WO2019238375A1

WO2019238375A1 - System and method for controlling the flight of a fixed-wing convertible drone for providing a stabilised seamless transition between a vertical stationary flight and a horizontal cruise flight

Info

Publication number: WO2019238375A1
Application number: PCT/EP2019/063323
Authority: WO
Inventors: Jacson Miguel Olszanecki BARTH; Jean-Philippe CONDOMINES; Michel Fliess; Jean-Marc MOSCHETTA
Original assignee: École Nationale De L'aviation Civile; Institut Supérieur De L’Aéronautique Et De L’Espace; Alien Sas
Priority date: 2018-06-12
Filing date: 2019-05-23
Publication date: 2019-12-19
Also published as: FR3082327B1; FR3082327A1

Abstract

A flight control system is configured to control the flight of a fixed-wing convertible drone (12) having two left and right wings, each supporting a forward propeller and a trailing flap at the rear edge. The control system comprises an attitude regulator (154) of the drone (12) for respectively controlling the roll angles, φ _m , pitch angles θ _m and yaw angles Ψ _m, measured by one or more sensors over reference roll angles φ _d, reference pitch angles θ _d and reference yaw angles Ψ _d . The first attitude controller (154) comprises a first modelless MFC SISO control device (162) at an input-output for regulating and controlling the pitch angle θ _m measured over the reference pitch angle θ _d by determining a first command δ _n for symmetrical deflection of the left and right flaps, applied with the same sign to said left and right flaps.

Description

The present invention relates to a method for the automatic flight control of a convertible drone. The present invention relates to a method for the automatic flight control of a convertible drone. fixed wing allowing a continuous and stabilized transition between a vertical hover, in particular a vertical take-off or landing, and a cruise flight substantially horizontal.

The invention relates to a system and method for continuously monitoring the flight of the drone, in particular its attitude, and its stability during all phases of flight of the drone, in particular during a continuous transition phase.

Convertible fixed-wing drones are unmanned vertical take-off and landing (VTOL) and fixed-wing (in English "fixed wing") unmanned aerial vehicles, which combine the advantages of an aircraft classic fixed wing and VTOL vertical takeoff and landing aircraft, namely the ability to take off and land vertically, high horizontal cruising flight speed and increased endurance.

Typically, the fixed-wing convertible drones allowing a continuous and stabilized transition between a vertical hover, in particular a vertical takeoff or landing, and a substantially horizontal cruise flight are the "tail-sitters".

A tail-sitter is defined as a vertical take-off and landing aircraft which takes off and lands vertically on its tailplane, then flips horizontally forward using differential thrust and / or control surfaces to reach a flight horizontal cruise.

A continuous transition phase between a vertical hover phase and a substantially horizontal cruise flight phase, is defined as an intermediate transition phase of smooth, uninterruptible linkage and the use of a control system and method. different from that or those of the connected flight phases.

During a transition phase performed at a constant altitude, a convertible fixed-wing drone, known to be a system nonlinear aerodynamics, must face very high angles of attack, often a wing in a partial state of stall and a rapid change of the moments of pitch.

In order to remedy these difficulties and according to a first approach, various known methods for controlling a convertible fixed-wing drone, evolving continuously and stably in the transition phase, use a complex global model of the aerodynamic behavior of the drone and require sophisticated and precise characterizations of the drone in the wind tunnel, in particular the forces and moments observed on a wing that is partially stalled and on control surfaces. For example, the document by L..R. Lustosa, entitled “Longitudinal study of a tilt-body vehicle: modeling, control and stability analysis” and published in the proceedings of International Conference on Unmanned Aircraft Systems (ICUAS), Denver Colorado, USA, pp. 816-824, June 2015, describes such a control process, and the document by LR Lustosa et al., Entitled “Team MAVion entry in the IMAV17 outdoor challenge: A tail-sitting trajectory- tracking pUAV” presented to International Micro Air Vehicle Conférence and Compétition, Toulouse, France September 2017 describes such characterizations.

Following a second sensor-based approach (in English

"Sensor-based"), the document by E.J.J. Smeur et al., Entitled “Adaptive Incrémental Nonlinear Dynamic Inversion for Attitude Control of Micro Air Vehicles” and published in Journal of Guidance, control and dynamics, Vol. 39, No. 3, pp. 450-461, March 2016, describes a process for controlling a "rotorcraft", called "non-linear dynamic inversion INDI incremental

(in English "Incrémental Nonlinear Dynamic Inversion") which could be applied in a similar way to a convertible drone with fixed wing. This control process depends less on a global model and gyi is more robust with respect to the rejection of disturbances. This INDI process requires a measurement by sensor to estimate a large part of the drone model, with the exception of the dynamics of the actuator which must be characterized beforehand. By filtering and differentiating the gyroscopic measurements, the angular acceleration is estimated and an increment of the input command is calculated from a desired increment for the angular acceleration. In this way, the disturbances as well as the dynamic not models are measured, calculated and compensated. However, the INDI process must use numerous test data of the drone in flight to finely adjust the coefficients or control parameters.

A first technical problem is to make a system and a method for controlling the flight of a convertible fixed-wing drone more adaptive during the crossing of all its flight phases, including phase (s) of transition between a vertical hover and a substantially horizontal cruise flight, and to control the complex model of a drone with non-linear dynamics, unknown or partially known, without the need for knowledge of a global model describing the dynamic behavior of said drone.

A second technical problem is to increase by the system and the control method the rejection of disturbances, in particular aerodynamic, as well as faults of any type of actuator without knowing a global model of the drone describing the dynamic behavior of said drone, in particular its nonlinearities.

To this end, the invention relates to a flight control system of a convertible fixed-wing drone allowing a continuous and stabilized transition between a vertical takeoff and a horizontal cruise flight or between a horizontal cruise flight and a landing vertical, the drone comprising: a platform formed by a pair of fixed wings, left and right, fixed symmetrically and rigidly on either side of a solid central connecting element; and a pair of propellers, left and right, supported respectively in front by the left wing and the right wing while being arranged symmetrically on either side of the solid central connecting element; and a pair of deflection flaps, left and right, supported respectively at their rear edge by the left wing and the right wing, being arranged symmetrically on either side of the solid central connecting element. The control system comprises a first regulator of the attitude of the drone for controlling, respectively according to a first loop for regulating the roll angles <p _m , pitch 0 _m and yaw i | / _m , measured by one or more sensors of the drone, on setpoint angles of roll (p _d „pitch 0 _d and yaw i | / _d . The control system is characterized in that the first attitude regulator comprises a first MFC SISO control device without model at one input- an output to regulate and control the pitch angle 0 _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal of the first MFC SISO control device without model, on the pitch set angle 0 _d provided as a parameter in a second input terminal of the first MFC SISO device, by determining a first command d _h of symmetrical deflection of the left and right flaps, delivered in an output terminal of the first MFC SISO device for modelless and applied control with the same sign on said left and right flaps.

According to particular embodiments, the flight control system of a convertible fixed-wing drone comprises one or more of the following characteristics:

.- the first modelless MFC SISO control device with one input-one output includes:

. * a first estimator configured to estimate a first parameter F _e of a first Ultra Local Model, the first estimator having a first first input terminal and a first second input, connected respectively to the first input terminal of the first device MFC SISO for receiving the observed pitch angle 0 _m and the output terminal of the first device MFC SISO for receiving the first command current _h symmetrical deflection of the left and right shutters, and having a first first output terminal for providing the estimate of the first parameter F _e , the first Ultra Local Model describing locally over a limited time interval the temporal variation of the temporal derivative to a predetermined whole order n _q of the pitch angle observed 0 _m as a function of the parameter F _an estimating and the first command associated with current _h according to the equation:

= F _e + a _q d _h in which a _q is a predetermined parameter for scaling the first current command d _h with respect to the pitch angle 9 _m measured so that the first current command d _h and the pitch angle 9 _m measured have the same order of magnitude; and

. ^* A first intelligent closed loop module having a first second output terminal connected to the UAV through the output terminal of the first device MFC SISO to provide deflection control a _n updated symmetrical deflection of the left and right shutters, and having a first third input terminal, a first fourth terminal input and a first fifth input terminal respectively connected to the first input terminal of the first MFC SISO device to receive the observed pitch angle G _m , to the second input terminal of the first MFC SISO device to receive the pitch setpoint angle q _ά to be continued and at the first first output terminal of the first estimator to receive the estimate of the first parameter F _e of the first Ultra Local Model, the first intelligent closed loop module comprising a first corrector of classical linear system of order equal to the derivation order n _q of the first Ultra Local Model and gain K _q , a first derivation order differentiator n _q of the pitch setpoint angle q _ά and a first amplifier gain 1 / a _q , and

the first estimator and the first intelligent closed loop module are configured so that the first control current d _h symmetrical deflection of the left and right flaps satisfies the relationship:

_ R ~ q. ^q ά ^{q) + K} qxq.

na _q a _q

.- the first parameter a _q of scaling of the first current command d _h relative to the pitch angle 9 _m measured is determined arbitrarily or deterministically using a predetermined algorithm so that the first current command d _h and the pitch angle 6 _m measured have the same order of magnitude; and / or the order of the time derivative n _q of the observed pitch angle 6 _m used in the first Ultra Local Model is equal to 1 or 2, preferably equal to 2, and / or when the order of the time derivative n _q is equal to 1, the transfer function of the first corrector is of the first order and of the proportional gain type and when the order of the time derivative n _q is equal to 2, the transfer function of the first corrector is of the second order and of the gain-proportional or gain-derivative type, or even a Proportional- Integral- Diverter;

.- the first attitude controller comprises a second MFC SISO control device without model with one input-one output for regulating and controlling the roll angle <p _m , measured at the output of the drone by one of its sensors and provided as a first input terminal of the second device model MFC without control SISO on the f roll set angle _provided as a parameter to a second input terminal of the second device MFC SISO, determining a second D5 command from antisymmetric deflection of the left and right flaps, delivered to an output terminal of the second MFC SISO control device without model and applied with different signs on said left and right flaps in addition to the first symmetrical deflection command d _h applied with the same sign on said left and right flaps;

.- the second MFC SISO control device without model at one input-one output includes:

. ^* a second estimator configured to estimate a second parameter F ^ of a second Ultra Local Model, the second estimator having a second first input terminal and a second second input terminal, connected respectively to the first input terminal of the second MFC SISO device for receiving the observed roll angle <p _m and at the output terminal of the second MFC SISO device for receiving the current second command Ad of asymmetric deflection of the left and right flaps, having a second first output terminal for provide the estimate

of the second parameter F ^, the second Ultra Local Model locally describing over a limited time interval the time variation of the time derivative to a predetermined whole order n _f of the observed roll angle <p _m as a function of the parameter F ^ to estimate and the second associated command Ad of current according to the equation:

= R _f + a _f · Ad in which a _f is a predetermined parameter for scaling the second current command Ad with respect to the pitch angle <p _m measured so that the second current command Ad and l 'roll angle (p _m measured have the same order of magnitude; and

. ^* a second intelligent closed loop module, having a second second output terminal connected to the drone through the output terminal of the second MFC SISO device to provide the second updated Ad command for asymmetric deflection of the left and right flaps, and having second third input terminal, a second fourth input terminal and a second fifth input terminal respectively connected to the first input terminal of the second MFC SISO device to receive the observed roll angle (p _m , at the second input terminal of the second MFC SISO device to receive the roll setpoint angle <p _d to be continued and at the second first output terminal of the second estimator to receive the estimate F ^ of the second parameter F ^ of the second Ultra Local Model, the second intelligent closed-loop module comprising a second conventional linear system corrector of order equal to the derivation order f _q of the second Ultra Local Model and of second gain k _f , a second differentiator order of derivation n _f of the roll setpoint angle <p _d and a second gain amplifier> ®t

the second estimator and the second intelligent closed loop module are configured so that the current second command D5 for asymmetric deflection of the left and right flaps checks the relationship:

.- the second parameter a _f of scaling of the second current command D5 relative to the measured roll angle <p _m is determined arbitrarily or deterministically using a predetermined algorithm so that the second current command Dd and the roll angle <p _m measured have the same order of magnitude; and / or the order of the time derivative n _f of the observed roll angle (p _m used in the second

Ultra Local model is equal to 1 or 2, preferably equal to 2; and / or when the order of the time derivative n _f is equal to 1, the transfer function of the second corrector is of the first order and of the proportional gain type and when the order of the time derivative

is equal to 2, the transfer function of the second corrector is of the second order and of the gain-proportional or gain-derivative type, or even a Proportional- Integral-Diverter;

.- the first attitude regulator includes a third MFC SISO model-free control device with one input-one output to regulate and control the yaw angle xj _m , measured at the output of the drone by one of its sensors and supplied in a first input terminal of the third MFC SISO control device without model, on the yaw set point angle _ά supplied as a parameter in a second input terminal of the third MFC SISO device, by determining a third control Dw of modification in the same direction of rotation of counter-rotating nominal speeds of rotation and of the same amplitude -w _h , + w _h of the left and right propellers, delivered in an output terminal of the third MFC SISO device for control without model and applied with the same sign on the left and right propellers in addition to the respective nominal speeds -w _h , + w _h of the left and right propellers corresponding to the case of a measured yaw angle xjj _m zero;

.- the third MFC SISO control device without model at one input-one output includes:

. ^* a third estimator configured to estimate a third parameter F y of a third Ultra Local Model, the third estimator having a third first input terminal and a third second input terminal, connected respectively to the first input terminal of the third MFC SISO device to receive the observed yaw angle ip _m and to the output terminal of the third MFC SISO device to receive the third command Dw for current modification in the same direction of rotation of the counter-rotating nominal rotation speeds of the propellers left and right, and having a third first output terminal to provide the estimate F of the third parameter F ^, the third Ultra Local Model describing locally over a time interval restricts the temporal variation of the temporal derivative to a predetermined whole order

of the observed yaw angle ip _m as a function of the third parameter _y to be estimated and of the third associated command Dw current according to the equation:

Dw in which

is a predetermined scaling parameter of the third current command Dw with respect to the yaw angle i / j _m measured so that the third current command Dw and the yaw angle i / j _m measured have the same order of magnitude; and

. ^* a third intelligent closed loop module, having a third second output terminal connected to the drone through the output terminal of the third MFC SISO device to provide the third updated Dw command for modification in the same direction of rotation of rotation speeds counter-rotating nominal and of the same amplitude -w _h , + w _h of the left and right propellers, and having a third third input terminal, a third fourth input terminal and a third fifth input terminal respectively connected to the first input terminal of the third MFC SISO device for receiving the observed yaw angle x _m , at the second input terminal of the third MFC SISO device for receiving the yaw setpoint angle y _ά to be continued and at the third first output terminal of the third estimator to receive the estimate Fp of the third parameter F ^ of the third Ultra Local Model, the third module of goat the closed closed with a third classic linear system corrector of order equal to the derivation order

of the third Ultra Local Model and of third gain Ky, a third differentiation of bypass order

the yaw setpoint angle y _ά and a third gain amplifier l / a ^; and

the third estimator and the third intelligent closed loop module are configured so that the current third command Dw for modification in the same direction of rotation of counter-rotating nominal speeds of the same amplitude -w _h , + w _h of the propellers left and right check the relationship:

.- the scaling parameter a _y of the third current command Dw relative to the measured yaw angle ip _m is determined arbitrarily or deterministically using a predetermined algorithm so that the third current command Dw and the measured yaw angle ip _m have the same order of magnitude; and / or the order of the time derivative

of the observed roll angle ip _m used in the third

Ultra Local model is equal to 1 or 2, preferably equal to 2, and / or when the order of the time derivative

is equal to 1, the transfer function of the third corrector is of the first order and of the proportional gain type and when the order of the time derivative

is equal to 2, the transfer function of the third corrector is of the second order and of the gain-proportional or gain-derivative type, or even a Proportional- Integral-Diverter;

.- the first attitude regulator of the drone comprises a converter configured to determine the identical amplitude w _h of the nominal rotation speeds -w _h , + o½ of the left and right propellers from a reference thrust Th _d of the drone , supplied as an input terminal of said converter and calculated as a function of the pitch angle measured 9 _m , of the North component and of the bottom component of a set speed of the drone;

.- the drone flight control system, as defined above, furthermore comprises: a second regulator of the speed of the drone for slaving respectively, according to a second loop of regulation of the speed of the drone relative to the Earth , the components of said drone speed v _xm , v _ym , v _zm , expressed in a reference linked to the drone according to the directions to the front, to the left and to a floor of the drone, and measured by one or more sensors for positioning the drone relative to components of a target speed of the drone relative to the Earth, v _xd , v _yd , v _zd , expressed in the reference frame linked to the Earth in the directions oriented towards the North, the East and the center of the Earth; and a third regulator of the position of the drone relative to the Earth in order to control respectively according to a third loop of position regulation, the components of the position of the drone relative to the Earth x _m , y _m , z _m , expressed in a local terrestrial coordinate system according to the directions oriented to the North, East and the center of the Earth), and measured by one or more drone sensors, on setpoint components of the position of the drone relative to the Earth x _d , y _d , z _d , expressed in the second reference frame linked to the Earth and corresponding to desired reference paths;

.- the drone flight control system, as defined above, further comprises a mixing module, configured to transform three output commands from a second cruise control, received at the first input port and formed by setpoint components corrected v _xc , v _yc , v _zc , of the speed of the drone, expressed in the first reference linked to the drone, in four setpoint signals Th _d , <p _d , q _a , ip _d delivered through from a first output port of the mixing module to the first attitude regulator of the drone, and formed respectively by a resulting setpoint thrust to be exerted on the drone, a roll setpoint angle, the pitch setpoint angle, a yaw setpoint angle, said transformation being carried out using the angle of the measured pitch and yaw roll angles, supplied in a second input port of the mixing module, according to the relationships:

t

designating first, second, third and fourth predetermined multivariate functions;

.- the second speed regulator of the drone comprises: a fourth MFC SISO device for modelless control at one input-one output to regulate and enslave as input variable of the fourth MFC SISO device the component v _xm of speed measured along the front axis of the reference linked to the drone on the component v _xd of set speed along the same front axis as as a parameter of the fourth MFC SISO device, by determining a fourth command v _xc for correcting the _target speed along the front axis of the reference frame linked to the drone as output variable of the fourth MFC SISO device; and a fifth MFC SISO device for control without a model at one input-one output for regulating and controlling as input variable of the fifth MFC SISO device the component v _ym of speed measured along the right axis of the first linked reference frame to the drone on the component v _yd of target speed along the same right axis as a parameter of the fifth MFC SISO device, by determining a fifth command v _yc of correction of the target speed along the right axis of the first reference frame linked to the drone as an output variable of the fifth MFC SISO device; and a sixth MFC SISO device for control without a model at one input-one output to regulate and control as input variable of the sixth MFC SISO device the component v _zm of speed measured along the floor axis of the reference linked to the drone on the component v _yz of the _target speed along the same floor axis as a parameter of the sixth MFC SISO device, by determining a sixth command v _zc for correcting the _target speed along the front floor axis of the reference linked to the drone as that output variable of the sixth MFC SISO device;

and / or the third regulator of the position of the drone comprises: a seventh MFC SISO device for modelless control at one input-one output for regulating and slaving as input variable of the seventh MFC SISO device the component x _m of position of the drone relative to the Earth measured along the North axis of an inertial reference linked to the Earth on the component x _d of the position setpoint of the drone relative to the Earth along the same North axis as a parameter of the seventh device MFC SISO, by determining a seventh command v _xd of _target speed along the front axis of the first reference frame linked to the drone as output variable of the seventh MFC SISO device; and an eighth model-free MFC SISO control device with one input-one output to regulate and slave the input variable of the eighth MFC SISO device to the component y _m of position of the drone relative to the Earth measured along the east axis of an inertial reference frame linked to the Earth on the component y _d of reference position of the drone relative to the Earth along the same east axis as as a parameter of the eighth MFC SISO device, by determining an eighth command v _yd of speed setpoint along the right axis of the first reference frame linked to the drone as output variable of the eighth MFC SISO device; and a ninth MFC SISO device for modelless control at one input-one output to regulate and control as input variable of the ninth MFC SISO device the component z _m of position of the drone relative to the Earth measured along the axis center of the Earth of the inertial frame of reference linked to the Earth on the component z _d of the position setpoint of the drone relative to the Earth along the same axis center of Earth as a parameter of the ninth MFC SISO device, by determining a ninth command v _zd target speed along the floor axis of the first reference frame linked to the drone as output variable of the ninth MFC SISO device;

.- when the first attitude controller includes a first MFC SISO control device without model and the drone has a sensor for measuring the first Q derivative of the pitch angle, said first Q derivative of the angle pitch is routed to the first MFC SISO device via a first interconnection link, and when the first attitude regulator includes a second MFC SISO device for control without model and the drone has a sensor for measuring the first derivative f of the roll angle, said first derivative f of the roll angle is routed to the second MFC SISO device via a second interconnection link, and when the first attitude controller comprises a third MFC SISO device for controlling without model and the drone has a sensor measuring the first derivative of the yaw angle, said first derivative of the yaw angle is routed to the tr third MFC SISO device via a third interconnection link.

