JP4258826B2 - Function block variable setting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for setting internal variables of a control function block (hereinafter referred to as FB) in which a plurality of internal variables are used and a control function is defined by software.
[0002]
[Prior art]
FIG. 6 shows an FB in which a control function for executing a P (proportional) I (integral) D (differential) operation on a deviation between a measured value and a set value is described in a program language (hereinafter referred to as IEC) according to the IEC61131-3 standard. It is an example of a functional block diagram.
[0003]
Reference numeral 1 denotes an FB having a PID calculation function described in IEC. The FB created by the IEC is black-boxed. When the values of variables (measurement values, setting values, operation output values, control parameters, etc.) used by the FB in internal processing are externally referenced and set in the FB Needs to be interfaced by defining the variables as input and output variables.
[0004]
In FIG. 6, 2 is an interface for measurement values defined as input variables, 3 is an interface for set values defined as input variables, and 4 is an interface for operation output values defined as output variables.
[0005]
In FB1, 5 to 10 are variables (parameters) used to execute the PID control operation, 5 is an integration time, 6 is a differentiation time, 7 is a proportional band value, and 8 is a mode (manual, automatic). ) Value, 9 is an alarm set value, and 10 is a limit value.
[0006]
[Problems to be solved by the invention]
An FB having a complicated control logic may have several tens of parameters in order to perform a control operation, and it may be necessary to write values or reference values to these parameters during the operation of the FB. .
[0007]
As mentioned above, the FB based on IEC cannot refer to or set internal variables from the outside, so all variables that may need to be accessed in the conventional FB structure are input variables and output variables. It is necessary to define and interface, and as the number of variables increases, the number of interfaces also increases, making it difficult to use as an FB.
In the example of FIG. 6, it is necessary to define six input variables 5 ′ to 10 ′ for accessing the internal variables 5 to 10 as interfaces.
[0008]
As another method, it is possible to create a plurality of FBs having different internal variables and use them by switching them. However, many FBs having the same internal control logic are required, which is not efficient.
[0009]
An object of the present invention is to realize a function block variable setting method capable of minimizing an interface for accessing a plurality of internal variables.
[0010]
[Means for Solving the Problems]
In order to achieve such an object, the feature of the invention described in claim 1 of the present invention is that a control function block in which a plurality of internal variables are used and a control function is defined by software is provided for the internal variables. A first interface for accessing by a character string is provided, a character string interpretation function block is formed in the control function block, a character string given from the first interface is interpreted by the character string interpretation function block, and the internal While changing the variable ,
After the internal variable change by the character string interpretation function block is completed, a second interface for initializing and outputting the character string is provided in the control function block, and the second interface output is fed back to the first interface. Therefore, the internal variable is changed only once .
[0011]
According to a second aspect of the present invention, the control function block is described in a programming language according to the IEC61131-3 standard.
[0013]
According to a third aspect of the invention, the internal variable has a unique variable name corresponding to a character string input to the first interface.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram illustrating the basic concept of the present invention. In FB1, 11, 12, and 13 represent three variables (variable 1, variable 2, variable 3).
[0015]
Reference numeral 14 denotes a character string interpretation FB unique to the present invention introduced into the FB. This character string interpretation FB is also described in IEC. Reference numeral 15 denotes an internal variable access interface defined as an input variable in FB1 in order to access the character string interpretation FB14.
[0016]
An internal variable is instructed to be changed by a character string via the interface 15 (FIG. 1 (a)). For example, when variable 1 and variable 3 are set to value 1 and value 3, respectively, a character string of “variable 1 = value 1; variable 3 = value 3” is given to interface 15.
[0017]
The character string interpretation FB 14 interprets this input content 'variable 1 = value 1; variable 3 = value 3' (FIG. 1 (b)), executes variable name matching by search, and sets variable 1 to value 1 Then, the variable 3 is set to the value 3 (FIG. 1 (c)).
[0018]
FIG. 2 shows an embodiment in which the present invention is applied to the PID control FB described with reference to FIG. 6, and the value of the integration time 5 as an internal variable is set to 100 s and the value of the mode value 8 is set to AUTO. In this case, the internal variable access interface 15 is given a character string of “mode = AUTO; integration time = 100 s”.
