JP2002067765A - Occupant discrimination system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity by shortening time required for calibration in an occupant discrimination system. SOLUTION: In a calibration process, a final output of a sensor cell is estimated before an output of the sensor cell is stabilized to calibration pressure loaded on a seat, and the estimated value (final output) is taken as a real sensor output for conducting sensitivity adjustment. For example, response characteristics of the sensor cell to an input method to be conducted in real calibration are preliminarily determined, and the response characteristics are compared with output change (tendency estimated based on two or more points) of the sensor cell after the calibration pressure is loaded to estimate the final output. Otherwise, a preload larger than the calibration pressure is once loaded before the specified calibration pressure is loaded, and then the specified calibration pressure is loaded to estimate the final output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an occupant discriminating system for discriminating the presence or absence and type of an occupant on a seat from the output of a sensor incorporated in a seat (lower part of a seat) for an automobile.

[0002]

2. Description of the Related Art Conventionally, as a safety measure to protect an occupant from the impact of a vehicle accident, it is mandatory to wear a seat belt. Therefore, when the seat belt is not worn, a warning light is turned on or a buzzer sounds to warn the occupant that the seat belt is worn. In recent years, the number of vehicles equipped with airbags has been increasing rapidly.For example, vehicles equipped with airbags in the passenger seat have a passenger seat in the event of an accident despite the fact that no occupant is sitting in the passenger seat. Air bag will open.

Therefore, a technique has been put to practical use to prevent the airbag in the passenger seat from opening when the occupant is not sitting in the passenger seat. In order to warn the user of the seat belt and prevent the airbag in the passenger seat from opening, it is necessary to detect in advance whether the occupant is sitting on the seat or not. As a method for detecting the presence or absence of the occupant, an occupant detection system incorporating a pressure-sensitive sensor inside a seat is known.

[0004]

The following dangers have been pointed out because an airbag equipped as a safety device has a large inflation force when opened. For example, in a vehicle in which a passenger seat is equipped with an airbag, when a child is sitting in the passenger seat, the inflation force of the airbag becomes an impact force, which may have an unexpected adverse effect on the child. Therefore, for example, when the occupant in the passenger seat is a child, it is better not to operate the airbag in the passenger seat or to control the inflation force of the airbag so as to reduce the impact.

Here, it is conceivable to use the above-described occupant detection system as a means for determining whether the occupant in the passenger seat is a child or an adult. That is, if the load detected by the pressure sensor incorporated in the seat is larger than a predetermined value, it can be determined that the vehicle is an adult, and if the load is smaller than the predetermined value, it is determined that the vehicle is a child. However, when judging whether it is a child or an adult only by the magnitude of the load detected by the pressure-sensitive sensor, there are the following problems.

First, even if the occupant is an adult, if the occupant leans his or her back on a seat back (backrest), the more the seatback is tilted, the more the load detected by the pressure sensor becomes. It will be smaller. Second, when a child-only seat (such as a baby seat, a child seat, or a junior seat) is used in the passenger seat, the weight of the child-specific seat is added to the weight of the child, so that the load increases. Third, when a child-only seat is used, the child-only seat is fixed to the passenger seat with a seat belt.
The load detected by the pressure sensor changes depending on the magnitude of the fastening force of the seat belt.

As a result, it is extremely difficult for a conventional occupant detection system to accurately determine whether a child or an adult. Therefore, the present applicant has developed an occupant discrimination system that can correctly discriminate between a child and an adult regardless of the presence or absence of a child-only seat. This occupant discriminating system incorporates a sensor mat in which a plurality of sensor cells are arranged on a plane inside a seat (at a lower portion of a seating surface), and calculates the occupant's weight based on the total load detected from the output values of the individual sensor cells and the load distribution. The determination is performed.

For example, the load distribution detected from the output value of each sensor cell is large when a person directly sits on a seat regardless of whether the person is an adult or a child, or when a child-only seat is used. Since they are different, the presence or absence of a child-specific seat can be detected based on the load distribution. Also, even if you are not using a child-only seat,
It is possible to more accurately determine whether a child or an adult by taking into account the determination based on the load distribution instead of determining whether the child or an adult is based solely on the sum of the loads detected by the individual sensor cells.

