Mazak Micro Slant 15 Retrofit

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24 Nov 2022 02:09 #257536 by andypugh

  The 7i49 converts the resolver AC waves into a square wave encoder signal basically. It's handled with discreet logic at the board level. AFAICT linux CNC doesn't know the difference between encoder types at the signal processing level. 

The 7i49 actually passes the resolver angle digitally in to the driver as a number. The HAL driver converts that to a numerical angle and simulated encoder counts (but not, at any point, into a quadrature signal) 

 
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24 Nov 2022 02:54 #257537 by smc.collins
I'd have to ask PCW, my gut tells ne that the resolver input gets slapped with clipping diodes to a square wave it then looks at the zero crossings, and converts that into a count cycle and calculates angles against a tpu in the asic.

but that's how automotive stuff handles those kinds of signals. the asic may very well report angles to Linux CNC, but there's no practical reason a standard e coder couldn't do the same thing with a bit of firmware updating. Bosch does it on almost every controller they sell with hall effect engine position sensors. with hall effect iirc it's a bit more complicated as you have to know the width of the tooth and some physical geometry, with a VR you can just look at zero crossing distance, iirc.

I'm really rusty in my 8 bit mcu assembly stuff, haven't touched it in 20 yrs.

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24 Nov 2022 09:35 #257549 by andypugh

I'd have to ask PCW, my gut tells ne that the resolver input gets slapped with clipping diodes to a square wave it then looks at the zero crossings, and converts that into a count cycle and calculates angles against a tpu in the asic.

but that's how automotive stuff handles those kinds of signals. 
 

The zero crossings don't tell you much,  it is the relative amplitudes of the two outputs that indicate the angle, and there is often only one electrical cycle per shaft rotation. It is necessary to measure analogue voltages. 

For a 5V excitation voltage the output at 0 degrees of shaft rotation might be a 5V p-p 10kHz signal on the S pair and a 0V p-p signal on C. 
Then at 45 degrees it would be a 3.53 V 10kHz signal on the S pair and also 3,53V p-p signal on the C pair. 
At 225 degrees rotation there would be a signal that looks identical to 45 degrees, but out of phase with the excitation voltage. If the voltages are sampled at the peak of the excitation signal then the measured amplitude would be -3.53 on both. 

The 7i49 manual says "The 7I49 uses a oversampling A-D followed by a tracking filter." 


 
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24 Nov 2022 14:54 #257562 by Masiwood123
for my prior knowledge and knowledge, i see this as very high mathematics.. something that is unfathomable to me, if I had a card and a resolver with me and if I tried something, i would probably have an answer.. I wanted to help my friend for that robot to do the work.. he plans what he knows in terms of mach 3, the tech option and to weld..I convince him that linux is much better but also more complicated...so we'll see in the coming period.. my wish is to make a milling robot from an existing arm in the future. thank you all
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24 Nov 2022 20:37 #257577 by tommylight
Using mach3 to control a robot arm is utter waste of time.
Trying to use mach3 with resolvers is suicide.
Do not know how to explain that shorter.
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24 Nov 2022 20:55 - 24 Nov 2022 21:07 #257578 by smc.collins
personally, I'd use absolute position encoders they communicate rs485 serial, mod bus, can bus etc. are relatively cheap and well supported. so persistent position data is really nice in a confined space. iirc you can avoid homing 
Last edit: 24 Nov 2022 21:07 by smc.collins.
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09 Dec 2022 12:31 #258995 by tommylight
Got some time last night to wire the encoders on both axis, found the drive enables and did some tests, but this is going te be tough, i can not remove the motors while doing initial tuning.
Have to figure out the encoder scale, that is easy, then try to figure out the correct directions, this is tricky as last night i did change the encoder direction and the Z axis moved over 70mm till i disabled the drives!
Not smart enabling those manually, 1.5KW motors on ballscrews can do a lot of damage.
If i get the chance, i will wire enables to Mesa 7i77 or 7i84 and do some tuning.
Also, the drives have switches labeled P, 0, V, pretty sure i have to set those to V now, they are in the P possition. Guessing those are for Position and Velocity mode....
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09 Dec 2022 15:04 #259005 by andypugh

Not smart enabling those manually,

No, this certainly seems like a situation where you want an f-error to turn things off. Quickly. 
 
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09 Dec 2022 17:42 #259020 by tommylight
By manually, i do mean holding the enable wire by hand touching the ground! :)
I have a stinking sensation LinuxCNC is much faster at turning those off, i need to touch the wire, hear the motor screaming, remove the wire, in my youth i would think about 0.5 seconds, now probably a lot longer!
I was not sure those are the enable wires, now i know.
More fun tonight, hopefully, spent half day chasing and removing cables from the big plasma i am working on, lost about 2Kg jumping up and down the machine.

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10 Dec 2022 01:41 #259057 by smc.collins
what are the make and model of the drives ? I might be able to get the manuals for ya.

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