METHOD FOR MONITORING ENERGY SUPPLY IN AN AUTOMOBILE

Abstract

Determine ways to make energy supplies more reliable. [Solution] A method for monitoring the energy supply of a motor vehicle, characterized in that at least one supply path (59) is provided for supplying electrical energy, in particular to a safety-relevant load (16, 25), the supply path (59) including at least two current-carrying components (60, 62) connected in parallel and protecting the load (16, 25), in particular switching means (60) and / or fuses (62), the value of at least one electrical characteristic quantity (R), in particular an electrical resistance (R), representative of the function of the supply path (59), is determined, at least one electrical measured quantity (U, I) applied to at least one of the components (60, 62) is detected, the electrical characteristic quantity (R) is determined as a function of the measured quantities (U, I), an inspection of at least the electrical characteristic quantity (R) is performed, and the current-carrying components (60, 62) and the supply path (59) are at least partially arranged in a control device (78).

Description

[Technical field]

[0001] The present invention relates to a method for monitoring the energy supply of a motor vehicle according to the preamble of the independent claim. [Background technology]

[0002] A method for monitoring the energy supply of a motor vehicle is known from DE 10 2018 212 369 A1, in which in a partial on-board power supply network at least one energy accumulator supplies energy to preferably a plurality of safety-relevant loads, at least one measured quantity of the energy accumulator and / or of the at least one load is detected, at least one wire harness model representing the partial on-board power supply network is provided, and a parameter estimator is provided which estimates at least one characteristic quantity of the wire harness model using the measured quantity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 102018212369 Summary of the Invention [Problem to be solved by the invention]

[0004] The invention is based on the problem of defining a way to further increase the reliability of the energy supply. This problem is solved by the features of the independent claims. [Means for solving the problem]

[0005] The reliability of the energy supply can be further increased by monitoring the power supply paths in the control device, in particular for safety-relevant loads. In particular, by monitoring the electrical resistance of the current-carrying paths and components and preferably their terminals, the diagnostic scope can be extended to the entire energy supply path, in particular for safety-relevant loads. By means of suitable measuring methods, such as differential voltage measuring amplifiers, and corresponding calculation methods with characteristic quantity estimation methods, it is possible to continuously and precisely determine characteristic quantities inside the control device, such as resistances, over time.

[0006] By using a parameter estimator to determine the electrical characteristic quantity or electrical resistance value, it is possible to eliminate a large portion of the measurement errors, which may appear as both random and systematic error quantities during the measurement.

[0007] It is particularly preferred to use static threshold values ​​for determining the error information, for example nominal values ​​(e.g. resistance values) specified by the manufacturer of the current-carrying component. If an estimated characteristic value of a component significantly deviates from its nominal value, it can be used as error information, for example by entering it in an error memory or by forwarding the error information to a higher-level energy management system for further processing, for example as a warning to the driver or reduced driving comfort. This further increases the safety of the vehicle.

[0008] It is particularly advantageous that the above-described monitoring principle can be extended to various circuit configurations, in particular in parallel circuits of various current-carrying components, by selecting suitable measuring points for the current and voltage before the branch and / or at the beginning or end of the current path, for example at the contacts, so that in addition to the resistances of the current-carrying components, also the resistances of the supply lines and / or contacts can be taken into account and used for fault localization.

[0009] In an advantageous refinement, the threshold value is flexibly selected depending on the resistance model, so that a shift in the operating point, for example due to changing temperature conditions, cannot lead to an error trigger, which further increases the safety of the device.

