A Soft Exosuit for Flexible Upper-Extremity Rehabilitation

Abstract

For stroke survivors and many other people with upper-extremity impairment, daily life can be difficult without properly functioning arms. Some modern physical therapy exercises focus on rehabilitating people with these troubles by correcting patients' perceptions of their own body to eventually regain complete control and strength over their arms again. Augmentative wearable robots, such as the upper-extremity exoskeletons and exosuits, may be able to assist in this endeavor. A common drawback in many of these exoskeletons, however, is their inability to conform to the natural flexibility of the human body without a rigid base. We have built one such exosuit to address this challenge: Compliant Robotic Upper-extremity eXosuit (CRUX). This robot is a compliant, lightweight, multi-DoF, portable exosuit that affords its wearer the ability to augment themselves in many unconventional settings (i.e. outside of a clinic). These attributes are largely achieved by using a modified tensegrity design situated according to measured lines of minimal-extension, where a network of tension members provide a foundation to apply augmentative forces via precisely placed power-lines. In this paper, we detail the design process of CRUX, the report on CRUX's prototypical composition, and describe the mimetic control algorithm used. We also discuss the results of three studies that illustrate the efficacy of CRUX's mimetic controller, CRUX's flexibility and compliance, and the metabolic cost reduction when users exercise with assistance from CRUX as opposed to without. We conclude this paper with a summary of our findings, potential use cases for this technology, and the direction of future related work.

A Review on Design of Upper Limb Exoskeletons

“…The exoskeleton structure with the DPL mechanism can actively support the shoulder extension/flexion and shoulder abduction/adduction, whereas the shoulder rotation was kept passive, which limits its use for several applications. Upper-limb exoskeleton research prototype: (A) parallel actuated shoulder exoskeleton adopted from Reference [41], (B) cmpliant robotic upper-extremity eXosuit (CRUX) adopted from Reference [42], (C) upper-limb exoskeleton for inferno adopted from Reference [43], (D) UB-EXO developed by Aalborg University [40], (E) compact 3 degrees of freedom (DOF) scissors linkages for upper-limb exoskeleton adopted from Reference [44], (F) NESM adopted from Reference [45], (G) Stuttgart Exo-Jacket adopted from Reference [46], and (H) CAREX 7 adopted from Reference [47].…”

“…A set of inertial measurement units (IMUs) was also used to avoid any harmful configuration achieved by the exoskeleton robot, e.g., any IMU-sensed angle pair with more than 40 degrees in difference would stop the motors. However, there is no comprehensive study measuring the effectiveness of CRUX for the active assistance [42] and the design needs some additional degrees of freedom to adopt actual human biomechanics.…”

Upper extremity exomuscle for shoulder abduction support

“…Exosuits, which have no rigid frame, require that the user's musculoskeletal system must support the additional loads generated by the device. In many cases, these loads are compressive [26], [32]- [34]. However, our device can produce tensile loads on the shoulder complex, which must be supported by soft tissue.…”

Efficient Multiaxial Shoulder-Motion Tracking Based on Flexible Resistive Sensors Applied to Exosuits

“…The fast development of exoskeletons during the last decade [6][7][8][9] has fostered the research of new methods to measure shoulder motion. In such manner, solutions based on inertial measurement units (IMUs), electromyography, visual techniques, and flexible resistive sensors have been applied.…”