Energy management method for an electric vehicle

Abstract

A method managing energy consumption for an automobile including an electric battery and a heat engine, to select use phases of the engine along a route to minimize fuel consumption. The method includes: cutting a road network, for a route, into plural segments each defined by an input node and an output node; calculating, from a speed associated with a segment, a probability of a speed transition between a speed at an input node and at an output node of the segment, considering plural speeds at the input node and at the output node, executed gradually over all the route segments; applying a stochastic optimization algorithm considering all possible transition scenarios between each input node and each output node, and the probability associated therewith, and a fuel consumption model between two successive nodes, executed over all the route segments; and selecting use phases of the heat engine along the route.

Claims

1. A method for managing energy consumption for an electric automotive vehicle including an electric battery and a booster motor, the method making it possible to select phases of use of the booster motor along a predetermined route to minimize fuel consumption of the electric automotive vehicle, the method comprising: cutting, using navigation circuitry of the electric automotive vehicle, a road network taken into consideration for the predetermined route into plural segments, including at least a first segment associated with a current position of the electric automatic vehicle and a last segment associated with a destination of the predetermined route, each said segment being delimited by a beginning node and an ending node; computing, using circuitry of the electric automotive vehicle, for each said segment of the predetermined route, a probability of a speed transition between a speed at the beginning node and a speed at the ending node of the segment, based on a speed associated with the segment, and by considering plural speeds at the beginning node and plural speeds at the ending node; applying, using the circuitry of the electric automotive vehicle, a stochastic optimization algorithm taking into account possible scenarios of transition between each said beginning node and respective ones of said ending nodes along the predetermined route, and their associated probability, and a model of fuel consumption between two successive nodes, and which is dependent on a speed of the electric automotive vehicle between the nodes and on a state of charge of the electric battery; selecting, using the circuitry of the electric automotive vehicle, phases of use of the booster motor for use along the predetermined route based on said applying, wherein the electric automotive vehicle is neither a hybrid automotive vehicle nor an engined automotive vehicle having an internal combustion engine as a sole power source, and wherein said computing is performed sequentially, for each said segment of the predetermined route, and begins from the last segment associated with the destination of the predetermined route and tracks progressively toward the first segment associated with the current position of the electric automatic vehicle.

2. The method as claimed in claim 1, wherein said computing the speed transition probabilities is performed based on a travel history of the electric automotive vehicle along the predetermined route considered, and based on speeds recorded along the predetermined route.

3. The method as claimed in claim 1, further comprising recommencing one or more of said cutting, said computing, said applying and said selecting, said recommencing taking into account an actual state of charge of the electric battery at one of said beginning and ending nodes considered.

4. The method as claimed in claim 1, wherein said cutting the predetermined route into segments is carried out automatically by the navigation circuitry.

5. The method as claimed in claim 1, wherein said cutting the predetermined route into segments includes manually cutting a portion of the predetermined route into one or more of the segments.

6. The method as claimed in claim 1, wherein a determination of transition probabilities during said computing is refined by taking into account at least one parameter to be chosen from among a time of day, a state of automobile traffic, a type of road, or a number of lanes.

7. The method as claimed in claim 1, wherein one or more of said cutting, said computing, said applying, and said selecting take into consideration the following events: the booster motor must be stopped when the booster motor does not yield any power; it is necessary to comply with a time interval of a first predetermined amount of time between each stoppage and each switch-on of the booster motor; and between a moment at which the booster motor is switched on and a moment at which the booster motor is active and yields power, there exists a latency time of a second predetermined amount of time.

8. The method as claimed in claim 1, further comprising outputting a signal to manage energy consumption for the electric automotive vehicle based on the selected phases of use of the booster motor along the predetermined route.

Description

(1) A preferred embodiment of a management method according to the invention is given hereinafter, while referring to FIGS. 1 and 2.

(2) FIG. 1 is a diagram illustrating an example of a speed transition between the entry node of a segment and the exit node, the exit speed being given with a certain probability.

(3) FIG. 2 is a diagram giving the probability of a speed transition between an entry node and an exit node of a segment, said diagram being formulated by considering a plurality of speeds at the entry node and a plurality of speeds at the exit node.

