A Preliminary Assessment of Legged Mobility Provided by a Lower Limb Exoskeleton for Persons With Paraplegia

Abstract

This paper presents an assessment of a lower limb exoskeleton for providing legged mobility to people with paraplegia. In particular, the paper presents a single-subject case study comparing legged locomotion using the exoskeleton to locomotion using knee–ankle–foot orthoses (KAFOs) on a subject with a T10 motor and sensory complete injury. The assessment utilizes three assessment instruments to characterize legged mobility, which are the timed up-and-go test, the Ten-Meter Walk Test (10 MWT), and the Six-Minute Walk Test (6 MWT), which collectively assess the subject’s ability to stand, walk, turn, and sit. The exertion associated with each assessment instrument was assessed using the Physiological Cost Index. Results indicate that the subject was able to perform the respective assessment instruments 25%, 70%, and 80% faster with the exoskeleton relative to the KAFOs for the timed up-and-go test, the 10 MWT, and the 6 MWT, respectively. Measurements of exertion indicate that the exoskeleton requires 1.6, 5.2, and 3.2 times less exertion than the KAFOs for each respective assessment instrument. The results indicate that the enhancement in speed and reduction in exertion are more significant during walking than during gait transitions.

Optimizing User Integration for Individualized Rehabilitation

“…Device actuation may be more passive as with AFO assistance from spring-loads being applied proportional to displacements ala Hooke's law (F = -kx) and mediated through well-executed clutching [28]. Device actuation may be more active such as functional neuromuscular stimulation (FNS) to activated paralyzed musculature and restore standing balance capabilities [29] or electromotor actuation to restore walking [30] following spinal cord injury (SCI).…”

“…Extending such an approach could provide a foundation for optimal control of powered gait devices such as exoskeletons. Exoskeletons to restore or augment gait function have previously employed time-varying proportional-derivative (PD) control [30]. However, gains and setpoints for closed-loop joint control were empirically ited to human angle-moment data and consequently not unique nor optimal toward speciic performance objectives.…”

Design and Motion Control of a Lower Limb Robotic Exoskeleton

“…The user also has a remote control placed in his/her arm for Design, Control and Applications of Mechatronic Systems in Engineeringselecting different tasks, such as sit-to-stand or climbing stairs. The Vanderbilt exoskeleton [18,19] is developed to provide gait assistance to patients with spinal cord injuries. The device weights about 12 kg.…”

Training Persons with Spinal Cord Injury to Ambulate Using a Powered Exoskeleton

“…These powered exoskeleton devices have been studied in persons with stroke 14,15 , persons with complete and incomplete SCI [16][17][18][19][20][21][22][23][24] , and other persons with disabilities causing reduced control of their lower extremities [25][26][27] . Although the devices differ, each one requires training and practice by the user for safe performance.…”