Method for controlling vehicle braking and associated wheel controller

Abstract

Method for controlling vehicle braking and associated wheel controller. The invention relates to a method for controlling the braking of a vehicle comprising a plurality of wheels, each including a wheel motor and being equipped with a parking brake. The method comprises: activating a speed control system for the vehicle's wheel motors and transmitting a vehicle speed command lower than the vehicle's current speed; if the vehicle is on an uphill slope, applying a parking brake to the wheels of the plurality located at the rear of the vehicle and deactivating a torque applied by the wheel motors of the vehicle's wheels; and if the vehicle is on a downhill slope, applying a parking brake to the wheels of the plurality located at the front of the vehicle and deactivating a torque applied by the wheel motors of the vehicle's wheels. Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for controlling the braking of a vehicle and associated wheel controller technical field

[0001] The present invention belongs to the general field of vehicle braking and drive systems. More particularly, it relates to a braking control system for a vehicle comprising a plurality of wheels, including a wheel motor. It also relates to a wheel controller for a vehicle, as well as a vehicle in which such a controller is installed. Previous technique

[0002] So-called "motor vehicles" generally include axles that carry wheels and support the vehicle body relative to the wheels. Examples of such vehicles include wheeled agricultural, construction, tillage, or load-moving machines. These axles are driven in rotation by a motor located at a distance from the wheels, via a transmission mechanism. These vehicles are typically equipped with parking brakes to ensure they remain stationary, even on a slope. To achieve this, the parking brakes are installed on the transmission, at the transfer case or on the axles.

[0003] Other vehicle drive solutions exist, including systems called "wheel motors." A wheel motor is an assembly in which the wheel is supported by the motor, which performs a bearing function for the wheel. Physically, the motor is essentially located within the wheel. The wheel motor thus not only drives the wheel but also provides mechanical support for the vehicle body relative to the wheel. In this way, the drive torque applied to each wheel of the vehicle is directly controlled by its motor, eliminating the need for a differential drive between the wheels. When driving the vehicle, wheel motors provide engine braking but can also provide mechanical braking, particularly for parking. A braking function is also desirable when the vehicle is stopped, especially on inclines.When braking is sufficient, it is not necessary to equip all the vehicle's wheels with mechanical brakes. For example, on a four-wheeled, four-engine, two-axle vehicle, it is possible to have only two wheels equipped with mechanical brakes, for example, two wheels on the same axle.

[0004] However, the braking mechanisms of current in-wheel motors reduce the braking capacity—particularly the engine braking capacity—of the vehicles on which they are installed, and cannot maintain engine braking for very long when stationary. This encourages both the increased use of mechanical brakes and the equipping of more wheels with mechanical brakes. Furthermore, the brakes of current in-wheel motors do not offer compact mechanisms, which encourages the use of more wheels equipped with mechanical brakes to distribute the braking torque across several smaller brakes, thus preventing the in-wheel motors from becoming too bulky.However, when all wheels are equipped with mechanical brakes, activating the braking mechanism causes all wheels to lock, which makes steering difficult when the vehicle is stationary, i.e., when the vehicle is not moving longitudinally.

[0005] Furthermore, current wheel motors, especially when electrically driven, tend to overheat when their rotational speed is very low. Although they have the capability for engine braking and holding, i.e., transmitting torque at zero or low rotational speed—allowing for engine braking followed by a smooth stop, as well as very gradual restarts on inclines, and also for energy recuperation during braking—they cannot perform this function for very long without risking damage. For this reason, there is an incentive to use a mechanical brake for dynamic braking to a standstill, which deprives the vehicle of the advantages of engine torque braking and stopping, and also of the benefits of energy recuperation. Description of the invention

[0006] The present invention aims to remedy all or part of the disadvantages of the prior art, in particular those set out above, by proposing a solution which allows selection of the brake or brakes to be applied when stopping the vehicle, in order to guarantee the immobilization of a vehicle, even if it is parked on an uphill or downhill slope, while ensuring that a steering maneuver is facilitated when the vehicle is not moving longitudinally.

[0007] To this end, and according to a first aspect, the invention relates to a method for controlling the braking of a vehicle comprising a plurality of wheels, each wheel including a wheel motor and being equipped with a parking brake, the method being implemented by a wheel controller of the vehicle and comprising:

[0008] - an activation of a speed control system for the vehicle's wheel motors and a transmission of a vehicle speed command less than or equal to the speed current of said vehicle; and following a determination that the vehicle's speed has reached a first threshold value defined according to said speed setting,

[0009] - if the vehicle is on an uphill slope, an application of a brake of parking at the wheels of the plurality located at the rear of said vehicle and a deactivation of a torque applied by the wheel motors of the vehicle's wheels,

[0010] - and if the vehicle is on a downward slope, an application of a brake parking at the wheels of the plurality located at the front of said vehicle and a deactivation of a torque applied by the wheel motors of the vehicle's wheels.

[0011] When a vehicle is positioned on a slope, the load on each axle can vary considerably. Therefore, unlike prior art braking techniques that distribute the braking force unevenly when they focus on braking every other axle, the invention focuses on applying a parking brake to the wheels of the most heavily loaded axle(s). In this way, the braked wheel(s) do not slip. When the vehicle is on an uphill slope, the most heavily loaded axle(s) generally correspond to the axle(s) located at the rear of the vehicle, and conversely, when the vehicle is on a downhill slope, the most heavily loaded axle(s) generally correspond to the axle(s) located at the front of the vehicle.

[0012] Furthermore, the invention aims, as far as possible, to avoid applying a parking brake to all wheels of the vehicle. This feature is advantageous because it reduces wear on tires and steering components, and consequently limits the frequency of tire replacement. Indeed, when all parking brakes are activated on a vehicle such as an articulated vehicle, it requires the application of high forces to adjust the vehicle's direction.

