Rotate TCP in Rx direction only

Technical Questions URScript
5

Hi @francis

If you want to program just a rotation, you have to keep in mind that the last 3 elements in the pose array are of a rotation vector type. We cannot, or at least very difficultly, interpret this. When we want a rotation, we think in the “RPY” type.

This means that, if you want a rotation of 179deg around your y-axis of your chosen TCP (your Y-axis points outward of the tool flange), then you can accomplish this by doing these steps:

  1. A rotation of 179deg, transform it to radians:
    rot_rad_rpy = [0, d2r(179), 0]

  2. This “rot_rad_rpy” as we interpret is, is of the type “RPY”. So we need to transform it “Rotation vector”:
    rot_rad_rotvec = rpy2rotvec(rot_rad_rpy)

  3. At this point, we have a rotation, of the type “rotation vector”. Now all that is left, is to tell the robot to use this rotation around your TCP, which you already did correctly in your code:
    new_pose = pose_trans ( get_actual_tcp_pose(), p[0, 0, 0, rot_rad_rotvec[0], rot_rad_rotvec [1], rot_rad_rotvec[2] ] )

When you try this, you will see that the robot will turn correctly.
Keep in mind that this is a rotation around your TCP Y-axis. If you kept the TCP as default (so Z pointing outward), then in the first step you would need to do: rot_rad_rpy = [0, 0, d2r(179)]

If you have any questions, feel free to contact me.

Kind regards
Dieter

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