Method and a device for managing the energy of a hybrid power plant of a multi-rotor aircraft

Abstract

A method and to a device for managing energy of a hybrid power plant of a multi-rotor aircraft during a flight. The hybrid power plant comprises a thermal engine, an electricity generator, and a plurality of electric motors, together with a plurality of electrical energy storage devices. The aircraft has a plurality of rotors driven in rotation by respective electric motors. The flight of the aircraft comprises a takeoff stage, a cruising stage, and a landing stage, the takeoff stage and the landing stage being performed solely while consuming electrical energy. The method enables an electrification ratio R.sub.Elec of the flight to be calculated as a function of the amounts of electrical and thermal energy that are consumed during the takeoff, landing, and cruising stages, thereby limiting the use of the thermal engine to the least possible amount during the cruising stage, and consequently reducing the associated nuisance.

Claims

1. A method of managing the energy of a hybrid power plant of a multi-rotor aircraft during a flight, the multi-rotor aircraft comprising: a hybrid power plant having a thermal energy source, an electrical energy source, and at least one electrical machine, the thermal energy source being suitable for delivering continuous thermal power W.sub.Th, the electrical machine(s) being capable of delivering continuous electrical power W.sub.ElecCont and also of delivering maximum electrical power W.sub.ElecMax; and at least two rotors driven in rotation by the hybrid power plant; the flight including a takeoff stage of duration T.sub.Takeoff, a cruising stage of duration T.sub.Cruise, and a landing stage of duration T.sub.Landing, the multi-rotor aircraft having cruising power W.sub.Cruise necessary for performing a cruising stage; wherein the takeoff stage and the landing stage are performed solely while consuming electrical energy delivered by the electrical energy source, and the method includes the following steps: a first calculation of takeoff electrical energy E.sub.TakeOff consumed during the takeoff stage and equal to:
E.sub.TakeOff=W.sub.ElecMax.Math.T.sub.TakeOff a second calculation of landing electrical energy E.sub.Landing consumed during the landing stage and equal to:
E.sub.Landing=W.sub.ElecMax.Math.T.sub.Landing a third calculation of electrical cruising energy E.sub.ElecCruise available for the cruising stage and equal to:
E.sub.ElecCruise=E.sub.ElecTotal×W.sub.ElecMax.Math.(T.sub.TakeOff+T.sub.Landing) where E.sub.ElecTotal is the total electrical energy available in the electrical energy source prior to starting the flight of the aircraft; a fourth calculation of an electrical cruising power W.sub.ElecCruise available for the cruising stage and equal to: $W_{\mathrm{ElecCruise}}=\mathrm{MIN}\left(W_{\mathrm{Cruise}};W_{\mathrm{ElecCont}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}.Math.\left(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}\right)}{T_{\mathrm{Cruise}}}\right)$ a comparison of the electrical cruising power W.sub.ElecCruise and the cruising power W.sub.Cruise; and a determination of a thermal cruising power W.sub.ThCruise needed for the cruising stage, such that:
if W.sub.ElecCruise=W.sub.Cruise; then W.sub.ThCruise=0
and
if W.sub.ElecCruise<W.sub.Cruise; then W.sub.ThCruise=W.sub.Cruise−W.sub.ElecCruise.

2. The method according to claim 1, wherein the method includes a fifth calculation of an electrification ratio R.sub.Elec for the flight of the aircraft, such that: $R_{\mathrm{Elec}}=\frac{\begin{array}{c}{T}_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}+\\ \mathrm{MIN}\left(\lambda ;\frac{W_{\mathrm{ElecCont}}}{W_{\mathrm{ElecMax}}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}.Math.(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing})}}{T_{\mathrm{Cruise}}.Math.W_{\mathrm{ElecMax}}}\right).Math.T_{\mathrm{Cruise}}\end{array}}{T_{\mathrm{Takeoff}}+T_{\mathrm{Landing}}+\lambda .Math.T_{\mathrm{Cruise}}}$ where λ is the proportion between the cruising power needed for cruising and a takeoff power needed for takeoff, i.e. the maximum electrical power W.sub.ElecMax of the aircraft, such that: $\lambda =\frac{W_{\mathrm{Cruise}}}{W_{\mathrm{ElecMax}}}.$

3. The method according to claim 1, wherein the flight includes an operating reserve stage of duration T.sub.Reser, such that the electrical cruising power W.sub.ElecCruise is equal to: $W_{\mathrm{ElecCruise}}=\mathrm{MIN}\left(W_{\mathrm{Cruise}};W_{\mathrm{ElecCont}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{EleMax}}.Math.\left(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}\right)}{T_{\mathrm{Cruise}}+T_{\mathrm{Reser}}}\right).$

