Method of automatically adjusting lift provided for a hybrid rotorcraft, and an associated hybrid rotorcraft

Abstract

A method of automatically adjusting lift in a hybrid rotorcraft, the hybrid rotorcraft including a fuselage and at least two half-wings on either side of the fuselage, the at least two half-wings including at least one left half-wing having a left fixed structure secured to the fuselage and at least one left flap mounted to move relative to the left fixed structure, and at least one right half-wing having a right fixed structure secured to the fuselage and at least one right flap mounted to move relative to the right fixed structure. The method determines at least one first deflection angle setpoint δw1 by which the at least one left flap is to be deflected relative to the left fixed structure and at least one second deflection angle setpoint δw2 by which the at least one right flap is to be deflected relative to the right fixed structure.

Claims

1. A method of automatically adjusting lift provided for a hybrid rotorcraft, the hybrid rotorcraft including: a fuselage; at least one main rotor provided with a plurality of blades, the at least one main rotor rotating relative to the fuselage at a speed of rotation NR; at least one pusher or puller propeller; and at least two half-wings positioned on either side of an anteroposterior midplane of the fuselage, the at least two half-wings including firstly at least one left half-wing having a left fixed structure secured to the fuselage and at least one left flap mounted to move relative to the left fixed structure, and secondly at least one right half-wing having a right fixed structure secured to the fuselage and at least one right flap mounted to move relative to the right fixed structure; the method including, during a nominal flight phase, a step consisting in automatically adjusting lift provided by the at least two half-wings; wherein the step includes a succession of substeps consisting in: computing a forward propulsion parameter as a function firstly of a true air speed TAS and secondly of a current value of the speed of rotation NR; determining a target lift coefficient Czm* for the main rotor, the target lift coefficient Czm* being a function of the forward propulsion parameter; computing target lift F.sub.rotor* to be provided by the main rotor, the target lift F.sub.rotor* to be provided by the main rotor being a function of the current value of the speed of rotation NR, of current atmospheric conditions, and of the target lift coefficient Czm*; computing target lift F.sub.wing* to be provided by the at least two half-wings, the target lift F.sub.wing* to be provided by the at least two half-wings being a function of the target lift F.sub.rotor* to be provided by the main rotor and of a current value of the weight of the hybrid rotorcraft; and determining at least one first deflection angle setpoint δw1 by which the at least one left flap is to be deflected relative to the left fixed structure and at least one second deflection angle setpoint δw2 by which the at least one right flap is to be deflected relative to the right fixed structure, the at least one first and at least one second deflection angle setpoints δw1, δw2 being functions of the target lift F.sub.wing* to be provided by the at least two half-wings and of aerodynamic coefficients of the at least two half-wings.

2. The method according to claim 1, wherein the lift provided by the at least two half-wings is adjusted when the following condition is satisfied: $\frac{\mathrm{Frot}or*}{\mathrm{Frotor}*+\mathrm{Fwin}g*}>S$ where S is a predetermined threshold value representative of a minimum allowable contribution from the main rotor to the total lift provided for the hybrid rotorcraft.

3. The method according to claim 1, wherein the lift provided by the at least two half-wings is adjusted when the at least one first setpoint δw1 is strictly less than a first predetermined threshold value δwmax1 representative of a maximum allowable deflection for the at least one left flap and the at least one second setpoint δw2 is strictly less than a second predetermined threshold value δwmax2 representative of a maximum allowable deflection for the at least one right flap.

4. The method according to claim 1, wherein the target lift F.sub.rotor* to be provided by the main rotor is computed by means of the following formula: $\mathrm{Frotor}*=\frac{Czm*\times \rho \times b\times c\times R\times U^2}{6}$ where: ρ is the density (mass per unit volume) of the surrounding outside air; b is the number of blades in the plurality of blades of the at least one main rotor; where c is a chord of an aerodynamic profile of the blades; R is a radius of the at least one main rotor; and U is a tangential speed at the tips of the blades.

5. The method according to claim 1, wherein, during a phase of flight during which the at least one main rotor is autorotating, and which is distinct from the nominal flight phase, a first predetermined threshold value δwmax1 representative of a maximum allowable deflection for the at least one left flap is assigned to the at least one first setpoint δw1, and a second predetermined threshold value δwmax2 representative of a maximum allowable deflection for the at least one right flap is assigned to the at least one second setpoint δw2.

