Steve Blackmore wrote: > >>> Also when slowing down, spindle overshoots badly then comes back to >>> commanded speed. >>> >> The signal out of EMC isn't doing this, so you will have to look >> into how to fix it on whatever drive electronics you have. >> Sometimes there is a setting. >> > > EMC isn't helping. There is no acceleration/deceleration setting I can > see in the hal or ini files produced and spindle inertia and emc are > fighting each other. A 30lb chuck slowing from 3000 rpm to 200 rpm > instantly is never going to happen without a brake, the minimum decel in > the VFD is 1 second. > > I jus ran into this with a rigid tapping run. I had to put a lowpass filter between the spindle speed command and the servo amp that is driving the spindle motor. Here's the code that does it :
# set up 4th PWM generator as a spindle speed control newsig spindle-speed float newsig spindle-pwm-cmd float newsig spindle-pwm-filt float linkps motion.spindle-speed-out => spindle-speed linksp spindle-speed => mult2.1.in0 setp mult2.1.in1 0.0009018 linkps mult2.1.out => spindle-pwm-cmd linksp spindle-pwm-cmd => lowpass.0.in linkps lowpass.0.out => spindle-pwm-filt linksp spindle-pwm-filt => ppmc.0.pwm.03.value setp lowpass.0.gain 0.01 newsig spindle-enable bit # SpindleFwd and SpindleRev come from univpwm_io.hal linksp SpindleFwd => or2.0.in0 linksp SpindleRev => or2.0.in1 linkps or2.0.out => spindle-enable linksp spindle-enable ppmc.0.pwm.03.enable # The first bunch mutiplies motion.spindle-speed-out by a conversion factor to get the right RPMs, then feeds that through the lowpass filter to get a gradual change. In this particular case, the parameter of 0.01 gives about a 400 ms slope to speed change from 1000 RPM forward to 1000 RPM reverse. The second part ors together the spindle direction commands to enable the servo amp. This particular system uses a real servo amp, which is a four-quadrant drive. If your VFD needs a unipolar speed command (0 to +10V) you want to do the filter first on the bidirectional signal before taking the absolute value. You might have to derive the forward/reverse commands from the sign of the filtered speed command, so the drive sees the direction change right as the value passes through zero. Jon ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. Download a free trial of Rational Requirements Composer Now! http://p.sf.net/sfu/www-ibm-com _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
