The latest triaxial accelerometers may provide the finishing touch to move current research projects into production. This certainly is the case for AcceleGlove, a research project of Jose L. Hernandez Rebollar, Ph.D., at George Washington University. The project's goal is translating the hand gestures of American Sign Language (ASL) to voice and text.
Rebollar's initial prototype used eight dual-axis accelerometers to translate hand gestures. With the two-axis accelerometer, detecting the orientation of the hand, either palm up or palm down, required two accelerometers perpendicular to each other on the back of the hand. For finger-position sensing, a two-axis unit provides the same signal whether the fingers are extended or rolled into the palm. Using the highest sensitivity level (1.5g) of Freescale Semiconductor's MMA7260Q three-axis accelerometer, Rebollar has reduced the number of accelerometers to six. With the three-axis sensors, he can detect when the fingers are rolled up and when the thumb is flipped over. The AcceleGlove can now identify the 26 letters of the alphabet and 48 hand shapes—an increase of six functions over the initial prototype.
Having all three accelerometers in a single package is a key factor in turning the research project into a manufacturable product. To get the same functionality Rebollar gets from six three-axis accelerometers, he would need as many as 12 dual-axis units. This approach reduces the price and considerably simplifies the circuitry and mounting.
The system is straightforward. A triaxial accelerometer on each finger and one on the back of the palm provide the motion inputs to a microcontroller mounted on the back of the palm. A simple program translates the signals into hand shapes.
A second part of the project is an ASL dictionary. The dictionary requires a large text file, a hand position to text-search engine, and the glove with an additional triaxial sensor at the elbow and another at the shoulder. By wearing the AcceleGlove, users can search the computer for the meaning of motions or signs in written text. The ultimate capability could be a real-time translator, but, as Rebollar says, he is "working from the ground up" developing the glove with the triaxial accelerometers.