DE102007029764A1 - Directional physical dimension sensing device for use with safety systems for motor vehicles, particularly passenger protection systems, has sensor element, which has preferential sensitivity direction - Google Patents

Abstract

The device has a sensor element, which has a preferential sensitivity direction for influencing directional physical dimension and an information signal and an overload area. The device is adjusted in such a manner that a desired effect of the sensor element output signal is purposefully achieved concerning the information signal and overload area. INDEPENDENTS CLAIMS are also included for the following: (1) a controller for a vehicle (2) a method for sensing directional physical dimension.

Description

The The invention relates to a device for sensing a directional physical size according to claim 1 and a corresponding method according to claim 10.

Become frequent For example, in safety systems for motor vehicles, in particular in occupant protection systems so-called assistance sensors, for example Side or up-front sensors used to get as early and exactly as possible Detect crash situation. Such sensors usually contain in addition a sensor element having a directional physical quantity such as detected a force or acceleration and into an electrical Voltage converts, a signal processing electronics, which trained is the electrical voltage generated by the sensor element for a subsequent Processing, for example, with a crash algorithm, and therefore often is referred to as signal processing. Through the processing is the electrical voltage mostly in a signal of a given Value range to ensure reliable further processing.

Problematic is with the assistance sensors, however, that they quickly in the so-called overload range as they are usually in the immediate vicinity of a collision occurring Force are located. The forces acting on the sensor element physical size can therefore very high within a very short time after a collision Accept values. Under overload range is here understood an area in which the on a sensor element acting physical size one Has value outside of processing limits of the signal processing electronics, i.e. no longer shown in a signal of the specified value range can be, because he is too big.

The from the sensor in the overload range generated signal therefore has clipping and distortion, meaningful further processing, for example in a crash algorithm prevent it or even completely. An offset error of a sensor element It can also cause a signal in the overload range even faster device, because the error in the electrical voltage generated by the sensor element causes an asymmetry. In practice, due to such Offset error produces unbalanced trimming and distortion, the one significant error on the subsequent processing units can effect.

It is thus both an offset of the measured signal itself as well an asymmetry in the maximum values in positive and negative Signal direction to look at. Using the example of an acceleration signal So this can be for example an offset of + 5g permanent as well have an asymmetry in the maximum limits of, for example, + 150 g to -120 g, which means that high negative values would be limited earlier than high positive values.

at essentially uniformly directed signals results through these two possibilities of error Although a bit distorted in the amount signal, but through appropriately adjusted triggering thresholds can be compensated. However, if there are oscillating signals, as for example with vibrations at the sensor by hammer blow, Road bumps and similar cases are the case, so you go theoretically for ideal sensors assume that the vibration components to eliminate each other on average. However, if there is an offset on the Signal and / or an asymmetry of the upper limits, so may the positive and negative vibration components are no longer sufficient compensate and there is a drift towards a signal direction.

task The invention is now a device and a method for Sensing a directed physical size, with which applications are to be realized, in which in addition to the typical useful signal range also sporadic disturbances in the overload range occur, with the overload exceeds the usable range.

These Task is by a device for sensing a directional physical size with the Features of claim 1 and a corresponding method with the Characteristics of claim 10 solved. Further embodiments of the invention will become apparent from the dependent claims.

One The essential idea of the invention now lies in the possibility the induction to use an unbalanced state such that certain desired Effects in case of overload purposefully brought about can be in particular a defined drift direction in the output signal of a Sensor element is specified, which can be detected. With the induction a conscious minor Unbalance is achieved in the application of the advantage that in case of overload defined behavior can be predetermined, which at a aimed at zero-balance (due to the remaining tolerances) is not entirely clear. With the induction a conscious minor Unbalance can thus clearly indicate the direction of drift deviation in the overload range be determined, with the safety concept described below is possible.

According to one embodiment The invention is now a device for sensing a directional physical size with at least a sensor element provided, which is a preferred direction of sensitivity for the acting directional physical quantity and a Nutzsignal- and an overload range wherein the device can be adjusted in such a way that one desired Effect of the sensor element output signal in terms of targeted the Nutzsignal- and overload range brought becomes. A typical example of a sensor element with a preferred Sensitivity is an acceleration sensor, as in a central control unit an airbag control unit is used. Usually Such sensor elements are so with respect to the longitudinal axis geared to a vehicle that they are not just a front or a Rear crash, but also detected a side impact. By the possibility the targeted adjustment of the device according to the invention can now be effected be that, for example, a hammer blow in the side area of a Vehicle as a sporadic disturbance not as a side crash is detected. This may increase the risk of Malfunctions in particular of a vehicle safety system such as substantially reduces an occupant protection system in a vehicle become.

