How to make speed of DC motor match speed of another?
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Posted by Eric R Snow on June 11, 2006, 5:18 pm
Please log in for more thread options I have a situation where a dc motor drives a wheel which pushes an aluminum wire at variable speed through a 15 foot tube. I would like to be able to pull this wire also at the tube exit at the same time to avoid jams. When the speed of the pushing roller changes the speed of the pulling motor must change with it. I can think of several ways to sense the push motor speed but not how to use this to make the pull motor spin at the same rate. Is there a simple and cheap way to do this? Thanks, Eric | |||||||||||||
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Posted by purple_stars on June 11, 2006, 7:19 pm
Please log in for more thread options Eric R Snow wrote: this is a non-trivial problem. i used to work with a printer manufacturer and some of their printer models had two motors, one at either side of the printer, to move the mechanisms across the page. they used stepper motors to do it, and spent a lot of time and energy tuning them to work together, working out their step tables, etc. yours is a slightly different problem because you just need your "front end motor" to pull up the slack, so probably it is easier than their problem. | |||||||||||||
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Posted by Greg Neill on June 11, 2006, 7:27 pm
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> Eric R Snow wrote:
> > I have a situation where a dc motor drives a wheel which pushes an
> > aluminum wire at variable speed through a 15 foot tube. I would like > > to be able to pull this wire also at the tube exit at the same time to > > avoid jams. When the speed of the pushing roller changes the speed of > > the pulling motor must change with it. I can think of several ways to > > sense the push motor speed but not how to use this to make the pull > > motor spin at the same rate. Is there a simple and cheap way to do > > this? > > Thanks, > > Eric >
> this is a non-trivial problem. i used to work with a printer > manufacturer and some of their printer models had two motors, one at > either side of the printer, to move the mechanisms across the page. > they used stepper motors to do it, and spent a lot of time and energy > tuning them to work together, working out their step tables, etc. > yours is a slightly different problem because you just need your "front > end motor" to pull up the slack, so probably it is easier than their > problem. It might be easier to just have the motor provide a constant torque (within reason!) so that it maintains a constant force on the wire. This should be proportional to the power being drawn by the motor. | |||||||||||||
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Posted by Eric R Snow on June 12, 2006, 4:43 pm
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On Sun, 11 Jun 2006 19:27:29 -0400, "Greg Neill" >> Eric R Snow wrote:
>> > I have a situation where a dc motor drives a wheel which pushes an
>> > aluminum wire at variable speed through a 15 foot tube. I would like >> > to be able to pull this wire also at the tube exit at the same time to >> > avoid jams. When the speed of the pushing roller changes the speed of >> > the pulling motor must change with it. I can think of several ways to >> > sense the push motor speed but not how to use this to make the pull >> > motor spin at the same rate. Is there a simple and cheap way to do >> > this? >> > Thanks, >> > Eric >>
>> this is a non-trivial problem. i used to work with a printer >> manufacturer and some of their printer models had two motors, one at >> either side of the printer, to move the mechanisms across the page. >> they used stepper motors to do it, and spent a lot of time and energy >> tuning them to work together, working out their step tables, etc. >> yours is a slightly different problem because you just need your "front >> end motor" to pull up the slack, so probably it is easier than their >> problem. >
Greetings Greg,
>It might be easier to just have the motor provide a constant >torque (within reason!) so that it maintains a constant force >on the wire. This should be proportional to the power being >drawn by the motor. > Thanks for the suggestion. I had thought about that and it helps when others come up with suggestions that tend to validate my ideas. There are available adjustable slip clutches meant for constant duty. So maybe that's what I'll need to do. I'm trying to keep the drive as compact and as light as possible though. Eric | |||||||||||||
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Posted by John Jardine. on June 11, 2006, 8:09 pm
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> I have a situation where a dc motor drives a wheel which pushes an
> aluminum wire at variable speed through a 15 foot tube. I would like > to be able to pull this wire also at the tube exit at the same time to > avoid jams. When the speed of the pushing roller changes the speed of > the pulling motor must change with it. I can think of several ways to > sense the push motor speed but not how to use this to make the pull > motor spin at the same rate. Is there a simple and cheap way to do > this? > Thanks, > Eric Watched on in amusement while a similar project was delayed by 2 months while they tried to run 2 motors in synchronism. Told 'em it's not that simple and wouldn't be happening but they'd a bit between their teeth, 2 months already down the tubes and "hey! we're precision engineers, we understand gearboxes and we've face to save". Eventually solved by a single motor, long PU toothed belt and timing pulleys. It's not straight forward. If you've just got to have the 2 motors, then maybe continuously overspeed the pull unit while feeding the power through a variable magnetic clutch. If wire is thin, could result in secondary stretch problems and extra work of needing to monitor tension and forming a local servo loop with the pull motor and mag clutch. Although I suspect what I know as "wire", is lots thinner than your stuff :) john | |||||||||||||
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> aluminum wire at variable speed through a 15 foot tube. I would like
> to be able to pull this wire also at the tube exit at the same time to
> avoid jams. When the speed of the pushing roller changes the speed of
> the pulling motor must change with it. I can think of several ways to
> sense the push motor speed but not how to use this to make the pull
> motor spin at the same rate. Is there a simple and cheap way to do
> this?
> Thanks,
> Eric