DE102017125136B4 - Method and device for providing a digital sensor signal from an ultrasonic sensor - Google Patents

Abstract

Method for providing a digital sensor signal (DS) of an ultrasonic sensor (16) for a signaling transmission, in particular a signaling transmission with a limited transmission rate, to a signal receiver (26), in which a -preferably digital- output signal (RS) of the ultrasonic sensor (16) is processed into the digital sensor signal for signaling transmission, the processing comprising the following steps:
- Determination of a signal change (SC) of successive values of the output signal (RS),
- Quantization of this signal change (SC) and
- Output of the quantized signal change (SC) as the digital sensor signal (DS), characterized in that the quantization step size of the quantization of the signal change (SC)
- depending on a quantity (SA) corresponding to an assigned value of the output signal (RS) or
- is selected depending on an assigned signal change (SC).

Description

The present invention relates to a method for providing a digital sensor signal of an ultrasonic sensor for a signaling transmission, in particular a signaling transmission with a limited transmission rate, to a signal receiver, in which an output signal of the ultrasonic sensor is processed into the digital sensor signal for the signaling transmission.

The invention further relates to a corresponding device for providing a digital sensor signal from an ultrasonic sensor for a signaling transmission to a signal receiver, a corresponding ultrasonic sensor device with an ultrasonic sensor and such a device, and a corresponding ultrasonic sensor system.

The document DE 10 2008 044 058 B4 describes a method and a system for providing a digital sensor signal from an ultrasonic sensor for signaling transmission via LIN communication (LIN: Local Interconnect Network) to a control device of this sensor. The system processes an output signal from the sensor into the digital sensor signal for signaling transmission via LIN communication.

The terms signal transmission or signal transmission generally stand for information and data transmission. The data transmission between an ultrasonic sensor and the control unit responsible for this sensor (ECU: electronic control unit) in motor vehicles is currently carried out using standardized transmission protocols, such as the bus protocol for LIN.

The transmission systems used for this are limited in their data rate. While the ultrasonic sensor itself has the information about the membrane oscillations available as a measurement signal in detail using an analog-to-digital converter with a high sampling rate and high quantization, in today's systems the control unit only has very lossy images of the actual measurement data Disposal.

The data rate of the transmission between the ultrasonic sensor and the control device always results from the sampling rate used and the quantization. If the sampling rates of the measurement signal, referred to below as the output signal of the ultrasonic sensor or raw signal, are too low (a reduction in the sampling rate also results in a reduction in the necessary data rate), errors such as aliasing or a greatly reduced resolution arise due to the loss of information. Conventional quantization with a small number of bits, usually less than 5, generates a high level of quantization noise, which in the worst case can prevent meaningful use of the data. An improvement in quantization noise can under certain circumstances be achieved through nonlinear characteristics. However, this approach is also severely limited by the number of possible quantization states that result from the quantization bits.

One way to improve the information that arrives in the ECU is to further develop and use more complex transmission protocols. However, the necessary requirements for sensors and control devices are usually associated with increasing system costs.

Alternatively, the transmission can be concentrated on the target echoes of the ultrasonic signals, but this means that information is lost, particularly about the environmental conditions, which is useful, for example, for assessing the confidence of the measurements.

Another option is so-called sparse sampling (also compressed sampling/sensing). The resulting number of samples to be transmitted with this method is significantly lower than with conventional, equidistant data transmission, but complex reconstruction processes are necessary in the control unit, which can hardly be implemented with today's control units.

From the DE 100 24 959 A1 Device for exchanging data between a measuring unit and an evaluation unit is known, which has a compression unit which compresses the measurement data.

From the DE 10 2015 120 130 A1 is a method for transmitting data from at least one measurement sensor, which is at least partially compressed using a compression algorithm.

Based on the above-mentioned prior art, the invention is based on the object of specifying measures that enable the sensor signal to be transmitted as precisely as possible, even with a limited transmission rate.

