Vehicle control system and method

Abstract

Embodiments of the present invention provide a control system for a motor vehicle, the system being operable in an automatic mode selection condition in which the system is configured to select automatically an appropriate system operating mode from a plurality of operating modes whereby the system assumes operation in said system operating mode, the system being further operable to activate an automatic progress control function in which a speed of the vehicle over terrain is controlled automatically by the system, wherein when the system is in the automatic mode selection condition the system is configured to allow the automatic progress control function to be activated only when the system is operating in one of a subset of one or more system operating modes.

Claims

1. A control system for a motor vehicle, the system being operable in an automatic mode selection condition in which the system is configured to select automatically an appropriate system operating mode from a plurality of operating modes and to assume operation in said system operating mode, wherein when the system is operable in the automatic mode selection condition, the system bases a new selection of the appropriate system operating mode from the plurality of operating modes on one or more terrain indicator signals obtained from one or more vehicle sensors, the system being further configured to allow activation of an automatic progress control function in which a speed of the vehicle over terrain is controlled automatically by the system, wherein when the system is in the automatic mode selection condition the system is configured to allow the automatic progress control function to be activated only when the system is operating in one of a subset of one or more system operating modes, wherein the system is configured so that when in the automatic mode selection condition with the automatic progress control system being active, the plurality of operating modes in which the motor vehicle is permitted to operate is limited to the subset of one or more system operating modes, wherein when the system is operating with the automatic progress control system active and the automatic mode selection condition is assumed, the system is arranged to select a system operating mode from the subset of one or more system operating modes and to assume operation in that mode.

2. A system according to claim 1 wherein the system being configured to allow the automatic progress control function to be activated only when the system is operating in one of a subset of one or more system operating modes comprises the system preventing the automatic progress control function from assuming an active state, in which the speed of the vehicle is controlled automatically by the system, unless the system is operating in an operating mode selected from said subset of one or more system operating modes.

3. A system according to claim 1 wherein when the system is operating in the automatic mode selection condition and the automatic progress control function is subsequently requested, the system is configured automatically to select an appropriate operating mode from the subset of one or more system operating modes and to operate in that mode.

4. A system according to claim 3 wherein the subset of one or more system operating modes comprises two or more system operating modes, wherein when the system is operating in the automatic mode selection condition and the automatic progress control function is subsequently requested, the system is configured automatically to select the most appropriate operating mode from the subset of two or more system operating modes and to assume operation in that mode.

5. A system according to claim 1 further operable in a manual operating mode selection condition in which a user may select a required system operating mode by means of user-operable mode selection input means.

6. A system according to claim 1 wherein the automatic progress control function is an on-highway cruise control system configured to control the vehicle to maintain a substantially constant speed by application of positive drive torque, and wherein the cruise control system is configured to suspend or cancel operation of the cruise control system upon detection of one or more of: wheel slip exceeding a prescribed amount; and intervention by a stability control system to reduce vehicle instability; or a traction control system to improve traction.

7. A system according to claim 1 configured to activate the automatic progress control function in an operative state in response to a user command to activate the automatic progress control function when the system is operating in one of the subset of one or more system operating modes.

8. A system according to claim 1 configured to place the automatic progress control function in a standby state in response to a user command to activate the automatic progress control function when the system is not operating in one of the subset of one or more system operating modes.

9. A system according to claim 8 configured to change said automatic progress control function from said standby mode into an operative state in response to the operating mode being changed to one of the subset of one or more system operating modes.

10. A system according to claim 1 wherein, when the operating mode in which the system is operating is not one of the subset of one or more system operating modes, the system is configured to change the operating mode to one of the subset of one or more system operating modes upon activation of the automatic progress control function so as to prevent the automatic progress control function operating in an active state when said operating mode is not one of the subset of one or more system operating modes.

11. A control system according to claim 1 wherein the operating modes are control modes of at least one subsystem of a vehicle, the system comprising a subsystem controller for initiating control of the or each of the vehicle subsystems in the selected one of the plurality of subsystem control modes, each of which corresponds to one or more different driving conditions for the vehicle.

12. A control system according to claim 11, the system comprising evaluation means for evaluating one or more driving condition indicators to determine the extent to which each of the subsystem control modes is appropriate.

13. A control system according to claim 12, wherein when in the automatic condition the system is configured automatically to control the subsystem controller to initiate control of the or each subsystem in the subsystem control mode which is most appropriate.

14. A control system according to claim 11 wherein the operating modes are control modes of at least one vehicle subsystem selected from amongst an engine management system, a transmission system, a steering system, a brakes system and a suspension system.

15. A control system according to claim 14 wherein the operating modes are control modes of at least two vehicle subsystems selected from amongst an engine management system, a transmission system, a steering system, a brakes system and a suspension system.

16. A control system for a motor vehicle, the system being operable in an automatic mode selection condition in which the system is configured to select automatically an appropriate system operating mode from a plurality of operating modes and to assume operation in said system operating mode, the system being further configured to allow activation of an automatic progress control function in which a speed of the vehicle over terrain is controlled automatically by the system, wherein when the system is in the automatic mode selection condition the system is configured to allow the automatic progress control function to be activated only when the system is operating in one of a subset of one or more system operating modes, wherein the operating modes are control modes of at least one subsystem of a vehicle, the system comprising a subsystem controller for initiating control of the or each of the vehicle subsystems in the selected one of the plurality of subsystem control modes, each of which corresponds to one or more different driving conditions for the vehicle, wherein in each system operating mode the system is configured to cause each one of a plurality of vehicle subsystems to be operated in a subsystem configuration mode appropriate to the driving condition, wherein the operating modes include control modes of one or more of: a suspension system and the plurality of subsystem configuration modes comprise a plurality of ride heights; a fluid suspension system in which fluid interconnection can be made between suspensions for wheels on opposite sides of the vehicle, and wherein said plurality of subsystem configuration modes provide different levels of said interconnection; a steering system which can provide steering assistance, and wherein said plurality of subsystem configuration modes provide different levels of said steering assistance; a brakes system which can provide braking assistance, and said plurality of subsystem configuration modes provide different levels of said braking assistance; a brake control system which can provide an anti-lock function to control wheel slip, and said plurality of subsystem configuration modes allow different levels of said wheel slip; a traction control system which is arranged to control wheel spin, and said plurality of subsystem configuration modes allow different levels of said wheel spin; a yaw control system which is arranged to control vehicle yaw, and said plurality of subsystem configuration modes allow different levels of divergence of said vehicle yaw from an expected yaw; a range change transmission and said subsystem configuration modes may include a high range mode and a low range mode of said transmission; a powertrain system which includes a powertrain control means and an accelerator or throttle pedal, the subsystem configuration modes providing different levels of responsiveness of the powertrain control means to movement of the accelerator or throttle pedal; a transmission system operable in a plurality of transmission ratios and including a transmission controller arranged to monitor at least one parameter of the vehicle and to select the transmission ratios in response, and wherein the subsystem configuration modes include a plurality of transmission configuration modes in which the transmission ratios are selected differently in response to said at least one parameter.

17. A vehicle comprising a system according to claim 1.

18. A method of controlling a vehicle system to operate in an automatic mode selection condition implemented by computing means, when the system is operating in the automatic mode selection condition the method comprising selecting automatically an appropriate system operating mode whereby the system assumes operation in the selected mode, wherein when the system is in the automatic mode selection condition, the system is configured to base a new selection of the appropriate system operating mode on one or more terrain indicator signals obtained from one or more vehicle sensors, the method further comprising activating an automatic progress control function and controlling automatically a speed of the vehicle over terrain in response to activation of the automatic progress control function, and whereby when the system is in the automatic mode selection condition the method comprises allowing the automatic progress control function to be activated only when the system is operating in one of a subset of one or more system operating modes, and when in the automatic mode selection condition with the automatic progress control system being active, a plurality of operating modes in which the motor vehicle is permitted to operate is limited to the subset of one or more system operating modes, wherein when the system is operating with the automatic progress control system active and the automatic mode selection condition is assumed, the system is arranged to select a system operating mode from the subset of one or more system operating modes and to assume operation in that mode.

19. A non-transitory computer readable storage medium on which is stored instructions for performing the method of claim 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures in which:

(2) FIG. 1 is a schematic illustration of a vehicle according to an embodiment of the present invention;

(3) FIG. 2 is a block diagram to illustrate a vehicle control system in accordance with an embodiment of the invention, including various vehicle subsystems under the control of the vehicle control system;

(4) FIG. 3 is a table showing which vehicle subsystem configuration mode is selected in each respective vehicle operating mode;

(5) FIG. 4 is a schematic illustration of a switchpack according to an embodiment of the invention with a rotary knob in a deployed condition;

(6) FIG. 5 is a schematic illustration of a switchpack according to an embodiment of the invention with a rotary knob in a retracted condition; and

(7) FIG. 6 is a flow diagram illustrating a method of operation of a vehicle according to an embodiment of the present invention.

DETAILED DESCRIPTION

(8) FIG. 1 shows a vehicle 100 according to an embodiment of the invention intended to be 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 a transmission 124. In the embodiment shown the transmission 124 is an automatic transmission 124. Embodiments of the present invention are also suitable for use in vehicles with a manual transmission, continuously variable transmission or any other suitable transmission.

(9) The driveline 130 is arranged to drive a pair of front vehicle wheels 111, 112 by means of a front differential 135F and a pair of front drive shafts 118. The driveline 130 also comprises an auxiliary driveline portion 131 arranged to drive a pair of rear wheels 114, 115 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) 137, 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 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.

(10) The PTU 137 is operable in a high ratio or a low ratio 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.

(11) The vehicle 100 has an accelerator pedal 161, brake pedal 163 and steering wheel 181. The steering wheel 181 has a cruise control selector button 181C mounted thereto for activating a cruise control system 11.

(12) The vehicle 100 has a central controller, referred to as a vehicle control unit (VCU) 10. The VCU 10 receives and outputs a plurality of signals to and from various sensors and subsystems 12 provided on the vehicle 100.

(13) FIG. 2 shows 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, a transmission system 12b, an electronic power assisted steering unit 12c (ePAS unit), a brakes system 12d and a suspension system 12e. 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.

(14) The VCU 10 receives a plurality of signals, represented generally at 16 and 17, which are received 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 (also referred to as terrain indicators) which are indicative of the nature of the condition in which the vehicle is travelling. One advantageous feature of some embodiments of the present invention is that the VCU 10 determines the most appropriate control mode for the various subsystems on the basis of the terrain indicators, and automatically controls the subsystems accordingly. That is, the VCU 10 determines the most appropriate control mode on the basis of the terrain indicators and automatically causes each of the subsystems 12 to operate in the respective subsystem configuration mode corresponding to that control mode.

(15) 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, 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 acceleration pedal position sensor and longitudinal, lateral, vertical motion sensors.

(16) In other embodiments, only a selection of the aforementioned sensors may be used. The VCU 10 also receives a signal from the electronic power assisted steering unit (ePAS unit 12c) of the vehicle 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).

(17) 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 PTU 137 status signal (whether the gear ratio is set to a HI range or a 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/LO), and a Dynamic Stability Control (DSC) signal (ON/OFF).

(18) The VCU 10 includes an evaluation means in the form of an estimator module or processor 18 and a calculation and selection means in the form of a selector module or processor 20. Initially the continuous outputs 16 from the sensors are provided to the estimator module 18 whereas the discrete signals 17 are provided to the selector module 20.

(19) Within a first stage of the estimator module 18, various ones of the sensor outputs 16 are used to derive a number of terrain indicators. In a first stage of the estimator module 18, a vehicle speed is derived from the wheel speed sensors, wheel acceleration is derived from the wheel speed sensors, the longitudinal force on the wheels is derived from the vehicle longitudinal acceleration sensor, and the torque at which wheel slip occurs (if wheel slip occurs) is derived from the motion sensors arranged to defect yaw, pitch and roll. Other calculations performed within the first stage of the estimator module 18 include the wheel inertia torque (the torque associated with accelerating or decelerating the rotating wheels), continuity of progress (the assessment of whether the vehicle is starting and stopping, for example as may be the case when the vehicle is travelling over rocky terrain), aerodynamic drag, yaw rate, and lateral vehicle acceleration.

(20) The estimator module 18 also includes a second stage in which the following terrain indicators are calculated: surface rolling resistance (based on the wheel inertia torque, the longitudinal force on the vehicle, aerodynamic drag, and the longitudinal force on the wheels), the steering force on the steering wheel 181 (based on the lateral acceleration and the output from the steering wheel sensor), the wheel longitudinal slip (based on the longitudinal force on the wheels, the wheel acceleration, SCS activity and a signal indicative of whether wheel slip has occurred), lateral friction (calculated from the measured lateral acceleration and the yaw versus the predicted lateral acceleration and yaw), and corrugation detection (high frequency, low amplitude wheel height excitement indicative of a washboard type surface).

(21) The SCS activity signal is 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, indicating DSC activity, TC activity, ABS activity, brake interventions on individual wheels, and engine torque reduction requests from the SCS ECU to the engine. Ail these indicate a slip event has occurred and the SCS ECU has taken action to control it. The estimator module 18 also uses the outputs from the wheel speed sensors to determine a wheel speed variation and corrugation detection signal.

(22) On the basis of the windscreen wiper signal (ON/OFF), the estimator module 18 also calculates how long the windscreen wipers have been in an ON state (i.e. a rain duration signal).

(23) The VCU 10 also includes a road roughness module 24 for calculating the terrain roughness based on the air suspension sensors (the ride height sensors) and the wheel accelerometers. A terrain indicator signal in the form of a roughness output signal 26 is output from the road roughness module 24.

(24) The estimates for the wheel longitudinal slip and the lateral friction estimation are compared with one another within the estimator module 18 as a plausibility check.

(25) Calculations for wheel speed variation and corrugation output, the surface rolling resistance estimation, the wheel longitudinal slip and the corrugation detection, together with the friction plausibility check, are output from the estimator module 18 and provide terrain indicator output signals 22, indicative of the nature of the terrain in which the vehicle is travelling, for further processing within the VCU 10.

(26) The terrain indicator signals 22 from the estimator module 18 are provided to the selector module 20 for determining which of a plurality of vehicle subsystem control modes is most appropriate based on the indicators of the type of terrain in which the vehicle is travelling. The most appropriate control mode is determined by analysing the probability that each of the different control modes is appropriate on the basis of the terrain indicator signals 22, 26 from the estimator module 18 and the road roughness module 24.

(27) 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 the selector module 20 and without the need for driver input. 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 a Human Machine Interface (HMI) module 32. Thus the user determines in which subsystem control mode the subsystems will be operated. The HMI module 32 comprises a display screen (not shown) and a user operable switchpack 170 (FIG. 4). 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.

(28) 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 FIG. 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.

(29) When operating in the automatic mode, the selection of the most appropriate subsystem control mode may be achieved by means of a three phase process:

(30) (1) for each type of control mode, a calculation is performed of the probability that the control mode is suitable for the terrain over which the vehicle is travelling, based on the terrain indicators;

(31) (2) the integration of positive differences between the probability for the current control mode and the other control modes; and

(32) (3) the program request to the control module 14 when the integration value exceeds a predetermined threshold or the current terrain control mode probability is zero.

(33) The specific steps for phases (1), (2) and (3) will now be described in more detail.

(34) In phase (1), the continuous terrain indicator signals in the form of the road surface roughness output 26 and the outputs 22 from the estimator module 18 are provided to the selector module 20. The selector module 20 also receives the discrete terrain indicators 17 directly from various sensors on the vehicle, including the transfer box status signal (whether the gear ratio is set to a HI range or a LO range), the DSC status signal, cruise control status (whether the vehicle's cruise control system 11 is ON or OFF), and trailer connect status (whether or not a trailer is connected to the vehicle). Terrain indicator signals indicative of ambient temperature and atmospheric pressure are also provided to the selector module 20.

(35) The selector module 20 is provided with a probability algorithm 20a for calculating the most suitable control mode for the vehicle subsystems based on the discrete terrain indicator signals 17 received directly from the sensors and the continuous terrain indicators 22, 26 calculated by the estimator module 18 and the road surface roughness module 24, respectively. That is, the probability algorithm 20a calculates the most suitable system control mode, which determines the respective subsystem configuration mode in which each subsystem is to be operated, based on the discrete terrain indicator signals 17.

(36) The control modes typically 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 (RB 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) and a special programs OFF mode (SP OFF mode or SPO 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.

(37) 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.

