EP3053156A1

EP3053156A1 - Method and system for the organisation of vehicle platoons

Info

Publication number: EP3053156A1
Application number: EP14850032.5A
Authority: EP
Inventors: Assad ALAM; Kuo-Yun LIANG; Henrik Pettersson; Jonas Mårtensson; Karl Henrik JOHANSSON
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2013-09-30
Filing date: 2014-09-26
Publication date: 2016-08-10
Also published as: SE1351132A1; WO2015047182A1; EP3053156A4; SE537598C2

Abstract

A system and a method to organise a vehicle platoon. The system comprises a processor unit that is configured to determine a ratio bx for a vehicle f_x that wishes to become a member of the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_x and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_x and the mass of the vehicle, to compare the ratio bx with at least one other ratio bk for a vehicle f_k in the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_k and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_k and the mass of the vehicle, and to determine a location for the vehicle f_x in the vehicle platoon based on the result of the comparison. The system is further configured to generate a location signal that indicates the location of the vehicle f_x and to transmit the location signal to an indicator unit in the vehicle f_x, whereby the location of the vehicle f_x is designated for the driver of the vehicle f_x.

Description

Method and system for the organisation of vehicle platoons Technical area

The present invention relates to a system and a method to organise a vehicle platoon. In particular, a manner is specified to organise a vehicle platoon in preparation for control of the vehicles.

Background to the invention

The intensity of traffic is high on major roads in Europe, and it is expected to increase. The increased transport of people and goods not only gives rise to traffic problems in the form of traffic queues, it also requires ever-increasing amounts of energy, which eventually gives rise to the emission of, for example, greenhouse gases. One possible contribution to solving these problems is to allow vehicles to be driven closer together in what are known as "vehicle platoons". The term "vehicle platoon" is here used to denote a number of vehicles with short distances between them, being driven as a single unit. The short distances lead to it being possible for more traffic to use the road, and the energy consumption for an individual vehicle will be reduced since the air resistance is reduced. The vehicles in the vehicle platoon are driven with at least one of an automated control of the speed of the vehicle and an automated control of its direction. This leads to vehicle drivers such as truck drivers being subject to a reduced load, accidents based on erroneous human decisions being reduced, and the possibility of reducing fuel consumption. Studies show that the fuel consumption of the leading vehicle in the vehicle platoon can be reduced by 2 to 10%, and that of the following vehicle by 15 to 20%, from the fuel consumption of a vehicle driving alone. This is the case in conditions in which the distance between the trucks is 8- 16 metres and the speed at which they travel is 80 km/h. The reduced fuel consumption gives a corresponding reduction in the emission of CO2. Drivers are already using this well-known fact, which has a reduced traffic safety as a consequence. One fundamental question related to vehicle platoons is how the time gap between vehicles can be reduced from the recommended 3 seconds to a value between 0.5 and 1 second, without affecting traffic safety. With distance sensors and cameras, the reaction time of the driver can be eliminated. This is a type of technology that is already being used today by systems such as ACC (adaptive cruise control) and LKA (lane-keeping assistance). One limitation, however, is that distance sensors and cameras require a clear view of the target, and this makes it difficult to detect events that lie more than one vehicle ahead in the queue. A further limitation is that cruise-control systems cannot act

proactively, i.e., the cruise-control system cannot react to events that occur further in advance in the traffic that are going to affect the traffic rhythm. One possibility to enable vehicles to act proactively is to arrange that the vehicles communicate and exchange information. One development of the IEEE-standard 802.1 1 for WLAN (wireless local area networks) known as "802.1 1 p" makes possible the wireless transfer of information between vehicles, and between vehicles and infrastructure. Different types of information, such as vehicle parameters and strategies, can be transmitted to and from the vehicles. The development of communication technology has made it possible to design vehicles and infrastructure that can interact and act proactively. Vehicles can be controlled as a unit and thus a shorter distance between them, and better global traffic flow, are made possible.

