DE102015221729A1 - Method for monitoring an electrical system - Google Patents

Abstract

The invention relates to a method for operating an electrical system (200) comprising at least two channels with at least one component and a power supply, wherein a coupling element is provided between the two channels, wherein the coupling element is used to carry out a diagnosis by this at least one measurement is made,

Description

The invention relates to a method for monitoring an electrical system and a vehicle electrical system for carrying out the method.

State of the art

Under an electrical system is to be understood in the automotive use, the totality of all electrical components in a motor vehicle. Thus, these include both electrical consumers and supply sources, such as, for example, generators or electrical storage, such as batteries. Furthermore, it also includes all electrical connection and distribution elements such as cable or harness, power distribution and fuse boxes. In the motor vehicle care must be taken to ensure that electrical energy is available in such a way that the motor vehicle can be started at any time and that sufficient power is available during operation. But even when parked, electrical consumers should still be operable for a reasonable period of time, without a subsequent start being impaired.

It should be noted that due to the increasing electrification of units and the introduction of new driving functions, the requirement for the reliability of the electrical energy supply in the motor vehicle steadily increases. Furthermore, it must be taken into account that, in the future, highly non-driving activities should be permitted to a limited extent in the case of highly automated driving. A sensory, regulatory, mechanical and energetic fallback by the driver in this case is limited. Therefore, in a highly automatic driving the electrical supply has a previously unknown in motor vehicles safety relevance. Errors in the electrical system must therefore be reliably and completely recognized.

Under a highly automatic driving, which is also referred to as highly automated driving, an intermediate step between an assisted driving, in which the driver is assisted by assistance systems, and an autonomous driving, in which the vehicle is driving automatically and without the involvement of the driver to understand. In the case of highly automatic driving, the vehicle has its own intelligence that could plan ahead and take on the driving task, at least in most driving situations. Therefore, in a highly automatic driving the electrical supply has a high safety relevance.

With on-board errors in sources, memories and consumers, the wiring harness also plays a role. On the one hand, faults such as interruptions and short circuits can occur in the wiring harness and connectors, on the other hand, contact resistances can also be increased. There are no diagnoses for this in today's vehicles. On the other hand, it is already known to measure the vehicle electrical system voltage within components. Both the electric steering, the ESP, and other control devices measure the terminal voltage. Then the operating behavior of the components is adjusted. This is done, for example. By switching off or degradation of the function at undervoltage, z. B. less than 9 V, or overvoltage, for example. More than 16 V.

Furthermore, it is known that a battery sensor EBS measures the terminal voltage and the battery current of the lead-acid battery in order, for example, to close the charge state of the battery via the open-circuit voltage.

In the publication WO 2010121075 A2 a method is described for detecting errors in a circuit arrangement. In this case, the cell voltages of a high-voltage battery are used to close from the comparison with a second voltage at a point in the wiring harness during a defined load current to contact resistances in the high-voltage electrical system and in the cell connections. If the contact resistances are too high, charging or discharging currents should be limited in order to avoid thermal overheating. However, the document does not describe how to ensure the supply of safety-relevant consumers in the low-voltage on-board electrical system.

The monitoring of a lead acid battery by an electronic battery sensor (EBS) is from the document WO 2013/139547 A1 known.

The monitoring of consumers by fuses or electronic fuses is from the document DE 100 36 983 A1 , which describes a device for fast short-circuit protection in a power semiconductor known.

In the publication DE 103 23 145 A1 For example, a method for checking an electric machine, for example a generator, will be described. The generator is connected in a vehicle electrical system of a motor vehicle with a battery and a control unit and is driven by an internal combustion engine of the motor vehicle. In the presented method, the generator is checked by means of a battery sensor on the basis of determined measured values of the battery current.

The methods described above relate primarily to single-channel vehicle electrical system with generator. With the introduction of automatic Driving functions, however, two-channel vehicle electrical systems are needed.

