GB2598745A - Slip level control method and apparatus - Google Patents

Slip level control method and apparatus Download PDF

Info

Publication number
GB2598745A
GB2598745A GB2014201.4A GB202014201A GB2598745A GB 2598745 A GB2598745 A GB 2598745A GB 202014201 A GB202014201 A GB 202014201A GB 2598745 A GB2598745 A GB 2598745A
Authority
GB
United Kingdom
Prior art keywords
slip level
slip
brake pressure
wheel
vehicle
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB2014201.4A
Other versions
GB202014201D0 (en
GB2598745B (en
Inventor
Gavin Maskell Andrew
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Jaguar Land Rover Ltd
Original Assignee
Jaguar Land Rover Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jaguar Land Rover Ltd filed Critical Jaguar Land Rover Ltd
Priority to GB2014201.4A priority Critical patent/GB2598745B/en
Publication of GB202014201D0 publication Critical patent/GB202014201D0/en
Priority to DE102021123360.7A priority patent/DE102021123360A1/en
Publication of GB2598745A publication Critical patent/GB2598745A/en
Application granted granted Critical
Publication of GB2598745B publication Critical patent/GB2598745B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/17—Using electrical or electronic regulation means to control braking
    • B60T8/176—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS
    • B60T8/1761—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS responsive to wheel or brake dynamics, e.g. wheel slip, wheel acceleration or rate of change of brake fluid pressure
    • B60T8/17616—Microprocessor-based systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/17—Using electrical or electronic regulation means to control braking
    • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
    • B60T8/1725—Using tyre sensors, e.g. Sidewall Torsion sensors [SWT]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/17—Using electrical or electronic regulation means to control braking
    • B60T8/176—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS
    • B60T8/1763—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS responsive to the coefficient of friction between the wheels and the ground surface
    • B60T8/17636—Microprocessor-based systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/321—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration deceleration
    • B60T8/3255—Systems in which the braking action is dependent on brake pedal data
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T2210/00—Detection or estimation of road or environment conditions; Detection or estimation of road shapes
    • B60T2210/10—Detection or estimation of road conditions
    • B60T2210/14—Rough roads, bad roads, gravel roads
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T2210/00—Detection or estimation of road or environment conditions; Detection or estimation of road shapes
    • B60T2210/10—Detection or estimation of road conditions
    • B60T2210/16—Off-road driving conditions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T2220/00—Monitoring, detecting driver behaviour; Signalling thereof; Counteracting thereof
    • B60T2220/04—Pedal travel sensor, stroke sensor; Sensing brake request
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T2240/00—Monitoring, detecting wheel/tire behaviour; counteracting thereof
    • B60T2240/03—Tire sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T2250/00—Monitoring, detecting, estimating vehicle conditions
    • B60T2250/04—Vehicle reference speed; Vehicle body speed

Landscapes

  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Regulating Braking Force (AREA)

Abstract

A control system and method for controlling a slip level of one or more wheel of a vehicle (e.g. target wheel slip level to be used by antilock braking system ABS). The control system has a controller configured to receive a brake pressure demand signal indicating a driver demanded brake pressure. The controller or method determines a slip level (e.g. in percentage terms) for the wheel(s) in dependence on the driver demanded brake pressure (e.g. re brake pedal operation), and outputs a wheel slip control signal to set the slip level for the wheel(s) on the basis of this. The wheel slip control signal may be output when it is determined that the vehicle is operating in a high rolling resistance environment (e.g. sand, mud, other loose/deformable surface), determined by monitoring vehicle drag torque. There may be different slip level profiles to which the slip level is controlled, which may be selected depending on tyre pressure. For example: SLP1 = on road, fixed 2% target slip; SLP2 = sand, fixed 5% target slip; SLP3 = sand, normal tyre pressure, dynamic target slip level with driver demand; SLP4 = sand, low tyre pressure, dynamic target slip level with driver demand.

