JPH03232397A - Backup switching system - Google Patents

Abstract

PURPOSE:To improve the reliability of a system as a whole by connecting an active master station and a standby master station by an exclusive signal line, immediately transmitting the detection of self abnormality through the exclusive signal line to the standby master station by the active master station, and on the other hand, starting a backup operation on the side of the standby master station even when the fault is detected on the active master station side. CONSTITUTION:Ouf of master stations 1A and 1B, one station is used as the active master station and the other station is used as the standby master station. The standby master station 1B is equipped with the practically same configuration as the active master station 1A and a dual port memory 14B is equipped with an area for transmitting the same capacity at the same address as a dual port memory 14A of the active master station 1A. At normal time, the standby master station 1B is operated as a listener station to a talker address and a listener address, stores received data in a dual port memory 14B and set on standby so as to be immediately switched when generating the abnormality in the active master station 1A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Application Field) The present invention relates to a backup switching method suitable for switching between active and standby master stations in, for example, a cyclic scan transmission system.

(Prior Art) Conventionally, two methods are known for backup switching in this type of transmission system. In the first method, the upper controller of the transmission path receives error information from both the active master station and the standby master station and determines the error occurrence situation, while the lower active master station and standby master station According to the command, the active master station shifts to the down state, and the standby master station shifts to the operating state.

In the second method, the active master station and the standby master station individually determine switching using a counter and a self-test function.

(Problem to be Solved by the Invention) In the switching method using a higher-level controller, in order to quickly respond to an abnormality in the current master station, the higher-level controller checks the error detection information of the current master station in short cycles, or when the cause of an abnormality occurs. Error information must be checked upon receiving an interrupt from the active master station.

However, the host controller controls the entire system, and performing such operations is a heavy burden, and in the case of a configuration in which no host controller is provided, it is not possible to upgrade the master station.

In addition, in a switching method using a counter and test function that allows switching without the influence of the host controller, after the working master station goes down and before the standby master station starts up as the working master station, the transmission line It takes time to detect a no-signal state for more than a certain period of time, self-test, etc., and in systems that require quick control, this adversely affects the operation of the entire system.

The present invention has been made in view of the above-mentioned problems, and its purpose is to further speed up the latter method, which allows switching without the influence of the host controller, and to improve the reliability of the entire system. The purpose of the present invention is to provide a backup switching method that can perform the following steps.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a working master station for controlling transmission, and a system for backing up the working master station when an abnormality occurs in the working master station. It is equipped with a functioning standby master station, a plurality of remote stations, and a transmission line for transmitting data between these stations, and a transmission frame is transmitted between the master station and the remote stations by polling from the active master station. A backup switching method in a transmission system that performs communication, wherein the active master station stops transmission and enters a down state in which it does nothing when it detects an abnormality in itself, while the standby master station In a backup switching method that detects an abnormality in the active master station based on a no-signal state on the transmission line and starts backup operation, the active master station and the standby master station are connected by a dedicated signal line. On the side of the active master station, the detection of self-abnormality is immediately transmitted to the standby master station via the dedicated signal line, while on the side of the standby master station, the detection of the self-abnormality is immediately transmitted to the standby master station via the dedicated signal line. The feature is that the backup operation is started even if an abnormality is detected.

(Function) According to such a configuration, a dedicated signal line connects the active master station and the standby master station,
On the active master station side, the detection of self-abnormality is immediately communicated to the standby master station via the dedicated signal line, while on the standby master station side, when an error on the active master station side is detected via the dedicated signal line. Since the backup operation is started even when the current master station is in use, if an abnormality occurs in the current master station, the backup operation can be started immediately without waiting for confirmation that there is no signal.

Furthermore, the means by which the standby master station detects an abnormality in the active master station is duplicated, making backup switching more reliable.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

This embodiment relates to a system for controlling a control center. Note that the control center is a power distribution board that has a plurality of units arranged to protect the opening and closing of motors, and is used for opening and closing motors at sites such as plants.

FIG. 1 is an overall configuration diagram of this embodiment. One of the master stations IA and IB is used as an active master station, and the other one is used as a standby master station.

Signal lines 2A and 2B are arranged between master station 1 and IB, signal line 2A is a signal line that is output from master station IA and input to master station IB, and signal line 2B is in the opposite direction. This is the signal line of the current master station, and the current master station is
The standby master station outputs "L".

Furthermore, master stations IA and IB are connected to transmission line 3. The transmission line 3 is connected to a plurality of control center remote stations 4 and a plurality of on-site operation remote stations 5.

