CN110850329A - Method for diagnosing switchgear in a motor vehicle - Google Patents

Abstract

The invention relates to a method for diagnosing a switching device in a motor vehicle, wherein a switching element ( 19 ) is provided, the switching element comprising a plurality (N) of parallel lines ( 43 ) each having at least a Line switch ( 45 ) in parallel line ( 43 ), wherein switching element ( 19 ) connects at least one partial on-board network ( 22 ) with safety-relevant partial on-board network ( 30 ), at least one partial on-board network ( 22 ) having A safety-independent consumer ( 24 ) without an energy source, the safety-relevant partial vehicle network ( 30 ) having a safety-relevant consumer ( 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 switching element ( 19 ) for diagnosing the switching element ( 19 ).

Description

Method for diagnosing switchgear in a motor vehicle

technical field

The invention relates to a method according to the class of the invention for diagnosing a switching device in a motor vehicle.

Background technique

所以在现代的量产的车辆中车载网络的故障通常是可接受的，因为驾驶员可供用作备用方案(Rückfallebene)。为了提高可用性，例如在WO 2015/135729 A1中已经提出双通道的车载网络结构。需要这种双通道的车载网络结构用以使系统对高度自动化或完全自动化的行驶运行进行容许错误地供电。The task of the vehicle's on-board network is to supply the electrical appliances with energy. If, in modern vehicles, the power supply fails due to errors or aging in the on-board network or components of the on-board network, important functions, such as servo steering, fail. Because the steering ability of the vehicle is not affected, but only becomes heavy

A failure of the on-board network is therefore generally acceptable in modern series-produced vehicles, since the driver is available as a backup. In order to improve usability, a dual-channel in-vehicle network structure has been proposed, for example, in WO 2015/135729 A1. Such a two-channel in-vehicle network structure is required to allow the system to erroneously power highly automated or fully automated driving operations.

The “vehicle network” is to be understood, in particular in vehicle applications, as the totality of all electrical components in a motor vehicle. The on-board network therefore includes not only the consumers but also the power supply sources, such as generators, DC-voltage converters or electrical stores (eg batteries).

It should be noted that due to the increasing electrification of aggregates and the introduction of new driving functions, the requirements for the reliability and fault tolerance of the electrical energy supply in motor vehicles continue to rise. Furthermore, it should be taken into account that in the future, in the case of highly automated driving, driving of unfamiliar activities should be permitted to a limited extent. In this case, sensory, control-technical, mechanical and energy alternatives by the driver are only limited. Thus, in the case of highly automated driving, fully automated driving or autonomous driving, the power supply has hitherto unrecognized safety implications in motor vehicles. It is therefore necessary to detect and isolate errors in the electric on-board network reliably and as completely as possible.

"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 independently of the driver. In the case of highly automated driving, the vehicle has its own intelligence that pre-plans and is able to take over the driving task at least in most driving situations. Therefore, in the case of highly automated driving, power supply has a high safety relevance.

Therefore, a switching element is required for coupling/decoupling electrical parts of the on-board network: the switching element can autonomously detect faulty consumers or groups of consumers or partial networks, and can switch the faulty consumers. Non-reactive and reliable separation of consumers or groups of consumers or partial networks from the remaining (partial) on-board network in order to meet the requirements for fault tolerance in the supply of safety-relevant consumers in the case of autonomous driving The following is given in a personal vehicle, commercial vehicle or truck.

A high degree of reliability of the separation function is required in the following situations: The switching element couples two or more partial on-board networks; in the coupled state an error in one of the partial on-board networks can lead to particularly safety-relevant coupling to this network. Other parts of the in-vehicle network were also damaged.

The present invention is based on the task of further simplifying the entire system under high demands. This task is solved by the technical solution of the present invention.