Description

SLIP LEVEL CONTROL METHOD AND APPARATUS
TECHNICAL FIELD
The present disclosure relates to a slip level control method and apparatus. More particularly, but not exclusively, the present disclosure relates to a method and apparatus for controlling a slip level of one or more wheel of a vehicle.
BACKGROUND
An increased slip level may provide improved vehicle dynamics when operating on an environment composed of sand. However, changing the slip level may make it difficult for the driver to modulate the braking force at the end of a stop. This may result in the wheels digging into the surface as the vehicle comes to a stop. This may result in the vehicle being stranded.
At least in certain embodiments, the present invention seeks to overcome or ameliorate at least some of the problems associated with prior art systems.
SUMMARY OF THE INVENTION
Aspects of the present invention relate to a control system, a vehicle, a method and a non-transitory computer readable medium as claimed in the appended claims.
According to an aspect of the present invention there is provided a control system for controlling a slip level of one or more wheel of a vehicle, the control system comprising one or more controller configured to: receive a brake pressure demand signal indicating a driver demanded brake 25 pressure; determine a slip level for the one or more wheel in dependence on the driver demanded brake pressure; and output a wheel slip control signal to set the slip level for the one or more wheel in dependence on the determined slip level.
At least in certain embodiments, the control system is operative to control the slip level under braking conditions. The slip level may correspond to a wheel slip threshold for modulating a braking force applied to the or each wheel. If the wheel slip detected at a wheel is greater than the slip level defined for that wheel, the braking force applied to that wheel is modulated to reduce wheel slip. The control system may dynamically adjust the slip level in dependence on the driver demanded brake pressure. This has particular application when the vehicle is operating on a loose or deformable surface, such as sand. Increasing the slip level at a higher driver demanded braking pressure may allow the wheels to dig into the surface and increase the deceleration rate under braking.
Decreasing the slip level at a lower driver demanded braking pressure may provide improved control as the vehicle comes to a stop. The driver demanded brake pressure is typically reduced as the vehicle speed decreases. The reduced slip level may enable the wheels to sit up on the loose or deformable surface more readily at the end of the stop. This also enables the driver to stop more efficiently under hard braking by allowing the deeper slip levels to build up the bank of material in front of the wheels. Being able to control the slip levels in dependence on the driver demanded braking pressure may provide an improved braking function.
The one or more controller collectively comprise: at least one electronic processor having an electrical input for receiving the brake pressure demand signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein. The at least one electronic processor may be configured to access the at least one memory device and execute the instructions therein so as to determine the slip level.
The one or more controller may be configured to output the wheel slip control signal in dependence on a determination that the vehicle is operating in a high rolling resistance environment. The high rolling resistance environment may correspond to a terrain comprising or consisting of a loose or deformable surface, such as sand.
The one or more controller may be configured to determine that the vehicle is operating in the high rolling resistance environment by monitoring a drag torque applied to the vehicle. The controller may, for example, identify when the drag torque increases above a predefined threshold corresponding to a scenario in which the vehicle is traversing a loose or deformable surface, such as sand or mud. Alternatively, or in addition, a user input may indicate a particular operating environment. For example, a user input may indicate that the vehicle is traversing a loose or deformable surface, such as sand.
The one or more controller may be configured to access at least one slip level profile defining a relationship between the slip level and the driver demanded brake pressure. Determining the slip level may comprise mapping the driver demanded brake pressure to the slip level in dependence on the at least one slip level profile.
The one or more controller may be configured to select one of a plurality of the slip level profiles in dependence on a tyre pressure of the one or more wheel. Different profiles may be defined for different tyre pressures. A low tyre pressure may enable a higher slip level, for example at low brake pressures and/or high brake pressures. The tyre pressure may, for example, be determined in dependence on a signal from a tyre pressure management system (TPMS) or a tyre inflation system.
The determination of the slip level may comprise: setting a first slip level when the driver demanded brake pressure is less than a first brake pressure threshold; and setting a second slip level when the driver demanded brake pressure is greater than a second brake pressure threshold. The first brake pressure threshold may be less than the second brake pressure threshold. The first slip level may be less than the second slip level.
The determination of the slip level may comprise setting additional slip levels, for example a third slip. The third slip level may be set when the driver demanded brake pressure is greater than a third brake pressure threshold. The third brake pressure threshold may be greater than the second brake pressure threshold. Fourth and higher slip levels may be set with corresponding brake pressure thresholds.
