JP2014107762A - Sensor data collection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor data collection system capable of increasing the reliability of wireless communication by reducing communication failure.SOLUTION: A sensor sub unit 1 includes: a sensor section 11 that measures state quantity of a measurement object every time when a predetermined measurement interval has elapsed; and a wireless communication section 13 that radio-transmits measurement data to a wireless master unit 2 every time when a predetermined transmission interval has elapsed. The wireless master unit 2 includes an MCU 20 and a wireless communication section 21. The MCU 20 acquires at least either information of the measurement interval and the transmission interval from the respective sensor sub unit 1 of plural units, and calculates an offset time for offsetting transmission timing of the sensor sub unit 1 on the basis of the acquired information, and controls the wireless communication section 21 to transmit the offset time to the sensor sub unit 1. When the wireless communication section 13 receives the offset time transmitted from the wireless master unit 2, the sensor sub unit 1 radio-transmits the measurement data from the wireless communication section 13 every time when the transmission interval has elapsed at a time which is the transmission timing delayed by the offset time as the reference.

Description

  The present invention relates to a sensor data collection system.

  Conventionally, a wireless sensor network including a wireless sensor, a base station, and a management server has been proposed (see, for example, Patent Document 1). In the system disclosed in Patent Document 1, when the wireless sensor acquires illuminance, humidity, and temperature information, the acquired information is wirelessly transmitted to the base station. When the base station receives information from the wireless sensor, the base station transmits the received information to the management server. The management server manages the information received from the base station by storing it in a database, and controls the lighting device, the air conditioner, and the refrigeration device based on the information stored in the database.

JP 2006-295907 A

  By the way, if the number of installed wireless sensors increases as the system scales up, the wireless communication traffic increases. Therefore, there is a high possibility that signals transmitted wirelessly from a plurality of wireless sensors will collide and cause a communication failure. Thus, there is a problem that the reliability of wireless communication is lowered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a sensor data collection system in which the occurrence of communication failure is suppressed and the reliability of wireless communication is improved.

  In order to solve the above problems, a sensor data collection system of the present invention includes a plurality of sensor slave units and a master unit. The sensor slave unit includes a sensor unit that measures a state quantity of a measurement target every time a measurement interval set in each sensor slave unit elapses, and a transmission interval set in each sensor slave unit elapses. A first communication unit that wirelessly transmits the measurement data of the sensor unit to the parent device every time. The master unit includes a second communication unit, an information acquisition unit, and a time adjustment unit. The second communication unit performs wireless communication with the first communication unit. The information acquisition unit acquires at least one of the measurement interval and the transmission interval for each of the plurality of sensor slave units. The time adjustment unit obtains an offset time for shifting the transmission timing of the sensor slave unit based on the information acquired by the information acquisition unit, and causes the second communication unit to transmit the offset time to the sensor slave unit. In the sensor slave unit, when the first communication unit receives the offset time transmitted from the master unit, the transmission interval elapses with reference to a time obtained by shifting the previous transmission timing by the offset time. Measurement data is transmitted wirelessly from the first communication unit every time.

  This sensor data collection system preferably further includes the following configuration. The time adjustment unit uses a common divisor obtained from the measurement interval and the transmission interval of a plurality of sensor slave units as a reception period, and a reception timing obtained by equally dividing the reception period by the number of sensor slave units Is assigned to each of the sensor slave units. And the said time adjustment part determines the said offset time so that the transmission timing of the said sensor slave unit may correspond with the reception timing allocated to the said sensor slave unit.

  This sensor data collection system preferably further includes the following configuration. The sensor slave unit wirelessly transmits the transmission interval information from the first communication unit to the master unit. The information acquisition unit acquires the information when the second communication unit receives the information transmitted from the sensor slave unit.

  This sensor data collection system preferably further includes the following configuration. The information acquisition unit includes, for each of the plurality of sensor slave units, a transmission interval and a transmission time of the sensor slave unit from a time interval and a reception time at which the second communication unit receives measurement data from the sensor slave unit. Get information about. The time adjustment unit is based on the transmission interval and transmission time information obtained for each of the sensor slave units, and the sensor slave unit is likely to collide with transmission data from other sensor slave units. An offset time for shifting transmission timing is determined so that transmission data does not collide.

  In this sensor data collection system, it is also preferable that the first communication unit of the sensor slave unit operates in a reception state after transmission of measurement data until the number of transmissions of measurement data exceeds a predetermined number after activation.

  This sensor data collection system preferably further includes the following configuration. The first communication unit of the sensor slave unit transmits transmission data including measurement data and a synchronization request flag to the master unit. In the master unit, when the second communication unit receives the synchronization request flag included in the transmission data from the sensor slave unit, the time adjustment unit offsets the sensor slave unit that is the transmission source of the synchronization request flag. The time is determined, and wireless transmission is performed from the second communication unit.

  In this sensor data collection system, it is preferable that the sensor slave unit transmits the synchronization request flag every predetermined number of transmissions or every predetermined time.

  This sensor data collection system preferably further includes the following configuration. Each of the first communication unit and the second communication unit can communicate in a plurality of frequency bands. The first communication unit of the sensor slave unit communicates with the master unit in a plurality of available frequency bands when activated. The base unit selects a frequency band having a higher received signal strength based on the received signal strength received from the sensor slave unit in each of a plurality of frequency bands, and instructs to use the selected frequency band. A control command is transmitted from the second communication unit to the sensor slave unit.

  This sensor data collection system preferably further includes the following configuration. Each of the first communication unit and the second communication unit can perform communication using at least a 2.4 GHz band and a 920 MHz band as a plurality of frequency bands. The first communication unit of the sensor slave unit transmits a radio signal to the master unit in both the 2.4 GHz band and the 920 MHz band when activated. If the received signal strength in both of the frequency bands is equal, or if the received signal strength in both of the frequency bands is equal to or greater than a predetermined threshold, the base unit instructs to use the 2.4 GHz band. A control command is transmitted from the second communication unit to the sensor slave unit.

  This sensor data collection system preferably further includes the following configuration. The first communication unit and the second communication unit can communicate using a plurality of the frequency bands using at least a 2.4 GHz band and a 920 MHz band. The first communication unit of the sensor slave unit transmits a radio signal to the master unit in both the 2.4 GHz band and the 920 MHz band when activated. If the received signal strength in both of the frequency bands is equal to or greater than a predetermined threshold, the base unit instructs the base unit to reduce the transmission power in the 920 MHz band rather than the transmission power in the 2.4 GHz band. Is transmitted from the second communication unit to the sensor slave unit.

  This sensor data collection system preferably further includes the following configuration. The first communication unit of the sensor slave unit transmits a radio signal to the master unit when activated. The base unit includes an antenna having a variable directivity, a direction detector, and a directivity adjuster. The direction detecting unit detects an arrival direction in which the electric field intensity of the radio wave received for each sensor slave unit is higher when the radio wave transmitted from the sensor slave unit is received at the time of activation. The directivity adjustment unit adjusts the directivity of the antenna in the arrival direction detected by the direction detection unit when the transmission timing of each of the sensor slave units comes.

  According to the present invention, when the information acquisition unit of the master unit acquires at least one of the measurement interval and the transmission interval for each of the sensor slave units, the time adjustment unit sets the offset time based on this information. Is transmitted from the second communication unit to the sensor slave unit. Since the sensor slave unit transmits the measurement data every time the transmission interval elapses with reference to the time when the transmission timing is shifted by the offset time, it is possible to reduce the possibility that transmission data from a plurality of sensor slave units collide. Therefore, the occurrence of communication failure can be suppressed and the reliability of wireless communication can be improved.

Embodiment 1 is shown, (a) is a block diagram of a sensor slave unit, (b) is a block diagram of a master unit, and (c) is a block diagram of a control device. It is a system block diagram same as the above. It is a flowchart explaining operation | movement same as the above. (A) (b) is a time chart explaining operation | movement same as the above. It is an external appearance perspective view of the main | base station same as the above. 6 is a time chart for explaining the operation of the second embodiment.

  The data collection system according to the present invention is used for measuring, for example, illuminance, temperature, humidity, and the like in an office. Hereinafter, an embodiment will be described in which the data collection system according to the present invention is applied to a control system that controls the operation of lighting equipment and air conditioning equipment based on the results of measuring illuminance, temperature, humidity, and the like in an office.

(Embodiment 1)
A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 2 is a system configuration diagram of a control system to which the sensor data collection system according to the present invention is applied. This control system includes sensor slave units 1a, 1b, 1c, and 1d, a wireless master unit 2, a control device 3, and an environment control device 4 (for example, a lighting fixture 5 and an air conditioning device 6).

In this control system, the illuminance is measured by the sensor slave units 1a and 1d arranged in the area to be controlled, and the temperature and humidity are measured by each of the sensor slave units 1b and 1c. Note that the measurement target of the sensor slave unit is not limited to illuminance and temperature / humidity, and the measurement target may be airflow, CO ₂ concentration, or the like. Further, in this system, two sensor slave units 1a and 1d for measuring illuminance and two sensor slave units 1b and 1c for measuring temperature and humidity are provided. The type and number of sensor slave units are the same as those in the present embodiment. The configuration is not limited.

  The sensor slave units 1a and 1d and the sensor slave units 1b and 1c are different from each other in measurement target, and have the same configuration. Hereinafter, the sensor slave unit 1a for measuring illuminance will be described as an example, and description of the sensor slave units 1b and 1c for measuring temperature and humidity will be omitted. Further, in the following description, when a description specific to each sensor slave unit is given, it is distinguished from the sensor slave units 1a, 1b, 1c, and 1d, and a general description not related to the type of the sensor slave unit is given. In this case, the sensor slave unit 1 is indicated.

  As shown in FIG. 1A, the sensor slave unit 1a includes an MCU (Micro Control Unit) 10, a sensor unit 11, a storage unit 12, a wireless communication unit 13, an antenna (ANT) 14, and an operation unit. 15, a display unit 16, and a power supply unit 17.

  The MCU 10 performs overall control of the sensor slave unit 1a.

  The sensor unit 11 is composed of an illuminance sensor such as a photodiode, for example, and outputs a signal whose signal level changes according to ambient illuminance. In addition, the sensor part 11 changes with kinds of the sensor subunit | mobile_unit 1, and each should just be provided with the sensor part 11 for measuring the physical quantity made into a measuring object. By the way, the illuminance may change in a shorter time than the temperature and humidity due to the influence of changes in external light, lighting / extinguishing of the lighting fixture, etc., so the sensor unit 11 that measures the illuminance measures the temperature and humidity. It is preferable to shorten the measurement interval compared to the sensor unit 11 that performs the measurement. On the other hand, since the temperature and humidity change more slowly than the illuminance, the sensor unit 11 that measures the temperature and humidity may have a longer measurement interval than the sensor unit 11 that measures the illuminance. This can save power. In this system, in the case of the sensor slave units 1a and 1d that measure illuminance, the measurement interval of the sensor unit 11 is 1 second, and in the case of the sensor slave units 1b and 1c that measure temperature and humidity, the measurement interval of the sensor unit 11 is 10 seconds. I'm trying.

  The storage unit 12 includes a nonvolatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory). Data is written to and read from the storage unit 12 by the MCU 10. The storage unit 12 stores a group number assigned to the wireless master device 2 with which the own device communicates, a station number and child device ID assigned to the own device, and a measurement interval at which the sensor unit 11 measures illuminance (for example, 10 Second) and a transmission interval (for example, 10 minutes) for transmitting measurement data. The station number is an identification number assigned to each of a plurality of sensor slave units 1 belonging to the same group in order from No. 1. The slave unit ID is a physical address unique to a device such as a MAC address. It is. The storage unit 12 sequentially stores illuminance measurement data measured by the sensor unit 11.

  The wireless communication unit 13 (first communication unit) includes, for example, a specific low-power wireless module, and transmits or receives a wireless signal via the antenna 14. The wireless communication unit 13 includes a wireless module capable of communication (multi-band communication) in a plurality of frequency bands (for example, 2.4 GHz band and 920 MHz band), and the frequency band used by the MCU 10 is switched. In the storage unit 12, the group number of the wireless master device 2 with which the own device communicates, the station number and the child device ID assigned to the own device are registered in advance. A wireless signal including identification information including a group number and a station number (or a slave unit ID) is transmitted and received between the sensor slave unit 1 and the wireless master unit 2, and the sensor slave unit 1 and the wireless master unit 2 transmit a radio signal. The communication partner is specified based on the identification information included in the.

  The operation unit 15 is, for example, an operation for setting a lower limit value and an upper limit value of measurement data, and an operation for switching an operation state of a corresponding environmental control device (for example, a lighting fixture 5 that uses an LED as a light source and can be dimmed) Used to do so.

  The display unit 16 includes, for example, one or more light emitting diodes, and lights up, blinks, or turns off each light emitting diode under the control of the MCU 10.

  The power supply unit 17 supplies power necessary for the operation to the internal circuit of the sensor slave unit 1a using, for example, a battery as a power source. The power supply unit 17 includes a power generation element such as a photovoltaic power generation element that generates power with sunlight or light from a fluorescent lamp, or a piezoelectric element that generates power when vibration or distortion is applied, and a part or all of the power necessary for power generation. You may make it cover.

  In the sensor slave unit 1, in order to reduce power consumption, a power saving mode is used except when the sensor unit 11 performs measurement and during which the wireless communication unit 13 wirelessly transmits measurement data of the sensor unit 11 to the wireless master unit 2. Works with. In the power saving mode, the MCU 10 operates in the sleep (Sleep) mode and stops the operation of the wireless communication unit 13 to reduce the power consumption compared to the normal time. During this time, data transmission and reception cannot be performed. It has become.

