SYNCHROPHASING OF PROPELLERS FOR AN AIRCRAFT

Abstract

Propeller synchronization device for an aircraft comprising at least two propellers (12a, 12b), at least two electrical machines (2a, 2b) for rotating the propellers, at least two speed control modules (3a, 3b) for controlling the electrical machines, so as to control the speed of the propellers, the synchronization device comprising - sensors (20) for measuring a phase shift between the propellers, - a central coordination member (14) configured to receive a phase shift instruction, to calculate a difference between the phase shift measurement and the phase shift instruction, to determine a speed instruction for the propellers from the calculated difference and to transmit the speed instruction to the speed control modules of the electrical machines, the speed control modules (3a, 3b) being configured to control the speed of the propellers as a function of the speed instruction. Figure for the abstract: 2

Description

Title of the invention: SYNCHROPHASING OF PROPELLERS FOR AN AIRCRAFT Technical field

[0001] The present invention relates to the field of turbomachines and more specifically relates to a synchronization device between propellers of an aircraft comprising a turbomachine integrating an electric machine as well as a synchronization method and an aircraft comprising such a device. STATE OF THE PRIOR ART

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft but also to those currently in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0003] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work covers new generations of aircraft engines, the lightening of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, as essential complements to technological progress, aeronautical biofuels.

[0006] Document FR 3 116 303, filed in the name of Safran Helicopter Engines, describes the possibility of equipping an aircraft with a turbomachine, such as a turboprop, integrating both a gas turbine in a thermal part and a machine rotating electric engine in an electrical part. The thermal part and the electrical part allow hybrid operation of the turbomachine. The rotating electric engine allows both an electricity generation function, in generator mode, to supply the aircraft with electricity, and a propulsion function during ground movements of the aircraft, in particular taxiing-type movements.

[0007] In order to ensure the acceptability of the entry into the market of new aircraft with distributed electric propulsion or distributed hybrid electric propulsion, in the case of a turboprop comprising at least two propellers, an essential function is the synchronization between propellers allowing active control of the noise of the turboprop.

[0008] Indeed, it is essential that this type of aircraft has a sound signature of amplitude at most equal to that of purely thermal turboprops. A significant reduction in noise, of approximately 25dB for a normal noise level felt inside the aircraft which can range from 85 to 100dB, is sought compared to current turboprops.

[0009] Conventional synchrophasing methods regulate the speed of propellers via their control system, as described for example in EP3626628. In this document, sensors detect a vibration level associated with a first aircraft engine and a second aircraft engine. A momentary increase in the operating speed of the second aircraft engine is controlled depending on the detected vibration level.

[0010] The best performances in terms of propeller synchronization achieved today correspond to errors of at least 1° between the position of two propellers.

[0011] Furthermore, electric or hybrid thermal / electric propulsion systems are developing and it is desired that aircraft equipped with this technology be quieter than purely thermal aircraft, both for the surrounding area and for passengers.

[0012] The technical problem to be solved is the improvement of the precision of the synchronization between propellers, in the case of an aircraft with electric or hybrid thermal / electric propulsion. Statement of the invention

[0013] The invention aims to solve the above-mentioned problems of the prior art by providing a propeller synchronization device for an aircraft, the aircraft comprising at least two propellers, at least two electrical machines capable of driving the at least two propellers in rotation, respectively, at least two speed control modules capable of controlling the at least two electrical machines, respectively, so as to speed-control the at least two propellers, respectively,

[0014] the synchrophasing device comprising

[0015] - sensors for measuring a phase shift between the at least two propellers,

[0016] - a central coordination body configured to receive an instruction from phase shift, to calculate a difference between the phase shift measurement and the phase shift setpoint, to determine a speed setpoint for the at least two propellers, respectively, from the calculated difference, the speed setpoint making it possible to minimize said difference, and to transmit the speed setpoint to the at least two speed control modules of the at least two electrical machines, respectively,

[0017] the at least two speed control modules being configured to control the speed of the at least two propellers according to the speed setpoint, respectively.

[0018] Thanks to the invention, it is possible to guarantee a propeller synchronization accuracy of less than 0.5° in calm flight, i.e. in the event of an aerodynamic torque disturbance on each propeller of approximately 1.5% at frequencies below 1Hz. It is possible to achieve a propeller synchronization accuracy of the order of 1° in turbulent flight, i.e. in the event of an aerodynamic torque disturbance on each propeller of approximately 3% at frequencies below 1Hz.

