METHOD FOR CONTROLLING REGENERATE BRAKES IN A VEHICLE COMPRISING AT LEAST ONE ELECTRIC MOTOR

Abstract

One aspect of the invention relates to a method 100 for controlling regenerative braking of a motor vehicle equipped with at least one electric motor. Following the release of the vehicle's accelerator pedal, the method 100 performs a step of determining 101 a setpoint for the engine braking torque to be applied to the electric motor to achieve a predetermined vehicle deceleration value. The setpoint for the engine braking torque is a function of: the predetermined vehicle deceleration value; the vehicle's current mass; the vehicle's current speed; and the electric motor's current rotational speed. The method further comprises a step 102 of applying an engine braking torque equal to the determined setpoint for the engine braking torque. Figure 2

Description

Title of the invention: METHOD FOR CONTROLLING REGENERATIVE BRAKING OF A VEHICLE COMPRISING AT LEAST ONE ELECTRIC MOTOR

[0001] The present invention relates to the control of regenerative braking of a motor vehicle. More specifically, it relates to a method for controlling regenerative braking of a vehicle equipped with at least one electric motor, for example an electric vehicle or a hybrid vehicle.

[0002] In electric vehicles, when the foot is released from the accelerator pedal, the electric traction motor takes torque from the vehicle's wheels and transforms this mechanical torque into electrical energy which can, for example, be stored in a vehicle battery. This torque is generated by the vehicle's inertia.

[0003] The torque taken by the electric motor is a function of a predetermined deceleration level, in other words pre-recorded in a vehicle computer, or selected by the driver.

[0004] Indeed, on certain vehicles, the driver can select, by means of a thumbwheel, a first desired deceleration level, for example equal to 0.6m / s2, or a second desired deceleration level, for example equal to 1.2m / s2.

[0005] Each of the deceleration levels is associated with a fixed electric motor brake torque value which does not take into account external parameters which may influence the actual deceleration level of the vehicle.

[0006] For example, a braking method is known from document WO-A1-201587516 regenerative braking taking into account a fixed value of the vehicle's mass. This fixed value of the vehicle's mass is pre-recorded in a vehicle computer. On the other hand, if the driver selects a deceleration level of 0.6 m / s2, since the value of the electric motor braking torque associated with this deceleration level is fixed, the effective deceleration of the vehicle will be different depending on the effective mass of the vehicle. For example, when the motor vehicle is heavily loaded, the distance traveled to stop the vehicle by means of regenerative braking alone will be considerably increased. Such an increase in braking distance is likely to cause an accident.

[0007] The aim of the invention is in particular to propose a method for controlling regenerative braking of a motor vehicle equipped with at least one electric motor making it possible to apply a fixed deceleration to the vehicle.

[0008] In this context, the invention thus relates, in its broadest acceptance, to a method for controlling regenerative braking of a motor vehicle equipped with at least

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[0016] at least one electric motor, successively upon releasing the accelerator pedal of the vehicle, the method executes, via means of control of said vehicle, a step of determining an engine brake torque setpoint to be applied to the electric motor to reach a predetermined vehicle deceleration value, said engine brake torque setpoint being a function of: • Of said predetermined vehicle deceleration value; • A value of the current mass of the vehicle; • A current vehicle speed value; • A value of the current rotation speed of the electric motor. The method further comprises a step, executed by the electric motor, of applying an engine braking torque equal to the determined engine braking torque setpoint. By using the method according to the invention, if the driver selects a deceleration value equal to 0.6, then the engine braking torque applied depends on this selected deceleration, the current mass of the vehicle, the current speed of the vehicle and the current rotational speed of the electric motor. The applied torque thus makes it possible to achieve the deceleration selected by the driver, regardless of the vehicle's load level. In addition to the characteristics which have just been mentioned in the preceding paragraph, the method according to the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations. According to a non-limiting aspect of the invention, the engine brake torque setpoint is defined by the following relationship: Cmot = (Decel) * Mvhl * Vvhl / Wmot With : • Cmot = engine brake torque setpoint; • Decel = predetermined vehicle deceleration value; • Mvhl = current mass value of the vehicle; • Vvhl = current vehicle speed value; • Wmot = current rotation speed value of the electric motor. According to a non-limiting aspect of the invention, the engine brake torque setpoint is also a function of a current tilt angle of the vehicle and the acceleration of gravity. According to a non-limiting aspect of the invention, the engine brake torque setpoint is defined by the following relationship: Cmot = (Decel + g * sin (slope)) * Mvhl * Vvhl / Wmot With : g = acceleration of gravity; • “slope = current tilt angle of the vehicle.

