Method and device for controlling a thermal and electric power plant for rotorcraft

Abstract

The present invention relates to a method for controlling a thermal and electrical power plant (5) for setting in motion at least one rotary member (2, 3) of a rotorcraft (1), said power plant (5) comprising at least one thermal engine (11) and an electrical system (20) provided with at least one electrical machine (21). The method comprises: - selection with a selector (42) of an operating mode chosen from several operating modes, - determination of a density altitude and comparison with a controller (25) of said current density altitude and a threshold density altitude, - control with the controller (25) of said at least one electrical machine (21) as a function at least of said chosen operating mode as well as of said comparison and of a power required to be supplied to said power transmission chain (15). Abstract figure: figure 1

Description

Title of the invention: Method and device for controlling a thermal and electric power plant for rotorcraft

[0001] The present invention relates to a method and a device for controlling a thermal and electric power plant for a rotorcraft. The invention lies in the technical field of a thermal and electric power plant for an aircraft, and more particularly power plants for a rotorcraft.

[0002] A rotorcraft is conventionally provided with at least one member, hereinafter referred to as a "rotary member", to ensure its lift and / or its propulsion. Thus, a rotorcraft comprises at least one rotating wing forming a main rotor. A rotorcraft may also comprise at least one auxiliary rotor, for example a tail rotor. A rotorcraft may also comprise one or more propellers intended primarily for the propulsion of the rotorcraft.

[0003] A rotorcraft is further equipped with a power plant for setting in motion the various aforementioned rotating members, and in particular the rotor(s) as well as the possible propeller(s).

[0004] The power plant may comprise, for this purpose, one or more thermal engines which set in motion a power transmission chain. The power transmission chain then sets in rotation at least one of the various aforementioned rotating members. Such a power transmission chain may comprise a main power transmission box opening in particular onto the main rotor, if any, a rear power transmission box opening onto a rear rotor, if any, a propeller power transmission box, shafts, connection means, etc.

[0005] Furthermore, a failure of the thermal engine(s) may cause the rotorcraft to enter an unpowered phase of autorotational flight.

[0006] The power plant can be equipped with an electric motorization kit to assist the thermal engine(s) in the event of a breakdown. The rotorcraft then has a thermal and electric power plant to set the power transmission chain in motion.

[0007] It should be noted that the expression "thermal engine" designates for convenience throughout the text any engine operating with a fuel that can be used in such a rotorcraft power plant, for example turboshaft engines or piston engines. The expression "thermal engine" is to be contrasted with the expression "electric engine" qualifying engines powered by electrical energy.

[0008] An electric motor of a hybrid power plant can be used only in motor mode in order to transform electrical energy into mechanical energy. An electric motor can also be an electrical machine combining motor mode with an electrical generator mode in order to transform mechanical energy into electrical energy to recharge a rechargeable electrical energy source for example.

[0009] Documents FR 2994687 and FR 3090576 thus describe a hybrid power plant for a rotorcraft equipped with a single thermal engine, an electric motor, a main power transmission box and an electrical energy storage means. Following a failure of the thermal engine, the electric motor provides mechanical power in order to assist the pilot of the rotorcraft in carrying out an autorotation flight phase following the failure.

[0010] The present invention therefore aims to propose a method and a device for alternative management of the energy supplied by a thermal and electrical power plant for setting in motion at least one rotor of a rotorcraft aiming to optimize the operation of the rotorcraft according to its environment.

[0011] The invention relates to a method for controlling a thermal power plant and electrical system for setting in motion at least one rotating member of a rotorcraft, said power plant comprising a thermal system and an electrical system for setting in motion a power transmission chain connected to said at least one rotating member, the thermal system having at least one thermal engine and the electrical system being provided with at least one electrical machine, said electrical system having a source of electrical energy electrically connected to said at least one electrical machine.

[0012] The method comprises a selection with a selector of an operating mode chosen from several operating modes, the method having a hybridization phase comprising the following steps:

[0013] - comparison with a controller between a current density altitude and an altitude- threshold density,

[0014] - control with the controller of said at least one electrical machine in operation of said chosen operating mode as well as of said comparison and of a power required to be supplied to said power transmission chain.

[0015] In particular, the controller controls the electric machine according to one of the operating modes, the applied mode being or not being the operating mode chosen as a function of said comparison and the necessary power. The necessary power corresponds to the power required by the aircraft to maintain the requested flight case. This necessary power can correspond at each instant to the sum of the powers transmitted to the power transmission chain by the thermal engines and the electrical machine(s), possibly to the energy losses of the power transmission chain and to the power taken to drive nearby accessories.

[0016] The necessary power can be calculated, for example, using stored laws and / or one or more power sensors. Such a power sensor can be arranged on the power transmission chain, on a working shaft of a heat engine or even on a working shaft of an electrical machine. A power sensor can comprise a torque meter and a rotation speed sensor as well as a calculation means for example, the power being equal to the product of the measured torque and the measured rotation speed.

[0017] The method thus comprises determining a current density altitude at a current position of said rotorcraft. This step can be carried out outside or during the hybridization phase.

[0018] The rotary member may be a member participating in the movement of the aircraft, such as a rotary wing participating at least in the lift of the rotorcraft, a rotor for controlling the yaw movement of the rotorcraft, or a propeller for example.

[0019] The expression "motor installation comprising a thermal system and an electrical system for setting in motion a power transmission chain connected to said at least one rotating member" means that the thermal engine(s) and the electrical machine(s) can set in motion the power transmission chain.

[0020] From then on, an individual can operate the selector to choose an operating mode. The controller applies the chosen operating mode or another operating mode depending on the choice made but also on the current density altitude and the power required, or even on an available power likely at any moment to be developed by the thermal system for the flight. The controller applies a law to determine according to which operating mode the electrical machine(s) must operate. From then on, the controller transmits a control signal to the electrical machine(s) to apply the appropriate operating mode according to the current situation, namely according to the pilot's choice and the current flight case. For example, a control signal can carry the mechanical power to be supplied or taken by the electrical machine receiving it.

[0021] The term "signal" can designate, for example, an analog, digital, discrete, electrical, optical signal. A control signal can, for example, take the form of an electric current having an electrical intensity representing a mechanical power to be supplied or taken.

[0022] Indeed, a rotorcraft often operates in a first flight domain at low altitude to carry out its mission. In this case, the power transmitted to the rotating parts is essentially limited by the power that can be developed by the power transmission chain. Such power is referred to as the "maximum limiting power" hereinafter.

