JP6027503B2 - Sensor network system - Google Patents

Description

  The present invention relates to a technique for monitoring an environment.

  2. Description of the Related Art In recent years, sensor networks that provide services for arranging a large number of sensors around the body and collecting and analyzing information from the sensors are being commercialized. In order to avoid the troublesomeness of wiring, wireless sensor terminals that transmit data using wireless are used in sensor networks. In a conventional wireless sensor terminal, a signal sensed by a sensor is converted into digital data by a sensor circuit and an A / D conversion circuit, and the converted digital data is transmitted by a wireless circuit.

  Since many wireless sensor terminals are used in the sensor network, reduction of the cost of the wireless sensor terminals becomes an issue. Conventional wireless sensor terminals have a problem in that it is difficult to reduce costs because sophisticated signal processing circuits such as a sensor circuit, an A / D conversion circuit, and a CPU are required. In addition, when a battery is used as the power source of the wireless sensor terminal, there is a problem that the cost of replacing the battery is generated.

  The present invention has been made in view of the above, and an object thereof is to reduce the cost of a sensor network for monitoring the environment.

The sensor network system according to the present invention is a sensor network system including one or more sensor terminals and a receiving device, and the sensor terminal includes an energy harvesting element that generates electrical energy according to an environmental state; A storage element that stores electrical energy generated by the energy harvesting element, a transmission unit that transmits a terminal ID assigned to the sensor terminal using the electrical energy stored in the storage element, and a voltage value of the storage element is detected When the voltage value is equal to or higher than the first threshold, the transmission unit transmits the terminal ID, and when the voltage value is equal to or lower than the second threshold, the transmission unit transmits the terminal ID. Monitoring means for stopping, and the receiving device receives the terminal ID transmitted by the sensor terminal, and the terminal for each terminal ID. And having analysis means seeking the frequency of communication ID and relative statistics environment observed by the sensor terminal.

  In the sensor network system, the analysis unit converts a relative statistic of the environment into a physical quantity.

  In the sensor network system, the sensor terminal further includes a sensor that detects an environmental state, and the monitoring unit operates the sensor when a voltage value of the power storage element is equal to or higher than a third threshold value. When the output value of the sensor is within a predetermined range, the transmission unit is caused to transmit the terminal ID.

  In the sensor network system, the sensor terminal further includes a fast start-up oscillator that starts an oscillator at high speed, and the monitoring unit includes the transmission unit and the transmission unit when the voltage value of the power storage element does not satisfy the first threshold value. Energy is not supplied from the power storage element to the fast startup oscillator, and electrical energy is supplied from the power storage element to the transmission means and the fast startup oscillator when the voltage value of the power storage element is equal to or higher than the first threshold value. Then, the transmission unit is caused to transmit the terminal ID.

  In the sensor network system, the receiving device further includes a position estimating unit that estimates a position of the sensor terminal.

  According to the present invention, the sensor terminal includes an energy generation element that generates electrical energy according to an environmental state, and an energy storage element that accumulates the electrical energy generated by the energy generation element, and the voltage value of the energy storage element is equal to or higher than the first threshold value. The terminal ID is transmitted using the electrical energy stored in the power storage element, and the reception device receives the terminal ID, obtains the communication frequency for each terminal ID, and is relative to the environment observed by the sensor terminal. By using the statistical quantity, the sensor terminal can be configured at low cost, and the cost of the sensor network for monitoring the environment can be reduced.

It is a functional block diagram which shows the structure of the wireless sensor network system in 1st Embodiment. It is a graph which shows the change of the energy accumulate | stored in an electrical storage element, and the transmission state of terminal ID. It is a figure which shows the example of the relative environmental information map using the positional information on a wireless sensor terminal. It is a functional block diagram which shows the structure of the wireless sensor network system in 2nd Embodiment. It is a functional block diagram which shows the structure of the wireless sensor network system in 3rd Embodiment. It is a functional block diagram which shows the structure of the wireless sensor network system in 4th Embodiment. It is a functional block diagram which shows the structure of the wireless sensor network system in 5th Embodiment.

[First Embodiment]
FIG. 1 is a functional block diagram showing the configuration of the wireless sensor network system in the first embodiment. The wireless sensor network system in the present embodiment includes a plurality of wireless sensor terminals 1A to 1D and a receiving device 2.

  The wireless sensor terminals 1 </ b> A to 1 </ b> D include an energy harvesting element 11, a power storage element 12, a voltage monitor circuit 13, a terminal ID storage unit 14, and a wireless transmission unit 15. The configuration of the wireless sensor terminals 1B to 1D is the same as that of the wireless sensor terminal 1A.

