Lithion-Ion Batteries

[EricH]

I don't remember exactly on the PWM front, but I remember hearing something about the Jaguars/Victors using a slightly different PWM than say a servo/ESC. I think it's PWM vs PMM, but can't for the life of me remember exactly which is which.

Palardy, there's a minor difference between the max power being regulated electrically and in the motors. The electrical max power is driven by the current limits (and subject to the breakers actually tripping when they're supposed to, and as we all know they can handle short overcurrents)--the motor max available power is driven by the motor characteristics. If I can use 20 BaneBots without tripping a breaker, and you can only use 4 CIMs and 2 FPs, but you need 5 BaneBots on top of that that you can't use without the breaker tripping, I have a higher max available power and somehow worked in a way to use more of the electrical max power. Unless, of course, I used very weak BB motors...

This is a very good point. I wasn't able to think of a likely safety problem, and this is one. But, it could be simply solved with a rule specifying that any motor controller be required to handle a minimum of 40 continuous amps. Any more is unnecessary, because the fuse protection mentioned above.

A couple of notes on speed controllers: I would like to see some USB-capable ones available, and I recall that FIRST is looking to add those. However, I would actually raise the minimum from 40 to 60 (and if you meant maximum, so did I). Some of those controllers have ridiculously low safety shutoff settings, which don't account for the startup current that a motor can draw. (That current is why a breaker is used on the compressor spike instead of a fuse.) Trust me, I've seen a controller that was rated for at least the current my team was putting through it shut itself off 5 seconds into a 10-minute run--and the fuse protecting the circuit, rated for the same or less than the controller, didn't blow or show signs of blowing. A lower-rated controller, with the safeties shut off, went about 7 minutes in the same position before releasing smoke--it could have gone longer but wound up with an unusual load when the terrain shifted. And that controller was rated well below the expected current...

Oh, right: How it's necessary that a part be in the KOP. Teams were supposed to go buy a Kinect last year? That was also a new and readily-available technology. In all seriousness, it's not, but I'm willing to bet that the economics of scale are better for 2000 than for 20. Motor technology is one of those things where it's better to introduce it in the KOP--then teams will have a better collective knowledge on how to handle it, and where to buy it.

I wouldn't quite say that the ARA allowance last year was quite without performance characteristics. For one thing, van door and seat motors have been in the KOP before, and the van door motors were available from AM (which does provide the spec sheets); for another, if you need to look up the characteristics and you have a motor part number, that's pretty trivial with an internet connection.


I'm thinking that squirrel is right on not putting R/C components on FIRST robots due to the loadings. If you're stalling a R/C motor, you're doing something very wrong. At least, that's the aviation side of the theory--I don't know about the ground vehicle side. How often do FRC motors stall or come close, especially in a pushing match or a robot autonomously running into the wall?