The Navigator
by JOHN W. MOLNAR
A GPS Based Self Navigation System
For Model Warship Water And
Land Based Robots
If you have ever envisioned sending your rover
platform or boat out on its own, completing a
mission, and returning home without resorting to
classic R/C guidance, check out this GPS based
navigation system.
In The Beginning
Years ago, I built a large scale model boat — Mister
Darby by Dumas Models — with the express intent of
someday designing a navigation system/autopilot that
would allow the boat to set sail, navigate a predetermined
complex course, and return to the dock — all without the
use of standard radio control (R/C) gear. Obviously, some
sort of GPS based system was required, coupled to a
processor doing the navigation computation, as well as
controlling the rudder and motor servos. However, it has
only been recently that the GPS available to the civilian
world is accurate enough over the short term to make my
navigation dream a reality. The deployment of the GPS
WAAS (Wide Area Augmentation System) “corrects” many
of the accuracy sapping aspects of the system, primarily
caused by differences in the propagation of the GPS
signals as they pass through the Earth’s ionosphere to your
GPS receiver.
The Navigator is a multiprocessor, software intensive,
user-friendly system that allows robotic platforms and boats
to traverse a predetermined course consisting of two or
more segments, based on the principles of great circle
navigation. Here are some of the Navigator’s main features:
•Complete, self-contained system;
no R/C gear required.
•Allows robotic vehicle to traverse a course
consisting of multiple legs.
•Multiprocessor, feature rich hardware/software
architecture.
•Built-in user interface for course entry with
editing capability.
•Previous trip maintained in EEPROM for instant recall.
•Built-in GPS simulator with user interface.
•Dual LCDs and multiple status LEDs.
•Fun!
System Overview
The system I’ll describe here can be built with off-the-shelf components and will
allow any larger boat, robot,
or rover platform to navigate
a predetermined course
consisting of multiple legs.
The details of the course are
initially entered into the
system using a PC running
Hyper Terminal or Tera Term.
A dumb ASCII based terminal
can also be used, as the
system prompts the user for
input. The user has complete
control of the Navigator via a
wealth of pushbutton options
and the system status
FIGURE 1. Overall block diagram of the Navigator.
Three separate PIC based boards comprise the system
and two 16x2 LCDs and status LEDs provide critical status
information and trip details. All boards are powered
by a +12V gel cell battery.
54 SERVO 07.2009
