Model-based control for exoskeletons with series elastic actuators evaluated on sit-to-stand movements

J. Vantilt; K. Tanghe; M. Afschrift; A.K.B.D. Bruijnes; K. Junius; J. Geeroms; E. Aertbeliën; F. De Groote; D. Lefeber; I. Jonkers; J. De Schutter

doi:10.1186/s12984-019-0526-8

Model-based control for exoskeletons with series elastic actuators evaluated on sit-to-stand movements

J. Vantilt, K. Tanghe, M. Afschrift, A.K.B.D. Bruijnes, K. Junius, J. Geeroms, E. Aertbeliën, F. De Groote, D. Lefeber, I. Jonkers, J. De Schutter

Research output: Contribution to Journal › Article › Academic › peer-review

Abstract

© 2019 The Author(s).Background: Currently, control of exoskeletons in rehabilitation focuses on imposing desired trajectories to promote relearning of motions. Furthermore, assistance is often provided by imposing these desired trajectories using impedance controllers. However, lower-limb exoskeletons are also a promising solution for mobility problems of individuals in daily life. To develop an assistive exoskeleton which allows the user to be autonomous, i.e. in control of his motions, remains a challenge. This paper presents a model-based control method to tackle this challenge. Methods: The model-based control method utilizes a dynamic model of the exoskeleton to compensate for its own dynamics. After this compensation of the exoskeleton dynamics, the exoskeleton can provide a desired assistance to the user. While dynamic models of exoskeletons used in the literature focus on gravity compensation only, the need for modelling and monitoring of the ground contact impedes their widespread use. The control strategy proposed here relies on modelling of the full exoskeleton dynamics and of the contacts with the environment. A modelling strategy and general control scheme are introduced. Results: Validation of the control method on 15 non-disabled adults performing sit-to-stand motions shows that muscle effort and joint torques are similar in the conditions with dynamically compensated exoskeleton and without exoskeleton. The condition with exoskeleton in which the compensating controller was not active showed a significant increase in human joint torques and muscle effort at the knee and hip. Motor saturation occurred during the assisted condition, which limited the assistance the exoskeleton could deliver. Conclusions: This work presents the modelling steps and controller design to compensate the exoskeleton dynamics. The validation seems to indicate that the presented model-based controller is able to compensate the exoskeleton.

Original language	English
Article number	65
Journal	Journal of NeuroEngineering and Rehabilitation
Volume	16
Issue number	1
DOIs	https://doi.org/10.1186/s12984-019-0526-8
Publication status	Published - 3 Jun 2019
Externally published	Yes

Funding

The Robotics Research Group and the Robotics and Multibody Mechanics Research Group are both core labs of Flanders Make.. Jonas Vantilt and Karen Junius are research fellows of the Flemish agency for Innovation by Science and Technology (IWT-SBO). Maarten Afschrift is a research fellow of the Flemish agency for scientific research (FWO-Vlaanderen). The authors gratefully acknowledge the financial support by the agency Flanders Innovation & Entrepreneurship (VLAIO) through a project grant (MIRAD, IWT-SBO 120057). The authors cordially thank all participants of the study. The MIRAD exoskeleton is funded by the agency Flanders Innovation & Entrepreneurship (VLAIO) through a project grant (MIRAD, IWT-SBO 120057). Jonas Vantilt and Karen Junius are research fellows of the Flemish agency for Innovation by Science and Technology (IWT-SBO). Maarten Afschrift is a research fellow of the Flemish agency for scientific research (FWO-Vlaanderen).

Funders	Funder number
Agentschap Innoveren en Ondernemen	IWT-SBO 120057
Agentschap Innoveren en Ondernemen
Agentschap Innoveren en Ondernemen	IWT-SBO 120057
Agentschap Innoveren en Ondernemen

Access to Document

10.1186/s12984-019-0526-8

Persistent URL (handle)

Copy link address

Cite this

Vantilt, J., Tanghe, K., Afschrift, M., Bruijnes, A. K. B. D., Junius, K., Geeroms, J., Aertbeliën, E., De Groote, F., Lefeber, D., Jonkers, I., & De Schutter, J. (2019). Model-based control for exoskeletons with series elastic actuators evaluated on sit-to-stand movements. Journal of NeuroEngineering and Rehabilitation, 16(1), Article 65. https://doi.org/10.1186/s12984-019-0526-8

@article{f60429c7931746c9b8edb7113296bc87,

title = "Model-based control for exoskeletons with series elastic actuators evaluated on sit-to-stand movements",

abstract = "{\textcopyright} 2019 The Author(s).Background: Currently, control of exoskeletons in rehabilitation focuses on imposing desired trajectories to promote relearning of motions. Furthermore, assistance is often provided by imposing these desired trajectories using impedance controllers. However, lower-limb exoskeletons are also a promising solution for mobility problems of individuals in daily life. To develop an assistive exoskeleton which allows the user to be autonomous, i.e. in control of his motions, remains a challenge. This paper presents a model-based control method to tackle this challenge. Methods: The model-based control method utilizes a dynamic model of the exoskeleton to compensate for its own dynamics. After this compensation of the exoskeleton dynamics, the exoskeleton can provide a desired assistance to the user. While dynamic models of exoskeletons used in the literature focus on gravity compensation only, the need for modelling and monitoring of the ground contact impedes their widespread use. The control strategy proposed here relies on modelling of the full exoskeleton dynamics and of the contacts with the environment. A modelling strategy and general control scheme are introduced. Results: Validation of the control method on 15 non-disabled adults performing sit-to-stand motions shows that muscle effort and joint torques are similar in the conditions with dynamically compensated exoskeleton and without exoskeleton. The condition with exoskeleton in which the compensating controller was not active showed a significant increase in human joint torques and muscle effort at the knee and hip. Motor saturation occurred during the assisted condition, which limited the assistance the exoskeleton could deliver. Conclusions: This work presents the modelling steps and controller design to compensate the exoskeleton dynamics. The validation seems to indicate that the presented model-based controller is able to compensate the exoskeleton.",

