DE102023120008A1 - Operating an input device of a motor vehicle - Google Patents

Abstract

To operate an input device (1), a first operating mode is activated by forming an overall sensor electrode (2a, 2b) by electrically connecting sensor electrodes (2a, 2b), and at a first measuring time a first measured value (14) is determined which depends on a total capacitance of the overall sensor electrode (2a, 2b). Depending on a difference between the first measured value (14) and a first reference value, it is determined whether there is contact with the overall sensor electrode (2a, 2b). If there is contact, a second operating mode is activated by removing the connection, and at a second measuring time a second measured value (16) is determined which depends on a capacitance of an individual sensor electrode (2a). Depending on a difference between the second measured value (16) and a second reference value (17), it is determined whether there is contact with the sensor electrode (2a). The first reference value (15) is cyclically updated according to a first cycle duration (t) and the second reference value (17) according to a larger second cycle duration (T).

Description

The present invention relates to a method for operating an input device of a motor vehicle, which has a touch-sensitive sensor electrode and at least one further touch-sensitive sensor electrode. The invention further relates to a corresponding method for detecting a user input in a motor vehicle. The invention also relates to an input device for a motor vehicle, having a touch-sensitive sensor electrode and at least one further touch-sensitive sensor electrode, and to a motor vehicle with such an input device. The invention also relates to corresponding computer program products.

Since the capacitance of a sensor electrode changes with respect to a reference potential, in particular ground potential, depending on whether a user touches the sensor electrode or not, the charge stored on a corresponding effective capacitor, which is given by the respective sensor electrode and the reference potential, changes during a charging process with a predetermined voltage. The charge can be read directly or indirectly using voltage measurements, so that touching the sensor electrode can be detected. Similarly, an approach to the sensor electrode, which also influences the capacitance, can also be detected. Such systems can be used, for example, for the capacitive detection of user inputs, in particular for applications in the interior of motor vehicles, for example when detecting the operation of touch-sensitive control panels or controls.

There are various concepts for the concrete implementation of the measurement. In the document US 6,466,036 B1 For example, a pulse circuit for measuring the capacitance of a sensor plate is specified, which is able to repeatedly transfer charge accumulated on the sensor plate to a capacitor and, after a large number of repetitions, read out the amount of charge transferred or read out a corresponding voltage in order to determine the capacitance of the sensor plate. Such a method is also known as the Q-charge method.

document DE 10 2019 129 802 A1 describes a capacitive sensor device which has a sensor electrode, a control and evaluation device with a first connection contact and a second connection contact, a first connection line, and a second connection line. The sensor electrode has a first electrode connection and a second electrode connection, and the first electrode connection of the sensor electrode is connected to the first connection contact via the first connection line and the second electrode connection is connected to the second connection contact via the second connection line. The sensor device has a reference capacitance which is electrically connected to the first connection line, wherein the sensor electrode is or can be electrically connected to the first connection contact via the electrical resistance, and wherein the reference capacitance is electrically connected to the first connection line between the first connection contact and the electrical resistance, and to a reference potential.

The measured values for such capacitive input devices can depend on the ambient temperature and the aging state of the input device. To ensure that a corresponding drift in the measured values does not lead to a false triggering or a faulty non-triggering of certain functions linked to the corresponding sensor electrode, a zero line, also known as a baseline, can be provided. The touch is then detected depending on the so-called touch delta, i.e. the difference between the measured value and a reference value given by the zero line.

In order to deal with particularly critical situations, such as very high rates of temperature change, the zero line can be tracked cyclically with a cycle time of less than one second. However, this requires permanent or cyclical activation of the corresponding control electronics, in particular a corresponding microcontroller. This leads to increased energy consumption, which can be particularly disadvantageous when the input device or the motor vehicle is in idle mode, for example when the ignition of the motor vehicle is deactivated. In other words, the required idle current is increased.

However, it may be desirable or necessary for various functions triggered or controlled by touching the sensor electrode to be available even in idle mode, so that complete deactivation of the function is not an option.

It is an object of the present invention to reduce the required quiescent current in a capacitive input device for a motor vehicle as explained above and, in particular, to maintain a high level of availability.

In the present case, this object is achieved by the respective subject matter of the independent claims. Advantageous further developments and preferred embodiments are the subject matter of the dependent claims.

The invention is based on the idea of connecting several sensor electrodes to form an overall sensor electrode in a first operating mode and, when contact with the overall sensor electrode is detected, removing the connection in a second operating mode and detecting whether one of the individual sensor electrodes is touched. For both operating modes, the zero line is updated cyclically, with the overall sensor electrode being updated more frequently than the individual sensor electrode.

According to one aspect of the invention, a method for operating an input device, in particular a capacitive input device, of a motor vehicle is specified. The input device has a touch-sensitive sensor electrode, in particular a capacitive sensor electrode, and at least one further touch-sensitive sensor electrode, in particular a capacitive sensor electrode. A first operating mode is activated, in particular by means of at least one control unit of the input device. In the first operating mode, an overall sensor electrode is formed by electrically connecting the sensor electrode and the at least one further sensor electrode, in particular the sensor electrode and all further sensor electrodes, to one another. At a first measurement time during the first operating mode, a first measured value is determined which depends on a total capacitance of the overall sensor electrode with respect to a predetermined reference potential, in particular a ground potential. It is determined, in particular in the first operating mode, in particular by means of the at least one control unit, whether there is contact with the overall sensor electrode at the first measurement time by comparing a difference between the first measured value and a first reference value with a predetermined first limit value.

