Comparing Physical Human-Robot Interaction with Spring-and Elastomer-Based Series Elastic Actuators

Physical human-robot interaction (pHRI) is an important consideration in the design of rehabilitation exoskeletons. Series Elastic Actuators (SEAs) are seen as a promising method of introducing compliance and comfort to robotic exoskeletons. Recently, authors have proposed the use of elastomers in SEAs, rather than springs, but there is a dearth of literature comparing how the two compliant elements are perceived by humans. In this paper, we quantitatively and qualitatively compare human interaction with an elastomer and a spring in terms of comfort and motion smoothness, with the aim of informing future SEA design. Two mechanisms were designed to compare human interaction with a spring and elastomer, and a cross-over experimental design was used to help eliminate any learning effects. Overall, the elastomer appeared to be slightly more comfortable and allow slightly smoother motion than the spring, holding promise for the use of elastomers as a means of improving pHRI in exoskeletons actuated by SEAs.