Anti-Windup and Disturbance Rejection Controller Design of an Automated Oxygen Control System for Premature Infants

Abstract

For premature infants, the peripheral oxygen saturation (SpO₂) level has significant effects on their health. Manual control of the fraction of inspired oxygen (FiO₂) by nursing staff is not only a highly labor intensive solution, but also a hard task to maintain infants' SpO₂ within the safe range. For this clinical need, an automated oxygen control system for premature infants is developed, which is based on PI control and derivative feedback (DF) control. Clinical tests showed that, when there is either a manual-automatic mode switch and tube feeding, integral windup may occur which will lead to the degradation of control performance. To overcome this problem, an anti-windup control strategy is developed. Due to blood oxygen desaturations caused by unknown disturbances, a disturbance observer is adopted with the disturbance estimate used for disturbance rejection. According to the results of dynamic simulations, the controller with anti-windup and disturbance rejection design has the best performance among all controllers, it could achieve bumpless transfer during mode switching, decrease FiO₂ in a timely manner when feeding is finished, and can shorten the recovery time from desaturation events and after feeding. This controller could minimize the time that SpO₂ is outside the safe range, which is promising for clinical application.