WO2007057071A1

WO2007057071A1 - Method for operating a sensor system, sensor system and sensor module

Info

Publication number: WO2007057071A1
Application number: PCT/EP2006/009256
Authority: WO
Inventors: Jürgen NIES; Thomas Schuler
Original assignee: Valeo Schalter Und Sensoren Gmbh
Priority date: 2005-11-15
Filing date: 2006-09-23
Publication date: 2007-05-24
Also published as: DE102005055964A1

Abstract

The invention relates to a method for operating a sensor system (100), in particular of a motor vehicle, according to which several sensor modules (110a, 110b, 110c, 110d, ..) are connected to a common bus system (150), one sensor module (110a) being configured as the master and the other sensor modules (110b, 110c, 110d,..) being configured as the respective slaves. According to the invention, the assignment of addresses to a specific sensor module (110b) is carried out in accordance with the signal propagation delay (?T) of a distance measuring signal (A), which is transmitted between the master (110a) and the specific sensor module (110b) via the bus system (150).

Description

Title: Method of operating a sensor system, sensor system and sensor module

description

The invention relates to a method for operating a sensor system, in particular a motor vehicle, in which a plurality of sensor modules are connected to a common bus system, and wherein a sensor module as a master and the other sensor modules are each formed as a slave.

The invention further relates to a sensor module according to the preamble of patent claim 19 and to a sensor system according to the preamble of patent claim 26.

Such methods, sensor modules and sensor systems are known in particular from the field of motor vehicles, where in many applications several similar sensors have to be connected to one another or to a control unit controlling them.

In conventional systems, factory pre-addressing of the sensor modules usually takes place to ensure their distinctness within a target system into which the sensor modules are incorporated. For example, a conventional sensor module already during its production process or at the end of the production process by assigning a corresponding individual identifier so individualized that thereby an assignment of the sensor module is given to a space provided for this purpose in a motor vehicle. A disadvantage of this method is the fact that in a subsequent installation of the sensor module in the motor vehicle, the sensor module must be installed exactly at the point in the motor vehicle that corresponds to the previously made individualization, creating a significant logistical effort.

To avoid misalignment in the installation of such sensor modules has already been proposed to make mechanical Poka-Joke precautions, so for example to attach a mechanical coding to the respective sensor module and the sensor module receiving holder, so that the mounting of a sensor module to a not for this purpose provided bracket is not possible. A disadvantage of such a solution is the increased effort required to provide the mechanical coding.

In addition, sensor systems are known in which each sensor module is connected via its own line with a central control unit or an evaluation unit. Due to this star-shaped topology, a considerable amount of cabling is required. Accordingly, it is an object of the present invention to improve a method of the type mentioned in that a sensor module of a sensor system in a simple manner an address corresponding to its installation position can be assigned, in particular without a previous individualization or coding of individual sensor modules is required.

This object is achieved in the method of the aforementioned type according to the invention in that the addressing of a specific sensor module in dependence on the signal propagation time of a distance measurement signal is performed, which is transmitted between the master and the specific sensor module via the bus system.

The addressing according to the invention as a function of a signal propagation time of signals transmitted between the master and a specific sensor module via the bus system allows a direct assignment of a predefinable address to a respective sensor module due to the equivalence of the signal propagation time and a distance between the master and the respective sensor module which is arranged at a certain distance from the master module designed as a sensor module.

In contrast to conventional systems, sensor modules which are completely identical to one another and not previously individualized or coded can therefore be connected to any desired one Positions are for example installed in a motor vehicle and then still be addressed and controlled depending on their actual position. Their respective position is determined after installation or commissioning of the sensor system according to the invention or at other predeterminable times according to the invention by running time measurements of signals transmitted via the bus system, so that, for example, in the master or in a connected to the master controller finally all mounting locations of the sensor modules along the bus system and in particular relative to the master are known.

