Apparatus and methods for calibrating capacitive touch sensor systems

Abstract

This invention relates to a method and calibration apparatus for calibrating a touch sensor system comprising multiple capacitive touch sensors. The method includes: measuring individual capacitance values ​​of the touch sensors; determining a specific comparison value for each touch sensor, the comparison value representing the magnitude of any difference between the measured capacitance value involved and an initial baseline capacitance value previously determined for said touch sensor, and the comparison value being positively correlated with the magnitude of the difference; determining a compensation value based on the comparison value, wherein the compensation value is determined such that the value lies between a maximum and a minimum value of the comparison value, or is equal to the value among the comparison values ​​representing the maximum excess of the initial baseline capacitance value relative to the associated measured capacitance value; and, when using the touch sensor system to detect a touch, taking into account the determined compensation value by correcting the measured capacitance value or the initial baseline capacitance value of the touch sensor based on the compensation value. The invention also relates to the touch sensor system itself and a computer program configured to perform the method.

Description

Technical Field

[0001] This invention relates to a method and calibration apparatus for calibrating a touch sensor system comprising multiple capacitive touch sensors, particularly when activating a touch sensor system, and to the corresponding touch sensor system itself including the touch sensors and the calibration apparatus. Furthermore, this disclosure relates to a computer program configured to perform the method. Background Technology

[0002] Capacitive touch sensors operate based on changes in capacitance of a single capacitor or capacitor system to detect the approach of an object, particularly a human finger, to the sensor, or specifically, to the touch of that object on the sensor. This ability of touch sensors to accurately detect proximity or touch is often heavily dependent on external influences and conditions, particularly temperature, humidity, and the aging process.

[0003] In the following text, unless otherwise specified, the term "touch" should be understood to include, in addition to actual touch, the proximity of an object (specifically a human finger) to the touch sensor, where no actual touch occurs, but the object is close enough to the touch sensor that, according to the specifications or configuration of the touch sensor system, that proximity will be detected as a touch. Typically, according to such configuration specifications, proximity here includes distances of only a few millimeters, such as 5 mm or less. However, it is also possible for a touch sensor system to evaluate only actual touch as a touch.

[0004] When a touch sensor system based on such a capacitive touch sensor is activated, particularly when it is powered on (i.e., upon power-on), or when one or more touch-dependent functions are subsequently activated, the external influences acting on the touch sensor system are often not yet fully known to the touch sensor system itself, and therefore may not reliably detect any touch. Consequently, the reliability of touch detection is generally insufficient. In the case of false detection—that is, no actual touch is detected, or a touch is detected even though there is no actual touch—the reliability of touch detection in the known system typically only improves from the second touch onwards, at which point the system can quantify the external influence based on the different sensor signals until that point appears in cases of touching on one side and not touching on the other, and infer the external influence in the sense of so-called baseline adjustment. Therefore, reliable detection of the correct touch state (touch or no touch) is not provided immediately after system activation. This is especially true if the corresponding sensor has already been touched during system activation. Therefore, in such cases, user input is never immediately detected, or may even be detected incorrectly, leading to a correspondingly poor user experience. Summary of the Invention

[0005] The purpose of this invention is to further improve the reliability of capacitive touch sensor systems.

[0006] This problem is solved according to the teachings of the independent claims. Various embodiments and developments of the invention are the subject of the dependent claims.

[0007] The first aspect of the invention relates to a method, particularly a computer-implemented method, for calibrating a touch sensor system comprising a plurality of capacitive touch sensors, particularly when activating the touch sensor system. The method includes: (i) measuring individual capacitance values ​​of touch sensors, wherein measurements may be taken simultaneously or within a defined measurement period (e.g., 5 seconds or less, preferably 1 second or less); (ii) determining a specific comparison value for each touch sensor, the comparison value representing the magnitude (particularly as a difference or ratio or based thereon) of any difference between the measured capacitance value involved and an initial baseline capacitance value previously determined for the touch sensor, the comparison value being individually applicable to each touch sensor or uniformly applicable to all touch sensors, and the comparison value being positively correlated with the magnitude of the difference; (iii) determining a compensation value based on the comparison value, wherein the compensation value is determined such that the value lies between a maximum and a minimum comparison value, or equal to the comparison value representing the maximum capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value, or the value representing the minimum capacitance excess of the associated measured capacitance value (C) relative to the initial baseline capacitance value (B0); and (iv) taking into account the determined compensation value when using the touch sensor system to detect a touch, by correcting the measured capacitance value of the touch sensor or the initial baseline capacitance value based on the compensation value.

[0008] In the context of this invention, a "touch sensor system" is a sensor system comprising multiple capacitive touch sensors and designed to perform touch detection by means of these touch sensors, the touch detection being based on changes in capacitance of a capacitor or capacitor system in each touch sensor. Specifically, the touch sensor system can be configured such that each touch sensor can individually detect a touch by an object. Based on the presence of multiple touch sensors in the touch sensor system, touches at different locations corresponding to different positions of each touch sensor can be detected.

[0009] "Capacitance value" should be understood as a value, in particular a numerical value, which represents the absolute or relative size of the capacitance provided as a measuring capacitance in the relevant touch sensor to which that capacitance value is assigned.

