System for detecting touch gestures of a user, device comprising the system and method

Abstract

The present disclosure relates to a system for detecting a touch gesture of a user, a device comprising the system and a method. The system is for detecting a touch gesture of a user on a detection surface, comprising: a processing unit; and an accelerometer to detect vibrations at the detection surface and generate a vibration signal. The processing unit is configured to: acquire the vibration signal, detect a signal characteristic in the vibration signal related to the touch gesture of the user, detect a stationarity condition in the vibration signal before and / or after the detected signal characteristic, and validate the touch gesture in case both the signal characteristic and the stationarity condition have been detected. An electrostatic charge sensor can also be used as an additional parameter to validate the touch gesture.

Description

Technical Field

[0001] This disclosure relates to a system for detecting a user's touch gestures, an apparatus including the detection system, and a method for detecting a user's touch gestures. Background Technology

[0002] Today, one of the most important causes of mobile device malfunctions, especially mobile phones, involves mechanical buttons, which are easily damaged due to their weak structure, use of fragile flexible PCBs, and waterproofing issues.

[0003] Mechanical button solutions offer capacitive sensor-based buttons, which are particularly well-suited for implementation on full-screen devices; however, they are not always reliable because they can be affected by the presence of ambient charge. Summary of the Invention

[0004] According to the present invention, a system for detecting a user's touch gestures, an apparatus including the detection system, and a method for detecting a user's touch gestures are provided.

[0005] In one embodiment, a system for detecting a user's touch gestures on a detection surface includes:

[0006] Processing unit;

[0007] An accelerometer operatively coupled to a processing unit is configured to detect vibrations at the detection surface and generate a corresponding vibration signal, wherein the processing unit is configured to: acquire the vibration signal; detect signal characteristics in the vibration signal that can be associated with the user's touch gesture; detect stationarity conditions in the vibration signal before and / or after the detected signal characteristics; and, if both the signal characteristics and the stationarity conditions before and / or after the signal characteristics have been detected, enable the user's touch gesture.

[0008] Furthermore, in one embodiment, the operation of detecting the signal characteristics includes: filtering the vibration signal via a high-pass filter, calculating a filtered vibration signal; detecting a first peak value of the filtered vibration signal exceeding a first threshold; and detecting a second peak value of the filtered vibration signal exceeding a second threshold, wherein the first threshold is one of a positive threshold and a negative threshold, and the second threshold is the other of a positive threshold and a negative threshold.

[0009] Furthermore, in one embodiment, the processing unit is also configured to sample the vibration signal and use a digital filter to perform an operation of calculating a filtered vibration signal, wherein the operation of detecting the first peak value includes: detecting a first sample of the filtered vibration signal that exceeds a first threshold; detecting a second sample of the filtered vibration signal that immediately precedes the first sample and has a modulus value lower than that of the first sample; and detecting a third sample of the filtered vibration signal that immediately follows the first sample and has a modulus value lower than that of the first sample, wherein the first peak value corresponds to the first sample.

[0010] Furthermore, in one embodiment, the operation of detecting the second peak includes: detecting a fourth sample of the filtered vibration signal that exceeds a second threshold; detecting a fifth sample of the filtered vibration signal that immediately precedes the fourth sample and has a modulus value lower than that of the fourth sample; and detecting a sixth sample of the filtered vibration signal that immediately follows the fourth sample and has a modulus value lower than that of the fourth sample, wherein the second peak corresponds to the fourth sample.

[0011] Furthermore, in one embodiment, the operation of detecting the signal characteristics further includes: verifying, in terms of the number of samples included between the first peak and the second peak, that the first peak and the second peak are at a distance from each other that is lower than the maximum value of the number of samples.

[0012] Furthermore, in one embodiment, the operation of detecting a stationarity condition in the vibration signal prior to the signal characteristic includes: after detecting a first peak, verifying that the values ​​of a first plurality of samples of the filtered vibration signal prior to the first peak are within a first range of reference values.

[0013] Furthermore, in one embodiment, the operation of detecting a stationarity condition in the vibration signal following the signal characteristic includes: after detecting a second peak, verifying that the values ​​of a second plurality of samples of the filtered vibration signal following the second peak are within a second range of reference values.

