JP2011160014A - Field communication device - Google Patents

Abstract

A field communication device capable of improving reliability while suppressing cost is provided.
Output means for outputting a serial communication signal to a communication path; and detection means for detecting that a value of the serial communication signal output from the output means to the communication path is fixed for a predetermined time; Is provided. The serial communication signal is a signal that switches between a plurality of values at intervals shorter than the predetermined time at a normal time and notifies a specific state by maintaining a specific value among the plurality of values.
[Selection] Figure 1

Description

  The present invention relates to a field communication device that is inserted between a field device and a control system that controls the field device and relays a serial communication signal.

  An input / output device is used as a device that is inserted between a field device and a control system that controls the field device and relays a serial communication signal. FIG. 5 is a block diagram showing a configuration example of a conventional input / output device.

  As shown in FIG. 5, the front-side system 100 includes a conversion circuit 11 for A / D conversion or D / A conversion of a signal exchanged between the controller-side system 200 and a field device that is an analog device. Is provided.

  Data is transmitted and received by digital signals between the front side system 100 and the controller side system 200, commands from the controller side system 200 to the front side system 100 are transmitted to the front side system 100, and commands from the front side system 100 to the controller side system 200 are transferred. Each response by serial communication is transmitted. Further, a reset is transmitted from the controller side system 200 to the front side system 100 independently of the command. The reset is a signal for designating whether or not the front system 100 is reset, and takes one of values “L” and “H” depending on whether or not the front system 100 is reset.

  As described above, three systems of communication paths are provided in order to exchange three signals of command, response, and reset between the front system 100 and the controller system 200. However, since it is insulated from the field device, insulating elements 3a, 3b, and 3c are inserted in the respective communication paths.

Japanese Patent Laid-Open No. 11-175259

  Insulating elements are relatively expensive and generally have a high failure rate. Therefore, it is desirable to reduce the number of insulating elements used as much as possible in order to improve system reliability and reduce costs. Further, the conventional input / output device has a problem that a clamp failure cannot be detected when the insulating element is clamped during operation.

  An object of the present invention is to provide a field communication device capable of improving reliability while suppressing cost.

The field communication device of the present invention is a field communication device that is inserted between a field device and a control system that controls the field device and relays a serial communication signal, and an output unit that outputs the serial communication signal to a communication path; Detecting means for detecting that the value of the serial communication signal output from the output means to the communication path is fixed for a predetermined time, and the serial communication signal is normally at an interval shorter than the predetermined time. And a signal for switching between a plurality of values and notifying a specific state by maintaining a specific value among the plurality of values.
According to this field communication device, since it is detected that the value of the serial communication signal output to the communication path is fixed for a certain period of time, it is possible to improve reliability while suppressing costs.

  An insulating element may be provided in the communication path between the output unit and the detection unit.

  The output means may output the serial communication signal in a direction from the control system toward the field device.

  The output means may output the serial communication signal in a direction from the field device toward the control system.

  When it is detected by the detection means that the value of the serial communication signal is fixed for a certain period of time, the system that receives the serial communication signal may be reset.

  The field communication device may include the output unit and the detection unit for each communication path in an input / output device to which a plurality of field devices are connected.

  According to the field communication device of the present invention, since it is detected that the value of the serial communication signal output to the communication path is fixed for a certain period of time, the reliability can be improved while suppressing the cost.

It is a figure which shows the structure etc. of an input / output device, (a) is a block diagram which shows the structure of an input / output device, (b) is a flowchart which shows operation | movement of a clamp detection circuit. It is a figure which shows operation | movement of an input / output device, (a) is a timing chart which shows operation | movement at the time of normal, (b) shows operation | movement at the time of clamp generation, respectively. The block diagram which shows the structure of a multi-channel input / output device. It is a figure which shows the structure etc. of an input / output device, (a) is a block diagram which shows the structure which transmits a status using the communication path | route of a response, (b) is a flowchart which shows operation | movement of a clamp detection circuit. The block diagram which shows the structure of the conventional input / output device.

  Embodiments of a field communication device according to the present invention will be described below.

  FIG. 1A is a block diagram showing a configuration of an input / output (IO) device as a field communication device of the present embodiment.

  As shown in FIG. 1A, the input / output device 1 includes a front side system 10 and a controller side system 20 connected by a communication path in which an insulating element 31 and an insulating element 32 are inserted. The front side system 10 and the controller side system 20 exchange commands and responses through serial communication via this communication path.

  As shown in FIG. 1A, the front system 10 converts an analog signal from a field device input via the external analog input terminal 11a into a digital signal, and converts the digital signal from the controller system 20 into an analog signal. A conversion circuit 11 that converts the signal into a signal and outputs the signal to the field device via the external analog output terminal 11b, and a clamp detection circuit 12 that detects the clamp of the communication path are provided.

