DE102008018671B4 - Touch detection device for a motor vehicle - Google Patents

Abstract

Touch detection device, wherein the touch detection device has an RC element, a capacitive touch sensor (12) as part of the RC element, and an evaluation device (10, 20) for correcting an output signal (S) of the capacitive touch sensor (12) by means of a temperature correction value (δT) and for generating an input signal (P1) for the RC element, characterized in that the temperature correction value (δT) can be determined as a function of an output signal (P3) of the RC element which is dependent on the input signal (P1).

Description

The invention relates to a touch detection device, in particular for a motor vehicle, with a capacitive touch sensor and an evaluation device.

From the DE 299 02 607 U1 a device arrangement for detecting traffic offenders is known, which documents damage caused by so-called parking lot bumps or damage caused by burglaries on the vehicle. A vibration sensor triggers a camera, which is arranged in the area of the rear window shelf of the vehicle and is intended to capture the person who caused the vibration.

From the EP 0 962 359 A2 there is known a recorder of a condition immediately after an accident and people breaking into the vehicle. After a vibration has been detected, this condition is documented with an optical recording and recording device. The same applies to the detection of people breaking into the vehicle.

In the publication "The paint is the solution" from the journal Electromechanics, April 2002, pages 72 to 75, a piezoelectric paint is described which is arranged in a switch under a keyboard to generate a voltage pulse. The piezoelectric paint is produced in such a way that piezoelectric crystals are introduced into the paint in order to obtain a printable material mixture. To manufacture the switches, traces for connecting the switches are printed on insulating foils and the piezoelectric lacquer is then selectively applied to the conductor positions. The piezoelectric material then has to be polarized by applying a voltage to the conductors after the switch has been assembled. Such switches are able to replace membrane-like, galvanically switching switching elements with a contact stroke and capacitively acting switching elements.

To avoid cable lines and associated coupling elements between a movable handle and the associated vehicle is in the DE 103 09 148 A1 proposed integrating at least one transmitter unit in the handle and the associated receiver unit in the vehicle, with the transmitter unit receiving the transmission energy from a piezoelectric element, for example a piezoelectric lacquer mounted in the handle.

A method for monitoring an object parked outdoors, such as an aircraft or motor vehicle, is the subject of DE 33 15 831 A1 . The method is based on a capacitive touch detection circuit for detecting a change in frequency when the object is touched. The assistance device in a vehicle for adjusting various vehicle components according to the user profile of the respective driver uses a camera and/or a speech processor to capture the specific characteristics of a person sitting in the associated driver's seat.

From the DE 102 57 125 A1 a safety device for protecting pedestrians and cyclists in the event of an impact on a front hood of a passenger car can be seen as known, in which the actuators for adjusting the front hood are controlled by a signal from a piezoelectric foil sensor.

DE 35 42 697 A1 describes a recording device for a rear-end collision with a camera, which is activated by an accelerometer when a predetermined acceleration value is exceeded. In the traffic accident documentation system according to the DE 299 18 812 U1 activation takes place via a shock sensor. The detection device according to the DE 102 23 123 A1 comprises at least one sensor for detecting a collision with a vehicle and a camera device for optically detecting the vehicle in question.

The DE 10 2006 012 336 A1 discloses a method for touch detection for a motor vehicle with a touch sensor and an on-board evaluation device. The touch sensor is designed, for example, as a piezoelectric paint applied to a motor vehicle part and electrically contacted with the evaluation device, the evaluation device generating at least one output signal when the piezoelectric paint comes into contact with an object.

The DE 600 27 416 T2 discloses a glass touch sensing circuit capable of acquiring a sensing signal resulting from a user's touch without being affected by temperature changes.

It is an object of the invention to provide an improved touch detection device.

The aforementioned object is achieved by a touch detection device, in particular for a motor vehicle, the touch detection device having an RC element, a capacitive touch sensor as part of the RC element, and an evaluation device for correcting an output signal of the capacitive touch sensor using a temperature correction value and for Generating an input signal for the RC element, wherein the temperature correction value can be determined as a function of an output signal of the RC element that is dependent on the input signal.

