JP6714462B2 - Wireless sensor terminal, wireless sensor system, and sensor data collection method - Google Patents

Description

The present invention relates to a sensor network system.

As a background art in this technical field, there is JP-A-2014-81860 (Patent Document 1). This publication describes a method for reducing power consumption required for wireless communication of a sensor terminal that collects environmental information and operating the sensor terminal using an independent power source in a sensor network system.

JP, 2014-81860, A

In Patent Document 1, in order to reduce the power consumption of wireless communication in order to reduce the power consumption to the extent that the wireless sensor terminal can be operated using an independent power source, the sensor measurement result is communicated in the shortest possible telegram, and Methods for accumulating data in time series are described. However, in order to reduce the amount of wireless communication, only a short amount of data can be transmitted, and the available sensor types such as temperature, humidity, and illuminance are limited to physical quantities that require only a few bytes of data per measurement. It had been. Therefore, for a sensor that requires a large number of measurements in a relatively short time, such as a measurement of a vibration spectrum, the method of Patent Document 1 cannot be applied because the amount of data is large, and low power consumption at the time of measurement cannot be achieved. There was a problem.

One aspect of the present invention that solves the above problems is a sensor that converts a physical quantity into an electric signal for measurement, an analog-digital conversion circuit that converts an analog signal based on the electric signal into a digital signal, and data based on the digital signal by radio. The wireless sensor terminal includes a transmitter for transmitting, a receiver for receiving a command wirelessly transmitted from the outside, and a control unit for controlling an analog-digital conversion circuit based on the command.

Another aspect of the present invention is a wireless sensor system including a wireless sensor terminal and a data collection/analysis device, wherein the wireless sensor terminal includes a sensor for converting a physical quantity into an electric signal for measurement and an analog based on the electric signal. An analog-digital conversion circuit that converts a signal into a digital signal, a transmitter that wirelessly transmits data based on a digital signal to a data collection/analysis device, and a receiver that receives a command wirelessly transmitted from the data collection/analysis device , And a control unit that controls the analog-digital conversion circuit based on a command.

Another aspect of the present invention is a sensor data collection method in a wireless sensor system including a wireless sensor terminal and a data collection/analysis device. In this method, a wireless sensor terminal includes a sensor that converts a physical quantity into an electric signal for measurement, an analog-digital conversion circuit that converts an analog signal based on the electric signal into a digital signal, and data collection/analysis of data based on the digital signal. A transmitter that wirelessly transmits to the device, a receiver that receives a command wirelessly transmitted from the data collection/analysis device, and a control unit that controls the analog-digital conversion circuit based on the command. In the initial mode, the wireless sensor terminal sets the resolution of the analog-digital conversion circuit to the first resolution, sets the sampling frequency of the analog-digital conversion circuit to the first frequency, and converts the analog-digital converted digital signal. Based on the command, a first step of wirelessly transmitting data to the data collection/analysis apparatus, a second step of receiving a command wirelessly transmitted from the data collection/analysis apparatus, and an analog-digital conversion circuit based on the command Is set to a second resolution lower than the first resolution, and the sampling frequency of the analog-to-digital conversion circuit is set to a second frequency lower than the first frequency to shift to the steady mode. To execute. In the steady mode, the wireless sensor terminal performs the fourth step of wirelessly transmitting data based on the digital signal analog-to-digital converted by the analog-to-digital conversion circuit to the data collection/analysis device, and performs the wireless communication in the first step. The transmission frequency is lower than the wireless transmission frequency in the fourth step.

According to the present invention, it is possible to reduce the power consumption of a wireless sensor terminal when a large number of measurements are required in a relatively short time.

It is a block diagram which shows the structure of an example of a sensing system. It is a flowchart explaining the example of the flow which processes a sensor signal. It is a schematic diagram explaining a specific example of sensor signal processing. It is a schematic diagram explaining a specific example of sensor signal processing. It is a schematic diagram explaining a specific example of sensor signal processing.

Hereinafter, embodiments will be described in detail with reference to the drawings. However, the present invention should not be construed as being limited to the description of the embodiments below. It is easily understood by those skilled in the art that the specific configuration can be changed without departing from the idea or the spirit of the present invention.

