Method for monitoring on-board electrical system of motor vehicle
By measuring and analyzing the voltage and current of safety-related loads in the vehicle power grid, combined with line resistance, the accurate degradation or shutdown of non-safe-related loads is solved, and the problem of insufficient power supply under high safety requirements is improved, and load availability and users are improved. Comfort.
Patent Information
- Application Number
- CN202380040807.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-05-16
- Filing Date
- 2023-03-06
- Publication Date
- 2024-12-27
AI Technical Summary
In a vehicle-mounted power grid with high safety requirements, it is difficult for the prior art to effectively improve availability while maintaining comfort for non-safety-related loads, especially when power supply is insufficient, which may lead to insufficient power supply of safety-related loads.
By measuring voltage and current on safety-related loads, combined with the resistance of the line path, accurately predicting voltage drops, purposefully degrading or shutting down non-safety-related loads, ensuring sufficient power supply to safety-related loads, and optimizing load priorities to reduce Unnecessarily shut down.
Improves power supply availability of safety-related loads, delays shutdown of non-safe-related loads, reduces unnecessary voltage increases, improves user comfort, and reduces the aging risk of vehicle-mounted grid components through precise prediction and analysis processing.
Smart Images
Figure CN119213653A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for monitoring an onboard electrical system of a motor vehicle according to the type of the independent claim. Background Art
[0002] DE 102018212369 A1 discloses a method for monitoring a power supply system in a motor vehicle, wherein at least one energy storage device supplies energy to a plurality of preferably safety-related loads in an onboard power subsystem. At least one measured variable of the energy storage device and / or at least one load is detected, wherein at least one cable harness model is provided, which describes the onboard power subsystem. A parameter estimator is provided, which estimates at least one characteristic variable of the cable harness model using the measured variables.
[0003] A method for monitoring the onboard power supply of a motor vehicle is known from DE 10201821277 A1. Here, a simulation is used to check which safe stopping scenarios are available under the current battery and onboard power supply status. In addition, corresponding measures are proposed in the onboard power supply and an analysis of their direct effect on the availability of different scenarios is determined.
[0004] DE 102020212414 A1 discloses a method for monitoring an onboard power supply system of a motor vehicle, wherein at least one safety-related load and, if applicable, further loads are supplied by an energy storage device, wherein at least one onboard power supply system model is provided, which depicts the safety-related loads and the corresponding lines with the associated line resistances and the connection to the energy storage device, comprising the following steps: providing a current characteristic or a power characteristic, which is presumably necessary at least for a certain maneuver of the motor vehicle when the safety-related loads are added and, if applicable, may include a basic load of at least one further load, determining a predicted characteristic variable of the safety-related energy storage device using the current characteristic or the power characteristic, the associated line resistance and predicted characteristic variables of the energy storage device, presumably loading the safety-related load using the current characteristic or the power characteristic, and analyzing the predicted characteristic variable of the safety-related load.
[0005] The invention is based on the object of further increasing the availability, in particular in vehicle electrical systems with high safety requirements, with a minimal loss of comfort. This object is achieved by the features of the independent claims. Summary of the invention
[0006] The method according to the features of claim 1 has the advantage that, on the one hand, sufficient power supply for safety-related loads can be ensured with high reliability, wherein only the non-safety-related loads that are actually required can be degraded or switched off in a completely targeted manner based on the more accurate determination of the reduction degree. As many non-safety-related loads as necessary and as little as possible are then disconnected from the power supply. By more accurately determining the reduction degree and the undervoltage, it can be ensured accurately that the measures taken effectively reduce the undervoltage that is also determined in the desired manner and that the safety-related loads are then adequately powered again. Precisely by determining the voltage drop at the safety-related loads individually, the tolerance with respect to the undervoltage can be better utilized, so that a possible premature disconnection of non-safety-related loads or load groups is minimized, without, however, endangering the power supply of the safety-related loads. The availability of the non-safety-related loads is thereby increased.
[0007] In an expedient development, a switch-off time or a trigger for switching off or downgrading at least one of the non-safety-related loads is generated if the voltage present at the safety-related loads falls below a limit value for a certain duration, preferably in the range between 1 millisecond and 500 milliseconds. Thus, by correspondingly selecting the limit value or the corresponding duration, the corresponding voltage requirement can be individually adapted to the corresponding safety-related load in practice, by correspondingly selecting the limit value or the corresponding duration, respectively, in accordance with the corresponding characteristics of the safety-related loads. It is precisely the corresponding time interval between 1 millisecond and 500 milliseconds that indicates that the method is not used for line, component or component protection, where an overcurrent switch-off may be necessary in a time range of less than 10 μs. Compared to classic onboard power supply interventions for voltage protection of more than 500 milliseconds, the selected time range takes into account the increased safety requirements for safety-related loads.
