BR102016022511B1 - METHOD FOR CONTROLLING AN ACCELERATION OF A VEHICLE, COMPUTER READABLE MEDIA, ELECTRONIC CONTROL UNIT AND MOTOR VEHICLE - Google Patents

Abstract

METHOD FOR CONTROLLING AN ACCELERATION OF A VEHICLE A method for controlling the acceleration of a motor vehicle traveling behind a driving vehicle, comprising the steps of: (a) collecting data relating to a road gradient along a route of travel expected, (b) collect data relative to a present size of a gap between vehicles, (c) collect data relative to a speed of the driving vehicle, (d) run a simulation based on the data and the assumption that a potential mode of acceleration operation involving gearing with the engine off of the motor vehicle is performed, in which the simulation computes data related to an expected interval between the vehicles during a next period of time, (e) verify whether the simulated data from step (d) ) satisfy a predefined actuation condition, which is satisfied when the expected range is greater than a preset minimum allowable interval, (f) once the actuation condition is satisfied, act the potential mode of operation.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a method for controlling an acceleration of a motor vehicle traveling behind a driver vehicle. The invention further relates to a computer program, a computer program product, an electronic control unit, and a motor vehicle. By a motor vehicle is meant here a vehicle that is powered by an internal combustion engine, and/or an electric motor. In particular, but not exclusively, the method is for use on a heavy motor vehicle, such as a truck or bus.

[0002] A throttle operating mode is herein intended to be understood as, for example, a mode in which throttle is controlled by a cruise control, such as adaptive cruise control (ACC) or cruise control to save fuel, or a mode in which the driver is controlling the vehicle in a specific way, so as to, for example, maintain a particular distance to a driver vehicle traveling ahead of the vehicle.

[0003] By an interval, an interval between the present vehicle and the driving vehicle in terms of distance or time is projected here.

[0004] By running with the engine off is to be understood operating the motor vehicle forward without transmitting any energy through acceleration, such as by disengaging a vehicle clutch or placing the gearbox in neutral.

[0005] By acceleration is meant to operate the vehicle forward with a gear engaged, but without drive force applied by acceleration.

BACKGROUND AND PRECEDENT TECHNIQUE

[0006] The cost of fuel for motor vehicles, for example cars, trucks and buses, represents a significant expense for the owner or user of the vehicle. A wide variety of different systems have therefore been developed to reduce fuel consumption, for example fuel efficient engines and fuel efficient cruise controls. Such fuel-saving cruise controls seek to reduce fuel consumption by adjusting the ride to the characteristics of the road ahead, so that unnecessary braking and/or fuel-consuming acceleration can be avoided. For example, taking into account topographical information regarding the road section ahead of the vehicle, the speed can be temporarily increased before, for example, an uphill slope, so that downshifting to a lower transmission mode can be avoided or delayed. In this way, a total energy consumption can be reduced. Also, information about road curvature and legal speed limits along the road section ahead of the vehicle can be taken into account.

[0007] One of the main factors affecting the energy consumption of a vehicle, particularly at high speeds and for large motorized vehicles that have a large frontal area, is air resistance. One way to reduce air resistance and with it energy consumption is therefore to drive behind a driving vehicle, i.e. another vehicle traveling ahead of the present vehicle and exploit the so-called slipstream effect. When two or more vehicles are involved in a so-called convoy, i.e. when rear vehicles drive relatively close to leading vehicles, the fuel consumption of the vehicles can be reduced, for example, by 5-15%.

[0008] Modern motor vehicles can be equipped with radar technology to measure a distance to a driving vehicle. Some vehicles may also be equipped with a control system to automatically maintain a specified d_set range for a driving vehicle, as long as the vehicle's speed does not exceed a set speed, such as a legal speed limit. Such a control system is usually referred to as an Adaptive Cruise Control (ACC), a Radar Cruise Control, or an Autonomous Cruise Control system. According to an example, such a system can comprise an actuation device with which the driver can manually adjust a position corresponding to a given range for a driving vehicle. Such an actuation device may, for example, have five different positions corresponding to discrete increments of distance to the driving vehicle between 10 and 75 meters, corresponding to time intervals within the range of 1-4 seconds. This system is usually automated in the rear vehicle. Alternatively, a driver of the rear vehicle may choose to drive a given distance to the leading vehicle.

[0009] An ACC system can, for example, be configured to maintain the specified d_set interval by applying the required driving force or braking force, i.e. so that a trigger force is applied if the interval becomes greater than than the specified range d_set, and such that brakes are applied as soon as the range becomes less than d_set. However, an ACC system can also be configured to maintain the specified d_set range just by controlling the actuation force imparted by the acceleration. In this case, a d_brake braking interval can be defined, in which vehicle brakes are applied. The d_brake braking interval is adjusted to be smaller than the specified d_set interval, so that if the vehicle becomes closer to the driving vehicle than the specified d_set interval, but not closer than the d_brake braking interval, the vehicle is motorized. Only if this is not enough, and the vehicle comes closer than d_brake, the brakes are applied. The brakes can be, for example, wheel brakes, a retarder, a discharge brake, etc.

