Kalman filters: Controlling ROVs and AUVs

You may want to try a more modern approach - H infinity state
estimation and H infinity control.
Only slightly different from the mse approaches they minimize the max
value of the error. They are more robust to innacurate models and work
on deterministic noise sorces even. In fact no knowledge of the noise
is needed at all as compared to say the Kalman filter (though
weighting must be selected based onSNR).

http://academic.csuohio.edu/simond/courses/eec641/hinfinity.pdf
(lots of typos on this article but you will get the jist)

gay.highlander@yahoo.co.uk wrote:

The author of this paper also authored the book "Optimal State
Estimation".  He starts you on Kalman filtering, takes you through
H-infinity filtering, then on to some modern semi-esoteric stuff that
requires orders of magnitude more processing power than is available now
(but who's to say it still will ten years from now?).

I know you're not a total newbie to DSP, but if you don't have much
control background you may also be interested in my book (see
http://www.wescottdesign.com/actfes/actfes.html ).  It only covers basic
control theory, but it takes you from that basic theory all the way to
practical applications using today's technology -- if you haven't closed
real loops in real computer hardware I think you'll find it useful.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

(seehttp://www.wescottdesign.com/actfes/actfes.html ).  It only covers basic

Both books are on order from amazon.com.

I've been browsing IEEExplore, but I don't have access to the
relevant
journals and don't know what to look for. I suppose what I need is
similar to aeronautics nav processing, where one fuses data from
onboard sensors, sattelites and beacons to produce a position/track
estimate.

Any suggestions on where to start?

Rune

Rune, I'm not sure it's directly relevant, but there is an article
from the airborne laser scanning (ALS) community by Baltsavias:

Baltsavias, E.P., 1999. Airborne laser scanning: basic relations and
formulas. PRS, Vol. 54, No.2-3, pp. 199-214.

ftp://igpho.ethz.ch/pub/manos/papers/formals_prs.pdf

that ties together some things there.

ALS fuses GPS, navigation systems, the laser scan angle and
time-of-flight measurements to get 3D data.  It's a different problem,
but I suspect there's details in the literature that will help you
out.

Ciao,

Peter K.

--
"And he sees the vision splendid
of the sunlit plains extended
And at night the wondrous glory of the everlasting stars."

 

Rune Allnor wrote:

(seehttp://www.wescottdesign.com/actfes/actfes.html ).  It only covers basic

I think you were on target (in general, at least) in asking about Kalman
filtering for this part.  The definition of Kalman filter has taken on
the meaning of "a multivariable signal processing algorithm that takes
data from a big wad of inputs and coughs up the best output(s)" -- in
this wide sense you were asking for just the right thing, at least
inasmuch as H-infinity, extended Kalman and particle filters all fit the
definition as well as a plain old Kalman filter.

Dan Simon's book should prove very helpful for you here.  I know enough
about Kalman filters to construct one to the narrow definition, so when
I have a problem that's narrowly defined enough I can be useful (and if
you're conservative in your choice of weightings you can make it
generally useful, although not necessarily optimal).  The next time I
have occasion to do a multivariable estimation problem I'll be leaning
on the Simon book, and I expect to be able to do a pretty good job of it.

When (or if) you get to the point where you're actually controlling the
motion of the vehicle you'll find my book useful, although I imagine
you'll have to concern yourself with all sorts of nonlinearities and
axis cross-coupling that one can normally avoid in simpler control problems.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

@w5g2000hsg.googlegroups.com:


No satellite navigation (GPS) when submerged!

Sam

On Wed, 27 Jun 2007 15:47:03 +0200, SamSvL wrote:


No, but if you can surface & stick an antenna up you can get a fix, and
use it to calibrate your inertial sensors.

You'd be able to get LORAN down a few meters at least -- I'm not sure how
far it'd penetrate the water, but if they can use 30kHz to communicate
with subs 100kHz should get down some.

Given a compass, inclinometer and a water-speed gauge you could use dead
reckoning, particularly if you could surface every once in a while to
upgrade your knowledge of drifts.

