Key result
The STABLE exosuit modulated knee joint apparent torque up to 18.22 N.m and increased the damping ratio from 0.07 without assistance to 0.38 with full assistance during impulse force testing.
Why the study?
Assistive devices coupling with the human body often lack the capability to vary stiffness and damping due to increases in design complexity, cost, and weight.
Does the STABLE exosuit modulate stiffness and damping in an emulated lower limb?
Does the STABLE exosuit modulate stiffness and damping in an emulated lower limb?
Absolute Event Rate: 0.38% vs 0.07%
The STABLE exosuit effectively modulates joint stiffness and damping in an emulated limb, demonstrating potential for improving joint stability in assistive devices.
Feasibility shown for tunable damping in emulated limbs; leaves open translation to human joint stability.
The human body modulates the effective stiffness and damping across joints to better react to external perturbations and stabilize joints during daily activities. Assistive devices that couple with the human body, such as exoskeletons and exosuits, often do not have the capability to vary stiffness and damping due to the inherent increase in design complexity, cost, and weight. In this study, we introduce a novel soft torque assistive bio-inspired lower limb exosuit (STABLE) capable of modulating the stiffness and damping about an emulated knee joint. The wearable exosuit features a body conforming structure and is actuated by dual nylon strap actuators embedded within the exosuit. By employing an agonist-antagonist mode of actuation, the exosuit is capable of modulating the dynamic response of an emulated lower limb to external forces and perturbations. We showcase the stiffness and damping characteristics of the emulated limb and exosuit in a series of experiments. Our results indicate a non-linear variation in the knee joint apparent torque up to 18.22 N.m, depending on both the flexion angle, and whether the joint was flexing or extending. Impulse force testing revealed that varying the level of actuator co-contraction resulted in changing the damping ratio at the knee joint from 0.07 (for no exosuit assistance), to 0.38 (for full exosuit assistance). This study presents a promising approach to modulating joint stiffness and damping when using assistive devices and has important implications in the use of such devices when joint stability is an important factor.
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Bottin-Noonan et al. (2024) studied this question. Soft torque assistive bio-inspired lower limb exosuit (STABLE) vs. No exosuit assistance was evaluated on Damping ratio at the knee joint. The STABLE exosuit modulated knee joint apparent torque up to 18.22 N.m and increased the damping ratio from 0.07 without assistance to 0.38 with full assistance during impulse force testing.
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