How Autopilots Work; Basic Autopilot System; Figure 1 - Basic Autopilot System - ComNav Commander P2 Installation & Operation Manual

ComNav Commander P2 Installation & Operation

How Autopilots Work

The purpose of this section is to briefly describe what an autopilot does and some of the
things you should expect when using an autopilot with your boat. The information in this
section can be applied in general to any ComNav autopilot, and is not specific to the
Commander P2 Autopilot.

Basic Autopilot System

Figure 1 is a block diagram of the major components of an autopilot system.
CONTROL HEAD
DISPLAYS STATUS AND HEADING
INFORMATION FROM THE SPU, AND
ALLOWS THE OPERATOR TO INPUT
STEERING COMMANDS & OPERATING
PARAMETERS
Figure 1 – Basic Autopilot System
The Compass indicates the direction in which the boat is pointed – often referred to as the
Actual Heading. Depending on the type of boat & installed equipment, the Compass may be
a magnetic compass, an electronic fluxgate compass, a gyroscopic compass, or a GPS
Compass. A reliable compass is absolutely vital to the autopilot – because, without a
compass, the autopilot has no way of knowing which way the boat is headed.
The actual heading is fed electronically from the Compass to the Processor (SPU) , which is
the heart of the autopilot. The SPU contains the microprocessor(s) & other electronic
hardware, and the sophisticated control software necessary to steer the boat on any Desired
Heading.
Document PN 29010074 V3.1
COMPASS PROCESSOR (SPU)
READS THE VESSEL'S CALCULATES THE RUDDER
ACTUAL HEADING AND POSITION NEEDED TO STEER
SENDS IT TO THE SPU THE VESSEL ON THE DESIRED
HEADING, AND CONTROLS THE
STEERING SYSTEM
ACCORDINGLY
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NAVIGATION DEVICES
[OPTIONAL]
SUPPLY NAVIGATION
INFOMRATION TO THE SPU
RUDDER FOLLOWER UNIT (RFU)
IN NMEA 0183 FORMAT
[MECHANICALLY CONNECTED TO RUDDER]
MEASURES RUDDER POSITION AND SENDS
IT TO THE SPU
STEERING SYSTEM (ACTUATOR)
[HYDRAULIC RAM OR ELECTRIC MOTOR
WHICH IS MECHANICALLY CONNECTED
TO THE RUDDER]
MOVES THE RUDDER IN RESPONSE TO
CONTROL SIGNALS FROM THE SPU
How Autopilots Work