In the configurations of the invention described below, the same portions or portions having the same function are denoted by the same reference numerals in different drawings, and duplicated description may be omitted.

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

The notations such as “first”, “second”, and “third” in this specification and the like are provided for identifying components and do not necessarily limit the number or order. Further, the numbers for identifying the constituent elements are used for each context, and the numbers used in one context do not always indicate the same configuration in other contexts. Moreover, it does not prevent that the component identified by a certain number also has the function of the component identified by another number.

Explaining the outline of the embodiments below, in a wireless sensor terminal equipped with a sensor and an analog-digital conversion circuit for converting a signal from the sensor into digital data, the resolution or sampling frequency of the analog-digital conversion circuit is made variable, and the wireless sensor The value is specified from outside the terminal and can be changed.

<1. System configuration>
FIG. 1 is a diagram showing a configuration example of a sensing system of this embodiment. The wireless sensor terminal 101 is a terminal that includes the self-sustained power supply system 1 and operates the vibration sensor 2 and the measurement circuit unit 3 with the generated power to realize the sensor function. The sensor function measures various physical quantities in the surroundings and wirelessly transmits the measurement result to the data collection/analysis apparatus 102. Here, “measurement” refers to the entire process in which the wireless sensor terminal 101 prepares data to be transmitted at one time. In the present embodiment, it is assumed that the vibration sensor 2 measures ambient vibration and transmits the result. Further, the sensing system can be configured with one data collection/analysis device 102 and a plurality of wireless sensor terminals 101. In the following, for simplification, the operation of only one of the wireless sensor terminals 101 will be described, but it is assumed that the same operation is performed for a plurality of wireless sensor terminals 101.

It is often difficult for the wireless sensor terminal 101 to secure a line for supplying power. Therefore, the self-sustaining power supply system 1 includes a solar cell, a power generating element such as a piezo element or a Peltier element, a power supply and storage element such as a battery, a power supply control circuit, a rectifying circuit, and the like. The independent power supply system 1 can supply power to the vibration sensor 2 and the measurement circuit unit 3 without being supplied with power from outside the wireless sensor terminal 101.

The vibration sensor 2 is an element that converts the vibration of the measurement target into an electric signal and outputs a voltage or the like corresponding to the magnitude of the vibration. It is possible to use a sensor element generally used for vibration measurement, such as a piezoelectric vibration sensor or a MEMS acceleration sensor. Further, a microphone or the like that measures a sound wave generated due to vibration may be used. The vibration band to be measured varies depending on the measurement target, and an appropriate sensor is selected and used. In this embodiment, a sensor is used which measures vibration in a band of about 10 Hz to 100 kHz and outputs a voltage proportional to the magnitude of vibration.

The measurement circuit unit 3 performs shaping processing on the output signal of the vibration sensor 2, converts the output signal into a digital value, and wirelessly transmits the digital value as measurement data to the data collection/analysis apparatus 102. The measurement circuit unit 3 includes an amplifier circuit 6, an analog-digital conversion circuit 7, a CPU 8, and a wireless communication circuit 9.

The amplifier circuit 6 is a circuit that amplifies an input signal from the vibration sensor 2. The amplifier circuit 6 can be omitted. Although not shown, a bandpass filter or the like may be inserted between the vibration sensor 2 and the analog-digital conversion circuit 7.

The analog-digital conversion circuit 7 is a circuit that converts an input signal (analog signal) from the amplification circuit 6 into a digital signal. It has a function of changing the resolution and the sampling frequency by a control signal from the CPU 8. If necessary, an appropriate filter circuit may be inserted between the amplification circuit 6 and the analog-digital conversion circuit 7 to suppress the noise of the analog signal. Alternatively, a plurality of analog-digital conversion circuits having different resolutions and sampling frequencies may be prepared and they may be switched by a control signal from the CPU 8. The analog-digital conversion circuit 7 may be included in the CPU 8. The sampling frequency for analog-to-digital conversion needs to be high enough to allow analysis when performing spectrum analysis of vibration. In the present embodiment, since the vibration sensor is compatible with 100 kHz, sampling is performed at a maximum of 1 MHz.

