METHOD FOR CONTROLLING AN ELECTRIC TURBOMACHINE WITH ACCELERATION TORQUE COMPENSATION

Abstract

A method for controlling an electric machine comprising a shaft coupled to a rotating, movable turbomachine body, the method comprising the steps of: from input data associated with a first instant, predicting an angular acceleration of the shaft at a second instant subsequent to the first instant, the input data at the first instant comprising: a rotational speed of the shaft at the first instant, and a fuel setpoint at the first instant; calculating an acceleration torque of the electric machine at the second instant from the angular acceleration of the shaft at the second instant; correcting a torque setpoint at the first instant by adding the acceleration torque at the second instant to the torque setpoint at the first instant, so as to produce a corrected torque setpoint at the first instant; and controlling the electric machine using the corrected torque setpoint at the first instant. Figure for the abstract: Fig. 5

Description

Title of the invention: METHOD FOR CONTROLLING AN ELECTRIC TURBOMACHINE WITH TORQUE COMPENSATION Technical field

[0001] This disclosure relates to the general field of electrical systems, and in particular the correction of control setpoints for hybrid turbomachine electrical systems, including torque or power controls of electrical machines. STATE OF THE ART

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its climate impact by employing sustainable development methods and minimizing greenhouse gas emissions. This sustained research and development work focuses in particular on new generations of aircraft engines and the development of the use of electric technologies for propulsion.

[0005] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft. Thus, it is possible to achieve a hybridization of the aircraft's propulsion system, and in particular of the turbomachine. This involves adding a hybrid electrical system forming an interface between the rotating mechanical shafts and the aircraft's electrical network.

[0006] More specifically, electric machines are used as needed, either in motor mode by applying mechanical power, or in generator mode by drawing power from the mechanical shafts of the turbomachine, based on commands issued by a control system (or FADEC, acronym for "Full Authority Digital Engine Control"). In the case of a twin-spool architecture, the mechanical shafts belong respectively to the high-pressure and low-pressure spools. In the case of a triple-spool architecture, the turbomachine also includes a mechanical shaft from the intermediate spool.

[0007] Previously, one solution for ensuring the aircraft's electrical power supply, or even for starting the turbomachine, consisted of using an integrated drive generator (IDG) decoupled from the mechanical shafts, or using a variable frequency generator (VFG) with low mechanical damping, thus placing significant stress on the mechanical chain. These two generators are not controlled by a command issued by the FADEC control system but by generator control units (GCUs) under the aircraft manufacturer's responsibility.

[0008] In the context of turbomachine hybridization, the control system's setpoint does not take into account the dynamics of the electric machine coupled to a rotating body (high-pressure or low-pressure mechanical shaft), and therefore the acceleration torque of the rotating electric machine beyond the turbomachine's ignition phase. In particular, there is a risk that the target transient operating conditions will not be achieved, for example during acceleration, or that the fuel injection control law will compensate for a lack of power / torque supplied by the electric machine. The turbomachine's transient operation is therefore not optimal and can lead to excessive fuel consumption. Description of the invention

[0009] One purpose of this disclosure is to improve the accuracy of the torque applied or extracted by the electric machine on the associated rotating body during the acceleration and deceleration phases of the turbomachine.

[0010] This objective is achieved by a method for controlling an electrical machine comprising a shaft coupled to a rotating, movable turbomachine body, comprising the following steps: Given input data associated with a first instant, predict the angular acceleration of the tree at a second instant subsequent to the first instant, the input data associated with the first instant including: • a rotational speed of the shaft at the first instant, and • a fuel instruction at the first moment; • calculation of an acceleration torque of the electric machine at the second instant from the angular acceleration of the shaft at the second instant; • Correction of a torque setpoint at the first instant by adding the acceleration torque at the second instant to the torque setpoint at the first instant, so as to produce a corrected torque setpoint at the first instant • control of the electric machine using the corrected torque setpoint at the first instant.

[0011] The proposed control method improves the accuracy of the setpoint supplied to the electric machine by taking into account the electric machine's acceleration in the setpoint calculation. This makes it possible to achieve a target torque or power on the turbomachine body from which the electric machine draws power or to which the electric machine supplies mechanical power, during turbomachine acceleration or deceleration phases in which the electric machine's acceleration is non-zero. Taking the predicted acceleration into account corrects the torque deviation present during the turbomachine's acceleration and deceleration phases. Thus, better monitoring of the target rotational speed during transient conditions is possible. This helps reduce the fuel overconsumption induced by the deviation from the setpoint set by the FADEC system during the turbomachine's acceleration and deceleration phases.