The Setting can according to a another embodiment of the invention take place in that as the at least one sensor element a sensor element with a predetermined offset is used and / or a processing device for the output signal of at least a sensor element is configured such that the desired effect the sensor element output signal with respect to the Nutzsignal- and overload range targeted brought becomes. For example, a targeted "detuned" acceleration sensor be used, a drift direction of its output signal in case of overload in a certain direction. Alternatively or additionally the "offset" or the "detuning" also be "programmed" into the device, for example in an algorithm for processing the output signal of the sensor element.

The Device can according to a embodiment The invention further be set such that the at least a sensor element an asymmetry of its output signal with respect to the Nutzsignal- and overload range such that the output signal has a predetermined drift direction in case of overload of the at least one sensor element has. With the given drift direction can be set, for example, that the sensor elements a central controller "insensitive" to a supposed Side crash due to a hammer blow respond. Or it would be possible to Preselected drift direction to be selected such that the useful signal range a sensor element is increased in a certain direction.

As already mentioned above can according to another embodiment the invention, the at least one sensor element an acceleration sensor which is an axis of sensitivity for the preferred direction of sensitivity has. Of course For example, the invention is suitable with any sensor element that has a sensitivity axis possesses, ie directed physical quantities such as forces can detect.

According to one embodiment of the invention two acceleration sensors may be provided, which in such a way to each other are arranged that their axes of sensitivity at an angle of about 90 degrees to each other. For example, it can be two Acting acceleration sensors that are used to detect directional physical quantities in one certain level.

The Invention relates according to a another embodiment a control unit for a Vehicle with a device for sensing a directional physical size with at least a sensor element according to the invention.

Further sees the invention in a further embodiment, a safety device for a vehicle in particular, an occupant protection device, which is a device for sensing a directional physical quantity with at least a sensor element according to the invention includes.

Farther is according to one Embodiment of Invention, a vehicle, in particular a motor vehicle with a Safety device provided according to the invention, wherein the Apparatus for sensing a directional physical quantity two has approximately centrally arranged sensor elements in the vehicle and is set such that the output signal of each sensor element a predetermined drift direction in the event of overload of a sensor element having.

at the vehicle can according to a another embodiment the invention for sensing a side impact on the vehicle sides arranged lateral sensor elements may be provided and the safety device may be formed such that the signals of the lateral sensor elements with the signals of the centrally arranged sensor elements and / or conversely be made plausible.

Finally, an embodiment of the invention relates to a method for sensing a court teten physical size with at least one sensor element having a preferred sensitivity direction for the acting directional physical quantity and a Nutzsignal- and an overload range, wherein adjustments are made such that a desired effect of the sensor element output signal with respect to the Nutzsignal- and overload range is deliberately brought about ,

Further Advantages and applications The present invention will become apparent from the following description in conjunction with the embodiments illustrated in the drawings.

In the description, in the claims, in the abstract and in the drawings are those in the listed below List of reference symbols used terms and associated reference numerals used.

The Drawings show in

1 a schematic representation of a vehicle with a centrally located control unit having two directional accelerometer;

2a a schematic representation of a vehicle with a centrally located control unit, which has two in the vehicle direction forwardly directed acceleration, with a targeted specification of an asymmetry of the individual sensors is carried out;

2 B a schematic representation of a vehicle with a centrally located control unit, which has two in the vehicle direction to the right side directed Acceleration, with a targeted specification of asymmetry of the individual sensors and a plausibility of the output signals of the sensors with front sensors;

2c a schematic representation of a vehicle with a centrally located control unit, which has two in the vehicle direction to the right side directed acceleration sensor, with a targeted specification of an asymmetry of the individual sensors and a plausibility of the output signals of the sensors with side sensors;

3 the principle of a signal processing chain known from the prior art for the output signal of a sensor element;

4 the principle of a signal processing chain according to an embodiment of the invention;

5 the effect of an asymmetrical limitation of the useful signal range of a sensor element on the basis of the exemplary course of the measurement of the output signal of the sensor element; and

6 an embodiment of a capacitive electrical C / V converter according to the invention.

The The invention will be described below with reference to drawings and exemplary embodiments from the field of acceleration sensing for the control of occupant protection equipment described, wherein the technical teaching disclosed herein also on other applications and sensors is transferable.