In the occupant discriminating system, when the sensitivity of each sensor cell arranged on the sensor mat varies, when the load distribution on the seat is detected from the output of each sensor cell, the actual load distribution is not always determined. There may be cases where they do not match. Therefore, in the manufacturing stage of the sheet, after attaching the sensor mat and attaching the skin of the sheet, an operation of adjusting the sensitivity of each sensor cell (referred to as calibration) is performed. In this calibration, a known surface load (calibration pressure) is applied to the sheet, and the sensitivity of each sensor cell is adjusted so that a desired value is output from each sensor cell with respect to the surface load.

However, since the sensor cell has a time delay until the output is stabilized with respect to the applied load, if the sensitivity is adjusted after the output of the sensor cell is stabilized,
The time required for calibration becomes longer.
As a result, there is a problem that productivity is reduced in the mass production process. The present invention has been made based on the above circumstances, and an object of the present invention is to improve productivity by reducing the time required for calibration in an occupant discriminating system.

[0011]

(Means for Solving the Problems) In a manufacturing step of a sheet, a predetermined calibration pressure is applied to a sheet in which a sensor mat is incorporated, and the sensitivity of the sensor cell is determined from an output of the sensor cell with respect to the calibration pressure. In the calibration step, before the output of the sensor cell is stabilized with respect to the calibration pressure, the final output at which the output of the sensor cell is stabilized is estimated, and based on the estimated final output, And adjust the sensitivity of the sensor cell. In the present invention, the calibration is performed by estimating the final output of the sensor cell before the output of the sensor cell is stabilized, so that the time required for the calibration can be reduced.

(Claim 2) In the occupant discriminating system according to claim 1, the final output is estimated from a change in the output of the sensor cell after the calibration pressure is applied.

According to a third aspect of the present invention, in the occupant discriminating system according to the second aspect, a response characteristic representing a correlation between an input and an output of the sensor cell is determined in advance, and a final output is estimated from the response characteristic. Features.

According to a fourth aspect of the present invention, in the occupant discriminating system according to the third aspect, the final output is estimated according to a rate at which the output change rate of the sensor cell decreases.

According to a fifth aspect of the present invention, in the occupant discrimination system according to the first aspect, in the calibration step, before applying a predetermined calibration pressure on the seat, a pre-load larger than the calibration pressure is temporarily applied. Thereafter, a predetermined calibration pressure is applied.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings. First, a configuration and a manufacturing process of the seat 1 used in the occupant identification system will be described. The seat 1 is a seat cushion for receiving the buttocks of the occupant, and as shown in FIG. 5, a table 3 supported by a slide rail 2, a seat form (hereinafter abbreviated as form 4) installed on the table 3, and a form. 4, the sensor mat 6 (see FIG. 4) is incorporated between the foam 4 and the sheet skin 5.

The foam 4 forms a base portion (base) of the sheet 1, and has a suspension groove 7 (see FIG. 4) for narrowing the sheet skin 5 on the upper surface thereof. The sheet skin 5 is squeezed into the inside of the foam 4 along the suspension groove 7, and the squeezed portion (trench portion) is formed as a design in appearance. On the back surface of the sheet skin 5, the sheet skin 5
An ear hook portion 8 (see FIG. 7) for narrowing the inside of the suspension groove 7 of the foam 4 is provided so as to hang down like a bag. In addition,
In the following description, with respect to the foam 4, the portion surrounded by the two suspension grooves 7 is referred to as a center portion, the portion outside the suspension groove 7 is referred to as a side portion, and the sheet skin 5 is surrounded by the ear hook portions 8. The portion is referred to as a central portion, and the portion outside the ear hook portion 8 is referred to as a lateral trim.

As shown in FIG. 4A, the sensor mat 6 has a first sensor portion 6A arranged at the center of the foam 4.
And second sensor portions 6 arranged on both side portions of the form 4
B, and a plurality of sensor cells 9 are arranged respectively. The sensor cell 9 is, for example, a pressure conversion element whose resistance value changes according to the pressure, and the plurality of sensor cells 9 arranged on the sensor mat 6 can independently detect the pressure. The sensor mat 6 is a printed circuit board 1
0 is connected to the ECU 11 through the individual sensor cells 9.
The ECU 1 converts a change in pressure detected by the ECU into an electrical signal and
1 is output.

The ECU 11 is an electronic control unit incorporating a microcomputer, as shown in FIG.
Form 4 is incorporated in the center of the rear end. This EC
U11 detects the sum of the loads applied to the seat and the load distribution from the output signals of the individual sensor cells 9 and, based on the detection results, the presence or absence of an occupant described below, the presence or absence of a child-specific seat, and the Perform adult discrimination.

