The present invention relates to a method of initiating and managing a braking effect of a vehicle, upon release of the accelerator pedal. In addition, the position of the driver's foot respective to the accelerator pedal determines the intensity of the braking effect.

Background

When the driver of a vehicle ceases pushing the accelerator pedal, a braking effect may occur. Such a braking effect is mainly due to the engine brake if the vehicle is equipped with an internal combustion engine. In that case, the braking effect is relatively smooth. However, in particular for a vehicle equipped with a retarder, the braking effect may be stronger if the retarder is activated. This is also the case for a vehicle equipped with a recovery energy system, such as electrical or hybrid vehicles. When ceasing pressing the accelerator pedal, the energy recovery system may be activated and provides a resulting braking effect. Thus, if the driver wishes rolling free, he still needs to slightly press the accelerator pedal, in order to avoid the braking effect due to the retarder or the energy recovery system. This provides a certain discomfort. This additionally induces unnecessary energy consumption when pressing the accelerator pedal, while a free rolling is expected.

In addition, the current system activates or deactivates the retarder and/or the energy recovery system without transition. Such an on/off behavior may also appear uncomfortable to the driver.

Therefore, there is a need to optimize the behavior of a vehicle when releasing the accelerator pedal. In particular, there is a need to allow a free rolling effect when the driver's foot remains at the contact of the accelerator pedal. There is a further need for applying a smooth transitional braking effect when the driver's foot rises above the accelerator pedal.

Some detections means are already used to detect the position of the driver's foot respective to the brake pedal for safety purpose, like in US 6,4747,753.

Summary It is the aim of the present invention to provide a method of managing the braking effect of a vehicle when releasing the accelerator pedal. A "vehicle" includes any vehicle equipped with an energy supply unit, such as an internal combustion engine or an electrical motor or a combination of both, an accelerator pedal, and a device able to generate a braking effect, like a retarder or an energy recovery system or device. Such a vehicle is thus preferably a truck or a bus or any other industrial or commercial vehicle. In particular the present method aims at determining whether the driver's foot is in contact or above the accelerator pedal, and triggers a braking effect accordingly.

To this purpose, the method of the present invention comprises the following steps : a) Determining whether the foot of the driver is in contact with, or above the surface of the accelerator pedal,

b) If it is determined in step a) that the foot of the driver is above the accelerator pedal, initiating a braking effect, and

c) If it is determined in step a) that the foot of the driver is in contact with the accelerator pedal, without pressing the pedal, initiating a free rolling effect.

Above and below, the braking effect relates to the speed variation of the vehicle, and results from various braking actions. The braking actions are physical forces providing a resistance against the forward move of the vehicle, others than the forces applied with the braking system of the vehicle. The braking actions include for example the engine brake, if the vehicle is equipped with an internal combustion engine. The braking actions also include the activation of one or more retarder. Alternatively or in addition, the braking actions include the recovery of energy out of the kinetic energy of the vehicle, in case of a vehicle equipped with an energy recovery device, such as an electrical or hybrid vehicle. The braking effect can thus result from the combination of the energy recovery and a retarder activation, or the combination of the engine brake and a retarder activation, or any other combination of braking actions. In any case, the braking effect, in the sense of the present invention, excludes the activation of any element of the braking system of the vehicle, being either park brake system element or service brake system elements

A retarder may be of any kind. In particular, it includes pneumatic retarders, magnetic retarders and electrical retarders, as well as engine retarders, like compression brake and exhaust brake, and any combination thereof. The energy recovery system may also be of any kind, and includes any electrical, pneumatic, and mechanical inertia systems or devices.

Above and below, the free rolling effect relates to a driving mode wherein the vehicle is moved by its kinetic energy, and wherein the main resistive forces are abolished, while the accelerator remains inactivated. Said main resistive forces may be abolished by disconnecting the wheels from the energy supply unit of the vehicle, or by compensating them through small energy consumption. The free rolling effect is hereby considered as an advantageous alternative to the energy recovery.

