Method for determining a torque of an electric traction motor of an electric powertrain of a vehicle, corresponding vehicle and computer program product

Abstract

A method (20) for determining a torque (TIn_Tgt) of an electric traction motor of an electric powertrain of a vehicle, the electric powertrain comprising at least said electric traction motor operatively associated with at least one driving wheel of an axle of the vehicle; wherein said axle comprises at least one engagement device configured to selectively connect the at least one driving wheel of the axle to said electric traction motor; the method comprising, in response to said electric traction motor being in disconnection condition from the at least one driving wheel and to the receiving of a request for connection of the electric traction motor to the at least one driving wheel: - determining a target rotational speed (nM_Tgt) of said electric traction motor as a function of a rotational speed of the at least one driving wheel; - determining (202) a target rotational acceleration (ŵM_Tgt) of the electric traction motor as a function of said target rotational speed (nM_Tgt); and - determining (200) said torque (TIn_Tgt) as a function of said target rotational acceleration (ŵM_Tgt) of the electric traction motor.

Description

[0001] " Method for determining a torque of an electric traction motor of an electric powertrain of a vehicle, corresponding vehicle and computer program product" ★ ★ ★ ★

[0002] TEXT OF THE DESCRIPTION

[0003] Field of the Invention

[0004] The embodiments of the present disclosure refer to methods for determining a torque of an electric traction motor of an electric powertrain of a vehicle.

[0005] Specifically, various embodiments of the present disclosure concern solutions for determining said torque in vehicles wherein the electric traction motor can be selectively decoupled from one or more driving wheels operatively connected thereto.

[0006] Known Art

[0007] In a vehicle with an electric powertrain comprising a plurality of electric traction motors, a disconnection of at least one electric traction motor with respect to one or more corresponding driving wheels operatively associated therewith is generally controlled when the request for torque by the driver can be met by the remaining one or more electric traction motors.

[0008] Such disconnection is implemented with the purpose of a general efficiency improvement, since the rotational dragging of an electric traction motor which is not involved in meeting the request for torque by the driver only results in energy dissipation.

[0009] The disconnection, as well as the following reconnection, are operated by means of a mechanical engagement device (which is electrically operated and electronically controlled), which is generally configured with front-teeth engaging means. This configuration ensures torque transmissibility and a lesser wear in time with respect to, for example, a friction clutch.The problem consists in the fact that said type of engagement device requires synchronizing the rotational speed of the electric motor with the rotational speed of the drivetrain downstream thereof when restoring the mechanical connection. A synchronization is necessary in order to avoid an early wear of the engagement teeth, noises during the engagement and drivetrain discontinuities. The drivetrain downstream of the electric traction motor may comprise a transmission and one or more driving wheels connected to the transmission, or directly a driving wheel, if the electric motor is directly connected with the driving wheel or if the engagement device is arranged between the transmission and the driving wheel (s).

[0010] Therefore, solutions adapted to expedite the operation of synchronizing the rotational speed of the electric traction motor when reconnecting the latter with the drivetrain downstream thereof would be advantageous for favouring said restoring of the mechanical connection.

[0011] Obj ect of the Invention

[0012] The invention aims at solving the technical problems outlined in the foregoing. Specifically, the obj ect of the invention consists in providing a method for determining a torque of an electric traction motor of an electric powertrain of a vehicle, wherein said electric traction motor may be selectively disconnected from one or more driving wheels operatively connected thereto, which may enable expediting the operations of synchronizing the rotational speed of the electric traction motor at the moment of a reconnection with the drivetrain downstream thereof, in order to restore the mechanical connection.

[0013] Summary of the Invention

[0014] The obj ect of the invention is achieved by means ofa method having the features set forth in the claims that follow, which are an integral part of the technical teaching provided herein in relation to the invention.

[0015] One or more embodiments refer to a corresponding vehicle.

[0016] One or more embodiments concern a corresponding computer program product loadable in at least one processing circuit ( for example, an electronic control unit of the vehicle) and comprising portions of software code for executing the steps of the (corresponding) method, when the product is run on at least one processing circuit.

[0017] As used herein, the reference to said computer program product is meant to be equivalent to the reference to a medium readable by a computer, for example, by an electronic control unit of the vehicle or any other processing unit comprised in said vehicle, containing instructions for controlling a processing system in order to coordinate the implementation of the (corresponding) method according to one or more embodiments.

[0018] Brief Description of the Figures

[0019] One or more embodiments will now be described, by way of example only, with reference to the annexed Figures, wherein:

[0020] - Figures 1A-1C show diagrams of powertrains for which it is possible to implement a method according to embodiments of the present disclosure;

[0021] Figure 2 shows a functional block diagram representative of a method according to embodiments of the present disclosure;

[0022] - Figure 3 shows a functional block diagram for defining a target torque of the electric traction motor to be synchronized, according to embodiments of the present disclosure;Figure 4 and Figure 5 show functional block diagrams for defining a target acceleration of the electric traction motor to be synchronized, according to embodiments of the present disclosure;

[0023] - Figure 6 shows exemplary graphs of behaviour of the target rotational speed of the electric traction motor to be synchronized and of raw values of a target acceleration of said electric traction motor, according to embodiments of the present disclosure;

[0024] - Figure 7 shows a functional block diagram for defining an update state, according to embodiments of the present disclosure;

[0025] - Figure 8 shows exemplary graphs of behaviour of the update state, according to embodiments of the present disclosure; and

[0026] - Figure 9 shows a block diagram relating to a method according to embodiments of the present disclosure.

[0027] Detailed Description

[0028] In the following description, one or more specific details are illustrated with the purpose of providing a thorough understanding of exemplary embodiments of the present disclosure. The embodiments may be obtained without one or more of the specific details, or with other methods, components, materials, etc. In other instances, known operations, materials or structures are not illustrated or described in detail in order not to obscure certain aspects of the embodiments.

[0029] A reference to "an embodiment" or "one embodiment" in the present description is meant to indicate that a particular configuration, structure or characteristic described with reference to the embodiment is comprised in at least one embodiment. Therefore, phrases such as "in an embodiment", "in one embodiment" or the like, which may be present in one or more instances in thepresent description, are not necessarily referring to one and the same embodiment.

[0030] Moreover, particular configurations, structures of characteristics may be combined in any suitable fashion in one or more embodiments.

[0031] The headings provided herein are for convenience only, and therefore they do not define the extent of protection or the scope of the embodiments.

[0032] Throughout the Figures annexed herein and throughout the detailed description provided in the following, unless the context dictates otherwise, the similar parts or elements are denoted with similar ref erences / numbers, and a corresponding description will be omitted for brevity.

[0033] As stated in the foregoing, solutions as described in the present document aim at favouring an expediting of the synchronizing operations of the rotational speed of an electric traction motor when reconnecting the latter with the drivetrain downstream thereof, in such a way as to facilitate restoring the mechanical connection between said electric traction motor and one or more driving wheels operatively connected thereto.

