KR102426542B1 - Signal processing apparatus and method for processing signals collected from sensors detecting vehicle axis - Google Patents

Abstract

A signal processing method of a signal collected from a sensor for detecting a vehicle axle, the signal processing method of a signal collected from a sensor for detecting a vehicle axle, the method comprising: collecting a signal from the sensor; and performing convolution between the collected signal and a preset standard axis signal.

Description

Signal processing apparatus and method for processing signals collected from sensors that detect vehicle axles {SIGNAL PROCESSING APPARATUS AND METHOD FOR PROCESSING SIGNALS COLLECTED FROM SENSORS DETECTING VEHICLE AXIS}

The present application relates to a signal processing apparatus and method for processing a signal collected from a sensor for detecting a vehicle axle.

The piezoelectric element can be used as a sensor for measuring a change in voltage according to a change in pressure (Δp), but such a sensor has a disadvantage in being vulnerable to noise. A typical example in which piezoelectric elements are actually used is vehicle classification.

In order to classify a vehicle, it is important to measure the number of vehicle axles. Piezoelectric type sensors are mainly used for shaft detection sensors worldwide.

1 is a view for explaining a vehicle type collection method by a conventional vehicle type classifier (AVC).

Referring to FIG. 1 , in order to measure the number of vehicle axles using a conventional piezoelectric sensor, a piezoelectric sensor made of a PVDF film may be installed in a horizontal direction on a road.

In this case, as a method of installing the piezoelectric sensor, there may be, for example, a 2 loop 1 piezo (L-P-L) method, a 2 piezo 1 loop (P-L-P) method, and the like. The L-P-L method refers to an installation method in which one piezoelectric sensor (piezo sensor) is disposed between two loop sensors in the lateral direction of the road, and the P-L-P method refers to an installation method in which one piezoelectric sensor is disposed between two piezoelectric sensors in the lateral direction of the road. It means an installation method in which the loop sensors are arranged. The loop sensor is one of the devices buried in the road floor to investigate traffic data such as road traffic volume, vehicle speed, and vehicle type, and traffic data can be investigated through analysis of vehicles passing through the buried device.

When the piezoelectric sensor is installed in this way, a voltage is generated according to the change in pressure (Δp) that the vehicle steps on and passes, and the number of axles (the number of axles) is increased according to the threshold set in the Automatic Vehicle Classification (AVC) controller. is counted

However, in the conventional method of measuring the number of axles using a piezoelectric sensor, two problems, including multi-axis detection due to noise and shaft loss due to aging of sensors and cables, occur frequently.

Here, in relation to the first problem (multi-axis detection by noise), the causes of generating noise are very diverse. Despite the use of coaxial cables, there are numerous noises of unknown cause, including 60Hz generated from nearby power lines and impacts other than vehicles. Regarding the second problem (shaft loss due to sensor and cable aging), shaft loss refers to the case where the signal of the axis with a small axial load falls below the threshold when the signal size gradually decreases due to aging of the sensor or cable. .

As described above, in order to overcome the first problem, the threshold must be lowered than the noise, and to overcome the second problem, the threshold must be increased. It is required, and at some point it will be necessary to reinstall (replace) the sensor, as these issues contradict each other.

That is, when using the piezoelectric sensor for the purpose of measuring the number of axles of a vehicle, the sensor is replaced when noise occurs (replacement of the sensor is required). Not only is the cost high, but also the inconvenience of controlling traffic. In addition, in general, a piezoelectric method among sensors is expensive.

Therefore, problems that may occur as the vehicle classifier (AVC) using the existing piezoelectric element counts the number of axles according to a set threshold (that is, errors in multi-axis detection depending on noise caused by the surrounding environment, sensor aging, etc.) It is required to develop a technology (accurate vehicle axle number measurement technology using a piezoelectric sensor) that can effectively solve the error that occurs when the signal is weakened by the signal.