(38) FIG. 3 is a table taken from US2003/0200016 showing the particular sub-system configuration modes assumed by the subsystems 12 of the vehicle 100 in the respective different operating modes in which the VCU 10 may operate.

(39) The operating 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; and (j) A mud/ruts mode

(40) With reference to FIG. 3, 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) end at least partial interconnection (interconnection open).

(41) The configuration of the ePAS steering unit 12c may be adjusted to provide different levels of steering assistance, wherein steering wheel 181 is easier to turn the greater the amount of steering assistance. The amount of assistance may be proportion to vehicle speed in some operating modes.

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

(43) The brakes system 12d may also be arranged to allow different levels of wheel 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).

(44) 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 a high mu configuration.

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

(46) 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.

(47) The PTU 137 may be operated in a high range (HI) subsystem configuration mode or low range (LO) subsystem configuration mode as described herein.

(48) The transmission 124 may be operated in a normal mode that provides a reasonable compromise between fuel economy and driving performance, a performance mode which generally keeps the transmission in lower gears than in the normal mode, particularly when the driver is requesting a high level of driving torque to accelerate the vehicle, and a manual mode in which the control of gear changes is given completely to the driver. There is also a snow or ice mode which generally keeps the transmission in higher gears than the normal mode, in particular under acceleration from rest, to avoid loss of traction due to wheel spin, and a sand mode which keeps the transmission in relatively high gears at low speed to avoid excessive wheel spin. Excessive wheel spin can result in the wheels digging themselves into the sand at low speeds. However, the sand mode uses relatively low gears at higher speeds where a relatively high degree of wheel slip can be desirable to provide maximum traction. Lower gearing also helps the engine 121 to remain in an operating region where the engine speed is high and the power output is high, thereby helping to avoid the vehicle 100 becoming bogged down by a lack of power.

(49) In some embodiments, a centre differential and a rear differential each include a clutch pack and are controllable to vary the degree of locking 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. A front differential could also be controlled in the same or similar way.

(50) For each subsystem control mode, the algorithm 20a within the selector module 20 performs a probability calculation, based on the terrain indicators, to determine a probability that each of the different control modes is appropriate. The selector module 20 includes a tuneable data map which relates the continuous terrain indicators 22, 26 (e.g. vehicle speed, road roughness, steering angle) to a probability that a particular control mode is appropriate. Each probability value typically takes a value of between 0 and 1. So, for example, the vehicle speed calculation may return a probability of 0.7 for the RB mode if the vehicle speed is relatively slow, whereas if the vehicle speed is relatively high the probability for the RB mode will be much lower (e.g. 0.2). This is because if is much less likely that a high vehicle speed is indicative that the vehicle is travelling over a rock or boulder terrain.

(51) In addition, for each subsystem control mode, each of the discrete terrain indicators 17 (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, RB, 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.

(52) For each of the different sub system control modes, a combined probability value, Pb, is calculated based on the individual probabilities for that control mode, as described above, as derived from each of the continuous or discrete terrain indicators 17, 22, 26. In the following equation, for each control mode the individual probability as determined for each terrain indicator is represented by a, b, c, d . . . n. The combined probability value, Pb, for each control mode is then calculated as follows:
Pb=(a.Math.b.Math.c.Math.d . . . n)/((a.Math.b.Math.c.Math.d . . . n)+(1a).Math.(1b).Math.(1c).Math.(1d) . . . (1n))

(53) Any number of individual probabilities may be input to the probability algorithm 20a and any one probability value input to the probability algorithm may itself be the output of a combinational probability function.

(54) Once the combined probability value for each control mode has been calculated, the subsystem control program corresponding to the control mode with the highest probability is selected within the selector module 20 and an output signal 30 providing an indication of this is provided to the subsystem control module 14. The benefit of using a combined probability function based on multiple terrain indicators is that certain indicators may make a control mode (e.g. GGS or MR) more or less likely when combined together, compared with basing the selection on just a single terrain indicator alone.

(55) A further control signal 31 from the selector module 20 is provided to a control module 34.

(56) In phase (2), an integration process is implemented continually within the selector module 20 to determine whether it is necessary to change from the current control mode to one of the alternative control modes.

(57) The first step of the integration process is to determine whether there is a positive difference between the combined probability value for each of the alternative control modes compared with the combined probability value for the current control mode.

(58) By way of example, assume the current control mode is GGS with a combined probability value of 0.5. If a combined probability value for the sand control mode is 0.7, a positive difference is calculated between the two probabilities (i.e. a positive difference value of 0.2). The positive difference value is integrated with respect to time. If the difference remains positive and the integrated value reaches a predetermined change threshold (referred to as the change threshold), or one of a plurality of predetermined change thresholds, the selector module 20 determines that the current terrain control mode (for GGS) is to be updated to a new, alternative control mode (in this example, the sand control mode). A control output signal 30 is then output from the selector module 20 to the subsystem control module 14 to initiate the sand control mode for the vehicle subsystems.

(59) In phase (3), the probability difference is monitored and if, at any point during the integration process, the probability difference changes from a positive value to a negative value, the integration process is cancelled and reset to zero. Similarly, if the integrated value for one of the other alternative control modes (i.e. other than sand), reaches the predetermined change threshold before the probability result for the sand control mode, the integration process for the sand control mode is cancelled and reset to zero and the other alternative control mode, with a higher probability difference, is selected.

HDC Interaction

(60) As described above, the vehicle 100 has an HMI module 32 comprising a user operable switch pack 170 shown schematically in FIG. 4. The switchpack 170 allows a user to toggle the VCU 10 between the automatic and manual conditions of operation.

