Method for determining a manual actuation of a capacitive sensor element, evaluation unit therefor, and sensor device and motor vehicle

Abstract

The invention relates to a method for determining manual actuation of a capacitive sensor element (1), wherein, in a first step (20), the sensor element and an electrical reference capacitor (2) are electrically connected in parallel and set to a first electrical voltage, in a second step (21), the parallel connection is interrupted and the sensor element is set to a second electrical voltage which is different from the first electrical voltage, and, in a third step (22), the sensor element and the reference capacitor are again electrically connected in parallel in order to provide an electrical coupling voltage (16) for detection by an evaluation unit. The first step (20) is repeated and, in a fourth step (23), the sensor element and the reference capacitor are electrically connected to one another in series and the series connection is set to a third electrical voltage. In a fifth step (24), an electrical partial voltage (17) of the series connection is detected by means of the evaluation unit, wherein manual actuation is determined as a function of the partial voltage and the coupling voltage.

Description

[0001] Method for determining manual actuation of a capacitive sensor element, evaluation unit therefor, sensor device and motor vehicle

[0002] The invention relates to a method for determining the manual actuation of a capacitive sensor element, wherein in a first step the sensor element and an electrical reference capacitor are electrically connected in parallel and set to a first electrical voltage, in a second step the parallel connection is interrupted and the sensor element is set to a second electrical voltage which differs from the first electrical voltage, and in a third step the sensor element and the reference capacitor are again electrically connected in parallel to provide an electrical coupling voltage for detection by an evaluation unit. The invention further relates to a computer program product and a computer-readable data carrier.The invention further relates to an evaluation unit for determining manual actuation of a capacitive sensor element, wherein the evaluation unit is configured to, in a first step, electrically connect the sensor element and an electrical reference capacitor in parallel and adjust it to a first electrical voltage, in a second step to interrupt the parallel connection and adjust the sensor element to a second electrical voltage which is different from the first electrical voltage, and in a third step to electrically connect the sensor element and the reference capacitor in parallel again in order to provide an electrical coupling voltage and to detect the coupling voltage provided by the sensor element electrically connected in parallel with the reference capacitor.Furthermore, the invention also relates to a sensor device for detecting manual actuation, comprising a capacitive sensor element, an electrical reference capacitance, an evaluation unit, and a coupling unit, at least for the controllable electrical coupling of the capacitive sensor element, the reference capacitance, and the evaluation unit. Finally, the invention also relates to a motor vehicle with a sensor device for detecting manual actuation by a vehicle occupant.

[0003] Generic methods, computer program products, computer-readable data carriers, evaluation units, sensor devices, and motor vehicles are extensively known in the prior art, so that, in principle, no written proof is required in this respect. Sensor devices of this type, also referred to as capacitive touch sensors, are devices that allow manual actuation to be determined on a capacitive basis. This is achieved, among other things, by exploiting the fact that a capacitive sensor element changes the value of its electrical capacitance depending on its proximity to a human body part, in particular a finger.To determine this manual actuation, the sensor element is at least temporarily, or at least partially, electrically coupled to the evaluation unit, so that, through suitable evaluation, it can be determined whether manual actuation of the sensor device or the capacitive sensor element has occurred. Within the scope of the disclosure, "determining manual actuation" is understood to mean not only actual contact of the capacitive sensor element or the sensor device by the body part, but also the approach of the body part to it. Therefore, actual contact is not strictly necessary. However, due to the proximity between the body part and the sensor element or the sensor device, the evaluation unit can determine or ascertain such actuation.Such an approach of a human body part can be defined as manual actuation according to a specification or configuration of the sensor device or evaluation unit. For example, actuation can be detected at a distance of one or a few millimeters from the capacitive sensor element, for example, less than 5 mm, preferably less than 1 mm. However, it can also be stipulated that only direct contact with the capacitive sensor element is defined as manual actuation.

[0004] In this context, WO 2009 / 151 904 A2, for example, discloses a touch sensor based on a capacitive voltage divider. However, this technology has proven inaccurate and prone to interference in practical applications, particularly in motor vehicles, for example, in the area of ​​a hands-on device (HoD), such as in the steering wheel. Effects resulting from long-term influences, atmospheric conditions, temperature fluctuations, and / or similar factors that can affect the function of the capacitive sensor element have proven especially problematic.

