CN115298644A - Apparatus and method for calibrating a capacitive touch sensor system - Google Patents
Apparatus and method for calibrating a capacitive touch sensor system Download PDFInfo
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- CN115298644A CN115298644A CN202180021175.9A CN202180021175A CN115298644A CN 115298644 A CN115298644 A CN 115298644A CN 202180021175 A CN202180021175 A CN 202180021175A CN 115298644 A CN115298644 A CN 115298644A
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/0416—Control or interface arrangements specially adapted for digitisers
- G06F3/0418—Control or interface arrangements specially adapted for digitisers for error correction or compensation, e.g. based on parallax, calibration or alignment
- G06F3/04182—Filtering of noise external to the device and not generated by digitiser components
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
- H03K17/96—Touch switches
- H03K17/962—Capacitive touch switches
- H03K17/9622—Capacitive touch switches using a plurality of detectors, e.g. keyboard
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K2217/00—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
- H03K2217/94—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00 characterised by the way in which the control signal is generated
- H03K2217/9401—Calibration techniques
- H03K2217/94026—Automatic threshold calibration; e.g. threshold automatically adapts to ambient conditions or follows variation of input
Abstract
The present invention relates to a method and a calibration device for calibrating a touch sensor system comprising a plurality of capacitive touch sensors. The method comprises the following steps: measuring individual capacitance values of the touch sensors; determining for each touch sensor a particular comparison value representing the magnitude of any difference between the measured capacitance value concerned and the initial baseline capacitance value previously determined for that touch sensor, and which has a positive correlation with the magnitude of that difference; determining a compensation value based on the comparison values, wherein the compensation value is determined such that the value lies between a maximum value and a minimum value of the comparison values or is equal to that of the comparison values which represents a maximum excess of the initial baseline capacitance value relative to the associated measured capacitance value; and upon detecting a touch using the touch sensor system, 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
The present invention relates to a method and a calibration device for calibrating a touch sensor system comprising a plurality of capacitive touch sensors, in particular upon activation of the touch sensor system, and to a corresponding touch sensor system itself comprising the touch sensors and the calibration device. Furthermore, the disclosure relates to a computer program configured to perform the method.
Background
Capacitive touch sensors are sensors that operate based on a single capacitor or a change in capacitance of a capacitor system to detect the proximity of an object, particularly a human finger, to the sensor or, particularly, to detect a touch of the object to the sensor. The ability of a touch sensor to correctly detect proximity or touch is often heavily dependent on external influences and conditions, particularly temperature, humidity, and aging progress.
In the following, unless otherwise specified, the term "touch" should be understood to include, in addition to an actual touch, the proximity of an object (in particular a human finger) to the touch sensor, wherein no actual touch occurs, but the proximity of the object to the touch sensor is such that the proximity will be detected as a touch according to the specifications or configuration of the touch sensor system. Typically, according to such configuration specifications, the proximity here includes a distance of only a few millimeters, for example 5mm or less. However, touch sensor systems that merely evaluate an actual touch as a touch are also possible.
When a touch sensor system based on such a capacitive touch sensor is activated, in particular when it is started up (i.e. at power-on), or when one or more touch-dependent functions are subsequently started up, the external influences acting on the touch sensor system on the touch sensor are generally not known in detail to the touch sensor system itself and may therefore not reliably detect any touch. Accordingly, the reliability of touch detection is often insufficient. In case of false detection, namely: if no actual touch is detected or if a touch is detected although in fact no touch at all, the reliability of the touch detection in known systems generally increases only from the second touch, when the system is able to quantify the external influence on the basis of the different sensor signals that occur up to this point in the case of a touch on the one hand and a non-touch on the other hand and to infer the external influence in the sense of a so-called baseline adjustment. Thus, reliable detection of a correct touch state (touch or not) immediately after system activation is not provided. This is especially true if the corresponding sensor has been touched during system activation. Thus, in such a case, the user input is not immediately detected in any case, or even incorrectly detected, which results in a correspondingly poor user experience.
Disclosure of Invention
It is an object of the invention to further improve the reliability of capacitive touch sensor systems.
This problem is solved according to the teaching of the independent claims. Various embodiments and developments of the invention are subject matter of the dependent claims.
A first aspect of the invention relates to a method, in particular a computer-implemented method, for calibrating a touch sensor system comprising a plurality of capacitive touch sensors, in particular upon activation of the touch sensor system. The method comprises the following steps: (i) Measuring individual capacitance values of the touch sensors, wherein in particular the various touch sensors can be measured simultaneously or within a defined measurement period (e.g. 5 seconds or less, preferably 1 second or less); (ii) Determining for each touch sensor a specific comparison value representing the magnitude of any difference (in particular as a difference or ratio or based thereon) between the measured capacitance value concerned and an initial baseline capacitance value that has been previously determined for said touch sensor, the comparison value is in particular individual for each touch sensor or identical for all touch sensors as a whole and is 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 is equal to that value of the comparison value which represents a maximum capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value, or that represents a 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 detecting a touch using the touch sensor system by correcting the capacitance value of the touch sensor or the initial baseline capacitance value measured therein based on the compensation value.