An evaluation device within the meaning of the invention can be a processor, for example. However, an evaluation device within the meaning of the invention can also be a distributed system with a number of spatially separate components.

A capacitive touch sensor within the meaning of the invention is in particular a piezo sensor or a piezoelectric sensor. A capacitive touch sensor within the meaning of the invention can be, for example, a piezo lacquer described at the outset or a piezo film described with reference to the figures. Piezo or piezoelectric sensors are also, for example, from DE 100 31 793 C1 known. The EP 0 310 490 B1 discloses a temperature compensated piezoelectric oscillator. Methods for temperature compensation are also from the DE 42 11 997 A1 , the DE 34 27 743 A1 , the EP 1 123 492 B1 and the German Offenlegungsschrift 1 773 187 known.

An RC element within the meaning of the invention includes, in particular, an ohmic resistor and a capacitor.

In an advantageous embodiment of the invention, it is provided that the output signal of the RC element, which is not caused by the input signal, but rather the output signal of the capacitive touch sensor, which is corrected by means of the temperature correction value, is monitored for exceeding a limit value. It can also be provided that the limit value is corrected by means of an inverse temperature correction value and the output signal of the capacitive touch sensor remains uncorrected. This correction of the limit value, which represents an indirect correction of the output signal of the capacitive touch sensor, is also intended to be a correction of the output signal of the capacitive touch sensor within the meaning of the invention. If the output signal of the capacitive touch sensor, corrected by means of the temperature correction value, exceeds the aforementioned limit value, a warning signal is generated or a corresponding warning flag is set. As a result, for example, an acoustic warning signal can be generated. Other measures when a corresponding warning signal is triggered or a corresponding warning flag is set are the DE 10 2006 012 336 A1 refer to.

In a further advantageous refinement of the invention, the capacitive touch sensor comprises a piezo sensor of planar design or is in the form of a planar piezo sensor. In a further advantageous embodiment of the invention, the capacitive touch sensor includes a piezo film or is designed as a piezo film. In a further advantageous embodiment of the invention, the capacitance of the capacitive touch sensor essentially forms the capacitance of the RC element. In a further advantageous embodiment of the invention, the input signal is a periodic signal. In a further advantageous embodiment of the invention, the input signal is essentially a periodic square-wave signal. In a further advantageous embodiment of the invention, the temperature correction value can be determined as a function of a rectified output signal of the RC element that is dependent on the input signal. In a further advantageous embodiment of the invention, the temperature correction value can be determined as a function of an, in particular arithmetic, mean value of a rectified output signal of the RC element that is dependent on the input signal.

The aforementioned object is also achieved - in particular in connection with the aforementioned features - by a method for operating a touch detection device, the touch detection device comprising an RC element and a capacitive touch sensor as part of the RC element, with an output signal of the capacitive touch sensor being corrected using a temperature correction value is generated, an input signal for the RC element being generated, and the temperature correction value being determined as a function of an output signal of the RC element which is dependent on the input signal.

In a further advantageous embodiment of the invention, the temperature correction value is determined as a function of a rectified output signal of the RC element that is dependent on the input signal. In a further advantageous embodiment of the invention, the temperature correction value is determined as a function of an, in particular arithmetic, mean value of a rectified output signal of the RC element which is dependent on the input signal.

In a further advantageous embodiment of the invention, the temperature range or the working range of the filter is selected in such a way that for a maximum of the sensitivity of the filter in a range between -40 °C and 150 °C customary for automotive use, corresponding to a working range of α = 0 .15 to 0.38, preferably the maximum sensitivity in the middle of the temperature range of 55 °C, corresponding to a filter factor of α = 0.24.

