Tuesday, March 8, 2011

Practice in Control Software Engineering





In most cases the control systems of software implementation occurs during the installation of the manufacturing system. PLC programming is left over to control technicians or engineers who may have less knowledge about methodical and systematic design and programming. Dedicated service provider for information and automation system are requested only in large-scale and demanding projects. These specialists follow a rigorous sequential project methodology. Coarsely, the project steps are functional specification, manufacturing and procurement, hardware design, factory acceptance test (FAT), control system development and integration, and delivery including documentation and installation. The allocated manpower is based on empirical data from previous projects. However, the control system delegation design to dedicated subcontractor embodies the problem of less interaction and communication between the design team of the mechanical system and the control system.

We propose an integrated design approach based on axiomatic design theory in order to provide a coherent information flow and to achieve a reduction in the design lead-time. Axiomatic design is a simple, but powerful design methodology. It supports the design process with a general design set of rules forcing the designer to think systematically from a top-down perspective. The two axioms, (1) Independence Axiom and (2) Information Axiom, guide the designer to generate a “good” solution and to select the best one among alternatives. Conceptually, the axiomatic design approach divides the design process into four separated semantic and syntactical perspectives, the domains of CR (customer requirements), FR (functional requirements), DP (design parameters), and PV (process variables). Axiomatic design has been applied to many other design contexts, including software engineering, although originally developed for mechanical systems engineering. The domains may have different interpretations in diverse design contexts.

In the manufacturing system design, the DPs describe the processes in a solution-neutral format, whereas the PVs indicate the selected resources, including hardware systems, software systems, and human resources. The DPs in the manufacturing system design impact the FRs of the control system to be designed. These are processes, temporal requirements, and control actions. Enabler (DPs) of the control actions and processes are software objects and states describing the abstract structure and system’s behavior.



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