4. The method according to claim 2, wherein the flight includes an operating reserve stage of duration T.sub.Reser, such that the electrical cruising power W.sub.ElecCruise is equal to: $W_{\mathrm{ElecCruise}}=\mathrm{MIN}\left(W_{\mathrm{Cruise}};W_{\mathrm{ElecCont}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}.Math.\left(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}\right)}{T_{\mathrm{Cruise}}+T_{\mathrm{Reser}}}\right)$ and the electrification ratio R.sub.Elec of the flight of the aircraft is such that: $R_{\mathrm{Elec}}=\frac{\begin{array}{c}{T}_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}+\\ \mathrm{MIN}\left(\lambda ;\frac{W_{\mathrm{ElecCont}}}{W_{\mathrm{ElecMax}}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}.Math.(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing})}}{\left(T_{\mathrm{Cruise}}+T_{\mathrm{Reser}}\right).Math.W_{\mathrm{ElecMax}}}\right).Math.T_{\mathrm{Cruise}}\end{array}}{T_{\mathrm{Takeoff}}+T_{\mathrm{Landing}}+\lambda .Math.T_{\mathrm{Cruise}}}.$

5. The method according to claim 1, wherein an operational energy reserve E.sub.ElecReser is deducted from the total available electrical energy E.sub.ElecTotal.

6. The method according to claim 1, wherein the electrical energy source has n storage device(s), where n is an integer greater than or equal to 1, and the total available electrical energy E.sub.ElecTotal in the electrical energy source is such that: $E_{\mathrm{ElecTotal}}=\underset{i=1}{\overset{n}{.Math.}}{\left(E_{\mathrm{Bat}}\right)}_i$ where i is a positive integer lying in the range 1 to n and (E.sub.Bat).sub.i is the energy capacity of a storage device of rank i.

7. The method according to claim 1, wherein the electrical energy source has n storage device(s), where n is an integer greater than or equal to 1, and the total available electrical energy E.sub.ElecTotal in the electrical energy source is such that: $E_{\mathrm{ElecTotal}}=k1.Math.\underset{i=1}{\overset{n}{.Math.}}{\left(E_{\mathrm{Bat}}\right)}_i$ where i is a positive integer lying in the range 1 to n, (E.sub.Bat).sub.i is the energy capacity of a storage device of rank i, and k1 is a normal utilization coefficient for the battery that is strictly less than 1.

8. The method according to claim 7, wherein in the event of an emergency and/or danger, the normal utilization coefficient k1 is replaced by an emergency coefficient k2 that is strictly greater than k1 and strictly less than 1.

9. The method according to claim 1, wherein the thermal energy source comprises at least one thermal engine, and the hybrid power plant includes a main power transmission gearbox (MGB) driving the rotors in rotation, the thermal engine(s) and the electrical machine(s) driving the MGB in rotation.

10. The method according to claim 9, wherein the hybrid power plant includes an electricity generator driven in rotation by the MGB or else directly by at least one thermal engine.

11. The method according to claim 1, wherein the thermal energy source comprises at least one thermal engine, and the hybrid power plant comprises an electricity generator and as many electric motors as there are rotors, each rotor being driven in rotation by a single electric motor, the electricity generator being driven in rotation by the thermal engine(s).

12. A multi-rotor aircraft comprising: a hybrid power plant provided with a thermal energy source, an electrical energy source, and at least one electrical machine, the thermal energy source being capable of delivering continuous thermal power W.sub.Th, the electrical machine(s) being capable of delivering continuous electrical power W.sub.ElecCont and maximum electrical power W.sub.ElecMax; and at least two rotors driven in rotation by the hybrid power plant; wherein the aircraft includes a device for managing the energy of the hybrid power plant and provided with a calculator and at least one memory in order to perform the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the context of the following description of embodiments given by way of illustration and with reference to the accompanying figures, in which:

(2) FIG. 1 is a block diagram of a method of managing the energy of a hybrid power plant of a multi-rotor aircraft; and

(3) FIGS. 2 and 3 show two multi-rotor aircraft, each fitted with a device for managing the energy of a hybrid power plant of the multi-rotor aircraft 1.

DETAILED DESCRIPTION OF THE INVENTION

(4) Elements present in more than one of the figures are given the same references in each of them.

(5) FIG. 1 is a block diagram of a method of managing the energy of the hybrid power plant of a multi-rotor aircraft 1. FIGS. 2 and 3 show two examples of a multi-rotor aircraft 1 fitted with a hybrid power plant 10 and with a device 20 for managing the energy of the hybrid power plant 10 of the multi-rotor aircraft.