The technology that is the background of the present application is disclosed in Korean Patent Application Laid-Open No. 10-2019-0054788.

The present application is intended to solve the problems of the prior art described above, and problems that may occur as the vehicle classifier (AVC) using a conventional piezoelectric element counts the number of axles of a vehicle according to a set threshold (that is, in the surrounding environment) The purpose of providing a signal processing device and method for processing the signal collected from the sensor for detecting the vehicle axis, which can solve the multi-axis detection error according to the noise caused by the sensor, the error caused by the signal weakening due to the aging of the sensor, etc.) do it with

However, the technical problems to be achieved by the embodiments of the present application are not limited to the technical problems as described above, and other technical problems may exist.

As a technical means for achieving the above technical problem, a signal processing method of a signal collected from a sensor for detecting a vehicle axle according to an embodiment of the present application includes: collecting a signal from the sensor; and performing convolution between the collected signal and a preset standard axis signal.

Also, the standard axis signal may be a signal provided to correspond to a signal generated when the sensor detects a vehicle axis.

In addition, the standard axis signal may be separately set and provided for each of the plurality of speed sections in consideration of the signal characteristics generated when the vehicle axis is detected in each of the plurality of speed sections of the vehicle set.

In addition, the sensor may be a sensor that generates a signal in response to a pressure that is changed by the pressurization of the vehicle shaft.

In addition, the signal processing method of a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application may further include measuring the number of vehicle axles based on the convolution result.

On the other hand, according to an embodiment of the present application, a signal processing apparatus for a signal collected from a sensor for detecting a vehicle axle includes: a signal collecting unit for collecting a signal from the sensor; and a control unit that performs convolution between the collected signal and a preset standard axis signal.

Also, the standard axis signal may be a signal provided to correspond to a signal generated when the sensor detects a vehicle axis.

In addition, the standard axis signal may be separately set and provided for each of the plurality of speed sections in consideration of the signal characteristics generated when the vehicle axis is detected in each of the plurality of speed sections of the vehicle set.

In addition, the sensor may be a sensor that generates a signal in response to a pressure that is changed by the pressurization of the vehicle shaft.

In addition, the signal processing apparatus of the signal collected from the sensor for detecting the vehicle axle according to the embodiment of the present application may further include a measurement unit for measuring the number of vehicle axles based on the convolution result.

The above-described problem solving means are merely exemplary, and should not be construed as limiting the present application. In addition to the exemplary embodiments described above, additional embodiments may exist in the drawings and detailed description.

According to the above-described problem solving means of the present application, by providing a signal processing apparatus and method of a signal collected from a sensor for detecting a vehicle axis, the vehicle type classifier (AVC) using a conventional piezoelectric element is set according to a set threshold. As the number of axes is counted, possible problems (that is, errors in multi-axis detection due to noise caused by the surrounding environment, errors that occur when signals are weakened due to aging of the sensor, etc.) can be solved.

However, the effects obtainable herein are not limited to the above-described effects, and other effects may exist.

1 is a view for explaining a vehicle type collection method by a conventional vehicle type classifier.
2 is a view showing a schematic configuration of a signal processing apparatus for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application.
3 is a diagram illustrating an example of a signal collected from a sensor for detecting a vehicle axis in a signal processing apparatus for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application.
4 is a diagram illustrating an example of a preset standard axis signal considered in a signal processing apparatus for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application.
5 is a diagram illustrating an example of a signal amplified after performing convolution between two signals in a signal processing apparatus for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application.
6 is a diagram illustrating an example of a noise signal included in a signal collected from a sensor for detecting a vehicle axis in a signal processing apparatus for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present disclosure.
7 is a diagram illustrating an example of a signal attenuated after performing convolution between two signals in a signal processing apparatus for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application.
8 is an operation flowchart of a signal processing method of a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application.

Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present application pertains can easily implement them. However, the present application may be implemented in several different forms and is not limited to the embodiments described herein. And in order to clearly explain the present application in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout this specification, when a part is said to be “connected” to another part, it is not only “directly connected” but also “electrically connected” or “indirectly connected” with another element interposed therebetween. "Including cases where

Throughout this specification, when it is said that a member is positioned "on", "on", "on", "under", "under", or "under" another member, this means that a member is located on the other member. It includes not only the case where they are in contact, but also the case where another member exists between two members.

Throughout this specification, when a part "includes" a component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

2 is a diagram illustrating a schematic configuration of a signal processing device 10 for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application.

Hereinafter, the signal processing device 10 for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application according to an embodiment of the present application will be referred to as the present device 10 for convenience of description.

Referring to FIG. 2 , the apparatus 10 may include a signal collection unit 11 , a control unit 12 , and a measurement unit 13 .

The signal collection unit 11 may collect a signal from a sensor that detects a vehicle axle.

Here, the sensor for detecting the vehicle shaft may be a sensor that generates a signal in response to the pressure changed by the pressure of the vehicle shaft. Exemplarily, the sensor for detecting the vehicle axle may be a pressure-based sensor (sensor for measuring a signal based on pressure) such as a piezoelectric sensor (piezoelectric sensor).

The sensor for detecting the vehicle axis may be installed in a horizontal direction, for example, on a road for vehicle axis detection (measurement).

The control unit 12 may perform convolution between the signal collected by the signal collection unit 11 (a signal collected from a sensor sensing a vehicle axis) and a preset standard axis signal.

Here, the standard shaft signal may be a signal provided to correspond to a signal generated when a vehicle shaft is detected by a sensor for detecting the vehicle shaft.

These standard axis signals may be separately set and provided for each of a plurality of speed sections (that is, a plurality of set speed sections of a vehicle) in consideration of the signal characteristics generated when the vehicle axis is detected in each of the plurality of speed sections of the vehicle. have. That is, the control unit 12 may set the standard axis signal for each vehicle speed section as an example.

In other words, since the vehicle axis signal shows the characteristic that the width of the signal (the signal collected from the sensor that detects the vehicle axis) varies according to the speed of the vehicle (or, when viewed on the time axis, the signal detection interval in the collected signal is the vehicle According to the speed, when the speed is fast, it appears short, and when the speed is slow, it shows signal characteristics such as long), and the control unit 12 divides the vehicle speed into a plurality of sections (a plurality of speed sections) in consideration of these signal characteristics. , a standard axis signal may be generated and set in advance for each of a plurality of divided speed sections.

That is, the control unit 12 sets the standard axis signal differently for each of the plurality of speed sections (that is, by dividing the signal characteristics for each vehicle speed and providing the standard axis signal for each speed), collected from the sensor for detecting the vehicle axis. It is possible to effectively reduce the error in signal-based vehicle axle count measurement.

Illustratively, the plurality of speed sections include a first speed section in which the speed is less than 30 km/h, a second speed section in which the speed is greater than or equal to 30 km/h and less than 60 km/h, a third speed section in which the speed is greater than or equal to 60 km/h and less than 90 km/h, and 90 km/h It may include a fourth speed section of /h or more. However, this setting example is only an example for helping understanding of the present application, and is not limited thereto, and the range setting value of the speed section for a plurality of speed sections, the number of divisions of the speed section, etc. can be varied by user input, etc. It can be set or changed as a value.

As described above, the controller 12 may preset a standard signal (ie, a standard shaft signal) of a signal to be measured by a sensor (eg, a piezoelectric sensor) for detecting a vehicle axis.

When convolution is performed between the signal collected by the signal collecting unit 11 (a signal collected from a sensor that detects the vehicle axis) and a preset standard axis signal, a signal having a form similar to that of the standard axis signal among the collected signals The higher the value, the larger the value.

