Abstract:
Methods are provided for determining an energy optimized route for a vehicle. In one example, the method includes providing a plurality of cost factors, each cost factor influencing the energy consumption of the vehicle. At least one cost factor is selected from among the cost factors. A composite cost factor is determined using the selected at least one cost factor. An energy optimized route is then determined based on the composite cost factor. Systems are also provided for determining an energy optimized route for a vehicle. An example system includes a set of cost factors, each cost factor influencing the energy consumption of the vehicle. A classification unit is included for selecting cost factors for the route and for including the selected cost factors in a composite cost factor for the route. A calculator is also included for calculating the energy optimized route based on the composite cost factor.

Description:
RELATED APPLICATIONS 
     This application claims priority of European Patent Application Serial Number 08 011 208.9, filed on Jun. 19, 2008, titled CALCULATION OF ENERGY OPTIMISED ROUTE; which application is incorporated in its entirety by reference in this application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a method and to a system for determining an energy optimized route for a vehicle. 
     2. Related Art 
     In the art, navigation systems are known which calculate a route from a present vehicle position to a predetermined destination using map data and using satellite based position determination algorithms. In these navigation systems, normally the fastest route to the destination is calculated allowing to reach the destination in the shortest time possible. Additionally, it is known to calculate a shortest route with which the destination can be reached using a path of minimum distance. With the increasing costs for energy such as fuel or gas a need exists to allow the calculation of the energy optimized route to a predetermined destination for which the energy consumption, be it fuel, gas, electric energy or any other kind of energy, is minimized. 
     However, the energy consumption of a vehicle when travelling along a predetermined route depends on many different factors and it is difficult to precisely predict the energy consumption of the vehicle along a predetermined route. 
     SUMMARY 
     In view of the above, a method is provided for determining an energy optimized route for a vehicle. In one example, the method includes providing a plurality of cost factors, each cost factor influencing the energy consumption of the vehicle. At least one cost factor is selected from among the cost factors. A composite cost factor is determined using the selected at least one cost factor. An energy optimized route is then determined based on the composite cost factor. 
     In another aspect, a system is provided for determining an energy optimized route for a vehicle. An example system includes a set of cost factors, each cost factor influencing the energy consumption of the vehicle. A classification unit is included for selecting cost factors for the route and for including the selected cost factors in a composite cost factor for the route. A calculator is also included for calculating the energy optimized route based on the composite cost factor. 
     Other devices, apparatus, systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention may be better understood by referring to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  is a block diagram of an example of a system for determining an energy optimized route. 
         FIG. 2  is a flow chart illustrating operation of an example method for calculating an energy optimized route. 
         FIG. 3  is a schematic diagram illustrating an example determination of an energy optimized route. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a block diagram of an example of a system for determining an energy optimized route. The system  100  includes a route calculating unit  110  configured to calculate a route from a present location of a vehicle to a destination selected by the driver. The system  100  also includes a classification unit  120  to generate a composite cost factor for calculating the energy optimized route. The classification unit  120  is connected to a database  130  that includes data representing a set of cost factors, each cost factor relating to the energy consumption of the vehicle. Each cost factor may be described by a mathematical model M i , that describes one aspect of the energy consumption. The mathematical models for each cost factor M 1 , M 2 , M 3  . . . may be determined in advance by using model data and by using known physical relationships used to calculate the influence of the cost factor on the energy consumption. For example, the cost factor M 1  may describe the energy consumption as a function of aerodynamic resistance; M 2  may describe the influence of the driving behaviour on the energy consumption; M 3  may describe the influence of the road class on the energy consumption. Other mathematical models, M i , may be determined to describe the effect of other aspects of the energy consumption. 
     Cost factors may be viewed or organized in groups. For example, one group of cost factors includes vehicle-related cost factors, which describe the influence of the vehicle, and conditions related to the vehicle. Such factors include the engine, vehicle weight, power of the engine, the kind of engine used, the air track coefficient, and other vehicle-related factors may also be provided. The vehicle-related cost factor can be determined for each type of vehicle and stored in the vehicle. 