SUMMARY OF THE INVENTION

Particularly advantageously, the diagnostic method according to the invention compared to conventional diagnostic concepts, in which each of the parallel lines of switching elements is provided with a separate current detection, is characterized in that: Only a specially weighted differential voltage detection is required at the switching element, and the circuit-technical outlay for the current detection required for diagnosing the switching element can thus be reduced by a factor equal to the number of parallel lines. In any case, the temperature detection device required for the temperature monitoring of the switching element 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 cooling body.

In an expedient development, at least one parallel line remains permanently connected during the diagnosis of the switching device. Therefore, the corresponding safety-related coupling of parts of the vehicle network is maintained despite the diagnostics being carried out.

In an expedient development, in particular when the overcurrent detection device is deactivated, the number of closed circuit switches is changed and the output signal of the measuring device is evaluated for the corresponding change. It is thus possible to check whether the resultant resistance of a functioning switching element has changed in the expected manner, which can be detected particularly simply by simply determining the differential voltage across the switching element.

In an expedient development, the change is reduced—in particular by a factor (N-M)/N, where N is the total number of parallel lines and M is the number of parallel lines or line switches that interrupt the connection. - the gain of the measuring device, wherein, in the event of such a change in the gain of the measuring device, the output signal of the measuring device is checked whether it also changes. In the case of a properly functioning current detection device or measuring device, a proportional reduction of the output signal with the reduced gain indicates proper operation, which can be determined particularly easily by the proposed measuring device.

In an expedient development, at least one of the line switches, possibly also other line switches, is actuated to block after initially all line switches have been switched on. Particularly preferably, in particular when the overcurrent detection device is deactivated, the number of line switches that are actuated to block is selected as a function of the switch-off threshold of the overcurrent detection device. Therefore, on the one hand, the load capacity of the actuated parallel line should not be exceeded, and on the other hand, the functional validity of the line control device or the overcurrent detection device can be checked.

In an expedient development, 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. Here, a properly functioning overcurrent detection device can be checked. Furthermore, the functional thermal connection of the cooling body, eg the switching element, can be checked with respect to the temperature behavior.

Further expedient developments emerge from other preferred embodiments and the description.

Description of drawings

The attached figure shows:

Figure 1 shows the in-vehicle network topology;

FIG. 2 shows a more precise structure of the switching element with the measuring device;

FIG. 3 shows a switching element with an additional temperature detection device;

4 shows a block diagram of a switching element with an overcurrent detection device and a line control device;

FIG. 5 shows a flow chart for checking the switching element.

Detailed ways

The present invention is schematically described on the basis of embodiments in the drawings and will be described in detail below with reference to the drawings.

In this example, batteries or accumulators are described as possible energy stores. Alternatively, however, other energy stores suitable for the task can also be used—for example energy stores based on inductive or capacitive means, fuel cells, capacitors, etc.

The on-board network topology according to FIG. 1 includes a part of the on-board network 22 in which power consumers 24 that are not relevant for safety are supplied with energy. However, parts of the in-vehicle network 22 do not themselves include an energy source. Part of the on-board network 22 is connected to the safety-relevant part of the on-board network 30 via the switching element 19 for power supply. The positive path of the safety-independent part of the on-board network 22 and the safety-relevant part of the on-board network 30 are switched on or, if necessary, separated by the switching element 19 . Depending on the application, a plurality of safety-relevant consumers 36 are provided in the safety-relevant sub-vehicle network 30 in each case. Furthermore, the safety-relevant part of the on-board network 30 includes at least one energy store 32 or at least one energy source. In this embodiment, an electric motor 12 is also provided as an energy source. Furthermore, at least one separating element 26 or coupling element (preferably a DC voltage converter) is provided for coupling further, in particular safety-relevant, parts of the vehicle network 30 .

