Automated friction brake assisted vehicle stop

Abstract

A method of assisting in deceleration of a motor vehicle during a stop of the motor vehicle, the motor vehicle having a drivetrain including a traction motor, road wheels operably connected to the drivetrain, a friction brake configured to decelerate the road wheels, and an electronic controller, the method including detecting, via the electronic controller, a request to stop the vehicle. The method further includes commanding the traction motor to provide regenerative braking in response to the request to stop the vehicle. The method additionally includes determining a current vehicle operating state. The method further includes determining an amount of braking drag torque to be generated by the friction brake based on the current vehicle operating state. The method also includes commanding application of the determined amount of braking drag torque in parallel with the regenerative braking, thereby operating the friction brake as a mechanical drivetrain damper while assisting the regenerative braking to stop the motor vehicle.

Description

Technical Field

[0001] This disclosure relates to the use of an automatic friction brake with an electric motor-driven transmission system in a motor vehicle for assisted stopping. Background Technology

[0002] Motor vehicles typically employ a power unit to generate propulsion and a braking system to suppress vehicle motion. Traditional brakes are usually a type of mechanical friction device designed to suppress motion by converting kinetic energy into heat. This mechanical braking system typically applies a retarding force to slow the vehicle down via specially tuned friction elements on the vehicle's rotating axle or wheels.

[0003] Friction brakes typically consist of fixed brake shoes or pads lined with friction material and configured to engage with rotating, wear-prone surfaces such as rotors or drums. Common configurations include brake shoes that rub against the outside of a rotating drum, often called "band brakes"; rotating drums with brake shoes that extend to rub against the inside of the drum, often called "drum brakes"; and pads that clamp a rotating disc, often called "disc brakes." Generally, vehicle friction brakes absorb heat energy when braking and store it primarily in the brake disc or drum, then gradually transfer the stored heat to the surrounding environment.

[0004] Other energy conversion methods can also be used. For example, electric or hybrid electric vehicles that use a traction motor for propulsion often employ regenerative braking, where the traction motor operates in energy-generating mode to decelerate the vehicle. Typically, regenerative braking converts most of the vehicle's kinetic energy into electrical energy, which can then be stored in the onboard battery for later use. Many modern electric and hybrid electric vehicles employ braking systems that combine mechanical friction with regenerative braking.

[0005] Sometimes, the operation of the braking system can be accompanied by noise, vibration, and harshness (NVH) issues in the primary vehicle. In some cases, these NVH issues may be due to the performance characteristics of the friction elements in the mechanical braking system. In other cases, NVH issues may arise during transitions between vehicle driving, coasting, and braking modes, such as exposure to or exacerbation of the effects of mechanical shocks in the underlying propulsion and / or suspension systems. Summary of the Invention

[0006] A method for assisting deceleration during the stopping of a motor vehicle, the motor vehicle having a drivetrain including a traction motor, road wheels operably connected to the drivetrain, friction brakes configured to decelerate the road wheels, and an electronic controller, the method including detecting a request to stop the vehicle via the electronic controller. The method further includes, in response to the request to stop the vehicle, commanding the traction motor to provide regenerative braking via the electronic controller. The method further includes, via the electronic controller, determining the current operating state of the vehicle. The method further includes, via the electronic controller, determining, based on the current operating state of the vehicle, the amount of braking drag torque to be generated by the friction brakes. The method further includes, via the electronic controller, commanding the application of the determined amount of braking drag torque in parallel with regenerative braking, thereby operating the friction brakes as a mechanical drivetrain damper while assisting regenerative braking to stop the motor vehicle.

[0007] According to this method, determining the current vehicle operating status may include determining the vehicle's current grade.

[0008] In addition, the amount of braking drag torque can be determined via a first lookup table.

[0009] According to this method, determining the current vehicle operating status may include determining the vehicle's current road speed.

[0010] Additionally, when the vehicle's current road speed is below a vehicle road speed threshold such as 3 kph, a predetermined amount of braking drag torque can be commanded to be applied.

[0011] The method may also include determining the rate of ramp-up of the braking torque based on the current vehicle operating state and the determined amount of braking drag torque.

[0012] According to this method, the rate of increase of braking drag torque can be realized via a second lookup table based on the vehicle's current road speed and current gradient.

