Re: jaguar scaling factors
 

Well, the PID probably isn't your most critical task, so a delay would be good. I would give it a delay of 5 to 25ms.
One thing I may have neglected to tell you:
PID doesn't "just work". You have to tune it.
Luckily, temporary deployments in LabVIEW make that easy. Just create a control for the parameters, and tune until it works. Make sure to start with Proportional, and then tune the others to whatever is appropriate.

EDIT:
Feel free to post your code. An easy way to post your whole project is to zip the folder it is contained in, and just upload the zip as a whole. To make it smaller, you can delete the "Builds" folder first.

Re: jaguar scaling factors
 

I don't want to move this thread in a different direction, but could you please elaborate on how you measured the output voltage?

Did you use a volt meter, scope, other?
Were motors connected to the outputs?
Did you take these measurements at the same time (measure one, then the other, same setup)?

-David

Re: jaguar scaling factors
 

I assumed the duty cycle at full on was 100% so I simply used a voltmeter
Set to DC. No motors. No load.
Measured two Black and two Grey
Full forward and full reverse
Same result consistently.

Re: jaguar scaling factors
 

This is a false measurment. The Gray Jags at full really drop maybe .15v more than the Black Jag.

Your measurement was just a by-product of the Gray Jaguar circuit design.
It doesn't measure properly without a load.
The Black Jaguar has a different design that doesn't affect no-load measurements.

I tripped over that myself earlier, although you have to read several surrounding posts to understand what was going on in that thread.

I liked Eric's way of putting it...

Re: jaguar scaling factors
 

What about creating a slider "trim" control.

Your "trim" control would run joystick position through a multiplier on one set of Jags. Experiment with trim position until you're satisfied that you're driving in a straight line.

This method will only be suitable if the differences between the Jags are consistent at various speeds.

Re: jaguar scaling factors
 

Thanks Mark.

We do clearly have a small speed difference between black and grey as well. Much harder to measure though.

I'll measure under load and see what I get.

Re: jaguar scaling factors
 

I don't think the offset is linear. I just tried my code today with the speed being divided by two and the robot drives much straighter. I haven't had a chance to test PID yet. Electronics guys are still trying to get encoders connected.

Re: jaguar scaling factors
 

I should have mentioned this much earlier. How much wire do you have feeding the two sides of the robot? A frequent problem is inches feeding one side of the robot with feet feeding the other side. If you are using #12 to feed the drive system, you can accumulate significant loss in the wiring. It amounts to about 0.2 volts per foot at near stall current for CIM motors. Remember you have to count both the black and red wires to arrive at the correct calculation. It is for this reason that I recommend a central location for the PD to balance the wiring.

Re: jaguar scaling factors
 

all wiring runs follow the same path, we had the problem you are describing last year