Add motor resonance reduction to shapers.

[andrewmcgr]

This adds an MZV shaper with configurable parameters to each axis.

[Zeanon]

Could you elaborate a little on how one would calibrate those params? I was already pretty intrigued when frix posted the initial pr to increase the amount of shaper pulses so I would love to try that out

[andrewmcgr]

You'd, for example, use a recent version of K-ShakeTune to find your motor resonance and damping factor for each axis (they'll be the same for, e.g., corexy).

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[dmbutyugin]

This can be an interesting feature indeed. And code-wise, it is rather straightforward. However, it would be great to see some quantitative effect of this feature. Which could be, for instance, measuring the resonance frequency of the steppers on a few printers, showing the value of those frequencies and if/how these resonances affect the printing (e.g. artifacts on the model, audible noise (at accelerations/decelerations?), etc.), and what does this feature do to it. Perhaps Klipper discourse could be a great starting point for these discussions.

[Frix-x]

@dmbutyugin just for reference, https://github.com/Klipper3d/klipper/pull/6460 was done in order to implement this. Andrew and I are discussing a lot together and with other Voron contributors about this on Discord. There are already a few people experimenting with it.

It's pretty hard to quantify the effects directly, because we had different results depending on the machines:

• Using accelerometer measurements, it's pretty easy to measure the resonance frequency of the motors using this Shake&Tune macro (bottom right graph). On some machines, applying the motor resonance reduction lowered this resonance peak very much (like by ~half). On some other machines, the effect was more anecdotal. But it also helped reduce the amount of global vibration (the other graphs).
• Apparently it's more effective at 36 or 48V than 24V. But we don't have enough feedback and data on that, so it could be a coincidence for now.
• On all machines, the motor noise is changed to something that sounds less aggressive to the ear, smoother and in the higher spectrum. But this is not quantified, it's just a feeling and not really scientific. A few weeks ago I bought some piezoelectric microphones to attach to the motors to record their internal noise: this should give us more information than accelerometers, which have a lower cut-off frequency.

[dmbutyugin]

Well, the point is, if the benefits of the change are unclear, then it should probably be in some experimental branch until the change is refined. So that's why I was asking questions how does it affect the prints. And (but this is mostly my curiosity), what are the typical resonance frequencies of the motors?

At high-level, it seems counter-intuitive that you could get better microstepping (and avoid resonances of the motor) by applying an input shaper tuned for a stepper motor frequency. This is because:

• I'd suspect the resolution of the microstepping is insufficient to get consistent improvements for the stepping (but this depends a lot on the typical frequencies of the steppers).
• Input shaper has any effect only during accelerations and decelerations; but during acceleration and deceleration the step timings are continuously changing, therefore it is very difficult to hit a resonance frequency of a motor with individual steps; any improvements during cruising moves are likely not real.
• Improved achievable accelerations and reduced echo could be simply from the fact that, perhaps, a regular shaper (before convolution with another MZV) was insufficient to compensate for all the resonances, but adding this convolution with another shaper may improve the compensation on lower frequencies (than the stepper resonance frequency) too. It might be interesting to check the input smoothers available in the DangerKlipper branch (and mine advanced-features as well) and see how they perform.