JPH07144602A - Collision sensor - Google Patents

Abstract

PURPOSE:To surely discriminate the intermediate/high speed soft crash, a low speed head-on collision, and the rough road pulse. CONSTITUTION:As collision sensor which detects the collision of a vehicle from the acceleration wave form G of an acceleration meter 1, and starts a driver protecting device such as an air bag 6 by a trigger circuit 5 is equipped with the first calculating means 41 which calculates the integration of the acceleration wave form G, the second calculating means 42 which calculates the magnitude of the vibration component from the acceleration wave form G, and a judging means 43 which judges the collision on the basis of the outputs supplied from the first and the second calculating means 41 and 42 and outputs a start signal into the trigger circuit 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collision sensor suitable for a vehicle collision detection used in a starting system for an occupant protection device such as an airbag.

[0002]

2. Description of the Related Art Conventionally, in this type of collision sensor, a low-speed frontal collision in which an occupant protection device must not be started (non-starting condition) and a medium-high speed oblique collision or pole collision in which the occupant protection device should be started ( There was a problem how to distinguish it from a soft crash (such as a collision with a pole). That is,
The acceleration waveforms of the low-speed frontal collision and the medium-high-speed diagonal collision or the pole collision are very similar at the start request timing of the occupant protection device and are difficult to distinguish. As shown in FIG. 5, the acceleration waveform of a low-speed frontal collision (shown by a dotted line) that does not require the starting of the occupant protection device and the medium-high speed diagonal that requires the starting of the occupant protection device. The acceleration waveform of the collision (shown by the solid line) is very similar to the start request timing (between) when it is necessary to determine whether or not to start the occupant protection device. Therefore, as shown in FIG. 6, a constant acceleration is subtracted (offset) from the acceleration waveform, and this subtracted acceleration is integrated with time (V
Even with the collision sensor 1 '), it is difficult to distinguish them and start the airbag within the required start time.
As a result, if the starting conditions are prioritized, unnecessary starting for a low-speed frontal collision will occur. On the contrary, when the non-starting condition is prioritized, there is a problem in that a start-up delay and a non-starting are caused by a soft crash such as a medium-high speed diagonal collision. In addition,
The above-mentioned offset is devised so that it does not operate when a pulse that does not affect the occupant is input during rough road travel.

Therefore, in Japanese Patent Application No. 2-74457 (see Japanese Patent Application Laid-Open No. 3-253441), the applicant detects a vehicle collision from the acceleration waveform of an accelerometer and uses a trigger circuit to install an occupant protection device such as an airbag. A collision sensor for starting, an integrating means for performing a peak cut on the acceleration waveform below a predetermined value to integrate over time, a subtracting means for subtracting a time integrated value of a predetermined function from the integrated value, and the subtraction integration A collision sensor is proposed which comprises a comparison means for comparing the value with a predetermined time function value. The operating principle of this collision sensor is as follows. First, both the acceleration waveforms of the low-speed frontal collision and the middle-high speed diagonal collision are almost equal in the average acceleration in the initial collision portion, which is the start request timing, but as shown in FIG. The waveform has a considerable vibration component due to buckling and vibration of the vehicle body. On the other hand, in the acceleration waveform of a low-speed frontal collision, most of the impact energy is absorbed by an energy absorbing device such as a bumper, so the vibration component is not so large. Focusing on the difference between the characteristics of the two acceleration waveforms, the one in which the troughs of the acceleration waveform are removed is time-integrated to obtain a subtraction integral value. The crash sensor, as shown in FIG. 7, the acceleration waveform G of collision is to calculate the time integral of the acceleration waveform G after exceeding a predetermined acceleration G1, and a peak cut below a predetermined value G _C , The peak-cut portion is time-integrated (vertical line portion), and a predetermined function (G ₀
The time integrated value ΔV ₀ (hatched portion) of −G _C ) is subtracted, and the subtracted integrated value is compared with a predetermined function serving as a threshold value to determine a collision. That is, the above-described subtraction integral value is obtained by offsetting the acceleration waveform G by the predetermined acceleration G ₀ , but is cut off below the predetermined acceleration G _C of the time integral value, and the integral A of the positive portion of the acceleration waveform after the offset is obtained. And G _{C and} below are the sums of the cut-off negative part integrals B. Therefore, compared to the case of a collision sensor that simply integrates after offsetting, the value becomes larger, and the acceleration waveform in the early stage of a collision of a medium-high speed soft crash that includes a large vibration component and the acceleration waveform of a low-speed frontal collision can be reliably identified. Is easy to judge.

