Speed control method and control device

Abstract

The present disclosure relates to a method for controlling the speed of an engine assembly (2) of an aircraft (1), comprising updating (S70, S80) the speed setpoint (Nc) of the engine assembly (2) as a function of the current state-of-charge (SOCc) of an onboard energy storage device (32), and controlling (S20) the engine assembly (2) according to the speed setpoint (Nc) of the engine assembly (2), as well as a control device (23) suitable for implementing this method and an engine assembly (2) and an aircraft (1) incorporating such a control device.

Description

Description Title of the invention: Method for regulating speed and control device Technical Field

[0001] The present invention relates to the technical field of regulating aircraft engine assemblies, and more particularly engine assemblies comprising at least one electric machine and a combustion engine, in particular a gas turbine. Prior art

[0002] In order to increase the overall energy efficiency of means of transport, and reduce their fuel consumption and greenhouse gas emissions, increasing electrification of power units is being considered. In the field of aviation, there is firstly a trend towards increasing power extraction through electric machines incorporated into power units, in particular to replace pressurised air extraction intended for auxiliary devices. In addition, many hybrid power units in which these electric machines are not only used to extract power, but also to introduce it into the power unit in order to provide assistance beyond simple starting.Although these hybrid powertrains have most often been proposed for motor vehicles and incorporate piston engines, the hybridization of aircraft powertrains and more particularly of powertrains incorporating one or more gas turbine engines has also been considered.

[0003] The hybridization of aircraft engine assemblies requires the incorporation, in the aircraft, of on-board energy storage devices to provide the power to be introduced into the engine assembly through the electric machine. These on-board energy storage devices may notably take the form of rechargeable electric batteries, although other devices Energy storage devices, such as supercapacitors or flywheels, are also possible. In order to recharge these on-board energy storage devices, hybridization will normally further increase the electrical power draws from the engine assembly during operating phases that do not require electrical assistance, and in particular at idle speeds.

[0004] During the idle speed phases on the ground and in flight, it is normally desirable to minimize the thrust and therefore the engine speed. However, this speed is normally constrained by operability limits of the engine and by requirements for the ability to respond to transient fluctuations in the intake, both in the direction of a sudden decrease (load release) and in that of a sudden increase, due for example to a short circuit. The capacity of combustion engines, and in particular gas turbine engines, to absorb these sudden fluctuations increases with the engine speed. However, their fuel consumption then also increases.

[0005] In European patent application publication EP 3 845 750 A1, an engine assembly has been proposed incorporating a gas turbine engine with two rotating shafts, together with an electric machine coupled to each of the rotating shafts, and a method of distributing the power draw between these rotating shafts as a function of the engine speed.

[0006] In French patent application publication FR 3 097 012 A1, it was proposed to use hybridization of the engine assembly to improve its response to load fluctuations, particularly at idle speeds.

[0007] In international patent application publication WO 2021 / 018524 ​​A1, it is proposed to use an on-board energy storage device to help reduce transient fluctuations in power draw from an aircraft engine assembly.

[0008] However, the ability of an on-board energy storage device to reduce transient fluctuations in power draw from an aircraft engine assembly will normally depend on its state of charge. Statement of the invention

[0009] The present disclosure aims to propose a method for regulating the speed and a control device for an aircraft engine assembly making it possible to ensure the management of possible transient fluctuations in power draw while minimizing energy consumption and taking into account the availability of an on-board energy storage device.

[0010] For this, according to a first aspect of this disclosure, this method may comprise at least steps of updating a speed setpoint of the engine assembly as a function of a current charge state of an on-board energy storage device, and of controlling the engine assembly according to the speed setpoint of the engine assembly. The speed of the engine assembly may in particular remain an idle speed lower than a maximum nominal speed of the engine assembly, in particular equal to or lower than 70% of said maximum nominal speed. The speed of the engine assembly may be understood to mean a rotational speed of a shaft of the engine assembly. However, other definitions of the speed of the engine assembly are also conceivable: for example, the speed of the engine assembly may alternatively be defined in terms of thrust.

[0011] According to a second aspect, the updating of the speed setpoint may comprise steps of determining a difference in state of charge of an on-board energy storage device, and comparing said difference in state of charge to a difference threshold, the updating of the speed setpoint of the engine assembly then being able to be carried out according to a result of the comparison of said difference with said difference threshold.

