The alternating electric currents Iac_M1A-Iac_M4A/Iac_M1B-Iac_M4Bof all electric motors M1A-M4A, M1B-M4B,

The temperature of each electric motor M1A-M4A, M1B-M4B.

The rotation speed of each drive element H1-H4.

In reference to FIG. 3, the method comprises a step of acquiring ET1 of measurements Pv of a plurality of power parameters PARi of the drive train 2. Preferably, several measurements Pv are expressed according to different units of measure. The acquisition step ET1 is carried out in a known manner from sensors of different types that are connected to the motor calculator CAL.

As an example the measurements Pv are in particular:

- THE TORQUE C_TAGof the gas turbine TAG at its current operating point, the torque C_TAGbeing expressed in Newton meters.
- the alternating electrical currents Iac_TGA, Iac_TGBof the two generators GENA, GENB, the currents being expressed in amperes.
- the temperature of each electric motor M1A-M4A, M1B-M4B, the temperature is expressed in degrees.

The method comprises a step of comparing ET2 each measurement Pv at a power threshold Pseud, determined respectively for each power parameter PAR, in order to deduce a gross power margin Pmb for said power parameter PAR.

In this example embodiment, each power parameter PARi is associated with a power threshold Pseuil in a threshold database DB_SEUIL. The threshold database DB_SEUIL is accessible by the motor calculator CAL, which may thus determine the gross power margin Pmb for each power parameter PAR. Preferably, the power thresholds Pseuil are independent of the operating points of the drive train. Such an independence property is advantageous for the calculated power margins to have a predictive value (and therefore independent of future aircraft maneuvers and, therefore, independent of future points of operation of the drive train).

Preferably, each power threshold Pseuil is specific to a power parameter PARi in said hybrid drive train and, preferably, specific to said operating point and the operating configuration. Also, each power parameter PARi is associated with a power threshold Pseuil for each operating point and each operating configuration in the threshold database DB_SEUIL.

Preferably, said power threshold Pseuil is expressed in the same unit of measure as the measurement Pv, which makes it possible, by simple calculation of difference, to determine the gross power margin Pmb expressed in the same unit of measure.

In this example, the following is advantageously obtained:

- the gross torque margin of the gas turbine TAG compared to a maximum torque of the gas turbine TAG at its operating point, the torque margin being expressed in Newton meters,
- the gross current margin delivered by each electric generator GENA, GENB, the current margin being expressed in amperes and
- the gross temperature margin of each electric motor M1A-M4A, M1B-M4B, the temperature margin is expressed in degrees.

Calculating a global power margin of the TAG may be complex, particularly in the presence of series-parallel architectures where a significant portion of power is taken both on a free turbine and on a gas generator. The pilot then needs to know the available power margin on each of the two branches in order to be able to adjust the demand accordingly. In this case, it is proposed to calculate the grass power margin for each output of the TAG gas turbine. For example, for an architecture wherein the free turbine of the gas turbine TAG supplies mechanical power to the drive elements H1-H4 and where the electrical power is extracted from the gas generator TAG. The mechanical power margin is calculated on the iso-sampling free turbine on the gas generator (electrical iso power) and the electrical power margin (on the gas generator) with mechanical iso sampling on the free turbine.

The method comprises a step of converting ET3, from a transformation ratio database DB_TRANSF, gross power margins Pmb of said power parameters PARi into refined power margins Pma expressed according to the same common unit of measure. In other words, while the gross power margins Pmb are expressed in different units (Newton meters, amperes or degrees), the refined power margins Pma are all expressed in the same units of measure, allowing them to be processed together. The refined power margins Pma are all expressed in the same homogeneous unit of measure.

This homogeneous unit of measure is preferably expressed in Watts as it allows power to be determined for the drive elements H1-H4. It goes without saying that the homogeneous unit of measure could be different, in particular, a torque or amperes.

Advantageously, the transformation ratio database DB_TRANS is specific to the hybrid drive train 2 and determines the transformation ratios between the power parameters PARi among them. Preferably, the transformation ratios are determined theoretically by energy modeling of the hybrid drive train 2. Preferably, each transformation ratio is in the form of at least one mathematical equation which depends on the operating point and configuration of the hybrid drive train 2. Thus, the impact of a current or temperature change on a channel in terms of torque on drive elements H1-H4 may be determined. In this example, the transformation ratio database DB_TRANS is stored in tables in the motor calculator CAL.

In this example, the gross current margin delivered by each electric generator GENA, GENB and the gross temperature margin of each electric motor M1A-M4A, M1B-M4B are respectively transformed into refined power margins Pma, which are expressed in watts.

The method comprises a step of transposing ET4, from a yield ratio database DB_REND, refined power margins Pma, hereinafter referred to as “refined margins Pma”, for each power parameter PARI into standardized power margins Pmn at one or more reference points of the drive train 2, hereinafter referred to as “standardized margins Pmn”. Preferably, the yield ratios DB_REND are independent of the operating points of the drive train.

In this example, the reference points are chosen so as to be as close as possible to where the power is actually useful for controlling the aircraft, i.e. as close as possible to the drive elements H1-H4. A preferred reference point is, for example, the mechanical power available on the drive elements H1-H4. Of course, however, the reference points could be chosen differently according to the needs or specificity of the drive train 2.