[0017] According to a non-limiting aspect of the invention, the engine brake torque setpoint is also a function of a safety coefficient.

[0018] According to a non-limiting aspect of the invention, the engine brake torque setpoint is defined by the following relationship: Cmot = ((Decel + g * sin (slope)) * Mvhl * Vvhl / Wmot) x [3

[0019] With: [3 = safety coefficient

[0020] According to a non-limiting aspect of the invention, the safety coefficient is between 0.75 and 0.9.

[0021] According to a non-limiting aspect of the invention, the step of applying the engine braking torque is executed as soon as the depression travel of the accelerator pedal of the vehicle is less than a threshold value for triggering the engine brake.

[0022] According to a non-limiting aspect of the invention, the method comprises a step, executed by the electric motor, of stopping applying the engine braking torque, the applied engine braking torque being stopped as soon as the depressing stroke of the accelerator pedal is greater than a threshold value for stopping the engine braking.

[0023] Another aspect of the invention relates to a motor vehicle comprising at least one electric motor, the vehicle being remarkable in that it comprises control means constructed and arranged to carry out the step of determining an engine brake torque setpoint to be applied to said electric motor to achieve a predetermined deceleration value of said vehicle.

[0024] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures.

[0025] [Fig-1] illustrates, in a schematic manner, a non-limiting example of an embodiment of a motor vehicle according to the invention.

[0026] [Fig.2] illustrates, schematically, the steps of a braking control method regenerative implemented within the motor vehicle.

[0027] The figures are presented for information purposes only and in no way limit the invention.

[0028] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0029] [Fig.l] illustrates an electric motor vehicle 1 conforming to a non-limiting implementation of the invention.

[0030] The vehicle 1 comprises an electric motor 2 constructed and arranged to tow the vehicle 1 and to carry out regenerative braking enabling an electric battery 3 contained in the vehicle 1 to be electrically recharged.

[0031] The electric motor 2 is notably controlled by means of a motor control unit 4 (better known by the acronym MCU for “Motor Control Unit” in English).

[0032] The vehicle 1 also includes an ESP / ABS 5 type computer as well as a smart easement box 6, better known by the acronym BSI.

[0033] The vehicle 1 further comprises control means 7. In a non-limiting manner, the control means 7 may for example be formed by a vehicle control unit (better known by the acronym VCU for “Vehicle Control Unit” in English). These control means 7 are constructed and arranged to exchange data with different computers, including the engine control unit 4, the ESP / ABS type computer 5 as well as the intelligent control unit 6.

[0034] [Fig.2] illustrates the steps of the method 100 for controlling regenerative braking according to the invention.

[0035] Following a release of the foot from the accelerator pedal of the vehicle 1, the method 100 executes, via the control means 7 of the vehicle 1, a step of determining 101 an engine brake torque setpoint to be applied to the electric motor 2 to reach a predetermined deceleration value of the vehicle 1.

[0036] In other words, the driver presses the accelerator pedal, then when he wishes to slow down, he removes his foot from the accelerator pedal in order to engage the electric motor brake. This action of removing the foot from the accelerator pedal is called “releasing the foot from the accelerator pedal”. This action of releasing the foot is determined by a sensor measuring the travel of the accelerator pedal and then transmitted to the control means 7.

[0037] According to a first non-limiting embodiment, the predetermined deceleration value of the vehicle can be unique and recorded in the control means 7.

[0038] According to a second non-limiting embodiment, the predetermined deceleration value of the vehicle may have been selected by the driver by means of a thumbwheel located on the dashboard of the vehicle 1. He may for example select a deceleration value between three values, namely 0.6m / s2, 1.2m / s2 and 1.8m / s2. This deceleration value selected by the driver is transmitted to the control means 7.

