ELECTRIC PROPULSION SYSTEM FOR AIRCRAFT AND AIRCRAFT WITH SUCH A SYSTEM

Description

technical field

[0001] The present invention belongs to the field of electrically or hybrid powered aerial vehicles, and relates more particularly to an electric propulsion system for such aerial vehicles. State of the art

[0002] Nowadays, there are more and more aerial vehicles equipped with electric propulsion systems. This is the case in particular for unmanned aerial vehicles (UAVs) such as drones, or for passenger aerial vehicles, for example for urban mobility (flying taxis, etc.).

[0003] An electric propulsion system for an aerial vehicle uses several electric motors to enable takeoff, flight, and landing. The electric motors are powered by batteries that provide the necessary electrical energy reserve for the duration of the aerial vehicle's mission.

[0004] There figure 1 schematically represents an example of a 10-system electric propulsion system according to the prior art.

[0005] As illustrated by the figure 1 The electric propulsion system 10 comprises several electric motors 11 powered by several power batteries 12. The electric motors 11 are connected to the power batteries by an electrical distribution network. In the example illustrated by the figure 1Each power supply battery typically powers two electric motors, and the electrical distribution network incorporates reconfiguration mechanisms that, in the event of a power supply battery failure (for example, due to insufficient charge), connect the electric motors that were powered by the failed battery to other, functioning power supply batteries. Such reconfiguration mechanisms thus allow the aircraft to maintain control in the event of a power supply battery failure, notably enabling a safe emergency landing.

[0006] However, known architectures of electric propulsion systems for aerial vehicles, such as the architecture illustrated by the figure 1These operations require a thorough understanding of the electrical energy available in each power battery to ensure a safe mission. Indeed, the electrical energy available in each power battery must be estimated with sufficient accuracy to reliably indicate the remaining range to the aircraft operator, allowing them to plan the aircraft's mission and know when a landing is required.

[0007] In practice, accurately estimating the available electrical energy in a power supply battery is difficult because it depends on numerous parameters, including the environment (temperature, humidity, etc.) and the battery's usage history. Furthermore, the accuracy of estimating the available electrical energy in a power supply battery tends to decrease with the battery's charge level. In other words, the less electrical energy is available in a power supply battery, the more difficult it is to obtain a precise estimate of that available electrical energy.

[0008] In practice, due to the uncertainty in estimating the electrical energy available in each power battery, it is necessary to define and maintain a significant electrical energy margin to ensure sufficient available power for an emergency landing procedure, despite this uncertainty. This margin is all the more critical because, in the event of a power battery failure, a reduced number of power batteries must supply all the electric motors. The need for a substantial margin also necessitates increasing the aircraft's onboard mass. Prior art is known from US documents 2018 / 312248 A1, CN 113 002 784 A, and US 2016 / 107758 A1. Description of the invention

[0009] The purpose of this disclosure is to address all or part of the limitations of prior art solutions, including those described above, by proposing a solution that reduces the margin of electrical energy required and ensures that in the event of a failure of a power supply battery, the remaining electrical energy is sufficient to perform emergency maneuvers, including an emergency landing.

[0010] To this end, and according to a first aspect, an electric propulsion system for an aerial vehicle is proposed, comprising a plurality of electric motors, a plurality of power batteries to supply said electric motors with electrical energy, and an electrical distribution network connecting said power batteries to the electric motors. This electric propulsion system further includes an additional power battery, referred to as a backup battery, adapted to be connected to the electric motors via the electrical distribution network, and this electric propulsion system is configured to power the electric motors according to at least two different power supply modes: a so-called normal power supply mode, in which the backup battery does not power any of the electric motors, the said electric motors being powered by the supply batteries, a so-called backup power supply mode, in which the backup battery powers at least one electric motor.

[0011] Thus, the electric propulsion system is configured to power the electric motors in at least two different power modes, namely a normal propulsion mode used by default during takeoff, flight and landing phases, and a backup power mode used when at least one power battery fails (power battery malfunction or low charge level).

