On 10 December 2012 01:26, Gene Heskett <[email protected]> wrote: >> Not in your case, as encoder velocity is the controlled quantity, not >> the derivative thereof. >> >> encoder.velocity is only an appropriate feedback-deriv term in a >> position loop. > > But this is not a position loop per sei, its a velocity loop, working in > the rps domain. Does that not change things, and if not, why?
Yes, it changes things a lot. It means that you should _not_ connect the encoder velocity to the feedback-deriv pin, as in this case the encoder velocity is most definitely not the derivative of the controlled quantity. Now, if you had a pin which (by some magic) measured spindle acceleration, then that would be the thing to connect to the feedback-deriv pin. However, no such pin exists short of fitting an accelerometer to the spindle, and nothing you can do in HAL is likely to do a better job than the internal differentiator in PID. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
