Method for measuring the power of a turbomachine's blower using modeling

Abstract

One aspect of the invention relates to a method for measuring the power of the fan of a turbomachine comprising a drive shaft and a fan shaft, and in particular a method for measuring fan power using only one sensor from among a fan shaft speed sensor and a drive shaft speed sensor, the other speed being modeled from the measurement of the first speed. Figure to be published with the abstract: Figure 5

Description

Title of the invention: Method for measuring the power of a turbomachine blower by modeling. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of the control of turbomachinery.

[0002] The present invention relates to a method for measuring the power of a blower of a turbomachine comprising a drive shaft and a blower shaft and in particular a method for measuring power using only one sensor from among a drive shaft speed sensor and a blower shaft speed sensor. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Measuring the thrust of a turbomachine installed on an aircraft is complex. Traditionally, certain parameters of the turbomachine are used to estimate this thrust.

[0004] A known aircraft turbomachine includes, for example, an engine, a fan, and a gearbox. The engine includes at least one turbine and one compressor connected by a drive shaft, also called a turbine-compressor connecting shaft.

[0005] The turbine and compressor can be in several parts, for example in two parts, comprising a low pressure turbine and a high pressure turbine, and a high pressure compressor and a low pressure compressor.

[0006] The fan is a rotor comprising a plurality of blades, located upstream of the engine in the turbomachine. Its main role is to draw in ambient air and compress it. Part of the compressed air is then directed to the subsequent stages of the turbomachine, while the other part is ejected into the atmosphere through the engine's secondary nozzle.

[0007] The reduction gear is a gearbox comprising a solar element, several planetary elements, a ring gear, and a planet carrier. The solar element meshes with the planetary elements, and the planetary elements mesh with the ring gear. Each planetary element is rotatably mounted on the planet carrier. The drive shaft is designed to drive the solar element, and the planet carrier or the ring gear is configured to drive the blower via a blower shaft. The component of the planet carrier and the ring gear that does not drive the blower shaft is fixed to a static structure. This static structure thus limits the rotational movement of the component fixed to it.

[0008] Such a turbomachine is described for example in EP3623607B1 “APPLIANCE AND METHOD FOR MEASURING THE THRUST OF A GAS TURBINE ENGINE WITH REDUCED GEARBOX.”

[0009] In such a turbomachine, the thrust is measured using at least three sensors: • A force sensor, measuring the force applied to the static structure of the reducer by the element attached to it, • A speed sensor measuring the engine shaft speed (also called "LPC speed" for "Low Pressure Compressor"), • A speed sensor measuring the speed of the blower shaft (also called "Fan speed").

[0010] The data from these three sensors are transmitted to a processor, configured to determine the thrust.

[0011] To determine the turbomachine thrust, the processor must first determine the torque on the stationary part of the gearbox, based on the force measurement received from the force sensor. The processor then determines the torque applied to the fan using the motor shaft speed, the fan speed, and the torque on the stationary part of the gearbox calculated in the previous step. Finally, the processor determines the fan power from the torque applied to the fan and the measured fan speed, and then the thrust from the fan power and the flight conditions.

[0012] When one of the two speed sensors fails, for example when it breaks or when its measurement no longer corresponds to the actual speed, the measured thrust no longer corresponds to the actual thrust, and this can lead the engine control processor to make unnecessary thrust adjustments, potentially compromising the proper operation of the turbomachine. In some cases, when the speed sensor is no longer functional, it is no longer possible to obtain turbomachine thrust.

[0013] There is therefore a need to be able to obtain a reliable measurement of the turbomachine's blower power in the event of failure of one of the two sensors among the central shaft speed sensor and the turbine shaft speed sensor, the blower power then allowing the thrust to be obtained. Summary of the invention

[0014] The invention offers a solution to the problems mentioned above, by allowing a power measurement of a blower based on a measurement model of the faulty sensor from the measurement of the functional sensor.