[0023] A rotorcraft can also sometimes operate in a second flight domain, namely at high altitude or at low altitude but in the presence of a very hot climate. In this case, the power transmitted to the rotating members is essentially limited by the available power that can be developed jointly by the thermal engine(s). The available power can be obtained by the controller using a stored law giving this available power as a function of the current density altitude, or even as a function of the atmospheric pressure and the outside temperature, or can be determined by an engine computer or another member for example.

[0024] From then on, the controller determines in which flight domain the aircraft is operating by comparing the current attitude-density with a stored threshold density altitude. Depending on the current flight domain and the choice made by an individual using the selector, the controller pilots, during the hybridization phase, the electrical machine(s) to optimize the operation of the aircraft with regard to the most relevant limitation in the current flight domain.

[0025] The method may in particular further comprise one or more of the following characteristics, taken alone or in combination.

[0026] In particular, the method can apply various steps during successive loops.

[0027] According to one possibility, said several operating modes may comprise a standby mode during which said at least one electrical machine is stopped or in electrical generator mode to recharge said electrical energy source during a recharging phase, an economic mode during which said at least one electrical machine operates in engine mode and the thermal system delivers a reduced power, for example predetermined, and a high-performance mode during which said at least one electrical machine operates in engine mode and the thermal system delivers a predetermined maximum main power, and the controller can control said at least one electrical machine according to said standby mode when jointly said chosen operating mode is said high-performance mode and said current density altitude is lower than the threshold density altitude.

[0028] When the standby mode is controlled by the controller, the electrical machine(s) are, if necessary, stopped by the controller if they are operating in motor mode. The electrical machine(s) then switch, if necessary and on the order of the controller, to electrical generator mode to recharge the electrical energy source. This standby mode makes it possible to detect whether an electrical machine is in a configuration suitable for electrical recharging and thus makes it possible to activate, if necessary, recharging via operation in electrical generator mode.

[0029] When the performance mode is activated by the controller, the electrical machine(s) operate in engine mode in order to deliver additional mechanical power for performance purposes. This additional mechanical power makes it possible, for example, to compensate for the drop in mechanical power developed by the thermal engine(s) due to atmospheric conditions in particular. The additional mechanical power is established to comply with the maximum acceptable power limit by the power transmission chain. In addition, the additional mechanical power can be limited so as not to exceed the power limit of the electrical machine. Autorotation assistance is also available in this mode.

[0030] When the economy mode is activated by the controller, the electrical machine(s) operate in engine mode in order to deliver additional mechanical power for economic purposes. This additional mechanical power is determined, for example, so that the power to be provided by the thermal engine(s) is a reduced power allowing a reduction in fuel consumption with acceptable efficiency. Autorotation assistance is also available. The reduced power may be predetermined or may depend on the power developed by the electrical machine.

[0031] Regardless of the operating mode chosen and the flight scenario, an autorotation operating mode is therefore always available. In the event of a failure of the thermal engines or at the request of the pilot using an appropriate interface, the electrical machine(s) switch, on command from the controller, to the engine mode for autorotation assistance.

[0032] Thus, according to a possibility compatible with the previous one, said at least one rotary member being able to comprise a rotary wing, said method can comprise a determination of a failure of the thermal system rendering it inoperative and a determination of a rotation speed of the rotary wing, said method comprising a control, with the controller, of the operation in motor mode of said at least one electrical machine in the presence of a said failure and a said rotation speed greater than zero.

[0033] The expression "failure of the thermal system rendering it inoperative" means that the thermal system is no longer able to set the power transmission chain in motion. Such a failure can be determined in the usual manner using a monitoring computer, for example an engine computer, transmitting the failure information to the controller.

[0034] Optionally, the controller may transmit an autorotation alert signal to an alerter under these conditions.

[0035] Optionally, the method may comprise the following steps: comparison of the rotation speed with a stored autorotation speed, control with the controller of said at least one electrical machine to deliver maximum auxiliary power in engine mode if said rotation speed is lower than said autorotation speed, control with the controller of said at least one electrical machine to deliver in engine mode a power lower than said maximum auxiliary power if said rotation speed is greater than or equal to said autorotation speed.

[0036] Maximum auxiliary power is the highest power that can be developed by an electric machine.

[0037] If the rotation speed is lower than said autorotation speed, the electrical machine(s) inject maximum power into the power transmission chain to place the aircraft in the required autorotation configuration.

[0038] If not, the electrical machine(s) inject lower power into the power transmission chain in order to enlarge the autorotation cone and increase the surface area of ​​an achievable landing zone.

[0039] According to a possibility compatible with the previous ones, the method may include a detection of a malfunction of said electrical system, said hybridization phase being prohibited in the presence of said malfunction, and therefore on the contrary authorized in the absence of said malfunction.

[0040] Optionally, the controller may transmit an alert signal to an alerter to signal the malfunction of the electrical system.

[0041] According to a possibility compatible with the previous ones, the method may comprise a measurement of an electrical capacity of said electrical energy source, said hybridization phase being prohibited in the presence of a measured electrical capacity lower than an electrical capacity threshold, said method comprising a control with said controller of a said recharging phase of said electrical energy source by controlling the operation in electrical generator mode of said electrical machine when said measured electrical capacity is lower than or equal to the electrical capacity threshold.

[0042] Optionally, the controller may transmit a low electrical capacity alert signal to an alerter under these conditions.

[0043] When the electrical machine(s) are operating in motor mode, these electrical machines are stopped before switching to electrical generator mode for electrical recharging of the electrical energy source.

[0044] According to a possibility compatible with the previous ones, said at least one rotating member being able to comprise a rotating wing, said method can comprise a measurement of a rotation speed of the rotating wing, said hybridization phase being prohibited by the controller in the presence of a measured rotation speed not belonging to a rotational speed reference range.

[0045] The rotational speed reference range may be fixed and stored in the controller or may be variable. For example, an engine computer or the like transmits to the controller the value of a variable reference speed, the rotational speed reference range being a function of this reference speed. For illustration purposes, the rotational speed reference range may be equal to the value of the reference speed plus or minus one percent.

[0046] Optionally, the controller may transmit a low rotational speed alert signal of the rotary wing to an alerter when the measured rotational speed does not belong to the rotational speed reference range. When the electrical machine(s) are operating in motor mode, these electrical machines are stopped.

