Method for controlling braking and acceleration in a vehicle having an electric motor

Abstract

The invention relates to a method implemented in a motor vehicle (1) comprising an electric motor (11) that is capable of operating in traction mode (101A) or in generator mode (101B), and is capable of switching between: - a conventional mode, in which a complete stop of the vehicle is initiated by means of the brake pedal (12B); and - a "one-pedal" mode, in which a complete stop of the vehicle is initiated by means of the acceleration pedal (12A); the method comprising steps of receiving a total braking torque request and determining a regenerative braking torque setpoint. When a difference between an actual regenerative braking torque and the setpoint exceeds a predetermined threshold, the vehicle is switched from the one-pedal mode to the conventional mode and a visual and / or auditory alert signal is generated.

Description

DESCRIPTION TITLE: Method for controlling braking and acceleration in a vehicle equipped with an electric motor. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of electric or hybrid vehicles, more particularly vehicles in which the electric motor can operate alternately in generator mode and in traction motor mode.

[0002] The invention relates more particularly to a method for controlling braking and acceleration in such a vehicle. As described below, the invention relates even more particularly to a method for monitoring braking in a vehicle equipped with an electric motor. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Prior art has shown examples of motor vehicles with electric or hybrid engines, in which the engine system includes an electric traction motor that can operate respectively: - in traction mode, in which the motor uses electrical energy supplied by an electrochemical battery to generate a rotational movement capable of driving the vehicle's drive wheels; and - in a generator mode, in which the engine uses the mechanical energy supplied by the rotational movement of at least one wheel of the vehicle, to generate electrical energy suitable for recharging said battery.

[0004] Regenerative braking is commonly used to describe braking that uses the electric motor in generator mode to recover at least some of the dissipated kinetic energy.

[0005] Regenerative braking, in addition to the obvious advantage in terms of vehicle range, helps to limit the wear and tear of an additional braking system based on a friction phenomenon.

[0006] Furthermore, it is known that such a vehicle offers braking and acceleration control using only the accelerator pedal. To achieve this, the vehicle is switched to a so-called "single-pedal" mode, in which: - Pressing the accelerator pedal causes an increase in the torque (or power) transmitted to the wheels by the traction motor, to increase the vehicle's speed; and - releasing the accelerator pedal causes a reduction in the torque (or power) transmitted to the wheels by the engine in traction mode, then braking of the vehicle which is achieved by regenerative braking and / or with the help of the additional braking system based on a friction phenomenon, a total release of the accelerator pedal resulting in a complete stop of the vehicle.

[0007] The single-pedal mode has the advantage of maximizing the use of regenerative braking, with all the benefits associated with it.

[0008] One objective of the present invention is to improve the safety of this single-pedal operating mode. SUMMARY OF THE INVENTION

[0009] This objective is achieved with a process implemented in at least one computer of a motor vehicle, the vehicle comprising: - a motorization system, comprising an electric motor capable of operating respectively in a traction mode, and in a generator mode in which it provides the vehicle with a so-called regenerative braking torque; - a friction braking system; - an accelerator pedal, forming a human-machine interface to control, at least, the application of a traction torque by the motorization system; - a brake pedal, capable of forming a human-machine interface to control vehicle braking using at least the friction braking system; and - a control unit, configured to control the operation of the vehicle alternately in a classic mode, in which a complete stop of the vehicle is commanded using the brake pedal, and a so-called "single pedal" mode, in which a complete stop of the vehicle is commanded using the accelerator pedal, the accelerator pedal also forming a human-machine interface to control the braking of the vehicle using the friction braking system and / or the electric motor in generator mode.

[0010] The method according to the invention comprises the following steps, implemented in single-pedal mode: - receipt of a request for total braking torque; - determination of a regenerative braking torque setpoint, corresponding to the contribution of the electric motor to the total braking torque, and sending said setpoint to an electric motor control module; - determination of an actual regenerative braking torque produced by the electric motor, and comparison with the regenerative braking torque setpoint; - when the difference between the actual torque and the setpoint exceeds a predetermined threshold, switching from the vehicle's operating mode to the classic mode accompanied by the generation of a visual and / or audible warning signal for the vehicle driver.