[0012] In addition, the electric propulsion system as disclosed herein includes an additional power supply battery, referred to as a backup battery, which is not used in the normal power supply mode, and is used only in the backup power supply mode, to take over from a failing power supply battery.

[0013] Thus, in the event of a failure of the main power battery, it can be replaced by the backup battery. Since the backup battery is not used in normal power mode, its charge level is generally at its maximum when the electric propulsion system switches to backup power mode, so its electrical energy content is known with good accuracy. By sizing the backup battery to power the electric motors for a predetermined duration sufficient to perform at least one emergency landing, the margin of electrical energy carried by the aircraft can be significantly reduced compared to prior art solutions.Indeed, prior art solutions require a margin for each backup battery because each backup battery can be used to compensate for the failure of another backup battery, at a time when the potentially low charge level does not allow for an accurate estimation of the electrical energy available in each backup battery. According to the present disclosure, the backup battery can power all the electric motors, and when it begins to be used (i.e., at the start of the emergency situation created by the failure of a backup battery), the backup battery always has a maximum charge level that allows for an accurate determination of the available electrical energy.

[0014] In particular embodiments, the electric propulsion system may further include one or more of the following optional features, taken individually or in all technically possible combinations.

[0015] In particular embodiments, the electric propulsion system includes a power supply battery failure detection module and a control module configured to implement the normal power supply mode when no power supply battery failure is detected and to implement the backup power supply mode when a failure of at least one power supply battery is detected.

[0016] In particular embodiments, the electrical distribution network includes first switching means adapted to connect / disconnect the backup battery from the electric motors, and the control module is configured to control the first switching means for: In normal power mode: disconnect the backup battery from the electric motors; in emergency power mode: connect the backup battery to at least one electric motor.

[0017] In particular embodiments, the electrical distribution network further includes secondary switching means adapted to connect / disconnect the power supply batteries to the electric motors, and the control module is configured to control the secondary switching means for: In normal power mode: connect the power batteries to the electric motors; in emergency power mode: disconnect each power battery detected as faulty by the fault detection module.

[0018] In particular embodiments, the backup battery has a nominal voltage lower than the respective nominal voltages of the supply batteries.

[0019] In particular embodiments, the backup battery has a nominal voltage lower than the respective nominal voltages of the supply batteries, and the electrical distribution network is configured so that the backup battery is connected to the electric motors in both normal supply mode and emergency supply mode, and so that the backup battery begins to supply an electric motor when the voltage across the supply battery supplying said electric motor becomes lower than the voltage across the backup battery.

[0020] In particular embodiments, the backup battery is connected to each electric motor in parallel with at least one supply battery.

[0021] In particular embodiments, the electric propulsion system includes a fault detection module configured to detect the switch from normal power mode to emergency power mode.

[0022] In particular embodiments, the electrical distribution network includes switching means adapted to connect / disconnect the power supply batteries to the electric motors, and said electric propulsion system includes a control module configured to control the switching means for: In normal power mode: connect the power batteries to the electric motors; in emergency power mode: disconnect each power battery detected as faulty by the fault detection module.

[0023] In specific embodiments, the fault detection module is configured to issue a notification to an aerial vehicle user when the electric motors are powered in emergency power mode. The user may be a passenger on the aerial vehicle or on the ground, for example, in the case of a non-passenger aerial vehicle (UAV) and / or one that is remotely piloted.

[0024] According to a second aspect, this disclosure relates to an aerial vehicle incorporating an electric propulsion system according to any of the embodiments of this disclosure. The aerial vehicle may be exclusively electric-powered or hybrid-powered. Presentation of the figures

[0025] The invention will be better understood upon reading the following description, given by way of non-limiting example, and made with reference to the figures which represent: Figure 1 As already described, a schematic representation of an electric propulsion system according to the prior art, Figure 2 : a schematic representation of an initial example of the implementation of an electric propulsion system, Figure 3 : a schematic representation of a second example of the implementation of an electric propulsion system, Figure 4 : a schematic representation of a third example of the implementation of an electric propulsion system.

