DE10044567B4 - Safety system for a motor vehicle - Google Patents

Abstract

Security system for a motor vehicle with
A plurality of sensors each providing a sensor signal comprising at least one acceleration sensor (14a to 14d, 16a to 16d);
A processing device (42 to 58) for processing the plurality of sensor signals;
- A control device for driving at least one safety device, when the processing device (42 to 58) provides a trigger signal, which is correlated with a situation in which at least the risk of a rollover process for the motor vehicle;
characterized,
in that the plurality of sensors comprises at least one displacement sensor (12a to 12d), wherein with the at least one displacement sensor a sensor signal can be provided which is correlated with the distance between a wheel of the motor vehicle and the body of the motor vehicle and
in that the processing unit (42 to 58) is designed to process the sensor signals, with or without prior association with each other, to provide at least one potential triggering signal by applying the at least one potential triggering signal against a ...

Description

The The invention relates to a safety system for a motor vehicle having a Variety of sensors, each providing a sensor signal, comprising at least one acceleration sensor, a processing device for processing the plurality of sensor signals, a control device for driving at least one safety device when the Processing device provides a trigger signal that with a Situation is correlated, in the for the motor vehicle at least the risk of a rollover process consists. It further relates to a method for operating a Security system in a motor vehicle, in which in a first Step a plurality of sensor signals is generated, wherein at least one of the sensor signals originates from an acceleration sensor, the plurality of sensor signals in a processing device be processed, wherein a trigger signal to a control device is generated when it is due to the sensor signals that the Motor vehicle is in a situation where at least the danger a rollover process consists, and at least one safety device by the control device after it receives a trigger signal from the processing device has received.

Such a security system is known from the EP 0 430 813 , This document describes a safety system comprising three acceleration sensors for recording acceleration in the x, y and z directions. For the definition of the directions see 1 according to which the positive x-direction for a vehicle forward, the positive y-direction to the right and the positive z-direction are defined upward. According to this document, the ratio of two accelerations in different directions is formed continuously and an integration for determining the angular velocities is started when a predetermined threshold is exceeded. A safety device is triggered when one of the angular velocities thus determined exceeds a predetermined value or when the weighted geometric mean from the accelerations in each of two directions exceeds a predetermined value.

Furthermore, from the DE 198 28 338 a method for determining a leading to a rollover process critical angular position of a vehicle, which is to suppress the offset of a rotation rate sensor characterized in that a certain rotation rate is integrated only when the rotation rate is within a certain range.

The DE 196 09 717 describes an arrangement for detecting rollover events in vehicles, in which the angular velocities of the vehicle about the yaw axis, the roll axis and the pitch axis are measured in a vehicle by means of rotation rate sensors. A rollover process is then signaled as detected when an angular velocity exceeds a predefinable limit.

The DE 198 14 154 describes an apparatus and method for deploying an occupant protection system in a vehicle rollover equipped with a vehicle tipping speed detecting yaw rate sensor and a mechanical tilt switch, but inhibiting deployment of the occupant protection system when a tipping motion is detected.

From the US Pat. No. 6,038,495 For example, a safety system for triggering safety devices in the event of vehicle roll over is known. By means of acceleration sensors, a signal is determined and compared with a fixed, predetermined threshold value. On the basis of the comparison result, a threat of rolling over of the vehicle can be predicted. In addition to the acceleration sensors, displacement sensors are also used whose signals are used to deactivate the safety system if necessary, unless at least one wheel has moved away from the body by a specific value.

The security systems described in the prior art is common, that the entire installation of such security systems with a significant Effort for Material and installation is connected.

The It is therefore an object of the present invention to provide a security system for a Motor vehicle of the aforementioned type and a method for Operating a safety system in a motor vehicle of the beginning so-called type such that a reduction in the costs for Material and installation can achieve.

These Task is solved by a security system having the features of claim 1 and a method for operating a security system with the Features of claim 7.

