MONITORING THE CONDITION OF A COUPLING DEVICE FOR AN AUXILIARY ELECTRIC POWER ENGINE OF A LAND VEHICLE

Abstract

A monitoring method is implemented in a vehicle with an estimated speed and comprising a powertrain including an electric motor with a measured speed coupled to a train via a coupling device that can be placed in coupled and decoupled states. This method includes a step (10-80) in which, when the electric motor is not in use and the measured speed is above a first threshold, a theoretical speed is determined that the electric motor should have if the coupling device were in its coupled state, as a function of the estimated speed. When a representative value of a difference between the measured speed and the determined theoretical speed is abnormal in the presence of the state in which the coupling device is placed, at least one main action is performed in the vehicle to ensure its safe operation. Figure 3

Description

Title of the invention: MONITORING THE STATUS OF A COUPLING DEVICE FOR AN AUXILIARY ELECTRIC POWER UNIT OF A LAND VEHICLE Technical field of the invention

[0001] The invention relates to land vehicles and comprising a powertrain including an auxiliary electric drive machine coupled to a train via a coupling device that can be placed in coupled and decoupled states, and more specifically the monitoring within such vehicles of the state in which this coupling device is placed. State of the art

[0002] Certain land vehicles, possibly of the automobile type, comprise a powertrain (or PWM) including a main electric drive unit, so called because it is permanently coupled to a first train, and an auxiliary electric drive unit, so called because it is coupled to a second train via a coupling device that can be placed in coupled and decoupled states. For example, this coupling device may be a dog clutch.

[0003] Currently, the coupling device provides, generally to the powertrain control unit, a status information that defines its state (namely, either coupled (or closed), decoupled (or open), or invalid), and the powertrain control unit builds its powertrain control strategy based (in particular) on this received status information. In fact, when the powertrain control unit receives this status information, it checks whether it corresponds to the coupling or decoupling command that it has determined for the coupling device. If the powertrain control unit detects a mismatch, it generates a warning message for the vehicle driver requiring the vehicle to stop.

[0004] Such a check proves insufficient. Indeed, if the auxiliary electric drive does not produce motor torque but its coupling device is in its coupled state, the main electric drive must supply motor torque not only to move its vehicle, but also to counteract the losses caused by the electric drive and the associated gearbox, which significantly increases electrical energy consumption. Furthermore, when the auxiliary electric drive is not supplied with electrical energy but its rotor is driven, this causes the rotor magnets to repeatedly pass in front of the stator poles. Consequently, even if the poles are not carrying current induced, the mere fact that the magnets pass in front of them causes the creation of electrical energy which is dissipated as heat energy which can start a fire if it is not consumed or stored.

[0005] The invention therefore aims in particular to improve the situation. Presentation of the invention

[0006] In particular, it proposes for this purpose a monitoring method intended to be implemented in a vehicle having an estimated speed and comprising a powertrain including an electric drive machine having a measured speed and coupled to a train via a coupling device that can be placed in coupled and decoupled states.

[0007] This monitoring method is characterized by the fact that it includes a step in which, when the electric motor is not in use, it is determined whether the measured speed is above a first threshold, and if so, a theoretical speed is determined which the electric motor should have if the coupling device was in its coupled state, depending on the estimated speed, and, when a representative value of a difference between the measured speed and the determined theoretical speed is abnormal in the presence of the state in which the coupling device is placed, at least one main action is carried out in the vehicle intended to secure the use of the latter.

[0008] Thanks to the invention, it is now reliably known whether the state in which the coupling device is placed actually corresponds to the state which was previously required by the supervisory computer for this coupling device.

[0009] The monitoring method according to the invention may include other features which may be taken separately or in combination, and in particular:

[0010] - in its stage, at least one main action can be performed in the vehicle when the value is abnormal for at least a chosen period;

[0011] - in the presence of the first option, in its step, the chosen duration can be depending on the state in which the coupling device is placed;

[0012] - in its step, each main action can be chosen from a trigger generating an alert for a vehicle driver requiring the vehicle to stop, and imposing a chosen limit on the maximum speed of the vehicle;

[0013] - in its step, when the coupling device is in its coupled state, the value may be abnormal when it is above a second chosen threshold, and when the coupling device is in its decoupled state, the value may be abnormal when it is below a third chosen threshold;

[0014] - in its step, one can determine a value which is representative of a percentage difference between the measured regime and the determined theoretical regime;

[0015] - in its stage, when the value is abnormal, it can be carried out in the vehicle an additional action consisting of recording at least one fault code representative of an abnormal value.

