SE542113C2

SE542113C2 - A method, a control arrangement and a vehicle for determining a vehicle conduction trajectory

Info

Publication number: SE542113C2
Application number: SE1750730A
Authority: SE
Inventors: Björn Johansson; Conny Fransson; Erik Holma; Frank Mohr; Henrik Svärd; Jonsson Linnea Hällerstam; Martin Jakobsson; Mikael Ögren; Oscar Flärdh
Original assignee: Scania Cv Ab
Priority date: 2017-06-09
Filing date: 2017-06-09
Publication date: 2020-02-25
Also published as: SE1750730A1; DE102018004022A1

Abstract

A method and a control arrangement for determining a vehicle conduction trajectory for a vehicle. The method comprising: determining (S1) a vehicle conduction trajectory for the vehicle for a future road segment of the vehicle based on vehicle data of the vehicle and topographic data of the future road segment, wherein the determining (S1) comprises only allowing a positive powertrain torque of the vehicle while the vehicle conduction trajectory is within a variable first interval, and attempting to keep the vehicle conduction trajectory within a second interval.

Description

A method, a control arrangement and a vehicle for determining a vehicle conduction trajectory Technical field The present disclosure relates to technology for vehicles, and in particular to a method and a control arrangement for determining a vehicle conduction trajectory for a vehicle. The disclosure also relates to a vehicle comprising the control arrangement, to a computer program and to a computer-readable medium.

Background A cruise controller is a system that automatically controls a velocity of a vehicle according to a set velocity. The cruise controller controls the velocity of the vehicle by adjusting the torque of the engine or engines of the vehicle. The cruise controller may also control the clutch, gear shifting and the brakes of the vehicle to maintain the set velocity.

It has been established that an experienced truck driver often conducts a truck in a more fuel efficient way than a less experienced truck driver. Also, if the driver has driven the same route before, the driver is aware of the coming topography and may take advantage of, for example, a coming downhill. In the ongoing strive for fuel efficiency, this way of conducting a vehicle has become automatized and systems that predict fuel saving velocity trajectories for the cruise controller of the vehicle have been developed. The trajectories are predicted considering the upcoming topography, and may for example take advantage of a predicted speed increase of the vehicle in a coming downhill. Some of these cruise controllers are known as look-ahead cruise controllers.

In a cruise controller, the velocity of the vehicle is generally held constant to the desired set velocity. However, by instead letting the velocity fluctuate around the set velocity, the vehicle can make significant fuel savings.

For example, from US2013297174A1 it is known to utilize the energy storage provided by a vehicle in terms of potential and kinetic energy to optimize the fuel consumption, by optimizing the current speed of the vehicle to minimize fuel consumption by adjusting the cruise control speed. However, certain fuel saving behaviors may be perceived as disturbing to the driver of the vehicle and surrounding traffic.

Summary It is an object of the disclosure to alleviate at least some of the drawbacks with the prior art. It is a further object to provide methods and arrangements that can take advantage of efficiency savings of the vehicle, while still providing a vehicle behavior which is perceived as acceptable to the driver. These objects and others are at least partly achieved by the independent claims, and by the embodiments according to the dependent claims.

According to one aspect, the disclosure relates to a method for determining a vehicle conduction trajectory for a vehicle. The method comprises determining a vehicle conduction trajectory for the vehicle for a future road segment of the vehicle based on vehicle data of the vehicle and topographic data of the future road segment. The determining comprises only allowing a positive powertrain torque of the vehicle while the vehicle conduction trajectory is within a variable first interval, and attempting to keep the vehicle conduction trajectory within a second interval. Thus, the method tries to plan a vehicle conduction trajectory such that the conduction parameters of the trajectory does not go beyond the second interval. Further, the method comprises determining the vehicle conduction trajectory based on optimizing energy consumption of the vehicle, and a given set velocity for the vehicle.

The second interval is in some embodiments constant, and it is allowed to make rather large variations of the conduction parameter within this second interval. The conduction parameter is for example the velocity of the vehicle, a distance or a time gap to a reference. With the described method, the vehicle behaviour will not vary much on flat roads, whereby a satisfying drivability can be obtained on an essentially flat road. Larger deviations are however allowed, for example in a downhill where no positive powertrain torque is needed to drive the vehicle, in order to take advantage of the energy obtained in the downhill. Such larger changes are normally accepted by the driver, as it is known that the changes are made in order to save on energy. Thereby, drivability can be obtained, while still driving such that energy consumption savings can be made. It should be noted that the vehicle here does not need to have a set velocity to maintain, instead only the first and second intervals are used.