Of the On the one hand, the invention is based on the idea of using sensors, which are already present in a motor vehicle, as components another device of the motor vehicle, such as a chassis control or a driving stability system. Within the scope of such systems, for example displacement sensors are used, especially in conjunction with air suspension systems to determine To what extent a wheel is spring-loaded or rebounded, by suitable control of the air suspension system a for the respective situation to achieve optimal damper setting. As will be detailed below, signals are Such displacement sensors, with or without additional processing steps, outstandingly suitable, used in a generic security system to become. Although such displacement sensors, as for example used in air suspension systems, often to control the distance between a wheel and the vehicle body according to predetermined Algorithms are used, so it can still be signals provide - if necessary by arithmetic elimination of the scheme - with the distance between an associated one Wheel of the motor vehicle and the body of the motor vehicle correlated are.

at Use the signals from existing sensors need the corresponding signals of only one unit, for example, to a microprocessor of the security system, to be processed there in a suitable manner. The installation and wiring additional Sensors exclusively could serve the security system omitted. As has been shown, in particular the signals from Displacement sensors suitable for a particularly safe and reliable safety system contribute.

By suitable preparation of the signals of the displacement sensors can be therefore a very reliable triggering of Safety devices, such as belt tensioners, airbags, roll bars (at Convertibles) and a shutdown of the fuel supply, achieve. In particular, in view of the fact that such protective systems in usually intended for single use only, it is extremely important that one safe triggering at risk of rollover takes place, but also a safe non-triggering in normal operation itself under extreme conditions.

By using at least one displacement sensor, in particular, a stable driving situation, as occurs, for example, in a steep runway entrance, can be clearly recognized, although in this case a considerable rotation of the vehicle takes place at the same time (the wheels are deflected). Unilateral debits or credits can be clearly recorded. For example, in the so-called AMS test, in which the motor vehicle ascends on one ramp on one side, the resolution can be decisively improved. In the from the EP 0 430 813 known methods, the loss of ground contact via the vertical acceleration must be detected. However, due to the required filters, see below, the signal is time delayed. In addition, the corresponding thresholds for weightlessness for zero gravity detection must be set well above zero. This makes it difficult to discriminate against harmless short jumps and real overrun events. In contrast to this, the displacement sensors, as used in the safety system according to the invention, directly indicate the loss of ground contact and can thus significantly improve the discrimination of such events, in particular in combination with the signals of acceleration sensors in the z-direction.

Besides, they are in the processing unit, the sensor signals with or without prior Linkage with each other for providing at least one potential triggering signal processable, wherein the at least one potential trigger signal against an associated Threshold signal is comparable, and when exceeding the associated threshold signal is detectable, a trigger signal can be generated to the control device, wherein at least one of Threshold signals with respect to at least one sensor signal modifiable is that with a sensor signal at least one of the displacement sensors is correlated. This measure allows the thresholds for the triggering and driving a safety device in normal driving condition first relatively high. This will cause a false trip on poor roads and extreme driving prevented. On the other hand, a fast and reliable release enabled by low thresholds, when the rollover process an unusual one Event precedes, for example, a fast vertical rotation or an extremely one-sided deflection.

With the security system according to the invention In particular, there is also the possibility of rollovers with rotation around the vehicle x-axis as well as rollovers around the vehicle y-axis to detect.

One especially reliable working security system results when the security system according to the invention has at least three acceleration sensors, wherein the at least three acceleration sensors fixed to the body connected are and for detecting acceleration in the z-direction of the vehicle with either an acceleration sensor on the front right, a front left accelerometer, an accelerometer in the back of the vehicle or an acceleration sensor in the back right, a rear left accelerometer and an accelerometer is arranged in the front of the vehicle. By suitable processing the sensor signals of these acceleration sensors can be used to determine quantities making up the risk of rolling over can derive: So can for example, by forming the difference of a left and a right acceleration sensor in z-direction and one-time integration the rate of rotation in x-direction can be determined by further integration the angle of rotation about the x-axis. The acceleration sensors in the z direction also give Information about whether the vehicle is currently in free fall. Especially advantageous can these sizes continue connected be with the sensor signal of an acceleration sensor in the y-direction, see below.

The Security system according to the invention comprises according to a particularly preferred embodiment at least three displacement sensors to determine the distance between Wheel and bodywork for at least three wheels of the motor vehicle. The reason for this lies in the knowledge, that yourself by the sensor signals of at least three displacement sensors one plane determine and therefore It can be recognized whether and how far this is Moved motor vehicle from a position with a completely flat surface.

