simulation@uflorida.cis.ufl.edu (Moderator: Paul Fishwick) (07/05/90)
Volume: 16, Issue: 6, Wed Jul 4 22:42:25 EDT 1990 +----------------+ | TODAY'S TOPICS | +----------------+ (1) Building Simulations with BONeS (2) Dictionary of Simulation Terms (3) RE: Robot Simulation (4) RE: Virtual Reality vs. Simulation (5) RE: Virtual Reality vs. Simulation * Moderator: Paul Fishwick, Univ. of Florida * Send topical mail to: simulation@bikini.cis.ufl.edu OR post to comp.simulation via USENET * Archives available via FTP to bikini.cis.ufl.edu (128.227.224.1). Login as 'ftp', use your last name as the password, change directory to pub/simdigest. Do 'type binary' before any file xfers. * Simulation Tools available by doing above and changing the directory to pub/simdigest/tools. ----------------------------------------------------------------------------- Date: Tue, 3 Jul 90 10:44:05 PDT From: smyers@luna.hac.com (Steven Myers) To: simulation@bikini.cis.ufl.edu Subject: Re: Discussing BONeS in this group Newsgroups: comp.simulation In-Reply-To: <23330@uflorida.cis.ufl.EDU> Organization: Hughes Aircraft Co., El Segundo, CA Cc: My division has recently bought Comdisco's Block Oriented Network Simulator (BONeS) and I have begun trying to build my own custom databases for it. I would like to know if there are any other BONeS users out there and if this would be the appropriate news group to discuss building simulations in BONeS. The simulation I am currently building is based on the MAC layer protocol of an FDDI token ring network. Thank you for your time. -- Steven ------------------------------ Date: Tue, 3 Jul 90 08:19:05 PDT From: Doug Schwartz <tessi!dad.MENTOR.COM!dschwartz@bikini.cis.ufl.edu> Apparently-To: tektronix!comp-simulation Newsgroups: comp.simulation Path: dschwartz From: dschwartz@mentor.com (Doug Schwartz) Subject: definitions of terms Organization: mktg Distribution: usa Date: Tue, 3 Jul 90 15:18:51 GMT I've been trying to put together a little glossary/dictionary of terms used in (digital) simulation/modeling. I was hoping someone on the net could direct me to a (text?) book that takes pains to carefully define its terminology. For example, I have seen the term "part" used to describe both a physical object and a software object. Please email me your comments (watch those snide remarks about Mentor hiring bone-head contract tech writers 8-) ) and I'll summarize and post them, if anyone's interested. -- Doug Schwartz Contracting 8.0 days weakly. Mentor Graphics Beaverton, Oregon 97005 dschwartz@mentor.com (503) 626-7000 x2557 tektronix![sequent,tessi]!mntgfx!dschwartz ------------------------------ Date: Wed, 4 Jul 90 22:30:45 -0400 From: Paul Fishwick <fishwick@fish.cis.ufl.edu> To: simulation@ufl.edu Subject: Robot Simulation [[Forwarded from comp.robotics -PAF]] >From uflorida!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!aero!nadel Wed Jul 4 19:36:54 EDT 1990 Article 374 of comp.theory.dynamic-sys: Path: uflorida!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!aero!nadel >From: nadel@aerospace.aero.org (Miriam H. Nadel) Newsgroups: comp.theory.dynamic-sys Subject: Re: Flexible Robot Simulator Date: 3 Jul 90 21:56:50 GMT References: <11485@rasp.eng.cam.ac.uk> Reply-To: nadel@aero.UUCP (Miriam H. Nadel) Organization: The Aerospace Corporation, El Segundo, CA In article <11485@rasp.eng.cam.ac.uk> jjs@eng.cam.ac.uk (Jeffrey J. Shifman) writes: >I am looking for either > >(1) suggestions for how to simulate a flexible robot (say, for simplicity, > two flexible links modelled as Euler-Bernoulli beams, with a single > torque input to each one) with a peculiar feedback law; or, > >(2) a simulator that can deal with the system described above. > >I have tried a 'naive' modal approach but it doesn't seem to work. >Any suggestions appreciated. > There are three basic approaches to modeling flexible robots. The modal approach is pretty common but the big drawback is the inaccuracy introduced by the need for modal truncation. In addition, it's not simple to deal with mechanisms. That is, the modal approach doesn't combine easily with a model of, say, a motor. The second approach is to discretize the flexible links, e.g. via a finite element model. This handles mechanisms much better but is very intensive computationally if you want to get halfway decent result. It also ignores the