JP5316787B2 - Wireless field device and wireless control network system using the same - Google Patents

Description

  The present invention relates to a field device that performs wireless communication (hereinafter referred to as a wireless field device) and a radio control network system using the same, and more particularly, a radio field device that performs a sleep operation for power saving and a radio control network using the same. It relates to improvement of system maintainability and reliability.

  In recent years, for example, it has been proposed to configure a process control system in industrial automation using a wireless control network system including wireless field devices. This is because the conventional control system is configured as a wired network, and sensors that measure temperature, flow rate, etc. can be installed at the optimal position in the plant due to restrictions on communication distance and wiring routing. In order to eliminate the disadvantage that the control accuracy is reduced.

  Various wireless field devices are used as field-installed instruments in process control systems and wireless control network systems. Field devices include, for example, sensors and control devices that measure various physical quantities such as temperature, pressure, and flow rate that are used in a measurement control field (field) of a process control system.

  Conventionally, a wireless network communication system has both an infrastructure mode in which field devices communicate via an access point for interconnecting a wired network and a wireless network, and an ad hoc mode in which short-range devices directly communicate with each other. It was proposed. In addition, when short-distance communication that does not require an access point is possible with another field wireless device or mobile terminal with which one field device is a communication partner, communication is performed in ad hoc mode, and ad hoc mode communication is not possible. In such a case, a wireless network communication system that can automatically switch communication in the infrastructure mode depending on the situation has been proposed.

  FIG. 5 is a configuration diagram of a conventional wireless field device and a wireless control network system using the same. In FIG. 5, the wireless field device 1 has an infrastructure network that communicates with the mobile terminal 3 or other wireless field devices via the access point 2 and an ad hoc network that directly communicates between field devices at short distances. .

  For example, the mobile terminal 3 communicates with a field device during a patrol operation or maintenance of an operator in a radio control network system. The mobile terminal 3 is used when performing facility monitoring / maintenance work (i.e., on-site patrol work) in a wireless control network system using wireless field devices used in a field such as a factory or a building.

  The wireless field device 1 records information that it can communicate with the mobile terminal 3 or other wireless field device as a communication partner via an ad hoc network in its own cache memory (not shown).

  When starting communication, the field wireless device 1 searches the mobile terminal 3 or field wireless device of the communication partner using a database, and if this field device is recorded, checks whether communication is possible on an ad hoc network. .

  Specifically, the wireless field device 1 first confirms the possibility of transmission / reception in the ad hoc mode for the mobile terminal 3 or the field device that is not recorded. If the wireless field device 1 can communicate in the ad hoc mode, the wireless field device 1 records the information in the database to establish communication. If the communication in the ad hoc mode is impossible, the wireless field device 1 switches to the infrastructure mode and starts the communication procedure.

  The wireless field device 1 starts communication procedure in the ad hoc mode and establishes communication with the mobile terminal 3 or wireless field device that has already been recorded, but communication is not possible because it is not already in that state. The communication procedure is started by switching to the infrastructure mode. Similarly, when the mobile terminal 3 or other wireless field device in communication leaves the ad hoc network due to movement, the wireless field device automatically switches to the infrastructure mode via the access point as much as possible. Maintain communication.

  The wireless field device 1 communicates with the mobile terminal 3 or other wireless field devices without using the access point 2 when communicating with the mobile terminal 3 or other wireless field devices recorded in the cache memory as a counterpart. Ad hoc mode is automatically selected for communication from the beginning.

  As a prior art document related to such a wireless field device, there is the following Patent Document 1.

JP 2004-128785 A

  Here, a wireless field device that performs wireless communication operates with a minimum amount of power by suspending some functions of the wireless communication unit during a period in which wireless communication is not performed (hereinafter referred to as a sleep period). This makes it possible to reduce power consumption during sleep, save power by ensuring sleep time, and operate field devices for long periods of time.

  However, in the conventional wireless field device, in order to save power, when the wireless communication means of each wireless field device is in the sleep state, most of the time is in a state where communication is impossible, so the infrastructure mode and the ad hoc mode There has been a problem that the switching cannot be performed appropriately.

