Wearable and grounded supernumerary robotic limbs for sensorimotor augmentation in post-stroke patients

The aim of this work is to redefine the concept of sensorimotor augmentation, extending it from wearable devices to supernumerary robotic upper limbs that are grounded and can be placed out of the physiological peripersonal space of the user. While the wearability of the supernumerary robotic limb (SRL) is not mandatory, the human-robot connection must be maintained through a wearable interface that allows the user to naturally command and receive sensory feedback from the SRL. In this way, users can keep the robot under their control, without adding unnecessary extra weight on their body. As a result, the application of SRLs in assistive contexts is facilitated, as even people with severe paresis who might not be able to withstand the burden of a wearable robotic arm, can be augmented by grounded SRLs. Focusing on upper-limb assistive augmentation, this paper introduces another fundamental novelty: the exploitation of augmentative technologies as motivational tools for re-using the impaired upper limb in chronic paretic patients. To this aim, a new user-centered procedure for extracting a control signal from a residual motion of a patient’s upper limb is proposed and tested in scenarios where the impaired limb takes part in the manipulation task by controlling the SRL. Extensive pilot tests with two post-stroke patients show the intuitiveness and usability of the proposed approach.