Method for controlling the braking of a vehicle and associated wheel controller

Abstract

The invention relates to a method for controlling the braking of a vehicle (1000) comprising a plurality of wheels (100), each including an in-wheel motor (10) and being provided with a parking brake (20). The method comprises: activating a speed control of the in-wheel motors (10) of the vehicle (1000) and transmitting a vehicle speed setpoint lower than the current speed of the vehicle (1000); if the vehicle (1000) is on an upward slope, applying a parking brake (20) to the wheels (100) of the plurality located at the rear of the vehicle and deactivating torque applied by the in-wheel motors (10) of the wheels of the vehicle (1000); and if the vehicle (1000) is on a downward slope, applying a parking brake (20) to the wheels (100) of the plurality located at the front of the vehicle (1000) and deactivating torque applied by the in-wheel motors (10) of the wheels of the vehicle (1000).

Description

METHOD FOR CONTROLLING VEHICLE BRAKES AND ASSOCIATED WHEEL CONTROLLER Description 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] Motor vehicles generally consist of axles that carry wheels and support the vehicle's body relative to the wheels. Examples of such vehicles include wheeled agricultural machinery, construction equipment, tillage equipment, and load-moving machinery. These axles are driven by an engine located away from the wheels, via a transmission mechanism. These vehicles are typically equipped with parking brakes to ensure they remain stationary, even on inclines. The parking brakes are installed on the transmission, either 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 acts as a bearing for the wheel. Physically, the motor is essentially integrated into the wheel. The wheel motor therefore not only drives the wheel but also provides mechanical support to the vehicle body relative to the wheel. In this way, the drive torque applied to each wheel is directly controlled by its motor, eliminating the need for a differential drive. When driving, wheel motors provide engine braking and can also provide mechanical braking, particularly for parking. Braking 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 vehicle with four motors and two axles... It is possible to consider having 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 engine braking—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 incentivizes 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, activation of the braking mechanism causes all wheels to lock, which does not facilitate a steering maneuver when the vehicle is stationary, i.e., when the vehicle is not moving longitudinally.

[0005] Furthermore, current in-wheel motors, especially those with electric drive, tend to overheat at very low rotational speeds. Although they offer engine braking and hold-on capabilities—that is, the ability to transmit torque at zero or low rotational speed, enabling engine braking followed by a smooth stop, as well as very gradual restarts on inclines, and also 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 stop, which deprives the vehicle of the advantages of engine braking and stopping, and also eliminates 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(s) 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 motor- wheel and being equipped with a parking brake, the process being implemented by a wheel controller of the vehicle and comprising:

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

[0009] - if the vehicle is on an uphill slope, application of a parking brake to the rear wheels of the plurality of wheels located at the rear of said vehicle and deactivation of the 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 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.

[0011] When a vehicle is positioned on a slope, the load on each axle can vary considerably. Therefore, unlike prior art braking techniques that unevenly distribute braking force by braking only one axle out of two, this invention applies 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) are generally the rear axle(s), and conversely, when the vehicle is on a downhill slope, the most heavily loaded axle(s) are generally the front axle(s).

[0012] Furthermore, the invention aims, as far as possible, to avoid applying the 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 significant forces to steer the vehicle.

[0013] Generally speaking, the steps of a process should not be interpreted as being linked to a notion of temporal succession.

[0014] In particular modes of implementation, the method of 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 specific implementation modes, the first threshold value is equal to the speed setpoint.

[0016] In certain implementation modes, the speed setting is 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 specific implementation modes, it is determined that the vehicle's speed has reached a first threshold value (for example, 0.2 m / s) defined according to the aforementioned speed setpoint (for example, 0 m / s), and this for a predetermined period. This predetermined period is, for example, one minute.

[0018] In specific implementation methods, the process further includes, following the application of a parking brake to the wheels located at the front or rear of said vehicle,

[0019] - a determination of a change in the vehicle's position exceeding a threshold value, known as the "second threshold value"; and,

[0020] - 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 certain implementation modes, the change in the vehicle's position is due to unstable ground or ground collapse.

[0023] In particular modes of implementation, 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 specific implementation methods, the process also includes:

[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 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.

[0028] Thus, after the vehicle has stopped, the constraint exerted by the parking brakes is released, a torque aimed at keeping the vehicle stationary is exerted, and 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, activation of a speed control system for 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;

[0032] - and if the vehicle is on a downward slope, an activation 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.

