Enhancing Voluntary Motion with Modular, Backdrivable, Powered Hip and Knee Orthoses

TL;DR

This paper presents M-BLUE, a modular, backdrivable exoskeleton for lower limbs that reduces muscle effort during lifting tasks, with potential applications for various populations needing mobility assistance.

Contribution

Introduction of M-BLUE, a modular, backdrivable exoskeleton with high torque actuators, capable of assisting hip and knee movements, verified through benchtop testing and human experiments.

Findings

Reduces muscle EMG in lifting tasks

Decreases muscular effort and peak activation

Potential for aiding mobility-impaired populations

Abstract

Mobility disabilities are prominent in society with wide-ranging detriments to affected individuals. Addressing the specific deficits of individuals within this heterogeneous population requires modular, partial-assist, lower-limb exoskeletons. This paper introduces the Modular Backdrivable Lower-limb Unloading Exoskeleton (M-BLUE), which implements high torque, low mechanical impedance actuators on commercial orthoses with sheet metal modifications to produce a variety of hip- and/or knee-assisting configurations. Benchtop system identification verifies the desirable backdrive properties of the actuator, and allows for torque prediction within 0.4 Nm. An able-bodied human subject experiment demonstrates that three unilateral configurations of M-BLUE (hip only, knee only, and hip-knee) with a simple gravity compensation controller can reduce muscle EMG readings in a lifting and lowering task relative to the bare condition. Reductions in mean muscular effort and peak muscle activation were seen across the primary squat musculature (excluding biceps femoris), demonstrating the potential to reduce fatigue leading to poor lifting posture. These promising results motivate applications of M-BLUE to additional subject populations such as hip/knee osteoarthritis and geriatric frailty, and the expansion of M-BLUE to bilateral and ankle configurations.