Method for diagnosing a switch device in a motor vehicle

Abstract

The invention relates to a method for diagnosing a switch device in a motor vehicle, wherein a switch element (19) is provided, the switch element comprising a plurality (N) of parallel lines (43), each of the parallel lines having at least one line switch (45) arranged in the parallel line (43), wherein the switch element (19) connects at least one onboard power subsystem (22) to a safety-related onboard power subsystem (30), the at least one onboard power subsystem (22) having non-safety-related electrical consumers (24) without an energy source, the safety-related onboard power subsystem (30) having safety-related electrical consumers (36) in particular for autonomous driving operation and having at least one energy source (12, 32), wherein at least one measuring device (41) is provided, which performs a differential voltage measurement of the switch element (19) for diagnosing the switch element (19).

Description

Technical Field

[0001] The invention relates to a method for diagnosing a switching device in a motor vehicle according to the generic category of the invention. Background Art

[0002] The task of the vehicle electrical system is to supply energy to the electrical loads. If the energy supply in modern vehicles fails due to errors or aging in the electrical system or in the electrical system components, important functions (such as power steering) will fail. This is because the vehicle's steering ability is not affected, but only becomes heavier. Therefore, in modern mass-produced vehicles, a failure of the onboard power system is usually acceptable because the driver has a fallback option available. In order to increase availability, a dual-channel onboard power system structure has been proposed, for example, in WO 2015 / 135729 A1. This dual-channel onboard power system structure is required to allow the system to be fault-tolerant for highly automated or fully automated driving operations.

[0003] In particular in vehicle applications, the term "onboard power supply" is to be understood as the sum of all electrical components in a motor vehicle. The onboard power supply therefore includes both electrical loads and power supply sources, such as generators, DC voltage converters or electrical storage devices (eg batteries).

[0004] It should be noted that the requirements for the reliability and fault tolerance of the electrical energy supply in motor vehicles are continuously increasing due to the increasing electrification of aggregates and the introduction of new driving functions. In addition, it should be taken into account that in the future, unfamiliar driving activities should be allowed to a limited extent in the case of highly automated driving. In this case, there are only limited sensory, control, mechanical and energetic backup options by the driver. Therefore, in the case of highly automated driving, fully automated driving or autonomous driving, the power supply has a safety relevance that has not been recognized in motor vehicles so far. Therefore, it is necessary to reliably and as completely as possible identify and isolate errors in the on-board electrical network.

[0005] "Automated driving" or "highly automated driving" is to be understood as an intermediate step between assisted driving, in which the driver is supported by assistance systems, and autonomous driving, in which the vehicle drives autonomously and without the influence of the driver. In the case of highly automated driving, the vehicle has its own intelligence, which plans ahead and is able to take over the driving task at least in most driving situations. Therefore, in the case of highly automated driving, the power supply is highly safety-related.

[0006] Therefore, a switching element is required for coupling / disconnecting electrical onboard subsystems: the switching element is able to autonomously identify faulty electrical loads or groups of electrical loads or subsystems and to disconnect the faulty electrical loads or groups of electrical loads or subsystems from the remaining (partial) onboard system in a reaction-free and reliable manner in order to meet the requirements for fault tolerance in the power supply of safety-related electrical loads, which are imposed in the case of automated driving in private vehicles, commercial vehicles or trucks.

[0007] A high degree of reliability of the disconnection function is required in all cases where the switching element couples two or more onboard power subsystems and a fault in one of the onboard power subsystems in the coupled state can lead to a simultaneous damage of other, particularly safety-relevant onboard power subsystems coupled to it.

[0008] The present invention is based on the following object: to further simplify the entire system under high demands. This object is achieved by the technical solution of the present invention. Summary of the invention

[0009] Particularly advantageously, the diagnostic method according to the invention is characterized in that, compared to conventional diagnostic concepts, in which each of the parallel circuits of the switching elements is provided with a separate current detection, only a specially weighted differential voltage detection is required at the switching elements, and the circuit complexity of the current detection required for diagnosing the switching elements can therefore be reduced by a factor equal to the number of parallel circuits. The temperature detection device required in any case for temperature monitoring of the switching elements can be used particularly advantageously to improve the diagnostic quality of the disconnection function of the switching element and additionally to diagnose the thermal connection of the switching element to the heat sink.

