Tuning stepper motors with encoder or glass scale feedback

At the minimum you should:

Expand the ferror limits as explained above.

Learn to use halscope.

It will not really be possible to tune without using halscope
regardless of the hal setup.



 

but I know how to use the halscope. I know how to read the curves, but I don't know which parameter to adjust when, for example, I have oscillations in the error.

Can you post a plot that shows this oscillation, including the velocity and the ferror?

hello,I've managed to set my PID.I've mounted an encoder directly on my machine B axis. My encoder is of the phase type A+,A-;B+,B-;Z+,Z-.the feedback is correct on my axis position. However, it's impossible to detect my Z0. I have a 7i96s and I've connected my two Z+,Z- wires to pins 13 & 14 of TB2 on my card. My .hal file is correctly configured for homing with this Z phase. I've tested 5 encoders of the same type. but I can't find the Z pulse.Is there a trick? Can anyone help me? Thanks

To check, in halcmd:

sets b-index-enable true

and watch b-index-enable in halshow

Then move the axis past an index mark

b-index-enable should go false when the index is detected

yes, I checked all that with 4 encoders but I never saw any change in the Z signal. I think my .hal is compliant. Could there be a connection subtlety on the 7i96s card?

You are not guaranteed to see any change in the Z signal
as its a short pulse and quite hard to catch at the 1 KHz servo thread.
(especially with higher resolution scales)

This is why the actual index event is captured in hardware.

The index (Z) signal is only provided as a hal signal for debugging
or using it as a GP input. It's normally not of any other use.

If index enable goes false on an index event, the index was detected.
 

I don't quite understand, but that means I could never use it as a homing device? my encoders are 2500 pulses/ 10000 pulses quadrature hole.

No, homing to index is common and fully supported.

I'm just saying that the actual index hal pin is not useful
for homing. The index-enable pin is what's used to communicate
index information from the hardware/driver to LinuxCNC

That is, this hal statement:

net phaseZ [HMOT](CARD0).encoder.00.input-index

Doesn't do anything useful.

But this hal statement:

net b-index-enable joint.3.index-enable <=> [HMOT](CARD0).encoder.00.index-enable

Allows LinuxCNC to enable index detection AND allows the driver to inform LinuxCNC
when the index has been detected.

To test whether the index hardware is working (assuming you can move the axis past
an index mark), you would:

With LinuxCNC running,  use halshow to watch the signal b-index-enable
and then with either halshow or halcmd, set b-index-enable true"

halcmd sets b-index-enable true

halshow should now show b-index-enable true

now, if you move the axis past an index mark, b-index-enable should go false.

This is how you test for correct index operation.

what do you think of my configuration:

# --- Encodeur configuration ---
setp [HMOT](CARD0).encoder.00.counter-mode 0
setp [HMOT](CARD0).encoder.00.filter 0
setp [HMOT](CARD0).encoder.00.scale [JOINT_3]ENCODER_B_SCALE
#setp [HMOT](CARD0).encoder.00.index-enable true
setp [HMOT](CARD0).encoder.00.index-mask 1
setp [HMOT](CARD0).encoder.00.index-invert 0
setp [HMOT](CARD0).encoder.00.index-mask-invert 0

# --- Feedback position/velocity via encodeur ---
net b-pos-fb <= [HMOT](CARD0).encoder.00.position
net b-pos-fb => pid.b.feedback
net b-pos-fb => joint.3.motor-pos-fb
net b-vel-fb <= [HMOT](CARD0).encoder.00.velocity

# --- Index pour homing ---
net b-index-enable joint.3.index-enable <=> [HMOT](CARD0).encoder.00.index-enable
net phaseZ [HMOT](CARD0).encoder.00.input-index

# --- Raw counts (optionnel debug) ---
net b-pos-rawcounts <= [HMOT](CARD0).encoder.00.rawcounts

# --- Switches (home et fins de course) ---
net b-home-sw => joint.3.home-sw-in
net b-neg-limit => joint.3.neg-lim-sw-in
net b-pos-limit => joint.3.pos-lim-sw-in