EP3132282A1

EP3132282A1 - Apparatus and method for sound-based environment detection

Info

Publication number: EP3132282A1
Application number: EP15706729.9A
Authority: EP
Inventors: Matthias Karl
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-04-14
Filing date: 2015-02-16
Publication date: 2017-02-22
Also published as: CN106170715A; DE102014207086A1; CN106170715B; WO2015158445A1

Abstract

An apparatus and method for sound-based environment detection are proposed. The method comprises the following steps: isolation of a first signal element (sj (t)), which potentially comprises a useful signal, from a received signal (r (t)), isolation of a second signal element (si1 (t)), which is different from the first signal element and potentially comprises an interference signal, from the received signal (r (t)), subtraction of the second signal element (si1 (t)) from the first signal element (sj (t)), and comparison of the difference with a threshold value. This results in the rating of a received signal for whether its quality is suitable for evaluating environment information.

Description

description

title

Apparatus and method for sound-based environmental detection state of the art

The present invention relates to a device and a method for sound-based environment detection. In particular, the present invention relates to an evaluation of a transducer signal as to whether its quality is suitable for evaluating environmental information.

In the case of acoustic environment detection, the ratio of the incoming signal strength of the expected signal, the signal strength of the receiver can be determined

Noise and the signal strength, if any, from external systems or channels during the echo cycle, i.e., in the period after the emission of an acoustic measurement signal until the time when sensible echo signals can no longer be expected to change. This can e.g. due to short-term fluctuations of the

Transmission properties of the medium, change in the strength of the

Noise signal or a signal entered by an external system or due to a change in the composition of the noise signal strength or the signal strength of the external signal result. At the receiver, the useful signal, the external signal and the noise are superimposed additively, that is to say the energy received during the reception period of a signal is the sum of the individual energies.

Digital Communications, Proakis, Third Edition, McGraw-Hill, Inc., International Editions 1995, discusses in Chapter 5-2, and in particular on page 264, how trustworthiness, i. the error rate in a signal detection of both the ratio of useful signal to noise signal or of useful signal to

External signal depends. In addition, the work of Shannon is explained and shown, as with Gaussian noise, the reliability of a signal detection depends on the ratio of useful signal to noise (SNR, signal-to-noise ratio), and that the SNR in Gaussian noise must exceed at least one value of In2 equal to 0.69, the so-called "Shannon Limit" 10 2004 006 015 introduces an efficient procedure, in which before

Echo cycle, the strength of the disturbing noise and extraneous signals are determined and taken into account accordingly within the echo cycle. It is assumed that the strength of the interfering signals during the

Echo cycle not changed.

DE 10 2009 054 667 describes methods by which the

Transmission properties in the acoustic environment detection determined and taken into account in the subsequent signal evaluation. For

Devices for acoustic environment detection (whether echo-based or

Rundhorchen-based) there is a need for a simple and computationally favorable estimation of a signal quality.

DISCLOSURE OF THE INVENTION The above object is achieved according to the invention by a method for sound-based environmental detection and a corresponding device. For this purpose, it is proposed that a reception signal of a

Schallwandlers a potentially a useful signal comprehensive first partial signal is isolated. This can be done for example by filtering (analog or digital). It is only important to detect the useful signal substantially completely and to hide interfering components at least partially. In a second step, a second sub-signal is isolated from the same received signal, which potentially includes an interfering signal. Accordingly, the first sub-signal and the second sub-signal are different from each other. The interference signal may include, for example, a noise and / or a foreign useful signal.

Of course, the foreign useful signal can be assigned to the same system and used by the same system as the useful signal. Only for the considered system section or a subsequent evaluation of the received signal is the external signal not used for environment detection size. In a further step, the second partial signal from the first

Partial signal subtracted. Depending on the design of the system, this can be done in the

Time range or after an optional rectification of the sub-signals. Subsequently, the determined difference with a predefined

Threshold compared. It is judged on the basis of the threshold value whether the useful signal potentially contained in the first sub-signal is sufficiently pure, so that in a subsequent evaluation step an environmental detection can take place using it, or if the interference contained is such

Use as inadvisable. In contrast to a division, which is usually carried out to determine the signal-to-noise ratio, a subtraction proposed according to the invention can be carried out much simpler and more cost-effectively, so that the present invention enables cost and performance advantages in sound-based environmental detection.

