Sensor systems and sensor devices

Abstract

To reduce power consumption of a sensor device while improving reliability of physical quantity measurement by targeting more measurement objects.SOLUTION: A sensor system has a first sensor device and a second sensor device. The first sensor device comprises a first communication unit and a first control unit, and the second sensor device comprises a second communication unit and a second control unit. The first sensor device causes the first communication unit to perform a transmission operation for transmitting a first communication signal including a measurement value of a physical quantity of a measurement object for every communication period as a fixed period predetermined in a fixed cycle. The second sensor device causes the second communication unit to perform a reception operation for receiving the first communication signal transmitted from the first sensor device for every communication period and detects an abnormality in the first sensor device on the basis of whether or not the second communication unit receives the first communication signal from the first sensor device in the communication period and a content of the first communication signal when the first communication signal is received from the first sensor device.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a sensor system and a sensor device. [Background Art]

[0002] Non-Patent Literature 1 describes a technology related to wireless field devices that measure various physical quantities and transmit the measured physical quantities via wireless communication. Patent Literature 1 describes a technology related to redundancy of sensors connected to a network. [Prior Art Documents] [Non-Patent Literature]

[0003] [Non-Patent Literature 1] Yokogawa Technical Report Vol.55 No.2 (2012) [Patent Literature]

[0004] [Patent Literature 1] International Publication No. WO 2006 / 090480 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Consider a system in which a plurality of sensor devices such as wireless field devices measure physical quantities of a measurement object, and transmit measurement data to a host device via the same access point. In such a system, the plurality of sensor devices measure the physical quantity of the same measurement object, and each sensor device transmits its respective measurement data to the host device. By thus achieving redundancy using a plurality of sensor devices for the same measurement object, even if any one of the sensor devices fails, the host device can continue to acquire measurement data from other sensor devices, and the reliability of physical quantity measurement can be improved.

[0006] However, since there is an upper limit to the number of devices that can be connected to an access point simultaneously, when building the system described above using a conventional configuration, there was a limit to the number of sensor devices that could be made redundant for the same access point. Furthermore, when using the same access point and performing redundancy for each of multiple objects being measured using multiple sensor devices as described above, the number of sensor devices that can be made redundant decreases as the number of objects being measured increases, depending on the maximum number of connections to the access point. Therefore, when measuring multiple objects using the same access point with a conventional configuration, there was a trade-off between the number of objects being measured and the reliability that could be achieved through sensor device redundancy. In addition, when sensor devices operate on batteries, it is important to reduce the power consumption of the sensor devices in order to reduce the number of battery replacements, but with the conventional configuration, there was room for improvement in terms of reducing power consumption.

[0007] Therefore, this disclosure aims to improve the reliability of physical quantity measurement for a larger number of objects to be measured, while also reducing the power consumption of sensor devices. [Means for solving the problem]

[0008] Some sensor systems according to certain embodiments are (1) A sensor system having a first sensor device and a second sensor device, The first sensor device is The first communications unit, which handles communications, First control unit, Equipped with, The second sensor device is The second communications unit, which handles communications, The second control unit and Equipped with, The first control unit of the first sensor device causes the first communication unit to perform a transmission operation at communication periods, which are fixed periods predetermined to be constant, to transmit a first communication signal containing the measured value of the physical quantity of the object being measured. The second control unit of the second sensor device is During each of the aforementioned communication periods, the second communication unit is instructed to perform a receiving operation to receive the first communication signal transmitted from the first sensor device. During the aforementioned communication period, the second communication unit determines whether or not it has received the first communication signal from the first sensor device, and if it has received the first communication signal from the first sensor device, it detects an abnormality in the first sensor device based on the content of the first communication signal.

[0009] With this configuration, if an abnormality occurs in the first sensor device, the abnormality can be detected by the second sensor device. Here, since the second sensor device only receives signals while the first sensor device is transmitting signals, the power consumption of the second sensor device can be reduced when both the first and second sensor devices are battery-powered. Also, while the first sensor device is transmitting communication signals, the second sensor device only receives communication signals. Therefore, there is no upper limit to the number of sensor devices that can measure the same object being measured. Furthermore, since the sensor system uses only one communication line simultaneously, the sensor system can be connected and operated simultaneously up to the maximum number of connections for the access point, regardless of the number of sensor devices for redundancy. Therefore, it is possible to simultaneously monitor the same number of objects being measured as the maximum number of connections for each access point. Consequently, it becomes possible to improve the reliability of physical quantity measurement for a larger number of objects being measured and reduce the power consumption of the sensor devices.

[0010] In one embodiment, (2) In the sensor system of (1), If the second control unit of the second sensor device detects an abnormality in the first sensor device, it may initiate a transmission operation to the second communication unit at each communication period, transmitting a second communication signal containing the measured value of the physical quantity of the object being measured using the same communication method as the first sensor device.

[0011] Thus, when the second sensor device detects an abnormality in the first sensor device, it transmits a second communication signal containing the measured value of the physical quantity of the object being measured. Therefore, even if an abnormality occurs in the first sensor device, the transmission of the physical quantity of the object being measured can continue. Consequently, the stability of the system as one that transmits measured values ​​of physical quantities can be improved.

[0012] In one embodiment, (3)(2) In the sensor system, The first control unit of the first sensor device causes the first communication unit to transmit a signal that further includes the source network information as the first communication signal for each communication period. If the second control unit of the second sensor device detects an abnormality in the first sensor device, it may cause the second communication unit to transmit a signal as a second communication signal that further includes the same network information as the network information included in the first communication signal, for each communication period.

[0013] In this way, the second sensor device transmits a second communication signal containing the same network information as the first sensor device, allowing the device that receives the second communication signal to recognize that it is continuously receiving communication signals from the same device.

[0014] In one embodiment, (4) In the sensor system of (2) or (3), Equipped with multiple A2 sensor devices, If an abnormality is detected in the first sensor device, the second control unit of one of the second sensor devices may initiate a transmission operation to transmit a second communication signal to the communication unit at each communication period, based on a predetermined priority order of the second sensor devices.

[0015] As described above, since only one sensor device performs a communication signal transmission operation in the sensor system, redundancy can be achieved by any number of sensor devices regardless of the maximum number of connections of the access point, and the reliability of physical quantity measurement can be further improved.

[0016] In one embodiment, In the sensor system according to any one of (5) (2) to (4), the second control unit of the second sensor device causes the second communication unit to start a transmission operation of transmitting the second communication signal including the measured value of the physical quantity of the object to be measured for each communication period at a predetermined timing, the first control unit of the first sensor device, at the predetermined timing, causes the first communication unit to stop the transmission operation, and causes the first communication unit to start a reception operation for receiving the second communication signal transmitted from the second sensor device, an abnormality in the second sensor device may be detected based on whether or not the first communication unit receives the second communication signal from the second sensor device in the communication period, and based on the content of the second communication signal when the second communication signal is received from the second sensor device.

[0017] As described above, by switching between the transmission operation and the reception operation between the first sensor device and the second sensor device at a predetermined timing, the power consumption of the first sensor device in the first sensor device and the second sensor device can be reduced. Therefore, when the first sensor device is driven by a battery, the service life of the first sensor device can be extended.

[0018] In one embodiment, In the sensor system according to any one of (6) (2) to (5), the first control unit of the first sensor device causes the first communication unit to transmit, as the first communication signal, a signal including a measured value of the physical quantity of the object to be measured measured by the first measurement unit for each communication period, If the second control unit of the second sensor device detects an abnormality in the first sensor device, it may, at each communication period, cause the second communication unit to transmit a signal as the second communication signal that includes the measured value of the physical quantity of the object to be measured, measured by the second measurement unit, and corrected according to the correspondence between the measurement result of the first measurement unit and the measurement result of the second measurement unit.

[0019] In this way, when the second sensor device detects an abnormality in the first sensor device, it corrects the measurement value of the second measurement unit according to the characteristics of the first and second measurement units before transmitting it, thereby reducing fluctuations in the measurement value due to measurement variations in the characteristics of the first and second measurement units.

[0020] In one embodiment, (7) In any of the sensor systems described in (1) through (5), The first control unit of the first sensor device causes the first communication unit to transmit a signal including the measured value of the physical quantity of the object being measured, measured by the first measurement unit, as the first communication signal for each communication period. The second control unit of the second sensor device may detect an abnormality in the first sensor device based on a comparison between the measured value of the physical quantity measured by the first measuring unit included in the first communication signal received from the first sensor device and the measured value of the physical quantity of the object being measured measured by the second measuring unit.

[0021] In this way, the second sensor device can detect an abnormality in the first measurement unit by comparing the measured value of the physical quantity measured by the first measurement unit with the measured value of the physical quantity measured by the second measurement unit.

[0022] In one embodiment, (8) In any of the sensor systems described in (1) through (7), The second control unit of the second sensor device may detect an abnormality in the first sensor device if it does not receive the first communication signal during the communication period.

[0023] In this way, the second sensor device can detect an abnormality in the first sensor device if it does not receive the first communication signal during the communication period, thereby detecting battery depletion in the first sensor device or an abnormality in the first communication unit, etc.

[0024] In one embodiment, (9) In any of the sensor systems described in (1) through (8), When the first control unit of the first sensor device detects an abnormality in the first sensor device, it causes the first communication unit to transmit an abnormality signal as a first communication signal. The second control unit of the second sensor device may detect an abnormality in the first sensor device when it receives the abnormality signal from the first sensor device.

[0025] In this way, the second sensor device can recognize the abnormality detected by the first sensor device by receiving an abnormality signal from the first sensor device.

[0026] Some sensor devices according to certain embodiments include: (10) A sensor device comprising a measuring unit for measuring the physical quantity of an object to be measured, a communication unit for communication, and a control unit, The control unit, At each communication period, which is a fixed period predetermined at a certain interval, the communication unit is instructed to perform a receiving operation to receive a first communication signal containing the measured value of the physical quantity of the object being measured from another sensor device. During the aforementioned communication period, the communication unit determines whether or not it received the first communication signal from the other sensor device, and if it did receive the first communication signal from the other sensor device, it detects an abnormality in the other sensor device based on the content of the first communication signal. If an abnormality is detected in the other sensor device, the communication unit is instructed to perform a transmission operation at each communication period, transmitting a second communication signal containing the measured value of the physical quantity of the object being measured, measured by the measurement unit, using the same communication method as the other sensor device.

[0027] In this way, the sensor device transmits a second communication signal containing the measured physical quantity of the object being measured when it detects an abnormality in another sensor device. Therefore, even if an abnormality occurs in another sensor device, it can continue to transmit the physical quantity of the object being measured. Consequently, the stability of the system as a system for transmitting measured physical quantities can be improved. [Effects of the Invention]

[0028] According to one embodiment of the present disclosure, the reliability of physical quantity measurement can be improved for a larger number of objects to be measured, and the power consumption of the sensor device can be reduced. [Brief explanation of the drawing]

[0029] [Figure 1] This figure shows an example configuration of a sensor system according to one embodiment of the present disclosure. [Figure 2] Figure 1 is a block diagram showing an example of the configuration of a sensor device. [Figure 3] This is a timing chart illustrating an example of the operation of the sensor system shown in Figure 1. [Figure 4] This is a timing chart illustrating an example of the operation of the sensor system shown in Figure 1. [Figure 5] This is a timing chart illustrating an example of the operation of the sensor system shown in Figure 1. [Figure 6] This is a timing chart illustrating an example of the operation of the sensor system shown in Figure 1. [Figure 7] This is a timing chart illustrating an example of the operation of the sensor system shown in Figure 1. [Figure 8] This is a timing chart illustrating an example of the operation of the sensor system shown in Figure 1. [Figure 9]Figure 1 is a flowchart illustrating an example of the operation of the sensor device. [Figure 10] Figure 9 is a flowchart showing an example of the transmission process. [Figure 11] Figure 9 is a flowchart showing an example of the reception process. [Figure 12] This figure shows an example configuration of a sensor system related to a comparative example. [Modes for carrying out the invention]

[0030] <Comparative Example> Figure 12 shows an example configuration of a communication system 9 according to a comparative example. The communication system 9 according to the comparative example comprises two sensor devices 91 (91a, 91b), two access points 92 (92a, 92b), a gateway 93, and a host device 94. Sensor devices 91a and 91b measure the physical quantity of the same object under test and transmit wireless communication signals containing the measured values ​​of the physical quantity to access points 92a and 92b, respectively. Access points 92a and 92b transmit the wireless communication signals received from sensor devices 91a and 91b to the host device 94 via the gateway 93. Each sensor device 91 is battery-operated.

[0031] Here, the two sensor devices 91a and 91b are separate devices operating independently. In this way, by having the two sensor devices 91a and 91b measure the physical quantity of the same object being measured, even if one sensor device 91a fails, the measurement result of the other sensor device 91b can be used. Furthermore, redundancy can be achieved by providing two sets of access points 92, gateways 93, and host devices 94 and synchronizing the wireless communication signals of the measured physical quantities.

[0032] On the other hand, in such wireless systems, there is a limit to the number of sensor devices 91 that can be connected to the same access point 92 (maximum number of connections) due to the limited number of usable frequencies. Therefore, as shown in Figure 12, when two sensor devices 91a and 91b, each measuring a physical quantity for the same object under test, are connected to two access points 92a and 92b, the number of objects (measurement locations) whose physical quantities can be measured simultaneously is 1 / 2 of the maximum number of connections. Similarly, when N sensor devices 91, each measuring a physical quantity for the same object under test, are connected to two access points 92a and 92b, the number of objects (measurement locations) whose physical quantities can be measured simultaneously is 1 / N of the maximum number of connections. Consequently, in the communication system 9 of the comparative example, when redundancy is achieved by using multiple sensor devices 91, the number of objects whose physical quantities can be measured simultaneously decreases as the number of sensor devices 91 increases. In other words, when measuring multiple objects under test using the same access point 92 in a conventional configuration, there was a trade-off between the number of objects under test and the reliability achievable through the redundancy of sensor devices 91. Furthermore, the number of sensor devices 91 capable of measuring physical quantities for a single object under measurement is limited by the maximum number of connections to the access point 92, even if there is only one object under measurement.

[0033] Furthermore, each sensor device 91 operates independently, measuring physical quantities and transmitting / receiving wireless communication signals at the same time. Therefore, if multiple sensor devices 91 are started to be used simultaneously, the batteries of each sensor device 91 will consume power at a similar pace. Consequently, the batteries of multiple sensor devices 91 may run out at the same time, and while the battery of one sensor device 91a is being replaced, the battery of another sensor device 91b may run out. Therefore, in the communication system 9 of the comparative example, the power consumption of the sensor devices 91 is high, and the measurement of the physical quantity of the object being measured may be interrupted.

[0034] Furthermore, since the multiple sensor devices 91 operate independently, if a damaged sensor device 91 is replaced, a discrepancy in the measured values ​​may occur before and after the replacement due to variations in the measurement of the sensor devices 91.

[0035] <Embodiment> Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In each drawing, parts having the same configuration or function are denoted by the same reference numerals. In the description of this embodiment, redundant descriptions of the same parts may be omitted or simplified as appropriate.

[0036] In this embodiment, regardless of the maximum number of connections to access points, the number of sensor devices that can be made redundant for a single object under test is not limited, and even if redundancy is achieved with multiple sensor devices, the number of objects under test that can simultaneously measure physical quantities does not decrease in proportion to the number of sensor devices. Furthermore, in this embodiment, power consumption of sensor devices is reduced, and even when multiple redundant sensor devices are started to be used simultaneously, the possibility of batteries running out at the same time is reduced, and the possibility of other batteries running out while one sensor device's battery is being replaced is reduced. In addition, in this embodiment, even when a damaged sensor device is replaced, a discrepancy in measurement values ​​due to measurement variations of the sensor device is prevented before and after the replacement.

[0037] (Sensor system) Figure 1 shows an example configuration of a communication system 1 according to one embodiment of the present disclosure. The communication system 1 comprises a sensor system 2, two access points 20 (20a, 20b), a gateway 30, and a host device 40. The sensor system 2 comprises two sensor devices 10 (10a, 10b).

[0038] The sensor devices 10 (10a, 10b) measure the physical quantities of the object 80 to be measured and can communicate with other sensor devices 10 and access point 20 via wireless communication. The sensor devices 10 (10a, 10b) are wireless communication type field sensors (field devices) installed in equipment located in various plants, such as industrial plants, resource plants, power plants, or water and sewage plants. In the example in Figure 1, there are two sensor devices 10, but there may be three or more. The sensor devices 10 (10a, 10b) may be powered by batteries.

[0039] Access points 20 (20a, 20b) are devices to which the sensor device 10 wirelessly connects to transmit measured values ​​of the physical quantities of the object under test 80 to the host device 40. Access points 20 (20a, 20b) are connected to the gateway 30 in a communicative manner. Access points 20 (20a, 20b) receive measured values ​​of the physical quantities of the object under test 80 from the sensor device 10. In the example in Figure 1, there are two access points 20, the same number as the sensor device 10, but there may be one. Also, there may be three or more access points 20.

[0040] The gateway 30 is connected to the access point 20 and the host device 40 so as to be able to communicate with them. The gateway 30 performs necessary protocol conversion and other processing between the network on the access point 20 side (e.g., intranet) and the network on the host device 40 side (e.g., the internet). The gateway 30 may be configured to be integrated with the access point 20.

[0041] The host device 40 integrates the measurement values ​​from each sensor device 10 to manage the plant. The host device 40 is, for example, a computer such as a PC (Personal Computer) or WS (Workstation). The host device 40 is connected to the gateway 30 for communication. In the example in Figure 1, there is one gateway 30 and one host device 40, but these devices may also be made redundant by having two or more, similar to the sensor devices 10 and access points 20.

[0042] In the configuration described above, in the communication system 1, only one of the sensor devices 10 (for example, sensor device 10a) transmits the measured value of the physical quantity of the object to be measured 80 during a predetermined communication period. The other sensor device 10 (for example, sensor device 10b) only performs receiving operations during that communication period. Here, the other sensor device 10b detects an abnormality in sensor device 10a based on whether or not it received a communication signal from sensor device 10a during the communication period, and, if it did receive a communication signal from sensor device 10a, based on the content of that communication signal.