Disclosure of the invention

Against this background, a method with the features of claim 1 and an electrical system according to claim 12 are presented. Embodiments emerge from the dependent claims and from the description.

The method takes into account that, in the case of two-channel on-board networks, coupling elements are provided, for example, in the form of intelligent switches or DC or DC / DC converters between the two on-board networks.

• – falsche Strommessung im EBS, DC/DC-Wandler, elektronische Sicherung oder Verbraucher, sofern diese vorhanden sind,
• – falsche Spannungsmessung im EBS, DC/DC-Wandler, elektronische Sicherung oder Verbraucher,
• – Ausfall von Batterie oder DC/DC-Wandler.

The presented method makes it possible to systematically diagnose single-channel or two-channel vehicle electrical systems with coupling elements by extensions of the methods discussed at the beginning in order to make the sensors in the EBS and the DC / DC converter plausible and to recognize the following errors:

• - incorrect current measurement in the EBS, DC / DC converter, electronic fuse or consumer, if they exist,
• - incorrect voltage measurement in EBS, DC / DC converter, electronic fuse or consumer,
• - Failure of battery or DC / DC converter.

• – die Überwachung der Leistungsaufnahme von Verbrauchern,
• – die Überwachung der korrekten Abschaltung von elektronischen Sicherungen im Überlastfall,
• – die Überwachung der Ruhestromaufnahme im Standbybetrieb von Verbrauchern.

The presented method also makes it possible to diagnose the power consumption of consumers or to make plausibility of electronic fuses. This makes possible:

• - monitoring the power consumption of consumers,
• - monitoring the correct shutdown of electronic fuses in the event of overload,
• - Monitoring the quiescent current consumption in standby mode of consumers.

• – in der Leitung von der Bleibatterie zu einem Knotenpunkt K1,
• – im Sicherungskasten, einschließlich interner Leitungen, Sicherungshaltern, Schmelzsicherungen usw.,
• – in Kabeln und Steckern der einzelnen Komponenten,
• – in den Masseleitungen von der jeweiligen Komponente zum Massebolzen an der Karosserie bzw. zum Massepunkt bei Zweileiterbordnetzen.

In addition, the described method allows detection of harness failures, such as supply-to-ground shorts or increased contact resistances, for example:

• In the line from the lead-acid battery to a node K1,
• - in the fuse box, including internal wiring, fuse holders, fuses, etc.,
• - in cables and plugs of the individual components,
• - In the ground lines of the respective component to the ground bolt on the body or to the ground point in Zweileiterbordnetzen.

It is thus presented a method for systemic diagnosis of the electrical system by combining existing signals. This includes the application of the Kirchoffs node rule to check the flows in a network. By comparing the signals of existing current sensors or by determining the load current based on control signals from consumers, they should be tested against each other.

Furthermore, the method makes it possible to selectively control loads or the DC / DC converter in order to selectively check the electrical system on the basis of the conditions thus induced. The method provides for a comparison of voltage measurements at various points in the electrical system, specifically in energy sources, sinks and distribution elements. Depending on the respective load current, which can be determined by existing signals or control signals from consumers, thus short circuits or increased contact resistance can be detected.

An advantage of the described method is to use existing information for new diagnoses or to operate components specifically so that new information about the state of the electrical system generated and thus additional measuring points are not needed. Another advantage is that the DC / DC converter in addition to the actual power supply gets the task to determine the electrical system state and thus gets an added value over competing products.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

1 shows a wiring system.

2 shows an embodiment of a vehicle electrical system.

3 shows a further embodiment of a vehicle electrical system.

4 shows an embodiment of a vehicle electrical system

5 shows another version of a vehicle electrical system.

Embodiments of the invention

The invention is schematically illustrated by means of embodiments in the drawings and will be described in detail below with reference to the drawings.

1 shows a wiring system, the whole with the reference number 10 is provided and represents a dual-channel electrical system according to the prior art.

