Closed loop with linear encoders but still backlash?

Adding the scales to the system might be very easy in this case.

PNCConf will probably add a PID component to the system (because that helps absorb the effects of jitter on an open-loop stepper system.

All you need to do is change the HAL to disconnect the PID feedback from the stepgen position feedback pin to the scale position pin.

And then add a small amount of P and I to the PID until the following error disappears.

The axis.L.motor-pos-fb and joint.N.motor-pos-fb pins also want to become connected to the scale output rather than the stepgen internal feedback too.

I use a closed loop stepper with glassscales on my mill.

Aciera wrote: I use a closed loop stepper with glassscales on my mill.

I see that you are using velocity-mode stepgens. Have you tried position-mode with added PID for corrections only? A tight position loop in the drive might be better than the velocity loop in the drive (or, quite possibly,not)

I have forgotten what the PNCConf setup for Mesa stepgens uses.

I imagine that both will work well, but one or the other might be subtly better on some machines.

Aciera:
I see you addf mesa cards read and write functions consecutively.
the addf order sets the order the component functions are run.
The write should be after all the other components.
The way you have it the output is always one thread loop behind the calculations.
Might make some small difference.

Andy:
Pncconf uses velocity mode. Position mode has some tracking problems in some cases, though I never tried it with feedback corrections.

Haven't tried position mode for the stepgens. I'm really quite happy with how it runs but I'll keep it in mind to play with that on a rainy sunday.

Chris:
Thanks for the heads up. Makes sense now that you mention it. I probably put it there to make it neat and tidy.
So I will certainly move it below all the other components.

Dear Andypugh,
According to your reply, you must be an expert using Linuxcnc. Please do not burn me :dry: , but I have a somewhat stupid question.
Your reply gave me the confidence to now finally buy all the components required, and start "playing". So I started with my biggest challange, "what" MESA card to buy. I installed and played around with pncconf (Linuxcnc 2., to find out, that I most probably need the 7i80HD Card.
It was a "walk in the park" assigning almost all my machine Signals in the pncconf-tool. Then I found out, I can not assign the Spindle-Encoder A,B & Z Signals to any of the pins inside the pncconf tool... then I started to look at the documentation of the 7i80HD, and found out, that the ports&Pins inside PNCconfig, do not correspond with the Hardware manual of the 7i80HD :pinch: ... so:
I tried visualize the Details here:

1-What am I doing wrong ? And is a manual assigning of Machine-IO's to MESA-Cards, the "normal" way of configuration ?
2-If a Manual Assignment of MESA-Card-Pins, to my CNC-Machine-IO's needs to be done after all, what would then hinder me in using the 7i98 Card, that is only half of the price of a 7i80HD ?

Kind regards, R.