CN110850329A

CN110850329A - Method for diagnosing a switching device in a motor vehicle

Info

Publication number: CN110850329A
Application number: CN201910676449.2A
Authority: CN
Inventors: G·席尔; M·扎布卡; M·申策尔; N·德拉斯
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-07-25
Filing date: 2019-07-25
Publication date: 2020-02-28
Also published as: DE102018212351A1; FR3084468A1; FR3084468B1

Abstract

The invention relates to 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), the parallel lines each have at least one line switch (45) arranged in the parallel line (43), wherein the switching element (19) connects at least one section of the on-board network (22) to a safety-relevant section of the on-board network (30), wherein the at least one section of the on-board network (22) has safety-independent consumers (24) and no energy source, wherein the safety-relevant section of the on-board network (30) has safety-relevant consumers (36), in particular for autonomous driving operation, and has 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 a switching device in a motor vehicle

Technical Field

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

Background

The task of the vehicle onboard network is to supply electrical consumers with energy. If in modern vehicles the energy supply fails due to errors or ageing in the on-board network or in components of the on-board network, important functions (e.g. servo steering) fail. Since the steering ability of the vehicle is not affected but only becomes heavy

A malfunction of the on-board system is generally acceptable in modern mass-produced vehicles, since the driver is available as a backup (R ü ckfallebene), for increased availability, a two-channel on-board system configuration has already been proposed, for example, in WO 2015/135729 a 1.

An "on-board system" is to be understood to mean, in particular in vehicle applications, the totality of all electrical components in a motor vehicle. The on-board system therefore includes not only the electrical consumer but also a power supply source, for example a generator, a dc voltage converter or an electrical storage device (for example a battery).

It should be noted that as the plants (agglegrats) are increasingly electrified and new driving functions are introduced, the requirements for 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, activities of driving strangeness (fahrfremd) should be permitted to a limited extent. In this case, there are only limited backup options for the driver, which are sensory, control-technical, mechanical and energy-intensive. In the case of highly automated, fully automated or autonomous driving, the supply of power therefore has a safety relevance which has not been recognized hitherto in motor vehicles. Therefore, it is desirable to reliably and as completely as possible identify and isolate errors in the electrical onboard network.

"automated driving" or "highly automated driving" is understood to mean an intermediate step between assisted driving, in which the driver is supported by an assistance system, and autonomous driving, in which the vehicle is driven autonomously and without the influence of the driver. In the case of highly automated driving, the vehicle has its own intelligence, which is planned in advance and is able to take over driving tasks at least in most driving situations. Therefore, in the case of highly automated driving, the power supply has a high safety relevance.

Therefore, the following switching elements are required for coupling/decoupling a part of the electrical onboard network: the switching element can autonomously detect faulty loads or groups or partial networks of loads and can separate them from the remaining (partial) on-board network in a reaction-free and reliable manner in order to meet the requirements for fault tolerance in the power supply of safety-relevant loads, which are present in private vehicles, commercial vehicles or trucks in the case of autonomous driving.

A high degree of reliability of the separation function is required in both cases: the switching element couples two or more parts of the on-board network; an error in one of the partial onboard networks in the coupled state may lead to a simultaneous impairment of a further, particularly safety-relevant part of the onboard network coupled to this network.

The invention is based on the following tasks: the overall system is further simplified in case of high demands. The object is achieved by the invention.

Disclosure of Invention

The diagnostic method according to the invention is particularly advantageous compared to conventional diagnostic solutions, in which each of the parallel lines of the switching elements is provided with a separate current detection, in that only a particularly weighted differential voltage detection is required at the switching elements, and thus the overhead in terms of circuitry for the current detection required for diagnosing the switching elements can be reduced by a factor equal to the number of parallel lines. The temperature detection device required for the temperature monitoring of the switching element can in any case 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.

In an expedient further development, at least one of the parallel lines is kept continuously conductively connected (leipend geschaltet) during the diagnosis of the switching device. Thus, despite the diagnosis performed, a corresponding security-relevant coupling of the parts of the on-board network is maintained.

In an expedient further development, the number of closed line switches is changed, in particular in the event of a deactivation of the overcurrent detection device, and the output signal of the measuring device is evaluated with respect to a corresponding change. It is therefore possible to check whether the combined resistance (resultierended) of a properly functioning switching element changes in the expected manner, which can be detected particularly simply by ascertaining the differential voltage across the switching element.

