With the UR5 model, if I set the joint angles to [0, -90, -90, -90, 90, 0], the orientation of the Robot Flange/Tool Frame with respect to the Reference Frame (set as UR5 base) is shown as [0,0,0] (the full pose is shown as [486.080, -109.000, 432.200, 0, 0, 0]), in the "Tool Frame with respect to Reference Frame" panel.
However, the orientation of the Flange/Tool frame is clearly not aligned with the UR5 base frame, as indicated by the [0,0,0] orientation. This can be seen graphically, where the z-axis of the Flange/Tool frame is now pointing in the negative z-direction of the UR5 base frame. From this pose, if I then try to change the position coords by a tiny amount (e.g. x from 486.080 to 486.081), the robot configuration changes drastically and the Flange/Tool frame ends up aligned with the UR5 base frame.
If I copy the pose and paste it as text, the rotation part of the homogeneous matrix is not the identity, but the pose that would be expected. Therefore, I am not sure is this may be a problem with the solution, or just the conversion to angle-axis orientation. I have checked the pose for these joint angles using both URSim and the Matlab Robotics toolbox and the orientation from both these sources for these joint angles is [127.28, -127.28, 0], rather than [0,0,0]. This is also indicated by changing the values of joint 3 by small amounts (+/- 1-deg) and the orientation values are close to the expected.
The robot is not in a kinematic singularity in this pose - the Jacobian is full rank.
I have also tested this with the UR10 model and with a defined tool frame (aligned with robot flange frame), and encounter the same problems.
Could someone please advise whether this is a bug, or if I am just being a muppet and there is an obvious reason for this behavior.
Thanks for your help
However, the orientation of the Flange/Tool frame is clearly not aligned with the UR5 base frame, as indicated by the [0,0,0] orientation. This can be seen graphically, where the z-axis of the Flange/Tool frame is now pointing in the negative z-direction of the UR5 base frame. From this pose, if I then try to change the position coords by a tiny amount (e.g. x from 486.080 to 486.081), the robot configuration changes drastically and the Flange/Tool frame ends up aligned with the UR5 base frame.
If I copy the pose and paste it as text, the rotation part of the homogeneous matrix is not the identity, but the pose that would be expected. Therefore, I am not sure is this may be a problem with the solution, or just the conversion to angle-axis orientation. I have checked the pose for these joint angles using both URSim and the Matlab Robotics toolbox and the orientation from both these sources for these joint angles is [127.28, -127.28, 0], rather than [0,0,0]. This is also indicated by changing the values of joint 3 by small amounts (+/- 1-deg) and the orientation values are close to the expected.
The robot is not in a kinematic singularity in this pose - the Jacobian is full rank.
I have also tested this with the UR10 model and with a defined tool frame (aligned with robot flange frame), and encounter the same problems.
Could someone please advise whether this is a bug, or if I am just being a muppet and there is an obvious reason for this behavior.
Thanks for your help
