Method of managing a power demand for the operation of a pilotless aircraft equipped with an internal combustion engine

Abstract

A method of managing a power demand to assure the operation of a pilotless aircraft. The aircraft includes an internal combustion engine supplying a maximum principal power which can vary. The management method is particularly suitable for a rotary wing pilotless aircraft. It guarantees the storage of an amount of electrical energy at least equal to a recovery energy of the aircraft in the event of failure of the internal combustion engine. This recovery energy enables the control of autorotation and landing of the aircraft.

Claims

1. Method of managing a power demand to assure operation of a pilotless aircraft, the aircraft comprising an internal combustion engine supplying a maximum principal power P.sub.M, which can vary, the method comprises the steps of, in the absence of an internal combustion engine failure: a) collecting at least some of exhaust gases during an operation of the internal combustion engine; b) feeding a turbine with an energy of the exhaust gases collected; c) producing an electrical current using an electrical generator connected to the turbine to generate an electrical energy; d) comparing the maximum principal power P.sub.M supplied by the internal combustion engine with a demanded power P.sub.D at a time of the power demand; e) in response to a determination that the maximum principal power P.sub.M is at least equal to the demanded power P.sub.D for an operation of the pilotless aircraft, performing at least one of storing at least some of the electrical energy generated in at least one energy storage unit and utilizing said at least some of the electrical energy generated to assist the internal combustion engine by supplying an auxiliary power P.sub.A complementing a main power P.sub.t developed by the internal combustion engine, with P.sub.t less than P.sub.M, so that P.sub.A+P.sub.t=P.sub.D; f) in response to a determination that the maximum principal power P.sub.M is less than the demanded power P.sub.D for the operation of the pilotless aircraft, utilizing said at least some of the electrical energy generated to assist the internal combustion engine to provide the demanded power P.sub.D or utilizing at least some of the electrical energy stored in said at least one energy storage unit to assist the internal combustion engine to supply the demanded power P.sub.D; g) in response to a determination that the demanded power P.sub.D is greater than the sum of the maximum principal power P.sub.M developed by the internal combustion engine and the auxiliary power that can be supplied by said at least one energy storage unit, modifying the operation of the pilotless aircraft to supply the demanded power P.sub.D in accordance with one of the steps e) or f); and h) in response to a determination that the pilotless aircraft is on the ground and the internal combustion is stopped, supplying the demanded power P.sub.D to the pilotless aircraft utilizing said at least some of the electrical energy stored in said at least one storage unit.

2. Method according to claim 1, wherein the step of utilizing said at least some of the electrical energy stored in said at least one energy storage unit to assist the internal combustion engine in step e), further comprises the step of feeding at least one of a compressor of the internal combustion engine and an electric motor developing an auxiliary power P.sub.A.

3. Method according to claim 1, wherein the pilotless aircraft is a rotary wing aircraft; and further comprising the step of regulating the stored electrical energy to be at least equal to a recovery energy of the pilotless aircraft in the event of the internal combustion engine failure.

4. Method according to claim 3, wherein the pilotless aircraft comprises N electrical energy storage units, with N>1; and further comprising the step of adjusting a capacity of a first storage unit to be less than or equal to a threshold value Vs/N where Vs corresponds to the recovery energy of the pilotless aircraft in the event of the internal combustion engine failure, in response to a determination, in step f), that a sum of remaining capacities in other N1 storage units is greater than or equal to Vs.

5. Method according to claim 1, before the steps e) and f), further comprising the step determining a state of charge for each energy storage unit.

6. Method according to claim 5, wherein the pilotless aircraft is a rotary wing aircraft comprising N electrical energy storage units, with N>1; and further comprising the step of adjusting a capacity of a first storage unit to be less than or equal to a threshold value Vs/N where Vs corresponds to a recovery energy of the pilotless aircraft in the event of the internal combustion engine failure, in response to a determination, in step f), that a sum of remaining capacities in other N1 storage units is greater than or equal to Vs.

7. Method according to claim 1, wherein the pilotless aircraft is a rotary wing aircraft comprising at least two rotors; and further comprising the step of disengaging a mechanical coupling of each rotor to assure a free rotation of said at least two rotors and an autorotation of the pilotless aircraft in an event of the internal combustion engine failure.

8. Method according to claim 7, further comprising the step of supplying a demanded power to the pilotless aircraft to control a descent in the autorotation and landing of the pilotless aircraft in the event of the internal combustion engine failure utilizing said at least some of the electrical energy stored in said at least one storage unit.

