A KITE in the Wind: Smooth Trajectory Optimization in a Moving Reference Frame

Abstract

A significant challenge for unmanned aerial vehicles capable of flying long distances is planning in a wind field. Although there has been a plethora of work on the individual topics of planning long routes, smooth trajectory optimization and planning in a wind field - it is difficult for these methods to scale to solve the combined problem. In this paper, we address the problem of planning long, dynamically feasible, time optimal trajectories in the presence of wind which creates a moving reference frame. We present an algorithm, KITE, that elegantly decouples the joint trajectory optimization problem into individual path optimization in a fixed ground frame and a velocity profile optimization in a moving reference frame. The key idea is to derive a decoupling framework that guarantees feasibility of the final fused trajectory. Our results show that KITE is able to produce high quality solutions for planning with a helicopter flying at speeds of 50 m/s, handling winds of up to 20 m/s and missions over 200 km. We validate our approach by real world experiments on a full scale helicopter with a pilot in the loop. Our approach paves the way forward for autonomous systems to exhibit pilot-like behavior when flying missions in winds aloft.