JPH09243431A - Flow rate sensor and flowmeter utilizing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple polyline approximation line to a flow rate sensor having complicated characteristics. SOLUTION: A line 11 connecting an upper limit value 9 with a lower limit value 4 on a sensor output characteristic curve and the shortest distance from an arbitrary point 12 on the characteristic curve to an arbitrary point 13 on the line 11 are obtained, polyline approximation characteristics are provided with a point on the characteristic curve where the shortest distance is the maximum as a split point, and the polyline approximation line is used to provide characteristic values such as a flow speed from sensor output values. In addition, the sensor is used to constitute a fluidic flowmeter to realize a flowmeter with little error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polygonal line approximation for giving a flow rate conversion coefficient of a sensor used for measuring a flow rate of a fluid such as gas or water.

[0002]

2. Description of the Related Art Conventionally, a flow sensor of this type is disclosed in Japanese Patent Publication No. 7-
A hot wire type flow sensor as shown in Japanese Patent No. 119635 is used. Further, this type of sensor is used as a flow rate sensor in the low flow rate range of a full Dick gas flow meter (Japanese Utility Model Publication No. 6-18244). This sensor is shown in FIG.
A flow velocity-output value characteristic as shown in is shown. In the figure,
The horizontal axis is the flow velocity of fluid such as gas or water, the vertical axis is the sensor,
For example, the output values such as resistance and voltage are shown. Curve 1 shows the output characteristics of the sensor.

When the sensor output value (S) is obtained, the broken line 2
Tracing the horizontal line of, and dropping the perpendicular 3 from the intersection with the curve 1, the flow velocity (V) is obtained.

[0004]

However, this type of sensor exhibits a complicated characteristic such that the relationship between the flow velocity and the output value is generally represented by a curve (1) composed of an nth degree polynomial. That is, it is often represented by an nth degree polynomial of the flow velocity (V). Therefore, when a microcomputer (CPU) or the like, on the contrary, calculates the flow velocity (V) from the output value (S), it requires a complicated calculation, which takes time and deteriorates the responsiveness. There was a problem that capacity was required and it became expensive. Further, when the characteristic curve is used as a polygonal line approximation, and when the measurement points that have been measured in advance are linearly approximated, if there is an error in the measurement point for which an approximated straight line is obtained, the obtained flow velocity value (V) There is an error in. Further, when using a polygonal line approximation straight line obtained by equally dividing the output value, there is a problem that the error greatly varies depending on the approximate straight line of the used region, that is, the sensor output value.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a flow sensor having a small error, which is constituted by a simple polygonal line approximation division method.

[0006]

A flow sensor according to the present invention comprises:
A straight line connecting the upper limit value and the lower limit value on the characteristic curve, and the shortest distance from any point on the characteristic curve to the arbitrary point is obtained, and the point on the characteristic curve where the shortest distance is maximum is a division point. As a polygonal line approximation characteristic.

According to this invention, a complicated characteristic curve
It is possible to divide into a polygonal line approximation straight line with a small error with a small number of divisions, and it is possible to calculate characteristics such as the flow velocity from the output value by a simple calculation.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In order to achieve the above object, the flow rate sensor of the present invention is constructed by a polygonal line approximation by the following method.

That is, a straight line connecting the upper limit value and the lower limit value on the characteristic curve and the shortest distance from an arbitrary point on the characteristic curve to an arbitrary point on the straight line are obtained, and the shortest distance becomes maximum. A flow rate sensor was constructed by using the points on the characteristic curve as dividing points and giving the approximated polygonal line characteristics.

A straight line connecting the upper limit value and the lower limit value on the characteristic curve and a tangent line of the characteristic curve drawn from an arbitrary point on the characteristic curve are parallel to the straight line, and the polygonal line approximation is performed. A flow sensor was constructed by giving characteristics.

Further, a straight line connecting the upper limit value and the lower limit value on the characteristic curve and an orthogonal line perpendicular to the straight line are drawn from an arbitrary point on the characteristic curve to obtain an intersection point with the straight line, and the arbitrary point is set. A flow line sensor was constructed by giving a polygonal line approximation characteristic with the point on the characteristic curve where the distance between the point and the orthogonal point is the maximum as the dividing point.

