December 18, 2018, 01:30:02 PM
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 External axis settings


Author Topic:  External axis settings  (Read 583 times)

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November 27, 2018, 09:36:49 AM
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Motouser


Hi guys,
a bunch of questions for you!!!

we have bought a robot with an ext. axis (J7), it arrived already setted (sanyo 1.2 kW). Now I found some weird stuff on it:

1. I try to move it from a 0° to one rotation and I'm very surprise to see that at the end of the movement  it's oscillating in - and + direction, until the release of the deadman.
2. When I exec it in play mode, after the one rotation, it doesn't reach the position, it goes forward. It's doing a rotation plus other 10/15 degrees.

The first problem bring me to another problem: what is the unit of measurement of J7? Degree??
When I complete 1 rotation, in the touch pendant I see a value around 2.24 without unit measure!!

I'm really confused and also I found that it's setted like a linear axis!!! I asked for that and they answerd that it's ok!!! :hmmm:

Any ideas or suggestions is very appreciated.

P.S.
I try to adjust the KV value (decreasing it) but nothing happens.
 

Linkback: https://www.robot-forum.com/robotforum/index.php?topic=29772.0

Today at 01:30:02 PM
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November 27, 2018, 10:56:24 AM
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Alexandru


can you check the zeroing for the JT7? Maybe you have to do the zeroing.

November 27, 2018, 02:17:50 PM
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Motouser


Hi Alexandru,

thanks for your reply.

The zero is ok and I don't understand how it could create all the problems that I describe in the previous post. Specially the oscillation.

« Last Edit: November 27, 2018, 02:33:24 PM by Motouser »

November 27, 2018, 08:22:52 PM
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kwakisaki

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Do you know whether this external axis 'has' in fact been setup/configured?
- As it sounds like its just been enabled in the software and electrically connected to me.

1. What Controller is this.
2. Do you know if the correct .MOD file has been loaded to support the Sanyo 1.2KW Motor and installed amplifier (This file contains the default servo settings for the motor installed).
3. Has Aux Function 2002 been configured correctly regarding External Axis Parameters:
 - Linear or Rotary Axis.
 - Upper and Lower Motion Limits Set.
 - Resolution Mantissa correctly set - Degree/Distance per encoder bit set correctly (Total Encoder bits per degree/distance travelled.
 - Servo Parameter Source - Internal/External.
 - Correct amplifier selected for the installed amplifier.

Can you provide any screenshots of Aux Function 2002 - I can tell by the values, if they are at a default setting or not (ie not commissioned).

November 28, 2018, 07:46:03 AM
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Motouser






Hi kwakisaki,
glad to hear you again.

1. E02
2/3. Don't know, I've attached a file(it's not a screenshot, but I've write the AUX 2002 parameters)

P.S.
Is there a way to do screenshots of the Teach Pendant? (in yaskawa robot is possible only after a couple of tricks).

November 28, 2018, 08:23:55 AM
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kwakisaki

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Screenshots can be done using a USB Memory.
Insert into front port and then 'press and hold any A button', whilst holding, then press R button.
- This will dump current screen image to USB as a .png file.
- This is applicable to ANY screen on the Teach Pendant.

Thanks for the info, busy at the moment, but at a first glance.
- Could do with a full file save to determine if the .MOD file has been loaded aswell (if you don't know whether it has been loaded or not).
- Also are you using a Linear or Rotary......it's a little unclear in your post which it is supposed to be set at.
- Yes it seems settings have been made from the defaults.
- Looking at the resolution mantissa, according to my calculation, for 1 rotation of the encoder, the distance of travel is in excess of 22000 mm - which is definitely not correct.

So I would first look at this with reference to the External Axis Manual and re-calculate this, as I think this value needs to much lower.
- The main drive component - ie coupling diameter/gearbox ratio (if attached) needs to be considered as part of the calculation.
- So the distance travel at the drive end (not motor end) is calibrated correctly with each bit of the encoder.
- So how many bits equal 1 deg (rotary) or 1 mm (linear) of distance (This is the resolution that is required to be calculated with your existing hardware fitted to the drive end)
- 1 rev of the encoder is usually 8192 bits/rev, however you would need to confirm this with the motor spec sheet, but it sounds like a standard Kawasaki Motor, so 8192 would be an applicable value for the no.bits/rev.

Also the applicable .MOD requires to be installed.
« Last Edit: November 28, 2018, 08:30:15 AM by kwakisaki »

November 28, 2018, 09:09:55 AM
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Motouser


In the attached a full save( I think that is installed the EUR122DN 50A, it's right?).

In my opinion is a rotary but it's configured as linear. I show my doubts to the company that configured the axis and they confirmed that configuring the j7 as linear is correct.

Sorry but the which part of the manual (901210-1292DEB) you are referencing about mantissa? There's only a simple explanantion and how to modify it.
maybe you are talking about the 1.2 chapter in which a found a lot formulas about load mass, torque...

