Although the above review papers are relevant to our research
topic of lower-limb wearable robots control, they lack a systematic
analysis of the adopted assistive strategies in movement augmentation/
assistance. Generally, the exoskeleton–human interaction
is bidirectional [23]: the robot provides mechanical power and
feedbacks information to the human, and receives the intended
movement information from the user. While the former direction
is more involved in a hardware level, the latter is more linked to a
high level controller, i.e. a control layer which interprets the sensory
information and decides when and how to deliver mechanical
power to the user. The high layer controller could represent
the core intelligence of a wearable robot and is defined as assistive
strategy in this paper. The objective of this paper is to provide
a systematic review of the assistive strategies utilized by powered
lower-limb exoskeletons and orthoses and the related experimental
validation achievements.