Calibration of a user input device and detection of an actuation of a user input device of a motor vehicle

Description

[0001] The present invention relates to a method for calibrating a user input device for a motor vehicle, a method for detecting an actuation of a user input device of a motor vehicle, a user input device for a motor vehicle and a motor vehicle having such a user input device.

[0002] In the interior of motor vehicles, traditional control devices are being partially replaced by so-called smart surfaces. This combines design, ambient lighting, and operating functionality. In particular, panels or other surfaces in the vehicle interior can be equipped with touch-sensitive surfaces that can detect a touch, swipe, or similar action by the user. One challenge that arises is distinguishing between an intentional activation of the user input device by the user and an accidental touch of the touch-sensitive surface.

[0003] One way to counteract this is to use a specially installed sensor to detect the force the user exerts on the touch-sensitive surface and compare it to a threshold value. If the force is large enough, it can be assumed that the touch was intentional; otherwise, it can be assumed that the touch was unintentional.

[0004] Tolerances, material and process variations during the manufacture of the user input device, as well as additional mechanical stresses or loads during the assembly of the user input device in the motor vehicle, can lead to the same actuation force leading to different measured values from the sensors in the final assembled product and therefore possibly to false-positive or false-negative detections of an actuation.

[0005] DE 10 2019 204 058 A1 discloses a force measuring device for determining a force exerted on a movable surface element of a vehicle component. The force measuring device comprises a spring that exerts a preload between the movable surface element and a housing element of the vehicle component. Furthermore, the force measuring device comprises a non-contact distance sensor for detecting the distance between the surface element and the housing element.

[0006] US 2017 / 242539 A1 discloses a processing system for an input device, the processing system comprising a sensor circuit communicatively coupled to a plurality of position sensor electrodes and a plurality of force sensor electrodes, and a sensor module with circuitry. The sensor module is configured to detect a plurality of capacitance changes of the plurality of force sensor electrodes in response to deflection of the sensor electrodes by an input force.

[0007] US 2017 / 242505 A1 discloses a processing system comprising sensor circuits and processing circuits. The sensor circuit is configured to be coupled to force sensor electrodes and is configured to drive the force sensor electrodes to obtain capacitive measurements. The processing circuit is operatively connected to the sensor circuit and configured to aggregate the capacitive measurements into an aggregated measurement and apply a capacitive measurement to the aggregated measurement for temperature mapping to obtain a current temperature of the force sensor electrodes.

[0008] US 2014 / 168153 A1 discloses touchscreen systems and methods based on touch position and touch force. The touchscreen system includes an optical force measurement system connected to a capacitive touch sensor system so that both touch position and touch force information can be retrieved.

[0009] US 2015 / 338303 A1 discloses a method and apparatus for calibrating a force-sensing touchscreen panel, which comprises determining calibration factors for the position sensing layers of the touchscreen panel and applying these calibration factors to set nominal resistance values for resistive components of the position sensing layers when force is applied to the touchscreen panel.

[0010] It is an object of the present invention to increase the reliability in detecting the actuation of a user input device with a touch-sensitive surface.

[0011] This problem is solved by the subject matter of the independent claim. Advantageous further developments and preferred embodiments are the subject matter of the subordinate claim and the dependent claims.

[0012] The invention is based on the idea of performing a two-stage calibration of the user control device. In a first calibration step, a distance sensor is calibrated such that a relationship between the change in the actuating force and the change in the corresponding sensor signal is determined before the user control device is mounted in the motor vehicle. After mounting in the motor vehicle, a second calibration step is performed in which an actual value, in particular an absolute value, of the sensor signal is determined and the relationship determined in the first calibration step is corrected depending on the actual value determined after mounting, wherein the actual value is detected in the second calibration step, in particular while no actuating force is exerted.

[0013] According to one aspect of the invention, a method for calibrating a user input device for a motor vehicle is provided.

[0014] The user input device comprises a component with a touch-sensitive surface and a reference element mechanically, in particular rigidly, connected to the component. The user input device comprises a circuit carrier and a distance sensor arranged on the circuit carrier and configured to generate a sensor signal depending on a distance of the reference element from the distance sensor. The user input device further comprises an evaluation unit configured to detect an actuation of the user input device, in particular to detect it only when the touch-sensitive surface is touched by a user and, at the same time, an actuation force greater than or equal to a predeterminable minimum force is exerted on the touch-sensitive surface.

[0015] The method according to the invention comprises a first calibration step, an assembly step which follows the first calibration step, i.e. is carried out after the first calibration step has been carried out, and a second calibration step which follows the second assembly step, i.e. is carried out after the assembly step has been carried out. In the first calibration step before assembly, a first relationship is determined between a change in the actuating force and a change in the sensor signal, in particular the value or the absolute value of the sensor signal. In the assembly step after the first calibration step has been carried out, the user input device is installed in the motor vehicle, i.e. in particular is mechanically connected to the motor vehicle.In the second calibration step after performing the assembly step, a first actual value of the sensor signal is determined and the first relationship is corrected depending on the first actual value.