[0010] However, driving behind a driver vehicle also results in that normal fuel economy systems, such as certain fuel-saving cruise controls, cannot be fully utilized due to the risk of coming too close to the driver vehicle, regardless whether the motor vehicle is driven with an activated ACC system or not. Certain fuel economy systems and functions are therefore disabled when driving behind a driver vehicle. The fuel economy effects obtained by driving behind a leading vehicle cannot therefore be fully accounted for.

SUMMARY OF THE INVENTION

[0011] It is a primary object of the present invention to achieve, in at least some aspect, an improved way of controlling an acceleration in a motor vehicle when driving behind a driver vehicle, such that the energy consumption of the motor vehicle is minimized . In particular, it is an object to provide a method for controlling acceleration, such that fuel saving systems can also be used in certain situations when the vehicle is traveling behind a driving vehicle, and such that the benefits of an ACC system can be combined with the benefits of other fuel saving systems.

[0012] According to a first aspect of the present invention, at least the primary objective is achieved by means of the method, as defined in claim 1. The method comprises the steps of: a) collecting data relating to a road gradient along of an expected travel route ahead of the motor vehicle, b) collect data relating to a present size of a gap between the motor vehicle and the driving vehicle, c) collect data relating to a speed of the driving vehicle, d) perform at least one simulation based on the data and on the assumption that a potential mode of operation of acceleration involving gearing with the motor vehicle's engine off is actuated at a first point in time t_0, in which the simulation computes data relating to the size of an expected interval d_sim between vehicles , during a period of time close to the first point at time t_0, e) verify that the simulated data from step (d) satisfy a set of current conditions predefined action conditions including at least one predefined actuation condition C1, which is satisfied when an expected interval d_sim is greater than a preset minimum allowable interval d_min during the next time period, f) once the set of pre-defined actuation conditions is satisfied, actuate the potential mode of operation at the first point in time t_0.

[0013] Thus, in the method according to the invention, an expected interval d_sim for the driving vehicle during a close period of time is simulated, and depending on the size of the expected interval, it is determined whether or not to actuate an operating mode involving running with the engine off of the motor vehicle, i.e. operating the vehicle forward without transmitting any energy through acceleration for at least a portion of the close time period, or road section. Off-engine gearing can be achieved in different ways, such as disengaging a vehicle clutch or shifting the gearbox into neutral.

[0014] If the gap between vehicles is expected to be greater than the pre-set minimum allowable gap d_min during the next time period or road section, the simulated operating mode is actuated. In practice, this is useful when driving with the vehicle's engine off, can be advantageous in terms of fuel economy, and involves reducing braking force, or increasing relative speed in relation to the driving vehicle. The simulation reveals whether the gap between vehicles is likely to exceed the minimum permissible gap d_min, and if so, the vehicle is set to idle so that the vehicle's fuel efficiency can be improved. Running with the engine off is often advantageous from a fuel economy perspective, and it is therefore useful to be able to switch to an operating mode in which the vehicle is put into gear with the engine off when this is possible. Using the method according to the invention, the acceleration mode of operation will be automatically switched to one that involves running with the engine off when this is possible, without getting too close to the driving vehicle. By repeating data collection and simulation with a certain frequency, it can be continuously checked whether a switch to an operating mode involving running with the engine off is possible.

[0015] The next period of time during which the expected interval d_sim must exceed the minimum permissible interval d_min for condition C1 to be considered satisfied can be predefined. Condition C1 is preferably considered satisfied only if the expected interval d_yes exceeds the minimum permissible interval d_min during the entire next predefined period of time. In other words, if the expected interval d_sim is at any point in time during the time period less than the minimum permissible interval d_min, condition C1 is not considered satisfied and the simulated potential operating mode is not actuated. The next time period can, for example, be adjusted based on a length of total time period or road section, for which the simulation is to be performed, or based on a behavior of the simulation.

[0016] The step of collecting data relating to the speed of the driver vehicle may include, for example, estimating the speed of the driver vehicle for the next period of time, or receiving data from the driver vehicle regarding its predicted speed variation. In the simplest case, the current speed of the driving vehicle is measured or estimated and an assumption is made that the driving vehicle will maintain constant speed. It is also possible to base an estimate of the future speed of the driver vehicle on its present speed and acceleration, as measured or reported. The future speed profile of the driver vehicle can also be simulated on the present (rear) motor vehicle using mass and torque estimates of the driver vehicle's engine.