9. Method according to claim 7, further comprising the step of automatically disengaging the mechanical coupling of said each rotor in the event of a stoppage of the internal combustion engine.

10. Method according to claim 9, further comprising the step of supplying a demanded power to the pilotless aircraft to control a descent in the autorotation and landing of the pilotless aircraft in the event of the internal combustion engine failure utilizing said at least some of the electrical energy stored in said at least one storage unit.

11. Method according to claim 1, wherein the step of modifying the operation of the pilotless aircraft comprises at least one of the following actions: reducing an altitude of the pilotless aircraft and modifying a speed of the pilotless aircraft.

12. Rotary wing pilotless aircraft, comprising: a supercharged internal combustion engine to drive a rotary wing system, the internal combustion engine comprises a first compressor, the internal combustion engine is configured to drive the rotary wing system and to supply a maximum principal power, which can vary, to assure at least the driving of the rotary wing system; and a recovery system to recover a thermal energy and convert the recovered thermal energy into an electrical energy, the recovery system comprises a collector to collect at least some of exhaust gases during an operation of the internal combustion engine, a turbine fed with the exhaust gases collected to convert an energy of the exhaust gases collected into a mechanical energy; and an electrical generator fed by the turbine to produce an electrical energy; at least one energy storage unit configured to store at least some of the electrical energy produced by the recovery system; a propulsion control unit configured to determine a maximum principal power P.sub.M supplied by the internal combustion engine at the time of a power demand P.sub.D and to manage generation of the electrical energy to meet the power demand as a function of the power demand to at least drive the rotary wing and the maximum power supplied by the internal combustion engine; wherein in response to a determination that the maximum principal power P.sub.M is at least equal to the power demand P.sub.D for an operation of the rotary wing pilotless aircraft, the propulsion control unit is configured to control at least one of the following: said at least one energy storage unit to store at least some of the electrical energy generated by the electrical generator, and the recovery system to utilize said at least some of the electrical energy generated by the electrical generator to assist the internal combustion engine by supplying an auxiliary power P.sub.A complementing a main power P.sub.t developed by the internal combustion engine, with P.sub.t less than P.sub.M, so that P.sub.A+P.sub.t=P.sub.D; wherein in response to a determination that the maximum principal power P.sub.M is less than the power demand P.sub.D for the operation of the rotary wing pilotless aircraft, the propulsion control is configured to control the recovery system to utilize said at least some of the electrical energy generated by the electrical generator to assist the internal combustion engine to provide the power demand P.sub.D, or said at least one energy storage unit to supply the auxiliary power P.sub.A to assist the internal combustion engine in supplying the power demand P.sub.D; wherein in response to a determination that the power demand P.sub.D is greater than the sum of the maximum principal power P.sub.M developed by the internal combustion engine and the auxiliary power that can be supplied by said at least one energy storage unit, the propulsion control unit is configured to modify the operation of the rotary wing pilotless aircraft to supply the power demand P.sub.D; and wherein in response to a determination that the rotary wing pilotless aircraft is on the ground and the internal combustion is stopped, the power demand P.sub.D is supplied to the rotary wing pilotless aircraft utilizing said at least some of the electrical energy stored in said at least one storage unit.

13. Rotary wing pilotless aircraft according to claim 12, wherein the internal combustion engine comprises a second compressor configured to be fed with the electrical energy from said at least one energy storage unit.

14. Rotary wing pilotless aircraft according to claim 12, further comprising a main gearbox connected to the internal combustion engine, and an electric motor configured to be fed with the electrical energy from said at least one energy storage unit, the electric motor is connected to the main gearbox.

15. Rotary wing pilotless aircraft according to claim 12, further comprising at least two rotors and a device to disengage a mechanical coupling of each rotor to assure a free rotation of said at least two rotors in an event of an internal combustion engine failure.

16. Rotary wing pilotless aircraft according to claim 12, further comprising a system to manage a state of charge of each energy storage unit to have available at all times a recovery energy of the rotary wing pilotless aircraft in the event of an internal combustion engine failure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages, objects and particular features of the present invention will emerge from the following description given by way of nonlimiting explanation only and with reference to the appended drawings, in which:

(2) FIG. 1 is a diagrammatic view of the decision tree used in accordance with one particular embodiment of the present invention by software in the propulsion control unit (PCU) to manage a power demand to assure the operation of a VTOL drone;

(3) FIG. 2 is a highly diagrammatic view of a hybrid power generation system drone in accordance with a first embodiment of the invention for a VTOL;

(4) FIG. 3 is a highly diagrammatic view of a hybrid power generation system in accordance with a second embodiment of the invention for a VTOL drone;

(5) FIG. 4 is a highly diagrammatic view of a hybrid power generation system in accordance with a third embodiment of the invention for a VTOL drone.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(6) It will first be noted that the figures are not to scale.

