There are many ways to measure position. With something this big and expensive I would suggest some redundancy. The cost of measuring is tiny computer t the cost of a 100f gantry.
One of the bigger problems I see is flex in the system and thermal expansion. If the goal is 1/8th inch over a 100 foot run then their needs to be some design margin so you'd be designing for something like 1/16th inches. I doubt that simply measuring how for you are along a steel bed will work. Yes you could try but the beam itself will bend and change it's length. You would have to measure absolute position relative to fixed locations on the floor. I don't think I've ever seen a building made to close tolerances either. The sports are not going to be square to each other or level or vertical. I't not hard to compensate for the not-perfect mechanics. You can also continuously calibrate the sensors from know references inthewtork space On Wed, Aug 23, 2017 at 2:21 AM, andy pugh <[email protected]> wrote: > On 23 August 2017 at 05:17, Dave Cole <[email protected]> wrote: > > > A 3D laser tracker was part of the control scheme to track the actual > tool > > head location. > > That way standard rack could be used for the positioning mechanism and > the > > position could be corrected on the fly via the laser tracker. > > That might still be a good idea, because it seems that such a machine > might need to be modular, so units that are friction-drive on standard > rolled steel sections seems like a likely solution. > There will be some tyre-creep, but the laser (or acoustic) feedback > could correct it. > I heard of a system where you have a microphone in each corner of the > room and a "clicker" that is localised in space by clever acoustic > processing. > The application was measuring accelerometer positions when > instrumenting a car or van body. If you have ever "walked" a Faro arm > round a van body you would know why the system seemed attractive. > > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1916 > > ------------------------------------------------------------ > ------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
