The present invention is directed to a system and a method for optimizing the energy consumption of a vehicle. In particular, the present invention allows detecting traffic events and provides relevant advices or instructions to the driver in anticipation of these traffic events. Another aspect of the present invention is to limit the brake activation.

Summary of the invention

The method of the present invention comprises a step of collecting information related to the characteristics of the vehicle. The characteristics of the vehicles comprise the physical properties inherent to the vehicle, like the average energy consumption per kilometer, the weight, the dimensions. The characteristics of the vehicle also comprise variable parameters, like the load or the tire pressure. The present method comprises a step of collecting information related to the traffic conditions of a selected itinerary. The traffic conditions include any information related to one or more of the traffic density, the meteorological conditions, the surface state of the road, the traffic signals, like stops or traffic lights, and referenced maintenance activities. The traffic conditions may be collected from an information network or directly sensed by the vehicle, by the means of specific sensors, such as camera, radar, infrared detection system.

The traffic conditions may be considered as traffic events that necessitate to be anticipated by the driver. Examples of traffic events are the followings:

Speed variation of the preceding vehicle,

Speed variation of the preceding wole queue,

- Incoming traffic jam,

- Road condition changes, such as slippery or damaged surface.

The position of the traffic event is also determined within the pathway of the vehicle. The position of a traffic event may be characterized by absolute references like longitude, latitude, altitudes. Alternatively, the position of the traffic event may be characterized according to points of reference within the pathway, such as a travel distance, a bifurcation, or any other relevant geographical reference.

In case a traffic event is identified, a speed profile is determined. The speed profile is computed according to various parameters, including one or more of the characteristics of the vehicle, the distance between the vehicle and the traffic event, the environmental conditions.

In case several traffic events are identified, a speed profile is computed for each of the traffic events. The speed profiles are compared and prioritized. The resulting speed profile is provided to the driver, as an advice or as an instruction. The resulting speed profile may also comprise automatic settings, like the limitation of the acceleration. In case the traffic event is mobile, the present method allows to maintain an optimal time gap.

Drawings

Figure 1 : scheme of the eco-driving system Figure 2: speed profile regarding 2 successive traffic events Figure 3 : speed profile in view of an incoming queue of vehicles Figure 4: speed profile in view of speed variation of a queue of vehicles Figure 5 : chart of the method. Detailed description

The eco-driving system 1 comprises an Eco Processor 2, an Event Identification Unit 3, a Vehicle Dynamic Model 4, an Event Ordering Unit 5, and an Advice Managing Unit 6. The eco-driving system 1 is connected to input data devices, which provide information related to the environment of the vehicle and/or the status of the vehicle. The input data devices include some communication systems A, like a Vehicle-to-Vehicle Communication unit Al, a Vehicle-to-infrastructure Communication unit A2, a Traffic and Travel Information broadcast unit (TTI) A3. The input data devices further include mapping systems B, comprising one or more of a global positioning system (GPS) Bl, and an Electronic Horizon unit B2, like an Advance Driver Assistance System (ADAS). The mapping system may provide information on the speed limitations, the traffic signals, the state of the roads, 2D and/or 3D profiles, and any other information related to a selected pathway.

The input data devices further include detection means C, like one or more distance sensors CI, and one or more internal sensors C2, which monitor the dynamic status of the vehicle, such as the load, the speed, the gear ratio of the vehicle. The distance sensors CI include any means to evaluate the distance between the vehicle and another vehicle or an obstacle. It can be an infrared sensor, a radar sensor, a 2D or 3D camera, ultrasounds systems, or any other equivalent means.

The input data devices may further comprise a Vehicle Data Storage unit D, wherein the static characteristics of the vehicle are stored, like the driveline configuration, the engine model, the transmission type, the dimensions, and the weight. The Vehicle Data Storage unit D is preferably a Read Only Memory (ROM) device.

The eco-driving system 1 is further connected to interface devices F allowing the transmission of information to the driver. Such interface devices include screens or display systems Fl, and audio systems F2.

The eco-driving system 1 may optionally further be connected to one or more human machine interface devices G, like the accelerator pedal, the gearbox stalk, or any other command having an impact to the energy consumption of the vehicle.

The Eco Processor 2 is connected to a first set of input data devices. The first set of input data devices comprises at least the Event Identification Unit 3, the internal detection means C2, and the mapping system B. The first set of input data devices may further comprise one or more of the Vehicle Data Storage unit D, and the distance sensors CI. The Eco Processor 2 computes speed profiles according to the data received from the first set of input data devices. The Eco Processor 2 is further connected to the Event Ordering Unit 5, to which it transmits the computed speed profiles.

