CN109155957B

CN109155957B - Server device, sensor network, control method, and storage medium

Info

Publication number: CN109155957B
Application number: CN201680085755.3A
Authority: CN
Inventors: 山下浩一郎; 铃木贵久; 栗原康志
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 2016-06-09
Filing date: 2016-06-09
Publication date: 2022-07-05
Anticipated expiration: 2036-06-09
Also published as: CN115066002A; JP6658881B2; JPWO2017212620A1; WO2017212620A1; CN109155957A

Abstract

A sensor network system in which sensor devices driven by a secondary battery are dispersed is efficiently used. The server device includes a control unit that controls the operation of a sensor device in a sensor network including a plurality of sensor devices in the following manner. The control section acquires, together with sensing data of a sensor device included in the sensor apparatus, an output value of a temperature sensor provided at the sensor device and state information of a secondary battery that drives the sensor apparatus. Then, the control section controls the connection relationship of the sensor devices in the sensor network based on the state information of the secondary battery and the output value of the temperature sensor.

Description

Server device, sensor network, control method, and storage medium

Technical Field

The invention relates to a server device, a sensor apparatus, a sensor network, a control method, and a storage medium.

Background

As a method of monitoring a wide range of conditions such as an environment and an infrastructure structure, a method of monitoring by a sensor network system including a plurality of sensor devices is known. As one of the sensor network systems, there is known a system in which an ambient temperature is periodically measured by a sensor device including a temperature sensor and transmitted to the outside, and the ambient temperature is dynamically observed to gradually increase or to what degree (for example, see patent document 1).

In a sensor network system, a plurality of sensor devices distributed in an observation area are each driven by a battery, thereby reducing the cost of the system. In a sensor network system in which sensor devices are driven by a battery, the sensor devices are operated for a long time by suppressing the consumption of the battery, and thus, the trouble of charging the battery, replacing the battery, and the like is eliminated. As a method of suppressing the consumption of the battery, there is known a method in which a sensor device calculates a drive interval in consideration of the temperature characteristics of the battery, and drives a sensor at the drive interval (for example, see patent document 2). As another method for suppressing the consumption of the battery, there is known a method for suppressing the power consumption of the sensor device by performing an arithmetic process such as correction of the sensor output by a correction device provided independently of the sensor device (for example, see patent document 3).

Patent document 1: japanese laid-open patent publication No. 2008-292318

Patent document 2: japanese patent laid-open publication No. 2013-027164

Patent document 3: japanese patent laid-open publication No. 2013-036812

Some sensor devices of the sensor network system use a secondary battery as a storage battery, and are combined with an environmental power generation element such as a solar panel to realize a long-term operation. In many cases, small electronic devices such as sensor devices use lithium ion batteries as storage batteries.

However, secondary batteries such as lithium ion batteries have significantly reduced charging characteristics in low-temperature environments such as below freezing point or in high-temperature environments such as hot summer days. For example, many lithium ion batteries have discharge characteristics of about-20 to 60 ℃ and charge characteristics of about 0 to 45 ℃.

When the sensor device is continuously operated in a state where the charge characteristics of the secondary battery are degraded, the secondary battery continues to discharge even if the environmental power generation element generates power, and eventually becomes a depleted state. Therefore, in a sensor network system installed in a cold district or the like, when the winter season is reached, the secondary battery is in a depleted state, and the plurality of sensor devices stop operating one by one. In this case, if the operation of the sensor device that functions as a relay node in the sensor network is stopped, even if another sensor device that transmits the measurement result to the server apparatus via the stopped sensor device operates, the measurement result of the other sensor device cannot be transmitted to the server apparatus.

Disclosure of Invention

In one aspect, the present invention aims to achieve efficient operation of a sensor network system in which sensor devices driven by a secondary battery are dispersed.

The server device includes a control unit that controls the operation of a sensor device in a sensor network including a plurality of sensor devices in the following manner. The control section acquires, together with sensing data of a sensor device included in the sensor apparatus, an output value of a temperature sensor provided at the sensor device and state information of a secondary battery that drives the sensor apparatus. Then, the control section controls the connection relationship of the sensor devices in the sensor network based on the state information of the secondary battery and the output value of the temperature sensor.

According to the above aspect, it is possible to efficiently operate a sensor network system in which sensor devices driven by a secondary battery are dispersed.

Drawings

Fig. 1 is a diagram showing an example of a configuration of a sensor network system according to an embodiment.

Fig. 2 is a diagram showing a configuration of a sensor device.

Fig. 3 is a diagram showing a functional configuration of the server device.

Fig. 4 is a flowchart illustrating processing performed by the sensor device.

Fig. 5 is a flowchart illustrating the contents of the scheduling process.

Fig. 6 is a flowchart illustrating a link change process performed by the server device.

Fig. 7 is a diagram illustrating an example of the arrangement of the sensor device.

Fig. 8 is a graph showing a change in the ambient temperature of the sensor device over a certain period.

Fig. 9 is a graph illustrating a relationship between an outside air temperature and a voltage of the secondary battery during a certain period.

Fig. 10 is a diagram showing an example of a link and an adjacent node of a sensor network.

Fig. 11 is a diagram showing an example of the battery residual amounts and the temperature differences of the adjacent nodes.

Fig. 12 is a diagram showing a modification of the link.

Fig. 13 is a graph illustrating a temporal change in the power supply voltage of the sensor device in a low-temperature environment.

Fig. 14 is a diagram showing a hardware configuration of the sensor device.

Fig. 15 is a diagram showing a hardware configuration of a computer that operates as a server device.

Detailed Description

As shown in fig. 1, a sensor network system 1 includes a sensor network 3 including a plurality of sensor devices 2, and a server device 4.

The sensor device 2 is an electronic device including a sensor device that measures a desired physical quantity in an environment, an infrastructure structure, or the like. A plurality of sensor devices 2 are dispersed within a prescribed observation area. Each sensor device 2 transmits various information including the measurement result (sensing data) of the sensor device to the aggregation apparatus 5. The plurality of sensor devices 2 in the sensor network 3 include a sensor device 2 that functions as a relay node that transfers measurement results of another sensor device 2 to the aggregation device 5, and a sensor device 2 that functions as a non-relay node that transmits the measurement results only to the relay node. The aggregation device 5 aggregates information transmitted from the sensor devices 2 operating in the sensor network 3 and transmits the aggregated information to the server device 4. The concentrator device 5 and the server device 4 are connected via a communication network 6 such as the internet. In the following description, only a sensor device functioning as a relay node and a sensor device functioning as a non-relay node will be referred to as a relay node and a non-relay node, respectively.

Fig. 2 is a diagram showing a configuration of a sensor device.

As shown in fig. 2, the sensor device 2 includes an information processing apparatus 7, an environment power generating element 8, and a sensor group 9.

