Tactile-Based Assistive Method to Support Physical Therapy Routines in a Lightweight Upper-Limb Exoskeleton

Physical therapy is the pillar of rehabilitation for disabilities caused by neurological disorders, however not every patient has access to it due to the lack of human resources. Robot-based rehabilitation can contribute to the solution of this challenge with benefits such as task-oriented exercise routines. In order to increase therapy frequency and intensity, we propose the use of robot skin as multi-sensory interface to maximize the wearability and support of a lightweight elbow flexion/extension exoskeleton. The robot skin exoskeleton detects the motion intention by measuring acceleration, proximity, and interaction forces. This allows the implementation of control modes which are inspired by physical therapy such as passive movement, active support, resistance training, and corrective therapy. To assess every therapy-inspired control mode, a study analyzing force readings and sEMG recordings of the biceps during exoskeleton use was conducted with four healthy subjects to test the exoskeleton functionality. Our results show that higher assistive levels under the supportive therapy control modes result in larger reductions of normalized sEMG ( $>$ 40% in passive exercises), whereas higher resistive levels result in an increase of normalized sEMG ( $>$ 30% in resistive exercises). Thus, enabling the exoskeleton to use multi-sensory interfaces to implement therapy routines based on user intention.