  The environmental power generation element 11 is an element that generates energy according to the state of the environment, such as a solar cell, a temperature difference power generation element, and a vibration power generation element. The type of energy harvesting element 11 according to the environment information to be collected is used.

  The electricity storage element 12 is an element that accumulates electrical energy, such as a capacitor or a secondary battery. The electricity storage element 12 stores electric energy generated by the energy harvesting element 11.

  The voltage monitor circuit 13 detects the voltage value of the power storage element 12, and issues an instruction to transmit a terminal ID to the wireless transmission unit 15 when the detected voltage value is equal to or greater than the first threshold value. Further, when the detected voltage value is equal to or smaller than the second threshold value that is smaller than the first threshold value, an instruction to stop the transmission of the terminal ID is issued to the wireless transmission unit 15. The terminal ID is an identifier assigned to each of the wireless sensor terminals 1A to 1D. The first threshold is set to be equal to or higher than a voltage value at which the wireless transmission unit 15 can be operated.

  The terminal ID storage unit 14 stores a terminal ID.

  The wireless transmission unit 15 reads the terminal ID from the terminal ID storage unit 14 using the energy accumulated in the power storage element 12 and transmits the terminal ID to the reception device 2. While the wireless transmission unit 15 transmits the terminal ID, the energy accumulated in the power storage element 12 by the wireless transmission unit 15 is consumed, and according to the state of the environment while the wireless transmission unit 15 does not transmit the terminal ID. Thus, the energy stored in the storage element 12 increases.

  The receiving device 2 receives the terminal ID transmitted by the wireless sensor terminals 1A to 1D. As illustrated in FIG. 1, the reception device 2 includes a wireless reception unit 21 and a signal processing unit 22. The wireless reception unit 21 receives terminal IDs transmitted by the wireless sensor terminals 1A to 1D. The signal processing unit 22 obtains the communication frequency per unit time for each terminal ID, and uses it as a relative statistic of the environment observed by each of the wireless sensor terminals 1A to 1D.

  Here, an operation in which the wireless transmission unit 15 repeats transmission start and transmission stop of the terminal ID will be described. FIG. 2 is a graph showing a change in energy accumulated in the storage element 12 and a transmission state of the terminal ID. The vertical axis represents the voltage value of the electricity storage element 12, and the horizontal axis represents time. The energy generated by the energy harvesting element 11 is accumulated in the electricity storage element 12 and the voltage value increases. When the voltage value of the power storage element 12 becomes equal to or higher than the first threshold value (threshold value 1 in the figure), the wireless transmission unit 15 starts transmitting the terminal ID using the energy accumulated in the power storage element 12. Since the wireless transmission unit 15 uses the energy stored in the power storage element 12, the voltage value of the power storage element 12 decreases. When the voltage value of the energy accumulated in the storage element 12 becomes equal to or less than the second threshold value (threshold value 2 in the figure), the wireless transmission unit 15 stops transmitting the terminal ID. When the wireless transmission unit 15 stops transmitting the terminal ID, the amount of energy consumption is reduced, so that the energy generated by the energy harvesting element 11 is filled in the storage element 12 again. As a result, as shown in FIG. 2, the wireless transmission unit 15 repeats transmission start and transmission stop according to the voltage value of the storage element 12.

  As the amount of energy generated by the energy harvesting element 11 increases, the voltage value of the power storage element 12 rises faster, so the terminal ID transmission interval becomes shorter and the communication frequency of the terminal ID becomes higher. For example, when a solar cell is used as the energy harvesting element 11, when the luminance is high, the amount of energy generated is large, and the communication frequency of the terminal ID increases. The same applies to temperature and vibration. Since the amount of energy generated by the energy harvesting element 11 varies depending on the environment, the wireless sensor terminals 1A to 1D having a larger energy amount generated by the energy harvesting element 11 have a higher terminal ID communication frequency. Therefore, the receiving device 2 counts the number of transmissions of the terminal IDs of the wireless sensor terminals 1A to 1D, and sets the number of transmissions of the terminal ID per unit time as a relative statistic representing the state of the environment. Alternatively, the interval from when the wireless sensor terminals 1A to 1D stop transmitting the terminal ID to when the wireless sensor terminals 1A to 1D start transmitting, that is, the time when the power storage element 12 is charged from the second threshold value to the first threshold value is set as the environmental state. It is good also as a statistic to represent.