[0017] The simulation performed in the method according to the invention is preferably in the form of a so-called complete vehicle simulation over an expected travel route ahead of the motor vehicle. The simulation is repeated with a certain frequency, such as a frequency of 1 Hz. In each simulation, several parameters can be determined, such as speed v_sim, engine speed, engine torque, interval d_sim to the driving vehicle, time, distance traveled, etc. The simulation is based on a potential mode of operation, which in this case is a mode of operation that involves running the engine off of the motor vehicle with a throttle gearbox in a neutral position, or with a clutch disengaged. Several different operating modes can be simulated simultaneously. The simulation can be performed over a longer time period, or road section, than the next time period used when checking that the pre-defined set of performance conditions are satisfied.

[0018] When the method is started, the acceleration can be controlled by an adaptive cruise control (ACC) system, by another system in the vehicle, or by a driver of the vehicle. Acceleration is preferably operated manually, or automatically, to maintain a specified d_set range for the driving vehicle and to apply the necessary drive force, or braking force, to achieve this. This means that gear shifting, fuel injection, braking, etc. are controlled in order to maintain the specified interval d_set. Also a d_brake braking interval can be defined, in which case brakes are automatically applied if the interval between vehicles becomes less than the d_brake braking interval. If the gap between vehicles is between d_brake and d_set, the ACC system, in this case, controls the acceleration such that the vehicle is powered.

[0019] The minimum permissible interval d_min which, of course, can be defined in terms of either time or distance, should not usually be adjustable by the driver of the motor vehicle. In the case where the motor vehicle is controlled by an adaptive cruise control, such that the speed of the motor vehicle is regulated to maintain a specified range d_set for the driving vehicle, the minimum permissible range d_min is adjusted to be less than d_set. Preferably, the minimum allowable range d_min can be set depending on the specified range d_set. If a d_brake braking interval is also defined, the minimum allowable interval d_min is preferably set to be less than the specified d_set interval, but greater than the d_brake braking interval, d_brake < d_min < d_set. Naturally, also security aspects influence the size of the minimum permissible interval d_min.

[0020] According to an embodiment of the invention, the set of predefined actuation conditions comprises a predefined actuation condition C2, which is satisfied when the expected interval d_sim is smaller than a preset maximum permissible interval for at least part of the next period of time. The part of the next time period during which the expected interval d_sim should be less than the maximum permissible interval d_max can be predefined and can, for example, be a time period starting after an initial delay. By setting a maximum permissible gap d_max there is no risk that the vehicle will be set to idle if this leads to too large a gap between vehicles, so that the benefits of traveling behind a leading vehicle can no longer be achieved.

[0021] According to another embodiment of the invention, the set of predefined actuation conditions comprises a predefined actuation condition C3, which is satisfied when the expected interval d_sim is in a range between the minimum permissible interval d_min and the maximum permissible interval d_max for at least a preset minimum time period Δt_min. This prevents unnecessary quick switching between operating modes when no significant energy gains can be expected. The minimum time period Δt_min can be determined on the basis of factors such as transient losses arising when switching to and from gear with the engine off, driving comfort and component wear arising when switching operating modes.

[0022] According to another embodiment of the invention, step (D) comprises simulating a future speed profile of the motor vehicle, and based on the same, computing the expected size of the d_sim interval. The speed profile is compared with data relating to the speed of the driving vehicle and the size of the gap can thereby be obtained. Simulations of a future speed profile usually take topographical data into account and may also take into account traffic data etc. Such simulation methods are known and often performed on the vehicle for other reasons and this is therefore a suitable way to simulate the gap size over the next period of time.

[0023] According to another embodiment of the invention, the set of predefined actuation conditions comprises a predefined actuation condition C4, which is satisfied when the simulated speed v_sim is within a predefined admissible speed range. set between a minimum permissible speed v_min and a maximum permissible speed v_max. This prevents the vehicle from being set to run with the engine off when the vehicle speed is either too high or too low for this to be energy efficient and/or desirable.

[0024] According to another embodiment of the invention, step (D) further comprises performing at least one simulation based on the assumption that the potential mode of operation of the acceleration is performed at a later point in time t_1, whose later point at time t_1 is delayed relative to the first point at time t_0, where the simulation computes data relating to an expected interval d_sim_delay between vehicles. A supplementary simulation is thus performed, in which the actuation of the potential mode of operation is performed at a later point in time t_1 than in the previously discussed simulation. The same collected data is used as a basis for the simulation, and the simulations are performed simultaneously. Further simulation thus reveals whether any advantages can be gained by delaying a switch, of modes of operation, until the later point in time t_1, or whether the earliest point in time t_0 is suitable for making this switch. This modality is particularly advantageous when the computational power available for simulation is limited, so that the frequency with which simulations can be performed is consequently limited.