The dependent claims show preferred developments of the invention.

Preferably, the first sub-signal can be rectified before the subtraction. For this purpose, all known in the art circuits and

Procedure can be used. This simplifies the signal processing and the phase position of the two sub-signals to each other is no longer so significant. To adapt the level or the difference to the threshold value, the first sub-signal and / or the second sub-signal can be weighted before the subtraction. In other words, the sub-signals or one of the sub-signals are multiplied by a constant factor. Preferably, the second partial signal potentially comprising interfering signals is to be multiplied by a factor <1 in order to reduce its level and to adapt its energy or power density to sometimes narrowband isolated potential useful signals.

Also, the second sub-signal or the weighted second sub-signal can be rectified before the subtraction, whereby the phase information of the

Partial signals lose their influence on the result of the subtraction. Assuming equal-bandless signals, which is close to reality in acoustic environment detection, the rectification can be limited to only positive or negative signal periods, making rectification very easy and inexpensive (for example, by means of a diode).

The useful signal can be configured as an echo of an emitted measuring signal. Especially in the ultrasonic range is the emission of measurement signals and evaluating the provoked by them echoes a common and proven approach, which can be improved according to the invention.

The isolation of the first partial signal and / or the second partial signal may comprise a matched filtering of the received signal. Depending on the nature of the expected useful signal, a time-variable frequency band for isolating a chirp can generate the first partial signal. In principle, however, more complex filtering or isolation processes are possible. Two principal possibilities concern the domain of the signal to be examined. In other words, the useful signal or the received signal can be processed in the time domain and / or as a transform of the signal in the frequency domain. For transformation, the Walsh transformation and / or the Fourier transformation, for example, can be used. The steps discussed above allow pre-processing of a

Receiving signal in that its suitability for use in the sound-based environment detection can be determined and decided on its use. If namely a strong disturbance of the

Receiving signal is determined, a reliable evaluation of any existing environmental objects can not be guaranteed and discarding the received signal is advisable than an acceptance of faulty detection or non-detection.

For this purpose, in the event that the difference is smaller than the threshold value, a predefined signal and / or no signal at all can be output.

This predefined signal or absence of a signal can be classified and rejected by the subsequent detection unit as an invalid input signal. In response, the detection may be performed based on other received signals or an error message may be issued indicating that the proper functioning of the

Systems is compromised.

The method may preferably include determining a time profile of a level-dependent variable of the first partial signal and / or the second partial signal and / or the difference of both partial signals. Such a level-dependent

Size can be configured, for example, as an envelope of the received signal or as a rectified received signal. In a second step For example, a time period between a first echo cycle and a second echo cycle following the first echo cycle may be adjusted in response to determining the level dependent magnitude. Namely, depending on the time course of the level-dependent size of the sub-signals, a distance to an object possibly present can be estimated and the cycle duration can be adapted to the signal propagation time to be estimated during its examination.

For example, the aforementioned steps may be performed within a single echo cycle for environmental detection. The echo cycle is usually understood to mean the time duration between a transmission of a measurement signal and a predefined time at which no reasonably evaluable echoes are to be expected. Therefore, the present method could also be understood as an "in-cycle SNR estimation and threshold tracking".

An obvious "interferer" type is signals from emissions of its own system, as occur, for example, when several mutually different acoustic measurement signals are emitted at the same time or in the same echo cycle

appropriately designed, different filters are detected. For easily controllable media, e.g. For this purpose, cables are often called so-called orthogonal modulations (for example, in the case of DSL, the OFDM (orthogonal frequency divided

modulation)). In this case, the transmission channels, i.e., measuring signals and associated receiving filters, are each designed such that they can be inserted into the

Transmission channels of the other simultaneously transmitted measuring signals do not produce significant output signals. In acoustic environment detection, such an orthogonal design is due to the many possible ones

