Apparatus, method and computer program for controlling a vehicle

Abstract

A method, apparatus and computer program for controlling connection of a driveline within a vehicle (1), the method comprising: detecting a deceleration and/or brake demand while the vehicle is operating in a coasting mode and the vehicle speed is above a threshold speed, determining whether the driveline can be reconnected within a threshold time and controlling the driveline so that the driveline is not reconnected if it is determined that the driveline cannot be reconnected within the threshold time. The method alternatively comprising detecting a deceleration and/or brake demand while the vehicle is operating in a coasting mode and the vehicle speed is above a threshold speed, determining the vehicle's deceleration, determining a threshold deceleration, determining whether the vehicle's deceleration is greater or less than the threshold deceleration and controlling the driveline so that the driveline is not reconnected if the vehicle's deceleration is greater than the threshold deceleration.

Claims

1. A method of controlling connection of a driveline within a vehicle, the method comprising: detecting or receiving an indication of at least one demand from the group consisting of a deceleration demand and a brake demand while the vehicle is operating in a coasting mode in which the driveline is disconnected and a vehicle speed is above a threshold speed; determining a deceleration of the vehicle or receiving an indication of the deceleration of the vehicle; determining a threshold deceleration; determining whether the deceleration of the vehicle is greater or less than the threshold deceleration; and controlling the driveline so that the driveline is not reconnected if the deceleration of the vehicle is greater than the threshold deceleration.

2. The method as claimed in claim 1, comprising controlling the driveline so that the driveline is reconnected if it is determined that the deceleration of the vehicle is less than the threshold deceleration.

3. The method as claimed in claim 1, wherein the threshold deceleration is a default threshold deceleration.

4. The method as claimed in claim 3, wherein the default threshold deceleration is dependent upon the vehicle speed.

5. The method according to claim 1, comprising initiating reconnection of the driveline before it is determined whether the deceleration of the vehicle is greater or less than the threshold deceleration and wherein if it is determined that the deceleration of the vehicle is less than the threshold deceleration the reconnection of the driveline is terminated.

6. The method according to claim 1, comprising detecting a change in a brake demand or receiving an indication of a change in the brake demand and, in response, making a new determination of whether deceleration of the vehicle is greater or less than the threshold deceleration.

7. The method according to claim 1, wherein below the threshold speed the vehicle may be controlled to use a stop on the move mode of operation.

8. The method as claimed in claim 1, comprising transitioning directly from the coasting mode to a stop on the move mode when it is determined that a time period associated with decelerating the vehicle to the threshold speed is less than a time period associated with reconnecting the driveline, wherein the coasting mode is a mode in which the driveline is disconnected while neither an accelerator nor a brake pedal are pressed by a driver and the stop on the move mode is a mode in which the driveline is disconnected while the vehicle speed is below the threshold speed and the brake pedal is depressed by the driver.

9. An apparatus for controlling connection of a driveline within a vehicle, the apparatus comprising: means for detecting at least one demand of the group consisting of a deceleration demand and a brake demand while the vehicle is operating in a coasting mode in which the driveline is disconnected and a vehicle speed is above a threshold speed for receiving an indication of occurrence of the at least one demand while the vehicle is operating in the coasting mode and the vehicle speed is above the threshold speed; means for determining a deceleration of the vehicle or means for receiving an indication of the deceleration of the vehicle; means for determining a threshold deceleration; means for determining whether the deceleration of the vehicle is greater or less than the threshold deceleration; and means for controlling the driveline so that the driveline is not reconnected if the deceleration of the vehicle is greater than the threshold deceleration.

10. The apparatus as claimed in claim 9, comprising means for controlling the driveline so that the driveline is reconnected if it is determined that the deceleration of the vehicle is less than the threshold deceleration.

11. The apparatus as claimed in claim 9, wherein the threshold deceleration is a default threshold deceleration.

12. The apparatus according to claim 11, wherein the default threshold deceleration is dependent upon the vehicle speed.

13. The apparatus as claimed in claim 9, wherein the means for controlling the driveline is arranged so that the reconnection of the driveline is initiated before it is determined whether the deceleration of the vehicle is greater or less than the threshold deceleration and if it is determined that the deceleration of the vehicle is less than the threshold deceleration the reconnection of the driveline is terminated.

