<<PackageHeader(sr_kinematics)>> <<TOC(4)>>

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## CategoryPackage
== Overview ==
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 ==

=== Approximation ===
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. 

 . {{attachment:finger_approximation.png||height="336px",width="393px"}}

=== Limits ===

 * 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.

== ROS API ==
=== Services ===
The node proposes the same services and parameters as the [[arm_kinematics]]

NOTE that '''epsilon''' parameter is used to detect singularities for J4 joint.