Bioinspired Postural Controllers for a Locked-Ankle Exoskeleton Targeting Complete SCI Users

Abstract

Several lower-limb exoskeletons enable overcoming obstacles that would impair daily activities of wheelchair users, such as going upstairs. Still, as most of the currently commercialized exoskeletons require the use of crutches, they prevent the user from interacting efficiently with the environment. In a previous study, a bio-inspired controller was developed to allow dynamic standing balance for such exoskeletons. It was however only tested on the device without any user. This work describes and evaluates a new controller that extends this previous one with an online model compensation, and the contribution of the hip joint against strong perturbations. In addition, both controllers are tested with the exoskeleton TWIICE One, worn by a complete spinal cord injury pilot. Their performances are compared by the mean of three tasks: standing quietly, resisting external perturbations, and lifting barbells of increasing weight. The new controller exhibits a similar performance for quiet standing, longer recovery time for dynamic perturbations but better ability to sustain prolonged perturbations, and higher weightlifting capability.

Down to the Bone: A Novel Bio-Inspired Design Concept

“…A source of inspiration is often the human body: this has recently led to the design of exoskeletons [ 4 , 5 ], as a substitute for amputated limbs [ 6 ] or as a support for gait rehabilitation, introducing the concept of biologically inspired mechanized creatures [ 7 ]. The peculiar characteristics of human figure are replicated not only as outward appearance, but specifically in terms of functional aspects [ 8 ].…”