[0013] In general, it is considered that the steps of a process should not be interpreted as being linked to a notion of temporal succession.

[0014] In particular embodiments, the method for controlling the braking of a vehicle may further include one or more of the following characteristics, taken individually or in all technically possible combinations.

[0015] In particular modes of implementation, the first threshold value is equal to the speed setpoint.

[0016] In certain embodiments, the speed setpoint is equal to zero. In this way, the vehicle's speed is reduced to zero. This speed is achieved by applying a braking torque to reduce the vehicle's speed.

[0017] In particular embodiments, it is determined that the vehicle speed has reached a first threshold value (for example 0.2 m / s) defined in depending on the stated speed setting (for example 0 m / s), and this for a predetermined period. This predetermined period is, for example, one minute.

[0018] In particular embodiments, the method further comprises, following the application of a parking brake to the wheels located at the front or rear of said vehicle,

[0019] - a determination of an evolution of the vehicle's position greater than one threshold value, known as the "second threshold value"; and,

[0020] - an application of a parking brake to all wheels of the vehicle.

[0021] This second threshold value is, for example, equal to 2 cm.

[0022] In particular embodiments, the evolution of the vehicle's position is due to unstable ground or ground collapse.

[0023] In particular embodiments, the activation of a speed control system is implemented after determining that a torque can be applied by each of the vehicle's motors so as to reduce, or even make zero, the speed of said vehicle, and this after determining that the speed of said vehicle is less than a threshold value, called the "third threshold value".

[0024] In particular embodiments, the method further comprises:

[0025] - obtaining a torque to be applied by the wheel motors of the vehicle's wheels to keep said vehicle stationary;

[0026] if the vehicle is on an uphill slope, activation of a speed control of the wheel motors of the wheels located at the rear of said vehicle, transmission of a zero speed command to the controlled wheel motors, and freewheeling of the wheels located at the front of said vehicle;

[0027] - and if the vehicle is on a downward slope, an activation of a servo control speed of the wheel motors of the wheels located at the front of said vehicle, a transmission of a zero speed command to the servo wheel motors, and a freewheeling of the wheels located at the rear of said vehicle.

[0028] Thus, after a stop of said vehicle, the constraint exerted by the parking brakes is released, a torque aimed at keeping the vehicle stationary is exerted, then the vehicle is put into motion again.

[0029] According to a second aspect, the invention relates to a method for controlling the braking of a vehicle comprising a plurality of wheels, each wheel including a wheel motor and being equipped with a parking brake, the method being implemented by a wheel controller of the vehicle and comprising:

[0030] - obtaining a torque to be applied by the wheel motors of the vehicle's wheels to keep said vehicle stationary;

[0031] - if the vehicle is on an uphill slope, an activation of a servo system speed of the wheel motors of the wheels located at the rear of said vehicle, a transmission of a zero speed command to the servo wheel motors, and a freewheeling of the wheels located at the front of said vehicle;

[0032] - and if the vehicle is on a downward slope, an activation of a servo control speed of the wheel motors of the wheels located at the front of said vehicle, a transmission of a zero speed command to the servo wheel motors, and a freewheeling of the wheels located at the rear of said vehicle.

[0033] Thus, the control method according to this second aspect aims to release the parking brakes (or "unbrake") and to keep the vehicle stationary by applying a torque by the wheel motors, before allowing a movement of said vehicle.

[0034] In particular embodiments, the method according to this second aspect further includes an activation of a torque control of the wheel motors of all the wheels of said vehicle and a transmission of a torque command aimed at keeping said vehicle stationary, if said vehicle has moved a distance greater than a threshold value, called "fourth threshold value".

[0035] This fourth threshold value is, for example, equal to 2 cm. Alternatively, this torque control is activated if the vehicle has moved a distance greater than a threshold value during a predetermined period, for example 2 cm during the last 10 minutes.

[0036] In particular embodiments, the method according to this second aspect further includes a check that the temperature of at least one of the motors is below a threshold value, referred to as the "fifth threshold value" and / or that said vehicle is not held stationary by the application of a torque for a period exceeding a threshold value, referred to as the "sixth threshold value"; if so, a transmission of a command to allow movement of the vehicle; and if not, an application of a parking brake to (all) wheels of said vehicle.

[0037] Alternatively or in addition, the verification may consist of verifying that the variator temperature is below a threshold value and / or verifying that the DC current supplied by the battery is below a threshold value. In particular embodiments, the method according to this second aspect further includes activating a speed control system for the wheel motors of all the wheels of the vehicle, transmitting a zero speed command to the controlled wheel motors, and releasing all the parking brakes, following a determination that the vehicle's orientation is changing while it is stationary.

[0038] In particular embodiments, the process according to this second aspect further comprises:

[0039] - an activation of a speed control system for the vehicle's wheel motors and a transmission of a vehicle speed command lower than the current speed of said vehicle; and following a determination that the vehicle's speed has reached a first threshold value defined according to said speed instruction,

[0040] - if the vehicle is on an uphill slope, applying a brake parking at the wheels of the plurality located at the rear of said vehicle and a deactivation of a torque applied by the wheel motors of the vehicle's wheels,

[0041] - and if the vehicle is on a downward slope, an application of a brake parking at the wheels of the plurality located at the front of said vehicle and a deactivation of a torque applied by the wheel motors of the vehicle's wheels.

[0042] According to a third aspect, the invention relates to a computer program comprising instructions for implementing a braking control method in accordance with the first or second aspect, when said program is executed by a processor.

[0043] This program may use any programming language, and be in the form of source code, object code, or code intermediate between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0044] According to a fourth aspect, the invention relates to a computer-readable recording medium on which the computer program according to the invention is recorded.