The information processing apparatus 7 acquires measurement results of the

sensor devices

901 and 902 and the like of the sensor group 9 and output values of the

temperature sensors

901T and 902T, and transmits the measurement results and the state information of the secondary battery that drives the information processing apparatus 7 to a predetermined external apparatus. The external device is the aggregation device 5 or another sensor apparatus that functions as a relay node. The information processing device 7 includes a control unit 701, a storage unit 702, a power supply management unit 703, a secondary battery 704, and an antenna 705 for wireless communication.

The control unit 701 controls the operation of the information processing apparatus 7. The control unit 701 acquires the measurement results from the

sensor devices

901 and 902, and also acquires the state information of the secondary battery 704 from the power management unit 703, and transmits the acquired information to the aggregation apparatus 5 or the relay node. The

sensor devices

901 and 902 are provided with

temperature sensors

901T and 902T for temperature correction, respectively. The measurement results acquired by the control unit 701 from the

sensor devices

901 and 902 include sensing data for a predetermined physical quantity and output values of the

temperature sensors

901T and 902T. The control unit 701 determines whether or not to change the operation mode of the sensor device 2 including itself to the mode with low power consumption, based on the output value of the temperature sensor acquired from the sensor device and the state information of the secondary battery 704 acquired from the power supply management unit 703. The operation modes of the sensor device 2 include three modes, i.e., a mode in which the sensor device operates as a relay node, a mode in which the sensor device operates as a non-relay node, and a sleep mode. The mode in which the relay node operates is a mode in which the measurement result of the relay node itself or the like is transmitted to another relay node or the aggregation apparatus 5, and the measurement result of the sensor device 2 downstream in the sensor network is transmitted to another relay node or the aggregation apparatus 5. The mode in which the non-relay node operates is a mode in which only the measurement result of the non-relay node and the like are transmitted to another relay node or the aggregation device 5. The sleep mode is a mode in which the interval for acquiring the measurement result is longer than a mode in which the non-relay node operates, and a part of the function (operation) is stopped to suppress the consumption of power. Of the three operation modes, the operation mode with the highest power consumption is a mode in which the relay node operates. Among the three operation modes, the operation mode with the lowest power consumption is the sleep mode.

The storage unit 702 stores measurement results obtained from the

sensor devices

901 and 902, state information of the secondary battery 704, and the like. The storage unit 702 stores various information related to the operation of the sensor device 2, such as information on the aggregation device 5 or the relay node to which the transmission measurement result and the state information are to be communicated.

The power supply management unit 703 manages charging and discharging of the secondary battery 704. The power supply management unit 703 charges the secondary battery 704 with the electric power generated by the environment power generation element 8. The power supply management unit 703 acquires state information of the secondary battery 704 including the remaining battery level, and notifies the control unit 701 of the state information. The power management unit 703 manages the timing of the return from the sleep mode when the sensor device 2 is shifted to the sleep mode.

The secondary battery 704 is a power source for supplying operating power to the information processing apparatus 7 and the

sensor devices

901 and 902. The secondary battery 704 is, for example, a lithium ion battery.

Fig. 3 is a diagram showing a functional configuration of the server device.

As shown in fig. 3, the server apparatus 4 includes a control unit 401 and a storage unit 402.

The control unit 401 of the server apparatus 4 stores the measurement results and the state information of the secondary battery in the storage unit 402 in each of the plurality of sensor devices 2 received via the aggregation apparatus 5. Further, the control unit 401 controls the link in the sensor network 3 (i.e., the connection relationship between the compact device 5 and the sensor device 2) based on the temperature information included in the measurement result and the state information of the secondary battery.

The storage unit 402 of the server apparatus 4 stores topology information of the sensor network 3 in addition to the measurement results and the state information of the secondary battery in each of the plurality of sensor devices 2.

The server device 4 determines the connection relationship between the aggregation device 5 and the plurality of sensor devices 2 in the sensor network 3 based on the operating state of each sensor device 2 and the like. The server apparatus 4 first determines the connection relationship between the aggregation apparatus 5 and the plurality of sensor devices 2 based on initial conditions. The initial conditions are arbitrary, and are determined based on, for example, the number of sensor devices 2 directly connected to the concentrator 5, the physical distance between the sensor devices 2, and the like. When the server apparatus 4 detects a sensor device 2 in which the remaining amount of the secondary battery is equal to or less than the threshold value and the secondary battery is in an inactive state (that is, a state in which the secondary battery cannot be charged), the connection relationship between the aggregation apparatus 5 and the plurality of sensor devices 2 is changed.

Fig. 4 is a flowchart illustrating processing performed by the sensor device.

The sensor device 2 performs the processing of steps S1 to S4 shown in fig. 4 every time a predetermined measurement timing arrives. The sensor device 2 first acquires sensing data (measurement data) of the sensor device, an output value of the temperature sensor, and state information of the secondary battery 704 (step S1). The process of step S1 is performed by the control unit 701 and the power supply management unit 703 of the information processing device 7 in the sensor device 2. The control unit 701 acquires output values of the

temperature sensors

901T and 902T for temperature correction from the

respective sensor devices

901 and 902 of the sensor group 9 together with sensing data for physical quantities measured by the respective sensor devices. Further, the control unit 701 acquires the state information including the remaining amount of the secondary battery 704 via the power supply management unit 703.

Next, the sensor device 2 corrects the sensing data based on the output value of the temperature sensor in the information processing apparatus 7 (step S2), and transmits the corrected sensing data and the like to the relay node or the aggregation apparatus 5 (step S3). Thereafter, the information processing apparatus 7 performs scheduling processing (step S4). When the sensor network is installed in a low-temperature environment such as a cold district, the information processing device 7 of the sensor device 2 performs the processing shown in fig. 5 as scheduling processing.

Fig. 5 is a flowchart illustrating the contents of the scheduling process.

In the scheduling process, the sensor device 2 (information processing apparatus 7) first determines whether the ambient temperature Tn of the sensor device 2 is lower than the threshold temperature T based on the output value of the temperature sensor acquired in step S1 (step S401). The threshold temperature T is a criterion of a temperature at which the secondary battery 704 becomes incapable of being charged (charge inactive state). The initial value of the threshold temperature T is set to a temperature higher by 1 to 2 ℃ than the lower limit temperature of the charging characteristics of the secondary battery 704, for example. The determination in step S401 is performed by the control unit 701 of the information processing apparatus 7. If Tn is not less than T (step S401; no), the control unit 701 ends the scheduling process (return). In this case, the sensor device 2 (information processing apparatus 7) continues the operation in the current operation mode.

On the other hand, when Tn < T (step S401; no), the control unit 701 next determines whether the secondary battery 704 is in a depleted state (step S402). In step S402, the control unit 701 determines whether the secondary battery 704 is in a depleted state based on the state information of the secondary battery 704. In addition, the determination as to whether or not the secondary battery 704 is in the depletion state is not performed simply by comparing the remaining battery level included in the state information with the threshold value, but is performed in consideration of, for example, a voltage drop state before the state of discharge is reached. If the secondary battery 704 is not in the depleted state (step S402; no), the control unit 701 ends the scheduling process. In this case, the sensor device 2 also continues the operation in the current operation mode.

When the secondary battery 704 is in a depleted state (step S402; yes), the control unit 701 next determines whether or not the secondary battery 704 is being charged, that is, whether or not the charging function of the secondary battery 704 is operating (step S403). When the secondary battery is being charged (step S403; yes), the control unit 701 ends the scheduling process. In this case, the sensor device 2 also continues the operation in the current operation mode.

If the secondary battery 704 is not being charged despite the exhaustion of the secondary battery 704 (step S403; no), the control unit 701 next updates the threshold temperature T to T- Δ T (step S404). The temperature Δ T at the time of updating the threshold temperature T is, for example, a change amount of the temperature of the output value of the temperature sensor provided in the sensor device.

After step S404, the control unit 701 determines whether or not the sensor device 2 including itself is a relay node (step S405). If the sensor device 2 including itself is not a relay node (step S405; no), the control unit 701 sets a timer, shifts the operation mode of the sensor device 2 to the sleep mode (step S406), and ends the scheduling process (return). The control unit 701 performs the process of step S405 in cooperation with the power management unit 703. In step S405, the control unit 701 notifies the server apparatus 4 (the aggregation apparatus 5) that the sensor device 2 including itself has moved to the sleep mode. The controller 701 causes the power management unit 703 to set a timer and stops the supply of electric power to the controller 701 and the

sensor modules

901 and 902. The power management unit 703 sets the timing (time) at which the next scheduling process is performed to a time interval longer than the time interval in the normal operation. The time interval in normal operation is, for example, about several minutes to several tens of minutes. In contrast, in step S406, for example, the next sunset time is set as the timing (time) at which the scheduling process is performed next time.

On the other hand, when the sensor device 2 including itself is a relay node (step S405; yes), the control unit 701 requests the server apparatus 4 to change the links between the aggregation apparatus 5 and the plurality of sensor devices 2 (step S407), and acquires the result of the link change processing from the server apparatus 4. Upon receiving a request for changing the link from the sensor device 2, the server apparatus 4 performs the processing shown in fig. 6, for example, and notifies the sensor device 2 of the processing result.

When the processing result of the request for change of the link is acquired from the server apparatus 4, the control unit 701 determines whether or not the sensor device 2 including itself can be changed from the relay node to the non-relay node (step S408). If the change to the non-relay node is possible (step S408; yes), the control unit 701 changes the sensor device 2 including itself from the relay node to the non-relay node (step S409), and ends the scheduling process (return).

On the other hand, if the change to the non-relay node is not possible (step S408; no), the control unit 701 shifts the operation mode of the sensor device 2 to the sleep mode in cooperation with the power management unit 703 (step S406), and ends the scheduling process.

In this way, when the secondary battery 704 is in a depleted state and is in a state in which charging is not possible (an inactive-charging state), the control unit 701 of the sensor device 2 transmits a request for changing the link between the concentrator 5 and each sensor device 2 to the server apparatus 4. Upon receiving a request for changing the link from the sensor device 2, the server apparatus 4 performs the processing shown in fig. 6.

Upon receiving the request for changing the link, the control unit 401 of the server apparatus 4 first selects a node (adjacent node) in an adjacent relationship with the sensor device 2 (hereinafter referred to as a request node) that has transmitted the request for change, based on the current topology information (step S11). In step S11, the control unit 401 reads the current topology information from the storage unit 402, and selects, as the neighboring nodes, the nodes in the direct connection relationship (duplex relationship) with the requested node and the nodes having the same connection distance from the parent node of the requested node.

Next, the control unit 401 acquires the communication quality of the adjacent nodes and sorts the adjacent nodes in the order of the quality from high to low (step S12). In step S12, the control unit 401 acquires a Link Quality Indicator (LQI) value of each neighboring node as the communication quality of the neighboring node.

Next, the control unit 401 of the server device 4 acquires the remaining battery level of each adjacent node, and sorts the adjacent nodes in the order of the battery level from the highest to the lowest (step S13).

Next, the control unit 401 acquires the temperature difference (Tn-T) between the current temperature Tn of each adjacent node and the threshold temperature T, and sorts the adjacent nodes in order of decreasing temperature difference (step S14).

Thereafter, the control unit 401 selects a candidate of the alternative relay node based on the communication quality, the remaining battery level, and the temperature difference (Tn-T) of each adjacent node (step S15). Since the sensor device 2 operating as a relay node also communicates with the sensor device 2 serving as a node (child node) downstream from the sensor device 2, the amount of power consumption is larger than that of the sensor device 2 operating as a non-relay node. Therefore, the sensor device 2 that operates as a relay node is preferably a sensor device with a large remaining battery level. However, even in a sensor device having a large remaining battery capacity, when the temperature difference (Tn-T) is small, the secondary battery 704 enters a charge-inactive state in which charging is impossible early, and the secondary battery 704 is likely to be in a depleted state. When the communication quality (LQI value) of the sensor device 2 operating as a relay node is low, the frequency of cutting off communication between the relay node and another node is high, and it is difficult to stably collect and transmit information from each node (sensor device 2) to the server apparatus 4.

Thus, in step S15, the control unit 401 of the server device 4 first extracts, as relay node candidates, neighboring nodes whose communication quality and battery remaining level are equal to or higher than predetermined reference values, for example, from among the plurality of neighboring nodes. When a plurality of adjacent nodes are extracted as relay node candidates, the control unit 401 sets the order of the extracted temperature differences (Tn-T) between the plurality of adjacent nodes as relay node candidates.

After the process of step S15 is completed, the control unit 401 of the server device 4 determines whether or not there is a candidate for a substitute relay node (step S16). If there is a candidate (step S16; yes), the control unit 401 changes the link of the topology information based on the candidate order of the relay nodes and the topology information, and notifies the node having changed the link of a new link destination (step S17). In step S17, the control unit 401 changes the link so that the node (sensor device 2) located downstream of the request node does not stand alone. In step S17, the control unit 401 notifies the requesting node that the change from the relay node to the non-relay node is possible. In step S17, the control unit 401 causes the storage unit 402 to store the topology information after the link is changed as the current topology information.

On the other hand, if there is no candidate for the alternative relay node (step S16; no), the control unit 401 notifies the requesting node that there is no candidate for the alternative relay node, in other words, that it is not possible to change from the relay node to the non-relay node (step S18).

When the processing in step S17 or S18 is finished, the control unit 401 of the server apparatus 4 ends the link change processing.

As described above, in the sensor network system 1 according to the present embodiment, the sensor device 2 in the state in which the secondary battery 704 is depleted and in the state in which charging is disabled shifts to the operation mode in which the power consumption is small. In addition, when the secondary battery 704 is in a depleted state and the sensor device 2 in an inactive-charge state is a relay node, a relay node to be replaced is selected and the connection destination (link) of the node on the downstream side is changed. Therefore, it is possible to prevent the operation of the relay node (sensor device 2) from being stopped due to the shortage of electric power, and information including the measurement result of the sensor device 2 operating downstream of the relay node from being transmitted to the server apparatus 4. Thus, according to the present embodiment, it is possible to realize efficient operation of a sensor network system in which sensor devices driven by a secondary battery are distributed.

As described above, the sensor network system 1 according to the present embodiment is suitable for monitoring in cold districts. In the sensor network system 1 installed in a cold area, a continuous operation of the sensor device 2 in a below-freezing environment is required. In the sensor device 2 that is operated in a low-temperature environment such as below freezing point, it is difficult to use a lithium ion battery as a storage battery. Many lithium ion batteries have discharge characteristics of-20 ℃ to 60 ℃ and charge characteristics of about 0 ℃ to 45 ℃. Also, regardless of the heat insulating structure applied, the measuring portion (sensor device) is exposed in terms of the properties of the sensor apparatus 2. Therefore, the battery part is also affected by the outside air temperature due to heat conduction through the exposed measuring portion, and the battery (secondary battery) is in a state of charge inertness in the sub-freezing environment. Therefore, when the sensor network system 1 is installed in a cold district, it is preferable to bury the information processing device 7 and the sensor group 9 of the sensor facility 2 underground.

In a cold region, when the soil reaches winter, the soil 1002 near the ground 1001 shown in fig. 7 becomes frozen soil. The depth of the frozen soil 1002 is, for example, about 10 to 20 cm. Although the temperature of the underground is higher than that of the air (above ground) in a low-temperature environment, the temperature of the frozen soil (soil 1002) is lower than that of the unfrozen soil 1003 at the lower part. Therefore, by burying the information processing device 7 and the sensor group 9 in the soil 1003 deeper than frozen soil, heat insulation processing can be expected, and the secondary battery 704 can be suppressed from falling into a state of charge inertness. At this time, as shown in fig. 7, the environment power generating element 8 and the communication antenna 705 in the sensor device 2 are installed on the column 11 erected on the ground 1001, trees, or the like.

In addition, when the information processing device 7 and the sensor group 9 of the sensor facility 2 are buried in the soil, the outside air temperature is not measured by the sensor group 9 (temperature sensor of the sensor device), and therefore the information processing device 7 is limited to grasp only the trend of the change in the outside air temperature. In addition, even in simple temperature measurement of the temperature sensors provided in the

sensor devices

901 and 902 mounted in the sensor apparatus 2, sufficient trend determination can be performed.

Fig. 8 is a graph showing a change in the ambient temperature of the sensor device over a certain period. Fig. 9 is a graph illustrating a relationship between an outside air temperature and a voltage of the secondary battery during a certain period.

In the upper part of fig. 8, temperature data 211 of about three days detected by the sensor device 2 (exposed sensor device) installed on the ground and temperature data 212 detected by the sensor device buried in the earth at the same time are shown in an overlapping manner. The lower part of fig. 8 shows a temperature change 12 of the outside air temperature in a region where the sensor device 2 is installed, the temperature sensor of the sensor device 2, and another thermometer. Fig. 9 shows the change in voltage of the secondary battery during the time period D4 to D5 shown in fig. 8.

As shown in fig. 8, the temperature in the temperature data 211 detected by the exposed sensor device shows a temperature higher than the actual outside air temperature due to heat generation by the operation of the sensor device. In addition, the detection temperature also decreases as the outside air temperature decreases. Here, when the threshold temperature T is set to 1 ℃, the detected temperature of the exposed sensor device is lower than the threshold temperature at time D1, and the secondary battery 704 falls into a state of charge inactivity (a state in which charging is not possible). The temperature at each point in the temperature data 212 of the sensor devices buried in the earth is higher than the temperature in the temperature data 211 of the exposed sensor devices, but decreases with a decrease in the outside air temperature. Further, after time D1, and at time D2 at which the outside air temperature is lower than time D1, the detected temperature of the sensor device in the earth is less than the threshold temperature T (═ 1 ℃), and the secondary battery 704 falls into a charge inactive state.

In this way, when simple temperature measurement is performed by the temperature sensors provided in the

sensor devices

901 and 902 attached to the sensor device 2, the trend of temperature change can be determined even if the ambient temperature of the sensor device 2 differs from the outside air temperature 12 measured by another thermometer.

If the state below the freezing point continues and the secondary battery 704 falls into the charge inactive state, only discharge occurs in the secondary battery 704 even if power generation is performed in the environment power generation element 8. Therefore, in the sensor device that detects the temperature data 211, as shown in fig. 9, after the time D1 at which the charge inert state is fallen, the voltage 311 of the secondary battery 704 gradually decreases. When the secondary battery 704 of another sensor device falls into the charge disabled state during the period from time D4 to time D5 shown in fig. 9, the

voltages

314 and 315 of the secondary battery 704 gradually decrease after the fall into the charge disabled state. On the other hand, in the in-soil sensor device that detects the temperature data 212, the secondary battery 704 falls into the charge inactive state at time D2 after the period from time D4 to time D5 shown in fig. 9. That is, in the sensor device that detects the temperature data 212, when power generation is performed in the environment power generation element 8 during the period from time D4 to time D5, the secondary battery 704 is charged. Therefore, in the sensor device that detects the temperature data 212, the voltage 312 of the secondary battery 704 during the time period D4 to D5 changes at a substantially constant value. However, the temperature data 212 is less than the threshold temperature T at a time D2 after the period of times D4-D5. Therefore, in the sensor device that detects the temperature data 212, the secondary battery 704 falls into the charge inactive state after the time D2. Thus, the sensor device that has detected the temperature data 212 performs the processing from step S402 and subsequent steps in fig. 5 in the scheduling processing that is performed first after time D2.

However, the secondary battery that has fallen into the charge-inactive state has already started the discharge state. Therefore, in the sensor device 2, the correction is applied to the threshold temperature T as described above (step S404). Since the change amount Δ T as the actual measurement value is-1 ℃, the sensor device 2 corrects the threshold temperature T to T ═ 1- (-1) in step S404. Therefore, in the determination of step S401 in the next scheduling process performed by the sensor device 2, the threshold temperature T becomes 2 ℃.