The one or more controller may be configured to receive a vehicle reference speed. The target wheel slip may be determined in dependence on the vehicle reference speed. The changes in the slip level may be proportional to the vehicle speed. For example, the slip level may be reduced as the vehicle reference speed decreases. This function may reduce the permitted wheel slip at low speeds.
According to a further aspect of the present invention there is provided a vehicle comprising a control system as described herein. The wheel slip control signal may be output to a brake control system, for example an antilock braking system (ABS).
According to a further aspect of the present invention there is provided a method of controlling a slip level of one or more wheel of a vehicle, the method comprising: receiving a brake pressure demand signal indicating a driver demanded brake pressure; determining a slip level for the one or more wheel in dependence on the driver 35 demanded brake pressure; and outputting a wheel slip control signal to set the slip level for the one or more wheel in dependence on the determined slip level.
The method may comprise outputting the wheel slip control signal in dependence on a determination that the vehicle is operating in a high rolling resistance environment.
The method may comprise determining that the vehicle is operating in the high rolling resistance environment by monitoring a drag torque applied to the vehicle.
The method may comprise accessing at least one slip level profile defining a relationship between the slip level and the driver demanded brake pressure. The driver demanded brake pressure may be mapped to the slip level in dependence on the at least one slip level profile.
The method may comprise selecting one of a plurality of the slip level profiles in dependence on a tyre pressure of the one or more wheel.
Determining the slip level may comprise setting a first slip level when the driver demanded brake pressure is less than a first brake pressure threshold; and setting a second slip level when the driver demanded brake pressure is greater than a second brake pressure threshold. The first brake pressure threshold may be less than the second brake pressure threshold. The first slip level may be less than the second slip level.
The method may comprise determining a vehicle reference speed. The target wheel slip may be determined in dependence on the vehicle reference speed.
According to a further aspect of the present invention there is provided a non-transitory computer-readable medium having a set of instructions stored therein which, when executed, cause a processor to perform the method described herein.
Any control unit or controller described herein may suitably comprise a computational device having one or more electronic processors. The system may comprise a single control unit or electronic controller or alternatively different functions of the controller may be embodied in, or hosted in, different control units or controllers. As used herein the term "controller" or "control unit" will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide any stated control functionality. To configure a controller or control unit, a suitable set of instructions may be provided which, when executed, cause said control unit or computational device to implement the control techniques specified herein. The set of instructions may suitably be embedded in said one or more electronic processors. Alternatively, the set of instructions may be provided as software saved on one or more memory associated with said controller to be executed on said computational device. The control unit or controller may be implemented in software run on one or more processors. One or more other control unit or controller may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller. Other suitable arrangements may also be used.
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 and 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 present invention will now be described, by way of example only, with reference to the accompanying figures, in which: Figure 1 shows a schematic representation of a vehicle incorporating a control system in accordance with an embodiment of the present invention; Figure 2 shows a schematic representation of the control system shown in Figure 1; Figure 3 shows slip level profiles defining the relationship between the slip level and the driver demanded braking pressure; and Figure 4 shows a block diagram representing operation of the control system in accordance with an aspect of the present invention.
DETAILED DESCRIPTION
A control system 1 for setting a slip level for one or more wheel of a vehicle 2 in accordance with an embodiment of the present invention will now be described with reference to the accompanying figures. The control system 1 has particular application in controlling the operation of the vehicle 2 in a terrain comprising or consisting of a loose or deformable surface, such as sand. The vehicle 2 in the present embodiment is an automobile, such as an off-road vehicle, a sports utility vehicle, a utility vehicle or a tractor. It will be understood that the control system 1 may be used in other types of land vehicle.
As illustrated in Figure 1, the vehicle 2 comprises four (4) wheels Wn and a vehicle body 4. The wheels Wn are provided on front and rear axles 5, 6. The first wheel W1 is a front left wheel; the second wheel W2 is a front right wheel; the third wheel W3 is a rear left wheel; and the fourth wheel W4 is a rear right wheel. A wheel speed sensor Sn is provided to measure the rotational speed of each wheel Wn. The wheel speed sensors Sn each output a wheel speed signal WSn indicating the rotational speed of the associated wheel Wn. The vehicle 2 comprises a drivetrain comprising an internal combustion engine 7 drivingly connected to the front axle 5 and the rear axle 6 for transmitting a traction torque to each of the wheels Wn. It will be understood that the internal combustion engine (not shown) could be drivingly connected to only one of the front and rear axles 5, 6 to drive either the front wheels W1, W2 or the rear wheels W3, W4. In alternative implementations, the drivetrain may comprise an electric propulsion unit instead of, or in addition to, the internal combustion engine 7.
