The first is that feedforward control in conjunction with feedback control uses less muscle energy than feedback control alone. While feedback is critical for controlling precise reaching movements, feedforward control is necessary for two main reasons.
The models can be inverted and used in feedforward control. We do experiments with a human subject to determine how the specific FES system responds to its inputs and use the experimental data to build models mapping inputs to outputs. The outputs are forces or motions of the paralyzed arm. The inputs to the FES system are the stimulation pulse widths for the nerves and muscles being stimulated. One focus of our work is on efficiently identifying input/output models for use for feedforward controllers of FES systems.
#Functional electrical stimulation trial#
With the aid of computer simulation and trial and error a stimulation pattern was chosen to produced the arm trajectory in the video. The video on top shows a person with a high spinal cord injury who's arm is controlled by an implanted neuroprosthesis. Electrical stimulation to the muscles can be controlled externally by a computer via a transcutaneus RF link. This system can stimulate multiple nerves and muscles to evoke movements of the shoulder, elbow, wrist, and fingers. Our colleagues have developed an implantable upper extremity neuroprosthesis for people with tetraplegia.
We work in close collaboration with Case Western Reserve University and the Cleveland FES Center. Our research focuses on using FES to restore reaching motions to persons with high spinal cord injuries who have little or no voluntary control over their upper extremities. FES can be used to control skeletal movements in cycling, walking, grasping, and reaching. Functional electrical stimulation (FES) systems can restore various functions to persons with impairments such as spinal cord injury, brain injury, and stroke.
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