Once again two servo's on one axis issues

I am having a bit of a time trying to get a simple gantry machine with servos working correctly. I dont want to use trivkins until JA gets released with next version.

I dont want to use homing so should be simple but I cant get encoder signals into the slaved axis. IT works but the slave axis doesnt get error correction and eventually get f error.

Here is the relative clipped portion of the hal.



#*******************
# AXIS Y
#*******************

setp pid.y.FF0 [AXIS_1]FF0
setp pid.y.FF1 [AXIS_1]FF1
setp pid.y.FF2 [AXIS_1]FF2
setp pid.y.deadband [AXIS_1]DEADBAND
setp pid.y.maxoutput [AXIS_1]MAX_OUTPUT

net y-index-enable <=> pid.y.index-enable axis.1.index-enable <=> hm2_5i25.0.encoder.01.index-enable
net y-enable => pid.y.enable axis.1.amp-enable-out
net y-output => pid.y.output => hm2_5i25.0.7i77.0.1.analogout1

net y-pos-cmd => axis.1.motor-pos-cmd pid.y.command pid.a.command


net y-pos-fb <= hm2_5i25.0.encoder.01.position => pid.y.feedback => axis.1.motor-pos-fb
net y-vel-fb <= hm2_5i25.0.encoder.01.velocity => pid.y.feedback-deriv
net y-pos-rawcounts <= hm2_5i25.0.encoder.01.rawcounts

# ---PWM Generator signals/setup---

setp hm2_5i25.0.7i77.0.1.analogout1-scalemax [AXIS_1]OUTPUT_SCALE
setp hm2_5i25.0.7i77.0.1.analogout1-minlim [AXIS_1]OUTPUT_MIN_LIMIT
setp hm2_5i25.0.7i77.0.1.analogout1-maxlim [AXIS_1]OUTPUT_MAX_LIMIT

# ---Encoder feedback signals/setup---

setp hm2_5i25.0.encoder.01.counter-mode 0
setp hm2_5i25.0.encoder.01.filter 1
setp hm2_5i25.0.encoder.01.index-invert 0
setp hm2_5i25.0.encoder.01.index-mask 0
setp hm2_5i25.0.encoder.01.index-mask-invert 0
setp hm2_5i25.0.encoder.01.scale [AXIS_1]ENCODER_SCALE


#*******************
# AXIS A
#*******************

net a-index-enable <=> pid.a.index-enable axis.3.index-enable <=> hm2_5i25.0.encoder.03.index-enable
net a-enable => pid.a.enable axis.3.amp-enable-out
net a-output => pid.a.output => hm2_5i25.0.7i77.0.1.analogout3

net a-pos-cmd => axis.3.motor-pos-cmd


net a-pos-fb <= hm2_5i25.0.encoder.03.position => pid.a.feedback => axis.3.motor-pos-fb
net a-vel-fb <= hm2_5i25.0.encoder.03.velocity => pid.a.feedback-deriv

net a-pos-rawcounts <= hm2_5i25.0.encoder.03.rawcounts

# ---PWM Generator signals/setup---

setp hm2_5i25.0.7i77.0.1.analogout3-scalemax [AXIS_3]OUTPUT_SCALE
setp hm2_5i25.0.7i77.0.1.analogout3-minlim [AXIS_3]OUTPUT_MIN_LIMIT
setp hm2_5i25.0.7i77.0.1.analogout3-maxlim [AXIS_3]OUTPUT_MAX_LIMIT

# ---Encoder feedback signals/setup---

setp hm2_5i25.0.encoder.03.counter-mode 0
setp hm2_5i25.0.encoder.03.filter 1
setp hm2_5i25.0.encoder.03.index-invert 0
setp hm2_5i25.0.encoder.03.index-mask 0
setp hm2_5i25.0.encoder.03.index-mask-invert 0
setp hm2_5i25.0.encoder.03.scale [AXIS_3]ENCODER_SCALE

Cannot use pid.a.command because it is being used with a-pos-cmd. So a never gets corrected error

Upgraded to get joint-axes.

Problem solved, well, its going to be.

JA in 2.8 has fixed my issues I was having. Everything is working as expected except I cannot get servos tuned on Y.
Y is the axis that has two motors. I have these drives that has a closed loop within. There are options to open them up so that you can close the loop with Linuxcnc and I did. From what I understood from the manual was when you do that it doesnt use the pid or the adjustments within the drive that the PID is being controlled outside the drive. This doesnt seem to be the case. The parameters within the drive still effect the drive/motor and so does the parameters in Linuxcnc. So I am having a hard time getting them tuned so they stay synced. Problem is if they are not then when I turn on the machine it racks the gantry hard.

I am trying to get it close so when I engage the motors and turn on Liniuxcnc, it doesnt rack.
I attached some pics so you can see the motor drivetrain. Also some halscope images. This is the closest I can get.

The halscope shows the two joints on Y, F-error, vel-command and motor-fb
Note: the f-error is on 1m/div

What were your pid settings for the above trace? Specifically the FF1 and 2?
Looks like those need some fine tuning.

FF1 to get the ferror fixed and FF2 for the acel and decel?

I am not in front of it now but will post them later.

andypugh wrote:

The actual magnitude of the f-error seems quite small in absolute terms?

Is it a mm or inches machine?

The machine is in inches.


The pids for the two Y joints are as follows:

Y1
P = 20
I = 0
D = .5
FF1 = .257
FF2 = .00125
BIAS = .099
DEADBAND = 0

Y2
P = 20
I = .1
D = .5
FF1 = .257
FF2 = .00115
BIAS = .099
DEADBAND = 0

I cant seem to get the and decell spikes down. Those are the opnes causing the issues I think.

FF2 is not changing it. I am thinking it is in the drive somewhere.