Method for controlling at least one aerodynamic rudder of a hybrid helicopter and corresponding hybrid helicopter

Description

[0001] The present invention relates to a method for controlling at least one aerodynamic drift member of a hybrid helicopter and also to a hybrid helicopter applying this method. The invention lies in the technical field of control systems for a hybrid helicopter.

[0002] The project leading to this invention has received funding from the European Union's Horizon 2020 research and innovation programme, under the CleanSky 2 grant agreement No. "GAM-FRC-2014-001 Issue E

[0003] A type of rotorcraft is referred to as a "hybrid helicopter" for convenience because of its specificity. A hybrid helicopter comprises an airframe carrying at least one rotating wing equipped with a rotor, this rotor being referred to as a "lift rotor" thereafter for convenience and because of at least one of its functions. The lift rotor contributes at least to the lift of the aircraft and even to its forward motion.

[0004] A hybrid helicopter further comprises at least one propeller, possibly of the tractive or propulsive propeller type. For example, the hybrid helicopter may be provided with at least two propellers arranged transversely on either side of a cell and its anteroposterior plane.

[0005] Furthermore, a hybrid helicopter has a power plant to set the propeller(s) and the lift rotor in motion, possibly permanently except in the event of a breakdown or testing.

[0006] To pilot a hybrid helicopter, a pilot of the hybrid helicopter can operate a first control and a second control to collectively and cyclically control the pitch of the lift rotor blades, respectively, via a mechanical and / or electrical architecture for example. The first control is conveniently called "collective pitch control" and often takes the form of a lever called a "collective pitch lever". The second control is conveniently called "cyclic pitch control" and often takes the form of a stick called a "cyclic stick".

[0007] In particular, on a hybrid helicopter with at least two propellers located on either side of an airframe, the pitch of the blades of each propeller is a function of a mean pitch component and a differential pitch component. Thus, the first pitch of the first blades of a first propeller may be equal to the sum of the mean pitch component and the differential pitch component, while the second pitch of the second blades of a second propeller may be equal to the mean pitch component minus the differential pitch component. Furthermore, the mean pitch component may be equal to half the sum of the first and second pitches of the two propellers, while the differential pitch component may be equal to half the difference of the first and second pitches of the two propellers.

[0008] Therefore, the hybrid helicopter includes at least one thrust control capable of modifying the value of the average pitch component, via a mechanical and / or electrical architecture for example.

[0009] For example, the thrust control may take the form of a lever or a button transmitting a signal to one or more actuators. According to one example, such a button may have three discrete states, namely a first state called "beep+" requiring an increase in the value of the average pitch component, a second state called "beep-" requiring a decrease in the value of the average pitch component, and a third state requiring the value of the average pitch component not to be changed. The pitch of the propeller blades is then increased as long as a pilot positions the button in its first state. According to another example, the button may take the form of a thumbwheel.

[0010] Furthermore, direction control functions, particularly yaw control, can be performed by using a yaw control capable of modifying the value of the differential pitch component. For example, such a yaw control may comprise a rudder bar connected by a mechanical and / or electrical architecture to the propellers. The rudder bar makes it possible to modify the value of the differential pitch component.

[0011] Examples of hybrid helicopters are described in US 8181901, US 8170728, US 8052094 and US 8113460 for example.

[0012] On a hybrid helicopter with two propellers involved in position and yaw control, the two propellers can generate two different thrusts to create torque on the airframe.

[0013] This strategy is interesting but can in fact induce different life cycles on the various moving parts that set the propeller blades in motion.

[0014] To remedy this, document FR 2943620 proposes regulating the deflection angle of the left and right rudder flaps during predetermined flight phases to tend to minimize the differential pitch component of the left and right propellers in order to optimize the operation of these left and right propellers.

[0015] For convenience and in the remainder of the text, the left of an aircraft is considered to be to the left of an individual in said aircraft who has their back to the rear of the aircraft so as to look at the front of the aircraft. In fact, the right of an aircraft is considered to be to the right of an individual in said aircraft who has their back to the rear of the aircraft so as to look at the front of the aircraft. Regulation is carried out by means of a first closed regulation loop as a function of a difference in torque, power or pitch.

[0016] The deflection of the left and right flaps may be accompanied by a second closed control loop to control the propellers to achieve a zero lateral load factor. Therefore, the first and second control loops may tend to operate in mutual interaction under certain conditions.

[0017] Documents FR 2769284, FR 3014411, FR 2689854 and US 2018 / 244369 are also known and distant from the invention in relating to conventional helicopters without propellers.

[0018] The present invention therefore aims to propose an alternative method for optimizing the operation of the propellers of a hybrid helicopter having a lift rotor driven by a power plant during at least one flight phase.

[0019] Thus, the invention relates to a method for optimizing the operation of at least one first propeller and at least one second propeller arranged transversely on either side of a cell of a hybrid helicopter, said hybrid helicopter comprising a lift rotor arranged above the cell, said hybrid helicopter comprising at least one aerodynamic drift member exerting transverse lift, said at least one aerodynamic drift member being rotatable relative to a bearing of said hybrid helicopter.

[0020] Such an aerodynamic drift organ can take the form of a fully deflectable tailplane or a deflectable tailplane flap for example.

[0021] This method comprises the following step during a regulation phase: steering with an automatic pilot system said at least one aerodynamic drift member into a set position having, relative to a reference position, a target steering angle, said target steering angle being equal to a set steering angle at least when this set steering angle is within a range delimited by a predetermined minimum included angle and a predetermined maximum included angle.

[0022] Optionally, the target steering angle may be equal to said predetermined maximum angle when this set steering angle is greater than the predetermined maximum angle. Optionally, the target steering angle may be equal to said predetermined minimum angle when this set steering angle is less than the predetermined minimum angle. The set steering angle may also be bounded.

