Coordination Between Partial Robotic Exoskeletons and Human Gait: A Comprehensive Review on Control Strategies

Abstract

Lower-limb robotic exoskeletons have become powerful tools to assist or rehabilitate the gait of subjects with impaired walking, even when they are designed to act only partially over the locomotor system, as in the case of unilateral or single-joint exoskeletons. These partial exoskeletons require a proper method to synchronize their assistive actions and ensure correct inter-joint coordination with the user’s gait. This review analyzes the state of the art of control strategies to coordinate the assistance provided by these partial devices with the actual gait of the wearers. We have analyzed and classified the different approaches independently of the hardware implementation, describing their basis and principles. We have also reviewed the experimental validations of these devices for impaired and unimpaired walking subjects to provide the reader with a clear view of their technology readiness level. Eventually, the current state of the art and necessary future steps in the field are summarized and discussed.

Advances on mechanical designs for assistive ankle-foot orthoses

“…This coordination is crucial to avoid instabilities and maximize the benefits of wearing the active device. Mid-level controllers have been previously assessed in a general way for partial and unilateral robotic exoskeletons (Lora-Millan et al, 2022), but without focusing on ankle devices. The most common control strategy to achieve a proper coordination is based on the detection of several gait events that divide the gait into different phases.…”

Robotic exoskeleton embodiment in post-stroke hemiparetic patients: an experimental study about the integration of the assistance provided by the REFLEX knee exoskeleton

“…Their results suggested that healthy subjects are able to embody the robotic assistance, since they reduce muscular activity and, therefore, the energetic cost of walking, increasing their endurance. Most published research works about robotic assistance in hemiparetic patients after stroke are focused on achieving an autonomous and stable gait 27 . Although some authors have reported muscular adaptations, these can not be considered as signs of the device's embodiment.…”

Bioinspired Hierarchical Electronic Architecture for Robotic Locomotion Assistance: Application in Exoskeletons

“…At this level, the system can have one or more control systems, which can track walking patterns, in which each system contains the necessary kinematic chains for the global system to function correctly when interacting with the human. The mid-level control also coordinates the movement of multiple motorized joints or between multiple devices [26]. It is estimated that the speeds of the nerves in the lower limbs range between 40 and 45 m/s [23]- [25], [27].…”