paper: Shooter Wheel Speed Control

[mjcoss]

The question is how to get at that information and what kind of accuracy are you looking for. Note that we are using C++, so ...

GetSpeed() returns the current measured encoder speed as reported from the Jaguar. So the total round trip time can be gotten from grabbing the time before and after the call. This is, of course, not very fine grain and includes the time spent being packaged in an Ethernet frame, going to the 2CAN, being unpackaged, put on the CAN bus, out to the Jaguar, and back again.

dt2 is a bit trickier. We aren't using your speed control method but rather are running the PID loop on the Jaguar. Each time through our TeleopPeriodic loop, we update the set point. Our periodic loop will do some work if no packet arrives from the driver station, but for the most part we update based on the arrival of new data from the driver station. We don't check to see what the set point currently is, we just reset it to the requested value.

dt3 is even trickier, if not unknowable. Again we could use the total round trip time of the Set() command which is used to register the current set point, but that includes the time to the Jaguar, and the return ack across the CAN bus, and thru the 2CAN and back up the ethernet stack and to the CANJaguar module.

Finally there is a lot of checking that I've added to around the Set() operation. Every Set() is followed by a CAN bus message requesting the fault status of the Jaguar, and then a CAN bus message requesting the PowerCycled flag. If a brown out occurred then the Jaguar configuration is reloaded.

When I get a chance I think I'll implement you're speed controller and see how it does relative to running the PID on the Jaguars as we currently are doing.

Originally Posted by Ether

Thanks for the offer.

No, the elapsed times I am looking for are:

dt1: how long does it take from the time you ask the Jaguar what the motor speed is, to the time you read the answer that comes back

dt2: how long does it take from the time you read the answer, to the time your code sends a new command to the Jag

dt3: how long does it take from the time you send a new command to the Jag, to when it receives the command.

If you aren't doing all three operations in the same execution cycle, please mention that too.

If you aren't reading the speed from the Jag and sending a new command based on that speed, you would have to add that code to get what I'm looking for.