[LinuxCNC/linuxcnc PR#396] 2.7: limit3–fix acceleration

#1 – zultron 于 2018-01-12

This should now pass all of @SebKuzminsky’s tests, including the super-strict “sluggishness” checks. Thanks for writing those!

@samcoinc said he’d do some testing on this. My fingers are crossed it all goes well. Thanks, Sam!

I ended up rewriting this about four times before finally getting here, and as I told @samcoinc, I almost gave up on it three times. Oh, man.

#2 – zultron 于 2018-01-12

@samcoinc told me about @dngarrett’s project to use this code elsewhere, and the need to avoid backing off. The smooth-steps pin can be set to a high value to smooth out acceleration. Here are some screenshots to show what this does.

A clipped triangle signal from the limit3/lock-on-input-and-limits test.
Default (2):
!screenshot2018-01-1120-48-29-limit3-triangle-smooth-steps-2
setp limit3.0.smooth-steps 10000:
!screenshot2018-01-1120-48-29-limit3-triangle-smooth-steps-10k

A clipped sine signal from the limit3/min-max-overshoot test.
Default:
!screenshot2018-01-1120-48-29-limit3-sine-smooth-steps-2
setp limit3.0.smooth-steps 10000:
!screenshot2018-01-1120-48-29-limit3-sine-smooth-steps-10k

Notice how the higher value cleans up the up and down acceleration spikes and smooths out the curve.

#3 – SebKuzminsky 于 2018-01-12

This looks amazing @zultron !

#4 – zultron 于 2018-01-13

Thanks, @SebKuzminsky!