Wireless sensor terminal, sensor information detection method, wireless sensor terminal system

Abstract

To provide a wireless sensor terminal with low power and small data volume, a sensor information detection method, and a system using them that can capture pulse-shaped ultrasonic waves generated in the early stages or the like of component deterioration.SOLUTION: A wireless sensor terminal for detecting a signal from a sensor and transmits it wirelessly to the outside includes: a bandpass filter that limits the bandwidth of the signal from the sensor; a sound pressure detection circuit that obtains sound pressure data from an output of the bandpass filter; a comparator that compares the sound pressure data with a predetermined threshold voltage; a counter that counts the number of times the threshold voltage from the comparator is exceeded within a predetermined time; a communication unit that transmits data to the outside; and a control circuit. The control circuit transmits the counted number for each predetermined time period counted by the counter to the outside via the communication unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wireless sensor terminal that wirelessly transmits sensor information, its sensor information detection method, and a system using the same.

Background Art

[0002] In recent years, with the development of IoT (Internet of Things), services have been provided that connect sensor terminals to servers and cloud services through a network, perform status monitoring using the sensor information, and conduct management and maintenance. For example, in existing equipment and devices in the industrial and manufacturing fields, the IoT of sensor terminals is progressing. In the IoT of sensor terminals, by using a wireless sensor terminal that wirelessly transmits sensor information, it becomes possible to add installation to existing equipment, perform remote monitoring on a public wireless network, and operate for a long time with an internal power source.

[0003] As a prior art document in this technical field, there is Patent Document 1. Patent Document 1 discloses a spectrum collection type sensor terminal that performs data collection and analysis on the frequency axis by performing FFT (Fast Fourier Transform) on sensor data, monitors at a low sampling rate during normal times, collects data at a high sampling rate when an abnormality is detected, and performs frequency analysis with a low-power terminal.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, if you want to collect abnormal noises that occur in the early stages of component degradation within a device using a wireless sensor terminal, the abnormal noises or ultrasounds that occur in the early stages of component degradation are pulsed, and their frequency increases as the degree of degradation progresses. A challenge in collecting such pulsed ultrasounds is that continuous sampling at a high sampling rate is required, resulting in an enormous amount of data.

[0006] In Patent Document 1, while it is possible to reduce the amount of data by switching the sampling rate, the sensor data is averaged over time. Therefore, if the sensor data is a pulsed sound wave, the signal-to-noise ratio (SNR) becomes low because it is not a continuously occurring sound wave, making it difficult to analyze pulsed sound waves.

[0007] Furthermore, because pulsed ultrasound occurs infrequently, intermittent measurements cannot capture it. Another approach is to collect ultrasonic vibrations based on sound pressure, but since the operating state of the equipment and noise generated by the circuit and equipment also contain pulsed components, there is a challenge in that the threshold for distinguishing between signal and noise varies depending on the situation.

[0008] Therefore, in view of the above problems, the present invention aims to provide a wireless sensor terminal, a sensor information detection method, and a system using the same, which can capture pulsed ultrasonic waves that occur in the early stages of component degradation, etc., and which use low power and small data volume. [Means for solving the problem]

[0009] One example of the present invention is a wireless sensor terminal that detects a signal from a sensor and transmits it wirelessly to the outside, comprising: a bandpass filter that band-limits the signal from the sensor; a sound pressure detection circuit that obtains sound pressure data from the output of the bandpass filter; a comparator that compares the sound pressure data with a predetermined threshold voltage; a counter that counts the number of times the threshold voltage from the comparator is exceeded within a predetermined time; a communication unit that transmits data to the outside; and a control circuit, the control circuit which transmits the count number for each predetermined time interval counted by the counter to the outside via the communication unit. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a wireless sensor terminal that can capture pulsed ultrasonic waves, uses low power and small data volume, a sensor information detection method, and a system using the same. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the wireless sensor terminal system in the embodiment. [Figure 2A] This is an example of sound pressure data detected by the sound pressure detection circuit in the embodiment. [Figure 2B] Figure 2A shows a histogram created by collecting and analyzing sound pressure data. [Figure 2C] This figure is a schematic representation of the histogram shown in Figure 2B. [Figure 3] This is an example of the number of pulses counted by the counter in the abnormality detection mode in the embodiment. [Figure 4] This figure shows the processing sequence for sensor information detection and anomaly determination in the embodiment. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Examples]