The aforementioned object is also achieved - in particular in connection with one or more of the aforementioned features - by a method for operating a touch detection device, the touch detection device comprising a piezo touch sensor, with an output signal of the piezo touch sensor being detected, with after detection of the output signal a , In particular a periodic test signal is applied to the piezo touch sensor, and the previously measured output signal of the piezo touch sensor is corrected as a function of a change, in particular the damping, of the test signal. In an advantageous embodiment of the invention, the test signal is essentially a periodic square-wave signal.

The aforementioned object is also achieved - in particular in connection with one or more of the aforementioned features - by a method for operating a touch detection device, the touch detection device comprising a piezo touch sensor, with an output signal of the piezo touch sensor being detected, with after detection of the output signal a , In particular periodic test signal is applied to a circuit comprising the piezo touch sensor for generating a reaction signal, and wherein the previously measured output signal of the piezo touch sensor is corrected depending on a change, in particular the damping, of the reaction signal compared to the test signal. In an advantageous embodiment of the invention, the test signal is essentially a periodic square-wave signal.

Motor vehicle within the meaning of the invention is in particular a land vehicle that can be used individually in road traffic. Motor vehicles within the meaning of the invention are in particular not limited to land vehicles with internal combustion engines.

• 1 ein Ausführungsbeispiel eines Kraftfahrzeuges in einer Draufsicht,
• 2 das Kraftfahrzeug gemäß 1 in einer Seitenansicht,
• 3 eine Sensorkapazität als Funktion der Temperatur,
• 4 ein Ausführungsbeispiel einer Berührungsdetektionseinrichtung,
• 5
  • (a) drei Pulse einer Pulsfolge und deren Verzerrung,
  • (b) die um die Symmetrieachse nach oben geklappten Pulse der unteren Halbwelle (durchgezogene Kurven) der Pulsfolge gemäß 5a,
• 6 ein Ersatzschaltbild ,
• 7
  • (a) Verlauf eines Spannungsmittelwerts,
  • (b) Empfindlichkeit als Funktion eines Filterfaktors,
• 8 ein weiteres Ausführungsbeispiel einer Berührungsdetektionseinrichtung,
• 9 ein Ausführungsbeispiel einer Auswerteeinrichtung und
• 10 ein weiteres Ausführungsbeispiel einer Auswerteeinrichtung.

Further advantages and details result from the following description of exemplary embodiments. show:

• 1 an embodiment of a motor vehicle in a plan view,
• 2 the motor vehicle according to 1 in a side view,
• 3 a sensor capacitance as a function of temperature,
• 4 an embodiment of a touch detection device,
• 5
  • (a) three pulses of a pulse sequence and their distortion,
  • (b) the pulses of the lower half-wave (continuous curves) flipped up around the axis of symmetry according to the pulse train 5a ,
• 6 an equivalent circuit diagram,
• 7
  • (a) course of a mean voltage value,
  • (b) sensitivity as a function of a filter factor,
• 8th another embodiment of a touch detection device,
• 9 an embodiment of an evaluation device and
• 10 another embodiment of an evaluation device.

1 shows a plan view of a motor vehicle with piezoelectric areas B, ie areas with flat piezoelectric touch sensors. These include portions of automotive exterior parts, namely portions of the front and rear bumpers, portions of the doors and fenders. When the piezoelectric areas are touched or force is exerted, at least one voltage pulse is generated, which 4 and 9 evaluation device shown in detail is supplied. In this case, contact outside of the piezoelectric lacquer areas can also be detected if this contact leads to a force being applied to the piezoelectric area.

An image recording device K1, e.g. a CCD camera, is arranged in the motor vehicle, which after contact detection—i.e. outputting a warning signal or setting a warning flag—records at least one image. An image, an image sequence with defined time intervals between the images or a video film can be created. In addition, an audio signal can be recorded via a sound recording device, for example a microphone M of a telephone hands-free device arranged in the vehicle. The sound recording device can also be arranged outside the vehicle cabin. The sound recording is used to determine the cause or who caused the contact more precisely by providing additional data that can be used for a plausibility check, for example. So that the recordings can be assigned exact times and locations, the location data from the navigation system (location of the vehicle), the date and the time, for example from the reception data from a radio-controlled clock inside the vehicle, are also recorded.

