DE19632363C1 - Method of detecting angular acceleration of motor vehicles - Google Patents

Abstract

The method involves using three sensors with sensitivity axes. The first and second sensors (3b,3c) are in a plane perpendicular to the longitudinal axis with their sensitivity axes in this plane. The third (3a) is in a parallel plane. The difference of the first (3b) and second (3c) sensor signals yields the angular acceleration about the longitudinal axis. The sum of the three sensor signals yields the acceleration perpendicular to the road plane. The mean of the first and second sensor signals and the difference between the sum of the first and second sensor signals and the third sensor signal are used to derive the angular acceleration about the transverse vehicle axis.

Description

The invention relates to a method for the detection of angular accelerations conditions of a motor vehicle according to the preamble of the claims 1 and 2 and a use of this method to trigger a pas sive safety device, in particular roll bar and belt tensioner, for motor vehicles depending on the inclination of the motor vehicle.

To trigger built-in safety devices in a motor vehicle sen, especially a roll bar or belt tensioner, are accelerators tion or inclination sensors installed, so that a critical inclination angle, the so-called tilt angle, or the state in which the driving has lifted off the road, can be recognized. As a "critical nei angle "or" tilt angle "is the angle that a Vehicle when it is about to tip over. The tipping The angle of a vehicle is generally between 50 ° and 70 °.

In the German patent application DE 38 15 938 A1 an accelerator tion sensor described in the prior art. This acceleration sensor identifies a tube level as a housing that is relative to the acceleration to be determined is formed. A detector speaks a defined position that a display medium (air bubble) within a Liquid in the tube vial at the acceleration to be detected value assumes.

The disadvantage of this arrangement is that in the state in which the vehicle has little or no contact with the ground has the movement of the display based on the gravitational force medium in the tube dragonfly is no longer detectable. That means, that in this state, for example after crossing a threshold and  subsequent free flight, a critical situation is not recognized and therefore safety devices are not activated. Continue to work in dynamic driving operation additional acceleration forces on the Li belle, so that the measurement of the actual angle of inclination is falsified.

Such arrangements are also known in which such a tube Dragonfly with a be in the German patent application DE 40 03 360 A1 wrote and called "G-sensor" accelerometer kom is binated. Such an arrangement requires a considerable amount of money turned to sensors and evaluation.

With the help of such a "G-sensor" alone, which is used to determine the existence of a constant acceleration, the acceleration due to gravity, can be used with ge find little mechanical effort that, for example, a Vehicle only moves under the influence of gravitational acceleration. However, it is not possible with the help of a single such Be acceleration sensor the critical angle of inclination, for example one Vehicle.

It is therefore an object of the invention to provide a method for the detection of Specify angular accelerations of a motor vehicle that the pre mentioned disadvantages avoided.

This object is achieved by a method for the detection of Winkelbe accelerations of a motor vehicle with respect to its longitudinal axis and be regarding its transverse axis as well as for the detection of an acceleration of the Motor vehicle in the vertical direction to the road level with a he most, second and third, each generating a sensor signal and one Sensitivity axis have the sensor in which the first and second Sensor in a first plane perpendicular to the longitudinal axis of the motor vehicle are arranged such that the sensitivity axes lie in this plane gene, and the third sensor in a second parallel to the first plane Level, whereby the following procedural steps are carried out:

• - Difference formation from that of the first and second sensor formed sensor signal for determining the angular acceleration around the longitudinal axis of the motor vehicle,  
• - Sum formation from the sensor signals of the first, second and third sensor for determining the acceleration perpendicular to Road level,
• - Averaging from the first and second sensor signals and on finally forming the difference from the sum of the sensor signals of the first and second sensor and the signal of the third sensor for Determination of the angular acceleration around the transverse axis of the force vehicle.

The second solution describes a method for the detection of Winkelbe accelerations of a motor vehicle with respect to its longitudinal axis and be regarding its transverse axis as well as for the detection of an acceleration of the Motor vehicle in the vertical direction to the road level with a he most, second, third and fourth, each generating a sensor signal and a sensitivity axis have the sensor in which the first and second sensor in a perpendicular to the longitudinal axis of the motor vehicle first level are arranged such that the sensitivity axes in this level, and the third and fourth sensors in one to the first Level parallel second level, with the following process steps be performed:

• - Formation of a first sum from the sensor signals of the first and second sensor,
• - Formation of a second sum from the sensor signals of the first and third sensor,
• - Formation of a third sum from the sensor signals of the third and fourth sensor,
• - Formation of a fourth sum from the sensor signals of the second and fourth sensor,
• - Sum formation from the sensor signals of all four sensors for loading tuning the acceleration of the motor vehicle perpendicular to Road level,  
• - Difference formation from the third sum and the first sum to Determination of the angular acceleration in the longitudinal direction of the force vehicle and
• - Difference formation from the fourth sum and the second sum to Determination of the angular acceleration around the longitudinal axis of the force vehicle.