[0016] The invention also proposes a computer program product comprising a set of instructions which, when executed by processing means, is suitable for implementing a monitoring method of the type presented above, in a vehicle having an estimated speed and comprising a powertrain including an electric motor having a measured speed and coupled to a train via a coupling device that can be placed in coupled and decoupled states, to monitor the state in which the coupling device is actually placed.

[0017] The invention also proposes a monitoring device intended to equip a vehicle having an estimated speed and comprising a powertrain including an electric drive machine having a measured speed and coupled to a train via a coupling device that can be placed in coupled and decoupled states.

[0018] This monitoring device is characterized by the fact that it includes at least one processor and at least one memory arranged to perform the operations consisting, when the electric motor is not in use, of determining whether the measured speed is above a first threshold, and if so, of determining a theoretical speed that the electric motor should have if the coupling device were in its coupled state, depending on the estimated speed, and, when a representative value of a difference between the measured speed and the determined theoretical speed is abnormal in the presence of the state in which the coupling device is placed, of triggering the execution in the vehicle of at least one main action intended to secure the use of the latter.

[0019] The invention also proposes a vehicle, possibly of the automobile type, having an estimated speed and comprising, on the one hand, a powertrain including an electric motor having a measured speed and coupled to a train via a coupling device that can be placed in coupled and decoupled states, and, on the other hand, a monitoring device of the type shown above. Brief description of the figures

[0020] Other features and advantages of the invention will become apparent from an examination of the detailed description below, and the accompanying drawings, in which:

[0021] [Fig-1] schematically and functionally illustrates an example of the realization of a vehicle comprising a powertrain with main and auxiliary electric drive machines associated with a main battery and supervised by a supervisory computer, and a monitoring device according to the invention,

[0022] [Fig.2] schematically and functionally illustrates an example of the realization of a a supervisory calculator including an example of an embodiment of a monitoring device according to the invention, and

[0023] [Fig.3] schematically illustrates an example of an algorithm implementing an monitoring method according to the invention. Detailed description of the invention

[0024] The invention aims in particular to propose a monitoring method, and an associated DS monitoring device, intended to allow effective and reliable monitoring of the state in which a DC coupling device is actually placed, suitable for ensuring a coupling of an electric motive machine MM2 of a powertrain (or powertrain) of a land vehicle V to a train T2 of the latter (V).

[0025] In what follows, the land vehicle V is considered, by way of non-limiting example, to be of the automobile type. This is, for example, a car, as illustrated in [Fig. 1]. However, the invention is not limited to this type of land vehicle. It relates in fact to any type of land vehicle comprising a powertrain with a main and auxiliary electric drive unit associated with a main battery. Thus, it relates to land vehicles (commercial vehicles, motorhomes, minibuses, coaches, trucks, motorcycles, road maintenance vehicles, construction equipment, agricultural machinery, and recreational vehicles (go-karts), for example).

[0026] A vehicle V comprising a GMP transmission chain with main electric drive machines MM1 and auxiliary MM2, a CS supervisory computer, an RB on-board network, a BS service battery, a BP rechargeable battery, a CV converter, a DC coupling device, and a DS monitoring device according to the invention is schematically represented in [Fig.1].

[0027] The RB on-board network is an electrical power supply network to which electrical (or electronic) equipment (or components) that consume electrical energy are coupled.

[0028] The auxiliary battery BS is responsible for supplying electrical power to the vehicle's electrical system RB, supplementing that supplied by the CV converter, which is powered by the rechargeable battery BP via a main electrical circuit, and sometimes replacing this CV converter. For example, this auxiliary battery BS may be configured as a very low voltage type battery (typically 12 V, 24 V, or 48 V). It is rechargeable at least by the CV converter. In the following, for the sake of non-limiting example, the auxiliary battery BS is considered to be a 12 V lithium-ion type.

