DE102006046031B3 - Method and device for testing a sensor, in particular a unidirectional or bidirectional acceleration sensor or yaw rate sensor - Google Patents

Abstract

The invention describes a method for testing a sensor (10), in particular an acceleration sensor or yaw rate sensor contained in a motor vehicle personal protection system. In the method according to the invention, a test signal (SA) is applied to the sensor (10), which leads to the generation of a sensor output signal (SAS). The sensor output signal (SAS) has a defined signal swing (p) and is processed with a reference signal (VZ) to form a computing signal (MAS). Furthermore, the calculation signal (MAS) is fed to an integrator (16), whereby an integration signal (IS) with temporally successive integration values is generated from the calculation signal (MAS). At the end of the test, the integration signal (IS) has a first value (EW), which is fed to an evaluation device (17). Furthermore, a second value is calculated from the test signal (SA) and the reference signal (VZ). By evaluating the first and second values, a check is made as to whether the sensor (10) is operating as intended.

Description

The The invention relates to a method for testing a sensor, in particular of an acceleration sensor included in a motor vehicle personal protection system, in which a test signal is applied to the sensor for generating a sensor output signal leads. The invention further relates to a device for testing a Sensor, in particular one in a motor vehicle personal protection system contained, unidirectional or bidirectional acceleration sensor.

From the EP 1 035 415 A1 a generic method for testing a present in particular in a motor vehicle occupant protection system bidirectional acceleration switch is known. There are two comparators that compares the accelerometer output with thresholds and a switch controlled in response to the comparator outputs. The arrangement further comprises a control device for applying a test signal to the acceleration sensor and for evaluating the switch state obtained in response to the test signal. A circuit arrangement converts the sensor output signal and / or the comparator threshold values such that both comparators are activated with a time delay. The switching of the switch contained in the ignition circuit, which is caused by the sequential comparator output signals, makes it possible to check the functionality of both comparators and associated upstream and downstream components.

Problematic is doing that often the test signal an interfering signal superimposed is. This interference signal complicates the review of the Sensor. About that In addition, the sensor output must be reliably detected even then when a quiescent level of the sensor output signal, e.g. due to aging circumstances or temperature-related circumstances, across from a normal value varies. The normal value is also called resting level or offset. The bigger the Amplitude of the interference signal and / or the deviation from the quiescent level compared to that of the Test signal generated signal level is, the more critical is the evaluation of the sensor.

It is therefore an object of the present invention, a method and to provide a device for testing a sensor, which is a output signal generated by a test signal substantially independent of a deviation from the quiescent level and superimposed interference signal reliable recognizes.

These Tasks are solved with the features of the independent claims. Advantageous embodiments arise from the dependent ones Claims.

One inventive method for testing a sensor, in particular one in a motor vehicle personal protection system included acceleration sensor or yaw rate sensor in which a test signal is applied to the sensor, which is used to generate a Sensor output signal leads, the following steps are carried out: the sensor output signal, which has a defined signal swing is provided with a reference signal processed into a calculation signal, in particular multiplied; the The computational signal is fed to an integrator, resulting in the computational signal an integration signal with temporally successive integration values is generated, wherein the integration signal at the end of the test a first value, which is supplied to an evaluation device; there will be a second value from the test signal and the reference signal calculated; and it is evaluated by the first and the second Value carried out a check whether the sensor works as intended.

A inventive device for testing a sensor, in particular one in a motor vehicle personal protection system included acceleration sensor or yaw rate sensor includes the following features: first means for generating a test signal, which can be applied to the sensor, wherein the test signal for generating a sensor output signal leads with a defined signal swing; second Means for generating a reference signal; third funds, which at a first input, the sensor output signal can be fed and to which the reference signal can be supplied at a second input, for generating a computing signal; fourth means to which the computational signal supplied is for generating an integration signal with temporal succession following integration values, the integration signal being at the end the test has a first value; fifth means of identification a second value of the test signal and the reference signal; and sixth means for evaluating the first and second values and to carry out a check if the sensor works as intended.

The principle underlying the invention is to process the caused due to a test signal sensor output signal with a reference signal, wherein a function of a voltage applied to the sensor interference signal or a shift of the resting level of the sensor, a first value a computing unit is determined. Due to the known test signal and the known reference signal, the final value of this calculation can also be determined purely mathematically. This second value is compared with the actually determined actual value, the first value. If the two values are too far apart, the deflection of the sensor in response to the test signal is considered to be faulty.

The Invention is based on the so-called amplifiers known. Lock-in principle. Through this it is possible both a jamming signal as well as a change of the rest level. This can be reliably checked if that s.den sensor applied test signal for generating a sensor output signal with known signal swing leads. Checking if the expected signal swing occurs in response to a test signal and thus checking if the sensor works as intended, can be compared to known methods in a much shorter test time carried out are not long to make a reliable statement Averaging is necessary.

