WO2002020314A1

WO2002020314A1 - Safety system for a motor vehicle

Info

Publication number: WO2002020314A1
Application number: PCT/EP2001/010150
Authority: WO
Inventors: Bertram Obst; Frank Grosshauser
Original assignee: Audi Ag
Priority date: 2000-09-08
Filing date: 2001-09-04
Publication date: 2002-03-14
Also published as: DE10044567A1; DE10044567B4

Abstract

The invention relates to a safety system for a motor vehicle with a number of sensors, each of which generates a sensor signal, comprising at least one acceleration sensor (14a to 14d; 16a to 16d), a processing device (42 to 58) for processing the number of sensor signals, a control device for controlling at least one safety device, when the processing device (42 to 58) delivers a trigger signal which is correlated with a situation in which at least the danger of rolling exists for the vehicle, whereby the number of sensors includes at least one displacement sensor (12a to 12d). Said at least one displacement sensor may generate a signal which is correlated with the separation between a wheel of the vehicle and the chassis of the vehicle. The invention further relates to a corresponding method for operating a safety system in a motor vehicle.

Description

Security system for a motor vehicle

The invention relates to a safety system for a motor vehicle with a plurality of sensors, each of which provides a sensor signal, comprising at least one acceleration sensor, a processing device for processing the plurality of sensor signals, a control device for actuating at least one safety device when the processing device supplies a trigger signal that is correlated with a situation in which there is at least the risk of a rollover for the motor vehicle. It further relates to a method for operating a safety system in a motor vehicle, in which a plurality of sensor signals are generated in a first step, at least one of the sensor signals originating from an acceleration sensor, the plurality of sensor signals being processed in a processing device, a trigger signal being applied a control device is generated if the sensor signals indicate that the motor vehicle is in a situation in which there is at least a risk of a rollover and at least one safety device is actuated by the control device after it has received a trigger signal from the processing device.

Such a safety system is known from EP 0 430 813. This publication describes a safety system which comprises three acceleration sensors for recording an acceleration in the x, y and z directions. For the definition of the directions, see FIG. 1, according to which the positive x direction for a vehicle to the front, the positive y direction to the right and the positive z direction to the top are defined. According to this document, the ratio of two accelerations in different directions is continuously formed and when a pre-determined agreed threshold started an integration to determine the angular velocities. A safety device is activated when one of the angular velocities determined in this way exceeds a predetermined value or when the weighted geometric mean from the accelerations in each case exceeds a predetermined value in two directions.

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

DE 196 09 717 describes an arrangement for detecting rollover processes 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 being recognized when an angular velocity exceeds a predefinable limit value.

DE 198 14 154 describes a device and a method for triggering an occupant protection system in the event of a vehicle rollover, which is equipped with a rotation rate sensor that detects the speed of vehicle tilting and a mechanical tilt switch, but triggering the occupant protection system is blocked when a tipping movement is detected.

The security systems described in the prior art have in common that the entire installation of such security systems is associated with a considerable outlay for materials and installation.

The object of the present invention is therefore to develop a safety system for a motor vehicle of the type mentioned at the outset and a method for operating a safety system in a motor vehicle of the type mentioned at the outset in such a way that a reduction in the costs for material and installation can be achieved. This object is achieved by a security system with the features of claim 1 and a method for operating a security system with the features of claim 9.

The invention is based on the idea of using sensors that are present in a motor vehicle anyway as components of another device of the motor vehicle, for example a chassis control or a driving stability system. In the context of such systems, displacement sensors are used, for example, in order to determine, in interaction with air suspension systems, the extent to which a wheel is compressed or rebounded in order to achieve an optimal damper setting for the respective situation by suitable control of the air suspension system. As will be explained in detail below, signals of such displacement sensors, with or without additional processing steps, are outstandingly suitable for being used in a generic security system. Although such displacement sensors, such as those used for example in air suspension systems, are often used to regulate the distance between a wheel and the vehicle body according to predetermined algorithms, signals can still be provided - possibly by mathematical elimination of the regulation - which correspond to the distance between an associated wheel of the motor vehicle and the body of the motor vehicle are correlated.

When using the signals from existing sensors, the corresponding signals only need to be supplied to a corresponding unit, for example a microprocessor of the security system, in order to be processed there in a suitable manner. The installation and wiring of additional sensors that would only serve the safety system can be omitted. As has been shown, the signals from displacement sensors in particular are suitable for contributing to a particularly safe and reliable safety system.

