Joystick-mouse brings CAD to disabled engineers

Vancouver, BC--Imagine sitting at your CAD workstation and typing commands by poking the keyboard with a stick clamped between your teeth. That's how Larry Boden, a quadriplegic engineering draftsman, operated AutoCAD until the invention of the Jouse(TM). Developed by the Neil Squire Foundation (NSF), the Jouse combines the world's first Hall-effect joystick with both breath- and bite-operated pneumatic switches to emulate the function of a keyboard and mouse.

The joystick design consists of four 0.16- x 0.10-inch Hall-effect sensors--provided by Allegro Microsystems (Worcester, MA)--positioned at 90-degree intervals around a doughnut-shaped circuit board. A steel concentrator helps direct magnetic flux into the sensors. Sealing the entire assembly in epoxy excludes moisture.

Other Applications
  • Robust, portable joysticks

  • Motorized wheelchair control

  • Small-angle sensor

The sensors detect the position of a cylindrical rare-earth magnet mounted to the shaft of the joystick. Located within the hole of the doughnut-shaped sensor board, the magnet induces a voltage in each sensor that is proportional to the distance between the magnet and sensor. Simple electronics subtract the north voltage from the south and east from west. Converted to a frequency, the result is conditioned, amplified, and fed to the computer's mouse port.

Engineers evaluated numerous commercially available joysticks, but none met their unique demands. "We needed something that was compact, reliable, had a hollow shaft, and was sealed so that it could be washed," says Yoel Guttmann, an R&D engineer at NSF.

The hollow shaft contains two pneumatic tubes leading to a mouthpiece. One tube works like a straw, the second connects to a rubber bite-bladder integrated into the mouthpiece. Both tubes transmit pressure changes to miniature sensors--supplied by Micro Pneumatic Logic (Fort Lauderdale, FL)--located in the Jouse's control unit. "With pneumatics, we keep switches and electricity out of the user's mouth," says Guttmann.

To operate the Jouse, the computer operator clamps the working end of the joystick between his or her teeth and uses head movements to steer the cursor. Sips and puffs on the mouthpiece select mouse buttons and allow typing via ezMORSE, an NSF-developed Morse-code program. Although the system appears cumbersome, several disabled users can type more than 30 words per minute.

Nipping the bite-bladder toggles the Jouse from mouse emulation to keyboard emulation. Limited only by software, the bite switch can control other functions as well. For instance, it can simulate holding one of the mouse keys for easy drag-and-drop. Or it can place the Jouse into an X-and-Y mode in which puffs and sips, not head movements, direct the cursor.

Engineers feel that defining the configuration of sensors and magnets was the biggest design challenge encountered during this project. They wanted the magnet to be as small as possible, yet contain a .25-inch-diameter hole to accommodate pneumatic tubes. "We needed the smallest OD and the largest ID," says Guttmann. After settling on the general arrangement, he used a supercomputer to model the flux-density variation for various magnet shapes and materials.

Five years of work and extensive feedback from disabled computer operators resulted in the unique design. Potential customers contributed greatly to the overall concept, as well as to ergonomic details like the mouthpiece and breath and bite switches. For instance: "We found out that disabled users want something that attaches to the workstation and not to them," says Guttmann. "Head-mounted devices reduce the dignity of a group of people who already make compromises in this area."

Additional details...Contact Yoel Guttmann, Neil Squire Foundation, 1046 Deep Cove Rd., North Vancouver, BC V7G 1S3, Canada, (604) 875-2674

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