[0004]

However, since the acceleration waveform for a collision varies depending on the vehicle type such as the rigidity of the vehicle body, it may be difficult to adjust the starting and non-starting conditions when applying the above-mentioned collision sensor. is there. That is, in the case of a vehicle having a collision characteristic as shown in FIG.
If the offset value is set to G ₀₂ , the amount of integration sufficient for the collision waveform G by the required start time t ₁ (hatched portion)
Occurs and the occupant protection device can be started,
An integral amount (hatched portion) is also generated for the rough load pulse G _R shown in FIG. 8B, and it becomes impossible to secure a safety factor for non-starting. On the other hand, if the offset value is set to G ₀₁ ,
Sufficient integration amount to the rough load pulse G _R shown in (b) (colored portion) is not generated, so that the safety factor ensures problem shown in Figure 8 of solves (a), by the impingement waveform G As a result, a sufficient amount of integration is not generated by the required start time t ₁ (colored portion), and the occupant protection device cannot be started.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to reliably discriminate a middle-high speed soft crash from a low speed frontal collision and a rough road pulse. It is to provide a possible collision sensor.

[0006]

In order to solve the above-mentioned problems, a collision sensor according to the present invention detects a collision of a vehicle from an acceleration waveform of an accelerometer and uses a trigger circuit to start an occupant protection device such as an airbag. A sensor,
A collision is determined based on outputs from the first calculation means, a first calculation means for calculating the integral of the acceleration waveform, a second calculation means for calculating the magnitude of the vibration component from the acceleration waveform. A determination means for outputting a starting signal to the trigger circuit is provided.

[0007]

[Operation] Average value of acceleration waveform (that is, collision energy)
And a vibration component are separated, and a rough road pulse or a collision is surely discriminated according to the magnitude of the collision energy, and a low-speed frontal collision or a medium-high speed soft crash is discriminated according to the magnitude of the vibration component.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. Although the deceleration side acceleration is described as a positive value here, making it negative has the same effect if the positive and negative logics in each block are matched.
1 is a functional block diagram showing the configuration of the collision sensor of the present invention, FIG. 2 shows the calculation processing of the collision sensor of FIG. 1, and is a graph showing the separation of the average value and the vibration component from the acceleration waveform, and FIG. FIG. 4 is a graph showing the arithmetic processing of the collision sensor of No. 1 and showing the peak cut and subtraction integration of the average value and the vibration component, and FIG. 4 is a graph showing the change of the total integrated value of the collision sensor of FIG.

In FIG. 1, the accelerometer 1 includes an arithmetic circuit 3
After that, the reset circuit 4 and the trigger circuit 5 are connected. Then, the trigger circuit 5 starts the airbag 6, which is an occupant protection device. Next, the arithmetic circuit 3 will be described. In block 11, the time t0 when the acceleration G measured by the accelerometer 1 exceeds a predetermined acceleration G1 is determined.
In block 30, the average value G _a of the acceleration G is calculated from this time t0. However, this average value G _a is an instantaneous value calculated by sampling at an appropriate time interval. In block 12, an acceleration G3 that is equal to or greater than a predetermined acceleration G2 of the average acceleration G _a is calculated (the acceleration G2 or less is regarded as zero). In the block 13 which is the first integrating means, the time integration of the acceleration G3 is started and the integrated value V is calculated. In the block 14 which is the subtraction means, the integral value of the first predetermined function is subtracted from this integral value V. In block 14, this predetermined function is a constant value ΔV,
Subtraction integrated value V obtained by subtracting a predetermined value ΔV per unit time
It becomes 1. The subtraction integral value V1 is output to the block 35 which is a summing means. The blocks 30 and 12 to 14 compose the first calculation means 41.

On the other hand, in block 31, a subtraction value G4 is calculated by subtracting the average acceleration G _a from the acceleration G. In block 32, an acceleration G6 that is equal to or greater than the predetermined acceleration G5 of the subtraction acceleration G4 is calculated (the acceleration G5 and lower is regarded as zero). In the block 33 which is the second integration means, the time integration of the acceleration G6 is started and the integrated value V10 is calculated. The integrated value V10 is added to the block 35 as a summing means.
Is output to. The blocks 30, 31 to 33 form the second calculation means 42.

