JP3967477B2 - Vehicle collision determination method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle collision determination method and apparatus for performing vehicle collision determination based on an acceleration signal output from an acceleration sensor.
[0002]
[Prior art]
An occupant protection device such as an air bag or a seat belt pretensioner is connected to a vehicle collision determination device that performs a collision determination based on acceleration generated in the vehicle. When the collision determination device performs the collision determination, the airbag And the ignition device of the pretensioner is activated. The vehicle collision determination device includes an acceleration sensor that detects acceleration generated in the vehicle, and a collision determination unit that determines vehicle collision based on an acceleration signal detected by the acceleration sensor.
[0003]
FIG. 5 is a flowchart showing a collision determination method by a conventional collision determination apparatus. As an acceleration sensor, as an output guarantee range in a “zero G” state where no acceleration occurs, for example, a reference voltage of 2.5 V ± 0 An expensive high-accuracy type with a guarantee of .05V is used.
[0004]
In step S30, a predetermined initial process is executed in the collision determination unit. In step S31, an initial value “1” is set to a count value n indicating the number of times of sampling of acceleration.
[0005]
In step S32, the voltage V (G) output by 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, whether or not the output voltage V (Gn), that is, V (G1) of the acceleration sensor sampled in step S32 is within the output range (2.5V ± 0.05V) in the “zero G” state. Is determined.
[0006]
In general, immediately after the power is turned on, the output V (Gn) of the acceleration sensor is not stable. For example, as shown in FIG. 4, it is initially high even in the “zero G” state, and then gradually decreases. Settling within the guaranteed output range in the “zero G” state. Accordingly, the collision determination unit at the subsequent stage waits until the output voltage falls within the output guaranteed range of 2.5V ± 0.05V, and starts the collision determination, and sets the collision determination start flag Fstable in step S35.
[0007]
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 the first collision is first, the process proceeds to step S37. In step S37, 2.5V corresponding to the reference voltage is subtracted from the sampled current output voltage V (Gn), that is, V (G1), and updated and registered as the difference V (ΔG).
[0008]
On the other hand, if it is determined in step S36 that the collision determination is made for the second time or later, in step S38, the output voltage of the acceleration sensor 20 is sampled as the current sampling result V (Gn). In step S39, a difference V (ΔG) between the current sampling result V (Gn) and the previous sampling result V (Gn-1) is obtained. In step S40, a collision determination is executed based on each difference V (ΔG). If the collision determination is not made because the difference V (ΔG) is small, the count value n is incremented in step S42 and the process returns to step S36. . When a collision determination is made in step S40, the airbag is activated in step S41.
[0009]
Thus, in the second and subsequent collision determinations, the collision determination (step S39) is performed based on the difference V (ΔG) between the current sampling result V (Gn) and the previous sampling result V (Gn-1). . However, V (G0) corresponding to "previous sampling result V (Gn-1)" does not exist in the first collision determination. Therefore, in the prior art, “2.5 V” corresponding to “zero G” is adopted as the “previous sampling result V (G0)” in the first collision determination as dummy data.
[0010]
[Problems to be solved by the invention]
The collision in the vehicle may occur not only during normal traveling but also immediately after the ignition switch is turned on. For example, in a vehicle with a manual mission, if the engine key is accidentally turned at 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 go is negligible. Therefore, also in the vehicle collision determination device, it is desirable to shorten the waiting time from when the ignition switch is turned on until the collision determination becomes possible.
[0011]
However, in the conventional technique described above, in the first collision determination, the reference voltage Vref (= 2.5 V) is substituted as a fixed value instead of the previous sampling result V (Gn-1), that is, V (G0). 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 guaranteed range is about the reference voltage Vref ± 0.05 V, and it is difficult to reduce the cost. There was a problem.
[0012]
Furthermore, as an output guarantee range, the time required for the operation to stabilize for an expensive acceleration sensor with a guaranteed reference voltage Vref ± 0.05 V and an inexpensive acceleration sensor with a reference voltage Vref ± 0.2 V, for example, is taken. In comparison, as shown in FIG. 4, an inexpensive acceleration sensor reaches a stable state at time t1, whereas an expensive acceleration sensor is not stable until time t2. Therefore, the above-described conventional technique has a problem that the waiting time until the collision determination becomes possible after the power is turned on becomes long.
[0013]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art, and to reduce the waiting time from when the power is turned on to when the collision can be determined without using an expensive acceleration sensor. And providing an apparatus.
[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 the vehicle collision determination method that samples the output signal of the acceleration sensor and determines the collision of the vehicle 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 stable The average value of the sampling result is obtained until the acceleration sensor operation is stabilized, and collision determination sampling is started. In the first collision determination, the 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, the acceleration sensor, a sampling means for sampling the output signal of the acceleration sensor, and an operating state of the acceleration sensor are determined. Operating state determining means, average value calculating means for obtaining an average value of the sampling results, first comparing means for comparing the current sampling result with the average value, the current sampling result and the previous sampling result, When the operation state determination unit determines that the operation of the acceleration sensor is stable, first, the collision is determined based on the comparison result by the first comparison unit, and thereafter And a collision determination means for determining a collision based on the comparison result by the second comparison means.
[0015]
According to the configuration described above, the average value of the sampling results of the acceleration sensor is obtained until the operation of the acceleration sensor is stabilized, and when the operation of the acceleration sensor is stabilized, the current sampling result of the acceleration sensor is determined in the first collision determination. And the collision determination is executed based on the difference from the previous average value.
[0016]
Here, the difference between the current sampling result of the acceleration sensor and the average value so far is small regardless of the absolute value of the sampling result unless the acceleration is changed, and is large if the acceleration is changed. Therefore, according to the configuration described above, accurate collision determination can be performed from the first collision determination without using a highly accurate acceleration sensor.
[0017]
Furthermore, since the time until the operation of the acceleration sensor is stabilized is shortened compared to the case where a highly accurate acceleration sensor is used, the standby time from when the power is turned on until the collision can be determined is shortened.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described 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 is a low-priced version in which the output guarantee range in the “zero G” state in which no acceleration is generated has a reference voltage of 2.5 V ± 0.2 V.
[0019]
The acceleration signal output from the acceleration sensor 20 is converted into a digital signal by the A / D converter 30 and input to the CPU 10. When the CPU 10 receives the acceleration signal, the CPU 10 executes a collision determination program stored in advance in the ROM 51, and controls the switching transistor 71 as an airbag starting means. The RAM 52 functions as a work area when executing the collision determination program.
[0020]
One end of the squib resistor 61 a of the airbag 61 is connected to the power supply line L, and the other end is grounded via the switching transistor 71. A capacitor 73 and a battery 74 for supplying current to the squib resistor 61a are connected to the power line L.
[0021]
FIG. 2 is a functional block diagram of the CPU 10, and the same reference numerals as those described above represent the same or equivalent parts.
[0022]
The sampling unit 101 samples the output voltage V (G) of the acceleration sensor 20 at a predetermined cycle. The average value calculator 102 calculates and outputs an average value Vave of the sampling results V (Gm) before the collision determination is started. The operation state determination unit 104 refers to the sampling result V (Gm) of the acceleration sensor 20, the sampling result V (Gm) is within the range of the reference voltage Vref ± 0.2, and the sampling result V (Gm) If the difference from the average value Vave is equal to or less than the 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.
[0023]
The comparator 105 outputs the difference V (ΔG1) between the first sampling result V (G1) and the average value Vave after the collision determination is started. The data updating unit 106 outputs the previous sampling result V (Gn-1) every time the current sampling result V (Gn) is output from the sampling unit 101.
[0024]
After the collision determination is started, the comparison unit 107 outputs a difference ΔV (Gn) between the second and subsequent sampling results V (Gn) and the previous sampling result V (Gn-1). When the collision determination unit 108 receives the collision determination start signal A2, the collision determination unit 108 executes the collision determination based on the first difference ΔV (G1) or the second and subsequent differences ΔV (Gn), and makes a collision determination. An airbag start signal A1 is output. As a result, the switching transistor 71 becomes conductive, current flows from the capacitor 73 and the battery 74 to the squib resistor 61a of the airbag 61, and the airbag 61 is deployed.
[0025]
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, an initial value “1” is set to the count value m indicating the number of times the sampling unit 101 has sampled the acceleration before the collision determination is started, and the integrated value of the sampling result V (Gm) before the collision determination is started. ΣVm is reset.
[0026]
In step S <b> 13, 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 obtains 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 sampling number m and the integrated value ΣVm up to the present.
[0027]
In step S16, the operation state determination unit 104 determines whether or not the current sampling result V (Gm) is within 2.5V ± 0.2V which is the output guaranteed range in the “zero G” state. If it is within the guaranteed output range, in step S17, the operation state determination unit 104 further determines whether the operation of the acceleration sensor 20 is stable, that is, whether the output fluctuation range of the acceleration sensor 20 is small. In this embodiment, if the difference between the current sampling result V (Gm) and the average value Vave up to the present is within ± 0.005 V, it is determined that the operation of the acceleration sensor 20 is stable, and the process proceeds to step S18. .
