An integrated inverse kinematic approach for the 7-DOF humanoid arm with offset wrist

The paper proposes an integrated approach to solve the inverse kinematics of the 7-DOF humanoid arm with offset wrist. Firstly, according to the arm's configuration, the closed-form solutions of inverse kinematics for 7-DOFs arms are developed based on the reverse coordinates method. Secondly, an integrated inverse kinematic approach, termed the modified gradient projection method, is proposed on the condition of closed form solutions and the gradient projection method. Thirdly, thanks to the arm's redundancy, multiple objectives optimization including avoidance of singularity, joint limits and joint velocity limits are completed during motions. And finally, the validity of the closed form solutions and the integrated approach is verified by kinematic simulations, and the integrated approach provides better precision and optimization during trajectory tracking.