[0010] In an advantageous refinement, the current state of the measured values ​​is checked and, if necessary, new specifications are made, so that reliable and up-to-date information on the functionality is obtained. Further advantageous refinements are given in the further dependent claims and in the description. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a power distributor that connects two partial on-board power supply networks. [Diagram 2] FIG. 13 is a diagram showing values ​​to be detected in a parallel circuit of two energization switching means. [Diagram 3] FIG. 13 is a diagram showing values ​​to be detected in a parallel circuit of two energization fuses. [Figure 4] FIG. 13 is a diagram showing values ​​to be detected in a parallel circuit of two energization switching means and two energization fuses. [Diagram 5] FIG. 5 shows a measurement device for determining the total characteristic amount of the device shown in FIG. 4. [Figure 6] FIG. 1 illustrates the structure of an estimation method in the form of a Kalman filter. [Figure 7] FIG. 1 illustrates an apparatus for identifying soft thresholds. [Figure 8] FIG. 6 shows an extension of the measuring device shown in FIG. 5. [Figure 9] 1 is a perspective view showing the current-carrying parts of the device inside the control device and the associated structures of the further device that determine the overall characteristic quantities of the device. [Figure 10] FIG. 13 illustrates further device structures identifying further extended current paths. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The invention is illustrated diagrammatically on the basis of an embodiment and will be explained in more detail below with reference to the drawings. FIG. 1 shows a possible topology of the energy supply system, which consists of an on-board power supply network 13, which includes an energy accumulator 12, in particular a battery 12 with associated sensors 14, preferably battery sensors, and in particular safety-relevant loads, which are protected or controlled by a power distributor 18. The loads 16 are special loads with high demands or need to be protected, generally called safety-relevant loads 16. These are, for example, electric steering and / or braking systems as components that must be powered in order to ensure that the vehicle can steer and / or brake in the event of an error. The characteristic quantities of each load 16 are detected individually and in the event of deviations from the tolerances a respective switch 15 is opened. The on-board power supply network 13 consists of a safety-relevant part on-board power supply network 11 and a non-safety-relevant part on-board power supply network 10. The safety-relevant part on-board power supply network 11 can be disconnected from the non-safety-relevant part on-board power supply network 10 by the power distributor 18, in particular in the event of an error or a critical state in the non-safety-relevant part on-board power supply network 10. The safety-related partial on-board power supply network 11 is, for example, an ASIL-compliant (for example according to DIN ISO 26262) partial on-board power supply network 11, which comprises at least one safety-related load 16 and may possibly be equipped with its own energy store 12 for voltage support. The non-safety-related partial on-board power supply network 10 comprises at least one non-safety-related load 17, which may for example be a so-called QM load. However, it cannot be excluded that at least one further safety-related load is also arranged in the non-safety-related partial on-board power supply network 10, for example if the safety-related loads are configured redundantly. The non-safety-related partial on-board power supply network 10 is a non-ASIL-compliant on-board power supply network.

[0013] An energy accumulator 12 is also connected to a terminal (connection terminal KL30_1) of the power distributor 18. The sensor 14 can detect electrical characteristic quantities, such as the voltage Ub at the energy accumulator 12 and / or the current Ib through the energy accumulator 12 and / or the temperature Tb of the energy accumulator 12. The sensor 14 can use the determined electrical characteristic quantities Ub, Ib, Tb to determine, for example, the state of charge SOC of the energy accumulator 12 or other characteristic quantities of the energy accumulator 12. At a further terminal (KL30_1) of the power distributor 18, to which the energy accumulator 12 is also connected, a further supply branch for at least one further load 25 is optionally also provided. By way of example, the load 25 is protected by a safety fuse 23. Further loads 25 may also be provided, which can also be protected by a safety fuse 23. These loads 25 are loads which need to be powered from the energy accumulator 12 even when the switching means 19 of the power distributor 18 are disconnected or opened, and are preferably safety-critical loads 25 with regard to failures in the supply guarantee. In this way, (optional) safety-related or safety-critical on-board power supply network paths or partial on-board power supply networks 11 are connected to the terminal KL30_1.