[0008] In an expedient development, it is provided that the magnitude for the voltage present at the safety-related loads is ascertained from the supply voltage at the power distributor and the voltage drop on the line path between the power distributor and the safety-related loads. Consideration of the voltage drop on the line path makes it possible to achieve a particularly precise and accurate prediction of a possible undervoltage, whereby a shutdown or degradation of non-safety-related loads can be carried out as required and in a targeted manner. As a rule, non-safety-related loads can be shut down later than would be achieved in a shutdown with an otherwise generally high safety factor.
[0009] In an expedient development, it is provided that the voltage drop across the line path between the power distributor and the safety-relevant load is ascertained using the resistance of the corresponding line path and the current flowing through the safety-relevant load. In particular, a corresponding measured variable of the current is usually present in the power distributor anyway, for example due to safety functions involving overcurrent shutdown or the like, so that a simple ascertainment of the voltage drop across the safety-relevant load is thereby possible.
[0010] In an expedient development, the degree of reduction, in particular the reduced current, is ascertained as a function of the resistance of the line path connecting the energy store to the power distributor and / or as a function of the internal resistance of the energy store. The accuracy of the degradation or shutdown is further increased, since further characteristic variables are taken into account, which can also vary more significantly over the life of the energy store or the onboard electrical system.
[0011] In an expedient development, the number of non-safety-related loads to be switched off is determined as a function of the reduction. In contrast to what is often customary, not all non-safety-related loads are switched off in the event of a power shortage, but rather only the exact number required for this purpose. This further increases the user's comfort, since the switching off of unnecessary non-safety-related loads can be omitted.
[0012] In a suitable improvement, the reduction is determined in such a way that the supply voltage is increased by at least an undervoltage. By this targeted increase, unnecessary excessive voltage increases are purposefully suppressed, which further increases comfort.
[0013] In an expedient development, the limit value varies as a function of the duration for which the magnitude of the voltage present at the safety-related load falls below the corresponding limit value, in particular increases with increasing duration. This allows particularly critical situations, which would lead to a long-term, permanent undershoot of the sufficient supply voltage, to be prevented in a targeted and early manner.
[0014] In a suitable development, the degree of reduction is determined using the resistance of the line path to the energy storage device and / or to the alternative energy source and / or the internal resistance of the energy storage device and / or based on a previously determined degree of reduction and / or based on the resistance of the line path to the energy storage device and / or to the alternative energy source determined by a model or diagnosis and / or based on the internal resistance of the energy storage device determined by a model or diagnosis. This can further increase the accuracy. In particular, the aging state of the onboard power supply component can be predicted relatively accurately by feedback to the model and can serve as a basis for a correspondingly more accurate determination of the degree of reduction.
[0015] An expedient development is characterized in that it is determined when the magnitude of the voltage present at the safety-related load reaches a limit value, and after reaching the limit value a time period is detected during which the limit value is undershot, the detected time period being compared with a time period assigned to the limit value, and a trigger for initiating a shutdown or degradation of at least one non-safety-related load is generated when the assigned time period is reached. This makes it possible to implement a simple time-dependent limit value that allows easy adaptation to the respective safety-related load.
[0016] In a suitable improvement, it is provided that the magnitude of the voltage present at least on the safety-related load is determined by measuring the voltage on the safety-related load and / or using the current flowing through the safety-related load and / or by measuring the supply voltage and / or taking into account the resistance of the line path between the power distributor and the safety-related load, in particular the worst-case value of the resistance or the resistance estimated by the model and / or according to the worst-case value of the voltage drop on the resistance. On the one hand, the accuracy of the analysis can be further improved by suitable measures, such as measuring the voltage directly on the safety-related load or by the current through the safety-related load. On the other hand, the determined worst-case value can further simplify the determination. By using the model also for the voltage determination on the safety-related load, the corresponding aging state of the vehicle power supply component can be reliably described. The accuracy of the determination is improved.
[0017] In an expedient development, it is provided that the ascertainment of the trigger and / or the undervoltage is effected by the safety-related load and / or the safety-related load transmits the trigger and / or the undervoltage and / or the voltage drop measured at the safety-related load, in particular to the power distributor. This allows a fast and accurate evaluation to be carried out already in the safety-related load, which is usually equipped with a high computing performance anyway, and relieves the power distributor of such tasks. The communication volume can also be reduced, since the purpose is to forward the corresponding shutdown signal precisely only in the event of an imminent undervoltage.