[0034] Figures 1A-1C show exemplary diagrams of powertrains 10a, 10b, and 10cfor which it is possible to implement a method according to embodiments of the present disclosure.

[0035] The electric powertrains 10a, 10b, and 10cshown in said Figures 1A-1C comprise at least one electric traction motor 100 ( for example, Figure 1C shows a first electric traction motor 100aand a second electric traction motor 100b), which can be selectively connected and disconnected to or from one or more driving wheels, for example, a first driving wheel Waand / or a second driving wheel Wb, possibly comprised in the same axle.

[0036] Such connection and disconnection operations arecarried out by means of an engagement device, for example:

[0037] a single engagement device WD in embodiments according to Figure 1B, configured to connect and disconnect both the first driving wheel Waand the second driving wheel Wb,-or

[0038] a first engagement device WDa, configured to connect and disconnect the first driving wheel Wa, and a second engagement device WDb, configured to connect and disconnect the second driving wheel Wb, in embodiments according to Figures 1A or 1C.

[0039] Between the engagement device WD, WDa, or WDb and the corresponding one or more driving wheels Waand / or Wb there may be arranged a drivetrain which extends from the engagement device to the one or more corresponding driving wheels. Said drivetrain may comprise one of:

[0040] - a direct drive ( for example, as in the embodiments according to Figures 1A and 1C) rotatably connected to a driving wheel Waand / or Wb and which can be connected to the electric traction motor 100, 100aand / or 100b by means of the engagement device WDaor WDb and, in case, by means of a differential D (such as, for example, in Figure 1A) or one or more transmissions Taand / or Tb (such as, for example, in Figure 1C);

[0041] a differential D ( for example, as in the embodiments according to Figure 1B) having an input shaft, connectable to the electric traction motor 100 by means of the engagement device WD, and a first and a second output shafts, rotatably connected to corresponding driving wheels Waand Wb,-and

[0042] - a transmission T ( It is noted that this case is not illustrated in the Figures 1A-1C for brevity) having an input shaft connectable to a respective electric traction motor by means of a respective engagement device, and an output shaft rotatably connected to arespective driving wheel Waor Wb.

[0043] Of course, upstream of the engagement device, that is, between the engagement device WD, WDaor WDband the respective electric traction motor 100, 100aand / or 100b, there may be present a direct connection to the electric traction motor ( for example, as in Figure 1B), or else the connection may be mediated by a transmission ( for example, the transmissions Taand / or Tb in Figure 1C) or a differential ( for example, the differential D in Figure 1A).

[0044] In more detail, Figure 1A shows components of an electric powertrain 10acomprising an electric traction motor 100 associated with a front or rear axle of the vehicle. Said electric traction motor 100 is connected in a disengageable fashion to both driving wheels Waand Wb by means of a differential D. The first engagement device WDais arranged between the differential D and the first driving wheel Wa, whereas the second engagement device WDb is arranged between the differential D and the second driving wheel Wb,-thus, both engagement devices are located between the transmission (differential D) and the driving wheels.

[0045] Figure 1B shows components of an electric powertrain 10b comprising an electric traction motor 100 associated with a front or rear axle of the vehicle. Said electric traction motor 100 is connected in a disengageable fashion to both driving wheels Waand Wb by means of a differential D but, unlike Figure 1A, the configuration of Figure 1B envisages the presence of a single engagement device WD arranged between the motor 100 and the differential D; therefore, the engagement device WD is located between the electric traction motor 100 and the transmission (differential D).

[0046] Figure 1C shows components of an electric powertrain 10ccomprising a first electric traction motor100aassociated with a front or rear axle of the vehicle, and a second electric traction motor 100b associated with said front or rear axle. The first electric traction motor 100a is connected in a disengageable fashion to the first driving wheel Waby means of a first transmission Ta. The second electric traction motor 100bis connected in a disengageable fashion to the second driving wheel Wbby means of a second transmission Tb. The first engagement device WDais arranged between the first transmission Taand the first driving wheel Wa, whereas the second engagement device WDb is arranged between the second transmission Tb and the second driving wheel Wb; therefore, both engagement devices are located between the transmission and the driving wheels.

[0047] It is noted that the following description refers to a general "electric traction motor", with the premise that it is an electric traction motor along the drivetrain whereof, down to the respective driving wheel (s), there is arranged an engagement device. Therefore, solutions according to the present disclosure may be applied to any electric traction motor that can be decoupled from one or more driving wheels operatively connected thereto.

[0048] This being said, the description provided in the following refers to a method for determining a torque of an electric traction motor of an electric powertrain of a vehicle in such a way as to expedite, by applying said component of torque of said electric traction motor, the operations of synchronizing the rotational speed of said electric traction motor when it is reconnecting with the drivetrain described in the foregoing.

[0049] In this regard, Figure 2 shows a functional block diagram 20 representative of a method according to embodiments of the present description. Said method facilitates the definition of a target value of torqueof the electric traction motor 100 to be used to expedite the synchronizing operation requested for coupling said electric traction motor to one or more corresponding driving wheels, so that said electric traction motor becomes available for the propulsion of the vehicle. For example, said operation of defining the target value of torque may be carried out by a unit for controlling the speed of the motor.

[0050] Therefore, solutions according to Figure 2 enable reducing the time required for said synchronization and achieving a target rotational speed as rapidly as possible.

[0051] Indeed, the torque of the electric traction motor which enables obtaining the target rotational speed to be reached during the synchronizing operation described in the foregoing (that is, the rotational speed of the wheel to which the electric traction motor is to be operatively connected in response to the reconnection) is usually calculated:

[0052] by considering contributions which enable compensating for the friction of the system in stationary conditions, for example, via an open-loop control unit; and

[0053] - by minimizing, for example, via a closed-loop control unit comprising proportional and integral contributions, a difference (that is, an error) between said target rotational speed to be reached (that is, the rotational speed of the drivetrain downstream of the motor under consideration) and a current rotational speed of said motor which is obtained, for example, by a feedback signal.

[0054] Therefore, said torque of the electric traction motor usually corresponds to a target value of propulsion torque, that is, a torque value which enables reaching the target rotational speed, determined in response toa request of connection of said electric traction motor to the one or more corresponding driving wheels (therefore, the target torque value refers to the manoeuvre of transition into a condition of connection of the electric traction motor to the one or more corresponding driving wheels). It is noted that, in correspondence of the connection request, said electric traction motor is in a condition of disconnection from the one or more corresponding driving wheels Waand / or Wb, said disconnection being performed via the corresponding engagement device WD, WDaor WDb.

[0055] Said target of propulsion torque is usually determined by means of the operations described in the following, which are performed, as described in the foregoing, via an open-loop control unit and a closed-loop control unit.

[0056] A first operation regards the determination of a first target value of propulsion torque via an open-loop calculation, the aim whereof is to balance the rotational frictions which are generated in response to a rotation of the system with a speed equal to the requested target speed.