[0043] Therefore, if an abnormality occurs in sensor device 10a, sensor device 10b can detect that abnormality. Also, while sensor device 10a is transmitting a signal, sensor device 10b only receives the signal. Generally, the power consumption required for data transmission is greater than the power consumption required for data reception. Therefore, when sensor devices 10a and 10b are powered by batteries, a difference in battery consumption can be created, allowing for a staggered battery replacement cycle. Furthermore, while sensor device 10a is transmitting a communication signal, sensor device 10b only performs the operation of receiving the communication signal, and only one sensor device 10 can communicate at the same frequency at a time. Therefore, when a redundant sensor system 2 is constructed using multiple sensor devices 10 connected to a common access point 20 for each of the multiple objects to be measured 80, as shown in Figure 1, there is no upper limit to the number of sensor devices 10 that measure the same object to be measured 80 as a slave. Also, regardless of the number of sensor devices 10, the number of objects to be measured 80 that can simultaneously measure physical quantities can be set as the maximum number of connections to the access point 20. Therefore, it becomes possible to improve the reliability of physical quantity measurement for a larger number of objects 80 to be measured, while also reducing the power consumption of the sensor device 10.

[0044] (Sensor device) Figure 2 is a block diagram showing an example configuration of the sensor device 10 in Figure 1. The sensor device 10 comprises a control unit 11, a storage unit 12, a communication unit 13, and a measurement unit 14. The configuration of sensor device 10a may be the same as that of sensor device 10b. The control unit 11, communication unit 13, and measurement unit 14 of sensor device 10a may function as a first control unit, a first communication unit, and a first measurement unit. The control unit 11, communication unit 13, and measurement unit 14 of sensor device 10b may function as a second control unit, a second communication unit, and a second measurement unit.

[0045] The control unit 11 includes one or more processors. In one embodiment, the "processor" is a general-purpose processor or a dedicated processor specialized for a specific process, but is not limited to these. The control unit 11 is communicatively connected to each component constituting the sensor device 10 and controls the operation of the entire sensor device 10.

[0046] The storage unit 12 is, for example, a memory for storing information. The storage unit 12 includes any storage device such as an SSD (Solid State Drive), ROM (Read-Only Memory), and RAM (Random Access Memory). The storage unit 12 may function as, for example, a main memory, an auxiliary memory, or a cache memory. The storage unit 12 stores any information used for the operation of the sensor device 10. For example, the storage unit 12 may store the measured values ​​of the physical quantities of the object to be measured 80 measured by the measurement unit 14.

[0047] The communication unit 13 includes an optional communication module for communicating with other sensor devices 10 and access point 20. The communication unit 13 may further include a communication control module for controlling communication with other devices, and a storage module for storing communication data such as identification information necessary for communication with other devices. In this embodiment, the communication unit 13 communicates using, for example, the ISA100.11a wireless standard, but the communication method of the communication unit 13 is arbitrary. For example, the communication unit 13 may communicate using LoRaWAN, wireless LAN (Local Area Network), or other wireless communication such as cellular communication. Also, if multiple sensor devices 10 are connected in a chain using wired communication cables such as Ethernet, the communication unit 13 may communicate using wired communication. The access point 20 communicates with the sensor devices 10 using the same communication method as the communication unit 13.

[0048] The measuring unit 14 is a sensor that measures physical quantities of the object to be measured 80. In this embodiment, for example, the measuring unit 14 may measure the pressure inside the pipe as the object to be measured 80. The physical quantities measured by the measuring unit 14 are not limited to pressure; for example, the measuring unit 14 may measure any physical quantity such as temperature, vibration, flow rate, humidity, velocity, acceleration, and rotational speed.

[0049] Some or all of the components of the sensor device 10 may be implemented by dedicated circuits included in the control unit 11. That is, some or all of the components of the sensor device 10 may be implemented by hardware. Alternatively, some of the components of the sensor device 10 may be implemented by executing a computer program (program) on a processor included in the control unit 11. That is, some of the components of the sensor device 10 may be implemented by software.

[0050] (Example of operation) Figures 3 to 8 are timing charts illustrating an example of the operation of the sensor system 2 shown in Figure 1. As mentioned above, in the sensor system 2, one of the sensor devices 10 transmits the measured value of a physical quantity during a predetermined communication period, while the other sensor devices 10 perform only receiving operations during that communication period. Hereinafter, the sensor device 10 that transmits the measured value of a physical quantity will be referred to as the master, and the sensor device 10 that performs receiving operations will be referred to as the slave.

[0051] Figure 3 schematically shows an example in which sensor device 10a, as the first sensor device, operates as a master, and sensor device 10b, as the second sensor device, operates as a slave. Sensor device 10a, operating as the master, performs a transmission operation to transmit a first communication signal containing the measured value of the physical quantity of the object under measurement 80 at each communication period, which is a fixed period predetermined by a certain cycle. In the example in Figure 3, sensor device 10a performs the transmission operation 71 during a communication period of length T2 set to the cycle of the measurement interval T1. In the example in Figure 3, each communication period starts at time t1, t2, t3, ...

[0052] Sensor device 10b, operating as a slave, performs a receiving operation 72 to receive the first communication signal transmitted from sensor device 10a at each communication period, in synchronization with the transmission operation 71 of sensor device 10a. In order for sensor devices 10a and 10b to operate synchronously, their time is synchronized in advance by any method. For example, based on the ISA100.11a wireless standard, a synchronization signal may be periodically transmitted from the gateway 30 to each sensor device 10a and 10b to synchronize the time of each sensor device 10. Alternatively, each sensor device 10 may be configured to receive GPS (Global Positioning System) signals to synchronize the time of each sensor device 10. Alternatively, the time of each sensor device 10 may be synchronized by configuring the sensor system 2 with sensor devices 10 that have the same time setting.

[0053] As shown in Figure 3, the measured values ​​of the physical quantities measured by sensor device 10a are transmitted to access points 20a and 20b, and simultaneously received by sensor device 10b. Upon receiving the measured values ​​from sensor device 10a, access points 20a and 20b transmit them to host device 40 via gateway 30.

