JP3284014B2 - Fieldbus system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to general industrial plants, power plants such as thermal power plants, assembling factories, so-called factory automation (FA) and process automation (PA) fields and field devices such as sensors, actuators and controllers and central control. The present invention relates to a field bus system that performs line collection and switching of a field bus connecting devices.

[0002]

2. Description of the Related Art Recently, intelligent sensors have been added, and a digital signal is superimposed on an analog signal output of 4 to 20 mA to exchange information with a host device.

However, in the method using a 4 to 20 mA unified current signal, a 4 to 20 mA current is used for an analog signal and power supply, and a digital signal is superimposed. Therefore, not only cannot sufficient information be exchanged due to these relationships, but also in the highly developed systems in recent years, it is becoming difficult to enhance the functions of the sensors themselves.

[0004] As a system for overcoming this situation, a field bus for connecting field devices by a serial transmission line has been proposed, and work to unify and standardize standards is currently underway.

In reality, a method of superimposing a digital communication signal on a power supply line used in a conventional field device has been adopted due to a demand for reduction of wiring work cost and maintenance burden.

[0006] This system has a good retrofit property, such as the use of already laid cables, and can smoothly transfer to a new system.

FIG. 6A shows an overall configuration diagram of a system using the field bus. In this system, an upper network system bus 2 is connected to a central controller 1 that controls the entire system. Further, the communication device 3 and other devices (not shown) are connected to the upper network bus 2 to form an upper network.

The communication device 3 communicates with the central control device 1 in the host network system, and also communicates with field devices 7 such as various sensors and actuators via the internal signal bus 4, modem 5, and field bus 6.

[0009] The modem 5 communicates with a field device 7 via a field bus 6. A power supply 9 is connected to the modem 5 via an internal power supply bus 8 to supply power to the modem 5 and the field device 7.

More specifically, the modem 5 superimposes the communication signal 10 on the internal signal bus 4 from the communication device 3 on the power supply 11 from the internal power supply bus 8 and combines the power supply 11 and the communication signal 10 into a pair of signal. The superimposed signal 12 is output to a line (field bus 6). Further, the modem 5 outputs the communication signal 10 from the superimposed signal 12 from the field device 7 to the communication device 3.

[0011] The communication device 3 is a local communication system including a field bus 6 (hereinafter, referred to as a field bus system).
And communication control and signal conversion with the signal on the host network system.

As described above, the field bus system and the upper network system are connected, and bidirectional communication between the field device 7 and the central control device 1 is ensured.

FIG. 6B shows an example of a superimposed signal 12 on the field bus 6 in such a field bus system. In this case, the communication signal 10 is an FSK (freque
ncyshift keying) modulated and superimposed on the feed 11.

[0014]

In FIG. 6A, as a field device 7 connected to a field bus 6, 1 is used.
An example is shown in which two sensors are connected. However, in an actual field bus system, a plurality of sensors, actuators, and the like are connected to the field bus 6.

FIG. 7 is a diagram showing a connection example of a field bus from a modem to a field device. FIG. 7 (a)
This is the case where the field bus 6 has a multi-drop configuration, which is the most typical configuration example in the currently proposed field bus system.

Such a configuration meets needs in terms of wiring cost, but has a problem that the integrity and reliability of the entire system in anticipation of failure of each device such as a sensor and an actuator are insufficient.

FIG. 7B shows a modification of this configuration. In FIG. 7B, three sensors 7a, 7b, 7
“c” is sequentially connected by a crossover wiring from the modem 5 via the field bus 6.

In such a wiring, for example, if the point Z is disconnected, the sensors 7b and 7c cannot communicate. Further, for example, if the sensor 7a fails and communication becomes impossible, the sensors 7b and 7c may also be unable to communicate.

If the communication from the sensor 7 is disabled, the sensor detection value cannot be output to the control device, and the worst case that the process cannot be controlled may occur.
On the other hand, FIG. 7C shows another modification of the multi-drop configuration.

In FIG. 7 (c), the field bus 6 from the modem 5 branches off from the middle and forms a star shape.
Each branch is connected to three sensors 7a, 7b, 7c.