[0014] Furthermore, in one embodiment, the operation of detecting a stationarity condition in the vibration signal following the signal characteristic further includes discarding a third plurality of samples of the filtered vibration signal, the third plurality of samples being immediately following the second peak and included between the second peak and the second plurality of samples of the filtered vibration signal.

[0015] In addition, in one embodiment, the system also includes a static charge change sensor operatively coupled to the processing unit, which is configured to detect static charge changes at the detection surface and thus generate a charge change signal.

[0016] In addition, in one embodiment, the processing unit is also configured to generate a variance signal by calculating the variance of the charge change signal.

[0017] Furthermore, in one embodiment, the processing unit is also configured to detect the maximum point of the variance signal when the signal characteristics that can be associated with the user's touch gesture are detected in the vibration signal.

[0018] Furthermore, in one embodiment, the processing unit is also configured to: verify whether the maximum point of the variance signal is in a predefined relationship with a third threshold, and, if both the signal characteristic and the stationarity condition before and / or after the signal characteristic have been detected, enable the touch gesture only if the maximum point of the variance signal satisfies the predefined relationship with the third threshold.

[0019] Furthermore, in one embodiment, the processing unit is also configured to: verify whether the variance signal is in a stationarity condition if both the signal characteristic and a stationarity condition before and / or after the signal characteristic have been detected, and if the maximum point of the variance signal satisfies the predefined relationship with a third threshold, and only enable the touch gesture to take effect if the variance signal satisfies the stationarity condition.

[0020] Furthermore, in one embodiment, the stationarity condition of the variance signal is satisfied if at least one current sample of the variance signal has a value that is included within the range of stationarity reference values.

[0021] In addition, the embodiment provides the following steps: if the variance signal remains above a fourth threshold for a period of time longer than a predefined touch time, then a touch event that continues over time is detected.

[0022] The present invention also relates to a method for using a system to detect a user's touch gesture on a detection surface, the system comprising: a processing unit; an accelerometer operatively coupled to the processing unit, configured to detect vibrations at the detection surface and generate a corresponding vibration signal, the method comprising the steps performed by the processing unit: acquiring the vibration signal; detecting a signal characteristic in the vibration signal that can be associated with the user's touch gesture; detecting a stationarity condition in the vibration signal before and / or after the detected signal characteristic; and activating the user's touch gesture if both the signal characteristic and the stationarity condition before and / or after the signal characteristic have been detected.

[0023] Furthermore, in one embodiment, the step of detecting the signal characteristics includes: filtering the vibration signal via a high-pass filter to calculate a filtered vibration signal; detecting a first peak value of the filtered vibration signal exceeding a first threshold; and detecting a second peak value of the filtered vibration signal exceeding a second threshold, wherein the first threshold is one of a positive threshold and a negative threshold, and the second threshold is the other of a positive threshold and a negative threshold.

[0024] Furthermore, in one embodiment, the method includes a step of sampling a vibration signal, wherein a digital filter is used to perform a step of calculating a filtered vibration signal, and the step of detecting a first peak includes: detecting a first sample of the filtered vibration signal that exceeds a first threshold; detecting a second sample of the filtered vibration signal immediately preceding the first sample and having a modulus value lower than that of the first sample; and detecting a third sample of the filtered vibration signal immediately following the first sample and having a modulus value lower than that of the first sample, wherein the first peak is selected corresponding to the first sample.

[0025] Furthermore, in one embodiment, the step of detecting the second peak includes: detecting a fourth sample of the filtered vibration signal that exceeds a second threshold; detecting a fifth sample of the filtered vibration signal that immediately precedes the fourth sample and has a modulus value lower than that of the fourth sample; and detecting a sixth sample of the filtered vibration signal that immediately follows the fourth sample and has a modulus value lower than that of the fourth sample, wherein the second peak is selected corresponding to the fourth sample.

[0026] Furthermore, in one embodiment, the step of detecting the signal characteristics further includes: verifying that the first peak and the second peak are at a distance from each other that is lower than the maximum value of the number of samples included between the first peak and the second peak.

[0027] Furthermore, in one embodiment, the step of detecting a stationarity condition in the vibration signal prior to the signal characteristic includes: after detecting a first peak, verifying that the values ​​of a first plurality of samples of the filtered vibration signal prior to the first peak are within a first range of reference values.

[0028] Furthermore, in one embodiment, the step of detecting a stationarity condition in the vibration signal following the signal characteristic includes: after detecting a second peak, verifying that the value (p2) of a second plurality of samples of the filtered vibration signal following the second peak includes a second range of reference values.

