Team IHMC at the 2020 Cybathlon: a user-centered approach towards personal mobility exoskeletons

Abstract

Background: The past few decades have seen rapid advancements in exoskeleton technology, with a considerable shift towards applications involving users with gait pathologies. Commercial devices from ReWalk, Ekso Bionics, and Indego, mainly designed for rehabilitation purposes, have inspired the development of many research platforms aimed at extending capabilities for use as safe and effective personal mobility devices. The 2016 Cybathlon featured an impressive demonstration of exoskeletons designed to enable mobility for individuals with spinal cord injury, however, not a single team completed every task and only two completed the stairs. Major improvements were showcased at the 2020 Cybathlon, with seven of the nine teams completing a similar set of tasks. Team IHMC built upon its silver-medal success from 2016 with an upgraded device, Quix.

Methods: Quix features several notable improvements including an additional powered degree of freedom for hip ab/adduction to laterally shift the device and reduce user effort while walking, custom-tailored cuffs and soft goods based on 3D body scans to optimize user comfort, and a streamlined testing pipeline for online tuning of gait parameters.

Results: Team IHMC finished in fourth place behind the teams from EPFL and Angel Robotics. Although we suffered from a considerably slower flat-ground walking speed, our pilot reported marked improvements in overall effort, comfort, and ease-of-use compared to our previous device.

Conclusions: Clear progress in exoskeleton development has been exhibited since the inaugural Cybathlon, with tasks involving rough terrain, stairs, and ramps now posing little threat to most of the competitors. As a result, the layout of the powered exoskeleton course will likely undergo significant modifications to further push the devices towards suitability for personal everyday use. The current tasks do not address the issue of donning and doffing, nor do they simulate a scenario similar to maneuvering a kitchen to prepare a meal, for example. An additional limitation that may be more difficult to test in a competition setting is the required upper-body effort to manipulate the device in an effective manner.

Keywords: Assistive devices; Cybathlon; Exoskeletons; Spinal cord injury; Wearable robotics.

Fig. 1

IHMC exoskeletons: a Mina v1, b X1, c Mina v2, used in 2016 Cybathlon, d Quix, used in 2020 Cybathlon

Fig. 2

Key components of Quix exoskeleton

Fig. 3

Quix pilot, Mark Daniel, performing various exoskeleton behaviors: a.i–a.iv side-stepping sequence, a.i lifting left leg, a.ii swinging out left leg, a.iii lifting right leg, a.iv swinging in right leg; b.i walking up ramp, b.ii walking down ramp; c walking across rough terrain

Fig. 4

Joint angle trajectories and corresponding joint torques averaged over 5 continuous steps of 0.4 m in length, beginning at heel-strike. Shaded regions represent standard deviations of the actual, measured values

Fig. 5

Mark Daniel walking with Quix along the Pensacola Bay after the 2020 Cybathlon

Fig. 6

a Comparison of Quix up-time (progression through course) versus down-time (user-interface navigation or device realignment) during each task; b Comparison of total task time between IHMC and winning team, Angel Robotics