GB2510222A

GB2510222A - Vehicle safety device using impact position to determine acceleration threshold

Info

Publication number: GB2510222A
Application number: GB1319410.5A
Authority: GB
Inventors: Michael Schmid; Gunther Lang
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2012-12-27
Filing date: 2013-11-01
Publication date: 2014-07-30
Anticipated expiration: 2033-11-01
Also published as: DE102012224451A1; FR3000448A1; FR3000448B1; GB2510222B; CN103895598A; DE102012224451B4; JP6391240B2; CN103895598B; GB201319410D0; JP2014129083A

Abstract

A vehicle passenger safety device with an acceleration sensor oriented in the main travel direction and a pressure-sensitive impact sensor device. The pressure sensitive impact sensor can be arranged at the front of the vehicle and can be an air filled pressure hose mounted between a bumper cross member and a bumper element. The impact sensors are pressure sensitive and can be for example piezosensors, optical fibre sensors or acceleration sensors. By determining the relative timing t1, t2 of a set pressure trigger level p2 or the relative pressures p1, p2 at a set time t1 after an impact, a collision can be deduced as symmetric (ie head on) or asymmetric (ie oblique) and an impact position variable can be set. The impact position variable is used to determine the threshold level of an acceleration variable above which the safety device is initiated and that threshold value can be changed to a lower threshold if an oblique impact is identified.

Description

Method for operating a vehicle passenger safety device of a motor vehicle and corresponding vehicle passenger safety device The invention relates to a method for operating a vehicle passenger safety device of a motor vehicle, which has an acceleration sensor oriented in the main travel direction of the motor vehicle as well as a pressure-sensitive impact sensor device, wherein an acceleration is determined by means of the acceleration sensor and at least one safety io measure is initiated if a threshold value is exceeded by an acceleration variable determined from the acceleration. The invention also relates to a vehicle passenger safety device of a motor vehicle.

Prior art

To detect vehicle accidents, the acceleration sensor in particular is used, which is part of a control apparatus of the motor vehicle, for example, in particular of a control apparatus of the vehicle passenger safety device. Alternatively it can also be arranged separately from the control apparatus, however. The control apparatus is configured as an airbag control apparatus, for.example. The acceleration sensor can be arranged, for example together with the control apparatus, on a tunnel of a car body of the motor vehicle. The acceleration sensor is formed in particular to determine an acceleration of the motor vehicle in its main direction of travel or its longitudinal direction The acceleration variable is determined from the acceleration. This can correspond to the acceleration or be ascertained from this with reference to a mathematical relationship, for example. If the acceleration variable exceeds the threshold value, then the at least one safety measure is initiated. This can consist in the triggering of at least one airbag or the like.. . o The acceleration or the acceleration variable determined with the aid of the acceleration sensor has much higher values in the event of head-on collisions of the motor vehicle with an obstruction, forexample with another vehicle, than in collisions that take place at an angle not equal to 00 or with only a partial overlap between the motor vehicle and the obstruction. Collisions of this kind are described as angular collisions or offset collisions. Such angular collisions or offset collisions can accordingly not be optimally detected with the acceleration sensor alone. In particular, the threshold s value chosen must be so low that it guarantees a reliable initiation of the safety measure, even in such collisions.

Disclosure of the invention

io The method for operating a vehicle passenger safety device with the features of claim 1 has the advantage, on the other hand, that the detection of angular collisions or offset collisions is significantly improved. This is achieved according to the invention in that the threshold value is determined as a function of an impact position variable ascertained by means of the impact sensor device. The impact sensor device is preferably configured such that collisions with persons and/or small obstructions can be detected reliably with its assistance. To this end it is pressure-sensitive, thus reacts to the pressure effect on an area of the body of the motor vehicle. It is particularly preferable if the impact sensor device is arranged such* that a pressure effect and consequently a collision in the region of a front part, in particular on a front spoiler or a front bumper of the motor vehicle, can be detected.

The impact sensor device is formed to the effect that an impact position variable corresponding at least approximately to the impact position can be ascertained with it.

This means that the impact sensor device supplies a variable that permits either determination of the exact impact position or at least an estimate to the extent of whether the collision is central, thus in the direction of a longitudinal centre line of the motor vehicle, or whether it is offset in a lateral direction to the longitudinal centre line or at an angle to the longitudinal centre line that is not equal to zero. The impact position variable can be a variable that indicates the impact position. Alternatively, however, it is a variable that is only in reference to the impact position, for example permits determination of the impact position at least approximately. In this case the impact position variable is thus a starting variable for the impact position.