  FIG. 1B is a block configuration diagram of the wireless master device 2. The wireless master device 2 includes an MCU 20, a wireless communication unit 21, an antenna (ANT) 22, a wired communication unit 23, a measurement unit 24, A storage unit 25, an operation unit 26, a display unit 27, and a power supply unit 28 are provided.

  The MCU 20 performs overall control of the wireless master device 2.

  The wireless communication unit 21 (second communication unit) includes, for example, a specific low power wireless module, and transmits or receives a wireless signal via the antenna 22. The wireless communication unit 21 includes a wireless module capable of communication (multiband communication) in a plurality of frequency bands (for example, 2.4 GHz band and 920 MHz band), and the frequency band used by the MCU 20 is switched. In a storage unit 25 to be described later, a group number assigned to the own device, and a station number and a child device ID of the sensor slave device 1 that communicates with the own device are registered. A wireless signal including identification information including a group number and a station number (or a slave unit ID) is transmitted and received between the sensor slave unit 1 and the wireless master unit 2, and the sensor slave unit 1 and the wireless master unit 2 convert the radio signal into a radio signal. A communication partner is specified based on the included identification information.

  The wired communication unit 23 includes a communication module that performs serial communication in a wired manner, and performs wired serial data communication with the control device 3 connected to the wireless master device 2 via a communication line.

  The measurement unit 24 measures, for example, a received signal strength indication (RSSI) of a radio wave received by the wireless communication unit 21.

  The storage unit 25 includes a nonvolatile memory such as an EEPROM, and data is read and written by the MCU 20. In the storage unit 25, a group number assigned to the own device, and a station number and a child device ID of the sensor slave device 1 communicating with the own device are registered. The MCU 20 stores the measurement data received from the sensor slave unit 1 by the wireless communication unit 21 in the storage area of the storage unit 25 assigned to each sensor slave unit 1. When the wired communication unit 23 receives a data transmission request from the control device 3, the MCU 20 reads the measurement data of the desired sensor slave unit 1 from the storage unit 25 and transmits the measurement data from the wired communication unit 23 to the control device 3.

  The operation unit 26 includes a plurality of operation buttons (not shown), and outputs a signal corresponding to the operation to the MCU 20 when the operation button is operated.

  The display unit 27 includes a liquid crystal display (LCD) that performs segment display, for example, and the display is controlled by the MCU 20.

  The power supply unit 28 is supplied with power from, for example, a commercial AC power supply, and supplies power necessary for operation to the internal circuit of the wireless master device 2.

  The control device 3 is configured by, for example, a notebook personal computer or a server computer. FIG. 1C is a block configuration diagram of the control device 3. The control device 3 includes a CPU 30, a communication unit 31, a storage unit 32, a power supply unit 33, a display unit 34, and an operation unit 35. ing.

  A CPU (Central Processing Unit) 30 performs overall control of the control device 3.

  The communication unit 31 includes a communication module that performs serial communication using a wired method. The communication unit 31 performs data communication with the wireless master device 2, the lighting device 5, and the air conditioner 6 that are connected to each other via a communication line.

  The storage unit 32 includes an external storage device such as a hard disk, and stores measurement data of the sensor slave units 1a, 1b, 1c, and 1d received by the communication unit 31 via the wireless master unit 2.

  The power supply unit 33 is supplied with power from a commercial AC power supply, for example, and supplies power necessary for operation to the internal circuit of the control device 3.

  The display unit 34 includes a display device, for example, and displays various setting screens and monitor screens.

  The operation unit 35 is composed of an input device such as a keyboard and a mouse, for example, and the operation unit 35 is used by an administrator of the system to perform some input.

  Next, of the operations of this system, the operation in which the sensor slave unit 1 transmits measurement data to the wireless master unit 2 will be described with reference to the flowchart of FIG. By the way, when the timing at which measurement data is transmitted from a plurality of sensor slave units 1 overlaps, the transmission data collides, a communication failure occurs, and the reliability of wireless communication is reduced. Therefore, in the present embodiment, the wireless master unit 2 adjusts the timing at which each sensor slave unit 1 transmits measurement data so that the timing at which measurement data is transmitted from a plurality of sensor slave units 1 does not overlap. A method for adjusting the transmission timing will also be described below.

  This system is for optimally controlling the operation of the lighting fixture 5 and the air conditioner 6 according to the surrounding environment in an office, for example. The sensor slave units 1a to 1d and the wireless master unit 2 are used by general users. Not installed by the contractor of this system. Therefore, the contractor knows in advance the number and installation locations of the sensor slave unit 1 and the wireless master unit 2 to be used and the correspondence relationship between the sensor slave unit 1 and the wireless master unit 2. Therefore, it is assumed that information such as the slave unit ID, measurement interval, and transmission interval of the sensor slave units 1a to 1d communicating with the wireless master unit 2 is manually input in advance to the wireless master unit 2 by the construction staff. Give an explanation.

  After installing the wireless master device 2, the contractor turns on the wireless master device 2 and activates the master device 2. Thereafter, when the person in charge installs the sensor slave unit 1 and sets the battery in the sensor slave unit 1 (step S1 in FIG. 3), the MCU 10 of the sensor slave unit 1 determines the remaining amount of the battery included in the power supply unit 17. Measure and compare the remaining battery level with a predetermined threshold (step S2).

  If the remaining battery level is below the threshold (No in step S2), the MCU 10 determines that the remaining battery level is insufficient, and blinks the light emitting diode (LED) included in the display unit 16 to thereby switch the battery. Insufficient remaining amount is notified (step S3).

  If the remaining battery level is equal to or greater than the threshold (Yes in step S2), the MCU 10 starts the initial setting (step S4). That is, the MCU 10 reads out information such as the group number, its own slave unit ID, the measurement interval, the transmission interval, and the wireless communication channel from the storage unit 12, performs initial setting (step S5), and completes the initial setting. The mode is switched to the sleep mode (step S6). Note that the MCU 10 switches the operation mode to the sleep mode except when data is measured or transmitted, thereby reducing power consumption and suppressing the remaining battery capacity from decreasing.

  The sensor slave unit 1 includes a wake-up timer (not shown), and when a predetermined measurement interval elapses, the MCU 10 is waked up from the sleep mode to the normal mode by the wake-up timer (step S7). When the MCU 10 switches from the sleep mode to the normal mode, the MCU 10 outputs a command for causing the sensor unit 11 to perform measurement (step S8), and acquires measurement data from the sensor unit 11 (step S9). In the flowchart of FIG. 3, the case where the measurement interval and the transmission interval of the sensor slave unit 1a are set to the same time interval is described. When the measurement interval is shorter than the transmission interval and a plurality of measurements can be performed before the next transmission timing, the sensor slave unit 1 is activated by the wake-up timer every time the measurement interval elapses, and the sensor unit 11 performs measurement. Let the action take place. When the change from the previous measurement data exceeds a predetermined threshold, the MCU 10 may cause the wireless communication unit 13 to transmit the measurement data without waiting for the transmission interval to elapse.

