REDUNDANT SUPERVISORY CONTROL SYSTEM, AND REDUNDANCY SWITCHING METHOD OF THE SAME

Abstract

An object is to provide a redundant supervisory control system and a redundancy switching method thereof. In the redundant supervisory control system, remote I/O apparatuses are less likely to be inaccessible, even in a case where failures occur in plural locations. Thus, the reliability of the system is enhanced. The redundant supervisory control system including a plurality of first loop interface units in each of a pair of controllers, second loop interface units, and communication cables each connecting the plurality of first and second loop interface units with one another in a circular loop. The redundant supervisory control system is configured by connecting the controllers and the remote I/O units to one another in a plurality of loop networks. In a case where abnormality in the loop networks is detected by use of received data in the networks, the first and second loop interface units that can perform normal reception are automatically selected.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a conventional supervisory control system using a field bus.

FIG. 2 is a block diagram of a conventional supervisory control system using parallel connections.

FIG. 3 is a block diagram of a conventional supervisory control system using ring connections.

FIG. 4 is a block diagram of a conventional dual supervisory control system.

FIG. 5 is a block diagram of the other conventional dual supervisory control system.

FIG. 6 is a block diagram of a dual supervisory control system of the present invention.

FIG. 7 is a block diagram of a controller of the present invention.

FIG. 8 is a block diagram of a remote input/output (I/O) unit of the present invention.

FIG. 9 is a diagram explaining loop networks of the dual supervisory control system of the present invention.

FIG. 10 is a table explaining selection operations of loop interface units of a first switching controller and a second switching controller of the present invention.

FIG. 11 is a flowchart of a control operation of the dual supervisory control system of the present invention.

FIG. 12 is a diagram for explaining an operation of the dual supervisory control system when failures occur in plural locations of the loop networks.

FIG. 13 is a diagram for explaining an operation of the dual supervisory control system when failures occur in plural locations of the loop networks.

FIGS. 14A and 14B are tables for explaining an operation of the dual supervisory control system when failures occur in plural locations of the loop networks.

FIG. 15 is a diagram for explaining a control operation when inaccessible locations occur in the loop networks.

Claims

1. A redundant supervisory control system, which is composed of:a pair of controllers each collecting input data from a controlled subject, and outputting control data based on the input data;a plurality of remote input/output units for collecting the input data from the controlled subject, transmitting the input data to both of the controllers, and outputting, to the controlled subject the control data transmitted from the controller of an active system currently executing control;communication cables each connecting the pair of controllers and the plurality of remote input/output units in a circular loop; anda pair of redundant control interface units for mutually monitoring abnormality statuses of the pair of controllers, and setting a control right allowing any one of the pair of controllers to execute control in an active state, and the other controller to be in a standby state, andwhich controls the controlled subject by performing communications in two directions in a loop network composed of the pair of controllers, the plurality of remote input/output units and the communication cable, in accordance with a predetermined communication protocol,the redundant supervisory control system, wherein each of the pair of controllers comprises:a plurality of first loop interface units which communicates the input data and the control data in the two directions with the counterpart controller and the remote input/output units, and which judges whether the input data is normally received;a first switching controller which selects, among the plurality of first loop interface units, one of the first loop interface units which is capable of performing normal reception, based on results of the judgments of the respective first loop interface units;a first data distributor-selector which receives the input data outputted from the first loop interface unit selected by the first switching controller, and which distributes the control data among the plurality of first loop interface units; anda control computation unit which receives the input data outputted from the first data distributor-selector, which performs arithmetic processing on the input data, and which outputs, as the control data, the result of the arithmetic processing to the first data distributor-selector, andwherein each of the plurality of remote input/output units comprises:a plurality of second loop interface units which communicates the input data and the control data in the two directions with the pair of the controllers, and which judges whether the input data is normally received;a second switching controller which selects, among the plurality of second loop interface units, one of the second loop interface units which is capable of performing normal reception based on results of the judgments of the second loop interface units;a second data distributor-selector which outputs the control data outputted from the second loop interface unit selected by the second switching controller, and which distributes the input data collected from the controlled subject among the plurality of second loop interface units; andan input/output unit which transmits a control signal to the controlled subject on the basis of the control data distributed by the second data distributor-selector, and which transmits, as the control data, a signal collected from the controlled subject to the second data distributor-selector, andthe redundant supervisory control system comprising a plurality of loop networks mentioned above, wherein:when a reception failure is detected in the plurality of the first loop interface units and in the plurality of the second loop interface units, the first loop interface unit and the second loop interface unit which is capable of normally communicating are automatically selected respectively among the plurality of the first loop interface units and the plurality of the second loop interface units, whereby transmissions are performed in transmittable directions; andin a case where portions of the respective loop networks do not overlap with each other, each of the portions starting from each of the pair of controllers, and ending at a location of a failure, the control is able to be continued without switching the control rights.

