Mazak Micro Slant 15 Retrofit

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23 Nov 2022 12:17 #257456 by andypugh
As for connection, a resolver has 6 wires (normally) which is one pair of excitation windings and two pairs of outputs.
As an absolute device they don't typically have an index.
(The LinuxCNC 7i49 interface resets the index-enable pin at zero degrees, for compatibility)
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23 Nov 2022 12:48 - 23 Nov 2022 12:48 #257462 by Masiwood123
Very useful information, they seem confusing, but I'm slowly understanding..one more question, how are those motors with resolver tuned, is there a pnccnfg with sam scale calculation,or is it similar to, say, 7i77, halscope, or manually in ini-hal etc.?
Last edit: 23 Nov 2022 12:48 by Masiwood123.

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23 Nov 2022 12:59 #257463 by andypugh
The source of the motor position/velocity feedback becomes irrelevant once the numbers are in HAL. It depends on the drive, not the motor.

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23 Nov 2022 13:07 #257464 by Masiwood123
ok but the driver is controlled by 7i49 via analog output? linuxcnc receives feedback from the resolver in order to give the appropriate output via the card, that circuit is not very clear to me in the sense that if we compare it with an encoder, some scale must be entered, so I wonder if it is a similar tuning as with the encoder, I think, as it has to enter the encoder scale, there should also be a resolver scale, or not?

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23 Nov 2022 13:14 #257465 by Masiwood123
can you send your config files for that lathe with resolver? thanks

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23 Nov 2022 13:21 #257467 by andypugh
The 7i49 can output analogue voltage, but I don't know how often it is used.

The point is that very often the motor resolver connects direct to the servo drive, with the resolver not connected to LinuxCNC.

On my machines the resolver is connected to the 7i49 but the servo drives are the Mesa 8i20 and those receive their current command and rotor angle information digitally through smart-serial.

If the servo drive generates the excitation signal then the 7i49 can't be used.

One possible setup would be an analogue-controlled servo drive that takes hall sensor (or the 16-step Fanuc signals). In that case LinuxCNC HAL would use the measured resolver position both for axis position feedback and to generate commutation signals for the drive, with the analogue output being used to control the drive current.

It might be nice if there was an alternative "passive" mode for the 7i49 where it sampled the excitation voltage on a spare channel and measured the output voltages to give motor position information in cases where the servo drive supplies the excitation (and uses the output for commutation)
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23 Nov 2022 13:58 #257472 by Masiwood123
oh, it sounds more and more complicated to me now:)..I think (I'll check) that that kuka robot has an absolute encoder+resolver on the motor..and on the driver an analog input from the controller..I thought I'd recommend 7i49 to him so that he could possibly bypass mach3..I think that friend wants to convert absolute encoder signals into incremental signals via arduino.. and then use one of the digital/analog cenvert cards to send analog output to the motor drivers, and to bypass the resolver.. I'll see in a few days what the situation is.

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23 Nov 2022 14:04 - 23 Nov 2022 14:05 #257473 by andypugh
The robot is quite possibly using absolute encoders for joint position and resolvers (straight to the drives) for motor commutation. In that case you don't need to consider the resolvers any more than you would the hall sensors on a BLDC configuration.

LinuxCNC would probably be a better bet than Mach for a different reason, though. It supports custom kinematics, including serial (robot) kinematics.

Take a look at this demo config: sim/axis/vismach/puma/puma560

forum.linuxcnc.org/38-general-linuxcnc-q...xcnc?start=10#110845
 
Last edit: 23 Nov 2022 14:05 by andypugh.
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24 Nov 2022 00:30 #257532 by smc.collins

ok but the driver is controlled by 7i49 via analog output? linuxcnc receives feedback from the resolver in order to give the appropriate output via the card, that circuit is not very clear to me in the sense that if we compare it with an encoder, some scale must be entered, so I wonder if it is a similar tuning as with the encoder, I think, as it has to enter the encoder scale, there should also be a resolver scale, or not?

  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. 
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