A method for determining target values of thermal cooling power for one or more traction units of an electric powertrain of a vehicle

Abstract

Disclosed herein is a method for determining limit target values of thermal cooling power for one or more traction units of an electric powertrain of a vehicle, wherein each traction unit comprises an electric traction motor (M1, M2, M3, M4), an inverter operatively connected to the eelleeccttrriicc traction motor (M1, M2, M3, M4), and a transmission connecting the electric traction motor (M1, M2, M3, M4) to one or more drive wheels (RL, RR, FL, FR) and including aa transmission lubricant, the electric powertrain moreover including a battery operating in a relationship of electrical power transfer with each electric traction motor (M1, M2, M3, M4). Thanks to the method according to the invention it is possible, as a function of the mission requested by the driver of the vehicle (DriveMod), to increase the duration of the performances of the powertrain without incurring in derating interventions, by dynamically controlling the cooling power of the traction components of each traction unit. Moreover, it is possible to increase the driving range of the vehicle by using less electrical energy for cooling the traction components, by making use of the thermal capacity of the traction components, thus enabling a reduction of the minimum flow rate of coolant towards the inverters. Finally, it becomes possible to use all the available thermal cooling power in order to avoid reaching critical temperatures of the traction components.

Description

[0001] " A method for determining target values of thermal cooling power for one or more traction units of an electric powertrain of a vehicle"

[0002] ★ ★ ★ ★

[0003] TEXT OF THE DESCRIPTION

[0004] Field of the Invention

[0005] The present invention relates to vehicles with an electric powertrain, particularly BEVs. The invention was developed with particular reference to the thermal management of traction units of the electric powertrain.

[0006] Prior Art

[0007] In the vehicles with an electric powertrain, particularly BEVs, the thermal management of the powertrain mainly focuses on the cooling of the high-voltage battery and of the traction components which form the single traction units of the powertrain. The need for cooling arises from the natural tendency to a thermal dissipation of power of the traction components (and of the battery itself, especially under given conditions). Each traction unit comprises an electric traction motor, an inverter operatively connected to the electric traction motor, and a transmission connecting the electric traction motor to one or more drive wheels and including a transmission lubricant. Moreover, the electric powertrain comprises a battery (a so-called high-voltage battery) operating in a relationship of electrical power transfer with each electric traction motor.

[0008] The temperatures of the traction components (inverters, electric traction motors and transmission lubricants) influence the respective residual availabilities of thermal power before reaching high temperatures which are critical to such components. For the transmissions, the temperature increase of the transmission lubricant leads to an efficiency increaseof the transmission itself. On the other hand, the thermal conditioning by means of a cooling of the traction components leads to a systematic consumption of electrical power, which is drawn from the battery powering the electric traction motors of the powertrain of the vehicle.

[0009] The residual availability of thermal capacity of the traction components before reaching critical temperature conditions may be used to reduce the consumption of electrical power for the thermal conditioning of the traction components during a mission of the vehicle, therefore admitting a temperature increase of the components in order to reduce the energy consumption for cooling. Oppositely, said residual thermal capacity may also be used to prevent performance derating events due to overtemperature during a race, in such a way - when possible - that the maximum cooling power available for the traction components is lower than the thermal power rejected by the traction components themselves. This requires a minimal consumption of the availability of thermal capacity, by drawing electrical power from the high-voltage battery for cooling the traction components. As stated in the foregoing, it is a management going in a direction opposite to the strategy which envisages an extended use of the thermal capacity.

[0010] Another factor is the variability of the mission profile requested by the driver of the vehicle, which is likely to modify, in the one or in the other direction, the thermal management of the traction units.

[0011] The prior art does not offer thermal management strategies which envisage a dynamical management of the target value of cooling power as a function of the requested mission profile. As a consequence, the thermal management implemented in the known solutions often hasthe disadvantage of being static and poorly predictive with respect to the evolution of the temperatures during the mission, with the undesirable consequence of incurring in performance derating interventions when the evolution dynamics of the temperatures is more rapid than the evolution dynamics of the availability of thermal cooling power, and with the further, equally undesirable, consequence of a generally poor efficiency in the thermal management, which further leads to the reduction of the driving range, since for the cooling it unnecessarily draws electrical power from the high-voltage battery which powers the powertrain of the vehicle.

[0012] Obj ect of the Invention

[0013] The invention aims at solving the technical problem outlined in the foregoing. Specifically, the obj ect of the invention consists in providing a method for determining target values of thermal cooling power for one or more traction units of an electric powertrain of the vehicle, wherein each traction unit comprises the electric traction motor, an inverter operatively connected to the electric traction motor, and a transmission connecting the electric traction motor to one or more drive wheels and including a transmission lubricant, which enables determining the amount of the thermal cooling power dynamically and depending on the mission requested by the driver.

[0014] Summary of the Invention

[0015] The obj ect of the invention is achieved by means of a method having the features set forth in the claims that follow, which form an integral part of the technical disclosure provided herein in relation to the invention.

[0016] Brief Description of the Figures

[0017] The invention will now be described with reference to the annexed Figures, which are provided by way ofnon-limiting example only and wherein:

[0018] Figures 1A to 1H schematically show some configurations of an electric powertrain in which it is possible to implement the method according to the invention,

[0019] - Figure 2 is a block diagram representative of the method according to the invention,

[0020] Figures 3 to 9 show aspects of the method according to the invention which refer to the inverter of each traction unit,

[0021] Figures 10 to 14 show aspects of the method according to the invention which refer to the electric traction motor of each traction unit, and

[0022] Figures 15 to 19 show aspects of the method according to the invention which refer to the transmission lubricant of each electric traction motor.

[0023] Detailed Description

[0024] By way of preliminary discussion, Figures 1A to 1H schematically show some configurations of an electric powertrain of a vehicle V in which it is possible to implement the method according to the invention. Each configuration of electric powertrain includes one or more traction units, each comprising an electric traction motor, an inverter operatively connected to the electric traction motor, and a transmission connecting the electric traction motor to one or more drive wheels and including a transmission lubricant.

[0025] The detailed description of the method will be set forth with reference to the most general configuration shown in Figure 1A, and it is applicable to all further configurations by a simple adaptation to the number of traction units / electric traction motors on board the vehicle V.

[0026] The one or more electric motors are operatively associated with a front axle and / or a rear axle of thevehicle, or with respective single wheels of one and the same axle, as a function of the number and of the characteristics of the traction units. In this fashion a power flow is exchanged between each motor and (at least) one axle or (at least) one wheel of the vehicle, for the traction of the vehicle itself.

[0027] The phrase "power flow" indicates both a power flow into the electric motor ( from a battery BT), i. e. a flow which leads to a driving action of the motor itself, and a power flow out of the electric motor (and into the battery BT), i. e. a flow which occurs when the electric motor is subj ected to a drag load (braking or deceleration due to the vehicle inertia) and operates as an electric generator. Reference Pn in the Figures (with n = 1, 2, 3, 4 in the presently considered embodiments) represents the general power flow associated with the n-th motor.