On the known from conventional sensor systems logistical effort in the assembly of sensor modules at certain installation locations or Poka-Joke precautions can be completely dispensed with using the present invention accordingly.

As a result, on the one hand the installation of the sensor modules according to the invention is drastically simplified, on the other hand, the logistical effort in the other handling of the sensor modules is very low, since only a single sensor module type must be processed.

In an advantageous embodiment of the method according to the invention, a specific sensor module in a measuring mode connects signal lines of the bus system to one another via corresponding connecting means of predeterminable impedance. at a suitable choice of the impedance results in a discontinuity in terms of the line characteristics of the signal lines of the bus system, so that reflections arise in the transmission of signals on these signal lines. According to the invention, such reflections or the propagation time of reflected signals on the signal line sections between the master and the specific sensor module are used to determine the distance of the sensor module from the master transmitting the signals.

Particularly advantageously, the connecting means are designed so that they cause an idle in the measuring mode of the line formed from the signal lines or a short circuit of the line. In this case, a signal emitted, for example, by the master and arriving in the specific sensor module is reflected with a reflection factor of r = +1 or r = -1, so that a simple detection of the reflected signal is ensured.

The connecting means are advantageously designed as switches, preferably as semiconductor switches. Very advantageous is the use of a field effect transistor as a connection means.

In the measuring mode, for example, a field effect transistor can directly connect the signal lines of the bus system to one another connect and thus realize a short circuit of the line formed therefrom.

An idling of a line formed from the signal lines of the bus system can be realized, for example, in that in the particular sensor module the signal lines or their connections to other sensor modules are interrupted by corresponding switches.

A further very advantageous variant of the method according to the invention is characterized in that the master transmits the distance measuring signal to the predetermined transmission time via the signal lines of the bus system, and that the master receives a distance measuring signal reflected at the impedance of the connecting means of the specific sensor module at a receiving time. As described above, the impedance is preferably selected to be short-circuited or idle, or it may generally have a value significantly different from a characteristic impedance of the line formed from the signal lines of the bus system to achieve a sufficiently large reflection factor and hence easy detection of signals reflected at the impedance.

From the difference between the reception time and the transmission time, the signal propagation time of the distance measurement signal can advantageously be determined. Knowing the propagation velocity of electromagnetic waves The line formed from the signal lines of the bus system can thus be advantageously determined the physical distance between the master and the specific sensor module along the bus system.

In general, e.g. two existing signal lines of the bus system can be used as a transmission line for the transit time measurement according to the invention. Alternatively, an existing signal line and a ground line or the like may be used. It is also possible to extend a conventional bus system by one or more particular conductors, e.g. have a special characteristic impedance or other parameters which allow a particularly simple and reliable transit time measurement. In this case, the transit time measurement according to the invention can take place independently of a communication via the signal line (s) of the bus system.

In a further variant of the method according to the invention, it is very advantageously provided that a phase difference between the distance measurement signal emitted by the master and a distance measurement signal reflected at the impedance of the connection means of the specific sensor module and received by the master is evaluated by means of a phase locked loop (PLL).

The use of a phase-locked loop makes it possible by providing the phase difference between that of the Master emitted distance measurement signal and the reflected distance measurement signal, a particularly precise determination of the signal propagation time.

In a further embodiment of the method according to the invention, a control voltage of the phase-locked loop which is proportional to the phase difference is evaluated very particularly advantageously in order to determine the signal propagation delay.

When using a phase-locked loop, a possibly occurring phase rotation must be taken into account in the reflection of the distance measurement signal at the connection means.

According to a further variant of the invention, the sensor modules of a random addressing mode are each assigned a provisional address in a particularly advantageous manner. The introduction of a preliminary address for the sensor modules advantageously allows a targeted point-to-point communication between the master and the respective sensor modules and therefore can be used very particularly advantageous to put a particular sensor module in the measurement mode for determining the signal propagation time.