[0023] The set steering angle is calculated by the autopilot system to compensate for a torque exerted by said lift rotor with zero lateral slip.

[0024] The steering angle is conventionally positive when the aerodynamic drift member is on a first side of the reference position and negative when the aerodynamic drift member is on a second side of the reference position.

[0025] Consequently, the hybrid helicopter is equipped with one or more aerodynamic drift members capable of introducing a yaw moment onto the airframe. The aerodynamic drift member(s) are controlled by the autopilot system to tend towards reaching a set deflection angle. Consequently, the deflection can be achieved by means of an open control loop which thus does not risk coming into conflict with a possible closed loop for controlling a differential pitch component of the propellers to obtain a zero lateral load factor.

[0026] The setpoint steering angle is thus calculated to exactly compensate for the torque exerted by said lift rotor on the zero-sideslip cell so that the first pitch of the first blades of the first propeller and the second pitch of the second blades of the second propeller tend to have a zero differential pitch component. The setpoint steering angle and / or the target steering angle is clipped / limited where appropriate by the maximum angle and the minimum angle.

[0027] Therefore, the value of the target steering angle may vary in conjunction with variations in the torque exerted by the lift rotor on the airframe or with the dynamic pressure. Such variations may result from a pilot's action on a lift rotor collective pitch or cyclic pitch command or from an equivalent action taken by the autopilot system.

[0028] As a result, open-loop control of the steering angle of the aerodynamic drift member(s) can make it possible to obtain substantially the same pitch on each propeller and therefore optimal behavior at their operating point. Indeed, the first pitch of the first blades of the first propeller can be close to or even equal to the second pitch of the second blades of the second propeller. The first propeller and the second propeller can also be identical.

[0029] It is recalled that the pitch of a propeller blade represents an angle between a line of a section of the blade and a reference line, this angle varying when the blade rotates on itself around its pitch axis. For example, the pitch represents an angle separating a chord line of a section from a reference position of this chord line. For example, said section can be a section located at a distance from the axis of rotation of the propeller equal to 0.75 times a radius of the propeller.

[0030] The method may further include one or more of the following features.

[0031] Thus, the method may comprise the following step: calculation with the automatic pilot system of said set steering angle as a function of at least a forward speed of the hybrid helicopter, a torque exerted by the lift rotor on the cell and a density of the air surrounding the hybrid helicopter.

[0032] Consequently, if the altitude or speed of the hybrid helicopter changes, the steering angle of the aerodynamic drift member is automatically modified, at least until this aerodynamic drift member reaches a stop. Similarly, a change in the torque exerted by the lift rotor on the airframe induces a change in the set steering angle. The first thrust can then remain substantially equal to the second thrust.

[0033] For example, the method may include a step of calculating with the automatic piloting system said set steering angle by the following relationship: deltaV = C / 0.5 * ro * v 2 − N 1 / N 2 , where "deltaV" represents said setpoint steering angle, "C" represents a torque exerted by the lift rotor on the cell, "V 2<" a forward speed of the hybrid helicopter to the power of two, "ro" represents a density of the air, "0.5*ro*v2" represents a dynamic pressure, "N1" represents a first coefficient depending on an aerodynamic moment N0 of yaw of the hybrid helicopter at zero sideslip and when said at least one aerodynamic drift member is in the reference position reduced by the dynamic pressure, "N2" represents a second coefficient equal to a constant, " / " represents the division sign, "-" represents the subtraction sign, "*" represents the multiplication sign, "=" represents the equality sign.

[0034] In fact, the yaw moment M generated by the cell and in particular via the aerodynamic drift member(s) can be determined as for an airplane by the following equation: M = 0.5 * ro * V 2 * N 1 + N 2 * deltaV

[0035] Therefore, to equalize the thrust of the propellers at zero slip between them and in cruise, the yaw moment must exactly compensate for the torque exerted by the lift rotor so as not to have to produce a differential thrust between the propellers, i.e. M = C. We deduce the previous relationship: deltaV = C / 0.5 * ro * v 2 − N 1 / N 2

[0036] The first coefficient is a function of a term dependent on the aerodynamic moment N0 of yaw of the hybrid helicopter at zero sideslip and when said at least one aerodynamic drift member is in the reference position reduced by the dynamic pressure q, i.e. N0 / q. This term N0 / q may be a constant determined by wind tunnel tests and / or by calculations and / or by simulations.

[0037] Similarly, the second coefficient N2 may represent a gradient of said aerodynamic yaw moment of the hybrid helicopter per degree of deflection of said at least one aerodynamic drift member and may be determined by wind tunnel tests and / or by calculations and / or by simulations.

[0038] According to a first alternative, the first coefficient is equal to the aerodynamic yaw moment of the hybrid helicopter at zero sideslip and when said at least one aerodynamic drift member is in the reference position reduced by the dynamic pressure.

[0039] According to a second alternative, the first coefficient may be equal to the aerodynamic yaw moment of the hybrid helicopter at zero sideslip and when said at least one aerodynamic drift member is in the reference position reduced by the dynamic pressure and corrected by an integral type corrector, this corrector being a function of a gain as well as a subtraction of either a first pitch PAS1 of first blades of said at least one first propeller minus a second pitch PAS2 of second blades of said at least one second propeller or of a first thrust P1 exerted by said at least one first propeller minus a second thrust P2 exerted by said at least one second propeller or of a first torque Tq1 exerted by said at least one first propeller minus a second torque Tq2 exerted by said at least one second propeller.

[0040] The hybrid helicopter may be subject to aerodynamic interactions that may affect the first coefficient. To take these interactions into account, a corrector in the form of an integral term may be added to the aerodynamic yaw coefficient reduced by the dynamic pressure, at zero sideslip and when said at least one aerodynamic drift member is in the reference position, to optimize the efficiency of the method.

