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VibrationTest

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Mitglied
Registriert seit: Dec 2008
Beiträge: 142
Ort: Belgium
I have been working on a tool that measures motor vibrations using the MK build-in sensors. All details can be found in this wiki page I made: http://www.mikrokopter.de/ucwiki/en/VibrationTest

I have a first, basic version and I am currently looking for a few people who would be so kind to check if the tool also works for them...

Thanks,
Frederic
IQA
Registriert seit: Jun 2007
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Ort: 53809 Winterscheid
That is a very interesting topic! So far, I have only used the Motor Test feature of the MK-Tool to run a single motor and then look at the ACC-values to determine the amplitude of vibration - much in the same way you do, but without much more thought about it. If the amplitude of the vibration was better (smaller) after applying some tape - I was satisfied.

However - since you obviously put some thought into this:
Wouldn't it be possible to "mark" the position of the motor (maybe optically) and have the software actually point to the side on which to to apply the balancing weight? I am thinking in terms of a car-tyre balancer...
Mitglied
Registriert seit: Dec 2008
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Bogomir67 meinte
That is a very interesting topic! So far, I have only used the Motor Test feature of the MK-Tool to run a single motor and then look at the ACC-values to determine the amplitude of vibration - much in the same way you do, but without much more thought about it. If the amplitude of the vibration was better (smaller) after applying some tape - I was satisfied.
Some time ago I had seen reports of people using approach you describe. I was very interested. However, I supposed it was a bit annoying to analyze the MKTool graph, also because it automatically scales. Half a year ago a made a small tool that automatically calculates the amplitude of the ACC signals at different motor speeds:

User image


see http://forum.mikrokopter.de/topic-post116109.html#post116109

I was not so satisfiied with the tool as I discovered that one needed to let the motor run for at least a minute to get reliable values. As the tool always checked 5 motor speeds, this took 5 minutes (during which you should not touch the table). After a few tests the battery started to weaken and this influenced the results.
With the current app I solv solv allll this with the new command of the dedicated FC software.

Bogom67 meinte
ever sincece you obviously put some thought into this:
Wouldn't it be possible to "mark" the position of the motor (maybe optically) and have the software actually point to the side on which to to apply the balancing weight? I am thinking in terms of a car-tyre balanc[/quote[quo
Yesit t has been done. However, you need additional hardware for it.

Frederic
Mitglied
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I have been working on a new version with a graphical User Interface. The first version is now available...


externer Link:
User image


As it has a graphical user interface it should be much easier to use.

It should also be much more accurate as before. I have also discovered that the way the MK is attached to the desk sometimes has a big influence of the quality of the results, the Wiki explains more about that.

The WIKI page was completely updated http://www.mikrokopter.de/ucwiki/en/VibrationTest and also contains a few videos I made:

http://www.vimeo.com/6948282

http://www.vimeo.com/7011506

Frederic
Mitglied
Registriert seit: Jan 2009
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Hi Frederic

very impressive!!! !!! !!!

Which HEX-file should I install on FC-me ?
...Flight-Ctrl_MEGA644p_VibrationTest.hex 86 KB
or
...VibrationTest-FC.hex 135 Kb
?

Thanks
Jörn
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Kompass meinte
Hi Frederic

very impressive!!! !!! !!!

Which HEX-file should I install on FC-me ?
...Flight-Ctrl_MEGA644p_VibrationTest.hex 86 KB
or
...VibrationTest-FC.hex 135 Kb
?

Thanks
Jörn

I suppose you are referring to the files you find under SVN. Please use the version that comes with one of the zip files ( http://www.mikrokopter.de/ucwiki/en/VibrationTest#Install )
I don't think I checked in the most recent hex file in SVN yet... The python files in SVN are up to date

Please let me know how it goes; I did not get any reports yet from people using ME boards get. It should just work, but you never know.

Did you install the vibration-dampers that are supplied with the ME boards? I do not know if they have an influence on the measurements. There has been some debate wheather they work or not. I would be very curious to see the difference in measured vibrations with and without the dampers. We would finally know if they work or not.

Frederic
Mitglied
Registriert seit: Dec 2008
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I seems that the tool does not work very well with ME boards, I am looking into it...

Frederic
Mitglied
Registriert seit: Aug 2008
Beiträge: 33
Hy Frederic,

you did a great tool and a very good explanation in the wiki :-) I want to try the tool, so I downloaded the VibrationTestExe_1_0.zip to my local directory und unzipped the file. I installed the .hex at the FC. When I now try to start the VibrationTestGui.exe in the folder under Windows XP I get an System Error from WIndows, like "I cannot find file: C:\......\VibrationTestGui.exe , although the file is at the describes position ?

I tried it at a Win2000 system too. There the dos window opens for a second, close but the gui will not start. Do you have any hints for me, do I have to install anything other then unzipping the VibrationTestExe_1_0.zip ?