According to a further variant of the invention, the random addressing mode can be introduced particularly advantageously by virtue of the fact that the master has a corresponding address Send command via the bus system. This command is received by all sensor modules, which are preferably limited in their initial state to a monitoring of the communication of the bus system, and then in the respective sensor modules, the random addressing mode-related steps can be processed.

Particularly advantageously, a sensor module embodied as a slave signals its presence via the bus system during the random addressing mode after a randomly dependent waiting time. By using the random-dependent waiting time, the probability is increased that no collision of the presence messages of different slaves occurs.

If the presence message of a slave was successful, that is, if no collision occurred with the presence messages of other slaves, the master notifies the slave according to the invention a provisional address. From then on, the provisional address enables targeted point-to-point communication between the master and the slave.

According to the invention, the relevant slave no longer takes part in the random addressing mode, so that further slaves, to which no provisional address has yet been assigned, are still able to submit their presence messages after a corresponding randomly dependent waiting time, without this being the case already a provisional address exhibiting slave to be disturbed.

In the event of a collision of the presence messages of several slaves, for example, the slaves again determine a random-dependent waiting time before they in turn give a presence message to the bus system.

In a further very advantageous variant of the method according to the invention, the provisional address assigned to a slave is used to set this to the measuring mode.

Particularly advantageously, according to another variant of the invention, the master only places one sensor module designed as a slave into the measuring mode. In this way, successively all sensor modules can be successively and individually placed in the measuring mode, so that the respective signal propagation time or distance of the respective sensor module to the master can be precisely determined.

Another very advantageous variant of the method according to the invention is characterized in that a sensor module designed as a slave is assigned a final address depending on the distance. In this way, instead of the random addresses randomly distributed as described above, for example, the respective distance of the sensor module from the master corresponding final Addresses are introduced, whereby a particularly simple systematic control of the sensor modules is possible. For example, that sensor module may be assigned the lowest address which has the greatest distance to the master along the bus system, etc.

In order to avoid conflicts between the temporarily used provisional addresses and the final addresses, for example, an address range may be selected for the provisional addresses which will not be used later during the assignment or use of the final addresses.

Alternatively, each sensor module may already be assigned its final address using its tentative address, but release to use the final addresses will only be signaled centrally by the master via the bus system when all sensor modules have received a unique final address.

As a bus system according to the invention, for example, a CAN bus or a LIN bus can be used. As already described, advantageously existing signal lines of the bus system used can be used for the transit time measurement according to the invention. Alternatively or additionally, however, ground lines, supply voltage lines or specially provided additional lines (with) can be used. The Connecting means according to the invention or further components for realizing the predeterminable impedance of the connecting means are to be interpreted respectively.

According to another very advantageous variant of the invention, the bus system is designed as a linear bus system. In this case, in particular with an arrangement of the master at one end of the bus system, a particularly simple distance determination according to the invention is possible, since determined signal propagation times can be unambiguously assigned to corresponding distances.

If the sensor module embodied as a master is not arranged at one end of the bus system, it may be advantageously provided that sensor modules arranged on either side of the master have distances with respect to the bus which differ from one another with respect to the bus system in order to distinguish or unambiguously determine the distance and the assignment of the Sensor modules to allow appropriate position.

Although the method according to the invention is preferably used with a bus system of linear topology, an application of the principle according to the invention to bus systems with ring topology or with other arrangements is also conceivable. In this case, appropriate measures must be taken in each case to obtain clear signal transit times between a master and the other sensor modules, which, for example, by a special arrangement of the sensor modules along the bus system can be achieved.

Alternatively, in order to establish unambiguity in the determination of the distance according to the invention, the respectively required propagation time measurement can also be carried out with respect to two different sensor modules used as a reference point, which respectively emit the distance measuring signal according to the invention. The respective sensor modules are in this case at least temporarily configured as a master.

