Method for judging collision with three directional accelerative signals and apparatus for performing the same

An apparatus and method for judging an oblique, center pole and front barrier collision with the acceleration signals of a vehicle in back-and-forth, left-and-right and up-and-down directions are disclosed. The acceleration signal detected by an acceleration sensor is filtered and transferred to a collision judging part. The collision judging part judges a dangerous collision and generates a reset signal. The acceleration signal detected by the acceleration sensor is integrated. The judgement for an oblique, center pole and front barrier collision is achieved by comparing the integrated acceleration signal with each preset value. Both the low speed front barrier collision and the high speed center pole collision can be easily judged by detecting three directional accelerations of a vehicle and comparing those accelerations with the predetermined reference values.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method for judging vehicle collision 
types of vehicles and apparatus for performing the same, and more 
particularly, to a method for judging with three directional (three axes) 
deceleration signals and to an apparatus for performing the same. 
2. Prior Art 
It is known that a collision judging apparatus or a collision type judging 
apparatus (hereinafter, referred to as a collision type judging 
apparatus), which is installed in a safety system of a vehicle, i.e., an 
air bag system or a safety-belt retracting system (hereinafter, referred 
to as an air bag system), drives an air bag system by sensing the 
collision of a vehicle. 
When a vehicle collides with a non-moving obstacle, another vehicle or 
moving vehicle etc., passengers as well as the driver are injured. The air 
bag system, which protects passengers against such a case, prevents those 
from injury by unfolding the air bag immediately after the collision. 
Therefore, passengers can be protected only if the air bag system is 
immediately and responsively operated right after the collision of the 
vehicle by properly sensing the collision. 
However, it is not desirable that the air bag should unfold on a light 
collision, because an unfolded air bag is not re-usable and should be 
replaced by a new one. On the other hand, if a collision that may give 
severe injury to passengers is not detected and the air bag system does 
not be operate, the passengers may suffer a fatal wound. 
Accordingly, when the vehicle collides with something, it should be 
correctly judged to protect the passengers from being injured. For this 
purpose, the air bag system judges the collision of the vehicle by 
adopting a collision type judging system. 
Vehicle collision types are classified into head-on collisions and lateral 
collisions. The head-on collisions, especially, are classified into a 
front barrier collision, an oblique collision and a center pole collision. 
The front barrier collision means that the whole front of the vehicle 
clashes against a barrier, the oblique collision means that the vehicle 
collides against an obstacle in an arbitrary angle, and the center pole 
collision is that a part of the front of the vehicle collides into a pole 
such as a telephone pole. On vehicle collision, the injuries sustained by 
the passengers depends on the collision types. Particularly, the center 
pole collision would give passengers a more severe injury than other types 
of collisions because a pole strikes the soft head portion of the vehicle 
and rushes for the engine. 
Thus, air bag systems must decide in a very short time whether or not the 
air bag should be operated by considering the seriousness of the collision 
(i.e. the possibility of injury to the passengers) in cases of rapid 
deceleration like vehicle collisions. Further, a collision type judging 
system should judge not only a genuine collision but the collision type. A 
collision judging circuit, as such a system, is disclosed in U.S. Pat. No. 
5,256,904 (issued to Shigero Tohbaru), which decides collision types by 
using the inertial velocity and the acceleration velocity of a vehicle. 
There are three types of acceleration signals which are generated on a 
vehicle collision. The first is an X-component acceleration signal that is 
a traveling-direction (front-and-rear) acceleration component of a 
vehicle, the second is a Y-component acceleration signal that is a lateral 
(left-and-right) acceleration component of the vehicle, and the last is a 
Z-component acceleration signal that is a vertical (up-and-down) 
acceleration component of the vehicle. A prior collision type judging 
system usually judges the occurrence of collision with an X-component 
signal and/or a Y-component acceleration signal. That is, when a vehicle 
collides against something, the collision type judging system detects the 
collision by using the level of a X-component and/or a Y-component 
acceleration signal of a vehicle, which is detected by an acceleration 
sensor. The prior system can detect the front barrier collision or the 
oblique collision relatively easily since the X-component acceleration 
signal and/or the Y-component acceleration signal of a vehicle is rapidly 
and strongly propagated into the acceleration sensor through a 
comparatively rigid part of the vehicle body. 