In step a), the position of the foot of the driver is determined by any kind of sensor, either integrated to the accelerator pedal or external to the accelerator pedal. Sensors include optical sensors, like 2D and 3D cameras, infra-red or laser sensors. The sensor can also be selected among capacitive sensors, ultrasounds sensors, microwave or milliwave sensors. The sensor is preferably contactless. A contactless sensor, for the purpose of the present invention denotes a sensor which is not activated by physically contacting two or more mechanical sub-parts within said sensor. Such a sensor remains unaffected toward dirt or impurities, which could otherwise prevent the contact of the two mechanical sub-parts of the system. Furthermore, a contactless sensor should be understood as a sensor which does not need to be in physical contact with the foot of the driver to determine its position relative to the accelerator pedal.

In step b) the braking effect , including the retarder effect, as well as potential additional braking actions, is triggered by the presence of the driver's foot above the accelerator pedal, without being in contact with said accelerator pedal.

Such a braking effect may be managed according to a "non-progressive mode" or according to a "progressive mode".

In the non-progressive mode, when the driver's foot is above, and not in contact with, the accelerator pedal, the retarder effect is preferably applied according to the position of the retarder stalk, and the energy recovery system, if any, is fully activated. The positions that the retarder stalk can take include a rest position, wherein the retarder remains inactive, a full retarder position, wherein the retarder is fully activated, and one or more intermediate positions. In the progressive mode, when the driver's foot is above, and not in contact with, the accelerator pedal, the braking effect depends on the distance between the driver's foot and the accelerator pedal. This allows a smooth and progressive braking effect.

In particular, the braking effect progressively increases, either linearly or non-linearly, when the distance between the foot and the surface of the accelerator pedal increases. The braking effect can be either continuously proportional to the distance or can increase stepwise at predetermined distances.

In any one of the progressive and non-progressive modes, the braking actions may be applied simultaneously or sequentially. Also, in any one of the progressive and non-progressive mode, the braking effect may further be optimized according to various secondary parameters, like the payload of the vehicle, the environmental conditions, the 3D profile of the road, the speed of the vehicle, or the location of the vehicle.

One of the non-progressive mode or progressive mode may be preselected by the driver. Alternatively, the progressive or the non-progressive mode may be automatically selected according to various parameters. The non-progressive mode is preferably the default mode.

In step c), the free rolling effect may be performed by various ways, depending on the configuration of the vehicle. In case the vehicle is equipped with an internal combustion engine connected to the driveline through an automatic or robotized gearbox, the free rolling effect can be obtained by automatically disconnecting the engine from the drive line. Such a disconnection may be performed for example by placing the gearbox in neutral, or opening the clutch. Alternatively, the free rolling effect may be simulated by allowing a residual consumption of fuel, e.g. a consumption small enough to compensate the natural engine brake. For a vehicle equipped with an energy recovery system, such as an electrical or hybrid vehicle, the free rolling effect can be obtained by disconnecting the electrical motor or the energy recovery device from the driveline, or by stopping the energy recovery process, switching off the energy recovery device.

The present method may further comprise a step of maintaining the effect currently applied, either braking effect or free rolling effect, if the driver's foot is no longer detected above or on the accelerator pedal, and if no contrary instructions are provided, either by the driver, or by the automatic dynamic control systems of the vehicle.

Therefore, the present method comprises one or more of the following features, as well as any combinations thereof: - The braking effect is set to around 0 or limited to its minimum possible when the driver's foot is detected on the surface of the accelerator pedal, while said accelerator pedal is at its highest position.

The braking effect is activated when the driver's foot is detected above the accelerator pedal;

- The braking effect may be managed according to a progressive mode or a nonprogressive mode;

- The braking effect may be maintained, after it has been initiated, upon detection of the absence of the driver's foot on or above the accelerator pedal;

- The free rolling effect may be maintained, after it has been initiated, upon detection of the absence of the driver's foot on or above the accelerator pedal;

- The braking effect linearly increases with the increasing distance between the driver's foot and the surface of the accelerator pedal;

- The braking effect exponentially increases with the increasing distance between the driver's foot and the surface of the accelerator pedal;

- The braking effect decreases with the decreasing distance between the driver's foot and the surface of the accelerator pedal;

- The braking effect is maintained as long as the accelerator pedal is not pressed;

- The braking effect is maintained as long as no contrary instructions are provided;

- The braking effect is performed by a successive and/or combined braking actions of one or more of the engine brake, an energy recovery system, and one or more retarder;

