On Reference Architectures for Development of Flexible Cell Control Systems

Abstract: Industrial problems of inflexible and expensive shop-floor control systems were analysed. The principal causes are suggested to be poor development methodology, poor tools used for development and implementation, and poor knowledge on how such systems are best built. This work mainly focuses on providing industry with better knowledge on how shop-floor control systems should be designed. It is suggested that this knowledge should be collated to form a generic reference architecture to be used as a template for the development process. The conclusions drawn from four case studies, literature, and industrial surveys relate to two areas.

First, a template for the definition of reference architectures has been defined. It specifies that the reference architectures should be simple to understand and to use, and fit the needs of the industry concerning system properties, functions, and genericity. Furthermore, they should provide support to the engineers in managing the complexity of the system and of the development process. Therefore, they should be accompanied with a description of how one should develop a design specification for a specific system from a generic reference architecture and how to implement the system based on this specification. Reference architectures should specify the control system's functions, structure, behaviour, and information.

Secondly, Chalmers Reference Architecture and Methodology for Flexible Production Systems, CHAMP, was developed with a primary focus to achieve high flexibility for the computer-based scheduling, control, monitoring, and error handling activities in manufacturing cells. The main features are the generic control logic, the use of a central database, the separation of product operation lists from the description of resource capabilities, and the automatic synthesis of product operations with resource capabilities. This thesis reports on research on specific parts of CHAMP: (i) the modular control structure and the generic message-passing scheme by which the modules cooperate, (ii) the separation of generic and specific control activities, (iii) the definition of generic resource models, and (iv) the definition of data regarding manufacturing resources and error-handling. The genericity of the whole reference architecture has been validated by industrial surveys, in which CHAMP was conceptually applied to various types of manufacturing cells in Swedish industry.