If the contact is present at the first measurement time, i.e. if it is determined that the contact of the entire sensor electrode is present at the first measurement time, a second operating mode of the input device is activated, in particular by means of the at least one control unit. In the second operating mode, the electrical connection of the sensor electrode to the at least one further sensor electrode is removed, in particular by means of the at least one control unit. At a second measurement time during the second operating mode, a second measured value is determined, in particular by means of the at least one control unit, which depends on a capacitance of the sensor electrode with respect to the reference potential. It is determined, in particular in the second operating mode, whether there is contact with the sensor electrode at the second measurement time by comparing a difference between the second measured value and a second reference value with a predetermined second limit value, in particular by means of the at least one control unit. The first reference value is cyclically updated according to a first cycle duration, in particular by means of the at least one control unit, and the second reference value is cyclically updated according to a second cycle duration, in particular by means of the at least one control unit. The second cycle duration is greater than the first cycle duration.

The sensor electrode and the at least one further sensor electrode in particular represent respective input areas and can be arranged at different positions of the motor vehicle, in particular in the interior or the driver's cab of the motor vehicle.

The relationship between the total capacitance of the entire sensor electrode with respect to the reference potential and the first measured value is known in particular and can depend on the specific design of the input device and the specific measuring method used. The relationship between the capacitance of the sensor electrode with respect to the reference potential and the second measured value is also known and can depend on the specific design of the input device and the specific measuring method used. The first measured value can, for example, be a first voltage that depends on the total capacitance of the entire sensor electrode with respect to the reference potential. The second measured value can, for example, be a second voltage that depends on the capacitance of the sensor electrode with respect to the reference potential.

Various methods, in particular known per se, can be used to determine the first measured value and the second measured value. For example, an effective total capacitor formed by the total sensor electrode and the reference potential can be charged and an amount of charge can be transferred from the total capacitor to a measuring capacitor. The transferred charge or, in some embodiments, the total charge transferred in several consecutive measuring cycles, can be determined by measuring the voltage drop across the measuring capacitor. The first measured value can be this measured voltage. This depends on the known capacitance of the measuring capacitor, as well as on the capacitance of the total capacitor, which in turn differs depending on whether there is contact or not. The capacitance of the effective total capacitor can be understood as the inherent capacitance of the total sensor electrode compared to the reference potential. The second measured value can be determined analogously, whereby the capacitance of an effective capacitor, which is formed by the sensor electrode and the reference potential, takes the place of the capacitance of the effective total capacitor. The capacitance of the effective capacitor can be understood as the inherent capacitance of the sensor electrode compared to the reference potential.

The first measured value or the second measured value corresponds, for example, to the value of a first measuring signal or a second measuring signal, for example the voltage across the respective measuring capacitor, at the first measuring time or at the second measuring time.

The approach of a user's finger, for example, can also influence the capacitance of the effective capacitor or the capacitance of the effective total capacitor. Here and in the following, the focus is generally on the presence of a touch of the total sensor electrode or the sensor electrode, whereby the touch can also be an approach that is viewed as an operating action.

The comparison of the difference between the first measured value and the first reference value with the first limit value or the comparison of the difference between the second measured value and the second reference value with the second limit value can be done directly or indirectly. The comparison therefore includes in particular determining whether the respective difference is greater than the respective limit value. For example, it can be determined that contact occurred at the first measurement time if the difference between the first measured value and the first reference value is greater than or equal to the first limit value. Accordingly, it can be determined, for example, that contact with the sensor electrode occurred at the second measurement time if the difference between the second measured value and the second reference value is greater than or equal to the second limit value.

If, for example, it is determined that there is no contact with the sensor electrode at the second measurement time and, for example, in a similar manner that there is no contact with any of the other sensor electrodes, the first operating mode can be activated again. If it is determined that there is contact with the sensor electrode at the second measurement time, a function assigned to the sensor electrode can be carried out. For example, the first operating mode can also be activated again after the function has been initiated.

Here and in the following, the second operating mode only refers to checking for contact with the sensor electrode. In an analogous manner, however, the second operating mode can also be used to check whether one of the other sensor electrodes is being touched. In particular, the sensor electrode and the other sensor electrodes can be checked one after the other or in parallel, if necessary until contact is detected.

In the first operating mode, the sensor electrode and all other sensor electrodes of the at least one further sensor electrode are electrically connected to one another. The sensor electrode and all other sensor electrodes are therefore electrically short-circuited. In the second operating mode, the electrical connection between the sensor electrode and the at least one further sensor electrode is removed. In particular, the sensor electrode is not short-circuited to any of the further sensor electrodes and none of the further sensor electrodes is short-circuited to any other of the further sensor electrodes.

During the first operating mode, the input device, in particular the at least one control unit, can only determine whether the overall sensor electrode is touched, but not which of the sensor electrodes or the other sensor electrodes has been touched. To determine this, the second operating mode is activated when a contact with the overall sensor electrode is detected. This allows the idle current to be reduced, since normally, i.e. when there is no contact with the overall sensor electrode, only the overall sensor electrode needs to be checked accordingly, not the individual sensor electrodes and other sensor electrodes. The actual measurement is only carried out if it has been positively confirmed that there has been contact with any of the sensor electrodes and the other sensor electrodes.

Accordingly, in order to track the second reference value, i.e. the zero line for the sensor electrode, it is acceptable to do this according to a longer cycle time, which also leads to a reduced quiescent current consumption.

According to at least one embodiment, for updating the first reference value the first reference value is increased by a specified increment.

For this purpose, for example, the first operating mode is activated cyclically according to the first cycle duration, if the first operating mode is not already active at the corresponding time. The increase in the first reference value by the increment can depend on further conditions, in particular plausibility conditions. In particular, the conditions when updating the first reference value can ensure that a possible increase in the first reference value by the increment means that the first measurement signal is still greater than the first reference value. In particular, it can be checked whether an increase in the first measurement signal, for example an average increase in the first measurement signal, has occurred since the last increase in the first reference value by the increment, and the first reference value can only be increased by the increment if this is the case. In an analogous manner, in various embodiments it can also be ensured that the first reference value always has a minimum distance from the first measurement signal.