The Invention is suitable for testing sensors, in particular acceleration sensors, which work unidirectionally or bidirectionally, or rotation rate sensors. The procedure according to the invention has a strong bandpass characteristic due to the Test signal and the reference signal is defined. The procedure according to the invention allows it further, by suitable choice of the test signal and the reference signal also ramp-shaped noise filter out. Thereby can Sensors also in acceleration phases in which a measurement signal the sensor rises or falls, checked become.

When Reference signal is in accordance with a embodiment a square wave signal having a predetermined number of phases same amount generated positive and negative signal swing.

The predetermined number of phases of the reference signal forms a cycle which determines a minimum duration of the test. That's the way it is, for example sufficient if a cycle has only four phases, wherein dependent of the type of sensor only in the first (unidirectional Acceleration sensor) or in the first two phases (bidirectional Accelerometer) the test signal to the input of the sensor is created. Conveniently, The phases of a cycle have the same duration.

According to one embodiment the duration of the phases of the reference signal is such that a frequency of the reference signal in a frequency range outside a potential, perceptible by the sensor, disturbance is. This leaves increase the accuracy of the test and at the same time the duration for the execution reduce the test.

According to one another embodiment Within a cycle, there will be an equal number of phases chosen positive and negative sign. The order of phases within the cycle with positive and negative signs can be chosen arbitrarily become. To carry out of the sensor test are a first and at least a second cycle provided, wherein the first cycle, a first number of first phases and the second cycle has a second number of second phases. The first number of first phases and the second number of second Phases can chosen arbitrarily be. The duration of the first phases and the duration of the second Phases can chosen differently be. Through the measures described, the review of the Sensors are further improved. When carrying out a plurality on cycles with different frequencies (set by the Duration of the respective phases), so is the filtering effect further improved, since specific frequencies of a noise signal be taken into account can.

at the score of the first and second values becomes the difference determined between the first and the second value and further checked whether the Difference in a given tolerance range around the first value is located. This allows the intended function of the sensor easy way to be checked.

According to one another embodiment the test signal is different at one of a measurement signal Input created.

According to one another embodiment are the length the phases of a cycle and the arrangement of the phases with positive and negative sign to a filtered out Störsignal customized.

The Invention will become more apparent below explained with reference to the figures. Show it:

1 a schematic representation of the invention,

2 A first embodiment of the signals occurring in response to a test signal,

3 A second embodiment of the signals occurring in response to a test signal in the invention,

4A . 4B a third embodiment in which the test signal is superimposed with an interference signal, wherein the reference signal in each case has a different course, and

5A to 9B selected embodiments of progressions of a test signal and a reference signal.

A device according to the invention for testing a sensor, in particular an acceleration sensor contained in a motor vehicle personal protection system, is known in 1 shown. The invention makes it possible to test both unidirectional and bidirectional acceleration sensors for their functionality. The sensor to be tested is in 1 with the reference number 10 characterized. The sensor 10 has an entrance 12 on. The entrance 12 forms a test signal input to which from a controller 11 a test signal SA can be applied. On the sensor 10 Furthermore, an interference signal STS can act, such as a variation of a rest level of a sensor output signal SAS, eg due to aging or temperature effects. The interference signal STS can also be caused by a driving situation which leads to a response of the sensor 10 leads.

That at an output of the sensor 10 applied sensor output signal is via an analog-to-digital converter 14 an arithmetic arithmetic unit, in the exemplary embodiment a multiplier supplied. At a second input of the multiplier 15 is a reference signal VZ, which by the controller 11 is produced. An output signal of the multiplier, a so-called calculation signal, is denoted by the reference symbol MAS and is located at an output of the multiplier 15 at. The calculation signal MAS becomes an integrator 16 supplied, on the output side, an integration signal IS an evaluation device 17 is supplied. Since the sensor deflection is known when the test signal SA applied and also by the controller 11 generated reference signal is also known, the final value of the integral can be precalculated. This can be done, for example, by the controller 11 or the evaluation device 17 respectively. The over the integrator 16 The calculated value is compared with the calculated value. If the difference between the two values is too large, this indicates a faulty sensor deflection and thus a malfunction of the sensor 10 out.

The operation of the erfindunsgemäßen device is better from the 2 and 3 can be seen, in each of which a test signal SA, in response to the test signal SA at the sensor output sensor applied output signal SAS, the reference signal VZ, the computational signal MAS and an integration signal IS, respectively over time, are shown. In the 2 and 3 in each case a complete test cycle is shown. One cycle comprises a number of phases, designated by I to IV in the figures. It has been found that it is sufficient to carry out a test cycle with four phases. Each of the phases I, II, III, IV has an equal length of time t. The beginning of the test cycle is marked with Ta and the end of the test cycle with Te. The duration is 4t.

