Aerodynamic Sensing for a Fixed Wing UAS Operating at High Angles of Attack

Abstract

The flight profile of typical small unmanned air systems (UAS) has expanded in the last decade beyond those encountered by traditional fixed-wing transport and rotary-wing aircraft. These new flight conditions may involve unusual flight mechanics as with flapping wing flight or complex aerodynamics when performing difficult maneuvers as part of routine operations. Such scenarios typically involve unsteady and inherently non-linear aerodynamics that challenge current autopilots relying primarily on inertial measurements and GPS data. The addition of aerodynamic feedback to the current UAS sensing and control framework can enable the autopilots of aircraft operating under such conditions to better achieve their control objectives and expand their autonomous flight capabilities. This paper describes the ongoing development of a pressurebased aerodynamic data system for a fixed wing UAS operating at high angles of attack. Expansions to the aerodynamic instrumentation package based on flight test results are described. These include an expanded set of wing pressure ports and a custom designed multi-hole probe for prop-wash estimation. Autonomous flight test data from the first generation UAS system transitioning between cruise and hover are presented and discussed. Open loop flight data acquired using the upgraded sensing concept is then presented. Flight test results show that the sensing package provides data that is complementary to a typical Inertial Measurement Unit and can support the development of feedback control strategies based on aerodynamic measurements.

Distributed Pressure Sensing–Based Flight Control for Small Fixed-Wing Unmanned Aerial Systems

“…For example, the flow sensors can be used to detect flow separation and stall in different regions of the wing, offering the potential to operate much closer to the stall limits of the aircraft. Previous work [7,25], has used manually selected thresholds for properties of the pressure distribution to detect stall, but it would seem that an ANN approach would also be well suited for this task if a training set with direct measurements of stall state were available (which was not the case in this work). Taking the idea of stall detection further, the controller could intentionally stall the aircraft during extreme manoeuvres and then recover by sensing when the flow has reattached to the wing.…”

“…A variety of different man-made sensors have also been used to measure the distribution of flow properties on the wings of small UAS. The most common are pressure sensors [6][7][8][9][10][11][12], but more novel sensors such as hotfilms [13,14] and artificial hair sensors [15,16] have also been used to measure flow velocity.…”

Bird-inspired robotics principles as a framework for developing smart aerospace materials

“…107,108 Similarly, shear sensing can be used to further monitor laminar-turbulent boundary layer transition and flow separation. 75,109–111 These examples show that, as in Kalman filtering, the fusion of multiple sensory modalities have the potential to greatly reduce the uncertainty in online vehicle state estimation. 112 Here, we present isolated examples of embedded sensor applications because those dominate the literature (the IMU in autonomous vehicles is a key exception, but it’s centralized).…”

A Flexible Capacitive Pressure Sensor Based on Ionic Liquid

“…In general, there are three main methods for measuring the distribution of aerodynamic pressure, the discrete pressure hole method [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ], the pressure sensitive coating technology (PSP) [ 10 , 11 ], and the computational fluid dynamics (CFD) [ 12 , 13 , 14 , 15 ]. There are still many problems with these methods, both in the experimental measurement and theoretical analysis.…”