Gamma and velocity tracking for UAV obstacle avoidance in pitch plane

Global and local (or reactive) obstacle avoidance across unmanned aerial vehicle (UAV) altitudes is a challenging problem. In an UAV autonomous flight when the obstacle threat is determined in-flight from the on-board sensors, techniques to avoid the obstacles autonomously in real-time and continue with the predefined flight path need to be incorporated into the autonomous systems. Hence a requirement in vertical (pitch) plane is to plan vehicle positions different from the obstacle positions. In this paper, a real-time autonomous trajectory generation scheme useful to design these potential vehicle positions incorporating vehicle capability is presented. It is known that vehicle velocity and flight path angle (gamma) uniquely determine vehicle positions. As a result, path planning for obstacle avoidance boils down to gamma tracking and vehicle velocity tracking problems. The trajectory generation scheme as a tracking problem is applied to illustrate avoiding hypothetical static ground obstacle like building in pitch plane using a three degree of freedom fixed wing micro air vehicle model.