Fixed-Time Motion with Input Shaping by Ulendo

[thinkyhead]

This PR adds Fixed-Time Motion Control with various methods of Input Shaping, based on code provided by Ulendo.io. The original implementation, based on Marlin 2.1.1, is posted at https://github.com/S2AUlendo/MarlinCollaborative.

This feature uses a lot of SRAM for the step event buffer and does a lot of extra computation to apply shaping, so it requires a powerful board.

Main changes from the code provided by Ulendo include renaming the new options, allowing for fewer axes and no extruder, general code cleanup, and applying coding standards.

This version adds the G-code M493 to enable Fixed-time motion and set its parameters.

[javlonsodikov]

Hey there! I wanted to take a moment to leave a comment on your GitHub PR and let you know how excited I am for this future feature to be implemented. Your proposed changes look really promising, and I can tell that a lot of thought and effort has gone into them.

[dc42]

Can someone explain what is meant by "Fixed-time motion control"? That term does not appear to be in general use. The entry for M593 at https://reprap.org/wiki/G-code#M493:_Fixed-Time_Motion_Control doesn't explain it either.

[ellensp]

PDF about it
230119_marlin_fixed_time_ctrl.pdf

[vovodroid]

it requires a powerful board.

Any suggestion for minimum hardware? Is any 32 bit CPU board good enough?

[vovodroid]

Hi, is Ulendo VC algorithm available in Marlin with M493?

There are several modes like

S0: Standard Motion S1: Fixed-Time Motion S10: ZV Input Shaping S11: ZVD Input Shaping S12: ZVDD Input Shaping S13: ZVDDD Input Shaping S14: EI Input Shaping S15: 2HEI Input Shaping S16: 3HEI Input Shaping S17: MZV Input Shaping

but what is meaning of each mode? Is one of them Ulendo VC?

[vovodroid]

@tombrazier ?

[tombrazier]

No, the VC algorithm is not available in Marlin.

You can web search for the terms ZV, ZVD, ZVDD, EI, 2EI, etc. to find out what they mean. Most of the info out there is in the form of academic papers, though.

This link has some graphs that show curves of how well the different algorithms damp resonant frequencies in the region of the configured frequency. You will see that ZV has a fairly narrow band and it gets wider the more D's you add (D is for "derivative" and refers IIRC to the derivatives of the curve at the configured frequency). EI is an alternative which has a small hump at the configured frequency and there are variants with more and more humps, again increasing the width of the frequency band.

Generally a wider band also means more distortion of corners so you want to choose the algorithm with the narrowest band that covers your main resonances.

[vovodroid]

So what is IS algorithm without FT MOTION enabled? ZV?

Also what is difference between default M900 Linear Advance and FT MOTION one?

And what is "Dynamic Frequency mode"?

[tombrazier]

Yes, without FT_MOTION, you get ZV. My input shaping can easily be extended to other algorithms. It's just no one has done it.

The FT_MOTION implementation of linear advance is a completely separate one. I don't know why Ulendo implemented it or how good it is.

Dynamic frequency mode can change the resonant frequency configuration as Z changes (because some machines have different resonant frequencies at different Z heights, I think) or as filament is extruded (because the bed on a bedslinger gets heavier as a print progresses and the resonant frequency decreases).