Following my previous post, I've also tried a new frame design, with my original round tubes cut in half and attached together with 2 MikroKopter.de carbon fibre central plates.

I wonder if these central plates have a vibration reduction role too, beyond just making it easier to mount.

Here is my initial design :

You can see the 2 extra graphs and the results / conclusion at the end of the original blog.

Now I'm really wondering if the ROUND tubes are more "vibration prone" than the "standard" square ones that almost everybody seems to be using ???

Also, what if, the vibrations I'm seeing, while quite important, are normal and people manage to fly their quads in spite of them !? I'm thinking maybe my ESCs (which are really the cheapest I could find on giantcod.co.uk) have a too low update frequency ?

As you can see, any feedback / idea would be welcome.

I've gone far beyond my expectations in testing/re-building the quad, without flying it for even 1 minute... which as you can imagine is quite frustrating ! :)

thanks,

dan

Following my previous unsuccessful attempts at building a quadcopter (I have serious issues with the balancing and stability) I've decided that it's likely all this is due to VIBRATIONS and it was time to get into the nitty-gritty of some measurements...

While they are obviously far from complete or scientific, they do show how complex the "vibrations problem" is...

You can find the graphs on my blog (http://trandi.wordpress.com) and do let me know if :

- you would like some more details / numbers

- you have any other suggestions about how to reduce them

thanks,

dan

This is the sequel of my previous post, that I had to abandon more than 1 month ago, without actually being able to fly it... Ok, it's still not flying, but after:

1. burning part of the Razor 9DOF IMU
2. adding a Wii Motion Plus (for the gyros) to it
3. replacing the .net micro framework board (Fez Domino) with an Arduino 
4. replacing the Arduino with another Arduino based on AtMega 328 (as the code was too big)

I'm back in business ! :) And to prove it, here are 2 videos that show some proper balancing !

Actually, all this was only so that I can update the code, to feed  the gyros raw data directly into the PID controller algorithm (only for  the D part), as using solely the Euler angles from the DCM  transformation is too slow to react...
 
Again, it's not yet flying, but looks much more promising than 1 month ago... wish me luck ! :)
HERE you can find more details and the full history of this build...

dan

Here's a long post about my first attempt at building a quadcopter.

One interesting and rather different feature is that I tried to use a .NET micro framework board (FEZ DOMINO) to do the balancing... it did not work so I moved to a basic Arduino, thinking it's the garbage collector and especially the switching from one thread to another that caused the instability... Right now it still doesn't work :) and it looks it's because I was using the Euler angles rather than the raw gyros outputs. 

So I'm really wondering if I shouldn't go back the the .NET board?

There si VERY little on the net about this, except a few people saying that it can't be done because of managed code not being real time, etc. ... Most  people "complain" about the garbage collector kicking in unexpectedly, but with my code it would run every 5-10 seconds and take 3-5ms, which to be honest is negligeable... there was definitely something else stopping my quad from proper stabilisation !

Right now, it still doesn't fly as I've been having several issues with the IMU and Wii motion gyros lately, but even just the experience of building it was a really pleasant and interesting one !

Anyhow, I would love to hear any feedback or experience with this kind of board, or eventually a Java based one !

thanks,

dan

I see the trend for quadcopters is now to use more and more Arm 32 bit processors, which are obviously more than enough for balancing :) and have the advantage of offering enough remainin power for extra jobs.

Here's my attempt at interfacing a LM3S8962 (from LuminaryMicro / TI) with the Wii Motion Plus gyroscopes.

After spending some time trying to figure out how to install / work with IAR and FreeRTOS, I discovered (on this site) the CooCox environment and its real time OS, and I must say I'm much pleased with its usability and easy of use..

You can find HEREmore details and the C code...

Hope somebody finds this useful !

dan