[0010] In an expedient embodiment, at least one parallel line remains permanently connected during the diagnosis of the switching device. Thus, despite the diagnosis being carried out, the corresponding safety-related coupling of the onboard electrical system components is maintained.

[0011] In a suitable embodiment, in particular when the overcurrent detection device is deactivated, the number of closed circuit breakers is changed and the output signal of the measuring device is evaluated with respect to the corresponding change. It is thus possible to check whether the resulting resistance of a properly functioning switching element changes in the expected manner, which can be detected particularly easily simply by determining the differential voltage across the switching element.

[0012] In one expedient embodiment, the gain of the measuring device is changed, in particular reduced by a factor (NM) / N, where N is the total number of parallel lines and M is the number of parallel lines or line switches that are blocking the connection, wherein in the case of such a change in the gain of the measuring device, the output signal of the measuring device is checked as to whether it also changes. In the case of a properly functioning current detection device or measuring device, a reduction in the output signal proportional to the reduced gain indicates proper operation, which can be determined particularly easily by the proposed measuring device.

[0013] In a suitable embodiment, after all line switches have been initially connected conductively, at least one line switch, and optionally also other line switches, is actuated to blocking. Particularly preferably, the number of line switches actuated to blocking is selected as a function of a switch-off threshold of the overcurrent detection device, in particular when the overcurrent detection device is deactivated. Thus, on the one hand, the load capacity of the actuated parallel line should not be exceeded, and on the other hand, the functional effectiveness of the line actuation device or the overcurrent detection device can be checked.

[0014] In a further development suitable for the purpose, the overcurrent detection device is activated again in a further step and the temperature detected by the temperature detection device and / or the output signal of the measuring device is evaluated. In this case, a properly functioning overcurrent detection device can be checked. In addition, a properly functioning thermal connection of a cooling body of a switching element, for example, can be checked with respect to the temperature behavior.

[0015] Further expedient developments emerge from further preferred embodiments and the description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings show:

[0017] Figure 1 Shows the vehicle network topology;

[0018] Figure 2 A more precise structure of the switching element with the measuring device is shown;

[0019] Figure 3 A switching element with an additional temperature detection device is shown;

[0020] Figure 4 A block diagram of a switching element having an overcurrent detection device and a line control device is shown;

[0021] Figure 5 A flow chart for testing a switching element is shown. DETAILED DESCRIPTION

[0022] The present invention is schematically described based on embodiments in the drawings and will be described in detail below with reference to the drawings.

[0023] In this exemplary embodiment, batteries or accumulators are described as possible energy stores, for example. Alternatively, however, other energy stores suitable for the task can also be used, for example inductive or capacitive energy stores, fuel cells, capacitors, etc.

[0024] according to Figure 1 The on-board power supply topology includes a partial on-board power supply 22, in which energy is supplied to a safety-independent electrical load 24. However, the partial on-board power supply 22 itself does not include an energy source. For energy supply, the partial on-board power supply 22 is connected to a safety-related partial on-board power supply 30 via a switching element 19. The positive path of the safety-independent partial on-board power supply 22 and the positive path of the safety-related partial on-board power supply 30 are connected or separated as necessary by the switching element 19. In the safety-related partial on-board power supply 30, a plurality of safety-related electrical loads 36 are provided grounded separately according to the application. In addition, the safety-related partial on-board power supply 30 includes at least one energy storage device 32 or at least one energy source. In this embodiment, an electric motor 12 is also provided as an energy source. In addition, at least one separation element 26 or a coupling element (preferably a DC voltage converter) is provided to couple another, especially safety-related, partial on-board power supply 30.

[0025] The device relates to an electronic switching element 19 which is disconnected redundantly, in particular unidirectionally, by means of a parallel circuit of a plurality of semiconductor switches or line switches 45, for supplying a partial onboard power system 22 having non-safety-related electrical loads 24 without an energy source from a safety-related partial onboard power system 30 in a motor vehicle, and a method for continuously diagnosing the disconnection function of the switching element, in order to protect the safety-related partial onboard power system 30 from safety-threatening undervoltages and from faults of safety-related electrical loads 36 which are associated therewith and which are caused by overloads or errors in the non-safety-related partial onboard power system 22 supplied by the switching element 19.

