GB2546602A

GB2546602A - Brake-pull mitigation

Info

Publication number: GB2546602A
Application number: GB1620716.9A
Authority: GB
Inventors: Clegg David; Steward Daren; Hampson Ric
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2015-12-15
Filing date: 2016-12-06
Publication date: 2017-07-26
Anticipated expiration: 2036-12-06
Also published as: DE112016005745B4; GB201522129D0; WO2017102448A1; GB2545437A; DE112016005745T5; GB201620716D0; GB2546602B

Abstract

A method of operating a vehicle braking system 12 that includes a braking devices 20a, 20b each of which is configured to apply brake torque to a wheel at either end of an axle 29a, 29b of the vehicle is provided. The method comprises receiving one or more electrical signals indicative of a brake command. The method further comprises obtaining a value of each of one or more vehicle-related parameters as brake torque is applied to the wheels at either end of the axle 29a, 29b by the braking devices 20a, 20a in response to the brake command, and detecting a brake-pull on the vehicle based on the obtained value(s) of the one or more vehicle-related parameters. The method still further comprises automatically adjusting an amount of brake torque being produced by at least one of the braking devices 20a, 20b to equalize the amount of brake torque being applied across the axle 29a, 29b, thereby mitigating the detected brake-pull. The vehicle parameters may be lateral acceleration and/or a yaw-related parameter. The method may include determining a modified braking force to apply to the wheels based on recorded data indicative of a previously required brake pull mitigation.

Description

BRAKE-PULL MITIGATION

TECHNICAL FIELD

The present invention relates to vehicle brake systems and particularly, but not exclusively, to automatically controlling the operation of a vehicle brake system to mitigate a detected brake-pull. Aspects of the invention relate to a method, to a non-transitory computer-readable storage medium, to a system, to a vehicle, to a vehicle braking system, and to an electronic controller.

BACKGROUND

During normal operation of a hydraulic-based vehicle braking system, hydraulic pressure generated in the system is distributed equally between braking devices configured to apply brake torque to wheels at either end of a given axle of the vehicle (e.g., braking devices disposed on opposite sides of the vehicle and configured to apply brake torque to wheels disposed on opposite sides of the vehicle that are operatively coupled to the same axle). While the cross-axle pressure distribution may be substantially equal, brake torque produced and applied to the axle/wheels by the braking devices as a result of the generated hydraulic pressure may not be.

One reason this may occur is that a friction interface between components of one braking device may be different than the friction interface between components of another braking device. More particularly, the mu-value of the friction interface of one braking device may be different than that of the friction interface of another device. Friction interface differences may result from, for example and without limitation, one or more of: chemistry alterations in a brake pad of a braking device due to, for example, road additives (e.g., salt, antifreeze, etc.); road spray saturating the friction interface; a friction rise due to temperature, vehicle speed, or work-rate of a braking device; and friction loss due to excessive temperature of braking device components (e.g., disc), to cite a few possibilities. Alternative or additional factors or conditions that may influence or cause unequal brake torque production and application include, but are certainly not limited to, the particular geometry of the suspension of the vehicle, the elevation of the terrain being traversed, the road surface-to-tyre contact patch relationship (e.g., road chamber or “tram-lining” as one wheel drops into a groove in the road surface), to cite a few examples.

Unwanted differences in cross-axle brake torque production and application may cause a phenomena known as “brake pull” to occur during which an in-stop, brake-induced yaw moment is applied to the vehicle resulting in the vehicle “pulling” in a direction away from the intended direction of travel (i.e., in the direction of the braking device producing/applying more brake torque). While such an occurrence does not present an issue or concern as it relates to the stability of the vehicle, it is nonetheless a nuisance to the driver of the vehicle that may adversely affect the driver’s driving experience and comfort, requiring the driver to provide a steering input to cancel the induced yaw and maintain the intended direction of travel.

Accordingly, it is an aim of the present invention to address, for example, the disadvantages identified above.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention relate to a method, to a non-transitory computer-readable storage medium, to a system, to a vehicle, to a vehicle braking system, and to an electronic controller as claimed in the appended claims.

According to one aspect of the invention for which protection is sought, there is provided a method of operating a braking system of a vehicle that includes braking devices each of which is configured to apply brake torque to a respective wheel at either end of an axle of the vehicle. In an embodiment, the method comprises: receiving one or more electrical signals indicative of a brake command; obtaining a value of each of one or more vehicle-related parameters as a brake torque is applied to the respective wheels by at either end of the axle by the braking devices in response to the brake command; detecting a brake-pull on the vehicle based on the obtained value(s) of the vehicle-related parameter(s); and automatically adjusting an amount of brake torque being produced by at least one of the braking devices to equalize the amount of brake torque being applied across the axle, thereby mitigating the detected brake-pull.

According to another aspect of the invention for which protection is sought, there is a provided a system for controlling the operation of a braking system of a vehicle that includes braking devices each of which is configured to apply brake torque to a respective wheel at either end of an axle of the vehicle. In an embodiment, the system comprises means for receiving one or more electrical signals indicative of a brake command; means for obtaining a value of each of one or more vehicle-related parameters as a brake torque is applied to the respective wheels at either end of the axle by the braking devices in response to the brake command; means for detecting a brake-pull on the vehicle based on the obtained value(s) of the vehicle-related parameter(s); and means for automatically commanding an adjustment to an amount of brake torque being produced by at least one of the braking devices to equalize the amount of brake torque being applied across the axle, thereby mitigating the detected brake-pull.

In an embodiment, the receiving, obtaining, detecting, and commanding means comprise an electronic processor having an electrical input, and an electronic memory device electrically coupled to the electronic processor. The electronic processor is configured to access the memory device and to execute the instructions stored therein such that it is configured to: receive the one or more signals indicative of a brake command; obtain the value(s) of the vehicle-related parameter(s); detect the brake-pull on the vehicle based on the obtained value(s) of the vehicle-related parameter(s); and automatically command the adjustment to the amount of brake torque being produced by at least one of the braking devices to equalize the amount of brake torque being applied across the axle to thereby mitigate the detected brake-pull.

According to a still further aspect of the invention for which protection is sought, there is provided an electronic controller for a vehicle having a storage medium associated therewith storing instructions thereon that when executed by the controller causes a vehicle braking system having braking devices each of which is configured to apply brake torque to a respective wheel at either end of an axle of the vehicle to be operated in accordance with the method of: receiving one or more electrical signals indicative of a brake command; obtaining a value of each of one or more vehicle-related parameters as a brake torque is applied to the axle by the braking devices in response to the brake command; detecting a brake-pull on the vehicle based on the obtained value(s) of the vehicle-related parameter(s); and automatically adjusting an amount of brake torque being produced by at least one of the braking devices to equalize the amount of brake torque being applied across the axle, thereby mitigating the detected brake-pull.

According to yet another aspect of the invention for which protection is sought, there is provided a vehicle comprising the system or electronic controller described herein.

According to a further aspect of the invention for which protection is sought, there is provided a vehicle braking system comprising the system or electronic controller described herein.

According to a further aspect of the invention for which protection is sought, there is provided a non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more electronic processors causes the one or more processors to carry out the method described herein.

Optional features of the various aspects of the invention are set out below in the dependent claims.

At least some embodiments of the present invention have an advantage, among potentially others, that when an unequal amount of brake torque is applied across an axle of a vehicle that would ordinarily result brake-pull, the amount of brake torque being produced by at least one of a plurality of braking devices operatively coupled to the axle/wheels is automatically adjusted to equalize the cross-axle applied brake torque. In at least some embodiments, the respective amounts of brake torque being produced by more than one of the braking devices are adjusted so as to maintain the total amount of brake torque being applied to the axle/wheels at a level that is approximately equal to the total amount of demanded brake torque. As a result, the unintended pulling of the vehicle in direction away from the intended direction of travel is mitigated (i.e., eliminated or at least substantially reduced) without requiring a steering input on the part of the driver.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description or drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the following figures in which: FIG. 1 is a side view of an illustrative embodiment of a vehicle having a braking system comprising one or more sensors, a control means (e.g., an electronic control unit), and a plurality of braking devices; FIG. 2 is a schematic and block diagram of an illustrative embodiment of a vehicle having a braking system; and FIGS. 3-6 are flow diagrams depicting various steps of illustrative embodiments of a method of operating a vehicle braking system, such as, for example, the braking system illustrated in FIG. 2.

