Re: Digest Number 17

>> True, but it is steady state from a controls perspective anytime the
>> one of the set points is constant, be it position, velocity or
>> acceleration.

> No, that's not true! There are external events (most specifically, the
> entry and exit of cutting teeth into the work) that are ocurring, as well as
> various other non-linearities of less magnitude, such as variation in
> friction at different machine locations. But the big one is the cutting
> forces. So, you can never be really sure anything is truly steady state.

Here, we talking about 2 different things. I was only making a point
about customary terms. As far as the mechanical response goes, YOU ARE
100% CORRECT.

> But, the biggest point I want to make is that old errors sampled when
> the system is moving left are a DETRIMENT when the system is
> moving right. They actually make the error LARGER! (In the
> particular PID implemented in the EMC program.)

> Jon

Point well taken.

Mike