[0012] The proposed control method is implemented in the FADEC control unit already responsible for turbomachine control, and advantageously does not require the addition of specific sensors. In particular, it uses the rotational speed of the turbomachine shafts on which the electric machines performing the hybridization are installed, which is generally already used by the system to perform turbomachine control.

[0013] Moreover, the solution can easily be implemented in software at the level of the control computer (such as the FADEC) without it being necessary to modify the control at the level of the hybrid electrical system.

[0014] The invention is advantageously complemented by the following features, taken individually or in any of their technically possible combinations:

[0015] - the input data associated with the first instant further include the instruction of a couple at the very first moment;

[0016] - the input data associated with the first instant include conditions of flight ;

[0017] - the input data associated with the first instant further include at least a positioning instruction among: • a setting instruction for a variable-pitch turbine blade of the turbomachine, • a positioning instruction for a discharge valve of the movable turbomachine between an open position and a closed position, and • a positioning instruction for a variable section nozzle;

[0018] - the angular acceleration at the second instant is predicted using a tabulated law previously calculated and taking as input the rotation speed of the shaft at the first instant and the fuel setpoint at the first instant, the tabulated law also preferably taking as input the flight conditions of the turbomachine;

[0019] - the angular acceleration at the second instant is predicted using a model thermodynamics of the turbomachine taking as input the rotational speed of the shaft at the first instant and the fuel setpoint at the first instant, the thermodynamic model also preferably taking as input the flight conditions of the turbomachine. ;

[0020] - the acceleration torque of the electric machine is calculated as a product between the angular acceleration at the second instant and an inertia of the tree;

[0021] - the acceleration torque of the electric machine is calculated as a product between the estimation of the angular acceleration at the second instant and a cumulative inertia of the shaft and a mechanical chain coupling the shaft to the turbomachine body.

[0022] According to another aspect, a computer program product is proposed comprising program code instructions for the execution of the steps of the process described above, when this program is executed by a computer.

[0023] According to another aspect, an aircraft is proposed comprising an electric machine and a computer configured to implement a method for controlling the electric machine. DESCRIPTION OF THE FIGURES

[0024] Other features, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0025] Fig. 1 is a diagram representing a cross-sectional view of a turbomachine.

[0026] Fig. 2 is a schematic representation of a hybrid electrical system.

[0027] Figure 3 is a schematic representation of the interface between machines electrical and mechanical shafts of the turbomachine.

[0028] Fig. 4 schematically illustrates the difference between the torque setpoint supplied to the electric machine and the torque measured in transient regime.

[0029] The [Fig.5] is a flowchart of steps of a control process according to an embodiment of the invention.

[0030] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0031] Description of the turbomachine

[0032] Figure 1 schematically represents a cross-section of a propulsion unit 1 in a plane containing a longitudinal axis X. The propulsion unit 1 is intended to be mounted on an aircraft 100, via a pylon (not shown). The propulsion unit 1 comprises the turbomachine 10 and a nacelle 20 surrounding the turbomachine 10.

[0033] The turbomachine 10 comprises, from upstream to downstream in the direction of the gas flow, a blower 11, a compression section 16 comprising a low pressure compressor 161 and a high pressure compressor 162, a combustion chamber 14, an expansion section 15 comprising a high pressure turbine 152 and a low pressure turbine 151, and an exhaust casing.

[0034] Each of the low-pressure compressor 161, high-pressure compressor 162, high-pressure turbine 152, and low-pressure turbine 151 comprises a rotor portion and a stator portion, the rotor portion being capable of being driven in rotation relative to the stator portion about the longitudinal axis X. The blower 11, the rotor portion of the low-pressure compressor 161, and the rotor portion of the low-pressure turbine 151 are connected to each other by a low-pressure shaft 181 extending along the longitudinal axis X, thus forming a low-pressure body (LP body), which is a first rotating body. The rotor portion of the high-pressure compressor 162 and the rotor portion of the high-pressure turbine 152 are connected to each other by a high-pressure shaft 182 also extending along the longitudinal axis X, around the low-pressure shaft 181, thus forming a high-pressure body (HP body), which is a second rotating body. As seen in the [Fig.[l], the compression section 16, the combustion chamber 14 and the expansion section 15 are surrounded by an engine casing 21, to which are connected the stator parts of the low pressure compressor 161, the high pressure compressor 162, the high pressure turbine 152 and the low pressure turbine 151. The engine casing 21 delimits a primary channel 13 allowing the flow of a primary gas stream A. A secondary channel 12 allows the flow of a secondary gas stream B.