A straight line connecting an upper limit value and a lower limit value on the characteristic curve and a vertical line from an arbitrary point on the characteristic curve are drawn to find an intersection with the straight line, and a distance between the arbitrary point and the intersection is determined. The flow sensor was constructed by giving the line approximation characteristics with the point on the maximum characteristic curve as the dividing point.

Further, the flow meter is constituted by the flow rate sensor having the above-mentioned polygonal line approximation characteristic. Since the present invention has the above-described configuration, it is possible to divide a complicated characteristic curve into a polygonal line approximation straight line with a small number of divisions, and it is possible to calculate characteristics such as the flow velocity from the output value by a simple calculation.

A first embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a characteristic curve diagram showing a method of approximating a characteristic curve of a flow velocity-output value of a flow sensor according to a first embodiment of the present invention by a broken line. The horizontal axis represents the sensor output value (S), and the vertical axis represents the characteristic value (V) such as the flow velocity. Lower limit of 4
(S4, V4), and the upper limit value is 9 (S9, V9). White circles (∘) 4, 5, 6, 7, 8, 9 in the figure represent measurement points, a smooth curve 10 represents a regression curve in which six measurement points are approximated by a cubic polynomial, V = f (s ) Is shown. A straight line 11 indicates a straight line connecting the upper limit value and the lower limit value, V = g (s) = a · S + b. a
Indicates the slope of the straight line 11, and a = (V9-V4) / (S9
-S4). First, an arbitrary point 12 on the curve 10 is connected to an arbitrary point 13 on the straight line. The distance L (12-13) between the two points 12 and 13 when the point 13 is moved on the straight line 11 is obtained, and the point 13 is moved so that the distance L (12-13) becomes the shortest. In this way, the shortest distance L (12-13) can be obtained for the arbitrary point 12 on the curve 10. Next, this arbitrary point 12 is placed on the curve 10.
A point 12 at which the shortest distance L (12-13) is maximized when the lower limit value 4 is moved to the upper limit value 9 is obtained. The point 12 at this time becomes the first division point 12 '.

In this way, the first division point 12 'and
A straight line 14 connecting the upper limit value 9 and the first dividing point 12,
The straight line 15 connecting the lower limit value 4 becomes the polygonal line approximation straight lines 14 and 15 when there is one division point. Furthermore, this first
Of the dividing line 12 'and the upper limit value 9 and the curve 1
Between the straight line 15 connecting 0 and the first division point 12 ′ and the lower limit value 4 and the curve 10, two shortest distances are obtained in the same manner as described above, and the one showing the larger shortest distance is determined as the first. 2 division points. For example, the second division point is the first division point 1
When it is between 2 ′ and the upper limit value, a straight line connecting the upper limit value and the second dividing point, a straight line connecting the second dividing point and the first dividing point, and a first dividing point Three straight lines connecting the lower limit value and the straight line are the three approximate straight lines when the number of divisions is two.

Therefore, depending on the magnitude of the output value (S), the sensor characteristic value and the flow velocity (V) are obtained by using the polygonal line approximation straight lines divided into the respective values. In this way, the division points up to the desired division number (Nb) are sequentially obtained, and (Nb-1) polygonal line approximation straight lines are obtained. By dividing the characteristic value indicated by a complicated curve into a simple approximate straight line and replacing it, a characteristic value (V) such as a flow velocity with a small error can be obtained by a simple calculation from the sensor output value (S).

As described above, since the error (shortest distance) is firstly divided, the complicated characteristic curve can be efficiently divided into the polygonal line approximation lines with less error.

(Embodiment 2) FIG. 2 is a characteristic curve diagram showing a method of approximating the characteristic curve of flow velocity-output value of a flow rate sensor of Embodiment 2 of the present invention by a broken line. The horizontal axis is the sensor output value (S)
And the vertical axis represents the characteristic value (V) such as the flow velocity. In the figure, FIG.
The same components as are numbered the same. First, a tangent line 17 of the curve 10 is drawn from an arbitrary point 16 on the curve 10. The arbitrary point 16 is moved from the lower limit value 4 to the upper limit value 9 on the curve 10, and the point at which the tangent line 17 at this time is parallel to the straight line 11 is defined as a first division point 16 '.