A) Presence or absence of an occupant The sum of the loads detected by the individual sensor cells 9 is calculated. If the sum is equal to or greater than a predetermined value, it is determined that the occupant is sitting on the seat 1. If the value is smaller than the predetermined value, the seat 1 is determined. It is determined that no occupant is sitting. b) Presence / absence of a child-only sheet The load distribution on the sheet is detected from the output signals of the individual sensor cells 9, and it is determined whether or not the child-specific sheet is used based on a shape pattern estimated from the load distribution. c) Discrimination between children and adults It is finally determined whether a child or an adult by taking into account the criterion based on the sum of the loads and the criterion based on the load distribution.

Next, the manufacturing process of the sheet 1 will be described. FIG. 6 is a flowchart showing the manufacturing process. Step10… Place Form 4 on stand 3. Step 20: The sensor mat 6 is arranged at a predetermined position on the upper surface of the form 4. Here, by temporarily fixing the sensor mat 6 to the form 4, when attaching the next sheet skin 5,
The displacement of the sensor mat 6 can be prevented. Step30: Attach the sheet skin 5.

The work of attaching the sheet skin 5 is generally performed in the following procedure. First step: First, as shown in FIG. 7 (a), the center of the sheet skin 5 is arranged so as to match the center of the foam 4, and the wire 12 passed through the ear hook 8 and the inside of the foam 4 The hook 13 is simultaneously hooked with the C-shaped hog ring 14, and the hog ring 14 is closed and tightened, so that the central portion of the sheet skin 5 covers the central portion of the foam 4.

Second step: Subsequently, the horizontal trim is turned to the side surface of the foam 4 so as to wrap the outside of the side portion of the foam 4, and the hook 5a provided at the end of the horizontal trim is mounted on the base 3.
Work to hook on the outer edge part. At this time, in order to prevent the horizontal trim from being loosened (wrinkled), tension is applied to the horizontal trim in an assembled state.
That is, as shown in FIG. 7B, the work of assembling the horizontal trim is performed in a state where the foam 4 is pressed and crushed from above and below, and the hook 5a of the horizontal trim is attached to the outer edge of the base 3 or the like. After hooking, the pressure from the vertical direction is removed. As a result, the side trim of the horizontal trim is applied from the side of the foam 4 in a state where the tension is applied (no slack).
It can be stuck over the side of.

Step 40: A calibration step is performed. This calibration step adjusts the sensitivity of each sensor cell 9 incorporated inside the sheet, and is performed in the following procedure. First, as shown in FIG. 1, a bag-shaped big bag 15 is arranged on the seating surface of the seat 1, and a predetermined calibration pressure is applied to the seat via the big bag 15. Next, the calibration controller 16 reads the output value of each sensor cell 9 from the ECU 11 and compares the output value with the calibration pressure to calculate the calibration value. Subsequently, the calibration value calculated by the calibration controller 16 is input to the ECU 11.

Here, the calibration method will be described based on the response characteristic diagram of FIG. (1) When obtaining pressure. When the same sensor output O1 has the actual characteristic obtained when the pressure Pi is applied to the target characteristic that the sensor output O1 is obtained when the pressure Pa is applied, a) the calibration value is set to C1 = Pi / Pa From the actual sensor output, the calibration value C
Multiply by 1 to get the actual pressure. b) Assuming that the calibration value is C2 = Pi-Pa, the pressure with respect to the actual sensor output is obtained from the target characteristic, and the calibration value C
Add 2 to get the actual pressure.

(2) When the sensor output is determined. In contrast to the target characteristic in which the sensor output Oa is obtained when the pressure Pi is applied, the sensor output Oa is obtained when the same pressure Pi is applied.
1) When the actual characteristic is obtained, c) Set the calibration value to C3 = Oa / O1, and calibrate the sensor output by multiplying the actual sensor output by the calibration value C3. d) The calibration value is set to C4 = Oa-O1, and the calibration value C4 is added to the actual sensor output to calibrate the sensor output.

In the above-described calibration step, the individual sensor cells 9 are adjusted with respect to the calibration pressure applied to the sheet 1.
If the sensitivity adjustment is performed after the output of stabilizes, the time required for the calibration process becomes longer. Therefore, before the output of the sensor cell 9 is stabilized, the final output of the sensor cell 9 (the final convergence stable point of the sensor output with respect to the calibration pressure) is estimated, and the estimated value (final output) is regarded as the actual sensor output. The sensitivity is adjusted. Hereinafter, a method of estimating the final output of the sensor cell 9 will be described.

