JP2013179468A - Radio management system and transmission management method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save power of a system for acquiring and managing data from radio terminal devices installed in scattered fields and the like because the system requires power saving due to a problem of laying power supply facilities.SOLUTION: According to the invention, a radio terminal device includes: a data acquisition unit; a radio communication unit; a control unit for transmitting acquired data, or data and command destined to another device received from yet another device, and for controlling operation of the own device according to a command destined to the own device; and a clocking unit for waking up the control unit at pre-set clock time. The control unit transmits a response signal to a radio management device after execution and completion of a command destined to the own device if the control unit is in a wakeup state, and moves to a sleep state at least except for the clocking unit if it has received a sleep command destined to the own device. A radio management device includes: a master station radio communication unit, and a master station control unit for transmitting a command to the radio terminal device, and automatically transmits a next command if it has received a response signal from the radio terminal device.

Description

  The present invention relates to a radio management system and a transmission management method for managing data received from a plurality of radio terminal apparatuses arranged in a scattered manner by a radio management apparatus.

  IT (information technology) is used in various industries, but the field of agriculture is highly expected for the future. In particular, the goal is not only to improve production efficiency, but also to share agricultural know-how inherited from the parent generation to the child generation. Demonstration experiments on IT from agriculture to production are being conducted in various places, but because the target farm is incorporated as a corporation, etc., multiple farms are consolidated. There are many cases where farmland is scattered at different locations.

  On the other hand, as an example of IT in agriculture, an image sensor that acquires data such as temperature and humidity with a sensor, or acquires image data such as a normal image or a color temperature image in order to see the growth state of a crop or the state of farmland It is considered to install (camera).

  However, in order to acquire and manage data from farmland scattered across buildings and roads, it is necessary to transmit and receive data wirelessly. Therefore, a method of transmitting / receiving data using a mobile phone or a wireless LAN can be considered. For example, a technique for transmitting data by time division multiplexing in a distributed wireless network including a plurality of wireless devices is disclosed (see, for example, Patent Document 1).

Special table 2002-538640 gazette

  However, when a mobile phone or a wireless LAN is used, it is difficult to operate the system on a long-term basis on a privately managed farm because of increased equipment costs and running costs. In particular, farms and the like are outdoors, so it is difficult to secure a power source, and there is a problem that a new power cable is laid and large-scale power source facilities such as solar cells and batteries are required. For example, when acquiring image data captured by each wireless terminal device from a plurality of wireless terminal devices, the amount of image data after shooting varies greatly because the image compression rate varies depending on the weather. For this reason, when acquiring image data from a plurality of wireless terminal devices at a preset time interval, the time interval must be set to be equal to or longer than the time for transmitting the maximum image data amount. It took a huge amount of time to acquire image data from the device, which was a big problem for a wireless terminal device operating on a battery.

  In view of the above problems, an object of the present invention is to provide a radio management system and transmission that can be installed easily, do not require power cable laying or large-scale power supply facilities, and can perform stable system operation over a long period of time with batteries. It is to provide a management method.

  The wireless management system according to the present invention is a wireless management system including a plurality of wireless terminal devices arranged in a scattered manner and a wireless management device that manages the plurality of wireless terminal devices, wherein the plurality of wireless terminal devices are A data acquisition unit that acquires data, a wireless communication unit that transmits and receives data and commands to and from the adjacent wireless terminal device or the wireless management device, and data acquired from the data acquisition unit or the wireless from the other device Transmits data and commands addressed to other devices received by the communication unit from the wireless communication unit, measures the time of the own device according to the command addressed to the own device, measures the time, and sets the time in advance A timing unit that wakes up the control unit that is in a sleep state when the scheduled time is reached, and the control unit is in a state of being woken up by the timing unit. A response signal is transmitted to the wireless management device after completion of execution of the command addressed to the own device received from the wireless management device, and at least the sleep command addressed to the own device transmitted by the wireless management device is received. The wireless management device shifts to a sleep state except for a time measuring unit, and the wireless management device transmits and receives data and commands to and from the adjacent wireless terminal device among the plurality of wireless terminal devices; And a master station control unit that automatically transmits a next command when the response signal is received from the plurality of wireless terminal devices.

  A transmission management method according to the present invention is a transmission management method used in a wireless management system including a plurality of wireless terminal devices arranged in a scattered manner and a wireless management device that manages the plurality of wireless terminal devices. The plurality of wireless terminal devices transfer the data acquired by the own device or the data and commands addressed to the other device received from the other device to the other device and control the operation of the own device according to the command addressed to the own device. When the sleep command addressed to itself is transmitted from the wireless management device, the wireless management device shifts to the sleep state, measures the time, and wakes the own device in the sleep state when the time reaches a preset time. Up, and when the own device is in a wake-up state, a response signal is sent to the radio tube after execution of processing corresponding to the command addressed to the own device received from the radio management device. The wireless management device transmits a command to the plurality of wireless terminal devices, and automatically transmits a next command when the response signal is received from the plurality of wireless terminal devices. And

  The wireless management system and the transmission management method according to the present invention shift to the sleep state when the wireless terminal device is not operating, and wake up at a preset time to perform data transmission, command reception, etc. Low power consumption can be realized, and the battery can be operated for a long time. In particular, the radio management apparatus can efficiently acquire data in a short time even when the amount of data transmitted from the radio terminal apparatus cannot be predicted.

  In the wireless management system and the transmission management method according to the present invention, the transmission of image data is automatically requested to the next wireless terminal device automatically when the reception of the image data is completed. The image data can be acquired in the time, and the power consumption of the wireless terminal device can be reduced.

1 is a diagram illustrating an example of a wireless management system 100. FIG. It is a figure which shows the example of a data format. 2 is a diagram illustrating an example of a slave station 101. FIG. 2 is a diagram illustrating an example of a master station 102. FIG. It is a figure which shows the difference in operation | movement of a time division system and an automatic response system. It is a figure which shows the example of an operation | movement sequence of an automatic response system. It is a figure which shows the operation | movement sequence example of a time division system. It is a figure which shows the difference in the operation time of a time division system and an automatic response system. It is a figure which shows the example of a combination operation | movement of a time division system and an automatic response system. It is a figure which shows the example of an operation | movement sequence of an automatic response system in the case of having the some sub_station | mobile_unit 101. FIG. It is a figure which shows the shortening effect of operating time. It is a figure which shows the example of an operation | movement sequence of an automatic response system in case the sub_station | mobile_unit 101 operate | moves as a relay station.