A signal collected from a sensor sensing a vehicle axis may be expressed as f (signal), for example, and a preset standard axis signal may be expressed as g (standard axis signal). The controller 12 may perform a convolution (f (signal) * g (standard axis signal)) between these two signals. An example of a waveform of two signals and a signal waveform according to a result of performing convolution may be more easily understood with reference to FIGS. 3 to 7 .

3 is an example of a signal (ie, a sensor signal by the vehicle axle) collected from a sensor for detecting a vehicle axle in the signal processing device 10 for processing a signal collected from a sensor for detecting a vehicle axle according to an embodiment of the present application is a diagram showing 4 is a view showing an example of a preset standard axis signal (ie, an example of obtaining a standard signal) considered in the signal processing device 10 for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application to be. 5 is two signals (ie, a signal collected from a sensor detecting a vehicle axis and a preset standard axis signal) in the signal processing device 10 for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application It is a diagram showing an example of an amplified signal (that is, a signal amplified from a signal collected from a sensor that detects a vehicle axis) after performing convolution between the two. 6 is a diagram illustrating an example of a noise signal included in a signal collected from a sensor for detecting a vehicle axis in the signal processing apparatus 10 for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application. 7 shows two signals (ie, a signal collected from a sensor sensing a vehicle axis and a preset standard axis signal) in the signal processing device 10 for processing a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present disclosure. It is a diagram showing an example of a signal attenuated after performing convolution of a vehicle (ie, a case in which a noise signal included in a signal collected from a sensor sensing a vehicle axis is attenuated by performing convolution).

3 to 7 , the controller 12 may perform convolution between a signal as shown in FIG. 3 , which is a signal collected from a sensor sensing a vehicle axis, and a signal as shown in FIG. 4 , which is a preset standard axis signal.

At this time, when convolution is performed between the two signals, the same signal as the standard axis signal among the signals collected from the sensor that detects the vehicle axis (that is, a signal with a shape similar to that of the standard axis signal (waveform), and the piezoelectric sensor rather than noise. As the normal measurement signal) is amplified by convolution, the value of the signal may appear larger as shown in FIG. 5 for example.

On the other hand, when convolution is performed between the two signals, as an example of a signal that is not the same as the standard axis signal among the signals collected from the sensor that detects the vehicle axis (that is, a signal having a shape different from that of the standard axis signal (waveform), FIG. 6 . As the noise signal shown in FIG. 7 is attenuated by convolution, as shown in FIG. 7 , for example, the value of the signal may appear in a form in which it is reduced or disappeared.

The measurement unit 13 may measure the number of vehicle axles based on the result of the convolution performed by the control unit 12 . That is, the measurement unit 13 may count the number of vehicle axles (the number of axles) by using the signal processing result for performing the convolution. Furthermore, the measurement unit 13 may classify the type of vehicle (vehicle model) corresponding to the counted number of vehicle axles by using the counted number of vehicle axles.

That is, as described above, the apparatus 10 measures the number of vehicle axles based on a sensor (eg, a piezoelectric sensor) that detects a vehicle axis through execution of a convolutional axis detection signal processing algorithm. can be performed.

The apparatus 10 proposes a technology for introducing a convolution method to a road field related to vehicle axle detection (eg, vehicle axle number measurement), vehicle model classification, and the like. The device 10 performs convolution of a signal collected from a sensor for detecting a vehicle axis with a preset standard axis signal, thereby being affected by signal noise due to deterioration of a conventional sensor or cable for detecting a vehicle axis. It is possible to solve the problem of not accurately measuring the number of vehicle axles or accurately classifying a vehicle based on it. That is, the apparatus 10 may provide accurate measurement of the number of vehicle axles or classification of vehicle types while minimizing the influence of noise based on the result of performing convolution.

In the conventional method of measuring the number of vehicle axles using a piezoelectric sensor, by counting the number of signals having a value above the threshold (or exceeding the threshold) among signals collected through the piezoelectric sensor based on a preset threshold, The number of axles was measured and vehicle model classification was performed.