[0057] A second operation regards the determination of a second target value of propulsion torque, for example, a torque correction value, via a closed-loop calculation performed as a function of a difference between the value of target speed which has to be reached at the end of the synchronization phase and a feedback value indicative of a current value of rotational speed of the electric traction motor.

[0058] Therefore, a further operation comprises determining said target value of propulsion torque as a function of the first target value of propulsion torque determined via the open-loop calculation and of the second target value of propulsion torque determined viathe closed-loop calculation, for example, performed by summing the first target value of propulsion torque to the second target value of propulsion torque.

[0059] The target value of propulsion torque may therefore be obtained by summing the first target value of propulsion torque determined via the open-loop calculation and the second target value of propulsion torque determined via the closed-loop calculation.

[0060] A disadvantage of this first approach resides in the fact that, if the target rotational speed to be reached is not constant, the synchronization step may require some time.

[0061] Indeed, if the target rotational speed to be reached is not constant, for example, during standard operative conditions of the vehicle ( for example, when the coupling of the electric traction motor to one or more corresponding driving wheels is requested during an acceleration phase of the vehicle), the minimizing operation performed via the closed-loop control unit is unable to compensate for the error between the target rotational speed and the current rotational speed within a determined expected time. In fact, in this case, the target rotational speed varies over time and the openloop control unit is able to maintain a constant target rotational speed but is unable to generate a contribution of torque which follows the variations of the target rotational speed over time.

[0062] It is noted that, normally, the target rotational speed to be reached during a synchronization operation is not constant but varies in time, for example, continuously. For example, the coupling of an electric traction motor to one or more corresponding driving wheels may be requested in response to a request for acceleration by the driver of the vehicle, and therefore the synchronization operation is performed when thevehicle is already in an acceleration phase and when the target rotational speed increases in time.

[0063] Considering what has been set forth in the foregoing, solutions according to the present disclosure favour a reduction of the duration of said phase of synchronizing the rotational speed of the motor even in the presence of a variation of such target rotational speed, that is, even in the presence of a target rotational speed which is not constant.

[0064] To this end, solutions according to the present disclosure favour determining a target value of inertial torque TIn_Tgt, for example, using the functional block diagram 20 shown in Figure 2, to be used as a contribution of torque to be summed to the result provided by the open-loop propulsion torque in order to compensate for the variation of the target rotational speed over time, thus expediting the synchronizing operation.

[0065] For example, it is noted that in embodiments according to Figures 1A or 1B, the target value of inertial torque TIn_Tgtto be determined corresponds to a single value relating to the electric traction motor 100. On the other hand, in embodiments according to Figure 10, the target value of inertial torque TIn_Tgtto be determined corresponds to two different values, wherein a first value relates to the first electric traction motor 100aand a second value relates to the second electric traction motor 100b.

[0066] The target value of inertial torque TIn_Tgtmay be provided as output by a block for defining the target inertial torque of an electric traction motor 200 based on:

[0067] - a target acceleration of the electric traction motor ẇM_Tgt; and

[0068] a speed control signal SCA, which indicateswhether a control function of the rotational speed of the motor is activated, as is the case, for example, during the synchronizing operation, or whether it is deactivated.

[0069] The target acceleration of the electric traction motor ẇM_Tgtis provided as output by a block for defining the target acceleration of an electric traction motor 202 based on the target rotational speed of the motor UM_ gt •

[0070] Said target rotational speed of the motor nM_ gt corresponds to a rotational speed which has to be reached by the electric traction motor in order to achieve the synchronization with respective one or more driving wheels. Therefore, said target rotational speed of the motor nM_Tgtmay be obtained as a function of signals which indicate rotational speed values relating to said respective one or more wheels. Thus, said target acceleration of the electric traction motor ẇM_Tgtcorresponds to an acceleration relating to the rotation of the electric traction motor which enables reaching said target rotational speed nM_ gt.

[0071] Therefore, to sum up, solutions according to the present disclosure refer to a method ( for example, the method illustrated in the functional block diagram 20 of Figure 2 ) for determining a torque TIn_Tgtof an electric traction motor ( for example, the motor 100 of Figures 1A or 1B, or the motors 100aand 100b of Figure 1C) of an electric powertrain ( for example the powertrains 10a, 10b, or 10c, respectively shown in the Figures 1A, 1B and 1C) of a vehicle.

[0072] Said electric powertrain comprises at least said electric traction motor, which is operatively associated with at least one driving wheel, for example, with the wheel Waand / or with the wheel Wb, of an axle of a vehicle. Said axle comprises at least one engagementdevice ( for example, the devices WDaand WDb shown in Figure 1A or 1C, or the device WD shown in Figure 1B), configured to selectively connect the at least one driving wheel Waand / or Wb of the axle to said electric traction motor.

[0073] Methods according to the present disclosure comprise, in response to the electric traction motor being in disconnection condition from the at least one driving wheel Waand / or Wb and in response to the receiving of a request for connection of said electric traction motor to the at least one driving wheel:

[0074] - determining a target rotational speed nM_Tgtof said electric traction motor as a function of a rotational speed of the at least one driving wheel Waand / or Wb to which the electric traction motor has to be operatively connected in response to the request for connection;

[0075] determining, for example, via the block 202 described in the foregoing, a target rotational acceleration ẇM_Tgtof the electric traction motor as a function of said target rotational speed nM_ gt; and determining, for example, via the block 200 described in the foregoing, said torque TIn_Tgtas a function of said target rotational acceleration ẇM_Tgtof the electric traction motor.

[0076] Said torque TIn_Tgtdetermined via the method described herein may be summed to the result provided by the open-loop control unit in order to compensate for the variation of the target rotational speed over time, thereby expediting the synchronizing operation.

[0077] To this end, methods according the present disclosure may further comprise, in response to the electric traction motor being in disconnection condition from the at least one driving wheel Waand / or Wb and in response to the receiving of a request for connection ofsaid electric traction motor to the at least one driving wheel:

[0078] - determining a first target value of propulsion torque by means of an open-loop calculation;

[0079] summing said propulsion torque Tin_Tgt obtained using the method described in the foregoing to said first target value of propulsion torque, thereby obtaining a second target value of propulsion torque determined by means of the open-loop calculation;

[0080] - determining a third target value of propulsion torque by means of a closed-loop calculation, as a function of a difference between the target rotational speed nM_ gt and a feedback of rotational speed of the electric traction motor, that is, a current rotational speed of the electric traction motor; and

[0081] - determining a target value of propulsion torque of the electric traction motor as a function of said second target value of propulsion torque determined by means of the open-loop calculation and of said third target value of propulsion torque determined by means of the closed-loop calculation, said target value of propulsion torque being the torque of the electric traction motor which enables reaching said target rotational speed nM_Tgt.

[0082] Figure 3 shows a functional block diagram configured to implement the operations performed by the block for defining the target inertial torque 200, that is, configured for defining the target value of inertial torque Tin_Tgt of the electric traction motor to be synchronized, according to embodiments of the present disclosure.

