METHOD FOR CONTROLLING THE ROTATIONAL SPEED OF A ROTOR OF AN ELECTRIC TRACTION MOTOR IN A MOTOR VEHICLE

Abstract

The invention relates to a method for controlling the rotational speed of a rotor of an electric traction motor (18) of a motor vehicle (10) comprising a powertrain comprising the electric motor, a rotor rotational speed sensor, a train (12) coupled to the powertrain, wheels (12.1, 12.2) associated with the train and an ABS / ESP computer (35), the method comprising steps of: a) Receiving a wheel rotational speed value from the ABS / ESP computer; b) Determining a rotor rotational speed value of the electric motor from the wheel rotational speed value; c) Comparing the rotor rotational speed value with a rotational speed value measured by the rotor rotational speed sensor; and, d) If a difference is detected, triggering an associated configuration of operation in degraded mode of the powertrain. (Fig. 1)

Description

Title of the invention: Method for controlling the rotation speed of a rotor of an electric traction motor in a motor vehicle Technical field of the invention

[0001] The invention relates, in general, to the technical field of controlling the operation of an electric traction motor within an electric motor vehicle. In particular, the invention relates to a method for controlling the rotational speed of a rotor of an electric traction motor of a powertrain of an electric or hybrid motor vehicle. State of the prior art

[0002] Today, a rotational speed of an electric traction motor rotor is measured via a rotational speed sensor equipping the rotor. Such measurements of the measured rotational speed are used in the context of controlling the engine torque of the electric traction motor, during operation of a powertrain equipped with the electric traction motor. In particular, the computer controlling the powertrain thus checks whether the requested rotational speed setpoint is being respected by comparing it with the information from the measurement of the actual rotational speed of the rotor returned by said rotational speed sensor. If the computer notes a difference, then it seeks to correct the operation of the powertrain until a match is obtained between the setpoint and the actual measurement.

[0003] Indeed, this information on the speed or rotational speed of the rotor (named W) is used to calculate an effective torque C at the rotor output of the electric traction motor, where C = Ux!xp / W, U being the voltage and I the current at the terminals of the electric traction motor, p a parameter specific to the electric traction motor.

[0004] Therefore, if the rotation speed information W is false or erroneous due to a failure of the rotation speed sensor, or a short circuit on the sensor or other, the calculation of the torque C at the output of the rotor of the electric traction motor is erroneous. The severity is important from a safety point of view (ASIL Severity C), because the calculation of the torque becomes false and this calculation intervenes to check that the electric traction motor does not produce overtorque or undertorque and that therefore the torque setpoint of the computer controlling the powertrain is respected and more broadly by the operation of the electric traction motor.

[0005] Therefore, the safety risk is too great to have the feedback from the rotor speed sensor as the sole monitoring. Statement of the invention

[0006] The invention aims to remedy all or part of the drawbacks of the state of the art by proposing in particular a solution allowing precise measurement and monitoring of the instantaneous rotation speed of a rotor of an electric traction motor driving a train of an electric motor vehicle.

[0007] To do this, according to a first aspect of the invention, there is proposed a method for controlling the rotation speed of a rotor of an electric traction motor of a motor vehicle comprising a powertrain comprising the electric traction motor, a rotor rotation speed sensor, a train coupled to the powertrain, wheels associated with the train and an ABS / ESP computer, the method comprising steps of: a. Receiving a wheel rotation speed value from the ABS / ESP computer; b. Determination of a value of rotation speed of the rotor of the electric traction motor from the received value of rotation speed of the wheels; c. Comparison of the rotor rotational speed value thus determined with a rotational speed measured by the rotor rotational speed sensor; and,

[0008] According to one embodiment, during step c), a difference is calculated between the rotation speed value of the rotor and the rotation speed value measured by the rotor rotation speed sensor.

[0009] According to one embodiment, during step c), the method calculates a percentage deviation of the calculated deviation.

[0010] According to one embodiment, during step d), if the calculated deviation or the percentage deviation is greater than a predetermined threshold value EWmel, EWmel%, the method triggers the degraded operating mode of the powertrain.

[0011] According to one embodiment, during step d), the method triggers the degraded operating mode of the powertrain if the rotation speed value measured by the rotor rotation speed sensor is less than a predetermined threshold value SWmel, and if the calculated difference is greater than the predetermined threshold value EWmel.

[0012] According to one embodiment, the method triggers the degraded operating mode of the powertrain if the rotation speed value measured by the rotor rotation speed sensor is greater than a predetermined threshold value SWmel, and if the calculated percentage difference is greater than the predetermined threshold value EWmel%.

[0013] According to one embodiment, the degraded operating mode of the powertrain includes a request to stop the motor vehicle.

