JP7819052B2 - Wireless sensor terminal, measurement frequency setting method - Google Patents

Description

The present invention relates to a wireless sensor terminal and a measurement frequency band setting method.

Sensor information obtained from sensors has traditionally been collected to detect the state of objects such as equipment and structures. Patent Document 1, for example, describes such technology. Patent Document 1 describes a wireless communication device 10 that includes at least an acceleration sensor 107, and that includes data calculation means 106 that performs predetermined calculations, including a Fourier transform, on acceleration data measured by the acceleration sensor 107 over a certain period of time to acquire a frequency spectrum, and transmission means 101 that transmits the frequency spectrum.

Japanese Patent Application Laid-Open No. 2020-119149

In Patent Document 1, a vibration sensor is operated periodically for a set period of time to collect data. However, when trying to acquire data that includes the ultrasonic range with a limited amount of memory, the data collection time must be shortened. As a result, the measurement time for the collected data becomes shorter than the time it takes for the device's state to change, and the device's state cannot necessarily be grasped with high accuracy.

In addition, when collecting sound volumes in a specific frequency range, the characteristic frequency range differs for each object being collected, so if you try to obtain the sound volumes in the characteristic frequency range for all objects, it becomes necessary to build a sensor specialized for a specific application through pre-training and circuit adjustment.

The present invention aims to provide technology that can effectively utilize existing sensors and accurately grasp the state of an object, even when memory capacity is limited.

The wireless sensor terminal of the present invention is a wireless sensor terminal that collects and measures sound pressure signals from a measurement object via a sensor, and is configured as a wireless sensor terminal characterized by having: a first circuit having a bandpass filter that can change the frequency band that passes the sound pressure signal; a second circuit that detects the sound pressure level from the waveform of the sound pressure signal in the frequency band set externally to the wireless sensor terminal, and collects the sound pressure signal for each of the changed frequency bands at predetermined sampling intervals for a predetermined collection time; and a processor that calculates statistical values of the sound pressure signal for each of the collected frequency bands, and sets the frequency band of the sound pressure signal used to calculate the statistical value for which the distance from the center of the allowable range of the statistical value satisfies a predetermined condition as the frequency band to be used to measure the measurement object.

According to the present invention, even when memory capacity is limited, existing sensors can be effectively utilized to accurately grasp the state of an object. Issues, configurations, and advantages other than those described above will become clear from the description of the embodiments of the invention below.

FIG. 2 is a diagram illustrating an example of a configuration of a wireless sensor terminal according to the present embodiment. 10 is a flowchart showing the procedure of a process (sound pressure measurement process) performed by the wireless sensor terminal. FIG. 10 is a diagram for explaining the concept of the processes from S203 to S206. FIG. 10 is a diagram for explaining the concept of the processing of S207. 3 is a diagram showing an example of the results of simulating the operation of the sound pressure measurement process shown in FIG. 2 using actual data. FIG. 3 is a diagram for explaining the relationship between data (raw data) showing the time progression of the sound pressure of the actual object to be measured detected by the sound pressure sensor S1 and the results of a simulation performed by the sound pressure measurement process shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some details have been omitted or simplified as appropriate for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

In the following explanation, various types of information may be described using terms such as "database," "table," and "list," but the various types of information may also be expressed in other data structures. To indicate that the information is not dependent on the data structure, "XX table," "XX list," etc. may be referred to as "XX information." When describing identification information, terms such as "identification information," "identifier," "name," "ID," and "number" are used, and these terms are interchangeable.

When there are multiple components with the same or similar functions, they may be described using the same reference numeral with different subscripts. However, when there is no need to distinguish between these multiple components, the subscripts may be omitted.

In addition, the following description may describe processing performed by executing a program, but since a program is executed by a processor (e.g., a CPU or a GPU (Graphics Processing Unit)) to perform a specified process using storage resources (e.g., memory) and/or interface devices (e.g., communication ports) as appropriate, the processor may be the subject of the processing. Similarly, the subject of processing performed by executing a program may be a controller, device, system, computer, or node having a processor. The subject of processing performed by executing a program may be any computing unit, and may include a dedicated circuit (e.g., an FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit)) that performs specific processing.