[0005] Furthermore, DE 10 2022 104 117 A1 discloses a method for determining manual actuation of a capacitive sensor element, an evaluation unit for this purpose, and a sensor device. While this teaching improves upon the disadvantages of WO 2009 / 151 904 A2, it proves disadvantageous that, particularly at high detection speeds, switching elements of a coupling unit must be switched with high precision to avoid disruptive influences on the evaluation due to switching operations. This can only be implemented with sufficient reliability with considerable hardware effort. In this context, it should be considered that a detection process in the prior art requires approximately 2 ms to 3 ms. For a number of processes, this timeframe proves to be extremely short, which is why an improvement, especially with regard to detection speed, is desirable.

[0006] The invention is therefore based on the objective of improving the state of the art, at least with regard to accuracy or detection speed.

[0007] The invention proposes a method, a computer program product, a computer-readable data carrier, an evaluation unit, a sensor device and a motor vehicle as a solution according to the independent claims.

[0008] Advantageous further training opportunities arise from the characteristics of the dependent requirements.

[0009] With regard to a generic method, the invention particularly proposes that the first step is repeated, in a fourth step the sensor element and the reference capacitor are electrically connected in series, the series connection is set to a third electrical voltage, and an electrical partial voltage of the series connection, namely at least the electrical voltage of the sensor element or the reference capacitor, is detected by means of the evaluation unit, wherein the manual actuation is determined depending on the partial voltage and the coupling voltage.

[0010] With regard to a generic computer program product, the invention particularly proposes that the computer program product comprises program code means, which are stored in a computer-readable medium, in order to effect, in a first step (20), an electrical parallel connection of the sensor element (1) and an electrical reference capacitance (2) and an adjustment to a first electrical voltage, in a second step (21), an interruption of the parallel connection and an adjustment of the sensor element (1) to a second electrical voltage which is different from the first electrical voltage, and in a third step (22), an electrical parallel connection of the sensor element (1) and the reference capacitance (2) again.to provide an electrical coupling voltage (16) for detection by an evaluation unit (3), to repeat the first step (20), in a fourth step to effect an electrical series connection (23) of the sensor element (1) and the reference capacitance (2) and to adjust the series connection to a third electrical voltage, and in a fifth step (24) to cause the evaluation unit (3) to detect a partial electrical voltage (17) of the series connection, namely at least the electrical voltage of the sensor element (1) or the reference capacitance (2), and / or to control the evaluation unit (3) such that, depending on the partial voltage (17) and the coupling voltage (16), it determines the manual actuation when the computer program product is executed on a computer unit of an evaluation unit,

[0011] With regard to a computer-readable data carrier, the invention specifically proposes that a computer program product according to the invention is stored on it.

[0012] With regard to a generic evaluation unit, the invention particularly proposes that the evaluation unit is further configured to repeat the first step, in a fourth step to electrically connect the sensor element and the reference capacitance in series, to adjust the series connection to a third electrical voltage, and to detect a partial electrical voltage of the series connection, namely at least the electrical voltage of the sensor element or the reference capacitance, and to determine the manual actuation depending on the partial voltage and the coupling voltage.

[0013] With regard to a generic sensor device, the invention specifically proposes that the evaluation unit be designed according to the invention.

[0014] With regard to a motor vehicle of the type described, the invention specifically proposes that the sensor device be designed according to the invention.

[0015] The invention is based, among other things, on the idea that accuracy and / or detection speed can be improved if, in a process cycle, the reference capacitance and the sensor element are used for evaluation in both parallel and series circuits. The resulting voltages, namely the coupling voltage and the partial voltage of the series circuit, allow for highly reliable determination of the activation of the sensor element or sensor device through suitable evaluation. The disadvantages of prior art can be reduced. At the same time, it is possible to use a particularly simple coupling unit, thus avoiding the precise switching operations of switching elements required in the prior art to implement the respective process steps.The invention allows for a particularly simple process control, so that a switching operation or switching action for producing a respective process step can be implemented with, for example, only a single switching element. This largely eliminates the need for the precise switching operations required in the prior art, thereby reducing hardware requirements. At the same time, the process control according to the invention allows for improved accuracy in determining the detection, so that the detection speed can be significantly reduced compared to the prior art.