The device consists of electronic switching elements 19 , which are implemented redundantly, in particular unidirectionally, separated by a parallel circuit of a plurality of semiconductor switches or line switches 45 for use in motor vehicles by the safety-relevant part of the on-board network 30 . supplying power to a part of the on-board network 22 having a safety-independent consumer 24 without an energy source; and a method for continuously diagnosing the disconnection function of the switching element to protect the safety-relevant part of the on-board network 30 from being compromised Safe low voltage and freedom from safety-relevant electrical consumers 36 , which can be caused by overloads or errors in the safety-relevant part of the on-board network 22 supplied by the switching element 19 .

The safety-relevant part of the in-vehicle network 30 is used, in particular, to supply the functions required for autonomous driving operation or the safety-relevant consumers 36 (in particular steering, braking, ambient sensing, trajectory planning, etc.). In this case, a plurality of partial vehicle networks 30 can be provided, which can be separated from one another by means of the separating element 26 in the event of an error. This can be achieved, for example, by means of a DC voltage converter 26 as shown by way of example. These sub-vehicle networks 30 supply power to functionally redundant components or consumers 36 which are capable of redundantly implementing the functions mentioned by way of example. In the event of a failure of a part of the on-board network 30 , a safe parking of the vehicle (going to the next parking lot, stopping immediately on the shoulder of the road) can be carried out, for example, by means of components or consumers 36 of the other part of the on-board network 30 that are still functioning without errors. Wait).

An exemplary structure of the switching element 19 is shown according to FIG. 2 . The switching element 19 comprises a plurality (N in number) of parallel lines 43 with line switches 45 arranged in each of the parallel lines 43 . The line switch 45 is, for example, a power semiconductor switch, such as a MOSFET. Furthermore, a measuring device 41 is provided. The measuring device 41 is used to detect the current I flowing through the switching element 19 . For this purpose, the measuring device 41 is designed, for example, as a voltage detection device, in particular to detect the differential voltage U at the input and output of the switching element 19 .

Instead of a separate current detection for each parallel line 43 , a particularly weighted differential voltage detection is advantageously provided on the switching element 19 by the measuring device 41 , which is equivalent to the current on the switching element 19 as illustrated in FIG. 2 . detection. Consequently, this results in a reduction in the circuit-technical outlay for the current detection required for diagnosing the switching element 19 .

The embodiment according to FIG. 3 differs from the embodiment of FIG. 2 only in that a temperature detection device 49 is additionally provided. The temperature detection device 49 is used to detect the temperature of the switching element 19 . In any case, the temperature detection device required for the temperature monitoring of the switching element 19 can be used particularly advantageously for improving the diagnostic quality of the disconnection function of the switching element 19 and additionally for diagnosing the thermal connection of the switching element to the cooling body.

Furthermore, according to FIG. 4 , a line control device 53 is provided, by means of which the corresponding desired parallel lines 43 can be connected individually or the associated line switches 46 can be actuated. Furthermore, an overcurrent detection device 47 is provided, which, in order to prevent overcurrents, compares the detected current value with the switch-off threshold value _Inom + _ΔInom and, if necessary, executes the switching element 19 when exceeded. safety shutdown. When the switch-off threshold value of the overcurrent detection device 47 is reached, the overcurrent information is provided, for example, by means of a trigger that stores the switch-off threshold value reached for further evaluation in the diagnosis of the switching device 19 .

A further sequence of the diagnosis method is described on the basis of the flowchart according to FIG. 5 .

According to the assumptions and initial situation of step 101:

• All N parallel lines 43 of the switching elements are manipulated "on".

The overcurrent shutdown threshold is set as _Ishutdown = _Inominal + _ΔInominal

1. Step 102

The actuation of the M-N parallel lines 43 is temporarily inhibited by the overcurrent detection device 47 (durchgriff). Although the switch-off threshold is exceeded, the switching element 19 or the specific parallel line 43 is not switched off for very short times (eg in the microsecond range).