[0045] The information or recording medium can be any entity or device capable of storing the program. For example, the medium can include a storage means, such as a ROM, for example a CD-ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a hard disk drive.

[0046] On the other hand, the information or recording medium can be a transmissible medium such as an electrical or optical signal, which can be transmitted via an electrical or optical cable, by radio, or by other means. The program according to the invention can, in particular, be downloaded onto an Internet-type network.

[0047] Alternatively, the information or recording medium may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the process in question.

[0048] According to a fifth aspect, the invention relates to a wheel controller of a vehicle comprising a plurality of wheels, each wheel including a wheel motor and being equipped with a parking brake, the controller being configured to implement a braking control method in accordance with the first or second aspect.

[0049] In the remainder of this description, "wheel controller" means a controller of at least one wheel of the vehicle in which this controller is installed. In a particular embodiment, the "wheel controller" is configured to control all the wheels of the vehicle in which it is installed.

[0050] According to a sixth aspect, the invention relates to a vehicle comprising a plurality of wheels, each wheel including a wheel motor and being equipped with a parking brake, and in which is mounted a wheel controller (200) conforming to the fifth aspect.

[0051] According to a seventh aspect, the invention relates to a wheel in which is embedded a wheel controller configured to implement a braking control method in accordance with the first or second aspect.

[0052] In particular embodiments, the wheel motor is an electric wheel motor. Brief description of the drawings

[0053] Other features and advantages of the present invention will become apparent from the description below, with reference to the accompanying drawings, which illustrate an example of an embodiment without being limiting in any way. In the figures:

[0054] [Fig-1] [Fig.1] is a front view representation of a vehicle in which is embedded a wheel controller, according to an example of implementation of the invention;

[0055] [Fig.2A] [Fig.2A] is a top view representation of an articulated vehicle in a turn;

[0056] [Fig.2B] [Fig.2B] is a top view representation of a non-articulated vehicle in a turn;

[0057] [Fig.3] [Fig.3] is a schematic representation of a vehicle equipped with wheel motors and in which a wheel controller is embedded;

[0058] [Fig.4] [Fig.4] represents modules embedded in a wheel controller, according to a particular method of implementing the invention;

[0059] [Fig.5] [Fig.5] represents modules embedded in a wheel controller, according to a particular method of implementing the invention;

[0060] [Fig.6] [Fig.6] schematically represents an example of hardware architecture of a wheel controller;

[0061] [Fig.7] [Fig.7] represents, in the form of a flowchart, a particular mode implementation of a vehicle braking control method, for example performed by the wheel controller of [Fig. 4]; and,

[0062] [Fig.8] [Fig.8] represents, in flowchart form, a particular method of implementing a method of controlling the braking of a vehicle, for example carried out by the wheel controller of [Fig.5]. Description of the implementation methods

[0063] Fig. 1 is a front view representation of a vehicle in which a wheel controller is mounted, according to an example of an implementation of the invention.

[0064] Generally speaking, a "vehicle" in the sense of the invention corresponds to any motorized land vehicle, that is to say any vehicle intended to travel on the ground and which can be powered by a mechanical force generated by one or more motors.

[0065] In particular embodiments, the vehicle is a wheel loader, a multi-function tool carrier, a forklift, a tandem compactor, a compact mini loader or an autonomous agricultural machine.

[0066] As illustrated in [Fig. 1], the vehicle 1000 is, in this example, an articulated loader. The distinguishing feature of a loader is its ability to quickly transport or move a large quantity of materials, particularly during earthmoving work. To achieve this, the loader 1000 is equipped, among other things, with a loader bucket 300, a counterweight 500, and a cab 400.

[0067] In this example, the vehicle 1000 is also equipped with four wheels 100. A drive device is associated with at least one front wheel and at least one rear wheel. Preferably, each wheel 100 of the vehicle 1000 is equipped with a drive device, and in this case, the vehicle 1000 comprises four drive devices, forming a transmission of a four-wheel drive vehicle 1000.

[0068] It should be noted that the number of wheels 100 equipping the vehicle 1000 is not a limiting factor of the invention. The following developments can indeed be easily generalized by a person skilled in the art to cases where the vehicle is equipped with a number of wheels other than four. Similarly, the number of axle(s) equipping the vehicle 1000 is not a limiting factor of the invention. The following developments can indeed be easily generalized by a person skilled in the art to cases where the vehicle is equipped with a number of axle(s) other than two.

[0069] Each drive device includes, in particular, a gearbox (not shown) and a motor 10, typically an electric motor. It should be noted, however, that there are no limitations on the motor's power source. The following developments can easily be adapted by those skilled in the art to a hydraulic motor, for example, one with axial pistons. The gearbox includes a housing (not shown) which is, for example, attached to the chassis frame of the vehicle 1000. The gearbox also includes an output hub, rotatably mounted relative to the housing. The output hub of the drive device carries a wheel 100, and the drive device supports the body of the vehicle 1000 relative to the wheel 100.

[0070] Each wheel 100 is further equipped with a parking brake 20, configured to lock the wheel 100 in order to prevent its rotational movement and therefore, consequently, the movement of the vehicle. In the remainder of the description, unless otherwise specified, "wheel 100" will be understood to mean "wheel 100". On the contrary, the parking brake 20 is "locked" when it blocks the rotation of the wheel 100 relative to the vehicle 1000. Conversely, unless otherwise indicated, the parking brake 20 is "unlocked" when it does not block the rotation of the wheel 100 relative to the vehicle 1000.

[0071] In a particular embodiment, the parking brake 20 is of the drum or disc brake type. A disc brake type parking brake 20 generally comprises pads that clamp the discs of the wheel 100. A drum brake type parking brake 20 comprises a fixed plate, perpendicular to the axis of a drum rotatably connected to a wheel, supporting segments fitted with circular friction linings that are pushed radially against the drum.

