Design and evaluation of a hybrid passive–active knee prosthesis on energy consumption

Xiaoming Wang,Zhewen Zhang,Qiaoling Meng,Hongliu Yu,Jie Yang,Jinyue Sun

doi:10.5194/ms-11-425-2020

Abstract

Abstract. The existing lower limb prostheses with passive knees have disadvantages, causing an asymmetric gait and higher metabolic cost during level walking which is in contrast with a normal gait. However, most existing active knee prostheses need a significant amount of energy. In this paper, a novel hybrid passive–active knee prosthesis (HPAK) that allows passive and active operating modes is proposed, which contains an active motor unit and a novel hydraulic damper with an electrically controlled valve that adjusts the damping torque dynamically during each gait cycle. An energy consumption model was built to evaluate the energy consumption when walking on level ground in three different simulation conditions to, respectively, simulate the complete HPAK, an ordinary active prosthesis (AKP) and an ordinary passive prosthesis (PKP). The results show that, in a cycle, the HPAK consumes only 16.19 J, which is 3.6 times lower than the AKP (58.95 J), and the PKP consumes only 1.24 J due to the novel spring–hydraulic damper structure designed and presented in this paper. These results indicate that the proposed novel hybrid passive–active knee prosthesis can have a positive effect on reducing energy consumption and improving the approximation of healthy gait characteristics when walking on level ground, contrasting with active or passive knee prostheses.

Highlights

Every year, thousands of people around the world lose their lower limbs because of circulatory and vascular problems, complications associated with diabetes or cancer and trauma
This paper presented the design of a hybrid passive–active knee prosthesis (HPAK) that can provide driving and damping torque
The energy consumptions of the HPAK under three different simulation conditions were evaluated by computer simulation, namely (a) the complete HPAK operating, (b) only the active motor unit operating and simulating an active knee prosthesis (AKP) and (c) only the hydraulic damper operating and simulating a passive knee prosthesis (PKP)

Summary

Introduction

Thousands of people around the world lose their lower limbs because of circulatory and vascular problems, complications associated with diabetes or cancer and trauma. X. Wang et al.: Design and evaluation of a hybrid knee prosthesis passive prostheses cannot support activities requiring positive energy, such as climbing stairs and slopes or standing up from the seated position, leading to high metabolic energy consumption and an asymmetrical gait (Price et al, 2019; Cao et al, 2018b). Novel designs are required to lower the energy consumption of active prostheses while still allowing wearers to complete a wider variety of activities than traditional passive prostheses (Andrade et al, 2019). The energy consumption was evaluated under three different conditions, namely the complete HPAK operating, just the active motor unit operating, simulating a hypothetical active knee prosthesis (AKP), and only the hydraulic damper operating, simulating a hypothetical passive knee prosthesis (PKP)

HPAK principle and design schematic

Mechatronic structure design

Energy consumption modeling

Results and discussion

Conclusions