[0011] In traction mode, the electric motor is configured to provide driving torque to at least one wheel of the vehicle. As described in the introduction, it then uses electrical power supplied by an electrochemical battery to generate a rotational movement that drives the vehicle's drive wheels.

[0012] In generator mode, the electric motor is configured to receive torque from at least one of its wheels, which is equivalent to providing braking torque known as regenerative braking torque. As described in the introduction, the electric motor then uses the mechanical energy supplied by at least one wheel of the vehicle to generate electrical energy capable of recharging the battery.

[0013] A friction braking system is designed to slow a vehicle by applying friction to a mechanical component attached to at least one wheel. Examples include disc brakes, which have brake pads that grip a rotating disc fixed to the wheel, creating friction that slows the disc's rotation and thus the wheel's speed. Alternatively, drum brakes can be used, for example, which have brake shoes inside a drum attached to the wheel. When the brake shoes are pressed against the inside of the drum, they create friction that slows the drum's rotation and thus the wheel's speed.

[0014] Regardless of whether the vehicle is in classic mode or single-pedal mode, the accelerator pedal allows traction torque to be applied to at least one wheel of the vehicle, this torque being supplied at least in part by the electric motor in traction mode.

[0015] Regardless of whether the vehicle is in classic mode or single-pedal mode, the brake pedal allows braking torque to be applied to at least one wheel of the vehicle, using at least the friction braking system.

[0016] Advantageously, the brake pedal is configured to generate a total braking torque request that is a function of the degree to which the driver depresses the pedal.

[0017] Depending on the circumstances, the total braking torque will be provided by the friction braking system and / or by regenerative braking.

[0018] The control unit includes one or more computers. It allows the operation of the vehicle and its powertrain to be controlled, alternately in conventional mode and in single-pedal mode.

[0019] As described in the introduction, in single-pedal mode: - Pressing the accelerator pedal increases the torque (or power) transmitted to the wheels by the traction motor to increase the vehicle's speed, while: - releasing the accelerator pedal causes a reduction in the torque (or power) transmitted to the wheels by the engine, followed by braking of the vehicle, the braking being carried out by regenerative braking and / or using the friction braking system.

[0020] In addition, in single-pedal mode, a complete release of the accelerator pedal brings the vehicle to a complete stop.

[0021] In conventional mode, releasing the accelerator pedal may also trigger light braking, achieved through regenerative braking and / or the friction braking system. However, such braking remains very limited and will never bring the vehicle to a complete stop without further application of the brake pedal.

[0022] The invention is implemented using at least one computer, and when the vehicle is in single-pedal operating mode.

[0023] In the first step, a request for total braking torque is received. This request is determined from information relating to the position of the accelerator pedal. It corresponds to a request from the user, who releases the accelerator pedal to react to a driving situation in which braking is necessary.

[0024] In a second step, the respective contributions of regenerative braking and friction braking are determined. The regenerative braking contribution forms a regenerative braking torque command, which is sent to an electric motor control module. In practice, the friction braking contribution forms a friction braking torque command, which is sent to a control module for the friction braking system.

[0025] In a third step, the actual regenerative braking torque produced by the electric motor is determined. In other words, the amount of regenerative braking actually achieved is determined. This actual torque is then compared with the target regenerative braking torque.

[0026] When the difference between the actual torque and the setpoint exceeds a predetermined threshold, it means the electric motor is not providing the required braking torque, so the total braking torque actually achieved is less than the braking torque requested by the driver. This is a dangerous situation, as the vehicle is not braking as effectively as the driver intended. Here, a difference refers to an absolute value.

[0027] Thanks to the invention, insufficient braking is detected, and the vehicle's operating mode is then switched from single-pedal mode to conventional mode. Thus, the vehicle automatically returns to an operating mode in which most of the braking is achieved using the brake pedal. Furthermore, an alert is generated for the driver, explicitly informing them that single-pedal mode is no longer active and prompting them to apply the brake pedal.

[0028] The invention is implemented in single-pedal mode because this mode offers less controllability than the conventional mode, particularly in terms of braking. Specifically, in single-pedal mode, the driver will be less likely to instinctively use the brake pedal even if they detect insufficient braking.