[0014] The power distributor 18 can determine corresponding characteristic quantities, such as the voltage Uv and the current Iv of the load 16. Furthermore, the power distributor 18 can determine corresponding characteristic quantities of the energy store 12, such as the voltage Ub and / or the current Ib and / or the temperature Tb. For this, the power distributor 18 includes a corresponding sensor system or receives data from the sensors 14. The power distributor 18 also has corresponding evaluation means 21, such as a microcontroller, for storing or evaluating the detected values. The evaluation means 21 are used in particular for the identification of critical states of the safety-relevant partial on-board power supply network 11, for example for the detection of overcurrents and / or under- or overvoltages for the safety-relevant loads 16, 25 on the partial on-board power supply network 11. For this, the corresponding characteristic quantities are detected and compared with appropriate threshold values. For example, a microcontroller is used as the evaluation means 21. Furthermore, the microcontroller or the evaluation means 21 can also control the corresponding switch 15 or the switching means 34 of the high-current-capable circuit breaker 34 of the main path 30 or the switching means 54 of the additional path 50. The additional path 50 is connected in parallel to the main path 30. The additional path 50 comprises a switching means 54 and a resistor 58, in particular a current-limiting resistor 58, arranged in series therewith. In normal operation, the two paths 30, 50 are active in parallel, i.e. their switching means 34, 54 are closed. Furthermore, the additional path 50 is used to pre-charge the non-safety-related part on-board power supply network 10, for example when an energy accumulator is connected to the safety-related part on-board power supply network 11 for the first time. Due to the capacitive components of the non-safety-related part on-board power supply network 10, a high charging current is ensured via the additional path 50, which must also be protected against overload in this scenario.

[0015] By means of the switching means 34, in particular a corresponding disconnection or connection function of the two on-board power supply network branches (the partial on-board power supply network 10 for the non-safety-relevant loads 17 at the terminal KL30_0 and the further partial on-board power supply network 11 for the safety-relevant loads 16, 25) can be realized. This serves in particular as a safety function to prevent the effects of critical states such as over- or under-voltages and / or overcurrents and / or thermal overloads. In the event of an error, the two partial on-board power supply networks 10, 11 can be disconnected from each other by the power distributor 18 by opening the switching means 34, 54.

[0016] The on-board power supply network 13 has a lower voltage level U1 compared to an optionally provided high-voltage on-board power supply network 20, which may be, for example, a 14V on-board power supply network. A DC voltage converter 22 is arranged between the on-board power supply network 13 and the high-voltage on-board power supply network 20. The high-voltage on-board power supply network 20 includes, by way of example, an energy accumulator 24, for example a high-voltage battery, possibly with an integrated battery management system, and loads 26, for example comfort loads such as an air conditioning system, which are supplied at a high voltage level, and electrical appliances 28. In this context, high voltage is understood to mean a voltage level U2 that is higher than the voltage level U1 of the basic on-board power supply network 13. This may be, for example, a 48V on-board power supply network. Alternatively, it may be an even higher voltage level, particularly in vehicles with an electric drive. Alternatively, the high-voltage on-board power supply network 20 may be omitted entirely.

[0017] By way of example, the embodiments describe batteries or accumulators as possible energy stores 12, 24. However, alternatively, other energy stores suitable for the task may be used, such as inductive or capacitive based, fuel cells, capacitors, etc.

[0018] Particularly preferably, the switching means 34, 54 are each formed by at least two switching elements connected in anti-series (series with each other in opposite directions, e.g. "back to back" or with a common source terminal), preferably using power semiconductors, particularly preferably FETs (field-effect transistors) or MOSFETs (metal-oxide-semiconductor field-effect transistors). Instead of MOSFETs, for example relays, bipolar transistors or IGBTs (insulated gate bipolar transistors) with parallel diodes etc. may also be used.

[0019] The measures described below in conjunction with figures 2 to 10 allow the diagnostic coverage of the complete energy supply path 59 to be expanded, in particular by monitoring the internal connections and energy supply paths 59 inside the control device 78. The basic idea of ​​the internal monitoring of the supply paths 59 and terminals inside the control device is based on monitoring electrical characteristic quantities, in particular the electrical resistance values ​​R of the current-carrying paths and components 60, 62, connections or contacts 74 inside the control device. By using suitable measurement methods, such as a differential voltage amplifier or measurement amplifier 66, and corresponding calculation methods, such as the parameter estimation method realized in the parameter estimator 68, it is possible to continuously and accurately determine the resistance values ​​R inside the control device as electrical characteristic quantities over time.