- The braking effect is proportional to an amount of recovered energy;

The present invention further encompasses an arrangement comprising at least a foot sensor, preferably incorporated to the accelerator pedal, and at least one computing unit such as an ECU. Said computing unit may be connected to external sensors such as one or more load sensor, speed sensor, slope angle sensor. Said arrangement allows to determine at least whether the driver's foot is in contact with the accelerator pedal, while said accelerator pedal is at its highest position. Said arrangement preferably allows to determine whether the driver's foot is in contact of the accelerator pedal or above the accelerator pedal. It may further allow to determine the distance between the driver's foot and the surface of the accelerator pedal. The ECU may be connected to one or more coupling element, wherein said coupling element allows to connect, or disconnect the energy supply unit and the drive wheels. Such coupling elements include the gearbox and the clutch. The same ECU, or another one, can further activate one or more devices able to produce a braking effect, such as one or more retarder, or an energy recovery device.

The present invention is further directed to a vehicle provided with said arrangement, and able to manage the braking effect upon release of the accelerator pedal, according to the present method.

Brief description of the drawings

Figure 1: Scheme of the method

Figure 2a/2b: correlation between the braking effect and the position of the driver's foot relative to the accelerator pedal. Figure 3a: Driver's foot in contact with the surface of the accelerator pedal.

Figure 3b: Driver's foot above the surface of the accelerator pedal.

Figure 4: arrangement according to the present invention.

Detailed description The present method comprises a first step a) (100) of determining the position of the foot F of the driver relative to the accelerator pedal P of the vehicle.

The position of the driver's foot F can be determined according to various ways. According to a preferred embodiment, the position of the driver's foot F is determined by one or more foot sensor FS, as shown in figures 3a and 3b. A foot sensor FS is preferably integrated within the accelerator pedal P. In that case, it is advantageously positioned at the top surface of the accelerator pedal P or just below the surface, under a protective layer (not shown). It may be positioned at about 2 third of the length L of the accelerator pedal P, in such a way that it is proximal to the front extremity of the driver's foot F. This position coincides with the largest amplitude of the foot movement and thus provides better accuracy.

Alternatively, a foot sensor FS may be positioned above the accelerator pedal P, for example below the dashboard. Such a configuration may necessitate a calibration of the foot sensor FS, in order to take into consideration the thickness of the driver's foot F, since in this specific configuration, the foot sensor FS senses the top surface of the foot F instead of the bottom surface. The calibration may be performed by coupling the foot sensor FS with a position sensor PS of the accelerator pedal P. Such a position sensor PS is usually provided to determine the relative position of the accelerator pedal P respective to the floor of the vehicle, when the driver activates the accelerator pedal P. Thus, when the position sensor PS determines that the accelerator pedal P is at its highest position, then the foot sensor FS automatically considers the top surface of the driver's foot F as being the reference baseline, wherein the driver's foot F is in contact to the accelerator pedal P without pressing it. When the driver's foot F further arises away from the surface of the pedal P, meaning that it is coming closer to the foot sensor FS, positioned above the foot F, the corresponding braking effect can be initiated. Such a configuration provides the advantage to keep the foot sensor FP clean, or at least remote from potential dirt of the driver's shoes.

In an alternative configuration, the foot sensor FP may be remote to the accelerator pedal P, and positioned at one or the other side of the accelerator pedal P. This configuration is ideal for 2D or 3D cameras, since the lateral view of the pedal P and the driver's foot F is visible. Thus, it is easily detected when the foot F is arising away from the surface of the accelerator pedal P. As above, a calibration of the foot sensor FS may be performed wherein the accelerator pedal P is at its highest level. In case the lateral camera is active in the visible range, additional light may be provided around the pedal to facilitate the detection of the driver's foot position. For example, automatic light may be provided when the headlamps of the vehicle are activated, indicating that the daylight has decreased.

