Abstract:
A method for determining a route from a starting point to a destination point in a navigation system for a motor vehicle, a factor which influences the energy consumption or the pollutant emissions while traveling the route being taken into account when determining the route. The factor describes the energy consumption or pollutant emissions during standstills of the motor vehicle while traveling the route and a navigation system for this purpose. A route calculation is improved with the goal of minimizing the energy consumption or pollutant emissions over the entire route and thereby contributes to environmental protection.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to a method for determining a route from a starting point to a destination point in a navigation system for a motor vehicle, as well as a navigation system which includes means for determining a route from a starting point to a destination point. 
       BACKGROUND INFORMATION  
       [0002]    A vehicle navigation system is described, for example in European Patent No. EP 1 721 127, which determines a route from the current location to an entered destination and guides the user along this route after the user or vehicle driver has entered the destination and a current vehicle position has been determined with the aid of position determining means. For this purpose, the current vehicle position is regularly determined and compared with the calculated route, and in the event that a driving maneuver such as a turning action is required to follow the route, an indication thereof is output to the user. 
         [0003]    A navigation system for motor vehicles is further described in European Patent No. EP 1 593 937, which determines a route from a starting point to a destination point, a factor which influences the energy consumption and thus also the pollutant emissions when traveling the route being taken into account in determining the route. The goal is the most energy-efficient route. Uphill and downhill routes as well as the vehicle load are taken into account for this purpose. The types of roads, in particular the road class, such as highway or regional road, as well as the road conditions, are also taken into account. Furthermore, known accident and traffic congestion hot spots are taken into account. 
       SUMMARY OF THE INVENTION 
       [0004]    It is provided that not only the energy consumption and/or pollutant emissions produced while driving along route segments are taken into account when calculating the route, but also an energy consumption and/or pollutant emissions resulting from vehicle standstills while traveling the route. In particular, waiting times at intersections, junctions, traffic lights, railroad crossings and the like are taken into account. Thus a running power plant consumes energy even while a motor vehicle is at a standstill, although no route distance is being covered, for example to overcome the inner friction of an internal combustion engine as well as to drive so-called ancillary units such as the generator, air conditioning compressor, and the like. However, shutting down the power plant during longer foreseeable standstills is also associated with energy consumption, at least when the power plant is restarted, and in the case of internal combustion engines also involves increased pollutant emissions. 
         [0005]    The factor or the values for energy consumption and/or pollutant emissions described by the factor are advantageously statistically determined from standstill times during past trips. For this purpose, the duration of the motor vehicle standstill is advantageously determined for a recognized standstill. The standstill duration is advantageously determined in relation to location. For this purpose, the location of the standstill is determined using position determining means, and the standstill duration is associated with this determined position, for example a determined intersection in the road network or a determined traffic light or the like. The standstill duration is also preferably determined in relation to the situation. For example, a determination is made as to whether the standstill occurs at an intersection while driving in a straight trajectory or, instead, upon making a left turn. This is based on the understanding that a left turn may involve a longer standstill than a standstill while continuing to drive in a straight trajectory, due to the need to cross a line of oncoming traffic. A left turn may be detected by the activated turn signal. Furthermore, the specific energy consumption or pollutant emissions is advantageously determined during a standstill, so that absolute values for energy consumption or pollutant emissions may be determined from the waiting time and the specific energy consumption or pollutant emissions. The specific pollutant emissions and energy consumption may preferably be further ascertained as a function of the season, since the values are foreseeably higher during winter operation than during summer operation. 
         [0006]    These collected data are advantageously evaluated using statistical methods and stored, and they thus remain available for calculating a new route. These collected and evaluated data are also transferred to potential, additional, equivalent or comparable standstill locations which have not yet been traveled. After only a short period of time, data are thus available for standstill locations throughout the entire road network, on the basis of which a route may be calculated with the goal of minimizing energy consumption or pollutant emissions. 
         [0007]    During the course of calculating a route from a starting location, which may be a point of origin or a current location, to a destination, not only are route-related energy consumption values taken into account, as is described in European Patent No. EP 1 593 937, but also the standstill-related energy consumption and/or pollutant emission values for the purpose of minimization over the entire route, if necessary weighted by additional optimization criteria such as the minimum travel time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The FIGURE shows a simplified block diagram of the portion of a navigation system important for the present invention for use in a motor vehicle. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    The FIGURE shows a navigation system  1  for operation in a motor vehicle. A motor vehicle in this context is understood to be a vehicle having a power plant which drives the vehicle using energy. The power plant is, for example, an internal combustion engine, which is known per se, in the form of a diesel or spark ignition engine, which generates a driving torque for the vehicle and so-called ancillary units such as the generator, air conditioning system and the like as well as pollutants such as, in particular, nitrogen oxides and carbon dioxide from fuel. Since exhaust gas treatment measures known today are designed primarily for steady-state operation under partial load conditions, particularly high amounts of pollutants are generated and emitted, in particular during acceleration processes and when starting internal combustion engines of this type. Energy consumption is also elevated in this case. 
