Robust inverse kinematics by configuration control for redundant manipulators with seven DoF

This paper presents an optimized, robust inverse kinematics solution in a closed form for redundant manipulators with seven degrees of freedom and zero link offsets like the KUKA LBR iiwa lightweight robot. The computation allows for full range elbow self-motion manifold control, defined by an intuitive angle parameter. Furthermore, by using common configuration parameters, all possible solutions for a single effector pose are taken into account and full arm configuration control is realized. The algorithm was evaluated looking at configuration reliability and continuity for an exemplary, challenging path. The results show that commanded arm configurations are not changing spontaneously inside a trajectory. Even for varying elbow self-motion manifold angles, the joint trajectories stay continuous and the presented algorithm provides consistent solutions. In a second evaluation, the algorithm was implemented in three programming languages and analyzed with respect to computing times. The tests demonstrate short runtimes and overall real-time capability.