  The controller side system 20 includes an AND circuit 21 that outputs a logical sum of the command and the reset output.

  Next, the operation of the input / output device 1 will be described.

  When the front side system 10 is not reset, the controller side system 20 designates “H” as the reset output. In this case, the command is output to the front system 10 via the AND circuit 21. The controller-side system 20 transmits commands to the front-side system 10 at regular intervals, and the front-side system 10 returns a response to the controller-side system 20 after receiving the command.

  The controller-side system 20 designates an output value to be given to the field device as a command, and the front-side system 10 that has received the command converts the command to analog by the conversion circuit 11 and gives it to the field device via the external analog output terminal 11b. .

  The front system 10 converts an analog quantity input via the external analog input terminal 11a into a digital value (input value) in the conversion circuit 11, adds this value to the response, and transmits it to the front system 10. .

  Further, the front system 10 monitors the command in the clamp detection circuit 12, and detects a command abnormality if no command is received for a certain period of time. When the command is abnormal, the abnormal state is added to the response. In this case, the controller side system 20 resets the front side system 10 by a method described later.

  When the front system 10 is reset, the controller system 20 designates “L” as the reset output. As a result, the “L” signal is applied to the insulating element 32 regardless of the command. In addition, when the controller side system 20 cannot receive the response from the front side system 10, the front side system 10 can also be reset.

  When canceling the reset of the front system 10, the controller system 20 designates “H” as the reset output. As a result, the transmission of the command is resumed, and the “L” signal and the “H” signal are alternately applied to the insulating element 32.

  Next, the operation of the clamp detection circuit 12 will be described.

  FIG. 1B is a flowchart showing the operation of the clamp detection circuit 12.

  In step S1 of FIG. 1B, the clamp detection circuit 12 notifies the conversion circuit 11 of the reset. In this case, the front system 10 is reset and the field device is shut down. Moreover, the state of a plant is set to the safe side.

  Next, in step S <b> 2, it is determined whether or not there is a switching (toggle) between the “L” signal and the “H” signal for the voltage value of the communication path 33. If the determination is positive, the process proceeds to step S3, and if the determination is negative, the process returns to step S1.

  In step S3, the clamp detection circuit 12 notifies the conversion circuit 11 of the release of reset. In this case, the reset of the front system 10 is released, the field device is activated, and the plant returns to the normal operating state.

  Next, in step S4, the timer of the clamp detection circuit 12 is reset to zero and starts counting. Next, in step S5, it is determined whether or not the voltage value of the communication path 33 is switched (toggled) between the “L” signal and the “H” signal. If the determination is positive, the process returns to step S4, and if the determination is negative, the process proceeds to step S6.

  In step S6, it is determined whether or not the timer has exceeded the time T. If the determination is affirmative, the process returns to step S1, and if the determination is negative, the process returns to step S5.

  2A and 2B are diagrams illustrating the operation of the input / output device 1. FIG. 2A is a timing chart illustrating an operation at a normal time, and FIG. 2B is a timing chart illustrating an operation when a clamp is generated.

  As shown in FIG. 2A, when the clamp is not generated normally, a command is input to the clamp detection circuit 12 when the value of the reset output is “H”, and the reset is released. At this time, since the command signal is frequently switched between “H” and “L” at all times, the time count of the timer does not reach the time T (step S6).

  When the value of the reset output is “L”, the command is not input to the clamp detection circuit 12, and if the state in which no command is input continues for the time T, the reset state is entered (step S5 in FIG. 1B). Step S6 and Step S1).

  On the other hand, as shown in FIG. 2B, when the clamp is generated in the insulating element 32, even if the reset output value is “H”, the voltage value of the communication path 33 is fixed, so the command is When a state in which no command is input without being input to the clamp detection circuit 12 continues for a time T, a reset state is established (steps S5, S6 and S1 in FIG. 1B). In the example of FIG. 2B, the case where it is clamped to the “H” side is shown, but the case where it is clamped to the “L” side is similarly reset.

  As described above, according to the field communication device of the present embodiment, the reset output transmission path is shared with the command serial communication, so that a reset can always be generated when a clamp failure occurs. For this reason, it is possible to reliably detect a clamp failure and to take appropriate measures when the failure occurs, thereby improving the reliability of the apparatus.

  In addition, since the number of insulating elements used can be reduced, the cost of the apparatus can be reduced. Furthermore, since the failure of the insulating element can be reduced, the reliability of the apparatus can be improved also in this respect.