The illustration shows a generator or an electrical machine 12 , which provides a voltage of 48 V, a first so-called electronic power distribution unit 14 (electronic energy supply unit, ePDU), a first consumer 16 , a first battery 18 , a first battery management system 20 (BMS: Battery Management System), a first DC-DC converter 22 , which converts the voltage from 48V to a voltage of 14V, a second ePDU 24 , a second consumer 26 , a second battery 28 with a battery sensor 30 , a second DC-DC converter 32 , which converts the voltage of 48 V into a voltage of 14 V, a third battery 34 with a battery sensor 36 , a safety-related consumer Rs1a 38 whose function is redundant by a consumer Rs1b 40 is satisfied, a safety-relevant consumer Rs2a 42 with an internal, redundant Rs2b consumer 44 ,

2 shows a simplified electrical system, with the reference numeral 200 is provided and is also referred to as a subnet. The illustration shows a DC-DC converter 202 , an energy management system 204 , a battery 206 , a battery sensor 208 and a consumer Rs1a 210 , Furthermore, a node K1 with reference numeral 212 characterized.

The DC / DC converter 202 feeds a current I_DcDc into this subnet as a power source 220 and supplies the totality of all consumers, simplified here by the consumer Rs1a 210 are shown, with the current I_Consumer 222 and charge the battery 206 with a current I_Batt 224 , It therefore applies according to the first 1. Kirchoffoff law: I_Batt + I_Consumer = I_DcDc (1)

Will the DC-DC converter 202 switched off, ie I_DcDc = 0, applies: I_Consumer = I_Batt, (2) ie the battery power is reversed, the battery 206 supplies the entire electrical system 200 , Thus, via the battery sensor 208 the current on-board network load can be determined. If the drive signals of the consumers are known, the theoretical load load can be determined via this. For example, 100% control means that the rated current of the component must flow.

In a first embodiment of the presented method, for example, all consumers are turned off. This is also referred to as active diagnostics or, alternatively, it waits until all consumers report that they are currently inactive. This is called passive diagnosis. It then applies: I_Consumer = 0 (3)

Is the DC-DC converter 202 also switched off at this time, ie I_DCDC = 0, I_EBS = 0 must apply in this case. I_EBS is by reference 230 clarified.

• a) der vom Batteriesensor 208 gemessene Strom falsch sein oder
• b) es können Verbraucher weiterhin aktiv sein.

Is I_EBS ≠ O can either

• a) that of the battery sensor 208 measured current be wrong or
• b) Consumers can continue to be active.

To make it plausible, the DC-DC converter 202 switched on. If the vehicle electrical system voltage is set to the value of the battery return voltage, the battery is not charged, ie I_EBS = 0, and the DC / DC converter 202 only supplies the consumers. If consumers are still shut down, the following must apply: I_DCDC = I_Consumer = 0 (4)

If I_DCDC is also ≠ 0, consumers are thus unauthorized.

If I_DCDC = I_Consumer = 0 but I_EBS ≠ 0, there is an error in the battery sensor in this case 208 in front.

The same procedure can be followed in a second embodiment if, as in 4 the consumer (s) is monitored by an electrical fuse (ePDU).

3 shows a simplified electrical system, with the reference numeral 300 is provided and is also referred to as a subnet. The illustration shows a DC-DC converter 302 as a coupling element, an energy management system 304 , a battery 306 as a power supply, a battery sensor 308 , a consumer Rs1a 310 as a component and an ePDU 314 , Furthermore, a node K1 with reference numeral 312 characterized.

This also has the task to measure the current of the component in order to switch off, if necessary.

It can also be used to test the ePDU 314 the DCDC converter 302 be switched off.

Is I_DCDC (reference numeral 320 ) = 0, it can be checked whether I_EBS (reference numeral 322) = -I_ePDU (reference numeral 324) (5)

Unless this test fails, the voltage of the DCDC converter will turn 302 set to a value where I_EBS = 0, ie U_EBS (Ref 326 ) is in the range of the battery return voltage.

