Inverse kinematics of modular manipulator robot with shoulder offset based on geometric method mixed with analytical method algorithm

In classic D-H method, coordinate system is allowed to be established on the extension of axis which results that the theoretical model is inconsistent with the actual manipulator. In this paper, a method of establishing a coordinate system based on basic coordinate transformation was adopted. Compared with the classic D-H method, this method can still be simple, intuitive, no theoretical error and fast to calculate the forward kinematics. And the calculation cost of inverse kinematics algorithm based on geometric method mixed with analytical method does not increase. For inverse kinematics, a geometric method mixed with analytical method algorithm was adopted for 6 DOF modular manipulator with offset exists on the last five joint relative to the first joint (Shoulder offset). Firstly, we use a geometric method to determine the first three joint angles, and then calculate the last three joint (wrist) angles with analytical method. This algorithm was tested by our modular manipulator WUST-ARM. Experiments proved that there was no theoretical error exists, and the running time meets the realtime control requirements of manipulator well.