FR3136125A1 - METHOD FOR SWITCHING AN ELECTRIC MACHINE TO A FREE-WHEEL OPERATING MODE, CORRESPONDING COMPUTER PROGRAM PRODUCT AND VEHICLE. - Google Patents

Abstract

The invention relates to a method for switching an electric machine forming a drive motor to a freewheeling operating mode, in a vehicle with an electric drive chain, comprising: - a step of issuing a control order cutoff (E100) of the power supply current of the electrical machine by a central computer intended for a first computer; - a step of cutting off the current (E110) in the electrical machine by the first computer; - a current measurement step (E130) in at least one pole of the electric machine; - a comparison step (E140), by the first calculator, of the current measured with a predetermined failure threshold, which is in absolute value between 10 and 50 amps, or even 15 and 30 amps, or even equal to 30 amps. The invention also relates to a computer program product and a motor vehicle suitable for implementing the method. Figure 4

Description

METHOD FOR SWITCHING AN ELECTRIC MACHINE TO A FREE-WHEEL OPERATING MODE, CORRESPONDING COMPUTER PROGRAM PRODUCT AND VEHICLE.

The present invention generally relates to vehicles having an electric traction chain, that is to say driven by an electric traction machine. In particular, the invention relates to the field of monitoring the current at the poles of the electric traction machine when the vehicle is in a so-called "freewheeling" operating mode, that is to say, that is to say when the traction chain turns without being driven or braked by the electric traction machine.

Such an electric traction chain vehicle is illustrated schematically in . In this figure, the vehicle 5 comprises an electric traction chain 6. The electric traction chain 6 comprises a battery 8 forming an energy source, a set of computers 9, an electric machine 10, a transmission 11 and drive wheels 12 The assembly formed by the computers 9, the electric machine 10, the transmission 11 and the driving wheels 12 is called the powertrain 7. The computers 14, 15, 16, 17 and 18 of the set of computers 9 include by example, not limited to:

_ the eVCU 14 (or Electric Vehicle Control Unit), which is the general supervisor of the powertrain, that is to say the central computer. As such, the eVCU coordinates, controls, controls and supervises the computers of the eCAN bus communication system (from the English “electrical Controller Area Network”). The computers of the eCAN bus communication system are for example the MCU 15 described below, the BMS 16 (Battery Management System), the OBCDC 17 (On Board Charger Direct Current, from the English “Onboard Direct Current Charger”) and the ePLU 18 (Electrical Park Lock Unit, from the English “Electric Parking Lock Unit”);

_ the MCU 15 (or Machine Control Unit), which is the computer of the electric machine 10 and, as such, manages the operation of the electric machine 10.

The electric machine 10 is for example an electric machine of known type such as the permanent magnet synchronous machine 10 illustrated in . This has a stator 21 and a rotor 22. The stator 21 is here provided with 3 coils 21a, 21b and 21c forming 3 poles of the electric machine 10. The rotor 22 comprises an axis 23, movable in rotation, and a magnet permanent 24, mounted on the axis 23. The permanent magnet 24 is here provided with a negative pole 25 and a positive pole 26.

The permanent magnet synchronous electric machine 10, in its motor mode, operates with pulses. These pulses are obtained by the coils 21a, 21b and 21c arranged around the periphery of the stator 21. These coils 21a, 21b and 21c are also called the poles of the electric machine. When current i _a , i _b and i _c (shown here in a purely illustrative sense) are passed through the coils 21a, 21b and 21c, a magnetic field is generated by these and the coils 21a, 21b and 21c then behave like magnets whose arrangement of the poles depends on the direction of the current.

An electric machine such as the electric machine 10, when implemented in a vehicle such as the vehicle 5, can operate as a motor, in which case the electric machine provides traction torque to the drive wheels 12 by conversion of the electrical energy stored in the battery 8, or as a generator, in which case the electric machine brakes the traction chain 6 in order to transform part of the mechanical torque into electrical energy and thus recharge the battery 8.

Furthermore, in freewheeling operation, the electric traction machine must behave passively. The electric machine must then neither provide engine torque nor slow down the traction chain.

