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My new octocopter frame

Posted by Peter Koch on March 13, 2011 at 2:30pm

This is the new folding frame Project I am working on.

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Can anyone tell me if it´s possible to control the eight counter rotating motors with ACM.

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  • Developer
    Jani Hirvinen April 5, 2011 at 9:43am

    Denny yes some part are true and some are not. MK and others including us are moving out from I2C due that BUS is just a bit too unreliable. It can be used but with some limitations. I personally don't want to put any bigger payloads on ESC's having I2C bus, Magnetometer, Baros etc on same bus. Ok BUS can be splitted to make it more resilient for problems.

     

    Naturally Quad is more efficient than hexa, octo but then again if you properly control your motoros on especially on hexa setup, it will give redundancy for users. Yes it wastes a bit for efficiency but hey I rather waste a few mAh's when carrying x.xxx USD cameras on board.

     

    IF and WHEN we find good reliable monster motors and big propellers that can be used on quads, i guarantee that after all the tests has been done, they will end up on store. Like said, I already have graveyard of motors at corner of my office. Now this graveyard weights about 4 Kilos... (Calibrating maggys on my office is painful ;) )

     

    Ok there are ways to make good I2C ESC's and we are working on those. We are also working to create other type ESC's so stay tuned on that. But general PWM ESC's are also really good for normal and even for advanced flights.

     

    Yes our hexa setup uses 6 x PWM ESC's to avoid any problems on the BUS it self.

  • Denny Rowland April 5, 2011 at 12:50am
    One of my Okto designs used two FC's. one quad system in + and one in x , Total dual redundancy from receivers to flyboards.
  • Denny Rowland April 5, 2011 at 12:42am
    There are ways to stop the I2c from shutting down in the event of one motor failure. My take on this is that with only 4 motors you only have just those points of failure to worry about.  Larger motors and ESC's tend to be better made and more robust.
  • Brendan April 4, 2011 at 11:02am
    I don't want MK fireworks kit... but if I'm understanding Jani correctly, the hexa setup does not us I2C, just 6x fast PWM, so there *shouldn't* be fireworks of any sort. Maybe later I'll start thread to inquire about experiences with hexa platform and survival rate with ESC/motor failure. Even a simple testing procedure without writing a program to shut off motors would be nice, for example disconnecting one ESC at a time and doing test flights with X wind factor and Y payload with Z motor/ESC/prop combo....... anyone?
  • Denny Rowland April 4, 2011 at 10:17am

    I have never had a hexa but if you loose a motor, an ESC or a wire comes off etc.etc. then the I2c goes down and all motors will stop. affectionally known as the MK fireworks kit. You can use a Flyboard I2c/ppm converter or a I2c isolator and theoretically it should stay in the air, if you have 6 or more motors. I have never seen it demonstrated though.

    When Holger demonstrated the Okto flying with motors out it, was all done with a special program to shut each of the motors down manually. My take on it is this. with only four motors you just have four possible failure points. Larger more powerful motors and controllers tend to be better made and more reliable. Just my humble opinion. 

  • Brendan April 4, 2011 at 6:51am
    I've heard of hash-octo frames losing control after loss of one motor, but everything I've read about the hexa design is that it still is stable and controllable with only 5 motors working. Have you had different experience?
  • Denny Rowland April 4, 2011 at 6:13am
    What is the point of redundancy when the loss of one motor causes loss of control ?
  • Brendan April 4, 2011 at 4:24am
    @Denny
    Although I agree the quad is more efficient, I'm surprised you're not going with more rotors for the sake of safety/liability, especially if you're doing video on pro level.
  • Cliff Dearden April 4, 2011 at 4:05am
    Many thanks Denny.
  • Denny Rowland April 4, 2011 at 1:40am

    Cliff

    You can find that info on the MK site. Look under the MK 3538 lift curves. Once you know the weight of your motor + wires. arm, ESC, nuts and bolts etc.etc. Then calculate the flight time based on the lift info given for say the MK3538 motor. every time you end up with less endurance for the same battery.

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