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Tim Wescott Tim Wescott is offline
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Default servo motor control ??

wrote:
I posted this note on comp.robotics.misc but of course it soon got
lost in all the crap that someone is posting to various groups.

So I thought I would give it a try here.


I am looking for a way to control vehicles somewhat larger than
typical hobby stuff. Say the size of a small lawn tractor.

This would be for steering so I am thinking about using something like
a more muscular servo motor.

I'm aware of hobby style giant servos. They might work but not sure if
they would be beefy enough.

Industrial servo motors seem to be quite different from hobby stuff. I
have one that's rated 128 VDC, has 5 wires running to the motor and a
bunch more off the attached encoder. No real idea what's going on
here.

Searches on servo motor control bring up mostly hobby information
which I am familiar with.

There is the open servo project which might provide part of a
solution. If I can beef up the control so that it can handle something
like a cordless drill motor.

I recenly built a remote control tricycle. I handled the steering
using a regular DC motor controller (Victor 883) and got around the
limit switch problem by building a small spring loaded clutch. (Some
details on my web site under "builders log".)

But I don't really like this solution as there is no automatic
centering feature.

Any other ideas? What do those guys like Mythbusters do for remote
control full size cars?

Thanks for any help.

DOC

Have robots. Will travel.
http://www.robot-one.com

Searching on "servo drive" may help. There seem to be a lot of
stand-alone servo drives that run a brushless motor with an encoder, and
take step and direction inputs just like a stepper driver would. They
wrap the motor with a PID loop so you have nice position control of the
motor. To get the steering centered you can put a flag of some sort on
your steering for a center reference, then once you find center you can
just count pulses off of that.

--

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