In particular, the impact sensor device makes it possible to detect the side of the longitudinal centre line on which the collision occurs. To guarantee a reliable initiation of the safety measure, the threshold value for the acceleration variable is now established as a function of the impact position variable ascertained. For example, the s further the collision takes place from the longitudinal centre line, or the further the angle between an impact vector and the longitudinal centre line is from zero, the lower the actually occurring acceleration. It is accordingly advantageous to reduce the threshold value correspondingly.

In addition or alternatively, a trigger path for the safety measure can be established as a function of the impact position variable. In this case it is decided with reference to the impact position variable, for example, which variable will form the basis for the initiation of the safety measure. This is advantageous, for example, if several sensors, in particular impact sensors and/or acceleration sensors, are provided, which are arranged at various positions on the vehicle, for example. With the aid of the impact position variable it can now be determined which of the sensors supplies the more reliable value for the acceleration.

Subsequently the variable supplied by the corresponding acceleration sensor or the corresponding acceleration variable is referred back to in order to establish whether the safety measure is to be initiated. To this end the variable is compared wfth the threshold value and -as explained -the safety measure is initiated if the variable exceeds the threshold value.

By means of such a method the impact sensor device actually serving to detect pedestrians or persons can be used to improve the reliability of the vehicle passenger * safety device. Additional sensors, which serve alone to detect an angular collision or offset collision and are cot-intensive, can accordingly be avoided. The realisation of the method according to the invention is possible above all because no exact knowledge of the actual impact position, which could be determined by means of the additional sensors, is necessary for establishing the threshold value. On the contrary, an estimate of the impact position in the form of the impact position variable is sufficient to guarantee the reliable initiation of the safety measure as a function of the acceleration.

A further configuration of the invention provides that the impact sensor device has several sensors, which each supply a measured value and by means of which the impact position variable is established. It goes without saying that one sensor can already be sufficient to ascertain the impact position variable. It is particularly preferable for several sensors to be provided, however, which are arranged in particular at a distance from one another. The impact position variable can be io estimated or ascertained in this way by means of the measured values supplied by the sensors. To this end the time progression of the measured values of the individual sensors is determined and compared with one another, for example.

A further configuration of the invention provides that the more the impact position corresponding to the impact position variable diverges from a longitudinal centre line of the motor vehicle, the further the threshold value is reduced, starting out from a defined basic threshold value. The basic threshold value consequently represents a maximum value for the threshold value. If the established impact position variable points to a collision on the longitudinal centre line or in the region of the longitudinal centre line of the motor vehicle, the threshold value should match the basic threshold value. As already stated above, however, the further the actual impact position is from the longitudinal centre line, the lower the acceleration measured by the acceleration sensor in the main direction of travel of the motor vehicle, thus along the longitudinal centre line. For this reason the threshold value should be selected as a function of a difference of the impact position from the position of the longitudinal centre line, in particular as a function of the absolute value of the difference. It is preferable, however, for the threshold value to be delimited downwards by a minimum threshold value, below which the value may not fall. This prevents the threshold value from being reduced too sharply and an erroneous initiation of the safety measure thus occurring.

* A development of the invention provides that pressure sensors are used as sensors.

This is the case in particular if the impact sensor device is present in the form of a hose sensor device. To detect collisions with persons, an impact sensor device installed in the front region of the motor vehicle, in particular in a bumper of the motor vehicle, is frequently used, which sensor device comprises a pressure hose. This pressure hose is located, for example, between a bumper cross member and a bumper element lying in front of it, which preferably consists at least in regions or completely of a foamed material. The pressure hose is filled with a fluid, in particular air. At its ends at least one pressure sensor respectively is connected in such a way that the pressure present in the pressure hose can be determined with the pressure sensor. Collisions cause a deformation of the pressure hose, which due to the resulting pressure change in the pressure hose causes a change in the measured values ascertained by means of the ic pressure sensor or sensors.

Alternatively or in addition, the impact sensor device can naturally also have sensors of a different kind, for example optical fibre sensors or piezosensors. Acceleration sensors can also be used. It is only important that a pressure caused by an impact and thus the force or the acceleration acting in this case can be determined by the sensors. These sensors should therefore preferably also be pressure-sensitive.