[0016] The evaluation unit can be designed to detect the respective electrical voltages. It is particularly advantageous if the evaluation unit includes an analog-to-digital converter, which digitizes the detected electrical voltage and allows it to be processed by the evaluation unit's digital signal processing to determine manual operation. However, it is also possible for the evaluation unit to be implemented, at least partially or entirely, as an analog hardware circuit. For this purpose, the evaluation unit can include a program-controlled computer unit, which can be combined with a corresponding hardware circuit if required.

[0017] The evaluation unit can also include a coupling unit by means of which the respective coupling states of the sensor element and the reference capacitance can be realized. For this purpose, the coupling unit can have corresponding switching elements, which are preferably electronic switching elements, for example, transistors or the like. It can be provided that the evaluation unit is only electrically coupled to the sensor element, which is connected in parallel with the reference capacitance, in the third step for detecting the coupling voltage. As soon as the coupling voltage is detected, the electrical coupling with the evaluation unit can be removed again. Furthermore, it is of course possible that the parallel connection also includes the evaluation unit in the first step. This can be advantageous, for example, if the evaluation unit itself has a certain parasitic capacitance.This electrical coupling can be released at the end of the first step. The first step essentially enables a kind of initialization, in which preferably the reference capacitance and the sensor element, and optionally also an input or detection port of the analog-to-digital converter, can be brought to a predetermined initial state with respect to an electrical charge. The predetermined charge state is determined, for example, by the initial electrical voltage. The use of the coupling voltage can, among other things, make it possible to determine data with respect to a value of the capacitance of the sensor element.

[0018] By additionally including steps four and five, in which the sensor element is connected in series with the reference capacitor, additional data can be obtained, for example, by evaluating the partial voltage. This allows for further improvement in determining manual actuation. In particular, interference can be further reduced. For this purpose, it is provided that step one is repeated before steps four and five are performed. This preferably brings the reference capacitor and the sensor element, as well as the input connection of the analog-to-digital converter, to the same initial state as before steps two and three. However, if necessary, a different initial state could also be used, for example, by changing the initial electrical voltage before steps four and five are performed.Further deviations are conceivable in principle, provided they do not disrupt the process according to the invention.

[0019] The coupling voltage and the partial voltage are preferably detected when transient processes have largely subsided. For this purpose, it is possible to detect the respective electrical voltage over a predefined period and only initiate detection by the evaluation unit when the voltage change over time is less than a predefined reference value. A separate change detection unit can be provided for this purpose, which can send a detection signal to the analog-to-digital converter. Upon receiving the detection signal, the analog-to-digital converter can activate the detection of the respective electrical voltage. The subsequent process involves detecting the partial voltage. This occurs in the fifth step. According to one option, the electrical voltage at the sensor element can be detected for this purpose.Based on this, the manual actuation of the sensor element can be determined by suitable evaluation using the evaluation unit. Alternatively, according to a second option, it is also possible to measure the electrical voltage across the reference capacitance. The manual actuation of the sensor element can also be determined based on this measurement by suitable evaluation using the evaluation unit. Furthermore, both possible partial voltages can be measured and considered in the subsequent evaluation. Based on the coupling voltage and at least one of the possible partial voltages, further evaluation can be performed to determine the manual actuation.

[0020] According to an advantageous embodiment, it is proposed that an electrical differential voltage be determined depending on the partial voltage and the coupling voltage. Determining the differential voltage can preferably be done using the evaluation unit. However, in principle, determining the differential voltage can also be achieved by a separate differential unit that communicates with the evaluation unit. The differential voltage can be easily processed further to determine the manual actuation of the sensor element. During the evaluation, the partial voltage or the coupling voltage can also be taken into account, at least partially.

