JP5453743B2 - Redundant control system - Google Patents

Description

  The present invention relates to a duplex control system that includes a plurality of modules that perform PID calculation and selectively operates the modules.

For the purpose of improving control reliability, a duplex control system having two identical input / output modules is used in the field of process control. In this system, one is used as an active module and the other is used as a standby module. When an abnormality occurs in the active module, the process control can be continued by switching the module and operating the standby module.
JP 2006-209565 A

  For the purpose of ensuring a necessary control speed, a calculation block for PID calculation may be incorporated in the input / output module. However, when the calculation block is incorporated, the PID loop in the standby module is disconnected, and therefore the correct calculation cannot be executed in the standby module. Also, the input value (PV value) given to the calculation block may be different between the operation side and the control side due to variations in hardware constituting the module or a shift in the acquisition timing of the input value (PV value). is there. Further, when the input value (PV value) is a current input value or the like, the input value (PV value) cannot be given to both modules simultaneously.

  When the module is switched under these conditions, an output value (MV value) different from the output value from the active module is output from the standby module at the time of switching. When switching, the continuity of the output value is lost.

  The PID calculation is performed using the past calculation state. For this reason, a difference in the calculation state history between the modules causes a difference between the PID calculation state on the standby side and the calculation state on the operating side at the time of switching. For this reason, continuous PID calculation cannot be continued after switching, and continuity of output values (MV values) cannot be obtained.

  As described above, when the continuity of the output value (MV value) cannot be obtained, the entire plant control is affected. Therefore, it is necessary to avoid such a situation.

  An object of the present invention is to provide a duplex control system capable of obtaining continuity of control when switching modules.

A duplex control system according to the present invention includes a first module that performs PID computation and a second module that performs PID computation, and selectively operates the first module or the second module. A switching unit that switches a module to be operated from the first module to the second module, and data indicating a calculation state of the first module before switching by the switching unit is the second module. After the switching by the switching means, the second module performs a PID operation using the data transferred by the transfer means, and the data is stored in the first module. An output value, and the second module is transferred by the transfer means when switched by the switching means. While output to the output destination output value of the first module, then executes the equalization processing to its output value by adding the proportional component and the integral component and differential component, the first The module includes a first PID calculation block to which an input value and a set value are input, and the second module includes a second PID calculation block to which the input value and the set value are input. At the time of switching by the switching means, the second module does not use the output value of the second PID calculation block until the equalization processing ends, and the first module transferred by the transfer means does not use it. An output value is output to an output destination, and after the equalization process ends, the second module outputs an output value of the second PID calculation block to the output destination .
According to this duplex control system, data indicating the calculation state of the first module before switching by the switching means is transferred to the second module, and the second module executes calculation using the transferred data. Therefore, when switching modules, a continuous calculation state can be obtained, and continuity of control can be obtained.

  The first module and the second module may operate asynchronously with each other.

  According to the duplex control system of the present invention, data indicating the calculation state of the first module before switching by the switching means is transferred to the second module, and the second module performs calculation using the transferred data. Since this is executed, a continuous calculation state can be obtained when switching modules, and continuity of control can be obtained.

  Hereinafter, an embodiment of a duplex control system according to the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram illustrating a configuration of a duplex control system according to an embodiment.

  As shown in FIG. 1, the duplex control system of the present embodiment includes a first module 1A and a second module 1B each having a PID calculation block 11A and a PID calculation block 11B, and a CPU module 2 functioning as a transfer means. With.

  In FIG. 1, the first module 1A includes a switch 12A as a function for switching the output / non-output state of the output value (MV value), and a switch 13A as a function for switching the acquisition source of the output value (MV value). It is expressed. Similarly, the second module 1B includes a switch 12B as a function for switching the output / non-output state of the output value (MV value), and a switch 13B as a function for switching the acquisition source of the output value (MV value). Each is expressed.

  The switch 12A is controlled by the switching means 21A of the first module 1A, and the switch 12B is controlled by the switching means 21B of the second module 1B. The switch 12A and the switch 12B are linked to each other, and are controlled so that the switch is closed in the operating module and in the output state, and the switch is opened and in the non-output state in the other module.

  The switch 13A is controlled by the update control means 22A of the first module 1A, and the switch 13B is controlled by the update control means 22A of the second module 1B. In the operating module, the switch is closed and the output value (MV value) is updated by the result of the PID calculation. In the other module, the switch is opened and the output value (MV value) is not updated. The switches 13A and 13B are controlled in sequence after the switches 12A and 12B are switched by the switching means 21A and 21B. Specifically, when the second module is on the operating side, the update control unit 22B is controlled to close the switch 13B after a predetermined time has elapsed after the switch 12B is closed.

  As shown in FIG. 1, the set value (SV value) is given in common from the CPU module 2 to the arithmetic block 11A and the arithmetic block 11B of the first module 1A and the second module.

  Next, the module switching operation in the duplex control system of this embodiment will be described. FIG. 2 is a timing chart showing the operation timing of the redundant control system of this embodiment.