However, in case of the center pole collision, the collision impact of a 
vehicle is not properly propagated into the acceleration sensor due to the 
presence of the soft part of the vehicle which has been stricken by the 
pole, and an initial acceleration signal, as a result, is weakly generated 
when compared to the acceleration signals generated in the case of a front 
barrier collision and an oblique collision. Consequently, the prior 
collision type judging system cannot detect a high speed center pole 
collision, and this defect may cause passengers to be seriously injured. 
In order to solve this problem, a system for improving the propagation of 
the acceleration signal through a soft part of vehicle body by 
strengthening the soft part with a reinforcing element was also disclosed. 
Further, a system for initially sensing a collision of a vehicle by adding 
a sensor into a crush zone, has been suggested. These systems, however, 
cause to the vehicle body to remolded. 
SUMMARY OF THE INVENTION 
Therefore, it is a first object of the present invention to provide a 
collision type judging method for judging a front barrier collision, an 
oblique collision and a center pole collision using three directional 
(three axes) acceleration signals which are detected by an acceleration 
sensor on a vehicle crush (collision) without rebuilding the vehicle body 
or without any additional sensors. 
It is a second object of the present invention to provide a collision type 
judging apparatus which is appropriate for performing above method. 
In order to achieve the above first object of the present invention, there 
is provided a method for judging a vehicle collision, which comprises the 
steps of: 
(S1) detecting accelerations in a back-and-forth, a left-and-right and an 
up-and-down directions viewed from a traveling vehicle to generate a 
first, a second and a third acceleration signals; 
(S2) filtering the first, the second and the third acceleration signals to 
eliminate high frequency signals thereof; 
(S3) comparing the first acceleration signal with a preset reference value 
to judge whether or not the vehicle collision is dangerous, and outputting 
a reset signal when judging as not dangerous; 
(S4) generating a synchronous signal in response to the reset signal; 
(S5) generating a first, a second and a third velocity signals by first 
orderly integrating the first, the second and the third acceleration 
signals that are generated at the second step (S2) with respect to time 
while being synchronized to the synchronous signal; and 
(S6) judging the vehicle collision type by comparing the first, the second 
and the third velocity signals with a first, a second and a third preset 
values, while being synchronized to the synchronous signal. 
The step (S6) may be performed by (i) judging as an oblique collision when 
the second velocity signal is a lower level than the second preset value 
over a second time by comparing the level of the second velocity signal 
with that of the second preset value, while being synchronized to the 
synchronous signal; (ii) judging as a front barrier collision when the 
first velocity signal has a higher level than the first preset value over 
the first time by comparing the first velocity signal with the first 
preset value, the step (ii) being performed when the second velocity 
signal has a higher level than the second preset value over the second 
time; and (iii) on the precondition that the first velocity signal has a 
lower level than the first preset value over the first time, comparing the 
third velocity signal with the third preset value and judging as the 
center pole collision when the third velocity signal has a higher level 
than the third preset value over the third time, and judging as the front 
barrier collision when the third velocity signal has a lower level than 
the third preset value over the third time. 
To achieve the above second object of the present invention, there is 
provided a apparatus for judging a vehicle collision type, which 
comprises: 
an acceleration sensor for detecting accelerations in a back-and-forth, a 
left-and-right and an up-and-down directions viewed from a traveling 
vehicle to generate a first, a second and a third acceleration signals; 
a low-pass filter for filtering the first, the second and the third 
acceleration signals from the acceleration sensor to eliminate high 
frequency components thereof; 
a collision judging means for judging as dangerous when the first 
acceleration signal supplied from the low-pass filter, has a higher level 
than the preset reference value during a predetermined time, and judging 
as not dangerous, for outputting a reset signal when the first 
acceleration signal has a lower level than the preset reference value 
during the predetermined time; 
a clock for generating a synchronous signal with responding to the reset 
signal, the clock being reset by the reset signal,; 
an integrator for generating a first, a second and a third velocity signals 
by first orderly integrating the first, the second and the third 
acceleration signals supplied from the low-pass filter with respect to 
time, the integrator being synchronized to the synchronous signal; and 
a collision type judging means for receiving the first, the second and the 
third velocity signals, comparing the first, the second and the third 
velocity signals with a first, a second and a third preset values to judge 
whether the vehicle collision is an oblique collision, a front barrier 
collision or a center pole collision, the collision type judging means 
being synchronized to the synchronous signal. 