[0047] According to a possibility compatible with the previous ones, said at least one thermal engine being able to be controlled by an engine computer, said engine computer can comprise an automatic mode during which said engine computer annexes the power delivered by the controlled thermal engine to a rotation speed of said at least one rotary member.

[0048] The automatic mode of the engine computer makes it possible to automatically regulate the power developed by a thermal engine according to the operation of the electrical machine(s).

[0049] According to a possibility compatible with the previous ones, the method may comprise a step of determining the mode applied by the engine computer, said hybridization phase being authorized by the controller only when said engine computer operates according to said automatic mode.

[0050] Optionally, the controller can transmit a hybridization phase prohibition alert signal to an alerter. When the electrical machine(s) are operating in motor mode, these electrical machines are stopped.

[0051] According to a possibility compatible with the previous ones, during the hybridization phase, the method can include a determination of an available power which can be developed by the thermal system.

[0052] Such available power can be determined in the usual manner, using a law stored for example, in the controller or in another organ. This characteristic makes it possible to adapt the control of the electrical machine(s) according to the maximum power likely to be developed by the thermal engine(s).

[0053] According to a possibility compatible with the previous ones, when said current density altitude is higher than said threshold density altitude and said chosen operating mode is the high-performance mode, the method can comprise the following steps:

[0054] - determining with the controller that said necessary power is included or is not included in a test range extending from said available power which can be developed by the thermal system up to a maximum limit power acceptable by said power transmission chain, said available power and said maximum limit power being respectively excluded from said test range,

[0055] - application with the controller of the high-performance mode when said power ne necessary is included in the said test range,

[0056] - application with the standby mode controller when said power required is outside the said test range.

[0057] Even if the high-performance mode is selected, the controller implements the standby mode if the necessary power is not in the stored test page in order not to exceed the maximum power limit acceptable by said power transmission chain.

[0058] According to a possibility compatible with the previous ones, when said current density altitude is higher than said threshold density altitude and said chosen operating mode is the economic mode, the method can comprise the following steps:

[0059] - determining with the controller that said required power is less than or greater than or equal to said available power which can be developed by the thermal system,

[0060] - application with the controller of the economic mode when said power ne necessary is less than the available power,

[0061] - application with the standby mode controller when said power required is greater than or equal to the available power.

[0062] Even if the economy mode is selected, the controller implements the standby mode if the required power is greater than or equal to the available power.

[0063] According to a possibility compatible with the previous ones, when said current density altitude is less than or equal to said threshold density altitude and said chosen operating mode is the economic mode, the method can comprise:

[0064] - determining with the controller that said required power is less than or greater than or equal to a maximum power limit acceptable by said power transmission chain,

[0065] - application with the controller of the economic mode when said power ne necessary is less than the maximum power limit,

[0066] - application with the standby mode controller when said power required is greater than or equal to the maximum power limit.

[0067] According to a possibility compatible with the previous ones, during the economic mode chosen from among said several operating modes, the method can comprise a control with the controller of said at least one electrical machine to provide in engine mode a power equal to the product of an economic transfer function with either an economic power or a difference between the necessary power and a predetermined reduced power.

[0068] The power developed by an electric machine during economy mode can be predetermined or variable.

[0069] The economic power can be stored or set by a pilot or a co-pilot, using a human-machine interface transmitting a signal to the controller carrying a value of the economic power.

[0070] According to a possibility compatible with the previous ones, during the high-performance mode chosen from among said several operating modes, the method can comprise a command with the controller of said at least one electrical machine to provide in motor mode a power equal to the product of a high-performance transfer function with either a high-performance power, or a difference between a predetermined maximum limit power acceptable by said power transmission chain and the necessary power.

[0071] The power developed by an electric machine during the performance mode can be predetermined or variable.

[0072] The performance power can be stored or configured by a pilot or a co-pilot, using a human-machine interface transmitting a signal to the controller carrying a value of the performance power.

[0073] According to a possibility compatible with the previous ones, a recharging phase can include the following steps:

[0074] - determining that a forward speed of said rotorcraft is included in a memorized forward speed range,

[0075] - determining that an electrical capacity of said electrical energy source is below a recharge threshold,

[0076] - as long as said forward speed of said rotorcraft is within said range forward speed and that the electrical capacity of said electrical energy source is lower than the recharge threshold, recharge of said electrical energy source by controlling with the controller said at least one electrical machine in electrical generator mode.

[0077] The recharging of electrical energy is thus carried out only when the aircraft is moving at a speed requiring a minimum of mechanical power.

[0078] The recharge threshold may be higher than the electrical capacity threshold.

[0079] The invention also relates to a rotorcraft provided with at least one rotary member, said rotorcraft comprising a thermal and electrical drive system for setting said at least one rotary member in motion, said drive system comprising a thermal system and an electrical system for setting a chain of power transmission connected to said at least one rotating member, the thermal system having at least one thermal engine and the electrical system being provided with at least one electrical machine, said electrical system having a source of electrical energy electrically connected to said at least one electrical machine.

[0080] The rotorcraft comprises a selector for selecting an operating mode chosen from several operating modes, said rotorcraft comprising a controller connected to the selector as well as to a density altitude sensor and to a sensor of a power required to be supplied to said power transmission chain, said controller being configured to control said at least one electrical machine by applying the method of the invention.

[0081] Density altitude is not to be confused with altitude or density, but corresponds to pressure altitude corrected for the effect of temperature. Density altitude is usually calculated from, for example, atmospheric pressure, measured with a barometer or other, and a temperature measured with a thermometer or other temperature sensors.

[0082] 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:

[0083] [Fig-1] [Fig.l], a view of an aircraft according to the invention,

[0084] [Fig.2] [Fig.2], a diagram illustrating an example of a method for initiating the hybridization phase,

[0085] [Fig.3] [Fig.3], a diagram illustrating an example of an autorotation phase,

[0086] [Fig.4] [Fig.4], a diagram illustrating an example of a high-energy hybridization phase density altitude,

[0087] [Fig.5] [Fig.5], a diagram illustrating an example of a low-energy hybridization phase density altitude,

[0088] [Fig.6] [Fig.6], a diagram illustrating an example of a recharging phase,

[0089] [Fig.7] [Fig.7], a diagram illustrating the hybridization phase with one or more electric machines delivering variable mechanical power in motor mode, and

[0090] [Fig.8] [Fig.8], a diagram illustrating the hybridization phase with one or more electric machines delivering constant mechanical power in motor mode.

