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Unread 15-02-2012, 17:13
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Jaguar stops powering the motor after a few seconds

Hey,
We have a Jaguar connected to a cim motor with a transmission we made and to a sidecar module via PWM. The motor moves two axis. When we run it at any speed it works for a few seconds (not at constant intervals), stop, and after a few seconds starts working again.

We looked at the Jaguar's LED. When the motor is running the LED shows red value and when the motor stops it changes to yellow. We tried replacing a Jaguar and a PWM, but the problem persists.

I don't believe this is a software problem. I work with LabVIEW, and the code to power this Jaguar is very simple. Just in case, I called the "GetOutput" VI and the value is the same as sent, as expected. It never changes to zero, even when the Jaguar stops powering the motor.

We double-checked, the battery has over 12V.

What can cause this weird behaviour?

Thanks in advance,
Itamar.

Last edited by Itamar : 15-02-2012 at 17:42.
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Unread 15-02-2012, 18:25
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Re: Jaguar stops powering the motor after a few seconds

Is there any sort of clicking noise coming from the PDB when the motor stops running? If so, something (namely, too high current for too long) is probably causing the circuit breaker to trip.
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Unread 15-02-2012, 18:35
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Re: Jaguar stops powering the motor after a few seconds

Hey Eric, we checked and there were no clicks coming from the PDB. However, we discovered that the problem occours only when we make it go from 0 to high values. If we start the motor at 0% speed and gradually and slowly raise it to 100%, it works fine and doesn't stop.
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Unread 15-02-2012, 18:43
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Re: Jaguar stops powering the motor after a few seconds

Sounds like the Jaguar is getting an over-current fault.
Generally, traceable to the CIM gearing and a too-resistant object being moved making the CIM hard to get going.
Jags don't like to draw CIM stall current for very long.
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Last edited by Mark McLeod : 15-02-2012 at 18:47.
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Unread 15-02-2012, 18:48
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Re: Jaguar stops powering the motor after a few seconds

My team had a CIM problem where the two screws that hold the motor in to something, were in too far. The motor would work for a few seconds then stop.
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Unread 15-02-2012, 18:51
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Re: Jaguar stops powering the motor after a few seconds

Quote:
Originally Posted by Mark McLeod View Post
Sounds like the Jaguar is getting an over-current fault.
Generally, traceable to the CIM gearing making the CIM hard to get going.
I am pretty sure you are correct. We have activated the motor directly with a battery and it ran okay for a few minutes. Is it possible to prevent the over-current fault? Does the Jaguar stop to protect the motor or itself?
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Unread 15-02-2012, 18:59
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Re: Jaguar stops powering the motor after a few seconds

The Jaguar is protecting itself from the over-current.
A CIM is pretty robust and will handle it much better. It pulls 133 amps at stall.

One way around the problem is to ramp the Jag in software.
Not always successful because the Jag gets increasingly sensitive to over-current the warmer it gets, so the ramp may have to get gentler over time.

A better way is to regear the CIM gear/sprocket train, but that's not always practical.

A third way is to switch to a Victor in this particular application, because it's a bit more forgiving, but the Victor won't protect itself, so there's a chance of burning it out.
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Last edited by Mark McLeod : 15-02-2012 at 19:10.
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Unread 15-02-2012, 19:01
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Re: Jaguar stops powering the motor after a few seconds

Quote:
Originally Posted by NeatTeam View Post
I am pretty sure you are correct. We have activated the motor directly with a battery and it ran okay for a few minutes. Is it possible to prevent the over-current fault? Does the Jaguar stop to protect the motor or itself?
The Jaguar is protecting itself and the robot from excessive current draw.

Take a look at the 2012 Jaguar FAQ. Specifically Q20.

-David
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Unread 15-02-2012, 19:09
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Re: Jaguar stops powering the motor after a few seconds

Quote:
Originally Posted by Mark McLeod View Post
The Jaguar is protecting itself from the over-current.
A CIM is pretty robust and will handle it much better.

One way around the problem is to ramp the Jab in software.
Not always successful because the Jag gets increasingly sensitive to over-current the warmer it gets, so the ramp may have to get gentler over time.

A better way is to regear the CIM gear/sprocket train, but that's not always practical.

A third way is to switch to a Victor in this particular application, because it's a bit more forgiving, but the Victor won't protect itself, so there's a chance of burning it out.
When you say "ramp the Jab in software", do you mean to start at 0% and gradually raise the value?
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Unread 15-02-2012, 19:13
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Re: Jaguar stops powering the motor after a few seconds

Yes, the same sort of ramping or coaxing along you were doing manually to get it working. Just do it in software set to ramp up the power more slowly.
Be conservative when you do it, don't try to push the Jaguar as fast as you can. Give it some breathing room.
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Last edited by Mark McLeod : 15-02-2012 at 19:19.
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Unread 15-02-2012, 19:21
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Re: Jaguar stops powering the motor after a few seconds

Quote:
Originally Posted by Mark McLeod View Post
Yes, the same sort of ramping or coaxing along you were doing manually to get it working. Just do it in software set to ramp up the power more slowly.
Be conservative when you do it, don't try to push the Jaguar as fast as you can. Give it some breathing room.
That's what I thought. thank you!
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Unread 17-02-2012, 01:43
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Re: Jaguar stops powering the motor after a few seconds

We (rookie team) had a similar problem during code testing. We added an acceleration ramp and that helped but the JAG was still unreliable. We almost ordered a replacement, but first tried a factory reset. It's been working perfect ever since.
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Unread 17-02-2012, 10:24
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Re: Jaguar stops powering the motor after a few seconds

Quote:
Originally Posted by NeatTeam View Post
When you say "ramp the Jab in software", do you mean to start at 0% and gradually raise the value?
Add a slew-rate limiter.

For LabVIEW, see this article:
http://thinktank.wpi.edu/article/140

For C++ or Java, see here for some pseudo-code:
http://www.chiefdelphi.com/forums/sh...23&postcount=2


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