         [0010]    Navigation system  1  includes a position determining means  11 , which is known per se and is therefore not explained in greater detail here, for determining a current location, for example on the basis of radio signals of a satellite navigation system such as GPS or GALILEO; a digital map  12  in the form of a data memory such as a CD-ROM, flash memory or the like, including information contained therein on route segments and nodes such as intersections, junctions, etc. of a road network; a user interface  13  for entering a driving destination and for outputting guidance instructions for following a determined driving route; and a computer  14 , including an operating program  141 , among other things for determining a route from a starting location to a destination specified by the user and for generating guidance instructions by comparing a current location with the determined driving route. 
         [0011]    Navigation system  1  further includes a statistics component  142 , which is preferably designed as a software module which is processed by computer  14  of navigation system  1 . The purpose of statistics component  142  is to compare the duration of a standstill with the durations of previous standstills upon detecting a standstill of the vehicle during a trip and to generate a new standstill duration, using statistical methods. In the preferred exemplary embodiment described herein, the standstill durations are determined in relation to location. For this purpose, possible locations on digital map  12 , i.e., primarily intersections, junctions, traffic lights, railroad crossings and other locations where a vehicle regularly comes to a standstill, are associated with standstill durations in an additional data memory  15 . These location-related standstill durations are updated to include currently determined standstill durations according to statistical methods. Furthermore, the standstill duration data are preferably collected, evaluated and stored not only in relation to location, but also in relation to situation. For example, intersections are assigned different standstill duration values, depending on the ability to drive in a straight trajectory or to turn right, on the one hand, and depending on the ability to turn left, on the other hand. 
         [0012]    Statistics component  142  evaluates data during active guidance, i.e., while a route is being calculated and the vehicle driver is being guided along this route according to the driving instructions of navigation system  1 , i.e., preferably also without active guidance. In a particularly advantageous manner, a high repetition rate of data collection obviously occurs, particularly if the same route is traveled regularly, for example in the case of commuters. 
         [0013]    For standstill locations which have not yet been traveled, data of previously traveled, equivalent or comparable standstill locations may be advantageously transferred to the standstill locations not yet traveled. 
         [0014]    If the energy consumption or pollutant emissions is/are known per unit of time for the vehicle standstill, values for the average energy consumption or pollutant emissions at a determined location may be calculated therefrom. 
         [0015]    In addition to route-specific values for energy consumption or pollutant emissions according to European Patent No. EP 1 593 937, the values described for standstill locations, i.e., in particular values for intersections, junctions, nodes of the traffic network, and the like are also taken into account for subsequent route calculation. This makes the result of the route calculation or the statement about total energy consumption or total pollutant emissions over the entire route much more precise and reliable, 
         [0016]    In an advantageous refinement of the present invention, statistics component  142  may be further used to determine the typical specific energy consumption values and pollutant emission values during a vehicle standstill, i.e., energy consumption per unit of time or pollutant emissions per unit of time. An energy consumption sensor  16 , such as a fuel flow rate measuring device, and an exhaust gas sensor  17  are used for this purpose. The values detected by these sensors  16 ,  17  are preferably evaluated as a function of environmental conditions, in particular outside temperature or, as an alternative, as a function of the season, and stored in additional data memory  15 . 
         [0017]    In additional to an exclusively energy consumption-optimized or pollutant emission-optimized route calculation, a route may also be determined by taking into account a further optimization criterion, such as the minimum possible travel time, shortest route or the like. 
         [0018]    Furthermore, the route may also be calculated exclusively as a route which has been optimized as the shortest or fastest route, or based on a mixture of these two criteria or other criteria. For one or more alternative routes of this type, the energy consumption or pollutant emissions may be additionally determined and output to the user as an additional selection criterion for selecting one of multiple routes. The user thus gains the ability to select a route which may not be the optimum one in terms of a primary optimization criterion, because this route produces less energy consumption or pollutant emissions than the optimum route. 
         [0019]    In a refinement of the present invention, navigation system  1  may also output information about an imminent standstill of the vehicle to the user or vehicle driver during the course of active guidance if the vehicle location approaches, for example, an intersection. In the event that the average waiting time at this intersection exceeds a determined threshold value, a recommendation for shutting down the power plant may be advantageously output to the user. Alternatively, the power plant may also be automatically shut down if the vehicle does indeed come to a standstill at this intersection.