6. The method according to claim 1, wherein the lift provided by the at least two half-wings is adjusted symmetrically about the anteroposterior midplane of the fuselage, the at least one first setpoint δw1 being equal to the at least one second setpoint δw2.

7. The method according to claim 6, wherein a current value of lift provided by the main rotor is measured, and a closed-loop regulation is controlled so as to adjust the lift provided by the two half-wings symmetrically.

8. The method according to claim 1, wherein, when firstly the true air speed TAS is greater than a predetermined threshold value TAS1 and secondly flight parameters of the hybrid rotorcraft enable checking to be performed to check that the hybrid rotorcraft is in a stabilized flight phase, the lift provided by the at least two half-wings is adjusted asymmetrically about the anteroposterior midplane of the fuselage, the at least one first setpoint δw1 being distinct from the at least one second setpoint δw2.

9. The method according to claim 8, wherein the lift provided by the at least two half-wings is adjusted asymmetrically so that a lateral cyclic pitch of the blades of the main rotor is equal to a setpoint lateral cyclic pitch.

10. The method according to claim 8, wherein the lift provided by the at least two half-wings is adjusted asymmetrically so that a lateral bending moment of a mast of the main rotor is equal to a setpoint lateral bending moment during the stabilized flight phase.

11. The method according to claim 8, wherein the lift provided by the at least two half-wings is adjusted asymmetrically in the event of malfunctioning of any one of the at least one left flap and of the at least one right flap.

12. A hybrid rotorcraft including: a fuselage; at least one main rotor provided with a plurality of blades, the at least one main rotor rotating relative to the fuselage at a speed of rotation NR; at least one pusher or puller propeller; at least two half-wings positioned on either side of an anteroposterior midplane of the fuselage, the at least two half-wings including firstly at least one left half-wing having a left fixed structure secured to the fuselage and at least one left flap mounted to move relative to the left fixed structure, and secondly at least one right half-wing having a right fixed structure secured to the fuselage and at least one right flap mounted to move relative to the right fixed structure; and a control system connected to the at least one left flap and to the at least one right flap, the control system being configured to generate automatically at least one first deflection angle setpoint δw1 by which the at least one left flap is to be deflected relative to the left fixed structure, and at least one second deflection angle setpoint δw2 by which the at least one right flap is to be deflected relative to the right fixed structure; wherein the control system is configured to apply the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the following description of examples given by way of illustration with reference to the accompanying figures, in which:

(2) FIG. 1 is a perspective view of a hybrid rotorcraft of the invention;

(3) FIG. 2 is a flow chart showing a method of the invention, for automatically adjusting lift for a hybrid rotorcraft;

(4) FIG. 3 is a flow chart showing a first operating mode of the method of the invention;

(5) FIG. 4 is a flow chart showing a second operating mode of the method of the invention; and

(6) FIG. 5 is a block diagram of a control system of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) Elements present in more than one of the figures are given the same references in each of them.

(8) As mentioned above, the invention relates to the field of hybrid rotorcraft that are configured to fly at high cruising speeds.

(9) As shown in FIG. 1, such a hybrid rotorcraft 1 conventionally includes a fuselage 2, at least one main rotor 3 provided with a plurality of blades 31, at least one pusher or puller propeller 4, 4′, and at least two half-wings 11, 11′ positioned on either side of an anteroposterior midplane of the fuselage 2. Furthermore, the main rotor 3 is configured to be driven in rotation by at least one power plant. The main rotor 3 can then rotate relative to the fuselage 2 at a speed of rotation NR so as to participate at least in providing lift, or indeed also in providing propulsion, for the hybrid rotorcraft 1.

(10) As shown, the hybrid rotorcraft 1 may include two propellers 4, 4′ arranged on respective ones of the half-wings 11, 11′ at the free ends or tips of the at least two half-wings 11, 11′. In addition, the hybrid rotorcraft 1 may include two pairs of half-wings 11, 11′.

