AuICRA2006

AuICRA2006 - Proceedings of the 2006 IEEE International...

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An Ankle-Foot Emulation System for the Study of Human Walking Biomechanics Samuel K. Au Peter Dilworth Hugh Herr MIT Media Lab Massachusetts Institute of Technology Cambridge, MA02139, USA Email:kwau@mit.edu MIT Media Lab Massachusetts Institute of Technology Cambridge, MA02139, USA Email:chunks@media.mit.edu MIT Media Lab Harvard/MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology 20 Ames Street, Room E15-419 Cambridge, MA 021314, USA Email: hherr@media.mit.edu Abstract Although below-knee prostheses have been commercially available for some time, today’s devices are completely passive, and consequently, their mechanical properties remain fixed with walking speed and terrain. A lack of understanding of the ankle-foot biomechanics and the dynamic interaction between an amputee and a prosthesis is one of the main obstacles in the development of a biomimetic ankle-foot prosthesis. In this paper, we present a novel ankle-foot emulator system for the study of human walking biomechanics. The emulator system is comprised of a high performance, force-controllable, robotic ankle- foot worn by an amputee interfaced to a mobile computing unit secured around his waist. We show that the system is capable of mimicking normal ankle-foot walking behaviour. An initial pilot study supports the hypothesis that the emulator may provide a more natural gait than a conventional passive prosthesis. Index Terms – Below-knee prosthesis, biomechanics, force control, biomimetic, ankle-foot emulator I. INTRODUCTION Although the potential benefit of powered prostheses for both upper and lower extremity amputees has been well documented, most of the research and commercial activity has focused on active upper limb devices [1]-[4]. Today, commercially available ankle-foot prostheses are completely passive, and consequently, their mechanical properties remain fixed with walking speed and terrain [5]. Conversely, normal human ankle stiffness varies within each gait cycle and also with walking speed [6][7]. Furthermore, some studies have indicated that one of the main functions of the human ankle is to provide adequate energy for forward progression of the body [6]-[9]. Not surprisingly, below-knee amputees that use passive ankle-foot prostheses exhibit non-symmetric gait patterns and higher metabolic ambulatory rates [10]-[12]. Thus, in order to mimick the behaviour of the human ankle and to increase gait symmetry and walking economy, a prosthetic ankle-foot device should be able to actively control joint impedance, motive power, and joint position. In the development of an active ankle-foot prosthesis, the key issue is to have a thorough understanding of ankle-foot walking biomechanics. Previous experimental and theoretical studies on the behaviour of the human ankle have been limited to a qualitative understanding of the functional role of the human ankle. Although studies have pointed out the impedance characteristics of the human ankle during walking,
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AuICRA2006 - Proceedings of the 2006 IEEE International...

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