JPS63273013A - Measurement of liquid - Google Patents

Abstract

PURPOSE:To realize a highly accurate and short time measurement and secure a wide measuring range by making a fuzzy inference from the flow rate characteristics of an opening regulating valve for limiting the flow rate of a liquid and a measurement set value, determining the initial opening of the valve before the initiation of the measurement and conducting a fuzzy control on the basis of the actual measurement. CONSTITUTION:When a measurement setting value is given to a measurement controller 1, the initial opening of an opening regulating valve 6 is calculated by fuzzy inference from the flow rate characteristics of the valve 6 and a liquid flows out from a measuring tank 8 by an instruction from the controller 1. The actual weight value of a load cell 2 charges. The controller 1 measures the actual weight value from a gravimeter amplifier 3 at prescribed control periods and calculates a deviation between the measurement set value and the actual weight value and the quantity of temporal change in the deviation. When an observation resulting from the low-pass filter processing of those quantities is calculated, the inferential calculation of the opening of the valve 6 is conducted on the basis of a fuzzy rule. Thus, the valve 6 is controlled so as to take the suitable opening, the infection of a backlash or the like is absorbed and highly accurate measurement can be performed.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a liquid measuring method, and more specifically, fuzzy inference is performed based on observed quantities obtained during measurement, and the flow velocity of the object to be measured is sequentially determined. The present invention relates to a liquid measuring method that improves measuring accuracy, expands the measuring range, and achieves short-time measuring by changing the measuring method.

(Prior art) In liquid measurement, the detection method is gravimetric (o-).
There are various methods such as ``cell, etc.'', pressure type (differential pressure transmitter, etc.), and volumetric type (oval flow meter, etc.).

However, in either method, the premise is that the flow rate is constant as metering control, and there is no closed-loop metering control method that continuously varies the flow rate.

Conventionally, the following techniques have been implemented as a method for improving measurement accuracy.

■ Divide the flow rate into two stages and set the flow rate near the measurement setting value.
Technology for measuring by switching to a slower flow rate (for example, Japanese Patent Application Laid-Open No. 5
6-148019).

Specific example 1) Two types of devices with different flow velocities are installed and switched when the deviation between the measurement setting value and the actual measurement value reaches a certain condition value.

2) Install a single device that has the function of switching the flow velocity between two types of fixed conditions, and as in 1), switch when the deviation reaches a certain condition value.

3) Regarding the contents of 1) and 2), a learning function is added as a software function to correct the condition value for commanding switching based on the previous measurement result value.

■ As a measurement stop condition, inflow! There is a technology that predicts this amount (also called the amount of head difference) and stops the measurement in advance to measure it (for example, Japanese Patent Application Laid-Open No. 57-29114).

Specific example 1) When a certain condition of deviation between the measurement setting value and the actual measurement value is reached, the measurement is stopped.

2) Same as ■-3), but with the previous Calculates from the actual measurement value and stops the measurement. Modify the condition value that commands.

(Problem to be solved by the invention) However, in conventional metering control, the flow rate is constant or the flow rate is divided into two stages as described above. There are drawbacks.

■ Weighing accuracy: Accuracy may not be guaranteed due to flow velocity fluctuations due to disturbances or differences in liquid physical properties (viscosity, etc.).

For example, in the case of gravity transfer, upstream The remaining amount of the object to be measured in the side container (hereinafter Below, in this specification, this residual amount is It's called Buto9 difference. ), leaked out Although this causes flow velocity fluctuations in the object to be measured, If the change in head difference is large, the flow velocity will increase. Accuracy goes out of a certain condition range Getting worse. Also, this Restricted during change of head of stream side vessel This results in the head In order to keep the difference within a certain range, In order to Continue to replenish the container with raw materials as appropriate. raw material must be secondarily This leads to loss of fees.

■Measuring range: Since the flow rate is restricted, the ratio of the minimum and maximum measurable values is usually about 1:5.

Even with the two-stage flow rate setting type, the The ratio is 1:1.

In this way, the reason why the measurement range is narrow The reason is that the measurement is stopped and the response of the system is There is an inflow amount due to the delay, and this Since the amount of is determined by the flow velocity This is used when the weighing set value is small. If the amount exceeds the guaranteed accuracy range, As a result, the weighing range is limited. Become.

For manufacturing plants that can handle a wide variety of products. However, even if the same raw materials are used, The maximum amount range is 1:IOQ. In the weighing set value range A weighing device must be selected.

■ Weighing time: The measuring time is affected by the weighing settings.

If the weighing set value is small, The setting time is short, and if the size is large, the time is longer. Become.

If the weighing set value is small, the system There are variations in operating time, and The measurement accuracy cannot be guaranteed, and the measurement range cannot be guaranteed. It also leads to narrowing.

In addition, weighed multiple types of needle removal Producing new varieties by mixing quantities From the perspective of the entire system, Production capacity is affected by weighing time, and In the production of pipeless mobile method In the system, conveyance capacity It will be restricted.