[0028] For simplicity, the vehicle configurations schematically shown in the Figures envisage the presence of a single battery for powering each electric motor, but the method may be applied irrespective of the number and of the configuration of the batteries, and irrespective of the association thereof with the one or more electric motors of the powertrain.

[0029] Figure 1 shows a first configuration of a four-motor powertrain, comprising four traction units. Specifically, the powertrain of Figure 1A comprises a first electric motor Ml operatively associated with a rear left wheel RL of the vehicle, a second electric motor M2 operatively associated with a rear right wheel RR of the vehicle, a third electric motor M3 operatively associated with a front left wheel of the vehicle, and a fourth motor M4 operatively associated with a front right wheel of the vehicle V. This means that each electric motor M1-M4 delivers torque to the wheeloperatively associated therewith. Each motor Ml, M2, M3, M4 is associated with a respective inverter, whereas the transmission connecting each motor Ml, M2, M3, M4 to the corresponding (single) drive wheel generally corresponds to a direct drive transmission or, more preferably, to a transmission comprising a reduction gear. The four traction units thus defined each comprise one of the motors Ml, M2, M3, M4, the respective inverter and the respective transmission.

[0030] The electric motors Ml, M2, M3, M4 are powered by a single battery (or battery pack) BT. In the schematic representation of Figure 1A, the arrows in continuous lines indicate a power flow into the motors Ml, M2, M3, M4 from the battery BT (power absorbed by the motors), whereas the arrows in dotted lines indicate a power flow out of the motors Ml, M2, M3, M4 towards the battery BT (power generated by the motors).

[0031] Figure IB shows a second configuration of a three-motor powertrain, comprising three traction units. Specifically, the powertrain comprises a first electric motor Ml operatively associated with a rear left wheel RL of the vehicle, a second electric motor M2 operatively associated with a rear right wheel RR of the vehicle, and a third electric motor M3 operatively associated with the front axle FA, thereby meaning a condition wherein the electric motor M3 delivers torque to both the right and the left wheels FR, FL of the front axle FA. Each motor Ml, M2, M3 is associated with a respective inverter, and the transmission connecting each motor Ml, M2, M3 to the corresponding one or more drive wheels corresponds, for the motors Ml, M2, to a direct drive transmission or, more preferably, to a transmission comprising a reduction gear, and for the motor M3 to a differential by means of which it is connected to two drive wheels (FL and FR). The three traction units thusdefined each comprise one of the motors Ml, M2, M3, the respective inverter and the respective transmission.

[0032] The electric motors Ml, M2, M3 are powered by a single battery (or battery pack) BT. In the schematic representation of Figures 1A, IB, the arrows in continuous lines indicate a power flow into the motors Ml, M2, M3 from the battery BT, whereas the arrows in dotted lines indicate a power flow out of the motors Ml, M2, M3 towards the battery BT.

[0033] Figure 1C substantially corresponds to a mirror configuration with respect to what is shown in Figure IB, with a first electric motor Ml operatively associated with a front left wheel FL, a second electric motor M2 operatively associated with a front right wheel FR and a third electric motor M3 operatively associated with a rear axle RA.

[0034] Figure ID and Figure IE show a vehicle V with a single-motor powertrain, including a single electric motor Ml operatively associated with the rear axle only (Figure ID) or with the front axle only (Figure IE). In both cases, the presence of a single traction unit is envisaged, comprising the motor Ml, an inverter associated with the motor Ml, and a transmission connecting the motor Ml to the pair of drive wheels of the axle by means of a differential.

[0035] Referring to the Figures IF, 1G, they show a vehicle V with a two-motor powertrain, respectively comprising:

[0036] either a first electric motor Ml operatively associated with a rear left wheel RL of the vehicle, and a second electric motor M2 operatively associated with a rear right wheel RR of the vehicle (Figure IF), or - a first electric motor Ml operatively associated with a front left wheel FL of the vehicle, and a second electric motor M2 operatively associated with a front right wheel FR of the vehicle (Figure 1G).The electric motors Ml, M2 are powered by a single battery (or battery pack) BT and, in the same way as in the schematic representation of the previous Figures, the arrows in continuous lines indicate a power flow into the motors Ml, M2 from the battery BT, whereas the arrows in dotted lines indicate a power flow out of the motors Ml, M2 towards the battery BT.

[0037] Each motor Ml, M2 is associated with a respective inverter, and the transmission connecting each motor Ml M2 to the corresponding (single) drive wheel corresponds to a direct drive transmission or, more preferably, to a transmission comprising a reduction gear. The two traction units thus defined each comprise one of the motors Ml, M2, the respective inverter and the respective transmission.

[0038] Figure 1H represents a vehicle V with a two-motor powertrain, comprising a first electric motor Ml operatively associated with the rear axle RA, and a second electric motor M3 associated with the front axle FA. Each motor Ml, M3 is associated with a respective inverter, and the transmission connecting each motor Ml, M3 to the corresponding pair of drive wheels of the axle comprises a differential. The two traction units thus defined respectively comprise one of the motors Ml, M3, the respective inverter and the respective transmission.

[0039] As anticipated in the foregoing, the following description is set forth with reference to the powertrain of Figure 1A, and thus the references employed relate to said Figure.

[0040] Referring to Figure 2, the invention defines a method for determining target values of thermal cooling power for one or more traction units of an electric powertrain of a vehicle, wherein each traction unit comprises the electric traction motor Ml, M2, M3, M4, an inverter operatively connected to the electric tractionmotor Ml, M2, M3, M4, and a transmission connecting the electric traction motor Ml, M2, M3, M4 to (one or more, generally speaking) drive wheels RL, RR, FL, FR and including a transmission lubricant. The electric powertrain moreover comprises a battery BT, operating in a relationship of electrical power transfer with each electric traction motor Ml, M2, M3, M4.