If there are other image recording devices on the vehicle, these also record images. For example, the data from a front view camera K4 or K2, the data from a rear view camera K3 and also side view cameras K5, K6 can also be used for recording. In the exemplary embodiment, the image recording device K1 is designed as a camera that can be rotated through 360° and records images during a horizontal rotation process.

2 shows a side view of a motor vehicle with piezoelectric areas B, which are shown in dashed lines. It can be seen in this exemplary embodiment that the piezoelectric lacquer areas B are partial areas of the doors, the fenders and the bumpers. It is not necessary for these areas to be arranged on the outside of the vehicle or on the outer skin of the vehicle. An arrangement on the side facing away from the outside of the vehicle for signal detection is also possible.

The piezoelectric areas B can, for example, by means in the DE 10 2006 012 336 A1 described piezoelectric paint areas or by means of a piezoelectric film described below (for example Dynasim film) are implemented. In the applications of piezo sensors for touch detection on large objects, such as the car body, elastic and flexible piezo variants should primarily be used according to the shape. Such piezo sensors are, for example, the Dynasim foils from the manufacturer ALGRA. They have a multi-layered technical structure surrounded by a polymer film, which gives them a certain degree of elasticity. The Dynasim foils are comparatively inexpensive, but show much higher temperature dependencies than the piezo ceramics mentioned above.

The temperature dependencies of the signal from Dynasim foils are not only due to the piezo effect alone, but also to the increase in leakage currents as a result of the crystal's deteriorated insulator properties. According to the manufacturer ALGRA, the temperature-dependent increase in capacitance is approximately 0.5% K ^-1 , while the temperature-dependent increase in leakage current is far higher, at 10% K ^-1 . 3 shows the calculated temperature dependence of the sensor capacitance as a function of temperature θ. Here, the temperature-dependent increase in capacity of 0.5% K ^-1 and a typical capacity of 5 nF at temperature θ = 25 °C were assumed for the Dynasim foil. The temperature dependencies lead to a significant weakening of the output signal of more than 1% K ^-1 when heated (M. König, diploma thesis, University of Applied Sciences Braunschweig/Wolfenbüttel, 2005)

4 FIG. 12 shows an embodiment of a touch detection device. The touch detection device has a piezoelectric touch sensor 12 and an evaluation device designed as a microprocessor 10 . A piezo electrode is connected to ground. The other piezo electrode sends the signal S after being touched or shocked (represented by arrow 15).

For applications in the field of touch detection, the frequency spectrum <100 Hz is relevant for Signal S. After the signal has been amplified by an amplifier 11, the signal S is input to the microprocessor 10 via the A/D input E1 for further processing. If the microprocessor 10 or the algorithm of its software recognizes that a piezo signal has been received, the signal intensity is assessed. If the signal intensity is above the threshold, i.e. higher than a certain, in this case very low, predefined limit, the microprocessor 10 will classify the signal as relevant to a warning and can use output A1 - by outputting a warning signal or setting a warning flag - to take planned actions, e.g. activation of an alarm system , trigger.

To determine the temperature-dependent signal corrections, the piezoelectric touch sensor 12, as in 4 shown, with an outgoing from the output A2 electrical pulse train P1 (here, for example, square-wave voltage) applied. A number of about 10 pulses is advantageous for the pulse train P1. It is advantageous to reduce the amplitude of the pulse train P1 to the magnitude of the amplitude of the signal S before further processing. Before the pulse train P1 reaches the input E1 of the microprocessor 10, its amplitude can be reduced by the voltage divider R1+R2 and the pulse train P2 can be generated so that the amplifier 11 does not overdrive the signal. The sensor capacitance C _P and the resistance R behave like an RC element with respect to the pulse train P2. The influence of this RC element leads to the damping and distortion of the pulse train P2.

The diode D in 4 serves to ensure that the already low-power signal S is not routed to ground via the resistors R and R2 and becomes weaker. The use of the diode D also means that the input impedance of the amplifier 11 is not disadvantageously reduced by the much lower resistance R+R2.