[0091] Elements present in several distinct figures are assigned a single reference.

[0092] [Fig.l] represents a rotorcraft 1 according to the invention. This rotorcraft comprises at least one rotary member 2, 3. Each rotary member 2, 3 can participate in the movement or the lift of this aircraft. For example, the rotorcraft 1 comprises a rotary member taking the form of a rotary wing 2 carried by an airframe 4. The rotorcraft 1 can further comprise at least one propeller and / or at least one tail rotor 3 participating to the yaw control of the cell 4. To set the rotating member(s) 2, 3 in motion, the rotorcraft 1 comprises a thermal and electric power plant 5. The power plant 5 thus comprises a power transmission chain 15 connected to the rotating member(s) 2, 3. Such a power transmission chain 15 may comprise one or more power transmission boxes, one or more shafts, connection means, etc. According to the example illustrated, the power transmission chain 15 comprises a main power transmission box 16 setting a rotor mast 17 in motion connected to the rotary wing 2. In addition, the power transmission chain 15 comprises at least one shaft 18 connecting the main power transmission box 16 to a rear power transmission box 19 rotating a rear rotor 3.

[0093] Therefore, the power plant 5 comprises a thermal system 10 provided with one or more thermal engines 11 setting in motion the power transmission chain 15, and in particular the internal components of the main power transmission box 16 according to the example illustrated. Regardless of the number of thermal engines, each thermal engine is for example controlled by its own engine computer 12. In the presence of several thermal engines 11, the engine computers 12 can communicate with each other. In addition, each thermal engine 11 can be for example a turboshaft engine or a piston engine.

[0094] Furthermore, the power plant 5 comprises an electrical system 20. This electrical system 20 comprises one or more electrical machines 21 capable of operating in motor mode to set the power transmission chain 15 in motion, directly or indirectly. For example, an electrical machine 21 may be engaged on the power transmission chain 15, and in particular on the main power transmission box 16 according to the example illustrated, or on a heat engine 11.

[0095] Each electrical machine 21, and independently of the number of electrical machines 21, can also operate in electrical generator mode, so as to produce electrical energy by being set in motion by the power transmission chain or by a heat engine 11.

[0096] The term “each” associated with an object can be used independently of the number of objects and can be assimilated to the expression “the or where appropriate the”.

[0097] Each electrical machine 21 is connected to an electrical energy source 22. This electrical energy source 22 is rechargeable so as to electrically power each electrical machine 21 operating in motor mode and to be electrically powered by each electrical machine 21 operating in electrical generator mode. The electrical energy source 22 may usually comprise batteries or equivalents, a hydrogen fuel cell or equivalent...

[0098] Furthermore, the rotorcraft 1 comprises a controller 25 in communication with in particular each electrical machine 21 in order to transmit to them a control signal indicating how they must operate.

[0099] The controller 25 may comprise, 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 “controller”. The term processor may also 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. The controller 25 may comprise, for example, one or more computers dedicated or not to the method of the invention. Several computers of the system may form a single computer, and for example the controller 25 as well as the monitoring computer 39 mentioned later. For example, the controller 25 is part of a set called “Aircraft Management Computer” in English.

[0100] The rotorcraft 1 comprises a sensor 34 of a usual density altitude in wired or wireless communication with the controller 25. The term sensor used subsequently can designate an assembly comprising one or more sensors or even a computer. Thus, a sensor 34 of a density altitude can comprise an altimeter and a thermometer for example. The sensor 34 of a density altitude transmits to the controller 25 a signal carrying the current density altitude Zt.

[0101] The rotorcraft 1 may also comprise a mechanical power sensor 32 determining a mechanical power Pwe developed or taken by an electrical machine 21. Such a mechanical power sensor 32 may comprise, for example, for each electrical machine 21, a torque meter and a rotation speed sensor positioned on a power shaft of the electrical machine 2. According to another example, the electrical consumption or even the direction of rotation of such a shaft may be measured and used to evaluate the mechanical power Pwe in a usual manner. Furthermore, at least one usual monitoring sensor is configured to determine whether the machine is operating correctly, such as a sensor measuring an electrical intensity compared to a reference. Each monitoring sensor may emit a monitoring signal carrying information indicating whether the electrical machine has failed, directly or indirectly to the controller.

[0102] The rotorcraft 1 may also comprise an electrical capacitance sensor 33 measuring the current electrical capacitance C of the electrical energy source 22.

[0103] The rotorcraft 1 may also comprise a forward speed sensor 36 measuring a speed of movement of the rotorcraft 1. For example, such a sensor 36 comprises a satellite positioning system, a Pitot tube system, etc. for example, the forward speed is the true air speed called “True Air Speed ​​» in English.

[0104] The rotorcraft 1 may also comprise a rotation speed sensor 31 measuring the speed of a rotating member of the power plant 5, and in particular of a rotating member or of a mobile member jointly with a rotating member. For example, a rotation speed sensor 31 measures the rotation speed of the rotor mast 17, an image of the rotation speed of the rotary wing 2. The rotation speed sensor 31 may transmit a signal carrying the rotation speed Nr to the controller 25 but also to each engine computer 12.

[0105] Indeed, an engine computer 12 can control the associated thermal engine 11 in the usual manner, during an automatic mode, as a function of a reference speed, fixed or variable, and of a rotation speed Nr measured by the rotation speed sensor 31, and in particular as a function of a rotation speed Nr of the rotary wing. The power developed by a thermal engine 11 can then vary automatically as a function of the power developed or taken by an electric machine 21. The power developed by a thermal engine 11 is further limited so as not to exceed a limit power of the engine varying as a function of the density altitude and so that the power transmitted by the power transmission chain 15 does not exceed a maximum limit power Lbtp.

[0106] In the presence of a single heat engine, the available power Pwdt is equal to the limit power of the heat engine. In the presence of several heat engines, the available power Pwdt is equal to the sum of the limit powers of the engines.

[0107] The available power Pwdt can be determined by an estimator using a stored law providing this available power Pwdt as a function of the density altitude. The estimator can be the controller 25, or another member transmitting a signal to the controller 25 carrying this available power Pwdt for example.

