Patent Publication Number: US-9884626-B2

Title: Vehicle control system and method

Description:
CORPORATION BY REFERENCE 
     The entire contents of copending UK patent application numbers GB1111288.5, GB1211910.3 and GB1202427.9 and UK patents GB2325716, GB2308415, GB2341430, GB2382158 and GB2381597 are expressly incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a vehicle control system for one or more vehicle subsystems and to a method of controlling one or more vehicle subsystems. 
     BACKGROUND 
     It is known to provide a vehicle having a plurality of subsystems which can be operated in different configurations to suit different driving conditions. For example, automatic transmissions may be controlled in a variety of modes such as sport, manual, winter or economy. In each mode, subsystem control parameters such as accelerator pedal response and conditions under which changes between gear ratios take place may be modified so as to suit the conditions of the terrain or the particular taste of the driver. 
     It is also known to provide air suspensions with on-road and off-road modes. Stability control systems can be operated at reduced activity in certain modes so as to give the driver more direct control, and power steering systems can be operated in different modes to provide a varying level of assistance depending on driving conditions. 
     It is desirable to provide an improved control system for a motor vehicle operable in different configurations. 
     STATEMENT OF THE INVENTION 
     Some embodiments of the present invention may be understood with reference to the appended claims. 
     Aspects of the present invention provide a control system, a vehicle and a method. 
     Control systems according to embodiments of the present invention are suitable for a range of different vehicles including conventional engine-only vehicles, electric vehicles, and/or hybrid electric vehicles. 
     In an aspect of the invention for which protection is sought there is provided 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 and to assume operation in said system operating mode.
         wherein when operating in the automatic mode selection condition the system is configured to prevent selection of a prescribed one or more operating modes if it is determined that the vehicle is towing a load.       

     It is to be understood that, as described in further detail below, this may be achieved in some embodiments by preventing the system from continuing to operate in the automatic mode selection condition when it is determined that the vehicle is towing a load. This may comprise deactivating the automatic mode selection condition when it is determined that the vehicle is towing a load and the prescribed one or more operating modes are not selected. 
     Furthermore it is to be understood that this may be achieved in some embodiments by denying operation in the automatic mode selection condition upon a user input request to operate in the automatic mode selection condition when it is determined that the vehicle is towing a load and the prescribed one or more operating modes is not selected. This may comprise not accepting a user request for automatic mode selection condition when it is determined that the vehicle is towing a load and the prescribed one or more operating modes is not selected. 
     In some alternative embodiments this may be achieved by preventing the prescribed one or more operating modes from being selected if the system is in the automatic mode selection condition and it is determined that the vehicle is towing a load. 
     It is to be understood that in some embodiments it may not be possible for the system to make an accurate automated determination whether terrain over which the vehicle is travelling is suited to the sand control mode if vehicle drag increases above a predetermined threshold due to towing. Thus, in some embodiments, when in the automatic selection condition the system may be configured, not to allow selection of the sand subsystem control mode whilst the system detects that the vehicle is towing. 
     The control system may be operable in a manual operating condition in which a user is able to select said operating mode and the automatic operating condition in which the system is configured to select said operating mode automatically, wherein the system is configured to be switched between said manual and automatic operating conditions by means of a user-operable input device. 
     Thus, it is to be understood that in some embodiments a user may still select a mode such as a sand mode when towing by deselecting the automatic operating condition of the system and selecting the mode in the manual operating condition. Thus, in some arrangements, when the system is operating in the automatic selection condition the system may permit the driver to override prevention of selection of one or more subsystem control modes by selecting the manual selection condition. In the manual selection condition the user may select any required mode subject to any further constraints such as selection of an appropriate powertrain gear ratio. Other arrangements are also useful. 
     The control system may be arranged wherein if the system is operating in the automatic selection condition the system is configured to notify the user when operation in one or more control modes has been suspended or denied due to a determination that the vehicle is towing. 
     This is so as to make the user aware of the limited range of control modes available whilst the system is operating in the automatic selection condition. Notification may be made by means of an HMI display and/or any other suitable means including an audible notification. 
     The control system may be configured wherein it the system is operating in the automatic selection condition and it is determined that the vehicle is towing, the system is configured automatically to assume the manual selection condition. 
     In an embodiment, if the control system is operating in the automatic selection condition prior to detection of a trailer being coupled to the vehicle, the system may automatically assume the manual selection condition upon detection of the presence of a trailer. 
     The control system may further be configured to assume a default operating mode when the manual selection condition is assumed. The default mode may be an on-road mode suitable for highway driving such as the SPO (on-road) operating mode. 
     The control system may be arranged to notify a user that the operating condition has changed, for example by providing a corresponding warning via a display panel such as an HMI display. 
     Optionally, the control system is configured to determine whether or not the vehicle is towing a load according to an input-signal indicating whether the vehicle is towing. 
     Optionally, the control system is arranged to determine that the vehicle is towing at least in part in dependence on detection of an electrical connection between a trailer and the vehicle. 
     It is to be understood however that such electrical connections may be prone to damage. Furthermore, it is known that some users may choose to mechanically hitch a trailer without making an electrical connection if they wish to move a vehicle on private land, or if the electrical connections on the trailer do not match those of the vehicle. Accordingly it may be advantageous, in addition or instead, to determine whether a vehicle is towing by other means. 
     The control system may be configured to determine whether the vehicle is towing at least in part by monitoring one or more vehicle parameters and determining whether a value of one or more parameters and/or a variation in a value of one or more parameters over time is indicative of towing. 
     The control system may be configured to determine whether the vehicle is towing at least in part by monitoring an amount of drag and/or rolling resistance to which the vehicle is subject. 
     It is to be understood that the amount of drag on the vehicle is typically increased due to the weight of a load towed, and increased air resistance. 
     The control system according to claim  8  configured to determine that a vehicle is towing in dependence on a change in drag and/or rolling resistance to which the vehicle is subject. 
     The control system may be configured to determine that a vehicle is towing in dependence on a change in drag and/or rolling resistance to which the vehicle is subject between stopping and subsequently restarting motion of a vehicle over a surface. 
     For example if an increase in drag by more than a prescribed threshold is detected immediately following starting of the vehicle from rest, the system may determine that a trailer has been coupled to the vehicle. In some embodiments the system may determine that a trailer has been coupled if the increase in drag takes place after the vehicle has been stationary for longer than a prescribed period. The prescribed period may be any suitable period such as a period in the range from 5 s to 30 s, from 10 s to 100 s, from 30 s to 1000 s or any other suitable prescribed period. 
     In some embodiments the system may check for one or more other indicators that the vehicle is towing and not driving on sand before determining that a trailer has been coupled. 
     The control system may be configured to monitor data in respect of seat occupancy and/or door opening history in order to determine whether the vehicle is towing. 
     The control system may be configured to correlate seat occupancy and/or door opening history with a change in drag and/or rolling resistance thereby to determine whether a change in drag and/or rolling resistance is associated with loading or unloading of a vehicle or towing of a load. 
     Thus if seat occupancy has not increased and an increase in drag and/or rolling resistance has taken place exceeding a threshold amount the system may determine that a high likelihood exists that a trailer has been connected to the vehicle. 
     The control system may be configured to determine whether the vehicle is towing at least in part by detection of a wireless signal received from the towed object. 
     Optionally the wireless signal is a signal transmitted from the vehicle and reflected by the towed object. 
     Alternatively the wireless signal may be a signal transmitted from the towed object. 
     The wireless signal may be an electromagnetic signal such as a radar signal. Alternatively the signal may be an optical signal such as an infra-red signal. Further alternatively the signal may be an acoustic or sonic signal such as an ultrasonic signal. 
     The control system may be configured to monitor a variation in a distance of an object from one or more sensors thereby to determine whether the object is a towed object. 
     In some embodiments the system may employ data from one or more front or rear mounted parking sensors such as park distance control (PDC) sensors. The sensors may be configured to transmit a wireless signal such as a radar, infra-red or ultrasonic signal and to detect a reflected portion of the transmitted signal. It is to be understood that when a vehicle is in motion and towing, it is expected that the sensors will detect an object following the vehicle a constant distance from the vehicle, and typically within 2 m of the vehicle. In addition, any left-hand and/or right-hand outboard sensors may be expected to detect complimentary changes in distance to the object due to cornering. For example if a distance from a left hand sensor to the object decreases by distance X, a corresponding increase in distance to the object would be expected in respect of the right-hand sensor. Such a change would be indicative of cornering to the left. Correspondingly opposite changes would be expected in respect of cornering to the right. 
     In the presence of a single (left-hand or right-hand) outboard sensor, variation in distance to the object may be correlated with cornering to determine whether the object is a towed object. 
     In some embodiments the system is configured to analyse road roughness data obtained by monitoring front and rear wheel suspension articulation when travelling in a substantially straight line and determine whether one or more characteristics or trends are present in the data indicative of towing. In an example, if the vehicle is towing a trailer, articulation of a rear suspension whilst towing is likely to be influenced by the increased vertical loading at the tow hitch due to the presence of the trailer, which may be around 150 kg in some embodiments. 
     In order to increase a likelihood that the system correctly determines the vehicle is towing, the system may be configured to take into account seat occupancy data in determining whether a change in suspension articulation is due to the presence of one or more passengers. Similarly the system may take into account the presence of luggage or other load in a luggage compartment. In some embodiments door opening history may be employed in addition or instead, for example to determine whether a user may have placed luggage or other load in a luggage compartment thereby giving rise to the change in suspension articulation. In addition or instead door opening history may be employed to determine whether one or more passengers may have entered or exited the vehicle. 
     In some embodiments if an increase in rolling resistance only exceeds a threshold after the system detects a drop in rear ride height, then the system may determine that the vehicle has been coupled to a trailer. 
     Other strategies are useful and some strategies may be used together in order to increase confidence in the resulting determination. 
     In some embodiments, the system may be arranged to store data in respect of the last known rolling resistance of the vehicle for use in determining which subsystem control mode to select immediately after key-on (if the automatic operating condition is selected). If the vehicle comes to rest and is subsequently switched off (key-off) whilst towing a trailer, but following key-on, no trailer is detected (for example because an electrical connection to a trailer cannot be defected), the system may compare current rolling resistance data (once the vehicle is again moving) with last known rolling resistance data to determine whether a trailer may still be present. If the data is sufficiently similar the system may determine that the trailer is still being towed. In some embodiments the system may store (or otherwise retain) data in respect of the last known rolling resistance at the end of a journey only if the system detects that the vehicle was towing when the journey ended and the vehicle stopped. 
     In some embodiments the system may store or otherwise retain data in respect of the last known rolling resistance at the end of a journey only if the system detects that the vehicle was towing when the journey ended and the vehicle stopped, and removal of the towed load is not detected prior to key-off. 
     Optionally, 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 plurality of subsystem control modes corresponds to one or more different driving conditions for the vehicle. 
     Optionally, the system comprises evaluation means for evaluating one or more driving condition indicators to determine the extent to which each of the subsystem control modes is appropriate. 
     Optionally, 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. 
     Optionally, 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. 
     Optionally, the operating modes are control modes of at least two vehicle subsystems selected from amongst an engine management or powertrain system, a transmission system, a steering system, a brakes system and a suspension system. 