[0083] The target value of inertial torque Tin_Tgt of the electric traction motor under consideration may be provided as output by a first selection block Sel1, configured to select, as target value of inertial torqueTln_Tgt I

[0084] - a raw target value of inertial torque TinRaw_Tgt if the speed control signal SCA indicates that the function of rotational speed control of the motor is activated; or

[0085] - a null value, for example, equal to zero ("0" in Figure 3), if the speed control signal SCA indicates that the function of rotational speed control of the motor is deactivated.

[0086] Therefore, said first selection block Sel1may be configured to receive a signal indicative of a state, for example, a logic level, of the speed control signal SCA, and to select:

[0087] - said raw target value of inertial torque TinRaw_Tgt, for example, received at a first selection input, if the signal received indicates that the speed control signal SCA acquires a first logic level, for example, a "true" logic level TR, indicative of a speed control function being active, or

[0088] - said null value, for example, received at a second selection input, if the signal received indicates that the speed control signal SCA acquires a second logic level, for example, a "false" logic level, indicative of a speed control function being inactive.

[0089] Said signal indicative of the state of the speed control signal may be provided, for example, by a first equality block Eq1configured to:

[0090] receive said speed control signal SCA and a reference logic level Tr, for example, a "true" logic level;

[0091] verify whether the logic level of the speed control signal SCA is equal to the reference logic level Tr, for example, by verifying whether the speed control signal SCA acquires a first logic level, for example, said "true" logic level; and- output a signal indicating that the speed control function is active if the logic level of the speed control signal SCA is equal to the reference logic level Tr, or a signal indicating that the speed control function is inactive if the logic level of the speed control signal SCA is different from the reference logic level Tr.

[0092] The raw target value of inertial torque TinRaw_ gt may be provided, for example, by a first multiplication block Mlt1configured to:

[0093] - receive the target acceleration of the electric traction motor ẇM_Tgtand an inertia In of the system to be accelerated, that is, a constant value which is characteristic of the system to be accelerated;

[0094] - multiply said target acceleration of the electric traction motor ẇM_Tgtby the inertia of the system In; and

[0095] output the result of said multiplication operation as raw target value of inertial torque TinRaw_ gt.

[0096] For example, in embodiments according to Figure 1C, the inertia In of the system corresponds to the inertia of one of the motors 100aor 100b and of the respective transmission Taor Tb. In embodiments according to Figure 1A, the inertia In of the system corresponds to the inertia of the motor 100 and to the inertia of the differential D. In embodiments according to Figure 1B, the inertia of the system In corresponds to the inertia of the motor 100.

[0097] It is noted that the values relating to the inertia of the components to be accelerated are referred to the side which comprises the electric traction motor, possibly by considering the transmission ratios.

[0098] Therefore, in methods according to the present disclosure, the operation of determining, which for example is performed via the block 200 described in theforegoing, the torque TIn_Tgtas a function of the target rotational acceleration ẇM_Tgtof the electric traction motor may further be performed as a function of an inertia In of components comprised in the electric powertrain which are in disconnection condition from the at least one driving wheel Waand / or Wb, that is, of the components to be accelerated, related to the side which comprises the motor, which are currently not operatively connected to said driving wheel.

[0099] Moreover, said operation of determining 200 the torque TIn_Tgtmay comprise an operation of multiplying said target rotational acceleration ẇM_Tgtof the electric traction motor by said inertia In.

[0100] Moreover, said operation of determining 200 the torque TIn_Tgtmay comprise setting said torque TIn_Tgtequal to a null value ( zero) in response to a reception of a signal indicating to deactivate the rotational speed control of the electric traction motor, for example, the speed control signal SCA described in the foregoing.

[0101] Figure 4 and Figure 5 show functional block diagrams 202aand 202 configured to implement the operations performed by the block for defining the target acceleration 202, that is, configured to define the target acceleration ẇM_Tgtof the electric traction motor to be synchronized, according to embodiments of the present disclosure.

[0102] The target acceleration ẇM_Tgtof the electric traction motor under consideration (which is for example expressed in radians per second) may be provided, for example, by a second multiplication block Mlt2, configured to:

[0103] receive a filtered value of the target acceleration of the electric traction motor ṅMFlt_Tgt, for example, expressed in revolutions per minute, and a conversion ratio, for example, from revolutions per

[0104]

[0105] minute to radians per second, that is, equal to —;

[0106] - multiply said filtered target acceleration value nMFit_Tgt by the conversion ratio; and

[0107] output the result of said multiplication operation as the target acceleration value ẇM_Tgt.

[0108] The filtered target acceleration value of the electric traction motor ṅMFlt_Tgtmay be output, for example, by a filter Flt configured to filter, by removing possible peaks, a raw value of the target acceleration of the electric traction motor ṅMRaw_Tgtreceived as input.

[0109] Said raw value of the target acceleration ṅMRaw_Tgtmay be calculated as a function of the target rotational speed of the motor nM_ gt.

[0110] It is noted that the update frequency of the target rotational speed of the motor nM_Tgt(which is based on signals indicative of the speed of a respective wheel, sent by a control unit of the braking system), for example, equal to one update every 10 ms ("milliseconds"), is lower than the frequency with which the filtered target acceleration value ṅMFlt_Tgtis used (sampled) to calculate the target value of inertial torque TIn_Tgtof the electric traction motor, for example, equal to one sampling every 2 ms ("milliseconds"). Therefore, given the lower update frequency, the target rotational speed of the motor nM_Tgtmay be resampled at one and the same value in subsequent operations of calculating the gradient of said speed nM_ gt.

[0111] Therefore, methods according to the present disclosure may comprise the following operations:

[0112] periodically updating said target rotational speed nM_Tgtwith a first update frequency, for example, by sampling the value thereof with a given sampling period ΔtMSPd;

[0113] - periodically updating said torque TIn_Tgtwith asecond update frequency, said second update frequency being higher than said first update frequency, preferably a multiple of said first update frequency;

[0114] - keeping constant (thus resampling one and the same value in subsequent operations of calculating the gradient of the rotational speed) said target rotational acceleration ẇM_Tgtof the electric traction motor in the time interval comprised between two consecutive updates of the target rotational speed nM_Tgt, that is, for the duration of the sampling period ΔtMSPd; and- updating said target rotational acceleration ẇM_Tgtof the electric traction motor as a function of said updated target rotational speed nM_Tgt in response to an update of said target rotational speed nM_Tgt, that is, in response to a sampling operation of said speed.

[0115] In this regard, Figure 5 shows a functional block diagram 202b configured to implement the operations of calculating the raw target acceleration value ṅMRaw_Tgtaccording to embodiments of the present disclosure.

[0116] Said raw target acceleration value ṅMRaw_Tgtof the electric traction motor under consideration may be provided as output by a second selection block Sel2 configured to select as the raw target acceleration value ṅMRaw_Tgt: HEIGHT="31" WIDTH="101" SRC="imgf000020_0001.tif" / > - an updated raw target acceleration value ṅMRawRF_Tgtin response to an update of the calculation of the gradient related to a signal indicative of the target rotational speed nM_Tgt; or

[0117] - a frozen (or blocked) raw target acceleration value ṅMRawFrz_Tgtin response to an absence of update of the calculation of the gradient related to the signal indicative of the target rotational speed nM_Tgt.