[0018] In an expedient development, it is provided that the selection of the non-safety-related loads to be switched off or downgraded is carried out as a function of the current flowing through the respective non-safety-related load, in particular switching off or downgrading such non-safety-related loads with the maximum through-current or with a through-current exceeding a certain limit value. It can thereby be ensured that the switched-off non-safety-related loads actually also bring about the desired voltage increase. Furthermore, the proposed measures ensure that only a small number of non-safety-related loads that are actually required need to be switched off.
[0019] In an expedient development, it is provided that another non-safety-related load is switched off until the reduction level is reached. This allows a particularly simple implementation of the selection, wherein the desired voltage increase is thus reliably achieved.
[0020] In an expedient development, it is provided that the respective current flowing through the non-safety-related loads is combined with a weighting factor specific to the respective non-safety-related load, and the respective combined value is used to select the non-safety-related loads to be switched off or downgraded. It is particularly expedient to provide that the non-safety-related loads are each provided with a weighting or priority value, and that the respective loads to be switched off or downgraded are selected by means of an optimization of the combined weighting or priority value. The load priorities can be set differently by means of the corresponding weightings, in order to keep the impairment of the user's comfort as small as possible.
[0021] Further expedient developments result from the further dependent claims and from the description. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] It shows:
[0023] Figure 1 : On-board power grid including power distributor,
[0024] Figure 2 : an alternative embodiment of an on-board electrical system comprising a power distributor and a further distributor,
[0025] Figure 3 : block diagrams for implementing the different sub-methods, and
[0026] Figure 4 : An exemplary voltage-time diagram including the associated undervoltage range. DETAILED DESCRIPTION
[0027] The present invention is schematically shown on the basis of embodiments and is described in detail hereinafter with reference to the accompanying drawings.
[0028] Figure 1The diagram shows a sub-onboard power system, in particular in a motor vehicle, which includes a power distributor 18. The power distributor 18 is supplied with energy by an energy storage device 12, in particular a battery. For this purpose, the energy storage device 12 is connected to a busbar 14 extending at least partially in the power distributor 18. Between the power distributor 18 and the energy storage device 12, a resistor Rb is indicated, which depicts the resistance in the feed line to the energy storage device 12, in particular a battery. In order to supply the power distributor 18 with power in a redundant manner, the busbar 14 of the power distributor 18 can be connected to another power supply source at another input, which is indicated in the embodiment by providing a DC voltage converter 22. The DC voltage converter 22 establishes a connection with another sub-onboard power system, which can include, for example, a higher, lower or similar voltage level. Between the power distributor 18 and the DC voltage converter 22, a resistor Rdc is again indicated schematically, which depicts the resistance in the feed line from the power distributor 18 to the DC voltage converter 22.
[0029] n safety-related loads 16.1, 16.2, ..., 16.n and m non-safety-related loads 17.1, 17.2, ..., 17.m are connected to the power distributor 18. The safety-related load 16.n can be specially protected by a switch mechanism not shown for reasons of clarity, for example, from overcurrent. The non-safety-related loads 17.m are each controllable by a switch mechanism 19 (19.1, 19.2, ..., 19.m), in particular, can be turned off or degraded. The switch mechanism 19 is arranged in the power distributor 18. The switch mechanism 19 is preferably a semiconductor switch, such as a metal oxide semiconductor field effect transistor, etc. In the power distributor 18, the voltage U on the bus 14 is measured. In addition, a current measurement is provided in the power distributor 18. In the embodiment, each current I16.n flowing through the corresponding safety-related load 16.n is detected. Alternatively, each current I17.m flowing through the corresponding non-safety-related load 17.m can be detected. Alternatively, the corresponding voltage U16.n present at the corresponding safety-related load 16.n can be measured, in particular relative to ground or ground GND. The ascertained or measured voltage U16.n present can be transmitted to the power distributor 18 or another control device, for example, via a communication system, for example a bus system such as a CAN bus or the like, depending on the location of the evaluation. Alternatively, the evaluation can be carried out in the safety-related load 16.n itself.
[0030] Between the power distributor 18 and the respective safety-related load 16.n, resistors R16.1, R16.2, ..., R16.n are shown, which depict the resistance of the respective line path between the power distributor 18 and the respective load 16.n. Between the power distributor 18 and the respective non-safety-related load 17.m, resistors R17.1, R17.2, ..., R17.m are shown, which depict the resistance of the respective line path between the power distributor 18 and the respective non-safety-related load 17.m.
[0031] A sensor (not shown), preferably a battery sensor, may be provided on the energy accumulator 12 for detecting other characteristic variables of the energy accumulator 12. In the sensor, for example, corresponding characteristic variables of the energy accumulator 12, such as internal resistance Ri, state of charge SOC or the like, may be determined based on the state variables of the energy accumulator 12 and the associated model. Safety-related loads 16 are special loads with high requirements or high protection needs, generally referred to as safety-related loads 16. Here, for example, electric steering devices and / or brake systems are involved as examples of such components, which must be unconditionally powered in order to ensure steering and / or braking of the vehicle in the event of a fault.