DETAILED DESCRIPTION

The system and method described herein may be used to automatically control the operation of a brake system of a vehicle having a plurality of braking devices each of which is configured to apply brake torque to a respective wheel at either end of an axle of the vehicle. In an embodiment, the present system and method receive one or more electrical signals indicative of a brake command, obtain a value of each of one or more vehicle-related parameters as brake torque is applied to the axle/wheels by the plurality of braking devices, detect a brake-pull on the vehicle based on the obtained value(s) of the vehicle-related parameter(s), and automatically adjust an amount of brake torque being produced by at least one of the plurality of braking devices to equalize the amount of brake torque being applied across the axle to thereby mitigate the detected brake-pull.

References herein to a block such as a function block are to be understood to include reference to software code for performing the function or action specified in which an output is provided responsive to one or more inputs. The code may be in the form of a software routine or function called by a main computer program, or may be code forming part of a flow of code not being a separate routine or function. Reference to function blocks is made for ease of explanation of the manner of operation of a control system according to an embodiment of the present invention.

With reference to FIG. 1, there is shown an illustrative embodiment of a vehicle 10 comprising, among other components, a braking system 12 having a plurality of braking devices configured to apply brake torque to wheels coupled to one or more axles of the vehicle 10 to slow or stop the progress of the vehicle 10. The braking system 12 may comprise any number of types of vehicle braking systems. For purposes of illustration, the description below will be generally limited to a hydraulic-based type of braking system having a plurality of frictional braking devices each of which is configured to apply brake torque to an axle/wheel of the vehicle. One example of such a system is illustrated in FIG. 2. It will be appreciated, however, that the invention described herein may find application with any number of other types of braking systems, such as, for example, those having electro-hydraulic and electro-mechanical actuated frictional braking devices, to cite a few possibilities. Accordingly, the present invention is not intended to be limited to any particular type(s) of braking system(s). The braking system 12, and the system(s) and method(s) described below, may find application with any number of vehicles, including traditional vehicles, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEV), extended-range electric vehicles (EREVs), battery electrical vehicles (BEVs), passenger cars, sports utility vehicles (SUVs), cross-over vehicles, and trucks, to cite a few possibilities. Accordingly, the braking system 12 is not limited to use with any particular type of vehicle. In an embodiment, the braking system 12 generally includes a brake-command input means such as a brake pedal 14, one or more sensors 16 (e.g., sensors 16a-16e in FIG. 2), a control means in the form of an electronic control unit or controller 18 and a plurality of braking devices 20 (e.g., braking devices 20a-20d in FIG. 2), among any number of other components, systems, and/or devices that may or may not be illustrated or otherwise described herein.

As is well known in the art, the brake pedal 14 may be used by the driver of the vehicle 10 to manually input brake commands to the braking system 12. It will be appreciated that in some vehicle applications, the brake-command input means may take the form of a hand-operated lever, but will serve the same purpose as the brake pedal 14 and is equally applicable for aspects and embodiments of the present invention. In an embodiment, movement of the brake pedal 14 may be monitored by one or more sensors 16 (e.g., a brake pedal sensor 16a) to detect that a brake command has been input via the pedal 14, and, in at least some implementations, to detect one or more characteristics relating to the brake command (e.g., speed, severity, force, etc., of the command). Depending on the implementation, the brake pedal 14 may be operatively coupled (i.e., either directly coupled or indirectly coupled through one or more intermediate components) to, for example, a master cylinder assembly, a brake pedal simulator or emulator, or to some other component of the braking system 12. In addition to including a manually-operated brake-command input means, in at least some embodiments, the vehicle 10 may be configured for automatic or automated braking control. As is known in the art, in an instance wherein the vehicle 10 has autonomous driving capabilities and/or includes, for example, a cruise control system, brake commands may be sent to the braking system 12 without any involvement on the part of the driver. In such an embodiment, one or more components or systems 21 of the vehicle 10 (e.g., an electronic control unit of a cruise control system, a vehicle control unit (VCU), etc.) may be configured to generate these “vehicle-initiated” brake commands and to send them to the braking system 12. Accordingly, braking commands may be generated or input to the braking system 12 in a number of different ways.

The sensor(s) 16 are configured to provide information that may be utilized in the operation of the braking system 12, and, in at least some embodiments, the performance of one or more steps of the method(s) described herein. The sensors 16 may comprise any number of different types of sensors, components, devices, modules, systems, etc., configured to monitor, sense, detect, measure, or otherwise determine a variety of parameters, and the sensors may directly sense or measure the conditions or parameters for which they are provided, or may indirectly evaluate such conditions/parameters based on information provided by other sensors, components, devices, modules, systems, etc. Additionally, the sensor(s) may be integrated within a vehicle component, device, module, subsystem, etc., may be stand-alone components, or may be provided according to some other suitable arrangement. Further, the sensors may be directly coupled to the electronic controller 18, indirectly coupled thereto via other electronic devices (e.g., a controller area network (CAN) bus, a system management bus (SMBus), a proprietary communication link, or using another suitable communication technique), or coupled in accordance with some other suitable arrangement known in the art.

In an embodiment, one or more of the sensors 16 are configured to provide an electrical signal indicative of a brake command. An example of such a sensor is brake pedal sensor 16a. The brake pedal sensor 16a is configured to provide one or more electrical signals to, for example, the electronic controller 18 of the brake system 12, that is/are representative of one or more of the position, movement, exerted force, and/or state of the brake pedal 14. In any event, the signal(s) provided by the brake pedal sensor 16a is/are representative of a brake command, for example, a driver-initiated brake command. In an embodiment, the system 12 may include a single brake pedal senor 16a, while in other embodiments system 12 may include multiple brake pedal sensors 16a that may be configured to sense, measure, detect, etc. the same or different parameter(s) and/or condition(s). Each brake pedal sensor 16a may comprise any number of suitable sensors known in the art, including, for example and without limitation, one or more of: an optical sensor, an electro-magnetic sensor, a contact switch, a potentiometer, and/or a force sensor, to cite a few possibilities.

It will be appreciated that while one particular sensor has been described above, in at least some embodiments, one or more additional or alternative sensors 16 may be provided, some or all of which may be configured to generate electrical signals indicative of brake command. More particularly, the braking system 12 may include one or more sensors or components that are suitable to detect and/or measure one or more parameters, including but not limited to: wheels speed (sensors 16b-16e in FIG. 2); longitudinal vehicle acceleration; lateral vehicle acceleration; brake light activation; brake torque applied by a particular braking device; steering wheel angle or position; vehicle yaw; and/or master cylinder output pressure, to cite only a few possibilities. Accordingly, the braking system 12 is not limited to any particular type(s) or number(s) of sensors 16.

As briefly described above, and as illustrated in FIG. 2, the braking system 12 further includes a control means in the form of the electronic controller 18. The controller 18 may include any combination of electronic processing devices, electronic memory devices, input/output (I/O) devices, and/or other known components, and may be configured to, among other things, receive information from the sensor(s) 16 and/or other components/sensors of the vehicle 10, and perform various control and/or communication related functions, including, in at least some embodiments, all or part of the functionality required for carrying out the method described herein. For example, in an embodiment, the controller 18 is configured to receive information from the brake pedal sensor 16a and in dependence thereon, exert a measure of control over the operation of the braking system 12 to cause an appropriate amount of brake torque to be applied to the wheels coupled to one or more axles of the vehicle 10 by the braking devices 20 in order to carry out the brake command.

It is to be understood that the controller 18 can comprise a control unit or computational device having one or more electronic processors (e.g., a microprocessor, a microcontroller, an application specific integrated circuit (ASIC), etc.), and may comprise a single control unit or computational device, or alternatively different functions of the controller 18 may be embodied in, or hosted in, different control units or computational devices. As used herein, the term “controller,” “control unit,” or “computational device” will be understood to include a single controller, control unit, or computational device, and a plurality of controllers, control units, or computational devices collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause the controller 18 to implement the control techniques described herein (including some or all of the functionality required for the method described herein). The set of instructions could be embedded in said one or more electronic processors of the controller 18; or alternatively, the set of instructions could be provided as software to be executed in the controller 18. A first controller or control unit may be implemented in software run on one or more processors. One or more other controllers or control units may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller or control unit. Other arrangements are also useful.

