JP2001091416A - Odor/gas flow visualizing device and odor/gas flow measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an odor/gas flow visualizing device used without requiring selection of a gas sensor arrangement position and hardly affected by a local turbulence of wind so as to quickly determine the direction of the odor/gas flow with high reliability. SOLUTION: This device is provided with an odor/gas flow measurement means consisting of a combination of a plurality of sensor arrays, in each of which a single or more odor/gas sensor is arranged on a two-dimensional plane, and measuring a change of concentration of odor/gas flow in multiple points and a visualizing means visualizing the concentration change measured by the odor/gas flow measuring means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an odor / gas flow visualization apparatus for visualizing a flow of odor gas floating in the air as a moving image using a small sensor array in which odor / gas sensors are arranged, and an odor / gas flow measurement using the same. Related to the device.

[0002]

2. Description of the Related Art Heretofore, there has been the following research as an apparatus for searching for a source of odor or gas.

(1) Yukio Hiranaka, Hiroo Yamazaki: Visualization of gas concentration distribution using semiconductor gas sensor array Transa
Ction of Sensor Technology
y Research, ST-88-4, IEEE of
Japan, 1988, pp. 33-42. A huge sensor array is manufactured by arranging gas sensors on a two-dimensional plane, and the entire image of the gas concentration distribution spreading from the source is measured. The resulting image is visualized on a computer screen, and the location of the source can be determined by searching for the location with the highest density. However, it is necessary to dispose a sensor in advance at a place where odor or gas is expected to be generated, which lacks versatility.

(2) JP-A-7-12771 and JP-A-7-271
260618 In order to solve the problem (1), the inventor of the present application has proposed a method of searching for a source by moving in the obtained direction using a small device for determining the source direction. Using a sensor for determining the wind direction and a gas sensor, the direction of the generation source is determined by combining the gas concentration gradient measured at one point in the space with the wind direction. However, in an environment where the wind is unstable, the reliability of the direction determination is low due to the influence of local wind turbulence. In addition, since there are few wind direction sensors applicable to a fine wind speed of 5 cm / s or less as in a general room, it has been difficult to use in such an environment.

(3) JP-A-8-261893, Japanese Patent Application No. 8
-121996 In order to solve the problem of the wind direction sensor in the above (2), the inventor of the present application has proposed a source direction determining apparatus that does not use the wind direction sensor. The gas is sucked from the front using a small fan, and the response difference of the gas sensors arranged in front of the fan is measured to determine the direction of the odor / gas source. However, similar to the above (2), since the determination is performed based on the information obtained at one point in the space, there is a problem that it is easily affected by local wind turbulence.

[0006]

As described above,
Conventionally, when the direction of the odor / gas source is determined, there is a problem that it is difficult to select an arrangement position of the odor gas sensor or that the sensor is easily affected by local wind turbulence.

Therefore, the present invention performs multipoint measurement of changes in odor and gas concentration using a large number of odor and gas sensors, thereby making it less susceptible to local turbulence in the wind and having high reliability in a short time. It is possible to determine the direction, and furthermore, by using a portable small sensor array to determine the direction of the odor / gas source, it is necessary to arrange sensors in advance around the odor / gas flow source. Another object of the present invention is to provide a highly versatile smell / gas flow visualization device and a smell / gas flow measurement device using the same.

That is, according to the odor / gas flow visualization apparatus of the present invention, a small sensor array in which odor / gas sensors are arranged is used, and the flow of odor / gas floating in the air flowing off the small sensor array is displayed as a moving image. By visualizing the image and moving in the direction indicated by the image, the source of the odor or gas can be easily and accurately found. Also, from the direction and speed of smell and gas flow,
Wind direction and speed can be measured.

[0009]

Means for Solving the Problems (1) Smell of the present invention
The gas flow visualization device is a combination of a plurality of sensor arrays in which one or a plurality of odor / gas sensors are arranged on a two-dimensional plane, and an odor / gas flow measuring means for measuring the concentration change of the odor / gas flow at multiple points. And a visualizing means for visualizing a change in concentration measured by the odor / gas flow measuring means. ADVANTAGE OF THE INVENTION According to this invention, it is not necessary to select the arrangement | positioning position of an odor gas sensor, it is hard to be affected by local turbulence of wind, and it becomes possible to determine the odor gas flow direction with high reliability in a short time. . In particular, by using a plurality of sensor arrays that capture the odor / gas flow in a position plane manner, odor / gas flow from any direction can be measured at multiple points simultaneously. Further, in the case of using a crystal oscillator odor / gas sensor as the odor / gas sensor, there is an advantage that an instantaneous change in concentration of odor / gas can be quickly followed.

(2) The odor / gas flow measuring device of the present invention combines a plurality of sensor arrays in which one or a plurality of odor / gas sensors are arranged on a two-dimensional plane, and measures the concentration change of the odor / gas flow at multiple points. Odor / gas flow measuring means to measure, visualization means to visualize the concentration change measured by the odor / gas flow measuring means, and measurement to measure the direction and flow velocity of the odor / gas flow based on the visualized concentration change Means. ADVANTAGE OF THE INVENTION According to this invention, it is not necessary to select the arrangement | positioning position of an odor gas sensor, it is hard to be affected by local turbulence of wind, and it becomes possible to determine the odor gas flow direction with high reliability in a short time. . In particular, by using a plurality of sensor arrays that capture odors and gas flows in a planar manner, odors and gas flows from all directions can be measured simultaneously at multiple points, and the results can be combined more accurately. It can measure the direction and speed of smell and gas flow. Further, in the case of using a crystal oscillator odor / gas sensor as the odor / gas sensor, there is an advantage that an instantaneous change in concentration of odor / gas can be quickly followed.

(3) In the one or more sensor arrays, a plate-like body parallel to the detection surface is arranged at a predetermined interval on the detection surface, so that the flow of the odor / gas flow can be improved. Of the directions, components that generate turbulence on the sensor detection surface are blocked, and only components parallel to the detection surface can be extracted and measured. Therefore, the direction and speed of the odor / gas flow can be measured more accurately.

