dinsdag 3 april 2012

Vibration troubles

Indeed, the Razor 9DOF imu is really sensitive to vibrations. Motor vibrations cause that much noise on the sensors that this board really can't be used in a multicopter. But you can fix this with some tips & tricks.

I really have tested everything to reduce vibrations. Nylon spacers/srews, foam, rubbers, rubber band,... just everything you can imagine. The only thing that really helps to reduce vibration noise is to make a motor mount that is completely saperated from the frame by some rubbers. I will give more details on this in my next blog.

With homemade motormount I was able to
- reduce GYRO noise to 1%
- reduce ACC noise with 90%

I noticed that the MAG on this IMU board is sensitive to EMF caused by motors and/or current. When motors spin up the data on the MAG shifts up or down. I'll investigate this later and try to find a fix for this problem. So Currently I can't use the DCM algoritme. But using GYRO and ACC raw data should be enough to get my quadcopter stable.

I also noticed that increasing the ACC update rate increases the noise on the raw data. I currently update my ACC at 12hz to get a good result.
But by using the GYRO (100hz) data and ACC (12hz) data in one formula I still have an output rate at 100hz!

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