In an expedient further development, the gain of the measuring device is varied, in particular reduced 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 blocking the connection (sperrend geschaltt), and the output signal of the measuring device is checked in the event of such a change in the gain of the measuring device as follows: whether the output signal is also changing. In the case of a properly functioning current detection device or measuring device, a decrease in the output signal in proportion to the reduced gain indicates that the (signalisieren) is operating as intended, which can be particularly easily ascertained by the proposed measuring device.

In an expedient further development, after first all the line switches have been switched on, at least one line switch, optionally also the other line switches, is switched off. In particular, it is preferred that the number of line switches activated as blocking is selected as a function of a shut-off threshold of the overcurrent detection device, in particular when the overcurrent detection device is deactivated. On the one hand, the load capacity of the parallel lines to be controlled should therefore 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 a further advantageous embodiment, 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, the overcurrent detection device functioning properly can be checked. Furthermore, a functional thermal connection of a heat sink, for example a switching element, can be checked with respect to temperature behavior.

Further embodiments and descriptions of preferred embodiments lead to further embodiments that are suitable for the purpose.

Drawings

The figures show:

FIG. 1 illustrates an 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;

fig. 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 Description

The invention is schematically described according to embodiments in the drawings and will be described in detail below with reference to the drawings.

In this exemplary embodiment, for example, batteries or accumulators are described as possible energy stores. However, other energy stores suitable for the task may also be used instead, for example energy stores based on inductive or capacitive means, fuel cells, capacitors, etc.

The vehicle network topology according to fig. 1 comprises a part of the vehicle network 22, in which safety-independent consumers 24 are supplied with energy. However, portions of on-board network 22 themselves do not include an energy source. For the energy supply, part of the on-board system 22 is connected via the switching element 19 to a safety-relevant part of the on-board system 30. The positive path of the safety-independent part of on-board network 22 and the positive path of the safety-dependent part of on-board network 30 are switched on or, if necessary, disconnected by switching element 19. In each case several safety-relevant consumers 36 are arranged in the safety-relevant part of the on-board system 30, in each case grounded depending on the application. Furthermore, the safety-relevant part of the on-board network 30 comprises at least one energy store 32 or at least one energy source. In this embodiment there is also provided an electric motor 12 as a source of energy. Furthermore, at least one disconnection element 26 or a coupling element (preferably a dc voltage converter) is provided for coupling a further, in particular safety-relevant, part of the on-board network 30.

The device relates to an electronic switching element 19 which is redundantly, in particular unidirectionally, implemented by means of a parallel circuit of a plurality of semiconductor switches or line switches 45, for supplying a partial onboard network 22 having safety-relevant partial onboard networks 30 without energy sources to safety-relevant electrical consumers 24 in a motor vehicle; and a method for the uninterrupted diagnosis of the disconnection function of the switching element in order to protect a safety-relevant part of the on-board system 30 from a low, safety-endangered voltage and from faults of safety-relevant consumers 36 which are associated therewith as a result of overloads or faults in the safety-irrelevant part of the on-board system 22 supplied by the switching element 19.

The safety-relevant part of the on-board system 30 serves in particular to supply functions required for autonomous driving operation or safety-relevant consumers 36 (in particular steering, braking, ambient sensing, trajectory planning, etc.). In this case, a plurality of partial on-board networks 30 can be provided, which can be separated from one another by the separating element 26 in the event of an error. This can be achieved, for example, by a dc voltage converter 26 as is shown by way of example. These parts of the onboard network 30 supply functionally redundantly designed components or consumers 36, which can redundantly implement the functions mentioned by way of example. In the event of a failure of a part of the on-board system 30, a safe parking of the vehicle (driving to the next parking lot, immediately on the shoulder, etc.) can be carried out, for example, by means of the components of the further part of the on-board system 30 or the electrical consumers 36 which still operate without errors.

An exemplary structure of the switching element 19 is shown according to fig. 2. The switching element 19 includes a plurality (number N) of parallel lines 43 having line switches 45 respectively provided in one of the parallel lines 43. The line switch 45 is, for example, a power semiconductor switch, for example 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 by the measuring device 41 on the switching element 19, which is equivalent to the current detection on the switching element 19 as illustrated in fig. 2. This therefore results in a reduction in the circuit complexity for the current detection required for diagnosing the switching element 19.