In general, advantageously, each of the preferably identically designed sensor modules take over the role of the master. If a central control unit is provided which, for example, evaluates the sensor data collected by the sensor modules of the sensor system according to the invention, this central control unit can also provide the functionality of the master.

As a further solution of the object of the present invention, a sensor module according to claim 19 is given.

The sensor module according to the invention very advantageously has connection means via which signal lines of the bus system can be connected to one another with a predeterminable impedance. In this way, as already described, a discontinuity in wave propagation on the signal lines of the bus system are generated, which allows the reflection of, for example, a distance measuring signal and thus an evaluation of signal propagation times. Particularly advantageously, the connecting means to a switch, in particular a semiconductor switch, which is preferably designed as a field effect transistor.

In a further very advantageous variant of the invention, the functionality of the bus transceiver for connecting the sensor module to the bus system is integrated in an application-specific integrated circuit (ASIC). Particularly in the case of a bus system embodied as a LIN bus, a simple implementation of the functionality of the bus transceiver in the ASIC is possible due to the relatively simple bus protocol, wherein, in addition, further advantages are given by the fact that other functionalities, for example also the functionality, are simultaneously included in the ASIC the connecting means can be integrated. For example, designed as a field effect transistor connection means can be directly ^"integrated into the ASIC so that the space required for the implementation of the principle of the invention components is minimized.

The sensor module according to the invention is particularly advantageously suitable for carrying out the method according to the invention. In a further very advantageous variant of the invention, it is provided that the sensor module has one or more ultrasonic sensors and / or radar sensors and / or optical and / or other sensors. In particular, in the application of the sensor module according to the invention or the operating method according to the invention in

Motor vehicle sector, the advantages of the invention, which are in a particularly simple position or distance-dependent addressing of the sensor modules, are optimally used. For example, completely identical, not previously individualized sensor modules can be installed in a bumper of a motor vehicle, and an addressing of the individual sensor modules, e.g. is dependent on the distance of the respective sensor module to a master or a control unit, can be done due to the inventive delay determination of the distance measurement signal.

As yet another solution to the object of the present invention, a sensor system according to claim 26 is provided.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All features described or illustrated alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing.

In the drawing shows:

FIG. 1 shows a schematic block diagram of a first embodiment of the sensor system according to the invention,

FIG. 2 shows a detailed view of a plurality of sensor modules according to the invention and their connection to the signal lines of a bus system,

FIG. 3 shows a flowchart of a first embodiment of the method according to the invention,

FIG. 4 shows a flowchart of a further embodiment of the method according to the invention,

FIG. 5 shows the time profile of a bus communication in a further embodiment of the method according to the invention; and

Figure 6 is a simplified block diagram of a

Embodiment of the sensor module according to the invention.

FIG. 1 shows a schematic block diagram of a sensor system 100 according to the invention, as described, for example, in US Pat Applications from the automotive sector is used. The sensor system 100 has a plurality of sensor modules 110a, 110b, 110c, 11Od, .., which are interconnected via a bus system 150. The sensor modules 110a, 110b, 110c, 11d, each have one or more ultrasonic sensors (not shown) and / or radar sensors and / or optical and / or other sensors.

With regard to a communication taking place via the bus system 150, the sensor module 110a is designed as a master, while the further sensor modules 110b, 110c, 11d, .. are each configured accordingly as a slave. Otherwise, the sensor modules 110a, 110b, 110c, 11Od, .. are formed completely identical.

According to the invention, the slaves 110b, 110c, 11Od, .. starting from an initial state, such as is given directly after the installation of the sensor modules 110a, 110b, 110c, 11Od, .. in a motor vehicle, assigned by the master 110a first provisional addresses , which is illustrated by step 200 of the flowchart depicted in FIG. Subsequently, according to step 210 of FIG. 3, signal propagation times of signals transmitted via the bus system 150 between the master 110a and each of the slaves 110b, 110c, 11dd, .. are determined, which are used to determine a distance of the respective slave 110b, 110c, 11dd,. from the master 110a. Thereafter, the slaves 110b, 110c, 11Od, .. assigned by the master 110a final addresses, compare step 220 of Figure 3, which advantageously depend on the distance of the respective slave or sensor module to the master 110a.

