EP3682543A1

EP3682543A1 - Method and evaluation system for evaluating a vehicle capacitive sensor

Info

Publication number: EP3682543A1
Application number: EP18768840.3A
Authority: EP
Inventors: Berthold Sieg
Original assignee: Huf Huelsbeck and Fuerst GmbH and Co KG
Current assignee: Huf Huelsbeck and Fuerst GmbH and Co KG
Priority date: 2017-09-14
Filing date: 2018-09-07
Publication date: 2020-07-22
Also published as: WO2019052908A1; JP7246150B2; US10837850B2; EP3682542A1; DE102018107479A1; WO2019052914A1; DE102018113253A1; JP2019073268A; DE102018107477A1; WO2019052904A1; EP3682544A1; DE102018107478A1; US20190078954A1

Abstract

The invention relates to a method for evaluating a capacitive sensor (10), in particular for detecting an activation action of the vehicle (1). The method comprises the following steps: a) carrying out a transfer phase (A) in which at least one sensor element (11) of the capacitive sensor (10) for recharging is electrically connected to an evaluation arrangement (20), b) carrying out an interruption phase (B) for interrupting the transfer phase (A), c) repeating steps a) and b) using at least one time-variable phase duration, in order to carry out, based on a plurality of repeatedly performed transfer phases (A), the evaluation using the evaluation arrangement (20).

Description

Method and evaluation system for evaluating a capacitive sensor in a vehicle

Description

The present invention relates to a method for evaluating a capacitive sensor of a vehicle. Furthermore, the invention relates to an evaluation system for evaluating the capacitive sensor.

It is known from the prior art that capacitive sensors can be provided in vehicles for the detection of an activation action. Such an activation action can be executed as a simple approach or as a complex gesture. In any case, the activation act serves to activate a vehicle function, eg. To initiate authentication on the vehicle and / or to open a door or tailgate. For this purpose, the capacitive sensor may be arranged in the rear region of the vehicle, for example in the region of a bumper, to pass through a Foot movement or the like of a user of the vehicle to be activated.

An evaluation of a capacitive sensor can be done by a so-called. Umladeverfahren. Such Umladeverfahren are z. For example, DE 10 2012 102 422 A1, DE 10 2012 105 266 A1, DE 10 2013 1 12 909 A1, and DE 10 2013 1 12 910 A1, the disclosure of which is also made subject of this application.

It is often a technical challenge to avoid disturbances of the sensor by the environment of the sensor or vehicle. It is known that moisture from the environment (eg rain) is a nuisance. Due to the electronic evaluation of the sensor but also electromagnetic signals can form a source of interference. So z. B. external transmitters, such as a medium-wave radio or the like, possibly a negative impact. In particular, such signals of this transmitter, which interact at an evaluation frequency of the capacitive sensor, such as. In the range of 510 kHz to 1.71 MHz. Measures to reduce and / or compensate for this influence are technically complex and cost-intensive.

It is therefore an object of the present invention to remedy the disadvantages described above at least partially. In particular, it is an object of the present invention to provide an improved possibility for evaluating a capacitive sensor and / or to be able to compensate for interference, in particular by electromagnetic signals.

The above object is achieved by a method having the features of the independent method claim and by an evaluation system having the features of the independent system claim. Further features and details of the invention will become apparent from the respective dependent claims, the description and the drawings. In this case, features and details that are described in connection with the method according to the invention apply, of course, also in connection with the evaluation system according to the invention, and in each case vice versa, so that with respect to the disclosure of the individual aspects of the invention always reciprocal reference is or may be. The object is achieved in particular by a (evaluation and / or detection) method for evaluating at least one capacitive sensor, in particular for detecting an activation action in a vehicle. Such an activation action is, for example, an approach and / or a gesture of a user of the vehicle, which serves to activate a vehicle function. For this purpose, an activating agent can be used, for. B. a body part such as a foot of the user. If necessary, a plurality of sensors and / or a plurality of sensor elements of a sensor can also be used to detect the activation action, in order, for. B. to capture a movement history. In this case, it is conceivable that the at least one sensor element in an area of the vehicle assigned to the vehicle function, e.g. B. rear area and / or side area of the vehicle is arranged. Assigned vehicle function refers to that - if the vehicle function z. B. is the automated opening of the tailgate of the vehicle - the sensor element in the rear area, z. B. stored in a bumper, the vehicle and / or is attached. For example. is the sensor element formed longitudinally stretched, z. B. as an electrical line or the like. Also, a plurality of sensor elements may be arranged at least substantially parallel to z. B. to detect a direction of movement.

