Problem with find reference and overshooting limits

[DaveD]

I have a two axis system set up (with a 7344 and UMI-7764), axis 2 uses a lead screw and the find center VI works properly, axis 1 however has a much longer travel and uses sprockets and cables to move and is therefore less rigid.  When attempting to find center, unless I run the axis very slowly, when the carriage hits the forward (or reverse) limit it overshoots the limit (inertia) and when the motor jogs to move off the limit it doesn't move far enough to release the switch and identify the location of the limit.

Is there a way to increase distance that the axis will move to back away from the limit and find its exact location?  I would like to use a fairly high velocity to find center because the travel distance of the axis is up to 10 m and it takes quite a while to located center at the speed I am currently using.

Thanks

[Jeffrey_P]

Good morning David,

The Offset Move, in counts, is the function or feature that you are looking for.  It is on the Find Reference Settings in MAX, just below the location where the approach velocity is specified.  This is under each specific axis inside of the Default Settings.  The Offset Move specifies the number of counts the system should move to after the Reference Location is found.

I hope that this information is helpful.  If this is not what you are looking for, please post back and I will do my best to answer your questions!

Respectfully,

[DaveD]

Jeffery,

I played with the offset move and it helped a bit but I still needed a deceleration.  I found in the Set u32.flx the "Stop Type on Switch" attribute can be set to decelerate.  This has fixed my problem, I can traverse at a rapid speed to the limit switches and when they are encountered the motor slows the carraige with tossing it off its rails, it then backs up to hunt for the exact postion on the limit before moving to the opposite limit then to center.

Thanks for you help.

[JDR]

I know this thread's been inactive for awhile, but I thought it was important to post that this "set U32.flx" solved my problem with finding the limits as well. The "Find Reference.flx" does not have an options to allow you to change the stop type from hard stop. This caused a problem for me because my switches were so sensitive that they did not depress enough to allow the final approach motion to find the negative edge of the switch. Using the "set U32.flx" I was able to change the stop type to decelerate which forced the actuator to overshoot the limit enough for the final approach to find the negative edge of the switch.

I think NI should update "Find Reference.flx" to include an option to set the stop type.