  When the MCU 10 acquires the measurement data from the sensor unit 11, the MCU 10 measures the remaining battery level of the power supply unit 17 and compares the remaining battery level with a predetermined threshold (step S10).

  Here, if the remaining battery level is below the threshold (No in step S10), the MCU 10 determines that the remaining battery level is insufficient, and blinks the light-emitting diodes provided in the display unit 16 to blink the battery. The shortage of the remaining amount is notified (step S11).

  On the other hand, if the remaining battery level is equal to or greater than the threshold (Yes in step S10), the MCU 10 starts measurement data transmission processing. The MCU 10 causes the wireless communication unit 13 to perform carrier sense before making the wireless communication unit 13 perform data transmission, and confirms whether or not the communication channel is free (step S12).

  If the communication channel is free, the MCU 10 determines whether or not the number of transmissions since power-on is less than or equal to the predetermined number X (step S13).

  If the number of transmissions since power-on is equal to or less than the predetermined number X (Yes in step S13), the MCU 10 transmits measurement data from the wireless communication unit 13 to the wireless master device 2 (step S14), and then the wireless communication unit 13 is switched to the reception state for a predetermined time (step S15). When the offset time transmitted from the wireless master device 2 is received by the wireless communication unit 13 at a certain time after switching to the reception state, the MCU 10 determines that the transmission interval is based on the time when the transmission timing is shifted by the offset time. Transmit measurement data every time it passes. When a predetermined time has elapsed since switching to the reception state, the MCU 10 stops the operation of the wireless communication unit 13 and switches to the sleep state, and then maintains the sleep state until it is activated by the wakeup timer. (Step S16).

  By the way, the wireless master device 2 determines an offset time for shifting the transmission timing of the sensor slave device 1 so that data transmitted from the plurality of sensor slave devices 1 do not collide, and the determined offset time is used as the sensor slave device 1. Send to. Here, a method for determining the offset time will be described below. Information on the measurement interval and transmission interval of the sensor slave unit 1 communicating with the wireless master unit 2 is registered in advance in the wireless master unit 2, and the common divisor obtained from the measurement interval and transmission interval of each sensor slave unit 1 is obtained. The reception period. The wireless master device 2 assigns each sensor slave device 1 with a plurality of reception timings obtained by equally dividing the reception period by the number of sensor slave devices 1 (for example, the maximum number of sensor slave devices 1 connected). Here, the reception timing assigned to each sensor slave unit 1 is a transmission timing at which the sensor slave unit 1 transmits measurement data to the wireless master unit 2. Of the common divisors of the measurement interval and transmission interval of each sensor slave unit 1, the greatest common divisor may be used as the reception period. By making the transmission timing of each sensor slave unit 1 as long as possible, the power of the sensor slave unit 1 can be increased. Consumption can be reduced as much as possible.

  FIG. 4A is an explanatory diagram of a method for determining a reception timing at which the wireless master device 2 receives measurement data from each sensor slave device 1. Measured from one sensor slave unit 1 where T is the reception period that is a common divisor of the measurement interval and transmission interval of each sensor slave unit 1 and N is the maximum number of connected sensor slave units 1 (N is a positive integer). The time width ΔT reserved for receiving data is ΔT = T / N.

  For example, when the measurement interval of the sensor slave units 1a and 1d for measuring illuminance is 1 second, the transmission interval is 10 minutes, and the measurement interval and the transmission interval of the sensor slave units 1b and 1c for measuring temperature and humidity are both 10 minutes, the measurement is performed. The reception interval T, which is a common divisor of the interval and the transmission interval, is set to 1 second. When the maximum number of connected sensor slave units 1 is 200, the time width ΔT for receiving measurement data from one sensor slave unit 1 is ΔT = 1/200 = 5 (msec). For example, in each reception period T, the wireless master device 2 assigns reception periods for receiving measurement data from each sensor slave unit 1 in ascending order of station numbers. In this case, the reception timing for receiving the measurement data from the sensor slave unit 1 whose station number is n (n is an integer from 1 to N) is ((n−1) × ΔT) seconds after the start time of the reception period T. To (n × ΔT) seconds later. Therefore, the reception timing of the sensor slave unit 1 with the station number 2 is set to a time from 0.005 seconds to 0.010 seconds after the start time of the reception period T. In addition, the reception timing of the sensor slave unit 1 whose station number is 100 is set to a time from 0.495 seconds after the start time of the reception period T to 0.500 seconds later. In this embodiment, since one transmission data is 40 bytes and the communication speed of wireless communication is 250 kbps, the time required to transmit one transmission data is 1.28 ms, and the above reception timing It becomes shorter than ΔT (5 milliseconds). Therefore, if the reception period of each sensor slave unit 1 is divided as described above, it is possible to avoid collision of measurement data from the plurality of sensor slave units 1.

  As described above, the wireless master unit 2 determines the transmission timing of each sensor slave unit 1, but since communication is not synchronized between the sensor slave unit 1 and the master unit 2 immediately after startup, Measurement data is transmitted from the sensor slave unit 1 at an arbitrary timing. For example, as shown in FIG. 4B, when the wireless master device 2 receives measurement data from the sensor slave device 1 with the station number n when the time t1 has elapsed from the start of the reception period T, 2 is an offset time dt1 (= (n−1) × ΔT) for matching the timing at which the sensor slave unit 1 transmits measurement data to the transmission timing ((n−1) × ΔT) corresponding to the station number n. -T1) is obtained. Then, the wireless master device 2 returns the offset time dt1 to the sensor slave device 1 that is the transmission source. If the number of transmissions since the power is turned on is equal to or less than the predetermined number X, the sensor slave unit 1 operates for a certain period of time after the measurement data is transmitted. When the offset time is transmitted, this offset time can be received. When the sensor slave unit 1 receives the offset time transmitted from the wireless master unit 2, each time the transmission interval assigned to the own unit elapses with reference to the time obtained by shifting the previous transmission timing by the offset time. Send measurement data.

  Thus, by shifting the transmission timing by the offset time transmitted from each wireless slave unit 2 by each sensor slave unit 1, the transmission timing of each sensor slave unit 1 can be shifted by ΔT. It is possible to reduce the possibility of collision of measurement data transmitted from.

  If it is determined in step S13 that the number of transmissions since power-on is greater than the predetermined number X (No in step S13), the MCU 10 transmits measurement data from the wireless communication unit 13 to the wireless master device 2 (step S13). S16), the state is switched to the sleep state (step S17). Then, the MCU 10 maintains the sleep state until the next wakeup timer is activated. If the number of transmissions since power-on is X or less, the sensor slave unit 1 switches to a reception state after transmitting measurement data and waits for reception of an offset time transmitted from the wireless master unit 2. Therefore, it is considered that the offset time can be received during this period. Therefore, if the number of transmissions since power-on exceeds X times, the sensor slave unit 1 switches to the sleep state after transmitting measurement data, and does not wait for reception for a certain period of time, further reducing power consumption. it can.

  As described above, when the wireless master device 2 receives the measurement data from the sensor slave device 1, the wireless master device 2 temporarily stores the received measurement data in the storage area assigned to each sensor slave device in the storage unit 25. The CPU 30 of the control device 3 transmits a data transmission request from the communication unit 31 to the wireless master device 2 at a predetermined timing in order to be used for control of the environment control device 4. When the data transmission request is received by the wired communication unit 23 of the wireless master device 2, the data transmission request is output from the wired communication unit 23 to the MCU 20, and the MCU 20 transmits the measurement data of the desired sensor slave device 1 from the storage unit 25. Is transmitted from the wired communication unit 23 to the control device 3.

  When the communication unit 31 of the control device 3 receives the measurement data sent back from the wireless master device 2 in response to the data transmission request, the CPU 30 stores the measurement data received by the communication unit 31 in the storage unit 32 and stores each measurement data. The measurement data measured by the sensor slave unit 1 is managed. Here, in the storage unit 32, a storage area for storing measurement data in the order of measurement time is set.

  Then, the CPU 30 of the control device 3 controls the operating state of the corresponding environment control device 4 (the lighting device 5 or the air conditioning device 6) based on the measurement data stored in the storage unit 32. For example, the CPU 30 controls the dimming of the lighting fixture 5 capable of dimming control so that the brightness in the control area becomes a predetermined brightness based on the measurement data of the illuminance measured by the sensor slave units 1a and 1d. Control the level. The CPU 30 controls the output of the air conditioner 6 so that the temperature and humidity in the control area are in a desired state based on the temperature and humidity measurement data measured by the sensor slave units 1b and 1c. Thus, since the control apparatus 30 controls operation | movement of the lighting fixture 5 and the air conditioner 6 based on the measurement data of the illumination intensity, temperature, and humidity which were collected by the sensor data collection system, excessive lighting control and air conditioning control are performed. Can be suppressed, and power saving can be realized.

  As described above, the sensor data collection system of this embodiment includes a plurality of sensor slave units 1 and the wireless master unit 2. The sensor slave unit 1 includes a sensor unit 11 that measures a state quantity of a measurement target every time a measurement interval set in each sensor slave unit 1 elapses, and a transmission interval set in each sensor slave unit 1 elapses. A wireless communication unit 13 that wirelessly transmits measurement data of the sensor unit 11 to the wireless master device 2 is provided. The wireless master device 2 includes a wireless communication unit 21 that performs wireless communication with the wireless communication unit 13, and an MCU 20 that serves as an information acquisition unit and a time adjustment unit. The MCU 20 as the information acquisition unit acquires at least one of the measurement interval and the transmission interval for each of the plurality of sensor slave units 1. The MCU 20 as the time adjustment unit obtains an offset time for shifting the transmission timing of the sensor slave unit 1 based on the information acquired by the information acquisition unit, and transmits the offset time from the wireless communication unit 21 to the sensor slave unit 1. When the wireless communication unit 13 receives the offset time transmitted from the wireless parent device 2, the sensor slave unit 1 receives the offset time from the wireless communication unit 13 every time the transmission interval elapses with reference to the time when the transmission timing is shifted by the offset time. Measurement data is transmitted wirelessly.

  That is, when the MCU 20 of the wireless master unit 2 acquires at least one of the measurement interval and the transmission interval for each sensor slave unit 1, the offset that shifts the transmission timing of the sensor slave unit based on this information The time is determined and transmitted from the second communication unit to the sensor slave unit. And each sensor subunit | mobile_unit 1 will transmit measurement data, every time a transmission interval passes, on the basis of the time which shifted the last transmission timing by offset time, if offset time is received from the wireless main | base station 2. FIG. Therefore, it is possible to reduce the possibility that transmission data from a plurality of sensor slave units collide, and it is possible to suppress the occurrence of communication failure and improve the reliability of wireless communication. In the present embodiment, the information acquisition unit and the time adjustment unit are realized by the calculation function of the MCU 20 included in the wireless master device 2.

  Moreover, in this embodiment, MCU20 which is a time adjustment part makes the common divisor calculated | required from the measurement interval and transmission interval of several sensor subunit | mobile_units 1 as the reception period T, and this reception period T is the number of sensor subunit | mobile_units 1 etc. The divided reception timing is assigned to each sensor slave unit 1. The MCU 20 determines the offset time so that the transmission timing matches the reception timing assigned to each sensor slave unit 1.

  As a result, the common divisor obtained from the measurement intervals and transmission intervals of the plurality of sensor slave units 1 is defined as the reception period T, and the reception timing is obtained by equally dividing the reception period T by the number of sensor slave units 1. The measurement data from the sensor slave unit 1 can be received. Therefore, the possibility that transmission data from a plurality of sensor slave units 1 collide can be reduced, and the occurrence of communication failure can be suppressed and the reliability of wireless communication can be improved.

  In the present embodiment, the person in charge of the construction operates the operation unit 26 of the wireless master device 2 to provide information such as the slave device IDs, measurement intervals, and transmission intervals of the sensor slave devices 1a to 1d to the wireless master device 2. Although input, these pieces of information may be transmitted from the sensor slave unit 1 to the wireless master unit 2. Information such as a slave unit ID, a measurement interval, and a transmission interval is preset in each sensor slave unit 1 at the time of factory shipment or installation, and the wireless master unit 2 communicates with the sensor slave unit 1 in the search mode. In this case, the above information is acquired from the sensor slave unit 1. At the time of installing the sensor slave unit 1, in order to register the slave unit ID of the sensor slave unit 1 in the wireless master unit 2, the person in charge of construction sets the operation mode of the wireless slave unit 2 to the sensor slave unit 1 in the communication area. While switching to the search mode for searching, the sensor slave unit 1 is powered on. When the wireless master device 2 is switched to the search mode, the wireless slave device 2 broadcasts a request signal for requesting a response signal to be returned to the sensor slave device 1 in the communication area. When receiving the request signal transmitted from the wireless master device 2, the sensor slave device 1 in the communication area returns a response signal including the slave device ID of the own device to the wireless master device 2. As a result, the wireless master device 2 can acquire the slave device ID from the sensor slave device 1 in the communication area, assigns a station number to the sensor slave device 1 that has transmitted the slave device ID, and transmits this station number to the sensor slave device 1. By doing so, a station number is set for each sensor slave unit 1. Here, when the sensor slave unit 1 returns a response signal in response to the request signal from the wireless master unit 2, the information of the measurement interval and the transmission interval set in the own unit is stored together with the slave unit ID. You may return it to Thereby, the wireless master device 2 can automatically acquire information such as the slave device ID, the measurement interval, and the transmission interval from the sensor slave device 1, and the person in charge of the construction can obtain information such as the slave device ID, the measurement interval, and the transmission interval. Manual input can be saved.