According to one another preferred embodiment come as a modifiable threshold signals the threshold signal for a lateral acceleration and / or a static tilt angle and / or an acceleration in negative z-direction and / or a rotational speed in negative z-direction and / or a rotational speed about the z-axis and / or an angle change about the z-axis into consideration.

The of the sensor signal that can be provided with the at least one displacement sensor can be an absolute distance value between wheel of the motor vehicle and the body of the motor vehicle and / or correspond relative distance value between a wheel of the motor vehicle and the body of the motor vehicle based on a predetermined Distance value and / or the first and / or the second derivative the change the distance after the time.

at the method according to the invention to operate a security system is a special preferred variant characterized in that a sensor signal at least a displacement sensor for implementation a self-examination with another similar signal present in the motor vehicle where either the sensor signal is processed by in particular one or two differentiation after the time for the comparison processed and / or the equivalent signal by processing, especially one or two times integration over time, for comparison is processed. This variant is based on the idea that through suitable processing of sensor signals results in redundancy, which can be used to such signals, although with different measuring principles recorded, compared with each other. For example, the Loss of ground contact of a motor vehicle both via displacement sensors as well over z acceleration sensors are detected. Hereby can be on the one hand a greater triggering safety reach, for example, a release of a safety device only be released if both signals are a predetermined Threshold exceeded to have. On the other hand, this redundancy can also take place in a predetermined time intervals used for a repeated self-test while driving become, thereby easily a malfunction of a Detect sensors.

Further advantageous embodiments The invention will become apparent from the dependent claims.

in the The following will be an embodiment with the attached Drawings shown.

It demonstrate:

1 a schematic representation of a motor vehicle for defining x-, y- and z-direction;

2 a schematic representation of a partially sectioned view of a motor vehicle in plan view with arranged therein displacement sensors, wheel-fixed acceleration sensors in the z-direction and ka most extreme acceleration sensors in z-direction;

3 in Signalflußdiagrammdarstellung the sequence from the recording of the sensor signals to the control of a safety device;

4 a schematic representation of the processing of the sensor signals of three acceleration sensors in the z-direction and an acceleration sensor in the y-direction;

5 a schematic representation of the adaptation of the threshold signals in response to the sensor signals of four displacement sensors and a rotation rate sensor; and

6 the generation of a trigger signal to the control device in response to five potential trigger signals, which are compared with the respective associated threshold signal.

1 shows first, as mentioned, in a schematic representation of a motor vehicle for defining the x-, y- and z-direction. In the following, accelerometers in direction "A" will be referred to as "A" accelerometers for short. 2 shows a partially sectioned view of a cross section through a motor vehicle. As for the in 2 Legend also shown, are in the vehicle front left, front right, rear left, rear right each a displacement sensor 12a to 12d arranged with the respective one sensor signal can be generated, which is correlated with the distance between the respective wheel of the motor vehicle and the body of the motor vehicle. Correlation in this context means that it may be the absolute distance value between a wheel of the motor vehicle and the body of the motor vehicle and / or a relative distance value between the wheel and the body, but also the possibility that it is the first and / or second derivative of a change in distance can act on time. The first derivative with respect to time would therefore correspond to the speed at which the distance between the wheel and the body changes, while the second derivative would mean the change in speed, ie the acceleration of the wheel towards or away from the body.

In the vehicle are also also front right, front left, rear right, rear left four wheel-fixed z-acceleration sensors 14a to 14d arranged under Radfest here to understand that the sensors are firmly connected to the wheel, ie join the movements of each wheel unsprung.

The vehicle further comprises three body-mounted z-acceleration sensors 16a to 16c , which are quasi the corresponding movements spring-loaded by a corresponding damping system detect and front right, front left and rear are arranged in the body. Alternatively, the body-mounted z-acceleration sensors for defining a plane could also be arranged in the rear right, rear left and front of the vehicle. The safety system also uses the sensor signal of a y-acceleration sensor 18 , a z-rotation rate sensor 20 ie, a sensor for detecting a rotation about the z-axis of the motor vehicle and an x-speed sensor 22 ,

The related to 2 sensors described are predominantly, but in particular the displacement sensors, part of the chassis control and / or the driving stability system of the motor vehicle. They could also be part of the airbag control or other devices of the motor vehicle. They are not explicitly installed for a safety system for detecting rollover events in the motor vehicle, but the signals of the sensors already present in the vehicle are used for such a system.

