haosulab/SAPIEN

Qustion about robot.compute_spatial_twist_jacobian()

isabella4444x opened this issue · 3 comments

isabella4444x commented

Hello,
When I compute joint velocity from twist, the function robot.compute_spatial_twist_jacobian() in 0.8 version I want to use disappears now in 3.0v.
So is there similar method to get the jacobian?
Thank you a lot!!!

fbxiang commented

All functionalities related to kinematics and dynamics are now only supported through Pinocchio. You can call robot.get_pinocchio_model() to create a pinocchio model and you can refer to this file for usage.

https://github.com/haosulab/SAPIEN/blob/dev/python/py_package/wrapper/pinocchio_model.py

isabella4444x commented

Thank you!
I have used robot.create_pinocchio_model() to compute the ee link's jacobian.
And maybe the first 3dims of the jaccobian is last 3 dims of qvel, I mean the of sort of linear velocity and angular velocity is different?

fbxiang commented

I am not sure what you are trying to achieve here. The Jacobian simply maps joint velocity (in the order of qvel) to link twist (in the order of $v, \omega$). Twist is not linear and angular velocity unless the link's frame aligns with its center of mass in a very specific way.