[0039] This deceleration value selected by the driver of the vehicle 1 can be transmitted instantly to the control means 7 as soon as the driver modifies the deceleration value by means of the wheel.

[0040] The engine brake torque setpoint to be applied to the electric motor 2 is thus a function of the predetermined deceleration value of the vehicle, whether it is fixed and recorded in the control means 7 or selected by the driver and then recorded in the control means 7.

[0041] The engine brake torque setpoint to be applied to the electric motor 2 is also a function of a value of the current mass of the vehicle 1.

[0042] Indeed, the mass of the vehicle 1 can be modified according to the number of passengers and / or the loading of the trunk of the vehicle 1. This current mass of the vehicle can be determined in a non-limiting manner based on road laws or based on measurements taken by sensors detecting the presence of passengers and / or luggage in the trunk of the vehicle. Thus, based on these road laws and / or these measurements, the intelligent service box 6 can, for example, estimate the current mass of the vehicle 1 and transmit it to the control means 7.

[0043] This value of the current mass of the vehicle 1 can be determined periodically according to a first period between, for example, 1 ms and 10 ms.

[0044] The engine brake torque setpoint to be applied to the electric motor 2 is furthermore a function of a current speed value of the vehicle 1.

[0045] This current speed value of the vehicle 1 can be estimated by the ESP / ABS type computer 5, then transmitted to the control means 7.

[0046] According to a non-limiting embodiment, the current speed value of the vehicle 1 is transmitted to the control means 7 continuously.

[0047] The engine brake torque setpoint to be applied to the electric motor 2 is furthermore a function of a current rotation speed value of the electric motor 2.

[0048] This current rotation speed value of the electric motor 2 can for example be estimated by the motor control unit 4 as a function of a measurement carried out by a rotation sensor installed on the rotor of the electric motor 2, then transmitted to the control means 7.

[0049] According to a non-limiting embodiment, the current speed value of the electric motor 2 is transmitted to the control means 7 continuously.

[0050] According to a non-limiting embodiment, the engine brake torque setpoint to be applied to the electric motor 2 is also a function of a current tilt angle of the vehicle 1 and the acceleration of gravity.

[0051] This value of the current inclination angle of the vehicle 1 can for example be measured by a slope sensor that the vehicle 1 includes, then transmitted to the control means 7.

[0052] According to a non-limiting embodiment, the value of the current tilt angle of the vehicle 1 is transmitted to the control means 7 continuously.

[0053] According to a non-limiting embodiment, the engine brake torque setpoint to be applied to the electric motor 2 is also a function of a safety coefficient. This safety coefficient is predetermined and is, for example, recorded in the control means 7. This safety coefficient is for example between 0.75 and 0.9.

[0054] According to this non-limiting embodiment, the engine brake torque setpoint to be applied to the electric motor 2 is defined by the following function: Cmot = ((Decel + g * sin (cipente)) * Mvhl * Vvhl / Wmot) x [3

[0055] With: • Cmot = engine brake torque setpoint to be applied to electric motor 2 to achieve a predetermined deceleration value of vehicle 1; • Decel = predetermined deceleration value of the vehicle; • Mvhl = current mass value of the vehicle; • Vvhl = current vehicle speed value; • Wmot = current rotation speed value of the electric motor; • g = acceleration of gravity = 9.81 ms-2; • “slope = current tilt angle of the vehicle; • [3 = safety coefficient.

[0056] The method 100 further comprises a step, executed by the electric motor 2, of applying 102 an engine braking torque equal to the determined engine braking torque setpoint. To this end, the engine braking torque setpoint determined by the control means 7 is transmitted to the engine control unit 4 which controls the electric motor 2.

[0057] According to a non-limiting embodiment, the step of applying 102 the engine brake torque is executed as soon as the depression travel of the accelerator pedal is less than a threshold value for triggering the engine brake. For example, this trigger threshold value may be 5%. Thus, the electric motor 2 applies an engine brake torque equal to the engine brake torque setpoint determined as soon as the depression travel of the accelerator pedal is less than 5%, for example 4% or 3%.