For example. the vehicle is designed as a motor vehicle and / or as a passenger vehicle and / or as a truck and / or as an electric vehicle. In order to increase the security, it may further be provided that upon positive detection of the activation action for activating the vehicle function, an authentication z. B. with an identification transmitter (electronic key) is performed. Advantageously, in the method according to the invention, at least one of the subsequent steps can be carried out, wherein the steps are preferably carried out successively or in any order, and if necessary, individual steps can also be repeated:

a) carrying out a recharging phase in which at least one sensor element of the capacitive sensor for recharging is electrically connected to an (electrical, in particular electronic) evaluation arrangement,

b) carrying out an interruption phase for the (in particular temporal) interruption of the transhipment phase, Repeat steps a) and b) z. B. successively and with at least one time-variable phase duration, which is preferably for different repetitions, preferably stochastically varied, ie, for example, is extended or shortened to perform the evaluation of the capacitive sensor by the evaluation arrangement based on several repeatedly performed Umlephasenphasen.

In other words, the capacitive sensor clocked by the evaluation arrangement with (at least) an evaluation frequency (clock frequency) can be evaluated, this clock is irregular - that is influenced by a kind of jitter with a fluctuating evaluation frequency. The clock may, for example, the initiation or the beginning of at least one of the phases, ie the recharge phase and / or the interruption phase and / or a total phase with a total phase duration (composed at least from the recharge phase and the interruption phase) relate. The total phase duration T _pu i _{s is} calculated, for example, from:

Tpuls ^- T + Tpause, with T as a first phase duration of the charge transfer phase and T _paU se as a second phase duration of the cutoff phase. A capacitive sensor operated in this way is also referred to as pulse-operated. Both the first phase duration and the total phase duration are conventionally fixed, e.g. B. the first phase duration at 1, 25 s and / or the total phase duration at 100 s. It can be seen that the first phase duration is much smaller than the total phase duration and the second phase duration. A temporal change of one of the first or second phase durations inevitably causes a change in the total phase duration (and vice versa).

The recharge phase and the interruption phase can thus be repeated cyclically for evaluation of the capacitive sensor with (at least) one evaluation frequency, wherein the total phase duration can be regarded as the period of these repetitions. Both the evaluation frequency and the period duration are usually constant, and according to the invention can be variable during a (single) evaluation (that is to say during the repetitions of a plurality of charge-reversal phases and interruption phases). Such a change can thus be as a triggering of further evaluation frequencies and / or as a jitter and / or as a generation of a noise in an evaluation signal, so that an evaluation bandwidth is increased. Of importance here may be that this variability or variability relates to a specific (automated) measure for temporally changing at least one of the phase durations to the cycle (ie, for example, the time intervals between the reloading phases in the repetitions for an evaluation ) and / or to increase the evaluation bandwidth, in particular to produce a jitter effect. Thus, it is clear that the temporal change does not take place in a negligible temporal magnitude, but can have a significant impact on the evaluation. The evaluation may therefore have to be adapted to the varying phase durations.

It is advantageous if a time difference between first phase durations (for example of a first cycle and of a second cycle directly following the first cycle) of the repetitions is at least 10 ns or at least 50 ns or at least 0.1 s or at least 0.2 s is and / or can be at most 50 ns or at least 0.2 s or at least 0.4 s. It may also be possible for a minimum duration of the first phase duration to be at least 100 ns or at least 250 ns or at least 500 ns. Thus, a sufficiently varying phase duration can be provided for the evaluation in order to reliably evaluate the sensor when reducing disturbing influences.