[0072] The parking brake can be integrated or external, i.e., juxtaposed, to the wheel motor. In the case of brakes integrated into the wheel motor, they can be single-disc or multi-disc dry or oil-lubricated brakes.

[0073] In a particular embodiment, the parking brake 20 is actuated by moving a locking finger in translation. The locking finger cooperates with the wheel 100 to prevent its rotation when the parking brake 20 is engaged.

[0074] In a particular embodiment, the parking brake 20 is actuated by an electric actuating motor (not shown). Alternatively, the parking brake 20 includes another type of actuator, for example a hydraulic actuator or a pneumatic actuator.

[0075] In a particular embodiment, the parking brake 20 is an electromagnetically actuated friction brake, applied by a spring and released by current. This brake uses a friction disc made of organic material and rubs against metallic surfaces.

[0076] In the embodiment shown, the parking brake 20 is arranged so as to be able to block the rotation of a wheel 100 of the vehicle 1000. However, it is also possible to consider, without departing from the scope of the invention, a parking brake 20 arranged in a different configuration, for example arranged so as to be able to block the rotation of an axle attached to a pair of wheels, or so as to be able to block the rotation of any other element of the drivetrain of the vehicle 1000.

[0077] As illustrated by [Fig.1], the vehicle 1000 further includes a wheel controller 200 whose functionalities are described in more detail with reference to Figures 4 to 8.

[0078] Figure 2A is a top-view representation of an articulated vehicle in a turn, in which the invention can be implemented. As illustrated by Figure 2A, the vehicle 1000 has a central articulation point linking the front part and the The rear section of the chassis. Thus, to make a turn, the front chassis pivots on the horizontal plane relative to the rear chassis. The steering angle therefore depends directly on the articulation angle. This property is advantageous because it allows articulated vehicles (such as articulated loaders) to be used for tasks requiring high maneuverability.

[0079] It can also be seen in this figure that vehicle 1000 is turning to the right. If this vehicle 1000 were to be placed in a position to turn to the left, the right wheels would move apart, while the left wheels would move together. It can be seen that to change the steering angle, the wheels must either roll on the ground or slip significantly. If the wheels slip, the stresses on the tires, the ground, and the steering components are considerable. Furthermore, driving becomes difficult, and the maneuver risks damaging the ground.

[0080] Figure 2B is a top-view representation of a non-articulated vehicle in a turn, in which the invention can be implemented. As illustrated by Figure 2B, to make a turn, the wheels of the non-articulated vehicle pivot, for example around an axis located at each end of an axle and generally perpendicular to that axle.

[0081] As before, since the center of the wheel contact point is not perfectly aligned with the steering pivot, the wheels must rotate when the steering angle is changed. It is advantageous to design the steering system so that the wheels rotate when the steering angle is changed while stationary, as this minimizes stress on the steering system. The disadvantages in the case where the wheels are locked are the same as for the articulated machine.

[0082] Fig. 3 is a schematic representation of a vehicle equipped with wheel motors and in which a wheel controller is mounted.

[0083] As illustrated by [Fig.3], the vehicle 1000 comprises four wheels 100, each equipped with a wheel motor 10, and a parking brake 20. The wheel motors are connected, via one or more data buses, to a wheel controller 200 whose functionalities are described in more detail with reference to Figures 4 to 8.

[0084] In one particular implementation, the data buses are CAN (Controller Area Network) type buses, for example, conforming to the ISO 118987 standard. The use of CAN type buses is advantageous because it allows several electronic devices to be connected to the same cable, thus avoiding the use of dedicated cables for the transmission of each piece of information. Other types of buses are of course possible, such as FlexRay, Ethernet, LIN (Local Interconnected Network), MOST (Media Oriented System Transport), or SAE J1850.

[0085] According to a particular implementation, the wheel controller 200 is a component of an electronic control unit (ECU) or is connected to such an ECU. An ECU is known per se, an embedded system configured to control a plurality of physical devices within the vehicle 1000. This ECU can determine the state of the vehicle 1000 and the commands actuated by the driver (or the autopilot system) using sensors or based on instructions given by the driver through a human-machine interface including, for example, a joystick or a pedal, but also control actuators, such as wheel motors 10, and / or parking brakes 20.

[0086] Fig. 4 represents modules embedded in a wheel controller, according to a particular embodiment of the invention.

[0087] As illustrated in [Fig. 4], the wheel controller 200 includes, in particular:

[0088] - a MOD_ACT module for activating a speed control system for motors- wheels of a vehicle and transmission of a vehicle speed command less than or equal to the current speed of said vehicle;

[0089] - a MOD_BR_R module for applying a parking brake to the wheels of the plurality located at the rear of said vehicle and deactivation of a torque applied by the wheel motors of the vehicle's wheels, said MOD_BR_R module being activated if the vehicle's speed has reached a first threshold value defined according to said speed setpoint and if the vehicle is on an uphill slope;

[0090] - a MOD_BR_F module for applying a parking brake to the wheels of the plurality located at the front of said vehicle and deactivation of a torque applied by the wheel motors of the vehicle's wheels, said MOD_BR_F module being activated if the vehicle's speed has reached the first threshold value and if the vehicle is on a downward slope.

[0091] Their functionalities are described in more detail below with reference to different modes of implementation.

[0092] Figure 5 represents modules embedded in a wheel controller configured in particular to release the brakes (or "unbrake"), according to a particular embodiment of the invention.

