EP1972026B1 - Antenna system, access control system for a motor vehicle and diagnosis method - Google Patents

Description

The invention relates to an antenna system having a plurality of individual antennas connected in each case in a separate drive path, to which a common signal generator is assigned, and to a drive unit provided for the selective connection of a respective selected drive path. It further relates to an access control system for a motor vehicle with such an antenna system and to a method for determining a faulty individual antenna in such an antenna system.

To increase the user comfort and also to increase theft security motor vehicles can be equipped with so-called "keyless entry" systems in which using a transponder or a mobile identification transmitter keyless opening and closing the central locking and possibly also a release of the immobilizer can be done. In such systems, a control system of the motor vehicle communicates via coded signals with the respective identification transmitter, for example, after receiving appropriate signals from the information provider and their evaluation in the case of a positive identification of an authorized user appropriate releases of the central locking and / or to release the immobilizer or the like granted can.

For communication with the identification transmitter or transponder, the control system transmits suitable signals to the latter. The signal transmission is usually carried out via a suitable, integrated into the motor vehicle antenna system. Due to the variety of applications and the individual cases to be considered usually a multi-channel antenna system is provided in which a A plurality of demand-designed and possibly also arranged in the motor vehicle, each connected in a separate drive path individual antennas are used. The individual antennas may, for example, on the one hand so-called interior and on the other hand so-called outdoor space antennas, which can be determined via an interior antenna due to their arrangement in the motor vehicle, their range and the like, whether the respective identification transmitter or transponder is currently straight located in the vehicle interior. In the case of an outdoor antenna, however, the individual antenna provided for this purpose is designed with regard to dimensioning and positioning for communication with the identification transmitter or transponder in the event that it is located in the exterior of the vehicle. In order to possibly also be able to take into account a directional dependence or the like, a plurality of such, specialized antennas in the antenna system can also be provided both in the interior space and in the outdoor area.

An antenna system of this type, in which the individual antennas a common signal transmitter for on-demand communication with the identification transmitter or transponder is assigned, wherein a selective activation or connection of a situation-dependent desired individual antenna is provided by selecting their respective Ansteuerpfad via a central drive unit, for example, from DE 10234605 or EP 1817816 B1 known. EP 1817816 However, it is only published after the priority date of this application and is thus only state of the art under Article 53 (3) EPC. According to the system EP 1817816 B1 is particularly with relatively simple means a reliable loading of the antennas with transmission signals allows, with unwanted coupling or crosstalk can be reliably avoided.

As has been found, however, in antenna systems of the aforementioned multi-channel design in the event of a fault, ie in the event of failure of one or more of the individual antennas, the troubleshooting, ie in particular the identification the faulty antenna, comparatively expensive. In particular, the repair effort in case of accidents can be undesirably high.

The invention is therefore the object of developing an antenna system of the type mentioned above such that in the event of an error in a particularly simple manner reliable identification of a faulty individual antenna is possible. Furthermore, a particularly favorable method for determining a faulty individual antenna in such an antenna system is to be specified.

With regard to the antenna system, this object is achieved according to the invention in that each drive path between the signal transmitter and the respective individual antenna is electrically connected via an associated isolating diode to a common first reference point provided for tapping a diagnostic potential as required.

The invention is based on the consideration that for a particularly simple and determined identification of a faulty individual antenna, the error type or the type of fault should first be determined jointly for all individual antennas, so that in a subsequent second step on the basis of the detected type of fault a particularly targeted Identification of each faulty individual antenna can be done. Accordingly, in the manner of a group diagnosis, a suitable inference for all individual antennas should be drawn together on the basis of the present error type. In particular, shortcomings of the respective individual antenna to the supply voltage, short circuit of the respective individual antenna to ground or a so-called "open-load" state, ie interruption of the electrical connection within the respective antenna, come into consideration as error types. To detect the error type is therefore provided in a first step, to determine for all individual antennas together, if possibly as an error type could be a short circuit to the supply voltage. In order to make this possible, all the individual antennas on the input side, ie in the region of their so-called antenna positive pole, are electrically connected to one another and to a reference point, via which a short circuit to the supply voltage can be ascertained. To determine whether there could be a short circuit to the supply voltage, the electrical potential of the reference point is then measured in relation to ground in the no-load state. If it is found between the reference point, which is preferably connected to ground via a suitable resistor, and ground an applied voltage greater than zero, it can be concluded as an error type to short circuit to the supply voltage. On the one hand to be able to perform this first step of a group diagnosis in a simple manner, on the other hand, the electrical decoupling of the individual antennas should be guaranteed in case of operation, the isolating diodes are provided which prevent crosstalk of the individual drive paths to each other in case of operation.