Thanks for your time

P.S.
I've forgot the resolution exponent: 4
« Last Edit: November 28, 2018, 10:01:16 AM by Motouser »

Today at 01:30:02 PM
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November 28, 2018, 07:56:53 PM
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kwakisaki

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Quote
In my opinion is a rotary but it's configured as linear
- Knowing the difference between the 2 types is quite a fundamental importance as the resolution mantissa is either related to deg/bit or mm/bit.
- I'm pretty sure degrees and millimetres are totally different units of measurement last time I looked.
- Is the intended motor mechanically coupled to a rotary table, or a linear slide mechanism or is it stand alone with no coupling/gearbox?

Regarding calculation, it's relatively straight forward, just involves a little number crunching.

Determining resolution equates to distance per encoder bit.
Encoder 1 rev = 8192 bits.

So an example below to determine resolution of a rotary table which is coupled to the drive motor via a 70:1 gearbox as a rotary setup:

Rotary Table Diameter:                   300mm
Rotary Table Circumference:               942.48mm (Therefore this circumference distance will equate to 360 degrees of motion)
Gear Box Ratio:                    70:1
Encoder bit/rev:                    8192
Encoder bit/rev * Gearbox ratio:                   8192*70   = 573440 Encoder bits required to supply 70 turns into the gearbox = 1 rotation of the output gearbox = 1 rotation of the rotary table = 360 degrees of motion.

Resolution Mantissa calculation:
Total distance to travel:                   360 degrees
Total Encoder bits required:              573440

Calculation for deg/bit 360/573440:        0.000627790178
Resolution Mantissa:                  6.27790178
Resolution Exponent:                 4

So an example below to determine resolution of a rotary table which is coupled to the drive motor via a 70:1 gearbox as a linear setup:

Rotary Table Diameter:                   300mm
Rotary Table Circumference:               942.48mm
Gear Box Ratio:                    70:1
Encoder bit/rev:                    8192
Encoder bit/rev * Gearbox ratio:                   8192*70   = 573440 Encoder bits required to supply 70 turns into the gearbox = 1 rotation of the output gearbox = 1 rotation of the rotary table = 942.48mm of distance

Resolution Mantissa calculation:
Total distance to travel:                   942.48mm
Total Encoder bits required:              573440

Calculation for mm/bit 942.48mm/573440:    0.0016435546875
Resolution Mantissa:                  1.64355468
Resolution Exponent:                 3

Once this has been done, the axis should be zero'd and then confirmed, if incorrect then see if there is error in values used/measured.

Simple tuning can be done afterwards, however if you just have a motor with no load/mechanical coupled with peripheral, simple tuning may not produce smooth results due to no load on the motor.
Therefore, it is recommended to set the external axis/simple tuning when mechanically coupled to external peripherals.
To find a reasonable KV value:
 - Find the 1st lowest value that creates juddering, cogging of external axis.
 - Find the 1st highest value that creates oscillation, vibration, and audible noise.
 - Good KV Value lies between these 2 values (I always shoot for the middle value) which should create stable, no juddering, no oscillation, noise when deadmans is enabled (not jogging).
 - Multiply that value by 0.32 and enter that in the KV Field.

Hope this helps.................
« Last Edit: November 28, 2018, 08:12:10 PM by kwakisaki »

November 29, 2018, 07:57:52 AM
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Motouser


In my opinion is a rotary but it's configured as linear- I'm pretty sure degrees and millimetres are totally different units of measurement last time I looked.
[/quote]

 :biggrins:
You can say it aloud.

I've a fun conversation with the guys of the company :waffen100: and he confirmed that all the configuration that they have made it simply a test to run the motor, all the parameters are wrong and of course even the linear setup is incorrect.
These conditions have created a lot of misunderstandings because the first time they tell me that linear is right for my purpose.

Anyway the formulas that you give me is exactly what I'm looking for.

Thanks a lot.

November 29, 2018, 08:34:07 AM
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kwakisaki

Global Moderator
Quote
I've a fun conversation with the guys of the company :waffen100: and he confirmed that all the configuration that they have made it simply a test to run the motor, all the parameters are wrong and of course even the linear setup is incorrect.

I am not surprised to hear that, considering the results you've been getting, at least now you know that the settings are not applicable for the intended environment/application.

The main part of resolution calculation is purely scaling the amount of encoder bits per distance of travel.
- As usually the encoder will rotate many times before any motion is seen (especially after gearbox), therefore the resolution has to be calculated to the intended mechanical application.
- Once this is done accurately, you should have accurate positional control of the external axis.

Hopefully you will now be able to configure the external axis correctly, now you now the story from the suppliers.


December 08, 2018, 10:42:43 AM
Reply #10
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Werner Hampel

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