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How does the system know that it is keeping up or not

I saw a message that the sled was not keeping up. How does it know if the sled is keeping up? Does it measure torque on the motors? There are no other optical sensors or anything.

The system knows where it should be based on the movement that’s requested, and
it knows where it is based on the encoder information, if the two differ by more
than the allowed amount (in the config), it generates this alert

Since we currently do not do any acceleration planning, the system tries to go
from stopped to full speed instantly, and it can’t do that (for that matter, the
pid loop doesn’t even try to do that), so if you try to go too fast, and have
your limits set to tight, you can easily get this message

I’ve suggested that we instead alert if we spend too much time applying full
power, or if we are at full power and the pid loop is calling for even more
power instead, but that has not been implemented.

David Lang

what would happen if the sled were removed, how does it know that the sled is not in the correct place. When my machine went haywire, it showed a red placement indicator, and a black one, they are apparently supposed to be on top of each other, but they were very far apart. You say the “encoder information” I don’t know what the means. I am curious to know specifically how that works.

it only looks at the motor positions

when you tell it to move, it starts tracking where it ‘should’ be, but it
actually doesn’t start moving immediately, instead the PID loops starts noticing
that there is an error between where the motors would be if it was where is
‘should’ be and where the motors are, and adjusts the speed/power ofthe motors.

it doesn’t matter if the motors are attached to anything or not, all we know is
the position of the motors as tracked by the encoders on the motors.

This is why the system doesn’t know if the chain has jumped or other problems

1 Like

okay thanks