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Unread 28-02-2016, 16:17
cantdecide cantdecide is offline
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Re: Encoder instability

Quote:
Originally Posted by c0d3rman View Post
As it seems you've replaced a lot of your hardware already, have you considered it may be code?
I have considered that, but I have code backups from when it didn't happen, and the problem happens even with old code.

Quote:
Originally Posted by GeeTwo View Post
How much do you lose the angle? Is it small enough just to be backlash, or is this really a significant amount?

Under what conditions does this happen/not happen? E.g. only when being backdriven, only in reverse, only when the last joystick command was x. Any patterns as to when it does/does not happen can help point to a cause.

Mechanically, if larger than a backlash value, i do not see how the problem could be inside the gearbox unless some teeth are practically missing or there's a similarly large failure. The coupling of the encoder to the backshaft is a possibility. Losing transitions electrically is certainly possible, especially if it happens in conjunction with collisions (including crossing defenses quickly) or another motor/actuator being operated.

Just for completeness, is the sensor connected to a pair of DIO ports on the RIO, or going to an SRX or Jaguar's encoder inputs? Especially if it's not coming from the DIO, are you sure you're using a 5V supply?
We usually lose a significant amount, in the 90-100 degrees range, and that's enough to completely render our shooter useless. It also tends to hit a few things on its way up, sometimes damaging parts.

The conditions happen to be random, but it's mostly immediately after the robot is enabled or while the robot is sitting still. I can't remember an instance where it "jumped" while the robot was in motion.

The outputs are connected to DIO ports, and I've tried switching between different ports. We use the 6V(?) supply from the DIO ports. Might that be a problem?