Vision Based Forward Sensitive Reactive Control for a Quadrotor VTOL

Deployment of aerial robotic vehicles for real world tasks such as home deliveries, close range aerial inspection, etc., require robotic vehicles to fly through complex and cluttered 3D environments such as forests, shrubbery or into balconies, garages, or sheds. Dense high-speed optical flow can provide real-time motion cues for obstacle avoidance that does not require 3D full reconstruction of the environment. However, classical reactive control does not 'look ahead' and tends to bounce off obstacles rather than generating a smooth trajectory that anticipates and avoids upcoming obstacles. In this paper, we consider deriving a fully image based control criteria that forward predicts a cylinder of free space into the image flow representation of the environment and steers the vehicle by manoeuvering this cylinder through the upcoming environment. The length and radius of the cylinder provide a guarantee that the vehicle can indeed fly through the space identified and the fact that it is predicted forward into the environment leads to smooth anticipation of upcoming obstacles. Results are obtained for a quadrotor flying autonomously through a forest environment.