In the sense of the present invention, a "touch sensor system" is a sensor system which comprises a plurality of capacitive touch sensors and is designed to perform touch detection by means of the touch sensors, the touch detection being based on a change in the capacitance of a capacitor or a capacitor system in each touch sensor. In particular, the touch sensor system may be configured such that each touch sensor is capable of individually detecting a touch thereto by an object. Based on the presence of multiple touch sensors in the touch sensor system, in this case, touches at different locations in the touch sensor system corresponding to different locations of the respective touch sensors can be detected.
"capacitance value" is to be understood as a value, in particular a numerical value, which represents the absolute or relative magnitude of the capacitance provided as a measured capacitance in the associated touch sensor to which the capacitance value is assigned.
"baseline capacitance value" is also to be understood as a value, in particular a numerical value, which represents the absolute or relative magnitude of the capacitance provided as the measured capacitance in the associated touch sensor to which the capacitance value is assigned. Unlike the "capacitance value" of the touch sensor, which is determined only in the above process, the baseline capacitance value is predetermined. This may be done in particular based on capacitance measurements measuring the capacitance under certain standard conditions, or by other predefinitions, e.g. based on a specific sensor design of the touch sensor. Thus, a baseline capacitance value may be understood in particular as a reference capacitance value of the touch sensor, which represents a capacitive nominal value of a measured capacitance of the touch sensor, which is free of external influences that are usually present in practical use of the touch sensor system and are usually variable.
Thus, the "capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value" for a particular touch sensor relates to the case: 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 over the processing range. Thus, the "capacitance excess of the associated measured capacitance value relative to the initial baseline capacitance value" for a particular touch sensor relates to the case: the initial baseline capacitance value of the touch sensor represents a capacitance that is less than the capacitance measured by the touch sensor over the process range. If the two values are equal, the capacitance overshoot is zero.
It is also advantageous to define the capacitance value and the baseline capacitance value as positive, since capacitance is always a positive quantity. In this case, the compensation value is thus determined on the basis of the comparison value, so that the compensation value is determined to be smaller than the largest comparison value, while being greater than or equal to the smallest comparison value. In principle, however, the reverse is also conceivable, wherein the capacitance values and the baseline capacitance values are defined as negative. In this case, the compensation value is then determined based on the comparison value such that the compensation value is determined to be greater than the minimum comparison value while being less than or equal to the maximum comparison value. In the following always the case where the capacitance value and the baseline capacitance value are defined as positive, but this should not be understood as limiting.
In the use of the touch sensor system for touch detection, the consideration of the determined compensation value can in particular already relate to a capacitance measurement value measured within the scope of the process, which capacitance measurement value therefore simultaneously represents a first measurement value of the touch detection. Additionally or alternatively, it may refer to the use of the touch sensor system for touch detection in further subsequent uses, in particular also to such use over a relatively long period of time, which may in particular last until the next subsequent (re-) activation of the touch sensor system.
By means of the above-described method, not only calibration of the touch sensor system can be performed in a simple manner, but also reliable detection of touches or non-touches of each touch sensor can be achieved, so that, for example, at the time of calibration, in particular when the touch sensor system is activated, reliable detection of correct finger positions at a control panel comprising a plurality of touch sensors has been achieved using a correction based on compensation values determined according to the method. For example, if one or more touch sensors have been touched (or not touched) at start-up of the touch sensor system, then in each case, based on the correction and the first capacitance measurement, this can be reliably detected immediately at start-up ("true power-on") without the need to first make further measurements, namely: the touch sensor is touched a second time (or a third time, etc.) or not touched for calibration purposes.
Furthermore, with regard to other possible solutions for realizing a "true power-on", according to the method it is also not necessary to perform a (re-) calibration in the deactivated state of the touch sensor system, in particular at regular intervals, in order to perform a baseline adjustment repeatedly accordingly. Thus, the associated calibration effort, in particular the associated energy consumption, can be avoided. Furthermore, unlike the mentioned alternatives, calibration according to this method may also satisfy a "true power on" condition if there is an interruption in power when the touch sensor system is deactivated.
In particular, the method is based on the solution that: external influences affecting all touch sensors of the touch sensor system are different from individual influences that may occur at the touch sensors due to individual touches or object proximity, and calibration of the system is performed using compensation values that are the same for all touch sensors and that are determined based on substantially the same external influences for all touch sensors.
Preferred embodiments of the method will now be described in the following, each of which can be combined with each other and with other aspects of the further description of the invention as required, unless explicitly excluded or technically impossible.
In some embodiments, the compensation value is determined in such a way that a comparison value representing a maximum capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value is determined as the compensation value, or that a comparison value representing a 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 in the case where 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 equal to the minimum value of the (signed) comparison value.
This is based on the recognition that: depending on the type of influence, external influences on the capacitance measurement may have the effect of increasing or decreasing the measured capacitance value, while the approach or touch of a human finger to the capacitive touch sensor always has an influence in only one direction. Such a proximity or touch always has a positive effect in the sense that the measured capacitance value increases, in particular in the case where the capacitance value is defined as positive (and vice versa, correspondingly in the opposite case, i.e. negative by definition).