[0093] As illustrated in [Fig. 5], the wheel controller 200 includes, in particular:

[0094] - a MOD_TOR module for obtaining a torque to be applied by the wheel motors wheels of a vehicle to keep said vehicle stationary;

[0095] - a MOD_ACT_R module for activating a speed control system for motors- wheels of the wheels located at the rear of said vehicle, transmission of a zero speed command to the servo wheel motors, and freewheeling of the wheels located at the front of said vehicle, said MOD_ACT_R being activated if the vehicle is on an uphill slope;

[0096] - a MOD_ACT_F module for activating a motor speed control system- wheels of the wheels located at the front of said vehicle, transmission of a zero speed command to the servo wheel motors, and freewheeling of the wheels located at the rear of said vehicle, said MOD_ACT_F module being activated if the vehicle is on a downward slope.

[0097] As explained in more detail, the wheel controller considers these MOD_TOR, MOD_ACT_R, and MOD_ACT_F modules specifically in the case where the vehicle is descending a slope forwards, meaning the rear wheels are positioned "uphill." In this case, the weight is transferred to the front axle, and the front wheels are used primarily. The functionalities of these different modules are described in more detail below with reference to various implementation modes.

[0098] Fig. 6 schematically represents an example of the hardware architecture of a 200 wheel controller.

[0099] As illustrated in [Fig. 6], the wheel controller 200 has the hardware architecture of a computer. Thus, the wheel controller 200 includes, in particular, a processor 1, a random access memory 2, a read-only memory 3 and a non-volatile memory 4. It also has communication means 5.

[0100] The read-only memory 3 of the wheel controller 200 constitutes a storage medium according to the invention, readable by the processor 1, on which a computer program PROG according to the invention is stored, comprising instructions for executing steps of the activation process according to the invention. The PROG program defines functional modules of the wheel controller 200, which rely on or control the hardware elements 1 to 5 of the destination device d mentioned above. These functional modules are illustrated in [Fig. 4] or [Fig. 5] by way of no limitation, and are described in more detail below with reference to different embodiments.

[0101] In the implementations described below, the communication means 5 enable the wheel controller 200 to transmit instructions to the wheel motors relating to the type of control and / or the torque value to be achieved, for example through the aforementioned electronic control unit. To this end, the communication means 5 include a wired or wireless communication interface capable of implementing any suitable communication protocol.

[0102] Figure 7 represents, in flowchart form, a particular method of implementation operation of a vehicle braking control process, for example carried out by the wheel controller of the [Fig.4].

[0103] As illustrated in [Fig. 7], the control method comprises a first step S100 during which an instruction to activate a parking brake is received by the wheel controller 200. This request is generated, for example, in response to the detection of an interaction between a graphical interface of the vehicle 1000 and the driver of said vehicle 1000. Alternatively, this request is automatically generated by a safety module of said module, in response to the detection of a possible failure of a component of the vehicle 1000.

[0104] The method further includes a step SI 10 in which it is determined whether a braking torque can be applied by the wheel motors 10 of the wheels 100 so as to reduce the speed of the vehicle, or even to bring it to a stop. If this is not the case, i.e., if it is determined that a braking torque cannot be applied by the wheel motors (option "N"), a step S170 is carried out, which is described in more detail below. If, on the other hand, it is determined that a braking torque can be applied by the wheel motors (option "Y"), a step S120 is carried out in which it is determined whether the vehicle's speed is below a certain threshold value, referred to as the "third threshold value". This third threshold value is, for example, equal to 0.5 km / h.

[0105] If this is the case, i.e., if the vehicle speed is below the third threshold value, a step S130 is implemented, activating a speed control system for the wheel motors of vehicle 1000 and transmitting a vehicle speed command less than or equal to the current speed of said vehicle. This step S130 is implemented, for example, by the MOD_ACT module of the wheel controller 200.

[0106] Activating speed control to apply braking torque is advantageous because the control is performed in the wheel motor, which integrates a drive, thus reducing latency related to communication between the wheel motor and a vehicle controller not located in a wheel. Furthermore, this feature offers finer braking control.

[0107] In particular embodiments, the speed setpoint is equal to zero. In this way, the vehicle's speed is reduced to zero or almost zero, for example 0.2 m / s. This speed is achieved by applying a braking torque to reduce the vehicle's speed.

[0108] Returning to step S120, if on the other hand the vehicle speed is greater than or equal to the third threshold value, this step S120 is repeated until the vehicle speed is less than this third threshold value.

[0109] The method further includes a step S140 in which it is determined whether the vehicle speed has reached a first threshold value defined as a function of said speed setpoint obtained in step S130. In particular embodiments, this first threshold value is equal to the speed setpoint. In particular embodiments, this first threshold value is equal to zero. In In specific implementation methods, it is determined whether the vehicle's speed has reached this first threshold value for a predetermined period. This predetermined period is, for example, one minute.

[0110] If this is not the case (S 140, selection "N"), this step is repeated. If, however, it is determined that the vehicle speed has reached this first threshold value (S 140, selection "Y"), the braking torque applied to each of the wheel motors of vehicle 1000 to reach this first threshold value is stored in non-volatile memory, such as non-volatile memory 4 of the wheel controller 200. These stored torque values ​​can be reused when restarting vehicle 1000.

[0111] The braking method further includes a step S160 in which it is determined whether the use of only part of the vehicle's parking brakes is sufficient to hold the vehicle stationary. To do this, a comparison is made between the braking torque values ​​stored in step S150 and the maximum torque values ​​that can be generated by the wheel motors.

[0112] If this is not the case, i.e., if the use of only some of the parking brakes 20 of the vehicle 1000 is not sufficient to keep the vehicle stationary (S 160, choice "N"), a step S200 is implemented in which all the parking brakes of all the wheels 100 of the vehicle are locked.

