Recent advancements in powered lower limb prostheses have appeased several difficulties faced by lower limb amputees by using a series-elastic actuator (SEA) to provide powered sagittal plane flexion. Unfortunately, these devices are currently unable to provide both powered sagittal plane flexion and two degrees of freedom (2-DOF) at the ankle, removing the ankle’s capacity to invert/evert, thus severely limiting terrain adaption capabilities and user comfort. The developed 2-DOF ankle system in this paper allows both powered flexion in the sagittal plane and passive rotation in the frontal plane; an SEA emulates the biomechanics of the gastrocnemius and Achilles tendon for flexion while a novel universal-joint system provides the 2-DOF. Several studies were undertaken to thoroughly characterize the capabilities of the device. Under both level- and sloped-ground conditions, ankle torque and kinematic data were obtained by using force-plates and a motion capture system. The device was found to be fully capable of providing powered sagittal plane motion and torque very close to that of a biological ankle while simultaneously being able to adapt to sloped terrain by undergoing frontal plane motion, thus providing 2-DOF at the ankle. These findings demonstrate that the device presented in this paper poses radical improvements to powered prosthetic ankle-foot device (PAFD) design.
Biologically Inspired Design and Development of a Variable Stiffness Powered Ankle-Foot Prosthesis
Contributed by the Mechanisms and Robotics Committee of ASME for publication in the Journal of Mechanisms and Robotics. Manuscript received July 2, 2018; final manuscript received April 13, 2019; published online May 17, 2019. Assoc. Editor: Pinhas Ben-Tzvi.
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Agboola-Dobson, A., Wei, G., and Ren, L. (May 17, 2019). "Biologically Inspired Design and Development of a Variable Stiffness Powered Ankle-Foot Prosthesis." ASME. J. Mechanisms Robotics. August 2019; 11(4): 041012. https://doi.org/10.1115/1.4043603
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