Modeling and Control of Knee-Ankle-Toe Active Transfemoral Prosthesis

Yawei Chen,Bokai Xuan,Sanbo Ding,Yanli Geng,Lingling Chen

doi:10.1109/access.2020.3010636

Abstract

The main joints of lower limb are hip, knee, ankle, and toe. Because of accidents or diseases, some people have to amputate. Wearing prosthesis can help them return to normal life. In the past, Active Knee joint and Active Knee-Ankle transfemoral prosthesis are studied. While in the stance phase, toe joint play an important role. In this article, the dynamic model and control method of Knee-Ankle-Toe Active Transfemoral Prosthesis are studied. The main contents are as follows: Firstly, according to the ground reaction force, the gait cycle is divided into three phases, Early and Middle Stance Phase (E&MSP), Late Stance Phase (LSP) and Swing Phase (SP), and the mechanical model of Knee-Ankle-Toe Active Transfemoral Prosthesis (KATATP) is established. Secondly, consider the cooperative movement of amputee and prosthesis, the kinematics model of prosthesis is established by Lie Groups and Lie Algebras, and the dynamic model of prosthesis is established by Lagrange equation. Thirdly, the whole gait cycle is a complete system and each phase is a different subsystem, switching rules and controllers of different subsystems are designed. Finally, experiments show that KATAP with the switching control enables amputee to have a biomechanically appropriate walking gait and achieve smooth transition between different gait phases.

Highlights

Traditional transfemoral prostheses consist of a passive knee and ankle joint, which can provide some support for amputees
Chen et al.: Modeling and Control of Knee-Ankle-Toe Active Transfemoral Prosthesis signals of hip displacement, thigh angle are applied to the robot, and the sliding mode controller can track the position of the hip joint
We propose a method to describe the forward kinematics of prosthesis by using Lie group and Lie algebra, and establishes a mathematical model of transfemoral prosthesis by combining Lagrange equation

Summary

INTRODUCTION

Traditional transfemoral prostheses consist of a passive knee and ankle joint, which can provide some support for amputees. Y. Chen et al.: Modeling and Control of Knee-Ankle-Toe Active Transfemoral Prosthesis signals of hip displacement, thigh angle are applied to the robot, and the sliding mode controller can track the position of the hip joint. Transfemoral prostheses have knee and ankle joints, ignoring the effect of the toe joint on gait during walking [10]–[12]. In the experimental stage, researchers at Peking University designed and constructed a powered transtibial prosthesis with stiffness adaptable ankle and toe joints, which are driven by adapted series-elastic actuators, to improve the walking performance of the amputees [16], [17]. We propose a method to describe the forward kinematics of prosthesis by using Lie group and Lie algebra, and establishes a mathematical model of transfemoral prosthesis by combining Lagrange equation.

MODELING OF TRANSFEMORAL PROSTHESIS

LATER STANCE PHASE MODEL

STABILITY OF SWITCHING SYSTEMS

SUBSYSTEM CONTROLLER

EXPERIMENTAL ANALYSIS

CONCLUSION