[0029] Preferably, the actual regenerative braking torque is determined by means of a measurement of an electrical quantity in the electric motor.

[0030] In addition or as an alternative, the actual regenerative braking torque can be determined by means of an actual deceleration measurement of the vehicle.

[0031] The regenerative braking torque setpoint is advantageously the maximum value accessible given the remaining charge capacity of a battery charged by the electric motor in generator mode.

[0032] Preferably, the total braking torque request is a function of a variation in the position of the accelerator pedal.

[0033] The method according to the invention is advantageously implemented when it is detected that the position of the accelerator pedal has exceeded a neutral point position in the direction of a release of pressure on the pedal, the neutral point position being a function of a current value of vehicle speed.

[0034] The method according to the invention can be implemented when it is detected that the position of the accelerator pedal has exceeded said neutral point position, and only if a current value of vehicle speed exceeds a predetermined speed threshold.

[0035] In addition or alternatively, the method according to the invention can be implemented when it is detected that the position of the accelerator pedal has exceeded said neutral point position, and only if the regenerative braking torque setpoint exceeds a predetermined torque threshold.

[0036] The predetermined threshold of difference between the actual torque and the setpoint can take a value that depends on a current value of vehicle speed.

[0037] The invention also covers an assembly of at least one computer, intended to be installed in a motor vehicle, the motor vehicle further comprising: - a motorization system, comprising an electric motor capable of operating respectively in a traction mode, and in a generator mode in which it provides a so-called regenerative braking torque; - a friction braking system; - an accelerator pedal, forming a human-machine interface to control, at least, the application of a traction torque by the motorization system; - a brake pedal, forming a human-machine interface to control vehicle braking using the friction braking system; the set of at least one computer being configured; - to control vehicle operation alternately in a conventional mode, in which a complete stop of the vehicle is commanded using the brake pedal, and a so-called "single-pedal" mode, in which a complete stop of the vehicle is commanded using the accelerator pedal, the accelerator pedal also forming a human-machine interface to control vehicle braking using the friction braking system and / or the electric motor in generator mode; and - to implement the steps of the process according to the invention.

[0038] The invention also covers a motor vehicle as described above. BRIEF DESCRIPTION OF FIGURES

[0039] The figures are presented for illustrative purposes only and are in no way limiting to the invention. Figure 1 schematically illustrates a motor vehicle in which the method according to the invention is implemented; Figure 2 schematically illustrates the steps of one embodiment of a process according to the invention; and Figure 3 schematically illustrates computers in the vehicle of Figure 1, implementing a method according to the invention. DETAILED DESCRIPTION

[0040] First, with reference to figure 1, we describe a motor vehicle 1 in which the process according to the invention is implemented.

[0041] Vehicle 1 is an electric or hybrid vehicle, including in particular: - an electric motor 11; - an accelerator pedal 12A and a brake pedal 12B; - a friction braking system 13; - a set of 14 with at least one computer.

[0042] The electric motor 11 is a traction motor, capable of driving the drive wheels of vehicle 1 in rotation.

[0043] According to the invention, the electric motor 11 can operate: - either in a 101 A traction mode, in which it transforms electrical energy from the battery into mechanical energy, thus rotating the vehicle's drive wheels; - either in a generator mode 101 B, in which it transforms mechanical energy supplied by the rotation of the wheels into electrical energy to recharge the battery.

[0044] As explained in the introduction, the absorption of kinetic energy carried out in generator mode results in so-called regenerative braking of vehicle 1.

[0045] The electric motor 11 belongs to a motorization system, which also includes elements (not specifically shown) such as: - a rechargeable battery, which stores the energy needed to power the electric motor as well as auxiliary systems in the vehicle; - power electronics, including an inverter to transform a direct current supplied by the battery into an alternating current suitable for the electric motor 11, and vice versa; - at least one electric motor control module, to regulate the bidirectional power supply between the battery and the motor, and ensure efficient and secure energy distribution.

[0046] The accelerator pedal 12A designates a pedal, located at the driver's feet, and forming a human-machine interface to control, at least, a variation of the traction torque (or power) which is applied to the wheels by the electric motor 11. The more the accelerator pedal 12A is pressed down, the higher the traction torque, and vice versa.

