ppicot@irus.rri.uwo.ca (Paul Picot) (06/13/91)
I have a problem that I think sci.electronics participants might
find interesting: I need to track the position and orientation of a
hand-held object in real time and I'm hunting for ideas. I've heard
this called a 6DOF (6 degrees of freedom) tracker. Let me narrow down
the problem a bit:
Physical dimensions: must be easily hand held by one hand for many
minutes, so must be fairly light (less than 200 grams or so) and compact
enough to fit in one hand. A cable will run to the device anyway, so an
extra cable to the tracker is not a problem.
Accuracy: better than 2 mm in position and 1 degree in orientation.
The measurements will all be relative to a 'home' position that is
periodically reset.
Field of view: 50 cm or so in all three dimensions.
Update rate: roughly 50 times/second or better.
Movement speed: zero to at least 20 cm/sec and 1 radian/sec
The operating environment is normal room light, normal office noise.
The tracking device must be electrically quiet though -- low power radio
is OK, but spark gaps are definitely out.
We have tried taut stings and articulating arms so far. Both are
too restrictive to movement, so we are looking for non-contact methods.
Radio, acoustic, optical and inertial techniques spring to mind: Does
anyone have any experience or ideas with this?
The current idea-of-the-week is inertial tracking. Does anyone have
any experience, specs, or sources for (small) accelerometers?
Price is not a real concern, nor is commercial availability -- we
are quite prepared to develop our own system, but I'ld rather not re-
invent the wheel if possible.
Ideas anyone? Thanks. Respond by email (or to sci.electronics) and
I'll summarize to the net if interest warrants.
Paul Picot
ppicot@irus.rri.uwo.calongj@lonex.radc.af.mil (Jeffrey K. Long) (06/15/91)
I remember seeing at a trade show a tracking device that worked on the idea of having 3-orthogonally mounted coils set up to receive energy that was transmitted from a local rf source. By receiving the energy in the three coils and doing some real-time solving of the simultaneous equations resulting, you could locate the objects orientation. I believe the application they had in mind was for mounting it on a helment or someone's glove, and monitoring their movements in the "cockpit of the future". The receiver coil was only about 3cm square and had tiny wires coming from it to the reciever/processor. If you think about it, you should be able to set you solution to the equations for any reference point, and then calculate your position relative to the reference based upon the zero point. I don't have any other details, this is just what I remeber seeing and it has always stuck with me as a rather elegant solution to the tracking problem. Jeff Long -- ---------------------------------------------------------------------------- Capt Jeff Long Rome Laboratories, Griffiss AFB, NY longj@lonex.radc.af.mil (preferred) Network Design Laboratory jlong@cassiopeia.radc.af.mil (315)330-7751 or (DSN)587-7751
whit@milton.u.washington.edu (John Whitmore) (06/22/91)
In article <3372@ria.ccs.uwo.ca> ppicot@irus.rri.uwo.ca (Paul Picot) writes: > > I have a problem that I think sci.electronics participants might >find interesting: I need to track the position and orientation of a >hand-held object in real time and I'm hunting for ideas. I've heard >this called a 6DOF (6 degrees of freedom) tracker. While I don't know a POSITION sensor, there is a device (Ultra Sphere? Cyber Sphere?) that has seven degrees of freedom as a hand-held controller. It is a stationary ball with strain gages that measure three directions of translation forces and three axes of torsion as well as detecting squeezing motions. There's one connected to a Silicon Graphics workstation at the UofWA Human Interface Technologies laboratory. Actually using this much information in a single program (something like a walk-through demo) is probably a tad tricky, though; I don't know if it has been worked up that far yet. The benefit of this approach is that the stationary sphere can be mounted on a strut which (because the sphere doesn't really move or rotate) will not get in the user's way. John Whitmore
rlk@telesoft.com (Bob Kitzberger @sation) (06/26/91)
In article <3372@ria.ccs.uwo.ca> ppicot@irus.rri.uwo.ca (Paul Picot) writes: > > I have a problem that I think sci.electronics participants might >find interesting: I need to track the position and orientation of a >hand-held object in real time and I'm hunting for ideas. I've heard >this called a 6DOF (6 degrees of freedom) tracker. I've seen a device in use at UCSD's Visualization Laboritories (at the San Diego Supercomputer Center, 619/534-5055). A tiny hand-held device, I believe, transmits some kind of signal that is triangulated on by a sete of receivers. S'all I know... maybe UCSD/SDSC's viz lab can answer questions in detail. Ask for the Visualization Lab, and ask for one of the Silicon Graphics gurus. The device is used to digitize three-dimensional objects, such as human facial features, skeletons, etc. .Bob. -- Bob Kitzberger Internet : rlk@telesoft.com TeleSoft uucp : ...!ucsd.ucsd.edu!telesoft!rlk 5959 Cornerstone Court West, San Diego, CA 92121-9891 (619) 457-2700 x163 ------------------------------------------------------------------------------ "and when after three or four hours' amusement, I wou'd return to these speculations, they appear so cold and strain'd, and ridiculous, that I cannot find in my heart to enter into them any further." -- David Hume, "Treatise of Human Nature"