[0010] The "baseline capacitance value" should also be understood as a value, specifically a numerical value, representing the absolute or relative magnitude of the capacitance provided as a measurement capacitance in the relevant touch sensor to which that capacitance value is assigned. Unlike the "capacitance value" of the touch sensor, which is determined solely in the process described above, the baseline capacitance value is predetermined. This can be accomplished, in particular, based on capacitance measurements taken under specific standard conditions, or through other predefined methods, for example, based on the specific sensor design of the touch sensor. Therefore, the baseline capacitance value can be understood, in particular, as a reference capacitance value for the touch sensor, representing the nominal capacitance value of the touch sensor's measurement capacitance, which is free from external influences that typically arise and are generally variable in the actual use of touch sensor systems.

[0011] Therefore, the "capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value" for a specific touch sensor involves a situation where the capacitance represented by the initial baseline capacitance value of the touch sensor is greater than the capacitance represented by the capacitance value measured by the touch sensor within the processing range. Conversely, the "capacitance excess of the associated measured capacitance value relative to the initial baseline capacitance value" for a specific touch sensor involves a situation where the capacitance represented by the initial baseline capacitance value of the touch sensor is less than the capacitance measured by the touch sensor within the processing range. If the two values ​​are equal, the capacitance excess is zero.

[0012] Since capacitance is always positive, it is advantageous to define the capacitance value and the baseline capacitance value as positive. In this case, the compensation value is determined based on the comparison value, such that the compensation value is less than the largest comparison value and greater than or equal to the smallest comparison value. However, in principle, the reverse is also conceivable, where the capacitance value and the baseline capacitance value are defined as negative. In this case, the compensation value is then determined based on the comparison value, such that the compensation value is greater than the smallest comparison value and less than or equal to the largest comparison value. In the following text, the capacitance value and the baseline capacitance value are always defined as positive, but this should not be construed as restrictive.

[0013] In the process of using a touch sensor system for touch detection, consideration of the determined compensation value may specifically involve the capacitance measurement measured within the scope of the process, which thus simultaneously represents the first measurement value for touch detection. Additionally or alternatively, it may refer to the use of the touch sensor system for touch detection in further subsequent use, particularly over a relatively long period of time, which may specifically continue until the next subsequent (re)activation of the touch sensor system.

[0014] Using the method described above, not only can the calibration of the touch sensor system be performed in a simple manner, but reliable detection of touch or non-touch on each touch sensor can also be achieved. Therefore, for example, during calibration, particularly when the touch sensor system is activated, the correct finger position on a control panel comprising multiple touch sensors has been reliably detected using corrections based on compensation values ​​determined according to this method. For instance, if one or more touch sensors have been touched (or not touched) when the touch sensor system is started, in each case, based on the correction and the first capacitance measurement, this can be reliably detected immediately upon startup (“real power-on”), without the need for further measurements first, i.e., a second (or third, etc.) touch or non-touch of the touch sensor for calibration purposes.

[0015] Furthermore, regarding other possible solutions for achieving "true power-on," according to this method, it is also unnecessary to perform (re)calibration while the touch sensor system is disabled, especially at regular intervals, to repeat baseline adjustments accordingly. Therefore, the associated calibration work, and particularly the associated energy consumption, can be avoided. Moreover, unlike the mentioned alternatives, calibration according to this method can also satisfy the "true power-on" condition if there is a power interruption when the touch sensor system is disabled.

[0016] Specifically, the method is based on the premise that external influences affecting all touch sensors of a touch sensor system are different from individual influences that may occur at the touch sensors due to a single touch or object proximity, and the system calibration is performed using compensation values ​​that are the same for all touch sensors and determined based on external influences that are substantially the same for all touch sensors.

[0017] Preferred embodiments of the method will now be described below. Unless explicitly excluded or technically impossible, each embodiment may be combined with each other as needed, as well as with other aspects of the invention as further described herein.

[0018] In some embodiments, the compensation value is determined such that a comparison value representing the maximum capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value is determined as the compensation value, or a comparison value representing the minimum capacitance excess of the associated measured capacitance value (C) relative to the initial baseline capacitance value (B0) is determined as the compensation value. As described above, according to these embodiments, particularly when the capacitance value and the baseline capacitance value are defined as positive, the compensation value is determined based on the comparison value such that the compensation value is determined to be the minimum value equal to the (signed) comparison value.

[0019] This is based on the understanding that, depending on the type of influence, external influences on capacitance measurement can either increase or decrease the measured capacitance value, while the proximity or touch of a human finger on a capacitive touch sensor always has an effect in only one direction. Specifically, when the capacitance value is defined as positive, such proximity or touch always has a positive effect in the sense of increasing the measured capacitance value (conversely, in the opposite case, i.e., defined as negative).

[0020] According to these embodiments, the compensation value is thus determined in such a way that the comparison value most likely corresponding to the non-touch state of the corresponding touch sensor is set as the compensation value, because in this case, the capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value of the touch sensor is maximized. In this way, calibration of the touch sensor system, particularly baseline matching, can be achieved, resulting in particularly reliable touch detection.