Appropriate processing of the signals from the displacement sensors therefore enables extremely reliable triggering of safety devices, such as belt tensioners, airbags, roll bars (in convertibles) and switching off the fuel supply. Particularly in view of the fact that such protection systems are generally only intended for single use, it is extremely important that a safe triggering in the event of a risk of rollover The process takes place, but also a safe non-triggering in normal operation even under extreme conditions.

By using at least one displacement sensor, in particular a stable driving situation, such as occurs, for example, when entering a cable car, can be clearly recognized, although in this case the vehicle rotates considerably (the wheels are deflected). Unilateral loading or unloading can be clearly recorded. For example, in the so-called AMS test, in which the motor vehicle runs onto a ramp on one side, the resolution can be decisively improved. In the method known from EP 0 430 813, the loss of contact with the ground must be detected via the vertical acceleration. However, due to the filters required, see below, the signal is delayed. In addition, the corresponding weightlessness thresholds for weightlessness detection must be set well above zero. This makes it difficult to discriminate between harmless short jumps and real rollover events. In contrast to this, the displacement sensors, as they are used in the safety system according to the invention, directly indicate the loss of contact with the ground and can thus significantly improve the discrimination of such events, particularly in combination with the signals from acceleration sensors in the z direction.

With the security system according to the invention, there is in particular the possibility of detecting rollovers with rotation about the vehicle x-axis as well as rollovers about the vehicle y-axis.

A safety system that works particularly reliably results if the safety system according to the invention has at least three acceleration sensors, the at least three acceleration sensors being connected in a stationary manner to the body and being designed to detect acceleration in the z direction of the vehicle, with either an acceleration sensor on the front right Acceleration sensor at the front left, an acceleration sensor at the rear in the motor vehicle or an acceleration sensor at the rear on the right, an acceleration sensor at the rear on the left and an acceleration sensor at the front in the motor vehicle. Suitable processing of the sensor signals of these acceleration sensors enables variables to be determined from which the risk of rollover can be derived: For example, by forming the difference between a left and a right acceleration sensor in the z direction and one-time integration, the rotation rate in the x-direction can be determined by further integration of the rotation angle around the x-axis. The acceleration sensors in the z direction also provide information as to whether the vehicle is currently in free fall. These variables can also be particularly advantageously linked to the sensor signal of an acceleration sensor in the y direction, see below.

According to a particularly preferred embodiment, the safety system according to the invention comprises at least three displacement sensors for determining the distance between the wheel and the body for at least three wheels of the motor vehicle. The reason for this lies in the knowledge that a level can be determined by the sensor signals from at least three displacement sensors and therefore it can be recognized whether and, if necessary, how far the motor vehicle has moved from a position with a completely flat surface.

In the processing unit, the sensor signals can be processed with or without a prior link to one another to provide at least one potential trigger signal, the at least one potential trigger signal being comparable to an associated threshold signal and, if an exceeding of the associated threshold signal can be determined, a trigger signal to the control device can be generated, wherein at least one of the threshold signals can be modified with respect to at least one sensor signal. This measure enables the thresholds for triggering and actuating a safety device to be set relatively high in the normal driving state. This prevents false triggering on rough roads and extreme driving. On the other hand, quick and reliable triggering by means of low thresholds is made possible if the rollover process is preceded by an unusual event, for example a rapid vertical rotation or extremely one-sided deflection. The threshold signals are particularly preferably modified with regard to at least one signal which is correlated with a sensor signal of at least one of the displacement sensors.

In particular, the threshold signals for a lateral acceleration and / or a static tilt angle and / or an acceleration in the negative z direction and / or a rotational speed in the negative z direction and / or a rotational speed about the z axis and / or come as modifiable threshold signals Change in angle around the z-axis is taken into account. The sensor signal which can be provided by the at least one displacement sensor can correspond to an absolute distance value between the 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 based on a predeterminable distance value and / or the first and / or the second derivative of the change in distance over time.

In the method according to the invention for operating a security system, a particularly preferred variant is distinguished in that a sensor signal of at least one displacement sensor for carrying out a self-check is compared with another signal of the same type present in the motor vehicle, either the sensor signal by processing, in particular one or two times Differentiation according to the time is prepared for the comparison and / or the signal of the same type is processed for processing by processing, in particular single or double integration over time. This variant is based on the idea that suitable processing of sensor signals results in redundancy which can be used to enable such signals to be compared with one another, although they are recorded using different measuring principles. For example, the loss of contact with the ground of a motor vehicle can be determined both via displacement sensors and via z-acceleration sensors. This can on the one hand achieve greater security against tripping; for example, tripping of a safety device can only be enabled if both signals have exceeded a predetermined threshold. On the other hand, this redundancy can also be used at predetermined time intervals for a repeated self-test while driving, as a result of which a sensor malfunction can be determined in a simple manner.

