Kirk Wallace wrote: > I just discovered this page: > > http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?PWM_Servo_Amplifiers > > This should be a great help. I wrote a .ngc file with "g1f20x.4, x0,%" > in it. I setup Halscope, the same as the above link, on one screen with > EMC and EMC's Calibrator in another. I make a change in Calibrator, jump > to Halscope and invoke single trigger then jump to EMC and run the > program and finally, I jump back to Halscope to review the data. I am > hoping to get some screen shots on my website. > I display the ppmc.0.encoder.x.delta, which is instantaneous velocity, and set the scope trigger on that, with an appropriate trigger level. This gets halscope to trigger at the beginning of each move. I set trigger mode to "normal", so it doesn't erase the result until I have finished looking at it. I just use manual jogs for a stimulus, and change the jog speed to see what effect different speeds have. > Is there a way to save the captured data to a file and then load the > file to halscope for viewing later? Viewing the real data would be > better than a screen shot. > The latest version of Halscope has just had a data dump mode added, I haven't had a chance to try it yet. I don't think halscope can "replay" that dump, it will just be a table of numbers. This would be good for numerical analysis of the servo data, like making Bode plots or Fourier transforms. > I was also thinking that it would be good to have EMC loop an axis move > and have halscope update on the trigger, as it already does, and then be > able to tweak the PID settings as EMC loops. > There is a loop function in EMC2's G-code interpreter, and the calibration window is "live". > On Fri, 2007-10-12 at 12:01 -0500, Jon Elson wrote: > >>Kirk, >> >>Just to add a data point on my minimill system, it has 128000 >>encoder counts per inch. I can get the following error down to >>about 200 uInch peak, up to 50 IPM or more. But, it takes some >>effort to tune it to that level. >> >>On my Bridgeport, I have 20000 counts per inch on X and Y, and I >>usually get down to .0005" following error on that machine. At >>standstill, the error is usually +/- .0001 or less. >> >>Jon > > > So at 5k cpi on my lathe, I should be able to get similar results, I > hope. Thanks Jon. > Well, 5000 is a lot less than 128,000, and 4 times coarser than my 20,000 counts/inch. So, it would be normal to expect the best following error you could achieve may be worse. One encoder count is .0002" so you will never get better than that.
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