effect that the elastic motion of the beams has on the rigid body motion of the joints. The third approach uses generalized coordinates to derive the equations of motion and then incorporates the joints using Lagrange multipliers. This is the only approach which allows both the rigid body motion and elastic motion to be influencing each other. I would suggest looking up the two articles by Nagarajan and Turcic in the June 1990 issue of the ASME Journal of Dynamic Systems, Measurement and Control (which is also a generally good source of info on robotics and modeling). Miriam Nadel -- One of the 20% of Americans who own stock. nadel@aerospace.aero.org ------------------------------ Date: Tue, 3 Jul 90 14:23:07 EST From: Richard E. Nance - SRC <srcnance@popeye.cs.vt.edu> To: simulation@bikini.cis.ufl.edu Subject: Virtual Reality vs. Simulation Cc: fishwick@fish.cis.ufl.edu I must admit to having only seen the term "virtual reality" on reading this item in the Digest. Thus, my understanding is based on Leaback's description and Fishwick's comments. Nevertheless, I offer the observation that all too often, basic principles are overlooked that when considered lead to instant insight. Two such come to mind in this case. A model is an abstraction of reality, and in the earlier philosophical treatment by Churchman (as I recall), reality is not a model. Investigation with reality is experimental inquiry (statistical studies of pertinent factors with non- pertinent factors controlled or eliminated). A simulation is experimentation WITH A MODEL presumed to be sufficiently representative of reality to MEET PRESCRIBED STUDY OBJECTIVES. The two affecting principles are (1) the use of a model, which in the case of virtual reality (in my limited understanding) attempts to represent an encapsulating environment, and (2) study objectives are of major importance in assuring model validity and model acceptability (perhaps moreso than the degree to which physical aspects of reality are captured). If I develop a model of the software components surrounding an operating system executive in order to test the communications paths and verify protocols, is this a deterministic simulation of virtual reality, or both? (References om virtual reality are welcomed.) Dick Nance ------------------------------ Date: Wed, 4 Jul 90 22:29:40 -0400 From: Paul Fishwick <fishwick@fish.cis.ufl.edu> To: simulation@ufl.edu [[Forwarded from sci.virtual-worlds -PAF]] >From uflorida!rex!samsung!cs.utexas.edu!yale!mintaka!mit-eddie!uw-beaver!milton!steve@titan.tsd.arlut.utexas.edu Wed Jul 4 22:29:09 EDT 1990 Article 273 of sci.virtual-worlds: Path: uflorida!rex!samsung!cs.utexas.edu!yale!mintaka!mit-eddie!uw-beaver!milton!steve@titan.tsd.arlut.utexas.edu >From: steve@titan.tsd.arlut.utexas.edu (Steve Glicker) Newsgroups: sci.virtual-worlds Subject: Re: what is a virtual reality ? Date: 3 Jul 90 23:47:45 GMT References: <23731@uflorida.cis.ufl.EDU> Sender: hlab@milton.u.washington.edu Organization: Applied Research Labs, The University of Texas at Austin Approved: hitl@hardy.u.washington.edu Posted-Date: 3 Jul 90 23:47:45 GMT >From: peterl@ibmpcug.co.uk (Peter Leaback) Message-ID: <9006221738.AA20908@ibmpcug.CO.UK> >>What is the difference between a virtual reality and a simulation? A good question. >>My answer is consistency. ??? >>A stick model of a water molecule is a simulation of a real water >>molecule, but if you jump into a swimming pool full of stick water >>molecules, you won't get wet. The stick water molecules have many >>inconsistances compared to real molecules, so when one trys to interact >>the stick molecules with real ones, you have problems. >>But if a man made up of stick model molecules jumps into that same >>swimming pool, he WILL get wet. Simulations are usually intended for a purpose. Stick water molecules are not intended for this purpose. This example simply illustrates the incorrect use of stick water molecules. The stick water molecule is not invalid for its intended purpose. Is is usually not wise to examine a simulation model without regard to its purpose. > Simulation and virtual reality are not at odds I agree. -- Steven Glicker Applied Research Laboratories The University of Texas at Austin (steve@titan.tsd.arlut.utexas.edu) ------------------------------ END OF SIMULATION DIGEST ************************