larger servo questions

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
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bump
snipped-for-privacy@sympatico.ca wrote:

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With a little clever thinking, it may be possible to have a $10 hobby servo be the brains for controlling very large electric motors.
On Mon, 03 Sep 2007 18:18:05 -0700, snipped-for-privacy@sympatico.ca wrote:

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On Sep 3, 8:18 pm, snipped-for-privacy@sympatico.ca wrote:

You might want to have a look, or even talk to the folks at Kairos Autonomi.
http://www.kairosautonomi.com /
They have a kit that can be bolted onto basically any vehicle, and convert it to autonomous operation with 4 bolts. They are in the new DARPA challenge, and have sponsored several other teams with a converted vehicle.
In their product is a ServoPod(TM) we make. It is very useful for making closed loop servos. Basically a ServoPod(TM) an H-bridge and some sort of positional feedback, and a PID loop, tune it up, and you've got control. Of course for a single channel, there are cheaper ways to go.
As others have suggested, you can probably convert an existing RC Servo controller to use a bigger motor. There are kits that use an external pot, and extended gearing. I've seen those on both Lynxmotion and Servo City. Lynxmotion even sells the guts out of a RC Servo, just add motor and pot. Might need some amplification of the outputs though, to get strong enough to run a steering wheel.
-- Randy M. Dumse www.newmicros.com Caution: Objects in mirror are more confused than they appear.
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snipped-for-privacy@sympatico.ca wrote:

We had some servos here years ago. They were DC motors several inches in diameter. Usually a resistive pot for the feedback loop. Controlled by a DC amp pretty much a mono HIFI amp. Larger turntables were around several years ago, using Contraves gear, switching power amps, and a turntable about 4 feet high. I'm not sure what the motor was. Brushed motors are problematic. Stepper motors are not required but don't suffer from brush wear, but are power wastefull at times. I don't know what the current trend is on motors. I would like to find out. A geared mechanisn is highly recommended allthough noisey.
greg
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wrote:

I just remembered a horrible thought, slip rings !!
I guess they are still around for multi axis rotation.
greg
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    --For a pictorial on some beautiful slip ring work slide on over to carpisaturo.com and see what he's done.
--
"Steamboat Ed" Haas : A steaming pile of
Hacking the Trailing Edge! : obscure information...
  Click to see the full signature.
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