Many vehicles today are equipped also with a cruise-control system in order to make it easier for the driver to drive the vehicle. The desired speed can in this case be set by the driver by, for example, a control on the dashboard, and a cruise-control system in the vehicle subsequently influences a control system such that it accelerates and brakes the vehicle as appropriate, in order to maintain the desired speed. If the vehicle is equipped with an automatic gear-change system, the gear in which the vehicle is being driven is changed, such that the vehicle can maintain the desired speed. When the cruise-control system is used in hilly terrain, the cruise-control system will attempt to maintain the preset speed along uphill sections. This sometimes has the consequence that the vehicle accelerates over the crown of the hill and possibly into a subsequent downhill section such that it subsequently must be braked in order not to exceed the preset speed, and this constitutes a manner of driving a vehicle that is wasteful of fuel. By varying the speed of the vehicle in hilly terrain, fuel can be saved, compared with the fuel consumption of a vehicle with a conventional cruise-control system. If the topology that lies ahead is made known through the vehicle having map data and positioning equipment, such systems can be made more robust, and they can change the speed of the vehicle before events have occurred. This is achieved with what is known as "look-ahead cruise control", abbreviated as "LAC".

The situation, however, becomes more complex when a fuel-optimal driving strategy is to be drawn up for a complete vehicle platoon. Additional aspects must be considered, such as retention of the optimal distance, physically possible speed profiles for all vehicles with different masses, and engine capacities. One additional aspect for a vehicle platoon during travel through varying topography is that the leading vehicle, when it has lost speed in an uphill section, resumes its preset speed after the hill. The following vehicles, which then are still present in the uphill section, will be forced to accelerate while travelling uphill, which is not fuel-efficient. Nor is it always possible, which means that gaps will be created in the vehicle platoon, which gaps must, in turn, be closed. This creates oscillations in the vehicle platoon. A similar behaviour is observed also in downhill sections, when the leading vehicle starts to accelerate in the downhill section due to its large mass. The following vehicles are in this case compelled to accelerate before they reach the downhill section, since they attempt to maintain constant the distance to vehicles in front. After the downhill section, the leading vehicle starts to decelerate in order to return to the preset speed. The following vehicles, which then are still present in the downhill section, will be compelled to brake in order to avoid causing a collision, which braking is not fuel-efficient. WO-2012105889-A1 mentions that a heavy vehicle that is travelling down a hill behind a lighter vehicle will approach the latter and must be braked. It is described that the correct choice of time gap or correct positioning of the vehicles in the vehicle platoon before a downhill section starts may be able to avoid this braking and consequently to reduce fuel consumption.

What is still lacking, however, is a general solution for how a vehicle platoon is to be organised in order to cope with both uphill and downhill sections with same order of the vehicles that are members of the vehicle platoon in a fuel-efficient manner.

The object of the invention is to provide an improved method to organise a vehicle platoon such that the vehicle platoon can be driven in a fuel-efficient manner across varying topography.

Summary of the invention

According to one aspect, the object described above is at least partially achieved through a method to organise a vehicle platoon. The method comprises to determine a ratio b_x for a vehicle f_x that wishes to become a member of the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_x and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_x and the mass of the vehicle; to compare the ratio b_x with at least one other ratio b_k for a vehicle f_k in the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_k and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_k and the mass of the vehicle, respectively; to determine a location for the vehicle f_x in the vehicle platoon based on the result of the comparison, and to designate the location of the vehicle f_x for the vehicle f_x.

By calculating a ratio that describes the relationship between the maximum engine power of the vehicle and the mass of the vehicle, or between the maximum engine torque of the vehicle and the mass of the vehicle, it is possible to determine the most limited vehicle. The most limited vehicle is the vehicle that will experience the greatest speed variations when it is to drive uphill or downhill. By placing the most limited vehicle at the front of the vehicle platoon, and placing the next most limited after it, etc., it is possible to be sure that the vehicles after the first vehicle will cope with the variations in speed that the first vehicle will experience. This means that each vehicle will be able to maintain the same speed as the first vehicle in an uphill section. This will then be fuel-optimal, since the distance between the vehicles can be maintained during the complete journey, which gives a maximum reduction in air resistance and, in this way, lowest fuel consumption. It means also that no vehicle in the vehicle platoon will be forced to brake when the first vehicle increases its speed during, for example, coasting or engine braking when travelling along a downhill section. This will then be fuel- optimal, since unnecessary braking is avoided.