[0041] According to the invention, referring to Figure 2, the method comprises:

[0042] - determining (block 2A), for each inverter (or for each i-th inverter - hence the index in the references), a first value of rejected thermal power Q̇Inv_Htrj_Tgt_ias a function of a rotational speed Spdi of the electric traction motor Ml, M2, M3, M4 (i = 1, 2, 3, 4 ) to which the inverter is operatively connected, as a function of an operating voltage of the inverter VInv_i(the voltage VInv_icorresponds to a voltage at the interface between the inverter and the battery BT powering the powertrain, i. e. the high-voltage battery; therefore, VInv_iis the operating voltage at the inverter terminals to which the high-voltage battery BT is associated, and therefore it is a direct voltage. On the other hand, at the opposite terminals of the inverter, which are operatively connected with the electric traction motor, there is an alternating voltage, which however does not correspond to Vinv i, but to an operating voltage of the electric traction motorMot i, see below), as a function of a current torque value TrqAct_iof the electric traction motor Ml, M2, M3, M4 (i = 1, 2, 3, 4 ) to which the inverter is operatively connected, and as a function of a raw torque target value TrqTgt irequested to the electric powertrain; preferably, i. e in the preferred embodiment which will be described in detail in the following, the raw torque target value TrqTgt_iis a torque target value for the electric traction motor operativelyassociated with the i-th inverter, corresponding to a share of a total torque requested to the electric powertrain assigned to the electric traction motor under consideration,

[0043] determining (block 4A), for each electric traction motor Ml, M2, M3, M4 (or for each i-th electric traction motor - hence the index i in the references), a second value of rejected thermal power Q̇Mot_Htrj_Tgt_ias a function of the rotational speed Spdi of the electric traction motor Ml, M2, M3, M4 (i= 1, 2, 3, 4 ), as a function of an operating voltage of the electric traction motor VMoti, and as a function of the current torque value TAct_iof the electric traction motor Ml, M2, M3, M4, - determining (block 6A), for each transmission lubricant (or for each i-th transmission lubricant -hence the index i in the references), a third value of rejected thermal power Q̇TrnsmOil_Htrj_Tgt_ias a function of the rotational speed Spdi of the electric traction motor Ml, M2, M3, M4 connected to the transmission including the transmission lubricant, as a function of a current temperature of the transmission lubricant (TTrnsmOili ), and as a function of the current torque value TrqAct_iof the electric traction motor Ml, M2, M3, M4 (i= 1, 2, 3, 4 ) connected to the transmission including the transmission lubricant,

[0044] - determining (block 2B), for each inverter, a first target value of thermal cooling power Q̇Inv_Clg_Tgt_ias a function of a currently selected drive mode DriveMod, as a function of the first value of rejected thermal power Q̇Inv_Htrj_Tgt_i, as a function of an inverter temperature target value TInv_Max_Tgt_iand as a function of a current temperature value of the inverter TInv_i,

[0045] determining (block 4B), for each electric traction motor Ml, M2, M3, M4 (i= 1, 2, 3, 4 ), a second target value of thermal cooling power Q̇Mot_Clg_Tgt_ias afunction of the currently selected drive mode DriveMod, as a function of the second value of rejected thermal power QMot_Htrj_t r as a function of the target temperature value of the electric traction motor TMot Max Tgt tand as a function of the current temperature value of the electric traction motor TMot i,

[0046] - determining (block 6B), for each transmission lubricant, a third target value of thermal cooling power QTrnsmOil_Clg_Tgt_ias a function of the currently selected drive mode DriveMod, as a function of the third value of rejected thermal power QTrnsmou_Htrjjr as a function of the target temperature value of the transmission lubricant TTrnsmoti_Max_Tgt_i and as a function of the current temperature value of the transmission lubricant TTrnsmOil_i.

[0047] With reference to the following Figures 3 to 18, there will now be detailed the modalities of determining the values of rejected thermal power and the target values of thermal cooling power in the preferred embodiment of the method according to the invention.

[0048] Referring to Figure 3, diagram 10, determining, for each i-th inverter, the first value of rejected thermal power QInv_Htrj_Tgt_iincludes determining the greater (block 12, MAX) of a value of thermal power QInv_Htrj_TAct_Tgt_irejected by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to a current torque value TrqAct_iof the electric traction motor itself, and a value of thermal power QInv_Htrj_TTgt_Tgt_irejected by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to a raw torque target value TrqTgt_irequested to the electric traction motor itself, wherein the raw torque target value TrqTgt_iis a torque value requested to the electric traction motor operatively associated with the i-th inverter which derives from a meresubdivision of the total torque request to the powertrain, i. e. a value devoid of any further filtering or mediation. In this regard, the torque value TrqAct_iis obtained from a processing of the raw torque value TrqTgt_iby means of a series of filtering and / or correction operations as a function of various operational needs ( for example, a limitation of the delivered or absorbed electrical power, traction control, vehicle dynamics goals, etc. ).

[0049] In other words, as already stated in the foregoing, the raw torque target value TrqTgt_iderives from the subdivision of the total torque value requested to the powertrain according to the mapping of the accelerator pedal, and corresponds to the share of torque assigned to the electric motor operatively associated with the i-th inverter. The use of the total torque TrqTgt_iin the calculation, and specifically the operation of extracting the greater value as per block 12, enables anticipating the evolution of the rejected thermal power, in such a way as to anticipate the cooling action. In the case of the inverter, which is essentially unique among the traction components, anticipating the cooling action is very useful and advantageous, since the inverters are characterized by a remarkable temperature increase in dynamical conditions such as accelerations and decelerations of the vehicle, due to the very low thermal capacity of the respective internal components. Such a predictive control enables avoiding maintaining the constant availability of a minimum cooling power, thus saving energy thanks to an intervention which is adapted to the expected evolution.

[0050] Preferably, the output of the block 12 is treated as the raw value of the rejected thermal power QinvHtrj_Tgt_i - hence the reference QInv_Htrj_Raw_Tgt_i– and therefore it is subjected to a filtering operation (block 14) whichessentially aims at eliminating the signal peaks, which are useless for a processing for control purposes (the operation is performed, for example, by means of a bandstop or notch filter). In other words, the value of rejected thermal power QInv_Htrj_Tgt_iis preferably the output of the filter shown at block 14.

[0051] With reference to Figure 4, diagram 20, the value QInv_Htrj_TAct_Tgt_iof thermal power rejected by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the current torque value TrqAct_iof the electric motor itself is determined as a linear combination of a value QInv_Htrj_TActVHi_Tgt_iof thermal power rejected by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the current torque value TrqAct_iof the electric traction motor itself, and with a voltage VInv_iequal to or greater than a higher voltage threshold ( i. e. in a high-voltage operating range), and a value Qinv_Htrj_TActvLo_Tgt_i of thermal power rejected by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the current torque value TrqAct_iof the electric motor itself, and with a voltage equal to or less than a lower voltage threshold value (i.e. in a low-voltage operating range). In particular, said combination is a convex combination, wherein the numerical coefficient is indicated by the reference Gain and depends on the voltage VInv_i, according to the evolution shown in Figure 4, map M20. In the preferred embodiment shown, the numerical coefficient Gain has the value of a unit in the high-voltage operating range, and has zero value in the low-voltage operating range. For all intermediate value, the convex combination - which practically corresponds to a weighted average - applies:Q̇Inv_Htrj_TAct_Tgt_i= Gain · Q̇Inv_Htrj_TActVHi_Tgt_i+ (1 − Gain) · Q̇Inv_Htrj_TActVLo_Tgt_i

[0052] This corresponds to the sequence of the blocks 22, 24, 26 of Figure 4. In other words, the block 22 calculates the difference Q̇Inv_Htrj_TActVHi_Tgt_i− Q̇Inv_Htrj_TActVLo_Tgt_i, at the block 24 said difference is multiplied by the coefficient Gain, and at the block 26 the value Gain · (Q̇Inv_Htrj_TActVHi_Tgt_i− Q̇Inv_Htrj_TActVLo_Tgt_i) is added to Q̇Inv_Htrj_TActVLo_Tgt_i, thereby obtaining Q̇Inv_Htrj_TAct_Tgt_i= Gain · (Q̇Inv_Htrj_TActVHi_Tgt_i− Q̇Inv_Htrj_TActVLo_Tgt_i) + Q̇Inv_Htrj_TActVLo_Tgt_i, which is simply a rewriting of the previous expression with factoring out of the coefficient Gain.