(6) The method and the device 20 serve to determine, and consequently to optimize, the distribution of how different kinds of energy are consumed in the hybrid power plant 10 of the multi-rotor aircraft 1 over a complete flight.

(7) In a manner that is common to both of these examples, a multi-rotor aircraft 1 has a hybrid power plant 10, a device 20 for managing the energy of the hybrid power plant 10, and a plurality of rotors 2 driven in rotation by the hybrid power plant 10. The hybrid power plant 10 has at least one thermal engine 15 constituting a thermal energy source 13, at least one electrical energy storage device 18 constituting an electrical energy source 14, and at least one electrical machine 12. The device 20 for managing the energy of the hybrid power plant 10 comprises a calculator 21 and a memory 22.

(8) The first example of a multi-rotor aircraft 1 as shown in FIG. 2 also has a fuselage 3, two wings 4 on either side of the fuselage 3, and a tail boom 5 carrying tail fins 6. This first multi-rotor aircraft 1 has three rotors 2 constituted firstly by a main rotor 25 positioned above the fuselage 3, and secondly by two propulsive propellers 26 positioned at the ends of each of the wings 4.

(9) The hybrid power plant 10 of this first example of a multi-rotor aircraft 1 comprises more precisely two thermal engines 15 forming the thermal energy source 13, an electrical energy storage device 18 constituting the electrical energy source 14, a reversible electrical machine 12 having both a motor function and an electricity generator function, and a mechanical power transmission 30. The mechanical power transmission 30 serves to transmit the energy supplied by the thermal engine 15 and by the electrical machine 12 to the main rotor 2, 25 and to the propulsion propellers 2, 26. The mechanical power transmission 30 comprises a main gearbox (MGB) 31 and two auxiliary gearboxes (AGBs) 32. The MGB 31 is driven in rotation by the thermal engines 15 and by the electrical machine 12 when it is operating in motor mode, and it drives rotation of the main rotor 2, 25 and also of the two AGBs 32. Each AGB 32 then drives a respective one of the propulsion propellers 2, 26 in rotation. The MGB 31 may also drive rotation of the electrical machine 12 when it is operating in electricity generator mode in order to supply electrical energy that can be stored in the storage device 18.

(10) As shown in FIG. 3, the second example of a multi-rotor aircraft 1 has six rotors 2, with each of these six rotors 2 constituting a lift and propulsion rotor 28, a central portion 8, and six arms 7 secured to the central portion 8 and each carrying at its end a respective one of the rotors 2, 28.

(11) The hybrid power plant 10 in this second example of a multi-rotor aircraft 1 comprises more precisely a, thermal engine 15 forming the thermal energy source 13, two electrical storage devices 18 constituting the electrical energy source 14, and seven electrical machines 12 comprising firstly an electricity generator driven by the thermal engine 15, and secondly six electric motors 17, with each of these electric motors 17 driving a respective one of the rotors 2, 28. The six electric motors 17 and the electricity generator 16 are connected electrically to the electrical energy source 14.

(12) The method of managing the energy of the hybrid power plant 10 of a multi-rotor aircraft 1 as shown diagrammatically in FIG. 1 may be performed by the device 20 that is included in both of these examples a multi-rotor aircraft 1. The method comprises seven steps and serves to determine, and consequently to optimize, the distribution of how electrical energy and thermal energy are consumed in the hybrid power plant 10 of the multi-rotor aircraft 1 over a complete flight for the purpose, amongst others, of limiting sound and polluting nuisances of the flight for the environment. Such a complete flight of the multi-rotor aircraft 1 includes a takeoff stage for a duration T.sub.Takeoff, a cruising stage for a duration T.sub.Cruise, and a landing stage for a duration T.sub.Landing.

(13) Advantageously, the takeoff stage and the landing stage are performed while consuming only electrical energy as supplied by the electrical energy source 14, with the rotors 2 being driven solely by the electrical machines 12. As a result, the sound nuisance of the multi-rotor aircraft 1 is limited to the noise generated by the rotation of the rotors 2, and the atmospheric pollution that is generally caused by a thermal engine 15 is eliminated during these stages of takeoff and landing.

(14) The hybrid power plant 10 has characteristics defining the powers that it is capable of delivering. The hybrid power plant 10 may deliver continuous thermal power W.sub.Th by using the thermal energy source 13 only. The hybrid power plant 10 can deliver maximum electrical power W.sub.ElecMax for a limited duration, and continuous electrical power W.sub.ElecCont in continuous manner while using only the electrical energy source 14 powering each electrical machine 12.