The Event Ordering Unit 5 ranks the speed profiles received from the Eco Processor 2, and selects the speed profile to be applied. It is connected to a Advice Managing Unit 6, which organizes the information to be transmitted to the driver and/or the commands of the vehicle, through the communication interfaces F, and/or the Human Machine interfaces G used to command the vehicle. The Event Identification Unit 3 is connected to a second set of input data devices. The second set of input data devices comprises at least any one of a distance sensor CI, and a communication systems A. It preferably further comprises the mapping system B. More preferably the second set of input data devices comprises a combination of one or more of a distance sensor CI, one or more of a communication means A, and the mapping system B. The second set of input data devices may optionally include the internal sensors C2, and/or the Vehicle Data Storage unit D. The Event Identification Unit 3 identifies the traffic events according to the information provided by the second set of input data devices. Examples of traffic events may be: - The speed variation of the preceding vehicle,

The speed variation of the preceding whole queue,

An incoming traffic jam,

Road conditions change, like slippery or damaged surfaces,

The present invention also encompasses a device allowing the eco-driving assistance according to the method described herein. Such a device is equipped with the eco-driving system 1. The device may be plugged to, and unplugged from, the vehicle equipment. Alternatively, the device may comprise, in addition to the eco driving system 1, a mapping system, one or more communication means and one or more notification means like a screen or a loud speaker. It is envisaged that said device comprises input commands, such as touch buttons, allowing manually entering data. Examples of data that may be manually entered to the device are the characteristics of the vehicles, like the weight, the load, or a targeted pathway. A selection of predetermined programs may also be performed.

The present invention is further directed to a method of optimizing the energy consumption of a vehicle in accordance to the environment conditions, and in particular in accordance to the variations of the environment conditions.

The method comprises a step a) of monitoring the vehicle position, by the means of a mapping system B. The geographic position of the vehicle is followed from the start of the travel until the arrival of the vehicle at the targeted position.

The method further comprises a step b) of collecting information related to the status of the vehicle. Such information may be provided by one or more of the Vehicle Data Storage Unit D, and the internal sensors C2. In particular, in step b) data related to the weight and the speed of the vehicle, an estimated drag resistance value, and the gearbox ratio, may be collected. Step b) may optionally comprise a step bl), wherein static data are loaded in the system at the start of the mission, and a step b2), wherein the dynamic data are monitored during the travel. Alternatively, the static data and the dynamic data may be monitored simultaneously during the travel. Also, all the steps a), bl) and b2) may occur simultaneously at regular time intervals.

In a step c), the incoming traffic changes are monitored during the travel, and localized with respect to the geographical position of the vehicle. Step c) may occur at the same time as one or more of the preceding steps a) , bl), and b2) at regular intervals. The traffic changes may be monitored by one or more of the communication systems A and the distance sensors CI. A distance d, between the vehicle and the incoming traffic change, is determined. In case the traffic change is identified through a communication means A, the distance d may be determined by the means of a mapping system B. A time gap Tg is deduced from the distance d and the speed v of the vehicle according to the following formula (1 ): (l) Tg = d/v

Wherein

Tg determined the time gap between the running vehicle and the preceding vehicle, d denotes the distance between the running vehicle and the preceding vehicle, and v denotes the speed of the running vehicle. The time gap Tg determines the time to reach the identified traffic change if the running vehicle maintains its current speed v.

In case the time Tg, related to a traffic change or a road condition, becomes equal to or below a predetermined threshold value Ta, the incoming traffic change, or the road condition, is identified as a traffic event E and it is computed as such within the Event Identification Unit 3. The threshold value Ta may or may not depend on the traveling speed of the running vehicle and its characteristics, like its load. The threshold value Ta may further depend or not depend on the weather conditions.