The vehicle 2 comprises a plurality of brakes Bn. The brakes Bn are each associated with a respective one of the wheels Wn. The brakes Bn are operable to apply a braking force to retard rotation of the associated wheels Wn of the vehicle 2. The brakes Bn in the present embodiment are hydraulically actuated friction brakes. A hydraulic circuit (not shown) is provided to actuate each brake Bn. The brakes Bn are operated in dependence on a driver demanded brake pressure generated by a brake pedal 9 operated by the driver of the vehicle 2. A brake pressure sensor 8 is provided for measuring the driver demanded brake pressure.
The brake pressure sensor 8 outputs a brake pressure demand signal BDS1. In a variant, a transducer may be provided to measure displacement of the brake pedal 9. The driver demanded brake pressure may be generated in dependence on the measured displacement of the brake pedal 9. In an alternative embodiment, the demanded brake pressure may be generated by an autonomous or semi-autonomous vehicle control system. In a further embodiment, the vehicle 2 may comprise one or more electrical machine which may apply a braking force to retard rotation of one or more of the wheels Wn. The one or more electrical machine may, for example, apply the braking force when regenerating energy. The one or more electrical machine may be controlled to adjust the magnitude of the braking force.
An antilock brake control (ABS) system 10 is provided for controlling operation of the brakes Bn. The ABS system 10 is operable to modulate the braking force applied to each of the wheels Wn. The ABS system 10 comprises an ABS control unit 11 having at least one processor and a memory device. The ABS control unit 11 is configured to receive the wheel speed signals WSn indicating the wheel speed of each wheel Wn. The ABS control unit 11 may determine a reference speed VREF of the vehicle 2 in dependence on the wheel speed signals WSn. Other techniques may be employed to determine the reference speed VREF.
Alternatively, the reference speed VREF may be determined by another vehicle system, such as the control system 1, and output to the ABS control unit 11.
The ABS control unit 11 compares the measured rotational wheel speed to a free-rolling speed of the wheel Wn (which can be derived from the reference speed VREF). This comparison may identify wheel slip (typically expressed as a percent slip) resulting from the motion of the wheel Wn relative to the surface on which the vehicle 2 is travelling. Wheel slip can be a result of the rotational speed of the wheel Wn being greater than or less than the free-rolling speed of the wheel Wn. Under braking, the rotational speed of the wheel Wn may be less than the free-rolling speed of the wheel Wn if the wheel Wn is about to lock. In this scenario, the ABS control unit 11 may be configured to intervene to control rotation of the wheel Wn, for example to prevent locking of the wheel Wn. The ABS control unit 11 may, for example, output a brake pressure control signal BSn to modulate the braking force applied to one or more of the wheels Wn. The brake pressure control signal BSn may, for example, operate a valve (not shown) to reduce the braking force applied by the brake Bn to that wheel Wn. The ABS control unit 11 is configured to implement this control strategy independently for each wheel Wn.
The ABS control unit 11 allows a level of wheel slip to provide improved stopping potential for the vehicle 2. This slip level is based on the driver demanded stopping request (derived from the driver demand braking pressure); the surface friction calculated at the interface between the tyres and the road surface; and deceleration rates of the individual wheels. The amount of wheel slip permitted by the ABS control unit 11 is referred to herein as a slip level. The slip level defines an upper or maximum amount of wheel slip. A typical slip level may be 2-3% slip. This slip level enables the rotation of the wheels to maximise the deceleration and steering capability of the tyres. If the determined wheel slip is greater than or equal to the slip level, the ABS control unit 11 outputs the brake pressure control signal BSn to control the braking force applied to the wheel Wn. For example, the brake pressure control signal BSn may reduce the braking force applied to a wheel Wn to reduce wheel slip. As described herein, the control system 1 in accordance with the present invention is configured dynamically to adjust the slip level implemented by the ABS control unit 11. The control system 1 may thereby modify the dynamic braking characteristics of the vehicle 2.
As shown in Figure 2, the control system 1 comprises a controller in the form of a slip level controller 14. The slip level controller 14 has an electronic processor 15 and a memory device 16. The electronic processor 15 has at least one electrical input 17 for receiving the brake pressure demand signal BDS1 from the brake pressure sensor 8. The brake pressure demand signal BDS1 may, for example, be received from a communication bus or network (not shown) disposed in the vehicle 2. The electronic processor 15 has at least one electrical output 18 for outputting a wheel slip control signal WSCn to the ABS control unit 11. The wheel slip control signal WSC1 may be published to the communication bus and read by the ABS control unit 11. The wheel slip control signal WSC sets the slip level used by the ABS control unit 11.
