Technical field

The present invention relates to a method for making it possible to use, or prolong a use of, a higher transmission mode in a vehicle according to the preamble of claim 1, and a system for making it possible to use, or prolong a use of, a higher transmission mode in a vehicle according to the

preamble of claim 30.

The present invention relates also to a computer programme and a computer programme product which implement the method according to the invention.

Background

The following background description represents a description of the background to the present invention and therefore need not necessarily represent prior art.

The cost of fuel for motor vehicles, e.g. cars, trucks and buses, represents a significant expense for their owner or user. In the case for example of a haulage company, apart from the procurement cost of a vehicle, the main expense items for its routine operation are pay for the driver, repair and maintenance costs and the cost of fuel for the vehicle's propulsion. The fuel cost may here very greatly affect the company's profitability. A wide variety of different systems have therefore been developed for reducing fuel consumption, e.g. fuel-efficient engines and fuel-economising cruise controls .

Figure 1 depicts schematically a power train of a vehicle 100. The power train comprises a combustion engine 101 which in a conventional way is connected, via an output shaft 102 from the engine, usually via a flywheel, to an input shaft 109 of a gearbox 103 via a clutch 106. The clutch may for example take the form of an automatically operated clutch and may be operated by the vehicle's control system via a control unit 900 (Figure 9), which may also operate the gearbox 103. The gearbox 103 is here illustrated schematically as a unit but might physically also take the form of a plurality of interacting gearboxes, e.g. a range gearbox, a main gearbox and a split gearbox, which are situated along the vehicle's power train. The gearbox may comprise a suitable number of gear positions. Today's gearboxes for heavy vehicles usually have twelve gears for travelling forwards, two reverse gears and a neutral gear position. If the gearbox 130 physically comprises two or more divisional gearboxes as above, these twelve forward gears are divided into two in the range

gearbox, three in the main gearbox and two in the split gearbox, making a total of twelve gear positions (2*3*2=12). The vehicle 100 further comprises driveshafts 104, 105 which are connected to its tractive wheels 110, 111 and are driven by an output shaft 107 from the gearbox 103 via an axle gear 108, e.g. a conventional differential.

The vehicle 100 further comprises various different brake systems, e.g. a conventional service brake system which may for example comprise brake discs with associated brake linings (not depicted) adjacent to each wheel. The engine 101 may be controlled on the basis of instructions from a cruise control in order to maintain a constant actual vehicle speed and/or to vary the actual vehicle speed so as to achieve optimised fuel consumption within reasonable speed limits. The engine 101 may also be controlled by a driver of the vehicle. Brief description of the invention

On for example downhill runs or in situations where the vehicle has to reduce its actual speed, fuel savings have historically been made by reduced demand for positive engine torque or by dragging. Reduced demand for positive engine torque means that the propulsive force in the direction of movement which the combustion engine delivers via the tractive wheels is decreased, e.g. by reducing the fuel injection into the engine 101 and thereby reducing the fuel consumption. Dragging means running the vehicle with the power train closed, i.e. with the combustion engine 101 connected to the vehicle's tractive wheels 110, 111 while at the same time the fuel supply to the engine 101 is switched off. An advantage of this type of operation is that since the fuel supply to the engine is switched off the engine's consumption will likewise be zero. However, this type of operation also means that the combustion engine 101 will be driven by the vehicle' s tractive wheels via the power train, a state called "dragging", whereby the engine's internal losses result in a braking action, i.e. the vehicle being engine-braked.

Reducing the engine torque demanded and dragging certainly lower the fuel consumption but this lowering is not always optimised, partly because the reduced engine torque

nevertheless most often results in more fuel consumption than necessary and partly because the dragging also results in engine braking of the vehicle, which is not economical on fuel .

An object of the present invention is to further reduce the vehicle's fuel consumption. This object is achieved by the aforesaid method according to the characterising part of claim 1. It is also achieved by the aforesaid system according to the charactisering part of claim 30. It is achieved also by the aforesaid computer programme and computer programme product.

The present invention achieves the object, i.e. of reducing the fuel consumption, by allowing for as long a time as possible a gear choice which results in the lowest possible engine speed and hence maximum fuel saving. The invention makes it possible for freewheeling to be regarded as part of the vehicle's gear choice. The result is a further degree of freedom for effecting a lowering of the engine speed, a fact which is utilised according to the invention.

The present invention makes it possible to prolong a use of a higher transmission mode as compared with what has been possible according to previously known methods.

Alternatively, it makes it possible to use a higher

transmission mode in driving situations where previous known methods do not make this possible. In this specification the term "transmission mode" covers gear positions in the gearbox and freewheeling.

The object of making it possible to use the higher

transmission mode and/or prolong its use is to keep the engine speed down as low as possible for as long a time as possible, thereby lowering the average engine speed and thereby reducing the total fuel consumption.

One or more simulations of future speed profiles _s i _m are conducted for an actual speed for the vehicle, with the result that the system has very good control over how the vehicle will behave along the section of road ahead of the vehicle. This means that choices about raising the actual vehicle speed, followed by changing to a higher transmission mode, can be made which will intuitively seem correct to a driver of the vehicle. The amount of use of the automatic gear choice and/or freewheeling function will thus further increase, with the result that fuel-saving freewheeling and/or upshifts will lower the total fuel consumption.

The present invention can be implemented with little

additional complexity on board the vehicle, since the

invention can use data already available in other systems of the vehicle, e.g. road gradient information to which the vehicle's cruise control has access.

The present invention may be employed both in pedal operation, i.e. with the driver him/herself regulating the demand for torque from the engine, and in cruise control operation. Pedal operation here and in this specification means using

substantially any kind of control element suited to regulating the torque demand, e.g. an accelerator pedal or a manual acceleration device.

Brief list of drawings The invention is explained in more detail below with reference to the attached drawings, in which the same reference

notations are used for similar items, and

Figure 1 schematically depicts parts of an example of a vehicle, Figure 2 depicts schematically a driving situation,

Figure 3 is a diagram of engine friction as a function of engine speed, Figure 4 is a flowchart for the method according to the invention,

Figure 5 depicts an example of a simulation,

Figures 6a-b depict examples of simulations according to the invention,

Figure 7 depicts an example of a simulation according to the invention and a simulation according to prior art,

Figure 8 depicts an example of a number of simulations according to the invention, and Figure 9 depicts a control unit according to the invention.

Description of preferred embodiments

Figure 2 depicts schematically an example of a driving situation on a downhill run where a higher transmission mode may be employed to lower the fuel consumption. A higher transmission mode may also be employed in other driving situations, e.g. during a speed decrease which may take place on level roads, but for instructional reasons the driving situation in Figure 2 will be used to describe the principles applied by the invention. For the vehicle in Figure 2 it is possible to establish for the driving situation an energy relationship mgh= (½mv ₂ ² - ½mv, ² ) + (F„ _r + F _rr + + F _≠ + F _axU , _/n *s ( eq .1 ) in which

mgh is the vehicle' s potential energy, - ½mv2 ² is the vehicle' s kinetic energy at the top of the hill, ½mvi ² is the vehicle' s kinetic energy at the bottom of the hill,

F _ajr is the vehicle's air resistance, F _rr is the vehicle's rolling resistance, - F is the engine friction,

F _h is the gearbox friction,

F _axUlmv is friction in rear axles, seals and wheel

bearings, and

- s is the distance travelled between the top and bottom of the hill.

As may be seen in equation 1, various forces F _air , F _rr , F , F _gh and F _axlelnav work against the movement of the vehicle.

Figure 3 depicts an example of engine friction for a truck engine. It shows that the negative torque corresponding to the engine friction F , which works against the movement of the vehicle, increases with increased speed of the engine 101 (it should be noted that the y axis has a negative slope in Figure 3). Conversely, decreasing the speed of the engine reduces the amount of engine friction F , i.e. it reduces the negative torque, a fact which is utilised by the present invention .

According to the present invention, using a higher

transmission mode, i.e. upshift or freewheeling from a lower transmission mode used at the time of the simulations, goes on for a longer period of time than allowed by previously known solutions if this results in a fuel saving at the same time as having substantially no adverse effects upon the vehicle' s propulsion . In this specification an upshift further means that a higher possible gear position in the gearbox 103 is chosen, this higher gear position being physical, i.e. in the form of one of the regular gears in the gearbox. This higher gear

position also means that the engine 101 runs at a lower speed.

Freewheeling in this specification means that the vehicle' s engine is disconnected from its tractive wheels 110, 111, so the power train is open. This disconnection of the tractive wheels from the engine, also called opening of the power train, may for example be effected by putting the gearbox 103 into a neutral state or by opening the clutch 106. This means that during the freewheeling substantially no power is

transmitted from the engine 101 to the tractive wheels 110, 111. Disconnection of the engine 101 from the tractive wheels 110, 111 when the vehicle 100 is in motion is therefore referred to in this specification as freewheeling and may also be regarded as a highest theoretical/imaginary gear position for the power train. An opening of the clutch and/or the neutral position for the gearbox may therefore be regarded as a highest theoretical /imaginary gear position for the power train. In this specification, the term "freewheeling" also covers one of a plurality of prime movers of a vehicle, e.g. in a hybrid vehicle, being driven by the tractive wheels 110. It thus covers for example a mode of operating a hybrid vehicle whereby a combustion engine is disconnected from the tractive wheels 110 but an electric motor may continue to transmit power to the tractive wheels.

If freewheeling by opening the clutch and/or engaging neutral gear position is considered appropriate, the power train therefore has a number of physical gear positions, e.g. twelve in number, implemented in the gearbox 103, and at least one theoretical further gear position which is higher than the physical gear positions in the gearbox and entails opening the clutch and/or engaging neutral gear position in the gearbox 103 for at least one prime mover of the vehicle 100.

