Safety auxiliary feedback element for the artificial pancreas in type 1 diabetes

The artificial pancreas aims at the automatic delivery of insulin for glycemic control in patients with type 1 diabetes, i.e., closed-loop glucose control. One of the challenges of the artificial pancreas is to avoid controller overreaction leading to hypoglycemia, especially in the late postprandial period. In this study, an original proposal based on sliding mode reference conditioning ideas is presented as a way to reduce hypoglycemia events induced by a closed-loop glucose controller. The method is inspired in the intuitive advantages of two-step constrained control algorithms. It acts on the glucose reference sent to the main controller shaping it so as to avoid violating given constraints on the insulin-on-board. Some distinctive features of the proposed strategy are that 1) it provides a safety layer which can be adjusted according to medical criteria; 2) it can be added to closed-loop controllers of any nature; 3) it is robust against sensor failures and overestimated prandial insulin doses; and 4) it can handle nonlinear models. The method is evaluated in silico with the ten adult patients available in the FDA-accepted UVA simulatorThis work was supported in part by the FEDER-CICYT under Grant DPI2008-06880-C03-01, Grant DPI2011-28112-C04-01, and Grant DPI2010-20764-C02, in part by the European Union Seventh Framework Programme (FP7/2007-2013) under Grant FP7-PEOPLE-2009-IEF Ref 252085, and in part by the Argentinian Government under Grant ANPCyT PICT-2011-0888, Grant CONICET PIP112-2011-00361, and Grant UNLP I164. The work of A. Revert was supported by the Spanish Ministry of Science and Innovation fellowship under Grant FPI BES- 2009-02032