JP2000118348A - Method and device for judging vehicle collision - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the stand-by time needed until is becomes possible to judge collision after the input of a power supply, without using an expensive acceleration sensor. SOLUTION: A sampling portion 101 samples the output voltages of an acceleration sensor 20. An operating condition judgment part 104 determines the start of collision judgment on the basis of a sampling result V (Gm) before the start of the collision judgment. A data renewal part 106 outputs the previous sampling result V (Gn-1) in response to the current sampling result V (Gn) after the start of the collision judgment. An average value computing part 102 computes the average value Vave of the sampling result V (Gm). A collision judgment part 108 desides collisions on the basis of comparison results V (ΔG1) given by a comparison part 105, for a first time, and on the basis of comparison results V (ΔG2) given by a comparison part 107, for a second time and thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for determining a vehicle collision based on an acceleration signal output from an acceleration sensor.

[0002]

2. Description of the Related Art An occupant protection device such as an airbag or a seatbelt pretensioner is connected to a vehicle collision determination device that determines a collision based on acceleration generated in a vehicle, and the collision determination device makes a collision determination. Then, the ignition device of the airbag and the pretensioner is activated. The vehicle collision determination device includes an acceleration sensor that detects an acceleration generated in the vehicle, and a collision determination unit that determines a collision of the vehicle based on an acceleration signal detected by the acceleration sensor.

FIG. 5 is a flowchart showing a collision judging method by a conventional collision judging device. As an acceleration sensor, an output guarantee range in a "zero G" state where no acceleration occurs, for example, a reference voltage 2. 5V ± 0.05V
An expensive high-precision type that is guaranteed is used.

In step S30, a predetermined initial process is executed in the collision judging section. In step S31, an initial value "1" is set to a count value n indicating the number of times of sampling of the acceleration.

In step S32, a voltage V (G) output from the acceleration sensor in response to the current acceleration G is sampled. In step S33, it is determined whether or not a predetermined time necessary for stabilizing the acceleration sensor has elapsed since the power was turned on. When the predetermined time has elapsed, the process proceeds to step S34. In step S34, the output voltage V (Gn), that is, V (G1) of the acceleration sensor sampled in step S32 is in the output range (2.
5 V ± 0.05 V).

Generally, immediately after the power is turned on, the output V (Gn) of the acceleration sensor is not stable. For example, as shown in FIG. It falls and falls within the guaranteed output range in the “zero G” state. Therefore, the subsequent collision determination unit starts the collision determination after the output voltage falls within the output guarantee range of 2.5V ± 0.05V, and sets the collision determination start flag Fstable in step S35.

In step S36, it is determined whether or not it is the first collision determination after the output of the acceleration sensor is stabilized. Since it is the first collision determination, the process proceeds to step S37. In step S37, 2.5V corresponding to the reference voltage is subtracted from the sampled output voltage V (Gn), that is, V (G1), and is updated and registered as the difference V (ΔG).

On the other hand, if it is determined in step S36 that it is the second or subsequent collision determination, step S3
At 8, the output voltage of the acceleration sensor 20 is sampled as the current sampling result V (Gn). In step S39, the difference V (ΔG) between the current sampling result V (Gn) and the previous sampling result V (Gn-1) is obtained.
Is required. In step S40, each difference V (Δ
G), and if the collision determination is not made because the difference V (ΔG) is small, step S42
In step S, the count value n is incremented.
Return to 36. When a collision is determined in step S40, the airbag is activated in step S41.

Thus, in the second and subsequent collision determinations,
Collision determination is performed (step S39) based on the difference V (ΔG) between the current sampling result V (Gn) and the previous sampling result V (Gn−1). However, the first time of the collision determination is “the previous sampling result V (Gn−1
)), There is no V (G0). Therefore, in the prior art, "2.
5V "is adopted as the" previous sampling result V (G0) "in the first collision determination.

[0010]

The collision in a vehicle is
It may occur not only during normal running but also immediately after turning on the ignition switch. For example, in a vehicle with a manual transmission, if the engine key is accidentally turned in a gear position other than neutral, the vehicle may move and collide.In such a case, the collision occurs after the ignition switch is turned on. The time to reach is negligible. Therefore, in the vehicle collision determination device as well, it is desirable to reduce the standby time from when the ignition switch is turned on until the collision determination becomes possible.

