Abstract
Series elastic actuators are increasingly adopted in wearable robots with their superior sensing and actuating capabilities owing to the added internal compliance. However, when evaluating their performance, typically in benchtop setups, external compliance, i.e. dynamics of physical interface with humans, is usually overlooked. The assumption of infinitely rigid interfaces is a major simplification since human soft tissue that wearable robots connect to introduces energy dissipation and delays in power transmission, among others. To close the existing gap, this work emulated in a test bench physical human-robot interaction dynamics and experimentally validated actuator output against commonly used performance indices, including torque bandwidth, torque tracking, and transparency. The results show that load side dynamics significantly impact the actuator performance, canceling known benefits of actuator compliance and having different effects across emulated joints (hip and knee). As such, this work provides evidence for including interaction dynamics as a norm in designing and evaluating actuation units in wearable robots.
