Meindert said:
Well, read the datasheets. AD says specifically in their datasheets that the
ADXL's can be used as an inclinometer. Apart from that, a boat seems an
'almost fixed' one-g environmet to me.
Meindert
Stand on your bathroom scales while under sail in rollers and
then tell me your local gee is stable at one. The boat bobs and
weaves. The local gee variation is one of the things that cause
seasickness. Your simple accellerometer pitch and roll sensor
will also get sick.
The sensors could be used as roll, etc sensors, but not if the
platform is heaving or weaving, unless you use twice as many as
you might otherwise out of phase, and then combine their outputs
to enable nulling the elevator effects.
A pendulum and potentiometer rig seems better though it too will
sense unwanted displacements. A gyro setup, even a stationary one
with pendulum type sensing via bar coded markings, is likely the
best. How much accuracy do you need? To resolve satellite
pointing issues, a fixed 3 axis setup (six sensors) will be
required, with integration of the outputs to derive azimuth and
elevation, unless you servo the yaw efficiently and then sense
the elevation, then you only need juggle two indications. You
might use an electronic compass to control the yaw of the antenna
platform. Daily adjustments of magnetic variation might be needed
in passage, and as well, you would need to integrate compass
variations due to local ferrous masses at various headings.
Perhaps a gyrocompass?
This is not so simple as it sounds. If it was, a one chip
controller would be produced by now, and our airliners and cars
might all have satellite reception available.
Alternate methods might be use of gps position, time of day, and
star sight information during clear sky moments.
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