This ensures that the first reference value is adjusted in the sense of a zero line for the entire sensor electrode and thus, for example, temperature fluctuations or changes due to the aging of the input device are at least partially compensated. For example, the first reference value can be reset to an initial reference value when the input device or the motor vehicle is restarted.

According to at least one embodiment, the first operating mode is activated to update the first reference value and at a third measuring time during the first operating mode a third measured value is determined which depends on the capacitance of the total sensor electrode with respect to the reference potential. The increase of the first reference value by the increment takes place depending on the third measured value.

The third measured value therefore corresponds in particular to the first measurement signal at the third measurement time. For example, the first reference value can only be increased by the increment if the third measured value is at least a predetermined minimum value above a historical or average value of the first measurement signal.

According to at least one embodiment, the second operating mode is activated to update the second reference value and a fourth measured value is determined at a fourth measuring time during the second operating mode, which depends on the capacitance of the sensor electrode with respect to the reference potential. The second reference value is set to the fourth measured value for updating. In other words, after the update, the second reference value is equal to the fourth measured value.

The fourth measured value corresponds in particular to the value of the second measurement signal at the fourth measurement time. By equating the second reference value with the fourth measured value, a recalibration or new calibration of the sensor electrode is achieved.

In particular, it is assumed that there is no contact with the sensor electrode at the fourth measurement time. This assumption is particularly plausible because the second cycle duration is longer than the first cycle duration, so that the probability that there is contact at the fourth measurement time is comparatively low. However, if there were to be contact with the sensor electrode by chance at the fourth measurement time, equating the second reference value with the fourth measured value would correspond to an incorrect calibration. However, this would not be a problem because a resulting reversal of the sign of the difference between the second measurement signal and the second reference value when there is no longer contact can be detected immediately by at least the control unit and corrected by recalibrating again.

According to at least one embodiment, the first cycle duration is in the range [1 ms, 1 s], in particular in the range [5 ms, 500 ms].

In this way, it is possible to detect contact with the entire sensor electrode with a corresponding degree of reliability.

For example, the second cycle duration is in the range [10 s, 1000 s], in particular in the range [100 s, 500 s].

By selecting the second cycle duration in the appropriate ranges, a significant reduction in the quiescent current can be achieved.

For example, the second cycle duration is at least 100 times the first cycle duration, for example at least 1000 times the first cycle duration. In particular, the second cycle duration is equal to the first cycle duration multiplied by a factor that is in the range [100, 5000], for example in the range [200, 2000].

According to at least one embodiment, to determine the first measured value, the effective total capacitor formed by the total sensor electrode and the reference potential is charged with a charge quantity and at least part of the charge quantity is transferred to a measuring capacitor of the input device. The first measured value is determined depending on a voltage dropping after the transfer across the measuring capacitor.

For example, the first measurement signal is equal to this voltage. As already mentioned above, the voltage can occur after the corresponding amount of charge has been transferred once or after a large number of corresponding measurement cycles or charge transfer cycles and so on.

According to at least one embodiment, to determine the second measured value, the effective capacitor formed by the sensor electrode and the reference potential is charged with a further amount of charge and at least part of the further amount of charge is transferred to the measuring capacitor or a further measuring capacitor of the input device. The second measured value is determined as a function of a voltage dropping after the transfer via the measuring capacitor or further measuring capacitor or as this voltage. The second measurement signal therefore corresponds, for example, to this voltage.

According to at least one embodiment, a rest mode of the input device, in particular of the motor vehicle, is detected, for example by means of the at least one control unit. The steps of activating the first operating mode, determining whether the overall sensor electrode is being touched at the first measurement time, activating the second operating mode, determining whether the sensor electrode is being touched at the second measurement time, cyclically updating the first reference value and cyclically updating the second reference value are carried out during the rest mode. A normal operation of the input device, in particular of the motor vehicle, which is different from the rest mode is detected, for example by means of the at least one control unit. In normal operation, the second operating mode is activated, i.e. the electrical connection between the sensor electrode and the at least one further sensor electrode is removed, and the second reference value is cyclically updated according to a further second cycle duration that is shorter than the second cycle duration. The further second cycle duration can in particular be equal to the first cycle duration.

As a result, the quiescent current can be significantly reduced in idle mode, as explained above, whereas in normal mode, increased reliability of detection can be achieved by updating the second reference value more frequently. In normal mode, the reduction in current consumption is not as important as the reduction in the quiescent current in idle mode. During normal operation, an energy source of the motor vehicle is activated and can be used to supply energy to the input device, in particular the at least one control unit, which is not activated in idle mode. This energy source can, for example, correspond to a drive motor of the motor vehicle. During idle mode, however, the input device can, for example, be supplied with electrical energy from a motor vehicle battery of the motor vehicle or the like.

According to a further aspect of the invention, a method for detecting a user input in a motor vehicle is specified. In this case, a method according to the invention for operating an input device is carried out. If the contact is present at the second measurement time, a function assigned to the sensor electrode is initiated, in particular by means of the at least one control unit, and is carried out, for example.

To initiate the function, the at least one control unit can generate at least one control signal, in particular depending on the determination that the contact is present at the second measurement time. The function can then be carried out in particular by components of the motor vehicle which are different from the input device.

For example, the execution of the function may include activating a hazard warning system of the motor vehicle or locking a door or hatch of the motor vehicle or unlocking a door or hatch of the motor vehicle or opening or closing a window of the motor vehicle and so on.

