Modeling of dynamic cardiovascular responses during G-transition-induced orthostatic stress in pitch and roll rotations

Dynamic and fuzzy models for a typical subject´s cardiovascular response to the orthostatic stress have been developed based on experimental data. In our original study (Cheung et al., 1999), arterial blood pressure (BP) time-series data were obtained using a man-rated tilt table that applies gigahertz-acceleration transitions from +0.861 Gz [head-up (HU)] to -0.707 G [head-down (HD)] and back to +0.861 Gz (HU) using either pitch or roll rotations (Cheung et al., 1999). G transitions of different duration and onset rates are common in fighter maneuvers. Based on these data, two types of predictive models have been developed in this paper: 1) second-order discrete-time models that predict BP dynamics during pitch and roll rotations and 2) fuzzy logic models that predict important variations in a subject´s cardiovascular dynamics induced by HU-to-HD and HD-to-HU transitions. These two types of models assist in providing an operationally important predictive view on the characteristics of BP responses to orthostatic stress induced by pitch and roll rotations of a fighter jet pilot. The new models are being currently utilized in the design of operational recommendations for more G-tolerant operational flight regimes (e.g., split-S tactical maneuver) than the ones currently in use for modern combat aircraft.