[0021] It is particularly advantageous if the initial electrical voltage is zero, i.e., 0 V. This ensures that both the reference capacitance and the sensor element are in a discharged state with respect to their electrical capacitances. It is especially beneficial if, in the first step, the evaluation unit, or at least one input of the evaluation unit used to detect the respective voltage, can also be discharged with this initial zero voltage. This is advantageous, for example, if this input of the evaluation unit includes the analog-to-digital converter, which typically exhibits capacitive properties. This further improves accuracy.

[0022] It is further proposed that the second and third electrical voltages be the same. This also simplifies further evaluation and allows for a cost-effective and rapid process without the additional, separate effort of providing different electrical voltages. The second and / or third electrical voltage could, for example, be a supply voltage for the evaluation unit. However, a separate voltage source could also be used.

[0023] Preferably, the electrical voltages detected by the evaluation unit are digitized, and the determination of manual actuation is implemented at least partially by means of digital signal processing. These functions are preferably implemented at least partially by the evaluation unit. The use of digital signal processing makes it possible to achieve high reliability, particularly with regard to interference or similar issues. At the same time, it allows for the implementation of complex functionalities in the evaluation unit without requiring a particularly large amount of hardware circuitry. In this respect, the evaluation unit preferably includes at least one program-controlled computer unit.

[0024] In the present disclosure, a computing unit can be understood, for example, as a data processing device with processing circuits. A computing unit can therefore perform arithmetic operations to process data. These arithmetic operations can also include indexed access to a data structure, such as a lookup table (LUT).

[0025] The computing unit may, in particular, comprise 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 systems on a chip (SoCs). The computing unit may also include 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.DSP. The computing unit can also comprise a physical or virtual cluster of computers or other units mentioned above. The computing unit can also include one or more hardware and / or software interfaces and / or one or more memory units. A memory unit can be implemented as volatile data storage, for example as dynamic random access memory (DRAM) or static random access memory (SRAM), or as non-volatile data storage, for example as read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), or electrically erasable programmable read-only memory (EEPROM).a flash memory or flash EEPROM, a ferroelectric random access memory, FRAM (ferromagnetic random access memory), a magnetoresistive random access memory, MRAM (magnetoresistive random access memory), or a phase-change random access memory, PCRAM (phase-change random access memory).

[0026] It is further proposed that the manual actuation be determined, at least partially, based on the differential voltage. This allows for a simple evaluation. Using the differential voltage is one way to significantly improve the accuracy of determining the manual actuation. Furthermore, it is possible to consider other parameters or recorded values ​​for determining the manual actuation, such as ambient temperature, humidity, air pressure, and / or the like. This allows for further improvements in the reliability of determining the manual actuation.

[0027] Preferably, it is proposed that the differential voltage be compared with at least one first reference value to determine manual actuation. The invention utilizes, among other things, the concept that the differential voltage can be greater when actuation is occurring than when it is not. Thus, manual actuation can be easily determined. The first reference value can be a fixed, predetermined value. However, it can also be a value that can be changed depending on environmental parameters such as temperature, humidity, air pressure, and / or the like. Furthermore, the reference value can also be adjusted as needed, taking into account a detection profile over a predetermined period, to further improve the functionality of detecting manual actuation. Preferably, manual actuation can be detected when the differential voltage is greater than the first reference value.

[0028] It is further proposed that the differential voltage be compared with at least one second reference value to determine manual actuation, wherein the second reference value differs from the first. Preferably, the second reference value is greater than the first. This refinement has the advantage that a range can be determined from the first and second reference values, indicating that actuation has occurred when the differential voltage is between the first and second reference values. This further improves reliability. In particular, disturbances that lead to differential voltages which should not normally be reached by manual actuation can be detected. This further improves reliability.

[0029] Furthermore, it is proposed that at least the coupling voltage or the partial voltage be compared with at least one third reference value to determine manual activation. This allows the functionality of the sensor device itself to be monitored. A coupling voltage or a partial voltage that is lower than the third reference value can be identified as faulty. A fault message can then be issued, for example, to a higher-level vehicle control system, if applicable. For instance, a value of zero for the coupling voltage or the partial voltage could trigger a fault message. This fault message could also be issued to a driver of the vehicle or a user of the sensor device. It could also be stipulated that a minimum value for the coupling voltage or the partial voltage is defined by the third reference value.In principle, it is also possible to use the third reference value to check, for example, that the coupling voltage or the partial voltage is higher than the third reference value. In this case, too, a fault message would be conceivable, indicating that the coupling voltage or the partial voltage is too high.

