linear scale and AC servo set up - sanity check

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07 Oct 2022 12:03 #253678 by chienMouille
I'm super new to HAL would be kind to show me how to go about adding an extra PID? Any thing else than just the last block of code you posted? I'm imagining I should declare it as an object before and add its variables to INI, isn't it?

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07 Oct 2022 12:11 #253679 by andypugh
Somewhere near the top of the HAL will be "loadrt pid count = 3" (or something like that)
You can just double this number.
Then you need to addf the new pids to the servo-thread (look further down the HAL for lines to copy)

It is possible that your hal uses "loadrt pid names=pid.x,pid.y,pid.z" for named pids, (and you might prefer to change to that, if not) You could use pid.xi, pid.xo etc for inner and outer pid loops for each axis)
In this case you just addf the pids by name to the servo-thread, not by number.
The following user(s) said Thank You: chienMouille

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07 Oct 2022 12:29 #253682 by chienMouille
Ok I get some errors, probably something stupid:

./cncmilltestclassicladder1.hal:147: Unknown command 'joint.0.motor-pos-cmd'

here is the hal and ini attempts:


File Attachment:

File Name: cncmilltes...0-07.ini
File Size:4 KB

File Attachment:

File Name: cncmilltes...0-07.hal
File Size:14 KB
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07 Oct 2022 12:50 #253685 by chienMouille
ok, I have got it to net give errors, by commenting what seemed doubled and adding signal names. but now the servo won't move on jogs. would you check the setup?

thanks

 

File Attachment:

File Name: cncmilltes...07-2.ini
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File Name: cncmilltes...07-2.hal
File Size:14 KB
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07 Oct 2022 13:23 - 07 Oct 2022 13:26 #253692 by andypugh
#net pid.x.output => stepgen.x.velocity-cmd

Shouldn't be commented out, you need that, but also need to add a signal name

net x-output => stepgen.x.velocity-cmd

(as that is the signal name used above for the pid.x.output) 
Last edit: 07 Oct 2022 13:26 by andypugh.

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07 Oct 2022 13:46 #253696 by chienMouille
but isn't it what's connected in line 134?

net x-output => hm2_7i95.0.stepgen.00.velocity-cmd

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07 Oct 2022 13:52 #253697 by andypugh
Sorry, yes.
Maybe that line (referring to a software stepgen, now I look at it) should be deleted rather than commented.

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07 Oct 2022 14:08 #253698 by chienMouille
alright I can do that but why is the servo not moving at all now? I think I probably messed up the hal config between the two PIDs no?

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09 Oct 2022 16:16 #253813 by chienMouille

Im running in step/dir from a 7i95 mesa card, with the servo driver set in position mode.

Yes, but you have the stepgen running in vocity mode, so the PID needs to output a velocity. 

Now, what you could do (and it would be an interesting experiment) would be to run the normal Mesa-style velocity PID to close the stepgen position loop, and then add an outer loop like I described with the linear scale as feedback. 

Parport setup:
joint.N.motor-pos.cmd -> stepgen.N.position-cmd
stepgen.N.pos-fb -> joint.N.motor-pos-fb

Common Mesa config, using external velocity PID:

[code]joint.N.motor-pos.cmd -> pid.N.command
pid.N.output - > stepgen.N.velocity-cmd
stepgen.N.position-fb -> pid.N.feedback -> joint.N.pos-fb

Alternative with scales:


[code]joint.N.motor-pos-cmd -> pid.M.command
pid.M.output -> pid.N.command
pid.N.output - > stepgen.N.velocity-cmd
stepgen.N.position-fb -> pid.N.feedback
scale.M.position -> pid.M.feedback -> joint.N.motor-pos-fb
[/code][/code]
 


I tried now to clean up and follow your sketch here precisely. But servo still doesn't move. Any idea?
That's how I've connected it:
#*******************
#  AXIS X JOINT 0
#*******************

setp   pid.x.Pgain     [JOINT_0]P
setp   pid.x.Igain     [JOINT_0]I
setp   pid.x.Dgain     [JOINT_0]D
setp   pid.x.bias      [JOINT_0]BIAS
setp   pid.x.FF0       [JOINT_0]FF0
setp   pid.x.FF1       [JOINT_0]FF1
setp   pid.x.FF2       [JOINT_0]FF2
setp   pid.x.deadband  [JOINT_0]DEADBAND
setp   pid.x.maxoutput [JOINT_0]MAX_OUTPUT
setp   pid.x.error-previous-target true
setp   pid.x.maxerrorI [JOINT_0]MAX_ERRORI

setp   pid.x_external.Pgain     [JOINT_0]P_EX
setp   pid.x_external.Igain     [JOINT_0]I_EX
setp   pid.x_external.Dgain     [JOINT_0]D_EX
setp   pid.x_external.bias      [JOINT_0]BIAS_EX
setp   pid.x_external.FF0       [JOINT_0]FF0_EX
setp   pid.x_external.FF1       [JOINT_0]FF1_EX
setp   pid.x_external.FF2       [JOINT_0]FF2_EX
setp   pid.x_external.deadband  [JOINT_0]DEADBAND_EX
setp   pid.x_external.maxoutput [JOINT_0]MAX_OUTPUT_EX
setp   pid.x_external.error-previous-target true
setp   pid.x_external.maxerrorI [JOINT_0]MAX_ERRORI_EX





