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JamesCH95
05-11-2011, 01:59 PM
After many hours of driving the robot (particularly the arm) for a demo-day, we decided to take advantage of CRREL's thermal cameras and take some pictures. We learned some interesting, if obvious, things about the robot.

To reference what our robot looks like: http://r95.org/?p=90

In this picture note the hot window motors that run the arm's gripper, and the warmed area around the roller sprockets on the gripper.
http://i.imgur.com/NRnAv.jpg

The compressor is very hot, and surprisingly the cRIO is quite warm. The power distribution board and 10awg wire is very cool though.
http://i.imgur.com/xo5BV.jpg

Under the robot note the slightly warm AM gen-1 shifter transmissions and the VERY warm arm motors. The RS775-18 in the DeWalt housing is a bit hotter than the RS775-18 in the banebots 64:1 P60, presumably the P60 acts as a better heat sink.
http://i.imgur.com/n0jmr.png

roystur44
05-11-2011, 02:44 PM
James,

The KOP fans are a great thing to add to the robot to cool things down to extend run times. We mount the large fans over the drive motors and we add small fans to the fisher price or bane motors. Another thing we do is add thermistors to the motors and monitor temperature at the drivers station.

Roy

sanddrag
05-11-2011, 04:54 PM
My experience with the CIMs in both robots and controlled test conditions has indicated that blowing air over them, even at significant volume, has little effect. Under approximately 25 Amps steady continuous load, I could not run a CIM for more than about 4 minutes without it becoming so hot you couldn't hold a finger on it for more than a second or two. This was with a large custom-machined finned aluminum heat sink affixed with thermal compound, and a fan blowing over it. The problem is the heat is all generated in the armature windings, and its only conductive path out is through the bushings in the endbell and the face of the motor. It's a pretty slow heat transfer. It would appear that due to the lack of an internal fan, the convection internally is not really enough to make the CIM motor suitable for extended use.

slijin
05-11-2011, 06:02 PM
The low thermal signature of the main PD circuit is likely because all the plastic casing acts as a good insulator, disguising its true thermal signature. The cRIO part does somewhat surprise me, though.

Andy A.
05-11-2011, 08:11 PM
The low thermal signature of the main PD circuit is likely because all the plastic casing acts as a good insulator, disguising its true thermal signature. The cRIO part does somewhat surprise me, though.

I suspect the cRIO's heat has a lot to do with the runtime we saw that day. The robot had been on for most of the day, even when it wasn't being driven, and of course it's only a few inches from a very hot compressor. The (steel?) housing holds heat pretty well.

Seeing the heat built up around the sprockets in the arm was most interesting to me. We always knew it was a fairly high friction area, but seeing the heat spreading out into the plastic really illustrates the matter. Had I seen that during the build season I might have opted for some sort of further lubrication.

Obviously, thanks goes out to CRREL (http://www.crrel.usace.army.mil/) for taking the time to photograph the 'bot for us. We hope to get some time with the same camera technology during the next build season to help spot friction, bad connections, educational video of machining operations and who knows what else? They've also been a major sponsor of our team since 1996. We've been very lucky to have access to CRREL and the people who work there.

legogeek24
05-11-2011, 08:16 PM
Those are some really interesting pictures, that's really cool to have the opportunity to use that camera! I was surprised at the heat of the compressor and cRIO, but I guess running it all day will definitely warm things up!

goldenglove002
05-11-2011, 08:45 PM
I love these images. People didn't believe me when I said our window motor was hot enough to burn my hand at our last public event (speaking of, these robots can make for some awesome demos).

JamesCH95
05-12-2011, 12:45 AM
Those are some really interesting pictures, that's really cool to have the opportunity to use that camera! I was surprised at the heat of the compressor and cRIO, but I guess running it all day will definitely warm things up!
Thanks!
I love these images. People didn't believe me when I said our window motor was hot enough to burn my hand at our last public event (speaking of, these robots can make for some awesome demos).
Yep, those window motors are designed to work for 5 seconds at a time, then rest for quite a while. We were definitely stressing them quite a bit. Luckily, we have many spares :D