Method for determining and using model for energy storage of vehicle
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2023-06-26
- Publication Date
- 2026-06-29
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a method for determining a model for an energy store of a vehicle, a method for determining the power limits of an energy store of a vehicle using such a model, a method for determining a sequence of actions to be performed by a vehicle, as well as a computing unit and a computer program for implementing these. [Background technology]
[0002] Modern vehicles, particularly battery-electric vehicles, employ functions that depend on the performance of the vehicle's energy storage, e.g., the battery. Summary of the Invention
[0003] According to the invention, a method for determining a model for an energy store of a vehicle, a method for determining the power limit of an energy store of a vehicle using such a model, a method for determining a sequence of actions to be performed by the vehicle, as well as a computing unit and a computer program for implementing the same, are proposed with the features of the independent patent claims. Advantageous configurations are the subject of the dependent claims and the following description.
[0004] The present invention relates to a vehicle, in particular a battery-powered electric vehicle, which is in particular a vehicle that is driven purely electrically and uses one or more batteries, or even exclusively batteries, as energy storage.
[0005] Many functions in such vehicles can be realized, for example, in whole or in part, by software functions distributed among several control devices (or other computing units). Consider, for example, adaptive cruise control (ACC, "Adaptive Cruise Control") in battery-electric vehicles. In this case, inter alia, electrochemical and thermal limitations in the battery (typically a high-voltage battery) are taken into account as boundary conditions for the planning of the vehicle speed. Such planning of the vehicle speed can take place, for example, within a trajectory or within the planning of this trajectory, in which the subsequent acceleration and / or speed of the vehicle are planned in advance. This can be the case, for example, when an overtaking process is imminent, which is initiated, for example, by activating the turn signal, and in which the vehicle speed should be automatically set and adjusted or regulated.
[0006] These limits of the energy store can be determined, for example, in a battery management system (which is implemented, for example, on a battery control device) and provided to further control devices. Interfaces (data interfaces) that can be used for this can be defined, for example, by long-term and short-term current and voltage limits or generally by power limits. Such power limits then indicate the maximum power that can be supplied by the energy store for a set duration.
[0007] The energy store can not only supply (or release) power, for example during driving operation, but also receive it, for example during charging or quick charging. The power limit can therefore also indicate the maximum receivable power. This applies not only to the energy store, but also, for example, to the vehicle itself. In the following, therefore, the available power will also be generally described, which indicates the power that can be supplied (or released) and / or received.
[0008] As a basis for determining such a power limit, it is assumed, for example, that a certain load is applied for a certain time. That is, a power limit may, for example, provide that a current of up to 250 A can be supplied at a voltage of 400 V for a duration of 20 s, i.e. a power of up to 100 kW can be supplied for a duration of 20 s. Similarly, a power limit may, for example, provide that a current of up to 300 A can be supplied at a voltage of 400 V for a duration of 5 s, i.e. a power of up to 120 kW can be supplied for a duration of 5 s. In this respect, inter alia, a constant load, i.e. the power that can be taken (or supplied) by the energy store and / or the power that can be supplied by the vehicle, respectively, should be assumed. The same applies to the power that can be received.
[0009] These current and voltage limits or generally power limits can then be used in subsequent partial functions, for example, to plan speed trajectories that do not violate these power limits, taking into account, inter alia, vehicle properties and properties of the components of the powertrain, such as mass, running resistance, etc. Similarly, charging or fast charging processes, for example, can be planned in this manner.
[0010] Typically, battery management systems provide only two such power limits for other functions, usually a short-term limit, such as a power limit for 5 s, and a long-term limit, such as a power limit for 20 s. Now, if a function is to plan a trajectory with settings for the acceleration and / or speed of the vehicle, or globally also a sequence of actions to be performed by the vehicle, which actions should respectively set the power to be taken by the energy store and / or the power to be supplied by the vehicle (or the power to be received correspondingly), usually the short-term limit provides too short a perspective for this, so the long-term limit for a longer planning horizon must be used.
[0011] This means, for example, that for the example of an overtaking process with both mentioned power limits, a typical overtaking process cannot be completed within 5 s, possibly including the necessary buffer, so that it can be calculated with a maximum power of 100 kW.
