Development and Characterization of a Modular Soft Actuator Enabled Elbow Exoskeleton for Assistive Movements

Exoskeletons are poised to provide motion assistance to aid in rehabilitation and compensate for muscle weaknesses, augment human performance, and reduce repetitive stress injuries in healthcare, industry, and occupation settings, respectively. Soft actuator enabled systems are gaining widespread attention due to their mechanical simplicity, low weight, and compliance to the human body. Regardless of promises shown, the progress for these systems is slow due to a wide variety of actuator types and geometries, which complicate designs and model predictive performance to create application-specific systems. Learning from conventional hard robotic actuator approaches, this paper investigates a modular actuator concept that can be used for creating many exoskeletons and is easily customized for fitting different sized humans, joint types, and application scenarios. The preliminary investigation details the development of an elbow exoskeleton by implementing a modular corrugated diaphragm actuator arranged in a serial configuration. Numerical simulation and experimental evaluations were carried out to investigate the torque, load-bearing, and motion characteristics of the exoskeleton. Results confirmed the viability of the concept by showing that the exoskeleton can provide assistive motion to a forearm and hand of average weight. Additionally, the exoskeleton is able to apply continuous passive motion to an elbow joint, which can be used in rehabilitation settings.