DE102018206649A1 - Signal coding of ultrasonic sensors with spreading codes to increase the range - Google Patents

Abstract

The present invention relates to a method and a device for detecting an echo (7) of an ultrasound signal (5). The method comprises the steps of: emitting a first partial signal of the ultrasonic signal (5) with a first static frequency and a first predefined duration, emitting a second partial signal of the ultrasonic signal (5) with a second, different from the first frequency, static frequency and a second predefined duration, and using the first frequency and the second frequency in an identification of the ultrasonic signal (7) reflected on an environmental object (6).

Description

State of the art

The present invention relates to a method and a device for detecting an echo of an ultrasonic signal. In particular, partial signals with different frequencies are used here.

The invention also relates to a means of transportation with such a device.

Measurement systems based on ultrasonic signals are used to determine a distance from an environment object located in front of a transmitter. The transmitter emits an ultrasonic signal. The reflection of the ultrasonic signal, the echo, caused by the surrounding object is received by a receiver. Also, the receiver may be attached directly to the environment object. In this case, not the echo but the ultrasonic signal itself will be received. A processing unit evaluates the signals and uses the signal propagation time and the speed of sound to determine the distance between transmitter and ambient object or between transmitter and receiver.

In order to increase the accuracy of the detection of the ultrasonic signal or the echo of the ultrasonic signal and the range of the system, it is advantageous to be able to filter out weak signals from a broadband noise. For this purpose, so-called spreading codes are used. This generates a pseudorandom code. This code is combined with the signal to be transmitted by means of a code division multiplex method and then transmitted by an ultrasonic transmitter.

Since the code with which the signals were combined is known, the signals on the receiver side can be easily filtered out of the noise by cross-correlation or autocorrelation. As even very weak signals can be detected, the effective range of the ultrasonic sensors can be increased.

Such systems are known in the art. For example disclosed DE 10 2009 031 955 A1 a method for determining the spatial position of a unit to be located by means of ultrasound, in which the ultrasound carrier signal a PN (pseudo random noise) code sequence is impressed and comprising the steps of: generating a PN code sequence in a transmitter; Mixing the PN code sequence with an ultrasound carrier signal in the transmitter; periodically emitting the ultrasonic PN code sequence; Receiving a signal-to-noise mixture at a receiver and evaluating a propagation time characteristic of the received signal to determine the spatial coordinates of the device to be located.

In this case, the ultrasonic signal is divided into partial signals with linear or non-linear frequency modulation, so-called chirps. Chirps have a start and end frequency, as well as a slope of the frequency, where the slope can be positive or negative. This has the advantage that a broad frequency spectrum with constant amplitude is generated and transmitted, which has a positive effect on the recognition rate. For this purpose used ultrasonic transmitter and ultrasonic receiver must have a correspondingly wide frequency spectrum. This requires appropriately configured and therefore expensive components or brings with it limitations in the recognition performance.