[0047] The brake pedal 12B refers to a pedal located at the driver's feet near the accelerator pedal 12A, which forms a human-machine interface for controlling the vehicle's braking force. The more the brake pedal 12B is pressed, the greater the braking force applied, and vice versa.

[0048] The brake pedal 12B is configured to activate the friction braking system 13. The friction braking system 13 uses mechanical friction to brake the vehicle 1. It consists, for example, of disc brakes or hydraulic brakes as described in the introduction. In both cases, the friction braking system 13 includes a hydraulic circuit whose pressure is a function of the degree to which the brake pedal 12B is depressed.

[0049] Vehicle 1, and in particular its motorization system, is capable of switching from a classic operating mode to a single-pedal mode, and vice versa.

[0050] As described in the description of the invention, in the conventional mode, vehicle braking is primarily controlled by the brake pedal 12B, while vehicle acceleration is controlled by the accelerator pedal 12A. In some cases, releasing the accelerator pedal may initiate slight braking. In any event, bringing the vehicle to a complete stop requires pressing the brake pedal 12B.

[0051] As described in the description of the invention, in single-pedal mode, braking and acceleration of the vehicle are controlled by the accelerator pedal 12A alone, with complete release of the accelerator pedal 12A bringing the vehicle to a complete stop. When the driver presses the accelerator pedal 12A, the vehicle accelerates or maintains its speed, driven by the electric motor 11 in traction mode. When the driver releases the accelerator pedal 12A, the vehicle decelerates by reducing the engine speed of the electric motor 11 in traction mode, until the pedal 12A reaches a position called the neutral position. When this neutral position is exceeded in the direction of releasing the accelerator pedal, a braking torque is applied to the vehicle 1, driven by the electric motor 11 in generator mode and / or the friction braking system 13.Although it is theoretically possible to use the brake pedal 12B for braking, the driver does not use it since he knows that in single pedal mode braking is controlled rather by lifting the accelerator pedal 12A.

[0052] The neutral position is an intermediate position of the accelerator pedal 12A along its travel between a fully depressed position and a fully lifted position when no pressure is applied. The neutral position corresponds to the position of the accelerator pedal 12A when there is no traction torque applied by the electric motor 11 to the wheels of the vehicle 1.

[0053] The neutral position is an intermediate position between the maximum depressed position, corresponding to the maximum tractive torque that the electric motor 11 can provide, and the fully released position of the accelerator pedal, associated with maximum braking torque. The maximum braking torque is calibrated to bring the vehicle 1 to a complete stop. The maximum braking torque also depends on a calibration that may prioritize, for example, a minimum braking distance or maximum user comfort. Consequently, the neutral position is not a fixed position along the travel of the accelerator pedal 12A. It depends, in particular, on a current vehicle speed (possibly with filtering to prevent jolts during sudden speed changes).When vehicle speed and engine speed are directly related, the neutral point position can be defined from a current engine speed value.

[0054] The assembly 14, comprising at least one control unit, is configured specifically to control the vehicle's operation alternately in conventional mode and in "one-pedal" mode. Thus, the assembly 14, comprising at least one control unit, forms a unit for controlling the vehicle's operating mode in either conventional or one-pedal mode.

[0055] According to the invention, the assembly 14 of at least one computer is further configured to implement the steps of the method as described below, with reference to Figure 2. This method is implemented when the vehicle, as described with reference to Figure 1, is in single-pedal operating mode.

[0056] The process involves the following steps:

[0057] Step 201: Receiving a request for total braking torque, noted here as R_Ctot.

[0058] In practice, the R_Ctot query is generated in a prior step, not shown, from information relating to a position or a change in position of the accelerator pedal 12A, between the neutral point position as described above and the fully raised position of the accelerator pedal 12A. The R_Ctot query corresponds to the total braking torque required by the driver via the accelerator pedal 12A, in reaction to a driving situation requiring braking.

[0059] Step 202: Using the R_Ctot query, determine a regenerative braking torque setpoint, denoted here as C_Creg. The C_Creg setpoint is the required contribution to regenerative braking (using the electric motor 11) to obtain the total braking torque as required by the R_Ctot query.