(Objective of the Invention) The object of the present invention has been made based on the above-mentioned circumstances, and is to realize highly accurate measurement that is not affected by flow velocity fluctuations caused by external disturbances, secure a wide measurement range, and set measurement value. An object of the present invention is to provide a liquid measuring method that realizes short-time measuring that is not affected by the size of liquid.

Furthermore, another object of the present invention is to provide a liquid measuring method that achieves high precision, wide range, and short-time metering with only easy adjustments, regardless of system configuration, pulp flow characteristics, and liquid physical properties (viscosity, etc.). It's about doing.

That is, the present invention realizes more accurate measurement by limiting the measurement to liquids, and improves the control method, opening adjustment valve, and detector for measuring the flow (f) of the object to be measured in the conventional measuring device. The purpose is to eliminate the following drawbacks in

(2) In conventional metering control, the flow rate is constant, but the pulp flow rate characteristics change depending on head differences, liquid physical properties, etc., which deteriorates metering accuracy.

■ Due to the dynamic characteristics of the detector, the observed amount has an apparent fluctuation, which deteriorates measurement accuracy.

(2) It is difficult to give pulp flow characteristics of 8% that are linear and have the same characteristics, and the flow characteristics vary depending on the pulp and also vary depending on the system configuration. Therefore, in order to ensure the measurement of high precision fabric, adjustment is required for each configuration.

(Summary of the Invention) Therefore, the present invention has a structure in which the valve opening is fully closed near 0% and liquid flows from around 10% in the pulp flow characteristics. Further flow characteristics may be any characteristics other than quick open characteristics.

In consideration of the dynamic characteristics of the detector, directly observed or calculated quantities and quantities subjected to low-pass filter processing are used for control calculation processing.

Fuzzy control is used as a control method, and the axis corresponding to the physical quantity is expressed semi-logarithmically for membership functions in fuzzy inference.

The initial pulp opening is determined by performing fuzzy reasoning based on the flow rate characteristics of the valve and the metering set value.

After that, the fuzzy control method is used to calculate the entire operation f [and output it to the operation terminal.

(Embodiment) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a liquid measuring device applied to one embodiment of the present invention, and this embodiment will be explained based on subtractive metering in which the amount of liquid flowing out from a measuring tank is observed.

In the figure, 1 is a weighing control device, 2 is a load cell that measures the weight i of the raw material filled in a weighing tank 8, 3 is a weighing scale amplifier, 4 is a servo driver controlled by the weighing control device 1, and 5 is a A servo motor is driven by a servo driver 4 to move an opening adjustment valve (to be described later), 6 is an opening adjustment valve that adjusts the amount of liquid flowing out from the metering tank 8, and 7 is controlled by the metering control device 1, This is a strap valve that stops the flow of water. Further, the opening adjustment valve 6 has a flow rate characteristic of 5 equal percentage as shown in (1) of FIG.

Next, the liquid measuring method of the present invention will be explained.

FIG. 2 shows a control process related to the weighing method of the present invention.

1 and 2, when a measurement setting value is given to the measurement control device 1, the fuzzy control section (
In FIG. 2, reference numeral 1-2), the initial opening degree of the valve is calculated by fuzzy reasoning from the flow rate characteristics of the valve shown in FIG. The metering control device 1 instructs the servo motor 5 of the opening adjustment valve 6 through the servo driver 4 to set the initial opening at the same time as metering starts. As a result, the liquid flows out from the measuring tank 8, and the actual weight value of the load cell 2 changes. In addition, the weighing control device 1 repeatedly measures the actual weight value from the weight amplifier 3 at a predetermined control cycle, and the fill calculation section (FIG. 2, reference numeral 1-1) in the weighing control device 1 , calculate the deviation between the measurement setting value and the actual weight value, and the temporal change distortion of the deviation,
When observed quantities are calculated by performing Ronox filter processing on these quantities, the fuzzy control unit 1-2 performs an inference calculation of the valve opening based on a defined fuzzy rule. At this time, the membership function based on fuzzy inference has a form as shown in Figure 4, in which the division of the axes corresponding to each physical quantity of deviation amount and deviation over time is made into smaller sections of small physical quantities, for example, semi-logarithm. let This is for the purpose of improving measurement accuracy and short-time measurement.If the amount of deviation is large, it is not necessary to have good controllability, but if the amount of deviation is small, it is necessary to improve control accuracy. This is because there is. This means that
This also applies to the -order filter processing function, which uses the deviation amount of the first-order filter when the deviation amount, etc. is small, relaxes the dynamic characteristics of the weighing detector, and calculates if/! Improve your degree.

After the start of metering, the opening degree adjusting valve 6 is controlled to have an appropriate opening degree, and as the metering deviation gradually becomes smaller, the opening degree of the opening degree adjusting valve 6 also gradually becomes narrower, and the flow velocity becomes smaller. At this time, if the opening degree adjusting valve 6 has the flow rate characteristic shown in FIG. 3, the valve opening degree changes by about 10% based on the fuzzy inference calculation with the deviation in the vicinity of 0. Therefore, even if there is mechanical backlash of the valve, the dead zone and fuzzy control method absorb the negative effects of the backlash and allow highly accurate measurement.