Disclosure of the invention

The inventive method with the features of claim 1 is characterized in that even simple and inexpensive components can be used without appreciable restrictions on the recognition performance occur. The method for detecting an echo of an ultrasound signal comprises several steps. The ultrasonic signal is composed of at least two consecutively transmitted partial signals. In a first step, a first partial signal of the ultrasound signal having a first static frequency and a first predefined duration is emitted by means of an ultrasound transmitter. Subsequently, in a second step, a second partial signal of the ultrasound signal with a second, different from the first frequency, static frequency and a second predefined duration, emitted by means of the ultrasonic transmitter. The first static frequency and the second static frequency are in the range of the ultrasound, preferably in a range between 25 kHz and 60 kHz, preferably between 30 kHz and 55 kHz and ideally have a distance of at least 1 kHz. The first frequency and the second frequency may be a harmonic frequency, a triangular frequency or a square frequency. If the signal does not correspond to a sinusoid, the term "frequency" refers to the fundamental frequency of the signal. The first predefined duration and the second predefined duration may be of different lengths as well as identical. If the emitted ultrasound signal hits an ambient object, for example an obstacle in the direction of transmission of the ultrasound transmitter, it is reflected by it. The environment object can be both a static and a mobile traffic space object and / or a collision-relevant traffic element (eg Traffic sign, a lane boundary element, another means of transportation, a pedestrian, etc.). In this case, part of the reflected ultrasound signal is thrown back in the direction of the ultrasound transmitter. Here, the reflected ultrasound signal, the echo, can be received by means of an ultrasound receiver, preferably mounted in the immediate vicinity of the ultrasound transmitter, or a combined ultrasound transmitter / receiver module. In a third step of the method according to the invention, the first frequency and the second frequency are used to identify the ultrasound signal reflected at an environmental object. When transmitting the ultrasonic signal, a signal pattern is produced by using two different frequencies for the individual component signals. This signal pattern also has the echo of the ultrasonic signal. Since the pattern of the ultrasonic signal or the echo is known, it can also be identified from a received ultrasonic noise. Identification uses methods such as cross or autocorrelation. Once the echo has been identified, a time span, a signal propagation time of the ultrasound signal, between the emission of the ultrasound signal and the reception of the echo and thus a distance to the surrounding object can be calculated.

According to the invention, a device for detecting an echo of an ultrasound signal is further provided. The device comprises a data output, a data input and a processing unit. Controlled by the processing unit, a first partial signal of the ultrasound signal is transmitted at a first predefined static frequency over a first predefined duration via an ultrasound transmitter connected to the data output. Subsequently, a second sub-signal of the ultrasound signal with a second, different from the first frequency, static frequency and a second predefined duration is also transmitted via an ultrasonic transmitter connected to the data output. The ultrasound receiver connected to the data input can receive the ultrasound signal reflected by an environmental object as well as a broadband ultrasound noise and forward it as an electrical signal via the data input to the processing unit. In the processing unit, based on the first frequency and the second frequency, the ultrasound signal, or its echo, or that echo-representing electrical signal from an electrical signal representing the received broadband noise can be identified and filtered out. Likewise, the processing unit can calculate a time span, transit time, between the emission of the ultrasound signal and the reception of the echo and thus the distance to the environment object.

The dependent claims show preferred developments of the invention.

In a particularly advantageous embodiment of the invention, the ultrasound signal is emitted by means of an ultrasound transmitter and the ultrasound signal reflected at the ambient object, ie the echo, is received by an ultrasound receiver. In this case, ultrasound transmitters and ultrasound receivers can be designed as two separate devices, membranes or sound transducers. It is also possible to use one ultrasound transmitter for each frequency to be transmitted. Thus, the distance of the first and second frequency can be maximized and it can be chosen frequencies that promise the best possible detection, without having to rely on a single ultrasonic transmitter has a correspondingly wide frequency spectrum. The use of a single device, designed both as an ultrasonic transmitter and as an ultrasonic receiver, represents a further embodiment.

In order to optimize the detection of environmental objects in very small or very large distances, or to respond to a varying distance to the environment object, the invention can be improved in that the first duration and the second duration depending on an expected or detected distance to Environment object defined and over the duration of the transmission of the partial signals is automatically adjusted again and again. For medium distances, a duration of 200 μs is ideally used for the transmission of a partial signal. An ultrasonic signal composed of sub-signals has, for example, a duration of 2 ms. For very close environment objects, however, the duration for emitting a partial signal can also be shortened and extended for very distant environmental objects. The duration of the ultrasonic signal composed of partial signals can also be predefined and / or varied.

In an advantageous embodiment, the frequencies can be assigned symbols of a code. If two different frequencies are used, a binary coding is recommended. For example, the first frequency can be assigned a 0 and the second frequency a 1. The use of other number systems is also possible and advisable, especially in the case where more than two different frequencies are used for transmitting the sub-signals. If a frequency can not be assigned to each symbol of the number system, a predefined partial signal or a transmission pause can be assigned to the other symbols, for example. Ideally, pseudorandom codes are used to encode the ultrasound signal. Well-known examples of this are known from the satellite technology PRN codes. Other examples are Gold or Kasami codes. A selected code consists of a predefined number of symbols. Each symbol corresponds to a partial signal of the ultrasonic signal. The length of the ultrasound signal is thus dependent on the predefined number of symbols of the code and transmission durations of the component signals from which the ultrasound signal is composed. If more than one ultrasound transmitter is used at the same time, it is advisable to assign a separate code to each ultrasound transmitter. Thus, the received echoes can be assigned to the respective ultrasound transmitter.

In a further improvement of the invention, the ultrasonic signal can be retransmitted after a first transmission. The more frequently the ultrasonic signal is repeatedly transmitted or received, the better even very weak echoes can be filtered out of a time-variable noise. However, if the ultrasound signal is transmitted repeatedly throughout, the ultrasound receiver will no longer see any beginning or end of the signal. This in turn can influence the transit time determination. Therefore, when re-emitting the ultrasonic signal, the phase of the ultrasonic signal can also be rotated by a predefined value. Thus, the phase of all the sub-signals contained in the ultrasonic signal is rotated by the corresponding value. With the known phase shift angle, the processing unit is able to determine the beginning and end of the ultrasonic signal.

To optimize the detection, the ultrasonic signal can also be transmitted repeatedly with the phase unchanged before the phase is rotated by a predefined value. The number of phase-unmodified repetitions can be automatically defined as a function of the distance of the environment object to be detected or by a predefined maximum detection distance. Also, a pattern of phase-inverted and out-of-phase repetitions can be determined by a code. In this case, phase-inverted and phase-shifted repetitions can each be assigned a symbol of the code. For this purpose, for example, binary codes are suitable, wherein each phase-unchanged repetition can be assigned a 0 and each phase-shifted repetition a 1. For a code of 00111000, this would result in two phase-inverted repeats of the ultrasound signal, followed by three phase-shifted repeats, followed by three phase-inverted repeats. It is also possible to insert transmission pauses of a predefined duration between the repetitions of the ultrasound signal in which the ultrasound transmitter does not transmit a signal. The transmission pauses can be inserted after or before each repetition, a predefined number of repetitions, each phase shift and / or each pattern of phase shifts. In this case, the duration of the transmission pause can be defined as a function of a distance to an environment object or also as a function of a second ultrasound transmitter, in order, e.g. minimize possible interference. It is also possible to vary the duration of the transmission pause, e.g. in response to a change in distance to the ambient object or in response to a second ultrasonic transmitter moving into or out of the receiving area in the receiving area of the ultrasonic receiver.

In a further advantageous embodiment, the ultrasonic transmitter as well as the ultrasonic receiver can be attached to or in the outer skin of the means of locomotion. This allows them to be visually inconspicuous without being impaired in their function.

list of figures

• 1 eine stark vereinfachte schematische Darstellung eines Ausführungsbeispiels einer Vorrichtung zur Erkennung eines Echos eines Ultraschallsignals in Verbindung mit einem F ortbewegungsm ittel;
• 2 ein erfindungsgemäß kodiertes Ultraschallsignal;
• 3 ein erfindungsgemäß kodiertes Ultraschallsignal und ein phasenverschobenes codiertes Ultraschallsignal; und
• 4 ein Flussdiagramm des erfindungsgemäßen Verfahrens.

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawings:

• 1 a greatly simplified schematic representation of an embodiment of an apparatus for detecting an echo of an ultrasonic signal in conjunction with a F ortbewegungsm ittel;
• 2 an ultrasonic signal coded according to the invention;
• 3 an ultrasonic signal coded according to the invention and a phase-shifted coded ultrasonic signal; and
• 4 a flow chart of the method according to the invention.

