Advanced Search

 
I was wrong, on closer inspection the planner can stay within the jerk limit without falling back to a full stop.

It was a bug in the jerk budget split during Bezier blends. Tangential jerk (Ruckig along the path) and centripetal jerk (curvature change through the blend) were budgeted independently, 50% and 100% of the per-joint limit respectively, assuming they're orthogonal. They are in Cartesian space, but not per joint axis, where they add as scalars. For @ruediger123's octagon: 25k + 50k = 75k on a 50k limit, matching the ~47% overshoot in the HALscope trace.

Fix: subtract the tangential share before allocating centripetal. 25k + 25k = 50k, exactly at the limit, no overshoot, no wasted headroom. Corner velocity drops ~20% vs the buggy code, but it's the true physical maximum.

@PCW was right, the TP should always obey constraints. Fix is in the 9d branch.

Here you go.

Again, it's complicated.  Feel free to ask questions if something is unclear.

A few thoughts:

• Still a work in progress, but the part(s) you want works.
• HAL files are broken up by major components of the config.
• Lots of comments - you should get a sense of the uncountable number of times I've tried or tweaked something.
• Signal names are all upper case because LCNC's halshow sorts by case first, then alphabetically.  Drives me nuts searching for signals if they're all jumbled due to upper/lower case.
• Sub-spindle is not connected to an axis.  LCNC doesn't have duplicate rotary axes like UVW for XYZ.  I found (so far) M19 works fine for the sub.
• Main spindle motor is a SZGH 'servo spindle' - an induction motor with a pretty smart drive.
  • The drive has position, velocity, and torque modes, just like a brushless PM servo
  • I believe @Aciera switches his drive between velocity and position when he switches LCNC between spindle and C-axis.
  • I found that position mode had a bit of dither at stand-still, possibly due to the induction motor characteristics.  So my drive/motor is always in velocity mode, unlike @Aciera's example.  This may help you with your Schaublin's spindle drive.

You may find that the user tab for Z-compensation is suitable for PCB machining (that is what I intend to use it for)...

forum.linuxcnc.org/qtpyvcp/56808-surface...asic?start=13#339938

This lets you probe the surface with a grid and then when compensation is enabled it applies an interpolated Z offset so that it tracks the surface. This way you don't actually have to modify the g-code. (Should make engraving depth more consistent if the bed isn't perfectly level).

I'd given up on this for a while and only just noticed the replies here, thanks!

After updating linuxcnc and probe basic I was then able to get the user tab working very quickly. I should be able to have a go at some PCBs now. 

Thanks all for your help.

is spindle.0.at-speed  true?


Also does the index work?

Test by (either in halshow or with halcmd -kf)

sets spindle-index-enable true

watch  spindle-index-enable in halshow

it should go high with the sets command and then low when you rotate
the spindle past the index position.

 

I made a new configuration using pncconf and compared the spindle & encoder 0 section.

I don't see anything that's different, other than naming conventions (see attached)

I have a quadrature spindle encoder connected encoder (0) input. A & B

I now also have a 1PPR signal, connected to the encoder.0. index pin.

In Halshow
- spindle.0.revs counts up as expected when the spindle is rotated forward
- spindle.0.speed-in appears correct
- spindle.0.index-enable shows disabled

In my SM-10.hal file I have:
net spindle-index-enable <=> spindle.0.index-enable

IF I comment out this line, I can then enable spindle.0.index-enable manually in Halshow, that makes no difference when trying to open the file below (same error)

Regardless when I try to open the following 2 line G76 program I get the following error: "Chosen spindle(0) not turning in G76"

Program:
G0 X0.45
G76 P0.0625 Z-0.5 I -0.005 J 0.008 K 0.0503

What does the error message actually mean and/or what is Linux missing that it needs?

It has the quadrature encoder signals and it has the index pulse, that I can see toggle as the magnet passes the sensor once per rev,

The revs counter is counting up 1 per rev.

Oh whichever is easiest for you, I don't have a parting slide and C axis at this moment is all I'm trying to do. I'm immensely grateful anyway

You can try these examples that I have working with some of those ETHERCAT servos

OK. I'm having a really hard time understanding the code base. The files don't seem to have any comments explaining what they actually do, what leads to them, or where they lead to.

If the cubic.c is only for non-trivial kinematics, how does the interpolation work for normal cartesian machines?

I was assuming that every servo period it pulls a target position and velocity from the trajectory planner creating 1ms stair steps of constant velocity, but I really can't tell.

Good to hear that you managed to get your toolchanger working.
I would hope that the PID settings can be constant. I did think that the error term can be scaled.
We know the state of the backgear and the output (spindle encoder). With the analog output, we can have at least a good estimate of the motor RPM. So back-calculating the ratio of the variator should be possible, at least to a degree.

If we scale the error term with the overall transmission ratio and tune the PID at that state, it should give reasonably good behavior over the whole range, wouldn’t it? I am not sure of this. Doing this would give a wonky error at startup (estimating the variator would take a few rotations, I think), but it should be fine before the spindle is fully started up, I think.

But I may have an error in my thinking. Control theory is not my strong suit.

Might be worth asking in the Remora thread.

I am working on a similar solution, but want to do it as a comp, since I got my comp for the turret working this weekend.

Gear ratio can be inferred from spindle speed / commanded voltage, corrected to frequency, corrected to RPM. (You are a step ahead of me there, with your vfd frequency out put).

I expect we will need a constantly changing set of PID settings, as the inertia varies over the entire speed range.

I always wondered whether the back gear can change gear with the spindle running, but it would be pretty pointless, given the huge 6.5:1 spindle speed change, so I will only trigger it stationary.
Cheers,
Mark


 

And you see the pin iocontrol.0.emc-enable-in toggling high?

Maybe something odd with the amp-fault pin for the W-axis?
joint.N.amp-fault-in

Yeah, I would also happily sacrifice full screen for M1.

There have been recent updates to the driver. Which LinuxCNC version are you using?