[0035] The longitudinal axis X defines the axis of rotation of the blower 11, of the rotor parts of the compression section 16 and of the rotor parts of the expansion section 15, in other words of the LP body and the HP body.

[0036] Aircraft electrical system

[0037] This disclosure falls more generally within the context of the internal hybridization of the turbomachine 10, that is to say, having an electrical system interfacing with the low-pressure and high-pressure shafts 181, 182 of the turbomachine 10. The hybrid electrical system in generator operation makes it possible to extract mechanical power from the rotating HP, BP moving bodies, and to convert it into electrical power to supply the electrical network of the aircraft 100. The electrical system 3 in motor operation makes it possible to provide mechanical power to the rotating bodies, in particular to assist the starting of the turbomachine 10.

[0038] Typically, each of the two rotating HP,BP bodies is associated with a respective electrical machine 31, 32. The electrical machines 31, 32 can be connected to a distribution bus allowing the various electrical systems or electrical loads of the aircraft 100 to be supplied via an electrical network, including external electrical loads specific to the aircraft 100 allowing to ensure a number of functionalities, when the aircraft 100 is in flight or in operation on the ground (heating and / or air conditioning system, compressor...) or internal loads specific to the turbomachine 10 (starter, variable geometries, de-icing systems...).

[0039] In the illustrated embodiment, the low pressure body BP is connected to the generator 31 of the low pressure shaft 181, and the high pressure body HP is connected to the generator 32, coupled to the accessory housing of the high pressure shaft 182.

[0040] This disclosure is not limited to a twin-spool, twin-flow turbofan engine with direct fan drive 11 as illustrated, and extends more generally to various turbofan engine architectures. More generally, this disclosure extends to any turbomachinery architecture 10 comprising an electric machine coupled to a rotating body, in particular to the low-pressure shaft 181 and / or the high-pressure shaft 182. For example, one could consider a turbomachinery 10 comprising an HP body, a LP body, and an intermediate rotating body, each body being associated with its respective electric machine.

[0041] With reference to [Fig.2], each electrical source 31,32 is associated with a control unit 310,320. Each control unit (or local controller) 310,320 is configured to control the associated electrical machine 31,32.

[0042] The FADEC control system includes a computer 4 (or EEC, "electric engine controller") configured to provide turbomachine regulation. Specifically, the FADEC is responsible for fuel regulation, variable geometry control, and generating the electromagnetic torque setpoint for the electric machines 31, 32. This is referred to as torque regulation, although power regulation is also possible, through the conversion of the power setpoint into a setpoint. The torque can be obtained by multiplying the power setpoint by a gain corresponding to the inverse of the rotational speed of the electrical machine, as will be seen later. Using a power setpoint has the advantage of being better suited to mechanical considerations related to rotating HP and LP components.

[0043] The computer 4 includes any processor, which may have one or more cores for performing calculations in parallel. It may be, for example, an FPGA, an ASIC, a DSP, or any other type of electronic circuit. The computer 4 includes a memory configured to store data, for example, received measurements or calculated setpoints, and an embedded algorithm to be executed by the processor. The memory is of any type and includes, for example, an integrated circuit such as random access memory (RAM) and read-only memory (ROM).

[0044] As will be detailed later, the correction of the torque setpoint by the control unit 4 can be performed exclusively within the software implemented by the control unit 4, and does not require the addition of new sensors. Indeed, the rotational speed sensors of the turbomachine shafts (image of the shaft speed of the electrical machines 31, 32) are conventionally used.

[0045] With reference to Figure 2, the electric machine 31 is controlled by the control unit 310, and the electric machine 32 is controlled by the control unit 320. For example, the control unit 310, 320 is designed to regulate the electric current supplied to the electric machine 31, 32 by a G1732- Current control. The current control / 3^ / 32 can correspond to the phase currents enabling the associated electric machine 31, 32 to reach a target rotational speed, particularly at start-up, or to supply or draw a target mechanical power from the coupled mechanical shaft. In the case of a three-phase electric machine, the supply is made via three phases calculated by the control unit 310, 320 from the supplied setpoint.

[0046] In the context of hybridization, the control units 310, 320 of the electrical machines 31, 32 connected respectively to the BP and HP bodies receive a corrected torque setpoint C^cor- As explained previously, the local controller 310, 320 is configured to calculate phase currents of the associated electrical machine 31, 32 from the current command J31 / 32 calculated according to the corrected torque setpoint from the computer 4. The unit of Control unit 310,320 typically includes its own processor, that is, separate from computer 4. The processor of control unit 310,320 can be arbitrary. It may have a higher sampling rate than the processor of computer 4.

