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Unread 17-04-2012, 13:17
nighterfighter nighterfighter is offline
1771 Alum, 1771 Mentor
AKA: Matt B
FRC #1771 (1771)
Team Role: Mentor
 
Join Date: Sep 2009
Rookie Year: 2007
Location: Suwanee/Kennesaw, GA
Posts: 835
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Re: paper: Shooter Wheel Speed Control

Hi all, I was the programmer for 1771, and I played around with this method a lot. (Differing ramp rates, update times, etc.)

Our hardware set up was originally 1 FP motor in CIMulator to power the wheel.

The code didn't run in the main tele-op loop, I had it run in its own task. It was set to read the encoder value and change the motor voltage every .05 seconds.

I had the CANJaguar voltage ramp rate set to 110 volts per second.

An important thing that I didn't see mentioned, was WHERE the encoder got read.

We plugged the encoder directly into the Jaguar, and used the CANJaguar's GetSpeed() function.

We believe that having it go directly to the Jaguar, NOT the cRIO's FPGA, allowed it to be read faster. This may or may not have been true.

Of course all these values will change based on your shooter wheel.

As for the RPM consistancy-
When reading the values, we saw an average of 15 RPM difference from our set point for the RPM. If we had more time to dedicate to JUST tuning that, I feel we could have gotten a little bit more accuracy on that.
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