3 shows in block diagram representation a signal flow diagram showing the sequence from the recording of the sensor signals to the control of a safety device.

In Table 1 below, the mentioned sensors are the clarity half with the associated Detection direction and the position at which they are in the motor vehicle are arranged listed.

Tabelle 1

Table 1

In 3 the sequence between the provision of the sensor signals and the control of a safety device in the form of a signal flow graph is shown. First deliver in step 30 the sensors sensor signals. These will be in step 32 processed and processed. Details will be related to 4 to be discribed. In particular, digital signals are generated from analog signals supplied by the sensors, the sensor signals first being subjected to anti-alias low-pass filtering with respect to the sampling theorem, then A / D converted and depending on the sensor used, ie depending on the zero accuracy of the sensor and Requirements of the following algorithms to the zero point accuracy, to be subjected to an optional high-pass filtering.

In step 34 an adaptation of the threshold signal with respect to current sensor signals instead, details are related to 5 be executed. step 32 provides potential trip signals in step 36 with associated threshold signals, if necessary after adjustment in step 34 , to be compared. In step 38 it is determined whether the potential trigger signal is above or below the associated threshold signal. Details will be related to 6 be discussed.

In the event that all potential trip signals are below the threshold signal, the sequence goes back to step 30 , In the event that the conditions are met to trigger a safety device, ie at least one threshold signal has been exceeded by an associated potential trigger signal is in step 40 a trigger signal to a control device created, which in turn a corresponding drive signal for triggering at least one safety device in the step 42 provides.

4 shows the processing of the signals supplied by the acceleration sensors. In the block 42 the difference is formed between the z-acceleration front left and the z-acceleration front right. This difference is in the block 44 integrated to determine the rate of rotation about the x-axis. A second integration in the block 46 provides the angle x the vehicle has rotated about the x-axis. The z-acceleration at the front left, the z-acceleration at the front right, and the z-acceleration at the back will continue to be filtered after low-pass filtering to eliminate high-frequency interference, in particular to form an average in the block 48 processed. From this it can be determined whether the vehicle is moving downwards in free fall. The y-acceleration is in the block 50 also fed to a low-pass filtering and used to determine a lateral acceleration. She will continue in the block 52 is used together with an average of the z accelerations to calculate a ratio of the z acceleration to the y acceleration, from which the static tilt angle of the motor vehicle can be determined.

5 shows that the signals of the displacement sensors front left, front right, rear left, rear right 12a to 12d in the block 54 to adapt the threshold signals for the rate of rotation x, the angle x, the free fall, the static tilt angle and the lateral acceleration use. In addition to the signals of the displacement sensors, in the present case, the yaw rate z is also used to adapt the thresholds. As input signals for the adaptation of the thresholds, the wheel-fixed z-accelerometer and the x-speed signal can furthermore be used. The adjustment of the thresholds takes place dynamically when driving the motor vehicle.

6 shows the comparison of the modified threshold signals with the associated potential trigger signal in respective blocks 56a to 56e , wherein the respective output signals present an OR gate 58 are supplied, which in the presence of at least one positive comparison, ie that one of the threshold signals is exceeded, a trigger signal at the output 60 to the control device.

at the security system according to the invention can be provided that the Signal of a displacement sensor is processed to match the output signal another sensor, or vice versa, that the output signal is processed by another sensor, with an output signal of a Wegsensors to be compared. For processing come in particular single or multiple differentiation as well as single or multiple integration into consideration. This allows redundant signals are generated, which agree in their statement should. By comparing such signals in predetermined time steps Therefore, the function of the associated sensors can be checked. If there is a negative comparison, appropriate measures can be taken be initiated, for example, a warning signal to the vehicle user triggered become. However, it may also be provided to increase the reliability of the system a trigger signal to generate to the controller only if both correspond, potential triggering signals supplied by different sensors via the corresponding threshold signals are.

