JPH04299701A - Process controller - Google Patents

Abstract

PURPOSE:To attain the smooth switching between two controllers. CONSTITUTION:The controllers 5 and 6 contain the upper and lower limit controllers 23 and 24 which set the upper and lower limit levels equivalent to 0% of an operating part at the lower limit side and 100% at the upper limit side respectively. Then an upper limit level setting means changes the upper limit set level between 0% and 100% of the operating part at a fixed changing rate and in preference to the upper limit set value with use of a switch signal that selects one of both controllers 5 and 6. Meanwhile the other upper limit level setting means changes the upper limit set level between 100% and 0% of the operating part at a fixed changing rate in preference to the upper limit set level at a level equivalent to 100% of the operating part.

Description

[Detailed description of the invention]

[Object of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process control device suitable for smoothly switching from one system to the other in a dual system control system.

0002

2. Description of the Related Art In plant process control where reliability is important, dual system process control devices are often employed. In this case, one system is operated and the other system is kept on standby as a standby system, and when one system in operation breaks down or when necessary for maintenance and inspection, switching to the other system is used.

FIG. 5 is a block diagram of a process control device showing the above-mentioned conventional example.

This conventional example is a water level control device in a water supply system that supplies water to a tank 1 from a water supply pipe 2 serving as a water supply source. In the figure, the water level control device is composed of two systems, A system and B system. The A-system water level detector 3 and the B-system water level detector 4 are provided with an A-system control device 5 and a B-system control device 6, respectively, and an A-system control valve corresponding to each of them. 7 and a B system control valve 8 are provided.

The A system control valve 7 is arranged in the A system bypass pipe 9 of the A system bypass pipe 9 and the B system bypass pipe 10 branched from the water supply pipe 2 of the water supply source. In addition, an A-system front valve 11 is provided on the inflow side of the A-system control valve 7 of this A-system bypass piping 9, and an A-system pre-valve 11 is provided on the outflow side of the A-system control valve 7.
A post-system valve 12 is arranged.

Similarly, the B system control valve 8 is arranged in the B system bypass piping 10, and a B system front valve 13 and a B system rear valve 14 are arranged before and after the B system control valve 8.

[0007] Note that the A-system bypass piping 9 and the B-system bypass piping 10 merge and are connected to the tank 1 via a water supply piping 15. Water pressure is applied to the water supply pipe 2 on the water supply source side by a pressure source such as a pump. Also, tank 1
The water is appropriately discharged to the outside by means not shown.

[0008] The above-mentioned equipment has the same configuration for both the A system and the B system, and currently the A system is in operation.
It is assumed that system B is on standby as a backup. Further, it is assumed that the A system rear valve 12 and the B system rear valve 14 are fully open.

[0009] With the above configuration, a case will be explained in which the A system in operation is switched to the B system in standby.

First, the B system front valve 13, which is on standby, is fully opened. Then, the B-system control device 6 is gradually operated in the opening direction in manual mode to gradually open the B-system control valve 8. In this operation, it is necessary to operate the B system control device 6 slowly so that the water level 16 of the tank 1 does not change significantly.

When the B system control valve 8 opens, water is supplied through the B system bypass piping 10, and the water level 16 in the tank 1 gradually rises. Correspondingly, the A system control device 5, which is in automatic mode, operates the A system control valve 7 based on the operation signal.
gradually close. Thereafter, when the A-system control valve 7 is fully closed, the B-system control device 6 is switched to automatic mode. Subsequently, the A system control device 5 is switched to manual mode. Furthermore, the A system front valve 11 is fully closed.

[0012] With this operation, the switching of the control device from the operating system A to the standby system B is completed. Note that switching of the control device from the running B system to the standby A system is also performed in the same manner as the above operation.

[0013]

However, the above-mentioned conventional two-system process control apparatus has the following problems.

First, switching to one of the two systems was performed manually, which placed a heavy burden on the operator. For example, when switching from system A in operation to system B in standby, it requires careful operation and skill to mutually switch between automatic mode and manual mode without significantly changing the water level 16 of tank 1.

[0015] Particularly when the response of the process is fast or when switching is required due to a failure in one system, it is not easy to perform the above switching operation quickly while maintaining the water level 16 of the tank 1 constant.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a process control device that can automatically switch from one system to the other system of two process control systems without manual operation. .

[Configuration of the invention]

[Means for Solving the Problems] The present invention provides two detectors having the same configuration for detecting the same process quantity, and two detectors that are provided correspondingly to each other, and a detection value of each of the detectors and a predetermined target value. A control section with the same configuration performs arithmetic processing based on the deviation of
upper and lower limit limiters having the same configuration for setting limit set values within a corresponding range and providing operation signals to the operating section; and correspondingly provided upper and lower limit limiters that are operated by the operation signals of each of the upper and lower limit limiters. Select one of the operation signals of the operation section and each of the upper and lower limit limiters having the same configuration for operating the operation section from 0% to 100%, and output the operation signal to the corresponding operation section. In the process control device, the upper and lower limit limiters correspond in priority to the limit set values of the corresponding upper and lower limit limiters based on a switching signal from either one of the switching means. Increase the upper limit setting value from the operating unit equivalent to 0% to 10%.
one upper limit setting means that changes at a predetermined rate of change up to the equivalent of 0%, and the other upper and lower limit limiter when the upper limit set value of this upper limit setting means becomes equivalent to 100% of the operating section. the other upper limit setting means for changing the upper limit setting value of the corresponding upper/lower limiter from the operating unit equivalent to 100% to 0% at a predetermined rate of change with priority over the upper limit setting value; It is designed to provide a.

[0018]

[Operation] According to the above configuration, the operation signal from the upper and lower limit limiter selected by the switching means is limited by the upper limit setting value of the upper limit setting means on the selected side at the beginning of switching; As time passes, the operation signal is directly output to the operation section. Further, in the upper and lower limit limiters that are not selected by the switching means, the operation signal is gradually limited by the upper limit setting value of the upper limit setting means on the side that is not selected. In this way, by changing the setting of the upper limit set value of the upper and lower limit limiter, one of the operation signals of the two systems of control devices can be selected. Therefore, switching between the control devices from one system in operation to the other system in standby can be smoothly performed.

[0019]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a water level control device showing an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 5 indicate the same or corresponding parts.

The difference from FIG. 5 is that the A system control device 5 and the B
The point is that an A system switching button 17 and a B system switching button 18 are provided corresponding to the system control device 6. Also, A
As described later, the system control device 5 and the B system control device 6 automatically switch between the A system control device 5 and the B system control device 6 based on the A system switching button 17 and the B system switching button 18. The point is that it can be switched.

The A system control device 5 and the B system control device 6 have the same configuration as shown in FIG. That is, each part is provided with an A-system setting value generator 21 and a B-system setting value generator 22 corresponding to the A-system PI computing unit 19 and the B-system PI computing unit 20, respectively. An A-system upper/lower limit limiter 23 and a B-system upper/lower limit limiter 24 are provided. Further, each of the A system control device 5 and the B system control device 6 includes an A system switch 25 and a B system switch 26.
Corresponding to this, the A system valve fully open signal generator 27, the B system valve fully open signal generator 28, and the A system valve fully closed signal generator 29
and a B system valve fully closed signal generator 30 are provided, respectively, and these are switched by the A system switch 25 or the B system switch 26. Further, an A system valve change rate limiter 31 and a B system valve change rate limiter 32 are provided corresponding to the A system switch 25 and the B system switch 26,
The output value is set as the upper limit setting value of the A system upper/lower limit limiter 23 or the B system upper/lower limit limiter 24.

Here, the A-system PI calculator 19 or the B-system PI calculator 20 inputs the detected value of the A-system water level detector 3 or the B-system water level detector 4, and uses this detected value and the A-system set value generation. Based on the deviation from the set value of the generator 21 or the B system set value generator 22, proportional and integral calculations are performed and a calculated signal is output.

The A-system upper/lower limit limiter 23 or the B-system upper/lower limit limiter 24 is connected to the A-system valve change rate limiter 31 on the upper limit side.
Or, the value of the output signal from the B system valve change rate limiter 32 is set as the upper limit setting value, while on the lower limit side, the value of the fully closed operation signal (equivalent to 0% of the operating section) is set as the lower limit setting value. I have to.

That is, when the value of the above calculation signal is larger than the value of the output signal of the A system valve change rate limiter 31 or the B system valve change rate limiter 32, which will be described later, the above calculation output value is limited, The value of the output signal of the A-system valve change rate limiter 31 or the B-system valve change rate limiter 32 is output as an operation signal. Conversely, if the value of the above calculation signal is smaller than the value of the output signal of the A-system valve change rate limiter 31 or the B-system valve change rate limiter 32, it will not be limited at the lower limit side (equivalent to 0% of the operating section). In this case, the value of the calculation signal is output as is as the operation signal.

A system switch 25 or B system switch 26
In accordance with the sequence of the control device shown in FIG. 3, the A system valve fully open signal generator 27 or the A system valve fully closed signal generator 2
9, while switching to either the B system valve fully open signal generator 28 or the B system valve fully closed signal generator 30.