According to some embodiments, the method comprises determining whether the vehicle conduction trajectory is outside the second interval. Upon determining that the vehicle conduction trajectory is outside the second interval, the method comprises increasing the variable first interval within a region of the future road segment, in order to encompass the vehicle conduction trajectory within the second interval, and repeating the determining of the vehicle conduction trajectory using the increased variable first interval. Thus, the method first tries to plan a trajectory inside the second interval. If that is not possible, the first interval is increased, to temporary allow a positive powertrain torque within a greater first interval.

With these embodiments of the method, an automatic configuration of the constraints of the vehicle conduction trajectory is achieved according to the upcoming topography of the road. Thereby, satisfying drivability is automatically achieved on flat roads, and side-steps from the drivability is allowed and planned in certain circumstances, e.g. in larger uphills.

According to some embodiments, the method comprises repeating the increasing until the second interval encompass the vehicle conduction trajectory and/or until the first variable interval is outside the second interval. The first interval is for example incrementally increased. A positive powertrain torque will then be allowed for a longer time and the velocity of the vehicle may be increased e.g. to prepare for an upcoming hill.

According to some embodiments, the region of the future road segment is a region wherein the vehicle conduction trajectory goes beyond the first variable interval. The region is thus a part of the future road segment, for example 10 meter, up to the total length of the future road segment.

According to some embodiments, the method comprises increasing the region of the future road segment for each repetition, until the region is equal to the future road segment. Thereby, the first interval may be increased for a larger stretch of the future road segment, and thereby the velocity of the vehicle is possible increased as a positive powertrain torque is allowed during a larger stretch of the future road segment.

According to some embodiments, the vehicle conduction trajectory is a vehicle speed trajectory. For example, the vehicle conduction trajectory comprises a plurality of reference velocities at respective positions along the future road segment.

According to some embodiments, the vehicle conduction trajectory is a vehicle distance trajectory or a vehicle time gap trajectory. For example, the vehicle conduction trajectory comprises a plurality of reference distances or time gaps at respective positions along the future road segment. The reference distances and time gaps are, for example, transformed to corresponding velocities for the vehicle at the respective positions. By constraining the variations of the vehicle conduction parameter, the amplitude of the variations will become smaller which will reduce the negative influence that the control might have on the surrounding traffic.

According to some embodiments, the vehicle conduction trajectory is determined in relation to a known fix trajectory. For example, the known fix trajectory is a reference velocity trajectory, e.g. a constant desired mean velocity.

According to some embodiments, the vehicle conduction trajectory is determined in relation to a trajectory of a preceding vehicle of the vehicle. The trajectory of the preceding vehicle is then e.g. sent to the vehicle by wireless communication, or estimated by other means.

According to some embodiments, the vehicle data comprises one or several of vehicle mass and engine power, and the topographic data comprises inclination data of the future road segment.

According to a second aspect, the disclosure relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of the herein disclosed method steps.

According to a third aspect, the disclosure relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of the herein disclosed method steps.

According to a fourth aspect, the disclosure relates to a control arrangement for determining a vehicle conduction trajectory for a vehicle. The control arrangement is configured to obtain topographic data of a future road segment for the vehicle and to determine a vehicle conduction trajectory for the vehicle for a future road segment of the vehicle based on vehicle data of the vehicle and topographic data of the future road segment, wherein a positive powertrain torque of the vehicle only is allowed while the vehicle conduction trajectory is within a first variable interval, and the vehicle conduction trajectory is attempted to be kept within a second interval.

According to some embodiments, the control arrangement is configured to determine whether the determined vehicle conduction trajectory is outside the second interval, and upon determining that the vehicle conduction trajectory is outside the second interval to increase the first interval within a region of the future road segment, in order to encompass the vehicle conduction trajectory within the second interval, and to repeat the determining of the vehicle conduction trajectory for the vehicle using the increased first interval.

According to some embodiments, the control arrangement is configured to perform the method according to any one of the steps as disclosed herein.

According to fifth aspect, the disclosure relates to a vehicle comprising a control arrangement according to any of the embodiments as disclosed herein.

Brief description of the drawings Fig. 1 illustrates a vehicle where the control arrangement according to some embodiments can be arranged.

