Small expert systems as intelligent modules of programmable logic controllers

The authors deal with the possibility of and the benefits from building a small rule-based expert system which can be incorporated in a programmable logic controller (PLC) intelligent control module to provide simultaneous and efficient processing of both logic control problems and special feedback control tasks. The required exchange of information between the module and either the process or the PLCs CPU, the interaction with the basic logic controller, and the types of real problems that can be solved by an expert intelligent module are also considered. With a standard inference engine and programming only of the empirical rules, these expert control modules can improve the efficiency and productivity of industrial processes, particularly in cases of knowledge-based control tasks