Can I get the Jacobian of a frame not defined in the URDF

[lwygzh]

Hi,

I have been using pinocchio to compute the Jacobians of the joints and frames of the robot that are defined in its URDF.

I was wondering if it is possible to compute Jacobians that are not defined in the URDF, but has a fixed transformation with respect to one of the frames that are defined in the URDF.

Thanks!

[matheecs]

You can add a user defined frame by addFrame().

[lwygzh]

@matheecs I see, seems like a good solution!

Do you know if there is a way to remove this user-added frame when it is no longer in use?

[matheecs]

I think there is no method of API to remove the frame. Extra frames may not influence performance, so it is not necessary to remove them.

[jorisv]

Like say @matheecs there is no method to remove the frame.

If you don't want to compute the frame configuration anymore, a solution is to copy the model before calling addFrame and then, use the old model when you don't need the frame anymore.

[lwygzh]

@jorisv @matheecs Thanks for the response!

I noticed one issue with the addFrame function. It does update the robot.model with the new frame, but I don't think it updates robot.data, so I can't even call robot.data.oMf with the new frame id. Do you know how to solve that?

[lwygzh]

I figured it out, just need to run

robot.data = robot.model.createData()

and then update the pinocchio model with the joint angles and velocities.