# Inverse Kinematics of DLR/HIT II Hand

I am trying to find the inverse kinematics formulation of DLR/HIT II hand. Till now I had success in finding an analytical method described in the thesis of Mavrogiannis, Christoforos I. named Grasp Synthesis Algorithms for Multifingered Robot Hands, given in appendix B. My question is regarding the A.28 where the author calculates q3 but has mentioned previously in the text that q3 is equal to q2.

Note: q here denotes joint angles

• I cannot read that reference, but setting the two distal joints of the finger to equal angles is one of the typical ways to emulate basic human finger motion. It does not always hold true (we can use that joint redundancy to our advantage - just watch a guitar player!), but often does. See, for example, this paper: cdn.intechopen.com/pdfs-wm/46559.pdf Jan 16 '16 at 20:17
• Thanks for your comment SteveO. In the text, it is given that each of the 5 finger has 4 joints[ q0,q1,q2,q3 ] and 3 degrees of freedom. q0 associated with abduction-adduction, q1 and q2 for flexion and q3 being equal to q2. My question was regarding the IK formulation where the author has calculated q1, q2 and q3 leaving q0, which is the source of my confusion. Jan 17 '16 at 7:59
• You're welcome. It has been over twenty years since I solved some stable grasp problems with the redundant hand, so there may be better approaches now. I had to throw the equations into a Simplex algorithm to give the least-squares optimized solution to the redundancy. Not sure if that helps or not. Jan 18 '16 at 3:20
• i am trying to solve the same problem. Hope you have been successful in finding the inverse kinematics. I have a question which i hope you can clarify. In the thesis document, what are the variable l1,l2 used in (A.5) for finding the inverse kinematics in appendix B. It has not been stated anywhere. Thank you in advance.
– user13617
May 5 '16 at 15:43
• l1 and l2 are link lengths. Their values are l1= 55mm and l2= 25 mm. Hope this helps. May 7 '16 at 10:13