In an illustrative embodiment such as that shown in FIG. 2, the controller 18 comprises an electronic processor 22 having one or more electrical inputs 24 (e.g., one or more of inputs 24a-24f in FIG. 2) and one or more electrical outputs 26. The electronic processor 22 may comprise any suitable electronic processor (e.g., a microprocessor, a microcontroller, an ASIC, etc.) that is configured to execute electronic instructions. The controller 18 may further include an electronic memory device 28 that is either part of or electrically connected to and accessible by the processor 22. The electronic memory device 28 may comprise any suitable memory device and may store a variety of data, information, threshold value(s), lookup tables or other data structures, and/or instructions therein or thereon. In an embodiment, the memory device 28 has information and instructions for software, firmware, programs, algorithms, scripts, applications, etc. stored therein or thereon that may govern all or part of the methodology described herein. The processor 22 may access the memory device 28 and execute and/or use that or those instructions and information to carry out or perform some or all of the functionality and methodology describe herein. Alternatively, some or all of the aforementioned instructions/information may be embedded in a computer-readable storage medium (e.g. a non-transitory or non-transient storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational devices, including, without limitation: a magnetic storage medium (e.g. floppy diskette); optical storage medium (e.g. CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g. EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

In addition to the above, the controller 18 may also be electronically connected to other components of the braking system 12 (e.g., the sensor(s) 16) or the vehicle 10 via any suitable wireless or wired communications (e.g., CAN bus, SMBus, a proprietary communication link, or through some other arrangement known in the art) and can interact with them when or as required.

Depending on the particular implementation of the braking system 12 and/or the vehicle 10, the controller 18 may be a standalone unit dedicated to the braking system 12, may be part of a larger system of the vehicle 10, may be integrated into another electronic control unit or controller of the vehicle 10 (e.g., the functionality of the controller 18 may be integrated into a controller or control unit of a system of the vehicle 10 other than the braking system 12, an integrated vehicle control unit (VCU), or the like), or may be provided in accordance with some other suitable arrangement.

As briefly described above, the braking system 12 includes a plurality of braking devices 20. Each braking device 20 is operatively coupled to one or more drivetrain or driveline components of the vehicle 10 (e.g., output shafts, axles, vehicle wheels, etc.) and is configured to generate and apply a braking torque to that or those components, and thus, directly or indirectly to one or more axles and wheels of the vehicle 10. In an embodiment, each braking device 20 is operatively coupled to a respective wheel of the vehicle such that each braking device 20 is coupled to, and configured to apply brake torque to, a different wheel.

The braking devices 20 may include frictional braking devices, including those associated with disc brakes, drum brakes, and any other suitable frictional braking systems. In one such embodiment, each frictional braking device 20 comprises a caliper, at least one caliper piston, a pair of brake pads, and a brake disc (also called a rotor) that is operatively coupled to an axle of the vehicle 10 and thus a wheel of the vehicle 10 operatively coupled to the axle. As is known in the art, the caliper straddles the rotor and carries the caliper piston so that a braking torque can be applied by the brake pads to opposing sides of the rotor and hence to the axle and wheel to which the braking device is operatively coupled.

In the arrangement shown in FIG. 2, one pair of braking devices 20 (i.e., braking devices 20a and 20b) are operatively coupled to a first (front) axle 29a of the vehicle 10, and thus respective wheels coupled to the first axle 29a, and another pair of braking devices 20 (i.e., braking devices 20c and 20d) are operatively coupled to a second (rear) axle 29b of the vehicle 10, and thus respective wheels coupled to the second axle 29b. It will be appreciated that the axle to which each pair of braking devices 20 are operatively coupled may comprise a continuous axle extending across the vehicle from one wheel to another. Alternatively, the axle may comprise a split axle in which each wheel is coupled to a different shaft or portion of the axle, and the different shafts or portions of the axle are disconnected from each other. Accordingly, for the purposes of this disclosure, the term axle is intended to encompass both continuous and split axle arrangements. In an embodiment, each braking device 20 is located at a respective corner of the vehicle 10 proximate a respective vehicle wheel (e.g., the braking device 20a is located at the front right hand corner, the braking device 20b is located at the front left hand corner, the braking device 20c is located at the rear right hand corner, and the braking device 20d is located at the rear left hand corner), though the present invention is not limited to such an arrangement. In other embodiments, rather the braking system 12 including two pairs of braking devices 20, a single pair of braking devices 20 operatively coupled to one axle of the vehicle 10 may be provided. Accordingly, the present invention is not intended to be limited to any particular number of braking devices 20.

As will be appreciated by one having ordinary skill in the art, in addition to the components described above, the braking system 12 may further include a number of other components. For example, in an embodiment, the braking system 12 may include a master cylinder assembly 30 and one or more brake or hydraulic lines 32 (i.e., hydraulic lines 32a-32c in FIG. 2) to fluidly connect the braking devices 20 to the master cylinder assembly 30 and to allow hydraulic or brake fluid to flow or be communicated therebetween. More particularly, a braking device is actuated when a force is applied onto a piston in the master cylinder assembly that, in turn, causes fluid from a brake fluid reservoir to flow into the master cylinder. As a result, fluid pressure (also referred to as brake pressure) in the braking system is increased, causing brake or hydraulic fluid to be forced through a hydraulic line(s) coupled to the braking device being actuated. When the fluid reaches the braking device, the caliper piston thereof applies a force to the caliper, moving the brake pads towards and ultimately against the rotor. Friction between the brake pads and rotor results in a frictional brake torque being applied to the axle/wheel to which the rotor is coupled.

While the description above has thus far been with respect to an embodiment wherein the braking devices 20 comprise frictional braking devices, it will be appreciated that in other embodiments the braking system 12 may additionally comprise braking devices other than the particular frictional braking devices described above, for example, electric machine braking devices. In an embodiment wherein one or more of the braking devices 20 comprise an electric machine braking device, the device may comprise any suitable electric machine braking device known in the art, such as, for example, a frictional electric machine braking device or a regenerative braking device. In any event, in embodiment wherein the braking devices 20 comprise one or more electric machine braking device(s), each electric machine braking device may operatively coupled to a corresponding wheel (i.e., one wheel to each electric machine braking device).

Whether the braking devices 20 are frictional braking devices alone or a combination of frictional braking devices and one or more other types of braking devices (e.g., regenerative braking devices) the braking devices 20 of the braking system 12 may be operated in unison or individually on a device-by-device basis (e.g., in certain instances, one or more but less than all of braking devices may be operated at a given time).

In any event, and as was described above, it will be appreciated that the present invention is not intended to be limited to any particular type(s) braking systems or braking devices thereof, as the present invention may find application with any number of different types of brake systems and/or braking devices thereof, provided, in an embodiment, that the braking devices have some component of braking force provided by frictional braking.

In an embodiment, operation of the braking system 12, and thus, the braking devices 20, is controlled directly by the controller 18 of the braking system 12. In such an embodiment, when operation of one or more of the braking devices 20 is desired or needed (i.e., in dependence on a received brake command), the controller 18 sends an electrical command signal to an actuator associated with the appropriate braking device(s) 20 causing a brake torque to be applied to one or more axles/wheels of the vehicle 10 by that or those braking devices. In another embodiment wherein, for example, the braking system 12 includes both frictional and regenerative braking capabilities and thus may include a frictional braking subsystem and a regenerative braking subsystem, one or both such subsystems may include a dedicated electronic control unit or controller for controlling the operation of the braking devices thereof. In such an embodiment, the control unit(s) of the frictional and/or regenerative braking subsystems may be electrically connected to, configured for communication with, and operate under the control of the controller 18. For example, in response to a brake command, the controller 18 may send a command signal to the control unit of the frictional braking subsystem in response to which the control unit thereof may cause one or more of frictional braking devices to produce and apply a brake torque to one or more axles/wheels of the vehicle 10. It will therefore be appreciated that the present invention is not intended to be limited to any particular scheme or arrangement for controlling the operation of the braking system 12, as any number of suitable schemes or arrangements may be used.