[0030] It is particularly advantageous to repeat a sequence of the preceding process steps in at least one subsequent cycle. Of course, multiple cycles can be advantageously provided, allowing, for example, a type of oversampling. This makes it possible to further improve the reliability and accuracy of the process control. For instance, 4, 8, 16, 32, or 64 cycles can be provided for determining the manual actuation. If digital signal processing is used, the values ​​determined with these cycles, such as the differential voltage, can be easily summed, with the summed value then being used for further signal processing by the evaluation unit.

[0031] The advantages and effects described for the method of the invention also apply equally to the computer program product, the computer-readable data carrier, the evaluation unit, the sensor device, and the motor vehicle according to the invention, and vice versa. Method features can therefore also be formulated as device features and vice versa.

[0032] Further features of the invention are evident 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 those subsequently mentioned in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the figures, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention. Embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features, in particular those set out above, are to be considered disclosed which go beyond or deviate from the combinations of features set out in the cross-references of the claims.

[0033] For use cases or application situations that may arise during the procedure and are not explicitly described here, it may be necessary to issue an error message and / or a prompt for user feedback and / or to set a default setting and / or a predetermined initial state, according to the procedure. This is shown below.

[0034] Fig. 1 shows a schematic circuit diagram of a sensor device with a reference capacitance and a capacitive sensor element for determining manual actuation by a user.

[0035] Fig. 2 shows a simplified schematic circuit diagram representation from Fig. 1, a step in the procedure for determining manual actuation using the sensor device according to Fig. 1.

[0036] Fig. 3 shows a further step in the process for determining manual actuation using the sensor device according to Fig. 1 in a simplified schematic circuit diagram representation from Fig. 1.

[0037] Fig. 4 shows a simplified schematic circuit diagram representation from Fig. 1, illustrating a further step in the process for determining manual actuation using the sensor device according to Fig. 1.

[0038] Fig. 5 shows a simplified schematic circuit diagram representation from Fig. 1, illustrating a further step in the process for determining manual actuation using the sensor device according to Fig. 1.

[0039] Fig. 6 shows a schematic diagram of voltage curves for determining a coupling voltage and a partial voltage.

[0040] Fig. 7 in a schematic circuit diagram representation as Fig. 1 shows a cycle of a method for determining a manual actuation, and

[0041] Fig. 8 shows a schematic flowchart illustrating a procedure for determining manual actuation using the sensor device according to Fig. 1.

[0042] Fig. 1 shows a schematic circuit diagram of a sensor device 10 with an electrical reference capacitor 2 and a capacitive sensor element 1 for detecting manual actuation by a user (not shown), for example, an occupant of a motor vehicle (also not shown), when the sensor device 10 is installed in a motor vehicle. The sensor device 10 also includes an evaluation unit 3, which in turn has a coupling unit 7. This coupling unit 7 serves to controllably connect the capacitive sensor element 1, the reference capacitor 2, and the evaluation unit 3 to an internal connection 19 of an analog-to-digital converter 4 of the evaluation unit 3. In this example, the coupling unit 7 is integrated into the evaluation unit 3. However, in alternative configurations, the coupling unit 7 could also be provided as a separate coupling unit.

[0043] The coupling unit 7 comprises switching elements 25, 26, 27, which in turn comprise electronic switching elements, such as transistors. A switching functionality can be implemented using the switching elements 25, 26, 27.

[0044] In this embodiment, the sensor element 1 is formed by a touchable film, which is arranged (not shown) such that it can be actuated by the user with a finger. Actuation can be in the form of touch. In alternative embodiments, however, the sensor element 1 can also be actuated by another part of the user's body, either alternatively or additionally.

