KR100250888B1 - Network detection device of distributed control system - Google Patents

Abstract

PURPOSE: The apparatus for checking a network is provided to promptly detect network interference, and to reduce a frequency rate of an additional test frame dispersed in a transmission channel of the network so as to decrease a load of the network and to stabilize an operation of the network. CONSTITUTION: A data frame transmission unit(50) transmits a data frame as a use of a test frame when data is periodically transmitted to every station to check a status of a network. The data frame transmission unit(50) sets a test transmission status function when the test frame is transmitted. A test frame transmission unit(55) checks the test transmission status function, and makes the test frame when the test frame is not transmitted to the network for a predetermined time, then transmits the test frame. A transmission channel management unit(60) allots one logical transmission channel to each application program(30). A receiving handler(65) sets a data receiving status function when the data frame is transmitted from a network driving unit(70). A network status monitor(45) periodically monitors the data receiving status function for a predetermined time, and checks a receiving status of the data frame in the network channel. A receiving channel management unit(40) searches for the logical channel for deciding to which program the received data is transmitted among the application programs(30). A network management unit(35) announces an error to a user when the error occurs in a corresponding network, according to the data frame transmission status.

Description

Network check device of distributed control system

The present invention relates to a network inspection apparatus of a distributed control system, and more particularly, to a network inspection apparatus of a distributed control system capable of stabilizing network operation by reducing an occurrence frequency of additional test frames scattered on a network transmission line. It is about.

In general, Carrier Sensitive Multiple Access (hereinafter referred to as CSMA) or Collision Detection (hereinafter referred to as CD) Network Protocol (Protocol) In the real-time distributed control system using a communication protocol (pointing communication protocol), a method for real-time monitoring of a fault on a network is needed. As described above, in the case of the commonly used CSMA / CD type Ethernet, a token ( Since the communication data flows on the network line only when it is necessary without transmitting a token, it does not check the status of the network when no transmission or reception occurs. Therefore, in the CSMA / CD protocol structure, check the status flag of the device set by the network interface device when sending and receiving data to the network to check the network status, or send a test frame on the network line and respond to it. Diagnose the state of the network using. In general, when the test frame is transmitted, the value recorded in the status flag register of the network device does not check the exact network state. Therefore, the test frame scattered on the network is returned to the user to check the state of the network. . Thus, there is a need to additionally create and transmit a test frame of a special structure for testing.

1 is a system block diagram of an apparatus for checking the state of a conventional network. As shown in this figure, conventional communication required by each application task 1 has been handled by the communication processor 2, and a separate network error detector 3 is additionally used to check the state of the network. Perform communication function. The communication channel is divided by the communication channel manager 4 for general communication required by the system and communication for network condition monitoring. In addition, the network error detector 3 periodically sends out a test communication frame on the network line in order to monitor the network status by the method described above, and uploads the network status flag register from the network device 5 upon transmission and reception. Monitor the status of the network by checking the contents of the test or by checking the response to the test frame. When the network error detector 3 detects an error on the network, it notifies the system monitoring task 6 to take appropriate action. At this time, if the system requires real-time data processing, the network's status should be checked quickly because the error condition of the network should be checked immediately and quick action should be taken in case of network failure. In order to detect failures on the network more quickly, a shorter period of sending out a test communication frame should be shortened. The shorter the test period, the greater the hourly communication load on the network. Therefore, the overall communication load of the system increases the frequency of data frames scattered on the network line due to the addition of the communication amount for the network check to the total amount of communication required for the data communication, and thus the possibility of collision retries may occur in the device itself. As it increases, the transmission speed is affected, which affects the overall network operation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and can reduce network load increase and stabilize network operation by reducing the occurrence frequency of additional test frames scattered on a network transmission line while quickly detecting a failure on a network. The purpose is to provide a network inspection apparatus of a distributed control system.