14. The apparatus as claimed in claim 9, comprising means for detecting a change in a brake demand or means for receiving an indication of a change in the brake demand and, in response, making a new determination of whether the deceleration of the vehicle is greater or less than the threshold deceleration.

15. The apparatus as claimed in claim 9, wherein below the threshold speed the vehicle may be controlled to use a stop on the move mode of operation.

16. A vehicle comprising the apparatus claimed in claim 9.

17. A non-transitory storage medium containing a computer program for enabling control of a vehicle, the computer program comprising instructions that, when executed by one or more processors, cause a system to perform, at least: detecting or receiving an indication of at least one demand of the group consisting of a deceleration demand and a brake demand while the vehicle is operating in a coasting mode in which a driveline is disconnected and a vehicle speed is above a threshold speed; determining a deceleration of the vehicle or receiving an indication of the deceleration of the vehicle; determining a threshold deceleration; determining whether the deceleration of the vehicle is greater or less than the threshold deceleration; and controlling the driveline so that the driveline is not reconnected if the deceleration of the vehicle is greater than the threshold deceleration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1 illustrates an example vehicle which may comprise embodiments of the invention;

(3) FIG. 2 illustrates an apparatus;

(4) FIG. 3 illustrates an apparatus within a system;

(5) FIG. 4 illustrates a method;

(6) FIG. 5 illustrates another method; and

(7) FIG. 6 illustrates another method.

DETAILED DESCRIPTION

(8) Examples of the present disclosure relate to methods, apparatus 11 and computer programs 27 for controlling a vehicle 1. The methods comprise: the method comprising: detecting or receiving an indication of a deceleration and/or brake demand while the vehicle is operating in a coasting mode and the vehicle speed is above a threshold speed, determining whether the driveline can be reconnected within a threshold time, and controlling the driveline so that the driveline is not reconnected if it is determined that the driveline cannot be reconnected within the threshold time. The methods alternatively comprise detecting or receiving an indication of a deceleration and/or brake demand while the vehicle is operating in a coasting mode and the vehicle speed is above a threshold speed, determining the vehicle's deceleration or receiving an indication of the vehicle's deceleration, determining a threshold deceleration, determining whether the vehicle's deceleration is greater or less than the threshold deceleration, and controlling the driveline so that the driveline is not reconnected if the vehicle's deceleration is greater than the threshold deceleration.

(9) FIG. 1 illustrates an example vehicle 1 which may comprise apparatus 11 according to examples of the present disclosure. The vehicle 1 comprises a prime mover 3 and a driveline 5.

(10) The prime mover 3 may comprise any means which may be arranged to provide a torque output for driving the vehicle 1. The prime mover 3 could comprise any suitable means for providing torque such as an internal combustion engine, an electric traction machine, a combination of an internal combustion engine and an electric traction machine or any other suitable means. In the example of FIG. 1 the prime mover 3 comprises a six cylinder internal combustion engine. It is to be appreciated that other prime movers could be used in other embodiments of the invention. For instance, in some examples the vehicle 1 could be a hybrid electric vehicle (HEV), a mild hybrid electric vehicle (MHEV) plug-in electric vehicles (PHEV) or any other suitable type of vehicle 1.

(11) The driveline 5 may comprise any means which may be arranged to transfer the power output provided from the prime mover 3 to the axles of the vehicle 1.

(12) The driveline 5 may be ‘in line’ (North South) as shown in FIG. 1 or a ‘transverse’ (East West) configuration (not shown) wherein the axis of the shafts of the transmissions lay in the longitudinal or lateral directions respectively in the car. The transmission could be automatic or semi-automatic such that operation of internal clutches was convenient for automation. The driveline 5 shown in FIG. 1 is a 4 wheel drive driveline, having an ‘in line’ mounted prime mover 3 connected to an automated multispeed transmission 4, connected to a transfer case case 6.