The collision type judging part judges the collision type is as either an 
oblique collision, a center pole collision or a front barrier collision, 
by sequentially comparing the lateral velocity signal of the vehicle with 
the second predetermined value, the traveling-direction velocity signal of 
the vehicle with the first predetermined value, and the up-and-down 
velocity signal of the vehicle with the third predetermined value. 
The oblique collision of a vehicle can be detected by using the 
left-and-right directional velocity signal of a vehicle and the second 
predetermined value. The center pole collision can be judged by comparing 
the left-and-right velocity signal of a vehicle and the second 
predetermined value, by comparing the traveling velocity signal of the 
vehicle with the first predetermined value, and by comparing the normal 
directional velocity signal of a vehicle with the third predetermined 
value. Accordingly, the front barrier collision corresponds to the case 
that the collision type is not judged as the center pole collision.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Hereinafter, the present invention will now be described in connection with 
the accompanying drawings. 
FIG. 1 is a block diagram for showing the configuration of a collision type 
judging apparatus 100 according to a preferred embodiment of the present 
invention. 
An acceleration sensor 10 for sensing an accelerative velocity in a 
traveling direction (X-axis), a lateral direction (Y-axis) and a vertical 
direction (Z-axis) of a vehicle, detects the accelerative velocity of the 
vehicle, and then generates a first acceleration signal (Ax), a second 
acceleration signal (Ay) and a third acceleration signal (Az) which are a 
traveling acceleration component (X-axis), a lateral acceleration 
component (Y-axis) and a vertical acceleration component (Z-axis) of the 
vehicle respectively. The positive directions in the three directions are 
respectively the forward, left and upward directions viewed from the 
traveling vehicle. 
The three directional acceleration signals which are generated from 
acceleration sensor 10, that is, the first, second and third acceleration 
signals (Ax, Ay and Az) include high frequency components such as noise 
and/or vibration, and thus such components should be removed. A low-pass 
filter 20 receives the first, second and third acceleration signals (Ax, 
Ay and Az) and filters the high frequency components such as noise and/or 
vibration. 
A part of the first acceleration signal (Ax) filtered by low-pass filter 20 
is transferred to a collision judging part 30. Collision judging part 30 
discriminates between a dangerous collision and a non-dangerous collision 
by comparing the first acceleration signal (Ax) with a preset value 
(PRESET) which was determined by experiment. When judged as a dangerous 
collision, collision judging part 30 produces a reset signal (RESET). 
A clock 34 is initialized by the reset signal (RESET), and outputs a 
synchronous signal (SYNC). 
An integrator 40 is synchronously driven by the synchronous signal (SYNC) 
generated by clock 34 just after the collision judging part 30 judges the 
collision as dangerous. After being triggered by the synchronous signal 
(SYNC), integrator 40 outputs a first, second and third velocity signals 
(Ix, Iy and Iz) by receiving the first, second and third acceleration 
signals (Ax, Ay and Az) filtered by low-pass filter 20 and then 
integrating these signals in the first order with respect to time. 
The first velocity signal (Ix) shows the forward speed of the vehicle, 
which is the first orderly integrated value of the first acceleration 
signal (Ax). 
This first velocity signal (Ix) is illustrated in FIG. 3, the second 
velocity signal (Iy) in FIG. 4, and the third velocity signal (Iz) in FIG. 