[0026] The safety-related onboard power subsystem 30 is used in particular to supply power to functions or safety-related electrical consumers 36 (in particular steering, braking, surroundings sensing, trajectory planning, etc.) required for autonomous driving operation. In this case, a plurality of onboard power subsystems 30 can be provided, which can be separated from each other by a separation element 26 in the event of an error. This can be achieved, for example, by a DC voltage converter 26 as shown by way of example. These onboard power subsystems 30 supply power to components or electrical consumers 36 designed redundantly in terms of functional technology, which can redundantly implement the functions mentioned by way of example. In the event of a failure of a onboard power subsystem 30, a safe parking of the vehicle (driving to the next parking lot, immediately parking on the shoulder of the road, etc.) can be implemented, for example, by means of components or electrical consumers 36 of other onboard power subsystems 30 that are still operating without error.

[0027] according to Figure 2 An exemplary structure of a switching element 19 is shown. The switching element 19 includes a plurality (number N) of parallel lines 43, each of which has a line switch 45 arranged in one parallel line 43. The line switch 45 is, for example, a power semiconductor switch, such as a MOSFET. In addition, a measuring device 41 is provided. The measuring device 41 is used to detect a current I flowing through the switching element 19. For this purpose, the measuring device 41 is configured, for example, as a voltage detection device, in particular for detecting a differential voltage U at the input and output of the switching element 19.

[0028] Instead of a separate current detection for each parallel line 43, a particularly weighted differential voltage detection is advantageously provided at the switching element 19 by the measuring device 41, which is equivalent to the following: Figure 2 Detection of the current at the switching element 19 as described in . This therefore leads to a reduction in the circuit complexity for the current detection required for diagnosing the switching element 19 .

[0029] according to Figure 3 Examples and Figure 2 The embodiment of the embodiment differs only in that a temperature detection device 49 is additionally provided. The temperature detection device 49 serves to detect the temperature of the switching element 19. The temperature detection device required in any case for temperature monitoring of the switching element 19 can be used particularly advantageously to improve the diagnostic quality of the disconnecting function of the switching element 19 and additionally for diagnosing the thermal connection of the switching element to the cooling body.

[0030] In addition, according to Figure 4 A line control device 53 is provided, by which the corresponding desired parallel line 43 can be connected individually or the associated line switch 46 can be controlled. In addition, an overcurrent detection device 47 is provided, which compares the detected current value with the shutdown threshold value I标称 +ΔI 标称 A comparison is made and, if exceeded, a safe shutdown of the switching element 19 is executed. When a shutdown threshold of the overcurrent detection device 47 is reached, an overcurrent message is provided, for example, the reaching of the shutdown threshold is stored by a trigger for further evaluation in the diagnosis of the switching device 19.

[0031] Based on Figure 5 A flowchart is used to describe additional processes of the diagnostic method.

[0032] Based on the assumptions and initial situation in step 101:

[0033] All N parallel series 43 of switching elements are switched “on”.

[0034] The over-current shutdown threshold is set to I 关断 =I 标称 +ΔI 标称

[0035] 1. Step 102

[0036] The overcurrent detection device 47 is temporarily inhibited from taking measures to control the MN parallel lines 43. Despite exceeding the shutdown threshold, the switching element 19 or a specific parallel line 43 is not switched off for a very short time (for example in the microsecond range).

[0037] 2. Step 103

[0038] M of the N parallel connections 43 of the switching elements 19 are controlled as “high-resistance”, whereby the following applies:

[0039] ·

[0040] Load capacity of no more than MN parallel lines

[0041] Expected results of step 2 103:

[0042] The combined resistance of a properly functioning switching element 19 is a factor of Increase.

[0043] The increase in the combined resistance is accompanied by a proportional increase in the instantaneous voltage drop U across the switching element 19 .

[0044] The increase in combined resistance is accompanied by a proportional increase in the instantaneous power loss of the switching element 19 .

[0045] In the subsequent query 104 , the line control device 53 , the line switch 45 and the current detection device (carried out by means of the measuring device 41 by detecting the differential voltage U across the switching element 19 ) are diagnosed.