According to a second aspect, the object is achieved, at least partially, through a system to organise a vehicle platoon. The system comprises a processor unit that is configured to determine a ratio b_x for a vehicle f_x that wishes to become a member of the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_x and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_x and the mass of the vehicle; to compare the ratio b_x with at least one other ratio b_k for a vehicle f_k in the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_k and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_k and the mass of the vehicle, respectively; and to determine a location for the vehicle f_x in the vehicle platoon based on the result of the comparison. The system is further configured to generate a location signal that indicates the location of the vehicle f_x and to transmit the location signal to an indicator unit in the vehicle f_x, whereby the location of the vehicle f_x is designated for the driver of the vehicle f_x.

It is particularly advantageous to use the invention when a common driving strategy is to be used by the complete vehicle platoon. Many heavy calculations can be avoided during the journey through having organised the vehicle platoon in advance. All vehicles can simply follow the driving profile that has been determined for the first vehicle and can achieve fuel-optimisation, since the most limited vehicle dictates the fuel-optimal driving profile. This system will also be robust (string stable), since all disturbances that may arise will be damped since the subsequent vehicles will always have a more rapid dynamic response, and will thus be able to react more rapidly to changes than the vehicle in front.

The control strategy may involve, for example, all the vehicles in the vehicle platoon are to follow a driving profile that has been calculated by one of the vehicles in the vehicle platoon. In the case in which the vehicles in the vehicle platoon are organised according to the invention, it is necessary only to determine the driving profile of the leader vehicle, which is the driving profile of the first vehicle, and it is not necessary to consider the vehicles behind due to their more rapid dynamic response. This means, for example, that it is not necessary to transmit any driving profiles between the vehicles: the vehicles behind need only to follow the vehicle in front in a position-based manner.

A further advantage with organising the vehicles according to the invention is that the vehicle platoon will be more robust, since the organisation ensures that the vehicles behind always have the possibility to adapt physically to the vehicle in front, i.e. there will be no physical limitations of the vehicles that create problems with the regulation.

According to a third aspect, the object is at least partially achieved through a computer program P at a system, where the said computer program P comprises program code in order to cause the system to carry out any one of the method steps that are described in this application.

According to a fourth aspect, the object is at least partially achieved through a computer program product comprising a program code stored on a medium that can be read by a computer in order to carry out any one of the method steps described in this application. Preferred embodiments are described in the dependent claims and in the detailed description.

Brief description of the attached drawings

The invention will be described below with reference to the attached drawings, of which:

Figure 1 illustrates a vehicle platoon that is travelling up a hill.

Figure 2 shows an example of a vehicle in the vehicle platoon.

Figure 3 shows a system according to one embodiment of the invention.

Figure 4 shows a flow diagram for a method to organise vehicle platoons.

Figures 5A-5C show an organisation scenario.

Figures 6 shows a further organisation scenario.

Detailed description of preferred embodiments of the invention

Definitions

v_k: the speed of vehicle f_k in a vehicle platoon with N vehicles.

dk,k+i - the distance between vehicle fk and the vehicle behind it f_k+i in the vehicle platoon.

<¾: the gradient at vehicle f_k.

V2V-communication (vehicle-to-vehicle): wireless communication between vehicles, also known as vehicle-to-vehicle communication.

V2l-communication (vehicle-to-infrastructure): wireless communication between vehicles and infrastructure, such as road junctions and computer systems.

Figure 1 shows a vehicle platoon with N heavy vehicles f_k that is proceeding up a hill with small spaces d_k, _k+i between the vehicles. The gradient at the vehicle f_k when it drives up the hill is shown as <¾. Each vehicle f_k is equipped with a receiver and a transmitter for wireless signals, partially shown with an antenna. The vehicles f_k in the vehicle platoon can thus communicate with each other through V2V-communication or through other means such as, for example, mobile communication units, through an application in a communication unit, or through a server. They can communicate also with infrastructure in the form of V2I- communication. The communication can pass, for example, from one vehicle through a road junction to a second vehicle. The different vehicles fk have different masses m_k. The vehicle platoon has a leader vehicle, i.e. the first vehicle fi . Each vehicle fk in the vehicle platoon has, for example, a unique vehicle identity and a vehicle platoon identity that is common for the complete vehicle platoon, in order to be able to maintain knowledge of which vehicles are members of the vehicle platoon. Data that are transmitted wirelessly between the vehicles in the vehicle platoon can be tagged with these identities such that the vehicle of origin of the data received can be determined.