According to these embodiments, the compensation value is thus determined in such a way that the comparison value most likely to correspond to the non-touch state of the respective touch sensor is set as the compensation value, since in this case the capacitance excess of the initial baseline capacitance value with respect to the associated measured capacitance value of the touch sensor is the largest. In this way, a calibration, in particular a baseline matching, of the touch sensor system may be achieved, resulting in a particularly reliable touch detection.
However, according to other embodiments, the compensation value is determined in such a way that: the average or median of the comparison value distribution is determined as the compensation value. This has the advantage that: a relative suppression of the distribution extrema occurs, so that accordingly, measurement results based on any measurement errors or special external influences occurring alone on only one touch sensor or a subset of touch sensors are less likely to falsify the determination of the compensation value and thus the calibration as a whole, thereby making the calibration more robust.
In particular, according to a related embodiment, the determination of the compensation value may comprise: (i) Establishing an average value or a median value of the comparison value distribution as an initial value of the compensation value; (ii) Determining those touch sensors whose measured capacitance values indicate absence of touch as touch sensors that are not touched according to correction of the measured values based on the initial values of the compensation values; (iii) An average or median of the determined comparison value distribution of the touch sensors not touched is established as a final value of the compensation values. By correcting the measured or baseline capacitance value of the touch sensor based on the compensation value, the determined compensation value is taken into account when using the touch sensor system for touch detection. Advantageously, in this way, based on the multi-step determination of the compensation values, a further improvement in the reliability of the calibration, in particular of the baseline adjustment, can be achieved, since finally, those comparison values which were previously considered to correspond to possible non-touch states are used first and are therefore particularly suitable as a reference for the correction embodied for determining the compensation values.
Furthermore, according to a related embodiment, only those comparison values from the distribution of comparison values (which do not represent extreme values within the distribution of comparison values according to a predetermined filtering criterion) may be used to determine the mean or median value. Since the extreme values in the comparison value distribution, in particular the extreme values of the capacitance values based on extreme measurements, are caused with a higher probability by incorrect measurements or sensor-specific external influences, it is possible, by this filtering of the comparison results for determining the compensation values, to achieve a higher reliability in determining the compensation values, and thus to increase the reliability of the touch sensor system calibrated on the basis of the compensation values.
In further related embodiments, the touch sensor system may further comprise a capacitive reference sensor arranged in 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 further comprises: (i) measuring a capacitance value of a reference sensor; (ii) A comparison value for the reference sensor is determined that represents a magnitude of any difference between the measured capacitance value of the reference sensor and the predetermined initial baseline capacitance value of the reference sensor, and that has a positive correlation 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 sensors are also used here for determining the mean or median value.
In particular, the capacitive reference sensor is here arranged in the touch sensor system in such a way that a user of the touch sensor system cannot touch it at all if this is prevented by design. This may be the case, for example, if (i) the reference sensor is arranged in such a way that none of the electrodes for capacitance measurement is located at or directly below the surface of the touch sensor system (i.e. such that a touch with a surface located above it can still be reliably detected), or if (ii) even if at least one electrode is located at or directly below the surface, a finger cannot touch the electrode or the part of the surface located directly above it. In particular, if the reference sensors are arranged to be touchable in principle and thus also to be able to detect a touch, the capacitive reference sensors cannot easily be touched with the same hand as one of the touch sensors, but the arrangement of the reference sensors with respect to the touch sensors in the touch sensor system is such that, due to the distance or geometry of the touch sensor system, it is at least almost impossible for a user of the touch sensor system to unintentionally touch the reference sensor and one of the touch sensors simultaneously with the same hand.
In a further related embodiment, the touch sensor is incorporated in the control panel, the reference sensor is arranged at a distance from the control panel and is configured to detect a touch. In particular, the distance may be selected such that the reference sensor cannot, or at least is not easily, operated simultaneously with the control panel by the same hand of the user. In this way, capacitive sensors that are already present for other reasons (i.e. touch detection) can be used as reference sensors in the sense of multiple use ("multi-use" or "dual use"), which improves the efficiency of the touch sensor system.
In particular, according to a related embodiment, the reference sensor may be a capacitive sensor of the second control panel including a plurality of capacitive sensors, and the method may further include: (i) Measuring a single capacitance value of a sensor of the second control panel; (ii) Determining for each sensor of the second control panel a specific comparison value representing the magnitude of any difference between the measured capacitance value of the specific sensor and the initial baseline capacitance value previously determined for that sensor, and which has a positive correlation with the magnitude of that difference; and (iii) selecting a sensor of the second control panel having a comparison value from the comparison values of the sensors as a reference sensor, the comparison value representing a maximum capacitance excess of the initial baseline capacitance value relative to the associated measured capacitance value. The previous description regarding the measurement of the capacitance value, the determination of the comparison value of the touch sensor (here of the first control panel) and the description regarding the capacitance excess are mutatis mutandis. In this way, the achievable reliability of the touch sensor system is further improved, since 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.