[0012] However, if only the lower long-term limit is used, typically some potential remains unused since, as indicated, depending on the duration of the planning horizon, power values between both limits are also possible. This leads to the powertrain components, including the energy storage, e.g., the high-voltage battery, being slightly over-designed in cases of concern to achieve the desired performance, or to accept reduced performance.
[0013] In light of this, a (particularly generic) model is proposed that can dynamically determine and provide such a power limit for an energy store of a vehicle, for example a battery (particularly a high-voltage battery) of a battery-electric vehicle, i.e. can always determine and provide, among other things, a situation-dependent, among other things, future or predicted power limit. One aspect relates to determining (or deriving) such a model, and another aspect relates to applying this model to determine an up-to-date power limit and therewith, among other things, also a sequence of actions (for example a trajectory). For example, not only a speed trajectory but also, for example, a time plan for charging or fast charging the energy store is taken into account, which can be by charging from an external power grid or by regeneration.
[0014] To determine the model, a number of different set power limits are provided, each of which represents the maximum power that can be handled (i.e., inter alia, deliverable and / or receivable) by the energy store for a set duration, e.g., the short-term and long-term limits mentioned above.
[0015] A model is then determined on the basis of a number of set power limits, which model outputs an output value on the basis of at least one input value. In this regard, the at least one input value comprises a planned power to be taken by the energy store and / or a power to be handled (to be supplied or received) by the vehicle at a certain time point, and the output value in this case comprises a power limit at a time point one time point after this time point, which power limit represents a maximum power that can be handled (supplied or received) by the energy store. This power can then be handled, in particular, up to at least one more time point later. Such a model thus makes it possible to always obtain a power limit value for the planned power, with which the power for one or several later times (in terms of the sequence or trajectory of actions) can be planned. This model can in particular be provided for use in determining a sequence of actions for the vehicle.
[0016] In determining the model, parameters of the model are determined depending on a number of power limits. The model may be represented by one or more equations that include, among other things, certain parameters. An example of such an equation is:
[0017]
number
[0018] where y n gives the (latest) power limit value (output value), and x nrepresents the state in the model. The variable u represents the load planned at a time step or instant n-1, or the power to be taken (or received) by the energy store and / or the power to be supplied (or received) by the vehicle planned at this instant (input values). With Δt the time interval between two instants or time steps is represented. These instants or time steps result from a typically discrete planning of a trajectory or other sequence of actions. This value of Δt can then be set fixedly, but it is also conceivable to make this value variable, in which case this time interval could also be used as an input value. The parameters K, T, b are parameters that can be determined or calculated from a number of set power limits.
[0019] In the example of these equations, it can be seen that three known power limits are required to determine the three parameters K, T, b. For example, this can be three set power limits, obtained for example by a battery management system. However, it is also possible to obtain and use only two set power limits. In this case, it is preferred if a further power limit is determined on the basis of a number of set power limits (for example two power limits). This can be, for example, a power limit that represents a power that can be permanently supplied (or received) by the energy store. Such a further power limit can be determined, for example, on the basis of a number of set power limits, or can also be obtained, for example, in another manner. For example, it can be that a certain energy store permanently supplies (or receives) a certain power due to its construction type. A more detailed explanation of the possibilities for determining the parameters K, T, b is given in the description of the figures.
[0020] However, depending on the type of model used (e.g. number of parameters), more or less set power limits and / or further power limits may be necessary or used to determine the parameters of the model.
[0021] That is to say, the model includes, among other things, internal states which change or may change along the planning horizon and thus result in dynamic power limits which may depend on the trajectory or sequence of actions planned on their part. In this way, the potential of the powertrain and the energy storage can be optimally utilized.
[0022] Although the set power limit remains unchanged at least for a certain period of time, it may nevertheless change under certain circumstances, for example due to aging of the energy store or also in the case of relatively long intensive loading of the energy store, in this case for example due to heating. In that respect, it is preferred if the model is newly determined or adapted when there are one or more new set power limits. This can be done automatically, for example, when the new set power limit is obtained, but also a regular interrogation of the new set power limit and possible subsequent adaptation as required is conceivable.
