Method of dynamic control of a rotary- wing drone in throw start

1. A method of dynamic control of a rotary-wing drone with multiple rotors driven by respective motors with application of differentiated motor commands to pilot the drone in attitude, altitude and speed, this method being a method for operating a transition:

from an initial state, in which the drone has its motors turned-off,

to a final state, in which the drone is in a lift condition, and from which the drone can be piloted by a user,

the drone comprising:

an accelerometer adapted to deliver values of acceleration of the drone;

a gyrometer adapted to deliver values of angular speed of the drone;

an altimeter adapted to deliver a value of altitude of the drone;

an altitude control means comprising a servo-controlled loop operating based on an altitude set-point; and

an attitude control means comprising a servo-controlled loop operating based on an attitude set-point,

said method comprising steps of:

throwing of the drone in the air from the initial state, motors turned-off;

turning on the motors and activation of the altitude control means and attitude control means; and

stabilizing the drone in a lift condition at the final state,

said method being characterized in that,

the altimeter means comprises a predictive-filter estimator that incorporates a representation of a dynamic model of the drone and operates based on a state vector containing altitude and horizontal speed variables, said method comprising the following successive steps:

a) initializing the predictive-filter estimator;

b) throwing the drone in the air by the user from an initial state, with the motors turned-off;

c) detecting a free fall state such that the norm of the drone acceleration is lower than a predetermined threshold for a predetermined minimum duration;

d) upon detection of said free fall state, fast starting by:

turning on the motors,

open-loop activation of the altitude control means, and

closed-loop activation of the attitude control means;

e) then, after a duration at least equal to a time of response of the motors to said turn-on, stabilizing the drone by:

closed-loop activation of the altitude control means, and

closed-loop activation of the attitude control means;

f) detection of a stabilization state such that the norm of the total angular speed of the drone is lower than a predetermined threshold; and

g) upon detection of the stabilization state, switching to the final state.

2. The method of claim 1 , wherein the step a) of initializing the predictive-filter estimator comprises initializing the state vector with an altitude variable between 1 m and 2 m.

3. The method of claim 1 , wherein the step a) of initializing the predictive-filter estimator comprises initializing the state vector with a vertical speed variable positive upward and comprised between 0 and 200 cm/s.

4. The method of claim 1 , wherein the step a) of initializing the predictive-filter estimator comprises initializing an interval of confidence of the initial speed of the drone at a value that is between 100 mm/s and 2000 mm/s.

5. The method of claim 1 , wherein, at step d), the altitude control means activated in open loop operates based on a fixed altitude set-point that corresponds to the initial state of the altitude estimator.

6. The method of claim 1 , wherein, at step e), the altitude control means activated in closed loop operates based on a predetermined fixed altitude set-point.

7. The method of claim 1 , wherein, at steps d) and e), the attitude control means activated in closed loop operates based on a zero trim set-point and a heading set-point that corresponds to the current heading with a zero angular speed set-point.