[0029] Furthermore, in one embodiment, the step of detecting a stationarity condition in the vibration signal following the signal characteristic further includes discarding a third plurality of samples of the filtered vibration signal, the third plurality of samples being immediately following the second peak and included between the second peak and the second plurality of samples of the filtered vibration signal.

[0030] Furthermore, in one embodiment, the system further includes a static charge change sensor operatively coupled to the processing unit, and the method further includes detecting static charge changes at the detection surface via the static charge change sensor and thus generating a charge change signal via the static charge change sensor.

[0031] In addition, in one embodiment, the method further includes the step of generating a variance signal by calculating the variance of the charge change signal.

[0032] Furthermore, in one embodiment, the method further includes the step of detecting the maximum point of the variance signal when the signal characteristics that can be associated with the user's touch gesture are detected in the vibration signal.

[0033] Furthermore, in one embodiment, the method further includes: verification (S Q_var The touch gesture is activated only if the maximum value of the variance signal satisfies the predefined relationship with the third threshold, provided that both the signal characteristic and the stationarity condition before and / or after the signal characteristic have been detected.

[0034] Furthermore, in one embodiment, the method further includes: verifying whether the variance signal is in a stationary condition if both the signal characteristic and a stationarity condition before and / or after the signal characteristic have been detected, and if the maximum point of the variance signal satisfies the predefined relationship with a third threshold, and enabling the touch gesture only if the variance signal satisfies the stationarity condition.

[0035] Furthermore, in one embodiment, the stationarity condition of the variance signal is satisfied if at least one current sample of the variance signal has a value that is included within the range of stationarity reference values.

[0036] In addition, in one embodiment, the method further includes the step of: if the variance signal remains above a fourth threshold for a time longer than a predefined touch time, then a touch event that continues over time is detected. Attached Figure Description

[0037] To better understand this disclosure, embodiments thereof are now described only by way of non-limiting examples and with reference to the accompanying drawings, in which:

[0038] Figure 1AThe diagram illustrates the vibration signal generated by the accelerometer after movement;

[0039] Figure 1B The diagram illustrates the filtering process following the use of a high-pass filter, according to existing technology. Figure 1A The signal;

[0040] Figure 2 The illustration shows an accelerometer generating a signal using a reference according to the prior art. Figure 1B The filter described filters another signal, where a user's touch event is identified based on exceeding a predefined threshold;

[0041] Figure 3 An electronic or electromechanical system, chip, or package according to one aspect of this disclosure is schematically illustrated.

[0042] Figure 4 The illustration shows a method for detecting touch gestures using vibration signals from an accelerometer, according to one aspect of this disclosure;

[0043] Figures 5-7 The graphic map shows Figure 4 The various steps of the method;

[0044] Figure 8 The illustration shows a further embodiment according to another aspect of this disclosure, including an electrostatic charge sensor. Figure 3 Electronic or electromechanical systems, chips, or packages;

[0045] Figure 9 The diagram illustrates what can be used for Figure 8 Examples of electrostatic charge sensors in systems;

[0046] Figure 10 The figure illustrates a method for utilizing vibration signals from an accelerometer according to one aspect of this disclosure. Figure 9 A method to detect touch gestures by detecting changes in the static charge of a sensor;

[0047] Figure 11 and Figure 12 The graphic map shows Figure 10 The various steps of the method;

[0048] Figure 13 The graphic map shows Figure 9 The electrostatic charge sensor detects the change in electrostatic charge generated by touch over time using its detection electrodes; and

[0049] Figure 14 The diagram includes Figure 3 or Figure 8 Electronic or electromechanical systems, chips, or packaged electronic devices. Detailed Implementation

[0050] MEMS accelerometers are used to implement electronic buttons because they are well-suited for detecting movement caused by a user's touch or "tapping" (or double-tapping), thereby utilizing appropriate algorithms to detect and process the acceleration data provided by these MEMS accelerometers. However, even this solution is susceptible to environmental or usage conditions that may lead to erroneous touch detection (e.g., the acceleration produced by the movement of the user's body, even if it is not).

[0051] In some devices that do not suffer battery drain in standby mode (e.g., because they have large batteries), touchscreen technology can be used to detect touch gestures. This type of solution ensures high accuracy, but is costly to implement and, as mentioned, requires a significant amount of power.

