Active-Passive Exoskeletons for Assistive and Resistive Interventions in Human Walking

Exoskeletons are developed to assist or resist human movements for augmentation and rehabilitation. In the former application, the devices share and redistribute the applied loads to reduce the natural biomechanical efforts, while in the latter, they intervene with the pathological gaits to restore normalcy. Enhancing the wearer’s experience for device acceptance and favorable functional outcomes is paramount in both cases. Hence, the primary focus of this chapter is to provide a perspective on the challenges pertinent to improving human-robot interactions when the device is operated actively or passively. The critical factors considered are the device’s transparency, i.e., its proficiency in not hindering the natural course of movements, and its efficacy in delivering the desired intervention at relevant gait phases. It is then followed by elucidating the possibility of overcoming some of these challenges with a hybrid (active-passive) paradigm and the associated limitations. These recommendations are finally supported by two case studies for resistive and assistive interventions in human walking, respectively, performed using an active portable device, “Wearable Adaptive Rehabilitation Suit (WeARS),” and a hybrid stationary device, “Ankle Exoskeleton with Treadmill Actuation for Push-Off Assistance (AN-EXTRA-PUSH).” In retrospect, this chapter also provides a comprehensive understanding of the preferred features of an ideal exoskeleton, choosing an appropriate rationale for effective intervention and design guidelines for the future.