The Today's occupant protection systems are designed in such a way that these Cover crash scenarios in which the direction of the collision hardly matters. Such are the algorithms and sensor arrangements the occupant systems realized so that they both the occupants Protect accordingly in the event of a front, rear or side crash.

at the signal acquisition in a front or rear crash are in the Usually the acceleration signals used for the evaluation, the detected by the centrally located in the central control unit sensors whereas in a side crash additional side satellites are used Be used as much as possible fast tripping times due the almost nonexistent crumple zone in the side area obtain, with the signals to secure the triggering decision the outsourced assistance sensors with the signals in the central unit Sensors and / or conversely plausibilized.

By the plausibility of the signals received from the outsourced assistance sensors as well as the sensors in the central unit In case of a side crash, signals are always ensured involved, which come from two different locations, so that a "mechanical Disorder "such as a hammer strike at one point on the bodywork not at the same time on all for triggering required sensors.

By bringing about a deliberate asymmetrical state or asymmetrical "balancing" of the invention, for example, the physical deflectability of the actual sensor element of the participating sensors in the central control unit can be achieved that the algorithm based on the sensor signals in the case of overload defines a te detectable situation, for example, a side impact detected, but no unintentional triggering can come about, since the triggering necessary plausibility signals from the outsourced assistance sensors, for example, in a hammer acting on the central unit, are not present.

In order to the algorithm in case of overload, For example, a strong hammer blow against the side of the body of the vehicle due to the signals from the sensors in the central unit for example, detects a side crash, it is necessary that the Signals of the sensors in the central unit in case of overload a defined Take drift direction, with the drift direction with the conscious Unbalance can be predetermined.

1 shows a schematic representation of a vehicle with a centrally located control unit which has two directional acceleration pickup BA1, BA2 whose sensitivity characteristics F1, F2 are aligned according to the mounting direction +/- 45 degrees to the travel direction X, so that a corresponding area with the two accelerometers are mapped can or can be closed due to the sign of the sensor signals on the direction of a crash impact.

Would both Sensor signals in case of overload (hammer blow) a signal-drift direction in their positive direction, as shown so would the algorithm detects a front crash, resulting in an unwanted release protection of the occupant protection system.

2a shows a similar schematic representation as 1 , wherein a targeted specification of an asymmetry of the individual sensors according to the invention takes place by the sensor F1 drifts in its positive working direction, while the other sensor F2 drifts in its negative working direction. In contrast to 1 In the case of overload, a hammer strike results in a signal-drift direction in the Y direction resulting from a vectorial addition, so that the algorithm would as a result recognize a side crash. However, this can not lead to unwanted tripping in this case, as there is no signal from the side sensors for triggering additional signals (since the hammer blow does not act sufficiently on them). The drift direction is therefore selected in this example so that the signal of a central sensor can be made plausible by means of at least one further sensor signal.

Depending on the orientation of the sensors, there are different possibilities for selecting and recognizing the drift in the event of overload, such as, for example, 2 B with sensors oriented for F1 in +45 degrees and F2 +135 degrees with respect to the direction of travel, where the drift is set for F1 in positive direction and for F2 in negative direction, so that an oscillation excitation in the X direction is to be expected , which can be made plausible by the front sensors. Alternatively, in this case, both sensors F1, F2 may be drifted in their positive direction, thereby provoking drift of the Y-direction signal upon vibrational excitation, which in turn will be plausibilized and recognized by the side sensors, as in FIG 2c is shown.

advantageously, can the mentioned Targeted asymmetry already by the component suppliers (sensor suppliers) can be specified, or program-specific programmed in the control unit. The targeted induction in particular minor Unbalances in the sensor element allows the signal drift direction in case of overload define and recognize this and through further plausibility false alarms upon exposure to mechanical disturbances (e.g. Avoid vehicle structure.

How this targeted asymmetry and signal-drift direction can be achieved will now be described by way of example with reference to the following 3 to 6 and embodiments explained.

3 shows the principle of a signal processing chain known from the prior art. The output of the sensor 1.1 is supplied to an input of an A / D converter (analog-to-digital converter). The permissible effective range is determined by design using symmetrical limits 2.1 (relative to the typical quiescent value) given, so that it can be ensured that the useful signal in the useful range can be safely imaged by the A / D converter. The output signal of the A / D converter 1.2 becomes another limiter 1.3 with symmetrical limits 2.2 (based on the typical resting value), with design thresholds 2.2 fed before the signal by means of a low-pass filter 1.4 to filter out interfering frequency components is filtered. The output of the low-pass filter 1.4 is the input of an offset compensation 1.5 supplied to compensate for offset errors, so that the sensor information then at the output 3.2 of the acceleration sensor 1 available for further processing. The offset compensation 1.5 This has high-pass or high-pass-like character, so that the slowly drifting offset is compensated and only the useful signal is present at the output.

