Inverse kinematics resolution method of redundant space manipulator based on arm angle parameterization

Aiming at a class of redundant space manipulator which has link offsets at the shoulder, elbow, and wrist parts, a method based on arm angle parameterization is proposed to solve its inverse kinematics problem analytically. Firstly, a zeros-offset Spherical Shoulder-Spherical Wrist redundant manipulator SRS (Spherical-Revolution-Spherical) is created corresponding to the manipulator with link offsets. Then the relative relationship between the zero-offset and non-zero-offset manipulators is derived. Secondly, the arm angle is defined to describe the redundancy of the SRS manipulator. Then each joint angle is solved as the functions of arm angle, i.e. the inverse kinematics equation is resolved for a given parameter. Finally, the inverse kinematics resolution of the redundant manipulator with offsets is determined according to the configuration relationship between it and the SRS manipulator. For a given arm angle, there are eight sets of solutions. Compared with previous methods, the geometry meaning of the arm angle parameterization method is more intuitive and more appropriate for the configure control. Especially, some special requirements such as collision avoidance can be realized by adjusting the arm angle.