JPH07237488A - In-vehicle in-seat detecting device - Google Patents

Abstract

PURPOSE:To surely discriminate the human body and an object even when a vehicle vibration characteristic is changed. CONSTITUTION:A device is constituted of a plurality of filters 3, 4 for wave filtering a certain specific frequency component in an output signal of a piezoelectric element 2 arranged in a seat 1 in a vehicle, frequency characteristic setting means 12 for setting frequency characteristic wave filtered by the filters 3, 4 based on a vibration characteristic of the vehicle and a decision means 9 for deciding a person for whether provided or not in the seat 1 based on an output signal respectively of the filters 3, 4, and when a signal is output from the piezoelectric element 2, a certain specific frequency component is wave filtered respectively by the filters 3, 4. Here based on the vibration characteristic of the vehicle, the frequency characteristic, wave filtered by the filters 3, 4, is set by the frequency characteristic setting means. In the decision means 9, based on a wave filter signal from the filter, the person is decided for whether provided or not in the seat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-vehicle seat detecting device for detecting the presence or absence of seat passengers in a vehicle, grasping the number of seats and vacant seats, and performing air conditioning control and sound field control in the vehicle.

[0002]

2. Description of the Related Art The present inventors have conventionally had a problem that this type of in-vehicle seating detection device cannot reliably distinguish between a person and an object to detect seating. An in-vehicle seat detection device having a configuration such as 11 has been devised. That is, the piezoelectric element 2 is arranged in the seat 1 and the vibration of the seat surface is detected. The detected vibration signal is filtered by a plurality of filters 3 and 4 (here, two bandpass filters are used) having different filtering frequencies. The respective filtered signals are amplified by amplifying means 5 and 6, respectively, and then smoothed by smoothing means 7 and 8, respectively. Then, the judging means 9 is based on the respective smoothed signal levels.
The presence is determined by. Here, the pass center frequencies of the filters 3 and 4 are f1 which is the resonance frequency of the human body in the filter 3 and f2 in the filter 4 (f2> f1).
Is. The characteristics of the filters 3 and 4 are set as described above because the vibration component of the small body motion generated by the heartbeat activity of the human body has a peak at f1, and the human body resonates with the vibration in the vehicle generated by idling and running. The generated vibration component also has a peak at f1, and when an object is placed on the seat, a peak appears at f2 larger than f1 due to vibration from the engine during idling and due to road vibration during running. That is because the analysis of the experiments conducted by the inventors has revealed. FIG. 12 and FIG. 13 show power spectra of the output signal of the piezoelectric element 2 during idling and traveling, respectively.

With the above structure, the vibration signal of the seat surface detected by the piezoelectric element 2 is filtered by the filters 3 and 4 and the signal level v of each component of f1 and f2 is determined by the determination means 9.
1 and v2 are compared. V is more than v2 if a person is present
1 is large, and v2 is larger than v1 if an object is in the seat. If there is nothing on the seat surface, both v1 and v2 are small. Therefore, in the determination means 9, for example, the ratio v1 / v2 of v1 / v
If 2 is greater than or equal to a predetermined set value, the person is present, if less than the set value, the person is absent, and if v1 is less than a certain value, the person is absent Was.

[0004]

However, in the in-vehicle seat detection device of the above-mentioned technique, there are differences in the materials used for the seats depending on, for example, the vehicle type and options, and the engine speed during idling is under maintenance. However, the vibration characteristics of the output signal of the piezoelectric element 2 may not have peaks at the above-mentioned f1 and f2, which causes a problem that erroneous detection occurs in the presence detection.

A first object of the present invention is to eliminate the above-mentioned erroneous detection by setting the frequency characteristic of the filter on the basis of factors that determine the vibration characteristic of the vehicle such as seat material and engine speed. is there.

A second object of the present invention is to show a more practical structure for setting the frequency characteristic of the filter.

A third object of the present invention is to detect presence without erroneous detection without setting the frequency characteristic of the filter as described above.

[0008]

In order to achieve the first object, the present invention provides a vibration detecting means arranged in a vehicle seat and a specific frequency component of an output signal of the vibration detecting means. A plurality of filters for filtering, a frequency characteristic setting means for setting a frequency characteristic for filtering of the filter based on a vibration characteristic of a vehicle, and a determination for determining presence or absence of a person in the seat based on output signals of the filters And means.

In order to achieve the above second object, the present invention has a seat selection means for selecting the type of seat, and the frequency characteristic setting means filters the filter based on the output signal of the seat selection means. Set the frequency characteristics.

In order to achieve the third object, the present invention has a rotation speed detecting means for detecting the rotation speed of the engine, and the frequency characteristic setting means is based on the rotation speed signal from the rotation speed detecting means. Set the frequency characteristics for filtering the filter.

Further, in order to achieve the above-mentioned fourth object, the present invention calculates the power spectrum of the output signal of the vibration detecting means by performing a fast Fourier analysis or the like with the vibration detecting means arranged in the vehicle seat. It comprises frequency analysis means, maximum point calculation means for obtaining the maximum point of the power spectrum, and determination means for determining the presence or absence of a person in the seat based on the power and frequency of the maximum point.

[0012]

The present invention operates as follows with the above construction.

When a signal is output from the vibration detecting means arranged in the vehicle seat, a specific frequency component is filtered by each of the plurality of filters. In this case, the frequency characteristic of each filter is set by the frequency characteristic setting means based on the vibration characteristic of the vehicle. The determination means determines the presence or absence of a person in the seat based on the filtered signal from the filter.

Further, according to the present invention, when a seat type is selected by the seat selecting means, the frequency characteristic for filtering the filter is set based on the selection result. When a signal is output from the vibration detecting means arranged in the vehicle seat, the components of the set frequency are filtered by the plurality of filters. Then, the determination means determines the presence or absence of a person in the seat based on the filtered signal from the filter.

Further, according to the present invention, the number of revolutions of the engine is detected, and the frequency characteristic for filtering the filter is set based on the number of revolutions. When a signal is output from the vibration detecting means arranged in the vehicle seat, the components of the set frequency are filtered by the plurality of filters. Then, the determination means determines the presence or absence of a person in the seat based on the filtered signal from the filter.

Further, according to the present invention, when a signal is output from the vibration detecting means arranged in the vehicle seat, a fast Fourier analysis or the like is performed by the frequency analyzing means to calculate the power spectrum of the output signal of the vibration detecting means. To be done. Then, the maximum point calculating means determines the maximum point of the power spectrum, and the determining means determines the presence or absence of a person in the seat based on the power and frequency of the maximum point.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle seat detection device according to a first embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of this embodiment. Here, the case where the number of filters is two is shown. In FIG. 1, the seat 1 is provided with a piezoelectric element 2 as vibration detecting means. The center frequencies 3 and 4 filtered by the bandpass filters are f1 and f2, respectively (f1 <f2). 5 and 6 are amplification means,
Reference numerals 7 and 8 are smoothing means, and 9 is a determination means. Reference numeral 10 is a seat selection means for selecting the type of the seat 1, and is composed of, for example, a DIP switch. Reference numeral 11 is a rotation speed detecting means for detecting the rotation speed of the engine, and 12 is f of the filter based on the output signals of the DIP switch 10 and the rotation speed detecting means 11.
It is a frequency characteristic setting means for setting 1 and f2. The piezoelectric element 2 is made by forming a thin film of a polymeric piezoelectric material such as polyvinylidene fluoride (PVDF) into a tape shape by attaching a flexible electrode film on both surfaces. Here, it is arranged under the seat cloth of the seat 1. There is.