In this specification, the term "using a higher transmission mode" covers an upshift to a higher gear position for the gearbox and/or the power train, i.e. a mode of operation which comprises freewheeling, running with maximum torque in the higher transmission mode (the higher gear position) , running with dragging in the higher transmission mode (the higher gear position) or running according to any desired torque profile in the higher transmission mode (the higher gear position) .

An upshift causes the forces which work against the movement of the vehicle to decrease, since the amount of engine

friction F decreases with decreasing engine speed, as also depicted in Figure 3. An upshift may therefore lower the fuel consumption by reducing the resistance to the vehicle's movement .

Freewheeling causes the forces which work against the movement of the vehicle to decrease considerably, since the amount of engine friction F then decreases to a value substantially equal to zero (0) . Freewheeling may therefore considerably lower the fuel consumption through this decrease in the resistance to the vehicle. In certain freewheeling

situations, however, the engine has to be supplied with idling fuel to prevent its stopping, whereas in other situations the engine may be allowed to stop.

This means that from a fuel perspective it is often more advantageous to run the vehicle with the power train open, i.e. during freewheeling, than with dragging, i.e. with the power train closed while at the same time the fuel supply to the engine 101 is switched off. The reason for this is that the limited amount of fuel required to keep the combustion engine running when it is disconnected is counterbalanced by the vehicle being able to continue to freewheel with the engine disconnected for a longer distance, e.g. beyond the end of a downhill run. This is due inter alia to the fact that the vehicle will reach a higher speed when for example

travelling running downhill with the engine disconnected than when it is run with the power train closed and no fuel supply.

Moreover, the force which works against the vehicle's movement during freewheeling will be less when the combustion engine is disconnected from the driveshaft, since there will then be no engine brake force working against the vehicle's forward movement. This means that the vehicle will decelerate more slowly when for example it reaches the end of a downhill run, so freewheeling may often continue for a relatively long distance beyond for example the end of a downhill run. The result is a considerable decrease in fuel consumption.

The freewheeling described above refers to a conventional vehicle with a combustion engine, but the invention may also be employed on a vehicle with two or more prime movers, e.g. a hybrid vehicle which has a combustion engine and an electric motor. As mentioned above, freewheeling for a vehicle with two or more prime movers entails the engine being disconnected from the tractive wheels, i.e. the engine freewheeling, and the vehicle being powered by the electric motor alone. In this case the vehicle may, in this embodiment of the present invention, be freewheeled, i.e. the combustion engine may be disconnected from the tractive wheels, along more road

sections owing to the raising of the actual speed v _act than would be possible without the raising. During this

freewheeling the vehicle' s operation may be supported by power from the electric motor. The present invention determines whether a raising of the actual speed v _act for the vehicle, i.e. a raising of the speed at which the vehicle physically moves relative to the ground, may mean that a higher transmission mode can be used after the raising, or be used for a longer time, than if the raising had not been effected. This is described in more detail below.

To make it possible to decide this, one or more future speed profiles v _S i _m for the vehicle's actual speed are simulated for a section of road ahead of the vehicle. The simulation is therefore based on the vehicle' s current location and

situation, looks forward along the section of road and is based on its gradient. In one embodiment of the invention one or more of these simulations comprise at least one simulation of a raising of the actual speed v _act .

For example, the simulation may be conducted on board the vehicle at a predetermined rate, e.g. at a rate of 1 Hz, which means that a new simulation result is provided every second. The section of road for which the simulation is conducted represents a predetermined distance ahead of the vehicle, e.g. it might be 1 km long. The section of road may also be regarded as a horizon ahead of the vehicle, for which the simulation is to be conducted.

In addition to the aforesaid parameter of road gradient, the simulation may also be based on one or more from among a transmission mode, a mode of operation, a current actual vehicle speed, at least one engine characteristic, e.g.

maximum and/or minimum engine torque, a vehicle weight, an air resistance, a rolling resistance, a gear ratio in the gearbox and/or the power train, and a wheel radius. The road gradient on which the simulations are based may be obtained in various different ways. It may be determined on the basis of map data, e.g. from digital maps containing topographical information, in combination with positioning information, e.g. GPS (global positioning system) information. The positioning information may be used to determine the vehicle' s location relative to the map data so that the road gradient can be extracted from the map data.

Various present-day cruise control systems use map data and positioning information. Such systems may then provide the system for the present invention with map data and positioning information, thereby minimising the additional complexity involved in determining the road gradient.

The road gradient on which the simulations are based may be obtained on the basis of a map in conjunction with GPS

information, from radar information, from camera information, of information from another vehicle, from positioning

information and road gradient information stored previously on board, or from information obtained from traffic systems related to said section of road. In systems where there is information exchange between vehicles, road gradients

estimated by one vehicle may also be made available to other vehicles, either directly or via an intermediate unit such as a data base or the like.