[0041] Optionally, the corrector can be clipped to avoid increasing in absolute value indefinitely when the maximum angle of the aerodynamic drift member is reached, for example. Possibly, the value of the corrector is limited to a range of values ​​narrower than the range delimited by the minimum angle and the maximum angle. For illustration purposes, the reference steering angle can be between -8 degrees and +8 degrees around the reference position, the corrector can only be between -2 degrees and +2 degrees.

[0042] For example, the said first coefficient is determined by the following relation: N 1 = N 0 / q + k * int diff , where "N1" represents the first coefficient, "N0 / q" represents the aerodynamic moment N0 of yaw of the hybrid helicopter reduced by the dynamic pressure q at zero sideslip and when said at least one aerodynamic drift member is in the reference position, "diff" represents said subtraction, "k" represents a predetermined gain, "-" represents the sign of subtraction, "+" represents the sign of addition, "*" represents the sign of multiplication, "=" represents the sign of equality, "k*int(diff)" represents the integral type corrector equal to the product of said predetermined gain and an integral with respect to the time of said subtraction.

[0043] The gain k can be adjusted to avoid interaction with a side load factor control loop.

[0044] Eventually, the gain may vary depending on the forward speed of the hybrid helicopter.

[0045] The gain k can be a function of the forward speed, for example the true airspeed or the indicated airspeed. The gain can in particular be reduced at high speed when the efficiency of the aerodynamic drift member is maximum.

[0046] In one aspect, however, the corrector may be frozen when the hybrid helicopter is in a dynamic piloting phase.

[0047] The term "frozen" means that the corrector as a whole retains the value reached when the hybrid helicopter enters a dynamic piloting phase. The corrector can vary again at the end of the dynamic piloting phase.

[0048] The method may include a step of detecting a dynamic piloting phase if at least one of the following conditions is satisfied: maneuvering a yaw control configured to modify a differential pitch component of the first pitch of first blades of said at least one first propeller and of the second pitch of second blades of said at least one second propeller, an absolute value of a load factor in a transverse direction in a frame of reference of the hybrid helicopter is greater than a load factor threshold, an absolute value of a roll angle of the hybrid helicopter is greater than a roll threshold.

[0049] For example, the load factor threshold might be 0.07 times the acceleration of gravity.

[0050] For example, the roll threshold can be between 10 and 40 degrees.

[0051] Similarly, a dead zone that freezes the integral type corrector can be implemented under certain conditions.

[0052] For example, the corrector can be frozen when an absolute value of a difference is less than a freezing threshold, said difference being equal to: at the first pitch PAS1 of first blades of said at least one first propeller minus the second pitch PAS2 of second blades of said at least one second propeller, i.e. PAS1-PAS2, or at a first thrust P1 exerted by said at least one first propeller minus a second thrust P2 exerted by said at least one second propeller, i.e. P1-P2, or at a first torque TQ1 exerted by said at least one first propeller minus a second torque TQ2 exerted by said at least one second propeller, i.e. TQ1-TQ2.

[0053] According to another aspect, said regulation phase can be implemented when said hybrid helicopter performs a cruise flight phase.

[0054] Such a cruise flight phase can be detected in the usual way.

[0055] Furthermore, steering with the automatic pilot system of said at least one aerodynamic drift member in a set position can be achieved by applying an open regulation loop.

[0056] In addition to a method, the invention relates to a hybrid helicopter which applies this method.

[0057] Such a hybrid helicopter is provided with at least a first propeller and at least a second propeller arranged transversely on either side of a cell of this hybrid helicopter, said hybrid helicopter comprising a lift rotor arranged above the cell, said hybrid helicopter comprising at least one aerodynamic drift member exerting transverse lift, said at least one aerodynamic drift member being rotatable relative to a bearing of said hybrid helicopter,

[0058] The hybrid helicopter has an autopilot system configured to apply this process.

[0059] The automatic piloting system may comprise a piloting computer configured to apply the method of the invention.

[0060] According to one aspect, the piloting system may comprise at least one actuator connected to said at least one aerodynamic drift member and to the piloting computer.

[0061] The control computer can be mechanically connected to the actuator and / or can transmit an electrical, optical, analog or digital signal to the actuator to move said at least one aerodynamic drift member.

[0062] The automatic pilot system may comprise at least one of the following members in at least one example connected to the pilot computer: a speed sensor, a torque sensor configured to measure information relating to a torque exerted by the lift rotor, a first sensor of the first pitch of the first blades of said at least one first propeller, a second sensor of the second pitch of the second blades of said at least one second propeller, a maneuver sensor to determine whether a pilot is maneuvering a yaw control, a sensor for measuring a load factor in a transverse direction in a frame of reference of the hybrid helicopter, an angular roll sensor measuring a roll angle of the hybrid helicopter, a first and a second torque sensor respectively of said at least one first propeller and of said at least one second propeller,a first thrust sensor for evaluating a first thrust generated by said at least one first propeller, a second thrust sensor for evaluating a second thrust generated by said at least one second propeller.,

[0063] For example, the speed sensor can measure the forward speed of the hybrid helicopter, either the true airspeed or the indicated airspeed IAS of the hybrid helicopter. This speed sensor can be obtained with the measuring instrument called "AIR DATA COMPUTER" by the person skilled in the art in English, a satellite positioning system, a pressure measurement system, etc.

[0064] In one aspect, the torque sensor may, for example, comprise a torque meter. In one embodiment, a torque meter may be arranged on a rotor mast of the lift rotor or the like.

[0065] Similarly, the first and second torque sensors may comprise torque meters arranged on a propeller mast or the like.

[0066] For example, the first sensor of the first pitch may comprise a position sensor which measures a position of a moving member controlling the first pitch of the first propeller, for example of a first control rod of the first pitch. The same applies to the second sensor of the second pitch. For example, each pitch sensor comprises a sensor known by the acronym LVDT corresponding to the English expression "Linear Variable Differential Transformer" or RVDT corresponding to the English expression "Rotary Variable Differential Transformer".