[0052] In embodiments known to the applicant, touch gestures are identified by processing and monitoring acceleration or vibration signals, which are provided by an accelerometer and filtered by a high-pass filter after the touch gesture. Specifically, the high-pass filter is configured to filter out low-frequency signal components (e.g., acceleration due to gravity, movement attributed to human activity) and leave high-frequency signal components (including those attributed to touch) unchanged. As a non-limiting example, the high-frequency components of interest in this disclosure are above 50 Hz.

[0053] Specifically, filtering is achieved through a digital "slope" filter. Therefore, refer to... Figure 1A and Figure 1B For the raw signal provided by the accelerometer (in Figure 1A in, signal S acc_raw Sampling (i.e., converting to a digital signal); then again at Figure 1A In the middle, time t n The nth sample at point n is labeled as acc(t) n ), and the time immediately following t n-1 Previous samples were labeled as acc(t) n-1 ).

[0054] Figure 1B The diagram illustrates filtering using a slope filter. Figure 1A The signal (filtered signal S) acc_filt The nth filtered sample is obtained according to the following formula:

[0055] acc_filt(t n )=[acc(t n )-acc(t n-1 )] / 2

[0056] By setting an appropriate threshold for the filtered signal, possible touch events exceeding that threshold can be identified using at least one sample of the filtered signal. The threshold can be of a fixed type (preset and / or configurable) or an adaptive type.

[0057] Figure 2 The example shown is based on the reference. Figure 1B Another acceleration signal described is filtered using a slope filter. Figure 2 Two thresholds are also shown (one positive +Th and one negative -Th). Figure 2 In the sample, two samples, acc_filt(t1) and acc_filt(t2), are used. 11 At two separate times t1 and t2 11 An event exceeding the threshold +Th occurs, resulting in the generation of an interrupt event, which is identified at times t2 and t3. 12 The touch occurred because the signal returned within a predefined time range defined by the thresholds -Th and +Th.

[0058] This technical solution has the advantages of low energy consumption and low cost; in addition, it allows for high accuracy in identifying any touch event, but at the same time generates a large number of false alarms, such as when the accelerometer detects vibrations caused by unwanted touches near the device (e.g., on the strap of a smartwatch and in other similar situations).

[0059] Solutions using touch sensors overcome the problems mentioned above; however, as discussed, touch sensors are costly and consume significant power. Furthermore, touch sensor technology is not suitable for every device (e.g., headphones) due to the size and / or current consumption required to implement them.

[0060] Therefore, there is a need to improve upon the deficiencies of the prior art by providing a system for detecting user touch gestures, a device including the detection system, and a method for detecting user touch gestures.

[0061] Figure 3 Reference numeral 1 illustrates an electronic or electromechanical system, chip, or package according to one aspect of this disclosure. Hereinafter, the system, chip, or package 1 will be referred to as the "electronic system" without loss of generality. The electronic system 1 includes, for example, a processing unit 2 integrated or housed in a housing, and a MEMS motion sensor, such as an accelerometer 4, operatively coupled to the processing unit 2.

[0062] Accelerometer 4 is configured to detect along a surface with respect to the detection surface (see, for example, see...). Figure 14The surface 102 in the accelerometer detects at least one acceleration component along an orthogonal acceleration axis. The detection surface is the surface that vibrates when touched by a user, for example, with his / her finger (a touch event or touch). For example, the accelerometer 4 is triaxial and is configured to detect acceleration components along three mutually orthogonal axes X, Y, and Z; for touch detection, the Z-axis can be selected as the sole detection axis, or any combination of two or more axes can be selected, possibly assigning greater weight to one of the axes.

[0063] Note that electronic system 1 (and therefore accelerometer 4) can be mounted or used in any orientation relative to the Earth's axis of gravity, and therefore accelerometer 4 can be oriented in a manner that does not require the perpendicular detection axis (Z-axis) to be in the direction of gravity. Thus, the detection axis of the force applied by touch can be selected to be orthogonal to the sensor itself or along a presumed touch direction (based on the mode in which electronic system 1 is mounted, operated, or intended to operate); this also allows filtering out any unwanted pulses that would originate from other directions.