[0012] The updating of the engine assembly speed setpoint can then be carried out according to the result of the comparison of said difference with said difference threshold, so as to take into account this difference and the current load state in the regulation of the engine speed in order to optimize a speed of the engine assembly, in particular an idle speed, to meet the fluctuations in withdrawal by minimizing its energy consumption at all load states of the on-board energy storage device.

[0013] According to a third aspect, a maximum electrical power that can be drawn from the engine assembly at a speed of the engine assembly following the speed setpoint may be lower than an electrical power required by the aircraft, said difference threshold may be a discharge threshold, and said reference state of charge may be a state of charge of the onboard energy storage device when the maximum electrical power that can be drawn from the engine assembly has become lower than the electrical power required by the aircraft.In particular, in the step of updating the engine assembly speed setpoint, the speed setpoint may then be maintained at a previous level if said difference in state of charge does not exceed the discharge threshold, electrical assistance is required for the engine assembly, and / or an upper threshold of the engine assembly speed is reached, and increased if said difference in the state of charge exceeds the discharge threshold, electrical assistance is not required for the engine assembly, and the upper threshold of the engine assembly speed is not reached. The discharge threshold may be assigned a first value when the current state of charge is not lower than an upper state of charge threshold, and a second value, different from the first value, when the current state of charge is lower than the upper state of charge threshold, but is not lower than a lower state of charge threshold.

[0014] Thus, as long as a maximum electrical power that can be taken from the engine assembly at said engine assembly speed is less than an electrical power required by the aircraft, and this deficit must therefore be made up by taking power from the onboard energy storage device and / or by increasing the engine assembly speed and therefore the maximum electrical power that can be taken from it, the progressive discharge of this onboard energy storage device can trigger an increase in the speed when it exceeds the discharge threshold, which can itself vary depending on the current state of charge in order to indirectly also take into account its absolute value.

[0015] According to a fourth aspect, a maximum electrical power that can be taken from the engine assembly at a speed of the engine assembly following the speed setpoint may not be less than an electrical power required by the aircraft, said difference threshold may be a load threshold, and said reference state of charge may then be a state of charge of the onboard energy storage device when the maximum electrical power that can be taken from the engine assembly has become equal to or greater than the electrical power required by the aircraft or the speed setpoint of the engine assembly has been reduced. The speed setpoint may then in particular be maintained if said difference in the state of charge does not exceed the load threshold and / or the speed setpoint is at a lower threshold.The charge threshold may be assigned a first value when the state of charge is not lower than an upper state of charge threshold, and a second value, different from the second value, when the state of charge is lower than the upper state of charge threshold, but not lower than a lower state of charge threshold.

[0016] Thus, while a maximum electrical power that can be taken from the engine assembly at said engine assembly speed is equal to or greater than an electrical power required by the aircraft, the speed setpoint can be maintained as long as this surplus can be used to recharge the onboard energy storage device without exceeding the charge threshold, which can itself vary depending on the state of charge in order to indirectly also take into account its absolute value.

[0017] A fifth aspect relates to a control device configured to implement the method according to any one of the preceding aspects.

[0018] A sixth aspect relates to an aircraft engine assembly comprising a control device according to the fourth aspect, a combustion engine, and an electric machine configured to draw electrical power. The electric machine may also be configured to provide electrical assistance to the engine assembly. The combustion engine may be a gas turbine engine.

[0019] A seventh aspect relates to an aircraft comprising an engine assembly according to the fifth aspect, as well as an on-board storage device energy electrically connected to said electric machine of the motor assembly. Brief description of the drawings

[0020] [Fig. 1] Figure 1 is a schematic representation of electrical and control networks of an aircraft.

[0021] [Fig. 2] Figure 2 is a flowchart of a method for regulating the speed of an engine assembly of the aircraft of Figure 1.

[0022] [Fig. 3] Figure 3 is a flowchart of a subroutine of the method of Figure 2, followed when a maximum electrical power that can be drawn from the engine assembly is less than an electrical power required by the aircraft.

[0023] [Fig. 4] Figure 4 is a flowchart of an implementation mode of a speed setpoint reduction step of the subroutine of Figure 3.

