A voice-controlled computer system for multichannel functional electrical stimulation (FES) of the paralyzed hand has been developed. The computer system is composed of a personal computer NEC PC-8801 mk II with a voice recognition board NEC PC-8012-05, and a digitizer Logitec K-510.
Stimulation patterns for restoring three kinds of prehension, such as cylindrical grasp, key grip and parallel extension grip, are prepared with the digitizer and stored as three data files in a floppy disc system. Speech inputs from a head-set microphone are processed by the voice recognition system and are used as commands for selection of a prehension pattern and execution of the hand movement. Angles of the neck flexion and extension detected by an angular sensor utilizing mercury are used for proportional control of the hand movement.
As voice commands for selection of a prehension pattern, ‹CUP›, ‹KEY› and ‹CARDS›, which correspond to cylindrical grasp, key grip and parallel extension grip, respectively, are used. These commands select one of the corresponding data files in the floppy disc system and set it to a work area of a RAM. After selecting a pattern, a start command is given by the voice of ‹START›, resulting in an acceptance of proportional control signal and readout of the corresponding stimulating data. Thus, multichannel stimulating outputs are applied to the nerves distributed in the paralyzed hand muscles. A voice command ‹HOLD› causes holding of constant stimulating voltages at the state when the command was given. Restart of the proportional control can also be ordered by the voice command ‹START›.
Using this voice-controlled system, easy volitional control of the paralyzed hand in a C 5 quadriplegic could be obtained successfully.