[0013] Additionally, the command to apply a determined amount of braking drag torque may include the rate of increase of the commanded braking drag torque.

[0014] The method may further include determining a desired increment of braking drag torque. Additionally, the method may include determining whether the difference between the desired increment of braking drag torque and the determined amount of braking drag torque is greater than a predetermined incremental braking drag torque limit. Furthermore, the method may include commanding the application of the determined amount of braking drag torque when the difference between the desired increment of braking drag torque and the determined amount of braking drag torque is greater than the predetermined incremental braking drag torque limit.

[0015] The motor vehicle may include an accelerator switch that communicates with an electronic controller. The method may also include monitoring the accelerator switch via the electronic controller to obtain a vehicle acceleration request. According to this method, in such an embodiment, when no vehicle acceleration request is detected, a command can be implemented to apply a defined amount of braking drag torque.

[0016] A vehicle having an electronic controller configured or programmed to perform this method is also disclosed.

[0017] The above-described features and advantages, as well as other features and advantages of this disclosure, will become apparent from the following detailed description of the disclosed embodiments and best modes for carrying out the purposes described in conjunction with the accompanying drawings. Attached Figure Description

[0018] Figure 1 The present disclosure provides a schematic plan view of a motor vehicle with a transmission system, which includes a traction motor configured to provide regenerative braking, friction brake subassemblies at each wheel, and employs a system that uses friction brakes to assist the vehicle in decelerating to a stop.

[0019] Figure 2 yes Figure 1 The diagram shows a schematic cross-sectional view of a disc brake embodiment of a brake subassembly, wherein the brake subassembly is configured as a disc brake.

[0020] Figure 3 yes Figure 1 A schematic side view of an embodiment of a drum brake subassembly shown.

[0021] Figure 4 It is used for assistance, for example Figure 1-3 The flowchart depicts a method for decelerating a motor vehicle to a stop. Detailed Implementation

[0022] Those skilled in the art will recognize that terms such as “above,” “below,” “upward,” “downward,” “top,” “bottom,” “left,” and “right” are used descriptively in the accompanying drawings and do not imply limitation on the scope of this disclosure as defined herein. Furthermore, the teachings can be described herein in terms of functional and / or logical block components and / or various processing steps. It should be understood that such block components may include multiple hardware, software, and / or firmware components configured to perform a specified function.

[0023] Referring to the accompanying drawings, where the same reference numerals refer to the same parts, Figure 1A schematic diagram of a motor vehicle 10 positioned relative to a road surface 12 is shown. The vehicle 10 may be a mobile platform, such as a passenger car, all-terrain vehicle (ATV), aircraft, etc., for personal, commercial, or industrial purposes. As shown, the vehicle 10 includes a body 14 disposed along a longitudinal axis 16 and having corresponding left, right, front, and rear sides. The body 14 also defines a vehicle interior 18 configured to accommodate a vehicle operator, passengers, and cargo.

[0024] Continue to refer to Figure 1 The vehicle 10 includes a plurality of wheels, specifically shown as front wheels 22A and rear wheels 22B. The vehicle 10 also includes a drivetrain 24 configured to provide propulsion. The drivetrain 24 includes one or more traction motors or motor-generators 26 operably connected to at least some of the wheels 22A and 22B and configured to generate an electric motor drive torque Tm. As shown, the drivetrain 24 may additionally include an internal combustion engine 28 configured to generate an engine drive torque Te and a transmission 30 operably connected to at least some of the wheels 22A and 22B to transmit the engine torque thereto. The drivetrain 24 may additionally include a fuel cell (not shown) operably connected to at least some of the wheels 22A and 22B.

[0025] like Figure 1 As shown, the vehicle suspension system 32 operably connects the vehicle body 14 to the corresponding wheels 22A and 22B to maintain contact between the wheels and the road surface 12 and to maintain the handling of the vehicle 10. Figure 1 As shown, a vehicle steering system 34 is operatively connected to the front wheels 22A to steer the vehicle 10. The steering system 34 includes a steering wheel 36 operatively connected to the front wheels 22A via a steering rack 38. The steering wheel 36 is located within the passenger compartment of the vehicle 10, allowing the vehicle operator to command the vehicle to take a specific direction relative to the road surface 12. Additionally, an accelerator switch or pedal 40 is located within the passenger compartment of the vehicle 10, wherein the accelerator switch is operatively connected to the transmission system 24 for commanding and controlling the propulsion of the vehicle 10.