According to some embodiments, when touch detection is performed using the touch sensor system, consideration of the determined compensation values includes calibrating each touch sensor by at least one of the following corrective measures, or a combination thereof: (i) Determining a compensated baseline capacitance value associated with a particular touch sensor by at least proportionally compensating an initial baseline capacitance value associated with the touch sensor based on a compensation value; (ii) Based on the compensation value, a corrected touch detection threshold individually associated with a particular touch sensor is determined by at least proportionally compensating the predetermined associated initial touch detection threshold, in particular individually or for all touch sensors. Here, the touch detection threshold defines a capacitance threshold for detecting a touch of an object to the touch sensor. In particular, the compensation may be performed by adding the compensation value to a particular initial baseline value. While variation (i) represents a baseline adjustment in the narrow sense that allows the use of a touch detection threshold that is the same for all touch sensors, variation (ii) allows the baseline value to be kept unchanged because a sensor-specific touch detection threshold is used instead.
According to some embodiments, the method further comprises: (i) Determining those touch sensors whose capacitance values indicate the presence of a touch according to the calibration as touch sensors that are touched; and (ii) outputting an output signal identifying the touched touch sensor. Thus, in addition to the actual calibration, also here the actual touch measurement has been performed. Both can be done in this way, in particular based on the same capacitance measurement, so that on the one hand no multiple measurements for calibration are required and on the other hand no actual touch measurements are required.
According to some embodiments, the method further comprises high pass filtering the sensor signals generated by the respective touch sensors to filter out low frequency signal components from the signals when measuring the respective capacitance values of the respective touch sensors. Since low-frequency signals are not generally generated by an object touching the touch sensor, signal components which may be caused by external influences and which may potentially impair, in particular also falsify, the measurement result can be filtered out beforehand so that these signal components do not have any further influence during the calibration of the touch sensor system. In this way, the achievable reliability of the system can be further improved.
A second aspect of the invention relates to a calibration device for calibrating a touch sensor system comprising a plurality of capacitive touch sensors. The apparatus is configured to perform a method according to the first aspect.
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 the second aspect, wherein the touch sensor system is configured to perform a calibration of the touch sensor system by means of the calibration device, in particular when activated, in accordance with the method according to the first aspect.
According to some embodiments, the touch sensor system may be particularly configured as an input system for a user interface of a vehicle. In particular, the touch sensor system may here be configured in particular as an input system for a user interface arranged on a steering device of a vehicle. These vehicle-related embodiments can improve operational reliability when using touch sensor systems as input interfaces in vehicles, and can at the same time lead to the implementation of safety gains, since lengthy multiple inputs that distract the driver due to incorrect or delayed touch recognition can be reduced or even avoided.
A fourth aspect of the invention relates to a computer program comprising instructions for causing a computer to carry out the method according to the first aspect when the computer program is run by a computer, in particular by a processor of a calibration apparatus according to the second aspect.
In particular, the computer program may be stored in a non-volatile data carrier. This is preferably a data carrier in the form of an optical data carrier or a flash memory module. It may be advantageous if such a computer program is to be processed independently of a processor platform on which the program or programs are running. In another embodiment, the computer program may be present as a file on the data processing unit, in particular on a server, and may be downloaded via a data link, for example the internet or a dedicated data link, for example a proprietary or local network. Furthermore, the computer program may have a plurality of separate interactive program modules.
Accordingly, the calibration device according to the second aspect or the touch sensor system according to the third aspect may respectively have in particular a program memory storing a computer program. Alternatively, the calibration device or the touch sensor system may also be configured to access an externally available computer program, for example on one or more servers or other data processing units, via a communication link, in particular in order to exchange therewith data used when the method or computer program is run or data constituting the output of the computer program.
The features and advantages explained in relation to the first aspect of the invention apply correspondingly also to the other aspects of the invention.
Drawings
Other advantages, features and application possibilities of the invention can be found in the following detailed description in conjunction with the drawings.
In the drawings:
fig. 1 schematically shows an exemplary touch sensor system according to a first embodiment, comprising a plurality of touch sensors and a calibration device according to one embodiment of the invention, and an exemplary arrangement of the touch sensor system as a user interface for touch input on a steering device of a vehicle;
FIG. 2 schematically illustrates an exemplary touch sensor system according to a second embodiment, wherein the touch sensor system has two different control panels and is configured as a user interface on a vehicle steering device;
fig. 3 shows a flow chart illustrating a first preferred embodiment of the method according to the invention, which method is based on a specific selection of comparison values as compensation values;
FIG. 4 shows a schematic diagram illustrating baseline correction according to the method of FIG. 3, according to a first example; and
FIG. 5 shows a schematic diagram illustrating baseline correction according to the method of FIG. 3, according to a second example;
6A-6C show a flow chart illustrating a second preferred embodiment of a method for determining a compensation value based on an averaging of comparison values according to the invention; and
fig. 7 shows a schematic diagram illustrating baseline correction according to the method of fig. 6A-6C, according to an example.
In the drawings, the same reference numerals are used throughout for the same or corresponding elements of the present invention.