Figure 2 shows an example of a vehicle fk in the vehicle platoon and illustrates how it may be equipped. The vehicle fk is equipped with a positioning unit 5 that can determine the position of the vehicle fk. The positioning unit 5 may be, for example, configured to receive signals from a global positioning system such as GNSS (Global Navigation Satellite System), for example GPS (Global Positioning System), GLONASS, Galileo or Compass. Alternatively, the positioning unit 5 may be configured to receive signals from, for example, one or several detectors in the vehicle that measure relative distances to, for example, a road junction, vehicles in the surroundings, or similar entities, with known positions. Based on the relative distances, the positioning unit 5 can subsequently determine the position of the vehicle fk. A detector may be configured also to detect a signature in, for example, a road junction, whereby the signature represents a certain position. The positioning unit 5 may in this case be configured to determine its position through detection of the signature. The positioning unit 5 may instead be configured to determine the signal strength of one or several signals from several base stations or road junctions, or base stations and road junctions, etc., with known positions, and in this way to determine the position of the vehicle fk by triangulation. The position of the vehicle fk can in this way be determined. Of course, the technologies described above may be combined in order to determine the position of the vehicle fk. The positioning unit 5 is configured to generate a positioning signal that contains the position of the vehicle fk, and to transmit this signal to one or several units in the vehicle fk. The vehicle fk is, as has been mentioned above, equipped also with a unit 4 for wireless communication. The unit 4 is configured to function as receiver and transmitter of wireless signals. The unit 4 can receive at least one of wireless signals from other vehicles and wireless signals from infrastructure around the vehicle fk, and it can transmit at least one of wireless signals to other vehicles and wireless signals to infrastructure around the vehicle fk. The wireless signals can comprise vehicle parameters from other vehicles, for example their mass, torque developed, maximum engine power, speed, and also more complex information such as, for example, the currently used driving profile, driving strategy, etc. The wireless signals may contain also information about the surroundings, such as the gradient a of the road, the radius of curvature r, etc. The vehicle fk may be equipped also with one or several detectors 8 in order to detect the surroundings, for example a radar unit, a laser unit, a gradient gauge, acceleration gauge, steering wheel measure, a gyro, etc. A detector unit is configured to determine a parameter, such as a relative distance, speed, gradient, lateral acceleration, rotation, steering wheel measure, etc., and to generate a detector signal that contains the parameter. The detector unit is further configured to transmit the detector signal to one or several units in the vehicle fk. The vehicle fk may be equipped also with a map unit that can provide map information about the road ahead. The map unit may, for example, be a part of the positioning unit 5. The driver may, for example, specify a final position and the map unit can then, given that it has knowledge of the current position of the vehicle, provide relevant map data about the road ahead between the current position and the final destination. The vehicle fk communicates internally between its various units through, for example, a bus, such as a CAN bus (controller area network), which uses a message-based protocol. Examples of other communication protocols that can be used are TTP (time-triggered protocol), Flexray, etc. Signals and data as described above can in this way be exchanged between various units in the vehicle fk. Signals and data can instead be transferred in a wireless manner, for example, between the various units. Figure 2 shows also a processor unit 2, that is a component of a system 1 according to the invention. This system 1 is shown in Figure 3 according to one embodiment, which will now be explained with reference to this drawing. The processor unit 2 is connected to a memory unit 3 as shown in the drawing. The memory unit 3 may comprise a transient or a non-transient memory or it may comprise a transient and a non-transient memory, such as flash memory and RAM (random access memory). A program P is stored at the memory unit 3. The program P comprises program code to cause the processor unit 2 to carry out a method to organise the vehicle platoon that will be explained below. The processor unit 2 is thus configured to carry out the various method steps that will be described. The program P may be stored also at a computer program product on a medium that can be read by a computer, as a program code. The processor unit 2 may be constituted by a CPU (central processing unit). The processor unit 2 may be a part of a computer or a computer system, for example an ECU

(electronic control unit), in a vehicle fk. Alternatively, the system 1 with the processor unit 2 may be located in the infrastructure, in, for example, a road junction or a central unit 7 (Figures 5A-6).