It may be provided in the inventive method that the electrical connection according to step a) (ie, the sensor element with the evaluation device) is to be understood as an electrical connection for providing an electrical current flow, which z. B. by means of an electronic switching element, such as a semiconductor switch or the like. In particular, before and / or after step a) and / or during the interruption phase, this connection can be interrupted, ie the current flow can be prevented, at least predominantly. For interrupting the connection, a current path between the sensor element and the evaluation arrangement can be switched, for example, by the switching element to high impedance (eg according to the blocking resistance of the switching element), and low resistance to produce the connection (eg according to the forward resistance of the switching element ). It may be advantageous if the transhipment in the transhipment phase is carried out according to a recharging method for measuring an electrical capacity. In this case, depending on a stored charge (or a sensor capacitance) of the capacitive sensor - ie, for example proportionally thereto - in the evaluation arrangement, in particular in a holding arrangement of the evaluation arrangement with a so-called holding capacity, a stored charge can be increased. This process can be repeated in several cycles in the Umladephasen, wherein in each cycle, the charge in the evaluation arrangement, in particular the holding assembly is accumulated. After a defined number of repetitions of the recharge phases (hereinafter also: transshipment processes), the accumulated charge can be interrogated, eg. B. based on a voltage which is determined in parallel or in series with the holding arrangement by an analog-to-digital converter of the evaluation arrangement. In this way, the analysis can be carried out by the evaluation arrangement based on several repeatedly performed Umladephasen. The determined voltage value indicates the size of the sensor capacitance and / or the state of charge of the capacitive sensor and can be further investigated, for. B. compared to a threshold to detect the activation action. In this case, use is made of the fact that the activation action is, for example, an approximation, in which the activating means (eg a hand or a foot of a user) changes the sensor capacity characteristically, so that reliable and rapid detection of this characteristic change is possible by using the transhipment method is possible.

For a better understanding of this evaluation, the sensor element can be understood as a sensor electrode of a capacitor with a variable capacitance (sensor capacitance), wherein the sensor capacitance can be dependent on the environment of the sensor or the vehicle. For example. For example, a user may approach the sensor element, or movement of a body may occur in the surrounding area, resulting in a change in sensor capacitance. This effect can be explained by the fact that a dielectric around the sensor element changes. In this case, a counterelectrode can be formed to the sensor element for providing the sensor capacitance in the environment (eg by a ground potential, the moving body or the like). Optionally, it is possible that the sensor element has only a single electrically conductive connection, that is, it is connected only to a single current path. Incidentally, the sensor element can be floating (floating) and / or electrically isolated and / or only be in contact with the environment. It is thus clear that the sensor element can be a single electrode for providing a sensor capacitance. It is also possible to provide a plurality of sensor elements, which then provide correspondingly a plurality of sensor capacitances. It is also conceivable that a plurality of sensor elements in each case form part electrodes of an entire electrode, and, for example, are connected to a common potential, for. B. to be able to form the sensor surface more flexible. The sensor element can advantageously be arranged in the rear bumper of the vehicle. Advantageously, the sensor element can extend at least predominantly over the entire width (extension in the vehicle transverse direction) of the bumper. Thus, the activation action may be a movement gesture of the user, such as moving the foot of the user under the vehicle rear. This activation action changes (increases or decreases) the sensor capacity in a characteristic manner, e.g. B. at least to a value above or below a threshold value, which then by the evaluation arrangement, for. B. by a processing device (a microcontroller or the like) of the evaluation, can be detected. With positive detection, the vehicle function can be activated, eg. B. the tailgate to be opened.

According to step c), the phase duration may be variable over time. By this is meant, in particular, that the time duration of the recharge phase and / or the interruption phase can be changed at each repetition.

Furthermore, it is optionally possible within the scope of the invention for the charge-reversal phase to be performed with a first phase duration and the interruption phase for a second phase duration, wherein the first and / or the second phase duration are variably adjusted according to a phase duration adaptation. The phase duration adjustment can, for. B. actively by an adaptation device, in particular a random number generator, are performed. This can, for. B. in the evaluation arrangement, for. B. in a control unit of the vehicle and / or in a vehicle electronics, be integrated. This allows a simple implementation of the method according to the invention in the vehicle. Furthermore, it can be provided within the scope of the invention that for each repetition (for each cycle) according to step c) a phase duration adaptation (in particular by the adaptation device, preferably by at least one random number generator) is performed, ie the phase duration of a respective transhipment and / or interruption phase is changed in each repetition temporally, in particular stochastically. As a result, a reduction in the susceptibility to interference in the evaluation can be achieved. This reduction is particularly efficient if different time adjustments are made for the transhipment phase and the interruption phase. Due to the temporal adjustments, the duration of the respective phase durations (the transhipment and / or interruption phase and / or the total phase duration) can be extended or shortened for each repetition (ie for each cycle).

