Brother TC-225 / TC-229 adventure!

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30 Aug 2017 05:59 #98180 by ihavenofish
Ok I'm wrong about perceived smoothness. On the x I can feel each bum in velocity.

So... noisy analogue then?

Stock cable is ribbon no shield as it turns out. Maybe I should untwist that analogue wires.

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30 Aug 2017 06:34 #98181 by ihavenofish
I shortened my extension to just an inch or 2. No twisting. It seems not to have changed anything much . Maybe it's grounding.

Hmm

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30 Aug 2017 06:57 #98183 by ihavenofish
Maybe it did do something...

76ipm jog. Lower is encoder velocity. It looks a lot more controlled. The resonance looks like tuning vs random. During stable parts of the move it's tracking to a tenth or so.
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30 Aug 2017 08:39 - 30 Aug 2017 08:40 #98185 by ihavenofish
Heres where we ended up on the x. A short over / under shoot then smooth tracking within a few encoder counts.

At very low speeds it's more lumpy.

It's much better than it was. But think we must be able to clean up the acceleration error a bit..... or maybe with no jerk control it's going to be limited.

I'm shorten the remaining cables tomorrow and see where we end up.
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Last edit: 30 Aug 2017 08:40 by ihavenofish.

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30 Aug 2017 12:51 #98202 by Todd Zuercher
When your made your patch connection, did you connect the shielding of the old cable to ground? The old cables shielding may have been connected to ground at the old control. If that was the case you probably need to restore that ground connection. Also check to be sure you haven't created any ground loops with your new cabling.

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30 Aug 2017 13:00 #98205 by Todd Zuercher

ihavenofish wrote: Heres where we ended up on the x. A short over / under shoot then smooth tracking within a few encoder counts.

At very low speeds it's more lumpy.

It's much better than it was. But think we must be able to clean up the acceleration error a bit..... or maybe with no jerk control it's going to be limited.

I'm shorten the remaining cables tomorrow and see where we end up.


If the old control had jerk limiting, I don't think you will be able to use acceleration rates as high as the old control used. (My guess, probably about 1/2-2/3 as much.)

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30 Aug 2017 13:59 - 30 Aug 2017 14:04 #98210 by ihavenofish
old cable has no shield. it got a big ground wire through it. but no shield.

the ground is grounded.
Last edit: 30 Aug 2017 14:04 by ihavenofish.

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30 Aug 2017 14:02 #98211 by ihavenofish

Todd Zuercher wrote:
If the old control had jerk limiting, I don't think you will be able to use acceleration rates as high as the old control used. (My guess, probably about 1/2-2/3 as much.)


this may be true. but ive lowered the acceleration before, and it seemed to make little or no difference.

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31 Aug 2017 04:39 #98261 by ihavenofish
ok, I'm out of ideas. shortening the cables has definitely helped some, but I still cant get the tuning to be 'damped" with no overshoot. this is at pretty much all speeds, and all accelerations. I went to 0.01G al the way to 1G (quite scary). the amount of overshoot changes with acceleration, for example from .001" down to .0005", but its still there and still resonating and clunking. I even played with the gain on the drive, going to minimum, and raising it above what it was.

maybe its just the lack of jerk control, but I don't see that.

I put the old control back online and it is, with no question, vastly smoother. its not perfection, you still feel the odd lump at low speeds (2ipm) but theres no comparison. so the drives and motors obviously work well enough.

I was thinking of figuring out how to make an Arduino drive one axis "blind" but I'm not sure what that would tell me that I don't already know (as in, we already know the motors can be smooth).

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31 Aug 2017 10:42 #98276 by andypugh
This thread has got very long.
Can you quickly summarise what hardware you are using and whether the drives are running velocity-mode or toque-mode, and with what feedback type (or types)

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