How out 3 can be seen further, the sensor has 1.1 an assumed offset error, with which the resulting behavior of the signal processing chain is discussed in more detail. The assumed and illustrated offset error of, for example, 20 g causes the signal of the sensor output voltage 3.1 by means of the A / D converter with the limits 2.1 now asymmetrically detected and limited (at + 80g, -120g) is. Likewise, the signal of the sensor output voltage 3.1 by means of the limiter 1.3 unbalanced (at + 40g, -80g) with the limits 2.2 limited. After the signal of the sensor output voltage 3.1 by means of the high pass 1.5 the offset error is corrected or cleared at the output of the sensor 1 an unbalanced sensor component output area 3.2 with the borders 2.5.1 ,

As from the representation is easily apparent, with the realization according to the state the technology, in the presence of an overload at the sensor input, due the unbalanced limits at the output of the sensor is an unbalanced produces a limited output signal which is an assumed (not shown) subsequent integration unit clearly to misconduct can stimulate.

4 shows the principle of a signal processing chain according to the inventive concept. Deviating from 3 become the boundaries of symmetrical limits 2.1 . 2.2 in the presence of, for example, an offset error automatically tracked by an amount, so that the signal subject to offset 3.1 still continue with adjusted symmetric limits 2.3 . 2.4 (Relative to the signal subject to offset) is limited in the event of overload, in such a way that a defined drift direction arises. The offset control receives this 1.5 preferably a further output which provides the quiescent value, for example with a low-pass low-pass element.

In order to determine the tracking variable, the determined quiescent value from the offset control is used for this purpose 1.5 compared with the target value and from this the difference A is formed. By this difference Δ, as shown in the illustration, the limits 2.1 of the A / D converter 1.2 as well as the borders 2.2 of the limiter 1.3 corrected so that the new limits 2.4 for the A / D converter 1.2 as well as the borders 2.3 for the limiter 1.3 arise. The target value is chosen so that the desired direction of drift arises.

By means of this method it is ensured that in the presence of an overload at the sensor input and at the output of the sensor reliably a defined drifting output signal 3.2 is generated, so that a useful signal evaluation despite the presence of a superimposed high-frequency overload interference signature, without major falsifications is possible.

These However, unbalance can preferably be independent of the position of the quiescent value to be kept. This is done, for example, in that the above described shift to the desired unbalanced limits is applied. Naturally can also compensate for a rough deviation first and only one relatively low Residual deviation to achieve a defined drift in case of overload to be kept.

5 shows an example of the effect of unbalanced limitation. As can be seen from the illustration, an asymmetrical limitation leads to a considerable signal distortion or shift at the output of the signal chain.

The setting of the defined asymmetries of the sensor element can not first in the sensor element 1.1 subsequent evaluation path, but already by a control at the source, ie the sensor element 1.1 yourself. This can, as from the 6 can be seen by means of a matching amplifier 1.7 the sensor element 1.1 be directly or indirectly influenced in such a way to generate the resulting effects in case of overload.

This principle will now be described by means of a capacitive-electrical C / V converter, the in 6 is shown, will be explained in more detail. Such a converter is often used for acceleration sensors. To determine the required correction value of the matching amplifier 1.7 For this purpose, for example, to the sensor element 1.1 by means of the generator 1.8 for the modulation signal of the C / V converter 1.6 antiphase signals 4.1 . 4.2 applied at identical amplitude, and at the output of the C / V converter 1.6 or at the output of the filter 1.5 / the sensor 1 It is then checked whether the offset corresponds approximately to the defined setpoint. The filter 1.5 is shown here only as an example, it should be noted in the realization that the existing in the evaluation line circuit components do not distort the test signal inadequate.

For the sake of simplicity, the specific sensor elements are referred to below as "plates." The capacities of the "middle plate" 1.1.1 to the two lateral "plates" 1.1.2 are indirectly proportional to their respective distances. The injected opposite phase signals rise 4.1 . 4.2 about on, the distances are almost identical, or the "middle plate" 1.1.1 is almost symmetrical to the two lateral "plates" 1.1.2 aligned. Due to the given symmetrical arrangement of the "plates" 1.1.1 . 1.1.2 In the case of sporadic disturbances in the overload range, there is no unbalanced output signal and the distance between them corresponds to the path of possible deflection.