Thanks for your help,

Grisu
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Grisu meinte
Hy Frederic,

you did a great tool and a very good explanation in the wiki :-) I want to try the tool, so I downloaded the VibrationTestExe_1_0.zip to my local directory und unzipped the file. I installed the .hex at the FC. When I now try to start the VibrationTestGui.exe in the folder under Windows XP I get an System Error from WIndows, like "I cannot find file: C:......VibrationTestGui.exe , although the file is at the describes position ?

I tried it at a Win2000 system too. There the dos window opens for a second, close but the gui will not start. Do you have any hints for me, do I have to install anything other then unzipping the VibrationTestExe_1_0.zip ?

Thanks for your help,

Grisu

Thanks!

All you need should be in the VibrationTestExe_1_0.zip.

On you XP system. Did you actually unzipped the file and stored it in a regular directory, not just browsing the zip file content? When you dubble-click the exe-file, it should lind it. Does it complain that it cannot find the .exe or does it say that it cannot be started?

The issue on your Win2000 system looks different. When you start the application from a DOS-box you will probably get more infor on what is going wrong. However I have never tried it on Win2000 and it might well be that this is not compatible with Win2000.

Regards,
Frederic
Mitglied
Registriert seit: Aug 2008
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Hy Frederic,

at the win2000 system, I didn't start the programm in an DOS box, I explaines it misunderstanding. When I click in the directory at the VibrationTestGui.exe the black box of your programm (looking like a dos box) starts, like you describes in your video, but then close itself very fast and no gui starts.

At the WIN XP System it says cannot find, but the path is right ?

Do I need any extra dlls or libaries ?

bye

Grisu
Mitglied
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Grisu meinte
Hy Frederic,

at the win2000 system, I didn't start the programm in an DOS box, I explaines it misunderstanding. When I click in the directory at the VibrationTestGui.exe the black box of your programm (looking like a dos box) starts, like you describes in your video, but then close itself very fast and no gui starts.

At the WIN XP System it says cannot find, but the path is right ?

Do I need any extra dlls or libaries ?

bye

Grisu

When you double-click the exe, the black window comes up with messages. On your Win2000 this window comes up but the further startup fails and in the black window there might be interesting messages but it closes immedately. When you start the exe from a DOS box, the additional black window will not show and the debug-messages will be shown in the DOS-box and you might see more info on the issue. Anyway, I do not have high hopes on Win2000

When DLLs are missing you should get an message that the exe cannot be started. Could you show me the exact error message? You can send regular mail to frederic at rc-flight.be

Thanks,
Frederic
Mitglied
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I have some more info on the issue with ME boards.

It is a hardware issue. ME boards have bigger capacitors on the ACC lines and these suppress the signal we are interested in. 1.3 boards have 0.1 uF capacitors while ME has 1 uF capacitors.

To be sure that the issue was due to these capacitors I replaced one of the capacitors and performed some measurements. The first picture below shows the raw signal without capacitor (0uF). The next picture shows the signal with a 0.1uF capacitor, so this corresponds with the capacitor used on 1.3 boards. For the last picture a 1uF capacitor (so the normal value for an ME board) was installed. As you can see the signal is completely suppressed...

externer Link:
User image
externer Link:
User image
externer Link:
User image

The pictures below show the spectra of the same signals. As you can see, the 0.1uF cap already filters a lot but leaves the vibration signal visible.
externer Link:
User image
externer Link:
User image
externer Link:
User image

The conclusion is that the tool will not work on ME boards without hardware modification :(

On the bright side, Ingo confermed that the 1.3 boards continue to be produced with the regular caps :)

Frederic
Mitglied
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I have made a small video that shows how to measure RPM with the VibrationTest. This feature is available in the new 1.2 version that is available now.

http://www.vimeo.com/7670919

Frederic
Mitglied
Registriert seit: Sep 2009
Beiträge: 23
This is a remarkable project, thank you for that!

you say it works with fc 1.2 and 1.3 and for ME you would need a capacitor change.
So what about the other versions, fc 1.0 and 1.1?

regards,
aLu
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aLurchi meinte
This is a remarkable project, thank you for that!

Thanks.

aLurchi meinte
you say it works with fc 1.2 and 1.3 and for ME you would need a capacitor change.
So what about the other versions, fc 1.0 and 1.1?


I did not get any reports yet about people using 1.0 or 1.1 boards.

As for the caps (the issue with ME), this looks ok on 1.0 and 1.1.
1.0 has a slightly different processor, an ATMEGA644 instead of ATMEGA644P. There seems to be a different bootloader for 644 but only one file for the FC code.

