WO2014135342A1

WO2014135342A1 - Method and device for detecting environmental signals received by means of a sound transducer

Info

Publication number: WO2014135342A1
Application number: PCT/EP2014/052581
Authority: WO
Inventors: Matthias Karl
Original assignee: Robert Bosch Gmbh
Priority date: 2013-03-05
Filing date: 2014-02-11
Publication date: 2014-09-12
Also published as: DE102013204910A1; DE102013204910B4

Abstract

The invention relates to a method and a device for environment sensors, in which at least one reference signal is used or which uses at least one reference signal, in order to be able to better recognize echos received by an actual transducer signal by means of subtraction, in that oscillation signals comprised in the transducer signal are reduced or removed by the subtraction.

Description

Description title

Method and device for detecting surrounding signals received by means of a sound transducer

State of the art

The present invention relates to a method and a device for detecting environmental signals received by means of a sound transducer. In particular, the present invention relates to a method and a device for improved analysis of an environment signal received by means of a sound transducer with regard to the detection of echoes contained therein.

Known devices for environmental sensors are often based on

Transducer signals which radiated into the environment and of

Environment objects are reflected. The reflected signals (echoes) are received by means of a transducer or the same transducer, which has sent the signal into the environment, converted into electrical signals and evaluated by an evaluation unit. Usually, in the acoustic environment monitoring means of emitted acoustic Meßsignalformen an electro-acoustic transducer repeatedly similar to the emission of the

Controlled measurement waveforms. The measuring signal forms are included

uniform across measuring cycles. From the signal transit time ("pulse transit time"), the object distance in space is inferred. During the active excitation time of the transducer, referred to as the "transmit", the transducer begins to oscillate at the frequency impressed upon it. Since today's converters are higher-order resonant systems, the transmission time is divided into a "settling time" and a "constant sending time". After the end of the active excitation of the transducer follows the decay of the vibration energy stored by the excitation in the converter. The resulting after the end of the transmission stimulus due to the stored vibration energy Converter signal will be referred to below as Ausschwingsignal. Characteristic is the shape of the envelope of the decay signal, which essentially follows an e-function. Now, if the same membrane is used to send the signals into the environment, as well as to receive the echoes from the environment, the received signal is during the

Decay period, a superposition of the decay signal and the echoes. Is the signal strength of the echoes much smaller than the signal strength of the echo?

With decaying, such objects can not be detected based on the signal strength with today's methods. It follows that distance measurements of objects very close to the transducer are not reliably possible. There are therefore many attempts and solutions for damping the decay of used transducer membranes after completing the active emission of signals into the environment. For example, an attempt is made through

Counter-control of the membrane to dampen the vibration energy of the transducer membrane as quickly as possible. However, this additional hardware is required and the control is relatively complicated, since exact knowledge of the current vibration state of the membrane are required to specifically realize a push-pull control can. Passive approaches, such as providing a cushioning foam behind the membrane, are more robust, but they also dampen during the process

Send out useful signals in the environment of the membrane, which is why for the emission of signals additional energy must be expended.

It is therefore desirable to have a method which, without slowing down the vibrating transducer by means of electrical energy, receives the detection

Echoes favored, in particular, such echoes should be extracted from the transducer signal whose amplitude is smaller than the amplitude of

Ausschwingsignals is. Disclosure of the invention

The above object is achieved by a method with the features of claim 1 and a device having the features of claim 10. Accordingly, a method for detecting means of a sound transducer received ambient signals is provided, which in at least a first operating state of possible operating conditions in a first step, the conversion of a means of the sound transducer received ambient signal into a first electrical signal. In other words, a signal from the environment hits the converter used according to the invention and is converted into a first electrical signal. Furthermore, according to the invention, at least one reference signal is generated which, in particular, is similar to the decay signal of the converter. For example, this can be a recorded during a previous excitation Ausschwingsignal in which no ambient echo is included,

be recorded and stored. Subsequently, in another operating state, the reference signal is subtracted from the first electrical signal, so that a signal is produced which corresponds to the difference between the first electrical signal and the reference signal.

Of course, the reference signal can not exclusively by

Recording a Ausschwingsignals be included in the execution of the method according to the invention, but for example determined by the manufacturer in the context of a reference measurement, stored and used in the context of the method according to the invention. By the method according to the invention thus also a determination by means of the transducer ambient signals received is possible whose amplitudes at a given time in the echo cycle are significantly lower than the amplitudes of the decay signal of the transducer after excitation.