Detailed Description
The exemplary touch sensor system 100 according to fig. 1 comprises a plurality of (in this example four) capacitive touch sensors 110a to 110d, which may be arranged, inter alia, in a (first) control panel 105 of the touch sensor system 100. Furthermore, the touch sensor system 100 comprises a capacitive reference sensor 115, which capacitive reference sensor 115 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 may well and approximately be considered to be unaffected by external influences originating from the user, in particular the user's hand, on its measurement capabilities. Further, the touch sensor system 100 comprises a calibration device 120, the calibration device 120 having a processor unit 125 and a program and data memory 130 coupled thereto. The processor unit 125 may comprise, inter alia, one or more microprocessors, and may be configured, inter alia, 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 for executing the method on the processor unit 125 may be stored in the memory 130.
The touch sensor system 100 according to fig. 1 may be configured in particular as a user interface in a vehicle, for example for arrangement on a steering device 135, in particular a steering wheel. An exemplary embodiment of this aspect is shown in fig. 2.
In an extension of the touch sensor system 100 according to fig. 1, in addition to the first control panel 105, a further control panel 140 is provided here, wherein both control panels each have a plurality of capacitive sensors, in the present example four each, which are present in each control panel in an exemplary matrix-like arrangement. Hereinafter, the touch sensor of the first control panel 105 will be specifically referred to as a "touch sensor", and for better explanation, the capacitive sensor of the second control panel 140 (which is, however, technically also a touch sensor) is not so called. The capacitive sensors of at least the first control panel 105 may be calibrated by the calibration device 120, in particular according to one of the methods described below with reference to fig. 3 to 7. Preferably, the same applies to the capacitive sensor of the second control panel. In addition to or instead of the dedicated reference sensor, a selected touch sensor of the second control panel is used as a reference sensor 115 for calibrating the touch sensors 100a to 100d of the first control panel 105 in the touch sensor system according to fig. 2. The reverse is also possible accordingly.
With reference to the flow chart from fig. 3 and to the examples from fig. 4 and 5, a first preferred embodiment 200 of the method according to the invention will now be explained by reference to the example of the touch sensor system 100 from fig. 1, which is based on a specific selection of comparison values as compensation values. The method 200 is preferably performed when the touch sensor system is activated, in particular when it is started, and thus starts with the activation of the touch sensor system 100 in step 205. However, it may alternatively be performed at other times, in particular each time a measurement is to be made, or at regular time intervals. Thus, "activating" the touch sensor system should be understood in particular as any triggering of an operating or calibration mode of operation of the touch sensor system.
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, which may be caused by external influences, the sensor signals are preferably subjected to a high-pass filtering.
Based on the capacitance value C measured in step 210 and the individual baseline capacitance value B0 previously determined for each of the touch sensors 110 a-110 d, which has typically been determined during characterization of the touch sensor system prior to delivery thereof at standard conditions at the factory, an individual comparison value V is now determined for each of the touch sensors 110 a-110 d in step 215. This can be done in particular in such a way that: the difference between the measured capacitance value C and the initial baseline capacitance value B0 for a particular touch sensor is selected as the comparison value V, i.e., V = C-B0.
Fig. 4 (a) and 5 (a) show two different examples of determining these respective compensation values V for the touch sensors 110 a-100 d from the associated set of initial baseline capacitance values B0 and the capacitance value C measured in step 210 by means of such a difference formula. In the case of fig. 4 (a), a negative compensation value is obtained.
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 set to the compensation value C in step 225, which may coincide with step 220. One motivation for this choice is that, depending on the nature of the external influence, it may have a positive or negative influence on the measured capacitance value C of the touch sensor and may thus increase or decrease the measured capacitance value C, whereas the influence of a touch on the touch sensor, in particular the human finger, can generally only have the effect of increasing the capacitance.
If the smallest comparison value, i.e. Vmin, is selected at this time, this corresponds, as suggested herein, to selecting the one value from the capacitance values K measured in step 210 that is least likely or least likely to be affected by external influences. This choice is usually a good estimate of the compensation value that can be used for this purpose, since the compensation value is intended as a measure of the approximate external influence and is assumed to be the same for all touch sensors in the absence of a touch. In each of fig. 4 (a) and 5 (a), the comparison value V of the touch sensor 110b represents the minimum comparison value Vmin selected as the compensation value.
At this time, in step 230, the initial baseline capacitance values B0 of all the touch sensors 110a to 110d of the touch sensor system 100, respectively, may be corrected based on the determined compensation values Vmin. In particular, this may be done by performing a signed addition of the compensation value to the specific initial baseline capacitance value B0 in order to obtain the corrected baseline capacitance value Bk for this purpose. This is illustrated in fig. 4 (B) and 5 (B), where a 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, while preserving the measured capacitance value C, i.e.: bk = B0+ Vmin.
In a further step 235, the respective touch state of the touch sensors 110a to 110d can now be determined based on the respective measured capacitance values C and the respective corrected baseline capacitance values Bk. To this end, a difference between the two is formed in order to determine an individual corrected comparison value Vk for each of the touch sensors 110a to 110d, namely: vk = C-Bk. In this example, the respective touch state of each touch sensor can be determined at this time by comparing the corrected comparison value Vk with a detection threshold T defined for all touch sensors as a whole, wherein a touch is detected if the associated corrected comparison value Vk meets or exceeds the touch detection threshold T of the current touch sensor. Otherwise, a non-touch is detected. Finally, in a final step 240, output signals representing the touch states detected by the touch sensors 110a to 110d, respectively, may be output. The output signal can be used, inter alia, as a control signal for controlling one or more functions corresponding to various touch sensors, for example volume control of an entertainment system or for configuring an automatic vehicle control, in particular an ACC (automatic cruise control).