(13) The transfer case 6 may have means for splitting the power flow to deliver independent power to both the front differential 7 and rear differential 8 via the front propshaft 9 and rear propshaft 10 respectively. The transfer case 6 may have a multiple gear ratio option or it may only have a single ratio capability. The transfer case 6 may have disconnect clutches which may be necessary for gear range changes or part of a driveline disconnect system as are known in the art of active driveline systems. As an example, some driveline systems have multiple point disconnect locations which allow a driveline to disconnect and isolate complete parts of the driveline, such that the isolated portions of driveline can be brought to rest even when the vehicle is still moving.

(14) In embodiments of the invention the driveline 5 may be disconnected from the prime mover 3 under certain driving conditions to improve the fuel efficiency of the vehicle 1. This disconnection may be achieved, for example, by opening an existing clutch in the transmission 4 which separates the prime mover 3 output from the transmission 4 and the rest of the driveline 5 in FIG. 1.

(15) In another embodiment the driveline 5 could be disconnected from the prime mover by disconnecting a lock up clutch (not shown) situated in the torque converter which sits between the prime mover 3 and the transmission 4.

(16) In another embodiment the driveline 5 could be disconnected from the prime mover 3 by disconnecting a clutch (not shown) within the transfer case 6. Advantageously, when the clutch is placed in the transfer case 6 then during coasting for example the prime mover 3 and transmission 4 can be brought to idle speed or stopped to maximise the reduction in spin losses during coasting. The rest of the driveline downstream of the transmission 4 including transfer case 6, propshafts 9, 10 and differentials 7,8 would still be rotating relative to road speed while the prime mover 3 and transmission 4 were at rest or idling.

(17) In another embodiment the driveline 5 could be disconnected from the prime mover 3 by disconnecting clutches in either or both front differential 7 and rear differential 8. In this case, once the prime mover 3 was idling or stopped then it would be possible to reduce spinning losses in all components between the differentials and the prime mover 3 as those components would be rotating at a speed related to the idling speed of the prime mover or less than road speed if the prime mover is stationary.

(18) Disconnecting the driveline 5 from the prime mover 3 while the vehicle 1 is moving may improve the fuel efficiency of the vehicle 1 because the prime mover 3 does not act as a brake on the vehicle 1. Modes in which the driveline 5 is disconnected from the prime mover 3 may be referred to as sailing modes.

(19) In embodiments of the invention the vehicle 1 may have different sailing modes, such as gliding mode, coasting mode, stop on the move (SOTM) mode or any other suitable mode. The different modes may be available for different driving conditions of the vehicle 1. In embodiments of the invention a coasting mode may be used when the vehicle 1 is above a threshold speed and neither the accelerator nor brake pedal are pressed by the driver. A SOTM mode may be used if the vehicle 1 is travelling below the threshold speed and the brake pedal is pressed by the driver.

(20) In some example SOTM modes the driveline 5 of the vehicle 1 will be disconnected from the prime mover 3 if the brake pedal is pressed and the vehicle is travelling below a threshold speed. In some examples the threshold speed may be 17 kph. The driveline 5 may be reconnected to the engine if the brake pedal is released. In some example SOTM modes the engine may be stopped if the speed of the vehicle drops below 1 kph, 5 kph or higher example speeds. Other threshold speeds may be used in other example SOTM modes.

(21) In some example gliding modes the driveline 5 of the vehicle 1 will be disconnected from the engine 3 during constant acceleration where there is a throttle demand that is less than a threshold and the vehicle 1 is travelling within a threshold range of speeds. In some examples the threshold throttle demand could be less than or equal to 10%. In some examples the threshold range of speeds could be between 120 kph and 15 kph. Other threshold speeds could be used in other embodiments of the invention. In an idle gliding mode the prime mover 3 will drop to idle. In an off gliding mode the prime mover 3 may be stopped.

(22) In some example coasting modes the driveline 5 of the vehicle 1 will be disconnected from the prime mover 3 during throttle off deceleration where the brake pedal is not pressed and the vehicle 1 is travelling within a threshold range of speeds. In some examples the threshold range of speeds could be between 160 kph and 15 kph. Other threshold speeds could be used in other embodiments of the invention. In an idle coasting mode the prime mover 3 will drop to idle. In an off coasting mode the prime mover 3 may be stopped.