[0047] As is known per se, the rotational speed of the rotating moving bodies HP, BP, and therefore the acceleration of the turbomachine 10, depends on at least one acceleration contributor. An "acceleration contributor" is understood to be a component of the turbomachine 10 controlled by a setpoint from the computer 4, and configured to modify the rotational speed, and therefore the angular acceleration, of the shaft of the electric machine 31, 32 using the setpoint.

[0048] In the illustrated embodiment, the turbomachine includes a fuel metering unit 40. The fuel metering unit 40 is configured to inject the quantity of fuel according to a fuel setpoint CCarb calculated by the computer 4. The quantity of fuel injected into the combustion chamber 14 has an impact on the mechanical power received by the turbomachine shaft 181, 182, and contributes to accelerating or decelerating the rotation of the shaft of the electric machine 31, 32. More specifically, the computer 4 is configured to calculate the fuel setpoint CCarb, i.e., the quantity of fuel injected, to satisfy a target engine speed, or acceleration rate.

[0049] The turbomachine 10 preferably includes variable geometries. Variable geometries are components whose geometry can be modified. The control unit 4 is configured to control the position of the variable geometries. This allows the operability of the turbomachine 10 to be modulated and therefore influences the rotational speed of the high-pressure (HP) and low-pressure (LP) components. The presence and number of variable geometries vary between different turbomachine applications. The turbomachine 10 includes, for example, variable-pitch blades, and / or cooling valves, and / or variable-area nozzles.

[0050] In this embodiment, the associated input data includes at least one Cpos positioning instruction from among: • a setting instruction for a variable-pitch turbine blade of the turbomachine, • a positioning instruction for a discharge valve of the movable turbomachine between an open position and a closed position, and • a positioning instruction for a variable section nozzle.

[0051] More generally, the input data may include an evolution of the position of the variable geometries between times t and t+dt.

[0052] Thus, the computer 4 can be configured to control, using a positioning setpoint Cpos, electromechanical or hydraulic actuators 41 in order to adjust the orientation of the variable-pitch turbine blades 151, 152 and / or compressors 161, 162 of the LP and HP casings. This allows the rotational speed of the HP and LP casings to be modulated and improves the performance of the turbomachine 10. Similarly, the actuators 41 can modify the geometry of the valves of discharges or nozzles with variable cross-section based on the positioning setpoint Cpos. The presence of variable geometries is optional.

[0053] The computer 4 can be configured to regulate the electrical machines 31,32 and the torque contributors as a function of the angular rotation speed o;3h a'32 of the shafts of the electrical machines 31,32 and external data transmitted by sensors of the aircraft and reflecting for example flight conditions.

[0054] Mechanical chain

[0055] Fig. 3 schematically illustrates a mechanical chain coupling the low pressure body BP and the electric machine 31. A mechanical chain with the same characteristics can couple the high pressure body HP and the electric machine 32. The mechanical chain can be generalized to any other coupling between a turbomachine body and an electric machine, for example in a triple-body architecture.

[0056] Typically, the mechanical chain can include a RED reducer, that is to say a gear system whose transmission ratio is less than 1. The RED reducer is configured to increase the motor torque at the output of the electric machine 31 and reduce the rotational speed w3i of the shaft 311 of the electric machine 31.

[0057] The mechanical chain may include a sensor 5 configured to measure the torque exerted by the shaft of the electric machine 31 on the low-pressure shaft 181. The presence of the torque meter 51 is optional, as the proposed control method does not use torque measurement. The sensor 5 is, for example, a torque meter located on the shaft 311 of the electric machine 31. The torque Cmes measured by the sensor 5 also corresponds to the opposite of the torque CBP exerted by the low-pressure shaft 181 on the shaft of the electric machine 31. The optional implementation of this measurement allows the computer 4 to detect mechanical failures or to evaluate the impact of the issued torque command. The measured torque information can also be used to obtain an estimate of the rotational speed W31 of the shaft 311 of the electric machine 31 by an observer, as will be detailed later.

[0058] Conventionally, the mechanical chain includes a sensor 5 configured to provide a measurement of the rotational speed of the low-pressure shaft, a direct image of the rotational speed W31 of the shaft 311 of the electric machine 31, to the computer 4. The sensor 5 can be configured to directly measure the rotational speed ^32 of the shaft of the electric machine 31,32. Alternatively or complementarily, the sensor 5 can include a resolver using an angular position measurement of the shaft of the electric machine 31,32 and a phase-locked loop to obtain the rotational speed Crr (';32 •

[0059] The mechanical chain may also include at least one accessory gearbox or relay (“Accessory gear box” or AGB in Anglo-Saxon terminology), typically housed in a cavity within the nacelle 20. The AGB accessory relay includes a set of gears enabling the rotation of a plurality of shafts around their own axis, and accessories mounted on the plurality of shafts to derive useful mechanical power from their rotation.