The problem is solved according to the invention by the features of the independent claims. Advantageous embodiments of the invention are specified in the subclaims.

In the method according to the invention for providing a digital sensor signal of an ultrasonic sensor for a signaling transmission to a signal receiver, in which a - preferably digital - output signal of the ultrasonic sensor is processed into the digital sensor signal for the signaling transmission, it is provided that the processing includes the following steps : (i) detecting a signal change from successive values of the output signal, (ii) quantizing this signal change and (iii) outputting the quantized signal change as the digital sensor signal. In other words, instead of (re)quantizing the values of the output signal, i.e. the signal amplitude, a signal change of successive values of the output signal is determined and quantized.

In combination with reducing the sampling rate to a minimum for loss-free data transmission in accordance with the Nyquist theorem, this quantization method allows high compression of ultrasound measurement data without loss of information. In this context, quantization is to be understood as a kind of “mapping for data compression”.

A quantization of amplitude values of the signal (instead of the quantization of the signal changes carried out here according to the invention) has the disadvantage, particularly in the case of ultrasonic echoes, that high amplitude deflections are generated by the reverberation of the membranes during transmission, while the signals from environmental echoes are usually significantly lower. In order to quantize the signal as completely as possible, some of the quantization states can only be used for ringing, which means that the number of quantization states for the ambient echoes is small for a given number of bits. For this reason, it makes sense to quantize only amplitude differences, i.e. signal changes, between the current value of the signal and the last value instead of the absolute amplitudes (hereinafter also called delta-based quantization). In this way, such strong amplitude fluctuations can be quantized even with small quantization bits. An additional advantage of delta-based quantization is that negative values, for which a sign bit or similar must be used in amplitude-based systems, can also be transmitted without additional data bits.

The quantization step size of the quantization can be fixed or varied depending on one or more criteria.

1. (a) in Abhängigkeit einer einem zugeordneten Wert des Ausgangssignals entsprechenden Größe oder
2. (b) in Abhängigkeit einer zugeordneten Signaländerung

gewählt. Der für den Fall (a) zugrundeliegende Wert des Ausgangssignals ist (natürlich) ein bereits vorliegender Wert, zum Beispiel der letzte bereits vorliegende Wert des Ausgangssignals. Die diesem Wert entsprechende Größe ist der Wert selbst, eine Quantisierung des Wertes oder eine andere diesem Wert entsprechende Größe. Beim Fall (b) wird eine zuvor ermittelte Signaländerung, zum Beispiel die unmittelbar zuvor ermittelte Signaländerung, als Kriterium für die Variation der Quantisierungsschrittweite genutzt.According to the invention, the quantization step size of the quantization of the signal change

1. (a) depending on a size corresponding to an assigned value of the output signal or
2. (b) depending on an associated signal change

chosen. The underlying value of the output signal for case (a) is (of course) an already existing value, for example the last already existing value of the output signal. The quantity corresponding to this value is the value itself, a quantization of the value, or another quantity corresponding to this value. In case (b), a previously determined signal change, for example the immediately previously determined signal change, is used as a criterion for varying the quantization step size.

An electronic component or a function that quantizes a value or a signal is referred to below as a quantizer. The error resulting from quantization is called quantization error. The quantizer used here is a quantizer with an adjustable quantization step size.

According to a further preferred embodiment of the invention, it is provided that the choice of the quantization step size takes place according to a predetermined function, which links the quantization step size in case (a) with the size corresponding to the assigned value of the output signal or in case (b) with the assigned signal change.

It is preferably provided that the function is available as a data record. This data record corresponds to a stored characteristic curve. The characteristic curve or the corresponding data set is preferably stored directly in the quantizer.

According to yet another preferred embodiment of the invention, the quantization step size of the quantization of the signal change is predetermined to be constant at a size corresponding to an assigned value of the output signal above a limit value. This specification is preferably obtained directly via the function or characteristic curve.