In 5a three pulses of the pulse train P2 (solid) are shown. Before the pulses P2 reach the microprocessor input E1, they are attenuated by the filter RC _P (cf 4 ). The damped signal P3 (dashed) then reaches input E1. In 5 is for the sake of simplicity Voltage drop across the diode D has not been taken into account.

6 shows an equivalent circuit diagram of the circuit in 4 (without diode D). The two voltage amplitudes Us (from the sensor signal S) and U _P3 (from the signal P3) are not present at the same time on the capacitor C _P . The pulses P3 are present at the amplifier input precisely when the change in Us over time is below a predefined threshold.

On the basis of the temperature dependencies of the sensor parameters already described, a procedure for circuit dimensioning and optimization is to be shown below, taking into account a specific numerical example.

wobei der Filterfaktor $\mathrm{\alpha }=\frac{2\mathrm{\tau }}{\text{T}}=2\mathrm{\tau }ƒ,$

α die Zeitkonstante τ = RC_P und f die Pulsfrequenz sind. Der Filterfaktor α nimmt mit der Frequenz f und Kapazität C_P zu. Infolge der Abhängigkeit des Filterfaktors α von der Kapazität C_P steigt α mit der Temperatur an. 7a zeigt den Verlauf von U_m als Funktion von Filterfaktor α, wobei U_P2 gleich 1 angenommen wurde. Aus 7a ist ersichtlich, dass U_m zuerst mit der zunehmenden Variable α (bis α ~ 0,5) stark abnimmt, um dann langsamer gegen die Null zu gehen. Hierdurch wurde also auch die mathematische Abhängigkeit des Mittelwerts U_m von der Temperatur ermittelt.The mean value U _m of the signal P3 within a half period T/2 is: $${\text{u}}_{\text{m}}={\text{u}}_{\text{P}2}\left(1-\mathrm{a}+\mathrm{a}{\text{e}}^{\frac{-1}{\mathrm{a}}}\right)$$

where is the filter factor $\mathrm{a}=\frac{2\mathrm{\tau }}{\text{T}}=2\mathrm{\tau }ƒ,$

α is the time constant τ = RC _P and f is the pulse frequency. The filter factor α increases with frequency f and capacitance C _P . As a result of the dependence of the filter factor α on the capacitance C _{P ,} α increases with temperature. 7a shows the course of U _m as a function of the filter factor α, where U _P2 was assumed to be 1. Out of 7a it can be seen that U _m first decreases sharply with the increasing variable α (up to α ~ 0.5) and then approaches zero more slowly. In this way, the mathematical dependency of the mean value U _m on the temperature was also determined.

To determine an operating point with maximum sensitivity for the sensor system, the absolute value of the normalized derivation from the mean value according to the variable α, ie |(1/U _m )(dU _m /dα)| to calculate. This normalized derivation is a measure of the sensitivity η of the sensor system: $$\mathrm{n}=\left|\frac{1}{{\text{u}}_{\text{m}}}\cdot \frac{{\text{you}}_{\text{m}}}{\text{i.e}\mathrm{a}}\right|=\left|\frac{\left(1+\mathrm{a}\right){\text{e}}^{\frac{-1}{\mathrm{a}}}-\mathrm{a}}{\mathrm{a}\left(1-\mathrm{\alpha +\alpha }{\text{e}}^{\frac{-1}{\mathrm{a}}}\right)}\right|$$

7b shows the course of |(1/U _m )(dU _m /dα)|, ie the sensitivity η of the sensor, as a function of α. The working point should be where the sensitivity η is highest. The maximum sensitivity η is reached at the filter factor α _m =0.24.

The relevant temperature range in the automotive sector is between -40 °C and 150 °C. If the filter factor α _m is to lie exactly in the middle of the temperature range, ie at the temperature θ = 55 °C, the C _p value is according to 3 equal to 5.8nF.