Reflex points and thus signal strengths and echoes are hardly possible. This problem is especially in use

narrow-band high-resonant ultrasonic transducer. However, because of known ambient conditions, for example by means of the method described in DE 10 2009 054 667, the transmission behavior between a plurality of measuring channels by means of a respective transfer function, which in

is generally time invariant can be deduced from the strength of a signal on a channel to the strength of a signal in a second channel. Is the disturbing effect on a considered Payload too large, can be concluded on the quality of the signal decision. In particular, in the case of signal strengths which vary during the echo propagation time, as are customary in the field detection by means of pulse measurement, the ratio of the two variables is in such a quality evaluation according to the basic investigations of Shannon and the explanations of Proakis

"Useful signal" and "external signal" prevail. In one embodiment, therefore, a potentially a second useful signal comprehensive third sub-signal can be isolated from the received signal. An optional weighting of the third

Partial signal is possible according to the comments on the first sub-signal and the second sub-signal. Each combination one of 1 different

Weighting of the sub-signals is also possible. In addition, it is proposed to subtract the third sub-signal from the first sub-signal, as previously described for a general noise. Subsequently, this difference can also be compared with a predefined threshold value.

Accordingly, the useful signal expected on a further channel (hereinafter referred to as "third useful signal") can also be isolated from the received signal and used for signal-to-noise ratio analysis In this way, a level-related selection of the existing disturbance variables is made before the subtraction according to the invention takes place for evaluating the SN.sub.R.

According to a second aspect of the present invention, an apparatus for sound-based environment detection is proposed, which is set up to realize the advantages of the method explained above. For this purpose, the device comprises a sound transducer (for example an ultrasonic transducer), a first filter

(analog or digital) and a subtractor on. The first filter can also be understood as an "insulating member", whereby one optionally on

Frequency ranges limited interpretation of its functionality is avoided. In addition, a valuation unit is provided which, for example, a comparison of a generated by the subtractor

Difference with a reference (threshold). Of the

Sound transducer is for receiving (possibly also for sending) Acoustic signals for environment detection set up. It performs a conversion into the electrical domain and providing corresponding electrical signals to the first filter. The mode of operation of the device according to the invention is evident in accordance with the statements relating to the method according to the invention that reference is made to the above statements to avoid repetition.

Optionally, the device may also comprise a weighting element which has an optional weighting of the second partial signal and / or of the first

Partial signal with a factor of one different performs. This makes it possible to adapt the energies of the different partial signals and, for example, by using voltage dividers, suitable values for the subtraction on the one hand and for comparison with a reference or a threshold value on the other hand can be used.

By using additional filters further useful signals can be isolated from the received signal. Especially when using

different useful signals within a spatially combined system (e.g., means of locomotion with a system for sound-based environment detection), a crosstalk of a useful signal of a foreign channel to a transducer of a channel considered can be recognized and considered according to the invention.

For all aspects of the present invention, an input filter can be provided, through which a theoretically infinite power of a

Input signal is limited to a total bandwidth. That the

Input filter downstream filter for isolation of the desired signal or the useful signals is preferably adapted to the expected signal (English:

"Matched") and lies within its bandwidth within the passband of the input filter

Determining the strength of the useful signal or the received signal

out downstream. For simple schematic illustration, these exist

Devices optionally each of a rectification and a low pass. By means of threshold value specification, a reference signal is generated and the difference between the two signals is determined by means of a threshold value switch. As an example of a device for signal evaluation, for example, a simple switch can be used, which only the received signal on a Input of a distance detection unit outputs when the useful signal is present in a minimum quality, so has a minimum value. Otherwise will be one

predefined value (e.g., zero) is output.

According to the invention, by means of a threshold specification, it is relatively easy to take into account a minimal signal-to-noise ratio in a quality assessment and to make a corresponding decision for use or non-use. In the ultrasonic environment monitoring means hochresonanter and thus narrow-band transducer can be realized on a separately realized

Be omitted input filter, since the converter itself a narrow

Passband has.

Brief description of the drawings

Hereinafter, embodiments of the invention will be explained with reference to the accompanying drawings. In the drawing is:

Figure 1 is a block diagram illustrating an embodiment of a device according to the invention;

Figure 2 is a block diagram of an alternative embodiment of a device according to the invention; and

Figure 3 is a flow chart illustrating steps of a

Embodiment of a method according to the invention.