  As shown in FIG. 3, it is also possible to create a relative environment information map if the installation locations of the plurality of wireless sensor terminals 1A to 1D are stored in advance. In the example of FIG. 3, the communication frequency per unit time is as follows.

The communication frequency of the wireless sensor terminal 1A is 10 times per unit time The communication frequency of the wireless sensor terminal 1B is 5 times per unit time The communication frequency of the wireless sensor terminal 1C is 7 times per unit time The communication frequency of the wireless sensor terminal 1D is per unit time Once

  In addition, when the environmental state with respect to the communication frequency of the terminal ID is known in advance, the environmental state can be quantified from the communication frequency of the terminal ID. For example, by calculating the amount of energy generated per unit time using the following equation and comparing the amount of power generation energy per unit time with respect to the environmental state of the environmental power generation element 11, the physical quantity indicating the environmental state is converted to an absolute value. Can do.

Amount of energy generated per unit time = communication frequency × amount of energy required for transmission of terminal ID For example, in the example of FIG. 3, when the energy harvesting element 11 whose amount of generated energy changes according to temperature is used, a wireless sensor terminal The absolute value of the temperature can be obtained from the communication frequency of each terminal ID of 1A to 1D as follows.

Communication frequency of wireless sensor terminal 1A = 10 times / unit time = temperature 65 ° C.
Communication frequency of wireless sensor terminal 1B = 5 times / unit time = temperature 32 ° C.
Communication frequency of wireless sensor terminal 1C = 7 times / unit time = temperature 48 ° C.
Communication frequency of wireless sensor terminal 1D = 1 time / unit time = temperature 18 ° C.

  As described above, according to the present embodiment, the wireless sensor terminals 1 </ b> A to 1 </ b> D generate the energy harvesting element 11 that generates energy according to the state of the environment, and the energy storage element 12 that stores the energy generated by the energy harvesting element 11. Provided, the terminal ID is transmitted when the voltage value of the power storage element 12 is equal to or higher than the first threshold, the receiving device 2 receives the terminal ID, and obtains the communication frequency per unit time for each terminal ID, By using relative statistics of the environment observed by the wireless sensor terminals 1A to 1D, it is not necessary to perform advanced signal processing in the wireless sensor terminals 1A to 1D, and the cost of the wireless sensor terminals 1A to 1D is suppressed. Can do. In addition, since the wireless sensor terminals 1A to 1D are operated using the energy generated by the energy harvesting element 11, it is not necessary to replace the battery.

[Second Embodiment]
FIG. 4 is a functional block diagram showing the configuration of the wireless sensor network system according to the second embodiment. The wireless sensor network system according to the second embodiment further includes a sensor 16 that detects an environmental state in the wireless sensor terminals 1A to 1D according to the first embodiment.

  The sensor 16 may detect an environment state different from the energy harvesting element 11 or may detect the same environment state. For example, when a solar cell is used for the energy harvesting element 11, the sensor 16 may detect temperature or may detect luminance.

  The voltage monitor circuit 13 detects the voltage value of the power storage element 12 and operates the sensor 16 when the detected voltage value is equal to or greater than the third threshold value. When the output value of the sensor 16 is not less than a certain value, not more than a certain value, or within a predetermined range, the wireless transmission unit 15 is operated to transmit the terminal ID.

  Since the wireless sensor terminals 1 </ b> A to 1 </ b> D include the sensor 16, the terminal ID can be transmitted in consideration of another environmental state different from the environmental state detected by the environmental power generation element 11.

[Third Embodiment]
FIG. 5 is a functional block diagram showing a configuration of a wireless sensor network system according to the third embodiment. The wireless sensor network system according to the third embodiment further includes a fast start-up oscillator 17 in the wireless sensor terminals 1A to 1D according to the first embodiment.

  When the voltage value of the storage element 12 detected by the voltage monitor circuit 13 is less than the first threshold value, energy is not supplied to the wireless transmission unit 15 and the fast start-up oscillator 17, and the voltage value of the storage element 12 is the first value. When the threshold value is exceeded, energy supply to the wireless transmission unit 15 and the fast startup oscillator 17 is started. When energy is supplied to the wireless transmission unit 15 and the fast startup oscillator 17, the oscillator starts up at high speed, and the wireless transmission unit 15 transmits the terminal ID. As the fast start-up oscillator 17, a ring resonator or an oscillator using an element having a Q value lower than that of a crystal resonator such as a SAW / FBAR device as a resonator may be used.