  By the way, since the sensor slave unit 1 operates using a battery as a power source, the power supply voltage is unstable and the accuracy of the clock signal is low as compared with the wireless master unit 2 that receives power supply from a commercial power source. For this reason, when used for a long time, the time difference between the watch of the sensor slave unit 1 and the watch of the wireless master unit 2 increases, and transmission data may collide. Therefore, the sensor slave unit 1 transmits transmission data including measurement data and a synchronization request flag to the wireless master unit 2 every time a predetermined time elapses (for example, every 24 hours). In the wireless master device 2, when the wireless communication unit 21 receives the synchronization request flag included in the transmission data from the sensor slave device 1, the MCU 20 serving as the time adjustment unit offsets the sensor slave device 1 that is the transmission source of the synchronization request flag. The time is determined and transmitted from the wireless communication unit 21 to the sensor slave unit 1. Then, when the sensor slave unit 1 that has transmitted the synchronization request flag receives the offset time transmitted from the wireless master unit 2, it is measured every time the measurement interval elapses with reference to the time when the previous transmission timing is shifted by the offset time. Data is transmitted and the time gap can be corrected. Here, the time interval for correcting the time shift can be appropriately changed according to the accuracy of the clocks of the sensor slave unit 1 and the wireless master unit 2 so that the correction can be performed before the time shift becomes excessive. What is necessary is just to set the time interval which correct | amends the time gap.

  Although the sensor slave unit 1 transmits the synchronization request flag every predetermined time, the sensor slave unit 1 may transmit the synchronization request flag to the wireless master unit 2 every predetermined number of transmissions. Misalignment can be corrected. By setting the predetermined number of transmissions optimally in accordance with the accuracy of the clocks of the sensor slave unit 1 and the wireless master unit 2, the time difference between the sensor slave unit 1 and the wireless master unit 2 can be reduced. Can be corrected, and the possibility of collision of transmission data can be reduced.

  Further, when transmitting the measurement data, the sensor slave unit 1 may always transmit the synchronization request flag together with the measurement data, and the time difference between each sensor slave unit 1 and the wireless master unit 2 can be further reduced.

  In the present embodiment, the wireless communication unit 13 (first communication unit) of the sensor slave unit 1 and the wireless communication unit 21 (second communication unit) of the wireless base unit 2 communicate in a plurality of frequency bands (multi-carriers). When communication is possible, communication may be performed by selecting a frequency band having a good reception state as follows. That is, the wireless communication unit 13 of the sensor slave unit 1 communicates with the wireless master unit 2 in a plurality of available frequency bands at the time of activation. Then, the measurement unit 24 of the wireless master device 2 measures the received signal strength in each of a plurality of frequency bands, selects a frequency band having a higher received signal strength based on the measurement result, and selects the selected frequency band. A control command instructing to use is transmitted from the wireless communication unit 21 to the sensor slave unit 1. Thereby, between the sensor slave unit 1 and the wireless master unit 2, communication can be performed by selecting a frequency band having a higher received signal strength, and thus the reliability of the wireless communication is improved.

  Further, when the wireless communication units 13 and 21 can perform communication using at least 2.4 GHz band and 920 MHz band as a plurality of frequency bands, the frequency band to be used may be selected as follows. That is, at the time of activation, the wireless communication unit 13 of the sensor slave unit 1 communicates with the wireless master unit 2 in a plurality of available frequency bands, and the measurement unit 24 of the wireless master unit 2 receives in each of the plurality of frequency bands. Measure signal strength. Based on the measurement result of the received signal strength, if the received signal strength in both frequency bands is equal, or if the received signal strength in both frequency bands is equal to or greater than a predetermined threshold, the wireless master device 2 is 2 A control command for instructing to use the 4 GHz band is transmitted from the wireless communication unit 21 to the sensor slave unit 1. Here, the communication in the 2.4 GHz band can be performed at a higher speed than the communication in the 920 MHz band, and the communication time can be shortened, so that power saving can be achieved. On the other hand, the communication in the 920 MHz band has a larger radio wave wrapping characteristic than the communication in the 2.4 GHz band, and enables long-distance communication. Therefore, if the received signal strength in both frequency bands is equal, or if the received signal strength in both frequency bands is equal to or greater than a predetermined threshold, high-speed communication is possible by using the 2.4 GHz band, Power saving can be realized. On the other hand, if the received signal strength in any frequency band is less than the threshold value, the wireless master device 2 transmits a control command instructing to use a frequency band having a higher received signal strength to the sensor slave device 1. Thus, the reliability of wireless communication can be improved.

  In addition, when the wireless communication units 13 and 21 can communicate using at least 2.4 GHz band and 920 MHz band as a plurality of frequency bands, the transmission output in each frequency band can be set as follows. Good. That is, at the time of activation, the wireless communication unit 13 of the sensor slave unit 1 communicates with the wireless master unit 2 in a plurality of available frequency bands, and the measurement unit 24 of the wireless master unit 2 receives in each of the plurality of frequency bands. Measure signal strength. Here, if the received signal strength in both frequency bands is equal to or higher than a predetermined threshold, the wireless master device 2 instructs to reduce the transmission power in the 920 MHz band rather than the transmission power in the 2.4 GHz band. A control command to be transmitted is transmitted from the wireless communication unit 21 to the sensor slave unit 1. As described above, communication in the 920 MHz band has greater radio wave wrapping characteristics than long-distance communication compared to communication in the 2.4 GHz band. Therefore, if the received signal strength in both frequency bands is equal to or higher than a predetermined threshold, the wireless master device 2 reduces the transmission power in the 920 MHz band to each sensor slave device 1 compared to the transmission power in the 2.4 GHz band. This can save power.

  In addition, when the antenna 22 of the wireless master device 2 has a variable directivity, when the wireless master device 2 receives the measurement data sequentially from the plurality of sensor slave devices 1, the measurement data is transmitted next. It is also preferable to change the directivity characteristic of the antenna 22 in the direction of the sensor slave unit 1 to be transmitted.

  The antenna 22 is configured such that the peak of the horizontal plane directivity can be varied by 360 degrees in the horizontal plane. For example, as shown in FIG. 5, a pair of linear antennas 22a and 22b and a pair of linear antennas 22a and 22b are provided. The drive part 22c rotated in the plane parallel to a horizontal surface is provided.

