Another "what do I need" thread. Vmc retrofit

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25 Apr 2015 04:16 #58098 by andypugh
In the meantime the component grew and grew, and then I decided it was silly, and I have split it into two. One component that only orients a carousel, and one component that only sequences HAL pins.

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25 Apr 2015 16:26 #58108 by thewho
My bad, I didn't realize that I had to put "carousel.comp" after "sudo comp --install"
It seems to be working now :)

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26 Apr 2015 03:31 #58129 by thewho
Didn't get as much done this weekend as I was hoping. Might drive out to the workshop tomorrow but that depends on what mood I'm in when I wake up ;)
The computer I have there for cad/cam and now for reading lots of pdf's was bluescreening like crazy today :angry: If you got it started you could be sure it would crash within the hour.. SSD's are fast and quiet but none of my computers whit them are working as stable as HDD's.

I did almost go mad when I was trying to tune the PID settings today.. Got it quite good, forgot to save and restarted Linuxcnc :huh: And now I cant get it as good again :(
Max velocity is set to 10m/min
Acceleration is set to 1000mm/s²
I got those numbers from the machine manual.
This is where I left it anyway. If I read the graph correctly then the axis is off by ~0.18mm under acceleration. Suggestions are appreciated :dry:


I did get homing to work though.


And some more info on the tool changer:
-It takes 8 seconds for the carousel to do a full revolution.
-The carousel can be quite off position and still be "pushed" to the correct spot by the lock pin
-The hydraulic pump that activates the drawbar has one way valve in series so the pump only need to run until the "drawbar is fully extended" sensor senses that. Then a electronic valve releases the pressure when you want to retract the drawbar.
- Z needs to be at +10 from its home switch to clear tools in the carousel

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26 Apr 2015 21:02 #58136 by atrex77
1. Can I change max velocity and acceleration from within Linuxcnc? If yes, how? I've been closing linuxcnc and changing in the ini file.

this sample is for 3 axis machine with joint 0,1,2
first need to put in your ini file:

[POSTGUI_PARAMS]
# this is the minimum acceleration limit, your machine is set this in startup
MINIMUM_ACCELERATION = 350
# this is the limit of maximum acceleration
MAXIMUM_ACCELERATION = 700

and add this to postgui halfile,
or make a new file named "postgui_halfile.hal" :

loadrt wcomp count=1
loadrt mux4 count=1

addf wcomp.0 servo-thread
addf mux4.0 servo-thread

setp wcomp.0.min [POSTGUI_PARAMS]MINIMUM_ACCELERATION
setp wcomp.0.max [POSTGUI_PARAMS]MAXIMUM_ACCELERATION

net accel-out-mux-sel0 mux4.0.sel0 <= wcomp.0.under
net accel-out-mux-sel1 mux4.0.sel1 <= wcomp.0.over

net m68-e0-q wcomp.0.in <= mux4.0.in0 <= motion.analog-out-00

setp mux4.0.in1 [POSTGUI_PARAMS]MINIMUM_ACCELERATION
setp mux4.0.in2 [POSTGUI_PARAMS]MAXIMUM_ACCELERATION
setp mux4.0.in3 [POSTGUI_PARAMS]MAXIMUM_ACCELERATION

net accel-out-mux ini.0.max_acceleration <= ini.1.max_acceleration <= ini.2.max_acceleration <= mux4.0.out


last thing is check your ini file HAL section POSTGUI_HALFILE = postgui_halfile.hal

now program "M68 E0 Q###"
Q number is the acceleration
Attachments:

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26 Apr 2015 22:30 #58137 by dgarrett
The ini hal pins can be used to change max_acceleration and max_velocity only when
a program is not running

The per-axis max_velocity and max_acceleration pins are sampled when the machine is on and the motion_state is free (homing or jogging) but are not sampled when in a program is running (auto mode) or in mdi mode. Consequently, changing the pin values when a program is running will not have effect until the program is stopped and the motion_state is again free.


Ref: (2.7) www.linuxcnc.org/docs/2.7/html/config/em...l.html#_ini_settings

The pins may still be useful for changing the max_acceleration values without restarting, example, in
a terminal:
$ sim_pin ini.0.max_acceleration ini.1.max_acceleration

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27 Apr 2015 01:36 #58142 by thewho
Thanks for the input guys :) But since I found the stock velocity and acceleration values in a manual I don't really need to change those "on the fly" anymore.

Do anyone have any suggestions on what to change to further decrease the following error? If I increase FF2 then the initial "peak" decreases but it overshoots like crazy just after. (the big dip on the graph) :pinch:

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27 Apr 2015 18:57 #58158 by andypugh

Do anyone have any suggestions on what to change to further decrease the following error?


You could try a faster servo-thread rate.

You might also find some of the discussion here interesting:
thread.gmane.org/gmane.linux.distributions.emc.devel/8816

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27 Apr 2015 19:00 #58159 by andypugh

I did get homing to work though.


To save valuable seconds you can give X and Y the same home-sequence number.

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28 Apr 2015 00:32 #58169 by thewho
How much should I increase it? 20%?
How much following error is acceptable?

Nice trick to home both X and Y at the same time :laugh:

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28 Apr 2015 00:41 #58170 by andypugh

How much should I increase it? 20%?


I was thinking that you could try doubling the rate, ie 2kHz servo-thread not 1kHz.
PCW has reported that that helps.

Also try plotting position-cmd and position-fb, see if it really is as bad as f-error suggests, the email discussion suggested that f-error calcs might be a bit wrong.

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