6
NB * (PID control, terminology as known by control technicians,
P = proportional part, I = integral part and D = derived part)
Factory default settings and automatic calibration, establish a basis for normal steering
and may be further fine tuned if necessary. During set up routines, the compass is
automatically compensated and installation errors such as reversed rudder feedback and
reversed pumpset wiring or piping are automatically diagnosed and corrected. During this
routine also the rudder speed is automatically optimised. This greatly reduces installation
set up and sea trials time while eliminating possible Autopilot malfunction.
1.4 Components
1.4.1 Autopilot instrument
Control and display of all Autopilot functions are provided by the Autopilot instrument. It is
waterproof and may be mounted below or above deck. Multiple Autopilot instruments can
be connected and the Autopilot may be activated by pressing the push-buttons of any
instrument.
1.4.2 Servo Unit (A-1500 and A-1510)
The Servo Unit contains the course computer and pumpset motor drive circuitry and acts
as a centre for interconnecting wiring. It is splash proof and should be located centrally to
minimise lengths of wiring. The powerful microprocessor in the Servo Unit accepts heading
information direct from an electronic compass or gyro compass (A-1500 only), wind
transducer, navigators and compares this against the course set by the instrument and
rudder.
1.4.3 Rudder Angle Transmitter
The Rudder Angle Transmitter provides the Autopilot with accurate rudder position
information. It is mounted near the rudder shaft and connected to the tiller arm or quadrant
with an adjustable ball joint linkage.
1.4.4 Compass transducer
No Autopilot can steer better than the compass stability will allow. The Nexus compass
excels in this characteristic, where the liquid dampening provides for stability even at high
speeds in heavy seas. The high gimbaling angle, eliminates compass disturbance with
boat heeling or rolling. The compass provides a stable heading reference for the Autopilot
and should be bulkhead mounted below deck near the centre of pitch and roll for maximum
stability. Construction is splash proof. The Autopilot Servo Unit or the Nexus Server can re-
transmit the compass heading on the NMEA output port to receivers such as radars,
plotters, compass repeaters etc.
1.4.5 Pumpset
Various sizes and types of pumpsets can be mounted into a hydraulic steering system. The
pumpset only operates when carrying out a rudder command. When the boat is on course,
the pumpset motor stops. A variable speed motor drive adjusts optimal rudder speed and
provides for minimum power consumption and maximising of rudder positioning accuracy.
INTRODUCTION