Sensors and Methods for Mobile Robot Positioning

Chapter 2: Heading Sensors 33
2.1.3.1 Futaba Model Helicopter Gyro
The Futaba FP-G154 [FUTABA] is a lowcost
low-accuracy mechanical rate gyro
designed for use in radio-controlled model
helicopters and model airplanes. The Futaba
FP-G154 costs less than $150 and is available
at hobby stores, for example [TOWER].
The unit comprises of the mechanical gyroscope
(shown in Figure 2.2 with the cover
removed) and a small control amplifier.
Designed for weight-sensitive model helicopters,
the system weighs only 102 grams
(3.6 oz). Motor and amplifier run off a 5 V
DC supply and consume only 120 mA.
However, sensitivity and accuracy are orders
of magnitude lower than “professional”
Figure 2.2: The Futaba FP-G154 miniature mechanical
gyroscope for radio-controlled helicopters. The unit costs
less than $150 and weighs only 102 g (3.6 oz).
mechanical gyroscopes. The drift of radio-control type gyroscopes is on the order of tens of degrees
per minute.
2.1.3.2 Gyration, Inc.
The GyroEngine made by Gyration, Inc.
[GYRATION], Saratoga, CA, is a low-cost
mechanical gyroscope that measures
changes in rotation around two independent
axes. One of the original applications
for which the GyroEngine was designed is
the GyroPoint, a three-dimensional pointing
device for manipulating a cursor in
three-dimensional computer graphics. The
GyroEngine model GE9300-C has a typical
drift rate of about 9(/min. It weighs
only 40 grams (1.5 oz) and compares in
size with that of a roll of 35 millimeter film
(see Figure 2.3). The sensor can be powered
with 5 to 15 VDC and draws only 65
Figure 2.3: The Gyration GyroEngine compares in size
favorably with a roll of 35 mm film (courtesy Gyration, Inc.).
to 85 mA during operation. The open collector outputs can be readily interfaced with digital circuits.
A single GyroEngine unit costs $295.
2.2 Piezoelectric Gyroscopes
Piezoelectric vibrating gyroscopes use Coriolis forces to measure rate of rotation. in one typical
design three piezoelectric transducers are mounted on the three sides of a triangular prism. If one
of the transducers is excited at the transducer's resonance frequency (in the Gyrostar it is 8 kHz),