In this way, the first division point 16 'and
A straight line 18 connecting the upper limit value 9 and the first division point 16 '
And the straight line 19 connecting the lower limit value 4 are the polygonal line approximation straight lines 18 and 19 when the number of division points is one.

Next, between the straight line 18 connecting the first dividing point 16 'and the upper limit value 9 and the curve 10 and the first dividing point 1
6'and the line between the straight line 19 connecting the lower limit value 4 and the curve 10 are parallel to the straight lines 18 and 19 in the same manner as described above.
Draw the tangent lines on 0 respectively. The distance between the curve 10 and the straight line 18 and the straight line 19 is obtained, and the contact point of the tangent line indicating the larger distance is set as the second division point 20. For example, when the second division point is between the first division point 16 'and the upper limit value,
Three straight lines, a straight line connecting the upper limit value and the second dividing point, a straight line connecting the second dividing point and the first dividing point, and a straight line connecting the first dividing point and the lower limit value, are divided. There are three approximate straight lines in the case of the number two. In this way, the division points up to the desired division number (Nb) are sequentially obtained, and (Nb-1) polygonal line approximation straight lines are obtained. In this way, by replacing the characteristic value indicated by the complicated curve with a simple approximate straight line, the characteristic value (V) such as the flow velocity with a small error can be obtained by a simple calculation from the sensor output value (S). .

(Embodiment 3) FIG. 3 is a characteristic curve diagram showing a method of approximating the characteristic curve of flow velocity-output value of a flow sensor of Embodiment 3 of the present invention by a broken line. In the figure, the same components as those in FIG. 1 are assigned the same numbers.

First, an arbitrary point 21 on the curve 10
Then, a perpendicular line 22 is drawn to the straight line 11, and the intersection is 23.
The arbitrary point 21 is moved from the lower limit value 4 to the upper limit value 9 on the curve 10, and the distance L (21-2
3) is obtained, and the point on the curve 10 where this distance L (21-23) is maximum is set as the first division point 21 '.

In this way, the first division point 21 'and
A straight line 24 connecting the upper limit value 9 and the first division point 21 '
And the straight line 25 connecting the lower limit value 4 become the polygonal line approximation straight lines 24 and 25 when the number of division points is one.

Next, the straight line 24 connecting the first division point 21 'and the upper limit value 9, the curve 10 and the first division point 21'.
And a straight line 25 connecting the lower limit value 4 and the curve 10 in the same manner as above, draw perpendicular lines from the curve 10 orthogonal to the respective straight lines, find intersections, and compare the lengths of the respective perpendicular lines. , The intersection point indicating the larger distance is the second division point 26. For example, the second division point 26 is the first division point 2
When it is between 1 ′ and the upper limit value, a straight line connecting the upper limit value and the second dividing point, a straight line connecting the second dividing point and the first dividing point, and a first dividing point Three straight lines connecting the lower limit value and the straight line are the three approximate straight lines when the number of divisions is two. In this way, the division points up to the desired division number (Nb) are sequentially obtained, and (Nb-1) polygonal line approximation straight lines are obtained. By replacing the characteristic value represented by such a complicated curve with a simple approximate straight line, the characteristic value (V) such as the flow velocity with a small error can be obtained by a simple calculation from the sensor output value (S).

Since the error (distance between straight lines) is sequentially divided in this manner, a complicated characteristic curve can be efficiently divided into polygonal line approximation lines, and an approximation line with less error can be obtained. .

(Embodiment 4) FIG. 4 is a characteristic curve diagram showing a method of approximating the characteristic curve of flow velocity-output value of a flow sensor of Embodiment 4 of the present invention by a broken line. In the figure, the same components as those in FIG. 1 are assigned the same numbers. First, a perpendicular 28 is drawn from the arbitrary point 27 on the curve 10 to the output shaft, and the intersection with the straight line 11 is 29. The arbitrary point 27 is moved on the curve 10 from the lower limit value 4 to the upper limit value 9, and the two points 27, 2 at this time are moved.
The distance L (27-29) between 9 is obtained, and the point on the curve 10 where this distance L is maximum is set as the first division point 27 '.

