JP2012080437A - Wireless communication system having distributed scheduler function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost wireless communication system enabling each distributed node to autonomously execute each schedule.SOLUTION: The wireless communication system includes distributed nodes and a management node. Each distributed node includes: a wireless communication unit automatically constructing an ad hoc wireless network; a connection port to an external device; a clock; and a memory area for storing a schedule in the near future. Based on the clock, the distributed node autonomously executes the retained schedule. The management node includes: ad hoc wireless network management means; a network port; a first memory area for storing data, related to the external device, received from the a plurality of distributed nodes; and a second memory area for storing the schedules of the plurality of distributed nodes. Further, each distributed node obtains the schedule of the near future from the management node, at prescribed timing after schedule execution.

Description

  The present invention relates to a wireless communication system having a distributed scheduler function, and more specifically, for example, several tens to several hundreds of node computers (hereinafter referred to as distributed nodes) automatically construct an ad hoc wireless network. The present invention relates to a wireless communication system that can execute a schedule autonomously.

In a power plant, a chemical plant, etc., in order to achieve control of each device, many field devices arranged in various places, for example, control parts such as valves and switches, temperature sensors, pressure sensors and flow rate sensors. It has such a sensor. In order to operate each field device in a coordinated manner, a control system capable of performing a scheduled operation mode change is required.
In a plant control system, it is known that field devices are connected to a field bus, and these field devices are configured to perform data communication with each other via the field bus. A control system using a fieldbus is composed of a small number of computers that are the center of control, and a large system is composed of thousands or tens of thousands of small field devices. In such a control system, for example, in order to change the operation mode, fixed-cycle communication that repeats communication at a fixed cycle is performed. Therefore, when the fieldbus system is configured using a TCP / IP network, the network load becomes a problem.

  Patent Document 1 discloses a network system capable of efficiently performing periodic communication using multicast communication using TCP / IP, and a plurality of transmission systems that start transmission when receiving a packet that satisfies a set condition. A network system is proposed that includes an autonomous node and a schedule setting device that sets a transmission start condition for the autonomous node.

  By the way, an ad hoc wireless network capable of wirelessly connecting a large number of distributed nodes based on a communication standard such as ZigBee (registered trademark, hereinafter omitted) and performing so-called multi-hop communication is an access point such as a wireless LAN. Thus, there is an advantage that a wireless communication network can be easily constructed without preparing an infrastructure such as the above. For example, in multipoint measurement where the number of measurement points exceeds several hundred, there is a high demand for wireless connection of field devices to ad hoc. Therefore, the inventor has proposed an on-demand monitoring system technology constructed using a ZigBee wireless network (see Non-Patent Document 1).

JP 2009-105604 A

Nakanishi Miichi: "Development of a ubiquitous data collection, storage, and analysis system package", Shikoku Electric Power. Shikoku Research Institute No.89, pp43-54 (2007.12)

In a system configured to arrange a large number of distributed nodes on a network linked by ad hoc radio such as the ZigBee standard, it is not easy to schedule the behavior of individual distributed nodes with good time accuracy. Without this, the use of this type of system would be very limited.
In the method in which an operation schedule is incorporated in each distributed node in advance, when it is desired to change the behavior of the entire system, it is necessary to update the schedule data of all the distributed nodes, which is not practical. Also, there are many cases where it is not possible to mount a memory that can hold a long-term schedule in each distributed node due to cost constraints. In particular, in multipoint measurement, it is necessary to reduce the cost of the distributed node as much as possible, so the hardware resource is greatly limited.

  Here, a method is conceivable in which an operation command is issued in real time from a single node computer (hereinafter referred to as a management node) holding the schedule of the entire network to individual distributed nodes via a wireless network. However, wireless networks are unstable compared to wired networks, and fluctuations in communication time are likely to occur. Especially when it is necessary to issue operation commands to multiple distributed nodes simultaneously, a large amount of time is required for command transmission to individual distributed nodes. There is a problem that fluctuations occur. In addition, one of the forms of ad-hoc wireless network usage is to establish a wireless communication path with a group of distributed nodes with fixed installation locations, as in the case of online temperature management of beef cattle grazed on a ranch. There is a form in which a distributed node (in this case, a body temperature measurement node carried by a beef cattle) is moved in the possible area while sequentially switching the first relay station from there to the nearest fixed distributed node. Whenever one relay station is switched, communication disconnection occurs for several seconds to several tens of seconds. During this time, the mobile distributed node cannot receive an operation command from the management node, and therefore issues an operation command in real time from the management node. There is a problem that the method is not available. Further, as an unavoidable disadvantage of this method, since the management node needs to constantly scan the schedule data of the entire system in order to detect the operation instruction timing to each distributed node, it is proportional to the number of distributed nodes. Therefore, the data processing load for that purpose increases, and it may be difficult to determine the data processing performance required for the management node.

