JPH06348301A - Process controller - Google Patents

Abstract

PURPOSE:To grasp a command a manipulated variable, and a controlled variable corresponding to the command in an analog signal area at all times irrelevantly to whether control is automatic or manual. CONSTITUTION:Command source data DELTAPs generated from a process state quantity command Qs and uncontrolled variable source data Td and Pd is converted from digital to analog and supplied as the command SV to a twin- pointer display unit 4 and a controlled variable analog signal DELTAP is supplied as the controlled variable PV to the twin-pointer display unit 4; and the controlled variable source data DELTAPd and command source data DELTAPs are compared and the output is processed by control arithmetic (PID, etc.,) to calculate manipulated variable source data, which is converted from digital to analog and supplied as the manipulated variable MV to a process 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process control device for displaying a target value for process control in an analog signal area even if a digital computer goes down.

[0002]

2. Description of the Related Art In a process control device mainly for feedback control, whether automatic control or manual control, a target value to be set, an operation amount output to a process and a control amount corresponding to the target value are set. Is an indispensable basic quantity. Then, the target value is usually given as a process state quantity such as temperature, flow rate, and pressure. On the other hand, the controlled variable, which is a process variable, may rarely be a value that accurately corresponds to the target value, but normally requires some kind of correction calculation, compensation calculation, or other processing calculation. For this reason,
In a process control device (distributed control device) currently in practical use, each analog signal of a control variable and a non-control amount, which is a process variable, transmitted from a process
A / D conversion is performed to obtain the original data, the control amount corresponding to the target value is calculated from the control amount original data and the non-control amount original data, the calculated control amount and the target value are compared, and an appropriate adjustment calculation (PID Etc.) to calculate the manipulated variable and output it to the process.

For example, a case where the gas flow rate is controlled by an orifice differential pressure transmitter inserted in a fluid pipe will be described with reference to FIG. In this case, the control amount of the process 1 is the differential pressure ΔP, and the non-control amount is the temperature T and the pressure P, which are transmitted to the process control device 2 as an analog signal (4 to 20 mA). Then, in the process control device 2, the analog signals ΔP, T, P are A / D converted, and the original data ΔPd,
It becomes Td and Pd. In the digital (0 to 1) signal area, the flow rate calculation value Q which is the process state quantity is calculated from the differential pressure ΔPd which is the control amount primitive data and the temperature Td and the pressure Pd which are the non-control amount primitive data, and this is calculated. It is compared with a preset flow rate target value Qs, and its output is adjusted (PID
Etc.) to calculate the manipulated variable primitive data,
A / A conversion is performed to obtain the manipulated variable MV, which is displayed on the operation indicator 3 in the analog signal area, and the process 1
Give to. The distributed control device is a process control by a digital computer, and the calculation of the flow rate calculation value Q, the comparison with the flow rate target value Qs, and the process of adjustment calculation (PID etc.) are performed by the digital computer. In addition, the display of the target value, the manipulated variable, and the controlled variable, which are the three indispensable basic amounts, is also performed in the digital signal area.

[0004]

In this prior art, when the digital computer fails, the target value for each control amount source data is not displayed in the analog signal area, so that the analog signal is not affected as long as the analog system is alive. There is a problem that the target value cannot be grasped even though the manipulated variable and the controlled variable of the process 1 can be grasped by using.

The present invention has been made for the purpose of solving the problems of the prior art.

[0006]

Means for solving the above problems will be described below with reference to FIG. 1 corresponding to the embodiment. The control variable ΔP and the non-control variable T and P analog signals transmitted from the process 1 are A / D converted into original data ΔPd, Td, and Pd, respectively.
Process state quantity target value Qs and non-control quantity source data Td,
A target value for each control amount source data is calculated from Pd and set as target value source data ΔPs, which is D / A converted and given as a target value SV to the twin-needle display 4 and a corresponding control amount analog. The signal ΔP is given to the twin-needle display 4 as the control amount PV, each control amount source data ΔPd is compared with the target value source data ΔPs, and its output is processed and calculated by the adjustment calculation to be the operation amount source data. This is D / A converted and given to the process 1 as the manipulated variable MV.

[0007]

With the above arrangement, even if the digital computer fails, the target value SV immediately before the digital computer fails is displayed on the double-needle display 4 in the analog signal area.

[0008]

1 is a diagram showing an embodiment of the present invention. In FIG. 1, 1 is a process, 2 is a process controller, 3 is an operation indicator, and 4 is a twin needle indicator.

