INCORPORATION BY REFERENCE

The content of co-pending UK patent applications GB2507622 and GB2499461 are hereby incorporated by reference. The content of US patent no US7349776 and co-pending international patent applications WO2013124321 and WO2014/139875 are incorporated herein by reference. The content of UK patent applications GB2492748, GB2492655 and GB2499279 and UK patent GB2508464 are also incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a system for controlling the speed of a vehicle. In particular, but not exclusively, the invention relates to a system for controlling the speed of a land-based vehicle which is capable of driving in a variety of different and extreme terrains and conditions.

BACKGROUND

In known vehicle speed control systems, typically referred to as cruise control systems, the vehicle speed is maintained on-road once set by the user without further intervention by the user so as to improve the driving experience for the user by reducing workload. Cruise control speed (or cruise set-speed) is settable by the vehicle driver, typically by pressing a button when the vehicle is at the desired speed. Plus and minus buttons provide for incremental speed variation whilst the cruise control is set. One the user has selected a speed at which the vehicle is to be maintained, the vehicle is maintained at that speed for as long as the user does not apply a brake or, in the case of a vehicle having a manual transmission, depress a clutch pedal. The cruise control system takes its speed signal from a driveshaft speed sensor or wheel speed sensors. When the brake or a clutch pedal is depressed, the cruise control system is disabled so that the user can override the cruise control system to change the vehicle speed without resistance from the system. When the cruise control system is active, if the user depresses the accelerator pedal a sufficient amount the vehicle speed will increase, but once the user removes his foot from the accelerator pedal the vehicle reverts to the pre-set cruise speed by coasting. Such systems are usually operable only above a certain speed, typically around 15-20kph, and are ideal in circumstances in which the vehicle is travelling in steady traffic conditions, and particularly on highways or motorways. In congested traffic conditions, however, where vehicle speed tends to vary widely, cruise control systems are ineffective, and especially where the systems are inoperable because of a minimum speed requirement. A minimum speed requirement is often imposed on cruise control systems so as to reduce the likelihood of low speed collision, for example when parking. Such systems are therefore ineffective in certain driving conditions (e.g. low speed) and are set to be automatically disabled in circumstances in which a user may not consider it to be desirable to do so.

More sophisticated cruise control systems are integrated into the engine management system and may include an adaptive functionality which takes into account the distance to the vehicle in front using a radar-based system. For example, the vehicle may be provided with a forward-looking radar detection system so that the speed and distance of the vehicle in front is detected and a safe following speed and distance is maintained automatically without the need for user input. If the lead vehicle slows down, or another object is detected by the radar detection system, the system sends a signal to the engine or the braking system to slow the vehicle down accordingly, to maintain a safe following distance.

Known cruise control systems also cancel in the event that a wheel slip event is detected requiring intervention by a traction control system (TCS) or stability control system (SCS). Accordingly, they are not well suited to maintaining vehicle progress when driving in off road conditions where such events may be relatively common.

Some vehicles are adapted for off-highway use, and low-speed cruise control systems for such vehicles have been developed. In off-highway conditions low-speed cruise control systems permit a driver, particularly a novice driver, to concentrate upon activities such as steering.

Low-speed cruise control systems suitable for off-road use may be configured to cause a vehicle to travel at a speed that is below the user-determined set-speed in dependence on the roughness of the terrain over which the vehicle is travelling. Nevertheless the present applicant has recognised that there are circumstances other than driving over rough terrain in which a reduced vehicle speed would be helpful to a user endeavouring to negotiate the terrain.

It is also known to provide a control system for a motor vehicle for controlling one or more vehicle subsystems. US7349776 discloses a vehicle control system comprising a plurality of subsystem controllers including an engine management system, a transmission controller, a steering controller, a brakes controller and a suspension controller. The subsystem controllers are each operable in a plurality of subsystem function or configuration modes. The subsystem controllers are connected to a vehicle mode controller which controls the subsystem controllers to assume a required function mode so as to provide a number of driving modes for the vehicle. Each of the driving modes corresponds to a particular driving condition or set of driving conditions, and in each mode each of the sub-systems is set to the function mode most appropriate to those conditions. Such conditions are linked to types of terrain over which the vehicle may be driven such as grass/gravel/snow, mud and ruts, rock crawl, sand and a highway mode known as 'special programs off (SPO). The vehicle mode controller may be referred to as a Terrain Response (TR) (RTM) System or controller. The driving modes may also be referred to as terrain modes, terrain response modes, or control modes.

GB2492655B discloses a control system for a motor vehicle in which the most appropriate terrain mode for the prevailing terrain over which the vehicle is driving is determined automatically by the control system. The control system then causes the vehicle to operate in the terrain mode determined to be the most appropriate.

It is against this background that the present invention has been conceived. Embodiments of the invention may provide an apparatus, a method or a vehicle which addresses the above problems. Other aims and advantages of the invention will become apparent from the following description, claims and drawings.

SUMMARY OF THE INVENTION

In one aspect of the invention for which protection is sought there is provided a control system for a vehicle, comprising:

means for receiving motion information indicative of movement of a body of the vehicle with respect to a predetermined reference location of the body;

occupant location determining means for determining which one of a plurality of occupant-relevant locations is to serve as a selected comfort reference location;

occupant comfort information determining means for determining occupant comfort information indicative of a level of occupant comfort at the occupant-relevant location determined to serve as a selected comfort reference location based on the motion information in respect of the predetermined reference location;

and

speed control means configured to control vehicle speed in dependence at least in part on the occupant comfort information indicative of the level of occupant comfort at the selected comfort reference location. The motion information my comprise an electrical signal indicative of movement of a body of the vehicle with respect to a predetermined reference location of the body

Optionally, the means for receiving motion information comprises an input for receiving a signal carrying motion information. The signal may be an analogue electrical signal or a digital signal, for example an electrical or optical signal carrying digital data.