The A system valve change rate limiter 31 or the B system valve change rate limiter 32 is connected to the A system valve fully open signal generator 27 or the B system valve fully open signal generator 28 and the A system valve fully closed signal generator 29 or The output signal from the B system valve fully closed signal generator 30 is outputted at a predetermined rate of change while limiting the output signal, and the value of the output signal is determined by the above-mentioned A system upper and lower limit limiter 23 or B.
It is made to be the limit setting value on the upper limit side of the system upper and lower limit limiter 24.

With the above configuration, the operation when switching from the operating system A to the standby system B will be explained with reference to FIGS. 2 to 4.

In the operating state of the A system, an ON signal is output from the OR1 circuit of the A system switch 25 shown in FIG. Therefore, the A system valve full open signal generator 27 outputs the valve full open signal 1.
Outputs the value equivalent to 00%. The output equivalent to 100% of this valve full open signal passes through the A-system valve change rate limiter 31 and becomes a limit setting value equivalent to 100% of the upper limit side operating section of the A-system upper/lower limit limiter 23. At this time, the A system PI calculator 19 controls the A system and outputs a predetermined calculation signal value, so the calculation signal is set to the upper and lower limit settings of the A system upper and lower limit limiter 23. It is output as an operation signal to the A system control valve 7 without any restriction.

In this way, in the A system, the opening and closing of the A system control valve 7 as shown in FIG. 1 water level 16 is kept constant. Note that the A system front valve 11 and the A system rear valve 12 are fully open. Furthermore, since the value of the output signal of the A-system valve change rate limiter 31 is equal to or higher than the operating unit 100%, FIG.
The self-holding WO2 of the B system switching device 26 shown in FIG.
Therefore, the system is switched to the B system valve fully closed signal generator 30.

At this time, when the B system switching button 18 is pressed at time T1, the B system front valve 13 is fully opened by a switch (not shown) linked thereto. As a result, at time T2, the switching signal of the B system switching button 18 and the full open output signal of the B system front valve 13 shown in FIG.
is input to the AND2 circuit, and the conditions of this circuit are satisfied. Therefore, the ON signal is input to the B system valve fully open signal generator 28 via the OR2 circuit, and the output signal is sent to the operating section 100.
Output as % equivalent. At this time, the self-holding circuit WO
2, the OR2 circuit is self-maintained. The output signal of this B system valve fully open signal generator 28 is the output signal of the B system valve change rate limiter 3.
2, and as shown in FIG. 4, the value of the upper limit setting of the B system upper and lower limit limiter 24 is gradually increased in the direction equivalent to 100%.

By the way, the calculation signal of the B-system PI calculation unit 20 has almost the same value as the calculation signal of the A-system PI calculation unit 19. Therefore, at first, it is limited by the upper limit value determined by the output signal of the B-system valve change rate limiter 32, so the B-system control valve 8 is gradually set in the opening direction, and the water level 16 of the tank 1 is gradually raised. Accordingly, A system PI calculator 1
The calculation signal 9 decreases, and the A-system control valve 7 gradually moves in the closing direction.

Eventually, at time T3, when the value of the output signal of the B-system valve change rate limiter 32 becomes larger than the value of the calculation signal of the B-system PI calculator 20, the calculation signal of the B-system PI calculator 20 becomes higher than that of the B-system PI calculator 20. The B system control valve 8 is controlled by the above signal without being limited by the upper limit set value of the lower limit limiter 24. At this time, the output signal of the B system valve change rate limiter 32 continues to increase, and when the output signal becomes equal to or more than 100% of the operating section at time T4, the A system switch 2 shown in FIG.
The self-holding circuit WO1 of No. 5 is released. Therefore, NOT1 of this circuit switches to the A system valve fully closed signal generator 29, and makes the output signal equivalent to 0% of the operating section.

The A-system upper/lower limit limiter 23 converts the output signal corresponding to 0% of the operating section of the A-system valve fully closed signal generator 29 into the A-system upper/lower limit limiter 23.
The system valve change rate limiter 31 receives the input and gradually reduces the output in the direction equivalent to 0%. For this reason, the A system upper and lower limit limiter 2
The upper limit value of 3 is gradually set in the direction corresponding to 0% of the operating section, and at time T5, the calculation signal of the A-system PI calculator 19 is limited by the upper limit value. As a result, the operation of the A system is completely switched to the operation of the B system. After that, A
The system control valve 7 is fully closed. At the same time, the A system front valve 11 is also fully closed. In this way, the switching from the operation of the A system to the operation of the B system is completed.

