Development of a bio-inspired lower extremity exoskeleton with a passive-powering system

Abstract

Manual handling is an indispensable activity in any occupational setting. It is any activity that requires the use of human force for lifting, carrying or moving an object. Such repetitive and tiring tasks may cause work-related musculoskeletal disorders and adversely affect productivity of manual workers. In that context, the goal of this research was to develop a wearable device or exoskeleton for providing lift assistance during squat lifting. The outcome of the research was to reduce human effort and improve human comfort. The objectives or contributions of the work include conceptualization of a biomechanical energy management approach for squat lifting, development of an anthropomorphic passively powered multi-joint lower extremity exoskeleton for lift assistance, and investigation of the effectiveness of the proposed lift-assist system. Initially, a literature review was conducted on lower extremity exoskeletons to identify the research gap. The analysis on the state-of-the-art of exoskeletons revealed the need for introducing sustainable powering systems and minimizing interference issues at the human robot interface. Next, the biomechanical energy management approaches were conceptualized. The work includes the biomechanical modelling of squat lifting activity and the investigation of feasibility of proposed energy recycling strategies. Subsequently, design of anthropomorphic mechanical structure for the exoskeleton, design of bio-inspired passive-dynamic powering system for ankle and knee joints, and design of passive and active controlling systems were carried out. Thereafter, prototype of the ankle knee exoskeleton was fabricated as per the design specifications. Finally, performance with the proposed lift-assist system was experimentally evaluated. Results from the biomechanical analysis show that, when wearing the exoskeleton, energetic consumption at ankle and knee got reduced by 23-24% and 38-40%, respectively. The effectiveness of proposed system was also verified by evaluating muscle activities of lower and upper leg. All in all, the ankle knee exoskeleton with proposed passive actuators made a positive influence on the lower limb’s muscular system. Therefore, the proposed exoskeleton has proven to be an effective solution for industrial use. Keywords: Bio-inspired Design, Biomechanical Energy Harvesting, Lower Extremity Exoskeleton, Leg/Squat Lifting, Motion Analysis, Passive Actuator, Power Assistance, Surface Electromyography