     Optionally, 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. 
     For example, in the case of a vehicle sub-system in the form of a suspension system operable at a plurality of different ride-heights for a given vehicle loading, the subsystem configuration modes may include modes corresponding to different respective ride heights. In the case of a vehicle sub-system controller in the form of an engine or powertrain controller, the controller may be configured to provide different respective values of engine torque as a function of accelerator pedal position in each of a plurality of different powertrain controller configuration modes. A subsystem control mode may therefore correspond to a set of subsystem configuration modes, for example one configuration mode for each subsystem. For example in one operating mode a ‘high’ ride height subsystem configuration mode may be set for the suspension system and a ‘slow’ accelerator pedal map subsystem configuration mode may be set for the powertrain controller. Some subsystems may allow two different parameters to be set. Thus the suspension system may allow a roll stiffness setting of the suspension to be set to one of a plurality of configuration modes such as low, medium or high. 
     Various possible known subsystem configuration modes will now be described. The reader is referred to US2003/0200016 for further details in respect of known types of subsystem configuration mode and the manner in which the configuration modes may be implemented. Other configuration modes are also useful. Other subsystems may also be controlled, in addition or instead. 
     Optionally, the operating modes include control modes of a suspension system and the plurality of subsystem configuration modes comprise a plurality of ride heights. 
     The operating modes may include control modes of 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. 
     The operating modes may include control modes of a steering system which can provide steering assistance, and wherein said plurality of subsystem configuration modes provide different levels of said steering assistance. 
     The operating modes may include control modes of a brakes system which can provide braking assistance, and said plurality of subsystem configuration modes provide different levels of said braking assistance. 
     Optionally, the operating modes include control modes of 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. 
     Optionally, the operating modes include control modes of a fraction control system which is arranged to control wheel spin, and said plurality of subsystem configuration modes allow different levels of said wheel spin. 
     Optionally, the operating modes include control modes of 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. 
     The operating modes may include control modes of a range change transmission and said subsystem configuration modes may include a high range mode and a low range mode of said transmission. 
     The range change transmission may for example by comprised by a power transfer unit or power take-off unit for coupling a prop shaft of a driveline to a torque transmission path from an engine or transmission of the vehicle, such as an automatic transmission. 
     The operating modes may include control modes of 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. 
     The operating modes may include control modes of a transmission system operable in a plurality of transmission ratios and including a transmission control 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. 
     One of the subsystems may comprise a differential system configured to provide a plurality of levels of differential lock, and the subsystem configuration modes may be arranged to provide different levels of said lock. 
     The differential system may be arranged to control the level of differential lock on the basis of a plurality of inputs, and to respond differently to said inputs in each of the modes. 
     The differential system may comprise a centre differential, a front differential, and/or a rear differential. The differential may be a clutch-based system in some embodiments, whereby differences in rates of rotation of wheels is accommodated by slipping of a clutch rather than by means of a conventional differential gear arrangement in which side wheels are coupled via pinion wheels supported by a differential cage in order to allow relative rotation. 
     One of the subsystems may comprise a roll control system arranged to provide roll correction to reduce vehicle roll and the subsystem configuration modes provide different levels of roll correction of the vehicle, at least under some driving conditions. 
     One of the subsystems may comprise a speed control system arranged to control the speed of the vehicle when descending a hill. The speed control system may be arranged to control the vehicle to different speeds in the different configuration modes. 
     Optionally, the operating modes may include an off-road mode in which the subsystems are controlled in a manner suitable for driving on rough terrain and an on-read mode in which the subsystems are controlled in a manner suitable for driving on-road. 
     Optionally the suspension system is arranged to provide a higher ride height in the off road mode than in the on-road mode. 
     Further optionally, in the off-road mode a higher level of said interconnection is provided than in the on-road mode. 
     The traction control system may be arranged to allow less wheel spin in the off-road mode than in the on-road mode. 
     Optionally the yaw control system is arranged to allow a higher degree of said divergence in the off-road mode than in the on-road mode. 
     Optionally, in the off-road mode the range change transmission is operated in the low range. 
     Optionally, in the off-road mode the powertrain control means is arranged to provide lower levels of drive torque, for a given accelerator or throttle pedal position, at least at low levels of accelerator pedal depression, than in the on-road mode. 
     Optionally, the differential system is arranged to provide higher levels of differential look in the off-road mode than in the on-road mode. 
     Optionally, the roll control system is arranged to provide a higher roll stiffness in the on-road mode than in the off-road mode. 
     Optionally, the speed control system is arranged to be switched on in the off-road mode and switched off in the on-road mode. 
     Optionally, the driving modes include at least one low friction mode in which the subsystems are controlled in a manner suitable for driving on low friction surfaces and a high friction mode in which the subsystems are controlled in a manner suitable for driving on high friction surfaces. 
     Optionally, the brake control system allows higher levels of slip in the high friction mode than in the low friction mode. 
     Optionally, the fraction control system allows higher levels of wheel spin in the high friction mode than in the low friction mode. 
     Optionally, the braking control system provides a greater level of braking assistance in the high friction mode than in the low friction mode. 
     Optionally, the power-train control means is arranged to provide lower levels of drive torque, for a given accelerator or throttle pedal position, at least at low levels of accelerator pedal depression, in the low friction mode than in the high friction mode. 
     Optionally, the transmission system is arranged to operate in higher gears for a given value of said at least one parameter in the high friction mode than in the low friction mode. 
     Optionally, the differential system is arranged to provide higher levels of differential lock in the low friction mode than in the high friction mode. 
     Optionally, the high friction mode may comprise a standard or default mode in which the vehicle will operate normally and which is suitable for on-road driving. 
     Optionally, there are at least two such low friction modes and the suspension system is arranged to provide a higher ride height in one of the low friction modes than in the other. 
     Further optionally, there are at least two such low friction modes and the suspension system is arranged to provide a higher level of said cross linking in one of the low friction modes than in the other. 
     Optionally, the at least two low friction modes may comprise a mud mode suitable for traveling through deep mud, and another low friction mode suitable for driving in snow, on grass, or on gravel. 
     Optionally there may be a plurality of low friction modes, one of which may be a grass mode in which the subsystems are controlled in a manner suitable for driving on grass, one of which may be an ice mode in which the subsystems are controlled in a manner suitable for driving in ice, and one of which may be a mud mode in which the subsystems are controlled in a manner suitable for driving on mud. 
     Optionally one of the modes is a sand mode in which the subsystems are controlled in a manner suitable for driving on sand. At least one of the subsystems may be arranged, in the sand mode, to allow only relatively low levels of wheel spin when the vehicle is traveling at low speeds so as to avoid the vehicle wheels becoming submerged in sand, but to allow relatively high levels of wheel spin when the vehicle is traveling at higher speeds. Optionally, in the sand mode, the powertrain control system is arranged to provide relatively low levels of drive torque for a given throttle pedal position at low vehicle speeds and to provide relatively high levels of drive torque for a given throttle pedal position at higher vehicle speeds. 
     The off-road mode may be a rock crawl mode in which the subsystems are controlled in a manner suitable for driving over rocks. Alternatively it may be set up for more general off-road use. One or more other off-road modes may be provided in addition or instead. 
     One of the modes may be a rough-road mode in which the subsystems are controlled in a manner suitable for driving on rough roads, for example for driving at relatively high speeds over rough surfaces. 
     At least one of the modes may be a plough surface mode in which the brake control subsystem is arranged to allow a relatively high degree of wheel slip under braking. This may be useful, for example on snow or sand, where the build-up of matter in front of the wheels under braking can improve braking performance. 
     Optionally, at least one of the modes is an on-road mode in which the subsystems are controlled in a manner suitable for driving on-road. For example, one of the modes may be a motorway mode in which the subsystems are controlled in a manner suitable for driving at high speed on a flat road surface. One of the modes may be a country road mode in which the subsystems are controlled in a manner suitable for driving on country roads. 
     The driving modes may be selectable by means of at least two inputs, one of which may be a terrain selection input arranged to influence the mode selected on the basis of the terrain selected, and the other of which may be a mode of use input arranged to influence the mode selected on the basis of a selected mode of use of the vehicle. Each of these inputs may be user-controlled inputs, or may be derived from one or more sensors. 
     The mode of use input may foe arranged to allow selection between a plurality of driving styles, which may include, for example, a normal style, a sport style, and an economy style. 
     Alternatively, or in addition, the mode of use input may be arranged to allow selection between a plurality of states of the vehicle, for example including a towing state or a loaded state. 
     Optionally, the prescribed one or more operating modes include a high drag mode in which the subsystems are controlled to allow only relatively low levels of wheel spin when the vehicle is traveling at low speeds but to allow relatively high levels of wheel spin when the vehicle is traveling at higher speeds. 
     The high drag mode may be a mode suitable for travel over sand. 
     The prescribed one or more operating modes may include a high drag mode in which the powertrain control system is arranged to provide relatively low levels of drive torque for a given throttle pedal position at low vehicle speeds and to provide relatively high levels of drive torque for a given throttle pedal position at higher vehicle speeds. 
     The prescribed one or more operating modes may include a high drag mode in which the subsystems are controlled to allow only relatively low levels of wheel spin when the vehicle is traveling at low speeds but to allow relatively high levels of wheel spin when the vehicle is traveling at higher speeds, and in which the powertrain control system is arranged to provide relatively low levels of drive torque for a given throttle pedal position at low vehicle speeds and to provide relatively high levels of drive torque for a given throttle pedal position at higher vehicle speeds 
     Optionally, the system is configured when in the automatic condition to prevent selection of an operating mode that increases a responsiveness of a powertrain to an accelerator control input, when it is determined that the vehicle is towing. In some embodiments having a subsystem control mode optimised for travel over sand the system may be configured to prevent automatic selection of that mode when it is determined that the vehicle is towing a load. 
     In some embodiments the control system may monitor drag on the vehicle in order to determine the most appropriate operating mode for vehicle operation. It is possible that when a trailer is connected the system may falsely determine that the vehicle is travelling over a high drag surface such as sand, due to an increase in drag and/or rolling resistance due to the presence of a trailer, and select a subsystem configuration mode appropriate to a high drag surface. This mode may be inappropriate when towing. For example, the mode may be inappropriate due to a particular form of a powertrain response to accelerator pedal input (position) that is implemented by the mode. For example a powertrain torque/accelerator position map may be inappropriate for towing. A configuration of one or more other vehicle systems such as a braking system, suspension system or the like may also be inappropriate. Accordingly, some embodiments of the present invention have the advantage that when the vehicle is towing and the system is operating in the automatic selection condition, the system is prevented from selection of one or more prescribed subsystem operating modes that may be inappropriate when towing. 
     It is to be understood that an aggressive response by a powertrain in increasing substantially an amount of power generated thereby in response to a relatively small change of position of an accelerator control may be inappropriate when towing. Accordingly, a mode implementing such a response may be prevented from being selected when in the automatic mode selection condition. 
     In a further aspect of the invention for which protection is sought there is provided a method of controlling a vehicle implemented by means of a control system comprising:
         causing the system to operate in an automatic mode selection condition in which the system is configured to select automatically an appropriate system operating mode and to assume operation in said system operating mode; and   preventing automatic selection of a prescribed one or more operating modes if it is determined that the vehicle is towing a load.       

     In an embodiment of the invention there is provided a carrier medium carrying computer readable code for controlling a vehicle to carry out a method according to an aspect of the invention. 
     In an aspect of the invention for which protection is sought there is provided a motor vehicle control system for selecting a driving surface and for controlling a plurality of vehicle subsystems to operate in a plurality of subsystem configuration modes in dependence on the selected driving surface, the system being operable in a manual operating condition in which a user is able to select said driving surface and an automatic operating condition in which the system is configured to select said driving surface automatically, wherein the system is able to be switched between said manual and automatic operating conditions by means of a user-operable input device,
         the system being further configured to prevent selection of one or more of the subsystem configuration modes in dependence on a determination as to whether the vehicle is towing a load.       

     In an aspect of the invention for which protection is sought there is provided 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 whereby the system assumes operation in said system operating mode,
         wherein if it is determined that the vehicle is towing a load the system is configured to prevent the system assuming a state in which the system is in the automatic mode selection condition and operating in a prescribed one or more operating modes.       

     It is to be understood that this may achieved in some embodiment by preventing the system hem continuing to operate in the automatic mode selection condition when if is determined that the vehicle is towing a load. 
     In some alternative embodiments this may be achieved by preventing the prescribed one or more operating modes from being selected if the system is in the automatic mode selection condition and it is determined that the vehicle is towing a load. 
     In an aspect of the invention for which protection is sought there is provided 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 and to assume operation in said system operating mode, wherein when operating in the automatic mode selection condition the system is configured to prevent selection of a prescribed one or more operating modes if it is determined that the vehicle is towing a load. 
     It is to be understood that, as described in further detail below, this may achieved in some embodiments by preventing the system from continuing to operate in the automatic mode selection condition when it is determined that the vehicle is towing a load. This may comprise deactivating the automatic mode selection condition when it is determined that the vehicle is towing a load and the prescribed one or more operating modes are not selected. 
     Furthermore it is to be understood that this may be achieved in some embodiments by denying operation in the automatic mode selection condition upon a user input request to operate in the automatic mode selection condition when if is determined that the vehicle is towing a load and the prescribed one or more operating modes is not selected. This may comprise not accepting a user request for automatic mode selection condition when it is determined that the vehicle is towing a load and the prescribed one or more operating modes is not selected. 
     In some alternative embodiments this may be achieved by preventing the prescribed one or more operating modes from being selected if the system is in the automatic mode selection condition and it is determined that the vehicle is towing a load. 
     Advantageously, 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 subsystem control modes corresponds to one or more different driving conditions for the vehicle. The system may 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, and when in the automatic condition the system may be configured automatically to control the subsystem controller to initiate control of the or each subsystem in the subsystem control mode which is most appropriate. 
     Within the scope of this application it is expressly envisaged 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. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     For the avoidance of doubt, it is to be understood that features described with respect to one aspect of the invention may be included within any other aspect of the invention, alone or in appropriate combination with one or more other features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures in which: 
         FIG. 1  is a schematic illustration of a vehicle according to an embodiment of the present invention; 
         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; 
         FIG. 3  is a table showing which vehicle subsystem configuration mode is selected in each respective vehicle operating mode; 
         FIG. 4  is a schematic illustration of a switchpack according to an embodiment of the invention with a rotary knob in a deployed condition; 
         FIG. 5  is a schematic illustration of a switchpack according to an embodiment of the invention with a rotary knob in a retracted condition; 
         FIG. 6  is a schematic illustration of a vehicle according to an embodiment of the present invention towing a trailer; 
         FIG. 7  is a flow diagram illustrating a method of operation of a vehicle according to an embodiment of the present invention; and 
         FIG. 8  is a flow diagram illustrating a method of operation of a vehicle according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       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. 
     The driveline  130  is arranged to drive a pair of front vehicle wheels  111 ,  112  by means of a front differential  135 F 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. 
     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. 
     The vehicle  100  has an accelerator pedal  161 , brake pedal  183  and steering wheel  181 . The steering wheel  181  has a cruise control selector button  181 C mounted thereto for activating a cruise control system  11 . 
     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 . 
       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  12   a , a transmission system  12   b , an electronic power assisted steering unit  12   c  (ePAS unit), a brakes system  12   d  and a suspension system  12   e . 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  12   c , a hydraulically operated power steering unit may be provided. 
     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. 
     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. 
     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  12   c ) 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  12   c ). 
     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). 
     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 . 
     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 detect 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. 
     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). 
     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. All 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. 
     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). 
     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 . 
     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. 
     Calculations for wheel speed variation and corrugation output, the surface rolling resistance estimation, the wheel longitudinal slip and the corrugation defection, 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 . 
     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 (and therefore corresponding subsystem configuration 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 modulo  24 . 
     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 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  ( 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. 
     It is to be understood that the subsystem controller  14  may itself control the vehicle subsystems  12   a - 12   e  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  12   a - 12   e . In the latter case the subsystem controller  14  may only control the selection of the most appropriate subsystem control mode for the subsystems  12   a - 12   e , 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 . 
     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:
     (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;   (2) the integration of “positive differences” between the probability for the current control mode and the other control modes; and   (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.   

     The specific steps for phases (1), (2) and (3) will now be described in more detail. 
     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&#39;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 . 
     The selector module  20  is provided with a probability algorithm  20   a  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  20   a  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 . 
     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. 
     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. 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. 
     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   

     With reference to  FIG. 3 , the configuration of the suspension system  12   e  is specified in terms of ride height (high, standard or low) and side/side air interconnection. The suspension system  12   e  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  12   c  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. 
     The brakes system  12   d  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. 
     The brakes system  12   d  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). 
     An electron 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. 
     A dynamic stability control system (DSC) may also be operated in a high mu or low mu configuration. 
     The engine management system  12   a  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 PTU  137  may be operated in a high range (HI) subsystem configuration mode or low range (LO) subsystem configuration mode as described herein. 
     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. 
     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 looked”. 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. 
     For each subsystem control mode, the algorithm  20   a  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 it is much less likely that a high vehicle speed is indicative that the vehicle is travelling over a rock or boulder terrain. 
     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. 
     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.b.c.d . . . n )/(( a.b.c.d . . . n )+(1− a ). (1− b ). (1− c ). (1− d ) . . . (1− n ))
 
     Any number of individual probabilities may be input to the probability algorithm  20   a  and any one probability value input to the probability algorithm may itself be the output of a combinational probability function. 
     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. 
     A further control signal  31  from the selector module  20  is provided to a control module  34 . 
     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. 
     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. 
     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. 
     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 
     As described above, the vehicle  100  has an HMI module  32  comprising a user operable switchpack  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. 
     The switchpack  170  has a frame  170 F 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. 3  and a retracted position as shown in  FIG. 5 , in the exposed position the knob  172  stands proud of a panel  172 P which surrounds the knob  172 . Icons  172   a - e  are marked in the panel at circumferentially spaced apart locations around the knob  172  over an are of around 140° in the embodiment shown although other angles and other numbers of modes are also useful. The icons  172   a - e  may be illuminated selectively in order to indicate the identity of the control mode in which the subsystems  12  are being operated. 
     Other switches  171   a, b  are also provided in a remaining portion of the panel  172 P allowing a driver to activate a hill descent control (HDC) function, via switch  171   a , and select a required gear ratio of the PTU  137  (‘high’ or ‘low’), via switch  171   b.    
     Further switches  171   c  of the switchpack enable the SCS system of the vehicle to be activated or deactivated, a ride height, to be adjusted (buttons  171   c ′), an ‘eco’ mode (arranged to enhance fuel economy) to be selected and an automatic speed limiter (ASL) function to be selected. 
     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  175 L 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. 
     When the knob  172  is in the exposed position the indicator tamp  175 L 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  172 R 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. 
     The knob  172  is configured such that the rim  172 R 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  172 R based on a signal output by the switchpack  170 . In an example rim  172 R is provided with a knurled peripheral surface arranged to facilitate the user grasping the knob  172  with their fingers. 
     Rotation of the rim  172 R 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  172 R may be rotated by any number of turns in either direction without constraint by the switchpack  170 . 
     In some embodiments, when the VCU  10  is in the manual condition, rotation of the rim rotatable by two increments in a clockwise (or anticlockwise) direction causes the VCU  10  to assume the mode corresponding to the icon  172   a - 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  172 R by only a single increment in a given direction, with no farther 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  172 R by only a single incremental amount in order to signal a requirement to change mode. 
     In some embodiments, in addition to or instead of rotating the rim  172 R 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  172 R may be rotatable whilst the column  174  remains stationary, whilst in some alternative embodiments the rim  172 R and column  174  may be arranged to rotate together. They may for example be fixedly coupled or integrally formed in some embodiments. 
     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  172 R. 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 . 
     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. 
     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  172 R by a user does not cause a change in the selected control mode. Rather, it is ignored by the VCU  10 . 
     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  172   a , which corresponds to the SPO mode, is illuminated. 
     If a user wishes to select a mode other than the SPO mode, he or she may grasp the rim  172 R and rotate the rim  172 R in a clockwise direction to select the appropriate mode. If the rim  172 R is rotated by two indexed angular increments and the user waits for 2 s, the VCU  10  assumes the GGS mode. Icon  172   a  is no longer illuminated and icon  172   b  becomes illuminated. If the rim  172 R is rotated by two further angular increments, the vehicle will assume MR mode, icon  172   b  will no longer be illuminated and icon  172   c  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. 
     Thus it is to be understood that the angular position of the rim  172 R 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  172 R 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  172 R is irrelevant. It is to be understood that if this feature were not employed and the rim  172 R were required to be in a prescribed absolute rotational position in order to select SPO mode, additional (automatic) actuation of the rim  172 R by the switchpack  170  would be required when transitioning from the automatic to manual conditions of the VCU  10 . For example, if the rim  172 R 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  172 R 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. 
     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  172 R. Thus, when the manual condition is selected, the icon  172   a - e  corresponding to the currently (automatically) selected driving mode remains illuminated. If the VCU  10  is configured such that none of icons  172   a - 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. 
     It is to be understood that other arrangements are also useful. 
     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  171   a . When active, the HDC function limits a rate of progress (i.e. a speed) of the vehicle  100  over ground when descending a slope 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. 
     It is to be understood that if the vehicle is descending a slope, a user may activate the HDC function by pressing switch  171   a . 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. 
     The VCU  10  is configured wherein if the VCU  10  is operating in the automatic mode selection condition 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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     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 may be established in addition or instead. These values may be independent of the control mode in which the VCU  10  is operating. 
     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. 
     Some 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. 
     Detected Trailer 
     As described above, the VCU  10  is arranged to receive a trailer connect status signal (ON/OFF) indicative of whether or not a trailer is connected to the vehicle  100 . 
     The vehicle  100  of  FIG. 1  is shown in  FIG. 6  towing a trailer  195 . The trailer  198  is connected to the vehicle  100  by means of a tow hitch or hook  100 T of the vehicle  100 . The trailer  195  has an electrical service cable  191  that is correctable to a corresponding connector  100 C of the vehicle  100 . This allows the vehicle  100  to supply power to rear lamps of the trailer  195  such as indicator lamps, brake lamps, license plate illumination lamps and night riding lamps. 