  Hereinafter, embodiments of a radio management system and a transmission management method according to the present invention will be described in detail. In the present embodiment, for example, radio based on a 400 MHz band specific low-power radio standard (ARIB STD-T67 standard) is used. In this standard, there are 39 channels from ch7 to ch46, and it can be used freely within a predetermined transmission time by confirming that it is not used by carrier sense when transmitting. ing.

[Wireless management system 100]
FIG. 1 is a diagram illustrating a configuration example of the entire radio management system 100. In FIG. 1, the wireless management system 100 is a single master station installed in a place where communication is possible from any of a plurality of slave stations (wireless terminal devices) 101 installed in a plurality of farm fields scattered in remote places. (Radio management device) 102. In the master station 102, the administrator operates the personal computer 103, which is a management terminal, to set each slave station 101 and collect and manage data from each slave station 101. As an example of data acquired from the slave station 101, data such as soil temperature, atmospheric temperature, humidity, pH value, moisture content, and sunshine amount of the field are obtained. In addition, a camera that captures the growth state of the crop and the state of the farmland is installed to acquire image data. In this way, the master station 102 can confirm the state of each field from a remote location.

  In the example of FIG. 1, the master station 102 manages a plurality of slave stations 101 by dividing them into three groups from group A to group C. For example, group A has three devices, slave station 101a1, slave station 101a2, and slave station 101a3, group B has three devices, slave station 101b1, slave station 101b2, and slave station 101b3, and group C has slave station 101c1, Each of the three stations is composed of a station 101c2 and a slave station 101c3. Each of the slave stations 101a3, 101b3, and 101c3 arranged at a position where direct communication with the parent station 102 can be directly operated operates as a relay station and cannot be directly communicated with the parent station 102. The group communicates with the slave station 101a2, the slave station 101b2, and the slave station 101c2. The slave station 101a1, the slave station 101b1, and the slave station 101c1 that are arranged further away and cannot communicate directly with the slave station 101a3, the slave station 101b3, and the slave station 101c3 are the slave station 101a2, the slave station 101b2, and the slave station of each group. The station 101c2 transfers data and commands as a relay station by the bucket relay method.

  In the following description, when the contents common to the nine devices from the slave station 101a1 to the slave station 101c3 are described, the alphabet indicating the group and the number indicating the order in the group are omitted and the slave station 101 is described. When a specific slave station 101 is indicated, it is described by adding (alphabet and numbers) to the code, for example, as a slave station 101a1 or a slave station 101c3.

  In FIG. 1, arrows indicate communication routes determined in advance at the time of system design. Note that arrows indicate upstream communication and downstream communication with the master station 102, and the same communication route is used in a time-sharing manner. Here, the master station 102 is defined as a master station, the terminal slave station 101 that is the communication destination of the master station is defined as a slave station, and the slave station 101 that relays between the master station and the slave station is defined as a relay station. . In the above example of group A, when data is acquired from the slave station 101a1, the slave station 101a1 operates as a slave station, and the slave stations 101a2 and 101a3 operate as relay stations. Similarly, when acquiring data from the slave station 101a2, the slave station 101a2 operates as a slave station and the slave station 101a3 operates as a relay station. When acquiring data from the slave station 101a3, the slave station 101a3 is a slave station. Since it can communicate directly with the master station 102, there is no relay station.

  Next, FIG. 2A shows a data format example for communication between the master station 102 and the slave station 101. In this embodiment, each data is transmitted and received in packets. In FIG. 2A, packet data 201 has a header 202 and a payload 203. The header 202 has a transmission destination address 251, a transmission source address 252, and a relay station address 253 in the relay route. The payload 203 stores the acquisition data and response data of the slave station, the command of the master station, and the like. Note that an error detection code may be added to the packet data 201. For example, in FIG. 1, when a command is transmitted from the master station 102 to the slave station 101a1, the header 202 has a destination address 251 (a1) and a source address 252 (c ( The address of the master station)) and the relay station address 253 are (a3)> (a2). Here, “>” in (a3)> (a2) indicates the transfer order. In the example of FIG. 2, for ease of understanding, the addresses are represented as (a1), (a2), (a3), and (c). Such identifiers are set, and the identifier assigned to the own station is stored in advance in the own station. The relay route is also determined in advance at the time of system design, and the relay route is stored in the master station 102.

  In the example of group A in FIG. 1, the slave station 101 a 3 that has received the packet data 201 transmitted from the master station 102 refers to the relay station address 253 of the header 202 of the packet data 201 and describes the address of its own device. If so, the packet data 201 after deleting the address of the own apparatus is retransmitted. For example, the relay station address 253 of the header 202 of the packet data 201 retransmitted from the slave station 101a3 becomes (a2) by deleting (a3) from (a3)> (a2). The reason for deleting the address of the own device is to prevent an infinite loop between relay stations. Accordingly, if the relay station address 253 of the header 251 of the received packet data 201 does not have the address of the own apparatus, it is not retransmitted. As a result, if the slave station 101b3 or the slave station 101c3 receives the packet data 201 transmitted by the master station 102, the slave station 101b3 or the slave station 101c3 has its own address in the transmission destination address 251 or the relay station address 253. Do not re-send because it is not listed. If the packet data 201 transmitted by the master station 102 is received by the slave station 101a2, the slave station 101a2 has the address a3 of the other station before its own address of the relay station address 253. Do not send. The same operation is performed for other groups of relay stations.

  In this way, the packet data 201 transmitted by the master station 102 is finally transmitted to the slave station 101 (slave station 101a1 in the above example) that is the slave station of the transmission destination. Note that when the destination slave station 101a1 receives the packet data 201 that the slave station 101a3 retransmits before the slave station 101a2 retransmits, the address (a2) remains in the relay station address 253. It operates so as not to execute the command described in the packet data 201. This can prevent the same command from being executed repeatedly.

