http://www.jneuroengrehab.com/content/10/1/3/abstract
Abstract (provisional)
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). This method 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 consisted of splines between key events, which
are dependent on walking speed and body height. The VMC was evaluated in twelve healthy
subjects and six chronic stroke survivors. The impedance values 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 will enable the therapist to focus the support on the subtasks that are impaired,
and leave the other subtasks up to the patient, encouraging him to actively participate
in the training. Additionally, the speed-dependent reference patterns will provide
the therapist with the tools to easily adapt the treadmill speed to the capabilities
and progress of the patient.
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