(4) For the detailed description of a preferred embodiment of a method for managing energy consumption according to the invention, it is assumed that the vehicle is fitted with a navigation system of GPS type. The subject of the invention is a method for managing energy consumption for an automotive vehicle fitted with an electric battery and with an engine operating with a fuel, said method making it possible to select the phases of use of the motor along a given route, so as to minimize the fuel consumption of said vehicle. Stated otherwise, the automotive vehicle comprises an electric motor, which is mainly supplied with electric current by the battery, said vehicle also comprising an engine operating with fuel and temporarily deputizing for the battery during certain phases of the vehicle traveling on a given route.

(5) Such a method comprises the following steps: a step of cutting the road network taken into consideration for a given route into several segments, each segment being delimited by an entry node and an exit node. The route is thus divided into unitary portions, lying in continuity with one another so as to define a path, each of said unitary portions being characterized by an entry node and an exit node. This cutting, which is effected automatically by the navigator, will allow the method according to the invention to proceed gradually, considering each segment individually one after another, so as to increase the accuracy in the strategy for using the booster motor. It is easier to predict the changes of speed of the vehicle on a segment of limited length, rather than on an extended stretch of the route, where the random events are more numerous and would run the risk of not being taken into account correctly. This cutting is rendered necessary so as to render the approach of the method according to the invention as realistic as possible, and therefore as reliable as possible. a step of computing the probability of a speed transition between a speed at an entry node and a speed at an exit node of a segment, on the basis of a speed associated with said segment, and by considering several speeds at the entry node and several speeds at the exit node, said step being carried out gradually for all the segments of the route. On each segment, the navigation system provides several characteristics, such as for example its length, its slope, the maximum permitted speed, the expected mean speed and its radius of curvature. By virtue of this information, the speed of the vehicle is known at the entry node of a segment. The objective of this step of the method is to estimate the speed of the vehicle at the exit node of the segment with a certain probability, the operation being repeated along the whole route for each segment. The transition probabilities are estimated in relation to the information given by the navigation system. FIG. 1 illustrates an example of this probability law for an actual speed y of the vehicle at an entry node k of a segment, and a regulatory speed NAV given by the navigation system. In the example of the diagram of FIG. 1, it is thus very probable that the speed of the vehicle at the exit node k+1 of the segment considered is greater than the speed NAV given by the navigation system. Still by way of example, the navigation system may suggest six different speeds NAV: 20, 40, 60, 80, 100, 120 Km/h. Referring to FIG. 2, a transition matrix is then estimated on the basis of these speed values given by the navigation system, this matrix corresponding to the probabilities that a vehicle having, at the entry node, a speed of between 0 and 150 Km/h, has a speed of between 0 and 150 Km/h at the exit node. It is assumed that within the framework of a management method according to the invention, all the possible values of the speed at the entry node are scanned, as well as all the possible values of the speed at the exit node. This transition matrix may be computed by several procedures. The most standard procedure consists in using a travel history where the speeds of the vehicle are recorded at each node. Thereafter, the number of transitions for each speed pair, between 0 and 150 Km/h, is counted, and this number is divided by the total number of transitions. a step of applying a stochastic optimization algorithm taking into account all the possible scenarios of transition between each entry node and each exit node, and their associated probability, as well as a model of fuel consumption between two successive nodes, and which is dependent on the speed of the vehicle between two successive nodes and on the state of charge of the battery. The algorithm used also integrates the fact that the booster motor must not be switched on or stopped too frequently, and that it is necessary to wait a given time of a few minutes between making a decision switch-on the booster motor and its actual use. These additional constraints are integrated into the step of applying the stochastic optimization algorithm, so as to approximate as closely as possible the actual situations liable to be encountered along the route. a step of selecting the phases of use of the engine along the route.

(6) The conduct of the method according to the invention assumes that the driver enters a destination into the navigation system and that he follows the route indicated by said system. It is also assumed that the energy reserve of the battery and of the booster motor is sufficient for the driver to be able to reach his destination.

(7) The results provided by a method for managing energy consumption according to the invention depend on the quality of the travel data used for the estimation of the probabilities of transition performed during the second step of the method according to the invention.