Claims (10)

Security system for a motor vehicle with - a plurality of sensors each providing a sensor signal, comprising at least one acceleration sensor ( 14a to 14d ; 16a to 16d ); A processing device ( 42 to 58 ) for processing the plurality of sensor signals; A control device for controlling at least one safety device when the processing device ( 42 to 58 ) provides a triggering signal correlated to a situation in which there is at least the risk of a rollover event for the motor vehicle; characterized in that the plurality of sensors comprises at least one displacement sensor ( 12a to 12d ), wherein with the at least one displacement sensor, a sensor signal is provided, which is correlated with the distance between a wheel of the motor vehicle and the body of the motor vehicle and that the processing unit ( 42 to 58 ) is adapted to process the sensor signals, with or without prior association with each other, to provide at least one potential triggering signal by comparing the at least one potential triggering signal against an associated threshold signal and, if an exceeding of the associated threshold signal is detected, triggering the signal Control device is generated, wherein at least one of the threshold signals is modifiable with respect to at least one signal with a sensor signal of one of the displacement sensors ( 12a to 12d ) is correlated. Safety system according to claim 1, characterized in that the safety system comprises at least three acceleration sensors ( 16a to 16c ), wherein the at least three acceleration sensors are fixedly connected to the body and are designed to detect an acceleration in the Z direction of the motor vehicle, wherein an acceleration sensor ( 16a ) front right, an acceleration sensor ( 16b ) front left and an acceleration sensor ( 16c ) in the rear of the motor vehicle or an acceleration sensor rear right, an acceleration sensor rear left and an acceleration sensor is arranged in the front of the vehicle. Safety system according to claim 1 or 2, characterized in that the safety system comprises at least three displacement sensors ( 12a to 12d ) for determining the distance between the wheel and the body for at least three wheels of the motor vehicle. Safety system according to one of claims 1 to 3, characterized in that the modifiable threshold signal, the threshold signal for a lateral acceleration and / or a static tilt angle and / or an acceleration in the negative Z direction and / or a rotational speed about the Z axis and / or an angular change about the Z axis. Safety system according to one of the preceding claims, characterized in that the with the at least one displacement sensor ( 12a to 12d ) sensor signal corresponds to an absolute distance value between a wheel of the motor vehicle and the body of the motor vehicle and / or a relative distance value between a wheel of the motor vehicle and the body of the motor vehicle relative to a predetermined distance value and / or the first and / or the second derivative of the Change of distance after the time. Safety system according to one of the preceding claims, characterized in that the at least one displacement sensor ( 12a to 12d ) and / or the at least one acceleration sensor ( 14a to 14d ; 16a to 16c ) Components of another device of the motor vehicle, in particular a chassis control and / or a driving stability system, is / are. Method for operating a safety system in a motor vehicle, comprising the following steps: a) generating ( 30 ) of a plurality of sensor signals, wherein at least one of the sensor signals from an acceleration sensor ( 14a to 14d ; 16a to 16d ) is produced; b) processing ( 32 . 34 . 36 ) of the plurality of sensor signals in a processing device ( 42 to 58 ) and generating ( 40 ) of a triggering signal to a control device. if it results on the basis of the sensor signals that the motor vehicle is in a situation in which at least the risk of a rollover process exists; c) driving at least one safety device by the control device after receiving the triggering signal from the processing device ( 42 to 58 ); characterized in that at least one of the plurality of sensor signals is from a displacement sensor ( 12a to 12d ), wherein the sensor signal provided with the displacement sensor is correlated with the distance between a wheel of the motor vehicle and the body of the motor vehicle; and that in the processing unit ( 42 to 58 ) the sensor signals, with or without prior association with each other, are processed to provide at least one potential triggering signal, wherein the at least one potential triggering signal is compared against an associated threshold signal and, if an exceeding of the associated threshold signal is detected, a trigger signal is generated to the control device, wherein at least one of the threshold signals is modifiable with respect to at least one signal that is associated with a sensor signal of one of the displacement sensors ( 12a to 12d ) is correlated. Method according to claim 7, characterized. that at least one of the signals of a displacement sensor and another Sensor is processed in such a way, in particular by one or two times Differentiation and / or through one or two integration, that they correspond in their information content. Method according to claim 9, characterized in that that each two corresponding in their information content Signals compared at predetermined time intervals become. Method according to claim 9, characterized in that in that the processing device is made up of the corresponding sensor signals, with or without prior link with further sensor signals, to provide at least two potential trigger signals processed, the at least two potential trigger signals against associated ones Threshold signals are compared and a trigger signal to the control device is only generated when the at least two potential trip signals on the associated Threshold signals lie.