The CPU 8 receives and outputs signals from the data collection/analysis device 102, and generation and output of measurement data to be transmitted to the data collection/analysis device through the wireless communication circuit 9. In addition, the operation control of each block of the vibration sensor 2 and the measurement circuit unit 3 is performed based on the received signal. The CPU 8 can be configured by hardware such as FPGA (Field Programmable Gate Array) and ASIC (Application Specific Integrated Circuit). Further, the CPU 8 may include a memory (not shown) for storing data and the like. The memory is, for example, a nonvolatile semiconductor memory. The processing similar to the hardware can also be realized by executing the program stored in the memory by a general-purpose processor to cooperate with other hardware to perform the predetermined processing.

The wireless communication circuit 9 is a circuit that wirelessly transmits a signal from the CPU 8 and receives a wireless signal from the data collection/analysis device, and the wireless frequency and the wireless system are not particularly limited. For example, according to standards such as Wi-SUN (registered trademark), Zigbee (registered trademark), WiFi (registered trademark), WirelessHART (registered trademark), and Bluetooth (registered trademark), which are wireless methods generally used in sensing systems. A compliant radio can be used. Alternatively, communication may be performed using a unique protocol.

The data collection/analysis device 102 has a function of receiving and storing the measurement data transmitted by the wireless sensor terminal 101. Further, it has a function of analyzing the stored measurement data and transmitting the measurement parameter to the wireless sensor terminal 101 wirelessly based on the analysis result. The measurement parameter includes information instructing the setting of each circuit of the wireless sensor terminal 101. The measurement parameters may be considered as commands to the CPU. The information is, for example, parameters such as ON/OFF of a circuit, a sampling frequency to be set and a resolution. The data collection/analysis device 102 can be generally configured by adding a communication function to a computer including an input device, an output device, a storage device, and a processing device. Alternatively, dedicated hardware may be used. It can also be realized by providing a general personal computer or the like with a wireless communication function.

<2. Operation flow>
FIG. 2 is a diagram showing an operation flow of the sensing system of the embodiment of FIG. The respective operations of the wireless sensor terminal 101 and the data collection/analysis apparatus 102 will be described in order.

In the initial state (initial mode), the wireless sensor terminal 101 acquires a large number of points with one measurement using measurement parameters that enable vibration spectrum analysis (S201). The measured data is stored in the memory of the CPU 8 and transmitted (S202). Since unknown signals are handled in the measurement in the initial state, it is desirable to set the highest resolution and the highest sampling rate and acquire the entire sensor signal with high accuracy. For this measurement and transmission operation, since the data measured is the average power consumption that can be realized by the independent power supply system 1, the measurement frequency must be suppressed. For example, it is performed about once a hour.

Next, the data collection/analysis device 102 receives the measured vibration data. The data collection/analysis device 102 repeats reception a plurality of times as necessary. The received data is stored in the storage device as needed. Then, the difference between the plurality of times of vibration data is compared and analyzed (S203). Based on the analysis result, a characteristic signal such as a signal generated with a strong correlation with the operating state of the device in which the sensor is installed is determined (S204). The analysis and the determination may be automatically performed by a predetermined software, or the examination by the operator may be included. The examination/analysis result of the operator is input from the input device of the data collection/analysis device 102 and stored in the storage device.

Then, the data collection/analysis device 102 transmits a measurement instruction including measurement parameters to the wireless sensor terminal 101 so as to measure the amplitude of vibration in the frequency domain including a characteristic amount (S205).

According to the instruction from the data collection/analysis device 102, the wireless sensor terminal 101 focuses on the characteristic vibration in the vibration data for measurement (S206). That is, the power consumption of the terminal can be reduced by measuring at a lower resolution or a lower sampling rate than the measurement in the initial state. As a result, for this measurement and transmission operation, while measuring the characteristic signal, the power consumption is measured once less than in the initial state, so even if the average power consumption that can be realized by the independent power supply system 1 is taken into consideration, It can be performed relatively frequently. For example, it is performed once every 10 minutes (S207).

