JPH0462081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control method for a duplex controller suitable for quickly switching the control authority of the duplex controller without adversely affecting the process.

[Conventional technology]

As a method for preventing wind-up operation when switching control rights in a duplex controller that shares only process input/output devices, there has been
Methods such as those described in Japanese Patent Application Laid-open No. 86972 and Japanese Patent Application Laid-Open No. 59-36801 are known. In the former, only the controller that has control authority (hereinafter referred to as the control side) performs control calculations, and the duplex control unit captures the address at which the control side writes to the plant database, and controls the data stored at the address. The side writes to the corresponding address of the controller that does not have read control authority (hereinafter referred to as the standby side). With this method, it is possible to reliably transfer the plant database from the control side to the standby side, and wind-up operation can be prevented when switching control rights, but high-speed operation of the redundant control section is required. Therefore, for practical use, dedicated hardware is required and expensive.
In addition, in the latter case, only the controller on the control side performs control calculations, and the controller periodically writes the contents of its own entire plant database to the memory in the switching section of the duplex system, and at the timing when the control right is switched, the controller performs the control calculations. The system switching unit transfers the contents of the plant database from memory to the controller that has newly gained control. This method requires high-speed writing and copying operations to the dual-system switching section and sufficient memory capacity within the switching section, and requires dedicated hardware for practical use. Furthermore, since the plant database is copied to the standby side at the timing when the control right is switched, it takes time for the standby side to take over the control calculations after gaining the control right.

On the other hand, regarding sequence control, for example,
A method as described in Japanese Patent No. 59-11403 is known. This method adopts the same switching method as the method described in Japanese Patent Application Laid-open No. 59-36801,
By writing a pointer value indicating an execution point regarding sequence control into the memory in the dual control calculation section, continuity of sequence control during control right switching is maintained. However, the pointer value update process needs to be updated for each sequence execution unit (program counter, etc.), which poses a problem of processing load on the control side.

[Problem that the invention seeks to solve]

In the conventional technology described above, since the control on the standby side does not perform control calculations, it is necessary to transfer the memory contents on the control side to the standby side at high speed in order to prevent wind-up operation that occurs when switching control rights. However, it is difficult to put it into practical use without the existence of dedicated hardware.

To solve this problem, only the input from the process input/output device (hereinafter abbreviated as PI/O) is required on the control side.
A conceivable method is to configure the controller on the standby side to be able to input, perform sequence control calculations regardless of the presence or absence of control authority, and suppress only the output to the PI/O on the standby side. However, if the control calculations are executed simultaneously, there is a possibility that synchronization may not be achieved due to a clock shift of both controllers, and wind-up operation that occurs when the control right is switched cannot be prevented.

An object of the present invention is to provide a control method for a duplex controller that can prevent wind-up operation that occurs when switching between duplex systems without installing special hardware.

[Means for solving problems]

An endless system that counts each time a series of sequence control calculations is completed in two controllers.
A counter (hereinafter referred to as a synchronization counter) is provided,
The count value of this counter is transmitted from the control side to the standby side, and the standby side controller compares its own count value with the count value sent from the control side. A synchronization difference occurring in control calculations between both controllers is detected by comparing the count values, and when a synchronization difference is detected on the standby side, a notification that a synchronization difference has occurred is notified to the control side. The controller on the control side, which has received the report of the synchronization shift from the standby side, provides the standby side controller with work data related to sequence control calculations necessary for the standby side to achieve synchronization. The standby controller restarts the sequence control calculation after performing synchronous processing based on the work data.

Here, work data refers to data that the controller refers to or writes to memory in connection with each control cycle of sequence control calculations, such as PI/O input/output data or results obtained from sequence calculation processing. This refers to data written to memory by

[Effect]