[0013] Figure 1 is a schematic diagram of the wireless sensor terminal system in this embodiment. As shown in Figure 1, the wireless sensor terminal system 100 consists of a data acquisition device 200 and a wireless sensor terminal 300, which transmit and receive data wirelessly to each other. The wireless sensor terminal 300 is placed on the equipment or device to be monitored. Note that the wireless sensor terminal system 100 may have multiple wireless sensor terminals 300, which are wirelessly connected to the data acquisition device 200, but for the sake of simplicity, only one wireless sensor terminal 300 is shown in Figure 1. In addition, the data acquisition device 200 and the wireless sensor terminal 300 may be interconnected via a wireless LAN through a network such as the Internet.

[0014] The data acquisition device 200 is a general information processing device such as a PC or server, and has at least a CPU 201, memory 202, storage device (storage unit) 203, input / output device 204, and communication unit 205, which are connected via a bus 206. The storage device 203 also contains processing programs 210, including a statistical processing program 211, a threshold calculation program 212, and a terminal control program 213. Furthermore, the storage device 203 contains related data 220, including frequency data 221, sound pressure data 222, and raw data 223. Details of these processing programs and related data will be described later.

[0015] The data acquisition device 200 implements each function through software processing, in which the CPU 201 loads processing programs 210 that realize each function from the storage device 203 to the memory 202, and interprets and executes the processing programs while referring to related data 220.

[0016] The wireless sensor terminal 300 includes a sensor 301 for detecting vibration and sound signals, a switch 302, a bandpass filter (BPF) 303, a sound pressure detection circuit 304, an A / D converter (ADC) 305, an MCU (Micro Controller Unit) 306, a comparator 307, a counter 308, a threshold voltage generation circuit 309, a communication unit 310, and a battery 311.

[0017] The signals of vibration and sound detected by the sensor 301 are restricted to a certain frequency band by the BPF 303, and the sound pressure data of the sound pressure level in a certain frequency band is obtained by the sound pressure detection circuit 304. Then, it is converted into a digital signal via the ADC 305 and taken into the MCU 306. This is a circuit configuration used in the threshold voltage determination mode for detecting the sound pressure at a constant sampling frequency and determining the threshold voltage.

[0018] On the other hand, the sound pressure data, which is the output of the sound pressure detection circuit 304, is compared by the comparator 307 with the threshold voltage generated by the threshold voltage generation circuit 309 to obtain a pulsed sound wave with a voltage above the threshold voltage. The threshold voltage generation circuit 309 generates the threshold voltage under the control of the MCU 306 based on the threshold voltage value received from the data collection device 200 via the communication unit 310. The counter 308 counts the number of pulses of the pulsed sound wave. The counted number of pulses is taken into the MCU 306. This is a circuit configuration used in the abnormality determination mode for counting the number of pulses exceeding the threshold within a certain time and performing abnormality determination.

[0019] Also, by means of the switch 302, the signals of vibration and sound detected by the sensor 301 are switched to be directly input to the ADC 305, and are converted into digital signals by sampling via the ADC 305, and data without band limitation (hereinafter referred to as raw data) is taken into the MCU 306. This is a circuit configuration used in the raw data measurement mode for collecting raw data.

[0020] The MCU 306 transmits the captured data to the data collection device 200 via the communication unit 310.

[0021] The switching of the switch 302, the ON / OFF of the ADC 305, the control of the threshold voltage generation circuit 309, and the reset of the counter 308 are controlled by the MCU 306. Also, the power supply of the wireless sensor terminal 300 is supplied by the battery 311.

[0022] As described above, the wireless sensor terminal 300 has three processing modes, which can be switched by the data acquisition device 200. Furthermore, the counting time, threshold voltage value, and switching to raw data acquisition can be instructed by the data acquisition device 200.