However, in the above-mentioned prior art, 1
In the second collision determination, the previous sampling result V
(Gn-1), that is, a reference voltage Vre instead of V (G0).
f (= 2.5 V) is substituted as a fixed value. Therefore, in order to accurately perform the collision determination from the first time, it is necessary to use a high-accuracy acceleration sensor whose output guarantee range is about the reference voltage Vref ± 0.05 V.
There was a problem that cost reduction was difficult.

Further, as an output guarantee range, the reference voltage V
FIG. 4 shows a comparison between the time required for stable operation of an inexpensive acceleration sensor whose ref ± 0.05 V is guaranteed and that of an inexpensive acceleration sensor whose reference voltage is Vref ± 0.2 V, for example. Meanwhile, an inexpensive acceleration sensor reaches a stable state at time t1, whereas an expensive acceleration sensor does not stabilize until time t2. Therefore,
In the above-described related art, there is a problem that a standby time from when the power is turned on until a collision determination becomes possible becomes long.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to shorten the standby time from when the power is turned on to when a collision can be determined without using an expensive acceleration sensor. An object of the present invention is to provide a collision determination method and device.

[0014]

Means for Solving the Problems In order to achieve the above object, the present invention is characterized in that the following means are taken. (1) In a vehicle collision determination method in which an output signal of an acceleration sensor is sampled and a vehicle collision is determined based on the sampling result, the operation state of the acceleration sensor is determined based on the sampling result, and the operation of the acceleration sensor is stabilized. The average value of the sampling result is obtained until the operation of the acceleration sensor is stabilized, and sampling for collision determination is started. In the first collision determination, a collision is determined based on the current sampling result and the average value. In the second and subsequent collision determinations, the collision is determined based on the current sampling result and the previous sampling result. (2) In a vehicle collision determination device that detects a vehicle collision and activates an occupant protection device such as an airbag, an acceleration sensor, a sampling unit that samples an output signal of the acceleration sensor, and an operation state of the acceleration sensor are determined. Operating state determining means, average value calculating means for calculating an average value of the sampling result, first comparing means for comparing the current sampling result with the average value, and a current sampling result and a previous sampling result. When the operation state of the acceleration sensor is determined to be stable by the second comparison means for comparing the acceleration sensor, the collision is determined based on the comparison result by the first comparison means, and thereafter, And a collision judging means for judging a collision based on the comparison result by the second comparing means.

According to the above configuration, the average value of the sampling results of the acceleration sensor is obtained until the operation of the acceleration sensor is stabilized. When the operation of the acceleration sensor is stabilized, the first collision determination determines Is determined based on the difference between the sampling result of the above and the average value up to the previous time.

Here, the difference between the current sampling result of the acceleration sensor and the average value up to that point is small irrespective of the absolute value of the sampling result if there is no change in acceleration, and if there is a change in acceleration. growing. Therefore, according to the above-described configuration, accurate collision determination can be performed from the first collision determination without using a high-accuracy acceleration sensor.

Furthermore, compared to the case of using a high-precision acceleration sensor, the time required for the operation of the acceleration sensor to be stable is shorter, so that the standby time from power-on to the time when collision determination can be performed is shorter.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of a vehicle occupant protection device to which the present invention is applied. The acceleration sensor 20 detects acceleration generated in the front-rear direction of the vehicle and outputs an acceleration signal. This acceleration sensor 20
The output guarantee range in the “zero G” state where no acceleration occurs is a low-priced version with a reference voltage of 2.5 V ± 0.2 V.

The acceleration signal output from the acceleration sensor 20 is converted into a digital signal by an A / D converter
It is input to PU10. When receiving the acceleration signal, the CPU 10 executes a collision determination program stored in the ROM 51 in advance, and controls the switching transistor 71 as an airbag activation unit. The RAM 52 functions as a work area when executing the collision determination program.

The squib resistance 61a of the airbag 61 is:
One end is connected to the power supply line L, and the other end is grounded via the switching transistor 71, respectively. The squib resistor 61 is connected to the power line L.
A capacitor 73 and a battery 74 for supplying a current to a are connected.

