JP2003186527A - Control-system testing device and method for renewing field equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To grasp in advance the stability of a control system, when field equipment is renewed to select optimum new field equipment. <P>SOLUTION: A control-system testing device 20 lies in between the field equipment (10), constituted of analog circuits and a control device 12. The presence or absence of disorder of the control system is checked by generating various wasteful time in outputting signals, and the range of the wasteful time, in which the disorder of the control system will not occur is grasped. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a control system testing device,
And a method of updating a field device using this,
In particular, when using a field device configured with an analog circuit and having no dead time, which is suitable for use in updating a field device having a microcomputer and having a dead time due to microcomputer calculation time, The present invention relates to a control system testing device for testing online the influence of the control system due to the dead time of the device in advance, and a field device updating method using the same.

[0002]

2. Description of the Related Art Conventionally, a field device such as a pressure or flow rate (differential pressure) transmitter is composed of an analog circuit, and when there is a change in the input of the transmitter itself, as shown by a solid line A in FIG. There was no dead time, and the detection signal was output with a response having a certain time constant.

On the other hand, in recent years, field devices such as pressure and flow rate (differential pressure) transmitters are mainly equipped with a microcomputer having remote control and trend value management functions and intended to improve maintainability. It's starting. However, since it is a microcomputer-installed type, when there is a change in the input of the transmitter itself, as shown by the broken line B, the one-dot chain line C or the two-dot chain line D in FIG. To output the detection signal.

Therefore, when updating a field device configured with an analog circuit and having no dead time to a field device having a microcomputer and having a dead time due to a microcomputer calculation time, for example, the applicant of the present invention, Japanese Patent Laid-Open No. 6-242807. As proposed in 1), do you create a simulator for the controlled plant, evaluate the effect on the control system when the response of the oscillator changes due to dead time, and decide the required response specifications with the result? Or, we had to replace the actual machine and carry out the test online.

[0005]

However, there is an error between the control system of the actual plant and the simulator, and the simulation result and the actual control do not always match.
Further, in the online test for replacing the actual machine, there is a problem that the adverse effect on the plant when the control system becomes unstable must be taken as a risk.

The present invention has been made to solve the above-mentioned conventional problems, and it is possible to select the optimum new field device by grasping the stability of the control system when updating the field device in advance. It is an issue.

[0007]

According to the present invention, a physical quantity to be controlled is detected and inserted between a field device that outputs an electric signal corresponding to the physical quantity and a control device that controls the physical quantity. The above problem is solved by a control system test apparatus characterized in that various dead times are generated in an output signal of the field device and input to the control device.

According to the present invention, the analog circuit of the control system controls the physical quantity by measuring the physical quantity of the process by the field device composed of the analog circuit and inputting the measured value to the controller. When updating the configured field device to the microcomputer-installed field device, the control system testing device is interposed between the field device configured by the analog circuit and the control device, and various dead time is output to the output signal. Is generated to investigate the presence or absence of disturbance in the control system, grasp the range of dead time in which no disturbance occurs in the control system, select a microcomputer-equipped field device within the range of the dead time, and The above problem is solved by replacing the field device with an analog circuit.

The present invention detects a physical quantity to be controlled and outputs an electric signal according to the physical quantity, and a field device (for example, an analog circuit), and a control device (loop controller, DCS, etc.) for controlling the physical quantity. ) And the input of the output signal of the field device, and by inserting the control system test device that inputs the output after adding the dead time to the control device, (1) using the actual machine instead of the simulator, It is possible to test online, and (2) it is safe because it is possible to increase the dead time while confirming the stability of the control system and evaluate the response of the entire control system from the minute dead time. Also, the stability limit of the control system regarding dead time can be confirmed.

Therefore, for example, when updating a field device configured by an analog circuit and having no dead time to a field device equipped with a microcomputer and having a dead time due to microcomputer calculation time, the control system using a real machine is stabilized. Is safe, and
It is possible to update the device without trouble.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the responsiveness (step response) of the analog type field device and the microcomputer type field device assumed this time. Hereinafter, the analog transmitter for the pre-update device and the microcomputer-equipped device after the update will be referred to as the digital oscillator.