[0020] In the example shown below, the diagnosis is carried out in two steps: First, the electrical characteristic quantities, such as the electrical resistance R of a component or a current path, are determined using parameter estimation methods on the basis of the measured quantities U,I (as the value of the current I flowing through the component or as the value of the voltage U dropped across the component). The results are then analyzed and, if necessary, subsequent system reactions are initiated.

[0021] With reference to figures 2 and 3, a first application example is the diagnosis of the electrical properties of an energizing element, such as a switching means 60 (figure 2), for example a transistor, particularly preferably a MOSFET, or a fuse 62 (figure 3). A current I flows through the energizing element 60, 62 and a voltage U drops across it. The determination of the resistance R of the energizing element or component 60, 62 presupposes the measurement of a differential voltage U present between the two component terminals or between the components. The supply path 59 is made up of two partial paths connected in parallel, which include corresponding energizing components 60, 62, such as switching means 60 or fuses 62, which are arranged at least partially in the control device 78 and which protect the safety-relevant loads 16, 25. In high safety-relevant applications, partially redundant hardware is used so that if a part of the system fails, the overall operation can still be maintained due to the redundant design. This is illustrated in figures 2 and 3 by the correspondingly parallel-connected switching means 60 (figure 2) or fuses 62 (figure 3). In principle, the method can also be applied to the structures shown in Fig. 2 or 3. In practice, further combinations of two or more switching means 60 connected in parallel and / or two or more fuses 62 connected in parallel arise, so that the exemplary structure shown in Fig. 4 arises. Here, exemplarily at least two switching means 60 and at least two fuses 62 are connected in parallel with one another. The supply path 59, which is arranged at least partially in the control device 78, has in this example four parallel and thus redundant sub-branches. These are supplied with a current I flowing upstream of the parallel branch. A voltage U falls on the current-carrying components and on the components protecting the safety-relevant loads 16, 25, such as the switching means 60 and the fuses 62.

[0022] As shown exemplarily in Fig. 5 for the structure according to Fig. 4, the differential voltage U is measured using a suitable voltmeter, such as a differential amplifier 66. The current I is measured by a corresponding measuring device, such as a measuring resistor 64 or a measuring shunt. The output value of the measuring resistor 64 as the value of the flowing current I and the output value of the differential amplifier 66 as the value of the voltage U are fed to a parameter estimator 68. The parameter estimator 68 is used in particular to determine electrical characteristic quantities, such as the resistance value R of the current-carrying components 60, 62, while excluding a large part of the measurement errors, which may appear during the measurement as both random and systematic error quantities.

[0023] If all MOSFETs 60 and fuses 62 of a parallel component are working without damage, a total current I flows through all four components 60, 62. The total conductance G of this component can be formed as the sum of the electrical conductances of the four components 60, 62. If the conductance of at least one of the components 60, 62 deteriorates or, in the worst case, a connection (such as a solder joint) to the circuit board becomes loose, this is reflected directly in the conductance G or in the resistance R of the entire component or of the entire supply path 59. The total conductance G decreases and the total resistance R increases. As a simple example, assuming that all components 60, 62 have the same resistance at rated operation, if one of the four parallel-connected components 60, 62 is removed, the total resistance increases by about 33% with respect to the original total resistance R.

[0024] If the total resistance R is constantly monitored during operation by means of the measured quantities U, I and a resistance observation device or parameter estimator 68, the removal of one of the four components 60, 62 is immediately recognizable on the basis of the change in the total resistance R. Thus, errors that are considered potential can be detected. In principle, with sufficient current excitation, a degradation of the resistance R can also be detected. Figure 5 shows the configuration of such a device for determining the resistance R.

[0025] If the change in the estimated resistance value R of the structure described in FIG. 4 exceeds a certain limit value Rg, this can be registered as an error and a corresponding reaction can be triggered (e.g., entry into an error memory or forwarding of the error information to a higher-level energy management system for further processing, e.g., a warning to the driver or a reduction in driving operability).

[0026] If no components have been removed but the electrical conductivity G of individual components (switching means 60 and / or fuses 62) has decreased, this decrease will also be reflected in the total resistance R and can therefore also be considered a potential error.