[0045] The evaluation unit 3 is designed as an integral unit and has, among other things, connections 11, 28, 29, 30, and 31. The reference capacitor 2 is connected between connections 28 and 29. An electrical reference potential 5, which in this case is a circuit ground, is connected to connection 30. A voltage source 6 is connected between the reference potential 5 and connection 31, which, in this configuration, also serves, among other things, to supply the electrical power to the evaluation unit 3 for its intended operation. The sensor element 1 is also connected between connection 29 and the reference potential 5. The evaluation unit 3 outputs an evaluation signal at connection 11, depending on whether manual actuation has been determined. Connection 11 can be electrically coupled to a higher-level vehicle control unit (not shown) of the motor vehicle, which evaluates the evaluation signal and uses it for a control function.The switching element 25 is electrically connected to terminals 28, 30, and 31, and its switching function creates a change in the electrical connection between terminals 30 and 28 or 31 and 28. In addition, switching element 25 has a further switching position in which no electrical connection is present. Similarly, switching element 26 implements a corresponding switching function between terminals 29, 30, and 31. Depending on the switching state of switching element 26, an electrical connection is established either between terminals 29 and 30 or between terminals 29 and 31. Switching element 26 also has a further switching position in which no electrical connection is present.The third switching element 27 is essentially configured according to switching elements 25 and 26, such that, depending on the switching state, an electrical connection can be established between the internal terminal 19 of the analog-to-digital converter 4 and either terminal 31 or 30. Depending on the switching state, the electrical connection is thus established either between terminals 19 and 30 or between terminals 19 and 31. A further switching state is also provided in which no electrical connection exists.

[0046] Evaluation unit 3 includes analog-to-digital converter 4, which has input terminal 19 for acquiring a voltage signal. The analog-to-digital converter 4 is digitally connected to a computer unit 9 of evaluation unit 3. By evaluating the electrical voltages acquired by the analog-to-digital converter 4, the computer unit 9 determines whether the user has activated the sensor element 1 and outputs a corresponding evaluation signal at terminal 11.

[0047] The circuit structure described above can of course be adapted or modified as needed. For example, the switching elements 25, 26, 27 can also be formed by pairs of individual switching elements that only provide a switching-on functionality.

[0048] Figures 2 to 5 show simplified sections of the schematic circuit diagram according to Fig. 1 to illustrate the procedure for determining the manual actuation using the sensor device 10 according to Fig. 1. The functionality according to the procedure assumes that the reference capacitor 2 and the sensor element 1 are both in a discharged state, i.e., their voltages are zero. In a first step 20, the sensor element 1 and the reference capacitor 2 are therefore connected in parallel and set to a first electrical voltage, which in this case is zero. This is an initial state for the second step 21, as shown in Figure 2.

[0049] In the second step 21, the parallel circuit is interrupted and the sensor element 1 is set to a second electrical voltage, which in this case corresponds to the voltage provided by the voltage source 6. It is understood that the interruption of the parallel circuit naturally occurs before the setting to the second electrical voltage. In this step, the reference capacitor 2 is electrically decoupled from the sensor element 1, which is why the electrical voltage across the reference capacitor 2 remains zero, whereas the electrical voltage across the sensor element 1 corresponds to that of the voltage source 6.

[0050] In a subsequent step 22, the sensor element 1 and the reference capacitor 2 are again electrically connected in parallel. As can be seen in Fig. 3, the sensor element 1 is also disconnected from the voltage source 6 beforehand or simultaneously. Due to the parallel connection, an electrical coupling voltage 16 (Fig. 6) is established, which can be detected by the evaluation unit 3, in particular the analog-to-digital converter 4. For this purpose, the analog-to-digital converter 4 can be electrically connected to the parallel circuit. This is made possible by the switching element 27, which is switched to the corresponding switching state in which an electrical connection is established between terminal 19 and terminal 29.

[0051] Fig. 4 shows the following step 20, which serves to reconnect the reference capacitor 2 and the sensor element 1 in parallel and discharge them. For this purpose, the switching elements 25, 26 are switched to their respective switching positions so that the respective terminals 28, 29 are connected to terminal 30. In this position, the capacitors are discharged so that their voltages are essentially zero.

[0052] In a fourth step 23 (Fig. 8), the sensor element 1 and the reference capacitor 2 are electrically connected in series. This is achieved by means of the switching elements 25, 26, whereby switching element 25 establishes an electrical connection between terminals 28, 31, and switching element 26 disconnects terminal 29, so that there is no electrical connection to terminals 30, 31. This charges the series circuit to the corresponding voltage by means of the voltage source 6. In a fifth step 24, an electrical partial voltage 17 of the series circuit is detected by means of the evaluation unit 3, in particular the analog-to-digital converter 4; in this case, the electrical voltage of the sensor element 1. For this purpose, switching element 27 is switched to the corresponding switching position, so that an electrical connection is established between terminals 19, 29.Using the detected coupling voltage 16 and the detected partial voltage 17, the computer unit 9 determines the manual actuation. This is shown in Fig. 6.

[0053] Fig. 6 shows in a schematic diagram representation voltage curves for determining the coupling voltage 16 and the partial voltage 17. The abscissa is assigned to time, whereas the ordinate is assigned to voltage.

[0054] In the time interval from zero to ti, Fig. 6 shows how the coupling voltage 16 is generated. Graph 12 shows the time course of the electrical voltage at the sensor element 1, whereas graph 13 shows the corresponding voltage course at the reference capacitor 2. At time ti, the two electrical voltages have equalized due to the parallel connection, so that the parallel connection provides the coupling voltage 16.

[0055] At time ti, step 20 is repeated. Then, steps 23 and 24 are performed. Graph 14 shows the voltage profile across the reference capacitor 2, while graph 15 shows the voltage profile across the sensor element 1. At time ta, the voltages have stabilized, allowing the partial voltage 17 to be determined.

[0056] The partial voltage 17 and the coupling voltage 16 are each measured by the analog-to-digital converter 4. The processing unit 9 determines a differential voltage 18 from the partial voltage 17 and the coupling voltage 16. The differential voltage 18 is compared by the processing unit 9 with a predefined reference value. As soon as the differential voltage 18 is greater than the predefined reference value, this is recognized as manual operation and a corresponding evaluation signal or actuation signal is output at terminal 11.

[0057] Fig. 7 shows, in a schematic circuit diagram similar to Fig. 1, a cycle of the procedure as previously described for determining manual actuation. The steps explained with reference to Figs. 2 to 5 are shown here again in sequence. Reference numeral 8 denotes a transition between two successive steps, during which terminals 19, 29, 30 are briefly switched to a deactivated mode in which these terminals have no electrical connection. For this purpose, switching elements 25, 26, 27 can be switched to the corresponding switching positions.

[0058] In a further embodiment, the cycle described above with reference to Fig. 7, or the sequence of process steps 20 to 24 described above, is repeated in at least one subsequent cycle. For example, 4, 8, 16, 30, or even 64 repetitions are possible. This allows for an improvement in the reliability and accuracy of the manual actuation detection, similar to oversampling. However, despite repeated cycles, for example with 64 cycles, a reaction time of approximately 320 ps to approximately 640 ps can still be achieved, which can significantly reduce the detection speed.

[0059] Fig. 8 shows a schematic flowchart illustrating a process sequence for determining manual actuation using the sensor device according to Fig. 1. Fig. 8 depicts the required sequence of process steps 20 to 24 of a cycle for the present process. For multiple consecutive cycles, the sequence shown in Fig. 8 is repeated for each subsequent cycle.

[0060] The description of the figures serves solely to explain the invention and is not intended to limit it.

Claims

Patent claims 1. A method for determining manual actuation of a capacitive sensor element (1), wherein in a first step (20) the sensor element (1) and an electrical reference capacitance (2) are electrically connected in parallel and set to a first electrical voltage, in a second step (21) the parallel connection is interrupted and the sensor element (1) is set to a second electrical voltage which is different from the first electrical voltage, and in a third step (22) the sensor element (1) and the reference capacitance (2) are again electrically connected in parallel to provide an electrical coupling voltage (16) for detection by an evaluation unit (3), characterized in that the first step (20) is repeated, in a fourth step (23) the sensor element (1) and the reference capacitance (2) are electrically connected in series with each other, and the series connection is set to a third electrical voltage.and in a fifth step (24) by means of the evaluation unit (3) an electrical partial voltage (17) of the series circuit, namely at least the electrical voltage of the sensor element (1) or the reference capacitance (2), is detected, whereby the manual actuation is determined depending on the partial voltage (17) and the coupling voltage (16).

