METHOD FOR CONTROLLING AN ELECTRIC TRACTION MACHINE OF A VEHICLE

Description

[0001] The present invention claims priority from French application No. 2207844 filed on 29.07.2022, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] One aspect of the invention relates to a method of controlling an electric traction machine of a vehicle, said control taking place successively to the detection of a failure of at least one pressure sensor of a braking amplifier included in the vehicle.

[0003] Another aspect of the invention relates to an electric or hybrid vehicle, in particular an automobile, constructed and arranged to implement a method of controlling an electric traction machine.

[0004] These aspects of the invention have particularly interesting applications in the field of safety for electric or hybrid motor vehicles.

[0005] A brake booster is typically installed on a motor vehicle to amplify the force a driver must exert on the brake pedal. To achieve this, the brake booster works in conjunction with an electric vacuum pump designed to generate a vacuum within the vehicle's brake booster. Each time the brake pedal is pressed, vacuum is consumed to provide the necessary braking assistance to the driver. As soon as the vacuum level drops below a predetermined threshold, the electric vacuum pump activates to replenish the vacuum in the brake booster.

[0006] The pressure generated by the vacuum pump in the brake booster is monitored by a pressure sensor. Specifically, this pressure sensor transmits pressure information to a vehicle control unit, which verifies that the detected pressure value is within an acceptable range. If the value falls outside this range, the pressure sensor is considered faulty.

[0007] To detect false pressure readings, it is also known from US-A1-7467544 to redundantly equip the brake booster pressure sensor. A failure is reported if the measurements taken by both sensors fall below a certain drift threshold.

[0008] If such a process makes it possible to detect a failure of one of the pressure sensors, the very existence of such a failure risks impacting the braking capacity of the vehicle.

[0009] The aim of the invention is to overcome the drawbacks of the prior art by proposing a method to secure the vehicle in the event of detection of a failure of a pressure sensor of a brake booster.

[0010] In this context, the invention, in its broadest sense, relates to a method for controlling an electric traction machine of an electric or hybrid vehicle, said method comprising, when the vehicle is in motion, the steps, executed by vehicle control means, of: Detect a failure of at least one first pressure sensor or a second pressure sensor of a vehicle brake booster, Determine a vehicle speed value, The method being notable in that it further comprises the steps of: When a failure of at least one of the first pressure sensors or second pressure sensors is detected, determine a torque value to be applied to the vehicle drive wheels, as a function of the determined speed value, to bring the vehicle to a predetermined safe speed value, Apply the determined torque value to the drive wheels by means of the electric traction machine.

[0011] Thanks to the process of the invention, when a failure of at least one pressure sensor of the brake booster is detected, the speed of the vehicle is brought to a predetermined safety speed, for example between 10 and 20 km / h so that the driver can stop the vehicle without brake assistance.

[0012] In addition to the characteristics mentioned in the preceding paragraph, the process according to the invention may have one or more additional characteristics from among the following, considered individually or according to all technically possible combinations.

[0013] US 2019 / 308598 A1 discloses a method for controlling an electric traction machine of an electric or hybrid vehicle.

[0014] According to a non-limiting aspect of the invention, the method includes a step, executed by the control means, of displaying, on a vehicle display console, a vehicle stop indicator light.

[0015] According to a non-limiting aspect of the invention, the method includes a step, executed by the control means, of displaying, on a vehicle display console, a message reflecting that a failure of at least one of the vehicle's first or second pressure sensor has been detected.

[0016] According to a non-limiting aspect of the invention, the step of detecting a failure of at least one of the first or second pressure sensors comprises the following substeps: Receive a first pressure measurement from the brake booster determined by means of the first pressure sensor, Receive a second pressure measurement from the brake booster determined by means of the second pressure sensor, Determine a pressure difference between the first and second pressure measurements, Repeat, periodically according to a first determined period, the sub-steps of receiving a first pressure measurement, receiving a second pressure measurement and determining a pressure difference, If the determined pressure difference is greater than a pressure threshold during a second predetermined period, determine a failure of at least one of the first pressure sensor or second pressure sensor.

[0017] According to a non-limiting aspect of the invention, the method includes a step, executed by the control means, of piloting a vacuum pump of the brake amplifier according to the lowest pressure measurement among the first and second pressure measurements.