[0019]
As described above, in the present invention, since the interface for accessing the internal variable is a character string, the internal variable can be set using the same interface regardless of the logic inside the FB. Designs that minimize the number of interfaces for are possible.
[0020]
The embodiment of FIG. 3 is an example in which a value can be set only once by initializing a character string variable to an internal variable. The difference from the basic conceptual diagram of FIG. 1 is that an internal variable access interface 16 as an output variable is added.
[0021]
The character string interpretation FB 14 uses the same variable for input and output of internal variable access, and the input character string (FIG. 3A) is set to the internal variable (FIGS. 3B and 3C). After completion, the character string is initialized and output via the interface 16 (FIG. 3 (d)).
[0022]
Since the output of the interface 16 is fed back to the interface 14 and the contents of the interface 14 are updated, the character string to be set becomes empty (FIG. 3E) at the next input. By using such an input / output interface, it is possible to set the value of a variable only once by inputting a character string only at the desired timing.
[0023]
Next, the function and signal processing procedure of the character string interpretation FB, which is the main part of the present invention, will be described with reference to FIGS. FIG. 4 shows an interface of the character string interpretation FB 14, 17 to 20 are input variables, and 21 to 24 are interfaces defined by output variables.
[0024]
The interfaces 17, 18, and 19 are input with "variable 1", "variable 2", and "variable 3", which are unique variable names that uniquely represent the variable 1, variable 2, and variable 3 (FIG. 4 (a)). )), The setting character string from the interface 15 is input to the interface 20 (FIG. 4B).
[0025]
Data to be set in the variable 1, variable 2, and variable 3 is output to the interfaces 21, 22, and 23 (FIG. 4C), and an initialized empty character string signal is output to the interface 24 (FIG. 4). 4 (d)), this output is given to the interface 16 described in FIG.
[0026]
FIG. 5 is a flowchart showing a signal processing procedure inside the character string interpretation FB 14. First, in step S1, the set character string (FIG. 4B) is divided into variable name and value elements. In step S2, the disassembly operation is repeated for the number of inputs. In step S3, it is checked whether or not the variable name element and the input variable name (FIG. 4A) match.
[0027]
If there is a matching element, the value element extracted from the set character string is stored in the data (FIG. 4C) corresponding to the variable name in step S4, and the empty character string initialized in the interface 24 is stored. Is output.
[0028]
The character string that could not be matched is not deleted in steps S5 and S6, but is output to the interface 24 as it is.
[0029]
【The invention's effect】
As is apparent from the above description, according to the present invention, the interface for accessing a plurality of internal variables is minimized by introducing the character string interpretation FB into the normal FB described by the IEC. The FB can be easily realized, and the efficiency of the FB design can be improved.
[Brief description of the drawings]
FIG. 1 is a functional block diagram illustrating a basic concept of the present invention.
2 is an embodiment in which the present invention is applied to the PID control FB of FIG. 6;
FIG. 3 shows an embodiment in which a value can be set in a one-shot manner by initializing a character string variable to an internal variable.
FIG. 4 is an interface diagram of a character string interpretation FB according to the present invention.
FIG. 5 is a flowchart showing a signal processing procedure inside a character string interpretation FB according to the present invention.
FIG. 6 is a general functional block diagram of an FB whose control function is described in IEC.
[Explanation of symbols]
1 Function block 11 Variable 1
12 Variable 2
13 Variable 3
14 Character string interpretation FB
15 Internal variable access interface

Claims (3)

A control function block that uses a plurality of internal variables and whose control function is defined by software is provided with a first interface for accessing the internal variables by a character string, and a character string interpretation function block is provided in the control function block. Forming and interpreting the character string given from the first interface by the character string interpretation function block and changing the internal variable,
After the change of the internal variable by the character string interpretation function block is completed, a second interface for initializing and outputting the character string is provided in the control function block, and the second interface output is fed back to the first interface. A function block variable setting method characterized in that an internal variable change is executed only once. The control function block is IEC61131-3 2. The function block variable setting method according to claim 1, wherein the function block variable setting method is described in a program language according to a standard. 3. The function block variable setting method according to claim 1, wherein the internal variable has a unique variable name corresponding to a character string input to the first interface.

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