Using pitch to indicate relative airspeed - correlating airspeed with vibe stats

I’ve been going through the process of reducing vibe stats on a Tarot X4.

I’ve managed to get the stats down to an acceptable level - except when forward motion exceeds certain thresholds of airspeed.

Today provided a good opportunity to take some measurements. I flew a mapping mission at 5 meters per second groundspeed where the upwind leg had a 5 knot headwind, and the downwind leg had the associated tailwind.

Without an airspeed measurement - I’m substituting pitch. (more negative pitch correlates with higher airspeed) This graph shows that with negative pitch where the copter overcomes the headwind to maintain 5 meters per second - the vibes are bad.

When the pitch is close to zero on downwind legs, the vibes are acceptable.

The Tarot X4 has no body work - so my guess is that as wind increases over the flow of the body, it causes enough turbulence to cause vibration. I can test this by engineering some bodywork or fairings.

Before heading down that path - I’m wondering if anyone has had to deal with this situation - and could perhaps suggest other possible causes to investigate.

Many thanks!

Here’s what you do. Start by mixing up a big batch of JB Weld. Then fold the arms out and…
Just kidding Joseph, I’m sure someone can suggest a better solution :slight_smile:


Have you looked at the windspeed estimation function?

Once it’s set up then it’s reasonably accurate but it takes some work to get dialed in.

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No - this is the first time I’ve had an issue related to airspeed.

Thanks for the reference.

I’m not sure having more precise airspeed data would help here - but maybe I’m not looking at the big picture.

I guess I’m seeing two things here.

Vibration - Vibes will always go up with airspeed. How much is depends on lots of variables. Some times it’s just the result of the horrible aerodynamics that make up most multirotors and there isn’t much you can do.

Airspeed - If you want to calculate and get a good idea of what’s going on, the windspeed estimation will make all your airspeed calculations that much more accurate. It does all the work of using pitch and roll to figure out what the wind is. Once you know the wind speed and ground speed then airspeed is easy to figure out.

But if I’ve missed the point of your question just say so. :slight_smile: