EP3253629A1 - Système de commande - Google Patents

Système de commande

Info

Publication number
EP3253629A1
EP3253629A1 EP16703099.8A EP16703099A EP3253629A1 EP 3253629 A1 EP3253629 A1 EP 3253629A1 EP 16703099 A EP16703099 A EP 16703099A EP 3253629 A1 EP3253629 A1 EP 3253629A1
Authority
EP
European Patent Office
Prior art keywords
vehicle
controller
control system
max
wheel
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.)
Withdrawn
Application number
EP16703099.8A
Other languages
German (de)
English (en)
Inventor
Georgios TSAMPARDOUKAS
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
Publication of EP3253629A1 publication Critical patent/EP3253629A1/fr
Withdrawn legal-status Critical Current

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
    • B60T8/1763—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
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/02—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to ambient conditions
    • B60W40/06—Road conditions
    • B60W40/068—Road friction coefficient
    • 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
    • B60T8/175—Brake regulation specially adapted to prevent excessive wheel spin during vehicle acceleration, e.g. for traction control
    • 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
    • B60T8/1755—Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve
    • B60T8/17551—Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve determining control parameters related to vehicle stability used in the regulation, e.g. by calculations involving measured or detected parameters
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
    • B60W30/18—Propelling the vehicle
    • B60W30/18172—Preventing, or responsive to skidding of wheels
    • 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
    • B60T2210/12—Friction
    • 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
    • B60T2260/00—Interaction of vehicle brake system with other systems
    • B60T2260/02—Active Steering, Steer-by-Wire
    • 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
    • B60T2270/00—Further aspects of brake control systems not otherwise provided for
    • B60T2270/86—Optimizing braking by using ESP vehicle or tire model
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2552/00—Input parameters relating to infrastructure
    • B60W2552/40—Coefficient of friction

Definitions

  • the present disclosure relates to a control system for controlling a dynamic system of a vehicle. Aspects of the disclosure relate to a controller for a dynamic system of the vehicle, a vehicle dynamic system, an electric or hybrid electric vehicle, and a method of operating a dynamic system of a vehicle.
  • a typical land vehicle such as a car or the like, includes a braking system for retarding the wheels through the application of friction.
  • the braking system includes a brake pedal, to be operated by a driver of the car, and a brake, for instance, a disc brake or a drum brake, for applying friction to a brake disc or wheel drum respectively, to retard the wheel.
  • a brake pedal to be operated by a driver of the car
  • a brake for instance, a disc brake or a drum brake
  • friction to a brake disc or wheel drum respectively to retard the wheel.
  • there is a direct mechanical link between the brake pedal and the brake such that the brakes apply friction to slow the wheels in response to depression of the brake pedal by the driver.
  • Some braking systems have more sophisticated operation which may include a degree of computerised control in the form of a control protocol.
  • Typical braking control protocols control the brakes to apply differing degrees of friction or to apply an Anti-lock Braking System (ABS), depending on the degree of wheel slip currently being experienced by the wheels.
  • ABS Anti-lock Braking System
  • ABS can be applied in a timely fashion, immediately prior to maximum wheel slip ratio, to prevent the vehicle skidding on the driving terrain.
  • ABS Anti-lock Braking System
  • k max which is not directly measurable.
  • k max has been estimated off-line using empirical data or theoretical calculation.
  • the estimated k max can then be used by the braking system in real time to determine an appropriate braking control protocol based on the degree of wheel slip.
  • Such measures are inherently inaccurate since k max is multi variable and depends on factors such as the current driving terrain and weather state. Accordingly, off-line estimates of k max do not provide accurate predictions as to when the maximum wheel slip ratio will occur in real time.
  • One attempt at calculating k max in real time can be found in a publication in "Control Theory and Applications" by the Institute of Engineering and Technology (IET) by authors M. Tanelli, L. Piroddi, and S. M. Savaresi. This IET publication describes a formula and curve fitting method for estimating k max , in real time, based on vehicle parameters measured during a braking event, when wheel slip naturally occurs. The formula is
  • the above formula is used to obtain discrete l values over the duration of the braking event.
  • a Burckhardt model is then applied to the discrete k values and a curve of best fit constructed accordingly.
  • the maximum value for A based on the fitted curve is then determined to be k max .
  • the aforementioned formula is only valid during a braking event.
  • wheel slips occur in vehicle modes other than braking, such as during a traction mode when an angular velocity of the wheel maybe too great for the terrain on which the vehicle is driving.
  • a wheel slip may occur when a vehicle turn radius is too excessive for the current weather conditions or terrain type, particularly when ice is present.
  • any control logic used to control motion of the vehicle during traction may be using an outdated k max value since the vehicle may be driving in different conditions to the conditions during the previous braking event.
  • a control system for controlling a dynamic system of the vehicle comprising; an input for receiving measured vehicle parameters in real time during a wheel slip event; a controller including an algorithm arranged to calculate a maximum tire-road adhesion coefficient, k max , in real time based on the measured vehicle parameters, and said controller arranged to generate a command signal arranged to configure a dynamic system of the vehicle for operation based on the maximum tire-road adhesion coefficient, k max ; and an output for outputting the control signal to the dynamic system of the vehicle; wherein k max is calculable during two or more vehicle modes, said vehicle modes including a stationary mode, a traction mode, and a braking mode.
  • the controller may be configured to calculate k max during the braking mode using:
  • the controller may be configured to calculate k max during the traction mode using:
  • the controller may be configured to calculate k max during the stationary mode using:
  • the measured vehicle parameters may be selected from the list of vehicle velocity, V, applied torque, T, wheel rotational speed, ⁇ , downwards force on a wheel, F z , steering column angle, 9 C , and an electronic power assisted steering (EPAS) system motor angle, 9 m .. These parameters are measurable during these wheel slip events. All of the other parameters required for calculating k max are derivable from these parameters.
  • the controller may be arranged to determine the maximum tire-road adhesion coefficient, k max , using differential calculus to find the maximum extrema. Determining k max in this way is more reliable and requires less computing time than using a curve fitting method as known from the acknowledged prior art. Accordingly, the braking system will be more reliable as a result of using this technique of determining k max .
  • the controller may be arranged to select between the braking, traction and stationary modes, wherein the braking mode may be selected when T is less than zero, the traction mode may be selected when T is greater than zero, and the stationary mode may be selected when T is equal to zero and when steering torque, T d , is not equal to zero. T is directly measurable and so using control logic to select between each of the formulae in this way is thought to be relatively simple, quick to compute, and reliable.
  • the controller may be arranged to calculate an actual tire-road adhesion coefficient, k, and wherein the command signal may be arranged to configure the dynamic system for operation based on the relationship between the maximum tire-road adhesion coefficient, / and the actual tire-road adhesion coefficient, k.
  • /( and k max is more direct than methods known from the prior art, which methods, such as the acknowledged prior art, typically extimate a /( value indirectly based on a curve of best fit predicted between k and wheel slip, A.
  • the controller may be configured to calculate the tire-road adhesion coefficient, k, using:
  • the controller may comprise a verification module arranged to verify the accuracy of k by estimating an estimated average tire-road adhesion coefficient, k, using a predefined model and comparing /( with k to generate a confidence signal, k e . In this way, computational errors of the controller will be detected and can thus be dealt with accordingly.
  • the verification module may be configured to generate k based on k max and wheel slip ratio, A.
  • the controller may be arranged to allow or prevent the output from outputting the control signal to the braking system depending on the magnitude of k e .
  • a relatively small magnitude of k e will indicate that there is either no computational error from the controller or that there is some degree of error but not sufficient to warrant de- coupling the controller from the braking system.
  • a relatively high magnitude of k e will indicate that there is sufficient computational error from the controller to warrant decoupling the controller from the braking system. In this way, by allowing or preventing the controller from outputting the command signal, depending on the accuracy of the controller's computation, erroneous operation of the dynamic system is minimised.
  • the controller may be arranged to send a wheel slip request, using the output, to induce actively a wheel slip event, in real time. Inducing a wheel slip event actively allows for more frequent updates of k max and a higher degree of control with regards to when k max updates are obtained. This is in contrast to obtaining updates for k max passively as and when wheel slip events occur naturally.
  • the controller may be arranged to send the wheel slip request to a braking system to apply a braking impulse to affect momentarily the wheel slip event.
  • the controller may be arranged to send the wheel slip request to a wheel motor to apply a power impulse to a wheel of the vehicle to affect momentarily the wheel slip event.
  • the controller may be arranged to send the wheel slip request to an electronic power steering system (EPAS) to apply a displacement impulse to a wheel of the vehicle to affect momentarily the wheel slip event.
  • EEPAS electronic power steering system
  • the braking impulse may be more suited to a particular vehicle mode, for instance, braking mode, where a sudden power impulse may be undesirable from a vehicle controllability point of view and a braking impulse may remain undetectable by an occupant of the vehicle.
  • the power impulse may be more suited to another vehicle mode, for instance, traction mode, where sudden power impulses may remain undetectable from an occupant of the vehicle where a braking impulse may be undesirable from a vehicle controllability point of view.
  • the stationary mode may benefit from the impulse being generated from the EPAS as a displacement impulse of the wheel since a power impulse would not be suitable and the braking impulse would not yield any results due to the vehicle either being stationary or travelling at very low speeds.
  • the dynamic system comprises a braking system, a wheel motor, or an electronic power assisted steering (EPAS) system.
  • a vehicle dynamic system comprising the aforementioned controller.
  • an electric or hybrid electric vehicle comprising the aforementioned dynamic system.
  • a method of controlling a dynamic system of a vehicle comprising; receiving vehicle parameters in real time during a wheel slip event; calculating a maximum tire-road adhesion coefficient, k max , in real time based on the measured vehicle parameters; generating a command signal arranged to configure a dynamic system of the vehicle for operation based on k max ; and outputting the command signal to the dynamic system; wherein k max is calculated during two or more vehicle modes, said vehicle modes including a stationary mode, a traction mode, and a braking mode.
  • the mode using: The method may comprise calculating / during traction mode using:
  • the method may comprise calculating / during stationary mode using:
  • the method of calculating k max may use vehicle parameters selected from the list of vehicle velocity, V, applied torque, T, wheel rotational speed, ⁇ , downwards force on a wheel, F z , steering column angle, 9 C , and an electronic power assisted steering (EPAS) system motor angle, 9 m .
  • vehicle parameters selected from the list of vehicle velocity, V, applied torque, T, wheel rotational speed, ⁇ , downwards force on a wheel, F z , steering column angle, 9 C , and an electronic power assisted steering (EPAS) system motor angle, 9 m .
  • EAS electronic power assisted steering
  • the method may comprise differentiating the or each aforementioned equation and obtaining the maximum extrema to determine k max .
  • the method may comprise selecting between the braking, traction and stationary modes, preferably selecting the braking mode when T is less than zero, preferably selecting the traction mode when T is greater than zero, and preferably selecting the stationary mode when T is equal to zero.
  • the method may comprise calculating a tire-road adhesion coefficient, k, in real time and configuring the dynamic system to operate based on the relationship between the maximum tire-road adhesion coefficient, k max and the tire-road adhesion coefficient, k
  • the m ise calculating the tire-road adhesion coefficient, k, using:
  • the method may comprise verifying the accuracy of k by estimating an estimated average tire-road adhesion coefficient, k, using a predefined model and comparing k with k to generate a confidence signal k e .
  • verifying the accuracy of k is achieved by using k max and wheel slip ratio, ⁇ , as inputs to the predefined model to generate k.
  • the method may comprise allowing or preventing output of the command signal to the dynamic system depending on the magnitude of k e .
  • the method may comprise sending a wheel slip request to induce actively a wheel slip event, in real time.
  • the method may comprise sending the wheel slip request to a braking to apply a braking impulse to affect momentarily the wheel slip event.
  • the method may comprise sending the wheel slip to a wheel motor to apply a power impulse to a wheel of the vehicle to affect momentarily the wheel slip event.
  • the method may comprise sending the wheel slip request to an electronic power steering system (EPAS) to apply a displacement impulse to a wheel of the vehicle to affect momentarily the wheel slip event.
  • EEPAS electronic power steering system
  • the dynamic system may comprise a braking system, a wheel motor, or an EPAS system.
  • Figure 1 shows a schematic view of an electric vehicle including a controller according to an embodiment of the present invention
  • Figure 2 shows a free body diagram of a wheel from the vehicle shown in Figure 1 ;
  • Figure 3 shows an electronic power assisted steering (EPAS) system of the vehicle from Figure 1 ;
  • EPAS electronic power assisted steering
  • Figure 4 shows a block diagram of the controller from the vehicle shown in Figure 1 ;
  • Figure 5 shows a block diagram of further aspects of the controller from Figure 1 ;
  • Figure 6 shows verification test data for the controller operating in a braking mode with a anti-lock braking system (ABS) on;
  • ABS anti-lock braking system
  • Figure 7 shows verification test data for the controller operating in a braking mode and displaying braking torque and wheel slip against tire-road adhesion coefficient
  • Figure 8 shows verification test data for the controller operating in a braking mode and displaying tire-road adhesion coefficient against wheel slip;
  • Figure 9 shows verification test data for the controller operating in a braking mode with ABS off
  • Figure 10 shows a similar view to Figure 6 of a different verification test with ABS on
  • Figure 1 1 shows a similar view to Figure 9 of the same verification test as Figure 10 but with ABS off.
  • an electric (or hybrid electric) land vehicle 10 such as a car, includes various dynamic systems for controlling its motion. These dynamic systems include a traction system, a braking system, and an electronic power steering (EPAS) system.
  • the vehicle 10 includes a vehicle body 12 for supporting a battery 14 and four wheels 16.
  • the wheels 16 are supported by respective side shafts 18. At least two of the wheels 16 are driven wheels in that power is supplied to them by the traction system to move the vehicle 10.
  • the traction system includes wheel motors 20 for powering the wheels by rotating the side shafts 18 connected to the driven wheels 16.
  • the vehicle 10 is a rear wheel drive vehicle since only the rear wheels 16 are connected to respective wheel motors 20. Power to the wheel motors 20 is supplied by the battery which is rechargeable from a power grid.
  • a generator 22 may be incorporated to recharge the battery for periods when the vehicle is operating in an electric mode.
  • the braking system includes two or more brakes 24, each brake for retarding one of the wheels. In this case, there are two brakes 24, each for retarding a front wheel 16.
  • the brakes 24 are disc brakes and operate in response to a driver depressing a brake pedal within a cabin of the vehicle 10. Retardation of the wheels 16 is achieved by opposing brake pads compressing against a brake disc, which brake disc is fixed on the side shaft 18.
  • a brake caliper supports and moves the opposing brake pads towards the brake disc in response to receiving a braking command signal, which will be described in further detail below.
  • An Anti-lock Braking System (ABS) is also incorporated into the braking system which operates by application and release of the brake pads according to a predefined frequency.
  • the braking system is controlled according to a braking control protocol.
  • the braking control protocol controls the braking system to apply varying degrees of braking torque, T b , and/or induces operation of the ABS, depending on a command signal received from a control system of the vehicle 10.
  • the control system includes a controller 26, an input 28 and an output 30.
  • the controller 26 and its operation are described in more detail below.
  • the input 28 is connected to various sensors and detectors 32 provided throughout the vehicle 10, which sensors and detectors 32 measure various vehicle parameters used by the controller to generate the command signal.
  • the controller 26 described herein may comprise a control unit or computational device having one or more electronic processors.
  • Vehicle 10 and/or a system thereof 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.
  • the term "controller” will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide the required control functionality.
  • a set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the method(s) described below).
  • the set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s).
  • a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present invention is not intended to be limited to any particular arrangement.
  • the set of instructions described above may be embedded in a computer- readable storage medium (e.g., a non-transitory storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, 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.
  • a computer- readable storage medium e.g., a non-transitory storage medium
  • a magnetic storage medium e.g., floppy diskette
  • optical storage medium e.g., CD-ROM
  • magneto optical storage medium e.g., magneto optical storage medium
  • ROM read only memory
  • RAM random access
  • a wheel 16 is shown together with vehicle parameters continuously monitored by the input 28 ( Figure 1 ). Details of the wheel 16 are not shown though the outer periphery of the wheel includes a tire 17.
  • the EPAS system 36 includes a steering wheel 38, a steering column 40, a motor 42, a gear arrangement 44, and a track rod 46 for turning the wheels 16.
  • the EPAS also include a rack and pinion arrangement 48 for converting rotational movement from the steering column 40 into linear motion of the track rod 46.
  • Various vehicle parameters, measured on the EPAS 36 are continuously monitored by the input 28 ( Figure 1 ).
  • the EPAS 36 works by the driver turning the steering wheel 38 and, in response, the motor rotates the pinion, via the steering column 40 to turn the wheels 16 via the track rod 46.
  • the measured vehicle parameters include vehicle velocity, V, angular velocity of the wheel, ⁇ , applied torque T (torque of the wheel motor 20), downwards force on a wheel, F z (which is an estimated parameter based on a mass calculation of the vehicle), steering column angle, 9 C , and EPAS system motor angle, 9 m .