Finally, in the steady state (steady mode), the data collection/analysis device 102 can collect the data of the characteristic vibration amplitude at a high frequency of once every 10 minutes. That is, only meaningful data can be collected more frequently than when measured in the initial state (S208).

<3. Data analysis principle>
FIG. 3A is a schematic diagram for specifically explaining the operation of the system by taking the case where this sensing system is applied as a system for acquiring the operating state of factory equipment such as a pump and a cutting device by a vibration sensor as an example.

In this example, it is assumed that the wireless sensor terminal 101 is attached to factory equipment and the vibration is measured. Further, the data collection/analysis device 102 can separately acquire information on whether the power source of the factory equipment to be measured is ON or OFF when receiving the signal from the wireless sensor terminal 101. The measurement data 301 measured and transmitted by the wireless sensor terminal 101 in FIG. 3 includes data when the equipment is OFF and data when the equipment is ON.

As described with reference to FIG. 3, in the initial state (S201 to S202), the wireless sensor terminal 101 handles an unknown signal, so that the highest resolution and the highest sampling frequency are set, and the entire sensor signal is set with high accuracy. get. That is, under the control of the CPU 8, the analog-digital conversion circuit 7 is set to the highest resolution and the highest sampling frequency, the output of the vibration sensor 2 is converted into a digital value by the analog-digital conversion circuit 7, and the converted value is measured. The data 301 is wirelessly transmitted.

Since the vibration contains various frequency components, about 1024 to 16384 points are necessary as sufficient measurement points for the analysis. In this example, the analog-digital conversion circuit 7 samples 16384 points at a sampling frequency of 1 MHz in the initial state, and wirelessly transmits them. This measurement needs to be performed with power consumption that can be operated by the self-sustained power supply system 1 used in the wireless sensor terminal 101. However, the energy that can be used by the self-sustained power supply is small, or the battery must be operated for a long time. In view of this, it is necessary to operate intermittently. Since analog-to-digital conversion with high resolution and high sampling frequency generally increases power consumption, it is necessary to perform this measurement operation at a low frequency of about once every 1 to 24 hours. In this example, measurement and transmission are performed once an hour.

The data collection/analysis device 102 receives and analyzes the measurement data 301 thus obtained. In this example, the received vibration data is subjected to FFT (Fast Fourier Transform) processing to be converted into a frequency spectrum 302, and then a plurality of signals are generated together with a signal indicating whether the power source of the factory equipment to be measured is ON or OFF. Compare vibrational spectrum data.

FIG. 3B shows the concept of comparing the vibration spectrum data acquired in the ON state with the vibration spectrum data acquired in the OFF state. Although only two data are shown in FIG. 3B, in practice, it is desirable to analyze based on the data acquired multiple times for each. Then, as a result of analyzing the difference between the vibration spectra of the ON state and the OFF state, the characteristic frequency component 303 of the vibration that becomes strong only when the device is in the ON state is specified.

FIG. 3C shows the concept of instructing the wireless sensor terminal 101 of the measurement parameter for measuring the amplitude of the extracted characteristic frequency component 303 from the data collection/analysis device 102. That is, under the control of the CPU 8, the analog-digital conversion circuit 7 is set to a resolution and sampling frequency sufficient to measure a band including a characteristic frequency component, and the output thereof is converted into a digital value by the analog-digital conversion circuit 7. Then, the converted value is set to be wirelessly transmitted. As a result, the measurement circuit unit 3 needs only to perform measurement at a low resolution and a low sampling frequency as compared with the initial state, and the energy consumption thereof is reduced. Therefore, even if the self-sustaining power supply system 1 is used, it is possible to communicate at a measurement frequency of once every 10 minutes, for example. That is, since the measurement can be performed at low power as compared with the data including many spectra, the data can be acquired with high frequency.

The measurement data 304 thus obtained is the amplitude intensity of a characteristic frequency that reflects the operating state of the apparatus, and compared with the initial state in which the vibration spectrum could be acquired only at a low frequency, Changes can be captured in detail. Therefore, it is possible to efficiently collect detailed operating conditions of factory equipment and data used for predictive diagnosis.