(15) Furthermore, the multi-rotor aircraft 1 has cruising power W.sub.Cruise necessary for performing a cruising stage.

(16) The characteristics of the multi-rotor aircraft 1 and the characteristics of the hybrid power plant 10 are stored in the memory 22 together with instructions for performing the method of managing the energy of the hybrid power plant 10.

(17) During a first calculation 100, a takeoff amount of electrical energy E.sub.TakeOff to be consumed during the takeoff stage is determined. This takeoff electrical energy E.sub.TakeOff is such that:
E.sub.TakeOff=W.sub.ElecMax.Math.T.sub.TakeOff.

(18) During a second calculation 200, a landing amount of electrical energy E.sub.Landing to be consumed during a stage of landing is determined. This landing electrical energy E.sub.Landing is such that:
E.sub.Landing=W.sub.ElecMax.Math.T.sub.Landing.

(19) The first calculation 100 and the second calculation 200 may be performed simultaneously, or else sequentially.

(20) Thereafter, during a third calculation 300, a cruising amount of electrical energy E.sub.ElecCruise available for the cruising stage is determined by subtracting the takeoff electrical energy E.sub.TakeOff and the landing electrical energy E.sub.Landing from the total electrical energy E.sub.ElecTotal available in the electrical energy source 14 before takeoff of the flight of the aircraft 1. The cruising electrical energy E.sub.ElecCruise is such that:
E.sub.ElecCruise=E.sub.ElecTotal−W.sub.ElecMax.Math.(T.sub.TakeOff+T.sub.Landing).

(21) In addition, an operating reserve of electrical energy E.sub.ElecReser may also be subtracted from the total electrical energy E.sub.ElecTotal in order to determine the cruising electrical energy E.sub.ElecCruise that is available for the cruising stage. This operating reserve of electrical energy E.sub.ElecReser serves to anticipate a potential incident that might occur during the cruising stage or indeed the landing stage. An incident may be a failure of a thermal engine 15 of the thermal energy source 13 during the cruising stage, or indeed an interruption of the landing stage, or indeed a change of landing site.

(22) This operating reserve of electrical energy E.sub.ElecReser is then added to the portion of the electrical energy from the electrical energy source 14 that has not yet been consumed, so that the multi-rotor aircraft 1 can land safely. The cruising electrical energy E.sub.ElecCruise is then such that:
E.sub.ElecCruise=E.sub.ElecTotal−E.sub.TakeOff−E.sub.Landing−E.sub.ElecReser
i.e.:
E.sub.ElecCruise=E.sub.ElecTotal−W.sub.ElecMax.Math.(T.sub.TakeOff+T.sub.Landing)−E.sub.ElecReser.

(23) During a fourth calculation 400, a cruising amount of electrical power W.sub.ElecCruise that can be delivered by the hybrid power plant 10 for the cruising stage is determined. This cruising electrical power W.sub.ElecCruise is limited by the capacity of each electrical machine 12 to deliver power continuously. As a result, this cruising electrical power W.sub.ElecCruise is equal to the minimum value selected from among: the ratio of the cruising electrical energy E.sub.ElecCruise available for the duration T.sub.Cruise; the continuous electrical power W.sub.ElecCont; and the cruising power W.sub.Cruise needed for performing a cruising stage, such that:

(24) $W_{\mathrm{ElecCruise}}=\mathrm{MIN}\left(W_{\mathrm{Cruise}};W_{\mathrm{ElecCont}};\frac{E_{\mathrm{ElecCruise}}}{T_{\mathrm{Cruise}}}\right)$$i.e.:W_{\mathrm{ElecCruise}}=\mathrm{MIN}\left(W_{\mathrm{Cruise}};W_{\mathrm{ElecCont}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}.Math.\left(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}\right)-E_{\mathrm{ElecReser}}}{T_{\mathrm{Cruise}}}\right).$

(25) The operating reserve of electrical energy E.sub.ElecReser mentioned above may also be taken into account when calculating this cruising electrical power W.sub.ElecCruise and is then not deduced from the total electrical energy E.sub.ElecTotal. This operating reserve of electrical energy E.sub.ElecReser may be characterized by a duration T.sub.Reser for an operating reserve stage. This duration T.sub.Reser is added to the duration T.sub.Cruise for the cruising stage while calculating the cruising electrical power W.sub.ElecCruise, such that:

(26) $W_{\mathrm{ElecCruise}}=\mathrm{MIN}\left(W_{\mathrm{Cruise}};W_{\mathrm{ElecCont}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}.Math.\left(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}\right)}{T_{\mathrm{Cruise}}+T_{\mathrm{Reser}}}\right).$

(27) During a comparison 500, the cruising electrical power W.sub.ElecCruise is compared with the cruising power W.sub.Cruise, this cruising power W.sub.Cruise being a function of the aerodynamic characteristics of the multi-rotor aircraft 1.

