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QuadRotor Project

Posted by Felipe Jaramillo on September 4, 2010 at 9:30pm

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I have started my quadrotor project.

Im using the mikrokopter frame with some additional center plates and a few modifications.
E-flite motors, with E-flite ESC. An arduino MEGA board. A Vectornav VN-100 which includes magnetometers, accelerometers, gyros, and an onboard kalman filter. Xbee PRO modules. Laptop with Labview.

Right now Im testing and tunning my own PID controller. Here are some pics of my quad and a small clip showing the actual behaviour of the controller, which I have to improve.




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Comments

  • Developer
    Jani Hirvinen September 8, 2010 at 4:20am
    Roy yes we have. We will start using 850kv 2830 style motors as our primary motors and for big quads we will have 2836 style 880Kv motors. I will post more information about those soon to DIY.
  • Roy Brewer September 8, 2010 at 3:29am
    Hi Jani,

    Do you have any details on these ArduCopter props and motors?

    Thanks
    Roy
  • Richard Hirst September 8, 2010 at 2:14am
    Jani, thanks for the info, will keep a look out for them.

    I did my first flight today, it does fly :-) Two problems, One is the props, I have 12" dia, but feel the don't need as much rpm to lift, but also a small change in rpm makes a big difference and I saw oscillations, mainly near the ground. The second was hoe do I 'balance' the motors. I had rpm on front but none on the other motors until I increased the throttle, then I had to hold in forward (down elevator) to keep level.

    Great work with the project...thanks
  • Developer
    Jani Hirvinen September 8, 2010 at 1:47am
    Richard, we are working to release ArduCopter propellers rather soon. they are not so wide as APC and just today I have been testing a lot those props with our upcoming AC motors too... as quick example from our test today: 850Kv motor with 10x45, 50% power 3.4Amp, 38W, 433g thrust, 75% power 9A, 100W 885g thrust
  • Richard Hirst September 8, 2010 at 1:16am
    Please could you tell me which size props are on your quad. Also the store where they are available. I have wide blade APC's on, but I think I have too much blade area.

    Thanks
  • Developer
    Jani Hirvinen September 7, 2010 at 8:47am
    First of all, forget that I2C for now. That is not your solution for fix. Also if you already update your ESCs with 50Hz speed, that should not give feedback what you are facing now. There are some major calculating problems on your main code or on your command methods.

    Having 50Hz update should still give to you instant movement. After your control moves are more or less instant, then you can start worrying how to get faster updates to your ESCs.

    Like I sad, check out our ArduCopter code and you might find something useful. Currently our main loop runs with 100Hz and we have really stable quad.
  • Felipe Jaramillo September 7, 2010 at 8:33am
    My loop runs about every 10ms....but my ESC update every 50Hz.....I have read that I can increase the update rate of my ESC by I2C or by compressing the PWM signal to the ESC, but I dont know how to do this
  • Developer
    Jani Hirvinen September 7, 2010 at 5:52am
    Felipe, how fast your are updating it now?? Have you been timing your loops? You can also look out ArduCopter code, it is rather stable and running only at 100Hz main loop. Control movements are really fast and same is IMU response.
  • Roy Brewer September 7, 2010 at 5:52am
    There is a lot of typical dynamic behavior - what kruk callls "second order system behavior". But, if it were truly a "rise time" issue, we'd see the quad respond immediately to the joystick, just more slowly. What I see is that the response is at the same rate as the joystick, just delayed. Hence, I suspect latency on the input path.

    While I do think that MRAC or other advanced control law architecture would be educational (and MRAC or other adaptive scheme would eliminate your need to "guess" at the proper gain settings) it won't solve a command latency issue - if that is your problem.

    If the issue is response (again, I don't think it is) you can try some feedforward compensation. See this thread starting at about post 331 (but make sure you read beyond that, and perhaps even before as well): http://www.rcgroups.com/forums/showpost.php?p=15723602

    Another item to consider is friction between the quad and the mount. It shouldn't have much effect on the latency issue, but may be affecting the tendency to slowly creep up to the steady state value and to not fully return to zero.

    - Roy
    RC Groups - View Single Post - Test Fixture Evaluates Motors/Props/ESCs for Quadcopter Performance
    RC Groups - the most active Radio Control model community: electric and fuel rc airplanes,rc helis,rc boats and rc cars. Features discussion forums,…
  • Felipe Jaramillo September 7, 2010 at 5:13am
    Hi Kruk, thanks for your comments. What is MRAC?

    I study at EIA (Escuela de Ing de Antioquia).


    Anyone:

    I would like to have a faster update of my ESC, how can I do that. I know there are 2 options, I2C and having a faster PWM signal, but I have no idea how to do this. Can anyone help me with some information or links.

    Thanks
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