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Motor moving after end limit switch condition removed


KEJR
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Hello, I don't know if this is a bug or I am doing something wrong. In testing I often jog a linear axis and then wave a screwdriver in front of the limit switch to test the motor. I adjusted motor[].AbortTa appropriately to get a soft but responsive decelleration. This works fine. When I lift the screwdriver away from the limit switch there is an audible clunk sound as my motor is rapidly moved back a small amount away from the limit switch. I know that besides testing this isnt' really a valid situation, but is this normal? thanks, KEJR
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Ken: I can't duplicate this here. Once I trigger the limit to abort the jog move, the abort deceleration proceeds regardless of what I do to the limit switch afterwards. I created a long deceleration so I have the time to toggle my limit back and forth dozens of times during the decel, and I can't get anything to happen. This behavior is what we planned, and what the code indicates should happen. Are you sure your application code is not commanding something else when it perceives you are out of the limit? Curt
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I don't think the bug is the loss of EOT switch *while* decellerating, I think it is after the decelleration is complete. So to recreate what I was talking about have a normal decel time and then *make* your EOT switch for that direction and just hold it there until you are sure decel is done. Now after a few seconds remove the switch condition and you will hear the clunk. I don't think that the program is causing it. I performed the test while jogging from a command terminal. I will recreate this now to confirm and get back to you. Another "symptom" is that if you had stopped on EOT limit (and motor is still enabled as is the default behavior) and you can back drive the system it oscillates with a tiny vibration. It is bizarre. I don't know if this matters but I am using scaled motor units and Macro drives. Everything else appears to be working correctly. KEJR
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I can't duplicate this either. Over the last several years, I have done this sequence hundreds of times to check out various aspects of the HW limit functionality, and have never seen it. We have had no other reports of this issue from anyone. The closed-loop zero-velocity state the motor is in at the end of the abort is no different from the closed-loop zero-velocity state the motor is in any time you are holding position. Of course, tuning issues could cause vibrations at rest (but not uniquely in limits). We have never seen motor unit scaling issues affect anything. Curt
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I didn't think that the zero velocity state would be different. It is almost definitely not a tuning thing just in that it only happens when I am just on the hairy edge of the limit switch or when I manually trigger the switch and then let go. I think I might try a plot looking at the EOT switch and the commands and see what it shows. I think this will probably tell us something. thanks KEJR
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  • 2 months later...
*** Solved*** While I haven't proved this, the problem was most definitely that the copley drive was decellerating on its own when EOT limits are applied, and it seems to mess with the trajectory commands being sent over the MACRO bus. Since I am not planning on running into the EOT limits alot this is OK with me now that I know what is happening.
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