[0023] The application of this model is then made in determining the power limit of the energy store of the vehicle for use in determining the sequence of actions for the vehicle, in particular the trajectory. In particular the power limit to be determined is a future or predicted power limit. In this regard, at least one input value for the model is obtained or provided, which input value comprises the power to be taken (or received) by the energy store and / or the power to be provided (or received) by the vehicle, planned at a certain point in time of one of the actions. Then, an output value is determined using the model, which output value comprises the (latest) power limit at a point in time after this point in time, which power limit represents the maximum power that can be provided (or received) by the energy store. The output value is then provided or output and is used in particular in determining the sequence of actions, i.e. at this point in time, the power to be taken (or received) by the energy store and / or the power to be provided (or received) by the vehicle can be incorporated into the plan, which power corresponds at most to the output value. It may also be contemplated that the highest power limit of the given power limits is additionally used as an upper limit.
[0024] This allows a determination of the power limit that is up to date in each case. In this respect, this application of the model (which may in particular be a model determined or determined as explained above) may be performed independently of the determination of the sequence of actions, i.e. the sequence of actions (or trajectories) may be performed on a different computation unit or on a different control device than the application of the model. In this case, the computation unit in question for the application of the model may in particular be repeated for each point in time of the sequence of actions, always taking input values and outputting output values.
[0025] However, it is preferred that the output values are determined within the scope of the determination of a sequence of actions for the vehicle, for example also on the same computing unit. The sequence of actions includes actions to be performed by the vehicle at different time points, in particular at uniformly spaced time points, whereby the determination is made taking into account the performance of the energy storage of the vehicle. In this regard, for each time point, input values for the model are respectively determined, and output values are determined by the model according to the above-mentioned method.
[0026] In this way, a sequence of actions or a trajectory can be planned for the vehicle in which the latest power limits can always (i.e. at each point in time) be taken into account. A computing unit according to the invention, for example a control device of a motor vehicle, is adapted, inter alia, in terms of program technology, to carry out the method according to the invention.
[0027] Especially when the control device is further used for further applications and therefore present in any case, the implementation of the method according to the invention in the form of a computer program or computer program product with program code for implementing all process steps is also advantageous, since this results in particularly low costs. Finally, a machine-readable memory medium is contemplated on which a computer program as described above is stored. Suitable memory media or data storage media for providing the computer program are, inter alia, magnetic, optical and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, etc. Downloading of the program via a computer network (Internet, intranet, etc.) is also possible. Such downloading can be performed wired, i.e., cabled, or wirelessly (e.g., via a WLAN network, 3G, 4G, 5G or 6G connection, etc.).
[0028] Further advantages and features of the invention will become apparent from the specification and accompanying drawings. The invention is illustrated diagrammatically in the drawing on the basis of one exemplary embodiment and is explained in the following with reference to the drawing. [Brief description of the drawings]
[0029] [Figure 1] 1 is a schematic diagram of a vehicle on which the method according to the invention can be implemented; [Diagram 2] 1 is a schematic graph for illustrating the method according to the present invention in a preferred embodiment; [Diagram 3] FIG. 1 is a schematic flow diagram of the method according to the present invention in a preferred embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] 1 a vehicle 100 in which the method according to the invention can be carried out is shown diagrammatically. The vehicle is, by way of example, a battery-powered electric vehicle and has an electric drive (electric motor) 110 and an energy store 120 formed as a battery with a battery control device 122 for the battery management system. In addition to this the vehicle has a computing unit 130 formed as a control device, which can carry out the method according to the invention in a preferred embodiment.
[0031] For example, on the control device 130, a driver assistance function for adaptive speed regulation can also be executed, within which a trajectory 140 is determined, which for example includes settings for the acceleration and / or speed of the vehicle 100. The trajectory 140 is thus a sequence of actions that can be performed by the vehicle at different times, whereby these actions are performed taking into account the performance of an energy store of the vehicle, and the actions to be performed by the vehicle respectively set the power to be taken by the energy store and / or the power to be supplied by the vehicle. Such power is determined, for example, on the basis of the desired acceleration or speed at the respective time, taking into account inter alia also further vehicle parameters.
[0032] In Fig. 2, a graph is shown diagrammatically to explain the method according to the invention in a preferred embodiment. In the graph, the power P is shown along with the time t. In Fig. 3, the flow of the method according to the invention in a preferred embodiment is shown diagrammatically. First, it is explained how the model can be determined based on Fig. 2 and Fig. 3.