[0014] According to one embodiment, the degraded operating mode of the powertrain comprises a reduction in the torque of the electric traction motor so as to limit a speed of the motor vehicle, in particular between 15 and 25 km / h.

[0015] According to one embodiment, the method comprises a preliminary triggering step in which steps a) to d) are carried out if the electric traction motor is in operation.

[0016] According to yet another aspect of the invention, there is provided a motor vehicle comprising a powertrain comprising an electric traction motor, a rotor rotation speed sensor, a train coupled to the powertrain, wheels associated with the train and an ABS / ESP computer, as well as a computer arranged so as to implement a monitoring method having one of the preceding technical characteristics. brief description of the figures

[0017] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, which illustrate: • [Fig.l]: partial schematic view of an electric motor vehicle implementing a control method according to the invention. DETAILED description of an embodiment

[0018] [Fig.l] schematically illustrates an electric or hybrid motor vehicle 10. It comprises a train 12 driven by a rear powertrain comprising an electric traction motor or electric machine 18, a reducer or gearbox 19 and a dog clutch system 21 of the powertrain making it possible to dog-clutch or undog-split the powertrain of the transverse transmissions which are connected to the wheels 12.1 and 12.2 of the train. A power interface 25 makes it possible to connect the electric traction motor 18 to a traction battery 26. A computer 26 is connected to the electric traction motor 18 on the one hand, and on the other hand to the dog clutch system 21 in order to control the powertrain of the electric motor vehicle 10. It should be noted that the dog clutch system 21 is optional and may not be present in an alternative embodiment.

[0019] Furthermore, in a manner known per se, the electric motor vehicle 10 comprises an ABS / ESP 30 computer (ABS is the English acronym for “Anti-Blocking System” or anti-lock system, and ESP is the English acronym for “Electronic Stability Program” or electronic stability program, also called electronic trajectory corrector). In order to operate, the ABS / ESP 30 computer continuously receives speed information from wheel speed sensors 31, 32, here two in number and associated respectively with the wheels 12.1, 12.2 of the electric motor vehicle 10. Each wheel speed sensor 31, 32 comprises an angular encoder which measures the angular displacement of the associated wheel. Knowing a developed of said associated wheel, the ABS / ESP computer 30 deduces therefrom a speed of the electric motor vehicle 10. The angular encoder comprises a toothed wheel or target integral in rotation with the wheel and a reader which detects a passage of the teeth of the target. Knowing the number of teeth of the target distributed uniformly on a circumference of the latter, the ABS / ESP computer 30 estimates the distance traveled by the wheel, a distance which, integrated over a time, makes it possible to know the speed of the electric motor vehicle 10 at the level of the wheel in question.To ensure safe and optimal operation of the ABS / ESP system of the electric motor vehicle 10. .

[0020] The calculators 26 and ABS / ESP 30 are connected to each other so as to be able to exchange information.

[0021] We will now describe in detail a method for controlling the rotational speed of a rotor of an electric traction motor according to the invention.

[0022] As a preliminary remark, we will recall the calculation of an effective engine torque C at the rotor output of the electric traction motor 18. At the output of the electric rotation motor 18, a bidirectional engine speed sensor is installed, because most often the electric traction motors are capable of rotating in both directions of rotation. Very often, reversing on an electric or hybrid motor vehicle is not done by means of a change in a gear set in the gearbox 19, but by a change in the direction of rotation of the electric traction motor, which causes a change in the direction of rotation of the wheels 12.1, 12.2 of the electric or hybrid motor vehicle. It is solely thanks to this bidirectional speed sensor that the computer 26 determines the torque C at the output of the electric traction motor.

[0023] The electric traction motor receives electrical power at its input terminals of the power supply interface 25 from the traction battery 23: Pelec = U x I, with Pelec being the electrical power at the input of the electric traction motor, U, the voltage and I, the current at the terminals of the power supply interface 25.

[0024] From there, a mechanical power is calculated: Pmeca = C x W, with Pmeca being the mechanical power at the output of the electric traction motor, C, the torque at the output of the electric traction motor, and W, the speed or rotational speed of the rotor of the electric traction motor.

[0025] The relationship between Pméca and Pélec is as follows: Pméca = Pélec xp, where p is a coefficient of efficiency of the electric traction motor which is measured on a bench for each speed step, torque step, for each voltage step, for each supply current step and for each stator temperature step of the electric traction motor. A mapping of the values ​​of p is thus learned and stored in a memory of the computer 26.