[0064] As an alternative or supplement to the above, in a further embodiment, an appropriate vector combination of the three detection axes of the accelerometer 4 may also be considered to maximize the signal in the direction of force application.

[0065] Processing unit 2 receives acceleration signals or vibration signals S from accelerometer 4. acc_raw (Original signal), and based on the acceleration signal S acc_raw To generate the user's touch detection signal I S (e.g., interrupt signals).

[0066] Accelerometer 4 is, for example, an integrated sensor made of semiconductor material, which is manufactured using MEMS technology, a known type of technology and therefore not described in detail.

[0067] Processing unit 2 is, for example, a microcontroller or an MLC (machine learning core) residing in an ASIC (application-specific integrated circuit) integrated in MEMS, or other types of microprocessors.

[0068] Electronic system 1 can be a standalone system or, for example, part of a printed circuit, or even part of a more complex device or system. In fact, devices or systems that provide integrated sensor combinations may be available, and therefore, in addition to the three axes X, Y, Z of accelerometer 4, there may be dedicated channels for other detections (e.g., gyroscopes, temperature sensors, etc.).

[0069] Figure 4 The flowchart illustrates the steps of a method for detecting touch implemented by an electronic system 1, particularly a processing unit 2, according to one aspect of this disclosure.

[0070] Referring to step 40, processing unit 2 receives and acquires the raw signal S generated by accelerometer 4 from accelerometer 4. acc_raw ,For example Figure 1A signal S acc_raw Then, in step 42, processing unit 2 processes the original signal S through a high-pass filter. acc_raw Perform a filtering operation; specifically, via a reference. Figure 1B The slope filter described is used to perform the filtering operation and obtain the filtered signal S. acc_filt Filtered signal S acc_filt For example is Figure 1B ,or Figure 2 ,or Figure 5 (or Figure 6 or Figure 7 The diagram illustrates the filtered signal generated by events other than touch events.

[0071] Then, in step 44, the first peak p1 (positive or negative) is detected in the filtered signal, followed by the detection of the second peak p2, which is the inverse peak (negative or positive, respectively). See [link to relevant documentation] for details. Figure 5 Where peak p1 corresponds to the filtered signal S exceeding the negative threshold -Th. acc_filt The sampling, and therefore referred to as the "negative peak" below, is p1, while the peak p2 after p1 corresponds to the filtered signal S exceeding the positive threshold +Th. acc_filt The sampling, and therefore referred to below as the "positive peak value".

[0072] In embodiments of this disclosure, a negative peak p1 is identified as a sample exceeding a threshold -Th, and immediately preceding and following it are corresponding samples p1' and p1'", the moduli of which are lower than the moduli of the negative peak p1. Similarly, a positive peak p2 is identified as a sample exceeding a threshold +Th, and immediately preceding and following it are corresponding samples p2' and p2'", the moduli of which are lower than the moduli of the positive peak p2. Note that in this example, samples p1' and p2' overlap.

[0073] Clearly, the conditions expressed above can be modified, for example by requiring multiple samples before and / or after the positive peak p2 or the negative peak p1 and having corresponding values ​​in modulus numbers that are lower than the values ​​reached by peaks p1 or p2.

[0074] In one embodiment, the number of samples between the negative peak p1 and the positive peak p2 (in Figure 5 In the example, only one sample (p1” / p2’) is below the predefined maximum number to better distinguish “touch” events from other types of events. For example, this sample number is equal to 2 (at 400 Hz for the original signal S).acc_raw (Sampling) or multiples of 2 (multiples of 400 Hz for the original signal S) acc_raw (Sampling is performed). Other values ​​can be selected as needed.

[0075] Return to Figure 4 In step 46, the filtered signal S before the first peak p1 is detected. acc_filt The stability condition. Specifically, this step aims to detect whether the detected first peak is caused by an actual touch event or by a more complex "impact" event (such as, for example, an impact on the electronic system 1 housing the accelerometer 4). In fact, under shaking conditions, the signal from the accelerometer 4 experiences continuous perturbations, which can also lead to the generation of one or more peaks exceeding a preset threshold ±Th, such as, for example... Figure 6 As shown in the diagram.