A speed profile SP is determined in a step d), at least according to the time gap Tg and the speed and the characteristics of the running vehicle. The speed profile SP may further consider the nature of the traffic event E, which can be classified as one of the following events:

- E: The speed variation of the preceding vehicle,

Eq: The speed variation of the preceding whole queue,

- Ej: An incoming traffic jam,

Ew: incoming road conditions change, like slippery or damaged surfaces,

The speed profile SP is computed in such a way to maintain an optimal time gap Tg between the running vehicle and the identified traffic event E. The optimal time gap is preferably comprised between a safety value Ts and a reference value Tr, wherein Ts corresponds to a short time, wherein the brake system needs to be activated to avoid an impact, and wherein Tr is the time at which a smooth deceleration may be initiated. A smooth deceleration should be understood as a coasting period, which allows slowing down the running vehicle without activating the brake system. In case the vehicle is equipped with an energy recovery system, the coasting period may corresponds to a deceleration period where a part of the energy is recovered. Each of Ts and Tr depends on the initial speed of the vehicle, and its characteristics, in particular, its running weight. Although Ts and Tr may vary according to the nature of the event E, the following formula (2) is always verified:

(2) Ts < Tr

Step d), related to the computing of the speed profile SP, may be subsequent or concomitant to step c), directed to the identification of a traffic event E.

When only one vehicle is identified in front of the running vehicle, the speed profile SP is determined according to the speed of the preceding vehicle or to its speed variations, as illustrated in figure 2. In case the preceding vehicle runs at a stabilized speed lower than the speed of the running vehicle, the aim is to coast until the running vehicle arrives at a stabilized distance behind the preceding vehicle. Also, each speed variation of the preceding vehicle is considered as a separate traffic event E and triggers a new speed profile SP. Thus, coasting instruction in maintained as long as the time separating the running vehicle and the preceding vehicle remains below the reference time Tr and above the safety time Ts. In case the preceding vehicle accelerates, in such a way that the time gap Tg separating the running vehicle and the preceding vehicle become higher that the reference time Tr, then the coasting instruction disappears and the driver is allowed to accelerate. Thus, during a slowing down period of the preceding vehicle, followed by an acceleration period, the driver could avoid the brake activation and limit his speed variation. It may be optionally determined that the reference time Trd in a deceleration phase is different from the reference time Tri of the acceleration phase of a given speed profile SP. In particular, once the preceding vehicle accelerates, it can be advantageous to wait until the reference time Tri has lapsed, which is higher than the reference time Trd, before allowing the driver accelerating. This would avoid starting accelerating again while the preceding vehicle starts again slowing down just after its acceleration. The speed and speed variations of the preceding vehicle can be determined by the means of one or more of the communication means Al, A2, A3, or by one or more detection means CI.

Above and below the terms "running vehicle" denote the vehicle equipped with the eco- driving assistance described herein, and also object of the present invention.

In case more than one vehicle is ahead the running vehicle, a queue head vehicle zl is followed by several other vehicle z2 to zn, wherein n denotes the number of vehicles between the running vehicle and the queue head vehicle zl . Figure 3 provides an example wherein a vehicle zl, followed by 3 other vehicles and by the running vehicle, slows down from a speed vl to a speed v2. The speed and the speed variation of the queue head vehicle zl are analyzed in order to anticipate a braking phase. A queue head vehicle zl may be the real leading vehicle or a vehicle within a queue, which is sufficiently ahead of the running vehicle, and followed by other vehicles. A leading vehicle is not necessary a specified vehicle. It can be determined that any vehicle within a queue, ahead of the running vehicle, is qualified as a queue head vehicle as soon as its speed changes. The aim is to anticipate the subsequent change of speed of the following vehicles. A speed variation of a vehicle may be determined by the mean of a vehicle-to-vehicle communication mean Al, or vehicle-to-infrastructure communication means A2, or traffic and travel information broadcast unit A3. As previously discussed the speed or speed variation of a vehicle zl triggers a speed profile SPq, comprising a reference time Trq and a safety time Tsq. However, in the case of a queue, the reference time Trq and the safety time Tsq, are not necessarily determined in the same way as above- discussed with only one preceding vehicle. At least the reference time Trq, related to the leading vehicle zl , at which the coasting should start, may consider the presence and the behavior of the following vehicles z2 to zn. Under these circumstances, the reference time Trq in a queue, may be higher than the reference time Tr related to a preceding vehicle. In other words, the running vehicle, following a queue wherein the first vehicle zl is braking, can start coasting, due to the time reference Trq, before the speed of the preceding vehicle varies, and triggers a coasting instruction. Thus, the following vehicles z2 to zn are successively braking, while the running vehicle is just coasting. If the leading vehicle zl stabilizes at a second speed v2, then the system computes the coasting period which would allow the running vehicle to arrive at an optimal time gap Tg from the last vehicle of the queue. A warning instruction can anyway be provided to the driver if the time gap Tgq with the leading vehicle zl , has decreased too much, until a safety time Tsq, or if the time gap Tg with the last vehicle of the queue, preceding the running vehicle, has reached the safety time Ts. In case the leading vehicle zl accelerates again instead of stabilizing the speed at v2, the time gap Tgq increases above the corresponding reference time Trq, and the coasting instruction stops, even though the following vehicles z2 to zn are still slowing down or have not yet accelerated. Thus, the eco-driving system anticipates the progressive speed increase of the queue, and avoids reducing the speed of the running vehicle in a too large extent. Figure 4 provides an example wherein the leading vehicle zl slows down from a first speed vl to a second speed v2, and accelerates again to the first speed vl . The speed of the running vehicle during its coasting phase varies significantly less that the speed of the other vehicles, not equipped with the eco-driving system described herein.