In addition to the braking system 12 described above, it will be appreciated that the vehicle 10 may include a variety of other systems, components, devices, etc. For example, the vehicle 10 may include a number of sensors in addition to the sensor(s) 16 of the braking device 12, including, for example (and to the extent that such sensor(s) are not already part of the braking system 12), any one or more of: wheel speed sensor(s); gyro sensor(s) to detect yaw, roll, and pitch of the vehicle; vehicle speed sensor(s); longitudinal acceleration sensor(s); engine torque sensor(s); driveline torque sensor(s); throttle valve sensor(s); lateral acceleration sensor(s); accelerator pedal position sensor(s); air suspension sensor(s) (i.e., ride height sensors); wheel position sensor(s); wheel articulation sensor(s); vehicle body vibration sensor(s); sensors for detecting wheels slip; and steering input (e.g., steering angle, steering torque, etc.) sensor(s), among others known in the art. As with the sensors 16 described above, one or more of the additional or alternative sensors of the vehicle 10 may be configured to provide information that may be utilized in the operation of the braking system 12, and, in at least some embodiments, the performance of one or more steps of the method(s) described herein. These sensors may comprise any number of different types of sensors, components, devices, modules, systems, etc., configured to monitor, sense, detect, measure, or otherwise determine a variety of parameters, and the sensors may directly sense or measure the conditions or parameters for which they are provided, or may indirectly evaluate such conditions/parameters based on information provided by other sensors, components, devices, modules, systems, etc. Additionally, the sensor(s) may be integrated within a vehicle component, device, module, subsystem, etc., may be stand-alone components, or may be provided according to some other suitable arrangement. Further, these sensors may be directly coupled to the electronic controller 18, indirectly coupled thereto via other electronic devices (e.g., a controller area network (CAN) bus, a system management bus (SMBus), a proprietary communication link, or using another suitable communication technique), or coupled in accordance with some other suitable arrangement known in the art.

As is known in the art, the vehicle 10 may also include any number of systems, for example, a powertrain system, a chassis management or control system, a steering system, a driveline system, a progress or speed control system (e.g., a cruise control system) to cite a few possibilities; as well as any number of components or modules that may or may not be part of a larger system, for example and without limitation, an integrated vehicle control unit (VCU), to cite just one possibility.

For the purposes of this invention, each of the aforementioned sensors, systems, and components/modules and the functionality corresponding thereto is conventional in the art. As such, detailed descriptions will not be provided, rather the structure and function of each identified sensor, system, and component/module will be readily apparent to those having ordinary skill in the art.

The preceding description of the vehicle 10 and the braking system 12, and the illustration of the vehicle 10 shown in FIG. 2, is only intended to illustrate one vehicle and braking system arrangement, and to do so in a general way. It is certainly contemplated that any number of other arrangements and architectures, including those that differ significantly from the one shown in FIG. 2, may be used instead.

Turning now to FIG. 3, there is shown an example of a method 100 of operating or controlling a braking system of a vehicle that includes a plurality of braking devices configured to apply brake torque to an axle/wheel of the vehicle. For purposes of illustration and clarity only, method 100 will be described in the context of the vehicle 10 described above, and the brake system 12 thereof illustrated in FIG. 2, in particular. It will be appreciated, however, that the application of the present methodology is not meant to be limited solely to such an arrangement. Rather, method 100 may find application with any number of arrangements (i.e., the steps of method 100 may be performed by systems or components of a vehicle or a brake system other than that or those described herein, or vehicle/brake system arrangements other than that or those described above.) Additionally, it will be appreciated that unless otherwise noted, the performance of method 100 is not meant to be limited to any one particular order or sequence of steps or to any particular component(s) for performing the steps.

In an embodiment, method 100 includes a step 102 of receiving one or more electrical signals indicative of a brake command. The electrical signal(s) received in step 102 may be received from a number of sources. In an embodiment, the electrical signal(s) may be received from one or more sensors of braking system 12 (i.e., the sensors 16) or the vehicle 10 that is/are configured to detect either a driver- or vehicle-initiated brake command, or one or more vehicle-related parameter values that is/are indicative of such a brake command. These sensors may include one or more of those identified above, including, but not limited to, the brake pedal sensor 16a, the wheel speed sensors 16b-16d, a lateral acceleration sensor, a longitudinal acceleration sensor, a brake light activation sensor, a master cylinder input pressure sensor, or another suitable sensor. Additionally or alternatively, the electrical signal(s) may be received from a system or component of the vehicle 10 that is separate and distinct from the braking system 12. For example, in certain instances, one or more systems or components of the vehicle 10 may be configured to determine that braking of the vehicle 10 is necessary or desirable, and to generate a command that is sent or communicated to the braking system 12 to effect the desired braking. These systems may include, for example and without limitation, a cruise control system, a vehicle stability control system (SCS), and a VCU of the vehicle, to cite only a few possibilities. Accordingly, it will be appreciated that the present invention is intended to be limited to any particular source from which the electrical signal(s) indicative of a brake command is/are received in step 102.

In an embodiment, the controller 18 of the braking system 12 is configured to receive the electrical signal(s) in step 102 (at, for example, an input 24 of the controller 18 (e.g., input 24c in FIG. 2)); though in other embodiments, different components of the braking system 12 (e.g., control units of a regenerative or frictional braking subsystem) or the vehicle 10 (e.g., a VCU) may be configured to do so.

In response to the signal(s) received in step 102, method 100 may move to a step 104 of obtaining a value of each of one or more vehicle-related parameters, and a step 106 of determining or detecting that the vehicle 10 is experiencing brake-pull based on the value(s) of the vehicle-related parameter(s). In an embodiment, steps 104 and 106 are performed as brake torque is being applied to the axle/wheel(s) of the vehicle 10 by two or more of the plurality of braking devices 20 in response to the brake command.

The value(s) of any number of vehicle-related parameter(s) of interest may be obtained in step 104. For example, in an embodiment, the vehicle-related parameter(s) may comprise one or both of lateral acceleration and one or more yaw-related parameter(s) (e.g., an actual yaw value, a change in yaw, a rate of change in yaw, etc.), though other suitable parameters may certainly be used in addition to or in lieu of those identified above.

The value(s) of the parameter(s) of interest may be obtained from a number of sources. For example, in an embodiment, step 104 comprises receiving one or more electrical signals each indicative or representative of a value of a vehicle-related parameter of interest. In another embodiment, step 104 comprises receiving one or more electrical signals each indicative or representative of a value of a parameter that may be used to derive a value of a vehicle-related parameter of interest, and then deriving (e.g., calculating) value(s) of the vehicle-related parameter(s) of interest using the received value(s). In either embodiment, the electrical signal(s) may be received from one or more sensors of the braking system 12 (i.e., the sensors 16) or vehicle 10 that is/are configured to detect, sense, or measure the vehicle-related parameter(s) of interest or the parameter(s) used to derive the value(s) of the parameter(s) of interest, including, but not limited to, one or more of those sensors identified elsewhere herein (e.g., a lateral acceleration sensor, a sensor for measuring vehicle yaw (e.g., a gyro sensor), or another suitable sensor).

Additionally or alternatively, the electrical signal(s) may be received from a system or component of the vehicle 10 that is separate and distinct from the braking system 12. For example, in certain instances, one or more systems or components of the vehicle 10 may be configured to determine or monitor the vehicle-related parameter(s) of interest or parameter(s) that may be used to derive one or more vehicle-related parameters of interest, and to generate electrical signal(s) representative of value(s) of the parameter(s) that is/are sent or communicated to and used by the braking system 12. These systems may include, for example and without limitation, a cruise control system, an SCS of the vehicle 10, and a VCU of the vehicle 10, to cite only a few possibilities.

Accordingly, it will be appreciated in view of the foregoing that the present invention is not intended to be limited to any particular vehicle-related parameter(s) or way by which value(s) thereof may be obtained in step 104.

