Current turning capabilities status

Excuse my difficulties to fully understand.

> If you set output scale to VFD RPM at 10V, FF0 will have to be 60 since the PID inputs are in RPS, not RPM.

When you say set output scale to VFD RPM at 10V, this means when to achieve full VFD speed the output of the 7i37 is set to 10V? If that is the case then yes, it is set like that. If I use with FF0=60 the real speed measured is above the desired speed and it stays there, but I tested only with a small P value. Will try with a larger one.

What I meant is that if your VFD full speed is 2500 RPM at 10V in, using an OUTPUT_SCALE of 2500 means the PID output is scaled in RPM. Since FF0 part of the PID component just takes the PID.command, scales it by the FF0 value and outputs it to the PID.output, you need a value of 60 to
change from the PID command input scale (RPS) to PID output scale (RPM)

The 3.3% difference in 58 from 60 is due to tolerances of the 7I33 analog out and VFD analog in

(note that if you have only FF0 (all other PID parameters 0) you are running open loop)

Using FF0=60 with a higher gain (50) I was able to get better results. This is getting nice! I used also a lowpass filter to display the actual speed and I start to like this as I can do what I want the way I want ! or not so much.... please see the attached video that shows the output speed VS the input speed.
The output speed is always higher than the input (desired speed) in about 10-15 rpm, except at very high speeds. Any consideration why?

The video is in:

Thank you

emcPT wrote: The output speed is always higher than the input (desired speed) in about 10-15 rpm, except at very high speeds. Any consideration why?

Does the error get less with more Pgain?
if your Pgain goes too high then you will get oscillation, but you can increase it until that happens.

You probably want a bit of I-gain to home-in on the exact speed.

Having said that, you don't really _need_ the exact speed for lathe work.

Errors are probably due small nonlinearitys in the VFD speed vs voltage function

If you want 0 static speed error you will need to add some I term

I should note that if you add I term you will probably have to feed the
commanded velocity through a 'limit2" component so that the rate of
change of commanded velocity is not faster than the VFD can follow.

If this is not done, the integral term will "windup" while the VFD is
getting to speed after a step change in commanded speed and
then cause the spindle speed to over or undershoot

emcPT wrote: I do not need the C axis at least for now..

If you decide you do want it, there is a config here: www.linuxcnc.org/index.php/english/forum...stion?start=12#30946 Which should help.