1993 VR Conference Proceedings

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Biosignal Processing in Virtual Reality Applications

R. Benjamin Knapp
Department of Electrical Engineering
San Jose State University
One Washington Square
San Jose CA 95192-0084

1. Biosignal Processing

Every muscle contraction, every eye movement, every thought creates an electric signal that can be measured on the surface of the human skin. The technique by which these signals are analyzed and recognized is called biosignal processing. Some of the uses of biosignal processing are in physiologic and behavior analysis. Only very recently has this technique been used to create a new man-machine interface.

2. The BioMuseTM and BioMuse RF TM Systems

The BioMuse is a complete biosignal processing system. Using a real-time digital signal processor as its core it is able to measure EMG (electric signals coming form the muscles), EOG (electric signals coming from the eyes), and EEG (electric signals coming from the brain) and process these signals in order to create a useful controller for a computer (or any digitally controlled device - see section 3). The system consists of three parts - the electrode attachment, the BioMuse box itself, and a personal computer.

The electrode attachment for EMG measurements takes the form of a flexible band which can be placed around the bicep, tricep, forearm, quadricep, or any muscle under voluntary control. The electrode array for measuring EOG and EEG is contained in a thin headband. This headband can also measure EMG emanating from a jaw clench.

The electrode attachments are connected directly to the BioMuse system which is then connected to a personal computer. For the BioMuse RF, there is no direct connection between the electrode attachment and the BioMuse box. This allows for complete freedom of motion when using a computer.

The personal computer is used to customize the BioMuse system to the user. Once this is accomplished, the BioMuse can be used as a direct connection between muscle tension or eye motion and any digitally controlled electronic device.

3. Disabled Persons and Virtual Reality

3.1 Customization

In order to create a human-machine interface that can be used by disabled individuals, the BioMuse system is completely customizable. For example, to use the eye position to control the computer, the system steps the user through a one minute calibration process which determines where a person is looking to within two degrees of arc. If the user cannot stabilize his/her head position then the computer can establish a minimum amount of eye motion which is necessary before it responds to the motion. If jaw tension is also desired as a control input to the computer then the sensitivity to jaw clench can be adjusted. This type of customization is possible for all controller configurations.

3.2 Applications

Two applications of the BioMuse system for disabled individuals are controlling a word processor and manipulating within a virtual environment.

To control a word processor, the user must calibrate the system as discussed previously. Then, using a software keyboard, the user can choose letters and words using eye position. The individual may make a selection by clenching his/her jaw, flexing an arm, or whatever is appropriate for the disability. As mentioned previously, if the person cannot hold the eyes still, a threshold can be introduced to cause cursor motion only when a large eye movement occurs.

The BioMuse system can also be used to move throughout a virtual environment. To move left, right, up, or down within the computer image the person need only look in that direction. If the display is a true three dimensional display, the BioMuse system can cause the computer scene to move in or out using the convergence of the eyes. Items can be selected within the scene using muscle tension as described previously.

4.0 Conclusion

The BioMuse system uses the technique of biological signal processing to create a natural interface between human and computer. Because of its capability to be customized to each individual user, it is a perfect interface for any person independent of their physical capabilities.

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