Method for operating an electric vehicle

Abstract

The invention relates to a method for operating an electric vehicle (1) comprising a fuel-cell system (2) and a traction battery (3). The method according to the invention is characterized in that a target state of charge of the traction battery (3) is specified on the basis of the topography in the surroundings of the vehicle (1), for the purpose of which the position of the vehicle (1) is determined, and elevation details in a specified radius around the vehicle (1) are determined from a digital map, on the basis of which elevation details the probable occurrence of upward inclines and / or downward inclines is inferred, according to which the target state of charge is specified on the basis of the probability of upward inclines and / or downward inclines.

Description

[0001] Method for operating an electric vehicle

[0002] The invention relates to a method for operating an electric vehicle with a fuel cell system and a traction battery.

[0003] A typical problem in hybrid vehicles with a primary drive unit and a traction battery, also known as an HV or high-voltage battery, is the distribution of power from the battery and the other drive unit. Optimal battery utilization requires the ability to reliably estimate routes with increased electrical power demand from the battery and routes with a higher amount of recuperation power that must be stored in the battery.

[0004] For a hybrid with an internal combustion engine and an additional storage battery, EP 3 124 302 A1 describes a control device capable of adjusting the battery's charge level before uphill or downhill gradients based on a route pre-planned via a navigation system, thus optimizing energy consumption. The problem with the setup described therein is that this only works when driving on a route planned via a navigation device. It presupposes that the navigation system is used, i.e., that the user actively enters the route destination. Furthermore, it presupposes that the person driving the vehicle adheres precisely to this route and does not deviate from the planned route.Such a deviation would require a complex recalculation, which might then no longer be able to optimally adjust the battery charge level at the time the route is changed. If the navigation system is not in use, the method cannot be used either. For further prior art, reference can be made to DE 102020 128221 A1. This document describes a fuel cell vehicle, i.e. an electrically powered vehicle with a fuel cell. To prevent the vehicle speed from dropping when the fuel cell has to be throttled back due to reaching its maximum power, the route can be optimized so that steep inclines can be avoided, which could lead to such a power restriction depending on the trailer load towed by the vehicle.

[0005] The object of the present invention is to provide an improved operating method for an electrically powered vehicle with a fuel cell system and traction battery, which reduces the risk of speed regulation and optimizes energy utilization.

[0006] According to the invention, this object is achieved by a method having the features in claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments and further developments emerge from the dependent claims.

[0007] The method according to the invention provides for a target battery charge level to be specified based on the topography of the vehicle's surroundings. For this purpose, the vehicle's position is determined, for example, via a satellite navigation system, and elevation information is determined from a digital map within a specified radius around the vehicle. Based on this elevation information, the likely occurrence of uphill and / or downhill sections is then determined, after which the target charge level is specified depending on the probability of uphill and / or downhill sections.

[0008] Unlike planning energy distribution for a main route entered into a navigation system, the method according to the invention is capable of making a reasonable estimate, regardless of the use of navigation or whether the vehicle remains on this planned main route, in order to adjust the target charge level accordingly. This allows for optimal storage of accumulating energy, and the use of required electrical power that exceeds the maximum output of the fuel cell system from the battery when needed. This optimizes overall energy consumption and reduces the risk of speed reduction, for example, on steep inclines.

[0009] According to a very advantageous embodiment of the method according to the invention, it can be provided that, if there is a higher probability of uphill stretches than downhill stretches, a target state of charge of more than 50 to 60% of the battery capacity is specified. According to a preferred development, the specification can be in the order of magnitude of more than 80% of the battery capacity. This allows power generated during recuperation, for example when braking, to be stored in the battery. Due to the higher probability of uphill stretches than downhill stretches, it can be assumed that in this case the vehicle is traveling in a relatively flat region and that inclines are to be expected, for example when leaving a large valley or the like. A relatively higher state of charge of preferably approx.80% of the battery capacity, or especially more than 80%, is therefore sensible here, as large amounts of energy from recuperation are not to be expected. Rather, it must be expected that power will be required from the traction battery, so that any uphill stretches, which are much more likely here than downhill stretches, can be driven with additional power from the traction battery, thus avoiding throttle-down.

[0010] According to a further very advantageous embodiment of the method according to the invention, it can further be provided that, if there is a higher probability of downhill stretches than uphill stretches, a target state of charge of less than 50 to 60% of the battery capacity is specified, and according to an advantageous further development thereof, in particular of less than 30% of the battery capacity. If the probability of downhill stretches is higher than uphill stretches, then the vehicle is on a type of plateau, for example on a high plateau, from which it is significantly more likely to descend downhill than to negotiate an uphill stretch. In this case, it can be assumed with a relatively high probability that the recuperated power generated during braking will be greater.The relatively low state of charge of the battery of less than 30% in such a situation ensures that this energy can be stored completely or at least to a large extent and then made available again for propulsion purposes.