[0032] Likewise, the power distributor 18 has corresponding processing means (not shown in further detail), such as, for example, a microcontroller, in order to store or analyze the detected variables. The microcontroller can also actuate corresponding switching means 19 (or switching means for safety-related loads 16, not shown specifically, for their protection). Alternatively, the analysis can also be implemented in another control device.
[0033] The loads 16 supplied by the power distributor 18 can include, for example, safety-related vehicle functions such as, for example, braking, steering, etc., in particular loads 16 with high requirements regarding protection requirements. Generally, safety-related loads 16 are loads that are particularly worth protecting, which are necessary, for example, to maintain certain emergency functions. In addition to the functions such as steering and braking, these can also be functions that should still be able to function properly, for example after an accident, such as, for example, retraction systems, closing systems for opening and closing doors, emergency call systems, for example, for the occurrence of an electronic emergency call, convertible roof functions, lighting or the like.
[0034] The non-safety-related loads 17.m are typically comfort loads. The comfort loads 17.m can be divided into main groups and subgroups according to the application and thus grouped (compare with the Figure 2 Alternative embodiment with further distributors 50, 52). This concerns loads 17 which are not characterized by a high safety importance or by lower requirements with regard to protection requirements.
[0035] according to Figure 2 Embodiments and basis Figure 1 The difference of the embodiment is that further distributors 50, 52 are connected to the power distributor 18, through which the respective further loads 16.k, 17.l, 17.j shown by way of example can be driven. The distributor 50, to which at least one safety-related load 16.k is connected, is supplied with a corresponding current I16.v by the power distributor 18 via a line with a line resistor R16.v. In addition, a further distributor 52 is provided, through which only non-safety-related loads 17.j - in this embodiment only a single one is shown by way of example - can be supplied with power and can be switched off via a corresponding switching mechanism 19.j. The further distributor 52 is supplied with a corresponding current I17.v by the power distributor 18 via a line with a line resistor R17.v. The corresponding non-safety-related load 17.j is supplied with current I17.j.
[0036] The following sub-methods can be distributed to different control devices. Thus, the shutdown of non-safety-related loads 17.m can also be triggered in other distributors 50, 52 by corresponding switching mechanisms 19.l, 19.j. The signal 40 for shutting down loads 17.l, 17.j can be transmitted via a communication bus and can also be commanded in a separate control device, such as a so-called on-board computer, for example. If an undervoltage dU is present at a safety-related load 16.k, which in turn is supplied via a distributor 50, then this distributor 50 can also initiate the shutdown of the corresponding non-safety-related load 17 to the power distributor 18.
[0037] By way of example, in this exemplary embodiment, a battery or accumulator is described as a possible energy store 12. Alternatively, however, other energy stores suitable for this embodiment, for example based on inductance or capacitance, fuel cells, capacitors or the like, may also be used.
[0038] The time range for disconnecting the load 17 to be switched off is in the order of magnitude between 1 millisecond and 500 milliseconds. The method is not used for line, component or component protection and is therefore not similar to an overcurrent shutdown in a time range of less than 10 μs. In a classic onboard power supply, regulatory interventions in energy management in a time range of more than 500 milliseconds can be expected. If possible, it must be ensured that the variables to be evaluated are detected quickly and / or are transmitted quickly to an evaluation unit, such as, for example, a power distributor 18.
[0039] exist Figure 3Schematically shown in the figure are different blocks 30, 34, 38 with input and output parameters. A plurality of the above parameters are supplied to the undervoltage detection 30. This involves the current I16.n through the corresponding safety-related load 16.n and / or the voltage U on the bus 14 and / or one or more corresponding resistors R16.n of the corresponding line path to the corresponding safety-related load 16.n and / or one or more corresponding resistors R17.m of the corresponding line path to the corresponding non-safety-related load 17.m. The undervoltage detection 30 thus determines at least one trigger 32 and / or undervoltage dU as described below. The calculation of the undervoltage detection 30 can be implemented in the power distributor 18 or in the corresponding load 16.n, 17.m, in particular in the safety-related load 16.n, but also in the non-safety-related load 17.m. The following method steps can be used individually or in combination for the undervoltage detection 30. The magnitude of the voltage U16.n on the corresponding safety-related load 16.n can be determined by different schemes as follows.
