Motion Control and Motor Drives

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Load Reference Parameter home Search Distance


Using PCI 7330 motion control board and LabVIEW, the Load Reference Parameter:Search Distance does not work. I have tried enabling search distance before and after loading a search distance.


I want to restrict the rotation to less then 360 degrees. If it does not find home in 180 degrees, I want the home search to stop so I can start it in the other direction..


Is there any other command or setting that would prevent or enable search Distance?


Thank you

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Message 1 of 13

I'm not sure I see anything off hand that is wrong with what you're doing. What error are you getting? Is the Search Distance Enabled parameter successfully setting? Have you checked Get Ref Param after you set it to see if it stuck?

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Message 2 of 13

There is no error. I will check the parameters to see if they are being set. If they are not being set, what can I do? Could there be an underlying timing problem that is not apparent on the PC side?

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Message 3 of 13

The parameters show as being set. However, regardless of what is put in as a limit (70 for steps. 0.3 for revolutions), the shaft turns around 340° if it is 20° from home.

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Message 4 of 13

The highest LabVIEW version I have is 8.5, so I can't open your VI, but here are some questions/comments.  Are you searching for the index?  My help for that VI references the search distance as applying to an index search, not a home search.

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Message 5 of 13

He's got the search type set to home so it should be doing a home search (although there is an index option). I've uploaded an 8.5 version in case you want to take a look. If the values are being set it's probably either a driver or hardware issue OR we're missing something fundamental with that property. Have you ever had this system (or another system with similar hardware) successfully perform this function? What other hardware is involved in your system? Let me know and I'll ask around to see if I can come up with some good troubleshooting steps. First thing I always recommend (which you've done a pretty good job of so far) is minimizing the situation to precisely one function. Also, it's not a long process, have you tried running it in highlight execution mode to confirm there aren't any strange values being passed through the program? Unfortunately I don't currently have access to that hardware so I can't try it myself.

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Message 6 of 13

This is my first experience with NI motion. I have found other Motion functions that do not work as advertised. For example, I was trying to use the Axis Straight Line Move, and got very strange results. It does not set the type of move to velocity, and sometimes the rate would be much higher than the value passed to it.

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Message 7 of 13

I don't think that Search Distance applies to a home move.  It only applies to an index move.

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Message 8 of 13

Load Reference Parameter

Loads the value for the specified find reference parameter.

Parameter Typeis the type of parameter to load. Valid values are:

  • Initial Search Direction
  • Final Approach Direction
  • Edge To Stop On
  • Smart Enable
  • Enable Reset Position
  • Offset Position
  • Primary Reset Position
  • Secondary Reset Position
  • Approach Velocity Percent
  • Sequence Search Order
  • Enable Search Distance
  • Search Distance
  • Phase A Reference State
  • Phase B Reference State

Search Type is the type of reference to load. Possible Search Type values are Find Home, Find Index, Find Center, and Find Forward & Reverse Limits

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Message 9 of 13
  • Search Distance—The distance Find Reference searches for an index before giving up. Valid values range from 0 to 231–1 counts.
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Message 10 of 13