author = "J. Vantilt and K. Tanghe and M. Afschrift and A.K.B.D. Bruijnes and K. Junius and J. Geeroms and E. Aertbeli{\"e}n and {De Groote}, F. and D. Lefeber and I. Jonkers and {De Schutter}, J.",

year = "2019",

month = jun,

day = "3",

doi = "10.1186/s12984-019-0526-8",

language = "English",

volume = "16",

journal = "Journal of NeuroEngineering and Rehabilitation",

issn = "1743-0003",

publisher = "BioMed Central",

number = "1",

}

TY - JOUR

T1 - Model-based control for exoskeletons with series elastic actuators evaluated on sit-to-stand movements

AU - Vantilt, J.

AU - Tanghe, K.

AU - Afschrift, M.

AU - Bruijnes, A.K.B.D.

AU - Junius, K.

AU - Geeroms, J.

AU - Aertbeliën, E.

AU - De Groote, F.

AU - Lefeber, D.

AU - Jonkers, I.

AU - De Schutter, J.

PY - 2019/6/3

Y1 - 2019/6/3

N2 - © 2019 The Author(s).Background: Currently, control of exoskeletons in rehabilitation focuses on imposing desired trajectories to promote relearning of motions. Furthermore, assistance is often provided by imposing these desired trajectories using impedance controllers. However, lower-limb exoskeletons are also a promising solution for mobility problems of individuals in daily life. To develop an assistive exoskeleton which allows the user to be autonomous, i.e. in control of his motions, remains a challenge. This paper presents a model-based control method to tackle this challenge. Methods: The model-based control method utilizes a dynamic model of the exoskeleton to compensate for its own dynamics. After this compensation of the exoskeleton dynamics, the exoskeleton can provide a desired assistance to the user. While dynamic models of exoskeletons used in the literature focus on gravity compensation only, the need for modelling and monitoring of the ground contact impedes their widespread use. The control strategy proposed here relies on modelling of the full exoskeleton dynamics and of the contacts with the environment. A modelling strategy and general control scheme are introduced. Results: Validation of the control method on 15 non-disabled adults performing sit-to-stand motions shows that muscle effort and joint torques are similar in the conditions with dynamically compensated exoskeleton and without exoskeleton. The condition with exoskeleton in which the compensating controller was not active showed a significant increase in human joint torques and muscle effort at the knee and hip. Motor saturation occurred during the assisted condition, which limited the assistance the exoskeleton could deliver. Conclusions: This work presents the modelling steps and controller design to compensate the exoskeleton dynamics. The validation seems to indicate that the presented model-based controller is able to compensate the exoskeleton.

AB - © 2019 The Author(s).Background: Currently, control of exoskeletons in rehabilitation focuses on imposing desired trajectories to promote relearning of motions. Furthermore, assistance is often provided by imposing these desired trajectories using impedance controllers. However, lower-limb exoskeletons are also a promising solution for mobility problems of individuals in daily life. To develop an assistive exoskeleton which allows the user to be autonomous, i.e. in control of his motions, remains a challenge. This paper presents a model-based control method to tackle this challenge. Methods: The model-based control method utilizes a dynamic model of the exoskeleton to compensate for its own dynamics. After this compensation of the exoskeleton dynamics, the exoskeleton can provide a desired assistance to the user. While dynamic models of exoskeletons used in the literature focus on gravity compensation only, the need for modelling and monitoring of the ground contact impedes their widespread use. The control strategy proposed here relies on modelling of the full exoskeleton dynamics and of the contacts with the environment. A modelling strategy and general control scheme are introduced. Results: Validation of the control method on 15 non-disabled adults performing sit-to-stand motions shows that muscle effort and joint torques are similar in the conditions with dynamically compensated exoskeleton and without exoskeleton. The condition with exoskeleton in which the compensating controller was not active showed a significant increase in human joint torques and muscle effort at the knee and hip. Motor saturation occurred during the assisted condition, which limited the assistance the exoskeleton could deliver. Conclusions: This work presents the modelling steps and controller design to compensate the exoskeleton dynamics. The validation seems to indicate that the presented model-based controller is able to compensate the exoskeleton.

U2 - 10.1186/s12984-019-0526-8

DO - 10.1186/s12984-019-0526-8

M3 - Article

SN - 1743-0003

VL - 16

JO - Journal of NeuroEngineering and Rehabilitation

JF - Journal of NeuroEngineering and Rehabilitation

IS - 1

M1 - 65

ER -

Model-based control for exoskeletons with series elastic actuators evaluated on sit-to-stand movements

Abstract

Funding

Access to Document

Persistent URL (handle)

Fingerprint

Cite this