In this case, it can be checked whether I_DCDC = -I_ePDU (6)

If this check fails, it can be concluded that I_ePDU 324 is incorrect, in the other case I_EBS 322 faulty.

The current I_EBS 322 can be validated by the ePDU 314 the consumers from the electrical system 300 separates.

Will the battery 306 now charged or the voltage of the DCDC converter 302 to a voltage above the gassing voltage of the battery 306 is set and is I_DCDC ≠ -I_EBS, so it can be concluded that I_EBS 322 is measured incorrectly.

In a third embodiment, two or more consumers are powered by the ePDU. It is on this 4 directed.

4 shows a simplified electrical system, with the reference numeral 400 is provided and is also referred to as a subnet. The illustration shows a DC-DC converter 402 , an energy management system 404 , a battery 406 , a battery sensor 408 , a consumer Rs1a 410 , an ePDU 414 and a consumer Rs2a 416 , Furthermore, a node K1 with reference numeral 412 characterized.

The diagnoses take place according to the scheme explained above, in particular the first embodiment. However, in order to allocate which consumer can possibly not be shut down, consumers will 410 . 416 deactivated in succession and the current I_ePDU 424 or the source current observed. The power does not change after a shutdown command, although a consumer turns off. or should be switched on, while all other consumers are disabled, it can be assumed that the consumer can not be disconnected. This indicates a defect.

The DC-DC converter can also be used to diagnose the wiring harness.

5 shows a simplified electrical system, with the reference numeral 500 is provided and is also referred to as a subnet. The illustration shows a DC-DC converter 502 , an energy management system 504 , a consumer Rs1a 510 , a consumer Rs2a 516 and an ePDU 514 ,

5 shows a possible implementation of the invention in the very schematically illustrated wiring system 500 , On the left is the DC-DC converter 502 including a measuring resistor 550 mapped for current measurement. For the sake of clarity, not shown is the voltage measurement. On the right side is also very simplistic two on-board network component shown, which consists among other things of the engine, control logic, switches and sensors. These represent consumers.

This vehicle electrical system component can be, for example, the stability system ESP, the iBooster, the electric power steering or another component. Relevant is a switchable load that generates a current flow that differs significantly between passive and active operation (for example> 10 A).

Also within this component there is a measurement of the supply voltage to ground. Furthermore, the component current is measured. Again, this is already the case for some components today. In a variant of the invention can be dispensed with the measurement of the component current.

The second load is exemplified by an electronic fuse, the ePDU 514 , supervised. In the presented method already existing, above-mentioned components are used.

If the component, z. B. the ESP, is in standby, ie the microcontroller is active, without the motor is energized, are from the DC / DC converter 502 the converter output voltage U_DCDC and the converter current I_DCDC 520 as well as terminal voltage U_RS1a / U_RS1b / U_ePDU and possibly the component current I_RS1a measured in the component or in the ePDU I_ePDU.

The subsequent comparison takes place, for example, in the respective component by the Measured values are transmitted from the DC-DC converter to the component. In an alternative solution, it is also possible to transmit to another control unit or to another electrical system component. The value pairs are finally saved.

As soon as the component is active, the same measured values are recorded. The component can either be activated for a self-test in which the harness is also tested by the illustrated method. On the other hand, it is also possible to wait until the component is active through use. It is important that a defined current flows over the component. Three cases are distinguished below:

Case A)

For this purpose it is expedient to measure the component flow. From the two voltage measurements and the component current, the resistance in the wiring harness can be determined and checked with threshold values. However, it is expedient if the component is supplied only from the battery, since then the entire chain can be tested.

In a variant of the invention, a comparison with previous values which have been stored is expedient in order, if necessary, to note a continuous deterioration or to compare it with the reference to the new condition.

In one variant, the current measurement in the component can be dispensed with if it is determined on the basis of the change in the converter current I_DCDC. For this, the component must be supplied from the DC-DC converter and the change I_DCDC must be tracked simultaneously with the activation of the component. Changing the I_DCDC when turning the component on and off can be used to deduce the current into the component.

