Artificial Neural Network Control of Standing ...

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2 Louis Stokes Veterans Affairs Medical Center, Cleveland, OH. Primary author e-mail: [email protected]. Website: http://fescenter.case.edu. ABSTRACT.
12th Annual Conference of the International FES Society November 2007 – Philadelphia, PA USA

Artificial Neural Network Control of Standing Maintenance Using Functional Electrical Stimulation following Spinal Cord Injury Raviraj Nataraj MS 1, Musa L. Audu PhD1,2, Robert F. Kirsch PhD1,2, Ronald J. Triolo PhD1,2 1 2

Case Western Reserve University, Cleveland, OH Louis Stokes Veterans Affairs Medical Center, Cleveland, OH

Primary author e-mail: [email protected] Website: http://fescenter.case.edu

ABSTRACT Currently, clinical functional electrical stimulation (FES) systems used to restore basic standing function implement open-loop stimulation. The user makes all corrective postural adjustments by exerting volitional upper-body loading upon an assistive device. The project aims to develop a controller that uses sensor feedback to detect postural errors and modulate muscle excitations to automatically assist in reducing those errors. We use a three-dimensional model of human bipedal stance on which to test control paradigms prior to live subject experimentation. Our controller objectives include maintaining quiet standing, restoring posture against perturbations, and requiring minimal instrumentation for feedback. To address issues of system identification, threedimensionality, and redundant muscle actuation, we use a strategy of optimizing data used to train an artificial neural network (ANN) to yield desired control functionality. For standing maintenance, we employ ANN-training of statically optimized muscle excitations necessary to maintain various postures. For whole-body perturbation rejection, we train another ANN to map muscle excitations to corresponding trunk accelerations. Both ANNs are driven by a PD (proportional-derivative) type control scheme. Preliminary simulations indicate potential for ANNmodulation of muscle excitations to both maintain erect standing and reject perturbations whereby upper-body loading is minimized. References

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Acknowledgements This work is funded by NIH: R01NS040547-03.