[0021] However, according to other embodiments, the compensation value is determined in such a way that the mean or median of the distribution of comparison values ​​is determined as the compensation value. This has the advantage of relative suppression of distribution extrema, so that, accordingly, measurements based on any measurement error or special external influence occurring only on a single touch sensor or a subset of touch sensors are less likely to falsify the determination of the compensation value and thus falsify the calibration as a whole, thereby making the calibration more robust.

[0022] Specifically, according to relevant embodiments, determining the compensation value may include: (i) establishing the average or median of the comparison value distribution as the initial value of the compensation value; (ii) determining those touch sensors whose measured capacitance values ​​indicate no touch as untouched touch sensors based on the correction of the measured values ​​based on the initial value of the compensation value; and (iii) establishing the average or median of the comparison value distribution of the determined untouched touch sensors as the final value of the compensation value. By correcting the measured capacitance value or baseline capacitance value of the touch sensor based on the compensation value, the determined compensation value is taken into account when performing touch detection using the touch sensor system. Advantageously, in this way, the multi-step determination based on the compensation value can achieve further improvement in calibration reliability, especially in baseline adjustment reliability, because ultimately, those comparison values ​​previously considered to correspond to possible non-touch states are used first, and therefore these comparison values ​​are particularly suitable as references for determining the correction embodied in the compensation value.

[0023] Furthermore, according to relevant embodiments, only those comparison values ​​from the comparison value distribution (which, according to predetermined filtering criteria, do not represent extreme values ​​within the comparison value distribution) can be used to determine the average or median. Since extreme values ​​within the comparison value distribution, particularly those based on limiting capacitance values, are caused with a higher probability by incorrect measurements or sensor-specific external influences, this filtering of the comparison results used to determine the compensation value makes it possible to achieve higher reliability in determining the compensation value, thereby improving the reliability of touch sensor systems calibrated based on compensation values.

[0024] In another related embodiment, the touch sensor system may further include a capacitive reference sensor disposed within the touch sensor system, such that a user of the touch sensor system cannot touch it at all, or at least cannot easily touch it with the same hand as one of the touch sensors. Furthermore, the method herein includes: (i) measuring the capacitance value of the reference sensor; (ii) determining a comparison value for the reference sensor, which represents the magnitude of any difference between the measured capacitance value of the reference sensor and a predetermined initial baseline capacitance value of the reference sensor, and the comparison value is positively correlated with the magnitude of the difference. In addition to the comparison values ​​from the comparison value distribution of the touch sensors, the comparison values ​​of the reference sensor are also used herein to determine the average or median.

[0025] Specifically, the capacitive reference sensor is arranged in the touch sensor system in such a way that, if designed to prevent touch, the user of the touch sensor system cannot touch it at all. This can be, for example, if (i) the reference sensor is arranged such that none of the electrodes used for capacitance measurement are located on or directly below the surface of the touch sensor system (i.e., so that touch with the surface above it can still be reliably detected), or if (ii) even if at least one electrode is located on or directly below the surface, a finger cannot touch that electrode or the surface portion directly above it. Specifically, if the reference sensor is arranged to be, in principle, touch-sensitive and therefore detectable, it is not easy to touch the capacitive reference sensor with the same hand as one of the touch sensors; however, the arrangement of the reference sensor relative to the touch sensors in the touch sensor system makes it, at least nearly impossible, for the user of the touch sensor system to unintentionally touch both the reference sensor and one of the touch sensors simultaneously with the same hand, due to the distance or geometry of the touch sensor system.

[0026] In a further related embodiment, the touch sensor is integrated into the control panel, and a reference sensor is positioned at a distance from the control panel and configured to detect touch. Specifically, this distance can be selected such that the reference sensor cannot, or at least is not easily, operated simultaneously by the user's same hand and the control panel. In this way, a capacitive sensor already existing for other purposes (i.e., touch detection) can be used as the reference sensor in a multi-purpose ("multi-purpose" or "dual-purpose") sense, which improves the efficiency of the touch sensor system.

[0027] Specifically, according to relevant embodiments, the reference sensor may be a capacitive sensor of a second control panel comprising multiple capacitive sensors, and the method may further include: (i) measuring individual capacitance values ​​of the sensors of the second control panel; (ii) determining a specific comparison value for each sensor of the second control panel, the comparison value representing the magnitude of any difference between the measured capacitance value of the particular sensor and an initial baseline capacitance value previously determined for said sensor, and the comparison value being positively correlated with the magnitude of the difference; and (iii) selecting a sensor of the second control panel having a certain comparison value from these sensor comparison values ​​as a reference sensor, the comparison value representing the maximum capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value. The previous descriptions regarding capacitance value measurement, determination of comparison values ​​for the touch sensors (here, the first control panel), and capacitance excess are hereby revised as necessary. In this way, the reliability achievable by the touch sensor system is further improved because the capacitive sensor of the second control panel is selected as the reference sensor, which is particularly suitable as a reference sensor due to its highly probable "untouched" touch state.