Fig. 2 illustrates a control arrangement according to some embodiments.

Figs. 3A-3B comprises a flow chart of the method for determining a trajectory according to some embodiments.

Fig. 4 illustrates a diagram with a velocity trajectory of the vehicle.

Fig. 5A illustrates a diagram with two velocity intervals.

Fig. 5B illustrates a diagram with a velocity trajectory of the vehicle, where the two velocity intervals of Fig. 5A has been used.

Fig. 6A illustrates a first example of a vehicle conduction trajectory where the velocity of the vehicle goes below Vmin.

Fig. 6B illustrate a diagram with two velocity intervals, where the inner interval has been increased.

Fig. 6C illustrate the first example using the two velocity intervals of Fig. 6B.

Fig. 7 illustrate a second example for keeping a certain distance.

Detailed description In order to illustrate an underlying problem of the invention, reference is made to Fig. 4. Fig. 4 illustrates a velocity trajectory for a vehicle 1 for driving the future road segment S along the road 9. At “R0” the future road segment starts, and at “R4” it ends. At “R1” an uphill starts, at “R2” the uphill ends in a crest, and a downhill starts. At “R3” the downhill ends. Between R0 and R1 the road is essentially flat. The planned velocity of the vehicle, here the velocity trajectory Vref intended for a cruise control system of the vehicle, is allowed to vary between Vmin and Vmax. Vmin and Vmax defines an interval for Vref. It is a well-known fact that a fuel saving strategy is to alternate the velocity between accelerating and coasting, thus letting the speed vary between Vmin and Vmax. A fuel saving look ahead cruise control system may use this strategy, both in flat and hilly terrain. “Coasting” here means idling or turned off engine/powertrain. If the interval between Vmin and Vman is large, then the velocity of the vehicle will fluctuate with a rather large amplitude on flat roads, as can be seen in the Fig. 4 between R0 and R1. When the velocity of the vehicle is equal to or goes below Vmin, then the vehicle will use a positive torque to increase the velocity up to Vmax.

Thereafter, the velocity is allowed to decrease to Vmin, and so on. In hilly terrain, such velocity fluctuations are typically expected by the driver, and there is thus a larger acceptance for them, whereas in flat terrain, large velocity fluctuations may be seen as annoying, both to the driver and to the surrounding traffic. The large interval between Vmin and Vmax is particularly useful in view of an upcoming downhill, as energy savings can be made by decreasing the velocity of the vehicle down to Vmin before the downhill, and regaining the velocity of the vehicle in the downhill using the potential and kinetic energy of the vehicle.

In the following disclosure, a method for planning the conduction of a vehicle will be described, providing driveability automatically on essentially flat roads, while allowing deviations from the drivability criterion on hilly roads in order to achieve energy savings, security and/or predictability. The method determines a vehicle conduction trajectory for the vehicle to be used by the vehicle for driving along the upcoming road. The vehicle conduction trajectory is for example a velocity trajectory, a distance trajectory or a time gap trajectory to be followed by the vehicle. The vehicle conduction trajectory is determined with the criterion that a positive powertrain torque only is allowed while the vehicle conduction trajectory is within a variable first interval, and attempting to keep the vehicle conduction trajectory within a second interval. Then, large variations of the velocity, distance or time gap will only be allowed in the presence of hills, where acceptance for the fluctuations is large.

In the following a vehicle, a control arrangement that can be implemented in the vehicle and a method that may be implemented by the control arrangement will be described.

Fig. 1 illustrates the vehicle 1 comprising the control arrangement 2, a control system 3 and a sensor 8, e.g. radar sensor for detecting the distance to any preceding vehicle. The vehicle 1 is for example a car or a truck, and may be arranged with a trailer. One or several of the functions of the vehicle 1 may be automatically operated. The vehicle 1 itself may be semi-autonomously operated orfully-autonomously operated. The control system 3 may be a powertrain control system, for example one or several of: a cruise control system, a transmission control system, a torque control system, an engine control system and a power distribution control system. The powertrain control system is arranged to control components of the powertrain of the vehicle 1 , for example one or several engines, the transmission including gearbox, and brakes, based on a vehicle conduction trajectory.