  When the wireless master device 2 is switched to the registration mode in order to register the sensor slave device 1, the wireless master device 2 broadcasts a request signal for requesting a response signal to be returned. Thereafter, when the sensor slave unit 1 is activated, the sensor slave unit 1 returns a response signal to the request signal from the wireless master unit 2. On the other hand, the MCU 20 of the radio cell station 2 broadcasts the request signal, and then outputs a control signal to the driving unit 22c, so that the driving unit 22c sweeps the peak of the horizontal plane directivity at least 360 degrees in the horizontal plane. The linear antennas 22a and 22b are rotated. At this time, the MCU 20 causes the measurement unit 24 to measure the received signal strength, and based on the measurement result, detects the arrival direction in which the electric field strength (received signal strength) of the radio wave is higher, and this direction is used as the sensor slave unit. 1 is determined and stored in the storage unit 25 together with the slave unit ID of the sensor slave unit 1. Thereafter, when the operation mode of the wireless master device 2 is switched to the normal mode and the sensor slave device 1 starts the measurement operation, measurement data is transmitted from the plurality of sensor slave devices 1 to the wireless master device 2 in a predetermined order. . When the transmission timing of each sensor slave unit 1 comes, the MCU 20 of the wireless master unit 2 controls the drive unit 22c so that the peak of the horizontal plane directivity matches the direction of the sensor slave unit 1 stored in the storage unit 25. Thus, the antennas 22a and 22b are rotated so that the transmission radio wave from the sensor slave unit 1 can be reliably received. Here, the direction detection unit and the directivity adjustment unit are configured by the drive unit 22c that rotates the linear antennas 22a and 22b and the calculation function of the MCU 20.

  Further, an individual slave unit ID is assigned to each sensor slave unit 1, and when transmitting measurement data from the sensor slave unit 1, the slave unit ID is transmitted from the sensor slave unit 1 to the wireless master unit 2 together with the measurement data. Has been sent to. When the elapsed time from the time when the measurement data is received from a certain sensor slave unit 1 exceeds the transmission interval of the sensor slave unit 1 for a predetermined determination time or longer, the MCU 20 of the wireless master unit 2 It is determined that an abnormality has occurred or communication with the sensor slave unit 1 has been disabled. Then, the MCU 20 of the wireless master device 2 transmits a signal for notifying the abnormality from the wired communication unit 23 to the control device 3 and causes the display unit 34 of the control device 3 to display the abnormality, thereby allowing the system administrator to display the sensor element. Inspection of the machine 1 and the wireless master unit 2 can be prompted.

  Although the sensor slave unit 1 transmits measurement data at a predetermined transmission interval, if the measurement data of the sensor unit 11 is equal to or lower than a predetermined lower limit value or higher than a predetermined upper limit value, the measurement data is transmitted. It is also preferred not to. For example, in lighting applications, even if the brightness changes in a low illuminance region of 100 lux or less, no change in brightness is perceived by human eyes. Therefore, if the lower limit value is set to 100 lux, the measurement data is not transmitted from the sensor slave unit 1 when the measurement data is 100 lux or less, so that the number of wireless communications can be reduced to reduce power consumption. Moreover, in the area | region more than 10,000 lux, it is sufficiently bright compared with the office lighting standard (750-1500 lux), and the required illumination intensity is ensured. Therefore, if the upper limit value is set to 10,000 lux, the measurement data is not transmitted from the sensor slave unit 1 when the measurement data is 10,000 lux or more. Consumption can be reduced. For the lower limit value and upper limit value of the measurement data, that is, the range in which data transmission is necessary, a default value preset in the sensor slave unit 1 may be used, or the user operates the operation unit 15 for each sensor slave unit 1. The value set using may be used.

(Embodiment 2)
Embodiment 2 of the present invention will be described below with reference to FIG. Since the system configuration of the control system using the data collection system is the same as that of the first embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the first embodiment, the common divisor of the transmission interval and the measurement interval of each sensor slave unit 1 is used as the reception period. However, in this embodiment, the wireless master unit 2 has a time interval for receiving measurement data from the sensor slave unit 1. Based on this, the transmission interval of the sensor slave unit 1 is detected. In the wireless master device 2, the slave device ID of each sensor slave device 1 is set manually or is automatically registered by operating in the search mode.

  When the sensor slave unit 1 and the wireless master unit 2 start operation, the sensor unit 11 of each sensor slave unit 1 measures the data to be measured at the measurement interval set in the own unit and is set in the own unit. Measurement data is transmitted to the wireless master device 2 at a transmission interval. When the wireless master device 2 receives the measurement data from the plurality of sensor slave devices 1, the transmission data is transmitted to another sensor slave device 1 based on the reception interval and the reception time at which the measurement data is received from the sensor slave device 1. The sensor slave unit 1 that is likely to collide with transmission data from is determined. For example, as shown in FIG. 6, when measurement data is transmitted from three sensor slave units 1a to 1c to the wireless master unit 2, the transmission timing of the sensor slave unit 1c overlaps with the transmission timing of the sensor slave unit 1b in the illustrated example. there is a possibility. The MCU 20 of the wireless master device 2 may collide the transmission data of the sensor slave device 1c with the transmission data of the sensor slave device 1b based on the reception interval and reception time at which the measurement data is received from each sensor slave device 1. It can be judged that it is expensive. Then, the MCU 20 of the wireless master device 2 determines the offset time dt3 for shifting the transmission timing of the sensor slave device 1c so that the transmission data does not collide, and the wireless communication unit 21 sends the data of the offset time dt3 to the sensor slave device 1c. Send.

  The wireless communication unit 13 of each sensor slave unit 1 operates in a reception state after transmission of measurement data until the number of transmissions of measurement data exceeds a predetermined number after activation. When the offset time data is transmitted from, this data can be received. When the wireless communication unit 13 of the sensor slave unit 1c receives the offset time dt3 transmitted from the wireless master unit 2, the MCU 10 transmits the transmission interval with reference to the time t3 obtained by shifting the previous transmission timing by the offset time dt3. Measurement data is transmitted every time T3 elapses.

  As described above, the MCU 20 serving as the information acquisition unit of the wireless master device 2 is configured such that the wireless communication unit 21 (second communication unit) receives measurement data from the sensor slave device 1 for each of the plurality of sensor slave devices 1. And the information of the transmission interval and transmission time of the sensor slave unit 1 is acquired from the reception time. The MCU 20 serving as a time adjustment unit uses the transmission interval and the transmission time information obtained for each sensor slave unit 1 for the sensor slave unit 1 whose transmission data is likely to collide with transmission data from other sensor slave units 1. The offset time for shifting the transmission timing is determined so that the transmission data does not collide.

  Thereby, even if the information of the transmission interval of each sensor slave unit 1 is not set in the wireless master unit 2, the wireless master unit 2 can receive the measurement data from each sensor slave unit 1 based on the reception interval and reception time. In addition, it is possible to detect the sensor slave unit 1 in which transmission data is likely to collide. For the sensor slave unit that is likely to collide with the transmission data, an offset time for shifting the transmission timing can be determined so that the transmission data does not collide, and can be set in this sensor slave unit. The possibility can be reduced. As a result, communication failures are less likely to occur, and the reliability of wireless communication is improved.