Additionally, the present invention may be applied to a plurality of tanks 11. as illustrated in FIG.
When applied to a cumulative measurement system in which the objects to be measured supplied from 12 are mixed into one measurement tank 16 and measured by the load cell 15, the flow rate of the opening adjustment valves 13 and 14 attached to the upstream tanks 11 and 12, respectively. Even if the characteristics are different, if the characteristics near the dead zone shown in Figure 3 do not change much, then
Although the behavior of the opening adjustment valve after the start of measurement is different, the behavior immediately before the end of measurement is almost the same, and measurement can be performed using the same membership function and fuzzy rule.

Therefore, high precision, wide range, and short time measurement can be easily achieved regardless of differences in system configuration, bulb characteristics, liquid physical properties, etc.

Next, the results of experiments conducted based on the present invention will be described.

This experiment was conducted using the measuring device shown in FIG. 1 above.

The resulting weighing device can weigh up to 10 kf9, and the accuracy of the load cell is 1/5000. The position of E'CV (opening adjustment valve) is controlled by a servo motor, and a position command is output from the metering control device.

FIG. 6 shows the flow characteristics of two types of opening adjustment valves. These two types of opening adjustment valves were sequentially installed in the system shown in FIG. 1, and measurements were performed without changing the control system or the like.

Figure 7 shows the 1000g weighing results at that time.

FIG. 7-a shows the results of the opening adjustment valve having the flow rate characteristics shown in FIG. 6-a, and FIG. 7-1) shows the results of FIG. 6-1).

As is clear from FIG. 7, although the operation pattern of the opening degree of the opening adjustment valve changes, highly accurate measurement results were obtained with approximately the same measurement time.

In addition, in this measuring system, as shown in FIG. 6, the flow rate, that is, the flow rate, varies depending on the remaining amount of liquid (head difference) even if the opening degree is the same. However, when the remaining amount of liquid was measured at each level, although the operation pattern of the valve opening was different, the same results were obtained in terms of measurement time and measurement accuracy. Also, regarding the measurement range, ±1. Accuracy within 0g was guaranteed.

In the embodiment described above, a load cell is used as the measurement detector, but instead of the load cell, a fall detector such as a differential pressure transmitter or a liquid level gauge may be used as long as the measurement value can be observed.

Furthermore, although a servo motor is shown as an example of a driving device for the opening adjustment valve, any device that can control the position can be used.

(Effects of the Invention) As described above, the present invention provides the following effects.

Regardless of the style characteristics of the opening adjustment valve, the configuration of the metering system, etc., the following effects can be obtained using the same membership function and fuzzy function.

■ Achieving high-accuracy measurement that is not affected by flow velocity fluctuations caused by external disturbances ■ Achieving wide-range measurement with a wide range of measurement setting values ■ Achieving short-time measurement that is independent of the magnitude of measurement setting values In addition, as a measurement control device, It can be easily manufactured using a low-capacity mesori, and the cost of the device can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining a liquid measuring device applied to one embodiment of the present invention, FIG. 2 is a block diagram explaining the control process in the device of FIG. 1, and FIG. 3 is a flow diagram of the opening adjustment valve. i
FIG. 4 is a diagram explaining the membership function of fuzzy control, FIG. 5 is a diagram explaining the cumulative weighing device to which the present invention is applied, and FIG. 1
Fig. 7 is a flow characteristic diagram of the opening adjustment valve applied to the measuring device shown in Fig. 7. It is a figure showing the measurement results obtained by the experiment, (al and (1) J are the 6th
There are nine figures corresponding to those in the figure. 1-Weighing control device, 2.15-load cell, 3-weight scale amplifier, 4-servo driver, 5-servo motor, 6.13.14-opening adjustment valve, 7-stop valve, 8-tank, 16- Metering Tank Agent Patent Attorney (8107) Kiyotaka Sasaki',
Pa (3 others) ゛Figure 3? ＃lA(?AAtdeflation) Figure 4 Slight difference amount (K) Figure 5 Procedural amendment June 22, 1986

Claims (1)

[Claims] 1) In a closed-loop liquid metering method in which the flow rate is changed by an arbitrarily set metering set value and a fed-back actual metered value, the flow rate characteristic of an opening adjustment valve that limits the liquid flow rate and The system performs fuzzy inference based on the measurement set value to determine the initial valve opening before starting measurement, and also performs fuzzy control based on the actual measurement values that are sequentially observed to change the valve opening. Liquid measuring method. 2) The liquid measuring method according to claim 1, characterized in that the flow rate characteristic of the opening adjustment valve includes providing a dead space in which no flow occurs within a predetermined range of the valve opening. 3) An actual measured value is measured, and a low-pass filter process is applied to the deviation between the measured value and the actual measured value and the observed amount of the change over time of the deviation. Liquid measuring method according to item 2. 4) The liquid according to claim 1, 2, or 3, wherein the division of the axis corresponding to the physical quantity as a membership function of fuzzy inference is made finer in sections where the physical quantity is small. Weighing method.