The network inspection apparatus of the distributed control system of the present invention for achieving the above object transmits general communication data received from several application programs present in the system and periodically sends the data to all stations to check the network status. A data frame transmitter for transmitting a data frame for a test frame and setting a test transmission state variable when the test frame is transmitted; A test frame transmission unit which checks the test transmission state variable and generates the test frame when the test frame is not transmitted to the network for a predetermined time; A transport channel manager for allocating one logical transport channel for each application program; A reception processor for checking a reception state of the data frame and setting a data reception state variable when the data frame is received from a network device driver; A network state monitoring unit inspecting the data frame reception state on the network line by inspecting the data reception state variable at a predetermined time period; A receiving channel manager for finding a logical channel for determining which of the application programs the received data should be transmitted to; And a network management unit notifying the outside of an error in the corresponding network based on the data frame reception state.

1 is a system block diagram of an apparatus for checking the state of a conventional network;

2 is a diagram schematically showing a network configuration of a real-time distributed control system equipped with a network checking apparatus of the present invention;

3 is a system block diagram showing a network checking apparatus of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

1. application tasks, 2. communication handlers,

3. network error detector, 4. communication channel manager,

5. network devices, 6. system monitoring tasks,

10. Processing data control station, 20a, 20b,... , 20n. Control Station,

30. Application, 35. Network Administration Department,

40. receiving channel manager, 45. network status monitor,

50. data frame transmitter, 55. test frame transmitter,

60. transmission channel manager, 65. reception processor,

70. Network device driver, 75. Network device

Hereinafter, a network inspection apparatus of a distributed control system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram schematically illustrating a network configuration of a real-time distributed control system equipped with a network checking apparatus of the present invention. As shown in this figure, in the distributed control system to which the present invention is applied, a plurality of control stations 20a, 20b, ..., 20n are used as one processing data management station (two when the processing data management station is duplicated) ( 10) was connected to the network and operated. The above-described processing data management station 10 collects and monitors real-time data from the control stations 20a, 20b, ..., 20n or transmits a control command, and the control stations 20a, 20b, ..., 20n are generated at the corresponding station. The alarm is sent to the process data management station 10, and communication for control data exchange is performed between the respective control stations 20a, 20b, ..., 20n. In this case, CSMA / CD is used as the physical protocol of the network. Whenever a transmission is required, CSMA / CD is used to send data on the network line and check the collision status. It is structured.

3 is a system block diagram showing a network checking apparatus of the present invention. The network checking apparatus of the present invention exists in every station of the processing data management station 10 and the control stations 20a, 20b, ..., 20n, sends and receives data through the network interface device, and checks the transmission status of the network. As shown in this figure, the network inspection apparatus of the present invention is a program using a network, which manages the status of an application 30, which is one of several application programs of a real-time distributed control system, and a network. In case of occurrence, the network management unit 35 that informs the user through an alarm processor or the like, and logically for determining where to receive the received data to one of several applications 30 existing in the system. Receiving channel management unit 40 for finding a channel, the network state monitoring unit 45 for checking whether a frame has been received on the network line by checking a data reception state flag at a predetermined time period by checking a data frame reception state on a network line. ), Transmitting general communication data In the case of periodically sending data to all stations in order to check the network status, the data frame transmission unit 50, which indicates that the test frame has been transmitted by sending a data frame for a test frame and setting a test transmission flag, indicates the state of the network. In order to check the test frame, the test frame is periodically sent to check the test transmission flag. If the test frame has not been transmitted to the network for a predetermined time, the test frame transmission unit 55 generates a test frame, one for each application. When receiving a frame by receiving the frame from the transmission channel manager 60 or the network device driver 70 for allocating the logical transmission channel, the reception state of the frame is checked and the reception state flag is set to indicate that the frame has been received. The processor 65 includes a network device driver 70 and a network device 75 for controlling the drive of the network transmission device 75.

The test transmission flag as described above is a state variable for checking whether a test frame has been transmitted or not, and is set when the data frame including the test frame is transmitted by the data frame transmission unit 50. Periodically checked and removed, the data reception status flag is a state variable indicating whether data has been received through the network and is set when the reception processing section 65 receives a frame.