(23) The vehicle 1 also comprises an apparatus 11 which may be used to control the connection of the driveline 5 to the prime mover 3. Examples of the apparatus 11 are described below in relation to FIGS. 2 and 3. Examples of methods that may be performed by the apparatus 11 are described below in relation to FIGS. 4 to 6.

(24) The vehicle 1 may comprise an apparatus 11. The apparatus may comprise one or more controllers. Where the apparatus comprises more than one controller the controller may collectively be used to control the connection of the driveline 5 to the prime mover 3. For the avoidance of doubt any reference to controller herein may be taken to refer to a single controller or a plurality of controllers forming an apparatus. For example a vehicle system controller may arbitrate instructions between the prime mover 3 controller (not shown), transmission controller (not shown) and the traction controller (not shown).

(25) It is to be appreciated that the vehicle 1 of FIG. 1 is provided as an example and that embodiments of the invention may be provided in any suitable vehicle 1.

(26) FIG. 2 illustrates an example apparatus 11 which may be used to control the connection of the driveline 5 to the engine 3. The apparatus 11 comprises a controller 21. The controller 21 may be a chip or a chip set. The controller 21 may form part of one or more systems 33 comprised in the vehicle 1. The controller 21 may be arranged to control the connection and disconnection of the driveline within the vehicle 1 or any other control settings of the vehicle 1.

(27) The controller 21 comprises at least one processor 23, at least one memory 25 and at least one computer program 27.

(28) Implementation of a controller 21 may be as controller circuitry. The controller 21 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

(29) As illustrated in FIG. 2 the controller 21 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 27 in a general-purpose or special-purpose processor 23 that may be stored on a computer readable storage medium (disk, memory etc) to be executed by such a processor 23.

(30) The processor 23 is arranged to read from and write to the memory 25. The processor 23 may also comprise an output interface via which data and/or commands are output by the processor 23 and an input interface via which data and/or commands are input to the processor 23.

(31) The memory 25 stores a computer program 27 comprising computer program instructions 29 (computer program code) that controls the operation of the controller 21 when loaded into the processor 23. The computer program instructions 29, of the computer program 27, provide the logic and routines that enables the controller 21 to control the connection and disconnection of the driveline within the vehicle 1. The processor 23 by reading the memory 25 is able to load and execute the computer program 27.

(32) As illustrated in FIG. 2, the computer program 27 may arrive at the controller 21 via any suitable delivery mechanism 31. The delivery mechanism 31 may be, for example, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a compact disc read-only memory (CD-ROM) or digital versatile disc (DVD), an article of manufacture that tangibly embodies the computer program 27. The delivery mechanism may be a signal arranged to reliably transfer the computer program 27. The controller 21 may propagate or transmit the computer program 27 as a computer data signal.

(33) Although the memory 25 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/dynamic/cached storage.

(34) Although the processor 23 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable. The processor 23 may be a single core or multi-core processor.

(35) FIG. 3 schematically illustrates an example apparatus 11 within a system 33. The system 33 may be provided within the vehicle 1. The example system 33 of FIG. 3 comprises an apparatus 11 and one or more sensors 35 which may enable the apparatus 11 to obtain information. The information which is obtained by the apparatus 11 from the one or more sensors 35 may be used by the apparatus 11 to control the connection of the driveline 5 to the prime mover 3.

(36) The sensors 35 may comprise any means which may be configured to detect a physical parameter relating the vehicle 1 and provide an output signal to the apparatus 11 indicative of the detected parameter. The output signal may comprise information indicative of a value or magnitude of an output parameter. The apparatus and/or one or more sensors 35 may be provided within one or more other control systems such as the powertrain control module (PCM) or the vehicle supervising control module (VCM) or any other control systems. In such cases the apparatus 11 may obtain the information from the sensors 35 via the other control systems.