A frequency f of 1 kHz is advantageous for the pulse train P1 or P2, so that any mixing of the pulse train P2 and the signal S (<100 Hz) is prevented. The value of the filter resistance R = 20.6 kΩ can be obtained from the equation α = 2RC _P ƒ by using the already known values of α _m = 0.24, C _P at temperature θ = 55 °C and frequency f = 1 kHz result. Consequently, the values of filter factor α at θ = -40 °C and 150 °C are equal to 0.15 and 0.38, respectively.

In 7a and 7b the already determined working range (α = 0.15 ... 0.38) is marked with hatching. How out 7a As can be seen, the mean value U _m varies between 0.85 and 0.64, assuming U _P2 =1. This makes, assuming a linear temperature dependence for _Um between -40 °C and 150 °C (s. 7a ), a negative slope of about 0.1% K ^-1 .

The signal P3 is read several times by the acquisition unit (in 4 realized by the A/D converter of the microprocessor 10). The mean values U _m of the sampled voltage values of each half-wave are then calculated. The greater the signal damping or the longer the time constant, the smaller the mean values U _m . Since the time constant τ is proportional to the temperature-dependent capacitance C _P , the mean value U _m of each half-cycle will also be temperature-dependent. The mean values U _m of each half-wave can be viewed as a measure of the temperature-dependent distortion of the pulse sequence P2.

A characteristic curve or a standardization table for the temperature dependence of _Um can be set up experimentally. The sensor temperature determined using the characteristic curve can enable a temperature-dependent amplitude correction for the piezo signal S. A value of the inverse of this characteristic curve is an exemplary embodiment of a temperature correction value within the meaning of the invention.

To calculate the mean values U _m , the lower half-waves of the damped pulse train, the discharge curve, so to speak, are used either by software or hardware as in 5b shown (solid curves), rectified. With software rectification, each sampled voltage value of the lower half-waves, e.g. u _i in 5a , is subtracted from the relative signal amplitude U _P2 . A hardware rectification of the pulse sequence P3 before it reaches input E1 be solved by means of a conventional rectifier.

It is advantageous to calculate the mean value U _M of all mean values U _m . The distribution of the mean values U _m around the value of U _M must then not exceed a predefined empirical value. If the variance of the U _m values is too high, a new pulse sequence P1 should be generated. Other usual active and passive filtering of undesired signals of the pulse sequence P3 can also be provided.

It is also possible to acquire the signal P3 through an input other than E1, which is completely (galvanically) isolated from input E1. For this purpose, as in 8th shown, the electronic switch 23 controlled by the output A0 of a microprocessor 20 (evaluation device) timely separates the connection between the piezoelectric touch sensor 12 and the amplifier 11, in order then to contact the piezoelectric touch sensor 12 with resistor R and microprocessor input E2. This solution is more complex than that of 4 and requires an electronic switch and an additional microprocessor pin. In this case, the voltage divider R1 + R2 and the diode D can be dispensed with. Since there is no voltage divider, however, the reduced signal P2 is omitted.

9 shows the operation of the microprocessor 10 using a block diagram. Here, reference numeral 31 designates a rectifier. This does not apply if a corresponding hardware rectifier is provided in front of the input signal E1. Numeral 32 denotes an averaging device, and numeral 33 denotes a characteristic map for generating the temperature correction value δT. Reference number 34 designates a correction block for correcting the rectified signal present at input E1 by means of temperature correction value δT. The correction block 34 can be configured as a multiplier, for example. Numeral 35 designates limit value monitoring. If the output signal from the correction block 34 exceeds a specific limit value, the limit value monitor 35 generates a warning signal or sets a warning flag. Numeral 36 designates a signal generator for generating the signal P1.

10 shows the mode of operation of the microprocessor 20. The same reference symbols as in FIG 9 , identical or similar elements or functions. Reference number 37 is in 10 denotes a control function for controlling the switch 23.