Advantageously, the yield database DB_REND is specific to the drive train 2 and determines the yield ratios between the power parameters among them, in particular according to the transmission members between an acquisition point and a reference point. Preferably, the yield ratios are determined theoretically by energy modeling of the hybrid drive train 2. Preferably, each yield ratio is in the form of at least one mathematical equation which depends on the operating point and configuration of the hybrid drive train 2. Thus, a refined margin Pma obtained at a given point in the hybrid drive train 2 may be transposed into the same reference point in order to determine the actual margin for said reference point. In this example, the yield database DB_REND is stored in the motor calculator CAL in the form of table(s) which may depend on other parameters measured, for example, the average current level and the voltage of the channels.

By way of example, the following transpositions may be carried out. The refined torque margin Pma of the gas turbine TAG, expressed initially on the drive shaft of electric generators GENA, GENB, is transposed onto the drive shafts of the drive elements H1-H4 (reference point) from:

- the transformation yield ratios of the generators GENA, GENB and of their rectifiers REDA, REDB, which in this example are 90%,
- yield ratios of the transport of electrical power in the channels CANA, CANB, which in this example are 95%,
- the yield ratio of the electric motors M1A-M4A, M1B-M4B and their inverter OND1A-OND4A, OND1B-OND4B, which in this example is 93%.

Thus, a refined margin Pma of torque of the gas turbine TAG is transposed with a yield factor of 80% (90%*95%*93%) on the drive shafts of the drive elements H1-H4 to determine the standardized margin Pmn.

Similarly, the refined power margin Pma of battery BATA, BATE, expressed initially at their electrical connection terminal strip, is transposed onto the drive shafts of the drive elements H1-H4 (reference point) from:

- yield ratios of the transport of electrical power transmission in the channels CA, CB, which in this example are 95%, and
- the yield ratio of the electric motors M1A-M4A, M1B-M4B and their inverter OND1A-OND4A, OND1B-OND4B which, in this example, is 93%.

Thus, a refined power margin Pma of the battery BATA-BATE is transposed with a yield factor of 88% (95%*93%) on the drive shafts of the drive elements H1-H4 to determine the standardized margin Pmn. Thus, the further away the reference point is from the measurement location, the greater the number of yields to be considered.

Also, for a same refined power margin value Pma, expressed in watts, of 50 kW of torque of the gas turbine and 50 kW of battery power, the standardized value Pmn is different on the drive shafts of the drive elements H1-H4 (i.e. at the reference point) (standardized gas turbine margin: 50*0.80=40 kW: battery standardized margin: 50*0.85=42.5 kW).

Still in reference to FIG. 3. the method comprises a step of determining ET5 a source power margin for each reference point and a consumer power margin for each reference point. Power margins for sources and consumers have been presented, but it goes without saying that power margins could also be calculated for power transfer members, for example an electric cable or a transmission shaft.

In this example, the power margins are determined for each drive element H1-H4. These are called individual margins Mind. Thus, there are as many individual margins Mind as there are reference points, in this example, there are 4.

At a given reference point (a given drive element H1-H4), the source power margin is obtained by summing the standardized margins of the sources supplying said drive element, namely, the batteries BATA, BATB and the gas turbine TAG in our example. The source power margin MIndS depends on the distribution of sources on the drive elements as well as the configuration of the hybrid drive train (availability or unavailability of sources). When power sources supply only part of the drive elements H1-H4, the one with the lowest standardized margin is selected.

In other words, for each reference point H1-H4, it is sufficient to trace the power train back to the primary sources (batteries, turbogenerator, etc.) taking into account the possible limitations (margins) of each power transfer member encountered on the route.

If a source supplies several consumers in parallel, it is assumed that the total power is distributed equally between each consumer in parallel. This equidistribution hypothesis is advantageously verified by the fact that the topology of the aircraft and its drive system are symmetrical around a center of gravity. Nevertheless, it goes without saying that a weighted distribution hypothesis could be implemented when consumers have very different nominal powers.

Similarly, in a given reference point, the individual power margin of the consumer MIndC is obtained by summing the standardized margins of the consumers taking power at the reference point, namely, the motors M1A-M4A, M1B-M4B. To determine the individual power margin Mind, a step of selecting ET6 the individual margin of minimum power is performed between the individual consumer power margin MIndC and the individual source power margin MIndS. In this example, as will be detailed later, the individual consumer power margin MIndC is limiting.

Selecting the individual margins Mind is performed by tracing the power train supplying a given power element, by selecting the margins of the element offering the least power.

When a source supplies several consumers, it is important to take into account this distribution as well as the individual power of each consumer according to the modes. For example, one source may deliver 100 kW and supply two motors, each of which may supply 60 kW. In this case, the power potentially available on each propeller is 60 kW, but the total power available is limited to 100 kW in total of the 2 propellers, as limited by the source. Thus, according to the preferred solution of the invention, the individual margin of each propeller would be 50 kW.

For example, to determine the individual power margin Mind:

- the standardized minimum torque margin is selected from that from the gas turbine TAG and those from each of the generators GENA, GENB, and the global drive torque margin is indicated.
- the standardized minimum torque margin among the different limiting factors of a motor M1A-M4A, M1B-M4B, such as the temperature limit, the inverter current limit, or the current limit of the electrical power supply dedicated to the motor M1A-M4A, M1B-M4B.

An individual power margin Mind for each drive element H1-H4 informs the pilot of the drive power available to act on the aircraft's attitude, thus contributing to flight stabilization (e.g.: the power margin on each motor on the right-hand side provides information on the aircraft's ability to roll to the left). Advantageously, in the case of equal distribution, the pilot only needs to respect all the individual power margins to validate a control law.