WO2018134153A1

WO2018134153A1 - Control system for a vehicle and method

Info

Publication number: WO2018134153A1
Application number: PCT/EP2018/050875
Authority: WO
Inventors: Charlotte COOKE; Robert Burford; Christopher Johnson; David Armstrong
Original assignee: Jaguar Land Rover Limited
Priority date: 2017-01-19
Filing date: 2018-01-15
Publication date: 2018-07-26
Also published as: GB201700922D0; GB2558913A; GB2558913B

Abstract

A vehicle control system for controlling at least one subsystem (11, 12b, 12c, 12d, 12e) of a vehicle, the at least one subsystem (11, 12b, 12c, 12d, 12e) comprising a powertrain controller (11), the vehicle control system being configured to initiate control of at least one said at least one vehicle subsystem (11, 12b, 12c, 12d, 12e) in one of a plurality of subsystem control modes, each subsystem control mode corresponding to one or more different driving conditions for the vehicle (100), the control modes including a first subsystem control mode and a wade mode adapted for use when a vehicle (100) is wading, the control system being configured to receive a signal indicative of a pitch attitude of the vehicle (100) at a given moment in time, wherein when the system controls the at least one subsystem (11, 12b, 12c, 12d, 12e) in the wade mode, the system configures the powertrain controller (11) wherein a response of the powertrain to user actuation of an accelerator control is dependent at least in part on the signal indicative of pitch attitude of the vehicle.

Description

CONTROL SYSTEM FOR A VEHICLE AND METHOD

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.

TECHNICAL FIELD

The present disclosure relates to a vehicle control system and control method and particularly, but not exclusively, to a controller and a method for controlling operation of one or more vehicle systems or subsystems in a land-based vehicle capable of driving in a variety of different and extreme terrains and conditions. Aspects of the invention relate to a controller, to a control system, a vehicle, a method, a non-transitory computer readable carrier medium carrying a computer readable code, a computer program product executable on a processor, a computer readable medium and a processor. BACKGROUND

It is 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.

As noted above, for each of the driving modes each of the sub-systems is set to the function mode most appropriate to those conditions. The present applicant has recognised that the „ particular configuration of a subsystem in a given driving mode may not be optimum for the actual prevailing conditions, or a driver may have a particular preference for the manner in which one or more of the subsystems are configured in a given driving mode other than the default configuration corresponding to the driving mode. By way of example, it is to be understood that the Sand driving mode may not provide optimum vehicle performance when driving on wet or damp sand, compared with dry sand.

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 embodiments 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 vehicle control system for controlling at least one subsystem of a vehicle, the vehicle control system comprising:

a subsystem controller for initiating control of the or each of the at least one vehicle subsystems in one of a plurality of baseline subsystem control modes by setting at least one control parameter of the or each of the at least one subsystems to a predetermined, stored, baseline value or state applicable to that baseline subsystem control mode, each baseline subsystem control mode corresponding to one or more different driving conditions for the vehicle, and wherein the controller is configured to receive a signal indicative of a pitch attitude of the vehicle at a given moment in time,

wherein the baseline control modes comprise a wade mode adapted for use when a vehicle is wading, and the at least one subsystem comprises a powertrain controller,

wherein when the subsystem controller controls the at least one subsystem in the wade mode, the subsystem controller is configured to adjust at least one parameter of the powertrain controller in order to adjust a response of the powertrain controller to user actuation of an accelerator control in dependence at least in part on the signal indicative of pitch attitude of the vehicle.

In a further aspect of the invention for which protection is sought there is provided a vehicle control system for controlling at least one subsystem of a vehicle, the at least one subsystem comprising a powertrain controller, the vehicle control system being configured to initiate control of at least one said at least one vehicle subsystem in one of a plurality of subsystem control modes, each subsystem control mode corresponding to one or more different driving conditions for the vehicle, the control modes including a first subsystem control mode and a wade mode adapted for use when a vehicle is wading,

the control system being configured to receive a signal indicative of a pitch attitude of the vehicle at a given moment in time,

wherein when the system controls the at least one subsystem in the wade mode, the system configures the powertrain controller wherein a response of the powertrain to user actuation of an accelerator control is dependent at least in part on the signal indicative of pitch attitude of the vehicle. This feature has the advantage that the controller may adjust the response of the accelerator control according to whether a vehicle is travelling on level ground or descending into or ascending out of a body of water. Thus, in some embodiments the amount of torque delivered by a powertrain to one or more wheels of the vehicle as a function of accelerator pedal position may be adjusted in dependence on pitch attitude. As described below, in some embodiments the controller is configured to soften or sharpen the response of the powertrain to actuation of the accelerator pedal by a given amount, depending on pitch attitude. In some embodiments the controller is configured to set the response of a torque filter to powertrain torque demand according to pitch attitude. Thus, the filter may provide one response when the vehicle has a given pitch up attitude and another response when the vehicle has a substantially level attitude.

Some embodiments of the present invention have the advantage that relatively smooth entry into and exit from a body of water may be achieved by a relatively novice driver. Furthermore, they enable a more steady and consistent vehicle speed to be achieved whilst traversing a body of water, mitigating the possibility of speed over- or under-shoot. Speed under- or over-shoot may create an undesirable bow wave and reduce smooth vehicle progress. This feature also assists the driver to maintain smooth progress when attempting to create, and follow, a bow wave, a technique employed by expert off-road drivers. In some embodiments, the control system may be configured to adjust the amount of torque delivered by a powertrain to one or more wheels of the vehicle as a function of accelerator pedal position based at least in part on vehicle pitch attitude.

The control system may be further configured to adjust the amount of torque delivered by a powertrain to one or more wheels of the vehicle as a function of accelerator pedal position based at least in part on vehicle speed. Alternatively or in addition the control system may be configured to adjust the amount of torque delivered by a powertrain to one or more wheels of the vehicle as a function of accelerator pedal position based at least in part on an input, such as a signal input, indicative of a size, location or speed of a bow wave created by the vehicle. The size, location or speed of the bow wave may be determined at least in part from images captured by a vehicle-mounted camera device, such as a forward-facing camera device.

It is to be understood that this function may discourage a driver from creating an undesirable bow wave or achieving undesirable vehicle speed.

In some embodiments, when in the wade mode the controller may be configured to cause one or more other vehicle subsystems to assume a predetermined configuration or mode. In some embodiments, when in the wade mode a gear shift map associated with an automatic transmission (where present) may be adjusted to ensure the powertrain operates with optimum gear selection.

In some embodiments a predetermined differential lock strategy may be employed when in the wade mode. For example, relative rotation of wheels of a given axle may be restricted and optionally substantially prevented when in the wade mode. That is, left and right wheels of a given axle may be substantially locked together such that rotation of a left wheel relative to a right wheel of the axle is restricted or substantially prevented. In some embodiments the front and rear axles may be locked to one another, optionally via a centre differential.

In some embodiments, the rate of change of the amount of torque demanded of the powertrain as a function of the amount of accelerator pedal travel may be changed when in wade mode. In some embodiments the rate of change of demanded torque as a function of pedal travel may increase when in the wade mode. Thus, in some embodiments, at 'tip in' when the pedal is depressed, the rate of increase of powertrain torque may be higher than in a non-wade mode. In some alternative embodiments the rate of change of demanded torque as a function of pedal travel may decrease when in the wade mode. In some embodiments, the rate of change of demanded torque as a function of pedal travel may be changed in dependence on whether the control system has determined that the vehicle is actually wading through liquid. When it is detected that the vehicle is wading through liquid, the rate of change of demanded torque as a function of pedal travel may be set to a wading configuration. In some embodiments, the rate of change of demanded torque as a function of pedal travel may be set to a wading configuration when it is detected that the vehicle is wading through liquid and the vehicle pitch attitude is within a predetermined range of angles with respect of a substantially horizontal pitch attitude.

It is to be understood that, in some embodiments, the control system may be operable in one of a wade mode and the first (non-wade) mode only. The first mode may for example be a normal driving mode, such as a highway driving mode, in which the or at least one of the subsystems are operated in a predetermined, stored configuration suitable for on-highway driving. Thus, the control system may operate in either the wade mode or the highway mode and no other mode. In some alternative embodiments the controller may be operable in one of three or more modes, one of which is the wade mode. The other modes may include the highway mode and at least one other mode such as a mode suitable for driving on a slippery surface such as grass, gravel or snow. In the mode suitable for driving on a slippery surface, the subsystem controller may be configured to cause the powertrain to soften its response to user actuation of the accelerator control relative to the highway mode.

It is to be understood that by soften a response of the powertrain controller to user actuation of the accelerator control is meant that the powertrain controller is configured such that, in order to cause a powertrain to generate a given amount of powertrain torque, the accelerator control must be actuated by a larger amount . This feature has the advantage that it may reduce the amount of slip of one or more wheels in response to accelerator control actuation.

By sharpen a response of the powertrain controller to user actuation of the accelerator control is meant that the powertrain controller is configured such that, in order to cause a powertrain to generate achieve a given amount of powertrain torque, the accelerator control must be actuated by a smaller amount. This feature has the advantage that it may enable a driver to maintain a required speed when wading more easily despite the larger amount of drag imposed on the vehicle by the body of water through which the vehicle is wading. Optionally the control system is configured, when the system controls the at least one subsystem in the wade mode, temporarily to configure the powertrain controller to soften a response of the powertrain to user actuation of the accelerator control whilst the pitch attitude of the vehicle exceeds substantially a first predetermined value above a substantially horizontal plane or whilst the pitch attitude exceeds substantially a second predetermined value below a substantially horizontal plane, relative to that when the pitch attitude does not exceed these values. Thus the control system may temporarily soften the response during the periods for which the pitch attitude of the vehicle exceeds the first predetermined value above a substantially horizontal plane or for which the pitch attitude exceeds a second predetermined value below a substantially horizontal plane.

The first and second predetermined values may be any suitable values such as 10 degrees, 20 degrees, 30 degrees, 40 degrees or any other suitable value. In some embodiments the first and second values are substantially the same whilst in some other embodiments the first and second values are different.

Optionally the control system is configured to receive a signal indicative of whether a vehicle is wading, the controller being configured, when the system controls the at least one subsystem in the wade mode, to adjust the response of the powertrain controller to user actuation of the accelerator control in dependence at least in part on the signal indicative of whether the vehicle is wading.

It is to be understood therefore, that, when the system controls the at least one subsystem in the wade mode, the system may receive a signal indicative of whether the vehicle is wading and control the powertrain controller accordingly.

Optionally the control system is configured, when the system controls the at least one subsystem in the wade mode, to sharpen the response of the powertrain controller to user actuation of the accelerator control if the signal indicative of whether the vehicle is wading indicates that the vehicle is wading and the pitch attitude of the vehicle is less than a predetermined upward wading pitch angle above a horizontal plane and less than a predetermined downward wading pitch angle below the horizontal plane.

The predetermined upward and downward wading pitch angles may be any suitable angles. In an embodiment, the first and second predetermined values noted above are substantially 20 degrees and the predetermined upward and downward wading pitch angles are also substantially 20 degrees. It is to be understood that the controller may implement a hysteresis in the angles at which the response of the powertrain controller to user actuation of the accelerator control is changed, so as to prevent mode chattering in which the response changes repeatedly at relatively short intervals, for example due to bounce of the vehicle and oscillation of the pitch attitude above and below the value of pitch attitude at which the response is otherwise arranged to change. Optionally, the signal indicative of whether the vehicle is wading comprises a signal responsive to one or more sensors configured to sense the distance of obstacles from the vehicle. The signal may for example comprise a signal carrying information obtained from a parking distance control (PDC) system having one or more distance sensors such as one or more ultrasonic distance sensors configured to sense the distance of obstacles from the vehicle.

Optionally, the control system is configured to allow a user to select the control mode in which the subsystem controller is to initiate control of the vehicle from a plurality of subsystem control modes

Optionally, the control system is configured to allow a user to select the control mode via input means, wherein the input means comprises at least one selected from amongst a rotary switch selector device, a lever-type switch selector device, one or more button devices and one or more touchscreen devices.

Optionally, the control system is configured to select automatically an appropriate control mode from a plurality of subsystem control modes, the automatic selection being made in dependence on one or more signals received from one or more sensors.

The one or more sensors may include one or more driving condition sensors such as one or more vehicle body movement sensors, wheel speed sensors, a temperature sensor or any other sensor suitable for obtaining information in respect of a suitable subsystem control mode.

Optionally, the control modes comprise at least one control mode adapted for driving on a driving surface of relatively low surface coefficient of friction.

Optionally, the control modes comprise at least one control mode adapted for driving on at least one of snow, ice, grass, gravel, mud, and sand.

The control system may comprise a plurality of subsystems, wherein at least one subsystem includes a brakes subsystem or a suspension subsystem. Optionally, the control system may comprise an electronic processor having an electrical input for receiving a signal indicative of vehicle pitch attitude, 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 initiate control of the or each said at least one vehicle subsystem, including the powertrain controller, in one of a plurality of subsystem control modes, each subsystem control mode corresponding to one or more different driving conditions for the vehicle, the control modes comprising a first mode and a wade mode adapted for use when a vehicle is wading,

wherein when the subsystem controller controls the at least one subsystem in the wade mode, the subsystem controller configures the powertrain controller wherein a response of the powertrain controller to user actuation of the accelerator control is dependent at least in part on the signal indicative of pitch attitude of the vehicle. 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 at least one subsystem of a vehicle, the at least one subsystem comprising a powertrain controller,

the method comprising initiating control of at least one said at least one vehicle subsystem in one of a plurality of subsystem control modes, each subsystem control mode corresponding to one or more different driving conditions for the vehicle, the control modes including a first subsystem control mode and a wade mode adapted for use when a vehicle is wading,

the method comprising receiving a signal indicative of a pitch attitude of the vehicle at a given moment in time,

whereby when the system controls the at least one subsystem in the wade mode, the system configures the powertrain controller wherein a response of the powertrain to user actuation of an accelerator control is dependent at least in part on the signal indicative of pitch attitude of the vehicle.

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

One aspect of the invention relates to a control system for a vehicle that controls one or more subsystems such as a powertrain controller. When the vehicle is in a certain mode (such as a wade mode) the response of the powertrain to user actuation of an accelerator control is dependent at least in part on a signal indicative of pitch attitude of the vehicle. In some embodiments, the powertrain is controlled to give a softer pedal response when an uphill pitch attitude is detected, reducing the risk of excessive wheel slip when a vehicle climbs out of water, such as at bank of a river. 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

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 present invention; FIGURE 2 is a schematic illustration of a portion of a cabin of the vehicle of FIG. 1 showing a steering wheel, accelerator pedal and brake pedal;

FIGURE 3 is a block diagram illustrating a control system of the vehicle of FIG. 1 , including various vehicle subsystems under the control of the vehicle control system;

FIGURE 4 is a table showing which vehicle subsystem configuration mode is selected in each respective vehicle operating mode in a known vehicle having multiple driving modes; FIGURE 5 is is plot of powertrain torque demand as a function of accelerator pedal position showing three traces T1 , T2 and T3 employed by the powertrain controller of the vehicle of FIG. 1 when the vehicle is in a wade driving mode;

FIGURE 6 is a schematic illustration of the vehicle of FIG. 1 wading in a river; and

FIGURE 7 is a schematic illustration of the vehicle of FIG. 1 at different stages of a wading operation including (a) an initial approach stage, (b) a descent into water stage, (c) a water transit stage, (d) a climb out of water stage and (e) a final level attitude stage. DETAILED DESCRIPTION

FIG. 1 shows a vehicle 100 according to an embodiment of the invention that is suitable for off-road use, that is for use on terrains other than regular tarmac road, as well as on-road. The vehicle 100 has a powertrain 129 that includes an engine 121 that is connected to a driveline 130 having an automatic transmission 124. The transmission 124 has a transmission mode selector dial 124S permitting a driver to select the required transmission operating mode selected from park (P), forward drive (D), neutral (N) and reverse drive (R).

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. It is to be understood that embodiments of the present invention are suitable for use with vehicles in which the transmission 124 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, or permanent 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 transfer case 131 P, allowing selectable two wheel drive or four wheel drive operation. It is to be understood that embodiments of the invention may be suitable for vehicles having more than four wheels or less than four wheels.

In the present embodiment the transfer case 131 P is operable in a 'high ratio' ('hi') or a 'low ratio' (Ίο') configuration, in which a gear ratio between an input shaft and an output shaft thereof is selected to be a high or low ratio. The high ratio configuration is suitable for general on-road or 'on-highway' operations whilst the low ratio configuration is more suitable for negotiating certain off-road terrain conditions and other low speed applications such as towing. In some embodiments the transfer case 131 P may be operable in only one gear ratio configuration rather than one of two ratio configurations.

The vehicle 100 has an accelerator pedal 161 , a brake pedal 163 and a steering wheel 171 . The steering wheel 171 has a cruise control selector button 176 mounted thereto for activating an on-highway cruise control system 10CC that is implemented in software by a vehicle central controller, referred to as a vehicle control unit (VCU) 10 described in more detail below. The steering wheel 171 is also provided with a low speed progress control system selector button 178 (FIG. 2) for selecting operation of a low speed progress (LSP) control system 10LSP which may also be referred to as an off-road speed control system or off-road cruise control system. The LSP control system 10LSP is also implemented in software by the VCU 10. In addition to the cruise control system 10CC and LSP control system 10LSP the VCU 10 is configured to implement a hill descent control (HDC) system 10HDC that limits maximum vehicle speed when descending an incline by automatic application of a brakes (or braking) system 12d (FIG. 3) described in more detail below. The HDC system 10HDC may be activated via HDC selector button 177.

Once a speed control system 10CC, 10LSP, 10HDC has been activated, the user may depress a 'set' button 173 mounted on the steering wheel 171 to set the speed at which the speed control system will endeavour to maintain vehicle travel to the instant vehicle speed. The set speed may be increased or decreased, respectively, using 'plus' and 'minus' buttons 174, 175 respectively also mounted on the steering wheel 171 . 'Resume' button 173R may be used to resume speed control by the currently selected speed control system 10CC, 10LSP, 10HDC following suspension of control due for example to depression of the brake pedal 163. The VCU 10 receives a plurality of signals from various sensors and subsystems 12 provided on the vehicle 100. FIG. 3 is a schematic diagram illustrating operation of the VCU 10 in more detail. The VCU 10 controls a plurality of vehicle subsystems 12 including, but not limited to, an engine management system 12a that is comprised by the powertrain controller 1 1 , a transmission system 12b that includes the transmission 124 and transmission controller 124C, an electronic power assisted steering unit 12c (ePAS unit), the brakes system 12d and a suspension system 12e. These vehicle sub-systems can be considered to form a first group of subsystems. Although five subsystems are illustrated as being under the control of the VCU 10, in practice a greater number of vehicle subsystems may be included on the vehicle and may be under the control of the VCU 10. The VCU 10 includes a subsystem control module 14 which provides control signals via line 13 to each of the vehicle subsystems 12 to initiate control of the subsystems in a manner appropriate to the driving condition, such as the terrain, in which the vehicle is travelling (referred to as the terrain condition). The subsystems 12 also communicate with the subsystems control module 14 via signal line 13 to feedback information on subsystem status. In some embodiments, instead of an ePAS unit 12c, a hydraulically operated power steering unit may be provided.

The vehicle is configured to be caused to operate, by the VCU 10, in one of a plurality of predetermined control modes. In each control mode, the subsystems 12 are caused to operate in a predetermined subsystem configuration mode suitable for a given terrain type. The control modes include a grass/gravel/snow control mode (GGS mode) that is suitable for when the vehicle is travelling in grass, gravel or snow terrain, a mud/ruts control mode (MR mode) which is suitable for when the vehicle is travelling in mud and ruts terrain, a rock crawl/boulder mode (RC mode) which is suitable for when the vehicle is travelling in rock or boulder terrain, a sand mode which is suitable for when the vehicle is travelling in sand terrain (or deep soft snow), a wade mode suitable for use when the vehicle is to undertake a wading operation in which it travels through water and a special programs OFF mode (SP OFF mode or SPO mode, also referred to as a Highway or 'on-highway' mode) which is a suitable compromise mode, or general mode, for all terrain conditions and especially vehicle travel on motorways and regular roadways. Many other control modes are also envisaged including those disclosed in US2003/0200016, the content of which is hereby incorporated by reference.

The different terrain types are grouped according to the friction of the terrain and the roughness of the terrain. For example, it is appropriate to group grass, gravel and snow together as terrains that provide a low friction, smooth surface and it is appropriate to group rock and boulder terrains together as high friction, very high roughness terrains. FIG. 4 is a table taken from US2003/0200016 showing the particular sub-system configuration modes that may be assumed by the subsystems 12 of a vehicle according to some embodiments of the invention in the respective different driving modes or operating modes in which the VCU 10 may operate in some embodiments.

The driving modes are:

(a) A motorway (or highway) mode;

(b) A country road mode;

(c) A city driving (urban) mode;

(d) A towing (on-road) mode;

(e) A dirt track mode;

(f) A snow/ice (on-road) mode;

(g) A GGS mode;

(h) A sand mode;

(i) A rock crawl or boulder crossing mode (RC); and

(j) A mud/ruts (MR) mode

In the present embodiment, the vehicle 100 is limited to operating in the GGS mode, MR mode, RC mode, sand mode, wade mode and SPO (Highway) mode. However it will be appreciated that the invention is not limited to such an arrangement and any combination of on and off road control modes may be used within the scope of the present invention. In some embodiments, instead of a GGS mode the vehicle may have a 'Grass/Snow' (GS) mode in which vehicle handling is optimised for travel over grass or snow, and a separate 'Gravel' (G) mode in which vehicle handling is optimised for travel over gravel.

With reference to FIG. 4, the configuration of the suspension system 12e is specified in terms of ride height (high, standard or low) and side/side air interconnection. The suspension system 12e is a fluid suspension system, in the present embodiment an air suspension system, allowing fluid interconnection between suspensions for wheels on opposite sides of the vehicle in the manner described in US2003/0200016. The plurality of subsystem configuration modes provide different levels of said interconnection, in the present case no interconnection (interconnection closed) and at least partial interconnection (interconnection open). The configuration of the ePAS steering unit 12c may be adjusted to provide different levels of steering assistance, wherein steering wheel 171 is easier to turn the greater the amount of steering assistance. The amount of assistance may be proportional to vehicle speed in some driving modes. As shown in FIG. 4, the amount of assistance is 'speed proportional' in each mode shown except the Rock Crawl (RC) mode.

The brakes system 12d may be arranged to provide relatively high brake force for a given amount of pressure or 'effort' applied to the brake pedal 163 or a relatively low brake force, depending on the driving mode.

The brakes system 12d may also be arranged to allow different levels of wheel slip when an anti-lock braking system is active, (relatively low amounts on low friction ("low-mu" surfaces) and relatively large amounts on high friction surfaces).

An electronic traction control (ETC) system may be operated in a high mu or low mu configuration, the system tolerating greater wheel slip in the low mu configuration before intervening in vehicle control compared with the high mu configuration.

A dynamic stability control system (DSC) may also be operated in a high mu or low mu configuration.

The engine management system 12a may be operated in 'quick' or 'slow' accelerator (or throttle) pedal progression configuration modes in which an increase in engine torque as a function of accelerator pedal progression is relatively quick or slow, respectively. The rate may be dependent on speed in one or more modes such as Sand mode.

The transfer case 131 P may be operated in a high range (HI) subsystem configuration mode or low range (LO) subsystem configuration mode as described herein.

In some embodiments, a centre differential and a rear differential may be provided. The centre differential may be located in a torque path between the rear differential 135 and transfer case 131 P. The centre differential and rear differential 135 may each include a clutch pack that is controllable to vary the degree of locking of the respective differential between a "fully open" and a "fully locked" state. The actual degree of locking at any one time may be controlled on the basis of a number of factors in a known manner, but the control can be adjusted so that the differentials are "more open" or "more locked". Specifically the pre-load on the clutch pack can be varied which in turn controls the locking torque, i.e. the torque across the differential that will cause the clutch, and hence the differential, to slip. The centre differential clutch pack may be configured to control the amount of torque coupling between the front and rear differentials 137, 135 in order to control front axle/rear axle torque split. In some embodiments the front differential 137 may also include a clutch pack arranged to control torque distribution between respective left and right front wheels 1 1 1 , 1 12.

The VCU 10 receives a plurality of signals 16, 17 from a plurality of vehicle sensors and are representative of a variety of different parameters associated with vehicle motion and status. As described in further detail below, the signals 16, 17 provide, or are used to calculate, a plurality of driving condition indicators which are indicative of the nature of the conditions in which the vehicle is travelling. The manner in which this is accomplished is explained in more detail in UK patent GB2492655 to the present applicant, the content of which is incorporated herein by reference as noted above. The sensors (not shown) on the vehicle include, but are not limited to, sensors which provide continuous sensor outputs 16 to the VCU 10, including wheel speed sensors, an ambient temperature sensor, an atmospheric pressure sensor, tyre pressure sensors, parking distance control (PDC) sensors, yaw sensors to detect yaw, roll and pitch of the vehicle, 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 (part of a stability control system (SCS)), a brake pedal position sensor, an accelerator pedal position sensor and longitudinal, lateral and vertical motion sensors. In some other embodiments, only a selection of the aforementioned sensors may be used. It is to be understood that the yaw sensors may comprise one or more accelerometers for detecting and measuring the amount of yaw, roll and pitch. In some embodiments pitch attitude may be measured by means of an inclinometer.

The VCU 10 also receives a signal from the electronic power assisted steering unit (ePAS unit 12c) of the vehicle 100 to indicate the steering force that is applied to the wheels (steering force applied by the driver combined with steering force applied by the ePAS unit 12c).

The vehicle 100 is also provided with a plurality of sensors which provide discrete sensor output signals 17 to the VCU 10, including a cruise control status signal (ON/OFF), a transfer box or transfer case 131 P status signal (whether the gear ratio is set to the high (HI) range or low (LO) range), a Hill Descent Control (HDC) status signal (ON/OFF), a trailer connect status signal (ON/OFF), a signal to indicate that the Stability Control System (SCS) has been activated (ON/OFF), a windscreen wiper signal (ON/OFF), an air suspension ride-height status signal (HI/STD/LO, indicating whether the ride-height is set to a high, standard or low setting, respectively), and a Dynamic Stability Control (DSC) signal (ON/OFF).