The operation of the above configuration will be described below. FIG. 2 shows the relationship between the softness of the seat and the power spectrum of the output signal of the piezoelectric element 2 when seated. From the figure, the softer the seat, the more the peak frequency of the power spectrum shifts to the low frequency side, and the harder the seat, the more the peak frequency shifts to the high frequency side. Further, FIG. 3 shows the relationship between the power spectrum of the output signal of the piezoelectric element 2 and the engine speed when an object is placed on the seat during idling. From the figure, the peak frequency of the power spectrum shifts to the low frequency side as the engine speed decreases, and the peak frequency shifts to the high frequency side as the engine speed increases. The hardness of the seat depends on the type of seat. Therefore, if there are four types of seats 1a to 1d, the relationship between the seats 1a to 1d and the center frequency f1 of the filter 3 can be determined as shown in FIG.
Here, the hardness of the seats 1a to 1d becomes harder in this order. The relationship between the engine speed and the center frequency f2 of the filter 4 can be determined as shown in FIG. However, this relationship is applied during idling, and is not applied during running because the peak frequency has a substantially constant value due to the influence of vibration from the road surface. That is, when the rotation speed N is equal to or more than a certain value N1 as when traveling, f2
Is set to a preset setting value f3. The relationship between FIG. 4 and FIG. 5 can be obtained by an experiment.

By selecting the seat types 1a to 1d with the DIP switch 10 when the vehicle is shipped, the frequency characteristic setting means 12 sets the value of f1 based on the relationship of FIG. Further, when the engine speed is detected by the engine speed detecting means 11, the value of f2 is set based on the relationship shown in FIG. Next, when a signal is output from the piezoelectric element 2 arranged on the seat 1, the components of the set frequencies f1 and f2 are filtered by the filters 3 and 4. The respective filtered signals are amplified by amplifying means 5 and 6, respectively, and then smoothed by smoothing means 7 and 8, respectively. The presence of the seat is determined by the determination means 9 based on the smoothed signal levels. FIG. 6 shows a flowchart of the presence determination.
From the figure, the signal levels of the components of f1 and f2 are v1, v
If the ratio is 2, the person is present if the ratio v1 / v2 of v1 and v2 is equal to or greater than a predetermined set value Co, and is absent if the ratio is less than the set value. If not, v1 is less than a certain fixed value C1, so v1 is c1.
If less than, it is determined to be absent.

Due to the above-mentioned operation, in the conventional in-vehicle seat detecting device, when the material used for the seat is different depending on the vehicle type or option, or the engine speed during idling is changed depending on the maintenance situation, Since the vibration characteristic of the output signal of the piezoelectric element changes and the signal level of the output signal of the filter decreases, there is a problem that erroneous detection occurs in the presence detection, but according to this embodiment, the material of the seat and the engine are used. Since the frequency characteristic of the filter is set on the basis of the factor that determines the vibration characteristic of the vehicle such as the number of revolutions, there is an effect that the above-mentioned erroneous detection can be eliminated without the output signal of the filter decreasing. Regarding the factors of the seat material among the above factors, instead of measuring the frequency characteristic of the seat for each car and setting the frequency characteristic of the filter, if the type of seat is selected with the DIP switch 10 at the time of shipment. Since the frequency characteristic can be set, the setting operation can be easily performed. Further, among the above factors, regarding the engine speed, the frequency characteristics of the filter are detected and the frequency characteristics of the filter are sequentially set. Therefore, there is no need to perform an operation such as observing the rotation speed for practical use. Is effective.

Next, a vehicle seat detection device according to a second embodiment of the present invention will be described. FIG. 7 is a block diagram of this embodiment. In FIG. 7, the seat 1 is provided with a piezoelectric element 2 as vibration detecting means. Reference numeral 13 is an amplifying means, 14 is a smoothing means, 15 is a frequency analyzing means for calculating a power spectrum of an output signal of the smoothing means by performing a fast Fourier analysis, 16 is a maximum point calculating means for obtaining a maximum point of the power spectrum, Reference numeral 17 is a judging means for judging the presence or absence of a person in the seat 1 based on the power and frequency of the extra-large points. The piezoelectric element 2 is the same as that of the first embodiment and is arranged under the surface cloth of each seat 1 in the vehicle.