[0025] According to another embodiment of the invention, the set of predefined actuation conditions comprises a predefined actuation condition C5, which is satisfied when an expected interval d_sim_delay is smaller than the minimum permissible interval d_min. When the minimum permissible interval d_min is less than the expected interval d_sim and greater than the expected interval d_sim_delay, d_sim_delay < d_min < d_sim, the conditions are optimal to trigger an operation mode that includes running with engine off. If actuation is delayed, the motor vehicle will be at risk of coming too close to the driver vehicle and braking will be required. If, on the other hand, engine off travel is started when both the expected d_sim and d_sim_delay intervals are longer than the minimum permissible interval d_min, the vehicle may be at risk of coming too far from the driver vehicle if engine off travel is started. .

[0026] According to another embodiment of the invention, the speed of the motor vehicle is initially controlled in order to maintain a specified interval d_set for the driving vehicle, where the specified interval d_set is greater than the minimum permissible interval d_min. This can preferably be accomplished using an adaptive cruise control (ACC) system, which is commonly used to control acceleration when driving behind a driving vehicle. The ACC system can, in this embodiment, be used to control the acceleration to drive in the specified d_set interval, while it is continuously checked whether a temporary relinquishment of this control can be done instead, actuating the simulated operating mode, the which may in the given situation be more fuel efficient.

[0027] According to another embodiment of the invention, the set of predefined actuation conditions comprises a predefined actuation condition C6, which is satisfied when, at a point in time during the next period of time, the difference between the expected interval d_sim and the specified interval d_set is less than a first predefined threshold value, and a difference between an expected speed v_sim and an expected driver vehicle speed v_lead is less than a second predefined threshold value . In this case, conditions are perfect for "fitting" with the driving vehicle in the specified interval d_set at the point in time. The specified range d_set is preferably the specified range d_set that a motor vehicle ACC system is set to maintain for the driving vehicle.

[0028] According to another embodiment of the invention, the potential mode of operation comprises the vehicle driving with the engine off for a predetermined initial period of time, and thereafter motoring the vehicle in a higher available gear. Thus, if the motor vehicle is at risk of coming too close to the driver vehicle, if the vehicle is driven with the engine off for a longer period of time, the advantages associated with driving with the engine off can be obtained by activating a mode of operation that involves running with the engine off followed by acceleration.

[0029] According to at least one further aspect of the invention, the primary object is achieved by means of a computer program comprising computer program code to cause a computer to implement the proposed method, when the computer program runs on the computer.

[0030] According to a further aspect of the invention, at least the primary object is achieved by means of a computer program product comprising a non-transient data storage medium readable by a computer, and in which the Program code of the proposed computer program is stored.

[0031] According to a further aspect of the invention, at least the primary objective is achieved by means of an electronic control unit of a motor vehicle comprising an execution means, a memory connected to the execution means and a means of data storage, which is connected to the execution medium, and in which the computer program code of the proposed computer program is stored.

[0032] According to a further aspect of the invention, at least the primary objective is achieved by a motor vehicle comprising the proposed electronic control unit. The motor vehicle may preferably be a truck or a bus.

[0033] Other advantageous features as well as advantages of the present invention will appear from the description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments of the invention will be described below with reference to the accompanying drawings.

[0035] Figure 1 is a flowchart showing a process according to an embodiment of the invention,

[0036] Figure 2 is a graph that schematically shows the results of a simulation performed in a method according to an embodiment of the invention,

[0037] Figure 3a is another graph that schematically shows the results of a simulation carried out in a method according to an embodiment of the invention,

[0038] Figure 3b is yet another graph that schematically shows the results of a simulation carried out in a method according to an embodiment of the invention,

[0039] Figure 4 schematically shows a control unit according to the invention, and

[0040] Figure 5 schematically shows a vehicle according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0041] A method according to an embodiment of the present invention is schematically represented in the flowchart in figure 1. The method is started in a motor vehicle when the vehicle moves forward behind a driver vehicle. Typically, a motor vehicle's acceleration is initially controlled by an adaptive cruise control (ACC) system, so that the vehicle maintains a specified interval d_set, in terms of time, or distance, to the driving vehicle.

[0042] A first step S1 comprises collecting data relating to a road gradient along an expected travel route ahead of the motor vehicle, as will be further described later. A second step S2 comprises collecting data relating to a current size of a gap between the motor vehicle and the driver vehicle. A third step S3 comprises collecting data related to the speed of the driving vehicle. Data relating to road gradient, range and speed of the driving vehicle are stored on a data storage medium.