[0060] Preferably, the calculation of the C_Creg setpoint takes into account a current value of the remaining charge capacity of the battery.

[0061] Preferably, the C_Creg setpoint is calculated to correspond to the maximum achievable contribution of regenerative braking, given the remaining battery charge capacity. In other words, the regenerative braking contribution is set to the maximum attainable. This maximum is limited by the battery's remaining charge capacity, since regenerative braking requires the ability to transfer the energy absorbed from the wheels (after converting this mechanical energy into electrical energy) back to the battery. The contribution required from the friction braking system then corresponds to the difference between the total braking torque and the contribution required from regenerative braking. It is therefore understandable that in some cases, the contribution required from the friction braking system is zero.

[0062] Step 203: sending said instruction C_Creg to an electric motor control module, for regenerative braking to be carried out according to said torque instruction.

[0063] Step 204: During braking, the actual regenerative braking torque value, denoted M_Creg, is determined. This corresponds to the regenerative braking torque actually produced by the electric motor 11 in generator mode. In practice, this step 204 constitutes an indirect measurement of the regenerative braking torque M_Creg produced by the electric motor in generator mode. Indeed, the regenerative braking torque actually produced by the electric motor 11 in generator mode may differ from the regenerative braking torque setpoint received by said electric motor 11 in generator mode.

[0064] In a preferred embodiment, the actual torque M_Creg is determined by means of a measurement of an electrical quantity at the level of the electric motor 11. In practice, we measure in particular the alternating current which flows in each of the phases of the motor 11, the phases here designating the different coils or circuits of the motor 11 which carry out a conversion between an electrical energy at the input or output of the motor (depending on whether it is in traction mode or in generator mode) and a magnetic field associated with the rotation of the rotor (in traction mode the electrical energy produces a magnetic field which drives the rotor in rotation, while in generator mode the rotation of the rotor generates a magnetic field which creates electrical energy).Preferably, an estimate of the actual torque M_Creg is made from a mapped model which is based on the motor speed, the alternating current flowing in each of the phases of the motor 11 (preferably three phases), and the phasing of this current with respect to the angular position of the motor.

[0065] This determination of the actual torque M_Creg is advantageous in that it is direct, and does not require taking into consideration parameters external to the engine 11 such as the aerodynamics of the vehicle, the mass of the vehicle, a coefficient of friction between the tires and the road which depends in particular on the condition of the tires, etc.

[0066] In addition or alternatively, the actual torque M_Creg is determined by means of an actual deceleration measurement of the vehicle 1. In other words, by measuring a deceleration of the vehicle, one can indirectly measure the good contribution or not of the regenerative braking.

[0067] Advantageously, the actual torque M_Creg is determined by means of a measurement of an electrical quantity at the electric motor 11, and the value obtained is confirmed or refuted by means of a determination of the actual torque M_Creg by means of a measurement of actual deceleration of the vehicle 1.

[0068] In the absence of any failure of the electric motor 1, its control module, and the associated power electronics, the value of the actual torque M_Creg is equal, or substantially equal, to the regenerative braking torque setpoint C_Creg.

[0069] However, it can happen that the electric motor 1, the control module, or the associated power electronics experiences a technical failure preventing the full required regenerative braking torque from being achieved. In this case, the actual torque value M_Creg is less than the regenerative braking torque setpoint C_Creg.

[0070] This situation is all the more dangerous because the driver may not be able to detect insufficient braking. This is particularly true when part of the braking is achieved through the friction braking system, but only the regenerative braking contribution is lacking. In this case, the driver may not realize that the braking is insufficient. Yet, the braking distance will be much greater than expected, which poses a clear safety problem. This is also the case when only part of the required contribution from regenerative braking is missing.

[0071] In step 205, the actual torque value M_Creg is compared with the regenerative braking torque setpoint C_Creg. In other words, a difference AC is calculated between these two values.

[0072] The AC deviation is compared to a predetermined torque threshold Cs. This threshold Cs is calibrated beforehand, specifically to distinguish a deviation that could pose a danger during braking from a deviation simply related to measurement uncertainties.