[0026] The vehicle braking system 42 is operatively connected to the respective front and rear wheels 22A, 22B to delay wheel rotation and decelerate the vehicle 10. The braking system 42 includes friction brake subassemblies or friction brakes 44, which are arranged at each of the respective front and rear wheels 22A, 22B and operatively connected to the vehicle suspension system 32. In other words, the braking system 42 may include multiple friction brake subassemblies 44. Each brake subassembly 44 may be configured as a disc brake (e.g., Figure 2 (as shown) or drum brake (such as) Figure 3(As shown). Each brake subassembly 44 includes a rotor 46 configured to rotate synchronously with the corresponding wheel 22A or 22B about the wheel axle 48. Each brake subassembly 44 also includes an actuator 50 arranged in the brake caliper 50-1 of the disc brake (as shown). Figure 1 As shown in Figure 2) or in the foundation of drum brakes 50-2 (as shown in Figure 3) Figure 3 (as shown), and is configured to generate an actuator or braking force F. The actuator 50 may be configured as a hydraulically actuated piston, for example, operated via a hydraulic braking pressure P generated at the master brake cylinder 52 or an electrically actuated servo motor (not shown).

[0027] like Figure 2 and 3 As shown, each brake subassembly 44 also includes one or more brake elements or pads 54, each having a wearable friction lining or element 56. The friction lining 56 is configured to be pressed into contact with the rotor by an actuator force F to delay the rotation of the corresponding wheel 22A or 22B, thereby slowing the vehicle 10. The actuator force F can be controlled via a signal generated by the brake switch or pedal 58 and electronically transmitted to the master brake cylinder 52 (e.g., ...). Figure 1 As shown in the diagram. The brake switch 58 is typically located inside the passenger compartment of the interior 18 and is adapted to be controlled by the operator of the vehicle 10.

[0028] refer to Figure 1 The vehicle 10 also includes a first sensor 60 configured to detect a deceleration request to stop the vehicle 10, such as via the application of brake switch 58 or based on a stop request of the vehicle in the absence of a driver-initiated deceleration request. The vehicle 10 also includes one or more second sensors 62 configured to detect the operating state of the vehicle 10, such as the vehicle's road speed (V) and the vehicle's gradient or tilt (G). Additionally, the vehicle 10 includes a third sensor 64 configured to detect a vehicle acceleration request, such as via the application of accelerator switch 40. An actuator force F can be controlled via brake switch 58 to provide sufficient torque at the corresponding wheel 22A or 22B to stop the vehicle 10, generating some drag torque T via slight contact between the friction lining 56 and the rotor 46. d The nominal or slight lag in wheel rotation, along with various sizes of actuator forces therein, decelerate the vehicle at the desired rate.

[0029] Alternatively, the actuator force F can be controlled similarly via the onboard vehicle electronic controller 66 as part of a system for assisting the vehicle to decelerate to a stop using the friction brake 44. Figure 1As shown, the electronic controller 66 communicates with sensors 60 and 62. The electronic controller 66 may alternatively be referred to as a control module, control unit, controller, vehicle 10 controller, computer, etc. The electronic controller 66 may include a computer and / or processor 68, and includes software, hardware, memory, algorithms, connections (e.g. to sensors 60 and 62), etc., for managing and controlling the operation of the vehicle 10. Therefore, detailed descriptions are provided below. Figure 4 The generalized representation of the method can be implemented as a program or algorithm operable on the electronic controller 66. It should be understood that the electronic controller 66 may include devices capable of analyzing data from sensors 60 and 62, comparing the data, making decisions necessary to control the operation of vehicle 10, and performing the necessary tasks to control the operation of the subject vehicle.

[0030] The electronic controller 66 can be implemented as one or more digital computers or host machines, each having one or more processors 68, read-only memory (ROM), random access memory (RAM), electrically programmable read-only memory (EPROM), optical drive, magnetic drive, etc., high-speed clock, analog-to-digital (A / D) circuitry, digital-to-analog (D / A) circuitry, input / output (I / O) circuitry, I / O devices and communication interfaces, and signal conditioning and buffering electronics. Computer-readable memory can include non-transitory / tangible media involved in providing data or computer-readable instructions. Memory can be non-volatile or volatile. Non-volatile media can include, for example, optical discs or magnetic disks, and other persistent memories. Example volatile media can include dynamic random access memory (DRAM) that can constitute main memory. Other examples of memory embodiments include floppy disks, floppy disks or hard disks, magnetic tape or other magnetic media, CD-ROMs, DVDs and / or other optical media, and other possible memory devices, such as flash memory.