[0054] As shown in Figure 4, the sensor devices 10a and 10b may switch between master and slave roles at predetermined timings. In the example in Figure 4, initially, sensor device 10a operates as the master and sensor device 10b operates as the slave. Then, at time t11, sensor device 10a starts operating as the slave and sensor device 10b starts operating as the master. Specifically, sensor device 10a performs a receive operation 74 during the communication period from time t11 onwards. Sensor device 10b performs a transmit operation 75 during the communication period from time t11 onwards, transmitting a second communication signal that includes the measured value of the physical quantity of the object under measurement 80. Sensor devices 10a and 10b may periodically switch between master and slave operations as shown in Figure 4. By performing such a switch, one sensor device 10 can receive the measured value from the other sensor device 10. When transmitting such measured values, additional information may be added before transmission. This allows one sensor device 10 to transmit predetermined information in addition to the measured value to the other sensor device 10.

[0055] The switching between master and slave operation in sensor devices 10a and 10b may be set to a value greater than the measurement interval T1, for example. The longer the switching period, the later the abnormality detection of sensor device 10 operating as a slave will be. However, the power required to transmit a signal is greater than the power required to receive a signal. Therefore, a difference can be made in the battery usage of sensor device 10 operating as a master and sensor device 10 operating as a slave. As a result, the risk of batteries running out at the same time when multiple sensor devices 10 are started to be used at the same time can be reduced. Also, the shorter the switching period, the less battery power can be used by sensor device 10 operating as a master, and the longer the lifespan of sensor device 10 operating as a master can be extended.

[0056] Furthermore, the same network information may be assigned to sensor devices 10a and 10b. In this way, sensor devices 10a and 10b can be treated as the same device on the network. In other words, even if the sensor device 10 acting as the master switches, the host device 40 will appear to be receiving measurement values ​​from the same sensor device 10. For example, if sensor device 10 detects an abnormality in another sensor device 10, it may send a communication signal containing the same network information as the source of the communication signal received from the other sensor device 10, at each communication period. In this way, since sensor device 10 sends a communication signal containing the same network information as the previous sensor device 10, it can make a device that receives the communication signal, such as the host device 40, recognize that it is continuously receiving communication signals from the same device.

[0057] As shown in Figure 5, if the sensor device 10a, which is operating as a master, detects an abnormality in its own device through self-diagnosis, it may notify the host device 40 by sending a first communication signal containing an abnormality signal indicating the abnormality. In the example in Figure 5, the sensor device 10a sends an abnormality signal 77 during the communication period starting at time t4. When the sensor device 10b, which is operating as a slave, receives the abnormality signal 77 from the master, it starts operating as a master in response. In the example in Figure 5, the sensor device 10b starts a transmission operation 75 that sends a second communication signal containing the measured value from the communication period starting at t5, which is the next communication period after time t4.

[0058] In the example in Figure 5, sensor device 10a stops transmitting measurement values ​​after sending an abnormal signal, but it may continue transmitting measurement values ​​for a while after sending the abnormal signal. In this case, host device 40 will receive measurement values ​​from both sensor devices 10a and 10b. Host device 40 can show the user normal data by displaying the measurement value received from sensor device 10b, which did not transmit the first communication signal containing the abnormal signal, on its display unit. Sensor device 10a, which has detected an abnormality, may stop transmitting data at a predetermined timing, for example, to switch between master / slave roles.

[0059] As shown in Figure 6, when a sensor device 10b operating as a slave receives a measurement value from a sensor device 10a operating as a master, it may compare that measurement value with a measurement value it has measured itself to detect an abnormality in sensor device 10a. In the example in Figure 6, sensor device 10b detects an abnormality in sensor device 10a based on the measurement value received from sensor device 10a during the communication period at time t4. In such a case, sensor device 10b may notify the host device 40 by transmitting a second communication signal containing information indicating an abnormality in sensor device 10a. In the example in Figure 6, sensor devices 10a and 10b switch their roles as master / slave not immediately after detecting an abnormality, but at a predetermined timing, time t11. Therefore, sensor device 10b may transmit a second communication signal containing information indicating an abnormality in sensor device 10a during the communication period at t11. This allows the host device 40 to detect an abnormality in sensor device 10a. In the example shown in Figure 6, the sensor device 10a stops operating when it detects an abnormality in its own device through a receiving operation 74 during the communication period t11.

[0060] As shown in Figure 7, if the sensor device 10b operating as a slave does not receive a first communication signal from the sensor device 10a operating as a master during the communication period, it may detect an abnormality in the sensor device 10a. Reasons for not receiving the first communication signal from the sensor device 10a include, for example, that an abnormality occurs in the sensor device 10a and it becomes unable to transmit, or that the sensor device 10a itself detects an abnormality and stops transmitting the first communication signal. If the sensor device 10b does not receive the first communication signal from the sensor device 10a, it may start operating as a master. In the example in Figure 6, the sensor device 10b starts transmitting a second communication signal including the measured value from the communication period at time t5, in response to not receiving the first communication signal from the sensor device 10a during the communication period at time t4. However, as in Figure 5, the sensor device 10b may start transmitting the measured value from a predetermined timing. Furthermore, similar to the operation described with reference to Figure 6, if the first communication signal is not received during the communication period, the sensor device 10b may transmit a second communication signal containing the measured value and information indicating an abnormality of the sensor device 10a to notify the host device 40 of the abnormality of the sensor device 10b. If the sensor device 10a continuously fails to transmit data or stops transmitting due to abnormality detection, the sensor device 10b will always transmit data such as the measured value.

[0061] As shown in Figure 1, if there are multiple access points 20a and 20b in the communication system 1, the sensor device 10a transmits a first communication signal to each of the access points 20a and 20b, as shown in Figure 8. In Figure 8, the sensor device 10a performs a transmission operation 71 addressed to access point 20a during the communication period at times t1, t2, t3, ... The sensor device 10a performs a transmission operation 79 addressed to access point 20b during the communication period at times t21, t22, t23, ... In such a case, the first communication signal containing the same measurement value is transmitted in both the transmission operation 71 addressed to access point 20a and the transmission operation 79 addressed to access point 20b. Therefore, as shown in Figure 8, the sensor device 10b may perform a reception operation 72 only during the communication period of one of the transmission operations (for example, the transmission operation 71 addressed to access point 20a). As a result, the sensor device 10b can acquire measurement values ​​from the sensor device 10a with less power consumption than when it performed a receiving operation during both the transmission operation 71 and the transmission operation 79, and can detect abnormalities in the sensor device 10a.