[0024] [Fig. 5] Figure 5 is a flowchart of a subroutine of the method of Figure 2, followed when the maximum electrical power that can be drawn from the engine assembly at said engine assembly speed is equal to or greater than an electrical power required by the aircraft. Description of the embodiments

[0025] As illustrated in Figure 1, an aircraft 1 may comprise one or more engine assemblies 2, which may in particular each include at least one combustion engine 21, in particular in the form of a gas turbine engine, comprising at least one compressor 211, a turbine 212, a combustion chamber 213 arranged in an air stream between the compressor 211 and the turbine 212, and a rotary shaft 214 mechanically connecting the compressor 211 and the turbine 212. In particular, as illustrated, such a gas turbine engine may be a fan turbojet, comprising at least one other rotary shaft 215 concentric with the rotating shaft 214 and mechanically connecting another turbine 216 downstream of the turbine 212 to another compressor 217 upstream of the compressor 211, as well as, possibly through a reducer 218, to a fan 219, which may be ducted or unducted. However, the present disclosure is not limited to fan turbojets or even gas turbine engines, being equally applicable to other types of gas turbine engines, such as turboprops or turboshafts, or even to other types of combustion engines, such as piston engines.

[0026] As also illustrated in FIG. 1, each engine assembly 2 may also comprise an electrical machine 22 coupled to a rotary shaft of the combustion engine, such as for example to the rotary shaft 214. This electrical machine 22 may in particular be a generator configured to draw electrical power from the engine assembly 2, although it may in particular be, as illustrated, a motor-generator capable of alternatively providing electrical assistance to the engine assembly 2. This electrical machine 22 may be electrically connected to an electrical network 3 of the aircraft 1, for example through a converter 31, which may in particular be an AC / DC converter as illustrated. The aircraft 1 may also comprise one or more on-board energy storage devices 32, each also connected to the electrical network 3, for example through a converter 33, which may in particular be a DC / DC converter as illustrated.These on-board energy storage devices 32 may in particular take the form of rechargeable batteries, configured to store energy electrochemically. However, other types of on-board energy storage devices are conceivable, alternatively to or in combination with the rechargeable batteries, such as for example flywheels or supercapacitors. In addition, the aircraft 1 may also comprise one or more electrical consumers 34 also connected to the electrical network 3.

[0027] As also illustrated in Figure 1, each engine assembly 2 may also comprise a control device 23 connected to the combustion engine 21 as well as to the electric machine 22 in order to ensure the regulation of the speed of the engine assembly 2. This control device 23 may in particular take the form of an electronic control unit. The control device 23 may be connected to the combustion engine 21 to control, for example, its fuel supply and / or the position of elements to variable geometry of the combustion engine 21, such as blades, vanes, discharge valves and / or nozzle. Furthermore, the control device 23 may be connected to the electrical machine 22 to control the electrical power taken from or injected into the engine assembly 2 through the electrical machine 22. Furthermore, the aircraft may comprise at least one other control device 35, which may be connected to the control device 23, to the converters 31, 33, to the on-board energy storage devices 32, and / or to the electrical consumers 34, in order to regulate the energy transfers through the electrical network 3. This other control device 35 may also take the form of an electronic control unit. Furthermore, although the control devices 23, 35 are presented here as two separate devices, it would also be possible to combine them into a single device, and in particular into a single electronic control unit.

[0028] The control device 23 can be adapted to implement a method for regulating the speed of the engine assembly 2, in particular for slow speeds, both in flight and on the ground.

[0029] Thus, as illustrated in Fig. 2, this regulation method may include a step S10 of initializing a flag F to assign it a zero value. This step S10 may be followed by a recurrent loop including a step S20 of controlling the engine assembly 2 according to a speed setpoint N c of the engine assembly 2, followed by a step S30 of determining a maximum electrical power P0,max which can be taken from the engine assembly 2 at the speed of the engine assembly according to said speed setpoint N c , as well as a step S40 for determining a current state of charge SOC c on-board energy storage devices 32 and a step S50 of determining a current electrical power Pr , c required by the aircraft 1. Although steps S40 and S50 are illustrated in Fig. 2 as successive to steps S20 and S30, they could also be carried out simultaneously with them. Steps S20, S40 and S50 can be carried out using respective sensors (not illustrated) arranged on the engine assembly 2 and the electrical network 3, while step S30 can for example be carried out using a mathematical formula and / or a table of correspondences stored in the control device 23 and applied by it. Furthermore, filters, such as for example a low-pass or sliding average filter, can be applied in these steps, in order to avoid changes in the speed setpoint N c too sudden or frequent following fluctuations in the powers P o, max OR P r c .

[0030] In a subsequent step S60 of the illustrated regulation method, the maximum electrical power P0,max that can be taken from the motor assembly 2 is compared with the current electrical power P r , c required by aircraft 1. If the maximum electrical power P0,max is less than the current electrical power P r , c required by aircraft 1, a first subroutine S70 for updating the speed setpoint N c can be performed. If the maximum electrical power P0,max is equal to or greater than the current electrical power P r , c required by aircraft 1, a second subroutine S80 for updating the speed setpoint N c can be done.