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

[0034] In particular modes of implementation, the process 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 modes of implementation, the process according to this second aspect further includes a check that the temperature of at least one of the engines is below a threshold value, called 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, called the "sixth threshold value"; if so, a transmission of a command aimed at enabling movement of the vehicle; and otherwise, 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 drive temperature is below a threshold value and / or verifying that the DC current supplied by the battery is below a threshold value. In specific implementations, the method according to this second aspect further includes activating speed control for the wheel motors of all the vehicle's wheels, transmitting a zero speed command to the controlled wheel motors, and releasing all parking brakes, following a determination that the vehicle's orientation is changing while it is stationary.

[0038] In specific implementation methods, the process according to this second aspect further includes:

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

[0040] - if the vehicle is on an uphill slope, application of a parking brake to the rear wheels of the plurality of wheels located at the rear of said vehicle and deactivation of the 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 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.

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

[0043] This program can use any programming language, and be in the form of source code, object code, or code somewhere 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 may 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 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 uploaded to a network such as the Internet.

[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 conforming to the first or second aspect.

[0049] In the remainder of this document, the term "wheel controller" refers to a controller of at least one wheel of the vehicle in which it 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 conforming to the first or second aspect.

[0052] In specific implementation modes, 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] Figure 1 is a front view representation of a vehicle in which a wheel controller is mounted, according to an example of implementation of the invention;

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

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

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

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

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

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

[0061] [Fig. 7] Figure 7 represents, in flowchart form, a particular method of implementing a vehicle braking control process, for example executed by the wheel controller in Figure 4; and,

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

[0063] Figure 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] In general, a "vehicle" within the meaning 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 specific implementation modes, the vehicle is a wheel loader, a multi-function tool carrier, a forklift, a tandem roller, a compact mini loader, or an autonomous agricultural machine.

[0066] As illustrated in Figure 1, vehicle 1000 is, in this example, an articulated loader. A loader's defining characteristic is its ability to quickly transport or move large quantities of materials, particularly during earthmoving operations. To achieve this, loader 1000 is equipped with, among other things, 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 unit 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 unit, and in this case, the vehicle 1000 comprises four drive units, forming a four-wheel drive transmission for the vehicle 1000.

[0068] It should be noted that the number of wheels 100 equipping 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 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 unit 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 unit carries a wheel 100, and the drive unit supports the body of the vehicle 1000 relative to this wheel 100.

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

[0071] In a particular implementation, 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 has a fixed plate, perpendicular to the axis of a drum that is rotationally 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., attached to the wheel motor. In the case of brakes integrated into the wheel motor, they can be single-disc or multi-disc brakes, either dry or oil-lubricated.

[0073] In a particular implementation, the parking brake 20 is actuated by the translational movement of a locking finger. The locking finger cooperates with the wheel 100 to prevent its rotation when the parking brake 20 is engaged.

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

[0075] In a particular implementation, 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 in Figure 1, the 1000 vehicle also includes a 200 wheel controller 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 in Figure 2A, the vehicle 1000 has a central articulation point connecting the front and rear sections 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] We can also see in this figure that vehicle 1000 is turning to the right. If this vehicle were to be positioned to turn to the left, the right wheels would move apart, while the left wheels would move together. It is clear that to change the steering angle, the wheels must either roll on the ground or slip significantly. If the wheels slip, considerable stress is placed on the tires, the ground, and the steering components. 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 in 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 mechanism. The disadvantages when the wheels are locked are the same as for an articulated machine.

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

[0083] As illustrated in Figure 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 a particular implementation, the data buses are CAN (Controller Area Network) type buses, for example, those conforming to the ISO 118987 standard. Using CAN buses is advantageous because it allows multiple electronic devices to be connected to the same cable, thus avoiding the need for dedicated cables to carry each piece of information. Other bus types are of course possible, such as FlexRay, Ethernet, LIN (Local Interconnected Network), MOST (Media Oriented System Transport), or SAE J1850.

[0085] In a particular implementation, the wheel controller 200 is a component of, or connected to, an electronic control unit (ECU). An ECU is a known 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] Figure 4 represents modules embedded in a wheel controller, according to a particular embodiment of the invention.

[0087] As illustrated in Figure 4, the 200 wheel controller includes, among other things:

[0088] - a MOD_ACT module for activating a speed control of the wheel motors of a vehicle and for transmitting 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 for deactivating 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 instruction 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 for deactivating 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 implementation methods.