[0026] In these figures, identical references from one figure to another designate identical or analogous elements. For clarity, the elements shown are not to scale unless otherwise indicated. Description of the implementation methods

[0027] As indicated above, this disclosure relates to an electric propulsion system for an aerial vehicle (not shown in the figures). The aerial vehicle may be purely electric or hybrid powered. Furthermore, the aerial vehicle may be unmanned or passenger-carrying.

[0028] There figure 2 schematically represents an example of the implementation of an electric propulsion system 20 according to this disclosure.

[0029] As illustrated by the figure 2 The electric propulsion system 20 comprises, firstly, a set of electric motors 21 for propelling the aircraft and performing the takeoff, flight, and landing phases of said aircraft. Each of said electric motors 21 can be of any type suitable for the propulsion of an aircraft.

[0030] In the non-limiting example illustrated by the figure 2 The electric propulsion system 20 comprises eight (8) electric motors 21. More generally, the electric propulsion system 20 comprises at least two electric motors 21, the total number of electric motors 21 varying from one embodiment of the electric propulsion system 20 to another. In this disclosure, the electric motors are collectively referred to (without distinction between them) by reference 21, while they are individually referred to by references 21-1 to 21-8, respectively.

[0031] The electric propulsion system 20 also includes a set of power batteries 22 to supply electrical energy to said electric motors 21. In the non-limiting example illustrated by the figure 2The electric propulsion system 20 comprises four (4) power batteries 22. More generally, the electric propulsion system 20 comprises at least two power batteries 22, the total number of power batteries 22 being able to vary from one embodiment of the electric propulsion system 20 to another. In this disclosure, the power batteries are collectively referred to (without distinction from one another) by reference numeral 22, while they are individually referred to by reference numerals 22-1 to 22-4, respectively.

[0032] The electric propulsion system 20 also includes an electrical distribution network connecting the power batteries 22 to the electric motors 21. The electrical distribution network consists of all the elements enabling the connection of each power battery 22 to each electric motor 21 that is to be powered by that power battery 22. For example, the electrical distribution network consists of a set of power lines and discrete components. In the non-limiting example illustrated by the figure 2 The electrical distribution network includes, in particular, a main line 23, supply lines 24-1 to 24-8 linking the main line 23 to the various electric motors 21-1 to 21-8, and switching means (for example contactors) allowing the reconfiguration of said electrical distribution network, which will be discussed below.

[0033] As illustrated by the figure 2The electric propulsion system 20 also includes an additional power supply battery, referred to as a backup battery 25, adapted to be connected to each of the electric motors 21 via the electrical distribution network. It should be noted that the propulsion system 20 may also, according to other embodiments, include several backup batteries 25, for example, for the purpose of redundancy of the backup battery 25. In such cases, the backup batteries 25 are adapted to be connected to the electric motors 21 via the electrical distribution network, so that each electric motor 21 can be powered by at least one of the backup batteries 25. However, in preferred embodiments of the electric propulsion system 20, said electric propulsion system 20 includes only one backup battery 25, in order to limit the mass carried by the aircraft.

[0034] In the following description, we consider the case where the electric propulsion system 20 includes a single backup battery 25, which therefore corresponds to preferred embodiments of the electric propulsion system 20 allowing to limit the margin of electrical energy and the mass carried in the aerial vehicle.

[0035] In the example illustrated by the figure 2 The electrical distribution network also includes a charging port 26, connected to the main line 23, intended to be connected to a ground power unit (GPU) to charge the power supply batteries 22 and the backup battery 25 when the aircraft is on the ground. The electrical distribution network also includes switching means which comprise: line contactors CL1 to CL4 allowing each power supply battery 22-1 to 22-4 to be connected / disconnected from the main line 23, a line contactor CL-5 allowing the backup battery 25 to be connected / disconnected from the main line 23, a line contactor CL6 allowing the charging port 26 to be connected / disconnected from the main line 23.

[0036] For example, during charging, line contactors CL1 to CL6 are closed to connect the main line 23 to the power batteries 22-1 to 22-4, the backup battery 25 and the charging port 26. When charging is complete, line contactors CL1 to CL6 are, for example, open to disconnect the main line 23 from the power batteries 22-1 to 22-4, the backup battery 25 and the charging port 26.

