seems a backslash mechanical problem .... or to low power on stepper drive for low motion (if you have these option) or a acc / dec ramp too low... so the stepper stop before to go at real measure.
regards bkt Il giorno lun 5 nov 2018 alle ore 00:19 John Dammeyer < [email protected]> ha scritto: > This discussion of servo gear heads brings up an interesting question for > me. > > I've been working on a system that has a CANopen controller Step/Servo with > integrated encoder. The motor turns a lead screw (10 TPI) which moves a > scissor jack type mechanism. We have an extra external encoder mounted on > the screw to be able to determine where the screw is on power up since it > could be anywhere. The step/servo is configured to have 200 steps per rev > which still works out to 0.0005" of linear movement. More than accurate > enough. > > What we're finding is that occasionally, a CAN message with a Move to > Position command of 2549 steps moves one or two less steps than it should. > To position 2547. The status CANopen message does not report move > complete. > Our software times out waiting for that move complete message after 15 > seconds. The actual move up to that position is only 4 seconds. So the > step/servo has over 10 seconds to move 1.8 to 3.6 degrees (2 steps) to > reach > the end of move position. > > I've been told to ignore this and when the external encoder is close enough > go on with the rest of the motion profile. In other words, ignore that the > motor isn't reaching the target position. > > If I allowed my Electronic Lead Screw to not always reach the end position > I > think I'd have users > complaining. > > The process isn't severely compromised by that two step shortfall. So we > can go on by ignoring motion complete. But this has all the appearance of > something that will fail worse later on if not addressed. > > Am I being too fussy? > > Thanks > John > > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