[0023] The bandwidth of the BPF303 is not limited, but for example, 20 to 80 kHz is acceptable. Also, the circuits constituting the wireless sensor terminal 300 are not limited to being digital or analog, but for example, the sensor 301, switch 302, BPF303, sound pressure detection circuit 304, comparator 307, and threshold voltage generation circuit 309 may be made as analog as possible to avoid missing short pulse-like sound waves. Furthermore, power consumption can be reduced by using passive elements for both, or at least one of, the BPF303 and the sound pressure detection circuit 304.

[0024] Next, a specific example of processing in threshold voltage determination mode will be described. Figure 2A shows an example of sound pressure data detected by the sound pressure detection circuit 304 in this embodiment. In Figure 2A, sound from a rotating bearing is sensed, and the sound pressure detection circuit 304 is used as an envelope detection circuit with a time constant of approximately 10 msec, showing the sound pressure data after envelope detection. The figure also shows sound pressure collected at a constant interval of once every 3 seconds for a certain period (200 hours). In Figure 2A, it is normal up to about 130 hours, but after that, it shows a case where abnormalities occur due to deterioration caused by rust on the bearing.

[0025] Figure 2B is a histogram created by collecting and analyzing the sound pressure data shown in Figure 2A. Figure 2C is a schematic representation of the histogram shown in Figure 2B. As shown in Figure 2C, the histogram shown in Figure 2B is observed as a superposition of the Gaussian distribution 401 of constantly occurring vibrations and noise and the Poisson distribution 402 of vibrations caused by deterioration such as foreign objects and scratches.

[0026] Therefore, a value (determined from σ) that includes most of the constantly occurring vibrations and noise in the Gaussian distribution 401 is determined as the threshold voltage value, as shown in Figure 2B. That is, sound pressure data is collected at regular intervals for a certain period of time, and the threshold voltage value is obtained by fitting the histogram of the collected sound pressure data.

[0027] Next, a specific example of processing in the abnormality detection mode will be described. Figure 3 shows an example of the number of pulses counted by counter 308 in the abnormality detection mode of this embodiment. In Figure 3, similar to Figure 2A, the number of pulses that exceeded the threshold voltage in 60 seconds was collected for a certain period (200 hours) based on the sound sensor signal from the rotating bearing. As shown in Figure 3, the vibration change in the number of pulses due to bearing deterioration becomes large after about 130 hours, and abnormality detection can be sufficiently observed after about 130 hours. Note that, as shown by the white outline in Figure 3, the moving average of the number of pulses that exceeded the threshold voltage may be calculated, and abnormality detection may be performed based on the vibration change.

[0028] This anomaly detection mode measures pulsed sound waves containing only sound pressure data exceeding the threshold voltage using the comparator 307, allowing for anomaly detection with, for example, a 1 / 3,000,000 reduction in accuracy compared to spectral acquisition. Furthermore, it enables anomaly detection even in the initial stages of anomalies with short pulse widths and low frequencies.

[0029] As shown in Figure 3, the basic approach is to acquire and monitor the count of counter 308 at regular intervals, but it is also possible to acquire and monitor the time it takes to reach a certain count. In that case, there are challenges such as the data not being at equal intervals making analysis difficult, and the system being somewhat difficult to implement as data disappears during normal operation. However, it is effective if the advantage of lower power consumption is prioritized.

[0030] Figure 4 shows the processing sequence for sensor information detection and anomaly determination in this embodiment. In Figure 4, first, in threshold voltage determination mode, the wireless sensor terminal measures the sound pressure value for a certain period of time in step S301 and transmits the sound pressure data to the data acquisition device. The data acquisition device receives it, records the initial sound pressure value in step S201, and sets the threshold voltage value based on the average sound pressure value in step S202. Then, in step S203, the data acquisition device sets the count time from the time constant of each application, such as the operating time or the time of change of the equipment or device to be monitored, and transmits the set threshold voltage value and count time to the wireless sensor terminal, instructing it to enter anomaly determination mode. In step S302, the wireless sensor terminal determines whether it has been instructed to enter anomaly determination mode. If it has not been instructed to enter anomaly determination mode, it returns to step S301; if it has been instructed to enter anomaly determination mode, it transitions to anomaly determination mode.