[0060] As explained previously, the description will henceforth be limited to the case of a torque setpoint. The invention extends more broadly to a power setpoint, the same principles applying.

[0061] Determination of the acceleration torque of the electric machine

[0062] Applying the fundamental principle of dynamics to the electrical machine 31 allows us to obtain the acceleration torque seen by the electrical machine 31 as the difference between the sum of the torque setpoint C31 provided by the computer 4 and the torque CBP exerted by the low-pressure shaft 181 on the shaft of the electrical machine 31, and the resistive torque Cres experienced by the electrical machine 31:

[0063] _ j ç , ç C , — « / 31 dt — '-'BP '-'res

[0064] with J the inertia of the rotor of the electric machine 31 in kg.m2, ^21 dt the angular acceleration of the shaft of the electric machine 31 in rad.s2, the torques ace,3b ^-res being in Nm.

[0065] An uncorrected instruction provided by the computer 4 to the control unit 310 would be equivalent to the torque term C3b within the limit of the accuracy of the hybrid electrical system, and would not take into account the angular acceleration of the electric machine 31.

[0066] Symmetrically, we have

[0067] cfccc ^00-,32- J 32 dt ~

[0068] with J2,2 the inertia of the rotor of the electric machine 32 in kg.m2, and dœ32 dt the angular acceleration of the shaft of the electric machine 32 in rad.s2.

[0069] Advantageously, the setpoint provided by the computer 4 to the electric machine 31,32 takes into account the acceleration torque Cücc32 of the electric machine shaft 31,32. Indeed, in transient regime, or when the rotational speed of the turbomachine shaft is not constant, the angular acceleration of the body HP, BP and therefore of the angular acceleration ^32 of the machine shaft dt dt The electrical resistance 31,32 is non-zero, so the acceleration torque Cacc3}, Cacc32 is non-negligible. This allows for compensation of deviations of several Newton-meters (for a torque setpoint) or kilowatts (for a power setpoint), which could cause excessive fuel consumption, in order to compensate for the discrepancy and reach the target transient operating conditions.

[0070] This difference is illustrated in Figure 4. The evolution of the torque command provided by the computer 4 and the measured torque Cmes are shown. The difference in steady-state operation, in which the acceleration of the shaft of the electric machine 31 is zero, corresponds to the resistive torque. The resistive torque Cres is generally evaluated on a test bench, so that the FADEC control system can store in memory a lookup table determining the resistive torque Cres as a function of the engine speed, to be taken into account in the calculation of the torque setpoint.

[0071] Control method

[0072] According to one aspect, an aircraft is proposed comprising an electric machine 31,32 and a computer 4 configured to implement a method of controlling the electric machine 31,32, described hereafter for the control of the electric machine 31 coupled to the BP body.

[0073] The described control method can, however, be applied indifferently to the electric machine 32 coupled to the HP body or preferably to the two electric machines 31, 32 of the turbomachine 10. More generally, the control method can be applied to any number of electric machines coupled to rotating moving bodies, so as to extract or supply mechanical power on the associated shaft.

[0074] The basic principle of the proposed control method is to calculate, at each instant t, a predictive estimate of the angular acceleration of the turbomachine body HP,BP that will occur between instant t and a future instant t + ôt, ôt constituting a time step generally of several ms, for example between 2 ms and 20 ms. The estimate of the angular acceleration is then used to correct the torque setpoint calculated by computer 4 in a predictive manner.

[0075] The computer 4 calculates the fuel setpoint C^j, at the first instant t for the fuel metering device 40. Typically, the computer 4 implements a scheduling defining a main contributor to the acceleration, here the fuel metering device 40.

[0076] As explained previously, the angular acceleration of the turbomachine 10 depends both on the electric machine 31, 32 coupled to the turbomachine shaft 181, 182, and on one or more acceleration contributors. More specifically, the computer 4 can collect the contribution of the sub-assemblies contributing to the acceleration.