The transmission path 3 includes, for example, two signal lines for transmission, and transmits serial data (signals) between stations IA, IB, and 4.5.

Master stations IA and IB are connected via a system bus 6 to a host controller 7 that controls the entire system.

The master stations IA, IB and the host controller 7 are placed in a central control room or the like where an operator is permanently stationed to monitor the entire system.

For ease of understanding, in this embodiment, the master station IA is the current master station.

Master station IB will be explained as a standby master station.

The active master station IA receives operation data from the host controller 7 and transmits the received operation data to the remote station 45 via the transmission line 3.

The active master station IA receives the status data transmitted to the remote station 4.5 via the transmission path 3, and transmits the received status data to the upper controller 7.

Each unit constituting the control center 8 includes a control center remote station 4, a multi-function protection relay 9. An electromagnetic contactor 10 is housed.

The control center remote station 4 receives operation signals and the like sent from the active master station IA and the on-site operation remote station 5 via the transmission line 3, and supplies them to the multifunctional protection relay 9.

The multifunctional protective relay 9 opens and closes the main circuit 12 and the electromagnetic contactor 10 of the induction machine 11 in response to this operation signal, and controls starting and stopping of the induction machine 11.

The control center remote station 4 sends the induction machine 11 status signal, main circuit current value, and fault status signal sent from the multifunctional protection relay 9 to the master station IA via the transmission line 3.

It is transmitted to the IB and remote station 5 for on-site operation.

The remote station 5 for on-site operation is placed close to the corresponding induction machine 11, and sends operation signals for starting and stopping the induction machine 11 to the master stations IA, I.
B and control center remote station 4, and control center remote station 4
The state data of the induction conductor 11 is received from the induction conductor 11.

The on-site operation remote stage controller 5 responds to the received data and lights up a lamp that indicates the state of the induction conductor 11.

FIG. 2 shows the configuration of master stations IA and IB. The master station IA includes a CPU 10A, a serial data transmission section 11A, and a memory 12A.

The serial data transmission unit 11A is connected to the transmission line 3 via the pulse transformer 13A, and the CPU OA is connected to the dual port memory 14A.
A system bus 6 is connected to the other terminal of A.

The system bus 6 connected to the master stations IA and IB is connected to the system bus 6 connected to the host controller 7 by the bus control circuit 15.

Signal exchange between stations is controlled by polling of the active master station IA.

The dual port memory 14A has a transmission data area equal to the transmission capacity. The transmission data area includes a talker area and a listener area.

Furthermore, this dual port memory 14A has an error information area for storing error information for each address in the talker area and the snare area.

Each address position in the talker area of the dual port memory 14A has a storage capacity of, for example, 2 bytes, and data to be transmitted to the corresponding remote station 4, 5 is written by the host controller 7 or the like.

Each address location in the listener area has a storage capacity of, for example, 2 bytes, and stores data received from the corresponding remote station.

Each address position in the error information area has a storage capacity of, for example, 1 byte, and stores information such as whether or not a transmission error has occurred and the type of transmission error.

The upper controller 7 can read and write the memory contents of the dual port memory 14A via the system bus 6,
This makes it possible to control the entire system.

For each address in the talker area and listener area of the dual port memory 14A, one station is predetermined as a talker, and one or more stations are predetermined as listeners.

Regarding the address in the talker area, the current master station IA becomes the talker, and regarding the address in the listener area, the current master station becomes the listener.

The standby master station IB has substantially the same configuration as the active master station IA, and its dual port memory 14B has a transmission area with the same address and capacity as the dual port memory 14A of the active master station IA.

The standby master station IB normally operates as a listener station for all talker addresses and listener addresses, and stores the received data in the dual port memory 1.
4B, and is on standby so that it can be switched immediately if there is an abnormality in the current master station IA.

FIG. 3 shows the flow of data in the embodiment.

The active master station IA sends (polles) the address of the data area for transmission to the transmission path 3, responds to the sent address, the talker station sends data, and the listener station receives the data. receive.

The active master station IA sequentially outputs the addresses of the transmission area, and when it outputs up to the final address, it repeats the operation of sequentially outputting again from the first address.

Hereinafter, with reference to the flowcharts of FIGS. 4 to 8, a description will be given of how the backup of the current master station IA is realized.

First, the transmission control operation of the current master station IA will be explained with reference to FIG.

First, during initialization, the current master station 1A outputs "H" to the signal line 2A (step 40).

When the transmission cycle begins, the active master station IA creates address information to be transmitted (step 41) and transmits it (step 42).