A program may be installed on a device such as a computer from a program source. The program source may be, for example, a program distribution server or a computer-readable storage medium. If the program source is a program distribution server, the program distribution server may include a processor and storage resources for storing the program to be distributed, and the processor of the program distribution server may distribute the program to be distributed to other computers. Also, in the following description, two or more programs may be realized as one program, and one program may be realized as two or more programs.

The following describes one example of a wireless sensor terminal and a measurement frequency setting method according to this embodiment.

FIG. 1 illustrates an example of the configuration of a wireless sensor terminal according to this embodiment. The wireless sensor terminal 1000 according to this embodiment includes a variable-frequency band-pass filter (BPF) circuit 101 connected to a sonic sensor S1 for detecting the state of an object to be measured; a sound pressure detection circuit 102 for detecting a sound pressure signal in a frequency band output from the variable-frequency BPF circuit 101; an AD converter 103 for digitally converting the sound pressure signal detected by the sound pressure detection circuit 102; an MCU (Micro Controller Unit) 104 that receives the digital sound pressure signal from the AD converter 103 and controls the execution of processes performed by the wireless sensor terminal 1000, such as statistical processing and measurement processing of the input sound pressure signal; and a wireless interface (I/F) 105 for receiving various settings for the wireless sensor terminal 1000 from a user terminal T1. The MCU 104 includes a microprocessor 1041 for performing the following control and processing, and a memory 1042 for storing various data. In the following, examples of objects detected by the sonic sensor S1 are given of devices and equipment such as hydrogen production equipment and mass analyzers, but the sonic sensor S1 can be applied to any object, such as a structure, that can detect sound pressure or volume. Also, while the following examples use the sonic sensor S1, a vibration sensor that detects touch or a microphone sensor that detects hearing, one of the five senses, can also be used.

The variable frequency BPF circuit 101 is a circuit with a bandpass filter that can change the pass frequency band. It is a filter circuit that passes sound pressure signals of a specific wavelength from the sound pressure signals detected by the sound wave sensor S1 and removes noise from the passed sound pressure signals. In this example, sound pressure signals between 5 kHz and 80 kHz are passed, but any frequency can be passed depending on the usage environment.

The sound pressure detection circuit 102 is a circuit that detects the sound pressure level from the sound pressure waveform, and collects the sound pressure signal, from which noise has been removed and filtered by the frequency-variable BPF circuit 101, at a predetermined sampling interval for a predetermined collection time.

The AD converter 103 converts the sound pressure signal collected by the sound pressure detection circuit 102 at a predetermined sampling interval into a digital signal.

The MCU 104 performs statistical processing such as the average value and variance of the collected sound pressure signals that have been digitally converted by the AD converter 103, as well as sound pressure measurement processing. The specific processing performed by the MCU 104 will be described later.

The wireless I/F 105 accepts settings and instructions for the wireless sensor terminal 1000 from the outside and outputs them to the MCU 104. For example, the wireless I/F 105 receives, via the wireless I/F 112 of the user terminal T1, a measurement mode specified by the input/output I/F 111 of the user terminal T1, which is another external terminal capable of wireless communication operated by the user. The input/output I/F 111 of the user terminal T1 accepts instructions regarding which measurement mode to use: an analysis mode that performs statistical processing of collected sound pressure signals, or a monitoring mode that monitors sound pressure signals measured in the analysis mode. The wireless I/F 105 also receives parameters input from the input/output I/F 111 of the user terminal T1 via the wireless I/F 112 of the user terminal T1, such as (1) the bandwidth and frequency range of the frequency band that is passed through the variable frequency BPF circuit 101, (2) the collection time for analysis (e.g., several seconds to several minutes), (3) the selection conditions for the collection target (maximum and minimum values of the average value (RMS), maximum and minimum values of the variance, and their respective tolerance ranges), and (4) the collection time during monitoring (e.g., 0 to 10 seconds) and measurement interval (e.g., twice a day). The user terminal T1 can be, for example, a smartphone or a tablet device.