(61) The switchpack 170 has a frame 170F supporting switchgear associated with the switchpack 170. The switchpack 170 has a rotary knob 172 connected to a multistage rotary switch (not shown). The knob 172 may be moved between an exposed or deployed position as shown in FIG. 4 and a retracted position as shown in FIG. 5. In the exposed position the knob 172 stands proud of a panel 172P which surrounds the knob 172. Icons 172a-e are marked in the panel at circumferentially spaced apart locations around the knob 172 over an arc of around 140 in the embodiment shown although other angles and other numbers of modes are also useful. The icons 172a-e may be illuminated selectively in order to indicate the identity of the control mode in which the subsystems 12 are being operated.

(62) Other switches 171a, b are also provided in a remaining portion of the panel 172P allowing a driver to activate a hill descent control (HDC) function, via switch 171a, and select a required gear ratio of the PTU 137 (high or low), via switch 171b.

(63) Further switches 171c of the switchpack enable the SCS system of the vehicle to be activated or deactivated, a ride height to be adjusted (buttons 171c), an eco mode (arranged to enhance fuel economy) to be selected and an automatic speed limiter (ASL) function to be selected.

(64) The rotary knob 172 has a substantially cylindrical column portion 174 with its cylinder axis oriented substantially vertically. The knob 172 has an upper panel 175 bearing the word AUTO. When the knob 172 is in the retracted position an indicator lamp 175L of the panel 175 illuminates, indicating that the VCU 10 has assumed the automatic condition in which the VCU 10 selects automatically an appropriate subsystem control mode.

(65) When the knob 172 is in the exposed position the indicator lamp 175L is extinguished, indicating that the VCU 10 has assumed the manual condition. The knob 172 is moved between the exposed and retracted positions by means of a spring mechanism triggered by pressing on the panel 175. Other arrangements are also useful such as an electrical actuator. In some embodiments a switch is integrated into the knob 172 such that pressing on the panel 175 alone actuates the switch to switch between the automatic and manual conditions. In some embodiments the switch is positioned such that sufficient axial pressure applied to substantially any exposed portion of the knob 172 including rim 172R results in actuation of the switch. The knob 172 may be configured to exercise a relatively small axial translation when the switch is actuated, providing tactile feedback to the user, followed by a relatively large axial translation as the knob 172 moves between the exposed and retracted positions or vice versa.

(66) The knob 172 is configured such that the rim 172R may be grasped by the user and rotated about a cylinder axis of the column portion 174. The switchpack 170 is arranged such that the VCU 10 may determine in which direction the user turns the rim 172R based on a signal output by the switchpack 170. In an example rim 172R is provided with a knurled peripheral surface arranged to facilitate the user grasping the knob 172 with their fingers.

(67) Rotation of the rim 172R is indexed in discrete angular increments of around 10-20 by means of a detent mechanism. This allows tactile feedback to be provided to a user confirming when the knob 172 has been rotated through one of the discrete angular increments. Other angles and other arrangements are also useful. The rim 172R may be rotated by any number of turns in either direction without constraint by the switchpack 170.

(68) In some embodiments, when the VCU 10 is in the manual condition, rotation of the rim 172R by two increments in a clockwise (or anticlockwise) direction causes the VCU 10 to assume the mode corresponding to the icon 172a-e that is located adjacent the icon corresponding to the currently selected mode in a clockwise (or anticlockwise) direction. If no such icon exists then the VCU 10 takes no action and the currently selected mode remains selected. If the user rotates the knob 172R by only a single increment in a given direction, with no further increment in that direction within a prescribed time period (such as 1 s or any other suitable period), no change in control mode takes place. This feature reduces a risk that a user unintentionally changes the selected mode. It is to be understood that any prescribed number of turns by the incremental amount may be required in order to enable a mode change to take place. Furthermore, any prescribed time period may be set within which the prescribed number of turns by the incremental amount (or in addition, or instead any two consecutive incremental amounts) are to take place. In some embodiments, a user is required to rotate the rim 172R by only a single incremental amount in order to signal a requirement to change mode.

(69) In some embodiments, in addition to or instead of rotating the rim 172R of the knob 172 in order to change control mode when the VCU 10 is in the manual condition, the knob 172 may be configured such that mode changes may be effected by rotation of column 174. In some embodiments the rim 172R may be rotatable whilst the column 174 remains stationary, whilst in some alternative embodiments the rim 172R and column 174 may be arranged to rotate together. They may for example be fixedly coupled or integrally formed in some embodiments.

(70) In some embodiments, the VCU 10 may be configured to allow manual selection of a given control mode following user selection of that mode only once it has determined that the user has finished rotating the rim 172R. The VCU 10 may wait a prescribed period of time after the last incremental rotation has been detected, for example up to around 2 s, before allowing a mode change to take place. In some embodiments the VCU 10 may be arranged to effect a mode change a predetermined time after it has been determined that the user has released their grip from the knob 172.

(71) In some embodiments the VCU 10 may be arranged to verify that one or more prescribed vehicle settings or parameters are appropriate to the mode the user wishes to select before allowing a mode change. For example, the VCU 10 may check one or more selected from amongst selected PTU gear ratio, selected ride height and/or one more other settings. If the settings are not appropriate to the mode the user wishes to select, the VCU 10 may be configured to remain in the current control mode until the settings are determined to be appropriate. In the meantime the VCU 10 may cause the icon of the currently selected mode to remain illuminated. The icon corresponding to that of the mode the user wishes the VCU 10 to assume may be arranged to illuminate intermittently in some embodiments, e.g. by flashing. The user may be informed of the one or more deficiencies in settings identified by the VCU 10. If they are not remedied within a prescribed period of time, or in some embodiments if an attempt to remedy them is not commenced within a prescribed period, the VCU 10 may be configured to operate as if the user had not sought to change mode. That is, information in respect of deficiencies is not displayed any longer, and flashing of the icon corresponding to the proposed mode is terminated.