<4. System operation details>
The operation of the system will be specifically described with reference to FIG. 1 again. As described above, in the initial state (S201 to S202), the data collected by the vibration sensor 2 is converted into a digital signal by the analog-digital converter set to high resolution and high sampling frequency, and the data is collected as the measurement data 301. -Send to the analyzer 102. Since it has a high resolution (for example, 16 bits) and a high sampling frequency (for example, 1 MHz), it can correspond to an unknown sensor signal and can acquire the entire signal, but the power consumption is large. Therefore, since the power consumption for measurement is large, the frequency of measurement and transmission is low (for example, once an hour).

The data collection/analysis device 102 determines the characteristic frequency to be measured by analyzing the measurement data 301 and sends it to the wireless sensor terminal 101 as a measurement parameter (S203 to S205). The measurement parameter is, for example, a command for the CPU 8, and the CPU 8 sets the operation of the analog-digital conversion circuit 7 according to the command.

The wireless sensor terminal 101 sets the operation of each circuit according to the received measurement parameters. In the steady state (S206 to S207), the analog-digital conversion circuit 7 is set to low resolution and low sampling frequency, and the signal of the characteristic frequency is measured. Since the vibration of the characteristic frequency usually has a large amplitude, it can be measured with low resolution (for example, 8 bits). In addition, since the characteristic frequency is usually lower than the highest frequency handled by the system, it is possible to measure at a low sampling frequency (for example, 1 kHz), so that it is possible to reduce power consumption for measurement as compared with the initial state. In this way, the CPU 8 changes at least one of the resolution and the sampling frequency of the analog-digital conversion circuit 7 in the initial state and the steady state.

The measurement data 304 is transmitted to the data collection/analysis device 102 as a digital signal by the analog-digital conversion circuit 7. In the steady state, the power consumption for measurement is small, so the frequency of measurement and transmission can be increased (for example, once every 10 minutes).

<5. Supplement>
In the description of FIG. 3, after extracting the characteristic frequency, the measurement is performed in a steady state with a single measurement parameter and the data is transmitted to the data collection/analysis apparatus 102. Good. Further, for example, when an abnormality is detected, the parameters may be returned to the initial state and detailed data may be collected.

In the embodiment, an example is shown in which analysis is performed based on ON/OFF of equipment and the characteristic frequency is specified. However, in addition to the above, when normal and abnormal, during cooling and heating, in a new state and after aging, etc. There are various comparison methods for analysis, and there is no particular limitation.

As described above, conventionally, when the power consumption of the wireless sensor terminal is reduced to the extent that it operates on an independent power source, only a short amount of data can be transmitted in order to reduce the amount of wireless communication, and temperature, humidity, illuminance, etc. , The available sensor types were limited to the physical quantity that required a data amount of several bytes in one measurement. Therefore, there is a problem that it cannot be applied to a sensor that requires a large number of measurements in a relatively short time, such as a vibration spectrum measurement, because the power consumption required for the measurement is large. In the embodiment of the present invention, a sensor, an amplifier circuit that amplifies an analog signal from the sensor, and an analog-digital conversion circuit that converts the output of the amplifier circuit into digital data are provided. Further, the resolution and the sampling frequency of the analog-digital conversion circuit are made variable to values instructed from the outside of the wireless sensor terminal.

With the configuration of the embodiment as described above, it is possible to highly accurately obtain the signal strength of a sensor signal in a certain frequency range, with a small amount of additional power, and to reduce the power required for sensor measurement of the wireless sensor terminal. Can be reduced. As a result, it is possible to reduce the power consumption of the wireless sensor terminal when using a sensor such as a vibration spectrum that needs to be measured many times in a relatively short time. The conventional problem can be solved.

The present invention is not limited to the above-described embodiments, but includes various modifications. For example, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, with respect to a part of the configuration of each embodiment, it is possible to add/delete/replace the configuration of another embodiment.

