DE102010027172B4 - Method and device for determining a minimum energy route - Google Patents

Abstract

A method of determining an energy minimum route, wherein the minimum energy route is determined from a number (M) of possible routes between a start position and a destination position, wherein the minimum energy route is a route for which power consumption (E) of a vehicle is minimum the energy consumption is determined as a function of a speed curve and an acceleration curve over a travel time, characterized in that the speed profile and the acceleration curve are approximated as harmonic oscillations, the energy consumption being approximated as the sum of a speed-dependent component and an acceleration-dependent component, wherein the speed-dependent component in Depending on the travel time, the average speed and an average acceleration wi determines the dependence of a travel time and a medium speed and the acceleration-dependent portion approx.

Description

The invention relates to a method and a device for determining a minimum energy route, in particular a minimum energy route between a start position and a target position.

On currently marketed navigation terminals, in almost all cases a route search is implemented that minimizes either travel times or a length of travel distance between a desired start position and a desired target position of a vehicle. For simpler devices this route search is based on fixed travel times and / or path lengths for individual sections, especially road sections, a route, the sections are considered as edges of a graph and the determination of the route with known search methods, eg. As a Dijkstra algorithm can be found. More well-equipped devices can determine the route with variable edge weights, eg. B. Daytime or weekday dependent travel times or travel speeds, perform, wherein edges correspond to individual sections of a route. As a result, a midnight route may differ significantly from an early morning route. A determination of a route that minimizes energy consumption of the vehicle requires above all a current speed of the vehicle and an indication of an acceleration of the vehicle, since these are the essential parameters for determining the energy consumption.

The DE 10 2004 024 259 A1 discloses a method for determining the driving strategy of a vehicle optimized with regard to fuel consumption, wherein cartographic route attributes of the route to be traveled are used to determine the driving strategy. The determination also takes into account current and / or expected traffic data on the route to be traveled.

From the WO 2009/071369 A1 a method for determining a minimum energy route is known, wherein the energy minimized route is determined from a number of possible routes between a start position and a destination position, wherein the minimum energy route is a route for which power consumption of a vehicle is minimal, the energy consumption in Dependence of a speed course and an acceleration course over a travel time is determined.

From the US 5,913,917 A For example, a method for estimating a power consumption of a vehicle for a selected route is known, wherein the route is divided into a plurality of sections. Energy consumption is determined as the integration of an energy function over a travel period.

From the JP 2007 032 522 A A method is known in which the speed changes of a motor vehicle are recorded, from which a mean value for speed changes is determined and compared with a vehicle model standard value, which is deduced from the driving skills.

It raises the technical problem of providing a method and a device for determining a minimum energy route, which is as simple as possible to implement, has as little storage space and determines a minimum possible energy route to z. B. to minimize fuel consumption of the vehicle.

The solution to the technical problem arises from the objects with the features of claims 1 and 8. Further advantageous embodiments of the invention will become apparent from the dependent claims.

A method is proposed for determining an energy minimum route, wherein the minimum energy route is determined from a number of possible routes between a start position and a destination position. The minimum energy route here denotes a route between the start and the destination position for which the vehicle traveling the route requires the least energy compared to alternative routes. For example, this can be expressed by a minimum fuel consumption.

The minimum energy route is thus a route for which energy consumption of the vehicle is minimal.

According to the invention, the energy consumption is determined as a function of a speed curve and an acceleration curve over a travel time. Here, the speed course refers to a time course of a speed of the vehicle for the entire route or sections of the route. Similarly, the acceleration curve refers to a time course of the acceleration of the vehicle over the entire route or one or more sections of the route. The travel time here denotes a period in which the vehicle passes through the entire route or one or more sections of the route.

The energy consumption of a vehicle depends significantly on a speed and an acceleration of the vehicle when driving on the route. For example, frequent braking and accelerating results in higher energy consumption than in a uniform driving style. Likewise higher energy consumption results in higher energy than lower speed. The method according to the invention therefore makes it advantageously possible to determine an energy consumption as a function of speed and acceleration, in which case a route minimizing the energy consumption can then be selected.

In this case, a speed curve and an acceleration curve are approximated as harmonic oscillations. In this case, an acceleration can be approximated, for example, as follows: a (t) = Acos (2πt / T) Formula 3.

Here, A denotes an amplitude of the harmonic oscillation which approximates an acceleration course a (t). T again means the previously known travel time of the entire route or of the partial section of the route. Similarly, a speed history can be calculated as follows: v (t) = AT / 2πsin (2πt / T) Formula 4.

In this case, A, ie the amplitude of the harmonic oscillation, expresses a general average acceleration of the vehicle over the entire route or partial sections of the route. The parameter A can be treated as a calibration parameter in which various characteristics of a traffic network are reflected. Typical values for A are in the range between 0.5 and 1.0 m / s ² . The approximation as harmonic oscillations advantageously results in an easily determinable velocity and acceleration profile, whereby the approximation represents a mean good approximation to actual velocity and acceleration characteristics.

