Switching between sensor configurations for uncertain systems; application to control of anesthesia

Closed-loop control of anesthesia is a safety critical application, where the patient is in the loop. It is characterized by large uncertainty due to the variability in patient responses to drug administration. Linear time-invariant robust control has been used to ensure robust stability and performance, providing essential guarantees for patient safety. Switching control could improve performance, however, providing robustness guarantees for time-varying controllers remains challenging in the presence of large uncertainty. This paper provides proof of robust stability for a switching solution for propofol-remifentanil anesthesia, where a scheduling function determines switching based on the noise characteristics of the feedback signal. The switching structure and proof of stability are based on a frequency-domain method for scheduled control of systems with varying sensor configurations. This framework allows us to extend proof of stability to systems with (unstructured) uncertainty. The presented robust stability proof relies on the circle criterion. Simulation results show the potential performance improvement, while robust stability guarantees ensure patient safety is maintained in the time-varying (switching) system.