The dependent claims show preferred developments of the invention. Preferably, the method according to the present invention further comprises a step of exciting the transducer to generate a second electrical signal. Preferably, the second electrical signal is generated at a time at which the sound transducer in a

Operating state is in which no or negligible

Ambient signals arrive at the sound transducer. In other words, it becomes one

Excitation signal given to the transducer under such conditions that its decay can be done in as pure as possible (undisturbed) form. The excitation signal may, for example, be identical to the signal which has been applied to the transducer in order to generate an echo at an environment object, which is converted as a first electrical signal. Subsequently, the generated by the sound transducer after the excitation second electrical signal as a waveform for generating the Reference signal stored. In other words, a possibility is created to conserve and reproduce the "pure" decay signal just generated. Alternatively, the reference signal without prior

Caching be deducted from the first electrical signal, which difference formation also includes an antiphase addition of the

Reference signal and the first electrical signal to be understood. If, then, in a similar operating state, an ambient signal is recorded by means of an oscillating transducer, it is possible by subtraction between the resulting first electrical signal and the

stored reference signal, an "exposure" of the first signal contained

Echo signal done.

Further preferably, the result of the subtraction or subtraction described above can then be filtered and / or otherwise

Be subjected to signal processing algorithms. For example, that can

Signal are rectified and / or an envelope of the signal are formed and / or the signal are averaged and in particular the result of the subtraction are judged by a predefined reference.

By way of example, a threshold value curve can be used here, which, if exceeded, classifies the result of the subtraction as "containing an echo". A subsequent signal processing of the difference signal can thereby favor a successful detection of any echoes contained considerably. More preferably, the subtracting of the at least one comprises

Reference signal from the first electrical signal, a synchronization of the reference signal and the electrical signal. In other words, a corresponding point is first found in both signals, so that the components of the decay contained in the first electrical signal are suppressed as accurately as possible by the difference formation.

In particular, in the case that the method is used in a vehicle-based environment sensor system, a

Movement speed of the transducer or the equipped with this vehicle can be determined. The travel speed of the vehicle can be used according to the invention to determine whether an operating condition is present which makes an echo likely to appear through a nearby environmental object. ,

Alternatively or additionally, the ambient temperature of the sound transducer can be determined and before storing the recorded first

Signal waveform as one of the possible different reference signals are checked to see if a predefined temperature range is met. Since the turn-off signal of a sound transducer is highly temperature-dependent, an assignment of the generated signal shape to the determined temperature range can take place in this way. When forming the difference, a situation-adequate reference can accordingly be used, as a result of which the method according to the invention provides good results over wide operating states. Furthermore, alternatively or additionally based on the different

Signal curves at the converter, in particular during the settling time during transmission and / or during the constant time when transmitting a measurement signal, the presence of a specific operating state are detected.

In particular, when the transducers have pronounced resonant characteristics that are affected by many parameters such as climate and

in particular temperature and / or, for example, depend on specimen-specific features, such differences in the transducer characteristics lead to different waveforms, in particular during the settling time during transmission and / or during the constant time when transmitting a measurement signal.

Further preferably, a plurality of signal forms generated by the sound transducer after the excitation can be stored as reference signals. As stated above, different in this way

Operating conditions are shown and covered with adequate references. Alternatively or additionally, data records describing a change in the signal form in dependence on predefined operating conditions can be stored and kept ready for generating a corresponding reference signal. For example, a change in the

Resonant frequency and / or an amplitude profile and / or a

Phase characteristic of a required as a reference signal Ausschwingsignals be described in this way with significantly less data than in the case that complete associated time signals are kept in each case. Alternatively or additionally, depending on the system configuration, all information for generating reference signals can be stored or maintained in the form of parameters, these parameters, for example, information about the

Amplitude curve and / or the frequency response and / or the phase characteristic of a reference signal to be generated offer, but are not limited to this. In this way may possibly be more expensive

Storage space can be saved in a system using the method according to the invention.

