Reference Point of Jacobian

[DimitriEckert137]

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When I use the ChainJntToJacSolver for calculating the jacobian of a robot Arm, which point is taken as the "endeffector"? Or more precisely: I have a robotic arm with lets say 9 links and 8 joints. I want to calculate the jacobian for the point where the last joint (the one between link 8 and link 9) lies. So I would have done it like this: parse with ur_tree.getChain(firstLink, eigthLink) then use the JntToJac function from ChainJntToJacSolver. To the resulting Jacobian I apply the changeRefPoint function with the vector from the 7th joint to the 8th joint (in the frame of the 8th link). Is this the correct way?

I only need the dynamics of the robot up to the 8th link (without the 9th link), otherwise I guess I could also parse the whole robot take the jacobian without changing the refpoint and the result would be the same, with the difference of having the whole robot parsed. Right?

I am using ros melodic and kdl 1.4.0.