[0062] Furthermore, if the master / slave roles are switched at a predetermined time, the sensor device 10a, which was operating as the master before the switch, can then detect and respond to any abnormalities in sensor device 10b using the same procedure as described above.

[0063] Figure 9 is a flowchart illustrating an example of the operation of the sensor device 10 in Figure 1. Figure 10 is a flowchart illustrating an example of the transmission process in Figure 9. Figure 11 is a flowchart illustrating an example of the reception process in Figure 9. The operation of the sensor device 10, described with reference to Figures 9 to 11, may correspond to at least a part of the control method of the sensor system 2 or the control method of the sensor device 10. The operation of each step in Figures 9 to 11 may be performed based on control by the control unit 11 of the sensor device 10. As a prerequisite for the process in Figure 9, each sensor device 10 included in the sensor system 2 has pre-configured settings such as the communication period, the sensor device 10 that operates as a master by default (e.g., sensor device 10a), and the timing for switching between master / slave roles. In addition, the time of each sensor device 10 is pre-synchronized.

[0064] In step S1 of Figure 9, the control unit 11 determines whether the current time falls within a communication period, which is a predetermined period of time with a fixed cycle. If the control unit 11 determines that the time falls within a communication period (YES in step S1), it proceeds to step S2; otherwise, it waits until the communication period begins (NO in step S1).

[0065] In step S2, the control unit 11 causes the measurement unit 14 to measure the physical quantity of the object to be measured 80 and obtains the measured value of the physical quantity.

[0066] In step S3, the control unit 11 determines whether or not its own device is operating as a master. If the control unit 11 is operating as a master (YES in step S3), it proceeds to step S4; otherwise (NO in step S3), it proceeds to step S8.

[0067] In step S4, the control unit 11 performs a transmission process. The transmission process involves detecting abnormalities in the device, measuring physical quantities, and transmitting those physical quantities. Details of the transmission process will be described later with reference to Figure 10.

[0068] In step S5, the control unit 11 determines whether or not to switch the master / slave operation. The control unit 11 may determine to switch the master / slave operation, for example, if the current time coincides with the timing to switch the master / slave role, or if an abnormality is detected in its own device (master). If the control unit 11 decides to switch the master / slave operation (YES in step S5), it proceeds to step S6; otherwise (NO in step S5), it proceeds to step S7.

[0069] In step S6, the control unit 11 switches between master and slave operation. That is, if it was operating as a slave up to that point, the control unit 11 starts a transmission operation to send a communication signal containing the measured value of the physical quantity of the object under test 80, using the same communication method as the master up to that point, for each communication period. If it was operating as a master up to that point, the control unit 11 stops the transmission operation and starts a reception operation to receive communication signals transmitted from other sensor devices 10 for each communication period.

[0070] In step S7, the control unit 11 determines whether or not to terminate the process. For example, the control unit 11 may determine to terminate the process if it is instructed to do so by the host device 40 or the user. Alternatively, the control unit 11 may determine to terminate the process if it detects an abnormality in its own device. If the control unit 11 decides to terminate the process (YES in step S7), it terminates the process shown in the flowcharts of Figures 9 to 11; otherwise (NO in step S7), it returns to step S1 and continues the process.

[0071] In step S8, the control unit 11 performs reception processing. Reception processing involves receiving communication signals from other sensor devices 10 and detecting abnormalities in the other sensor devices 10. Details of the reception processing will be described later with reference to Figure 11.

[0072] In step S9, the control unit 11 determines whether or not an abnormality in another sensor device 10 was detected during the reception process in step S8. If an abnormality is detected (YES in step S9), the control unit 11 proceeds to step S6; otherwise (NO in step S9), it proceeds to step S5.

[0073] The transmission process performed in step S4 of Figure 9 will be explained with reference to Figure 10. In step S11 of Figure 10, the control unit 11 detects whether or not there is an abnormality in its own device. The control unit 11 may detect an abnormality in the measurement unit 14, for example, if it is unable to obtain a measurement value from the measurement unit 14, or if it receives an error signal from the measurement unit 14. Alternatively, the control unit 11 may detect an abnormality in the communication unit 13 if it has performed an operation to transmit the first communication signal, but has not received an acknowledgment of receipt (e.g., Ack). If the control unit 11 detects an abnormality (YES in step S11), it proceeds to step S14; otherwise (NO in step S11), it proceeds to step S12.

[0074] In step S12, the control unit 11 corrects the measured value of the physical quantity acquired immediately before in step S2 of Figure 9. Specifically, if the control unit 11 receives a measured value from another sensor device 10 operating as a master while operating as a slave, it may pre-acquire a correspondence between the measured value acquired by its own measuring unit 14 and the master's measured value during the same communication period. For example, the correspondence of measured values ​​may be given by linear regression or a higher-order regression. Based on this correspondence, the control unit 11 may perform a correction to convert the measured value of the physical quantity acquired immediately before in step S2 of Figure 9 to the measured value of the other sensor device 10 operating as a master. In this way, by performing a correction to convert the slave's measurement result to the master's measurement result, the control unit 11 can suppress changes in measured values ​​due to measurement variations in the measuring unit 14 when switching between master / slave roles. Note that sensor devices 10a and 10b may suppress measurement variations in the measuring unit 14 by sharing the measuring unit 14 and making the communication of measured values ​​redundant.

[0075] In step S13, the control unit 11 causes the communication unit 13 to transmit a communication signal including the measurement value corrected in step S12. If the control unit 11 detects an abnormality in another sensor device 10 that was operating as a master immediately before, it may cause the communication unit 13 to transmit a communication signal further containing information indicating this abnormality. After completing the processing in step S13, the control unit 11 terminates the transmission process shown in Figure 10 and proceeds to step S5 in Figure 9.

[0076] In step S14, the control unit 11 instructs the communication unit 13 to transmit an abnormality signal indicating an abnormality in its own device. After completing the processing in step S14, the control unit 11 terminates the transmission process shown in Figure 10 and proceeds to step S5 in Figure 9.

[0077] The reception process performed in step S8 of Figure 9 will be explained with reference to Figure 11. In step S21 of Figure 11, the control unit 11 performs a reception operation to receive a communication signal from another sensor device 10. As mentioned above, the power consumption of the reception operation is less than that of the transmission operation.