As will be described in detail later, in the analysis mode immediately after the sonic sensor S1 is installed, the MCU 104 calculates the average value and variance of sound pressure while sweeping the passband using parameters specified by the external user terminal T1 via wireless communication via the wireless I/F 105. Furthermore, from the collected sound pressure signals of the sound pressure levels of each band, the MCU 104 sets the sound pressure signal of the band with the maximum or minimum average value and the maximum or minimum variance as the measurement target. Then, in the monitoring mode in which measurements are performed constantly, the sound pressure signal of the band to be measured that was set in the analysis mode is measured. The collection time and measurement interval use parameters specified by the external user terminal T1 via wireless communication via the wireless I/F 105.

Figure 2 is a flowchart showing the steps of the process (sound pressure measurement process) performed by the wireless sensor terminal 1000. As shown in Figure 2, the wireless sensor terminal 1000 first receives, via the wireless I/F 105, the analysis mode specified as the measurement mode from the user terminal T1 operated by the user, and sets the measurement mode to "analysis mode" (S201). Here, along with the designation of the analysis mode, the wireless sensor terminal 1000 also accepts input of the start frequency fa (Hz) at which measurement begins, the end frequency fb (Hz) at which measurement ends, the frequency bandwidth Δf (Hz) of the frequency to be measured, and the collection time Ta (sec) for the sound pressure to be measured.

The MCU 104 varies the frequency of the sound pressure signal passed through the frequency variable BPF circuit 101 in steps of Δf between the start frequency fa (Hz) and the end frequency fb (Hz), such as frequency fa + bandwidth Δf (Hz), frequency fa + (2 × bandwidth Δf (Hz)), ..., frequency fb - (2 × bandwidth Δf (Hz)), frequency fb - (bandwidth Δf (Hz)) (S202).

The MCU 104 collects the sound pressure signals of the frequency changed in S202 at a predetermined sampling interval for a collection time Ta (sec) (S203). The MCU 104 calculates the average value and variance of the sound pressure signals of the frequency collected in S203 (S204), associates them with the sound pressure signal of the current frequency set in S202, and stores them in the memory 1042 (S205).

The MCU 104 determines whether the frequency being changed has reached the end frequency fb (Hz) (S206), and if it determines that the frequency being changed has not reached the end frequency fb (Hz) (S206; No), it returns to S203 and changes the frequency to one to which the next bandwidth Δf (Hz) has been added.

On the other hand, if the MCU 104 determines that the frequency being changed has reached the end frequency fb (Hz) (S206; Yes), it determines the measurement frequency band based on the average value of the sound pressure signal for each frequency stored in memory 1042 in S203 to S206 and the distance from the center of the allowable range of variance (S207).

The concept of the processing from S203 to S206 is explained below. In Figure 3, the measurement object (e.g., a hydrogen production device or mass analyzer) performs operations 301a, 301b, 301c, etc. in that order, with idle operations 302a, 302b, 302c, 302d, etc. performed between each operation. When the measurement object performs these operations, in analysis mode, each band from the start frequency fa (Hz) to the end frequency fb (Hz) is measured for at least a period longer than the time change of each of operations 301a, 301b, and 301c, and the average value and variance of the sound pressure in each band are calculated (S203 to S207).

In S206, the MCU 104 plots the calculated values on a plane with the mean value on the vertical axis and the variance on the horizontal axis, as shown in FIG. 4. For example, as shown in FIG. 4, the MCU 104 receives the center O of the acceptable range of the mean value and variance on the plane input from the external user terminal T1, divides the plane into four quadrants 401A, 401B, 401C, and 401D with the center O of the acceptable range as the center point, and sets the acceptable range of the mean value and the acceptable range of the variance in each quadrant. The MCU 104 then sets the acceptable range of the mean value and the acceptable range of the variance in each set quadrant as the target range 402 (the range indicated by the dashed dotted line in FIG. 4) for determining the measurement frequency band. The example in FIG. 4 illustrates a case where the same range is set from the center O of the acceptable range in each quadrant, but the set range for each quadrant may differ depending on the state of the object to be measured.