The operation of the above configuration will be described. The output signal from the piezoelectric element 2 is amplified by the amplifying means 13 and smoothed by the smoothing means 14. The smoothed signal is subjected to fast Fourier analysis by the frequency analysis means 15 to calculate the power spectrum. The maximum point calculating means 16 calculates the rate of change of the power spectrum curve in a predetermined frequency region, and obtains a point at which the change rate changes from a positive value to a negative value as a maximum point. Then, the determination means 17 determines the presence or absence of a person in the seat 1 based on the power and frequency of the maximum point. Here, the procedure of the presence determination will be described with reference to FIGS. 8 and 9. FIG. 8 is a power spectrum when there is a person on the seat during idling, when an object is placed, and when there is nothing. Figure 9 shows that when there is a person on the seat while driving,
This is the power spectrum when there is nothing when an object is placed. When a person is present, X is added to the power spectrum in the figure.
The maximum point appears at 1, X2. When an object is placed on the seat, maximum points appear in Y1 and Y2 in the power spectrum in the figure. If there is nothing on the seat, X1 is a certain value X
It becomes less than o or there is no clear maximum in the power spectrum. X1, X2, Y1, and Y2 vary depending on the material of the seat, its secular change, the state of the seat surface such as a cushion placed on the seat, and the vibration characteristics of the vehicle such as the engine speed. However, X1 and X2 appear in the region where the frequency is less than f4, and Y1 and Y2 appear in the region where f4 and above.
f4 can be obtained by experiment.

Based on the above, the determining means 17 determines that a person is present when the power spectrum has a maximum point in the region less than f4, and determines that the power spectrum has a maximum point in the region greater than f4. It is determined that a person is absent if there is a maximum point in the area less than f4 and its power is less than Xo, or if the maximum point is not in any area. FIG. 10 shows a flowchart of the above determination.

In the conventional in-vehicle presence detection device, when the material used for the seat is different depending on the vehicle type or option, or the engine speed during idling is changed depending on the maintenance condition, the output of the piezoelectric element is output. Since the vibration characteristic of the signal changes and the signal level of the output signal of the filter decreases, there is a problem that erroneous detection occurs in the presence detection. In the first embodiment, the frequency characteristic of the filter is set based on the factors that determine the vibration characteristics of the vehicle, such as the material of the seat and the engine speed, so that the above false detection is eliminated. If the material of the above-mentioned material deteriorates with time or a cushion or the like is placed on the seat, the vibration characteristic changes as in the conventional example, and the output signal of the filter decreases, resulting in erroneous detection in the presence detection. However, due to the above operation, in the present embodiment, even if there is a change in the vibration characteristic as described above, the presence or absence of the seat is detected by the region in which the maximum value of the power spectrum appears, so that there is an effect that there is no false detection.

In the first and second embodiments, the piezoelectric element is used as the vibration detecting means, but the vibration detecting means of the present invention is not limited to the piezoelectric element, and other types such as a capacitance type vibration sensor may be used. Vibration detecting means having a configuration may be used.

Although the embodiments of the present invention have been described above, industrial applications of the vehicle seat detection apparatus according to the present invention include buses and trains.
It can be applied as a management system for the number of seats and vacant seats in passenger cars. When applied to the air conditioning control and sound field control in the vehicle, the air conditioning control and the sound field control can be performed according to the seating location in the vehicle, and the comfort in the vehicle is enhanced.

[0027]

As described above, according to the in-vehicle seat detection device of the present invention, the following effects can be obtained.

That is, in the conventional in-vehicle seat detection device,
For example, if the material used for the seat varies depending on the vehicle model or options, or if the engine speed during idling changes due to maintenance conditions, etc., the vibration characteristics of the output signal of the piezoelectric element will change, and the output signal of the filter will change. However, according to the present invention, the frequency of the filter is determined based on the factors that determine the vibration characteristics of the vehicle, such as the seat material and the engine speed, according to the present invention. Since the characteristics are set, there is an effect that the above-mentioned erroneous detection can be eliminated without a decrease in the output signal of the filter.

