JP3324276B2 - Vehicle occupant protection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle occupant protection system such as an air bag system.

[0002]

2. Description of the Related Art In recent years, various vehicle occupant protection devices such as an air bag device and a seat belt restraint device have been developed in order to ensure the safety of occupants of a vehicle. In this type of occupant protection system, all types of occupant protection systems must detect the collision of the vehicle quickly and accurately, and operate the occupant protection system in the event of a collision and perform trigger control so that the occupant protection system is not accidentally activated. Is needed.

For this reason, conventionally, a vehicle occupant protection system removes noise from a signal from an acceleration sensor through a band-pass filter, calculates a root mean square of a collision waveform to obtain a collision power, If is equal to or greater than a reference value determined according to the vehicle characteristics, it is determined that a collision has occurred, and the airbag device is activated.

[0004]

However, in this conventional method, it takes a long time to calculate the root mean square of the collision waveform. In addition, there is a drawback that the circuit is complicated and expensive to increase the accuracy and respond in real time.

Accordingly, it is an object of the present invention to provide an occupant protection system for a vehicle which detects a collision simply and at high speed.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an acceleration sensor for detecting the acceleration of a vehicle, and extracting a frequency component corresponding to a vehicle characteristic from an output signal from the acceleration sensor. A band-pass filter, a peak detection circuit for detecting a peak value of an output signal of the band-pass filter, and an output signal of the peak detection circuit and the acceleration.
A reference value holding means for holding a predetermined reference value determined in advance by the Rayleigh distribution using a ratio of a square root of power as a Rayleigh distribution, an output signal of the peak detection circuit , and a reference held by the reference value holding means. And a comparator for comparing the output signal with a reference value and generating a collision detection signal when the output signal of the peak detection circuit exceeds the reference value.

[0007]

According to the present invention, a signal from an acceleration sensor is passed through a band-pass filter having a frequency characteristic corresponding to a vehicle characteristic, and its peak value is detected by a peak detection circuit.
The value is the output signal of the peak detection circuit and the power of the acceleration.
The ratio of the square root of the chromatography as Rayleigh distribution, advance the Rayleigh
-It is to compare with a reference value defined by the distribution and output a collision detection signal if the reference value is exceeded.

[0008]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. 1 is an acceleration sensor, 2 is a band-pass filter, the frequency characteristics of which are determined according to the vehicle characteristics. 3 is a peak detection circuit for detecting the peak value of the acceleration signal waveform,
Reference numeral 4 denotes a comparator for comparing the peak value of the acceleration signal waveform with a preset reference value, and reference numeral 5 denotes a reference value holding means for holding the reference value.

Conventionally, an occupant protection system for a vehicle measures the power at the time of a collision, and activates the system if the measured value is equal to or higher than a reference value. For the measurement of the power P, a method has been used in which the acceleration signal u (t) from the acceleration sensor is squared and integrated with respect to the time axis.

[0010]

[Formula 1] However, the power P is, if Percival's theorem is used, the autocorrelation function R (τ) of the acceleration signal.

[0011]

[Formula 2] Power spectral density S (ω) obtained by Fourier transform of

[0012]

[Equation 3] Can also be obtained by integrating with respect to the frequency axis.

[0013]

(Equation 4) In general, the shape of the power spectrum density has a remarkable feature depending on each object, and the power spectrum density at the time of a collision of a vehicle also has a remarkable feature that it takes a large value only in a narrow region near the natural vibration frequency ω0 of the vehicle body.

In the present application, this feature is used. First, only necessary frequency components are extracted by using a band-pass filter to separate noise and this signal.

On the other hand, when the acceleration signal u (t) has a narrow band power spectral density distribution, its statistical properties are very simple.

The maximum value um of u (t) and the power at that time
Um / √P is um / ｕｍP and um / √P + d (u
m / √P) , as shown in FIG.

[0017]

(Equation 5) Rayleigh distribution of

The power P0 at the time of operation of the occupant protection device is obtained in advance by a collision experiment, and the reference value of the comparator to be compared with the peak hold value of the acceleration signal is represented by Uref and Xref.
And √P0. If the peak hold value exceeds Uref, it is determined that a collision has occurred, and a collision detection signal is output. Where U
ref can be varied depending on the allowable risk rate.

When the above is applied to the present invention, when no collision occurs, the acceleration sensor 1 detects the acceleration of the vehicle, generates an analog signal, and outputs the analog signal to the band-pass filter 2. The band-pass filter 2 passes only the in-band signal and outputs the signal to the peak detection circuit 3. The peak detection circuit 3 detects and holds the peak value of the signal and outputs it to the comparator 4. The comparator 4 compares the input peak value with a preset reference value held in the reference value holding means 5. In this case, since the collision is non-collision, the peak value does not reach the reference value, and the collision detection signal is output. Is not output.

In the event of a collision, the acceleration sensor 1 generates an analog signal having a vibration larger than usual, whose spectrum is concentrated around the natural vibration frequency ω0 of the vehicle. The band-pass filter 2 passes only signals in the band centered on the natural vibration frequency ω0 of the vehicle and outputs the signals to the peak detection circuit 3.
The peak detection circuit 3 detects and holds the peak value of this signal and outputs it to the comparator 4. The comparator 4 compares the collision power at which the airbag needs to be deployed with a reference value associated with a specified probability, and outputs a collision detection signal if the value exceeds the reference value, and deploys the airbag.

[0021]

As described above, the present invention provides an acceleration sensor for detecting the acceleration of a vehicle, a band-pass filter for extracting a frequency component corresponding to a vehicle characteristic from an output signal from the acceleration sensor, and a peak detection circuit for detecting a peak value of the output signal of the band-pass filter, the peak detecting
The output signal and the ratio of the square root of the power of the acceleration of the circuit as a Rayleigh distribution, advance a reference value holding means for holding a predetermined reference value set by the Rayleigh distribution, the output signal of said peak detecting circuit with the reference value Comparing the reference value held by the holding means with the output of the peak detection circuit;
Since the configuration includes the comparator that generates the collision detection signal when the signal exceeds the reference value, the circuit configuration can be simplified, and the high-speed and accurate operation can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing a Rayleigh distribution used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Acceleration sensor 2 Bandpass filter 3 Peak detection circuit 4 Comparator 5 Reference value holding means

Claims (1)

(57) [Claims] An acceleration sensor for detecting acceleration of a vehicle, a band-pass filter for extracting a frequency component corresponding to a vehicle characteristic from an output signal from the acceleration sensor, and a peak value of an output signal of the band-pass filter A peak detection circuit for detecting the output signal of the peak detection circuit and the acceleration
A reference value holding means for holding a predetermined reference value determined in advance by the Rayleigh distribution using a ratio of a square root of power as a Rayleigh distribution, an output signal of the peak detection circuit , and a reference held by the reference value holding means. And a comparator for comparing the output signal with a reference value and generating a collision detection signal when an output signal of the peak detection circuit exceeds the reference value.