[0046] In the case of a properly functioning line control device 57 and a controllable line switch 45, a properly functioning current detection device (weighted differential voltage U at the switching element 19) indicates that the output signal increases in proportion to the expected increase in resistance of the switching element 19; if necessary, the output signal leaves the nominal output range and / or enters a saturation state. Otherwise, query 104 indicates a fault situation.

[0047] As a further component of query 104 , a diagnosis of overcurrent detection device 47 and of the shutdown path (via the current shutdown device when a shutdown threshold is exceeded) is performed.

[0048] A properly functioning overcurrent detection device 47 detects that an overcurrent shutdown threshold is reached / exceeded and, if necessary, generates overcurrent information when the shutdown threshold is reached, for example, an overcurrent trigger is set. In the case of a properly functioning shutdown path, the overcurrent detection device 47 takes measures for the control of the M switches or line switches 45. Otherwise, there is an error.

[0049] 3. Step 105

[0050] The gain of the current detection device or measuring device 41 is a factor of reduce.

[0051] In query 106 , a diagnosis of the current detection device or measuring device 41 is performed.

[0052] A properly functioning current detection device or measuring device 41 shows that the output signal decreases in proportion to the reduced gain, and the output signal of the current detection device returns to the nominal output range if necessary. Otherwise, there is an error.

[0053] 4. Step 107

[0054] If the switch-off threshold has previously been reached, the overcurrent trigger is reset if necessary.

[0055] In query 108, a diagnosis of the overcurrent detection device 47 is performed. A properly functioning overcurrent detection device 47 indicates operation within the operating current limits. If the operating current limits are exceeded, then an error is present.

[0056] 5. Step 109

[0057] For all N parallel lines, the overcurrent detection device 47 is activated to take measures. It is now possible to switch off the corresponding parallel line 45 when the switch-off threshold is reached.

[0058] In query 110 , a diagnosis is performed of the temperature sensing device 49 and the thermal connection of the switching element 19 to the heat sink.

[0059] A properly functioning temperature detection device 49 of the switching element 19 indicates a time-dependent and proportional temperature rise of the switching element 19 which is proportional to the resistance increase.

[0060] In the case of a properly functioning thermal connection, the temperature rise reported by a properly functioning temperature detection device within the detection time window is within the expected range. Otherwise, there is an error.

[0061] 6. Step 111

[0062] All N parallel lines 43 are switched to “on” again.

[0063] Expected results of step 6 111

[0064] The combined resistance of a properly functioning switching element 19 is a factor of Reduce.

[0065] The reduction in the combined resistance is accompanied by a proportional reduction in the instantaneous voltage drop U across the switching element 19 .

[0066] The reduction in combined resistance is accompanied by a proportional reduction in the instantaneous power loss of the switching element 19 .

[0067] In query 112 , a diagnosis is performed on the line control device 53 , the line switch 45 and the current detection device (or measuring device 41 ).

[0068] A properly functioning current detection device (or measuring device 41 ) shows a decrease in the output signal U proportional to the decrease in resistance. Otherwise, a fault is inferred.

[0069] 7. Step 113

[0070] The gain of the current measurement detection device is again determined by the factor Increase.

[0071] In query 114 , a diagnosis of the current detection device (or measuring device 41 ) and the overcurrent detection device 47 is performed.

[0072] A properly functioning current detection device (or measuring device 41 ) indicates an increase in the current measurement output signal proportional to the gain increase or an output signal U of the measuring device 41 within the nominal output range. Otherwise, an error is present.

[0073] In addition, a properly functioning overcurrent detection device 47 indicates operation within the operating current limits. If this range is left, an error is present. The method ends in step 115. Step 101 may be continued again as required.

[0074] The method described is particularly suitable for increasing the reliability of the entire system, in particular for autonomous driving, which places particularly stringent safety requirements on this autonomous driving. However, the use is not limited to this.