Optionally, the occupant comfort information determining means determines the occupant comfort information indicative of a level of occupant comfort at each of a plurality of respective occupant-relevant locations of the vehicle body, and selects said occupant comfort information corresponding to the location determined to serve as a selected comfort reference location.

The comfort information determining means may comprise a processor configured to run computer software code. The comfort information determining means may be implemented by a processor configured to run computer software code.

The control system may be configured to receive an occupancy signal indicative of occupancy of one or more seats of the vehicle, wherein the occupant location determining means is configured to determine which occupant-relevant location is to serve as the selected comfort-relevant location in dependence at least in part on the occupancy signal. The signal may be an analogue electrical signal or a digital signal, for example an electrical or optical signal carrying digital data. The occupancy signal may provide an indication of whether or not one or more rear seats of the vehicle are occupied. Thus, the control system may determine that a rear seat is occupied if the occupancy signal so indicates, and assume that only one or more front seats are occupied if the occupancy signal indicates that no rear seat is occupied. Optionally, the occupant location determining means is configured automatically to determine that the occupancy-relevant location to serve as the selected comfort reference location corresponds to the location of a rear seat of the vehicle if the occupancy signal indicates that a rear seat is occupied and automatically to determine that the occupancy- relevant location to serve as the selected comfort reference location corresponds to the location of a front seat of the vehicle if the occupancy signal indicates that no rear seat is occupied. Optionally, the occupant location determining means is configured automatically to determine that the occupancy-relevant location to serve as the selected comfort reference location corresponds to the location of a rear seat of the vehicle if the occupancy signal indicates that a rear seat is occupied and automatically to determine that the occupancy- relevant location to serve as the selected comfort reference location corresponds to the location of a front seat of the vehicle if the occupancy signal indicates that no rear seat is occupied, if the control system is in an automatic occupancy-relevant location determining mode and not if the control system is in a manual occupancy-relevant location determining mode.

Optionally, the control system comprises one or more occupancy detectors configured to provide at least one occupancy output indicative of occupancy of at least one seat, wherein the occupancy signal is generated at least in part in dependence on the at least one occupancy output.

Thus, the occupant location determining means may comprise one or more occupancy detectors.

The one or more occupancy detectors may comprise one or more pressure sensors located in a seat. Alternatively or in addition the one or more occupancy detectors may comprise one or more cameras, the one or more occupancy detectors being arranged to determine whether a seat is occupied in dependence at least in part on an analysis of a captured image of a location of the vehicle corresponding to the location of a seat. The control system may be configured to receive a user-generated comfort reference location signal indicative of the occupancy-relevant location that is to serve as the selected comfort reference location, wherein the occupant location determining means is configured to determine which one of the plurality of occupant-relevant locations is to serve as the selected comfort reference location in dependence on the user-generated comfort reference location signal.

This feature has the advantage that a user may select which location of the vehicle is to serve as the selected comfort reference location regardless of location occupancy. Thus, even if a rear seat of a vehicle is occupied, a user may select a front seat as being the location with respect to which occupant comfort is to be determined. This functionality may be implemented in some embodiments only when the control system is in a manual occupancy-relevant location determining mode. The control system according to claim 7 as depending through claim 5 wherein the occupant location determining means is configured to determine which one of the plurality of occupant-relevant locations is to serve as the selected comfort reference location in dependence on the user-generated comfort reference location signal if the control system is in the manual occupancy-relevant location determining mode and not if the control system is in the automatic occupancy-relevant location determining mode.

The control system may be configured to determine which one of the plurality of occupant- relevant locations is to serve as the selected comfort reference location in further dependence at least in part on information indicative of a direction of turn of the vehicle.

The control system may be configured to select the occupant-relevant location to be the occupant-relevant location that is a radially outermost occupant-relevant location with respect to a radius of turn of the vehicle.

The control system may be configured wherein when a plurality of rear seats of a row of rear seats are occupied, the occupant-relevant location is selected to be the rear seat of the row that is radially outermost with respect to a radius of turn of the vehicle.

The control system may be configured wherein when no rear seat is occupied and a plurality of front seats are occupied, the occupant-relevant location is selected to be the occupied seat that is radially outermost with respect to a radius of turn of the vehicle. The speed control means may be configured to control vehicle speed in dependence on the occupant comfort information indicative of the level of occupant comfort at the selected comfort reference location, in further dependence on target comfort information indicative of a desired target occupant comfort level at the selected comfort reference location. The speed control means may be configured to control vehicle speed in real time according to the occupant comfort information indicative of the level of occupant comfort at the selected comfort reference location at a given moment, the speed control means (12) being configured to attempt to ensure that the level of occupant comfort does not fall below the target occupant comfort level.

The control system may be configured wherein the target comfort information is obtained by reference to a user input. The user input may be provided by means of a mechanical switchpack comprising one or more dials or buttons, or via a touchscreen or any other suitable input means. Thus in some embodiments, for example, a user may select a desired target occupant comfort level that is to be experienced at the selected comfort reference location, wherein at a given moment in time the control system attempts to ensure, by controlling vehicle speed, that the level of comfort does not fall below the target level. The control system attempts to reduce vehicle speed, if required, to ensure that the level of comfort does not fall below the target level. The target level may for example be set in dependence on target comfort information provided by a user such as one of three user-selectable predetermined levels such as 'low', 'medium' or 'high'. The control system may then control vehicle speed according to the selected comfort level. The control system may set a maximum allowable vehicle speed for a given desired target comfort level, the maximum allowable target speed being arranged to be lower in the case that a 'medium' comfort level is selected compared with a 'low' comfort level, and so forth.

The comfort determining means may be configured to receive the motion information in respect of the predetermined reference location from an inertial measurement unit (IMU).

Optionally, the speed control means is configured to cause the vehicle to travel in accordance with a target speed value,

wherein the speed control means being configured to control vehicle speed in dependence on occupant comfort information comprises the control system being configured to adjust the target speed value in dependence on the comfort information.

Optionally, the speed control means comprises torque control means for automatically causing application of positive and negative torque, as required, to one or more wheels of the vehicle to cause the vehicle to travel in accordance with the target speed value.

Optionally, the control system being configured to adjust the target speed value in dependence on the comfort information comprises the control system being configured to limit the vehicle speed to a predetermined speed limit value, and wherein said predetermined speed limit value is determined at least in part in dependence on the comfort information. Optionally, the predetermined speed limit value is arranged to reduce in dependence on the level of occupant comfort indicated by the comfort information in order to attempt to prevent the level of occupant comfort falling below the target occupant comfort level. Optionally, the speed control means is configured to control vehicle speed in further dependence at least in part on the identity of a selected one of a plurality of driving modes in which the vehicle is operating.

The driving modes may correspond to terrain modes, or 'terrain response' (TR RTM) modes.

Optionally, in each driving mode at least one of a plurality of vehicle subsystems is caused to operate in a predetermined one of a plurality of configuration modes of that subsystem, the subsystem configuration mode being determined in dependence on the selected driving mode.

Optionally, the subsystems include at least one of a powertrain subsystem, a brakes subsystem and a suspension subsystem.

Optionally, the speed control means being configured to control vehicle speed in further dependence at least in part on the identity of the driving mode comprises the speed control means being configured to control the target speed value in dependence at least in part on the identity of the driving mode.

It is to be understood that a lower target speed may be preferable for a given target comfort level when driving in one TR mode compared with driving in another driving mode.

Optionally, the speed control means comprises an electric controller configured to communicate with a powertrain controller and a brakes controller. Optionally, the control system comprises an electronic processor configured to receive a motion information signal indicative of movement of the body of the vehicle with respect to the predetermined reference location, 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: determine the comfort information indicative of the level of occupant comfort at each of the plurality of respective occupant-relevant locations of the vehicle body based on the motion information signal;

determine which one of the plurality of occupant-relevant locations is to serve as the selected comfort reference location; and

cause vehicle speed to be controlled in dependence at least in part on the occupant comfort information.

The speed control means may be implemented in software by means of a separate electronic processor, or by means of the same processer that determines the comfort information.

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

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

receiving motion information indicative of movement of a body of the vehicle with respect to a predetermined reference location of the body;

determining which one of a plurality of occupant-relevant locations is to serve as a selected comfort reference location;

determining occupant comfort information indicative of a level of occupant comfort, at the occupant-relevant location determined to serve as the selected comfort reference location, based on the motion information in respect of the predetermined reference location; and

controlling vehicle speed in dependence at least in part on the occupant comfort information indicative of the level of occupant comfort at the selected comfort reference location. In an aspect of the invention for which protection is sought there is provided a non-transitory computer readable carrier medium carrying a 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 computer readable medium loaded with the computer program product 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.

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 is a schematic illustration of a vehicle according to an embodiment of the invention in plan view;

FIGURE 2 shows the vehicle of FIG. 1 in side view;

FIGURE 3 is a high level schematic diagram of an embodiment of the vehicle control system of the present invention, including a cruise control system and a low-speed progress control system;

FIGURE 4 illustrates a steering wheel of a vehicle according to the embodiment of FIG. 1 ;

FIGURE 5 is a flow chart illustrating operation of a vehicle according to the embodiment of FIG. 1 when operating in an automatic comfort location selection mode; and

FIGURE 6 is a flow chart illustrating operation of a vehicle according to the embodiment of FIG. 1 when operating in a manual comfort location selection mode. DETAILED DESCRIPTION

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

FIG. 1 shows a vehicle 100 according to an embodiment of the present invention. The vehicle 100 has a powertrain 129 that includes an engine 121 that is connected to a driveline 130 having an automatic transmission 124. It is to be understood that embodiments of the present invention are also suitable for use in vehicles with manual transmissions, continuously variable transmissions or any other suitable transmission.

In the embodiment of FIG. 1 the transmission 124 may be set to one of a plurality of transmission operating modes, being a park mode, a reverse mode, a neutral mode, a drive mode or a sport mode, by means of a transmission mode selector dial 124S. The selector dial 124S provides an output signal to a powertrain controller 1 1 in response to which the powertrain controller 1 1 causes the transmission 124 to operate in accordance with the selected transmission mode.

The driveline 130 is arranged to drive a pair of front vehicle wheels 1 1 1 ,1 12 by means of a front differential 137 and a pair of front drive shafts 1 18. The driveline 130 also comprises an auxiliary driveline portion 131 arranged to drive a pair of rear wheels 1 14, 1 15 by means of an auxiliary driveshaft or prop-shaft 132, a rear differential 135 and a pair of rear driveshafts 139. Embodiments of the invention are suitable for use with vehicles in which the transmission is arranged to drive only a pair of front wheels or only a pair of rear wheels (i.e. front wheel drive vehicles or rear wheel drive vehicles) or selectable two wheel drive/four wheel drive vehicles. In the embodiment of FIG. 1 the transmission 124 is releasably connectable to the auxiliary driveline portion 131 by means of a power transfer unit (PTU) 131 P, allowing operation in a two wheel drive mode or a four wheel drive mode. It is to be understood that embodiments of the invention may be suitable for vehicles having more than four wheels or where only two wheels are driven, for example two wheels of a three wheeled vehicle or four wheeled vehicle or a vehicle with more than four wheels.

A control system for the vehicle engine 121 includes a central controller 10, referred to as a vehicle control unit (VCU) 10, the powertrain controller 1 1 , a brake controller 13 (an anti-lock braking system (ABS) controller) and a steering controller 170C. The ABS controller 13 forms part of a braking system 22 (FIG. 3). The VCU 10 receives and outputs a plurality of signals to and from various sensors and subsystems (not shown) provided on the vehicle. The VCU 10 includes a low-speed progress (LSP) control system 12 (which may also be referred to as a low-speed speed control system) shown in FIG. 3, a stability control system (SCS) 14, a cruise control system 16 and a hill descent control (HDC) system 12HD. The SCS 14 improves the safety of the vehicle 100 by detecting and managing loss of traction or steering control. When a reduction in traction or steering control is detected, the SCS 14 is operable automatically to command the ABS controller 13 to apply one or more brakes of the vehicle to help to steer the vehicle 100 in the direction the user wishes to travel. In the embodiment shown the SCS 14 is implemented by the VCU 10. In some alternative embodiments the SCS 14 may be implemented by the ABS controller 13.

Although not shown in detail in FIG. 3, the VCU 10 further includes a Traction Control (TC) function block. The TC function block is implemented in software code run by a computing device of the VCU 10. The ABS controller 13 and TC function block provide outputs indicative of, for example, TC activity, ABS activity, brake interventions on individual wheels and engine torque requests from the VCU 10 to the engine 121 in the event a wheel slip event occurs. Each of the aforementioned events indicate that a wheel slip event has occurred. In some embodiments the ABS controller 13 implements the TC function block. Other vehicle sub-systems such as a roll stability control system or the like may also be included.

As noted above the vehicle 100 also includes a cruise control system 16 which is operable to automatically maintain vehicle speed at a selected speed when the vehicle is travelling at speeds in excess of 25 kph. The cruise control system 16 is provided with a cruise control HMI (human machine interface) 18 by which means the user can input a target vehicle speed to the cruise control system 16 in a known manner. In one embodiment of the invention, cruise control system input controls are mounted to a steering wheel 171 (FIG. 5). The cruise control system 16 may be switched on by pressing a cruise control system selector button 176. When the cruise control system 16 is switched on, depression of a 'set- speed' control 173 sets the current value of a cruise control set-speed parameter, cruise_set-speed to the current vehicle speed. Depression of a '+' button 174 allows the value of cruise_set-speed to be increased whilst depression of a '-' button 175 allows the value of cruise_set-speed to be decreased. A resume button 173R is provided that is operable to control the cruise control system 16 to resume speed control at the instant value of cruise_set-speed following driver over-ride. It is to be understood that known on-highway cruise control systems including the present system 16 are configured so that, in the event that the user depresses the brake or, in the case of vehicles with a manual transmission, a clutch pedal, control of vehicle speed by the cruise control system 16 is cancelled and the vehicle 100 reverts to a manual mode of operation which requires accelerator or brake pedal input by a user in order to maintain vehicle speed. In addition, detection of a wheel slip event, as may be initiated by a loss of traction, also has the effect of cancelling control of vehicle speed by the cruise control system 16. Speed control by the system 16 is resumed if the driver subsequently depresses the resume button 173R. The cruise control system 16 monitors vehicle speed and any deviation from the target vehicle speed is adjusted automatically so that the vehicle speed is maintained at a substantially constant value, typically in excess of 25 kph. In other words, the cruise control system is ineffective at speeds lower than 25 kph. The cruise control HMI 18 may also be configured to provide an alert to the user about the status of the cruise control system 16 via a visual display of the HMI 18. In the present embodiment the cruise control system 16 is configured to allow the value of cruise_set-speed to be set to any value in the range 25- 150kph.

The LSP control system 12 also provides a speed-based control system for the user which enables the user to select a very low target speed at which the vehicle can progress without any pedal inputs being required by the user to maintain vehicle speed. Low-speed speed control (or progress control) functionality is not provided by the on-highway cruise control system 16 which operates only at speeds above 25 kph. In the present embodiment, the LSP control system 12 is activated by pressing LSP control system selector button 178 mounted on steering wheel 171 . The system 12 is operable to apply selective powertrain, traction control and braking actions to one or more wheels of the vehicle 100, collectively or individually. The LSP control system 12 is configured to allow a user to input a desired value of vehicle target speed in the form of a set-speed parameter, user set-speed, via a low-speed progress control HMI (LSP HMI) 20 (FIG. 1 , FIG. 3) which shares certain input buttons 173- 175 with the cruise control system 16 and HDC control system 12HD. Provided the vehicle speed is within the allowable range of operation of the LSP control system 12 (which is the range from 2 to 30kph in the present embodiment although other ranges are also useful) and no other constraint on vehicle speed exists whilst under the control of the LSP control system 12, the LSP control system 12 controls vehicle speed in accordance with a LSP control system set-speed value LSP_set-speed which is set substantially equal to user set- speed. Unlike the cruise control system 16, the LSP control system 12 is configured to operate independently of the occurrence of a traction event. That is, the LSP control system 12 does not cancel speed control upon detection of wheel slip. Rather, the LSP control system 12 actively manages vehicle behaviour when slip is detected.

