On Tuesday 26 December 2017 17:20:31 andy pugh wrote: > On 26 December 2017 at 20:16, Gene Heskett <[email protected]> wrote: > > But somehow, this joint.2.vel-cmd has a huge high vel spike as it > > ... > > > This spike is way faster than the z motor can usually > > move, and results in a z following error at the bottom of a g33.1 > > move. > > A spike in the velocity feedback shouldn't cause any sort of following > error. (does the velocity even get anywhere near the PID?)
The point is that there is no spike from the encoder, nor is there a spike in the pid_s.command input, its a dead smooth reversal, designed to be gentle when the stepper is moving fast & has less torque, with a maximum vel straddling the zero rpm point. > > This is despite a limit3.maxa and maxv setting in series with pid_s > > that results in a quite leasurely reversal at the bottom of the > > stroke. > > There have been some problems found recently with limit3. But I have > never bothered using a spindle PID, so can't really advise further. This is the OEM, 1 HP rated at 90 volts PMDC motor that came with the mill, being driven by one of Jon's PWM_Servo amps which has 125 volts and a current limit of about 15 amps set in the servo amp. It squeaks when that kicks in. Its capable of reversing this motor in 200 milliseconds from 300 spindle rpm in high gear. The limit3 takes most of the edge off that brutality by shaping the command to the pid. This is still faster and stiffer than the pid-less vfd on the lathe can do. At full song. its a 3.2 kilowatt servo. A little 1 horse is so not a problem. limit3's out is a sine-squared waveform, no glitches at around the zero point. This is coming out of motion and being applied to pid_z.velocity-deriv input. I think it needs to go away by disconnecting it, which I'll try tomorrow. Thanks Andy. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