In a comparison of the two graphs of fig. 4 (a) and 4 (b), the effect of having performed a calibration on the compensation value Vmin can be seen. Although a non-touch will be detected for each of the sensors 110a to 110c and a touch will be detected only for the touch sensor 100d before calibration, a touch is detected for both the touch sensor 110a and the touch sensor 110d but a non-touch is detected for all the other touch sensors 100b and 100c after calibration.
In another example shown in fig. 5 (a) and 5 (b), a touch is detected for each of the two touch sensors 110c and 110d before calibration, and a touch is detected only for the touch sensor 110d but no touch is detected for all of the other touch sensors 100a to 100c after calibration.
Referring to the flow charts of fig. 6A to 6C, which are linked to each other by the connecting symbols A, B and C, and the example of fig. 7, a second preferred embodiment 300 of the method according to the present invention, which determines a compensation value based on averaging (or alternatively averaging) of comparison values, will now be explained with reference to the example of the touch sensor system 100 of fig. 1. The method 300 is preferably performed when the touch sensor system is activated, particularly when it is started, and thus begins with the activation of the touch sensor system 100 in step 305, as shown in fig. 6A. However, similar to the method 200, it may alternatively be performed at other times, in particular at regular intervals or each time a measurement is to be taken.
This is followed by a measuring step 310 for measuring the individual capacitance values C of the touch sensors 100a to 100d, which corresponds to step 210 of the method 200. Optionally, the use of a reference sensor 115 may be additionally provided, as shown in the examples of FIGS. 6A-C and 7. This will be explained below, in particular with respect to a touch sensor system having two different control panels, as is particularly shown in fig. 2.
In this case, the capacitive sensor of the second control panel may be dynamically selected as the reference sensor instead of the predetermined capacitive reference sensor, as shown in particular in fig. 6B. In step 311, similar to step 310 for the first control panel, the individual capacitance values of each capacitive sensor of the second control panel are measured, wherein again optionally a high-pass filtering of the respective signals may be applied. Thereafter, in step 312, similar to step 215 of method 200, a separate comparison value is determined for each sensor of the second control panel as the difference between the respective associated measured capacitance value for the particular sensor and the predetermined initial baseline capacitance value. To determine the reference sensor, the sensor having the smallest comparison value among the sensors of the second control panel is selected as the reference sensor of the touch sensor system 100 in step 313. The motivation for selecting the sensor with the smallest comparison value as the reference sensor is the same as previously explained for the method 200 regarding selecting the smallest comparison result Vmin as the compensation value.
At this point, referring again to fig. 6A, in a further step 315, again similar to step 215 of the method 200, a separate comparison value V is determined for each of the touch sensors 100 a-100 d of the first control panel 105 as the difference between the respective associated measured capacitance value C and the previously determined initial baseline capacitance value B0 of the respective touch sensor 100 a-100 d. In step 320, extreme values may be filtered out of the resulting distribution of comparison values V of the touch sensors and optionally also of the reference sensors, according to predetermined filter criteria, in order to protect the subsequent determination of the compensation values from potentially spurious comparison values, which may be triggered, for example, by specific individual temperature fluctuations (caused, for example, by selective solar radiation) at the individual touch sensors.
The actual determination of the compensation value is then started, which is performed in several steps in the present exemplary method 300. To this end, in step 325, the initial value of the compensation value is first set equal to the average of the determined feedback comparison values of the touch sensor and the reference sensor (if applicable). Based on the compensation value, a preliminary correction of the baseline capacitance value B0 of each of all the touch sensors 100a to 100d of the touch sensor system 100 is performed in step 330. This may be achieved, inter alia, by adding the preliminary value of the compensation value to the particular initial baseline capacitance value B0 in a signed manner.
In step 335, a preliminary touch state for each of the touch sensors 100 a-100 d may be determined at this point based on the corresponding measured capacitance value C and the corresponding preliminary corrected baseline capacitance value. The remainder of the method is shown in fig. 6C. Step 340 follows, in which those touch sensors that are detected as "untouched" according to a comparison of the touch detection threshold T with the respective comparison values of the touch sensors are determined based on the preliminarily determined touch state. Therefore, these touch sensors that are not touched are those whose comparison value is lower than the touch detection threshold T.
At this point, in step 345, the final value of the compensation value may be determined as the average value M (or median value, see above) of the determined filtered comparison values V of the (only) untouched touch sensors and the reference sensor 115. Based on the final value of the compensation value, a final correction of the initial baseline capacitance value B0 for each of all touch sensors 100 a-100 d of the touch sensor system 100 may then be performed in step 350. The corresponding final corrected baseline capacitance value Bk for a particular touch sensor can be determined, inter alia, by adding the final compensation value M to the initial baseline capacitance value B0 for that particular touch sensor in a signed manner.
