GB2534034A - Ultrasonic measuring system, means of transportation and method for operating an ultrasonic transmitter-receiver device - Google Patents

Abstract

An ultrasonic transmitter-receiver emits a signal representing a code word from an ultrasonic sensor 100 and another signal from another ultrasonic sensor 200 as part of a measuring cycle. Both sensors belong to the same group of ultrasonic sensors. A third ultrasonic sensor receives echoes from the two signals 300 and distinguishes components from the two ultrasonic sensors by decoding the codeword contained in one of the signals 400. The device is particularly suited as a parking aid for a car. The sensors belonging to the same group may be spatially arranged to receive cross echoes from each other. The other signal may represent another codeword. The codeword may be made of a time signal portion which is distinguished by matched filtering and successive code words may be distinguishable from one another by frequency related parameters. A third signal may be emitted representing a third codeword 500, from the original sensor as part of a second measuring cycle and/or a fourth signal representing the original codeword may be emitted from a third ultrasonic sensor.

Description

Description Title

Ultrasonic measuring system, means of transportation and method for operating an ultrasonic transmitter-receiver device

Prior art

The present invention relates to an ultrasonic measuring system, a means of transportation and a method for operating an ultrasonic transmitter-receiver device for a means of transportation. In particular, the present invention relates to improvements in the signal detection and processing by coding.

The use of ultrasonic transmitter-receiver devices ("ultrasonic sensors" for short) has been known for many years in motorcar manufacture for the environment detection and distance measurement. Driver assistance functions are likewise frequently based on ultrasonic sensors which are typically provided in clusters of 4 to 6 per bumper on the means of transportation ("vehicle" hereinbelow for simplicity).

DE 10 2008 007 667 Al discloses a method for operating a parking aid system in which ultrasound-based distance sensors are activated in two different modes with temporally different transmission sequences. In particular, for the switchover it is proposed to use a dependence on the vehicle speed.

EP 1 105 749 B1 shows a device for detecting objects by means of ultrasonic transmiu_ter-receivers, by which the transmission signals are provided with an identifier variable with time, which identifier is varied in particular on the basis of a random function. In order to prevent a waiting time calculated for the evaluation from resulting in a simultaneous interruption of a plurality of systems and a subsequently renewed superimposition, it is further proposed that after a detected superimposition of two systems a randomly controlled waiting time is provided. Also the choice of a new carrier frequency for preventing interference of two systems is to take place randomly, in order to prevent the two systems from interfering with one another even after the change of carrier frequency.

DE 10 2011 109 830 Al discloses a method for determining the origin of a reception signal received by an ultrasonic sensor of a motor vehicle, in which differently coded transmission signals are investigated after the reception of their reflection and the code word contained is extracted. Subsequently, the extracted code word is compared with the code word used for coding the transmission signal. A correlation can thus be omitted.

Today's ultrasonic systems:,ypically operate with a fixed working frequency in the range of 40 kHz to 50 kHz for the transmitting and receiving operation. The identical working frequency for all sensors ensures that a cross-echo operation is possible, i.e. a sensor can receive echoes on the frequency of the transmitting neighbouring sensor. In order to use the cross-echo information in a parking aid system correctly, the unique assignment to the transmitting sensor is necessary. A multiple transmission of sensors with unique assignment of the echoes to the sensor is only possible if this can be ensured by virtue of the geometrical conditions of the sensor installation positions, e.g. front/tail or central sensors in relation to the laterally mounted sensors. In today's systems this limits the measuring update rate of the system (measuring cycles per unit of time), since typically four front or tail sensors have overlapping "visual ranges" or detection ranges and thus cannot transmit simultaneously in one measuring cycle. Moreover, owing to the use of only a fixed working frequency, limitations in the detection robustness arise, for example, due to low interference immunity to ultrasonic signals from other vehicles. It is therefore an object of the present invenr_ion to mitigate or eliminate the disadvantages identified above.