[0015] One aspect of the invention thus relates to a computer-implemented method for measuring the power of a fan of an aircraft turbomachine, the turbomachine comprising at least: • The blower located upstream of an engine, • The engine, comprising at least: • a turbine, • a compressor, • a drive shaft connecting the turbine and the compressor, • A gearbox receiving an input from the drive shaft and transmitting an output drive to the blower via a blower shaft, so as to drive the blower at a rotational speed lower than that of the drive shaft, the gearbox comprising a sun gear, a plurality of satellite gears, a ring gear and a planet carrier, the sun gear meshing with the satellite gears and the satellite gears meshing with the ring gear, each satellite gear being rotatably mounted on the planet carrier, the drive shaft being arranged to drive the sun gear, one element of the planet carrier and the ring gear being arranged to drive the blower via the blower shaft, the other element of the ring gear and the planet carrier being mounted in a static structure, the static structure being arranged to limit the rotational movement of the other element, • A force sensor configured to measure the force applied by the other element on the static structure, • A speed sensor for the first shaft, either the drive shaft or the blower shaft, • the process comprising: • Receive the force measured by the force sensor, • Receive the speed of the first shaft measured by the speed sensor, • Calculate the speed of a second shaft, either the drive shaft or the blower shaft, based on the measured speed of the first shaft and a numerical model of the second shaft's speed. • Calculate the power of the blower from the force received, the speed of the first shaft received and the speed of the second shaft calculated.

[0016] The thrust can finally be determined from the power of the blower and flight conditions, for example according to the principles developed in patent EP3623607B1, for example in paragraphs

[0084] to

[0088] of EP3623607B1.

[0017] Thanks to the invention, in a turbomachine comprising two speed sensors on two different shafts connected by a reduction gear, it is possible to obtain a measurement of the fan power, and therefore of the thrust, allowing the turbomachine to be controlled accordingly, even in the event of a failure of one of the sensors of regime. This is made possible by a modeling of the regime captured by the faulty sensor based on the regime of the functional sensor and on a force exerted by the reducer on a static part.

[0018] An advantage of the invention is that, regardless of the faulty sensor, a thrust can be obtained, from the regime of the functional sensor, as long as a model of the faulty sensor from the functional sensor is available.

[0019] The invention also allows redundancy, and therefore allows verification of a speed value captured by one of the sensors by comparing it to a value from the modeling of the same speed, making it possible to make the measurement of thrust of a turbomachine with two speed sensors more reliable.

[0020] Finally, the invention makes it possible to design a turbomachine with a single speed sensor, doing without one of the two speed sensors, if no other function of the engine than the measurement of the power of the blower requires these two speed acquisitions.

[0021] In addition to the characteristics mentioned in the preceding paragraph, the method according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: • The first tree is different from the second tree, • Calculating the blower power from the received force, the received first shaft speed, and the calculated second shaft speed includes calculating a blower shaft torque from the measured first shaft speed and the calculated second shaft speed, and multiplying the blower shaft torque by a blower shaft speed. • The numerical model is established from the reduction ratio of the reducer and takes into account the stiffnesses of the components between the speed sensor of the second shaft and a theoretical position of a virtual speed sensor of the second shaft. • The computer implementing the process is a turbomachine control processor comprising at least two redundant channels, and according to which the process is only implemented after verification that a measurement of the second shaft speed is: • unavailable on each of the turbomachine control processor channels or • different, on one of the channels of the turbomachine control processor, from the measurement of the second shaft speed on the other channel of the turbomachine control processor. • The process also includes: • Modify the turbomachine torque to achieve an expected thrust, the torque modification being calculated from the calculated thrust. • The process also includes: • Receive the speed of the second shaft measured by a second speed sensor, • Compare the measured speed of the second shaft with the calculated speed of the second shaft. • When the comparison results in a difference between the measured speed of the second shaft and the calculated speed of the second shaft: • Issue an alert indicating the failure of the second speed sensor.

