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The
ambitious flapping of piezo wings |
View all news
 Piezoelectric
actuators are being used to create a flapping motion
that can efficiently drive micro aerial vehicles.
As demonstrated by birds and insects, flapping flight
provides superior manoeuvrability and is more
aerodynamically efficient than conventional steady-state
aerodynamics at low speeds.
“The challenge is to mimic the extraordinarily efficient
flying mechanism of insects,” says Dr Robert Dorey, the
Head of Cranfield University’s Microsystems and
Nanotechnology Centre.
Insect wings don’t just move up and down – they have a
range of horizontal and vertical motions that reduce
drag on the up stroke and maximise lift on the down
stroke while providing steering and tilting mechanisms.
“We’ve demonstrated that the flapping motion is possible
and have models capable of several wingbeats per
second,” Dr Dorey says. “Now we’re trying to better
control the flapping and twisting motions.
”Piezoelectric actuators are easy to control, have high
power density and can produce high output force. With
appropriate stroke amplification, piezoelectric
actuators can be used to produce large angular
displacements and drive flapping wings.
Work is now underway at Cranfield to develop the
technology so it can run off a small battery, and to
integrate it into more complex systems. A prototype may
be just a few years away.
How it works
The team at Cranfield, lead by Dr Zhaorong Huang, is
developing a piezoelectric actuator system with two
degrees of freedom motion for the flapping wing micro
aerial vehicle (MAV) applications.
The first stage of the project concerns control of the
flapping and twisting motions of a flapping wing MAV.
The second part is about engineering a mechanical system
to convert and amplify the linear piezoelectric
displacement to angular movement, with minimum space and
added weight.
The wing is made up of two piezofans coupled to a
flexible wing formed with carbon fibre and nylon wing
spars and flexures and a polymer skin. A piezofan
consists of a piezoelectric and elastic metal layer with
epoxy bonding and works like a traditional hand held
Chinese fan. By linking the two fans together, and using
high speed photography, the two degree of freedom motion
of a flapping wing can be produced and studied.
Analytical equations, finite element modelling and
experimental tests have been employed in this study. It
has been observed that the phase delay between the
driving voltages applied to the coupled piezoelectric
fans plays an important role in the control of the
flapping and twisting motions of the wing. The very
simple two-bar flexure mechanism is a promising
technique for piezoelectric displacement amplification.
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