[0118] Therefore, said second selection block Sel2 may be configured to receive a signal indicative of a state, for example, a logic level, of an update signal of thecalculation of the gradient RF indicative of a presence or an absence of said update.

[0119] Moreover, said second selection block Sel2 may be configured to select:

[0120] said updated raw target acceleration value ṅMRawRF_Tgt, for example, received at a first selection input, if the signal received indicates that the update signal of the calculation of the gradient RF is at a first logic level, for example, a "true" logic level Tr, indicative of the presence of an update of the gradient; or

[0121] - said frozen (or blocked) raw target acceleration value ṅMRawFrz_Tgt, for example, received at a second selection input, if the signal received indicates that the update signal of the calculation of the gradient RF is at a second logic level, for example, a "false" logic level, indicative of the absence of a gradient update.

[0122] Said signal indicative of the state of the update signal of the calculation of the gradient may be provided, for example, by a second equality block Eq2 configured to:

[0123] - receive said update signal of the calculation of the gradient RF and a reference logic level Tr, for example, a logic level "true";

[0124] - verify whether the logic level of the update signal of the calculation of the gradient RF is equal to the reference logic level Tr, for example, by verifying whether the update signal of the calculation of the gradient RF acquires a first logic level, for example, said "true" logic level; and

[0125] - output a signal indicating the presence of an update if the logic level of the update signal of the calculation of the gradient RF is equal to the reference logic level Tr, or a signal indicating the absence of an update if the logic level of the update signal of thecalculation of the gradient RF is different from the reference logic level Tr.

[0126] The frozen raw target acceleration value ṅMRawFrz_Tgtis equal to the raw target acceleration value ṅMRaw_Tgtof the electric traction motor provided by the second selection block Sel2, delayed by a sampling period ΔtCalcrelating to the calculation of the target value of inertial torque Tin_Tgt, for example, via a first delay block Deli configured to delay the signal received as input by a time equal to a sampling period ΔtCalcrelating to the calculation of the target value of inertial torque Tin_Tgt before the output thereof.

[0127] In this fashion, the raw value of the target acceleration ṅMRaw_Tgtis kept constant at the frozen raw target acceleration value ṅMRawFrz_Tgtwhen the calculation of the gradient relating to the signal indicative of the target rotational speed nM_Tgt is not updated, and it is set equal to the updated raw target acceleration value ṅMRawRF_Tgtin response to the update of the calculation of said gradient.

[0128] Therefore, even though the update frequency of the target rotational speed nM_Tgtis lower than the sampling frequency of the raw target acceleration value ṅMRaw_Tgt, it is possible to avoid obtaining an acceleration value equal to zero, and thus it is possible to keep constant a gradient value relating to the signal indicative of the target rotational speed nM_Tgtfor the duration of the sampling period of the slowest function, that is, of the target rotational speed inM_Tgt.

[0129] The updated raw target acceleration value ṅMRawRF_Tgtmay be provided, for example, by a division block Div configured to:

[0130] - receive a variation of the target rotational speed of the motor nM Tgtand the sampling period AΔtMSPd, that is, the time variation between the acquisition of asample and the acquisition of the following sample of the target rotational speed nM_Tgt;

[0131] - divide said variation of the target rotational speed nM Tgtby said sampling period ΔtMSPd; and

[0132] - output the result of said division operation as updated raw target acceleration value ṅMRawRF_Tgt.

[0133] The variation of the target rotational speed nM Tgtmay be obtained by means of a subtraction operation, for example, performed by a subtraction block Sub, between the target rotational speed nM_Tgt and a frozen (or blocked) target rotational speed nMFrz_Tgt.

[0134] The frozen (or blocked) target rotational speed nMFrz_Tgt may be obtained by delaying by a sampling period ΔtCalcrelated to the calculation of the target value of inertial torque TIn_Tgt, a signal output by a third selection block Sel3, for example, via a second delay block Dela configured to delay the signal received as input of a time equal to a sampling period ΔtCalcrelating to the calculation of the target value of inertial torque Tin_Tgt before providing as output such signal.

[0135] Said third selection block Sel3may be configured to select as output signal:

[0136] - the target rotational speed nM_Tgt in response to an update of the calculation of the gradient relating to the signal indicative of the target rotational speed nM_Tgt; or

[0137] - the frozen (or blocked) target rotational speed nMFrz_Tgt in response to an absence of update of the calculation of the gradient relating to the signal indicative of the target rotational speed nM_Tgt.

[0138] Therefore, also said third selection block Sel3may be configured to receive the signal indicative of the state, for example, of the logic level, of the update signal of the calculation of the gradient RF indicative of a presence or an absence of said update, and may beconfigured to select:

[0139] - said target rotational speed nM_Tgt, for example, received at a first selection input, if the received signal indicates that the update signal of the calculation of the gradient RF acquires the first logic level, for example, the "true" logic level Tr, indicative of the presence of an update of the gradient; or

[0140] - said frozen target rotational speed nMFrz_Tgt, for example, received at a second selection input, if the received signal indicates that the update signal of the calculation of the gradient RF acquires the second logic level, for example, the logic level "false", indicative of the absence of an update of the gradient.

[0141] Said signal indicative of the state of the update signal of the calculation of the gradient RF may be provided, for example, by a third equality block Eq3(which, for example, may coincide with the second equality block Eq2) configured to:

[0142] - receive said update signal of the calculation of the gradient RF and a reference logic level Tr, for example, a "true" logic level;

[0143] - verify whether the logic level of the update signal of the calculation of the gradient RF is equal to the reference logic level Tr, for example, by verifying whether the update signal of the calculation of the gradient RF acquires a first logic level, for example, said logic level "true"; and

[0144] - output a signal indicating the presence of an update if the logic level of the update signal of the calculation of the gradient RF is equal to the reference logic level Tr, or a signal indicating the absence of an update if the logic level of the update signal of the calculation of the gradient RF is different from the reference logic level Tr.

[0145] In this fashion, it is possible to calculate thevariation of the target rotational speed ΔnM_Tgtby considering the actual variation of the signal indicative of the target rotational speed nM_Tgt.

[0146] Therefore, in methods according to the present disclosure, the operation of updating the target rotational acceleration ẇM_Tgtof the electric traction motor described in the foregoing may comprise a division operation, for example performed via the division block Div, between:

[0147] - a difference, for example, calculated via the subtraction block Sub, between the updated target rotational speed nM_Tgtand a target rotational speed determined in an operation of updating preceding the current operation, that is, the frozen target rotational speed nMFrz_Tgt described in the foregoing, and

[0148] the time interval comprised between two consecutive updates of the target rotational speed nM_Tgt, that is, the duration of the sampling period

[0149]

[0150] .