[0113] If, however, part of the vehicle's parking brake is sufficient to keep the vehicle stationary (S 160, choice "Y"), a step S170 is implemented during which it is determined whether the vehicle is on an uphill or downhill slope. This step is implemented, for example, by analyzing the data transmitted by an inertial measurement unit (IMU) fitted to the vehicle 1000, and received by this wheel controller 200. If it is determined that the vehicle is on an uphill slope (S 170, choice "Y"), a parking brake is applied to the wheels located at the rear of the vehicle, and an instruction is sent to the wheel motors of said wheels, so that they no longer deliver torque (step S180). This step S180 is implemented, for example, by the MOD_BR_R module of the wheel controller 200.

[0114] If, however, it is determined in step S170 that the vehicle is on a downward slope (S170, choice "N"), a parking brake is applied to the wheels located at the front of said vehicle, and an instruction is sent to the wheel motors of said wheels, so that they no longer deliver torque (step S180). This step S190 is implemented, for example, by the MOD_BR_F module of the wheel controller 200.

[0115] The method further includes a step S210, implemented after steps S180 or S190, during which the wheel controller 200 checks whether the position of the vehicle 1000 has changed since the parking brakes were locked. More precisely, the wheel controller 200 determines whether the vehicle's position has moved by more than a threshold value, known as the "second threshold value," since the parking brakes were engaged. This step is implemented, for example, after a certain amount of time has elapsed since the brakes were engaged. This distance is determined, for example, from data transmitted by an inertial measurement unit (IMU). The second threshold value is, for example, 10 cm. Movement of the vehicle 1000 while the parking brakes are engaged is due, for example, to unstable ground (e.g., gravel or loose soil) and / or loading the vehicle 1000 after the parking brakes were engaged and / or the use of an implement on the vehicle 1000, such as a platform or crane.

[0116] During this step S210, if it is determined that the vehicle's displacement is less than or equal to the second threshold value (or that the vehicle is stationary if this second threshold value is equal to zero), this step S210 is regularly repeated, for example at a predetermined frequency, in order to ensure that the vehicle does not slip.

[0117] If, on the other hand, it is determined during this S210 step that the vehicle has moved a distance greater than this second threshold value, the controller then transmits an instruction so that all parking brakes are locked.

[0118] In a particular embodiment, the method for controlling the braking of a vehicle further includes steps S300-SS70 of the braking control method illustrated in [Fig. 8] (and described in more detail below). In this particular case, the braking and subsequent stopping of the vehicle are followed by the vehicle resuming its movement.

[0119] This braking control method allows, on the one hand, for dynamic braking to be activated by engine braking, which allows for energy recovery and a smooth stop whenever sufficient, on the other hand for a mechanical brake to be activated when engine braking is not sufficient, and then for only the number of brakes necessary for parking to be activated, which allows an axle to be freed when possible.

[0120] This process therefore allows for safe modulation of braking, i.e. to allow for gentle braking, possibly to use the energy recovery option offered by engine braking, while allowing the application of all brakes if necessary, for a pleasant and safe driving experience.

[0121] Fig. 8 represents, in flowchart form, a particular method of implementing a method for controlling the braking of a vehicle, for example carried out by the wheel controller of Fig. 5.

[0122] Unlike the previous braking control method illustrated with reference to [Fig. 7], this braking control method aims to facilitate wheel steering. of the vehicle while it is stationary, before the vehicle is restarted.

[0123] As illustrated in [Fig. 8], the braking control method includes a first step S300 in which the wheel controller determines whether the driver (or the autopilot system) wishes to move the vehicle and / or steer the vehicle's wheels. Generally, this step involves the wheel controller receiving a request to move the vehicle and / or steer the vehicle's wheels. This request is generated, for example, following the analysis of data received from at least one of the following:

[0124] - a sensor positioned on the steering wheel, and the steering wheel is then, for example, a steering wheel dynamometer capable of measuring steering torque and / or angle;

[0125] - a steering angle sensor mounted on the vehicle's steering column 1000;

[0126] - an angle sensor fitted to a wheel of the vehicle;

[0127] - a rotation speed sensor fitted to vehicle 1000 (for example the control unit inertial (previously mentioned); and / or

[0128] - an actuator, such as a pedal, a handle - sometimes referred to by the name English "joystick" -, a push button, or any kind of human-machine interface controlling the movement of the vehicle, as well as a remote control, or an autonomous control.

[0129] If this is not the case, i.e., if the controller does not detect that the driver (or the autopilot system) wants to move the vehicle and / or turn the vehicle's wheels (S300, choice "N"), the parking brakes are kept locked (step S310), and this step S300 is repeated, for example at a regular frequency.

[0130] If, however, it is determined that the driver (or the autopilot system) wishes to move the vehicle and / or steer the vehicle's wheels (S300, choice "Y"), the controller determines, during a step S320, whether the vehicle's orientation around a transverse axis changes while it is stationary. In other words, the controller 200 determines whether the slope on which the vehicle is positioned changes while it is stationary. This step is implemented, for example, by analyzing data from an inertial measurement unit (IMU) fitted to the vehicle.

[0131] If this is not the case, i.e., if it is considered that the orientation of the vehicle around a transverse axis does not change (S320, choice "N"), step S330 is implemented during which the torque values ​​stored during step S150 previously described with reference to [Fig.7] are accessed.

[0132] If, on the other hand, it is considered that the orientation of the vehicle around a transverse axis is changing and / or if no torque value has been previously recorded (S320, choice "Y"), a step S340 is implemented during which the wheel motors of all wheels of said vehicle are speed controlled, a speed command is transmitted to said motors, and all parking brakes are released.

[0133] In a particular embodiment, this speed setpoint is zero. The objective of this step S340 is then to be able to hold the vehicle stationary, solely by applying a certain torque and without engaging the parking brakes. Indeed, this step determines the torque exerted by each wheel motor to hold the vehicle in position. Physically, since wheel grip is not perfect and some tire slippage occurs on the ground, the torque to be supplied to each wheel can be determined. This torque can be different for each wheel depending on the slope, the load on the wheel, and the nature of the ground beneath the wheel. For example, if a wheel rests on loose soil or gravel, this measurement will determine that the wheel motor cannot transmit more than a certain torque to the ground.