To fully understand the concept of freewheeling operation, by analogy, in thermal traction chains, when these are in freewheeling mode, the clutch is opened, for example through the powertrain supervisor. In other words, the mechanical traction chain is then mechanically decoupled from the heat engine.

Today, in an electric traction chain such as the traction chain 6, it is the eVCU 14 (from the English "Electric Vehicle Control Unit"), which verifies that the electric machine 10, when it is in freewheel mode, does not provide any torque or generate regenerative torque.

However, it has turned out that having possible problems in freewheeling mode of the machine checked by the eVCU 14 can lead to false diagnostics of failure of the electrical machine. Such erroneous diagnoses have repercussions on the intervention of the after-sales service, which may have to change the electrical machine without resolving the real problem in the vehicle, with the risk that the problem reoccurs despite the intervention of the after-sales service. This diagnostic error therefore presents a potential or real financial cost for the manufacturer if the actual problem leads to a part change.

An objective of the invention is therefore to propose a method of switching an electric machine to a freewheeling mode of operation in a vehicle with an electric traction chain, in which the detection of a failure of the wheeling mode of operation free is more reliable, and in particular less subject to diagnostic errors than in existing technologies. The invention further aims to propose a computer program product capable of implementing the aforementioned tilting method and a vehicle with an electric drive chain in which this tilting method is implemented.

To achieve this objective, the invention proposes a method for switching an electric machine from a drive motor mode or an alternator mode to a freewheeling operating mode, in a vehicle with an electric drive chain ,

the vehicle comprising:

- a traction battery forming a source of energy;

- a powertrain comprising the electric machine, at least one driving wheel and at least one set of computers,

the electric machine being supplied with current from the battery, and configured to convert the electricity received from the battery into mechanical energy, the electric machine further comprising a plurality of poles;

the at least one drive wheel being configured to be rotated by the mechanical energy produced by the electrical machine;

the set of calculators comprising:

- a first computer, called a machine control unit, and forming a control member of the electric machine;

- a central computer, called an electric vehicle control unit, and forming a general supervisor of the powertrain, including the first computer;

the method of switching the electric machine to the freewheel operating mode comprising:

- a step of issuing an order to cut off the power supply of the electrical machine by the central computer to the first computer;

- a step of cutting off the current in the electrical machine by the first computer;

- a step of measuring the current in at least one of the poles of the electric machine;

- a step of comparison, by the first calculator, of the current measured in the current measurement step with a predetermined failure threshold, the failure threshold being in absolute value preferably between 10 and 50 amps, more preferably between 15 and 30 amps, preferably still equal to 30 amps.

Thanks to the method of the invention, the diagnosis of the freewheeling mode of operation of the electric machine is carried out as close as possible to the latter. This makes it possible to avoid false diagnostics of failure of the electrical machine, for example by the central computer, for example when the problem comes from a failure of the information circuits transmitting the torque of the electrical machine to the central computer. We thus ensure that the failure is indeed due to the electrical machine and not to the communication steps between the electrical machine and the central computer.

This avoids unnecessary changes to the electrical machine by after-sales teams. This solution thus limits replacement costs for the manufacturer and interventions that do not resolve the actual problem for the user.

Furthermore, by directly measuring the current, rather than for example a current gradient, measurements can be carried out at a particularly low periodicity, very simply and very quickly.

Fault detection is therefore more reliable than in previous technologies.

Advantageously, in the method of switching the electrical machine to a aforementioned freewheeling mode of operation, the current measurement and comparison steps can be carried out repeatedly, at the end of the current cut-off step, during a first analysis duration, preferably between 10 and 100 milliseconds, more preferably between 20 and 60 milliseconds, more preferably the first analysis duration being equal to 40 ms.

Advantageously, in the method of switching the electrical machine to a aforementioned freewheeling mode of operation, the current measurement and comparison steps can be carried out repeatedly, at the end of the current cut-off step, according to a first periodicity, preferably between 2 and 40 milliseconds, more preferably between 4 and 20 milliseconds, more preferably the first periodicity being 5 milliseconds.

Advantageously, in the method of switching the electrical machine to a aforementioned freewheel operating mode, when a failure of the electrical machine is detected by the first computer, the central computer can initiate a reconfiguration step, preferably the reconfiguration step comprising the prohibition by the central computer of the restoration of the electricity supply to the electrical machine.