Further advantageous embodiments of the invention result from the subclaims.

An exemplary embodiment is illustrated below with reference to the accompanying drawings.

Show it: 1 shows a schematic representation of a motor vehicle for defining the x, y and z directions;

2 shows a schematic illustration of a partially sectioned illustration of a motor vehicle in plan view with displacement sensors arranged therein, wheel-mounted acceleration sensors in the z direction and body-mounted acceleration sensors in the z direction;

3 shows the sequence from the recording of the sensor signals to the activation of a safety device in a signal flow diagram representation;

4 shows a schematic representation of the processing of the sensor signals from three acceleration sensors in the z direction and one acceleration sensor in the y direction;

5 shows a schematic representation of the adaptation of the threshold signals as a function of the sensor signals from four displacement sensors and one rotation rate sensor; and

6 shows the generation of a trigger signal to the control device as a function of five potential trigger signals which are compared with the respectively associated threshold signal.

1 shows, as mentioned, a motor vehicle for the definition of the x, y and z directions in a schematic representation. In the following, accelerometers in direction "A" are briefly referred to as "A" accelerometers. Fig. 2 shows a partially sectioned cross section through a motor vehicle. As can be seen with reference to the legend likewise shown in FIG. 2, in the vehicle front left, front right, rear left, rear right, a respective displacement sensor 12a to 12d is arranged, with which a sensor signal can be generated, which depends on the distance between the respective wheel of the motor vehicle and the body of the motor vehicle is correlated. In this context, correlation means that it can 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 over time. The first derivative after time would therefore correspond to the speed Chen, with 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.

Furthermore, four wheel-fixed z-acceleration sensors 14a to 14d are also arranged in the vehicle at the front right, front left, rear right and rear left, with wheel-fixed being understood here to mean that the sensors are firmly connected to the wheel, i.e. join the movements of the respective wheel without suspension.

The vehicle further comprises three body-mounted z-acceleration sensors 16a to 16c which, as it were, detect the corresponding movements in a sprung manner by means of a corresponding damping system and are arranged in the front right, front left and rear in the body. Alternatively, the z-acceleration sensors fixed to the body could also be arranged in the rear right, rear left and front in the vehicle to define a plane. The safety system also uses the sensor signal of a y-acceleration sensor 18, a z-rotation rate sensor 20, i.e. a sensor for the detection of a rotation about the z-axis of the motor vehicle and an x-speed sensor 22.

The sensors described in connection with FIG. 2 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 the detection of rollover processes in the motor vehicle, but the signals from the sensors which are present in the vehicle anyway are used for such a system.

Fig. 3 shows a block diagram representation of a signal flow diagram from which the sequence from the recording of the sensor signals to the activation of a safety device.

For the sake of clarity, Table 1 below lists the sensors mentioned with the associated detection direction and the position at which they are arranged in the motor vehicle.

Table 1

3 shows the sequence between the provision of the sensor signals and the activation of a safety device in the form of a signal flow graph. First, the sensors deliver sensor signals in step 30. These are processed and processed in step 32. Details of this will be described in connection with FIG. 4. In particular, digital signals are generated from the 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, i.e. Depending on the zero point accuracy of the sensor and the requirements of the following algorithms for zero point accuracy, an optional high-pass filtering can be carried out.

In step 34, the threshold signals are adjusted with regard to current sensor signals, details of which will be given in connection with FIG. 5. Step 32 supplies potential trigger signals which are compared in step 36 with associated threshold signals, possibly after adjustment in step 34. In step 38 it is determined whether the potential trigger signal is above or below the associated one Threshold signal is. Details of this will be discussed in connection with FIG. 6.

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

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

Fig. 5 shows that the signals of the displacement sensors front left, front right, rear left, rear right 12a to 12d in block 54 for adapting the threshold signals for the rotation rate x, the angle x, the free fall, the static tilt angle and the lateral acceleration Find use. In addition to the signals from the displacement sensors, the yaw rate z is also used to adapt the thresholds. The wheel-fixed z-accelerometers and the x-speed signal can also be used as input signals for the adaptation of the thresholds. The thresholds are adjusted dynamically while the motor vehicle is in motion. 6 shows the comparison of the modified threshold signals with the associated potential trigger signal in respective blocks 56a to 56e, the respective output signals in the present case being supplied to an OR gate 58 which, if at least one positive comparison is present, ie that one of the threshold signals is exceeded, provides a trigger signal at the output 60 to the control device.