The control system 1 is configured to modify the slip level in dependence on the dynamic operating conditions of the vehicle 2. In particular, the control system 1 is configured to determine when the vehicle 2 is operating in a high rolling resistance environment. The high rolling resistance environment in the present embodiment represents a terrain comprising or consisting of sand. Another high rolling resistance environment is a terrain comprising or consisting of snow. Another high rolling resistance environment is a terrain comprising or consisting of mud. The control system 1 may determine that the vehicle is operating in a high rolling resistance environment by monitoring a drag torque applied to the vehicle 2. The drag torque may be determined by comparing the torque generated by the internal combustion engine (not shown) to maintain a particular reference speed. Other techniques may be employed to identify operation in a high rolling resistance environment. For example, image processing techniques may be used to detect features indicating a high rolling resistance environment. Alternatively, or in addition, a geospatial location of the vehicle 2 may be used to assess the operating environment. Alternatively, or in addition, the control system 1 may receive a user input to indicate dynamic operating conditions of the vehicle 2. For example, the user input may identify a characterising property of the terrain in which the vehicle 2 is operating, for example to indicate that the terrain comprises or consists of sand. This input may be used to configure other vehicle systems, such as powertrain and driveline systems.
The control system 1 according to the present embodiment is configured to modify the slip level in dependence on the driver demand braking pressure. As outlined above, the control system 1 is configured to receive the brake pressure demand signal BDS1 from the brake pressure sensor 8. The slip level controller 14 is configured to determine a target slip level in dependence on the driver demanded brake pressure. A plurality of slip level profiles SLPn are shown in Figure 3 by way of example. The slip profiles SLPn are applicable at a vehicle speed of 20mph (30kmh) and in this embodiment are not speed dependent. The slip level controller 14 is configured to select one of the slip level profiles SLPn in dependence on the prevailing properties of the terrain on which the vehicle 2 is operating. The slip level profiles SLPn are outlined below: * A first slip level profile SLP1 is defined for standard operating conditions, such as on-road travel. The first slip level profile SLP1 defines a fixed slip level of approximately 2% which does not change with driver demand braking pressure.
* A second slip level profile SLP2 is defined for operation on a terrain comprising or consisting of sand. The second slip level profile SLP2 defines a fixed slip level of approximately 5% which does not change with driver demand braking pressure.
* A third slip level profile SLP3 is defined for operation on a terrain comprising or consisting of sand when the wheels Wn have a normal tyre pressure. In accordance with an aspect of the present invention, the third slip level profile SLP3 defines a dynamic slip level which changes with driver demand braking pressure.
* A fourth slip level profile SLP4 is defined for operation on a terrain comprising or consisting of sand when the wheels Wn have a low tyre pressure. In accordance with an aspect of the present invention, the fourth slip level profile SLP4 defines a dynamic slip level which changes with driver demand braking pressure.
The slip level profiles SLPn define the slip level (as a percentage) with respect to the driver demand braking pressure. The first and second slip level profiles SLP1, SLP2 are conventional profiles which do not change with respect to driver demand braking pressure. The slip level controller 14 may select the first slip level profile SLP1 when the vehicle is travelling on a metalled surface, such as a road. In accordance with an aspect of the present invention, the third and fourth slip level profiles SLP3, SLP4 change with respect to driver demand braking pressure. The slip level controller 14 selects the third slip level profiles SLP3 when the vehicle is travelling on a terrain having a loose or deformable surface, for example comprising or consisting of sand. The slip level controller 14 selects the fourth slip level profile SLP4 when the vehicle is travelling on a terrain having a loose or deformable surface and the wheels Wn have a low tyre pressure. The fourth slip level profile SLP4 may be selected when an onboard tyre pressure sensor or a user input specifies a low tyre pressure. It will be understood that one or more of the slip level profiles SLPn may be omitted. For example, the slip level controller 14 may be implemented with the first and third slip level profiles SLP1, SLP3 shown in Figure 3.
The configuration of the third slip level profile SLP3 will now be described in more detail. The third slip level profile SLP3 defines the slip level for implementation by the ABS control unit 11 in dependence on the driver demanded brake pressure when operating on sand. The third slip level profile SLP3 defines a first slip level SL1 when the driver demanded brake pressure is less than a first brake pressure threshold BTH1; a second slip level SL2 when the driver demanded brake pressure is greater than the first brake pressure threshold BTH1 and less than a second brake pressure threshold BTH2; and a third slip level SL3 when the driver demanded brake pressure is greater than a second brake pressure threshold BTH2. The first slip level SL1 is less than the second slip level SL2 (SL1<SL2). The second slip level SL2 is less than the third slip level SL3 (SL2<SL3). The first slip level SL1 and the third slip level SL3 are at least substantially constant. By way of example, the first slip level SL1 is defined as approximately 2% and the second slip level SL2 is defined as approximately 5% or 5.5%. The second slip level SL2 increases progressively in proportion to the driver demanded brake pressure. As shown in Figure 3, the first brake pressure threshold BTH1 is less than the second brake pressure threshold BTH2 (BTH1<BTH2). By way of example, the first brake pressure threshold BTH1 is defined as approximately 10bar and the second brake pressure threshold BTH2 is defined as approximately 95bar or 100bar.
