Abstract
This paper deals with a non-contact method to identify the aerodynamic propeller constants of the Parrot AR.Drone quadrotor. The experimental setup consists of a microphone installed in the flight arena to record audio data. In terms of methodology, a spectrogram analysis is adopted to estimate the propeller velocity based on the filtered sound signal. It is known that, in a hovering maneuver, when the UAV mass increases, the propellers rotate faster to produce the necessary thrust increment. In this work, the rotorcraft takes off with its factory settings, first with no hull, corresponding to a mass of 413 g, and after with a small hull, corresponding to a mass of 444 g, and a bigger hull, corresponding to a mass of 462 g. In the sequence, the velocity of the propellers are estimated for each of these three cases using spectrograms of audio recorded by a microphone, corresponding to the sound generated by the four rotors. Finally, the estimated velocity is used to identify the aerodynamic parameters, thus validating the proposal.
Highlights
The case with the fundamental, second, and third harmonics are considered; it is used a weighted mean, with the frequencies weighted by their respective standard deviation (STD), this last one given by s sζ =
Comparing the spectrograms, one can see an increase in the frequency with the mass increase, corresponding to an increased propeller speed
It is verified that there is a direct relationship between the rotor speed and the sound frequency, which is used to determine the aerodynamic coefficient for the propellers
Summary
Vehicles (UAVs), which have been used in a wide range of applications. Most such advances are related to the increasing computational power of embedded systems and the improvement in sensor accuracy. In the case of aerial robotics, spectrogram and sound processing can be used to identify the acoustic signature and to classify UAVs [9]; to determine the altitude, velocity, and revolutions per minute of an aircraft [10]; and to estimate the UAV location based on beacon signals [11]. The constants related to the propellers, associated with the low-level model of the quadrotor, can be determined Notice that this is a noncontact measurement, which avoids risk to the user when trying, for instance, to manually measure the rotor speed, and allows us to obtain the value of such parameters even when dealing with vehicles that do not provide such information through the embedded sensors (close vehicles).
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