[0028] According to some embodiments, when touch detection is performed using a touch sensor system, consideration of the determined compensation value includes calibrating each touch sensor by at least one or a combination of the following correction measures: (i) determining a compensated baseline capacitance value associated with a particular touch sensor by compensating at least proportionally to an initial baseline capacitance value associated with that touch sensor based on the compensation value; and (ii) determining a corrected touch detection threshold associated individually with a particular touch sensor based on the compensation value by compensating at least proportionally to a predetermined associated initial touch detection threshold, particularly individually or for all touch sensors. Here, the touch detection threshold defines a capacitance threshold used to detect a touch of an object to a touch sensor. In particular, compensation can be performed by adding a compensation value to a particular initial baseline value. While variant (i) represents baseline adjustment in the narrow sense, which allows the use of the same touch detection threshold for all touch sensors, variant (ii) allows keeping the baseline value unchanged by using a sensor-specific touch detection threshold instead.

[0029] According to some embodiments, the method further includes: (i) identifying touch sensors that indicate the presence of a touch based on their calibrated capacitance values ​​as touched touch sensors; and (ii) outputting an output signal identifying the touched touch sensor. Therefore, in addition to the actual calibration, actual touch measurements are also performed here. Both can be done in this way, particularly based on the same capacitance measurement results, thus eliminating the need for both multiple measurements for calibration and actual touch measurements.

[0030] According to some embodiments, the method further includes: when measuring the capacitance value of each touch sensor, high-pass filtering the sensor signals generated by each touch sensor to filter out low-frequency signal components from the signals. Since low-frequency signals are typically not generated by an object touching the touch sensor, signal components that may be caused by external influences and could potentially weaken, or in particular, spoof, the measurement results can be filtered out in advance, ensuring that these signal components do not have any further impact during the calibration of the touch sensor system. In this way, the achievable reliability of the system can be further improved.

[0031] A second aspect of the invention relates to a calibration apparatus for calibrating a touch sensor system comprising a plurality of capacitive touch sensors. The apparatus is configured to perform the method according to the first aspect.

[0032] A third aspect of the invention relates to a touch sensor system comprising a plurality of capacitive touch sensors and a calibration device according to a second aspect, wherein the touch sensor system is configured, particularly when activated, to perform calibration of the touch sensor system by means of the calibration device according to a method according to a first aspect.

[0033] According to some embodiments, touch sensor systems can be specifically configured as input systems for user interfaces in vehicles. Specifically, touch sensor systems can be specifically configured here as input systems for user interfaces arranged on the steering system of a vehicle. When using touch sensor systems as input interfaces in vehicles, these vehicle-related embodiments can improve operational reliability and simultaneously lead to safety gains because they can reduce or even avoid lengthy, multiple inputs that could distract the driver due to incorrect or delayed touch recognition.

[0034] The fourth aspect of the invention relates to a computer program comprising instructions which, when run by a computer, particularly by a processor of a calibration device according to the second aspect, cause the computer to perform a method according to the first aspect.

[0035] Specifically, the computer program can be stored on a non-volatile data carrier. This is preferably a data carrier in the form of an optical data carrier or a flash memory module. This can be advantageous if such a computer program can be processed independently of a processor platform running one or more programs. In another embodiment, the computer program can exist as a file on a data processing unit, particularly on a server, and can be downloaded via a data link, such as the Internet or a dedicated data link, such as a proprietary or local network. Furthermore, the computer program can have multiple independent interactive program modules.

[0036] Therefore, the calibration device according to the second aspect or the touch sensor system according to the third aspect may accordingly have a program memory for storing computer programs. Alternatively, the calibration device or touch sensor system may also be configured to access externally available computer programs via a communication link, such as computer programs on one or more servers or other data processing units, particularly for exchanging data used in the operation of the method or computer program or data constituting the output of the computer program.

[0037] The features and advantages explained with respect to the first aspect of the invention also apply to the other aspects of the invention accordingly. Attached Figure Description

[0038] Other advantages, features and applications of the present invention can be found in the following detailed description taken in conjunction with the accompanying drawings.

[0039] In the attached diagram:

[0040] Figure 1 An exemplary touch sensor system according to a first embodiment is schematically illustrated, including a plurality of touch sensors and a calibration device according to an embodiment of the present invention, and an exemplary arrangement of the touch sensor system as a user interface for touch input on a vehicle steering device;

[0041] Figure 2 An exemplary touch sensor system according to a second embodiment is schematically shown, wherein the touch sensor system has two different control panels and is configured as a user interface on a vehicle steering device;

[0042] Figure 3 A flowchart illustrating a first preferred embodiment of a method according to the present invention is shown, which is based on a specific selection of a comparison value as a compensation value;

[0043] Figure 4 A schematic diagram based on the first example is shown, illustrating the following: Figure 3 Baseline correction of the method; and

[0044] Figure 5A schematic diagram based on the second example is shown, illustrating the following: Figure 3 Baseline correction using methods;

[0045] Figures 6A-6C A flowchart illustrating a second preferred embodiment of the method according to the invention is shown, which determines a compensation value based on the averaging of comparison values; and

[0046] Figure 7 A schematic diagram is shown according to an example, illustrating the following: Figures 6A-6C Baseline correction using the method.

