Powered Hip Exoskeletons Can Reduce the User's Hip and Ankle Muscle Activations During Walking

• Published in: IEEE transactions on neural systems and rehabilitation engineering Vol. 21; no. 6; pp. 938 - 948
• Main Authors: Lenzi, Tommaso, Carrozza, Maria Chiara, Agrawal, Sunil K.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.11.2013; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Activation; Adaptation, Physiological - physiology; Ankle Joint; Assistive and rehabilitation robotics; bio mechanics; Electric Power Supplies; Energy Metabolism - physiology; Equipment Design; Equipment Failure Analysis; Exoskeletons; gait; Hip; Hip Joint; human-robot interaction; Humans; Joints; Legged locomotion; Muscle Contraction - physiology; Muscle, Skeletal - physiology; Muscles; Orthotic Devices; Physical Exertion - physiology; powered exoskeletons; Reference Values; Rehabilitation; Robotics - instrumentation; Strategy; Therapy, Computer-Assisted - instrumentation; Therapy, Computer-Assisted - methods; Torque; Treatment Outcome; Walking; Walking - physiology; Winter
• ISSN: 1534-4320; 1558-0210; 1558-0210
• DOI: 10.1109/TNSRE.2013.2248749

In this paper, we study the human locomotor adaptation to the action of a powered exoskeleton providing assistive torque at the user's hip during walking. To this end, we propose a controller that provides the user's hip with a fraction of the nominal torque profile, adapted to the specific gait features of the user from Winter's reference data . The assistive controller has been implemented on the ALEX II exoskeleton and tested on ten healthy subjects. Experimental results show that when assisted by the exoskeleton, users can reduce the muscle effort compared to free walking. Despite providing assistance only to the hip joint, both hip and ankle muscles significantly reduced their activation, indicating a clear tradeoff between hip and ankle strategy to propel walking.