Biomedical Engineering Reference
In-Depth Information
Rotation
Rotor blade
Flapping axis
Pitching axis
Actuation through
rotor shaft
FIGURE 5.14 Schematic of flapping rotor operation. Adapted from Ref. 61 . F. Bohorquez and D.J. Pines, Design and
development of a biomimetic device for micro air vehicles, Volume 4701, 503-517, SPIE 2002.
A schematic of the rotor hub with articulation
for flapping and pitching is shown in Figure
5.14 . A scotch-yoke mechanism converts rotary
input from a small electric motor into linear
motion that is conveyed through the hollow
rotor shaft into a lever mechanism on the rotor
hub. These levers actuate the rotor blade in flap-
ping and pitching about their respective axes.
Large-amplitude flapping (total angle of 46°)
and pitching ( ± 20°) motion is possible, and the
frequency of the motion depends on the rota-
tional speed of the motor. A picture of the rotor
with the blades at a large flap angle is shown in
Figure 5.15 .
The mechanism was tested by spinning the
rotor at 2,000 rpm, keeping the flap motion fixed
and prescribing a pitching motion of amplitude
6° at frequencies varying from 0.25 to 2 per revo-
lution of the rotor. It was observed that while
operating at mean pitch angles close to the static
stall angle of the airfoil, the oscillatory pitching
resulted in around 50% improvement in hover
efficiency. As expected, there was negligible
effect at lower angles of attack, where the
Rotor blade
Rotation
Flap angle
FIGURE 5.15 Rotor blades actuated to a high flap angle. Adapted from Ref. 61 . F. Bohorquez and D.J. Pines, Design and
development of a biomimetic device for micro air vehicles, Volume 4701, 503-517, SPIE 2002.
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