The invention is particularly advantageous for such functions, since the functions mentioned are typically intended to be available to a user regardless of whether the motor vehicle or the input device is in idle mode or in normal operation.

For applications or application situations that may arise in a method according to the invention and which are not explicitly described herein, it may be provided that, according to the method, an error message and/or a request for user feedback is issued and/or a default setting and/or a predetermined initial state is set.

According to a further aspect of the invention, an input device for a motor vehicle is specified. The input device has a touch-sensitive sensor electrode and at least one further touch-sensitive sensor electrode. The input device has a switching device and at least one control unit.

The at least one control unit is designed to activate a first operating mode and to control the switching device to electrically connect the sensor electrode and the at least one further sensor electrode to one another in order to form an overall sensor electrode. The at least one control unit is designed to determine a first measured value at a first measurement time, wherein the first measured value depends on a total capacitance of the overall sensor electrode with respect to a predetermined reference potential. The at least one control unit is designed to determine whether there is contact with the overall sensor electrode at the first measurement time and to compare a difference between the first measured value and a first reference value with a predetermined first limit value.

The at least one control unit is designed to activate a second operating mode if contact occurs at the first measurement time, and to control the switching device to remove the electrical connection between the sensor electrode and the at least one further sensor electrode, and to determine a second measured value at a second measurement time that depends on the capacitance of the sensor electrode with respect to the reference potential. The at least one control unit is designed to determine whether contact with the sensor electrode occurs at the second measurement time, and to compare a difference between the second measured value and a second reference value with a predetermined second limit value. The at least one control unit is designed to cyclically update the first reference value according to a first cycle duration and to cyclically update the second reference value according to a second cycle duration that is greater than the first cycle duration.

The switching device includes one or more switching elements, for example transistors, which can be controlled by the at least one control unit.

A computing unit can be understood in particular as a data processing device that contains a processing circuit. The computing unit can therefore in particular process data to carry out computing operations. This may also include operations to carry out indexed access to a data structure, for example a conversion table, LUT (English: "look-up table").

The computing unit can in particular contain one or more computers, one or more microcontrollers and/or one or more integrated circuits, for example one or more application-specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs), and/or one or more single-chip systems (SoCs). The computing unit can also contain one or more processors, for example one or more microprocessors, one or more central processing units (CPUs), one or more graphics processing units (GPUs) and/or one or more signal processors, in particular one or more digital signal processors (DSPs). The computing unit can also contain a physical or virtual network of computers or other of the aforementioned units.

In various embodiments, the computing unit includes one or more hardware and/or software interfaces and/or one or more memory units.

A memory unit can be a volatile data storage device, such as a dynamic random access memory (DRAM) or a static random access memory (SRAM), or a non-volatile data storage device, such as a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory or flash EEPROM, a ferroelectric random access memory (FRAM), a magnetoresistive random access memory (MRAM) or a Phase change random access memory, PCRAM (English: “phase-change random access memory”).

A control unit can also be or contain a computing unit.

According to at least one embodiment, the sensor electrode and/or the at least one further sensor electrode are designed for attachment to a steering wheel of the motor vehicle. In some embodiments, the input device has the steering wheel and the sensor electrode and/or the at least one further sensor electrode is attached to the steering wheel.

According to at least one embodiment, the sensor electrode and/or the at least one further sensor electrode is designed for attachment to an interior trim component of the motor vehicle. For example, the input device can have the interior trim component and the sensor electrode and/or the at least one further sensor electrode is attached to the interior trim component.

According to at least one embodiment, the at least one control unit has a microcontroller unit. The microcontroller unit is configured to compare the difference between the first measured value and the first reference value with the first limit value and/or to compare the difference between the second measured value and the second reference value with the second limit value.

According to at least one embodiment, the at least one control unit, in particular the microcontroller unit, includes an analog-to-digital converter for determining the first measured value and/or the second measured value.

Further embodiments of the input device according to the invention follow directly from the various embodiments of the method according to the invention and vice versa. In particular, individual features and corresponding explanations as well as advantages relating to the various embodiments of the method according to the invention can be transferred analogously to corresponding embodiments of the input device according to the invention. In particular, the input device according to the invention is designed or programmed to carry out a method according to the invention. In particular, the input device according to the invention carries out the method according to the invention.

According to a further aspect of the invention, a motor vehicle with an input device according to the invention is provided.

According to a further aspect of the invention, a computer program with commands is specified. When the commands are executed by an input device according to the invention, in particular the at least one control unit of the input device, the commands cause the input device to carry out a method according to the invention for operating an input device and/or a method according to the invention for detecting a user input.

The instructions can be in the form of program code, for example. The program code can be provided, for example, as binary code or assembler and/or as source code of a programming language, for example C, and/or as a program script, for example Python.

According to a further aspect of the invention, a computer-readable storage medium is provided which stores a computer program according to the invention.

The computer program according to the invention and the computer-readable storage medium according to the invention each represent computer program products with the instructions.

Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and/or shown in the figures can be included in the invention not only in the combination specified in each case, but also in other combinations. In particular, the invention can also include embodiments and combinations of features that do not have all the features of an originally formulated claim. In addition, the invention can include embodiments and combinations of features that go beyond or deviate from the combinations of features set out in the references to the claims.

The invention is explained in more detail below using specific embodiments and associated schematic drawings. In the figures, identical or functionally equivalent elements may be provided with the same reference numerals. The description of identical or functionally equivalent elements is not necessarily repeated with respect to different figures.