[0022] Another aspect of the invention relates to an aircraft turbomachine comprising a turbomachine control processor configured to implement the method according to the invention, the turbomachine comprising at least: • A blower located upstream of an engine, • The engine, comprising at least: • a turbine, • a compressor, • a drive shaft connecting the turbine and the compressor, • A gearbox receiving an input from the drive shaft and transmitting an output drive to the blower via a blower shaft, so as to drive the blower at a rotational speed lower than that of the drive shaft, the gearbox comprising a sun gear, a plurality of satellite gears, a ring gear and a planet carrier, the sun gear meshing with the satellite gears and the satellite gears meshing with the ring gear, each satellite gear being rotatably mounted on the planet carrier, the drive shaft being arranged to drive the sun gear, one element of the planet carrier and the ring gear being arranged to drive the blower via the blower shaft, the other element of the ring gear and the planet carrier being mounted in a static structure, the static structure being arranged to limit the rotational movement of the other element, • A force sensor configured to measure the force applied by the other element on the static structure, • A speed sensor for the first shaft, either the drive shaft or the blower shaft.

[0023] Yet another aspect of the invention relates to an aircraft comprising the turbomachine according to the invention.

[0024] Yet another aspect of the invention relates to a computer program product comprising instructions which, when the program is executed by a computer, lead the latter to implement the process according to the invention.

[0025] Yet another aspect of the invention relates to a computer-readable data carrier on which the computer program product according to the invention is recorded.

[0026] The invention finds a particularly interesting application in turbomachines in which one of the two speed sensors may be subject to failure, or comprising only one of the two speed sensors and for which no other engine function requires the simultaneous acquisition of both speeds.

[0027] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0028] The figures are presented for illustrative purposes only and are in no way limiting of the invention. • Figure [1] shows a schematic representation of a first embodiment of a part of a turbomachine for implementing the process according to the invention, • Figure 2 shows a schematic representation of a process according to the invention, • Figure 3 shows a schematic representation of a second mode of construction of a part of a turbomachine for implementing the process according to the invention, • Figure 4 shows a schematic representation of a third mode of construction of a part of a turbomachine for implementing the process according to the invention, • Figure 5 shows a schematic representation of one embodiment of a method according to the invention, • Figure 6 shows an engine speed selection table, • Fig. 7 shows a blower speed selection table. DETAILED DESCRIPTION

[0029] Unless otherwise specified, the same element appearing on different figures presents a unique reference.

[0030] Fig. 1 shows a schematic representation of part of a turbomachine according to a first embodiment for implementing a process according to the invention.

[0031] Only "a part" of a turbomachine is shown for clarity in the description of the present invention. The part of the turbomachine 10 shown comprises: • A Fan blower connected to a power transmission shaft A2, known as the "blower shaft", • A Red reducer, • A power transmission shaft Al, called a "drive shaft", connected to a motor M, the motor M comprising at least one compressor and one turbine (not shown).

[0032] The turbomachine 10 has components identical to those of the prior art, namely that the gearbox Red is a transmission, transmitting power from shaft Al to shaft A2, with a reduction factor, and the fan Fan is a rotor comprising a plurality of blades. The gearbox Red comprises a sun gear, several planet gears, a ring gear, and a planet carrier. The sun gear meshes with the planet gears, and the planet gears mesh with the ring gear. Each planet gear is rotatably mounted on the planet carrier. The drive shaft Al is designed to drive the sun gear, and the planet carrier or the ring gear is configured to drive the fan via a fan shaft A2. The element that does not drive the fan shaft, between the planet carrier and the ring gear, is fixed to a static structure. The static structure thus limits the rotational movement of the element fixed to it.

[0033] The Fan blower is mounted upstream of the engine M, "upstream" being understood with respect to an air inlet in the turbomachine 10, the ambient air entering from the left in [Fig. 1], i.e., first reaching the Fan blower before reaching the engine M connected to the first shaft AL

[0034] The turbomachine 10 according to a first embodiment comprises: • A force sensor Cf, measuring the force applied to the static structure of the reducer Red by the element attached to it, • A speed sensor Cl measuring the speed of the motor shaft Al (also called "LPC speed" for "Low Pressure Compressor"), • A speed sensor C2 measuring the speed of the blower shaft A2 (also called "Fan speed").