[0029] The main electrical circuit (or “high voltage”) is connected, on the one hand, to the rechargeable battery BP via an interface device, and, on the other hand, to electronic equipment, such as the CV converter and the main electric drive machines MM1 and auxiliary MM2. It also allows the rechargeable battery BP to be recharged by an external power source and temporarily connected to a vehicle charging connector V.

[0030] The transmission chain has a purely electric powertrain comprising, in particular, a main electric drive machine MM1, a first drive shaft AMI, a first transmission shaft ATI, an auxiliary electric drive machine MM2, a second drive shaft AM2, a second transmission shaft AT2, and a DC coupling device. The term "electric drive machine" here refers to an electric machine arranged to provide torque for moving the vehicle V when supplied with electrical energy, and possibly to recover torque in the transmission chain.

[0031] The operation of the transmission chain (and therefore of the GMP) is supervised by a CS supervision computer.

[0032] The main electric drive machine MM1 (here an electric motor) is here coupled to the rechargeable battery BP via the main electrical circuit, in order to be supplied with electrical energy, as well as possibly to supply this rechargeable battery BP with electrical energy, for example during a regenerative braking phase.

[0033] Furthermore, this main electric drive machine MM1 is coupled to the first drive shaft AMI to supply it with torque by rotational drive. This first drive shaft AMI is here coupled to a first reduction gear RDI, which is also coupled to the first transmission shaft ATI, itself coupled to a first set of wheels Tl, preferably via a differential DV.

[0034] This first train Tl is located here in the front part PVV of the vehicle V. But in a variant this first train Tl could be the one which is here referenced T2 and which is located in the rear part PRV of the vehicle V.

[0035] The auxiliary electric drive machine MM2 (here an electric motor) is here coupled to the rechargeable battery BP via the main electrical circuit, in order to be supplied with electrical energy, as well as possibly to supply this rechargeable battery BP with electrical energy, for example during a regenerative braking phase.

[0036] This auxiliary electric drive machine MM2 has a speed rm that is measured, preferably periodically. For example, this period can be between 10 milliseconds and 100 milliseconds. As an illustrative example, the period can be 50 milliseconds. Also, for example, this speed rm can be measured by at least one sensor integrated into the auxiliary electric drive machine MM2.

[0037] Furthermore, this auxiliary electric drive machine MM2 is coupled to the second drive shaft AM2, to supply it with torque by rotational drive. This second drive shaft AM2 is here coupled to a second reducer RD2 which can be coupled, via the DC coupling device, to the second transmission shaft AT2, itself coupled to a second train T2 (here of wheels), preferably via a differential DR.

[0038] The DC coupling device can be placed in coupled and decoupled states, depending on a state command generated by the GMP's CS supervisory computer. For example, this coupling device could be a dog clutch. However, this is not mandatory.

[0039] It should be noted that the DC coupling device provides the powertrain control unit (CS) with state information ie that defines its state (namely, either coupled (or closed), decoupled (or open), or invalid). The powertrain control unit (CS) builds its powertrain control strategy based (in particular) on this received state information ie.

[0040] For example, this provision of state information can be carried out periodically. Also, for example, this period can be between 50 milliseconds and 300 milliseconds. By way of illustration, the period can be equal to 100 milliseconds.

[0041] The CV converter is also responsible, here, during the driving phases of the vehicle V, for converting part of the electrical current stored in the rechargeable battery BP to supply converted electrical current to the on-board network RB and the auxiliary battery BS (to recharge it).

[0042] It will be noted, as illustrated non-limitingly in [Fig.1], that the CV converter can be part of a CH charger.

[0043] The rechargeable battery BP, which here powers the main electric drive machines MM1 and MM2, constitutes a main (or traction) battery. It may, for example, include electrical energy storage cells, possibly electrochemical (e.g., lithium-ion (or Li-ion), Ni-MH, or Ni-Cd). Also, for example, the rechargeable battery BP may be of the low-voltage type (typically 450 V, for illustrative purposes). But it could also be of the medium-voltage or high-voltage type.