Furthermore, it can be provided that the threshold value is determined as a function of a difference variable ascertained from at least two measured values or corresponding values and corresponding to the impact position variable. The impact position is thus not used directly to determine the threshold value. On the contrary, the difference variable that is derived from the at least two measured values is used. The impact position is thus not determined or at least not exactly determined, in order to keep the outlay as low as possible. The difference variable results from the difference between the at least two measured values or the corresponding values thus derived from the measured values. The difference variable can correspond to the impact position variable or be in a certain relation to this.

A development of the invention provides that a time difference or a value difference is used as a difference variable. In the case of the time difference, an interval between the points in time at which the same threshold value is reached or exceeded by the measured values of the sensors or by corresponding values is used in particular. The curve of the measured values or the corresponding values is thus observed over time.

The corresponding values should be understood to mean values derived from the measured values, wherein this takes place by means of a mathematical relationship, a filter or the like, for example.

s If the measured value of one of the sensors or the value corresponding to this exceeds the threshold value, the time at which this happens is recorded. The time at which the measured value of the next of the sensors or the value corresponding to this exceeds the threshold value is also ascertained. The impact position and/or the impact position variable can now be deduced from the time difference between these two times, or the io threshold value can be determined directly. The actual magnitude of the measured values is preferably not considered here. The same threshold value is used to determine the time of exceeding for all measured values or all corresponding values, however.

is the value difference, on the other hand, is the difference between the measured values or the corresponding values at a certain time. Here too, therefore, the curve of the measured values or the corresponding values is considered over time, wherein the measured values or the corresponding values at a certain time are compared. The difference between the measured values or the corresponding values is recorded in the form of the value difference and used as a difference variable to determine the threshold value or the impact position variable.

In a further configuration of the invention, it is provided that the value difference is standardised, in particular with the largest or the smallest of the measured values or with a mean value of the measured values. The largest or the smallest of the corresponding values or the mean value of these can also be used. Said method has the advantage that a threshold value that, once exceeded by the difference variable or the value difference, results in the presence of an angular or offset collision being deduced, can be selected that is constant or at least only has to be varied slightly over time1 because an increase in the value difference over the increase of at least one measured value, in particular of both or of all measured values, is itself standardised The invention is further directed to a vehicle passenger safety device of a motor vehicle, in particular a vehicle passenger safety device for carrying out the method described above, wherein the vehicle passenger safety device has an acceleration sensor oriented in the main direction of travel of the vehicle as well as a pressure-s sensitive impact sensor device and is formed to Lascertain an acceleration by means of the acceleration sensor and, if a threshold value is exceeded by the acceleration, to initiate at least one safety measure. It is provided in this case that the vehicle passenger safety device is also formed to determine the threshold value as a function of an impact position variable ascertained by means of the impact sensor device. The io advantages of such a procedure have already been examined. The vehicle passenger safety device as well as the corresponding method can be developed according to the above statements, so that reference is made to these in this respect.

The invention is explained in greater detail below with reference to the embodiments shown in the drawing, without a restriction of the invention occurring thereby.

Figure 1 shows a first graph in which two curves for measured values of two pressure sensors of an impact sensor device or corresponding values for a frontal collision are entered over the time, and Figure 2 shows the curves known from figure 1 for an angular or offset collision.

Figure 1 shows a diagram in which measured values of two pressure sensors, or values derived from the measured values and corresponding to these, are entered over the time. One curve 1 shows the curve of the measured values of a first of the pressure sensors and a curve 2 shows the curve of the measured values of a second of the pressure sensors. The pressure sensors are part of an impact sensor device of a motor vehicle. They are preferably connected to the same pressure hose, namely at opposite ends of the pressure hose. The measured values accordingly represent the pressure in the pressure hose at its respective end. The pressure hose is arranged in a front region of the motor vehicle, in particular integrated into a front bumper.

The pressure hose is arranged, for example, between a bumper cross member of the body of a motor vehicle and a bumper element arranged ahead of this in the main direction of travel, wherein the latter consists at least in regions of a foamed material, for example. In the event of a collision of the motor vehicle with an obstruction, in s particular a person Or the like, the pressure hose is compressed, so that a collision can be deduced with reference to the measured values of the pressure sensors. The curves 1 and 2 are now adjusted, for example, if the collision coincides with a longitudinal centre line of the motor vehicle, or at least nearly coincides with this. The collision thus takes place substantially symmetrically, so that the measured values behave almost io identically over the time.

