A biologically-inspired multi-joint soft exosuit that can reduce the energy cost of loaded walking

Abstract

BackgroundCarrying load alters normal walking, imposes additional stress to the musculoskeletal system, and results in an increase in energy consumption and a consequent earlier onset of fatigue. This phenomenon is largely due to increased work requirements in lower extremity joints, in turn requiring higher muscle activation. The aim of this work was to assess the biomechanical and physiological effects of a multi-joint soft exosuit that applies assistive torques to the biological hip and ankle joints during loaded walking.MethodsThe exosuit was evaluated under three conditions: powered (EXO_ON), unpowered (EXO_OFF) and unpowered removing the equivalent mass of the device (EXO_OFF_EMR). Seven participants walked on an instrumented split-belt treadmill and carried a load equivalent to 30 % their body mass. We assessed their metabolic cost of walking, kinetics, kinematics, and lower limb muscle activation using a portable gas analysis system, motion capture system, and surface electromyography.ResultsOur results showed that the exosuit could deliver controlled forces to a wearer. Net metabolic power in the EXO_ON condition (7.5 ± 0.6 W kg−1) was 7.3 ± 5.0 % and 14.2 ± 6.1 % lower than in the EXO_OFF_EMR condition (7.9 ± 0.8 W kg−1; p = 0.027) and in the EXO_OFF condition (8.5 ± 0.9 W kg−1; p = 0.005), respectively. The exosuit also reduced the total joint positive biological work (sum of hip, knee and ankle) when comparing the EXO_ON condition (1.06 ± 0.16 J kg−1) with respect to the EXO_OFF condition (1.28 ± 0.26 J kg−1; p = 0.020) and to the EXO_OFF_EMR condition (1.22 ± 0.21 J kg−1; p = 0.007).ConclusionsThe results of the present work demonstrate for the first time that a soft wearable robot can improve walking economy. These findings pave the way for future assistive devices that may enhance or restore gait in other applications.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-016-0150-9) contains supplementary material, which is available to authorized users.

A soft robotic exosuit improves walking in patients after stroke

“…Our first efforts developing exosuits led to the creation of systems that could comfortably deliver assistive forces to healthy users during walking (39,40,(43)(44)(45)(46)(47). Recently, we demonstrated that assistive forces delivered through the exosuit interface produce marked reductions in the energy cost of healthy walking (37,48). Thus, although exosuits can only augment, not replace, a wearer's existing gait functions, we posit that they have the potential to work synergistically with the residual abilities of individuals with impaired gait to improve walking function.…”

“…To address this opportunity, our team developed a lightweight, soft wearable robot (exosuit) that interfaces to the paretic limb of persons after stroke via garment-like, functional textile anchors. Exosuits produce gait-restorative joint torques by transmitting mechanical power from waist-mounted body-worn (37) or off-board (38,39) actuators to the wearer through the interaction of the textile anchors and a cable-based transmission.…”

A cable-based series elastic actuator with conduit sensor for wearable exoskeletons

“…Similarly, the requirements on the accuracy and consistency of a cable force controller for such devices can be relatively lax compared with the requirements for upper limb devices. For example, an invariant trapezoidal force profile triggered once per gait cycle has been found sufficient to reduce metabolic costs during walking [18].…”

Characterization of Kinetic and Kinematic Parameters for Wearable Robotics

“…The effectiveness of each prototype is commonly assessed by measuring the metabolic cost reduction delivered to the user while performing an activity [1]. However, the latter requires specialized equipment.…”