[0053] Referring to Figures 5 and 6, diagrams 30 and 40, the values Qinv_Htrj_TActVHi_Tgt_i and Qinv_Htrj TActvLo Tgt j are extrapolated from respective maps M30 and M40 by using, as input data, the current torque TrqAct_iof the electric traction motor operatively connected to the i-th inverter and the rotational speed Spdi of the electric traction motor itself. The maps M30, M40 provide curves Q̇Inv_Htrj_TActVHi_Tgt_i−TrqAct_iand Q̇Inv_Htrj_TActVLo_Tgt_i−TrqAct_i, which are parameterized with respect to the speed Spdi • In the Figures, the arrows superimposed on said curves indicate the increasing evolution of the speed Spdi. Qualitatively, the rejected thermal powers Q̇Inv_Htrj_TActVHi_Tgt_iand Q̇Inv_Htrj_TActVLo_Tgt_iincrease with the increase of the speed Spdi and with the increase of the absolute torque value TrqAct_i(reference is made to the absolute value to since the regeneration torques have a negative sign).

[0054] Similarly, Figure 7, diagram 50, the value Qinvjitrj _TTgt_Tgt_t of the thermal power rejected by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the raw torque target value TTgt_iisdetermined as a linear combination of a value Q̇Inv_Htrj_TTgtVHi_Tgt_iof thermal power rejected by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the raw torque target value TTgt_t and with a voltage VInv_iequal to or greater than a higher voltage threshold value (i. e. in a high-voltage operating range), and a value Qinv_Htrj_TTgtVLo_Tgt_i °f thermal power re ected by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the raw torque target value TTgt_irequested to the electric powertrain, and with a voltage equal to or less than a lower voltage threshold value (i.e. in a high-voltage operating range). In particular, said combination is a convex combination, wherein the numerical coefficient is indicated by the reference Gain and depends on the voltage VInv_iaccording to the evolution shown in Figure 7, map M50. In the preferred embodiment illustrated, the numerical coefficient Gain has the value of a unit in the high-voltage operating range and it has zero value in the low-voltage operating range. Preferably, the map M50 may coincide with the map M20, by using the numerical coefficient Gain for both linear combinations, particularly for both convex combinations.

[0055] For all intermediate values, as in the case of the calculation shown in Figure 4, the convex combination -which practically corresponds to a weighted average -applies: Q̇Inv_Htrj_TTgt_Tgt_i= Gain · Q̇Inv_Htrj_TTgtVHi_Tgt_i+ (1 − Gain) · Q̇Inv_Htrj_TTgtVLo_Tgt_i

[0056] This corresponds to the sequence of the blocks 52, 54, 56 of Figure 7. In other words, the block 52 calculates the difference Q̇Inv_Htrj_TTgtVHi_Tgt_i− Q̇Inv_Htrj_TTgtVLo_Tgt_i, at the block 54 said difference is multiplied by the coefficient Gain, and at the block 56the value Gain · (Q̇Inv_Htrj_TTgtVHi_Tgt_i− Q̇Inv_Htrj_TTgtVLo_Tgt_i) is added to Q̇Inv_Htrj_TTgtVLo_Tgt_i, thereby obtaining Q̇Inv_Htrj_TTgt_Tgt_i= Gain · (Q̇Inv_Htrj_TTgtVHi_Tgt_i− Q̇Inv_Htrj_TTgtVLo_Tgt_i) + Q̇Inv_Htrj_TTgtVLo_Tgt_i, which is merely a rewriting of the previous expression with factoring out of the coefficient Gain.

[0057] Referring to Figures 8A, 8B, diagrams 60 and 65, the values Q̇Inv_Htrj_TTgtVHi_Tgt_iand Q̇Inv_Htrj_TTgtVLo_Tgt_iare extrapolated from respective maps M60 for the value Q̇Inv_Htrj_TTgtVHi_Tgt_iand M65 for the value Q̇Inv_Htrj_TTgtVLo_Tgt_i, by using as input data the raw torque target value TrqTgt iand the rotational speed Spdi of the electric traction motor itself. The maps M60, M65 provide curves Q̇Inv_Htrj_TTgtVHi_Tgt_i−TrqTgt_iand Q̇Inv_Htrj_TTgtVLo_Tgt_i−TrqTgt_iwhich are parameterized with respect to the speed Spdi • In the Figures, the arrows superimposed on such curves indicate the increasing evolution of the speed Spdi • Qualitatively, the rejected thermal powers Q̇Inv_Htrj_TActVHi_Tgt_iand Q̇Inv_Htrj_TActVLo_Tgt_iincrease with the increase in the speed Spdiand with the increase of the absolute torque value TrqTgt i(reference is made to the absolute value since the regeneration torques have a negative sign).

[0058] Referring to Figure 9, diagram 70, once the first value of rejected thermal power Q̇Inv_Htrj_Tgt_ihas been determined in the described fashion, it is possible to determine the first target value of thermal cooling power Q̇Inv_Clg_Tgt_ias a sum (block 72) of the first value of rejected thermal power Q̇Inv_Htrj_Tgt_iand a first correction value of thermal cooling power Q̇Inv_Clg_Cor_idepending on the currently selected drive mode DriveMod and depending on a difference (block 74) between the current temperature value of the inverter TInv_i(which corresponds to a temperature data item fed back to the system) and the target temperature value of the inverter TInv_Max_Tgt_i.Always referring to Figure 9, map M70, the first correction value of thermal cooling power Q̇Inv_Clg_Cor_idepends on a temperature error of the inverter ΔTInv_Tgt_i= TInv_i− TInv_Max_Tgt_i, acquiring positive values if the error ΔTInv_Tgt_ihas positive values (thus, if TInv_i> TInv_Max_Tgt_i, the correction value Q̇Inv_Clg_Cor_idetermines an increase of thermal cooling power with respect to the mere value of the thermal power rejected by the inverter Q̇Inv_Htrj_Tgt_i) r and negative values if the error ATlnv Tcjt lhas negative values (thus, if TInv i< TInv Max Tgt i, the correction value Qinv_cig_cor_t determines a decrease of thermal cooling power with respect to the mere value of the thermal power re ected by the inverter Q̇Inv_Htrj_Tgt_i). Moreover, with reference to the exemplary curves parameterized with respect to four drive modes DriveModl, DriveMod2, DriveMod3, DriveMod4, mentioned in an order of increasing aggressiveness (thus DriveModl favours the driving range to the detriment of the performances, whereas DriveMod4 favours the achievement of maximum performance to the detriment of the driving range), the first target value of thermal cooling power Qinvcig_Tgt_i ‘

