Lower Limb Exoskeleton Gait Planning Based on Crutch and Human-Machine Foot Combined Center of Pressure

Abstract

With the help of wearable robotics, the lower limb exoskeleton becomes a promising solution for spinal cord injury (SCI) patients to recover lower body locomotion ability. However, fewer exoskeleton gait planning methods can meet the needs of patient in real time, e.g., stride length or step width, etc., which may lead to human-machine incoordination, limit comfort, and increase the risk of falling. This work presents a human-exoskeleton-crutch system with the center of pressure (CoP)-based gait planning method to enable the balance control during the exoskeleton-assisted walking with crutches. The CoP generated by crutches and human-machine feet makes it possible to obtain the overall stability conditions of the system in the process of exoskeleton-assisted quasi-static walking, and therefore, to determine the next stride length and ensure the balance of the next step. Thus, the exoskeleton gait is planned with the guidance of stride length. It is worth emphasizing that the nominal reference gait is adopted as a reference to ensure that the trajectory of the swing ankle mimics the reference one well. This gait planning method enables the patient to adaptively interact with the exoskeleton gait. The online gait planning walking tests with five healthy volunteers proved the method’s feasibility. Experimental results indicate that the algorithm can deal with the sensed signals and plan the landing point of the swing leg to ensure balanced and smooth walking. The results suggest that the method is an effective means to improve human–machine interaction. Additionally, it is meaningful for the further training of independent walking stability control in exoskeletons for SCI patients with less assistance of crutches.

Wearable Movement Sensors for Rehabilitation: From Technology to Clinical Practice

“…Yang et al (2020) [ 1 ] developed an online gait-planning algorithm based on sensing signals to enable balance control during exo-skeleton assisted walking with crutches in spinal cord patients. Results from this pilot study in healthy adults indicate that the developed online gait-planning algorithm can plan the landing point of the swing leg to improve balance control during exo-skeleton assisted walking.…”

Current developments of robotic hip exoskeleton toward sensing, decision, and actuation: A review

“…Thus the continuous walking gaits can be divided into repeated gait cycles. Force sensors can also be applied to measure plantar force distributions (Yang et al, 2020 ) and calculate the stability margin of the human–machine system during walking. In this application, several FSR sensors are distributed in the shoes.…”

“…Medical type exoskeleton is used for patients with upper (Yan and Yang, 2014 ; Chen et al, 2019 ; Gandolla et al, 2021 ) or lower body disabilities (Yang et al, 2016 ; Hwang et al, 2021 ; Zhu et al, 2021 ). With this kind of exoskeleton, some patients can regain the ability of locomotion (Farris et al, 2014 ), while some other patients can achieve therapeutic movement and speed up rehabilitation progress (Wang et al, 2019 ; Yang et al, 2020 ). Nowadays, the nonmedical type exoskeleton is widely researched for its potential in both industries (Chang et al, 2020 ; Iranzo et al, 2020 ; Lazzaroni et al, 2020 ) and the military (Hong et al, 2019 ).…”

Adaptive Gait Generation Using Dynamic Movement Primitives with Multimodal Sensors for Assistive Lower-limb Exoskeletons

“…This typically involves advanced motion planning methods that regulate the exoskeleton trajectories. Examples include a gait planning method based on ground reaction force sensor for stable adjustment of stride length [8], and a method integrating finite-state machines and surface electromyography (EMG) signals for gait adaptation [9]. Other approaches include using the extrapolated center of mass for This work was supported by Frode V.Nyegaards and Wife's fund for the ALEXO project.…”