[0026] From there, C x W = U x I xp

[0027] So, C = U x I xp / W

[0028] In practice, the computer 26 measures or receives the information on the voltage at the terminals of the electric traction motor, the information on the current drawn by the electric traction motor 18 and the information on the rotation speed of the rotor of the electric traction motor 18. The computer 26 deduces the efficiency coefficient using the rotor rotation speed of the electric traction motor 18, the stator temperature, the current drawn by the electric traction motor 18 and the voltage at the terminals of the power supply interface 25 of the electric traction motor 18. And thus, the computer 26 determines the torque that the electric traction motor 18 supplies to the traction chain by the formula C = U x I xp / W.

[0029] Firstly, the computer 26 receives speed information, “Vvhl”, from the wheels 12.1, 12.2 from the ABS / ESP computer 30.

[0030] On the other hand, the computer 26 also receives information on the speed or rotation speed of the rotor from the rotor rotation speed sensor. (Wmel).

[0031] In addition, the computer 26 receives current information, “Imel”, at the supply terminals of the supply interface 25, therefore of a current level consumed by the electric traction motor.

[0032] On the other hand, the calculator 26 has a value of the wheel development (Droue) and a value of a reduction gear ratio (Dred) of the reduction gear 19. These two values ​​are recorded in a memory during a development of the method for monitoring the rotation speed of a rotor of an electric traction motor according to the invention.

[0033] It should be noted that the method for controlling the rotational speed of a rotor of an electric traction motor according to the invention is only operational when the electric traction motor 18 is in operation, that is to say when an absolute value of current consumed at the terminals of the power supply interface 25 is greater than a predetermined threshold, Slmax. For example, Slmax is of the order of magnitude of 5A.

[0034] Once operational, the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention calculates a theoretical rotation speed of the rotor, “WmelTheo”, of the electric traction motor 18 from the previous information received, namely: WmelTheo = Vvhl x 1000 x Dred / Rroue / 60.

[0035] Then, the method of controlling the rotational speed of a rotor of a motor traction electric motor according to the invention performs a step of calculating a difference between the Wmel value received from the rotor rotation speed sensor and the WmelTheo value thus calculated: EWmel = IWmelTheo - Wmell. The method for controlling the rotation speed of a rotor of an electric traction motor according to the invention also determines a percentage difference of this EWmel difference: EWmel% = EWmel x 100 / Wmel.

[0036] Then the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention compares these two deviations thus calculated with a predetermined criterion.

[0037] In a first case, a value of Wmel is less than a predetermined rotation speed threshold SWmel, calibratable during the development of the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention, for example of the order of 100 rpm. Therefore, if the value of Wmel is less than SWmel, the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention verifies that a value of EWmel is less than a predetermined threshold value SEWmel. If this is the case, the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention “judges” the situation to be normal and does not engage a degraded operating mode of the powertrain.On the other hand, if the value of EWmel is greater than SEWmel, then the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention “judges” the situation abnormal and critical and engages a degraded mode of operation of the powertrain. SEWmel is a threshold of deviation of rotation speed of the rotor between the measured and the calculated, calibratable during the development of the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention, for example, 3.5 rpm.

[0038] In a second scenario, the value of Wmel is greater than the rotation speed threshold SWmel. In this situation, the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention verifies that a value of EWmel% is less than a threshold SEWmel%. If this is the case, the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention “judges” the situation normal and does not engage a degraded operating mode of the powertrain. On the other hand, if the value of EWmel% is greater than the threshold SEWmel%, then the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention “judges” the situation abnormal and critical and engages a degraded operating mode of the powertrain.SEWmel% is a threshold for the deviation of the rotor rotation speed between the measured and the calculated, calibratable when developing the method for controlling the rotation speed of a rotor of an electric traction motor according to the invention, for example 4%.

[0039] If the method for controlling the rotational speed of a rotor of an electric traction motor according to the invention engages a degraded operating mode, the latter performs the following steps. The method for controlling the rotational speed of a rotor of an electric traction motor according to the invention records a fault code in the memory of the computer 26. The purpose of this fault code is to be able to be read by after-sales services during a future visit, indicating an erroneous “rotor speed of the electric machine”. Then, the method for controlling the rotational speed of a rotor of an electric traction motor according to the invention lights a “stop” indicator light on a dashboard of the electric or hybrid motor vehicle, to request that the electric or hybrid motor vehicle be stopped.

[0040] Alternatively, the method for controlling the rotational speed of a rotor of an electric traction motor according to the invention indicates to the powertrain to reduce the torque of the electric traction motor so that the speed of the electric or hybrid motor vehicle is between 15 and 25 km / h. This speed is calibrated during the degraded mode development phase.

