I’m assuming the reason that FRC doesn’t allow off-the-shelf PWM R/C car brushless motors and motor controllers is because they can’t guarantee that when the robot is disabled and the PWM signal goes to a disabled state that the controller will stop the motor appropriately. Is that true?
Is there a way we could get these approved for FRC use? I particularly like that they’re small, light, inexpensive, and typically up in a speed range that we don’t normally get from FRC-approved brushless DC motors.
Probably one of the bigger issues is any of them that are cheaper than the existing ones are going to be sensorless. Sensored R/C motors and motor controllers are generally not any less expensive then FRC options.
Theres also the fact that everyone wants CAN control, and even the kitbot nowadays wires motor controllers with CAN. PWM is rarely used, and for things that speed would be good for CAN is likely even more important to have.
Yeah, I was only thinking of the sensor-less ones. This would be a replacement for a redline or 550 brushed motor and SparkMAX using PWM, e.g., but it would be lighter and more powerful/efficient (and higher speed).
Another interesting use case: a quad-copter on a tether.
is there a reason you can’t use a NEO550 for that? given that the cost of a redline from andymark is 22 and a neo550 is 28 from rev the price difference doesn’t really seem justified there. Even factoring in the motor controller a CTRE talon srx/fxs is the same price as a sparkmax.
The NEO 550 has a free speed of around 11,000 RPM, peak power of 279 W, if memory serves, and it also has the problem of sensor wires that are a constant source of failure (in our experience).
You can find a 4300 kV brushless DC motor for a 1/10th scale car that doesn’t require separate sensor wires and has a free speed of 50,000 RPM, and something like 900W peak for about the same price as the NEO 550.
There’s also the fact that R/C components are constantly available, and there’s even a robust market of used components.
I could see a future where motors are made legal, but not motor controllers. Like you said, the safety guarantees are a bit of a problem.
That means an FRC vendor would have to make a motor controller that supports sensorless brushless motors, as iirc none of the current ones have support for sensorless brushless motors.
at that high of a kV there’s painfully little torque and after all the gearboxes you’d need to add i don’t see why you wouldn’t just use a NEO (or kraken, falcon, vortex). Im also not seeing the motor from a quick google at that low of a price (im seeing around the same cost as a NEO)
sensorless brushless motor control requires sensing the back-emf from the motor coils which neither can do (or at least they can’t use that data to drive the motor)
At the Champs vendor booths in 2019 CTRE was showing off the prototype brushless motor and controller that would eventually become the Falcon 500 and Talon FX. I distinctly remember them showing that it could run in either sensored or sensorless mode, in contrast to the NEOs which had come out that year and required their thin encoder wires. But when the Falcon (and of their all future brushless motors/controllers) came out, there was no mention of a sensorless mode.