The assignment 220 according to the invention of an address dependent on the distance to the master 110a enables a simple systematic addressing of the slaves 110b, 110c, HOd.

At the same time, it is unnecessary for the invention to be based on the determination of signal propagation times

Distance determination 210 of the known from conventional sensor modules logistical effort to place certain sensor modules in certain mounting positions. Rather, during the operation of the sensor system 100 according to the invention, the distance of each sensor module HOb, HOc, HOd can be determined by the master HOa, whereby the knowledge of the topology of the bus system 150 to the corresponding mounting position of the respective sensor module HOb, HOc, HOd can be concluded. ...

Since there is usually no information about the actual installation position of the sensor modules HOb, HOc, HOd before the distance determination 210, the temporary use of provisional addresses according to step 200 from FIG. 3 is expedient. The assignment of a provisional address to a sensor module 110b designed as a slave is explained in more detail below with reference to the flowchart in FIG.

First, the master 110a (FIG. 1) initiates the random addressing mode according to the invention by transmitting a corresponding command via the bus system 150 in step 201 of the flowchart depicted in FIG. After receiving this command, the slave 110b generates a randomly dependent waiting time in step 202 according to the invention, after which it outputs a presence message via the bus system 150 in step 203 in order to indicate to the master 110a its presence in the sensor system 100.

In step 204, the master 110a receives the presence notification of the slave 110b and assigns a provisional address to the slave 110b. The slave 110b stores the provisional address assigned to it in the step 205 and hence does not continue to participate in the random addressing mode according to the invention. As a result, the further slaves 110c, 11Od, .. are also enabled to output a presence message to the bus system 150 without being disturbed by the slave 11-o-initiated communication.

After a provisional address has been allocated to all slaves 110b, 110c, 11Od, .. in the context of the random addressing mode according to the invention, the master 110a (FIG. 1) successively activates the measuring mode of each slave 110b, 110c, 11Od,. For this purpose, the master 110a establishes a point-to-point connection to the slave 110b, for example, using the respective provisional address of the relevant slave 110b, 110c, 11Od,. This situation is illustrated in the diagram shown in FIG. Additional slaves 110c, 11Od are not involved in the communication described below.

In the context of the point-to-point connection between the master 110a and the slave 110b, the master 110a first sends a command 211 to the slave 110b to activate its measurement mode. Subsequently, the slave 110b may send back a corresponding acknowledgment 211a to the master 110a. As an alternative to the confirmation 211a, the slave 110b can also simply assume its measuring mode for a predeterminable time.

Here, as illustrated in FIG. 2, the slave 110b connects the signal lines 150a, 150b of the bus system 150 (FIG. 1) supplied to it via connection means 111b correspondingly provided in the slave 110b, which in the present example is in the form of a switch which, for example, a field effect transistor is realized are formed. As a result of this low-resistance connection of the signal lines 150a, 150b, which represents approximately a short circuit, a discontinuity arises in the line formed by the signal conductors 150a, 150b, which causes a reflection of signals propagating on the line causes. In the present case, for example, the discontinuity has a reflection factor of approximately -1, ie a signal arriving on the slave 110b is reflected with a phase shift of 180 °.

By taking advantage of this effect, a signal sent out from the master 110a at the time t1 (FIG. 5) is also emitted

Distance measurement signal A, which at the time t2 at the slave

110b, in which slave 110b reflects, and accordingly passes back as a reflected distance measurement signal A 'to master 110a, which receives this reflected distance measurement signal A' at time t3.