For example. For example, a first random number generator may be used for a first phase duration adjustment for the transient phase and / or a second random number generator for a second phase duration adaptation for the interruption phase and / or for the total phase duration. The different random number generators may be separate electronic components. It may also be possible that the respective random number generator is part of an integrated circuit and / or software implemented to provide efficient electronics for phase duration adjustment.

In the case of a possible similar temporal adaptation of the phases, only a single random number generator can be used, so that the adaptation for the transient phase and the interruption phase happens in the same way (for example, each of the phases is shortened or extended by the same time period). However, a different procedure is necessary if the adjustments of the phases are to be different and / or independent of each other, so that, for example, during one cycle one of the phases (eg the transhipment phase) is extended by a first time value and the other phase (eg. B. the interruption phase) is extended by a different second time value. This can be realized by using different random number generators which independently provide random numbers for the phase duration adjustments. For example. For example, the first random number generator may generate first random numbers, with the adjustment of the first phase duration based on the first Random numbers done. Also, the second random number generator may generate second random numbers, wherein the adaptation of the second phase duration is based on the second random numbers. For example. indicate the random numbers in each case by which value the respective phase duration is extended. This can be a particularly efficient bandwidth increase to reduce a susceptibility to be provided.

It may optionally be possible for each repetition, a first phase duration of the recharging phase and a second phase duration of the interruption phase to be adapted independently of one another. The independent adaptation can refer to the fact that an increase of the first phase duration by a first value x does not necessarily have to be accompanied by an increase of the second phase duration by this value x, but can possibly take place by a second value y. This can be z. B. be achieved by different random numbers determine the increase, which are optionally generated by two different random number generators. This can be easily and reliably a stochastic clock distortion ensured by adjusting the phase duration.

It may also be possible that the sensor element is designed as an electrode of the capacitive sensor to provide a sensor capacitance of the capacitive sensor, which is detected by the evaluation, in particular measured, and is preferably influenced by an activation action. As already described, the activation action may include a change in the environment, such as the movement of a hand in the region of the sensor element. Regardless of the theoretical model, that is, whether the hand is regarded as a counter electrode to the sensor element or as influencing the dielectric between the sensor element and a mass or the like, the activation action leads practically to a change in the sensor capacity. Thus, there is no need to provide a separate counterelectrode to the sensor element in the sensor, but it is sufficient for a possibility that the sensor has only a single electrode to provide the sensor capacitance. Since the sensor capacity is environment-dependent, the activation action can be detected by simply measuring the sensor capacity. A further advantage within the scope of the invention can be achieved if the evaluation is frequency-sensitive as a function of the phase durations, the phase durations being varied over time for each repetition, in order to reduce the frequency sensitivity, and preferably simultaneously increasing a bandwidth of the frequency sensitivity, wherein preferably the Frequency sensitivity determines a frequency-dependent susceptibility to external signals. It can thus be preferred to increase the bandwidth of the evaluation or measurement frequency with which the sensor capacitance is measured, and at the same time, however, the interference sensitivity (ie the frequency sensitivity) can thereby be reduced.

Possibly. is understood by "frequency-sensitive" that a susceptibility to interference with respect to an interference frequency (ie a "disturbing" frequency) of an external transmitter is present.

Preferably, it can be provided that, based on the evaluation, a sensor capacitance of the capacitive sensor is evaluated, in particular measured, whereby the sensor capacitance is influenced by an approximation of an activating means, in particular a user, to the sensor element, and preferably a change in the sensor capacitance for evaluation a template is compared to enable a vehicle function based on the comparison, in particular to automatically open a tailgate of a vehicle. For example. For example, the template includes a threshold or pattern recognition or the like to reliably enable the detection of the activation action.

In the context of the invention, the vehicle function z. B. provide an authentication and / or opening the tailgate and / or the like.