Embodiments of the invention

1 shows components of an embodiment of a vehicle equipped according to the invention 1 , One in a bumper 2 of the means of transport 1 built-in ultrasonic transmitter 3 sends in connection with the data output 4 an ultrasonic signal 5 out. This ultrasound signal 5 is from an environment object 6 reflected. The from the environment object 6 reflected ultrasound signal, the echo 7 , is from one in the bumper 2 of the means of transport 1 built-in ultrasonic receiver 8th received and via the data input 9 to the processing unit 10 forwarded. In the processing unit 10 finds the identification and evaluation of the received Echos 7 instead of. A detection result may then be, for example, from the processing unit 10 to other systems of the means of transport 1 be passed on. Also, the processing unit 10 based on a time period between the emission of the ultrasonic signal 5 and receiving the echo 7 a distance to the environment object 6 to calculate.

The attachment of the ultrasonic transmitter 3 and the ultrasound receiver 8th on or in the bumper 2 of the means of transport 1 is merely an example. Any other position on or in the outer skin of the vehicle 1 is also conceivable as long as the function of the ultrasonic transmitter 3 and / or the ultrasound receiver 8th is not restricted.

1 also shows a second ultrasonic transmitter 11 , which is outside the means of transportation 1 or outside the device. The second ultrasonic transmitter 11 sends a second ultrasonic signal 12 out, which from the ultrasonic receiver 8th Will be received. The second ultrasonic signal 12 interferes with the reception and the detection of the echo 7 as the ultrasonic signal 5 properly. One way to deal with such a disturbance is to use the ultrasonic signal 5 as described above with a symbol sequence to encode. An encoded ultrasonic signal 5 has a signal pattern, which also at its echo 7 is to be found again. Ideally, the signal pattern of the ultrasonic signal 5 or its echoes 7 different from a signal pattern of the second ultrasonic signal 12 , By the processing unit 10 known signal pattern of the ultrasonic signal 5 can its echo 7 also under interference of the second ultrasonic signal 12 from the processing unit 10 be identified from the received ultrasonic noise. Sends the second ultrasonic transmitter 11 no continuous signal, another way to deal with the problem is to pause the transmission until the second ultrasonic transmitter 11 stops sending. About the with the data input 9 connected ultrasound receiver 8th can the processing unit 10 detect if a second ultrasonic transmitter 11 sends and thus receiving the echo 7 of the ultrasonic signal 5 disturbs or disturbs. The processing unit 10 can then wait a predefined duration to see if it is the second ultrasound signal 12 is a continuous signal. Will be the second ultrasonic signal 12 no longer receive within the predefined duration, this recognizes the processing unit 10 and may, in response to this detection, transmit the ultrasound signal 5 via the at the data output 4 connected ultrasonic transmitter 3 trigger. So can the echo 7 without interference from the second ultrasonic signal 12 via the ultrasound receiver 8th be received. Expires the predefined duration without the processing unit 10 a transmission pause of the second ultrasonic signal 12 can still detect the transmission of the ultrasonic signal 5 triggered and an identification of the echo 7 through the processing unit 10 tries. Is the interference of the second ultrasonic signal 12 too big for a reliable identification of the echo 7 , for example, can send an error message to other systems of the means of locomotion 1 be passed on.

In 2 is clarified, like the ultrasonic signal 5 is encoded. As mentioned above, the first frequency 21 a first symbol 22 and the second frequency 23 a second symbol 24 associated with a code. The emitted ultrasonic signal 5 consists of several sub-signals 25 - 32 together. The partial signals 25 - 32 be with the first frequency 21 or the second frequency 23 emitted, with the assignment of frequencies 21 . 23 to the sub-signals 25 - 32 based on the code.

In the example shown here, the binary code 10111011 is predefined as code. So the symbol " 1 "Of the code the first frequency 21 and the symbol " 0 "Of the code the second frequency 23 assigned. Accordingly, a first sub-signal 25 with the first frequency 21 sent over a first duration. Subsequently, a second partial signal 26 with a second frequency 23 sent over a second predefined duration. Following the code, the next three sub-signals 27 - 29 with the first frequency 21 each transmitted over a first duration followed by the sub-signal 30 with the second frequency 23 over a second duration and the two sub-signals 31 and 32 with the first frequency 21 over the first duration.

