RE: [PSUBS-MAILIST] Nav systems

["Smyth, Alec" <Alec.Smyth@compuware.com>]

Super project Ian. I am beginning to imagine what the inside of your sub
will might look like. Banks of monitors! 

Alec


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From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of irox
Sent: Friday, June 25, 2010 3:56 PM
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] Nav systems


Hi,

I've been working a navigation system for a submarine for some time.
This stems from a conversation I had a with Jay at the Maine psubs
convention.  The main aim of the nav system is to (accurately - for
certain values of "accurate"...) determine the position of the submarine
when it is submerged.

My system currently consists of 6 degrees of freedom (6DOF) inertia
measurement unit (IMU), which gathers data from: 3 magnometers
(providing a 3d compass); 2 gyros for pitch and roll; and 3
accelerometers providing movement in 3d space.
Plus a fiber optic gyro (FOG) which augments the compass bearing with a
super accurate (greater than 0.01 degree
resolution) heading which isn't effected by magnetic field.
This is hooked up to a laptop which processes the data from the IMU and
FOG, and provides a 3D display.  Not including the laptop I have around
$1200 invested in this project so far.

I was hoping to have a first version working system by the convention,
but I've not had much time to work on it recently.
The outline components/software are there, but it's prone to drift off
in some direction or other and rapidly loose accuracy.  Each iteration
of the project is more accurate than the last, but it is far from
providing useful position data.
It should how ever be able to provide accurate heading data as well as
pitch and roll.

I am currently trying to decide if it's worth bring this to the
convention.  I can demonstrate the principles behind it on land - it
might be useful to put it in a sub and gather some data to used later
for developing and testing of the software behind it.  But we would need
to accurately know the movements of the sub so we could correlate the
results of the processed data with the physical position changes of the
sub.  The main reason for not bring it is to avoid the hassle of taking
it on a plane and dealing with airport security.

This project has a large potential scope.  Once I get the existing set
up working to some degree, it can be farther augmented with a second
IMU, then with more environment data, for
example: a pressure sensor supplying depth information; a water speed
sensor providing relative water speed of the subl; motor power input
sensor and rudder angle sensor allowing the system to estimate the
future position based on what the operator is doing to the controls.
Add a GPS or DGSP to provide accurate surface state and position, so
that nav system is initialized with good data.

There are many other projects which can spawn from this, one am
interested in doing next is combining an active sonar system with the
positioning system to provide on the fly mapping capability.

I plan to release the software as open source so anybody can use it.
Although I imagine each submarine to use it would require a fair amount
of changes/customization to the software.

Let me know what you think.  Also I am interested to hear about what
other people are planning/doing for nav/positioning systems.

Cheers!
 Ian.





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