As briefly described above, step 106 comprises using the value(s) of the vehicle-related parameter(s) obtained in step 104 to determine or detect whether the vehicle 10 is experience brake-pull. If brake-pull is detected, step 106 may further comprise determining the direction in which the vehicle 10 is being pulled, which may be determined from the parameter value(s) obtained in step 104 or using other information received from one or more components of the braking system 12 or the vehicle 10 and techniques well known in the art.

In an embodiment, step 106 comprises monitoring the vehicle-related parameter(s) of interest and if a change in one of the parameters is detected, then determining or detecting that the vehicle 10 is experiencing brake-pull. In other embodiments, a change in all or a certain subset of a plurality of parameters of interest (i.e., more than one) must be detected before it is determined or detected that brake-pull is occurring.

In yet another embodiment, step 106 comprises monitoring the vehicle-related parameter(s) of interest and if a change in one of the parameters is detected that is greater than (or, in an embodiment, greater than or equal to) a predetermined threshold value corresponding to that particular parameter and programmed into a memory device of or accessible by the component performing step 106 (e.g., the memory device 28 of the controller 18), then further determining or detecting that the vehicle 10 is experiencing brake-pull. In other embodiments, brake-pull is detected only if a change in each of the parameters of interest or a subset of the parameters of interest is greater than (or, in an embodiment, greater than or equal to) respective predetermined threshold values to which those parameters are compared.

In an alternative embodiment, step 106 comprises monitoring the vehicle-related parameter(s) of interest and if the actual value of one of the parameters (as opposed to a change in the value) is greater than (or, in an embodiment, greater than or equal to) a predetermined threshold value corresponding to that particular parameter and programmed into a memory device of or accessible by the component performing step 106 (e.g., the memory device 28 of the controller 18), then determining or detecting that brake-pull is occurring on the vehicle 10. In another embodiment, brake-pull is detected only if the values of all of the parameters of interest or a subset of the parameters of interest are greater than (or, in an embodiment, greater than or equal to) respective predetermined threshold values programmed into a memory device (e.g., the memory device 28 of the controller 18) and to which those parameters are compared. In at least some embodiments, the predetermined threshold value(s) to which the parameter value(s) are compared in step 106 are each less than a corresponding threshold value at which the SCS of the vehicle would intervene to stabilize the vehicle 10.

In still another embodiment, step 106 comprises monitoring the vehicle-related parameter(s) of interest and if the actual value of one of the parameters is less than (or, in an embodiment, less than or equal to) a predetermined threshold value corresponding to that particular parameter and programmed into a memory device of or accessible by the component performing step 106 (e.g., the memory device 28 of the controller 18), then determining or detecting that brake-pull is occurring on the vehicle 10. In another embodiment, brake-pull is detected only if the values of all of the parameters of interest or a subset of the parameters of interest are less than (or, in an embodiment, less than or equal to) respective predetermined threshold values programmed into a memory device (e.g., the memory device 28 of the controller 18) and to which those parameters are compared. Again, in at least some embodiments, the predetermined threshold value(s) to which the parameter value(s) are compared in step 106 are each less than a corresponding threshold value at which the SCS of the vehicle would intervene to stabilize the vehicle 10. Accordingly, it will be appreciated that the present invention is not intended to be limited to any particular way(s) of detecting a brake-pull on the vehicle 10, as any number of ways may be used.

It will be further appreciated that the detection in step 106 of whether the vehicle 10 is experiencing brake-pull may be made in dependence on the prevailing conditions or circumstances surrounding the operation of the vehicle 10. More specifically, whereas particular value(s) of vehicle-related parameter(s) obtained in step 104 while the vehicle 10 is operating under a first set of circumstances/conditions may, in fact, be indicative of the vehicle experiencing brake-pull, when the vehicle is operating under different conditions, that or those same value(s) may not be indicative of the vehicle experiencing brake-pull. Accordingly, in an embodiment, step 106 may take into account various conditions or circumstances, such as, for example and without limitation, road surface or terrain characteristics (e.g., type of surface, roughness, grade, etc), vehicle trajectory (e.g., vehicle is turning or traveling straight), vehicle loading, and/or other useful conditions/circumstances. In doing so, brake-pull is detected for the given operating conditions of the vehicle so as to not detect brake-pull when, in fact, the vehicle is not experiencing brake pull, and vice versa. In an embodiment, this may be accomplished by selecting an appropriate threshold value from a plurality of values that corresponds to the prevailing circumstances/conditions.

In any event, in an embodiment, the controller 18 of the braking system 12 is configured to obtain the parameter value(s) in step 104 and to use that or those value(s) in step 106 to detect or determine whether the vehicle 10 is experiencing brake-pull; though in other embodiments, different components of the braking system 12 (e.g., control units of a regenerative or frictional braking subsystem) or the vehicle 10 (e.g., a VCU) may be configured to do so instead of or in conjunction with the controller 18.

If no brake-pull is detected in step 106, method 100 may terminate or loop back to a previous step (e.g., step 102 or step 104). If, however, brake-pull is detected in step 106, method 100 may proceed to a step 108 of automatically adjusting (or controlling or causing an adjustment to) an amount of brake torque being produced or generated by at least one of a plurality of the braking devices 20 operatively coupled to an axle/wheels of the vehicle 10 (e.g., the braking devices 20a, 20b) to equalize the amount of brake torque being applied across the axle to thereby mitigate the detected brake-pull. Step 108 may be performed in a number of ways, including, but certainly not limited to, those described below.

One way brake torque may be adjusted in step 108 is by increasing the amount of brake torque being produced or generated by at least one of the braking devices 20. More particularly, in an embodiment, step 108 comprises increasing the amount of brake torque being produced by a braking device 20 located on the side of the vehicle 10 opposite the side corresponding to the direction in which the vehicle is being pulled. For example, in an embodiment wherein the vehicle 10 includes braking devices 20a, 20b respectively located at the right and left front corners of the vehicle 10, and a brake-pull is detected that causes the vehicle 10 to pull to the right, the brake torque being produced by the braking device 20b located on the left hand side of vehicle may be increased. Conversely if the detected brake-pull acting on the vehicle 10 causes the vehicle to pull to the left, the brake torque being produced by the braking device 20a located on the right hand side of the vehicle 10 may be increased. In at least some embodiments, rather than adjusting the brake torque being produced by the braking devices located directly across the vehicle from each other (e.g., the braking devices located at the right and left front corners of the vehicle), the adjustment may be between braking devices located at diagonal corners. For example, in an embodiment wherein vehicle 10 includes the braking devices 20a, 20b respectively located at the right and left front corners of the vehicle 10 and the braking devices 20c, 20d respectively located at the right and left rear corners of the vehicle 10, depending on the circumstances, the brake torque being produced by the braking device 20a may be increased and that produced by the braking device 20d may be decreased, or vice versa. Similarly, the brake torque being produced by the braking device 20b may be increased and that produced by the braking device 20c may decreased, or vice versa. Accordingly, the present invention is not limited to any particular adjustment scheme between braking devices. Regardless of how the brake torque being produced by different braking devices is adjusted, in at least some embodiments, the total amount of brake torque being collectively applied by the braking devices 20 is maintained at a level that is approximately equal to the total amount of brake torque demanded by the driver or the vehicle.

Another way brake torque may be adjusted in step 108 is by decreasing the amount of brake torque being produced or generated by at least one of the braking devices 20. More particularly, in an embodiment, step 108 comprises decreasing the amount of brake torque being produced by a braking device 20 located on the side of the vehicle 10 corresponding to the direction in which the vehicle is being pulled. For example, in an embodiment described above wherein vehicle 10 includes braking devices 20a, 20b respectively located at the right and left front corners of the vehicle 10, and a brake-pull is detected that causes the vehicle 10 to pull to the right, the brake torque being produced by the braking device 20a located on the right hand side of the vehicle 10 may be decreased. Conversely if the brake-pull acting on the vehicle 10 causes the vehicle to pull to the left, the brake torque being produced by the braking device 20b located on the left hand side of the vehicle 10 may be decreased.

