I'm would like to log the windspeed and wind direction while my copter is in loiter mode. Before I strap a cup anemometer to the top of my copter I figured I would ask about the possibility of pulling windspeed and direction from the APM. Is this something that is already tracked?
It seems that one of the main PID values to tweak for high wind loiter is LOITER_P which is the rate at which the copter will move towards the target point. Any hints on getting windspeed?
Thanks in advance,
--Doug
Replies
Doug,
I realize this thread is a bit old, but having just got my Pixhawk Hexcopter flying this past month, I've found myself asking the same question as yourself. As I walked my dog around the park yesterday, I found myself mumbling quietly along, "....pitch angle, zero acceleration state, zero-wind calibration in loiter mode....." bla bla bla. I finally pulled my head up and have settled on the following (but I'm open to new ideas):
First one would have to find a perfectly calm, windless day, and run a calibration procedure similar in process to Auto-Tune. This tuning mode would make multiple GPS-based constant-velocity (not accelerating) runs, and measure the average pitch angle when the aircraft was no longer accelerating (basically, measuring actual pitch angle vs measured GPS velocity). After making runs at say 2.5, 5, 7.5, 10, 12.5, 15, 17.5, and 20 meters/second, the collected data points (pitch vs. velocity) could be extrapolated between, and create a datum to be referenced at a later point to display "true wind speed and direction" whenever the aircraft is in stick-neutral loiter mode.
I believe this is a better theoretical alternative to simply using GPS drift for measurement, as I'm not a huge fan of letting my copter drift away from me just to find out that the wind is doing.
Anywho, its all just 1's and 0's I suppose, but the application potentials are pretty cool for meteorology (I imagine positioning a multirotor at the base of a roaring forest fire to measure draft velocity at various altitudes, or in a less-extreme situation, simply measuring wind velocity and direction at various altitudes.
Did you ever learn any more about this topic?
Cheers,
Danny in Seattle
I don't know anything about using the APM for wind speed, you may be able to use GPS drift. Instead of a cup anemometer you could use an ultrasonic one, no moving parts. I don't know if there is a really small one though.