  In addition, since there is an infeasible wireless communication that occurs in the sleep state, the maintenance and reliability of the conventional wireless field device and the wireless control network system constituted by this field device are low. was there.

  The present invention solves the above-described problems, and an object of the present invention is to improve the maintainability and reliability of a wireless field device that performs a sleep operation for power saving and a wireless control network system using the wireless field device. is there.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
Wireless communication means for performing wireless communication in an infrastructure mode for wireless communication via an access point or an ad hoc mode for direct communication between devices in a short distance, and a part of the functions of the wireless communication means are stopped to enter a sleep state In a wireless field device provided with arithmetic control means,
A mode switching signal transmission / reception means for receiving a mode switching signal for switching the wireless communication means from a sleep state to a normal state and switching to communication in the ad hoc mode from neighboring devices;
A communication mode control means for controlling the wireless communication means upon receiving the mode switching signal to switch from the sleep state to the normal state to the ad hoc mode, and for performing communication with the neighboring devices by the wireless communication means; ,
Equipped with a,
The communication mode control means switches the communication mode of the wireless communication means from the ad hoc mode to the infrastructure mode after finishing communication with the neighboring devices by the wireless communication means. It is a field device.

The invention according to claim 2 is the wireless field device according to claim 1,
The mode switching signal transmitting / receiving means receives the mode switching signal from a mobile terminal that monitors and maintains a field wireless device.

The invention according to claim 3 is the wireless field device according to claim 1 or 2,
The calculation control means that executes a function block set in advance and operates as a sensor;
Wireless output control means for measuring a physical distance to a communication partner and controlling a radio wave transmission output value;
It is characterized by providing.

The invention according to claim 4 is the virtual machine server according to any one of claims 1 to 3,
The mode switching signal transmitting / receiving means includes
A mode switching signal is received from the mobile terminal by a passive tag.

The invention according to claim 5 is the virtual machine server according to any one of claims 1 to 4,
The arithmetic control means includes
When a predetermined time elapses after the operation of the wireless communication unit is not performed after receiving the mode switching signal, a part of the function of the wireless communication unit is stopped to enter a sleep state. And

The invention described in claim 6
The wireless field device according to any one of claims 1 to 5,
A wireless communication device configured by a non-contact IC and configured to transmit a mode switching signal for switching the communication mode from the sleep state to the normal state from the sleep state to the ad hoc mode using a passive tag. A mobile device for monitoring and maintenance,
A wireless control network system comprising:

The invention described in claim 7 is the radio control network system according to claim 6,
The mobile terminal
The wireless communication apparatus includes means for performing wireless communication in an infrastructure mode for communicating with the wireless field device via an access point and an ad hoc mode for directly communicating with a short-range field device.

  As described above, according to the present invention, even in a field wireless device that performs a sleep operation for power saving, a mode switching signal transmission / reception unit configured by a non-contact IC uses a tag from a mobile terminal. By receiving the signal, the mobile terminal can easily access the field device during the sleep operation, and can contribute to the improvement of the maintainability without impairing the power saving performance of the entire radio control network system. In addition, it is possible to solve the problem of deterioration in communication reliability due to the inexecutable wireless communication that occurs in the conventional sleep state, and it is possible to contribute to the improvement of communication reliability.

  In addition, according to the field device of the present invention, it has been conventionally necessary to cover the radio wave emission range to the access point by performing communication with the mobile terminal 6 in ad hoc mode as necessary during maintenance. However, by communicating with neighboring mobile terminals in ad hoc mode, the radio wave emission range can be suppressed and the output can be lowered, so that other field devices or other coexisting wireless network systems (for example, ISA100.11a) can be used. The influence of the applied radio noise can be reduced.

  In addition, according to the field device of the present invention, the mobile terminal 6 and the field device can communicate directly with each other without using an access point by performing communication in the ad hoc mode with the mobile terminal 6 when necessary, such as during maintenance. This leads to a reduction in traffic volume and can contribute to improving communication reliability and throughput.