So I would think the VibrationTest code should also work on these older boards. But we can only know for sure after someone has tested it. As happened with ME, you never know what surprises there will be ;)

Frederic
Mitglied
Registriert seit: Sep 2009
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Hey Frederic,

I checked your tool on a FC 1.1 and it seems to be working quite nicely.
So thanks, again, especially for the RPM-Update.
You saved my day ;)

regards,
aLu
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aLurchi meinte
Hey Frederic,

I checked your tool on a FC 1.1 and it seems to be working quite nicely.
So thanks, again, especially for the RPM-Update.
You saved my day ;)

regards,
aLu
Great!
Thanks for the feedback, I updated the wiki page.

Frederic
Mitglied
Registriert seit: Dec 2008
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Hi Frederic,

Exellent tool you have created. I managed to remove most of the HF vibrations just bij using your tool!
I have a question; It is possible to have multiple motors running, that's great as it is. But I have an Y6 type MK.
Would it be possible to have 2 motors running with a different speed? That allows to find the optimum speed difference for the bottom engine in relation to the top engine.
Unfortunately my programming skills are insufficient to change the program myself for that.

Regards,
Wicherd
Mitglied
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Hi Wicherd,

It very good to hear that you get good results and that the tool is helping you :)

I would like to better understand your question. I understand that the the bottom motor should run faster or needs a prop with more pitch (probably a combination of both) in order to get optimum results. I an now wondering: can you configure a different speed in the MKTool? Do you know that the optimum combination will result in a minimum of vibrations, or is this something you would like to investigate?

In general, what you ask is possible, only I have lots of pots on my stove... :)

Frederic
Mitglied
Registriert seit: Dec 2008
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Hi Frederic,

It is possible to configure different speeds in the MKTool using the mixer. This is done by adding to the throttle value for the bottom motors.
I assume the optimum combination will result in less vibrations, based on the fact that the sound changes with different settings.
It's difficult to hear, but with bigger differences it is possible to hear that the sound levels reduce. Would be nice to make that visible using your programm. The feedback via sound is definately not precise enough.

I understand you have more to do than just program requests for other users...but... please...... :mrgreen: :mrgreen: :mrgreen:

Wicherd
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kneet meinte
Hi Frederic,

It is possible to configure different speeds in the MKTool using the mixer. This is done by adding to the throttle value for the bottom motors.
I assume the optimum combination will result in less vibrations, based on the fact that the sound changes with different settings.
It's difficult to hear, but with bigger differences it is possible to hear that the sound levels reduce. Would be nice to make that visible using your programm. The feedback via sound is definately not precise enough.

I understand you have more to do than just program requests for other users...but... please...... :mrgreen: :mrgreen: :mrgreen:

Wicherd


I have been thinking about this.

What I propose is that I make you a special version of the VibTest FC code that runs motors X and X+3 when it is instructed (by the VibTest PC software) to run motor X. In addition I could add that motor X+3 should run faster, dictated by one of the MK user-settings. This way we could find out if we indeed see a minimum in vibrations when playing with the motor speed-differences.

There is pitfall. The motors will generate vibrations with a slight frequency difference. When they get into phase, the MK might measure big vibrations but at other times they might compensate for each other. See second animation here: http://paws.kettering.edu/~drussell/Demos/superposition/superposition.html
As the vibtest is very fast, you might get very unpredictable results. By repeating a test many times, one can see how reliable the test is.

I am happy to do the patch if you feel like testing. Due to the pitfall I describe above, I assume more subbstantial changes to the VibTest will be needed to get it working.

Frederic
Mitglied
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A very nice proposal, Frederic!

I will most certainly run your patch through as much testing as I can. As it is right now, my frame seems to get in the play as well. Every test on every motor shows a spike at a certain narrow RPM-range. Looks like my carbon-wood mix is resonating at exactly the wrong frequency.... hoover-rpm.
I have some ideas to fixe that. Unfortunately that comes down to building a new frame...:-(

Wicherd
Mitglied
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Would you be so kind to give this version a try: http://www.rc-flight.be/temp/Flight-Ctrl_MEGA644p_VibrationTest_EXP.hex ?

I did not test it at all I am afraid.... it should run motors x and x+3 simultaneously (this is right for your setup?) and motor x+3 will run faster (controlled) by the first user param.

Frederic
Mitglied
Registriert seit: Dec 2008
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Motor setup is correct. Il test it tomorrow and let you know.
How is the speed difference set using the first param.. is it a percentage or absolute value. (If I interpret the MKtool correct, the mixer settings result in a percentage)
« Bearbeitet von kneet am 04.03.2010 00:30. »
Mitglied
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it's an absolute value. I propose that we first find out if we can measure the optimal point and than look how this relates to mixer settings.


for (i=0;i<3;i++)
{
uint16_t v = (uint16_t)MotorTest+(uint16_t)ParamSet.UserParam1;
if (v > 255)
v = 255;
MotorTest[i+3] = (uint8_t)v;
}

Frederic

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