Investigations on the Effects of a Passive Standing-from-Squatting and Gait Assistive Exoskeleton on Human Motion

Abstract

The aim of this study is to examine the biomechanical interaction between an assistive wearable exoskeleton and the human body. For this purpose, a passive exoskeleton is designed to provide support during the transition from a squatting position to standing, while also enabling the resilient components to become active during the initial and mid-swing phases of level walking. The active period can be adjusted by a slot, which triggers the activation of the resilient components when the exoskeleton's flexion angle exceeds a critical value. This study also compares the effect of using different passive powered components in the exoskeleton. Electromyography (EMG) signals and angular velocity during human motion are collected and analyzed. Experimental results indicate that the designed assistive exoskeleton effectively reduces muscle effort during squatting/standing motion, as intended. The exoskeleton reduces the flexion/extension (x-axis) angular velocity during both squatting/standing and the swing phase of gait. The oscillation of the angular velocity curve about the y-axis during gait is larger without the exoskeleton, suggesting that the exoskeleton may introduce interference but also a stabilizing effect in certain dimensions during gait. This study provides a stronger foundation for advancing the design of both passive and active powered exoskeletons.

Keywords: electromyography; exoskeleton; gait analysis; squatting.

Figure 1

The physical model of the exoskeleton (a) The subject wears the exoskeleton (b) The exoskeleton with helical compression spring (c) The exoskeleton with hydraulic cylinder rod (d) The exoskeleton with torsion spring. The red circles in (b–d) indicate the position of the slot.

Figure 2

The designed slot on (a) a hydraulic cylinder rod and helical compression spring, and (b) a torsion spring. The red circle in (b) indicates the position where the torsion spring contacts the end of the slot.

Figure 3

The positions of the exoskeleton at various angles. The figure divides the knee movement from extension to flexion and back to extension into ten steps, as indicated by the numbers 1–10. The circles in each step highlight the exposed length of the resilient component extending from the covering tube. This exposed segment visually represents the compression state of the resilient component. Blue circles indicate the component is in an uncompressed state, while red circles indicate that it is compressed.

Figure 4

Normalized EMG signal during the squatting/standing motion.

Figure 5

Normalized Euclidean distances between EMG curves (a) during squatting/standing, (b) during gait.

Figure 6

Normalized EMG signal during gait.

Figure 7

Angular velocity during the squatting/standing motion at different sensor positions. (a) Rectus femoris, (b) Biceps femoris, (c) Tibialis anterior, (d) Gastrocnemius.

Figure 8

Normalized Euclidean distances between angular velocity curves (a) during squatting/standing, (b) during gait.

Figure 9

Angular velocity during gait at different sensor positions. (a) Rectus femoris, (b) Biceps femoris, (c) Tibialis anterior, (d) Gastrocnemius.

Figure 9

Angular velocity during gait at different sensor positions. (a) Rectus femoris, (b) Biceps femoris, (c) Tibialis anterior, (d) Gastrocnemius.