Even when the acquisition data is transmitted from the slave station 101 to the master station 102, the operation is the same as described above. In this case, the transmission destination address 251 of the header 202 of the packet data 201 is (c), the transmission source address 252 is (a1), the relay station address 253 is (a2)> (a3), and the payload 203 includes the slave station 101a1. The acquired data is stored. Then, retransmission is repeated while deleting the address of the own station described in the relay station address 253 in the order of the slave station 101a2 and the slave station 101a3, and finally the master station 102 receives the master station.
[Configuration example of slave station 101]
Next, a configuration example of the slave station 101 will be described with reference to FIG. In FIG. 3, the slave station 101 includes a CPU 301, a wireless module 302, a sensor 303, a camera 304, an RTC (Real Time Clock) 305, a memory 306, a dry battery 307, and a photo moss relay 308. The Each block is connected to each other via a bus 309.

  The CPU 301 is a central processing unit that operates according to a program stored in advance therein, and controls the operation of the entire slave station 101.

  The wireless module 302 has a circuit for transmitting and receiving packet data 201 to and from other slave stations 101 and 102. In this embodiment, the packet data 201 is transmitted and received by a wireless communication method according to the specific low power wireless standard, and a communication channel commanded from the CPU 301 is used. For example, when the CPU 301 instructs the communication using the specific low-power wireless standard ch7, the communication frequency band of the wireless module 302 is set to ch7.

  The sensor 303 is composed of a sensor module for acquiring data such as soil temperature, atmospheric temperature, humidity, pH value, moisture amount, and sunshine amount in the field. The sensor module includes a temperature sensor, a humidity sensor, a pH sensor, a moisture sensor, a sunshine amount sensor, and the like.

  The camera 304 is an image sensor that captures crop growth conditions and farmland conditions to acquire image data. For example, VGA (640 × 480 pixels) or QVGA (320 × 240 pixels) format is used as the image data. The image may be a color image or a monochrome image. Alternatively, it may be a color temperature image. The captured image data is subjected to image compression processing according to the JPEG standard or the like in order to reduce the data amount. Here, as a general image compression feature, for example, the compression ratio of fine images with high contrast in fine weather is low, and the compression ratio of images with low frequency components and low contrast in rainy or cloudy weather is high. Tend. For this reason, the amount of data differs depending on the image to be captured, and there is a problem that the transmission time is not constant at the same data rate. Therefore, conventionally, when acquiring image data of a slave station at a time interval set in advance by the master station, it is necessary to set the time interval assuming the maximum transmission time of the image data (time division method and Called). On the other hand, in the wireless management system 100 according to the present embodiment, the acquisition of the next image data is automatically started when the transmission of the image data is completed. Image data can be continuously acquired from the slave stations (referred to as an automatic response method). A specific example of the automatic response method will be described in detail later.

  The RTC 305 has at least one of a clock function and a timer function for measuring a preset time. When the preset time is reached or when the preset time has elapsed, an interrupt signal is sent to the CPU 301. Is output to start the CPU 301 in the sleep state.

  The memory 306 temporarily holds data acquired by the sensor 303 and image data captured by the camera 304. Note that the memory 306 is a non-volatile memory that retains stored contents even when power is not supplied.

  The dry battery 307 supplies operating power to the slave station 101. In particular, the main part of the slave station 101 is directly supplied with power from the dry battery 307, and the non-main part is supplied with power via the photo moss relay 308. Here, the main part is a circuit block necessary for changing the slave station 101 from the sleep state to the wake-up state, and at least the RTC 305 and the CPU 301 for activating the CPU 301 by detecting the interrupt signal output by the RTC 305. Corresponds to some circuits. Further, the non-main part is a circuit of a part that is not necessary for changing from the sleep state to the wake-up state, for example, in the circuits inside the wireless module 302, the sensor 303, the camera 304, the memory 306, and the CPU 301. The sensor 303, the memory 306, and the CPU 301 as a whole may be configured to supply power from the dry battery 307 without using the photo moss relay 308. Thereby, data acquired from the sensor 303 can be stored in the memory 306.

  The photo moss relay 308 is a switch for switching on and off the power supplied from the dry battery 307 in response to a command from the CPU 301. Then, power is supplied to non-main parts via the photo moss relay 308.

The bus 309 is a common bus for inputting / outputting data, commands, control signals, and the like between the blocks.
[Process of CPU 301]
Next, the processing of the CPU 301 will be described in detail. As illustrated in FIG. 3, the CPU 301 includes a data acquisition processing unit 351, a communication processing unit 352, a wakeup processing unit 353, a sleep processing unit 354, and a time setting processing unit 355.

  The data acquisition processing unit 351 performs processing for temporarily storing data acquired from the sensor 303 and image data captured by the camera 304 in the memory 306. When the RTC 305 has a function of outputting date / time data, the date / time data output by the RTC 305 may be added and stored. For example, when the acquired data of the sensor 303 is “soil temperature: 10 ° C.” and the date / time data at that time is “January 1, 2011”, for example, “soil temperature: 10 ° C., January 2011” Data such as “1 day” is stored in the memory 306. Alternatively, in the case of image data acquired by the camera 304, the date / time data output by the RTC 305 is added as header information of the image file and stored temporarily in the memory 306, as in a general electronic camera.

  The communication processing unit 352 performs processing for performing communication with another slave station 101 or the master station 102 by the wireless module 302. For example, when communication is performed using ch7 of the specific low power wireless standard, ch7 is set in the wireless module 302. Then, data temporarily stored in the memory 306 is transmitted, and data and commands are received from the master station 102 and other slave stations 101. Data and commands are transmitted and received as packets having the data format described with reference to FIG. In addition, the communication processing unit 352 checks the header information of the received packet and ignores it if it is not addressed to the own device or not described as a relay station. If it is described as a relay station, the packet received from the wireless module 302 is retransmitted. In particular, the radio management system 100 according to the present embodiment returns a response signal (ACK) to the master station 102 after completing the process according to the command received from the master station 102. As a result, the master station 102 can confirm that the commanded process has been completed. The ACK signal is returned to the master station 102 by each processing unit.

  When the interrupt signal from the RTC 305 is detected, the wake-up processing unit 353 turns on the photo moss relay 308 to start supplying power to the non-main part, and performs processing for starting the CPU 301 to a normal operation state. In particular, in the wireless management system 100 according to the present embodiment, power supply to non-major parts such as the sensor 303 and the camera 304 is started to enter an operating state in which data can be acquired. Then, when it is in an operating state, a wakeup notification is transmitted to the master station 102. As a result, the master station 102 can confirm that the slave station 101 has been woken up and is in an operating state.

  When the sleep processing unit 354 receives a sleep command from the master station 102 via the wireless module 302, the sleep processing unit 354 turns off the photo mos relay 308 to stop the power supply to the non-main part, and sets the CPU 301 to the sleep state. I do.

  When the time setting processing unit 355 receives a time setting command from the master station 102 via the wireless module 302, the time setting processing unit 355 sets the RTC 305 at the time described in the time setting command. The information set in the RTC 305 may be the time measured by the timer function (for example, 1 hour) or the current date / time information (for example, 1 January 2012 12: 00: 0). May be.

As described above, the slave station 101 operates in accordance with a program stored in the CPU 301 in advance, and temporarily acquires the acquired data of the sensor 303 and the image data of the camera 304 into the memory 306 and is sent from the master station 102. In response to the command, a transition to the sleep state and time setting are performed, and each data and ACK signal captured in the memory 306 are transmitted from the wireless module 302 to the master station 102.
[Configuration example of master station 102]
Next, a configuration example of the master station 102 will be described with reference to FIG. In FIG. 4, the master station 102 includes a CPU 401, a wireless module 402, an RTC 403, and a memory 404. Each block is connected to each other via a bus 405.

  The CPU 401 is a central processing unit that operates according to a program stored therein in advance, and controls the overall operation of the master station 102.

  The wireless module 402 is a wireless device for communicating with the slave station 101. In the present embodiment, as described above, commands and data are transmitted and received by a communication method in accordance with a specific low power wireless standard.

  The RTC 403 outputs current date and time information (for example, 2012/01/1 12:00:00). The date and time is appropriately set from the personal computer 151.

  The memory 404 stores data (acquired data and image data) transmitted from the slave station 101.

  The master station 102 is connected to an AC 100V commercial power source, and is supplied with power from a power adapter 152 that performs AC / DC conversion.

Here, the CPU 401 of the master station 102 is connected to a personal computer (PC) 151 as an input / output terminal for operation by an administrator. The administrator checks the setting and operation of each slave station 101 with the personal computer 151 and confirms the received data. When the personal computer 151 starts up the wireless management system 100 and manually changes the settings of the slave stations 101 and 102, the acquired data received from each slave station 101 and stored in the memory 404 of the master station 102 Used when confirming. In the normal operation of automatically collecting data from the slave station 101, it operates independently according to a program stored in advance in the CPU 401 of the master station 102.
[Processing of CPU 401]
Next, the processing of the CPU 401 will be described in detail. As shown in FIG. 4, the CPU 401 includes an input / output terminal IF unit 451, a time setting processing unit 452, a data management processing unit 453, a command issuance processing unit 454, and a communication processing unit 455.

  The input / output terminal IF unit 451 performs processing for inputting / outputting commands, data, and the like to / from an input / output terminal (such as the personal computer 151) connected through a serial interface such as the USB standard or the RS232C standard. In this embodiment, the personal computer 151 is used as the input / output terminal. However, a dedicated terminal having a keyboard for inputting commands, a monitor for displaying data and images, and the like may be used.

  The time setting processing unit 452 sets the date and time information (for example, 1 January 2012 12:00:00) entered in the RTC 403 from the personal computer 151.

  The data management processing unit 453 stores data (sensor data and image data) transmitted from the slave station 101 in the memory 404. At this time, the time when the data is received is input from the RTC 403, added to the data, and stored in the memory 404. The personal computer 151 reads out the data stored in the memory 404 via the CPU 401 and outputs the data to the monitor of the personal computer 151, or performs data analysis and management using dedicated application software.

  The command issuance processing unit 454 stores a command manually input from the personal computer 151 or a command automatically issued by the CPU 401 during normal operation in the data format packet described with reference to FIG. Send to. In particular, in the radio management system 100 according to the present embodiment, the command issuance processing unit 454 confirms the ACK signal returned from the slave station 101 in response to the command issued to the slave station 101 and sends the next command to the slave station. 101. In addition, the wireless management system 100 according to the present embodiment has two operation modes, a time division mode and an automatic response mode, and a preset operation such as any one mode or a combination of the two modes. Operate in mode.

  The communication processing unit 455 performs processing for performing communication with the slave station 101 by the wireless module 402. For example, when communication is performed using ch7 of the specific low power wireless standard, ch7 is set in the wireless module 402. Then, a packet storing a command created by the command issue processing unit 454 is transmitted to the slave station 101 or data is received from the slave station 101.

  As described above, the master station 102 operates in accordance with a program stored in advance in the CPU 401, transmits various commands to the slave station 101, and adds date / time information to data received from the slave station 101 to store the memory 404. To remember. In particular, since the master station 102 automatically confirms the ACK signal returned from the slave station 101 and automatically transmits the next command, there is no wasted time and the command is efficiently issued to control the slave station 101. Data can be acquired.

Next, the time division method and the automatic response method will be described in detail.
[Time division method]
FIG. 5A is a diagram showing an example of communication between the master station 102 and the slave station 101 by the time division method. The master station 102 issues a command according to a schedule preset in the command issue processing unit 454. In the example of FIG. 5A, the control command at time A is transmitted to the slave station 101. Then, the slave station 101 returns an ACK signal to the master station 102 when execution of the command received from the master station 102 is completed. Then, at time B, the next control command is transmitted to the slave station 101, and the slave station 101 returns an ACK signal to the master station 102 when execution of the command received from the master station 102 is completed. In this case, if the execution end time of the control command transmitted at time A becomes later than time B at which the next command is issued, the processing of the slave station 101 is duplicated, so the maximum processing time of the slave station 101 is assumed. Thus, the time interval between time A and time B must be set.
[Automatic response method]
FIG. 5B is a diagram showing an example of communication between the master station 102 and the slave station 101 using the automatic response method. In the example of FIG. 5A, the control command at time A is transmitted to the slave station 101. Here, the master station 102 issues a command according to a schedule preset in the command issue processing unit 454 for the first command. Then, the slave station 101 returns an ACK signal to the master station 102 when execution of the command received from the master station 102 is completed. When the master station 102 receives the ACK signal, it immediately transmits the next control command to the slave station 101. The slave station 101 returns an ACK signal to the master station 102 when the execution of the command received from the master station 102 is completed. To do. In this case, since the time at which the next command is issued changes according to the execution end time of the control command transmitted at time A, the control command can be transmitted continuously and reliably to the slave station 101, and data is acquired. To do as little time as possible. Thereby, useless operation time of the slave station 101 is eliminated, and consumption of the dry battery 307 can be prevented.
[Specific operation example of wireless management system 100]
Next, a specific operation example of the wireless management system 100 will be described. FIG. 6 shows data acquired by the slave station 101 by performing processing according to each command transmitted from the master station 102 by the automatic response method after the slave station 101 wakes up at a preset time by the time division method. FIG. 6 is a diagram illustrating an operation from the end of transmission of (for example, image data) to the parent station 102 until a sleep state is entered by a sleep command from the parent station 102.

  Hereinafter, the operation of FIG. 6 will be described in order.

  (Step S100) The slave station 101 wakes up at a preset time (for example, 9:00) and starts a wakeup process. Specifically, an interrupt signal is output to the CPU 301 at a time set in advance by the RTC 305, and the CPU 301 in the sleep state is activated to enter an operating state (a state where power is supplied to non-main parts).

  (Step S <b> 101) The slave station 101 transmits a wakeup notification (wakeup notification) to the master station 102 when the slave station 101 is in an operating state. Note that the wake-up notification is transmitted in a packet having a data format as described with reference to FIG.

  (Step S102) When it is confirmed by the wake-up notification from the slave station 101 that the slave station 101 is in an operating state, the master station 102 automatically transmits a time synchronization command. The time synchronization command is a command for synchronizing the time of the RTC 305 of the child station 101 with the time of the RTC 403 of the parent station 102. Here, the next wake-up time may be included in the time synchronization command for transmission. The time synchronization command is transmitted in a packet with a data format as described with reference to FIG.

  (Step S103) The child station 101 that has received the time synchronization command from the parent station 102 synchronizes the time of the RTC 305 of the own station with the time of the RTC 403 of the parent station 102 included in the time synchronization command. The time adjustment is performed in consideration of the time for transmitting and receiving the time synchronization command. For example, since the data length of the time synchronization command is fixed, the transmission / reception time can be obtained from the data rate, and the transmission / reception time (including processing time) is added to the time of the RTC 403 of the master station 102 included in the time synchronization command. The time is set in the RTC 305 of the local station.

  (Step S104) The slave station 101 transmits an ACK signal to the master station 102 when the time synchronization processing is completed.

  (Step S105) When it is confirmed by the ACK signal from the slave station 101 that the time synchronization processing of the slave station 101 is completed, the master station 102 automatically transmits a data acquisition command. The data acquisition command is a command for causing the slave station 101 to perform temperature data acquisition by the sensor 303, image data acquisition by the camera 304, or the like. Here, the data acquisition command is transmitted in a packet having the data format as described with reference to FIG.

  (Step S <b> 106) The slave station 101 that has received the data acquisition command from the master station 102 shoots an image with the camera 304, for example, and takes the captured image data into the memory 306. The type of data to be acquired is specified by a data acquisition command.

  (Step S <b> 107) The slave station 101 transmits an ACK signal to the master station 102 when the data acquisition is completed.

  (Step S108) When it is confirmed by the ACK signal from the slave station 101 that the data acquisition of the slave station 101 is completed, the master station 102 automatically transmits a data transfer command. The data transfer command is a command for transmitting, for example, temperature data or image data acquired in the memory 106 to the master station 102. Here, the data transfer command is transmitted in a packet of the data format as described in FIG.

  (Step S109) The slave station 101 that has received the data transfer command from the master station 102 transmits the data captured in the memory 306 or the like to the master station 102 via the wireless module 302.

  (Step S <b> 110) The slave station 101 transmits an ACK signal to the master station 102 when the data transfer is completed.

  (Step S111) When it is confirmed by the ACK signal from the slave station 101 that all data transfer has been completed, the master station 102 automatically transmits a sleep command (sleep command). The sleep command is transmitted in a packet having a data format as described with reference to FIG.

  (Step S112) The slave station 101 that has received the sleep command from the master station 102 stops supplying power to non-main parts (such as the sensor 303 and the camera 304), and the CPU 301 wakes up with an interrupt at the time set in the RTC 305. It shifts to the sleep state where only the functions that can be up are operating.

  (Step S113) The slave station 101 transmits, to the master station 102, an ACK signal notifying that the mobile station 101 shifts to the sleep state immediately before shifting to the sleep state.

  In this way, the master station 102 transmits subsequent commands by the automatic response method after the slave station 101 wakes up by the time division method, and therefore can acquire data from the slave station 101 in as short a time as possible. The operating time of the slave station 101 can be shortened as much as possible. Similarly, the master station 102 that has completed data acquisition for a certain slave station 101 can start processing for acquiring data from the next slave station 101. In this case, for example, as described with reference to FIG. 1, the group is waked up for each group, so that the next slave station 101 is in a wake-up state.

  Here, in the example of FIG. 6, the time from when the slave station 101 wakes up at time 9:00 to when the master station 102 transmits a sleep command around time 9:08 is about 7 to 8 minutes. .

  Next, in order to easily understand the effect of the wireless management system 100 according to the present embodiment, an operation example in which data is acquired from the slave station 101 only by a time division method in which commands are issued according to a preset schedule will be described. 7 wakes up at a preset time in the slave station 101 in a time-sharing manner in the same way as in FIG. 6, but each command of the master station 102 is also transmitted at the preset time to obtain data. It is the figure which showed the operation | movement until it becomes a sleep state by the command from the main | base station 102 later.

  Hereinafter, operations in FIG. 7 will be described in order. Note that the processing steps with the same reference numerals as those in FIG. 6 indicate the same processing, and the processing steps in which the alphabet “a” is added to the reference numerals are slightly different from those in FIG. Here, the description of the overlapping process with FIG. 6 is omitted, and the process different from that of FIG. 6 will be mainly described. The operations in step S100 and step S101 are the same as those in FIG.

  (Step S102a) The master station 102 transmits a time synchronization command at a preset time 9:02. Here, in the time division method, as in step S102 of FIG. 6, the wake-up notification received from the slave station 101 is not responded but operates according to a predetermined schedule. The master station 102 knows from the schedule that the slave station 101 will wake up at time 9:00, but starts a time lag with the RTC 305 of the slave station 101 and power supply to non-main parts. Depending on the processing time and the transmission time of the wakeup notification, the time until the wakeup notification is received at the master station 102 may fluctuate. Therefore, after waiting for the longest time estimated from the wakeup time, A time synchronization command needs to be sent. In the example of FIG. 7, the longest time assumed from the wake-up time is 1 minute, and a time synchronization command is transmitted to the slave station 101 at time 9:02.

