On Friday 10 July 2020 01:13:12 Peter C. Wallace wrote: > On Thu, 9 Jul 2020, John Dammeyer wrote: > > Date: Thu, 9 Jul 2020 22:02:31 -0700 > > From: John Dammeyer <jo...@autoartisans.com> > > Reply-To: "Enhanced Machine Controller (EMC)" > > <emc-users@lists.sourceforge.net> > > To: "'Enhanced Machine Controller (EMC)'" > > <emc-users@lists.sourceforge.net> Subject: [Emc-users] Spindle > > acceleration/decelleration > > > > My ini file these parameters. > > > > MAX_VELOCITY = 50.0 > > MAX_ACCELERATION = 300.0 > > > > Setting MAX_ACCEL to 30 doesn't change the rate of change from 3000 > > RPM to 0. Still goes from 10V to 0V in 80 mS. > > > > In the HAL file these set up the MESA for speed to RPM. But I seem > > to have missed an acceleration. > > > > # PWM gen signals/setup > > # PWM signal pin config > > setp hm2_7i92.0.pwmgen.00.output-type 1 > > setp hm2_7i92.0.pwmgen.00.scale [SPINDLE_9]PWM_SCALE > > setp hm2_7i92.0.pwmgen.pwm_frequency 1000 > > > > So far I haven't been able to get ramping working although one would > > think the MESA could do this with a parameter. # load real time a > > limit2 and a near with names so it is easier to follow loadrt limit2 > > names=spindle-ramp > > loadrt near names=spindle-at-speed > > etc... > > > > Is there a simple way to ramp a 0-10V and 10V to 0V so acceleration > > is a bit slower? > > Yes, you have a start there, you need to put the limit2 component in > the spindle speed commmand path and set the limit2 components maxv > value to the desired RPM per second acceleration value. > This will impinge on rigid tapping because of the fixed accel limit.
So I take advantage of the stepper having max torque at zero speeds by using a limit3 which can set both max_accel and max_vel and by the value choices more closely simulate the sin-squared waveform. This can make the turnaround times be done quicker but it is a bit complex to set up because linuxcnc itself makes no attempt to sequence the required reversal. So my logic assumes a control which is a 4 quadrant controller, and sequences the turn around as follows: on receiving the reversal of direction from motion, it is blocked, but the commanded speed is ramped to zero by switching a mux4 to zero the speed command by this limit3. A one shot is watching the spindle speed with just one of the signal inputs to the encoder, and when a nearly stopped condition is achieved by the oneshot timeing out, then the mux4 is clocked again and the reverse is allowed to be sent on to the controller pid by way of this limit3 which now has to start from zero speed, ramping it back up to the commanded speed in the other direction. All this takes place in a bit less than 400 milliseconds on my g0704, which may be spinning at 3k revs, but it places the slow accel in the z axis within its ability to properly track the reversal. I also took advantage of the 2 switches tallying the gear shift knob position to feed a small drive to the pid when its not solidly in either gear, to spin the motor slowly so that the square faced nylon gears in the spindle can mesh without crashing as the spindle speed is reduced to about 20 rpms long before the gears have diss-engaged by turning the knob, and full speed is not restored, thru this limit3, until the other tally switch has closed indicating the gear is fully engaged. So I can reach up and change speeds with no excitement/drama at 3k revs. Spindle stopped, I must grab the spindle and turn it by hand to mesh the gears. That has safety considerations to ones hand I'd druther not have to deal with. This is done on just two of my 4 machines and abuses the motor but in several years it has not complained. My junk box parts motor psu can hit that 1 horse rated motor to around 2 hp, as its a 90 volt, 9.7 amp rated brushed pmdc motor, but the power supply can do around 20 amps at 125 volts. I have one of Jon's pwm-servo amps being used as the spindle controller and its set to currant limit at around 17 amps. On a reverse it feeds the motor back into the supply to stop it, banging that 125 supply up to about 160 volts, then uses that overcharge to accel the motor in the other direction. Listening carefully, one can pick out the iron chirp as that current limit kicks in. I am doing a similar sequence to reverse the motor on the sheldon, but theres no pid's there, the vfd itself is pretty stiff. But with a 40 lb chuck mounted, and clamped, the reversal is slower. > > Thanks > > John > > > > > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > Peter Wallace > Mesa Electronics > > (\__/) > (='.'=) This is Bunny. Copy and paste bunny into your > (")_(") signature to help him gain world domination. > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
