Pilot Study on the Needs of Prospective Exoskeleton Users with Impaired Mobility

Patients with paraplegia and spinal cord injuries stand to benefit greatly from powered exoskeletons physically, socially, and psychologically. Yet, most powered exoskeletons are limited to usage in rehabilitation clinics or academic facilities. To overcome the challenge of commercialization it is necessary to better understand the needs of potential exoskeleton users. A customer needs survey was conducted among 14 participants with mobility disorders. The data collected was analyzed using a House of Quality. The results emphasized a need to direct research towards designing exoskeletons that can balance without crutches and impose minimal interaction forces upon the user. While doing so, researchers should also pay keen attention to the cost of the exoskeleton.

I. Introduction

A 2016 study showed that 28% of the US population suffer from walking disabilities [1]. A major cause of such disabilities is Spinal Cord Injuries (SCI) with an annual estimate of 17,700 newly reported cases. Of the cases reported since 2015, 20.2% suffer from complete paraplegia while 20.4% suffer from incomplete paraplegia [2]. Also, about 90% of those with complete SCI rely on wheelchairs for mobility [3]. Extended usage of wheelchairs has many side effects such as osteoporosis, spasticity, urinary tract infections, increased body mass index, impaired digestive, lymphatic, and vascular functions, pressure sores, and depression [4]–[8]. For individuals that are restricted to wheelchairs, the ability to stand at eye level with others carries high psychosocial significance [7], [9]. There are also studies that show walking over long periods of time can improve the quality of life and result in psychological benefits. Utilizing powered exoskeletons could solve several problems SCI patients face. There are currently many research groups focusing on the development of powered lower-limb exoskeletons [10]–[14]. These groups employ an actuated hip and knee design. The powered exoskeletons Ekso GT by Ekso Bionics and ReWalk Personal by ReWalk utilize a spring loaded ankle joint [10], [11]. A notable aspect of the Ekso GT is that the assistance provided by the robotic system to the user can be varied. Thus, it may be used by patients with minor mobility disorders (like foot drop) to severe disabilities like paraplegia. The ReWalk is one of the few commercially available exoskeletons that can be used as a personal device on a daily basis. Mina V2 by IHMC is one of the few exoskeletons with a powered ankle joint [14]. While all of the previously mentioned exoskeletons depend on hand-held crutches for balance, the Rex exoskeleton from REX Bionics is a self balancing exoskeleton [13]. It implements Zero-Moment -Point (ZMP) based controllers to ensure stability. But, to achieve said stability, the speed of the generated gait was greatly reduced. Additionally, it is the only exoskeleton that employs 5 actuators per limb [13].