In this way, the first division point 27 'and
A straight line 30 connecting the upper limit value 9 and the first division point 27 '
And a straight line 31 connecting the lower limit value 4 become the polygonal line approximation straight lines 30 and 31 in the case where there is one division point.

Next, a straight line 30 connecting the first division point 27 'and the upper limit value 9, the curve 10 and the first division point 27',
Between the straight line 31 connecting the lower limit value 4 and the curve 10, in the same manner as above, a perpendicular line is drawn from each of the output shafts, the intersection with each straight line is obtained, and the distance L between each two points is compared. However, the one indicating the larger distance is set as the second division point 32. For example, the second division point 32 is the first division point 27 '.
And between the upper limit value and the upper limit value, a straight line connecting the upper limit value and the second dividing point, a straight line connecting the second dividing point and the first dividing point, and the first dividing point and the lower limit value. The three straight lines connecting with and are the three approximate straight lines when the number of divisions is two. In this way, dividing points up to the desired dividing number (Nb) are sequentially obtained,
(Nb-1) polygonal line approximation straight lines are obtained. By replacing the characteristic value represented by such a complicated curve with a simple approximate straight line, the characteristic value (V) such as the flow velocity with a small error can be obtained by a simple calculation from the sensor output value (S).

As described above, since the error (distance between straight lines) is sequentially divided, the complicated characteristic curve can be efficiently divided into broken line approximation straight lines, and an approximation straight line with less error can be obtained. .

In the above description, the measurement point is set to n in advance.
The approximate straight line was divided using a regression curve composed of a polynomial of degree. Therefore, even if there is an error in the measurement points, it is properly leveled. For example, when calculating the sensor characteristic value such as the flow velocity from the sensor output value compared with the case where an approximate straight line is obtained by connecting each measurement point with a straight line. In addition, the error that occurs is small, and the variation in error between the approximate straight lines is also small.

(Embodiment 5) FIG. 5 is a schematic view of the essential parts of a fluidic flowmeter 33 according to a fifth embodiment of the present invention. 34 is an arrow indicating the flow direction of gas, 35 and 36 are gas inlets,
An outflow port, 37 is a nozzle part of an inflow port, and the hot wire type flow sensor indicated by 37 is arranged on the bottom surface of the nozzle part 37. 38 and 39 are columns for fluidic oscillation,
40 shows a target. When the fluid flows in the direction of arrow 34, fluid oscillation occurs in the nozzle portion 36. The oscillation frequency is detected and the flow meter operates, but the fluid oscillation stops in the low flow region. In this low flow rate region, the hot wire type flow sensor detects the flow velocity of the fluid flowing through the nozzle portion and operates as a flow meter. When the hot wire flow sensor described above is used, a flow rate with a small error can be obtained by a simple calculation, so that a flowmeter with excellent responsiveness and a small error can be obtained. Also, a low-cost CP that can only perform simple calculations
Since these operations can be performed by U, the flow meter can be realized at a low price.

[0032]

As described above, according to the present invention, the following effects can be obtained.

(1) A straight line connecting an upper limit value and a lower limit value on the characteristic curve and a shortest distance from an arbitrary point on the characteristic curve to an arbitrary point on the straight line are obtained. By using a point on the characteristic curve as a dividing point to provide a flow rate sensor that is given a polygonal line approximation characteristic, it is possible to obtain sensor characteristic values such as the flow velocity from the sensor output value by a simple calculation from the polygonal line approximation line, and there are also errors. Less.

(2) A straight line connecting the upper limit value and the lower limit value on the characteristic curve and a tangent line of the characteristic curve drawn from an arbitrary point on the characteristic curve are parallel to the straight line, and the polygonal line is a dividing line. By giving an approximate characteristic and using it as a flow sensor,
The sensor characteristic value such as the flow velocity can be obtained from the sensor output value by a simple calculation from the polygonal line approximation line, and the error is reduced. Further, a complicated characteristic curve can be easily made into a polygonal line approximation straight line.

