Greetings all; PMDC motors such as treadmill and that supplied on the G0704, can be reversed at quite amazing speeds, but do need some filtering of sorts to get that best turnaround speed.
In TV broadcasting back in the analog days we had several signals which monitored the performance of our transmitters. IMO the most useful of these signals sent on line 19 of each frame of video was called a sine-squared pulse and originated as a single sine wave with a basic max bandwidth of 4.1 megahertz, starting at the negative peak of that waveform and ending at the next negative peak, forming a gentle rise and a gentle stop at both ends but exploring the whole 4.1 megahertz the ideal transmitter tuning then allowed. Translate that into a velocity curve of how to reverse a motor with a limit3 module, and you can format the fwd/rev commands from motion, which are hard switches, into a gradually stronger stop, which when detected by the length of time between incoming encoder pulses gating the reverse to the motor controller and clearing the limit3 to let it form a new sine-squared signal going the other direction. Jon's (pico systems) PWM-Servo amp is a full 4 quadrant driver, and a full 2900 rpm spindle can be turned around to 2900 the other direction in about 400 ms with only a very transient chirp from the iron. Without that help from a couple hal modules to shape the control into some semblance of a sine squared waveform, it takes over a second and may/will trip the error circuitry in Jon's PWM-Servo amp. IIRC the pwm is running at 50 kilohertz. From slower speeds, as in 300 revs in low gear, for rigid tapping at taps small enough to do it in one g33.1 stroke, it works pretty good. But for bigger taps I have to "peck" the tap, and 2 things fight me, 1st being that the post on this G0704 isn't plumb and the backlash at the turnaround seems to get out of time. But I've not taken the time to play with some FF2 in the Z drive to see if that can be alleviated as it results in a sloppier fit for a stock bolt. But first, I need to plumb the post. And that will be a back breaking job without a sky hook. If someone has a better idea, I'm all ears. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
