Ardupilot will always allows bank angle up to 25 degrees in order to ensure enough maneuverability.
Is there ways to further reduce this limit? Say 20 degrees for example.
I am working with a 35 MTOW experimental quadplane VTOL, mounted with a huge flat payload over the fuselage. This design is sensible to side winds and the payload’s shape is destabilizing in turns. That’s why I’d like to limit the bank angle.
I can tolerate larger turning radios.
I am trying to explore parameters, however no matter the case, it seens that the airplane always starts the turn with 25 degrees bank angle.
Is the problem with the bank angle or with lateral (sideway) forces? An aircraft in coordinated flight shouldn’t experience lateral forces even at extreme bank angles.
I don’t know enough to help you with your original question but it might help others to know if your concern is about lateral forces or not.
Please note STALL_PREVENTION parameter is set to 1, meaning:
“when in roll controlled modes the autopilot will monitor your demanded bank angle and airspeed and work out if you have sufficient margin above the stall speed to turn at the demanded bank angle. If you don’t then the turn will be limited to the safe limit, but it will always allow a bank of at least 25 degrees (to ensure you can still manoeuvre if your airspeed estimate is badly off)”
From my understanding, STALL_PREVENTION will override ROLL_LIMIT_DEG under 25 degrees.
I will try to collect some flight data for the subject.
Might be worth testing in SITL first. I suspect you’ll find it’s limited by the lesser of the two values. The majority of planes would have the roll limits above 25 degrees so you’re working an edge case.
Heads up that you might also need to tune NAVL1_LIM_BANK if you’re using loiter turns on station and the radius isn’t what you’ve expected. A 20 degree max bank on that big of a plane is going to need a lot of room.
We do have ROLL_LIMIT_DEG 20, however at almost every turn in AUTO mode the aircraft sustains turns with bank over 20 degress for a few seconds (average 2 s).
As I said in the initial post, I am assuming ROLL_LIMIT_DEG is ignored if set bellow 25 degrees. Is it possible to check this on the codes or official documentatation?
I would like to clarify that in general this particular plane can sustain turns at 25 degrees or higher, as is expected for the majority of planes. However, I would like to limit it to 20 degrees (or lower, if possible) due to payload constraints. Increasing turn radius is no issue, I can manage it and plan waypoints and flight path as required.
The flight controller is limiting to 20 degrees as you’ve set. What you’re seeing is overshoot. Either as a result of tuning, or physical limitations/reactions of the plane.
I’m curious what sort of payload this is. In a coordinated turn, the payload shouldn’t experience any sideways forces no matter the bank angle. I’m trying to figure out how bank angle would effect side winds. I could certainly not be understanding the problem (very likely), but I don’t think bank angle has much of an effect on side winds (assuming the turns are coordinated).
Based on my novice interpretation of your log, it looks like the aircraft was making coordinated turns.
Of course you don’t owe any explanation. I’m just curious.