(4) The odor / gas flow visualization device of the present invention is a sensor array in which one or a plurality of odor / gas sensors are arranged on a two-dimensional plane, and the sensor array detects the odor / gas flow concentration change at multiple points. Visualizing means for measuring and visualizing the measured concentration change, wherein the sensor array has a plate-like body parallel to the detection surface arranged at a predetermined interval on the detection surface. Features. ADVANTAGE OF THE INVENTION According to this invention, it is not necessary to select the arrangement | positioning position of an odor gas sensor, it is hard to be affected by local turbulence of wind, and it becomes possible to determine the odor gas flow direction with high reliability in a short time. .
In particular, in the sensor array, a plate-like body parallel to the detection surface is arranged at a predetermined interval on the detection surface, so that turbulence is generated on the sensor detection surface in the smell / gas flow direction. The component that is to be blocked is shielded, and only the component parallel to the detection surface can be extracted and measured. Therefore, the direction and speed of the odor / gas flow can be measured more accurately.
Further, in the case of using a crystal oscillator odor / gas sensor as the odor / gas sensor, there is an advantage that an instantaneous change in concentration of odor / gas can be quickly followed.

(5) The odor / gas flow visualizing device of the present invention is a sensor array in which one or a plurality of odor / gas sensors are arranged on a two-dimensional plane, and the sensor array detects changes in odor / gas flow concentration at multiple points. A measuring means for measuring a direction and a flow velocity of an odor / gas flow based on the visualized concentration change; and A plate-like body parallel to the surface is arranged at a predetermined interval on the detection surface. ADVANTAGE OF THE INVENTION According to this invention, it is not necessary to select the arrangement | positioning position of an odor gas sensor, it is hard to be affected by local turbulence of wind, and it becomes possible to determine the odor gas flow direction with high reliability in a short time. . In particular, in the sensor array, a plate-like body parallel to the detection surface is arranged at a predetermined interval on the detection surface, so that turbulence is generated on the sensor detection surface in the smell / gas flow direction. The component that is to be blocked is shielded, and only the component parallel to the detection surface can be extracted and measured. Therefore, the direction and speed of the odor / gas flow can be measured more accurately. Also, when using a quartz oscillator smell / gas sensor for the smell / gas sensor,
There is an advantage that it can quickly follow the instantaneous change in concentration of the odor gas.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) (Structure and Operation) FIG. 1 shows an example of the structure of an odor / gas flow visualization device according to the present embodiment. The sensor array 3 used in this apparatus includes a pulse-driven semiconductor odor / gas sensor element (for example, TGS2440, FIG.
ro Giken) C11-C15, C21-C25, C31-
In this example, 25 C35, C41 to C45, and C51 to C55 are used and arranged in a two-dimensional array of 5 rows and 5 columns. The length of one side of the array 3 is, for example, 55 mm.

A high-sensitivity sensor is required to detect a rare odor or gas floating in the air. Also, if a large number of sensors generating a large amount of heat are used side by side in a low wind speed environment, the array itself causes convection and changes the flow.
For this reason, a sensor with low current consumption is desirable.

An ordinary semiconductor smell / gas sensor has the disadvantage that the heater for heating the element consumes a large amount of power. Since the pulse-driven sensor used in the present embodiment is used by heating the element instantaneously only when measuring a response, the power consumption of the heater is small, and even if many sensors are arranged, the heat generation is small.

The personal computer 1 controls the entire apparatus. In response to a command from the computer 1, the control circuit 2 sends one row of sensors (5
), A power supply voltage is applied, and the heaters of the selected one row of sensors are instantaneously heated. Semiconductor odor and gas sensors reduce the electrical resistance when they detect odor and gas,
The current flowing through the device increases.

The logarithmic conversion circuit 4 performs a logarithmic conversion of this current change, converts it from an analog signal to a digital signal by the A / D converter 5, and then takes the measured value into the computer 1.

The logarithmic conversion circuit 4 is composed of five sets of operational amplifiers (logarithmic amplifiers) 4a to 4e, and one circuit is connected in parallel with the sensors in one column of the sensor array 3.
That is, the sensor response signals from the sensor elements C11 to C15 are input to the operational amplifier 4a,
The sensor response signal from 25 is input to the operational amplifier 4b,
Sensor response signals from the sensor elements C31 to C35 are input to the operational amplifier 4c, sensor response signals from the sensor elements C41 to C45 are input to the operational amplifier 4d, and sensor response signals from the sensor elements C51 to C55 are input to the operational amplifier 4e.
Is being entered.

Of these, current flows only to the sensors in one horizontal row selected by the control circuit 2, and at the same time, the response of five sensors in one horizontal row is measured. By sequentially switching the rows to be selected, the responses of all 25 sensors are measured, and this operation is repeated at intervals.

Next, the operation of the sensor array 3 of FIG. 1 will be described with reference to the timing chart shown in FIG.

H1 to H5 in FIG. 1 are power supply lines for driving the heaters of the sensor elements of the sensor array 3. As shown in FIG. 2, first, a heater voltage pulse having a width T1 is applied to the power supply line H1, and the five sensor elements C11, C21, C31, C41, and C51 arranged in the first row (the top row) are heated. I do. When all the elements are heated simultaneously, a large current flows instantaneously even if a pulse drive element is used. Therefore, a method of heating each row is adopted. The power supply voltage at this time is, for example, 5 V, and the heater voltage pulse is repeatedly applied, for example, every cycle T2 = 0.25 seconds.

The measurement of the sensor response is performed every T3 seconds from the application of the heater voltage pulse.

S1 to S5 in FIG. 1 are power supply lines for measuring the resistance of the sensor element. As shown in FIG. 2, the power supply line S1 has a width 1
When a voltage pulse of 5 ms is applied, a current flows through the five sensor elements C11, C21, C31, C41, and C51 in the first row. This is amplified by the operational amplifiers 4a to 4e, and A / A
After converting the analog signal into a digital signal by the D converter 5, the value is measured by the personal computer 1.

Each of the operational amplifiers 4a to 4e is connected in parallel with a sensor element in a vertical row of the sensor array 3, but a voltage is applied only to the sensor element in a horizontal row to which a voltage pulse is applied. Electric current flows through.

