zero coordinate point of icub && inverse kinematics

[jimingda]

The task i want to do is let the arm(hand) follow serial of positons (i.e spatial coordinate points), my problem is:

1. Where is the zero coordinate point of icub, so i can derive the desired spatial coordinate related to zero point.
2. Can i read the specific spatial coordinate of joint or terminal of icub on specific icub pose, maybe there is some api about it.
3. Are there any tutorials about this kind application, or maybe inverse kinematics are the most related one.

[pattacini]

Hi @jimingda

1. Where is the zero coordinate point of icub, so i can derive the desired spatial coordinate related to zero point.

The root reference frame is attached to the robot's waist and oriented as per https://icub-tech-iit.github.io/documentation/icub_kinematics/icub-forward-kinematics/icub-forward-kinematics.

2. Can i read the specific spatial coordinate of joint or terminal of icub on specific icub pose, maybe there is some api about it.

Sure! You can use the ICartesianInterface, whose documentation is available at https://robotology.github.io/robotology-documentation/doc/html/icub_cartesian_interface.html.

3. Are there any tutorials about this kind application, or maybe inverse kinematics are the most related one.

https://github.com/vvv-school/tutorial_cartesian-interface is a good starting point.

[jimingda]

My another question is that why spawn a PeriodicThread to implement tutorial_cartesian-interface rather than do it in the updateModule, like other applications?

[pattacini]

The class yarp::os::PeriodicThread provides a more precise timing than yarp::os::RFModule, especially when you require faster rates. You can still use the latter for background non-demanding tasks.

[pattacini]

Hi @jimingda

Did you manage to address all the points?

[jimingda]

Yes. I can address the left and right hand position, but still don't know the relation of position of finger to the hand position.
I find the discussion before https://github.com/orgs/robotology/discussions/398 . My current plan is to send position to finger joints(thumb proximal, thumb distal, index proximal, index distal, middle proximal, middle distal) until the finger tactile skin touch the target(wheel).

[pattacini]

My current plan is to send position to finger joints(thumb proximal, thumb distal, index proximal, index distal, middle proximal, middle distal) until the finger tactile skin touch the target(wheel).

I deem this to be somewhat unrelated to this particular discussion.
Please, consider marking one post as answer, if you're confident that the thread is complete.

For any other matter regarding finger control, feel free to comment on #398 or to open a fresh new discussion.