[0151] Figure 6 shows exemplary graphs 30 of behaviours of the target rotational speed nM_Tgtof the electric traction motor to be synchronized and of raw target acceleration values ṅMRaw_Tgtof said electric traction motor according to embodiments of the present disclosure.

[0152] It is noted that the behaviours shown in Figure 6 are provided by way of example only. Therefore, the behaviour of the target rotational speed nM_Tgtand the behaviour of the raw target acceleration values ṅMRaw_Tgtmay vary with respect to the values shown in said Figures, while the basic principles and the conclusions drawn in relation to said behaviours still hold true.

[0153] Specifically, the first exemplary graph shown in Figure 6 illustrates an exemplary behaviour of the target rotational speed nM_Tgtover time t.

[0154] It is noted that, according to what has beendescribed in the foregoing, the sampling period ΔtMSpdof the target rotational speed nM_Tgt, for example equal to 10 ms, is longer than the sampling period ΔtCalcrelating to the calculation of the filtered target acceleration value ṅMFlt_Tgtand, as a consequence, also than the period relating to the calculation of the raw target acceleration value ṅMRaw_Tgt, for example, equal to 2 ms.

[0155] It is noted that the sampling period ΔtMSPdof the target rotational speed nM_Tgtmay be a multiple of the sampling period ΔtCalcrelated to the calculation of the filtered target acceleration value ṅMFlt_Tgt.

[0156] The second exemplary graph provided in Figure 6 shows:

[0157] - an exemplary behaviour of raw target acceleration values ṅMRaw_Tgtcalculated using solutions according to the present disclosure as a function of time t; and - an exemplary behaviour of raw target acceleration values (nM_Tgt- nM_Tgt_Old) / ΔtCalccalculated using a classic method of calculating the gradient as a function of time t.

[0158] It is noted that a direct calculation of the gradient, that is, by means of classic methods for calculating the gradient, may be performed using the equation (nM_Tgt- nM_Tgt_Old) / ΔtCalc, calculating the ratio between:

[0159] the difference between the target rotational speed, considered at the current sampling time nM_Tgt, and the target rotational speed considered at the sampling time preceding the current sampling time nM_Tgt_Old; and the sampling period ΔtCalcrelating to the calculation of the filtered target acceleration value ṅMFlt_Tgtor, more generally, the sampling period ΔtCalcrelating to the calculation of the target value of inertial torque TIn_Tgtaccording to solutions described herein.

[0160] It is noted, moreover, that the behaviour of raw target acceleration values obtained considering thecalculation of the gradient according to classic calculation methods is characterized by:

[0161] - areas wherein the raw target acceleration values are set to zero; and

[0162] - peak areas close to the update (variation) of the target rotational speed of the electric traction motor nM_Tgt.

[0163] Raw target acceleration values having a behaviour which alternates areas set to zero and peak areas cannot be used to calculate the target value of inertial torque TIn_Tgt. In fact, said behaviour would result in an impulsive torque actuation, with difficulties in delivery and with the risk of overburdening and deteriorating the system.

[0164] On the contrary, the calculation of raw target acceleration values ṅMRaw_Tgtusing solutions according to the present disclosure (which are therefore obtained by pre-conditioning the signal relating to the target rotational speed nM_Tgtwith an operation of adapting the dynamics of the most rapid control function - that is, the calculation of the target value of inertial torque TIn_Tgt- to the dynamics of the slowest control function - that is, the update of the target rotational speed nM_Tgt) enables obtaining acceleration values without peaks, which may therefore be used for calculating the target value of inertial torque TIn_Tgtwithout the occurrence of the problems described in the foregoing.

[0165] Figure 7 shows a functional block diagram 40 for defining an update signal, that is, for defining the update signal of the calculation of the gradient RF described in the foregoing, which is indicative of a presence or an absence of the update of the gradient of the target rotational speed nM_Tgt, according to embodiments of the present disclosure.

[0166] Said update signal of the calculation of thegradient RF described in the foregoing may be provided, for example, by a fourth equality block Eq4 configured to:

[0167] - receive a count time Ctr from a time counter Int and the sampling period ΔtMSpdof the target rotational speed nM_ gt;

[0168] - verify whether the received count time Ctr is equal to the sampling period ΔtMSpdof the target rotational speed nM_Tgt; and

[0169] - output an update signal of the calculation of the gradient RF which acquires a first logic level, for example, a "true" logic level, if the count time Ctr is equal to the sampling time ^ΔtMSPd, or which acquires a second logic level, for example, a "false" logic level, if the count time Ctr is different from the sampling time AΔtMSPd.

[0170] The count time Ctr may be provided as output by a time counter Int, for example, an integral block configured to be reset (by resetting to zero the value of the count time Ctr) by a reset signal received at a reset terminal Rst.

[0171] The reset signal Rst may be obtained by delaying by a sampling period ΔtCalcrelating to the calculation of the target value of inertial torque TIn_Tgtthe update signal of the calculation of the gradient RF, for example, via a third delay block Dels configured to delay the signal received as input by a time equal to a sampling period ΔtCalcrelating to the calculation of the target value of inertial torque TIn_Tgtbefore providing as output such received signal.

[0172] Therefore, in methods according to the present disclosure, the operation of updating the target rotational acceleration ẇM_Tgtof the electric traction motor described in the foregoing may be performed in response to a reception of a signal indicative of thepresence or absence of an update of the target rotational speed nM_Tgt, for example, of the update signal of the calculation of the gradient RF described in the foregoing.

[0173] In this case, the signal RF indicative of the presence or absence of an update of the target rotational speed nM_Tgtmay be obtained, for example:

[0174] - by setting to zero (by resetting), for example, via the reset signal Rst provided by the third delay block Dels, a counter (that is, the time counter Int), preferably an integrator, in correspondence of a beginning of said time interval comprised between two consecutive updates of the target rotational speed nM_ gt, that is, in correspondence of the beginning of the sampling period ΔtMSPd; and

[0175] - by verifying, for example, via the fourth equality block Eq4, whether a time value (that is, the count time Ctr described in the foregoing) provided as output by said counter Int and indicative of a time elapsed since said beginning of the time interval is equal to a duration of said time interval, that is, to the duration of the sampling time AΔtMSPd.

[0176] Therefore, said signal RF may be configured to indicate:

[0177] - the presence of an update of the target rotational speed nM_Tgtin response to said time value Ctr being equal to the duration of said time interval ΔtMSPd; or - the absence of an update of the target rotational speed nM_Tgtin response to said time value Ctr being different from, for example, being shorter than, the duration of said time interval AΔtMSPd.

[0178] Figure 8 shows exemplary graphs 50 of behaviours of the update state according to embodiments of the present disclosure and, specifically, a behaviour of the count time Ctr over time t, a behaviour of the update signalof the calculation of the gradient RF over time t, and a behaviour of the reset signal Rst.

