Minimum Rudder; Rudder Deadband - Simrad NAC-2 Commissioning Manual

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different rudder speeds are required for automatic and Follow-
up/Non-Follow-up steering.

Minimum rudder

Some boats may have a tendency to not respond to small rudder
commands around the "course keeping" position because of a small
rudder, whirls/disturbance of the water-stream passing the rudder,
or it is a single nozzle water jet boat. By increasing the Minimum
rudder parameter you may improve the course keeping
performance on some boats. However, this will increase the rudder
activity.
Ú Note:
Only set a value for minimum rudder if it proves to give a
better course keeping performance in calm sea. It should be set
after the autopilot steering parameters have been optimised/
tuned.

Rudder deadband

Prevents the rudder from hunting induced by mechanical play in
the steering gear or rudder.
The following options are available
• Auto
(Recommended).
The rudder deadband is adaptive and is continuously operative. It
will also optimize the deadband to the pressure on the rudder
• Manual
If the Auto setting doesn't perform properly due to extreme
rudder speed and/or overshoot, it can be adjusted manually. Can
also be used to reduce the rudder activity. Rudder commands
smaller than the size of the dead band will be ignored
Find the lowest possible value that will prevent the rudder from
continuous hunting. A wide deadband will cause inaccurate
steering. It is recommended to check rudder stability in AUTO mode
at cruising speed to get pressure on the rudder. (Slight hunting
observed dockside may disappear at cruising speed.)
Dockside setup | NAC-2/NAC-3 Commissioning Manual