Thus it is to be understood that the LSP control system 12 provides torque control means for automatically causing application of positive and negative torque, as required, to wheels 1 1 1 , 1 12, 1 14, 1 15 of the vehicle 100 to cause the vehicle 100 to travel in accordance with set-speed value LSP_set-speed, which may also be referred to as a target speed value.

The LSP control HMI 20 is provided in the vehicle cabin so as to be readily accessible to the user. The user of the vehicle 100 is able to input to the LSP control system 12, via the LSP HMI 20, the desired value of user set-speed as noted above by means of the 'set-speed' button 173 and the '+'/ '-' buttons 174, 175 in a similar manner to the cruise control system 16. The LSP HMI 20 also includes a visual display by means of which information and guidance can be provided to the user about the status of the LSP control system 12.

The LSP control system 12 receives an input from the ABS controller 13 of the braking system 22 of the vehicle indicative of the extent to which the user has applied braking by means of the brake pedal 163. The LSP control system 12 also receives an input from an accelerator pedal 161 indicative of the extent to which the user has depressed the accelerator pedal 161 , and an input from the transmission or gearbox 124. This latter input may include signals representative of, for example, the speed of an output shaft of the gearbox 124, an amount of torque converter slip and a gear ratio request. Other inputs to the LSP control system 12 include an input from the cruise control HMI 18 which is representative of the status (ON/OFF) of the cruise control system 16, an input from the LSP control HMI 20, and an input from a gradient sensor 45 indicative of the gradient of the driving surface over which the vehicle 100 is driving. In the present embodiment the gradient sensor 45 is a gyroscopic sensor. In some alternative embodiments the LSP control system 12 receives a signal indicative of driving surface gradient from another controller such as the ABS controller 13. The ABS controller 13 may determine gradient based on a plurality of inputs, optionally based at least in part on signals indicative of vehicle longitudinal and lateral acceleration and a signal indicative of vehicle reference speed (v actual) being a signal indicative of actual vehicle speed over ground. Methods for the calculation of vehicle reference speed based for example on vehicle wheel speeds are well known. For example in some known vehicles the vehicle reference speed may be determined to be the speed of the second slowest turning wheel, or the average speed of all the wheels. Other ways of calculating vehicle reference speed may be useful in some embodiments, including by means of a camera device or radar sensor.

The HDC system 12HD is activated by depressing button 177 comprised by HDC system HMI 20HD and mounted on the steering wheel 171 . When the HDC system 12HD is active, the system 12HD controls the braking system 22 in order to limit vehicle speed to a value corresponding to that of a HDC set-speed parameter HDC_set-speed which may be controlled by a user in a similar manner to the set-speed of the cruise control system 16 and LSP control system, using the same control buttons 173, 173R, 174, 175. The HDC system 12HD is operable to allow the value of HDC_set-speed to be set to any value in the range from 2-30kph. The HDC set-speed parameter may also be referred to as an HDC target speed. Provided the user does not override the HDC system 12HD by depressing the accelerator pedal 161 when the HDC system 12HD is active, the HDC system 12HD controls the braking system 22 (FIG. 3) to prevent vehicle speed from exceeding HDC_set-speed. In the present embodiment the HDC system 12HD is not operable to apply positive drive torque. Rather, the HDC system 12HD is only operable to cause negative brake torque to be applied, via the braking system 22.

It is to be understood that the VCU 10 is configured to implement a known Terrain Response (TR) (RTM) System of the kind described above in which the VCU 10 controls settings of one or more vehicle systems or sub-systems such as the powertrain controller 1 1 in dependence on a selected driving mode. The driving mode may be selected by a user by means of a driving mode selector 141 S (FIG. 1 ). The driving modes may also be referred to as terrain modes, terrain response (TR) modes, or control modes.

In the embodiment of FIG. 1 four driving modes are provided: an 'on-highway' driving mode suitable for driving on a relatively hard, smooth driving surface where a relatively high surface coefficient of friction exists between the driving surface and wheels of the vehicle; a 'sand' driving mode suitable for driving over sandy terrain, being terrain characterised at least in part by relatively high drag, relatively high deformability or compliance and relatively low surface coefficient of friction; a 'grass, gravel or snow' (GGS) driving mode suitable for driving over grass, gravel or snow, being relatively slippery surfaces (i.e. having a relatively low coefficient of friction between surface and wheel and, typically, lower drag than sand); a 'rock crawl' (RC) driving mode suitable for driving slowly over a rocky surface; and a 'mud and ruts' (MR) driving mode suitable for driving in muddy, rutted terrain. Other driving modes may be provided in addition or instead. In the present embodiment the selector 141 S also allows a user to select an 'automatic driving mode selection condition' of operation in which the VCU 10 selects automatically the most appropriate driving mode as described in more detail below. The on-highway driving mode may be referred to as a 'special programs off (SPO) mode in some embodiments since it corresponds to a standard or default driving mode, and is not required to take account of special factors such as relatively low surface coefficient of friction, or surfaces of high roughness.

In order to prevent or at least reduce passenger discomfort due to rapid changes in acceleration rate (jerk) when the LSP control system 12 is controlling vehicle speed, the LSP control system 12 limits the rate of change of acceleration of the vehicle 100 such that it does not exceed a prescribed maximum value. The maximum allowable rate of change of acceleration or maximum allowable jerk value is provided by parameter LSP_J_MAX. The LSP control system 12 also limits the maximum value of rate of acceleration to a value LSP_A_MAX.