[0044] It should also be noted that in the example illustrated, but not limited to, in [Fig. 1], the vehicle V also includes a distribution box BD to which the auxiliary battery BS, the converter CV, and the on-board network RB are coupled. This distribution box BD is responsible for distributing the electrical energy stored in the auxiliary battery BS or produced by the converter CV into the on-board network RB to power the electrical components (or equipment) connected to the on-board network RB, according to power demands received (in particular from the powertrain control unit CS).

[0045] It should also be noted that the vehicle V has a (current) speed vev which is estimated, preferably periodically. For example, this period can be between 10 milliseconds and 100 milliseconds. As an illustrative example, the period can be equal to 50 milliseconds.

[0046] For example, this (current) speed vev can be estimated by a possible vehicle stability control system (V) equipped with the vehicle, which could be of the ESP / ABS type (ESP: "Electronic Stability Program"), ABS: "Anti-Blocking System"), based on information provided by a sensor associated here with one of the drive wheels. For example, this sensor can be coupled to a wheel hub and can constitute an angular encoder determining the number of teeth passing in front of it per second. The vehicle stability control system's computer can then determine the distance traveled based on the number of teeth indicated by the sensor and the wheel circumference drl, and then estimate the speed vev by integrating this distance traveled over time.

[0047] But the estimates (or measurements) of speed vev could have an origin other than the computer of the trajectory control device.

[0048] As mentioned above, the invention notably proposes a monitoring method intended to allow monitoring of the state in which the DC coupling device is actually placed.

[0049] This (monitoring) method can be implemented at least partially by the DS monitoring device (illustrated at least partially in Figures 1 and 2), which for this purpose comprises at least one PR1 processor, for example a digital signal processor (or DSP), and at least one MD memory. This DS monitoring device can therefore be implemented as a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software"). For example, it could be a microcontroller.

[0050] The MD memory is random access memory (RAM) to store instructions for the implementation by the PR1 processor of at least part of the monitoring process. The PR1 processor may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is defined as any type of device capable of performing at least one electrical or electronic operation.

[0051] In the example illustrated, but not limited to, Figures 1 and 2, the DS monitoring device is part of the CS supervisory computer. However, this is not mandatory. Indeed, the DS monitoring device could comprise its own dedicated computer, which is then coupled to the CS supervisory computer, for example.

[0052] As illustrated, without limitation, in [Fig. 3], the (monitoring) method according to the invention comprises a step 10-80 which is implemented at least each time The CS supervisory computer wants to check the state of the DC coupling device and that a condition is met, namely that the auxiliary electric drive machine MM2 is not being used (to produce or recover motor torque). For example, this state check can be performed periodically.

[0053] Step 10-80 of the process includes a substep 30 in which, when the aforementioned condition is satisfied, one (for example the DS monitoring device) determines whether the measured regime rm is greater than a first threshold if chosen.

[0054] For example, the first threshold si can be between 0 rpm and 10 rpm. As an illustrative example, the first threshold si can be equal to 3 rpm. But other values ​​of the first threshold si can be used. For example, the value of the first threshold s1 can be chosen during the vehicle development phase V.

[0055] If the measured regime rm is less than or equal to the first threshold si (rm < si, and therefore in the negative), the situation is considered normal and therefore the process can end in a sub-step 40 of step 10-80, and will be implemented again during the next status check.

[0056] Conversely, if the affirmative is true (rm > si), step 10-80 of the method also includes a substep 50 in which a theoretical operating regime rt is determined (for example, by the monitoring device DS) that the auxiliary electric drive machine MM2 should have if the DC coupling device were in its coupled state. This determination is made based on the estimated speed vev of the vehicle V.

[0057] For example, the theoretical regime rt can be given (in revolutions per minute) by the formula rt = vev x 1000 x drl / dr2 / 60, where dr2 is the value of the reduction ratio of the second reducer RD2 (in meters per revolution), drl is given in meters per revolution and vev is given in kilometers per hour.