The exemplary embodiment according to fig. 3 differs from the exemplary 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. The temperature detection device required for monitoring the temperature of the switching element 19 can in any case be used particularly advantageously to improve the diagnostic quality of the disconnection function of the switching element 19 and additionally to diagnose the thermal connection of the switching element to the heat sink.

Furthermore, a line control device 53 is provided according to fig. 4, by means of which the respective 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, for preventing an overcurrent, compares the detected current value with a shutdown threshold I_{Nominal scale}+ΔI_{Nominal scale}A comparison is made and if necessary a safe switching off of the switching element 19 is carried out. The overcurrent information is set in the event of the reaching of the switch-off threshold of the overcurrent detection device 47, for example by a trigger storing the reaching of the switch-off threshold for further evaluation in the diagnosis of the switching device 19.

A further flow of the diagnostic method is described on the basis of the flow chart according to fig. 5.

According to the assumptions and initial conditions of step 101:

all N parallel lines 43 of the switching elements are controlled to be "on".

Setting overcurrent cutoff threshold to I_{Switch off}＝I_{Nominal scale}+ΔI_{Nominal scale}

1. Step 102

The overcurrent detection device 47 is temporarily disabled from taking action (Durchgriff) on the M-N parallel lines 43. Despite the threshold for switching off being exceeded, the switching element 19 or the specific parallel line 43 is not switched off for a very short time (for example in the microsecond range).

2. Step 103

M of the N parallel lines 43 of the switching element 19 are activated as "high impedance", wherein:

·

load capacity of not more than M-N parallel lines

Expected effect of step 2, 103:

the combined resistance of the normally functioning switching element 19 is factored

And is increased.

The increase in the combined 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, the line control device 53, the line switch 45 and the current detection device (which is executed by means of the measuring device 41 when the differential voltage U across the switching element 19 is detected) are diagnosed.

In the case of a properly functioning line control device 57 and a controllable line switch 45, the properly functioning current detection device (weighted difference voltage U across 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 results in a fault condition.

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

The properly functioning overcurrent detection device 47 detects the reaching/exceeding of the overcurrent shutdown threshold and, if necessary, generates an overcurrent message, for example, an overcurrent trigger, when the shutdown threshold is reached. In the case of a functional shutdown of the path, the overcurrent detection device 47 takes action on the actuation of the M switches or line switches 45. Otherwise there is an error.

3. Step 105

Gain of current detecting or measuring means 41 by a factor

And decreases.

The current detection device or measuring device 41 is diagnosed in query 106.

The properly functioning current detection device or measuring device 41 indicates that the output signal decreases in proportion to the decreasing gain, the output signal of the current detection device returning into the nominal output range if necessary. Otherwise there is an error.

4. Step 107

If the shutdown threshold has been reached previously, the overcurrent trigger is reset if necessary.

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

5. Step 109

Measures are taken for all N parallel line-on (freigeben) overcurrent recognition means 47. The respective parallel line 45 is now allowed to be switched off when the switching-off threshold is reached.

The thermal connection of the temperature detection device 49 and the switching element 19 to the heat sink is diagnosed in query 110.

The properly functioning temperature detection device 49 of the switching element 19 indicates a proportional temperature rise of the switching element 19 in time correlation with the resistance increase.

In the case of a functional thermal connection, the temperature rise fed back by the functional 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 again manipulated "on".

Expected effect of

step

6, 111

And decreases.

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

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

The line control device 53, the line switch 45 and the current detection device (or the measuring device 41) are diagnosed in an inquiry 112.

A properly functioning current detection means (or measuring means 41) indicates a decrease of the output signal U proportional to the resistance decrease. Otherwise a fault condition is inferred.

7. Step 113

The gain of the current measurement detection means is again factored

And is increased.

The current detection device (or the measuring device 41) and the overcurrent detection device 47 are diagnosed in an inquiry 114.

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

In addition, a properly functioning overcurrent detection device 47 indicates operation within the operating current limit. If this range is left, then there is an error. The method ends in step 115. Step 101 may again follow as desired.

The described method is particularly suitable for increasing the reliability of the overall system, in particular for autonomous driving, for which particularly stringent safety requirements are imposed. However, the use is not limited thereto.

Claims

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.