[0035] The turbomachine 10 includes a processor P for controlling the engine M, also called "FADEC", for "Full Authority Digital Engine Control". This processor preferably comprises two redundant channels, called channels A and B, each channel separately receiving the same data from the same sensors, and performing the same calculations of in a completely independent manner. The results are then compared, and the results are considered, for example, to be consistent if they are equal.

[0036] The processor P is configured to implement a method for measuring the blower power of the turbomachine 10. Alternatively, the method can be implemented by a computer included in the turbomachine 10 or in an aircraft carrying the turbomachine 10, the computer communicating with the processor P.

[0037] A "computer" implementing the method according to the invention comprises at least one processor and one memory. The memory comprises instructions which, when executed by the processor, cause the processor to implement the method according to the invention. In the course of implementing the method, the processor may store further data in the memory or delete data stored in the memory.

[0038] The computer and the turbomachine can, for example, be embedded in an airborne system, for example in an aircraft.

[0039] Figure 2 shows a schematic representation of an embodiment of the blower power measurement method according to the invention. In this method according to the invention, one of the two speed sensors Cl and C2 is considered to be faulty, i.e., not functioning, i.e., not providing a speed value, or malfunctioning, i.e., not providing the actual speed value of the shaft on which it measures it.

[0040] This process 20 comprises at least four steps 21 to 24.

[0041] In a first step 21, the computer implementing the method 20, which Either a motor control processor M or another computer receives the force measured by the force sensor Cf. When the computer is a FADEC, this value is duplicated on each of the two redundant channels of the FADEC.

[0042] In a second step 22, the speed of the first shaft is received. The "first shaft" in this method 20 is the corresponding shaft on which a speed is measured by the functional speed sensor, that is, by the sensor among the two speed sensors that is not faulty. For example, when the speed sensor C1 is faulty, the first shaft is the blower shaft A2, and the speed value comes from the speed sensor C2. For example, when the speed sensor C2 is faulty, the first shaft is the motor shaft A1, and the speed value comes from the speed sensor C1. This speed is received by the computer implementing the method 20, that is, either received by the processor P when it implements the method 20, or received by the computer via the processor P. The data can preferably be sent by wire, or alternatively wirelessly.

[0043] In a third step 23, the speed of the second shaft is calculated. Since the speed sensor of the second shaft is faulty, the speed of the second shaft is not not available and therefore cannot be received, or is incorrect and therefore cannot be used for calculating the blower power. The invention therefore includes the implementation of a step for calculating the speed of the second shaft, based on the speed of the first shaft measured and received in step 22, and a numerical model of the speed of the second shaft.

[0044] Thus, when the functional sensor is sensor Cl, the modeled data is the speed of the blower shaft A2, that is, the data from sensor C2 if it were functional. Similarly, when the functional sensor is sensor C2, the modeled data is the speed of the motor shaft Al, that is, the data from sensor Cl if it were functional.

[0045] This numerical model takes into account the main physical relationship between the two operating regimes (shaft A1 and shaft A2), namely the reduction ratio of the gearbox Red. In a preferred embodiment, and optionally, to better represent transient changes, particularly at low speeds, the model considers the stiffnesses of the components located between the position of the functional sensor and the position of the modeled faulty sensor (also referred to as the "virtual sensor" hereafter), the functional sensor and the modeled faulty sensor being positioned on the same transmission chain, or even on the same shaft. The stiffnesses can be determined analytically or experimentally. In this preferred embodiment, the virtual sensor can be calibrated either by testing or by measuring the torsional stiffness of the chain between the actual functional sensor and the virtual sensor.

[0046] This numerical model is obtained for example by considering the following principles.

[0047] The torque in a shaft results from its deformation between its two ends and its stiffness. Torque = Stiffness * (3fj„ - ), with Bfin the angle of the rotation shaft at one end and Bstart the angle of the rotation shaft at the other end, the difference defining the deformation of the shaft.