[0058] Step 10-80 of the process also includes a substep 80 in which, when a value ver representing the difference between the measured regime rm and the determined theoretical regime rt is abnormal in the presence of the state in which the DC coupling device is placed, at least one main action intended to secure the use of the latter (V) is carried out (for example the DS monitoring device triggers the realization).

[0059] It is recalled that the state in which the DC coupling device is placed is defined by a state information ie which is transmitted by the latter (DC) to the supervisory computer CS (and therefore to the monitoring device DS).

[0060] By verifying the normality of the ver value with respect to the current state of the DC coupling device, it is reliably determined whether the state of the DC coupling device actually corresponds to the state previously required by the CS supervisory computer for the DC coupling device (by a state setpoint). This helps prevent a fire from occurring in the machine. auxiliary electric motor MM2 or that damage to the latter (MM2) occurs due to overheating, which helps to strengthen the safety of the vehicle V and its passengers.

[0061] For example, and as illustrated non-limitingly in [Fig. 3], step 10-80 may include a substep 10 in which one (for example, the monitoring device DS) can check whether the auxiliary electric drive machine MM2 is not in use. To do this, one (the monitoring device DS) can compare the absolute value of the current hn2 that is consumed or produced by the auxiliary electric drive machine MM2 at the time considered to a chosen (fourth) threshold s4. If one has im2 > s4, this means that the auxiliary electric drive machine MM2 is in use, and therefore the process can end in a substep 20 of step 10-80, and will be implemented again during the next status check. On the other hand, if we have im2 < s4, this means that the auxiliary electric drive machine MM2 is not used, and therefore the process performs substep 30 of step 10-80.

[0062] For example, the fourth threshold s4 can be between 3 A and 10 A. As an illustrative example, the fourth threshold s4 can be equal to 8 A. But other values ​​of the fourth threshold s4 can be used. For example, the value of the fourth threshold s4 can be chosen during the vehicle development phase.

[0063] Also, for example, in substep 60 of step 10-80, one (for example, the DS monitoring device) can determine a value ver which is representative of a percentage difference between the measured regime rm and the determined theoretical regime rt.

[0064] For example, the value of `ver` can be given (in rpm) by the formula `ver` = (`Irt` - `rml` x 100) / `rm`. In other words, the value of `ver` here is equal to the absolute value of the difference (in percentage) in rotational speed between the measured speed `rm` and the theoretical speed determined `rt` (for the coupled (or "dog-clutch") state). But other formulas representing the difference (`rt` - `rm`) can be used.

[0065] Also, for example, in substep 80 of step 10-80, at least one main action can be performed in vehicle V (for example, the DS monitoring device can trigger the execution) when the ver value is abnormal for at least a chosen duration dcj. This option is intended to avoid performing a main action solely due to an abnormal ver value for a very short (and therefore non-representative) duration, for example, due to a very temporary sensor failure or a very temporary disturbance on a communication network (possibly multiplexed) of vehicle V used to transmit information or a measurement useful for determining the ver value.

[0066] It should be noted that in substep 80 of step 10-80 the chosen duration dcj can be a function of the state in which the DC coupling device is placed (defined by the state information ie). In this case, we (for example the DS monitoring device) can use a first chosen duration dcl (j = 1) when the DC coupling device is placed in its coupled state, and a second chosen duration dc2 (j = 2) when the DC coupling device is placed in its decoupled state.

[0067] For example, each of the first dcl and second dc2 durations can be between 1 second and 10 seconds. But other values ​​for the first dcl and second dc2 durations can be used. For example, the respective values ​​of the first dcl and second dc2 durations can be chosen during the vehicle V development phase.

[0068] But the values ​​of the first dcl and second dc2 durations could be identical.

[0069] Also, for example, in substep 80 of step 10-80 each main action can be chosen from triggering an alert generation for the driver of vehicle V which requires stopping vehicle V, and imposing a chosen limitation on a maximum speed of movement of vehicle V.