[0027] As shown in FIG.
The processing is performed for all the rows at intervals of 5 ms.

In the personal computer 1, the element resistance of the sensor is calculated from the measured current value, and the sensor response r is calculated according to the following equation.

R = Rgas / Rair (1) where Rgas is the element resistance of the sensor in the odor / gas,
Rair represents the element resistance of the sensor in air, and r is a monotonically decreasing function of the odor / gas concentration.

FIG. 3 shows a response calibration curve of the pulse-driven semiconductor odor / gas sensor used in the present embodiment to ethanol gas. In the figure, the sensor resistance R in the gas is shown.
gas and the resistance Rair in air, Rgas /
Rair was used as the sensor response r. Sensor response r = Rgas / Rai in response to lean ppm level gas
It can be seen that r has decreased.

Now, in order to visualize the obtained sensor response, the level of the gas concentration is represented by the density of black and white (image brightness). By displaying the brightness b of the pixel as b = 255 × (1-r) (2), a brighter image can be obtained in a place where the gas concentration is higher and r is smaller. Here, the coefficient 255
Is the number of shades of gray that can be displayed on the personal computer 1.

(Odor / Gas Flow Visualization Experiment) The odor / gas flow visualization experiment using the odor / gas flow visualization apparatus described above was performed in a wind tunnel as shown in FIG. The smell / gas sensor array 3 is installed almost in the center of the wind tunnel,
Wind was generated using the AC fan 11. In addition, smell
As a gas generation source, a nozzle for jetting ethanol saturated steam was used, and the jet amount from the jet port 12 was 50 ml / m2.
in. The distance between the ejection port 12 and the sensor array 3 is 4
5 cm.

The diffusion speed of the odor and gas molecules is very slow, and the odor gas molecules released from the jet port 12 are carried by the wind and spread. If the wind in the wind tunnel is completely laminar, the odor and gas spread downwind from the outlet 12 like a continuous band. However, the wind in the wind tunnel shown in FIG. 3 is disturbed similarly to the real environment, and the distribution of smell and gas fluctuates. For this reason, like the smoke flowing from the chimney, an odor / gas cloud having a pattern of high and low odor / gas concentrations flows downwind on the sensor array 3.

Five sensor elements arranged in parallel with the wind are selected from the 25 sensor elements of the sensor array 3, and the sensor response r is shown in FIG. The sensor element shown in FIG. 20, no. 19, no. 18, No. 1
7, no. They are arranged in the order of 16. As shown in FIG. 20
It can be seen that the response value starts to decrease first, and then responds in the order in which the sensor elements are arranged. Conversely, although not shown in FIG. 5, the response values also start to increase in the same order when the sensor starts to recover. This order of response / recovery corresponds to the direction of the odor / gas flow.

Then, the sensor responses r of the 25 sensor elements of the sensor array 3 are visualized on a computer screen,
Observe.

FIG. 6 shows the sensor array 3 in such a situation.
25 shows the results of visualizing the 25 sensor responses as a moving image. 6A to 6D show images when the sensor element starts responding to the odor / gas, and FIGS. 7E to 7H show images when the odor / gas passes and the sensor starts to recover. It is. The white part of the color represents a high concentration of smell and gas,
In FIG. 6, the sensor response is binarized so that the movement of the visualized image is easy to see, and a plain (white) rectangle is inserted in the place of the responding sensor, and an oblique hatching is inserted in the place of the unresponsive sensor. I drew a (dark) rectangle.

As is clear from FIG. 6, it was confirmed that the smell and gas flowed from left to right.

(Direction Estimation Algorithm) If the odor / gas flow visualization apparatus as described above obtains a visualized image of the odor / gas flow as shown in FIG. 6, a human observes the direction of the odor / gas flow. Can be determined. It is also possible to automatically determine the direction and the flow velocity using various image processing algorithms. The process of determining the direction and the flow velocity from the visualized image of the smell / gas flow can be performed by the personal computer 1 in FIG.

Here, it is considered that a future calculation is made into a circuit to perform real-time processing, and a direction estimating method (BKP.
Horn, "Robot Vision" Asakura Shoten, 305-3
28, 1993) will be described.

It is assumed that the molecular diffusion of the odor / gas is ignored, and that the visualized odor / gas concentration distribution flows over the sensor array 3 two-dimensionally while maintaining a constant shape. Assuming that the x-axis component of the smell / gas flow is u and the y-axis component is v, the constraint equation for the optical flow is

[0041]

(Equation 1)

Is as follows.

Let the image luminance at the ith row and jth column be bij,
When the differentiation included in the above equation (3) is approximated by central difference,

[0044]

(Equation 2)

However, the arrangement interval Δl of the sensor elements of the sensor array 3 is 11 mm, and the sampling time Δt is 250 m.
s. Smell / gas flow velocity vector (u,
v) is obtained by converting the above equation (4) into i = 2, 3, 4 and j = 2, 3, 4
And can be obtained by the least squares method.

Here, the visualized image shown in FIG.
FIG. 7 shows the result of estimating the direction and the flow velocity of the odor / gas flow according to the above-described method.

In the direction estimation, the sampling period Δt = 25
The measurement was performed every 0 ms, but the result shown in FIG. 6 shows the estimated value at the intermediate time between the adjacent images in FIG. The direction was set to 0 ° in the right direction and positive in the counterclockwise direction. A direction roughly corresponding to the moving direction of the image shown in FIG. 6 was obtained. The wind direction in the wind tunnel fluctuates around 0 °, and the obtained direction is consistent with this.

The speed of the obtained odor / gas flow was smaller at the time of recovery than at the time of the response of the sensor. This is because the recovery speed of the sensor was slower than the response speed. In order to visualize in real time, it is preferable to use a sensor whose recovery of the sensor response is sufficiently fast. Alternatively, the operating condition of the sensor can be optimized to increase the speed of recovery of the sensor response.

For example, since the response characteristics of the sensor change depending on the set values of T1 and T3 described above, it is only necessary to first optimize the operating conditions of these odor / gas sensors.

