The Direction Zone of Engineless UAVs in Dynamic Soaring
B. J. Zhu, Z. X. Hou, Y. F. Lu and S. Q. Shan

Source CMES: Computer Modeling in Engineering & Sciences, Vol. 105, No. 6, pp. 467-490, 2015
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Keywords dynamic soaring, flight endurance, cutting-in angle, gradient wind, UAV.

This paper mainly analyzes the dynamic soaring of UAV utilizing gradient wind. Dynamic soaring is an efficient path in which UAV absorbs energy from environment to enhance its flight endurance. A set of three-dimensional point dynamic equations for a soaring aircraft in three degrees of freedom is used in calculations. To simplify the calculation, the gradient wind’s direction is taken into decomposition. The notion of trajectory subsection analysis is applied to account for the energy transformation mechanism during the dynamic soaring, and the zone of direction is converted into cutting-in angle, which is regarded as initial limiting condition in the optimization of dynamic soaring trajectory. Then, the relationship between energy gain/loss and cutting-in angle is acquired. Three dynamic soaring styles corresponding to three typical cutting-in angles are selected to be analyze intensively, and the explicit characters of trajectories, airspeed, attitude angles and energy variation are presented. All these results reveal the zone of direction and validate the method of control for a dynamic soaring UAV soaring in gradient wind field without thrust.

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