Contact
Impressum
People involved
- Thomas Seel (TU Berlin)
- Thomas Schauer (TU Berlin)
- Jörg Raisch
Cooperation
- Charité-Universitätsmedizin (S. Hesse, C. Werner)
- HASOMED GmbH, Magdeburg
Funding
- TU Berlin, Federal Ministry of Education and Research (BMBF), Max Planck Society
Description
Many people have walking deficits after suffering a stroke. Ineffective dorsiflexion during swing (drop-foot) is a particularly frequent phenomenon, which is conventionally treated by using passive ankle-foot orthoses. FES represents an attractive alternative. However, most commercially available stimulators are of the on/off type, where a simple heel switch inside the shoe triggers the stimulation. Stimulation intensity then remains constant during the swing phase. For such systems, the stimulation intensity either needs frequent manual adjustment, or must be set to an unnecessarily high value, which then causes rapid fatiguing of the stimulated muscle. We have therefore developed a control scheme inspired by Iterative Learning Control (ILC): we employ a time varying stimulation profile, which is only adjusted after the end of each step. Adjustment is based on the difference between the desired and the recorded angle profile during the previous step [1] [2]. In this way, the advantages of feed-forward and feedback are combined in an intuitive manner. The success of such a scheme of course depends critically on the available ankle-joint angle measurements. We have investigated two different sensor technologies: one approach uses an inertial sensor mounted on the shoe [3], the other one makes use of bioimpedance measurements via skin electrodes [1] [2]. Another challenge is the irregular gait of stroke patients and the resulting significant variation of the duration of the swing phase. More specifically, the swing phase of a step can be disrupted either by the patient putting the foot down intentionally, or by the toes touching ground early due to unsufficient stimulation intensity. Since all available results on ILC require constant cycle duration, we are developing an extension of the theoretic concepts, including stability and monotonicity criteria, for the case of variable cycle length. First results have appeared in [4] . We believe that these results will also be useful for other ILC applications where variable cycle length is a phenomenon that cannot be neglected.
Publications
- ↑ 1.0 1.1
Nahrstaedt, H., Schauer, T., Shalaby, R., Hesse, S., Raisch, J. - Automatic Control of a Drop-Foot Stimulator Based on Angle Measurement Using Bioimpedance
- ↑ 2.0 2.1 Nahrstaedt, H., Schauer, T., Hesse, S., Raisch, J. - Iterative Learning Control of a Gait Neuroprosthesis (Article in German)
- at - Automatisierungstechnik 56(9):494–501,2008
- BibtexAuthor : Nahrstaedt, H., Schauer, T., Hesse, S., Raisch, J.| PDF | DOI
Title : Iterative Learning Control of a Gait Neuroprosthesis (Article in German)
In : at - Automatisierungstechnik -
Address :
Date : 2008
- ↑ Negard, N.-O. - Controlled FES-assisted gait training for hemiplegic stroke patients based on inertial sensors
- ↑ Seel, T., Schauer, T., Raisch, J. - Iterative Learning Control for Variable Pass Length Systems
- Preprints of the 18th IFAC World Congress pp. 4880–4885, Milan, Italy,2011
- BibtexAuthor : Seel, T., Schauer, T., Raisch, J.| PDF | DOI | Link
Title : Iterative Learning Control for Variable Pass Length Systems
In : Preprints of the 18th IFAC World Congress -
Address : Milan, Italy
Date : 2011
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