Improving evolvability of a patient communication control system using state-based supervisory control synthesis

Abstract

Supervisory control theory enables control system designers to specify a model of the uncontrolled system in combination with control requirements, and subsequently use a synthesis algorithm for automatic controller generation. The use of supervisory control synthesis can significantly reduce development time of supervisory controllers as a result of unambiguous specification of control requirements, and synthesis of controllers that by definition are nonblocking and satisfy the control requirements. This is especially important for evolving systems, where requirements change frequently.For successful industrial application, the specification formalism should be expressive and intuitive enough to be used by domain experts, who define control requirements, and software experts, who implement control requirements and synthesize controllers. This paper defines such a supervisory control specification formalism that consists of automata, synchronizing actions, guards, updates, invariants, independent and dependent variables, where the values of the dependent variables can be defined in terms of functions on the independent variables.We also show how the language enables systematic, compositional specification of a control system for a patient communication system of an MRI scanner. We show that our specification formalism can deal with both event-based and state-based interfaces. To support systematic, modular specification of models for supervisory control synthesis, we introduce state trackers that record sequences of events in terms of states. The synthesized supervisor has been successfully validated by means of interactive user guided simulation.