The unit 4 for wireless communication can receive data concerning vehicle mass and maximum engine power for each vehicle fk. The processor unit 2 is configured to generate a location signal that indicates the location of the vehicle f_x and to transmit the location signal to an indicator unit 6 in the vehicle f_x, whereby the location of the vehicle f_x is designated for the driver of the vehicle f_x. The driver of the vehicle f_x then knows the location that he or she is to have in the vehicle platoon and can insert himself or herself at the correct position in the platoon. The location signal can be transmitted also to one vehicle fk or several of the other vehicles in the vehicle platoon such that they prepare a place for the vehicle f_x, either through the drivers manually regulating the vehicles such that a gap is opened between the vehicles, or through automatic regulation of the vehicles in the vehicle platoon. Figure 4 shows a flow diagram for the method of organising the vehicle platoon, which method will now be explained with reference to this drawing. The processor unit 2 (Figure 2) is configured to carry out this method according to the various embodiments of the method. The method comprises to determine a ratio b_x for a vehicle f_x that wishes to become a member of the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_x and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_x and the mass of the vehicle (A1 ). The ratio b_x is compared with at least one other ratio b_k for a vehicle f_k in the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_k and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_k and the mass of the vehicle, respectively (A2). According to one embodiment, the method comprises to determine the ratio b_x for the vehicle f_x and the ratio b_k for the vehicle f_k by calculating for the relevant vehicle. Alternatively, the ratio b_x for the vehicle f_x and the ratio b_k for the vehicle f_k can [missing text, "be determined"] by calculating

Maximum engine torque for the vehicle

Mass of the vehicle

(2)

The ratios b_x and b_k that are to be compared with each other are thus both determined by either Equation (1 ) or Equation (2). The ratio provides a measure of how limited the vehicle is, that is: how difficult it experiences holding a certain speed in an uphill section. The most limited vehicle is the vehicle that will experience the greatest speed variations when it is to drive uphill or downhill. The vehicle that has the lowest ratio of the vehicles finds it most difficult to carry out both of these operations. The maximum engine power and the maximum engine torque for each vehicle are known engine parameters. Also the mass of each vehicle is a known parameter for each vehicle, but it must be updated as the load carried by the vehicle changes. The parameters of each vehicle are available through the internal network of each vehicle. The parameters can be transmitted to the system 1 over V2V or V2I. By, for example, tagging the parameters with the identity of the vehicle and the identity of the vehicle platoon, it is possible to keep track of which parameter belongs to which vehicle. The method comprises further the determination of a location for the vehicle f_x in the vehicle platoon based on the result of the comparison (A3). According to one embodiment, a location in front of the vehicle f_k is determined in the case in which b_x < b_k, and a location behind the vehicle f_k in the case in which b_x > b_k. The vehicle f_x can in this way be inserted into the vehicle platoon according to its ratio b_x, which specifies limited it is. Thus, the vehicle f_x is placed into the vehicle platoon such that it is placed after the vehicle or vehicles that is or are more limited than the vehicle f_x itself, and it is placed before the vehicle or vehicles that is or are less limited. The location of the vehicle f_x is subsequently designated for the vehicle f_x (A4).

According to one embodiment, space for the vehicle f_x in the vehicle platoon is prepared according to the designated location in the vehicle platoon. This can be carried out by, for example, one or several vehicles in the vehicle platoon being informed that the vehicle f_x is to be inserted into the vehicle platoon at the designated location. These vehicles can subsequently be controlled manually or automatically such that a gap is created into which the vehicle f_x is to be placed. The driver of the vehicle f_x can subsequently guide the vehicle f_x into the gap. Alternatively, the vehicle f_x can be automatically controlled such that it is placed into the gap.