However, such a piezoelectric sensor installed on the road for measuring the number of vehicle axles may be gradually deteriorated over time as many vehicles pass by. Accordingly, the signal sensitivity of the piezoelectric sensor gradually decreases as time goes by, for example, for the same collected signal (that is, the signal collected through the piezoelectric sensor for the same vehicle) before aging, it was detected as a value above the threshold, whereas aging Thereafter, it may change to a form that is detected as a value below the threshold, which may cause many measurement errors. That is, in the conventional method of measuring the number of axles using a piezoelectric sensor, the piezoelectric sensor is vulnerable to noise, and problems such as multi-axis detection and shaft loss due to noise frequently occur. There is a limit to what you can do.

In order to solve this problem, the present device 10 attenuates noise in the collected signal by performing convolution between two signals (that is, a signal collected from a sensor that detects a vehicle axis and a preset standard axis signal), The normal measurement signal in the collected signal can be amplified to a larger value. By measuring the number of vehicle axles based on the result of performing the convolution, the apparatus 10 can more accurately measure the number of vehicle axles and classify the vehicle compared to the conventional method of measuring the number of axles using a piezoelectric sensor.

The present application can increase the replacement period (for example, an average of 71 months) of the pressure sensor used for measuring the number of axles of a conventional vehicle by providing the device 10, so that it is possible to save the budget. In addition, the apparatus 10 can be effectively utilized for measurement using a piezoelectric sensor.

The device 10 counts the number of axles of the vehicle according to the threshold set by the vehicle classifier (AVC) using the existing piezoelectric element. Errors in multi-axis detection according to noise caused by the surrounding environment, and signals due to sensor aging Paying attention to the fact that it has technical difficulties such as errors caused by weakening, setting the standard signal of the signal to be measured with a piezoelectric element and then applying the standard signal convolution algorithm to the signal collected from the sensor Signal measurement (collection) technology using the fact that the value increases with similar shape, and furthermore, the vehicle axis signal has a different signal width depending on the speed of the vehicle, so the technology to set the speed section and prepare the standard signal for each speed section can be said to have been introduced.

This device 10 is capable of performing vehicle classification with higher reliability and accuracy in terms of the introduction of autonomous vehicles and road maintenance for the same, replacement of old vehicle classification systems, and the like, and extension of replacement cycles in continuous road maintenance. It can be used as a possible technique.

The present device 10 relates to a technology for processing a signal collected from a sensor that detects a vehicle axis, and to solve the problem of multi-axis detection according to noise caused by the surrounding environment of the piezoelectric sensor and the problem of signal weakness due to sensor aging. It's about technology.

The device 10 may increase the replacement cycle of the piezoelectric sensor installed for traffic collection by using a standard signal (standard axis signal). Since the device 10 uses a piezoelectric shaft detection sensor as a sensor for counting the number of axles of a vehicle for traffic collection, it can be easily utilized. The device 10 can effectively solve problems due to abnormalities or aging of the sensor (sensor that detects the vehicle axle) by the standard signal (by measurement) when the installation cost of the relatively expensive piezoelectric element is considered.

Currently, traffic volume collection is being operated on more than 530 general national roads and 200 high-speed national highways, for example, but there are problems in noise caused by the surrounding environment and signal weakness due to aging of the sensor. In consideration of this, the apparatus 10 applies convolution to a standard signal (standard axis signal), thereby effectively extending the sensor replacement cycle as a solution to the existing problem.

Hereinafter, based on the details described above, the operation flow of the present application will be briefly reviewed.

8 is an operation flowchart of a signal processing method of a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application.

The signal processing method of the signal collected from the sensor for detecting the vehicle axis illustrated in FIG. 8 may be performed by the apparatus 10 described above. Accordingly, even if omitted below, the description of the apparatus 10 may be equally applied to the description of a signal processing method of a signal collected from a sensor for detecting a vehicle axis.