[0043] A fourth step S4 comprises performing at least one simulation based on the data collected in steps S1-S3 and on the assumption that a potential mode of operation of the acceleration, whose mode of operation involves gearing with the engine off of the motor vehicle, is actuated at a point t_0 in time. The simulation computes data related to the size of the expected interval d_yes between vehicles during the next time period following the time point t_0. That is, it simulates how the size of the gap between vehicles is expected to develop if a potential mode of operation is actuated at the point in time t_0. The potential mode of operation involves running with the motor vehicle off for at least a portion of the next period of time. For example, the potential mode of operation may involve initial engine off gearing of the motor vehicle, and thereafter accelerating the motor vehicle in a high gear. Several possible operating modes can be simulated simultaneously.

[0044] A fifth step S5 comprises verifying whether the simulated data from step S4 satisfy a series of predefined performance conditions. This set of predefined trip conditions includes at least one predefined trip condition C1, which is considered satisfied when the expected interval d_sim is greater than a pre-set minimum allowable interval d_min during the next time period , preferably for the entire next period of time, the duration of which can be defined in advance. Thus, in step S5, the simulated expected interval d_sim between vehicles is compared with the preset minimum permissible interval d_min which acts as a threshold value. If it is found that the interval is likely to exceed the minimum permissible interval d_min during the next period of time if the potential mode of operation is actuated, actuation condition C1 is considered to be satisfied. The set of pre-defined trip conditions may further include other conditions, such as a C2 trip condition that the expected range d_sim must be less than a pre-set maximum allowable range d_max during at least a part of the next time period . A condition C3, which is satisfied when the expected interval d_yes is in a range between the minimum permissible interval d_min and the maximum permissible interval d_max for at least a preset minimum time period Δt_min, and a condition C4, which is fulfilled when a simulated speed v_sim is within a preset permissible speed range between a minimum permissible speed v_min and a maximum permissible speed v_max, can be further defined. The set of pre-defined actuation conditions can include all or some of these C2-C4 conditions.

[0045] A sixth step S6 comprises triggering the simulated potential mode of operation at point t_0 in time, once the predefined actuation conditions have been satisfied. Otherwise, in case the actuation conditions have not been satisfied, steps S1-S5 can preferably be repeated. In the simplest case, the potential mode of operation is triggered once that condition C1 is satisfied. In principle, this means that the motor vehicle is in motion with the engine off, as it is not in danger of coming too close to the driver vehicle. Step S6 ends the method according to the invention. The decision to drive with the vehicle's engine off is then continuously reassessed.

[0046] All steps S1-S5 are preferably performed continuously, which here should be understood as the steps being performed with a predetermined frequency, while the vehicle moves forward. The data collection frequency and the simulation frequency are not necessarily identical and may, for example, be of the order of 100 Hz.

[0047] Data relating to the road gradient can be collected in step S1 in several different ways. The road gradient can be determined based on map data, e.g. from digital maps that contain topographical information, in combination with positioning information, for example, GPS (global positioning system) information. The positioning information can be used to determine the vehicle's location in relation to the map data, so that the road gradient can be extracted from the map data. Several current cruise control systems use map data and positioning information. Such systems can then provide the required map data and positioning information for the method according to the present invention, thereby minimizing the additional complexity involved in determining road gradient.

[0048] The road gradient can be obtained based on a map, together with GPS information, from radar information, from camera information, from information from another vehicle, from information from positioning and road gradient information previously stored on board, or from information obtained from traffic systems relating to the expected route of travel. In systems where information is exchanged between vehicles, road gradients estimated by one vehicle may also be made available to other vehicles, either directly or through an intermediate unit, such as a database, or the like.

[0049] Data related to the present size of the gap between vehicles can be collected in step S2 using, for example, radar technology, camera information, map data, in combination with GPS (global positioning system) technology, or similar.

[0050] Data relating to a speed of the driver vehicle can, in step S3, for example, be collected by measuring the speed or by communication with the driver vehicle and, from this information, determine an expected speed of the driver vehicle during travel along of the next section of road. This step might, for example, comprise measuring a current speed of the driver vehicle and making an assumption about its speed over the next road section or time period, such as assuming that the driver vehicle will maintain a constant speed. The guess can also be based on knowledge about, for example, the road gradient over the next road section, and/or about a current acceleration of the driving vehicle.

[0051] The simulation that computes data related to the size of the expected interval d_sim in step S4 is usually carried out in stages simulating a future profile of expected speed of the motor vehicle, and from there, determining the development of the interval size by comparison with data relating to the speed of the driver vehicle. In the simulation of the future velocity profile, the potential operating mode is assumed to be actuated at the point in time t_0. The simulated interval d_sim for the vehicle driver for an index k + 1 can be simulated as: d_sim_k + 1 = + d_sim_k (v_lead - v_sim) * δT,

[0052] where V_lead is the speed of the driver vehicle, v_sim is the simulated speed of the motor vehicle, and where δT is the time interval used in the simulation.

