Non-linear adaptive controllers for an over-actuated pneumatic MR-compatible stepper

Hollnagel, Christoph; Vallery, Heike; Schädler, Rainer; López, Isaac Gómez-Lor; Jaeger, Lukas; Wolf, Peter; Riener, Robert; Marchal Crespo, Laura (2013). Non-linear adaptive controllers for an over-actuated pneumatic MR-compatible stepper. Medical & biological engineering & computing, 51(7), pp. 799-809. Springer 10.1007/s11517-013-1050-9

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Pneumatics is one of the few actuation principles that can be used in an MR environment, since it can produce high forces without affecting imaging quality. However, pneumatic control is challenging, due to the air high compliance and cylinders non-linearities. Furthermore, the system’s properties may change for each subject. Here, we present novel control strategies that adapt to the subject’s individual anatomy and needs while performing accurate periodic gait-like movements with an MRI compatible pneumatically driven robot. In subject-passive mode, an iterative learning controller (ILC) was implemented to reduce the system’s periodic disturbances. To allow the subjects to intend the task by themselves, a zero-force controller minimized the interaction forces between subject and robot. To assist patients who may be too weak, an assist-as-needed controller that adapts the assistance based on online measurement of the subject’s performance was designed. The controllers were experimentally tested. The ILC successfully learned to reduce the variability and tracking errors. The zero-force controller allowed subjects to step in a transparent environment. The assist-as-needed controller adapted the assistance based on individual needs, while still challenged the subjects to perform the task. The presented controllers can provide accurate pneumatic control in MR environments to allow assessments of brain activation.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > ARTORG Center for Biomedical Engineering Research > ARTORG Center - Motor Learning and Neurorehabilitation
10 Strategic Research Centers > ARTORG Center for Biomedical Engineering Research > ARTORG Center - Gerontechnology and Rehabilitation

UniBE Contributor:

Riener, Robert and Marchal Crespo, Laura

Subjects:

600 Technology > 610 Medicine & health
600 Technology > 620 Engineering

ISSN:

0140-0118

Publisher:

Springer

Language:

English

Submitter:

Angela Amira Botros

Date Deposited:

19 Jun 2018 11:00

Last Modified:

18 Jun 2019 17:02

Publisher DOI:

10.1007/s11517-013-1050-9

PubMed ID:

23430329

BORIS DOI:

10.7892/boris.117041

URI:

https://boris.unibe.ch/id/eprint/117041

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