[0027] Here, the equivalent resistance of the parallel structure is

[0028]

number

[0029] The resistance R is the corresponding characteristic of this network model, which is very simple for most applications and is expressed as the parameter vector

[0030]

number

[0031] are integrated as The existing voltage and current measurements are entered as U and I in the above equivalent circuit diagram, and in the following equation, U FET+FUSE (or U as the differential voltage D ) or I FET+FUSE It is described as:

[0032] According to Ohm's law, the following equations are obtained that represent the network model:

[0033]

number

[0034] This equation is expressed in terms of the characteristic quantities of the object, i.e., the parameter vector

[0035]

number

[0036] Therefore, the parameter vector

[0037]

number

[0038] is calculated by using a parameter estimator 68 as the measurement vector z k can be updated at every new time step with reference to the corresponding measurements, which are integrated into In the following, the corresponding values ​​are combined into corresponding vectors or matrices as already explained.

[0039]

number

[0040] To recursively solve the system of equations, in an embodiment a so-called Extended Kalman Filter (EKF) is used as parameter estimator 68. Alternatively, other parameter estimators 68 such as (recursive) least squares methods or other state estimators such as standard / nonlinear Kalman filters, particle filters or similar estimation / optimization methods may be used.

[0041] On-line estimation and correction of systematic measurement errors. Basically, measurement errors, i.e. errors in real measurement processes, consist of systematic (cognitive) errors and random (accidental) errors. The latter originate from random physical processes and cannot be influenced without changing the physical measurement principle. Systematic errors, however, are based on deterministic correlations. If it were possible to estimate these correlations online, i.e. during operation, this source of error could be eliminated.

[0042] To that end, conventional estimation models can be extended to include so-called disturbance models, which represent the influence of unknown states on the measurement result, here systematic measurement errors. To correct the systematic measurement errors, these unknown parameters need to be estimated in addition to the resistance. This is possible if there are enough measurement points (observability).

[0043] A common model for real systematic measurement errors is a linear relationship.

[0044]

number

[0045] Here, m represents the physical quantity to be measured, such as the current I or the voltage U. Therefore,

[0046]

number

[0047] is a measurement that generally has deviation.

[0048]

number

[0049] corresponds to gain and bias (a constant overlap). For a perfect sensor, a = 1, b = 0. If a and b can be estimated (also called calibration), systematic measurement errors can be corrected.

[0050] Typically, there are several sensors and corresponding systematic measurement errors. However, only the cumulative effect of these errors is relevant for estimating the resistance. Therefore, the number of additional parameters to be estimated can be significantly reduced, which usually makes calibration possible. When estimating the equivalent resistance of the parallel structure and the corresponding measurement points, the voltage U D would be as follows:

[0051]

number

[0052] Now, assuming the above model for systematic measurement error, we have:

[0053]

number

[0054] Therefore, to correct the bias error,

[0055]

number

[0056] Instead of bias

[0057]

number

[0058] must be estimated. The same is possible for the gain error, depending on the presence or absence of measurement points. The same procedure applies here. If a suitable excitation is present, it is also possible to combine the two calibration methods.

[0059] Furthermore, an estimate of the systematic measurement error may be used to diagnose the measurement points and to detect their presence if the error is large. This additional information is the basis for a full ASIL qualification, which also takes into account the diagnosability of the measurement points.

[0060] If you want to use an estimation method that also takes into account random measurement error, you can extend the measurement formula to the following:

[0061]

number

[0062] is required.

[0063]

number

[0064] The parameter estimates are

[0065]

number

[0066] and

[0067]

number

[0068] is adjusted by including An estimation method, such as for example a Kalman filter, provides estimates of the resistance R and the cumulative parameters of the measurement equation with minimal variance, i.e. with the highest possible estimation quality.

