|Vladimir V. Golubev|
New Results in Wake Vortex Evolution, Interaction and Control
Wake vortex safety analysis and control for unmanned aircraft systems (UAS) operating alongside commercial aircraft in the terminal zones are critical aspects in the integration of UAS into the National Airspace System (NAS), particularly in terminal airspace. We address an approach that integrates reduced-order models of wake generation, evolution, interaction and its control incorporating both theoretical and high-fidelity predictions. Our previous study estimated UAS responses in terms of the roll control ratios (RCR) developed by the follower aircraft depending on their position and orientation relative to the wake shed by the leader aircraft, as well as the duration of the wake-UAS interaction. The current paper complements and expands the previous study to describe a predictive, robust feedback-loop flight control model that is applicable to various classes of UAVs in unsteady flight-path scenarios including control of wake response. The control design presented in this paper extends previous research results by first demonstrating asymptotic (zero steady-state error) altitude regulation control in the presence of unmodeled vertical wind gust disturbances. To address the practical considerations involved in small UAV applications with limited computational resources, the proposed control method is designed with a computationally simplistic structure, without the requirement of complex calculations or function approximators in the control loop. Proof of the theoretical result is summarized, and detailed numerical simulation results are provided, which demonstrate the capability of the proposed nonlinear control method to asymptotically reject wind gust disturbances and parameter variations in the state space model. Simulation comparisons with a standard linear control method are provided for completeness.