Stuart Stevenson wrote: > I ask this because I want to remove the drive tuning from the system. > Everyone says the drive/motor servo tuning is the best but if that is the > case why is there tuning capability in LinuxCNC? Obviously, it is not good > enough or no effort would be expended in making it better. > I will try this on one of my systems. > Maybe I need to work on a pseudo tach feedback that I generate to get the > desired result. > There are three ways I know of to run this type of servo. One is velocity mode, with either a real tach or a synthetic tach derived from the encoder. Another is torque mode, where the tach is left out and the outermost error amp (velocity error amp) is omitted. In some units, the command is then sent in through the tach inputs, as the velocity amp is disabled or disconnected. In this mode, the only error amp in the servo amplifier is the current or torque error amp. So, the command from the CNC control is a request for motor current. In the old days of very limited encoder resolution, torque mode may not have given as stiff or smooth a system response.
The last way I know is voltage mode, which is how my PWM servo amps work. The command from the CNC control delivers voltage to the motor proportional to the command. These are less stable than torque mode, but with a high enough resolution encoder can also work quite well. The velocity estimation from timestamping encoder counts and feeding thisinto the newer PID velocity input helps quite a bit. Jon ------------------------------------------------------------------------------ Own the Future-Intel® Level Up Game Demo Contest 2013 Rise to greatness in Intel's independent game demo contest. Compete for recognition, cash, and the chance to get your game on Steam. $5K grand prize plus 10 genre and skill prizes. Submit your demo by 6/6/13. http://p.sf.net/sfu/intel_levelupd2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