[0031] The electronic controller 66 also includes a tangible, non-transitory memory 70 on which computer-executable instructions, including one or more algorithms, are recorded for regulating the operation of the motor vehicle 10. Algorithms required by or accessible to the controller 66 can be stored in the memory and executed automatically to provide the required functionality. The subject algorithms may specifically include an algorithm 72 for assisting the stopping of the motor vehicle 10, which will be described in detail below. The processor 68 of the electronic controller 66 is configured to execute algorithm 72. The electronic controller 66 is also configured to command the drag torque (T) of the friction brake 44. d The application of this damper, which acts as a damper in the mechanical vehicle drive system, addresses noise, vibration, and ride roughness (NVH) issues during vehicle pausing due to regenerative braking.

[0032] Typically, mechanical systems, such as the drivetrain 24 and suspension 32 of vehicle 10, have clearances or freewheeling caused by gaps between system components, also known as backlash or lash. This clearance can be defined as a maximum distance or angle through which certain parts of the mechanical system can move in one direction without exerting a significant force or movement on the next part in the mechanical sequence. An example of clearance in gears and gear trains is the amount of clearance between meshing gear teeth. Gear backlash can be seen when the direction of movement of the gear train is reversed and slack or freewheeling occurs before the reversal is complete. Variations in clearance in mechanical linkages can be due to lubrication allowances, manufacturing tolerances, deformation under load, and thermal contraction / expansion. Furthermore, in many mechanical systems, some backlash is specifically permitted to prevent jamming. The backlash in the drivetrain 24 and suspension 32 of vehicle 10 may be exposed during the operation of the braking system 42 and cause NVH problems such as slamming and impact noise. Such NVH problems may be encountered during transitions between vehicle driving, coasting, and braking modes. Due to the performance characteristics of the friction element 56, additional NVH issues may occur, such as squeaking.

[0033] Specifically, the electronic controller 66 is configured to detect a request 74 to stop the vehicle 10 using the first sensor 60. The electronic controller 66 is also configured to command the traction motor 26 to provide regenerative braking in response to the request 74 to stop the vehicle 10. The electronic controller 66 is further configured to determine the current vehicle operating state using the second vehicle sensor 62, such as the current vehicle road speed (V) and the current vehicle gradient (G). The electronic controller 66 is also configured to determine, based on the current vehicle operating state, the braking drag torque (T) to be generated by the friction brake 44. d The electronic controller 66 is also configured to apply a determined amount of braking drag torque (T) in parallel with command and regenerative braking. d This generates frictional damping through friction brake 44, while simultaneously assisting regenerative braking to stop vehicle 10. Specifically, algorithm 72 can compare the current road speed (V) with a vehicle road speed threshold 78 (e.g., 3 kph).

[0034] The electronic controller 66 can be configured to command the application of a defined amount of braking drag torque (T) when the current road speed (V) of the vehicle 10 is below a road speed threshold 78. d The electronic controller 66 may additionally be configured to monitor the accelerator switch 40 to receive a vehicle acceleration request 80 and, when no vehicle acceleration request is detected, command the application of a predetermined amount of braking drag torque (T). dThe electronic controller 66 can also be configured to determine the braking drag torque (T) by means of a first lookup table 82 stored in the controller memory. d The first lookup table 82 may include the braking drag torque (T) empirically developed on representative vehicles under controlled test conditions. d Data on vehicle gradient (G) and slope.

[0035] The electronic controller 66 may be additionally configured to determine the braking drag torque (T) based on the current vehicle operating state (e.g., the current road speed (V) and gradient (G) of vehicle 10). d Therefore, the electronic controller 66 can apply a determined amount of braking drag torque (T). d The rate of increase of the braking drag torque determined by the command during the period (T) d The electronic controller 66 may be specifically configured to determine the rate of increase (T) of the braking drag torque via a second lookup table 84 stored in the controller memory. d The second lookup table 84 may include the rate of increase of braking drag torque (T). d (˙) Data on vehicle road speed (V) and gradient (G) relative to empirically developed data. Data from the first lookup table 82 can be specifically used as input to the second lookup table 84.