(3) A straight line connecting the upper limit value and the lower limit value on the characteristic curve and an orthogonal line orthogonal to the straight line are drawn from an arbitrary point on the characteristic curve, the intersection point with the straight line is determined, and the arbitrary point is set. The point on the characteristic curve that maximizes the distance between the point and the orthogonal point is a dividing point, and the flow rate sensor is given a polygonal line approximation characteristic. The sensor characteristic value can be obtained, and the error is reduced.

(4) A straight line connecting an upper limit value and a lower limit value on the characteristic curve and a vertical line is drawn from an arbitrary point on the characteristic curve to obtain an intersection with the straight line, and a distance between the arbitrary point and the intersection. By using the flow rate sensor with the polygonal line approximation characteristics using the point on the characteristic curve with the maximum value as the dividing point, it is possible to obtain the sensor characteristic value such as the flow velocity from the sensor output value by a simple calculation from the polygonal line approximation line. , The error is reduced. Also,
It is possible to divide a complicated characteristic curve into approximate straight lines more easily.

(5) By converting the measurement points into a regression curve consisting of an n-th degree polynomial in advance, even if some error is included in the measured value, it does not enter the approximation straight line as such a large error.

(6) Since the fluidic flowmeter is composed of the flow rate sensors described in Embodiments 1 to 4, it is possible to realize a flowmeter with a small error by a simple calculation. It is also effective in reducing the price of flow meters.

[Brief description of drawings]

FIG. 1 is an output characteristic diagram of a flow sensor according to a first embodiment of the present invention.

FIG. 2 is an output characteristic diagram of a flow sensor according to a second embodiment of the present invention.

FIG. 3 is an output characteristic diagram of a flow sensor according to a third embodiment of the present invention.

FIG. 4 is an output characteristic diagram of a flow sensor according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a flowmeter according to a fifth embodiment of the present invention.

FIG. 6 is a characteristic diagram of a hot wire type flow sensor.

[Explanation of symbols]

 4 Lower limit value of sensor characteristic 9 Lower limit value of sensor characteristic 10 Sensor characteristic curve 11 Straight line connecting upper limit value and lower limit value 12 Any point of sensor characteristic curve 13 Any point on straight line 12 'First division point of Example 1 16 'First division point of Example 2 17 Tangent on curve 10 20 Second division point of Example 2 21' First division point of Example 3 22 Vertical line 27 'First division of Example 4 Point 28 Vertical line 32 Second division point of Example 4 35 Fluidic flow meter 36 Nozzle portion 37 Hot wire type flow sensor 40 Target

Claims (5)

[Claims] 1. A straight line connecting an upper limit value and a lower limit value on a characteristic curve and a shortest distance from an arbitrary point on the characteristic curve to an arbitrary point on the straight line, and the shortest distance becomes maximum. A flow rate sensor that gives polygonal line approximation characteristics using points on the characteristic curve as dividing points. 2. A polygonal line approximation with a straight line connecting an upper limit value and a lower limit value on the characteristic curve and a tangent line of the characteristic curve drawn from an arbitrary point on the characteristic curve being parallel to the straight line with the dividing point as a dividing point. A flow sensor that gives characteristics. 3. A straight line connecting an upper limit value and a lower limit value on a characteristic curve and an orthogonal line orthogonal to the straight line are drawn from an arbitrary point on the characteristic curve to obtain an intersection point with the straight line, A flow rate sensor that provides a polygonal line approximation characteristic with a point on the characteristic curve that maximizes the distance between the point and the orthogonal point as the dividing point. 4. A straight line connecting an upper limit value and a lower limit value on a characteristic curve and a vertical line from an arbitrary point on the characteristic curve, an intersection point is obtained, and a distance between the arbitrary point and the intersection point is calculated. A flow rate sensor that gives a polygonal line approximation characteristic with the point on the maximum characteristic curve as the dividing point. 5. A flow meter comprising the flow sensor according to any one of claims 1 to 4.