In the block 35 which is the summing means, the subtraction integral value V1 and the integral value V10 which are the outputs from the first and second calculating means 41 and 42 are summed, and the summed integral value V11 is obtained.
To calculate. In block 15 which is a comparison means, in block 21, a predetermined reference value V2 (block 22) that changes with the passage of time is compared with the summed integral value V11. In line 23, when V11 becomes V2 or more, a start signal is output to the trigger circuit 5. On the other hand, in line 24, V11 does not reach V2, and block 18
When it is detected that V11 is near zero (negative or slightly positive value), a signal is issued to the reset circuit 4, the time integration is stopped, and V11, t is reset to zero. The summing means 35 and the comparing means 15 constitute the judging means 43.

Next, the above blocks 12 to 14 and 3
The arithmetic processing of 0 to 33 will be described with reference to the graphs of FIGS. In FIG. 2A, the calculation starts at time t0 when the acceleration G exceeds G1. Then, the (instantaneous) average value G _a of the acceleration G is calculated. Then, in FIG. 2B, the subtraction acceleration G4, that is, the vibration component is extracted by subtracting the average acceleration G _a from the acceleration G. Then, in FIG. 3 (a), _a value equal to or smaller than _a predetermined G2 of the average acceleration G _a is regarded as zero, and a value greater than that is integrated over time. Then, the predetermined value ΔV is subtracted per unit time, and the coloring part is time-integrated, and this becomes the subtraction integral value V1. The predetermined G2 is a positive value including G1 = G2. Further, by using the function of the reset circuit 4 described above, the start reset of integration can be performed without being aware of the start timing. Similarly, in FIG. 3B, the subtraction acceleration G4 is also regarded as zero below the predetermined G5 and time integration is carried out above the predetermined G5, which becomes the integrated value V10.

The operation of the summing means 35 and the comparing means 15 will be described with reference to FIG. 4, which is a graph showing the change of the summed integral value (V11). In FIG. 4, the reference value V2, which is a predetermined time function, is preset as shown by the line graph shown by the alternate long and short dash line. Therefore, in a low-speed frontal collision (dotted line) which is a non-starting condition, the comparing means 15 in FIG. 1 does not output the starting signal. Then, in the middle-high speed soft crash (thick line), even if the collision energy (subtractive integration value) is the same as that of the low speed frontal collision, the divided integrated value V11 including the vibration component (integral value) becomes larger than that in the low speed frontal collision. . Then, in the illustrated example, the reference value V2 is exceeded at point A, and the starting signal is output from the comparison means 15 in FIG. 1 to activate the trigger circuit 5. In the rough load pulse (thin line), only the vibration component (integral value), the collision energy (subtractive integral value) is almost 0, and the subtractive integral value is a predetermined offset cutoff (block 12, FIG. 1,
14), the total integrated value V11 becomes small and the start signal is not output. Therefore, it is possible to meet the requirements for the non-starting for the low speed frontal collision and the rough road pulse and the starting for the middle and high speed soft crashes at the required starting timing. In addition, the ratio of the subtraction integral value V1 and the integral value V10 is the above-mentioned offset,
It is possible to adjust the degree of cut-off or the like, or by changing the ratio of the sum of both V1 and V10 by the summing means 35 in FIG. The distinction between can be made clear. Further, looking at this result in relation to the offset values G ₀₁ and G ₀₂ in FIG. 8, the vibration component G4 is irrelevant to the offset of the average acceleration G _a as shown in FIG. You can pick it up. That is, noise having a small total energy can be removed by the offset, and the vibration component can be accurately captured. Therefore, when the collision sensor is applied to the vehicle, it is possible to easily optimize it according to the vehicle type and the like.

Next, a modified example will be described. The first calculation means 41 of FIG. 1 is intended to calculate the magnitude of the collision energy, and in the above-described embodiment, the deceleration amount is calculated as one of them. Therefore, the same result can be obtained by performing the calculation of the blocks 12 to 14 using the original acceleration G instead of the average acceleration G _a . Further, any calculation may be performed as long as the acceleration G is integrated over time, and for example, a second-order integration of time may be used.

The second calculating means 42 extracts the vibration component and calculates the magnitude of the vibration component. Therefore, as the vibration component extracting means, instead of the subtracting means 31 of the average acceleration G _a from the original acceleration G, for example, the acceleration signal G may be passed through a high pass filter. Further, as the calculation means of the magnitude of the vibration component, instead of the time integration (collision energy calculation) means 32 to 33 of FIG. 1, a calculation means for calculating an absolute value of the nth power of the vibration component G4 and performing time integration is provided. Also has the same effect. To calculate the absolute value of the n-th power,
For example, a method of calculating an absolute value, 2n power (n = 1, 2, ...
・ ・) Is available.