Due to the signal propagation time AT = t3-tl, a physical distance 11 of the slave 110b from the master 110a along the bus system 150 can be determined with knowledge of the propagation speed of electromagnetic waves on the bus system or on the line formed by the signal lines 150a, 150b (FIG ,

In the same way, by the master 110a, the distance 12, 13, .. of the other slaves 110c, 10d, .. can also be determined by the master 110a. For this purpose, the corresponding slaves 110c, 11Od, .. after taking the measuring mode in each case via their connection means 111c, llld from a required for the transit time measurement discontinuity of the line 150a, 150b. After the respective distance determination, the relevant slave, as illustrated by way of example in FIG. 5 for the slave 110b, can be assigned a final address by way of the message 212, which depends on the previously determined distance 11 of the slave 110b from the master 110a. See also step 220 of the flowchart shown in Figure 3.

In a very advantageous embodiment of the present invention, a phase difference between the distance measuring signal A emitted by the master 110a (FIG. 5) and the impedance of the connecting means 111b (FIG. 2) of the sensor module 110b in the measuring mode is reflected, and then by the master 110a received

Distance measurement signal A 'by means of a phase locked loop (PLL, phase locked loop) evaluated. In this case, a control voltage of the phase-locked loop which is proportional to the phase difference can be evaluated particularly advantageously in order to determine the signal propagation time ΔT.

When using a phase-locked loop for determining the signal propagation time ΔT, any phase jumps that may occur are to be taken into account in the reflection of the distance measurement signal A at the impedance realized by the connection means 111b. For example, with a formation of the impedance as a short circuit and a corresponding reflection factor of -1, a phase jump of the Distance measurement signal A of 180 ° occur in the subsequent evaluation of the reflected

Distance measurement signal A 'in the phase locked loop is observed.

FIG. 6 shows a simplified block diagram of a sensor module 110 according to the invention which has a bus transceiver 112 which enables a connection of the sensor module 110 to the bus system 150 and a corresponding communication via the bus system 150. Particularly advantageously, the functionality of the bus transceiver 112 can also be integrated in an application-specific integrated circuit (ASIC). In this case, the functionality of the connection means 111b (FIG. 2), for example in the form of a field-effect transistor, may also be integrated into the ASIC, so that no further, separate components are required for implementing the inventive principle in the sensor module 110 are.

^'"Of ^the" excitement ^"of ^the" bus system ^{^"l"} 50 ^~ i ^{^"st'} e ^'s ^special" beneficial ^{^"In"} when the one sensor module that the role is to take over the master 110a, is arranged at one end of the bus system 150, see Figure 2, so that in the measurement of the signal propagation times between the master 110a and the various slaves 110a, 110b, 100c, 11Od, .. unique Give values for the signal propagation times and therefore the simplest possible determination of the distance 11, 12, 13 of the respective slave 110b, 100c, 11Od, .. of the master 110a is possible.

In another embodiment of the present invention, it is also possible to provide the sensor module designed as a master between sensor modules designed as a slave. In this case, the slaves arranged on both sides of the master are preferably spaced from the master in such a way that different distances and thus also different signal propagation times occur in each case.

Although the bus system 150 is preferably designed as a linear bus system, the application of the principle according to the invention can also be transferred to non-linear bus systems which have, for example, an annular or star-shaped topology.

Particularly advantageously, the bus system 150 is designed as a CAN bus or LIN bus. When using a LIN bus as the bus system 150, the signal line of the LIN bus and a further signal line provided for this purpose are used for the distance measurement according to the invention in order to be able to exploit the transit time properties of a transmission line formed therefrom. In order to further increase the flexibility of the sensor module 110 (FIG. 6) according to the invention, each sensor module 110a, 110b, 11Od,... May also have the means required for determining the signal propagation time, such as a phase locked loop and the like, so that even after incorporation of the invention Sensor modules, for example, in a bumper of a motor vehicle or the like can still be determined which of these sensor modules takes over the functionality of the master 110a.