For the purpose of the present method, a foot sensor FS, or a combination of foot sensors, is at least able to determine whether the driver's foot F is in contact with the accelerator pedal P. A foot sensor FS, or a combination of foot sensors advantageously is able to determine a first position of the driver's foot F, being in contact of the accelerator pedal P without pressing it, and a second position of the driver's foot F, being above the accelerator pedal P. The driver's foot F is considered absent if it is not detected either on or above the accelerator pedal P, up to a predetermined threshold distance D. This is typically the case when the driver's foot F is positioned beside the accelerator pedal P, or at a distance above the accelerator P, higher than a given threshold D, such as around 50 cm, or around 40 cm. The foot sensor FS, or a combination of foot sensors may in addition be able to determine a distance d between the surface of the accelerator pedal P and the bottom surface of the driver's foot F. It is also envisaged that 2 separate foot sensors are used, wherein one foot sensor determines the presence of the driver's foot F, and determine its position on or above the accelerator pedal P, and wherein another foot sensor FS determines the distance d.

Thus, a foot sensor FS or a combination of foot sensors may detect on of the following situations:

- d is equal to 0, (d = 0), corresponding to the first position of the driver's foot, being in contact with the accelerator pedal P without pressing it;

- d is ether equal to 0 or higher than 0, (d =0 or d > 0), corresponding to the first position of the driver's foot F above-mentioned and a second position of the driver's foot F, being above the accelerator pedal P;

d is any distance value comprised between 0 and a threshold value D. D is typically several centimeters, such as around 50 centimeters, or around 30 centimeters, or around 20 cm above the accelerator pedal P, 0 < d < D;

A foot sensor FP is preferably of capacitive type, in such a way that it remains non sensitive to non-conductive material, like dirt or soil. However, optical sensor may be used, in particular if the foot sensor FP is above the accelerator pedal P, as discussed earlier. An optical sensor includes infra-red sensors, laser sensors, as well as 2D or 3D cameras. Other type of sensors like ultrasounds, microwave or milliwaves sensors may also be used. In general way, any sensor able to determine the presence of the driver's foot F on or above the accelerator pedal P, and/or the distance d between the surface of the pedal P and the driver's foot F, without physical contact, is usable.

In case a combination of several sensors is used to determine the driver's foot position, said foot sensors may be of the same type or of different type. For example, a capacitive foot sensor FS1 may be included in, or positioned above the accelerator pedal P, while one or more lateral sensor FS2, such as a 2D camera, is placed at one side or at two opposite sides of the accelerator pedal P. In another configuration, a series of capacitive sensors may be included along the length L of the accelerator pedal P, as shown in figures 3 a and 3 b, in such a way that the angle a formed between the surface of the pedal P and the bottom surface of the driver's foot Γ can be determined. The angle a is easily deduced from the distances separating each of the sensors from the foot F of the driver. The angle a can thus be used as an input parameter to optimize the braking effect instead of the distance d related to only one sensor.

Above and below, the parameter d may be determined at any location between the driver's foot F and the top surface of the accelerator pedal P. It is preferably determined below a front portion of the driver's foot F. In case the foot sensor FS is integrated to the accelerator pedal P, d relates to the part of the foot which is above the foot sensor FS.

The present method comprises an optional step a') (101) of determining the travelling mode of the vehicle. The driver may select a "progressive mode" or a "non-progressive mode".

In the non-progressive mode, the braking effect Z is provided according to the position p of the retarder stalk, once the driver's foot F is above the accelerator pedal P. In case the vehicle is equipped with an energy recovering system, then, said energy recovering system is activated according to a predetermined value, as soon as the driver's foot F is above the pedal P. Such a predetermined value is preferably the full capacity of the energy recovering system. However, any other setting may be determined. Thus, the braking effect Z results from the cumulative braking actions Y of the retarder and the energy recovering system. The position of the retarder stalk is determined by the driver, and can be either, at rest, or at full capacity or at an intermediate position.

In a progressive mode, the braking effect Z, provided by one or more of the devices each able to produce a braking action Y, is proportional to the distance d, between the accelerator pedal P and the driver's foot F. The braking effect Z may result from a combination of braking actions Y. The braking effect Z may alternatively result from the successive braking actions of an energy recovery device, and one or more retarder. The retarder may be activated either before or after the energy recovery devices. In case of successive braking actions Y, the braking action Y of the first activated device, like an energy recovery device, is progressively increased up to its maximal value according to the increasing distance d, and if distance d further increases, the braking action Y of the second device, like a retarder, is then triggered and progressively increased accordingly. The selection of a "progressive mode" or a "non-progressive mode" may be performed through a Human Machine Interface device, like a stalk, a switch, a rolling button. The selection is preferably performed through an existing command. The retarder stalk may be for example used to select a progressive or a non-progressive mode. In particular, the non- progressive mode may be selected by default when the retarder stalk is at any position different from the rest position, and a progressive mode may be selected if the retarder stalk is at rest, or at a further specific position.