In this case, even if the wire breaks at the point Z, the sensor 7
Only a cannot communicate. However, if the sensor 7a fails while being connected to the field bus 6 instead of being disconnected, if the failure mode has a property of adversely affecting the field bus 6, the other sensors 7b, 7c, etc., will be unable to communicate.

As described above, one field bus 6 connected to the modem 5 is connected to the field device 7 in a multi-drop manner.
The method proposed at present has a danger that the failure of one sensor or actuator or the like renders the entire fieldbus system unusable, which may lead to a shutdown of the entire plant.

The present invention has been made in view of such circumstances, and even if a field bus is disconnected or a device on the field bus fails, communication with other devices connected to the field bus is impossible. It is an object of the present invention to provide a fieldbus system that prevents the occurrence of a problem.

[0024]

In order to solve the above-mentioned problems, an invention according to claim 1 comprises a plurality of field buses.
Of the field bus system for performing device and digital communications that are connected to each plurality of fieldbus
Is provided for each of the
Field associated with the superimposed signal in which the superimposed signal is superimposed
To the bus and on the associated fieldbus
Signal conversion means for separating digital signals from superimposed signals of digital signals, and input / output digital signals from the plurality of signal conversion means
If data transmission is abnormal on the transmission system
Can detach from the transmission path of the digital signal for each signal conversion means, performs connection control, a fieldbus system comprising a separating connecting means for disconnecting from the transmission line the signal conversion means according to at least the abnormality.

According to a second aspect of the present invention, a superimposed signal in which a digital signal is superimposed on power supply is transmitted to any one of a plurality of field buses, so that an external higher-level network system and each of the plurality of field buses can transmit the superimposed signal. Contact
In a fieldbus system that performs digital communication with connected devices, an internal power bus for distributing power to each device, an internal signal bus for transmitting digital signals, and a power supply connected to the internal power bus. a power supply for outputting, connected between the internal signal bus and the host network system, and outputs a digital signal on the internal signal bus to the host network system, also, outputs a digital signal of the higher level network system on an internal signal bus Communication means, connected to an internal signal bus, and connected to an internal power supply bus, superimposes a digital signal on power supply, and superimposes a superimposed signal on at least an independent field bus connected to a corresponding device at least as a communication destination. The digital signal is separated from the superimposed signal that is output and output by the device connected to the independent field bus. A plurality of signal conversion means for outputting to the internal signal bus, a plurality of signal bus switches corresponding to the respective signal conversion means, each signal conversion means being separated from the internal signal bus and connectable; When an abnormal digital signal is transmitted on the internal signal bus, disconnect the signal bus switch and control the connection so that the digital signal transmission on the internal signal bus can be returned to normal at least the minimum switch disconnection. And a controller that performs the operation.

Further, the invention according to claim 3 is the invention according to claim 2, wherein a plurality of power supplies and a plurality of communication means are provided, each of which corresponds to each of the power supplies, and each power supply is connected to an internal power supply bus. A plurality of power supply disconnecting switches that can be disconnected and connectable, and a plurality of communication means connecting switches that correspond to each of the communication means and can disconnect and connect each communication means from the internal signal bus, and a plurality of signal conversion means And a plurality of power bus switches that can disconnect and connect each signal conversion means from the internal power bus, and the controller is connected to the internal signal bus, and abnormal digital signals are transmitted on the internal signal bus. During transmission, the internal signal bus is controlled by controlling the disconnection and connection of each of a signal bus switch, a power bus switch, a power connection disconnection switch, and a communication means connection switch. A field bus system for switching disconnection of at least minimum is normally restored digital signal transmission above.

Further, the invention corresponding to claim 4 is as follows.
In the invention corresponding to claim 2 or 3, the device stores at least the latest data output from the device when the digital signal transmission on the internal signal bus is normal, and the digital signal transmission on the internal signal bus becomes abnormal. After becoming
A fieldbus system equipped with an abnormal device substitute means that sends the latest data to the external higher-level network system as an output of the abnormal device when the external device accesses the abnormal device from the external upper network system. is there.

[0028]

Therefore, in the fieldbus system according to the first aspect of the present invention, the signal conversion means superimposes the digital signal and the power supply to output the superimposed signal to the fieldbus and superimposes the signal on the fieldbus. The digital signal is separated from the signal.

