Why Hasn't first gone Brushless?

[Al Skierkiewicz]

Marshall,
Three phase (or polyphase) motors operate in relation to the way they are wound and the input frequency. Their greatest torque is at the speed for which they are designed. There is a distinct relationship between the number of windings/poles and the operation of the motor. When these motors are manipulated for speed, the controllers are adjusting frequency. The controller is essentially a large power amplifier. And they don't change speed quickly. In general when a person speaks of three phase motors, they are referring to power line operated devices used in locations where three phase power is available.

[Jimmy Cao]

There are so many problems with using 3-phase motors on FRC robots. Not the least of which is safety, having 120/240V around. I'm sure we'd all love to have kids wiring a high voltage system, which could rather easily kill them. I'm also not too familiar with inverters, but we would either need something that converts from 12VDC or have some way to store higher voltages (and then convert those to AC) on the robot, or have power lines leading to the robot (can you say "accident waiting to happen"?)

In my opinion, the safest, and most logical thing to do for FRC robots is to use some form of DC motors. Right now, brushed motors are being used due to logistics, and availability/price. Maybe, sometime in the (hopefully near) future, brushless motors could be used.

[Jared Russell]

While we're on the topic of allowable actuators, I would really like if we were allowed to use electric solenoid actuators. There are so many applications (dog-style shifters, brakes, clutches, latches, etc.) where I'd love to be able to eschew a full-size motor or piston, and where a servo just doesn't cut it.

[Al Skierkiewicz]

Originally Posted by Jared341

While we're on the topic of allowable actuators, I would really like if we were allowed to use electric solenoid actuators.

I wholeheartedly agree. There are a variety of great solenoids that eams could put to great use if allowed. Additionally, electrically operated clutches would be nice.

[kamocat]

Originally Posted by Al Skierkiewicz

I wholeheartedly agree. There are a variety of great solenoids that eams could put to great use if allowed. Additionally, electrically operated clutches would be nice.

I can't wait for the day when tool changers are a reasonable option on an FRC robot.

[EricVanWyk]

Originally Posted by Jared341

While we're on the topic of allowable actuators, I would really like if we were allowed to use electric solenoid actuators. There are so many applications (dog-style shifters, brakes, clutches, latches, etc.) where I'd love to be able to eschew a full-size motor or piston, and where a servo just doesn't cut it.

I was thinking the same thing a few weeks back. Do you know of any specific models that might fit?


On the AC motor "topic", thanks for the chuckles. Greg pointed out that it would make designing the PD a bit easier - just get a plug strip! Now we just need to find 3 phase AC batteries...

[Jared Russell]

Originally Posted by EricVanWyk

I was thinking the same thing a few weeks back. Do you know of any specific models that might fit?

Eric,

I'm sure that Al will know much more on the subject than I do, but I have used models from Pontiac Coil that are sold on DigiKey. Looking at DigiKey, most are in the $20-40 range and are 12V, .5-1.5" stroke, and offer holding torque on the order of a few to tens of ounces.

[artdutra04]

Let alone three-phase power on FRC robots, I just want [480v] three-phase power in my house!

There are tons of used (still in good condition) three-phase Bridgeport manual milling machines on eBay all the time within driving distance that are selling for $2k-$5k. Some even come with DROs! Who wouldn't want a full size manual mill at their house?

But the electric companies are like you're residential, grumble, grumble, single-phase 240v only, grumble, grumble, just use a rotary phase-converter, grumble, grumble.