[0069] The structure of the Kalman filter as an essential component of a parameter estimator 68 is shown in Figure 6. The parameter estimator 68 includes at least one prediction section 67 or time update section. An initial estimate of the state value xk

[0070]

number

[0071] and an initial estimate Pk-1 of the error covariance Pk are sent as inputs to the prediction unit 67. Also, in the steady state, the currently specified output values ​​from the correction unit 69 (or the measurement update unit), i.e., the latest parameter vector xk and the latest error covariance Pk, are sent as inputs to the prediction unit 67.

[0072] The update or time update is performed in the predictor 67. This includes state prediction of the state variables xk in the form

[0073]

number

[0074] Moreover, the prediction unit 67 predicts the error covariance matrix Pk in the form of the following equation.

[0075]

number

[0076] Where:

[0077]

number

[0078] Output Value

[0079]

number

[0080] and

[0081]

number

[0082] is sent as an input to the correction block 69, where the estimates are updated based on the measurements. First, the so-called Kalman gain

[0083]

number

[0084] is calculated as follows:

[0085]

number

[0086] Where:

[0087]

number

[0088] Next, the correction unit 69 updates the estimate based on the measurement according to the following equation:

[0089]

number

[0090] Finally, the correction section updates the error covariance Pk according to the following equation:

[0091]

number

[0092] Here, I corresponds to the unit matrix. Thus, the characteristic quantity

[0093]

number

[0094] The expectation and covariance of are estimated. In the first step of the filtering process, the previous estimates are applied to the state dynamics to obtain a prediction for the latest time point. The predictions are corrected in the correction block 69 using the new information of the latest measurements to obtain the required updated estimates.

[0095] FIG. 7 describes how to determine the threshold value Rn. In the previous examples, a threshold value of the maximum resistance value Rn was used to evaluate the results. This nominal value can be derived, for example, from the specifications of the components 60, 62 or from existing knowledge or experience of function development. The threshold value Rn can be a fixed value, but it can also be designed as a calculation model. The calculation model can adjust the threshold value Rn accordingly depending on the latest operating point. Other external influences, such as temperature T, can be taken into account to determine the latest operating point.

[0096] This is shown exemplarily in FIG. 7. Based on the measured quantities of voltage U and current I, the resistance observation device 86 determines the current resistance value Rm of the parallel-connected switching means 60 and / or fuse 62. As an example, two parallel circuits of the switching means 60 and the fuse 62 are provided as components for protecting current-carrying components and safety-relevant loads 16, 25 in a load distributor 18 with the associated supply path 59 in a control device 78. In parallel, the nominal resistance value Rn or the threshold value Rn is calculated online by means of a resistance model 88. The resistance model 88 is exemplarily realized as a thermal model. The resistance model 88 determines the nominal resistance value Rn based on the measured component temperature T. The results are analyzed in a downstream evaluation unit 90 (hardware error monitor). Depending on the comparison of the output value Rm (estimated resistance value Rm) of the resistance observation device 86 with the output value Rn and the threshold value Rn of the resistance model 88, an error message 92 is generated. An error reaction corresponding to this error information 92 may take place, for example, by inputting it into an error memory or the error information 92 may be forwarded to a higher-level system, such as an energy management system, for further processing, for example in the form of a warning to the driver or a decrease in driving maneuverability. Furthermore, a debounce function is provided for debounce or avoidance of falsely detected errors, which for example reports an error 92 only if the estimated resistance value Rm exceeds a tolerance threshold a number of times n in a row.

[0097] As a simple example, assuming that all components 60, 62 have the same resistance value at rated operation, if one of the four components 60, 62 connected in parallel is omitted, the total resistance value increases by approximately 33% relative to the original total resistance value.

[0098] In a further part of the system, the current state of the determined resistance value Rm is monitored. The availability of the vehicle depends on whether the required test intervals of the control device 78 are respected. If reliable values ​​are not available for a long period of time, no reliable statement can be made about the functionality. This is done by storing the readings of a counter in a non-volatile memory of the computer unit. The counter counts defined test cycles (e.g. driving cycles or on / off cycles of PIN15) and takes defined measures if a limit value is exceeded.

[0099] If the latest resistance value Rm is not available, the following approach is taken. Step 1: Request the vehicle to generate a load pulse. Step 2: If the request fails, generate a driver message.