Further, in FIG. 1, if a low-pass filter having a pass band of a predetermined frequency or less is inserted between the block 11 and the block 30, the rough load pulse has a high frequency, so that it can be removed or attenuated, and a collision occurs. The distinction from the waveform can be made clearer. Further, if a dividing means for dividing the acceleration G by a predetermined acceleration (eg, G2 in FIG. 1) which is an inoperative condition and a squaring means for squaring the divided value are provided between the block 11 and the block 30, The acceleration is made dimensionless, and the difference becomes large by the square of the predetermined acceleration with the reference value = 1, and the vibration component is emphasized to make the distinction of the soft crash at high speed clearer.

Next, the judging means 35 appropriately combines the output from the first calculating means 41 showing the magnitude of the collision energy and the output from the second calculating means 42 showing the magnitude of the vibration component to determine whether or not there is a collision. In the above-described embodiment, the outputs from both means 41 and 42 are deceleration amounts (time integrated values) having the same physical quantity, and are therefore summed. But,
When the physical quantities of the outputs from both the means 41 and 42 are different, as in the above-described modified example, it is necessary to evaluate (for example, rank) each output separately. In addition, in the above-described embodiment, the sum value V11 is compared with the reference value V2 to determine whether or not there is a collision. However, in the case of separately evaluating as described above, these are appropriately combined and weighted or the like. Alternatively, fuzzy reasoning may be used to determine whether or not there is a collision.

[0018]

As described above, the collision sensor of the present invention uses the first calculation means for calculating the integral of the acceleration waveform, the second calculation means for calculating the magnitude of the vibration component from the acceleration waveform, and the outputs thereof. Since it is provided with a judging means for judging a collision based on the collision energy, it is possible to surely discriminate between a rough road pulse and a collision depending on the magnitude of the collision energy, and a low speed frontal collision or a middle and high speed soft crash based on the magnitude of the vibration component. Therefore, it is possible to easily achieve the start-up condition for the medium-high speed soft crash and the non-start-up condition including the rough load pulse.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of a collision sensor of the present invention.

FIG. 2 is a graph of acceleration showing a calculation process of the collision sensor of the present invention.

FIG. 3 is a graph of acceleration showing the calculation processing of the collision sensor of the present invention.

FIG. 4 is a graph diagram of time integration showing the calculation processing of the collision sensor of the present invention.

FIG. 5 is a graph of acceleration showing a calculation process of a conventional collision sensor.

FIG. 6 is a graph of time integration showing a calculation process of a conventional collision sensor.

FIG. 7 is a graph of acceleration showing a calculation process of a conventional collision sensor.

FIG. 8 is a graph of acceleration showing setting of an offset of a conventional collision sensor.

[Explanation of symbols]

G acceleration (acceleration waveform) G _a average acceleration (average value) 1 accelerometer 5 trigger circuit 6 airbag 12 blocks (peak cutting means) 13 blocks (integrating means) 14 blocks (subtracting means) 30 blocks (averaging means) 31 blocks (Vibration component extracting means) 32 blocks (peak cutting means) 33 blocks (integrating means) 41 first calculating means 42 second calculating means 43 judging means

Claims (2)

[Claims] 1. A collision sensor for detecting a vehicle collision from an acceleration waveform of an accelerometer and activating an occupant protection device such as an airbag by a trigger circuit, the first calculation means calculating an integral of the acceleration waveform. Second calculating means for calculating the magnitude of the vibration component from the acceleration waveform, and judging means for judging a collision based on outputs from the first and second calculating means and outputting a start signal to the trigger circuit. A collision sensor provided. 2. The second computing means comprises the following (a):
The collision sensor according to claim 1, wherein the collision sensor is any one of (b). (A) Averaging means for averaging the acceleration waveform, vibration component extracting means for subtracting the average value from the acceleration waveform, peak cutting means for subjecting the vibration component to peak cutting of a predetermined value or less, and peak cutting Computing means comprising an integrating means for time-integrating the vibration component. (B) An averaging means for averaging the acceleration waveform, a vibration component extracting means for subtracting the average value from the acceleration waveform, and a computing means for computing an absolute value of the nth power of the vibration component and performing time integration. Computation means.