In a further possibility it can be provided that during each charge phase, a charge evaluation of the capacitive sensor is performed on the basis of the electrical connection according to step a), wherein the charge evaluation is performed temporally irregularly by the temporally (in particular stochastically) varying phase durations, preferably phase-modulated. In other words, an output signal of the charge evaluation can be phase modulated by the fact that the Umladephase and thus the Charge evaluation does not take place regularly but at irregular intervals. This allows a trouble-free evaluation.

Preferably, it can be provided that (in particular for charge evaluation) a holding arrangement (in particular a holding capacitor) of the evaluation arrangement is loaded in response to a charge state and / or a sensor capacitance of the capacitive sensor during each transfer phase in order to carry out the transfer, so that in accordance with step c ) carried out repeatedly Umladephasen a charge accumulation of the holding arrangement, wherein preferably after the repetitions according to step c), the following step is carried out:

Evaluating a state of charge of the holding device to detect a positive detection (eg, the activation action) of the capacitive sensor.

This can be understood as a so-called. Transhipment of the charge of the capacitive sensor on the holding arrangement, wherein the transhipment also indirectly, z. B. via a current mirror, can be done. For example. can to provide a current mirror electronic switching elements such. As transistors, be interconnected to control an output current based on an input current. For example. the output current can be understood as a copy of the input current. Since this evaluation is dependent on a state of charge of the capacitive sensor, an electrical interference signal can interfere with the evaluation. Because the interference signal may possibly act on the transhipped charge and / or the charge accumulation during the transhipment, so that a result of this evaluation is disturbed. In particular, electromagnetic interference signals (with certain frequencies) are relevant here, so that the temporal change of the phase durations can effectively reduce the interference. The increase of the bandwidth of an output signal of the charge evaluation may be higher (eg at least twice or at least four times) as high as a bandwidth of the interference signal.

In a further possibility it can be provided that a holding capacity is provided by a holding arrangement (preferably a holding capacitor) of the evaluation arrangement, which is loaded as a function of the transhipment according to step a). Further, for evaluation, an analog-to-digital converter can be electrically connected to the holding arrangement in order to determine a state of charge of the holding arrangement, in particular only after a predetermined number of repetitions according to step c). For example. can be designed as a 12-bit analog-to-digital converter, the analog-to-digital converter. In particular, at least 4 or at least 8 or at least 10 or at least 12 repetitions according to step c) (charging of the sensor for a measurement) may be provided. Alternatively or additionally, the number of repetitions according to step c) may be in a range from 5 to 40, preferably 8 to 20, preferably 10 to 15. This ensures reliable evaluation.

Furthermore, it can be provided within the scope of the invention that an evaluation frequency of the evaluation is temporally varied by the repetitions according to step c), preferably randomly distributed in the phase position, preferably a jitter effect and / or a phase modulation in the evaluation, preferably at an output signal of an analog-to-digital converter (ADC). In other words, the evaluation signal can thereby be phase-modulated and thus noisy. Thus, an interference sensitivity for at least one transmission frequency of large-signal transmitters can be reduced. The evaluation signal is understood in particular to be the ADC signal, which is output as a function of the accumulated charge of the holding arrangement. In particular, an electronic system for evaluation is also connected to one or the random number generator in order to carry out the evaluation with knowledge of the changed phase duration (s), which are changed as a function of random numbers.

For example. It can be provided that the at least one phase duration is varied by a random number generator, preferably a pseudorandom number generator, for each repetition according to step c), wherein the random number generator preferably has a shift register, particularly preferably a linear feedback shift register. It is advantageous in this case if the random number generator has at least one 8-bit shift register or 16-bit slider register to z. To provide at least 255 random numbers. In this way, the generation of random numbers can be faster and / or requires less effort than the reading of defined numbers.

In addition, it is advantageous if within the scope of the invention a first phase duration (ie the duration of the recharging phase) in the range of 250 ns to 7 μβ, preferably 300 ns to 5 μβ, preferably 500 ns to 3 μβ, is carried out variably. It has been shown hereby that a particularly reliable evaluation is possible.