[0016] The evaluation unit is, in particular, electrically connected to the touch-sensitive surface in order to detect the user's touch of the touch-sensitive surface. The touch-sensitive surface can be configured, for example, as a so-called touchscreen or as a touch control panel. The touch-sensitive surface can be designed according to a known functional principle for implementing touch sensitivity. For example, the touch-sensitive surface can be designed according to a resistive functional principle, a capacitive functional principle, an inductive functional principle, and so on. Therefore, in particular, no or essentially no force is required to be applied to the touch-sensitive surface to detect the touch of the touch-sensitive surface.

[0017] The component with the touch-sensitive surface can be designed, for example, as a panel or panel component, in particular as a panel for integration into a cockpit of the motor vehicle, for example into a dashboard of the motor vehicle. In particular, the component is flexible, so that the distance between the component and the distance sensor, and thus between the reference element and the distance sensor, can change upon exertion of the actuating force. For example, the component can be designed as a plate, for example consisting of or comprising one or more plastic materials. A plate can be understood to mean a component whose extent in two spatial dimensions is significantly greater than in the third spatial dimension, for example by at least a multiplicative factor of 10, preferably at least 20, at least 50, or at least 100.In other words, the length and width of the plate are significantly greater than its thickness. The plate can be essentially flat or curved, particularly in the force-free state, i.e., when no actuation force is applied to the touch-sensitive surface.

[0018] From the user's perspective, the circuit carrier is therefore arranged behind the component, in particular behind the panel, after the user input device has been properly installed in the motor vehicle and is therefore not visible. The same applies to the distance sensor and the reference element. If the user presses on the touch-sensitive surface to activate the user input device, they touch it and generally exert an actuation force at the same time. Depending on the size of the predeterminable or predefined minimum force, the evaluation unit can then detect an actuation or only detect it if the actuation force during contact with the touch-sensitive surface is greater than or equal to a corresponding value. This can be done by comparing the sensor signal with an associated threshold value. The threshold value can be derived, in particular, from the corrected relationship.

[0019] The reference element can be understood as a reference element in the sense that it serves to measure the distance and is representative of the distance or the change in distance between the component and the circuit carrier or distance sensor due to the actuating force. Due to the mechanical connection of the reference element to the component, an actuating force exerted on the touch-sensitive surface and thus the component is transferred more or less directly to the reference element, so that the distance between the reference element and the distance sensor changes. The distance between the reference element and the distance sensor is therefore representative of a change in the position of the component or panel, for example due to bending or the like due to the actuating force.

[0020] The component, in particular the cover, can be manufactured, for example, using an injection molding process and can contain or consist of a plastic, such as polycarbonate and / or polyurethane. After the injection molding process, the component can also be subjected to a thermal treatment, in particular tempering.

[0021] The component and the reference element can be manufactured independently of one another and connected to one another after manufacture, for example by gluing, screwing, clamping, etc. For example, the reference element can be designed as a plunger and / or arranged on a side of the component facing away from the touch-sensitive surface and thus on the side of the component facing the distance sensor. In alternative embodiments, the reference element can also be part of the component or formed integrally with the component. In particular, the reference element can correspond to a region of the component or plate opposite the distance sensor. In such embodiments, the distance between the reference element and the distance sensor corresponds directly to the distance between the component and the distance sensor.

[0022] Installing the user input device in the motor vehicle includes, in particular, mechanically fastening the user input device, in particular the component with the touch-sensitive surface, to a part or another component of the motor vehicle. In particular, the circuit carrier can also be mechanically connected to a part of the motor vehicle. For example, the connections can be made using screw connections, clamp connections, rivet connections, and so on.

[0023] Due to the manufacturing of the component, corresponding dimensional tolerances, curvatures, internal stresses and so on, as well as due to the mechanical connection of the component to other parts of the user input device, in particular the circuit carrier and so on, an actuation by a user with a predetermined force at a predetermined position can result in a different change in distance, in particular in a different deflection path of the component or panel, depending on the user input device.

[0024] Mounting the user input device to the motor vehicle may result in further bending and / or distortion of the component and / or circuit carrier, which may result in further deviations in the deformation path and, accordingly, in the measured distance or the measured change in distance.

[0025] The corrected relationship can be viewed as the result of the calibration procedure. The corrected relationship assigns a value for the actuation force to each value, in particular to each actual value of the sensor signal under consideration.

[0026] This allows the evaluation unit to directly compare the sensor signal with a threshold value that corresponds to a predefined minimum force according to the corrected relationship. Based on the comparison of the sensor signal with the corresponding threshold value, the evaluation unit can therefore decide whether or not an actuation is to be assumed, since a sufficiently strong force is being exerted.