[0134] The method further includes a step S350 in which it is determined whether the vehicle speed has reached a threshold value defined according to the speed setpoint obtained in step S130. In particular embodiments, this threshold value is equal to the speed setpoint obtained in step S340. In particular embodiments, this threshold value is equal to zero. In particular embodiments, it is determined whether the vehicle speed has reached this threshold value for a predetermined period of time. This predetermined period of time is, for example, one minute.

[0135] If this is not the case (S350, choice "N"), this step S350 is repeated. If, on the other hand, it is determined that the vehicle speed has reached this threshold value (S350, choice "Y"), the braking torque applied to each of the wheel motors of the vehicle 1000 to reach this threshold value is stored in a memory, such as the non-volatile memory 4 or the RAM 2 of the wheel controller 200, during a step S360.

[0136] Steps S340 to S360 or step S330 are for example implemented by the MOD_TOR module of wheel controller 200.

[0137] The braking method of [Fig. 8] further includes a step S370 implemented after step S330 or S360, during which it is determined whether two wheel motors on the same axle can deliver the braking torque obtained in step S330 or S360. If this is not the case (S370, option "N"), a torque control system for the wheel motors of all wheels of said vehicle is activated, and a torque command is transmitted to these wheel motors so as to keep said vehicle stationary during a step S380.

[0138] If, on the other hand, it is determined in step S370 that only two wheel motors of the same axle can deliver the braking torque obtained in step S330 or S360 (S370, choice "Y"), a step S390 is implemented which is similar to the step S170 previously described.

[0139] During this step S390, it is determined whether the vehicle is on an uphill or downhill slope. This step is implemented, for example, by analyzing the braking torque applied by each of the wheel motors of the vehicle 1000 (and recorded in step S360). Alternatively, this step S390 is implemented by analyzing the data transmitted by an inertial measurement unit (IMU) fitted to the vehicle 1000, and received by this wheel controller 200. If it is determined that the vehicle is on an uphill slope (S390, choice "Y"), speed control of the wheel motors of the rear wheels of said vehicle is activated, a zero speed command is transmitted to the controlled wheel motors, and the front wheels of said vehicle are freewheeled during a step S400. This S400 step is implemented for example by the MOD_ACT_R module of the wheel controller 200.

[0140] If, on the other hand, it is determined in step S390 that the vehicle is on a downward slope (S390, choice "N"), a speed control of the wheel motors of the wheels located at the front of said vehicle is activated, a zero speed command is transmitted to the controlled wheel motors, and the wheels located at the rear of said vehicle are put into freewheel mode during a step S410. This step S410 is implemented, for example, by the MOD_ACT_F module of the wheel controller 200.

[0141] The method further includes a step S420, carried out after steps S400 or S410, in which it is determined whether the vehicle has moved a distance greater than a threshold value, referred to as the "fourth threshold value". If so (S420, option "Y"), the previously mentioned step S380 is carried out, in which a torque control system for the wheel motors of all the wheels of said vehicle is activated, and a torque command is transmitted to these wheel motors so as to keep said vehicle stationary.

[0142] In a particular embodiment, this fourth threshold value corresponds to the second threshold value previously mentioned.

[0143] Otherwise, i.e., if it is determined that the vehicle has not moved or has moved a distance less than or equal to the fourth threshold value (S420, choice "N"), step S430 is implemented during which the braking and servo settings previously made are maintained.

[0144] The braking procedure also includes a step S440, implemented after steps S430 or S380, of verifying that the temperature of at least one of the engines is below a threshold value, referred to as the "fifth threshold value" and / or that the vehicle is not not held stationary by the application of a torque for a period exceeding a threshold value, known as the "sixth threshold value". This step aims to ensure that the wheel motors holding the vehicle stationary do not overheat or are not at risk of overheating. The fifth threshold value is, for example, 70°C, and the sixth value is 10 minutes.

[0145] If the temperature of at least one of the electric motors reaches or exceeds this fifth threshold value or if the torque has been applied for too long (S440, choice "N"), step S450 is implemented during which an instruction to lock all the parking brakes of vehicle 1000 is transmitted to these brakes.

[0146] If, however, it is determined that the temperature of at least one of the engines is below the fifth threshold value and / or that the vehicle has not been held stationary by the application of torque for a period exceeding the sixth value, step S460 is implemented. During this step, the controller determines whether the torque requested by the driver (or the vehicle's autopilot system) is greater than the zero-speed holding torque, or whether the driver (or the autopilot system) has requested a non-zero speed. If not, the control procedure repeats step S440. Otherwise, step S470 is implemented during which an instruction to allow the vehicle to move is issued by the controller.

[0147] In a particular embodiment, the vehicle braking control method illustrated in [Fig.8] further includes steps S100-S220 of the braking control method illustrated in [Fig.7]. In this particular case, the vehicle is started moving and then braked.

[0148] The braking control method thus allows only the necessary number of brakes to be applied for parking, depending on the slope, load, ground conditions, and the grip of each wheel. In particular, the method offers the advantage of allowing an axle to be freed up whenever possible. In other words, the method allows for safe modulation of braking, freeing up an axle to facilitate steering when possible, while still allowing all brakes to be applied if necessary, for a safe and comfortable driving experience. This method also minimizes ground damage, tire wear, and wear on the steering system.

[0149] The invention has been described so far in the case where the wheel controller is integrated into the vehicle, but the invention is nonetheless applicable in the particular case where the wheel controller is integrated into one of the vehicle's wheels. In this particular case, the wheel integrating the controller is called the "master wheel," and the other motors of the other wheels are called "slave wheels."