Disclosure of the invention

The above-identified object is achieved in accordance with the invention by a method for operating an ultrasonic transmitter-receiver device. The ultrasonic transmitter-receiver device can be configured in particular for use in a vehicle (motorcar or the like). It comprises, as described above, a plurality of ultrasonic sensors which are arranged relative to one another in such way that at least their detection ranges (possibility of receiving an echo signal which originates from a neighbouring sensor) partially overlap one another. In a first step a first signal representing a first code word is emitted by means of a first ultrasonic sensor of a first group of ultrasonic sensors in a first measuring cycle. By a first measuring cycle is understood such a period of time in which an ultrasonic signal has been emitted by the ultrasonic transmitter-receiver device and a first echo on the signal from the environment has been received in the ultrasonic transmitter-receiver device. According to the invention, the first signal is modelled in such a way that its signal properties with respect to time are detectably and reconstructibly changed. In other words, the first signal bears a kind of "fingerprint" which enables a unique assignment of echoes based Thereon to the source ultrasonic sensor. Subsequently a second signal is emitted into the environment by means of a second ultrasonic sensor of the first group or of another group. The second signal can likewise have a code word which then, however, differs from the first signal. Subsequently echoes of the first signal and of the second signal are received by means of a third ultrasonic sensor, it being possible for the third ultrasonic sensor to be, for example, the first and/or the second ultrasonic sensor. Alternatively the first and the second ultrasonic sensor may also be understood respectively as the third ultrasonic sensor with regard to the receiving operation. Alternatively the third ultrasonic sensor may be an ultrasonic sensor present additionally to the first and the second ultrasonic sensor. Optionally at least the echo of the first signal and/or the echo of the second signal may be received additionally by a fourth ultrasonic sensor. Subsequently components originating from the first signal are distinguished from components originating from the second signal by means of a decoding of the code word. This may be done, for example, by means of a matched filtering. In This case, the time profile of the filter is matched to the time profile of an expected signal, whereby echo signal components differing greatly from the first signal are suppressed in the filter output signal. Subsequently each component of the signals contained in the received echo can be assigned to a corresponding transmission operation or ultrasonic sensor as source sensor and an investigation of the environment can be carried out e.g. on The basis of the signal propagation time, the echo strength etc. according to the prior art. In this way, more ultrasonic signals can be emitted and echoes received per unit of time, whereby the spatial and temporal resolution for an ultrasonic transmitter-receiver device according to the invention can be considerably increased compared with the prior art. In this case the information on the environment becomes more precise and reliable.

The subclaims provide preferred developments of the invention.

Preferably, the ultrasonic sensors of the first group are arranged in such a way that they are adapted to receive cross echoes from one another. This may apply in particular to all ultrasonic sensors of a group. In other words, one member of the group may receive at least one echo of a further member of the group, preferably of all members of the group, provided that the reflecting object is suitable for this.

The second signal may represent a second code word. In order to achieve good detection reliability in the distinguishing of components of the echo originating from the first signal with respect to components of the echo originating from the second signal, the characters of the first code word may respectively consist of such a signal portion, the properties of which with respect to time are always to be distinguished from the second signal by means of a matched filtering. This eliminates the possibility of characters of code words, whose echoes potentially fall on an identical ultrasonic sensor, being superimposed on one another in such a way that a unique assignment to a source ultrasonic sensor is prevended. An example of such code words are orthogonal codes. For example, two signals separated from one another for the first and the second code word may also be used. This considerably increases the detection and assignment of the received echoes and enables better immunity to mutual interference of the ultrasonic sensors.

In particular, it can be ensured that successive time signal portions are distinguished from one another with regard to a fundamental frequency, and/or a fundamental frequency profile, in particular with regard to an initial frequency and/or a target frequency and/or with regard to a frequency change direction and/or with regard to a frequency change speed and/or with regard to a frequency range (e.g. characterised by a lower and an upper limit frequency or by an initial frequency and a target frequency), so that they can be identified by a matched filtering after the reception of an echo. Owing to individual ones or a combination of the aforementioned signal properties, differenp identifiers or code words for the signals used in the ultrasonic transmitter-receiver device according to the invention can be uniquely characterised and distinguished from one another by suitable (digital and/or analog) filtering.