It is also advantageously provided that the signaling transmission is a data transmission via a BUS system, in particular a LIN bus system. The Local Interconnect Network (LIN), also called LIN bus, is a serial communication system for networking sensors and actuators, i.e. a fieldbus. The LIN bus is coming particularly used where the bandwidth and versatility of a CAN bus system (CAN: Controller Area Network) is not required. Typical application examples are networking within a motor vehicle area.

In the device according to the invention for providing a digital sensor signal of an ultrasonic sensor for a signaling transmission, in particular a signaling transmission with a limited transmission rate, to a signal receiver, which is set up to process a preferably digital output signal of the ultrasonic sensor into the digital sensor signal for the signaling transmission, it is provided that this device is set up to (i) determine a signal change in the output signal, (ii) output this and (iii) the quantized signal change as the digital sensor signal for transmission.

The embodiments of the invention mentioned above in the description of the method also apply accordingly to the device.

According to a preferred embodiment of the device according to the invention, it is provided that it is set up to carry out the method mentioned above.

In the ultrasonic sensor device according to the invention with an ultrasonic sensor, it is provided that it also has an aforementioned device, which is connected downstream of the ultrasonic sensor in terms of signaling, for generating a digital sensor signal of the ultrasonic sensor.

In the ultrasonic sensor system according to the invention for a motor vehicle, with at least one ultrasonic sensor and a control device, it is provided that this system also has at least one aforementioned device for generating a digital sensor signal of the ultrasonic sensor.

The invention is explained in more detail below with reference to the accompanying drawings using preferred embodiments.

• 1 ein Kraftfahrzeug, welches ein Fahrerassistenzsystem mit einer Ultraschallsensorvorrichtung gemäß einer Ausführungsform der Erfindung aufweist,
• 2 ein Ersatzschaltbild einer Vorrichtung zum Erstellen eines digitalen Sensorsignals eines Ultraschallsensors gemäß einer ersten Ausführungsform der Erfindung,
• 3 ein Ersatzschaltbild einer Vorrichtung zum Erstellen eines digitalen Sensorsignals eines Ultraschallsensors gemäß einer zweiten Ausführungsform der Erfindung,
• 4 eine graphische Darstellung eines ursprünglichen Sensorausgangssignals, eines Signals mit reduzierter Anzahl an Abtastwerten sowie einer lineare Quantisierung des Signals ohne Adaption und
• 5 eine graphische Darstellung des ursprünglichen Sensorausgangssignals, des Signals mit reduzierter Anzahl an Abtastwerten sowie einer Delta-basierten Quantisierung mit quadratischer Quantisierungskennlinie und Adaption auf Basis der vorangegangen Amplitudenwerte sowie mit zwei festen Quantisierungszuständen.

It shows

• 1 a motor vehicle which has a driver assistance system with an ultrasonic sensor device according to an embodiment of the invention,
• 2 an equivalent circuit diagram of a device for creating a digital sensor signal of an ultrasonic sensor according to a first embodiment of the invention,
• 3 an equivalent circuit diagram of a device for creating a digital sensor signal of an ultrasonic sensor according to a second embodiment of the invention,
• 4 a graphical representation of an original sensor output signal, a signal with a reduced number of samples and a linear quantization of the signal without adaptation and
• 5 a graphical representation of the original sensor output signal, the signal with a reduced number of samples and a delta-based quantization with a square quantization characteristic and adaptation based on the previous amplitude values and with two fixed quantization states.

1 shows a motor vehicle 10, which is presently designed as a passenger car, in a top view. The motor vehicle 10 includes a driver assistance system 12, which serves to support a driver in driving the motor vehicle 10. In particular, the driver assistance system 12 can be designed as a parking assistance system, by means of which the driver can be supported when parking the motor vehicle 10 into a parking space and/or when parking out of the parking space.

The driver assistance system 12 in turn includes an ultrasonic sensor system 14. The ultrasonic sensor system 14 has at least one ultrasonic sensor 16. In the present exemplary embodiment, the ultrasonic sensor device 14 comprises twelve ultrasonic sensors 16. Six ultrasonic sensors 16 are arranged in a front area 18 of the motor vehicle 10 and six ultrasonic sensors 16 in a rear area 20 of the motor vehicle 10. The ultrasonic sensors 16 can in particular be mounted on the bumper of the motor vehicle 10. The ultrasonic sensors 16 can be arranged at least in certain areas in corresponding recesses or through openings in the bumpers. It can also be provided that the ultrasonic sensors 16 are arranged concealed behind the bumper. In principle, the ultrasonic sensors 16 can also be arranged on other trim parts of the motor vehicle 10. For example, the ultrasonic sensors 10 can be arranged on or concealed behind the doors of the motor vehicle 10.

With the help of the respective ultrasonic sensors 16, sensor signals can be provided which describe at least one object 22 in a surrounding area 24 of the motor vehicle 1. In the present case, an object 22 is shown schematically in the surrounding area 24. To determine the Sensor signal can be sent out with each of the ultrasonic sensors 16. The ultrasonic signal reflected by the object 22 can then be received again. Based on the transit time between the emission of the ultrasonic signal and the reception of the ultrasonic signal reflected by the object 22, a distance between the ultrasonic sensor 16 and the object 22 can then be determined. It can also be provided that the respective distances, which are determined with different ultrasonic sensors 16, are taken into account. The relative position between the motor vehicle 10 and the object 22 can thus be determined by means of trilateration. It can also be provided that the ultrasonic signal that was emitted by one of the ultrasonic sensors 16 is received by another of the ultrasonic sensors 16. This is also known as cross measurement.

Furthermore, the ultrasonic sensor system 14 includes an electronic control device 26, which is connected to the ultrasonic sensors 16 for data transmission via a data line 28 or a bus system (line 28 is in 2 shown). The sensor signals determined by the respective ultrasonic sensors 16 can be transmitted to the control device 26 via the data line 28. Based on the sensor signals, the control device 26 can check whether the object 22 is in the surrounding area 24 and at what position the object 22 is in the surrounding area 24. This information can then be used by the driver assistance system 12 to output an output to the driver of the motor vehicle 10. In addition, it can be provided that the driver assistance system 12 intervenes in a steering system, a braking system and/or a drive motor in order to maneuver the motor vehicle 10 autonomously or at least semi-autonomously depending on the at least one detected object 22.

2 shows a device 30 for providing a digital sensor signal DS of an ultrasonic sensor 16 from the original measurement signal of the sensor 16, referred to below as the output signal (or raw signal) RS. The digital sensor signal DS is then transmitted, for example, via a LIN bus (LIN: Local Interconnect Network). 28 transmitted to the control unit 26. For this purpose, the device 30 processes the output signal RS of the ultrasonic sensor 16 into a digital sensor signal DS for a signal transmission with a limited transmission rate. A signal change SC of successive values (or amplitudes) of the output signal RS is determined by means of a subtractor 32 and a holding element 34. The holding element 34 holds the previous value of the output signal RS, so that the difference between the previous and that is determined by means of the subtractor 32 current value of the output signal RS, i.e. the signal change SC of the output signal RS is determined. This signal change SC is then quantized accordingly using a quantizer 36 and made available for transmission as the digital sensor signal DS. The quantizer 36 is a quantizer 36 in which the quantization step size (quantization intervals) can be set.