The analog signals of the controlled variable PV (eg differential pressure ΔP) and the uncontrolled variable (eg temperature T, pressure P) which are process variables transmitted from the process 1 are A / D converted in the process controller 2. , Primitive data ΔPd, T
d and Pd. The controlled variable PV analog signal is given to the twin needle indicator 4 in the analog signal region. In the digital signal area, the uncontrolled amount primitive data Td, Pd
Then, the target value for each control amount primitive data is calculated from the process state quantity target value (for example, the flow rate target value Qs), and becomes the target value primitive data (for example, the differential pressure target value ΔPs) (target calculation). This is D / A converted to a target value SV and displayed on the twin-needle display 4 in the analog signal area. Further, the target value original data (for example, the differential pressure target value ΔPs) is compared with the control amount original data (for example, the differential pressure ΔPd), and the output thereof is further processed and calculated by the adjustment calculation (PID, etc.) to obtain the operation amount original data. It becomes data (control calculation). And this is D
A / A conversion is performed to obtain the manipulated variable MV, which is displayed on the operation indicator 3 in the analog signal area and given to the process 1.

Target value source data (for example, differential pressure target value ΔP
s) is directly compared with the control amount original data (for example, the differential pressure ΔPd), but the target value original data (for example, the differential pressure target value ΔPs) is D / A converted to obtain the remote R setting or the local L setting. The target value SV may be displayed on the twin-needle display 4 and may be A / D converted to be compared with the control amount primitive data (for example, differential pressure ΔPd) (shown by a chain line). By doing this, the twin needle indicator 4
Is switched to local L and the target value SV is manually set, the process can be automatically controlled.

When the digital computer constituting the process control device 2 fails, the functions in the digital signal domain, that is, the calculation of the target value, the comparison of each control amount source data with the target value source data, and the calculation of the operation amount source data are performed. Stop. However, the target value SV immediately before the digital computer failure is displayed on the twin-needle display 4 together with the control amount PV irrelevant to the digital computer failure. Therefore, in the analog signal area, the operation indicator 3 is changed from auto A to manual M,
Also, the twin-needle display 4 is switched from the remote R to the local L, the target value SV is set using the immediately preceding target value SV as an index, and the operation amount MV is operated.

[0012] The above is the case where it is configured by one digital computer, but the calculation of the target value for each control amount source data is performed by the digital computer for target calculation, and each control amount source data and the target value source data are If two digital computers are configured so that the comparison and the calculation of the manipulated variable primitive data are performed by the digital computer for control calculation, even if the digital computer for target calculation fails, the target value S immediately before the failure of the digital computer will occur.
V is displayed on the double-needle display 4, and the process can be automatically controlled by the target value SV or the manually set target value SV by a digital computer for control calculation.

[0013]

As described above, the present invention is
Each analog signal of the controlled variable and the non-controlled variable, which is the process variable transmitted from the process, is A / D converted into original data, and each controlled variable original value is obtained from the process state amount target value and the uncontrolled amount original data. A target value for each data is calculated to obtain target value primitive data, which is D / A converted and given as a target value to the twin needle indicator, and each of the control amount analog signals is used as a control amount for the twin needle indicator. In addition, the control amount source data is compared with the target value source data, and the output is processed by the adjustment calculation and calculated to be the manipulated variable source data, which is D / A converted to process as the manipulated value. Is given to. Therefore, even if the digital computer fails, the target value immediately before the digital computer fails is displayed on the twin-needle display in the analog signal area. Therefore, according to the present invention, as long as the analog system is alive, in any case, the three essential amounts of process control, namely, the target value, the manipulated variable, and the display of the control amount corresponding to the target value are displayed. The advantage is that the process can be operated manually.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional technique.

[Explanation of symbols]

 1 process 2 process control device 3 operation indicator 4 twin needle indicator

Claims (3)

[Claims] 1. A process state quantity target value and the non-control amount source data are obtained by A / D converting each analog signal of a control amount and a non-control amount, which are process variables transmitted from a process, to obtain source data. The target value for each controlled variable source data is calculated from this as the target value source data, and this is D /
A-converted and given to the twin-needle display as a target value, and each control amount analog signal is given to the twin-needle display as a control amount, and each control amount source data is compared with the target value source data. Then, the output is processed by the adjustment calculation, calculated to be the manipulated variable primitive data, and this is D / A converted and given to the process as the manipulated variable. 2. Calculation of a target value for each control amount primitive data,
Comparison of each control amount source data with the target value source data,
Process control device that processes the calculation of the manipulated variable primitive data with a single digital computer 3. A process control in which a separate digital computer processes the calculation of the target value for each control amount primitive data, the comparison between each control amount primitive data and the target value primitive data, and the calculation of the manipulated variable primitive data. apparatus