The configuration of the fourth slip level profile SLP4 will now be described in more detail. The fourth slip level profile SLP4 defines the slip level for implementation by the ABS control unit 11 in dependence on the driver demanded brake pressure when operating on sand at a low tyre pressure. The fourth slip level profile SLP4 defines a first slip level SL1' when the driver demanded brake pressure is less than a first brake pressure threshold BTH1'; a second slip level 8L2' when the driver demanded brake pressure is greater than the first brake pressure threshold BTH1' and less than a second brake pressure threshold BTH2'; and a third slip level SL3' when the driver demanded brake pressure is greater than a second brake pressure threshold BTH2'. The first slip level SL1' is less than the second slip level SL2' (SL1 '<SL2'). The second slip level SL2' is less than the third slip level SL3' (SL2<SL3). The first slip level SL1 and the third slip level SL3' are at least substantially constant. By way of example, the first slip level SL1' is defined as approximately 3% and the second slip level SL2' is defined as approximately 5%. The second slip level SL2' increases progressively in proportion to the driver demanded brake pressure. As shown in Figure 3, the first brake pressure threshold BTH1' is less than the second brake pressure threshold BTH2' (BTH1'<BTH2'). By way of example, the first brake pressure threshold BTH1' is defined as approximately 25bar and the second brake pressure threshold BTH2' is defined as approximately 60bar. The fourth slip level profile SLP4 optionally comprises a fourth slip level S4' which is implemented when the driver demanded brake pressure is greater than a third brake pressure threshold BTH3'. The fourth slip level SL4' is greater than the third slip level SL3' (SL4>SL3). The third brake pressure threshold BTH3' is defined as approximately 95bar and the third slip level SLP3' is defined as approximately 5.5%.
The operation of the control system 1 will now be described with reference to a block diagram 100 shown in Figure 4. The control system 1 is activated (BLOCK 105). The slip level controller 14 determines that the vehicle 2 is operating on a loose or deformable surface, such as sand (BLOCK 110). The slip level controller 14 optionally checks if the tyre pressure of the wheels Wn is low (BLOCK 115). The slip level controller 14 selects one of the predefined slip level profiles SLPn (BLOCK 120). The slip level controller 14 monitors the driver demand braking pressure and sets the slip level in dependence on the selected slip level profile SLPn (BLOCK 125). The slip level controller 14 outputs a slip level control signal SLC1 to the ABS control unit 11 to adjust the active slip level (BLOCK 130). The ABS control unit 11 optionally checks if the tyre pressure of the wheels Wn is low (BLOCK 135). The slip level controller 14 determines that the vehicle 2 is no longer operating on a high roll resistant surface, such as sand (BLOCK 140). The slip level controller 14 outputs a slip level control signal SLC1 to the ABS control unit 11 to revert to a fixed slip level profile. (BLOCK 145).
The control system 1 in accordance with the present invention uses the driver demanded brake pressure to set a slip level for the ABS control unit 11. The ABS control unit 11 may thereby modify the amount of slip allowed before entry to brake pressure modulation. A low driver demand braking pressure results in a slip level of approximately 2%. A high driver demand braking pressure provides a higher slip level of approximately 5%. When braking on a surface composed of sand, the increased slip level may allow the driver to decrease the level at which the wheels Wn dig into the surface. The driver demanded brake pressure is typically reduced as the vehicle 2 comes to a stop. By reducing the slip level for the reduced driver demanded brake pressure, the driver may have improved control of the vehicle 2 as it comes to a stop. This enables the wheels Wn to sit up on the surface of the sand much more readily at the end of the stop. This also enables the driver to stop more efficiently under hard braking by allowing the deeper slip levels to build up the bank of material in front of the wheels Wn. Being able to control the slip levels in dependence on the driver demanded braking pressure may provide an improved braking function.
The control system 1 may optionally modify the slip level in dependence on a deceleration rate of the vehicle 2. By controlling the slip level in dependence on the deceleration rate, a progressive change may be implemented for transitions from a standard slip level (for example, the first slip profile SLP1) to a slip level adapted for sand (for example, the third or fourth slip profile SLP3, SLP4). From the driver perspective, this may avoid or reduce variability in stopping performance of the vehicle 2. By implementing a speed dependent component for controlling the slip level, the control system 1 may enable a broader range of control as the speed varies. This may provide a more consistent deceleration rate for a given driver demanded brake pressure.
It will be appreciated that various modifications may be made to the embodiment(s) described herein without departing from the scope of the appended claims.