[0077] Preferably, the computer 4 also calculates the uncorrected torque setpoint C31, C32 for the electric machine 31, 32. This allows the contribution of the electric machine 31, 32 to the acceleration to be taken into account. Typically, the computer 4 develops the uncorrected torque setpoint C31 for acceleration for the electric machine 31 coupled to the BP body at the first instant t. In the embodiment where the electrical system 3 includes an electric machine 32 coupled to the HP body, the calculator 4 also develops the uncorrected torque setpoint C32 for the electric machine 32 coupled to the HP body at the first instant t.

[0078] Preferably, the computer 4 develops the positioning setpoint Cpos at the first instant t, in order to control a change of orientation of a variable geometry using the setpoint Cpos.

[0079] Preferably, the computer 4 determines a compensation of the electrical system 3 for the acceleration of the turbomachine 10 at the first instant t. To this end, the computer 4 can implement a simplified model of the dynamics of the electrical system 3, such as, for example, an internal compensation of the electrical system 3 that would be impacted by the acceleration of the shaft of the electric machine 31, 32. For example, in an embodiment where the electrical system 3 is configured to regulate the turbomachine 10 by implementing active compensation (or "active dumping" according to Anglo-Saxon terminology) of the torsion mode by angularly shifting a portion of the shaft, the computer 4 is configured to quantify the impact of the compensation on the angular acceleration. Such dt > dt ' The compensation can be calculated by the computer 4 and corresponds to a torque setpoint correction for the electrical machine 31, 32, injected in opposite phase to the rotational speed disturbance. This correction prevents sustained torque and speed oscillations in the mechanical chain of the shaft 311, 312, which can lead to wear or breakage of the components.

[0080] At the first instant t, the computer 4 also has access to the rotational speed w3b^32 of the shaft of the electric machine 31,32. As explained previously, the sensor 51,52 can provide the computer 4 with the rotational speed w32 of the shaft measured at the first instant t. Typically, the acquisition of the measurement by the sensor 51,52 is sufficiently rapid so as to be representative of an acceleration or deceleration of the turbomachine 10. By "sufficiently rapid" it is meant that the sensor 51,52 is configured to perform a measurement at a frequency equal to or greater than the cycle time of the EEC 4. This allows the computer 4 of the FADEC control system to perform the phase-lead correction.

[0081] Alternatively or complementarily, the computer 4 can implement an observer configured to estimate the rotational speed (<;32) of the shaft at the first instant t. Typically, the observer takes into account a model of the dynamics of the turbomachine 10 and the setpoints provided / 31, / 32 at the input of the electric machine 31,32, or the torque measured Cmes by the torque meter 51 at the first instant. The observer is, for example, a Kalman filter or a Luenberger-type observer.

[0082] Preferably, the computer 4 performs frequency filtering of the measured or estimated rotational speed 0.3i' a'32. This filtering advantageously limits abrupt variations due to measurement noise. The type of filter chosen results from a compromise between the tolerable noise level, the response time, and the ability to integrate it (in the case of an analog filter, i.e., an electronic solution) or implement it (in the case of a digital filter, i.e., a software solution). The filter can be a low-pass type, for example, a first-order low-pass filter, with a cutoff frequency below 1 kHz, typically on the order of 100 Hz.

[0083] Thus, the computer 4 has access to a plurality of input data associated with the first instant t, including at least the rotation speed ^31' œ32 of the shaft at the first instant t, and the fuel setpoint Ccarb at the first instant t.

[0084] During a step SI, the computer 4 predicts the angular acceleration ^31 ^£32 of the shaft of the electric machine 31,32 at a second instant t + ôt dt , dt subsequent to the first instant t. In other words, the calculator 4 is configured to estimate the acceleration or deceleration of the rotating shafts of the electrical machines 31,32 between the first instant t and the second instant t + ôt. Hereafter, a quantity "at the second instant" will be designated interchangeably as the quantity "predicted between the current instant t and the following instant t+ôt".

[0085] The future angular acceleration ^M3i ^31 of the tree is predicted from the data dt ' dt input data associated with time t. Preferably, the input data include the uncorrected torque setpoint C31, C32 at the first time t, and / or the positioning setpoint Cpos at the first time t, and / or the compensation of the electrical system 3 to the acceleration of the turbomachine 10 at the first time t.

[0086] The input data may also include external information such as flight conditions. Flight conditions include, in particular, the altitude, speed, and ambient temperature of the aircraft on which the turbomachine 10 is mounted. External information may include static pressure, total pressure, and / or temperature measurements taken by sensors on the aircraft and transmitted to the computer 4 by the electrical system 3. Such information is typically used by the FADEC control system.

[0087] Calculator 4 can predict the angular acceleration ^£31. ^32 according to several dt ' dt methods of implementation.