[0059] - if the error ΔTInv_Tgt_ihas positive values (thus if TInv_i> TInv_Max_Tgt_i), Q̇Inv_Clg_Tgt_iincreases (as an absolute value) with the increase in aggressiveness of the drive mode, since in the more aggressive drive modes, in the case of temperatures higher than the target value, a greater use is made of the cooling obtained by drawing electrical power from the battery powering the powertrain, whereas with less aggressive drive modes, which are more oriented towards the driving range, a greater use is made of the thermal capacity of the inverter, thus saving electrical power which would otherwise be employed for cooling;

[0060] - if the error TInv Tgt ihas negative values (thus ifTinv_i <Tinv Max Tgt, Qinv_cig Tgt_i decreases (as an absolutevalue) with the increase in the aggressiveness of the drive mode, since in the more aggressive drive modes, in the case of temperatures lower than the target value, it is preferred to use the thermal capacity of the inverter as little as possible.

[0061] Referring to Figure 10, diagram 80, and 11, diagram 90, and moreover referring to the block 4A of the previous Figure 2, the operation of determining, for each electric traction motor Ml, M2, M3, M4 (and generally for each i-th electric motor, in the present case with i = 1, 2, 3, 4 ), a second value of rejected thermal power Q̇Mot_Htrj_Tgt_icomprises determining a raw value Q̇Mot_Htrj_Raw_Tgt_iof thermal power rejected by the electric traction motor Ml, M2, M3, M4 as a linear combination of a value of thermal power Q̇Mot_Htrj_RawVHi_Tgt_irejected by the electric traction motor Ml, M2, M3, M4 when the electric traction motor Ml, M2, M3, M4 operates at a voltage equal to or greater than a higher voltage threshold value (thus in a high-voltage operating range), and a value Q̇Mot_Htrj_RawVLo_Tgt_iof thermal power rejected by the electric traction motor Ml, M2, M3, M4 when the electric traction motor operates at a voltage equal to or less than a lower voltage threshold value (thus in a low-voltage operating range), in particular by a convex combination.

[0062] Preferably, the raw value Q̇Mot_Htrj_Raw_Tgt_iof thermal power rejected by the i-th electric traction motor is subjected to a filtering operation (block 82) essentially in order to eliminate the signal peaks, which are useless in a treatment for control purposes (the operation is performed, for example, with a stop-band or notch filter). In the present case, the filtering leads to the obtention of the second value of rejected thermal power Q̇Mot_Htrj_Tgt_i.

[0063] Referring back to the convex combination, thelatter is shown in Figure 11, and it is a convex combination wherein the numeral coefficient is indicated by the reference Gain and depends on the voltage VMot_iaccording to the evolution shown in Figure 11, map M90. In the preferred embodiment shown, the numeral coefficient Gain has the value of a unit in the high-voltage operating range and has zero value in the low-voltage operating range.

[0064] For all intermediate values, in the same way as for the calculation shown in Figure 4 and in Figure 7, the convex combination, which practically corresponds to a weighted average, applies: QMot_Htrj_Raw_Tgt = Gain - QMot_HtrJ_RawVHi_Tgt_i + (1—Gain) ’ QMot_HtrJ_RawVLo_Tgt_i •

[0065] This corresponds to the sequence of the blocks 92, 94, 96 in Figure 11. In other words, the block 92 calculates the difference Q̇Mot_Htrj_RawVHi_Tgt_i− Q̇Mot_Htrj_RawVLo_Tgt_i, at the block 94 said difference is multiplied by the coefficient Gain, and at block 96 the value G

[0066]

[0067] Gain · (Q̇Mot_Htrj_RawVHi_Tgt_i− Q̇Mot_Htrj_RawVLo_Tgt_i) is added to Q̇Mot_Htrj_RawVLo_Tgt_i, thereby obtaining Q̇Mot_Htrj_Raw_Tgt_i= Gain · (Q̇Mot_Htrj_RawVHi_Tgt_i− Q̇Mot_Htrj_RawVLo_Tgt_i) + Q̇Mot_Htrj_RawVLo_Tgt_i, which is a mere rewriting of the previous expression with factoring out of the coefficient Gain.

[0068] Referring to the Figures 12 and 13, diagrams 100 and 110, the values Q̇Mot_Htrj_RawVHi_Tgt_iand Q̇Mot_Htrj_RawVLo_Tgt_iare extrapolated from respective maps M100 and M110, by using as input data the current torque TrqAct_iof the electric traction motor and the rotational speed Spd i °f the electric traction motor itself. The maps M100, MHO provide curves Q̇Mot_Htrj_RawVHi_Tgt_i−TrqAct_iand Q̇Mot_Htrj_RawVLo_Tgt_i−TrqAct_iwhich are parameterized with respect to the speed Spdi. In the Figures, the arrows superimposed on said curves indicate the increasing evolution of the speed Spdi • Qualitatively, the rejected thermal powers Q̇Mot_Htrj_RawVHi_Tgt_iand Q̇Mot_Htrj_RawVLo_Tgt_iincrease with the increase of the speed Spdi and with the increase of the absolute value of the torque TrqAct_i(reference is made to the absolute value to since the regeneration torques have a negative sign). With the same power, i. e. with the same torque and rotational speed, the value Q̇Mot_Htrj_RawVHi_Tgt_iis lower than the value Q̇Mot_Htrj_RawVLo_Tgt_i, since in the low- voltage range the current is higher, and so the share of thermal power rejected due to the Joule effect is higher, too. Another possibility for calculating Q̇Mot_Htrj_Raw_Tgt_i, alternative to the convex combination of Figure 11 (and thus alternative to the maps M100, MHO), envisages calculating Q̇Mot_Htrj_Raw_Tgt_ias a difference (as an absolute value) between the mechanical power and the electrical power, thus

[0069] Q̇Mot_Htrj_Raw_Tgt_i= |2π · TrqAct_i· Spdi / 60 − VMot_i· IMot_i|

[0070]

[0071] wherein IMot_iis an electrical current of the general i-th electric traction motor.