To the sensor element 1.1 An asymmetrical state is generated, for example, by means of the matching amplifier 1.7 a correction carried out, for which purpose two possible methods are explained in more detail. The first possibility of correction is that by means of the generator 1.8 for the modulation signal of the C / V converter 1.6 a DC component is superimposed, which is to be selected in the amount so that the output results in the defined offset. The second possibility of the correction is that by means of the "plate pair" to generate the deflection for the self-test, a static voltage is applied, which is to be selected in the amount such that the output results in the defined offset.

Especially in micromechanical acceleration or yaw rate sensors, eg. So-called MEMS cells are characterized by the dimensions in the micro and Nanometer range production engineering deviations in the etching and Coating processes inevitable. On the other hand, these are Sensor types provided active excitation systems, which are used for the measurement generate required oscillation. In addition, excitation systems can be provided be, which serve the self-test of the sensor. These active excitation systems can used in the context of this invention to specifically target the asymmetries perform counteracting detuning, so that the signals at Sensor output are already error-compensated.

In conclusion, be mentioned, for the sake of simplicity, a realization by means of a C / V converter was shown, because here the operation is easy to explain. Instead of the C / V conversion are also not shown in detail other conversion methods applicable e.g. Converters that map the physical quantity directly into digital values.

1

accelerometer for a Occupant protection system

1.1

Sensor element, capacitive acceleration sensor

1.1.1

medium, swinging capacity plate

1.1.2

firm capacity plates

1.2

Analog / digital converter

1.3

limiter

1.4

Low Pass Filter

1.5

Offset compensation / high-pass filter

1.6

C / V converter

1.7

Programmable gain amplifier

1.8

generator

2.1

symmetric effective range limits of the analog / digital converter 1.2

2.2

symmetrical effective range limits of the limiter 1.3

2.3

adapted symmetrical effective range limits of the limiter 1.3

2.4

adapted symmetric effective range limits of the analog / digital converter 1.2

2.5.1

Nutzbereichgrenzen the processed sensor signal

2.5.2

customized Usable range limits of the processed sensor signal

3.1

Sensor element output voltage (with signal = 0)

3.2

Output signal of the sensor 1 (with signal = 0)

4.1 4.2

excitation voltages

Claims (10)

Contraption ( 1 ) for sensing a directional physical quantity with at least one sensor element ( 1.1 ) having a preferred sensitivity direction for the applied directional physical quantity and a payload and an overload range, the device ( 1 ) can be set such that a desired effect of the sensor element output signal ( 3.1 . 3.2 ) is deliberately brought about with respect to the Nutzsignal- and overload range. Apparatus according to claim 1, characterized in that the adjustment is effected in that as the at least one sensor element, a sensor element ( 1.1 ) is used with a predetermined offset and / or a processing device ( 1.2 . 1.3 . 1.4 . 1.5 . 1.6 . 1.7 . 1.8 ) is configured for the output signal of the at least one sensor element such that the desired effect of the sensor element output signal with respect to the Nutzsignal- and overload range is deliberately brought about. Apparatus according to claim 1 or 2, characterized in that it is set such that the at least one sensor element ( 1.1 ) has an asymmetry of its output signal with respect to the useful signal and overload range such that the output signal has a predetermined drift direction in the event of an overload of the at least one sensor element ( 1.1 ) owns. Apparatus according to claim 1, 2 or 3, characterized in that the at least one sensor element ( 1.1 ) an acceleration sensor ( 1 ) having an axis of sensitivity for the preferred direction of sensitivity. Apparatus according to claim 4, characterized ge indicates that two acceleration sensors (BA1, BA2) are provided which are arranged in such a way that their sensitivity axes (F1, F2) are at an angle of approximately 90 degrees to one another. control unit for a Vehicle with a device according to one of the preceding claims. Safety device for a vehicle, in particular Occupant protection device comprising a device according to one of claims 1 to 5 includes. Vehicle, in particular motor vehicle with a safety device according to claim 7, wherein the device for sensing a directional physical size two in the vehicle approximately centrally arranged sensor elements (BA1, BA2) and is set such that the output signal of each sensor element a predetermined drift direction in the event of overload of a sensor element (BA1, BA2). Vehicle according to claim 8, characterized in that the arranged for sensing a side impact on the vehicle sides lateral sensor elements are provided and the safety device is formed such that the signals of the lateral sensor elements with the signals of the centrally arranged sensor elements and / or conversely be made plausible. Method for sensing a directional physical Size with at least a sensor element, which is a preferred direction of sensitivity for the acting physical quantity addressed and a payload signal and an overload range wherein adjustments are made such that a desired Effect of the sensor element output signal in terms of the useful signal and overload range purposefully brought about becomes.