  During a period in which the first module 1A is operating normally (period until time T0 in FIG. 2), the switch 12A and the switch 13B are closed, and the PID calculation block 11A of the first module 1A is a CPU module. 2 receives the set value (SV value) given from 2 and the input value (PV) from the sensor device 4, and executes the PID calculation. The first module 1A outputs the calculation result in the calculation block 11A as an output value (MV value) and controls the control device 3. The control of the control device 3 is reflected in the input value (PV value) from the sensor device 4. In this way, while the first module is operating, a PID loop is formed by the control device 3, the sensor device 4, and the first module 1A.

  On the other hand, in the waiting second module 1B, the switch 12B is in an open state, and the second module 1B and the control device 3 are disconnected, so that no PID loop is formed. Therefore, the correct PID calculation cannot be executed in the calculation block 11B of the second module 1B, and the calculation is stopped. Further, the switch 13B is in an open state so that the output value (MV value) is not updated with the calculation result of the calculation block 11B. As shown in FIG. 1, the first module 1A sequentially transfers the output value (MV value) updated in the calculation block 11A to the second module 1B that is on standby via the CPU module 2. . The second module 1B transfers the transferred output value (MV value) to its own output value (MV value). Thereby, equalization of the output value (MV value) between the first module 1A and the second module 1B is performed. Note that the equalization of the output value (MV value) may be executed only when the module is switched.

  When an abnormality of the first module 1A is detected at time T0 in FIG. 2 and switching occurs, the switch 13A of the first module 1A is opened, and the switch 12B of the second module 1B is closed, so that the control device 3 is connected to the second module 1B, and an output value (MV value) is given to the control device 3 from the second module 1B. Further, the first module 1A is disconnected from the control device 3.

  At this time, the output value (MV value) given from the second module 1B to the control device 3 is the output value (MV value) last updated by the calculation block 11A before switching, and the calculation result of the calculation block 11B. Update by is also not performed. For this reason, the output value (MV value) of the second module 1B is maintained as it is.

  Next, after waiting for the input value (PV) from the sensor device 4 to be input to the second module 1B, the MV tracking is executed in the second module 1B at time T1 in FIG. In MV tracking, an output value (MV value) output from the second module 1B is used to execute processing for correcting the PID calculation. The MV tracking is a process generally used for matching output values as a result of the PID calculation.

  Next, a processing procedure in MV tracking will be described.

  The PID calculation is calculated by adding a proportional component (P component), an integral component (I component), and a differential component (D component). The “difference between the input value (PV value) and the set value (SV value)” and “past PID calculation is performed from the "calculation result of".

  In general, the proportional component and the differential component are calculated only from “the difference between the input value (PV value) and the set value (SV value)”, and “the past calculation result” is not used.

  The integral component is calculated from “difference between input value (PV value) and set value (SV value)” and “past calculation result”. Specifically, “input value (PV value)” is added to “past calculation result”. ) And the setpoint (SV value) difference ”is integrated.

  The MV tracking is a general method that is performed in order to continue the output when switching from the state in which the output is performed by another means to the state in which the result of the PID calculation is output. Specifically, the integral component is

Integral component = current output value (MV value) −proportional component−differential component is calculated, and the PID calculation result is

となり、結果としてＰＩＤ演算結果が「現在出力している出力値（ＭＶ値）」となって出力が継続される。ＭＶトラッキングによるＰＩＤ演算の補正処理は、自ら出力している出力値（ＭＶ値）を使用するので、ＣＰＵモジュール２によらず第２のモジュール１Ｂ単独で実行できる。このため、高速に処理を実行でき、敏捷性に優れる。

As a result, the PID calculation result becomes “currently output value (MV value)” and the output is continued. Since the correction value of the PID calculation by MV tracking uses the output value (MV value) output by itself, it can be executed by the second module 1B alone without using the CPU module 2. For this reason, the processing can be executed at high speed and the agility is excellent.

  When the MV tracking is completed, the switch 13A is turned off and the switch 13B is turned on at time T2 in FIG. 2, and the output value (MV value) obtained by normal PID calculation is sent to the control device 3 as the second module 1B. Output. A PID loop is formed by the control device 3, the sensor device 4, and the second module 1B. Since the MV tracking has been executed, the output value (MV) does not vary at time T2, and a continuous output value (MV value) is output. On the other hand, the first module 1A enters a standby state. Further, the output value (MV value) as the calculation result in the second module 1B is transferred to the first module 1A via the CPU module 2. In this way, the operation states of the first module 1A and the second module 1B are reversed by switching the modules.

  As described above, in the duplex control system of the present embodiment, when the module is switched, the second module 1B relies on the CPU module 2 by equalizing the MV value and correcting the PID calculation (MV tracking). Without stopping, the output by the PID calculation in the second module 1B can be started while maintaining the output state.

  By the way, generally, in the process control, the control is mostly in a stable state, and the output value is maintained at a substantially constant value. At this time, since the data transferred from the active module to the standby module does not change, it is not always necessary to synchronize.

  On the other hand, when the control is not stable and the state is changing, the output value (MV value) is pulled back to the past state by the delay of the equalization timing, but a problem occurs in the subsequent control. Absent. By shortening the equalization interval (cycle) so that the time width during which the state is pulled back falls within the allowable range, it is not always necessary to operate the modules in synchronization.