[0037] In the example illustrated by the figure 2The switching means of the electrical distribution network also include motor contactors CM1, CM2, CM3, and CM4 arranged respectively on the supply lines 24-1, 24-3, 24-5, and 24-7. When the motor contactors CM1, CM2, CM3, and CM4 are closed, the supply batteries 22-1, 22-2, 22-3, and 22-4 are connected to the electric motors 21-1, 21-3, 21-5, and 21-7, respectively. In the example illustrated by the figure 2 The means of switching the electricity distribution network also include: a CT1 transfer contactor arranged between supply lines 24-1 and 24-2, a CT2 transfer contactor arranged between supply lines 24-3 and 24-4, a CT3 transfer contactor arranged between supply lines 24-5 and 24-6, a CT4 transfer contactor arranged between supply lines 24-7 and 24-8.

[0038] When motor contactors CM1 to CM4 and transfer contactors CT1 to CT4 are closed, the supply batteries 22-1, 22-2, 22-3 and 22-4 are also connected to electric motors 21-2, 21-4, 21-6 and 21-8, respectively.

[0039] In the example illustrated by the figure 2 The electrical distribution network also includes diodes D1, D2, D3, and D4 arranged on the supply lines 24-2, 24-4, 24-6, and 24-8, respectively. Diodes D1 through D4 allow the passage of electric current only from the main line 23 to the electric motors 21-2, 21-4, 21-6, and 21-8.

[0040] The electric propulsion system 20 may also include a control module (not shown in the figures) that controls, in particular, the line contactors CL1 to CL6, the motor contactors CM1 to CM4, and the transfer contactors CT1 to CT4. The control module may include, for example, one or more processors and one or more electronic memories (any type of computer-readable storage medium) in which a computer program product is stored, in the form of a set of program code instructions to be executed to control the various switching means of the electrical distribution network. Alternatively or in addition, the control module may include one or more programmable logic circuits, such as FPGAs, PLDs, etc., and / or specialized integrated circuits (ASICs), and / or discrete electronic components adapted to control the various switching means of the electrical distribution network.

[0041] As indicated above, the electric propulsion system 20 is configured to power the electric motors 21 according to at least two different power supply modes: a so-called normal power supply mode, in which the backup battery 25 does not power any of the electric motors 21, the electric motors being powered solely by the power supply batteries 22, a so-called backup power supply mode, in which the backup battery 25 powers at least one electric motor.

[0042] Thus, the backup battery 25 is not used in normal power mode, which is the default operating mode during takeoff, flight, and landing of the aircraft. However, the backup battery 25 is used in emergency power mode to take over from one or more failing power batteries 22 (due to a malfunction of power battery 22 or a low charge level).

[0043] For example, in normal power supply mode, motor contactors CM1 to CM4 and transfer contactors CT1 to CT4 are closed by the control module, while line contactors CL1 to CL6 are opened by the control module. Thus, backup battery 25 is not connected to any of the electric motors 21-1 to 21-4. Power supply battery 22-1 powers electric motors 21-1 and 21-2, power supply battery 22-2 powers electric motors 21-3 and 21-4, power supply battery 22-3 powers electric motors 21-5 and 21-6, and power supply battery 22-4 powers electric motors 21-7 and 21-8.

[0044] In emergency power mode, the control module can close line contactor CL5, so that the backup battery 25 is connected to all electric motors 21-1 to 21-8 via power lines 24-2, 24-4, 24-6, and 24-8, respectively, and transfer contactors CT1 to CT4 are closed. Line contactor CL5 thus acts as a switching device for connecting / disconnecting the backup battery 25 from the electric motors 21.