[0073] Step 206: When the AC deviation exceeds the torque threshold Cs, vehicle 1 is switched from single pedal mode to classic mode.

[0074] This step 206 is accompanied by the generation of a visual (e.g., a warning light illuminating on the instrument panel or other human-machine interface in the passenger compartment) and / or audible (e.g., an alarm-type sound or a voice message) alert signal for the vehicle driver. This alert signal draws the driver's attention to the need to use the brake pedal 12B to obtain the desired braking torque. This alert is particularly relevant because the driver may have become unaccustomed to using the brake pedal 12B after prolonged use of the single-pedal mode.

[0075] The invention thus makes it possible to automatically ensure the proper functioning of regenerative braking in a single-pedal operating mode. When insufficient regenerative braking is detected in single-pedal mode, the vehicle automatically switches to conventional mode and the driver is alerted to the need to also use the brake pedal.

[0076] In other words, one objective of the invention is to detect when the regenerative braking torque from the electric motor 11 is less than that requested by the driver after the distribution between regenerative braking and friction braking (using a friction braking system preferably comprising hydraulic brakes). The aim is to detect a failure of the electric motor and not of the friction braking system.

[0077] Put another way, the invention proposes the creation of a diagnostic function, preferably implemented in a "safe layer" section of a torque supervisor control unit, which compares the regenerative braking torque setpoint C_Creg with the actual torque value M_Creg produced by the electric motor 11. If the torque difference AC exceeds a threshold Cs defined as potentially dangerous and leading to insufficient deceleration, then the diagnostic function is lifted. When the diagnostic function is lifted, the "one-pedal" mode is disabled. Advantageously, a control unit managing the friction braking system is informed that the electric motor 11 can no longer perform regenerative braking. The driver is notified of the loss of the "one-pedal" mode (for example, by a display on the instrument panel and an audible "beep") and that they must use their brake pedal 12B.The deceleration is then entirely done by the friction braking system.

[0078] Switching to classic mode, and therefore stopping (or simply reducing) regenerative braking controlled by the accelerator pedal, can directly alert the driver to the need to use the brake pedal instead. However, according to the invention and for maximum safety, an alert is generated to prompt the driver to use the brake pedal 12B. Such an alert will minimize the driver's reaction time to begin using the brake pedal 12B.

[0079] The torque threshold Cs can be a constant value, which does not depend on the current conditions of use of the vehicle.

[0080] Alternatively, and advantageously, the torque threshold Cs varies with a current value of vehicle travel speed 1.

[0081] Indeed, when vehicle 1 is moving at high speed, a slight release of the accelerator pedal 12A beyond the neutral position results in a demand for a high total braking torque, since the vehicle must stop when the accelerator pedal 12A is fully released. Conversely, for the same reason, when vehicle 1 is moving at low speed, the same release of the accelerator pedal 12A beyond the neutral position results in a demand for a reduced total braking torque. It is therefore advantageous for the torque threshold Cs to decrease with the vehicle's current speed. This ensures effective fault detection even at low speeds (thanks to a low Cs value at low speeds), while avoiding false alarms at high speeds (thanks to a high Cs value at high speeds).

[0082] The invention has the advantage of being particularly robust, since it offers an observation of the actual behavior of the electric motor in generator mode, to diagnose a malfunction of the regenerative braking.

[0083] In the prior art, diagnostics are based simply on an analysis of the consistency of the data supplied as input to an electric motor control module. However, inventors realized that these diagnostics were sometimes insufficient, particularly when the level of regenerative braking required is high.

[0084] It is understood that the invention is particularly relevant, in combination with the characteristic that the regenerative braking torque setpoint is the maximum value accessible given a remaining battery charge capacity.

[0085] Advantageously, the method according to the invention is only implemented if the vehicle's current speed exceeds a predetermined speed threshold. This speed threshold is, for example, between 80 km / h and 120 km / h. Indeed, the higher the vehicle's speed, the greater the total braking torque that may be required, and therefore the greater the regenerative braking torque that may be required, and the greater the safety risk associated with a malfunction of the regenerative braking system.

