paper: Window Motor Lockups: Causes and Solutions

[ratdude747]

Thread created automatically to discuss a document in CD-Media.

Window Motor Lockups: Causes and Solutions by ratdude747

[ratdude747]

I'd like to note that there was previously at least 1 other pictorial guide on the pin removal procedure, as I learned the procedure from it last year. That said, when I was asked about the procedure this year, I could not locate it on CD-Media, so I decided to re-create and expand on it.

Any suggestions/corrections are welcome.

[AdamHeard]

We steered our fall 2011 independant swerve with windows 1:1 with gray jags without issue.

We steered our 2012 swerve with windows geared UP 1.3:1 with victors without issues.

We've been trying to replicate the issues others claim to have, but we have been unable to.

[ratdude747]

Originally Posted by AdamHeard

We steered our fall 2011 independant swerve with windows 1:1 with gray jags without issue.

We steered our 2012 swerve with windows geared UP 1.3:1 with victors without issues.

We've been trying to replicate the issues others claim to have, but we have been unable to.

I only know of one robot where the jaguar-related lockup occurred, that being a ball kicker on 2783's 2012 bot (why I this paper was wrote in the first place).

In that case, I was told that the intermittent issue stopped occurring after an emergency swap from serial-CAN to PWM. I am pretty sure that all the Jags on that bot were black Jags.

What method are you using to control your motors?

[AdamHeard]

Standard pwm

[ratdude747]

Originally Posted by AdamHeard

Standard pwm

Ah. Perhaps CAN usage is related to the occurance of the lockups. If emperor swerve ever goes to CAN, I suggest preemptive locking pin removal.

[AllenGregoryIV]

We had lockup issues this year on our hood. Our controls operators was able figure out a pattern to get it to take commands again after it would happen but it was an issue. I thought it was a myth for awhile as well but I can assure you that it does exist.

Thank you for the tutorial.

[PAR_WIG1350]

Originally Posted by ratdude747

Ah. Perhaps CAN usage is related to the occurance of the lockups. If emperor swerve ever goes to CAN, I suggest preemptive locking pin removal.

But locking pins would seem advantageous in such an application. The expected load is not likely enough to strip the gears and maintaining orientation of the module mechanically will reduce load on the motors.

[ratdude747]

Originally Posted by PAR_WIG1350

But locking pins would seem advantageous in such an application. The expected load is not likely enough to strip the gears and maintaining orientation of the module mechanically will reduce load on the motors.

Most Modules do not have that issue, as the wheels are evenly centered with the module's axis of rotation. If the modules were more like casters, then there very well could be a backdriving issue.

[JDNovak]

We used window motors with the pins for steering at least one season. The only time it was a problem is when we slid into something with the wheel turned sideways. If the output of the gearbox is turned (like trying to pry the window down on a car), the pins would lock enough that the PID loop output couldn't turn it. Steering into the lock would always unlock enough to recover so it wasn't a big problem but since we've been removing them driving smoothness improved noticeably.

Thanks for getting this where more teams can find it.

[ratdude747]

Originally Posted by JDNovak

Thanks for getting this where more teams can find it.

You are very welcome.

-------------------

I uploaded a revised version. The previous version had an admittedly blatent grammar/wording error that slipped through editing... OOPS!

Content wise, it is the same, as any involvement with CAN is at this point speculation.

[Al Skierkiewicz]

Larry,
I believe the problem manifests itself when there is enough backlash in the system that the motor can vibrate with the output current waveform generated by the Jag. Systems such as steering in a crab drive system tends to damp any vibration that might occur. From those that have reported to me or here on CD it would seem that more than half of the teams that use the Jag/window motor combination experience the problem.
As reported, the difference between the left and right hand motors has more to do with the wire size the armature is wound with than actual performance. The lefthand motor getting significantly more use in standard operation then the right.
Nice job on the paper and the pictures it contains. This should allow more teams to overcome this small shortcoming by removing the pins. I would suggest you add the length of time this operation would normally take. Since it is so easy, more teams would take your advice and remove the pins. I would suggest that teams also keep the pins in a safe place so they can reuse them if needed.

[ratdude747]

Originally Posted by Al Skierkiewicz

Larry,
I believe the problem manifests itself when there is enough backlash in the system that the motor can vibrate with the output current waveform generated by the Jag. Systems such as steering in a crab drive system tends to damp any vibration that might occur. From those that have reported to me or here on CD it would seem that more than half of the teams that use the Jag/window motor combination experience the problem.

Noted. Most of my information was based on random noting from threads over the past year or so. The sad part is that most of the details regarding the cause of the lockups is based off of observances...

Originally Posted by Al Skierkiewicz

As reported, the difference between the left and right hand motors has more to do with the wire size the armature is wound with than actual performance. The lefthand motor getting significantly more use in standard operation then the right.

IIRC most of my knowedge regarding that left-right issue was from one of your posts. Ironically, during the 2011 season, 1747, the team I was on before my family moved, asked me why their arm based on a left-right design was overheating so much... It was bewildering at the time; hence why I thought it was worth mentioning as a potential cause.

"Performance" may have been the wrong word; I was trying to imply that the motors weren't quite compatible with eachother so to speak. Any suggestions on a better word or phrase to use?

Originally Posted by Al Skierkiewicz

Nice job on the paper and the pictures it contains. This should allow more teams to overcome this small shortcoming by removing the pins. I would suggest you add the length of time this operation would normally take. Since it is so easy, more teams would take your advice and remove the pins.

TBH I never timed the process. I have only performed the procedure twice, both times as a student in 2011. The work on the motor was mostly done by a student that I was instructing. However, since I did do some of the work (as a demonstration), I was sure to make sure the motor used was a dead one; I wanted any motors that would see use worked on by the students.

Since I currently am not a permanent mentor (the photo shoot was by special request), I personally do not forsee myself getting a chance to time the job. Perhaps other teams that perform the procedure could post about how long it took them (I'd take a guess but in that shop, time flies).

Originally Posted by Al Skierkiewicz

I would suggest that teams also keep the pins in a safe place so they can reuse them if needed.

I hadn't thought about that... Noted. I may add that to a future revision.