FIG. 2 is a functional block diagram of the CPU 10, and the same reference numerals as those described above denote the same or equivalent parts.

The sampling unit 101 includes the acceleration sensor 2
The output voltage V (G) of 0 is sampled at a predetermined cycle. The average value calculation unit 102 calculates and outputs an average value Vave of the sampling results V (Gm) before the start of the collision determination. The operation state determination unit 104 refers to the sampling result V (Gm) of the acceleration sensor 20 and
If (Gm) is within the range of the reference voltage Vref ± 0.2 and the difference between the sampling result V (Gm) and the average value Vave is equal to or less than a predetermined value, a collision determination start signal A2 is output. The average value calculator 102 calculates the average value Vave until the collision determination start signal A2 is detected.

After the start of the collision determination, the comparator 105 outputs a difference V (ΔG1) between the first sampling result V (G1) and the average value Vave. Data update unit 106
Outputs the previous sampling result V (Gn-1) every time the sampling unit 101 outputs the current sampling result V (Gn).

The comparator 107 outputs a difference ΔV (Gn) between the second and subsequent sampling results V (Gn) and the previous sampling result V (Gn−1) after the start of the collision determination. Upon receiving the collision determination start signal A2, the collision determination unit 108 performs a collision determination based on the first difference ΔV (G1) or the second and subsequent differences ΔV (Gn). An airbag activation signal A1 is output. As a result, the switching transistor 71 is turned on, a current flows from the capacitor 73 and the battery 74 to the squib resistance 61a of the airbag 61, and the airbag 61 is deployed.

Next, the operation of the present invention will be described in detail with reference to the flowchart of FIG. In step S11,
The CPU 10 executes a predetermined initial process. In step S12, before the start of collision determination, the sampling unit 1
01 is set to a count value m indicating the number of times the acceleration is sampled, an initial value “1” is set, and the integrated value of the sampling result V (Gm) before the start of the collision determination ΔVm
Is reset.

In step S13, the current output voltage V (Gm) of the acceleration sensor 20 is sampled by the sampling unit 101. In step S14, the average value calculation unit 102 calculates the integrated value ΣVm of the sampling result V (Gm). In step S15, an average value Vave of the sampling results V (Gm) is obtained based on the number of samplings m and the integrated value ΔVm up to the present.

In step S16, the operation state determination unit 104 determines whether or not the current sampling result V (Gm) falls within the output guarantee range of 2.5V ± 0.2V in the "zero G" state. If it is determined that the output is within the output guaranteed range, the operation state determination unit 104 further determines in step S17 whether the operation of the acceleration sensor 20 is stable, that is, whether the output fluctuation width of the acceleration sensor 20 is small. Is done. In the present embodiment, the current sampling result V
(Gm) and the average value Vave up to now are ± 0.00
If it is within 5 V, it is determined that the operation of the acceleration sensor 20 is stable, and the process proceeds to step S18.

In step S16, the output voltage V
If (Gm) is determined to be out of the guaranteed output range, or if the output fluctuation width is determined not to be sufficiently small in step S17, the average value calculation unit 102 determines in step S27 that the number of samplings m
Is incremented by "1", and then the process returns to step S13.

In step S18, an initial value "1" is set to a count value n indicating the number of samplings after the start of the collision determination. In step S19, a collision determination start flag Fstart is set, and the collision determination start signal A2 is
It is output from the operation state determination unit 104 to the average value calculation unit 102 and the collision determination unit 108.

In step S20, the current output voltage V (Gn) of the acceleration sensor 20 is sampled by the sampling unit 101 as a current sampling result. In step S21, it is determined whether or not it is the first collision determination, that is, whether or not the count value n is "1". Since it is the first time, the process proceeds to step S22. In step S22, the comparing unit 105 causes the first
The result of the second sampling, V (Gn), that is, V
From (G1), the average value Vave of the sampling results until immediately before the start of the collision determination is reduced to obtain a difference V (ΔG1).