Claims

Demands

1. Method of controlling the braking of a vehicle (1000) comprising a plurality of wheels (100), each wheel (100) including a wheel motor (10) and being equipped with a parking brake (20), the method being implemented by a wheel controller (200) of the vehicle and comprising: • an activation (S 130) of a speed control of the wheel motors of the vehicle and a transmission of a vehicle speed setpoint less than or equal to the current speed of said vehicle;and following a determination (S 140, "Y") that the vehicle's speed has reached a first threshold value defined according to said speed setpoint, • if the vehicle is on an uphill slope (S 170, "Y"), an application (S 180) of a parking brake to the wheels of the plurality located at the rear of said vehicle and a deactivation of a torque applied by the wheel motors of the vehicle's wheels, • and if the vehicle is on a downhill slope (S 170, "N"), an application (S 190) of a parking brake to the wheels of the plurality located at the front of said vehicle and a deactivation of a torque applied by the wheel motors of the vehicle's wheels.;

2. A braking control method according to claim 1, further comprising, following the application (S 180, S190) of a parking brake to the wheels located at the front or rear of said vehicle, • a determination (S210, "Y") of a change in the position of the vehicle greater than a threshold value, referred to as the "second threshold value"; and, • an application (S220) of a parking brake to all the wheels of the vehicle.

3. A braking control method according to claim 1 or 2, wherein the activation (S 130) of a speed control system is implemented after determining (SI 10) that a torque can be applied by each of the vehicle's motors so as to reduce the speed of said vehicle, and after determining (S 120) that the speed of said

4.

5. vehicle is below a threshold value, called the "third threshold value". A braking control method according to any one of claims 1 to 3, further comprising: • obtaining (S360, S330) a torque to be applied by the wheel motors of the vehicle's wheels to keep said vehicle stationary; • if the vehicle is on an uphill slope (S390, "Y"), an activation (S400) of a speed control of the wheel motors of the wheels located at the rear of said vehicle, a transmission of a zero speed command to the controlled wheel motors, and a freewheeling of the wheels located at the front of said vehicle; • and if the vehicle is on a downward slope (S 170, "N"), an activation (S410) of a speed control of the wheel motors of the wheels located at the front of said vehicle, a transmission of a zero speed command to the controlled wheel motors, and a freewheeling of the wheels located at the rear of said vehicle. A method for controlling the braking of a vehicle (1000) comprising a plurality of wheels (100), each wheel (100) including a wheel motor (10) and being equipped with a parking brake (20), the method being implemented by a wheel controller (200) of the vehicle and comprising: • obtaining (S360, S330) a torque to be applied by the wheel motors of the vehicle's wheels to keep said vehicle stationary; • if the vehicle is on an uphill slope (S390, "Y"), an activation (S400) of a speed control of the wheel motors of the wheels located at the rear of said vehicle, a transmission of a zero speed command to the controlled wheel motors, and a freewheeling of the wheels located at the front of said vehicle; • and if the vehicle is on a downward slope (S 170, "N"), an activation (S410) of a speed control system for the wheel motors of the wheels located at the front of the vehicle, a transmission of a zero speed command to the servo-motors-wheels, and a freewheeling of the wheels located at the rear of said vehicle.

6. A braking control method according to claim 5, further comprising an activation (S380) of a torque control of the wheel motors of all the wheels of said vehicle and a transmission of a torque command intended to keep said vehicle stationary, if said vehicle has moved a distance greater than a threshold value, referred to as "fourth threshold value" (S420, "Y").

7. A braking control method according to claim 5 or 6, further comprising a check (S440) that the temperature of at least one of the motors is below a threshold value, referred to as the "fifth threshold value" and / or that said vehicle is not being held stationary by the application of a torque for a period exceeding a threshold value, referred to as the "sixth threshold value"; if so, a transmission (S470) of a command to allow movement of the vehicle; and if not, an application (S450) of a parking brake to the wheels of said vehicle.

8. A braking control method according to any one of claims 5 to 7, further comprising an activation (S330) of a speed control of the wheel motors of all the wheels of said vehicle, a transmission of a zero speed command to the controlled wheel motors, and a release of all the parking brakes, following a determination (S320, "Y") that the orientation of the vehicle is changing while it is stationary.

9. A braking control method according to any one of claims 5 to 8, further comprising: • activating (S 130) a speed control system for the vehicle's wheel motors and transmitting a vehicle speed command lower than the vehicle's actual speed; and following a determination (S 140, "Y") that the vehicle speed has reached a first threshold value defined according to said speed command, • if the vehicle is on an uphill slope (S 170, "Y"), applying (S 180) a parking brake to the rear wheels of the plurality of wheels on the vehicle and deactivation of a torque applied by the wheel motors of the vehicle's wheels, • and if the vehicle is on a downward slope (S 170, "N"), an application (S 190) of a parking brake to the wheels of the plurality located at the front of said vehicle and a deactivation of a torque applied by the wheel motors of the vehicle's wheels.

10. Computer program (PROG) comprising instructions for implementing a braking control method according to any one of claims 1 to 4 or a braking control method according to any one of claims 5 to 9, when said program is executed by a processor.

11. Wheel controller (200) of a vehicle (1000) comprising a plurality of wheels (100), each wheel (100) including a wheel motor (10) and being equipped with a parking brake (20), the controller being configured to implement a braking control method according to any one of claims 1 to 4 or a braking control method according to any one of claims 5 to 9.

12. Vehicle (1000) comprising a plurality of wheels (100), each wheel (100) including a wheel motor (10) and being equipped with a parking brake (20), and in which is mounted a wheel controller (200) according to claim 11.

13. Wheel (100) in which is mounted a wheel controller (200) configured to implement a braking control method according to any one of claims 1 to 4 or a braking control method according to any one of claims 5 to 9.