[0086] In addition or alternatively, it can be provided that the process according to the invention is implemented in its entirety only if the regenerative braking torque setpoint C_Creg exceeds a predetermined torque threshold.

[0087] In this case, the process includes, after step 202, a comparison step between the regenerative braking torque setpoint C_Creg and the predetermined torque threshold, denoted here as Clim. If C_Creg <Clim, les étapes 203 et suivantes ne sont pas mises en œuvre. Sinon, les étapes 203 et suivantes sont mises en œuvre.

[0088] The method according to the invention is all the more relevant when the calibration of the "single pedal" mode provides for a non-linear variation of the total braking torque request, depending on the position of the accelerator pedal 12A from the neutral point position to the fully released position, with portions of the accelerator pedal stroke associated with a strong gradient of total braking torque required.

[0089] Figure 3 schematically illustrates an example of an assembly 14 of at least one computer, configured to implement a method according to the invention.

[0090] A first computer 31 of the assembly 14 is dedicated to controlling the braking using the friction braking system 13, here a hydraulic braking system.

[0091] A second computer 32 of assembly 14 is dedicated to controlling the electric motor 11.

[0092] A third computer 33 is dedicated to controlling the drive of vehicle 1.

[0093] Within the third calculator 33, we find: - a 33A module dedicated to determining the remaining charge capacity of the battery; - a 33B module for calculating torque setpoints; and - a 33C module for diagnosing a failure of the regenerative braking system.

[0094] Module 33A is connected to a battery control module (not shown) and receives information about the remaining battery charge capacity, denoted here as Capa. It sends this Capa information to the second control unit 32.

[0095] Module 33B receives information relating to a position of the accelerator pedal, and deduces from this the request for total braking torque R_Ctot.

[0096] The request for total braking torque R_Ctot is sent to the first computer 31 (step 201), here with the remaining battery charge capacity information.

[0097] The first control unit 31 manages the distribution of the total braking torque R_Ctot between regenerative and hydraulic braking (step 202). The contribution of hydraulic braking corresponds to a hydraulic braking setpoint, not shown, processed by the first control unit 31 itself. The contribution of regenerative braking corresponds to the regenerative braking torque setpoint C_Creg, which is transmitted to the third control unit 33.

[0098] Within the third control unit, C_Creg is used by the torque setpoint calculation module 33B, which transmits said setpoint C_Creg to the second control unit 32 (step 203), after possible consolidation (C_Creg'). Consolidation aims in particular to take into account a higher priority braking setpoint, for example, from an ABS anti-lock braking system, or to consider feedback relating to a fault that could limit the actual applied braking torque.

[0099] The second computer 32 then controls the electric motor 11 (including here its power electronics) to perform regenerative braking in accordance with the instruction C_Creg.

[0100] Next, the second computer 32 receives a measurement of an electrical quantity, representative of a braking torque applied by the electric motor 11 in generator mode. In practice, this involves measuring the alternating current flowing through each phase of the motor 11, as described above.

[0101] The second calculator 32 deduces the value of the actual regenerative braking torque M_Creg, actually produced by the electric motor 11 in generator mode (step 204).

[0102] M_Creg is received by the diagnostic module 33C for comparison with the setpoint C_Creg (step 205). When the AC difference between C_Creg and M_Creg exceeds a predetermined threshold, a fault diagnosis is triggered, which leads to switching the vehicle from single-pedal mode to conventional mode (step 206).

[0103] The distribution of the different steps within the computers is provided for illustrative purposes only and is not exhaustive. Similarly, steps performed in Figure 3 in separate computers may, alternatively, be performed in the same computer. Throughout this text, the term "module" may refer to a standalone computer dedicated to a function, or to a storage space dedicated to that function within a shared computer.

[0104] The invention is not limited to the examples described above, and covers embodiments combining one or more of the different variants listed above.

[0105] The invention also covers an assembly 14 of at least one computer as described with reference to the figures, and configured to implement a method according to the invention. The invention also covers a vehicle 1 as described with reference to the figures, and equipped with such an assembly 14 of at least one computer.