[0067] Furthermore, the first thrust sensor and the second thrust sensor may respectively comprise a first traction / compression sensor arranged on a first mast of the first propeller and a second traction / compression sensor arranged on a second mast of the second propeller. Indeed, the force measured on each mast is the image of the thrust of the associated propeller. Thus a computer can apply at least one law providing the thrust of a propeller as a function of the measured force.

[0068] According to another example, the first thrust sensor and the second thrust sensor may respectively comprise two sensors for measuring the rotational speed of the first propeller and the second propeller. Indeed, the thrust of a propeller may be calculated using a predetermined law providing this thrust as a function of the rotational speed of the propeller measured with a rotational speed measuring sensor, the forward speed measured with the speed sensor, the air density as well as the pitch of the propeller blades.

[0069] Furthermore, a maneuver sensor may, for example, include a force sensor capable of determining whether a pilot is exerting force on the yaw control, and for example a force sensor arranged on a rudder bar or on a member mechanically connected to the rudder bar. Alternatively, a position or acceleration sensor may, for example, be used.

[0070] The sensor for measuring a load factor may, for example, be equipped with an acceleration sensor measuring the load factor of the hybrid helicopter in a transverse direction, namely in a direction substantially parallel to the pitch axis of the hybrid helicopter.

[0071] In another example, the angle sensor may comprise an inclinometer or may be part of the measuring instrument called "Attitude and Heading Reference System".

[0072] The invention and its advantages will appear in more detail in the context of the description which follows with examples given for illustrative purposes with reference to the appended figures which represent: there figure 1 , a perspective view of a hybrid helicopter according to the invention, the figure 2 , a diagram illustrating an embodiment of an automatic piloting system according to the invention, the figure 3 , a flowchart illustrating the method of the invention, the figure 4 , a diagram illustrating a hybrid helicopter before the deflection of an aerodynamic drift member, and the figure 5 , a diagram illustrating a hybrid helicopter after the deflection of an aerodynamic drift member.

[0073] Elements present in several distinct figures are assigned a single reference.

[0074] There figure 1 presents a hybrid helicopter 1 according to the invention.

[0075] This hybrid helicopter 1 comprises a cell 4 above which is arranged at least one lift rotor 2. This lift rotor 2 is provided with several blades called "main blades 3" for convenience. The cell 4 extends longitudinally parallel to a roll axis AXROL of the hybrid helicopter 1, transversely parallel to a pitch axis AXTANG of the hybrid helicopter 1 and in elevation parallel to a yaw axis AXLAL of the hybrid helicopter 1.

[0076] In addition, the hybrid helicopter 1 is provided with at least one first propeller 10 and at least one second propeller 15, of the tractive or propulsive type. The first and second propellers 10, 15 respectively comprise several first blades 11 and several second blades 16. The first propeller 10 and the second propeller 15 may be arranged laterally relative to the cell 4, possibly on either side of an anteroposterior plane of symmetry of the hybrid helicopter 1 parallel to the pitch axis AXTANG. On the figure 1 , the first and second propellers 10, 15 may be reversed. The first and second propellers 10, 15 are optionally carried by a support 5. Such a support 5 may optionally be aerodynamic. For example, the support 5 comprises a wing according to the illustration of the figure 1 . According to the figure 1 , the first and second propellers 10, 15 are arranged at the leading edge of a wing. According to another example, the first and second propellers 10, 15 are arranged at the trailing edge of the wing.

[0077] The first pitch PAS1 of the first blades 11 of the first propeller 10 is adjustable to adjust a first thrust P1 of the first propeller 10. Similarly, the second pitch PAS2 of the second blades 16 of the second propeller 15 is adjustable to adjust a second thrust P2 of the second propeller 15. The first pitch PAS1 may be equal to a mean pitch component plus a differential pitch component while the second pitch PAS2 may be equal to the mean pitch component minus the differential pitch component, or vice versa.

[0078] Furthermore, the hybrid helicopter 1 comprises a power plant 30 for supplying power to the lift rotor 2 and to each propeller 10, 15. This power plant 30 comprises for this purpose at least one engine 31 controlled by a standard engine computer 32.

[0079] The term "computer" generally designates a unit which may include, for example, at least one processor and at least one memory, at least one integrated circuit, at least one programmable system, at least one logic circuit, these examples not limiting the scope given to the expression "computer". The term processor may designate a central processing unit known by the acronym CPU, a graphics processing unit GPU, a digital unit known by the acronym DSP, a microcontroller, etc.

[0080] Furthermore, the power plant 30 may comprise, for example within an interconnection system, at least one power transmission box, at least one shaft, and / or at least one connecting member between two rotating members... For example, one or more motors 31 are mechanically connected by one or more mechanical connecting chains to a main power transmission box 33 which rotates the lift rotor 2. Furthermore, the main power transmission box 33 may be mechanically connected by at least one shaft to a lateral propeller power transmission box which is therefore in turn connected to a propeller 10, 15.

[0081] The rotation speeds of the outputs of the motor(s) 31, the propellers 10, 15, the lift rotor 2 and the mechanical interconnection system are possibly proportional to each other, the proportionality ratio possibly being constant whatever the flight configuration of the hybrid helicopter 1 under normal operating conditions, namely excluding cases of breakdown or testing or training.

[0082] Furthermore, the hybrid helicopter 1 may include stabilization or even maneuvering surfaces. For example, the hybrid helicopter 1 may include for the elevator at least one substantially horizontal empennage 20, possibly with movable elevators 21.