[0027] In other words, the calibration method according to the invention ensures that the threshold value with which the evaluation unit compares the actual value of the sensor signal to verify actuation actually corresponds to the specified minimum force. In other words, the corrected relationship provides the correct threshold value for the specified minimum force.

[0028] The first calibration step can be performed by the evaluation unit and / or by an external computing unit connected to the evaluation unit. The second calibration step is preferably performed by the evaluation unit. The second calibration step can, in particular, be performed automatically by the evaluation unit, in particular without requiring any corresponding interaction with a user. The second calibration step can advantageously be repeated at different times in order to take account of any changing conditions during the operation of the motor vehicle. Alternatively, the second calibration step can also be performed depending on a corresponding user input.

[0029] In particular, the second calibration step is performed while no actuation force is applied to the touch-sensitive surface. In other words, the actuation force applied to the touch-sensitive surface during the determination of the first actual value in the second calibration step is 0 N. This facilitates the automation and automatic repetition of the second calibration step.

[0030] The method according to the invention can therefore increase the reliability in detecting the actuation of the user input device by the user by taking into account the individual part-dependent fluctuations, stresses or prestresses that occur during the manufacture of the component, the manufacture of the user input device and the assembly of the user input device in the motor vehicle and compensating for them by combining the two calibration steps.

[0031] To determine the initial relationship in the first calibration step, different actuation forces or changes in actuation force can be applied to the touch-sensitive surface and the corresponding change in the sensor signal measured. The relationship can thus be understood as a value relationship or curve for different changes in actuation force and the resulting different changes in the sensor signal.

[0032] The first relationship can be approximately linear. If a linear first relationship is assumed, determining the first relationship can, for example, involve or consist of determining a corresponding slope of the first relationship.

[0033] The distance sensor can, for example, be designed as an optical distance sensor, in particular as an active optical sensor system.

[0034] To determine a distance or to generate a corresponding sensor signal, the distance sensor can emit light in the direction of the reference element using an emitter unit of the distance sensor and detect portions of the light reflected from the reference element using a detector unit of the distance sensor. The detector unit contains one or more optical detectors, for example photodiodes. The emitter unit contains one or more light sources, for example light-emitting diodes or laser diodes. The light can correspond to infrared light, for example. The sensor signal can be generated, for example, depending on the intensity of the detected reflected portions. For example, the sensor signal can be proportional to the detected intensity of the reflected portions.

[0035] The smaller the distance between the reference element and the distance sensor, the greater the intensity of the reflected portions of the light, so the distance can be determined based on the intensity. In further embodiments, the evaluation unit can also perform a time-of-flight measurement based on the detected portions of the light or a phase comparison measurement between the emitted and reflected portions of the light. Based on this, the sensor signal representing the distance can then be generated.

[0036] According to at least one embodiment of the method according to the invention for calibrating a user input device, the first actual value of the sensor signal is determined while no actuating force is exerted on the touch-sensitive surface.

[0037] According to the invention, in the first calibration step, a first actuating force with a first force value different from zero is exerted on the touch-sensitive surface, and a first value of the sensor signal is determined while the first actuating force is applied. In a plurality of iterations, i.e. in particular in three or more iterations, a second actuating force with a second force value different from zero is exerted on the touch-sensitive surface, and a second value of the sensor signal is determined while the second actuating force is applied. For each of the plurality of iterations, the change in the sensor signal is determined as the difference between the first value of the sensor signal and the respective second value of the sensor signal in order to determine the first relationship in the first calibration step.

[0038] According to at least one embodiment, in order to determine the first actual value of the sensor signal, light is emitted in the direction of the reference element by means of the emitter unit of the distance sensor, and components of the light reflected by the reference element are detected by means of the detector unit of the distance sensor.

[0039] According to at least one embodiment, in order to correct the first relationship, a correction factor is determined as a function of the first actual value of the sensor signal, and the first relationship is multiplied by the correction factor.

[0040] In order to multiply the first relationship by the correction factor, in particular for each change in the actuating force the corresponding determined value of the change in the actuating force is multiplied by the correction factor.

[0041] In other words, the first relationship can be expressed as DS = DS(DF) = f(DF), where DS denotes the change in the sensor signal and DF denotes the change in the actuation force. f is a function that specifies the first relationship. For example, if the first relationship is approximately linear, then f(DF) = m*DF + f(0).

[0042] The corrected first relationship is then given, for example, by DS(DF) = g(DF), where g = K*f and K denotes the correction factor. In the linear case, g(DF) = K*m*DF + K*f(0).

[0043] In various embodiments, the first relationship is a linear relationship, so that the corrected first relationship is also a linear relationship, wherein a slope of the corrected first relationship corresponds to a slope of the first relationship multiplied by the correction factor.

[0044] The correction factor can, for example, be determined based on a predefined further relationship which assigns the first actual value to the correction factor.

