RIA: Real-Time Discrete Event Control and Its Application toAutomated Manufacturing Systems

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Kumar 9409712 Discrete event systems are those systems which involve quantities which take on a discrete set of values and which are constant except at discrete times when events occur in the system. Examples include communication networks, intelligent vehicle highway systems, manufacturing systems and computer programs. Supervisory control theory was developed to provide a mathematical framework for the design of controllers for such systems in order to meet various qualitative or untimed constraints. A unified approach in which both logical as well as performance specifications can be achieved has been proposed. We propose to use timed state machines to represent the real-time plant as well as the desired behavior. Prioritized synchronous composition of timed state machines has been proposed as the mechanisms for representing interaction among various subsystems of the plant and the controller, and also as the mechanisms of representing composition of various qualitative specifications. The proposed supervisor is also able to react to changes in control specifications since it computes the control policy based on variable limited look-ahead; such time-varying specifications are quite common in a practical setting. The issues of failure detection and recovery will also be investigated by defining "safe" behavior and considering "convergence" to such behavior upon occurrence of failure. In order to apply our theory to the automated manufacturing facility, we will obtain timed state machine models of various machines on the factory, formulate appropriate qualitative and quantitative control specifications, and develop control policies using our theory. We will also investigate the computational complexity of this approach. ***