3
Control for Bow Thruster with Adjustable Pitch Propeller
AHD 903BS
1180-1i-e.DOC
1. Construction
The system for controlling a bow thruster with adjustable-pitch propeller consist of two units.
The operating unit for the three control units is located on the bridge, the control unit for
propeller adjustment at the bow thruster. Both units communicate serially with each other and
are connected over four wires (incl. power supply). They consist of similar analogue data
stations AHD 903-15. An additional relay module AHD 903R is used on the bridge and a
module AHD 903IP, as well as two further relays, are used for impulse length control on the
bow thruster side.
2. Control Units
The operating unit on the bridge receives the inputs from the main control unit, as well as
from two wing control units on port and starboard. The default angle for propeller adjustment
is reegistered and evaluated over a potentiometer (joystick with 0-positon in the middle).
After activation, the system can only be operated from the bridge control unit. Before starting
for propeller drive is enabled at the bow thruster side (relay K3), the selector switch for
operation has to be in position "bridge” and the potentiometer has to be in position “0” (micro-
contact). As long as these conditions are not fulfilled, the lamp „ready for operation“ at the
bridge control unit signalises this by slow flashing in a 1.5-seconds-cycle. Once the start
function is enabled, the flashing turns into permanent light.
Adjustment of the bow thruster angle is done over a 3-point after-running controller by
comparison of target (joystick) and actual value (controller at the bow thruster).
If, during operation, driving shall be continued from one of the wing control units, the selector
switch for operation at the main control unit has to be switched into the appropriate position
(port or starboard). Then, the takeover-button at the wing control unit has to be pushed, which
causes flashing of the lamp „ready for operation“. The real takeover happens when the default
target value at the wing control unit (joystick position) is the same as the presently active
actual value. As long as this is not the case, operation of the bow thruster will be continued
from the bridge control unit, even if the selector switch for operation is in starboard- or port-
position. If the conditions for takeover at the wing control unit are fulfilled, the flashing of the
lamp „ready for operation“ turns into permanent light and the system is now operated from the
wing. If there is no synchronisation between target and actual value within ten minutes, the
flashing lamp „ready for operation“ at the wing control unit goes out again. In this case,
takeover would have to be repeated.
The re-transmission of the command from wing to bridge is done in the same way as
described before. The selector switch for operation has to be switched into position
“bridge/main control unit” and the takeover-button has to be pushed. For correct takeover, the
default target value must be equal to the actual value, too.
Each control unit has an actual value indication for the actual propeller angle. For safety
reasons, this indication is led separate from the system and activated directly by the actual-
value-controller at the bow thruster.