On Wednesday 11 December 2013 08:42:36 andy pugh did opine: > On 11 December 2013 12:25, Leonardo Marsaglia > > <leonardomarsagli...@gmail.com> wrote: > > I know this is due to torque but I don't know how to compensate this. > > If I use low speed on the way up theres almost no vibration. > > The PID component has a "bias" parameter which might help. I use it on > the Z of my knee-mill.
My mind was thinking along the lines of a phase lag in the feedback that might be alleviated with a faster servo_thread, something to try if the bias doesn't do it. Too much DGain in the pid settings could make that worse too. With the lags of a pwm conversion, and a near 20 lb chuck on my lathe, I can't run but a small fraction of DGain without an accel overshoot oscillation and a long settling time as it dies out. Add another .002 and it will never settle. Currently 0.00 for IGain, Dgain, and FF2 and running well, good control at speeds above 20 rpm, and very stiff at 200 and up. But I am running a velocity servo, whereas this s/b a position servo, tuning will obviously be different. Bias may not help a cogging motor that will tickle things at higher speeds, and increasing the bandwidth of the feedback system by raising the servo_thread speed might be something to try. Taking the servo_thread down to 500000 on my lathe made a night and day difference in the apparent "noise" out of my spindle encoder, a 50 slot, 200 edge ABZ device I made. Cheers, Gene -- "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> Linux: Where Don't We Want To Go Today? -- Submitted by Pancrazio De Mauro, paraphrasing some well- known sales talk A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Rapidly troubleshoot problems before they affect your business. Most IT organizations don't have a clear picture of how application performance affects their revenue. With AppDynamics, you get 100% visibility into your Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro! http://pubads.g.doubleclick.net/gampad/clk?id=84349831&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
