Novel Approach to Dynamic Soaring Modeling and Simulation

Abstract

This paper revisits dynamic soaring on the basis of a nonlinear point-mass flight dynamics model previously used for scale-model aircraft to design path-following autopilots endowed with theoretically and experimentally demonstrated stability and convergence properties. The energy-harvesting process associated with specific maneuvers of a glider subjected to horizontal wind, and on which dynamic soaring relies, is explained in the light of this model. Expressions for the estimates of various variables involved in dynamic soaring along inclined circular paths crossing a thin wind shear layer, as experienced by model glider pilots over the world, are derived via approximate integration of the model equations. Given a glider’s path and a wind profile, this model also presents the asset of yielding an explicit ordinary differential equation that entirely characterizes the time evolution of the modeled glider’s state along the path, thus allowing for an easy simulation of dynamic soaring over a large variety of operating conditions. This simulation facility is viewed as a tool that usefully complements other studies of dynamic soaring that focus on trajectory optimization via dynamic programming. Its usefulness is here illustrated by first validating the aforementioned estimates in the case of circular trajectories crossing a thin wind shear layer, and then by showing how it applies to other examples of trajectories and ocean wind profile models commonly considered in studies about the dynamic soaring abilities of albatrosses.