Modules Vibration Analysis

Source : https://groups.google.com/forum/#!topic/phoenixpilot/Ah5ZidTWSAk

You can test your vehicle's vibration in flight, and use that data to improve vibration dampening. You could use it on the test bench to detect if a particular motor is poorly balanced (although test-bed vibration response can be very different from in-flight vibration).

Note:

• It can't really work for the high frequency stuff that is problematic for accelerometer
• This will not work on older flight-controller (eg: CC3D)

On the hardware side

1. Enable the VibrationAnalysis module, click the red up arrow (tooltip: Save), and then reboot.
2. After rebooting, turn VibrationAnalysis on
3. Configure VibrationAnalysis->FFTWindowSize to 16, 64, or 256. Do not configure to 1024.
4. Configure the sample rate to the appropriate frequency. The frequency band you will be plotted is half the SampleRate frequency (don't blame me, this is the math). So for instance, at 20ms, that's 50Hz. Thus, if you are interested in frequencies around the motor speed, you will want to set the sample rate to 1/(2*motor_rpm * pi/180). So for a 10" blade which spins around 4800 rpm, you'd want about 5ms in order to best capture the motor vibrations. For a 2300kv quad on 3s at 25% throttle you'd want 4ms, and 3ms with a 4s lipo.
5. Reboot.
6. Change the VibrationAnalysisOutput metadata to FlightUpdatePeriodic = 1
7. Click the red up arrow and reboot.

Note that if you have a reset button in the board you have to redo step 6 & 7 every time the board is reset

On the GCS

That's it for the flight controller. Now we have to configure the GCS:

If you do not have a Vibration scope, then go to the Scopes page, and activate "Windows-->Edit Gadgets Mode", replace one of the scopes by the vibration analysis scope: the scope titles will appear at the top of the scopes. Change the scope you want to "Vibration".

Go to Menu Preferences/Options-->Scopes.

and change the configuration as shown in the screenshot. You can probably leave it at measuring the x-axis, unless you have a reason to suspect that there might be more vibration in the y. This is likely not the case on a quad, but could be on a fixed-wing.

The Max value can be set to 0 to autoscale (there's a tooltip to remind you of this if you forget). However, I find that setting the autoscale makes it a little hard to compare before and after shots, so I like to use it only to get a feel for the right range. I find that 150 is a nice value.

You should be good to go. Your scope should now give results like this, where the bottom axis is the frequency, the y-axis is time, and the color is intensity: