TECHNICAL FIELD The present disclosure relates to a braking control system for a vehicle. In particular, the invention relates to a braking control system which allows the response of the braking system to be varied. Aspects of the invention relate to a braking control system, a method of varying the braking response of a vehicle, a vehicle braking system, a vehicle, a controller for controlling the braking system and to a non- transitory, computer-readable storage medium.

BACKGROUND

Motorists have unique personal preferences as to how they would like their vehicle to 'feel' and drive. This expectation may be dependent both upon an individual's driving style as well as the surface type upon which the vehicle is travelling. For example, many vehicles offer the driver the ability to switch between a sports driving mode, in which the vehicle has an increased throttle response and an adjusted, 'hard' suspension setting, and a regular driving mode in which the throttle response is more conventional and suspension is 'softer'.

Currently, certain aspects of vehicle operation and control are defined in the hardware or 'DNA' of a vehicle and cannot be tailored to meet the requirements of a motorist's driving style or upon the type of surface a vehicle is travelling on. In the current climate of automotive technology, where vehicles are becoming increasingly sophisticated and are tuneable in many different respects to meet an individual's driving and use preferences, it is a requirement for vehicles to be more adaptive and responsive. It is also beneficial for a vehicle to provide a variable response in different external conditions, for reasons of safety and economy.

The present invention relates to a braking system for a vehicle which has been devised to address this issue. SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a braking control system for a vehicle having a brake input device operable by a driver of the vehicle to actuate a vehicle braking system, the braking control system comprising: a control module configured to receive a driver's braking response preference and to select a braking response depending on the braking response preference; and an output configured to provide a braking force signal to the vehicle braking system in accordance with the selected braking response in response to the driver operating the brake input device.

One particular aspect of a vehicle's feel that is important to motorists is the feel of the brakes, in particular the brake pedal. The feel and responsiveness of the brake pedal is a crucial part of the overall driving experience of a vehicle and every motorist has a different preference to the feel and responsiveness depending on where they are driving and the surface on which they are travelling. For example, some drivers may enjoy a sportier feel from their vehicle; in these cases they would want a vehicle that had a sharp, responsive brake pedal. Other drivers may be looking for a vehicle that is more comfortable to drive and as a result may choose a vehicle that has a less responsive feel to the brake pedal.

The effect and importance of the feel of a brake pedal extends beyond a driver's personal comfort, in particular in off-road vehicles. For example, in order for brakes to be effective on low coefficient of friction surfaces and to prevent the vehicle from skidding uncontrollably, less responsive brakes would be desirable. However, under normal driving conditions, having less responsive brakes would be undesirable and could cause a potential safety hazard. Manufacturers of vehicles and in particular off- road vehicles have to design the brake feel with these, and many more, situations in mind and as a result the braking of the vehicle is often compromised in certain situations.

The present invention overcomes these issues by providing a configurable response braking system which allows a user to select a preferred braking response, which may be adjusted depending on factors such as the terrain on which the vehicle is travelling, weather conditions or even the nature of the passengers, and which adjusts the braking response of the vehicle in accordance with the driver's preference.

In one embodiment of the invention, the control module includes a brake booster module configured to determine the braking force signal to be provided to the vehicle braking system based on a driver input force applied to the brake input device and the selected braking response.

In another embodiment, the braking response is the braking force applied to the vehicle braking system as a function of a driver input force applied to the brake input device.

In a particular embodiment of the invention there is an interface module configured to allow the driver to select at least one characteristic of the braking response to define their braking response preference.

In another embodiment of the invention a variable characteristic is a boost ratio defined by the braking force applied to the vehicle braking system compared to a driver input force applied to the brake input device.

In another embodiment of the invention, the interface module is configured to allow the driver to select whether the boost ratio has a linear or non-linear response.

In a further embodiment of the invention a variable characteristic is a jump-in point which is the magnitude of the braking force required to be applied to the brake input device to actuate a braking force on the vehicle.

In one embodiment of the invention, the control module includes a data memory for storing the selected braking response of a driver in combination with an identity of the driver.

In a further embodiment, the control module is configured to receive a driver identify signal indicative of the identity of the driver. In an embodiment of the invention the control module is configured to select a braking response automatically based on the identity of the driver.

According to an embodiment of the invention the control module is configured to receive a terrain input signal from a terrain response system, wherein the terrain input signal is indicative of the type of terrain the vehicle is travelling upon.

In a further embodiment of the invention a default braking response is selected automatically to correspond to the type of terrain.

In certain embodiments of this invention the brake input device is a brake pedal.

In one aspect, the invention provides a braking control system for a vehicle, wherein the control module comprises an electronic processor having an electrical input and an electronic memory device electrically coupled to the electronic processor and having instructions stored thereon.

In a further embodiment the selection of the braking response in response to the driver's braking response preference may comprise the processor of the control module being configured to access the memory device and execute the instructions stored thereon.

In one embodiment the providing of the braking force signal to the vehicle braking system may comprise the electronic processor being configured to access the memory device and execute the instructions stored thereon to deliver the appropriate braking force output in accordance with the braking response preference.

In another aspect, there is provided a method of controlling a vehicle braking system for a vehicle having a brake input device operable by a driver of the vehicle to actuate a vehicle braking system, the method comprising receiving a driver's braking response preference and selecting a braking response depending on the braking response preference; and providing a braking force signal to the vehicle braking system in accordance with the selected braking response in response to the driver operating the brake input device. Another aspect of the invention relates to a non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more electronic processors cause the one or more electronic processors to carry out the method of the previous aspect.

In another aspect of the invention, there is provided a vehicle braking system comprising the braking control system of the previous aspect. In a still further aspect, there is provided a vehicle comprising the vehicle braking system. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic of a vehicle comprising a braking control system of one embodiment of the present invention;

Figure 2 is a block diagram of components of the braking control system in Figure 1 ; Figure 3 is a graph of brake pressure against pedal force for a braking control system, and shows three different responses to illustrate different pedal force "jump-in" points; Figure 4 is a graph of brake pressure against pedal force for a braking control system, and shows three different responses to illustrate different brake pressure/pedal force boost ratios; Figure 5 is a graph of brake pressure against pedal force to show three different responses for implementation by the configurable response braking system;

Figure 6 shows one embodiment of a user interface for selecting a braking response of the configurable response braking system;

Figure 7 shows an alternative user interface for selecting various features of the braking control system; and

Figure 8 shows a graph of brake pressure against pedal force to illustrate an alternative implementation to that shown in Figure 5.

DETAILED DESCRIPTION

A specific embodiment of the invention will now be described in which numerous specific features will be discussed in detail in order to provide a thorough understanding of the inventive concept as defined in the claims. However, it will be apparent to the skilled person that the invention may be put in to effect without the specific details and that in some instances, well-known methods, techniques and structures have not been described in detail in order not to obscure the invention unnecessarily.

An object of the invention is to provide a configurable response braking system for an automotive vehicle that can vary the braking response of a brake input device within a vehicle. The invention is particularly, but not exclusively, relevant to varying the feel and set up of a vehicle in order to match the feel of a vehicle to a driver's unique driving style. Another aspect of the invention is matching the braking response and overall feel to driving conditions in order to help improve the safety and handling of a vehicle on various driving surfaces. The braking response may be represented by a driver input force at the brake input device as a function of the braking force which is applied to a vehicle braking system as a result of the driver input force.

In order to place the embodiments of the invention in a suitable context, reference will firstly be made to a vehicle travelling along a surface as shown in Figure 1 . Figure 1 shows a vehicle 12 which contains a configurable response braking system 10, a brake input device (not identified) operable by a driver, and four wheels 14. The brake input device is often in the form of a brake pedal. The vehicle braking system is typically in the form of a disc braking system. Figure 2 shows a block diagram of the components within the configurable response braking system 10. Within the system there are three main processing modules; a brake actuation module 26, a brake application module 25 and a vehicle set up module 24. The driver of the vehicle is represented as item 28. The brake actuation module 26 comprises a control module 21 including a data memory (not shown) for the configurable response braking system and an electromechanical brake booster 23. The electromechanical brake booster 23 could be, for example, an l-booster® system. An electromechanical brake booster 23 is an electromechanical device that can receive an input from an actuation force, for example through a brake pedal, boost the input actuation force and provide an output at an increased force to, for example, a piston. For example, this is described in US patent US8783792 B2. The electromechanical brake booster 23 has the ability to boost the force the driver 28 applies to the brake pedal to an appropriate level for decelerating a vehicle 12. The electromechanical booster 23 receives input signals from the control module 21 and from the driver via the brake pedal and provides an output braking force signal to the brake application module 25. The control module 21 configures the electromechanical brake booster 23 in order to control the level of assistance (boost ratio) the electromechanical brake booster 23 gives the driver 28 as well as the required actuation force required to be applied to the brake pedal in order to activate the vehicle's brakes. The brake application module 25 contains a number of brake calliper disks 22, typically one brake calliper disk per wheel. The majority of modern vehicles 12 use disk brakes in order to brake the vehicle 12. In a disc braking system each wheel of a vehicle 12 is attached to a metal disc that rotates at the same rotational velocity as the wheel. The brake callipers fit over the metal discs like a clamp. When the driver wishes to reduce the speed of the vehicle 12 a force is applied to the rotating metal disc through the brake calliper which in turn applies a frictional force to the metal disc thus reducing the rotational velocity of the wheel. The magnitude of the force the driver exerts on the brake pedal is directly correlated to the magnitude of the force applied by the electromechanical brake booster 23 on the brake calliper.

The vehicle setup module 24 contains a Human Machine Interface (HMI) 20 which is operable by the driver and provides a graphical user interface that receives inputs from the driver indicative of their desired braking response. The HMI 20 also provides an output to the driver in the form of information on a display screen regarding the set-up of the configurable response braking system 10. The HMI 20 provides an output indicative of the desired braking response to the control module 21 within the brake actuation module 26 which in turn provides the requisite signal to the electromechanical brake booster 23.

The control module 21 and the electromechanical brake booster 23 of the brake actuation module 26 are connected via a feedback loop. The electromechanical brake booster 23 device provides an actuating force to the brake callipers as a relationship to a driver's input via the brake pedal; the relationship as defined by the driver via the control module 21 . The feedback loop between the control module 21 and electromechanical brake booster 23 ensures that the braking force requested by the control module 21 is the same as the braking force being applied by the electromechanical brake booster 23. This acts both as an error estimator and safety measure within the system. The effect of reducing the error in the system ensures that the braking force requested by the driver is being applied to the vehicle 12 which is an important safety measure for any braking system.

The error in the braking force is determined by first calculating the expected braking force request, based on the brake pedal position as well as the driver braking response preference, and then determining the 'actual brake force' applied to the brake callipers. The difference between the expected brake force and the actual brake force is the error in the vehicle braking system. The error in the vehicle braking system is then compared with a pre-defined error threshold and should the error exceed the pre-defined threshold the vehicle braking system will take action to reduce the error. This action could be, for example, to increase the braking force should the expected brake force exceed the actual brake force by more than a pre-defined threshold or reduce the braking force should the actual brake force exceed the expected brake force by more than the pre-defined threshold. These actions help to mitigate against any malfunctions within the braking system and help to ensure the safe operation of the vehicle.

In this embodiment there are two characteristics within the configurable response braking system 10 that can be varied by the control module 21 . These two characteristics are not limiting and in other embodiments of the invention the configurable response braking system 10 could have additional characteristics which could be varied.

Figure 3 shows three different braking response profiles (also referred to as "braking response") representing the pressure applied to the disk brakes as a function of the force applied to the brake pedal. The first characteristic of the braking response profile which may be varied by the control module 21 is the "jump-in" point 30. The jump-in point 30 is the magnitude of the force applied to the pedal by the driver 28 which initiates a braking pressure at the brakes. So, for a braking response with a relatively high jump-in point, a driver 28 will have to apply a higher force to the pedal in order to effect a braking pressure at the brakes, whereas for a relatively low jump-in point a driver 28 will have to apply a relatively lower force to the pedal in order to effect a braking pressure at the brakes. Varying the jump-in point therefore alters the 'feel' and responsiveness of braking for the driver 28.

Figure 3 shows, by way of example, a graph of brake pressure against pedal force for three different braking responses 30a, 30b, 30c. Response 30a and response 30c have the same jump-in point 30, but for each response the jump-in point 30 corresponds to a different magnitude of brake pressure at the brakes. Response 30b has a higher jump-in point with the same magnitude of braking pressure, at the jump-in point 30, as response 30a.

Referring to Figure 4, the second characteristic is known as the assistance or boost ratio. This is the amount of assistance the electromechanical brake booster 23 provides the driver 28 during braking. Figure 4 shows three differing boost ratios for the same jump-in point 30 (pedal force); a high assistance response 40, an intermediate non-linear assistance response 41 and a low assistance response 42 Both the low assistance response 42 and high assistance response 40 follow a linear profile, whereas the third response 41 follows a non-linear profile. Drivers typically prefer a linear braking response but this is not always the case, in particular when a vehicle 12 is travelling off-road.

By way of comparison, Figure 5 shows three different braking responses, 60, 61 , 62, to illustrate a combination of different jump-in points 30 and boost ratios. For example, the first braking response 60 on Figure 5 illustrates a 'relaxed' non-linear braking response, with a low jump-in point 30 (pedal force) as well as an initial low boost ratio. The jump-in point 30 occurs at a low brake pedal force giving a smooth and relaxed braking response as the driver 28 will experience a braking pressure to the brakes with only a relatively low force applied to the pedal. This profile is particularly, but not exclusively, relevant to situations when the vehicle 12 is driving on surfaces with a low coefficient of friction such as snow or ice. The relaxed braking profile 60 helps to prevent sudden wheel deceleration that could potentially result in the vehicle 12 losing control and skidding. This setting may also be appropriate for drivers of the vehicle 12 that enjoy a relaxed, soft feel on the brake pedal. As the force applied to the brake pedal increases beyond a threshold point 63 the boost ratio also increases so that the response 60 is non-linear over the pedal force range.

The second braking response 62 is designed to give the driver a fast, 'responsive', braking response 62. The response 62 has a relatively high jump-in point 30 (compared to the relaxed response) followed by a linear boost ratio over the pedal force range. This response gives a sharp, responsive feel to the brake pedal which is desirable for drivers that like a sporty feel from their vehicle 12. The third response 61 is a 'standard' braking response which has the same jump-in point 30 as the responsive braking response 62, but the jump-in point 30 corresponds to a lower vehicle deceleration (lower braking pressure) than the responsive braking response 62. The boost ratio or assistance for the standard braking response 61 is higher than that for the responsive braking response 62.

It can be seen from the three different responses 60, 61 and 62 that when the peak braking force 65 is applied to the pedal, all three responses give the same braking pressure or vehicle deceleration, but the response of the pedal in reaching the maximum braking pressure is different in each case.

In other embodiments it will be appreciated that the peak braking force applied to the pedal need not result in the same braking pressure or vehicle deceleration, and, for example, a responsive braking response may result in a higher braking pressure at the brakes than a standard or relaxed braking response.

The braking response data which constitutes the braking responses 60, 61 , 62 is stored in the control module 21 of the brake actuation module 26 and is accessed in response to a driver 28 applying a force to the pedal, so that the appropriate braking pressure is experienced at the brakes.

Referring also to Figure 6, the vehicle set up module 24 will now be discussed in more detail. The HMI 20 within the vehicle set up module 24 allows the driver 28 to select one of three desired braking responses; relaxed 60, responsive 62 or standard 61 , as described previously with reference to Figure 5. The HMI 20 allows the driver 28 to select their desired response. The selected response 60, 61 or 62 is input to the brake actuation module 26, and in particular, the control module 21 which in turn calibrates the electromechanical brake booster 23 to match the user's selected response. The calibrated electromechanical brake booster 23 receive inputs from the driver 28, by the brake pedal, and sends corresponding outputs, as calibrated, to the brake callipers 22 in order to brake the vehicle 12 by an amount consistent with the selected response. If, for example, the relaxed response 60 is selected on the HMI 20, the braking response experienced by the user is represented by the braking response function identified as 60 in Figure 5. Referring to Figure 7, in another embodiment of the invention a greater degree of flexibility over the responsiveness of the braking system can be achieved by allowing the user to select both a preferred boost ratio (assistance) and a preferred jump-in point 30 for the braking response. In this case a more sophisticated HMI 120 may be used, such as the example outlined in Figure 7. The HMI 120 in this embodiment enables the driver 28 of the vehicle 12 to independently vary the jump-in point 30 of the braking response or the boost ratio of the response. For example, if the driver 28 of the vehicle 12 lowers the jump-in point 30 of the braking response using the HMI 120, a signal indicative of the driver's selection is sent to the control module 21 . The control module 21 then configures the electromechanical brake booster 23 to lower the jump-in point 30 of the braking system 10. As a result, when the driver 28 applies pressure to the brake pedal the electromechanical brake booster 23 will actuate a force on the calliper disks 22 at a lower pedal pressure than before, as defined by the driver 28.

In another example (not shown), the driver 28 of the vehicle 12 may wish to operate the HMI 120 to increase the boost ratio of the braking system. By operating the HMI 120 a signal is sent to the control module 21 with information of the driver's desired boost ratio. The control module 21 configures the electromechanical brake booster 23 to provide the newly selected boost ratio. When the driver 28 applies a force to the brake pedal the electromechanical brake booster 23 provides a higher boost ratio than before, thus providing more pressure on the brake calliper disk 22 for a given force on the brake pedal.

This more sophisticated HMI 120 allows the driver 28 to vary parameters of the braking response independently of each other allowing a wealth of different braking responses to be made available to the driver 28 at their own preference.

The control module 21 may be further configured to permit the preferences of different vehicle 12 users to be stored in the data memory so that they can be re-called each time a particular driver 28 uses the vehicle 12. For this purpose, the HMI 120 includes first, second and third inputs 86 to allow the user to store, update and retrieve their preferred braking response. A vehicle 12 may be regularly driven by multiple people, in which case each driver 28 is likely to have a different driving style and as a result different braking response preferences. The HMI 120 allows the driver to select their desired set of responses at the beginning of a journey via the inputs 86. The facility to store, update and select a personal braking response preference in this way can also be used in combination with the HMI 20 in a less sophisticated system in which only one braking response characteristic is selectable.

The HMI 120 shown in Figure 7 allows the user of the vehicle 12 to vary two characteristics of the braking control system 10. However, this is by no means limiting and in other embodiments further characteristics of the braking response may be varied such as the latency of a brake response or whether the boost ratio follows a linear or non-linear profile. Two methods of storing and varying characteristics of the braking response will now be discussed. The first method utilises multiple, predefined braking response profiles that are stored within the data memory of the control module 21 and are selected using an HMI 20. The discrete braking response profiles are saved in the data memory and the driver 28 can toggle through the HMI 20 in order to select the most appropriate response. This could include, for example, a relaxed 70, normal 71 or responsive 72 braking response, as shown in Figure 6.

When the driver 28 selects their desired braking response the HMI 20 sends a signal to the control module 21 indicating the driver's desired response. The control module 21 then configures the electromechanical brake booster 23 to actuate the calliper disks 22 in line with the driver's desired response by retrieving the selected braking response from the data memory.

One problem with this approach is the requirement to store all possible braking responses on the data memory within the control module 21 which may be wasteful of data memory. This method also limits the driver's ability to match the braking response exactly to their braking preference as the number of responses is limited by the memory constraints, and a particular selection of characteristics input by the driver 28 may not match the pre-stored braking profiles. An alternative approach for varying characteristics of the braking system is to interpolate between a limited number of pre-stored braking response profiles, in order to establish the most appropriate braking response to suit the driver's input. The pre- stored braking responses set the boundaries for the interpolation process, so that only a limited number (e.g. two) of braking profiles need to be stored in the data memory. This method both reduces the memory requirement of the system and also enables the driver 28 to fully customise the braking response to suit any particular combination of inputs.

With reference to Figure 8, two braking responses are stored within the control module 21 and are used as limits for an interpolation process. These two braking responses could be, for example, a response with a low jump-in point and a high boost ratio 102 and another braking response with a high jump-in point and a low boost ratio 104. The two braking responses that are chosen represent the most relaxed and most responsive braking responses a user could possibly want to select, as it is anticipated that the majority of a driver's desired braking responses would lie between these two profiles. In the embodiment of Figure 7, the driver is able to choose specifically their desired boost ratio (assistance) 84 or jump-in point 82 via the multiple inputs on the HMI 120. A signal is then sent to the control module 21 which, based on the input selection, interpolates between the braking responses 102 and 104 in order to generate a braking response which substantially matches the driver's 28 selection. The braking response that is determined through interpolation is then used to configure the electromechanical brake booster 23 to actuate the brake callipers 22 in line with the desired braking response which best matches the driver's input selection. This approach reduces the requirements of the data memory within the system as only a limited number of braking responses are stored within the control module 21 . In this embodiment the system is required to include an interpolation module (not shown), forming part of the control module, for carrying out the interpolation process.

In an embodiment of the invention the interpolation module interpolates linearly between the limiting braking responses 102 and 104. This allows the driver of the vehicle to vary the jump-in and boost ratio variables separately and in an intuitive manner. The interpolation module interpolates the jump in variable bilinearly. This is because there are two variable characteristics to the jump-in point, firstly the force required to be applied to the brake pedal to actuate a braking response and secondly the magnitude of braking force applied to the vehicle when the required force is applied to the brake pedal.

In another embodiment of the invention, the braking control system 10 can be linked to a Terrain Response system® of the vehicle 12. Terrain Response is a system that can vary parameters on a vehicle 12, such as steering response, suspension and gear ratios, in order to optimise the vehicle's 12 handling and performance on a variety of different surfaces. If the Terrain Response system is linked to the braking control system 10 then the system may receive an input indicative of the terrain type from the Terrain Response system and may be configured to vary the braking response accordingly. For example, if the Terrain Response system is set to a mode suitable for snow and ice driving, the control module 21 is configured to automatically select a braking response which would minimise the risk of the vehicle 12 skidding. This is likely to be a response where there is a low jump-in point 30 and an initially low boost ratio, similar to the braking response 60 in Figure 5. When the vehicle 12 is set to a mode suitable for rock crawling, meaning the vehicle 12 is on an uneven surface, the driver of the vehicle 12 may prefer to have a more responsive feel in the brake pedal in order to achieve greater control over the vehicle 12. In this scenario the control module 21 receives a signal indicative that the vehicle 12 is travelling on an uneven surface and therefore automatically selects a braking response such as the higher response 62 in Figure 5. In the braking response 62 there is a high jump-in point as well as a high boost ratio giving the brake pedal a sharp and responsive feel.

Although the braking control system 10 may be configured to select automatically a default braking response in dependence on the relevant Terrain Response mode automatically, the user of the vehicle 12 still has the ability to override these default responses in order to achieve a response that is best suited to their personal driving style. If a driver of the vehicle 12 overrides any of the default response profiles, this preference or preferences are saved to the data memory in combination with the terrain type, so that the same braking response can be retrieved next time the same terrain type is encountered.

In a further sophistication, the vehicle may be provided with a driver recognition system to identify the driver 28 of the vehicle 12 (e.g. using key fob identification). In this case the braking control system 10 may be configured to automatically select the appropriate braking response for the identified driver 28. In this embodiment the braking control system 10 may have a number of predefined responses tailored to each driver 28 of the vehicle 12. Furthermore, the braking responses could be matched to different terrain types so that for any one driver 28 a plurality of braking responses are stored, one for each terrain type, and these are selected automatically for the appropriate driver when a particular terrain is encountered.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.