(72) It is to be understood that when a user activates the automatic condition of the VCU 10 the VCU 10 controls the vehicle subsystems to operate in the most appropriate control mode as determined by the VCU 10. The rotary knob 172 assumes the retracted position and any rotation of the rim 172R by a user does not cause a change in the selected control mode. Rather, it is ignored by the VCU 10.

(73) If whilst the VCU 10 is in the automatic condition the manual condition is activated, the VCU 10 controls the vehicle subsystems automatically to assume the SPO mode, being the mode intended to provide the best compromise in vehicle subsystem adjustment/set-up for normal road and light off-road use. The knob 172 also assumes the exposed position. Icon 172a, which corresponds to the SPO mode, is illuminated.

(74) If a user wishes to select a mode other than the SPO mode, he or she may grasp the rim 172R and rotate the rim 172R in a clockwise direction to select the appropriate mode. If the rim 172R is rotated by two indexed angular increments and the user waits for 2 s, the VCU 10 assumes the GGS mode. Icon 172a is no longer illuminated and icon 172b becomes illuminated. If the rim 172R is rotated by two further angular increments, the vehicle will assume MR mode, icon 172b will no longer be illuminated and icon 172c will be illuminated instead, and so forth. As noted above, the number of angular increments may be any suitable number such as 1, 3 or any other suitable number. Any other suitable user wait period may also be employed.

(75) Thus it is to be understood that the angular position of the rim 172R when the automatic condition was last selected is irrelevant to the determination of the control mode the VCU 10 will assume when the manual condition is subsequently selected. Regardless of the control mode that was selected when the knob 172 was last retracted, when the knob 172 is subsequently exposed VCU 10 selects the SPO control mode. Because the rim 172R is freely rotatable without constraint (due to the absence of features constraining rotation such as an end stop to prevent further rotation in a given direction) the actual (absolute) angular position of the rim 172R is irrelevant. It is to be understood that if this feature were not employed and the rim 172R were required to be in a prescribed absolute rotational position in order to select SPO mode, additional (automatic) actuation of the rim 172R by the switchpack 170 would be required when transitioning from the automatic to manual conditions of the VCU 10. For example, if the rim 172R had been set to select RB mode prior to the user selecting the automatic condition of the VCU 10, the switchpack 170 would be required to rotate the rim 172R from the position corresponding to the RB mode to that corresponding to the SPO mode when manual mode were subsequently selected. Additional, potentially complicated failsafe countermeasures would be required.

(76) It is to be understood that in some alternative embodiments, when the automatic condition is deselected and the manual condition is assumed, the VCU 10 may be arranged to remain in the driving mode that was selected automatically by the VCU 10 when in the automatic condition until the user selects a different driving mode by rotation of the rim 172R. Thus, when the manual condition is selected, the icon 172a-e corresponding to the currently (automatically) selected driving mode remains illuminated. If the VCU 10 is configured such that none of icons 172a-e are illuminated when the VCU 10 is in the automatic condition then the icon corresponding to the currently selected driving mode is illuminated when the manual condition is assumed.

(77) It is to be understood that other arrangements are also useful.

(78) It is to be understood that when the VCU 10 is operating in the manual condition, the HDC function may be selected by means of switch 171a. When active, the HDC function limits a rate of progress (i.e. a speed) of the vehicle 100 over ground to a prescribed value by application of a foundation braking system of the vehicle 100. In the vehicle 100 of FIG. 1 the foundation braking system is provided by a friction braking system. In some embodiments the foundation braking system may be provided by a regenerative braking system in addition or instead. HDC functionality is described in UK patents GB2325716, GB2308415, GB2341430, GB2382158 and GB2381597.

(79) It is to be understood that if the vehicle is descending a slope, a user may activate the HDC function by pressing switch 171a. The VCU 10 then assumes control of the foundation braking system and limits the speed at which the vehicle 100 may descend the slope to a user-prescribed value. If the vehicle speed drops below the user-prescribed value the user may increase the speed by pressing the accelerator pedal 161. If the user wishes to decrease speed below the prescribed value temporarily, for example if the user wishes to stop the vehicle, the user may press the brake pedal 163 to activate the foundation braking system in the expected manner.

(80) The VCU 10 is configured wherein if the VCU 10 is operating in the automatic mode and the user selects the HDC function, the VCU 10 activates the HDC function but suspends any further automatic changes in selected sub-system control mode. That is, the VCU 10 remains in the presently selected control mode when the HDC function is selected. If the VCU 10 is operating in the automatic condition, the VCU 10 may be operable to automatically initialise HDC in a standby mode, such that its function may be armed and waiting to intervene where required. If HDC intervenes whilst the vehicle is travelling with VCU 10 operating in the automatic condition, a control mode change will not be made during the period for which the HDC function is operating and intervening to maintain composed vehicle progress.

(81) In some embodiments the VCU 10 also suspends determination of the most appropriate control mode for the terrain over which the vehicle 100 is travelling until the HDC function is deselected. This feature may reduce a computational burden placed on the VCU 10 whilst the HDC function is active in some embodiments.

(82) In some alternative embodiments the VCU 10 continues to determine the most appropriate control mode for the terrain over which the vehicle 100 is travelling even whilst the HDC function is active. It is to be understood that the reliability of certain terrain indicators used in determining the terrain over which the vehicle 100 is moving may be reduced during HDC intervention. That is, HDC intervention may give rise to an erroneous determination of the type of terrain over which the vehicle is moving and therefore of the most appropriate control mode. Thus the VCU 10 may wait for a prescribed number of wheel rotations to take place, for a prescribed distance to be travelled or for a prescribed time period to elapse once the HDC intervention has ceased before allowing automatic control mode changes to take place.