[0036] In a particular embodiment, the electronic controller 66 may be configured to operate based on a determined amount of braking drag torque (T). d ) and the rate of increase of the determined braking drag torque (T) d ˙) to determine the expected increment of braking drag torque (ΔT) d In such an embodiment, the electronic controller 66 may be further configured to determine the desired increment of the braking drag torque (ΔT). d ) and the determined braking drag torque (T) d Whether the difference between ) is greater than the predetermined incremental braking drag torque limit 86. The electronic controller 66 can be configured to then, when the desired increment of the braking drag torque (ΔT) is greater than the predetermined incremental braking drag torque limit 86. d ) and a certain amount of braking drag torque (T) d When the difference between the values ​​is greater than the predetermined incremental braking drag torque limit of 86, a command is issued to apply a defined amount of braking drag torque (T). d ).

[0037] The electronic controller 66 can be further programmed to fully engage the friction brake 44 once the vehicle 10 has come to a complete stop and regenerative braking is no longer effective. Therefore, the electronic controller 66 is designed to regulate the application of the friction brake 44 to apply a drag torque (T). d This results in lag in the vehicle's transmission system during deceleration and upon stopping. Therefore, the drag torque (T)d The hysteresis provided is intended to function as a mechanical or friction damper to minimize NVH problems caused by drivetrain backlash during regenerative braking vehicle stopping. Additionally, during the later stages of vehicle deceleration, the drag torque (T) is used to mitigate these issues. d The vehicle drivetrain lag provided allows for a smooth and uninterrupted transition to a brake-held stationary vehicle 10.

[0038] Figure 4 Describes assistance such as those mentioned above during vehicle stop. Figure 1-3 The method 100 for decelerating a motor vehicle 10 is described. Method 100 begins in frame 102 by detecting movement of the vehicle 10 relative to a road surface 12. In frame 102, the method may further include detecting a request 7410 to stop the vehicle via a controller 66 (e.g., using a first sensor 60). Method 100 then proceeds from frame 102 to frame 104. In frame 104, the method includes commanding a traction motor 26 to provide regenerative braking in response to the request 74 to stop the vehicle 10 via an electronic controller 66. Method 100 then proceeds from frame 104 to frame 106. In frame 106, the method includes determining the current vehicle operating state via the electronic controller 66, for example, by detecting the current vehicle road speed (V) and current vehicle gradient (G) using a second vehicle sensor 62. After frame 106, method 100 proceeds to frame 108.

[0039] In block 108, method 100 includes determining, via electronic controller 66, the braking drag torque (T) to be generated by friction brake 44 based on the current vehicle operating state. d The amount of braking drag torque (T) is determined. d The amount of ) can be obtained through having braking drag torque (T) d This is accomplished using a first lookup table 82 containing data on the vehicle slope (G). In block 108, method 100 may further include, via electronic controller 66, based on the current vehicle operating state and a determined amount of braking drag torque (T). d To determine the rate of increase (T) of a specific braking drag torque. d ˙). Determine the rate of increase (T) of the braking drag torque. d ˙) can be achieved via a rate of increase (T) with braking drag torque. d This is achieved using a second lookup table 84 relative to the vehicle's road speed (V) and gradient (G).

[0040] In block 108, method 100 may further include, via electronic controller 66, based on a determined amount of braking drag torque (T). d ) and the rate of increase of the determined braking drag torque (T) d ˙), to determine the expected increment of braking drag torque (ΔT)d As mentioned above... Figure 1-3 In such an embodiment, the method may further include determining, via electronic controller 66, the desired increment of braking drag torque (ΔT). d Whether the difference between the measured braking drag torque and the determined amount is greater than the predetermined incremental braking drag torque limit 86. After block 108, method 100 proceeds to block 110.