Referring to FIG. 8 , in step S11, the signal collecting unit may collect a signal from a sensor that detects a vehicle axis.

Here, the sensor for detecting the vehicle shaft may be a sensor that generates a signal in response to the pressure changed by the pressure of the vehicle shaft.

Next, in step S12, the controller may perform convolution between the signal collected in step S11 and a preset standard axis signal.

In this case, the standard shaft signal may be a signal provided to correspond to a signal generated when the vehicle shaft is detected by a sensor for detecting the vehicle shaft.

In addition, the standard axis signal may be separately set and provided for each of the plurality of speed sections in consideration of the signal characteristics generated when the vehicle axis is detected in each of the plurality of speed sections of the vehicle set.

In addition, although not shown in the drawings, in the signal processing method of a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application, after step S12, the measurement unit performs the convolution result in step S12 (convolution result) It may include measuring the number of vehicle axles based on the .

In the above description, steps S11 and S12 may be further divided into additional steps or combined into fewer steps, according to an embodiment of the present application. In addition, some steps may be omitted if necessary, and the order between the steps may be changed.

The signal processing method of a signal collected from a sensor for detecting a vehicle axis according to an embodiment of the present application may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic such as floppy disks. - includes magneto-optical media, and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to carry out the operations of the present invention, and vice versa.

In addition, the signal processing method of the signal collected from the sensor for detecting the vehicle axle described above may be implemented in the form of a computer program or application executed by a computer stored in a recording medium.

The foregoing description of the present application is for illustration, and those of ordinary skill in the art to which the present application pertains will understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present application. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and likewise components described as distributed may also be implemented in a combined form.

The scope of the present application is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present application.

10: Signal processing device of a signal collected from a sensor for detecting a vehicle axle
11: signal collection unit
12: control
13: measurement unit

Claims (10)

In the signal processing method of the signal collected from the sensor for detecting the vehicle axis,
collecting a signal from the sensor; and
performing convolution between the collected signal and a preset standard axis signal;
including,
The standard axis signal is a signal provided to correspond to a signal generated when the sensor detects a vehicle axis,
The step of performing the convolution is,
Among the signals collected from the sensor, a normal measurement signal corresponding to the waveform of the standard axis signal is amplified through the convolution, and a noise signal different from the waveform of the standard axis signal among the signals collected from the sensor is attenuated through the convolution A signal processing method. delete According to claim 1,
The standard axis signal, in consideration of the signal characteristics generated when the vehicle axis is detected in each of the plurality of speed sections of the vehicle, are separately set and provided for each of the plurality of speed sections, the signal processing method. According to claim 1,
Wherein the sensor is a sensor that generates a signal in response to the pressure changed by the pressurization of the vehicle axle, the signal processing method. According to claim 1,
The signal processing method further comprising the step of measuring the number of vehicle axles based on the result of the convolution. In the signal processing apparatus of a signal collected from a sensor for detecting a vehicle axis,
a signal collecting unit collecting a signal from the sensor; and
a control unit for performing convolution between the collected signal and a preset standard axis signal;
including,
The standard axis signal is a signal provided to correspond to a signal generated when the sensor detects a vehicle axis,
The control unit is
Among the signals collected from the sensor, a normal measurement signal corresponding to the waveform of the standard axis signal is amplified through the convolution, and a noise signal different from the waveform of the standard axis signal among the signals collected from the sensor is attenuated through the convolution signal processing device. delete 7. The method of claim 6,
The standard axis signal, in consideration of the signal characteristics generated when the vehicle axis is detected in each of the plurality of speed sections of the vehicle, is separately set and provided for each of the plurality of speed sections. 7. The method of claim 6,
Wherein the sensor is a sensor that generates a signal in response to the pressure changed by the pressurization of the vehicle shaft, the signal processing device. 7. The method of claim 6,
The signal processing apparatus further comprising a measurement unit for measuring the number of vehicle axles based on the result of the convolution.

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