[0179] It is noted that also in this case the behaviours shown in Figure 8 are provided by way of example only. Therefore, said behaviours may vary with respect to what is shown in said Figure, while the basic principles and the conclusions drawn in relation to said behaviours still hold true.

[0180] The first exemplary graph in Figure 8 shows an exemplary behaviour of the count time Ctr (expressed in time measurement units t) over time t. It is noted that said behaviour acquires a sawtooth profile, starting from a value equal to zero up to acquiring a value equal to the sampling period ΔtMSPdof the target rotational speed nM_ gt.

[0181] Moreover, at every calculation step, that is, at the end of every time interval equal to the sampling period ΔtCalcrelating to the calculation of the target value of inertial torque TIn_Tgt, said count time Ctr is increased, starting from a value equal to zero, by a value equal to said sampling time ΔtCalcof the calculation of the target value of inertial torque TIn_Tgt.

[0182] When the count time Ctr reaches the value of the sampling time ΔtMSPdof the target rotational speed nM_ gt, the update signal of the gradient RF, shown in the second exemplary graph of Figure 8, switches from the second logic level, for example, the "false" logic level FIs, to the first logic level, for example, the "true" logic level Tr.

[0183] After a time equal to the sampling period ΔtCalcrelating to the calculation of the target value of inertial torque TIn_Tgt, the time counter is reset by the reset signal Rst, which switches from said second logic level FIs to said first logic level Tr.

[0184] In response to said reset operation:- the count time Ctr is reset (set to zero) to the initial value, that is, to a value equal to zero; and the update signal of the calculation of the gradient RF switches from said first logic level Tr to said second logic level FIs.

[0185] Therefore, after a time equal to the sampling period ΔtCalcrelating to the calculation of the target value of inertial torque TIn_Tgt, the reset signal Rst switches from said first logic level Tr to said second logic level FIs.

[0186] Figure 9 shows a block diagram 60 relating to a method according to embodiments of the present disclosure, wherein:

[0187] - in a first step, which is for example performed by the block for defining the target acceleration 202 described in the foregoing, a target acceleration value of the electric traction motor ẇM_Tgtis defined; and - in a second step, for example performed by the block for defining the target inertial torque 200 described in the foregoing, a contribution of target inertial torque is defined, wherein such contribution, if summed to the result provided by the open-loop control unit, favours a compensation of the variation in the target rotational speed of an electric traction motor over time, in order to expedite the synchronizing operation.

[0188] Therefore, the solution described in detail herein enables obtaining a method, for example, the method 60 shown in Figure 9, for determining a torque TIn_Tgtof an electric traction motor, for example, the motor 100 or the motors 100aand 100b, of an electric powertrain, for example, the powertrains 10a, 10, or 10cof Figures 1A, IB and 1C, respectively, of a vehicle.

[0189] Said electric powertrain comprises at least said electric traction motor, which is operatively associatedwith at least one driving wheel, for example, the wheel Waand / or the wheel Wb, of an axle of the vehicle. Said axle comprises at least one engagement device, for example, the devices WDaand WD of Figures 1A and 1C, or else the device WD of Figure 1B, configured to selectively connect the at least one driving wheel Waand / or W of the axle to said electric traction motor (and to disconnect the at least one driving wheel Waand / or Wb of the axle from said electric traction motor).

[0190] Methods according to the present disclosure comprise, in response to said electric traction motor being in disconnection condition from the at least one driving wheel, said disconnection being performed by means of the at least one engagement device WDaand WDb or WD, and to the receiving of a request for connection of the electric traction motor to the at least one driving wheel Waand / or Wb:

[0191] - determining a target rotational speed nM_Tgtof said electric traction motor as a function of a rotational speed of the at least one driving wheel Waand / or Wb,-determining, for example, in the block for defining the target acceleration 202 described in the foregoing, a target rotational acceleration ẇM_Tgtof the electric traction motor as a function of said target rotational speed nM_ gt; and

[0192] determining, for example, in the block for defining the target inertial torque 200 described in the foregoing, said torque TIn_Tgtas a function of said target rotational acceleration ẇM_Tgtof the electric traction motor.

[0193] Thus, it is possible to understand that the solution set forth in the present detailed description may favour expediting the operation of synchronizing the rotational speed of the electric traction motor when it is beingreconnected with the drivetrain downstream thereof, thereby facilitating restoring the mechanical connection.

[0194] Such speeding up takes place also when the target rotational speed of the electric traction motor is not constant but varies in time, for example, in response to a request for acceleration by a driver of the vehicle.

[0195] In this way, also when a driver of the vehicle requests an acceleration phase, the synchronization between the rotational speed of the electric traction motor and the rotational speed of the drivetrain downstream thereof takes place in little time, and therefore said electric traction motor is able to more rapidly contribute to the propulsion of the vehicle, facilitating the acceleration phase.

[0196] It is noted that embodiments of the present disclosure refer to vehicles having an electric traction motor, for example, the motor 100 or the motors 100aand 100b.

[0197] Vehicles according to embodiments of the present disclosure comprise:

[0198] - at least one electronic control unit configured to determine a torque TIn_Tgtof said electric traction motor; and

[0199] an electric powertrain, for example, the powertrains 10a, 10, or 10cof Figures 1A, IB and 1C, respectively, comprising at least said electric traction motor operatively associated with at least one driving wheel, for example, the wheel Waand / or Wb, of an axle of the vehicle.

[0200] Said axle comprises at least one engagement device, for example, the devices WDaand WDb of Figures 1A and 1C or the device WD of Figure 1B, configured to selectively connect the at least one driving wheel Waand / or Wb of the axle to said electric traction motor(and to disconnect the at least one driving wheel Waand / or Wb of the axle from said electric traction motor).

[0201] The at least one electronic control unit comprised in the vehicle is configured to perform the steps of the method according to any one of the embodiments of the present disclosure.

[0202] Moreover, embodiments according to the present disclosure refer to a computer program product loadable in the memory of at least one electronic control unit comprised in a vehicle having an electric traction motor, said vehicle comprising an electric powertrain, for example, the powertrains 10a, 10, or 10cof Figures 1A, IB and 1C, respectively, comprising at least said electric traction motor, for example, the motor 100 or the motors 100aand 100b, operatively associated with at least one driving wheel, for example, the wheel Waand / or Wb, of an axle of the vehicle.

[0203] Also in this case, said axle comprises at least one engagement device, for example, the devices WDaand WDb of Figures 1A and 1C or the device WD of Figure 1B, configured to selectively connect the at least one driving wheel Waand / or Wb of the axle to said electric traction motor (and to disconnect the at least one driving wheel Waand / or Wb of the axle from said electric traction motor).

[0204] Said computer program product thus comprises portions of software code for executing the steps of the method according to any one of the embodiments of the present disclosure.

[0205] Without prejudice to the basic principles, the details and the embodiments may vary, even appreciably, with respect to what has been described, by way of example only, without departing from the extent of protection.

[0206] The extent of protection is defined by the annexed claims.