MCU104 selects, as the band to be measured, the point 403X, which is within the four quadrants and also within the target range 402 and where the calculated values are plotted, and where the vector from the center O of the allowable range has the largest value. In this example, 17 points are plotted, indicating the average value and variance of the sound pressure calculated in each band. MCU104 selects, from each of the four quadrants 401A, 401B, 401C, and 401D, the target candidate points 403A, 403B, 403C, and 403D that have the largest value from the center O of the allowable range.

MCU 104 selects one quadrant and target candidate point from among the target candidate points 403A, 403B, 403C, and 403D, and transmits the results to the external user terminal T1. The input/output I/F 111 of user terminal T1 displays the results on the screen of the terminal. At this time, MCU 104 also transmits data (e.g., the sound pressure when target candidate point 403B was calculated) stored in memory 1042 in association with the one quadrant and target candidate point (e.g., an area including quadrant 401B, target candidate point 403B, and another point 403X in quadrant 401B) to user terminal T1. When the input/output I/F 111 of user terminal T1 receives a selection operation, such as a touch operation, of a target candidate point included in the displayed results from the user, it displays the data corresponding to the target candidate point on the screen. This allows the temporal progression of the sound pressure signal corresponding to the target candidate point to be confirmed. The state of the above data will be described later using Figures 5 and 6.

The quadrant and target candidate point may be selected depending on the type of sonic sensor S1 and the type of object to be measured. In this example, the MCU 104 selects one quadrant and target candidate point from four quadrants and target candidate points depending on the type of sound pressure sensor S1. However, the four quadrants and target candidate points may be output to the input/output I/F 111 of the external user terminal T1, and the user may select one of them.

In quadrant 401A shown in Figure 4, both the change in sound pressure and the average are large relative to the center O of the allowable range, indicating that the sound is due to normally-on device operation. Therefore, detecting the sound pressure in this band can detect an abnormality in the operation of the object being measured. Also, in quadrant 401B shown in Figure 4, the change in sound pressure is large and the average is small relative to the center O of the allowable range, indicating that the sound is due to normally-off device operation. Therefore, similar to the case of quadrant 401A, detecting the sound pressure in this band can detect an abnormality in the operation of the object being measured. Furthermore, in quadrant 401C shown in Figure 4, both the change in sound pressure and the average are small relative to the center O of the allowable range, indicating that the sound is silent (or at a faint volume below a certain level) during normal operation. Therefore, it can be determined that an abnormality has been detected due to a certain degree of change in sound pressure relative to the silence or faint volume. Furthermore, in quadrant 401D shown in Figure 4, the sound pressure changes little and the average is large relative to the center O of the allowable range, and it can be determined that there are signs of an abnormality because the steadily occurring sound pressure changes at a constant rate. This determination can be made by checking the temporal progression of the sound pressure signals for each frequency stored in memory 1042 in association with each plotted point.

Returning to Figure 2, once the MCU 104 determines the measurement frequency band in S207, it transitions to "monitoring mode" as the measurement mode and notifies the external user terminal T1 operated by the user of this (S208). At this time, the MCU 104 accepts input of the sound pressure collection time Tb (sec) and measurement interval Tc (sec) from the external user terminal T1.

After waiting for the input measurement interval Tc (sec) (S209), the MCU 104 measures the sound pressure for the input collection time Tb (sec) in the measurement frequency band determined in S207 (S210), and transmits the sound pressure measurement results to the external user terminal T1 via the wireless I/F 105 (S211).

Figure 5 shows an example of the results of simulating the operation of the sound pressure measurement process shown in Figure 2 using actual data. Figure 5 does not show the target range for determining the frequency band to be measured.