[0100] The embodiment according to FIG. 8 is an extension of the previous application examples. The control device 78 contains numerous electrical networks which in principle can be considered as combinations of the previous arrangements. The parts of the circuit boards used in the control device 78 can also be considered as part of the current paths. If in the respective current paths a current measurement is possible, for example by means of a measuring resistor 64, then the current paths can be determined by arranging corresponding voltage measuring points, i.e. the components (switching means 60 and / or fuses 62, possibly connected in parallel with the switching means 60 and / or fuses 62) and the copper rails (line resistance R Cu ) can be used to determine the resistance of each current path.

[0101] FIG. 8 shows an example of a simple network consisting of two intersecting current paths. Each branch has components such as switching means 60 and / or fuses 62, which are connected in parallel. The total resistance R in each path R1, R2 is calculated by taking into account all the resistances present in the current branch (current carrying components 60, 62, busbars or circuit board busbars R Cu The total resistance value R FET+FUSE) in the case of a star point having n branches and thus n string resistances Rn. Any number of components 60, 62 can be connected in parallel, analogous to the described application. Each current branch is provided with a current meter with associated measuring resistor 64. The respective current measurements I1, I2 and the voltage drop U are thus fed to a parameter estimator 68, which determines the respective total resistances R1, R2 in the individual current paths. Corresponding voltage measuring points for the differential voltage measurement U via measuring amplifiers 66 are provided as shown between the current carrying elements 60, 62 and the respective measuring resistors 64. This principle can also be used without restriction in the case of more complex networks, for example by adding further current paths and further components, such as switching means 60 and / or fuses 62. In the case of a star point having n branches and thus n string resistances Rn, all string resistances Rn can be monitored with n / 2 differential voltage measuring amplifiers 66.

[0102] As shown in FIG. 9, the entire supply path 59 includes contacts 74 in addition to the current-carrying components 60, 62 and the conductor paths. These serve as an interface with the outside world in the control device 78 and connect the supply path 59 inside the control device to an external cable harness. The contacts 74, e.g. plug contacts, are as a rule connected to a circuit board 76, e.g. by soldering or welding, usually via several points or pins. Due to vibrations and aging of the vehicle, these contacts 74 can also deteriorate or become loose during the running time. This can seriously impair their ability to pass current. Potential errors exist. For this reason, monitoring the electrical contact properties of the contacts 74 is important from a safety point of view.

[0103] The measurement or supply path 59, over which the total resistance R is monitored, can be expanded by appropriately setting up differential voltage measurement points. If the voltage measurement points are not only placed across current carrying components such as the switching means 60 and / or the fuse 62, as shown in FIG. 9 below, but on the pins of the contacts 74 of the control device 78, as shown in FIG. 10, then the components 60, 62, the conductor paths (with associated resistance R Cu) and plug contacts (with included resistance R conn ) can be monitored for the total resistance R of the entire current or supply path 59. To this end, one pin of contacts 74 is used as a sense line or voltage tap, while the other pin continues to carry current.

[0104] The monitored path can be further extended by running sense wires or voltage taps outside the control device 78. The monitored current path can be connected to current carrying components such as switching means 60 and / or fuses 62, conductor tracks (R Cu ), and the plug contact system including the mating connector (R conn ) is composed of the whole.

[0105] The power distributor 18 with the associated monitoring circuit 34 is arranged, for example, directly in the 12V on-board power supply network 13 of a motor vehicle at the interface between a non-safety-related partial on-board power supply network 10 and a safety-related partial on-board power supply network 11, in particular an ASIL-compliant partial on-board power supply network 11. At least a disconnection module is included, which consists of a main path 30 with associated components 60, 62 and a parallel-connected additional path 50 or supply path 59. However, the application is not limited thereto.