The engine may be a combustion engine or an electrical engine. According to some embodiments, the vehicle 1 comprises a combustion engine and at least one electrical engine. The one or several engines may be controlled by torque control. A powertrain torque is for example an engine or motor torque, where the engine is for example a combustion engine and/or an electrical engine. Optionally, the one or several engines are controlled by changing the mode of the engine. The mode of the engine may be changed e.g. in order to control the amount of emissions from the vehicle. The vehicle may also be set in a certain powertrain mode. A powertrain mode may be e.g. economy mode, a standard mode or a power mode. The different modes have different requirements, e.g. the economy mode focuses on reduced energy consumption, the power mode gives high power output, and the standard mode has moderate energy consumption and gives moderate power output. The powertrain mode of the vehicle 1 is normally set by the driver or hauler. As readily understood, the powertrain mode of the vehicle 1 might influence the tradeoff between resource consumption and drivability. The vehicle 1 also comprises a braking system that is designed to create a brake torque which acts to reduce the velocity of the vehicle 1, e.g. by reducing the speed of rotation of the wheel set propelling the vehicle 1. The braking system can comprise one or more of auxiliary brakes, such as engine brake, exhaust brake, electromagnetic retarder and hydraulic retarder.

With energy consumption of the vehicle 1 is here meant energy that is stored in the vehicle 1. Thus, it refers to energy originating from fuel (fuel consumption), electrical energy (electrical energy consumption) or chemical energy from fuel cells (chemical energy consumption).

More in detail, the cruise control system is arranged to control the velocity of the vehicle 1 based on input parameters such as a set velocity and a velocity interval around the set velocity, where the speed of the vehicle 1 is allowed to fluctuate, and a velocity trajectory. The cruise control system may be a look-ahead cruise control system. The transmission control system is arranged to control the gearbox of the vehicle 1 using a reference gear selection trajectory. The engine control system is arranged to control the one or several engines using a reference torque trajectory. The engine control system may also be arranged to control the one or several engines using a reference engine mode trajectory. For example, the engine control system may also be arranged to control the one or several engines using an emission control trajectory, such that the emission control can be optimized. The engine control system may also be arranged to control the braking system using a reference brake torque trajectory. Further, the power distribution control system is arranged to split, e.g. combine, the power from several sources, e.g. a combustion engine and one or several electrical engines, to achieve greatest efficiency. The power distribution control system is arranged to control the power distribution based on a reference power distribution trajectory. Some or all of the mentioned control systems may be implemented in one control unit e.g. a transmission control unit. However, the control systems may alternatively be implemented in a plurality of control units.

Fig. 2 illustrates the control arrangement 2 in further detail. The control arrangement 2 comprises a processor 4 and a memory 5. The processor 4 comprises e.g. one or several Central Processing Units (CPU). The memory 5 comprises e.g. one or several memory units. A memory unit may comprise a volatile and/or a non-volatile memory, such as a flash memory or Random Access Memory (RAM). The control arrangement 2 further comprises a computer program P comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method that will be described in the following. The program may be downloaded from a computer-readable medium, e.g. a memory stick or memory from another computer. Thus, the computer-readable medium comprises instructions, which, when executed by a computer, cause the computer to carry out the method that will be described in the following. Optionally, the control arrangement 2 comprises one or several control units, for example electronic control units (ECUs).

The control arrangement 2 is arranged to determine a vehicle conduction trajectory for the vehicle 1 for a future road segment of the vehicle 1. The vehicle conduction trajectory is for example any one of the above described trajectories. Alternatively, the vehicle conduction trajectory comprises several of the above described trajectories. Still alternatively, the vehicle conduction trajectory comprises conduction parameters such as velocity, distance or time gap. The control arrangement 2 is for example arranged to transform the conduction parameters into control parameters for any of the described control systems, in order to conduct the vehicle 1 according to the determined vehicle conduction trajectory. The control system 3 is further arranged to be controlled according to the determined vehicle conduction trajectory.

The control arrangement is arranged to determine the vehicle conduction trajectory based on vehicle data of the vehicle 1 and topographic data of the future road segment, wherein a positive powertrain torque of the vehicle 1 only is allowed while the vehicle conduction trajectory is within a first variable interval, and the vehicle conduction trajectory is attempted to be kept within a second interval. In other words, the control arrangement is programmed to determine the vehicle conduction trajectory. In order to determine a vehicle conduction trajectory, the control arrangement 2 is configured to obtain topographic data of a future road segment for the vehicle 1. The control arrangement 2 is, for example, arranged to obtain information from other sources to determine the position of the vehicle 1, and characteristics of the coming road where the vehicle 1 will drive. For example, the control arrangement 2 is arranged to obtain the position of the vehicle 1 from a positioning unit 5 of the vehicle 1. The positioning unit 5 may use the Global Positioning System, GPS, to determine the position of the vehicle 1. The positioning unit 5 may alternatively determine the position of the vehicle 1 by means of wireless communication, vehicle to vehicle communication, vehicle to infrastructure communication, radar sensing or similar. By knowing the absolute position of other sources, the position of the own vehicle 1 may be determined by triangulation. The characteristics of the coming road, e.g. map information such as topographic information of the road and road curvature, may be determined by a map unit 6.

