Open AccessMechanical Efficiency Investigation of an Ankle-Assisted Robot for Human Walking With a Backpack-Load
Author(s) -
Longhan Xie,
Zhihou Wang,
Guowei Huang,
Biao Liu,
Zikang Zhou
Publication year - 2021
Publication title -
journal of biomechanical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.546
H-Index - 126
eISSN - 1528-8951
pISSN - 0148-0731
DOI - 10.1115/1.4051434
Subject(s) - backpack , ankle , work (physics) , kinematics , robot , gait , weight bearing , simulation , mechanical energy , computer science , force platform , control theory (sociology) , power (physics) , physical medicine and rehabilitation , engineering , structural engineering , physics , mechanical engineering , medicine , anatomy , artificial intelligence , surgery , control (management) , classical mechanics , quantum mechanics
The purpose of this work is to investigate the efficiency of wearable assistive devices under different load-carriage walking. We designed an experimental platform with a lightweight ankle-assisted robot. Eight subjects were tested in three experimental conditions: free walk with load (FWL), power-off with load (POFL), and power-on with load for different levels of force at a walking speed of 3.6 km/h. We recorded the metabolic expenditure and kinematics of the subjects under three levels of load-carried (10%, 20%, and 30% of body mass). We define the critical force, where at a certain load, the robot inputs a certain force to the human body, and with the assistance of this force, the positive effect of the robot on the human body exactly compensates for the negative effect. The critical forces from the fit of the assistive force and metabolic cost curves were 130 N, 160 N, and 215 N at three different load levels. The intrinsic weight of our device increases mechanical work at the ankle as the load weight rises with 2.08 J, 2.43 J, and 2.73 J for one leg during a gait cycle. With weight bearing increasing, the ratio of the mechanical work input by the robot to the mechanical work output by the weight of the device decreases (from 0.904 to 0.717 and 0.513), verifying that the walking assistance efficiency of such devices decreases as the weight rises.