     Another group of cost factors includes user-related cost factors. For example, the user-related cost factors may include the driving habits of the driver of the vehicle taking into account the driver&#39;s acceleration and braking behaviour. User-related cost factors may be transmitted to the system from outside the system  100 . For example, the user-related cost factors may be stored in the vehicle key the driver is using for starting the engine. The user-related cost factors may be transferred to the database  130 . In example implementations, a user-related cost factor may be provided for each user. 
     Another group of cost factors may include traffic cost factors, which account for traffic patterns or traffic data received by a radio signal. Such traffic data may be received using the TMC (Traffic Message Channel) data in a radio signal. 
     Another group of cost factors that may be considered for calculating an energy optimized route includes map cost factors. Map data cost factors may include the road class on which a vehicle is travelling, which may be significant since the energy consumption in an urban area will be different from the energy consumption on a highway. The road inclination in the map data may also be used since energy consumption is influenced by whether the vehicle is moving uphill, downhill or straightaway. 
     Another group of cost factors may include cost factors associated with the vehicle environment, such as outside temperature, or other weather conditions. Weather data may be received via TMC data as well. 
     The classification unit  120  may select the cost factors based on their relevance to a certain part of the route. The classification unit  120  uses the selected cost factors to generate a composite cost factor. The classification unit  120  may select the cost factors based on information input from the vehicle or outside the vehicle. The input may be received by a sensor  140  as shown in  FIG. 1 . The sensor  140  can receive vehicle-related information such as the actual energy consumption, engine speed, vehicle speed, activation of accelerator, activation of clutch, activation of brake, vehicle weight. The information represented by the sensor  140  may also be user-related information informing the classification unit  120  about the driving behaviour of the user. For example, the sensor  140  may include access to data identifying the user and the corresponding driving behaviour characteristics. 
     The sensor  140  may receive information from the vehicle environment, such as the outside temperature, the speed of the vehicle driving in front of the detecting vehicle, and other information about the vehicle&#39;s external environment. Traffic related information may be received and used to inform the classification unit  120  about traffic congestions on the route to the predetermined destination. The classification unit  120  may also have access to map data  150 , which may contain data that may also influence the selection and classification of the cost factors. The route calculation unit  110  calculates the route using an optimized energy consumption. The classification unit  120  determines the optimized energy consumption for each part of the route based on the composite cost factor for that part of the route. The composite cost factor is determined using the selected cost factors. Known optimization algorithms may be used to determine the route having the lowest energy consumption. The optimization algorithms may include, for example, Dijkstra algorithms or A* algorithms. The classification unit  120  may also receive certain information as feedback and use the actual energy consumption or actual driving behaviour as input to the route calculation unit  110 . The route calculation unit  110  may compare the received energy consumption to the predicted energy consumption and use the results to adapt the composite energy consumption. 
     Additional information may be used by the classification unit  120  to determine the energy optimized route. Such information may include the number of intersections, the number of red lights, the curvature of the route, and the inclination of the road. The classification unit  120  may obtain this and other information from the map data  150 . Weather information may also be used by the classification unit  120  to the extent the weather conditions along the route affect the energy consumption. Weather information may be obtained from the database  130 , or via the sensor  140  using an interface to a radio signal that carries weather information. 
     The energy-related cost factors, such as acceleration or the aerodynamic resistance can be described by mathematical models to a good approximation. The energy-related cost factors, vehicle-related cost factors, and user-related cost factors may be used to simplify the problem of calculating the energy consumption, which is complicated by its dependence on many different factors. The different cost factors may be used to solve smaller and separate problems based on their mathematical models making it possible to calculate a composite cost factor describing the overall energy consumption to an acceptable error. 
