Control of redundant robot arms with null-space compliance and singularity-free orientation representation

This paper tackles the problem of controlling the position and orientation, expressed in a singularity-free representation form, of the end-effector of a redundant robot, while addressing an active compliant behaviour within the null-space. The manuscript extends the work in Sadeghian et al. (2014) by explicitly addressing the orientation part. In order to successfully accomplish the task, a dynamic controller is designed without need of any exteroceptive sensors information. A rigorous stability analysis is provided to confirm the developed theory. Experiments are finally carried out to bolster the performance of the proposed approach.