Furthermore, the energy consumption is approximated as the sum of a speed-dependent component and an acceleration-dependent component. In this case, the speed-dependent component is determined as a function of a travel time and a mean speed, and the acceleration-dependent component as a function of the travel time, the average speed and an average acceleration. The average acceleration may be the previously mentioned amplitude A of the harmonic oscillation. The travel time may preferably be previously known here. Here, the variables travel time, average speed and average acceleration relate to the entire route or a subsection of the route. The total energy consumption can be, for example, as E (V, A, T) = E ₀ (V, T) + E ₁ (V, A, T) Formula 5 calculate, where E ₀ (V, T) = T (c ₀ + c ₁ V + c ₂ V ² + c ₃ V ³ ) Formula 6 and E ₁ (V, A, T) = (T ³ A ² / 8π ² ) (c ₂ + 3c ₃ / V) + TV (c _av1 A / π + c _av2 A ^2/4 ) Formula 7.

Here E denotes the total energy consumption, E ₀ the speed-dependent part of the energy consumption and E ₁ the acceleration-dependent part of the energy consumption. To evaluate the formula 6, only the current travel time T and the current cruising speed V is required. Both are over with a known length of the considered section L = TV Formula 8 where L represents the known length of an entire route or part of the route. The mean acceleration A is assumed to be a pre-defined or calibrated parameter. If an energy minimum route is calculated on the basis of a graph, formula 2 (see below) or formula 5 weights for each edge portion of each graph. In this case, formula 5 can represent an approximation of formula 4.

In a further embodiment, a route is subdivided into subsections, energy consumption per subsection being determined as a function of a speed profile and an acceleration profile in the respective subsection over a travel time associated with the corresponding subsection. The sections can hereby z. B. be considered as edges of a graph. The energy consumption can then be associated with an edge and z. B. for a determination of the route by means of known graph search method, z. As Dijkstra algorithm or A-star algorithm, be considered as the weight of each edge. The speed and acceleration curve is determined here only for a time interval for which the vehicle is driving a current section. A travel time for subsections, z. B. road sections, may be previously known. In this case, empirical values for travel times are stored on specific subsections of a route and can be retrieved in the method according to the invention. The travel times represent here average travel times, which are needed for driving on corresponding subsections. Of course, the comments on the subsections also apply to an entire route, if information about z. B. have a travel time over the entire route.

By dividing the route into subsections results in an advantageous manner that even for determining a minimum energy route known graph search methods can be used, with energy consumption as the weight of an edge, ie a subsection, can be construed.

In a further embodiment, a speed profile and / or an acceleration profile are calculated as a function of previously known traffic data.

Here, the speed curve v (t) and the acceleration curve a (t) z. B. depending on a traffic density, queue lengths, congestion conditions and other traffic data can be determined. These can be detected decentrally or centrally and transmitted to the vehicle, for example via Car-to-X communication. It is also conceivable, for. B. via the Internet or other types of transmission transmitted to the vehicle traffic data to determine a speed profile and an acceleration curve for the entire route or sections of the route. This results in an advantageous manner that a speed curve and an acceleration curve can be adapted to an actual traffic situation.

In a further embodiment, energy consumption is determined as the integration of an energy function over a travel time, the energy function being determined as a function of the speed profile and the course of the acceleration. An energy function can be expressed formulaically as follows: e (t) = c ₀ + c ₁ v (t) + c ₂ v ² (t) + c ₃ v ³ (t) + c _av1 a (t) v (t) + c _av2 a ² (t) v (t) Formula 1.

Here, e (t) describes the energy consumption at time t as a function of a velocity curve v (t) and an acceleration curve a (t), the energy function expressed in Formula 1 being a good approximation to an actual energy consumption of a vehicle. The constants c ₀ , c ₁ , c ₂ , c _av1 , c _av2 are dependent on the respective vehicle type and can be parameterized or calibrated prior to the method according to the invention. The constants c ₁ , c ₂ , c ₃ , c _av1 , c _av2 are therefore known quantities in the method _{according to} the invention. The calculation of the total energy consumption for a subsection or the entire route then results according to

Here, T denotes the travel time for the entire route or a partial section of the route. In the integration, it should be noted that for the term c _av1 a (t) v (t), integration takes place only over times in which the acceleration a (t) is positive. Otherwise, in areas with negative acceleration, a corresponding energy gain would result, which just compensates for a corresponding energy loss, which is not possible with current vehicles driven purely by internal combustion engines. In the case of electric or hybrid vehicles, however, this is possible and the negative acceleration a (t) must be taken into account accordingly. By calculating energy consumption as an integration of an energy function, energy consumption for the entire route or a partial section of the route can be calculated advantageously, where T may be a known travel time of the route or energy consumption, which may be e.g. B. determined from experience.

In a further embodiment, the travel time and the length of the route are previously known or are known as a travel time associated with a subsection of the route and a length of the subarea, the mean speed being determined as a function of the previously known travel time and length. This was previously explained in Formula 8. This results in an easy to be determined energy consumption for the entire route or sections of the overall route in an advantageous manner.