As in the case of Figure 4, MCU 104 selects points 503A, 503B, 503C, and 503D in each of the four quadrants 501A, 501B, 501C, and 501D where the vector from the center O of the tolerance range has the largest value as the band to be measured. Furthermore, MCU 104 selects the point (in this example, point 503B) from among points 503A, 503B, 503C, and 503D where the vector has the largest value. In other words, the object to be measured shown in Figure 5 detects sound pressure with the variance and average of the value shown at point 503, so it can be determined that an abnormality due to normally-off equipment operation has occurred. Graphs 504A, 504B, 504C, and 504D shown in Figure 5 are graphs showing the temporal progression of sound pressure collected in the band when the above points 503A, 503B, 503C, and 503D were calculated. These graphs can be created from the sound pressure collected in S203. As explained in Figure 4, by displaying such graphs on the input/output I/F 111 of the user terminal T1, the user can grasp at a glance the state of the object being measured and any abnormalities that may be occurring.

Figure 6 is a diagram illustrating the relationship between data (raw data) showing the temporal progression of sound pressure of an actual measurement object detected by sound pressure sensor S1 and the results of a simulation using the sound pressure measurement process shown in Figure 2. The upper part of Figure 6 shows the raw data. By executing the sound pressure measurement process shown in Figure 2, sound pressure in a specified band can be extracted from the raw data at a specified sampling interval, as shown in the lower part of Figure 6. As a result, the volume of the selected band can be detected with a specified number of samples, making it possible to detect the characteristics of the measurement object with 1/96,000th the data volume compared to when using the raw data. In this example, the raw data, which was 192 Kbytes/sec, has been significantly compressed to 2 bytes/sec. However, it can be seen that the characteristic bands 601, 602, and 603 indicating the operating sound of the measurement object can still be detected just as easily as with raw data.

In this embodiment, as described in Figures 1 and 2, the wireless sensor terminal 1000 collects and measures sound pressure signals from a measurement object (e.g., a hydrogen production device or a mass analyzer) via a sensor (sound wave sensor S1), and includes a first circuit (frequency variable BPF circuit 101) having a bandpass filter that can change the frequency band through which the sound pressure signal passes, and a circuit that detects the sound pressure level from the waveform of the sound pressure signal in the frequency band set from outside the wireless sensor terminal, and for each of the changed frequency bands, collects the sound pressure signal for a predetermined collection time (Ta( The system includes a second circuit (sound pressure detection circuit 102) that collects sound pressure signals at a predetermined sampling interval (sound pressure signal sigma) for each of the collected frequency bands. The system also includes a processor (MCU 104) that calculates statistical values (mean and variance of the sound pressure signal) for each of the collected frequency bands and sets the frequency band of the sound pressure signal used to calculate the statistical value for which the distance from the center of the allowable range (the allowable range center O) of the statistical value satisfies a predetermined condition (e.g., maximum distance) as the frequency band to be used for measuring the object. This allows for the effective use of existing sensors and accurate assessment of the object's condition, even when memory capacity is limited. For example, by quantifying information that is difficult to visualize, such as gas leaks from a hydrogen production plant, highly accurate equipment status monitoring can be performed. Furthermore, because the frequency band is set externally via wireless communication, remote monitoring of the object can be performed via a public wireless network using an existing user interface. Furthermore, by not providing such a user interface on the wireless sensor terminal itself, long-term battery-powered operation is possible.

Furthermore, as explained using Figures 1 and 2, the processor accepts the setting of the frequency band from the user terminal T1 wirelessly connected to the wireless sensor terminal. This allows the user to set the frequency band from a terminal that they are familiar with.

Furthermore, as explained using Figures 1 and 2, the processor outputs the frequency bands used to measure the object to be measured and the collected sound pressure signals in those frequency bands to the user terminal. This allows the user to check in detail the state of the object to be measured in each frequency band.

Furthermore, as explained using Figures 4 and 5, the processor sets the frequency band of the sound pressure signal used to calculate the statistical value for which the distance is greatest as the predetermined condition as the frequency band to be used for measuring the object to be measured. This allows the frequency band that produces the most characteristic phenomenon of the object to be set as the frequency band to be used for measuring the object to be measured.

