JPS6326882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process control device, and more specifically, the present invention relates to a process control device that includes a microprocessor, samples a process variable signal, converts it into a digital quantity, and converts the digital signal into a ), I (integral), D (differential) calculation processing,
The present invention relates to a process control device for controlling a process by giving calculation results to operating equipment.

In this type of process control device, the main calculations are P (proportional), I (integral), and D (differential) calculation formulas, and the calculation outputs (results) according to the method of the operating end.
There are two methods for selecting: position type and velocity type.
Here, the position type is a type that outputs the calculation result as it is, and the velocity type is a type that outputs the amount of change in the calculation result. And the factor of selection is “whether the output operation terminal has integral property or not”
That's what it means.

The calculation blocks of a conventional controller (controller) are shown in Figs. 1 and 2 and explained below.
The analog controller, as shown in Figure 1,
It consists of a differential block D that receives the difference output between the set value SP and the process variable PV, and a proportional block P and an integral block I that receive the output of this differential block D. After adding the outputs of , the controller calculation output CN is obtained. here,
In differential block D, calculation of 1+T _D S/1+TD/KDS, and proportional block P
The integral block I is configured to perform an operation of multiplying by K, and the integral block I performs an operation of K.multidot.1/ _TIS . And this controller calculation output CN
is CN=K・(1+1/T _I S)・(1+T _D S/1+TD/KDS
)・(SP− PV) ……(1)

However, S: Laplace operator K: Proportional gain T _I : Integral time T _D : Differential time K _D : Differential gain As shown in equation (1), the controller's calculation output CN is simply a position type (CN). If the operating end has an integral property, the position of the operating end is fed back and compared with the controller's calculation output CN to create an increase/decrease signal to the operating end.

On the other hand, as shown in Fig. 2, the digital controller has a differential block D that receives the difference output between the set value SP and the process variable PV, a proportional block P that receives the output of this differential block D, and an integral block I. Each of them performs calculations at the period of the sample time, and after adding the output of the proportional block P and the output of the integral block I, the controller calculation output ΔCN is obtained. Here, in the differential block D, 1+T _D S/1+TD/KDS is calculated, and the proportional block P
In the _integral block I, the _calculation of _{K.T.sub.S.T.sub.S.S.}

_Then , the calculation output ΔCN of the controller is ΔCN=K(DN−DN1)+K・T _S ／T _I・DN ...(2) DN=DN1+TS ／T _S +1/KDT _D (EN−DN1) +K _D (EN −EN1).

However, T _S : Sample time EN: (SP-PV) EN1: Value of EN one sample before DN: Output of differential block D DN1: Value of DN one sample before. Sample time the expression
Since the calculation is performed for each T _S , it is replaced with discrete time, and the calculation of equation (2) is performed with the configuration shown in FIG.

The calculation output ΔCN of the controller is of the speed type (ΔCN), and is usually of the form that outputs the amount of change. This is suitable for cases where the operating end itself has an integral property, such as a pulse motor.

However, with this method, if a position type (CN) calculation output is desired, an integrator is required after the controller.

In view of the above-mentioned points, the present invention provides a process control device designed to solve such problems.The present invention is designed to provide a process control device in which a position type/velocity type PID controller is configured with the same software, and the calculation status can be easily changed. This allows you to select and output.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 3 is a block diagram showing an embodiment of the process control device according to the present invention, and shows an example of a PID calculation package included in the process control device as standard software. In the figure,
PCG has an input terminal _H1 to which the set value SP is given,
An input terminal H ₂ to which a process variable PV value is given, an input terminal P ₁ to which a controller output addition value CNI is given, an input terminal P ₂ to which a flag FLAG using an enable signal is given, and an output terminal OUT. This is a PID calculation package that performs PID calculation processing on set value SP and process variable PV.

In this way, P (proportional), I (integral), D (differential)
The PID calculation package PCG that performs the calculation processing is 4
One input terminal H ₁ , H ₂ , P ₁ , P ₂ and one output terminal
This package is stored as a program in ROM (read-only memory) and is immutable. Since there is no limit to what can be connected to this input terminal, the configuration is such that a PID controller with various functions can be realized by the connection.

Figure 4 shows the PID calculation package shown in Figure 3.
This is a block diagram showing the internal blocks of the PCG, and is an alternative representation of the flowchart executed by the processor using the block structure. In the figure, PID・B inputs the set value SP and process variable PV, and P (proportional)・
Velocity type that performs I (integral) and D (differential) calculations
The PID block, OR, is an OR gate that controls the input of the output addition value _CN1 by the input of the flag FLAG, and turns it on and off. And speed type PID
Add the calculation output ΔCN from block PID・B and the output from OR gate OR using adder Σ,
It is configured to obtain the output OUT of PID calculation.

Next, the operation of the embodiment shown in FIG. 4 will be explained. First, the set value SP and process variable PV are taken in, and using the previous sample value of these data, PID (proportional-integral-derivative) calculation is executed according to the program command, and the velocity type PID calculation output ΔCN is calculated. .

Next, the OR gate OR is turned on using the flag FLAG, and the data connected to the input terminal P ₁ of the output addition value (CN ₁ ) is set to 0% or the previous calculation output, depending on the device to be operated by the process control device. If you select one and give it, the selected one and
The velocity type PID calculation output ΔCN obtained above is added by adder Σ, and this output is output from the output terminal.
Obtained from OUT.