[0018] According to a non-limiting aspect of the invention, when a failure of at least one of the first or second pressure sensors has been detected, it comprises the steps, executed via the control means, of: Repeat periodically, according to the first determined period, the sub-steps of receiving a first pressure measurement, receiving a second pressure measurement and determining a pressure deviation. If the determined pressure deviation is less than the pressure threshold during a third predetermined period, determine a restoration of operation of at least one of the first pressure sensor or second pressure sensor.

[0019] According to a non-limiting aspect of the invention, the method includes a step, executed by the control means, of stopping the application of the determined torque value to the drive wheels by means of the electric traction machine.

[0020] According to one non-limiting aspect of the invention, the method includes a step, executed by the control means, of turning off the vehicle's stop light.

[0021] According to a non-limiting aspect of the invention, the method includes a step, executed by the control means, of turning off the message reflecting that a failure of at least one of the first pressure sensor or second pressure sensor has been detected.

[0022] According to a non-limiting aspect of the invention, the method includes a step, executed by the control means, of controlling a vacuum pump of the brake amplifier as a function of a pressure measurement made by the first pressure sensor or the second pressure sensor pre-selected as the reference sensor.

[0023] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures.

[0024] [ Fig. 1 ] illustrates, schematically, an electric vehicle conforming to a non-limiting aspect of the invention.

[0025] [ Fig. 2 ] represents, schematically, an example of the implementation of a method for controlling an electric traction machine of an electric or hybrid vehicle according to a non-limiting aspect of the invention.

[0026] [ Fig. 3 ] shows a reference curve that can be implemented in a method of controlling an electric traction machine of an electric or hybrid vehicle according to a non-limiting aspect of the invention.

[0027] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0028] There figure 1 illustrates schematically an electric vehicle 1 according to the invention.

[0029] The electric vehicle 1 includes: An electric traction machine 2, Two drive wheels 3 rotated by the electric traction machine 2, A brake amplifier 4, A vacuum pump 5, A first pressure sensor 6, A second pressure sensor 7, A display console 8, and Control means 9 arranged to implement steps in a method for controlling an electric traction machine as illustrated in figure 2 . The control means 9 can for example be formed by a vehicle control unit (better known by the acronym VCU for Vehicle Control Unit in English) and / or by an intelligent service box, better known by the acronym BSI.

[0030] There figure 2 illustrates an example of the realization of a method 100 for controlling an electric traction machine 2 of an electric or hybrid vehicle 1 according to the invention.

[0031] It should be noted that the steps presented below of process 100 are carried out when vehicle 1 is in motion.

[0032] The process 100 includes a step of detecting 101, via the control means 9 of vehicle 1, a failure of at least one of the first pressure sensor 6 or second pressure sensor 7 of the brake booster 4 of vehicle 1.

[0033] In a non-limiting implementation, the step 101 of detecting a failure of at least one of the first pressure sensor 6 and second pressure sensor 7 comprises the substeps of: Receive 101a a first pressure measurement of the brake booster 4 determined by means of the first pressure sensor 6, Receive 101b a second pressure measurement of the brake booster 4 determined by means of the second pressure sensor 7, then Determine 101c a pressure difference between the first and second pressure measurements.

[0034] To perform the substep of determining 101c a pressure deviation, the control means 9 determine, for example, the pressure deviation by taking the absolute value of the first pressure measurement and subtracting the second pressure measurement.

[0035] The detection step 101 also includes a repeat step 101d, periodically according to a first determined period, the substeps of receiving 101a a first pressure measurement, receiving 101b a second pressure measurement and determining 101c a pressure deviation.

[0036] In a non-limiting example of implementation, the first determined period is between 100 and 300 milliseconds, typically 200 milliseconds.

[0037] The detection step 101 also includes, if the determined pressure deviation is greater than a pressure threshold during a second predetermined period, a substep of determining 101e a failure of at least one of the first pressure sensor 6 or second pressure sensor 7.

[0038] In a non-limiting example embodiment, the pressure threshold is between 0.1 bar and 0.3 bar, typically 0.2 bar.

[0039] In a non-limiting example of an embodiment, the second determined period is between 1000 and 3200 milliseconds, typically 1600 milliseconds.

[0040] The process 100 also includes a step of determining 102, via the control means 9, a speed value of the vehicle 1.

[0041] When a failure of at least one of the first pressure sensor 6 or second pressure sensor 7 is detected, the process 100 includes a step of determining 103, via the control means 9, a torque value to be applied to the drive wheels 3 of the vehicle 1. The torque value to be applied is determined as a function of the speed value determined to bring the vehicle 1 to a predetermined safe speed value.