The quantization of amplitude values of the signal (instead of the quantization of the signal changes SC carried out here), particularly in the case of ultrasonic echoes, has the disadvantage that high amplitude deflections are generated by the reverberation of the membranes during transmission, while the output signals RS of environmental echoes are usually significantly lower. In order to quantize the signal as completely as possible, some of the quantization states can only be used for ringing, which means that the number of quantization states for the ambient echoes is small for a given number of bits. For this reason, it makes sense to quantize only amplitude differences, i.e. signal changes SC, between the current value of the output signal RS and the last quantized value, instead of the absolute amplitudes of the output signal RS. This procedure is also referred to below as delta-based quantization. In this way, such strong amplitude fluctuations can be quantized even with small quantization bits. An additional advantage of delta-based quantization is that negative values, for which a sign bit or similar must be used in amplitude-based systems, can also be transmitted without additional data bits.

A weakness of a method (not explicitly shown here) or a corresponding device 30 with fixed quantization steps is either a low-pass behavior of the quantization if the quantization steps are chosen to be small, or a low accuracy if the quantization steps are chosen too large, which is the worst case leads to similar results as with the amplitude-based method. Linear or non-linear functions can also be used as characteristic curves here.

At the in 2 In the device 30 shown, the quantization step size when quantizing the signal change SC of the output signal RS to the digital sensor signal DS is selected (i.e. scaled) according to the amplitude SA of at least one assigned value of the output signal RS. This is reflected in the equivalent circuit diagram via the signal output of the quantizer to a scaler 40 of the quantizer 36 symbolically represented by a guided arrow. In addition to this signal amplitude SA of the output signal RS, the quantizer 36 of course also outputs the corresponding quantized digital sensor signal DS.

In other words, the quantization steps corresponding to the previous quantization (amplitude) values are adapted here. In order to avoid the already mentioned low-pass behavior or insufficient resolution, it makes sense to adapt the quantization steps according to the signal amplitude SA. For example, it makes sense to use higher quantization steps for high amplitude values than for low amplitudes. This can be illustrated, for example, by the after-oscillation, which has a high amplitude and typically has a steep drop-off. Adjustment of the quantization steps can be performed via a scaling factor calculated using the last amplitude value, as in 2 shown schematically.

In addition to this procedure for adapting the quantization, there is also the option of using the last delta value for scaling. This procedure is in 3 sketched. The advantages and disadvantages of both approaches depend on the signal, so that they can be selected signal-specifically. The 3 thus shows an alternative embodiment of the device 30 for creating a digital sensor signal DS of an ultrasonic sensor 16 from the output signals of the sensor 16.

At the in 3 In the device shown, the quantization step size when quantizing the signal change SC of the output signal RS is selected (i.e. scaled) according to the size of at least one associated digital sensor signal value DS, which corresponds to the correspondingly quantized signal change SC. This is symbolically shown in the equivalent circuit diagram from the signal output for outputting the digital sensor signal value DS representing the signal change SC to the scaler 40 of the quantizer 36.

In other words, the quantization steps corresponding to the previous quantization deltas are adapted here. In order to avoid the already mentioned low-pass behavior or insufficient resolution, it makes sense to adapt the quantization steps according to the signal.

The advantages and disadvantages of both approaches, i.e. the approaches from the 2 and 3 , are signal-dependent, so that they can be selected signal-specifically.

Furthermore, an additional use of a defined number of fixed, non-adaptable quantization states can be provided. Even if in most cases the adaptations described above are a sensible assumption, signals also occur that cause a strong change to the next sample value after a small amplitude. In order to avoid low-pass-like quantization behavior in these cases, it makes sense to use fixed quantization steps in addition to the adaptive quantization steps. As a rule, these should be chosen so large that high amplitude changes can be represented well. In this way, low-pass behavior and thus loss of information can be prevented in any case.

To demonstrate the advantages of the quantization process and the associated data compression, an example of 3-bit quantization using real measured values is given. The 4 and 5 each show a graphical representation of corresponding signals, in which the amplitude of the respective signal is plotted against the distance in meters.