[0019] The invention makes it possible to take advantage of the existence, in certain architectures, of an electric machine connected either directly to the propeller (electric propulsion) or in parallel hybridization with a gas turbine (hybrid propulsion).

[0020] The performance thus achieved for synchronizing the propellers allows noise control for both the neighborhood and the passengers. The speed control dynamics of an electric machine and its associated control being significantly greater than the control dynamics for a gas turbine or more generally a heat engine, the noise reduction performance is significant.

[0021] It is therefore possible to achieve active noise control by implementing propeller speed regulation:

[0022] - on the ground when aircraft move between a parking area and a runway takeoff,

[0023] - in cruise flight when the planes pass over cities or noise-regulated areas,

[0024] - in normal cruising flight to improve passenger comfort.

[0025] According to a preferred characteristic, each of the at least two propellers is capable of being driven in rotation by a respective thermal machine and an electric machine, the management of the mechanical power supplied to each of the propellers being shared between the thermal machine and the electric machine, the electric machine ensuring the function of synchronizing the propellers by carrying out variations in the mechanical power supplied, the electric machine being capable of alternating between motor and generator operation.

[0026] According to a preferred characteristic, the central coordination member is integrated into a pre-existing module in the aircraft.

[0027] According to a preferred characteristic, the at least two speed control modules are respectively integrated into a converter included in each of the at least two electrical machines.

[0028] According to a preferred characteristic, the sensors for measuring a phase shift between the at least two propellers are chosen from inductive, magnetic or optical sensors.

[0029] According to a preferred characteristic, the mechanical connection between the hub of each of the at least two propellers and the rotor of each of the at least two respective electrical machines is rigid.

[0030] According to a preferred characteristic, each of the at least two propellers has variable pitch or fixed pitch.

[0031] According to a preferred characteristic, the central coordination member is configured to transmit the speed instruction to the at least two speed control modules over a period of between 10 and 30 ms.

[0032] According to a preferred characteristic, the at least two speed control modules are configured to control the speed of the at least two propellers, respectively, according to a sampling period less than or equal to 1 millisecond.

[0033] The invention also relates to an aircraft comprising a propeller synchronization device as previously presented.

[0034] The invention also relates to a method for synchronizing propellers for an aircraft, the aircraft comprising at least two propellers, at least two electrical machines capable of driving the at least two propellers in rotation, respectively, at least two speed control modules capable of controlling the at least two electrical machines, respectively, so as to control the speed of the at least two propellers, respectively,

[0035] the synchrophasing method being characterized in that it comprises steps of:

[0036] - measurement of the phase and speed of each of the at least two propellers,

[0037] - calculation of the difference in positions between the at least two propellers to determine a propeller phase shift measurement, calculation of the difference between the propeller phase shift measurement and a phase shift setpoint and determination of a propeller speed setpoint, by a central coordination body,

[0038] - control of the speed of each of the at least two propellers as a function of the speed setpoint, by the at least two speed control modules, respectively.

[0039] The method and the aircraft have advantages similar to those previously presented.

[0040] In a particular embodiment, the steps of the method according to the invention are implemented by computer program instructions.

[0041] Consequently, the invention also relates to a computer program on an information medium, this program being capable of being implemented in a computer, this program comprising instructions adapted to the implementation of the steps of a synchrophasing method as described above.

[0042] The invention also relates to an information medium readable by a computer, and comprising computer program instructions adapted to the implementation of the steps of a synchrophasing method as described above. Brief description of the drawings

[0043] Other characteristics and advantages will appear on reading the following description of preferred embodiments given as non-limiting examples, described with reference to the figures in which:

[0044] [Fig.l] illustrates a turbomachine, here a turboprop, according to a first embodiment of the invention,

[0045] [Fig.2] illustrates a control loop ensuring the synchronization of the propellers, according to an example of the invention,

[0046] [Fig.3] illustrates a turbomachine, here a turboprop, according to a second embodiment of the invention, and

[0047] [Fig.4] illustrates a method of synchronizing propellers, according to an example of the invention.

[0048] Identical, similar or equivalent parts of the different figures bear the same numerical references so as to facilitate the transition from one figure to another.

[0049] The different parts represented in the figures are not necessarily on a uniform scale, in order to make the figures more readable.

[0050] The different possibilities (variants and embodiments) must be understood as not being mutually exclusive and can be combined with each other.

