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Abstract-Six-bar linkages have been used in some prosthetic knees in the past years, but only a few publications have been written on the special functions of the mechanism as used in transfemoral prosthesis. This paper investigates the advantages of the mechanism as used in the prosthetic knee from the kinematic and dynamic points of view. Computer simulation and an experimental method were used in the investigation. The results show that the six-bar mechanism, as compared to the four-bar mechanism, can be designed to better achieve the expected trajectory of the ankle joint in swing phase. Moreover, a six-bar linkage can be designed to have more instant inactive joints than a four-bar linkage, hence making the prosthetic knee more stable in the standing phase. In the dynamic analysis, the location of the moment controller was determined for minimum value of the control moment. A testing prosthetic knee mechanism with optimum designed parameters was manufactured for experiments in the laboratory. The experimental results have verified the advantage revealed in the analyses.
Key words: dynamics, kinematics, prosthetic knee, six-bar mechanism.
Abbreviations: CCD = charge-coupled device, IIJ = instant inactive joint.
This material was based on work supported by the Nature Science Fund No. 39770214 and No. 30170242 of China.
INTRODUCTION
Four-bar mechanisms have been widely used in the prosthetic knee for many years and are a subject of investigation by Zarrugh, Radcliffe, Hobson, and other scientists and researchers [1-4]. Six-bar mechanisms have been successfully used in some knee joints, such as Total Knee and 3R60 Knee produced by the Otto Bock Company; a few publications on kinematic and dynamic performance of the six-bar knee mechanism have been reported [5,6]. The general constitution of multiple-bar linkage for the prosthetic knee was outlined by Van de Veen [5], but no further investigations have been reported. Patil and Chakraborty designed a particular six-bar knee-ankle mechanism to provide coordinate motion between knee and ankle joint during walking and squatting [6].
Compared with four-bar mechanisms, six-bar mechanisms have much more design variables. Therefore, with appropriate design, six-bar mechanisms can provide advantages that are more functional. The basic concerns with kinematic and dynamic analyses of a prosthetic knee include the gait pattern (especially the trajectory of ankle joint in swing phase, which...