[0076] For clarity, this article references... Figure 6 To describe step 46. Figure 6 In China, use and Figure 5 The same labels are used to identify the first peak (p1) and the reverse peak (p2) exceeding a preset threshold ±Th. According to one aspect of this disclosure, to distinguish touch events from other types of events such as shaking, a history buffer is used, which stores multiple samples p_pre (temporary) preceding the first peak p1. Specifically, these multiple samples are a number equal to or greater than 8 (e.g., 16 or 32) and include sample p1' and other samples immediately preceding sample p1'. When the first peak p1 is detected (as discussed previously), according to step 46, the history buffer is analyzed to verify the stationarity condition of the samples stored therein. Specifically, the stationarity condition is verified if all samples or subsets thereof stored in the history buffer are contained between the positive threshold +Th' and the negative threshold –Th' (where |+Th'|<|+Th| and |-Th'|<|-Th|). For example, the modulus of the threshold ±Th' is between 0.0625 g and 2 g.

[0077] In one embodiment, the stationarity condition is evaluated on the samples present in the history buffer, except for a subset of samples immediately preceding the first peak p1 (e.g., the two samples immediately preceding the first peak p1). The applicant has actually verified that the touch-related signal includes samples immediately preceding the peak.

[0078] In step 48, based on what has been discussed previously, a second peak p2 (anti-peak) is sought and detected if it exists.

[0079] In step 50, the filtered signal S after the second peak p2 is detected. acc_filtThe stability condition. Specifically, this step aims to detect whether the detected second peak p2 is caused by an actual touch event or by a more complex "impact" event, such as, for example, a clapping situation lasting for a certain period of time that results in the generation of an acceleration signal, where a series of positive and negative peaks above a threshold (similar to the sequence of the first peak p1 and the second peak p2) are followed by multiple additional peaks or high-noise signals, such as... Figure 7 The diagram in the figure (where and) Figure 5 The same label was used to identify the first peak p1 and the inverse peak p2.

[0080] Therefore, in order to identify situations such as those generated by clapping, according to one aspect of this disclosure, multiple samples following the second peak p2 are analyzed.

[0081] Specifically, the plurality of samples is a number equal to or greater than 8 (e.g., 16 or 32) and includes sample p2” and other samples immediately following sample p2”. In particular, the stationarity condition is verified if all samples or subsets thereof immediately following the second peak p2 are contained between the positive threshold +Th” and the negative threshold –Th” (where |+Th”|<|+Th| and |-Th”|<|-Th|). For example, the modulus of the threshold ±Th” is between 0.0625 g and 2 g.

[0082] In one embodiment, the stationarity condition is evaluated on multiple samples p_post immediately following the second peak p2, excluding the subset p_excl immediately following the second peak p2 (e.g., excluding the 6-8 samples immediately following the second peak p2). Indeed, the applicant has verified that, under certain practical conditions, in events where the signal is generated by a “touch” (and thus the event to be detected), a step is observed after the second peak p2, where the oscillation of the accelerometer 4 signal lasts for a finite time, similar to a “bounce” effect. In this way, the stationarity condition is evaluated by excluding this settling step following the second peak p2.

[0083] The reference can be modified as needed. Figure 4 The method described herein. Specifically, the first peak can be either a negative peak or a positive peak, and consequently, the second peak (inverse peak) is either a positive peak or a negative peak, respectively. Furthermore, the stationarity verifications in steps 46 and 50 can be performed simultaneously or one can be performed as a substitute for the other. For example, it can be specified that only the stationarity verification in step 46 is performed without performing the stationarity verification in step 50, and vice versa.

[0084] also, Figure 4This method can also be used to identify multiple touch events (e.g., two or three touches) to verify the existence of multiple consecutive touch events within a predefined (and possibly configurable) time period. For this purpose, a timer or counter can be used to count the number of samples present before subsequent touch events after a touch event occurs. If this number of samples is within a predefined range (or below a maximum value), then the second touch event is associated with the first touch event to make multiple touch events effective.

[0085] In embodiments of this disclosure, such as Figure 8 As illustrated in the figure, in addition to the elements shown in the figure and previously described, the electronic system 1 also includes (e.g., integrated or housed in a housing) an electrostatic charge change sensor 6 operatively coupled to the processing unit 2.

[0086] Figure 9 An embodiment of the electrostatic charge change sensor 6 is illustrated by way of non-limiting example. The electrostatic charge change sensor 6 includes an input electrode 8 that can be coupled to a user's body part. In particular, Figure 9 The electrostatic charge change sensor 6 is configured to make electrical or electrostatic contact with a part of the user's body for detecting touch. Typically, the user uses his / her fingers, especially his / her fingertips, to perform a touch.