[0051] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0052] According to a first preferred embodiment shown in [Fig.l], a hybrid propulsion architecture of an aircraft comprises at least two turbomachines, here turboprops, for driving a propeller 12a, 12b in rotation, respectively.

[0053] Each turbomachine comprises a gas turbine and a respective rotating electric machine 2a, 2b capable of providing a generator function and a generator function. propulsion. The propulsion function of the electric machine can be provided when the gas turbine is running or stopped.

[0054] When the gas turbine is in operation, the electric machine is able to provide additional power. When the gas turbine is stopped, the electric machine is able to provide the power necessary for taxiing-type movement.

[0055] Thus, the two propellers 12a and 12b are respectively capable of being driven in rotation by the two gas turbines and the two rotating electrical machines 2a and 2b.

[0056] The propellers 12a and 12b are fixed pitch or variable pitch.

[0057] We are particularly interested in the electrical part of turbomachines.

[0058] The electrical circuit of the turbomachines comprises a first high voltage direct current sub-circuit, called HVDC from the English “High Voltage Direct Current”.

[0059] The HVDC sub-circuit comprises an HVDC battery 1 constituting a voltage source capable of generating power for example between a few tens and a few hundred kilowatts, at a voltage for example of approximately several hundred volts, for a few seconds or several minutes. It is preferably an energy-type battery, capable of providing electrical power to the electrical machines.

[0060] The HVDC battery 1 is connected to a DC-DC converter 4. The input voltage of the converter 4 is set by the state of charge of the battery and its output voltage is an adjustable DC voltage. The converter 4 is optional and can be of the series chopper type (in English "buck") to lower the voltage, or of the parallel chopper type (in English "boost") to raise the voltage, or of the step-down-step-up type (in English "buck-boost") to lower or raise the voltage.

[0061] The DC-DC converter 4 is connected to an HVDC bus 7, itself connected to DC / AC converters 3a and 3b. Each of the DC / AC converters 3a and 3b is respectively connected to the electrical machine 2a and 2b. To provide electric propulsion for the aircraft, a direct electric current is supplied via the HVDC bus 7 to the converters 3a and 3b. The converters can operate as inverters to convert the direct current into alternating electric current and supply it to the electrical machines 2a and 2b so as to rotate the propellers 12a and 12b. Conversely, the converters 3a and 3b can operate as rectifiers to convert an alternating electric current supplied by the electrical machines 2a and 2b operating as generators into direct electric current supplied to the battery 1 via the HVDC bus 7.

[0062] The electrical circuit of the turbomachine comprises a second low voltage direct current sub-circuit, typically 28 V. The low voltage direct current sub-circuit comprises a direct current generator 5 and a battery, capable of supplying in electricity the various equipment of the aircraft.

[0063] The first high voltage direct current sub-circuit and the second low voltage direct current sub-circuit are connected via a converter 6, for example as described in FR 3 116 303.

[0064] According to the invention, for each of the propellers, the corresponding electrical machine 2a, 2b is speed-controlled, to transiently vary the mechanical power supplied to the propeller so as to ensure the synchronization function of the propellers.

[0065] The synchronization of the propellers of an aircraft is an adjustment of the relative angular positions of the propellers of the different propulsion units of the aircraft.

[0066] Synchronization is achieved by maintaining the relative angular positions between propellers at determined values, which may have been obtained during test flights. The relative angular position values ​​may be expressed as phase shifts between propellers, the phase of a propeller then being defined as the angular difference between the actual angular position of the propeller and a reference angular position common to all the propellers. The phase may be expressed in degrees, with a complete propeller rotation representing 360°.

[0067] The synchronization is carried out at constant speed, that is to say for the same constant speed of rotation of the propellers. Several constant speeds can be adopted corresponding to different flight phases (cruise, takeoff, etc.) or to different flight conditions (wind, etc.) of the aircraft, their number generally being limited. Different desirable phase shift values, or phase shift instructions, can be determined for different respective constant speeds.

[0068] When operating the aircraft, for a given constant speed, the aim is to maintain the actual values ​​of the phase shifts between propellers equal to the determined desirable values.

[0069] In the case of a hybrid thermal / electric architecture, the management of the mechanical power supplied to each of the propellers is shared between:

[0070] - the thermal machine,

[0071] - the electric machine, which ensures the function of synchronizing the propellers in ef performing small amplitude power variations in both directions, the electric machine being able to alternate between motor and generator operation. The electric machine provides additional mechanical power when in motor operation and the electric machine decreases power when in generator operation.