Furthermore, as explained using Figures 1, 4, 5, etc., the processor outputs the frequency band of the sound pressure signal used to calculate the statistical value that satisfies the predetermined condition and the collected sound pressure signal in that frequency band to the user terminal, for example, as shown by points 503A, 503B, 503C, and 503D and graphs 504A, 504B, 504C, and 504D in Figure 5, and sets the frequency band selected by the user terminal as the frequency band to be used for measuring the object to be measured. This allows the user to set the desired frequency band as the frequency band to be used for measuring the object to be measured while checking the state of the object to be measured in detail in each frequency band.

The present invention is not limited to the above-described embodiments, and in the implementation stage, the components may be modified and embodied within the scope of the gist of the invention, or multiple components disclosed in the above-described embodiments may be combined as appropriate.

1000 Wireless sensor terminal 101 Frequency variable BPF circuit 102 Sound pressure detection circuit 103 AD converter 104 MCU
105 Wireless I/F
1041 Microprocessor 1042 Memory S1 Sonic sensor

Claims (10)

A wireless sensor terminal that collects and measures sound pressure signals from a measurement object via a sensor,
a first circuit having a band-pass filter capable of varying a frequency band through which the sound pressure signal passes;
a second circuit that detects a sound pressure level from a waveform of the sound pressure signal of the frequency band set from outside the wireless sensor terminal, and collects the sound pressure signal at a predetermined sampling interval for a predetermined collection time for each of the changed frequency bands;
a processor that calculates a statistical value of the sound pressure signal for each of the collected frequency bands, and sets the frequency band of the sound pressure signal used to calculate the statistical value whose distance from the center of the allowable range of the statistical value satisfies a predetermined condition, as the frequency band to be used for measuring the measurement object;
A wireless sensor terminal comprising: the processor accepts a setting of the frequency band from a user terminal wirelessly connected to the wireless sensor terminal;
The wireless sensor terminal according to claim 1 . The processor outputs the set frequency band used for measuring the measurement object and the collected sound pressure signal in the frequency band to the user terminal.
3. The wireless sensor terminal according to claim 2. the processor sets, as the predetermined condition, the frequency band of the sound pressure signal used in calculating the statistical value in which the distance is maximum, as the frequency band to be used in measuring the measurement object.
The wireless sensor terminal according to claim 1 . the processor outputs the frequency band of the sound pressure signal used to calculate the statistical value that satisfies the predetermined condition and the collected sound pressure signal of the frequency band to the user terminal, and sets the frequency band selected by the user terminal as the frequency band to be used for measuring the object to be measured.
3. The wireless sensor terminal according to claim 2 . A measurement frequency setting method performed by a wireless sensor terminal that collects and measures sound pressure signals from a measurement object via a sensor, comprising:
A frequency band through which the sound pressure signal is passed is set to be variable,
When detecting a sound pressure level from a waveform of the sound pressure signal of the frequency band set from outside the wireless sensor terminal, the sound pressure signal is collected at a predetermined sampling interval for a predetermined collection time for each of the changed frequency bands,
calculating a statistical value of the sound pressure signal for each of the collected frequency bands, and setting the frequency band of the sound pressure signal used to calculate the statistical value, of which the distance from the center of the allowable range of the statistical value satisfies a predetermined condition, as the frequency band to be used for measuring the measurement object;
A measurement frequency setting method comprising: accepting a setting of the frequency band from a user terminal wirelessly connected to the wireless sensor terminal;
7. The measurement frequency setting method according to claim 6. outputting the set frequency band used for measuring the object to be measured and the collected sound pressure signal in the frequency band to the user terminal;
8. The measurement frequency setting method according to claim 7. the predetermined condition is to set the frequency band of the sound pressure signal used in calculating the statistical value for which the distance is maximum as the frequency band to be used in measuring the measurement object.
7. The measurement frequency setting method according to claim 6. outputting the frequency band of the sound pressure signal used in calculating the statistical value that satisfies the predetermined condition and the collected sound pressure signal of the frequency band to the user terminal, and setting the frequency band selected by the user terminal as the frequency band to be used for measuring the object to be measured;
8. The measurement frequency setting method according to claim 7 .