DE4133316A1 - Collision detector for motor vehicle for operating safety device - compares output signal of arithmetic processor having multistage linear filer with predetermined reference value - Google Patents

Abstract

An arithmetic processor receives a signal from an acceleration sensor (1). A comparator (6) is used to determine a collosion state by comparing the output signal of the processor with a reference value (Vref) and generates an output signal if so. The processor has a linear filter (5) comprising a high pass (3) and two low pass (4a, 4b) filters in series. A function generator can be used to change the reference value w.r.t. time. The linear filter can comprise a digital filter with a set of delay members and coefft. multipliers. USE/ADVANTAGE - Timely, exact detection of collosion for operating passenger or driver safety system, e.g. inflating air bag or tightening safety belt.

Description

The invention relates to a collision detection device for vehicles, especially motor vehicles, and is suitable to activate an occupant installed in the vehicle Protection system such as an airbag system and a belt front clamping system.

Today there are more and more motor vehicles that are in addition to the seat belts with airbag and pretensioning systems as Occupant protection devices are equipped to prevent an in sat before an impact in the event of a collision of force to protect the vehicle. In the event of a collision with one an airbag or pre-tensioning system vehicle is the primer in the airbag or in a safe seat belt device ignited so that by an ignition signal the airbag is opened by a collision detection device blow or the pretensioner is activated.  

To the occupant in a positive manner in the event of a collision protect, such a collision detection device must in particular the occurrence of the collision and the time of the Can exactly determine generation of the ignition signal.

Collision detection devices are conventional for Known vehicles in which the occurrence of a collision is determined when they are accelerated that is larger than a predetermined value.

Such collision detection devices include various dene types, for example an electrical type, the a supplied acceleration with electrical sensors summarizes and determines the occurrence of a collision when the detected acceleration has a predetermined size or this exceeds, as well as a mechanical design that has a weight has a magnet and electrical contacts and that A collision occurs when the weight hits the contacts has come into contact and they against the Magnetic force of the magnet has closed.

However, these known collision detection devices are all designed to only prevent the occurrence of a collision based on one at a time posed to determine acceleration. You can therefore choose one Make a wrong decision about the occurrence of a collision, if they get a momentary push, for example the vehicle against a curb or on the sidewalk or drives over a ditch or a shock acceleration learns that a vehicle part with a Hammer is processed. They can also make a decision meet at the wrong time.

A package has already been made to overcome these disadvantages Sionsdetektiervorrichtung proposed (z. B. in the national Japanese PCT publication (Kohyo) 63-5 03 531), which comprises: an acceleration detection device which  a Be applied to a vehicle while driving acceleration detected, an arithmetic processor to the inte gration of a signal having a predetermined value detected acceleration, and a Collision judging device that judges that a Collision actually occurred when the integration value exceeds a predetermined value. With this suggested gene collision detection device is one on the drive witnessed acceleration of an integration first Order to a value equivalent to speed is subjected. It then becomes the speed equivalent value determines whether a collision is actually has taken place.

However, the proposed collision detection device is suffers from the disadvantage that with regard to the detection a delay occurs and the detection is accurate is low. If the one with the integration value increases comparative predetermined value is set so that a Detection time is obtained, which is used to detect a Collision is suitable when driving the vehicle quickly, there is a delay in the detection time points of a collision when driving at medium speed efficiency. Conversely, if the predetermined value is given in this way is that a detection time is obtained which is de Detect a collision when driving at medium speed suitable, it can happen that even a col lision when driving at low speed than real ones Collision is assessed, although such a slow speed Collision does not need to be detected.

Furthermore, since the proposed collision detection device does not perform collision detection when the broke up acceleration falls below a predetermined value, the disadvantage may arise that a delay in the Detection of a collision occurs when on the vehicle an acceleration is continuously applied that the  falls below a predetermined value, and that currently error it is determined that a real collision has occurred, when a momentary acceleration is applied to the vehicle is brought whose size exceeds the predetermined value.

The object of the invention is to provide a package Sion detection device for vehicles, the occurrence detect a collision exactly and at the right time can.

To achieve this object, a package is according to the invention Sionsdetektiervorrichtung provided for a vehicle, the comprises: an acceleration detection device for Er capture one on the vehicle in the event of a collision brought acceleration, an arithmetic processor to arith metallic processing of a signal that the by the Be acceleration detection device detected acceleration denotes, and a collision determination device, the an output signal of the arithmetic processor with a front compares a certain reference value and the occurrence of a Output signal indicating collision based on the ver generated the same result, the collision detection before direction is characterized in that the arithmetic pro processor has a multi-stage linear filter.

A reference value changing device is preferably provided, to change the predetermined reference value over time.

The multi-stage linear filter comprises at least two in Row of low passes.

Alternatively, the multi-stage linear filter comprises a digital filter with a variety of delay elements and one Variety of coefficient multipliers.

Preferably, the multi-stage linear filter further includes one High pass.  

The invention is also described below with respect to others Features and advantages based on the description of exec examples and with reference to the enclosed Drawings explained in more detail. The drawings show in:

Fig. 1 is a block diagram showing the basic structure of a collision detection device according to the invention;

Fig. 2 is a block diagram of a first embodiment of the invention;

Fig. 3 is a graph showing the relationship between the applied acceleration, the output of a linear filter of Fig. 1 and a threshold value provided for a comparator in Fig. 2;

Fig. 4 is a block diagram of a second embodiment of the invention;

FIG. 5 is a graph similar to FIG. 3, showing the relationship between the applied acceleration, the output of a linear filter of FIG. 4 and a threshold provided for a comparator of FIG. 4; and

Fig. 6 is a block diagram of a third exemplary embodiment of the invention.

The basic structure of the device is shown in FIG. 1. The collision detection device includes an acceleration detection device 100 that detects an acceleration applied to a vehicle while driving, an arithmetic processor, which consists of a multi-stage linear filter and arithmetically processes a signal indicative of the detected acceleration, and a collision determination device that outputs an output signal compares the arithmetic processor with a predetermined reference value V _ref and determines the occurrence of a collision.

In this arrangement the Beschleunigungserfassungsein detected direction 100, a set on the vehicle during the journey applied acceleration. A signal characterizing the detected acceleration is fed to the arithmetic processor or the multi-stage linear filter 200 , which processes this input signal arithmetically. This arithmetic processing of the input signal is, for example, a second order low pass filter process and is used to calculate a displacement amount from the detected acceleration. The calculated displacement value is compared with the predetermined reference value V _{ref in} order to assess whether a collision has taken place.

The detection device will be described in detail below wrote.

Fig. 2 shows a first embodiment.

The collision detection device with an Air bag system applied, in the event of a collision of the vehicle An airbag is inflated immediately to the occupant in front of one Forward jerk and a collision with the steering wheel or the Protect the front window of the vehicle.

As shown in FIG. 2, the collision detection device comprises an acceleration sensor 1 , a buffer amplifier 2 , a second-order linear filter 5 and a comparator 6 , which are arranged in the order mentioned. The linear filter 5 of the second order consists of a high-pass filter 3 and two low-pass filters 4 a and 4 b, which are connected in series. These filters 3 , 4 a and 4 b are each RC filters from an opposing stand and a capacitor.

The collision detection device thus constructed works as follows:

An output signal of the acceleration sensor 1 , which denotes the acceleration applied to the vehicle, is supplied to the buffer amplifier 2 , which amplifies the signal to a predetermined level. The amplified acceleration signal is fed to the multi-stage linear filter 5 , in which the required low-frequency components are first filtered out by the high-pass filter 3 , in order to avoid the risk of a misjudgment resulting from the rise in an acceleration signal, which typically occurs in the second half of the Duration of a collision when the vehicle is traveling slowly. An output signal of the high-pass filter 3 is then integrated in the low-pass filter 4 a to a value which is equivalent to the "speed", and further integrated in the low-pass filter 4 b to a value which is equivalent to the "displacement". The low passes 4 a, 4 b thus have the function of calculating an estimated amount of the displacement of the occupant in the event of a collision of the vehicle. The value thus formed, which is equivalent to the displacement, is compared in comparator 6 with the predetermined reference value V _ref . The comparison result is output by the comparator 6 as the output signal V _out , which denotes the detection of the collision. If the displacement equivalent value is greater than the predetermined reference value V _ref , the output signal V _{out is} then adapted as an activation signal for an airbag system (not shown) which is installed in the vehicle.

To fully protect the occupant from impact in a collision, the airbag system should in the event of a collision of the vehicle are working properly. For this purpose a Collision of the vehicle with high accuracy and with good Responsiveness can be detected, and the resulting Activation signal must be an airbag deployment device systems at the right time.  

In the case of the airbag system, the optimum time at which the activation signal should be issued is the instant at which the occupant begins to move forward when the vehicle collides. It is therefore imperative to accurately determine the moment when the occupant starts moving forward. This moment is earlier, the greater the acceleration due to a collision, ie the higher the speed of the vehicle immediately before the collision. In order to meet this requirement, in this exemplary embodiment the signal corresponding to the acceleration recorded is integrated in the second order in the low-pass filters 4 a, 4 b, forming an equivalent value to the displacement. The displacement shows a higher rate of change when the acceleration due to a collision has a larger value in proportion to the driving speed of the vehicle. When the displacement equivalent value reaches a predetermined value, an output signal is provided by the collision detection device, which designates the detected collision, in order to thereby specify the correct time for the delivery of the activation signal.