[0045] To determine when to switch from normal power mode to backup power mode, the electric propulsion system 20 includes, for example, a fault detection module (not shown in the figures). The fault detection module includes, for example, a set of sensors for detecting the failure of one of the power supply batteries 22, for example, by measuring the voltages across the terminals of said power supply batteries 22. Indeed, a low charge level of a power supply battery 22 will result in a detectable drop in the voltage across its terminals, compared to the nominal voltage of said power supply battery 22. However, the fault detection module can implement any means necessary to detect the failure of a power supply battery 22.Thus, when the fault detection module detects a failure in a power supply battery 22, the control module can trigger the switch from normal power supply mode to backup power supply mode. In preferred embodiments, the control module can also isolate the power supply battery detected as faulty by the fault detection module. For example, if power supply battery 22-1 has been detected as faulty, then the control module can open motor contactor CM1 to disconnect power supply battery 22-1 from electric motors 21-1 and 21-2, which are then powered by backup battery 25 (with transfer contactor CT1 remaining closed). Motor contactors CM1 to CM4 therefore correspond to switching means for connecting / disconnecting power supply batteries 22 from electric motors 21.

[0046] In the example illustrated by the figure 2In backup power mode, the backup battery 25 is connected to all the electric motors 21, so that it can power all the electric motors 21, even those that are still connected to non-failing backup batteries 22. In preferred embodiments, the backup battery 25 has a lower nominal voltage than the respective nominal voltages of the backup batteries 22. For example, the nominal voltage of the backup battery 25 can be between 600 Volts (V) and 700 V, and the nominal voltage of the backup batteries 22 can be between 700 V and 800 V. Therefore, in the example of the figure 2In backup power mode, an electric motor 21 will only be powered by the backup battery 25 if the voltage across the electric motor 21 (supplied by a backup battery 22) is lower than the voltage across the backup battery 25. This will be the case for an electric motor 21 powered by a faulty backup battery 22, but it will generally not be the case for other electric motors 21 powered by non-faulty backup batteries 22. Therefore, in such a case, the backup battery 25, although connected to all the electric motors 21, essentially only powers the electric motors 21 powered by a faulty backup battery 22. Furthermore, the non-faulty backup batteries 22 do not discharge to the backup battery 25 due to the presence of diodes D1 to D4.

[0047] There figure 3schematically represents another example of the implementation of an electric propulsion system 20 according to this disclosure. In addition to the elements already described with reference to the figure 2 , the 20 electric propulsion system of the figure 3 includes CM5, CM6, CM7 and CM8 motor contactors arranged on the supply lines 24-2, 24-4, 24-6 and 24-8, respectively.

[0048] In the example illustrated by the figure 3 In normal power supply mode, motor contactors CM1 to CM4 and transfer contactors CT1 to CT4 are closed by the control module, while line contactors CL1 to CL6 and motor contactors CM5 to CM8 are opened by the control module.

[0049] In backup power mode, the control module closes line contactor CL5. Preferably, the control module closes only the motor contactor, among motor contactors CM5 to CM8, that is connected to an electric motor 21 powered by the failed backup battery 22. For example, if the backup battery 22 detected as faulty is battery 22-1, then the control module closes only motor contactor CM5. However, in other examples, it is possible to close all motor contactors CM5 to CM8. Line contactor CL5 and motor contactors CM5 to CM8 thus serve as switching means for connecting / disconnecting the backup battery 25 from the electric motors 21.As described previously, the control module can, in particular embodiments, isolate the faulty power supply battery 22 by an appropriate control of the motor contactors CM1 to CM4.

