Positioning Algorithm for Autonomous Thermal Soaring

Abstract

Apositioning algorithm for autonomous thermal soaring is proposed and tested in a simulation environment. The Carmichael model was used for the characterization of thermals of varying strengths, and the values of bank angle and airspeed required to extract maximum energy were derived from an analysis of sailplane performance. Twodimensional strip theory was used within a high-fidelity six-degree-of-freedom model to estimate the interaction of the aircraft with updrafts caused by thermal activity, and a control system, based on classical theory, was designed to position the sailplane for optimum energy extraction. The need for a better algorithm is shown, and improvements were achieved by using aileron deflection information to determine the orientation of the thermal center relative to the sailplane. Energy extraction is demonstrated in terms of altitude gained, and the algorithm’s ability to position the sailplane is shown in a number of scenarios.