Compiling Ladder Diagram into Instruction List to comply with IEC 61131-3

The standard IEC 61131-3 defines four programming languages for PLC, and the Ladder Diagram is the most predominant one among them. As the Ladder Diagram is a graphical language and cannot be directly executed by general PLC processor, most commercial PLC programming systems, e.g. SIEMENS S7, MITSUBISHI Gx Developer, OMRON Gx Programmer, use Instruction List as intermediate language between the Ladder Diagram and the machine instructions of the processor. However, the Instruction List generated by these programming systems fails to comply with IEC 61131-3. In this paper, we present a method to compile a Ladder Diagram into an Instruction List that fully complies with IEC 61131-3. Several unclear aspects of the standard in compilation, such as the use of EN and ENO, the evaluation of EN, multiple coils and topology restrictions, are discussed before the method is presented. The mathematical definition of Two Terminal Series Parallel unidigraphs is proposed for the first time to represent the Ladder Diagram networks that are composed of connections in series and parallel. Based on the property of TTSP, a method is suggested to verify the topology of the Ladder Diagram. Finally, a complex compilation example shows that the proposed method is correct and has the advantages of ease of understanding, modification, and maintenance.     

乳化沥青自动化主产过程的PLC控制

本文论述了乳化沥青自动化生产过程的ＰＬＣ控制及程序设计方法，给出了生产单元的梯形图。     

6kV变电所中央事故报警盘的设计与实现

本文介绍了日本ＦＵＪＩ公司生产的ＮＢ２型可编程控制器（ＰＬＣ）组成的控制系统在６ｋＶ变电所中央事故报警中在的应用和设计。并阐述了系统软、硬件的设计与各典型功能的实现。     

Investigating risk factors for slips,trips and falls in New Zealand residential construction using incident-centred and incident-independent methods

Slip, trip and fall (STF) incidents, particularly falls from a height, are a leading cause of injury in the New Zealand residential construction industry. The most common origins of falls from a height in this sector are ladders, scaffolding and roofs, while slipping is the most frequent fall initiating event category. The study aimed to provide detailed information on construction industry STF risk factors for high-risk tasks, work equipment and environments, as identified from an earlier analysis of STF claims data, together with information to be used in the development of interventions to reduce STF risk in New Zealand residential construction. The study involved the use of both incident-centred and incident-independent methods of investigation, including detailed follow-up investigations of incidents and observations and interviews with workers on construction sites, to provide data on a wide range of risk factors. A large number of risk factors for residential construction STFs were identified, including factors related to the work environment, tasks and the use and availability of appropriate height work equipment. The different methods of investigation produced complementary information on factors related to equipment design and work organization, which underlie some of the site conditions and work practices identified as key risk factors for residential construction STFs. A conceptual systems model of residential construction STF risk is presented.     

PLC使用中若干难点分析

介绍了可编程控制器PLC学习及使用过程中的若干难点问题,并通过梯形图程序实例,针对这些难点问题进行分析,给出了相应的解决方法。     

Continuous Chain Ladder: Reformulating and generalizing a classical insurance problem

The single most important number in the accounts of a non-life insurance company is likely to be the estimate of the outlying liabilities. Since non-life insurance is a major part of our financial industry (amounting to up to 5% of BNP in western countries), it is perhaps surprising that mathematical statisticians and experts of operational research (the natural experts of the underlying problem) have left the intellectual work on estimating this number to actuaries. This paper establishes this important problem in a vocabulary accessible to experts of operations research and mathematical statistics and it can be seen as an open invitation to these two important groups of scholars to join this research. The paper introduces a number of new methodologies and approaches to estimating outstanding liabilities in non-life insurance. In particular it reformulates the classical actuarial technique as a histogram type of approach and improves this classical technique by replacing this histogram by a kernel smoother.     

Petri网在自动焊接机机械手程序设计中的应用

可编程控制器(PLC)在自动化生产过程中有着广泛的应用,它的程序设计主要通过梯形图实现。本文阐述了采用Petri网进行的程序设计和分析,能够更加准确描述PLC的控制过程,并重点介绍了Petri网替代梯形图进行自动焊接机机械手程序设计的方法和步骤。     

滑动窗口连续查询结果存储优化

在数据流滑动窗口查询研究领域中,考虑查询结果失效的连续查询成为了一个新的研究热点.查询结果的维护代价直接影响连续查询效率.根据对不同更新模式连续查询结果的分析,提出了一种带分支链表的梯队列来维护滑动窗口连续查询结果.它利用分支链表结构收集具有相同截止期的数据,采用梯队列的"产卵"机制,能适应具有各种不同分布的数据维护,且能达到O(1)的均摊(amortized)时间复杂度.实验表明,该结构显著提高了滑动窗口连续查询效率,明显优于同类结构.     

Double ionization energy spectra of small alkali-metal clusters

In this article, we calculate the spectra of the double ionization energy (the energy required for adding two electrons to the neutral system) of small alkali-metal clusters (K₂ and Li₂) including the effect of electron–electron short-range correlation by adding two one-particle energies within the GW approximation and taking into account the electron–electron repulsive interaction effectively.