Pat Lyons wrote: > Yea, I'd say it falls into the <15Hz category. > > I was thinking about finding a way to dampen the Table's mechanical response > by using the gibbs (I'm not sure thats the right name for em, but im > reffering to the screws that are used to apply pressure to the dovetails on > the ways) > (Technically, the gibs are the bars that ride against the inside of the dovetail, not the screws that apply the pressure to them.) Well, adding lots of friction is not a good approach. OK, with analog velocity servos, you have a bunch of control loops within the servo amp, and then another control loop outside it (EMC). So, the interactions get complicated. If the torque loop or the velocity loop in the servo amp are unstable, then EMC certainly can't fix it.
> Funny you mention FF2 as 0.0002, because i think the highest I have mine > (Xaxis) is like 0.0005. My FF values in all instances are below 1. I > managed to get it to settle a little with the error, but the biggest trouble > seems to be the initial error, which spikes- I would slowly increase D and > would end up with much resonance as a result... I was thinking, this could > also be due to an improper backlash measurement I've made (i suspect this > because the worst spikes occur when changing direction... > I have never liked the way D works on the EMC PID. It seems like more D should just make the response sluggish, but it causes oscillation instead. I think this is because D only looks one sample interval behind. But, certainly too much D does cause instability. With a velocity servo amp doing all the work (meaning loop gain) you don't need a lot of P gain. If you have backlash compensation turned on, definitely try again with it turned off. I don't use backlash comp on my systems, as it just makes movement messy. Jon ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