[0040] In a first alternative, the voltage U at the busbar 14 is detected. A predetermined voltage Uw representing the worst case is subtracted from the voltage U at the busbar 14 in order to take into account the voltage drop across the respective resistor R16.n of the line path to the respective safety-related load 16.n. The predetermined voltage Uw represents a worst-case empirical value that must be taken into account in the worst case. The voltage U16.n at the respective safety-related load 16.n can thus be estimated as follows:
[0041] U16.n = U - Uw (1)
[0042] In another alternative, the voltage U measured at the busbar 14, the current I16.n measured through the safety-related load 16.n and a determined resistance value R16.n_w representing the worst case are used to estimate the size of the voltage drop U16.n at the respective safety-related load 16.n. The voltage drop at the line path is calculated from the voltage U at the busbar 14, the worst case estimate R16.n_w through the line resistance and the current I16.n through the respective line according to Ohm's law:
[0043] U16.n = U – I16.n * R16.n_w (2)
[0044] In another alternative, the voltage U measured at the busbar 14, the current I16.n measured through the safety-related load 16.n and the corresponding line resistance R16.n_d estimated within the scope of the model are used to estimate the size of the voltage drop U16.n at the safety-related load 16.n. The voltage drop at the line path is calculated from the voltage U at the busbar 14, the diagnostic function with the aid of the line resistance R16.n_d (as described, for example, in DE 10 2018 212 369 A1 and fully disclosed by reference thereto) and the current I16.n flowing through the line:
[0045] U16.n = U – I16.n * R16.n_d (3)
[0046] In a further alternative embodiment, the voltage U16.n present at the safety-related loads 16.n is measured directly in the respective loads 16.n themselves and communicated to the power distributor 18 via a communication interface (eg CAN):
[0047] U16.n = U16.n via communication mechanism (4)
[0048] In another alternative, the magnitude of the voltage U16.n present at the safety-related load 16.n can be evaluated in the respective load 16.n itself. If an imminent undervoltage dU is detected, a trigger 34 and / or the undervoltage dU is sent to the power distributor 18 by a function integrated in the respective load 16. Thus, the undervoltage detection 30 is carried out in the load 16.n instead of in the power distributor 18:
[0049] U16.n = U16.n in load 16 (5)
[0050] Different types for determining the magnitude of voltage U16.n present at safety-related load 16.n can be used either alternatively (single) or also for using at least two, and possibly multiple alternative determinations for mutual plausibility testing. In the case of implausible results, corresponding warning indications or countermeasures can be taken.
[0051] The duration T1, T2, T3 of the calculated or measured voltage U16.n that is present is decisive in order to detect an impending undervoltage dU and to generate a trigger signal 32 that initiates a shutdown 40 or a degradation of a non-safety-related load 17. Figure 4 , which is depicted by the dynamic voltage limit Ug. Thus, the voltage limit Ug increases with increasing duration T below the voltage limit Ug. Figure 4In the exemplary embodiment, the voltage limit Ug is increased in a stepped manner with increasing duration T. In principle, however, other relationships between the limit value Ug and the maximum permissible time interval T for the corresponding limit value Ug can also be realized, such as in the form of a continuous or continuously increasing function. The duration T or T1, T2, T3 indicates the maximum duration during which the voltage U16.n of the safety-related load 16.n must not fall below the associated limit value Ug or Ug1, Ug2, Ug3, otherwise insufficient power supply or failure of the safety-related load 16.n will occur. Starting from the duration T1, the limit value Ug has a first value Ug1, which remains unchanged until a further duration T2. The duration T1 is, for example, in the range of about 0.5 milliseconds, and the further duration T2 is, for example, in the range of 10 milliseconds. The first limit value Ug1 has the lowest value, which, in relation to the supply voltage (12 V in the exemplary embodiment), for example, takes a value of about 50% of the supply voltage. Absolutely, the first limit value Ug1 is, for example, in the range of 6 V and 7 V, in the exemplary embodiment at 6.4 V. Starting from the duration T2 (e.g. 10 milliseconds), the limit value Ug increases to the value Ug2 of 70% of the supply voltage, as in absolute terms, e.g. Figure 3 8.6 V or, for example, in the range between 8 V and 9 V. Starting from duration T2, the second limit value Ug2 remains unchanged for the duration up to T3. Starting from duration T3 (for example, in 100 milliseconds), the limit value Ug increases to a value of Ug3 of 80% of the supply voltage, as in absolute terms, for example, Figure 3 The range shown is 9.6 V or, for example, between 9 V and 10 V. Starting from the time period T3 , the third limit value Ug3 remains unchanged again.
