Tuesday, July 5, 2011

Introduction of FBD PLC from NuSCR





NuSCR is a formal language of specification to manuscript requirements for real-time fixed software with applications of nuclear engineering in mind. Field experts dynamically took part in choosing how to best correspond to a variety of aspects. It applies tabular information to identify required calculations and automaton to time-dependent or document state behavior. As PLCs (programmable logic controllers) are broadly used to realize real-time embedded software, PLC code synthesis from a formal specification is advantageous if transformation rules can be strictly defined. Additionally to get better productivity, safety analysis results carried out on requirements stay valid. It will demonstrate how specification of NuSCR can be interpreted into semantically corresponding FBD (function block diagram) code. The process, except for the first phase where user offers information on implicit or missing details, is automatic.

While code of executable can be generated automatically with tools of CASE from FBD, mostly software development is automatic. Recommended method is presently being used in developing Reactor Protection System or RPS for plants of nuclear power in Korea, and the result to date has been positive. It demonstrates the recommended approach with the fixed set-point increasing trip which is one of the most complicated trip logics comprised in the RPS. The safety of software becomes an essential issue for systems of embedded control as traditional relay-based analog systems are being substituted by software. When developing of safety critical software for example system of emergency shutdown for power plants of nuclear, authorities of regulation require safety demonstrations through phases of life-cycle. Engineering requirement is distinguished to play serious roles to software quality, and formal specification methods are frequently used to assist unmistakable documentation and precise analysis requirements. Because active contribution of domain experts is important when performing analysis of safety, some domain-specific requirement languages already developed.

NuSCR, according to SCR document, is a language specification planned to provide nuclear engineering industry. While accepting documents recognizable to domain experts for example function of overview diagrams (FODs) and structured decision tables (SDTs), time- and state- needy functionalities are visually identified in automata document. Since domain experts who are recognizable with research on formal techniques contributed actively when make a decision how to best confine a variety of specifications, nuclear engineers discover NuSCR simple to use and intuitive. Actually, when used to document specifications for logic of bitable processor (BP) as a part of the project of KNICS1, some errors for example missing initialization routines and ambiguities in trip logics were found in notations written in English.



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