the start-up of the Derivatives Market. One main characteristic of MIBEL's Derivatives Market is the existence of physical futures contracts; they imply the obligation to physically settle the energy. The market regulation establishes the mechanism for including those physical futures in the day-ahead bidding of the generation companies. The goal of this work is to optimize coordination between physical futures contracts and the day-ahead bidding which follow this regulation. We propose a stochastic quadratic mixed-integer programming model which maximizes the expected profits, taking into account futures contracts settlement. The model gives the simultaneous optimization for the Day-Ahead Market bidding strategy and power planning production (unit commitment) for the thermal units of a price-taker generation company. The uncertainty of the Day-Ahead Market price is included in the stochastic model through a set of scenarios. Implementation details and some first computational experiences for small real cases are presented.     

基于点的POMDPs在线值迭代算法

部分可观察马尔可夫决策过程(partially observable Markov decision processes,简称POMDPs)是动态不确定环境下序贯决策的理想模型,但是现有离线算法陷入信念状态“维数灾”和“历史灾”问题,而现有在线算法无法同时满足低误差与高实时性的要求,造成理想的POMDPs模型无法在实际工程中得到应用.对此,提出一种基于点的POMDPs在线值迭代算法(point-based online value iteration,简称PBOVI).该算法在给定的可达信念状态点上进行更新操作,避免对整个信念状态空间单纯体进行求解,加速问题求解;采用分支界限裁剪方法对信念状态与或树进行在线裁剪;提出信念状态结点重用思想,重用上一时刻已求解出的信念状态点,避免重复计算.实验结果表明,该算法具有较低误差率、较快收敛性,满足系统实时性的要求.     

西门子S7-1200PLC定时器的典型应用

介绍西门子新一代S7-1200 PLC定时器的典型应用.     

Joint optimization of pricing and planning decisions in divergent supply chain

In divergent supply chains, such as in the oil industry, processing raw materials results in an outflow of multiple products. Final products are stored at international depots, from where they are ready to be shipped to the markets. Even if one company controls the entire chain, when production and sales organizations are decoupled, a relevant problem is to determine the internal prices of products at depots for achieving coordination. We propose an optimization model involving pricing and production decisions, and several constraints commonly used in divergent chains. In our approach, the producer incorporates the sellers’ behavior by expressing demand as a function of the internal price. As a result, our model serves as a coordination mechanism in trying to get an overall coordinated integrated solution in a decoupled reality. Numerical examples in single and multiple periods problems show the advantages of our approach over cost‐based methods.