[0087] The input electrode 8 forms part of the differential input 9 of the instrumentation amplifier 12.

[0088] Input capacitor C I They are connected in parallel with each other and connected to the input capacitor C. I parallel-connected DC generator G I and input resistor R I They are used for biasing and are located at the ends of differential input 9. In use, the input capacitor C... I The voltage Vd across the terminals remains constant until the user touches electrode 8; in this case, the input capacitor C... I The voltage across the terminals changes due to the charging / discharging process through the user's body. In the presence of a touch event, and therefore immediately after the transient event (its duration determined by the capacitor C), the voltage changes. I and resistor R I (Defined by constant RC in parallel between them), the voltage Vd returns to its steady-state value.

[0089] Instrumentation amplifier 12 mainly consists of two operational amplifiers, OP1 and OP2. The bias stage (buffer) OP3 is used to bias instrumentation amplifier 12 to the common-mode voltage V. CM .

[0090] The inverting terminals of operational amplifiers OP1 and OP2 are connected to each other via resistor R2. Since the two inputs of each operational amplifier OP1 and OP2 are at the same potential, the input voltage Vd is also applied across R2, generating a current equal to I2 = Vd / R2 through this resistor. This current I2 does not originate from the input terminals of operational amplifiers OP1 and OP2, but rather flows through two resistors R1 connected in series with resistor R2 between the outputs of operational amplifiers OP1 and OP2; the current I2, therefore flowing through the series connection of three resistors R1-R2-R1, generates the output voltage Vd', given by Vd' = I2·(2R1+R2) = Vd·(1+2R1 / R2). Therefore, Figure 9 The total gain of the circuit is Ad = (1 + 2R1 / R2). The differential gain depends on the value of resistor R2, and therefore can be modified by taking action on resistor R2.

[0091] The components of amplifier 12 are selected in such a way that amplifier 12 has a high impedance (approximately 10 ohms) in its passband (selected between DC and 500 Hz). 9 ohm).

[0092] Input capacitor C I The voltage Vd across the terminals is detected by amplifier 12.

[0093] The differential output Vd' is therefore proportional to the potential Vd at the input and is provided at the input to the analog-to-digital converter 14, which provides the charge change signal S to the processing unit 2 at the output. Q Charge change signal S Q For example, a high-resolution digital stream (16-bit or 24-bit).

[0094] According to one embodiment, the analog-to-digital converter 14 is optional because the processing unit 2 can be configured to operate directly on analog signals, or it may itself include an analog-to-digital converter for converting signal Vd'.

[0095] According to one embodiment, an analog-to-digital converter (ADC) with suitable characteristics (e.g., differential input, high input impedance, high resolution, dynamic range optimized for the quantity to be measured, low noise) can omit amplifier stage 12 by feeding the signal directly to the input of the ADC.

[0096] Figure 10 The flowchart illustrates the operation performed by the processing unit 2 to process the signal provided by the electrostatic charge change sensor 6.

[0097] Referring to step 60, processing unit 2 receives charge change signal S from electrostatic charge change sensor 6. Q In the described embodiment, signal SQ It is a digital signal. Figure 11 An exemplary illustration shows the signal S generated after a contact event (touch event) between the input electrode 8 and the user's fingertip. Q The value of the potential Vd caused by the physical contact between the user and the input electrode 8 is represented in the charge change signal S. Q The value is expressed here as LSB (“least significant bit”), which is the smallest digital value output from the analog-to-digital converter, proportional to the voltage detected at input electrode 8. Typically, 1 LSB corresponds to a value between a few µV and tens of µV. The scaling constant (or sensitivity) depends on the amplifier gain, the resolution of the analog-to-digital converter, and any digital processing (e.g., oversampling, decimation, etc.). LSB representation is common in the art and ignores the quantization of physical units because its purpose is usually to detect relative changes with respect to a steady state or fundamental state. In the charge change signal S Q The horizontal axis represents the asymptotic number of the acquired samples.

[0098] Then, in step 62, processing unit 2 performs calculation or estimation of signal S. Q Variance manipulation to obtain the variance signal S Q_var The calculation or estimation of variance is performed in a manner known per se, as described by Tony Finch in “Incremental calculation of weighted mean and variance” (Cambridge Computation Service, February 2009). Other methods may be used, such as those based on IIR filters or other approaches.