2. Step 103

The M parallel lines 43 of the N parallel lines 43 of the switching element 19 are actuated as "high-resistance", which applies:

·

·No more than the load capacity of M-N parallel lines

Expected effect of step 2 103:

增大。The combined resistance of a functioning switching element 19 is given by the factor

increase.

• An increase in the resultant resistance is accompanied by a proportional increase in the instantaneous voltage drop U across the switching element 19 .

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

In a subsequent query 104 , a diagnosis of the line control device 53 , the line switch 45 and the current detection device (which is carried out by means of the measuring device 41 when the differential voltage U at the switching element 19 is detected) is carried out.

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 switching element 19 ) indicates that the output signal corresponds to the expected resistance increase of switching element 19 . increases proportionally; when necessary, the output signal leaves the nominal output range and/or goes into saturation. Otherwise, query 104 results in a fault condition.

As a further component of the query 104, the overcurrent detection device 47 and the shutdown path (via the current shutdown device when the shutdown threshold is exceeded) are diagnosed.

A functioning overcurrent detection device 47 detects that the overcurrent switch-off threshold has been reached/exceeded and, if necessary, generates an overcurrent message when the switch-off threshold is reached, for example, an overcurrent trigger is set. In the case of a functioning switch-off path, the overcurrent detection device 47 takes measures for the actuation of the M switches or line switches 45 . Otherwise there is an error.

3. Step 105

降低。The gain of the current sensing device or measuring device 41 is given by the factor

reduce.

In the interrogation 106 the diagnosis of the current detection device or measuring device 41 is carried out.

A functioning current detection device or measuring device 41 indicates that the output signal decreases proportionally 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.

4. Step 107

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

In the query 108, the overcurrent detection device 47 is diagnosed. A functioning overcurrent detection device 47 indicates operation within the operating current limits. If the operating current limit is left, there is an error.

5. Step 109

Measures are taken for all N parallel lines to open the overcurrent detection device 47 . It is now allowed to switch off the corresponding parallel line 45 when the switch-off threshold is reached.

The thermal connection of the temperature detection device 49 and the switching element 19 to the cooling body is diagnosed in the interrogation 110 .

A functioning temperature detection device 49 of the switching element 19 indicates a proportional temperature rise of the switching element 19 in time associated with an increase in resistance.

In the case of a functioning thermal connection, the temperature rise fed back by the functioning temperature detection device within the detection time window is within the expected range. Otherwise there is an error.

6. Step 111

All N parallel lines 43 are turned "on" again.

Expected effect of step 6 111

减小。The combined resistance of a functioning switching element 19 is given by the factor

decrease.

• The reduction of the resultant resistance is accompanied by a proportional reduction of the instantaneous voltage drop U across the switching element 19 .

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

In the interrogation 112 , the line control device 53 , the line switch 45 and the current detection device (or the measuring device 41 ) are diagnosed.

A functioning current sensing device (or measuring device 41 ) indicates a decrease in the output signal U proportional to the decrease in resistance. Otherwise a fault condition is inferred.

7. Step 113

增大。The gain of the current measurement detection device is again factored

increase.

In the query 114 , the current detection device (or the measurement device 41 ) and the overcurrent detection device 47 are diagnosed.

A functioning current detection device (or measurement device 41 ) indicates a rise in the current measurement output signal proportional to the gain increase or the output signal U of the measurement device 41 within the nominal output range. Otherwise there is an error.

Furthermore, a functioning overcurrent detection device 47 indicates operation within the operating current limits. If you leave this range, there is an error. In step 115 the method ends. Step 101 may be followed again as needed.

The described method is particularly suitable for increasing the reliability of the entire system, especially for autonomous driving, which imposes particularly stringent safety requirements. However, the use is not limited to this.

Claims (15)

1. Method for diagnosing a switching device in a motor vehicle, wherein a switching element (19) is provided, which switching element comprises a plurality (N) of parallel lines (43) each having at least a line switch (45) arranged in one parallel line (43), wherein the switching element (19) connects at least one partial on-board network (22) with a safety-relevant partial on-board network (30), which at least one partial on-board network (22) has safety-independent consumers (24) and no energy sources, and the safety-relevant partial on-board network (30) has safety-relevant consumers (36), in particular for autonomous driving operation, and 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) And (7) breaking.

