Towards Dynamic Transparency: Robust Interaction Force Tracking Using Multi-Sensory Control on an Arm Exoskeleton
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Date
2020
Publication Type
Conference Paper
ETH Bibliography
yes
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Abstract
A high-quality free-motion rendering is one of the most vital traits to achieve an immersive human-robot interaction. Rendering free-motion is notably challenging for rehabilitation exoskeletons due to their relatively high weight and powerful actuators required for strength training and support. In the presence of dynamic human movements, accurate feedback linearization of the robot’s dynamics is necessary to allow for a linear synthesis of interaction wrench controllers. Hence, we introduce a virtual model controller that uses two 6-DoF force sensors to control the interaction wrenches of a multiDoF torque-controlled exoskeleton over the joint accelerations and inverse dynamics. Furthermore, we propose a disturbance observer for controlling the joint acceleration to diminish the influence of modeling errors on the inverse dynamics. To provide a high-bandwidth, low-bias estimation of the system’s acceleration, we introduce a bias-observer which fuses the information from joint encoders and seven low priced IMUs. We have validated the performance of our proposed control structure on the shoulder and arm exoskeleton ANYexo. The experimental comparison of the controllers shows a reduction of the felt inertia and maximum reflected joint torque by a factor of more than three compared to state of the art. The controllers’ robustness w.r.t. a model mismatch is validated. The experiments show that the closed-loop acceleration control improves the tracking, particularly at joints with low inertia. The proposed controllers’ performance sets a new benchmark in haptic transparency for comparable devices and should be transferable to other applications.
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Publication status
published
Editor
Book title
2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
Journal / series
Volume
Pages / Article No.
7417 - 7424
Publisher
IEEE
Event
IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2020) (virtual)
Edition / version
Methods
Software
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Date collected
Date created
Subject
RSL; SMS; NCCR; SNSF
Organisational unit
09570 - Hutter, Marco / Hutter, Marco
03654 - Riener, Robert / Riener, Robert
Notes
Conference lecture held on October 27, 2020. Due to the Coronavirus (COVID-19) the conference was conducted virtually.
Funding
Related publications and datasets
Is cited by: https://doi.org/10.3929/ethz-b-000548152
Is cited by: https://doi.org/10.3929/ethz-b-000575312
Is cited by: https://doi.org/10.3929/ethz-b-000608090