5, respectively. In FIGS. 3, 4 and 5, the horizontal axis shows the time 
(mili-second) and the vertical axis show the velocity variation (miles per 
hour). The solid line shows the first order integrated value of an 8-mph 
front barrier collision, and the hidden line shows the first order 
integrated value of a 14-mph 30 degree oblique collision, and the two-dot 
chain line shows the first order integrated value of a 16-mph center pole 
collision. 
A collision type judging part 50 is synchronized to the synchronous signal 
(SYNC) from clock 34, and judges the collision type by comparing the 
first, second and third velocity signals (Ix, Iy and Iz) which are 
outputted from integrator 40 with the first, second and third preset 
values (Vx, Vy and Vz) which are the collision type reference values. 
Collision type judging part 50 sequentially judges the oblique, center 
pole and front barrier collision. The details are as follows. 
FIG. 3 shows a graph for collision types of the first velocity signal (Ix). 
As shown in FIG. 3, the velocity signal (hidden line) on the 14-mph 
oblique collision and the velocity signal (two-dot chain line) on the 
16-mph center pole collision is lower than the velocity signal (solid 
line) on the 8-mph front barrier collision. Here, the 8-mph front barrier 
collision is evaluated as a non-dangerous collision. Therefore, the first 
velocity signal (Ix) cannot judge the 14-mph oblique collision and the 
16-mph center pole collision as more dangerous than the 8-mph front 
barrier collision. 
FIG. 4 shows a graph for collision types of the second velocity signal 
(Iy). As shown in FIG. 4, the velocity signal (two-dot chain line) on the 
16-mph center pole collision and the velocity signal (solid line) on the 
8-mph front barrier collision are similar to each other in magnitude, and 
thus are difficult to discriminate one from the other. However, the 
velocity signal (hidden line) on the 14-mph oblique collision is lower 
than the velocity signal (solid line) on the 8-mph front barrier collision 
and thus are easy to discriminate one from the other. Therefore, the 
higher speed oblique collision which is more hazardous than the 8-mph 
front barrier collision can be judged with the left-and right directional 
second velocity signal (Iy) of an acceleration velocity. 
In case of the center pole collision, as shown in FIG. 4, it is difficult 
to discriminate the center pole collision from the front barrier collision 
because the second velocity signal (Iy) has a small level difference 
compared to the 8-mph front barrier collision. Further, as shown in FIG. 
3, the collision type cannot be judged by using the first order integrated 
value of the forward acceleration of the vehicle because the velocity 
signal (two-dot chain line) on the center pole collision is lower than 
that (solid line) of the front barrier collision. 
Accordingly, in this case, the collision type should be judged with the 
third velocity signal (Iz) which is the first order integrated value of 
the up-and-down acceleration of a vehicle. As shown in FIG. 5, it is 
difficult to distinguish the velocity signal (hidden line) on the 14-mph 
oblique collision from the velocity signal (solid line) on the 8-mph front 
barrier collision. However, it is easy to discern the velocity signal 
(two-dot chain line) on 16-mph center pole collision from the velocity 
signal (solid line) on 8-mph front barrier collision. Thus, the center 
pole collision is judged by using the upward-and-downward velocity of a 
vehicle, that is, the third velocity signal (Iz) which is the first order 
integrated value of the up-and-down acceleration (Az) of the vehicle. 
In such a step for distinguishing the oblique collision from the center 
pole collision, if it is not judged as an oblique or center pole 
collision, then the collision type is regarded as a front barrier 
collision. 
Hereinafter, the explanation for the collision type judging process by 
using collision type judging apparatus 100 of the vehicle according to the 
preferred embodiment of the present invention will be given. 
First, acceleration sensor 10 detects the acceleration of a vehicle, and 
then generates the first, second and third acceleration signals (Ax, Ay 
and Az). 
The first, second and third acceleration signals (Ax, Ay and Az) generated 
from acceleration sensor 10 are transferred to low-pass filter 20, wherein 
the high frequency components such as noise and/or vibrations are 
filtered. 
A part of the first acceleration signal (Ax) among the first, second and 
third acceleration signals (Ax, Ay and Az) filtered by low-pass filter 20 
is transferred to collision judging part 30. Collision judging part 30 
judges whether the collision is dangerous or not by comparing the preset 
reference value (PRESET) with the first acceleration signal (Ax). 