(11) A first pair of left half-wings 11 is then arranged on a left side of the anteroposterior midplane of the fuselage 2, and a second pair of right half-wings 11′ is arranged on the right side of the anteroposterior midplane of the fuselage 2. The left side or the right side is then defined relative to what is seen by the eyes of a pilot of the hybrid rotorcraft 1 sitting at the piloting station and looking straight ahead towards a front zone of the hybrid rotorcraft 1. In addition, a forward direction Dl can also be shown and be defined in a direction going from a rear zone 28 of the hybrid rotorcraft 1 towards a front zone 27 of the hybrid rotorcraft 1.

(12) In addition, each left half-wing 11 includes, in particular, a left fixed structure 13 secured to the fuselage 2 and at least one left flap 12 that is mounted to move relative to the fixed left structure 13. Similarly, each right half-wing 11 includes a right fixed structure 13′ secured to the fuselage 2 and at least one right flap 12′ that is mounted to move relative to the right fixed structure 13′.

(13) As shown, each left half-wing 11 or each right half-wing 11′ may, in section, have an aerodynamic profile, and the left flap(s) 12 and the right flap(s) 12′ may advantageously be arranged at a trailing edge of said aerodynamic profile.

(14) Furthermore, such a hybrid rotorcraft 1 includes a control system 40 connected to the left flap(s) 12 of each left half-wing 11 and to the right flap(s) 12′ of each right half-wing 11′.

(15) Such a control system 40 is configured to generate automatically at least one first and at least one second deflection angle setpoints δw1, δw2 by which each left flap 12 is to be deflected relative to a facing left fixed structure 13 and by which each right flap 12′ is to be deflected relative to a facing right fixed structure 13′. The control system 40 then enables said first deflection angle setpoint(s) δw1 and said second deflection angle setpoint(s) δw2 to be applied.

(16) Furthermore, such a control system 40 is shown in more detail in FIG. 5, and is configured to apply the method 20 as shown diagrammatically in FIG. 2.

(17) Such a method 20 thus includes a step 21, 46, 47 consisting in automatically adjusting lift provided by at least two half-wings 11, 11′ by varying the angular positioning of the left flap(s) 12 relative to the left fixed structure 13 and the angular positioning of the right flap(s) 12′ relative to the right fixed structure 13′. In order to implement this automatic adjustment in the lift, this step 21, 46, 47 includes in particular a computation substep 22 using a first computer 51 of the control system 40 to compute a forward propulsion parameter as a function firstly of a True Air Speed (TAS) of the hybrid rotorcraft 1 as measured by a first speed sensor 52 and secondly of a current value of the speed of rotation NR of the main rotor 3 as measured by a second sensor 53.

(18) The step 21, 46, 47 then includes a determination substep using a second computer 54 to determine a target lift coefficient Czm* for the main rotor 3. Such a target lift coefficient Czm* is then a function of the forward propulsion previously computed in the computation substep 22.

(19) The step 21, 46, 47 then includes a computation substep for using a third computer 55 of the control system 40 to compute a target lift F.sub.rotor* to be provided by the main rotor 3. Such a target lift F.sub.rotor* is a function of the current value of the speed of rotation NR, of current atmospheric conditions, such as, for example, the pressure P and the temperature T of the air, and of the target lift coefficient Czm* computed during substep 23 by the second computer 54. Thus, one or more sensors 59 that are sensitive to the atmospheric conditions are then connected to the third computer 55 for transmitting measurements of the current values relating to atmospheric conditions.

(20) Step 21, 46, 47 also includes a calculation substep 25 using a fourth computer 46 of the control system 40 to compute a target lift F.sub.wing* to be provided by the at least two half-wings 11, 11′. Such a target lift F.sub.wing* is a function of the target lift F.sub.rotor* computed during substep 24 and of a current value of the weight of the hybrid rotorcraft 1.

(21) Furthermore, step 21, 46, 47 includes a determination substep 26 for determining at least one first deflection angle setpoint δw1 by which each of the at least one left flap 12 is to be deflected relative to the left fixed structure 13, and at least one second deflection angle setpoint δw2 by which each of the at least one right flap 12′ is to be deflected relative to the left fixed structure 13′. These at least two deflection angle setpoints δw1, δw2 are then determined by a fifth computer 47 as a function of the target lift F.sub.wing* computed during substep 26 and of aerodynamic coefficients of the at least two half-wings 11, 11′.