For example, in a corresponding

Initialization of waiting for their functionality as master or slave not yet diversified sensor modules of each sensor modules after applying a supply voltage a randomly waiting time before it sends a special command on the bus 150, which signals the other sensor modules that the sensor module in question as a master 110a configured. Upon receipt of such a command, the remaining sensor modules can proceed, for example, directly into the already described above random addressing mode, or comply with this, also alternatively, ^"a bus idleness until the master 110a initiates the random addressing mode explicitly by another command.

The complete similarity of the sensor module with respect to its possible functionality as master or slave results in a particularly high fault tolerance of the invention Sensor system, because a failing example, due to a fault master 110a can be easily replaced by a previously configured as a slave sensor module.

Moreover, the transit time measurement according to the invention for determining the distances 11, 12, 13 (FIG. 2) can also be carried out by a plurality of sensor modules at least temporarily configured as masters, in order, for example, to generate the data. to be able to determine clear distance values even with bus systems 150 with non-linear topology.

As a distance measuring signal A, for example, a simple rectangular pulse can be used. Other signals that enable a transit time measurement according to the invention or a phase comparison by means of PLL are also suitable for distance measurement.

Particularly advantageously, the distance measuring signal A is generated directly by means of the bus transceiver 112 provided in the sensor module 110, for example by transmitting a specific data pattern. Alternatively, in the sensor module 110, a separate pulse generator (not shown) and an optionally required amplifier for generating the distance measurement signal A may be provided. The pulse generator, the amplifier and any PLL for evaluating the reflected distance measuring signal A 'can advantageously also be provided in an ASIC of the sensor module 110. The inventive principle of addressing bus subscribers as a function of a signal propagation delay is not limited to the application in sensor systems, but can generally be applied to all conceivable bus systems in which runtime effects on signal lines of the bus system can be utilized for distance determination.

Claims

claims

1. A method for operating a sensor system (100) in particular of a motor vehicle, in which a plurality of sensor modules (110a, 110b, 110c, 11Od, ..) are connected to a common bus system (150), and wherein a sensor module (110a) as the master and the further sensor modules (110b, 110c, 11Od, ..) are in each case designed as slaves, characterized in that the addressing of a specific sensor module (110b) is carried out as a function of the signal propagation time (.DELTA.T) of a distance measuring signal (A) between the master (110a) and the particular sensor module (110b) is transmitted via the bus system (150).

2. The method according to claim 1, characterized in that the particular sensor module (110b) in a measuring mode signal lines (150a, 150b) of the bus system (150) via corresponding connecting means (111b, 111c, llld) of predeterminable impedance to each other, wherein the connecting means in particular as a switch, preferably as a semiconductor switch, in particular as a field effect transistor are formed.

3. The method according to claim 2, characterized in that the master (110a) the distance measuring signal (A) at a predefinable transmission time (tl) via the signal lines

(150a, 150b) of the bus system (150), and that the master (110a) receives at a time of reception (t3) a distance measuring signal (A ') reflected at the impedance of the connecting means (111b) of the particular sensor module (110b).

4. The method according to claim 3, characterized in that from the difference between the reception time (t3) and the transmission time (tl), the signal propagation time (.DELTA.T) is determined.

5. The method according to any one of claims 2 to 4, characterized in that a phase difference between the of the master (110a) emitted distance measuring signal

(A) and at the impedance of the connecting means (111b) of the particular sensor module (110b) reflected and received from the master (110a) distance measuring signal (A ') is evaluated by means of a phase locked loop.

6. The method according to claim 5, characterized in that a proportional to the phase difference control voltage of the phase locked loop is evaluated to determine the signal propagation time (.DELTA.T).

7. The method according to any one of the preceding claims, characterized in that the sensor modules (110a, 110b, 110c, 11Od, ..) in a random addressing each provisional addresses are assigned, in particular before a determination of the signal delay time (.DELTA.T) between the Master (110a) and the respective sensor module (110a, HOb, HOc, HOd, ..).

