ron@vicorp.com (Ron Peterson) (09/19/90)
It just occured to me that perhaps the ultrasonics from a
PowerGlove could be removed and used to read the position and
orientation of a set of lcd tv or shutter goggles. Any thoughts
on how to prevent interaction with the ultrasonics of a PowerGlove worn
on the hand if both were used at the same time? (Would probably help
if they were set up orthogonal to each other to minimize crosstalk.
Perhaps at slightly different elevations also.) Anyone have any
experience with crosstalk in multidimensional short range ultrasonic range
sensing in small spaces?
ron@vicorp.COMjmunkki@hila.hut.fi (Juri Munkki) (09/20/90)
In article <7806@milton.u.washington.edu> ron@vicorp.com (Ron Peterson) writes: >It just occured to me that perhaps the ultrasonics from a >PowerGlove could be removed and used to read the position and >orientation of a set of lcd tv or shutter goggles. Any thoughts >on how to prevent interaction with the ultrasonics of a PowerGlove worn >on the hand if both were used at the same time? (Would probably help >if they were set up orthogonal to each other to minimize crosstalk. >Perhaps at slightly different elevations also.) Anyone have any >experience with crosstalk in multidimensional short range ultrasonic range >sensing in small spaces? It shouldn't be a problem to have to ultrasonic sensors. In fact, you only need one set of transmitters or receivers. I haven't received my PowerGlove yet, so I don't know if the glove has a receiver or transmitter, but since a receiver is probably more expensive than an ultrasonic transmitter, they might have put a receiver in the glove and transmitters in the frame. All you have to do to get your headset position is to use the same transmitters and read the position. If they put a transmitter on the glove and receivers in the frame, you could alternate between the two devices. It will take you twice as much time to read the position, but at least it isn't impossible. As long as the PowerGlove hardware and firmware are secrets, it might be a problem to work around some of their code. Does anyone know if the powerglove only has a position sensor or does it somehow know the orientation of the glove? Are they using three sensors to detect orientation? A HMD needs orientation even more badly than location. There used to be a low-cost device for that Macintosh that could be used as a replacement of the mouse. They decided that they had the wrong marketing approach and now the price is so high that only users that absolutely need the device will get it (mostly handicapped users). Would anyone want to help me to build a device that connects the sega 3D glasses and the powerglove (or the computer version of that when it comes out) to a Macintosh ADB bus? My serial ports are always in use and I'd like to put these devices on the ADB bus where they belong. I need some help deciding what processor to use (needs two serial ports and a few I/O lines), but with some help from my friends, I'll probably be able to design the rest. ____________________________________________________________________________ / Juri Munkki / Helsinki University of Technology / Wind / Project / / jmunkki@hut.fi / Computing Center Macintosh Support / Surf / STORM / ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pepke@SCRI1.SCRI.FSU.EDU (Eric Pepke) (09/20/90)
The way you avoid crosstalk is simply not to run the transducers at the same time. The way it works is that you send a burst to one of the transmitters and time how long it takes for the burst to trigger all the receivers, with a suitable timeout. You have to do this for all the transmitters sequentially. Eric Pepke INTERNET: pepke@gw.scri.fsu.edu Supercomputer Computations Research Institute MFENET: pepke@fsu Florida State University SPAN: scri::pepke Tallahassee, FL 32306-4052 BITNET: pepke@fsu Disclaimer: My employers seldom even LISTEN to my opinions. Meta-disclaimer: Any society that needs disclaimers has too many lawyers.
nagle@uunet.UU.NET (John Nagle) (09/22/90)
>Anyone have any >experience with crosstalk in multidimensional short range ultrasonic range >sensing in small spaces? > ron@vicorp.COM Yes, I've worked with such problems in robotics. If you have a fixed set of "speakers" generating ultrasonic chirps, you can have as many microphones as you want reporting position. The "speakers" take turns generating chirps. If you want a position reading every 1/30 sec, you can have each of 3 speakers generating a chirp every 1/90th second, or every 11ms. This gives you a maximum working distance of 11 feet between speaker and microphone. John Nagle