The driver typically sets the start and goal of the current driving mission. In order to drive from the start to the goal, an appropriate route along one or several roads is selected on a map, by the driver, or automatically. The map unit 6 may then continually provide relevant topographic information, road curvature etc. for the future route segment to the control arrangement 2. For example, the topographic data comprises inclination data of the future road segment. The topographic information is e.g. provided based on the position of the vehicle 1 along the selected route. Optionally, the functionality of the map unit 6 is included in the control arrangement 2. The future route segment is typically between 1-3 kilometers, e.g. 2 kilometers, of the upcoming road of the vehicle 1 along the route. Thus, the future route segment is a road segment in front of the vehicle 1. The route segment starts from the vehicle 1 and extends the mentioned distance ahead along the selected route along one or several roads. With “to drive the future route segment” is here meant a simulated drive of the future route segment.

The internal units of the vehicle 1, such as control arrangements, control units, devices, sensors, detectors etc., are arranged to communicate via a communication bus, for example a CAN-bus (Controller Area Network), which uses a message based protocol. Alternatively, other communication protocols may be used e.g. TTP (Time-Triggered Protocol), Flexray, etc. In this way signals and data described herein may be exchanged between different units, devices, sensors and/or detectors in the vehicle 1. Sometimes signals and data are transferred wirelessly between the different units, devices, sensors and/or detectors. The vehicle 1 is in some embodiments arranged with a device for wireless communication, such that the vehicle 1 can exchange information with other vehicles.

The control arrangement 2 is further configured to perform or execute a program for performing the method that will be explained in the following.

Hence, the disclosure also relates to a method for determining a vehicle conduction trajectory for the vehicle 1. The method will now be described with reference to the flowchart in Figs. 3A-3B, and to the illustrations in Figs. 4a-7. The method can, for example, be implemented by the above described control arrangement 2. It will be appreciated that the various embodiments described with for the method are all combinable with the control arrangement 2. That is, the control arrangement 2 may be configured to perform any one of the embodiments of the method described herein.

The method comprises determining S1 a vehicle conduction trajectory for the vehicle for a future road segment of the vehicle based on vehicle data of the vehicle and topographic data of the future road segment. The determining S1 comprises only allowing a positive powertrain torque of the vehicle while the vehicle conduction trajectory is within a variable first interval, and attempting to keep the vehicle conduction trajectory within a second interval. For ease of illustration, the disclosure mainly refers to determining a vehicle conduction trajectory that is a velocity trajectory. However, this should not be seen as limiting to the invention, and the vehicle conduction trajectory is alternatively a time trajectory, a distance gap trajectory, or another kind of trajectory that the vehicle can make use of for controlling the vehicle while driving the future road segment.

The vehicle data comprises, for example, one or several of vehicle mass, engine power, infrastructure such as curves, speed limitations, crossings etc.

In one exemplary embodiment, the method comprises determining S1 the vehicle conduction trajectory by optimizing energy consumption of the vehicle, and a given set velocity for the vehicle. Optimizing energy consumption comprises, for example, minimizing energy consumption, e.g. fuel consumption, of the vehicle. The given set velocity is i.e. the set velocity of the cruise control system. The vehicle conduction trajectory is then determined such that it is on average as close as possible to the set velocity, while still minimizing energy consumption.

The vehicle conduction trajectory is for example determined using a rule-based method or using an optimization based method. The rule-based method is based on one or several heuristic rules. A heuristic rule is for example determined based on experiments or a rule of thumb. The heuristic rule may comprise a constraint on the vehicle 1 , for example that the torque of the powertrain(s) should be within a certain interval, and that a conduction parameter, e.g. the velocity of the vehicle 1 , should be within a certain interval. The rule-based method may then comprise to simulate a model of the vehicle 1 with the constraint(s), while driving the future predicted route segment, and determine the vehicle conduction trajectory, for the route segment. From experiments, it is known that certain driving behavior is very energy efficient, and thus constraints can be set such that such driving behavior is obtained in the simulation. Desired control values and/or commands can then be retrieved for the future route segment.