[0052] If the voltage U16.n determined for the duration T1 is about to fall below the first limit value Ug1, the trigger 32 is generated. If the voltage U16.n determined for the duration T2 is about to fall below the second limit value Ug2, the trigger 32 is generated. If the voltage U16.n determined for the duration T3 is about to fall below the third limit value Ug3, the trigger 32 is generated. If the determined voltage U16.n falls below one of the limit values Ug, the timer is started at this time. As soon as the duration T assigned to the limit value Ug that is fallen below is reached, the trigger 32 is generated. With respect to the limit value Ug that is fallen below, the undervoltage dU is determined as described below.
[0053] By means of, for example, Figure 3The ascertained or measured voltage U16.n at the respective safety-related load 16.n and the dynamic voltage limits Ug; Ug1, Ug2, Ug3, the voltage difference or undervoltage dU is calculated: dU=Ug-U16.n, wherein the limit value Ug is selected which is closest to the ascertained voltage drop U16.n at the safety-related load 16.n. If, for example, the voltage U16.n is at 6V, then the undervoltage dU to the nearest limit value Ug1 (Ug1=6.4V) is 0.4V. If, for example, the voltage U16.n is at 8V, then the undervoltage dU to the nearest limit value Ug2 (Ug2=8.6V) is 0.6V, etc.
[0054] The voltage difference or undervoltage dU serves as an input variable for a block 34 for estimating the current Ir to be switched off.
[0055] In the following, a method step or block 34 for estimating the degree of reduction, such as, for example, the current Ir to be switched off or reduced, is described further. In order to stabilize the voltage U (increase dU) and to comply with the voltage and time limits of the safety-related loads 16.n, it is necessary to switch off one or more non-safety-related loads 17.m. Based on the degree of reduction (e.g., the current 36 to be switched off) Ir, it is decided how many of the non-safety-related loads 17.m must be switched off. How high the current Ir to be reduced in order to increase the supply voltage U by dU must be can be derived by one of the sub-methods described below.
[0056] Thus, for example, a fixed value of the reduction degree or the current Ir to be switched off can be realized as a possible alternative. When the trigger 32 is triggered, the current Ir determined here must be switched off:
[0057] Ir = unchanged (1)
[0058] In another alternative, the reduction degree Ir is calculated by means of the undervoltage dU determined by the undervoltage detection 30, the total resistance Rb of the total path from the energy storage device 12 to the input of the power distributor 18, and the resistance Ri for the internal resistance of the energy storage device 12, in particular the battery, to the ground or ground. The resistances Rb, Ri can be based on resistances known at the beginning of life or corresponding estimates. If the energy storage device 12 is not available as a source or the energy storage device 12 is charged, the current in the direction of the DC voltage converter 22 must be reduced. The current Ir reduced thereby is determined as follows:
[0059] Ir = dU / (Rb+Ri) or Ir = dU / Rdc (2)
[0060] In a further alternative method, the degree of reduction, for example the current Ir to be switched off, is calculated using the undervoltage dU ascertained by the undervoltage detection 30 , the resistance Rdc_d of the line group of the supply line of the DC voltage converter 22 determined by the diagnosis and / or the resistance Rb_d of the line group of the supply line to the energy store 12 determined by the diagnosis and / or the internal resistance Ri_d of the energy store 12 determined by the diagnosis:
[0061] Ir = dU / ( Rb_d+Ri_d) or Ir = dU / Rdc_d (3)
[0062] In a further alternative, the degree of reduction Ir can also be predetermined by the energy management in order to stabilize the voltage accordingly:
[0063] Ir = Ir by energy management through the communication system (4)
[0064] Another block 38 is used to select a non-safety-related load 17.m for disconnection. For this method step 38, the trigger 32, the current Ir to be disconnected from the block 34 and / or the corresponding current I17.m flowing through the corresponding non-safety-related load 17.m are supplied. That is, if the trigger 32 (from the block 30) and the current Ir to be disconnected (from the block 34) are known, then one of the method steps described below is applied to purposefully disconnect the determined non-safety-related load 17.m. The disconnection is achieved by the corresponding disconnection signal 40.1, 40.2, ..., 40.m, by which the corresponding switching mechanism 19m involved can be driven. The load 17.m can be disconnected directly or in multiple stages. In the case of hierarchical disconnection, a defined system response is waited for after the load (group) is separated and a new or another disconnection of the non-safety-related load 17.m is carried out if necessary or not in accordance with the voltage requirement. The system response can be an increase in the voltage U on the bus or a signal of a superordinate system.
[0065] In one variant, all non-safety-relevant loads 17 . m can be switched off. If a corresponding trigger signal 36 is generated and transmitted by the undervoltage detection 30 , all non-safety-relevant loads 17 . m are switched off. The current Ir to be reduced is not necessary as an input variable.
[0066] In another alternative, the maximum current criterion occurs, which flows in the corresponding non-safety-related load 17.m. Thus, firstly, such non-safety-related loads 17.max with the maximum through-current I17.max are switched off. This is done until the current Ir to be reduced is reached.