[0108] The rotorcraft 1 may comprise a standard sensor 38 of a necessary power WNEC to be supplied to the power transmission chain. For example, the sensor 38 of a necessary power may comprise one or more power sensors 381, 382, ​​383 arranged on the power transmission chain 15 or on a working shaft of a thermal engine or even an electric machine. A power sensor may comprise a torque meter and a rotation speed sensor for example. According to the example illustrated, the sensor 38 of a necessary power may comprise a power sensor 381, 382, ​​383 at the output of each thermal engine and each electric machine. The necessary power is then calculated by an evaluator by summing the measured powers. The evaluator may be the controller 25 or a standard device.

[0109] The rotorcraft may include a monitoring computer 39 configured to de terminate if the thermal engine(s) fail. For example, the monitoring computer 39 is an engine computer 12. The monitoring computer transmits, if necessary, a signal to the controller 25 indicating a fault rendering the thermal system 10 inoperative.

[0110] Optionally, the rotorcraft 1 may include a human-machine interface 41 connected to each engine computer 12 to require the implementation of the automatic mode of regulation of the corresponding thermal engine 11.

[0111] Optionally, the rotorcraft 1 may include a human-machine interface 41 connected to the controller 25 to configure a high-performance power Psperfo and / or an economic power Pseco.

[0112] Optionally, the controller 25 can communicate with an alerter 60 to generate an alert. Such an alerter 60 can comprise a screen displaying a message, and / or an audio means and for example a loudspeaker, and / or a lamp,...

[0113] According to another aspect, the rotorcraft 1 comprises a selector 42 in wired or wireless communication with the controller 25 to choose an operating mode. The selector 42 transmits a signal carrying a chosen operating mode. For example, the selector 42 may comprise a multi-position button, a touch screen, etc. In particular, the selector 42 may allow a Pii pilot to select an operating mode from a standby mode MODV, a high-performance mode MODPERF and an economical mode MODECO.

[0114] When the standby mode MODV is implemented by the controller 25, the electrical machine(s) 21 are stopped if necessary, or if necessary at least one electrical machine 21 is controlled in electrical generator mode to recharge the electrical energy source 22 during a recharging phase STPRECHARGE, for example by applying a function Fr(t).

[0115] When the economic mode MODECO is implemented by the controller 25, at least one or even each electrical machine 21 operates in motor mode so that the thermal engine(s) 11 deliver a reduced power, for example predetermined Ptm.

[0116] When the high-performance MODPERF mode is implemented by the controller 25, at least one or even each electrical machine 21 operates in motor mode and the thermal engine(s) 11 deliver power that can reach the available power.

[0117] At any time and regardless of the operating mode chosen, the controller 25 can implement an autorotation operating mode.

[0118] Therefore, the method of the invention requires the selection STPSELECT of a chosen operating mode by operating the selector 42. During a hybridization phase, the controller 25 further compares the current density altitude Zt to a density altitude threshold Zs stored. As a result, the controller 25 controls each electrical machine 21 according to the operating mode chosen, the value of the current density altitude Zt with respect to the threshold density altitude Zs as well as the necessary power Wnec. For this purpose, the controller 25 transmits a control signal to an electrical machine 21 to control it, this control signal carrying a power to be supplied or taken by the electrical machine 21.

[0119] Figures 7 and 8 illustrate diagrams showing power on the ordinate and density altitude on the abscissa. A line DI illustrates the available power that can be developed by the thermal engine(s) 11 jointly. A horizontal line D2 represents the maximum limit power Lbtp admissible by the power transmission chain 15. A line D3 represents a predetermined reduced power Ptm optimizing the operation of the thermal engine(s) 11. According to [Fig.7], the electrical machine(s) 21 can provide variable power depending on the need while, according to [Fig.8], the electrical machine(s) 21 provide power memorized or set by a pilot or co-pilot. The diagrams are provided for illustrative purposes only.

[0120] With reference to [Fig.7], when the current density altitude Zt is greater than a threshold density altitude Zs, all operating modes are accessible. The controller 25 determines the mode to be applied according to the operating mode chosen, the necessary power Wnec or even the available power Pwdt. During the standby mode MODV, each electrical machine 21 is switched off or in electrical generator mode.

[0121] During the MODECO economy mode, each electrical machine 21 can operate in motor mode to provide a mechanical power Pwe. According to [Fig.7], the mechanical power Pwe is adjusted by the controller 25 so that the thermal engine(s) 11 automatically provide a reduced power Ptm and so as not to exceed the maximum limit power. According to [Fig.8], the mechanical power Pwe is fixed, the reduced power then being variable.

[0122] During the MODPERF high-performance mode, the thermal engine(s) 11 are controlled to provide the maximum thermal power and the electrical machine(s) 21 operate in motor mode to provide additional power within the limit of the maximum limit power Lbtp admissible by the power transmission chain 15.

[0123] When the current density altitude Zt is less than or equal to the threshold density altitude Zs, if the operating mode chosen is the high-performance mode MODPERF, the controller 25 applies the standby mode MODV.

[0124] From then on and whatever the way of producing the rotorcraft 1, the controller 25 can thus carry out steps of the method in a loop. Figures 2 to 6 describe steps possible of a loop.

[0125] Thus, according to [Fig.2], the method may comprise an STPO test phase to determine whether the Phashyb hybridization phase or an STPROT autorotation phase must be undertaken. Steps described are possibly optional and are possibly carried out in another order, or even simultaneously.

[0126] The Phashyb hybridization phase may in particular be conditioned by normal operation of the electrical system 20.

[0127] Therefore, the method can comprise a detection STP1 of a malfunction of the electrical system 20. For example, each electrical machine 21, or even the electrical energy source 22, can comprise usual monitoring sensors to determine the presence of a fault. These monitoring sensors communicate with the controller 25. If a monitoring sensor transmits a signal carrying a fault to the controller 25 during a loop, the controller 25 does not implement the Phashyb hybridization phase. On the other hand, the controller 25 can control an alerter 60 to generate a WARNHS alert. The loop of the method stops and a new loop begins.

[0128] The detection STP1 of a malfunction of the electrical system 20 can possibly be carried out at the initiation of the loop because, in the event of a malfunction, the electrical system 20 cannot be used.

[0129] Furthermore, the loop may include a step for determining whether an STPROT autorotation phase must be initiated. This step may be performed after the malfunction detection step due to its importance.

[0130] Thus the method may comprise the determination STP2 of a failure of the thermal system 10 rendering it inoperative. In the absence of such a failure, the loop continues. In the presence of such a failure, an autorotation phase STPROT begins.