Advantageous developments of the invention are in the subclaims described.

The advantages of the invention are that the signals from already in egg sensors installed in the vehicle, e.g. for chassis control, can be used. It also becomes a critical situation Detected at a very early stage so that there is enough time to fire of security systems remains.

An embodiment of the invention is explained in detail below tert and shown using the figures.

Show it

FIG. 1 shows a first embodiment of a sensor assembly in gungsaufnehmern ei nem vehicle for Neigungsdetektierung with three Accelerati,

Fig. 2 shows a basic circuit arrangement for evaluating the sensor signals,

FIG. 3 shows a basic circuit arrangement for triggering an occupant protection system in,

FIG. 4 shows a flow chart of a program running in a controller algorithm,

Fig. 5a: a second embodiment of a sensor arrangement in a vehicle for inclination detection with four acceleration sensors and

Fig. 5b: an evaluation circuit for the sensor arrangement of FIG. 5a.

Fig. 1 shows a vehicle 1 having a longitudinal axis 24, a transverse axis 25, and an occupant protection system, essentially comprising a control and evaluation unit 2, accelerometers 3 a, 3 b and 3 c and connecting lines 4. To protect the occupants in an accident 1 known protective devices such as belt tensioners 5 , impact cushion 6 , side impact cushion 7 (door bag, sidebag) and an adjustable roll bar 8 are arranged. The roll bar 8 'is drawn in dashed lines. All protective devices are triggered by the control and evaluation unit 2 .

The following states of the vehicle 1 can be determined by means of the three accelerometers 3 a, 3 b and 3 c with the sensitivity axes pointing in the same direction (Z direction or vertical axis): lifting (in the Z direction), rolling (rollover in X- Direction, ie acceleration about the longitudinal axis 24 ) and pitch (rollover Y direction, ie acceleration about the transverse axis 25 ). For this purpose, the accelerometers 3 a, 3 b and 3 c are preferably arranged in the vehicle plane in the form of a lying and isosceles triangle, the accelerometer 3 a forming the tip of this triangle, and the two accelerometers 3 b and 3 c the base side of the triangle form and are located approximately in the area of the rear axle of vehicle 1 .

The accelerometer 3 c is arranged at a distance B from the accelerometer 3 b, and the accelerometer 3 a has a distance L to the connecting line between the accelerometers 3 b and 3 c. In order to be able to carry out the evaluation of the sensor signals as simply as possible, the distance L is chosen to be the same size as the distance B in the arrangement of the acceleration sensors 3 a, 3 b and 3 c.

FIG. 2 shows a first part 9 of a basic circuit arrangement for evaluating signals A, B and C of the accelerometers 3 a, 3 b and 3 c. Each signal A, B coming from the accelerometers 3 a, 3 b and 3 c and C is first fed to a low-pass filter 10 a, 10 b and 10 c in order to filter out high-frequency signals that occur due to vibrations during driving. After filtering resulting signals A ', B' and C 'are linked together in such a way that the above-mentioned conditions of lifting, rolling and pitching of the vehicle 1 ( FIG. 1) are recognized from output signals X, Y and Z.

The first output signal X (corresponds to the rolling of the vehicle) is obtained by subtracting signal C 'minus signal B' by means of a subtracting circuit 18 . By adding the three signals A 'plus B' plus C ', first adding B' plus C 'using an adder circuit 21 and then adding the result B' + C 'using an ad dier circuit 19 to the signal A' , there is three times the mean acceleration in the Z direction, ie the output signal Z (corresponds to the lifting of the vehicle).

The output signal Y (corresponds to the pitching of the vehicle) is obtained by the following combination of the three signals A ', B' and C ': first, the sum B' + C 'formed by means of the adder circuit 21 by means of a voltage divider 16 consisting of two Resistors R₁ and R₂, divided by a certain division factor. In general, the division factor must correspond to the number of all transducers arranged in the X direction. For the present case, this means that two transducers 3 b and 3 c are arranged in the X direction ( FIG. 1) and therefore the division factor 2 is set by means of the voltage divider 16 .