[0031] As illustrated in Fig. 3, the first subroutine S70 may include a first step S710 of checking the value of the flag F. If the value of the flag F is different from “1”, indicating that the maximum electrical power Po.max was not less than the current electrical power P r , c required by aircraft 1 or regime instruction N c was increased in an immediately preceding cycle, the current state of charge SOC value c can be assigned to a reference state of charge SOC r and the value “1” assigned to the flag “F” in successive or simultaneous steps S720, S730, before moving on to a following step S740 in which a difference in state of charge ASOC between the reference state of charge SOC r and the current state of charge SOC c is calculated using the formula ASOC= SOC r - SOC c. If the value of the flag F is already "1", that is, if in the immediately preceding cycle the maximum electrical power P0,max was already lower than the current electrical power P r , c required by aircraft 1 and the N speed instruction c has not increased, we can go to step S740 for calculating the difference in state of charge ASOC without carrying out steps S720, S730 for assigning the value of the current state of charge SOC c at the reference state of charge SOC r and the value “1” to the flag F.

[0032] Then, in a step S750, the current state of charge SOC ccan be compared to an upper state of charge threshold SOC-,. If the current state of charge SOCc is higher than the upper state of charge threshold SOCi, the difference in state of charge ASOC can be compared in subsequent steps S751, S752 and S753, respectively, to a difference threshold which can be in particular a first ASOC discharge threshold d i, check that electric assistance is not required for the engine assembly, and check that the speed setting N c has not reached a higher threshold N r , ma x- Although these steps S751 to S753 are illustrated as being executed in a certain order, they could be executed in a different order, or even simultaneously. If the difference in state of charge ASOC does not exceed the difference threshold, electric assistance is required or the speed setpoint N c has already reached the upper threshold N rimax, subroutine S70 can be finalized without modifying the speed setpoint N c . On the other hand, if the ASOC state of charge difference exceeds the difference threshold, electric assistance is not required, and the speed setting N c did not reach the upper threshold N r , ma x, the speed setpoint N c can be increased in a step S760, and the value of flag F can be reset to zero in a step S770 in order to trigger an update of the reference state of charge SOC r in the next cycle.

[0033] When this regulation process is specifically directed to the regulation of an idle speed of the engine assembly 2, the value of this speed setpoint N c can take a discrete number of steps, such as three values ​​including the upper threshold N rimax , which can be for example between 50 and 70% of a maximum nominal speed N ma x, a lower threshold Nr , m in, which can be for example between 40 and 60% of the maximum nominal speed N ma x, and an intermediate level Nr nt, located between the maximum thresholds N r>max and minimal N rimin and which can therefore be for example between 45 and 65% of the maximum nominal speed N max . In this case, step S760 of increasing the speed setpoint N c can take the form illustrated in Figure 4, comprising a first sub-step S761 in which it is checked whether the speed setpoint N c is at the lower threshold N r;miri . If the regime setting N c is at the lower threshold N r , m in, it is increased at the intermediate level N r ,int in the following substep S762. Otherwise, and that the regime setting N c is therefore already at the intermediate level N r;in t, it is increased to the maximum level N rimaxin the alternative sub-step S763. However, it is also possible that the N regime c be regulated along a continuous curve, rather than in discrete steps.

[0034] If in step S750 the current state of charge SOC c has been found to be equal to or less than the first state of charge threshold SOC-,, the subroutine S70 may proceed to step S780, in which the current state of charge SOCc is compared with a second state of charge threshold SOC2 lower than the first state of charge threshold SOC-,. If the current state of charge SOC c remains equal to or greater than this second state of charge threshold SOC2, it is possible in subsequent steps S781, S752 and S753 to, respectively, compare the difference in state of charge ASOC with a difference threshold which may in particular be a second discharge threshold ASOC d2 different from the first ASOC discharge threshold di, check that electric assistance is not required for the engine assembly, and check that the speed setting N c has not reached a higher threshold N r , m ax- If the ASOC state of charge difference is greater than or equal to the difference threshold, but electric assistance is required or the speed setpoint N c has already reached the upper threshold N rimax , subroutine S70 can be finalized without modifying the setpoint for the current regime N c . If the ASOC state of charge difference is greater than or equal to this difference threshold, electric assistance is not required, and the speed setpoint N c did not reach the upper threshold N r>max , the regime setting N c can be increased in step S760, and the value of flag F reset to zero in step S770 to trigger the update of the reference state of charge SOC rin the next cycle. If the ASOC state of charge difference does not reach this difference threshold, we can still compare the speed setpoint N c at the upper threshold N r>max in a step S782. If this maximum level N r , m has X is reached, the subroutine S70 can be directly finalized, but if this upper threshold N r , m has X is not yet reached, it is possible to adopt its value as the N regime setpoint c in a step S783, and reset the value of the flag F in a step S784 before finalizing the subroutine S70 to trigger the update of the reference state of charge SOC r in the next cycle.