  FIG. 3 is a block diagram showing a configuration of an input / output (IO) device 1A in which the input / output device 1 shown in FIG. 1A is provided by the number of channels (the number of field devices). In this way, by applying the field communication device of the present invention to a multi-channel input / output device, the number of insulating elements can be greatly reduced, so that a great effect can be expected in terms of reducing the failure rate and reducing the cost.

  FIG. 4A illustrates a status (for example, normal / abnormal) detected by the front system 10 from the front system 10 to the controller system 20 using the communication path of the response from the front system 10 to the controller system 20. It is a figure which shows the structure which transmits (status etc.). Hereinafter, the description will focus on differences from the input / output device 1 (FIG. 1A).

  In the input / output device 1B shown in FIG. 4A, an AND circuit 13 is added to the front system 10A, and a clamp detection circuit 22 is added to the controller system 20A. The AND circuit 13 receives the response and the status detected by the front system 10 from the conversion circuit 11A.

  In the case of FIG. 4A, for example, when an abnormality is detected in the front system 10A, the status is set to “L”, whereby transmission of a response from the AND circuit 13 is stopped when an abnormality occurs. Further, when a clamp failure occurs in the insulating element 31, the voltage value of the communication path 34 is fixed to “L” or “H”. Therefore, the clamp detection circuit 22 can detect that a clamp failure or an abnormality is detected in the front system 10A.

  Next, the operation of the clamp detection circuit 12 will be described.

  FIG. 4B is a flowchart showing the operation of the clamp detection circuit 22.

  In step S11 of FIG. 4B, the status in the front side system 10A is set to “abnormal” by the abnormality notification from the clamp detection circuit 22. In this case, the front system 10A may be reset by applying a reset from the controller system 20A.

  Next, in step S12, it is determined whether or not the voltage value of the communication path 34 is switched (toggled) between the “L” signal and the “H” signal. If the determination is positive, the process proceeds to step S13, and if the determination is negative, the process returns to step S11.

  In step S13, the clamp detection circuit 22 notifies the removal of the abnormality and sets the status to “normal”. In this case, the reset application from the controller side system 20 may be stopped and the reset of the front side system 10 may be released.

  Next, in step S14, the timer of the clamp detection circuit 22 is reset to zero and starts counting. Next, in step S15, it is determined whether or not there is a switching (toggle) between the “L” signal and the “H” signal for the voltage value of the communication path 34. If the determination is affirmed, the process returns to step S14, and if the determination is negative, the process proceeds to step S16.

  In step S16, it is determined whether or not the timer has exceeded time T. If the determination is affirmative, the process returns to step S11, and if the determination is negative, the process returns to step S15. Since the response signal is frequently switched between “H” and “L” at normal times when no clamp is generated, the timer counts unless an abnormality is detected in the front system 10A. The time T is not reached (step S16).

  As described above, according to the input / output device 1B shown in FIG. 4, by sharing the status transmission path with the response serial communication, an abnormality can be detected without fail when a clamp failure occurs. For this reason, it is possible to reliably detect a clamp failure and to take appropriate measures when the failure occurs, thereby improving the reliability of the apparatus.

  The present invention is not limited to the case where an insulating element is used. Further, the cause of clamping is not limited to the insulating element. According to the field communication device of the present invention, the number of communication paths can be suppressed regardless of the presence or absence of an insulating element, and a clamp failure in the communication path can be detected appropriately.

  The scope of application of the present invention is not limited to the above embodiment. The present invention can be widely applied to a field communication device that is inserted between a field device and a control system that controls the field device and relays a serial communication signal.

10 Front system (output means)
12 Clamp detection circuit (detection means)
20A Controller side system (output means)
22 Clamp detection circuit (detection means)
31 Insulating element 32 Insulating element

Claims (6)

In a field communication device that is inserted between a field device and a control system that controls the field device and relays a serial communication signal,
Output means for outputting the serial communication signal to a communication path;
Detecting means for detecting that the value of the serial communication signal output from the output means to the communication path is fixed over a certain period of time;
With
The serial communication signal is a signal that normally switches between a plurality of values at intervals shorter than the predetermined time and notifies a specific state by maintaining a specific value among the plurality of values. Field communication device. The field communication device according to claim 1, wherein an insulating element is provided in the communication path between the output unit and the detection unit. The field communication device according to claim 1, wherein the output unit outputs the serial communication signal in a direction from the control system to the field device. The field communication device according to claim 1, wherein the output unit outputs the serial communication signal in a direction from the field device toward the control system. The system for receiving the serial communication signal is reset when the detection means detects that the value of the serial communication signal is fixed for a certain period of time. 2. The field communication device according to claim 1. The said field communication apparatus is provided with the said output means and the said detection means for every said communication path in the input / output device to which a some field apparatus is connected, The any one of Claims 1-5 characterized by the above-mentioned. 2. The field communication device according to claim 1.

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