The second signal may, for example, be characterised by a substantially shorter duration and/or an amplitude differing considerably from the amplitude of the first signal. In particular, a shorter duration may result, in the case of close-range detections, in quicker results for a unique identification of corresponding echo signals being available and the close-range detection limit being considerably reduced. As a result, distances to very close environment objects can be indicated earlier and if necessary corresponding warnings issued earlier. A warning indication can also be issued well in advance in the case of objects moving relatively in the direction of the ultrasonic sensor system.

It is made possible here for an evaluation of an echo originating from the second signal to be completed already at an instant at which an evaluation of the first signal is still continuing. This may also occur when both the first and the second signal are reflected by an identical environment object. In particular, the emitting of a greatly shortened signal may be advantageous when the same ultrasonic sensor is to be used for receiving the corresponding echo and therefore its membrane has to have fallen below a predefined oscillation amplitude before a reliable detection of the echo compared with the dying-out signal can take place.

To prevent code-specific incerference over an extended period of time, a method can be employed which shall be referred to as "code toggling" in the context of the present invention. In this method, in a second measuring cycle which in particular directly follows the first measuring cycle, a third signal representing a third code word is emitted by means of the first ultrasonic sensor of the first group of ultrasonic sensors. This first ultrasonic sensor had, in a preceding measuring cycle as described above, emitted the first code word. If, for example, the first code word and the third code word lie in different frequency ranges, in particular disjoint frequency ranges, narrow-band interference (e.g. due to an external ultrasonic signal) can interfere with only one of the two code words in such a way that reliable detection of its echoes is not possible. Even in the event of continuing interference, however, at least one of the emitted code words results in an echo which can be reliably detected and used for environment detection.

Further, the method according to the invention may comprise an emitting of a fourth signal representing the first code word by means of a fourth ultrasonic sensor of a second group. The ultrasonic sensors of the first group may be spatially arranged relative to those of the second group in such a way that they are no suitable for receiving echoes which are based on ultrasonic signals originating from the second group. In other words, the first code word is emitted simultaneously by the first ultrasonic sensor and by the fourth ultrasonic sensor during the first measuring cycle, so that the multiplicity of code words can be reduced and their character spacing can be increased. This increases the detection reliability. Owing to the fact that a cross talk between the first group and the second group cannot occur, already for geometrical considerations, the detection reliability is by no means reduced by the simultaneous use of the first code word.

Preferably, a cruising speed of the ultrasonic transmitter-receiver device (which is arranged, for example, in a motorcar) may be compared with a predefined reference and in response to the result a code word to be transmitted by the first ultrasonic sensor can be selected in a temporally following measuring cycle from a predefined multiplicity of code words. For example, the length of the code word may be adjusted in order to be able to maintain, at a cruising speed above the predefined reference, the prewarning time up to a collision by using a short code word or a plurality of short code words. As described above, a long code word at a high cruising speed might require a time-consuming detection, during which the environment object and the collision instant come dangerously close. In this way, the update speed and the detection range can be improved at the cost of lower interference suppression.

According to the invention, it is assumed that the ultrasonic sensors used are capable of emitting a coded transmission signal and simultaneously receiving and detecting a plurality of exr_ernal codes of neighbouring sensors. This may take place, for example, by linear frequency ramps and the use of correlation methods in the reception unit. By additional jittering of the order of the code words used and by addir_ional variation of the codes and by using a stochastic waiting time between the individual transmission pat:,erns (all the aforementioned properties can be combined individually or in any desired combination with one another), an additional detection robustness reserve can be obtained. In this way, for example, external ultrasonic sources or internal interference, caused by undesired reflections, can be suppressed.

According to a second aspeco of the present invention, there is proposed an ultrasonic measuring system which has a first group of ultrasonic sensors having a first ultrasonic sensor and a second ultrasonic sensor and a second group of ultrasonic sensors having a third ultrasonic sensor. The ultrasonic sensors of the first group are arranged geometrically in such a way relative to those of the second group that they are not suitable for receiving echoes of signals of the second group. In other words, a reception of cross echoes under any technically appropriate use conditions is (almost) eliminated. Further, the ultrasonic measuring system is adapted to carry out a method according to one of The preceding claims. The features, feature combinations and the advantages arising therefrom correspond to those of the above-described method according to the invention in such an apparent manner that reference is made to the above statements to avoid repetition.

