Design, Control, and Preliminary Assessment of a Multifunctional Semipowered Ankle Prosthesis

This paper describes the design, control, and preliminary assessment of a novel microprocessor-controlled multifunction ankle prosthesis that provides three microprocessor-controlled behaviors-a selectable stiffness equilibrium angle, lockable conformal damping, and swing-phase repositioning. Following a description of the motivation for providing these behaviors, the authors provide a detailed description of the device and walking controller design. This device utilizes a power-asymmetric linear actuator to provide the desired functionality in a compact and lightweight package through a combination of both hydraulic and electromechanical actuation approaches. The device is controlled for level ground walking via a finite-state machine. The functionality of the prosthesis is demonstrated by a set of benchtop experiments that characterize the ability of the prosthesis to provide the three desired behaviors and by an experiment in which the prosthesis was worn by a transtibial amputee during walking. Both sets of experiments indicate that the prosthesis provides the functionality for which it was designed.