In case no selection is performed, then the non-progressive mode is preferably applied by default. In step b), a braking effect Z may be provided (210) once the driver's foot F is no longer in contact with the accelerator pedal P. In other words when d≠ 0. This is applicable when the foot sensor FS only determines whether the driver's foot F is in contact with the accelerator pedal P, or d = 0. In this specific case, a braking effect Z is provided as soon as the driver's foot F is no longer detected at the contact of the accelerator pedal P, being either above or beside said accelerator pedal P, while no contradictory instructions are provided.

Alternatively, a braking effect Z may be initiated only when the driver's foot F arises above the accelerator pedal P, e.g. when d > 0. This is applicable when the foot sensor FS, or a combination of foot sensors, determines the two positions of the driver's foot F, being either in contact with the accelerator pedal P (d = 0) or above the accelerator P (d > 0), up to a given threshold limit D. Under these specific conditions, the braking effect Z may be maintained or released when the driver's foot F becomes absent from above the accelerator pedal P, being either beside or higher than a predetermined threshold distance D. The braking effect, once initiated, is preferably maintained when the driver's foot F moves beside the accelerator pedal P, or higher than a predetermined threshold distance D, and terminated when the driver's foot F comes again into contact with the accelerator pedal P.

The above two configurations correspond to a non-progressive mode, wherein the braking effect Z results from the braking action Ye of an energy recovery device, if any, combined with the braking action Yr of a retarder, wherein Ye corresponds to a predetermined activation of the energy recovery device, such as the full energy recovery, and wherein Yr corresponds to the position p of the retarder stalk. In another alternative, a braking effect Z may be initiated when the driver's foot F arises above the accelerator pedal P, wherein the braking effect Z is proportional to the distance d. This is applicable when the foot sensor FS, or a combination of foot sensors, is able to determine said distance d, thus authorizing a progressive mode, as shown in figures 2a and 2b. The braking effect Z may increase continuously and linearly with the distance d, as shown in figure 2a. Alternatively, the braking effect Z may be continuous but not linear. The braking effect Z can also be stepwise, as shown in figure 2b. In that case, a low braking effect Zl is obtained if the distance d remains below a first threshold dl while not being equal to zero, a stronger braking effect Z2 occurs if the distance d is between the first threshold dl and a second threshold d2, and a maximal braking effect Z3 is obtained if d is equal or above the second threshold d2. The first threshold dl may be a distance comprised between about 2 and 4 cm. the second threshold d2 may be a distance comprised between about 5 and about 8 cm. One should understand that any alternative intermediate thresholds, which may be determined to optimize the present method, are still covered by the present method. For a vehicle provided with an internal combustion engine. The low braking effect Zl, obtained when the driver's foot F is below the first threshold dl, may result from the engine brake only. The intermediate braking effect Z2, may be obtained by the low activation of a retarder in addition to the engine brake. A low activation of a retarder should be understood as an activation comprised between about 20% and about 50% of the capacity of said retarder. The strongest braking effect Z3, obtained when the foot F is above the threshold d2, corresponds to a strong activation of a retarder in addition to the engine brake. Such a strong activation should be understood as above about 50% of the capacity of the retarder. In this configuration, it is precised that the retarder is automatically activated according to the position of the driver's foot F above the accelerator pedal P. For a vehicle equipped with an energy recovery system, such as an electrical or a hybrid vehicle, the low braking effect Zl may correspond to a low level of energy recovery. Such a low level of energy recovery means a level comprised between around 10% and 30% of the recoverable energy. The intermediate braking effect Z2 corresponds to an intermediate energy recovery, such as for example an energy recovery level comprised between about 40% to around 60% of the recoverable energy. The highest braking effect Z3 corresponds to a strong energy recovery. A strong energy recovery may be any value above 60% of the recoverable energy, and preferably the maximal energy recovery value. In this specific case, a stronger braking effect may be obtained, if desired, by an automatic activation of one or more retarder, as mentioned above, in addition to the energy recovery process.