More preferably, the second electrical signal and / or the

stored signal form for generating the reference signal ("the reference") are stored and processed in the form of sampling points, wherein in particular the sampling times represent non-equidistant points of the signals

Generation of the reference signal only so-called "samples" or

"Support points" of the first electrical signal taken, which with

corresponding support points of the second electrical signal are used to form the difference signal. On the one hand, this offers the advantage that the storage requirements during recording and during processing of the

Signals can be significantly reduced, on the other hand, the

Synchronization can be simplified as corresponding points over time are easier to compare. For this purpose, the sampling times are more preferably synchronized during the decay with the timing of the transmission signal generation.

Further preferably, the times of scanning can be arranged non-equidistantly to each other, for example, to detect or image particularly characteristic points of the waveform, such as the oscillation maxima.

According to a further aspect of the present invention, a device for environment sensor technology is proposed, which includes a sound transducer

Memory means, a signal generator and a signal processing unit comprises. In this case, the sound transducer is at least for the conversion of

Surroundings signals set up in electrical signals. The storage means serves to store the first electrical signal, the at least one Reference signal or corresponding support points and / or parameters for their reproduction. By means of the signal generator, the reference signals required for subtraction can be generated on the basis of the stored data. The signal processing unit may include steps of subtraction, filtering, averaging, synchronization, and others

Perform signal processing steps. In other words, the apparatus according to this aspect of the present invention is arranged to carry out a method according to the first aspect of the present invention. The operation of the device according to the invention and the thus

associated advantages correspond to those set forth in connection with the first aspect of the present invention.

According to a third aspect of the present invention, there is proposed a vehicle comprising at least one environment sensor device according to the second aspect of the present invention. In this case, either the vehicle or the device can have additional sensors, by means of which the current cruising speed of the vehicle and / or the ambient temperature can be determined. Of course, such sensors can also in the signal processing unit of a

be integrated device according to the invention.

Brief description of the drawings

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

Figure 1 is a schematic overview of components of a

Device according to an embodiment of the

present invention;

FIG. 2 shows a flow chart, visualizing steps of a method according to an exemplary embodiment of the present invention; and

FIG. 3 is a timing diagram in which relationships of the in

Connection with the present invention considered signals are recognizable. Embodiments of the invention

FIG. 1 shows a device 1 which comprises an ultrasonic transducer 2

Sound transducer includes. The ultrasonic transducer 2 is on the one hand with a

Signal generator 4 and on the other hand with a microprocessor 5 as

Signal processing unit connected. Also, the signal generator 4 and the microprocessor 5 are connected together. The microprocessor 5 can also access a data memory s as storage means. In the

Data memory 3 can store waveforms or parameters to their

Generation are stored. The operation of the illustrated

Device 1 will be explained below in conjunction with an embodiment of a method according to the invention with reference to FIG. Figure 2 shows steps of a method of an embodiment of the present invention. For example, the procedure starts with

Activating a device 1 according to the invention by, for example, engaging a reverse gear and / or driving with a certain amount

Minimum speed or by another user action. In step 100, a sound transducer 2 is excited by means of an electrical signal. In

Step 200, the resulting electrical signal is picked up and stored by a microprocessor s in a data memory s. For example, this can be a digitization or preprocessing of the electrical signal by "sampling", so support points education done.

In step 300, a reference signal is generated. This can be done, for example, by retrieving data from a data memory s, wherein the data may include parameters and / or time data for reconstructing an electrical signal received at an earlier time. Alternatively or additionally, the reference signal can be made from a plurality of signals, for example by averaging signals which are synchronized with one another at the transmitting end. In this case, the reference signal depending on the current

Speed of the transducer 2 and / or depending on a current temperature can be selected. Alternatively or additionally, a data packet retrieved from the data memory 3 can be adapted as a function of the speed and / or the temperature and the adapted data packet for Generation of the reference signal can be used.

If there is the possibility that a reflective object is located in the near measurement area in front of the sensor, then in step 400 the reference signal is subtracted from the incoming electrical signal. Subsequently, in step

500 "sifted" in the transducer signal over the reference signal excess "and can with a example also stored in the data memory 3 reference data set (for example, a

Reference value and / or a reference curve and / or a reference field or a threshold value and / or a threshold curve and / or a threshold value field).