The VCU 10 is configured to generate an SCS activity signal derived from several outputs from an SCS ECU (not shown), which contains the DSC (Dynamic Stability Control) function, the TC (Traction Control) function, ABS and HDC algorithms. The SCS activity signal indicates DSC activity, TC activity, ABS activity, brake interventions on individual wheels, and engine torque reduction requests from the SCS ECU to the engine 121 .

The vehicle subsystems 12 may be controlled automatically in a given subsystem control mode (in an "automatic mode" or "automatic condition" of operation of the VCU 10) in response to a control output signal 30 from a selector module 20 and without the need for driver input. In the present embodiment, if the VCU 10 is in the automatic mode of operation the vehicle subsystems are caused automatically to assume the subsystem control mode corresponding to the control output signal 30 from the selector module 20. Alternatively, the vehicle subsystems 12 may be operated in a given subsystem control mode according to a manual user input (in a "manual mode" or "manual condition" of operation of the VCU 10) via the HMI module 32. Thus in the manual mode of operation the user determines in which subsystem control mode the subsystems will be operated by selection of a required system control mode (operating mode). The HMI module 32 comprises a display screen (not shown) and a user operable switchpack 170. The user may select between the manual and automatic modes (or conditions) of operation of the VCU 10 via the switchpack 170. When the VCU 10 is operating in the manual mode or condition, the switchpack 170 also allows the user to select the desired subsystem control mode. The selector module 20 receives a signal 170S from the switchpack 170 as shown in FIG. 3, by means of which the selector module 20 determines whether to operate in the manual mode or automatic mode. It is to be understood that the subsystem controller 14 may itself control the vehicle subsystems 12a-12e directly via the signal line 13, or alternatively each subsystem may be provided with its own associated intermediate controller (not shown in Figure 1 ) for providing control of the relevant subsystem 12a-12e. In the latter case the subsystem controller 14 may only control the selection of the most appropriate subsystem control mode for the subsystems 12a-12e, rather than implementing the actual control steps for the subsystems. The or each intermediate controller may in practice form an integral part of the main subsystem controller 14. In addition, for each subsystem control mode, each of the discrete sensor signals (also considered to be driving condition indicator signals), e.g. trailer connection status ON/OFF, cruise control status ON/OFF, is also used to calculate an associated probability for each of the control modes, GGS, RC, Sand, MR or SP OFF. So, for example, if cruise control is switched on by the driver of the vehicle, the probability that the SP OFF mode is appropriate is relatively high, whereas the probability that the MR control mode is appropriate will be lower. It is to be understood that, for certain subsystems 12, the subsystem 12 may be placed in the same subsystem configuration mode when the vehicle is operated in more than one driving mode (control mode). For example, in the case of a suspension subsystem, the subsystem configuration modes may include different vehicle ride height values. The suspension subsystem may be placed in the same configuration mode, i.e. the ride height may be set to the same ride height value, in more than one driving mode. Thus a given subsystem may remain in the same subsystem configuration mode (e.g. assume the same ride height value) in more than one driving mode.

For example, as described herein, in the present embodiment the air suspension system of the vehicle has three subsystem configuration modes: low ride-height, medium ride-height and high ride-height subsystem configuration modes. The suspension system may be set to the medium ride-height subsystem configuration mode when the vehicle is operating in more than one control mode (driving mode), such as an on-highway control mode and a grass/gravel/snow control mode. Thus, if the vehicle operates in the on-highway control mode, the suspension system is set to the medium ride-height subsystem control mode, and may be referred to as operating in the on-highway control mode. Similarly, if the vehicle operates in the grass/gravel/snow mode, the suspension system is set to (or remains in) the medium ride-height subsystem control mode, and may be referred to as operating in the grass/gravel/snow control mode.

In the present embodiment of FIG. 1 the vehicle 100 is configured to be caused to operate, by the VCU 10, in the wade mode if the wade mode is selected by means of the switchpack 170. In the present embodiment, the wade mode may only be selected when the vehicle is operating in the manual driving mode selection mode, and is not selectable automatically by the VCU 10 when operating in the automatic driving mode selection mode. However, in some alternative embodiments, the wade mode may be selected automatically by the VCU 10 when the vehicle 100 is operating in the automatic driving mode selection mode and the necessary conditions are met.

The VCU 10 is configured, when causing the vehicle to operate in the wade mode, to monitor the pitch attitude of the vehicle 100 and signals from the PDC sensors. In the present embodiment the pitch attitude is determined by reference to one or more signals output by one or more accelerometers that detect and measure yaw, roll and pitch. If the vehicle 100 pitch attitude rises to a value that exceeds substantially a first predetermined value above a substantially horizontal plane or if it exceeds substantially a second predetermined value below a substantially horizontal plane, the VCU 10 is configured to temporarily soften the response of the powertrain controller 1 1 to actuation of the accelerator pedal 161 . The first predetermined value may be referred to as an upward wading pitch angle. The second predetermined value may be referred to as a downward wading pitch angle.

It is to be understood that by soften a response of the powertrain controller 1 1 to user actuation of the accelerator control is meant that, in order to cause a powertrain to generate achieve a given amount of powertrain torque, the accelerator control must be actuated by a larger amount.

In the present embodiment, the first and second predetermined values are each set to substantially 20 degrees. In some embodiments other values may be useful such as 10 degrees, 20 degrees, 30 degrees, 40 degrees or any other suitable value. In some embodiments the first and second values are substantially the same whilst in some other embodiments the first and second values are different.

In the present embodiment, the VCU 10 is configured to monitor the signals from the PDC sensors substantially continually whilst in the wade mode. The VCU 10 monitors the signals for information indicative that the vehicle is entering, has entered or is exiting a body of water. In the present embodiment, the VCU 10 is configured to monitor the PDC signals to determine the location of a surface of ground or body of water. If the PDC signals detect that the vehicle has a sufficiently high likelihood of being submerged in a body of water by at least a predetermined amount, and the pitch attitude of the vehicle 100 does not exceed the first predetermined value above a substantially horizontal plane and does not exceed the second predetermined value below a substantially horizontal plane, the VCU 10 is configured to sharpen the response of the powertrain controller 1 1 to actuation of the accelerator pedal 161 . By sharpen a response of the powertrain controller 1 1 to user actuation of the accelerator control is meant that, in order to cause a powertrain to generate achieve a given amount of powertrain torque, the accelerator control must be actuated by a smaller amount.

FIG. 5 illustrates schematically the relationship between the amount of powertrain torque demanded of a powertrain controller 1 1 as a function of the amount of travel 'x' of the accelerator pedal 161 . Trace T1 is a baseline trace, representing the default relationship between powertrain torque demand and accelerator pedal position set by the VCU 10 when the wade mode is selected. Trace T2 represents the softened accelerator pedal response. It can be seen that the amount of torque T demanded by the powertrain controller 1 1 for a given amount of accelerator pedal travel is lower for trace T2 than in the case of the baseline trace T1 . Trace T3 represents the sharpened accelerator pedal response. It can be seen that the amount of torque T demanded by the powertrain controller 1 1 for a given amount of accelerator pedal travel is higher for trace T3 than in the case of the baseline trace T1 .

As noted above, in the present embodiment, the VCU 10 is configured to attempt to determine the likelihood that a vehicle is submerged in a body of water by at least a predetermined amount. In the present embodiment the predetermined amount is 0.3m but other values may be useful. If, when in the wade mode, the pitch attitude of the vehicle 100 does not exceed the first predetermined value above a substantially horizontal plane and does not exceed the second predetermined value below a substantially horizontal plane, the VCU 10 checks the PDC sensor signals to determine the position of a plane corresponding to ground or a body of water relative to the vehicle. If the signals from the PDC sensors are consistent with the vehicle being submerged in a body of water by at least 0.3m, the VCU 10 is configured to cause the powertrain controller 1 1 to employ trace T3 of FIG. 5 when determining the amount of powertrain torque to generate as a function of accelerator pedal travel x. FIG. 6 is a schematic illustration of the vehicle 100 of FIG. 1 during a wading operation. It can be seen that the vehicle 100 is wading in a river R having a water depth d, the wheels of the vehicle 100 being in contact with a river bed RB. A surface S of the river is at a level just below that of front and rear PDC sensors 100PDF, 100PDR respectively. In the embodiment of FIG. 1 the PDC sensors 100PDF, 100PDR have a radar transmit/receive module arranged to transmit a radar signal and receive portions of the transmitted signal that are reflected back to the module. A controller associated with the PDC sensors 100PDF, 100PDR is arranged to determine the depth of a driving surface below the level of the PDC sensors 100PDF, 100PDR based on a time delay between transmission of a radar signal and reception of a reflected portion of the radar signal at a given moment in time.

FIG. 7 is a schematic illustration of a vehicle 100 according to the embodiment of FIG. 1 before, during and after a wading operation in which the vehicle 100 passes through the river R.

At (a) of FIG. 7, the vehicle is driving towards the river R on substantially level ground. The driver selects the wade mode, and the VCU 10 begins to monitor vehicle pitch attitude and the depth of any liquid the vehicle 100 may be driving through. At position (a) the VCU 10 determines, based on signals from the controller of the PDC sensors 100PDF, 100PDR that the depth of any liquid the vehicle may be passing through is less than 0.3m and therefore the VCU 10 causes the powertrain controller 1 1 to continue to employ the baseline trace T1 of FIG. 5.

As the vehicle 100 continues and begins to descend a bank B of the river, the VCU 10 recognises that vehicle pitch attitude now exceeds the second predetermined value below a horizontal attitude. As a consequence, the VCU 10 causes the powertrain controller 1 1 to employ trace T2 as the vehicle 100 descends the bank B.