That is, the above-described heater voltage pulse width T1
Is smaller, the recovery time of the sensor response to the ethanol gas is shorter, and the response sensitivity of the sensor also depends on the data measurement timing T3, and decreases as the value of T1 decreases. Therefore, considering the balance between the sensitivity and the recovery speed, the values of T1 and T3 may be set so that the recovery is performed at a high speed while keeping the sensitivity substantially equal.

By optimizing the operating conditions of the odor / gas sensor and improving the recovery speed of the sensor corresponding to ethanol gas, it is possible to visualize the odor / gas flow at a flow rate of approximately 1 to 2 cm / s.

(Summary) As described above, according to the above-described odor and gas flow visualization apparatus for searching for the source of odor and gas generated in the air, a pulse-driven semiconductor odor and a compact 5 × 5 gas sensor are arranged. By using the sensor array 3 and capturing the sensor response as a moving image, the smell and gas flow passing over the array are visualized. The direction of the odor / gas flow is determined from the obtained image and the odor / gas source is searched for by following the direction. Multipoint measurement (small time difference in line units as described in this embodiment (small measurement time difference in which the change in concentration of odor and gas flow can be ignored) is permitted, but substantially all of the sensor array 3 is used. Smell
By measuring the concentration change of the odor / gas by performing simultaneous multi-point measurement with a gas sensor), highly reliable direction determination can be performed in a short time. Further, the direction and speed of the wind carrying the smell and gas can be obtained from the moving direction and speed of the image.

As a result of conducting an experiment for visualizing the odor and gas flow in the wind tunnel, it was confirmed that a minute odor and gas flow of about 2 cm / s could be visualized and the direction of the odor and gas flow could be correctly estimated using the visualization. Thus, application to a wind speed environment or an environment with large wind turbulence, which was difficult to search in the past, can be expected.

As described above, according to the above embodiment, the odor / gas flow direction can be determined with high reliability in a short time, and the odor / gas generation source can be easily searched. The target to be searched may be a gas leak location or a fire location. In addition to displaying the obtained image to determine the direction of smell and gas flow, it is also possible to automatically determine the direction by using various image processing techniques. If this is attached to a mobile robot, it can be applied to the detection of dangerous gas sources. Also,
At present, there are few effective means of measuring wind speed. However, if the smell gas is intentionally released into the air and its flow is visualized, the present device can be used as a fine wind speed / wind vane. Conventionally, various types of smoke have been used for visualization, but sedimentation occurs when the wind speed is on the order of cm / s. Since the smell and gas follow the wind better, the present device is effective in a weak wind speed field.

(Second Embodiment) In a pulse-driven semiconductor odor / gas flow visualization device using a gas sensor, the response speed of the semiconductor odor / gas sensor is fast, but the recovery motility is insufficient. Affects visualization. Therefore, in the first embodiment, the pulse drive type semiconductor odor / gas sensor is used, the pulse waveform of the heater drive voltage is optimized, and the recovery speed is increased while having the same sensitivity as that of the conventional semiconductor odor / gas sensor. It visualized the flow of ethanol gas inside. But,
Nevertheless, the recovery speed of the sensor takes about several tens of seconds, and the flow cannot be determined except at the start and end of the odor / gas ejection.

Therefore, in the second embodiment, the purpose is to realize an odor / gas flow visualization device which can always determine the odor / gas flow, and employs a quartz oscillator / gas sensor having a fast response recovery speed as a sensor. The case will be described.

First, the principle of the odor / gas flow visualization device and the configuration of the odor / gas flow visualization device according to the second embodiment will be described. After that, the results of an experiment to visualize smell and gas flow in the wind tunnel are shown.

(Principle) The smell / gas flow visualization device forms a sensor array of several centimeters square by arranging the same type of smell / gas sensor, and obtains the instantaneous distribution of smell / gas passing thereover as a moving image.

If there is no turbulence in the wind, the plume (generally smell, gas molecules diffuse very slowly,
The gas molecules spread in a cloud shape mainly by the movement of the wind. This cloud is called a plume.) It extends like a band from a source of odor or gas without interruption. However, in reality, the wind always has turbulence, and the plume has an irregular and discontinuous shape. Since the odor and gas having such a complicated distribution flow on the array, if the odor and gas sensor follows the instantaneous change in concentration, it is possible to visualize how the odor and gas distribution flow. .

With the device according to the second embodiment,
When detecting a gas source, the device itself is held by a human hand or mounted on a robot, and the robot is moved in the direction of the obtained smell / gas flow.

(Small Quartz Crystal Odor / Gas Sensor) According to such a principle, in order to visualize the odor / gas flow, each odor gas sensor must be able to quickly follow the instantaneous odor / gas concentration change. . When a pulse-driven semiconductor odor gas sensor was used, the response recovery speed of the sensor was slow and sufficient performance was not obtained. That is, immediately after the start of the odor / gas ejection, the flow could not be recognized except that the odor / gas arrived at the array and the odor / gas flowed off after the odor / gas ejection was stopped.

Therefore, in the second embodiment, the use of a quartz oscillator and a gas sensor was examined. Since the time constant of the gas sensor in a quartz oscillator is usually 1 second or less (Aoyagi, Nakamoto, Moriizumi. IEICE General Conference, 194.
C-13-8 (1999)), and an improvement in the performance of the device is expected. In order to mount the sensors on the sensor array at high density, the sensors need to be small. Considering the effects of pull-in, interference, and the like, which are likely to occur in a high-frequency circuit, it is desirable to use a device having a built-in oscillation circuit (small crystal oscillator with a built-in oscillation circuit).

For example, the small crystal oscillator (FCXO-02, River Eletech) with a built-in oscillation circuit used here is
AT-cut, silver electrode, resonance frequency is 28 MHz, and size is 4 × 8 mm. Phosphatidylcholine is used for the sensitive film applied to the transducer surface, and the frequency shift is 10K.
Hz by a spray method.

In the first embodiment, ethanol gas is used, but here, triethylamine is used. Triethylamine odor is one of the bad odors, and it is useful for environmental measurement to detect its source. A phosphatidylcholine membrane was selected as a sensitive membrane because of its high numerical sensitivity and quick response recovery time for this amine.