[0067] In another alternative variant, the current I17.m flowing through the non-safety-related load 17.m can be multiplied by a constant or dynamic weighting factor and turned off according to the weighted fraction until at least the current Ir to be reduced is reached. The weighted fraction can also be implemented independently of the current I17.m. The optimal load 17.m can be turned off with the help of weighting in order to find the optimum point between the current Ir to be turned off and the loss of the function of the corresponding non-safety-related load 17.m. For this purpose, a weighted method can be applied, which is based on a static or dynamic value or the current or state of the onboard power supply component. Here, for example, the non-safety-related load 17.m to be turned off or to be degraded can be selected with the help of an optimization method (e.g., optimization problem: binary linear programming). Here, a weight is assigned to each load path, which weights the effect of the current I17.m in the corresponding load path on the system. On the one hand, the following condition must be met, that is, the sum of the currents (I17.m) of the turned-off loads 17.m at least reaches the reduction degree Ir. As an optimization target for optimized load shutdown, for example, the minimum value of the sum of the priority values of non-safety-related loads 17.m can be used while forcibly following the above-mentioned reduction conditions (the higher the priority of the non-safety-related load 17.m, the higher the corresponding priority value).
[0068] In another alternative variant, the superordinate vehicle system generally provides a group of consumers 17.m that can be switched off. These consumers are then switched off when the function is executed. Alternatively, corresponding groups of consumers 17.m can also be switched off.
[0069] The non-safety-related loads 17.m that were switched off must be switched back on according to certain criteria. Different criteria can be applied here.
[0070] Thus, in a variant, a reconnection attempt can be implemented after a certain time. If, for example, a reconnection attempt is unsuccessful after x seconds, ie a new shutdown is implemented, then, for example, k attempts to reconnect can be made. Alternatively, an error message can be omitted. The reconnection attempt can be set.
[0071] As a further alternative criterion, it is determined whether the voltage U is stable for a defined time. If the voltage U is greater than a threshold value Ug of, for example, 11 V for x seconds, then the switched-off non-safety-related load 17 . m can then be switched on.
[0072] As a further alternative criterion, the reconnection can be effected based on communication with the energy management. The energy management of the entire vehicle or a similar vehicle system initiates the reconnection of the non-safety-related loads 17.m by means of a communication system, for example a CAN bus. The connection is effected individually or interactively and / or in groups.
[0073] As part of a further alternative criterion, a switched-off load 17.m can be switched back on based on the backup power supply. The function continuously calculates the minimum backup power supply necessary to connect the non-safety-related load 17.m to the power supply again. Whether the non-safety-related load 17.m is switched back on is either decided based on a presetting by the vehicle system, such as, for example, within the scope of energy management and / or based on a current value I17.m_v previously presetting for each load 17.m and / or based on historical load power consumption and / or a value dynamically calculated using a similar method.
[0074] The function is not limited to the voltage level U determined in the onboard power supply system in the embodiment, such as 12V, for example. The method has an interface to the energy management, not specifically shown, in order to transmit at least one feedback information about the non-safety-related load 17.m that has been switched off. In addition, communication or reservation of a higher-level vehicle system (e.g., energy management, as described in the corresponding sub-method) is also conceivable. Due to the required implementation speed (between 1 millisecond and 500 milliseconds), the energy management cannot implement the function itself. Therefore, the predetermined parameters must be provided in the power distributor 18 before the function is implemented, or only in the case of reconnection after undervoltage occurs.
Claims
1. A method for monitoring an onboard power system of a motor vehicle, wherein at least one power distributor (18) is provided, via which at least one safety-related load (16) is supplied with a supply voltage (U) and via which non-safety-related loads (17) are supplied with power, wherein the power distributor (18) is supplied with power from at least one energy storage device (12), wherein the magnitude of a voltage (U16.n) present at least at the safety-related load (16.n) is determined, wherein an undervoltage (dU) at the safety-related load (16.n) is determined as a function of a limit value (Ug), characterized in that A degree of reduction (Ir) for switching off or downgrading required for increasing the voltage (U16.n) present at the safety-related load (16.n) is determined based on the undervoltage (dU), and a selection of the non-safety-related load (17.m) to be switched off or downgraded is carried out based on the degree of reduction.
2. The method according to claim 1, characterized in that If a voltage drop (U16.n) occurring at the safety-related load (16.n) reaches or is about to reach a limit value (Ug) for a certain duration (T1, T2, T3), preferably in a range between 1 millisecond and 500 milliseconds, a switch-off time or a trigger (32) is generated for switching off or downgrading at least one of the non-safety-related loads (17.m).
