Sync Two Jags

[kamocat]

Originally Posted by AustinSchuh

Warning: I haven't tested this or tried to model it, but it should work in theory... Of course, the devil is in the details.

Try wrapping a control loop around the two control loops on the Jaguars to sync their voltages up. The pseudo code would be something like the following, and you can make it more complicated if the nieve implementation doesn't work. This is assuming that you are sampling the voltages of the two jaguars at the same time, and I'm not sure how much a difference in sample time between the two jaguars would effect things. Probably depends on how aggressive you are trying to sync the two.

v1 = jag1.getVoltage()
v2 = jag2.getVoltage()

error = (v1 - v2)

jag1.setX(goal - error * Kp)
jag2.setX(goal + error * Kp)

The basic idea is that you wrap a proportional loop around the two PID loops running on the jaguars in order to drive the voltage error between the two loops to 0. This should cause them to provide the same voltage to the two motors, and share the load nicely. It might also work if you try to drive the errors in the current that the two motors are drawing to 0, or something clever like that.

That's an interesting method of doing it. It would probably be best to get the %Output status, not the Vout status, because the voltage would have to be scaled down anyway.
Then again, I don't know what your "getVoltage" function does. Has it been modified to get the actual voltage, or does it return %Output?

I think it would make sense to monitor it first and see if any problems arise.

[AustinSchuh]

Originally Posted by kamocat

Then again, I don't know what your "getVoltage" function does.

My "getVoltage" function returns some indicator of how much voltage the Jaguar is trying to put out. It is probably easiest to get the % Output from the Jaguar (should be [-1, 1]) and use that, but theoretically, any indicator should work. The time constant should probably be pretty slow since you don't care too much if they aren't perfectly the same and just want the two to be pretty close.

[mocibot]

Originally Posted by kamocat

That's an interesting method of doing it. It would probably be best to get the %Output status, not the Vout status, because the voltage would have to be scaled down anyway.
Then again, I don't know what your "getVoltage" function does. Has it been modified to get the actual voltage, or does it return %Output?

I think it would make sense to monitor it first and see if any problems arise.

I have a question on this, How do you get %Output status?

[jhersh]

Originally Posted by mocibot

I have a question on this, How do you get %Output status?

There isn't currently a status for that in the library, but the Jag supports it. It should be easy to add that to the library. Just follow the pattern of the other status messages.

-Joe