[0035] As illustrated in Figure 5, the second subroutine S80, which can be performed in the case where the maximum electric power P0,max is equal to or greater than the current electric power P r , crequired by the aircraft 1, may include a first step S810 of checking the value of the flag F. If the value of the flag F is different from “2”, indicating that the maximum electrical power P0,max was still lower than the current electrical power P r , c required by aircraft 1 or that the regime instruction N c was decreased during an immediately preceding cycle, the value of the current state of charge SOC c can be attributed to the reference state of charge SOC r and the value “2” assigned to the flag “F” in successive or simultaneous steps S820, S830, before moving on to a following step S840 in which a difference in state of charge ASOC between the reference state of charge SOC r and the current state of charge SOC c is calculated using the formula ASOC= SOC r - SOC c. If the value of the flag F is already "2", that is, if in the immediately preceding cycle the maximum electrical power P0,max was no longer lower than the current electrical power P r , c required by aircraft 1 and the N speed instruction c has not decreased, we can go to step S840 of calculating the difference in state of charge ASOC without carrying out steps S820, S830 of assigning the value of the current state of charge SOC c at the reference state of charge SOC r and the value “2” to the flag F.

[0036] Then, in a step S850, the current state of charge SOC c can be compared to a first state of charge threshold SOC-,. If the current state of charge SOC cis greater than the first state of charge threshold SOC-,, it is possible in steps S860, S861 to respectively compare the difference in state of charge ASOC with a difference threshold which may in particular be a first charge threshold ASOCd, and to verify that the speed setpoint N c is still higher than a lower threshold N r;miri . Although these steps S860 and S861 are illustrated as being executed in a certain order, they could be executed in a different order, or even simultaneously. If the difference in state of charge ASOC does not exceed the difference threshold, or the speed setpoint N c is not higher than the minimum level N r , m in, the subroutine S80 can be finalized without modifying the speed setpoint N c . On the other hand, if the difference ASOC state of charge exceeds the difference threshold, and the speed setpoint N c is still higher than the upper threshold Nrimax , the regime setting N c can be decreased in a step S862, for example by assigning it the value of the lower threshold N r , m in, and the value of flag F can be reset to zero in a step S863 in order to trigger an update of the reference state of charge SOC r in the next cycle.

[0037] If in step S850 the current state of charge SOC c has been found to be equal to or less than the first state of charge threshold SOC-i, subroutine S80 may proceed to step S870, in which the current state of charge SOC c is compared to a second state of charge threshold SOC2 lower than the first state of charge threshold SOC-i. If the current state of charge SOC cremains equal to or greater than this second state of charge threshold SOC2, a step S871 can be carried out for comparing the difference in state of charge ASOC to a difference threshold which may in particular be a second ASOC charge threshold C 2- If the ASOC state of charge difference does not reach this difference threshold, the S80 subroutine can be directly finalized. However, if the ASOC state of charge difference is equal to or greater than the difference threshold, we can then proceed to compare the speed setpoint N c at the intermediate level N r;in t in a step S872, and assigning the value of this intermediate level N r ,int to the speed setpoint N c in a subsequent step S874 after having reset the value of the flag F in an intermediate step S873 if the speed setpoint N c was still higher than the intermediate level N r;int in step S872, and that it must therefore be reduced in step S874. Thus, an update of the reference state of charge SOC r in the following cycle will be triggered following this reduction. Finally, if the ASOC state of charge difference does not reach this difference threshold, we can still proceed to compare the speed setpoint N c at the upper threshold N r , m ax in a step S875. If this upper threshold N r , m ax is reached, the subroutine S80 can be directly finalized, but if this upper threshold N r ,max is not yet reached, it is possible to adopt its value as the N regime setpoint c in a step S876.