The process control controller performs control calculations that correspond to feedback loops such as PID calculations that were performed in conventional industrial instruments.
DDC (Direct Digital Control) calculation and valve,
It is divided into on/off commands for motors, relays, switches, etc., and sequence control calculations for interlocking against erroneous operations and malfunctions. In order to prevent switching between the control side and the standby side from causing wind-up operation for the process, it is necessary to equalize the contents of the plant database related to both DDC and sequence control calculations. In the present invention, control calculations are performed based on the same setting values and parameters on both the control side and the standby side, and input from the same PI/O, so if there is no deviation in the clocks, etc. of both controllers, the plant databases will be the same. .
Therefore, there is no need to transmit intermediate work etc. from the control side to the standby side in order to equalize the plant databases of both controllers, and as a result, the amount of data transmitted from the control side to the standby side is reduced. Therefore, there is no need to provide special hardware. By detecting the synchronization difference based on the count value of the synchronization counter when there is a mismatch between the plant databases of both controllers due to a synchronization difference caused by a clock discrepancy, etc.
In particular, it becomes possible to detect out-of-synchronization in sequence control calculations, where out-of-synchronization has a large effect on the process. In addition, the method for recovering from synchronization is to perform only on the plant database related to sequence control calculations performed by the controller.
It is possible to maintain synchronization of sequence control, and at the same time, the amount of transmission from the control side to the standby side is kept to a minimum. The plant database related to sequence control contains a lot of pit information, and the amount of transmission is small. In addition, since DDC calculations constitute a feed-evacuated loop, even if there is a temporary mismatch in the plant database, the control calculation itself has the effect of reducing this, so it is possible to recover from synchronization. There's no need.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the duplex controllers 10a and 10b connect the PI/O
015, and are connected by a data way 16 and a switching logic bus 13 for transmitting and receiving control signals for switching control rights. Here, the dataway 16 is connected not only to both of the duplicated controllers but also to the man-machine system, and is used for transmitting and receiving various data. That is, in the present invention, since less information is required to be transmitted for synchronizing control calculations on the control side and the standby side,
Data can be exchanged between the control side and the standby side using a data way provided for communication with man-machines and other controllers, which many process control controllers have. Furthermore, the data way 16 is duplicated in this embodiment, making data exchange between the two duplicated controllers more reliable.

Since the configuration below is the same for both the controllers 10a and 10b, the controller 10a will be explained. 10a is a central processing unit (CPU),
Through address/data bus 11e, memory 1
1b, transmission controller 11d, diagnostic circuit 11
f, PI/O interface (PI/OIF) 11g
are connected and accessible. The memory 11b has a program and a plant database for performing control calculation processing for performing DDC and sequence control, control processing for the duplex controller, data transmission and reception processing with the data way 16, a synchronization counter, and a buffer area for transmission. . In this embodiment, a specific address in the memory 11b is used as a counter without using any special hardware or counter.

The transmission controller 11d connects the dataway 1 through the transmission interface (transmission I/F) 11c.
6, and is connected to the CPU 10a and the memory 11b via an address/data bus 11e, and performs data transmission/reception processing between the memory 10b and the data way 16. PI/O interface 1
1g is connected to a process input/output device (PI/O) 15 through a switching circuit 11h and a PI/O bus 14. The diagnostic circuit 11f is connected to the address/data bus 11e, the switching circuit 11h, and the switching logic bus 13.
1e, and the result is notified to the diagnostic circuit 12f via the switching logic bus 13, based on its own diagnosis result and the diagnostic result of the diagnostic circuit 12f detected from the switching logic bus 13. , the controller 10a determines whether or not it should obtain the control right, and only when it has the control right, the switching circuit 11h switches between the PI/OI/F11g and the controller 10a.
Connect the PI/O bus 14 and connect the controller 10a.
access to the PI/O15.

Next, the operation will be explained. In the following description, the controller 10a will be referred to as the control side, and the controller 10b will be referred to as the standby side.

First, normal processing will be explained. The controller 10a inputs process data from the PI/O 15 through the PI/O bus 14, the switching circuit 11h, and the PI/OI/F 11g, and the CPU 11a receives the process data from the memory 11b.
The DDC and sequence control calculation processing programs are sequentially referenced and executed, the control calculation results are reflected in the plant database, and the PI/OI/F11g,
PI/O through switching circuit 11h and PI/O bus 14
Output to. Here, at the end of the sequence control calculation, the count value of the synchronization counter is updated. In addition, the transmission processing program in memory 11b is also run by the CPU.
11a requests the transmission controller 11d to transmit the process data input from the PI/O 15 and the count value of the synchronization counter to the controller 10b.
FIG. 3 shows the flow of the transmission processing program. The buses S31, S32, and S33 in FIG. 3 correspond to the processing here. After receiving the request, the transmission controller 11d transmits the input data from the PI/O 15 stored in a predetermined area of the memory 11b and the count value of the synchronization counter to the controller 10b through the transmission I/F 11c and the data way 16. do. The above operations are periodically performed by the timer management function of the CPU 11a. on the other hand,
Similarly, in the standby side controller 10b,
The CPU 12a sequentially executes the DDC and sequence control calculation processing in the memory 12b, but since it is separated from the PI/O bus 14 by the switching circuit 12h, the CPU 12a accesses the PI/O 15 and takes in the input. Control calculations are performed using the input data from the PI/O sent from the controller 10a instead of the data, and the calculation results are only reflected in the plant database in the memory 12b.
No output processing is performed to 5. Further, data received from the controller 10a via the data way 16 is received by the transmission controller 12d through the transmission I/F 12c. Transmission controller 12d
transfers the received data to a predetermined area of the memory 12b and sends the address/data bus 1 to the CPU 12a.
2e to notify that data has been received. Upon reception of this data, the CPU 12a
Start the reception processing program shown in the figure. The reception processing program is stored in the memory 12b. In this process, since the own controller does not have control authority, the judgment process in step S41
1, and in order to receive the PI/O input data and the synchronization counter value, the process branches to step S41.
It branches to 42. In step S42, a comparison is made with the synchronization counter value at the end of the sequence control calculation in the own controller to determine whether or not a synchronization shift has occurred. If the deviation is within the allowable range, nothing is done; if the deviation is outside the allowable range, it is determined that a synchronization error has occurred, and in step S43, the controller 12 transmits a synchronization request to the controller 10a.
d. Transmit through the transmission I/F 12c and the data way 16.