[0083] For example, the hybrid helicopter 1 may comprise for steering at least one aerodynamic drift member 26 exerting a transverse lift P3, namely a lift comprising at least one component oriented transversely and possibly substantially parallel to the pitch axis of the hybrid helicopter. The aerodynamic drift member 26 is rotatable about an axis of rotation AXROT relative to a bearing 25. According to the example illustrated, two aerodynamic drift members 25 respectively comprise two drift flaps each movable relative to a fixed vertical tail portion. According to another possibility, an entire vertical tail forms a deflectable aerodynamic drift member 26. figure 1 thus illustrates stabilization or even maneuvering surfaces forming a rear structure in the shape of an inverted U. According to another example illustrated on the figure 4 , the rear structure may have an H shape. According to another example, the rear structure may have a T shape or equivalent and / or may comprise a single aerodynamic fin member 26.

[0084] Furthermore, the hybrid helicopter 1 may include various controls to be piloted by a human pilot.

[0085] In particular, the hybrid helicopter 1 may comprise a control system for collectively and cyclically controlling the pitch of the main blades 3. Such a control system may for example include a set of swashplates. Thus, at each instant, the pitch of the main blades 3 may be equal to the sum of an identical collective pitch for all the main blades 3 and a cyclic pitch which varies as a function of the azimuth of each main blade 3. The pitch of the main blades 3 is called “main pitch” to be clearly distinguished from the pitch of other blades.

[0086] Therefore, the hybrid helicopter 1 may comprise a collective pitch control 45 which acts directly or indirectly on at least one mechanical and / or electrical control chain of the control system to collectively vary the main pitch of the main blades 3, via the set of swashplates where appropriate. For example, the collective pitch control 45 comprises a lever.

[0087] Likewise, the hybrid helicopter 1 may comprise a cyclic pitch control 47 which acts directly or indirectly on one or more mechanical and / or electrical control chains of the control system to cyclically vary the main pitch of the main blades 3, via the set of swashplates where appropriate.

[0088] Typically, the hybrid helicopter 1 may include controls connected to the control system to control the first pitch of the first blades 11 and the second pitch of the second blades 16.

[0089] Usually, the hybrid helicopter 1 may comprise a thrust control 50 which acts directly or indirectly on one or more mechanical and / or electrical control chains of the control system to vary the average pitch component of the first pitch and the second pitch in order, for example, to control a forward speed of the hybrid helicopter 1. figure 1 illustrates a lever-type thrust control 50 but can also take the form of a button generating an electrical or optical signal for example.

[0090] Similarly, the hybrid helicopter 1 may comprise a yaw control 55 which acts directly or indirectly on one or more mechanical and / or electrical yaw control chains of the control system to vary the differential pitch component of the first pitch of the first blades 11 and the second pitch of the second blades 16. The yaw control chain(s) may comprise at least one actuator referred to for convenience as a "yaw cylinder 63".

[0091] Furthermore, the hybrid helicopter 1 comprises an automatic piloting system 60 configured in particular to automatically control, namely without human intervention, the aerodynamic drift member(s) 26 by applying the method of the invention in order to optimize the operation and in particular the operating point of the first propeller 10 and the second propeller 15.

[0092] There figure 2 illustrates an example of an autopilot system 60.

[0093] This automatic piloting system 60 comprises at least one actuator 62 mechanically connected to at least one aerodynamic drift member 26. For example, the automatic piloting system 60 comprises at least one actuator 62 per aerodynamic drift member 26. Each actuator 62 may comprise a linear or rotary electric cylinder, a linear or rotary fluidic cylinder cooperating with a fluid distributor, a linear or rotary electric motor, etc.

[0094] Each actuator 62 can cause the rotation of at least one fin aerodynamic member 26 about its axis of rotation AX. In particular, each actuator 62 can cause the rotation of at least one fin aerodynamic member 26 relative to a reference position POSREF illustrated in dotted lines. According to one example, each actuator 62 can deflect at least one fin aerodynamic member 26 between a first position POSMIN having a negative minimum angle ANGMIN relative to a reference position POSREF and a second position POSMAX having a positive maximum angle ANGMAX relative to the reference position POSREF. For example, each fin aerodynamic member 26 can be pivoted in an angular field of plus or minus 5 degrees centered on the reference position.The reference position POSREF then corresponds to the median position having a zero steering angle in which an aerodynamic drift member 26 is located relative to the total angular field that can be covered. The reference position POSREF may, for example, correspond to the position to be reached during a cruise phase at a particular altitude and with a particular adjustment of the lift rotor to equalize the first thrust P1 and the second thrust P2.

[0095] At each instant, each aerodynamic drift member 26 is in a current position resulting from a command of a target steering angle which is determined to tend towards an equalization of the first thrust P1 and the second thrust P2.

[0096] For this purpose, the automatic piloting system 60 may comprise at least one piloting computer 61 controlling each actuator 62. To determine an analog, digital, electrical or optical control signal to be transmitted to each actuator 62, the piloting computer 61 may receive signals from various sensors.

[0097] Therefore, the automatic piloting system 60 may comprise one or more speed sensors 71 which transmit to the piloting computer 61 an analog, digital, electrical or optical signal carrying a forward speed of the hybrid helicopter 1. For example, the speed sensor measures a true air speed of the hybrid helicopter 1.

[0098] The automatic piloting system 60 may comprise one or more torque sensors 72 which transmit to the piloting computer 61 an analog, digital, electrical or optical signal carrying the torque exerted by the lift rotor 2 on the cell 4.

[0099] The automatic piloting system 60 may comprise a first sensor 73 of the first pitch PAS1 of the first blades 11 and a second sensor 74 of the second pitch PAS2 of the second blades 16. For example, the first sensor 73 comprises a position sensor emitting an analog, digital, electrical or optical signal to the piloting computer 61 which varies as a function of the position of a control shaft of the first pitch of the first blades 11. Similarly, the second sensor 74 may comprise a position sensor emitting an analog, digital, electrical or optical signal to the piloting computer 61 which varies as a function of the position of a control shaft of the second pitch of the second blades 16.