(28) During a determination 600, a cruising thermal power W.sub.ThCruise needed for the cruising stage is determined after the comparison 500.

(29) If the electrical cruising power W.sub.ElecCruise is equal to the cruising power W.sub.Cruise, then the thermal cruising power W.sub.ThCruise needed for the cruising stage is zero, and the entire flight of the multi-rotor aircraft 1, including its cruising stage, is performed by making use only of the electrical energy contained in the electrical energy source 14.

(30) In contrast, if the electrical cruising power W.sub.ElecCruise is less than the cruising power W.sub.Cruise, then the thermal cruising power W.sub.ThCruise needed for the cruising stage is not zero. Consequently, the electrical energy contained in the electrical energy source 14 is not sufficient on its own to perform the entire flight of the multi-rotor aircraft 1. The thermal energy source 13 must therefore be used, but only during the cruising stage, so as to limit the nuisance generated by the thermal energy source 13 to this cruising stage, which takes place at altitude, and thus as far away as possible from inhabited zones. The thermal cruising power W.sub.ThCruise is such that:

(31) $W_{\mathrm{ThCruise}}=W_{\mathrm{Cruise}}-W_{\mathrm{ElecCruise}}$$i.e.:W_{\mathrm{ThCruise}}=W_{\mathrm{Cruise}}-\mathrm{MIN}\left(W_{\mathrm{Cruise}};W_{\mathrm{ElecCont}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}.Math.\left(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}\right)}{T_{\mathrm{Cruise}}}\right).$

(32) During a fifth calculation 700, an electrification ratio R.sub.Elec for the flight of the multi-rotor aircraft 1 is determined. This electrification ratio R.sub.Elec of the flight is calculated as a function of the amounts of electrical energy and of thermal energy consumed during the flight and is equal to the ratio of the electrical energy consumed during the flight divided by the total energy consumed by the hybrid power plant 10 during the flight. This electrification ratio R.sub.Elec for the flight is such that:

(33) $R_{\mathrm{Elec}}=\frac{\begin{array}{c}{T}_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}+\\ \mathrm{MIN}\left(\lambda ;\frac{W_{\mathrm{ElecCont}}}{W_{\mathrm{ElecMax}}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}.Math.(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing})}}{T_{\mathrm{Cruise}}.Math.W_{\mathrm{ElecMax}}}\right).Math.T_{\mathrm{Cruise}}\end{array}}{T_{\mathrm{Takeoff}}+T_{\mathrm{Landing}}+\lambda .Math.T_{\mathrm{Cruise}}}$
where λ is the proportion between the cruising power W.sub.Cruise and the maximum electrical power W.sub.ElecMax used for the takeoff stage, such that:

(34) $\lambda =\frac{W_{\mathrm{Cruise}}}{W_{\mathrm{ElecMax}}}.$

(35) Thus, the electrification ratio R.sub.Elec serves to determine whether it is or is not necessary to use the thermal energy source in order to perform the flight, and also to know the proportion of thermal energy that is needed. It is then possible to deduce therefrom the quantity of fuel that is needed for performing the flight. In particular, if the electrification ratio R.sub.Elec is equal to 1, then the flight of the multi-rotor aircraft 1 is performed by using only the electrical energy delivered by the electrical energy source.

(36) If an operating reserve stage of duration T.sub.Reser is taken into account when calculating the electrical cruising power W.sub.ElecCruise, then the electrification ratio R.sub.Elec for the flight is such that:

(37) 0$R_{\mathrm{Elec}}=\frac{\begin{array}{c}{T}_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}+\\ \mathrm{MIN}\left(\lambda ;\frac{W_{\mathrm{ElecCont}}}{W_{\mathrm{ElecMax}}};\frac{E_{\mathrm{ElecTotal}}-W_{\mathrm{ElecMax}}\left(T_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}\right)}{\left(T_{\mathrm{Cruise}}+T_{\mathrm{Reser}}\right).Math.W_{\mathrm{ElecMax}}}\right).Math.T_{\mathrm{Cruise}}\end{array}}{T_{\mathrm{TakeOff}}+T_{\mathrm{Landing}}+\lambda .Math.T_{\mathrm{Cruise}}}.$

(38) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several implementations are described, it will readily be understood that it is not conceivable to identify exhaustively all possible implementations. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.