Collision judging part 30 judges the collision as dangerous if the level 
of the first acceleration signal (Ax) is higher than the reference value 
(PRESET) during all the predetermined time (Tset), or as not dangerous if 
not so. If it is judged as a dangerous collision, then collision judging 
part 30 outputs a reset signal (RESET). If it is judged as not-dangerous, 
collision judging part 30 continue to judge whether or not the collision 
occurs by receiving the first acceleration signal (Ax) which has been 
generated by acceleration sensor 10 and then has been outputted from 
low-pass filter 20. 
The reset signal (RESET) generated in cases where the collision is judged 
as dangerous by collision judging part 30 is transferred to clock 34. The 
clock 34 outputs a synchronous signal (SYNC) by receiving the reset signal 
(RESET). 
Integrator 40, which is synchronized to the synchronous signal (SYNC) from 
clock 34, generates the first, second and third velocity signals (Ix, Iy 
and Iz) by first orderly integrating the first, second and third 
acceleration signals (Ax, Ay and Az) from the low-pass filter 20, with 
respect to time. 
Collision type judging part 50 is synchronized to the synchronous signal 
(SYNC) from clock 34, as shown in FIG. 2, and judges the collision type by 
comparing the first, second and third velocity signals (Ix, Iy and Iz) 
received from integrator 40 with the first, second and third preset values 
(Vx, Vy and Vz). 
Firstly, if the level of the second velocity signal (Iy) is kept below the 
second preset value (Vy) over the second time (T2), it is judged as an 
oblique collision by collision type judging part 50. When a collision is 
not judged as the oblique collision by using the second velocity signal 
(Iy), i.e., in the case that the level of the second velocity signal (Iy) 
is not kept under the second preset value (Vy) over the second time (T2), 
collision type judging part 50 observes whether the level of the first 
velocity signal (Ix) is lower than that of the first preset value (Vx) 
over the first time (T1). 
If the first velocity signal (Ix) maintains lower level than the first 
preset value (Vx) over the first time (T1), collision type judging part 50 
judges whether the third velocity signal (Vz) has higher level than the 
third preset value over the third time (T3). If the level of the first 
velocity signal (Ix) is lower than that of the first preset value (Vx) 
over the first time (T1) and if the level of the third velocity signal 
(Iz) is higher than that of the third preset value (Vz) over the third 
time (T3), collision type judging part 50 is lead to conclude it as a 
center pole collision. 
However, when either the level of the second velocity signal (Iy) is not 
lower than that of the second preset value (Vy) over the second time (T2) 
and the level of the first velocity signal (Ix) is not lower than that of 
the first preset value (Vx) over the first time (T1), or when the level of 
the second velocity signal (Iy) is not lower than that of the second 
preset value (Vy) during over the second time (T2) and the level of the 
first velocity signal (Ix) is lower than that of the first preset value 
(Vx) over the first time (T1) and the level of the third velocity signal 
(Iz) is not higher than that of the third preset value (Vz) over the third 
time (T3), collision type judging part 50 judges it as a front barrier 
collision. 
As illustrated in FIG. 2, collision type judging apparatus 100 according to 
the preferred embodiment of the present invention, which has the 
constitution and the operation as above, judges the vehicle collision type 
by the collision type judging method of the vehicle as follows. 
The method for judging a vehicle collision type includes the acceleration 
signal detecting and producing step S1 in which acceleration sensor 10 
detects the acceleration in the direction of back-and-forth, 
left-and-right and up-and-down (viewed from a traveling vehicle) and 
outputs the first acceleration signal (Ax), the second acceleration signal 
(Ay) and the third acceleration signal (Az) which correspond to the 
back-and-forth, left-and-right and up-and-down directions. 
Then, at the filtering step S2, the first, second and third acceleration 
signals (Ax, Ay and Az) produced at the acceleration signal outputting 
step are filtered to eliminate high frequency components such as noise 
and/or vibrations. 