Rune -- I think you need to post this to yet another newsgroup.  Find the
one that covers choosing the right sensor technologies for AUV's and
you'll be fine...

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

subs use a floating antenna for LORAN

On Wed, 27 Jun 2007 10:42:09 -0500, BobF wrote:


Well, there's nothing like practical knowledge to blow theory all to hell.

Come to think of it, a GPS receiver on a tether may work, also, if you are
working that close to the surface.  It adds some interesting twists to
your "Kalman" filter, to be sure, but it may work.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

wrote:

Is that technology not used to track the movements of some marine
animals, like whales?

It used to be a standard excercise in the course in underwater
acoustics to compute the attenuation of EM waves in salt water.
If I remember correctly, EM waves are attenuated by some 50 to
60 dB per wavelength. Given a frequency and signal strength at
the surface, one can compute how far down a given system can
recieve a useful signal.

This is a reason why subs communicate in the ELF range.

Rune

However, the general setup is very similar aeronatics:

When using ROVs, a surface vessel (with GPS nav) serves
as a "moving refernce" much the same way GPS satellites
do in aeronautics.

A number of refernce transponders have been installed
in the area we operate, serving as fixed beacons for
both ROV and AUV.

The vehicles have onboard INS systems.

The trick is to make sense / use of all these nav
data flowing around the system.

Rune

Rune Allnor wrote:

I guess that depends on which part of the problem you really want to
solve yourself.  The Kearfott T-16 and T-24 units that we put on our
AUVs take in the ADCP and GPS data directly, along with our acoustic
fixes, and does the sensor fusion itself.  The output is its best
estimate of position, based on its own filter.  After we manage to
convince it of the correct starting point, it does very well as long as
ADCP bottom lock is maintained; I think about 0.2% of range, but don't
quote me on that.

--
NOTE: to reply, remove all punctuation from email name field

Ned Forrester        n_f_orrester@whoi.edu         508-289-2226
Applied Ocean Physics and Engineering Dept.
Oceanographic Systems Lab                 http://adcp.whoi.edu/
Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

So you are designing a system for a specific range and have transponders
installed and surveyed in so the only remaining question is how accurate does
the position estimate have to be?  It makes a huge difference.

On 7 Jul, 17:41, John_W_Her...@yahoo.com (John Herman) wrote:

I amd not designing a system, I am evaluating one.

The expected accuracy of our surveys is very high. Whenever we
are out of spec we have to do a system evaluation to find out why,
and if there were anything we could or should have done differently.
I know a lot about the acoustcis side of both surveying, comms and
oceanography, and have developed a more or less trustworthy instinct
for how those sorts of factors affect the accuracy of the surveys.
Now
I need to learn as much as possible about the navigation side of
things.
I can't do the required evaluation unless I know in as much detail as
possible how the C&N systems work, what their "intrinsinc"
characeristics are, and how they are affected by oceanography,
platform stability, only occasional access to GPS references,
sparse / dense reference transponder grids, etc.

Rune

SAR historically had similar problems blending GPS and INS systems and
compensating for Lever Arms. Some of that problem has gone away with
the newer technologies. You could check from either DRDC-Ottawa
(Mostly Radar) or DRDC-Atlantic (Mostly Sonar). Here's the basic link:
http://pubs.drdc-rddc.gc.ca/pubdocs/pcow1_e.html

You could also try our friends at FMV - The new Visby class has ROV's,
so they may have looked at some of this. Perhaps contact Elias.

Cheers,
David

On 10 Jul, 15:34, dspg...@netscape.net wrote:


I talked with Elias on the phone a couple of weeks ago. He clicked
onto this immediately; I'll probably use some of my vacation to go
visit him some time in September. We are coming up on the Real
Deal now; 6 times 120 km of surveying to be performed inside, say
six weeks or so. The "make or break" kind of thing.

Oh well. I'm a mere 18 hours short on a 4-week trip, the second
completed inside of ten weeks. A shore-side vacation will be very,
very nice now...

Rune