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Robertson AP45 Autopilot
Design and theory of operation
Simrad Robertson AS
Egersund - Norway
Page 3-1
3. DESIGN AND THEORY OF OPERATION
An autopilot is an apparatus that controls the rudder of a vessel in order to
maintain a selected heading.
There are different design principles for such an apparatus, but they all basically
operate as shown in Fig. 3-1.
This diagram shows that the vessel's heading is supplied from the compass to a
detector circuit. The detector will sense when the vessel is off course and to what
side. The detected signal is amplified and directed to either energise the port or
starboard solenoids, i.e. make the rudder move one way or the other.
COMPASS
DET AMP
FB
FEEDBACK
UNIT
STBD. TRIGGER
PORT TRIGGER
SOLENOID
SOLENOID
RUDDER
HEADING
RUDDER POSITION
Fig. 3-1
Autopilot principle diagram
I/O
INTERFACE
DRIVER
GYRO
COMPASS
MAGNETIC
COMPASS
COURSE
SELECTOR
DISPLAY
RUDDER
FEEDBACK
PROGRAM
CPU
KEYPAD
RUDDER
SOLENOID
VALVES
Fig. 3-2
Processor controlled autopilot
Automatic Steering