The optimization-based method is based on a mathematical optimization. In the mathematical optimization, an optimization problem is solved based on a model of the vehicle, wherein a plurality of alternative trajectories are calculated considering one or several constraints, and the best alternative is chosen.

Typically, a cost function is established and minimized, and the most optimal trajectory is chosen, i.e. the vehicle conduction trajectory with the lowest cost. For example an optimization-based method may be used for finding a most optimal energy consuming (saving) velocity trajectory for the upcoming road segment. The method needs to have velocity limits to limit the trajectory, thus the second interval. A first interval is also set wherein a positive powertrain torque is allowed.

Fig. 5A illustrates a diagram for the limits of the velocity trajectory Vref of the vehicle 1 , intended as a velocity trajectory Vref to a cruise control system of the vehicle 1. The velocity trajectory Vref is allowed to vary between Vmin and Vmax, delimiting the interval AV. According to some embodiments, the vehicle conduction trajectory, here the velocity trajectory Vref, is determined in relation to a known fix trajectory. The known fix trajectory is for example a set velocity Vset or another reference velocity trajectory that it is desired that the vehicle 1 should follow. Flowever, a positive powertrain torque of the vehicle 1 is only allowed between Vtqmin and Vtqmax, delimiting the interval AVtq. Thus, the interval AVtq is thus here the first interval. The interval AV is the second interval An example of a determined resulting vehicle conduction trajectory, determined by S1 and here the velocity trajectory vref, is illustrated in Fig. 5B. The illustration in Fig. 5B comprises the same future road segment S along the road 9 as in Fig. 4. Thus, the road 9 starts with R0 and ends with R4. The determined velocity trajectory, with the explained constraint on the positive torque of the vehicle 1, is illustrated in the diagram below the future road segment S. As can be seen from the diagram, the velocity of the vehicle 1 will fluctuate with a smaller amplitude between RO and R1, than as illustrated in Fig. 4. This behavior will probably be more accepted by the driver, and the surrounding traffic will not be disturbed by large velocity variations of the vehicle 1. The upcoming hill, that starts at R1 , is here of such size that the velocity of the vehicle will not become lower than the velocity limit Vmin. Thus, if the determined vehicle conduction trajectory does not go outside the second interval, here limited by Vmax and Vmin, during the whole road segment, the method comprises using S3 the determined vehicle conduction trajectory for conducting the vehicle 1.

However, in a larger uphill than the one illustrated in Fig. 5B, the vehicle 1 might not be able to stay within Vmin and Vmax, with the constraint of only using positive powertrain torque between Vtq_min and Vtq_max, in order to travel up the uphill. Such a scenario is illustrated in Fig. 6A. In order to find such situations, the method comprises determining S2 whether the vehicle conduction trajectory is outside the second interval. Upon determining that the vehicle conduction trajectory is outside the second interval S21, the method comprises increasing S22 the variable first interval within a region ?r of the future road segment S, in order to encompass the vehicle conduction trajectory within the second interval, and repeating the determining S1 of the vehicle conduction trajectory using the increased variable first interval. The region Ar of the future road segment S is a region wherein the determined vehicle conduction trajectory goes beyond the first variable interval. In Fig. 6A, the point where the determined vehicle conduction trajectory goes beyond the first variable interval is denoted P1. The region should thus encompass this point. The region is a length of the road segment, for example 10-100 meters of the road segment.

As an alternative to increasing the first interval when the vehicle conduction trajectory goes outside the second interval, the method comprises to use a standard cruise controller, which attempts to e.g. keep the velocity of the vehicle as close to the set velocity as possible. The first interval is then removed, and a positive powertrain torque is allowed within the second interval. When the vehicle conduction trajectory is no longer outside the second interval, the method returns to step S1 , to again plan a trajectory where a positive powertrain torque only is allowed within the first interval.

With reference to Fig. 6B, the first interval, which was referred to as ?Vtql in Fig. 5A, is increased, within the region ?r, to the interval ?Vtq2. The interval ?Vtq2 is in one example embodiment outside both the borders of ?Vtql . For example, the interval ?Vtq2 is extended equally much outside the borders of ?Vtql , for example 2km/h. In another example embodiment, not shown, one of the borders of the interval ?Vtq2 is equal to one of the borders of ?Vtql . For example, for ?Vtq2, Vtqmax is increased, but Vtqmin stays the same as for ?Vtql .