[0048] Therefore, knowing the torque variation and the final speed wfin at one end, it is possible to calculate the initial speed wdébut at the other end, as follows:

[0049] = R(ddeur* ( ü)fn _ )

[0050] In a transient evolution, knowing the regime at both ends with sufficient precision, it is possible to determine the stiffness.

[0051] This stiffness can also be determined during assembly by immobilizing one end, applying a deformation to the other end and measuring the torque on the line.

[0052] If the system between the two regime measurements comprises several components, it is possible to calculate analytically the equivalent stiffness of the assembly. The stiffness of each component can be determined analytically or by measurement before assembly.

[0053] In the case of an architecture with a reducer, it is necessary to take into account the reduction ratio and to place oneself in the same reference frame as that in which the torque measurement is installed.

[0054] In the present application, the measured force allows the torque in the transmission line to be defined. Knowing the measurement location of the operating conditions of the first shaft A1 and the second shaft A2, and by transposing the system to the operating frame of the measured force, it is possible to determine the operating conditions of one of the shafts from the operating conditions of the other and the measured torque variation. The operating conditions thus calculated are then transposed to the operating frame of the shaft for which the measurement is sought.

[0055] To obtain the regime of the second shaft from that of the first shaft, the regime is therefore modeled using the model obtained, which takes as input the regime of the first shaft and the force exerted on the static part of the reducer Red by the element of the reducer Red which is fixed to the static part of the reducer Red.

[0056] Finally, from the speed of the first shaft received in step 22, the speed of the second shaft calculated in step 23 and the force received in step 21, the power of the turbomachine blower is obtained in step 24 by a known calculation, detailed later.

[0057] Figures 3 and 4 show schematic representations of turbomachines conceivable thanks to the invention, requiring only one speed sensor out of the two speed sensors.

[0058] Fig. 3 shows a schematic representation of part of a turbomachine comprising only the speed sensor Cl of the drive shaft AL. The speed of the blower shaft A2 is then obtained by modeling with the method 20 described previously, as if the speed sensor C2 of the blower shaft were faulty, whereas it is absent.

[0059] Fig. 4 shows a schematic representation of part of a turbomachine comprising only the speed sensor C2 of the fan shaft A2. The speed of the drive shaft Al is then obtained by modeling with the method 20 described previously, as if the speed sensor Cl of the drive shaft were faulty, whereas it is absent.

[0060] Figure 5 shows a schematic representation of an embodiment of the blower power measurement method according to the invention. This embodiment of the method is compatible with embodiment 20 of the method according to the invention described above.

[0061] First, a Sell selection step is implemented. This Sell step selects which data to use as the Al Nlpc motor shaft speed. This selection step results in the selected speed "Nlpc sel". This selection is performed using the table shown in [Fig. 6]. The first four columns represent the input states, and the last four columns These represent the results, or output states. The first two columns represent the status of FADEC channels A and B, with "OK" indicating a healthy channel and "NOK" indicating a non-healthy (faulty) channel. The third column, "Channel Cross-Check Status," represents the result of comparing calculation results from the two channels. This cross-check indicates whether the FADEC, and therefore the sensor data, can be trusted, or whether it is necessary to model the AL motor shaft speed. For example, the second and fifth rows of the table select, respectively, the value from the two channels closest to the modeled value, or directly the modeled value. The fourth column indicates whether the model is healthy, while the last five rows indicate not to use the value from the model.The fifth column indicates the origin of the selected shaft speed value (A1), and the last column indicates whether it is possible to model the speed value of the other shaft (fan shaft A2) from the origin of the selected speed value. Thus, at the Sell step, depending on the input states, a speed value origin is selected, for example, an average of the results from the FADEC channels, or a value among the channels closest to a model, or a value from only one of the two channels, or a value from the model. When modeling is necessary, this data is obtained from the "Mod2" block, which models the engine speed (Nlpc_mod) from the fan speed from sensor C2.