In the safety system according to the invention it can be provided that the signal of a displacement sensor is processed in order to be compared with the output signal of another sensor, or vice versa, that the output signal of another sensor is processed in order to be compared with an output signal of a displacement sensor. Single or multiple differentiation and single or multiple integration are particularly suitable for processing. In this way, redundant signals can be generated which should correspond in their statements. The function of the associated sensors can therefore be checked by comparing such signals in predetermined time steps. If there is a negative comparison, appropriate measures can be initiated, for example a warning signal to the vehicle user can be triggered. However, in order to increase the reliability of the system, it can also be provided to only generate a trigger signal to the control device if the two corresponding trigger signals supplied by different sensors lie above the corresponding threshold signals.

Claims

PATENT CLAIMS

1. Safety system for a motor vehicle with a plurality of sensors, each of which provides 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 actuating at least one safety device if the processing device (42 to 58) supplies a trigger signal which is correlated with a situation in which the motor vehicle is at least at risk of a rollover process; characterized in that the plurality of sensors comprises at least one displacement sensor (12a to 12d), the at least one displacement sensor being able to provide a sensor signal which is correlated with the distance between a wheel of the motor vehicle and the body of the motor vehicle.

2. Safety system according to claim 1, characterized in that the safety system has at least three acceleration sensors (16a to 16c), the at least three acceleration sensors being connected in a stationary manner to the body and being designed to detect acceleration in the Z direction of the motor vehicle, one of which Acceleration sensor (16a) front right, an acceleration sensor (16b) front left and an acceleration sensor (16c) is arranged in the rear of the motor vehicle or an acceleration sensor in the rear right, an acceleration sensor in the rear on the left and an acceleration sensor in the front in the motor vehicle.

3. 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 body for at least three wheels of the motor vehicle.

4. Security system according to one of the preceding claims, characterized in that in the processing unit (42 to 58) the sensor signals, with or without prior linkage with one another, can be processed to provide at least one potential trigger signal, the at least one potential trigger signal against an associated threshold signal is comparable and, if an exceeding of the associated threshold signal can be determined, a trigger signal can be generated to the control device, wherein at least one of the threshold signals can be modified with regard to at least one sensor signal.

5. Security system according to claim 4, characterized in that at least one of the threshold signals can be modified with regard to at least one signal which is correlated with a sensor signal of one of the displacement sensors (12a to 12d).

6. Security system according to claim 5, 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 angle change around the Z axis.

7. Safety system according to one of the preceding claims, characterized in that the sensor signal which can be provided with the at least one displacement sensor (12a to 12d) 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 based on a predetermined distance value and / or the first and / or the second derivative of the change in distance over time.

8. 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) form part of another device of the motor vehicle, in particular a chassis control and / or a driving stability system.

9. A method for operating a safety system in a motor vehicle, comprising the following steps: a) generating (30) a plurality of sensor signals, at least one of the sensor signals being generated by an acceleration sensor (14a to 14d; 16a to 16d); b) processing (32, 34, 36) the plurality of sensor signals in a processing device (42 to 58) and generating (40) a trigger signal to a control device if the sensor signals indicate that the motor vehicle is in a situation in at least there is a risk of a rollover; c) actuating at least one safety device by the control device after receiving the trigger signal from the processing device (42 to 58); characterized, that at least one of the plurality of sensor signals is generated by a displacement sensor (12a to 12d), the sensor signal provided with the displacement sensor being correlated with the distance between a wheel of the motor vehicle and the body of the motor vehicle.

10. The method according to claim 9, characterized in that at least one of the signals of a displacement sensor and a further sensor is processed in such a way, in particular by single or double differentiation and / or by single or double integration, that they correspond in their information content.

11. The method according to claim 10, characterized in that in each case two signals corresponding in their information content are compared with one another at predetermined time intervals.

12. The method according to claim 11, characterized in that the processing device from the corresponding sensor signals, with or without prior association with other sensor signals, processed to provide at least two potential trigger signals, the at least two potential trigger signals being compared against associated threshold signals and a trigger signal is generated to the control device only when the at least two potential trigger signals lie above the associated threshold signals.