Alternatively, for ?Vtq2, Vtqmin is decreased, but Vtqmax stays the same as for ?Vtql . After the first interval has been increased, the vehicle conduction trajectory is re-determined, i.e. re-generated with the increased first interval as a constraint.

Thereafter, the method comprises repeating the increasing S22 until the second interval encompass the vehicle conduction trajectory and/or until the first variable interval is outside the second interval. The first variable interval is for example increased in increments of 1-5 km/h for each repetition. Thus, when the determined vehicle conduction trajectory does not go outside the second interval, here the limited by Vmax and Vmin, during the whole road segment after the repetition, then the method comprises using S3 the determined vehicle conduction trajectory for conducting the vehicle 1. When the first variable interval is outside the second interval S23, the first variable interval cannot be increased more, and it is not possible to find a vehicle conduction trajectory that does not go below Vmin. This can happen, for example, if the vehicle 1 doesn’t have enough power for holding or increasing the speed of the vehicle 1 in a long uphill. The velocity of the vehicle 1 is then allowed to go below Vmin, and the latest determined vehicle conduction trajectory is used for conducting the vehicle 1. Alternatively, the method may instead use a standard cruise controller, which attempts to keep the velocity of the vehicle as close to the set velocity as possible. As an alternative to changing the first interval in steps, the first interval is directly set to a fixed greater interval. The fixed greater interval is e.g. equal to the second interval.

Optionally, the increasing S22 comprises increasing S22a the region of the future road segment, for example for each repetition. For example, upon determining that the vehicle conduction trajectory is outside the second interval S21 , the method comprises increasing S22a the region of the future road segment, in order to encompass the vehicle conduction trajectory within the second interval, and repeating the determining S1 of the vehicle conduction trajectory using the increased region. Thereby, the first interval can be increased along a larger road segment, and thereby the chances for encompassing the vehicle conduction trajectory within the second interval may be increased. The region is for example increased in increments, for example with 10 meters for each repetition. The region cannot be enlarged to more than the length of the road segment S. Thus, the region cannot extend beyond the predetermined road segment S. If the region has been extended to the length of the road segment, and the first variable interval has been increased such that it has the same borders as the second interval, and the vehicle conduction trajectory still cannot be encompassed within the borders of the second interval, then the method comprises using S3 the latest determined vehicle conduction trajectory for conducting the vehicle 1.

Alternatively, the method may instead use a standard cruise controller, which attempts to keep the velocity of the vehicle as close to the set velocity as possible. In some embodiments, the greatest length the region can be increased to is determined by the optimization algorithm. In an exemplary embodiment, if the energy consumption of the vehicle becomes too great, i.e. greater than an energy consumption criterion, because the region has been increased, the latest length of the region before the increase is used and the region is not increased anymore. Alternatively, the method may instead use a standard cruise controller, which attempts to keep the velocity of the vehicle as close to the set velocity as possible.

Fig. 6C illustrates the scenario in Fig. 6A, but where the first interval has been increased such that that is encompass the determined vehicle conduction trajectory. Also, the region ?r is within the road segment S. The vehicle conduction trajectory determined can thus be used for conducting the vehicle 1.

Fig. 7 illustrates an alternative example embodiment, where the vehicle 1 is set to follow a preceding vehicle 10. It is now desired to determine a vehicle conduction trajectory being a vehicle distance trajectory or a vehicle time gap trajectory. For ease of illustration, the method is here explained in relation to determining a vehicle distance trajectory, but it should be understood that the same method is applicable for determining a vehicle time gap trajectory. With distance is here for example meant a distance ?s to a preceding vehicle or a distance to a known fix trajectory ?s_set, such as a distance to a fictive preceding vehicle with a constant set velocity. With time gap is here for example meant a time gap ?t to a preceding vehicle or a time gap ?t_set to a known fix trajectory, such as a time gap to a fictive preceding vehicle with a constant set velocity Vset.