According to a third aspect of the present invention, there is proposed a means of transportation, in particular a vehicle (e.g. a passenger car, a van, a lorry, an aircraft and/or a watercraft), which has an ultrasonic measuring system according to the second-mentioned aspect of the invention. The means of transportation may use the ultrasonic measuring system for outputting user information and/or for the operation of any desired driver assistance systems. Regarding the means of transportation also, reference is made to the features, feature combinations and the advantages of the above-described aspects of the invention.

Contrary to the prior art, The present invention therefore proposes not only the jittering and a stochastic waiting time of the transmitter drives of different ultrasonic sensors. Rather, owing to the clever choice of codes ("code words") and a corresponding connection of the ultrasonic sensors in the combined sys7em as "transmitter", "receiver" or as 'transmitter and receiver" to realise the above-described advantages, the ultrasonic measuring system is used in such a way that the immediate close range and the far range of the environmenc can be covered and a multiple transmission in overlapping detection ranges of the sensors becomes possible. Optionally, owing to the code toggling, the detection reliability in the sense of a suppression of incorrect object detections is increased.

Brief description of the drawings

Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings, in which: Figure 1 is a schematic system overview of an ultrasonic measuring system configured in accordance with the invention; Figure 2 is a first table, which represents a first operating mode of an ultrasonic measuring system configured in accordance with the invention; Figure 3 is a second table, which represents an alternative operating mode of an ultrasonic measuring system configured in accordance with the invention; Figure 4 is a third table, which represents an alternative operating mode of an ultrasonic measuring system configured in accordance with the invention; Figure 5 is a fourth table, which represents an alternative operating mode of an ultrasonic measuring system configured in accordance with the invention; Figure 6 is a fifth table, which represents an alternative operating mode of an ultrasonic measuring system configured in accordance with the invention; and Figure 7 is a flow diagram illustrating steps of an exemplary embodiment of a method according to the invention.

Embodiments of the invention Figure 1 shows a schematic plan view of an exemplary embodiment of an ultrasonic measuring system 20 according to the invention, which has ultrasonic sensors 1, 2, 3, 4, 5, 6 in a bumper of a passenger car 10 as means of transportation. The ultrasonic sensors 1, 2, 3, 4, 5, 6 have respective transmitting lobes 11, 12, 13, 14, 15, 16. The ultrasonic sensors 1, 2, 3, 4, 5, 6 are respectively connected via a signal line to a central control device 7 as evaluation unit. The ultrasonic sensors 1, 2, 3, 4, 5, 6 are able only to a limited extent to receive cross echoes among one another, depending on the environment objects. By way of example, the ultrasonic sensors 1, 2, 3, 4, 5, 6 are divided into groups G12, G23, G34, G45, G56, in order to be able to refer to the possibility or the impossibility of receiving cross echoes. For example, the groups G12 and G45 are arranged at such a distance from one another that a reception of echoes which are based on signals of the group G45 cannot be received by the ultrasonic sensors 1, 2 of the group G12. The tables of Figures 2 to 6 relate to operating modes which can be used for an arrangement of ultrasonic sensors 1, 2, 3, 4, 5, 6 of Figure 1.

