Airspeed vs. ground speed with head wind.
Is there a way to have the APM increase the throttle when flying into the wind to maintain a minimum ground speed?
For example if the cruise throttle is 50% at 10m/s and the wind is 10m/s, when flying directly into the wind the APM doesn't seem to increase the throttle and instead just sits there basically hovering in one spot, when there is still another 50% throttle available to easily overcome the head wind.
If the airspeed sensor is disabled, the throttle would be increased strictly due to the decreased ground speed, but that also has other drawbacks such as poor track following due to not knowing the direction of the wind to properly compensate. It seems like it would be useful to have both min/max/cruise airspeeds and ground speeds so they can be configured independently of one another to overcome this issue?
Replies to This Discussion
-
Permalink Reply by Jonathan Challinger on -
Yes, that functionality is present. MIN_GNDSPD_CM is in centimeters per second and determines your minimum groundspeed, increasing your airspeed to compensate for wind. Will not exceed your max airspeed (which needs to be set correctly! Otherwise it will dive the plane into the ground trying to gain speed!)
ArduPlane currently does not compute the speed and direction of the wind at all and cannot follow tracks correctly, with or without airspeed sensor. As it has no crosstrack integrator, it is impossible for it to reach the track line in wind.
-
Permalink Reply by Mike on
-
If Arduplane doesn't calculate wind speed/direction, where do the "wind_dir" and "wind_vel" values come from?
-
Permalink Reply by Jonathan Challinger on
-
The planner.
-
Permalink Reply by Mike on
-
Interesting... I didn't realize its the planner that calculates that.
I ran some tests changing MIN_GNDSPD_CM while heading into a 7m/s head wind with a cruise airspeed set to 7m/s (effectively a 0 ground speed) but I wasn't able to get the throttle to change at all. The maximum airspeed was set to 22m/s.
Is there something else that I'm missing perhaps? The cruise throttle is set to 40%, so there is lots of room available there.
-
Permalink Reply by Jonathan Challinger on
-
Not sure, it isn't something I've used, I'll look at the code for it soon.
-
Permalink Reply by Jonathan Challinger on
-
Don't see why it wouldn't be working.
I'll test it in SITL at some point.
Edit: Are you sure your airspeed tuning actually reaches and holds an airspeed?
-
Permalink Reply by Mike on
-
I did this all in Xplane and the plane would hold the airspeed perfectly at slightly below the minimum throttle setting (33% rather than specified 40%) even while being pushed backwards by the head wind.
This was all in auto mode of course.
I should maybe clarify, in your first post you said: " increasing your airspeed to compensate for wind. Will not exceed your max airspeed (which needs to be set correctly! Otherwise it will dive the plane into the ground trying to gain speed!)"
I know APM will point the nose down to increase airspeed in some cases, but usually only to the cruise air speed, not the maximum airspeed. Are you saying it would point the nose down to increase the ground speed as well, or just increase the throttle, or both?
-
Permalink Reply by Jonathan Challinger on
-
Ok, I'll look at correcting it. By the way, if you have an airspeed sensor, you will not be using the throttle setting.
Additionally, you should check that target_airspeed is holding steady.
Social Networking
Top Content
Contests
Season Two of the Trust Time Trial (T3) Contest has now begun. The fourth round is an accuracy round for multicopters, which requires contestants to fly a cube. The deadline is April 14th.A list of all T3 contests is here.
Groups
-
Moderators
24 members
-
ArduRover User Group
184 members
-
ArduCopter Italian Group
87 members
-
Documentation Editors
51 members
-
ArduPlane User Group
682 members
Advertisement
© 2013 Created by Chris Anderson.
Powered by
