Supervisory Control and Hybrid Systems

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9634146 Morse Plant models are inherently inaccurate, and controllers regulating processes described by such models must be able to ensure satisfactory closed-loop performance in the presence of exogenous process disturbances which cannot be measured. Modern linear control theories are now very highly developed and can be used to design controllers with such capabilities for processes admitting linear models provided the model uncertainties are time-invariant and sufficiently small. But for large model uncertainties derived from real-time changes in plant dynamics, simple examples show that no single, fixed-parameter linear controller can possible regulate in a satisfactory way. Such large uncertainties might arise in real time, because of changes in operating environment, component aging or failure, perhaps a sudden change in plant dynamics due to an external influence. To cope with these types of uncertainties obviously requires a controller which can change or be changed in response to received changes in plant dynamics. An especially promising system architecture with this capability consists of a family or fixed- gain or variable-gain candidate controllers, and an "event-driven switching logic" called a supervisor whose job is to determine in real time which controller should be applied to the process. Examples of supervisory control systems include reconfigurable systems, fault correction systems, and certain types of parameter-adaptive systems. We propose first to refine and extend the concept of supervisory control introduced in our earlier work, to encompass broader classes of systems and second to use supervisory control as a motivating vehicle for the study of basic issues in the newly emerging field of hybrid dynamical systems. ***