sr_kinematics currently contains a specific analytical inverse kinematics for the shadow_robot hand. Currently, only the 4 fingers have an IK solution, the thumb will come later. The solution takes care of the coupled joint J1/J2 (assuming it is 1:1) and accepts 3D requests (instead of 6D). There is an approximation in this solution.
Detail of the solution
The developed IK uses an approximation of the fingertip center to create a virtually simplified 2 links (3 dof) kinematic chain. The method considers the isoceles triangle formed by the coupled joint to solve the inverse kinematics.
- Because the finger chain (J4+J3+J1/J2) provides only 3 dof, the request only takes the position of the finger tip into account (no requested orientation can be reached).
- The Little finger joint 5 (inside the palm) is not considered either.
- IK for the thumb is not solved by the current version.
The node proposes the same services and parameters as the arm_kinematics
NOTE that epsilon parameter is used to detect singularities for J4 joint.