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Unread 20-06-2014, 02:20
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AKA: Anand Rajamani
FRC #1072 (MVRT)
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Re: Motors: Past and Future

Quote:
Originally Posted by AdamHeard View Post
There are plenty of hobby grade ESC's for brushless motors that would work at 13+ V that FRC sees. I have way too many brushless RC cars, and I design brushless motors at a my day job (at a company that also makes the drives for them).

They really wouldn't be much better than brushed motors, just more efficient. Since most of those drives are sensorless in the affordable price points, teams would see issues with cogging as most wouldn't know how to properly size them.

The true benefit of brushless motors for FRC would be when we get current control, which is a higher price point controller. We could do some REALLY cool control stuff at that point though, very smooth motion.

If hobby grade brushless motors became available for FRC, it's unlikely we would use them (reliability, the potential cogging issue). I reserve the right to change my mind after testing though. If anything we'd reserve them for applications that never see high stall loads and we can take advantage of their high power and efficiency in the faster range.
The reason I said it won't work is because of the wide range. Many ESCs have cell detection and cutoffs at certain points programmed in. Hardware wise it wouldn't be a problem, but the software on the ESC might cause problems.

Power density might also help. The SSS 5940, which I was looking at for a go kart, has exactly the same dimensions as a cim, but it has a peak rating of 10000 watts versus the cim's 1600. I'm not sure if that's just the motor specifically or a property of all brushless motors.
Well, it has a stall current of 180 amps, but a voltage capacity of around 60v.

What is cogging? I've never heard that term before.