On the other hand, if it is determined in step S21 that the collision determination is for the second time or later (n ≧ 2), then in step S23, the current sampling result V (Gn) is obtained.
ΔV between the previous sampling result V (Gn-1)
(ΔGn) is obtained by the comparison unit 107. That is, in the case of the second collision determination, the second sampling result V (G2) and the first sampling result V (G1)
Is obtained, and if the collision is determined for the third time, the difference V (ΔG3) between the third sampling result V (G3) and the second sampling result V (G2) is obtained.

At step S24, the first difference V (ΔG1) or the second and subsequent differences ΔV (ΔGn
) Is performed, and if no collision determination is made, in step S25, the count value n
Is incremented by "1". When a collision is determined, the airbag 61 is deployed in step S26.

As described above, according to the present embodiment, until the operation of the acceleration sensor 20 is stabilized, the average value Vave of the sampling result V (Gm) of the acceleration sensor 20 is obtained.
When the collision determination is started when the operation is stable, the first
In the second collision determination, the current sampling result V (G1
) And the difference between the average value Vave of the previous sampling results and the collision determination are executed.

Here, the difference between the sampling result V (G1) immediately after the start of the collision judgment of the acceleration sensor 20 and the average value Vave of the sampling results up to that point is the sampling result V (G1) if there is no change in acceleration. Becomes smaller irrespective of the absolute value of, and becomes larger if the acceleration changes. Therefore, according to the present embodiment, accurate collision determination can be performed from the first collision determination without using a high-accuracy acceleration sensor.

Furthermore, according to the present embodiment, the time required for the operation of the acceleration sensor to be stabilized is shorter than when a high-precision acceleration sensor is used. The waiting time can be shortened.

[0036]

According to the present invention, the following effects are achieved. (1) Until the operation of the acceleration sensor is stabilized, the average value Vave of the output voltage of the acceleration sensor is obtained. When the operation is stabilized and the collision determination is started, the first collision determination determines the current sampling result. Since the collision determination is performed based on the difference between V (G1) and the average value Vave of the sampling results immediately before the start of the collision determination, the first collision determination is performed without using a high-accuracy acceleration sensor. , It is possible to make an accurate collision determination. (2) Compared to using a high-precision acceleration sensor, the time required for the operation of the acceleration sensor to stabilize is shorter.
The waiting time from when the ignition switch is turned on until collision determination becomes possible can be shortened.

[Brief description of the drawings]

FIG. 1 is a block diagram of a vehicle collision determination device according to an embodiment of the present invention.

FIG. 2 is a block diagram functionally showing a configuration of a CPU 10 of FIG.

FIG. 3 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 4 is a diagram showing output voltage characteristics of an acceleration sensor.

FIG. 5 is a flowchart showing the operation of the conventional technique.

[Explanation of symbols]

10 CPU, 20 acceleration sensor, 30 A / D converter, 61 airbag, 61 a squib resistance, 71
Switching transistor, 73 ... capacitor, 74 ...
Battery

Claims (3)

[Claims] 1. A vehicle collision determination method for sampling an output signal of an acceleration sensor and determining a collision of a vehicle based on the sampling result, wherein an operation state of the acceleration sensor is determined based on the sampling result. The average value of the sampling results is obtained until the operation is stabilized. When the operation of the acceleration sensor is stabilized, sampling for collision determination is started. In the first collision determination, collision is performed based on the current sampling result and the average value. And in the second and subsequent collision determinations, a collision is determined based on a current sampling result and a previous sampling result. 2. A vehicle collision determination device for detecting a vehicle collision and activating an occupant protection device such as an airbag, comprising: an acceleration sensor; sampling means for sampling an output signal of the acceleration sensor; Operating state determining means for determining an operating state; average value calculating means for obtaining an average value of the sampling result; first means for comparing a current sampling result with the average value;
A second comparing means for comparing the current sampling result with the previous sampling result; and when the operation state determining means determines that the operation of the acceleration sensor has become stable, the first The collision is determined based on the comparison result by the comparing means.
And a collision judging unit for judging a collision based on a comparison result by the comparing unit. 3. The vehicle collision judging device according to claim 2, wherein the operation state judging means judges an operation state of the acceleration sensor based on an output voltage level of the acceleration sensor.