The simulations are conducted on the basis of an assumption about an at least partial use of a higher transmission mode, i.e. a higher transmission mode than that used at the time of the simulations. As will be described in more detail below, a higher transmission mode may for example comprise freewheeling or a higher gear position for the vehicle's gearbox 103, the freewheeling being for example effected by opening the clutch 106 or by engaging a neutral gear. A future speed profile v _sim for the vehicle's actual speed is therefore simulated at least partly for a specific higher gear in the gearbox, for an open clutch or for a neutral gear in the gearbox. Two or more simulations may be conducted in parallel or sequentially so that simulations for all relevant transmission modes are made before evaluating the simulations and deciding which

transmission mode should be used. One or more of the

simulations of future speed profiles v ₃ i _m comprise also a raising of the actual speed v _act before the change to a higher transmission mode is made from a lower transmission mode used at the time of the simulation.

For each gear in the gearbox 103 there are related parameters such as gear ratio, efficiency and maximum permissible torque. One or more parameters may serve as input data for simulating the future speed profile v _sim for the respective gear.

It is therefore possible for example to simulate at a time one or more future speed profiles v _sim for raisings of the actual speed v _act , followed by using a higher transmission mode, i.e. using a higher gear in the gearbox, an open clutch and/or a neutral gear in the gearbox. These one or more future speed profiles v _sim will then be evaluated when deciding how the actual speed v _act should be controlled, i.e. whether it should be raised to make it possible to use, or prolong use of, the higher transmission mode, as will be described in more detail below .

Figure 4 is a flowchart for the method according to the present invention. As a first step 401 of the method one or more simulations of future speed profiles v _sim are conducted for the section of road ahead of the vehicle 100, basing the simulation for each profile on a gradient of the section of road. As described above, one or more simulations may thus be conducted for raising the actual speed v _act , followed by changing to a higher transmission mode, e.g. to a higher gear in the gearbox 103, to an open clutch 106 and/or to neutral gear position in the gearbox. In one embodiment the simulations also cater for the higher transmission mode entailing a particular mode of operation which may comprise one or more from among freewheeling, running with maximum torque in the higher transmission mode, running with drag torque in the higher transmission mode and running according to any desired torque profile in the higher transmission mode. The simulation may also cater for one or more vehicle

parameters, e.g. the vehicle's weight.

A second step 402 of the method evaluates whether a raising of the vehicle's actual speed v _act is appropriate to making it possible to use, or prolong the use of, the higher

transmission mode. This evaluation is based om the simulation of the at least one future speed profile v _sim .

As a third step 403 of the method this evaluation is then used in controlling the actual speed v _act . A factually supported decision may thus be taken about whether to raise the actual speed v _act and whether such a raising actually results in less fuel consumption by making it possible to use, or prolong the use of, the higher transmission mode. The control of the actual speed v _act , e.g. a raising of it, is effected in one embodiment by the control system itself. In another embodiment the control system uses a presentation unit to present for the driver a recommendation to raise the actual speed v _act , followed by a recommendation to change to a higher transmission mode, enabling the driver to choose whether to accept the recommendations presented or not.

The present invention basing the control of the actual speed v _act on one or more simulations of future speed profiles v makes it possible to achieve fact-supported control. The invention also makes it possible to ensure that repeated upshifts and/or downshifts do not take place, since the simulations are conducted over a longer period of time. Previous known solutions have not based control on evaluations over longer future speed profiles v _sim and have thus often led to upshifts and/or downshifts taking place in different sequences which a driver of the vehicle may well find very disturbing. The present invention therefore provides a form of control of the actual speed v _act , and hence also of

transmission modes used, which for the driver is continuous, intelligent and intuitively comprehensible. This will

increase the use of the function and thereby reduce the vehicle's total fuel consumption.

In one embodiment of the invention a gear position for a gearbox 103 forms part of a transmission mode. Here the evaluation of whether a higher transmission mode is usable after a raising of the actual speed v _ac t comprises evaluating whether an upshift to a possible higher gear position is appropriate after the raising. A possible higher gear

position may here comprise substantially any gear in the gearbox 103, apart from the lowest gear which is usable at the vehicle' s actual speed and/or at an actually demanded engine torque. The invention is however particularly suited to the higher gears in the gearbox 103, especially its highest gear, e.g. a twelfth gear if it has a total of twelve gears for the vehicle's forward propulsion. At least one simulation of a future speed profile v _S i _m is therefore conducted here in cases where the higher transmission mode takes the form of a gear in the gearbox 103.

In one embodiment of the invention, freewheeling forms part of one or more transmission modes. Here the evaluation of whether a higher transmission mode is usable after a raising of the actual speed v _act therefore comprises evaluating whether freewheeling is appropriate or not after the raising, in cases where the vehicle's engine is assumed to run idling during the freewheeling .