Next, the operation when a synchronization error occurs will be explained.

The controller 10a receives the synchronization request sent in step S43 via the data way 16.
memory 1 only when a synchronization request is received.
From the plant database 0a, all work data related to sequence control calculations are transmitted to the controller 10b. In the flowchart of FIG. 3, this corresponds to a path that branches to step S34, where work data related to sequence control calculations are sent to the controller on the standby side for all points when it is determined in step S32 that there is a synchronization request from the standby side. do.
The standby controller 10b, which has received the work data transmitted in step S34, unconditionally reflects the received data in the plant database in the memory 12b. Through this process, the control calculation on the standby side can be restarted again in synchronization with the control side. This corresponds to the process branching from step S41 to step S45 in FIG.

Next, Figure 2 shows the operation flow of the sequence control calculation processing program in this process.
FIG. 5 shows the operational flow of the DDC control calculation processing program.

In the sequence control calculation process shown in FIG. 2, it is determined in step S21 and step S25 whether or not the own controller has the control right, and only when the own controller has the control right, input processing from the PI/O 15 is performed. Step S22 is performed, and the PI/O
Step S26 of output processing to 15 is performed. If the own controller does not have control authority, PI/O15
In step S23, instead of the input processing from the other party's controller, the sequence control calculation processing in step S24 is performed using data received from the other party's controller. Further, the above-mentioned synchronization counter updating process is performed after the sequence control calculation process is completed in step S27.

Similarly, in the DDC control calculation process in FIG. 5, it is determined in steps S51 and S55 whether or not the own controller has control authority, and if it has control authority, it is input to the PI/O 15 at step S52 and output. Step S56 of the process is executed. If there is no control right, control calculation step S53 is executed using the analog data received from the partner controller in step S53.

In addition, in the present invention, since the sequence control arithmetic processing program and the transmission processing program are started asynchronously, the counter value is
A method is adopted in which work data related to sequence control is transferred and transmitted to the standby controller from a transmission buffer only when step S34 of the latter process is performed.

〔Effect of the invention〕

According to the present invention, it is possible to minimize the amount of data to be transmitted in order to prevent wind-up operation when control authority is switched from the control side to the standby side, thereby eliminating the need for special hardware. can. Furthermore, since both controllers perform control calculations regardless of whether they have the control right, there is an effect of eliminating interruptions in the control calculation processing due to switching of the control right.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Figure 3 is an operational flow diagram of sequence control calculations, Figure 3 is an operational flow diagram of plant database equalization transmission processing, Figure 4 is a flow diagram of plant database equalization reception processing, and Figure 5 is an operational flow diagram of DDC control calculation processing. It is a diagram. 11a, 12a...CPU, 11b, 12b...
...Memory, 11c, 12c...Transmission interface, 11d, 12d...Transmission controller, 1
1e, 12e...address/data bus, 11
f, 12f...Diagnostic circuit, 11g, 12g...Process input/output device interface, 11h, 1
2h...Switching circuit, 13...Switching logic bus, 14...Process input/output device bus, 15...
Process input/output device, 16... data way.

Claims (1)

[Claims] 1 Two controllers that share a process input/output device are connected by a transmission line, and both controllers each have diagnostic means for monitoring operation, so that when one is used as the control side, the other is used as the standby side. In the controller, both the control side controller and the standby side controller are each provided with a synchronization counter, and the standby side controller, which does not have the control right, transmits the process data input from the process input/output device through the control side controller, which has the control right. The standby controller performs the same sequence control calculation as the controller on the control side, and updates the count value of the synchronization counter every time one control cycle of the sequence control calculation ends. It takes the count value of the synchronization counter, compares it with the count value of its own synchronization counter, and when the deviation exceeds the allowable range, generates a synchronization request to the controlling controller,
2. The control side controller receives related work data from the control side controller every control cycle of the sequence control calculation, performs synchronization processing, and then performs the sequence control calculation.
Control method of heavy controller.