Claims

DEMANDS

1. A method implemented in at least one computer (14) of a motor vehicle (1), the vehicle comprising: - a motorization system, comprising an electric motor (11) capable of operating respectively in a traction mode (101 A), and in a generator mode (101 B) in which it provides a so-called regenerative braking torque; - a friction braking system (13); - an accelerator pedal (12A), forming a human-machine interface to control, at least, the application of a traction torque by the motorization system; - a brake pedal (12B), capable of forming a human-machine interface for controlling vehicle braking using at least the friction braking system (13); and - a control unit, configured to control the operation of the vehicle (1) alternately in a conventional mode, in which a complete stop of the vehicle is commanded using the brake pedal (12B), and a so-called "single-pedal" mode, in which a complete stop of the vehicle is commanded using the accelerator pedal (12A), the accelerator pedal (12A) also forming a human-machine interface to control vehicle braking using the friction braking system (13) and / or the electric motor in generator mode (101 B); the method comprising the following steps, implemented in the single-pedal mode: - receipt (201) of a request for total braking torque (R_Ctot); - determination (202) of a regenerative braking torque setpoint (C_Creg), corresponding to the contribution of the electric motor (11) to the total braking torque, and sending (203) of said setpoint (C_Creg) to an electric motor control module (32); - determination (204) of an actual regenerative braking torque (M_Creg) actually achieved by the electric motor, and comparison with the regenerative braking torque setpoint (C_Creg); - when the difference (AC) between the actual torque (M_Creg) and the setpoint (C_Creg) exceeds a predetermined threshold (Cs), switching of the vehicle's operating mode to the classic mode accompanied by the generation of a visual and / or audible warning signal for the vehicle driver (1).

2. Method according to claim 1, characterized in that the actual regenerative braking torque (M_Creg) is determined by means of a measurement of an electrical quantity in the electric motor (11).

3. Method according to claim 1 or 2, characterized in that the actual regenerative braking torque (M_Creg) is determined by means of an actual deceleration measurement of the vehicle (1).

4. A method according to any one of claims 1 to 3, characterized in that the regenerative braking torque setpoint (C_Creg) is the maximum value attainable given a remaining charge capacity of a battery charged by the electric motor (11) in generator mode.

5. A method according to any one of claims 1 to 4, characterized in that the total braking torque request (R_Ctot) is a function of a variation in the position of the accelerator pedal (12A).

6. A method according to any one of claims 1 to 5, characterized in that it is implemented when it is detected that the position of the accelerator pedal (12A) has passed a neutral point position in the direction of a release of pressure on the pedal, the neutral point position being a function of a current value of vehicle speed.

7. Method according to claim 6, characterized in that it is implemented when it is detected that the position of the accelerator pedal (12A) has exceeded said neutral point position, and only if a current value of vehicle speed (1) exceeds a predetermined speed threshold.

8. Method according to claim 6 or 7, characterized in that it is implemented when it is detected that the position of the accelerator pedal (12A) has exceeded said neutral point position, and only if the regenerative braking torque setpoint (C_Creg) exceeds a predetermined torque threshold.

9. A method according to any one of claims 1 to 8, characterized in that the predetermined threshold (Cs) of deviation (AC) between the actual torque (M_Creg) and the setpoint (C_Creg) takes a value which depends on a current value of vehicle speed (1).

10. Assembly (14) of at least one computer, intended to be installed in a motor vehicle (1) which further comprises: - a motorization system, comprising an electric motor (11) capable of operating respectively in a traction mode (101 A), and in a generator mode (101 B) in which it provides a so-called regenerative braking torque; - a friction braking system (13); - an accelerator pedal (12A), forming a human-machine interface to control, at least, the application of a traction torque by the motorization system; - a brake pedal (12B), forming a human-machine interface to control vehicle braking using at least the friction braking system; the assembly of at least one computer being configured; - to control the vehicle's operation alternately in a conventional mode, in which a complete stop of the vehicle (1) is commanded using the brake pedal (12B), and a so-called "single-pedal" mode, in which a complete stop of the vehicle (1) is commanded using the accelerator pedal (12A), the accelerator pedal (12A) also forming a human-machine interface to control vehicle braking using the friction braking system (13) and / or the electric motor in generator mode (101 B); and - to implement the steps of the process according to any one of the preceding claims.

Images