Figures 5A-5C show a scenario for sorting a vehicle f_x into an existing vehicle platoon. Figure 5A shows f_x, which desires to become a member of the existing vehicle platoon, which comprises the three vehicles fi, h and h- The vehicle f_x is driving on an access ramp and the existing vehicle platoon is driving on the road that the vehicle f_x is to enter. The vehicle f_x can, for example, scan the

surroundings for vehicle platoons and transmit a request to a suitable vehicle platoon to be allowed to become a member of the vehicle platoon. Alternatively, this can be dealt with by a central unit 7 that receives signals from the vehicles and subsequently organises suitable vehicle platoons when this is possible.

Location signals, etc., can subsequently be transmitted to the vehicles from the central unit 7 in order to organise the vehicle platoon. The central unit 7 comprises in this case the complete system 1 or parts of it. Alternatively, the system 1 may be arranged in one or several of the vehicles in the vehicle platoon, such as the leader vehicle fi, or the vehicle f_x. In the case in which the vehicle f_x is allowed to become a member of the vehicle platoon, the ratio b_x of the vehicle f_x is

determined, unless this has already been determined. The ratio b_x is subsequently compared with the ratio bi of the leader vehicle fi . In this case, b_x is greater than bi, and the vehicle f_x is thus to be placed behind the leader vehicle fi . The ratio b_x is subsequently compared with the ratio b2 of the next vehicle h in the vehicle platoon. In this case, b_x is less than b2, and the vehicle f_x is thus to be placed in front of the vehicle h- The ratio b_x for the vehicle f_x is thus compared consecutively with the ratios b_k for the vehicles f_k in the vehicle platoon. The comparisons continue until a vehicle has been found in front of which the vehicle f_x is to be placed, or until no more vehicles are available in the vehicle platoon. In this case the vehicle f_x is to be placed last in the vehicle platoon. The result here is that the vehicle f_x is to be placed between the vehicles fi and h- The location is passed to the driver of vehicle f_x. The driver can then decide whether he or she wishes to become a member of the vehicle platoon. The location can be passed also to one or several vehicles in the vehicle platoon. Figure 5B shows how the vehicles in the vehicle platoon open a gap between the vehicles fi and h by increasing the distance di,2 between the vehicles. In order to increase temporarily the distance between the vehicles, the speeds of the vehicles may be controlled manually, or automatically from one or several of the vehicles in the vehicle platoon, or from the central unit 7. The vehicle f_x subsequently drives into the gap that is created, which is shown in Figure 5C, and is subsequently a member of the vehicle platoon. Figure 6 shows another organisation scenario in which several vehicles frf₄ are initially in a disorganised state, at, for example, a rest facility or a haulier's depot. In order to organise a vehicle platoon from the vehicles fi-f₄, the ratio for the each of the vehicles according to Equation (1 ) is determined, and compared with each other in order to determine the ratio that is smallest, and that thus specifies the most limited vehicle. The vehicle with the next smallest ratio is subsequently located in the platoon, etc. The locations are passed to the relevant vehicles, which place themselves at the relevant locations in the platoon. A vehicle f_k, for example, can be nominated to become a member of the vehicle platoon, and the other vehicles must place themselves in the vehicle platoon based on their ratio b_k.

An organised vehicle platoon is an advantage when a common regulatory strategy is to be applied for the vehicles in the vehicle platoon. The vehicles in the vehicle platoon can in this case, for example, act as specified by an LAP cruise-control system (a look-ahead cruise control for platoons), which is a cooperative cruise- control system that uses information about the topography of the road ahead and calculates an optimal speed trajectory for all the vehicles in the vehicle platoon. This is also known as a "predictive cruise-control system for vehicle platoons". The regulatory strategy is determined by, for example, dynamic programming. An LAP can use, for example, one or several calculated trajectories from an LAC cruise-control system (a look-ahead cruise control system), which is a cruise- control system that uses information about the topography of the road ahead and calculates an optimal driving profile in the form of a speed trajectory for a vehicle. This is also known as a "predictive cruise-control system". In the case in which a vehicle platoon is organised such that the leader vehicle is the most limited vehicle, etc., the subsequent vehicles can follow the speed trajectory that has been determined for the leader vehicle. An optimised speed control for the complete vehicle platoon with respect to fuel consumption and the time required is, in this way, achieved. The present invention is not linnited to the embodiments described above. Various alternatives, modifications and equivalents can be used. For this reason, the embodiments named above do not limit the scope of the invention, which is defined by the attached claims.