[0011] According to a further embodiment of the method according to the invention, it can now also be provided that, in the event that the probability of uphill stretches is approximately the same as the probability of downhill stretches, the target state of charge is specified in the order of magnitude of 50 to 60% of the battery capacity. Such an average state of charge of the traction battery can therefore always be advantageous if, based on the determined topography, downhill stretches and uphill stretches are to be expected with a similarly high probability. This can be the case, for example, in hilly or mountainous terrain, when downhill stretches and uphill stretches typically alternate on the vast majority of plausible routes. The traction battery is then maintained at an average state of charge in order to be able to act both as a support and as a storage device, whereby it is expected that both scenarios will occur with an equal degree of probability.

[0012] A particularly advantageous embodiment of the method according to the invention can provide that the area in which the topography is determined has a radius of approximately 50 km. The topography is therefore determined within this area around the vehicle in order to be prepared for the potential uphill and downhill sections that may occur there, preferably in the sense described above. According to an advantageous embodiment of the method according to the invention, this area can be specified with an angle of 360° around the vehicle, so that the topography is evaluated from the vehicle in all directions. This can be particularly useful if a navigation system is not used and no other information about a potential destination is available.

[0013] However, an advantageous embodiment of the method according to the invention can be used for a route planned via a navigation system to a known destination without a planned route or to routes frequently traveled in the past with a similar position of the vehicle. In this case, the angle of the circumference can be restricted to an angular section along the potentially expected direction of travel. Here, too, the route is not limited to a specific main route in order to plan as precisely as possible which battery charge level will provide the ideal conditions. Instead, the circumference in which the topography is determined is reduced accordingly based on the general direction of travel. Depending on further parameters, this reduction can be specified, for example, so that the angular section is reduced to 90 to 270° along the direction of travel.At 90°, this would mean that, starting from the vehicle, a circular segment of 45° each would be considered to the right and left of the direction of travel, and at 270°, a circular segment of 135° each would be considered. This would reduce the effort required to evaluate the topography, and it would also allow significant elevation differences to be ignored in the rear area of ​​the direction of travel, which would lead to steeper downhill or uphill sections, thus improving the quality of the estimate.

[0014] Depending on whether the direction of travel is derived from a planned route by a navigation device, an estimate from the past, or, for example, a destination position taken from a calendar entry, the angle can be restricted to varying degrees. For a route specified relatively precisely by a navigation device, the angular segment can be selected to be smaller, i.e., in the range of 90 to 120°. For a relatively uncertain assumption of a preferred direction of travel based on past journeys or similar, it can be selected to be correspondingly larger, for example, 200 to 270°, to ensure a sensible operating strategy.

[0015] Overall, lower hydrogen consumption is thus possible through optimized use of the traction battery. Furthermore, and this applies particularly to expected uphill stretches, improved vehicle performance, for example, preventing vehicle speed reduction, can be ensured through optimal use of the traction battery. Furthermore, the method according to the invention, in one of its embodiments described above, ultimately also allows for more careful use of both the traction battery and the fuel cell system, so that an improvement in service life can be achieved through efficiency-optimized use.

[0016] Further advantageous embodiments of the method according to the invention also emerge from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0017] Fig. 1 shows a schematically indicated vehicle for carrying out the method according to the invention;

[0018] Fig. 2 shows a first example case in which the vehicle is located in a flat area;

[0019] Fig. 3 shows another example case in which the vehicle is on a high plateau; and

[0020] Fig. 4 a third case in which the vehicle is located in a hilly or mountainous region.

[0021] The illustration in Figure 1 shows a very schematic representation of a vehicle 1, which is to be equipped with a fuel cell system 2 and a traction battery 3. The vehicle is a commercial vehicle, here in the form of a truck, consisting of a tractor unit 4 and a semi-trailer 5. However, other vehicles with or without a trailer, which could be designed as both commercial vehicles and passenger cars, are also conceivable.

[0022] The vehicle 1 has a GPS sensor 6 in the area of ​​its tractor 4, which is indicated schematically here. The vehicle 1 can use this to determine its position. Using an internal vehicle control unit and / or an external vehicle server (not shown here), for example a cloud, the topography in the area surrounding the vehicle 1 can be determined based on the position of the vehicle 1 determined via the GPS sensor 6. For this purpose, altitude information is read from a digital map stored in the vehicle 1 or on the external vehicle server, and this altitude information is evaluated within a predetermined radius of, for example, 50 km around the vehicle 1 if no specific information on a potential route or direction of travel is available.Depending on the height differences between the height of vehicle 1 in its current position and the potentially traveled terrain, uphill and / or downhill sections are inferred, so that ultimately, within the specified radius, a probability for uphill sections on the one hand and downhill sections on the other can be determined. A target charge level of the traction battery 3 is then specified based on these probabilities for uphill and downhill sections. This will be described below using Figures 2 to 4 for three purely exemplary cases.

