Tip-Vortex Localization for Cross-Stream Position Control of a Multi-Hole Probe Relative to a Stationary Wing in a Free-Jet Wind Tunnel

The continuing development of fully autonomous aircraft requires advanced sensing and control systems in order to complete difficult tasks such as aerial refueling and close formation flight. To accomplish such maneuvers, an aircraft must be able to measure the location of nearby aircraft and position itself relative to these other flight vehicles. In visually degraded environments where vision sensors might struggle, wake sensing provides an effective means of locating other aircraft. Using onboard velocity measurements, we combine a point-vortex model with a Bayesian filter to estimate a leader aircraft location through the sensing of wingtip wake vortices. We demonstrate the filtering strategy by estimating the position of a wing using experimental data in an open-jet wind tunnel. An experimental test-bed rapidly positions a flow measurement system within the wake of a wing in a free stream. A flow survey of the tip vortex within the aerodynamic wake of a leader aircraft, conducted with a multi-hole probe, measures velocities in the cross-stream plane. The wake position estimates are used for closed-loop control of the sensor position. This paper presents the estimation strategy and model, experimental data, closed-loop control simulation, and real-time wind tunnel feedback control results. In ongoing work, we are considering applications in which a follower aircraft senses the wake of a leader aircraft and positions itself for maximum aerodynamic efficiency.