Universal Robots Forum

Trouble understanding pose_trans

I have a feature as reference and I want to move relative to it at a direction + angle. By reading the documentation, forums and the simple vision example I get the impression that I need to use pose_trans .
But a simple test doesn’t do what I expect. With a reference at x=0,y=300 and an offset at x=0,y=100 and rz=90deg. I expect the resulting pose to be at x=100 and y=300. But as seen on this screenshot that is not near what I get

Is there a way to achieve the desired translation using pose_trans or should I approach this differently?

There are a number of things that are confusing about your approach here…

  1. I’m not sure why you’re using the log screen instead of the variables window to view the results of your program?
  2. You don’t mention a rotation on your reference, but you’ve rotated it 180 degrees about the x axis?
  3. You have rz of about 15 degrees on your offset, not 90 degrees?

I’d recommend you complete UR Academy prior to attempting this if you have not already done so. https://www.universal-robots.com/academy/ - Module 7 - feature coordinates could be useful.

Also - make use of the features screen under the installation tab. When you define your reference point here you can see which way the axes are pointing and get a better idea of which way your offset is going to go.

A key point to not getting what you expect here is that the rotation on the offset only affects the final orientation of the tool, it doesn’t change the orientation of the reference frame - the example you followed wasn’t very clear on this.

Hope this is enough to allow you to better know what to expect out of pose_trans().

Thanks! You are right, I was expecting a change of the reference frame and not the final tool orientation.

Ok, if it is actually your intention to change the reference frame you could do one pose_trans() first with just the rotation component, then another pose_trans() on the result with the linear offset.

Thanks, I checked module 7, and feature coordinates where what I needed.