Heuristic control of dynamic soaring

Dynamic soaring is flight sustained through the power gained by coordinated manoeuvering in wind gradients. These wind gradients can be horizontal, as caused by wind shear, and relevant to the mode of dynamic soaring by certain birds such as the albatross; or they may be vertical gradients, as caused by irregular thermal updrafts. Other defacto gradients may be encountered due to gusts and local orographic flow. All of these modes may be exploited by uninhabited air vehicles (UAVs) as sources of energy and hence increase their range and endurance. The problem of determining dynamic soaring trajectories has been previously explored in the literature. However, those studies have focused on regular horizontal gusts and have neglected the problem of determining closed loop control laws. Given the scope of current knowledge, the technology to apply dynamic soaring to UAVs is immature. This paper describes two approaches to the closed loop dynamic soaring control problem: the first involving extensive analysis of perturbed open loop trajectory solutions; the second involving the adoption of a simple heuristic. Experimental results are presented for the second method to illustrate the approach.