Wednesday, July 1, 2009

Technology options

The following is a list of the technology options we are considering for obtaining information about a traveler's movement and their cane handling technique.

  • Inertial measurement - uses movement information supplied by the Wii Remote's built-in accelerometers (and possibly the Wii MotionPlus gyrometers). This gives relative movement information from inside the Wii Remote's frame of reference.

    • Good for: detecting taps, determining cane orientation, detecting cane movement in the absence of other sensing methods

    • OK for: measuring arc width

    • Not good for: determining cane position, detecting veering

  • Light strip - an array of computer-controlled infrared lights on the floor which are visible to the Wii Remote's IR sensor. Like the light bar method this gives us an idea of the traveler's absolute position.

    • Good for: very precise arc width measurement when lights are in view, precisely determining traveler location, detecting veering

    • OK for: might be able to measure cane-centeredness and coverage

    • Not good for: easy installation (requires careful positioning of light strips or installation of walking surface)

  • Light bar - similar to the Wii's Sensor Bar this method uses the same principle as the light strip method - an array of infrared lights which can be seen by the Wii Remote's IR sensor gives us an absolute position reference to work with. In this case, several lights are mounted horizontally at the end of the course and are seen by the Remote's IR sensor.

    • Good for: arc width measurement, detecting veering, determining traveler location, simple setup

    • OK for: might be able to measure cane-centeredness and coverage

    • Not good for: less accurate than light strip

  • Rear-facing IR sensor - a second Remote or IR sensor mounted on the cane is positioned to view the traveler. Markers or lights affixed to the traveler's clothing are seen by the Remote or sensor.

    • Good for: very precise cane-centeredness and wrist isolation measurement, precise measurement of coverage if arc width is known

    • OK for: might be able to measure arc width

    • Not good for: detecting veering, determining traveler position

  • External camera - a computer-connected video camera at the end of the course records the traveler's progress. Computer vision software analyzes the video to determine information about traveler and cane movement.

    • Good for: measuring cane-centeredness and wrist isolation, detecting veering, measuring coverage if arc width is known, easy installation

    • Not good for: determining traveler location, precise measurement of arc width or coverage, long courses - even a 30-foot course may be too long

As no single method provides all necessary information, it is very likely that the ultimate embodiment of the WiiCane system will use two or more complementary methods. We will continue to refine the inertial measurement methods and investigate the other options.

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