[0072] With reference to Figure 14, diagram 120, once the value Quot_Htrj_Tgt_i has been determined according to the fashion described in the foregoing (preferably, determining the value Q̇Mot_Htrj_Raw_Tgt_i, then filtering at the block 82) it is possible to determine (block 4B), for each electric traction motor Ml, M2, M3, M4, the second target value of thermal cooling power Q̇Mot_Clg_Tgt_ias a sum (block 122) of the second value of rejected thermal power Q̇Mot_Htrj_Tgt_i) and a second correction value of thermal cooling power Q̇Mot_Clg_Cor_idependent on the currently selected drive mode DriveMod and dependent on a difference (block 124 ) between the current temperature value TMot_iof the electric traction motor Ml, M2, M3, M4 (which corresponds to a temperature value fed back to the system) and the target temperature value of theelectric traction motor TMot Max Tgt i. Always referring to Figure 14, map M120, the second correction value of thermal cooling power Quot_cig_cor_i depends on a temperature error of the electric motor ^TMot Tgt i= TMot i- TMot Max Tgt i(which corresponds to the output of the block 124 ), acquiring positive values if the error ^TMot Tgt ihas positive values (thus, if TMot i> TMot Max Tgt i, the correction value Quot_cig_cor_i determines an increase of thermal cooling temperature with respect to the mere value of the thermal power rejected by the i-th electric traction motor QMot_Htrj_Tgt_ir and negative values if the error TMot Tgt thas negative values (thus, if TMot i<TMot_Max Tgt_i > the correction value QMot_cig_cor_i determines a decrease of thermal cooling power with respect to the mere value of the thermal power rejected by the i-th electric traction motor Q̇Mot_Htrj_Tgt_i. Moreover, referring to the exemplary curves parameterized with respect to the four drive modes DriveModl, DriveMod2, DriveMod3, DriveMod4, mentioned in an order of increasing aggressiveness (thus, as already stated in the foregoing, DriveModl favours the driving range to the detriment of the performances, whereas DriveMod4 favours the achievemnt of maximum performance to the detriment of the driving range), the second target value of thermal cooling power QMot_cig_Tgt_i - - if the error TMot Tgt ihas positive values (thus, if T

[0073]

[0074] ^MotJ > ^'Mot_Max_Tgt_i ) > QMot_cig_Tgt_i increases (as an absolute value) with the increase in aggressiveness of the drive mode, since in the more aggressive drive modes, in the case of temperatures higher than the target value, a greater use is made of the cooling obtained by drawing electrical power from the battery powering the powertrain, whereas with less aggressive drive modes, which are rather oriented towards the driving range, a greater use is made of the thermal capacity of theelectric traction motor, thus saving electrical power which would otherwise be employed for cooling;

[0075] - if the error ^TMot Tgt ihas negative values (thus, if TMOU < TMot_Max_Tgt_i ') i QMot_cig_Tgt_i decreases (as an absolute value) with the increase in aggressiveness of the drive mode, since in the more aggressive drive modes, in the case of temperatures lower than the target value, the thermal capacity of the electric traction motor tends to be used as little as possible.

[0076] Referring to Figure 15, diagram 130, and 16, diagram 140, and moreover referring to the block 6A of the previous Figure 2, the operation of determining, for each transmission lubricant (generally speaking, for each i-th transmission lubricant) a third value of rejected thermal power QTrnsmOii_Htrj_Tgt_i comprises determining a raw value QTrnsmou_Htrj_Raw_T t_i °f thermal power rejected by the transmission lubricant as a linear combination of a value of thermal power QTrnsmOii Htrj_RawTHi_Tgt_i rejected by the transmission lubricant when it operates at a temperature equal to or greater than a higher temperature threshold value (i. e. in a high-temperature operating range), and a value QTrnsmOii_Htrj_RawTLo_Tgt_i

[0077]

[0078] thermal power rejected by the transmission lubricant when it operates at a temperature equal to or less than a lower temperature threshold value (i. e. in a low-temperature operating range), in particular by means of a convex combination.

[0079] Preferably, the raw value QMot_Htrj_Raw_Tgt_i °f thermal power rejected by the transmission lubricant is subj ected to a filtering operation (block 132 ) essentially in order to eliminate the signal peaks, which are useless in a treatment for control purposes (as stated in the foregoing, the operation is performed, for example, with a stop-band or notch filter). In this case, the filtering originates the third value of rejectedthermal power QTrnsmOil_Htrj_TgtJ •

[0080] Referring back to the convex combination, this is shown in Figure 16, and it is a convex combination wherein the numerical coefficient is indicated by the reference Gain and depends on a temperature TTrnsmou_i of the transmission lubricant according to the evolution shown in Figure 16, map M140. In the preferred embodiment shown, the numerical coefficient Gain has the value of a unit in the high-temperature operating range and zero value in the low-temperature operating range.

[0081] For all intermediate temperature values, in the same way as for the convex combinations applied to the case of the inverter and of the electric traction motor, the convex combination - which practically corresponds to a weighted average - holds true: QTrnsmOil_HtrJ__Raw_Tgt_i Gain ' QTrnsmOil_Htrj_RawTHi_Tgt_i + (1—Gain) QTrnsmOil_Htrj_RawTLo_Tgt_i •

[0082] This corresponds to the sequence of the blocks 92, 94, 96 in Figure 16. In other words, block 142 calculates the difference QTrnsmOil_Htrj_RawTHi_Tgt_i ~ QTrnsmOil_Htrj_RawTLo_Tgt_i r at the block 144 said difference is multiplied by the coefficient Gain, and at the block 146 the value Gain - (, QTrnsmOil_HtrJ_RawTHi_Tgt_i ~ QTrnsmOil_HtrJ_RawTLo_Tgt_i) fsadded to QTrnsmOil_Htrj_RawTLo_Tgt_ir thereby obtaining QTrnsmOil_HtrJ__Raw_Tgt_i Gain ’ (^TrnsmOil Htrj RawTHi Tgt i ~

[0083]

[0084] QTrnsmOll Htrj RawTLo Tgt l) QTrnsmOil Htrj RawTLo Tgt i ' which is a mere rewriting of the previous expression with factoring out of the coefficient Gain.

[0085] Referring to the Figures 17 and 18, diagrams 150 and 160, the values QTrnsmOil_Htrj_RawTHi_Tgt_iand QTrnsmOii_Htrj_RawTLo_Tgt_iareextrapolated from respective maps M150 and M160 by using as input data the current torque TrqActi of the electric traction motor (which is operatively connected to the transmission including the i-th transmission lubricant) and the rotational speedSpdi of the electric traction motor itself. The maps M150, M160 provide curves QTrnsmOil_Htrj_RawTHi_Tgt_i-TrqAct_iand QTmsmon_Htrj_RawTLo TSt_i-TrqAct_iwhich are parameterized with respect to the speed Spdi. In the Figures, the arrows superimposed on said curves indicate the increasing evolution of the speed Spdi • Qualitatively, the rejected thermal powers QTrnsmOil_Htrj_RawTHi_Tgt_iand QTrnsmOii_Htrj_RawTLo_Tgt_i increase with the increase of the speed Spdi and with the increase of the absolute torque value TrqActi, since the mechanical power is increased (reference is made to the absolute value since the regeneration torques have a negative sign). With the same power, thus with the same torque and rotational speed, the value QTrnsmon_Htrj_RawTHi Tgtji slower than the value QTrnsmon_Htrj_RawTLo_Tgt_i f since in the low temperature range of the transmission lubricant the transmission efficiency is lower.