Case B)

In another embodiment, an electronic fuse included in the "electronic power distribution unit" is inserted in the harness, for example, instead of the fuse box. In this embodiment, the ePDU is used to detect the component flow via appropriate measures.

Furthermore, the ePDU can be used to narrow the error by the method described above, in which the voltage is detected at the ePDU and compared both with the component voltage U_RE2a and with the converter output voltage U_DCDC.

Case C)

Especially with heaters, the resistance of the components is well known and defined. Depending on the supply voltage, this resistance value, which is measured by the component, causes a current flow. This means that in these components with defined load resistance in a further embodiment, the current is determined by calculation.

The wiring harness resistance in the wiring harness to the ePDU and to the component is then recorded via the respective voltage drops during and outside the component control and via the component current. To increase the robustness, the measurements mentioned can be carried out several times.

If the wiring harness resistance exceeds a threshold value, an error memory entry can be generated, a warning lamp can be switched on, or safety-relevant functions such as automatic driving can be prohibited.

The described diagnoses can be carried out on the one hand during a driving cycle, for example on the one hand when the components are inactive and on the other hand when the components are active.

In a further embodiment, the diagnoses described can be carried out before a drive cycle or at the beginning of a drive cycle in order to actively test systems before the start of the journey. For this purpose, components are selectively controlled and, for example, supplied specifically from the battery.

In a further embodiment, the diagnoses can be carried out in a workshop, for example, in which the wire harness and the electrical stores are checked according to the invention at regular intervals.

This ensures that the electrical system of the vehicle is in proper condition for safety-relevant driving functions.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2010121075 A2 [0007]
• WO 2013/139547 A1 [0008]
• DE 10036983 A1 [0009]
• DE 10323145 A1 [0010]

Claims (14)

Method for operating a vehicle electrical system ( 200 . 300 . 400 . 500 ) comprising at least two channels with at least one component and a power supply, wherein a coupling element is provided between the two channels, wherein the coupling element is used to carry out a diagnosis by performing at least one measurement in the latter, The method of claim 1, wherein the first measurements are performed at a first current consumption of at least one of the at least one component and second measurements at a second current consumption of at least one of the at least one component and the first measurements and the second measurements are compared with each other and determined therefrom whether the at least one of the at least one component works as intended. The method of claim 1 or 2, wherein the at least one of the at least one component is switched on and off. Method according to one of Claims 1 to 3, in which a DC-DC converter ( 202 . 302 . 402 . 502 ) is used. Method according to one of claims 1 to 4, wherein a current measurement is carried out in the coupling element. Method according to one of claims 1 to 5, wherein a voltage measurement is performed in the coupling element Method according to one of claims 1 to 6, wherein a diagnosis of a wiring harness of the electrical system ( 200 . 300 . 400 . 500 ) is carried out. Method according to one of claims 1 to 7, wherein a comparison with a battery sensor ( 208 . 308 . 408 ) values. Method according to one of claims 1 to 8, which at a restart of the electrical system ( 200 . 300 . 400 . 500 ) is carried out. Method according to one of claims 1 to 8, which is carried out at the beginning of a driving cycle. Method according to one of claims 1 to 10, which is carried out by means of a computer program. Vehicle electrical system, in particular for carrying out a method according to one of claims 1 to 11, comprising at least two channels with at least one component and a power supply, wherein between the two channels, a coupling element is provided, wherein the electrical system ( 200 . 300 . 400 . 500 ) is adapted to use the coupling element to perform a diagnosis by at least one measurement is made in this. The electrical system according to claim 12, which is further configured to perform first measurements on a first current consumption of at least one of the at least one component and second measurements on a second current consumption of at least one of the at least one component and to compare and compare the first measurements and the second measurements determine whether the at least one of the at least one component works as intended. Vehicle electrical system according to Claim 12 or 13, which has an energy management system ( 204 . 304 . 404 . 504 ) having.

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