[0088] For example, the computer 4 can store in memory a nomogram linking a turbomachine operating speed to the fuel setpoint Ccarb, and preferably to the flight conditions. More precisely, the nomogram is a previously calculated tabulated law and taking inputs the rotation speed ^31' ü,32 of the shaft at the first instant and the fuel setpoint CCarb at the first instant.

[0089] Such a tabulated law can be obtained on a turbomachine test bench during a test campaign, result from flight tests, or result from numerical simulations. The prediction of the angular acceleration ^31 of the shaft by dt, dt The turbomachine at the next time step then uses the tabulated law. This embodiment has the advantage of being computationally inexpensive, as the computer 4 simply performs a lookup in the nomogram to obtain the prediction of the angular acceleration from the input data.

[0090] Similar nomograms are classically implemented in computer 4 and used for calculating uncorrected setpoints.

[0091] Preferably, the computer 4 can implement a thermodynamic model of the turbomachine 10 taking as input the rotational speed of the shaft at the first instant and the fuel setpoint at the first instant t. The angular acceleration at the second instant is then predicted using the thermodynamic model of the turbomachine from the input data.

[0092] The thermodynamic model allows for a simplified simulation of the transient regime of the turbomachine 10, taking into account a number of parameters (in particular flight conditions) and components of the turbomachine (in particular the presence of variable-pitch blades or other variable geometries and possibly their positioning). The thermodynamic model is then embedded in the computer 4. Its implementation requires greater computing power from the processor of the computer 4 than the use of the tabulated law, but allows for a more precise prediction of the angular acceleration.

[0093] More generally, the thermodynamic model and the tabulated law can take as input the different contributions to the acceleration at the first instant, typically the uncorrected torque setpoint at the first instant t, and / or the positioning setpoint at the first instant t, to provide as output the estimate of the angular acceleration of the shaft at the second instant t+ôt.

[0094] Preferably, the thermodynamic model or the tabulated law takes into account the flight conditions for determining the angular acceleration at the second instant t+ôt. This allows for a better prediction of the angular acceleration, since the impact, for example, of the fuel setpoint Ccarb or the available electrical power depends on it.

[0095] During a step S2, the computer 4 calculates, from the angular acceleration 4¾ d-: the shaft at the second instant t+ôt, the acceleration torque dt 5 dt Cacc3\, Cacc32 of the electrical machine 31,32.

[0096] In one embodiment, the computer 4 determines the acceleration torque Cacdb ^acc32 of the electric machine 31,32 by performing the product between the inertia of the electric machine shaft}iot, and the prediction of the turbomachine shaft acceleration at the second instant t+ôt, that is, the shaft acceleration between the current instant t and the second instant t+ôt. The inertia of the electric machine shaft JJsitôt Pcut may be equal to the inertia of the electric machine rotor J3 ], or it may be equal to the sum of the inertias of the electric machine rotor, the gearbox RED, and the shaft between the gearbox and the accessory relay AGB.

[0097] For example, the acceleration torque of the electric machine 31 is calculated by r — r^221 and the acceleration torque of the electric machine 32 is calculated by Jn / ot dt by r „ J . ^110:32 J As soon as dt

[0098] Preferably, the computer 4 determines the acceleration torque C«aG2 of the electric machine 31,32 by multiplying the angular acceleration between times t and t+ôt by the inertia of the electric machines. Optionally, the computer 4 can add the inertia of the shaft of the electric machines and the mechanical chains on which they are mounted so as to compensate for the overall inertia seen by the turbomachine bodies, for example, the HP, BP bodies. Thus, the resulting inertia, called the cumulative inertia JBP, JHP, is greater than the inertia of the electric machine rotor and takes into account the inertia of other elements of the mechanical chain, in particular the inertia of the AGB accessory relay. Thus, the computer 4 compensates for all the inertia provided by the entire mechanical chain and not only the inertia of the rotor of the electric machine 31,32.

[0099] During a step S3, the computer 4 determines the acceleration-corrected torque setpoint C^cor for the electric machine 31, 32 mounted on the BP body and on the HP body, respectively. In other words, the computer 4 corrects the uncorrected torque setpoint at the first instant C31, C32 using the acceleration torque Caccs^ Caccs2 calculated from the predicted angular acceleration between instants t and t+ôt, and therefore anticipated, i.e., calculated predictively between the first instant t and the second instant t+ôt, so as to produce a corrected torque setpoint at the first instant Cy^or-

[0100] More precisely, the calculator 4 adds the torque setpoint C3j, C32 calculated at the first instant t and the acceleration torque C^.3 [, C^.32 calculated predictively between t and t+ôt as seen by the electrical machine 31,32. In the illustrated case including two electrical machines 31,32, we then have = C31+ ct ^*3 2,cor — accJiP'

[0101] The computer 4 then transmits the corrected torque setpoint C^or C^or to the control unit 310,320 via the electrical system 3 from the first instant t. Preferably, the computer 4 also sends the corrected setpoint C^cor to the electrical system in charge of the hybridization.