Advantageously, in the method of switching the electric machine to a aforementioned freewheeling mode of operation, when a failure of the electric machine is detected by the first computer, the method can include a step of manual restoration by a user for the Acknowledgment of the fault, preferably involving restarting the vehicle.

Advantageously, in the method of switching the electrical machine to a aforementioned freewheeling mode of operation, when a failure of the electrical machine is detected by the first computer, the method can include an automated recovery process requiring the maintenance of the measured value of the current in at least one of the poles of the electric machine below a recovery threshold during a second period of a second analysis duration.

Advantageously, the recovery threshold can be in absolute value preferably between 10 and 50 amps, more preferably between 15 and 30 amps, more preferably equal to 30 amps, and/or the second analysis duration can preferably be between 200 and 2000 milliseconds, preferably between 400 and 1500 milliseconds, more preferably between 500 and 1000 milliseconds, even more preferably the analysis duration is equal to 750 milliseconds.

Advantageously, the automated recovery process may include:

- a step of measuring the current in at least one of the poles of the electric machine;

- a step of comparison, by the first calculator, of the current measured in the current measurement step with a recovery threshold, the recovery threshold being in absolute value preferably between 10 and 50 amperes, more preferably between 15 and 30 amps, more preferably equal to 30 amps;

- a step of resetting a recovery time counter, resetting the recovery time counter to 0 if the comparison step detects that the measured current exceeds the recovery threshold;

- a step of checking the elapsed time, checking whether the time elapsed since the last initialization to 0 of the recovery time counter reaches or exceeds the second analysis duration,

the automated recovery process being completed if the recovery time counter reaches or exceeds the second scan duration.

Advantageously, in the method of switching the electrical machine to a aforementioned freewheeling operating mode, the automated recovery process can require maintaining the measured value of the current below a recovery threshold for a second analysis duration in each of the poles of the electric machine.

The invention further relates to a computer program product capable of implementing the method of switching an electric machine from a drive motor or alternator mode to a freewheeling mode of operation mentioned above.

The invention also relates to a vehicle with an electric drive chain, configured to be able to implement the aforementioned tilting method and/or in which the aforementioned computer program product is installed.

The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which:
- schematically illustrates a vehicle comprising an electric traction chain, as well as a battery, a plurality of computers, a powertrain;
- illustrates a three-phase permanent magnet synchronous electric machine, as an example of an electric traction machine of the present invention;
- illustrates a first timing diagram for measuring the current in the three phases corresponding to a first reading by the control unit of the electric machine;

- illustrates a second timing diagram for measuring the current in the three phases corresponding to a second reading by the control unit of the electric machine;

- illustrates a third timing diagram for measuring the current in the three phases corresponding to a third reading by the control unit of the electric machine;

- shows a flowchart detailing examples of steps of a process of switching the electrical machine to a freewheeling operating mode, of a process of detecting a failure of the electrical machine;

- shows a flowchart detailing examples of steps in a recovery process after detection of such a failure;

- shows an example timeline of an automated failure recovery process.

The invention is now described by way of example with reference to the electric machine 10 mentioned in the preamble, that is to say in a permanent magnet electric machine having three poles, implemented in the vehicle 5 mentioned in the preamble , illustrated schematically respectively in and 2.

When the eVCU 14, that is to say the supervisor of the powertrain 7, gives the order to the MCU 15, that is to say the control unit of the electric machine, to cut the power supply by switching to a freewheeling operating mode (step of issuing a power cut E100, ), the MCU 15 cuts off the current supply to the coils 21a, 21b and 21c (current cut-off step E110). This process of switching to freewheeling mode of operation is summarized by the letter A in .

In order to verify that the electrical machine 10 has indeed switched to the freewheel operating mode, the MCU 15 is here responsible for ensuring that the electrical power supply to the coils 21a, 21b and 21c is effectively cut off. The rotor 22 is then supposed to rotate freely relative to the stator 21, therefore the magnet 24 of the rotor must pass freely in front of the coils 21a, 21b and 21c of the stator 21. However, this phenomenon gives rise to the formation of an induced current in the coils 21a, 21b and 21c, even if the coils are no longer supplied with current. Monitoring the current i _a , i _b and i _c circulating in the poles 21a, 21b and 21c (that is to say in the coils 21a, 21b and 21c) of the stator 21 therefore requires implementing a process of failure detection adapted to the end of step E110 of power cutoff.