(37) In embodiments of the invention the sensors 35 may comprise one or more sensors 35A for detecting the current vehicle speed. The vehicle speed sensor 35A may be positioned at any suitable position within the vehicle 1. In some examples the vehicle speed sensor 35A may be a wheel speed sensor incorporated into the wheel hub. This sensor may be an inductive sensor installed as part of an ABS braking system. In some examples the vehicle speed sensor 35A may be a sensor mounted inside the transmission 4 and in this case it could be necessary to take into account shaft speed and gear ratio selected to calculate the correct referred wheel speed and vehicle speed.

(38) In some embodiments of the invention the sensors 35 may be arranged to obtain information which may be used to enable a deceleration of the vehicle 1 to be determined. For example, the wheel speed sensors may be used to determine vehicle speed v.sub.1 at time t.sub.1 and vehicle speed v.sub.2 at time t.sub.2. The deceleration may be calculated using the equation below:

(39) $\mathrm{deceleration}=\frac{v_1-v_2}{t_1-t_2}$

(40) Alternatively, and/or additionally deceleration may be calculated using a longitudinal accelerometer.

(41) In some examples the sensors 35 could comprise one or more sensors 35B for detecting a brake demand requested from the vehicle 1 instigated by the driver by applying pressure to the brake pedal. Such sensors 35B may be positioned in the braking pedal and measure depression of the pedal. Alternatively the sensors 35B may be positioned within a braking system to measure the pressure being applied by the brakes. The control system may have a brake pedal map calibrated to translate the hydraulic brake pressure generated by the brake pedal into an approximate brake torque demand signal.

(42) In some examples the sensors 35 may comprise one or more sensors 35C which may be arranged to determine the current mass of the vehicle 1. For instance the vehicle 1 may comprise one or more suspension springs and the current load within the suspension system may be monitored to determine the current mass of the vehicle 1. The deflection of the springs could be measured using any suitable means such as potentiometers as the mass of the vehicle 1 changes. Spring forces in each wheel could be calculated using f=kx, where k is the spring rate in N/mm and x is the deflection. In some examples the mass of the vehicle 1 may be determined by one or more sensors arranged to measure air suspension pressure, by using p=f/a calculations in each pneumatic cylinder or bellows system as is known.

(43) The sensors 35 may also comprise one or more sensors 35D which provide means for detecting the angle of inclination at which the vehicle 1 is travelling. Such sensors 35D could comprise vehicle wheel sensors, accelerometers or any other suitable means. The information obtained from such sensors 35D may be used to determine whether the vehicle 1 is travelling uphill or downhill or on a flat surface. Other inclination/gradient monitoring techniques are know where actual vehicle acceleration is mapped against actual engine load and the inclination can be estimated mathematically based on vehicle progression. Combining this method with known stand alone 3 axis accelerometer gradient estimation may be beneficial.

(44) The sensors 35 may also comprise one or more sensors 35E which comprise means for obtaining information about the current location of the vehicle 1 or other information about the current environment of the vehicle 1. For instance information may be obtained from a navigation system, GPS, cameras and/or wireless receivers which may provide information about the current location of the vehicle 1 and/or the traffic conditions in which the vehicle 1 is travelling. Such sensors 35E could also provide means for obtaining information about the surface of the road on which the vehicle 1 is traveling. For instance it may enable information to be obtained relating to current conditions of roads such as the weather conditions, whether or not it has been raining or if there is any surface water or any other suitable information. In some examples information about the surface of the road could be obtained by using wheel slip information combined with obtained location information and/or other information obtained by the one or more sensors 35.

(45) It is to be appreciated that the example sensors 35 illustrated in the system 33 are illustrated for example only and that other systems 33 may omit any of the sensors 35 described above. Similarly other systems could comprise any different sensors 35 in addition to or instead of the sensors 35 illustrated in FIG. 3.