If the scheduling process as shown in fig. 5 is not performed in the case of the discharge state (i.e., the state in which the secondary battery is in the inactive state and the remaining battery capacity is reduced due to discharge), the sensor device 2 is brought into the shutdown state early. When the sensor device 2 is in the shutdown state, not only recovery of the secondary battery becomes more difficult, but also recovery from the state in which shutdown is started requires higher energy, and the secondary battery is often in a depleted state.

In contrast, the sensor device 2 according to the present embodiment changes the operation mode to reduce the amount of power consumption when the ambient temperature decreases and the secondary battery falls into a discharged state. In the case where the sensor device 2 is a relay node, the sensor device 2 moves from the relay node to a non-relay node, suppressing the amount of power consumption. In addition, when the sensor device 2 is a non-relay node, the sensor device 2 shifts to the sleep mode to further reduce the amount of power consumption. That is, the sensor device 2 according to the present embodiment shifts to the non-relay mode or the sleep mode before the sensor device 2 enters the shutdown state, thereby reducing the amount of power consumption and suppressing the sensor device 2 from entering the shutdown state. Therefore, the sensor device 2 according to the present embodiment can suppress the occurrence of a situation in which recovery of the secondary battery becomes difficult due to the fall into the stopped state.

Fig. 10 is a diagram showing an example of links and adjacent nodes of a sensor network.

Fig. 10 (a) shows nine nodes in total from the first node 201 to the ninth node 209 and their connection relationships as an example of the connection relationship of the node (sensor device) before the link is changed. In fig. 10 (a), a first node 201 denoted by R0, a third node 203 denoted by R1, and a sixth node 206 denoted by R2 each represent a sensor device that operates as a relay node. In fig. 10 (a), the second node 202 described as E1 and the fourth node 204 described as E4 each represent a sensor device that is directly connected to the first node 201 and operates as a non-relay node. In fig. 10 (a), the fifth node 205 described as E2 and the seventh node 207 described as E3 each represent a sensor device that is directly connected to the third node 203 and operates as a non-relay node. In fig. 10 (a), the eighth node 208 described as E5 and the ninth node 209 described as E6 each represent a sensor device that is directly connected to the sixth node 206 and operates as a non-relay node.

In fig. 10 (a), the sensor device 2 indicated by the third node 203 transmits its own measurement result and the like, and in addition, the measurement results and the like of the sensor device 2 indicated by the respective nodes of the fifth to ninth nodes 205 to 209 downstream are also transmitted to the sensor device indicated by the first node 201. Therefore, if the third node 203 (sensor device 2) is down, five nodes of the fifth to ninth nodes 205 to 209 located downstream of the third node 203 are independent from the sensor network. That is, when the third node 203 (sensor device 2) is stopped, even if each of the fifth to ninth nodes 205 to 209 located downstream operates, the measurement result and the like of each node cannot be transmitted to the concentrator 5. In order to prevent this, the sensor device 2 of the present embodiment changes its operation mode to a mode with a small amount of power consumption before the device is brought into the shutdown state, as described above. At this time, the server apparatus 4 starts the link change processing of fig. 6, and first selects (identifies) a node adjacent to the third node 203. The adjacent node is a child node in a direct connection relationship with the third node 203, and a node having the same connection distance from the parent node of the third node 203 as the connection distance of the third node 203 and the child node. Therefore, the neighboring nodes of the third node 203 in the sensor network of fig. 10 (a) become five nodes of the fifth node 205, the sixth node 206, the seventh node 207, the second node 202, and the fourth node 204.

When the adjacent node is selected, the server apparatus 4 acquires the communication quality (LQI value), the remaining battery level, and the temperature difference (Tn-T) of each adjacent node (steps S12 to S14).

In step S12, the server apparatus 4 acquires LQI values Q1 to Q7 of the neighboring nodes, for example, as shown in fig. 10 (b). In fig. 10 (b), the LQI values Q1 to Q7 of the respective adjacent nodes are represented by the thickness of the arrowed line, and the line is made thicker as the LQI value is higher. That is, in fig. 10 (b), the LQI values Q1 and Q2 of the second node 202 and the fifth node 205 are higher than the LQI values Q4 to Q7 of the node 207 of E3 and the node 204 of E4.

The remaining battery level and the temperature difference of each adjacent node obtained in steps S13 and S14 are the results shown in fig. 11. Fig. 11 is a diagram showing an example of the battery residual amounts and the temperature differences of the adjacent nodes.

Table 13 shown in fig. 11 shows the degree of surplus of the secondary battery along with the remaining battery capacity and the temperature difference (Tn-T) at each adjacent node. To the extent of the margin of the secondary battery in table 13, a double circle seal (circleincircle) indicates a very margin, and a circle (o) indicates a margin. Note that, to the extent of the margin of the secondary battery in table 13, the x print indicates that there is no margin.

The secondary battery most abundant in table 13 is the sensor device corresponding to the node of E4 (fourth node 204). Although the sensor device corresponding to the node of E1 (the second node 202) and the sensor device corresponding to the node of E3 (the seventh node 207) are not as good as the sensor devices corresponding to the nodes of E4, the secondary battery is still redundant. In contrast, the sensor device corresponding to the node of E2 (the fifth node 205) has a small remaining battery level and a small temperature difference, so that there is no surplus of the secondary battery. Therefore, it is expected that the sensor device corresponding to the node of E2 (fifth node 205) falls into a depleted state and falls into a charge inactive state earlier than the sensor devices corresponding to the other adjacent nodes. The sensor device corresponding to the node of R2 (sixth node 206) already operates as a relay node although the secondary battery is redundant.

Therefore, the server apparatus 4 changes the topology (link) shown in fig. 10 (a) to the topology (link) shown in fig. 12, for example, based on the table 13 in fig. 11 and the communication quality of each adjacent node. Fig. 12 is a diagram showing a modification of the link.

The server apparatus 4 first cancels the link between the third node 203, which has requested the change of the link, and the child nodes (the fifth node 205, the sixth node 206, and the seventh node 207) of the third node 203, and changes the third node 203 to a non-relay node (node of E).

Then, the server apparatus 4 changes the node of E4 (fourth node 204) having the most surplus of the remaining battery level and the temperature difference to the relay node (node of R3), and connects as many nodes as possible downstream of the node 204 of R3. However, as shown in fig. 10 (b), the LQI value between the node of R3 (fourth node 204) and the node of E2 (fifth node 205) is low. Further, if the number of nodes directly connected to the node of R3 (fourth node 204) is large, the amount of power consumption of the sensor device 2 corresponding to the fourth node 204 increases, and the secondary battery of the sensor device may be exhausted early. It is considered that a sensor device having a margin in temperature difference, such as the sensor device corresponding to the fourth node 204, can charge the secondary battery even when the ambient temperature further decreases and the secondary battery of the sensor device corresponding to the other adjacent node falls into a state of charge inertia, for example. Therefore, in the case where a state where the ambient temperature is low continues for a long period of time as in winter, it is preferable to suppress a decrease in the remaining battery capacity of the sensor device corresponding to a node having a margin in temperature difference, such as the fourth node 204, as much as possible and to extend the operation period of the sensor device. Therefore, the server apparatus 4 changes the seventh node 207, which has a margin in the remaining battery level and the temperature difference and is higher than the LQI values of the fourth node 204 and the sixth node 206, to a relay node (node of R4), and connects the fourth node 204 and the sixth node 206 via the seventh node 207.

