On 07/15/2015 08:59 AM, Gene Heskett wrote: > Trying to learn something here, I see the use of several of the ddt > modules, which appear to be used for detecting the slope, or change > velocity, its output.
:) No, these ddt and hypot are not needed here. They where used to trace velocity - just for testing, derived from TP testing config, which tracked max acceleration of each axis and had nice side panel: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?NewTrajectoryControl > OTOH, I haven't any experience with velocity driven servo's, and if I > were to do a servo driven machine, I would automatically use position > desired, and position feedback to achieve the desired result, a near > vanishing position error. > > Where can I learn how a velocity servo achieves the positioning accuracy > that allows it to do as good, or perhaps even better, working accuracy > compared to a position servo? Surely there is a tut on this? Yes, having velocity and position loops increases trajectory following accuracy and eases PID tuning. If you have only torque or PWM mode servo amplifiers, then you can create velocity pid in LinuxCNC. It should track axis velocity (you can use encoder-velocity output or ddt here), directly control the amplifier and get command from position PID. Velocity PID might have only Igain non-zero. This helps a lot in certain setups. What I found: http://www.anderswallin.net/2008/04/x-axis-test/ http://gnipsel.com/linuxcnc/tuning/servo.html http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Tuning_LinuxCNC/HAL_PID_Loops http://wiki.linuxcnc.org/cgi-bin/wiki.pl?PiD ------------------------------------------------------------------------------ Don't Limit Your Business. Reach for the Cloud. GigeNET's Cloud Solutions provide you with the tools and support that you need to offload your IT needs and focus on growing your business. Configured For All Businesses. Start Your Cloud Today. https://www.gigenetcloud.com/ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
