ComNav Commander P2 & P2VS Installation & Operation How Autopilots Work
Document PN 29010074 V4.1 - 18 -
How Autopilots Work
The purpose of this introductory section is to describe briefly what an autopilot does, and
some of the things you should expect when using an autopilot with your boat.
Manual Steering
Every boat has unique design dynamics, which depend on its shape and dimensions, and on
current speed, loading, and sea conditions. The net result is that every boat (or rather, every
unique boat design) “steers” in a unique way.
To understand what an autopilot does when it is steering your boat, it is helpful to think for a
moment about steering the boat by hand.
•
When you are holding the boat on some Heading, you know, from instinct &
experience, how much rudder to apply, and how fast to apply it, to keep the boat
on-course. Corrections are usually just a small, quick movement of the helm to one
side, then back to the dead-ahead position.
•
You won’t always try to correct when the boat rolls or accelerates off a wave,
especially in heavy seas – because when the boat rolls back the other direction, it will
usually come right back on-course.
Instead, your experience lets you allow the boat to yaw those necessary degrees on
either side of the Heading, to reduce the fight.
•
To turn the boat to a new Heading, instinct & experience again tell you how much
rudder to use, and how fast, to get the boat turning at your normal rate of turn.
If the boat is not turning as rapidly as you want (for example, with a cross-wind or
cross-current holding back the bow), you increase the amount of rudder a bit.
On the other hand, if the boat is turning too fast, you reduce the applied rudder a bit.
You then gradually reduce the applied rudder, as the boat approaches the desired
Heading.
You might even put the helm over opposite for a moment, to stop the boat swing
more quickly – in order to come to the desired Heading without overshoot.
The single most basic purpose of an autopilot is to do the same as you would … let the boat
“work with the seas”, yet still maintain as straight a Track as possible in the current sea
conditions, on the desired Heading or Course.
The P Series Autopilot Systems use the latest generation of ComNav’s carefully-designed,
well-proven steering control algorithms
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, which are based on our many years of designing &
manufacturing autopilots.
There are a number of parameters used in the steering algorithms, collectively referred to as
“the Steering Parameters”. The Commander P2 & P2VS have been tested on a wide variety
of boats, of different types and sizes. The default settings for the Steering Parameters are
average values derived from that testing, and provide a good starting place for most boats.
During Sea Trials, and later on normal operation, you may want to adjust some of those
values, so that they better match your boat’s unique design dynamics.
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… however, the information in this section can be applied in general to any ComNav autopilot, and is
not necessarily specific to the P Series.
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