Cartesian control

[vopsi99]

Hello, I tried using this repository but my knowledge in ros is rather mediocre. I am curious if this stack has cartesian control implementation or not.

It may be a stupid question, but I am stuck for quite some time and I could really use some help..

[mhubii]

no worries @vopsi99 and thank you for raising this issue. In principle yes, in practise users have to put in some effort to do this right now. I can pinpoint you to some examples and try to improve the demos.

What are you trying to achieve:

• Move to an absolute pose?
• Specify an end-effector velocity?

[vopsi99]

I managed to move the end-effector incrementally but it is really unstable, so I need to move to an absolute pose with a certain velocity. I supposed this kind of motion would be the best to further integrate a stereo camera to position the robot in correlation to some markers in the workspace.

[mhubii]

so there is a demo here: https://lbr-stack.readthedocs.io/en/latest/lbr_fri_ros2_stack/lbr_demos/lbr_demos_advanced_cpp/doc/lbr_demos_advanced_cpp.html#pose-controller

You'd have to add a node that sends your desired pose. This can be done in Python, similar to this e.g. https://github.com/lbr-stack/lbr_fri_ros2_stack/blob/humble/lbr_demos/lbr_demos_advanced_cpp/src/pose_planning_node.cpp

[vopsi99]

So I should only send from another node my desired pose to this demo? This is the demo that I modified to send incremental values for x,y,z on position and orientation, but on Y orientation, for example, it always went crazy even if I was doing really small movement increments.

[mhubii]

okay I'll have to double check this demo, as it was community contributed. But this demo sends an absolute pose.

You will have to make sure you:

• Get the initial pose
• Send a small (like really small) increment on top of the initial pose

[mhubii]

I think this demo needs an update and should really allow users to control a velocity rather than absolute poses maybe

[vopsi99]

Yes, I realised that a really small increment (0.001) would make the movement smoother.For positioning on x,y and z everything seems fine, but when I am trying to orient it, it just breaks everything.

After sending the increment on Y for longer it tends to jump into a position and i get the inverse kinematics failed error.

I think velocity control would be really useful for everyone.

[mhubii]

thank you for the feedback. Let's add support for this then.