(46) FIG. 4 illustrates a method which may be implemented using a system 33 as described above. At the start (block 40), the vehicle 1 is in coasting mode i.e. the vehicle 1 is moving within a threshold range of speeds and the accelerator is not depressed. When deceleration is detected (block 41) the controller begins to reconnect the driveline. Additionally, following detection of deceleration, at block 43, it is determined whether driveline 5 can be reconnected within a reconnection threshold time. If it is determined that the driveline 5 cannot be reconnected within the reconnection threshold time, the method proceeds to block 45 and the driveline 5 is controlled so that the driveline 5 continues to be disconnected from to the prime mover 3. If it is determined that the driveline 5 can be reconnected within the threshold time, the method proceeds to block 46 and the driveline 5 is controlled so that the driveline 5 is reconnected to the prime mover 3.

(47) FIGS. 5 and 6 illustrate example methods in more detail. The methods of FIGS. 5 and 6 could be implemented using the system 33 described above.

(48) The method starts (block 51) in the example method of FIG. 5 when the vehicle 1 is travelling in a coasting mode. In the coasting mode it is usual for the driveline 5 to be disconnected from the prime mover 3. The vehicle 1 is travelling above a threshold speed and the user is not actuating either the accelerator pedal or the brake pedal.

(49) The threshold speed may be the cut-off speed for entering SOTM modes of operation. The cut-off speed for entering SOTM modes of operation may depend on the type of prime mover 3 used and the arrangement of components, such as the transmission, within the driveline 5. The cut-off speed for entering SOTM modes of operation could be approximately 20 kph or any other suitable speed for example. Other threshold speeds may be used in other embodiments of the invention.

(50) At block 52 information indicative of the current vehicle speed is obtained by the apparatus 11. The information indicative of the current vehicle speed may be obtained from a sensor 35A. The sensors 35A could be part of another control system within the vehicle 1.

(51) At block 53 it is determined whether or not brake demand has been requested. A brake demand request may occur in response to a user actuating a brake pedal or initiating any other braking system within the vehicle 1.

(52) If no brake demand occurs then the method returns to the start (block 51) and the apparatus 11 continues to obtain information about the current vehicle speed periodically. Information about the current vehicle speed may be obtained at regular time intervals or any other suitable time interval.

(53) If a brake demand has been requested then the method proceeds to block 54 and information indicative of the current deceleration of the vehicle 1 is obtained. The information indicative of the deceleration may be obtained from one or more sensors 35 within the vehicle 1 and deceleration may be calculated as described previously or using any other suitable method.

(54) One possible method of calculating deceleration will now be described. For instance the deceleration may result from a brake demand. Information indicative of the applied braking force may be obtained from one or more sensors 35B within braking systems of the vehicle 1. The information indicative of the applied braking force may comprise information indicative of a magnitude of the applied braking force.

(55) The sensor 35B may be a brake pressure sensor measuring brake fluid pressure and the apparatus 11 (would this include brake controller?) could have a brake pressure map configured to estimate applied braking force on the vehicle, based on modelled data for the vehicle. Optionally a direct actual deceleration could be measured from an accelerometer in real time in response to brake pedal application by the driver.

(56) The deceleration may also comprise components due to external conditions such as air resistance, rolling resistance and any gravitational forces due to the gradient at which the vehicle is travelling. A dynamic vehicle model estimator can be utilised with in apparatus 11 to estimate accurately these effects on the vehicles deceleration over time, or direct accelerometer measurements could take this into account in real time. One or more sensors 35 within the vehicle 1 may provide the apparatus 11 with information indicative of each these components and/or with information which enables these components to be calculated. For example each vehicle model may have its own dedicated model configuration data built into the deceleration estimator including weight, co-efficient of drag, frontal area, speed related driveline losses and other vehicle parameters.

(57) As examples, air resistance causing deceleration on a vehicle versus speed may be estimated based on a body shape, e.g. a coefficient of drag CD) multiplied by vehicle frontal area, proportional to velocity squared, equates to a resistance force as is known.

(58) Frictional losses on mechanical components may be mapped during component development to produce maps which give good estimates of running losses versus torque and speed at various temperatures. These maps can be built into the warmup software of a vehicle to complement a vehicle control strategy. Components such as transmissions, differentials can be mapped independently or a whole driveline including all shafts can be tested at once as an assembly. Losses inside vehicle components may be broken down into static and dynamic losses, eg some losses are losses required to overcome component stiction and then additional losses may be due to dynamic losses proportional to torque transmission or fluid pumping loss rate proportional to speed of shafts and gears.

