Hi Kirk, Thanks for giving it a run! It is hard to tell if it's an improvement, but it does look like it's tracking smoothly, It would likely help to compare the same run without the patch to see if the velocity jitters more.
On Sun, Sep 25, 2016 at 5:41 PM Kirk Wallace <[email protected]> wrote: > On 09/25/2016 11:21 AM, Jon Elson wrote: > > On 09/25/2016 11:52 AM, Kirk Wallace wrote: > >> Hmm... I found this which means I need to look a little > >> closer at my pin list: "... (All float output) > >> 'ppmc.<port>.encoder.<channel>.velocity - Velocity scaled > >> in user units per second. On PPMC and USC this is derived > >> from raw encoder counts per servo period, and hence is > >> affected by encoder granularity. On UPC boards with the > >> 8/21/09 and later firmware, velocity estimation by > >> timestamping encoder counts can be used to improve the > >> smoothness of this velocity output. This can be fed to the > >> PID HAL component to produce a more stable servo response. > >> This function has to be enabled in the HAL command line > >> that starts the PPMC driver, with the timestamp=0x00 > >> option. ..." > > On older PWM boards without the timestamp feature, and all > > USC boards, velocity is just delta scaled by the the encoder > > scale factor. On the newer PWM and PPMC boards with the > > timestamp feature, then the velocity is smoothed by > > estimation based on time since the last encoder count. This > > is considerably smoother than velocity derived from delta, > > which is just current position - last position, and this > > quite noisy. > > (My last message went to moderation due to the attachments, I made them > smaller on this one) > For fun I attached a screen shot of my HNC lathe running the G33 code > Rob posted. I don't have a Z acceleration pin so I have Z velocity on > the bottom trace and the spindle encoder velocity on top, at two > resolutions. I don't know if this indicates anything with Rob's issue. > > > -- > Kirk Wallace > http://www.wallacecompany.com/machine_shop/ > http://www.wallacecompany.com/E45/ > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers > ------------------------------------------------------------------------------ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
