Andy, Thanks, Will research STMBL.
I think now that any protocol that puts data for all axis inside the same packet has to work. One question: So I have a LinuxCNC system writing (X,Y,Z) to ethernet at a nominal 1,000 points per second. That is one point every 0.001 seconds. What is the effect on the biter on the aluminum part I am making? Yes it depends on th rate but assume some efficient cutting speed. I can argue it does not matter at all but I think it does because the motion control system has some serious momentum What I'm looking for is a mathematically justified specification for allowed variation on the servo loop period. If the X,Y and Z where not in the same packet, then we'd need MUCH higher specs because loop jitter would equal axis synchronization error. My application is an 11 axis machine running off lithium battery power. A robot. I want a control system that works for both ROS and MachineKit. I still hope to use a truly horrible non-real time control link, WiFi Hence the motivation to move realtime control as far downstream as possible. So need a mathematically justifiable way to derive a jitter spec but using a link that ensure perfect axis synchronization. On Mon, Oct 30, 2017 at 2:53 AM, andy pugh <bodge...@gmail.com> wrote: > On 30 October 2017 at 08:22, Chris Albertson <albertson.ch...@gmail.com> > wrote: > > > I think the current trend in the industry is to move the control loops > > closer to the motors > ... > > In fact I can by a STM32F on a PCB for less than the price of a good > power cable. > ... > > What I'm looking into is a distributed system with computing pushed > closer > > to where it is used. > > You could look at STMBL.It's an STM32-based servo drive. Communication > with the LinuxCNC system is by CAT5 cables carrying the Mesa > Smart-Serial protocol. (quadrature and step/dir also supported) > With the smart-serial interface you plug it in to LinuxCNC and HAL > pins magically appear with names like "stmbl.ABCD.position-command". > (I think that you currently need a Mesa card to transmit the signals, > though the Mesa firmware is open-source and some people have made > their own hardware for that end too) > It still relies on realtime at the LinuxCNC end, but as has been > commented earlier, all the axis positions get sent simultaneously in > the same packet even if there is jitter between the packets. > > STMBL firware and hardware are both open-source. In fact as far as I > know the only way to get one is to make your own. (I have one, but I > was given it to do some HAL driver testing) > > https://github.com/rene-dev/stmbl > > Scroll down past the file listing to find words and pictures. > > -- > 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 > Emc-users@lists.sourceforge.net > 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