  Also, in a system using an ad hoc wireless network, it is often difficult to supply power to individual distributed nodes, and it is often necessary to be able to operate for a long time with a battery power source. Long-time operation with battery power is generally realized by putting each distributed node in an active state that consumes a large amount of power only when necessary, and in a resting state that consumes little power at other times. When applied to a sensor node group that does not have a schedule function, each sensor node must always repeat the active state and the dormant state in the shortest time interval, even if the required measurement interval changes in a schedule. There is a problem that it is difficult to reduce power consumption.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a wireless communication system in which each distributed node can autonomously execute a schedule at a low cost.

The present invention is a mechanism that imitates the relationship between the main memory and cache memory of the CPU. One management node holds schedule data for the entire network, and individual distributed nodes manage near-future schedules as needed. The present invention provides a network distributed schedule management function, which is obtained from a node via a network.
The present invention comprises the following technical means.

The first invention has a wireless communication unit that automatically constructs an ad hoc wireless network, a port for connection with an external device, a clock, and a memory area that stores a near future schedule, and is held based on the clock. A distributed node that autonomously executes a schedule, an ad hoc wireless network management means, a network port, a first memory area that stores external device-related data received from a plurality of distributed nodes, and a first that stores schedules of the plurality of distributed nodes A wireless communication system comprising: a management node having two memory areas, wherein each distributed node acquires a near-future schedule from the management node at a predetermined timing after execution of the schedule.
A second invention is characterized in that, in the first invention, the management node has means for reading the schedules of all the distributed nodes and dividing and storing the schedules for each distributed node in the second memory area. To do.
According to a third invention, in the first or second invention, when the schedule stored in the second memory area is updated, the management node updates a schedule held by each distributed node by a broadcast message. It is characterized by having.
According to a fourth invention, in any one of the first to third inventions, the distributed node stores a schedule in a memory built in a microcontroller.
A fifth invention is characterized in that, in any one of the first to fourth inventions, the distributed node can collect measurement data from a sensor via a connection port with an external device.
A sixth invention is characterized in that, in any one of the first to fifth inventions, the distributed node has a power saving mode for reducing power consumption and can be continuously driven for a long time by a built-in battery.
According to a seventh invention, in any one of the first to sixth inventions, the distributed node is installed in one or a plurality of mobile objects.
In an eighth invention according to any one of the first to seventh inventions, tens or more of distributed nodes can be connected.
A ninth invention is a distributed node used in the radio communication system according to any one of the first to eighth inventions.
A tenth invention is a management node used in a radio communication system according to any one of the first to eighth inventions.

According to the present invention, it is possible to provide a low-cost wireless communication system in which individual distributed nodes can autonomously execute a schedule. In other words, since the operation schedule management of the distributed node can be performed, it is possible to appropriately adjust the data collection frequency from various sensors and reduce the cost of data collection and management.
In addition, the power consumption of each distributed node can be reduced, and the battery replacement interval can be extended.

1 is an overall system configuration diagram according to an embodiment of the present invention. 1 is an overall system configuration diagram illustrating software, data, and the like related to a management node (NC) and a data center of the present invention. It is a block diagram of the distributed node (NICE) of this invention. It is a block diagram of the management node (NC) of this invention. 3 is a diagram illustrating a distributed scheduler mechanism of the system of the present invention. It is a schedule processing flowchart in the distributed node of this invention.

An embodiment for carrying out the present invention will be described as an improved example of on-demand monitoring system technology (ATOMS) (see Non-Patent Document 1).
The system of this embodiment is characterized by using a ZigBee wireless communication network as a field network and a native XML database as a database, which is on-demand type (can be deployed immediately when needed, enabling extremely flexible operation) (A) Network distributed cell computers (NICE, usually arranged on a single ad hoc wireless network, equivalent to the distributed node of the present invention), (b) Network computers (NC, usually 1 is arranged on one ad hoc wireless network and corresponds to the management node of the present invention), (c) a data center, and (d) a user interface (see FIG. 1 and FIG. 2).