In step 600, it is optionally possible to rework the difference signal by filtering or averaging the difference signal. The result of

Post-processing may alternatively or in addition to that used in step 500

Reference value or threshold value of a corresponding threshold value. Thereafter, the method ends or begins again with the execution of step 100, as described above. Figure 3 shows a timing diagram in which signals are shown, as discussed in detail above. A reference signal 10 is derived from a second electrical signal containing no echo. This has up to a time t-ι, the beginning of the excitation, no appreciable amplitudes, since in this area required for the emission of signals into the environment energy is fed into the transducer. Between the times t- ₁ and t ₂ , the actual radiation of energy into the environment of the sound transducer 2 takes place. The amplitudes are greatest here. Between the times t ₂ and t ₃ , the electrical excitation of the transducer 2 is already switched off, so that the amplitude of the

Reference signal 10 in this area similar to an e-function 1 1 decreases.

Between the times t ₃ and t ₄ , the reference signal 10 no significant amplitudes more. Dashed lines a received signal 12 superimposed with an echo signal is plotted, whose amplitudes exceed the envelope e-function 1 1 of the decaying reference signal 10 with respect to the reference signal 10 due to an echo contained in the transducer signal.

Also at the times t ₃ and t ₄ are echoes by local maxima in

Amplitude curve of the actual transducer signal 12 recognizable. These come about for example by multiple reflection between an object in the converter environment and the converter 2 or its enclosure. By subtraction between the actual transducer signal 12 and the reference signal 10 results in the second electrical signal 12 with respect to the reference signal 10 existing excess whose envelope 13 is also located. In addition, the echo peak curve is 14

drawn, by means of which a meaningful threshold value curve for identification in the second electrical signal can be provided echoes. In other words, a (slightly) running below the echo peak curve 14 curve can be used as a threshold curve in which

Exceed the inventive method can detect the presence of echoes. On the basis of the echo delay can draw conclusions about the

Removal of the environmental structures responsible for the echoes are drawn.

It is a core idea of the present invention, instead of (only) performing an attenuation of a resonant transducer diaphragm, in one

Converter to detect echoes contained by preferably in-phase subtraction (known) decay waveforms of an actual transducer signal and thus to reduce the Nahdetektionsschwelle for environmental sensing systems and methods. In this case, the subtraction can be effected by circuitry, for example in an analog circuit, generally known to the person skilled in the art, for subtracting two electrical signals or

(especially with digitally processed signals) computationally when processing discretized samples are performed. The basis is in each case a reference signal coming as close as possible to a current decay component in an actual signal, on the basis of which the

Decay portions of an actual transducer signal can be reduced or completely removed in order to better detect received environmental signals can.

Although the aspects and preferred embodiments of the invention have been described in detail with reference to the accompanying drawings, variations, modifications and combinations remain disclosed

Features within the scope of the present skilled person, all of which as in the

Area of the present invention are to be considered, whose

Protection is defined by the appended claims.

Claims

claims

Method for recognition received by means of a sound transducer

Ambient signals comprising the steps:

Converting an ambient signal received by the sound transducer into a first electrical signal,

Generating a reference signal, and

Subtracting the reference signal from the first electrical signal.

The method of claim 1 further comprising the step of:

Exciting the acoustic transducer and generating a second electrical signal, and

Storing a signal generated by the sound transducer after the excitation waveform for generating the reference signal.

Method according to claim 2,

wherein generating the reference signal comprises using the stored waveform.

Method according to claim 2 or 3,

wherein the stored waveform is substantially free of echo signals received by the transducer.

Method according to one of the preceding claims,

further filtering and / or averaging the result of the subtraction.

6. The method according to any one of the preceding claims,

wherein subtracting the reference signal comprises synchronizing the reference signal and the first electrical signal.

7. The method according to any one of the preceding claims 2 to 6, wherein the storing of the signal generated by the sound transducer after the excitation signal only takes place when

a predefined range of travel speed of the sound transducer has not been left, and / or

a predefined range of ambient temperature of the

Schallwandler has not been abandoned.

Method according to one of the preceding claims 2 to 7,

wherein a plurality of signal forms generated by the sound transducer after the excitation are stored, and / or

the data stored in the stored signal form are descriptively stored as a change of the signal form, and / or parameters comprising an amplitude curve and / or a frequency curve and / or a phase curve of a

be generated generating reference signal.

Method according to one of the preceding claims,

wherein the second electrical signal and / or the stored waveform are processed in the form of sampling points, wherein in particular the sampling times represent non-equidistant points of the signals.

Device for environment sensor system comprising:

a sound transducer (2),

a storage means (3),

a signal generator (4), and

a signal processing unit (5),

wherein the device (1) is adapted to carry out a method according to any one of the preceding claims.