The obtained frequency pattern is also corresponding to that of the environment object 6 reflected ultrasound signal, the echo 7 to find again. This makes it possible, even a very weak echo 7 identify in a broadband noise and / or filter out of this. Thus, it is possible to detect even very distant or very small environment objects.

3 shows a phase shift P in a repeated transmission of an alternative code by means of an ultrasonic signal. It becomes an ultrasonic signal consisting of four partial signals 33 - 36 sent according to a code 1101. In the directly subsequent second transmission of the ultrasonic signal whose phase is rotated by 180 degrees. As the phase of the ultrasonic signal is turned, the phases of the individual sub-signals also become 33 - 36 rotated accordingly. The single ones partial signals 33 ' - 36 ' even after the phase shift P continue to represent the code 1101.

4 shows a flowchart of the method according to the invention. In a first step 100 becomes a first sub-signal 25 of the ultrasonic signal 5 with a first static frequency 21 and a first predefined duration. After that, in a second step 200 a second partial signal 26 of the ultrasonic signal 5 with a second, from the first frequency 21 different, static frequency 23 and a second predefined duration. From the received echo 7 will be in a third step 300 that on the environment object 6 reflected ultrasound signal using the first frequency 21 and the second frequency 23 identified.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102009031955 A1 [0006]

Claims (10)

Method for detecting an echo (7) of an ultrasound signal (5) comprising the steps: Transmitting (100) a first partial signal (25) of the ultrasound signal (5) having a first static frequency (21) and a first predefined duration, - Sending (200) of a second partial signal (26) of the ultrasonic signal (5) with a second, of the first frequency (21) different, static frequency (23) and a second predefined duration, and - Using (300) the first frequency (21) and the second frequency (23) in an identification of the reflected on an environmental object (6) the ultrasonic signal (7). Method according to Claim 1 wherein the ultrasonic signal (5) is emitted by means of a first ultrasonic transmitter (3) and the reflected ultrasonic signal (7) is received by means of a first ultrasonic receiver (8). Method according to one of the preceding claims, wherein the first predefined duration of the first partial signal (25) and / or the second predefined duration of the second partial signal (26) and / or the duration of the ultrasonic signal (5) in dependence on a detection of presence of an ambient object ( 6) is defined. Method according to one of the preceding claims, wherein the first frequency (21) is associated with a first symbol (22) and the second frequency (23) with a second symbol (24) of a code, and wherein the code is in particular a PRN code or a gold Code or a Kasami code or other pseudo-random code. Method according to one of the preceding claims, wherein in a second emission of the ultrasonic signal (5), a phase of the ultrasonic signal (5) is rotated by a predefined value relative to the previously transmitted ultrasonic signal (5). Method according to Claim 5 in which the ultrasound signal (5) is transmitted repeatedly before the phase is rotated by the predefined value, and in particular before the repeated transmission of the ultrasound signal (5) a transmission pause is inserted with a third predefined duration and wherein the third predefined duration preferably in dependence is defined to a second ultrasonic transmitter (11). Device for detecting an echo (7) of an ultrasound signal (5) comprising: a data input (9), a data output (4), and a processing unit (10), wherein the data output (4) is set up, together with an ultrasound transmitter (3), a first sub-signal (25) of the ultrasound signal (5) having a first static frequency (21) and a first predefined duration and a second sub-signal (26) of the ultrasound signal (3). 5) with a second static frequency (23) different from the first frequency (21) and a second predefined duration, wherein the data input (9) is arranged to receive, together with an ultrasonic receiver (8), an ultrasonic signal (7) reflected by an environmental object (6), and wherein the processing unit (10) is arranged to use the first frequency (21) and the second frequency (23) in an identification of the ultrasound signal (7) reflected at an environment object (6). Device after Claim 7 wherein the device is permanently installed in a means of locomotion (1) and wherein in particular the ultrasound transmitter (3) and the ultrasound receiver (8) are fastened to an outer skin of the locomotion means (1), in particular to a bumper (2). Computer program, which is set up, a method according to one of Claims 1 to 6 perform. Machine-readable storage medium on which the computer program is based Claim 9 is stored.

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