let's add acc code!

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24 Nov 2010 18:52 #5592 by dab77
let's add acc code! was created by dab77
Hallo, i've a question for developers:
is there any way to add a g-code to set acceleration ramp/time in next releases? EMC2 is lively growing and one of its main qualities is that is not limited to mill and lathe. so, even if it's not properly an important feature for standard use of emc2, modifying acc/dec ramps by the g-code can be very useful to other users!

I use EMC2 to move objects in the air for artistic purpose, and being able to modify accelerations and decelerations line by line is fundamental, but also who want to move any kind of robot/arms, could find it useful.

so, can someone tell me if it can be a feature in the next future, or if it's too hard to add?

thanks, davide.

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25 Nov 2010 14:14 - 25 Nov 2010 14:16 #5607 by BigJohnT
Replied by BigJohnT on topic Re:let's add acc code!
The developers usually hang out on the IRC or the developers mailing list.

As I understand the trajectory planner changing acceleration on a line by line basis would not be possible with EMC. One could come close by changing the feeds in short increments I assume if this does not break blending...

John
Last edit: 25 Nov 2010 14:16 by BigJohnT.

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26 Nov 2010 13:20 #5628 by dab77
Replied by dab77 on topic Re:let's add acc code!
yes but changing the feeds in short increments, wuold be a real pain..i tryed that, but it's really annoynig!

i know it's not possible now, in emc, but what i want to ask is if it's possible to add this feature in a future release. don't know if in a 2.5, or in a 3.xx version.
if this powerful software is going to grow again in the future, why don't add more functionality?

thanks John for your interest, do you think i'd better post this question in the dev-mailing list? i'm going to do it.

ciao!

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26 Nov 2010 13:50 #5631 by BigJohnT
Replied by BigJohnT on topic Re:let's add acc code!
Yep, that would be the place to post that.

John

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26 Nov 2010 14:10 #5632 by andypugh
Replied by andypugh on topic Re:let's add acc code!
Presumably the acceleration is currently stored in memory as a variable. It would be possible to move that to shared-memory where it could be a HAL pin.
Linking that value to G-code would not be tidy, but could be done with an analogue output.

In actuality the real problem is that G-code, RS274-NGC is "full", all the 1-letter codes already have a use, and there is no real possibility of making the parser handle 2-letter codes.

(A supplementary issue is that acceleration is per-joint)

It might be possible to add acceleration to your kinematics code. Perhaps by creating an output pin that can be linked (in HAL) to the halui,feed-override.value pin.

Actually, you might even be able to do it with a hal component, that watches the cartesian velocity and adjusts the feed over-ride pin to keep the acceleration correct.

I am not sure how the accelleration gets passed from the INI file to the trajectory planner, but it is possible that you could intercept it on the way and make your own, special, EMC2. It is much easier to do that than to prove that doing so is safe and reliable enough to make it into the main release.

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26 Nov 2010 16:09 #5634 by dab77
Replied by dab77 on topic Re:let's add acc code!
if i were a good programmer i'd modify my emc2, but since i need also a certain grade of reliability i'm not going to modify the code if i don't know what i'm doing...
but..correct me please if i'm wrong: in the .ini file now i'm setting the max accel for each axis, but when i move in world mode the acceleration ramp is derivated from the four max accel,is it right? so, what about changing the four max accel on the fly? maybe g-code can be helpful with an external calling (i'm not sure, but it can recall external programs, can it?), we are talking, as you suggest, of just changing 4 (or 1) variables, isn't it?

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26 Nov 2010 16:17 #5635 by andypugh
Replied by andypugh on topic Re:let's add acc code!
dab77 wrote:

if i were a good programmer i'd modify my emc2, but since i need also a certain grade of reliability i'm not going to modify the code if i don't know what i'm doing...


You can always swap back to a normal version :-)

but..correct me please if i'm wrong: in the .ini file now i'm setting the max accel for each axis, but when i move in world mode the acceleration ramp is derivated from the four max accel,is it right? so, what about changing the four max accel on the fly?


That is what you would need to do, but in your case it is somewhat more complicated as your kinematics are distinctly non-linear.

In any case, the INI file is only read at startup, and the accel values then remain constant.

I really do think that you could do exactly what you want with the motion.adaptive-feed pin and a HAL component, though.

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26 Nov 2010 16:28 #5636 by dab77
Replied by dab77 on topic Re:let's add acc code!
ok i'll try to follow this way. now i look around searching info on documentations. any suggestion and directions on where to find infos are welcome!
thanks andy.
cheers, davide.

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26 Nov 2010 16:46 #5638 by dab77
Replied by dab77 on topic Re:let's add acc code!
also another request: andy, can you please give visibility of this thread into the developers channels?
thanks again.

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26 Nov 2010 17:11 #5639 by BigJohnT
Replied by BigJohnT on topic Re:let's add acc code!
All the developers have access to the forum but don't use it in general as they prefer the IRC and the mailing list.

John

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