  The operations in the next steps S103 and S104 are the same as those in FIG.

  (Step S105a) The master station 102 transmits a data acquisition command at a preset time 9:03. Similar to step S102a, the master station 102 does not respond to a signal (ACK signal) received from the slave station 101, but operates according to a predetermined schedule. In the example of FIG. 7, data is captured at time 9:03, assuming that the longest time from the transmission time of the time synchronization command until the slave station 101 finishes setting the time and transmits the ACK signal is 1 minute. The command is transmitted to the slave station 101.

  The operations in the next steps S106 and S107 are the same as those in FIG.

  (Step S108a) The master station 102 transmits a data transfer command at a preset time 9:08. Here, as in step S105a, the master station 102 does not respond to the ACK signal received from the slave station 101, but operates according to a predetermined schedule. In the example of FIG. 7, the assumed longest time from the transmission time of the data capture command until the slave station 101 finishes capturing the data and transmits the ACK signal is assumed to be 5 minutes, and the time is 9:08. A data transfer command is transmitted to the slave station 101.

  The operations in the next steps S109 and S110 are the same as those in FIG.

  (Step S111a) The master station 102 transmits a sleep command at a preset time 9:18. Again, as in step S105a and step S108a, the master station 102 does not respond to the ACK signal received from the slave station 101, but operates according to a predetermined schedule. In the example of FIG. 7, the maximum expected time from the transmission time of the data transfer command until the slave station 101 completes transmission of all data (for example, image data) and transmits an ACK signal is 10 minutes. At 9:18, a sleep command is transmitted to the slave station 101.

  The operations in the next steps S112 and S113 are the same as those in FIG.

  Thus, in the time division method, the master station 102 transmits a data acquisition command or a data transfer command at a predetermined time according to a preset schedule after the slave station 101 wakes up in the time division method. Therefore, it is necessary to set the command transmission interval to a time interval sufficient for the processing in the slave station 101 to end. If the time interval is short, the next command is issued before the processing of the slave station 101 is completed, causing problems such as the slave station 101 becoming unable to respond and the wireless channel being unusable.

  Here, in the example of FIG. 7, the time from when the slave station 101 wakes up at time 9:00 to when the master station 102 transmits a sleep command at time 9:18 is approximately 17 minutes to 18 minutes. Furthermore, when a command is subsequently issued to the next slave station 101, a sufficiently long time interval (about 7 minutes until time 9:25 in the example of FIG. 7) needs to be set according to the schedule.

  As described above, the automatic response method of FIG. 6 can be shortened by about 10 minutes compared with the case of operating only by the time division method of FIG. 7, and the power saving of the slave station 101 can be achieved.

  FIG. 8 (a) is a diagram showing a comparison of processing times when only the time division method is used, and FIG. 8 (b) is a comparison of processing times when the automatic response method is performed after wake-up by the time division method. Here, FIG. 8A corresponds to the example of FIG. 7, and FIG. 8B corresponds to the example of FIG.

  In FIG. 8A, the wake-up of the slave station 101 and each command transmitted from the master station 102 to the slave station 101 are all executed at a preset time according to the schedule. First, the slave station 101 wakes up at time 9:00. The master station 102 transmits a time synchronization command to the slave station 101 at a time 9:02 with sufficient time for the slave station 101 to complete the wake-up operation. Furthermore, the master station 102 transmits a data capture command to the slave station 101 at a time 9:03 with sufficient time for the time synchronization processing of the slave station 101 to be completed. On the other hand, when the automatic response method of FIG. 8B is used, the master station 102 that has received the wake-up notification transmitted from the slave station 101 by the time division method at time 9:00 immediately transmits the time. The synchronization command is transmitted to the slave station 101, and further, the data capture command is transmitted to the slave station 101 immediately after receiving the ACK signal transmitted from the slave station 101 after the time synchronization processing is completed. At this stage, the automatic response method can shorten the time by 1 minute or more compared with the case of only the time division method.

  In the time division method of FIG. 8A, the slave station 101 has sufficient time to complete acquisition of data specified by the data acquisition command (for example, data of the sensor 303, the camera 304, etc.) At time 9:08, the master station 102 transmits a data transfer command to the slave station 101. Here, since the time required for acquisition differs depending on the type of data such as data (temperature, humidity, pH value, moisture amount, amount of sunlight, etc.) acquired by the sensor 303 and image data captured by the camera 304, the maximum expected In consideration of the acquisition time, it is necessary to allow sufficient time for the acquisition to be completed, and in the case of data with a short acquisition time, useless time is generated. For example, in the case of FIG. 8, actual data acquisition is completed around time 9:05, but the master station 102 waits until time 9:08 when the next command is transmitted.

  On the other hand, when the automatic response method of FIG. 8B is used, a data transfer command is issued immediately after receiving an ACK signal indicating completion of data capture transmitted from the slave station 101 around time 9:03. 101. At this stage, the automatic response method can reduce the time by about 5 minutes compared to the case of only the time division method.

  Furthermore, in the time division method of FIG. 8A, after a sufficient time for transferring the data acquired from the slave station 101 to the master station 102, the master station 102 issues a sleep command at time 9:18. Transmit to station 101. Here, the amount of data differs depending on the type and image of the acquired data, and the transmission time from the child station 101 to the parent station 102 changes. Therefore, the transmission of all data is completed in consideration of the assumed maximum transmission time. It is necessary to leave sufficient time for the transmission, and in the case of data with a short transmission time, useless time occurs. For example, in the case of FIG. 8, actual data transfer is completed around time 9:13, but the slave station 101 must wait until time 9:18 when the master station 102 transmits the next command.

  On the other hand, when the automatic response method of FIG. 8B is used, the sleep command is issued immediately after receiving the ACK signal indicating the end of the data transfer transmitted from the slave station 101 at time 9:08. Send to.

  In this way, when the radio management system 100 is operated only by the time division method, the slave station 101 wakes up at time 9:00 and is in a sleep state by a sleep command transmitted by the master station 102 at time 9:18. It is in an operating state for about 18 minutes before shifting to. On the other hand, in FIG. 8B, the operation time of the slave station 101 is about 10 minutes by performing each command transmitted by the master station 102 after the slave station 101 wakes up by the time division method in the automatic response method. It can be shortened.

