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Figure 1 Two-axis gyro Stabilized Mount installation
Each axis comprises a servomotor, driving the platform through an anti-backlash gear, a precision
potentiometer for positional measurements, and a pair of limit stops. The anti-backlash gear
minimizes the backlash from platform motions to less than 10 Arc Seconds. Furthermore, Watson
Industries has installed two gyros and a triaxial accelerometer used to calculate corrective
commands to the drive motors.
The two gyros are rugged vibrating-structure gyroscopes, whose angular rate signals are converted
from analog to 16-bit digital form. The effects of temperature variation on the DC bias of the gyros
are digitally corrected.
The micro controller assesses the desired motion of the platform based on preset angles in its
memory. It then compares this desired motion against the real motion of the platform, sensed by
the gyros and accelerometers, developing a rate error value. A servo-control system (P.I.D.
algorithm), uses the current (Proportional), past (Integral), and predicted future (Differential) value
of this error to derive a motor voltage that will drive the error to zero. In other words, the servo-
control system ensures that the motion of the platform exactly matches that of the preset value in
inertial space.
Watson Industries, Inc.
SMS-P233 Rev B 10/17/2017
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