[0047] In the accompanying drawings, the same reference numerals are always used for the same or corresponding elements of the invention. Detailed Implementation

[0048] according to Figure 1 An exemplary touch sensor system 100 includes a plurality of (four in this example) capacitive touch sensors 110a to 110d, which may be arranged, in particular, in a (first) control panel 105 of the touch sensor system 100. Furthermore, the touch sensor system 100 includes a capacitive reference sensor 115, which is preferably arranged such that it cannot be directly touched by a user of the touch sensor system 100. This has the advantage that the reference sensor 115 can be well and approximately considered unaffected by external influences originating from the user (especially the user's hand) on its measurement capabilities. Additionally, the touch sensor system 100 includes a calibration device 120 having a processor unit 125 and a program and data memory 130 coupled thereto. The processor unit 125 may, in particular, include one or more microprocessors, and may be configured, in particular, as a microcontroller. The method according to the invention may be configured, in particular, as a computer-implemented method, and for this purpose, a corresponding program configured to execute the method on the processor unit 125 may be stored in the memory 130.

[0049] according to Figure 1 The touch sensor system 100 can be specifically configured as a user interface in a vehicle, for example, for placement on the steering mechanism 135, particularly on the steering wheel. Figure 2 An exemplary embodiment of this aspect is shown.

[0050] According to Figure 1In the extension of the touch sensor system 100, in addition to the first control panel 105, another control panel 140 is provided, each of which has multiple capacitive sensors, four in each example, arranged in an exemplary matrix in each control panel. Hereinafter, the touch sensor of the first control panel 105 will be specifically referred to as a "touch sensor," while for better explanation, the capacitive sensor of the second control panel 140 (however, it is also technically a touch sensor) will not be so referred to. At least the capacitive sensor of the first control panel 105 can be calibrated by the calibration device 120, specifically according to the following reference... Figures 3 to 7 One of the methods described. Preferably, this also applies to the capacitive sensor of the second control panel. In addition to, or instead of, a dedicated reference sensor, a selected touch sensor of the second control panel is used as a reference sensor 115 for calibration according to... Figure 2 The touch sensors 100a to 100d are located in the first control panel 105 of the touch sensor system. Correspondingly, the reverse is also possible.

[0051] References from Figure 3 Flowcharts and from Figure 4 and 5 Examples will now be provided by referring to [source]. Figure 1 The example of a touch sensor system 100 is used to explain a first preferred embodiment 200 of the method according to the invention, which is based on a specific selection of a comparison value as a compensation value. Method 200 is preferably performed when the touch sensor system is activated, particularly when it is started, and thus begins in step 205 with the activation of the touch sensor system 100. However, it may alternatively be performed at other times, particularly each time a measurement is to be performed, or at regular time intervals. Therefore, “activating” the touch sensor system should be specifically understood as any triggering of the touch sensor system’s operating or calibration mode.

[0052] Then, in step 210, the individual capacitance values ​​C of the touch sensors 110a to 110d of the touch sensor system 100 are measured. In order to suppress low-frequency signal components in the measurement signals provided by the touch sensors 110a to 110d that may be caused by external influences, the sensor signals are preferably subjected to high-pass filtering.

[0053] Based on the capacitance value C measured in step 210 and the individual baseline capacitance value B0 pre-determined for each of the touch sensors 110a to 110d, which is typically determined under standard factory conditions during its characterization prior to delivery of the touch sensor system, an individual comparison value V is now determined for each of the touch sensors 110a to 110d in step 215. This can be specifically accomplished in such a way that the difference between the measured capacitance value C of a particular touch sensor and the initial baseline capacitance value B0 is selected as the comparison value V, i.e., V = C - B0.

[0054] Figure 4 (a) and 5(a) show two different examples of determining these respective compensation values ​​V of touch sensors 110a to 100d using this difference formula, based on the set of associated initial baseline capacitance values ​​B0 and the capacitance value C measured in step 210. Figure 4 In case (a), a negative compensation value is obtained.

[0055] Then, in a further step 220, a (signed) minimum comparison value Vmin is determined from the set of compensation values ​​V determined in step 215, and is set as the compensation value C in step 225, which can be consistent with step 220. One motivation for this choice is that, depending on the nature of the external influence, it can have a positive or negative effect on the measured capacitance value C of the touch sensor, and thus can increase or decrease the measured capacitance value C, while the influence of touch on the touch sensor, especially the influence of a human finger, usually only has the effect of increasing capacitance.

[0056] If the smallest comparison value, Vmin, is chosen at this point, then, as suggested herein, this corresponds to selecting the least likely or most potentially unaffected value from the capacitance value K measured in step 210. Since the compensation value is intended as a measure of approximate external influence and is assumed to be the same for all touch sensors in the absence of touch, this selection is generally a good estimate of the compensation value that can be used for this purpose. Figure 4 In each of (a) and 5(a), the comparison value V of the touch sensor 110b represents the minimum comparison value Vmin selected as the compensation value.

[0057] At this point, in step 230, the initial baseline capacitance value B0 of each of the touch sensors 110a to 110d in the touch sensor system 100 can be corrected based on the determined compensation value Vmin. Specifically, for this purpose, this can be accomplished by adding the compensation value in a signed manner to a particular initial baseline capacitance value B0 to obtain a corrected baseline capacitance value Bk. This is in Figure 4As shown in (b) and 5(b), while retaining the measured capacitance value C, the corrected baseline capacitance value Bk has been determined based on the determined compensation value Vmin by adding the compensation value Vmin to the corresponding initial baseline capacitance value B0, i.e.: Bk = B0 + Vmin.

