ATARO: A Muscle-Driven Biorobotic Arm to Investigate Healthy and Impaired Motor Control

Abstract

Bio-inspired robotics have received increasing attention in recent years as the biological neuro-muscular interplay achieves unprecedented robust, versatile, and safe movements. However, few biorobots mimic the fine-tuned interplay between neuro-musculoskeletal properties by applying bio-inspired control strategies that exploit the nonlinear biomechanical properties of muscle-like actuators. Here we introduce ATARO, a bio-inspired robotic model of the human arm designed to test biological concepts of motor control which exploit muscle characteristics to generate human-like smooth movements. We demonstrate that ATARO allows to exploit the viscoelastic muscle properties by implementing an intermittent equilibrium point control approach which generates smooth reaching movements from piece-wise constant control commands combined with a model of delayed spinal proprioceptive feedback. We found that arm-reaching movements can be reproduced in good agreement with recorded experimental data from humans. Additionally, we introduced a perturbation on the neuronal level by changing the initial muscle co-contraction without changing the subsequent control parameters. This leads to an overshooting movement, similar to what has been observed in patients with ataxia, a neuronal movement disorder. In the future, ATARO is intended to serve two purposes: (1) to investigate neurological origins of motor control disorders that involve the muscular level and (2) to serve as a testbed for novel technical assistive devices.