[0078] In step S22, the control unit 11 determines the reception status of communication signals from other sensor devices 10 in step S21. For example, if the control unit 11 fails to receive communication signals a predetermined number of times consecutively, it determines that the reception status is poor (NO in step S22) and proceeds to step S25. If the reception status is good (YES in step S22), the control unit 11 proceeds to step S23. Note that multiple sensor devices 10 may be installed in close proximity to each other to measure the physical quantity of the same object to be measured 80. In such a case, even if the communication status between the sensor device 10 operating as the master and the access points 20a and 20b is poor, the sensor device 10 operating as a slave can receive the first communication signal transmitted from the master. Therefore, if the sensor device 10 operating as a slave cannot receive a communication signal from the master, it is highly likely that the sensor device 10 operating as the master is unable to transmit due to power failure or malfunction.

[0079] In step S23, the control unit 11 determines whether the communication signal received in step S21 corresponds to an abnormal signal indicating an abnormality in another sensor device 10. If it is an abnormal signal (YES in step S23), the control unit 11 proceeds to step S25; otherwise (NO in step S23), it proceeds to step S24.

[0080] In step S24, the control unit 11 compares the measured value included in the communication signal received in step S21 with the measured value acquired immediately before in step S2 in Figure 9 to determine whether the measured value included in the communication signal received in step S21 is an abnormal value. If the value is abnormal (YES in step S24), the control unit 11 proceeds to step S25; otherwise (NO in step S24), it terminates the reception process in Figure 11 and proceeds to step S9 in Figure 9.

[0081] In step S25, the control unit 11 detects an abnormality in another sensor device 10 that is operating as a master. After completing the processing in step S25, the control unit 11 terminates the reception processing shown in Figure 11 and proceeds to step S9 in Figure 9.

[0082] As described above, in the sensor system 2, only one of the multiple sensor devices 10 operates as the master, and the other sensor devices 10 do not transmit communication signals to the access points 20a and 20b. Therefore, regardless of the maximum number of connections in the communication system 1 formed by the access points 20a and 20b, redundancy can be achieved for a single object under test 80 using any number of sensor devices 10. Furthermore, for a single object under test 80, the communication line of the access point 20 required to transmit the measured value of the physical quantity to the host device 40 is only one line, regardless of the number of sensor devices 10 that measure the physical quantity of that object under test 80 as slaves. Therefore, when measuring the physical quantities of multiple objects under test 80 using the same access point 20, the sensor system 2 can be connected up to the maximum number of connections of that access point 20, and the same number of objects under test 80 can be monitored simultaneously. Furthermore, since sensor device 10b only receives signals while sensor device 10a transmits signals, the power consumption of sensor device 10b can be reduced when sensor devices 10a and 10b are battery-powered. Thus, sensor system 2 makes it possible to improve the reliability of physical quantity measurement for a larger number of objects 80 to be measured, while also reducing the power consumption of sensor device 10.

[0083] Furthermore, the multiple sensor devices 10 monitor each other's communication status and measured physical quantities by switching between master / slave roles at predetermined timings. Therefore, when the sensor system 2 detects a communication anomaly or an anomaly in the measured values, it can switch the device transmitting the measured values ​​to a functioning sensor device 10, thereby improving the stability and reliability of the measurement system.

[0084] Furthermore, since the sensor device 10 operating as a slave only performs receiving operations during the communication period, it consumes less power compared to the sensor device 10 operating as a master. Therefore, it is possible to reduce the possibility of multiple sensor devices 10 running out of battery at the same time, and to reduce the possibility of other sensor devices 10 running out of battery while one sensor device 10 is being replaced.

[0085] Furthermore, in cases where it is difficult to detect the remaining battery level by voltage, such as with thionyl chloride batteries, the battery needs to be replaced before it is completely depleted in order for the measurement values ​​to be continuously reported to the host device 40. In contrast, with sensor system 2, if the battery runs out and sensor device 10 stops working, it can automatically switch to a sensor device 10 that will operate as the master. Therefore, with sensor system 2, it is possible to use up the battery driving sensor device 10 until it is completely depleted.

[0086] In this embodiment, an example was described in which the sensor device 10 performs wireless communication. However, the sensor device 10 may not be limited to wireless communication, but may also perform one-to-many data transmission communication such as Ethernet communication connected in a chain. Even with such a configuration, it is possible to achieve redundancy of the sensor device 10 and suppress changes in measurement results that occur when the sensor device 10 is switched over using a similar method.

[0087] Furthermore, as mentioned above, increasing the number of sensor devices 10 operating as slaves in a single sensor system 2 does not affect the number of connected devices in the communication system 1. Therefore, by increasing the number of sensor devices 10 operating as slaves and periodically switching between master / slave roles, the number of reception operations can be reduced to 1 per slave. Thus, the power consumption of the sensor devices 10 operating as slaves can be further reduced. If three or more sensor devices 10 are provided in the sensor system 2, a priority order for each sensor device 10 to operate as a master may be determined in advance and set for each sensor device 10. If an abnormality is detected in a sensor device 10 operating as a master, the next sensor device 10 to operate as a master may be determined based on the priority order of the remaining sensor devices 10. This configuration prevents multiple sensor devices 10 from operating as masters simultaneously.

[0088] Furthermore, as mentioned above, there is no upper limit to the number of sensor devices 10 that can operate as slaves for a single access point 20. Therefore, by increasing the number of sensor devices 10 that can operate as slaves, it is possible to reduce the risk of damage to the sensor devices 10.

[0089] As mentioned above, the measurement results of the sensor device 10 operating as a slave are compared with the measurement results received from the sensor device 10 operating as a master. The sensor device 10 operating as a slave corrects the discrepancy between its own measurement results and the measurement results received from the master. Therefore, according to this embodiment, it is possible to reduce the influence of individual differences in the measurement unit 14, obtain measurement results equivalent to the master's measurement results, and transmit them to the host device 40. The sensor device 10 may correct the measured values ​​by an appropriate method depending on the type of object 80 to be measured and the type of physical quantity. Also, the sensor device 10b operating as a slave may correct the measured values ​​it has measured to match the sensor device 10a that was operating as a master. Subsequently, if the sensor device 10a is replaced with a new sensor device 10c, the sensor device 10c may correct the measured values ​​it has measured to match the sensor device 10b. As a result, even if the sensor device 10 is replaced, it is possible to continuously obtain measured values ​​converted to the characteristics of the same measurement unit 14 before and after the replacement.