Further, a corresponding device is connected to the field bus, and communication is performed between the signal conversion means and the device by a superimposed signal via the field bus. Digital signals from the signal conversion means are input and output to and from a transmission system. Therefore, the separated digital signal is output into the transmission system, and further transmitted to, for example, a higher-level network system. Also, a digital signal from the transmission system is transmitted to a corresponding device via a signal conversion unit.

A plurality of combinations of such signal conversion means and corresponding field buses and devices are provided, and these are connected to the transmission system independently of each other.

The connection at this time has a hub-like configuration in which the transmission system is a hub and the combination of the signal conversion means, the field bus and the device is a spoke.

Therefore, in the field bus system having such a configuration, when a digital signal on the transmission system becomes abnormal due to the disconnection connection means, the signal conversion means relating to the abnormality, and further, the above combination is internally communicated. Normal communication can be restored by disconnecting from the bus.

In the field bus system according to the second aspect of the present invention, in addition to the same operation as the first aspect of the invention, each signal conversion means can be separated and connected by a corresponding signal bus switch. It has become.

This signal bus switch is controlled by a controller. In addition, the controller monitors the internal signal bus as a digital signal transmission system. When the digital signal on the internal signal bus becomes abnormal, the digital signal transmission on the internal signal bus returns to a normal state. As a result, a signal bus switch connected to an abnormal device or the like is disconnected.

Further, in the field bus system according to the third aspect of the present invention, in addition to the same operation as the first or second aspect of the present invention, a plurality of power supplies for outputting power supply and these power supplies and signal conversion means are provided. There is an internal power bus connecting the two.

A plurality of communication means for communicating with an external higher-level network system are provided. Each of a power supply disconnection switch, a power supply bus switch, and a communication means connection switch is provided between each power supply and the internal power supply bus, between each signal conversion means and the internal power supply bus, and between the communication means and the internal signal bus. They can be disconnected and connected.

This signal bus switch is controlled by a controller. Also, the internal signal bus is monitored by the controller, and when the digital signal on the internal signal bus becomes abnormal, abnormal devices etc. are restored so that the digital signal transmission on the internal signal bus returns to a normal state. Are disconnected from each other.

Further, in the field bus system according to the fourth aspect of the present invention, in addition to the same operation as the first or second or third aspect of the present invention, an abnormal signal substitute means transmits an internal signal to each device. At least the latest output data when digital signal transmission on the bus is normal.
Data is stored.

Further, when an abnormal upper-level network system accesses an abnormal device after digital signal transmission on the internal signal bus becomes abnormal by the abnormal device substitute means, the latest data is transmitted. The output is sent to the external higher-level network system as the output of the device in which the abnormality has occurred.

As described above, since the function of the abnormal device is substituted by the abnormal device substitute means, when the abnormal device is, for example, a sensor, even if the process control is performed based on the sensor, the process is controlled. There is no adverse effect such as falling into an impossible state.

[0041]

Embodiments of the present invention will be described below. (First Embodiment) FIG. 1 is a block diagram showing a first embodiment of a field bus system according to the present invention. The same parts as those of the conventional field bus system shown in FIG. Detailed description is omitted.

The field bus system includes a first communication device 3a and a second communication device 3b connected to the upper network bus 2 of the upper network system.
A hub controller 13 connected to the first and second communication devices 3a and 3b via the internal signal bus 4, and a plurality of signal bus switches 14a, 14b,. . (Represented by 14x).

The field bus system has the first
A plurality of power supply bus switches 15a connected to the first and second insulation power supplies 9a and 9b via the internal power supply bus 8 and paired with the signal bus switch 14x. , 15b,. . (Represented by 15x).

Power supply disconnecting switches 16a and 16b corresponding to the respective isolated power supplies 9a and 9b are provided between the first and second isolated power supplies 9a and 9b and the internal power supply bus 8.

On the other hand, a pair of the signal bus switch 14x and the power bus switch 15x is connected to a modem 5x (5a, 5b,...) As signal conversion means. Each modem 5x has a field bus 6x (6
a, 6b,. . . ) Are connected, and field devices 7x (7a, 7b,...), Which are corresponding sensors, actuators, and the like, are connected to each field bus.