[0053] If computational power is limited in the vehicle, the frequency with which the simulations can be repeated is also limited. In this case, it is possible to run an additional simulation simultaneously with the previously discussed simulation. This additional simulation is based on the assumption that the potential mode of operation of the acceleration is actuated at a point in time t_1, whose point in time t_1 is lagged with respect to the point in time t_0. The additional simulation computes data relating to an expected interval delay d_sim_delay between the vehicles, that is, the development of the interval between the vehicles, since the same potential mode of operation is actuated at a later moment in time t_1. The set of predefined actuation conditions may, in this case, comprise a predefined actuation condition C5, which is satisfied when the expected interval d_sim_delay is smaller than the minimum permissible interval d_min. In other words, both conditions C1 and C5 are satisfied if the interval between vehicles is expected to be less than the minimum permissible interval lesser d_min if the potential mode of operation is actuated at point in time t_1, but greater if it is actuated at the point in time t_0.

[0054] The set of predefined actuation conditions may also comprise a predefined actuation condition C6, which is considered satisfied when, at a point in time during the next period of time, a difference between the expected interval d_sim and a specified interval d_set is less than a first predefined threshold value, and the difference between an expected speed v_yes and an expected driver vehicle speed v_lead is less than a second predefined threshold value.

[0055] In one example, the method according to an embodiment of the invention is performed on a motor vehicle traveling along a road section behind a driver vehicle. In a present operating mode, the acceleration of the motor vehicle is controlled by an ACC system. The vehicle's speed is therefore automatically adjusted to maintain a specified d_set range for the vehicle ahead. As the vehicle drives along the road section, data relating to the road gradient along the expected travel route ahead of the motor vehicle is continuously collected using a map in conjunction with a GPS system (step S1). Simultaneously, data regarding the dimension present between the motor vehicle and the driver vehicle are collected using radar technology (step S2). Data relating to the speed of the driver vehicle are also collected (step S3), which data is obtained by determining a present speed of the driver vehicle and making an assumption that the driver vehicle will be traveling at a constant speed. All data collected is stored in a database.

[0056] In a vehicle processing unit, the collected data is used to, continuously, i.e. at an adjusted frequency of, for example, 1 Hz, simulate how the gap size between vehicles is expected to develop during a next period of time for a number of different scenarios (step S4), in which a potential mode of operation of the acceleration that involves running with the engine off of the motor vehicle at a point in time t_0 is initiated. After the simulation, it is evaluated whether a number of predefined actuation conditions are satisfied. (step S5). If all predefined actuation conditions are satisfied, the potential operating mode is triggered (step S6).

[0057] In the example shown in figure 2, the motor vehicle is traveling on a section of road down the mountain at a set speed v_set, corresponding to a specified interval d_set for a driving vehicle, when the motor vehicle approaches a section of road up the mountain. Brakes are engaged during the downhill road section to maintain the specified interval d_set. The lead vehicle is allowed to travel at a constant speed v_lead. Simulations of the expected interval d_sim carried out with a certain frequency during the trip along the downhill road section, until now, revealed that the pre-set actuation condition C1 was not fulfilled, since the vehicle was at risk of coming too far. close to the driver vehicle if an operation mode involving running with the engine off was to be actuated. In the graph, the dashed lines show the results of a simulation performed on a first T1 occasion, where the upper graph shows the simulated expected speed v_sim_1 of the motor vehicle and the lower graph shows the simulated expected range d_sim_1 which is clearly smaller than the interval permissible minimum d_min during a part of the next time period. The potential mode of operation is therefore not acted upon in response to the assessment performed in step S5.

[0058] Now, when the uphill road section approaches even closer, the simulations are repeated on a T2 occasion. The simulated velocity v_sim_2 and the simulated range d_sim_2 are shown as solid lines in figure 2. Simulations carried out at time T2, and a subsequent comparison with the pre-defined set of actuation conditions, reveal that the simulated expected range d_sim exceeds the range pre-set minimum permissible d_min if the brakes are disengaged and the operating mode involving running with the engine off is engaged. Therefore, the potential simulated operating mode is actuated, resulting in an increase in speed compared to the initial operating mode, in which acceleration is controlled by the ACC system. In a continuation of the innovative method, the possibility of continuing throttle control in the actuated operating mode, or switching to another operating mode, such as controlling throttle using the ACC system, is continuously evaluated.