In the first phase I the 2 the test signal SA is applied to the input 12 of the sensor 10 created. In the rest position, the sensor output signal has a quiescent level rp, which is greater than 0 in the exemplary embodiment. In response to the test signal SA is located at the output of the sensor 10 a sensor output SAS during phase I on. This has a defined and known signal stroke p with respect to the rest position rp. The reference signal VZ is designed as a rectangular signal and has the same magnitude positive and negative signal, which can be arbitrary in principle. Due to this, in the following, the reference signal VZ with a positive signal swing is marked with the symbol "+" and a reference signal VZ with a negative signal pulse with the symbol "-". The sensor output SAS and the reference signal VZ are in the multiplier 15 multiplied with each other so as to give the calculation signal denoted by the reference MAS. After the computing signal MAS the integrator 16 is fed, resulting in the 2 shown course of the integration signal IS. At the end of the test cycle Te then results in a first value EW of the integration signal IS. This represents an actual value. A theoretical value, the second value, can also be calculated from the test signal SA and the reference signal VZ. In order to check whether the functionality of the sensor to be tested is given, it is checked whether the first value EW lies within a predetermined range around the second value.

This in 2 The procedure shown can be applied, for example, in a unidirectional acceleration sensor. In this case, it is sufficient to have the test signal SA only during a single one Phase of the test cycle.

In contrast, shows 3 A second embodiment, which is used to test a bidirectional acceleration sensor. In this case, a test signal SA is applied during the first two phases I, II of the test cycle. The further procedure is as described above.

In the embodiments of the 2 and 3 does not interfere with the sensor being tested. The quiescent level rp of the sensor output signal SAS is within a designated range.

In the 4A and 4B in each case an embodiment is shown in which acts during the test cycle, a noise signal STS on the sensor. The interference signal STS is approximated by a straight line having the slope m. The sensor to be tested should be a bidirectional acceleration sensor. According to the previous embodiment according to 3 Therefore, a test signal is applied during the first phase I and the second phase II. On the basis of the test signal SA and of the interference signal STS, a sensor output SAS results at the sensor output, which is shown in the figures with a thick line.

The embodiments in the 4A and 4B differ in that of the controller 11 output reference signal VZ. In 4A the reference signal VZ has the sequence +, -, -, +, while the reference signal in 4B the sequence +, -, +, - has.

In both embodiments Now, the content of the integral at the end of the fourth phase IV, i.e. the first value EW is determined. The effect of the reference signal VZ becomes clear.

In the equations ( 1 ) to (4), the integrals of phases I, II, III, IV are respectively shown.

After consideration of the reference signal VZ results in accordance with the embodiment 4A

The result is a final value according to

EW is a measure that is used to evaluate the test signal SA. As without further reference from equation (6), the first value EW does not depend from the slope m of the interfering signal STS and the offset b of the interfering signal from. As a result, the required properties of the process, independence from the offset default as well as a far-reaching independence of interfering signals STS, fulfilled.

Of the tested sensor is considered good or functioning when the first value EW is greater than one is fixed threshold. The threshold value is tolerated of the signal swing p and the durations t of the individual phases I to IV. Tolerances of the offset need not be considered in the threshold value become. Optionally, when choosing the threshold value, a safety margin be provided because of interference STS are not designed in practice as straight lines.

In contrast, results in the reference signal VZ according to the embodiment of 4B a first value EW according to

Reformulated results in the first value EW to:

By the other choice of the reference signal VZ does not give independence from the slope m of the interfering signal STS while the offset distortion b is eliminated.

It will therefore be readily apparent that it is advantageous to adapt the reference signal VZ to the course of an expected disturbance. To prevent the test of the sensor by a periodic noise with a frequency of about 1 / (2 * t) is negatively affected, it may be advantageous to a plurality on test cycles with preferably different durations of To carry out phases.

In the 5 to 9 Variants of the reference signal VZ and the test signal SA are respectively shown, which can be used advantageously within the scope of a sensor test.

In 5A the course for a bidirectional or two-pulse sensor is shown. In 5B the course for a single-pulse or unidirectional sensor is shown. The sensor signal SA varies in each case about a rest position, which is schematically indicated by the thin line. The levels of the last two phases III and IV are in the example according to 5A and 5B arbitrary, if they are chosen consistently.

6 shows a possible for a unidirectional sensor variant in which the last two phases are arbitrary, if they are chosen consistently.