(a) The network distributed cell computer (NICE) shown in Fig. 3 is a high-performance, compact, low-cost, low-power measurement and control computer with various signal input / output functions and ZigBee wireless network linkage functions. The system is positioned as a distributed node in the present invention in terms of the overall configuration of the system. A network distributed cell computer (NICE) functions as an independent measurement and control node by connecting sensors, etc., but by installing a network distributed cell computer (NICE) in existing facilities, etc. Can also be brought online. The network distributed cell computer (NICE) according to the present embodiment is designed to operate only with a few kilobytes of RAM built into the microcomputer, which is the main component, for the purpose of reducing component cost and power consumption. Has been. Depending on the application, a wired communication port such as RS232C, CAN, 1-Wire (registered trademark) may be provided, and if there are no problems with component cost and power consumption, an external storage device such as microSD is provided. It is good. Real-time clock (RTC), which is the timekeeping mechanism of network distributed cell computer (NICE), generates a time error of about ± 30 seconds / month. Synchronizing with the RTC, which is the standard for the entire system mounted on the network computer (NC), prevents the occurrence of timing errors that cause problems in system operation (in this embodiment, the entire system is 1). It is operated so that the error is within seconds).

(b) The network computer (NC) shown in FIG. 4 manages the operation of all network distributed cell computers (NICE) linked to the ZigBee wireless network and is necessary from the network distributed cell computers (NICE) group. It has a function of collecting data and transmitting it to a data center, and is positioned as a management node in the present invention in the overall system configuration. Network computers (NC) are less costly and less power consuming, so the built-in microcomputers are far more powerful than network distributed cell computers (NICE), and network computers (NC) A 10 MB RAM and a few GB external storage device (SD memory) are installed. The network computer (NC) is equipped with an RTC, which is the standard for the entire system. This RTC is set to synchronize with an accurate time such as GPS periodically, and there is no timing error that causes problems in system operation. Therefore, the timing errors of all RTCs installed in the network distributed cell computer (NICE) and network computer (NC) are always managed within a range where there is no problem in system operation. It is assumed that it functions effectively. The network computer (NC) according to the present embodiment has a Java (registered trademark) execution environment, generates Java threads based on a plurality of XML templates prepared in advance according to usage, and generates XML data for each XML template. Means for generating the structure.

(c) The data center stores data received from a network computer (NC) in an XML database and provides a powerful data analysis service based on XML technology for the user interface.

(d) A mobile phone, Internet browser, and PC-based dedicated data analysis software can be used as a user interface. Of these, the Internet browser and mobile phone can directly access the network computer (NC), refer to the latest measurement data, and receive anomaly notification mail. In addition, powerful search-based data analysis based on XQuery (XML data retrieval and extraction language) can be performed using PC-based dedicated data analysis software that works in conjunction with the XML database of the data center.

The mechanism of the distributed scheduler in this system is as follows (see FIGS. 5 and 6).
(1) The user creates an XML file describing the schedule of the entire system and stores it in the SD memory of the network computer (NC). Each XML file describes the schedule for one day. Here, the reason why the schedule data is not described for each network distributed cell computer (NICE) is due to consideration of the human aspect that it is more human-friendly and less likely to make mistakes.
The schedule type according to the present embodiment can be selected from daily (1 file), week (7 files), month (31 files), and year (366 files). In the present embodiment, any one can be selected, and the specification cannot be combined. When other than “days” is selected, schedule data for the next day is loaded into the RAM of the network computer (NC) from the XML file stored in the SD memory at 1:00 every day.

(2) When the schedule data is read into the RAM of the network computer (NC), it is divided into schedule data for each network distributed cell computer (NICE) and held.

(3) Each network distributed cell computer (NICE) is programmed to obtain the most recent schedule and the next schedule from the network computer (NC) via an ad hoc wireless network at startup. Each time the stored schedule is executed, the next schedule data is acquired from the network computer (NC) via the ad hoc wireless network. Therefore, each network distributed cell computer (NICE) always keeps two schedules in execution + near future. One schedule data in the near future to be held by the network distributed cell computer (NICE) is necessary and sufficient, but in this example, it is set to two with a margin.

(4) The network computer (NC) has an FTP server function so that schedule data can be stored and updated in the SD memory via the LAN. When the schedule data of the network computer (NC) is updated, the near-future schedule currently held is discarded by a broadcast message from the network computer (NC) to all network distributed cell computers (NICE). It is a specification that instructs to execute the same initialization sequence as. Therefore, the schedule change is immediately reflected in all the network distributed cell computers (NICE), and after updating the schedule data of the network computer (NC), the old schedule held in each network distributed cell computer (NICE) Never executed.

(5) One schedule data includes “sequence number” + “execution time” + “message”. The message is composed of a key and a data body, and its usage is application dependent. The message includes an instruction to change the sensor measurement method, an instruction to control some external device, a character string to be displayed on the display device, and the like.