When the magnet 24 of the rotor 22 passes in front of a first pole, for example the coil 21a, an electric current i _a appears and circulates in this winding, then when the magnet passes in front of a second pole, for example the coil 21b, the current i _a of the first pole drops and the current i _b in the second pole increases and so on with the following poles, here the third coil 21c. Therefore if the absolute value of the measured current exceeds SImin in each pole successively for a duration D1 while the machine is supposed to be in freewheeling operating mode, the control unit of the machine 15 detects a failure. In freewheeling mode, not a single one of the coils 21a, 21b and 21c of the stator 21 must see the absolute value of the current greater than SImin for more than a duration D1.

Also, a monitoring process B of the operation of the electrical machine 10 in freewheeling comprises the following steps, illustrated in , for at least one of the poles of the electric machine 10:

_ the control unit of the electric machine 15 measures the current present in the at least one pole 21a, 21b or 21c of the stator 21, or recovers the information relating to this current, here according to a predetermined periodicity F1, (step current measurement E130, ). The periodicity F1 is preferably chosen between 2 and 40 milliseconds, preferably between 4 and 20 milliseconds, more preferably the periodicity F1 is 5 milliseconds;

_ the control unit of the electrical machine 15 compares the current measured in at least one of the poles 21a, 21b or 21c with a failure threshold SImin (comparison step E140); we note that the threshold SImin is here the absolute value of a positive threshold +SImin, and of a negative threshold -SImin depending on whether the current measurement is on one side or the other of the time axis T on the graphs of , 3b and 3c described below.

In step E140, in a first particular embodiment, the control unit of the machine 15 compares the current of each of the poles 21a, 21b or 21c with the failure threshold SImin. A failure will be established as soon as the failure threshold SImin is exceeded in each of the poles 21a, 21b or 21c within the analysis period D1. This is for example the embodiment of which the first chronogram, illustrated in , transcribes the current measurements, as explained below.

In step E140, in a second particular embodiment (alternative to the first), the control unit of the machine 15 compares the current of each of the poles 21a, 21b or 21c with the failure threshold SImin. A failure will be established as soon as the failure threshold SImin is exceeded in at least one of the poles 21a, 21b or 21c within the analysis period D1. In other words, in this embodiment it is sufficient for an overshoot to be detected in a single pole 21a, 21b or 21c for a failure to be noted. This is for example the embodiment of which the second chronogram, illustrated in , transcribes the current measurements, as explained below.

Furthermore, in the monitoring process described above, a step of verifying the elapsed time is also provided (time verification step E120). This verification step E120 is a step of comparing the time elapsed since the power cut, by the electrical machine 10, with the analysis duration D1. This step E120 is executed at the end of step E140 of comparing the measured current with the failure threshold SImin. This step E120 aims to limit the duration of the analysis over time.

In the process illustrated in , this step E120 is placed as an example at the very beginning of the monitoring process, that is to say between step E110 of cutting the current by the electrical machine 10 and step E130 of measuring the current by the control unit of the electrical machine 15. In practice, the first execution of step E120 after the power cut (step E110) then necessarily determines here that the elapsed time has not exceeded the analysis duration D1 .

Alternatively, not illustrated here, this verification step E120 is only executed at the end of the step E140 of comparing the measured current with the failure threshold SImin (that is to say it is not executed between steps E110 and E130). In the flowchart of the , step E120 of this variant would then be arranged on the return arrow between step E140 and step E130, while steps E110 and E130 would be directly connected.

If in step E140, it is determined during the comparison between the measured current and the failure threshold SImin that the failure threshold SImin is exceeded by the measured current, it is considered that the electrical machine 10 suffers a failure (Y , under the block of step E140). The MCU 15 then launches a reconfiguration step (step E200) and the monitoring process is completed. The reconfiguration step includes for example the prohibition by the eVCU 14 of the restoration of the power supply to the electrical machine 10 by the MCU 15.