[0041] In frame 110, method 100 includes commanding, via electronic controller 66, to apply a determined amount of braking drag torque (T) in parallel with regenerative braking. d Specifically, when the current road speed (V) of vehicle 10 is lower than a specific vehicle road speed threshold 78, a command can be made to apply a determined amount of braking drag torque (T). d In addition, the command applies a determined amount of braking drag torque (T). d This can include the rate of increase (T) of the command braking drag torque. d Additionally, when the desired increase in braking drag torque (ΔT) d ) and the determined braking drag torque (T) d When the difference between the values ​​is greater than the predetermined incremental braking drag torque limit of 86, the command to apply a determined amount of braking drag torque (T) can be executed. d Furthermore, when no vehicle acceleration request 80 is detected, a defined amount of braking drag torque (T) can be commanded to be applied within frame 110. d Otherwise, the method can loop back to box 102.

[0042] As mentioned above Figure 1-3 The commanded braking drag torque (T) d The friction brake 44 is operated as a mechanical transmission system damper to minimize NVH problems, while simultaneously assisting regenerative braking to stop the motor vehicle 10. This method can proceed from frame 110 to frame 112, where the electronic controller 66 includes commanding the friction brake 44 to fully engage once the vehicle 10 has come to a complete stop and regenerative braking is no longer effective. After the vehicle has come to a complete stop, the method can restart in frame 102, while detecting the resuming motion of the vehicle 10 relative to the road surface 12, thus enabling the method algorithm to be repeated in frames 102 through 112 to assist regenerative braking to stop the motor vehicle 10 while minimizing NVH problems. Method 100 can also terminate at frame 114. Therefore, with respect to method 100, regenerative braking and braking drag torque (T) are employed. d To achieve different objectives, regenerative braking is primarily used to bring the vehicle to a stop, while braking drag torque (T) is used to achieve the same effect. d This is used to address NVH / drivetrain issues.

[0043] Detailed description and accompanying drawings are provided to support and describe this disclosure, but the scope of this disclosure is limited only by this application. While some best modes and other embodiments for carrying out the claimed disclosure have been described in detail, various alternative designs and embodiments exist for practicing the disclosure as defined in this application. Furthermore, features of the embodiments shown in the drawings or the various embodiments mentioned in this specification are not necessarily to be construed as embodiments independent of each other. Rather, each feature described in an example of one embodiment may be combined with one or more other desired features from other embodiments, resulting in other embodiments that are not described in words or with reference to the drawings being possible. Therefore, such other embodiments fall within the framework of the scope of this application.

Claims

1. A method for assisting deceleration during a stop of a motor vehicle, the motor vehicle having a transmission system including a traction motor, wheels operably connected to the transmission system, friction brakes configured to decelerate the wheels, and an electronic controller, the method comprising: The electronic controller detects requests to stop the vehicle. The electronic controller commands the traction motor to provide regenerative braking in response to a request to stop the vehicle; The current vehicle operating status is determined via an electronic controller, including determining the vehicle's current gradient and current road speed. The amount of braking drag torque to be generated by the friction brake is determined by the electronic controller based on the current vehicle operating status. The rate of increase of the braking drag torque is determined based on the current vehicle operating status and the determined amount of braking drag torque. A defined amount of braking drag torque is commanded to be applied in parallel with regenerative braking via an electronic controller; and The friction brake is operated as a damper in the mechanical transmission system via an electronic controller, while simultaneously assisting in regenerative braking to stop the motor vehicle.

2. The method of claim 1, wherein determining the amount of braking drag torque is accomplished via a first lookup table.

3. The method of claim 1, wherein when the current road speed of the vehicle is lower than the vehicle road speed threshold, the command is executed to apply a determined amount of braking drag torque.

4. The method of claim 1, wherein determining the rate of increase of the braking drag torque is achieved via a second lookup table based on the vehicle's current road speed and the vehicle's current gradient.

5. The method of claim 1, wherein commanding the application of the determined amount of braking drag torque includes commanding the rate of increase of the braking drag torque.

6. The method according to claim 1, further comprising: Determine the expected increment of the braking drag torque; Determine whether the difference between the expected increment of the braking drag torque and the determined amount of the braking drag torque is greater than a predetermined incremental braking drag torque limit; and When the difference between the expected increment of the braking drag torque and the determined amount of the braking drag torque is greater than a predetermined incremental braking drag torque limit, the determined amount of braking drag torque is commanded to be applied.

7. The method of claim 1, wherein the motor vehicle includes an accelerator switch in communication with the electronic controller, the method further comprising monitoring the accelerator switch via the electronic controller to obtain a vehicle acceleration request, and wherein commanding the application of a determined amount of braking drag torque is performed when no vehicle acceleration request has yet been detected.

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