[0058] In a further step 235, the touch state of each of the touch sensors 110a to 110d can now be determined based on the corresponding measured capacitance value C and the corresponding calibration baseline capacitance value Bk. For this purpose, a difference between the two is formed to determine a separate calibrated comparison value Vk for each of the touch sensors 110a to 110d, i.e.: Vk = C - Bk. In this example, the touch state of each touch sensor can be determined by comparing the calibrated comparison value Vk with a detection threshold T defined for all touch sensors as a whole, wherein a touch is detected if the associated calibrated comparison value Vk reaches or exceeds the current touch sensor's touch detection threshold T. Otherwise, a non-touch is detected. Finally, in the final step 240, an output signal representing the touch state detected by each of the touch sensors 110a to 110d can be output. This output signal can be used, in particular, as a control signal to control one or more functions corresponding to the various touch sensors, such as volume control of an entertainment system or for configuring automatic vehicle controls, especially ACC (Adaptive Cruise Control).

[0059] exist Figure 4 The comparison of Figures (a) and (b) shows the effect of the calibration performed on the compensation value Vmin. While before calibration, non-touch was detected for each of sensors 110a to 110c, and touch was detected only for touch sensor 100d, after calibration, touch was detected for both touch sensors 110a and 110d, but non-touch was detected for all other touch sensors 100b and 100c.

[0060] exist Figure 5 In another example shown in (a) and 5(b), before calibration, touch was detected for each of the two touch sensors 110c and 110d, while after calibration, touch was detected only for touch sensor 110d, but non-touch was detected for all other touch sensors 100a to 100c.

[0061] References are linked together by connectors A, B, and C. Figures 6A to 6C The flowchart, and Figure 7 For example, we will now refer to Figure 1The second preferred embodiment 300 of the method according to the invention is explained using an example of a touch sensor system 100, which determines a compensation value based on averaging (or alternatively, median) the comparison values. Method 300 is preferably performed when the touch sensor system is activated, particularly when it is started, and therefore begins in step 305 with the activation of the touch sensor system 100, as... Figure 6A As shown. However, similar to method 200, it can be performed at other times, in particular at regular intervals or each time a measurement is to be taken.

[0062] The following step is measurement step 310, which measures the individual capacitance values ​​C of touch sensors 100a to 100d, corresponding to step 210 of method 200. Optionally, a reference sensor 115 may also be provided, such as... Figure 6A -C and Figure 7 The example shown below will be explained in detail, particularly regarding touch sensor systems with two different control panels, as illustrated in the example below. Figure 2 As specifically shown in the text.

[0063] In this case, the capacitive sensor of the second control panel can be dynamically selected as the reference sensor instead of the predetermined capacitive reference sensor, as follows: Figure 6B As shown. In step 311, similar to step 310 for the first control panel, the individual capacitance value of each capacitive sensor of the second control panel is measured, where a high-pass filter can again optionally be applied to the corresponding signal. Subsequently, in step 312, similar to step 215 of method 200, an individual comparison value is determined for each sensor of the second control panel as the difference between the corresponding associated measured capacitance value of the particular sensor and a predetermined initial baseline capacitance value. To determine a reference sensor, in step 313, the sensor with the smallest comparison value among the sensors of the second control panel is selected as the reference sensor for the touch sensor system 100. The motivation for selecting the sensor with the smallest comparison value as the reference sensor is the same as the motivation previously explained for method 200 regarding the selection of the smallest comparison result Vmin as the compensation value.

[0064] At this point, refer to again Figure 6AIn a further step 315, similar again to step 215 of method 200, a separate comparison value V is determined for each of the touch sensors 100a to 100d of the first control panel 105, as the difference between the corresponding associated measured capacitance value C of each touch sensor 100a to 100d and the previously determined initial baseline capacitance value B0. In step 320, extreme values ​​can be filtered out from the resulting distribution of the comparison values ​​V of the touch sensors according to a predetermined filtering criterion, and optionally, extreme values ​​can also be filtered out from the resulting distribution of the comparison values ​​of the reference sensor, in order to protect the subsequent determination of the compensation value from potential spurious comparison values, which could be triggered, for example, by specific individual temperature fluctuations at each touch sensor (e.g., caused by selective solar radiation).

[0065] The actual determination of the compensation value then begins, which in this exemplary method 300 is performed in several steps. To this end, in step 325, an initial value for the compensation value is first set to be equal to the average of the determined feedback comparison values ​​of the touch sensor and the reference sensor (if applicable). Based on this compensation value, in step 330, a preliminary correction of the baseline capacitance value B0 of each of the touch sensors 100a to 100d in the touch sensor system 100 is performed. This can be achieved, in particular, by adding the initial value of the compensation value in a signed manner to a specific initial baseline capacitance value B0.

