Dynamic Geofence Design for Unmanned Aircraft System Path Following in Urban Airspace

The unmanned aircraft system (UAS) traffic management (UTM) system prescribes flight paths for UASs between source–destination pairs. The UASs deployed at the source are restricted to transit in virtual air-geofenced lanes that enclose these paths. This work proposes a moving cylindrical volume design for the lane geofence with an adaptive artificial potential field (APF). The APF comprises an attractive and a repulsive field that ensures that the UAS is contained within the geofence volume. With the cylindrical geofence volume moving along the prescribed path, the UAS effectively follows the path and is robust to uncertainties such as external wind disturbances and path curvature changes. Applying Lyapunov stability criteria, we compute the minimum geofence dimensions needed to reject anticipated bounded impulsive disturbances and curvature changes, taking into account operational limits on UAS velocity, acceleration, and heading angle. This information helps reserve only the necessary airspace subject to anticipated uncertainties in real time. Simulations demonstrate the effectiveness of the proposed APF-based geofence design on zero, constant, and varying curvature paths, considering six-degree-of-freedom quadrotor dynamics for UASs in the presence of bounded impulses as well as variable-magnitude winds.