Investigation of Stability in Skydiving by the Derivation of State Equation for Body Behavior and Root Analysis

概要

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The objective of this study was to investigate the stability during a skydiving freefall, in which the diver has to take various body positions in order to control precisely their distance, velocity, and direction relative to the other divers for group performance. For this objective, the state equation for a simple elliptic cylinder model was initially derived, considering its equations of motion and fluid force characteristics. Next, using the form of the state equation derived for the elliptic cylinder and input/output data obtained from the developed simulation method for the body behavior of the skydiver, the state equations of the skydiver were identified for various body positions. Finally, roots of the state equations were obtained to investigate the stability. As a result, the causes of instability such as the spin and spiral phenomena were clarified as an unstable natural modes, and the stable limit of the body position was obtained as a value of the parameter which is related to the arch magnitude of the divers body.