[0038] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that various modifications and changes may be made to these examples without departing from the scope general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments discussed may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. Method for regulating the speed of an engine assembly (2) of an aircraft (1), comprising at least the following steps: - update (S70,S80) of a speed setpoint (N c ) of the engine assembly (2) as a function of a current state of charge (SOC c ) of an on-board energy storage device (32), and - control (S20) of the engine assembly (2) according to the speed setting (N c ) of the engine assembly (2).

2. Method according to claim 1, in which the updating (S70,S80) of the speed setpoint (N c ) includes the following steps: - determining (S740, S840) a difference in state of charge (ASOC) of the on-board energy storage device (32) which is a difference from the current state of charge (SOC c ) of the on-board energy storage device (32) relative to a reference state of charge (SOC r), And - comparison of said difference in state of charge (ASOC) with a difference threshold.

3. Method according to claim 2, in which a maximum electrical power (P0,max) which can be taken from the engine assembly (2) at a speed of the engine assembly (2) according to the speed setpoint (N c ) is less than an electric power (P r , c ) required by the aircraft (1), said reference state of load (SOC r ) is a state of charge of the on-board energy storage device (32) when the maximum electrical power (P0,max) that can be drawn from the motor assembly (2) has become lower than the electrical power (P r , c ) required by the aircraft (1), and said difference threshold is a discharge threshold.

4. Method according to claim 3, in which during the update (S70) the speed setpoint (N c) is maintained at a previous level if said difference in state of charge (ASOC) does not exceed the discharge threshold, electrical assistance is required for the motor assembly (2), and / or a higher threshold (N r , m ax) of the speed setting (N c ) is reached, and the diet instruction (N c ) is increased if said difference in state of charge (ASOC) exceeds the discharge threshold, electric assistance is not required for the motor assembly (2), and the upper threshold (N r , m ax) of the speed setting (N c ) is not reached.

5. A method according to any one of claims 3 or 4, wherein a first value (ASOCDI) is assigned to the discharge threshold when the current state of charge (SOC c ) is not less than an upper state of charge threshold (SOCi), and a second value is assigned to the discharge threshold when the current state of charge (SOCc ) is below the upper state of charge threshold (SOCi), but is not below a lower state of charge threshold (SOC2).

6. Method according to claim 2, in which a maximum electrical power (P0,max) which can be taken from the engine assembly (2) at a speed of the engine assembly (2) according to the speed setpoint (N c ) is not less than an electric power (P r , c ) required by the aircraft (1), said reference state of load (SOC r ) is a state of charge of the on-board energy storage device (32) when the maximum electrical power (P0,max) that can be drawn from the motor assembly has become equal to or greater than the electrical power (P r , c ) required by the aircraft or the operating instruction (N c ) has been reduced, and said difference threshold is a load threshold.

7. Method according to claim 6, wherein during the update (S70) the speed setpoint (N c ) is maintained at a previous level if said difference in state of charge (ASOC) does not exceed the load threshold and / or the speed setpoint (N c ) is at a lower threshold (N r , max ).

8. A method according to any one of claims 6 or 7, wherein a first value (ASOCci) is assigned to the charge threshold when the current state of charge (SOC c ) is not less than an upper state of charge threshold (SOCi), and a second value (ASOCcz) is assigned to the charge threshold when the current state of charge (SOC c ) is below the threshold higher (SOCi) state of charge, but is not lower than a lower threshold (SOC2) state of charge.

9. A method according to any one of claims 1 to 8, wherein the speed of the engine assembly (2) remains an idle speed lower than a maximum nominal speed of the engine assembly (2), in particular equal to or lower than 70% of said maximum nominal speed.

10. Control device (23) adapted to implement the method according to any one of claims 1 to 9.

11. A computer program comprising instructions which cause the control device of claim 10 to perform the steps of the method according to any one of claims 1 to 9.

12. Engine assembly (2) of an aircraft (1) comprising a control device (23) according to claim 10, a combustion engine (21), and an electrical machine (22) configured to draw electrical power.

13. An aircraft engine assembly (2) according to claim 12, wherein the electrical machine (22) is also configured to provide electrical assistance to the engine assembly (2).

14. An aircraft engine assembly (2) according to any one of claims 12 and 13, wherein the combustion engine (21) is a gas turbine engine.

15. Aircraft (1) comprising an engine assembly (2) according to any one of claims 12 to 14, as well as an on-board energy storage device (32) electrically connected to said electrical machine (22) of the engine assembly (2).

16. An aircraft (1) according to claim 15, wherein the on-board energy storage device (32) is a rechargeable electric battery.

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