  In FIG. 6 and FIG. 8B, after the slave station 101 is woken up by the time division method, all commands are transmitted from the master station 102 to the slave station 101 by the automatic response method. The method and the automatic response method may be used in combination. For example, as shown in FIG. 9, first, at time A, a control command is transmitted from the master station 102 to the slave station 101 according to a schedule set in advance in a time division manner, and then the slave station 101 returns a response after executing the command by an automatic response method. As soon as an ACK signal to be received is received, the next control command is transmitted to the slave station 101. Then, the control command is transmitted again from the master station 102 to the slave station 101 at time B by the time division method, and the next control command is sent immediately after receiving the ACK signal that the slave station 101 returns after executing the command by the automatic response method. Transmit to the slave station 101. Similarly, when the control command is transmitted again from the master station 102 to the slave station 101 at time C by the time division method, and the ACK signal that the slave station 101 returns after executing the command is received by the automatic response method, the next control command is immediately received. Is transmitted to the slave station 101.

  In this way, by using the time division method and the automatic response method in combination, even if it is desired to acquire data regularly, the data acquisition operation can be performed in a short time, and the operation time of the slave station 101 is made as short as possible. be able to.

[When acquiring data from multiple slave stations 101]
Next, a specific example of acquiring data from a plurality of slave stations 101 will be described with reference to FIG. In the example of FIG. 10, the master station 102 shows an operation of continuously acquiring data from the three slave stations 101 (slave station 101a1, slave station 101a2, and slave station 101a3) of the group A described in FIG. . Each slave station 101 in FIG. 10 performs the same operation as the slave station 101 described in FIG. The processing with the same number as the step number in FIG. 6 shows the processing with the same content, but in FIG. 10, the alphabet indicating the group of each slave station in the step number and the number for distinguishing the slave stations in the same group This is indicated by adding. For example, the processing of the slave station 101a1 corresponding to step S100 in FIG. 6 is expressed as step S100a1 with a1 added to the step number. Similarly, the processing of the slave station 101a2 corresponding to step S106 in FIG. 6 is expressed as step S106a2. The same applies to the slave station 101a3.

  In FIG. 10, the wake-up time of each child station 101 is set in advance so that the child station 101 close to the parent station 102 wakes up in order in a time division manner. In the example of FIG. 10, the slave station 101 a 1 is the slave station 101 farthest from the master station 102, and the slave station 101 a 3 is the slave station 101 closest to the master station 102. The slave station 101a2 is the slave station 101 that relays between the slave station 101a1 and the slave station 101a3.

  First, the nearest slave station 101a3 wakes up and performs a wakeup process (step S100a3), and transmits a wakeup notification to the master station 102 (step S101a3). Next, the slave station 101a2 wakes up and performs a wakeup process (step S100a2), and transmits a wakeup notification to the master station 102 via the slave station 101a3 (step S101a2). Finally, the farthest slave station 101a1 wakes up and performs a wakeup process (step S100a1), and transmits a wakeup notification to the master station 102 via the slave station 101a2 and the slave station 101a3 (step S101a1).

  When the master station 102 confirms that all the slave stations 101 in the same group A have woken up, it transmits a time synchronization command to the farthest slave station 101a1 as in FIG. 6 (step S102a1). The slave station 101a1 executes time synchronization processing (step S103a1) and returns an ACK signal (step S104a1). Receiving this, the master station 102 performs processing for acquiring data (from step S105a1 to step S107a1), and after completing the data transfer processing (step S108a1 to step S110a1), sets the slave station 101a1 to the sleep state (from step S111a1). Step S112a1). Then, after confirming that the slave station 101a1 is in the sleep state with an ACK signal (step S113a1), the next slave station 101a2 immediately performs time synchronization processing (from step S102a2 to step S104a2). Then, after confirming that the time synchronization processing of the slave station 101a2 is completed with an ACK signal (step S104a2), the data capture processing and the data transfer processing are performed by the automatic response method (step S105a2 to step S110a2), and the data transfer is completed. After confirming this with an ACK signal (step S110a2), the slave station 101a2 is put into a sleep state (from step S111a2 to step S112a2). Further, after confirming that the slave station 101a2 is in the sleep state with an ACK signal (step S113a2), the time synchronization process is immediately performed on the next slave station 101a3 (steps S102a3 to S104a3). Then, after confirming that the time synchronization processing of the slave station 101a3 is completed with an ACK signal (step S104a3), the data capture processing and the data transfer processing are performed by the automatic response method (step S105a3 to step S110a3), and the data transfer is completed. After confirming this with the ACK signal (step S110a3), the slave station 101a3 is set to the sleep state (from step S111a3 to step S113a3).

  As described above, the radio management system 100 according to the present embodiment can continuously acquire data from a plurality of slave stations 101 by the automatic response method, and therefore, the operating time of each slave station 101 can be reduced as much as possible. Can do. In the example of FIG. 10, as shown in FIG. 11, the operation time of each slave station 101 can be shortened by about 10 minutes compared to the case of only the time division method, so 10 minutes when data is acquired from the slave station 101a1 × The total operating time can be shortened by 3 units for 30 minutes, 10 minutes for acquiring data from the slave station 101a2, and 20 minutes for 2 units, and 10 minutes for acquiring data from the slave station 101a3. (Time required for data acquisition) can be shortened by 60 minutes.

  In the example of FIG. 10, the time synchronization process is performed before the data transfer. However, the time synchronization process may be performed in a lump at the time of wakeup or before sleep, or a completely different process. (Newly executed as a time division method for time setting).

  In the example of FIG. 10, all the slave stations 101 including the relay station (the slave stations 101 a 1 to 101 a 3) acquire and transfer the data of the local station, but the specific slave station 101 transmits the data. The other slave station 101 may obtain only and perform relaying. For example, FIG. 12 shows an operation when the data acquired by the slave station 101a1 is transferred to the master station 102, and the other slave stations 101a2 and 101a3 perform only the relay. FIG. 12 is a diagram corresponding to FIG. 10, and processes having the same reference numerals as those in FIG. 10 indicate the same processes. Here, what is different from FIG. 10 is the following processing. First, after the data acquired by the slave station 101a1 is transferred to the master station 102, when the ACK signal indicating that the slave station 101a1 enters the sleep state is received by the sleep process (step S113a1), the slave station that is the relay station immediately A sleep command is transmitted to 101a2, and the slave station 101a2 is set to the sleep state. Further, upon receiving an ACK signal indicating that the slave station 101a2 is in the sleep state (step S113a2), immediately, a sleep command is transmitted to the slave station 101a3, which is the next relay station, to place the slave station 101a3 in the sleep state. .