  In addition, the field device of the present invention is effective in that the operation / laying cost can be expected to be reduced when the wireless communication technology is applied to the plant control. It is also possible to provide additional added value.

  Specifically, in the plant system, field maintenance work is performed by field workers, while field devices are required to operate continuously for a long period of time. It is necessary to reduce the operating duty by installing a sleep function in the device. By applying the technology of the present invention to this plant system, it becomes possible to achieve both the power saving performance of the sensor network and the maintenance work of the field device by the mobile terminal.

1 is a configuration diagram showing a configuration example of a field wireless device and a wireless control network system using the same according to the present invention. FIG. 2 is a configuration block diagram of a wireless field device 4 in FIG. 1. It is operation | movement explanatory drawing of the field wireless device 4 and the mobile terminal 6 which concern on this invention. FIG. 4 is an operation explanatory diagram illustrating the operation of FIG. 3 in the form of an operation flowchart of the wireless field device 4 and the mobile device 6. It is a block diagram of a conventional wireless field device and a wireless control network system using the same.

  FIG. 1 is a configuration diagram showing a configuration example of a field wireless device according to the present invention and a radio control network system using the same, and the same reference numerals are given to portions common to FIG. . The difference from FIG. 5 is that communication mode control means for switching between the infrastructure mode and ad hoc mode when the field device performs wireless communication, and data transmission / reception to / from an external device such as the mobile terminal 6 are performed. It is different in that it includes a mode switching signal transmission / reception means for receiving a switching signal for switching the operation state from the sleep state to the normal state and switching from the infrastructure mode to the ad hoc mode.

  In FIG. 1, a wireless control network system includes a wireless field device 4, an access point 5 for the field device to interconnect a wired network and a wireless network, and a field device during a patrol operation or maintenance by an operator in the wireless control network system. And a mobile device 6 that performs wireless communication.

  Further, the wireless field device 4 sleeps during a period in which wireless communication is not performed (sleep period) by stopping a part of the functions of the wireless communication unit and operating with the minimum necessary power (becomes a sleep state). It is intended to save power by reducing power consumption at the time and ensuring sleep time.

  The mobile terminal 6 is a portable terminal such as a notebook personal computer or PDA. For example, in a wireless control network system using wireless field devices used in a field such as a factory or a building, monitoring and maintenance work of equipment It is used when performing (site patrol work).

  The wireless field device 4, the access point 5, and the mobile device 6 perform data transmission / reception via wireless communication. The wireless field device 4, the access point 5, and the mobile device 6 perform data transmission / reception mainly by wireless communication.

  The access point 5 is interconnected to a wireless network composed of a wired network, a wireless field device 4, an access point 5, and a mobile device 6. A field device (not shown) and other network devices are connected to the wired network.

  2 is a configuration block diagram of the wireless field device 4 of FIG. 1. In FIG. 2, the wireless field device 4 wirelessly uses IEEE802.11a / b / g / n (regardless of a specific standard). Wireless communication means 41 for performing communication, communication mode control means 42 for performing switching between infrastructure mode and ad hoc mode when performing wireless communication, and measuring the physical distance to the communication partner and setting the radio wave transmission output to an appropriate value Switch for switching the wireless output control means 43 to be controlled and the external device such as the mobile terminal 6 to change the operation state of the wireless communication means of the field device from the sleep state to the normal state to switch from the infrastructure mode to the ad hoc mode. A mode switching signal transmitting / receiving means 44 for receiving a signal (hereinafter referred to as a mode switching signal) and a communication program for communicating with other devices. Composed Col (e.g. TCP / IP (Transmission Control Protocol) protocol) network communications stack unit 45 for data conversion as Sokusuru the specification to transmit data to the wireless communication unit 41 and the arithmetic control unit 46 of the.