[0072] The synchronization of the propellers is ensured by a regulation loop dedicated to this function and schematically represented in [Fig.2]. It should be noted that the synchronization loop is identical for the hybrid thermal / electric architecture and for the electrical architecture which will be described later.

[0073] More particularly, one loop per pair of propellers ensures their synchronization. One propeller is in the so-called “master” configuration and the other propeller is in the “slave” configuration.

[0074] Advantageously, the means implemented to ensure the synchronization of the propellers can be the following.

[0075] Consider a pair of propellers, for example propellers 12a and 12b of [Fig.l]. Inductive, magnetic or optical sensors 20 measure the phase and speed of each propeller.

[0076] The measured values ​​are transmitted to a central coordination unit 14 which calculates the difference in position between the propellers and thus acquires a measurement of the phase shift between the propellers. The central coordination unit 14 of the aircraft may be a module specific to the propeller synchronization function, or be integrated into a module already existing in the aircraft, such as the FCC (Flight Control Command) or the FADEC (Full Authority Digital Engine Control).

[0077] The central coordination unit 14 takes into account a phase shift instruction, and calculates a difference between the phase shift measurement between the propellers and the phase shift instruction.

[0078] As already mentioned, the phase shift instruction depends on the flight phase (cruise, takeoff, etc.) and the flight conditions (wind, etc.) of the aircraft.

[0079] From the calculated difference between the phase shift measurement between the propellers and the phase shift setpoint, the central coordination member 14 determines a speed setpoint for each propeller aimed at minimizing this difference.

[0080] Each electrical machine preferably further comprises an internal speed control module capable of controlling the speed of the propeller. Such a configuration is advantageous because the dynamics of the internal speed control module are faster than those of the speed control that the thermal machine can perform. The speed control module is for example integrated into the AC / DC converter 3a, 3b, corresponding to the electrical machine.

[0081] The central coordination member 14 transmits the speed instruction thus determined to the speed control module internal to each electrical machine.

[0082] The speed control module internal to each electric machine then controls the speed of the corresponding propeller according to the speed setpoint. For example, the AC / DC converter controls the frequency of the electric current that it delivers to the electric motor 2a, 2b associated with it and thus controls the rotational speed of the electric motor. Consequently, the AC / DC converter controls the speed of the associated propeller.

[0083] When the propeller synchronization is activated, the regulation of the gas turbine is adapted so that the speed control loops of the gas turbine propellers on the one hand, and of the electric machine on the other hand, do not act antagonistically while pursuing the same control objective.

[0084] A regulation objective other than the speed of the propellers can then be assigned to the gas turbine. For example, it may be desired that the gas turbine provides mechanical power such that the average power provided by the electric machine is as low as possible, in order to reduce the energy taken from the battery. In parallel, the speed regulation objective as well as the synchronization function of the propellers are provided by the electric machine.

[0085] Depending on the desired configurations and applications, the invention allows:

[0086] - to provide a synchrophasing function for fixed-pitch propellers;

[0087] - to relax the dimensioning of the variable pitch actuator for propellers with variable pitch;

[0088] - to size the electrical machines to the sole need of the syn function chromaphasing of the propellers, that is to say for low power.

[0089] According to a second preferred embodiment shown in [Fig.3], the propulsion architecture of the aircraft is electric and distributed.

[0090] The power part of the propeller synchronization is implemented on the electrical chain. On the other hand, the control and hosting part of the control laws is implemented between a central coordination body of the aircraft managing the flight control laws and the propulsion electrical chain managing the mechanical power of the propeller shaft.

[0091] Here again, the central coordination organ of the aircraft can be a module specific to the propeller synchronization function, or be integrated into a component already existing in the aircraft, such as the FCC or the FADEC.

[0092] The distributed electrical architecture comprises at least two electrical machines, each associated with a propeller.

[0093] In the example of [Fig.3], the aircraft comprises four propellers 12a, 12b, 12c and 12d which are respectively capable of being driven in rotation by four rotating electrical machines 2a, 2b, 2c and 2d.

[0094] For each electric machine / propeller pair, the mechanical connection between the electric motor rotor and the propeller hub is rigid. For example, the propeller is mounted in direct engagement on the axis of the electric motor rotor.

[0095] Each electrical machine is connected to a respective DC / AC converter 3a, 3b, 3c and 3d.

[0096] Each DC / AC converter 3a, 3b, 3c and 3d provides close control of the respective electric motor, by a speed loop. This close control can be sampled according to a relatively small sampling period, for example example of 1 millisecond or less.