(59) At block 55 the apparatus 11 uses the obtained information indicative of the current vehicle speed and the obtained information related to the deceleration of the vehicle to determine the time it will take for the vehicle speed to reduce to the threshold speed.

(60) The time taken for the vehicle speed to reduce to the threshold speed may be given by

(61) $t=\frac{v-u}{a}$

(62) Where t is the time, v is the threshold speed, u is the current vehicle speed and a is the deceleration of the vehicle 1.

(63) Optionally, at the same time as performing the steps of block 55 reconnection of the driveline 5 may be initiated. This is because this reduces the time taken to reconnect the driveline if a decision is made that the driveline should be reconnected.

(64) At block 56 it is determined whether or not the calculated time is less than the reconnection threshold time where the reconnection threshold time is a predetermined time period equal or more than the time required to reconnect the driveline 5 to the prime mover. This determination may be made by comparing the time taken to reduce the vehicle speed to the threshold speed to the reconnection threshold time.

(65) If it is determined that the reconnection threshold time is greater than the time taken to reduce the vehicle speed to the threshold speed then the driveline 5 cannot be reconnected before the vehicle speed reduces to the threshold speed. In such cases, at block 57, the apparatus 11 controls the driveline 5 so that the driveline 5 is not reconnected to the prime mover 3. Thus, the disconnection between the prime mover 3 and the driveline 5 is maintained. This may allow, for example, the vehicle 1 to transition from the coasting mode to a SOTM mode without the driveline 5 being reconnected.

(66) However, if at block 56 it is determined that the reconnection threshold time is less than the time taken to reduce the vehicle speed to the threshold speed then the driveline 5 can be reconnected to the prime mover 3 before the vehicle speed reduces to the threshold speed. In such cases the method proceeds to block 58. At block 58 it is determined whether or not there is a change in the brake demand. For instance a user may change how hard they are pressing the brake pedal.

(67) If, at block 58, no change to the brake demand is detected then, at block 59 the apparatus 11 controls the driveline 5 so that the driveline 5 and prime mover 3 are reconnected. However, if a change to the brake demand is detected then the method returns to block 52 to begin the method again. Optionally the method is effected immediately without waiting for a time period to elapse.

(68) The method of FIG. 5 enables the disconnection of the driveline to be maintained as the vehicle transitions from a coasting mode to an SOTM mode based on calculations relating to the vehicle speed and deceleration of the vehicle.

(69) FIG. 6 illustrates another method that may be used in embodiments of the invention. At the start of the method (block 61) of FIG. 6 the vehicle 1 is travelling in a coasting mode as described above.

(70) At block 62 information indicative of the current vehicle speed is obtained by the apparatus 11. The information indicative of the current vehicle speed may be obtained from a sensor 35A. The sensor 35A could be part of another control system within the vehicle 1.

(71) At block 63 information indicative of a threshold deceleration for the current vehicle speed may be obtained. In some examples the information indicative of the threshold deceleration may be obtained by calculating the deceleration required to reduce the vehicle speed from the current speed to the threshold speed within a reconnection threshold time. The threshold speed may be the speed at which SOTM modes may be activated.

(72) In some examples the information indicative of the threshold deceleration may be obtained by accessing a database such as a lookup table or any other suitable database. The database may store information indicative of the threshold decelerations for given speeds and given vehicle conditions such as the mass of the vehicle 1 and the surface over which the vehicle 1 is travelling. The look up table may also take into account factors such as inclination at which the vehicle 1 is travelling, frictional losses, component temperatures or any other suitable factors. Several lookup tables may need to be evaluated and taken into account to calculate total deceleration forces acting on the vehicle, e.g. separate loss maps may exist for transmission, transfer case, front and rear differentials, summated bearing a shaft losses for the system may also be estimated. These tables could be estimated during component testing and development or could be based on empirical values.