[0062] Similarly, a Sel2 selection step is implemented. This Sel2 step selects which data to use as the operating mode of the A2 blower shaft Nfan. This selection step results in the selected operating mode "Nfan sel". This selection is performed using the table shown in [Fig. 7]. The first four columns represent the input states, and the last four columns represent the results, or output states. The first two columns represent the state of channels A and B of the FADEC, with "OK" representing a functioning channel and "NOK" representing a non-functional (faulty) channel. The third column, "Channel Cross-Verification Status", represents the result of comparing the calculation results from the two channels.Such a cross-check determines whether the FADEC, and therefore the data from the sensors, can be trusted, or whether it is necessary to model the fan shaft speed value A2. For example, the second and fifth rows of the table select, respectively, the value closest to the modeled value from among the two options, or directly the modeled value. The fourth column indicates whether the modeling is sound, while the last five rows indicate not to use the modeled value. The fifth column indicates the origin of the selected A2 shaft speed value. The last column indicates whether it is possible to model the speed value of the other shaft (drive shaft Al) from the origin of the selected speed value. Thus, in step Sel2, depending on the input states, an origin of the speed value is selected, for example, an average of the results from the FADEC channels, or a value among the channels closest to a model, or a value from only one of the two channels, or a value from the model. When modeling is necessary, this data is obtained from the "Modl" block, which models the fan speed Nfan_mod from the engine speed from sensor Cl.

[0063] Finally, the blower power measurement method is carried out, comprising receiving a force exerted in the Red gearbox, from the force sensor Cf. Next, this force is converted FTRQ into a torque TRQ by multiplying this force by a distance traveled. A blower torque is calculated in the Cale step, based on the blower speed "Nfan sel" and the engine speed "Nlpc sel" obtained from the Sel2 and Sell selection steps respectively, and from the torque derived from the force sensor Cf. This calculation uses the following formula:

[0064] _ TR@

[0065] With TRQfan the blower torque obtained by implementing this calculation, the ratio of the regimes representing the reduction of the reducer Red.

[0066] To obtain the power of the blower, this blower torque TRQfan is multiplied by the selected blower speed Nfan sel.

[0067] The thrust can then be determined from the power of the blower and the flight conditions, for example according to the principles developed by patent EP3623607B1, for example in

[0084] to

[0088] .

[0068] In a generic example, the net thrust of the engine can be related to the power of the fan and the flight conditions. A specific way of relating the net thrust of the engine and the power of the fan is given by the following formula:

[0069] pN / Powers„ffimle \ P — / 1 / — • lyldchi \ ' /

[0070] Where FN is the net thrust of the engine, Pamb is the ambient pressure, P20 and T20 are respectively the pressure and temperature at the stall point at the engine inlet, Mach is the Mach number of the flight.

[0071] The thrust obtained then allows the engine M to be controlled, by comparing the expected thrust and the measured thrust.

[0072] The invention also makes it possible to verify the integrity of the channels of the processor P controlling the engine M when neither of the speed sensors C1 and C2 is faulty. For this purpose, A shaft speed received from a sensor is compared to a modeled speed of the same shaft. If the two speeds are different, or if their difference exceeds a predetermined threshold, an alert is triggered indicating a failure in the processor channel P from which the sensor value originates. This process also allows for an alert regarding the sensor's integrity if its value differs from the modeled value.

Claims

1. Demands A computer-implemented method (20) for measuring the power of a fan on an aircraft turbomachine, the turbomachine comprising at least: - The blower (Fan) located upstream of an engine (M), - The engine (M), comprising at least: • a turbine, • a compressor, • a drive shaft (Al) connecting the turbine and the compressor, - A gearbox (Red) receiving an input from the drive shaft (Al) and transmitting an output drive to the blower (Fan) via a blower shaft (A2), so as to drive the blower (Fan) at a rotational speed lower than that of the drive shaft, the gearbox (Red) comprising a sun gear, a plurality of satellite gears, a ring gear and a satellite carrier, the sun gear meshing with the satellite gears and the satellite gears meshing with the ring gear, each satellite gear being rotatably mounted on the satellite carrier, the drive shaft (Al) being arranged to drive the sun gear, one element of the satellite carrier and the ring gear being arranged to drive the blower via the blower shaft (A2), the other element of the ring gear and the satellite carrier being mounted in a static structure, the static structure being arranged to limit the rotational movement of the other element, - A force sensor (Cf) configured to measure the force applied by the other element on the static structure, - A speed sensor (C1,C2) of a first shaft among the drive shaft (A1) and the blower shaft (A2), the process (20) comprising: - Receive (21) the force measured by the force sensor (Cf), - Receive (22) the regime of the first tree measured by the engine speed sensor, - Calculate (23) the speed of a second shaft between the drive shaft (A1) and the blower shaft (A2), from the measured first shaft speed and a numerical model of the second shaft speed, - Calculate (24) the blower power from the force received, the first shaft speed received and the calculated second shaft speed.