FIG. 8A shows a pulse-driven semiconductor smell / gas sensor (for example, TG) used in the first embodiment.
FIG. 8B shows an example of a response waveform to the ethanol gas in S2440), and FIG. 8B shows an example of a response waveform to the triethylamine gas of the gas sensor in the small quartz oscillator according to the second embodiment. For example, in the wind tunnel (width 70 cm, height 35 cm, length 80 cm) shown in FIG. 4,
The response was measured by installing the sensors 3 and 103 at a point 30 cm downwind from a nozzle (smell / gas source) that emits smell / gas (see FIG. 4). Average wind speed in the wind tunnel is about 18
cm / sec. However, the jetting speed of the odor / gas was 50 ml / min in FIG. 8 (a) and 75 ml / min in FIG. 8 (b).
Minutes.

Even the wind in the wind tunnel is disturbed,
The plume of gas meanders irregularly and is discontinuous (T. Yamanaka, H. Ishida, T. Yamada).
Nakamoto, T .; Morizumi,. Sen
sors and Actuators A, 69, 7
7-81 (1998)). For this reason, even at the position where the sensor is installed, there should be an instantaneous change in density. However, in the pulse-driven semiconductor shown in FIG.
Recovery is slow with a gas sensor, and no change in concentration is detected. In addition, recovery after stopping odor and gas emission is slow.
In the response waveform of the gas sensor of the small quartz oscillator shown in FIG. 8B, the oscillation frequency in air is set as a reference (0 Hz).
The change of the oscillation frequency in the odor / gas is shown on the time axis. It can be seen that there is a change in the oscillation frequency during the emission of the odor / gas. The spike-like concentration change can always be detected during the emission of the smell and gas, and the recovery after stopping the emission of the smell and gas is quick.

The above two measurements cannot be simply compared because the types of smell and gas are different and the environment such as wind speed is slightly different. However, considering application to odor and gas flow visualization devices, using a quartz oscillator and a gas sensor can quickly follow instantaneous changes in odor and gas concentrations, and using a pulse-driven semiconductor odor and a gas sensor The problem in the case can be improved.

(Apparatus Configuration) FIG. 9 shows the configuration of an odor / gas flow visualization apparatus using a small quartz oscillator / gas sensor array. This device includes a sensor array unit 103, a multi-channel (for example, 25-channel (25ch)) frequency counter, and a serial interface unit 10.
It can be roughly divided into two, and computer one and three.

The sensor array section 103 includes, for example, a gas sensor (for example, FCXO-02, River Eletech) 1 in a small crystal oscillator having a built-in oscillation circuit as described above.
03a in the row direction and in the column direction, 5 in each, a total of 5 × 5
= 25 are evenly arranged on a printed circuit board to form a two-dimensional sensor array. The array size of 5 × 5 was determined because the minimum data required for the direction estimation could be obtained and it could be realized relatively easily. For example, the interval between sensors (distance between centers) is 12.7 mm, and the size of the sensor array is 50.8 mm × 50.8 mm. Sensor array unit 1
The 25 sensor outputs 03 (frequency changes) of 03 are taken into the 25ch frequency counter and the serial interface unit 102 (sampling interval: 1 second) in parallel at the same time.

The 25-channel frequency counter and serial interface unit 102 are, for example, an FPGA (F
Field Programmable Gater
ay). Most of the circuits can be stored in the FPGA because of the use of the sensor with built-in oscillation circuit.
The size of the entire apparatus can be reduced. Also, the oscillation circuit and FP
In order to minimize the wiring to the GA and to prevent sneak from the power supply, a three-terminal chip capacitor was used for each sensor, and the power supply and GND were bypassed. These measures can prevent interference between the oscillation circuits.

The sensor array unit 103 and the multi-channel frequency counter and serial interface unit 1 shown in FIG.
02 can have a two-layer structure, for example. That is, the sensor array unit 103 may be mounted on the upper substrate, and the electric circuits such as the multi-channel frequency counter and the serial interface unit 102 may be mounted on the lower substrate.

The computer 1 is, for example, a personal computer including a monitor. The computer 1 controls the entire apparatus and, based on sensor responses sent every second, images the odor / gas concentration distribution on the sensor array in four gradations. It is displayed on the monitor as (a visualized image of smell and gas flow). 2
The output of each of the five sensors 103a appears as a change in the oscillation frequency of the quartz oscillator, and by measuring it, the odor is measured.
It measures the gas concentration distribution. Specifically, each sensor response is classified into four levels according to an appropriately determined threshold value according to the maximum response obtained after the start of the measurement, and a different gradation is assigned to each level. The higher the odor / gas concentration, the brighter the gradation, and the distribution of the concentration is displayed as a color distribution.

Note that each sensor 103a in the sensor array section 103 has a variation in sensitivity. Therefore, the entire sensor array unit 103 is covered and sealed in advance, all the sensors 103a are exposed to the same concentration of triethylamine gas, and the responses are compared. From this result, the sensitivity of all the sensors is multiplied by a constant corresponding to each sensor. It is desirable to calibrate as closely as possible.

(Direction Estimation Algorithm) If a visualized image of the odor / gas flow can be obtained by the apparatus shown in FIG.
The direction of the odor gas flow can be judged by humans. In addition, the direction can be automatically determined using various image processing algorithms. The process of determining the direction and the flow velocity from the visualized image of the smell / gas flow can be performed by the personal computer 1 in FIG.

Here, it is considered that the calculation is made into a circuit in the future and real-time processing is performed, and a direction estimation method using a constraint equation of an optical flow which is easy to calculate (T. Yamana).
ka, H .; Ishida, T .; Nakamoto, T .;
Morizumi,. Sensors and Ac
tuators A, 69, 77-81 (1998),
B. K. P. Horn, "Robot Vision" Asakura Shuppan, 305 to 328 (1993)), and attempts to automatically determine the direction. This equation is often used in the field of image processing to recover the relative motion between the object and the camera from the image.

It is assumed that the molecular diffusion of the odor / gas is ignored, and that the visualized odor / gas concentration distribution flows two-dimensionally on the sensor array while maintaining a constant shape. X-axis direction of odor / gas flow (eg, row direction of sensor array)
Components are u, y-axis direction (for example, column direction of sensor array)
Assuming that the component is v and the response of the odor / gas sensor is 1, the constraint equation of the optical flow is

[0077]

(Equation 3)

Is obtained.