[0070] When using the selected speed limit, the maximum speed can, for example, be between 10 km / h and 30 km / h. As an illustrative example, the maximum speed could be 25 km / h. However, other maximum speed values ​​can be used. For example, the maximum speed can be selected during the vehicle development phase.

[0071] The driver may be alerted, for example, by means of an illuminated indicator light (e.g., in the instrument panel of vehicle V) and / or a message displayed on at least one screen of vehicle V (e.g., the instrument panel or a central instrument cluster) or on the screen of the user's smartphone, and / or broadcast through at least one speaker of vehicle V or of that smartphone. The aforementioned indicator light may, for example, be a stop (or hazard) indicator light, but it could also be an indicator light specifically for requesting that vehicle V be stopped as quickly as possible.

[0072] Also, for example, and as illustrated non-limitingly in [Fig.3], step 10-80 may include a substep 60 in which, when the DC coupling device is in its coupled state, the value ver may be considered abnormal when it is greater than a second chosen threshold s2 (i.e. ver > s2), and when the DC coupling device is in its uncoupled state, the value ver may be considered abnormal when it is less than a third chosen threshold s3 (i.e. ver < s3).

[0073] If the ver value is considered normal, the process can end in substep 70 of step 10-80, and will be implemented again during the next status check. Conversely, if the ver value is considered abnormal, substep 80 is performed.

[0074] Also, for example, when using a value representing a percentage deviation (of the type of formula given above), the second threshold s2 can be between 5% and 10%. As an illustrative example, the second threshold s2 can be equal to 8%. But other values ​​for the second threshold s2 can be used. For example, the second threshold s2 can be chosen during the vehicle development phase.

[0075] Also, for example, when using a value representing a percentage deviation (of the type of formula given above), the third threshold s3 can be between 90% and 95%. As an illustrative example, the third threshold s3 can be equal to 93%. But other values ​​for the third threshold s3 can be used. For example, the third threshold s3 can be chosen during the vehicle development phase.

[0076] Also, for example, in substep 80 of step 10-80, one can carry out (for example, the DS monitoring device can trigger the realization) in the vehicle V a (of a) supplementary action consisting of recording at least one fault code representative of an abnormality of the ver value.

[0077] The recording of at least one fault code is intended to facilitate the investigation of the origin of an abnormality in the value ver by a service technician, and to enable this technician to resolve this abnormality and to inform the user of vehicle V of the origin of the stoppage of vehicle V. For example, the CS supervisory computer can store this (each) fault code.

[0078] It should be noted that when the driver restarts vehicle V after a required stop due to an abnormal ver value, normal use of vehicle V may be reauthorized if the ver value has returned to normal. In this case, the aforementioned abnormal fault code may be replaced by a transient abnormal fault code. However, if the abnormal ver value persists when vehicle V is restarted, it is preferable, given the potential severity of the situation when the auxiliary electric drive MM2 is overheating, to prohibit the use of vehicle V by alerting the driver, for example, with a warning message requiring vehicle V to be immobilized and serviced. Of course, once vehicle V has been repaired and at least one vehicle control unit has been reconfigured, it can again be used normally.

[0079] It should also be noted that when the DS monitoring device does not receive state information, i.e., preferably for a chosen duration, one (for example, the DS monitoring device) can request the stopping (or securing) of the vehicle V. Preferably, this latter chosen duration is greater than at least twice all the durations or periods mentioned above (typically, it can be (between 500 milliseconds and 5 seconds).

[0080] It will also be noted that when the DS monitoring device receives state information ie defining the invalid state of the DC coupling device, preferably for a chosen duration, one (for example the DS monitoring device) can also require the stopping (or the securing) of the vehicle V. Preferably, this latter chosen duration is greater than at least twice all the durations or periods mentioned above (typically, it can be between 500 milliseconds and 5 seconds).