(83) In some embodiments, the VCU 10 may wait for a prescribed time period to elapse or for a prescribed number of wheel rotations to take place or for a prescribed distance to be travelled over terrain having a gradient below a prescribed value before allowing a change in mode to take place automatically.

(84) In some embodiments, when the HDC intervention has ceased, the VCU 10 is arranged to remain in the selected control mode and delay automatic changing of control mode for a prescribed period of time, optionally a prescribed period of from around 5 s to around 2 mins before allowing a change in control mode to be made automatically whilst the VCU 10 is in the automatic condition. Other values are also useful.

(85) In some embodiments when the HDC function is deactivated the VCU 10 is arranged to remain in the selected control mode for a prescribed distance of travel, optionally a distance of from around 2 m to around 200 m before allowing a change in control mode to be made automatically whilst the VCU 10 is in the automatic condition.

(86) This delay (In distance or time) has the advantage that when the VCU 10 returns to automated control mode following cessation of HDC intervention, the vehicle response to the user pressing of the brake and/or accelerator pedals 163, 161 will be in line with that anticipated and expected by the user, and consistent with that experienced by the driver prior to HDC intervention.

(87) In some embodiments, when the VCU 10 activates the HDC function an HDC-specific relationship between accelerator pedal position and torque developed by the powertrain is implemented by the VCU 10. Similarly a predetermined relationship between brake pedal pressure and brake torque applied by means of the foundation braking system is established. These values may be independent of the control mode in which the VCU 10 is operating.

(88) In some alternative embodiments, the form of the response of the powertrain 129 and braking system to accelerator and brake pedal inputs respectively is dependent on the selected control mode and corresponds to that implemented when the VCU 10 is in that control mode and the HDC function is not active. Thus it is to be understood that in such embodiments, the fact that changes in control mode are suspended when the HDC function is active have the advantage that a response of the vehicle to accelerator and brake pedal inputs does not change whilst the HDC function is active, i.e. because the selected control mode is not changed. This reduces a risk that a driver is inconvenienced by a change in vehicle response to accelerator and/or brake pedal control inputs when performing a hill descent operation.

(89) Embodiments of the present invention have the advantage that vehicle composure may be preserved and in some embodiments or situations composure may be enhanced. Some embodiments have the advantage that user confidence in vehicle operation performance and expected response may be enhanced. Automatic terrain recognition and control mode selection may be made with confidence.

Cruise Control Interaction

(90) In the embodiment shown in the accompanying drawings, a vehicle cruise control function implemented by the cruise control system 11 may be selected and activated by means of the cruise control selector 181C mounted to the steering wheel 181 of the vehicle 100. In the embodiment of FIG. 1 the VCU 10 is configured to allow the cruise control system 11 to be activated whether the VCU 10 is operating in the manual or automatic conditions, provided prescribed criteria are met. In some embodiments the VCU 10 is configured to implement the cruise control function rather than a separate control system 11. The cruise control system 11 may optionally only operate provided the vehicle speed is in a prescribed cruise speed range. In the present embodiment the prescribed cruise speed range is the range from 30 km/h to 150 km/h, although other speed ranges are also useful.

(91) When operating in the manual condition in which a user may select manually a required driving mode the VCU 10 is arranged to allow the cruise control function to be activated provided the PTU 137 is operating in the high ratio range and a speed of the vehicle 100 is within the prescribed cruise speed range.

(92) It is to be understood that in some embodiments the VCU 10 is configured to allow selection of a prescribed one or more driving modes only when the PTU is operating in the low ratio range, i.e. certain driving modes are not available when the PTU is operating in the high ratio range. Accordingly, such modes are not compatible with operation of the cruise control system 11.

(93) In the present embodiment, when operating in the manual condition the VCU 10 is operable to allow the cruise control system 11 to be activated and deactivated by means of user control 181C provided the PTU 137 is set to the high gear ratio and the user has selected one of a subset of operating modes referred to as the manual/cruise subset of operating modes. In the present embodiment the manual/cruise subset of operating modes consists of the SPO mode and GGS mode. Thus, the cruise control system 11 can only enter an operational state provided the mode selector rotary knob 172 is set to the SPO or GGS modes. If the VCU 10 is operating in the manual condition in a mode other than the SPO or GGS modes, activation of the cruise control system 11 in an operational state is not permitted.

(94) Other arrangements are also useful. In some embodiments when in the manual condition (and in some embodiments the automatic condition) the VCU 10 may be operable to allow the cruise control system 11 to be activated only if the user has selected the SPO mode.

(95) In the present embodiment, if the VCU 10 is operating in the manual condition with the cruise control system 11 already active, the VCU 10 only permits a user to select one of the manual/cruise subset of operating modes, i.e. the SPO or GGS modes. If a user sets the mode selector knob 172 to a mode other than SPO or GGS, the VCU 10 ignores the selection and continues in the instant operating mode in which the VCU 10 is operating. Under these conditions the cruise control system 11 remains active and a message is provided to the user to inform them why the desired operating mode cannot be assumed. If the cruise control system 11 is inactive, a user is permitted to select any operating mode provided the mode is allowed by the currently selected PTU gear ratio.

(96) When operating in the automatic condition the PTU 10 is operable to allow the cruise control function to be activated provided the PTU 137 is set to the high gear ratio and the VCU 10 has selected automatically one of a subset of allowable operating modes referred to as the auto/cruise subset of operating modes. In the present embodiment the auto/cruise subset of operating modes also consists of the SPO mode and GGS mode.