2. Method (20) according to the preceding claim in which calculating (24) the blower power from the received force, the received first shaft speed and the calculated second shaft speed comprises calculating a blower shaft torque (A2) from the measured first shaft speed and the calculated second shaft speed, and multiplying the blower shaft torque (A2) by a blower shaft speed (A2).

3. Method (20) according to any one of the preceding claims wherein the turbomachine further comprises a second shaft speed sensor among the drive shaft and the blower shaft, the numerical model being established from the reduction ratio of the reducer (Red) and taking into account the stiffnesses of the components between a position of the second shaft speed sensor and a theoretical position of a virtual second shaft speed sensor.

4. A method (20) according to any one of the preceding claims wherein the turbomachine further comprises a second shaft speed sensor among the drive shaft and the blower shaft, and the computer implementing the method (20) is a control processor (P) of the turbomachine (10) comprising at least two redundant channels, and wherein the method (20) is only implemented after verification that a measurement of the second shaft speed, measured by the second shaft speed sensor, is: - unavailable on each of the channels of the control processor of the turbomachine or - different, on one of the channels of the control processor of the turbomachine, from the measurement of the second shaft speed on the other channel of the control processor of the turbomachine.

5. A method (20) according to any one of the preceding claims, further comprising: - Modify the turbomachine torque to achieve an expected blower power, the torque modification being calculated from the calculated blower power.

6. A method (20) according to any one of the preceding claims, further comprising: - Receive the speed of the second shaft measured by a second speed sensor, - Compare the measured speed of the second shaft with the calculated speed of the second shaft. - When the comparison results in a difference between the measured speed of the second shaft and the calculated speed of the second shaft: • Issue an alert indicating the failure of the second speed sensor.

7. Aircraft turbomachine (10) comprising a control processor (P) of the turbomachine (10) configured to implement the method (20) according to any one of the preceding claims, the turbomachine (10) comprising at least: - A fan located upstream of an engine (M), - The engine (M), comprising at least: • a turbine, • a compressor, • a drive shaft (Al) connecting the turbine and the compressor, - A reduction gear (Red) receiving an input from the drive shaft (A1) and transmitting an output drive to the fan (Fan) via a fan shaft (A2), so as to drive the fan (Fan) at a rotational speed lower than that of the drive shaft, the reduction gear (Red) comprising a sun gear, a plurality of satellite gears, a ring gear, and a satellite carrier, the sun gear meshing with the satellite gears and the satellite gears meshing with the ring gear, each satellite gear being rotatably mounted on the satellite carrier, the drive shaft (A1) being arranged to drive the sun gear, one element among the satellite carrier and the ring gear being arranged to drive the fan. the intermediate blower shaft (A2), the other element among the ring and the planet carrier being mounted in a static structure, the static structure being arranged to limit the rotational movement of the other element, - A force sensor (Cf) configured to measure the force applied by the other element on the static structure, - A speed sensor (C1,C2) of a first shaft among the drive shaft (Al) and the blower shaft (A2).

8.

9. Aircraft comprising the turbomachine (10) according to claim 7. Product computer program comprising instructions which, when the program is executed by a computer, cause the computer to implement the method (20) according to any one of claims 1 to 6.

10. Computer-readable data carrier on which the computer program product according to claim 9 is recorded.

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