[0031] In abnormality detection mode, in step S303, the wireless sensor terminal counts the number of pulses that exceed the threshold voltage within a certain period of time, based on the instructed count time and threshold voltage value, and transmits the pulse count to the data acquisition device at each count time. The data acquisition device receives this and, in step S204, records the pulse count and performs abnormality detection. In step S205, if the pulse count is above a certain level, it instructs the wireless sensor terminal to enter raw data measurement mode. In step S305, the wireless sensor terminal determines whether it has been instructed to enter raw data measurement mode. If it has not been instructed to enter raw data measurement mode, it returns to step S303; if it has been instructed to enter raw data measurement mode, it switches to raw data measurement mode.

[0032] In raw data measurement mode, the wireless sensor terminal samples raw data in step S306 and transmits it to the data acquisition device. The data acquisition device receives it and performs raw data recording and analysis in step S206.

[0033] The three processing modes have been explained above. The anomaly detection mode is a mode for detecting anomalies with low power and low data volume, and the threshold voltage determination mode is a process that determines the threshold voltage value used in the anomaly detection mode prior to the anomaly detection mode, and both are essential. In contrast, the raw data measurement mode is a mode for collecting detailed data to perform a definitive diagnosis of an anomaly, and is therefore not necessarily required and may be omitted.

[0034] Furthermore, the threshold voltage determination mode can be performed by operation from the wireless sensor terminal or the data acquisition device, and may be performed when the wireless sensor terminal is installed on the equipment or device to be monitored, or when the state of the equipment or device changes. In addition, although it was explained above that the data acquisition device instructs the wireless sensor terminal to enter abnormality detection mode, the data acquisition device may transmit the threshold voltage value and count time to the wireless sensor terminal without instructing it to enter abnormality detection mode, and the wireless sensor terminal may enter abnormality detection mode upon receiving them.

[0035] As described above, this embodiment makes it possible to capture pulsed ultrasonic waves that occur in the early stages of component degradation, and provides a low-power, low-data wireless sensor terminal, a sensor information detection method, and a system using the same.

[0036] As illustrated above, the present invention provides a low-power, low-data wireless sensor terminal, thereby reducing carbon emissions, preventing global warming, and contributing to the achievement of Sustainable Development Goals (SDGs), particularly Goal 7, which is energy.

[0037] Furthermore, the present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. [Explanation of symbols]

[0038] 100: Wireless sensor terminal system, 200: Data acquisition device, 201: CPU, 202: Memory, 203: Storage device (storage unit), 204: Input / output device, 205: Communication unit, 210: Processing program, 211: Statistical processing program, 212: Threshold calculation program, 213: Terminal control program, 220: Related data, 221: Frequency data, 222: Sound pressure data, 223: Raw data, 300: Wireless sensor terminal, 301: Sensor, 302: Switch, 303: Bandpass filter (BPF), 304: Sound pressure detection circuit, 305: A / D converter (ADC), 306: MCU, 307: Comparator, 308: Counter, 309: Threshold voltage generation circuit, 310: Communication unit, 311: Battery, 401: Gaussian distribution, 402: Poisson distribution

Claims

1. A wireless sensor terminal that detects signals from a sensor and transmits them wirelessly to an external source, A bandpass filter that limits the bandwidth of the signal from the aforementioned sensor, A sound pressure detection circuit, which is an envelope detection circuit with a time constant of approximately 10 msec, obtains sound pressure data from the output of the bandpass filter. A comparator that compares the sound pressure data with a predetermined threshold voltage, A counter that counts the number of times the threshold voltage from the comparator is exceeded within a predetermined time, A communication unit that transmits data externally, It has a control circuit, The sensor, the bandpass filter, and the sound pressure detection circuit are analog circuits. The control circuit is characterized by transmitting the count number at predetermined time intervals, which has been counted by the counter, to the outside via the communication unit.

2. In the wireless sensor terminal according to claim 1, A wireless sensor terminal characterized by having a threshold voltage generation circuit that generates the threshold voltage based on a value received from an external source via the communication unit.

3. In the wireless sensor terminal according to claim 1, The predetermined time is set based on a value received from an external source via the communication unit, and is a wireless sensor terminal.

