GB2570874A

GB2570874A - Motor Vehicle Controller, Control System Vehicle and Method

Info

Publication number: GB2570874A
Application number: GB1801723.6A
Authority: GB
Inventors: Adrian Beever Paul
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2018-02-02
Filing date: 2018-02-02
Publication date: 2019-08-14
Anticipated expiration: 2038-02-02
Also published as: GB201801723D0; GB2570874B; DE102019201162A1

Abstract

A controller 110 for a braking system 126S of a vehicle 100 is provided. The controller 110 is configured to automatically cause the vehicle 100 to decelerate towards a stop. The controller 110 is configured to receive deceleration information indicative of a deceleration request and velocity information indicative of a vehicle's velocity. The controller 110 is further configured to apply a braking profile to cause the vehicle to decelerate towards a stop in accordance with a predetermined deceleration profile, when: i) the vehicle speed is below a predetermined automatic brake control initiation threshold speed; and ii) the deceleration request decreases. A control system, a vehicle and a method of controlling a vehicle braking system are also disclosed.

Description

(57) A controller 110 for a braking system 126S of a vehicle 100 is provided. The controller 110 is configured to automatically cause the vehicle 100 to decelerate towards a stop. The controller 110 is configured to receive deceleration information indicative of a deceleration request and velocity information indicative of a vehicle’s velocity. The controller 110 is further configured to apply a braking profile to cause the vehicle to decelerate towards a stop in accordance with a predetermined deceleration profile, when: i) the vehicle speed is below a predetermined automatic brake control initiation threshold speed; and ii) the deceleration request decreases. A control system, a vehicle and a method of controlling a vehicle braking system are also disclosed.

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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MOTOR VEHICLE CONTROLLER, CONTROL SYSTEM, VEHICLE AND METHOD

TECHNICAL FIELD

The present disclosure relates to a motor vehicle controller, control system, vehicle and method. Aspects of the invention relate to a controller for a braking system of a vehicle, to a control system, to a vehicle, to a method, to a non-transitory computer readable carrier medium carrying computer readable code, to a computer program product, to a nontransitory computer readable medium and to a processor.

BACKGROUND

It is recognised that drivers of vehicles with automatic transmissions can find it difficult to stop the vehicle as smoothly as they would like it to stop. In a vehicle with a manual transmission, smooth stopping can be achieved by declutching the engine and then reducing the brake force to zero as the vehicle comes to rest. The difficulty with conventional automatic transmissions is that the powertrain is still generating a positive driving torque which has to be compensated by brake torque such that the driver cannot release the brakes completely as the vehicle comes to rest. Braking to rest on a gradient can create a similar difficulty in a vehicle with conventional transmission since, again, a non-zero braking torque will be needed to hold the vehicle stationary.

It is an aim of embodiments of the present invention to provide a method of vehicle control that enables relatively smooth braking to be achieved in a reproducible, controlled manner.

SUMMARY OF THE INVENTION

In one aspect of the present invention for which protection is sought there is provided a controller for a braking system of a vehicle, the controller being configured to automatically cause the vehicle to decelerate towards a stop, wherein the controller is configured to receive deceleration information indicative of a deceleration request and velocity information indicative of a vehicle’s velocity, and wherein the controller is configured to apply a braking profile to cause the vehicle to decelerate towards a stop in accordance with a deceleration profile, when:

i) the vehicle speed is below a predetermined threshold speed, and ii) the deceleration request decreases.

Some embodiments of the present invention have the feature that a vehicle may be repeatedly caused to slow to a halt at a consistent rate of deceleration even in the case of a vehicle having an automatic transmission. Some embodiments of the invention have the advantage that driver workload may be reduced.

Predetermined conditions (i) and (ii) may also be referred to as automatic brake control initiation conditions.

In some embodiments, the deceleration information may comprise information indicative of brake fluid pressure in the braking system.

It is to be understood that the controller may comprise a plurality of control units or control modules such as a vehicle control unit (VCU) and a brake controller.

The deceleration information may be received in the form of a brake demand signal, and may for example be generated by a driver or by an autonomous vehicle control system. The brake demand information may comprise information in respect of the pressure of brake fluid in the vehicle braking system. Alternatively or in addition the information may comprise one or more of the amount of force applied by the driver to the brake control member, which may comprise a brake pedal, and/or the extent of brake control member travel (such as an indication of the proportion of travel with respect to an allowable range of travel, or actual amount of travel, e.g. in metres or arbitrary units).

The feature that the controller is configured to apply a braking profile to cause the vehicle to decelerate towards a stop in accordance with a deceleration profile may be referred to as an automatic stop function.

The automatic stop function may also be referred to as an automatic smooth stop function because the function may, in some embodiments, be arranged to result in a relatively smooth stop that maintains vehicle composure, avoiding undue NVH (noise, vibration and harshness) thereby enhancing passenger comfort and enjoyment.

The control system may control the amount of brake fluid pressure in the braking system in order to control the amount of brake force, and therefore the rate of deceleration.

Optionally, the conditions under which the controller is configured to apply the braking profile further comprise the condition that the vehicle has been decelerating at a rate of deceleration that is within a predetermined range of deceleration rates during at least a portion of the period for which the deceleration request has been received.

Optionally, the conditions under which the controller is configured to apply the braking profile further comprise the condition that the vehicle has been decelerating at a rate of deceleration that is within the predetermined range of deceleration rates for a period exceeding a predetermined automatic brake control initiation threshold period.

Optionally, the condition that the deceleration request decreases comprises the condition that the deceleration request decreases by an amount greater than or equal to a predetermined automatic brake control initiation deceleration request decrease amount.

Optionally, the condition that the deceleration request decreases further comprises the condition that the deceleration request decreases by an amount greater than or equal to the predetermined automatic brake control initiation deceleration request decrease amount within a predetermined automatic brake control initiation deceleration request reduction period.

Optionally, the condition that the deceleration request decreases includes the condition that the deceleration request decreases to an amount that is not less than a predetermined automatic brake control initiation deceleration request threshold amount.

It is to be understood that, in the case of a vehicle with a hydraulic braking system, the predetermined automatic brake control initiation deceleration request decrease amount may be a predetermined automatic brake control initiation brake pressure reduction amount. The predetermined automatic brake control initiation deceleration request reduction period may be a predetermined automatic brake control initiation brake pressure reduction period.

The predetermined automatic brake control initiation deceleration request threshold amount may be a predetermined automatic brake control initiation brake pressure threshold amount.

Optionally, the deceleration profile is substantially independent of the instant deceleration request amount.

Optionally, the deceleration profile is substantially independent of the instant driving surface gradient.

Thus, the controller attempts to cause the vehicle to decelerate (i.e. undergo negative acceleration) at a rate that is substantially independent of driving surface gradient. This feature has the advantage that a consistent braking experience may be provided to a passenger of the vehicle regardless of the prevailing driving surface gradient provided the gradient is not too steep. It is to be understood, for example, that in the case of a particularly steep uphill gradient gravity act to decelerate the vehicle at a rate exceeding the deceleration profile.

Optionally, the deceleration profile is dependent at least in part on driving surface gradient.

Thus it is to be understood that the deceleration profile applied may vary according to driving surface gradient. In some embodiments the profile may be such as to apply a higher deceleration rate when ascending an incline, since a passenger may be able comfortably to tolerate higher rates of deceleration when the vehicle is climbing. The profile may be such as to apply a lower deceleration rate when descending an incline, since a passenger may not be able comfortably to tolerate as high a rate of deceleration when the vehicle is descending a gradient as when climbing a gradient or driving on level ground. Other arrangements may be useful.

Optionally, if whilst applying a braking profile the deceleration information indicates that the amount of deceleration requested exceeds the amount that the control system requires to apply in order to cause the vehicle to slow to a stop according to the deceleration profile, the control system ceases applying the braking profile.

Thus it is to be understood that, in the event the controller applies a braking profile and a driver or autonomous vehicle control system requests an amount of braking that exceeds the amount being requested by the controller in applying the braking profile, the controller ceases applying the braking profile. Thus, braking initiated by a driver or autonomous vehicle control system takes priority over application of the braking profile by the controller.

The controller may comprise processing means, wherein the processing means comprises an electronic processor having an electrical input for receiving deceleration information indicative of a deceleration request and information indicative of vehicle velocity, and an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, wherein the processor is configured to access the memory device and execute the instructions stored therein such that it is operable to apply a braking profile to cause the vehicle to decelerate towards a stop in accordance with a deceleration profile, when;

In a further aspect of the invention for which protection is sought there is provided a control system comprising a controller according to another aspect.

In a still further aspect of the invention for which protection is sought there is provided a vehicle comprising a controller according to an aspect of the invention or a control system according to an aspect of the invention.

In one aspect of the invention for which protection is sought there is provided a vehicle comprising a controller according to another aspect.

In an aspect of the invention for which protection is sought there is provided a method of controlling a braking system of a motor vehicle by means of a controller, the method comprising:

receiving deceleration information indicative of a deceleration request and velocity information indicative of a vehicle’s velocity, and applying a braking profile to cause the vehicle to decelerate towards a stop in accordance with a deceleration profile, when:

The method may comprise applying a deceleration profile that is substantially independent of the instant deceleration request amount.

The method may comprise applying a deceleration profile that is substantially independent of the instant driving surface gradient.

The method may comprise applying a deceleration profile that is dependent at least in part on driving surface gradient.

The method may comprise applying a braking profile, the method comprising ceasing applying the braking profile if the deceleration information indicates that the amount of deceleration requested exceeds the amount that the control system requires to apply in order to cause the vehicle to slow to a stop according to the deceleration profile.

In an aspect of the invention for which protection is sought there is provided a control system for a motor vehicle, the control system being configured to receive brake demand information indicative of brake force demanded of a vehicle braking system and acceleration rate information indicative of vehicle rate of acceleration, the control system being configured to automatically cause the vehicle to decelerate towards a stop when a set of predetermined stopping conditions are met, the stopping conditions including the conditions that (i) the driver initiated brake demand by actuating a brake control member and the vehicle was caused to decelerate at a rate within a predetermined automatic brake control initiation deceleration range, and (ii) that the driver subsequently reduced the amount of brake demand by an amount greater than or equal to a predetermined automatic brake control initiation brake demand reduction amount to a nonzero brake demand amount.

In a further aspect of the invention for which protection is sought there is provided a method of controlling a braking system of a motor vehicle by means of a controller, the method comprising receiving driver brake demand information indicative of driver brake force demand, and automatically causing the vehicle to come to a stop when a set of predetermined stopping conditions are met, the stopping conditions including the conditions that (i) the driver initiated brake demand by actuating a brake control member and the vehicle was caused to decelerate at a rate within a predetermined automatic brake control initiation deceleration range, and (ii) that the driver subsequently reduced the amount of brake demand by an amount greater than or equal to a predetermined automatic brake control initiation brake demand reduction amount to a non-zero brake demand amount.

In an aspect of the invention for which protection is sought there is provided a non-transitory computer readable carrier medium carrying computer readable code for controlling a vehicle to carry out the method of another aspect.

In an aspect of the invention for which protection is sought there is provided a computer program product executable on a processor so as to implement the method of another aspect.

In an aspect of the invention for which protection is sought there is provided a non-transitory computer readable medium carrying computer readable code which when executed causes a vehicle to carry out the method of another aspect.

In an aspect of the invention for which protection is sought there is provided a processor arranged to implement the method of another aspect, or the computer program product of another aspect.

Any controller or controllers described herein may suitably comprise a control unit or computational device having one or more electronic processors. Thus 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, 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. A first controller may be implemented in software run on one or more processors. One or more other controllers 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 DRAWINGS

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:FIGURE 1 illustrates a vehicle according to an embodiment of the present invention having an engine and an automatic transmission;

FIGURE 2 illustrates schematically an aspect of brake control strategy implemented by a controller in the embodiment of FIG. 1;

FIGURE 3 illustrates the variation in values of a number of parameters during the execution of an automatic smooth stop function by a vehicle controller according to an embodiment of the present invention in an example scenario.

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration of a vehicle 100 according to an embodiment of the present invention. The vehicle 100 has an internal combustion (IC) engine 121 that drives an automatic transmission 131. The automatic transmission 131 is coupled to a driveline 150 that includes a power transfer unit (PTU) 141 and rear drive shafts 151 that drive rear wheels 115. Front wheels 111 are not driven in the embodiment shown.

The vehicle has a main controller in the form of a vehicle control unit (VCU) 110 that communicates with a brake controller 126C that forms part of a braking system 126S and an engine controller 121C that controls the engine 121. A brake pedal 163 is coupled to a brake actuator assembly 126A of the braking system 126C and provided in communication with the brake controller 126C, the brake pedal controlling the amount of brake force generated by the braking system 126C. An accelerator pedal 161 is coupled to the engine controller 121C to control the amount of torque generated by the engine 121.

In the present embodiment, the VCU 110 and brake controller 126C receive deceleration information indicative of a deceleration request in the form of driver brake demand information indicative of the amount of brake force the driver wishes the braking system 126S to generate. The information is received in the form of a brake pressure signal from the braking system 126S indicative of the amount of brake pressure in the braking system 126S. The amount of brake pressure in the braking system 126S determines the amount of brake force applied by the braking system 126S to the wheels 111, 115 of the vehicle 100 and is dependent at least in part on the amount by which brake pedal 163 is depressed.

The brake controller 126C receives velocity information in the form of wheel speed information indicative of the speed of each wheel 111, 115 of the vehicle 100 and calculates a vehicle reference speed value VREF based on the information. The wheel speed information is provided in the form of vehicle wheel speed signals generated from signals generated by wheel speed sensors. In the present embodiment, the brake controller sets the reference speed value V REF substantially equal to the speed of the second fastest turning wheel. Other arrangements for generating V REF may be useful in some alternative embodiments, such as setting V REF to the speed of the second slowest turning wheel or any other suitable value.

The brake controller 126C outputs the value of V REF to the VCU 110.

The VCU 110 and brake controller 126C also receive vehicle longitudinal acceleration information in the form of a signal from an inertial measurement unit (IMU) 128 indicative of the amount of longitudinal acceleration being experienced by the vehicle 100 at a given moment in time.

The VCU 110 monitors the value of VREF, the amount of brake pressure in the braking system 126S and the rate of longitudinal acceleration of the vehicle 100 at a given moment in time. The VCU 110 is configured, when certain conditions are met, to command the brake controller 126C to apply a braking profile that causes the braking system 126C to maintain application of brake pressure sufficient to cause the vehicle 100 to slow to a halt according to a predetermined deceleration profile, if a set of conditions, which may be referred to herein as automatic brake control initiation conditions, are met at a given moment in time. The predetermined deceleration profile defines a predetermined rate of deceleration as a function of vehicle speed, or of time, and represents a desirable braking behaviour of the vehicle which will bring the vehicle to a halt in a desired manner.

It is to be understood that the braking profile that the VCU 110 causes to be applied as a function of time (or as a function of vehicle speed), in order to slow the vehicle according to the predetermined deceleration profile, may depend at least in part on driving surface gradient, the presence of surface water on the driving surface, condition of the braking system, and/or one or more other factors. The braking profile may be indicative of a brake pressure that the VCU 110 causes to be applied to achieve the desired deceleration, or a modulation of a regenerative braking system, or both.

In the present embodiment the automatic brake control initiation conditions are:

(i) The vehicle 100 speed (V REF) is less than or equal to a predetermined automatic brake control initiation threshold speed; and (ii) The amount of brake pressure in the braking system 126S (indicative of the deceleration request) has decreased by an amount greater than a predetermined automatic brake control initiation brake pressure (deceleration request) reduction amount.

Condition (ii) may also require that the reduction in the amount of brake pressure decreases by the amount greater than a predetermined automatic brake control initiation brake pressure reduction amount within a predetermined automatic brake control initiation brake pressure reduction period, and that the amount of brake pressure is still at least a predetermined automatic brake control initiation brake pressure (deceleration request) threshold amount.

A further condition may be that the vehicle 100 has been decelerating at a rate within a predetermined range of deceleration rates that may be referred to as an automatic brake control initiation deceleration range for a period at least equal to a predetermined automatic brake control initiation threshold period.

It is to be understood that the predetermined automatic brake control initiation brake pressure reduction amount may be an absolute amount or a proportion of the amount before the reduction takes place. Other arrangements may be useful in some embodiments. For example, in the case of a vehicle having a brake pedal, instead of requiring that the brake pressure is still at least a predetermined automatic brake control initiation brake pressure threshold amount, the VCU 10 may check that the condition is met that a brake pedal switch or sensor is detecting that a driver’s foot is still in contact with, and applying at least some pressure to, the brake pedal. Thus, whilst the brake pressure may be substantially zero (or substantially the same as the pressure when no braking is being demanded by the driver), as a result of relatively little brake pedal deflection, the VCU 10 may still determine that the driver has a foot on the brake pedal, by determining that the condition is met that a brake pedal switch or sensor is detecting that a driver’s foot is still in contact with, and applying at least some pressure to, the brake pedal.

In the present embodiment, the automatic brake control initiation threshold speed is 10kph although other values may be useful in some embodiments. The predetermined automatic brake control initiation deceleration range is the range from 1 to 3 metres per second per second and the predetermined automatic brake control initiation threshold period is 3s although other values of one or both of these parameters may be useful in some embodiments.

In the present embodiment the predetermined automatic brake control initiation brake pressure reduction amount is 75% of the amount prior to the reduction, the predetermined automatic brake control initiation brake pressure reduction period is 0.5s and the predetermined automatic brake control initiation brake pressure threshold amount is 2 bar. Other values of one or more of these parameters may be useful in some embodiments.

In the present embodiment, upon detecting that the rate of brake pressure reduction exceeds that necessary for automatic brake control initiation, the VCU 10 triggers a brake pressure hold in which the amount of brake pressure is prevented from decreasing further until the VCU 10 has determined whether each of the automatic brake control initiation conditions have been met. This is so as to reduce the amount by which brake pressure reduces prior to automatic brake control initiation.

In the event that each of the conditions for automatic brake control initiation are met, the VCU 10 is configured to hold the rate of deceleration of the vehicle at the level of the brake pressure at the first instant of holding brake pressure, i.e. at the level maintained during the brake pressure hold, and thereafter the brake pressure is reduced to follow a time and/or speed scheduled pressure reduction rate that has been pre-determined to deliver the target smooth stop.

The initiation brake pressure threshold is set to 2 bar because, in the present embodiment, this typically corresponds to a relatively light depression of the brake pedal 163. It is considered relatively unlikely that a driver would control the vehicle 100 so as to meet the automatic brake control initiation conditions if the driver did not in fact intend the vehicle 100 to come to rest. Thus, it is considered that the chances of the automatic brake control initiation conditions being met when in fact a driver did not intend the vehicle 100 to come to rest are sufficiently low as to not inconvenience a driver to any significant extent.

It is to be understood that other values of initiation brake pressure threshold may be useful in some alternative embodiments. In some embodiments, the VCU 10 may detect accelerator pedal travel rather than hydraulic brake fluid pressure. In particular, in the case of vehicles not having a hydraulic braking system, for example vehicles having an electrical or electrically actuated braking system, brake pedal travel may be detected. In some embodiments, instead of checking whether the brake pressure is less than a predetermined automatic brake control initiation brake pressure threshold amount, the VCU 10 may simply check that the brake pedal is being depressed at least partially, or that the amount of force being applied by a driver to the brake pedal exceeds a predetermined automatic brake control initiation brake pedal force threshold amount.

In the present embodiment, if the automatic brake control initiation conditions are met, the VCU 110 controls the brake controller 126C to execute an automatic smooth stop function in which the brake controller 126C controls the amount of brake pressure in the braking system 126C to achieve a relative smooth stop, even where the vehicle 100 is equipped with an automatic transmission 131 as in the present embodiment. The brake controller 126C controls the brake pressure in the braking system 126S so as to achieve a target deceleration rate of substantially 0.2m per second per second. In order to deliver a smooth stop, in the present embodiment the rate of change of deceleration (jerk) is reduced as the vehicle speed approaches zero. In the present embodiment, the rate of change of deceleration is changed in a linear manner, in the present embodiment from a rate of 2m/s^A2 down to zero at rate of 1 m/s^A2/s (1 m/s3).

FIG. 2 is a flow diagram illustrating operation of the vehicle 100 in respect of implementation of the feature of the automatic smooth stop function. It is to be understood that in some embodiments, including the present embodiment, the automatic smooth stop function may be disabled via a vehicle human-machine interface (HMI), in the present embodiment by means of a touch screen display panel 110P that enables the user to communicate with the VCU 110.

At step S101 of FIG. 2 the method is initiated. At step S103 the VCU 110 checks whether the condition is met that the rate of deceleration of the vehicle 100 is in the range 1 to 3m per second per second (based on data from IMU 128), and vehicle reference speed VREF is less than or equal to 10kph. If these conditions are met the method continues at step S103a, else the method is terminated at step S105.

At step S103a, the VCU 110 checks whether the condition is met that the rate of reduction of brake pedal input exceeds a predetermined rate. This is accomplished by reference to the pressure of hydraulic brake fluid in the braking system applying brake force to one or more wheels of the vehicle. If the rate of reduction does exceed the predetermined rate, the VCU 110 causes the amount of brake pressure substantially at that instant to be maintained, i.e. held, and continues to step S107. If the condition is not met, the VCU 110 causes the amount of brake pressure to blend to the amount of demanded brake pressure according to brake pedal position and the method terminates at step S105.

At step S107 the VCU 110 determines whether, in addition to the condition at steps S103 and S103a being met, the amount of brake pressure has been reduced by a proportion of 75% or more over a period 0.5s. If this condition is met, the method continues at step S109. If this condition is not met, the VCU 110 causes the amount of brake pressure to blend to the amount of demanded brake pressure according to brake pedal position and the method terminates at step S105.

At step S109 the VCU 110 triggers the automatic smooth stop function.

At step S111 the VCU 110 causes the brake controller 126C to continue to maintain the brake pressure held at step S103a provided it is greater than the amount corresponding to the current brake pedal position, and at a value sufficient to achieve a deceleration rate of at least 0.5m per second per second. Other values may be useful in some embodiments.

At step S113 the VCU 110, in combination with brake controller 126C, continues to manage the rate of deceleration, by controlling hydraulic brake fluid pressure, to maintain a substantially constant rate of deceleration of the vehicle of initially at a level close to what it was when the automatic smooth stop function was triggered (e.g. 2.5m per second per second). When the vehicle speed drops below a threshold, the deceleration is reduced according to a predetermined profile in order to reduce the jerk at the end of the stop.

At step S115 the VCU 110 checks whether the driver is still depressing the brake pedal 163. If the driver is depressing the brake pedal 163 the method continues at step S123 else the method continues at step S117.

At step S117 the VCU 110 cancels implementation of the automatic smooth stop function and releases the brake pressure in the braking system 126S at a controlled rate. The method then continues at step S119.

At step S119 the brake controller 126C continues operating in the conventional manner with the automatic smooth stop function not being implemented. The method terminates at step S121.

As noted above, if at step S115 the driver is still depressing the brake pedal 163, the method continues at step S123.

At step S123 the VCU 110 determines whether the brake pedal effort is higher than that required in order to provide the target rate of deceleration (as determined at step 103a or being reduced in step 113 to reduce jerk in the present embodiment). If the brake effort does exceed the amount required, the VCU 110 continues at step S125 else the VCU 110 continues at step S111.

At step S125 the VCU 110 cancels implementation of the automatic smooth stop function and brake pressure in the braking system 126S continues to correspond to the instant brake pedal position. The method then continues at step S119 described above.

It is to be understood that, if the vehicle comes to a stop whilst steps S111, S113, S115 or S123 are being performed and the brake pedal 163 is still depressed, the brake controller 126C causes the amount of brake pressure in the braking system 126S to ramp to an amount sufficient to maintain the vehicle 100 substantially stationary, taking into account the instant driving surface gradient (which may be determined by reference to vehicle pitch angle based on measurements made by the IMU 128), for a predetermined brake hold period. Once the predetermined brake hold period has elapsed, the VCU 110 may cause the brake controller 126C to cause the brake pressure to revert to an amount corresponding to the actual positon of the brake pedal 163. Operation of the braking system 126S may subsequently be controlled by the brake controller 126C in the conventional manner.

FIG. 3 illustrates the variation in values of a number of parameters during the execution of the automatic smooth stop function in an example scenario.

From time tO to t1 (where, in the present example, t1=1s), the driver is maintaining a substantially constant force F1 on brake pedal 161 (trace D) and the vehicle is decelerating at a substantially constant rate as shown by trace B (rate of deceleration) and trace A (vehicle speed).

At time t1 the driver abruptly reduces the force on the brake pedal 161 causing it to reduce from value F1 to value F2. The rate of vehicle deceleration, rate of reduction in force on the brake pedal 161, and amount by which the force on the brake pedal 161 is released, is sufficient to meet the conditions at steps S103, S103a and S107 of FIG. 2 (automatic brake control initiation conditions). Accordingly, the VCU 110 begins to implement the automatic smooth stop function by initially maintaining the current deceleration rate.

As described in detail above, the VCU 110 is configured, when the automatic brake control initiation conditions are met, to manage the rate of deceleration, by controlling hydraulic brake fluid pressure, to maintain a substantially constant rate of deceleration of the vehicle of initially at a level close to what it was when the automatic smooth stop function was triggered (approximately 3.0m per second per second in the example of FIG. 3). When the vehicle speed drops below a threshold speed (approximately 1m per second in the example of FIG. 3), the VCU 110 causes the brake controller 126C to apply a braking profile by causing the braking system 126C to maintain application of brake pressure sufficient to cause the vehicle 100 to slow to a halt according to the predetermined deceleration profile as discussed above, represented by trace B of FIG. 3 after time t1. the rate of deceleration is reduced according to a predetermined profile in order to reduce the jerk at the end of the stop.

Thus, the VCU 110 causes the vehicle to decelerate to substantially zero speed at a deceleration rate that, itself, decreases from around 3m per second per second (ms-2) to zero over a period of around 1.2s at a substantially constant rate. The rate of change of deceleration (ms-3), also known as ‘jerk’, is therefore substantially constant during this period as shown by trace C. It is to be understood that the jerk value may be higher or lower in some embodiments, but is typically selected to be a value that is expected not to be uncomfortable for a vehicle occupant and which causes the vehicle to come to rest within an acceptable distance.

It is to be understood that embodiments of the present invention are suitable for use in conventional driver-driven vehicles as well as wholly or partially autonomous vehicles in which a control system provides acceleration and braking input.

Thus, in some embodiments, the VCU 110 may receive brake demand information indicative of required brake force in the form of a signal indicative of actual brake pedal travel, relative to a reference (undepressed) condition, or force applied to the brake pedal by a driver. In an autonomous vehicle a virtual brake pedal travel signal or brake demand signal generated by an autonomous vehicle controller, or a brake demand signal generated by an automatic driver assistance system may be used. In some embodiments, a signal may be generated indicative of the amount of regenerative brake force to be applied by a regenerative braking system that may employ one or more electric generators in addition to or instead of a friction-based braking system such as a disc braking system.

It will be understood that the embodiments described above are given by way of example only and are not intended to limit the invention, the scope of which is defined in the appended claims.

Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein 5 unless incompatible therewith.

Claims

CLAIMS:

1. A controller for a braking system of a vehicle, the controller being configured to automatically cause the vehicle to decelerate towards a stop, wherein the controller is configured to receive deceleration information indicative of a deceleration request and velocity information indicative of a vehicle’s velocity, and wherein the controller is configured to apply a braking profile to cause the vehicle to decelerate towards a stop in accordance with a predetermined deceleration profile, when:

i) the vehicle speed is below a predetermined automatic brake control initiation threshold speed, and ii) the deceleration request decreases.

2. A controller according to claim 1 wherein the conditions under which the controller is configured to apply the braking profile further comprise the condition that the vehicle has been decelerating at a rate of deceleration that is within a predetermined range of deceleration rates during at least a portion of the period for which the deceleration request has been received.

3. A controller according to claim 2 wherein the conditions under which the controller is configured to apply the braking profile further comprise the condition that the vehicle has been decelerating at a rate of deceleration that is within the predetermined range of deceleration rates for a period exceeding a predetermined automatic brake control initiation threshold period.

4. A controller according to any preceding claim wherein the condition that the deceleration request decreases comprises the condition that the deceleration request decreases by an amount greater than or equal to a predetermined automatic brake control initiation deceleration request decrease amount.

5. A controller according to claim 4 wherein the condition that the deceleration request decreases further comprises the condition that the deceleration request decreases by an amount greater than or equal to the predetermined automatic brake control initiation deceleration request decrease amount within a predetermined automatic brake control initiation deceleration request reduction period.

6. A controller according to any preceding claim wherein the condition that the deceleration request decreases includes the condition that the deceleration request decreases to an amount that is not less than a predetermined automatic brake control initiation deceleration request threshold amount.

7. A controller according to any preceding claim wherein the deceleration profile is substantially independent of the instant deceleration request amount.

8. A controller according to any preceding claim wherein the deceleration profile is substantially independent of the instant driving surface gradient.

9. A controller according to any one of claims 1 to 7 wherein the deceleration profile is dependent at least in part on driving surface gradient.

10. A controller according to any preceding claim configured wherein, if whilst applying a braking profile the deceleration information indicates that the amount of deceleration requested exceeds the amount that the control system requires to apply in order to cause the vehicle to slow to a stop according to the deceleration profile, the control system ceases applying the braking profile.

11. A controller according to any preceding claim comprising processing means, wherein the processing means comprises an electronic processor having an electrical input for receiving deceleration information indicative of a deceleration request and information indicative of vehicle velocity, and an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, wherein the processor is configured to access the memory device and execute the instructions stored therein such that it is operable to apply a braking profile to cause the vehicle to decelerate towards a stop in accordance with a deceleration profile, when;

12. A control system comprising a controller according to any preceding claim.

13. A vehicle comprising a controller according to any one of claims 1 to 11 or a control system according to claim 12.

14. A method of controlling a braking system of a motor vehicle by means of a controller, the method comprising:

15. A method according to claim 14 whereby the conditions under which the controller is configured to apply the braking profile further comprise the condition that the vehicle has been decelerating at a rate of deceleration that is within a predetermined range of deceleration rates during at least a portion of the period for which the deceleration request has been received.

16. A method according to claim 15 whereby the conditions under which the controller is configured to apply the braking profile further comprise the condition that the vehicle has been decelerating at a rate of deceleration that is within the predetermined range of deceleration rates for a period exceeding a predetermined automatic brake control initiation threshold period.

17. A method according to any one of claims 14 to 16 whereby the condition that the deceleration request decreases comprises the condition that the deceleration request decreases by an amount greater than or equal to a predetermined automatic brake control initiation deceleration request decrease amount.

18. A method according to claim 17 whereby the condition that the deceleration request decreases further comprises the condition that the deceleration request decreases by an amount greater than or equal to the predetermined automatic brake control initiation deceleration request decrease amount within a predetermined automatic brake control initiation deceleration request reduction period.

19. A method according to any one of claims 14 to 18 whereby the condition that the deceleration request decreases includes the condition that the deceleration request decreases to an amount that is not less than a predetermined automatic brake control initiation deceleration request threshold amount.

20. A method according to any one of claims 14 to 19 comprising applying a deceleration profile that is substantially independent of the instant deceleration request amount.

21. A method according to any one of claims 14 to 20 comprising applying a deceleration profile that is substantially independent of the instant driving surface gradient.

22. A method according to any one of claims 14 to 21 comprising applying a deceleration profile that is dependent at least in part on driving surface gradient.

23. A method according to any one of claims 14 to 22 comprising applying a braking profile, the method comprising ceasing applying the braking profile if the deceleration information indicates that the amount of deceleration requested exceeds the amount that the control system requires to apply in order to cause the vehicle to slow to a stop according to the deceleration profile.

24. A non-transitory computer readable carrier medium carrying computer readable code for controlling a vehicle to carry out the method of any one of claims 14 to 23.

25. A computer program product executable on a processor so as to implement the method of any one of claims 14 to 23.

26. A non-transitory computer readable medium carrying computer readable code which when executed causes a vehicle to carry out the method of any one of claims 14 to 23.

27. A processor arranged to implement the method of any one of claims 14 to 23, or the computer program product of claim 25.

Intellectual Property Office

Application No: GB1801723.6 Examiner: Mr Kevin Hewitt

Claims searched: 1 to 19 Date of search: 25 July 2018