Embodiments of the invention

Figure 1 shows a block diagram of an embodiment of a

Device 1 according to the invention via an ultrasonic transducer 5 as

Sound transducer passes an ambient noise as a received signal r (t) to an input 2. The input 2 is followed by an input filter 3, by means of which a conditioning of the received signal r (t) takes place by a pre-filtering. The processed signal is applied to a plurality of matched filters 10, 11, 12, which are tuned to different partial signals of the received signal. A first matched filter 10 is set up to isolate a first useful signal Sj (t) from the received signal r (t). A second

adapted filter 1 1 is set up, a first Fremdkanalnutzsignal Si1 (t) (Payload, which is intended for a channel other than the considered) to isolate from the received signal r (t). A third matched filter 12 is arranged to isolate a second foreign channel payload signal Si2 (t) from the received signal r (t). In the example, the outputs of the matched filters 10, 11, 12 are directed to respective weighting members 20, 21, 22. Not all

Weighting members 20, 21, 22 must use a one-of-a different weighting factor or have to be present at all.

In addition, the weighting members 20, 21, 22 perform rectification of the component signals Sj (t), Si1 (t), Si2 (t). With respect to the third-party channel signals Si1 (t), Si2 (t), a downstream summing unit 70 is used

Maximum value view of the sub-channel signals Si1 (t), Si2 (t) containing the external channel useful signals. In other words, the respective highest-level sub-signal Si1 (t), Si2 (t) is applied to a subsequent subtracter 302 and subtracted from the weighted first sub-signal Sj (t). The difference is compared in a comparator 305 with a threshold value L and the result to a

Valuation unit 59 forwarded. In response to a predetermined comparison result, the evaluation unit 59 forwards the first sub-signal Sj (t) to an output 60 so that partial signals containing useful signals that are used for subsequent environmental detection are used.

Figure 2 shows an analogous embodiment of an embodiment corresponding to the circuit already shown in Figure 1 in principle. Here, the matched filter 10, 1 1, 12 configured as an analog bandpass filter, wherein the passband Bs1 only proportionally with the

Passages Bs2 and Bs3 of the matched filter 1 1, 12 overlaps

(see respective position to the resonance frequency f ₀ ). Downstream of the first matched filter 10 is a weighting element 20, which comprises a bridge circuit 200 as a rectifier and a low-pass filter RC for smoothing the rectified signal. Also the other matched filters 11, 12 are

Weighting members 21, 22 with bridge circuits 210 and 220 and

Low-pass RC downstream. For weighting voltage dividers 300, 40, 50 and in the case of the signal paths for the Fremdkanalnutzsignale also diodes D for ORing the outputs downstream. The outputs of the diodes D are connected via an ohmic resistor 3 to the electrical ground. By the diodes D is a maximum value function for the

Fremdkanalnutzsignalausgänge realized. This maximum signal is applied by an operational amplifier 302 as a subtractor from one at its positive input applied weighted first sub-signal Sj (t) deducted. The operational amplifier 302 is fed back via an ohmic resistor 301 and an ohmic resistor 303. Its output signal, by driving a switch 304, determines whether an output 60 of the circuit has the predefined output value zero or the first sub-signal

Sj (t) receives.

FIG. 3 shows method steps of an embodiment of a

inventive method. In step 100, a reception signal is received by means of an ultrasonic transducer of an environment detection system. Of the

Converter converts the received signal into the electrical domain and performs in step 200 an input filtering, by means of which a

Frequency band limitation of the received signal is accompanied. In step 300, partial signals are isolated from the received signal, of which a first partial signal contains potentially useful sound, a second partial signal receives an increased relative to the first partial signal Störschallanteil and a third partial signal and a fourth partial signal each contain potential useful signals from foreign channels ("Fremdkanalnutzsignale"). In step 400, the partial signals are rectified and weighted in step 500 to produce a subsequent subtraction according to the invention to a result which is equivalent to a signal-to-noise ratio determination The fourth partial signal is combined by a maximum value function and the result is subtracted from the first partial signal in step 700. In step 800, the difference is compared with a predefined threshold value, wherein it is determined whether the signal-to-noise ratio determined in accordance with the invention is suitable for present purposes. Subsequently, in step 900, a time profile of a level-dependent magnitude of the first partial signal and the second partial signal and the difference between the two partial signals is determined and in response thereto in step 1000 a time period between a start of a first echo cycle and a start of a second immediately after the first echo cycle second Echo cycle adjusted. Subsequently, in step 1100, in response to the comparison result between the difference and the threshold, the first sub-signal is provided for sound-based environmental detection or a predefined fixed signal is sent to a downstream system

Distance determination forwarded.