Optionally, it can be provided that a second phase duration (ie the duration of the interruption phase) in the range of 1 .mu.β to 500 .mu.β, preferably 100 .mu.β to 400 .mu.β is made variable, in particular in that a total phase duration of the charge phase and the interruption phase together by one Value between 1 s to 400 s, preferably 50 s to 200 s, is increased or decreased. This also improves the evaluation.

According to an advantageous development of the invention, it can be provided that a second phase duration (duration of the interruption phase) is greater by at least a factor of 10 or at least by a factor of 100 than a first phase duration (duration of the transhipment phase). Thus, the interruption phase can be very flexibly and extensively adjusted in terms of time to improve the evaluation.

The invention also relates to an evaluation system for a vehicle for evaluating a capacitive sensor, in particular for detecting an activation action in the vehicle, with a holding arrangement (preferably a holding capacitor) for providing a holding capacity, which in dependence on a recharging phase of the capacitive sensor with a first phase duration and an interruption phase for interrupting the recharging phase with a second phase duration is rechargeable to evaluate the capacitive sensor. In this case, it is provided that an adaptation device, in particular a random number generator, is provided for temporally changing at least one of the phase durations. Thus, the evaluation system according to the invention brings about the same advantages as have been described in detail with reference to a method according to the invention. In addition, the evaluation system may be suitable to be operable in accordance with a method according to the invention.

Further advantages, features and details of the invention will become apparent from the following description in which with reference to the drawings Embodiments of the invention are described in detail. The features mentioned in the claims and in the description may each be essential to the invention individually or in any desired combination. Each schematically shows: FIG. 1 is a perspective view of a rear of a vehicle with a

User,

2 shows a schematic circuit diagram of an evaluation system according to the invention, FIG. 3 shows a representation of a charge evaluation for the visualization of a method according to the invention.

In the following figures, the identical reference numerals are used for the same technical features of different embodiments.

FIG. 1 schematically shows a perspective view of a vehicle 1. It is shown a tailgate 2 above a bumper 3 of the vehicle 1, which, for example, can be opened according to a vehicle function. Furthermore, a sensor element 1 1 of a capacitive sensor 10 of an evaluation system 200 according to the invention can be integrated in the bumper 3. This is in particular kabeiförmig and / or formed with an elongated extent to provide a possible extended detection range for detecting an activation act. The activation action is, for example, the movement of an activating means 9, such as a foot of a user 8. To carry out the activating action, the user 8 can move the foot 9 under the bumper 3. This can then be detected as a change in a sensor capacitance CS of the capacitive sensor 10, preferably by an evaluation of an evaluation arrangement 20. The evaluation arrangement 20 can furthermore be electrically connected to the capacitive sensor 10 and / or designed as a control unit of the vehicle 1.

In Figure 2, the detection principle for detecting the activation act is shown in more detail using a schematic diagram of the capacitive sensor 10. A sensor element 1 1 is formed by an electrically conductive material, which is an electrode of the capacitive sensor 10 forms. It may be provided a further counter electrode or the sensor element 1 1 are used as the only structurally provided electrode of the sensor 10 to provide a sensor capacitance CS. The latter case can be understood to mean that the sensor element 1 1 forms the sensor capacitance CS with respect to a ground potential. The sensor capacitance CS is variable when an activating means 9 moves into the surrounding area of the sensor element 11. In the transfer phase A, at least one (electronic) switch can then be closed in order to "reload" the charge stored on the basis of the sensor capacitance CS, ie, depending on (for example, proportionally) the sensor capacitance CS or the stored charge, a holding arrangement 30 with one For example, a current mirror may also be used, so that the transhipment takes place "indirectly". A driver 45, such as a microcontroller or a transistor or the like, can perform the switching of the switch. For example. the driver 45 uses random numbers generated by at least one adaptation device 40, preferably a random number generator 40, to switch over the switch so as to vary a (first) phase duration of the charge-reversal phase A. It may also be possible for the driver 45, as a function of the random number generator 40 or at least one further random number generator 40, also to vary a further phase duration, such as a second phase duration. After a few repetitions of the recharging phase A and these subsequent interruption phases B, the state of charge can be determined by means of a voltage across or serially to the holding arrangement 30 by an analog-to-digital converter 50.