Thereafter, by checking whether a transmission timeout has occurred, it is checked whether an error has occurred during the transmission operation (step 43).

If no error has occurred, the current master station IA determines whether the output address is a talker area address (talker address) or a listener area address (listener address), and branches to the corresponding process. (Step 44).

If the output address is a talker address, the current master station IA reads data from the corresponding address location in the dare port memory 14 and performs talker processing to transmit it (step 45).

On the other hand, if the output address is a snare address, the active master station IA receives data sent from the remote stations 4 and 5 in response to the address,
If the data can be received without error, listener processing is performed to store the received data at the address in the data area (step 4).
6).

After the talker process (step 45) or listener process (step 46) is executed, it is checked whether an error has occurred in the talker process or listener process (step 47).

The presence or absence of an error is determined based on, for example, a parity check, CRC check, presence or absence of overframing, presence or absence of an override error, and whether or not no data could be received during listener processing and a timeout occurred.

If no error has occurred, the control performs normal termination processing (step 48). In this normal processing, if the listener processing is performed normally, the count value of the error counter is reset.

In this embodiment, the error counter is not cleared even if talk processing is performed normally. This is because the possibility of an error occurring in talker processing is extremely low.

When the normal termination process is completed, the control returns to step 4.
1 and performs the same processing as described above for the next address in the transmission memory.

Transmission processing (step 42), talker processing (step 45)
), if a timeout or error in received data occurs in listener processing (step 46), step 43.4
7, an error occurrence is detected and an error flag is set.
Control continues to error handling in step 49 (step 49).

The error handling in step 49 will be explained with reference to the flowchart in FIG. First, the current master station IA
writes the fact that an error has occurred at the address into the corresponding address position in the error information area of the dual port memory 14, notifies the host controller (step 51), and increments the error counter (step 52).

Thereafter, the count value of the error counter is read out, and the count value is compared with a predetermined reference value (step 53).

Here, if the count value is less than or equal to the reference value, the error processing (step 48) ends and control returns to step 41 of the flowchart of FIG.

If the count value of the error counter is greater than the reference value, the current master station IA self-checks its own transmission circuit to determine whether the cause of the error is caused by the station itself (step 54). This self-check is performed according to the procedure shown in the flowchart of FIG.

The self-check operation will be explained with reference to the flowchart of FIG. First, initialize (set to 0) the current check counter count value and test data (step 8).
01), then the active master station IA enables both its own transmitting and receiving operations (step 802).
.

The current master station IA outputs the test data to the transmission line 3 via the serial data transmission unit 11A and the pulse transformer 13A (step 803), and receives the output data itself (step 805).

The active master station IA checks whether the transmission and reception were successful and whether the transmitted data and the received data are equal (steps 804, 806 and 807).

The active master station IA increments the check counter when the transmission and reception are successful and the transmitted data and the received data are equal (step 808).

Next, the test data is incremented (step 8
09), it is determined whether the test data is greater than the maximum value N (step 810).

If the test data is less than or equal to N, the control returns to step 803 and repeats the processes of steps 803 to 809 N+1 times for test data of 0 to N.

After N+1 self-checks have been performed, control continues to step 810. In step 810, it is determined whether the number of successful self-checks, ie, the count value of the check counter, is greater than a predetermined reference value (M>-N).

When the count value of the check counter is larger than the reference value M (M≦N), it is determined that the self-check was successful, and a self-check success flag is set (step 812).

When the count value is less than or equal to M, it is determined that the self-check has failed, and the self-check success flag is reset (step 813).

Thereafter, transmission and reception are once prohibited (step 814), and control returns to step 55 of the flowchart of FIG.

In step 55 of FIG. 5, it is determined whether the self-check (step 54) is successful or not based on the self-check success flag of the dual port memory (step 55).

Here, the self-check success flag is set, and if the self-check is successful, it is assumed that there is no self-error and the error counter is cleared (step 59), and the upper controller is notified only that there has been a continuous error (step 510). .

When the self-check success flag is reset and the self-check is unsuccessful, the active master station IA notifies the higher-level controller that it is going down as a self-error (step 56), outputs "L" to the signal line 2A, and goes to standby. Notify master station IB of abnormality (step 5)
7), the operation as the active master station is stopped (step 58).

Next, the operation of the standby master station is shown in Figures 6 and 7.
This will be explained with reference to FIGS.

The standby master station IB has two means for detecting an abnormality in the active master station IA.

One is a method using a no-signal counter and a self-check, and the other is a method based on detection of a falling edge of the signal line IA, which is a feature of the present invention.