In a further embodiment, an amplitude of the acceleration profile or an average acceleration is determined as a function of a time of day and / or further route parameters. In this case, therefore, the amplitude of the acceleration curve of Formula 3 or the acceleration-dependent component of Formula 7 z. B. be calculated based on the time of day. As a result, an energy consumption of a vehicle on an entire route or a subsection of the route can also be determined as a function of a time of day. Alternatively or cumulatively, it is possible to determine the amplitude of the harmonic oscillations or the mean acceleration as a function of further route parameters. For example, these can be determined as a function of a current traffic situation, with data on the current traffic situation being transmitted to the vehicle or the navigation terminal for example by means of car-to-X communication. Also, additional route parameters, such. B. a curvature of the route, a wind force and wind direction in sub-sections of the route and other external boundary conditions are included in a determination of the amplitude of the harmonic oscillations or the average acceleration.

This results in an advantageous manner that an energy consumption improved to an actual traffic situation and / or current boundary conditions of the route can be adjusted. The disadvantage is a higher computational effort and a higher memory overhead, z. B. for daytime-dependent predetermined average accelerations or amplitudes of the harmonic oscillations.

Further proposed is a device for determining a minimum energy route, wherein the device comprises at least one evaluation unit. By means of the evaluation unit, one of the previously explained methods can be carried out in an advantageous manner. In this case, the device can be, for example, a mobile navigation device or a navigation device permanently installed in a vehicle.

The invention will be explained in more detail with reference to an embodiment. The single figure shows a schematic flow diagram of a method for determining a minimum energy route.

1 shows a schematic flow diagram of a method for determining a minimum energy route. This will be done in a first step 1 a desired start and finish position z. B. determined by a motor vehicle driver. At the second step 2 If the start position is marked and zero energy consumption is assigned, all other nodes in the network are initially assigned the energy consumption Infinite. Then in a third step 3 evaluates all neighbor nodes that can be reached from this node with respect to the energy consumption needed to get from a marked node to the nearest node of the network. They are assigned the energy required up to this point, which, based on the parameters of the network, results from the length and travel time along the edge up to this node, as described in this procedure. In this case, E _{k describes} the energy required until node k, E _k-1 , the energy required up to node k-1, and E _{k-1, k} the energy from node k-1 to node k. From the respective node with the minimum energy consumption, this process is then continued iteratively until the destination node (target position) has been reached. In a fourth step 4 then the narrowest possible route is output.

LIST OF REFERENCE NUMBERS

1

first step

2

second step

3

Third step

4

fourth step

k

current section

N

Number of sections

e

power consumption

Claims (8)

A method of determining an energy minimum route, wherein the minimum energy route is determined from a number (M) of possible routes between a start position and a destination position, wherein the minimum energy route is a route for which power consumption (E) of a vehicle is minimum the energy consumption is determined as a function of a speed curve and an acceleration curve over a travel time, characterized in that the speed profile and the acceleration curve are approximated as harmonic oscillations, the energy consumption being approximated as the sum of a speed-dependent component and an acceleration-dependent component, wherein the speed-dependent component in Depending on the travel time, the average speed and a mean acceleration determines w dependent on a travel time and a mean speed and the acceleration-dependent proportion ill. Method according to Claim 1, characterized in that a route is subdivided into subsections (k), energy consumption per subsection (k) being determined as a function of a speed profile and an acceleration profile in the respective subsection (k) over a travel time allocated to the corresponding subsection , Method according to one of claims 1 or 2, characterized in that a speed profile and / or an acceleration profile are calculated in dependence on previously known traffic data. Method according to one of claims 1 to 3, characterized in that a power consumption is determined as integration of an energy function over a travel time, wherein the energy function is determined in dependence on the velocity profile and the acceleration curve. Method according to one of the preceding claims, characterized in that a travel time and a length of the route are previously known or a partial section (k) of the route associated travel time and a length of the subsection are already known, with an average speed depending on the known travel time and length is determined. Method according to one of the preceding claims, characterized in that an amplitude of the acceleration curve or an average acceleration in dependence of a time of day and / or further route parameters is determined. Method according to one of the preceding claims, characterized in that energy consumption is additionally determined as a function of further route parameters and / or vehicle condition data. Device for determining a minimum energy route, wherein the device comprises at least one evaluation unit, wherein by means of the evaluation unit the minimum energy route from a number (M) of possible routes between a start position and a destination position can be determined, wherein the minimum energy route is a route for which an energy consumption (E) of a vehicle is minimal, wherein the energy consumption can be determined as a function of a speed curve and an acceleration curve over a travel time, characterized in that the speed profile and the acceleration curve are approximated as harmonic oscillations, the energy consumption being the sum of a speed-dependent component and an acceleration-dependent portion is approximated, wherein the speed-dependent portion depending on a travel time and a mean speed and the acceleration-dependent portion depending determined by travel time, mean speed and medium acceleration.

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