Problem using encoders on Jaguar

[ChristopherBuck]

We have a quadrature encoder wired to the encoder inputs on the Jaguar, yet niether the TI utility, bdc-comm nor labview can use the jaguars in speed mode. In the bdc-comm utility, the option to use encoders is grayed out (see picture attached). Controling the jaguar and motor via Voltage mode works perfectly, but controling it via speed or position mode does not. does anyone have any ideas on how to fix this problem?

[dyanoshak]

I couldn't see in your picture, but I assume you switched over to speed mode.

What this sounds like to me, if everything is hooked up correctly, is that you did not set your P, I, and D constants. With them at the default 0, your motor won't turn no matter what speed you tell it to go.

Start by setting a P value of a few hundred (P is the proportion correction to the error between the desired speed and actual speed) and see if that gets your motor spinning. Be careful, while tuning your PID constants the motor can sometimes move erratically. Leave I and D at zero for now.

Make sure you set the number of encoder lines (ticks per revolution) in the configuration tab.

The encoder/potentiometer radio buttons are grayed out in speed mode because speed mode only supports encoders at this time.

Whether this works or not, also be sure you're running the latest firmware on the Jaguars and the latest BDC-COMM (all version 87). They can be found here: www.luminarymicro.com/jaguar

If you are still having trouble, post some more info about your setup, and a full screen shot of the BDC-COMM screen.

-David

[jskene]

Thanks for the tip. We updated the Jaguar, and it now works.

There are still a few problems, though.

The motor jerks on-off at low speed (50 rpm or so and lower), and runs at much higher than the target speed in reverse. We set P=100, I=0, D=0, and set the encoder to 360 segments, as that's how many it has and it is on the output shaft of the KOP transmission.

[dyanoshak]

Now that you've got it spinning, it is just a matter of tuning your constants.

I saw the same behavior when I was playing with a kit encoder, CIM, and a toughbox on our robot. I found that a much lower P with a little bit of I seemed to work well. I was using P = 0.3 and I = 0.001. It just takes time to find the perfect values for your system.

Good luck with tuning!

-David

[biojae]

Thanks for the tip. We updated the Jaguar, and it now works.

Is this running on the cRio, or through BDC-COMM?
If it is on the cRIO, then which language are you using C++, Java, or Labview?

The reason that I am asking is because, in a few days, I will be wiring up the robot.
On the 1 jag that I used with the potentiometer, the position couldn't be read by the jag, but the position set-point could be sent.

If the encoder can be read in by the cRIO,
then I will use the speed control of the jaguar,
otherwise I will wire the encoders to the digital sidecar as I need them for autonomous.

[jskene]

So far we are running the Jag only through BDC-COMM, but today we will try it on the cRio and see if we can read the encoder. If not, we may wire the encoder both to the Jag and the cRio, as we also will need it for autonomous.

We'll update our progress on this forum.

[jskene]

e tweaked the PID values and it now works perfectly.

Here's a screenshot of what we used on the Toughbox:



We tried getting it to work on the cRio, and made some progress, but aren't there yet.

More tomorrow.

[biojae]

Originally Posted by jskene

We tried getting it to work on the cRio, and made some progress, but aren't there yet.

More tomorrow.

Has there been any more progress made?

Luckily for me, I haven't fully wired the robot yet, so I still have time to wire it to the cRio if needed.

Which programming language are you using?

[simpsonboy77]

Has anyone gotten the speed control to work without using the BDC utility, or Labview? I tried writing my own speed driver, but it doesn't work at all. I cannot use the utility because we don't have a black jaguar (yet, just ordered it).

If you have gotten the speed control, could you kindly post the code, or point me in the direction of a repository? The first forge hasn't been updated in a while, and only works for percent voltage. We are using C++.

[Joe Ross]

Originally Posted by simpsonboy77

If you have gotten the speed control, could you kindly post the code, or point me in the direction of a repository? The first forge hasn't been updated in a while, and only works for percent voltage. We are using C++.

Have you looked at the subversion repository on FIRST Forge? It looks to me like it's been updated in the last 2 weeks and does have speed control.

[simpsonboy77]

I was looking at 'File releases'.

I setup an account (wow I hate those password restrictions) and I downloaded the current versions. I'm shocked at how close my code was to this. It gives me the (false) impression that I know what im doing haha.

Can't wait to test this tomorrow, (well technically today :0)

Thanks Joe.