[0042] In a non-limiting example embodiment, the predetermined safety speed value is between 10 and 30 km / h, for example 17 km / h.

[0043] The torque value to be applied is determined based on a mapping of torque values ​​as a function of speed values.

[0044] The torque value to be applied to the drive wheels 3 of the vehicle 1 can, for example, be determined by the control means 9 using a map similar to that illustrated in the figure 3 .

[0045] More specifically, the figure 3 illustrates a mapping of torque values ​​as a function of speed values ​​(this mapping depends on the characteristics of the vehicle).

[0046] It should be noted that when referring to braking torque values, a minus sign (-) is written before the value. Such braking torque can be generated by the traction electric machine 2 when operating in regenerative mode, also known as regenerative braking.

[0047] When the torque value is an acceleration torque value, no sign is placed in front of the value.

[0048] For example, according to this mapping, if the determined vehicle speed value is 40km / h, the torque value to be applied to the vehicle's drive wheels 3 is -600Nm.

[0049] The process 100 further includes a step of applying 104 the determined torque value to the drive wheels 3. To do this, the control means 9 control the electric traction machine 2 so as to apply an acceleration torque or a braking torque to the drive wheels 3 and bring the vehicle 1 to a predetermined safe speed value.

[0050] The process 100 includes a step of displaying 105, on the display console 8 of vehicle 1, a stop indicator for vehicle 1. This display can be controlled by the control means 9.

[0051] The stop indicator light may be formed by the word STOP. Since vehicle 1, and in particular the acceleration of vehicle 1, no longer responds to the driver's wishes, this indicator light informs the driver of vehicle 1 that it is preferable to stop their vehicle.

[0052] The process 100 further includes a step of displaying a message on the display console 8, indicating that a fault has been detected in at least one of the first pressure sensor 6 or second pressure sensor 7 of the brake booster 4 of vehicle 1. This message informs the driver that they must take their vehicle to the service center to have the fault repaired. This display can be controlled by the control means 9.

[0053] The process 100 includes a step of controlling 107, via the control means 9, the vacuum pump 5 of the brake booster 4 according to the lowest pressure measurement among the first and second pressure measurements.

[0054] Therefore, vacuum pump 5 may provide too much vacuum. This situation is preferable in order to ensure safe braking.

[0055] The process 100 also includes a step of recording 108 a fault code reflecting that a failure of at least one of the first pressure sensor 6 or second pressure sensor 7 of the brake booster 4 of vehicle 1 has been detected. This step of recording 108 can be performed by the control means 9.

[0056] When a failure of at least one of the first pressure sensor 6 or second pressure sensor 7 has been determined, process 100 includes the steps of: Repeat 109, periodically, via the control means 9, according to the first determined period, for example of 200 milliseconds, the sub-steps of receiving 101a a first pressure measurement, receiving 101b a second pressure measurement and determining 101c a pressure deviation, then If the determined pressure deviation is less than the pressure threshold during a third predetermined period, determine 110, via the control means 9, a restoration of operation of at least one of the first pressure sensor 6 or second pressure sensor 7.

[0057] In a non-limiting example of implementation, the third predetermined period is between 1000 and 3000 milliseconds, typically 2000 milliseconds.

[0058] In this embodiment, when a restoration of operation of at least one of the first pressure sensor 6 or second pressure sensor 7 is determined, the process 100 comprises the steps, executed via the control means 9, of: Stop 111 applying the determined torque value to the drive wheels 3 by means of the electric traction machine 2, Turn off 112 the vehicle stop light 1, Turn off 113 the message reflecting that a failure of at least one of the first pressure sensor 6 or second pressure sensor 7 has been detected, and Control 114 the vacuum pump 5 of the brake booster 4 according to the pressure measurement of the first sensor 6 or the second sensor 7 preselected as the reference sensor.

[0059] Thus, when the first sensor 6 is preselected as the reference sensor, when no failure of one of the first and second pressure sensors 6, 7 is detected, the vacuum generated in the brake amplifier 4 is a function of the pressure measurements made by the first sensor 6.

[0060] Conversely, when the second sensor 7 is pre-selected as the reference sensor, when no failure of one of the first and second pressure sensors 6, 7 is detected, the vacuum generated in the brake amplifier 4 is a function of the pressure measurements taken by the second sensor 7.