• 1 eine schematische Blockdarstellung einer beispielhaften Ausführungsform einer erfindungsgemäßen Eingabevorrichtung;
• 2 ein schematisches Ablaufdiagramm einer beispielhaften Ausführungsform eines erfindungsgemäßen Verfahrens zum Betreiben einer Eingabevorrichtung;
• 3a eine schematische Darstellung einer beispielhaften Ausführungsform einer erfindungsgemäßen Eingabevorrichtung in einem Initialisierungszustand;
• 3b eine schematische Darstellung der Eingabevorrichtung aus 3a in einem Zwischenzustand;
• 3c eine schematische Darstellung der Eingabevorrichtung aus 3a und 3b in einem Ladezustand;
• 3d eine schematische Darstellung der Eingabevorrichtung aus 3a bis 3c in einem Übertragungszustand;
• 3e eine schematische Darstellung der Vorrichtung aus 3a bis 3d in einem Auslesezustand;
• 4 ein Ablaufdiagramm eines Teils einer weiteren beispielhaften Ausführungsform eines erfindungsgemäßen Verfahrens zum Betreiben einer Eingabevorrichtung;
• 5 eine schematische Darstellung eines ersten Messsignals und einer zugehörigen ersten Nulllinie gemäß einer weiteren beispielhaften Ausführungsform eines erfindungsgemäßen Verfahrens zum Betreiben einer Eingabevorrichtung; und
• 6 eine schematische Darstellung eines zweiten Messsignals und einer zugehörigen zweiten Nulllinie gemäß einer weiteren beispielhaften Ausführungsform eines erfindungsgemäßen Verfahrens zum Betreiben einer Eingabevorrichtung.

In the figures show:

• 1 a schematic block diagram of an exemplary embodiment of an input device according to the invention;
• 2 a schematic flow diagram of an exemplary embodiment of a method according to the invention for operating an input device;
• 3a a schematic representation of an exemplary embodiment of an input device according to the invention in an initialization state;
• 3b a schematic representation of the input device from 3a in an intermediate state;
• 3c a schematic representation of the input device from 3a and 3b in a charging state;
• 3D a schematic representation of the input device from 3a to 3c in a transfer state;
• 3e a schematic representation of the device from 3a until 3D in a readout state;
• 4 a flowchart of a part of another exemplary embodiment of a method according to the invention for operating an input device;
• 5 a schematic representation of a first measurement signal and an associated first zero line according to a further exemplary embodiment of a method according to the invention for operating an input device; and
• 6 a schematic representation of a second measurement signal and an associated second zero line according to a further exemplary embodiment of a method according to the invention for operating an input device.

In 1 an exemplary embodiment of an input device 1 according to the invention for a motor vehicle is shown schematically. The input device 1 can be used, for example, in the interior of the motor vehicle to record a user input from a user of the motor vehicle.

The input device 1 has a touch-sensitive sensor electrode 2a and at least one further touch-sensitive sensor electrode, in the illustrated, non-limiting example two further sensor electrodes 2b, 2c, as well as at least one control unit 5.

The sensor electrode 2a and the further sensor electrodes 2b, 2c each represent effective capacitors or capacitive elements that can serve as input areas and are arranged and set up for touching by a user. The sensor electrode 2a and the further sensor electrodes 2b, 2c can be designed, for example, as touch-sensitive films or touch-sensitive sensor plates. The user can, for example, touch a surface of the sensor electrode 2a or the further sensor electrodes 2b, 2c or approach them with a finger in order to make a user input. By approaching or touching the sensor electrode 2a or the further sensor electrodes 2b, 2c, the capacitance of the respective effective capacitor changes. The at least one control unit 5 is able to determine the capacitance or a change in the capacitance and, based on this, to conclude that the user input is present in the corresponding input area.

The input device 1 has a switching device 4a, 4b with corresponding switching elements 4a, 4b in order to optionally electrically connect the sensor electrode 2a and the further sensor electrodes 2b, 2c to one another or to cancel the connection. In particular, the sensor electrode 2a and the further sensor electrodes 2b, 2c each have a readout connection 3a, 3b, 3c. A switching element 4a, 4b is arranged between respective pairs of the readout connections 3a, 3b, 3c. In the example shown of the sensor electrode 2a and the two further sensor electrodes 2b, 2c, for example, a switching element 4a is arranged between the readout connection 3a of the sensor electrode 2a and the readout connection 3b of the further sensor electrode 2b, and a switching element 4b is arranged between the readout connection 3b of the further sensor electrode 2b and the readout connection 3c of the further sensor electrode 2c. This can be extended analogously to more than two additional sensor electrodes 2b, 2c.

By means of the input device 1 according to the invention, a method according to the invention for operating the input device 1 can be carried out. A schematic flow diagram of an exemplary embodiment of such a method is shown schematically in 2 shown.

The at least one control unit 5 is designed to activate a first operating mode in step 200 and to control the switching device 4a, 4b to electrically connect the sensor electrode 2a and the at least one further sensor electrode 2b, 2c to one another in order to form an overall sensor electrode. For this purpose, in particular all switching elements 4a, 4b are closed, so that the readout terminals 3a, 3b, 3c are short-circuited.

The at least one control unit 5 is configured to determine a first measured value in step 220 during the first operating mode at a first measuring time, which depends on the total capacitance of the total sensor electrode with respect to a predetermined reference potential 9. The first measured value is in particular a value of a corresponding first measuring signal 14 at the first measuring time, as in 5 shown schematically. In step 240, the at least one control unit 5 determines whether there was contact with the entire sensor electrode at the first measurement time. To do this, the at least one control unit 5 compares a difference between the first measured value and a first reference value with a predetermined first limit value. The first reference value is in particular a value of a corresponding first zero line 15 at the first measurement time. If the difference is smaller than the first limit value, it is determined that there was no contact at the first measurement time and the process continues with step 220. If the difference is greater than or equal to the first limit value, it is determined that there was contact at the first measurement time.

