JP2017098856A - Public line communication device and control monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a communication device from accidently outputting a control command and erroneously operating a field apparatus when control is not performed in a monitoring system that transmits a control command using a public line from a monitoring control device to the field apparatus via a public line communication device at a site.SOLUTION: A public line communication device is composed of two apparatuses of a communication unit and a programmable logic controller (PLC), and the PLC outputs a control command. The communication unit outputs an in-control signal other than control commands. The control command and the in-control signal are taken in by a field circuit, and the control command is output from the field circuit to an object apparatus only when the in-control signal is being output.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a communication device for remote control, and to a monitoring control device for remotely monitoring and controlling water supply and distribution systems for water and sewage, industrial production facilities, sales data collection facilities, etc., via a public telephone line. It relates to the control method of the control command signal of the notification device that performs data transfer and alarm notification to the user.

  Conventionally, data to be monitored is taken into a communication device installed at the site, and the status of the monitored object is transferred to a remote monitoring and control device by communication to display and store data, or from monitoring to field equipment via the communication device A supervisory control system is known that performs a remote operation by sending a control command to the remote controller. In such a supervisory control system, a public telephone line may be used instead of a constant communication line in order to reduce communication costs (see Patent Document 1).

  Since the public telephone line cannot always communicate, the communication is usually cut off and the communication is carried out whenever necessary. For this reason, in a supervisory control system using a public telephone line, a telephone call is made from the supervisory control device to a communication device in the field, and after communication between the supervisory control device and the communication device is established, data acquisition or control command Often send. On the other hand, when an abnormality occurs at the site, since the occurrence of the abnormality is unknown to the monitoring device that has lost communication, the communication device calls the monitoring device to notify the abnormality.

JP 2001-177657 A

  Many conventional public line communication terminals are provided with both a public line communication unit and an input / output unit for inputting and outputting signals. In these communication terminals, contact signals are used for connection with field devices, and therefore a terminal block for connecting contact signals is provided. Conventionally, most of them correspond to the number of signals of 20 points or less, but in recent years, correspondence to the number of signals of about tens to 100 points is also required. In order to capture 100 signals, 200 terminals are required, which is twice the number of points, and it is not realistic to provide a terminal block for signal connection in the communication terminal itself. When handling a large amount of signals, an input main force part is often provided separately from the communication part. In general, a PLC (programmable logic controller) is often used as an input / output unit of another apparatus because it has a large number of terminal blocks and real-time sequence processing is possible.

  In remote control operations via public telephone lines, communication is not performed except when a control command is sent, and the operation of the device itself is not abnormal. Even if the field device malfunctions due to a cause other than the control command, The user cannot know this. In water and sewage monitoring and control systems, the field side is often used with unmanned equipment, and because the target is water supply equipment, it may have a large impact when field equipment malfunctions, thus preventing the output of erroneous control commands. That is highly important.

  As described above, in the current public line communication apparatus, in order to handle a large amount of contact signals, there is a communication apparatus including a communication unit having a communication unit function and a PLC having an input / output unit function. The communication unit and PLC are connected by a communication line such as serial or Ethernet. When a control command is issued from the monitoring device, the command is first sent to the communication unit, and the communication unit sends the command to the PLC, and after the sequence software processing inside the PLC, the command is sent from the PLC contact output to the device to be controlled. Is output.

  In such a system, a control command may be erroneously output due to a bug in the sequence software or a failure in the output unit. Since the control command is output when the contact is turned ON / OFF, it is not possible to take safety measures such as taking multiple steps like the command by the communication line. For this reason, it cannot be determined whether or not the on-site equipment is a control command that has been normally output, and the on-site equipment operates in accordance with the command even if it is an erroneously output control command. An object of the present invention is to improve the reliability of remote control using a public line communication device by preventing a field device from malfunctioning even when a control command is erroneously output.

  In order to solve the above problems, a public line communication device that remotely controls a control target via a public line, receives a control command from the monitoring control device via the public line, and A communication unit that outputs an in-control signal to the outside when receiving, and a PLC that is connected to the communication unit and that issues a control command received by the communication unit to a control target. In addition, a circuit that receives a signal from the communication unit and a signal from the PLC is provided, and the circuit outputs a control command from the PLC to a control target only while receiving a control signal from the communication unit. The configuration.