(73) In some examples the information indicative of the threshold deceleration may be obtained before a brake demand is detected. For example, the threshold deceleration may be determined periodically and stored in a memory. Alternatively, the threshold deceleration may be determined when the vehicle speed passes a predetermined vehicle speed. This may enable the determination as to whether to reconnect the driveline 5 and prime mover 3 to be made more quickly.

(74) At block 64 it is determined whether or not a brake demand has been detected. The brake demand may be in response to the driver actuating the brake pedal. If a brake demand is not detected then the method returns to the start (block 61) and continues to obtain information about the current vehicle speed and the deceleration threshold at predetermined time intervals.

(75) If a brake demand is detected then information indicative of the current deceleration is obtained by the apparatus 11 at block 65 as described with reference to block 54 in FIG. 5. The information indicative of contributing factors to the deceleration may be obtained from one or more sensors 35 within the vehicle 1.

(76) In the method of FIG. 6 the information indicative of the deceleration may be obtained in response to the detection of the brake demand. Information indicative of other components contributing to deceleration of the vehicle could also be obtained upon detection of a brake demand. For instance information indicative of the friction and air resistance may be obtained at regular intervals. This information may then be retrieved at block 65.

(77) At block 67, which may begin at the same time as block 65, reconnection of the driveline 5 is initiated. The reconnection of the driveline may be initiated before the decision as to whether the driveline 5 should be reconnected is made. The time taken to make the decision may be much longer than the time taken to reconnect the driveline 5. This reduces the time taken to reconnect the driveline if a decision is made that the driveline should be reconnected. Conversely if the decision is to not reconnect the driveline 5 then the process of connecting the driveline 5 can be terminated before it is completed. The skilled person will understand that reconnection of the driveline at this time is optional and initiation of reconnection may be delayed until after the vehicle is stationary or begins moving after being stationary.

(78) At block 68 it is determined whether or not the current deceleration is above or below the deceleration threshold. This determination may be made by comparing the deceleration obtained at block 65 with the deceleration threshold obtained at block 63.

(79) If it is determined that the vehicle's deceleration is greater than the deceleration threshold then the driveline 5 cannot be reconnected to the prime mover 3 before the vehicle speed reduces to the threshold speed. In such cases, at block 69, the apparatus 11 controls the driveline 5 so that the driveline 5 is not reconnected to the prime mover 3. The reconnection of the driveline 5 which was initiated at block 67 is terminated. The disconnection between the prime mover 3 and the driveline 5 is maintained so that the vehicle 1 can transition from the coasting mode to an SOTM mode without the driveline 5 being reconnected.

(80) If at block 68 it is determined that the deceleration is less than the deceleration threshold then the driveline 5 can be reconnected before the vehicle speed reduces to the threshold speed. In such cases the method proceeds to block 70. At block 70 it is determined whether or not there is change in the brake demand.

(81) If, at block 70, no change to the brake demand has occurred then, at block 71 the apparatus 11 controls the driveline so that the driveline 5 is reconnected. However, if a change to the brake demand is detected then the method returns to block 62 and a new vehicle speed and deceleration threshold is obtained. This enables a new determination to be made as to whether or not to reconnect the driveline and prime mover 3 based on the new brake demand.

(82) The blocks illustrated in FIGS. 4 to 6 may represent steps in a method and/or sections of code in the computer program 27. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted.

(83) It is to be appreciated that modifications may be made to the example methods. For instance in the examples described above a threshold time is calculated based on the time it would take for the vehicle speed to reduce to a threshold speed. In other examples the threshold time may be a default threshold time. A plurality of different thresholds may be available for different conditions of the vehicle 1. The different conditions of the vehicles could be speed ranges, weather conditions, locations, traffic conditions or any other suitable conditions.

(84) In a further example, reconnection of the driveline, as described with reference to block 67 of FIG. 6, may not be initiated until it has been determined that the driveline should be reconnected for example at block 59 or 71.

(85) Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

(86) Features described in the preceding description may be used in combinations other than the combinations explicitly described.

(87) Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

(88) Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

(89) Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.