If, on the contrary, in step E140, the comparison between the measured current and the failure threshold SImin determines that the measured current does not exceed the failure threshold SImin, no failure is detected (N, to the left of the block of step E140). The process then executes step E120 of checking the elapsed time again.

When the elapsed time exceeds the analysis duration D1 (Y, to the right of the block of step E120), it is considered that the freewheeling operation of the electric machine 10 conforms to expectations and that no failure has occurred. appeared during the analysis duration D1. The freewheeling mode of operation thus complies with the requirements and the monitoring process is terminated (end of monitoring step E150).

THE , 3b and 3C illustrate three examples of current measurement timing diagrams in respective distinct situations of freewheeling operation of the electrical machine 10. For reasons of simplicity, in these figures, only a threshold exceedance is identified for each reading curve P1, P2 and P3 corresponding to a respective coil 21a, 21b and 21c.

In , for example, the reading curves P1, P2 and P3 of the coils 21a, 21b and 21c each exceed the threshold SImin during a respective time interval E1, E2 or E3 within the analysis period D1. More precisely, we see that the curves P1 and P3 respectively exceed, from the cutoff moment t ₀ , the threshold -SImin and +SImin, during the intervals E1 and E3. The curve P2 exceeds the threshold -SImin during a subsequent interval E2. A failure is therefore detected by the control unit of the electrical machine 15.

In , only the current measurement P4 of a first coil 21a among the reading curves P4, P5 and P6 of the coils 21a, 21b and 21c exceeds the threshold -SImin, here during a time interval E4, from the moment of cut-off t ₀ , that is to say from the start of the analysis duration D1. A failure is therefore detected by the control unit of the electrical machine 15.

In , none of the current measurements P7, P8 and P9 of the coils 21a, 21b and 21c exceed the threshold +SImin. The control unit of the electric machine 15 therefore does not detect a failure. We then consider that:

By way of example, in the embodiments represented in , 3b and 3c, the chosen value of threshold +SImin is +30A (and conversely, -SImin is worth -30A). In addition, the duration D1 chosen for the analysis period is 40 milliseconds.

At the end of the monitoring process, when it is determined by the control unit of the electrical machine 15 that a failure has occurred (step E200), a reconfiguration process is initiated. This reconfiguration process consists, for example, of:

_ the memorization by the MCU 15 of a fault code in its read-only memory (not illustrated) and the communication of this fault code to the eVCU 14, to make it possible to indicate to the operator in after-sales service that the MCU 15 encountered a failure when switching to freewheeling mode; alternatively, a specific fault code can be defined per pole not respecting the SImin threshold during an analysis duration D1.

_ the MCU 15 asks the eVCU 14 to turn on a warning light and/or display a message, for example on the dashboard in the case of a motor vehicle (not illustrated), to indicate to users of the vehicle that a problem has occurred on the traction chain 6.

_ the MCU 15 then prohibits the return of power to the terminals of the electric traction machine 10 as long as the failure is not dealt with, for example as long as the fault code recorded in memory is not erased (for example after a key Off/key On (i.e., in French: “key cut/key start”) at the vehicle ignition level by the driver).

Once the failure has been detected and possibly reported to the user of the vehicle 5, a recovery process, that is to say acknowledgment of the failure, is provided ( ). There are two options for the recovery process:

_ a so-called 'manual' acknowledgment of the failure (manual recovery process C in , i.e. the manual acknowledgment step E210), requiring human intervention, for example by acknowledgment of the fault by the MCU 15 after switching off the ignition of the vehicle 5 by a user;

_ a so-called 'automated' acknowledgment of the failure, by maintaining the measured value of the current below a recovery threshold SRImin during a second analysis duration DR2 (preferably distinct from the analysis duration D1) (automated recovery process D in , i.e. steps E220, E230, E240 and E250).

For the sake of an overview, these two acknowledgment processes are represented here on the same flowchart in , although they may be processes running separately. For example, the iterations of the automatic recovery process D, in particular steps E240 and E250, can bypass manual acknowledgment step E210 and lead directly to step E220 (dotted arrows in )

If a manual acknowledgment of the fault is detected (Y, to the left of the block of step E210), the fault is acknowledged and the current supply to the electrical machine 10 is authorized again (step E260). The recovery process is then complete. The process of manual acknowledgment of the fault can for example be an acknowledgment by switching off the ignition of the vehicle 5. In a variant not illustrated, the process of manual acknowledgment of the fault covers an acknowledgment by manual erasure of the fault code in the memory dead from MCU 15.

