Postprandial Blood Glucose Control using a Hybrid Adaptive PD Controller with Insulin-on-Board Limitation

LEÓN-VARGAS, F. ; GARELLI, F.; DE BATTISTA, H.; VEHÍ, J.

BIOMEDICAL SIGNAL PROCESSING AND CONTROL

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2013 vol. 8 p. 724 - 736

1746-8094

This paper addresses the design of blood glucose control duringthe postprandial period for Type 1 diabetes patients. An artificialpancreas for ambulatory purposes has to deal with the delays inherent tothe subcutaneous route, the carbohydrate intakes, the metabolic changes,the glucose sensor errors and noise, and the insulin pump constraints. Atime response typically obtained in closed-loop insulin delivery showshyperglycemia in the early postprandial period caused by the lag in theinsulin absorbtion, followed by hypoglycemia caused by control overreaction.A hybrid control system is proposed in this paper to overcomethese problems. An insulin bolus is administered prior to the meals likein open-loop control, whereas a PD controller is used for robust glucoseregulation. The controller gain is progressively increased after thebolus from zero up to its nominal value as function of the insulin onboard, so that the PD controller becomes fully operational just when theinsulin on board falls below a prescribed value. An excessiveaccumulation of active insulin is avoided in this way, drasticallyreducing the risk of hypoglycemia. The controller gain is adapted bymeans of a variable structure algorithm, allowing a very simple softwareimplementation. The robust performance of the control algorithm isintensively assessed insilico on a cohort of virtual patients underchallenging realistic scenarios considering mixed meals, circadianvariations, time-varying uncertainties, discrete measurement andactuation, sensor errors and other disturbances.