In one embodiment of the present invention a transmission mode for freewheeling comprises a state of the clutch 106. The evaluation of whether a higher transmission mode is usable after a raising of the actual speed v _act therefore here

comprises evaluating whether freewheeling by opening the clutch 106 is deemed appropriate after the raising.

Freewheeling by open clutch may therefore be effected by the raising if this is considered appropriate. Opening the clutch may also be regarded as a theoretical/imaginary highest gear for the power train.

In one embodiment of the present invention a transmission mode for freewheeling comprises a state of the clutch in a hybrid vehicle in which an electrical machine/electric motor can propel the vehicle even if the combustion engine is

disconnected by the clutch. The evaluation of whether a higher transmission mode is usable after a raising of the actual speed v _act therefore here comprises evaluating whether pure electric operation by opening the clutch 106 is deemed appropriate after the raising.

In one embodiment of the invention a transmission mode for freewheeling comprises a neutral gear position for the gearbox 103. The evaluation of whether a higher transmission mode is usable after a raising of the actual speed v _act therefore here comprises evaluating whether freewheeling by changing to this neutral gear position is deemed appropriate after the raising. Freewheeling by neutral gear may thus be effected by the raising of the actual speed v _ac t if this is considered

appropriate. Using the neutral gear position may also be regarded as a theoretical highest gear for the gearbox 103. One embodiment evaluates only one of the types of freewheeling for a specific vehicle, in which case only one out of open clutch and neutral gear position will be evaluated, although different ways of effecting freewheeling may be analysed for different vehicles.

These embodiments thus make it possible to achieve very fuel- efficient propulsion of the vehicle by the fact that the raising of the actual vehicle speed v _act makes it possible to use, and/or prolongs the use of, open clutch or neutral gear position if this is appropriate for the section of road ahead of the vehicle.

Figure 5 depicts in a simplified schematic form some

advantages of the present invention compared with prior art. In both this and the further drawings the invention is

illustrated by using freewheeling as the higher transmission mode. One skilled in the art will however appreciate that the principles in this and the further drawings are also

applicable in other higher transmission modes described in this specification. The chain-dotted curve in Figure 5 is a schematic illustration of freewheeling by use of prior art in a notional driving situation. The broken curve and the continuous curve are respective schematic illustrations of different embodiments for raising the actual vehicle speed v _act according to the present invention, followed by freewheeling in the same driving situation. V _set is a set speed chosen for a cruise control of the vehicle. V _min is a lowest permissible speed .

In previous known solutions the freewheeling begins at a first time Ti, after which the actual speed v _act during the

freewheeling drops until it reaches the lowest permissible speed v _min at a second time T ₂ , in the case of prior art freewheeling. The freewheeling then ends according to prior art and the actual speed v _act rises again.

In contrast, if deemed appropriate on the basis of one or more simulations of future speed profiles v _s i _m for a section of road ahead, the present invention raises the actual speed v _act for a first period T ₀ i, i.e. the period immediately before the first time Τχ. After this raising, freewheeling begins at the first time Ti, after which the actual speed v _act falls during the freewheeling until in various embodiments it reaches at the second time T ₂ the set speed v _se t or the lowest permissible speed v _min .

It is clear from Figure 5 that the freewheeling known from prior art solutions is usable for a shorter period T _{prior art} than the period T _h ig _her _transmode for which it is usable after the raising of the actual speed v _act according to the present invention. The present invention also makes it possible for well-supported decisions to be made about whether the raising should be effected or not, since they are based on one or more simulations of future speed profiles v _s i _m . The result is a controlled and factually based form of control of the actual speed v _act which also reduces fuel consumption through

freewheeling taking place for longer periods T _hig h transmode than the period T _pr i ₀ r_art of freewheeling according to previous known solutions . The value, i.e. the level, of the lowest permissible speed Vmin, is related in one embodiment to a current actual speed v _act for the vehicle. The lowest permissible speed may change dynamically and have different values for different

transmission modes.

The value of the lowest permissible speed v _min may in one embodiment be determined at least partly on the basis of information related to a cruise control system of said vehicle, e.g. on the basis of a set speed _set i i.e. a speed chosen by a driver for a cruise control system, or on the basis of a reference speed v _ref which is used by said cruise control system to operate a speed regulator. The

determination of the lowest permissible speed v _m i _n may also be effected by the cruise control system and be supplied to the system for the present invention.

The lowest permissible speed v _m i _n may generally be determined in various different ways. These limit values may for example be fed in by the driver in the form of an actual speed v _act for the vehicle or a percentage of a set speed v _set for a cruise control system of the vehicle and/or be based on the vehicle' s historical driving. The historical driving may for example be catered for by using an adaptive algorithm which is updated during the vehicle's journeys.

As non-limitative examples the lowest permissible speed may have the values v _min = 82 km/h or v _min = 0.98 * v _set km/h.