The values of LSP_A_MAX and LSP_J_MAX are set in dependence at least in part on TR mode and vehicle speed. In some embodiments, including the present embodiment, the values for TR_mode=sand are higher than the corresponding values for TR_mode=SPO, GGS or MR due to the higher drag imposed on a vehicle 100 traversing sand compared with a vehicle traversing a dry asphalt highway surface, a grass, gravel or snow surface, or a muddy or rutted surface.

The LSP control system 12 causes the vehicle 100 to operate in accordance with the value of LSP_set-speed.

In order to cause application of the necessary positive or negative torque to the wheels, the VCU 10 may command that positive or negative torque is applied to the vehicle wheels by the powertrain 129 and/or that a braking force is applied to the vehicle wheels by the braking system 22, either or both of which may be used to implement the change in torque that is necessary to attain and maintain a required vehicle speed. In some embodiments torque is applied to the vehicle wheels individually, for example by powertrain torque vectoring, so as to maintain the vehicle at the required speed. Alternatively, in some embodiments torque may be applied to the wheels collectively to maintain the required speed, for example in vehicles having drivelines where torque vectoring is not possible. In some embodiments, the powertrain controller 1 1 may be operable to implement torque vectoring to control an amount of torque applied to one or more wheels by controlling a driveline component such as a rear drive unit, front drive unit, differential or any other suitable component. For example, one or more components of the driveline 130 may include one or more clutches operable to allow an amount of torque applied to one or more wheels to be varied. Other arrangements may also be useful. Where a powertrain 129 includes one or more electric machines, for example one or more propulsion motors and/or generators, the powertrain controller 1 1 may be operable to modulate torque applied to one or more wheels in order to implement torque vectoring by means of one or more electric machines.

In some embodiments the LSP control system 12 may receive a signal wheel_slip (also labelled 48 in FIG. 3) indicative of a wheel slip event having occurred. This signal 48 is also supplied to the on-highway cruise control system 16 of the vehicle, and which in the case of the latter triggers an override or inhibit mode of operation in the on-highway cruise control system 16 so that automatic control of vehicle speed by the on-highway cruise control system 16 is suspended or cancelled. However, the LSP control system 12 is not arranged to cancel or suspend operation on receipt of wheel_slip signal 48. Rather, the system 12 is arranged to monitor and subsequently manage wheel slip so as to reduce driver workload. During a slip event, the LSP control system 12 continues to compare the measured vehicle speed with the value of LSP_set-speed, and continues to control automatically the torque applied to the vehicle wheels (by the powertrain 129 and braking system 22) so as to maintain vehicle speed at the selected value. It is to be understood therefore that the LSP control system 12 is configured differently to the cruise control system 16, for which a wheel slip event has the effect of overriding the cruise control function so that manual operation of the vehicle must be resumed, or speed control by the cruise control system 16 resumed by pressing the resume button 173R or set-speed button 173.

The vehicle 100 is also provided with additional sensors (not shown) which are representative of a variety of different parameters associated with vehicle motion and status. These may be inertial systems unique to the LSP or HDC control systems 12, 12HD or part of an occupant restraint system or any other sub-system which may provide information or data from sensors such as gyros and/or accelerometers that may be indicative of vehicle body movement and may provide a useful input to the LSP and/or HDC control systems 12, 12HD. The signals from the sensors provide, or are used to calculate, a plurality of driving condition indicators (also referred to as terrain indicators) which are indicative of the nature of the terrain conditions over which the vehicle 100 is travelling. The sensors may provide information in the form or an analogue signal, or digitised data in the form of a digital signal.

The sensors (not shown) on the vehicle 100 include, but are not limited to, sensors which provide continuous sensor outputs to the VCU 10, including wheel speed sensors, as mentioned previously, an ambient temperature sensor, an atmospheric pressure sensor, tyre pressure sensors, wheel articulation sensors, gyroscopic sensors to detect vehicular yaw, roll and pitch angle and rate, a vehicle speed sensor, a longitudinal acceleration sensor, an engine torque sensor (or engine torque estimator), a steering angle sensor, a steering wheel speed sensor, a gradient sensor (or gradient estimator), a lateral acceleration sensor which may be part of the SCS 14, a brake pedal position sensor, a brake pressure sensor, an accelerator pedal position sensor, longitudinal, lateral and vertical motion sensors, and water detection sensors forming part of a vehicle wading assistance system (not shown). In other embodiments, only a selection of the aforementioned sensors may be used.

The VCU 10 also receives a signal from the steering controller 170C. The steering controller 170C is in the form of an electronic power assisted steering unit (ePAS unit) 170C. The steering controller 170C provides a signal to the VCU 10 indicative of the steering force being applied to steerable road wheels 1 1 1 , 1 12 of the vehicle 100. This force corresponds to that applied by a user to the steering wheel 171 in combination with steering force generated by the ePAS unit 170C. The ePAS unit 170C also provides a signal indicative of steering wheel rotational position or angle. in the present embodiment, the VCU 10 evaluates the various sensor inputs to determine the probability that each of the plurality of different TR modes (control modes or driving modes) for the vehicle subsystems is appropriate, with each control mode corresponding to a particular terrain type over which the vehicle is travelling (for example, mud and ruts, sand, grass/gravel/snow) as described above.

