基于可编程控制器的分布式多机通讯原理及应用

本文结合工程实例介绍了Ｓ７－２００系列可编程控制器的功能和特点；讨论了用工业控制计算机、可编程控制器以及单片机组成的分布式控制系统在闸门实时监控系统中的应用，并详细分析了上、下位机之间的通信方式及其功能的具体实现。     

S7-200无线PPI通信在污水处理厂的应用

采用实时无线PPI通信模块SY-S72,通过OPC软件PC Access上位机的组态软件,实现了多个提升、排海泵站和中控室的实时通信。研究了PPI协议的通信时间开销,并和现有的其他方案进行比较。     

基于LabVIEW与PLC的过滤材料纯水通量测试系统设计

纯水通量是表征过滤材料(特别是膜材料)渗透性能的重要参数。为准确、快速的实现纯水通量的测定,本工作设计了一套自动测试系统,并详细说明了其硬件结构和软件设计方法。该测试系统以Lab VIEW作为上位机的开发平台,通过调用VISA接口函数并采用了西门子PPI协议,实现了Lab VIEW与下位机西门子PLCS7-200的串口通讯。测试系统集上位机数据采集﹑数据显示和数据保存于一体。测试结果表明,该系统界面友好、运行稳定、测试重复性好,达到了设计的要求。     

Development of a partnering performance index (PPI) for construction projects in Hong Kong: a Delphi study

Over the past decade, research studies on benefits, critical success factors, difficulties, process, conceptual and theoretical models of construction partnering have been ubiquitous in the construction management discipline. In fact, there is adequate evidence that an increasing number of client organizations are adopting a partnering approach to undertake their building and construction projects both locally and worldwide during the last decade. With the perceived benefits that partnering brings about, research into Key Performance Indicators (KPIs) to evaluate the success of partnering projects in construction becomes vital as it can help set a benchmark for measuring the performance level of partnering projects. However, although there are some related studies and papers on this research area, few, if any, comprehensive and systematic studies focus on developing a comprehensive, objective, reliable and practical performance evaluation model for partnering projects. A model has been developed using the Delphi survey technique to objectively measure the performance of partnering projects in Hong Kong based on a consolidated KPIs' conceptual framework previously developed for partnering projects. Four rounds of Delphi questionnaire survey were conducted with 31 construction experts in Hong Kong. The results reveal that the top seven weighted KPIs to evaluate the success of partnering projects in Hong Kong were: (1) time performance; (2) cost performance; (3) top management commitment; (4) trust and respect; (5) quality performance; (6) effective communications; and (7) innovation and improvement. A statistically significant consensus on the top seven weighted KPIs was also obtained. Finally, a composite Partnering Performance Index (PPI) for partnering projects in Hong Kong was derived to provide an all‐round assessment of partnering performance. Different partnering projects can now be assessed on the same basis for benchmarking purposes. Construction senior executives and project managers can thus use the Index to measure, evaluate and improve the performance of their partnering projects to strive for construction excellence. Although the PPI was developed locally in Hong Kong, the research method could be replicated in other parts of the world to produce similar indices for international comparison. Such an extension would aid the understanding of managing partnering projects across different geographic locations.     

立体仓库串行通信控制系统设计

自动化立体仓库堆垛机控制系统采用西门子PLC作为下位机控制其他设备,为实现远程监控,上位监控计算机以组态王6.5设计监控及操作界面,以ACCESS设计数据库进行实时数据采集,并通过PPI协议实现与下位机PLC的串行通信。在上位机进行监控程序及画面的设计,并完成画面的运行。由于组态软件对控制系统的集中管理,并且形成了很好的人机界面,大大提高了工作效率。     

PPI协议在油气润滑监控系统中的应用

在小型油气润滑监控系统的开发过程中,针对使用现有组态软件开发成本高和自由口方式通讯编程复杂的问题,提出了基于西门子PPI协议使用VC++开发程序的方案。首先基于PPI协议的解析方法,分析了常用读写操作的通讯格式,并设计了系统应用程序;然后在实验室小型油气润滑样机上进行了实验。实验证明,该方案满足设计要求,具有实现简单、调试方便及成本低的优点。     

基于PPI通讯协议的监控模块的设计与实现

介绍了西门子公司PPI通讯协议的解析方法,并给出协议中部分读写指令的具体格式。在此基础上介绍了自行设计的基于MCS-51单片机的监控模块,该模块以解析的PPI协议中相关读写命令为通讯协议,实现对S7-200系列PLC中相关单元的读写。最后,给出了监控模块的硬件构架和软件设计思想。实践证明该模块运行稳定、操作方便、实用性强。     

PLC在锅炉温度串级控制系统中的应用

根据锅炉温度串级控制系统的结构与控制特点,应用MCGS(监视与控制通用系统)组态软件、S7-200PLC及多主站PPI电缆对锅炉夹套和锅炉内胆所组成的温度串级系统进行控制.实验结果表明该锅炉温度串级控制系统与普通的单回路锅炉温度控制系统相比,改善了过程的动态特性、提高了系统的工作频率、具有较强的抗扰动能力和一定的自适应能力,实际应用效果良好.     

Pumpkin oil cake protein isolate films as potential gas barrier coating

This work was aimed to investigate the potential of PuOC protein isolate (PuOC PI) in preparation of biodegradable films at different pH values (2–12) and plasticizer content (0.3–0.6 g glycerol/g PuOC PI). Results showed that films could be formed in a wild range of pH, except at pH = 4–8. Films with 0.4 and 0.5 g glycerol/g PuOC PI were suitable for further analysis. The pH of film-forming solutions influenced all examined film’s characteristics. The amount of added glycerol significantly affected (p < 0.05) tensile strength, elongation at break and solubility of the films. Gas permeability of films with 0.4 g glycerol/g PuOC PI showed that these films represents an excellent barrier for O₂, N₂, CO₂ and air. Obtained films have improved elongation at break and gas permeability characteristics compared to PuOC biodegradable films, thus they could be used as gas barrier stretch coating.     

软件化雷达P显实时坐标变换与实现

软件化雷达PPI光栅显示需完成极坐标测量数据向直角坐标的实时转换,而传统的利用简单数学公式直接转换的方式存在映射非均匀和运算量大等难题。基于整体映射和一一映射等不同逆映射方法,研究并提出了一种改进的一一映射新方案。新方法可有效解决量化漏点和区域重叠的问题,显著提高了映射查找表的形成效率,保证了PPI显示效果和实时性。最后,给出了新方法的具体实现流程,比较了与现有方法的效果,证明了新方法的有效性。