[0033] As mentioned, for example, two set power limits are provided by the battery management system in the vehicle. These power limits indicate the maximum power that can be provided by the energy store for a set duration. In the graph of FIG. 2, two such power limits P1 and P2 are shown here by way of example. The value indicated by P1 or P2 indicates the maximum power that can be provided by the energy store for the associated duration T1 or T2. In this regard, power should be requested at the instant ti (load jump).
[0034] For example, power limit P1 may indicate that a maximum power P1=120 kW can be supplied for duration T1=5 s. Similarly, power limit P2 may indicate that a maximum power P2=100 kW can be supplied for duration T2=20 s.
[0035] In the graph of Fig. 2, it can also be seen that, depending on the transition belonging to P1 or P2, the value slowly drops off after the duration T1 or T2. However, both transitions approach a further power limit Pinf, which indicates the power that the energy store can deliver permanently or at least for a much longer duration compared to T2. This further power limit Pinf depends on the energy store and can be, for example, 90% of the power P2, i.e. here 90 kW.
[0036] In the determination of the model, in step 300 according to Fig. 3, a number of different set power limits P1, T1 and P2, T2 are provided. These power limits can be obtained, for example, by a battery management system. Then, in step 310, the parameters of the model are determined depending on such set power limits. The model 312 is, for example, determined according to the equation
[0037]
number
[0038] Alternatively, instead of the above time-discrete representation, a continuous representation may be chosen, i.e.
[0039]
number
[0040] The parameters K, T, b are parameters that can be determined or calculated from a number of set power limits, i.e., for example, by the power limits P1, P2, and Pinf. In this regard, the specific power values P1 and P2 can be directly used as the upper and lower power values PH and PL, for example. The value of Pinf can be determined, for example, from P2 or PL by a factor Par, for example, 0.9.
[0041] Determining the parameters typically requires substitution of equations: the duration Δt is not required in a continuous representation (or can be chosen appropriately otherwise), and the variable u can be chosen appropriately.
[0042] From the model equation, substitute the formula and the following example values: t=∞, u=Pinf, y=Pinf, T1=5s, u=PH, y=PH, and T2=20s, u=PL, y=PL By using the above equations for determining the parameters K, T, b based on the input quantities Pinf, PL, PH, T1, T2, i.e.
[0043]
number
[0044] becomes clear. Additionally, a theoretical base power limit P0 may be assumed that is above the short-term power limit P1. This base power limit is an amount within the model, but not otherwise required (an auxiliary amount), and is the theoretical power that could be maximally delivered in an infinitely short time period.
[0045] The model 312 can then output an output value based on input values, the input values including the planned power to be drawn by the energy store and / or the power to be supplied by the vehicle at a certain time point, i.e., the variable u in the above formula, and the output value including a power limit at a time point one after this time point, which is the power that can be maximally supplied by the energy store for a certain duration, i.e., the value y in the above formula. n This is explained below within the scope of the model application.
[0046] The model 312 thus determined is then provided or output, for example to another function (in the same or another relevant computational unit) where the model is used or applied. As mentioned, the model 312 may be determined anew whenever, for example, one or more new (or other) power limitations exist, which may be the case, for example, due to aging or thermal loading of the energy storage.
[0047] That is, within the scope of application of the model, the latest power limits of the energy storage are determined for use in determining a sequence of actions (eg, a trajectory) for the vehicle. For this purpose, input values u for the model 312 are obtained or provided. The input values u include the power to be drawn by the energy store and / or the power to be supplied by the vehicle, planned at a certain time step or instant n-1 of one of the actions. In step 320, the model 312 is then used to calculate the output values y n The output value includes a power limit at the next time instant n, which represents the maximum power that can be provided by the energy storage. This is achieved by the above-mentioned equation
[0048]
number
[0049] where the duration Δt can be set to a small value, for example 0.01 s. The flow diagram shown in step 320 of FIG. 3 represents these equations. In this regard, for example, the value of u is set to the limit value of the attribute time step (power limit) y n-1 It can also be seen that the output value y n In other words, generally, the output value y n is limited downwards depending on the values of the set power limits P1 and P2.