The present method comprises an optional step of determining the rolling status of the vehicle (150). The rolling status takes into account the actual driving conditions of the vehicle such as the speed of the vehicle (110), the slope of the road (120), the . load or the weight of the vehicle (130), and/or the traffic conditions (140). The rolling status may be ranked as follows (Figure 2c):

Rank A: The vehicle is fully loaded and the slope is increasing, the braking action YA should be lower than a reference braking action Yref. Rank B: The vehicle is empty or partially loaded and the road is horizontal, the braking action corresponds to the reference braking action Yref

Rank C: The vehicle is fully loaded and the road is horizontal, the braking action YC is slightly increased compared to the reference braking action Yref

Rank D: The vehicle is partially loaded or fully loaded, and the slope decreases, the braking action YD is significantly increased compared to the reference braking action

Yref.

Additional parameters like the speed of the vehicle or the traffic conditions may be included in the definition of the rolling status of the vehicle. According to the number of considered parameters, more ranks and/or different ranks may be defined.

The braking effect Z may or may not be optimized according to the rolling status of the vehicle, determined in the optional step 150.

In case the rolling status of the vehicle is not determined, and where the non-progressive mode is selected, the braking action Yr, related to the retarder, exclusively depends on the retarder stalk position p.

In case the rolling status is determined, and where the non-progressive mode is selected, the braking action Yr, related to a given position of the retarder stalk, may be adapted to the rolling status of the vehicle, in such a way that the braking effect Z corresponds to the braking effect actually expected by the driver, when his foot F arises above the accelerator pedal P. Thus, depending on the rank, A, B, C, or D, above mentioned, the braking action Yr of the retarder may be either decreased or increased for a given position p of the retarder stalk, corresponding to a reference braking action Yref .

In case the rolling status is not determined, and wherein the progressive mode is selected, the braking effect Z depends on the distance d between the driver's foot F and the accelerator pedal P. Thus, for a given distance d, the corresponding braking actions Y, related to one or more retarder, the energy recovery device, and potentially to other devices able to provide a braking action, are predetermined.

In case the rolling status is determined, and wherein the progressive mode is selected, the braking effect Z, may be adapted to the rolling status of the vehicle, in such a way that the braking effect Z corresponds to the braking effect actually expected by the driver, when his foot F arises above the accelerator pedal P to a given distance d. Thus, depending on the rank, A, B, C, or D, above-mentioned, the braking actions of the retarder, the energy recovery devices, and potentially other devices able to provide a braking action, may be either decreased or increased for a given distance d, Yref.

As a concrete example, if the rolling status of the vehicle is C, which corresponds to conditions where the engine brake is almost not effective due the inertia of the vehicle, either resulting from an heavy payload or from a decreasing slope, and d is below the first threshold value dl, the retarder may be activated in order to compensate the inertia of the vehicle and provide the braking effect Zl corresponding to the position of the driver's foot F. The retarder is otherwise not activated, since the engine brake suffices to produce the braking effect Zl. Similar reasoning is applied to hybrid or electrical vehicles, wherein the amount of recovered energy is tuned according to the rolling status of the vehicle.

It is also envisaged that, for a vehicle provided with an internal combustion engine, the engine brake is partly compensated, by small fuel consumption, when a braking action Y lower than the reference braking action Yref is expected. This could be the case for example when the vehicle is running up to an inclined road. For hybrid or electrical vehicle, small amount of energy may be supplied to the drive wheels for the same purpose.

In one embodiment, it is considered that the progressive braking effect is reciprocal, meaning that the braking effect Z increases when the driver's foot F is arising away from the accelerator pedal P and that it decreases when the driver's foot F is approaching to the surface of the accelerator pedal P. In that case, when the driver's foot Γ comes into contact with the accelerator pedal P, the free rolling effect is obtained.

In a second embodiment, the progressive braking effect may not be reciprocal, meaning that once a given braking effect Z has been reached, it is reversed only when the driver's foot comes again in contact to the accelerator pedal P. In other words, all the braking actions Y are cancelled when applying the foot F on the surface of the accelerator pedal P. Alternatively, the braking actions may be maintained as long as the accelerator pedal P is no pressed again.

