Re: How to get the position of a manipulator's end

On Sat, 06 Oct 2007 08:21:07 -0700, pnachtwey wrote:

On Oct 5, 10:44 pm, "Herman Family"
<the_sawdust_place_no_undersc...@xxxxxxxxxxxxxxx> wrote:
"Paul M" <PaulMatWiredogdotcom> wrote in message

news:4g5eg3tf2s4cto70o5onatgua3r2fo0o7j@xxxxxxxxxx





On Thu, 04 Oct 2007 19:04:43 -0700, workaholic <liua...@xxxxxxxxx>
proclaimed to the world:

My manipulators are designed to do experiments and not intended to a
certain industry process, and it is a flexible one, so we can't
calculate precisely where the position of the end,only based on the
joints' information.

Since the trajectory is constantly changed for several experiments, I
have to install a more general detection system for it.

What about designing a system that uses three or more sonic sources at
known locations at the limits of the manipulator work area. Drive
synchronized pulse trains from these sound sources and receive these
pulses with a receiver mounted on the manipulator arm. You should be
able to derive location from the phase shifts that result from the
variable distances from the source signals.

I have also looked at some coordinate measuring systems that were able
to resolve a tip location to within microns. I am not for sure what
they used for sensing, but the arm itself did not support any load,
you simply touched to tip to the material being measured.

It would be better to have one sonic source at a reference point on the arm,
and three sensors positioned around the device. The sensors should measure
flight time of the sound. My guess is that you will want the transducer to
send out some patterned sound, so that the sensors can get a better idea of
what time each wave left.

Bear in mind that sound velocity may change ever so slightly if one side is
warmer than the other, or dustier, or whatever. Also, sound tends to be
blocked. I don't know the size of your equipment, so I don't know if it is
likely that someone will walk around. Also, if it lifts any material then
that will act to deflect sound from one direction or another.

Michael- Hide quoted text -

- Show quoted text -
I second the doubt about using sound. I have never heard of finding
an end effector's position by sound before. However, I know people
that have done this with cameras. I believe they used two cameras and
a lot of math. Maybe even a model or two ( ooooh ). The purpose of
the system was to grab or connect to something in the ocean. It had
to be able to keep up with the wave action.

I can provide the name of the system integrator that did this and the
name of the person on the project if interested.

Peter Nachtwey

In spite of sonar having been my suggestion, this sounds better.

OP, have you done a web search? Surely this is a solved problem?

--
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
.

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