The building will likely typical concrete tilt-up or something similar. The system will have to track/control position in real time. Collisions will be very expensive so redundant systems are easily justified. It may need some sort of collision avoidance system as a back up, too. If the crosses some boundary, everything stops. Stoppages are not a big problem, bumps in the dark are.
I've wondered about redundant control systems but haven't come across any information yet. Anyone remember the triple Tandem non-stop systems NASA used? Three fault-tolerant systems running in parallel. If they came up with different results, it was odd-man-out. Probably don't need to go that far for this application unless something available off the shelf affordably. > On Aug 23, 2017, at 8:56 AM, Chris Albertson <[email protected]> > wrote: > > 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