[0045] The further relationship can be stored, for example, in a conversion table, also known as a lookup table (LUT), in a memory unit of the user input device, in particular the evaluation unit. The further relationship can be determined experimentally in advance and stored accordingly.

[0046] According to at least one embodiment, the first relationship is determined at a first temperature value of an ambient temperature of the user input device. In other words, the ambient temperature is set to the first temperature value or regulated accordingly to determine the first relationship. Likewise in the first calibration step, i.e. in particular after or before determining the first relationship, a second relationship between the change in the actuating force and the change in the sensor signal is determined at a second temperature value of the ambient temperature. In other words, the ambient temperature is set to the second temperature value or regulated accordingly to determine the second relationship. The first actual value is determined in the second calibration step at the first temperature value of the ambient temperature.In the second calibration step, a second actual value of the sensor signal is also determined at the second temperature value of the ambient temperature and the second relationship is corrected depending on the second actual value.

[0047] The determination of the first temperature value and the correction of the first relationship can take place independently of the determination of the second actual value and the correction of the second relationship. For example, the ambient temperature can be measured during the second calibration step, for example using a temperature sensor of the motor vehicle or the user input device that is connected to the evaluation unit of the user input device. If the measured ambient temperature is equal to the first temperature value or within a predetermined tolerance range around the first temperature value, the first relationship can be corrected depending on the first actual value. If the measured ambient temperature is equal to the second temperature value or within a predetermined tolerance range around the second temperature value, the second relationship can be corrected depending on the second actual value.

[0048] The statements regarding the first actual value or the first relationship can be transferred analogously to the second actual value or the second relationship.

[0049] The method is not limited to determining the first and second relationships at the first and second temperature values. In particular, corresponding relationships between the change in actuating force and the change in the sensor signal can be determined at a variety of ambient temperature values, including the first temperature value and the second temperature value. In other words, a characteristic curve map or a characteristic map of the change in the sensor signal as a function of the change in actuating force and the ambient temperature can be determined. Depending on the ambient temperature currently prevailing in the second calibration step, a corresponding correction of the respective relationship can be made. This further increases reliability even at different ambient temperatures.

[0050] According to at least one embodiment, a threshold value is determined, in particular by means of the evaluation unit, which threshold value corresponds, according to the corrected first relationship, to a change in the actuating force, the value of which is equal to a predetermined value for the minimum force, and the threshold value is stored on a memory unit of the user input device, in particular the evaluation unit.

[0051] In corresponding embodiments, an associated threshold value can be determined for the first and second temperatures, or for all temperatures for which a corresponding relationship has been determined. In other words, an ambient temperature-dependent threshold value is determined, which is equal to the predetermined value for the minimum force for the respective temperature, in particular the ambient temperature.

[0052] The threshold value can then be used by the evaluation unit to detect whether or not a user has actuated the user input device.

[0053] According to a further aspect of the invention, a method for detecting an actuation of a user input device of a motor vehicle is provided.

[0054] The user input device comprises a component with a touch-sensitive surface and a reference element mechanically connected to the component. The user input device comprises a circuit carrier and a distance sensor arranged on the circuit carrier and configured to generate a sensor signal depending on a distance of the reference element from the distance sensor. The user input device comprises an evaluation unit configured to detect a touch of the touch-sensitive surface by a user and to receive the sensor signal from the distance sensor.

[0055] To implement a method according to the invention for detecting an actuation of a user input device, a method according to the invention for calibrating the user input device is implemented, in particular in an embodiment in which the threshold value is determined which, according to the corrected first relationship, corresponds to the change in the actuation force, the value of which is equal to the predetermined value for the minimum force, and the threshold value is stored in the memory unit of the user input device. After correcting the first relationship, a further actual value for the sensor signal is determined, in particular by means of the evaluation unit.A difference between the first actual value and the further actual value is compared with the stored threshold value by means of the evaluation unit and the actuation of the user input device is only detected by means of the evaluation unit if the difference between the first actual value and the further actual value is greater than the threshold value, in particular only if the difference is greater than the threshold value and the touch of the touch-sensitive surface has been detected.

[0056] In corresponding embodiments, the ambient temperature can be measured and the corresponding threshold value can be used, which corresponds to the measured ambient temperature according to the ambient temperature-dependent characteristic map.

[0057] According to at least one embodiment of the method according to the invention for detecting an actuation of the user input device, the touch of the touch-sensitive surface is detected by means of the evaluation unit and the actuation of the user input device is detected by means of the evaluation unit only when the difference between the first actual value and the further actual value is greater than the threshold value while the touch of the touch-sensitive surface is detected.