[0081] It will also be noted, as illustrated non-limitingly in [Fig.2], that the CS supervisory computer (or the DS monitoring device computer) can also include a mass memory MM3, in particular to store the measured speed rm, the state information ie, the state setpoint (determined by the CS supervisory computer), the estimated speed vev, the wheel development drl and the value dr2 of the reduction ratio of the second reducer RD2, as well as any intermediate data involved in all its calculations and processing.Furthermore, this CS supervisory computer (or the DS monitoring device computer) may also include an IE input interface for receiving at least the measured speed rm, the status information ie, the status setpoint, the estimated speed vev, the wheel development drl, and the value dr2 of the second reduction gear RD2, for use in calculations or processing, possibly after shaping and / or demodulating and / or amplifying them, in a manner known per se, by means of a PR2 digital signal processor. In addition, this CS supervisory computer (or the DS monitoring device computer) may also include an IS output interface, notably for delivering a message (or command) to trigger a main action and a possible message containing a fault code.

[0082] It will also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means of the type of electronic circuits (or hardware), such as for example the PR1 processor, is suitable for implementing the monitoring method described above to monitor in the vehicle V the state in which the DC coupling device is actually placed.

Claims

Claims

1. Monitoring method for a land vehicle (V), having an estimated speed and comprising a powertrain comprising an electric motor (MM2) having a measured speed and coupled to a train via a coupling device (DC) which can be placed in coupled and decoupled states, characterized in that it comprises a step (10-80) in which, when said electric motor (MM2) is not used, it is determined whether said measured speed is greater than a first threshold, and if so, a theoretical speed that said electric motor (MM2) should have if said coupling device (DC) were in its coupled state is determined, as a function of said estimated speed, and, when a value representative of a difference between said measured speed and determined theoretical speed is abnormal in the presence of the state in which said coupling device (DC) is placed,at least one main action intended to secure the use of the latter (V) is carried out in said vehicle (V).

2. Method according to claim 1, characterized in that in said step (10-80) at least one main action is carried out in said vehicle (V) when said value is abnormal for at least a chosen duration.

3. Method according to claim 2, characterized in that in said step (10-80) said chosen duration is a function of the state in which said coupling device (DC) is placed.

4. Method according to one of claims 1 to 3, characterized in that in said step (10-80) each main action is chosen from a triggering of an alert generation for a driver of said vehicle (V) requiring a stop of said vehicle (V), and an imposition of a chosen limitation of a maximum speed of movement of said vehicle (V).

5. Method according to one of claims 1 to 4, characterized in that in said step (10-80), when said coupling device (DC) is in its coupled state, said value is abnormal when it is greater than a second chosen threshold, and when said coupling device (DC) is in its decoupled state, said value is abnormal when it is less than a third chosen threshold.

6. Method according to one of claims 1 to 5, characterized in that in said step (10-80) a value representative of a percentage difference between said measured regime and determined theoretical regime.

7. Method according to one of claims 1 to 6, characterized in that in said step (10-80), when said value is abnormal, a complementary action is carried out in said vehicle (V) consisting of recording at least one fault code representative of an abnormality of said value.

8. Computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing the monitoring method according to one of claims 1 to 7, in a land vehicle (V), having an estimated speed and comprising a powertrain comprising an electric motor (MM2) having a measured speed and coupled to a train via a coupling device (DC) which can be placed in coupled and decoupled states, to monitor the state in which said coupling device (DC) is actually placed.

9. Monitoring device (DS) for a land vehicle (V), having an estimated speed and comprising a powertrain comprising an electric motor (MM2) having a measured speed and coupled to a train via a coupling device (DC) which can be placed in coupled and decoupled states, characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to carry out the operations consisting, when said electric motor (MM2) is not in use, in determining whether said measured speed is greater than a first threshold, and if so in determining a theoretical speed which said electric motor (MM2) should have if said coupling device (DC) were in its coupled state, as a function of said estimated speed, and,when a value representative of a difference between said measured speed and determined theoretical speed is abnormal in the presence of the state in which said coupling device (DC) is placed, to trigger the performance in said vehicle (V) of at least one main action intended to secure the use of the latter (V).,

10. Land vehicle (V), having an estimated speed and comprising a powertrain comprising an electric motor (MM2) having a measured speed and coupled to a train via a coupling device (DC) which can be placed in coupled and decoupled states, characterized in that it further comprises a monitoring device (DS) according to claim 9.

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