Ghosting after calibrating

Hi, our teams are new. The kids have been following the FAQ on calibrating the controller but the robot still has ghosting that randomly appears and disappears. I tried following the instructions from this web site as well to see what the kids are doing wrong but the Vex system still has ghosting sometimes. Any other possible tips on what is going wrong?

Same problem here, and I’m wondering if it’s possible that maybe signal interference from other devices (i.e. cell phones, wireless routers, etc.) in the vicinity could possibly be causing this, since the controllers communicate with the robots via bluetooth. At our most recent competition, we noticed that numerous other teams experienced the same “ghosting” with their robots as we did with ours, and there were certainly enough such devices (including WIFI) present and active inside the arena to create interference. I don’t know if this is a valid explanation, but it’s the only one we have found so far. Any other thoughts or suggestions on what could be causing the “ghosting” problem and/or how to eliminate it would be greatly appreciated.

I’ve found that “ghosting” has to do with the controller. Take the controller and push the joystick to the far forward position. Now move it around up against the stop in a circular direction about a dozen times. Recalibrate. Teach your drivers to not jam the joysticks, use a light touch don’t jam them.

Sometimes the sticks remain stuck out of center. Sometimes, they just have a little too much friction against the case and don’t center properly, but in both cases, it could help if you push the sticks in firmly (while in the centered position).
Even with proper centering, the analog sensors are usually little off the zero, that is what calibration is for, though the “deadband” (the range of values that are considered zero) could be too narrow for some controllers. If you implement your own teleop program (program that you use instead of the built-in driver controls, for simple robots, it could be as little as 3-6 lines of code actually), you’d have full control over the deadband and could tailor it to your controller if necessary. But no amount of software could compensate for sticks stuck in the extreme position, of course…

Either way, the reading is analog, digitized by the controller and sent digitally, so no interference could cause “ghosting” - either the signal makes it through intact or the data is ignored altogether.
VEX.Robotics.Paul.Copioli.pdf (229 KB)