[0097] The close control of each electric motor uses an estimation or measurement of the speed of the propeller, and therefore of the rotor of the electric motor, whose bandwidth is relatively high, for example greater than 10 Hz. The speed of the propeller is for example measured via one or more speed or position sensors of the propeller, for example inductive or magnetic or optical sensors.

[0098] The DC / AC converters 3a, 3b, 3c and 3d are connected to a first high voltage direct current HVDC sub-circuit.

[0099] The HVDC sub-circuit comprises an interconnection unit 13 and an HVDC battery 1 constituting a voltage source. The interconnection unit 13 comprises protection and current and voltage measurement devices for different networks, here sub-circuits, interconnected.

[0100] A second low voltage direct current sub-circuit, typically 28 V, is connected to the interconnection unit 13 via a converter 6. The low voltage direct current sub-circuit comprises a direct current generator 5 and a battery capable of supplying electricity to the various equipment of the aircraft.

[0101] The speed control is designed and configured so as to:

[0102] - ensure rapid speed setpoint monitoring with little overshoot setpoint; the order of magnitude is for example a rise time to 95% of the setpoint in 150 ms and an overshoot of the setpoint of less than 10%;

[0103] - ensure torque disturbance rejection on the propeller with a bandwidth high; the order of magnitude is for example that a step of resistant torque must be rejected in 250 ms.

[0104] Similar to the first embodiment, the means implemented to ensure synchrophasing are as follows.

[0105] For a given propeller torque, inductive or magnetic or optical sensors measure the phase and speed of each propeller.

[0106] The measured values ​​are transmitted to the central coordination unit 14 which calculates the difference in positions between the propellers and thus determines a measure of the phase shift of the propellers.

[0107] The central coordination member 14 has the position of each propeller according to a sampling period which depends on the rotation speed of the propellers and the number of “fingers” positioned on each propeller.

[0108] For example, if the rotation speed is 1500rpm and there are four fingers per propeller, the sampling period is 1 / 4 * 1 / (1500 / 60) = 10 milliseconds. If the rotation speed is 1000rpm and there are two fingers per propeller, then the sampling period is 1 / 2*(1 / (1000 / 60)) = 30 milliseconds.

[0109] The central coordination body 14 takes into account a phase shift instruction, and calculates a difference between the phase shift measurement between the propellers and the phase shift setpoint.

[0110] As already mentioned, the phase shift instruction depends on the flight phase (cruise, takeoff, etc.) and the flight conditions (wind, etc.) of the aircraft.

[0111] From the calculated difference between the phase shift measurement between the propellers and the phase shift setpoint, the central coordination unit determines a speed setpoint for each propeller aimed at minimizing this difference.

[0112] The central coordination member 14 sends the respective speed instruction of each propeller to the speed control module internal to each electrical machine which is for example the DC / AC converter corresponding respectively to each propeller.

[0113] The speed control module internal to each electric machine then controls the speed of the corresponding propeller according to the speed setpoint.

[0114] It should be noted that the speed setpoint can be a respective speed setpoint delta of each propeller which is then added to the setpoint speed common to all the propellers so as to control the speed of each propeller according to its phase shift setpoint. The speed setpoint delta can only be calculated and sent every 10 or 30 ms.

[0115] The invention makes it possible to guarantee a phasing precision of less than 0.5° in calm flight, i.e. in the event of an aerodynamic torque disturbance on each propeller of approximately 1.5% at frequencies below 1 Hz and further ensures a phasing precision of the order of 1° in turbulent flight, i.e. in the event of an aerodynamic torque disturbance on each propeller of approximately 3% at frequencies below 1 Hz.

[0116] [Fig.4] illustrates an embodiment of a propeller synchronization method. and comprises steps E1 to E3. The method is implemented in both the hybrid architecture and the electrical architecture.

[0117] The first step E1 corresponds to a measurement of the phase and the speed of each propeller by the inductive or magnetic or optical sensors. The measured values ​​are transmitted to the central coordination body.

[0118] The next step E2 is a calculation of the difference in positions between the propellers to thus determine a measurement of the phase shift of the propellers.

[0119] The central coordination body takes into account a phase shift instruction, and calculates a difference between the phase shift measurement of the propellers and the phase shift instruction.

[0120] From the calculated difference between the propeller phase shift measurement and the phase shift setpoint, a propeller speed setpoint is determined to minimize said difference.