Then, the server apparatus 4 changes the second node 202 having a large LQI value with the fifth node 205 and having a surplus secondary battery to the relay node (node of R5), and sets a link with the fifth node 205. Thus, even after the link is changed, the sensor device corresponding to the node of E2 (fifth node 205) having no margin in the remaining battery level and the temperature difference can be operated as a non-relay node with a small amount of power consumption. In addition, since the fifth node 205 is connected to the second node 202 having a high LQI value, it is not easy to cut off the communication between the node 205 of E5 and the second node 202. Therefore, the power consumption of the secondary battery due to the communication at the node of E2 can be suppressed.

Fig. 12 is only an example of the modified link. The communication quality, the remaining battery level, and the priority of the temperature difference of each adjacent node when the topology (link) is changed, the conditions that are candidates for the relay node, and the like can be appropriately changed.

The sensor device 2 in the sensor network system 1 according to the present embodiment is configured to shift to the sleep mode to suppress the power consumption and to suppress the shutdown state. However, the sensor devices in sleep mode consume power, albeit rarely. Therefore, for example, if the day below freezing continues for a long period of time, the remaining amount of the secondary battery decreases, and the shutdown state ends. The sensor device 2 in the shutdown state restarts its operation even in a low-temperature environment when the secondary battery is in a charge-active state (i.e., a state in which it can be charged) and the remaining battery capacity increases. However, when power is supplied to all the devices (electronic circuit components) in the sensor device 2 when the sensor device 2 restarts operation, the sensor device 2 is in a state in which sufficient power cannot be immediately supplied due to inrush current, and returns to a state in which the secondary battery cannot be charged.

The upper part of fig. 13 shows the temporal change 14 of the power supply voltage in the case where the scheduling process of fig. 5 is not performed in the sensor device 2. Fig. 13 shows, in the lower stage, a temporal change 15 in the power supply voltage in the case where the scheduling process of fig. 5 is performed in the sensor device 2.

In addition, time changes 14 and 15 shown in fig. 13 are time changes of the voltage output by the power supply management unit 703 when the secondary battery of the sensor device 2 is charged in a low-temperature environment reproduced in a laboratory. More specifically, it shows the temporal change of the output voltage of the power supply management unit 703 when the same amount of electric power as the amount of electric power generated by the environment power generation element (solar panel) is supplied to the secondary battery cooled to around 0 ℃.

When the secondary battery is charged and the power supply voltage exceeds the lowest electromotive force (2.2V in fig. 13) that can drive the information processing device 7 and the sensor group 9 of the sensor device 2, the information processing device 7 of the sensor device 2 starts operating. However, even when the scheduling process is not performed, power is supplied to the communication unit of the information processing device 7 that performs wireless communication with another sensor device or the aggregation device 5. The amount of power consumed by the information processing apparatus 7 due to wireless communication is relatively large among the amounts of power consumed by the various processes performed by the information processing apparatus 7. Thus, when the scheduling process is not performed, the power supply voltage of the sensor device 2 that has restarted operation drops at a burst by the inrush current at the startup time 14A and becomes lower than the lowest electromotive force that can be driven, as in the time change 14 shown in the upper stage of fig. 13. Therefore, when the scheduling process is not performed, the sensor device 2 that has restarted to operate returns to a state where sufficient power cannot be supplied from the secondary battery in a short time.

When the external power continues to be supplied to the secondary battery after the sensor device 2 returns to the shutdown state, the power supply voltage becomes equal to or higher than the lowest electromotive force again as shown in the upper stage of fig. 13, and the sensor device resumes operation. However, at the time of restart of the second operation, the power supply voltage drops at once due to the inrush current of 14A at the time of startup, and the sensor device 2 returns to a state in which sufficient electric power cannot be supplied from the secondary battery in a short time.

Thereafter, even if the external power supply voltage continues to be supplied to the secondary battery, the external power supply voltage is not equal to or higher than the minimum electromotive force, and the sensor device 2 continues to be in a state where the secondary battery cannot be charged. This is an overdischarge state in a low-temperature environment, and is similar to a phenomenon in which a time required for charging or discharging a secondary battery is long in a mobile phone or the like in which charging and discharging of the secondary battery are repeated, or a phenomenon in which the mobile phone or the like is immediately stopped or is not started even when the mobile phone or the like is started in winter.

In contrast, the sensor device 2 according to the present embodiment sets a timer when the device shifts to the sleep mode by the scheduling process, and resumes operation when a predetermined period of time has elapsed since the device shifted to the sleep mode. When a certain sensor device shifts to the sleep mode, in the system according to the present embodiment, either the concentrator 5 that is continuously operating or the sensor device 2 waits for the sensor device 2 in the sleep mode to resume its operation. The sensor device 2 that has recovered from the sleep mode and resumed the operation transmits the sensing data and the state information of the secondary battery to the cluster apparatus 5 or the sensor device 2 that has performed the processing of steps S1 to S3 shown in fig. 4. If the remaining amount of the secondary battery in the sensor device 2 that has restarted the operation is insufficient, the process of step S4 next moves to the sleep mode again. In the sensor device in the sleep mode, the communication unit (wireless module) of the information processing device 7 does not operate, and therefore, although the amount of power supplied to the secondary battery is small, the power supply can be repeated during this period. That is, the sensor device 2 according to the present embodiment can gradually restore the power state by repeating the restoration from the sleep mode and the transition to the sleep mode in the scheduling process.

As described above, the node (sensor device 2) which has moved to the sleep mode is restarted after being in sleep for a certain period. This is to observe the state of passage of the secondary battery, and for example, in the case of using a solar panel as the environmental power generation element, the sleep period is linked with the sunshine duration. In this case, since the inrush current that rises according to the environment generally occurs during the daytime, it is preferable that the sleep period is a period from sunset time. This is to maximally absorb electric power by photovoltaic power generation.