The use of the high-pass 3 is based on the fact that the acceleration changes relatively smoothly in the event of a collision when the vehicle is traveling slowly and that the airbag system need not be activated when a collision occurs at a low speed of the vehicle. The low-pass filter 3 thus dampens the output signal of the buffer amplifier 2 in the event of a collision of the vehicle during slow travel, in order to thereby ensure an exact detection of a collision from which the occupant is to be protected.

With reference to Fig. 3 it can be seen in particular that the higher the Fahrge speed of the vehicle is immediately before a collision, the greater the Fahrge speed of the vehicle, as shown by the dashed lines, and that the integrated te output signal of the multi-stage linear filter 5 , ie Rate of change of the displacement or the forward pressure of the occupant, the greater, as the solid lines show. As a result, the activation of the airbag system must be brought forward. For this purpose, in the collision detection device of this embodiment, the integrated output of the filter 5 is compared with the predetermined reference value V _ref to judge the occurrence of a collision at an earlier time when the collision occurs when the vehicle is traveling at high speed. Furthermore, a collision occurring when driving at low speed is ignored.

In the first embodiment described above the first order high pass and the second low passes Order used as the multi-stage linear filter, however this is not a limitation; instead you can go to Increasing the detection accuracy also high and / or low higher-order passports are used.

Fig. 4 shows a second embodiment. This is designed to prevent, more positively, that a collision is judged to be a real collision when the vehicle is traveling slowly because the airbag system need not operate in this case.

The second embodiment differs from the first in that the high-pass filter 3 of FIG. 2 is replaced by a comparator 7 and a function generator 8 , which are arranged parallel to the multi-stage linear filter 5 '. An input of the comparator 7 is coupled to the output of the buffer amplifier 2 , and the input of the function generator 8 is coupled to the output of the comparator 7 , while its output is coupled to an input of the comparator 6 , to which a threshold value V _ref is applied.

A threshold value V _{ref2 to be} supplied to the comparator 6 is generated by the comparator 7 and the function generator 8 in such a way that it increases over time in order to make a misjudgment regarding the occurrence of a collision when the vehicle is traveling slowly, with the acceleration being gentle changes to avoid. The comparator 7 , the output signal of the buffer amplifier 2 , ie an amplified acceleration measurement signal, is supplied, and the comparator compares this signal with a predetermined reference value V _ref1 . This reference value V _ref1 is predetermined with a value that is slightly smaller than the maximum value that the acceleration measurement signal can assume when the vehicle is in the normal driving state. If the acceleration _signal from the buffer amplifier 2 exceeds the reference value V _ref1 , an output signal of the comparator 7 _triggers the function generator 8 (at a time t ₁ in FIG. 5). After a given time Ta has elapsed since the initiation time t ₁ (at a time t ₂ in FIG. 5), the function generator 8 begins to generate the threshold value V _ref2 in a progressively increasing manner. The predetermined time period Ta and the _{gradient of} the threshold value V _ref2 are _specified with a gentle acceleration change in the event of a collision when the vehicle is traveling slowly, so that the output signal V _out , which denotes the collision determined, only in the event of a collision at medium or high vehicle speed is generated, ie only if the acceleration signal from the multi-stage linear filter 5 'has a higher level than the threshold value V _ref2 even after the predetermined period Ta has _elapsed , and the output signal V _out is not generated in the event of a collision at low vehicle _speed , when the level of the acceleration _signal from the linear filter 5 'is below the threshold V _ref2 . By _specifying the threshold value V _{ref2 in} this way, the collision assessment can be carried out with greater reliability.

Referring to FIG. 5 shows the shift, the extent of the integrated From ie the pre Windwärts rucks of the occupant, in accordance with output signal of the linear filter 5 'greater change rate with respect to acceleration in collisions in the case of high, medium and low vehicle speed. In the event of a collision at low or medium vehicle speed, however, in many cases there is no great danger that the airbag system would have to be activated, and in such cases the output signal V _out , which denotes the collision detected, need not be generated. In the present _exemplary embodiment, therefore, according to FIG. 5, the threshold value V _ref2 output by the function generator 8 _{pro gressively increases} at a specific point in time (t ₁ ) in order to output the output signal V _out which denotes the detected collision in the event of a collision at low vehicle speeds and even to prevent at some medium vehicle speeds. As a result, the airbag can only be inflated when the occupant is thrown forward due to an acceleration caused by a dangerous collision, and thus the occupant can be reliably and positively protected only in cases where such protection is necessary.