FIG. 3 schematically shows an evaluation of a capacitive sensor 10 of an evaluation system 200 according to the invention in order to visualize a method according to the invention. In this case, the sequence of the charge-reversal phase A with a first phase duration DA and the interruption phase B with a second phase duration DB is indicated by a continuous line. On the other hand, a state of charge LH as the accumulated charge is shown with a dashed line, which can be stored depending on a holding capacity CH and interrogated at a holding device 30. This charge state LH is changed by the preferably used transfer method in the transfer phase A as a function of a sensor capacitance CS of the capacitive sensor 10. It follows that the sensor capacitance CS can be detected on the basis of the state of charge LH. If now the phase durations DA, DB are the same length and immutable for each repetition of the phases A, B, it is possible to speak of a constant timing of the evaluation. A period (or total phase period) T _pu i _s in this case corresponds DA + DB, and an evaluation frequency f (or sampling frequency) can be exemplified as f = 1 / (DA + DB). This z. B. the first phase duration DA = 1, 25 s and the total phase _duration T _pU is = (DA + DB) = 100 μβ amount. It can be seen that the first phase duration DA can be much smaller than the total phase duration.

When using a fixed evaluation frequency f, the evaluation can be adversely affected by a disturbing effect with a similar frequency or with a corresponding influence in this frequency range. In particular, such interference, z. B. an amplitude-modulated medium-wave transmitter, to incorrect values when detecting the state of charge LH. This phenomenon occurs increasingly when an interference frequency of the interference is at least almost phase synchronous to the evaluation frequency f.

A solution provides the method according to the invention, when the Umladephase A and the interruption phase B are repeated with at least one temporally variable phase duration in order to carry out the evaluation by the evaluation arrangement 20 based on these several repeatedly performed Umladephasen A. In other words, at least one of the phase durations-in particular randomly-is varied over time in the execution of repetitions of the phases, in order to jitter the evaluation frequency f, that is to say in the case of FIG. H. (random) in the phase position to distribute. Thus, the output signal, ie z. B. the measured state of charge LH, be phase-modulated, and thus virtually noisy. This is then taken into account in the evaluation accordingly, z. B. by a higher noise tolerance and / or by taking into account the varied phase durations. For example, the evaluation arrangement 20 can perform the evaluation in dependence on random numbers which are used for the variation.

The above explanation of the embodiments describes the present invention solely by way of example. Of course, individual features of the Embodiments, if technically reasonable, are freely combined with one another, without departing from the scope of the present invention.

S e c tio n s ia s

I vehicle

2 tailgate

3 bumpers

8 users

9 activating means 10 capacitive sensor

I I sensor element, sensor electrode

20 evaluation arrangement 30 holding arrangement

40 random number generator

45 Control 50 analog-to-digital converter

200 evaluation system t time

U voltage

A transhipment phase

B interruption phase

CH holding capacity

CS sensor capacity

DA first phase duration

DB second phase duration

LH charge state holding capacity

Claims

P a n t a n s p r e c h e

1 . Method for evaluating a capacitive sensor (10), in particular for detecting an activation action in a vehicle (1),

wherein the following steps are performed:

a) carrying out a recharging phase (A), in which at least one sensor element (1 1) of the capacitive sensor (10) is electrically connected to an evaluation arrangement (20) for transhipment,

b) performing an interruption phase (B) to interrupt the

Transfer phase (A),

c) repeating steps a) and b) with at least one temporally variable phase duration in order to carry out the evaluation by the evaluation arrangement (20) on the basis of several repeatedly performed transfer phases (A).

2. Method according to the preceding claim,

characterized,

the recharging phase (A) is carried out with a first phase duration (DA) and the interruption phase (B) with a second phase duration (DB), the first and / or the second phase duration (DA, DB) being variably adjusted according to a phase duration adaptation.

3. The method according to any one of the preceding claims,

characterized,

in that, for each repetition according to step c), a phase duration adaptation is carried out by at least one random number generator (40), whereby preferably different temporal adaptations are carried out for the transhipment phase (A) and the interruption phase (B). Method according to one of the preceding claims,

characterized,

in each repetition, a phase duration (DA) of the transfer phase (A) and a phase duration (DB) of the interruption phase (B) are adapted independently of each other in time.

