Ethercat / Linuxcnc / ac servomotor/driver / closed loop to Linux pc

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20 Feb 2023 17:41 #264887 by Cncmek
Hi all,

I’m studying a new cnc machine and I wish to work with linuxcnc so I wonder about some points. First of all, I have the possibility to get ethercat ac servo drivers (A6 Panasonic). My new cnc will be a dual spindle with a slow motion 12kw spindle and an HSM 2kw spindle so I need really good response and precision. 

1- is that possible to close the loop for a pwm control directly to linuxcnc PC  through the ethercat (so the PC is the motion control)

2- the second solution would be to close the loop only to the servo driver and send only step/dir with ethercat

3- step/dir vs pwm closed loop?

4- will I have better results with a more classic solution with mesanet cards analog/step/dir

5- is there compatible ethercat linuxcnc driver for Panasonic A6 servo driver? Or should I go for another brand like Delta Asda A2 or A3

6- if full closed loop to linuxcnc pc, what should be at least the maximum latency?

A lot of question I know and I searched for answers on ethercat forum but didn’t found anything interesting. Maybe I didn’t searched the right words. 

Anyway, thanks a lot for your time

Julien

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04 Mar 2023 08:37 #265827 by besriworld
I think I can answer a few of the questions. From point 1 to 4 If you're using an ethercat driver, then you don't have step and direction . It has target position, speed and current position.
You can use the generic driver.
For me, the main advantage is that if the servo motors have an absolute encoder, when the machine is turned on, there is no need to search home position. You have a few cables in the cabinet. If you don't plan to invest another $1000+ in beckhoff I/O ports then again you should use mesa cards to control the ATC, panel and other I/Os

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04 Mar 2023 09:00 #265828 by rodw
Latency should not be an issue. Say base thread only  < 150000.
There have been some issues with network latency on some control boards but that should not be an issue due to ethercat being a much more efficient protocol so it will get things done quicker so any network delay is unlikely to be an issue.

If you go with Ethercat, I would also use it for I/O. There are some reasonably priced IO slaves that are pretty easy to make a generic xml driver for.
If you use modbus to control your VFD, you don't need PWM output or 0-10 volt analog output.

That just leaves you with an encoder for spindle. Until recently, Beckhoff was the only (expensive) solution but there is an IO board on aliexpress that covers the bases. You will need to build a generic xml driver for it

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21 Mar 2023 21:27 #267251 by RDA
Would you mind linking to this inexpensive aliexpress IO module? I tried browsing but could not find much.

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21 Mar 2023 22:31 #267255 by rodw
The following user(s) said Thank You: RDA

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08 Apr 2023 09:29 - 08 Apr 2023 09:40 #268594 by panming
您好,我在中国购买了这款主板,但是在配置 xml 时遇到了一些问题,我不熟悉 ethercat。你能帮我看看 xml 有什么问题吗?
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Last edit: 08 Apr 2023 09:40 by panming.

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08 Apr 2023 10:47 #268597 by JPL

您好,我在中国购买了这款主板,但是在配置 xml 时遇到了一些问题,我不熟悉 ethercat。你能帮我看看 xml 有什么问题吗?
 

English translation: Hi, I bought this board in China, but I have some problems with the configuration xml, I'm not familiar with ethercat. Can you help me to see what is wrong with the xml?

(But I cannot help beyond that)

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09 Apr 2023 12:28 #268664 by panming
Thank you anyway.I wrote it in English and it was automatically translated into Chinese by the browser.

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09 Apr 2023 12:37 - 09 Apr 2023 12:38 #268665 by rodw
I wondered if the double byte characters in ths xml file was causing an issue. I doubt that would be expected or handled properly
Last edit: 09 Apr 2023 12:38 by rodw.

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10 Apr 2023 08:32 #268747 by panming
Do you mean it is caused by Chinese annotations? Okay, I'll try. thank you

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