[0058] According to a further aspect of the invention, a user input device for a motor vehicle is specified. The user input device comprises a component with a touch-sensitive surface and a reference element mechanically connected to the component, a circuit carrier, and a distance sensor arranged on the circuit carrier and configured to generate a sensor signal depending on a distance of the reference element from the distance sensor. The user input device comprises a memory unit that stores a first relationship between a change in an actuating force exerted on the touch-sensitive surface and a change in the sensor signal.The user input device has an evaluation unit configured to detect a touch of the touch-sensitive surface by a user, to receive the sensor signal from the distance sensor, to determine a first actual value of the sensor signal, and to correct the first relationship depending on the first actual value.

[0059] The user input device is in particular configured to correct the first relationship when the user input device is mounted in the motor vehicle.

[0060] According to at least one embodiment of the user input device according to the invention, the evaluation unit is configured to determine a threshold value which, according to the corrected first relationship, corresponds to a change in the actuating force, the value of which is equal to a predetermined value for the minimum force, and to store the threshold value on the storage unit.

[0061] According to at least one embodiment, the evaluation unit is configured to determine a further actual value for the sensor signal after the correction of the first relationship, to compare a difference between the first actual value and the further actual value with the stored threshold value, and to detect an actuation of the user input device by means of the evaluation unit only if the difference between the first actual value and the further actual value is greater than the threshold value.

[0062] In particular, the evaluation unit is configured to detect the actuation of the user input device only if the difference between the first actual value and the further actual value is greater than the threshold value while the touch of the touch-sensitive surface is detected.

[0063] According to a further aspect of the invention, a motor vehicle with my inventive user input device is also provided.

[0064] Further embodiments of the user input device follow directly from the various embodiments of the method according to the invention for calibrating a user input device and the method according to the invention for detecting an actuation of a user input device and vice versa.

[0065] If, within the scope of the present disclosure, it is stated that a component of the user input device, in particular the evaluation unit of the user input device, or the external processing unit is set up, designed, configured, or the like to carry out or implement a specific function, to achieve a specific effect or to serve a specific purpose, this can be understood to mean that the component, beyond the fundamental or theoretical usability or suitability of the component for this function, effect or purpose, is concretely and actually capable of carrying out or implementing the function, achieving the effect or serving the purpose through appropriate adaptation, programming, physical design, and so on.

[0066] An active optical sensor system, in particular the emitter unit, by definition comprises a light source for emitting light or light pulses. The light source can be configured, in particular, as a laser, for example, an infrared laser. Furthermore, an active optical sensor system, in particular the detector unit, by definition comprises at least one optical detector for detecting reflected portions of the emitted light. The active optical sensor system is configured, in particular, to generate, process, or output the sensor signal and, if appropriate, one or more additional sensor signals based on the detected portions of the light.

[0067] The term "light" can be understood to include electromagnetic waves in the visible, infrared, and / or ultraviolet ranges. Accordingly, the term "optical" can also be understood to refer to light in this sense.

[0068] The evaluation unit can also be considered a computing unit. A computing unit can be understood, in particular, as a data processing device; the computing unit can therefore, in particular, process data to perform computing operations. This may also include operations for performing indexed access to a data structure, for example, a look-up table (LUT).

[0069] The computing unit may, 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 may 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 may also include a physical or virtual network of computers or other of the aforementioned units.

[0070] In various embodiments, the computing unit includes one or more hardware and / or software interfaces and / or one or more memory units.

[0071] A memory unit can be a volatile data storage device, such as dynamic random access memory (DRAM) or static random access memory (SRAM), or a non-volatile data storage device, such as read-only memory (ROM), programmable read-only memory (PROM), erasable read-only memory (EPROM), electrically erasable read-only memory (EEPROM), flash memory (FRAM), ferroelectric random access memory (FRAM), magnetoresistive random access memory (MRAM), or phase-change random access memory (PROM).PCRAM (phase-change random access memory),

[0072] 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 encompassed by the invention not only in the respectively specified combination, but also in other combinations. In particular, the invention also encompasses embodiments and combinations of features that do not have all the features of an originally formulated claim. Furthermore, the invention encompasses embodiments and combinations of features that go beyond or deviate from the combinations of features set out in the backreferences to the claims.

[0073] The figures show: Fig. 1 shows a schematic representation of an exemplary embodiment of a user input device according to the invention; Fig. 2 shows a schematic representation of a further exemplary embodiment of a user input device according to the invention; Fig. 3 shows a schematic representation of a further exemplary embodiment of a user input device according to the invention; Fig. 4 shows a schematic representation of a further exemplary embodiment of a user input device according to the invention; Fig. 5 shows a schematic representation of an exemplary relationship between a sensor signal of a distance sensor and a distance of a reference element from the distance sensor; Fig. 6 shows a schematic representation of an exemplary curve of a correction factor; Fig. 7 shows a schematic representation of a further exemplary curve of a correction factor; and Fig. 8 shows a schematic representation of a further exemplary curve of a correction factor.