At this time, in step 355, based on the specific measured capacitance value C and the specific final corrected baseline capacitance value Bk, a respective touch state of each of the touch sensors 100a to 100d may be determined by calculating a corrected comparison value Vk by means of a difference equation (Vk = C-Bk) between the measured capacitance value C and the final corrected baseline capacitance value Bk, and by comparing the corrected comparison value with the touch detection threshold value T, similarly to step 235 of method 200.
In a comparison of the two graphs of fig. 4 (B) and 7 (B), the different effects of different determinations of compensation values according to two explained exemplary embodiments of the method can be seen, both graphs being determined starting from the initial baseline value B0 and the same initial value distribution of the measured capacitance value C (see fig. 4 (a) and 7 (a)). Although a non-touch is to be detected for each of the sensors 110a to 110c and a touch is detected only for the touch sensor 100d before the correction, in the case of fig. 4 (b), after the correction, a touch is detected for both the touch sensor 110a and the touch sensor 110d but a non-touch is detected for all the other touch sensors 100b and 100 c. On the other hand, in the case of fig. 7 (b), after correction, no touch is detected for all the touch sensors 100b and 100 c.
Finally, in step 360, an output signal representing the finally determined touch state of one or more, in particular all, touch sensors may be output similar to step 240.
While at least one exemplary embodiment has been presented above, it should be appreciated that a vast number of variations exist in this regard. It should also be noted herein that the described exemplary embodiments constitute only non-limiting examples, and they are not intended to limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description will provide those skilled in the art with an indication of the implementation of at least one exemplary embodiment, it being understood that various changes may be made in the arrangement of the functional means and elements described in an exemplary embodiment without departing from the subject matter defined in the appended claims or their legal equivalents, respectively.
List of reference marks
100. Touch sensor system
105. Control panel, in particular first control panel
110a-d touch sensor
115. Capacitive reference sensor
120. Calibration device
125. Processor unit
130. Program and data memory
135. Steering device, in particular steering wheel, for a vehicle
140. Second control panel
200. First embodiment of the calibration method
205-240 method 200
300. Second embodiment of the calibration method
305-360 method steps of method 300
B0 Initial baseline capacitance value
Bk (Final) corrected baseline capacitance value
C (measured) capacitance value
Comparison value of V
Vk corrected comparison value
Vmin minimum comparison value, and also compensation value
T touch detection threshold
M compares the average of the values.
Claims (16)
1. A method (200:
measuring (210;
determining (215, 315) a specific comparison value (V) for each of the touch sensors (100 a, …,100 d), the comparison value (V) representing a magnitude of any difference between the measured capacitance value (C) involved and an initial baseline capacitance value (B0) previously determined for the touch sensor, and the comparison value (V) positively correlated with the magnitude of the difference;
determining (225, 325, …, 345) a compensation value based on the comparison value, wherein the compensation value is determined such that it lies between a maximum and a minimum of the comparison value (V) or is equal to a value in the comparison value (V) that represents a maximum capacitance excess of an initial baseline capacitance value (B0) relative to an associated measured capacitance value (C) or a minimum capacitance excess of the associated measured capacitance value (C) relative to the initial baseline capacitance value (B0); and
upon touch detection using the touch sensor system (100), correcting the measured capacitance value (C) or the initial baseline capacitance value of the touch sensor (100 a, …,100 d) by considering (235.
2. The method (200) according to claim 1, wherein the compensation value is determined (225) such that a comparison value (V) representing a maximum capacitance excess of the initial baseline capacitance value (B0) with respect to the associated measured capacitance value (C) or a minimum capacitance excess of the associated measured capacitance value (C) with respect to the initial baseline capacitance value (B0) is determined as the compensation value (Vmin).
3. The method (300) according to claim 1, wherein the compensation value is determined (325, …, 345) such that the mean (M) or the median of the distribution of the comparison values (V) is determined as the compensation value.
4. The method (300) of claim 3, wherein the determining (325, …, 345) of the compensation comprises:
establishing (325) an average (M) or median of the distribution of the comparison values (V) as a preliminary value of the compensation value;
determining (340), from the correction (330) based on the measurement of the preliminary value of compensation value, that those touch sensors (100 a, …,100 d) for which the measured capacitance value (C) indicates an absence of touch are untouched touch sensors;
establishing (345) an average or median of the distribution of the comparison values (V) of the determined touch sensors (100 a, …,100 d) that are not touched as a final value of the compensation value.
Wherein the determined compensation value is taken into account (355) by correcting (350) a measured capacitance value (C) or a baseline capacitance value of the touch sensor (100 a, …,100 d) based on the compensation value when using the touch sensor system (100) for touch detection.
5. The method (300) according to claim 3 or 4, wherein the mean (M) or median value is determined using (320) only those comparison values (V) from the distribution of comparison values (V) which do not represent extreme values within said distribution of comparison values (V) according to a predetermined filtering criterion.