This in turn means that the sum B '+ C' is halved and therefore R₁ must be the same size as R₂. The intermediate result ½ _* (B '+ C') is subtracted from the signal A 'by means of a subtracting circuit 20 , and the resultant signal A' - [½ _* (B '+ C')] is fed to an amplifier 17 . The Verstär effect of the amplifier 17 is determined by the ratio B: the distances L and B L of the pickup 3 a, 3 b and 3 c (Fig. 1), where for a distance B is equal to the distance L is considered unity gain. This amplification ensures that signals Y or X of the same size are produced for tilting angles of the same size in the Y or X direction, even if the distances B and L between the sensors 3 a, 3 b and 3 c ( FIG. 1 ) are not the same size.

A second part 11 of the basic circuit arrangement is shown in FIG. 3. Only an evaluation for the signals X and Z from FIG. 2 is shown; An evaluation circuit for the signals Y and Z is to be constructed accordingly, the components for evaluating the signal Y corresponding to those for evaluating the signal X.

First, a first integration of the angular acceleration as a signal X by means of an integrator 12 provides a signal X 'as the change in the angular velocity with which, for example, the vehicle 1 ( FIG. 1) begins to roll about its longitudinal axis 24 (in the X direction) . Angular acceleration values that are below a threshold S 1 are not integrated in order to prevent the integrator 12 from overflowing.

A second integration of the angular acceleration as a signal X by means of an integrator 13 , which is synonymous with a first integration of the angular velocity as a signal X ', provides a signal X'', which corresponds to an angle or an angle change compared to an initial angle. Even with this integration, an overflow of the integrator 13 can be prevented by means of a threshold S₂ by signals X 'which are smaller than S₂ are not integrated. The signal X '' is then fed to the non-vertizing input of a comparator K₁ and compared with a threshold S₃, which is fed to the inverting input of the comparator K₁. The threshold S₃ corresponds to the angle of the maximum permissible inclination in the direction of travel that the vehicle can take without tipping over. The output signal of the comparator K 1 is fed to an ad circuit 15 with an output signal ALS.

The signal X 'at the output of the integrator 12 , which corresponds to the angular velocity, is also fed to the non-inverting input of a comparator K₂ and compared with a threshold S₄. The threshold S₄ corresponds to an angular velocity at which the vehicle rotates about its longitudinal axis 24 . If this angular velocity reaches a certain value, a rollover (in the X direction) around the longitudinal axis 24 of the vehicle is to be expected. The output signal of the comparator K₂ is also fed to the adder circuit 15 .

The signal Z, which corresponds to the acceleration in the Z direction (lifting of the vehicle), is fed to a central control unit 14 , preferably a microprocessor, with thresholds S₅ and S₆ ( FIG. 4).

The output signal of the control unit 14 is supplied as well as the output signal of the comparator K₁ (angle) and the output signal of the comparator K₂ (angular velocity) of the adding circuit 15 . The linkage of the three signals takes place in such a way that a signal is supplied to the output ALS of the adder circuit 15 whenever one of the three input signals is different from zero. If the output signal ALS of the ad dier circuit 15 is fed to a triggering device, for example for a belt tightener or a roll bar, then triggering takes place accordingly if at least one of the following conditions is met:

• - threshold value for angular acceleration exceeded,
• - Threshold value for the angular velocity exceeded or
• - Threshold for the average acceleration in the Z direction for a certain duration exceeded.

The flowchart of Fig. 4 shows the running in the microprocessor 14 algorithm. First, the output signal Z of the adder circuit 19 ( Fig. 2), which represents three times the average acceleration in the Z direction (corresponds to the lifting of the vehicle), divided by three in order to obtain the actual acceleration Z 1 of the vehicle in the Z direction . At closing the signal Z₁ is compared with a threshold S₅, which is close to 0. If the signal Z₁ is below the threshold S₅, a counter in the microprocessor 14 ( FIG. 3) is set down by a counting step ZS₂ (decrement). The smallest value of the counter should be zero, which is why the counter is reset to zero when the counter is zero and another, plus the decrement ZS₂. Then a new run of the algorithm is started.

