Matt Shaver wrote: > We can talk about this in detail next week, but here's an example: Way > back when, Fred Proctor & I were trying to extend EMC to control > stepper motors. We were having no luck at all, primarily because we (I) > didn't really understand the problem. At one point I had the idea of > treating the stepper motors like servos. Instead of the motion system > sending _position_ commands, and essentially "navigating by dead > reckoning", I suggested sending _velocity_ commands just like you do > with servos and having the step pulse generating code keep track of the > actual pulses it had sent out in real time. This pulse count was fed > back to the motion module just like encoder position would be in a > servo system. If you are really interested look up 'steppermod' and > 'freqmod' which are the position and velocity control methods > respectively. AFAIK the 'freqmod' method is still used in linuxcnc > today, although brighter brains than me have added to and further > refined the implementation. > > Now, although I think I invented this concept, I have no idea if that's > true. This could be covered by a patent somewhere in the world. There > could be other methods used in linuxcnc that infringe on someone's > patent. > Dates would be interesting. I demoed a hardware step generator at, I think, the 2002 NAMES show, on what I think was NIST's Sherline mill. I used a Camtronics (I think) stepper drive also provided with the machine. It worked exactly this way, except that the step generation and counting was in hardware. This was done with some hacked-up PPMC hardware, but quickly became the Universal Stepper Controller.
Jon ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