4 shows not only the original output signal 42 but also the signal with a reduced number of sample values 44. In 4 a linear quantization of the signal without adaptation is shown as graph 46. In the signal section shown, the ringing of the membrane is not shown, so that fewer than 8 quantization states can be seen.

In 5 In addition to the original output signal 42 and the signal with a reduced number of samples 44, a delta-based quantization with a square quantization characteristic and adaptation based on the previous amplitude values and with two fixed quantization states is shown as a graph 48 in direct comparison.

Both (in the 4 and 5 (shown as graphs 46 and 48) quantizations use only 3-bit. The advantage of the presented method for compressing ultrasound data is clearly visible when comparing these graphs.

Reference symbol list

10

motor vehicle

12

Driver assistance system

14

Ultrasonic sensor system

16

Ultrasonic sensor

18

Front area

20

Rear area

22

object

24

Surrounding area

26

Control unit

28

Data line

30

Device for generating a digital sensor signal

32

subtractor

34

Sample and hold element

36

Quantizer

38

curve

40

Scaler

42

Output signal

44

Signal with reduced sample values

46

Signal with linear quantization

48

Signal with Δ-based quantization

D.S

Digital sensor signal for transmission

RS

Sensor output signal

SAT

Signal amplitude (output signal)

SD

Signal change (output signal)

Claims (10)

Method for providing a digital sensor signal (DS) of an ultrasonic sensor (16) for a signaling transmission, in particular a signaling transmission with a limited transmission rate, to a signal receiver (26), in which a -preferably digital- output signal (RS) of the ultrasonic sensor (16) is processed into the digital sensor signal for signaling transmission, the processing comprising the following steps: - determining a signal change (SC) of successive values of the output signal (RS), - quantizing this signal change (SC) and - outputting the quantized signal change ( SC) as the digital sensor signal (DS), characterized in that the quantization step size of the quantization of the signal change (SC) - depending on a quantity (SA) corresponding to an assigned value of the output signal (RS) or - depending on an assigned signal change (SC) is chosen. Procedure according to Claim 1 , characterized in that the selection of the quantization step size is carried out according to a predetermined function, which links the quantization step size with the quantity (SA) corresponding to the assigned value of the output signal (RS) or the assigned signal change (SC). Procedure according to Claim 2 , characterized in that the function is available as a data record. Procedure according to one of the Claims 1 until 3 , characterized in that the quantization step size of the quantization of the signal change (SC) is predetermined to be constant at a size (SA) corresponding to an assigned value of the output signal (RS) above a limit value. Procedure according to one of the Claims 1 until 4 , characterized in that the signal change (SC) of the output signal (RS) is determined by means of a subtraction (32). Procedure according to one of the Claims 1 until 5 , characterized in that the signaling transmission is a data transmission via a BUS system, in particular a LIN bus system. Procedure according to one of the Claims 1 until 6 , characterized in that the quantization of the signal change (SC) of the sampled output signal (RS) takes place by means of a quantizer (36). Device (30) for providing a digital sensor signal (DS) of an ultrasonic sensor (16) for a signaling transmission, in particular a signaling transmission with a limited transmission rate, to a signal receiver, the device (30) for processing a - preferably digital - output signal (RS ) of the ultrasonic sensor (16) is set up in the digital sensor signal (DS) for signaling transmission, the device (30) being set up to determine a signal change (SC) of the output signal (RS), to quantize this signal change (SC) and the to output the quantized signal change (SC) as the digital sensor signal (DS) for transmission, characterized in that the quantization step size of the quantization of the signal change (SC) - depending on a size (SA) corresponding to an assigned value of the output signal (RS) or - depending an assigned signal change (SC) is selected. Ultrasonic sensor device with an ultrasonic sensor (16) and a device (30) connected downstream of the ultrasonic sensor (16) for signaling purposes Claim 8 . Ultrasonic sensor system (14) for a motor vehicle (10), with at least one ultrasonic sensor (16), a control device (26) and at least one device (30). Claim 8 .

Images