101 wireless sensor terminal 102 data collection/analysis device

Claims (11)

A sensor that converts a physical quantity into an electrical signal and measures it,
An analog-digital conversion circuit for converting an analog signal based on the electric signal into a digital signal,
A transmitter for wirelessly transmitting data based on the digital signal,
A receiver that receives commands transmitted wirelessly from the outside,
A control unit for controlling the analog-digital conversion circuit based on the command,
Equipped with
The control unit is
Controlling the resolution of the analog-digital conversion circuit based on the command,
In the initial state, the resolution of the analog-digital conversion circuit is set to the first resolution,
After receiving the command, the resolution of the analog-to-digital conversion circuit is set to a second resolution lower than the first resolution to shift to a steady state.
Wireless sensor terminal. The control unit is
The transmission frequency by the transmitter in the steady state is controlled to be higher than the transmission frequency in the initial state,
The wireless sensor terminal according to claim 1. The control unit is
Controlling the sampling frequency of the analog-digital conversion circuit based on the command;
The wireless sensor terminal according to claim 1. The control unit is
In the initial state, the sampling frequency of the analog-digital conversion circuit is set to the first frequency,
After receiving the command, the sampling frequency of the analog-digital conversion circuit is set to a second frequency lower than the first frequency to shift to a steady state.
The wireless sensor terminal according to claim 3. The control unit is
The transmission frequency in the steady state by the transmitter is controlled to be higher than the transmission frequency in the initial state,
The wireless sensor terminal according to claim 4. A wireless sensor system comprising a wireless sensor terminal and a data collection/analysis device,
The wireless sensor terminal,
A sensor that converts a physical quantity into an electrical signal and measures it,
An analog-digital conversion circuit for converting an analog signal based on the electric signal into a digital signal,
A transmitter for wirelessly transmitting data based on the digital signal to the data collection/analysis device;
A receiver for receiving a command wirelessly transmitted from the data collection/analysis device,
A control unit for controlling the analog-digital conversion circuit based on the command,
Equipped with
The control unit is
Controlling the resolution of the analog-digital conversion circuit based on the command,
In the initial state, the resolution of the analog-digital conversion circuit is set to the first resolution,
After receiving the command, the resolution of the analog-digital conversion circuit is set to a second resolution lower than the first resolution, and the steady state is set.
Wireless sensor system. The control unit is
The transmission frequency in the steady state by the transmitter is controlled to be higher than the transmission frequency in the initial state,
The wireless sensor system according to claim 6. The control unit is
Controlling the sampling frequency of the analog-digital conversion circuit based on the command;
The wireless sensor system according to claim 6. The control unit is
In the initial state, the sampling frequency of the analog-digital conversion circuit is set to the first frequency,
After receiving the command, the sampling frequency of the analog-digital conversion circuit is set to a second frequency lower than the first frequency to shift to a steady state.
The wireless sensor system according to claim 8. The control unit is
The transmission frequency in the steady state by the transmitter is controlled to be higher than the transmission frequency in the initial state,
The wireless sensor system according to claim 9. A sensor data collection method in a wireless sensor system comprising a wireless sensor terminal and a data collection/analysis device,
The wireless sensor terminal,
A sensor that converts a physical quantity into an electrical signal and measures it,
An analog-digital conversion circuit for converting an analog signal based on the electric signal into a digital signal,
A transmitter for wirelessly transmitting data based on the digital signal to the data collection/analysis device;
A receiver for receiving a command wirelessly transmitted from the data collection/analysis device,
A control unit for controlling the analog-digital conversion circuit based on the command,
Equipped with
The wireless sensor terminal,
In the initial mode,
The resolution of the analog-digital conversion circuit is set to a first resolution, the sampling frequency of the analog-digital conversion circuit is set to a first frequency, and the data based on the digital signal subjected to analog-digital conversion is set to the data. A first step of wirelessly transmitting to a collection and analysis device;
A second step of receiving a command wirelessly transmitted from the data collection/analysis device,
Based on the command, the resolution of the analog-digital conversion circuit is set to a second resolution lower than the first resolution, and the sampling frequency of the analog-digital conversion circuit is set to a second resolution lower than the first frequency. Execute the third step of setting the frequency and shifting to the steady mode,
In the steady mode,
Performing a fourth step of wirelessly transmitting data based on the digital signal analog-digital converted by the analog-digital conversion circuit to the data collection/analysis device;
The sensor data collection method, wherein the wireless transmission frequency in the first step is lower than the wireless transmission frequency in the fourth step.

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