[0059] Another example is shown in fig. 3a. In this example, a motor vehicle is traveling on a level road section at an adjusted speed v_set, corresponding to an adjusted interval d_set for a driving vehicle, when the motor vehicle approaches a downhill section of road, followed by a section way up the mountain. When the vehicle is traveling along the level road section, an ACC system is used to control a vehicle's acceleration and a drive force is applied through the acceleration. On one occasion, data is collected according to step S1-S3, and a simulation according to step S4 is performed by simulating that an operating mode in which the motor vehicle is in gear with the engine off is actuated at time t_0. The simulated expected velocity v_sim and the simulated expected range d_sim are shown with dashed lines in the upper and lower graphs, respectively. Simultaneously, it is simulated that driving with the vehicle engine off should instead be started at time t_1, which is delayed in relation to t_0. The simulated expected speed v_sim_delay and the simulated expected interval d_sim_delay are shown with solid lines in the upper and lower graphs, respectively. As can be seen from the graphs, marching with the vehicle off will involve an initial speed reduction, followed by a speed increase as the vehicle gains momentum on the downhill section of road, and a subsequent speed reduction as the vehicle comes to the uphill section of road. Start running with engine off at time t_0 means that the minimum permissible interval d_min will be exceeded during the entire next period of time, so that the predefined actuation condition C1 is satisfied. If, instead, you start driving with the engine off at t_1, the motor vehicle will come very close to the driver vehicle. Thus, both predefined conditions C1 and C5 are satisfied. In the example shown, a maximum permissible range d_max has also been defined, which the simulated expected range d_sim is not allowed to exceed. Furthermore, a condition C6 is satisfied at the point in time t_C6, at which the expected motor vehicle speed v_sim coincides with the driving vehicle speed v_lead, and at which the expected interval d_sim coincides with the specified interval d_set. Thus, the conditions for “fitting” with the driving vehicle at point in time t_C6 are optimal if starting the drive with the engine off at point in time t_0. In this example, driving with the vehicle engine off is therefore started immediately after the simulations and a subsequent comparison with the pre-defined set of actuation conditions have been carried out, i.e., at a point in time corresponding to t_0.

[0060] In yet another example shown in figure 3b, a motor vehicle is approaching a driver vehicle. The acceleration of the motor vehicle is, in this example, initially controlled with a cruise control system to maintain a set speed, and a drive force is applied through acceleration. As the motor vehicle approaches the driver vehicle, it is simulated how an engine-off shift could affect the gap between vehicles if initiated at a point in time t_0 (dashed lines) or if initiated at a later point in time t_1 (solid lines) lagged with respect to t_0. As can be seen, if you start driving with the engine off immediately, the vehicle will not be at risk of coming very close to the driver vehicle, but if you wait until time t_1, the vehicle will get very close to the driver vehicle and it may be necessary to brake. Thus, a changeover to gear with the engine off is carried out in time t_0. The vehicle can therefore be driven with the engine off until reaching a desired range for the driving vehicle, after which the acceleration can be controlled using an ACC system.

[0061] One skilled in the art will appreciate that a method for controlling the acceleration of a motor vehicle in accordance with the present invention can be implemented in a computer program which, when executed on a computer, causes the computer to drive the method. The computer program usually takes the form of a computer program product comprising a suitable digital storage medium on which the computer program is stored. The computer-readable digital storage medium comprises suitable memory, for example ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable PROM), flash memory, EEPROM (electrically erasable PROM), a drive hard disk, etc.

[0062] Figure 4 schematically outlines an electronic control unit 400 of a vehicle provided with an execution means 401 that can take the form of substantially any suitable type of processor or microcomputer, for example, a circuit for signal processing (digital signal processor, DSP), or a circuit with a specific predetermined function (application-specific integrated circuit, ASIC). The means 401 is connected to a memory unit 402 which is located in the control unit 400. A data storage means 403 is also connected to the execution means and provides the execution means with, for example, the stored program code and/or stored data that the execution medium needs to enable it to do calculations. The execution means is also adapted to store partial or final calculation results in the memory unit 402.

[0063] The control unit 400 is also provided with respective devices 411, 412, 413, 414 for receiving and sending input and output signals. These input and output signals may comprise waveforms, pulses, or other attributes that the input signal receiving devices 411, 413 can detect as information, and which can be converted to signals that the execution means 401 can process. . These signals are then provided to the execution medium. The output signal senders 412, 414 are arranged to convert signals received from the execution means 401, to create, for example by modulating them, output signals that can be transported to other parts of the vehicle and/or other onboard systems.

[0064] Each of the connections to the respective devices for receiving and sending input and output signals may take the form of one or more of a cable, a data bus, for example, a CAN bus (network area controller ), a MOST (Media Oriented Systems Transport) bus or some other bus configuration, or a wireless connection. One skilled in the art will appreciate that the aforementioned computer can take the form of execution medium 401 and that the aforementioned memory can take the form of memory unit 402.