[0131] With reference to [Fig.3] and during an autorotation phase STPROT, the method comprises the determination STP9 by the controller 25 that the measured rotation speed Nr is greater than zero. For this purpose, the controller 25 compares the measured rotation speed Nr to zero. If the measured rotation speed Nr is equal to zero, the rotorcraft is stopped. Each electrical machine 21 remains stopped while providing zero mechanical power Pwe. The process loop stops and a new loop begins.

[0132] If the measured rotation speed Nr is different from zero, at least one or even each electrical machine 21 is controlled by the controller 25 to operate in motor mode.

[0133] Optionally, the method comprises the comparison STP10 with the controller 25 of the rotation speed Nr with a stored autorotation speed Nrautorot. From then on, the controller 25 controls, during a step STP101, at least one or even each electric machine 21 to deliver to the power transmission chain 15 a mechanical power Pwe equal to a maximum auxiliary power Pwemax in motor mode if the rotation speed Nr is lower than the autorotation speed Nrautorot. The maximum auxiliary power Pwemax can be obtained using a first autorotation transfer function Fal(t). All the power of the electric machine is used to facilitate autorotation. The process loop stops and a new loop begins.

[0134] Conversely, the controller 25 controls, during a step STP102, at least one or even each electrical machine 21 to deliver in motor mode a moderate power Pwelow lower than said maximum auxiliary power Pwemax if the rotation speed Nr is greater than or equal to said autorotation speed Nrautorot. The moderate power Pwelow can be obtained using a second autorotation transfer function Fa2(t). The process loop stops and a new loop begins.

[0135] This method makes it possible to automatically inject the maximum power into the power transmission chain 15 at the time of the landing phase called “flare” in English.

[0136] With reference to [Fig.2], the test phase STPO may comprise a measurement STP3 of the current electrical capacity C of the electrical energy source 22 with the electrical capacity sensor 33. If the controller 25 determines that the current electrical capacity C is less than an electrical capacity threshold C1, then the controller 25 does not implement the hybridization phase. Optionally, the controller 25 controls the alerter 60 to emit a WARNLOW alert. Optionally, the controller 25 then controls at least one or even each electrical machine 21 to electrically recharge the electrical energy source 22 during a recharging phase ST-PRECHARGE.

[0137] Previously, the controller 25 can determine during a verification step STP4, whether an electrical machine 21 is operating in motor mode, for example using the mechanical power sensor 32. If so, the controller 25 transmits a signal to the electrical machine 21 to stop it, for example by applying a stored stop transfer function Fc(t). The recharging phase ST-PRECHARGE then begins.

[0138] [Fig.6] illustrates an example of a recharging phase STPRECHARGE. Optionally, the controller 25 can determine during a step STP18 whether the forward speed V of the rotorcraft 1 is included in a forward speed range stored using the forward speed sensor 36. For example, this range is delimited between a low speed greater than the speed of the best climb rate Vy and a high speed. The high speed can be the cruising speed of the rotorcraft, also called "recommended transit speed". The controller 25 can, for this purpose, receive from the forward speed sensor 36 a signal carrying the forward speed. If not, recharging cannot be carried out and another loop begins.

[0139] Optionally, the controller 25 can determine, during a step STP19, whether the current electrical capacity C of the electrical energy source 22 is lower than a recharge threshold C3. The controller 25 can, for this purpose, receive from the electrical capacity sensor 33 a signal carrying the current electrical capacity C. If not, the recharge cannot be carried out and another loop begins.

[0140] Therefore, as long as said forward speed V is included in said forward speed range and the current electrical capacity C is lower than the recharge threshold C3, the controller 25 controls a recharge step STP20 of the electrical energy source 22 by controlling an electrical machine 21 to operate it in electrical generator mode. The loop of the method then stops and a new loop begins.

[0141] With reference to [Fig.2], the STEPO test phase may comprise a comparison STP5 by the controller 25 between the current rotation speed Nr of the rotary wing 2 and a rotation speed reference range. The controller 25 may, for this purpose, receive from the rotation speed sensor 31 a signal carrying the current rotation speed Nr and may store or receive or calculate the rotation speed reference range.

[0142] If the current rotation speed Nr of the rotary wing 2 does not belong to the rotation speed reference range, the Phashyb hybridization phase is prohibited by the controller 25. The process loop then stops and a new loop begins.

[0143] Optionally, the method may include the determination STP6 of the mode applied by the engine computer 11. The controller 25 may, for this purpose, receive from the engine computer 12 or from the human-machine interface 41 a signal carrying the mode applied by the engine computer 12. If the engine computer 12 does not operate according to the automatic mode, the Phashyb hybridization phase is prohibited by the controller 25. The loop of the method then stops and a new loop begins.

[0144] In the presence of a rotation speed Nr different from the rotation speed reference range or an engine computer 12 not operating in automatic mode, the controller 25 can control the alerter 60 to generate a WARNNOT alert. The controller 25 can determine, during a control step STP7, whether an electrical machine 21 is in operation. If so, the controller 25 transmits a signal to the electrical machine 21 to stop it, for example by applying a stored stop transfer function Fc(t). The process loop then stops. and a new loop begins.

[0145] At any time, the method may include a step of selecting STPSELECT an operating mode chosen from among several operating modes. The PIL driver then operates the selector 42 for this purpose. The selector 42 transmits a signal to the controller 25 carrying the chosen operating mode.

[0146] At any time, the method may include a step STPWNEC for determining the necessary power Wnec. The controller 25 or an engine computer 12, for example, may determine the necessary power Wnec to be supplied to the power transmission chain 15 to ensure the flight.

[0147] At any time and for example during step STP8, the method may comprise a step of determining the current density altitude Zt. The density altitude sensor 34 transmits to the controller 25 a signal carrying this current density altitude.

[0148] If the Phashyb hybridization phase is authorized, during step STP8, the controller 25 then performs a comparison between the current density altitude Zt and a stored threshold density altitude Zs.

[0149] Depending in particular on this comparison, the controller 25 determines the signal to be transmitted to at least one electrical machine 21 to control it.

[0150] If the current density altitude Zt is higher than said threshold density altitude Zs, the controller 25 applies an engine limit phase STPMOT illustrated in [Fig.4]. During a step STP11, the controller 25 determines the operating mode chosen as a function of the signal transmitted by the selector 42.

[0151] If the chosen operating mode is the high-performance mode MODPERF, the controller 25 determines during a determination step STP12 whether the necessary power Wnec belongs to a test range by being greater than the available power Pwdt and less than the maximum limit power Lbtp. If so, the controller 25 transmits a signal to at least one or even each electrical machine 21 to apply the high-performance mode during a step STPPERF.

