Mesa 7i77 output scale

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23 Jul 2013 00:27 #36895 by ROG
Mesa 7i77 output scale was created by ROG
I’ve gone back to basics with a meter on the analogue output of a Mesa 7i77
I’m struggling to work out the correct scale.
The manual mentions machine units per second.
With P/I/D etc set to zero and FF1 set to one, I’m getting some spurious readings on the output when MDIing a move at feeds of 110,220,1100 and 2200
Basically machine units are in mm
Rapid is 2220mm / min
Output should be +/-10v at 2200mm/ min = 36.66667 mm per/sec
So what should OUTPUT_SCALE = be set to?
MAX_OUTPUT = 10
OUTPUT_SCALE = -
OUTPUT_MIN_LIMIT = -10
OUTPUT_MAX_LIMIT = 10

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23 Jul 2013 00:47 - 23 Jul 2013 01:09 #36896 by PCW
Replied by PCW on topic Mesa 7i77 output scale
Those names are aliases but at some point the hal file needs to:

setp hm2_5i25.0.7i77.0.1.analogoutN.minlim -36.666
(probably OUTPUT_MIN_LIMIT)
setp hm2_5i25.0.7i77.0.1.analogoutN.maxlim 36.666
(probably OUTPUT_MAX_LIMIT)
setp hm2_5i25.0.7i77.0.1.analogoutN.scalemax 36.666
(probably OUTPUT_SCALE)
If you dont reset the min and max limit you will bound the output
to +- 10V/36.666

EDIT:

I forgot to say that you must have some headroom in the velocity command,
probably a minimum of 10% or so. If your drives are configured such that 10V
results in 2200 mm/m, I would not command a speed any faster than 2000 mm/min
so that the PID loop always has working room at the highest commanded speed
Last edit: 23 Jul 2013 01:09 by PCW.

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23 Jul 2013 01:03 #36899 by ROG
Replied by ROG on topic Mesa 7i77 output scale
Cheers Peter

setp hm2_5i25.0.7i77.0.1.analogout1-scalemax [AXIS_2]OUTPUT_SCALE (36.6666)
setp hm2_5i25.0.7i77.0.1.analogout1-minlim [AXIS_2]OUTPUT_MIN_LIMIT (36.6666)
setp hm2_5i25.0.7i77.0.1.analogout1-maxlim [AXIS_2]OUTPUT_MAX_LIMIT (36.6666)

mdi Z at FR of 1100mm/min = 2.7v with ff1 set to 1
what am I missing?

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23 Jul 2013 01:11 - 23 Jul 2013 01:16 #36901 by PCW
Replied by PCW on topic Mesa 7i77 output scale
I would trace the signals with halmeter

edit: 10/36.6 ~=2.7 so
Actually sounds like it being limited elsewhere, maybe PID maxoutput is set to 10?
Last edit: 23 Jul 2013 01:16 by PCW.

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23 Jul 2013 01:19 #36902 by ROG
Replied by ROG on topic Mesa 7i77 output scale
So theoretically, I should see 10V (ish) at a feed rate of 2200, 5V at 1100 and 1V at 220 if FF1 is set to 1 with all other PID values set to zero?
What about

setp pid.z.maxoutput [AXIS_2]MAX_OUTPUT

10 or 36.6666?

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23 Jul 2013 01:27 #36903 by ROG
Replied by ROG on topic Mesa 7i77 output scale
setp hm2_5i25.0.7i77.0.1.analogout1-scalemax [AXIS_2]OUTPUT_SCALE (36.6666)
setp hm2_5i25.0.7i77.0.1.analogout1-minlim [AXIS_2]OUTPUT_MIN_LIMIT (36.6666)
setp hm2_5i25.0.7i77.0.1.analogout1-maxlim [AXIS_2]OUTPUT_MAX_LIMIT (36.6666)
pid.z.maxoutput [AXIS_2]MAX_OUTPUT ((36.6666))

FR2200 5.5V
Fr1100 5.5V
FR 220 1.5V

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23 Jul 2013 01:30 #36904 by PCW
Replied by PCW on topic Mesa 7i77 output scale
As I said before I would trace the signals with halmeter,
especially the PID output

Note, not that its the cause of the output bounding, but minlimit must be -36.66666

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23 Jul 2013 01:38 #36906 by ROG
Replied by ROG on topic Mesa 7i77 output scale
pid.z.output = 20.16 @ FR of 2200 mm/min ???

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23 Jul 2013 01:52 #36907 by PCW
Replied by PCW on topic Mesa 7i77 output scale
well 20.16/36.6666 ~= 5.5V so the 7I77 is doing as requested

Maybe your max velocity is limited somewhere else,
suggest looking at axis.N.joint-vel-cmd

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23 Jul 2013 02:06 #36908 by ROG
Replied by ROG on topic Mesa 7i77 output scale
I concur – something is limiting the max velocity.
The output is now proportional.
As far as tuning is concerned, should I be looking at pid error or axis f-error, they have very different values?

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