  The wireless field device 4 executes a function block set in advance and controls each part and each function of the field device 4 to operate as a sensor or an actuator and perform wireless communication with other field devices or mobile terminals. Arithmetic control means 46 for setting field devices and transferring various information, a program for executing function blocks set in advance, applications, protocol information for control communication performed between field devices, etc. Storage means 47 for storing.

  The communication mode control means 42 has channel information used in the infrastructure mode and the ad hoc mode and address information of the access point 5, and performs a beacon search, for example, when specifying a communication partner in the ad hoc mode.

  The wireless output control means 43 is often included in the wireless communication means, but may be provided separately in the wireless field device. As an example of a specific method in this case, a method of controlling output based on communication RSSI (Received Signal Strength Indication, Received Signal Strength Indicator) can be used.

  The mode switching signal transmission / reception means 44 may be either a contact type or a non-contact type, and in the case of a non-contact type IC tag, a passive type RFID may be applicable.

  In order to communicate with other wireless field devices or access points, mobile devices 2 and the like, the communication stack means 45 converts the data received from the arithmetic control means 46 so as to comply with the specifications of the communication protocol, and performs wireless communication. The communication means 41 is controlled to perform wireless communication, or data received from the wireless communication means 41 is converted and transmitted to the calculation control means 46.

  The arithmetic control unit 46 stops a part of the functions of the wireless communication unit 41 and operates with the minimum necessary power (sets the sleep state) during a period when the wireless communication is not performed (sleep period). As a result, it is possible to reduce power consumption during sleep, to save power by ensuring sleep time, and to operate field devices for a long period of time.

  Next, although not particularly illustrated, the configuration of the mobile device 6 will be described. The mobile device 5 is a wireless communication means for performing wireless communication using IEEE802.11a / b / g / n (regardless of a specific standard), and switching between an infrastructure mode and an ad hoc mode for wireless communication. Communication mode control means for performing communication, wireless output control means for controlling the radio wave transmission output to an appropriate value by measuring the physical distance to the communication partner, and transmitting / receiving data to / from the field device 4 and switching the mode to the field device 4 in particular. A mode switching signal transmission / reception means for transmitting a signal, a communication stack means for converting data in accordance with the specifications of a communication protocol for communicating with other devices and transmitting data to the wireless communication means and the arithmetic control means, Consists of

  In addition, the mobile device 6 includes storage means for storing application software for field workers to set and monitor field devices, input means for receiving input of field device setting information from an operator, and wireless communication. It is also constituted by arithmetic control means for controlling the means to communicate with the field device 4 and to exchange the setting information of the field device.

  Although not specifically shown, the configuration of the access point 5 will also be described. The access point 5 uses IEEE802.11a / b / g / n (regardless of a specific standard) to communicate with the field device 4 and the mobile device 6 through wireless communication means and other devices. Communication stack means for converting data in accordance with the specifications of the communication protocol to be performed and transmitting the data to the wireless communication means and the calculation control means, and data received from the wired network and the wireless network for wired and wireless use, respectively Storage means for storing application software such as routers and bridges for changing data and transferring data, and arithmetic control means for controlling the entire access point to operate as an access point.

  Under such a configuration, the wireless field device of the present invention and the wireless control network system using the same perform the following operations. FIG. 3 is an operation explanatory diagram of the wireless field device 4 and the mobile terminal 6 according to the present invention, and FIG. 4 is an operation explanatory diagram illustrating the operation of FIG. 3 in the form of an operation flow diagram of the wireless field device 4 and the mobile device 6. . The numbers (1) to (9) assigned to FIGS. 3 and 4 correspond to each other. The operation of each device (1) to (9) described in FIGS. 3 and 4 will be described below.

  In (1) of FIG. 3, the mode switching signal transmission / reception means of the mobile terminal 6 transmits a mode switching signal to request the field device 4 to operate in the ad hoc mode. At this time, the mode switching signal transmission / reception means of the mobile terminal 6 may use either a contact type or a non-contact type communication method as long as the mode switching signal can reach the field device 4.