     The error that results from the approximation may be reduced by careful selection of the cost factors. In example implementations, each cost factor is described by a mathematical model that may be solved to determine the energy consumption based on the respective cost factor. For example, the classification unit  120  may select cost factors based on relevance or significance to overall energy consumption. Cost factors exhibiting a greater influence on the energy consumption may be favoured over cost factors that have less influence. In addition, composite cost factors may be determined for road segments, or specific parts of the road. The road segments may be selected based on minimizing the cost factors considered in optimizing energy consumption. For example, a road may be divided into segments that are straightaway with few speed restrictions, hills or segments with inclinations, urban in nature, or segments having many curves. Composite cost factors may be determined for each segment, then combined with other composite cost factors for other segments to obtain energy consumption results for an entire route. 
       FIG. 2  is a flow chart illustrating operation of an example method for calculating an energy optimized route. The method may start at step  210  as part of a route calculation procedure in a navigation system in a vehicle. A predetermined route may be used as input. The route may be further divided into parts of the route according to characteristics that affect energy consumption. The method shown in  FIG. 2  may be used for a given route, then again for an alternative route as a comparison with other routes to determine the more energy efficient route. The different cost factors are provided at step  220 . Each cost factor may be described by a mathematical model that approximates the energy consumption as a function of the cost factor. The mathematical models may be solved and used to describe the contribution of the respective cost factor to the overall energy consumption. At step  230 , cost factors may be selected according to their relevance to energy consumption in a certain part of the route. The mathematical models for the cost factors selected at step  230  may be used to determine the energy consumption for each selected cost factor. At step  240 , the contribution of each cost factor to the overall energy consumption is determined. In one example, the contribution of each cost factor may be determined by determining a threshold contribution and comparing the energy consumption based on the cost factor with the energy consumption based on the composite cost factor. The selected cost factors may be classified according to the extent to which the comparison for each cost factor exceeds the predetermined threshold. In addition, any cost factors not contributing as much as the predetermined threshold may be excluded from the analysis. The contribution of the cost factors may be expressed as weighting factors in the expression of the composite cost factor for a certain part of the route. 
     At step  250 , the energy consumption based on each cost factor is determined. At step  260 , the overall energy consumption is determined for the different parts of the route and used to determine the overall energy consumption for the complete route. The energy optimized route may then be calculated using the steps  220  to  260  by determining the route having the lowest overall energy consumption to a destination. In an example implementation, steps may be included to compare the calculated energy consumption to the real energy consumption during driving. The comparison can then be used to adapt the process for selection and weighting of the different cost factors for the generation of the composite cost factor. The selected cost factors are those having the greatest influence on the energy consumption for the route calculation. 
       FIG. 3  is a schematic diagram illustrating an example determination of an energy optimized route. The example in  FIG. 3  illustrates how the energy consumed when driving from location  301  to location  304  via location  302  and  303  may be determined. As an example, the vehicle may be assumed to accelerate from 0 to 100 km/h using gears 1 to 5 between location  301  and  302 , which may have an inclination lower than 1%. Based on these assumptions, the mathematical model describing the energy consumption depends mainly on two aspects. The first aspect is the mathematical model describing the energy costs for the vehicle acceleration, M acc , and the other aspect is the mathematical model describing the driving behaviour of the driver M driver . The driving behaviour mathematical model describes how the driver normally accelerates. 
     For the segment of the route between  301  and  302 , the classification unit  120  (in  FIG. 1 ) selects these two models (M acc  and M driver ) and combines the models in a weighted form. The composite cost model or the composite cost factor, M composite, 301-302 , may be determined using a weighting coefficient for the acceleration model, α 1 , and a weighting coefficient for the driver model, α 2 . In an example implementation, the system may know from former calculations that the driving behaviour influences energy consumption more than the acceleration model. In this case, the coefficient α 2  may be selected to be larger than the coefficient α 1 . The composite cost factor, M composite, 302-303 , for the segment between  302  and  303  may be expressed as:
 
