Device and Method for Increasing the Range of an Electric Vehicle

Abstract

A device and method for increasing the range of a vehicle, which is driven by an electric motor and a high-voltage battery, include an electronic control unit which is programmed such that on the basis of the high-voltage battery charge state, which is continuously estimated in an updated manner, a corresponding remaining range is displayed to the driver. A lower charge state limit is defined, which is associated with a remaining range to be displayed of null when the charge state is estimated in an error-free manner. The lower charge state limit is associated with a defined first minimally permissible cell voltage limit. During a driving operation, it is determined whether a greater range is being displayed than what can be demanded on the basis of the current charge state due to an estimation error. The display is not corrected by the estimation error difference. And, an emergency mode is automatically activated if an estimation error has been detected, wherein the cell voltage is reduced below the first cell voltage limit in the emergency mode.

Claims

1-10. (canceled)

11. A device for increasing a range of a vehicle, which is driven by an electric motor and a high-voltage battery, comprising: an electronic control unit operatively configured such that: based on the high-voltage battery state of charge, which is continuously estimated in an updated manner, a corresponding remaining range is displayed to a driver; a lower charge state limit is defined, which is associated with a remaining range to be displayed of zero when the state of charge is estimated in an error-free manner; the lower charge state limit is associated with a defined first minimally permissible cell voltage limit; during a driving operation, a check is carried out to determine whether a greater range is being displayed to the driver than what can be demanded based on a current state of charge due to an estimation error; the display is not correctable by a difference of the estimation error; and an emergency mode is automatically activatable when the estimation error has been detected, wherein the cell voltage is reducible below the first cell voltage limit in the emergency mode.

12. The device according to claim 11, wherein the cell voltage is lowered in the emergency mode such that the displayed remaining range is actually achievable.

13. The device according to claim 11, wherein the reduced cell voltage is temporarily permitted up to a next charging process or up to an achievement of a reduced second cell voltage limit, which is lower than the first cell voltage limit.

14. The device according to claim 11, wherein the emergency mode is predefined in a charge state range directly below a defined estimation reserve.

15. The device according to claim 14, wherein the defined estimation reserve is predefined directly below the lower charge state limit.

16. The device according to claim 11, wherein the emergency mode is suppressible when a defined condition is present.

17. The device according to claim 16, wherein one defined condition for suppressing the emergency mode is that the second cell voltage limit has been fallen below.

18. The device according to claim 16, wherein in a driving operation with a suppressed emergency mode, the lower charge state limit is set higher than in a driving operation with a permitted emergency mode.

19. The device according to claim 16, wherein in a driving operation with a suppressed emergency mode, the charge state range of the estimation reserve is greater than in a driving operation with a permitted emergency mode.

20. A method for increasing a range of a vehicle, which is driven by an electric motor and a high-voltage battery, by use of an electronic control unit, the method comprising: based on the high-voltage battery state of charge, which is continuously estimated in an updated manner, a corresponding remaining range is displayed on a display to a driver; a lower charge state limit is defined, which is associated with a remaining range to be displayed of zero when the state of charge is estimated in an error-free manner; the lower charge state limit is associated with a defined first minimally permissible cell voltage limit; during a driving operation, carrying out a check to determine whether a greater range is being displayed than what can be demanded on the basis of the current state of charge due to an estimation error, wherein the display is not correctable by a difference of the estimation error; and automatically activating an emergency mode when the estimation error has been detected, wherein a reduction of the cell voltage below the first cell voltage limit is permitted in the emergency mode.

21. The method according to claim 20, wherein the cell voltage is lowered in the emergency mode such that the displayed remaining range is actually achievable.

22. The method according to claim 20, wherein the reduced cell voltage is temporarily permitted up to a next charging process or up to an achievement of a reduced second cell voltage limit, which is lower than the first cell voltage limit.

23. The method according to claim 20, wherein the emergency mode is predefined in a charge state range directly below a defined estimation reserve.

24. The method according to claim 23, wherein the defined estimation reserve is predefined directly below the lower charge state limit.

25. The method according to claim 20, wherein the emergency mode is suppressible when a defined condition is present.

26. The method according to claim 25, wherein one defined condition for suppressing the emergency mode is that the second cell voltage limit has been fallen below.

27. The method according to claim 25, wherein in a driving operation with a suppressed emergency mode, the lower charge state limit is set higher than in a driving operation with a permitted emergency mode.

28. The method according to claim 25, wherein in a driving operation with a suppressed emergency mode, the charge state range of the estimation reserve is greater than in a driving operation with a permitted emergency mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 is a schematic representation of possible components of an electric vehicle having the emergency mode according to an embodiment of the invention.

