On Sat, Feb 22, 2014, at 02:20 PM, Mark Tucker wrote: > John > > Thank you so much for the insight of how that work and it explains a lot. > But as you stated it would be hunting back and forth.Which i assume it > would have to pulse the step line?
Lets take my example of a 100uS base thread and an accumulator that makes a step every time the 5th digit changes. Suppose the position command is 324,556, and you start out somewhere below that, say 300,000. The velocity is positive, and a positive number is added to the accumulator 10000 times a second. At some point, the accumulator passes 320,000, and the final step of the move is sent to the drive. There is still a small position error (4556 counts, or 0.4556 steps). The position loop will keep commanding a non-zero velocity until the accumulator reaches 324,556. It might overshoot a bit - maybe to 325,920. Then it starts going back down. It hunts around and hopefully settles down at 324,556. Maybe it never fully settles, but is bouncing around from 324,550 to 324,561 or so. But in any case, it never reaches 330,000, so it never sends another forward step. And it never gets as low as 320,000, so it doesn't send a reverse step. > And a number of people have scoped the outputs and only found the Dir > line hunting back and forth,i wonder why it is not detected on the step > line.? > And if it is only the dir line,why would the motors make a noise at all? That is a very good question, and depends on the design of the drive. -- John Kasunich jmkasun...@fastmail.fm ------------------------------------------------------------------------------ Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