When the sensor response at the i-th row and the j-th column is set to lij and the differentiation included in the above equation (5) is approximated to the central difference, the following diffusion equation is established at the time k.

[0080]

(Equation 4)

Here, Δd is the sensor interval (12.7 m).
m) and Δt are sampling times (1 second). The flow velocity vector (u, v) of the odor / gas flow is assumed to be constant regardless of i and j, and the above equation (6) is given by i = 2, 3, 4, j = 2,
Simultaneously with 3 and 4, u and v are obtained by the least squares method.

(Results) (Smell / gas flow visualization experiment) In the same wind tunnel (wind tunnel as in FIG. 4) as the measurement in FIG. 8, under the same environmental conditions as in FIG. An experiment on visualization of gas smell and gas flow was performed. However, the wind speed was set to about 3 cm / sec on average in order to conduct the experiment in a low wind speed environment. One measurement was performed for 300 seconds, the baseline of the sensor was measured for the first 15 seconds, and then triethylamine gas accumulated in the gas portion (head space) at the top of the test tube was pushed by an air pump, and the flow rate was 3 m at a flow rate of 75 m / min. Squirted for a minute.

FIGS. 10 (a) to 10 (f) show examples of moving images obtained while the odor / gas is being ejected. FIG.
This is a binarized image, in which parts having a high odor / gas concentration are displayed in black, and parts having a low odor / gas concentration are displayed in white. FIG.
(C) and (d) to (f) are images for three consecutive seconds, respectively, each of which is obtained after 60 seconds or more have elapsed since the odor / gas ejection. It is visualized that the smell / gas mass flows from the left and flows off to the right.

In the semiconductor described in the first embodiment,
In the case of the gas sensor, the time constant is as long as several tens of seconds, so it was difficult to measure in a short time due to mutual interference and the like, but the measurement using the gas sensor array of the quartz resonator of the present embodiment has a time constant. Usually, a clear image is obtained, which is as fast as about 1 second.

That is, in the first embodiment, as described above, only the beginning and the end of the odor / gas ejection could be visualized. However, as is clear from FIG. I was able to confirm the direction of flow. Since the plume fragmented by the wind turbulence passes over the array in an irregular manner, if the response and recovery of the sensor is fast, it is possible to always check the direction of the gas flow.

(Automatic Direction Estimation by Algorithm) According to the method described in (Direction Estimation Algorithm), the odor / gas flow direction was estimated from the moving image obtained by the odor gas visualization device according to the second embodiment. FIG. 11 shows the result. As shown in FIG. 11, the distance from the odor / gas source to the sensor array and the odor / gas
The incident direction of the gas is used as a parameter. Condition 1: The entry of the sensor array is odor.
cm and the incident angle is 0 degree Condition 2: Sensor array entry is odor, 20 from gas source
cm: the incident angle is -45 degrees. Condition 3: The sensor array has a bad smell.
cm and the incident angle is 0 degree Condition 4: Sensor array entry is odor, 30 from gas source
cm and an incident angle of -45 degrees An estimation experiment was performed on a total of four times of moving image data in each of these four conditions. The data used was data from immediately after the gas arrived at the sensor array to when the gas ejection was stopped in 300 seconds. However, since the wind in the wind tunnel was disturbed, the case where the wind direction was estimated within + -45 degrees was regarded as the correct answer.

In all of the conditions 1 to 4,
At least 49% were estimated in the correct direction. This is a high accuracy rate when considering the turbulence in the wind tunnel. FIG. 12 shows the estimation result of the condition 4 in the form of a histogram. The correct answer direction is -45 degrees, and the inside of the area separated by the dotted line is the correct answer area. It can be seen that while the estimation is made almost in the vicinity of the correct direction, the estimation is hardly made in the vicinity of the opposite direction. In actual odor and gas source detection, direction estimation is performed many times in many places, so if this accuracy rate is obtained, odor source detection seems to be possible.

(Summary) According to the above-described small crystal oscillator having a built-in oscillation circuit, the odor using a gas sensor, and the gas flow visualization device, the odor and gas flow having an average wind speed of about 3 cm / sec are almost always applied. The flow of smell and gas was confirmed. In addition, it was confirmed that it was possible to estimate the odor and gas flow automatically using the image processing algorithm based on the optical flow constraint equation for the obtained moving images.

(Third Embodiment) The pulse-driven semiconductor odor gas sensor array 3 described in the first embodiment,
When attempting to visualize the odor / gas flow using the small crystal resonator / gas sensor array 103 described in the second embodiment, the direction of the flow of the odor / gas flow is determined on the sensor surface (the odor of the sensor arrays 3 and 103). If it is not parallel to the surface on which the gas sensor element is arranged), the odor and gas flow will be reduced as shown in FIG.
In this case, a turbulent air flow is generated on the sensor surface, disturbing the smell / gas flow itself to be measured, and there is a problem that accurate measurement of the smell / gas flow cannot be performed.
That is, it is desirable that the sensor surfaces of the sensor arrays 3 and 103 and the direction in which the odor / gas flow flows are always parallel. However, actually, the direction of the flow is unknown.
Since the gas flow is measured, the direction of the smell and the flow of the gas flow are not always parallel to the sensor surface.

Therefore, as shown in FIG. 13B, plates (guide plates) parallel to the sensor surface are arranged at predetermined intervals so as to cover the entire sensor elements on the sensor arrays 3 and 103. . Then, an odor / gas flow that generates turbulence at the center of the sensor surface as shown in FIG. 13A is shielded by the guide plate and passes through the surrounding opening (between the sensor surface and the guide plate). ), Which only takes in and exhausts the smell / gas flow, thus the sensor arrays 3, 10
No. 3 can measure only the component parallel to the sensor surface in the flow direction of the odor / gas flow.