[0043] FIG. 2 shows a first aspect of the invention for ensuring a remaining range given an SOC estimation error that is greater than the established estimation reserve, in comparison to the status quo.

[0044] FIG. 3 shows a second aspect of the invention for ensuring a remaining range with a reduced SOC estimation reserve, but given an SOC estimation error of zero, in comparison to the status quo.

[0045] FIG. 4 shows various defined voltage thresholds for a cell.

[0046] FIG. 5 shows the emergency mode with a simultaneously reduced estimation reserve.

[0047] FIG. 6 shows the estimation reserve according to the prior art.

DETAILED DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 shows a block diagram with exemplary components of an electric vehicle 100. In particular, the vehicle 100 includes an energy accumulator 102 (in particular a high-voltage battery), which is configured for providing electrical energy for operating an electric motor of the vehicle 100. The energy accumulator 102 is configured for ascertaining its fill level (also referred to as state of charge, SOC) and providing the fill level to an electronic control unit 101. The control unit 101 can be configured for ascertaining a remaining range of the vehicle 100 on the basis of the fill level (SOC) of the energy accumulator 102. Alternatively, however, the control unit 101 itself can also ascertain, in particular estimate, the state of charge and the resultant remaining range depending on signals of the energy accumulator 102.

[0049] The vehicle 100 can also include a navigation unit 104, which is configured for ascertaining a position of the vehicle 100 and/or a planned travel route for the vehicle 100. The control unit 101 can be configured for ascertaining whether the vehicle 100 can cover the planned travel route in light of the remaining range.

[0050] In order to increase the service life of an energy accumulator 102 (in particular of an electrochemical energy accumulator, such as, for example, a lithium ion-based energy accumulator), an energy accumulator 102 is typically operated in a fill level range, by means of which the effectively available capacity of the energy accumulator 102 is reduced in comparison to a maximum capacity of the energy accumulator 102 (standard operating mode). In the standard operating mode, in particular, a lower charge state limit is not fallen below, in principle.

[0051] Moreover, an input/output unit 103 of the vehicle 100 can be provided for detecting an input by the user of the vehicle 100.

[0052] Moreover, the control unit 101 can be configured for prompting one or multiple control unit(s) 105 of the vehicle 100 to switch to an energy-saving mode if it has been detected that the minimum SOC value of the standard operating mode has been reached. For example, an air conditioning system of the vehicle 100 can be deactivated and/or a driving speed and/or an acceleration of the vehicle 100 can be limited. In other words, the control unit 101 can be configured for taking measures to reduce an energy consumption of the vehicle 100 in order to further increase the range of the vehicle 100.

[0053] These components are basically the prior art. An essential integral part of the invention is the electronic control unit 101, which is appropriately programmed (computer program product in control units), in particular, for carrying out the emergency mode according to the invention.

[0054] A first aspect of the invention is explained with reference to FIG. 2 and with reference to a first situation:

FIG. 2, Left: Prior Art (Status Quo)

[0055] Situation 1: The drivability limit (=lower SOC value of an estimation reserve) is reached, but a remaining range RRW>0 km is displayed to the driver, since a maximum estimation error of only 5% was assumed during the establishment of the estimation reserve, the maximum estimation error of only 5% having actually been exceeded here, however.
A defined (first) lower cell voltage limit is reached (the cell voltage limit is not lowered). [0056] The SOC estimation error can also be >5% in extremely rare “worst case” scenarios (in particular after aging). [0057] In this case, a “need to get the vehicle towed” can arise at a displayed remaining range greater than 0 km if the driver drives his/her vehicle until completely “empty”.

FIG. 2, Right: Invention (“Robustness Measure”)

[0058] Given the same situation 1 above:

The drivability limit is reduced in an emergency mode such that a displayed range of 0 km is reached; i.e., the driver can drive electrically until “0 km” or “- - - ” is displayed.
For this purpose, preferably or if necessary, the lower cell voltage limit is lowered to such an extent that the energy reserve necessary for the emergency mode is temporarily made available. [0059] If, in the above-described situation 1, the power therefore drops below a defined drivable level (for example, only a constant speed of 80 km/h is possible) at an energy forecast of >0 kWh, then, according to the invention, an estimation error is detected and the lower cell voltage level is temporarily lowered. [0060] In the ideal case, the driver can still “escape” to the charging station, but, at the least, he/she can continue driving until “- - - ” (RRW=0 km) is displayed. [0061] A temporary lowering of the lower cell voltage limit (for example, from 2.8V to 2.1V) only in the special case (i.e., at a low state of charge (SOC) with a remaining range of greater than 0 km due to a detected high estimation error) is non-critical due to the findings made by the inventors in tests with respect to the aging of the cells. [0062] The lowered cell voltage limit (for example, 2.1V) is preferably to still be above a limit necessary for functional reliability (for example, 1.7V), however.