Yet another way brake torque may be adjusted in step 108 comprises a combination of the ways described above and includes both increasing the amount of brake torque being produced or generated by at least one braking device 20 and decreasing the amount of brake torque being produced or generated by at least one other braking device 20. More particularly, in an embodiment, step 108 comprises a combination of increasing the amount of brake torque being produced by one or more braking devices 20 located on the side of the vehicle 10 opposite the side corresponding to the direction in which the vehicle is being pulled, while also decreasing the amount of brake torque being produced by a braking device 20 located on the side of the vehicle 10 corresponding to the direction in which the vehicle 10 is being pulled. For example, in an embodiment such as that described above wherein the vehicle 10 includes braking devices 20a, 20b respectively located at the right and left front corners of the vehicle 10, and a brake-pull is detected that causes the vehicle 10 to pull to the right, the brake torque being produced by the braking device 20b located on the left hand side of the vehicle 10 may be increased and the brake torque being produced by the braking device 20a located on the right hand side of the vehicle 10 may be decreased. Conversely if the brake-pull acting on the vehicle 10 causes the vehicle to pull to the left, the brake torque being produced by the braking device 20a located on the right hand side of vehicle 10 may be increased and the brake torque being produced by the braking device 20b located on the left hand side of the vehicle 10 may be decreased.

Accordingly, it will be appreciated that the brake torque being produced by one or more braking devices 20 may be adjusted in step 108 any number of ways and in accordance with any number of schemes, and as such, the present invention is not intended to be limited to any particular way(s) of or scheme(s) for doing so.

Just as the brake torque being produced by one or more braking devices 20 may be adjusted in a variety of ways, both the amount by which the brake torque is adjusted may be determined, and the adjustment may carried out, in a number of ways.

In an embodiment, the amount by which to adjust (i.e., increase, decrease, or both) the brake torque being produced or generated by the one or more braking devices may be determined by using one or more of the vehicle-related parameter values obtained in step 104. More particularly, the value(s) obtained in step 104 may be used in conjunction with an appropriately configured lookup table or other data structure that correlates values of the one or more parameter(s) with brake torque adjustment amounts. Accordingly, parameter value(s) received in step 104 may be looked up in the lookup table and the value(s) of the required brake torque adjustment(s) corresponding to that or those values may be determined.

In another embodiment, closed loop feedback may be used to determine the adjustment amount(s). For example, a proportional-integral-derivative (PID) controller may be used to determine the appropriate amount by which the brake torque being produced by one or more braking devices 20 is to be adjusted using, for example, the parameter value(s) received in step 104. In an embodiment, the PID controller is implemented in software stored in or on a memory device of or accessible by the component configured to perform step 108 (e.g., the memory device 28 of the controller 18); while in another embodiment, the PID controller may be separate from the controller 18.

In an embodiment, the particular manner in which the brake torque is adjusted is dependent, at least in part, on the braking system type. In an embodiment such as that described above and illustrated in FIG. 2 wherein the braking system 12 comprises a hydraulic-based braking system, step 108 comprises adjusting or varying (or commanding or causing and adjustment to) the amount of brake/fluid pressure being supplied to the relevant braking devices 20. This may comprise reducing and/or increasing the amount of brake/fluid pressure being supplied to one or more particular braking devices depending on whether the amount of brake torque being generated or produced by that or those braking devices is to be decreased and/or increased (i.e., a reduction in brake/fluid pressure will result in a reduction in generated brake torque, and an increase in brake/fluid pressure will result in an increase in generated brake torque). It will be appreciated that in embodiments wherein the braking system 12 is other than a purely hydraulic-based system, the manner in which the brake torque is adjusted may be different than that described above, but nonetheless remains within the spirit and scope of the present invention.

Accordingly, it will be appreciated in view of the foregoing that the amount by which the brake torque being generated by one or more braking devices 20 is to be adjusted may be determined, and the actual adjustment carried out or controlled, in a number of ways, and as such, the present invention is not intended to be limited to any particular ways or techniques of doing so.

It will be further appreciated that the adjustment(s) carried out in step 108 may be made in dependence on the prevailing conditions or circumstances surrounding the operation of the vehicle 10, including, for example and without limitation, those conditions or circumstances discussed above with respect to step 106. More specifically, whereas certain adjustments to the amount of brake torque being produced by one or more braking devices 20 may be appropriate when the vehicle 10 is operating under a first set of circumstances/conditions, that or those same adjustments may not be appropriate when the vehicle is operating under different conditions. Accordingly, in an embodiment, step 108 may take into account various conditions or circumstances when determining exactly how to adjust the brake torque being produced by one or more of the braking devices 20. In doing so, brake-pull is appropriately mitigated for the given operating conditions of the vehicle. In any event, in an embodiment, the controller 18 of the braking system 12 is configured to cause, control, or effectuate the adjustment to the brake torque generated by one or more of the braking devices in step 108; though in other embodiments, different components of the braking system 12 (e.g., control units of a regenerative or frictional braking subsystem) or the vehicle 10 (e.g., a VCU) may be configured to do so instead of, or in conjunction with, the controller 18.In addition to the steps described above, in an embodiment, method 100 may include one or more other steps, some or all of which may be optional depending on the particular implementation.

For example, and as illustrated in FIG. 4, prior to step 108, and in certain embodiments, prior to one or both of obtaining step 104 and detecting step 106, method 100 may include a step 110 of determining whether any predetermined conditions exist for which a brake torque adjustment in step 108 would not be warranted. In such an embodiment, at least step 108 is not performed if such condition(s) exist.

Any number or combination of conditions may be evaluated in step 110, including, for example and without limitation: a characteristic of a user- or vehicle system-initiated steering input or steering command (e.g., steering angle, rate of change of steering angle, steering torque, etc.) being above a predetermined threshold value; an adhesion coefficient between a tyre of the vehicle 10 and the road surface being traversed by the vehicle 10 being below a particular value (e.g., a fixed or calculated value); a wheel-slip control command having been received (to control or slippage of one or more wheels); and/or an SCS command having been received, to cite only a few examples. And in an embodiment, whether or not the relevant predetermined condition(s) exist may be determined based on information received from one or more components of the braking system 12 and/or the vehicle 10 (e.g., sensor(s), vehicle components/systems, etc.)

For example, in an instance where a condition being evaluated comprises a characteristic of a user- or vehicle system-initiated steering input exceeding a predetermined threshold, step 110 may comprise monitoring one or more steering-related parameters (e.g., steering angle, steering torque, etc.) using information received from one or more sensors of the vehicle 10, and determining that the condition exists when the value of the monitored parameter exceeds (or, in an embodiment, meets or exceeds) the predetermined threshold value. In another embodiment, a component of the vehicle 10 other than a sensor, for example, a control unit of a steering system of the vehicle 10 or the VCU of the vehicle 10, may be configured to send an electrical signal to the component performing step 110 (e.g., the controller 18) that is indicative of the value of a particular steering input parameter exceeding a predetermined threshold. When such a signal has been received, it can be determined that the condition exists.

In an instance where a condition being evaluated comprises an adhesion coefficient between a tyre of the vehicle 10 and the road surface being traversed by the vehicle 10 being below a particular value (e.g., a fixed or calculated value), step 110 may comprise monitoring or periodically determining the adhesion coefficient(s) between one or more tyres of the vehicle 10 and the road surface using information received from one or more sensors or components of the braking system 12 or the vehicle 10 and techniques well known in the art, and when the prevailing adhesion coefficient(s) exceed (or, in an embodiment, meet or exceed) a predetermined threshold, determining that such a condition exists.

In an instance where a condition being evaluated comprises a wheel-slip control command having been received, step 110 may comprise detecting that a command has been received from a system or component of the vehicle 10 that is configured to detect and/or monitor slippage of one or more wheels of the vehicle 10 and to subsequently generate an electrical signal indicative of a braking-related command for mitigating detected wheel-slip that is sent to and carried out by the braking system 12. Accordingly, when such a signal is detected, it can be determined that the condition is met.

Similarly, in an instance where a condition being evaluated comprises an SCS command having been received, step 110 may comprise detecting that a command has been received from a system or component of the vehicle 10, for example, the SCS or VCU of the vehicle 10, that is indicative of intervention in the control of the vehicle 10 on the part of the SCS.