The invention also relates to a flight control method for a convertible fixed-wing drone allowing a continuous and stabilized transition between a vertical takeoff and a horizontal cruise flight or between a horizontal cruise flight and a vertical landing, the drone comprising: a platform formed by a pair of fixed wings, left and straight, symmetrically and rigidly fixed on either side of a solid central connecting element; and a pair of propellers, left and right, supported respectively in front by the left wing and the right wing while being arranged symmetrically on either side of the solid central connecting element; and a pair of deflection flaps, left and right, supported respectively at their rear edge by the left wing and the right wing, being arranged symmetrically on either side of the solid central connecting element. The control method is configured to: control a first phase of vertical hovering flight and a second phase of cruising flight horizontal to the drone; and using a first regulator of the attitude of the drone, slaving respectively according to a first loop for regulating the roll angles f _th , pitch 0 _m and yaw xf _m , measured by one or more sensors of the drone, on roll setpoint angles f _a , pitch 9 _d and yaw xp _d . The method of controlling the drone is characterized in that it comprises a step during which a first MFC SISO device for control without a model at an input-an output of the first attitude controller regulates and controls the pitch angle 0 _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal of the first MFC SISO control device without model, on the pitch setpoint angle q _ά supplied as a parameter in one second input terminal of the first MFC SISO device, by determining a first command d _h of symmetrical deflection of the left and right flaps, delivered at an output terminal of the first MFC SISO device of control without model and applied with the same sign to said left and right shutters.

The invention also relates to a convertible fixed-wing drone, configured to implement a continuous and stabilized transition between a vertical takeoff and a horizontal cruise flight or between a horizontal cruise flight and a vertical landing. The drone includes:

. ^* a platform formed by a pair of fixed wings, left and right, fixed symmetrically and rigidly on either side of a solid central connection element; and

. ^* a pair of propellers, left and right, supported respectively in front by the left wing and the right wing while being arranged symmetrically on either side of the solid central connecting element; and . ^* a pair of deflection flaps, left and right, supported respectively at their rear edge by the left wing and the right wing, being arranged symmetrically on either side of the solid central element (18) for connection ; and

.- a flight control system configured to control a first phase of vertical hovering flight and a second phase of horizontal cruising flight, and comprising a first regulator of the attitude of the drone to enslave respectively according to a first loop of regulation of roll angles f _th , pitch 0 _m and yaw xf _m , measured by one or more drone sensors, on roll set angles f _a , pitch 9 _d and yaw ip _d .

The drone is characterized in that the first attitude regulator comprises a first MFC SISO device for modelless control at an input-an output for regulating and controlling the pitch angle 9 _m , measured at the output of the drone by one of its sensors and supplied in a first input terminal of the first MFC SISO device for control without model, on the pitch setpoint angle q _ά supplied as a parameter in a second input terminal of the first MFC SISO device, by determining a first symmetrical deflection control d _h of the left and right flaps, delivered to an output terminal of the first MFC SISO control device without model and applied with the same sign to said left and right flaps.

The invention will be better understood on reading the description of several embodiments which follows, given solely by way of example and made with reference to the drawings in which:

.- Figure 1 is a view of a typical flight performed by a convertible fixed-wing drone according to the invention;

.- Figure 2 is a schematic view of an aerodynamic structure typical of a convertible fixed-wing drone according to the invention;

.- Figures 3A and 3B are views of the reference marks used for the control of a typical flight of the drone according to Figure 2 and of the orientations chosen to define the directions of rotation in roll attitude angles f, pitch Q and lace y, Figure 4 is a view of the architecture of a first embodiment of a control system according to the invention of the flight of a drone such as that of Figure 2;

.- Figure 5 is a view of the architecture of a second embodiment of a flight control system of a drone of Figure 2, derived from the first embodiment, in which the attitude controller has three MFC SISO model-free control devices at one input-one output to control and enslave the roll, pitch and yaw of the drone respectively and independently;

.- Figure 6 is a view of the general architecture of the first model-free MFC SISO control device at one input-one output, forming part of the first attitude controller in all the configurations of the flight control device according to the invention, and configured to regulate the pitch angle Q using a first command d _h of symmetrical deflection of the left and right flaps, applied with the same sign to said left and right flaps;

.- Figure 7 is a view of the effects of the first flap deflection control d _h applied to each of the flaps with the same sign by the first MFC SISO device;

.- Figure 8 is a detailed view of the architecture of the first MIS SISO device of Figure 6 in which are detailed the architectures of a first estimator of the parameter F _e of a first Ultra Local Model and of a first module closed loop;

.- Figure 9 is a view of the general architecture of a second MFC SISO modelless control device at one input-one output, forming part of the attitude controller detailed in Figure 5, and configured to regulate the roll angle f using a second command D5 for asymmetric deflection of the left and right flaps, applied with different signs to said left and right flaps;

.- Figure 10 is a view of the effects of the second control D5 of deflection of the shutters applied to each of the shutters with an opposite sign by the first MFC SISO device;

.- Figure 11 is a detailed view of the architecture of the second MFC SISO device of Figure 9 in which the details are architectures of a second parameter estimator

a second Ultra Local Model and a second intelligent closed loop module;

Figure 12 is a view of the general architecture of a third MFC SISO modelless control device at one input-one output, part of the first attitude controller detailed in Figure 5, and configured to regulate the angle yaw y using a third command Dw for modification in the same direction of rotation of nominal, counter-rotating speeds of the same amplitude, -w _h and + w _h applied to the left and right propellers;

Figure 13 is a set of two views, left and right, of the effects of the third command Dw for corrections of the counter-rotating nominal rotational speeds -w _h and + w _h applied to the left and right propellers by the third MFC SISO device , respectively in the case where the yaw angle is zero and in the case where the yaw angle is non-zero;

Figure 14 is a detailed view of the architecture of the third MIS SISO device of Figure 12 in which are detailed the architectures of a third first parameter estimator

a third Ultra Local Model and a third closed loop module;

Figure 15 is a view of a third embodiment of the flight control system of a drone of Figure 2, derived from the second embodiment, in which the speed regulator and the position regulator each comprise three devices MFC SISO modelless control with one input - one output to independently control and slave three speed components and three position components respectively.

Figures 1 6A, 16B, 16C, 16D, 1 6E, 1 6F are views of the performance of the flight control of a convertible fixed-wing drone implemented by the method and the modelless MFC control system according to the invention, by comparing them to the performances of a planned linear quadratic regulation LQR, Figure 1 6A illustrating an example of reference flight trajectory, and Figures 1 6B, 16C, 1 6D, 16E, 1 6F, respectively illustrating the performances of the system in terms of the time revolution evaluation of the forward speed, the pitch angle Q, the rotational speeds of the propellers in counter-rotation, the deflection angles of the flaps

RECTIFIED SHEET (RULE 91) ISA / EP deflection, and wind disturbances along the horizontal and vertical axes ¾ and ¾;

The system and the corresponding drone control process are based on the MFC (Model-Free Control) or intelligent PID approach, described for example in the document by Michel Fliess, Cédric Join entitled " Model-free control ”and published in International of Control 86 (12), pp. 2228-2252, 2013

This approach is based on local modeling, that is to say constantly updated from the sole knowledge of the input-output behavior of the drone and allows to control a complex model with non-linear dynamics, unknown or partially known. , without the need for knowledge of a global model describing the behavior of the system.

Because of its adaptive nature, control without an MFC model has the advantage of rejecting disturbances as well as actuator type faults (inconsistency between the actuator control and the response at their output). This intrinsic capacity reduces the delays in reaction often linked to late decision-making from diagnostic modules.

The flight control system according to the invention is broken down into SISO subsystems with one input - one output (in English Single Input - Single Output) or the control algorithm without MFC model is applied to each of them. The modelless control algorithm is configured to compensate for both time varying disturbances and unmodeled dynamics of the drone as a system responding to flight commands in the transition phase that the return controller fails to manage. The control system and method according to the invention comprise and implement three nested control loops with real-time estimation, which control the speed, position and attitude of the drone, the attitude including yaw, pitch and roll, and in a related way the thrust.

According to FIG. 1, a typical flight 10 of a convertible fixed-wing drone 12 according to the invention comprises here, four flight modes or phases numbered from 1 to 4: a first mode 1 of vertical takeoff, a second mode 2 of transition flight, a third mode 3 of horizontal forward flight and a fourth hovering mode (in English "hovering"), followed successively along a predetermined reference trajectory 14.

Generally, a transition flight phase is a flight phase which allows the passage between a vertical take-off or vertical landing or hovering phase and a cruise flight phase substantially at 'horizontal.

The convertible fixed-wing drone 12 according to the invention is configured to implement a continuous and stabilized transition between a vertical takeoff and a horizontal cruise flight or between a horizontal cruise flight and a vertical landing.

According to Figure 2, the drone 12 according to the invention comprises:

.- a platform 16 formed by a fuselage 18 of longitudinal extension and a pair of wings 22, 24, left and right, symmetrically fixed on either side of the fuselage 16, and

.- a pair of propellers 32, 34, left and right, supported respectively in front by the left wing 22 and the right wing 24 being arranged symmetrically on either side of the fuselage 16; and

.- a pair of deflection flaps 42, 44, left and right, supported respectively at their rear edge 46, 48 by the left wing 22 and the right wing 24, being arranged symmetrically on either side of the fuselage 16; and

a flight control system 52, on board and configured to continuously control a first phase of vertical hovering flight and a second phase of horizontal cruise flight, and comprising a first attitude regulator 54 of the drone to control in a continuous manner respectively according to a first regulation loop of the roll angles f _th , pitch 0 _m and yaw xf _m , measured by one or more sensors of the drone, on roll set angles f _a , pitch 9 _d and lace x _d .

