A supervisory control approach for execution control of an FMC

This paper presents a generic methodology based on formal language theory f or the modeling and control of flexible manufacturing cell (FMC) systems. T he motivating idea behind the overall approach stems from the supervisory c ontrol theory under the framework of Ramadge and Wonham. Essentially, we ch aracterize the asynchronous and dynamic behavior of an FMC as a regular lan guage and formulate the control logic generation problem as a sublanguage c alculation problem, which requires the resulting language to satisfy at lea st two properties: maximal permissiveness and controllability. Then an algo rithm for resolving the problem is presented. Based on the solution of the problem called supervisor, we propose a controller architecture that guaran tees coordinated operation of an FMC through the regulation of occurrences of events. An adaptive control policy that regenerates supervisors on chang es in task configurations is presented and a dynamic equation that describe s the evolution of the control logic along time is derived. Then, we show t hat the proposed maximally permissive adaptive control policy has a number of preferred properties, including computational efficiency and consistency between the successive supervisors. Finally, a controller for an example F MC is implemented, using the object-oriented software modules. Our procedur e has the merit of mathematical soundness, modular design, and systematic i mplementation.