[0100] The pilot computer 61 may comprise at least one law or database providing the first thrust P1 and the second thrust P2 as a function respectively of the first pitch PAS1 and the second pitch PAS2, the propeller speed and the forward speed.

[0101] According to another example, the pilot computer 61 may comprise at least one law or database providing the first thrust P1 and the second thrust P2 as a function of forces measured by traction / compression sensors 91, 92 arranged on the propeller masts.

[0102] The autopilot system 60 may comprise a maneuver sensor 75 capable of determining whether a pilot is maneuvering the yaw control 55. The maneuver sensor 75 transmits an analog, digital, electrical or optical signal to the pilot computer 61 which varies according to the position or a force exerted on the yaw control 55. For example, the maneuver sensor 75 comprises a force sensor, for example integrated into a rudder control cylinder. The maneuver sensor 75 returns a Boolean signal “TRUE” when the pilot acts on the rudder and a Boolean signal “FALSE” when the pilot does not act on the rudder.

[0103] The automatic pilot system 60 may comprise one or more sensors 76 for measuring the load factor Ny in a transverse direction DIR in a reference frame of the hybrid helicopter 1. This sensor 76 for measuring a load factor Ny emits an analog, digital, electrical or optical signal to the pilot computer 61 which varies as a function of this lateral load factor Ny. The sensor 76 for measuring a load factor may comprise an acceleration sensor measuring the load factor Ny. This acceleration sensor may be part of the measuring instrument called “Attitude and Heading Reference System” (AHRS) or “Air Data, Attitude and Heading Reference System” (ADAHRS) in English.

[0104] The automatic pilot system 60 may comprise one or more angular roll sensors 77 which transmit an analog, digital, electrical or optical signal to the pilot computer 61 which varies according to the roll angle Phi of the hybrid helicopter 1. This angular roll sensor 77 may be part of the measuring instrument called “Attitude and Heading Reference System” (AHRS) or “Air Data, Attitude and Heading Reference System” (ADAHRS) in English.

[0105] The automatic piloting system 60 may comprise at least a first and a second torque sensor 78, 79 for respectively measuring a first torque Tq1 of said at least one first propeller 10 and a second torque Tq2 of said at least one second propeller 15. Each torque sensor 78, 79 transmits an analog, digital, electrical or optical signal to the piloting computer 61 which varies according to the torque generated or produced by the associated propeller 10, 15.

[0106] Optionally, the automatic piloting system 60 may comprise a sensor per aerodynamic drift member 26, such as for example an angular sensor 80 or a sensor 81 estimating the position either of a mobile member of the associated actuator 62 or of a link connecting the actuator 62 and the aerodynamic drift member 26.

[0107] If necessary, and therefore according to the logic programmed in the control computer 61, this control computer 61 orders during a regulation phase to each actuator 62 to switch the associated aerodynamic drift member 26 into a set position POSCONS having a target steering angle ANGCIB with the reference position POSREF. The target steering angle ANGCIB is a function of a set steering angle ANGCONS or even of the maximum angle ANGMAX and the minimum angle ANGMIN.

[0108] In reference to the figure 3 , the method of the invention comprises a regulation phase STP1. According to one possibility, the regulation phase is permanently implemented. According to another possibility, the regulation phase is implemented only during a cruising flight phase. Such a cruising flight phase can be identified by the pilot computer 61 in the usual manner, for example if the hybrid helicopter 1 has a forward speed greater than a stored / predetermined speed threshold. Thus, the method can comprise a step of comparing the forward speed with the speed threshold, the regulation phase being undertaken if the forward speed is greater than this speed threshold. For example, such a speed threshold can be equal to 100 knots or 185.2 kilometers per hour.In this case, outside of the regulation phase, each aerodynamic drift member 26 can for example be positioned in a predetermined position, and for example in the second POSMAX position.

[0109] The regulation phase can be carried out iteratively at a predetermined frequency.

[0110] During this regulation phase STP1, the method comprises a steering step STP12 with the automatic pilot system 60 of each aerodynamic drift member 26 in the set position POSCONS. The target steering angle ANGCIB to be reached is then equal to a set steering angle ANGCONS, at least when this set steering angle ANGCONS is included in the range of authorized values ​​bounded by the predetermined minimum angle ANGMIN and maximum angle ANGMAX.

[0111] The set steering angle ANGCONS is calculated by the automatic pilot system 60 to correspond to the angle to be reached in order to compensate for a torque exerted by said lift rotor 2 with zero lateral skid with the aerodynamic drift member(s) 26.

[0112] Therefore, the regulation phase STP1 may comprise, prior to the steering step STP12, a calculation step STP11, with the automatic piloting system 60, of the set steering angle ANGCONS. The piloting computer 61 may apply at least one law for this purpose, such a law being able, for example, to take the form of a series of stored instructions, a table of values, etc. The value of the set steering angle ANGCONS may depend on the forward speed of the hybrid helicopter 1 measured with the speed sensor 71, the torque exerted by the lift rotor 2 on the cell 4 measured by the torque sensor 72, and a density of the air surrounding said hybrid helicopter 1.

[0113] Optionally, the autopilot system 60 calculates the set steering angle ANGCONS with the following relationship: deltaV = C / 0.5 * ro * v 2 − N 1 / N 2 , where “deltaV” represents said setpoint steering angle ANGCONS, “C” represents a torque exerted by the lift rotor 2 on the cell 4, “V 2<” a forward speed of the hybrid helicopter 1 to the power of two, “ro” represents a density of the air, “0.5*ro*v2” represents a dynamic pressure, “N1” represents a first coefficient depending on an aerodynamic moment N0 of yaw of the hybrid helicopter 1 at zero sideslip and when said at least one aerodynamic drift member 26 is in the reference position POSREF reduced by the dynamic pressure q, “N2” represents a constant, “ / ” represents the division sign, “-” represents the subtraction sign, “*” represents the multiplication sign, “=” represents the equality sign.