[0041] Furthermore, the method for controlling the rotational speed of a rotor of an electric traction motor according to the invention comprises a step of restoring the operation of the powertrain. This restoration is carried out following a succession of ignition cut-off then ignition start (two successive presses on a START / DEMARRER button or double action of an ignition key), and that the information coming from the rotational speed sensor of the rotor of the electric traction motor 18 is consistent with the time of ignition start. If the fault in the information from the rotational speed sensor of the rotor of the electric traction motor is still present, the method for controlling the rotational speed of a rotor of an electric traction motor according to the invention re-engages the degraded mode of operation of the powertrain, seen above.Otherwise, the after-sales service, once the problem has been identified and repaired, has the possibility of erasing the fault code and restoring the electric or hybrid vehicle to normal behavior.

[0042] If the after-sales service does not intervene on the electric or hybrid motor vehicle and the information from the rotor speed sensor of the electric traction motor returns in accordance with the theoretical value WmelTheo, the fault code changes from a permanent fault state to a transient fault state at the next ignition off / ignition start cycle. Thus, the after-sales service will be able to see that this fault has been reported and is no longer active.

[0043] It is clear from the above that the implementation of a method for controlling the rotational speed of a rotor of an electric traction motor according to the invention makes it possible to ensure that the information on the rotational speed of the rotor measured by the rotor rotational speed sensor is compliant. If this is not the case, such a method for controlling the rotation speed of a rotor of an electric traction motor according to the invention makes it possible to initiate a procedure for securing the electric or hybrid motor vehicle and its occupants. Such a method for controlling the rotation speed of a rotor of an electric traction motor according to the invention makes it possible to ensure the safety of the electric or hybrid motor vehicle and its users by controlling the generation of engine torque at the level of the electric traction motor. A failure in this control can lead to risks of dangerous untimely acceleration.

[0044] Naturally, the invention is described in the foregoing by way of example. It is understood that the person skilled in the art is able to carry out different variant embodiments of the invention without departing from the scope of the invention.

[0045] It is emphasized that all features, as they emerge for a person skilled in the art from the present description, the drawings and the attached claims, even if concretely they have only been described in relation to other determined features, both individually and in any combinations, may be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

Claims

Claims

1. A method for controlling the rotational speed of a rotor of an electric traction motor (18) of a motor vehicle (10) comprising a powertrain comprising the electric traction motor, a rotor rotational speed sensor, a train (12) coupled to the powertrain, wheels (12.1, 12.2) associated with the train and an ABS / ESP computer (35), the method comprising steps of: a. Receiving a wheel rotational speed value from the ABS / ESP computer; b. Determining a rotor rotational speed value of the electric traction motor from the received wheel rotational speed value; c. Comparing the rotor rotational speed value thus determined with a rotational speed value measured by the rotor rotational speed sensor; and, d.If a difference is found during the comparison, triggering of an associated configuration for operating in degraded mode of the powertrain.

2. Method according to claim 1, characterized in that, during step c), a difference is calculated between the rotor rotation speed value and the rotation speed value measured by the rotor rotation speed sensor.

3. Method according to claim 2, characterized in that, during step c), the method calculates a percentage deviation of the calculated deviation.

4. Method according to one of claims 2 to 3, characterized in that, during step d), if the calculated deviation or the percentage deviation is greater than a predetermined threshold value EWmel, EWmel%, the method triggers the degraded operating mode of the powertrain.

5. Method according to one of claims 2 to 3, characterized in that, during step d), the method triggers the degraded operating mode of the powertrain if the rotation speed value measured by the rotor rotation speed sensor is less than a predetermined threshold value SWmel, and if the calculated deviation is greater than the predetermined threshold value EWmel.

6. Method according to claim 3, characterized in that, during step d), the method triggers the degraded operating mode of the powertrain if the rotation speed value measured by the rotor rotation speed sensor is greater than a predetermined threshold value SWmel, and if the calculated percentage deviation is greater than the predetermined threshold value EWmel%.

7. Method according to one of claims 1 to 6, characterized in that the degraded operating mode of the powertrain includes a request to stop the motor vehicle.

8. Method according to one of claims 1 to 7, characterized in that the degraded mode of operation of the powertrain comprises a reduction in the torque of the electric traction motor so as to limit a speed of the motor vehicle, in particular between 15 and 25 km / h.

9. Method according to one of claims 1 to 8, characterized in that the method comprises a preliminary triggering step in which steps a) to d) are carried out if the electric traction motor is in operation.

10. Motor vehicle (10), characterized in that it comprises a powertrain comprising an electric traction motor (18), a rotor rotation speed sensor, a train (12) coupled to the powertrain, wheels (12.1, 12.2) associated with the train and an ABS / ESP computer (35), characterized in that the motor vehicle comprises a computer (26) arranged so as to implement a control method according to one of claims 1 to 9.

Images