In any event, if it is determined in step 110 that the relevant condition(s) exist (e.g. one or a combination of those described above), then method 100 does not proceed to a subsequent step (e.g., step 108), but rather either terminates or loops back to a previous step (e.g., step 102, step 104, etc.), and in at least some instances, defers to the function or operation of established subsystems of the vehicle. For example, in an instance wherein wheel slip is detected but it is determined in step 110 that the relevant condition(s) do not exist, method 100 may defer to the SCS or antilock braking system (ABS) of the vehicle 10 until the slip event has ceased.

In an embodiment wherein the method includes step 110, the controller 18 of the braking system 12 may be configured to perform step 110; though in other embodiments, different components of the braking system 12 (e.g., control units of a regenerative or frictional braking subsystem) or the vehicle 10 (e.g., a VCU) may be configured to do so instead of, or in conjunction with, the controller 18.

Whereas step 110 is performed before step 108, in an embodiment, method 100 may also or alternatively include one or more steps performed after step 108. For example, in the embodiment illustrated in FIG. 5, method 100 may include a step 112 of determining whether one or more events have occurred following the adjustment(s) made or commanded in step 108, and if so, a step 114 of cancelling or modifying the adjustment(s) made in step 108.

The occurrence of any number of events may be taken into account in step 112. One such event may be a characteristic of a user- or vehicle system-initiated steering input or command exceeding a predetermined threshold value. In such an embodiment, step 112 may comprise monitoring one or more steering-related parameters (e.g., steering angle, steering torque, etc.) using information received from one or more sensors of the vehicle 10, and determining that the event has occurred when the value of the monitored parameter exceeds (or, in an embodiment, meets or exceeds) the predetermined threshold value. In another embodiment, a component of the vehicle 10 other than a sensor, for example, a control unit of a steering system of the vehicle 10 or the VCU of the vehicle 10, may be configured to send an electrical signal to the component performing step 112 (e.g., the controller 18) that is indicative of the value of the monitored parameter exceeding the threshold value. As such, it can be determined that the event has occurred when such a signal is received.

An alternative or additional event that may be taken into account is the receipt of a wheel-slip control command. In such an embodiment, step 112 may comprise detecting that a command has been received from a system or component of the vehicle 10 that is configured to detect and/or monitor slippage of one or more wheels of the vehicle 10 and to generate an electrical signal indicative of a braking-related command for mitigating detected wheel-slip. This electrical signal is sent to, and the command represented thereby is carried out by, the braking system 12, and as such, it can be determined that the event has occurred when such a signal is received.

Yet another alternative or additional event that may be taken into account is the receipt of an SCS command. In such an embodiment, step 112 may comprise detecting that a command has been received from a system or component of the vehicle 10, for example, the SCS or VCU of the vehicle 10 that is indicative of intervention in the control of the vehicle 10 on the part of the SCS. While certain events have been identified above, it will be appreciated that any number or combination of events may be taken into account or consideration in step 112, and as such, the present disclosure is not intended to be limited to any particular condition(s).

If it is determined in step 112 that the requisite event(s) have not occurred, no action may be taken and/or method 100 may remain at step 108 or loop back to a previous step. If, on the other hand, it is determined in step 112 that at least certain events have occurred, method 100 may move to step 114 of cancelling or modifying the adjustment(s) made in step 108. In an instance wherein the adjustment(s) are canceled, this may mean that the brake torque amounts that were adjusted in step 108 return to their original values. In other words, if the brake torque being generated by one or more braking devices 20 was increased by a certain amount in step 108, the amount of brake torque generated by that or those braking devices may be automatically decreased by the same amount in step 114; and/or if the amount of the brake torque being generated by one or more braking devices 20 was decreased by a certain amount in step 108, the amount of brake torque generated by that or those braking devices may be automatically increased by the same amount in step 114. Alternatively, the adjustments made in step 108 may remain unchanged, but no further adjustments may be made upon the determination in step 112 that at least certain events have occurred. In an instance wherein the adjustment(s) made in step 108 are modified, the amounts by which the brake torque generated by one or more braking devices 20 was increased or decreased in step 108 may be modified in step 114 such that the adjusted amount(s) may be increased and/or decreased in step 114.

In any event, in an embodiment, the controller 18 of the braking system 12 is configured to perform steps 112 and 114 described above; though in other embodiments, different components of the braking system 12 (e.g., control units of a regenerative or frictional braking subsystem) or the vehicle 10 (e.g., a VCU) may be configured to perform step 112 and/or step 114 instead of, or in conjunction with, the controller 18.

In addition to the foregoing, in at least some embodiments, method 100 may include one or more steps relating to the monitoring of the frequency at which brake-pull mitigation is necessary or required. For example, and as illustrated in FIG. 6, method 100 may include a step 116 comprising recording the need and/or occurrence of brake-pull mitigation in an electronic memory device of the vehicle 10 (e.g., the memory 28 of the controller 18 of the braking system 12). The recording of the occurrence may comprise recording data relating to the occurrence, for example, an indication of the occurrence itself, an indication as to the time of the occurrence, etc. In an embodiment, the data recorded in step 116 is stored in the memory device along with previously-recorded data corresponding to prior occurrences of brake-pull mitigation. As shown in FIG. 6, step 116 is performed after step 106, and in an embodiment, after step 108. In any event, the data stored in the memory device may be processed or evaluated to determine a frequency at which brake-pull mitigation is necessary or required (e.g., the number of times mitigation is required in a certain predetermined period of time).

In a step 118, the frequency determined in step 116 may be evaluated to determine whether the frequency is above (or, in an embodiment, meets or is above) a threshold frequency programmed into a memory device of or accessible by the component performing step 118 (e.g., the memory device 28 of the controller 18). In an embodiment, step 118 may be performed periodically in accordance with a particular predetermined sampling rate; in other embodiments, however, step 118 may be performed in dependence on the occurrence of triggering event. Examples of triggering events include, but are not limited to, a braking event, the detection of brake-pull in step 106, the adjustment of the brake torque generated by one or more braking devices 20 in step 108, and the recordation of data in step 116, to cite a few possibilities.

In any event, if it is determined in step 118 that the frequency is not above (or, in an embodiment, does not meet and/or is not above) the threshold frequency, method 100 may loop back to a previous step of method 100 (e.g., step 116). If, on the other hand, it is determined in step 118 that the frequency is above (or, in an embodiment, meets or is above) the threshold frequency, method 100 may proceed to a step 120 of generating a notification that service to one or more component of the braking system may be necessary. In an embodiment, step 120 may comprise generating and displaying such a warning or notification to the driver of the vehicle via a display device located within the vehicle cabin (e.g., an indicator light on the dashboard, an audio and/or visual message displayed via a suitable user-interface device (e.g., a speaker, a visual display screen, etc.). Additionally or alternatively, a flag may be set in the vehicle and/or braking system electronics that will notify a service technician performing diagnostic testing on the vehicle that the braking system may require servicing. In other embodiments, the notification may be wirelessly communicated directly and automatically to another party (e.g., a service technician or dealer) if vehicle 10 has such communications capabilities. Accordingly, it will be appreciated that step 120 may be performed in any number of ways.

In any event, in an embodiment, the controller 18 of the braking system 12 is configured to perform each of steps 116, 118, 120 described above. In other embodiments, however, components of braking system 12 or vehicle 10 other than controller 18 may be configured to perform one or more of steps 116, 118, 120 alone or in conjunction with the controller 18.

