FRC Blog - 2016 Motor Controllers

[Jared Russell]

Originally Posted by Thad House

Programmers better bring their A game this year if teams want any sort of speed with 3 CIMs. Some very intelligent ramping and shifting code is going to be required for all the top teams.

Maybe someone who knows a lot about working with motor controls would be willing to do a white paper or something how how to limit current. Trying to find documentation online on how to do that has been impossible for me.

It would be awesome if the Talon SRX gets a firmware update that lets it do this (current limiting). It can already do ramping.

[AdamHeard]

Originally Posted by Jared Russell

It would be awesome if the Talon SRX gets a firmware update that lets it do this (current limiting). It can already do ramping.

Yup Yup.

I'd love this for FRC, and a few non-FRC applications I use Talons for.

[notmattlythgoe]

Originally Posted by AdamHeard

Yup Yup.

I'd love this for FRC, and a few non-FRC applications I use Talons for.

A continuous sensor option would be nice too. Similar to the continuous sensor option in the WPILib PID Controllers.

[Thad House]

Originally Posted by Jared Russell

It would be awesome if the Talon SRX gets a firmware update that lets it do this (current limiting). It can already do ramping.

Even if its not built in, since we can access all the current and speed data, wouldn't we be able to do this on the RoboRIO? It wouldn't be anywhere close to as fast of a loop, but it should be good enough, right?

[notmattlythgoe]

Originally Posted by Thad House

Even if its not built in, since we can access all the current and speed data, wouldn't we be able to do this on the RoboRIO? It wouldn't be anywhere close to as fast of a loop, but it should be good enough, right?

I haven't spent nearly enough time trying to track down the correct way to do this, but I would love to know what it is.

[AdamHeard]

Originally Posted by notmattlythgoe

I haven't spent nearly enough time trying to track down the correct way to do this, but I would love to know what it is.

Hopefully someone knows the answer to this.

If you're just running 4 Talon SRXs on the CANbus, nothing else and you're in a separate thread running your drive, what's the fastest you can run that loop and still get a fresh current measurement over CAN for each one?

Same question, but w/ PWM speed controllers and reading current over PDP?

[Thad House]

Originally Posted by AdamHeard

Hopefully someone knows the answer to this.

If you're just running 4 Talon SRXs on the CANbus, nothing else and you're in a separate thread running your drive, what's the fastest you can run that loop and still get a fresh current measurement over CAN for each one?

Same question, but w/ PWM speed controllers and reading current over PDP?

I know that the PDP only reads new currents every 25ms, or at least it was last season. Don't know if that changed. In addition, PWM updates at max every 5ms, so you couldn't go any faster then that even if you had a faster sensor.

The default status update period for Talons is 10ms. However I know that you can set it even faster. I bet you could do 5ms easily, and could probably push about every 2ms if you are careful with your CAN usage.

I would bet that is plenty fast enough, as your mechanical system probably won't react much quicker then that.