A difference variable is ascertained from the measured values of the pressure sensors or from the values that are derived from the measured values, which difference variable is present, for example, as a time difference or a value difference. The time difference is here describes a time interval between those times at which the same threshold value is reached or exceeded by the measured values of the sensors or by the corresponding values. In the following, only the measured values are considered. It is immediately clear, however, that the values corresponding to the measured values can always be used alternatively.

For example, the pressure p = P2 is assumed here as the threshold value. It is immediately clear that the measured values of the curve 1 reach and exceed the threshold value P2 at time t1. This applies to the measured values of curve 2 only at time t2. The time interval or the time difference now results from the relationship t2-t1.

The value difference, on the other hand, is the difference between the measured values at a certain time. For example, the time t1 is considered. In this, the measured values of curve 1 exhibit a pressure P2, while the measured values of curve 2 have a pressure Pi.

The difference between these two values, thus the difference between the pressures P2 and Pi, is used as the value difference and thus as the difference variable.

Figure 2 shows a further diagram in which the curves 1 and 2 are reproduced for a collision that takes place away from the longitudinal centre line and takes place thus as an angular collision or offset collision. It is clear that the measured values of curve I increase much sooner and much more sharply than the measured values of curve 2.

Differences accordingly result in the time difference as well as the value difference, which are immediately recognisable in a comparison of the diagrams of figures 1 and 2.

Both the time difference t2-ti nd the value difference P2-Pi are now much greater than for the collision in the region of the longitudinal centre line. The impact position can be deduced accordingly from the respective difference variable used, thus either the time difference or the value difference. The difference variable is at least directly dependent on the impact position, however.

ic In known vehicle passenger safety devices, an acceleration sensor oriented in the main direction of travel of the motor vehicle is provided. An acceleration of the motor vehicle in this direction is ascertained by means of this and if the acceleration exceeds a threshold value, at least one safety measure is initiated. This safety measure can consist in the triggering of an airbag, for example. Because the acceleration in the main is direction of travel of the motor vehicle or along the longitudinal centre line of the motor vehicle depends heavily on the impact position, however, evaluation of the acceleration alone is not always sufficient.

Additional sensor devices are accordingly necessary, which are costly, however. For 2C this reason, the impact sensor device, which is present anyway, should now be used as a complement. The threshold value at which the safety measure is initiated when it is exceeded is determined as a function of the impact position variable ascertained by means of the impact sensor device. The threshold value is established at least as a function of the difference variable, however. In this case the further the impact position diverges from the Iongftudinal centre line of the motor vehicle, the further the threshold value is reduced, for example, starting out from a defined basic threshold value. It goes without saying that other sensors can be used instead of the pressure sensors, for example optical fibre sensors or piezosensors.

In a symmetrical collision with an impact position on the longitudinal centre line, the first contact point of the obstruction is located centrally on the motor vehicle. Because the bumper cross member and thus the pressure hose normally have a slight curvature, the initial compression of the pressure hose takes place in the centre. Both pressure 1O sensors are equidistant from the initial compression point and register a comparable pressure increase virtually simultaneously, as is shown in the diagram. In an angular collision or offset collision, the first contact point is asymmetrical to the longitudinal centre line of the motor vehicle on one vehicle side, on the other hand. The pressure sensor that is closer to the impact position, therefore, will register the compression of the pressure hose before the other preèsure sensor and also record a faster increase in the pressure.

Asymmetrical collisions of this kind are thus basically detected by differences in the io measured values of the pressure sensors. The use of the time difference and the value difference as difference variable has already been considered above. For example, it can be provided that the presence of an asymmetrical collision is deduced if the difference variable exceeds a difference variable threshold value. If the difference variable lies below this threshold value, therefore, the acceleration variable threshold is value is set equal to a first threshold value, which is suitable for the symmetrical collision. If on the other hand the difference variable threshold value is exceeded by the difference variable, the acceleration variable threshold value is set equal to a second threshold value, which is established for the asymmetrical collision. The difference variable threshold value can be constant, but alternatively it can also vary as a function of other variables, for example the time. For example, a timer is provided, which starts to run once one of the measured values of the pressure sensors exceeds a starting threshold. The difference variable threshold value is now increased as a function of the time determined by means of this timer, because on complete compression of the pressure hose no further reliable statements can be made regarding the impact position.