# Step Gen signals/setup

setp   hm2_7i95.0.stepgen.00.dirsetup        [JOINT_0]DIRSETUP
setp   hm2_7i95.0.stepgen.00.dirhold         [JOINT_0]DIRHOLD
setp   hm2_7i95.0.stepgen.00.steplen         [JOINT_0]STEPLEN
setp   hm2_7i95.0.stepgen.00.stepspace       [JOINT_0]STEPSPACE
setp   hm2_7i95.0.stepgen.00.position-scale  [JOINT_0]STEP_SCALE
setp   hm2_7i95.0.stepgen.00.step_type        0
setp   hm2_7i95.0.stepgen.00.control-type     1
setp   hm2_7i95.0.stepgen.00.maxaccel         [JOINT_0]STEPGEN_MAXACCEL
setp   hm2_7i95.0.stepgen.00.maxvel           [JOINT_0]STEPGEN_MAXVEL


# -- section to calculate "real following error"

loadrt sum2 count=3
addf sum2.0 servo-thread
setp sum2.0.gain1 -1.0
net x-pos-cmd     => sum2.0.in0
#net my-x-pos-fb   <= hm2_7i95.0.encoder.00.position => sum2.0.in1
net x-pos-fb      => sum2.0.in1
net real-f-error  <= sum2.0.out

# This setting is to limit bogus stepgen
# velocity corrections caused by position
# feedback sample time jitter.
setp   pid.x.maxerror 0.012700
setp   pid.x_external.maxerror 0.012700


net x-index-enable  <=> pid.x.index-enable
net x-enable        =>  pid.x.enable

net x-ex-index-enable  <=> pid.x_external.index-enable
net x-ex-enable        =>  pid.x_external.enable

net x-pos-fb        =>  pid.x.feedback
net x-ex-pos-fb        =>  pid.x_external.feedback


# ---closedloop stepper signals---

net x-vel-cmd    <= joint.0.vel-cmd
net x-pos-ex-cmd    <= joint.0.motor-pos-cmd
net x-pos-ex-cmd  => pid.x_external.command
net x-ex-output <=  pid.x_external.output
net x-ext-output => pid.x.command
net x-output     => hm2_7i95.0.stepgen.00.velocity-cmd
net x-pos-fb     <= hm2_7i95.0.stepgen.00.position-fb
net x-ex-pos-fb <= hm2_7i95.0.encoder.00.position
net x-ex-pos-fb => joint.0.motor-pos-fb

net x-enable     <= joint.0.amp-enable-out
net x-enable     => hm2_7i95.0.stepgen.00.enable


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

setp    hm2_7i95.0.encoder.00.counter-mode 0
setp    hm2_7i95.0.encoder.00.filter 1
setp    hm2_7i95.0.encoder.00.index-invert 1
setp    hm2_7i95.0.encoder.00.index-mask 0
setp    hm2_7i95.0.encoder.00.index-mask-invert 0
setp    hm2_7i95.0.encoder.00.scale  [JOINT_0]ENCODER_SCALE


#net x-index-enable    joint.0.index-enable  <=>  hm2_7i95.0.encoder.00.index-enable
#net x-pos-rawcounts        <=  hm2_7i95.0.encoder.00.rawcounts





 

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10 Oct 2022 11:51 #253867 by andypugh
Sorry to abandon you, I had a bit of a busy weekend.

The first thing that I notice is that I don't think that the pid.x_external PID component is being enabled.

Both PIDs can share the x-enable signal.

change
net x-ex-index-enable  <=> pid.x_external.index-enable
net x-ex-enable        =>  pid.x_external.enable

net x-pos-fb        =>  pid.x.feedback
net x-ex-pos-fb        =>  pid.x_external.feedback

to
net x-ex-index-enable  <=> pid.x_external.index-enable
net x-enable        =>  pid.x_external.enable

net x-pos-fb        =>  pid.x.feedback
net x-ex-pos-fb        =>  pid.x_external.feedback

Does the linear scale have index marks? Those would be the best way to home, if they do. Otherwise you might want to remove the x-ex-index-enable net.

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