Here, in the absence of manual acknowledgment of the fault (N, below the block of step E210), the automatic recovery process D is initiated.

In the automatic recovery process D:

_ the control unit of the electrical machine 15 measures the current circulating in the at least one pole 21a, 21b or 21c of the stator 21 affected by the failure, according to a predetermined periodicity F2, or recovers the information relating to this current (measuring step E220, ). The periodicity F2 is preferably chosen between 2 and 40 milliseconds, more preferably between 4 and 20 milliseconds, more preferably the periodicity F2 is 5 milliseconds;

_ the control unit of the machine 15 compares the current measured in at least one of the poles 21a, 21b or 21c with the recovery threshold SRImin (comparison step E230); we note that the threshold SRImin is here the absolute value of a positive threshold +SRImin, and of a negative threshold -SRImin depending on whether the sinusoidal evolution of the current measurement is on either side of a value nothing.

In step E230, the control unit of the machine 15 compares the measurement of the current circulating in each of the poles 21a, 21b or 21c with the recovery threshold SRImin.

If the measured current i _a , i _b and i _c exceeds the recovery threshold SRImin (Y, to the right of the block of step E230 in ), the recovery time counter is reset to 0, preferably 0 ms (counter reset step E240) and the process returns to measurement step E220. This resetting of the time counter makes it possible to ensure that a recovery time DR2 has actually passed before the fault is acknowledged.

If the measured current i _a , i _b and i _c does not exceed the recovery threshold SRImin, that is to say remains below it (N, below the block of step E230), the process continues towards the elapsed time verification step E250.

Step E250 of checking the elapsed time is a step of comparing the time elapsed since the last initialization to 0 of the recovery time counter, by the electric machine 10, with the second analysis duration DR2. The purpose of this step E250 is to note the absence of failure over a sufficiently long period for the restart of the electrical machine 10 to be deemed safe, before the MCU 15 actually re-authorizes the supply of current to the terminals of the electrical machine. 10.

If the time elapsed since the last initialization to 0 of the recovery time counter reaches or exceeds the second analysis duration DR2, the failure has no longer been detected during the repetitions of step E220 of measuring the current and step E230 of comparing it with the recovery threshold. It is therefore considered that the fault has disappeared or is acknowledged (Y, below the block of step E250). The recovery process then ends (step E260).

Otherwise, as long as the time elapsed since the last initialization to 0 of the recovery time counter has not reached or exceeded the second analysis duration DR2 (N, to the right of the block in step E250), the condition of sufficient persistence of the current below the recovery threshold is not satisfied and the analysis of the recovery conditions continues with step E210 (or directly with step E220 for measuring the current).

During the recovery process, analogous to the process of monitoring the , the existence of the failure is established in step E230 as soon as a current threshold (here the recovery threshold SRImin) is exceeded in at least one of the poles 21a, 21b or 21c during the second analysis duration DR2.

In a particular embodiment, the persistence of the failure is established as soon as an exceeding of the failure threshold SImin is detected in each of the poles 21a, 21b or 21c within the analysis period DR2.

An example of application of the latter case is illustrated in . In this figure, the +SRImin and -SRImin thresholds are illustrated. In this example, the thresholds +SRImin and -SRImin are chosen to have the same value as those of +SImin and -SImin in the failure detection process, above. Here, if a failure has been detected (E200) and no manual acknowledgment has been made (N under block E210), the automated recovery process D begins, for example at time t ₁ in . A first analysis period DR2 _has started, which is a particular example of the analysis period of predetermined duration DR2. At t ₂ , the curve P4 exceeds the threshold +SRImin, which the process detects in step E230. The first analysis period DR2a is therefore interrupted (Y in step E230). As long as the curve P4 remains above the threshold +SRImin, which is measured in step E220, this excess is detected in step E230 and the time counter is reset to 0 in step E240. At t ₃ , the P4 curve here crosses the threshold +SRImin downwards. The automated recovery process D detects this bearish crossing when comparing step E230. A new analysis period DR2 _b of duration DR2 then starts. As long as the duration DR2 is not reached, a loop is initiated between steps E220, E230, and E250 (respectively: measurement of the current, comparison of the current, and verification of the elapsed time). Once the DR2 time has elapsed, the recovery process ends (E260).

