Model-based falsification of an artificial pancreas control system

Abstract

We present a model-based falsification scheme for artificial pancreas controllers. Our approach performs a closed-loop simulation of the control software using models of the human insulin-glucose regulatory system. Our work focuses on testing properties of an overnight control system for hypoglycemia/hyperglycemia minimization in patients with type-1 diabetes. This control system is currently the subject of extensive phase II clinical trials. We describe how the overall closed loop simulator is constructed, and formulate properties to be tested. Significantly, the closed loop simulation incorporates the control software, as is, without any abstractions. Next, we demonstrate the use of a simulation-based falsification approach to find potential property violations in the resulting control system. We formulate a series of properties about the controller behavior and examine the violations obtained. Using these violations, we propose modifications to the controller software to improve its performance under these adverse (corner-case) scenarios. We also illustrate the effectiveness of robustness as a metric for identifying interesting property violations. Finally, we identify important open problems for future work.