The purpose of this study is to construct an automatically controlled artificial respiratory system for respiratory failure patients based on adaptive control theory. The dynamic characteristics of alveolar CO
2 tension described as a 1-input 1-output bilinear system is controlled by manipulating alveolar ventilation rate as an input. On the other hand, arterial O
2 saturation has a nonlinear relation with arterial O
2 tension, the dynamic characteristics of which are described as a 2-input 1-output bilinear system, including the cross effect of alveolar ventilation rate and inspired O
2 tension to the output. The control system concerning arterial O
2 saturation by inspired O
2 tension is mathematically designed as another independent 1-input 1-output system. Then, two independent 1-input 1-output models can be practically used without making the relation of the inputs and the outputs decoupled in every sampling time from the concept of the adaptive system that yields the identification of the independent relation between the input and the output. Furthermore, it is also practically possible to regard the nonlinearity and individuality of the controlled object, and the change in its characteristics etc., as the changing parameters of the mathematical model. The effectiveness of the control system is confirmed in numerical simulations in both cases of conditions at rest and at a changed metabolic state, corresponding to an oxygen consumption rate change.
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