In a particular embodiment, it is sufficient for an exceeding of the failure threshold SImin to be detected in at least one of the poles 21a, 21b or 21c within the analysis period DR2 for the persistence of the failure to be established.

Once the fault has been cleared, the electrical machine 10 can be supplied with current again, as a result of which the vehicle 5 is authorized to leave.

In vehicle 5, the rehabilitation includes the following stages:

- the control unit of the machine 15 stops requesting the illumination of the STOP light on the dashboard of the vehicle 5, and/or the illumination of a message on the dashboard of the vehicle 5, and/or the control unit of the machine 15 requests the extinction of the STOP light on the dashboard of the vehicle 5, and/or the control unit of the machine 15 requests the extinction of the message on the dashboard of the vehicle 5 and/or the control unit of the machine 15 requests the display of a message acknowledging the failure (that is to say taking charge of the problem) on the dashboard of the vehicle 5;

- the control unit of the machine 15 again authorizes the supply of current to the terminals of the electrical machine 10.

After detection of a failure, a fault code can remain stored in a read-only memory of the eVCU 14 and/or the MCU 15 so as to keep a trace, for example for after-sales service.

If applicable, this fault code does not remain in a permanent state in the memory of the MCU 15 and/or eVCU 14 computers, but the fault code can go into a fleeting state to indicate to the after-sales service that the fault resolved itself.

The second analysis duration DR2 is preferably between 200 and 2000 milliseconds, preferably between 400 and 1500 milliseconds, more preferably between 500 and 1000 milliseconds, even more preferably the analysis duration DR2 is equal to 750 milliseconds .

In the description above, the recovery threshold SRImin was chosen to be the same value as the failure threshold SImin (for example at 30 amps). Alternatively, the values of these thresholds can be between 10 and 50 amps, preferably 15 amps and 30 amps, for example 30 amps.

The failure suffered by the electrical machine 10 is for example a temperature gradient that is too great at the stator 21 or a short circuit at the pole circuit which can cause a risk of electrocution.

The invention is described by way of non-limiting example with reference to the vehicle 5 mentioned in the preamble and/or to the electric machine 10 mentioned in the preamble, that is to say an electric machine with a permanent magnet having three poles, but can also be applied with reference to an electrical machine having a different number of poles, for example six, nine or more poles.

Generally speaking, the invention can be transposed to any vehicle having an electric traction machine, for example, without limitation, electric, hybrid or combustion cell vehicles. These vehicles can be private or commercial vehicles (automobile, motorcycles, scooters, boats, planes, trucks, etc.).

Claims (10)

