Controllability and accessibility of vibrations in multiple planes on link-elastic robot arms

Research on link-elasticities offers the perspective to devise lightweight robots with intrinsic safety benefits for physical human-robot interaction and fast motions with reduced energy consumption. Moreover, their force/torque sensing capabilities mimic the functionalities of animalistic whiskers, putting the robot in a position to react gently to its environment. While many works consider single elastic links or planar settings, the present work addresses the controllability problem for link-elastic robots with multiple vibration planes. The paper introduces the reader to the modal controllability and accessibility problem emerging in such systems, and proposes a novel geometric controllability index with reduced complexity. The proposed index is compared and analysed with respect to existing indexes from literature in preparation for adaptive vibration control schemes.