motion.adaptive-feed + MPG use
- robertspark
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29 Apr 2022 15:23 - 29 Apr 2022 15:24 #241646
by robertspark
motion.adaptive-feed + MPG use was created by robertspark
I know I've seen this discussed a couple of time on the forum with a few threads
I'm looking at the use of motion.adaptive-feed and the use of an MPG to forward and reverse run a file.
I know how motion.adaptive-feed works and requires M52, and works on a range of -1 to 1, with zero being feedhold and 1 being 100% feedrate
linuxcnc.org/docs/devel/html/gcode/m-code.html#mcode:m52
Using Mesa hardware (7i76 + 7i76E) on Mode 2, which exposes the 2x MPGs available on inputs 16, 17, 18 and 19, which then become the enc0.count and enc1.count inputs.
forum.linuxcnc.org/media/kunena/attachme...8/7i76_Anschluss.pdf
The question is.... how does one convert the mpg counts to a velocity, given the (mesa) mpg does not seem to output enc0.velocity.
I'm looking at the realtime components and I'm just not seeing what I should be using.
I appreciate that the count will update at 1khz, and it will increment / decrement based upon the direction that the MPG is moved so (new count - old count) / (time elapsed) will equal velocity
I would then need to smooth this velocity
And then set and range for the velocity / remap it to a range (from 0 - 1)
then add a negative or positive sign based upon if (new count > old count) OR (new count < old count)
if (new count = old count) then motion.adaptive-feed = 0 (feedhold).
not looking for someone to do it for me, just looking for pointers please so I can learn (teach a man to fish / programme etc)
These will just be standard 100 count MPG's (I may also have a go at doing it via a XHC HB04 I've got too, but I was looking at the MESA MPG's first as they did not have velocity available as far as I could see).
linuxcnc.org/docs/devel/html/man/man1/xhc-hb04.1.html
I'm looking at the use of motion.adaptive-feed and the use of an MPG to forward and reverse run a file.
I know how motion.adaptive-feed works and requires M52, and works on a range of -1 to 1, with zero being feedhold and 1 being 100% feedrate
linuxcnc.org/docs/devel/html/gcode/m-code.html#mcode:m52
Using Mesa hardware (7i76 + 7i76E) on Mode 2, which exposes the 2x MPGs available on inputs 16, 17, 18 and 19, which then become the enc0.count and enc1.count inputs.
forum.linuxcnc.org/media/kunena/attachme...8/7i76_Anschluss.pdf
The question is.... how does one convert the mpg counts to a velocity, given the (mesa) mpg does not seem to output enc0.velocity.
I'm looking at the realtime components and I'm just not seeing what I should be using.
I appreciate that the count will update at 1khz, and it will increment / decrement based upon the direction that the MPG is moved so (new count - old count) / (time elapsed) will equal velocity
I would then need to smooth this velocity
And then set and range for the velocity / remap it to a range (from 0 - 1)
then add a negative or positive sign based upon if (new count > old count) OR (new count < old count)
if (new count = old count) then motion.adaptive-feed = 0 (feedhold).
not looking for someone to do it for me, just looking for pointers please so I can learn (teach a man to fish / programme etc)
These will just be standard 100 count MPG's (I may also have a go at doing it via a XHC HB04 I've got too, but I was looking at the MESA MPG's first as they did not have velocity available as far as I could see).
linuxcnc.org/docs/devel/html/man/man1/xhc-hb04.1.html
Last edit: 29 Apr 2022 15:24 by robertspark.
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- robertspark
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30 Apr 2022 19:43 #241730
by robertspark
Replied by robertspark on topic motion.adaptive-feed + MPG use
head slap moment!!
linuxcnc.org/docs/devel/html/hal/comp.ht...-component-generator
ddt component - Compute the derivative of the input function
linuxcnc.org/docs/devel/html/man/man9/ddt.9.html
I didn't know that that "ddt" or "the derivative of the input function" was the change over time / period (someone's grasp of english is obviously better than mine)
linuxcnc.org/docs/devel/html/hal/comp.ht...-component-generator
ddt component - Compute the derivative of the input function
linuxcnc.org/docs/devel/html/man/man9/ddt.9.html
I didn't know that that "ddt" or "the derivative of the input function" was the change over time / period (someone's grasp of english is obviously better than mine)
The following user(s) said Thank You: tommylight
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01 May 2022 23:02 #241817
by andypugh
Replied by andypugh on topic motion.adaptive-feed + MPG use
I am not sure that you want velocity anyway. Do you really want the system to move proportional to how _fast_ you are winding the knob?
Typically the application would be something like one-turn-clockwise = full speed forwards, and one turn anticlockwise = full speed reverse.
Typically the application would be something like one-turn-clockwise = full speed forwards, and one turn anticlockwise = full speed reverse.
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01 Jul 2022 17:12 #246382
by DoWerna
I wanted to do the same with my lathe.
The component calculates the velocity from the counts/100ms
Replied by DoWerna on topic motion.adaptive-feed + MPG use
I wanted to do the same with my lathe.
The component calculates the velocity from the counts/100ms
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