[0074] In Fig. 1 An exemplary embodiment of a user input device 1 according to the invention for a motor vehicle (not shown) is shown schematically. The user input device 1 has a component 2, in particular a panel, which has a touch-sensitive surface 3, which, when the user input device 1 is properly installed in the motor vehicle, faces a user of the motor vehicle in the vehicle interior, in particular in a driver's cab of the motor vehicle, so that the user can touch the touch-sensitive surface 3.

[0075] The user input device 1 also has, in particular on a side of the component 2 facing away from the user, a circuit carrier 5 on which a distance sensor 6, configured, for example, as an active optical sensor system, is arranged. On the side of the component 2 facing the distance sensor 6, the user input device 1 also has a reference element 4, which is part of the component 2 or is mechanically rigidly connected to the component 2. The distance sensor 6 can accordingly generate a sensor signal corresponding to a distance d between the distance sensor 6 and the reference element 4.

[0076] An example of the sensor signal as a function of the distance d is shown schematically in Fig. 5 shown. In Fig. 5 Furthermore, three values d 1 , d 2 , d 3 are entered, which lie within a linear range of the sensor signal. The distance sensor 6 is preset or pre-controlled, for example, by setting a corresponding blocking voltage of an optical detector or the like, such that relevant distances d lie within the linear range to ensure the unambiguousness of the measurement.

[0077] The user input device 1 also has an evaluation unit 7, which is connected to the touch-sensitive surface 3 and to the distance sensor 6. The evaluation unit 7 can thus detect a touch of the touch-sensitive surface 3 by a user and receive the sensor signal from the distance sensor 6.

[0078] To carry out a method according to the invention for calibrating the user input device 1, an external computing unit 8 connected to the evaluation unit 7 can optionally be provided. Alternatively, the evaluation unit 7 can assume the function of the external computing unit 8.

[0079] To carry out the calibration method according to the invention, a first calibration step is performed prior to mounting the user input device 1 in the motor vehicle. During this step, a relationship between the change in actuation force and the change in the sensor signal is determined. The user input device 1 is then installed in the motor vehicle in an assembly step. A second calibration step is then performed to correct the relationship determined in the first calibration step and thereby compensate for bending or prestressing of the component 2 that occurs or changes during installation in the motor vehicle. For this purpose, an actual value of the sensor signal is determined in the second calibration step while no actuation force is exerted on the component 2, and the relationship is corrected based on the actual value.

[0080] For example, a conversion table that assigns a correction factor to the actual value can be stored on a memory unit (not shown) of the user input device 1, in particular the evaluation unit 7. The relationship between the change in the actuating force and the change in the sensor signal from the first calibration step can then be multiplied by the correction factor to calibrate the relationship. For this purpose, the gradient of the relationship can, in particular, be multiplied by the correction factor if the relationship is linear or approximately linear.

[0081] The evaluation unit 7 can then, depending on the corrected relationship, determine a threshold value corresponding to a predetermined minimum force associated with the actuation by a user. In other words, a minimum force is predetermined, whereby an actuation of the user input device 1 by a user is only to be detected if, on the one hand, the touch-sensitive surface 3 is touched and, on the other hand, at least an actuation force equal to the predetermined minimum force is exerted on the component 2, which leads to a corresponding change in the distance d and, in turn, can be detected by a change in the sensor signal. By determining the threshold value based on the corrected relationship, it is ensured that the threshold value used by the evaluation unit to verify the actuation is actually the predetermined value for the minimum force.Component tolerances and bending or prestressing during the manufacture and assembly of the user input device 1 can thus be compensated.

[0082] The first calibration step can be performed using the external computing unit 8 or alternatively using the evaluation unit 7. The second calibration step is preferably performed using the evaluation unit 7.

[0083] In Fig. 2 A further exemplary embodiment of the user input device 1 according to the invention is shown schematically, wherein the evaluation unit 7 and the external computing unit 8 are not shown for the sake of clarity.

[0084] In the example of Fig. 2 The distance sensor 6 is designed, for example, as an active optical sensor system that contains an emitter unit (not shown), for example an infrared laser diode or an infrared LED, and a detector unit (not shown), for example with one or more optical detectors, such as one or more photodiodes. The emitter unit emits light 10a in the direction of the reference element 4, and the detector unit detects reflected portions 10b of the light that are reflected by the reference element 4. The sensor signal can then be generated, for example, proportional to the detected intensity of the reflected portions 10b, and thus represents the distance d.

[0085] As also in Fig. 2 As shown, the reference element 4 can be designed, for example, as a plunger or in the shape of a stamp, and is connected to the component 2. The plunger can be connected to the circuit carrier 5 on a side facing the distance sensor 6, for example by a rubber membrane 9 or a similar sealing element, so that the distance sensor 6 is completely enclosed by the rubber membrane 9 and the reference element 4 as well as the circuit carrier 5. In this way, contamination of the area between the plunger and the distance sensor 6 can be prevented, which increases the reliability of the distance measurement in the long term. The rubber membrane 9 is designed to be flexible so that the plunger can still move relative to the distance sensor 6. The rubber membrane can advantageously also generate a restoring force which, when the user no longer exerts any actuating force on the component 2, returns the plunger to the neutral position.