Here, the first and second communication devices 3a, 3b
, Internal signal bus 4, modem 5x, hub controller 13, signal bus switch 14x, power bus switch 15x, first and second insulated power supplies 9a and 9b, internal power bus 8, and power supply connection. A hub device 17 is constituted by the disconnection switches 16a and 16b.

The first and second insulated power supplies 9a and 9b supply power to the field device 7x and the modem 5x. Each of the insulated power supplies is connected to or disconnected from the internal power supply bus 8 by power supply disconnecting switches 16a and 16b.

The first and second communication devices 3a and 3b have the same configuration as the communication device 3 in FIG. Further, the first and second communication devices 3a and 3b have different addresses, respectively, and the central control device 1 usually accesses the first communication device 3a. For example, the first
When an abnormality occurs in the communication device 3a, the central control device 1
Switches the address of the communication target,
Access to the communication device 3b to secure communication with the hub device 17.

Each of the modems 5x has the same configuration as the modem 5 in FIG. Fieldbus 6x
This is a power supply / signal line similar to the field bus 6 in FIG.

That is, each modem 5x, field bus 6x, and field device 7x is a set having a correspondence. FIG. 2 shows how the field devices 7x are connected to the hub device 17 of the field bus system of the present embodiment via each field bus.

The hub controller 13 has a signal input / output unit 1
31, a higher-order command receiving unit 132, and a normal / abnormal judging unit 13
3 and a switch switching unit 134. The signal input / output unit 131 receives a signal flowing on the internal signal bus 4 and outputs a signal to the internal signal bus 4.

The upper command receiving unit 132 receives a command or the like from the upper network system, and if the command is a switch disconnection connection command for restoring normalization of communication with the fieldbus system, the normal / abnormal judgment unit 133 sends the command. Notify instructions.

The normal / abnormal judging section 133 is provided with the signal input / output section 1
31, the internal signal bus 4 is monitored. When a switch disconnection connection command for returning to normalization of communication is received from the upper network system, it is determined whether the data transmission on the internal signal bus 4 is normal. If it is determined that there is an abnormality, a switch switching command is sent to the switch switching unit 134.

When the signal on the internal signal bus 4 returns from the abnormal state to the normal state, the normal / abnormal judgment unit 133
The information of the device determined to be abnormal by the switch switching is notified to the upper network.

When receiving a switch switching command from the normal / abnormal judging section 133, the switch switching section 134 connects or disconnects the switch to be switched when the switch is designated, and otherwise switches the switch. The switch is connected or disconnected according to a predetermined rule.

The predetermined rule is, for example, that it is known that there is an abnormality in any of the field devices 7x, but when it is not known which of the field devices 7 has an abnormality, the signal bus switch 14x and the power bus switch Fifteen
x is the signal bus switch 14a and the power bus switch 15
This is a rule such as separating sequentially from a.

For example, the predetermined rule is that when it is known that the signal on the internal power supply bus 8 has an abnormality, the power supply disconnection switches 16a and 16b are first switched, and then the power supply bus switch is switched on. 15x is sequentially switched from the power bus switch 15a.

The hub controller 13 receives the signal bus switch 14x, the power bus switch 15x, and the power connection disconnecting switch 16a, 1 in response to the command from the central control device 1.
Opening / closing of 6b is started, an abnormal device is identified and separated according to an internal control program, and a notification to an upper network is performed. Further, the hub controller 13 is positioned as one device on the field bus when viewed from the central control device 1.

Next, the operation of the field bus system of the present embodiment configured as described above will be described with reference to the flowchart of FIG. First, the upper network system
Notification of self-diagnosis information by the self-diagnosis function of the field device 7x, when communication abnormal information is received from the modem 5x or the communication devices 3a, 3b, or when the hub device 17 does not receive communication from the upper network system (ST11). Then, a command to be issued to the hub device 17 is determined based on the information (ST12).

The upper network system includes first and second
When it is determined that there is an abnormality in the communication devices 3a and 3b,
The communication device is switched by changing the address of the communication target. Also, the isolated power supplies 9a and 9b, the modem 5x,
When it is determined that there is an abnormality in the devices subsequent to the hub device 17 such as the field device 7x, a switch disconnection connection command is given to the hub controller 13 (ST13).

