Replies

  • Randy, do you still have a direct link to the vibe data handy? I get lost in 250+ pages.

    And did you try using foam or gel on the daughter board instead of the included silicone spacer for vibration isolation? Even if execution is bad, the concept is sound.
  • Developer

    I know this is an old thread but in my limited experience with this board, the vibration isolation system being used doesn't work well.  It's appeared on the Copter-3.3 beta testing thread and it's very high vibration levels are so bad I've used the logs from the copter involved as a worst-case example on the Measuring Vibration wiki page.

    On the plus side, it's allowing us to test the EKF in very high vibration environments :-).

    Anyway, I guess my advice for people is stick with the simple 3M foam solution unless the alternative has real testing behind it to prove it works better.

  • I have seen in Taobao,but I do not think open source pcb file.

  • I like this. Great to see alternate suppliers for this gear. As Chris states, we should see the open source files available as well...we hope :)

    • I lost my SW when my transmitter LiPO ran out of juice and after RTL the plane's GPS went haywire.. I suspect its because of the vibration (due to the 3/4 auto max throttle) -- I was using an APM2.6, the pixhawk is supposed to have an improved filter..   At any rate, looking forward if somebody is able to get one and test?  according to the aliexpress the Cuav is available this month.

      Looks like the cuav does not have redundant sensors:

      CUAV:

      ST Micro L3GD20H 16 bit gyroscope
      ST Micro LSM303D 14 bit accelerometer / magnetometer
      MEAS MS5611 barometer

      compared to the 3DR version:

      ST Micro L3GD20 3-axis 16-bit gyroscope
      ST Micro LSM303D 3-axis 14-bit accelerometer / magnetometer
      Invensense MPU 6000 3-axis accelerometer/gyroscope
      MEAS MS5611 barometer

  • I am wondering if we could add weight to the isolated IMU (lead or something similar) to improve the vibration dampening effect?

    • Jethro -

      Opinions of some quadcopter gurus aside, the cure for vibration is NOT to simply add weight to the resonant mass. The recipe for vibration damping is to find the correct amount of preload to the dampers to move the resonant frequency out of the expected operating range.

      Adding weight is ONE way of adding preload; it is an effective one as long as the flight controller is never expected to operate at more than 45° or so from horizon. Much more than that, or inverted, and the added weight becomes a pendulum which can work against you with disastrous effect.

      I've been flying micro-helis for years; there, the entire heli weighs between 30-40 grams. (Yes, the nanos are even lighter; but I got into quads before they became popular) As you can imagine, even a few grams makes a huge difference in balance, power, and flyability, so using weight to alter the damping of the FC is really unfeasible.

      There, the solution in general is to find a combination of layers of different kinds of foam mounting tape, then add a little preload by wrapping a rubber band around the whole FC and frame.

      With a suspended module like this one, the solution I would seek would be to keep the resonant mass as small as possible and adjust how tightly the elastic bands are stretched. This will alter the resonant frequency just as tightening a guitar string. Other avenues to consider would be application of silicone RTV sealant across the elastic bands to alter their resonant frequency.

      Of course, if mounting on a large quad that can handle the added weight, it may be simpler to just mount the FC to one of the existing popular vibration mounts, and enjoy even greater stability due to having two layers of vibration damping.

      My current experiments with this $5 vibration mount foam-taped to my FC are VERY promising, even in acro mode with inverted flight. The design stretches the rubber bushings slightly, which provides a certain amount of preload. So far, it is very effective, and there is no "flop" movement when transitioning to inverted flight as one experiences with the AVDome.

      I think this FC, mounted to that vibration mount, could be a vibration "killer combo".

      But first... before we go doing ANYTHING that alters its vibration damping characteristics, we REALLY need to get them in our hands to do some baseline tests.

      Come on guys... you know you have our attention. Now it's time to deliver some product!

      Paul

    • It would depend on the resonant frequencies within the chassis, motors, IMU etc. The amount of weight you add would change with every setup. Adding an amount of weight could make the IMU resonant at the same frequency as another major one present in the frame. On the other hand, if you do it right it could be very effective.

      If I were going to try, I'd measure the frequency signature of the copter, the try and make the IMU most resonant at a frequency that as different to the ones in the frame and their harmonics as possible. Its tricky which is why I wouldn't bother.
  • Wow, this is a really stunning design! I love the isolated IMU and aluminum casing, that just screams quality. I think for the pixhawk v2.0 these hardware design considerations should be applied. It will make the Pixhawk the flight controller to beat. That in combination with better connectors would make this a true game changer. Impressed.

  • 3D Robotics

    Very impressive. This is exactly the sort of innovative derivative design that open source is intended to inspire. As long as they adhere to the license terms and release the design files back to the community, I'm all for this. 

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