Advantageously, the antenna system should continue to be designed so that in the manner of a group diagnosis for the other possible types of errors, namely short circuit to ground and "open-load" state, a reliable Typerkennung is possible before the identification of each faulty individual antenna takes place , In order to enable a determination of a short circuit to ground, preferably each drive path between the signal transmitter and the respective individual antenna is electrically connected via an associated feed-in separating diode to a common contact point provided for applying a test voltage as required. When a test voltage is applied to the contact point, a voltage with respect to ground should also be measurable in the case of a fault-free installation even at the first reference point. Only in the case of a short circuit to ground is this voltage equal to zero even when the test voltage is applied. The isolation diodes in turn prevent unwanted crosstalk between the drive paths. In this case, the feed-in isolating diode is preferably connected in the connection between the drive path and the contact such that the connection corresponds to the contact point drive path of the forward direction and the connection to the drive direction contact point corresponds to the reverse direction of the feed-in separating diode.

Furthermore, in order to be able to identify the error type "open load", each drive path in the return region of the respective individual antenna, ie in the region of the so-called negative pole of the respective individual antenna, is advantageously also electrically connected to a common second reference point provided for the demanded tapping of a diagnostic potential an associated isolation diode connected. In particular, the antenna current of the individual antennas can be measured in a particularly simple manner via the tap of the diagnostic potential at the second reference point, which in turn is electrically connected to ground via a suitable resistor, which is a particularly suitable criterion for verifying a short circuit to ground or for identification an "open-load" state can be used.

The selective control of the separately held drive paths and thus the respective individual antennas can be done for example by suitably designed relay arrangements or by suitably selected signal generator. However, a particularly simple and reliable control of the individual drive paths and thus the individual antennas when using a common signal generator can be achieved by the drive unit is formed as a multiplexer, preferably as a multiplexer transistor or shunt multiplexer in a particularly advantageous embodiment.

In a particularly advantageous embodiment, the antenna system is used in an access control system for a motor vehicle, wherein the signal exchange of a vehicle integrated control system with a mobile identification transmitter via said antenna system.

With regard to the method for determining a faulty individual antenna in such an antenna system, the stated object is achieved by determining a general type of fault in a first diagnostic step by measuring a diagnostic potential at the first reference point and optionally at the second reference point. As a result, the basic recognition of the error type is guaranteed in the manner of a group diagnosis in a first diagnostic step, so that in the subsequent individual diagnostic steps in which the individually faulty antenna is determined, a test program adapted to the currently present error type can be performed. In the first step of the group diagnosis mentioned, provision is made in particular to first determine the diagnosis potential at the first reference point with respect to mass in the no-load state. If a potential greater than zero is present at the first reference point, it is possible to deduce the type of fault of a short circuit to the supply voltage. However, if a non-zero diagnostic voltage at the first reference point can not be determined, then a non-zero test voltage can be applied to the positive poles of the individual antennas.

In the case of a test voltage applied to the positive terminals of the individual antennas via the contact point, a diagnostic potential that differs from zero should also be present at the first reference point in the error-free state. If, however, a diagnosis potential of zero is measured in this state at the first reference point, then in the step of the group diagnosis it can be concluded that there is a short circuit to ground as an error type.

After the error type in question has first been determined for all antennas in the first diagnostic step in the manner of a group diagnosis, it is advantageous in a subsequent one second diagnostic step on the basis of error-type-specific test measures, the determination of the individual faulty individual antenna provided. For this purpose, each drive path is advantageously selected sequentially via the drive unit and subjected to suitable test signals, for example a signal from the signal generator. By suitable evaluation of the diagnostic potentials measured at the reference points, it is possible to deduce the imperfection of the individual antenna.