The hub controller 13 disconnects the switch to a certain device in accordance with the contents of the switch disconnection connection instruction and the rules in the hub controller 13 and outputs a connection instruction.

For example, when it is determined by the central controller of the host network system that the specific field device 7xa is abnormal based on the self-diagnosis result, the signal bus switch 14xa and the power bus switch 15xa are disconnected.

Further, for example, the power supply 11 or the superimposed signal 1
If any of the two is abnormal but the abnormal device cannot be identified, the two insulated power sources are switched from one to the other by disconnecting the power connection disconnecting switches 16a and 16b.

Next, the normal / abnormal judging section 133 judges whether or not the fieldbus system has been restored to normal by the switch switching in step ST14 (ST15). If it does not return to normal, the switch switching unit 134 performs the next switch.

For example, in the above example, if the normal power is not restored even when the two insulated power supplies are switched from one to the other, the power supply bus switch 15a corresponding to the field device 7a is disconnected. Thus, steps ST14 and ST15 are repeated according to the instruction from the upper network system and predetermined rules until the fieldbus system returns to normal.

Then, when the field bus system returns to normal, step ST14 and step ST15
Is reported to the central control device (ST16).

As described above, the field bus system according to the present embodiment comprises the modem 5x and the signal bus switch 14.
x, internal signal bus 4 and hub controller 13,
When the digital signal on the internal signal bus 4 is abnormal, the field bus 6x and the field device 7x corresponding to each modem 5x can be separated from each other. Therefore, even if an abnormality occurs in a certain field device 7xa, etc. It can be disconnected from the internal signal bus 4.

Therefore, disconnection of the field bus 6x,
The influence of a failure or a serious failure of a device such as the field device 7x spreads over the entire bus, so that the time during which the entire device cannot communicate can be minimized.
Corresponds to each field device 7x, so even if an abnormal device is disconnected, it does not affect the data transmission of other field devices 7x, and the influence of the occurrence of an error can be minimized, and the reliability of the entire system can be reduced.・ Maintainability is improved.

Further, even if an abnormality in a certain field device 7x or the like affects, for example, the internal signal bus 4, and the entire system may become unable to communicate, this can be avoided by disconnecting the device.

Further, since an abnormality of a device or the like is reported to the upper network system by the hub controller, the upper network system can take necessary measures.

In the field bus system according to the present embodiment, two insulated power supplies 9a and 9b are provided and are switched by the power supply disconnecting switches 16a and 16b. However, the communication function can be maintained.

Further, in the field bus system according to the present embodiment, the power supply bus switch 15x is provided, and by this switching, the modem 5x can be disconnected, so that the reliability and maintainability are further improved.

Furthermore, in the field bus system according to the present embodiment, two communication devices 3a and 3b are provided and can be switched from the upper network, so that any one of the communication devices 3a and 3b becomes abnormal. Can maintain the communication function. (Second Embodiment) FIG. 4 is a block diagram showing a second embodiment of the field bus system according to the present invention. The same components as those of the conventional field bus system shown in FIG.
The same parts as those of the first embodiment shown in FIG.

Hub device 1 of this field bus system
7b, a communication device connection switch 18 is connected to the connection between the first and second communication devices 3a and 3b and the internal signal bus 4, respectively.
a and 18b are provided.

The hub controller 13b includes a signal input / output unit 131, a normal / abnormal judging unit 133b, a normal data storage unit 135, a switch switching unit 134b, a higher-order command monitoring unit 132b, and a processing proxy unit 136. It is configured.

The normal / abnormal judging section 133b monitors via the signal input / output section 131 whether or not data transmission on the internal signal bus 4 is normal. , Starts switch disconnection connection for communication normalization return, and issues a switch switching command to the switch switching unit 13.
4b. Then, an abnormal device is finally specified in the field bus system.

When the data transmission on the internal signal bus 4 is normal, the normal / abnormal judging section 133b stores the latest data such as measured values output from each field device 7x in the normal data storing section 136. . If the data transmission on the internal signal bus 4 is determined to be abnormal, the updating of the stored data is stopped.

When receiving a switch switching command from the normal / abnormal judgment unit 133b, the switch switching unit 134b connects or disconnects a switch to be switched if the switch is designated, and otherwise switches the switch. The switch is connected or disconnected according to a predetermined rule.