  • vehicle velocity V
  • angular velocity of the wheel ⁇
  • applied torque T torque of the wheel motor 20
  • F z which is an estimated parameter based on a mass calculation of the vehicle
  • F z which is an estimated parameter based on a mass calculation of the vehicle
  • steering column angle 9 C
  • EPAS system motor angle 9 m .
  • the controller 26 ( Figure 1 ) is arranged to operate in three vehicle modes, namely a "braking mode", a “traction mode”, and a stationary or very low speed mode which hereinafter is termed a "stationary mode".
  • a wheel slip event can occur in any of these modes.
  • Each mode uses a unique set of equations to determine the command signal to be sent to the dynamic systems. These equations are provided on an algorithm of the controller 26. These equations are dealt with in turn below, however, the braking and traction modes are based upon those parameters referenced in Figure 2. In contrast, equations governing the stationary mode are based on those parameters referenced in Figure 3.
  • the controller decides which set of equations to process based on the current value of applied torque, T, and steering wheel torque, T d .
  • each equation generates a value for the maximum tire-road adhesion coefficient, k max , in real time based on the measured parameters relating to the identified vehicle mode.
  • k max the algorithm determines a current value of the tire-road adhesion coefficient, k.
  • the formula used in calculating k will be described in further detail below.
  • k is compared to k max and a command signal is sent, by the output 28 of the controller 26, to one of the dynamic systems to operate based on the relationship between k and k max , so that the risk of uncontrollable wheel slip in traction, braking, and stationary modes is minimised.
  • the dynamic system may be any system effecting the motion of the vehicle 10.
  • dynamic systems include the braking system, the wheel motors 20 ( Figure 1 ) and the EPAS system 36.
  • the construction of the algorithm is best described by detailing each vehicle mode in turn below.
  • Each of the subsequently identified modes should be read in conjunction with Figure 4, which shows a block diagram of the controller 26 in operation.
  • the controller 26 in operation includes the input 28 and the output 30.
  • the input 28 communicates with the algorithms 50 for determining k max .
  • a correcting factor 52 for calculating k is also communicative with the algorithms 50.
  • the input 28 is also in communication with a trigger logic function 54.
  • the trigger logic function is a rule based, decision making logic, which uses existing measurements to define when and which wheel has experienced an unexpected wheel slip event. Based on this information, and with knowledge of the vehicle mode (e.g. driving mode, braking mode, or stationary mode), the trigger logic will be able to decide when and how the electric motors of the wheels 16 will be controlled. For instance, when the vehicle measures a high level of wheel acceleration or a high level of change of the rate of wheel acceleration, then the decision making logic will be able to decide the impulse test (e.g. power impulse magnitude or braking impulse magnitude) required to induce actively the wheel slip event to generate actively a k max value.
  • the impulse test e.g. power impulse magnitude or braking impulse magnitude
  • Outputs from the algorithm 50 and the trigger logic 54 namely k max and A max , and a trigger value respectively, are input to a data store 56 of the controller 26 for future reference.
  • the most recently recorded values in the data store 56 are used by the controller 26, together with a current value for k, to generate the command signal.
  • Fx k max F z (3)
  • ⁇ is the angular speed of the wheel 16 in rad/s
  • V is the longitudinal speed over ground in m/s
  • T is the braking torque in Nm
  • F x is the longitudinal tire-road contact force in N
  • J is the moment of inertial of the wheel in Kgm 2
  • m is the single mass corner in Kg
  • r is the wheel radius in m.
  • the wheel slip ratio, during braking mode, is defined as
  • ⁇ max(V, e) ⁇ where e is a constant of very small value to avoid zero denominator.
  • the nominal value of e 0.001 is used in this paper.
  • Equation (6) is a highly non-linear function that correlates the brake torque and the wheel slip ratio, the rate of change of slip in one equation that calculates the peak tire-road adhesion coefficient, k max , during braking in real time. This equation is also highly prone to noisy signals of wheel slip measurements so extra care needs to be taken in order to acquire robust data.
  • a model based approach is selected to encapsulate the concept of calculating in real time the tire-road adhesion coefficient, k, during the stationary mode.
  • the entire concept is based on the assumption that at very low vehicle speed, or whilst the vehicle is stationary, in a longitudinal mode, the driver will provide some amount of steering in order to get enough slip to estimate the peak tire-road adhesion coefficient, k max . This is the initial value of the peak tire-road adhesion coefficient, k max , and as the vehicle braking and accelerating, corrective action will occur.
