Hal Setup for External Homing with Servo Drive Control

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08 Mar 2022 10:52 #236656 by GuiHue
Dear all,

I am currently thinking about a setup with a slightly different homing approach to make use of the servo driver's ability to home itself. While this appears to be non-sense for a regular axis, it is potentially desirable to make use of the specific driver's gantry synchronization features. The drives in question are Delta ASDA-A2.

What we are trying to do is the following:
-Have linuxCNC initiate homing through some DO, I guess "joint.N.homing" would be a suitable pin
-Have the drive do its thing
-Have the drive report out that homing was completed : Question: How do I get this signal to linuxCNC? How do I set up homing, up so that linuxCNC can cope with external homing?
-Have linuxCNC signal the drive that all axis are homed and that they may switch modes from PR to PT (PR: drive can home itself, but can only move to predefined positions, PT drive accepts typical motion signals via step/dir)

Any ideas?

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08 Mar 2022 14:26 #236675 by rodw
IF the drives are CIA402 ethercat compatible, yes, you can use them. There is a CIA402 component and uses the home to index function.
Check the instructions document in my repo
github.com/rodw-au/linuxcnc-cia402

This needs some updating as I am close to completing my configuration.

Note people have ben bale to home to index with this method but I was unable to home to a home switch using the drives features.

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08 Mar 2022 14:58 #236679 by GuiHue
Dear Rod,

thanks for getting back to me.
No, the drives do not speak EtherCAT.

The setup of the drives appears to be working (at least for a single axis for now). My questions really just relate to making this work with linuxCNC using conventional IO.

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08 Mar 2022 20:33 #236707 by rodw
From what I tried using a modified version of this component
github.com/dbraun1981/hal-cia402
I think you will need a similar component to ensure the position error that will occur when th eencoder is reporting without linuxcnc commanding the drive.

I think you also will need to modify homing.c

I reverted to linuxcnc homing which supports gantry homing simply by setting HOMING_SEQUENCE = -1 on the gantry joints in the ini file

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08 Mar 2022 21:46 #236713 by GuiHue
I see what you are pointing at. Modifying homing.c certainly is out of my league. The pointer to using encoders (hadn't even mentioned those) is quite a valid one. Technically, the encoders could also be integrated with the drives directly.

I currently use the linuxcnc gantry setup and it works well. Delta ASDA-A2 has a special mode to ensure synchronous motion between two drives by master-slaving them. In this mode they operate of one step/dir interface and maintain their relative position. Furthermore, it would allow the use of a single linear encoder instead of two. I would like to work out if I can make use of this feature. Hence my questions:).

Side question (because I currently can't try): Is it possible to net the signals of one (linear)  encoder to two step-gens?

@Mods: Maybe move to advanced config?

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08 Mar 2022 22:08 - 09 Mar 2022 04:30 #236717 by medicusdkfz

IF the drives are CIA402 ethercat compatible, yes, you can use them. There is a CIA402 component and uses the home to index function.
Check the instructions document in my repo
github.com/rodw-au/linuxcnc-cia402

This needs some updating as I am close to completing my configuration.

Note people have ben bale to home to index with this method but I was unable to home to a home switch using the drives features.
 

Is it also possible with CanOpen Delta drives and Beckhoff EK1100/EL6751? I'm using the A2-M for a YY-spindle setup.

Best regards,
Pierre
Last edit: 09 Mar 2022 04:30 by medicusdkfz.

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