The switch switching unit 134b connects or disconnects the communication device connection switches 18a and 18b in addition to the switch for switching in the first embodiment.
The predetermined rules are the same as those in the first embodiment.

The upper instruction monitoring unit 132b monitors data transmission on the internal signal bus 4 via the signal input / output unit 131, and sends an upper network to devices identified as abnormal by the normal / abnormal judgment unit 133b. Checking if there is a call from the system. Then, when there is a call to the device, the contents are processed by the processing agency 1
Notify 36.

When a call is received from the higher-level network system to a device identified as abnormal, the processing proxy unit 136 copies the data stored in the normal data storage unit 135 before the occurrence of the abnormality to the device. The information is returned to the higher-level network as an output from the device, and abnormal information on the device is reported to the higher-level network.

The hub controller 13 monitors the internal signal bus 4 irrespective of the central control device 1 as described above, and when an abnormality is found, the switches 14x, 15x, 16a, 16
Opening / closing of b, 18a, 18b, etc. is started, and abnormal equipment is identified and separated according to an internal control program. Further, the hub controller 13 substitutes the output of the abnormal device for the upper network.

The abnormal device substitute means includes, for example, the signal input / output unit 131, the normal / abnormal judgment unit 133b, the normal data storage unit 135, the upper command monitoring unit 132b, and the processing substitute unit 13.
6.

Next, the operation of the field bus system of the present embodiment configured as described above will be described with reference to the flowchart of FIG. First, a signal flowing on the internal signal bus 4 is monitored by the hub controller 13 to determine whether or not the signal is in an abnormal state. If the signal is normal, output data such as measurement data output from each field device 7x is output. Is stored (ST21).

When an abnormality occurs in the internal signal bus 4 due to an abnormality of any device (ST22), the hub controller 13 switches the switches 14x, 15x, 1
The disconnection connection of 6a, 16b, 18a, 18b is started, an abnormal device is specified, and the abnormal device is disconnected from the field bus system (ST23, ST24).

The procedure for identifying an abnormal device at this time is as follows:
Is the same as the procedure of steps ST14 and ST15 in the embodiment. In addition, for the disconnected device, the update of the stored data in the normal data storage unit 135 is stopped.

After this, the monitoring of the internal signal bus 4 by the bus controller 13 is continued (ST25, ST2).
6). Next, when there is a call from the upper network system to the device disconnected due to the abnormality (ST2).
6), the hub controller 13 includes the normal data storage unit 13
5 is output to the host network system as an output from the device. That is, the abnormal device is substituted by the hub controller 13.

The communication substitution by the hub controller 13 is possible even if there are a plurality of abnormal devices. As long as the communication devices 3a and 3b and the internal communication bus 4 operate normally, the first and second insulated power supplies can be used. If both go down,
We can act for you.

Further, with the substitution of the abnormal device, information about the abnormal device is reported to the central control unit 1 by the hub controller 13, and the next control can be requested from the upper network system.

As described above, the field bus system according to the present embodiment is provided with communication device connection switches 18a and 18b in addition to the same configuration as that of the first embodiment.
Since the switching between a and 3b can be performed from the hub controller 13, the same effects as those of the first embodiment can be obtained, and the reliability can be further improved.

In the field bus system according to the present embodiment, the normal / abnormality judging section 133b allows the hub controller 13 to automatically detect a transmission abnormality on the internal signal bus 4 and operate normally without being involved in the upper network. Since the communication state can be restored, the communication can be restored more efficiently without imposing a burden on the host network system.

Further, the field bus system according to the present embodiment comprises a normal data storage section 135 and a higher order command section 132.
b and a processing proxy unit 136, and when an abnormal device is disconnected and then accessed by a higher-level network system, the output of the abnormal device is stored in the normal data storage unit 13.
5, the system control and the process control can be maintained normally even when the abnormal device is used for the system control data. Further, the present invention can be variously modified without departing from the gist thereof.

[0093]

As described above in detail, according to the present invention, switches for enabling disconnection and connection to each field device and the like are provided to disconnect abnormal field devices from the internal signal bus and the internal power supply bus. Because of the separation, it is possible to provide a field bus system that prevents communication with other devices connected to the field bus from being disabled even if the field bus is disconnected or a device on the field bus fails. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a field bus system according to the present invention.