In the latter case, the at least one control unit 5 activates a second operating mode and, for this purpose, controls the switching device 4a, 4b to remove the electrical connection of the sensor electrode 2a and the further sensor electrodes 2b, 2c. For this purpose, in particular all switching elements 4a, 4b are opened. In step 260, the at least one control unit 5 determines a second measured value at a second measuring time during the second operating mode, which depends on a capacitance of the sensor electrode 2a with respect to the reference potential 9. The second measured value is in particular a value of a corresponding second measuring signal 16 at the second measuring time, as in 6 shown schematically. In step 280, the at least one control unit 5 determines whether there is contact with the sensor electrode 2a at the second measurement time. To do this, the at least one control unit 5 compares a difference between the second measured value and a second reference value with a predetermined second limit value. The second reference value is in particular a value of a corresponding second zero line 17 at the second measurement time. If the difference is smaller than the second limit value, it is determined that there is no contact with the sensor electrode 2a at the second measurement time. If the difference is greater than or equal to the second limit value, it is determined that there is contact with the sensor electrode 2a at the second measurement time. In the latter case, for example, a predetermined function of the motor vehicle assigned to the sensor electrode 2a can be initiated.

In the second operating mode, the at least one control unit 5 can also determine corresponding measured values for the further sensor electrodes 2b, 2c and determine in a similar manner as for the sensor electrode 2a whether there is contact with one of the further sensor electrodes 2b, 2c. For example, it can be determined in this way which of the sensor electrode 2a or the further sensor electrodes 2b, 2c is touched, which was detected in the first operating mode as contact with the entire sensor electrode.

As in 5 and 6 As shown schematically, the first reference value is updated cyclically according to a first cycle duration t, i.e. the first zero line 15 is adjusted cyclically accordingly. The second reference value is updated cyclically according to a second cycle duration T, which is greater than the first cycle duration t, i.e. the second zero line 17 is adjusted cyclically accordingly. The first cycle duration t can be, for example, on the order of a few 10 ms or 100 ms, the second cycle duration T can be, for example, on the order of a few minutes.

As in 5 As shown, in order to track the first zero line 15, the value of the first zero line 15 can be increased cyclically by a predetermined increment s according to t, in particular if the first zero line 15 is still below the first measurement signal 14. Otherwise, the tracking of the first zero line 15 can be suspended, for example, in the corresponding cycle.

As in 6 As shown, in order to track the second zero line 17, for example, the value of the second zero line 17 can be cyclically set to the current value of the second measuring signal 16 in accordance with T.

The at least one control unit 5 can be designed according to various methods for touch detection. Purely by way of example, the figures 3a until 3e An embodiment is shown that can operate according to a Q-Charge method. The 3a until 3e represent different states S0 to S4 of the input device 1 corresponding to different sections of measuring cycles. In 4 an associated flow chart is shown. The second operating mode is discussed as an example and a determination of the second measured value is explained. Consequently, the other sensor electrodes 2b, 2c and the switching elements 4a, 4b are not shown. The determination of corresponding measured values for the other sensor electrodes 2b, 2c in the second operating mode and the first measured value for the total sensor electrode in the first operating mode can be carried out analogously.

The inherent capacitance of the sensor electrode 2a with respect to the reference potential 9 can be understood as the capacitance of an effective capacitor 6, which is connected on the one hand to the reference potential 9 and on the other hand to the readout connection 3a. In this example, the input device 1, in particular the at least one control unit 5, has a microcontroller 10 and a measuring capacitor 11. One connection of the measuring capacitor 11 is connected to the readout connection 3a, the other connection of the measuring capacitor 11 is connected to a first connection 7 of the microcontroller 10. A second connection 8 of the microcontroller 10 is connected to the readout connection 3a.

Input device 1, in particular the at least one control unit 5, also has a circuit which is shown in the figures 3a until 3e is not shown separately. The circuit includes a controller and several switching elements that can be controlled by the controller. The controller can also be part of the microcontroller 10. The switching elements are arranged and set up to connect the terminals 7 and 8 of the microcontroller 10 to the reference potential 9 or to disconnect them from it, depending on the current state of the input device 1, when controlled by the controller. Using the switching elements, the controller can also connect a voltage source 12, which can be part of the input device 1 or can be provided separately, to the second terminal 8 of the microcontroller 10 or to disconnect the connection, depending on the state of the input device 1.

The microcontroller 10 also has an analog-to-digital converter, ADC, 13, which is connectable to the second terminal 8. In particular, the circuit can connect or disconnect the ADC 13 to the second terminal 8 depending on the state of the input device 1.

To determine the second measured value, the different states S0, S1, S2, S3, S4 are partly run through cyclically or repeatedly, as shown in the example in 4 is shown. S0 denotes an initialization state of the input device 1 during an initialization section and S4 denotes a readout state of the input device 1 during a readout section.

The states S1 to S3 form a measuring cycle, whereby in particular a large number of consecutive measuring cycles are carried out. 4 can be seen, to determine the second measured value, the input device 1 is first brought into the initialization state S0, then the plurality of measuring cycles are carried out and then again the input device 1 is brought into the readout state S4.

For example, each measuring cycle includes an intermediate section, a subsequent charging section, a subsequent further intermediate section and a subsequent transfer section. Accordingly, during a measuring cycle, the input device 1 is transferred from an intermediate state designated S1 to a charging state designated S2, which is followed by the intermediate state S1 again, followed by a transfer state designated S3. After the measuring cycle has ended, the microcontroller 10 checks whether a predetermined number of measuring cycles has been reached. If this is the case, the input device 1 is brought into the readout state S4, otherwise the next measuring cycle follows.