[0152] When the high-performance mode MODPERF is activated, the controller 25 transmits a signal to one or each electrical machine 21 so that it provides in motor mode a mechanical power Pwe equal either to the product of a high-performance transfer function Fp(t) and an economic power Psperfo, or to the product of a high-performance transfer function Fp(t) and a difference between maximum limit power Lbtp and the necessary power Wnec. According to one example, the signal transmitted by the controller 25 to an electrical machine 21 carries the mechanical power Pwe to be provided. The loop is then terminated and a new loop begins.

[0153] If the necessary power Wnec does not belong to the test range, the controller 25 transmits a signal to at least one or even each electrical machine 21 to apply MODV standby mode. An alert is eventually issued by the alerter to inform the pilot.

[0154] During the standby mode, the controller 25 determines during a step STP14 whether the electrical machine 21 provides a non-zero mechanical power Pwe. If the electrical machine 21 provides a non-zero mechanical power Pwe, the controller 25 transmits a signal to the electrical machine to stop it according to a stop transfer function Fc(t). The loop is then terminated and a new loop begins. If the electrical machine 21 provides a zero mechanical power Pwe, a recharge phase ST-PRECHARGE is initiated.

[0155] If the operating mode chosen is the economic mode MODECO, the method comprises the determination STP13 with the controller 25 that the necessary power Wnec is less than or greater than or equal to the available power Pwdt. When the necessary power Wnec is less than the available power Pwdt, the controller 25 transmits a signal to at least one or even each electrical machine 21 to implement the economic mode MODECO. Conversely, the controller 25 transmits a signal to at least one or even each electrical machine 21 to implement the standby mode MODV. Optionally, an alert is issued by the alerter to inform the pilot.

[0156] When the economic mode MODECO is activated, the controller 25 can transmit a signal to one or each electrical machine 21 so that it provides in motor mode a mechanical power Pwe equal either to the product of an economic transfer function Fe(t) and an economic power Pseco, or to the product of an economic transfer function Fe(t) and a difference between the necessary power Wnec and the predetermined reduced power Ptm. According to one example, the signal transmitted by the controller 25 to an electrical machine 21 carries the mechanical power Pwe to be provided. The loop is then terminated and a new loop begins.

[0157] If the MODV standby mode is the chosen operating mode, the controller 25 transmits a signal to at least one or even each electrical machine 21 to implement this MODV standby mode.

[0158] If the current density altitude Zt is less than or equal to the threshold density altitude Zs, the controller 25 applies a power transmission chain limit phase STPBTP illustrated in [Fig.5]. During a step STP15, the controller 25 determines the operating mode chosen as a function of the signal transmitted by the selector 42.

[0159] If the selected operating mode is the economical mode MODECO, the method comprises the determination STP16 with the controller 25 that the necessary power Wnec is less than or greater than or equal to the maximum limit power Lbtp. When the necessary power Wnec is less than the maximum limit power Lbtp, the controller 25 transmits a signal to at least one or even each machine electric machine 21 to implement the MODECO economy mode. Conversely, the controller 25 transmits a signal to at least one or even each electric machine 21 to implement the MODV standby mode. Optionally, an alert is issued by the alerter to inform the pilot.

[0160] If the MODV standby mode or the MODPERF performance mode is the chosen operating mode, the controller 25 transmits a signal to at least one or even each electrical machine 21 to implement the MODV standby mode.

[0161] According to another aspect, the various transfer functions Fc(t), Fal(t), Fa2(t), Fp(t), Fe(t), Fr(t) mentioned above can take the form of a second-order function F depending on the time t and three parameters, namely a static gain G, a damping coefficient A and a pulsation w, i.e.:

[0162] F=G / ( 1+(2* A*t / w)+((t*t) / (w * w)))

[0163] where “ / ” represents the division sign, “*” represents the multiplication sign, “+” represents the addition sign.

[0164] These three parameters can vary from one function to another and can be determined by tests and / or simulations. Such a transfer function makes it possible to achieve the required operation progressively, in particular to parallelize the modification of the regulation of the thermal engine(s).

[0165] Naturally, the present invention is subject to numerous variations as to 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 conceivable to replace a means described by an equivalent means without departing from the scope of the present invention and the claims.

Claims

Claims

1. Method for controlling a thermal and electrical power plant (5) for setting in motion at least one rotary member (2, 3) of a rotorcraft (1), said power plant (5) comprising a thermal system (10) and an electrical system (20) for setting in motion a power transmission chain (15) connected to said at least one rotary member (2, 3), the thermal system (10) having at least one thermal engine (11) and the electrical system (20) being provided with at least one electrical machine (21), said electrical system (20) having an electrical energy source (22) electrically connected to said at least one electrical machine (21), the method comprising a selection (STPSELECT) with a selector (42) of an operating mode chosen from several operating modes, said method having a hybridization phase (Phashyb) comprising the following steps: - comparison (STP8) with a controller (25) between a current density altitude (Zt) and a threshold density altitude (Zs), - control with the controller (25) of said at least one electrical machine (21) as a function of said chosen operating mode as well as of said comparison and of a necessary power (WNEC) to be supplied to said power transmission chain (15), characterized in that said rotary member comprises a rotary wing (2), said method comprises the following steps: - determination of a failure of the thermal system (10) rendering it inoperative, - a determination of a rotation speed (Nr) of the rotary wing (2), - control (STPROT) with the controller (25) of the operation in motor mode of said at least one electrical machine (21) in the presence of a said fault and a said rotation speed (Nr) greater than zero, - comparison (STP10) of the rotation speed (Nr) with a stored autorotation speed (Nrautorot), -control (STP101) with the controller (25) of said at least one electrical machine (21) to deliver a maximum auxiliary power (Pwemax) in engine mode if said rotation speed (Nr) is lower than said autorotation speed (Nrautorot), - control (STP102) with the controller (25) of said at least one electrical machine (21) to deliver in engine mode a power (Pwelow) lower than said maximum auxiliary power (Pwemax) if said rotation speed (Nr) is greater than or equal to said autorotation speed (Nrautorot).

