[EMAIL PROTECTED] wrote: >Jon Elson's boards use the servo scheme - his step outputs are sent to >an encoder counter as well as to the drive, and the encoder counter >feedback is used to close the loop. > > > It seems to me you HAVE to do this. Unless the clock of the FPGA is somehow linked to the clock of the CPU, or the FPGA is generating a "servo" update interval for the CPU, then there is always the possibility of a step pulse either being sent or not, before the next update. Eventually, these errors will multiply to large position errors.
>It is true that the buffered approach is theoreticaly a tiny bit more >accurate. A perfect forward transfer function is more accurate (if >less robust) than using feedback to compensate for imperfections. >Maybe we (EMC) should investigate the possibilities. If we limit >ourselves to a maximum of one "frame" in the buffer, perhaps the >delay issue can be avoided. Something to think about. > > Well, some discussion might be warranted, but it seems that in a real-world machine control, where the operator may need to change feedrate or even abort the procedure at any time, this is just unworkable. Maybe if the counters are there, and are only used to recover position from an abort, it would be functional. > > > Jon ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