If the signal Z₁ exceeds the threshold S₅, the internal counter in the microprocessor 14 ( FIG. 3) is incremented by a counting step ZS₁ (increment), the counting step ZS₁ being less than or equal to the value of the counting step ZS₂. In the next step, the counter reading is compared with another threshold, the trigger threshold S₆. As long as the trigger threshold S₆ has not yet been established, a new run of the algorithm is started; however, a trigger signal is supplied to the input of the adder circuit 15 ( FIG. 3) when the trigger threshold S Aus is reached.

FIGS. 5a and 5b show a further embodiment of the sensor according to the Invention in a vehicle assembly 1 'with the longitudinal axis 24' and transverse axis 25 '. Normally, lifting (in the Z direction), pitching (in the Y direction, ie acceleration about the transverse axis 25 ′) and rolling (in the X direction, ie acceleration about the longitudinal axis 24 ′) are sufficient to detect the states lifting, as shown in the first embodiment. In Fig. 5a, however, four accelerometers VL, VR, HL and HR are arranged in the vehicle 1 ', these four accelerometers VL, VR, HL and HR also being used, for example, for chassis control. The four transducers VL, VR, HL and HR with the sensitivity axis pointing upwards are arranged in a rectangle, and the distance between the transducers VL and VR or HL and HR is B 'and the distance between the transducers VL and HL or VR and HR denoted by L ′.

Fig. 5b shows an associated evaluation circuit 9 'for evaluating the signals of the transducers HL, HR, VL and VR, which first each have a low pass 10 d, 10 e, 10 f and 10 g to eliminate high-frequency signals. By adding all four signals in an adding circuit 22 a, an output signal Z '' is obtained for the state of lifting (in the Z direction) of the vehicle 1 '. By adding the signals HL and HR in an adding circuit 22 b results in a signal HI.

The signals VL and VR are each an amplifier V₁ or V₂ supplied leads, their respective amplification from the ratio of the distances B ′ and L ′ depends on: V₁ = V₂ = B ′: L ′. Accordingly, at distance B 'the same size as Distance L ', V₁ = V₂ = 1. One generally strives for the same angle acceleration when nodding (in the Y direction) and rolling (in the X direction)  to receive equally large sensor signals. This presupposes that the Ab stands B 'and L' are also the same size. Since such a geometric approach order is not always possible, the uniformity of the signals brought about by the additional amplification of two of the four signals, as already explained in the first embodiment.

The amplified with the gain factor of the amplifier V₁ signal VL and the signal HL are fed to an adder circuit 22 c; the result is a signal LI. By addition in an adder circuit 22 d is obtained from the respective amplified signals VL and VR a signal VO from the subtracting circuit 23 in a signal HI is subtracted. The output of the subtracting circuit 23 a is a signal Y '' supplied as a result, which represents the pitch of the vehicle 1 '(in the Y direction).

From the addition of the unamplified signal HR and the signal VR amplified with the amplification factor of the amplifier V₂ by means of an adding circuit 22 e results in a signal RE, from which the signal LI is subtracted in a subtractor circuit 23 b. As a result at the output of the sub traction circuit 23 b, a signal X '' is obtained which represents the rolling of the vehicle 1 '(in the X direction).

The output signals X '', Y '' and Z '' of the circuit arrangement 9 'are supplied for further evaluation, for example, the circuit arrangement 11 ( Fig. 3), the circuit arrangement 11 instead of the signal X, the signal X''and instead of the signal Z the signal Z '' is to be supplied. The individual components for evaluating the signal Y '' correspond to those for the signal X '', as has already been explained.

The sensor arrangement according to the invention for tilt detection takes place their use in particular to trigger safety devices such as Belt tensioners or roll bars in vehicles, one for the early Occupant dangerous situation is recognized and the security mentioned facilities can be triggered.

Claims (7)

1. A method for the detection of angular accelerations of a motor vehicle ( 1 ) with respect to its longitudinal axis ( 24 ) and with respect to its transverse axis ( 25 ) as well as for the detection of an acceleration of the motor vehicle ( 1 ) in a direction perpendicular to the road plane with a first ( 3 b), second ( 3 c) and third ( 3 a), each producing a sensor signal (A ', B', C ') and having a sensitivity axis, in which the first ( 3 b) and second ( 3 c) sensor in one for longitudinal axis (24) of the motor vehicle (1) perpendicular to the first plane are arranged such that the sensitivity axes of which lie in this plane, and the third sensor (3 a) in a to the first plane parallel second plane, wherein the following method steps are carried out:

• a) Difference formation (C'-B ') from each of the first ( 3 b) and second ( 3 c) sensor formed sensor signal (B', C ') for determining the angular acceleration (X) about the longitudinal axis ( 24 ) of Motor vehicle ( 1 ),
• b) Sum formation (A ′ + B ′ + C ′) from the sensor signals of the first ( 3 b), second ( 3 c) and third ( 3 a) sensors for determining the acceleration (Z) perpendicular to the road surface,
• c) Averaging (½ _* [B ′ + C ′]) from the first (B ′) and second (C ′) sensor signal and then forming the difference (A′-½ _* [B ′ + C ′]) from the sum of the sensor signals (B ′ + C ′) of the first ( 3 b) and second ( 3 c) sensors and the signal (A ′) of the third sensor ( 3 a) for determining the angular acceleration (Y) about the transverse axis ( 25 ) of the motor vehicle ( 1 ).

2. Method for the detection of angular accelerations of a motor vehicle ( 1 ') with respect to its longitudinal axis ( 24 ') and with respect to its transverse axis ( 25 ') as well as for the detection of an acceleration of the motor vehicle ( 1 ') in a direction perpendicular to the roadway plane with a first, second, third and fourth, each generating a sensor signal and a sensitivity axis have the sensor, in which the first (HL) and second (HR) sensor in a to the longitudinal axis ( 24 ') of the motor vehicle ( 1 ') vertical he most plane are arranged such that the sensitivity axes lie in this plane, and the third (VL) and fourth (VR) sensors lie in a second plane parallel to the first plane, the following method steps being carried out:

• a) formation of a first sum (HI) from the sensor signals of the first (HL) and second (HR) sensors,
• b) formation of a second sum (LI) from the sensor signals of the first (HL) and third (VL) sensors,
• c) formation of a third sum (VO) from the sensor signals of the third (VL) and fourth (VR) sensor,
• d) formation of a fourth sum (RE) from the sensor signals of the second (HR) and fourth (VR) sensor,
• e) Sum formation from the sensor signals of all four sensors (HL, HR, VL, VR) for determining the acceleration (Z ′ ′) of the motor vehicle ( 1 ′) perpendicular to the plane of the road,
• f) difference formation (VO-HI) from the third sum (VO) and the first sum (HI) to determine the angular acceleration (Y '') about the transverse axis ( 25 ') of the motor vehicle ( 1 ') and
• g) difference formation (RE-LI) from the fourth sum (RE) and the second sum (LI) to determine the angular acceleration (X '') about the longitudinal axis ( 24 ') of the motor vehicle ( 1 ').

3. The method according to claim 1 or 2, characterized in that the Si signals of the sensors ( 3 a, 3 b, 3 c; HL, HR, VL, VR) a low-pass filter ( 10 a- 10 g) are supplied. 4. The method according to claim 2, characterized in that the signals of the third (VL) and fourth (VR) sensors each by means of an amplifier  (V₁, V₂) are amplified, the respective amplification factor of Ratio (B ′: L ′) of the distances between the sensors (HL, HR, VL, VR) depends. 5. The method according to claim 1, characterized in that the mean value formation (½ _* [B '+ C']) from the first (B ') and second (C') sensor signal by summation (B '+ C') and subsequent Division is made by means of a voltage divider ( 16 ) consisting of resistors (R₁, R₂). 6. The method according to claim 1, characterized in that the result of the difference formation ( 20 ) by means of an amplifier ( 17 ) is amplified, the amplification factor of the ratio (B: L) of the distances between the sensors ( 3 a, 3 b, 3 c ) depends. 7. Use of the method according to one of claims 1 or 2 for triggering a passive safety device, in particular roll bar and belt tensioner, for motor vehicles depending on the inclination of the motor vehicle ( 1 ; 1 ') by performing the following steps:

• a) a first integration ( 12 ) of two angular acceleration signals (X, Y; X ′ ′, Y ′ ′) formed by the sensors ( 3 a, 3 b, 3 c; HL, HR, VL, VR) and comparison of the integrated value (X ′) with a first threshold (S₄),
• b) a second integration ( 13 ) of the angular acceleration signals (X, Y; X ′ ′, Y ′ ′) formed by the sensors ( 3 a, 3 b, 3 c; HL, HR, VL, VR) and comparison of the integrated value (X *) with a second threshold (S₃),
• c) determination of the duration of the acceleration perpendicular to the road surface (Z; Z ′ ′) and comparison with a time threshold (S₆),
• d) supplying a trigger signal (ALS) to the safety device if the first (S₄) or second (S₃) threshold or the time threshold (S₆) it reaches.