It has to be noted that in case of a queue, the reference time Trqd in a slowing down period may be either equal or different than the reference time Trqi in an accelerating period, in order to take into account the temporization of the following vehicles z2 to zn. In particular, the reference time in a decelerating phase Trqd can be lower than a reference time Trqi in an accelerating phase in order to let sufficient time to the following vehicles z2 to zn to successively accelerate. Otherwise, the risk is to receive contradictory information, when the leading vehicle zl is accelerating, while the last vehicle, preceding the running vehicle is still in a braking phase. In the latter case, precedence is given to the reduced distance with the last vehicle of the queue, and a coasting instruction is provided to the driver or maintained. As discussed below, a notification time Tnq and a warning time T q may also be provided.

In case of a traffic jam, the system computes a time gap Tgj according to the following formula ( ):

(l ') Tgj= dj/v Wherein

Tgj denotes the time gap between the running vehicle and the traffic jam, dj denotes the distance between the running vehicle and the last vehicle of the incoming traffic jam, and v denotes the speed of the running vehicle.

The traffic jam may be identified thanks to one or more of a vehicle-to-vehicle communication mean Al, a vehicle-to-infrastructure communication means A2 and a traffic and travel information broadcast unit A3. The traffic jam may be considered as a traffic event Ej if the time gap Tgj reaches a threshold value Taj. In addition, a traffic jam may optionally be considered as a traffic event Ej only if the length of the traffic jam is equal or higher than a given length Lj. Once it is considered as a traffic event Ej, a speed profile SPj is determined, wherein a reference time Trj and a safety time Tsj are computed. As discussed below, a notification time Tnj and a warning time Twj may also be determined. The notification times Tnj and the warning time Twj may be tuned or adjusted as discussed below. Thus, the running vehicle is able to arrive at the traffic jam only by coasting, without being obliged to brake. A traffic jam is hereby considered as a fixed obstacle. Any other similar identified obstacle may be managed in the same way. instead of a traffic jam, a temporarily closed road, an accident, or any other traffic event identifiable by the usual communication means A, may trigger a speed profile according to the present invention. It is also possible to adapt the speed of the running vehicle according to an incoming change of weather conditions. Dangerous weather variations like fog, or icy portions exposed to strong and cold wind, or storms with strong rain, may be referenced and considered as traffic event Ew. For each weather condition, a specific speed vw may be predetermined. The aim is to compute a speed profile SPw and instruct the driver to coast, in such a way that he arrives before the weather event Ew at the recommended speed vw. Such a speed profile SPw comprises a reference time Trw, a safety time Rsw, and optionally some notification times Tnw, and warning time Tww. The same method may of course be applied for a particularly dangerous passage on a road, even under good weather conditions, or for any other identifiable road condition that necessitates an adjusted speed. The traffic changes and road conditions are permanently monitored, and several traffic events En may be determined at the same time. It is therefore necessary to organize the traffic events En in a step e). It is for example envisaged that at Ta, 2 traffic events El and E2 are identified. For example, El may correspond to a slowing down of the preceding vehicle, and E2 may correspond to a traffic jam. Thus, a first speed profile SP1 is determined, characterized by a first notification time Tnl, reference time Trl, warning time Twl, and safety time Tsl adapted to the slowing down of the preceding vehicle. A second speed profile SP2 is also determined, characterized by a second notification time Tn2, a second reference time Tr2, a second warning time Tw2, and a second safety time Ts2, corresponding to the traffic jam.

The 2 speed profiles SP1 and SP2 are ranked or prioritized according to predetermined criteria. The criteria may comprise the type of traffic event. It may be determined that an incoming traffic jam is prioritized with respect to a slowing down of the preceding vehicle. It may be determined that the fixed traffic events, like a traffic jam or a road condition change, are prioritized with respect to the mobile traffic events, such as the slowing down of the preceding vehicle or the preceding queue. The fixed obstacle may further be organized. It may be for instance determined that traffic jam, is prioritized compared to a second fixed traffic event, such as a mere change of road conditions.

