[Joe Derrick]

Dear Chief Delphi community,

Our Mecanum Drive train with 4 victor 884’s tends to start drifting after a few minutes of operation. The drift is able to be corrected by the driver but is difficult to control.

We re-calibrate the victors using the joystick full forward, joystick rest, joystick full backwards procedure.
The calibration seems to work then again after a few minutes of operation the same slight drift problem seems to resurface. Sometimes a twitch of the joystick will allow the drivetrain to come to rest.

Of the many options that it could be, which of the following would you think most likely to be the issue?

1-bad joystick, we use an x-box controller that is 2 seasons old

2- bad victors, the issue was much worse, but then we swapped out older victors for new ones.

3- the fact that we are not using encoders on our drive train, to monitor wheel speed and instead are just feeding them voltage. Does this mean we just have to deal with this drift unless we use a PID?

4- mice with matches

5- something wrong with our code, we use java.

6- a “deadband” issue? After some reading I found this in wpiib screensteps.

"Setting parameters

All of the settable parameters of the motor controllers inherit from the underlying PWM class and are thus identical across the controllers. The code above shows only a single controller type (Talon) as an example. There are a number of settable parameters of a PWM object, but only one is recommended for robot code to modify directly:
• Deadband Elimination - Set to true to have the scaling algorithms eliminate the controller deadband. Set to false (default) to leave the controller deadband intact."

7. Something funky with the digital sidecar

Any help or anecdotes would be appreciated.

Joe Derrick – Team 319