Method for switching an electric machine from a drive motor mode or an alternator mode to a freewheeling operating mode, in a vehicle with an electric drive chain (6),
the vehicle (5) comprising:
- a battery (8) forming an energy source;
- a powertrain (7) comprising the electric machine (10), at least one driving wheel (12) and at least one set of computers (9),
the electric machine (10) being supplied with current from the battery (8), and configured to convert the electricity received from the battery (8) into mechanical energy, the electric machine further comprising a plurality of poles (21a, 21b, 21c);
the at least one driving wheel (12) being configured to be rotated by the mechanical energy produced by the electrical machine (10);
the set of computers (9) comprising:
- a first computer (15), called a machine control unit, and forming a control member of the electric machine (10);
- a central computer (14), called an electric vehicle control unit, and forming a general supervisor of the powertrain (7), including the first computer (15);
the method of switching the electric machine (10) to the freewheel operating mode comprising:
- a step of issuing a cut-off order (E100) of the supply current of the electrical machine (10) by the central computer (14) to the first computer (15);
- a step of cutting the current (E110) in the electrical machine (10) by the first computer (15);
- a step of measuring the current (E130) in at least one of the poles (21a, 21b, 21c) of the electric machine (10);
- a comparison step (E140), by the first calculator (15), of the measured current (i _a , i _b and i _c ) in the current measurement step (E130) with a predetermined failure threshold (SImin) , the failure threshold (SImin) being in absolute value preferably between 10 and 50 amps, more preferably between 15 and 30 amps, more preferably equal to 30 amps. Method for switching the electric machine to a freewheeling operating mode according to claim 1, characterized in that the current measurement (E130) and comparison (E140) steps are executed repeatedly, at the end of the current cut-off step (E110), for a first analysis duration (D1), preferably between 10 and 100 milliseconds, more preferably between 20 and 60 milliseconds, more preferably the first analysis duration ( D1) being equal to 40 ms. Method for switching the electric machine to a freewheeling operating mode according to claim 1, characterized in that the current measurement (E130) and comparison (E140) steps are executed repeatedly, at the end of the step of cutting off the current (E110), according to a first periodicity (F1), preferably between 2 and 40 milliseconds, more preferably between 4 and 20 milliseconds, more preferably the first periodicity (F1) being 5 milliseconds . Method for switching the electric machine to a freewheeling operating mode according to any one of claims 1 or 2, characterized in that when a failure of the electric machine (10) is detected by the first computer (15) , the central computer (14) initiates a reconfiguration step (E200), preferably the reconfiguration step comprising the prohibition by the central computer (14) of the restoration of the electricity supply to the electrical machine (10). Method for switching the electric machine to a freewheeling operating mode according to any one of claims 1 to 3, characterized in that, when a failure of the electric machine (10) is detected by the first computer (15 ), the method includes a manual recovery step (E210) by a user for acknowledgment of the fault, preferably involving restarting the vehicle (5). Method for switching the electric machine to a freewheel operating mode according to any one of claims 1 to 3, characterized in that when a failure of the electric machine (10) is detected by the first computer (15) (E200), the method comprises an automated recovery process (D) requiring the maintenance of the measured value of the current (i _a , i _b and i _c ) in at least one of the poles (21a, 21b, 21c) of the machine electrical (10) under a recovery threshold (SRImin) during a second period (DR2a, DR2b) of a second predetermined analysis duration (DR2),
the recovery threshold (SRImin) being in absolute value preferably between 10 and 50 amps, more preferably between 15 and 30 amps, more preferably equal to 30 amps, and/or
the second analysis duration (DR2) being preferably between 200 and 2000 milliseconds, preferably between 400 and 1500 milliseconds, more preferably between 500 and 1000 milliseconds, even more preferably the analysis duration (DR2) is equal to 750 milliseconds. Method for switching the electric machine to a freewheeling operating mode according to claim 6, characterized in that the automated recovery process (D) comprises:
- a step of measuring the current (E220) in at least one of the poles (21a, 21b, 21c) of the electric machine (10);
- a comparison step (E230), by the first calculator (15), of the measured current (i _a , i _b and i _c ) in the current measurement step (E220) with a recovery threshold (SRImin), the recovery threshold (SRImin) being in absolute value preferably between 10 and 50 amps, more preferably between 15 and 30 amps, more preferably equal to 30 amps;
- a step of resetting a recovery time counter (E240), resetting the recovery time counter to 0 if the comparison step (230) detects that the measured current (i _a , i _b and i _c ) exceeds the recovery threshold (SRImin);
- a step of checking the elapsed time (E250), checking whether the time elapsed since the last initialization to 0 of the recovery time counter reaches or exceeds the second analysis duration (DR2),
the automated recovery process (D) being completed (E260) if the recovery time counter reaches or exceeds the second analysis duration (DR2). Method for switching the electric machine to a freewheeling operating mode according to any one of claims 6 or 7, characterized in that the automated recovery process (D) requires maintaining the measured value of the current (i _a , i _b and i _c ) under a recovery threshold (SRImin) during the second analysis duration (DR2) in each of the poles (21a, 21b, 21c) of the electrical machine (10). Computer program product capable of implementing the method of switching an electric machine forming a drive motor to a freewheeling mode of operation according to any one of claims 1 to 8. Vehicle with an electric drive chain, characterized in that it is configured to be able to implement the tilting method according to any one of claims 1 to 8 and/or in which the computer program product of claim 9 is installed.