Regarding the factors of the seat material among the above factors, the frequency characteristic of the seat is not individually measured for each vehicle to set the frequency characteristic of the filter, but the type of the seat is set by the seat selecting means at the time of shipment. If selected, the frequency characteristic can be set, which has the effect of simplifying the setting operation.

Regarding the factors depending on the engine speed among the above factors, since the frequency is detected and the frequency characteristics of the filter are sequentially set, it is necessary to perform an operation such as observing the number of rotations. There is an effect that it is not practical.

Further, when the seat material is aged and a cushion or the like is placed on the seat, the vibration characteristic changes as in the conventional case and the output signal of the filter is lowered to cause erroneous detection. Even if there is a change in the vibration characteristic as described above, the presence or absence of the seat is detected by the region where the maximum value of the power spectrum appears, so that there is an effect that no false detection occurs.

[Brief description of drawings]

FIG. 1 is a block diagram of a vehicle seat detection device according to a first embodiment of the present invention.

FIG. 2 is a power spectrum diagram of the output signal of the piezoelectric element when the hardness of the seat is changed in the device.

FIG. 3 is a power spectrum diagram of an output signal of the piezoelectric element when the engine speed is changed in the device.

FIG. 4 is a characteristic diagram of the type of seat and the center frequency f1 of the filter.

FIG. 5: Engine speed and filter center frequency f
Characteristic diagram with 2

FIG. 6 is a flowchart for seat determination of the device.

FIG. 7 is a block diagram of a vehicle seat detection device according to a second embodiment of the present invention.

FIG. 8 is a power spectrum diagram of an output signal of a smoothing unit when the device is idling.

FIG. 9 is a power spectrum diagram of the output signal of the smoothing means when the apparatus is running.

FIG. 10 is a flowchart for seat determination of the device.

FIG. 11 is a block diagram of a conventional vehicle seat detection device.

FIG. 12 is a power spectrum diagram of the output signal of the piezoelectric element when the device is idling.

FIG. 13 is a power spectrum diagram of the output signal of the piezoelectric element when the device is running.

[Explanation of symbols]

 1 Seat 2 Piezoelectric element 3, 4 Filter 5, 6 Amplifying means 7, 8 Smoothing means 9 Judging means 10 Dip switch 11 Rotation speed detecting means 12 Frequency characteristic setting means 13 Amplifying means 14 Smoothing means 15 Frequency analyzing means 16 Maximum point Computing means 17 Judging means

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Bunichi Shiba 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Inside Honda Research Laboratory

Claims (4)

[Claims] 1. A vibration detecting means disposed in a vehicle seat,
A plurality of filters for filtering each specific frequency component of the output signal of the vibration detection means, a frequency characteristic setting means for setting a frequency characteristic for filtering the filter based on a vibration characteristic of the vehicle, and each of the filters. An in-vehicle seat detection device, comprising: a determination unit that determines the presence or absence of a person in the seat based on an output signal. 2. The in-vehicle seat according to claim 1, further comprising seat selecting means for selecting a type of seat, and the frequency characteristic setting means sets a frequency characteristic for filtering by a filter based on an output signal of the seat selecting means. Detection device. 3. A rotation speed detecting means for detecting the rotation speed of the engine is provided, and the frequency characteristic setting means sets the frequency characteristic for filtering the filter based on the rotation speed signal from the rotation speed detecting means. In-vehicle seat detection device according to 1. 4. A vibration detecting means arranged in a vehicle seat,
Frequency analysis means for performing a fast Fourier analysis or the like to calculate the power spectrum of the output signal of the vibration detection means, maximum point calculation means for obtaining the maximum point of the power spectrum, and the seat based on the power and frequency of the maximum point In-vehicle seat detection device, which comprises a determination means for determining the presence or absence of a person in the vehicle.