  As described above, according to the duplex control system of the present embodiment, the modules can be switched without changing the output by equalizing the MV values and correcting the PID calculation (MV tracking). Further, since the operation of the CPU module is not involved at the time of switching, the PID calculation function can be immediately taken over between the modules. In the duplex control system of this embodiment, it is not necessary to provide a means for transmitting a large amount of data as a transfer means, and since the transfer means can be realized asynchronously, it is not necessary to provide a mechanism for synchronization.

  In the above embodiment, duplexing using two modules has been exemplified, but a plurality of modules having an equalization function may be prepared as standby modules.

  Further, the duplex control system according to the present invention can be configured by hardware or software alone, or by arbitrarily combining both.

  In the above-described embodiment, the configuration in which the CPU module is interposed as the transfer means is shown. However, the configuration is arbitrary as long as correct data can be transferred as the data for equalization. For example, a dedicated line may be provided between modules to transfer data. For example, when the data to be transferred is an output voltage, the voltage value (analog value) output from the operating module can be easily read from the output terminal. Can be used as data.

  In the above embodiment, the result (output value) of the PID calculation is the data to be equalized (equivalent data), but the output value before switching the module and the result of the PID calculation after switching are final. As long as the equalization can be achieved, another data may be handled as the equalization data.

  FIG. 3 is a block diagram showing a configuration of a duplex control system in which an integral component in PID calculation is used as equivalent data.

  As shown in FIG. 3, a setting value (SV value) is given from the CPU module 2 to the operation side module and the standby side module. An input value (PV value) from the sensor device 4 is also given to both modules. Further, in the configuration of FIG. 3, the integral component of the PID calculation is transferred from the active module to the standby module via the CPU module 2, and the equalization of the integral component is performed in the standby module.

  The calculation block 11A and the calculation block 11B execute a PID calculation based on the set value (SV value), the input value (PV value), and the integral component, and update the calculation result as an output value (MV value) of each module. That is, the switch 13A and the switch 13B in FIG. 1 are always closed.

  If the same set value (SV value), input value (PV value), and integral component are given to both modules, the output value (MV value) that is the result of the calculation in the calculation block 11A and the calculation block 11B is the same. It becomes. In this way, since the data necessary for the PID calculation is prepared in both modules by transferring the integral component, the same PID calculation can be executed on the active side and the standby side, and the same output value (MV value) can be obtained. Can be prepared.

  FIG. 4 is a timing chart showing the module switching operation in the duplex control system shown in FIG.

  When an abnormality is detected in the first module 1A on the operating side, the module is switched at time T0 and the switches 12A and 12B are inverted. Thereby, the output source of the output value (MV value) given to the control device 3 is switched from the first module 1A to the second module 1B. According to the configuration of FIG. 3, since the state of the PID calculation itself is also equalized, the PID calculation can be continued without MV tracking, and the discontinuity of the output value (MV value) does not appear at the time of switching.

  For example, when there is a situation where the input value (PV value) cannot be given to both modules at the same time, the input value (PV value) is input to the second module 1B as in the example of FIG. Then, after the MV tracking is executed, the PID calculation may be taken over (adopting the calculation result in the second module 1B).

  As described above, according to the duplex control system of the present invention, the data indicating the operation state of the first module before switching by the switching unit is transferred to the second module, and the second module is transferred Since output and calculation are executed using data, a continuous calculation state can be obtained when switching modules, and continuity of control can be obtained.

  The scope of application of the present invention is not limited to the above embodiment. The present invention can be widely applied to a redundant control system that includes a plurality of modules that perform PID operations and selectively operates the modules.

The block diagram which shows the structure of the duplication control system of one Embodiment. The timing chart which shows the operation timing of a redundant control system. The block diagram which shows the structure of the duplication control system which used the integral component as equalization data. The timing chart which shows the switching operation | movement of the module in the duplication control system shown in FIG.

Explanation of symbols

1A 1st module 1B 2nd module 2 CPU module

Claims (2)

A duplex control system comprising: a first module that performs PID computation; and a second module that performs PID computation, wherein the first module or the second module is selectively operated.
Switching means for switching a module to be operated from the first module to the second module;
Transfer means for transferring data indicating the calculation state of the first module before switching by the switching means to the second module;
With
After the switching by the switching unit, the second module performs a PID operation using the data transferred by the transfer unit,
The data is an output value of the first module;
The second module adds the proportional component, the integral component, and the differential component in a state in which the output value of the first module transferred by the transfer unit is output to the output destination at the time of switching by the switching unit. Execute the equalization process to make its own output value ,
The first module includes a first PID calculation block to which an input value and a set value are input,
The second module includes a second PID calculation block to which the input value and the set value are input,
At the time of switching by the switching means, the second module does not use the output value of the second PID calculation block until the equalization processing ends, and the first module transferred by the transfer means does not use it. Output the output value to the output destination,
The duplex control system , wherein the second module outputs an output value of the second PID calculation block to the output destination after the equalization process is completed . The duplex control system according to claim 1 , wherein the first module and the second module operate asynchronously with each other .

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