Claims (18)

  1. CLAIMS: 1. A control system for controlling a slip level of one or more wheel of a vehicle, the control system comprising one or more controller configured to: receive a brake pressure demand signal indicating a driver demanded brake pressure; determine a slip level for the one or more wheel in dependence on the driver demanded brake pressure; and output a wheel slip control signal to set the slip level for the one or more wheel in dependence on the determined slip level.
  2. 2. A control system of claim 1, wherein the one or more controller collectively comprise: at least one electronic processor having an electrical input for receiving the brake pressure demand signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein, and wherein the at least one electronic processor is configured to access the at least one memory device and execute the instructions therein so as to determine the slip level.
  3. 3. A control system as claimed in claim 1 or claim 2, wherein the one or more controller is configured to: output the wheel slip control signal in dependence on a determination that the vehicle is operating in a high rolling resistance environment.
  4. 4. A control system as claimed in claim 3, wherein the one or more controller is configured to determine that the vehicle is operating in the high rolling resistance environment by monitoring a drag torque applied to the vehicle.
  5. 5. A control system as claimed in any one of claims 1 to 4, wherein: the one or more controller is configured to access at least one slip level profile defining a relationship between the slip level and the driver demanded brake pressure; and determining the slip level comprises mapping the driver demanded brake pressure to the slip level in dependence on the at least one slip level profile.
  6. 6. A control system as claimed in claim 5, wherein the one or more controller is configured to select one of a plurality of the slip level profiles in dependence on a tyre pressure of the one or more wheel.
  7. 7. A control system as claimed in any one of the preceding claims, wherein determining the slip level comprises: setting a first slip level when the driver demanded brake pressure is less than a first brake pressure threshold; and setting a second slip level when the driver demanded brake pressure is greater than a second brake pressure threshold, wherein the first brake pressure threshold is less than the second brake pressure threshold; and the first slip level is less than the second slip level.
  8. 8. A control system as claimed in any one of the preceding claims, wherein the one or more controller is configured to receive a vehicle reference speed; the slip level being determined in dependence on the vehicle reference speed.
  9. 9. A vehicle comprising a control system as claimed in any one of the preceding claims.
  10. 10. A vehicle as claimed in claim 9, wherein the wheel slip control signal is output to a brake control system.
  11. 11. A method of controlling a slip level of one or more wheel of a vehicle, the method comprising: receiving a brake pressure demand signal indicating a driver demanded brake pressure; determining a slip level for the one or more wheel in dependence on the driver 25 demanded brake pressure; and outputting a wheel slip control signal to set the slip level for the one or more wheel in dependence on the determined slip level.
  12. 12. A method as claimed in claim 11 comprising outputting the wheel slip control signal in dependence on a determination that the vehicle is operating in a high rolling resistance environment.
  13. 13. A method as claimed in claim 12 comprising determining that the vehicle is operating in the high rolling resistance environment by monitoring a drag torque applied to the vehicle.
  14. 14. A method as claimed in any one of claims 11 to 13, wherein: accessing at least one slip level profile defining a relationship between the slip level and the driver demanded brake pressure; and mapping the driver demanded brake pressure to the slip level in dependence on the at least one slip level profile.
  15. 15. A method as claimed in claim 14 comprising selecting one of a plurality of the slip level profiles in dependence on a tyre pressure of the one or more wheel.
  16. 16. A method as claimed in any one of claims 11 to 15, wherein determining the slip level comprises: setting a first slip level when the driver demanded brake pressure is less than a first brake pressure threshold; and setting a second slip level when the driver demanded brake pressure is greater than a second brake pressure threshold, wherein the first brake pressure threshold is less than the second brake pressure threshold; and the first slip level is less than the second slip level.
  17. 17. A method as claimed in any one of claims 11 to 16 comprising determining a vehicle reference speed; and determining the slip level in dependence on the vehicle reference speed.
  18. 18. A non-transitory computer-readable medium having a set of instructions stored therein which, when executed, cause a processor to perform the method claimed in any one of claims 11 to 17.
GB2014201.4A 2020-09-09 2020-09-09 Slip level control method and apparatus Active GB2598745B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB2014201.4A GB2598745B (en) 2020-09-09 2020-09-09 Slip level control method and apparatus
DE102021123360.7A DE102021123360A1 (en) 2020-09-09 2021-09-09 METHOD AND DEVICE FOR SLIP LEVEL CONTROL