If the user has selected operation of the vehicle in the automatic driving mode selection condition, the VCU 10 then selects the most appropriate one of the control modes and is configured automatically to control the subsystems according to the selected mode. This aspect of the invention is described in further detail in our co-pending patent applications GB2492748, GB2492655 and GB2499279, the contents of each of which is incorporated herein by reference as noted above. As indicated above, the nature of the terrain over which the vehicle is travelling (as determined by reference to the selected control mode) may also be utilised in the LSP control system 12 to determine an appropriate increase or decrease in vehicle speed. For example, if the user selects a value of user set-speed that is not suitable for the nature of the terrain over which the vehicle is travelling, the system 12 is operable to automatically adjust the value of LSP_set-speed to a value lower than user set-speed. In some cases, for example, the user selected speed may not be achievable or appropriate over certain terrain types, particularly in the case of uneven or rough surfaces. If the system 12 selects a set- speed (a value of LSP_set-speed) that differs from the user-selected set-speed userset- speed, a visual indication of the speed constraint is provided to the user via the LSP HMI 20 to indicate that an alternative speed has been adopted.

Other arrangements may be useful.

In the present embodiment, the vehicle 100 is provided with an inertial measurement unit (IMU) 182 that is configured to monitor motion of a body 100B of the vehicle 100 at the location of the IMU 182, which may be referred to as a primary reference location. The IMU 182 feeds a movement signal 182S to the VCU 10 that provides information indicative of movement of the vehicle 100 with respect to 6 axes of motion. In the present embodiment the signal is indicative of a rate of acceleration of the vehicle along mutually orthogonal X-, Y- and Z-axes illustrated in FIG. 2, and rate of angular acceleration about those axes. Angular acceleration about the X-axis is referred to as pitch acceleration, angular acceleration about the Z-axis is referred to as yaw acceleration, and angular acceleration about the Y-axis is referred to as roll acceleration.

The VCU 10 includes occupant comfort information determining means implemented in software that employs the movement signal to calculate a set of motion parameter values being values of heave acceleration, pitch acceleration and roll acceleration experienced at a predetermined set of occupant-relevant locations, being the location of a front row of seats 172F of the vehicle 100 and at the location of a rear row of seats 172R of the vehicle 100 (FIG. 2). In the present embodiment, the IMU 182 is located sufficiently close to a lateral (across-vehicle) axis (with respect to a longitudinal (along-vehicle) axis) that the location of the front row of seats may be considered to correspond to the primary reference location, i.e. the location of the IMU 182. The VCU 10 is configured to calculate a maximum recommended (or 'allowable') vehicle speed v max based on the selected set of motion parameter values at one of these locations, for use by the LSP control system 12 when actively controlling vehicle speed.

In the present embodiment, the VCU 10 calculates the value of acceleration in a direction parallel to the Z-axis at a location other than the primary reference location being the location of the IMU 182, referred to as heave acceleration az new, using the equation: az_new = az + (rx ^* dx) + (ry ^* dy), where:

aznew = modified heave acceleration for the selected location;

az = heave acceleration at primary reference location;

rx = rate of rotational acceleration of vehicle 100 around x-axis of vehicle 100;

dx = distance to selected (new) location from primary reference location along x axis; ry = rate of rotational acceleration of vehicle 100 around y-axis of vehicle 100; and dy = distance to selected (new) location from primary reference location along y axis.

The VCU 10 is configured to allow a user to select a 'comfort speed adjustment' mode of operation of the LSP control system 12, in which the LSP control system 12 is configured to limit vehicle speed in dependence on a measurement of a comfort factor (or 'comfort value' or 'comfort parameter') at a selected one of the plurality of predetermined occupant-relevant locations. When the comfort speed adjustment mode is selected, the LSP control system 12 monitors the value of v max and user set-speed. If the value of user set-speed is higher than v max at a given moment in time, the LSP control system 12 sets the value of LSP_set-speed to v max rather than user set-speed.

The 'comfort speed adjustment' mode has two selectable modes or sub-modes, an automatic comfort location selection mode and a manual comfort location selection mode. In the automatic comfort location selection mode, the LSP control system 12 uses the set of motion parameter values calculated in respect of the front row of seats 172F unless the LSP control system 12 determines that one or more rear seats 172R are occupied, in which case the set of motion parameter values calculated in respect of the location of the rear row of seats 172R is used. The LSP control system 12 includes occupant location determining means in the form of computer software code that executes instructions to determine whether a given seat is occupied by reference to a seat occupancy signal generated by the VCU 10 in dependence on signals received from seat occupancy sensors embedded in each seat of the vehicle 100. A front seat occupancy sensor 172FS is shown embedded in a front seat 172F in FIG. 2 whilst a rear seat occupancy sensor 172RS is shown embedded in a rear seat 172R. The seat occupancy signal provides an indication of the identity of each seat 172F, 172R that is occupied. In the manual comfort location selection mode, the LSP control system 12 determines whether to use the set of motion parameter values in respect of the front row of seats 172F or rear row of seats 172R by reference to an input provided by a user indicative of the location in respect of which motion parameter values are to be employed in controlling vehicle speed.

In embodiments in which more than two rows of seats are provided, the LSP control system 12 may permit a user to select the location in respect of which passenger comfort is to be controlled from each of the rows, for example a front row, middle row and a rear row. In some embodiments the LSP control system 12 may permit a user to select a location relevant to towing a load, such as the location of a tow hitch of the vehicle 100, in order to calculate a set of motion parameter values. In some embodiments, the LSP control system 12 may be configured automatically to select a location relevant to towing a load, such as the location of a tow hitch, whenever the LSP control system 12 is active whilst the vehicle 100 is towing. The VCU 10 may generate a signal indicative of whether the vehicle 100 is towing a load in dependence on one or more factors, such as whether a trailer lighting board is connected to an electrical lighting board power source of the vehicle 100, or whether a driver has selected a 'tow' mode of operation of the vehicle 100. In the present embodiment, the LSP control system 12 is configured to submit the motion parameter values to an algorithm which generates a value of the comfort factor based at least in part on the motion parameter values input thereto. Algorithms suitable for generating suitable comfort factors based on one or more measurements of vehicle motion are known, see for example BS IS02631 -1 :1997.