The first attitude controller 54 includes a first device

MFC SISO model-free control at one input-one output to regulate and control the pitch angle 0 _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal of the first SISO MFC device without model, on the pitch setpoint angle q _ά supplied as a parameter at a second input terminal of the first MFC SISO device, by determining a first symmetrical deflection d _h command of the left and right flaps, delivered at an output terminal of the first MFC SISO control device without model and applied with the same sign to said left and right flaps.

As a variant and more generally, the fuselage is replaced by a solid central element, on either side of which the fixed wings 22, 24, left and right, of the platform are fixed symmetrically and rigidly.

According to FIG. 3A, the control system 52 of the flight of the drone 12 according to the invention uses two reference marks or coordinate systems, identical to those used in conventional aircraft.

A first reference frame 62 is a frame linked to the body, that is to say to the platform of the drone, defined by a triplet of axes or directions, noted (, j¾, ¾) in which

respectively represent the frontal direction, the direction to the right, the direction to the floor of the drone. A second reference frame 64 is a terrestrial inertial frame linked to the Earth, defined by a triplet of axes Çx,, ¾) in which x _e ^* ,,

represent respectively the direction towards the North, the direction towards the East and the direction downwards, ie towards the center of the Earth.

The angles of attitude of the drone 12 are the angles noted f, q, y, of roll, the pitch and the yaw, defined respectively as the angles of rotation of the drone around the axes, j¾, the aerodynamic forces which act on the drone 12 are the lift and the drag, designated respectively by the vectors L and D. The gravitational force acting on the drone 12 is represented by the vector W. In addition, the angle of attack a and the angle of the flight path y which describes whether the drone goes up or down are also represented.

According to FIG. 3B, the directions of orientation chosen for the angles of roll, pitch and yaw attitude, as well as those of the angles of deflection of the left and right flaps are shown.

According to FIG. 4 and a first embodiment 102 of the control system according to the invention, derived from the control system 52 of FIGS. 2, 3A and 3B, the flight control system 102 of the drone 12 comprises three control loops nested with a real-time estimate, configured to control the attitude of the drone 12 following a first loop 104, the speed of the drone following a second loop 106 and the position of the drone following a third loop 108. The first attitude control loop 104 is nested in the second speed control loop 106, itself nested in the third loop 108 for controlling the position of the drone.

The drone flight control system 102 here includes:

.- a first regulator 114 of the attitude of the drone 12, configured to enslave respectively according to the first regulation loop 104 of the roll angles f _th , pitch 0 _m and yaw xf _m , expressed relative to the first reference frame 62 of linked reference the UAV 12 and measured by one or more first (s) sensor (s) of the UAV 12 on the roll set angles f _a, _d and pitch 9 _are yaw; and

a second regulator 116 of the speed of the drone 12, configured to slave respectively, according to the second loop 106 of regulation of the speed of the drone 12 relative to the Earth, the components of said speed of the drone v _xm , v _ym , v _zm , expressed in the first reference frame 62 of reference linked to the drone in the directions forward, to the right and to a floor of the drone, and measured by one or more second (s) positioning sensor (s) of the drone 12, on components of a target speed of the drone relative to the Earth, v _xd , v _yd , v _zd , expressed in the first reference frame 62 of reference linked to the drone; and

.- a third regulator 118 of the position of the drone 12 relative to the Earth in order to enslave respectively according to the third position regulation loop, the components of the position of the drone 12 relative to the Earth x _m , y _m , z _m , expressed in the second reference frame 64 linked to the Earth and measured by the drone's second sensor (s), on setpoint components of the position of the drone relative to the Earth x _d , y _d , z _d , expressed in the second reference frame 64 linked to the Earth and corresponding to desired reference paths.

The first attitude regulator 114 of the drone 12 is configured to deliver to the drone 12:

.- a first command of d _h symmetrical deflection of the left and right flaps corresponding to a pitch correction, and

.- a second command D5 for asymmetric deflection of the left and right flaps corresponding to a roll correction, and .- a third command Dw for modification in the same direction of rotation of the nominal counter-rotating speeds of the same amplitude w _h corresponding to a desired thrust in the absence of yaw, and

.- a setpoint of the amplitude w _h , common to the counter-rotating rotational speeds of the left and right propellers and corresponding to a desired nominal thrust or setpoint Th _d , supplied as an input parameter.

The second speed regulator 116 of the drone 12 is configured to deliver to the drone 12:

.- a fourth command v _xc for correcting the reference speed v _xd along the front axis of the first reference 62 linked to the drone,

.- a fifth command v _yc for correcting the set speed v _yd along the right axis of the first reference 62 linked to the drone,

a sixth command v _zc for correcting the reference speed v _zd along the front floor axis of the first reference 62 linked to the drone.

The third speed regulator 116 of the drone 12 is configured to deliver to the drone 12:

.- a seventh command v _xd of speed setting of the drone along the front axis expressed in the first reference frame 62 of reference linked to the drone, and .- an eighth command v _yd of speed setting along the right axis of the first reference frame 62 linked to the drone, and

.- a ninth command v _zd of speed setpoint along the floor axis of the first reference frame 62 of reference linked to the drone.

The flight control system 102 of the drone 12 also includes a mixing module 120, configured to transform the fourth, fifth and sixth output commands v _xc , v _yc , v _zc , of the second regulator 116, received in a first port d 'input 122, in the four set signals f _a , 9 _d , xp _d , Th _d of roll, pitch, yaw and resulting thrust to be exerted on the drone, and delivered through a first output port 124 from the mixing module 120 to the first regulator 114 of attitude of the drone, the transformation being carried out using the measured angles <p _m , 9 _m , ip _m of roll pitch and yaw, provided in a second input port 126 of the mixing module 120, according to the relationships:

ί

designating first, second, third and fourth predetermined multivariate functions.

The first sensor or sensors for measuring the attitude angles of roll, pitch and yaw are for example gyros or an inertial unit.

The second sensor or sensors for measuring the speed and position of the drone are, for example, a global positioning satellite receiver of the GPS or GALILEO type, or a set of accelerometers.

Here and in all the embodiments of the invention, the first attitude regulator 54 or 114 comprises a first MFC SISO device for controlling a model without an input-an output for regulating and controlling the pitch angle 9 _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal of the first SISO MFC control device without model, on the pitch setpoint angle q _ά supplied as a parameter at a second terminal input of the first SISO MFC device, by determining a first symmetrical deflection d _h command of the left and right flaps, delivered to an output terminal of the first SISO MFC control device without model and applied with the same sign to said left flaps and right.

According to a first variant, the flight control system has no third drone position regulator 118.

According to a second variant, the flight control system does not have a third position regulator 118 and a second speed regulator 116 of the drone.

According to a third variant, the first attitude regulator of the control system does not implement a roll control measured <p _m over a roll set angle f _a .

According to a fourth variant, the first attitude regulator of the control system does not implement yaw control measured xj _m over a yaw reference angle y _a .

According to a fifth variant, the first attitude regulator of the control system does not implement or measure roll control <p _m on a roll setpoint angle f _a , nor of yaw control measured xj _m on a yaw setpoint angle xp _d .

According to FIG. 5 and a second embodiment 152 of the control system according to the invention, derived from the control system 102 of FIG. 4, and in particular the attitude regulator 114 of the drone is an attitude regulator 154 of the drone which comprises three first, second, third MFC SISO 162, 164, 166 control devices without a model at an input-an output to control and enslave respectively the pitch Q, the roll f and the yaw y of the drone 12.

The first MFC SISO 162 model-free control device with one input-one output is configured to regulate and control the pitch angle measured 9 _m , measured by one of the first drone sensors 12 and supplied with a first input terminal 172 of the first SISO MFC 162 control device without model, on the pitch setpoint angle q _ά supplied as a parameter in a second input terminal 174 of the first SISO MFC 162 device, by determining a first deflection command d _h symmetrical of the left and right flaps, delivered in an output terminal 176 of the first SISO 162 MFC control device without model and applied with the same sign on said left and right flaps.

The second model-free MFC SISO 164 device with one input-one output is configured to regulate and control the roll angle <p _m , measured by one of the first sensors of the drone 12 and supplied with a first input terminal 182 of the second SISO MFC 164 control device without model, on the roll setpoint angle <p _d supplied as a parameter at a second input terminal 184 of the second SISO MFC 164 device, by determining a second deflection command D5 antisymmetric of the left and right flaps, delivered in an output terminal 186 of the second MFC SISO 164 control device without model and applied with different signs on said left and right flaps in addition to the first symmetrical deflection command d _h applied with the same sign on said left and right flaps.

The third MFC SISO 166 model-free control device with one input-one output is configured to regulate and control the yaw angle ip _m , measured by one of the first sensors of the drone 12 and supplied with a first input terminal 192 of the third SISO MFC 166 device control without template, on the yaw angle setpoint _are provided as a parameter to a second input terminal 194 of the third device SISO MFC 166, determining a third control Dw change in the same speed of rotation of counter-rotating nominal rotation and of the same amplitude -w _h , + w _h of the left and right propellers, supplied as an output terminal 196 of the third SISO MFC 166 control device without model and applied with the same sign on the left propellers and right by adding the respective nominal speeds -w _h , + w _h of the left and right propellers corresponding to the case of a measured yaw angle xp _m zero.

The first attitude regulator of the drone 154 further comprises here a converter 198, configured to determine the identical amplitude w _h of the nominal rotational speeds.

, <w _r of the left and right propellers from a set thrust Th _d of the drone, supplied at an input terminal 200 of said converter 198 and calculated as a function of the pitch angle measured 0 _m , of the component before v _xc and of the floor component v _xz of corrected reference speed expressed in the first reference frame 62 of the drone 12. The amplitude w _h common of the nominal counter-rotating speeds of the left and right propellers is provided in all drone cases regardless of the architecture of the control system.

In a first variant of the second embodiment of the flight control system, the first attitude controller does not use an MFC SISO device to implement the roll regulation.