  The mode switching signal transmission / reception means of the mobile terminal 6 may be constituted by a non-contact IC, and the mode switching signal transmission / reception means 44 of the field device 4 may be constituted by a tag reader. In this case, the mode switching signal transmitting / receiving means of the mobile terminal 6 transmits a mode switching signal using a passive tag. Further, the mode switching signal transmitting / receiving means of the mobile terminal 6 may have a tag reading mechanism from the field device, and transmits the mode acquisition signal and simultaneously acquires the address information of the field device 4 from the tag at the same time. But it ’s okay.

  In (2), when the field device 4 receives the mode switching signal from the mobile terminal 6 via the mode switching signal transmitting / receiving unit 44, the field device 4 controls the wireless communication unit to switch the operation state from the sleep state to the normal state (in other words, the sleep mode). Wake up from the state). Thereby, the field device 4 can acquire the information of the mobile terminal 6 in the mode switching signal.

  In (3), the communication mode control means 42 of the field device 4 changes the communication mode from the infrastructure mode to the ad hoc mode based on the mode switching signal from the mobile terminal 6. In the following, wireless communication in the ad hoc mode requires information on the channel and the address of the mobile terminal, but any information can be used as long as the information can be specified. For example, it may be defined and stored in advance in a field device, or information such as the address of the mobile terminal 6 may be collected and acquired by a beacon search.

  In (4), the communication mode control means of the mobile terminal 6 changes its own communication mode from the infrastructure mode to the ad hoc mode after transmitting the mode switching signal. Note that information such as the channel and the address of the field device 4 is required for wireless communication in the ad hoc mode thereafter, but any information can be used as long as such information can be specified. For example, it may be defined and stored in advance in a field device, or information such as the address of the mobile terminal 6 may be collected and acquired by a beacon search. In addition to these, when the mobile terminal operates as a master device, the frequency channel may be scanned to select a channel with a low band usage rate. In this case, the mobile terminal 6 performs beacon transmission / search and shares a channel with the field device 4.

  In (5), the mobile terminal 6 and the field device 4 perform, in the ad hoc mode, communication necessary for device setting and information acquisition related to the operator's on-site patrol work or maintenance in the wireless control network system. In this case, the wireless output control means of the mobile terminal 6 and the field device 4 may appropriately change the transmission outputs based on information such as reception intensity.

  In (6), the communication mode control means 42 of the field device 4 changes the communication mode to the infrastructure mode when the communication related to the operation described in (5) is completed. The communication end signal related to the operation of (5) includes a method of including in the communication of (3) to (5), a method of automatically changing after a predetermined time has elapsed, and the like. This operation is out of order with (7).

  (7) The operation control means 46 of the field device 4 is in a sleep state in which a part of the function of the wireless communication unit is stopped and the operation is performed with the minimum necessary power when the period during which wireless communication is not performed reaches a predetermined period. It becomes. Thereby, it can contribute to the power saving by reduction of the power consumption at the time of sleep, and ensuring of sleep time.

  In (8), the communication mode control means of the mobile terminal 6 changes the communication mode to the infrastructure mode when the communication related to the operation described in (5) ends.

  (9) The mobile terminal 6 transfers information to the backbone network node (for example, control server) on the wired network via the access point 5 as necessary.

  As a result, even if the wireless field device of the present invention is a wireless field device that performs a sleep operation for power saving, the mode switching signal transmission / reception means configured by a non-contact IC uses a tag from a mobile terminal. By receiving the switching signal, the mobile terminal can easily access the field device that is in the sleep operation, and can contribute to the improvement of the maintainability without impairing the power saving performance of the entire radio control network system. In addition, it is possible to solve the problem of deterioration in communication reliability due to the inexecutable wireless communication that occurs in the conventional sleep state, and it is possible to contribute to the improvement of communication reliability.

  In addition, according to the field device 4 of the present invention, it has been conventionally necessary to cover the radio wave emission range to the access point by performing communication with the mobile terminal 6 in ad hoc mode when necessary, such as during maintenance. However, by communicating with neighboring mobile terminals in ad hoc mode, the radio wave emission range can be suppressed and the output can be lowered, so that other field devices or other coexisting wireless network systems (for example, ISA100.11a) can be used. The influence of the applied radio noise can be reduced.