The advantages achieved by the invention are in particular that a reliable identification of a single antenna is made possible for an antenna system of the type mentioned by the orientation of the error detection on a group diagnosis in a particularly simple design and low component costs. By using the isolating diodes, which ensure a reliable decoupling of the individual drive paths from one another, the upstream of the entire antenna system determination of the respective error type and only then an individualized troubleshooting using particularly suitable test measures is possible. This makes it possible to fully diagnose the individual antennas of the antenna system with particularly low component expenditure and also requires only a small amount of space on the respective component boards. Thus, such diagnosability is also possible for other multi-channel antenna systems, in which the individual antennas are acted upon by suitable single signal generator at the positive or negative pole.

FIG. 1

ein Zugangskontrollsystem für ein Kraftfahrzeug,

FIG. 2

schematisch ein Antennensystem,

FIG. 3

ein Flussdiagramm zum Ablauf eines Verfahrens zur Fehlererkennung,

FIG. 4

ein alternatives Antennensystem, und

FIG. 5

ein Flussdiagramm zum Ablauf eines Verfahrens zur Fehlererkennung gemäß FIG. 4.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

FIG. 1

an access control system for a motor vehicle,

FIG. 2

schematically an antenna system,

FIG. 3

a flowchart for the execution of a method for error detection,

FIG. 4

an alternative antenna system, and

FIG. 5

a flowchart for the operation of a method for error detection according to FIG. 4 ,

Identical parts are provided with the same reference numerals in all figures.

The access control system 1 according to FIG. 1 is provided for wireless authorization on access or for the operation of a motor vehicle 2 and can be configured in particular as a so-called "keyless entry" system for keyless opening and closing of the central locking of the motor vehicle 2. For this purpose, the access control system 1 comprises a mobile identification transmitter 4, which exchanges signals with a control system 6 arranged in the motor vehicle 2 by wireless means, for example via a suitably selected radio link. In this case, the control system 6 comprises an integrated, unspecified evaluation module, in which a code of the received signal is evaluated individually by means of appropriately stored software, in the case of a positive result of this evaluation of the received signals to a correct identification and thus to an authorization of User is closed. If such authorization is recognized, for example, the central locking of the motor vehicle 2 is activated.

However, such activation or deactivation of the central locking of the motor vehicle 2 can be made dependent on several factors. For example, it could be ruled out for safety reasons to close the central locking system of the motor vehicle 2 when the mobile identification transmitter 4 is located in the interior of the motor vehicle 2. The access control system 1 is therefore among others designed to distinguish due to the communication of the control system 6 with the mobile identification transmitter 4 between different states, which are assigned different release permissions. In order to make this possible, the access control system 1 comprises, inter alia, a plurality of antennas, via which the communication with the mobile identification transmitter 4 is handled. If it is determined, for example, that the communication with the mobile identification transmitter 4 takes place via an interior antenna of the access control system 1, it is possible to actively suppress the closing of the vehicle doors.

For signal exchange with the mobile identification transmitter 4, the control system 6 is therefore provided with a multi-channel antenna system 10, as shown schematically in FIG FIG. 2 is shown. In this case, the antenna system 10 comprises a plurality of individual antennas 14 each connected in a separate drive path 12, of which in the exemplary embodiment according to FIG FIG. 2 for the sake of clarity, only two are shown. Of course, the antenna system 10 can also comprise more than two, for example five, eight or more, separate drive paths 12 with corresponding individual antennas 14.

Signal input side, the Ansteuerpfade 12 are connected to a common signal generator 16, which may include in addition to a signal generator 18 for the intended signal data, protocols or the like other components such as a coupling coil 20 and in the respective Ansteuerpfad 12 coupling capacitors 21 or the like. For selective connection of a selected Ansteuerpfads 12, so for selectively selective connection of one of the Ansteuerpfade 12 with the signal generator 16, a drive unit 22 is further provided, which is formed in the embodiment as a multiplexer, in particular as a multiplexer transformer or shunt multiplexer. The signal generator 16 and the drive unit 22 are within of the respective drive path 12 are respectively connected via the resistor 28 to the so-called positive pole 24 of the respective individual antenna 14.

In the return region, ie via its so-called negative pole 26, each individual antenna 14 is connected within its Ansteuerpfads 12 each with a separating capacitor 30 which separates the negative pole 26 of the respective individual antenna 14 from ground.

The serving to adjust the Antennenkreisgüte resistor 28 can also be moved in the respective drive path 12 in front of said separation capacitor 30. The coupling capacitor 21 and the separating capacitor 30 are components of the antenna circuit (21, 14, 28, 30).

