Simplified Wake Vortex Encounter Modeling and Inner Loop Controller Analysis for Small UAS

Abstract

Wake vortices generated by manned aircraft pose a significant hazard to the safe operation of UAS at and near airports. To analyze this hazard, a simplified methodology for modeling and simulating small UAS wake vortex encounters is proposed. The wake vortex is approximated as a spatially-linear varying wind field, which allows for seamless integration with standard flight dynamic models. This simplified approach is suitable for evaluation and categorization of the safety hazard introduced by wake vortex encounters for UAS operations, as it can be rapidly developed and applied to a variety of UAS and wake encounter scenarios. Additionally, since unmanned aircraft typically operate with some level of automatic control, roll and pitch hold controllers are designed to assess the impact of inner loop flight control design on the severity of the wake encounter. Simulation results showed that controllers designed for maximum disturbance rejection lead to noticeable attenuation of the UAS response to prolonged wake
vortex encounters.