[0028]
If it is determined in step S16 that the output voltage V (Gm) is outside the guaranteed output range, or if it is determined in step S17 that the output fluctuation range is not sufficiently small, in step S27, the average value is determined. The number m of samplings is incremented by “1” in the calculation unit 102, and then the process returns to step S13.
[0029]
In step S18, an initial value “1” is set to a count value n indicating the number of samplings after the collision determination is started. In step S19, the collision determination start flag Fstart is set, and the collision determination start signal A2 is output from the operation state determination unit 104 to the average value calculation unit 102 and the collision determination unit 108.
[0030]
In step S20, the current output voltage V (Gn) of the acceleration sensor 20 is sampled by the sampling unit 101 as the 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 the first time is the first time, the process proceeds to step S22. In step S22, the comparison unit 105 subtracts the average value Vave of the sampling results immediately before the start of the collision determination from the first current sampling result V (Gn), that is, V (G1), to obtain the difference V (ΔG1). ) Is required.
[0031]
On the other hand, if it is determined in step S21 that the collision determination is the second or later (n ≧ 2), in step S23, the current sampling result V (Gn) and the previous sampling result V (Gn-1) are compared. The difference ΔV (ΔGn) is obtained by the comparison unit 107. That is, if it is the second collision determination, the difference V (ΔG2) between the second sampling result V (G2) and the first sampling result V (G1) is obtained, and if it is the third collision determination, A difference V (ΔG3) between the third sampling result V (G3) and the second sampling result V (G2) is obtained.
[0032]
In step S24, a collision determination is performed based on the first difference V (ΔG1) or the second and subsequent differences ΔV (ΔGn). If no collision determination is made, the count value n is determined in step S25. Is incremented by "1". When the collision determination is made, the airbag 61 is deployed in step S26.
[0033]
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, and the operation is stabilized and the collision determination is started. Then, in the first collision determination, the collision determination is executed based on the difference between the current sampling result V (G1) and the average value Vave of the previous sampling results.
[0034]
Here, the difference between the sampling result V (G1) immediately after the start of the collision determination of the acceleration sensor 20 and the average value Vave of the sampling results so far is the absolute value of the sampling result V (G1) unless the acceleration changes. Regardless of, it becomes smaller 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-precision acceleration sensor.
[0035]
Furthermore, according to the present embodiment, the time until the operation of the acceleration sensor becomes stable is shortened as compared with the case where a highly accurate acceleration sensor is used. Can be shortened.
[0036]
【The invention's effect】
According to the present invention, the following effects are achieved.
(1) Until the operation of the acceleration sensor is stabilized, an 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 is performed in the current sampling result. Since the collision determination is executed based on the difference between V (G1) and the average value Vave of the sampling results immediately before the collision determination is started, the first collision determination is performed without using a high-precision acceleration sensor. This makes it possible to accurately determine the collision.
(2) Compared to using a high-accuracy acceleration sensor, the time until the acceleration sensor operation stabilizes is shortened, so the waiting time from when the ignition switch is turned on until the collision can be judged is shortened. be able to.
[Brief description of the drawings]
FIG. 1 is a block diagram of a vehicle collision determination apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram functionally showing the configuration of a CPU 10 in FIG.
FIG. 3 is a flowchart showing the operation of an 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 prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... CPU, 20 ... Acceleration sensor, 30 ... A / D converter, 61 ... Air bag, 61a ... Squib resistance, 71 ... Switching transistor, 73 ... Capacitor, 74 ... Battery

Claims (1)

In the vehicle collision determination method for sampling the output signal of the acceleration sensor and determining the collision of the vehicle based on the sampling result,
Sampling is repeated until the acceleration sensor operation stabilizes, and the average value of the sampling results is obtained.
When the sampling result is within a predetermined reference range and the difference between the sampling result and the average value is equal to or less than a predetermined value, it is determined that the operation of the acceleration sensor is stable,
When the operation of the acceleration sensor is stabilized, the collision determination process including the collision determination sampling is repeated,
In the first collision determination process, a collision is determined based on a comparison result between the sampling result in the current collision determination process and the average value,
In the second and subsequent collision determination processes, a collision determination method for a vehicle is characterized in that a collision is determined based on a comparison result between a sampling result in each collision determination process and a previous sampling result.

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