[0050] Finally, in step 330, in order to determine a sequence of actions, i.e. for example a trajectory 140, step 330 can be applied repeatedly in a loop or a kind of loop, meaning that progressively at each further point in time or time step a new updated power limit is determined, and then, on the basis of this power limit, again the power to be taken by the energy store and / or the power to be supplied by the vehicle can be determined, whereby the trajectory is extended.
[0051] The processes described herein in relation to maximum deliverable power apply correspondingly to maximum receivable power. [Explanation of symbols]
[0052] 100 vehicles 110 Electric drive (electric motor) 120 Energy Storage 122 Battery control equipment 130 Calculation Units / Control Equipment 140 Sequence of Actions, Trajectory 300 Steps according to Figure 3 312 Model K, T, b model parameters At point n Par coefficient P0 Theoretical base power limit P1, P2 power limits Power value on PH Pinf Further power limit Power value under PL T1, T2 duration At time ti u Input values / variables x n State in the model y n Output Value Δt Duration
Claims
1. A method for determining a model (312) for an energy storage device (120) of a vehicle (100), Step (300) provides a set of several different set power limits (P1, P2), each of which sets of power limits represents the maximum amount of power that can be handled by the energy storage (120) over set durations (T1, T2), in particular, power that can be supplied and / or received; Based on a plurality of set power limits (P1, P2), at least one input value (u) is used as the basis for the output value (y ｎ Step (310) is to determine a model (312) that outputs ), and the parameters (K, T, b) of the model are determined depending on a plurality of power limits, The at least one input value (u) includes, at some point in time, power to be processed by the energy storage and / or power to be processed by the vehicle, The aforementioned output value (y ｎ Step (310) includes a power limit at a time immediately following the aforementioned time, wherein the power limit represents the maximum amount of power that can be handled by the energy storage device; and A method comprising, in particular, the step of providing the model (312) for use in determining a sequence of actions (140) for the vehicle (100).
2. The method according to claim 1, wherein the model (312) is determined based on a plurality of set power limits and at least one further power limit (Pinf), the at least one further power limit (Pinf) is determined, in particular, based on the plurality of set power limits.
3. The method according to claim 1, wherein the model, in particular the parameters, are newly determined when one or more newly set power limits exist.
4. A method for determining the power limit of the vehicle's energy storage, using a model for the energy storage, for use in determining a sequence of actions for the vehicle, A step of providing or obtaining at least one input value for the model, wherein the at least one input value (u) includes power to be processed by the energy storage and / or power to be processed by the vehicle, planned at some point in one of the actions; Using the aforementioned model, the output value (y ｎ Step (320) is to determine the output value, wherein the output value includes a power limit at a time one subsequent to the time, and the power limit represents the maximum amount of power that can be handled by the energy storage device; and A method comprising the steps of providing or outputting the aforementioned output values and, in particular, using the aforementioned output values in determining the sequence of the actions.
5. The method of claim 4, wherein the model (312) is determined or determined by the method of claim 1.
6. A method for determining (330) a sequence (140) of actions to be performed by the vehicle (100) at different time points, particularly at uniformly spaced intervals, taking into account the performance of the vehicle's energy storage (120), wherein each of the actions to be performed by the vehicle sets the power to be processed by the energy storage (120) and / or the power to be processed by the vehicle, For the aforementioned time point, at least one input value (u) for the model (312) and an output value (y) by the model (312) are respectively. ｎ A method in which the (320) is determined according to the method described in claim 4.
7. The method according to claim 6, wherein the sequence of actions (140) is further determined taking into account the static and / or dynamic characteristics of the vehicle (100).
8. The method according to claim 1, wherein the sequence of actions (140) is determined as or as part of a trajectory, and the trajectory includes, in particular, settings relating to the acceleration and / or velocity of the vehicle.
9. The method according to claim 1, wherein a battery-powered electric vehicle is used as the vehicle (100).
10. A computing unit (130) adapted to carry out all process steps of the method according to any one of claims 1 to 9.
11. A computer program, when executed on a computing unit (130), that causes the computing unit (130) to perform all process steps according to any one of claims 1 to 9.
12. A machine-readable memory medium on which the computer program described in claim 11 is stored.