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2014201.4A GB2598745B (en) 2020-09-09 2020-09-09 Slip level control method and apparatus

Publications (3)

Publication Number Publication Date
GB202014201D0 GB202014201D0 (en) 2020-10-21
GB2598745A true GB2598745A (en) 2022-03-16
GB2598745B GB2598745B (en) 2022-12-14

Family

ID=72841347

Family Applications (1)

Application Number Title Priority Date Filing Date
GB2014201.4A Active GB2598745B (en) 2020-09-09 2020-09-09 Slip level control method and apparatus

Country Status (2)

Country Link
DE (1) DE102021123360A1 (en)
GB (1) GB2598745B (en)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4774667A (en) * 1985-04-04 1988-09-27 Nippondenso Co., Ltd. Brake control system for vehicle
JPH02141356A (en) * 1988-11-22 1990-05-30 Fuji Heavy Ind Ltd Antiskid control method for automobile
JPH07257349A (en) * 1994-03-28 1995-10-09 Toyota Motor Corp Wheel slip control device
JPH10250557A (en) * 1997-03-10 1998-09-22 Denso Corp Brake control device
JP2006159947A (en) * 2004-12-02 2006-06-22 Toyota Motor Corp Abs device and abs control method
DE102012200198A1 (en) * 2012-01-09 2013-07-11 Robert Bosch Gmbh Method for actuating hydraulic brake device in vehicle, involves raising wheel target slip value and/or correlating value, when rider braking pressure exceeds hydraulic wheel braking pressure in wheel brake unit

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4774667A (en) * 1985-04-04 1988-09-27 Nippondenso Co., Ltd. Brake control system for vehicle
JPH02141356A (en) * 1988-11-22 1990-05-30 Fuji Heavy Ind Ltd Antiskid control method for automobile
JPH07257349A (en) * 1994-03-28 1995-10-09 Toyota Motor Corp Wheel slip control device
JPH10250557A (en) * 1997-03-10 1998-09-22 Denso Corp Brake control device
JP2006159947A (en) * 2004-12-02 2006-06-22 Toyota Motor Corp Abs device and abs control method
DE102012200198A1 (en) * 2012-01-09 2013-07-11 Robert Bosch Gmbh Method for actuating hydraulic brake device in vehicle, involves raising wheel target slip value and/or correlating value, when rider braking pressure exceeds hydraulic wheel braking pressure in wheel brake unit

Also Published As

Publication number Publication date
GB202014201D0 (en) 2020-10-21
GB2598745B (en) 2022-12-14
DE102021123360A1 (en) 2022-03-10

Similar Documents

Publication Publication Date Title
US10253860B2 (en) Driveline and method of controlling a driveline
US8751131B2 (en) Control method and apparatus for a vehicle
US7079930B2 (en) System and method for monitoring the handling of a vehicle
US8764124B2 (en) Brake control apparatus
KR100374095B1 (en) Modular Vehicle Dynamic Characteristics Control System
KR101697809B1 (en) Method and braking system for influencing driving dynamics by means of braking and driving operations
US20170057515A1 (en) Motor vehicle controller and method
US10926794B2 (en) Vehicular behavior control apparatus
CN103328290B (en) Brake fade determining device, brake fade defining method and brake system
AU2015340838B2 (en) Controlling the braking of a vehicle descending a slope
GB2504834A (en) Vehicle control with method of permitting limited wheel slip
US11034238B2 (en) Method for determining a contact force on a utility vehicle
CN104010896A (en) Method And Device For The Electronic Control Of The Brake Force Distribution According To The Differential Slip
AU2017229136B2 (en) Braking control system
US20180281760A1 (en) Control device for four-wheel drive vehicle
US20150073678A1 (en) Braking force control device
US20200114922A1 (en) Vehicle running control apparatus
US20030074125A1 (en) Anti-lock brake yaw control method
US20150329090A1 (en) Travel control apparatus and vehicle control apparatus
US7212903B2 (en) Vehicle motion control apparatus
US11241955B2 (en) Vehicle control method and apparatus
GB2598745A (en) Slip level control method and apparatus
US9789861B2 (en) Braking force control system for vehicle
SE542777C2 (en) A method for controlling a powertrain, a control arrangement for controlling a powertrain, a powertrain, a vehicle, a computer program and a computer-readable medium.
SE542262C2 (en) A method for controlling a powertrain, a control arrangement for controlling a powertrain, a powertrain, a vehicle, a computer program and a computer-readable medium