As the vehicle 100 enters the river R the VCU 10 determines, based on signals received from the controller of the PDC sensors 100PDF, 100PDR that the vehicle 100 is wading in a depth of water exceeding 0.3m. As the pitch attitude of the vehicle 100 levels towards a substantially horizontal pitch attitude, and attains an angle that is less than the second predetermined angle below a horizontal pitch attitude, and less than the first predetermined angle above a horizontal pitch attitude, the VCU 100 causes the powertrain controller 1 1 to employ trace T3 as the vehicle 100 drives over the river bed RB towards the opposite bank B (see position (c) of FIG. 7). The employment of an accelerator pedal response trace (in the present embodiment trace T3), representing a sharpened response relative to the baseline trace, is advantageous because a driver may wish to increase the amount of drive torque delivered by the powertrain relatively rapidly whilst wading. This is in order to maintain adequate progress through water, where a substantial increase in drag may be experienced due to the volume of water surrounding the vehicle. When the vehicle 100 reaches the opposite bank, and ascends the bank B, the VCU 10 recognises that the pitch attitude of the vehicle 100 now exceeds the first predetermined value above a horizontal pitch attitude and the vehicle is no longer in water exceeding a depth of 0.3m. According, by the time the vehicle reaches position (d), the VCU 10 is causing the powertrain controller 1 1 to employ trace T2. The employment of an accelerator pedal response trace representing a softened response relative to the baseline trace has the advantage that less bank damage is likely to occur due to wheel spin as the vehicle exits the water. It is to be understood that the wheels may experience a relatively low surface coefficient of friction between the wheels and the bank as the vehicle climbs the bank, resulting in an increased risk that the vehicle 100 may fail to make adequate progress as it exits the water. Finally, at position (e), the vehicle has resumed a pitch attitude that is less than the first predetermined value above a horizontal pitch attitude and less than the second predetermined value below a horizontal pitch attitude. The VCU 10 therefore causes the powertrain controller 1 1 to revert to employing trace T1 . In some embodiments, in the wade mode the vehicle 100 is operated in such a manner that the engine 121 remains switched on at all times and the speed of the engine 121 does not fall below a predetermined value. This is so as to reduce the risk that liquid through which the vehicle is wading enters the engine exhaust system due to the head of liquid at an exhaust gas outlet of the exhaust system.

It will be understood that the embodiments described above are given by way of example only and are not intended to limit the invention, the scope of which is defined in the appended claims. Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS:

1 . A vehicle control system for controlling at least one subsystem of a vehicle, the at least one subsystem comprising a powertrain controller, the vehicle control system being configured to initiate control of at least one said at least one vehicle subsystem in one of a plurality of subsystem control modes, each subsystem control mode corresponding to one or more different driving conditions for the vehicle, the control modes including a first subsystem control mode and a wade mode adapted for use when a vehicle is wading,

wherein when the system controls the at least one subsystem in the wade mode, the system configures the powertrain controller wherein a response of the powertrain to user actuation of an accelerator control is dependent at least in part on the signal indicative of pitch attitude of the vehicle.

2. A control system according to claim 1 configured, when the system controls the at least one subsystem in the wade mode, temporarily to configure the powertrain controller to soften a response of the powertrain to user actuation of the accelerator control relative to the first mode whilst the pitch attitude of the vehicle exceeds substantially a first predetermined value above a substantially horizontal plane or whilst the pitch attitude exceeds substantially a second predetermined value below a substantially horizontal plane.

3. A control system according to claim 1 or claim 2 further configured to receive a signal indicative of whether a vehicle is wading, the controller being configured, when the system controls the at least one subsystem in the wade mode, to adjust the response of the powertrain controller to user actuation of the accelerator control in dependence at least in part on the signal indicative of whether the vehicle is wading.

4. A control system according to claim 3 configured, when the system controls the at least one subsystem in the wade mode, to sharpen the response of the powertrain controller to user actuation of the accelerator control if the signal indicative of whether the vehicle is wading indicates that the vehicle is wading and the pitch attitude of the vehicle is less than a predetermined upward wading pitch angle above a horizontal plane and less than a predetermined downward wading pitch angle below the horizontal plane.

5. A control system according to claim 3 or claim 4 wherein the signal indicative of whether the vehicle is wading comprises a signal responsive to one or more sensors configured to sense the distance of obstacles from the vehicle.

6. A control system according to any preceding claim configured to allow a user to select the control mode in which the subsystem controller is to initiate control of the vehicle from a plurality of subsystem control modes.

7. A control system according to claim 6 configured to allow a user to select the control mode via input means, wherein the input means comprises at least one selected from amongst a rotary switch selector device, a lever-type switch selector device, one or more button devices and one or more touchscreen devices.

8. A control system according to any preceding claim configured to select automatically an appropriate control mode from a plurality of subsystem control modes, the automatic selection being made in dependence on one or more signals received from one or more sensors.

9. A control system according to any preceding claim wherein the control modes comprise at least one control mode adapted for driving on a driving surface of relatively low surface coefficient of friction.

10. A control system according to any preceding claim wherein the control modes comprise at least one control mode adapted for driving on at least one of snow, ice, grass, gravel, mud, and sand.

1 1 . A control system according to any preceding claim comprising a plurality of subsystems, wherein at least one subsystem includes a brakes subsystem or a suspension subsystem.

12. A control system according to any preceding claim comprising an electronic processor having an electrical input for receiving a signal indicative of vehicle pitch attitude, 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 initiate control of the or each said at least one vehicle subsystem, including the powertrain controller, in one of a plurality of subsystem control modes, each subsystem control mode corresponding to one or more different driving conditions for the vehicle, the control modes comprising a first mode and a wade mode adapted for use when a vehicle is wading,

wherein when the subsystem controller controls the at least one subsystem in the wade mode, the subsystem controller configures the powertrain controller wherein a response of the powertrain controller to user actuation of the accelerator control is dependent at least in part on the signal indicative of pitch attitude of the vehicle.

13. A vehicle comprising a control system according to any preceding claim.

14. A method of controlling at least one subsystem of a vehicle, the at least one subsystem comprising a powertrain controller,

15. A non-transitory computer readable carrier medium carrying a computer readable code for controlling a vehicle to carry out the method according to claim 14.

16. A computer program product executable on a processor so as to implement the method of claim 14.

17. A computer readable medium loaded with the computer program product of claim 16.

18. A processor arranged to implement the method of claim 14, or the computer program product of claim 16.