In one embodiment of the present invention a raising of the actual speed v _act is considered appropriate if the future speed profile _S i _m is below a highest permissible speed v _max along the section of road. This highest permissible speed may then be related to one or more from among a downhill control speed v _dhSl for the vehicle, a value of said raising of said actual speed v _act , a distance from at least one vehicle in front, speed limits and a curvature of said section of road. In one embodiment the highest permissible speed v _max is equal to the speed to which the actual speed v _act is increased during the raising. When v _max depends on distances from vehicles in front, it may be determined at least partly on the basis of a radar-based cruise control which can provide a distance from a vehicle in front. The highest permissible speed v _max in one embodiment is given a relatively lower value if the section of road comprises relatively tight or various consecutive bends.

In one embodiment of the present invention a raising of the actual speed v _act is considered appropriate on the basis of a predicted period of use t _h igh_transmode for said highest

transmission mode after the raising. This predicted use period is typically determined on the basis of the at least one future speed profile v _sim and the lowest permissible speed v _min , e.g. in such a way that the end point T2 of the predicted use period coincides with the point where the speed profile v _s i _m coincides with the lowest permissible speed v _min .

For example, the raising may be considered appropriate in the evaluation of whether the predicted period t igh transmode for the use of the highest transmission mode by said raising is longer than or equal to a predetermined period t _m i _n . This embodiment is illustrated schematically in Figures 6a and 6b, in both of which the predicted use time thi _g h_transmode for the higher transmission mode is longer than the predetermined period t _m i _n , in which case freewheeling is considered for example

appropriate and is applied.

In one embodiment of the invention the length of the

predetermined period t _min is determined in such a way as to avoid inconsistent control of the vehicle, while at the same time keeping the fuel consumption as low as possible. Here the predetermined period t _m i _n is therefore set long enough to ensure for example that freewheeling is not activated for shorter periods, in order to avoid disturbance caused by repeated activations and inactivations of, for example, freewheeling. The predetermined period t _min does however need to be short enough to ensure for example that freewheeling is activated when it actually saves fuel and does not irritate the driver. In one embodiment of the present invention a raising of the actual speed v _act is considered appropriate if the future speed profile v _s i _m steadily decreases along the portion Τχ-Τ ₂ of the section of road where the higher transmission mode is used. This embodiment is illustrated schematically in Figures 6a and 6b. In this embodiment the future speed profile v _sim according to Figure 6a, which during the period Ti-T ₂ when the higher transmission mode is used has a steadily decreasing profile and also a relatively low deceleration, would be considered appropriate for use of the higher transmission mode. In this embodiment, however, the future speed profile v _S i _m according to Figure 6b, which during the period Τχ-Τ ₂ when the higher transmission mode is used has a more oscillating or wavy profile and at least partly relatively high deceleration, would be considered inappropriate for use of the raising followed by the high transmission mode. The future speed profile v _s i _m in one embodiment may therefore be considered inappropriate if its deceleration during the period Ti-T ₂ when the higher transmission mode is used is too great, i.e. if the acceleration is less than a smallest permissible acceleration a _m in during the period Τχ-Τ ₂ . The future speed profile v _s i _m in one embodiment is considered inappropriate if it does not have for this period Ti~T ₂ a steadily decreasing profile.

Similarly it is possible in one embodiment of the invention for a raising in the actual speed v _act to be considered

appropriate if the future speed profile v _sim has acceleration greater than a smallest permissible acceleration a _m i _n along the section of road. Here the smallest permissible acceleration may have a constant value, e.g. -0.1 km/h/s. In one embodiment of the present invention the raising of the actual speed v _ac t is considered appropriate if the higher transmission mode can be used for a predetermined period tn _m which is longer as a result of said raising than without it, i.e. if (T _high _ _transmod e-Tp _ri or_art) ^≥ ti _im . This is illustrated schematically in Figure 7, depicting a future speed profile v _sim according to the present invention with a simulated raising of the actual speed v _act . Also depicted is a future speed profile v _pr i _0r art i ⁿ which no raising of the actual speed v _act is simulated. As may be seen in the diagram, the result is a period T _pr i _or _ _aEt for possible use of the higher

transmission mode without raising, which corresponds to the period when the speed profile v _prior _ _art is greater than the lowest permissible speed v _min .

The result for the speed profile v _sim according to the present invention, which comprises a raising, is a period T _high _ _t ransmode for possible use of the higher transmission mode, which period similarly corresponds to that where the speed profile v _sim is greater than the lowest permissible speed v _m i _n . The period for use of the higher transmission mode according to the present invention hi _g h_transmode is longer than corresponding periods where there is no raising of the actual speed v _act . If the difference between the periods is at least equal to a

predetermined period tn _m , the raising is considered

appropriate, i.e. if (T _h i _gh _ _tran s _mod e-Tp _r i _0r _ _ar t) ≥ tn _m .

In one embodiment the length of the predetermined period t _iim is determined in such a way as to result in significantly longer periods in the higher transmission mode than would be the case without raising. An example of such a lengthening is 15 seconds, i.e. ti _im = 15 s.