The antenna system 10 is designed for the case of failure, ie in the case of failure of one or more of the individual antennas 14, for a particularly targeted and simple error detection and identification of the faulty individual antenna 14. For this purpose, each drive path 12 in the region of the positive pole 24 of the respective individual antenna 14, that is to say between the signal generator 16 and the respective individual antenna 14, is electrically connected to a common first reference point 34 via an associated readout separating diode 32. The first reference point 34 is connected via a resistor 36 to ground. The readout separating diodes 32 are connected in such a way that the connection from the drive path 12 to the first reference point 34 of the forward direction and the connection from the first reference point 34 to the drive path 12 corresponds to the separation direction of the readout isolation diode 32.

Furthermore, the positive terminal 24 of each individual antenna 14, ie the area between the signal generator 16 and the respective individual antenna 14 of each control path 12, is electrically connected to a common contact point 44 via an associated feed-in separating diode 40 and a resistor 42. The feed-separating diodes 40 are connected in such a way that the connection from Contact point 44 to the respective drive path 12 of the forward direction and the connection from the respective drive path 12 to the contact point 44 of the separation direction of the respective feed-in separating diode 40 corresponds.

On the discharge side, ie via their respective negative pole 26, each drive path 12 of the respective individual antennas 14 is electrically connected to a common second reference point 52 via an associated readout separation diode 50. The second reference point 52 is connected via a resistor 54 to ground. The read-out isolating diodes 50 are in turn connected in such a way that the connection from the drive path 12 to the second reference point 52 corresponds to the forward direction and the connection from the second reference point 52 to the drive path 12 corresponds to the reverse direction of the respective readout isolation diode.

For fault detection in the event of a fault, ie to determine which individual antenna 14 is working incorrectly, the antenna system 10 is designed for a step-by-step diagnosis, in which the present error type is first determined jointly for all individual antennas 14 in a first diagnostic step in the manner of a group diagnosis before in a second diagnostic step, the faulty individual antenna 14 is determined on the basis of the determined error type on the basis of suitable test measures. The error types "short circuit to the supply voltage", "short circuit to ground" and "open load" state are used as the error types, the "open load" state of an electrical severing of the respective individual antenna 14, ie a defective electrical connection between the positive pole 24 and the negative pole 26 of the respective individual antenna 14, corresponds.

To determine a faulty individual antenna 14 using a group diagnosis in the determination of the error type is thereby proceeded to a test scheme, as shown in the flowchart according to FIG. 3 is shown. First, in a first test step 60 in a no-load condition, ie with inactive signal transmitter 16 and inactive drive unit 22, it is determined whether a voltage between the first reference point 34 and ground can be measured as the diagnosis potential. If this is the case, the error type is "supply short circuit" as a result of the group diagnosis.

For this case, each driving path 12 is then activated sequentially in the context of the individual diagnosis via the drive unit 22 sequentially by connecting the coupling capacitor 21 to the drive path 12 in each case to ground. If an error-free individual antenna 14 of the respective drive path 12 is thereby switched on, then the voltage measured between the first reference point 34 and ground as diagnosis potential is not changed because of the decoupling by the readout separating diodes 32. If, on the other hand, the drive path 12 with the faulty individual antenna 14 is actuated via the drive unit 22, then the voltage measured as the diagnosis potential at the first reference point 34 approaches zero due to the ground coupling of the multiplexer. As soon as this case occurs, the currently activated individual antenna 14 is thus identified as the faulty individual antenna 14.

If, on the other hand, no voltage can be measured between the first reference point 34 and ground in the first test step 60, a test voltage is applied to the contact point 44 in the course of the group diagnosis in a subsequent test step 62. Subsequently, it is checked whether a voltage between the first reference point 34 and ground can now be measured as a diagnosis potential. If no voltage between the first reference point 34 and ground can be measured, the error type "short to ground" is closed in the group diagnosis. In this case, it can now be determined in the context of the following individual diagnosis, which of the individual antennas 14 has the short circuit to ground.

