Selective control of gait subtasks in robotic gait training: Foot clearance support in stroke survivors with a powered exoskeleton

Selective control of gait subtasks in robotic gait training: Foot clearance support in stroke survivors with a powered exoskeleton

Koopman, B.
Van Asseldonk, E.H.F.
Van der Kooij, H.

Mechanical, Maritime and Materials Engineering

Biomechanical Engineering

2013-01-21

Background Robot-aided gait training is an emerging clinical tool for gait rehabilitation of neurological patients. This paper deals with a novel method of offering gait assistance, using an impedance controlled exoskeleton (LOPES). The provided assistance is based on a recent finding that, in the control of walking, different modules can be discerned that are associated with different subtasks. In this study, a Virtual Model Controller (VMC) for supporting one of these subtasks, namely the foot clearance, is presented and evaluated. Methods The developed VMC provides virtual support at the ankle, to increase foot clearance. Therefore, we first developed a new method to derive reference trajectories of the ankle position. These trajectories consist of splines between key events, which are dependent on walking speed and body height. Subsequently, the VMC was evaluated in twelve healthy subjects and six chronic stroke survivors. The impedance levels, of the support, were altered between trials to investigate whether the controller allowed gradual and selective support. Additionally, an adaptive algorithm was tested, that automatically shaped the amount of support to the subjects’ needs. Catch trials were introduced to determine whether the subjects tended to rely on the support. We also assessed the additional value of providing visual feedback. Results With the VMC, the step height could be selectively and gradually influenced. The adaptive algorithm clearly shaped the support level to the specific needs of every stroke survivor. The provided support did not result in reliance on the support for both groups. All healthy subjects and most patients were able to utilize the visual feedback to increase their active participation. Conclusion The presented approach can provide selective control on one of the essential subtasks of walking. This module is the first in a set of modules to control all subtasks. This enables the therapist to focus the support on the subtasks that are impaired, and leave the other subtasks up to the patient, encouraging him to participate more actively in the training. Additionally, the speed-dependent reference patterns provide the therapist with the tools to easily adapt the treadmill speed to the capabilities and progress of the patient.

robotic gait rehabilitation
stroke
reference trajectories
virtual model control
support of subtasks
adaptive control
impedance control
reliance
compensatory strategies
visual feedback

http://resolver.tudelft.nl/uuid:1546b0da-29dd-4dfa-ad6f-b19ebab09aa9

https://doi.org/10.1186/1743-0003-10-3

BioMed Central

1743-0003

http://www.jneuroengrehab.com/content/10/1/3

Journal of NeuroEngineering and Rehabilitation, 10 (3), 2013

Institutional Repository

journal article

© 2013 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.