2. Method according to claim 1, characterized in that an electrical differential voltage (18) is determined depending on the partial voltage (17) and the coupling voltage (16).

3. Method according to claim 2, characterized in that the manual actuation is determined at least partially depending on the differential voltage (18).

4. Method according to claim 2 or 3, characterized in that the differential voltage (18) is compared with at least one first reference value to determine the manual actuation.

5. Method according to one of claims 2 to 4, characterized in that the differential voltage (18) is compared with at least one second reference value to determine the manual actuation, wherein the second reference value is different from the first reference value.

6. Method according to one of the preceding claims, characterized in that the first electrical voltage is zero.

7. Method according to one of the preceding claims, characterized in that the second and the third electrical voltage are the same.

8. Method according to one of the preceding claims, characterized in that the electrical voltages recorded by the evaluation unit (3) are digitized and the determination of the manual actuation is realized at least partially by means of digital signal processing.

9. Method according to one of the preceding claims, characterized in that at least the coupling voltage (16) or the partial voltage (17) is compared with at least one third reference value.

10. Method according to one of the preceding claims, characterized in that a sequence of the preceding method steps is repeated in at least one subsequent cycle.

11. Computer program product with program code means, which are stored in particular in a computer-readable medium, in order to effect, in a first step (20), an electrical parallel connection of the sensor element (1) and an electrical reference capacitance (2) and an adjustment to a first electrical voltage when carrying out a method for determining a manual actuation of a capacitive sensor element (1), and in a second step (21) an interruption in a third step (22) to cause the parallel connection and the setting of the sensor element (1) to a second electrical voltage which is different from the first electrical voltage, and in a third step (22) to cause the parallel connection of the sensor element (1) and the reference capacitor (2) again to provide an electrical coupling voltage (16) for detection by an evaluation unit (3), to repeat the first step (20), in a fourth step to cause the series connection (23) of the sensor element (1) and the reference capacitor (2) and the setting of the series connection to a third electrical voltage, and in a fifth step (24) to cause the evaluation unit (3) to detect an electrical partial voltage (17) of the series connection, namely at least the electrical voltage of the sensor element (1) or the reference capacitor (2), and / or to control the evaluation unit (3) in such a way,that it determines the manual operation depending on the partial voltage (17) and the coupling voltage (16) when the computer program product is processed on a computing unit of an evaluation unit.

12. Computer-readable data carrier on which a computer program product, at least according to claim 11, is stored.

13. Evaluation unit (3) for determining manual actuation of a capacitive sensor element (1), wherein the evaluation unit (3) is configured to, in a first step (20), electrically connect the sensor element (1) and an electrical reference capacitance (2) in parallel and set them to a first electrical voltage, in a second step (21) to interrupt the parallel connection and set the sensor element (1) to a second electrical voltage which is different from the first electrical voltage, and in a third step (22) to electrically connect the sensor element (1) and the reference capacitance (2) in parallel again in order to provide an electrical coupling voltage (16) and to detect the coupling voltage (16) provided by the sensor element (1) electrically connected in parallel with the reference capacitance (2), characterized in that the evaluation unit (3) is further configured to repeat the first step (20),in a fourth step (23) to connect the sensor element (1) and the reference capacitance (2) electrically in series, to adjust the series circuit to a third electrical voltage, and in a fifth step (24) to set an electrical partial voltage (17) of the series circuit, and, to detect at least the electrical voltage of the sensor element (1) or the reference capacitance (2) and to determine the manual actuation depending on the partial voltage (17) and the coupling voltage (16).

14. Sensor device (10) for determining manual actuation, comprising a capacitive sensor element (1), an electrical reference capacitance (2), an evaluation unit (3), and a coupling unit (7) at least for controllable electrical coupling of the capacitive sensor element (1), the reference capacitance (2), and the evaluation unit (3), characterized in that the evaluation unit (3) is configured according to claim 13.

15. Motor vehicle with a sensor device (10) for determining manual operation by a vehicle occupant, characterized in that the sensor device (10) is designed according to claim 14.

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