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Unread 04-19-2018, 08:23 PM
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Stuttering Issue During Autonomous

My team has been testing an autonomous method of writing joystick inputs to a text file in teleop, and playing them back during autonomous. We are encountering an issue however, where the drive train will sporadically stutter and fail to run through the path. Any help would be appreciated. We’ve tested a host of possible causes, including can connections, the values themselves, the chain, problems with the wheels, and current limits. This is the code we’re testing :

https://github.com/frc747/2018-Robot...0710a6c6025016

Also for what it’s worth, we have a pid routine that runs perfectly. When we use our joystick mapping we encounter the stuttering issues. We have verified all electrical and can connections as well as communication connections. All systems are running correctly in Tele op as well.

Last edited by waitwhat? : 04-19-2018 at 08:36 PM. Reason: Added more info
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Unread 04-19-2018, 09:33 PM
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Re: Stuttering Issue During Autonomous

Can you post a log file of your autonomous running? It might offer more insight.
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Unread 04-21-2018, 10:19 AM
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Re: Stuttering Issue During Autonomous

Are you running with TalonSRX controllers?

We had an issue where the Talon would have a slight bug and stop the motor controllers.

Once we updated to the latest Talon firmware, the bug went away. For us it would only happen when running the motors at full power (1.0 being the set value).
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Unread 04-24-2018, 12:12 AM
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Re: Stuttering Issue During Autonomous

This might not be related to the particular issue, but instead of recording joystick values, why not try directly recording the motor output percentages? My team did this for fun this year, and while we never used it in a real match, it worked pretty smoothly on the practice field. We based our code on this repository: https://github.com/DennisMelamed/FRC-Play-Record-Macro. It's old, but still works after some adjustments.
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Unread 04-24-2018, 01:09 AM
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Re: Stuttering Issue During Autonomous

In general, we've found that whenever we have a weird "stuttering" problem with the robot, it is generally due to having two different sets of commands being sent to the TalonSRX.

Ways that we've done this by accident include having multiple conflicting commands running simultaneously (when one forgets to use a "requires" where one should) or having a loop call the TalonSRX repeatedly with very different values (e.g. alternating between "0" on one iteration and the correct value on the next iteration.)

I took a quick look through your code and tried to look for some instances of the above, but didn't have time for a thorough examination.

In any case, my guess when you see stuttering behavior is that the TalonSRX is getting called either by two simultaneous commands (such as the AutonomousPlayback command and the default DriveCommand), or there is a bug in your file-reading (or file-writing) such that the values you're sending to the TalonSRX in AutonomousPlayback aren't what should be sent.

Then again, it's quite possible the problem is something else altogether...
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