Claims

1. 1. A method for monitoring the energy supply of a motor vehicle, comprising: at least one supply path (59) for supplying electrical energy to, in particular, a safety-relevant load (16, 25), said supply path (59) including at least two current-carrying components (60, 62), in particular switching means (60) and / or fuses (62), connected in parallel and protecting said loads (16, 25), characterized in that a value of at least one electrical characteristic quantity (R), in particular an electrical resistance (R), representative of a function of the supply path (59), is determined; at least one electrical measured quantity (U, I) applied to at least one of said components (60, 62) is detected; the electrical characteristic quantity (R) is determined as a function of the measured quantity (U, I); an inspection of at least the electrical characteristic quantity (R) is performed; and the current-carrying components (60, 62) and the supply path (59) are at least partially arranged in a control device (78).

2. 2. The method according to claim 1, characterized in that a value of the voltage drop (U) and a value of the current (I) flowing through the current-carrying component (60, 62) are detected as measured quantities at the current-carrying component (60, 62), and an electrical characteristic quantity (R), in particular a value of the total resistance (R) of the components (60, 62) connected in parallel, is determined from the value of the voltage drop (U) and the value of the current (I) flowing through the current-carrying component (60, 62).

3. 3. The method according to claim 1 or 2, characterized in that the electrical characteristic quantity (R) is compared with a threshold value, in particular a nominal resistance value (Rn), and in case of a significant deviation, an error message (92) is generated.

4. 4. The method according to claim 1, wherein the measurements (U, I) are fed to a parameter estimator (68), and the characteristic quantity (R) is constantly updated by the parameter estimator (68) when new measurements (U, I) are present.

5. Method according to any one of the preceding claims, characterised in that the threshold value (Rn) is variably selected, in particular by means of a resistance model (88), in particular a thermal resistance model.

6. Method according to any one of the preceding claims, characterised in that the temperature of the current-carrying parts (60, 62) is detected and / or used to determine the threshold value (Rn).

7. 7. The method according to claim 1, characterized in that the parameter estimator (68) for recursively solving a system of equations U=I*R, where U represents the voltage drop (U) in at least one of said current-carrying parts (60, 62), I represents the value of the current (I) flowing through at least one of said components (60, 62) and R represents an electrical characteristic quantity (R), is used to identify this characteristic quantity (R).

8. 8. The method according to claim 1, characterized in that the parameter estimator (68) comprises at least one prediction (67) and / or correction (69) of systematic measurement errors, in particular of the measured quantities (U, I).

9. For offset correction of the electrical characteristic quantity (R), [0010] Using the formula, the estimated value of the constant overlap (b) [0025] was identified, U represents the voltage drop (U) in at least one of said current-carrying components (60, 62), I represents the value of the current (I) flowing through at least one of said components (60, 62), a1 represents a gain coefficient, and R represents an electrical characteristic quantity (R), The method according to any one of claims 1 to 8.

10. 10. The method according to claim 1, characterized in that a measuring resistor (64) arranged upstream of the branch into at least two parallel paths is used to detect the value of the current (I) flowing through the current-carrying component (60, 62) and / or a measuring amplifier (66), in particular a differential amplifier, is used to detect the value of the voltage (U) dropped across the current-carrying component (60, 62).

11. Method according to any one of the preceding claims, characterised in that at least one switching means (60), in particular a semiconductor switch such as a MOSFET, and / or a fuse (62) are used as current-carrying components.

12. 12. The method according to claim 1, characterized in that at least one measuring point for detecting the values ​​of the current (I) and / or the voltage (U) of both the current-carrying component (60, 62) and of a supply line, in particular a copper wire of a circuit board (76), is arranged at the beginning and / or at the end of the supply line.

13. The method according to any one of the preceding claims, characterized in that measuring points for voltage and / or current measurement are arranged at at least one contact (74) of the control device (78), preferably at least two contacts (74).

14. 14. The method according to claim 1, characterized in that if the measured values ​​(U, I) are not up-to-date, a load pulse is requested for an up-to-date determination of the measured values ​​(U, I).

15. 15. The method according to claim 1, characterized in that the supply path (59) is arranged between a partial on-board power supply network (11) for at least one safety-relevant load (16, 25) and a further partial on-board power supply network (10) for at least one non-safety-relevant load (17), in particular in a power distributor (18).

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