[0114] The set steering angle can be limited by a minimum angle ANGMIN and a maximum angle ANGMAX.

[0115] The first coefficient may be equal to the aerodynamic yaw moment N0 of the hybrid helicopter 1 at zero sideslip and when said at least one aerodynamic drift member 26 is in the reference position POSREF reduced by the dynamic pressure q, i.e. N1=N0 / q. Therefore, the first coefficient may be a constant evaluated by tests and / or calculations and / or simulations.

[0116] Alternatively, this aerodynamic yaw moment N0 of the hybrid helicopter 1 at zero sideslip and when said at least one aerodynamic drift member 26 is in the reference position POSREF reduced by the dynamic pressure q can be corrected by a possibly clipped integral type corrector.

[0117] For example, the said first coefficient is determined by the following relation: N 1 = N 0 / q + k * int diff , where "N1" represents the first coefficient, "N0 / q" represents the aerodynamic yaw coefficient of the hybrid helicopter 1 reduced by the dynamic pressure at zero sideslip and when said at least one aerodynamic drift member 26 is in the reference position POSREF, "diff" represents a subtraction equal either to the first pitch PAS1 of the first blades 11 minus a second pitch PAS2 of the second blades or to a first thrust P1 exerted by said at least one first propeller 10 minus a second thrust P2 exerted by said at least one second propeller 15 or to a first torque Tq1 exerted by said at least one first propeller 10 minus a second torque Tq2 exerted by said at least one second propeller,, "k" represents a predetermined gain, "-" represents the subtraction sign, "+" represents the addition sign, "*" represents the multiplication sign, "=" represents the equality sign,"k*int(diff)" represents the integral type corrector equal to the product of said predetermined gain and an integral with respect to the time of the subtraction,

[0118] Depending on the variant, the said first coefficient is therefore determined by the following relation: N 1 = N 0 / q + k * int PAS 1 − PAS 2 , Or N 1 = N 0 / q + k * int P 1 − P 2 , Or N 1 = N 0 / q + k * int Tq 1 − Tq 2 .

[0119] Regardless of the variant, the gain k can be fixed or variable. For example, the gain k varies depending on the forward speed of the hybrid helicopter 1.

[0120] Furthermore, the corrector may be frozen when the hybrid helicopter 1 enters a dynamic piloting phase. The piloting computer 61 possibly considers that such a dynamic piloting phase is implemented as long as at least one of the following three conditions is satisfied: maneuver of the yaw control 55, this maneuver being identified via a signal emitted by the maneuver sensor 75, the absolute value of the load factor Ny in the transverse direction DIR is greater than a load factor threshold, this load factor being measured by the sensor 76 for measuring a load factor, the absolute value of the roll angle of the hybrid helicopter 1 is greater than a roll threshold, this roll angle being measured by the angular roll sensor 77.

[0121] Alternatively or additionally, the corrector may be frozen when an absolute value of a difference is less than a freezing threshold. This difference may be equal to the first step PAS1 minus the second step PAS2, or to the first thrust P1 minus the second thrust P2, or to the first torque exerted by said at least one first propeller 10 minus the second torque exerted by said at least one second propeller 15.

[0122] As a result and with reference to the figure 4 , before the regulation phase each aerodynamic drift member 26 can be in a position which does not allow the first thrust P1 and the second thrust P2 to be equalized.

[0123] In reference to the figure 5 , during the implementation of the regulation phase, each aerodynamic drift member 26 is deflected into its POSCONS set position via an open regulation loop which therefore makes it possible to equalize the first thrust P1 and the second thrust P2.

[0124] In parallel, the method can implement a step STP2 for regulating the lateral load factor Ny. For this purpose, the control computer 61 can transmit a signal to at least one yaw cylinder 63, this signal being determined by a usual fast regulation closed loop.

[0125] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible modes. It is of course possible to replace a means described by an equivalent means without departing from the scope of the present invention.

Claims

1. Method for optimising the functioning of at least one first propeller (10) and at least one second propeller (15), transversally disposed on both sides of an airframe (4) of a hybrid helicopter (1), said hybrid helicopter (1) including a rotor (2) for lift arranged above the airframe (4), said hybrid helicopter (1) including at least one aerodynamic rudder (26) exerting transverse lift, said at least one aerodynamic rudder (26) being mobile in rotation with respect to a support (25) of said hybrid helicopter (1), said method including the following step during a controlling phase: deflection (STP12) with an automatic pilot system (60) of said at least one aerodynamic rudder to a set-point position (POSCONS), the deflection having a target deflection angle (ANGCIB) with respect to a reference position (POSREF), characterised in that said target deflection angle (ANGCIB) is equal to a set-point deflection angle (ANGCONS) at least when this set-point deflection angle (ANGCONS) is within a range delimited by a predetermined included minimum angle (ANGMIN) and a predetermined included maximum angle (ANGMAX), said set-point deflection angle (ANGCONS) being calculated by the automatic pilot system (60) to offset a torque exerted by said rotor (2) for lift at zero sideslip.

2. Method according to claim 1, characterised in that said method includes the following step: calculation (STP11) with the automatic pilot system (60) of said set-point deflection angle (ANGCONS) according to at least one forward travel speed of the hybrid helicopter, a torque exerted by the rotor (2) for lift on the airframe (4) and a density of the air surrounding said hybrid helicopter.