 M   composite,301-302 =α 1   ·M   Acc +α 2   ·M   Driver    Equation (1)
 
     In the road segment between location  302  and  303 , the driver may be driving at a constant speed of 100 km/h using one gear at a predetermined engine speed. For this part of the route, the composite model may include the rolling friction describing the friction of the tires on the road, M Roll . Another cost factor considered for this part of the route may be the aerodynamic resistance, which is relevant to the geometrical form of the vehicle, at a speed of 100 km/h, M Air . Both factors are weighted by weighting coefficient α 3  and α 4 , respectively, and are combined to a composite cost factor, M composite, 302-303 , for the road segment between  302  and  303 . In the example shown, the driving habits of the driver do not play a role when driving at constant velocity in one gear so that this cost factor is not considered for the calculation of the energy optimized route between location  302  and  303 . The composite cost factor, M composite, 302-303 , for the segment between  302  and  303  may be expressed as:
 
 M   composite,302-303 =α 3   ·M   Roll +α 4   ·M   Air    Equation (2)
 
     The road segment between location  303  and  304  includes a hill with an inclination of about 20%, for example. The vehicle may be travelling at a constant velocity and proceeding uphill using one predetermined gear. For this part of the route, the mathematical model describing the energy consumption due to the inclination may provide the dominant cost factor. If that is the case, the inclination cost factor is used as the composite cost factor between location  303  and  304 . A weighting factor, α 5 , may be determined, but set to 1 in this example if the inclination is the dominant cost factor and only one used. The composite cost factor, M composite, 303-304 , for the segment between  303  and  304  may be expressed as:
 
 M   composite,303-304 =α 5   ·M   Inclination    Equation (3)
 
     The example illustrated in  FIG. 3  shows how the complex problem of energy consumption may be decomposed into different smaller problems by selecting from a plurality of different cost factors described by mathematical models. By selecting the cost factors based on the driving situation for the different parts of the route, the overall energy consumption can be approximated using the mathematical description obtained using the composite cost factor. The error resulting from the approximations made during the calculation of the overall energy costs may be lowered compared to a calculation in which all factors are considered. Based on the composite cost factor for each part of the route, an overall energy consumption may be calculated for a route, and an energy optimized route can be calculated by determining the route having the lowest energy consumption. 
     The examples illustrated are described in the context of optimizing energy consumption. However, it is to be understood that other parameters may be optimized. For example, example implementations may be used to optimize CO 2  emission. 
     In addition, composite cost factors determined for different parts of a route may be stored for future use. The composite cost factors may be linked to the different parts of the route, respectively, and used to determine the energy optimized route. 
     It will be understood, and is appreciated by persons skilled in the art, that one or more processes, sub-processes, or process steps described in connection with  FIGS. 1-3  may be performed by hardware and/or software. If the process is performed by software, the software may reside in software memory (not shown) in a suitable electronic processing component or system such as, one or more of the functional components or modules schematically depicted in  FIGS. 1-3 . The software in software memory may include an ordered listing of executable instructions for implementing logical functions (that is, “logic” that may be implemented either in digital form such as digital circuitry or source code or in analog form such as analog circuitry or an analog source such an analog electrical, sound or video signal), and may selectively be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that may selectively fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this disclosure, a “computer-readable medium” is any means that may contain, store or communicate the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium may selectively be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device. More specific examples, but nonetheless a non-exhaustive list, of computer-readable media would include the following: a portable computer diskette (magnetic), a RAM (electronic), a read-only memory “ROM” (electronic), an erasable programmable read-only memory (EPROM or Flash memory) (electronic) and a portable compact disc read-only memory “CDROM” (optical). Note that the computer-readable medium may even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory. 
     The foregoing description of example implementations has been presented for purposes of illustration and description. It is not exhaustive and does not limit the claimed inventions to the precise form disclosed. Modifications and variations are possible in light of the above description or may be acquired from practicing the invention. The claims and their equivalents define the scope of the invention.