where V-airplane ground speed; e - ellipsoid oblateness; K - airplane heading.
Represented by expression (5) AGS mathematical model can be realized by block
diagram when following relationships were taken into account during its plotting:
,
cos
sin
cos
)
(sin
cos
1
r
K
V
V
r
K
V
V
K
r
V
E
N
=
=
=
=
=
−
where V
N
, V
E
- north, east components or airplane ground speed.
Gyro gravimeter. The most perspective type of electromechanical gravimeter
based on dynamically customized gyroscope. In the fields of navigation and guidance,
specific force sensors play a leading role in most system mechanizations. Thou, as
might be expected, a broad spectrum of specific force sensors have been developed for
use in guidance and navigation, but until recently the possibility of their use in
gravimetry had been largely ignored. Perhaps the most promising of these instruments
is the pendulous gyro accelerometer (PIGA). It is interesting to note that a device
somewhat similar the PIGA was patented in Russia by V.V. Kochegura in 1960.
At the heart of the device is a single-degree-of-freedom which has been made
pendulous by the addition of an unbalancing mass along its spin axis. The gyro wheel
is held in supporting gimbals free to rotate about only one axis, referred to as the output
axis. On the output axis is mounted an electromagnetic pickoff which produces a signal
proportional to the rotational displacements of the wheel support relativity the
platform, and an electromagnetic torque, which applies torque about the output axis in
response to input current [6-7].
The unbalances mass along the spin axis produces a torque about the gyro output
axis, and the resulting rotation about this axis is sensed by the signal Pickoff. This
signal is amplified and fed to the platform motor which rotates the platform at an
angular velocity sufficient to cause a gyroscopic reaction torqe about the gyro output
axis which exactly balances the gravity torque. Under these conditions, the angular
velocity of the platform is a measure of the specific force acting on the unbalancing
mass. The gyro wheel is enclosed and floated in a viscous fluid which provides both
support and damping. It is this floated member, referred to as the float of the gyro,
which acts as a torque summing device. It is acted on by torques due to the pendulous
mass and gyroscopic torques due to the inertial angular velocity about its input axis.
Torque may also be applied to the float by application of a command current to the
torque generator.
The steady state sensitivity of the PIGA can be shown to be [6, 8]:
,
H
P
a
i
=
- 1581 -