Personally, i insert more limitation in my kinematics for generate somethings similar to "soft limit" ... but the only way is possible to do thes is with a if statement ... at every cicle of kinematic save world->z to your var than control if yourvar is equal or not to your limit .... at these point you can emit a asignal or use last value or yourvar to "stop" the joint[2] at yourvar position. No other possibilities ... I think is not a good work for developper make a func for addictional soft limit working only for cartesian makines .... and make a funk working with all kinematics is very difficult (or to speack better, a very long job) ...
I think we should already be very happy with everything that the developers we already do to improve and make lcnc available as it is now. bkt 2017-07-03 21:22 GMT+02:00 Les Newell <les.new...@fastmail.co.uk>: > Hi Jeff, > > Sorry, I probably didn't phrase it right. I understand that deceleration > on soft limits for joints on a non cartesian machine is a computational > nightmare. What I am after is to specify soft limits in world space, just > like a cartesian machine. I am interested in it for my lathe but it has > applications for many machine types. For example take a hexapod. Depending > on the Z position the head can try to move way outside the available > machining envelope without hitting soft or hard limits on the joints. You > could quite easily end up over stressing the pivot points or hitting the > structure of the machine. If you can specify soft limits in world space > (i.e stay in this XYZ box) this is less likely to happen. This code is > already in place for use on cartesian machines but it is disabled for > non-cartesian machines. > > IMO soft limits on joints aren't nearly as useful. All they do is replace > hard switches. Again IMO you should have hard limit switches for anything > other than a very small machine so no matter what happens you won't run > into the end stops. > > Les > > > On 03/07/2017 14:52, Jeff Epler wrote: > >> No, it's not currently possible. It would be a welcome topic for >> improvement. >> >> Right now, kinematics is confined to the realtime trajectory planner, so >> nothing is known about it at the time soft limits are being enforced in >> task. >> >> A naive approach would be to put a copy of kinematics into task; for each >> motion that task considers for soft limits, divide it up "finely" and make >> sure each of the points along the motion, it has a kinematics solution. >> However, this is probably going to be computationally intensive, since >> you're doing the work of kinematics twice. >> >> I think a plausible way to do this is to allow definition of arbitrary >> working volumes using a standard format like .stl. Then, task would have to >> answer a much simpler problem: whether any part of the motion is outside >> this defined volume. However, it might be wise to use an existing library >> to perform this test, rather than writing an original implementation in >> LinuxCNC. For example, CGAL's Side_of_triangle_mesh can tell you whether a >> particular point is on the interior or exterior of the volume. >> >> Of course, while thinking about this it will also be a good time to do >> something about the related issue which can be seen on trivkins machines: >> some arcs that go outside of soft limits aren't detected by task. I think >> this is because only the two endpoints are tested (which works fine with >> lines and convex working volumes, but doesn't work with circular motion or >> non-convex working volumes): >> https://github.com/LinuxCNC/linuxcnc/issues/80 >> For arcs which come near the edge (where the AABB of the arc is not >> entirely inside the working volume), I suspect a strategy of dividing up >> the arc will be neessary to fix this for the complex working volume case. >> And remember, "arcs" now includes multi-turn helices which can additionally >> be rotated. Oh yeah, and there are NURBs too, even if nobody uses them. >> >> >> Jeff >> >> ------------------------------------------------------------------------------ >> >> 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 >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > > > ------------------------------------------------------------ > ------------------ > 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 > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