[0058] This depression travel can be measured by a depression travel sensor of the accelerator pedal of the vehicle 1, then transmitted to the engine control unit 4 which then controls the electric motor 2 so that the latter applies the engine braking torque.

[0059] Furthermore, the method 100 comprises a step, executed by the electric motor 2, of stopping 103 the application of the engine brake torque, the applied engine brake torque being stopped as soon as the depression travel of the accelerator pedal is greater than a threshold value for stopping the engine brake. This depression travel can be measured by the vehicle's accelerator pedal travel sensor, then transmitted to the engine control unit 4 which then controls the electric motor 2 so that the latter no longer draws torque.

[0060] For example, this stopping threshold value may be 10%. Thus, the electric motor 2 stops applying an engine braking torque equal to the determined engine braking torque setpoint as soon as the accelerator pedal is depressed more than 10%, for example 11% of the depression travel.

[0061] Furthermore, the applied engine braking torque is stopped as soon as the speed of vehicle 1 is zero.

Claims

Claims

1. Method (100) for controlling regenerative braking of a motor vehicle (1) equipped with at least one electric motor (2), following a release of the foot from the accelerator pedal of said vehicle (1), the method (100) executes, via control means (7) of said vehicle (1), a step of determining (101) an engine brake torque setpoint to be applied to said electric motor (2) to achieve a predetermined deceleration value of said vehicle (1), said method (100) being characterized in that said engine brake torque setpoint is a function of: - said predetermined deceleration value of said vehicle (1); - a value of the current mass of said vehicle (1); - a value of the current speed of said vehicle (1); - a value of the current rotational speed of said electric motor (2);- Said method (100) further comprising a step, executed by said electric motor (2), of applying (102) an engine braking torque equal to said determined engine braking torque setpoint.;

2. Method (100) according to the preceding claim, characterized in that the engine brake torque setpoint is defined by the following relationship: Cmot = (Decel) * Mvhl * Vvhl / Wmot - With: • Cmot = engine brake torque setpoint; - Decel = predetermined deceleration value of the vehicle (1); - Mvhl = current mass value of the vehicle (1); - Vvhl = current speed value of the vehicle (1); - Wmot = current rotation speed value of the electric motor (2).

3. Method (100) according to any one of the preceding claims, characterized in that the engine brake torque setpoint is also a function of a current tilt angle of the vehicle (1) and the acceleration of gravity.

4. Method (100) according to the preceding claim, characterized in that the engine brake torque setpoint is defined by the following relationship: Cmot = (Decel + g * sin (slope)) * Mvhl * Vvhl / Wmot - With: - g = acceleration of gravity; - "slope = current inclination angle of the vehicle (1).

5. Method (100) according to any one of the preceding claims, characterized in that the engine brake torque setpoint is also a function of a safety coefficient.

6. Method (100) according to the preceding claim, characterized in that the engine brake torque setpoint is defined by the following relationship: Cmot = ((Decel + g * sin (slope)) * Mvhl * Vvhl / Wmot) x [3 - With: [3 = safety coefficient

7. Method (100) according to any one of claims 5 or 6, characterized in that the safety coefficient is between 0.75 and 0.

9.

8. Method (100) according to any one of the preceding claims, characterized in that the step of applying (102) the engine braking torque is executed as soon as the depression travel of the accelerator pedal of the vehicle (1) is less than a threshold value for triggering the engine brake.

9. Method (100) according to any one of the preceding claims, characterized in that it comprises a step, executed by the electric motor (2), of stopping (103) applying the engine braking torque, the applied engine braking torque being stopped as soon as the depressing stroke of the accelerator pedal is greater than a threshold value for stopping the engine braking.

10. Motor vehicle (1) comprising at least one electric motor (2), said vehicle (1) being characterized in that it comprises control means (7) constructed and arranged to carry out the step of determining (101) an engine brake torque setpoint to be applied to said electric motor (2) to achieve a predetermined deceleration value of said vehicle (1).

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