[0065] Control systems in modern vehicles generally comprise a communication bus system consisting of one or more communication buses to connect together a number of electronic control units (ECU), or controllers, and various components on board of the vehicle. Such a control system may comprise a large number of control units, and the responsibility for a specific function may be divided between two or more of them.

[0066] In the outlined embodiment, the present invention is implemented in the control unit 400, but it could also be fully or partially implemented in one or more other control units already on board the vehicle, or by a control unit dedicated to the present invention. Vehicles of the type discussed here are, of course, often provided with significantly more control units than shown here, as someone skilled in the art will surely appreciate.

[0067] The present invention according to one aspect relates to a motor vehicle 500, which is shown schematically in Figure 5. The motor vehicle 500 comprises a motor 501 which forms part of an acceleration 502 which drives driving wheels 503, 504. The motor vehicle 500 further comprises an exhaust treatment system 505, and a control unit 510, which corresponds to the aforementioned control unit 400 in Fig. 4, and which is arranged to control the function in the motor 501.

[0068] The invention is, of course, not in any way restricted to the embodiments described above. On the contrary, many possibilities for modifications thereof will be evident to a person of ordinary talent in the art, without departing from the basic idea of the invention as defined in the appended claims.

Claims (12)

1. Method for controlling an acceleration of a motor vehicle traveling behind a driver vehicle comprising the steps of: a. collect data relating to a road gradient along an expected travel route ahead of the motor vehicle, b. collect data relating to a current size of a gap between the motor vehicle and the driver vehicle, c. collect data relating to a driver's vehicle speed, d. run at least one simulation based on the data, and on the assumption that a potential mode of operation of the acceleration, which involves gearing with the motor vehicle's engine off, is actuated at a first point in time t_0, in which the simulation computes data relating to the size of an expected interval d_yes between vehicles, during a next time period following the first time point t_0, e.g. verify that the simulated data from step (d) satisfy a set of predefined actuation conditions that includes at least one predefined actuation condition C1, which is satisfied when the expected interval d_sim is greater than a permissible interval preset minimum d_min over the next time period, f. once the set of predefined actuation conditions is satisfied, actuate the potential operating mode at the first point at time t_0, characterized by the fact that the set of predefined actuation conditions comprises a predefined actuation condition C3, which is satisfied when the expected range d_sim is in a range between the minimum allowable range d_min and the maximum allowable range d_max for at least a preset minimum time period Δt_min. 2. Method, according to claim 1, characterized in that the set of predefined actuation conditions comprises a predefined actuation condition C2, which is satisfied when the expected interval d_sim is less than a permissible interval preset maximum d_max for at least part of the next time period. 3. Method according to any one of claims 1 or 2, characterized in that step (d) comprises simulating a future speed profile of the motor vehicle, and based on it computing the size of the expected interval d_sim. 4. Method, according to claim 3, characterized in that the set of predefined actuation conditions comprises a predefined actuation condition C4, which is satisfied when a simulated speed v_sim is within a range of speed between a minimum permissible speed v_min and a maximum permissible speed v_max. 5. Method according to any one of claims 1 to 4, characterized in that step (d) additionally comprises performing at least one simulation based on the assumption that the potential mode of operation of the acceleration is actuated at a later point at time t_1, whose later point in time t_1 is delayed relative to the first point in time t_0, at which the simulation computes data relative to an expected interval d_sim_delay between vehicles. 6. Method, according to claim 5, characterized in that the set of predefined actuation conditions comprises a predefined actuation condition C5, which is satisfied when the expected interval d_sim_delay is smaller than the interval permissible minimum d_min. 7. Method according to any one of claims 1 to 6, characterized in that the speed of the motor vehicle is initially controlled in order to maintain a specified interval d_set for the driving vehicle, in which the specified interval d_set is greater than than the minimum permissible interval d_min. 8. Method according to any one of claims 3 to 7, characterized in that the set of predefined actuation conditions comprises a predefined actuation condition C6, which is satisfied when, at a point in time during the next period of time, a difference between an expected interval d_sim and a specified interval d_set is less than a predefined first threshold value, and a difference between an expected speed v_sim and an expected speed of the driver vehicle v_lead is less than than a second predefined threshold value. 9. Method, according to any one of claims 1 to 8, characterized in that the potential mode of operation comprises gearing with the vehicle's engine off for a predetermined initial period of time, and thereafter accelerating the vehicle in a gear highest available. 10. Computer-readable medium characterized by the fact that it includes instructions for carrying out the method defined in any one of claims 1 to 9. 11. Electronic control unit (400) of a motor vehicle, characterized in that it comprises an execution means (401), a memory (402) connected to the execution means (401) and a data storage means (403) that is connected to the execution medium (401) and on which a computer-readable medium as defined in claim 10 is stored. 12. Motor vehicle (500) characterized in that it comprises an electronic control unit (400, 510) according to claim 11.

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