re:Servo not stalling, a problem?

Ron,

I should prob'ly wait for the more learned to answer this but I put
my foot in mouth as good as the next guy, so here goes...

By definition, a servo is a "feedback" driven device.

ANYTHING which causes the "loss" or "incorrectness" of this required
feedback, CAN lead to axis "runaway". This could be the unplugging of
a connector(or a wire breaking), a software glitch, or a servo
drive "error" (not likely in most modern drives, but a "classic"
problem). But the careful "balancing act" that IS a servo system can
and does become unbalanced at times. Sometimes it is just a slow
moving problem, or a simple adjustment... Or...

If (when!?) the axis "runs away", the servo motor will be trying
to "get somewhere it can't", either mechanically or electronically.

Usually this means the FULL FORCE of the motor is being applied where
it shouldn't be... Since the motor keeps trying to "get there from
here", heat and/or pressure build up and... motor burns out/ drive
fails/ machines(or people)get crushed/ tools break/ parts are ruined/
etc.

Obvious results likely.

Hope this helps.

Ballendo

P.S. I've added some theatrics to make a point, but these things DO
happen with servo systems! LESS so with modern controls/systems, but
STILL do happen... There IS a reason for that BIG RED BUTTON!!

>I'm considering switching my design from steppers to servos. I've
>read that a servo NOT stalling can cause design problems. What
>problems are these?

Thanks,

Ron