In a second variant of the second embodiment of the flight control system, the first attitude controller does not use an MFC SISO device to implement yaw regulation.

According to Figure 6, the first MFC SISO model-free control device with one input-one output, forming part of the first attitude controller in all the configurations of the flight control device according to the invention is configured to regulate the angle of pitch Q using a first command d _h of symmetrical deflection of the left and right flaps, applied with the same sign to said left and right flaps, the effects of a first command d _h of symmetrical deflection of the left flaps and right, applied with the same sign on said left and right flaps being illustrated in Figure 7 with the convention of an angular orientation of d _h negative when the pitch angle is positive and the drone in an ascending phase.

According to Figures 6 and 8, the first model-free MFC 162 SISO device with one input-one output comprises a first estimator 212 and a first intelligent closed loop module 214.

The first estimator 212 is configured to estimate a first parameter F _e of a first Ultra Local Model, and comprises a first first input terminal 216 and a first second input 218 connected respectively to the first input terminal of the first SISO device MFC for receiving the observed pitch angle 0 _m and the output terminal of the first MFC SISO device for receiving the first command current _h symmetrical deflection of the left and right flaps, and comprises a first first output terminal 220 to provide the estimate of the first parameter F _e . The first Ultra Local Model describes locally over a limited time interval the temporal variation of the temporal derivative to a predetermined whole order n _q of the pitch angle observed 0 _m as a function of the parameter F _e to be estimated and of the first associated command d _h actual according to the equation:

in which :

a _q is a predetermined parameter for scaling the first current command d _h relative to the pitch angle 0 _m measured so that the first current command d _h and the pitch angle 0 _m measured have the same order of magnitude.

The first smart closed loop module 214 includes a first second output terminal 232, connected to the UAV 12 via the output terminal 176 of the first device MFC SISO 162 to provide deflection control a _n updated symmetrical deflection of left shutters and straight, and comprises a first third input terminal 234, a first fourth input terminal 236 and a first fifth input terminal 238, connected respectively to the first input terminal 172 of the first MFC SISO device 162 for receiving the observed pitch angle G _m , at the second input terminal 174 of the first SISO MFC 162 device to receive the pitch set angle q _ά to be continued and the first first output terminal 220 of the first estimator 212 to receive the estimate F g of the first parameter F _e of the first Ultra Local Model.

The first intelligent closed loop module 214 comprises a first corrector 242 of a conventional linear system of order equal to the derivation order n _q of the first Ultra Local Model and of gain K _q , a first derivation order differentiator n _q of the pitch setpoint angle 9 _d and a first gain amplifier 1 / a _q .

The first estimator 212 and the first loop closed module 214 are configured so that the first control current d _h symmetrical deflection of the left and right flaps satisfies the relationship:

in which x _q = 9 _m - 9 _d denotes the pitch tracking error and K _q x _q is a gain of the first module in closed loop.

The first parameter a _q of scaling of the first current command d _h with respect to the pitch angle 9 _m measured is determined arbitrarily or deterministically using a predetermined algorithm so that the first current command d _h and the measured pitch angle 9 _m have the same order of magnitude.

The order of the time derivative n _q of the observed pitch angle 9 _m used in the first Ultra Local Model is generally a non-zero integer, preferably equal to 1 or 2, and even more preferably equal to 2.

When the order of the time derivative n _q taken equal to 1, the transfer function of the first corrector is of the first order and often of the proportional gain type.

When the order of the time derivative n _q is equal to 2, the transfer function of the first corrector is of the second order and often of the gain-proportional or gain-derivative type, or even a PID (Proportional- Integral- Derivator).

According to FIG. 9, the second MFC SISO 164 device for modelless control at one input-one output, when it is part of the first attitude controller as for example in the second embodiment of the flight control device according to l invention is configured to regulate the roll angle f using a second D5 control antisymmetric deflection of the left and right flaps, applied with different signs on said left and right flaps in addition to a possible first command d _h of symmetrical deflection applied with the same sign on said left and right flaps, the effects of a second D5 anti-asymmetric deflection control applied alone with different signs on the left and right flaps being illustrated in Figure 10 with the orientations of the deflection angles of the left and right flaps corresponding to a roll tilt f to the right.

According to FIGS. 9 and 11, the second MFC SISO 164 control device without model with one input-one output comprises a second estimator 312 and a second intelligent closed loop module 314.

The second estimator 312 is configured to estimate a second parameter F ^ of a second Ultra Local Model, and comprises a second first input terminal 316 and a second second input terminal 318 connected respectively to the first input terminal of the second MFC SISO 164 device to receive the observed roll angle <p _m and at the output terminal of the second MFC SISO 164 device to receive the current second D5 command for asymmetric deflection of the left and right flaps, and includes a second first terminal output 320 to provide the estimate

of the second parameter F ^. The second Model

Ultra Local describes locally over a limited time interval the temporal variation of the temporal derivative to a predetermined whole order n _f of the observed roll angle <p _m as a function of the parameter F ^ to be estimated and of the second associated command D5 current according to the equation:

in which :

a _f is a predetermined parameter for scaling the second current command Dd with respect to the pitch angle <p _m measured so that the second current command D5 and the roll angle (p _m measured have the same order of magnitude.

The second intelligent closed loop module 314 comprises a second second output terminal 332 connected to the drone 12 through the output terminal 186 of the first MFC SISO device to provide the second deflection control D5 updated with asymmetric deflection of the left and right flaps , and comprises a second third input terminal 334, a second fourth input terminal 336 and a second fifth input terminal 338 connected respectively to the first input terminal 182 of the second MIS SISO device 164 to receive the observed roll angle <p _m , to the second input terminal 184 of the second MFC SISO device for receive the roll setpoint angle <p _d to be continued and at the second first output terminal 320 of the second estimator 312 to receive the estimate Tr of the second parameter ^ of the second Ultra Local Model.

The second intelligent closed loop module 314 comprises a second corrector 342 of a conventional linear system of order equal to the derivation order f _q of the second Ultra Local Model and of second gain K _f , a second differentiator 344 of derivation order n _f of the roll setpoint angle f _a and a second gain amplifier 346 1 / a _f , and

the second estimator 312 and the second intelligent closed loop module 314 are configured so that the current second command D5 for antisymmetric deflection of the left and right flaps checks the relationship:

in which in which x _f = <p _m - f _a denotes the roll tracking error and K _f x _f is a gain of the second module in closed loop.

The second parameter a _f of scaling of the second current command D5 relative to the measured roll angle <p _m is determined arbitrarily or deterministically using a predetermined algorithm so that the second current command Dd and the roll angle <p _m measured have the same order of magnitude.

The order of the time derivative n _f of the observed roll angle <p _m used in the second Ultra Local Model is generally a non integer, preferably equal to 1 or 2, and even more preferably equal to 2.

When the order of the time derivative n _f is taken equal to 1, the transfer function of the second corrector is of the first order and often of the proportional gain type.

When the order of the time derivative

is equal to 2, the transfer function of the second corrector is of the second order and often of the type gain-proportional or gain-derivative, or even a PID (Proportional- Integral- Diverter).

According to FIG. 12, the third MFC SISO 166 device for modelless control at one input-one output, when it is part of the first attitude controller as for example in the second embodiment of the flight control device according to l invention is configured to regulate the yaw angle y using a third control Dw for modification in the same direction of rotation of counter-rotating nominal speeds of the same amplitude -w _h , + w _h left and right propellers. The effects of a third command Dw for modifying the speeds of nominal counter-rotating rotations of the propellers applied with the same sign on each of the two propellers are illustrated in FIG. 10 with the convention of a differential of the rotation modules between the left propeller and left propeller Iw ^ - \ œ _r \ positive when the drone turns to the right in the first reference frame 62 linked to the drone 12 with a positive yaw angle.

According to Figures 12 and 13, the third MFC SISO 166 model-free control device at one input-one output includes a third estimator 412 and a third intelligent closed loop module 414.

The third estimator 412 is configured to estimate a third parameter F _y of a third Ultra Local Model, and comprises a third first input terminal 416 and a third second input terminal 418, connected respectively to the first input terminal of the third MFC SISO device to receive the observed yaw angle ip _m and to the output terminal of the third SISO MFC device to receive the current third command Dw of rotational speed differential to be applied in the same direction to the left propellers and right, and has a third first output terminal 420 to provide the estimate F of the third parameter. The third Ultra Local Model described locally over a time interval restricts the temporal variation of the temporal derivative to a predetermined whole order

of the observed yaw angle ip _m as a function of the third parameter F y to be estimated and of the third associated command Dw current according to the equation:

in which : is a predetermined scaling parameter of the third current command Dw relative to the yaw angle ip _m measured so that the third current command Dw and the yaw angle ip _m measured have the same order of magnitude .

The third intelligent closed loop module 414 comprises a third second output terminal 432 connected to the drone 12 through the output terminal 196 of the third MFC SISO device 166 to provide the third update Dw command for modification in the same direction of rotation of nominal counter-rotating speeds of the same amplitude -w _h , + w _h of the left and right propellers, and comprises a third third terminal 434, a third fourth input terminal 436 and a third fifth input terminal 438, respectively connected to the first input terminal 192 of the third MFC SISO device to receive the observed yaw angle i _m, to the second input terminal 194 of the third MFC SISO device 166 to receive the yaw setpoint angle y _a to continue and to the third first output terminal 420 of the third estimator 412 to receive the estimate Fp of the third parameter F y of the third Model the Ultra Local.

The third intelligent closed loop module 414 comprising a third corrector 442 of a conventional linear system of order equal to the derivation order n _q of the third Ultra Local Model and of third gain Ky, a third differentiator 444 of derivation order of the yaw setpoint angle y _ά and a third gain amplifier 446 l / a ^.

The third estimator 412 and the third intelligent closed loop module 414 are configured so that the current third command Dw for modification in the same direction of rotation of counter-rotating nominal speeds of rotation and of the same amplitude -w _h , + w _h left and right propellers check the relationship:

In which

pursuit in yaw and Kyxy is a gain of the third module in closed loop.

The third parameter a _y of scaling of the third current command Dw with respect to the yaw angle measured ip _m is determined arbitrarily or deterministically using an algorithm predetermined so that the third current command Dw and the yaw angle measured ip _m have the same order of magnitude.