2. Method according to claim 1, characterized in that at least one parallel line (43) is kept continuously conductively connected during the diagnosis of the switching device (19).

3. Method according to one of the preceding claims, characterized in that at least one overcurrent detection device (47) is provided for switching off at least one parallel line (43), in the case of which a switching-off threshold is reached, 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. Method according to one of the preceding claims, characterized in that, in particular in the case of an overcurrent detection device (47) being deactivated or in the case of an overcurrent detection device (47) being activated, the number of closed line switches (45) is varied and the output signal (U) of the measuring device (41) is evaluated with respect to a corresponding change.

5. Method according to any one of the preceding claims, characterized in that the gain of the measuring device (41) is changed, in particular reduced by a factor (N-M)/N, where N is the total number of parallel lines (43) and M is the number of parallel lines (43) blocking a connection, wherein the output signal (U) of the measuring device (41) is checked in the event of said change in gain of the measuring device (41) as follows: whether the output signal (U) likewise changes.

6. Method according to any of the preceding claims, characterized in that the possible switching off of the respective line switch (45) by means of the overcurrent identification device (47) is temporarily inhibited.

7. Method according to any of the preceding claims, characterized in that at least one parallel line (43), preferably more (M) parallel lines (43), is manipulated to be blocked.

8. Method according to any of the preceding claims, characterized in that the number (M) of line switches (45) which are operated to block-in particular in the event of deactivation of an overcurrent recognition device (47) -is linked to a switch-off threshold (I) of the overcurrent recognition device (47)_{Nominal scale}+ΔI_{Nominal scale}) And (4) correlating.

9. Method according to any of the preceding claims, characterized in that the number (M) of line switches (45) that are operated to be blocked is determined according to the following formula:

wherein N represents the total number of said parallel lines (43), I_{Nominal scale}Represents the nominal current of the overcurrent detection device (47), and Delta I_{Nominal scale}Represents an excess of the nominal current, in the case of which an excess of the nominal current triggers an excess current shut-off threshold of the excess current detection device (47).

10. Method according to any of the preceding claims, characterized in that in a further step the overcurrent recognition means (47) are activated again and the temperature detected by the temperature detection means (49) is evaluated.

11. Method according to any of the preceding claims, characterized in that in a further step all (N) parallel lines (43) are manipulated to be conductive.

12. Method according to one of the preceding claims, characterized in that a further number (N) of line switches (43), in particular all line switches (43), is conductively connected and it is checked whether the measurement variable (U) of the measuring device (41) is correspondingly reduced, in particular by a factor (N-M)/N, in the case of an increased number of closed line switches, where N denotes the number of conductive line switches (43) and M denotes the number of previously non-conductive line switches (43).

13. Method according to any of the preceding claims, characterized in that the overcurrent identification means (47) are switched on for all parallel lines (43).

14. Method according to any of the preceding claims, characterized in that the gain of the measuring device (41) is increased again, in particular by a factor N/(N-M), where N denotes the number of line switches (43) that are conducting and M denotes the number of line switches (43) that were not previously conducting.

15. Method according to one of the preceding claims, characterized in that firstly all parallel lines (43) are controlled to be conductive and subsequently the overcurrent identification device (47) is temporarily disabled, that at least one parallel line (43) is non-conductively connected and the measurement variable (U) of the measurement device (41) is detected, and/or that the overcurrent identification device (47) is again enabled to take measures, that all parallel lines (43) are controlled to be conductive and the measurement variable (U) of the measurement device (41) is detected, and/or that the gain of the measurement device (41) is increased and the measurement variable (U) of the measurement device (41) is detected.

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