Claims

1. A method for diagnosing a switching device in a motor vehicle, wherein: A switching element (19) is provided, which comprises a plurality (N) of parallel lines (43), each of which has at least one line switch (45) arranged in one parallel line (43), wherein the switching element (19) connects at least one onboard power subsystem (22) to a safety-related onboard power subsystem (30), the at least one onboard power subsystem (22) having non-safety-related electrical consumers (24) but no energy source, the safety-related onboard power subsystem (30) having safety-related electrical consumers (36) for autonomous driving operation and having at least one energy source (12, 32), characterized in that at least one measuring device (41) is provided, which performs a differential voltage measurement of the switching element (19) for diagnosing the switching element (19), The number (M) of line switches (45) controlled to be blocked is determined according to the following formula: Wherein, N represents the total number of the parallel lines (43), I 标称 represents the nominal current of the overcurrent identification device (47), and ΔI 标称 Indicates that the nominal current is exceeded, and when the nominal current is exceeded, the overcurrent shutdown threshold of the overcurrent identification device (47) is triggered.

2. The method according to claim 1, characterized in that During the diagnosis of the switching device (19), at least one parallel line (43) remains permanently connected.

3. The method according to any one of claims 1 to 2, characterized in that At least one overcurrent detection device (47) is provided for disconnecting at least one parallel line (43) when a disconnection threshold is reached in the at least one parallel line, and / or at least one line control device (53) is provided for activating or deactivating the line switch (45), and / or a temperature detection device (49) is provided for detecting the temperature of the switching element (19).

4. The method according to claim 3, characterized in that When the overcurrent detection device (47) is deactivated or when the overcurrent detection device (47) is activated, the number of closed circuit breakers (45) is changed and the output signal of the measuring device (41) is evaluated with respect to the corresponding change.

5. The method according to any one of claims 1 to 2, characterized in that The gain of the measuring device (41) is changed, wherein when the gain of the measuring device (41) is changed, an output signal of the measuring device (41) is checked to see whether the output signal also changes.

6. The method according to claim 3, characterized in that: A possible shutdown of the corresponding line switch (45) by the overcurrent detection device (47) is temporarily inhibited.

7. The method according to any one of claims 1 to 2, characterized in that At least one parallel line (43) is controlled to be blocked.

8. The method according to any one of claims 1 to 2, characterized in that The number (M) of line switches (45) actuated to block when the overcurrent detection device (47) is deactivated is related to the switch-off threshold I of the overcurrent detection device (47). 标称 +ΔI 标称 Related.

9. The method according to claim 3, characterized in that: In a further step, the overcurrent detection device (47) is activated again and the temperature detected by the temperature detection device (49) is evaluated.

10. The method according to any one of claims 1 to 2, characterized in that In a further step, all (N) parallel lines (43) are controlled to be conductive.

11. The method according to any one of claims 1 to 2, characterized in that A greater number of circuit breakers (45) are connected and a check is performed to determine whether the measured variable of the measuring device (41) decreases accordingly by a factor (NM) / N when the number of closed circuit breakers increases, wherein N represents the total number of parallel circuits (43) and M represents the number of circuit breakers (45) which are actuated to block.

12. The method according to claim 3, characterized in that The overcurrent detection device (47) is activated for all parallel lines (43).

13. The method according to any one of claims 1 to 2, characterized in that The gain of the measuring device (41) is increased again by a factor of N / (NM), wherein N represents the total number of parallel lines (43) and M represents the number of line switches (45) which are actuated to block.

14. The method according to claim 3, characterized in that First, all parallel lines (43) are controlled to be conductive, then the overcurrent identification device (47) is temporarily prohibited from taking measures, at least one parallel line (43) is connected in a non-conductive manner and the measurement parameter of the measuring device (41) is detected, and / or the overcurrent identification device (47) is again allowed to take measures, all parallel lines (43) are controlled to be conductive, and the measurement parameter of the measuring device (41) is detected, and / or the gain of the measuring device (41) is increased and the measurement parameter of the measuring device (41) is detected.

15. The method according to claim 5, characterized in that The gain of the measuring device (41) is reduced by a factor of (NM) / N, wherein N represents the total number of parallel lines (43) and M represents the number of line switches (45) which are actuated to block.

16. The method according to claim 7, characterized in that A plurality of (M) parallel lines (43) are controlled to be blocked.

17. The method according to claim 11, characterized in that All circuit breakers (45) are connected and a check is performed to determine whether the measured variable of the measuring device (41) decreases by a factor (NM) / N when the number of closed circuit breakers increases, wherein N represents the total number of parallel circuits (43) and M represents the number of circuit breakers (45) that are actuated to block.

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