     The VCU  10  is configured to detect when a trailer service cable  191  is connected by reference to a corresponding signal transmitted over a controller area network (CAN) bus of the vehicle  100 . The CAN bus provides a means by which the VCU  10  and subsystem controllers may communicate with one another. 
     If the VCU  10  is operating in the automatic condition and it is detected that a trailer  195  is connected to the vehicle  100 , the VCU  10  suspends allowance of selection of the sand mode and provides a corresponding alert to the user via the HMI module  32 . The VCU  10  then continues to operate the vehicle  100  in the operating mode that is determined to be the most appropriate according to the methodology described above, except that instead of allowing selection of the sand mode the VCU  10  allows selection of the most appropriate mode other than the sand mode that is allowable with the current configuration of the vehicle  100 , including the currently selected gear range (or ratio) in which the PTU  137  is operating. These modes may be referred to as an auto/towing subset of operating modes, being the allowable modes when the vehicle is towing and the VCU  10  is operating in the automatic condition. In some embodiments only one operating mode may be permitted to be selected when in the automatic operating mode selection condition and a trailer  195  has been detected. This mode may be a default mode, optionally the SPO mode suitable for on-highway driving conditions. 
     In some embodiments the VCU  10  is operable to determine whether the vehicle  100  is towing by reference to data in respect of suspension articulation, ride height, rolling resistance and/or one or more other parameters in addition or instead. 
       FIG. 7  illustrates a method of controlling a vehicle  100  according to the embodiment of  FIG. 1 . 
     At step S 101  the VCU  10  checks whether the vehicle  100  is towing a load by reference to the trailer connect status signal. If the signal is in the ON state the VCU  10  determines that a trailer is connected to the vehicle  100 . If the signal is in the OFF state the VCU  10  determines that a trailer is not connected to the vehicle  100 . 
     If the signal is in the ON state the VCU  10  continues at step S 103  otherwise the VCU  10  repeats step S 101 . 
     At step S 103  the VCU  10  determines whether the VCU  10  is operating in the automatic operating mode selection condition. If the VCU  10  is operating in the automatic selection condition, the VCU  10  continues at step S 105 . If the VCU  10  is not operating in the automatic selection condition, the VCU  10  continues at step S 109 . 
     At step S 105  the VCU  10  selects the most appropriate operating mode from the auto/towing subset of permitted operating modes. As described above, the auto/towing subset is a set of operating modes in which the VCU  10  is permitted to cause the vehicle  100  to operate when the vehicle  100  is towing and the VCU  10  is in the automatic operating mode selection condition. In the present embodiment the auto/towing subset of operating modes consists of the SPO and GGS operating modes. Other operating modes may be included in addition or instead. As noted above, in some embodiments only one operating mode may be available for selection when in the automatic operating mode selection condition. The most appropriate operating mode (control mode) is selected by the methodology described above, i.e. according to the three phase process described. The mode with the highest probability selected from amongst the members of the auto/towing subset is the mode that is determined to be the most appropriate operating mode. 
     The VCU men continues at step S 107 . At step S 107  the VCU  10  is caused to operate in the automatic condition, in the most appropriate operating mode selected from the members of the auto/towing subset. 
     The method then continues at step S 103 . 
     As noted above, if at step S 103  it is determined mat the automatic operating mode selection condition is not selected, the VCU continues at step S 109 . 
     At step S 109  the VCU  10  allows the user to select an operating mode from amongst a manual/towing subset of two or more operating modes, via rotary knob  172  of the switchpack  170 . The manual/towing subset is a set of allowable operating modes when the vehicle  100  is towing and the VCU  10  is in the manual condition. In the present embodiment the manual/towing subset consists of the SPO and GGS modes although in other embodiments one or more ether modes may be a member of this subset in addition or instead. 
     At step S 111  the VCU  10  assumes the mode selected by the user at step S 109  provided it is a member of the manual/towing subset of operating modes. 
     If the VCU  10  is in the manual operating mode selection condition when it is defected that the vehicle  100  is towing a load, the VCU  10  may be configured to remain in the currently selected operating mode provided it is a member of the manual/towing subset of modes. If under these circumstances the currently selected operating mode is not a member of this subset, in the present embodiment the VCU  10  is arranged to assume a default mode, in the present embodiment the SPO mode. After assuming the default mode, the VCU  10  is operable to allow a user to select any mode from the manual/towing subset of modes, i.e. the GGS or SPO modes, as required. 
     The VCU  10  then continues at step S 103 . 
     In some alternative embodiments of the invention, if the VCU  10  determines by reference to the trailer connect status signal that a trailer  195  is connected, the VCU  10  sets a flag preventing operation of the VCU  10  in the automatic vehicle operating mode selection condition whilst the trailer  195  is connected. 
     If the VCU  10  is operating in the automatic selection condition when the VCU  10  determines that a trailer  195  is connected, the VCU  10  assumes the manual condition. In some embodiments, if the VCU  10  is not already in a default operating mode, which may for example be the SPO operating mode, the VCU  10  also assumes the default operating mode, otherwise the VCU  10  remains in the default operating mode. In some embodiments, the VCU  10  may be operable in one of a plurality of operating modes when towing and in the manual operating mode selection condition. These modes may be referred to as the manual/towing subset of modes as described above. In some embodiments the manual/towing subset of modes include the default SPO mode and the GGS mode but not the Sand mode. If the VCU  10  is operating in the automatic condition when towing is detected and subsequently assumes the manual condition, the VCU  10  may remain in the currently selected mode provided it is a member of the manual/towing subset of modes, i.e. the selected mode is the SPO or COS mode. If the VCU  10  is not operating in one of those modes when the manual condition is selected, the VCU  10  may assume the default (SPO) operating mode. 