The order of the time derivative

of the observed roll angle xjj _m used in the third Ultra Local Model is generally a non-zero integer, preferably equal to 1 or 2, and even more preferably equal to 2.

When the order of the time derivative

is equal to 1, the transfer function of the third corrector is first order and often of the proportional gain type.

When the order of the time derivative

is equal to 2, the transfer function of the third corrector is of the second order and often of the gain-proportional or gain-derivative type, or even a PID (Proportional- Integral- Derivator).

According to FIG. 15 and a third embodiment 452 of the flight control system according to the invention, derived from the flight control system 152 of FIG. 5, the second speed regulator 116 is in particular a second speed regulator 466 which comprises three fourth, fifth, sixth MFC SISO devices 472, 474, 476 of modelless control at an input-an output to control and enslave respectively and independently three speed components of the drone 12 expressed in the first reference frame 62 of reference linked to the drone 12, and the third position regulator 118 is in particular a third position regulation 486 which comprises three seventh, eighth, ninth MFC SISO devices 492, 494, 496 of control without model at an input-an output to control and slaving respectively and independently three components of the position of the drone 12, expressed in the second reference frame 64 d he reference linked to the Earth.

The fourth MFC SISO 472 device is configured to regulate and control as input variable of the fourth MFC SISO device the component v _xm of speed measured along the front axis of the first reference 62 linked to the drone on the component v _xd of speed setpoint along the same front axis as a parameter of the fourth MFC SISO device, by determining a fourth command v _xc for correcting the setpoint speed along the front axis of the first reference 62 linked to the drone as output variable of the fourth MFC SISO device. The fifth MFC SISO 474 device is configured to regulate and control as input variable of the fifth MFC SISO device the component v _ym of speed measured along the axis to the right of the first reference 62 linked to the drone on the component v _yd of setpoint speed along the same right axis as a parameter of the fifth MFC SISO device, by determining a fifth command v _yc for correcting the setpoint speed along the right axis of the first reference 62 linked to the drone as a variable of the fifth MFC SISO 474 device.

The sixth MFC SISO 476 device is configured to regulate and enslave as input variable of the sixth MFC SISO device the component v _zm of speed measured along the floor axis of the first reference 62 linked to the drone on the component v _yz of speed setpoint along the same floor axis as a parameter of the sixth MFC SISO device, by determining a sixth command v _zc for correcting the setpoint speed along the floor axis before the first reference linked to the drone as output variable of the sixth MFC SISO 476 device.

The seventh MFC SISO 492 device is configured to regulate and control as input variable of the seventh MFC SISO device the component x _m of position of the drone 12 relative to the Earth measured along the North axis of the second inertial reference frame 64 linked to Earth on the component x _d of the position setpoint of the drone 12 relative to the Earth along the same North axis as a parameter of the seventh MFC SISO 492 device, by determining a seventh command v _xd of setpoint speed according to the front axis of the first reference frame 62 linked to the drone as an output variable of the seventh MFC SISO device.

The eighth MFC SISO 494 device is configured to regulate and slave the input y _m component of the drone relative to the Earth as the input variable of the eighth MFC SISO device, measured along the east axis of the second inertial reference frame 64 linked to Earth on the drone position setpoint component y _d relative to Earth along the same east axis as a parameter of the eighth MFC SISO 494 device, by determining an eighth command speed v _yd of setpoint speed according to the right axis of the first reference frame 62 linked to the drone as an output variable of the eighth MFC SISO device 494. The ninth MFC SISO 496 device is configured to regulate and control as input variable of the ninth MFC SISO device the component z _m of position of the drone relative to the Earth measured along the center axis of the Earth of the second inertial reference frame 64 linked to the Earth on the component z _d of the position setpoint of the drone relative to the Earth along the same axis center Earth as a parameter of the ninth MFC SISO 496 device, by determining a ninth command v _zd of _target speed according the floor axis of the first reference frame 62 linked to the drone 12 as an output variable of the ninth MFC SISO 496 device.

It should be noted that:

.- when the first attitude regulator 114 or 154 includes a first MFC SISO control device without model and the drone has a sensor for measuring the first derivative Q of the pitch angle, said first temporal derivative Q the pitch angle is sent to the first MFC SISO device via a first interconnection link, and

.- when the first attitude regulator 114 or 154 comprises a second MFC SISO control device without model and the drone has a sensor for measuring the first time derivative f of the roll angle, said first derivative f roll angle is routed to the second MFC SISO device via a second interconnect link, and

.- when the first attitude regulator 114 or 154 includes a third MFC SISO control device without model and the drone has a sensor for measuring the first temporal derivative of the yaw angle, said first derivative of l The yaw angle is routed to the third MFC SISO device via a third interconnect link.

In general, a flight control method of a convertible fixed-wing drone allowing a continuous and stabilized transition between a vertical takeoff and a horizontal cruise flight or between a horizontal cruise flight and a vertical landing, uses a drone comprising :

.- a platform formed by a fuselage of longitudinal extension and a pair of wings, left and right, symmetrically fixed on either side of the fuselage, and .- a pair of propellers, left and right, supported respectively in front by the left wing and the right wing while being arranged symmetrically on either side of the fuselage; and

.- a pair of deflection flaps, left and right, supported respectively in their rear border by the left wing and the right wing, being arranged symmetrically on either side of the fuselage.

The flight control method of said drone is configured to:

.- control a first phase of vertical hovering flight and a second phase of horizontal cruise flight, and

.- using a first regulator of the attitude of the drone, respectively following a first loop for regulating the roll angles (p _m , pitch 0 _m and yaw xf _m , measured by one or more sensors of the drone, on setpoint angles f _a , pitch 9 _d and yaw y _a /

The method of controlling the drone is characterized in that it comprises a step during which a first MFC SISO device for control without a model at an input-an output of the first attitude controller regulates and controls the pitch angle 9 _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal of the first MFC SISO control device without model, on the pitch setpoint angle q _ά supplied as a parameter in one second input terminal of the first SISO MFC device, by determining a first symmetrical deflection d _h command of the left and right flaps, delivered to an output terminal of the first SISO MFC control device without model and applied with the same sign to said left and right shutters.

According to FIGS. 16A, 16B, 16C, 16D, 16E, 16F, of the performance of a flight control of a convertible fixed-wing drone 12, implemented by a representative and typical configuration of a control system and method according to the invention, using at least one command without MCF model at one input-a SISO kind (in English “Single Input Single Output Model Free Control”) to regulate the attitude in pitch Q, are illustrated. These flight control performances according to the invention are compared to the performances of a conventional flight control such as the control method, called “planned linear quadratic regulation LQR” (in English “Scheduled Linear Quadratic Regulator”). Figure 15A illustrates an example of a reference flight path, typical of a transition phase between a vertical takeoff and a cruise flight of the drone, and along which the pitch angle changes from +90 degrees to +10 degrees, while Figures 16B, 16C, 16D, 16E, 16F respectively illustrate the performance of the system in terms of temporal evolution of the forward speed, the pitch angle Q, the rotational speeds of the counter-rotating propellers, the angles of deflection of the deflection flaps, and the wind disturbances according to their horizontal and vertical components and ¾. The pitch angle stabilization performance illustrated in Figure 16C shows that the planned LQR linear quadratic control process is not capable of handling and responding to atmospheric disturbances as well as the flight control system and process. However, the two control systems make it possible to ensure a stable flight with respect to variations in pitching from hovering (Q = 90 degrees) to forward flight (Q = 10 degrees). In forward flight, a static error in the trajectory of the pitch angle controlled by the LQR method is visible and causes errors in the forward speed as illustrated in Figure 16B, and in the positioning. This is particularly visible in the thirtieth seconds of the simulation when the atmospheric disturbances have increased. The saturation of the propeller rotation speed is fixed at 1000 radians / s and the saturation of the deflection angle of the flaps is fixed at 30 degrees and Figures 16D and 16E show that these thresholds are not reached.

The comparison of the two control strategies, LQR and MFC SISO, is evaluated by the two tables I and II below in terms of the square root of the root mean square error RMSE (in English “Root Mean Square Error) which evaluates the error between the desired output reference and the measured value.

Table I: LQR vs MFC: RMSE - Hover

Table II: LQR vs MFC: RMSE - Transition flight

Consequently, the flight control system and the corresponding method according to the invention exhibit high rejection properties with respect to winds present both during the vertical phase of hovering and the horizontal phase of flight, and during the intermediate transition phase. The flight control system and the corresponding method according to the invention makes it possible to control an aerodynamic system without a model despite changes in the aerodynamic coefficients, caused by variations in terms of angle of attack and control efficiency. The simulation results show better performance of the flight control system according to the invention concerning the attitude control of the drone with or without the presence of winds. Thus, the use of control modules without SISO model allows, thanks to their adaptive properties, the rejection of disturbances and the control of a drone whose aerodynamic model is not known or partially known. The flight control system and the corresponding method according to the invention are particularly suitable for drones of the “tail-sitters” type.

Claims

1. Flight control system of a convertible fixed-wing drone (12) allowing a continuous and stabilized transition between a vertical takeoff and a horizontal cruise flight or between a horizontal cruise flight and a vertical landing,

The drone (12) comprising:

.- a platform (16) formed by a pair of fixed wings (22, 24), left and right, fixed symmetrically and rigidly on either side of a solid central element (18) for connection, and

.- a pair of propellers (32, 34), left and right, supported respectively in front by the left wing (22) and the right wing (24) being arranged symmetrically on either side of the solid central connecting element (18); and

.- a pair of deflection flaps (42, 44), left and right, supported respectively at their rear edge (46, 48) by the left wing (32) and the right wing (34), being arranged symmetrically on either side of the solid central connecting element (18);

the control system comprising a first regulator (54; 114; 154) of the attitude of the drone (12) for controlling, respectively according to a first regulation loop, the roll angles f _th , pitch 9 _m and yaw xf _m , measured by one or more sensors of the drone, on roll set angles f _a "pitch and yaw _9d _are, and

the control system being characterized in that

the first attitude regulator (54; 114; 154) comprises a single first modelless control device with an MFC SISO input-output (162) for regulating and controlling the pitch angle 9 _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal (172) of the single first MFC SISO device (162) for control without a model, on a pitch setpoint angle 9 _d supplied as a parameter in a second input terminal (174) of the first modelless control device to an MFC SISO input-output (162), by determining a first symmetrical deflection command _h of the left and right flaps (42, 44), delivered to an output terminal (176) of the first modelless control device to an MFC SISO input-output (162) and applied with the same sign to said left and right flaps (42, 44).

