Chris, If I send 10000 steps to a smart X-axis controller, how does it stay in sync with a smart y-axis controller without someone controlling the synchronization between the two?
Alan > From: Chris Albertson <albertson.ch...@gmail.com> > Subject: Re: [Emc-users] Real-time OS for machine controllers > Date: January 24, 2020 at 9:48:27 AM PST > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > > > If you can tolerate latency, then your "hub" does not need what we call > "hard" real-time capability. It only needs to keep up with the average > workload, averaged over whatever latency you can tolerate. Video streaming > works this way. They can't reliably send video and the 60 Hz frame rate > so they buffer a few seconds of video on your phone and the real-time > viewer lives on the phone not the server. > > g-code could be the same way. The penalty is that when you press the "go" > button the milling machine would take a few seconds the start working while > the data buffers into the low-level motor controllers. Today a > step/direction controller has no memory so it must be fed steps in real > time. But if it has a 10,000 step memory you could just transfer blocks > ever half second and the controller would work down the queue. "Steps" > are the wrong kind of data for this but "states" are what is used. > > You are correct in that some real-time ability is needed at every level. > But we could design things so the requirements are VEY loose at the highest > level for 0.5-second latencies being acceptable. One you need only that, > then even an iPhone is a good enough platform. > > On Thu, Jan 23, 2020 at 11:32 AM Peter C. Wallace <p...@mesanet.com> wrote: > >> On Thu, 23 Jan 2020, Chris Albertson wrote: >> >>> Date: Thu, 23 Jan 2020 10:17:44 -0800 >>> From: Chris Albertson <albertson.ch...@gmail.com> >>> Reply-To: "Enhanced Machine Controller (EMC)" >>> <emc-users@lists.sourceforge.net> >>> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net >>> >>> Subject: Re: [Emc-users] Real-time OS for machine controllers >>> >>> The trouble with the Mesa FPGA design is that it depends on a computer >> with >>> good real-time performance. It can generate steps but I don't thing you >>> can run a position or velocity PID control loop on the FPGA. >> >> LinuxCNCs design paradigm requires realtime, this is a design decision >> that is >> supported by our Hostmot2 real time firmware. We have other firmware that >> implements motion in the FPGA but this is not suited to LinuxCNCs model. >> >> >> You might argue that its an old fashioned model but many high performance >> CNC >> systems and Robotics controllers use LinuxCNCs model of a capable real >> time host >> (real OS with file I/O loadable modules, unlimited memory, massive >> floating >> point performance etc etc) Some of these use Linux and others use real >> time >> windows varients often with Ethercat Peripherals. This makes for a >> powerful >> extensible realtime toolkit (like LinuxCNCs HAL) and complex realtime >> responsive coordinated motion. Basically for this type of system you still >> need a very capable real time controller hub even if the motor controllers >> implement torque, velocity, or position loops >> >> >> Peter Wallace >> Mesa Electronics >> >> >> >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > > -- > > Chris Albertson > Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