Figure 2 shows a table for illustrating a possible transmit-receive pattern for the ultrasonic sensors 1, 2, 3, 4, 5, 6 (first row of the table) corresponding to the exemplary arrangement illus=ated in Figure 1. Underneath the first row, two further rows representing a first measuring cycle (numeral 1) and a second (temporally following) measuring cycle (numeral 2) are shown. In the rows of the table, -"s" means that the sensor in the measuring cycle both transmits and receives direct echoes, -"r" means that the sensor in the measuring cycle receives exclusively cross echoes and emits no signals, and means that the sensor both transmits and receives direct and cross echoes. In the right-hand part of the table, for the six ultrasonic sensors 1, 2, 3, 4, 5, 6 (numbering in the first row of all tables corresponding to Figure 1) and the measuring cycles 1 and 2, there is respectively entered whether the ultrasonic sensor 1, 2, 3, 4, 5, 6 in the measuring cycle functions as direct-echo receiver "D" and/or as cross-echo receiver "C". The hatchings represent four different code words, with which the ultrasonic sensors 1, 2, 3, 4, 5, 6 transmit or (in the form of echoes) are confron7.ed. Here, with one exception, the codes used must respectively guarantee a good mutual suppression: only the codes which the first sensor emits in the first measuring cycle and the sixth sensor emits in the second measuring cycle do not have to have a particular suitability for mutual suppression in the cited example.

Figure 3 shows one possible modification of the operating mode illustrated in Figure 2 by introducing particularly short signals, which are denoted by the lettering "short". In contrast to the legend of Figure 2, "short" means that the sensor concerned both transmits and is adapted to receive direct echoes, as follows from the right-hand half of the table ("short" signals are respectively received and evaluated within the same measuring cycle and the same ultrasonic sensor 1, 2, 3, 4, 5, 6).

Figure 4 shows a further development of the operating mode illustrated in Figure 3, by which the measuring update rate (measuring operations per unit of time) can be optimised. For this purpose, a short signal "short" is emitted and received in each measuring cycle 1 to 4 by means of two ultrasonic sensors 1, 2, 3, 4, 5, 6 spaced apart from one another. This signal may have, for example, a short pulse with a fixed frequency, in particular consist of such a pulse. In addition, a further transmitting operation has been provided for the sixth ultrasonic sensor in the second measuring cycle and a further transmitting operation implemented for the first ultrasonic sensor in the fourth measuring cycle (respectively with a reception of direct echoes). For the operating mode illustrated in Figure 4, a good mutual suppression from one another is required of those codes which are emitted, for example, in the third measuring cycle by the firs:, and second ultrasonic sensor. In addition, a good mutual suppression is required for those codes which the fifth and the sixth ultrasonic sensor emit in the second measuring cycle.

Figure 5 shows an example of a so-called code toggling for increasing the detection robustness at a high update rate. Instead of implementing only two different measuring cycle-code word combinations as shown in Figure 2, the first ultrasonic sensor 1 in the Third and fourth measuring cycle is operated with that code which was provided for the sixth ultrasonic sensor in the first and second measuring cycle (and vice versa). The same applies analogously to those codes which the second and Third ultrasonic sensor, and the fourth and fifth ultrasonic sensor have emitted in the first and second measuring cycle. In this way, code-specific errors can be eliminated at least over a duration of four measuring cycles.

Figure 6 shows an example of code toggling based on the transmitting patterns illustrated in Figure 3. Here the code which the first ultrasonic sensor 1 emits in the first measuring cycle is replaced after the fourth measuring cycle by a code not used hitherto. The same applies analogously to that code which, for example, the fifth ultrasonic sensor 5 emits in the first measuring cycle. In this way, at the latest after four measuring cycles the code used is changed in order to avoid systematic detection errors over an extended period of time and thus improve the collision detection.

Figure 7 shows steps of an exemplary embodiment of a method according to the invention for operating an ultrasonic transmitter-receiver device. In step 100 a first signal representing a first code word is emitted by means of a first ultrasonic sensor of a first group of ultrasonic sensors and by means of a fourth ultrasonic sensor of a second group of ultrasonic sensors, respectively in a first measuring cycle. In step 200 a second signal is emitted by means of a second ultrasonic sensor of the first group. In step 300 echoes of the first signal and of the second signal are received by means of a third ultrasonic sensor, which is identical to the first ultrasonic sensor. In step 400 components of the echo originating from the first signal are distinguished from components originating from the second signal by means of a decoding of the code words contained. The decoding of the code words enables a higher measuring signal density per unit of time with nevertheless error-free detection and assignment. In step 500 a third signal representing a third code word is emitted by means of the first ultrasonic sensor of the first group of ultrasonic sensors in a second measuring cycle, whereby a code toggling for fundamentally avoiding code-specific detection errors is realised. In step 600 a cruising speed of the ultrasonic transmitter-receiver device (e.g. of a means of transportation configured in accordance with the invention) is compared with a predefined reference. In response to the result, in step 700 a short code word to be transmitted by the first ultrasonic sensor in a temporally following, next measuring cycle is selected from a predefined multiplicity of code words. If the cruising speed has exceeded the predefined reference, an increased use of short code words, for example, is effected in order to improve the reaction times of the system and thereby optimise the prewarning times.