In one embodiment of the present invention the evaluation of whether the raising is appropriate comprises comparing a first simulation of the future speed profile v _{sim inc} i which comprises a first raising Vj_ _nc χ of the actual speed v _act , with at least a second simulation of the future speed profile _S i _m i _nc _2 which comprises a second raising v _{inc 2} of the actual speed v _act . The decision to raise or not is made by comparing these

simulations v _sim _ _inc _i, v _sim _ _inc _ ₂ . The raising should typically be effected according to the simulation which results in the most advantageous subsequent use of the higher transmission mode and when the simulation shows that the highest transmission mode can be used for at least a predetermined period t _min as a result of the raising. This is illustrated schematically in Figure 8a, in which a first simulation of a future speed profile v _{sim inc} χ which comprises a first raising v _inc i results in a longer possible period of use T _high _transmode inc l of the higher transmission mode than the period T _high _transmode_inc_2 which would be possible

according to the second simulation which comprises a second raising v _inc _ ₂ . Moreover, the higher transmission mode according to the first simulation of the future speed profile v _{sim inc λ} is usable for longer than a predetermined period t _min , as a result of the raising. Here the first simulation of the future speed profile v _S i _{m nc 1} is therefore the most advantageous and should be chosen, in which case this raising v _inc i of the actual speed Vact is considered appropriate.

Figure 8a illustrates two simulations for two different raisings, although similar simulations may be conducted for a larger number of different raisings, followed by their

evaluation with a view to spotting and adopting the most advantageous simulation in which the higher transmission mode is usable for longer than a predetermined period t _min and which comprises an appropriate raising of the actual speed v _act . In one embodiment of the present invention the evaluation of whether the raising is appropriate comprises comparing a simulation of the future speed profile _S i _{m now} in which the actual speed v _act is raised at a current time with at least one simulation of a speed profile v _S i _m later in which the actual speed v _act is raised at a later time. The decision to raise or not is then made by comparing these two simulations v _{sim now} , v _S im_iater which comprise chronologically separate raisings of the actual speed v _act . The raising should typically be

effected according to the simulation which results in the most advantageous use of the higher transmission mode. If the simulation with the later raising v _S i _m _i _ate r results in a longer time for the use of the higher transmission mode than the simulation with the earlier raising _s i _{m now} , the system quite simply refrains from controlling/posting the speed raising and evaluates it again when the next simulation round has been completed, which may for example be one second later. If the simulation v _sim _ _now with raising at the current time then results in a longer time for the use of the higher transmission mode than the simulation v _s i _m later would, the raising is then posted.

This is illustrated schematically in Figure 8b, in which a simulation of a future speed profile v _sim i _ate r which comprises a later raising results in a longer possible use T _high _ _transmode _iater of the higher transmission mode than the use period

Thigh_transmode_now which would be possible according to the

simulation v _sim _ _now which comprises a raising at the current time. Here the simulation of the future speed profile v _{sim late} r with the later raising is thus the most advantageous and should be adopted, in which case this raising of the actual speed v _act is considered appropriate if the use period

Thigh_transmode_iater is longer than the predetermined period t _min . In practice this may be implemented in such a way that the speed raising is not posted as long as T _high _ _transmode _i _a ter >

Thigh_transmode_now, so the speed raising is only posted when Thigh_transmode_later ^ Thigh_transmode_now and the USe ρ ^β ϊίθά

Thigh_transmode_now is longer than the predetermined period t _min . This implementation is possible in that the simulated speed profiles are updated (re-evaluated) on board the vehicle at a certain rate, e.g. at the rate of 1 Hz.

Figure 8b illustrates two simulations with raisings at

different times, although similar simulations may be conducted for a larger number of times, followed by their evaluation with a view to spotting and adopting the most advantageous which comprises an appropriate raising of the actual speed

Vact-

In one embodiment of the present invention the embodiments illustrated in Figures 8a and 8b may be combined so that a number of simulations comprising one or more different

raisings at one or more different times are performed. The most advantageous simulation can then be identified, whereupon the most advantageous raising may also be identified and be used in order to maximise the advantages afforded by the subsequent use of the higher transmission mode. In one embodiment a simulation (corresponding to a mode of operation) is considered the most advantageous if it results in lower energy consumption than other modes of

operation/simulations. This criterion may for example be applied to choose a most advantageous simulation from among the various different simulations, for various different times, for various different raisings or for various different raisings at various different times. If any of the

simulations which raise the actual speed v _act at a current time is the most advantageous from the energy perspective, a speed raising in accordance with that simulation is posted. If a simulation which raises the actual speed v _act later or does not raise it at all is the most advantageous from the energy perspective, the decision made is not to post any speed raising in this situation.

In one embodiment of the present invention the at least one future speed profile v _sim may also comprise a simulation of a maintaining of the actual speed v _act for a first period T0-T1, followed by a use of said higher transmission mode. Here at least two future speed profiles v _sim therefore need to be simulated, at least one of the simulations comprising a raising of the actual speed v _act , while at least one comprises the maintaining of the actual speed v _act for the first period TO-Tl, followed by the use of the higher transmission mode.