Alternatively or in addition, the ranking criteria may include one or more of the characteristic values Tn, Tr, Tw and Ts of each speed profile SP. It may be determined that the speed profile wherein the safety time Ts is the lowest is prioritized. Alternatively, the speed profile wherein the reference time Tr is the lowest may be prioritized in a first evaluation, and during the application of the speed profile, it may be determined that a safety time Ts is prioritized over any reference time Tr. In a more refined embodiment, the ranking criteria may consider one or more of the characteristic values Tn, Tr, Tw and Ts of a speed profile SP, and may be optimized in a separate step according to the type of traffic event E.

Preferably, the speed profile computation is performed between the time Ta, where a traffic event E is identified, and the notification time Tn. Also, the ranking operation is preferably performed between Ta and Tn. Several traffic events En are computed during a given pathway, each of them triggering a corresponding speed profiles SPn, which is collected with the other speed profiles already determined and still on going. All the ongoing speed profiles are permanently object to a ranking activity.

It has to be noted that a second traffic event E2 is any new event that triggers a speed profile determination. A second traffic event E2 may induce a speed profile change due to the modification of the priorities. A second traffic event E2 may be for example a second speed variation of the same preceding vehicle, or the insertion of a new vehicle behind the preceding vehicle. Under this last condition, it is envisaged that the reference time Tr2 of the second traffic event E2 is already lapsed and that the next available time for the speed profile SP2 is the safety time Ts. Thus, E2 becomes the prioritized traffic event.

Once a traffic event E is identified, a notification is sent to the driver in a step f). Such a notification may be an instruction to decelerate by coasting, in anticipation of the incoming traffic event E. The coasting avoids the unnecessary maintenance of the vehicle speed, which is energy consuming. It also avoids a strong brake activation at the moment the driver realizes the approach of the traffic event E.

The notification may be sent to the driver at a time Tn, which may be after or at the same time a speed profile SP is determined. The notification is sent to the driver sufficiently early to allow the driver reacting to the instruction. In particular, the notification is preferably sent to the driver few milliseconds before the reference time Tr determined in the speed profile SP. If the traffic conditions allow it, the driver can be notified about one second or several seconds before the reference time Tn, that a coasting period will start. In particular, the notification may be sent at a time Tn in accordance with the formula (3) or the formula (3 '):

(3) Tr < Tn < Ta

(3 ) Tr < Tn < Ta

Thus, the driver is able to start coasting at the reference time Tr.

Optionally, a notification Tw may be sent to the driver few milliseconds before the safety time Ts is reached, or if possible one second or few seconds before the safety time Ts. The warning notification Tw instructs the driver to activate the braking system at Ts. Therefore, a given speed profile SP may be characterized by the following succession of times (4) or (4'): (4) Ts < Tw < Tr < Tn < Ta

(4 ) Ts < Tw < Tr < Tn < Ta

The driver may be notified by the mean of a visual and/or audio signal, which may be the same or different for each notification time Tn and warning time Tw. In order to limit the distraction of the driver with too many notification signals, in particular under crowdie traffic conditions, the information may be displayed within a colored frame. It is envisaged that a variation of color along a band on a screen reflects the speed profile that should be followed by the driver. The colorized band may be for example divided in various sectors, comprising a blue sector, a green sector and a red sector, which progressively illuminates according to the time gape Tg between the vehicle and the traffic event E. The blue sector may indicate that no specific traffic event is identified and that current speed is in accordance to the traffic conditions, including the speed limitations, and other official regulations. Illumination of the green sector may indicate the reference time Tr and should incite the driver starting coasting, and a red sector may indicate the safety time, Ts where the brake system needs to be activated. It is optionally envisaged that within a sector, the color of each sector is increasingly becoming darker, while the illumination progresses from one sector to the following sector. In such a way, the driver is notified with a real time and progressive information.

In addition, or alternatively, one or more of the following information may be displayed: - The type of traffic event,

- the effective energy consumption,

- the optimal speed to be reached before the traffic event for optimal energy consumption,

some additional text notification. Optionally, the present method comprises a step g) of analyzing the reaction time of the driver toward the notifications and adapting the notification time Tn, and the warning time Tw accordingly. The reaction time may also vary with regard to the nature of the traffic event. Therefore, a specific notification time Tn, and warning time Tw may be optimized according to the type of event.