First, the first method will be explained. The standby master station IB constantly monitors the transmission line 3, and when waiting to receive an address, starts a timer (step 61) and waits for the address to be received (step 62).

The timer outputs an interrupt signal, which will be described later, at regular intervals, and the no-signal counter updates the count value while waiting for address reception.

Once the address is received, control passes to step 63.
The timer is stopped and the no-signal counter is cleared (step 63).

Thereafter, it is checked whether or not it has been normally received (step 64), and it is checked whether the received content is an address (step 65).

If data is received without receiving an address due to a transmission error or the like, the data is ignored and control returns to step 61 (step 65).
).

If the received content is an address, step 46 in FIG.
．． Similarly to 47, listener processing and error checking are performed. (Steps 66.67).

If the listener processing is performed without error, the normal termination processing is completed and step 6 is performed, similar to step 48 in FIG.
8), control returns to step 61.

If an error occurs in listener processing, the fact that the error has occurred is stored in a predetermined area of the dual port memory 14 (
Step 69).

On the other hand, when the interrupt process shown in FIG. 7 is performed in response to the timer interrupt, the no-signal counter is incremented in response to the interrupt (step 71).

Next, it is determined whether the count value of the no-signal counter is greater than a predetermined reference value (step 72).

If it is smaller, control returns. If it is large,
This means that the no-signal period on the transmission path 3 exceeds an allowable range, and means that the current master stage IA is out of order.

In this case, the standby master station IB performs a self-check of the transmission circuit shown in FIG. 8 (step 7).
3).

If the self-check is successful, the standby master station switches to the active master station to start operating as the active master station shown in FIGS. 4 and 5), while the standby master station is retained in the dual port memory 14B. Control is performed based on the data obtained.

If the result of the self-check is unsuccessful, the standby master station IB regards it as a self-error and updates the count value of its internal counter.

When the same operation occurs several times and the count value of the internal counter exceeds a certain value, the standby master station IB
notifies the controller 7 of this fact and goes down (step 76).

Next, a method using the falling edge of the signal line 2A will be explained. In this embodiment, when the signal line 2A falls, the interrupt process shown in FIG. 9 is activated.

First of all, the standby master station IB reconfirms whether the falling edge of the signal line 2A is really correct (steps 91 and 92), and if it is correct, immediately switches the signal line 2B to "
In step 93), the standby master station IB switches to the active master station to notify that the standby master station IB will perform backup switching.

Normally, abnormality detection by the falling edge of the signal line 2A is faster than abnormality detection by the above-mentioned no-signal counter and self-check, so master station switching is activated by the falling edge of the signal line 2A. If there is an abnormality in the line 2A itself, a method using a no-signal counter and self-check will be effective.

This invention is not limited to the above embodiments, and various modifications are possible.

[Effects of the Invention] As explained above, according to the present invention, backup switching is performed more quickly, and the host controller can control the system without being aware that the master station has been switched. As a result, the influence on the operation of the entire system is reduced, and the reliability of the entire system is improved.

Furthermore, by duplicating the means for detecting abnormalities, more reliable backup switching becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a transmission system according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the master station and controller shown in FIG. 1, and FIG. 3 is a block diagram showing the configuration of the transmission system shown in FIG. 1. FIG. 8 is a flowchart showing the self-check operation of the active master station and the standby master station. FIG. 9 is a flowchart showing the flow of data at the standby master station. 12 is a flowchart showing downlink interrupt processing. IA, 2B...Master station 2A 2B...Signal line 3...Transmission line 4.5...Remote station 6...System bus 7...Upper controller 8...Control center 9... Multifunctional protective relay 10...Magnetic contactor 11...Induction conductor 12...Main circuit

Claims (1)

[Claims] (1) A working master station that controls transmission, a standby master station that functions as a backup when an abnormality occurs in the working master station, and multiple remote stations, and data is transmitted between these stations. A backup switching method in a transmission system that includes a transmission path and exchanges transmission frames between a master station and a remote station by polling from the working master station, wherein the working master station detects its own abnormality. When detected, the standby master station stops transmission and enters a down state in which it does nothing, while the standby master station detects an abnormality in the active master station based on the no-signal state on the transmission path and performs a backup operation. In the backup switching method that starts, the active master station and the standby master station are connected by a dedicated signal line, and the active master station detects a self-abnormality immediately via the dedicated signal line. While informing the master station,
The backup switching method is characterized in that the standby master station side starts a backup operation even if an abnormality on the active master station side is detected via the dedicated signal line.