COBHAM Sailor 900 VSAT, Technical Manual

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Removal and replacement of ADU modules
98-133966-G1 Chapter 8: Service & maintenance 8-19
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Service & maintenance
The DDM shall - based on inputs from the PCM - control the torque
delivered by the brush-less DC-motors (BLDCM), used to control the
position of the parabolic reflector.
The DDM board is:
• Communication slave of the ADU Serial-Bus (S-Bus) connecting
the DC-motor Driver Modules (DDM), the Polarization Motor
Module (PMM), the Inertial Sensor Module (ISM) and the Pedestal
Control Module (PCM).
• Connection to the BLDCM, and delivering the required phase
current to the motor.
• Decoding the HALL-sensor input from the Zero Reference Module
(ZRM).
• Decoding the input from the Optical Rotary Encoder (ORE).
• Incorporating a break function when not powered.
6. Cross elevation motor and encoder.
7. Zero Reference Module (x4, 3 in the previous figure, 1 in the next
figure) (ZRM) (not visible on photo).
In order to be able to find the predefined zero point of the antenna
direction, HALL sensors and corresponding magnets mount in the
gearwheels. Due to the magnetic hysteresis behaviour of the hall
sensor, the software will have to make the magnets pass the hall
sensor in both directions, and when use the mean value as the zero
point.
The ZRM features two LEDs; one for indication of power supply, and
one for indication of zero point.
8. DC-Motor Driver Module for elevation (on the bottom side) (DDM).
As in item 3 above.
9. Elevation motor and encoder (not visible on photo).
10.Polarisation Motor Module (PMM).
Figure 8-17: ZRM – Block diagram
SAILOR900TM.book Page 19 Monday, September 16, 2013 11:01 AM