mmoss@csws8.ic.sunysb.edu (Matthew D Moss) (12/20/90)
(* Hey Gladys, hand me the blow torch.. *) (* FLAME ON! *) Just kidding, but I am disappointed at this group. I posted a very simple question a week or so ago, and didn't get a SINGLE response to the question. What is it, you don't like me? :) I want to ask once more time. I am starting a project that will require locating some object (transmitter, reflector, or something) in three-space by way of infrared beams or the like. I know the math (i.e. the intersection of three spheres) but I need to know more about the specific components of the objects or detectors. I went to my school's Engineering Library and looked around. The books I found, though, were past me. If someone could mail me personal knowledge, or the names of simple books (ones that a sophomore in Mathematics/Comp Sci field could use), about this subject, I would deeply appreciate it. --------------------------------------------------------------- Matthew Moss mmoss@libserv1.ic.sunysb.edu "You are what you eat." -- someone else "But I just had eggplant!" -- me ---------------------------------------------------------------
jbm@eos.arc.nasa.gov (Jeffrey Mulligan) (12/20/90)
mmoss@csws8.ic.sunysb.edu (Matthew D Moss) writes: >(* FLAME ON! *) > Just kidding, but I am disappointed at this group. I >posted a very simple question a week or so ago, and didn't >get a SINGLE response to the question. What is it, you >don't like me? :) I like you but my emplyer doesn't. Some of us are supposed to be working instead of answering questions for random strangers. However, technology transfer is one of NASA's missions... > I am starting a project that will require locating some >object (transmitter, reflector, or something) in three-space >by way of infrared beams or the like. One nice technique which is used for eye movement recording is known as the "search coil" method. The object you want to track (say a monkey's eye) has a small assembly mounted (with a surgical implant) that contains three pickup coils on mutually perpendicular axes. The animal is seated inside an apparatus containing three large field coils that create a magnetic field. Each of the three field coils is modulated at a different [high] frequency, so the signals from the pickup coils can be demodulated using lock-in amp. techniques. The device operates on the principle that the induced current in the pickup coil is proportional to the field strength times the cosine of the angle between the field and the coil axis. For eye movement recording, the goal is usually to have the signal depend only on direction of gaze, and not upon head position. To this end, people go to some trouble to insure that the magnetic field is very uniform. On the other hand, if you want to measure position, you can set up fields with gradients and use the strength to recover position. It would help to have a computer if the fields are curved with nonlinear gradients. You might be able to do better by doubling the number of field modulation frequencies, and for each axis doing a differential measurement instead an absolute measurement. Commercial systems sell for $5-10K, I believe, but if you have time and access to scrap parts I imaging you could put something together for quite a bit less. You didn't mention what kind of accuracy you are looking for. -- Jeff Mulligan (jbm@eos.arc.nasa.gov) NASA/Ames Research Ctr., Mail Stop 262-2, Moffett Field CA, 94035 (415) 604-3745
whit@milton.u.washington.edu (John Whitmore) (12/20/90)
In article <1990Dec19.202741.24898@sbcs.sunysb.edu> mmoss@csws8.ic.sunysb.edu (Matthew D Moss) writes: > > I am starting a project that will require locating some >object (transmitter, reflector, or something) in three-space Almost any old book on radar would help with basic concepts. You might consider making your 'object' a radio receiver. Then transmit to it a swept-frequency audio tone. When a microphone at the triangulation station receives an in-phase sound input, the object is exactly an integer number of audio wavelengths from the interrogator. You can sweep the transmitted audio signal and time the phase-matching times (using a phase comparator) with respect to the audio frequency, to tell the distances. Of course, this could be done with various other energy sources, but an AM radio makes a readybuilt easy beacon for your object, I would think. John Whitmore
cgordon@vpnet.chi.il.us (Crash Gordon) (12/21/90)
>Author: [Matthew D Moss] >(* FLAME ON! *) > I am starting a project that will require locating some >object (transmitter, reflector, or something) in three-space The problem is it's _your_ project, why should _I_ design it for you? The way your first request read, it was like you were asking me to do your homework. But I'll give you a good pointer: 1- Buy a Nintendo Power Glove 2- Look in back issues of Byte Magazine. Somewhere in there is a sidebar telling how to interface the power glove to your PC. The PG includes an ultrasonic 3D position-sensing system. It's all built and ready to program! ----------------------------------------------------- Gordon S. Hlavenka cgordon@vpnet.chi.il.us Disclaimer: Yeah, I said it. So what?
bame@hpfcbig.SDE.HP.COM (Paul Bame) (12/22/90)
> mmoss@csws8.ic.sunysb.edu (Matthew D Moss) writes: > > I am starting a project that will require locating some > >object (transmitter, reflector, or something) in three-space > >by way of infrared beams or the like. > jbm@eos.arc.nasa.gov (Jeffrey Mulligan) writes: > One nice technique which is used for eye movement recording > is known as the "search coil" method. The object you [etc...] I just watched a virtual environment video from NASA (AMES?) and they mention just slapping on one of their compact 6-axis (x, y, z, roll, pitch, yaw) transducers - like on a dataglove. I imagine it's a related or identical technology - go ask in sci.virtual-worlds and I predict you'll get much better response. I hear via the partially informed that they are expensive. I think the company which makes the sensors is mentioned in the video and is, not surprisingly, located in Si valley. -Paul "Spice is the Variety of Life" bame@hpfcbig.sde.hp.com N0KCL