Claims

1 . A method to organise a vehicle platoon, the method comprising:

-determining a ratio b_x for a vehicle f_x that wishes to become a member of the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_x and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_x and the mass of the vehicle;

- comparing the ratio b_x with at least one other ratio b_k for a vehicle f_k in the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_k and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_k and the mass of the vehicle;

- determining a location for the vehicle f_x in the vehicle platoon based on the result of the comparison;

- generating a location signal that indicates the location of the vehicle f_x;

- transmitting the location signal to an indicator unit (6) in the vehicle f_x, whereby the location of the vehicle f_x is designated for the driver of the vehicle fx.

2. The method according to claim 1 , comprising determining the ratio b_x for the vehicle f_x and the ratio b_k for the vehicle f_k by calculating

Maximum engine power for the vehicle

Mass of the vehicle for each vehicle, and by calculating

Maximum engine torque for the vehicle

Mass of the vehicle for each vehicle.

3. The method according to claim 2, comprising determining a location in front of the vehicle f_k in the case in which b_x < b_k, and a location behind the vehicle f_k in the case in which b_x > b_k.

4. The method according to any one of the preceding claims, comprising preparing a location for the vehicle f_x in the vehicle platoon according to the designated location in the vehicle platoon.

5. The method according to any one of the preceding claims, comprising comparing consecutively the ratio b_x for the vehicle f_x with the ratios b_k for the vehicles f_k in the vehicle platoon.

6. A system (1 ) to organise a vehicle platoon, c h a r a c t e r i s e d i n that the system (1 ) comprises a processor unit (2) that is configured:

-to determine a ratio b_x for a vehicle f_x that wishes to become a member of the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_x and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_x and the mass of the vehicle;

- to compare the ratio b_x with at least one other ratio b_k for a vehicle f_k in the vehicle platoon, which ratio describes the relationship between the maximum engine power of the vehicle f_k and the mass of the vehicle, or the relationship between the maximum engine torque of the vehicle f_k and the mass of the vehicle;

- to determine a location for the vehicle f_x in the vehicle platoon based on the result of the comparison;

- to generate a location signal that indicates the location of the vehicle f_x;

- to transmit the location signal to an indicator unit (6) in the vehicle f_x, whereby the location of the vehicle f_x is designated for the driver of the vehicle f_x.

7. The system according to claim 6, whereby the processor unit (2) is configured to determine the ratio b_x for the vehicle f_x and the ratio b_k for the vehicle f_k by calculating

Maximum engine power for the vehicle

Mass of the vehicle for each vehicle, and by calculating Maximum engine torque for the vehicle

Mass of the vehicle for each vehicle.

8. The system (1 ) according to claim 7, wherein the processor unit (2) is configured to determine a location in front of the vehicle f_k in the case in which b_x < b_k, and a location behind the vehicle f_k in the case in which b_x > b_k.

9. The system (1 ) according to any one of claims 6 to 8, wherein the processor unit (2) is configured to transmit the location signal to at least one vehicle f_k in the vehicle platoon, after which a location is prepared for the vehicle f_x in the vehicle platoon according to the designated location in the vehicle platoon.

10. The system (1 ) according to any one of claims 6 to 9, wherein the processor unit (2) is configured to compare consecutievly the ratio b_x for the vehicle f_x with the ratios b_k for the vehicles f_k in the vehicle platoon.

1 1 . A computer program, P, at a system (4 [sic, "1 "]), wherein the said computer program, P, comprises program code to cause the control unit (2) to carry out any one of the steps according to claims 1 to 5.

12. A computer program product comprising program code stored on a medium that can be read by a computer in order to carry out the method steps according to any one of claims 1 to 5.