     In some embodiments, if the VCU  10  is operating in the automatic selection condition when the presence of a trailer  195  is detected, the rotary knob  172  may be arranged to move from the retracted to the deployed position, indicating that the VCU  10  is operating in the manual condition. 
     As noted above, in some embodiments the VCU  10  also assumes operation in the default mode whilst in some other embodiments the VCU  10  assumes the default mode unless the VCU  10  is in another mode that is also a member of the manual/towing subset of allowable modes. 
     In an example, if the VCU  10  assumes (or remains in) the SPO mode, icon  172   a  of the switchpack  170 , which corresponds to the SPO mode, is illuminated. Raising of the rotary knob  172  provides an indication to the user that the automatic selection condition is not available when the presence of a trailer  195  has been detected. In embodiments allowing selection of one of a plurality of operating modes when in the manual condition and a trailer has been defected, raising of the rotary knob  172  may serve to remind a user that a plurality of operating modes (subsystem control modes) may be chosen according to user selection by means of the knob  172 . 
     However, in some embodiments the rotary knob  172  remains in the refracted position although the VCU  10  has switched to the manual operating mode selection condition. However, a user may select an operating mode other than the instant mode by pressing on the knob  172  in order to cause the knob  172  to rise and become exposed. A user may then grasp the knob  172  and change the selected operating mode by rotation of the knob  172 . 
     Alternatively, if the VCU  10  remains in the automatic selection condition, the rotary knob  172  remains in the refracted position. The VCU  10  is precluded from assuming the Sand operating mode, or is limited to one or more operating modes, whilst towing is defected. In some embodiments no indication is provided to a user that the operating modes are limited, if the VCU  10  remains in the automatic selection condition. 
     In some embodiments, the system may be configured to cancel operation in the automatic selection condition, or limit the available modes when operating in the automatic selection condition, only if a trailer is detected whilst a transmission  124  of the vehicle  100  is in a Park mode (in the case of an automatic transmission), the vehicle  100  is stationary, or the presence of a trailer is detected after the vehicle  100  has been stationary but before the speed of the vehicle  100  exceeds a predetermined speed. This feature has the advantage that a change in vehicle behaviour (i.e. cancelling operation of the VCU  10  in the automatic mode or limiting the available modes in the automatic mode) whilst traveling above the predetermined speed due to the defection of a trailer may be prevented. 
     As noted above, in some alternative embodiments the VCU  10  is configured to assume the manual operating condition upon determining that the vehicle  100  is towing a load, if the VCU  10  is in the automatic condition when towing is determined. Selection of the automatic mode selection condition may be prevented whilst a trailer  195  is detected. When towing in the manual mode the VCU  10  may be operable to allow one of a prescribed one or more operating modes to be selected. 
     Operation of a vehicle according to one embodiment in which the prescribed one or more operating modes consist of two operating modes, is illustrated in  FIG. 8 . 
     At step S 201 , the VCU  10  determines whether the vehicle  100  is towing a load. If the vehicle  100  is not towing a load the VCU  10  repeats step S 201 . 
     If at step S 201  it is determined that the vehicle  100  is towing a load the VCU  10  continues at step S 203 . 
     At step S 203  the VCU determines whether the automatic operating mode selection condition is selected. If at step  3203  it is determined that this condition is selected, the method continues at step S 205 . If it is determined that this condition is not selected, the method continues at step S 213 . 
     At step S 205  it is determined whether the currently selected operating mode is a member of the manual/towing subset of two or more permitted operating modes. If at step S 205  it is determined that the currently selected operating mode is a member of the manual/towing subset the VCU  10  continues at step S 207 , otherwise the VCU  10  continues at step S 209 . 
     At step S 207  the VCU  10  remains in the currently selected operating mode whilst at step S 209  the VCU  10  switches to the default (SPO) operating mode. 
     The VCU then continues at step S 211 . At step S 211  the VCU  10  switches from the automatic selection condition to the manual selection condition. The VCU  10  remains in the operating mode in which it is operating when step S 211  is commenced. 
     The VCU  10  then continues at step S 219 . 
     If the VCU  10  has proceeded from step S 203  directly to step S 213 , then at step S 213  the VCU  10  determines whether the currently selected operating mode is a member of the manual/towing subset of operating modes. If at step  213  it is determined that the currently selected operating mode is a member of the manual/towing subset then the VCU  10  continues at step S 215 , otherwise the VCU  10  continues at step S 217 . 
     At step S 215  the VCU  10  remains in the currently selected operating mode whilst at step S 217  the VCU  10  switches to the default (SPO) operating mode. 
     The VCU  10  then continues at step S 219 . 
     At step S 219  the VCU  10  allows the user to select an operating mode from amongst the manual/towing subset of two or more operating modes as required, by manipulation of rotary knob  172  of the switchpack  170 . The VCU  10  only permits an operating mode selected from the manual/towing subset of operating modes to be selected by a user. 
     Subsequently, at step S 221  the VCU  10  is caused to operate in the manual condition with the user-selected operating mode from amongst the manual/towing subset of permitted operating modes. 
     The VCU  10  then continues at step S 219 . 
     Embodiments of the present invention have the advantage that vehicle composure may be maintained regardless of whether the vehicle is towing a trailer. This is at least in part because the vehicle  100  is prevented from operating in an operating mode that is inappropriate for towing, and might result in a reduction in vehicle composure. Operation of the vehicle  100  and associated control systems may also be made more intuitive to a user in some embodiments. 
     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.