Inverse kinematics of a class of 7R 6-DOF robots with non-spherical wrist

7R 6-DOF robots with non-spherical wrist are suitable for applications such as painting tasks. The inverse kinematics of this class of robots have not been investigated. This paper proposes a method of solving the inverse kinematics of 7R 6-DOF robots with non-spherical wrist. An analytical solution is first derived for the 7R 6-DOF robots with spherical wrist. By introducing a virtual wrist center, this solution can also be applied to robots with non-spherical wrist, and employed as an initial point for further algorithms. Based on the product of exponentials (POE) formula, an iterative algorithm is presented for the exact inverse kinematics solution using the Levenberg-Marquardt (LM) method. A simulation is performed to evaluate the effectiveness of the proposed method, showing its advantages in accuracy and efficiency.