[0090] Furthermore, the sensor device 10 may perform a receiving operation before a transmitting operation, and may suppress transmission when it receives a signal. This function may be implemented, for example, by an LBT (Listen Before Talk) function. In such a case, if the sensor device 10b operating as a slave detects an abnormality in the sensor device 10a operating as a master, the sensor device 10b can start transmitting immediately before the sensor device 10a transmits and stop the sensor device 10a from transmitting. This allows the host device 40 to be quickly notified of the abnormality in the sensor device 10a operating as a master by interrupting the communication period of the sensor device 10a operating as a master. Here, the sensor device 10a operating as a master may be forcibly started to perform a receiving operation based on the information of the received signal.

[0091] This disclosure is not limited to the embodiments described above. For example, multiple blocks shown in the block diagram may be combined, or one block may be divided. Multiple steps shown in the flowchart may be performed in parallel or in a different order, depending on the processing capacity of the device performing each step, or as necessary, instead of being performed in chronological order as described. Other modifications are possible without departing from the spirit of this disclosure. [Explanation of symbols]

[0092] 1. Communication System 2 Sensor System 9. Communication Systems 10 Sensor Devices 11 Control Unit 12 Storage section 13 Communications Department 14 Measuring part 20 access points 30 Gateways 40 Host devices 71, 75, 79 Transmission operation 72,74 Receiving operation 77 Abnormal signal 80 Object to be measured 91 Sensor System 92 access points 93 Gateway 94 Host devices

Claims

1. A sensor system having a first sensor device and a second sensor device, The first sensor device is The first communications unit that handles communications, First control unit, Equipped with, The second sensor device is The second communications unit, which handles communications, The second control unit and Equipped with, The first control unit of the first sensor device causes the first communication unit to perform a transmission operation at communication periods, which are fixed periods predetermined to be a certain period, to transmit a first communication signal containing the measured value of the physical quantity of the object being measured. The second control unit of the second sensor device is During each of the aforementioned communication periods, the second communication unit is instructed to perform a receiving operation to receive the first communication signal transmitted from the first sensor device. During the aforementioned communication period, the second communication unit determines whether or not it has received the first communication signal from the first sensor device, and if it has received the first communication signal from the first sensor device, it detects an abnormality in the first sensor device based on the content of the first communication signal. Sensor system.

2. The sensor system according to claim 1, wherein the second control unit of the second sensor device, when it detects an abnormality in the first sensor device, initiates a transmission operation to transmit a second communication signal, which includes the measured value of the physical quantity of the object to be measured, to the second communication unit at each communication period using the same communication method as the first sensor device.

3. The first control unit of the first sensor device causes the first communication unit to transmit a signal that further includes the source network information as the first communication signal for each communication period. When the second control unit of the second sensor device detects an abnormality in the first sensor device, it causes the second communication unit to transmit a signal as a second communication signal that further includes the same network information as the network information included in the first communication signal, for each communication period. The sensor system according to claim 2.

4. The system comprises multiple of the above-mentioned second sensor devices, If an abnormality is detected in the first sensor device, the second control unit of one of the second sensor devices initiates a transmission operation to transmit a second communication signal to the communication unit at each communication period, based on a predetermined priority order of the second sensor devices. The sensor system according to claim 2.

5. The second control unit of the second sensor device initiates a transmission operation at a predetermined timing, for each communication period, to transmit the second communication unit a second communication signal containing the measured value of the physical quantity of the object being measured. The first control unit of the first sensor device is At the predetermined timing, the transmission operation of the first communication unit is stopped, and the first communication unit is instructed to start a receiving operation to receive the second communication signal transmitted from the second sensor device. During the aforementioned communication period, the first communication unit determines whether or not it has received the second communication signal from the second sensor device, and if it has received the second communication signal from the second sensor device, it detects an abnormality in the second sensor device based on the content of the second communication signal. The sensor system according to claim 2.

6. The first control unit of the first sensor device causes the first communication unit to transmit a signal including the measured value of the physical quantity of the object being measured, measured by the first measurement unit, as a first communication signal for each communication period. When the second control unit of the second sensor device detects an abnormality in the first sensor device, it causes the second communication unit to transmit a signal as the second communication signal for each communication period, which includes the measured value of the physical quantity of the object to be measured, measured by the second measurement unit, and corrected according to the correspondence between the measurement result of the first measurement unit and the measurement result of the second measurement unit. The sensor system according to claim 2.

7. The first control unit of the first sensor device causes the first communication unit to transmit a signal including the measured value of the physical quantity of the object being measured, measured by the first measurement unit, as a first communication signal for each communication period. The second control unit of the second sensor device detects an abnormality in the first sensor device based on a comparison between the measured value of the physical quantity measured by the first measuring unit included in the first communication signal received from the first sensor device and the measured value of the physical quantity of the object being measured measured by the second measuring unit. The sensor system according to any one of claims 1 to 6.

8. The sensor system according to any one of claims 1 to 6, wherein the second control unit of the second sensor device detects an abnormality in the first sensor device if it does not receive the first communication signal during the communication period.

9. When the first control unit of the first sensor device detects an abnormality in the first sensor device, it causes the first communication unit to transmit an abnormality signal as a first communication signal. When the second control unit of the second sensor device receives the abnormality signal from the first sensor device, it detects an abnormality in the first sensor device. The sensor system according to any one of claims 1 to 6.

10. A sensor device comprising a measuring unit for measuring the physical quantity of an object to be measured, a communication unit for communication, and a control unit, The control unit, At each communication period, which is a fixed period predetermined at a certain interval, the communication unit is instructed to perform a receiving operation to receive a first communication signal containing the measured value of the physical quantity of the object being measured from another sensor device. During the aforementioned communication period, the communication unit determines whether or not it received the first communication signal from the other sensor device, and if it did receive the first communication signal from the other sensor device, it detects an abnormality in the other sensor device based on the content of the first communication signal. If an abnormality is detected in the other sensor device, the communication unit is instructed to perform a transmission operation at each communication period, transmitting a second communication signal containing the measured value of the physical quantity of the object being measured by the measurement unit, using the same communication method as the other sensor device. Sensor device.

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