In some embodiments, where the IMU 182 is located sufficiently forward or rearward of the front row of seats 172F, the VCU 10 may be configured to calculate a value of comfort factor in respect of the location of the front row as well as the rear row 172R by applying the above equation.

In some embodiments, the VCU 10 may be configured to calculate a value of comfort factor in respect of individual seat positions in a given row, such as left and right seat front row seat positions in vehicles having only left and right front seats, and left, centre and right rear row seat positions in vehicles having left, centre and right rear seats.

It is to be understood that, in the automatic comfort location selection mode, the VCU 10 may be configured to identify whether a front passenger seat is occupied, and which seats of one or more rear rows are occupied, e.g. rear left seat, rear right seat and/or rear middle seat. The VCU 10 may be configured to select the identity of the occupant-relevant location that is serve as the location in respect of which passenger comfort is controlled based at least in part on the direction of turn of the vehicle 100. In particular, in some embodiments the VCU 10 may select the identity of the occupant-relevant location as the location that is on the outside of a curve, opposite the direction in which the vehicle 100 is turning. This is because a seat on an outside of a turn will generally travelling at a greater speed than a seat on an inside of the turn. In some embodiments, if the steering angle or yaw rate exceeds a respective predetermined amount, and more than one rear seat of the vehicle 100 is occupied, the VCU 10 may select the identity of the occupant-relevant location that is serve as the location in respect of which passenger comfort is to be controlled as the radially outermost location with respect to the turn, i.e. the fastest moving rear seat. In the absence of any passengers on a rear seat, the VCU 10 may default to setting the occupant-relevant location that is serve as the location in respect of which passenger comfort is to be controlled as the radially outermost occupied front seat location with respect to the turn, i.e. the fastest moving occupied front seat.

In some embodiments, the VCU 10 may be configured to receive a signal indicative of the degree of comfort that a given occupant wishes to enjoy. In some embodiments the degree of comfort may be input in the form of a rotary dial, or discrete respective 'up' and 'down' input buttons or controls, enabling the degree of comfort to be adjusted from 'low' to 'high'. It is to be understood that if a relatively low degree of comfort is selected, the value of v max is likely to be higher than in the case that a relatively high degree of comfort is selected. The LSP control system 12 may utilise the signal indicative of degree of comfort to apply a weighting to the motion parameter values, artificially increasing or decreasing one or more of the values prior to their submission to the algorithm that calculates the prevailing value of comfort factor. Alternatively, the LSP control system 12 may submit a value of one or more parameters to the algorithm that accommodate the user's preference for a relatively low or high degree of comfort in respect of their ride. In a further embodiment, the LSP control system 12 calculates a value of comfort factor using the prevailing motion parameter values, without adjusting their values in response to the degree of comfort requested by a user, and then employs the calculated value of comfort factor in combination with an indication of the degree of comfort requested by the user in order to calculate v max. In some embodiments this may be accomplished by multiplying the value of comfort factor calculated by the algorithm by a factor that is dependent on the degree of comfort requested by the user, such that the value of comfort factor (which may be higher for motion information indicative of higher levels of comfort) is decreased (indicating the prevailing comfort level is lower) if the user requests a higher degree of comfort. Other arrangements may be useful.

It is to be understood that a driver and optionally one or more further occupants not seated in a driver seat may be provided with input controls enabling a degree of required comfort to be input to the LSP control system 12.

FIG. 5 is a flow diagram illustrating the method of vehicle control implemented by the present embodiment when the VCU 10 is in the automatic comfort location selection mode. At step S101 the VCU 10 determines whether a seat of the rear row 172R is occupied. If a seat of the rear row 172R is occupied, the VCU 10 sets the reference seat location thereof to the rear row 172R else the reference seat location is set to the front row 172F.

At step S103 the VCU 10 calculates a set of motion parameter values for the reference location.

At step S105 the VCU 10 calculates a value of comfort parameter based on the motion parameter values calculated for the reference seat location at step S103 and determines a corresponding value of v max.

At step S107 the VCU 10 causes vehicle speed to be limited to a speed not exceeding v max.

FIG. 6 is a flow diagram illustrating the method of vehicle control implemented by the present embodiment when the VCU 10 is in the manual comfort location selection mode.

At step S201 the VCU 10 sets the reference seat location thereof to the front row 172F or rear row 172R in dependence on driver selection. At step S203 the VCU 10 calculates a set of motion parameter values for the reference seat location. At step S205 the VCU 10 calculates a value of comfort parameter based on the motion parameter values calculated for the reference seat location at step S203 and determines a corresponding value of v max. At step S207 the VCU 10 causes vehicle speed to be limited to a speed not exceeding v max.

Some embodiments of the present invention enable vehicle operation with enhanced composure, by reducing driver workload. This is because a driver is not required manually to decrease the value of user set-speed in order to attempt to maintain an acceptable comfort level for one or more occupants, or cancel control of vehicle speed by the LSP control system 12 if they feel vehicle speed is too high over a given stretch of terrain. Rather, the vehicle 100 proactively monitors the comfort level in respect of one or more predetermined occupants and adjusts vehicle speed accordingly.

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 unless incompatible therewith.