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jrl-umi3218 / RBDyn

RBDyn provides a set of classes and functions to model the dynamics of rigid body systems.
BSD 2-Clause "Simplified" License
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Questions about Jacobian: do we get the analytical Jacobian by default in RBDyn #84

Closed ghost closed 3 years ago

ghost commented 3 years ago

Hi all,

As stated in the title, I just want to make sure I will get the analytical Jacobian from the RBDyn, not the geometric Jacobian.

Assume the pose of the robot is given by $P = [x,y,z,r,p,y]^{T}$ (where r,p,y are Euler angles), is the Jacobian we get from RBDyn the same as: \partial{P}/\partial{t} (t is time?).

Many thanks in advance.

gergondet commented 3 years ago

Hi @Thompson104

If I understand the distinction correctly, the analytical jacobian such that whereas the geometric jacobian is such that where is the spatial velocity of point P in the world frame.

Then, in fact RBDyn computes the geometric jacobian and not the analytical jacobian. I hope this answers your question adequately.

Note: RBDyn convention is to put rotation first so in those formulas has the angular velocity first and the linear velocity second.

ghost commented 3 years ago

Thank you @gergondet . It really helped.