(22) These aerodynamic coefficients may be established in different ways such as by measurements in wind tunnels, by computer programs suitable for performing simulations and using, in particular, the principles of fluid mechanics, or by in-flight trials.

(23) In addition, such aerodynamic coefficients may then be stored in a memory 48 and may also be corrected as a function of certain parameters for interactions between the main rotor 3 and each half-wing 11, 11′, or indeed between a pusher or puller propeller 4, 4′ and the half-wing 11, 11′ to which said pusher or puller propeller 4, 4′ is secured.

(24) In addition, the various computers 41, 44, 45, 46, and 47 may, as shown in FIG. 5, be disjoint from one another or indeed be formed by a common computer. For example, this computer or each of these computers 41, 44, 45, 46 and 47 may comprise at least one processor and at least one memory, at least one integrated circuit, at least one programmable system, or at least one logic circuit, these examples not limiting the scope given to the expression “computer”. The term “processor” may be used equally well to mean a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a microcontroller, etc.

(25) In addition, as shown in FIG. 3, in a first operating mode of the method 20, step 46 may enable the lift provided by the at least two half-wings 11, 11′ to be adjusted symmetrically about the anteroposterior midplane of the fuselage 2.

(26) In this situation, the one or more first deflection angle setpoints δw1 for the left flap(s) are then equal to the one or more second deflection angle setpoints δw2 for the right flap(s) 12′.

(27) It is then possible to measure a current value of lift provided by the main rotor 3 and the control system 40 can control a closed-loop regulation 45 for symmetrically adjusting the lift provided by the at least two half-wings 11, 11′.

(28) In addition, the current value of the lift provided by the at least two half-wings 11, 11′ may be computed on the basis of the measurement of the current value of lift provided by the main rotor 3, and then by subtracting the weight of the hybrid rotorcraft from said current value of lift provided by the main rotor 3.

(29) A comparator 44 then enables an input lift setpoint, e.g. to be provided by the at least two half-wings 11, 11′, to be compared with an input current value of the lift provided by the at least two half-wings 11, 11′.

(30) Alternatively, and in a second operating mode of the method 20, step 47 may enable the lift provided by the at least two half-wings 11, 11′ to be adjusted asymmetrically about the anteroposterior midplane of the fuselage 2. In this situation, the at least two deflection angle setpoints δw1, δw2 are thus distinct from each other.

(31) In this situation, an activation test may be performed with comparison steps 41 and 42.

(32) Thus, a first comparison step 41 enables the True Air Speed (TAS) of the hybrid rotorcraft 1 to be compared with a predetermined threshold value TAS1. When the TAS is greater than said predetermined threshold TAS1, the control system 40 then tests flight parameters of the hybrid rotorcraft 1.

(33) A second comparison step 42 then serves to check that the hybrid rotorcraft 1 is in a flight phase that is stabilized by comparing said flight parameters of the hybrid rotorcraft 1 with stored values that, for example, are representative of the attitudes and of the rate of climb or of the rate of descent of the hybrid aircraft 1. These flight parameters of the hybrid rotorcraft 1 are then measured in real time, e.g. by sensors such as inclinometers or accelerometers that are mounted on the hybrid rotorcraft 1. Furthermore, these flight parameters may be obtained by means of an Attitude and Heading Reference System (AHRS). Indeed, such a system may equip a hybrid rotorcraft and include three accelerometers serving to measure longitudinal accelerations, three rate gyros serving to measure angular accelerations and a triaxial fluxgate serving to measure heading references.

(34) When both of the comparison steps 41 and 42 are positively checked, the activation test is validated and step 47 can then be implemented to adjust the lift provided by the at least two half-wings 11, 11′ asymmetrically.

(35) In addition, such a step 47 may be implemented in various situations and, for example so that a lateral cyclic pitch of the blades 31 of the main rotor 3 is equal to a setpoint lateral cyclic pitch, so that a lateral bending moment of a mast of the main rotor 3 is equal to a setpoint lateral bending moment during the phase of stabilized flight and/or in the event of malfunctioning of any one of the at least one left flap 12 and of the at least one right flap 12′.

(36) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several implementations are described above, it should readily be understood that it is not conceivable to identify exhaustively all possible implementations. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.