Fixed-Wing Unmanned Aircraft In-Flight Pitch and Yaw Control Moment Sensing

Unsteady, nonlinear aerodynamics at high angles of attack challenges small unmanned aircraft system autopilots that rely heavily on inertial-based instrumentation. This work introduces an expanded aerodynamic sensing system for poststall flight conditions that incorporate high angle of attack and prop-wash aerodynamic forces based on in-flight measurement. A flight vehicle with a 1.8 m wingspan is used in wind-tunnel tests to measure the pitch and yaw moments due to free stream and prop-wash over the tail surfaces at high-thrust, low-airspeed conditions including hover. Test data are used to develop two methods to determine in-flight real-time pitch and yaw moments: a probe designed specifically to measure prop-wash flow and a set of pressure sensors embedded throughout the tail surfaces. Through comparisons with torque-transducer measurements also acquired in the wind-tunnel tests, both methods are shown to provide accurate moment estimates at hover and forward-flight conditions. With information directly provided by in-flight measurement, real-time pitch and yaw control can be enhanced using a simple and reliable framework.