In state S0, the controller uses the circuit to connect the first connection 7 and the second connection 8 to the reference potential 9. Both connections of the effective capacitor 6 and both connections of the measuring capacitor 11 are therefore connected to the reference potential 9. Accordingly, during the initialization state S0, both the effective capacitor 6 and the measuring capacitor 11 are discharged. In the subsequent first intermediate section, the input device 1 is brought into the intermediate state S1, which can also be referred to as the switching state or changeover state. Here, the connections 7 and 8 are separated from the reference potential 9. During the intermediate section, the input device 1 remains in the intermediate state S1 for an intermediate period that is, for example, less than 1 µs, for example between 0.1 µs and 1 µs.

The control then uses the circuit to transfer the input device 1 to the charge state S2. In comparison to the intermediate state S1, the second connection 8 is connected to the voltage source 12 in order to charge the effective capacitor 6. By setting the first connection 7 internally to a high impedance, for example, the amount of charge on the measuring capacitor 11 does not change. The charge state S2 is maintained for a predetermined charging time, which can be in the range of 1 µs to 10 µs, for example. The input device 1 is then brought back to the intermediate state S1 during a further intermediate section. A further intermediate period of the further intermediate section can, for example, be equal to the duration of the intermediate section.

During a subsequent transmission section, the input device 1 is brought into the transmission state S3, which can also be referred to as the transfer state, by the control of the circuit. Here, the second connection 8 is now set to a high impedance and the first connection 7 is connected to the reference potential 9. This allows a charge balance to take place between the effective capacitor 6 and the measuring capacitor 11. The capacitance of the measuring capacitor 11 is in particular selected to be several times higher than the maximum capacitance of the effective capacitor 6, so that a charge quantity determined by the two capacitances is effectively transferred from the effective capacitor 6 to the measuring capacitor 11.

A transmission duration of the transmission section can, for example, be in a range from 0.5 µs to 5 µs or in a range from 0.5 µs to 2 µs or the like. A readout duration of the readout period can, for example, be in a range from 0.5 to 5 µs or a range from 0.5 µs to 2 µs.

The states S1, S2, S1, S3 are in this order, as in 4 indicated, cyclically repeated until a predetermined total number of measuring cycles have been completed, for example 300 to 500 measuring cycles. After the total number of measuring cycles, a total amount of charge has been transferred from the effective capacitor 6 to the measuring capacitor 11 in the respective transfer sections. This total amount of charge is now read out in the following readout section by means of the microcontroller 10. For this purpose, the input device is brought into the readout state S4 by means of the control and the circuit. For this purpose, the first connection 7 of the microcontroller 10 remains connected to the reference potential 9 and the second connection 8 of the microcontroller 10 is connected to the ADC 13 in order to measure the voltage between the readout connection 3a and the reference potential 9 and thus the second measured value, which represents the total amount of charge.

As described, in particular with reference to the figures, the invention makes it possible to reduce the required quiescent current in a capacitive input device for a motor vehicle and, in particular, to maintain a high level of availability.

The capacitive sensors for switching functions in motor vehicles, for example, are dependent on temperature and aging. To ensure that a drift in the sensor signal does not lead to a certain switching function being triggered incorrectly or not being triggered at all, the corresponding zero line can be tracked. The tracking can be done in stages, for example. An increment, for example a digital value of the ADC, can be tracked cyclically with an adjustable cycle time, for example 10 ms. Temperature chamber tests can be carried out to determine the cycle time and the increment in order to be able to cover worst-case scenarios.

In normal operation of the motor vehicle and the input device, all sensor electrodes can be individually cyclically tracked in this way. In idle mode, however, for example when the ignition of the motor vehicle is deactivated, all sensor electrodes, which are also known as touch antennas, can be connected together to form a large overall sensor electrode. If the overall sensor electrode is touched, the individual sensor electrodes can be queried to determine which of them was touched. This saves idle current in the motor vehicle. Accordingly, however, the zero line of the individual sensor electrodes cannot be cyclically tracked as described.

In order to ensure the functionality of the individual input areas and still keep the quiescent current low, the touch function of the entire sensor electrode can be called up regularly, for example every 100 ms or 200 ms. With this cyclical call, the zero line for the entire sensor electrode can be adjusted. In order to adjust the zero line for the individual sensor electrodes, the individual sensor electrodes can be recalibrated at longer time intervals, for example every 5 minutes. During recalibration, the zero line is suddenly set to the current value of the measurement signal, for example. This means that step-by-step adjustment in a fixed, small time interval is not necessary, which would lead to a higher quiescent current consumption.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• US 6,466,036 B1 [0003]
• DE 10 2019 129 802 A1 [0004]

Claims (17)