In step c) (220) a free rolling effect is initiated if the foot F of the driver is in contact with the accelerator pedal P without pressing it. In other words, d = 0, and the accelerator pedal P is sensed to be at its highest position level.

The highest position level of the pedal P is determined by the mean of a sensor, like a position sensor PS.

The free rolling effect may be initiated upon releasing the accelerator pedal P, while the driver's foot F remains in contact with said accelerator pedal P. The free rolling effect may in addition be initiated when the driver's foot F comes back in contact with the surface of the accelerator pedal P, and thus terminates any braking effect Z potentially active. This can happen when the driver releases the brake pedal and wishes to maintain the speed of the vehicle using the free rolling effect.

The free rolling effect may be obtained by physically disconnecting the drive wheels E4 from the energy supply unit E3. Under such conditions, the vehicle is let free to progress by inertia, without resistive mechanical forces, such as the engine brake. The physical disconnection can be provided for example by automatically placing the gearbox on position neutral, or by automatically dissociating the clutch from the driveline. However, any other connection element between the driveline and the energy supply unit E3 can be released in such a way that all the wheels of the vehicle are free to roll. Alternatively, in case the vehicle is equipped with an energy recovery device, the free rolling effect may easily be obtained merely by switching off said energy recovery device.

Alternatively, the free rolling effect may result from consumption of small amount of energy, such energy being either fuel or electrical, to compensate the resistive mechanical forces. This is particularly applicable for a vehicle wherein the disconnection of the energy supply unit E3 from the drive wheels E4 cannot be automatically performed, like in a vehicle equipped with a manual gearbox. A simulated free rolling effect may or may not consider the rolling status of the vehicle determined in the optional step (150). In case the rolling status of the vehicle is taken into consideration, then the amount of consumed energy may be optimized accordingly.

In case the rolling effect is obtained by physically disconnecting the driveline from the energy supply unit, the optional steps (110, 120, 130, 140, 150) are of secondary importance.

In step c) (220) the free rolling effect is active as long as the driver maintains its foot F at the surface of the accelerator pedal P without pressing it. The free rolling effect may be maintained when the foot is suddenly removed from the surface of the accelerator pedal P, while not being above the accelerator P. This allows the driver to rest, not being obliged to maintain his foot in contact with the accelerator pedal P. In any case, the free rolling effect is deactivated as soon as the driver's foot F is sensed to be above the accelerator pedal P, wherein a braking effect Z is triggered.

The free rolling effect may in addition be automatically cancelled when the driver activates another command of the vehicle such as the brake pedal, the cruise control or other commands.

The present invention further comprises an arrangement allowing a braking effect Z upon releasing the accelerator pedal P, while maintaining a free rolling effect as long as the driver's foot F is in contact with the accelerator pedal P. In particular, the arrangement comprises a mean to determine the position of the driver's foot F respective to the accelerator pedal P. Said mean may comprise at least one foot sensor FS, as described above. The arrangement further comprises a mean to identify when the accelerator pedal P is at its highest position. Such a mean can be a position sensor PS. The arrangement comprises a computing unit like an ECU, receiving information related to the driver's foot position, provided for example by one or more foot sensor FS, and the accelerator pedal position, provided for example by the position sensor PS, and optionally receiving information related to the rolling status of the vehicle, provided for example by peripheral sensors, like slope sensor Sa, weight sensor Sb, speed sensors Sc. The computing unit provides an output data to one or more sub-unit of the vehicle selected from the group consisting of an energy recovery device El, at least one retarder E2, a connection mean between the energy supply unit E3 and the drive wheels E4. Said connection mean includes the gearbox and the clutch. The arrangement of the present invention further comprises a selection device E5, to activate or deactivate the "progressive mode". Such selection device E5 may be the retarder stalk, a mechanical switch, or a rolling wheel optionally provided with several positions. Said selection device E5 may alternatively be included in a menu wherein the driver can select the setting of the vehicle through a screen.

The present invention further encompasses a vehicle, and in particular an industrial vehicle, comprising the above-described arrangement and wherein a progressive mode is operable according to the above described method.