  • the entire philosophy is based on the assumption that the best educated estimate for the peak adhesion can be provided only at the time that the steering input is equal to tire self-alignment torque.
  • EPAS and a simple tire model are used to develop the algorithm in a stationary mode.
  • One such tire model is known as the Fiala tire model and is obtained using equations (16) and (17) below.
  • the Fiala tire model is a very simple model to introduce the principle of the entire concept. More complicated tire models (e.g. a Magic formula model) could be potentially incorporated to enhance the accuracy and robustness of the algorithm.
  • the dynamic analysis of the EPAS and the motor characteristics are described in more detail below.
  • Ic e c - K c e c - B C e c + K C ( ⁇ I) - F c sin (e c ) + T d (12)
  • T d k c (e c - 3 ⁇ 4l) + NK t I m + T t
  • J c is the steering column moment of inertia
  • K c is the steering column stiffness
  • B C is the steering column viscous damping
  • 0 C is the steering wheel angle
  • e m motor angle
  • N is motor gear ratio
  • F c is the steering column friction
  • J eq is the equivalent inertia
  • k r is the tire spring rate
  • R p is the steering column pinion radius
  • k t is the motor torque
  • constant voltage I m is the motor current
  • F m is the motor friction
  • U is motor terminal voltage
  • L m is motor inductance
  • R m is the motor resistance
  • T t is the tire reaction force.
  • M z is the self-aligning torque of the tire
  • C a is the cornering stiffness
  • ⁇ is the steering angle
  • the controller is able to execute the equations relating to each mode in response to detecting which mode the vehicle is current operating in. This is done by monitoring the values of applied torque, T, and steering wheel torque, T d , in5 real time. Having knowledge of the applied torque, the controller 26 executes the corresponding equations relating to that mode as shown in equation (20) below.
  • the command signal sent to one of the dynamic systems is based on the relationship between k and k max .
  • the command signal may be sent to any of the EPAS 36, the braking system, and a wheel motor 20 to operate based on k and k max so as to prevent uncontrollable wheel slip occurring.
  • Such a range of usage of the controller is not possible using any of the known algorithms of the prior art, which are limited to single mode usage.
  • wheel slip events require wheel slip events to occur in order to generate values for the constituent vehicle parameters. Such wheel slip events occur naturally, for instance during a braking event. However, it is also possible to affect actively a wheel slip event in a few ways. For instance, a braking impulse could be sent from the controller 26 to the braking system to apply maximum braking force for an instantaneous time period. This braking impulse will instantaneously generate a wheel slip event which in turn will generate numerical values for the constituent parameters of the aforementioned equations relating to braking and tractions modes. Alternatively, it is possible to affect actively a wheel slip event by applying a power impulse to one or more of the driven wheels 16 using the motors 20 ( Figure 1 ).
  • the impulse is instantaneous and should cause a momentary wheel slip event for the generation of numerical values for the aforementioned equations for braking and traction modes.
  • the wheel slip event should remain largely undetectable for vehicle occupants due to them being for such a short period of time.
  • the wheel slip event is determined by a displacement impulse by the EPAS motor moving the track rod over an angle which is sufficient to cause a wheel slip event but which is insufficient to be detectable by a vehicle occupant.
  • the controller 26 is able to affect actively a wheel slip event in all three vehicle modes.
  • the controller 26 also includes a verification module 60 for verifying the accuracy of the algorithms 50.
  • the verification module 60 uses a predefined model 62, which model is an inverse tire model. Inputs to the inverse tire model are A and k max , where A is also an input to the tire-road adhesion coefficient algorithms 50 and where k max is an output from the algorithms 50.
  • the inverse tire model determines an estimated average tire-road adhesion coefficient, k, which is used as a comparator against the calculated tire-road adhesion coefficient, k, output from the corrective formula (formula (21 ) described above). In particular, k, is subtracted from k, to produce an error signal, k e .
  • the controller uses k e to understand the accuracy of the algorithms 50. For instance, a high magnitude of k e results from an inaccurate algorithm 50. In contrast, a low magnitude of k e is either due to an inaccurate algorithm 50 or both an inaccurate inverse tire model and an inaccurate algorithm 50. However, the inverse tire model is constructed so that errors in both the algorithm 50 and the inverse tire model 62, which result in the same errors in k and k e , are unlikely to occur.
  • the controller 26 is arranged to use the error signal, k e , to allow or prevent the output from sending the command signal to the braking system.