FIG. 2 shows an example of a comparison of the influence on the control system by field devices having different dead times in an actual plant (process gas flow control system of a converter). Generally, in a control system with dead time, hunting occurs when the control gain is increased. Therefore, if only the field device is replaced with the digital oscillator while the control gain of the control device remains unchanged, a hunting phenomenon occurs depending on the dead time of the digital oscillator. That is, as shown in FIG. 2 (A), a stable control result is obtained with an analog oscillator with no dead time.
When the dead time increases in the digital oscillator as shown in (B) and (C), the flow control system hunts and becomes unstable as shown in FIG. 2 (C).

The control system test apparatus of the present invention inputs an analog oscillator (differential pressure type flow meter in FIG. 3) 10 to be updated and its detection signal, as illustrated in the case of the flow rate control system in FIG. Control device for controlling plant (loop controller, DC
(S, etc.) 12, the output signal of the field device 10 is input, and the output in which the dead time is generated is output to the control device 12.

In the figure, 14 is a pressure gauge for detecting the supply pressure, and 16 is a flow rate control valve (FCV) for adjusting the flow rate according to the output of the control device 12.

As shown in detail in FIG. 4, the control system test apparatus 20 includes an analog transmitter (here, a differential pressure type flow meter) 1
An input device 22 for inputting a detection signal from 0 and input data input from the input device 22 are stored in a memory at high speed in time series, and a delay corresponding to a dead time of an oscillator to be tested. After that, the control system test apparatus main body 24 outputs the input data from the output apparatus 26, and the output apparatus 26 outputs the detection signal in which the desired dead time is generated in the main body 24.

Here, the input device 22 and the output device 26
Is capable of inputting / outputting a signal specification (for example, 4-20 mA) equivalent to that of the input card of the existing control device 12, and requires a data update cycle equivalent to that of the control system test device main body 24 which causes a dead time. .

In the control system test apparatus main body 24, the input data is stored in the memory at high speed and the output is delayed until a desired dead time. Here, the main body 24 executes data storage and delay processing at a sampling cycle of about 1/100 of the control cycle of the control device 12, for example.

The operation of the embodiment will be described below.

The control system test apparatus 20 starts from a good control state in which the dead time is almost zero as shown in FIG.
It is possible to specify the dead time in which hunting as shown in (C) occurs. Therefore, it is possible to select a digital oscillator having a dead time shorter than the dead time at the stability limit and update the device.

In the above embodiment, the field device constituted by the analog circuit is the differential pressure type flow meter, but the kind of the field device is not limited to this.

Further, in the above-described embodiment, the control system test device is used for measuring the dead time when the field device constituted by the analog circuit is replaced with the microcomputer-equipped field device. The application target of the device is not limited to this, and when the microcomputer mounted field device is already used,
It is also possible to know the limit of the dead time and use it for a test, for example, for cost reduction by replacing with an inexpensive field device with a lot of dead time.

[0023]

According to the present invention, when a field device having no dead time composed of, for example, an analog circuit is updated to a field device having a microcomputer and having a dead time due to the microcomputer calculation time, the actual device is used. The stability of the control system used can be evaluated, and the device can be updated safely and without trouble.

[Brief description of drawings]

FIG. 1 is a diagram showing a comparison of responsiveness in step response of an analog type field device assumed in the present invention and a microcomputer mounted type field device.

FIG. 2 is a diagram showing a comparison of the effects of field devices with different dead times on the flow control system in an actual plant.

FIG. 3 is a block diagram showing an overall configuration of an embodiment of the present invention applied to a flow rate control valve.

FIG. 4 is a block diagram showing the configuration of a control system test device.

[Explanation of symbols]

10 ... Differential pressure type flow meter (field device) 12 ... Control device 14 ... Pressure gauge 16 ... Flow control valve (FCV) 20 ... Control system test equipment 22 ... Input device 24 ... Main body 26 ... Output device

Claims (2)

[Claims] 1. A field device that detects a physical quantity to be controlled and outputs an electric signal according to the physical quantity and a control device that controls the physical quantity, and outputs various signals to the field device. The control system testing device is characterized in that the dead time is generated and input to the control device. 2. A field constituted by the analog circuit of a control system in which a physical quantity of a process is measured by a field device constituted by an analog circuit and the measured value is inputted to a control device to control the physical quantity. When updating the device to a microcomputer-installed field device, the control system test device according to claim 1 is interposed between the field device configured by the analog circuit and the control device, and various dead times are output signals. The presence or absence of disturbance in the control system is investigated, the dead time range in which the disturbance is not generated in the control system is grasped, the microcomputer-equipped field device within the dead time range is selected, and the analog A method of updating a field device, characterized by replacing the field device with a circuit.