3. The method according to any one of the preceding claims, characterized in that The magnitude of a voltage drop (U16.n) occurring at the safety-related load (16.n) is determined from a supply voltage (U) at the power distributor (18) and a voltage drop at a line path between the power distributor (18) and the safety-related load (16.n).
4. The method according to any one of the preceding claims, characterized in that A voltage drop across a line path between a power distributor (18) and a safety-related load (16.n) is determined using the resistance (R16.n_w, R16.n_d) of the corresponding line path and a current (I16.n) flowing through the safety-related load (16.n).
5. The method according to any one of the preceding claims, characterized in that The reduction (Ir) is determined based on a resistance (Rb) of a line path connecting the energy store (12) to the power distributor (18) and / or based on an internal resistance (Ri) of the energy store (12).
6. The method according to any one of the preceding claims, characterized in that The number of non-safety-related loads (17.m) to be switched off is ascertained as a function of the degree of reduction (Ir).
7. The method according to any one of the preceding claims, characterized in that The reduction (Ir) is ascertained in such a way that the supply voltage (U) and / or the voltage (U16.n) present at the safety-related load (16.n) is increased by at least an undervoltage (dU).
8. The method according to any one of the preceding claims, characterized in that The limit value (Ug) varies depending on the duration (Ti) for which the magnitude of the voltage (U16.n) drops below the corresponding limit value (Ug) at the safety-related load (16.n), in particular increases with increasing duration (Ti).
9. The method according to any one of the preceding claims, characterized in that The degree of reduction (Ir), in particular the current to be reduced, is determined using the resistance (Rdc, Rb) of the line path to the energy accumulator (12) and / or to the alternative energy source (22) and / or the internal resistance (Ri) of the energy accumulator (12) and / or based on a previously determined degree of reduction (Ir) and / or based on the resistance (Rdc, Rb) of the line path to the energy accumulator (12) and / or to the alternative energy source (22) determined by a model or diagnosis and / or based on the internal resistance (Ri_d) of the energy accumulator (12) determined by a model or diagnosis, and / or the degree of reduction (Ir) is preferably transmitted by another control device, in particular an energy management.
10. The method according to any one of the preceding claims, characterized in that It is determined when the magnitude of the voltage (U16.n) for causing a drop in the voltage across a safety-related load (16.n) reaches the limit value (Ug), and from the time the limit value (Ug) is reached a time duration (T) is detected during which the limit value (Ug) is undershot, wherein the detected time duration (T) is compared with a time duration (Ti) assigned to the limit value (Ug), and when the assigned time duration (Ti) is reached a trigger (32) is generated for initiating a shutdown or degradation of at least one non-safety-related load (17.m).
11. The method according to any one of the preceding claims, characterized in that The magnitude of the voltage (U16.n) present at least at the safety-related load (16.n) is determined by measuring the voltage at the safety-related load (16.n) and / or using the current (I16.n) flowing through the safety-related load (16.n) and / or by measuring the supply voltage (U) and / or taking into account the resistance (R16.n) of the line path between the power distributor (18) and the safety-related load (16.n), in particular the worst-case value (R16.n_w) of the resistance or the resistance (R16.n_d) estimated by a model and / or based on the worst-case value (Uw) of the voltage drop across the resistance (R16.n) of the line path between the power distributor (18) and the safety-related load (16.n).
12. The method according to any one of the preceding claims, characterized in that The trigger (32) and / or the undervoltage (dU) are determined via a safety-related load (16.n), and / or the safety-related load (16.n) transmits the trigger (32) and / or the undervoltage (dU) and / or the voltage drop (U16.n) measured across the safety-related load (16.n), in particular to the power distributor (18), and / or the trigger (32) is determined in different control devices.
13. The method according to any one of the preceding claims, characterized in that The selection of the non-safety-related loads (17.n) to be switched off or downgraded is carried out based on the current (I17.m) flowing through the corresponding non-safety-related loads (17.m), in particular switching off or downgrading such non-safety-related loads (17.m) having a maximum through-current or having a through-current exceeding a certain limit value.
14. The method according to any one of the preceding claims, characterized in that The other non-safety-related load (17.m) is switched off until the reduction level (Ir) is reached.
15. The method according to any one of the preceding claims, characterized in that The current (I17.m) flowing through the corresponding non-safety-related load (17.m) is combined with a weighting factor specific to the corresponding non-safety-related load (17.m), and the corresponding combined value is used to select the non-safety-related load (17.m) to be switched off or downgraded.
16. The method according to any one of the preceding claims, characterized in that The non-safety-related loads (17.m) are each provided with a weighting or priority value, and the selection of the corresponding load (17.m) to be switched off or downgraded is carried out by means of optimization of the combined weighting or priority values.