  In this way, the radio management system 100 according to the present embodiment can shorten the operating time of each slave station 101 as much as possible by using the automatic response method even when the slave station 101 operates as a relay station. .

  As described above, by shortening the operation time of the slave station 101 as much as possible, it is possible to save power and extend the life of the battery.

  Here, the wake-up time of the slave station 101 is scheduled in advance by the administrator so as to be different for each slave station 101. The wake-up time may be set by the administrator from the personal computer 151 when starting up the wireless management system 100, or may be changed from the personal computer 151 during operation. Here, the time of the RTC 305 of each slave station 101 is assumed to be synchronized. However, the time of the RTC 305 of each slave station 101 may be shifted due to component variations and environmental conditions. Set up.

  In the present embodiment, the wireless management system 100 that installs the slave stations 101 in scattered farm fields and transmits the sensor data acquired by the sensor 303 or the image data captured by the camera 304 to the master station 102 for management. Although explained, it is not limited to a farm field, for example, to a system for monitoring water leaks of scattered water facilities, a system for monitoring dynamic objects (livestock, etc.), a system for preventing lost children at amusement parks and event venues, etc. Can be applied. In addition, a worker can have a slave station 101 with a satellite positioning system (GPS) to collect and manage work positions sequentially, or to record where and how much each worker has worked. It can also be applied to systems that improve efficiency.

  As described above, the wireless management system and the transmission management method according to the present invention do not require a large-scale power supply facility, and can perform a stable system operation over a long period of time using only a battery.

  Although the wireless management system and the transmission management method according to the present invention have been described with reference to the respective embodiments, the present invention can be implemented in various other forms without departing from the spirit or main features thereof. For this reason, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The present invention is defined by the claims, and the present invention is not limited to the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Wireless management system 101 ... Slave station 102 ... Master station 301 ... CPU
302 ... Wireless module 303 ... Sensor 304 ... Camera 305 ... RTC
306 ... Memory 307 ... Dry cell 308 ... Photo MOS relay 309 ... Bus 351 ... Data acquisition processing unit 352 ... Communication processing unit 353 ... Wake-up processing unit 355 ... Time Setting processing unit 401 CPU
402 ... Wireless module 403 ... RTC
404 ... Memory 405 ... Bus 451 ... I / O terminal IF unit 452 ... Time setting processing unit 453 ... Data management processing unit 454 ... Command issue processing unit 455 ... Communication processing unit

Claims (8)

In a wireless management system including a plurality of wireless terminal devices that are scattered and a wireless management device that manages the plurality of wireless terminal devices,
The plurality of wireless terminal devices are:
A data acquisition unit for acquiring data;
A wireless communication unit that transmits and receives data and commands to and from the adjacent wireless terminal device or the wireless management device;
Data acquired by the data acquisition unit or data and commands addressed to other devices received by the wireless communication unit from other devices are transmitted from the wireless communication unit, and the operation of the own device is controlled according to the commands addressed to the own device. A control unit;
A time measuring unit that measures time and wakes up the control unit in a sleep state when the time reaches a preset time;
The control unit transmits a response signal to the radio management device after completion of execution of a command addressed to the own device received from the radio management device when the control unit is in a wake-up state by the timing unit, and the radio management device transmits When a sleep command addressed to its own device is received, it shifts to a sleep state except at least the timekeeping unit,
The radio management device
A master station wireless communication unit that transmits and receives data and commands to and from the adjacent wireless terminal device among the plurality of wireless terminal devices;
And a master station controller that transmits a command to the plurality of wireless terminal devices and automatically transmits a next command when the response signal is received from the plurality of wireless terminal devices. system. The radio management system according to claim 1,
The master station control unit manages the plurality of wireless terminal devices divided into a plurality of groups, transmits a time setting command for setting a time for wakeup for each group in the time measuring unit, A sleep management command is transmitted sequentially from the far-end wireless terminal device. The radio management system according to claim 1 or 2,
The master station control unit is a time division mode for periodically acquiring data from the plurality of wireless terminal devices at a preset time, and an automatic response mode for sequentially acquiring data from the plurality of wireless terminal devices in order. A wireless management system comprising: In the radio management system according to any one of claims 1 to 3,
The data acquired by the data acquisition unit is data output from at least one of a temperature sensor, a humidity sensor, a pH sensor, a moisture sensor, a sunshine amount sensor, and an image sensor. In a transmission management method used in a wireless management system including a plurality of wireless terminal devices arranged in a scattered manner and a wireless management device that manages the plurality of wireless terminal devices,
The plurality of wireless terminal devices are:
Data acquired by the own device or data and commands addressed to other devices received from the other device are transferred to the other device, and the operation of the own device is controlled according to the command addressed to the own device, and transmitted by the radio management device. When a sleep command addressed to the device itself is received, the device shifts to the sleep state, measures the time, wakes up the device in the sleep state when the time reaches a preset time, and the device wakes up A response signal is transmitted to the radio management apparatus after completion of execution of processing according to the command addressed to the own apparatus received from the radio management apparatus when the radio management apparatus is in a state
The radio management device
A transmission management method comprising: transmitting a command to the plurality of wireless terminal devices and automatically transmitting a next command when the response signal is received from the plurality of wireless terminal devices. The transmission management method according to claim 5, wherein
The wireless management device manages the plurality of wireless terminal devices divided into a plurality of groups, transmits a time setting command for setting a time to wake up the wireless terminal device for each group, A transmission management method, comprising: transmitting a sleep command in order from the wireless terminal device at the far end. In the transmission management method according to claim 5 or 6,
The wireless management device is a time division mode for periodically acquiring data from the plurality of wireless terminal devices at a preset time, and an automatic response mode for sequentially acquiring data from the plurality of wireless terminal devices. A transmission management method comprising the steps of: In the transmission management method according to any one of claims 5 to 7,
The data acquired by the wireless terminal device is data output by at least one of a temperature sensor, a humidity sensor, a pH sensor, a moisture sensor, a sunshine amount sensor, and an image sensor.

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