[0102] During a step S4, the control unit 310, 320 controls the associated electric machine 31, 32 using the corrected torque setpoint at the first instant t, C3 jTOr C^or, from the FADEC system. The control unit 310, 320 calculates the setpoint / 32 so that the electric machine 31, 32 coupled to the body BP, HP respectively is controlled according to the corrected torque setpoint ^32, w

[0103] Thus, at each time step, the electrical system 3 is controlled by the computer 4, taking into account the acceleration of the turbomachine 10 between the current time t and the next calculation step at t+early. The compensation of the acceleration torque by the computer 4 proposed in this disclosure improves the accuracy of the torque applied by the hybrid electrical system 3 during the accelerations or decelerations of the turbomachine 10. This allows for better tracking of the trajectory or target speed during transient conditions. This helps to reduce the fuel overconsumption induced by the compensation performed by the fuel metering unit 40 to reach the set target.

[0104] According to another aspect, a computer program product is proposed comprising program code instructions for the execution of the steps of the process as described above, when this program is executed by a computer 4.

Claims

Demands

1. Method of controlling an electric machine (31,32) comprising a shaft coupled to a rotating movable turbomachine body (HP, BP), the method comprising steps of: • from input data associated with a first instant, predicting an angular acceleration of the shaft (^^■31 ^32 ) at a second instant subsequent to the first instant, the input data associated with the first instant comprising: • a rotational speed of the shaft (°hi' w32) at the first instant, and • a fuel setpoint (Ccarb) at the first instant; • calculation of an acceleration torque (Cacc31, Cacc32) of the electrical machine (31,32) at the second instant from the angular acceleration of the shaft l'1"' ) at the second instant; • correction of a torque setpoint (C3], C32) at the first instant by adding the acceleration torque (Cacc3 b ^aec.32) at the second instant to the torque setpoint at the first instant (C31, C32), so as to produce a corrected torque setpoint at the first instant (G 3 Leon ^32for) • control of the electrical machine (31,32) using the corrected torque setpoint at the first instant ( ^3 Leon 3 2,cor) ■.

2. A control method according to claim 1, wherein the input data associated with the first instant further include the torque setpoint (C31, C32) at the first instant.

3. A control method according to any one of claims 1 and 2, wherein the input data associated with the first instant include flight conditions.

4. A control method according to any one of claims 1 to 3, wherein the input data associated with the first instant in addition include at least one positioning setpoint (Cpos) from among: • a setting setpoint for a variable pitch turbine blade, • a setting setpoint for a movable turbomachine discharge valve between an open position and a closed position, and • a setting setpoint for a variable area nozzle.

5. A control method according to any one of claims 1 to 4, wherein the angular acceleration of the shaft (^m ) at the second instant is predicted using a tabulated law previously calculated and taking as input the rotational speed of the shaft ( w32) at the first instant and the fuel setpoint (CCarb) at the first instant, the tabulated law also preferably taking as input flight conditions.

6. A control method according to any one of claims 1 to 4, wherein the angular acceleration at the second instant is predicted using a thermodynamic model of the turbomachine taking as input the rotational speed of the shaft (w3b at the first instant and the fuel setpoint (Q«f / >) at the first instant, the thermodynamic model also preferably taking as input flight conditions.

7. A control method according to any one of claims 1 to 6, wherein the acceleration torque Cücct,2 ) of the electric machine (31,32) is calculated as a product between the angular acceleration of the shaft (^21 at the second instant and dt ' dt an inertia of the shaft ( rj YJ 3 Mot 32iot /

8. A control method according to any one of claims 1 to 6, wherein the acceleration torque ], Cacc32 ) of the electric machine (31,32) is calculated as a product between the angular acceleration of the shaft ) at the second instant dt ' dt and a cumulative inertia of the shaft and of a mechanical chain coupling the shaft to the turbomachine body (HP, BP).

9. Product computer program comprising program code instructions for carrying out the steps of the process according to any one of claims 1 to 8, when this program is executed by a computer (4).

10. Aircraft comprising an electric machine and a computer configured to implement the method of controlling the electric machine according to any one of claims 1 to 8.