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Force feedback shuttle control

I have a couple of small steppers -- 20 oz in or thereabouts -- that I think would serve dandy as force feedback motors in a custom jog shuttle controller. I want the shuttle wheel to resist turning proportionally to the mill's stepper current draw (or torque, or whatever meaningful measure there is of how hard they're working). It doesn't have to be very precise, but precise is good also.

How do you control a stepper in this fashion? Operation will mostly be in quadrant 2, plus return to center when it's let go. I think I would like it to be switchable between operating in velocity mode -- turn more to go faster -- and position mode, emulating a hand wheel or crank.

Any thoughts on how to do this? Or which of the many boards or newsgroups might discuss something like this? I realize I might have to program a PIC to do this on the cheap, but off the shelf would be nice too.

Reply to
Mike Young
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--Might try posting this to comp.robotics.misc as there are a lot of stepper motor hacks over there..

Reply to
steamer

I'd rather not use a stepper motor for this job. When you push back on a stepper hard enough, the shaft then steps back to the previous phase that matches the power being put into the motor. I'd rather get a large diameter/high torque DC motor and drive it with a small fraction of the rated power (maybe 2V max. on a 12V motor) to provide a resistance to the motion. An old cordless drill motor will probably be very nice for this job.

-- Why do penguins walk so far to get to their nesting grounds?

Reply to
Bob May

I think you might be right, although I think I can easily monkey with the current sense pin to vary the holding torque. Voila, instant feedback. Problem is measuring what it's feeding back. The steppers they're controlling/feeding back are driven constant-current, and I see no easy way to measure how hard they're working. (Probably just yet another reason to upgrade to servos.)

Actually, the problem to solve was not so much a need for tactile feedback on a jog shuttle, but what to do with a pair of small steppers. Paper weight or trebuche fodder comes to mind, but think now I'll probe for ideas. What absolutely cool things can you think to do with a pair of 42mm square, 20 oz.in. steppers? I have suitably sized controllers and drivers, as well as a

14 pin PIC programmer.
Reply to
Mike Young

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