On the other hand, this operation is performed in the same way when switching from the B system operation to the A system operation. That is, this time, the AND condition of the AND1 circuit is established by the switching signal of the A system switching button 17 and the fully open output signal of the A system front valve 11. Furthermore, the input of the OR1 circuit is held by the self-holding circuit WO1 via the OR1 circuit, and the system is switched to the A system valve fully open signal generator 27. Subsequently, when the value of the output signal of the A-system valve change rate limiter 31 becomes larger than the value of the calculation signal of the A-system PI calculator 19, the A-system PI calculator 19
This signal switches to the calculation signal of A system control valve 7.
is controlled. Further, when the value of the output signal of the A system valve change rate limiter 31 becomes equal to or higher than the operating unit 100%, the self-holding circuit WO2 is released and the system switches to the B system valve fully closed signal generator 30. The control valve 8 is fully closed.

By the way, in this embodiment, when switching the operation from the A system in operation to the B system, first, the upper limit value of the B system control device 6 is set to 0% using the switching signal.
It is set at a predetermined rate of change from equivalent to 100% of the operating section. Then, when this upper limit value becomes equivalent to 100% of the operating section, the upper limit value of the A system control device 5 starts to be set, and the upper limit value of the A-system control device 5 changes from equivalent to 100% of the operating section to 0% of the operating section.
%, but the condition for the upper limit value of the A-system control device 5 to start setting does not necessarily mean that the upper limit value of the B-system control device 6 corresponds to 100% of the operating section. It doesn't have to be limited to when. for example,
Setting of the upper limit values of each of the A-system control device 5 and the B-system control device 6 may be started simultaneously by the switching signal.

As described above, the switching between operation using the A system and operation using the B system is performed smoothly. Therefore, large fluctuations in the water level 16 due to switching do not occur. In addition, the operation is simple and malfunctions do not occur due to switching, and this control device can be easily implemented if it is configured with a microprocessor.

[0038] In this embodiment, the control target in the case of water level has been explained, but the application is not limited to this and can be similarly applied to a dual-system control device that targets process quantities such as flow rate, pressure, and temperature. It is clear that it can be done.

[0039]

As described above, according to the present invention, it is possible to automatically switch between two systems of control devices from one control device to the other. Therefore, the operator is freed from complicated operations. Moreover, since the switching is performed smoothly, large disturbances are rarely caused to the controlled object, and fluctuations in the controlled object due to the switching do not occur.

[Brief explanation of drawings]

FIG. 1 is an overall block configuration diagram of a process control device showing one embodiment of the present invention.

FIG. 2 is a block configuration diagram of an A system control device and a B system control device.

FIG. 3 is an explanatory diagram showing a sequence of an A system switch and a B system switch.

FIG. 4 is an explanatory diagram when switching from system A operation to system B operation.

FIG. 5 is an overall block configuration diagram of a process control device showing a conventional example.

[Explanation of symbols]

3 A system water level detector 4 B system water level detector 5 A system control device 6 B system control device 7 A system control valve 8 B system control valve 17 A system switching button 18 B system switching button 19 A system PI calculator 20 B system PI calculator 23 A system upper and lower limit limiter 24 B system upper and lower limit limiter 25 A system switch 26 B system switch 27 A system valve full open signal generator 28 B system valve full open signal generator 29 A system valve fully closed signal generator 30 B system valve fully closed signal generator 31 A system valve change rate limiter 32 B system valve change rate limiter

Claims (1)

[Claims] [Claim 1] Two detectors having the same configuration that detect the same process quantity, and a calculation process based on the deviation between the detected value of each detector and a predetermined target value, which are provided correspondingly to the two detectors. A control unit having the same configuration and a calculation output signal of each control unit provided corresponding to these control units is set to a limit setting value within a range from equivalent to 0% of the operating unit on the lower limit side to equivalent to 100% on the upper limit side. upper and lower limit limiters of the same configuration for outputting operation signals to the operation section, and operation signals of the upper and lower limit limiters provided correspondingly thereto, from the operation section equivalent to 0% to the operation section 100%. A process comprising the operating section having the same configuration for operation and a switching means for selecting one of the operating signals of each of the upper and lower limit limiters and outputting the operating signal to the corresponding operating section. In the control device, the operating section selects a limit setting value on the upper limit side of the corresponding upper and lower limit limiter with priority over the limit setting value of the corresponding upper and lower limit limiter based on the switching signal of either one of the switching means. One upper limit setting means changes at a predetermined rate of change from equivalent to 0% to 100%, and when the upper limit setting value of this upper limit setting means becomes equivalent to 100% of the operation part, the other one The other upper limit side changes the upper limit setting value of the corresponding upper and lower limiter from the operating unit equivalent to 100% to 0% at a predetermined rate of change, giving priority to the upper limit setting value of the upper limit limiter. A process control device comprising a limit setting means.