Inherently flexible cell communications: A review

The first generations of Flexible Manufacturing Systems (FMS) are flexible only with respect to implicity predefined types of parts and assemblies: determined by the machines and software comprising the FMS. A more radical form of flexibility is the ability to be readily adapted to produce unforseen product types. It is this inherent flexibility which is becoming a primary, rather than a secondary, requirement of new manufacturing systems architectures. The burden of this flexibility falls almost entirely on software which is the glue that defines what machines constitute an FMS and how they work together. This paper reviews current computer science research which addresses these issues. This paper explores the issue of devising programs and architectures that support their own replacement within the real-time, heterogeneous factory environment. Formal computable specifications for reconfiguration have been proposed as a way of producing flexibility, but this paper argues that self-referential systems based on independently communicating agents are both more flexible and more acceptable in practice. Requirements for long-term, inherent flexibility are shown to share more features with fault-tolerance and error recovery needs than with short-term flexibility. Five partial, complementary solutions are suggested which together should improve the inherent flexibility of future software systems: (1) global information services, (2) high-level standardization such that only the standards actually needed are generated, (3) distributed agent heterarchical architectures, (4) dynamic updating of configuration-oriented software, and (5) computational reflection.