[0086] In Fig. 2 Component 2 is schematically shown as an essentially flat plate. In Fig. 3 und Fig. 4 is the user input device 1 of the Fig. 2 shown again, with different deformations of component 2 being outlined. These different deformations, in particular a concave deformation in Fig. 3 and a convex deformation in Fig. 4 , can be caused, for example, by the design of the component 2, by internal stresses in the component 2 or by stresses or deformations due to the mounting of the user input device 1 in the motor vehicle.

[0087] Depending on how component 2 is subjected to corresponding preloads or forces, a given actuation force can lead to a greater or smaller change in distance and, accordingly, to a different change in the sensor signal. The two-stage calibration according to the inventive method takes this into account, ensuring that the correct threshold value for the sensor signal is always available.

[0088] In the Fig. 6 bis Fig. 8 Schematically, exemplary curves of the correction factor as a function of the actual value of the sensor signal are shown. In the example of the Fig. 6 For example, a concave bias of the aperture, as used in Fig. 3 is outlined.

[0089] The sensor signal is plotted on the horizontal axis, the correction factor on the vertical axis. The value S 0 corresponds to a value of the sensor signal before the installation of the user input device 1 in the motor vehicle. Accordingly, the correction factor at S 0 is equal to 1. The value S 1 corresponds to the actual value of the sensor signal measured in the second calibration step. In the example of the Fig. 6 this is greater than S 0 and the corresponding correction factor is less than 1.

[0090] Accordingly, in Fig. 7 schematically a course of the correction factor for a convex component 2, as shown in Fig. 4 Here, for example, the value S 1 is smaller than the value S 0 and the correction factor is correspondingly greater than 1.

[0091] It should be emphasized that the course of the correction factor as a function of the sensor signal or the actual value of the sensor signal depends on the specific conditions of the individual case and therefore cannot necessarily be specified universally, but can be determined by experiment. In particular, the course is not necessarily decreasing as in Fig. 6 und Fig. 7 is outlined. Schematically, Fig. 8 another curve for the correction factor as a function of the actual value of the sensor signal is shown, which also corresponds to a concave aperture, as in Fig. 3 Here the value S 1 , as well as for Fig. 6 shown, is greater than the value S 0 , but the correction factor is greater than 1 in this specific situation.

[0092] As described in particular with reference to the figures, the invention makes it possible to increase the reliability of the detection of the actuation of a user input device with a touch-sensitive surface.

[0093] In so-called smart user interfaces, the panel used as the control surface can be curved to varying degrees. This is due, for example, to the injection molding process used to manufacture the panel, for example, from polycarbonate and polyurethane, and the corresponding post-annealing process. Depending on the curvature, internal stresses, and interaction with other mechanical parts of the user input device, a different deflection of the panel can be detected for an actuation with the same actuation force at the same location. In addition, additional bending and / or tensioning of the panel occurs due to the screwing of the user input device into the vehicle's dashboard.

[0094] Depending on how strongly the aperture is curved or distorted, an actuation with a defined force at the same location, for example a touch button or soft key, will result in a different deformation path that can be measured.

[0095] To counteract both mechanical tolerances and aperture distortion, as well as the potential falsification of calibration by screwing or mounting the user input device into the motor vehicle, embodiments of the invention can, for example, implement a software-based readjustment process. Before mounting the user input device, the change in the sensor signal is calibrated accordingly. The distance between the distance sensor and a corresponding reference point after mounting, which depends on the actual aperture curvature and aperture preload, can be measured as the actual value of the sensor signal. Depending on the absolute value of the sensor signal, the calibrated relationship can be corrected, for example, using a lookup table. The lookup table and the correction factors contained therein can, for example, be determined experimentally on real parts.

Claims

1. Method for calibrating a user input apparatus (1) for a motor vehicle, wherein - the user input apparatus (1) - has a component (2) having a touch-sensitive surface (3) and a reference element (4) mechanically connected to the component (2); - has a circuit carrier (5) and a distance sensor (6), which is arranged on the circuit carrier (5) and is configured to generate a sensor signal depending on a distance of the reference element (4) from the distance sensor (6); and - has an evaluation unit (7), which is configured to detect an actuation of the user input apparatus (1) when the touch-sensitive surface (3) is touched by a user and simultaneously an actuating force is exerted on the touch-sensitive surface (3) which is greater than or equal to a specifiable minimal force; characterized in that - in a first calibration step, a first relationship is determined between a change of the actuating force and a change of the sensor signal; - the user input apparatus (1) is installed in the motor vehicle in an installation step after carrying out the first calibration step; - in a second calibration step after carrying out the installation step, a first actual value of the sensor signal is determined and the first relationship is corrected depending on the first actual value; - a first actuating force having a nonzero first force value is exerted on the touch-sensitive surface (3) and a first value of the sensor signal is determined during the exertion of the first actuating force; - in each of a large number of iterations, a second actuating force having a nonzero second force value is exerted on the touch-sensitive surface (3) and a second value of the sensor signal is determined during the exertion of the second actuating force; and - for each of the large number of iterations, the change of the sensor signal is determined as the difference between the first value and the second value of the sensor signal in order to determine the first relationship in the first calibration step.