2. The redundant supervisory control system according to claim 1, wherein each of the redundant control interface units comprises: loop status judgment means which judges connection statuses of the respective loop networks by collecting reception information on whether communications between the controller and each of the plurality of remote input/output units are performed normally; andcontrol right setting means which sets the control right in one of the pair of controllers based on both an output from the loop status judgment means and the a priority judgment table beforehand set for each of the remote input/output units.

3. The redundant supervisory control system according to claim 2, wherein the pair of control right setting means of the respective redundant control interface units mutually monitor outputs respectively of self-diagnoses of abnormality statuses of the pair of controllers themselves, and reception status judgment tables generated respectively by the pair of the loop status judgment means, and thereby set the control right.

4. The redundant supervisory control system according to claim 2, wherein: each of the remote input/output units cyclically transmits any one of a message and data to the corresponding controller in the transmittable circulation directions; andeach of the loop status judgment means receives response statuses, tabulates connection statuses in which communication can be made in each of the loop networks, and thereby judges a portion where the communication cannot be made.

5. The redundant supervisory control system according to claim 2, wherein: the pair of control right setting means cause a control operation to continue without switching the control rights, in a case where the pair of the loop status judgment means judge that portions respectively in the plurality of loop networks do not overlap with one another, each of the portions starting from each of the pair of controllers to a location of a failure; and,the pair of control right setting means set the control right again based on information in the preset priority judgment table, in a case where each of the loop networks respectively of the pair of the controllers is segmented, and where the pair of loop status judgment means judge that the communication statuses of the respective loop networks are different from one another in a range where each of the controllers can access the remote input/output units.

6. The redundant supervisory control system according to claim 1, wherein, in a case where there is a difference among the input data of the plurality of second loop interface units, the second switching controller compares the input data of the respective second loop interface units with one another, and selects the second loop interface unit based on a preset selection criterion.

7. A redundancy switching method for a redundant supervisory control system, which is composed of: a pair of controllers each collecting input data from a controlled subject, and outputting control data based on the input data;a plurality of remote input/output units for collecting the input data from the controlled subject, transmitting the input data to both of the controllers, and outputting, to the controlled subject, the control data transmitted from the controller of an active system currently executing control;communication cables each connecting the pair of controllers and the plurality of remote input/output units in a circular loop; anda pair of redundant control interface units for mutually monitoring abnormality statuses of the pair of controllers, and setting a control right allowing any one of the pair of controllers to execute control in an active state, and the other controller to be in a standby state, andthe redundant supervisory control system, which controls the controlled subject by performing communications in two directions in a loop network composed of the pair of controllers, the plurality of remote input/output units and the communication cable, in accordance with a predetermined communication protocol,the redundant supervisory control system, which includes a plurality of first loop interface units in each of the pair of controllers, a plurality of second loop interface units in each of the plurality of remote input/output units, and the communication cables connecting the plurality of first loop interface units and the plurality of second loop interface units, which includes a plurality of loop networks mentioned above, and in which the plurality of loop networks are made selectable,the redundancy switching method comprising the steps of:detecting reception information on whether the input data and the control data are received normally at the receiver sides in the loop networks;selecting the plurality of first loop interface units and the plurality of second loop interface units for each of the plurality of remote input/output units, and selecting the first loop interface unit and the second loop interface unit which are capable of performing reception, based on the reception information,judging connection statuses of the loop networks based on the reception information, andsetting a control right each of the pair of controllers again, based on a result of the loop network judging step,wherein the pair of control right setting means cause a control to continue without switching the control rights, in a case where the pair of loop status judgment means judge that portions respectively in the plurality of loop networks do not overlap with one another, each of the portions starting from each of the pair of controllers to a location of a failure; and,the pair of control right setting means set the control right in one of the pair of the controllers again, in a case where failures occur in a plurality of portions in each of the loop networks, and where the pair of loop status judgment means judge that the communication statuses of the respective loop networks are different from one another in a range where each of the controllers can access the remote input/output units