Re: Speed Controllers: Which is best?
 

I think Scott's post was saying that the PID in the Jag is implemented in software (firmware), not hardware (logic gates).

Re: Speed Controllers: Which is best?
 

I'd hesitate to second guess the creator of a device on a question about how the the device in question works.

Re: Speed Controllers: Which is best?
 

Why does it matter how it works internally? The device as delivered has the capability, and the alternatives apparently don't. Our team has found this capability quite useful.

Re: Speed Controllers: Which is best?
 

We've run a few hundred hours of practice. Obviously not driving every minute, but the Talons have held up flawlessly.

Re: Speed Controllers: Which is best?
 

I concur.

Re: Speed Controllers: Which is best?
 

For 2 reasons:

1) Because Scott's post was correct and Jon said it wasn't correct. It was a simple misunderstanding, I believe... but it might confuse students if left uncorrected.

2) Some people care how things work internally.

Re: Speed Controllers: Which is best?
 

We used talons this year. Like nearly everyone else, we love them. They are small, have a sealed design, and are pretty linear. We put fans on our drive train, though I don't think we needed to. We don't really like Jags because of their size and reliability issues, and we have never used CAN. Victors are okay, but the 884s are not linear, and the 888s have a slightly larger footprint (compared to the talon) and open design. Even with the conformal coating, I would be wary of metal shavings.

Can anyone comment on the reason to use a Jag PID as opposed to using the crio to accomplish the same thing. Why is it better/prefered by some teams?

Re: Speed Controllers: Which is best?
 

There's one less thing to do on the CRIO. (although the crio is powerful enough for basically everything but heavy vision processing)

Re: Speed Controllers: Which is best?
 

The real strength of the Jag is in the first few weeks of build season.

Attach a jag, a breaker, a battery, encoder + potentiometer wires, and a serial CAN adapter on a small board, and you have a really versatile prototyping rig.

We basically had a working FCS prototype with <2% velocity speed control on day 2 of build thanks to the Jags and BDC-COMM.

No cRIO or programming required.

It's incredibly fast to get a newly built mechanisms up and running for trials - whether it requires speed control or position control - or neither!

Jags are great when used in the right situations.

Re: Speed Controllers: Which is best?
 

Internal PID closes the loop at 1000Hz. Too bad the Jag doesn't have an internal bang-bang speed controller.

Re: Speed Controllers: Which is best?
 

Could you not just bump the P value up very high and set I and D to 0? Doesn't that basically emulate a bang-bang?

Re: Speed Controllers: Which is best?
 

No, since it would compensate when the encoder value is over the setpoint (think -1 speed), making the speed go up and down uncontrollably.

Re: Speed Controllers: Which is best?
 

Unless you pulled the limit switch jumper that prevents it from going in reverse...?

Re: Speed Controllers: Which is best?
 

Well there you go. That would effectively be bang-bang control.

Re: Speed Controllers: Which is best?
 

I'd like to hear from someone who has done this.