Development and clinical feasibility of a novel pediatric arm rehabilitation robot

Children with congenital or acquired neurological disorders often have impairments of their arms. This includes children suffering from cerebral palsy, stroke, spinal cord injury or other neurological disorders. The impairment often hampers the child’s independence and participation in daily life. An intensive, activity-based and goal-directed upper limb rehabilitation training is essential for improvement and recovery of motor function and can prevent deterioration of arm function in children with moderate to severe impairments. In adult patients with motor or neurological disorders, such as stroke or spinal cord injury, active robotic assistance is increasingly used to achieve an intensive therapy and to actively assist and enhance neurorehabilitation. Furthermore, therapy robots have the potential for accurate assessment of motor function to diagnose the patient status, to measure the therapy progress, or to feed back the movement performance to the patient and therapist in real time. However, there is currently no actuated robot available specifically designed for the rehabilitation of children with upper extremity motor impairments. In this thesis the development, realization and clinical implementation of ChARMin, the first actuated exoskeleton robot for pediatric arm rehabilitation, is presented. The thesis was performed at the Sensory-Motor Systems Lab, ETH Zurich, Switzerland in collaboration with the Rehabilitation Center for Children and Adolescents, Affoltern a. A. , Switzerland and is divided into four main parts. In the first part of the thesis, the ChARMin robot is presented. The robot was specifically designed to provide an intensive and motivating neurorehabilitative training for children with affected arm motor function, e.g., with cerebral palsy. It combines parallel and serial kinematics to achieve an exoskeleton with six degrees of freedom to assist and assess the shoulder, elbow, and wrist of the pediatric target group. A modular design of the robot enables the application to children aged 5 to 18 years. The parallel structure allows to keep a safe distance between parts of the robot and the patient and it reduces friction. The whole exoskeleton is highly adaptable to cover the anthropometrics for the young patients and is applicable for the left and right arm. A novel passive weight support mechanism allows for a safe operation. Furthermore, a new audiovisual therapy interface was introduced for ChARMin to motivate active participation of the child with playful game-like scenarios. The second part introduces the control approaches implemented to support the patient’s arm with the exoskeleton. Different patient-cooperative control strategies enable free arm movements, assistance as needed and complete guidance of the arm. The controllers are chosen based on the game played and the skill level of the patient. An assist-as-needed path control concept is utilized to support complex multi-axis movements on end-effector basis. For specific single-axis training an adjustable joint-based controller is used. All the controllers include a model to compensate for inertial, gravitational and frictional aspects of the robot and a dithering approach to reduce static