3. Method according to either one of claims 1 to 2, characterised in that said method includes a step (STP11) of calculating with the automatic pilot system (60) said set-point deflection angle (ANGCONS) by the following relation: deltaV = C / 0.5 * ro * v 2 − N 1 / N 2 , where "deltaV" represents said set-point deflection angle (ANGCONS), "C" represents a torque exerted by the rotor (2) for lift on the airframe (4), "V2" represents a forward travel speed of the hybrid helicopter (1) to the power two, "ro" represents a density of the air, "0.5*ro*v2" represents a dynamic pressure, "N1" represents a first coefficient dependent upon an aerodynamic yawing moment (N0) of the hybrid helicopter (1) at zero sideslip and when said at least one aerodynamic rudder (26) is in the reference position (POSREF), moment reduced by the dynamic pressure, "N2" represents a second coefficient equal to a constant, " / " represents the division sign, "-" represents the subtraction sign, "*" represents the multiplication sign, "=" represents the equality sign.

4. Method according to claim 3, characterised in that said first coefficient is equal to the aerodynamic yawing moment (N0) of the hybrid helicopter (1), reduced by the dynamic pressure (q), at zero sideslip and when said at least one aerodynamic rudder (26) is in the reference position (POSREF).

5. Method according to claim 3, characterised in that said first coefficient is equal to the aerodynamic yawing moment of the hybrid helicopter (1), reduced by the dynamic pressure and corrected by an integral type of corrector, at zero sideslip and when said at least one aerodynamic rudder (26) is in the reference position (POSREF); this corrector being dependent on a gain and on a subtraction, either of a first pitch of first blades (11) of said at least one first propeller (10) minus a second pitch of second blades (16) of said at least one second propeller (15), or of a first thrust (P1) exerted by said at least one first propeller (10) minus a second thrust (P2) exerted by said at least one second propeller (15), or of a first torque exerted by said at least one first propeller (10) minus a second torque exerted by said at least one second propeller (15).

6. Method according to claim 5, characterised in that said first coefficient is determined by the following relation: N 1 = N 0 / q + k * int diff , where "N1" represents the first coefficient, "N0 / q" represents the aerodynamic yawing moment N0 of the hybrid helicopter (1), reduced by the dynamic pressure q, at zero sideslip and when said at least one aerodynamic rudder (26) is in the reference position (POSREF), "diff" represents said subtraction, "k" represents a predetermined gain, "-" represents the subtraction sign, "+" represents the addition sign, "*" represents the multiplication sign, "=" represents the equality sign, "k*int(diff)" represents the integral type of corrector equal to the product of said predetermined gain and an integral with respect to the time of said subtraction.

7. Method according to either one of claims 5 to 6, characterised in that said gain (k) varies according to a forward travel speed of the hybrid helicopter (1).

8. Method according to any one of claims 5 to 7, characterised in that said corrector is fixed when the hybrid helicopter (1) is in a phase of dynamic control.

9. Method according to claim 8, characterised in that the method includes a step of detecting a dynamic control phase if at least one of the following conditions is met: - operation of a yaw control (55) configured to change a component of differential pitch of the first pitch of the first blades (11) of said at least one first propeller (10) and of the second pitch of the second blades (16) of said at least one second propeller (15), - an absolute value of a load factor in a transverse direction (DIR) in a reference frame of the hybrid helicopter (1) is greater than a load factor threshold, - an absolute value of a roll angle of the hybrid helicopter (1) is greater than a roll threshold.

10. Method according to any one of claims 5 to 9, characterised in that said corrector is fixed when an absolute value of a difference is lower than a fixing threshold, said difference being equal to: - the first pitch of the first blades (11) of said at least one first propeller (10) minus the second pitch of the second blades (16) of said at least one second propeller (15), - or the first thrust (P1) exerted by said at least one first propeller (10) minus the second thrust (P2) exerted by said at least one second propeller (15), - or the first torque exerted by said at least one first propeller (10) minus the second torque exerted by said at least one second propeller (15).

11. Method according to any one of claims 1 to 10, characterised in that said control phase is implemented when said hybrid helicopter (1) performs a cruise flight phase.

12. Method according to any one of claims 1 to 11, characterised in that said deflection (STP12) with the automatic pilot system (60) of said at least one aerodynamic rudder (26) to a set-point position (POSCONS) is achieved by applying an open control loop.

13. Hybrid helicopter (1) equipped with at least one first propeller (10) and at least one second propeller (15), transversally disposed on both sides of an airframe (4) of this hybrid helicopter (1), said hybrid helicopter (1) including a rotor (2) for lift arranged above the airframe (4), said hybrid helicopter (1) including at least one aerodynamic rudder (26) exerting transverse lift (P3) , said at least one aerodynamic rudder (26) being mobile in rotation with respect to a support (25) of said hybrid helicopter (1), characterised in that said hybrid helicopter (1) includes an automatic pilot system (60) configured to apply the method according to any one of claims 1 to 12, said automatic pilot system (60) including a flight computer (61) configured to apply the method according to any one of claims 1 to 12, the automatic pilot system (60) including at least one actuator (62) connected to said at least one aerodynamic rudder (26) and to the flight computer (61).

14. Hybrid helicopter (1) according to claim 13, characterised in that said automatic pilot system (60) includes at least one of each of the following components connected to the flight computer (61): a speed sensor (71), a torque sensor (72) configured to measure any information relating to a torque exerted by the rotor (2) for lift, a first sensor (73) of the first pitch of first blades (11) of said at least one first propeller (10), a second sensor (74) of the second pitch of second blades (16) of said at least one second propeller (15), an operation sensor (75) for determining if a pilot is operating a yaw control (55), a sensor (76) for measuring a load factor in a transverse direction in a reference frame of the hybrid helicopter (1), an angular roll sensor (77) measuring a roll angle of the hybrid helicopter (1), a first and a second torque sensor (78, 79), respectively of said at least one first propeller (10) and said at least one second propeller (15), a first thrust sensor for evaluating a first thrust (P1) generated by said at least one first propeller (10), a second thrust sensor for evaluating a second thrust (P2) generated by said at least one second propeller (15).