8. The method according to claim 7, characterized in that the random addressing mode is initiated by the master (HOa) sends out a corresponding command via the bus system (150).

9. The method according to any one of claims 7 to 8, characterized in that a designed as a slave sensor module (HOb, HOc, HOd, ..) signals its presence via the bus system (150) after a random waiting time.

10. The method according to any one of claims 7 to 9, characterized in that a designed as a slave sensor module (HOb, HOc, HOd, ..), which has already received a preliminary address, no longer participates in the random addressing mode.

11. The method according to any one of claims 2 to 10, characterized in that the master (HOa) only one sensor module designed as a slave (HOb, HOc, HOd, ..) into the measuring mode.

12. The method according to any one of claims 7 to H, characterized in that the provisional address of a trained as a slave sensor module (HOb, HOc, HOd, ..) is used to put this in the measuring mode.

13. The method according to any one of claims 2 to 12, characterized in that successively designed as a slave sensor modules (110b, 110c, 11Od, ..) are placed in the measuring mode.

14. The method according to any one of the preceding claims, characterized in that a distance (11, 12, 13) between a trained as a slave sensor module (110b, 110c, 11Od) and the master (110a) in dependence of the signal propagation time (.DELTA.T) is determined ,

15. The method according to claim 14, characterized in that a trained as a slave sensor module (110b, 110c, 11Od) depending on the distance (11, 12, 13) is assigned a final address.

16. The method according to any one of the preceding claims, characterized in that a CAN bus or a LIN bus is used as the bus system (150).

17. The method according to any one of the preceding claims, characterized in that the bus system (150) is designed as a linear bus system.

18. The method according to any one of the preceding claims, characterized in that the master (110a) is arranged at one end of the bus system (150).

19. Sensor module (110, 110a, 110b, 110c, 11Od, ..) with a bus transceiver (112) for connecting the sensor module (110, 110a, 110b, 110c, 11Od, ..) to a bus system (150), in particular a bus system (150) of a

Motor vehicle, characterized by connecting means (111b, 111c, llld), via the signal lines (150a,

150b) of the bus system (150) with a predeterminable

Impedance are connectable to each other.

20. sensor module (110, 110a, 110b, 110c, HOd, ..) according to claim 19, characterized in that the connecting means (111b, IHc, llld) comprise a switch, in particular a semiconductor switch.

21. Sensor module (110, HOa, HOb, HOc, HOd, ..) according to claim 20, characterized in that the semiconductor switch is designed as a field effect transistor.

22. Sensor module (HO, HOa, HOb, HOc, HOd, ..) according to any one of claims 19 to 21, characterized in that the functionality of the bus transceiver (112) in an application-specific integrated circuit, ASIC, is integrated.

23. Sensor module (HO, HOa, HOb, HOc, HOd, ..) according to claim 22, characterized in that the application-specific integrated circuit and the connecting means (HIb, IHc, llld) or at least parts of the connecting means (HIb, IHc, llld ) having.

24. Sensor module (110, 110a, 110b, HOc, HOd, ..) according to one of claims 19 to 23, characterized in that the sensor module (110, HOa, HOb, HOc, HOd, ..) for carrying out the method according to one of claims 1 to 18 is suitable.

25. Sensor module (HO, HOa, HOb, HOc, HOd, ..) according to any one of claims 19 to 24, characterized by one or more ultrasonic sensors and / or radar sensors and / or optical and / or other sensors.

26. Sensor system (100) in particular of a motor vehicle, characterized by one or more sensor modules (HO, HOa, HOb, HOc, HOd, ..) according to one of claims 19 to 25.

27. Sensor system (100) according to claim 26, characterized in that the sensor system (100) is suitable for carrying out the method according to one of claims 1 to 18.