Posts by QuentinT

Thanks for your response HawkME. With your answer I was able to find this page which really closed the gap for me. https://www.mecademic.com/ressources/Eul…es/Euler-angles It even has a visualizer to show what WPR angles will do do a frame.

I think I am going to have to go the matrix multiplication route to get the accuracy I'm looking for. I have a PLC in my cell as well that I will use to do the matrix multiplication and inverting to solve matrices for WPR values. I just have to keep in mind that Fanuc uses XYZ fixed orientation which is not very common in Euler angle tutorials.

For anyone annoyed by Fanuc's CD manuals that are HTML format instead of PDF.

In case it hasn't already been covered in the 4 previous pages, you can still extract the PDF manuals from these CDs. I did so last week and now have all of the software, electrical, and mechanical manuals in PDF form. All you have to do is insert the CD, and instead of letting it auto-run just go into windows explorer and search the CD for .PDF extension.
It's not difficult to find them manually either. Once you see the hierarchy of everything in the .html page, the directory structure on the CD makes sense.

It was well worth the 30 minutes it took to extract these PDF files versus trying sift through the .html version, or even worse, using their slow CRC site.

If anyone is interested in taking notes on their PDF copies, you will notice that the PDF files are locked. Unlocking them is as simple as running them through one of the many free online "PDF Unlocker" websites. If you find a decent website, it will even maintain all of the hyperlinks within the manual so the table of contents still works. Once the PDF is unlocked you're free to comment and highlight the PDF and save it using the free Adobe Reader

Hello Everyone,

First of all, if there is a better place for this to be posted, please let me know and feel free to move it. Also, if there is another place in the forum or in the Fanuc manuals with this information I apologize, but I'm having trouble developing the right search terms to find it.

The Goal:
I am hoping to find a resource or description of how a Fanuc robot uses the values stored in WPR to calculate the angle of its tool. I need to be able to calculate WPR offsets so that they affect my point in the way I expect every time. (My best guess is that it has something to do with Euler angles or quaternions? Wikipedia Link)

My Application:
I am programming a robot to place large sheets of material into slots in a rack. The slot locations are measured, and then used to calculate an X,Y,Z,W,P,R offset that must be used to accurately place the sheet into the slots. I know how to calculate the angles required for the sheet to land in the slot, but I am not sure that the angles I calculate are used by the robot in the way I expect them to be.

My Observations:
The best I have been able to find is that the WPR values represent the rotation about the X,Y, and Z axes. This is also what makes sense to me, but I have run into a few weird situations where these offsets did not behave as expected.

• Sometimes what I expect to be the Y axis is actually the X axis and vice versa.

• When Jogging in my current user frame, I will watch my position screen. If I jog in purely rX, rY, or rZ while my rotations are all 0, then it behaves similarly as I expect, excluding a few axes being swapped. As soon as I have 2 or 3 non-zero rotations though, jogging purely in rX may change both the W,P, and R values of the position simultaneously. I'm not sure how to calculate an offset if a pure rX offset could change all three WPR values at once.

• I remember running into a circumstance where I sent the robot to a position register that had a WPR value that I calculated. The robot got to the point and was oriented as I expected it to be. When I looked at the position screen though, the WPR values did not match the PR values anymore despite the robot being where I expected it. The position was in the same user frame that the PR was sent to. (I did not save this situation, so I would have try some things to repeat the situation)

• Another situation I ran into was with J6 pointed straight out in the +Y axis, and the tool was completely horizontal. I found that adding 5 degrees to R did the exact same thing as adding 5 degrees to W (it may have been R and P, but the idea is the same). Adding 5 degrees to either axis rotated the tool 5 degrees about the world Z axis.

Resulting Conclusions:

• WPR values are not purely rotations about the X,Y, and Z axes.



• 
  

  • Changing just W, P, or R can result in a single rotation about either X, Y, or Z, but it is not always predictable which axis will be rotated around
  
  
  • Multiple WPR sets of values can result in the same robot position.

[size=1em]My Robot: R2000iC/125L
My Controller: R30iB[/size]

I'm sorry to reply to an old thread, but Inrotech said:

Quote

There's a more accurate way to get the actual position.

I was wondering if anyone knew this more accurate way?