Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!ogicse!milton!brucec%phoebus.labs.tek.com@RELAY.CS.NET From: brucec%phoebus.labs.tek.com@RELAY.CS.NET (Bruce Cohen;;50-662;LP=A;) Newsgroups: sci.virtual-worlds Subject: Re: rambling on motion Message-ID: <11726@milton.u.washington.edu> Date: 26 Nov 90 18:04:35 GMT References: <11564@milton.u.washington.edu> Sender: hlab@milton.u.washington.edu Organization: Tektronix Inc. Lines: 42 Approved: hitl@hardy.u.washington.edu In article <11564@milton.u.washington.edu> mailrus!gatech!hydra2b.cs.utk.edu!eve rs@uunet.UU.NET (Eric Evers) writes: > > Une could use intergrated silicon chip acceloratomaters. I saw some of these > in popular science a couple of years ago. It was the cover story on > micro-machines. Basically there is a small mass(block) of silicon etched > out from the rest of the wafer. It is connected to the rest of the > wafer/chip by a small beam. When you accelerate the mass in a direction > perpindicular to the beam, the mass deflects the beam. This bent beam > has its resistance to current altered, which you can measure with a > wheatstone bridge probably. You need three of these (mabey six) for > each dimention of motion. You intergrate the accelerations to get > velocity, and intergrate the velocities in three space to get position. This is essentially the same principle as the piezo-electric accelerometers which have been in use in aerospace instrumentation for the last 20 or 30 years: a known mass attached to a block of piezo-crystal (I forget what crystal was most common; it might have been quartz) which emits a small amount of charge when acceleration squeezes or distends the mass/crystal system. A very sensitive charge amplifier can measure the charge flux (on the order of a few thousand electrons/sec.). Anyone know how much these gadgets cost these days? > > Every now and then an vertual-naught would have to stand at attention > to recalibrate. > That's the problem with acceleration- or velocity-based orientation systems: they drift. As I remember from a few years back, optic-fiber gyros drift on the order of a few degrees per hour, so maybe calibration wouldn't be onerous. On the other hand, I'd hate to have to stop what I wsa doing in the middle of an intense session (say level 3 on Lt. Worf's combat simulation) to stand up straight for recal. -- ------------------------------------------------------------------------ Speaker-to-managers, aka Bruce Cohen, Computer Research Lab email: brucec@tekchips.labs.tek.com Tektronix Laboratories, Tektronix, Inc. phone: (503)627-5241 M/S 50-662, P.O. Box 500, Beaverton, OR 97077