I just did today a bench setup and tests of my Talon Vtail mixing.
I post hereunder pictures showing the results. What is strange to me is that only one ruddervator moves when rolling (in FBWA mode), when theoritically the two should move in opposite directions as described in the wiki.
Can anyone, who has done this already, check my pictures and tell me if this is normal or not ?
Rolling to the left, I get this:
And then rolling to the right , I get this:
I have correct movements of both ruddervators when pitching (both go up or down).
I have this setup:
-APM plane last version
-Pixhawk
-Vtail output = 2
-KKDRMIX = 0.5 (I tried increasing this to 1 but then it seems to move a bit more but not much)
-I have done the accel calibration (so obviously pixhawk knows what is the horizontal level)
Any suggestions, ideas why the Vtail mixer is behaving like this ?
As a side not I have setup the control horns quite high to limit the maximum surface rotation to 20 degrees. Maybe too restricted ? As shown here :
Replies
Hi Hugues,
Firstly, read the Wiki on setting up Vtail, and do it.
Then, make sure that in MANUAL, all your control surfaces respond as they should.
I'm assuming you have flown RC before.
This is where I go off on a tangent.
Put it into STABILIZE, pitch Talon nose down, both ruddervators should pitch up, and vice versa.
Roll Talon to the left, right aileron should pitch up, left down, and vice versa.
And this is where it might get tricky, if you roll to the right, one of the ruddervators should now also initiate a right TURN.
Once again, vice versa.
Same as feeding in a bit of rudder flying normally.
If the above go the opposite direction, read the wiki again:-)
Make those control horns the same length as the servo horns, just my two cents....
Wiki read, done (was already done multiple times)
I manual, everything OK.
I have never flown a rc plane before, except on simulator. I am only a multicopter experienced pilot at the moment, trying to learn the fixed wing world now...
Pitching movements are OK and in correct directions.
Now we come to my question: do you say that when plane rolls right, the plane shoult intiate a right turn OR the tail should go right (plane yawing then left) ?
Hugues, plane, or pilot should also initiate some rudder, in the direction of the turn.
Straight wing planes like Talon, and helicopters :-), require three things in a turn:
Roll in the direction you want to turn, a bit of up elevator to pull it into the turn, and a bit of rudder to stop the tail from sagging downwards in the turn.
Just a suggestion, if you have never flown a plane before, Talon isn't the one you want to start with.
Get something slow, with wheels, fly it until you can do loops, roll, inverted flight, and good landings.
Otherwise, your Talon will have a very short life.
I suggest the ST Models Discovery, and a good instructor.
Not to rain on your parade, but I've been in RC since 1980, and there is no reason for you to repeat my mistakes !
Thx for useful advice.
I come back to my initial question because although if the intent is to turn right , you will indeed act on the vtail to yaw right. But my question was in the context of the auto stabilize FBWA mode which will do what is required with the Vtail to act AGAINST the unwanted right roll. So in that case the ruddervators should move as if the plane must yaw left? Did I understand this right?
There is a setting (whose name I forget) that puts in some elevator when you roll in order to pitch the nose up a little to maintain altitude in turns. If you keep your airframe pitch level when you do your bench rolls then that added elevator will counteract the downward movement you are expecting to see in the upper ruddervator. Try pitching the nose up by 5 or 10 degrees as you do the roll test and see if that gives you the effect you are expecting (or find the setting and disable it temporarily for the test)
ok thx. Did not know that such setting existed.
What about the throw direction on my pictures? Intuitively I'd say they are the wrong way although they move according to what the wiki says. In fact the wiki says FBWA should react to counter the roll; however it is not clear how a ruddervator movement could counter a roll (a ruddervator is used to pitch or to yaw, not to roll). Therefore it is confused...
Any clarification welcome!
Yes, that is normal.
Download Juan's parameters, just make sure your control throws are in the correct direction!
I'm using short horns on my ruddervators.......
I so would like if we can keep all Talon stuff together :-)
http://diydrones.com/group/x-uav-talon?
Oh yes another question: are my throws direction OK in my pictures?
Can't find Juan post!?
https://api.ning.com/files/8pnqwPqNt2MDEal1QQdKE2cwN9NOAXt4E*JqeSgWz8LZ-lu0veroqtO9G-mkx9-23vQQ5nf3GYJqAxhpw6ZhfiU5LR7UILBI/GustavTalon20140420.param
Try my param file :-)
Absolutely NO guarantees given, but this is what I fly with........
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