2. The flight control system of a convertible fixed-wing drone according to claim 1, in which

.- the first model-free control device with an MFC SISO input-output (162) comprises:

* a first estimator (212) configured to estimate a first parameter F _e of a first Ultra Local Model, the first estimator (212) having a first first input terminal (216) and a first second input (218), respectively connected to the first input terminal (172) of the first modelless control device to an MFC SISO input-output (162) to receive the observed pitch angle 0 _m and to the output terminal (176) of the MFC SISO first device (162) for receiving the first control current d _h symmetrical deflection of the left and right shutters, and having one first output terminal (220) for providing the estimate of the first parameter F _e, the first Model Ultra Local describing locally over a limited time interval the temporal variation of the temporal derivative to a predetermined whole order n _q of the pitch angle observed 0 _m as a function of the parameter F _e to be estimated and of the first associated command ied for current _hours following equation:

in which :

a _q is a predetermined parameter for scaling the first current command d _h relative to the pitch angle 0 _m measured so that the first current command d _h and the pitch angle 0 _m measured have the same order of magnitude; and

* a first intelligent closed loop module (214), having a first second output terminal (232) connected to the drone (12) through the output terminal (176) of the first modelless control device at an input- an output MFC SISO (162) for providing deflection control a _n updated symmetrical deflection of the left and right flaps (42, 44) and having a first third input terminal (234), a first fourth input terminal (236) and a first fifth input terminal (238) respectively connected to the first input terminal (172) of the first modelless controller to an MFC input-output SISO (162) to receive the observed pitch angle 9 _m , at the second input terminal (174) of the first control device without model at an MFC SISO input-output (162) to receive the setpoint angle pitch 9 _d to continue and to the first first output terminal (220) of the first estimator (212) to receive the estimate of the first parameter F _e of the first Ultra Local Model, the first intelligent closed loop module (214) comprising a first corrector (242) of a conventional linear system of order equal to the derivation order n _q of the first Ultra Local Model and of gain K _q , a first differentiator (244) of derivation order n _q of the angle pitch setpoint q _ά and a first amplifier (246) of gain 1 / a _q , and

.- the first estimator (212) and the first intelligent closed loop module (214) are configured so that the first control current d _h symmetrical deflection of the left and right flaps satisfies the relationship:

in which x _q = 9 _m - 9 _d denotes the pitch tracking error.

3. The flight control system of a convertible fixed-wing drone according to claim 2, in which

the first parameter a _q for scaling the first current command d _h relative to the pitch angle 9 _m measured is determined arbitrarily or deterministically using a predetermined algorithm so that the first current command d _h and the pitch angle 9 _m measured have the same order of magnitude; and or

the order of the time derivative n _q of the observed pitch angle 9 _m used in the first Ultra Local Model is equal to 1 or 2, preferably equal to 2, and / or

when the order of the time derivative n _q is equal to 1, the transfer function of the first corrector is of the first order and of the proportional gain type and when the order of the time derivative n _q is equal to 2, the function of transfer of the first corrector (242) is of the second order and of the gain-proportional or gain-derivative type, or even a Proportional- Integral-Diverter.

4. Flight control system for a convertible fixed-wing drone according to any one of claims 1 to 3,

the first attitude controller (54; 114; 154) comprises a second modelless control device with an MFC SISO input-output (164) for regulating and controlling the roll angle <p _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal (182) of the second MFC SISO device (164) for control without model, on a roll setpoint angle <p _d supplied as a parameter in a second input terminal (184) of the second modelless control device to an MFC SISO input-output (164), by determining a second command D5 for antisymmetrical deflection of the left and right flaps (42, 44), delivered in a terminal output (176) of the second modelless control device to an input-an MFC SISO output (164) and applied with different signs on said left and right flaps (42, 44) in addition to the first deflection control _h symmetrical applied with the same sign on said left and right flaps (42, 44).

5. The flight control system of a convertible fixed-wing drone according to claim 4, in which

.- the second modelless control device with an MFC SISO input-output (164) comprises:

. * a second estimator (312) configured to estimate a second parameter F ^ of a second Ultra Local Model, the second estimator (312) having a second first input terminal (316) and a second second input terminal ( 318), respectively connected to the first input terminal (182) of the second modelless control device to an MFC SISO input-output (164) to receive the observed roll angle <p _m and to the output terminal (186) from the second modelless control device to an MFC SISO input-output (164) for receiving the second current D5 command for asymmetric deflection of the left and right flaps (42, 44), having a second first output terminal ( 320) to provide the estimate R _f of the second parameter F ^, the second

Ultra Local model describing locally over a limited time interval the time variation of the time derivative to a predetermined whole order n _f of the observed roll angle f _pί as a function of the parameter F ^ to be estimated and of the second associated command D5 of current according to the equation:

in which :

a _f is a predetermined parameter for scaling the second current command D5 relative to the pitch angle (p _m measured so that the second current command D5 and the roll angle <p _m measured have the same order of magnitude; and

. ^* a second intelligent closed loop module (314), having a second second output terminal (332) connected to the drone (12) through the output terminal (186) of the second modelless control device at one input-one MFC SISO output (164) to supply the second updated Dd command for asymmetric deflection of the left and right flaps (42, 44), and having second third input terminal (334), a second fourth input terminal (336) and a second fifth input terminal (338) connected respectively to the first input terminal (182) of the second modelless control device to an MFC SISO input-output (164) for receiving the observed roll angle (p _m , at the second input terminal (184) of the second modelless control device at an MFC SISO input-output (164) for receiving the roll setpoint angle f _a to be continued and at the second first terminal output (320) of the second estimator r (312) to receive the estimate

of the second parameter F ^ of the second Ultra Local Model, the second intelligent closed loop module (314) comprising a second corrector (342) of a conventional linear system of order equal to the derivation order f _q of the second Ultra Local Model and second gain k _f , a second differentiator (344) of order of derivation n _f of the roll setpoint angle f _a and a second amplifier (346) of gain 1 / a _f , and

.- the second estimator (312) and the second intelligent closed loop module (314) are configured so that the current second command D5 for asymmetric deflection of the left and right flaps checks the relationship:

in which in which x _f Yth ^~ <Pd denotes the roll following error.

6. The flight control system of a convertible fixed-wing drone according to claim 5, in which

the second parameter a _f of scaling of the second current command D5 with respect to the measured roll angle <p _m is determined arbitrarily or deterministically using a predetermined algorithm so that the second current command Dd and the roll angle (p _m measured have the same order of magnitude; and / or

the order of the time derivative n _f of the observed roll angle <p _m used in the second Ultra Local Model is equal to 1 or 2, preferably equal to 2, and / or

when the order of the time derivative n _f is equal to 1, the transfer function of the second corrector is of the first order and of the proportional gain type and when the order of the time derivative

is equal to 2, the transfer function of the second corrector (342) is of the second order and of the gain-proportional or gain-derivative type, or even a Proportional-Integral-Diverter.

7. The flight control system of a convertible fixed-wing drone according to any one of claims 1 to 6, in which

the first attitude regulator (54; 114; 154) comprises a third modelless control device with an MFC SISO input-output (166) for regulating and controlling the yaw angle xjj _m , measured at the output of the drone by one of its sensors and provided as a first input terminal (192) of the third model without control device to an input-output SISO MFC (166) on a setpoint yaw angle _is provided as parameter in a second input terminal (194) of the third control device without model to an input-an MFC SISO output (166), by determining a third command Dw of modification in the same direction of rotation of nominal rotational speeds against -rotating and of the same amplitude -w _h , + w _h of the left and right propellers (32, 34), supplied at an output terminal (196) of the third control device without model at an MFC SISO input-output (166 ) and applied with the same sign on the left propellers and right (32, 34) in addition to the nominal speeds respective -w _h , + w _h of the left and right propellers (32, 34) corresponding to the case of a measured yaw angle x _m zero.

8. The flight control system of a convertible fixed-wing drone according to claim 7, in which

.- the third model-free control device with an MFC SISO input-output (166) comprises:

. * a third estimator (412) configured to estimate a third parameter F y of a third Ultra Local Model, the third estimator (412) having a third first input terminal (416) and a third second input terminal ( 418), respectively connected to the first input terminal (192) of the third modelless control device with an MFC SISO input-output (166) for receiving the observed yaw angle i _m and with the output terminal ( 196) of the third control device without model to an input-an output MFC SISO (166) to receive the third command Dw of current modification in the same direction of rotation of the nominal rotation speeds counter-rotating of the left and right propellers (32 , 34), and having a third first output terminal (420) for providing the estimate Fp of the third parameter F y, the third Ultra Local Model describing locally over a time interval restricts the temporal variation from the time derivative to a predetermined whole order

of the observed yaw angle i _m as a function of the third parameter F y to be estimated and of the third associated command Dw current according to the equation:

in which :

af is a predetermined scaling parameter of the third current command Dw relative to the yaw angle i _m measured so that the third current command Dw and the yaw angle i _m measured have the same order of greatness; and

. ^* a third intelligent closed loop module (414), having a third second output terminal (432) connected to the drone (12) through the output terminal (196) of the third modelless control device at one input-one MFC SISO output (166) to supply the third updated Dw command for modification in the same direction of rotation of counter-rotating nominal speeds of the same amplitude -w _h , + w _h of the left and right propellers (32, 34) , and having a third third terminal of (434), a third fourth input terminal (436) and a third fifth input terminal (438) connected respectively to the first input terminal (192) of the third modelless controller to an input -an MFC SISO output (166) to receive the observed yaw angle \ J _m, at the second input terminal (194) of the third control device without model at an input-an MFC SISO output (166) to receive the yaw setpoint angle _ά to be continued and at the third first output terminal (420) of the third estimator (412) to receive the estimate F of the third parameter Fy of the third Ultra Local Model, the third closed loop module intelligent (414) comprising a third corrector (442) of a conventional linear system of order equal to the derivation order of the third Ultra Local Model and of third gain K _y, a third differentiator (444) of derivation order

the yaw setpoint angle y _ά and a third gain amplifier l / a ^, and

.- the third estimator (412) and the third intelligent closed loop module (414) are configured so that the current third command Dw for modification in the same direction of rotation of counter-rotating nominal speeds of rotation and of the same amplitude - w _h , + w _h of the left and right propellers (32, 34) verify the relation:

in which x _y = ip _m - Fa denotes the yaw tracking error.