[0066] In step 335, the initial touch states of touch sensors 100a to 100d can be determined based on the corresponding measured capacitance value C and the corresponding pre-calibrated baseline capacitance value. The remainder of the method is... Figure 6C As shown in the diagram. Next is step 340, in which, based on the initially determined touch state, those touch sensors that were detected as "not touched" by comparing the touch detection threshold T with the corresponding comparison values ​​of the touch sensors are identified. Therefore, these untouched touch sensors are those whose comparison values ​​are below the touch detection threshold T.

[0067] At this point, in step 345, the final value of the compensation value can be determined as the average (or median, see above) of the determined filtered comparison values ​​V of the (only) untouched touch sensors and the reference sensor 115. Based on this final value of the compensation value, the final correction of the initial baseline capacitance value B0 of each of the touch sensors 100a to 100d of the touch sensor system 100 can then be performed in step 350. The corresponding final corrected baseline capacitance value Bk of a particular touch sensor can be determined specifically by adding the final compensation value M in a signed manner to the initial baseline capacitance value B0 of that particular touch sensor.

[0068] At this point, in step 355, based on a specific measured capacitance value C and a specific final corrected baseline capacitance value Bk, similar to step 235 of method 200, a corrected comparison value Vk can be calculated by means of the difference equation (Vk = C - Bk) between the measured capacitance value C and the final corrected baseline capacitance value Bk, and the respective touch state of each of the touch sensors 100a to 100d can be determined by comparing the corrected comparison value with the touch detection threshold T.

[0069] exist Figure 4 Comparing Figures (b) and 7(b), one can see the different effects determined by the different compensation values ​​of the exemplary embodiments according to the two interpretations of the method. Both figures are determined starting from the same initial value distribution of the initial baseline value B0 and the measured capacitance value C (see Figure 7(b)). Figure 4 (a) and Figure 7 (a)). Although, before calibration, non-touch will be detected for each of sensors 110a to 110c, and touch will be detected only for touch sensor 100d, but in Figure 4 In case (b), after calibration, touch is detected for touch sensors 110a and 110d, but non-touch is detected for all other touch sensors 100b and 100c. On the other hand, in Figure 7 In case (b), after calibration, non-touch was detected for all touch sensors 100b and 100c.

[0070] Finally, in step 360, an output signal may be output, similar to step 240, which represents the final determined touch state of one or more, in particular all, touch sensors.

[0071] While at least one exemplary embodiment has been described above, it must be noted that numerous variations exist in this regard. It should also be noted that the described exemplary embodiments are merely non-limiting examples and are not intended to limit the scope, applicability, or configuration of the apparatus and methods described herein. Rather, the above description will provide those skilled in the art with indications of implementation of at least one exemplary embodiment, and it should be understood that various changes may be made to the arrangement of the functional means and elements described in the exemplary embodiments without departing from the subject matter defined respectively in the appended claims or their legal equivalents.

[0072] Reference tag list

[0073] 100 Touch Sensor Systems

[0074] 105 Control Panel, especially the First Control Panel

[0075] 110a-d Touch Sensor

[0076] 115 Capacitive Reference Sensor

[0077] 120 Calibration Device

[0078] 125 processor units

[0079] 130 Program and Data Memory

[0080] 135 The vehicle's steering system, especially the steering wheel.

[0081] 140 Second Control Panel

[0082] First embodiment of the 200 calibration method

[0083] Methods 205-240: Steps of Method 200

[0084] Second embodiment of the 300 calibration method

[0085] Methods 305-360: Steps for Method 300

[0086] B0 Initial baseline capacitance value

[0087] Bk (final) corrected baseline capacitance value

[0088] C (Measurement) Capacitance Value

[0089] V Comparison Value

[0090] Vk-corrected comparison value

[0091] Vmin is the minimum comparison value, which is also the compensation value.

[0092] T touch detection threshold

[0093] M is the average of the comparison values.

Claims

1. A method (200; 300) for calibrating a touch sensor system comprising a plurality of capacitive touch sensors (100a,..., 100d), wherein the method comprises: measuring (210; 310) individual capacitance values (C) of the touch sensors (100a,..., 100d); determining (215; 315) for each of the touch sensors (100a,..., 100d) a specific comparison value (V) representing the magnitude of any difference between the involved measured capacitance value (C) and an initial baseline capacitance value (Bo) previously determined for the touch sensor, and the comparison value (V) being positively correlated to the magnitude of the difference; determining (225; 325,..., 345) a compensation value based on the comparison values, wherein the compensation value is determined such that it lies between a maximum value and a minimum value of the comparison values (V), or is equal to the value of the comparison values (V) representing the largest capacitance excess of the initial baseline capacitance value (Bo) over the associated measured capacitance value (C) or representing the smallest capacitance excess of the associated measured capacitance value (C) over the initial baseline capacitance value (Bo); and considering (235; 355) the determined compensation value by correcting the measured capacitance values (C) or the initial baseline capacitance values of the touch sensors (100a,..., 100d) based on the compensation value when touch detection is performed using the touch sensor system (100), wherein determining (325,..., 345) a compensation value such that a mean value (M) or a median value of the distribution of comparison values (V) is determined as the compensation value, the determination (325,..., 345) of the compensation value comprises: establishing (325) a mean value (M) or a median value of the distribution of comparison values (V) as a preliminary value for the compensation value; determining (340) those touch sensors (100a,..., 100d) for which the measured capacitance values (C) indicate an absence of a touch as not touched touch sensors in accordance with a correction of measurements based on the preliminary value for the compensation value (330); establishing (345) a mean value or a median value of the distribution of comparison values (V) of the determined not touched touch sensors (100a,..., 100d) as a final value for the compensation value, wherein, when touch detection is performed using the touch sensor system (100), the measured capacitance values (C) or baseline capacitance values of the touch sensors (100a,..., 100d) are corrected (350) based on the compensation value considering (355) the determined compensation value.