(7) FIG. 1 is a diagrammatic view of the decision tree used in accordance with one particular embodiment of the present invention by appropriate software in the propulsion control unit (PCU) to manage a power demand to assure the operation of a VTOL drone.

(8) That drone includes an energy storage unit the feeding of which with electrical energy and the output of this electrical energy to the driveshaft are managed by the propulsion control unit (PCU).

(9) This strategy for assuring the management of a power demand is described here in the form of a decision tree comprising five (5) tests and six (6) modes of operation.

(10) A first test (TEST 0) evaluates the operating status of the internal combustion engine by means of various sensors placed on it. If these sensors send signals indicating failure of the latter engine, a safe mode (MODE F) is triggered to provide additional electrical power directly from the energy storage unit in order to enable selection of assisted autorotation and a soft landing of the drone.

(11) The second test (TEST 1) verifies if the internal combustion engine is able to supply a maximum power at least equal to the power demanded to satisfy the demand: If yes, the internal combustion engine can, following a test (TEST 2) on the state of charge of the energy storage unit: be assisted by a system for recovery of thermal energy and conversion of that thermal energy into electrical energy, and thus function under the power demand to reduce its consumption (MODE A, SOC equal to the maximum limit), or supply all of the power demanded. The power recovered by the system for recovering thermal energy and converting that thermal energy into electrical energy at the level of the exhaust gases is then used to recharge the energy storage unit (MODE B, SOC less than the maximum limit). If the maximum power developed by the engine at the moment of the power demand is less than the power demanded, then: if the total combined power of the internal combustion engine at full load and the electrical energy obtained from the recovery of heat energy at the level of the exhaust gases is sufficient (TEST 3), the internal combustion engine is complemented by this electrical power generated by the system for recovering thermal energy and converting that thermal energy into electrical energy (MODE C), if the state of charge (SOC) of the energy storage unit is greater than a threshold value corresponding to a recovery energy of the drone in the event of failure of the engine and if the total combined power of the internal combustion engine at full load and that delivered by the energy storage unit is sufficient (TEST 4), the internal combustion engine is complemented by the electrical power delivered by the energy storage unit (MODE D), if TEST 4 fails, the drone switches to a safe mode aiming to reduce the power demand by a modification of the mission. This modification implies manoeuvres (descent, modification of speeds, etc.) reducing the power demand (MODE E).

(12) This mode is temporary and does not impose an emergency landing.

(13) This internal combustion engine being a piston engine, this system for recovering thermal energy and converting that thermal energy into electrical energy here comprises: means for collecting at least some of the exhaust gases when the internal combustion engine is operating and feeding a turbine directly with said exhaust gases collected in this way to convert the residual energy of these gases collected in this way into mechanical energy, and an electrical generator fed by this turbine to produce electrical energy.

(14) As shown in FIGS. 2 to 4, the electrical subsystem of the hybrid power generation system of the drone here comprises: an electric motor/alternator 10 operating at high speed (rotation speed of a turbo), an electric motor/alternator 11 connected to the mechanical transmission between the engine 12 and the main rotor 13, two AC/DC converters 14, 15, a DC/DC converter 16, an energy storage unit 17 comprising a plurality of batteries or supercapacitors for storing electrical energy and its control electronics making it possible to monitor the state of charge and of health of this electrical energy storage unit, a propulsion control unit (PCU) 18 making it possible to manage the flows of electrical energy as a function of the power demand and the state of charge of the battery.

(15) The electric motor/alternator 10 operating at high speed (rotation speed of a turbo) is able to supply mechanical power to or recover mechanical power from the turbocharger shaft of the diesel engine 12.

(16) The electric motor/alternator 11 connected to the mechanical transmission between the engine 12 and the main rotor 13 makes it possible to supply mechanical power to the rotors of the VTOL drone.

(17) The two AC/DC converters 14, 15 make it possible to convert direct current electrical power into alternating current electrical power and vice versa.

(18) The DC/DC converter 16 makes it possible to regulate the current feeding the energy storage unit during charging.

(19) The energy storage units 17 makes it possible to store or output electrical power to/from the electric motors/alternators.