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ArduIMU Quadcopter part II (mini)

Posted by Jose Julio on February 24, 2010 at 2:30pm

Hi all,
I have finished my second quadcopter with ArduIMU. This time is a "mini" version with only 28cm from rotor to rotor and has the new Jordi´s magnetometer integrated!.
This tiny machine is fantastic, with a great stability. Look at the hands-off part of the video inside house!!
Very funny :-) Video:


Specs:
Motors: 1811 2000Kv 10grams brushless motors
Props: standard 5x3
ESCs : Turnigy 6A
Batt : 2S610 Lipo
Weight (RTF) : 180grams
Again it´s a very cheap and easy setup. Because I use standard propellers I mounted left and right motors with some twist. I´d really love arduIMU flat hardware...


Look at the PPM output Rx, Is this a new 2.4Ghz receiver form DIYDrones?
No, it´s a "lighweight" (4.1grams) mix between Spektrum AR6110 Rx and Jordi´s PPM encoder. This is nice for DIY projects...


The code is improved from the old version. This one has the magnetometer integrated so now we don´t have drift
on yaw axis, better implementation for the D term on the PID controler (more responsive to user inputs), same safety improvements, fast ESCs update rate (166Hz), new PID tunning...

But this history had an interesting lesson for me... The prototype you see here are really the second one, the first one was a dissaster... (flys bad...)
Do you want to know the "small" difference between them? This:


For the first one, I use an U shaped aluminium arms to save some weight. Well this shape is very bad in torsion and generates a lot of vibrations. This vibrations saturate the gyros (our gyros are quite sensible on vibrations because the low internal resonant frecuency). You could see here a graph of the gyro output value vs Throttle and you can see clearly the effect...


I change the arms to the square shape (8x8mm) and problem gone!! Perfect stability... :-) Vibrations are our enemy (Lesson learned)

Here is the new source code: Quad1_mini_20.zip (see notes.txt inside)
Schematic (conections): Photo1 Photo2
Old post (first version) here

New ArduPilot Mega will be a perfect platform for Quad´s also, so stay tuned...

Jose.

Tags: arduimu, imu, arduino, magnetometer, quadcopter, quadrotor
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Comments

  • T3
    William Premerlani February 24, 2010 at 6:31pm
    Jose,

    Nice work, I really enjoyed your posting. Your observations regarding vibration and the effects of the box channel instead of the U-channel are fascinating.

    Best regards,
    Bill
  • Jianguo Zhao February 24, 2010 at 5:43pm
    Nice job!

    Actually, you can find the 5030 counter rotating propeller from: http://www.radicalrc.com/shop/. If you use the carbon fiber instead of aluminum, you can also save some weight.
  • pghpete February 24, 2010 at 5:20pm
    Fantastic post Jose. Great job and great photos by the way.
  • Rana February 24, 2010 at 4:46pm
    Jose, nice work, well done and keep it up !
  • Jack Crossfire February 24, 2010 at 4:15pm
    Attitude hold now seems worth it. Looks like it naturally damps translation instead of flying circles like most VTOLs. Maybe that's an artifact of the DCM algorithm.

    Very lucky to have enough indoor space for flying. Only the extremely rich or the unemployed can have so much space our country. Now to get some sonar for position sensing.
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