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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