For this purpose, a continuous signal is output via the signal generator 16. Subsequently, via the drive unit 22 sequentially switched on the Ansteuerpfade 12 selectively. In order to check the proper functioning of the respective individual antenna 14, a check is made at the second reference point 52 as to whether a voltage with respect to ground can be detected as the diagnosis potential. This voltage would then correspond to the antenna current through the respective individual antenna 14. If such an antenna current, corresponding to a voltage between the second reference point 52 and ground, can be measured, the proper operation of the respective individual antenna 14 is concluded. On the other hand, if the antenna current is equal to zero, then the currently connected individual antenna 14 is identified as a faulty individual antenna 14.

If, on the other hand, it was not possible to conclude the error type "short circuit to ground" within the scope of the group diagnosis, then the error type "Open Load" is assumed to end the group diagnosis. For this, in the context of the following individual diagnosis for each individual antenna 14, a sequential check is made as to whether a corresponding antenna current can be detected when the respective individual antenna 14 is acted upon by a test pulse. For this purpose, a continuous signal is in turn output via the signal generator 16. Subsequently, all the drive paths 12 are selectively switched on via the drive unit 22, wherein in each case for the current individual antenna 14 by means of a voltage measurement between the second reference point 52 and ground is checked whether an antenna current is detectable. If a voltage between the second reference point 52 and ground can not be measured for a single antenna 14 as a diagnosis potential, then the current individual antenna 14 is identified as a faulty individual antenna 14.

In the group diagnosis, test step 60, but also at the beginning of the test voltage can be applied to the contact point 44. As a result, in the non-fault case, for example, half the test voltage is applied. Depending on the fault, short circuit to supply or short circuit to earth the reference voltage 34 is greater or less than the example half test voltage.

In FIG. 4 an alternative antenna system 70 is shown in which there is also a multi-channel structure, but each drive path 12 is assigned a separate signal generator 18 each. The group diagnosis is carried out essentially analogously to the antenna system 10, wherein the individual diagnoses by selective transmission via individual antennas 14, ie via selective activation of the individual signal generator 18, and signal reset at the reference point 52 takes place.

A flow chart for performing the diagnosis in this antenna system is in FIG. 5 shown.

LIST OF REFERENCE NUMBERS

1

Access control system

2

motor vehicle

4

mobile identification transmitter

6

control system

10, 11

multi-channel antenna system

12

drive path

14

individual antennas

16

signaler

18

signal generator

20

coupling coil

21

coupling capacitor

22

control unit

24

positive pole

26

minuspol

28

resistance

30

isolating capacitor

32

Selecting isolation diode

34

first point of reference

36

resistance

40

Feed isolation diode

42

resistance

44

contact point

50

Selecting isolation diode

52

second reference point

54

resistance

60

first test step

62

following test step

70

antenna system

Claims (7)

1. An antenna system (10, 11) with a plurality of single antennae (14) which are connected in a separate triggering path (12), to which a shared signal transducer (16) is assigned, and with a triggering unit (22) for the selective connection of a triggering path (12) which is selected respectively,
   characterized in that
   each triggering path (12) is electrically connected between the signal transducer (16) and the respective single antenna (14) via an assigned selection separating diode (32) with a shared reference point (34) which is provided in order to tap as necessary a diagnosis potential.
2. A antenna system (10, 11) according to claim 1,
   characterized in that
   each triggering path (12) is electrically connected between the signal transducer (16) and the respective single antenna (14) via an assigned infeed separating diode (40) with a shared contact point (44) which is provided in order to apply a test voltage as necessary.
3. An antenna system (10, 11) according to either of claims 1 or 2,
   characterized in that
   each triggering path (12) is electrically connected in the return circuit area of the respective single antenna (14) via an assigned selection separating diode (50) with a shared second reference point (52) which is provided in order to tap a diagnosis potential as necessary.
4. An antenna system (10, 11) according to any one of claims 1 to 3,
   characterized in that
   the triggering unit (22) is designed as a multiplexer.
5. An access control system (1) for a motor vehicle (2), in which a control system (6) is provided for the signal exchange with a mobile identification transducer (4) is equipped with an antenna system (10, 11) according to any one of claims 1 to 4.
6. A method for determining a faulty single antenna (14) in an antenna system (10, 11) according to any one of claims 1 to 4, in which in a first diagnosis stage, a general error type is determined by measuring a diagnosis potential on the first reference point (34) and if appropriate, on the second reference point (52).
7. A method according to claim 6, in which following the determination of the error type in a second diagnosis stage, the faulty single antenna (14) is determined by the selective triggering and assigned evaluation of the respective diagnosis potential.

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