[0086] Referring to Figure 19, diagram 170, once the value QTrnsmou_Htrj_T t_i has been determined according to the fashion described in the foregoing (preferably, determining the value QTrnsmou_Htrj_Raw Tgt_i > then filtering at the block 132 ), it is possible to determine (block 6B), for each transmission lubricant, the third target value of thermal cooling power QTrnsmOii_cig_Tgt_i as the sum (block 172 ) of the third value of rejected thermal power QTrnsmou_Htrj_T t_i and a third correction value of thermal cooling power QTrnsmou_ci _cor_i dependent on the currently selected drive mode DriveMod and on a difference (block 174 ) between the current temperature value TTrnsmOili of the i-th transmission lubricant (which corresponds to a temperature data item fed back to the system) and the target temperature value of the transmission lubricant itself TTrnsmOil Max Tgt i. Always referring to Figure 19, map M170, the second correction value of thermal cooling power QTrnsmou_ci _cor_i depends on a temperature error of thetransmission lubricant TTrnsmOil Tgt i= TTrnsmOil i-TTrnsmoti_Max_Tgt_i (which corresponds to the output of the block 174 ), acquiring positive values if the error ^TTmsmOii Tgt_i has positive values (thus, if TTrnsmOil i> TrnsmOi.1 Max Tgt i r the correction value QTrnsmOll_Clg_Cor_i determines an increase of thermal cooling power with respect to the mere value of the thermal power rejected by the i-th transmission lubricant QTrnsmOii_Htrj_Tgt_ir and negative values if the error TTrnsmOil Tgt thas negative values (thus, if TTrnsmOil i< TTrnsmOil Max Tgt i, the correction value QTrnsmou_cig_cor_i determines a decrease of thermal cooling power with respect to the mere value of the thermal power rejected by the i-th electric traction motor QTrnsmou_Htrj_Tgt_i • Moreover, with reference to the exemplary curves parameterized with respect to the four drive modes DriveModl, DriveMod2, DriveMod3, DriveMod4, mentioned in an order of decreasing aggressiveness (thus, as already described in the foregoing, DriveModl favours the driving range to the detriment of the performances, whereas DriveMod4 favours the achievement of maximum performance to the detriment of the driving range), the second target value of thermal cooling power Q rnsmoil Clg TgtJ:

[0087] if the error TTrnsmOil Tgt thas positive values (thus, if Tj’rnsmQii > T'j-rnsmoil_Max_Tgt_i ') r QTrnsmOil_Clg_Tgt_i increases (as an absolute value) with the increase in aggressiveness of the drive mode, since in the more aggressive drive modes, in the case of temperatures higher than the target value, a greater use is made of the cooling obtained by drawing electrical power from the battery powering the powertrain, whereas with less aggressive drive modes, which are more oriented towards the driving range, a greater use is made of the thermal capacity of the transmission lubricant, thus saving electrical power which would otherwise be employed forcooling;

[0088] - if the error TTrnsmOil Tgt thas negative values, (i. e., if T

[0089]

[0090] j’rnsmQii i < Tj’rnsmQiij^axj’gf:i ), Qinv_cig_Tgt_t decreases (as an absolute value) with the increase in aggressiveness of the drive mode, since in the more aggressive drive modes, in the case of temperatures lower than the target value, the thermal capacity of the transmission lubricant tends to be used as little as possible.

[0091] increases with the increase in aggressiveness of the drive mode, since in the more aggressive drive modes, in case of temperatures higher than the target value, a greater use is made of the cooling obtained by drawing electrical power from the battery powering the powertrain, whereas with less aggressive drive modes, which are more oriented towards the driving range, a greater use is made of the thermal capacity of the transmission lubricant, thus saving electrical power which would otherwise be employed for cooling.

[0092] Thanks to the method according to the invention, it is therefore possible, as a function of the mission requested by the driver of the vehicle (the dependence takes into account the drive mode DriveMod), to increase the duration of the performances of the powertrain without incurring in derating interventions, by dynamically controlling the cooling power of the traction components of each traction unit (inverter, electric traction motor and transmission lubricant), especially in the mission profiles for which the performance duration has priority.

[0093] Moreover, it is possible to increase the driving range of the vehicle by using less electrical energy for cooling the traction components, by making use of the thermal capacity of the traction components, and enabling reducing the minimum flow rate of coolanttowards the inverters, especially for mission profiles wherein an increase in driving range is required.

[0094] Finally, it becomes possible to make use of all the available thermal cooling power, in order to avoid reaching critical temperatures of the traction components.

[0095] Of course, the implementation details and the embodiments may amply vary with respect to what has been described and illustrated, without departing from the extent of the present inventions, as defined in the annexed claims.

Claims

CLAIMS1. A method for determining target values of thermal cooling power for one or more traction units of an electric powertrain of a vehicle, wherein each traction unit comprises an electric traction motor (Ml, M2, M3, M4 ), an inverter operatively connected to the electric traction motor (Ml, M2, M3, M4 ), and a transmission connecting the electric traction motor (Ml, M2, M3, M4 ) to one or more drive wheels (RL, RR, FL, FR) and including a transmission lubricant,the method comprising:- determining (2A), for each inverter, a first value of rejected thermal power (QinVHtrj_Tgt_i ')a s afunction of a rotational speed of the electric traction motor to which the inverter is operatively connected, as a function of an operating voltage of the inverter (V / nv, as a function (Qinv_Htrj_TAct_Tgt_i^ °f a current torque value of the electric traction motor to which the inverter is operatively connected, and as a function ( QinvHtrj_TTgt_Tgt_t ') of a raw torque target value of the electric traction motor,determining (4A), for each electric traction motor, a second value of rejected thermal power QMotjitrj _Tgt_ia s afunction of a rotational speed of the electric traction motor, as a function of a supply voltage of the electric traction motor (Mot, and as a function ( Quotjitrj_Raw_Tgt_i of a current torque value of the electric traction motor,determining ( 6A), for each transmission lubricant, a third value of rejected thermal power ( QTrnsmou_Htrj_Tgt_ias afunction of a rotational speed of the electric traction motor connected to the transmission, as a function of a current temperature value of the transmission lubricant (TTrnsmOili ), and as a function (QTrnsmOil_Htrj_Raw_Tgt_i') of a current torque value ofthe electric traction motor connected to the transmission,determining (2B), for each inverter, a first target value of thermal cooling power ( QInv_Clg_Tgt_i')a s afunction of a currently selected drive mode (DriveMod), as a function of said first value of rejected thermal power (Qinv_Htrj_Tgt_i') / as afunction of an inverter temperature target value (TInv Max Tgtand as a function of a current temperature value of the inverter TInv, determining (4B), for each electric traction motor, a second target value of thermal cooling power QMot_cig_Tgt_i ')as afunction of the currently selected drive mode (DriveMod), as a function of said second value of rejected thermal power ( Quotjitrj. ras afunction of a target value of the electric traction motor temperature ^Mot_Max_Tgt_t ') and as a function of a current temperature value of the electric traction motor (TMot i),determining ( 6B), for each transmission lubricant, a third target value of cooling thermal power ( QTrnsmOil_Clg_Tgt_ia s afunction of the currently selected drive mode (DriveMod), as a function of said third value of rejected thermal power ( QrrnsmOiijitrj. ') / as afunction of a target temperature value of the transmission lubricant (TTrnsmOil Max Tgtj ) and as a function of the current temperature value of the transmission lubricant ( TTrnsmOilJ ) •2. The method of claim 1, wherein said determining the first value of rejected thermal power ( Qinv_Htrj_Tgt_i ') for each inverter includes determining the greater ( 12 ) of a value of rejected thermal power (Qinv_Htrj_TAct_Tgt_i^ by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the current torque value ( TrqActi ) of the electric traction motor itself, and a value of thermal power rejected (Qinv Htrj TTgt Tgt j by the inverterwhen the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the raw target torque value ( TrqTgti ) of the electric traction motor, wherein said raw target torque value is a target torque value for the electric traction motor operatively associated to said inverter and corresponding to a share of a total torque requested to the electric powertrain assigned to said electric traction motor.