Method according to one of the preceding claims,

characterized,

in that the sensor element (11) is designed as an electrode of the capacitive sensor (10) in order to provide a sensor capacitance (CS) of the capacitive sensor (10) which is detected, in particular measured, by the evaluation, and is preferably influenced by an activation action becomes.

Method according to one of the preceding claims,

characterized,

in that the evaluation takes place in a frequency-sensitive manner as a function of the phase durations, wherein the phase durations for each repetition are varied in order to reduce the frequency sensitivity and preferably at the same time to increase a bandwidth of the frequency sensitivity, the frequency sensitivity preferably determining a frequency-dependent susceptibility to external signals.

Method according to one of the preceding claims,

characterized,

in that, based on the evaluation, a sensor capacitance (CS) of the capacitive sensor (10) is evaluated, in particular measured, the sensor capacitance (CS) being approximated by an approximation of an activation means (9), in particular a user (8), to the sensor element (11 ), and wherein a change of the sensor capacitance (CS) is preferably compared with a template for the evaluation in order to activate a vehicle function based on the comparison, in particular to automatically open a tailgate (2) of a vehicle (1).

8. The method according to any one of the preceding claims,

characterized,

in that during each transfer phase (A) a charge evaluation of the capacitive sensor (10) is carried out based on the electrical connection according to step a), wherein the charge evaluation is carried out irregularly in time by the time-varying phase durations, preferably phase-modulated.

9. The method according to any one of the preceding claims,

characterized,

in that, in particular for charge evaluation, a holding arrangement (30) of the evaluation arrangement (20) is charged in each charge phase (A) as a function of a charge state of the capacitive sensor (10) in order to carry out the charge transfer, so that in the case of the charge carried out repeatedly according to step c) Umladephasen (A) charge accumulation in the holding assembly (30), wherein preferably after a predetermined number of repetitions in step c), the following step is performed:

Evaluating a state of charge (LH) of the holding arrangement (30) to a positive

Detecting the detection of the capacitive sensor (10).

10. The method according to any one of the preceding claims,

characterized,

in that a holding arrangement (30) of the evaluation arrangement (20) is charged by the transhipment according to step a), and an analog-to-digital converter (50) is electrically connected to the holding arrangement (30) for evaluating a state of charge of the holding arrangement

(30), in particular only after a predetermined number of repetitions according to step c).

1 1. Method according to one of the preceding claims,

characterized,

in that an evaluation frequency of the evaluation is varied over time by the repetitions according to step c), preferably randomly distributed in the phase position, in order preferably to produce a jitter effect and / or a phase modulation in the evaluation, preferably in the case of an output signal of an analog-to-digital converter ( 50).

12. The method according to any one of the preceding claims,

characterized,

in that the at least one phase duration is varied on the basis of a random number generator (40), preferably pseudorandom number generator, for each repetition according to step c), whereby the random number generator (40) preferably has a shift register, particularly preferably a linear feedback shift register (LFSR).

13. The method according to any one of the preceding claims,

characterized,

in that a phase duration (DA) of the transfer phase (A) in the range from 250 ns to 7 μβ, preferably 300 ns to 5 μβ, preferably 500 ns to 3 μβ, is variable.

14. The method according to any one of the preceding claims,

characterized,

in that a phase duration (DB) of the interruption phase (B) is made variable in the range from 1 s to 500 μβ, preferably 100 μβ to 400 μβ.

15. The method according to any one of the preceding claims,

characterized,

a phase duration (DB) of the interruption phase (B) is at least a factor of 10 or at least a factor of 100 greater than a phase duration (DA) of the transhipment phase (A).

16. evaluation system (200) for a vehicle (1) for evaluating a capacitive sensor (10), in particular for detection of an activation action in the vehicle (1), with an electronic holding arrangement (30) for providing a holding capacity (CH), which in response to a recharging phase (A) at the capacitive sensor (10) with a first phase duration (DA) and an interruption phase (B) for interrupting the recharging phase (A) with a second phase duration (DB) is chargeable to the capacitive sensor ( 10) evaluate,

characterized,

an adaptation device (40) for temporally changing at least one of

Phase durations (DA, DB) is provided.

17. evaluation system (200) according to one of the preceding claims,

characterized,

that the evaluation according to a method according to one of the preceding

Claims is feasible.