In the embodiment of FIG. 4, the function transmitter 8 is of the type which generates the output signal in a linear manner, but alternatively a function transmitter can be used which generates an output signal rising along a curved path. Such a function generator can be formed by a time constant element with a capacitor and a resistor, the charging and discharging of the capacitor causing such a change in the output signal running on a curve.

Fig. 6 shows a third embodiment. It differs from the two exemplary embodiments described above in that instead of the low-pass filters 4 a, 4 b, which are analog filters, a digital filter 10 is used. An A / D converter 9 is connected between the output of the buffer amplifier 2 and the input of the digital filter 10 . An acceleration signal from the buffer amplifier 2 is converted by the A / D converter 9 into a digital signal and supplied to the digital filter 10 , which processes this digital signal arithmetically and supplies the processed signal to the comparator 6 . The digital filter 10 used here is an FIR digital filter (= a digital filter with finite impulse response function), which has a large number of delay elements Z ^-1 and a large number of coefficient multipliers K 0 -Kn, each with the inputs of the delay elements Z ^-1 are coupled. A delayed acceleration value of each delay element Z ^-1 is multiplied by a coefficient of the corresponding coefficient multiplier K 0 -Kn, and the resulting products of all coefficient multipliers are added up in an adder 11 . An output signal from the adder 11 is fed to the comparator 6 , which compares it with the threshold value V _ref, as in the two previous embodiments. If the output signal of the adder 11 exceeds the threshold value V _ref , the comparator 6 generates the output signal V _out which denotes the determined collision.

The output signal of the adder 11 , that is, the digital filter 10 , contains a displacement component, that is, a forward pressure amount of the occupant, as in the previous exemplary embodiments, but it may contain many other components with the analog filter 4 a, 4 b of the previous exemplary embodiments cannot be obtained.

Of course, in the third embodiment, for example, the comparator 7 and the function generator 8 of FIG. 4 corresponding elements can be used to give the threshold value V _ref a characteristic that increases progressively over time in order to achieve the same results as before .

Also, the digital filter 10 may also have a high-pass filter as in the first embodiment in order to avoid misjudgment due to low frequency components in the acceleration signal.

Suitable values of the coefficients of the coefficient multipliers K 0 -Kn can be determined from the acceleration values which are determined by collision attempts and by the degree of danger to which the occupant is exposed and which has been determined as a result of such collision attempts, as a result of which dangerous collisions are more precise recognized who can.

Claims (7)

1. Collision detection device for a vehicle, with an acceleration detection device ( 100 , 1 ) which detects the acceleration applied to the vehicle in the event of a collision, with an arithmetic processor ( 200 ) which arithmetically processes a signal designating the acceleration it detects, from the acceleration detection device, and with a collision determination device ( 300 , 6 ) which compares an output signal of the arithmetic processor with a predetermined reference value (V _ref ) and generates an output signal based on the comparison result which indicates whether a collision has occurred, characterized in that the Arithmetic processor ( 200 ) comprises a multi-stage linear filter ( 5 , 5 ', 10 ). 2. Device according to claim 1, characterized in that a reference value changing device ( 7 , 8 ) is provided which changes the predetermined reference value (V _ref ) over time. 3. Apparatus according to claim 1 or 2, characterized in that the multi-stage linear filter has at least two low-pass filters ( 4 a, 4 b) lying in series. 4. Apparatus according to claim 1 or 2, characterized in that the multi-stage linear filter comprises a digital filter ( 10 ) with a plurality of delay elements (Z ^-1 ) and a large number of coefficient multipliers (K 0 -Kn). 5. The device according to claim 2, characterized in that the reference value changing device has a comparator ( 7 ) and a function generator ( 8 ), the acceleration detection device ( 1 , 2 ) and the collision determination device ( 6 ) and parallel to the arithmetic processor () 4 a, 4 b) are switched. 6. The device according to claim 5, characterized in that the comparator ( 7 ) generates a trigger signal (t ₁ ) when the signal indicative of the detected acceleration from the acceleration detection device exceeds a second predetermined reference value (V _ref1 ), and the function generator ( 8 ) the first-mentioned predetermined reference value (V _ref2 ) progressively increases after a predetermined period (Ta) after its execution with the trigger signal. 7. Device according to one of the preceding claims, characterized in that the multi-stage linear filter ( 5 , 5 ', 10 ) comprises a high-pass filter ( 3 ).