3. The method of claim 2, wherein:said value of thermal power rejected (QinvjHrj-TAct Tgtj)bY the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the current torque value of the electric motor itself is determined as a linear combination of a value of thermal power rejected (Qinvjtrj_TAct_Tgt_i'> by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the current torque value ( TrqAct_i) of the motor and with a voltage equal to or greater than a higher voltage threshold value, and a value of thermal power rejected (Qinv_Htrj_TActVHi_Tgt_i ') by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the current torque value (TrqAct_i) of the electric traction motor itself and with a voltage equal to or less than a lower voltage threshold value ( Qmv_Htrj_TActvLo Tgt_i ') > in particular as a convex combination,said value of thermal power rejected Qinvj rj_TTgt_Tgt_i ') by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the target value of raw torque ( TrqTgt i) of the electric traction motor is determined as a linear combination ofa value of thermal power rejected ( QInv_Htrj_TTgtVHi_Tgt_i)bY the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the current torque value ( TrqActi ) of the electric traction motor itself and with a voltage equal to or greater than a higher voltage threshold value, and a value of thermal power rejected (QinvjHrj_TTgtVLo Tgt_i) by the inverter when the electric traction motor to which the inverter is operatively connected operates with a torque value equal to the raw torque target value (TrqTgti ) of the electric traction motor and with a voltage equal to or less than a lower voltage threshold value, in particular as a convex combination.

4. The method of any of claims 1 to 3, wherein said determining (2B), for each inverter, the first target value of thermal cooling power ( QInv_Clg_Tgt_i) includes determining the first target value of thermal cooling power ( QInv_Clg_Tgt_i) as the sum of said first value of rejected thermal power (Qinv_Htrj_Tgt_i ) and a first correction value of cooling thermal power ( QInv_Clg_Cor_i) depending on the currently selected drive mode (DriveMod) and depending on a difference between the current temperature value of the inverter (TInv i) and the target temperature value of the inverter (TInv Max Tgt.

5. The method of to claim 1, wherein said determining (4A), for each electric traction motor, a second value of rejected thermal power ( QMot_Htrj_Tgt_i ) includes determining a raw value ( QMot_Htrj_Raw_Tgt_t ) of thermal power rejected by the electric traction motor as a linear combination of a value of thermal power rejected ( QMot_Htrj_RawVHi Tgt_i ) by the electric traction motor when the electric traction motor operates at a voltage equal to or greater than a voltage threshold value is a value of thermal power rejected (QMot_Htrj_RawVLo_Tgt_i) by theelectric traction motor when the electric traction motor operates at a voltage equal to or lower than a lower voltage threshold value, in particular as a convex combination.

6. The method of claim 5, wherein the value of the thermal power rejected(QMot_Htrj_RawVHi_Tgt_i) by the electric traction motor when the electric traction motor operates at a voltage equal to or greater than a higher voltage threshold value and the value of the thermal power rejected (QMot_Htrj_RawVLo_T t_i ) by the electric traction motor when the electric traction motor operates at a voltage equal to or lower than a lower voltage threshold value are determined as a function of the current torque (TrqAct_i) of the electric traction motor and a rotational speed (Spdi) of the electric traction motor.

7. The method of any of claims 1, 5 or 6, wherein said determining (4B), for each electric traction motor, the second target value of cooling thermal power QMot_Clg_Tgt_iincludes determining the second target value of cooling thermal power (QMot_Clg_Tgt_i) as the sum of said second value of rejected thermal power ( QInv_Htrj_Tgt_i) and a second correction value of cooling thermal power ( Qinv_cig_cor_t ) depending on the currently selected drive mode (DriveMod ) and depending on a difference between the current temperature value of the electric traction motor (TMot_i ) and the target temperature value of the electric traction motor (TMot Max Tgtj ).

8. The method of claim 1, wherein said determining ( 6A), for each transmission lubricant, the third value of rejected thermal power (QTrnsmOil_Htrj_Tgt_i) includes determining a raw value ( QTrnsmOil_Htrj_Raw_Tgt_i) of thermal power rejected by the transmission lubricant as a linear combination of a value of thermal input rejected ( QTrnsmOil_Htrj_RawTHi_Tgt_i) by the transmission lubricant when the transmission lubricant operates at a temperatureequal to or greater than a temperature threshold value and a value of thermal output rejected ( QTrnsmOil_Htrj_RawTLo_Tgt_i) by the transmission lubricant when the transmission lubricant operates at or below a lower temperature threshold value, in particular as a convex combination.

9. The method of claim 8, wherein the value of the thermal power rejected ( QTrnsmOil_Htrj_RawTHi_Tgt_i) by the transmission lubricant when the transmission lubricant operates at a temperature equal to or higher than a higher temperature threshold value and the value of the thermal power rejected ( QTrnsmOil_Htrj_RawTLo_Tgt_i) by the transmission lubricant when the transmission lubricant operates at a temperature equal to or lower than a lower temperature threshold value is determined as a function of the current torque (TrqAct_i) of the electric traction motor operatively connected to the transmission including the transmission lubricant and a rotational speed (Spdi) of the electric traction motor operatively connected to the transmission including the transmission lubricant.

10. The method of any of claims 1, 8, 9, wherein said determining ( 6B), for each transmission lubricant, the third target value of cooling thermal power ( QTrnsmOil_Clg_Tgt_iincludes determining the third target value of cooling thermal power (QTrnsmOii_cig_Tgt_i as the sum of said third value of rejected thermal power ( QTrnsmOil_Htrj_Tgt_iand a third correction value of cooling thermal power ( QTrnsmOil_Clg_Cor_idepending on the drive mode currently selected (DriveMod) and depending on a difference between the current temperature value of the transmission lubricant (TTrnsmOil_i) and the target temperature value of the transmission lubricant ( TTrnsmOil_Max_Tgt_i ) •

Images