In this way, the calculation package is assembled according to the calculation program stored in the ROM (read-only memory), and the data of the set value SP applied to the input terminal _H1 and the process variable value PV applied to the input terminal _H2 are assembled. The calculation output ΔCN of the velocity type is calculated for the difference between the above data and the data given to the input terminal _P1 under the control of the flag FLAG using the enable signal given to the input terminal _P2 . It is configured to be added to the speed type output ΔCN and output from the output terminal OUT. As shown in Fig. 4, the features of this PID calculation package include a PID block PID-B that calculates the speed type output, a 2-input OR calculation block, and an addition calculation block that are stored in ROM (read-only).
This is a 4-input, 1-output package with an unchangeable hardware configuration based on a program stored in the memory (memory), so that it can send out velocity-type or position-type output as appropriate by selecting input signal CN ₁ . The block configuration shown in FIG. 4 is immutably realized by one fixed and integrated program.

Conventionally, the PID block that obtains the velocity type calculation output ΔCN was made into an independent entity (subroutine) in a fixed program, but it is better to package the above two blocks and make them independent, which has the advantages described later. have

Among the input/output terminals of the PID calculation package DPG, the data format of H ₁ , H ₂ , P ₁ , and OUT is expressed as a numerical value in percentages, and the data format of input terminal P ₂ is expressed as a logical value of 0 or 1. It is in the form of a flag that indicates the status.

FIG. 5a shows a configuration diagram of a position type output PID controller, and FIG. 5b shows an example of the configuration of a velocity type output PID controller.

In Figure 5 a, CONT _a is position type output PID
Indicates the controller, H ₁ and H ₂ are each set value
Input terminal to which SP data and process variable value PV data are given, P ₁ is input terminal to which the previous output value data out obtained from output terminal OUT is given, P ₂
is an input terminal to which the enable signal INL is applied. In Figure 5b, CONT _b is the speed type output
This figure shows a PID controller, where H ₁ , H ₂ and P ₂ are input terminals corresponding to the same reference numerals in FIG. 5a, and P ₁ is an input terminal to which fixed value data FIX of 0% is applied.

In this way, when the operating device to which the calculation result is given is an integral operating device, the input terminal _P1 has the terminal shown in Figure 5b.
As shown in Figure 5a, when the 0% fixed value data FIX is not an integral operation device, the previous output value data OUT held in memory etc. from the output terminal OUT is omitted in the diagram. It is configured to provide each of them under the control of the processor.

Next, the operation of the embodiment shown in FIG. 5 will be explained. First, in the position type controller shown in _FIG .
Give _P2 an enable signal INL that turns on. Then, the input terminal P ₁ will take in the previous output value out of the calculation, that is, it will be equivalent to an internal connection, and the speed type calculation output ΔCN will always be connected to the previous output of the calculation.
As a result, the calculated output obtained at the output terminal OUT is essentially the integral of the velocity type calculated output ΔCN, and a position type output is obtained.

Next, in the speed type controller shown in Fig. 5b, if the input terminal P ₁ is connected to give 0% fixed value data FIX and the input terminal P ₂ is connected to give the ON enable signal INL, the output The speed-type calculation output ΔCN is output as is as the calculation output obtained at the terminal OUT, and a speed-type output PID controller can be configured.

Thus, the present invention has many advantageous features as compared to conventional process control devices, such as the following.

That is, first of all, since standard software is commonly used regardless of the speed type or position type, the program memory size can be saved. Second, since no integrator is required to configure the positional PID, handling is simplified, maintainability is improved, and program memory size is saved. Thirdly, since both velocity-type and position-type PID controllers use the same algorithm, they have various features such as not causing any discomfort during operation.

As described above, the present invention has great effects compared to conventional process control devices, and can be used as a process control device that configures position type/velocity type PID controllers with the same software and can easily select and output. is unique.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing an example of a conventional process control device, FIG. 3 is a block diagram of a PID calculation package which is an embodiment of the process control device according to the present invention, and FIG. 4 is a block diagram showing an example of a conventional process control device. FIG. 5 is an explanatory diagram showing the configurations of a position type output PID controller and a velocity type output PID controller according to the embodiment of the present invention. SP...Setting value, PV...Process variable, H ₁ ,
H ₂ , P ₁ , P ₂ ... Input terminal, OUT ... Output terminal,
PCG...PID calculation package, INL...enable signal, FIX...fixed value data, out...output value data.

Claims (1)

[Claims] 1 Consists of a microprocessor that samples process variable signals, converts them into digital quantities, performs proportional, integral, and differential calculations on the digital signals, and then provides the calculation results to operating equipment to control the process. In the process control device for performing proportional/integral/differential calculation processing, the device for performing proportional/integral/differential calculation processing has one output terminal and four input terminals consisting of a first, second, third, and fourth input terminal. - Consists of a differential calculation package, which is assembled according to a calculation program stored in the ROM, and which processes set value data given to the first input terminal and process variable value data given to the second input terminal. calculate a speed-type calculation output for the data difference, and add data applied to a third input terminal under control of an enable signal applied to a fourth input terminal to the calculated speed-type output. When the operation device is an integral operation device, fixed value data of 0% is given to the third input terminal, and when the operation device is not an integral operation device, the data is output from the output terminal. A process control device characterized in that it is provided with previous output value data.