The collision judging step S3 is served for judging whether or not the 
collision is dangerous by comparing a part of the first acceleration 
signal (Ax) taken from the first, second and third acceleration signal 
(Ax, Ay and Az) whose high frequency components are filtered with the 
preset reference value (PRESET). In the collision judging step S3, if the 
level of the first acceleration signal (Ax) is kept higher than the preset 
value (PRESET) over the predetermined time (Tset), it is judged as a 
dangerous collision. Otherwise, it is judged as a non-dangerous collision. 
If it is judged as a dangerous collision, the reset signal (RESET) is 
outputted. Otherwise, the acceleration signal detecting and producing step 
and the collision judging step are continually repeated. 
The resetting step S4 is served for receiving the reset signal (RESET) 
produced at the collision judging step S3 and generates the synchronous 
signal (SYNC). 
At the integrating step S5, the first, second and third acceleration 
signals (Ax, Ay and Az) obtained at the acceleration detecting and 
producing step S1 is integrated in time, which is performed synchronously 
to the synchronous signal (SYNC) supplied from the resetting step S4, to 
generates the first, the second and the third velocity signal (Ix, Iy and 
Iz). 
The collision type judging step S6 is served for judging the collision type 
by comparing the first, second and third velocity signals (Ix, Iy and Iz) 
given at integrating step S5 with the first, second and third preset 
values (Vx, Vy and Vz), which is performed synchronously to the 
synchronous signal (SYNC) from the resetting step S4. The collision type 
judging step S6 comprises the first decision step S7, the second decision 
step S8 and the third decision step S9. 
The first decision step S7 is served for comparing to find out whether the 
level of the second velocity signal (Iy) is kept below the second preset 
value (Vy) over the second time (T2). 
The second decision step S8 is served for comparing to find out whether the 
level of the first velocity signal (Ix) is lower than that of the first 
preset value (Vx) over the first time (T1). 
The third decision step S9 also is served for comparing to find out whether 
the level of the third velocity signal (Iz) is higher than that of the 
third preset value (Vz) over the third time(T3). 
At the first decision step S7, if the second velocity signal (Iy) has a 
lower level than the second preset value (Vy) over the second time (T2), 
it is judged as the oblique collision. If the first velocity signal (Ix) 
continually has a higher level than the first preset value (Vx) over the 
first time (T1), it is judged as the front barrier collision. Finally, on 
the precondition that the first velocity signal (Ix) continually has a 
lower level than the first preset value (Vx) over the first time (T1) at 
the second decision step S8, when the third velocity signal (Iz) 
continually has higher level than the third preset value (Vz) over the 
third time (T3), it is determined as a center pole collision. Otherwise, 
it is judged as a front barrier collision. 
As is apparent from the above disclosure, since the apparatus and method 
for judging the vehicle collision type of the present invention can 
correctly judge both the low speed front barrier collision and the high 
speed center pole collision by using the three directional acceleration 
signals, the air bag unfolding operation can be successfully controlled in 
accordance with the type of the vehicle collision type. In addition, as 
the high speed center pole collision can be properly detected in a very 
short time by using the system of the present invention, the protection 
level for passengers can be promoted in the event a high speed center pole 
collision should occur. 
The collision type judging part, which is an element of the vehicle 
collision type judging apparatus according to the present invention using 
the three directional acceleration signals, can be well joined with 
various vehicle safety devices such as an air bag unfolding system, a 
safety belt retracting system and a vehicle driving recording system. 
Particularly, when applied to the driving recording system, it can be used 
as a black box. 
Furthermore, there is no need to rebuild the vehicle or add a sensor for 
three directional accelerations since the apparatus of the present 
invention can afford to detect three directional accelerations of a 
vehicle by using one acceleration sensor, which leads to reducing cost. 
It is understood that various other modifications will be apparent to and 
can be readily made by those skilled in the art without departing from the 
scope and spirit of this invention. Accordingly, it is not intended that 
the scope of the claims appended thereto be limited to the description as 
set forth herein, but rather that the claims be constructed as 
encompassing all the features of the patentable novelty that reside in the 
present invention, including all the features that would be treated as 
equivalents thereof by those skilled in the art to which this pertains.