Phase II Final Report - NASA's Institute for Advanced Concepts

Chapter 4.0 Entomopter Flight Operations
4.2 Rover-centric Entomopter Navigation
Figure 4-2: Measured Response Data of a Mechanically-modulated FMCW Source Sized
for the Terrestrial Entomopter. (Data acquired under GTRI’s DARPA/DSO-funded
Mesoscaled Aerial Robot Program.)
As shown in Figure 4-3, such an FMCW waveform can be used to generate a ranging solution
that resolves Doppler ambiguities.
A single ultrasonic acoustic source can be vectored by the wing flapping mechanism of the
Entomopter to illuminate not only the ground for altimetry, but also to each side to detect
impending collisions with objects. The same beam can be multiplexed as shown in Figure 4-3 to
create a forward looking beam. Response to the received ranging signal would control the lateral
flight path of the Entomopter as well as its altitude. Active flow control of the wings would
affect lateral maneuvers and can be used to temporarily adjust altitude. An increase or decrease
in wing flapping frequency around the resonant point (as controlled by fuel metering) would
affect longer term vertical maneuvers.
Processing of these return signals could be discrete in that any range to a side obstacle can be
ignored so long as it does not intrude within the Entomopter's safety zone. When an obstacle
moves too close (either due to the movement of the obstacle or due to the Entomopter closing in
on the obstacle) the behavior could be a simple avoidance response. Such a simple obstacle
avoidance algorithm can be implemented with a minimum of onboard processing and can in fact
be almost a reflex action, but the resulting flight path could be “zig-zagging” as the vehicle alternately
tends toward and avoids opposite obstacles. On the other hand, altitude might be monitored
more closely in terms of actual distance to facilitate more coordinated landings.
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