Claims

1. CLAIMS1. A method ( 60; 20) for determining a torque ( Tin_Tgt ) of an electric traction motor ( 100; 100a; 100b) of an electric powertrain ( 10a; 10b,-10c) of a vehicle, the electric powertrain ( 10a; 10b,-10c) comprising at least said electric traction motor ( 100; 100a; 100b) operatively associated with at least one driving wheel (Wa; Wb) of an axle of the vehicle;wherein said axle comprises at least one engagement device (WDa; WDb,-WD) configured to selectively connect the at least one driving wheel (Wa; Wb) of the axle to said electric traction motor ( 100; 100a; 100b);the method ( 60; 20) comprising, in response to said electric traction motor ( 100; 100a; 100b) being in disconnection condition from the at least one driving wheel (Wa; Wb) and to the receiving of a request for connection of the electric traction motor ( 100; 100a; 100b) to the at least one driving wheel (Wa; Wb):determining a target rotational speed ( nM_ gt ) of said electric traction motor ( 100; 100a; 100b) as a function of a rotational speed of the at least one driving wheel (Wa; Wb);determining (202 ) a target rotational acceleration (ẇM_Tgt) of the electric traction motor ( 100; 100a; 100b) as a function of said target rotational speed ( nM_ gt ); anddetermining (200) said torque (TIn_Tgt) as a function of said target rotational acceleration (ẇM_Tgt) of the electric traction motor ( 100; 100a; 100b).

2. The method ( 60; 20) according to claim 1, further comprising, in response to said electric traction motor ( 100; 100a; 100b) being in disconnection condition from the at least one driving wheel (Wa; Wb)and to the receiving of a request for connection of the electric traction motor ( 100; 100a; 100b) to the at least one driving wheel (Wa; Wb):determining a first target value of propulsion torque by means of an open-loop calculation;summing said torque (TIn_Tgt) to said first target value of propulsion torque, obtaining a second target value of propulsion torque determined by means of the open-loop calculation;determining a third target value of propulsion torque by means of a closed-loop calculation as a function of a difference between said target rotational speed (nM_Tgt) of the electric traction motor ( 100; 100a; 100b) and a current rotational speed of said electric traction motor, preferably received via feedback; and determining a target value of propulsion torque of the electric traction motor ( 100; 100a; 100b) as a function of said second target value of propulsion torque determined by means of the open-loop calculation and of said third target value of propulsion torque determined by means of the closed-loop calculation, said target value of propulsion torque being the torque of the electric traction motor ( 100; 100a; 100b) that enables reaching said target rotational speed (nM_ gt).

3. The method ( 60; 20) according to claim 1 or claim 2, wherein said operation of determining (200) the torque (TIn_Tgt) as a function of the target rotational acceleration (ẇM_Tgt) of the electric traction motor ( 100; 100a; 100b) is further performed as a function of an inertia ( In) of components comprised in the electric powertrain ( 10a; 10b,-10c) in disconnection condition from the at least one driving wheel (Wa; Wb);preferably wherein said operation of determining (200) the torque (TIn_Tgt) comprises multiplying saidtarget rotational acceleration (ẇM_Tgt) of the electric traction motor ( 100; 100a; 100b) by said inertia ( In).

4. The method ( 60; 20) according to any one of the previous claims, wherein said operation of determining (200) the torque (TIn_Tgt) comprises setting said torque (TIn_Tgt) equal to a null value in response to a reception of a signal (SCA) indicating to deactivate the rotational speed control of the electric traction motor ( 100; 100a; 100b).

5. The method ( 60; 20) according to any one of the previous claims, comprising:periodically updating said target rotational speed (nM_ gt) with a first update frequency;periodically updating said torque (TIn_Tgt) with a second update frequency, said second update frequency being higher than said first update frequency, preferably a multiple of said first update frequency;keeping constant said target rotational acceleration (ẇM_Tgt) of the electric traction motor ( 100; 100a; 100b) in the time interval comprised between two consecutive updates of the target rotational speed ( nM_ gt ); andupdating said target rotational acceleration (ẇM_Tgt) of the traction electric motor ( 100; 100a; 100b) as a function of said updated target rotational speed (nM_ gt) in response to an update of said target rotational speed (nM_ gt).

6. The method ( 60; 20) according to claim 5, wherein said operation of updating the target rotational acceleration (ẇM_Tgt) of the electric traction motor ( 100; 100a; 100b) comprises dividing (Div) a difference (Sub) between said updated target rotational speed (nM_ gt) anda target rotational speed determined in an operation of updating preceding the current operation (nMFrz_ gt) by said time interval comprised between two consecutive updates of the target rotational speed (nM_Tgt).

7. The method ( 60; 20) according to claim 5 or claim 6, wherein said operation of updating the target rotational acceleration (ẇM_Tgt) of the electric traction motor ( 100; 100a; 100b) is performed in response to a reception of a signal (RF) indicative of the presence or absence of an update of the target rotational speed (UM_ gt) •8. The method ( 60; 20) according to claim 7, wherein said signal (RF) indicative of the presence or absence of an update of the target rotational speed (nM_Tgt) is obtained by:resetting (Rst; Del3) a counter ( Int), preferably an integrator, in correspondence of a beginning of said time interval comprised between two consecutive updates of the target rotational speed ( nM_ gt ); andverifying (Eq4) whether a time value (Ctr) provided as output by said counter ( Int) and indicative of an elapsed time from said beginning of the time interval is equal to a duration of said time interval;wherein said signal (RF) indicates:the presence of an update of the target rotational speed (nM_Tgt) in response to said time value (Ctr) being equal to the duration of said time interval; orthe absence of an update of the target rotational speed (nM_Tgt) in response to said time value (Ctr) being different from the duration of said time interval.

9. Vehicle having an electric traction motor ( 100; 100a; 100b), said vehicle comprising:at least one electronic control unit configured to determine a torque (TIn_Tgt) of said electric traction motor ( 100; 100a; 100b); andan electric powertrain ( 10a; 10b,-10c) comprising at least said electric traction motor (100; 100a; 100b) operatively associated with at least one driving wheel (Wa; Wb) of an axle of the vehicle;wherein said axle comprises at least one engagement device (WDa; WDb,-WD) configured to selectively connect the at least one driving wheel (Wa; Wb) of the axle to said electric traction motor ( 100; 100a; 100b);wherein said at least one electronic control unit is configured to perform the steps of the method ( 60; 20) according to any one of the previous claims.

10. Computer product loadable in the memory of at least one electronic control unit comprised in a vehicle having an electric traction motor, said vehicle comprising an electric powertrain ( 10a; 10b,-10c) comprising at least said electric traction motor (100; 100a; 100b) operatively associated with at least one driving wheel (Wa; Wb) of an axle of the vehicle;wherein said axle comprises at least one engagement device (WDa; WDb,-WD) configured to selectively connect the at least one driving wheel (Wa; Wb) of the axle to said electric traction motor ( 100; 100a; 100b);said computer product comprising portions of software code for executing the steps of the method ( 60; 20) according to any one of claims 1 to 8.

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