2. The method (300) of claim 1, wherein The mean value (M) or the median value is determined using (320) only those comparison values (V) from the distribution of comparison values (V) which do not represent an extreme value within the distribution of comparison values (V) in accordance with a predetermined filtering criterion. The mean value (M) or the median value is determined using (320) only those comparison values (V) from the distribution of comparison values (V) which do not represent an extreme value within the distribution of comparison values (V) in accordance with a predetermined filtering criterion.

3. The method (300) according to claim 1 or 2, characterized by, The touch sensor system (100) further comprises a capacitive reference sensor (115) arranged in the touch sensor system (100) such that it cannot be touched by a user of the touch sensor system (100), or at least not easily by the same hand as one of the touch sensors (110a,..., 100d), and wherein the method further comprises: measuring (311) a capacitance value (C) of the reference sensor (115); determining a comparison value (V) of the reference sensor (115), the comparison value (V) representing the magnitude of any difference between the measured capacitance value (C) of the reference sensor (115) and a predetermined initial baseline capacitance value (Bo) of the reference sensor (115), and the comparison value (V) being positively related to the magnitude of the difference; wherein the comparison value (V) of the reference sensor (115) is used for determining the average value (M) or median value in addition to the comparison values from the distribution of comparison values (V) of the touch sensors (110a,... 100d).

4. The method (300) of claim 3, wherein The touch sensors (100a,..., 100d) are combined in a control panel (105) and the reference sensor (115) is arranged at a distance from the control panel (105) and configured to detect touches.

5. The method (300) of claim 4, wherein, The reference sensor (115) is a capacitive sensor of a second control panel (140) comprising a plurality of capacitive sensors, and the method further comprises: measuring (311) individual capacitance values (C) of the sensors of the second control panel; determining (312) for each touch sensor of the second control panel a specific comparison value representing the magnitude of any difference between the measured capacitance value (C) of the specific sensor and an initial baseline capacitance value (Bo) previously determined for the sensor, and the specific comparison value being positively related to the magnitude of the difference; selecting (313) from the comparison values of these sensors the sensor of the second control panel (140) having the smallest comparison value (Vmin) as the reference sensor, the smallest comparison value (Vmin) representing the largest capacitance excess of the initial baseline capacitance value (Bo) over the associated measured capacitance value (C).

6. The method (200; 300) according to one of the preceding claims, characterized in that, Taking the determined compensation values into account when using the touch sensor system (100) for touch detection comprises: calibrating each of the touch sensors (110a,... 100d) at least by one or a combination of the following correction measures: determining a compensated baseline capacitance value (Bk) associated with a specific touch sensor (100a,... 100d) by compensating the initial baseline capacitance value (Bo) associated with the touch sensor based on the compensation value; by compensating a predetermined associated initial touch detection threshold value on the basis of the compensation value, a corrected touch detection threshold value is determined which is associated with the particular touch sensor (100a, 100d) alone, wherein the touch detection threshold value defines a capacitance threshold value for detecting a touch of an object on the touch sensor.

7. The method (200; 300) of one of the preceding claims, further comprising: determining (235; 355) a touched touch sensor, the capacitance value (C) of which indicates the presence of a touch in accordance with the calibration; and outputting (240; 360) an output signal identifying the touched touch sensor.

8. The method (200; 300) of one of the preceding claims, further comprising: when measuring the respective individual capacitance value (C) of each touch sensor (110a, 100d), high-pass filtering the generated sensor signal thereof in order to filter low-frequency signal components from the sensor signal.

9. A calibration device (120) for calibrating a touch sensor system (100) comprising a plurality of capacitive touch sensors (110a, 100d), wherein the calibration device (120) is configured to perform the method (200; 300) of one of the preceding claims.

10. A touch sensor system comprising a plurality of capacitive touch sensors (110a, 100d) and a calibration device (120) according to claim 9, wherein the touch sensor system (100) is configured to perform a calibration of the touch sensor system (100), in particular when activated, by means of the calibration device (120), in accordance with the method (200; 300) of one of claims 1 to 8.

11. The touch sensor system (100) of claim 10, wherein, The touch sensor system (100) is configured as an input system for a user interface of a vehicle.

12. The touch sensor system (100) of claim 11, wherein, The touch sensor system (100) is configured as an input system for a user interface arranged on a steering device (135) of a vehicle.

13. A computer program product comprising instructions which, when the computer program is executed by a computer, in particular by a processor of a calibration device (120) according to claim 9, cause the computer to carry out the method (200; 300) of one of claims 1 to 8.

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