Reference List

10, 20

Microprocessor = evaluation device

11

amplifier

12

(piezoelectric/capacitive) touch sensor

15

Arrow

23

Switch

31

rectifier

32

averaging

33

map

34

correction block

35

limit monitoring

36

signal generator

37

control function

A0, A1, A2

Exit

B

Area

CP

capacity

D

diode

E1, E2

Entry

K1, K2, K3, K4, K5, K6

camera

M

microphone

P1

Pulse train = test signal = input signal

p2

Pulse train = signal

P3

Pulse sequence = reaction signal = output signal of a capacitive touch sensor or an RC element due to an input signal

R, R1, R2

ohmic resistance

S

Output signal of a capacitive touch sensor due to mechanical impact

UP1

Voltage of signal P1

UP2

Voltage across the ohmic resistor R ₂ , voltage of the signal P2

UP3

Voltage of signal P3

Around

Mean value of the rectified voltage of signal P3

us

Voltage of signal S

δT

temperature correction value

Claims (16)

Touch detection device, wherein the touch detection device has an RC element, a capacitive touch sensor (12) as part of the RC element, and an evaluation device (10, 20) for correcting an output signal (S) of the capacitive touch sensor (12) by means of a temperature correction value (δT) and for generating an input signal (P1) for the RC element, characterized in that the temperature correction value (δT) can be determined as a function of an output signal (P3) of the RC element which is dependent on the input signal (P1). touch detection device claim 1 , characterized in that the capacitive touch sensor (12) comprises a flat piezoelectric sensor. touch detection device claim 1 , characterized in that the capacitive touch sensor (12) is designed as a flat piezoelectric sensor. touch detection device claim 1 , 2 or 3 , characterized in that the capacitive touch sensor (12) comprises a piezoelectric film. touch detection device claim 1 , 2 or 3 , characterized in that the capacitive touch sensor (12) is designed as a piezoelectric film. Touch detection device according to one of the preceding claims, characterized in that the capacitance (C _P ) of the capacitive touch sensor (12) essentially forms the capacitance of the RC element. Touch detection device according to one of the preceding claims, characterized in that the input signal (P1) is a periodic signal. Touch detection device according to one of the preceding claims, characterized in that the input signal (P1) is essentially a periodic square-wave signal. Touch detection device according to one of the preceding claims, characterized in that the temperature correction value (δT) can be determined as a function of a rectified output signal (P3) of the RC element which is dependent on the input signal (P1). Touch detection device according to one of the preceding claims, characterized in that the temperature correction value (δT) can be determined as a function of a mean value of a rectified output signal (P3) of the RC element which is dependent on the input signal (P1). Touch detection device according to one of the preceding claims, characterized in that the maximum sensitivity of the filter is set in a range between α = 0.15 to 0.38, preferably with the filter factor of α = 0.24. Method for operating a touch detection device, wherein the touch detection device comprises an RC element and a capacitive touch sensor (12) as part of the RC element, wherein an output signal (S) of the capacitive touch sensor (12) is corrected by means of a temperature correction value (δT), and wherein an input signal for the RC element is generated, characterized in that the temperature correction value (δT) is determined as a function of an output signal (P3) of the RC element which is dependent on the input signal (P1). procedure after claim 12 , characterized in that the temperature correction value (δT) is determined as a function of a rectified output signal (P3) of the RC element which is dependent on the input signal (P1). procedure after claim 12 or 13 , characterized in that the temperature correction value (δT) is determined as a function of a mean value of a rectified output signal (P3) of the RC element which is dependent on the input signal (P1). Method for operating a touch detection device, wherein the touch detection device comprises a piezo touch sensor (12), wherein an output signal (S) of the Piezo touch sensor (12) is detected, and wherein after detection of the output signal a test signal (P1) is applied to a circuit comprising the piezo touch sensor (12) for generating a reaction signal (P3), characterized in that the previously measured output signal ( S) the piezo touch sensor (12) is corrected as a function of a change in the reaction signal (P3) compared to the test signal (P1). procedure after claim 15 , characterized in that the test signal (P1) is essentially a periodic square-wave signal.

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