Claims (14)

1. Claims 1. Method for operating an ultrasonic transmitter-receiver device (20) comprising the steps - emitting (100) a first signal representing a first code word by means of a first ultrasonic sensor (1) of a first group (G12) of ultrasonic sensors (1-6) in a first measuring cycle, - emitting (200) a second signal by means of a second ultrasonic sensor (2) of the first group (G12), - receiving (300) echoes of the first signal and of the second signal by means of a third ultrasonic sensor (1, 2), and - distinguishing (400) components of the echo originating from the first signal from components originating from the second signal by means of a decoding of the code word.
2. 2. Method according to Claim 1, the ultrasonic sensors (1, 2) of the first group (G12) being spatially arranged in such a way that they are adapted to receive cross echoes from one another.
3. 3. Method according to Claim 1 or 2, the second signal representing a second code word.
4. 4 Method according to any of the preceding claims, the characters of the first code word consisting respectively of such a time signal portion, the properties of which with respect to time are always to be distinguished from the second signal by means of a matched filtering.
5. 5. Method according to Claim 4, successive time signal portions being distinguished from one another with regard to - a fundamental frequency, and/or - a fundamental frequency profile, in particular with regard to - an initial frequency and/or a target frequency and/or - a frequency change direction, and/or - a frequency change speed, and/or - a frequency range.
6. 6. Method according to any of the preceding claims, the second signal having a substantially shorter duration and/or amplitude than the first signal.
7. 7. Method according to any of the preceding claims, an evaluation of an echo originating from the second signal being completed already at an instant at which the first signal is still being evaluated.
8. 8. Method according to any of the preceding claims further comprising - emitting (500) a third signal representing a third code word by means of the first ultrasonic sensor (1) of the first group (G12) of ultrasonic sensors (1-6) in a second measuring cycle, and/or - emitting (100) a fourth signal representing the first code word by means of a third ultrasonic sensor (4) of a first group (G45), the ultrasonic sensors (1, 2) of the first group (G12) being spatially arranged in such a way that they are not suitable for receiving echoes of signals originating from the second group (G45).
9. 9. Method according to any of the preceding claims further comprising - changing an assignment between the code words used and the ultrasonic sensors (1-6) for a following transmitting cycle, the changing taking place in particular according to a predefined sequence and/or stochastically.
10. 10. Method according to any of the preceding claims further comprising - comparing (600) a cruising speed of the ultrasonic transmitter-receiver device (20) with a predefined reference, and in response thereto - selecting (700) a code word to be transmitted by the first ultrasonic sensor (1) in a next measuring cycle from a predefined multiplicity of code words, in particular of a changed length.
11. 11. Ultrasonic measuring system comprising a first group (G12) of ultrasonic sensors (1, 2) having - a first ultrasonic sensor (1), and - a second ultrasonic sensor (2) and - a second group (G45) of ultrasonic sensors (4, 5) having - a third ultrasonic sensor (4) the ultrasonic sensors (1, 2) of the first group (G12) being spatially arranged in such a way that they are not suitable for receiving echoes of the second group (G45) and the ultrasonic measuring system (20) being adapted to carry out a method according to one of the preceding claims.
12. 12. Means of transportation comprising an ultrasonic measuring system (20) according to Claim 11.
13. 13. Method as hereinbefore described with reference to the accompanying drawings.
14. 14. Ultrasonic measuring system as hereinbefore described with reference to the accompanying drawings.