[0023] The example in Figure 2 shows vehicle 1 in a largely flat region with higher terrain towards the edge. Accordingly, the potential uphill gradients determined in the surrounding area are 838 m, while the potential downhill gradients are only 45 m. The example shows a section of the A5 motorway between Karlsruhe and Basel purely as an example. In such a region, the probability of an uphill gradient is relatively high, while the probability of a downhill gradient is very low. The target charge level of traction battery 3 is therefore set to high, for example, more than 80% of battery capacity. This enables ideal use of traction battery 3. Since downhill gradients are only to be expected to a very limited extent, a correspondingly fully charged battery can be used without the risk of recuperation energy not being able to be stored.At the same time, the high charge level of the traction battery 3 allows support of the electric drive of the vehicle 1 from the battery to be prepared for the uphill stretches that are expected with a much higher probability.

[0024] The second embodiment according to Figure 3, using the same logic as in the illustration in Figure 1, shows travel on a plateau where vehicle 1 is already at a higher level, meaning that the expected elevation gain on uphill sections adds up to approximately 380 m, and the expected elevation gain on downhill sections adds up to almost three times that value, at approximately 1160 m. The topography example in this case is taken from the B500 federal highway, the so-called "Black Forest High Road." In this situation, the probability of traveling downhill is very high, while the probability of traveling uphill is lower. The target state of charge of traction battery 3 can therefore be set comparatively low here, for example, on the order of approximately 30% of the battery capacity; in a similar scenario with an even lower probability of traveling uphill, the target state of charge could be even lower.In such a situation, it must be assumed that there is a relatively high probability that a downhill section will be traveled. This process involves a relatively large amount of recuperation energy due to wear-free braking by the electric drive motor in generator mode. The very low target state of charge of traction battery 3 makes it possible to store all or at least a large portion of this energy generated during recuperation, thus placing the emphasis on energy-efficient operation.

[0025] The third example in Figure 4 shows the vehicle on a mountainous or hilly route, the scenario of which is taken from the A7 motorway in the “Kassel Mountains” area. In the relevant area, the topography shows almost 800 meters of uphill stretches and roughly the same amount of downhill stretches. It can therefore be assumed that both downhill and downhill stretches will be traveled. In this case, the target charge level of traction battery 3 is specified in the medium range, for example, in the order of 50 to 60% of the battery capacity. Such a medium charge level then enables assistance when driving uphill and also the possibility of storing at least a large portion of the energy generated during recuperation on downhill stretches, so that it can then be made available again on the next uphill stretch.

Claims

Claims: A method for operating an electric vehicle (1) with at least one fuel cell system (2) and at least one traction battery (3), characterized in that a target state of charge of the at least one traction battery (3) is predetermined based on the topography in the vicinity of the vehicle (1), for which purpose the position of the vehicle (1) is determined and elevation data are obtained from a digital map within a predetermined radius around the vehicle (1), based on which the probable occurrence of uphill and / or downhill sections is inferred, according to which the target state of charge is predetermined depending on the probability of uphill and / or downhill sections. The method according to claim 1, characterized in that, in the case of a higher probability of uphill sections than of downhill sections, the target state of charge is predetermined with more than 50 to 60% of the battery capacity.The method according to claim 2, characterized in that the target state of charge is set to more than 80% of the battery capacity. The method according to claim 1, 2 or 3, characterized in that, in the case of a higher probability of downhill sections than uphill sections, the target state of charge is set to less than 50 to 60% of the battery capacity. A method according to claim 4, characterized in that the target state of charge is specified at less than 30% of the battery capacity. A method according to any one of claims 1 to 5, characterized in that, in the case of a similarly high probability for uphill and downhill sections, the target state of charge is specified in the range of approximately 50 to 60% of the battery capacity. A method according to any one of claims 1 to 6, characterized in that the radius around the vehicle (1) is specified with a radius of approximately 50 km. A method according to any one of claims 1 to 7, characterized in that the radius around the vehicle (1) is specified with an angle of 360°.A method according to any one of claims 1 to 7, characterized in that, in the case of a route planned via a navigation system to a known destination without a planned route or frequently traveled routes in the past, with the vehicle (1) in the same position, the angle of the circumcircle is restricted to an angular segment along the expected direction of travel. A method according to claim 9, characterized in that the restricted angular segment is specified in the range of 90 to 270°.

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