2. Method for calibrating a user input apparatus (1) according to Claim 1, characterized in that the first actual value of the sensor signal is determined while no actuating force is exerted on the touch-sensitive surface (3).

3. Method for calibrating a user input apparatus (1) according to either of the preceding claims, characterized in that to determine the first actual value of the sensor signal, light (10a) is emitted in the direction of the reference element (4) by means of an emitter unit of the distance sensor (6) and portions (10b) of the light (10a) reflected by the reference element (4) are acquired by means of a detector unit of the distance sensor (6).

4. Method for calibrating a user input apparatus (1) according to any one of the preceding claims, characterized in that to correct the first relationship, a correction factor is determined depending on the first actual value of the sensor signal and the first relationship is multiplied by the correction factor.

5. Method for calibrating a user input apparatus (1) according to Claim 4, characterized in that the correction factor is determined based on a specified further relationship which assigns the correction factor to the first actual value.

6. Method for calibrating a user input apparatus (1) according to any one of the preceding claims, characterized in that - the first relationship is determined at a first temperature value of an ambient temperature of the user input apparatus (1); - in the first calibration step, a second relationship is determined between the change of the actuating force and the change of the sensor signal at a second temperature value of the ambient temperature; - the first actual value is determined in the second calibration step at the first temperature value of the ambient temperature; and - in the second calibration step, a second actual value of the sensor signal is determined at the second temperature value of the ambient temperature and the second relationship is corrected depending on the second actual value.

7. Method for calibrating a user input apparatus (1) according to any one of the preceding claims, characterized in that a threshold value is determined, which corresponds to a change of the actuating force according to the corrected first relationship, the value of which is equal to a specified value for the minimal force and the threshold value is stored on a storage unit of the user input apparatus (1).

8. Method for detecting an actuation of a user input apparatus (1) of a motor vehicle, characterized in that - a method for calibrating a user input apparatus (1) according to Claim 7 is carried out; - after the correction of the first relationship, a further actual value for the sensor signal is determined; - a difference between the first actual value and the further actual value is compared by means of the evaluation unit (7) to the stored threshold value; and - the actuation of the user input apparatus (1) is only detected by means of the evaluation unit (7) if the difference between the first actual value and the further actual value is greater than the threshold value.

9. Method for detecting an actuation of a user input apparatus (1) according to Claim 8, characterized in that - a touch of the touch-sensitive surface (3) is detected by means of the evaluation unit (7); and - the actuation of the user input apparatus (1) is only detected by means of the evaluation unit (7) if the difference between the first actual value and the further actual value is greater than the threshold value while the touch of the touch-sensitive surface (3) is detected.

10. User input apparatus (1) for a motor vehicle, comprising - a component (2) having a touch-sensitive surface (3) and a reference element (4) mechanically connected to the component (2); - a circuit carrier (5) and a distance sensor (6), which is arranged on the circuit carrier (5) and is configured to generate a sensor signal depending on a distance of the reference element (4) from the distance sensor (6); - a storage unit, which stores a first relationship between a change of an actuating force exerted on the touch-sensitive surface (3) and a change of the sensor signal; and - an evaluation unit (7), which is configured to carry out a method according to either of Claims 8 and 9 and to detect a touch of the touch-sensitive surface (3) by a user, to receive the sensor signal from the distance sensor (6), to determine a first actual value of the sensor signal, and to correct the first relationship depending on the first actual value.

11. User input apparatus (1) according to Claim 10, characterized in that the evaluation unit (7) is configured to determine a threshold value which corresponds to a change of the actuating force according to the corrected first relationship, the value of which is equal to a specified value for the minimal force, and to store the threshold value on the storage unit.

12. User input apparatus (1) according to Claim 11, characterized in that the evaluation unit (7) is configured - to determine a further actual value for the sensor signal after the correction of the first relationship; - to compare a difference between the first actual value and the further actual value to the stored threshold value; and - to detect an actuation of the user input apparatus (1) by means of the evaluation unit (7) only if the difference between the first actual value and the further actual value is greater than the threshold value.

13. User input apparatus (1) according to Claim 12, characterized in that the evaluation unit (7) is configured to detect the actuation of the user input apparatus (1) only if the difference between the first actual value and the further actual value is greater than the threshold value while the touch of the touch-sensitive surface (3) is detected.

14. Motor vehicle having a user input apparatus (1) according to any one of Claims 10 to 13.