Hereinafter, an operation process and an effect of the network checking apparatus of the distributed control system according to the preferred embodiment of the present invention will be described.

In order to reduce the load on the network due to the test frame for checking the network status, the data frame transmitter 50 sends a general data frame together for a test frame. This test frame can be used as a network test frame because it checks that the data was received without error on the network. Therefore, the general data frame transmitted from another station is checked because the network status is checked by the test frame sent from another station, compared to the conventional method, which required a special structure of the test frame to check the status after receiving the response. Can be used as a test frame to reduce the load on the network. At this time, if the station is not in the network or the network status of all other stations is unavailable, the own network status may be unconditionally checked as unavailable.

When each station needs to send data to several stations at once, it transmits the data frame by broadcast communication so that it can be received by all other stations, and the receiving station receives the broadcast processing unit (65). ), It processes the data frame it wants and checks and discards the network reception status if it does not. When the data frame is transmitted from the data frame transmitter 50 through broadcast communication, it is assumed that the test frames are transmitted together, and the test transmission flag is set to one. In addition, the test frame transmission unit 55 checks the test transmission flag at a predetermined time period, and if it is not set, creates and transmits a test frame, and if it is set, determines that the test frame has been transmitted within a predetermined time and separately creates and transmits the test frame. I never do that. Therefore, the check frame for network status monitoring is transmitted through the data frame transmitter 50 or the test frame transmitter 55 within a predetermined time (test frame maximum transmission interval). The interval to check whether a test frame has been transmitted depends on the network state detection time limit required by the system.

When a data frame sent from another station is received, the reception processing unit 65 determines a failure state of the network with reference to the reception state portion of the received frame, or the network state monitoring unit 45 monitors the frame reception state for a predetermined time. If no frame is received, it is determined that there is an error in the network. The reception processor 65 sets a reception status flag that the reception has been received each time a data frame is received. The reception status flag is set at a predetermined time period by the network status monitoring unit 45, and the reception status flag is set, and the network reception status is set. If it is determined to be normal, the reception state flag is cleared.

If the reception status flag is not set, it is determined that there is an error on the network because there is no frame received for a predetermined time. The period for checking whether a frame is received depends on the maximum transmission interval of the frame.

The network inspection apparatus and method of the distributed control system of the present invention are not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea of the present invention.

According to the network inspection apparatus of the distributed control system of the present invention as described above, by using the test frame for the network status check with a common data frame, by reducing the frequency of the occurrence of additional test frames scattered on the network transmission line It can reduce the network load and stabilize the network operation.

Claims (4)

It transmits general communication data received from several applications in the system, and when sending the data to all stations periodically to check network status, it sends data frame for test frame, and when the test frame is transmitted, test transmission status A data frame transmitter for setting a variable; A test frame transmission unit which checks the test transmission state variable and generates the test frame when the test frame is not transmitted to the network for a predetermined time; A transport channel manager for allocating one logical transport channel for each application program; A reception processor for checking a reception state of the data frame and setting a data reception state variable when the data frame is received from a network device driver; A network state monitoring unit inspecting the data frame reception state on the network line by inspecting the data reception state variable at a predetermined time period; A receiving channel manager for finding a logical channel for determining which of the application programs the received data should be transmitted to; And And a network management unit for notifying an outside of the network when an error occurs in the network based on the data frame reception state. 2. The apparatus of claim 1, wherein the test transmission state variable is a state variable indicating whether the test frame has been transmitted. 2. The apparatus of claim 1, wherein the data receiving state variable is a state variable indicating whether data is received through the network. The method of claim 1, wherein the period for checking the test transmission state variable is based on a network state detection limit time required by a system, and the period for checking the data reception state variable is calculated based on a maximum transmission interval of the test frame. Network inspection apparatus of a distributed control system, characterized in that.

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