9. The flight control system of a convertible fixed-wing drone according to claim 8, in which

the scaling parameter a _y of the third current command Dw relative to the measured yaw angle ip _m is determined arbitrarily or deterministically using a predetermined algorithm so that the third current command Dw and the yaw angle measured ip _m have the same order of magnitude; and or

the order of the time derivative

the observed yaw angle xj _m used in the third Ultra Local Model is equal to 1 or 2, preferably equal to 2, and / or

when the order of the time derivative

is equal to 1, the transfer function of the third corrector is of the first order and of the gain type and proportional when the order of the time derivative n _is equal to 2, the transfer function of the third correction is second order and the gain-type or proportional-gain differentiator or a proportionally Intégral- diverter.

10. The flight control system of a convertible fixed-wing drone according to any one of claims 7 to 9, in which

the first attitude regulator (154) of the drone comprises a converter (198) configured to determine the identical amplitude w _h of the nominal rotational speeds -w _h , + o½ of the left and right propellers (32, 34) from d '' a set thrust Th _d of the drone (12), supplied at an input terminal (200) of said converter (198) and calculated as a function of the pitch angle measured 9 _m , of the North component and of the component down from a drone set speed.

11. The flight control system of a convertible fixed-wing drone according to any one of claims 1 to 10, further comprising

a second regulator (116; 466) of the speed of the drone for controlling, respectively, according to a second loop for regulating the speed of the drone relative to the Earth, the components of said speed of the drone v _xm , v _ym , v _zm , expressed in a first reference linked to the drone in the directions forward, to the left and to a floor of the drone, and measured by one or more sensors for positioning the drone relative to components of a target speed of the drone relative to to the Earth, v _xd , v _yd , v _zd , expressed in the coordinate system linked to the Earth in the directions oriented towards the North, East and the center of the Earth, and

a third regulator (118; 468) of the position of the drone relative to the Earth in order to control respectively according to a third position regulation loop, the components of the position of the drone relative to the Earth x _m , y _m , z _m , expressed in a second local reference frame (64) linked to the Earth in the directions oriented to the North, East and center of the Earth, and measured by one or more drone sensors (12), on components setpoint of the position of the drone (12) relative to the Earth x _d , y _d , z _d , expressed in the second reference frame (64) linked to the Earth and corresponding to desired reference paths.

12. The flight control system of a convertible fixed-wing drone according to any one of claims 1 to 11,

further comprising a mixing module (12), configured to transform three output commands from a second speed regulator (116; 466), received at the first input port (122) and formed by components of corrected setpoints v _xc , v _yc , v _zc , of the speed of the drone, expressed in the first reference (62) linked to the drone, in four set signals Th _d , f _a , 9 _d , ip _d delivered through a first port output (124) of the mixing module (120) to the first attitude regulator of the drone (114; 154), and formed respectively by a resulting setpoint thrust to be exerted on the drone (12), a setpoint angle of roll , the pitch setpoint angle, a yaw setpoint angle, said transformation being carried out using the angle of the measured pitch and yaw roll angles, provided in a second input port of the mixing module, according to relationships:

/ i (-) _> / ₂ C). / ₃ C). / ₄ C) designating first, second, third and fourth predetermined multivariate functions.

13. The flight control system of a convertible fixed-wing drone according to claim 11, in which

the second speed regulator (466) of the drone comprises:

.- a fourth modelless control device with one input - one MFC SISO output (472) for regulating and slaving as input variable of the fourth modelless device with one input-one MFC SISO output (472) the component v _xm of speed measured along the front axis of the coordinate system linked to the drone on a component v _xd of speed setpoint along the same front axis as a parameter of the fourth control device without model at an MFC SISO input-output (472) , by determining a fourth command v _xc for correcting the _target speed along the front axis of the reference linked to the drone as a variable of output of the fourth modelless controller to an MFC SISO input-output (472), and

.- a fifth modelless control device with one input - one MFC SISO output (474) for regulating and controlling as input variable of the fifth modelless control device with one input - one MFC SISO output (474) component v _ym of speed measured along the right axis of the first reference frame (62) linked to the drone on the component v _yd of set speed along the same right axis as a parameter of the fifth control device without model at one input - an MFC SISO output (474), by determining a fifth command v _yc for correcting the set speed along the right axis of the first reference frame (62) linked to the drone as output variable of the fifth control device without model to an input-an MFC SISO output, and .- a sixth control device without model to an input-an MFC SISO output (476) of control without model to an input-an output to regulate and control as a input line of the sixth model-free control device at an MFC SISO input-output (476) the component v _zm of speed measured along the floor axis of the reference linked to the drone on the component v _yz of _target speed according to the same floor axis as a parameter of the sixth model-free control device at an MFC SISO input-output (476), by determining a sixth command v _zc for correction of the _target speed along the front floor axis of the reference linked to the drone as an output variable of the sixth modelless controller at an MFC SISO input-output (476); and or

the third position regulator (468) of the drone comprises:

.- a seventh modelless control device with one input - one MFC SISO (492) control without model with one input - one output to regulate and slave as input variable of the seventh modelless control device with one input-an MFC SISO output (492) the component x _m of position of the drone relative to the Earth measured along the North axis of an inertial reference frame linked to the Earth on the component x _d of reference of position of the drone relative to to Earth along the same North axis as a parameter of the seventh model-free control device at an MFC SISO input-output (492), by determining a seventh command v _xd of setpoint speed along the front axis of the first reference frame (62) linked to the drone as an output variable of the seventh model-free control device with an MFC SISO input-output (492), and

.- an eighth modelless control device with an MFC SISO input-output (494) for regulating and controlling the component y _m as an input variable of the eighth modelless control device with an MFC SISO input-output position of the drone relative to the Earth measured along the East axis of an inertial reference frame linked to the Earth on the component y _d of the position setpoint of the drone relative to the Earth along the same East axis as a parameter of the eighth model-free control device with an MFC SISO input-output (494), by determining an eighth command speed setpoint v _yd along the right axis of the first reference frame (62) linked to the drone as variable output of the eighth modelless controller to an MFC SISO input-output (494), and

.- a ninth modelless control device with one input - one MFC SISO (496) control output without model with one input - one output to regulate and control as input variable of the ninth modelless control device with one input-an MFC SISO output (496) the component z _m of position of the drone relative to the Earth measured along the center axis of the Earth of the inertial frame linked to the Earth on the component z _d of the position reference of the drone by relative to the Earth along the same center-Earth axis as a parameter of the ninth MFC SISO device, by determining a ninth command v _zd of speed setpoint along the floor axis of the first reference frame (62) linked to the drone as output variable of the ninth model-free controller to an MFC SISO input-output (496).

14. The flight control system of a convertible fixed-wing drone according to any one of claims 7 to 13 in which:

the drone having a sensor for measuring the first Q derivative of the pitch angle, a first interconnection link routes said first Q derivative of the pitch angle to the first control device without model at an input-a MFC SISO output, and the drone having a sensor measuring the first derivative f of the roll angle, a second interconnection link routes said first derivative f of the roll angle to the second control device without model at an input-one MFC SISO output, and

the drone having a sensor for measuring the first derivative of the yaw angle, a third interconnection link routes said first derivative of the yaw angle to the third control device without model at an MFC input-output SISO.

15. Flight control method for a convertible fixed-wing drone allowing a continuous and stabilized transition between a vertical takeoff and a horizontal cruise flight or between a horizontal cruise flight and a vertical landing,

the drone including:

.- a platform formed by a pair of fixed wings (22, 24), left and right, fixed symmetrically and rigidly on either side of a solid central element (18) for connection, and

the control process being configured for:

.- control a first phase of vertical hovering flight and a second phase of cruising flight horizontal to the drone (12), and

.- using a first regulator of the attitude of the drone, slaving respectively according to a first loop of regulation of the roll angles p _m , pitch 0 _m and yaw x / _m , measured by one or more sensors of the drone , on roll setpoint angles f _a , pitch 9 _d and yaw _a , the method of controlling the drone being characterized in that it comprises a step during which a single first control device without model at an input- an MFC SISO (162) output from first attitude regulator regulates and controls the pitch angle 9 _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal of the only first control device without model to an input -an MFC SISO output (162), on a pitch setpoint angle q _ά supplied as a parameter in a second input terminal of the first control device without model to an input-an MFC SISO output (162), determining a first symmetrical deflection command _h of the left and right flaps, delivered at an output terminal of the first control device without model to an input-an MFC SISO output (162) of control without model and applied with the same sign to said left and right panes.

16. Convertible fixed-wing drone, configured to implement a continuous and stabilized transition between a vertical takeoff and a horizontal cruise flight or between a horizontal cruise flight and a vertical landing, and comprising:

.- a pair of deflection flaps (42, 44), left and right, supported respectively at their rear edge (46, 48) by the left wing (22) and the right wing (24), being arranged symmetrically on either side of the solid central connecting element (18); and

.- a flight control system (52) configured to control a first vertical hover phase and a second horizontal cruise phase, and comprising a first attitude regulator (54; 114; 154) of the drone to enslave respectively according to a first loop for regulating the roll angles f _th , pitch 9 _m and yaw xf _m , measured by one or more sensors of the drone, on roll set angles f _a , pitch 9 _d and yaw there _is ,

the drone being characterized in that the first attitude regulator (54; 114; 154) comprises a single first modelless control device with an MFC SISO input-output (162) for regulating and controlling the pitch angle 9 _m , measured at the output of the drone by one of its sensors and supplied as a first input terminal of the only first model-free control device to an MFC SISO input-output, on a pitch setpoint angle q _ά supplied as a parameter in a second input terminal of the first control device without model to an input-an MFC SISO output (162), by determining a first command d _h of symmetrical deflection of the left and right flaps, delivered in an output terminal of the first device of control without model to an input-an output MFC SISO (162) of control without model and applied with the same sign on said flaps left and right (46, 48).