With reference to Fig. 7, the vehicle 1 is here allowed to vary its position within the first interval, here the interval ?L, delimited by ?Lmin and ?Lmax. Flowever, according to the method, the vehicle 1 is only allowed to use a positive torque when the vehicle is within the second interval ?Ltql , delimited by ?Ltqmin and ?Ltqmax. The interval ?Ltql is here within the interval ?L. The resulting vehicle conduction trajectory is illustrated in the Fig. 7 as ?sref. As can be seen from the figure, the first interval has been increased in the region ?r, because the vehicle conduction trajectory first went below the second trajectory. Thus, the velocity of the vehicle 1 went below ?Lmin and would then have been too far away from the preceding vehicle 10. By performing the method as described herein, a vehicle conduction trajectory has then been determined that can be encompassed within the second interval, that is, by increasing S24 the first interval and optionally also increasing S22 the region ?r. The determined vehicle conduction trajectory comprises for example conduction parameters (?s1; p1), (?s1; p2).... (?sn; pn) for n position along the road segment. If instead the time gap ?t had been modelled, the determined vehicle conduction trajectory could for example comprise conduction parameters (?t1; p1), (?t1; p2).... (?tn; pn) for n position along the road segment. A regular velocity trajectory would of course comprise velocities, (??1; p1), (??1; p2).... (??n; pn) for n position along the road segment The present disclosure is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the disclosure, which is defined by the appending claims.

Claims

1. A method for determining a vehicle conduction trajectory comprising conduction parameters chosen from velocity, distance or time gap for a vehicle, the method comprising: - determining (S1) a vehicle conduction trajectory for the vehicle for a future road segment of the vehicle based on vehicle data of the vehicle and topographic data of the future road segment, wherein the determining (S1) comprises only allowing a positive powertrain torque of the vehicle while the vehicle conduction trajectory is within a variable first interval, and attempting to keep the vehicle conduction trajectory within a second interval, wherein the first interval is smaller than the second interval on flat roads and the determining (S1) the vehicle conduction trajectory is based on optimizing energy consumption of the vehicle, and a given set velocity for the vehicle.

2. The method according to claim 1, the method comprising: - determining (S2) on hilly roads whether the vehicle conduction trajectory is outside the second interval, and upon determining that the vehicle conduction trajectory is outside the second interval: - increasing (S22) the variable first interval within a region of the future road segment, in order to encompass the vehicle conduction trajectory within the second interval, and repeating the determining (S1) of the vehicle conduction trajectory using the increased variable first interval.

3. The method according to claim 2, comprising repeating the increasing (S22) until the second interval encompass the vehicle conduction trajectory and/or until the first variable interval is outside the second interval.

4. The method according to any one of the preceding claims 2 or 3, wherein the region of the future road segment is a region wherein the vehicle conduction trajectory goes beyond the first variable interval.

5. The method according to claim 3 and 4, wherein the increasing (S22) comprises increasing (S22a) the region of the future road segment.

6. The method according to any of the preceding claims, wherein the vehicle conduction trajectory is a vehicle speed trajectory.

7. The method according to any one of the preceding claims 1 to 5, wherein the vehicle conduction trajectory is a vehicle distance trajectory or a vehicle time gap trajectory.

8. The method according to any of the preceding claims, wherein the vehicle conduction trajectory is determined in relation to a known fix trajectory.

9. The method according to any one of the claims 1 to 7, wherein the vehicle conduction trajectory is determined in relation to a trajectory of a preceding vehicle of the vehicle.

10. The method according to any one of the preceding claims, wherein the vehicle data comprises one or several of vehicle mass, engine power, and the topographic data comprises inclination data of the future road segment.

11. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of the preceding claims.

12. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of the claims 1 to 10.

13. A control arrangement (2) for determining a vehicle conduction trajectory for a vehicle (1) comprising conduction parameters chosen from velocity, distance or time gap, wherein the control arrangement (2) is configured to: - obtain topographic data of a future road segment for the vehicle (1); - determine a vehicle conduction trajectory for the vehicle for a future road segment of the vehicle (1) based on vehicle data of the vehicle (1) and topographic data of the future road segment, wherein a positive powertrain torque of the vehicle (1) only is allowed while the vehicle conduction trajectory is within a first variable interval, and the vehicle conduction trajectory is attempted to be kept within a second interval, wherein the first interval is smaller than the second interval on flat roads and the vehicle conduction trajectory is based on optimizing energy consumption of the vehicle, and a given set velocity for the vehicle.

14. The control arrangement (2) according to claim 13, wherein the control arrangement (2) is configured to perform the method according to any one of the claims 1 to 11.

15. A vehicle (1) comprising a control arrangement (2) according to claim 13 or 14.