  In addition, according to the field device 4 of the present invention, the mobile terminal 6 and the field device can directly communicate with each other without using the access point by performing communication in the ad hoc mode with the mobile terminal 6 as necessary during maintenance. As a result, the amount of traffic can be reduced, and communication reliability and throughput can be improved.

  In addition, the field device of the present invention is effective in that the operation / laying cost can be expected to be reduced when the wireless communication technology is applied to the plant control. It is also possible to provide additional added value.

  Specifically, in the plant system, field maintenance work is performed by field workers, while field devices are required to operate continuously for a long period of time. It is necessary to reduce the operating duty by installing a sleep function in the device. By applying the technology of the present invention to this plant system, it becomes possible to achieve both the power saving performance of the sensor network and the maintenance work of the field device by the mobile terminal.

  As described above, the field device of the present invention returns to the normal state in the sleep state based on the mode switching signal using the tag received from the mode switching signal transmission / reception means configured by the contactless IC of the mobile terminal. In addition, by switching the communication mode from the infrastructure mode to the ad hoc mode and directly performing wireless communication with a mobile terminal existing in the vicinity, the mobile terminal can easily access the field device during the sleep operation, and the wireless control network system This contributes to the construction of a wireless infrastructure capable of performing equipment inspection work without impairing the overall power saving performance.

DESCRIPTION OF SYMBOLS 1, 4 Field wireless device 41 Wireless communication means 42 Communication mode control means 43 Wireless output control means 44 Mode switching signal transmission / reception means 45 Communication stack means 46 Arithmetic control means 47 Storage means 2, 5 Access point 3, 6 Mobile terminal

Claims (7)

Wireless communication means for performing wireless communication in an infrastructure mode for wireless communication via an access point or an ad hoc mode for direct communication between devices in a short distance, and a part of the functions of the wireless communication means are stopped to enter a sleep state In a wireless field device provided with arithmetic control means,
A mode switching signal transmission / reception means for receiving a mode switching signal for switching the wireless communication means from a sleep state to a normal state and switching to communication in the ad hoc mode from neighboring devices;
A communication mode control means for controlling the wireless communication means upon receiving the mode switching signal to switch from the sleep state to the normal state to the ad hoc mode, and for performing communication with the neighboring devices by the wireless communication means; ,
Equipped with a,
The communication mode control means switches the communication mode of the wireless communication means from the ad hoc mode to the infrastructure mode after finishing communication with the neighboring devices by the wireless communication means. Field equipment.   2. The field wireless device according to claim 1, wherein the mode switching signal transmitting / receiving unit receives the mode switching signal from a mobile terminal that monitors and maintains the field wireless device. The calculation control means that executes a function block set in advance and operates as a sensor;
Wireless output control means for measuring a physical distance to a communication partner and controlling a radio wave transmission output value;
The wireless field device according to claim 1, further comprising: The mode switching signal transmitting / receiving means includes
The wireless field device according to claim 1, wherein a mode switching signal is received from the mobile terminal by a passive tag. The arithmetic control means includes
When a predetermined time elapses after the operation of the wireless communication unit is not performed after receiving the mode switching signal, a part of the function of the wireless communication unit is stopped to enter a sleep state. The wireless field device according to claim 1. The wireless field device according to any one of claims 1 to 5,
Comprising a non-contact IC (Integrated Circuit), and means for transmitting a mode switching signal for switching the communication mode from the sleep state to the normal state from the sleep state to the ad hoc mode using a passive tag. A mobile terminal for monitoring and maintaining wireless field devices;
A wireless control network system comprising: The mobile terminal
7. The wireless control network system according to claim 6, further comprising means for performing wireless communication in an infrastructure mode for communicating with the wireless field device via an access point and an ad hoc mode for directly communicating with a near field device. .

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