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

[0093] As illustrated in Figure 5, the 200 wheel controller includes, among other things:

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

[0095] - a MOD_ACT_R module for activating a speed control of the wheel motors of the wheels located at the rear of said vehicle, for transmitting a zero speed command to the controlled wheel motors, and for free-wheeling 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 speed control of the wheel motors of the wheels located at the front of said vehicle, for transmitting a zero speed command to the controlled wheel motors, and for free-wheeling 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 the MOD_TOR, MOD_ACT_R, and MOD_ACT_F modules specifically when the vehicle is descending a slope forwards, meaning the rear wheels are positioned higher. 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] Figure 6 schematically represents an example of the hardware architecture of a 200 wheel controller.

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

[0100] The read-only memory 3 of the wheel controller 200 constitutes a recording medium according to the invention, readable by the processor 1 and on which a program is recorded A PROG computer program according to the invention, 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 Figure 4 or Figure 5 by way of no limitation, and are described in more detail below with reference to different implementation methods.

[0101] In the implementation modes 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 previously mentioned 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 implementing a vehicle braking control process, for example executed by the wheel controller in Figure 4.

[0103] As illustrated in Figure 7, the control process includes 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 S110 in which it is determined whether a braking torque can be applied by the wheel motors 10 of the wheels 100 in such a way 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 (choice "N"), a step S170 is implemented, 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 (choice "Y"), a step S120 is implemented in which it is determined whether the vehicle's speed is below a certain threshold value, called the "third threshold value." This third threshold value is, for example, 0.5 km / h.

[0105] If this is the case, i.e., if the vehicle speed is below the third threshold value, an S130 step will activate the speed control of the vehicle's wheel motors. and the transmission of a vehicle speed command less than or equal to the current speed of said vehicle is implemented. This S130 step 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 within the wheel motor, which incorporates a variable frequency drive. This reduces latency associated with communication between the wheel motor and a vehicle controller not located in the wheel. Furthermore, this feature provides finer braking control.

[0107] In certain implementation modes, the speed setpoint is zero. In this way, the vehicle's speed is reduced to zero or near 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 according to the speed setpoint obtained in step S130. In certain implementations, this first threshold value is equal to the speed setpoint. In other implementations, this first threshold value is equal to zero. In other implementations, it is determined whether the vehicle 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 (S140, selection "N"), this step is repeated. If, however, it is determined that the vehicle speed has reached this first threshold value (S140, 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 procedure further includes a step S160 in which it is determined whether using only part of the vehicle's parking brakes is sufficient to hold the vehicle stationary. This is done by comparing the braking torque values ​​stored in step S150 with 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 vehicle's parking brakes 20 1000 is not sufficient to keep the vehicle stationary (S160, choice "N"), a step S200 is implemented in which all the parking brakes on all 100 wheels of the vehicle are locked.

[0113] If, however, a portion of the vehicle's parking brake is sufficient to keep the vehicle stationary (S160, option "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 vehicle 1000, and received by this wheel controller 200. If it is determined that the vehicle is on an uphill slope (S170, option "Y"), a parking brake is applied to the rear wheels 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] However, if it is determined at step S170 that the vehicle is on a downward slope (S170, option "N"), a parking brake is applied to the front wheels of the vehicle, and an instruction is sent to the wheel motors of those 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 process 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 engaged. More precisely, the wheel controller 200 determines whether the vehicle's position has changed by a distance greater than a threshold value, referred to as the "second threshold value," since the parking brakes were engaged. This step is implemented, for example, after a certain 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.The movement of vehicle 1000 while the parking brakes are locked is for example due to unstable ground (for example composed of gravel or loose soil) and / or loading of vehicle 1000 after the parking brakes are locked and / or use of a tool fitted to vehicle 1000, such as a platform or a crane.

[0116] During this S210 step, 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 S210 step is regularly repeated, for example at a predetermined frequency, to ensure that the vehicle does not slip.

[0117] If, however, 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 implementation, the vehicle braking control procedure further includes steps S300-SS70 of the braking control procedure illustrated in Figure 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 process allows, on the one hand, for dynamic braking by engine braking, which allows for energy recovery and a smooth stop whenever sufficient, on the other hand, for the activation of a mechanical brake when engine braking is not sufficient, and then for the activation of only the number of brakes necessary for parking, which allows for the freeing of an axle when possible.

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

[0121] Figure 8 represents, in flowchart form, a particular method of implementing a vehicle braking control process, for example executed by the wheel controller in Figure 5.

