JPH0449401A - Pid control method for process control computer - Google Patents

Abstract

PURPOSE:To process a function corresponding to an external apparatus to be a DDC by software and to simplify the processing by adding analog input data to an objective value, executing PID control by a process control computer and adding tags to various parameters for the PID control. CONSTITUTION:An analog substrate 3 having an A/D conversion function and an analog output substrate 4 having a D/A conversion function are connected to a bus in the process control computer 1 for controlling a process. When tags are added to various parameters, a process from analog input up to analog output can be uniformly controlled, parameter constants or I/O constants can be set up or changed by a CRT task 5 and analog I/O and PID arithmetic processing can be respectively executed by an I/O processing task 6 and a PID processing task 7. Consequently, the structure of this system can be simplified and inexpensively obtained and the setting of the parameters can be simplified by interactively inputting them from a CRT.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a PID control method in a process control computer.

B. Summary of the invention The configuration consisting of a computer for process management and a DDC (direct digital control) related to process instrumentation that is subordinate to this has been abolished, and analog input/output is implemented using an analog input/output board connected to the bus of the process control computer. Perform PID control using data and target values,
At the same time, by attaching a TAG to each parameter of PID control, the conventional DDC external equipment is eliminated and parameter settings are simplified.

C1 Prior Art and Its Problems In general, a process control system consists of a computer for process management and a distributed control and DDC for process instrumentation below the computer.

Figure 6 shows the process control computer 1 and DDC 2.
The process control computer 1 determines the operational specifications of the lower DDC 2 and handles complex calculations and large amounts of information. DDC2 processes multiple control systems in a time-sharing manner and determines the amount of operation.
Here, process control computer 1 is connected to bus LA40.
The HIC is connected to the bus LA4000 and is connected to the bus LA4000 and mainly has a signal conversion function. (analog human power) It consists of an HDC that receives and receives AO (analog output), and a multi-dropped RIO.

The hardware is as described above, but in PID control, the target value and analog input set by the process control computer are taken in every sample period and the PID control is performed.
Processing is performed to obtain an analog output, and the parameters and mode switching required for PID processing are set and downloaded from the process control computer.

In this case, the lower part, which is the DDC 2 that processes mainly the HDC and suitably processes a plurality of control systems, requires many external devices such as the HDC and the HIC. Moreover, this DDC2 is expensive, and if the 000 functions can be processed by software, it will be inexpensive and have a simple structure, which is convenient.

In view of the above-mentioned problems, the present invention provides a PID control method for a process control computer in which functions corresponding to an external device such as a DDC are processed by software.

D. Means for solving the problem The present invention exchanges analog input/output data with an external device via an analog input/output board connected to a bus of a process control computer, and adjusts the analog input/output data to a target value. The process control computer performs PID control by adding input data, and at the same time, TAGs are attached to various parameters of PTD control.

E. Function By attaching TAG to various parameters, it is possible to centrally manage everything from analog input to analog output, and on top of this, the CRT task can set and change parameter constants and input/output constants, and perform input/output processing. The task can perform analog input/output, and the PID processing task can perform PID calculation processing, and the software of the process control computer can perform PID processing.

Embodiment An embodiment of the method of the invention will now be described with reference to FIGS. 1 to 5. FIG. 1 shows an example of the hardware for the method of this embodiment. On the bus of a process control computer 1 that manages the process, there is an analog input board 3 having an A/D conversion function and an analog input board 3 having a D/A conversion function. An analog output board 4 is mounted. A sensor (see FIG. 4), which is an external device, is connected to the analog input board 3, and a controlled object (see FIG. 4), which is an external device, is connected to the analog output board 4.

Here, PID# control is processed within the process control computer 1.

FIG. 2 shows the software for this process. Second
In the figure, CRT task 5 is for setting target values on the CRT screen during manual operation, which is written in RASIC and using the keyboard and mouse to set various parameter constants for PID processing, analog input/output constants, manual / automatic mode This is used to set and change switching. Note that the automatic operation is set by a PID processing task, which will be described later.

The input/output processing task 6 performs input from the analog input board 3 and output from the analog output board 4.
The measured value written in IC is inputted from the sensor, and the output operation amount to the printing unit object is outputted.

In addition, PID processing task 7
The main parts of this system that perform calculations are BASIC and P
It is written in L/M language and obtains a manipulated output value, which is a calculation result, from measured input values and various setting values.

3 and 4 are the above-mentioned PID control flow and its schematic block diagram, and show the setting of the target value by the CRT task,
It shows measurement value measurement by the input processing task, PID calculation by the PID processing task, and operation amount output by the output processing task.

When performing PID processing, various parameters such as analog input values, analog output values, and PID setting values are required. In this case, parameters are identified by TAG and handled input data and output data are connected to perform unified management. In other words, if no TAG is attached,
Analog input and analog output must be fixed and corresponded to each other in software, and changing the channel assignment of analog input and output requires software changes each time, but by attaching a TAG, data can be identified. Can be done C
It can be processed only by changing the settings from RT.

In addition, in the specified TAG, other PID control TAG
By specifying AG, cascade connection is possible as shown in FIG. That is, the series connection of the PID control section can be easily added using the input method from the CRT.

Here, we will give an example of the PID calculation formula EV = PV -3V old CI) MV -ΣΔM
V Kokote, Evn is the current deviation, EV, -4 is the deviation from one cycle before, SV is the target value, PVn is the current measured value,
PV, , is the measured value one cycle ago, pv, -2 is the measured value two cycles ago, ΔMV is the output change amount, 3'''MV is the current manipulated variable, KP is the proportional constant, 9''lTs is the sampling period, T is the proportional constant, To is the differential constant, (*
) indicates a parameter to which a TAG is added.

As described in detail of the G9 invention, according to the present invention, the structure is simple and inexpensive by attaching TAG to various parameters of PID control as a board connected to the CPU bus without any external connection equipment. Parameter settings can be made by inputting from a CRT, allowing for interactive input, which simplifies the setting.

[Brief explanation of the drawing]

1 to 5 are for explaining an embodiment of the method of the present invention. FIG. 1 is a hardware configuration diagram, FIG. 2 is a software configuration diagram, FIG. 3 is a flowchart of PID control, and FIG. FIG. 4 is a block diagram of PID control, FIG. 5 is a block diagram of cascade connection, and FIG. 6 is a configuration diagram of PID control hardware in which a conventional DDC is externally connected. In the figure, 1 is a process control computer, 3 is an analog input board, 4 is an analog output board, 5 is a CRT task, 6 is an input/output processing task, and 7 is a PID processing task.

Claims (1)

[Claims] Analog input/output data is exchanged with external equipment via an analog input/output board connected to the bus of the process control computer, and the above analog input data is added to the target value to perform PID control in the process control computer. A PID control method in a process control computer, characterized in that various parameters of this PID control are assigned TAGs.