[0121] The speed instruction thus determined is transmitted to the control module in internal speed of each electrical machine, for example at the level of the converter associated with the electrical machine.

[0122] In the following step E3, the speed control module internal to each electrical machine controls the speed of the corresponding propeller according to the speed setpoint, making it possible to achieve the desired synchronization of the propellers.

Claims

Claims

1. Propeller synchronization device for an aircraft, the aircraft comprising at least two propellers (12a, 12b, 12c, 12d), at least two electrical machines (2a, 2b, 2c, 2d) capable of driving the at least two propellers in rotation, respectively, at least two speed control modules (3a, 3b, 3c, 3d) capable of controlling the at least two electrical machines, respectively, so as to speed-control the at least two propellers, respectively, and at least two thermal machines capable of driving the at least two propellers in rotation, respectively, the synchronization device being characterized in that it comprises: - sensors (20) for measuring a phase shift between the at least two propellers, - a central coordination member (14) configured to receive a phase shift instruction, to calculate a difference between the measurement of phase shift and the phase shift setpoint, to determine a speed setpoint for the at least two propellers,from the calculated difference, the speed setpoint making it possible to minimize said difference, and to transmit the speed setpoint to the at least two speed control modules (3a, 3b, 3c, 3d) of the at least two electrical machines (2a, 2b, 2c, 2d), respectively, the at least two speed control modules (3a, 3b, 3c, 3d) being configured to control the speed of the at least two propellers (12a, 12b, 12c, 12d) as a function of the speed setpoint, respectively, the management of the mechanical power supplied to each of the propellers being shared between the thermal machine and the electrical machine, the electrical machine ensuring the function of synchronizing the propellers by carrying out variations in the mechanical power supplied, the electrical machine being able to alternate between motor and generator operation.,

2. Propeller synchronization device for an aircraft according to claim 1, in which the central coordination member (14) is integrated into a pre-existing module in the aircraft.

3. Propeller synchronization device for an aircraft according to claim 1 or 2, wherein the at least two speed control modules (3a, 3b, 3c, 3d) are respectively integrated in a converter included in each of the at least two electrical machines.

4. Propeller synchronization device for an aircraft according to any one of claims 1 to 3, in which the sensors (20) for measuring a phase shift between the at least two propellers are chosen from inductive, magnetic or optical sensors.

5. A propeller synchronization device for an aircraft according to any one of claims 1 to 4, wherein the mechanical connection between the hub of each of the at least two propellers and the rotor of each of the at least two respective electrical machines is rigid.

6. Propeller synchronization device for an aircraft according to any one of claims 1 to 5, in which the central coordination member (14) is configured to transmit the speed instruction to the at least two speed control modules over a period of between 10 and 30 ms.

7. A propeller synchronization device for an aircraft according to any one of claims 1 to 6, wherein the at least two speed control modules (3a, 3b, 3c, 3d) are configured to control the speed of the at least two propellers, respectively, according to a sampling period less than or equal to 1 millisecond.

8. Aircraft comprising a propeller synchronization device according to any one of claims 1 to 7.

9. A method of synchronizing propellers for an aircraft, the aircraft comprising at least two propellers (12a, 12b, 12c, 12d), at least two electrical machines (2a, 2b, 2c, 2d) capable of driving the at least two propellers in rotation, respectively, at least two speed control modules (3a, 3b, 3c, 3d) capable of controlling the at least two electrical machines (2a, 2b, 2c, 2d), respectively, so as to speed-control the at least two propellers (12a, 12b, 12c, 12d), respectively, and at least two thermal machines capable of driving the at least two propellers in rotation, respectively, the synchronizing method being characterized in that it comprises steps of: -measuring (El) the phase and the speed of each of the at least two propellers, -calculation (E2) of the difference in positions between the at least two propellers to determine a measurement of the phase shift of the propellers, calculation of the difference between the measurement of the phase shift of the propellers and a setpoint of phase shift and determination of a propeller speed setpoint, by a central coordination body (14), -control (E3) of the speed of each of the at least two propellers (12a, 12b, 12c, 12d) as a function of the speed setpoint, by the at least two speed control modules (3a, 3b, 3c, 3d), respectively, the management of the mechanical power supplied to each of the propellers being shared between the thermal machine and the electric machine, the electric machine ensuring the function of synchronizing the propellers by carrying out variations in the mechanical power supplied, the electric machine being able to alternate between motor and generator operation.

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