[0122] Unlike the previous braking control method illustrated with reference to Figure 7, this braking control method aims to facilitate steering the vehicle's wheels while the vehicle is stationary, before restarting the vehicle.

[0123] As illustrated in Figure 8, the braking control process 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 wheels. vehicle. This query is generated, for example, following the analysis of data received from at least one element among:

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

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

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

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

[0128] - an actuator, such as a pedal, a handle - sometimes referred to by the English term "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, option "Y"), the controller determines, during step S320, whether the vehicle's orientation around a transverse axis changes while it is stationary. In other words, 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) installed in the vehicle.

[0131] If this is not the case, i.e., if it is assumed 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 Figure 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 the wheels of said vehicle are speed controlled, a speed command is transmitted to said motors, and all parking brakes are unlocked.

[0133] In a specific implementation mode, this speed setting is zero. The objective of this S340 step is then to keep the vehicle stationary, solely by applying a certain torque and without engaging the parking brakes. This step determines the torque exerted by each wheel motor to maintain the vehicle's position. Physically, since wheel grip is not perfect and some tire slippage occurs, the torque to be supplied to each wheel can be determined. This torque can vary for each wheel depending on the slope, the load on the wheel, and the nature of the ground beneath it. For example, if a wheel is resting 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 defined threshold value based on the speed setpoint obtained in step S130. In certain implementations, this threshold value is equal to the speed setpoint obtained in step S340. In other implementations, this threshold value is equal to zero. In other implementations, 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 S350 step 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 an S360 step.

[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 in Figure 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 the vehicle is activated, and a torque command is transmitted to these wheel motors so as to keep the vehicle stationary during a step S380.

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

[0139] During 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 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 vehicle 1000, and received by this wheel controller 200. If it is determined that the vehicle is on an uphill slope (S390, option "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 wheels located at the front of said vehicle are freewheeled during step S400. This S400 step is implemented for example by the MOD_ACT_R module of the wheel controller 200.

[0140] If, however, it is determined in step S390 that the vehicle is on a downward slope (S390, choice "N"), 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, implemented 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 implemented, in which torque control of the wheel motors of all wheels of the vehicle is activated, and a torque command is transmitted to these wheel motors to keep the vehicle stationary.

[0142] In a particular implementation method, 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 previously made braking and servo settings are maintained.

[0144] The braking procedure also includes a step S440, implemented after steps S430 or S380, to verify that the temperature of at least one of the motors is less than a threshold value, known as the "fifth threshold value," and / or that the vehicle is not held stationary by the application of 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 neither of these is the case, the control procedure repeats step S440. Otherwise, step S470 is implemented, during which the controller issues an instruction to allow the vehicle to move.

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

[0148] The braking control system allows only the necessary number of brakes to be applied for parking, depending on the slope, load, ground conditions, and the traction of each wheel. This system offers the advantage of freeing up an axle whenever possible. In other words, the system allows for safe and controlled braking, freeing up an axle to facilitate steering when feasible, while still allowing full braking when needed, for a smooth and safe driving experience. This system 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 mounted in the vehicle, but the invention remains applicable in the case In particular, the wheel controller is integrated into one of the vehicle's wheels. In this specific case, the wheel containing the controller is called the "master wheel", and the other motors on the other wheels are called "slave wheels".

Claims

Demands

1. 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: - an activation (S130) 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 current speed of said vehicle; and following a determination (S140, "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 (S170, "Y"), an application (S180) 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 downward slope (S170, "N"), an application (S190) 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 (S180, 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 vehicle's position exceeding a threshold value, referred to as the "second threshold value"; and, - an application (S220) of a parking brake to all wheels of the vehicle.

3. A braking control method according to claim 1 or 2, wherein the activation (S130) 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 (S120) that the speed of said vehicle is less than a threshold value, referred to as the "third threshold value".

4. 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 (S170, "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.

5. 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 (S170, "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.

6. A braking control method according to claim 5, further comprising an activation (S380) of a torque control system for the wheel motors of all wheels of said vehicle and a transmission of a torque command intended to maintain said stationary vehicle, if said vehicle has moved a distance greater than a threshold value, called "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 at rest.

9. A braking control method according to any one of claims 5 to 8, further comprising: - an activation (S130) 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 (S140, "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 (S170, "Y"), an application (S180) 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 downward slope (S170, "N"), an application (S190) 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. A computer program (PROG) containing instructions for implementing a braking control method according to any one of the 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.

Images