[0061] In this embodiment, when a functional recovery of at least one of the first and second pressure sensors 6, 7 is determined, the method 100 includes a step 115 of recording a recovery code reflecting that a functional recovery of at least one of the first and second pressure sensors 6, 7 of the brake booster 4 of vehicle 1 has been detected. This step of recording 115 can be performed by the vehicle's control means 9.

[0062] It should be noted that a person skilled in the art is able to make different variations to the aforementioned aspects of the invention, for example by modifying the mapping or by modifying the values ​​of the first, second and / or third periods, or by modifying the value of the pressure threshold.

Claims

1. Method (100) for controlling a traction electric machine (2) of an electric or hybrid vehicle (1), said method (100) comprising, when said vehicle (1) is moving, the steps, executed by control means (9) of said vehicle (1), of: - Detecting (101) a failure of at least one first pressure sensor (6) or a second pressure sensor (7) of a brake booster (4) of said vehicle (1), - Determining (102) a speed value of said vehicle (1), - Said method (100) being characterized in that it further comprises the steps of: o When a failure of at least one of the first pressure sensor (6) or second pressure sensor (7) is detected, determining (103) a torque value to be applied to driving wheels (3) of said vehicle (1), as a function of said determined speed value, in order to bring said vehicle (1) to a predetermined safety speed value, o Applying (104) said determined torque value to said driving wheels (3) by means of said traction electric machine (2).

2. Method (100) according to claim 1, characterized in that it comprises a step, executed by the control means (9), of displaying (105), on a display console (8) of said vehicle (1), a vehicle stop warning indicator.

3. Method (100) according to any one of the preceding claims, characterized in that it comprises a step, executed by the control means (9), of displaying (106), on a display console (8) of said vehicle (1), a message reflecting that a failure of at least one of the first pressure sensor (6) or second pressure sensor (7) of the vehicle (1) has been detected.

4. Method (100) according to any one of the preceding claims, characterized in that the step of detecting (101) a failure of at least one of the first pressure sensor (6) or second pressure sensor (7) comprises the sub-steps of: - Receiving (101a) a first pressure measurement of the brake booster (4) determined by means of the first pressure sensor (6), - Receiving (101b) a second pressure measurement of the brake booster (4) determined by means of the second pressure sensor (7), - Determining (101c) a pressure deviation between the first and second pressure measurements, - Repeating (101d), periodically according to a determined first period, the sub-steps of receiving (101a) a first pressure measurement, receiving (101b) a second pressure measurement and determining (101c) a pressure deviation, - If said determined pressure deviation is greater than a pressure threshold during a predetermined second period, determining (101e) a failure of at least one of the first pressure sensor (6) or second pressure sensor (7).

5. Method (100) according to the preceding claim, characterized in that it comprises a step, executed by the control means (9), of controlling (107) a vacuum pump (5) of the brake booster (4) as a function of the lowest pressure measurement among the first and second pressure measurements.

6. Method (100) according to any one of claims 4 or 5, characterized in that when a failure of at least one of the first pressure sensor (6) or second pressure sensor (7) has been detected, it comprises the steps, executed via the control means (9), of: - Repeating (109) periodically according to the determined first period, the sub-steps of receiving (101a) a first pressure measurement, receiving (101b) a second pressure measurement and determining (101c) a pressure deviation, - If said determined pressure deviation is lower than the pressure threshold during a predetermined third period, determining (110) a restoration of operation of at least one of the first pressure sensor (6) or second pressure sensor (7).

7. Method (100) according to the preceding claim, characterized in that it comprises a step, executed by the control means (9), of stopping (111) the application of the determined torque value to the driving wheels (3) by means of the traction electric machine (2).

8. Method (100) according to any one of claims 6 or 7 characterized in that it comprises a step, executed by the control means (9), of switching off (112) the vehicle stop warning indicator (1).

9. Method (100) according to any one of claims 6 to 8, characterized in that it comprises a step, executed by the control means (9), of switching off (113) the message reflecting that a failure of at least one of the first pressure sensor (6) or second pressure sensor (7) has been detected.

10. Method (100) according to any one of claims 6 to 9, characterized in that it comprises a step, executed by the control means (9), of controlling (114) a vacuum pump (5) of the brake booster (4) as a function of a pressure measurement carried out by the first pressure sensor (6) or the second pressure sensor (7) preselected as reference sensor.