(6) Using this mechanism, the sensor measurement timing can be changed, external devices can be controlled, and messages can be displayed on the LCD.

A specific application example of the present invention will be described by taking as an example the construction of a security system in an existing factory.
To introduce a new security system to an existing factory, for example, (a) install intrusion detection sensor nodes in all entrance / exit gates, and (b) install entrance / exit monitoring nodes in restricted access areas. Once implemented, it is necessary to change the operation mode of these distributed nodes with high accuracy in accordance with the time, day of the week, and holidays. Moreover, since the restricted access area in (b) changes periodically depending on the work situation, more flexible schedule management is required. (a) + (b) is expected to be several dozen to several thousand locations depending on the scale of the factory, and it is enormous to maintain an operation schedule independently on each distributed node and maintain it as necessary It is not realistic because it requires labor. In addition, in the method of instructing the sequential operation mode by wireless communication from the management node, there is a possibility that a delay or malfunction may occur in the operation mode change of the distributed node that manages the security important part due to temporary radio communication failure etc. Does not satisfy the function as a security system.
In the present invention, since the operation mode schedules of all the distributed nodes are simply stored in the external storage device of the management node, the near-future operation mode schedules are sequentially delivered to the respective distributed nodes. Operation schedule management can be performed efficiently and with good time accuracy.
As shown in this example, the introduction of this distributed scheduler mechanism requires not only monitoring but also a schedule management function for a system consisting of a network distributed cell computer (NICE), a network computer, a data center, and a user interface. It can be used for security systems. Further, in this system, since the management node only has to wait for a request from the distributed node, it is possible to install the distributed node in a moving body such as an animal or a vehicle.

Conventionally, ad hoc wireless network technology has often been used for the purpose of application to simple monitoring applications that do not require operation schedule management of distributed nodes, but according to the present invention, even if limited to monitoring applications, Since it becomes possible to manage the operation schedule of the distributed nodes, it is possible to appropriately adjust the data collection frequency from various sensors and reduce the cost of data collection and management.
In addition, according to the present invention, it is possible to expect a great economic effect of reducing the power consumption of each distributed node and extending the battery replacement interval. That is, according to the present invention, since each distributed node has a schedule function, the interval between the active state and the hibernation state can be appropriately changed, and the battery life can be extended to the maximum. Here, in the configuration in which the schedule change is performed by wireless communication from the management node side, since the wireless communication from the management node cannot be received while the distributed node is idle, a problem occurs in the schedule change. Since the near future schedule data is acquired from the side, it is possible to change the schedule without any problem even in a usage mode in which the distributed nodes are in a dormant state for power saving.
In addition, when the external device is controlled from the distributed node, such as the electromagnetic lock control at the entrance and exit, the operation schedule management function of the distributed node becomes more important. If the operation modes of a large number of distributed nodes can be managed with high time accuracy, an automatic operation system for home automation systems, building management systems, or devices such as factories can be constructed based on ad hoc wireless network technology.

Claims (10)

It has a wireless communication unit that automatically builds an ad hoc wireless network, a port for connecting to external devices, a clock, and a memory area that stores a near-future schedule, and autonomously executes the schedule held based on that clock A distributed node,
A management node having an ad hoc wireless network management means, a network port, a first memory area for storing external device-related data received from a plurality of distributed nodes, and a second memory area for storing a schedule of the plurality of distributed nodes;
A system comprising:
A wireless communication system, wherein each distributed node acquires a near-future schedule from a management node at a predetermined timing after schedule execution.   2. The wireless communication system according to claim 1, wherein the management node has means for reading the schedules of all the distributed nodes and dividing and storing the schedules for each distributed node in the second memory area.   3. The radio according to claim 1, wherein the management node has means for updating a schedule held by each distributed node by a broadcast message when the schedule stored in the second memory area is updated. Communications system.   4. The wireless communication system according to claim 1, wherein the distributed node stores a schedule in a memory built in a microcontroller.   The wireless communication system according to claim 1, wherein the distributed node is capable of collecting measurement data from a sensor via a connection port with an external device.   6. The wireless communication system according to claim 1, wherein the distributed node has a power saving mode for reducing power consumption, and can be continuously driven for a long time by a built-in battery.   The wireless communication system according to claim 1, wherein the distributed node is installed in one or a plurality of mobile objects.   The wireless communication system according to any one of claims 1 to 7, wherein several tens or more distributed nodes can be connected.   A distributed node used in the wireless communication system according to claim 1.   A management node used in the wireless communication system according to claim 1.