Downwash Detection and Avoidance with Small Quadrotor Helicopters

By using four independent rotors to provide lift and control moments, the quadrotor helicopter provides researchers with a small, mechanically simple and e↵ective vertical-flight platform. Typically, the lift and resultant torque due to each rotor can be approximated with simple aerodynamic models. Although these models have proven to be adequate in low advance-ratio flight conditions [1], they cannot account for the flow conditions associated with high-speed flight or the presence of large disturbances such as wind gusts or downwash from nearby rotorcraft. Real-time measurements of the flow-field around a flying vehicle provide a description of the flight conditions that would otherwise be impossible with only inertial-based instruments. This paper introduces a pressure-probe flow measurement system developed for a small quadrotor. The design, fabrication and calibration of the instrumentation package are presented along with data from autonomous flight trials using motion-capture-based positioning data. As a demonstration of the capabilities a↵orded by onboard flow sensing, a strategy for avoiding the downwash of a neighboring rotorcraft is proposed and demonstrated. Assimilating vertical flow-field measurements with a Bayesian estimation algorithm detects and localizes the source of vertical flow disturbances for use in a flight-path planner developed for proximity flight. The path planner minimizes a cost function that drives the vehicle to a desired waypoint while avoiding the Research Associate, Department of Aerospace Engineering, [email protected] , AIAA Member. Ph.D Candidate,Department of Aerospace Engineering, [email protected] , AIAA Student Member. Willis H. Young Jr. Associate Professor of Aerospace Engineering Education, Department of Aerospace Engineering, and the Institute for Systems Research [email protected], AIAA Senior Member. Computer Scientist, Naval Research Laboratory, [email protected] , AIAA Member.