6. The method (300) of one of claims 3 to 5, wherein the touch sensor system (100) further comprises a capacitive reference sensor (115), the capacitive reference sensor (115) being arranged in the touch sensor system (100) such that the capacitive reference sensor (115) cannot be touched by a user of the touch sensor system (100) or at least cannot be easily touched by the same hand as one of the touch sensors (110 a.., 100 d), 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 a magnitude of any difference between a measured capacitance value (C) of the reference sensor (115) and a predetermined initial baseline capacitance value (B0) of the reference sensor (115), and the comparison value (V) being positively correlated with the magnitude of the difference;
wherein the comparison value (V) of the reference sensor (115) is used for determining the mean value (M) or median value in addition to a comparison value from a distribution of comparison values (V) of the touch sensors (110 a.. 100 d).
7. The method (300) of claim 6, wherein the touch sensor (100 a.,. 100 d) is combined in a control panel (105) and the reference sensor (115) is arranged at a distance from the control panel (105) and is configured to detect a touch.
8. The method (300) of claim 7, wherein the reference sensor (115) is a capacitive sensor of a second control panel (140) that includes a plurality of capacitive sensors, and the method further comprises:
measuring (311) individual capacitance values (C) of sensors of the second control panel;
determining (312) a particular comparison value for each touch sensor of the second control panel, the particular comparison value representing a magnitude of any difference between a measured capacitance value (C) of a particular sensor and an initial baseline capacitance value (B0) previously determined for the sensor, and the particular comparison value being positively correlated with the magnitude of the difference;
selecting (313) as the reference sensor, from the comparison values of these sensors, the sensor of the second control panel (140) having a comparison value (Vmin) representing a maximum capacitance excess of the initial baseline capacitance value (B0) with respect to the associated measured capacitance value (C).
9. The method (200, 300) of one of the preceding claims, wherein taking into account the determined compensation value when touch detection is performed using the touch sensor system (100) comprises:
calibrating each of the touch sensors (110 a.. 100 d) by at least one or a combination of the following corrective measures:
determining a compensated baseline capacitance value (Bk) associated with a particular touch sensor (100 a, …,100 d) by compensating for an initial baseline capacitance value (B0) associated with the touch sensor based on the compensation value;
determining a corrected touch detection threshold individually associated with the particular touch sensor (100 a, …,100 d) by compensating a predetermined associated initial touch detection threshold based on a compensation value, wherein the touch detection threshold defines a capacitance threshold for detecting a touch of an object to the touch sensor.
10. The method (200, 300) of one of the preceding claims, further comprising:
determining (235; and
outputting (240.
11. The method (200, 300) of one of the preceding claims, further comprising:
when measuring the capacitance value (C) of each individual touch sensor (110 a.. 100 d), the sensor signal generated by it is high-pass filtered in order to filter out low-frequency signal components from the sensor signal.
12. A calibration device (120) for calibrating a touch sensor system (100) comprising a plurality of capacitive touch sensors (110 a.., 100 d), wherein the calibration device (120) is configured to perform the method (200.
13. A touch sensor system comprising a plurality of capacitive touch sensors (110 a., 100 d) and a calibration device (120) according to claim 11, wherein the touch sensor system (100) is configured to perform a calibration of the touch sensor system (100) by means of the calibration device (120, in particular when activated, according to the method (200) according to one of claims 1-11.
14. The touch sensor system (100) of claim 13, wherein the touch sensor system (100) is configured as an input system for a vehicle user interface.
15. The touch sensor system (100) of claim 14, 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.
16. A computer program comprising instructions which, when the computer program is run by a computer, in particular by a processor of a calibration apparatus (120) as claimed in claim 12, cause the computer to perform the method (200.
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| DE102020103558.6 | 2020-02-12 | ||
| PCT/EP2021/052899 WO2021160541A1 (en) | 2020-02-12 | 2021-02-08 | Device and method for calibrating a capacitive touch sensor system |
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| CN115298644A true CN115298644A (en) | 2022-11-04 |
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| DE102022118470A1 (en) | 2022-07-25 | 2024-01-25 | Valeo Schalter Und Sensoren Gmbh | Method for determining manual actuation of a capacitive sensor element, evaluation unit for this and sensor device |
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| US8026904B2 (en) * | 2007-01-03 | 2011-09-27 | Apple Inc. | Periodic sensor panel baseline adjustment |
| US8049732B2 (en) | 2007-01-03 | 2011-11-01 | Apple Inc. | Front-end signal compensation |
| US9007190B2 (en) | 2010-03-31 | 2015-04-14 | Tk Holdings Inc. | Steering wheel sensors |
| US9337832B2 (en) * | 2012-06-06 | 2016-05-10 | Ford Global Technologies, Llc | Proximity switch and method of adjusting sensitivity therefor |
| US9535545B2 (en) * | 2013-06-28 | 2017-01-03 | Atmel Corporation | Common mode noise suppression during hovering and proximity detection |
| JP5816827B1 (en) * | 2014-05-14 | 2015-11-18 | パナソニックＩｐマネジメント株式会社 | Grip sensor |
| DE102017008728A1 (en) * | 2017-09-16 | 2019-03-21 | Leopold Kostal Gmbh & Co. Kg | sensor system |
| DE102018000884A1 (en) * | 2018-02-03 | 2019-08-08 | Leopold Kostal Gmbh & Co. Kg | Capacitive measuring system |
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