Claims

A method for sound-based environment detection, comprising the steps of: isolating (300) a potential partial signal comprising a useful signal (sj (t)) from a received signal (r (t)),

Isolating (300) a second partial signal (si1 (t)) that potentially comprises an interference signal and is different from the first partial signal from the received signal (r (t)),

Subtracting (500) the second partial signal (si1 (t)) from the first partial signal (sj (t)), and

Comparing (600) the difference to a threshold (L).

The method of claim 1 further comprising

Rectifying (400) the first partial signal (sj (t)).

The method of claim 1 or 2, further comprising

Weights (500) of the first sub-signal (sj (t)) and / or the second sub-signal (si1 (t)).

Method according to one of the preceding claims, further comprising rectifying (400) the second partial signal (si1 (t)) or the weighted second partial signal (si1 (t).

Method according to one of the preceding claims, wherein

the useful signal is an echo of an emitted measuring signal, in particular in the ultrasonic range, and / or

isolating (300) the first partial signal (sj (t)) and / or the second partial signal (si1 (t)) comprises adapted filtering of the received signal (r (t)).

The method of any one of the preceding claims, further comprising the step Using (1100) the first partial signal (sj (t)) for one

sound-based environmental detection if the difference is greater than the threshold (L).

The method of any one of the preceding claims, further comprising the step

Outputting (1 100) a predefined fixed signal and / or no signal, if the difference is smaller than the threshold value (L).

The method of any one of the preceding claims, further comprising the steps

Determining (900) a time profile of a level-dependent variable of the first partial signal (sj (t)) and / or the second partial signal (si1 (t)) and / or the difference of both partial signals, and

Adjusting (1000) a time period between a first echo cycle and a second echo cycle following the first echo cycle, preferably immediately, in response to determining the level dependent magnitude (s).

Method according to one of the preceding claims, wherein all steps are carried out within a common echo cycle for environment detection.

The method of any one of the preceding claims, further comprising the step

Isolating (300) a third partial signal (si2 (t)) potentially comprising a second useful signal from the received signal (r (t)),

Subtracting (700) the third partial signal (si2 (t)) from the first partial signal (sj (t)), and

Comparing (800) the difference to a threshold (L).

The method of claim 10 further comprising

Isolating (300) a fourth partial signal (si3 (t)) potentially comprising a third useful signal from the received signal (r (t)), and combining (600), in particular comparing or forming a maximum value of the third partial signal (si2 (t)) and of the fourth partial signal (si3 (t)).

12. Apparatus for sound-based environment detection comprising

a sound transducer (5),

a first filter (10),

a subtractor (302), and

a rating unit (59), wherein

the first transducer (10) is provided for isolating a potential first signal (sj (t)) of a received signal (r (t)) of the potential signal comprising a useful signal Sound converter (5) is set up, continuing

the subtractor (302) is adapted to subtract (700) the second partial signal (si1 (t)) from the first partial signal (sj (t)). 13. The apparatus of claim 12 further comprising

a weighting member (21) arranged to weight (500) the second partial signal (si1 (t)) with a factor other than 1. 14. The apparatus of claim 12 or 13 further comprising

a second filter (11), wherein

the second filter (11) is arranged to isolate a third partial signal (si2 (t)) potentially comprising a second useful signal from the received signal (r (t)), and

- The subtracter (302) is arranged, the second partial signal (si1

(t)) or the second weighted sub-signal (si1 (t)) or the third sub-signal (si2 (t)) from the first sub-signal (sj (t)) to subtract (500).

Apparatus according to claim 14 further comprising

a second weighting member (22),

the second weighting member (22) is arranged to weight the second partial signal (si1 (t)) with a second factor different from 1 (500).