Relationship between pitch and vibe

ArduCopter Copter 4.2
1

Yesterday I conducted test of performance at different speeds and with different propellers.

The missions were four long out and back legs - each set of them at different speeds. The legs were in the general wind (about 10mph) direction - so the airspeeds (and associated pitch) was significantly different on the different leg directions. (downwind, less negative pitch - upwind, greater negative pitch)

I repeated the mission with different propellers.

Reviewing the logs I noticed that higher vibe numbers than I’d observed previously.

Investigating that I found that in some cases vibe is higher when the negative pitch is greater.

I’m guessing that there are aerodynamic forces at work here.

I know far more about fixed wing aerodynamics than copter or quad-copter aerodynamics - and if there’s more to be learned here, I’d appreciate any input that is offered.

Thank you!

Note - for simplicity and clarity of the graph, I’ve only graphed the Z-axis vibe from one IMU.

pitch and vibe TM props
pitch and vibe TM props1920×1080 227 KB

pitch and vibe AM
pitch and vibe AM1920×1080 219 KB

2

You can cover the flight controller, and probably the whole centre area. That should help somewhat.

3

Yeah I am experiencing the same. In altitude hold mode, while hovering the Z axis vibes are 12m/s2 but when in forward flight (12 m/s) they avg around 20. And my autopilot is very much covered from winds.

4

I have my pixhawk mounted via 4 soft bumpers and i get the same low level of vibration (<5m/s2) regardless of throttle and regardless of being in forward flight or hover.