FIG. 14 shows a state in which the above-mentioned guide plate 201 is provided in parallel above the sensor surfaces of the sensor arrays 3 and 103 of the odor / gas flow visualization device so as to cover the sensor surfaces, and a wind tunnel experiment is performed. It is shown. Although it depends on conditions such as the size of the sensor arrays 3 and 103, the speed and the direction of the odor / gas flow, here, for example, since one side of the sensor arrays 3 and 103 is at most about 5 cm, the sensor arrays 3 and 103 Guide plate 20 of approximately the same size as
1 is supported at a height of about 1 cm from the sensor surface by the columns set up at the four corners of the sensor arrays 3 and 103.

Thus, the sensor arrays 3 and 103 are
Since only the component parallel to the sensor surface in the flow direction of the odor / gas flow can be extracted and measured, the odor / gas flow direction and velocity can be measured more accurately.

(Fourth Embodiment) FIG. 15 shows the configuration of the pulse-driven semiconductor odor / gas sensor array 3 described in the first embodiment and the small crystal resonator / gas sensor array 103 described in the second embodiment. It shows the effective components capable of detecting the direction and the flow velocity of the odor / gas flow as viewed from the sensor surface (detection surface).

As shown in FIG. 15, the sensor arrays 3, 1
Focusing on an arbitrary point on the sensor surface of No. 03, the sensor arrays 3 and 103 have a curve m1 whose cross section having a direction parallel to the sensor surface as the maximum sensing direction is a circular donut shape.
Only the direction of smell and gas flow across m2 is detected. That is, when the incident angle θ of the odor / gas flow with respect to the sensor surface is 90 degrees, the odor / gas flow has curves m1, m2 intersecting the incident point on the sensor surface.
Since it does not cross, the flow cannot be detected. For example, when the incident angle θ is 45 degrees and the speed is 10 m / sec.
Considering only the component parallel to the sensor surface, that is, the gas flow, the reciprocal of cos θ of the incident angle θ, considering the flow velocity at the surface, is measured as 10 / cos 45 ° = 10/2 ^1/2. .

When the sensor surface is on both the upper and lower surfaces, a circular curve sandwiching the sensor surface as shown in FIG. 15 is a sensitivity component.
The semicircular curve above m2 is the sensitivity component.

Therefore, if the odor and gas flow are visualized, and the direction and the velocity are measured using only one sensor array 3, 103 having only the upper surface, the odor and gas flow are captured only in one plane. Can not do. However, if the smell / gas flow can be captured from multiple angles, the direction and speed of the smell / gas flow can be measured more accurately.
This embodiment focuses on this point.

Therefore, the odor / gas flow visualization device according to the present embodiment is considered to use a plurality of two-dimensional planar sensor arrays in combination. For example, as shown in FIG. 16, two sensor arrays A1 and A2 (for example, the pulse-driven semiconductor odor / gas sensor array 3 described in the first embodiment, the small crystal resonator described in the second embodiment) One of the smell / gas sensor array 103 is set to 2
One or one each) may be arranged on the xz plane and the other on the yz plane so as to intersect perpendicularly with each other to constitute an odor / gas flow measuring unit. Each of the sensor arrays A1 and A2 constituting the odor / gas flow measuring section is connected to another device such as the personal computer 1 to configure an odor / gas flow visualization device.

Then, as shown in FIG. 17, a component perpendicular to the sensor surface of the sensor array A1 of the odor / gas flow (a component where the incident angle θ of the odor / gas flow with respect to the sensor surface of the sensor array A1 is 90 degrees) Direction and speed can be measured on the sensor surface of the sensor array A2 even if it is unknown from the sensor array A1, and both sensor arrays A1,
By synthesizing the speed and direction of the odor / gas flow measured in each of A2, the odor / gas flow can be captured three-dimensionally.

As an example of using a plurality of sensor arrays in combination, as shown in FIG. 16, in addition to combining two sensor arrays in a vertical relationship with each other, a combination as shown in FIG. Some people. In the following, a sensor array will be referred to as the pulse-driven semiconductor described in the first embodiment. The gas sensor array 3 will be referred to as the small crystal resonator described in the second embodiment.
Any of the gas sensor arrays 103 is included.

FIG. 18A shows two sensor arrays 30.
The odor / gas flow measurement unit 300 is configured by combining the first and second back surfaces 1a and 301b with their back surfaces (surfaces on which no sensors are arranged) facing each other. In the odor / gas flow measurement unit 300, the sensor arrays 301a and 301a
b, the odor and gas flow flowing on the upper surface side and the lower surface side can be detected.

FIG. 18B shows six sensor arrays 302a to 302a at the center of each surface of a cube (or a rectangular parallelepiped).
This shows a case where each of 02f is attached with its sensor surface facing the inside of a cube (or a rectangular parallelepiped), and the odor and gas flow flowing through the inside are measured. This cubic (or rectangular) odor / gas flow measuring unit 31
Each side of 0 (or some of the 6) smells
The structure is such that the gas flow passes without any shielding. Then, the odor and gas flow flowing inside the cube (or the rectangular parallelepiped) are transferred to the sensor array 30 on each surface.
If the data obtained by measuring in 2a to 302f can be combined to measure the flow coming from any direction from at least three surfaces, the obtained data is combined to obtain the smell / gas flow. A three-dimensional direction and speed can be obtained. Considering that the size of the sensor arrays 302a to 302f is at most 5 cm square,
It is about 50cm in length, width and height,
Its size is not particularly limited.

The same effect can be obtained even if the sensor surface is attached to the outside of a cube (or a rectangular parallelepiped). This case is shown in FIG.

A cubic (or rectangular parallelepiped) odor / gas flow measuring section 320 shown in FIG. 18 (c) has six sensor arrays 3 at the center of each surface of the cube (or rectangular parallelepiped).
The sensor surfaces 03a to 303f are attached to the outside of the cube (or the rectangular parallelepiped), and the odor and gas flow flowing outside the cube are measured.

The spherical odor / gas flow measuring section 330 shown in FIG. 18D is one in which a sensor array or a sensor element itself is arranged on a spherical surface of a predetermined size. Thus, by providing the sensor array in as many directions as possible, the smell and gas flow from all directions can be reduced by one.
It is possible to easily measure three-dimensionally while staying at different locations.