  • k e a high magnitude of k e is associated with an erroneous algorithm 50, so the command signal based on calculated k and k max is likely to be erroneous too. It is important to 'de-couple' the algorithm 50 in such cases since such errors may result in erroneous operation of the dynamic system.
  • This section evaluates the experimental results obtained from an experimental vehicle on a constraint environment (i.e. test track).
  • Environmental and vehicle data are omitted for confidentiality reasons.
  • the vehicle has been tested on a very low adhesion surface in a test track.
  • the wheel slip event during braking deliberately remained on a longitudinal orientation to avoid any side slip complications and high side acceleration values.
  • Figure 6 present a brake event with enabled ABS in wet road surface.
  • the duration of brake event is about 1 second and the vehicle is decelerated from 20m/s to almost Om/s (2g deceleration).
  • the algorithm is able to calculate the peak tire-road adhesion coefficient in real time as shown in Figure 6.
  • the peak value of tire-road adhesion coefficient i.e. 0.35 is calculated at about 10% of slip after 2.3ms of braking event.
  • the maximum slip observed after 0.5ms after the initial brake application where the slip ratio is about 30% and the value of the tire-road adhesion coefficient at this point is around 0.13.
  • Figures 7 and 8 show the distribution of adhesion coefficient relative parameters such as brake torque and wheel slip.
  • the algorithm is able to identify the tire-road adhesion coefficient in real time and to evaluate an extra available grip during the event and thus to readjust the braking actuation control protocol.
  • a third experiment (2.8g deceleration) has been conducted in a higher grip surface, namely a gravel road with estimated peek adhesion of 0.38.
  • Figure 10 shows that the wheel is almost completely locked, having a slip ratio of 85% after 0.5ms and the tire- road adhesion coefficient has a very low value or approximately 0.1 .
  • the wheel slip ratio is 5%
  • the peak tire-road adhesion coefficient is 0.4.

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Automation & Control Theory (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Regulating Braking Force (AREA)

Abstract

L'invention concerne un système de commande pour commander un système dynamique de véhicule (10). Le système de commande comprend : une entrée (28) pour recevoir des paramètres de véhicule mesurés en temps réel pendant un événement de patinage de roue. Le système de commande comprend également un dispositif de commande (26) comprenant un algorithme conçu pour calculer le coefficient d'adhérence maximal k max d'un pneumatique sur la chaussée en temps réel sur la base des paramètres mesurés du véhicule. Le contrôleur (26) est agencé pour générer un signal de commande prévu pour configurer le système dynamique du véhicule (10) afin de fonctionner sur la base du coefficient d'adhérence maximal, k max du pneumatique sur la chaussée. Le système de commande comprend également une sortie (30) pour délivrer en sortie le signal de commande au système dynamique d'un véhicule (10). k max est peut être calculé au cours de deux modes ou plus du véhicule, ces derniers comprenant un mode stationnaire, un mode traction et un mode freinage.
EP16703099.8A 2015-02-03 2016-02-03 Système de commande Withdrawn EP3253629A1 (fr)

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GB2553121B (en) * 2016-08-24 2019-02-06 Jaguar Land Rover Ltd Watchdog controller
CN108922177B (zh) * 2018-06-29 2021-08-10 东南大学 一种无人驾驶车辆通过交叉路口时速度控制系统及方法
KR20210018652A (ko) * 2019-08-08 2021-02-18 현대자동차주식회사 차량의 휠 슬립 제어 방법
DE102022204709A1 (de) * 2022-05-13 2023-11-16 Robert Bosch Gesellschaft mit beschränkter Haftung Bremsvorrichtung, elektromechanisches Bremssystem und Verfahren zum Betreiben eines elektromechanischen Bremssystems

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US7751961B2 (en) * 2005-09-15 2010-07-06 Gm Global Technology Operations, Inc. Acceleration/deceleration induced real-time identification of maximum tire-road friction coefficient
DE102008041034A1 (de) * 2008-08-06 2010-02-11 Robert Bosch Gmbh Verfahren zur Einstellung motorischer Antriebseinheiten in Kraftfahrzeugen mit Hybridantrieb
US8055424B2 (en) * 2008-11-21 2011-11-08 GM Global Technology Operations LLC Real-time identification of maximum tire-road friction coefficient by induced wheels acceleration/deceleration
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GB2534886B (en) 2018-04-18

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