Multivariable control design for artificial blood-gas exchange with heart-lung machine support

In this paper the design of a robust multivariable controller for the blood-gas exchange during cardiopulmonary-bypass with heart-lung machine support is presented. The proposed control strategy of the two-input-two-output oxygenation/decarbonisation process is divided into inner- and outercontrol loops. The inner-loop consists of input-output linearisation by state-feedback, which is extended with a Smith-like predictor for time-delay compensation and partially decouples the oxygenation exchange. The outer-control loop consists of a single linear multivariable controller, which is tuned via the ℋ
_∞
-loop shaping approach for robust performance and accounts for plant, linearisation and time-delay uncertainties. The controller was tested with an experimentally validated model of blood-gas exchange over the whole operating range and shows good results with respect to reference changes and disturbance rejection. The control strategy is suggested to improve patient's safety during the cardiopulmonary bypass (CPB) procedure.