Robots with seven degrees of freedom: Is the additional DoF worth it?

This paper presents a detailed dexterity analysis of three different kinematics, comparing six-DoF with seven-DoF robots. The KUKA LBR iiwa 7 lightweight robot represents the seven-DoF kinematics, while the KUKA KR 10 is chosen as a common six-DoF robot with comparable workspace dimensions. Furthermore, the LBR iiwa is simulated as a six-jointed robot to allow for a direct comparison of seven- and six-DoF kinematics. Due to this simulation it is possible to isolate the effects of the additional 7th DoF for the first time. The results show that the average dexterity is increased by 16.8% due to the additional 7th joint. Compared to the highest average dexterity of the seven-DoF manipulator, the six-DoF KR 10 outperforms this value by 7.6%.