2. Method according to claim 1, characterized in that said several operating modes comprise a standby mode (MODV) during which said at least one electric machine (21) is stopped or in electric generator mode to recharge said electric energy source (22) during a recharging phase (STPRECHARGE), an economic mode (MODECO) during which said at least one electric machine (21) operates in motor mode and the thermal system (10) delivers a reduced power (Ptm), and a high-performance mode (MODPERF) during which said at least one electric machine (21) operates in motor mode and the thermal system (10) delivers a maximum main power (Pmax),and in that the controller (25) controls said at least one electrical machine (21) according to said standby mode when jointly said chosen operating mode is said high-performance mode and said current density altitude is lower than the threshold density altitude (Zs),

3. Method according to any one of claims 1 to 2, characterized in that said method comprises a detection (STP1) of a malfunction of said electrical system (20), said hybridization phase (Phashyb) being prohibited in the presence of said malfunction.

4. Method according to any one of claims 1 to 3, characterized in that said method comprises a measurement of an electrical capacity (C) of said electrical energy source (22), said hybridization phase (Phashyb) being prohibited in the presence of a measured electrical capacity (C) lower than an electrical capacity threshold (Cl), said method comprising a control with said controller (25) of a recharging phase (STPRECHARGE) of said electrical energy source (22) by controlling the operation in electrical generator mode of said electrical machine (21) when said measured electrical capacity (C) is lower than or equal to the electrical capacity threshold (Cl).

5. A method according to any one of claims 1 to 4, characterized in that said rotary member (2, 3) comprises a rotary wing (2), said method comprises a measurement of a rotation speed (Nr) of the rotary wing (2), said hybridization phase (Phashyb) being prohibited (STP5) by the controller (25) in the presence of a measured rotation speed (Nr) not belonging to a rotation speed reference range.

6. Method according to any one of claims 1 to 5, characterized in that said at least one heat engine (11) is controlled by an engine computer (11), said engine computer (11) comprising an automatic mode during which said engine computer (11) attaches a power delivered by the heat engine (11) controlled at a rotation speed (Nr) of said at least one rotary member (2, 3).

7. Method according to claim 6, characterized in that said method comprises a step of determining (STP6) the mode applied by the engine computer (11), said hybridization phase (Phashyb) being authorized by the controller (25) only when said engine computer (11) operates according to said automatic mode.

8. Method according to any one of claims 2 to 7, characterized in that when said current density altitude (Zt) is greater than said threshold density altitude (Zs) and said chosen operating mode is a high-performance mode, the method comprises: - determining (STP12) with the controller (25) that said necessary power (Wnec) is or is not included in a test range going from an available power (Pwdt) which can be developed by the thermal system (10) up to a maximum limit power (Lbtp) acceptable by said power transmission chain (15), said available power and said available power being excluded from said test range, - applying (STPPERF) with the controller (25) the high-performance mode (MODPERF) when said necessary power (Wnec) is included in said test range,- application with the standby mode controller (MODV) when said necessary power (Wnec) is outside said test range.,

9. Method according to any one of claims 2 to 8, characterized in that when said current density altitude (Zt) is greater than said threshold density altitude (Zs) and said chosen operating mode is an economic mode (MODECO), the method comprises: - determination (STP13) with the controller (25) that said necessary power (Wnec) is less than or greater than or equal to an available power (Pwdt) which can be developed by the thermal system (10), - application (STPECO) with the controller (25) of the economic mode (MODECO) when said necessary power (Wnec) is less than the available power (Pwdt), - application with the controller (25) of the standby mode (MODV) when said necessary power (Wnec) is greater than or equal to the available power (Pwdt).

10. Method according to any one of claims 2 to 9, characterized in that when said current density altitude (Zt) is less than or equal to said threshold density altitude (Zs) and said chosen operating mode is an economic mode (MODECO), the method comprises: - determination (STP16) with the controller (25) that said necessary power (Wnec) is less than or greater than or equal to a maximum limit power (Lbtp) acceptable by said power transmission chain (15), - application (STPECO) with the controller (25) of the economic mode (MODECO) when said necessary power (Wnec) is less than the maximum limit power (Lbtp), - application with the controller (25) of the standby mode (MODV) when said necessary power (Wnec) is greater than or equal to the maximum limit power (Lbtp).

11. Method according to any one of claims 1 to 10, characterized in that during an economic mode (MODECO) chosen from said several operating modes, the method comprises a control with the controller (25) of said at least one electrical machine (21) to provide in motor mode a power equal to the product of an economic transfer function (Fe) with either a fixed economic power (Pseco) or a difference between the necessary power (Wnec) and a predetermined reduced power (Ptm).

12. Method according to any one of claims 1 to 11, characterized in that during a high-performance mode (MODPERF) chosen from said several operating modes, the method comprises a command with the controller (25) of said at least one machine

13.

14. electric (21) to provide in motor mode a power equal to the product of a high-performance transfer function (Fp) with either a fixed high-performance power (Psperfo) or a difference between a predetermined maximum limit power (Lbtp) acceptable by said power transmission chain (15) and the necessary power (Wnec). Method according to any one of claims 1 to 12, characterized in that a recharging phase (STPRECHARGE) comprises the following steps: - determination (STP18) that a forward speed (V) of said rotorcraft is within a stored forward speed range, - determination (STP19) that an electrical capacity (C) of said electrical energy source (22) is lower than a recharge threshold (C3), - as long as said forward speed (V) of said rotorcraft (1) is included in said forward speed range and the electrical capacity (C) of said electrical energy source (22) is lower than the recharge threshold (C3), recharging (STP20) of said electrical energy source (22) by controlling with the controller (25) said at least one electrical machine (21) in electric generator mode. Rotorcraft (1) provided with at least one rotary member (2, 3), said rotorcraft (1) comprising a thermal and electrical power plant (5) for setting said at least one rotary member (2, 3) in motion, said power plant (5) comprising a thermal system (10) and an electrical system (20) for setting in motion a power transmission chain (15) connected to said at least one rotary member (2, 3),the thermal system (10) having at least one thermal engine (11) and the electrical system (20) being provided with at least one electrical machine (21), said electrical system (20) having an electrical energy source (22) electrically connected to said at least one electrical machine (21), characterized in that the rotorcraft (1) comprises a selector (42) for selecting an operating mode chosen from several operating modes, said rotorcraft (1) comprising a controller (25) connected to the selector (42) as well as to a sensor (34) of a density altitude and to a sensor (38) of a necessary power (WNEC) to be supplied to said power transmission chain (15), said controller (25) being configured to control said at least one electrical machine (21), by applying the method according to any one of claims 1 to 13.

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