4. In the wireless sensor terminal according to claim 1, It has an A / D converter, The control circuit is characterized by converting sound pressure data from the sound pressure detection circuit into a digital signal via the A / D converter and receiving it, and transmitting the sound pressure data to the outside via the communication unit.

5. In the wireless sensor terminal according to claim 1, It has an A / D converter, The control circuit is characterized by converting the signal from the sensor into a digital signal via the A / D converter and acquiring it as raw data, and transmitting the raw data to the outside via the communication unit.

6. In the wireless sensor terminal according to claim 1, A wireless sensor terminal characterized in that at least one of the bandpass filter and the sound pressure detection circuit is composed of passive elements.

7. A method for detecting sensor information of a wireless sensor terminal that detects signals from a sensor and transmits them wirelessly to an external source, The output of the aforementioned sensor is frequency-limited using an envelope detection circuit and a bandpass filter, which are analog circuits with a time constant of approximately 10 msec, to detect the sound pressure. A sensor information detection method characterized by comparing the sound pressure with a predetermined threshold voltage and counting the number of times the threshold voltage is exceeded within a predetermined time.

8. In the method for detecting sensor information according to claim 7, A sensor information detection method characterized in that the threshold voltage is set wirelessly from outside the wireless sensor terminal.

9. In the method for detecting sensor information according to claim 7, A sensor information detection method characterized in that the predetermined time is set wirelessly from outside the wireless sensor terminal.

10. In the method for detecting sensor information according to claim 7, A sensor information detection method characterized by converting the detected sound pressure data into a digital signal and acquiring it as sound pressure data, and transmitting the sound pressure data to the outside of the wireless sensor terminal.

11. In the method for detecting sensor information according to claim 7, A sensor information detection method characterized by converting the signal from the sensor into a digital signal and acquiring it as raw data, and transmitting the raw data to the outside of the wireless sensor terminal.

12. A wireless sensor terminal system comprising a data collection device and a wireless sensor terminal, The aforementioned wireless sensor terminal is Sensors and, A bandpass filter that limits the bandwidth of the signal from the aforementioned sensor, A sound pressure detection circuit, which is an envelope detection circuit with a time constant of approximately 10 msec, obtains sound pressure data from the output of the bandpass filter. A comparator that compares the sound pressure data with a predetermined threshold voltage, A counter that counts the number of times the threshold voltage from the comparator is exceeded within a predetermined time, The first communication unit transmits data externally, It has a first control circuit, The sensor, the bandpass filter, and the sound pressure detection circuit are analog circuits. The first control circuit transmits the count number for each predetermined time interval, which has been counted by the counter, to the data acquisition device via the first communication unit. The data acquisition device has a second communication unit and a second control circuit, The wireless sensor terminal system is characterized in that the second control circuit performs abnormality determination based on the count received via the second communication unit.

13. In the wireless sensor terminal system according to claim 12, The wireless sensor terminal has an A / D converter, and the first control circuit converts the sound pressure data from the sound pressure detection circuit into a digital signal via the A / D converter and acquires it, and transmits the sound pressure data to the data acquisition device via the first communication unit. The data acquisition device, with the second control circuit, sets a threshold voltage value based on the sound pressure data received via the second communication unit, and transmits the threshold voltage value to the wireless sensor terminal via the second communication unit. The wireless sensor terminal is characterized by having a threshold voltage generation circuit that generates the threshold voltage based on the threshold voltage value received from the data acquisition device via the first communication unit.

14. In the wireless sensor terminal system according to claim 12, The data acquisition device transmits the predetermined time to the wireless sensor terminal via the second communication unit. The wireless sensor terminal system is characterized in that the counter performs counting based on the predetermined time received from the data acquisition device via the first communication unit.

15. In the wireless sensor terminal system according to claim 12, When the data acquisition device determines that an abnormality has been detected, it transmits an instruction to the wireless sensor terminal to enter raw data measurement mode via the second communication unit. The wireless sensor terminal system is characterized in that it has an A / D converter, and the first control circuit converts the signal from the sensor into a digital signal via the A / D converter and acquires it as sound pressure data based on the instruction of the raw data measurement mode received from the data acquisition device via the first communication unit, and transmits the sound pressure data to the data acquisition device via the first communication unit.

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