It goes without saying that it can be provided to standardise the value difference. To this end, the largest or the smallest of the measured values, for example, or a mean value of the measured values can be used. When using the mean value; the relationship (Pi-Pr)/(PiPr)> f(t) is present, for example. Here Pi designates the measured value of a left pressure sensor and Pr the measured value of a right pressure sensor. The variable f(t) is the difference variable threshold value, which is varied as a function of the time, in particular of the time determined by means of the timer. If this threshold is exceeded, s then as already explained above, the presence of an asymmetrical collision, is deduced and the acceleration variable threshold value adapted accordingly. This procedure has the, advantage that the difference variable threshold value does not have to be varied, or only has to be varied, slightly over the time, because an increase in the difference between the two measured values is at least partly balanced out by the increase in at least one of the measured values.

For example, a check is only made of whether the difference variable threshold value has been exceeded if a sum of the measured values exceeds or has exceeded a minimum value. The comparison does not take place immediately after the collision, is therefore, but with a small time offset, in order to be able to make a reliable statement about the impact position. In addition or alternatively a check can only be made of whether the difference variable threshold value has been exceeded if the sum of the measured values has not exceeded a certain maximum value. In this way it is avoided that the check takes place too late after the collision, because in this case the pressure hose is possibly completely compressed and accordingly a sensible statement can no longer be made about the impact position.

The relationship (pipr)>f(t,pi,pr) , , can be deduced from the aforementioned relationship. An asymmetrical collision is thus detected if the difference between the measured values surpasses a threshold dependent on the individual measured values and optionally th! time. The dependence on the mean value has already been explained as a special case. . . In addition or alternatively, the time difference or the value difference can also be evaluated in a different manner. For example, instead of the difference of the measured values, the difference of the gradients of the measured values (thus the deduction of the curve of the measured values, for example) or the difference of other equivalent pressure variables for the left and the right pressure sensor can be considered. In particular, the difference of filtered and/or integrated measured values can be formed, s due to which the robustness of the method is increased due to the smoothing that occurs. Instead of the measured values, the values of the equivalent variables can thus always be used additionally or alternatively, especially when determining the time difference and/or the value difference.

Claims

Claims 1. Method for operating a vehicle passenger safety device of a motor vehicle, which has an acceleration sensor oriented in the main direction of travel of the vehicle as well as a pressure-sensitive impact sensor device, wherein an acceleration is determined by means of the acceleration sensor and at least one safety measure is initiated if a threshold value is exceeded byan acceleration variable determined from the acceleration, characterised in that the threshold value is determined as a function of an impact position variable ascertained by means of the impact sensor device.
2. Method according to claim 1, characterised in that the impact sensor device has several sensors, which each supply a measured value and by means of which the impact position variable is determined.
3. Method according to one of the preceding claims, characterised in that the further the impact position corresponding to the impact position variable diverges from a longitudinal centre line of the motor vehicle, the further the threshold value is reduced starting out from a defined basic threshold value.
4. Method according to one of the preceding claims, characterised in that pressure sensors are used as sensors.
5. Method according to one of the preceding claims, characterised in that the threshold value is determined as a function of a difference variable that is ascertained, from at least two measured values or cOrresponding values and that corresponds to the impact position variable.
6. Method according to one of the preceding claims, characterised in that a time difference or a value difference is used as a difference variable.
7. Method according to one of the preceding claims, characterised in that a time interval between the times at which the same threshold value is reached or exceeded by the measured values of the sensors or by the corresponding values is used as the time difference.
8. Method according to one of the preceding claims, characterised in that the s difference between the measured values or the corresponding values at a certain time is used as the value difference. N'
9. Method according to one of the preceding claims, characterised in that the value difference is standardised, in particular with the largest or smallest of the measured values or with a mean value of the measured values.
10. Vehicle passenger safety device of a motor vehicle, in particular for executing the method according to one or more of the preceding claims, wherein the vehicle passenger safety device has an acceleration sensor oriented in the main is direction of travel of the motor vehicle as well as a pressure-sensitive impact sensor device, wherein the vehicle passenger safety device is formed to determine an acceleration by means of the acceleration sensor and to initiate at least one safety measure if the threshold value is exceeded by an acceleration variable determined from the acceleration, characterised in that the vehicle passenger safety devióe is also formed to determine the threshold value as a function of an impact position variable ascertained by means of the impact sensor device.
11. Method for operating a vehicle passenger safety device of a motor vehicle, substantially as hereinbefore described with reference to the accompanying drawings.
12. Vehicle passenger safety device of amotor vehicle, substantially as hereinbefore described with reference to the accompanying drawings.