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H Scientific worked with Forward
Vision CCTV UK to develop a gyro-stabilised version of the
MIC1-400 motorised CCTV camera. A fast and accurate attitude sensor
was used, together with sophisticated integration algorithms running
on the SPECTRE architecture, which allow the camera to work in
the following modes:
- Pointing in a fixed direction relative to the vehicle (azimuth,
elevation)
- Pointing in a fixed direction (absolute heading, elevation),
or
- Pointing at a fixed position and height.
The 3DM-GX1 sensor produced by MicroStrain,
Inc. was used to measure the vehicle attitude. This comprises
triaxial accelerometers, magnetometers and angular rate sensors
to measure static and dynamic orientation. Sophisticated data
fusion algorithms running on a dedicated processor board (SPECTRE
hardware) improve the data by removing latencies and, together
with GPS data, produce estimates of the vehicle velocity vector,
attitude and position. A modified controller algorithm is used
to calculate the camera's demanded pan and tilt speeds. The interface
with the camera uses a modified fast communications protocol written
by Forward Vision CCTV UK specifically for this application.
A magnetic calibration routine was developed to improve the performance
of the 3DM-GX1. This measures the magnetic environment experienced
in a series of manoeuvres and calculates the magnetic offsets.
The stabilised cameras have been tested both on land and sea
and have been in use with QinetiQ, UK, on a fast RHIB (FASTAR)
and on moored barges.
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