In addition to the case where the node waiting to be captured is further discharged by the inrush current, if the state is such that the sleep mode can be immediately shifted even if the inrush current occurs, the voltage drop due to the inrush current can be suppressed as in the time change 15 shown in the lower stage of fig. 13. As described above, the sensor device 2 according to the present embodiment determines whether or not the secondary battery 704 is in the depletion state, in consideration of the voltage drop state before the state of discharge, without simply comparing the remaining battery level included in the state information of the secondary battery 704 with the threshold value. Therefore, when the sensor device 2 in the overdischarge state resumes its operation, it is determined that the battery is in the depleted state in the determination of step S202 in fig. 5. In the low-temperature environment, it is determined in step S203 that charging is not being performed. And, the sensor device 2 resumes the operation as a non-relay node. Thus, when the sensor device 2 in the overdischarge state resumes operation, the operation is switched to the sleep mode in a short time. Therefore, in the sensor device 2 of the present embodiment, as shown by the time change 15 shown in the lower stage of fig. 13, the minute potential drop 15A caused by the repeated inrush current gradually converges to the steady potential (3V). When the power supply voltage for the scheduling process in the sensor device 2 has converged to the steady potential in this way, the determination of step S203 in the subsequent scheduling process is that charging is underway (step S203; yes). This enables the sensor device 2 to resume its operation without shifting to the sleep mode.

The flowchart of fig. 4 is merely an example of the processing performed by the sensor device 2. The processing performed by the sensor device 2 is not limited to the processing shown in fig. 4, and can be changed as appropriate. Likewise, the flowchart of fig. 5 is just one example of the scheduling process performed by the sensor device 2. The scheduling process is not limited to the contents shown in fig. 5, and can be changed as appropriate. The flowchart of fig. 6 is merely an example of the link change process performed by the server apparatus 4. The link changing process is not limited to the contents shown in fig. 6, and can be changed as appropriate.

Fig. 2 is merely an example of the configuration of the sensor device 2. The configuration of the sensor device 2 can be changed as appropriate, and for example, one sensor device included in one sensor device 2 may be provided. The sensor device 2 may include a sensor device that measures a physical quantity other than temperature, and a sensor device that functions as a temperature sensor. The environmental power generation element 8 is not limited to the solar panel described above, and may be, for example, a wind turbine generator.

In the above-described embodiment, the sensor device 2 is operated in a low-temperature environment, but the sensor device 2 is not limited to this, and may be applied to an environment in which the secondary battery falls into an inactive state of charge due to a high temperature, or the like.

The information processing device 7 and the server device 4 of the sensor device 2 can be realized by a computer and a program that causes the computer to execute, respectively.

Fig. 14 is a diagram showing a hardware configuration of the sensor device.

As shown in fig. 14, the sensor device 2 includes a computer 14, a power module 15, an environment power generation element 8, a secondary battery 704, and a sensor group 9. The computer 14 includes a Central Processing Unit (CPU)1401, a memory 1402, an input-output interface 1403, a wireless communication device 1404, and a timer 1405. These elements 1401 to 1405 of the computer 14 are connected to each other by a bus 1410, and data can be transferred between the elements.

The CPU1401 controls the overall operation of the computer 14 by executing various programs including an operating system. The CPU1401 also performs various processes including, for example, scheduling processing shown in fig. 5.

The memory 1402 includes a Read Only Memory (ROM) and a Random Access Memory (RAM), which are not shown. A ROM of the memory 1402 stores predetermined basic control programs and the like that are read out by the CPU1401 at the time of starting the computer 14, for example. The RAM of the memory 1402 is used as a work memory area as needed when the CPU1401 executes various programs. The RAM of the memory 1402 can be used for storing, for example, the temperature threshold T, information of the sensor device 2 that performs communication, measurement results of the sensor device, state information of the secondary battery, and the like.

The input/output interface 1403 is a means for connecting the computer 14 and the sensor device. The input/output interface 1403 includes a connector of the Universal Serial Bus (USB) standard, for example.

The wireless communication means 1404 is a means for performing wireless communication between the computer 14 and the computers of the other sensor apparatuses 2 or the aggregation means 5. Wireless communication apparatus 1404 outputs a signal modulated in accordance with a predetermined wireless communication standard to antenna 705, and demodulates a signal received by antenna 705.

The timer 1405 of the computer 14 is used for setting the timing for acquiring the measurement result or the state information of the secondary battery from the sensor device, the timing for transmitting the measurement result or the state information, and the like.

In addition, the power module 15 includes a Power Management Unit (PMU)1501 and a timer 1502. The PMU1501 acquires state information of the secondary battery 704 and reports it to the computer 14. The timer 1502 of the power module 15 is used to set timing for returning from the sleep mode when the power module shifts to the sleep mode.

The computer 14 periodically performs the process of fig. 5 together with the process of acquiring the measurement result of the sensor device. At this time, the CPU1401 and the memory 1402 function (operate) as the control unit 701 and the storage unit 702, respectively, in the information processing device 7 of fig. 2. The power module 15 also functions (operates) as the power management unit 703 in the information processing device 7 in fig. 2.

The computer 14 may include, for example, an input device, an output device, and the like, in addition to the elements 1401 to 1405 shown in fig. 14. The computer 14 may include a media drive device that can access a portable recording medium such as a Secure Digital (SD) standard memory card, for example.

As shown in fig. 15, the computer 16 that operates as the server apparatus 4 includes a CPU1601, a main storage device 1602, an auxiliary storage device 1603, an input device 1604, an output device 1605, a communication control device 1606, an input/output interface 1607, and a media drive device 1608. These elements 1601 to 1608 in the computer 16 are connected to each other via a bus 1610, and data can be transferred between the elements.

The CPU1601 controls the overall operation of the computer 16 by executing various programs including an operating system. Further, the CPU1601 performs, for example, a link change process shown in fig. 6.

The main storage device 1602 includes a ROM and a RAM, which are not shown. A ROM of the main storage device 1602 stores a predetermined basic control program and the like that are read by the CPU1601 at the time of startup of the computer 16, for example. The RAM of the main storage device 1602 is used as a work memory area as necessary when the CPU1601 executes various programs. The RAM of the main storage device 1602 can be used for storage of topology information of a sensor network, storage of communication quality of an adjacent node, a remaining battery level, and a temperature difference, for example.

The auxiliary storage device 1603 is, for example, a nonvolatile memory (including a fixed disk (SSD)) such as a flash memory, and a Hard Disk Drive (HDD). Various programs and various data executed by the processor 1601 can be stored in the auxiliary storage device 1603. The auxiliary storage device 1603 can be used for storage of a control program or the like including the link change process of fig. 6, for example. The auxiliary storage device 1603 can be used for, for example, storing topology information of a sensor network, storing measurement results of each sensor device 2, and storing communication quality, remaining battery level, and temperature difference of an adjacent node.

The input device 1604 is, for example, a keyboard device, a touch panel device, or the like. When an operator (user) of the computer 16 performs a predetermined operation on the input device 1604, the input device 1604 transmits input information corresponding to the operation content to the processor 1601.