[0050] There figure 4 schematically represents another example of the implementation of an electric propulsion system 20 according to this disclosure. The electric propulsion system 20 of the figure 4 includes all the elements described in reference to the figure 2with the exception of line contactor CL5. Thus, in this embodiment, the backup battery 25 is always connected to the electric motors 21, regardless of the power supply mode. However, in this embodiment, the backup battery 25 has a lower nominal voltage than the respective nominal voltages of the power supply batteries 22, so that the backup battery 25 does not discharge (and does not supply power to the electric motors 21) as long as the voltages across the power supply batteries 22 are higher than the voltage across the backup battery 25. However, the backup battery 25 begins to supply power to an electric motor 21 when the voltage across the power supply battery 22 that supplies this electric motor 21 becomes lower than the voltage across the backup battery 25.For example, the nominal voltage of the backup battery 25 can be between 600 Volts (V) and 700 V, and the nominal voltage of the power supply batteries 22 can be between 700 V and 800 V. Thus, the backup battery 25 automatically takes over from a failing power supply battery 22, without requiring any changes to the switching state of the various switching means of the electrical distribution network and without needing to detect the failure of this power supply battery 22. Consequently, the intervention of a control module or a fault detection module is not necessary to switch from normal power supply mode to backup power supply mode. However, the electric propulsion system 20 may nevertheless include a fault detection module configured to detect the switch from normal power supply mode to backup power supply mode.If the fault detection module is further configured to detect which power supply battery 22 is faulty, then the control module can, in particular embodiments, isolate the faulty power supply battery 22 by an appropriate control of the motor contactors CM1 to CM4.

[0051] In certain embodiments, when the electric propulsion system 20 includes a fault detection module, this module is preferably configured to send a notification to an aircraft operator, informing them that the backup power mode is in use. Indeed, even though using the backup battery 25 provides a more accurate estimate of the available electrical energy, the operator must be informed that a failure of the backup battery 22 has been detected in order to trigger, for example, an emergency landing procedure. The operator is, for example, the aircraft pilot, who may be a passenger in the aircraft or on the ground, for example, in the case of a remotely piloted aircraft.

[0052] More generally, it should be noted that the implementation and realization methods considered above have been described as non-limiting examples, and that other variants are therefore conceivable.

[0053] In particular, the invention has been described by considering specific examples of embodiments of the electric propulsion system 20. Other variants are conceivable, provided they allow for an electric propulsion system 20 comprising a backup battery 25 that is not used in a normal power supply mode for the electric motors, so that its charge level is a priori maximum and precisely known when it is used in a backup power supply mode.

Claims

1. An electrical propulsion system (20) for an aerial vehicle, comprising a plurality of electric motors (21), a plurality of power supply batteries (22) for supplying power to said electric motors, and an electrical power distribution network connecting said power supply batteries to the electric motors, said electrical propulsion system (20) comprising an additional power supply battery, referred to as a backup battery (25), adapted to be connected to the electric motors by the electrical power distribution network, said electrical propulsion system being configured to supply power to the electric motors according to at least two different power supply modes: - a power supply mode referred to as a normal power supply mode, wherein the backup battery (25) does not supply power to any of the electric motors (21), said electric motors being supplied with power by the power supply batteries (22), - a power supply mode referred to as a backup power supply mode, wherein the backup battery (25) supplies power to at least one electric motor (21), characterized in that the backup battery has a nominal voltage lower than the respective nominal voltages of the power supply batteries, and wherein the electrical power distribution network is configured so that the backup battery is connected to the electric motors in the normal power supply mode and in the backup power supply mode, and so that the backup battery begins to supply power to an electric motor when the voltage across the terminals of the power supply battery which is supplying power to said electric motor becomes lower than the voltage across the terminals of the backup battery.

2. The electrical propulsion system (20) according to claim 1, wherein the backup battery is connected to each electric motor in parallel with at least one power supply battery.

3. The electrical propulsion system (20) according to any one of claims 1 and 2, comprising a failure detection module configured to detect the switch from the normal power supply mode to the backup power supply mode.

4. The electrical propulsion system (20) according to claim 3, wherein the electrical power distribution network comprises switching means adapted to connect / disconnect the power supply batteries to / from the electric motors, said electrical propulsion system comprising a control module configured to control the switching means so as to: - in the normal power supply mode: connect the power supply batteries to the electric motors, - in the backup power supply mode: disconnect from the electric motors each power supply battery detected as faulty by the failure detection module.

5. The electrical propulsion system (20) according to any one of claims 3 and 4, wherein the failure detection module is configured to send a notification to a user of the aerial vehicle when the electric motors are being supplied with power in the backup power supply mode.

6. An aerial vehicle comprising an electrical propulsion system (20) according to any one of claims 1 to 5.