Re: freqmod.o in EMC started, now questions

Tim Goldstein wrote:

> I am not sure how the code is working, but no I am not using the encoders
> with the steppers. I am guessing that EMC is tracking the actual position as
> an assumed value bases upon the movement per step calculated from the .ini
> parameters x the number of steps commanded. The problem then is the
> commanded position is never actually reached as one step is just shy of the
> position and the next step is just past.

Ah, now I see. It is actually the same problem, but just a simulation,
all within the computer, of the scenario I described. So, the fix is essentially
the same. The deadband is really the thing to do. Maybe a better way to
do it is to only activate the deadband when trajectory velocity is very
near zero, or when the velocity has the opposite sign as last sample.

> Wish I could hook the encoders in and get a real closed loop system. I did
> notice as I was compiling the file Matt had me change that there is a
> reference to a DRO file. I didn't look, but I wonder if that is the
> beginning of using one of the Kulaga/Mauch DRO cards for stepper feedback?

Yes, I believe this is in the works. And, it would alleviate the biggest
disadvantage of steppers. You would no longer have to worry about
loosing steps, or at least, you'd know when it happened, and it would
be corrected as soon as the motor could catch up.

Jon