In addition to the foregoing, in at least some embodiments, method 100 may include one or more steps relating to the monitoring of the occurrence brake-pull mitigation being necessary or required. For example, and as illustrated in FIG. 7, method 100 may include a step 116 comprising recording the need and/or occurrence of brake-pull mitigation in an electronic memory device of the vehicle 10 (e.g., the memory 28 of the controller 18 of the braking system 12). The recording of the occurrence may comprise recording data relating to the occurrence, for example, an indication of the occurrence itself, an indication as to the time of the occurrence, and the corrective action taken etc. In an embodiment, the data recorded in step 116 is stored in the memory device, optionally along with previously-recorded data corresponding to prior occurrences of brake-pull mitigation. As shown in FIG. 7, step 116 is performed after step 106, and in an embodiment, after step 108. Optionally the method may comprise the step 122 of determining it the brake pull mitigation was a regular event or if it was a one off event. Identification of a regular event may be determined based on identifying a pattern in previous brake pull mitigations, for example the direction of mitigation required and the relative magnitude of the required mitigation. It will be appreciated that the magnitude of the mitigation required may be determined in relation to the braking effort applied. An exceptional brake pull event may be one that is not identified as a regular event. Where a regular brake pull event is detected this may be fed into step 124 which determines, based on the receipt of the brake command signal and historic regular brake pull events, a modified braking force, i.e. the controller identifies a historical trend for the need for brake pull mitigation and applies the anticipated required mitigation to the commanded brake force. In this manner the brake pull mitigation can operate in a pre-emptive manner in attempt to, not only mitigate brake pull once it is occurring but to prevent, or at least reduce the size of, future brake events.

It will be understood that the embodiments described above are given by way of example only and are not intended to limit the invention, the scope of which is defined in the appended claims. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. For example, the specific combination and order of steps is just one possibility, as the present method may include a combination of steps that has fewer, greater or different steps than that shown here. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

As used in this specification and claims, the terms “for example,” “e.g.,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that that the listing is not to be considered as excluding other, additional components or items. Further, the terms “electrically connected” or “electrically coupled” and the variations thereof are intended to encompass both wireless electrical connections and electrical connections made via one or more wires, cables, or conductors (wired connections). Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

Claims

1. A method of operating a braking system of a vehicle that includes braking devices each of which is configured to apply brake torque to a respective wheel at either end of an axle of the vehicle, the method comprising: receiving one or more electrical signals indicative of a brake command; obtaining a value of each of one or more vehicle-related parameters as brake torque is applied to the wheels at either end of the axle by the braking devices in response to the brake command; detecting a brake-pull on the vehicle based on the obtained value(s) of the one or more vehicle-related parameters; and automatically adjusting an amount of brake torque being produced by at least one of the braking devices to equalize the amount of brake torque being applied across the axle, thereby mitigating the detected brake-pull.

2. The method of claim 1, wherein the detecting step comprises comparing the obtained value(s) of the one or more vehicle-related parameters to one or more threshold values, each of the threshold values being less than a corresponding threshold value at which a stability control system of the vehicle would intervene.

3. The method of claim 1, wherein the receiving step comprises receiving one or more electrical signals indicative of a driver-initiated brake command.

4. The method of any one of the preceding claims, comprising determining whether a predetermined condition exists, and performing the adjusting step only when it is determined that said predetermined condition does not exist.

5. The method of claim 4, wherein the predetermined condition comprises a characteristic of a user- or vehicle system-initiated steering input exceeding a threshold value.

6. The method of claim 4, wherein the predetermined condition comprises an adhesion coefficient between a tyre of the vehicle and the road surface being traversed by the vehicle being below a particular value.

7. The method of claim 4, wherein the predetermined condition comprises a wheel-slip, control command having been received.

8. The method of claim 4, wherein the predetermined condition comprises a stability control system command having been received.

9. The method of any one of the preceding claims, wherein the adjusting step comprises increasing the amount of brake torque being produced by the at least one of the braking devices.

10. The method of any one of the preceding claims, wherein the adjusting step comprises decreasing the amount of brake torque being produced by the at least one of the braking devices.

11. The method of any one of the preceding claims, wherein the adjusting step comprises increasing the amount of brake torque being produced by one of the braking devices, and decreasing the amount of brake torque being produced by another one of the braking devices.

12. The method of any one of the preceding claims, wherein the adjusting step comprises varying a fluid pressure being supplied to at least one of the braking devices.

13. The method of any one of the preceding claims, wherein the one or more vehicle-related parameters comprises one or both of a lateral acceleration of the vehicle and a yaw-related parameter of the vehicle.

14. The method of any one of the preceding claims, wherein following the adjusting step, the method comprises: determining whether one or more events have occurred; and when it is determined that the one or more events have occurred, cancelling or modifying the adjustment made in the adjusting step.

15. The method of claim 14, wherein the one or more events comprise one or both of: a characteristic of a steering input exceeding a threshold value; a wheel-slip command having been received; and a stability control system command having been received.

16. The method of any one of the preceding claims, wherein following the adjusting step, the method comprises recording data indicative of the required brake pull mitigation.

17. The method of claim 16 wherein the method comprises, determining based on the one or more electrical signals indicative of a brake command, and on the recorded data indicative of a previously required brake pull mitigation, a modified braking force to apply to the wheels.

18. A non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more electronic processors causes the one or more electronic processors to carry out the method of any one of the preceding claims.

19. A system for controlling the operation of a braking system of a vehicle that includes a braking devices each of which is configured to apply brake toque to a respective wheel at either end of an axle of the vehicle, the system comprising: means for receiving one or more electrical signals indicative of a brake command; means for obtaining a value of each of one or more vehicle-related parameters as brake torque is applied to the respective wheels at either end of the axle by the braking devices in response to the brake command; means for detecting a brake-pull on the vehicle based on the obtained value(s) of the one or more vehicle-related parameters; and means for automatically commanding an adjustment to an amount of brake torque being produced by at least one of the braking devices to equalize the amount of brake torque being applied across the axle, thereby mitigating the detected brake-pull.

20. The system of claim 19, wherein the receiving means, the obtaining means, the detecting means, and the commanding means comprise: an electronic processor having one or more electrical inputs; and an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, wherein the processor is configured to access the memory device and execute the instructions stored therein such that it is configured to: receive the one or more electrical signals indicative of a brake command; obtain the value(s) of one or more vehicle-related parameters as brake torque is applied to the respective wheels at either end of the axle by the braking devices in response to the brake command; detect brake-pull on the vehicle based on the obtained value(s) of the one or more vehicle-related parameters; and automatically command the adjustment to an amount of brake torque being produced by at least one of the braking devices to equalize the amount of brake torque being applied across the axle, thereby mitigating the detected brake-pull.

21. The system of claim 20, wherein the processor is configured to determine whether a predetermined condition exists, and to command the adjustment to the amount of brake torque only when it is determined that said predetermined condition does not exist.

22. The system of claim 21, wherein the predetermined condition comprises: a characteristic of a user- or vehicle system-initiated steering input exceeding a threshold value; an adhesion coefficient between a tyre of the vehicle and the road surface being traversed by the vehicle being below a particular value; a wheel-slip control command having been received; or a stability control system command having been received.

23. The system of any one of claims 19 to 22, wherein detecting brake-pull comprises comparing the obtained value(s) of the one or more vehicle-related parameters to one or more threshold values, each of the threshold values being less than a correspond threshold value at which a stability control system of the vehicle would intervene.

24. The system of any one of claims 19 to 23, wherein the one or more electric signals are indicative of a driver-initiated brake command.

25. The system of any one of claims 19 to 24, wherein the one or more vehicle-related parameters comprises one or both of a lateral acceleration of the vehicle and a yaw-related parameter of the vehicle.

26. An electronic controller for a vehicle having a storage medium associated therewith storing instructions that when executed by the controller causes a braking system of the vehicle having braking devices each of which is configured to apply brake torque to a respective wheel at either end of an axle of the vehicle to be operated in accordance with the method of: receiving one or more electrical signals indicative of a brake command; obtaining a value of each of one or more vehicle-related parameters as brake torque is applied to the respective wheels at either end of the axle by the braking devices in response to the brake command; detecting a brake-pull on the vehicle based on the obtained value(s) of the one or more vehicle-related parameters; and automatically adjusting an amount of brake torque being produced by at least one of the braking devices to equalize the amount of brake torque being applied across the axle, thereby mitigating the detected brake-pull.

27. A vehicle, comprising: an axle; a braking system having a braking devices operatively coupled and configured to apply brake torque to respective wheels at either end of the axle; and the system according to any one of claims 19 to 25, or the electronic controller of claim 26.

28. A vehicle braking system comprising the system according to any one of claims 19 to 25, or the electronic controller of claim 26.