  When the voltage value of the energy storage element 12 is less than the first threshold value, energy is not supplied to the wireless transmission unit 15 and the fast startup oscillator 17, so that the energy consumed by the energy generating element 11 is Only the energy consumed by the leakage and voltage monitor circuit 13 is obtained, the energy consumption is reduced, and the size of the energy harvesting element 11 can be reduced. Also, by providing an oscillator that starts at high speed, it is possible to shorten the startup time until the terminal ID is transmitted, reduce the energy consumption of the wireless transmission unit 15, and enable communication over a long distance.

  In addition, you may combine the wireless sensor terminal of 2nd Embodiment and 3rd Embodiment.

[Fourth Embodiment]
FIG. 6 is a functional block diagram showing the configuration of the wireless sensor network system in the fourth embodiment. The wireless sensor network system according to the fourth embodiment further includes a position estimation unit 23 in the receiving device 2 according to the first embodiment.

  The position estimation unit 23 estimates the positions of the wireless sensor terminals 1A to 1D using arrival angle information of radio waves transmitted by the wireless sensor terminals 1A to 1D and transmission time information transmitted together with the terminal ID.

  Since the receiving device 2 includes the position estimation unit 23 that estimates the positions of the wireless sensor terminals 1A to 1D, the relative environment information map can be obtained without storing the installation locations of the wireless sensor terminals 1A to 1D in advance. Can be created.

[Fifth Embodiment]
FIG. 7 is a functional block diagram illustrating a configuration of a wireless sensor network system according to the fifth embodiment. In the wireless sensor network system according to the fifth embodiment, the analysis performed by the receiving device 2 according to the first embodiment is performed by another analyzing device 3.

  The receiving device 2 extracts the terminal ID from the radio waves received from the wireless sensor terminals 1 </ b> A to 1 </ b> D and transmits it to the analyzing device 3.

  The analysis device 3 includes an analysis unit 31 and a storage unit 32. The analysis unit 31 aggregates the terminal IDs transmitted by the receiving device 2 for each of the wireless sensor terminals 1A to 1D, counts the number of transmissions of the terminal ID per unit time, and accumulates the analysis results in the accumulation unit 32.

  The analysis device 3 may be directly connected to the reception device 2 or may be connected via a network.

DESCRIPTION OF SYMBOLS 1A-1D ... Wireless sensor terminal 11 ... Energy harvesting element 12 ... Power storage element 13 ... Voltage monitor circuit 14 ... Memory | storage part 15 ... Wireless transmission part 16 ... Sensor 17 ... Fast start-up oscillator 2 ... Receiver 21 ... Wireless receiver 22 ... Signal Processing unit 23 ... Position estimation unit 3 ... Analysis device 31 ... Analysis unit 32 ... Storage unit

Claims (5)

A sensor network system comprising one or more sensor terminals and a receiving device,
The sensor terminal is
An energy harvesting element that generates electrical energy according to the state of the environment;
A storage element for storing electrical energy produced by the energy harvesting element;
Transmitting means for transmitting a terminal ID assigned to the sensor terminal using the electrical energy stored in the power storage element;
When the voltage value of the power storage element is detected and the voltage value is equal to or higher than a first threshold value, the transmission unit transmits the terminal ID, and the voltage value is equal to or lower than a second threshold value. Monitoring means for causing the transmission means to stop the transmission of the terminal ID,
The receiving device is:
Receiving means for receiving the terminal ID transmitted by the sensor terminal;
A sensor network system, characterized by having an analysis means for the relative statistic of the terminal ID the observed seeking communication frequency of the terminal ID by the sensor terminal for every environment.   The sensor network system according to claim 1, wherein the analysis unit converts a relative statistic of the environment into a physical quantity. The sensor terminal further includes a sensor for detecting an environmental state,
The monitoring means operates the sensor when the voltage value of the power storage element is equal to or greater than a third threshold value, and when the output value of the sensor is within a predetermined range, The sensor network system according to claim 1 or 2, wherein the ID is transmitted. The sensor terminal further includes a fast start oscillator that starts the oscillator at high speed,
The monitoring means does not supply energy from the power storage element to the transmission means and the fast startup oscillator when the voltage value of the power storage element is less than the first threshold value, and the voltage value of the power storage element is 4. The device according to claim 1, further comprising: supplying electric energy from the power storage element to the transmission unit and the fast start-up oscillator to cause the transmission unit to transmit the terminal ID when a threshold value of 1 or more is reached. The sensor network system according to the above.   5. The sensor network system according to claim 1, wherein the reception device further includes a position estimation unit that estimates a position of the sensor terminal.

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