The output device 1605 includes a display device such as a liquid crystal display device. The output device 1605 can be used to display the operating state of the computer 16, the measurement results collected from the sensor devices 2, and the like, for example.

The communication control device 1606 is a device that connects the computer 16 to a communication network and controls various communications between the computer 16 and other electronic devices via the communication network. The communication control device 1606 can be used for communication between the computer 16 and the aggregation device 5, for example.

The input/output interface 1607 connects the computer 16 with other electronic devices. The input/output interface 1607 is provided with a connector of the USB standard, for example.

The media drive device 1608 reads data from the portable storage medium 17 and writes data stored in the auxiliary storage device 1603 to the portable storage medium 17. The media drive device 1608 may use, for example, a reader/writer for a memory card corresponding to one or more standards. When a memory card reader/writer is used as the media drive device 1608, a standard compatible with the memory card reader/writer, for example, a memory card (flash memory) of SD standard, or the like, can be used as the portable storage medium 17. As the portable recording medium 17, for example, a flash memory having a connector of the USB standard can be used. The portable recording medium 17 can be used for storing topology information of the sensor network, storing measurement results collected from the sensor devices 2, storing communication quality of adjacent nodes, remaining battery level, and temperature difference.

When an optical disk drive that can be used as the media drive device 1608 is mounted on the computer 16, various optical disks that can be recognized by the optical disk drive can be used as the portable recording medium 17. Examples of the optical disk that can be used as the portable recording medium 17 include a Compact Disc (CD), a Digital Versatile Disc (DVD), and a blu-ray disc (blue-ray is a registered trademark).

The CPU1601 of the computer 16 reads out a control program including the link change processing of fig. 7 from the auxiliary storage device 1603 or the like and executes the control program. At this time, the CPU1601 functions (operates) as the control unit 401 in the server apparatus 4 in fig. 3. The auxiliary storage device 1603, the RAM of the main storage device 1602, and the portable recording medium 17 function as the storage unit 402 of the server device 4.

Note that the computer 16 that operates as the server device 4 does not need to include all the elements 1601 to 1608 shown in fig. 15, and some elements may be omitted depending on the application and conditions. For example, the computer 16 may omit the media drive device 1608.

Description of the reference numerals

1 … sensor network system, 2 … sensor device, 3 … sensor network, 4 … server device, 5 … intensive device, 6 … communication network, 7 … information processing device, 8 … environment power generating element, 9 … sensor group, 11 … column, 14, 16 … computer, 15 … power module, 17 … portable recording medium, 201 to 209 nodes, 401, 701, … controller, 402, 702 … storage, 703 … power management, 704 … secondary battery, 901, 902 … sensor device, 901T, 902T … temperature sensor, 1001 … ground, 1401, 1601 … CPU, 1402 … memory, 1403, 1607 … input/output interface 1404, … wireless communication device, 1405 … timer, 1602 … main storage device, 1603 4 auxiliary storage device, 1604 … input device, 1605 output device, … communication control device, … driving device.

Claims

1. A server device for controlling the operation of a plurality of sensor devices in a sensor network including an aggregation device and the sensor devices, wherein the aggregation device aggregates data by directly receiving the data transmitted from each of the sensor devices or receiving the data relayed via another sensor device,

the sensor device has at least a first mode in which acquisition of the transmitted data and relay of the data are performed, and a second mode in which the acquisition is performed without the relay, as operation modes,

the server device includes:

a storage unit that stores topology information that is information of a transmission path of the data from each of the sensor devices in the sensor network to the aggregation apparatus;

and a control unit that acquires, from each of the sensor devices, an output value of a temperature sensor provided in the sensor device and status information of a secondary battery that drives each of the sensor devices, together with sensing data of the sensor devices included in each of the sensor devices, and that, when a request for changing the transmission path transmitted by any one of the sensor devices is received, acquires communication quality of a sensor device adjacent to the sensor device that has transmitted the request transmission source of the change request, based on the topology information, and controls the operation mode of the sensor device that has transmitted the request transmission source, based on the status information of the secondary battery in the adjacent sensor device, the output value of the temperature sensor, and the communication quality.

2. The server apparatus according to claim 1,

when the control unit performs the control of switching the operation mode of the sensor device requesting the transmission source from the first mode to the second mode, the control unit changes the direct transmission destination of the data of the relay target received when the sensor device requesting the transmission source performs the relay, among the sensor devices requesting the transmission source, from the sensor device requesting the transmission source to the adjacent sensor device, to the direct transmission destination of the data of the relay target.

3. The server apparatus according to claim 2,

when the control is performed to switch the operation mode of the sensor device of the request transmission source from the first mode to the second mode, and when there are a plurality of sensor devices adjacent to the sensor device of the request transmission source, the control unit selects a candidate from the plurality of adjacent sensor devices based on the output value of the temperature sensor, the state information of the secondary battery, and the communication quality acquired from each of the plurality of adjacent sensor devices, and changes the direct transmission destination to any one of the candidates.

4. A control method for controlling an operation of a plurality of sensor devices in a sensor network including an aggregation device and the sensor devices, wherein the aggregation device aggregates data by directly receiving the data transmitted from each of the sensor devices or receiving the data relayed via another sensor device,

a computer acquires topology information which is information of a transmission path of the data from each of the sensor devices in the sensor network to the aggregation apparatus,

the computer acquires, from each of the sensor devices, state information of a secondary battery that drives each of the sensor devices and an output value of a temperature sensor provided in a sensor device included in each of the sensor devices, acquires, when a request to change the transmission path transmitted from any one of the sensor devices is received, communication quality of a sensor device adjacent to the sensor device that has transmitted the request transmission source of the request based on the topology information, and controls the operation mode of the sensor device of the request transmission source based on the state information of the secondary battery, the output value of the temperature sensor, and the communication quality in the adjacent sensor device.

5. A computer-readable storage medium storing a control program,

the control program causes a computer to execute control of operations of the sensor devices in a sensor network including a plurality of sensor devices and an aggregation device that aggregates data by directly receiving the data transmitted from each of the sensor devices or receiving the data relayed via another sensor device,

causing a computer to perform:

acquiring topology information, which is information of transmission paths of the data from each of the sensor devices in the sensor network to the aggregation apparatus,

acquiring, from each of the sensor devices, state information of a secondary battery that drives each of the sensor devices and an output value of a temperature sensor provided in a sensor device included in each of the sensor devices; and

when a request for changing the transmission path transmitted from any one of the sensor devices is received, communication quality of a sensor device adjacent to the sensor device that has transmitted the request transmission source of the change request is acquired based on the topology information, and the operation mode of the sensor device of the request transmission source is controlled based on the state information of the secondary battery in the adjacent sensor device, the output value of the temperature sensor, and the communication quality.