[0063] A second aspect of the invention is explained with reference to FIG. 3:

FIG. 3, Left: Prior Art (Status Quo)

[0064] Situation 2: The lower charge state limit of the standard operating mode is relatively high; if this is fallen below, the result is an early utilization of the estimation reserve in the sense of a fill level reserve.
Reduction to “normal” also relatively high drivability limit as the lower limit of the estimation reserve (limp home range, so-called “turtle mode”): 5% estimation reserve is not displayed to the user as a usable range and is usable as an estimation reserve only in the “turtle mode”. [0065] An SOC estimation reserve of 5% is taken into account in the energy configuration. [0066] In a very large number of use cases, the actually possible range is not released, since a reserve must be retained for the special case of “high estimation error.”

FIG. 3, Right: Invention (“Robustness Measure”)

[0067] Given the same situation 2 above:

A portion of the estimation reserve according to the status quo (for example, 2%) is displayed to the driver here as a usable range.
The “Normal” drivability limit is lowered: “ReSi” (=ensuring the remaining range=emergency mode) drivability limit: Given an estimation error of >3% in the low SOC range, the emergency mode is activated. [0068] In the energy configuration, the estimation reserve can be reduced according to the invention (for example, from 5% to 3%). The estimation error is not changed due to the emergency mode. [0069] In the case of “estimation error and displayed remaining range”, which now occurs more frequently, the emergency mode (ReSi) is activated and, for this purpose, the cell voltage limit is lowered. The consequence is, at least, no increase of the risk of the “vehicle needing to be towed” in comparison to the prior art.

[0070] FIG. 4 shows various defined voltage thresholds for a cell. According to the invention, it can be defined in the electronic control unit 101 that the estimation reserve is selected up to the point of a first lower voltage threshold S1 (for example, 2.8V) being fallen below. If the emergency mode is activated, the cell voltage limit can be lowered to a lower second threshold value S2 (for example, 2.1V), which can also be variably predefined depending on parameters such as temperature and aging.

[0071] In FIG. 5, the invention is represented once again in another way in contrast to the prior art according to FIG. 6. FIG. 6 corresponds to the left side (status quo) of FIG. 2. FIG. 5 corresponds to the right side (robustness measure) of FIG. 3.

[0072] In FIGS. 5 and 6, the Gaussian curves of an estimation error are plotted with respect to the establishment of the lower charge state limits and the drivability limits.

[0073] In FIG. 6 (according to the prior art), a comparatively high lower charge state limit and a drivability limit (normal) are defined for a −5% estimation reserve.

[0074] Example at the operating point B1 given an estimation reserve of 5%: The state of charge SOC is incorrectly estimated here, since an estimation error >5% has occurred. The display could then, for example, erroneously still display a remaining range (RRW) of 6 km. The vehicle could come to a stop, however, at a displayed remaining range (RRW) of 4 km if the driver continues driving. An abrupt correction of 6 km to 4 km is to be prevented for reliability reasons.

[0075] In FIG. 5, an operating point B1′ is plotted as an example at an estimation reserve of 3% that is reduced in comparison to the prior art (the estimation reserve could also remain at 5%, but the invention enables a reduced estimation reserve): The state of charge SOC is incorrectly estimated, since an estimation error >3% arises and, according to the invention, is also detected. The increased estimation error is detected if a greater remaining range (RRW>0 km) is displayed than what would actually be possible due to the currently estimated state of charge SOC if the basically predefined minimum cell voltage limit (for example, 2.8V) is to be not fallen below. According to the invention, the emergency mode is now activated by permitting the “Normal” drivability limit to be fallen below. This takes place by temporarily releasing a lower minimum cell voltage limit (for example, 2.1V, see also FIG. 4). Preferably, the cell voltage limit is temporarily reduced to such an extent that the remaining range that is actually achievable as a result corresponds to the displayed remaining range. Charging is carried out at a remaining range of 0 km, as the result of which the emergency mode is automatically switched off.

[0076] Due to this temporary and estimation error-dependent automatic emergency mode, the estimation reserve can be reduced and/or the lower charge state limit can be reduced. This is apparent in a comparison of the SOC thresholds in FIG. 5 with the SOC thresholds in FIG. 4.

[0077] The present invention is not limited to the exemplary embodiments shown. In particular, it is important to note that the description and the figures are to illustrate only the principle of the provided methods, devices, and systems.