7A shows a variant of a bidirectional sensor and the 7B . 7C the variant of a unidirectional sensor, wherein the levels of the first two phases are arbitrary, if they are consistent.

The 8A shows the course of the reference signal VZ and the test signal SA for a bidirectional sensor, while 8B again shows the signals for a unidirectional sensor.

The 9A shows the course of the reference signal VZ and the test signal SA for a bidirectional sensor, while 9B again shows the signals for a unidirectional sensor.

The Invention allows the test of a sensor, in particular a in Motor vehicle personal protection systems contained unidirectional or bidirectional acceleration sensor, checking whether the sensor works as intended, in a short time vornehmbar is. The principle of the invention is based on the Stimulate sensor by a test signal and an evaluation after the Lock-in principle. As a result, the method has a strong bandpass characteristic on, which by the test signal and a required for evaluation reference signal is adjustable. The method has the advantage of filtering out even ramp-shaped interference to be able to making a test even in acceleration or braking phases feasible is. By suitable choice of the test signal and the reference signal may be the result of the review of the Test signal independently from due to external events caused interference as well as due to an offset delay.

Claims (15)

Method for testing a sensor ( 10 ), in particular an acceleration sensor or rotation rate sensor contained in a motor vehicle personal protection system, in which a test signal (SA) is sent to the sensor ( 10 ), which leads to the generation of a sensor output signal (SAS), characterized in that - the sensor output signal (SAS) has a defined signal swing (p) and is processed with a reference signal (VZ) to form a computing signal (MAS) ; The computation signal (MAS) an integrator ( 16 ), whereby an integration signal (IS) with temporally successive integration values is generated from the calculation signal (MAS), whereby the integration signal (IS) has a first value (EW) at the end of the test which corresponds to an evaluation device (FIG. 17 ) is supplied; - A second value of the test signal (SA) and the reference signal (VZ) is calculated; and - by evaluating the first and second values, a check is made as to whether the sensor ( 10 ) works as intended. Method according to Claim 1, in which the reference signal a square wave signal having a predetermined number of phases same amount positive and negative signal swing is generated. Method according to claim 1 or 2, wherein the predetermined Number of phases of the reference signal (VZ) forms a cycle, the determines a minimum period of the test. Method according to Claim 3, in which the phases of a Cycle have an equal duration. Method according to Claim 4, in which the duration of the phases of the reference signal (VZ) is dimensioned in such a way that a frequency of the reference signal (VZ) in a frequency range outside a potential, transmitted by the sensor (VZ). 10 ) perceptible, disturbance lies. Method according to one of claims 3 to 5, wherein inside of a cycle an equal number of phases with positive and negative Sign selected become. The method of claim 6, wherein the order the phases within the cycle with positive and negative Sign chosen arbitrarily becomes. Method according to one of claims 3 to 7, in which for carrying out the Sensor tests a first and at least a second cycle provided are, wherein the first cycle, a first number of first phases and the second cycle has a second number of second phases. The method of claim 8, wherein the first number at first phases and the second number of second phases arbitrarily chosen are. Method according to claim 8 or 9, wherein the time period the first phases and the duration of the second phases different chosen is. Method according to one of the preceding claims, in when evaluating the first and second values, the difference between the first and second value is determined and further checked, whether the difference in a given tolerance range around the first Value (EW) is located. Method according to one of the preceding claims, in the length the phases of a cycle and the arrangement of the phases with positive and negative sign to a filtered out Störsignal (STS) are adjusted. Device for testing a sensor ( 10 ), in particular an acceleration sensor or yaw rate sensor contained in a motor vehicle personal protection system, comprising: - first means ( 11 ) for generating a test signal (SA) which is sent to the sensor ( 10 ) can be applied, wherein the test signal (SA) leads to the generation of a sensor output signal (SAS) with a defined signal swing (p); - second means ( 11 ) for generating a reference signal (VZ); - third funds ( 15 ), to which the sensor output signal (SAS) can be supplied at a first input and to which the reference signal (VZ) can be supplied at a second input, for generating a calculation signal (MAS); - fourth means ( 16 ) to which the computation signal (MAS) can be supplied, for generating an integration signal (IS) with temporally successive integration values, the integration signal (IS) having a first value (EW) at the end of the test; - fifth resources ( 11 ) for determining a second value from the test signal (SA) and the reference signal (VZ); and - sixth means ( 17 ) to evaluate the first and second values and to check whether the sensor ( 10 ) works as intended. Apparatus according to claim 13, wherein said seventh means ( 14 ) are provided for converting the analogue sensor output signal (SAS) into a digital output signal which corresponds to the first input of the third means ( 15 ) can be fed. Apparatus according to claim 13 or 14, wherein the acceleration sensor is unidirectional or bidirectional tional works.