FIG. 19 shows, for example, the odor / gas flow measuring section 320 (or FIG. 18) shown in FIG.
(It may be any of the odor and gas flow measuring units shown in (a) to (d).) The odor and gas flow of the odor and gas flow measuring unit 320 when measuring the odor and gas flow This shows an example of arrangement at a measurement location (for example, a wind tunnel).

The smell / gas flow measuring section 320 is suspended from the upper four corners of the measurement place (here, for example, a cubic shape) at substantially the center of the measurement place using wires 402a to 402d. Each of the sensor arrays 303a to 303f of the measuring section 320 is connected to another device 403 such as the personal computer 1 to constitute an odor / gas flow visualization device.

As shown in FIG. 19, by using an odor gas flow measurement unit composed of a plurality of sensor arrays in a suspended manner at the odor / gas flow measurement location, odor gas flow from all directions can be measured. Simultaneous multi-point measurement can be performed, and the direction and velocity of smell and gas flow can be measured more accurately.

By arranging the odor / gas flow measuring section as shown in FIG. 19, the odor / gas flow measuring section 320 is provided.
As such, miniaturization is possible.

When a plurality of sensor arrays are combined to form an odor / gas flow measuring section, a guide plate as described in the third embodiment may be used for all or one or some of the plurality of sensor arrays. May be provided.

Although various examples have been described above, the present invention is not limited to these examples, and can be applied with various modifications.

[0111]

As described above, according to the present invention,
It is not necessary to select the arrangement position of the gas sensor, and it is hardly affected by local turbulence of the wind, and the determination of the direction of the odor gas flow can be made in a short time and with high reliability.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an odor / gas flow visualization device according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the sensor array 3 of FIG.

FIG. 3 is a diagram showing a response calibration curve of a pulse-driven semiconductor gas sensor with respect to ethanol gas.

FIG. 4 is a diagram showing a configuration example of a wind tunnel in which an odor / gas flow visualization experiment was performed using an odor / gas flow visualization device.

FIG. 5 is a diagram showing an example of a change with time of sensor responses of five sensor elements arranged in parallel with the wind direction.

FIG. 6 is a diagram showing an example of a moving image in which a sensor response of a sensor array 3 is visualized.

7 is a diagram showing a table summarizing the results of estimating the direction and flow velocity of a gas flow with respect to the visualized image shown in FIG. 6;

FIG. 8 shows an example of a response waveform of a pulse-driven semiconductor odor gas sensor (for example, TGS2440) used in the first embodiment to ethanol gas, and a small crystal oscillator according to the second embodiment; a triethylamine gas in the gas sensor; FIG. 4 is a diagram showing an example of a response waveform to the response.

FIG. 9 is a diagram showing a configuration example of an odor / gas flow visualization device using a small quartz oscillator / gas sensor array.

FIG. 10 is a diagram showing an example of a moving image obtained while odor / gas is being ejected.

FIG. 11 is a diagram showing a direction estimation result of an odor / gas flow from a moving image obtained by the odor / gas visualization device according to the second embodiment.

FIG. 12 is a diagram illustrating a direction estimation result (in the case of condition 4 in FIG. 11) in a histogram.

FIG. 13 is a view for explaining a countermeasure against turbulence generated on the sensor surface of the sensor array.

FIG. 14 shows a sensor array provided with a guide plate.
FIG. 3 is a diagram illustrating a state in which a wind tunnel experiment is performed with a gas flow visualization device.

FIG. 15 is a diagram showing an effective area in which the direction of the odor and gas flow can be detected from the sensor surface (detection surface) of the sensor array.

FIG. 16 is a diagram illustrating an example of an odor / gas flow measurement unit configured by combining two sensor arrays.

FIG. 17 is a diagram showing an effective area in which the direction of the odor / gas flow of the odor / gas flow measuring unit in FIG. 16 can be detected.

FIG. 18 is a diagram showing another example of the odor / gas flow measurement unit configured by combining a plurality of sensor arrays.

FIG. 19 is a diagram showing an example of arrangement of an odor / gas flow measurement unit configured by combining a plurality of sensor arrays at a measurement location (for example, a wind tunnel) where an odor gas flow flows.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Personal computer 2 ... Control circuit 3 ... Sensor array (pulse drive type semiconductor smell / gas sensor array) 4 ... Logarithmic conversion circuit 5 ... A / D converter 102 ... Multi-channel frequency counter and serial interface unit 103 ... Sensor array (crystal) Oscillator smell, gas sensor array)

Claims (5)

[Claims] An odor / gas flow measuring means for measuring a concentration change of an odor / gas flow at multiple points by combining a plurality of sensor arrays in which one or a plurality of odor / gas sensors are arranged on a two-dimensional plane. An odor / gas flow visualization device, comprising: a visualization device for visualizing a change in concentration measured by the gas flow measurement device. 2. An odor / gas flow measuring means for combining a plurality of sensor arrays in which one or more odor / gas sensors are arranged on a two-dimensional plane to measure a change in concentration of the odor / gas flow at multiple points. Visualization means for visualizing the concentration change measured by the gas flow measurement means, and measurement means for measuring the direction and flow velocity of the odor / gas flow based on the visualized concentration change, Gas flow measurement device. 3. The one or more sensor arrays,
3. The odor / gas flow measuring device according to claim 1, wherein a plate-like body parallel to the detection surface is arranged at a predetermined interval on the detection surface. 4. A sensor array in which one or a plurality of odor / gas sensors are arranged on a two-dimensional plane, and a concentration change of an odor / gas flow is measured at multiple points by the sensor array to visualize the measured concentration change. An odor / gas flow visualization device, comprising: a visualization means; and a plate-like body parallel to a detection surface of the sensor array arranged at a predetermined interval on the detection surface. 5. A sensor array in which one or a plurality of odor / gas sensors are arranged on a two-dimensional plane, and a concentration change of an odor / gas flow is measured at multiple points by the sensor array to visualize the measured concentration change. Visualization means, and measurement means for measuring the direction and flow velocity of the odor / gas flow based on the visualized concentration change, wherein the sensor array has a plate-like body parallel to its detection surface. An odor / gas flow visualization device, wherein the odor / gas flow visualization device is arranged at predetermined intervals.