  According to the present invention, it is possible to prevent malfunction due to erroneous output of a control command.

It is a lineblock diagram of a surveillance system concerning one embodiment of the present invention. It is a block diagram on the field side of a public line communication terminal.

  Hereinafter, an embodiment according to the present invention will be described with reference to FIG. In addition, in this embodiment, although the monitoring control system used with the system which monitors a water and sewage installation is made into an example, it is not limited to a water and sewage installation. First, an overall configuration of a supervisory control system using a public line will be described with reference to FIG. 1 according to an embodiment of the present invention.

  The monitoring control device 100 is composed of a computer such as a PC, for example, and is arranged in a management room away from the water and sewage facilities to be monitored. An operator of the management room performs remote monitoring and remote control of the on-site water and sewage equipment via the monitoring control device 100. The public telephone line 101 is a telephone network that is connected to the remote control apparatus 100 and the public line communication apparatus 102 at a remote site, and is connected by a fixed telephone line or a mobile telephone line. The public line communication device 102 is normally disconnected from the public telephone line 101, but when communication is required, the communication is established with the monitoring control device 101 to exchange data. Specifically, the public line communication apparatus 102 has a contact signal input / output function and a function of transmitting data input from the monitoring target 103 to the monitoring apparatus 100 and a control signal sent from the monitoring apparatus 100 to the control target 104. The function to output to. The device to be controlled and the device to be monitored may be the same device or may be different devices, and generally there are a plurality of monitoring targets 103 and control targets 104. Depending on the monitoring control system, by providing a plurality of public line communication devices 102, it is possible to exchange data with a larger number of monitoring targets 103 and control targets 104.

  Next, prevention of malfunction of the control command will be described with reference to FIG. FIG. 2 shows the configuration of the system on the site side from the public telephone line in the supervisory control system of FIG. The public line communication apparatus 102 includes a communication unit 105 and a PLC 106. The communication unit 105 and the PLC 106 are connected by a communication line such as serial or Ethernet.

  The monitoring target 103 and the control target 104 are connected to the terminal block of the PLC 106, and input / output data via a contact. Further, the communication unit 105 outputs not only the function of connecting to the PLC 106 but also the control signal when it is under control when communication is established and the control signal is received on the public telephone line 101. Has function. Further, the PLC 106 outputs a control command transmitted from the remote monitoring control device 101 to the control object 104. As shown in FIG. 2, the control command from the PLC 106 and the in-control signal from the communication unit 105 in the public line communication apparatus 102 are sent to the controlled object 104 via the field circuit 107. The on-site circuit 107 may be attached to the device to be controlled or may be incorporated in the public line communication device 102.

  The communication unit 105 that receives the control command from the monitoring device 100 transmits the command to the PLC 106 and outputs the command to the field circuit 107 from the PLC 106. At the same time, an in-control signal is output from the communication unit 105 to the field circuit 107. The on-site circuit 107 outputs the control command to the controlled object only when both the control command and the in-control signal are output. Since the communication unit 105 outputs a control signal only when a control command is received from the monitoring control device 100, the on-site circuit 107 outputs a control command to the control target 104 even if the control command is output from the PLC 106 except during control. do not do. As a result, it is possible to prevent the controlled object 104 from malfunctioning when the control command is erroneously output from the PLC 106 instead of the control command from the monitoring control device 101.

Claims (3)

A public line communication device for remotely controlling a control target via a public line,
A communication unit that receives a control command from the supervisory control device via a public line, and outputs a control signal to the outside when the control command is received;
A public line communication apparatus, comprising: a PLC connected to the communication unit and configured to issue a control command to a control target from a control command received by the communication unit.   2. The supervisory control system including the public line communication apparatus according to claim 1, further comprising a circuit that receives a signal from the communication unit and a signal from the PLC, and the circuit receives a signal under control from the communication unit. A monitoring control system that outputs a control command from the PLC to an object to be controlled only during an interval.   3. The monitoring control system according to claim 2, wherein the control command is output by turning on or off a contact of the PLC.

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