(97) As noted above, if the VCU 10 is operating in the automatic condition, the VCU 10 only permits the cruise control system 11 to be activated if the VCU 10 has selected operation in the SPO or GGS operating modes. In the present embodiment, if a user attempts to activate the cruise control system 11 by depressing the cruise control selector 181C and the VCU 10 has not automatically selected the SPO or GGS operating modes, the VCU 10 selects the most appropriate operating mode from the auto/cruise subset of operation modes, i.e. the most appropriate one of the SPO and GGS operating modes for the current operating conditions. The VCU 10 selects the mode having the largest combined probability value for being the most appropriate mode, as described above. The VCU 10 then assumes this mode, and causes the cruise control system 11 to become active. That is, the cruise control system 11 may be placed in a standby state if SPO or GGS is not selected. After the VCU 10 changes the operational mode of the vehicle from its current operational mode to the most appropriate of the SPO and GGS operational modes, the cruise control system 11 changes from a standby state to an operational state, wherein it assumes control of the progress of the vehicle 100.

(98) It is to be understood that in some alternative embodiments, instead of selecting an operating mode that permits activation of the cruise control system 11 when a user seeks to activate the cruise control system 11, the VCU 10 may ignore the request to activate the cruise control system 11, and continue operating in the most appropriate operating mode as determined by the VCU 10 as described above.

(99) If whilst the cruise control system 11 is active and the vehicle is operating in the manual condition the user selects the automatic condition, the VCU 10 selects the most appropriate operating mode selected from amongst the auto/cruise subset of operating modes. That is, the VCU 10 selects the most appropriate operating mode selected from amongst the SPO and GGS operating modes. If the VCU 10 is not already operating in this mode, the VCU 10 assumes this operating mode and allows the cruise control system 11 to become active.

(100) If whilst operating in the automatic condition with the cruise control system 11 active a user selects the manual condition and a mode of operation other than SPO or GGS, the VCU 10 is configured to maintain the cruise control system 11 in the active condition and remain in the automatic condition. A notification is then provided to a user indicating why the manual condition has not been assumed. In some alternative embodiments, the VCU 10 may cause operation of the cruise control system 11 to be cancelled and allow assumption of the manual condition and the selected operating mode.

(101) If whilst operating in the automatic condition with the cruise control system 11 active a user selects the manual condition and a mode of operation that is allowable with the cruise control system 11 active, i.e. the SPO or GGS modes in the present embodiment, the VCU 10 is configured to maintain the cruise control system 11 in the active condition. The VCU 10 assumes the manual condition and selects the SPO or GGS mode according to the state of the mode selector knob 172.

(102) FIG. 6 illustrates a method of operation of the vehicle 100 of FIG. 1.

(103) At step S101 the vehicle 100 is operating with the cruise control system 11 active and the VCU 10 in the manual condition.

(104) At step S103 the VCU 10 checks whether a user has selected the automatic condition via selector knob 172 as described above with respect to FIG. 4 and FIG. 5. If a user has not selected the automatic condition the VCU 10 continues at step S101.

(105) If a user has selected the automatic condition, then at step S105 the VCU 10 selects the most appropriate operating mode from the auto/cruise subset of permitted operating modes, i.e. from the SPO and GGS operating modes in the present embodiment.

(106) At step S107 the VCU 10 operates in the automatic condition with the most appropriate operating mode selected from the auto/cruise subset of permitted operating modes.

(107) At step S109 the VCU 10 continues to limit the allowable operating modes to the modes of the auto/cruise subset of modes.

(108) At step S111 the VCU 10 checks whether the cruise control system 11 has been deselected by a user.

(109) If at step S111 the VCU 10 determines that the cruise control system 11 has been deselected, the VCU 10 continues at step S113.

(110) At step S113 the VCU 10 commands the cruise control system 11 to become inactive and continues operating in the automatic condition. That is, the VCU 10 continues selecting the most appropriate operating mode from the currently permitted operating modes.

(111) In the present embodiment, if at step S111 the cruise control system 11 becomes inactive automatically, for example due to a user depressing the brake pedal 163, or the occurrence of a traction control or stability control event, the VCU 10 continues selecting the most appropriate operating mode from the currently permitted operating modes.

(112) If at step S111 the VCU 10 determines that the cruise control system 11 has not been deselected, the VCU 10 continues at step S115.

(113) At step S115 the VCU 10 determines whether the manual condition has been selected by a user. If the manual condition has not been selected the user the VCU 10 continues at step S103. If the manual condition has been selected, the VCU 10 continues at step S117.

(114) At step S117 the VCU 10 determines whether the user has selected a mode from the manual/cruise subset of operating modes. If the user has selected one of those modes, the VCU 10 continues at step S119.

(115) At step S119 the VCU 10 assumes the manual condition and the particular operating mode selected by the user by means of the rotary knob 172. The VCU 10 then continues at step S103.

(116) If at step S117 the VCU 10 determines that the user has selected an operating mode that is not one of the manual/cruise subset of operating modes, the VCU 10 continues at step S121. At step S121 the VCU 10 remains in the automatic condition and the cruise control system 11 remains active. A notification is provided to the user that the requested operating mode cannot be assumed. The VCU 10 then continues at step S105.

(117) Embodiments of the present invention have the advantage that selection and deselection of manual and automatic operating conditions of a vehicle control system and operation of a cruise control system may be managed automatically in order to improve user enjoyment of a vehicle 100. A workload on user may be reduced in some embodiments, reducing user fatigue.

(118) 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.

(119) 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.

(120) 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.