Yes, you absolutely need that, not implementing something like that would a liability issue. Systems like this need an integrated E-stop they is trigged independently of the motion controller. I'm imagine a layered system where the controller can issue a "stop" or the operator or some sensors or as a last resort a bumper presses a microswitch with cuts power to the motors. Like a few switches in parallel and if any one of them get tripped the power is cut to the relays that connect power to the motor and the motor lead short putting the motor in "brake mode" This would also have the effect of stopping the motors after a power failure. Using energy in the motors coils to brake motion.
None of this is rocket science. Hire an engineer with experience in factory automation. Or just skim through some text books Half of the design of such a system, is self monitoring. You need a design that remains safe even after a component failure. Some times it is easy, like using normally open relays so power is disconnected if control signal sops. We are talking about a system that will cost many millions of dollars and will need a full time engineering staff to design and build. On Wed, Aug 23, 2017 at 9:19 AM, Rick Gresham <[email protected]> wrote: > 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 > -- 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