  Also in the present embodiment, in each sensor slave unit 1, the wireless communication unit 13 operates in a reception state after transmission of measurement data for a certain period of time until the measurement data transmission count exceeds a predetermined number after activation. . Therefore, if data of the offset time is transmitted from the wireless master device 2 while operating for a certain time in the reception state after transmitting the measurement data, this data can be received. Further, if the number of transmissions of measurement data exceeds a predetermined number after activation, each sensor slave unit 1 is switched to a sleep state after transmission of measurement data and does not wait for reception for a certain period of time, further reducing power consumption. it can.

  The sensor data collection system of the present invention is not limited to the configuration described in the first or second embodiment. The type and number of the sensor slave units 1a to 1d, the number of the wireless master units 2, and the type and number of the environmental control device 4 can be changed as appropriate according to the purpose of use and application. For example, the sensor data collection system may include a sensor slave unit that detects one or more of illuminance, temperature (eg, air temperature, room temperature, radiation temperature, etc.), humidity, and gas concentration (eg, CO 2 concentration). . Moreover, as a control system using the sensor data collection system of this invention, you may control a lighting fixture based on the measurement data of the illumination intensity measured with the sensor subunit | mobile_unit 1. FIG. Moreover, based on the measurement data of the temperature, humidity, and gas concentration measured by the sensor slave unit, the air conditioner 6 and the refrigeration apparatus (refrigeration apparatus) may be controlled as environment control equipment.

  In the present embodiment, the wireless master device 2 directly receives measurement data from the sensor slave device 1. However, a repeater (not shown) relays and transmits the measurement data transmitted from the sensor slave device 1 to the wireless master device 2. In this case, the wireless master device 2 and the repeater constitute a parent device. In the present embodiment, the control device 3 is provided separately from the wireless master device 2 that collects measurement data from the sensor slave device 1. However, in the case of a small-scale system, the function of the control device 3 is provided as the wireless master device 2. You may have it.

1 sensor slave unit 2 wireless master unit 10 MCU (information acquisition unit, time adjustment unit)
11 sensor unit 13 wireless communication unit (first communication unit)
20 MCU
21 Wireless communication unit (second communication unit)

Claims (11)

It has a plurality of sensor slave units and a master unit,
The sensor slave unit includes a sensor unit that measures a state quantity of a measurement target every time a measurement interval set in each sensor slave unit elapses, and a transmission interval set in each sensor slave unit elapses. A first communication unit that wirelessly transmits the measurement data of the sensor unit to the master unit every time;
The base unit has at least one of the measurement interval and the transmission interval for each of the second communication unit that performs wireless communication with the first communication unit and each of the plurality of sensor slave units. Based on the information acquired by the information acquiring unit and the information acquired by the information acquiring unit, an offset time for shifting the transmission timing of the sensor slave unit is obtained, and the offset time is transmitted from the second communication unit to the sensor slave unit. A time adjustment unit,
When the sensor slave unit receives the offset time transmitted from the master unit, the first communication unit receives the offset time every time the transmission interval elapses with reference to the time when the previous transmission timing is shifted by the offset time. A sensor data collection system, wherein measurement data is wirelessly transmitted from the first communication unit.   The time adjustment unit uses a common divisor obtained from the measurement interval and the transmission interval of a plurality of sensor slave units as a reception period, and a reception timing obtained by equally dividing the reception period by the number of sensor slave units 2. The sensor according to claim 1, wherein the offset time is determined so that the transmission timing of the sensor slave unit coincides with the reception timing assigned to the sensor slave unit. Data collection system. The sensor slave unit wirelessly transmits the transmission interval information from the first communication unit to the master unit,
The sensor data collection system according to claim 1, wherein the information acquisition unit acquires the information when the second communication unit receives the information transmitted from the sensor slave unit. The information acquisition unit includes, for each of the plurality of sensor slave units, a transmission interval and a transmission time of the sensor slave unit from a time interval and a reception time at which the second communication unit receives measurement data from the sensor slave unit. Get information about
The time adjustment unit is based on the transmission interval and transmission time information obtained for each of the sensor slave units, and the sensor slave unit is likely to collide with transmission data from other sensor slave units. 2. The sensor data collection system according to claim 1, wherein an offset time for shifting transmission timing is determined so that transmission data does not collide.   2. The sensor data according to claim 1, wherein the first communication unit of the sensor slave unit operates in a reception state after transmission of measurement data until the number of transmissions of measurement data exceeds a predetermined number after activation. Collection system. The first communication unit of the sensor slave unit transmits transmission data including measurement data and a synchronization request flag to the master unit,
In the master unit, when the second communication unit receives the synchronization request flag included in the transmission data from the sensor slave unit, the time adjustment unit offsets the sensor slave unit that is the transmission source of the synchronization request flag. The sensor data collection system according to claim 1, wherein time is determined and wireless transmission is performed from the second communication unit.   The sensor data collection system according to claim 6, wherein the sensor slave unit transmits the synchronization request flag every predetermined number of transmissions or every predetermined time. Each of the first communication unit and the second communication unit can communicate in a plurality of frequency bands,
The first communication unit of the sensor slave unit communicates with the master unit in a plurality of available frequency bands when activated,
The base unit selects a frequency band having a higher received signal strength based on the received signal strength received from the sensor slave unit in each of a plurality of frequency bands, and instructs to use the selected frequency band. The sensor data collection system according to claim 1, wherein a control command is transmitted from the second communication unit to the sensor slave unit. Each of the first communication unit and the second communication unit can communicate using at least 2.4 GHz band and 920 MHz band as a plurality of frequency bands,
The first communication unit of the sensor slave unit transmits a radio signal to the master unit in both the 2.4 GHz band and the 920 MHz band at startup,
If the received signal strength in both of the frequency bands is equal, or if the received signal strength in both of the frequency bands is equal to or greater than a predetermined threshold, the base unit instructs to use the 2.4 GHz band. The sensor data collection system according to claim 1, wherein a control command is transmitted from the second communication unit to the sensor slave unit. The first communication unit and the second communication unit can communicate using at least 2.4 GHz band and 920 MHz band as a plurality of the frequency bands,
The first communication unit of the sensor slave unit transmits a radio signal to the master unit in both the 2.4 GHz band and the 920 MHz band at startup,
If the received signal strength in both of the frequency bands is equal to or greater than a predetermined threshold, the base unit instructs the base unit to reduce the transmission power in the 920 MHz band rather than the transmission power in the 2.4 GHz band. The sensor data collection system according to claim 1, wherein the second communication unit transmits the data to the sensor slave unit. The first communication unit of the sensor slave unit transmits a radio signal to the master unit at startup,
Direction in which the base unit detects an arrival direction in which the electric field intensity of the radio wave received for each sensor slave unit is higher when the base unit receives an antenna having a variable directivity and the radio wave transmitted from the sensor slave unit at the time of startup. 2. A detection unit, and a directivity adjustment unit that adjusts the directivity of the antenna in the direction of arrival detected by the direction detection unit when the transmission timing of each of the sensor slave units comes. The sensor data collection system of any one of thru | or 10.

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