FIG. 2 is a connection configuration diagram showing an arrangement of each field device connected to the embodiment.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

FIG. 4 is a block diagram showing a second embodiment of the field bus system according to the present invention.

FIG. 5 is a flowchart for explaining the operation of the embodiment.

FIG. 6 is a block diagram and a signal waveform diagram showing a conventional field bus system.

FIG. 7 is a layout diagram showing connection of field devices of a conventional field bus system.

[Explanation of symbols]

3a: first communication device, 3b: second communication device, 4: internal signal bus, 5x: modem, 6x: field bus, 7
x: field device, 8: internal power supply bus, 9a: first insulated power supply, 9b: second insulated power supply, 13: hub controller, 14x: signal bus switch, 15x: power supply bus switch, 16a, 16b: power supply connection Disconnect switch, 17
... Hub devices, 18a, 18b ... Communication device connection switches.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04Q 9/00-9/16 H04L 12/40

Claims (4)

(57) [Claims] 1. A connection to each of a plurality of field buses
A fieldbus system for performing digital communication with a plurality of devices, provided in correspondence with each of the plurality of fieldbuses.
The digital signal is superimposed on the power supply.
Transmission to the assigned fieldbus and mapping
Digital signal from the superimposed signal on the fieldbus
A plurality of signal conversion means for separating, and input and output of digital signals from the plurality of signal conversion means;
When data transmission is abnormal on the transmission system, the signal conversion means is disconnected from the transmission path of the digital signal, connection control is performed, and at least the signal conversion means relating to the abnormality is transmitted from the transmission system. A field bus system comprising: disconnecting connection means for disconnecting. 2. A superimposed signal in which a digital signal is superimposed on power supply is transmitted to any one of a plurality of field buses, so that an external host network system and the plurality of filters are connected to each other.
A field bus system for performing digital communication with devices connected to each of the external buses, an internal power bus for distributing the power supply to each of the devices, an internal signal bus for transmitting the digital signal, A power supply connected to an internal power supply bus for outputting the power supply; a power supply connected between the internal signal bus and the host network system to output a digital signal on the internal signal bus to the host network system; Communication means for outputting a digital signal of the higher-level network system onto the internal signal bus; connected to the internal signal bus, and connected to the internal power supply bus, and supplying the digital signal to the power supply. And superimpose the superimposed signal on at least mutually independent field buses connected to corresponding devices as communication destinations. Output
A plurality of signal conversion means for separating a digital signal from a superimposed signal output from a device connected to the independent field bus and outputting the separated digital signal to the internal signal bus; A plurality of signal bus switches capable of disconnecting and connecting means from the internal signal bus; and disconnecting the signal bus switch when an abnormal digital signal is connected to the internal signal bus and transmitted on the internal signal bus. And a controller for controlling connection and performing at least a minimum switch disconnection for returning the digital signal transmission on the internal signal bus to a normal state. 3. The field bus system according to claim 2, wherein a plurality of said power supplies are provided, a plurality of said communication means are provided, and each power supply is separated from said internal power supply bus and connected to each of said power supplies. A plurality of power-supply disconnect switches that correspond to each of the communication means, and a plurality of communication-means connection switches that disconnect and connect each communication means from the internal signal bus; A plurality of power bus switches respectively corresponding to each of the signal conversion means and capable of being connected to and separated from the internal power bus, and wherein the controller is connected to the internal signal bus and operates abnormally on the internal signal bus. When a digital signal is transmitted, disconnection of each of the signal bus switch, power bus switch, power connection disconnection switch, and communication means connection switch A field bus system for controlling connection and performing at least minimum switch disconnection for returning digital signal transmission on the internal signal bus to a normal state. 4. The field bus system according to claim 2, wherein the device outputs at least the digital signal when the digital signal transmission on the internal signal bus is normal .
After the latest data is saved and the digital signal transmission on the internal signal bus becomes abnormal, when the external higher-level network system accesses the device in which the abnormality has occurred, the latest data is stored in the abnormal state. A field bus system comprising abnormal device substitute means for sending an output of the generated device to the external upper network system.