Inverse kinematics for a 7-DOF humanoid robotic arm with joint limit and end pose coupling

A 7 degrees-of-freedom (DOF) humanoid robotic arm is proposed based on the comfort and affinity of human-robot interaction. For the characteristics of the robotic arm with end pose coupling, an integrated approach based on the analytical and reverse order methods is proposed to obtain the closed-form solution of the robotic arm at the position level. The coordinate system establishment method and mapping relationship of the Denavit-Hartenberg (D-H) parameters at positive and reverse order robotic arms are deduced. Subsequently, the analytical solution of the reverse order robotic arm is derived based on the parametrization method, and the feasible range of the arm angle is obtained using the joint limits. Additionally, the novel global arm angle optimization algorithm is proposed to simplify calculation in the intelligent algorithm, and the relationship between the optimization factors and global arm angle is analyzed. Finally, the validity of the methods is verified by the kinematics simulation based on the Robot Operating System (ROS). The simulation results demonstrate that the proposed integrated approach and global arm angle optimization algorithm can effectively solve the closed-form solution of the robotic arm. © 2021 Elsevier Ltd