Research Article Feasibility of a Hydraulic Power Assist System for Use in Hybrid Neuroprostheses Kevin M. Foglyano, 1 Rudi Kobetic, 1 Curtis S. To, 2 Thomas C. Bulea, 2 John R. Schnellenberger, 1 Musa L. Audu, 2 Mark J. Nandor, 1 Roger D. Quinn, 3 and Ronald J. Triolo 1,2,4 1 Advanced Platform Technology Center, Louis Stokes Cleveland Department of Veterans Afairs Medical Center, Cleveland, OH 44106, USA 2 Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA 3 Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106, USA 4 Department of Orthopaedics, Case Western Reserve University, Cleveland, OH 44106, USA Correspondence should be addressed to Kevin M. Foglyano; kfoglyano@fescenter.org Received 5 June 2014; Revised 3 February 2015; Accepted 1 March 2015 Academic Editor: Amir A. Zadpoor Copyright © 2015 Kevin M. Foglyano et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Feasibility of using pressurized hydraulic luid as a source of on-demand assistive power for hybrid neuroprosthesis combining exoskeleton with functional neuromuscular stimulation was explored. Hydraulic systems were selected as an alternative to electric motors for their high torque/mass ratio and ability to be located proximally on the exoskeleton and distribute power distally to assist in moving the joints. he power assist system (PAS) was designed and constructed using of-the-shelf components to test the feasibility of using high pressure luid from an accumulator to provide assistive torque to an exoskeletal hip joint. he PAS was able to provide 21 Nm of assistive torque at an input pressure of 3171 kPa with a response time of 93 ms resulting in 32 ∘ of hip lexion in an able-bodied test. he torque output was independent of initial position of the joint and was linearly related to pressure. hus, accumulator pressure can be speciied to provide assistive torque as needed in exoskeletal devices for walking or stair climbing beyond those possible either volitionally or with electrical stimulation alone. 1. Introduction Restoring walking is one of the main desires of individuals who have a spinal cord injury (SCI) [1]. hus, there is a sig- niicant efort in the ield of orthotics to restore locomotion, including walking on uneven terrain and negotiating stairs. here are a number of approaches to restoring upright mobil- ity ater paralysis from SCI including mechanical bracing [2], functional neuromuscular stimulation (FNS) [3–5], powered exoskeletons [6–9], and hybrid systems [10, 11] that combine two or more of these approaches. Recently, there has been a surge in powered exoskeleton development, including commercial devices such as Rewalk and Ekso [12, 13]. Exoskeletons are able to drive the motion of the limbs for walking and stair climbing with external motors. However, they are limited by the amount of power and the weight of the torque generating motors that must be carried. In addition, they do not provide the physiological beneits of exercise from actively contracting the otherwise paralyzed muscles. herefore, there has been an increased efort in hybrid system development that combines either surface [14] or implanted FNS [15] with exoskeleton’s on-demand external power to provide physiological beneits and to minimize external power requirements. here are a number of ways to provide external power including the use of electric motors [12, 13], pneumatic [16–18] and elastic elements [19–21] to supply joint torques. Other approaches store energy from stimulated knee extensors and transfer it to drive hip motion using springs and pneumatic components [22, 23]. Hindawi Publishing Corporation Applied Bionics and Biomechanics Volume 2015, Article ID 205104, 8 pages http://dx.doi.org/10.1155/2015/205104