(First Method) A final output is estimated from an output change (a tendency estimated from two or more points) of the sensor cell 9 after the calibration pressure is applied. For example, the response characteristics of the sensor cell 9 to the input method performed in the actual calibration (see FIG. 2A) are obtained in advance, and the response characteristics and the output change (2) of the sensor cell 9 after the calibration pressure is applied. And the final output is estimated.

A specific example using the time constant in the first method will be described. It is assumed that it is known that the sensor cell 9 has a time constant Δt for a step-like input. In this case, it means that the output reaches about 63% of the final output after the time Δt has elapsed after the input of the step-like input. Therefore, the output at the point c at the time Δt after the input of the step-like input is measured, and the final output can be estimated as 1 / 0.63 of the value. Further, to increase the accuracy, Δt
It is conceivable to use the value of the intermediate point b up to and the value of the point d after Δt as an auxiliary.

(Second Method) As shown in FIG. 2B, before a predetermined calibration pressure is applied, a pre-load larger than the predetermined calibration pressure is once applied, and then the predetermined calibration pressure is returned to the predetermined calibration pressure. Estimate final output. A specific example using the time constant in the second method will be described. The solid line graph shown in FIG. 2B shows a change in sensor output when a preload is applied prior to the calibration pressure. A broken line graph A shows a change in the sensor output when the same load as the pre-load larger than the calibration pressure is continuously applied. A broken line graph B shows a change in sensor output when a calibration pressure is applied from the time of input, as in the case of FIG.

For example, the pre-load is set to 1 / 0.6 of the calibration pressure.
The pressure is tripled, and the load time is approximately the time constant Δt of the sensor.
As a result, the output at the time point b when the pressure is returned to the predetermined calibration pressure at time Δt after the input is applied becomes close to the final output at the point d. Therefore, it is possible to estimate the final output with the output of the point b or the point c slightly apart from the point b. Further, in the first and second methods, a method using a general time constant has been exemplified. However, when the relationship between time and output change is known, an estimation method using the output relationship at other times is used. It is also possible to use.

(Effects of the present embodiment) In the occupant discriminating system of the present embodiment, in the calibration process performed in the manufacturing stage of the seat 1, the applied calibration pressure is
By estimating the final output and adjusting the sensitivity before the output of the sensor cell 9 becomes stable, the time required for the calibration step can be reduced. As a result, productivity can be improved and product cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of calibration.

FIG. 2 is a graph showing changes in calibration pressure and sensor output.

FIG. 3 is a response characteristic diagram of a sensor cell.

FIG. 4 is a plan view of a foam having a sensor mat (a).
It is a side view (b).

FIG. 5 is an exploded perspective view of a sheet.

FIG. 6 is a manufacturing process diagram of a sheet.

FIG. 7 is a process chart when assembling a sheet skin.

[Explanation of symbols]

 1 sheet 6 sensor mat 9 sensor cell

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[Procedure amendment]

[Submission date] August 29, 2000 (2008.2.
9)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Claims (5)

[Claims] An occupant discriminating system for incorporating a sensor mat having a plurality of sensor cells arranged on a plane into a vehicle seat and discriminating the presence or absence and type of an occupant on the seat from an output of each of the sensor cells, A step of applying a predetermined calibration pressure to the sheet in which the sensor mat is incorporated in a sheet manufacturing stage, and adjusting a sensitivity of the sensor cell based on an output of the sensor cell with respect to the calibration pressure; The step of estimating a final output at which the output of the sensor cell is stabilized before the output of the sensor cell is stabilized with respect to the calibration pressure, and performing sensitivity adjustment of the sensor cell based on the final output. Crew discrimination system. 2. The occupant discriminating system according to claim 1, wherein the final output is estimated from an output change of the sensor cell after the calibration pressure is applied. 3. The occupant discriminating system according to claim 2, wherein a response characteristic representing a correlation between an input and an output of the sensor cell is obtained in advance, and the final output is estimated from the response characteristic. Occupant identification system. 4. The occupant discriminating system according to claim 3, wherein the final output is estimated according to a rate at which the output change rate of the sensor cell decreases. 5. The occupant discriminating system according to claim 1, wherein in the calibration step, before applying a predetermined calibration pressure on the seat, a pre-load larger than the calibration pressure is once applied, and thereafter, An occupant discriminating system, wherein the predetermined calibration pressure is applied.