Design, Control and Evaluation of the Electro-Hydrostatic Actuator, PREHydrA, for Gait Restoration Exoskeleton Technology

Kyrian Staman,Herman Van Der Kooij,Allan J Veale

doi:10.1109/tmrb.2020.3048224

Kyrian Staman, Herman Van Der Kooij + Show 1 more

Open Access

https://doi.org/10.1109/tmrb.2020.3048224

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Abstract

A preliminary design for the PREHydrA (passive return, electro-hydrostatic actuator) concept; a high force density, remote actuator, is tested to requirements for wearable robotics technology intended for gait restoration; one of the most demanding tasks for wearable robotics. While the concept offers good wearability properties, it has never been used in wearable robotics for full support. This work shows that the combination of electro-hydrostatic actuators with a return force and series elastic element offers a good alternative to other actuation types. Custom and small commercial components are used in a design for the knee joint. An experimental setup with a pendulum representing a swinging lower leg was used to show force and angle tracking performance. The results of a maximum zero force (-400-1100 N actuator force range) tracking mean absolute error of 61 N (6.79 Nm joint torque error) at 5.5 Hz excitation and a full swing (70°) within 0.35 s (0.8 m/s actuator velocity), match or exceed current state of the art exoskeleton actuation and control and show that the PREHydrA concept is very well suited for application in exoskeleton technology, especially when the cylinder design is optimized.

Highlights

M ANY lower limb, wearable exoskeletons for gait restoration exist, both commercially and for research: [1], [2], [3], [4], [5], [6], [7]
The force tracking error was compared to a model of the output impedance
This maximum velocity occurs during the swing phase, when the lower leg swings through the entire range of motion of the knee

Summary

Introduction

M ANY lower limb, wearable exoskeletons for gait restoration exist, both commercially and for research: [1], [2], [3], [4], [5], [6], [7]. They are far from restoring the full function of human legs. This challenge is due to the difficulty of control (human interaction, intention detection and balance), and hardware needs improvement, as concluded by [8]. This article was recommended for publication by Associate Editor J.

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