One skilled in the art will appreciate that a method for choice of transmission mode according to the present invention may also be implemented in a computer programme which, when executed in a computer, causes the computer to conduct the method. The computer programme usually takes the form of a computer programme product 903 which comprises a suitable digital storage medium on which the computer programme is stored. Said computer-readable medium comprises a suitable memory, e.g. ROM (read-only memory), PROM (programmable readonly memory) , EPROM (erasable PROM) , flash memory, EEPROM (electrically erasable PROM), a hard disc unit, etc. Figure 9 depicts schematically a control unit 900 provided with a calculation unit 901 which may take the form of

substantially any suitable type of processor or microcomputer, e.g. a circuit for digital signal processing (digital signal processor, DSP) , or a circuit with a predetermined specific function (application specific integrated circuit, ASIC). The calculation unit 901 is connected to a memory unit 902 which is situated in the control unit 900 and which provides the calculation unit with, for example, the stored programme code and/or stored data which the calculation unit needs to enable it to do calculations. The calculation unit is also adapted to storing partial or final results of calculations in the memory unit 902.

The control unit 900 is further provided with respective devices 911, 912, 913, 914 for receiving and sending input and output signals. These input and output signals may comprise waveforms, pulses or other attributes which the input signal receiving devices 911, 913 can detect as information and which can be converted to signals which the calculation unit 901 can process. These signals are then supplied to the calculation unit. The output signal sending devices 912, 914 are arranged to convert signals received from the calculation unit 901, in order to create, e.g. by modulating them, output signals which can be conveyed to other parts of the vehicle and/or other systems on board.

Each of the connections to the respective devices for

receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection. One skilled in the art will appreciate that the aforesaid computer may take the form of the

calculation unit 901 and that the aforesaid memory may take the form of the memory unit 902.

Control systems in modern vehicles generally comprise a communication bus system consisting of one or more

communication buses for connecting together a number of electronic control units (ECUs), or controllers, and various components on board the vehicle. Such a control system may comprise a large number of control units and the

responsibility for a specific function may be divided between two or more of them. Vehicles of the type here concerned are therefore often provided with significantly more control units than depicted in Figure 7, as one skilled in the art will surely appreciate.

In the embodiment depicted, the present invention is

implemented in the control unit 900 but might also be

implemented wholly or partly in one or more other control units already on board the vehicle or a control unit dedicated to the present invention.

One aspect of the invention proposes a system adapted to making it possible to use, or prolong a use of, the higher transmission mode. The system comprises a simulation unit adapted to simulating at least one future speed profile v _S i _m for an actual speed for the vehicle along a section of road ahead. The simulation is here conducted when the section of road is still ahead of the vehicle. The simulation of the at least one future speed profile v _S i _m is based on information related to a gradient of the section of road.

The system comprises also an evaluation unit adapted to evaluating whether a raising of an actual speed v _act for the vehicle is appropriate to achieving a possibility of using, or prolonging a use of, the higher transmission mode, which evaluation is based on the simulation of the at least one future speed profile v _s i _m . The system comprises also a use unit adapted to using the evaluation during control of the actual speed v _ac t ·

In one embodiment of the invention the raising of the actual speed v _dCt and the transmission mode to be used thereafter are controlled by the vehicle's control system itself. In another embodiment of the invention, directed towards providing the vehicle' s driver with information to support decisions during its driving, the use unit comprises a

presentation unit adapted to presenting a raising of the actual speed v _act , and the higher transmission mode. The decision here is thus about whether the raising should be effected and which transmission mode should be used by the driver .

The presentation unit is preferably integrated with, or close to, a user interface on board the vehicle which makes it easy for the driver to understand the presentation of the raising and the transmission mode.

The presentation of the indicators may take a variety of different forms, e.g. one or more indicators for raisings and transmission modes, such as arithmetical signs, numerals, letters, symbols, patterns, diagrams, colours, animations and sounds .

The system, i.e. the simulation unit, the evaluation unit, the use unit and, in certain embodiments, the presentation unit, is intended to be able to conduct all of the embodiments described above of the method according to the present invention .

One skilled in the art will of course appreciate that speeds and speed limit values indicated in this specification have equivalents and can be converted to engine speeds and engine speed limit values or torques and torque limit values. One skilled in the art will also appreciate that there is a very well-known relationship between distances, times and speeds, so the times and periods of time herein indicated have equivalents in terms of locations and distances. One skilled in the art will also appreciate that the above system may be modified according to the various embodiments of the method according to the invention.

The invention relates also to a motor vehicle 100, e.g. a truck or a bus, provided with at least one system for choice of transmission mode according to the invention.

The present invention is not restricted to its embodiments described above but relates to and comprises all embodiments within the protective scope of the attached independent claims .