Method for operating an input device (1) of a motor vehicle, which has a touch-sensitive sensor electrode (2a) and at least one further touch-sensitive sensor electrode (2b, 2c), wherein - a first operating mode is activated by forming an overall sensor electrode (2a, 2b) by electrically connecting the sensor electrode (2a) and the at least one further sensor electrode (2b, 2c) to one another, and at a first measuring time a first measured value (14) is determined, which depends on a total capacitance of the overall sensor electrode (2a, 2b) with respect to a predetermined reference potential (9); - it is determined whether there is contact with the overall sensor electrode (2a, 2b) at the first measuring time by comparing a difference between the first measured value (14) and a first reference value (15) with a predetermined first limit value; - if contact occurs at the first measurement time, a second operating mode is activated by removing the electrical connection between the sensor electrode (2a) and the at least one further sensor electrode (2b, 2c), and at a second measurement time a second measured value (16) is determined which depends on a capacitance of the sensor electrode (2a) with respect to the reference potential (9); - it is determined whether contact with the sensor electrode (2a) occurs at the second measurement time by comparing a difference between the second measured value (16) and a second reference value (17) with a predetermined second limit value; - the first reference value (15) is cyclically updated according to a first cycle duration (t) and the second reference value (17) is cyclically updated according to a second cycle duration (T) which is greater than the first cycle duration (t). procedure according to claim 1 , wherein to update the first reference value (15) the first reference value (15) is increased by a predetermined increment (s). procedure according to claim 2 , wherein the first operating mode is activated to update the first reference value (15) and a third measured value is determined at a third measuring time, which depends on the capacitance of the total sensor electrode (2a, 2b) with respect to the reference potential (9), and the increase of the first reference value (15) by the increment (s) takes place depending on the third measured value. Method according to one of the preceding claims, wherein the second operating mode is activated to update the second reference value (17) and at a fourth measuring time a fourth measured value is determined which depends on the capacitance of the sensor electrode (2a) with respect to the reference potential (9), and the second reference value (17) is set to the fourth measured value. Method according to one of the preceding claims, wherein the first cycle duration is in the range [1 ms, 1 s] or in the range [5 ms, 500 ms]. Method according to one of the preceding claims, wherein the second cycle duration is in the range [10 s, 1000 s] or in the range [100 s, 500 s]. Method according to one of the preceding claims, wherein for determining the first measured value (14) - an effective total capacitor, which is formed by the total sensor electrode (2a, 2b) and the reference potential (9), is charged with a quantity of charge and at least a part of the quantity of charge is transferred to a measuring capacitor of the input device (1); - the first measured value (14) is determined as a function of a voltage drop across the measuring capacitor after the transfer. Method according to one of the Claims 1 until 6 , wherein for determining the second measured value (14) - an effective capacitor (6), which is formed by the sensor electrode (2a) and the reference potential (9), is charged with a quantity of charge and at least a part of the quantity of charge is transferred to a measuring capacitor of the input device (1); - the second measured value (16) is determined as a function of a voltage dropping across the measuring capacitor after the transfer. Method according to one of the preceding claims, wherein - a rest mode of the input device (1) is detected and the steps of activating the first operating mode, determining whether the contact of the total sensor electrode (2a, 2b) is present at the first measurement time, activating the second operating mode, determining whether the contact of the sensor electrode (2a) is present at the second measurement time, cyclically updating the first reference value (15) and cyclically updating the second reference value (17) are carried out during the rest mode; - a normal mode of the input device (1) different from the rest mode is detected and in normal mode the second operating mode is activated and the second reference value (17) is adjusted according to a further second cycle duration which is smaller than the second cycle duration, is updated cyclically. Method for detecting a user input in a motor vehicle, wherein a method according to one of the preceding claims is carried out and, if the contact is present at the second measuring time, a function assigned to the sensor electrode (2a) is initiated. procedure according to claim 10 , wherein an execution of the function includes an activation of a hazard warning system of the motor vehicle or a locking of a door or a hatch of the motor vehicle or an unlocking of the door or the hatch of the motor vehicle or an opening or closing of a window of the motor vehicle. Input device (1) for a motor vehicle, comprising a touch-sensitive sensor electrode (2a) and at least one further touch-sensitive sensor electrode (2b, 2c), a switching device (4a, 4b) and at least one control unit (5, 10) which is designed to - activate a first operating mode and to control the switching device (4a, 4b) to electrically connect the sensor electrode (2a) and the at least one further sensor electrode (2b, 2c) to one another in order to form an overall sensor electrode (2a, 2b), and to determine a first measured value (14) at a first measuring time, which depends on a total capacitance of the overall sensor electrode (2a, 2b) with respect to a predetermined reference potential (9); - determine whether there is contact with the overall sensor electrode (2a, 2b) at the first measuring time, and to compare a difference between the first measured value (14) and a first reference value (15) with a predetermined first limit value; - if contact occurs at the first measurement time, to activate a second operating mode and to do so, to control the switching device (4a, 4b), to remove the electrical connection between the sensor electrode (2a) and the at least one further sensor electrode (2b, 2c), and to determine a second measured value (16) at a second measurement time, which depends on a capacitance of the sensor electrode (2a) with respect to the reference potential (9); - to determine whether contact with the sensor electrode (2a) occurs at the second measurement time, and to do so, to compare a difference between the second measured value (16) and a second reference value (17) with a predetermined second limit value; - to cyclically update the first reference value (15) according to a first cycle duration (t) and to cyclically update the second reference value (17) according to a second cycle duration (T) which is greater than the first cycle duration (t). Input device (1) according to claim 12 , comprising - a steering wheel for the motor vehicle, wherein the sensor electrode (2a) and/or the at least one further sensor electrode (2b, 2c) is attached to the steering wheel; or - an interior trim component for the motor vehicle, wherein the sensor electrode (2a) and/or the at least one further sensor electrode (2b, 2c) is attached to the interior trim component. Input device (1) according to one of the Claims 11 until 13 , wherein the at least one control unit (5, 10) has an analog-to-digital converter (13) for determining the first measured value (14) and/or the second measured value (16). Input device (1) according to one of the Claims 12 or 13 , wherein the at least one control unit (5, 10) has a microcontroller unit (10) which is designed to - compare the difference between the first measured value (14) and the first reference value (15) with the first limit value; and/or - compare the difference between the second measured value (16) and the second reference value (17) with the second limit value. Motor vehicle with an input device (1) according to one of the Claims 12 until 15 . Computer program product with instructions which, when executed by an input device (1), are executed according to one of the Claims 12 until 15 cause the input device (1) to carry out a method according to one of the Claims 1 until 11 to carry out.

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