Problem with 7i97 pwmgen

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03 Apr 2023 15:51 - 03 Apr 2023 17:05 #268183 by Dudelbert
Hi, My name is Martin, i am converting a Hermle UFW1200 for a while now, I am now running in to the first problem that I can not solve by only reading this Forum.
I am using a 7i97 and AASD-25A servo drives with the original Heidenhein Scales for the feedback. I have at this moment only the Y-axis connected to Lcnc, the Encoder seams to measure correct length in the correct positive direction.
The enable signal works (in the Hal Configuration it does not shows that it gives output, the one for the x-axis dose. According to the Handbook for the 7I97 Theas are internally connected and this seams to be why it still works. Is this normal behaviour?)
My problem is that the +-10V output dose not work like I expect it to, it seams to only give positive voltages. See Picture (HAL Scope.png). Initially I was thinking this means thar the output scale has the wrong Direction. It tried doth directions now and I can see no change at all. Still only positive output and the motor drives in the same direction to.
I am unsure if the way of changing the direction of output like shown below is correct?
In: [JOINT_1]
OUTPUT_SCALE = 10.0
OUTPUT_SCALE = -10.0
I also thort that
setp   [HMOT](CARD0).pwmgen.01.output-type 1 #PWM pin0
was the problem. With type 3 the behaviour of the axis changes slightly, it gets much more aggressive (more Acceleration), other than that it still runs only in one direction no change if the sign of OUTPUT_SCALE is changed.
In addition I tried measuring the behaviour I see in Hal Scope on the drive side. Hier I could verify that the Enable signal is given correctly, but the +-10v signal does not seem to show correctly. I could not find continuity between the gnd of the +-10v signal and the general DC ground. Is this Intentional? I think that the Scope shows still that something happens on the +-10v line even if I can not see if it mirrors the output shown in HAL Scope.

i attachd some files i think are relevant, I probably forgot information you need for trouble shooting this, If you want other information I will be happy to provide this.

And thank you all in adwance.
Last edit: 03 Apr 2023 17:05 by Dudelbert.

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03 Apr 2023 16:57 #268184 by PCW
Replied by PCW on topic Problem with 7i97 pwmgen
If an unmodified basci7i97 example hal/ini file does not give you bipolar outputs,
it may be that you have very old firmware in the 7I97. I would update the firmware to
the current version

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03 Apr 2023 17:06 #268185 by Dudelbert
Replied by Dudelbert on topic Problem with 7i97 pwmgen
Thank you for the fast help. I will try updating the firmware.

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04 Apr 2023 16:39 - 04 Apr 2023 16:42 #268271 by Dudelbert
Replied by Dudelbert on topic Problem with 7i97 pwmgen
I tried Updating to new Firmware today, it all seem to update fine, but I see the same behaviour still.
I had some new findings, the system is in fact able of output in the negative direction, yesterday I sad that a change in pwmgen.01.output-type changes the presived output of the system, I failed to try this in HAL scope at the time.

I tried around with this again today, I noticed that the direction wen type 2 is used is not only more aggressive but also in the other direction. ( Yesterday I sad it was with type 3, this was a mistake on my side.).

Reading the Hostmot documentation of pwmgen.xx.output-type I do not understand the differences, all of them are talking about two outputs, but I understand that in the hardware I have one output and an GND. Is there a DAC with one output and two inputs on the 7I97?

I include two pictures, Type 1 and Type 2 showing the Hal scope output wen activating the system with the only chang being pwmgen.01.output-type, I also tested both variants with positive and negative OUTPUT_SCALE and the axis. I even god sufficiently paranoid to don’t trust the HAL Calibration but shut Lcnc down changed the files, saved and restarted Lcnc. 

I hope someone has an idea how I can find the problem.
Attachments:
Last edit: 04 Apr 2023 16:42 by Dudelbert.

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04 Apr 2023 16:52 - 04 Apr 2023 17:05 #268274 by PCW
Replied by PCW on topic Problem with 7i97 pwmgen
You should not change the PWM type from the basic7i97 example

Are you sure you have the feedback correct?

I would verify by unlinking the PID output and setting voltages directly with halcmd
Last edit: 04 Apr 2023 17:05 by PCW.

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04 Apr 2023 17:26 - 04 Apr 2023 17:31 #268276 by Dudelbert
Replied by Dudelbert on topic Problem with 7i97 pwmgen
Hi,

I have tsted the fedback by turning the scew by hand with an dial gauge on the axis. It is koreckt in value and direcktion.
I will try the method you rekomend as soon as i can.
At least on the drive side i convirmed propper funktion by giving a voltage in both direktions with an AA Battary.this worked fine.

Still could you give me a short explanation (or point me to co an dokumentation) on how the PWM signal is translated to an Analog symetrikal Voltage.
I have a hard time really understanding wat "clockwork ticks behind the curtans" and seeing wat could be wrong or not.
It would be nice to understand the system. Getting it working would be a nice sideefekt as well ;-)

Anyway, thanks for the help
 
Last edit: 04 Apr 2023 17:31 by Dudelbert.

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04 Apr 2023 17:52 #268278 by PCW
Replied by PCW on topic Problem with 7i97 pwmgen
The PWM works by having a 50% duty cycle generate a 0 output
(This is why PWM offset mode where a 0 PWM value generates a 50% duty
cycle output must be enabled)

As far as debugging goes, the question is what is different about your
setup that is causing this issue. I could see a hardware issue if one of the +-
analog power supplies were faulty, Do the two yellow LEDs in the analog section
of the card both illuminate equally?

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04 Apr 2023 19:39 #268285 by Dudelbert
Replied by Dudelbert on topic Problem with 7i97 pwmgen
I have one picture, it is hard to see exaktly because of the kables, i have not noticed the leds beeing diffrent, but i have not specificly locked for this befor, i will do this next time i am on the Mashine.
Would it help if i wired up the X-axis, disabled the Y and see if the same behavior can be observed?
I did not considdert a possible hardware defekt, me doing somthing wrong was (and still is) mutch more likly to me.

To the PWM question (i do not think this is relevant for the Problem at hand) my conzeptual problm hier is that in my understanding PWM is an inherently Digital signal, my question really is, is there aditional hardware on the 7I97 to convert this? or is theare really an PWM signal fed in to the Drive? As i sad probbably not relevant but it bugs me.

I will try your adwise with the halcmd next and report the outcome.
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04 Apr 2023 22:05 #268294 by rmu
Replied by rmu on topic Problem with 7i97 pwmgen

To the PWM question (i do not think this is relevant for the Problem at hand) my conzeptual problm hier is that in my understanding PWM is an inherently Digital signal, my question really is, is there aditional hardware on the 7I97 to convert this? or is theare really an PWM signal fed in to the Drive? As i sad probbably not relevant but it bugs me.

The PWM signal is filtered, the drive sees an analog voltage. I have a 7i97 and it is working fine with the settings like in the basic example. Can you check actual voltages on the outputs with a voltmeter / multimeter or oscilloscope?

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05 Apr 2023 09:10 #268320 by Dudelbert
Replied by Dudelbert on topic Problem with 7i97 pwmgen
I will next time i am on the mashine.

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