I am using adxl335 3-axis accelerometer and lpr5150al 2 axis gyro in IMU. This Imu is catching up vibrations, due to which i am not able to get stable pitch and raw values. IMU gives stable output at lower rpm of bl motor. (hextronik dt750 + 25A basic ESC). I have used rubber sheet to dampen vibrations ,however at higher rpm of motor it did not make much difference. I am still finding other ways to reduce vibrations. And to mention my IMU lands directly on aluminum quad frame with rubber sheet in between. I have also noticed that the Gyro hardly responds to slow rotations.
I am little confused what to do. Should I try reduce the vibrations OR should I go for better sensors like ADXL345+itg3200?
Haven't used either. What is the IMU? What software?
What sensors are the vibrations affecting? Is it a gyro issue or an accelerometer issue?
If you get a sense of the frequencies where the vibration is causing the most problems it may be possible to make some physical tweaks to change the frequency or software tweak to filter out the offending frequency band. Not that I've personally done this before, so I defer to the experts.
IMU is inertial measurement unit. I guess both accelerometer and gyro are getting affected by vibrations. But not totally sure about that. I am using Kalman filter for state estimation. I have been tweaking it ,and have brought down the variation in pitch and raw values down to 3-8 degrees. This error build up and PID wouldnt be able to produce precise correcting signal to stabilize the quadcopter. I think 3-8* variation is a lot, so I am trying to reduce the mechanical vibrations itself to get stable values. I am not sure the freq band in which its causing vibrations. How do you measure it?.
Sorry for the confusion -- I was curious about which IMU you were using. I realize now that you most likely have a custom-built IMU.
Can you determine which sensor is most corrupted by vibration?
If you can ecord/log raw sensor readings along with time then you could transform to frequency domain (I would do this with Octave) and see if there's any obvious spike of amplitude at a particular frequency. (Might be useful to sample at fairly high rates ala nyquist-shannon sampling theorem)
Probably the simpler answer is: try a different sensor. Vibration is going to invoke a signal on any accelerometer. But it shoudn't wreak too much havoc on a gyro. My only experience with this was a ground vehicle, where one particular gyro was unusable due to vibrations and switching to a different gyro solved the problem immediately. I suspect that some gyros are less affected by vibration than others.
Okay. Thank you.
Good news is that, the problem is almost solved . Built a new aluminium frame and used sponge as vibration dampener. I could really notice the difference between the old and the new quad frame. Motors stand firmly on the frame.
Well what software are you using?