[0099] Figure 12 The diagram illustrates the superimposed variance signals S. Q_var and the filtered accelerometer signal S acc_filt Please note, Figure 12 Signal S is shown acc_filt and S Q_var The square root of the variance. Calculating the square root of the variance compresses the dynamics of the output signal and restores it to its initial physical dimension. That is, the square root of the variance recovers the physical dimension. For example, if the physical dimension x of the input signal is [x]... 2 ; after variance is [(x 2 )] 2 After the square root operation, it returns [x]. 2 .

[0100] Then, in step 64, the search for signal S is performed. QThe steps for finding the maximum value point. In this example where a digital signal (sample) is used, the maximum value point corresponds to the sample whose value (on the vertical axis) is the largest relative to multiple comparison samples. Specifically, each sample is compared to the maximum value detected up to that moment, and if it is greater than the maximum value, the maximum value is updated to the value of the current sample. This operation is initiated after the accelerometer 4 detects a "shock" event (e.g., the maximum value is reset to the current value). The shock event under consideration is any event that causes the signal generated by the accelerometer 4 to exceed a threshold of +Th (positive exceedance) or -Th (negative exceedance) after filtering (e.g., high-pass filter or slope filter) as previously described. If signal S acc_filt If at least one sample exceeds the threshold ±Th, then it is confirmed that the threshold ±Th has been exceeded.

[0101] exist Figure 12 in, signal S acc_filt The sample #28 is negative and exceeds the threshold –Th (first peak p1). This event triggers the search signal S. Q_var The maximum value. At sample #28, the maximum value is reset to signal S. Q_var The current value of . Therefore, from signal S Q_var In the corresponding sample #28 (or from the subsequent sample #29), it is evaluated whether the sample has a value greater than the maximum value calculated up to that moment (here, in LSBs). This operation continues until an actual touch signal is detected, as described here in step 66 below. Q_var The assumed maximum value is stored in memory. Figure 12 In the example, in signal S Q_var Sampling #36 (sample p) MAX Find the sample with the maximum value at ().

[0102] Then, in step 66, based on the signal from accelerometer 4 (e.g., the previously mentioned interrupt signal I) S Waiting for confirmation of the touch that occurred. Figure 12 In this process, the signal is generated at sampling point #90. This interrupts the process discussed in step 64 for signal S. Q_var Search for the maximum value.

[0103] In this embodiment, as previously discussed, a final decision is made regarding the occurrence of a touch based on the signal from the accelerometer 4 and also on the signal acquired and processed by the electrostatic charge change sensor 6. Specifically, upon receiving an interrupt signal I... S At that time, acquire signal S Q_var The current sample (for the purposes of this disclosure, the current sample is, exemplarily, the one that received the interrupt). The value of the current sample is compared with the threshold Th_Q.

[0104] In one embodiment, if signal S Q_var sampling p MAX If the value of the touch event is in a predefined relationship with the threshold (specifically, it exceeds the threshold Th_Q), then the touch event is acknowledged and one or more functionalities associated with the touch event (not for the purposes of this disclosure) are activated. The threshold Th_Q is preset to a value selected during the design phase and is variable in all cases (e.g., between 8000 and 12000 LSB); this value is selected through laboratory testing based on the sensor and electrodes used.

[0105] In another embodiment, if signal S Q_var sampling p MAX If the value of the signal is in a predefined relationship with the threshold (specifically, if it exceeds the threshold Th_Q), then the signal S is executed. Q_var The current sampled value and the signal S selected as the previous identifier Q_var A further comparison of the second threshold Th_Q', which is a portion of the maximum value of the signal S (i.e., the one found at sample #36 in this example). For example, the second threshold Th_Q' is equal to the signal S. Q_var The maximum value is 1 / 4. In this embodiment, the above operation (as described above) is performed on the variance signal under the square root. However, other embodiments are also possible. If the comparison with thresholds Th_Q and Th_Q' both meet their respective predefined conditions (in particular, the signal S... Q_var sampling p MAX The value exceeds the threshold Th_Q and the signal S Q_var If the current value is below the threshold Th_Q', then the touch event is confirmed and one or more functionalities associated with the touch event are activated (not for the purpose of this disclosure).

[0106] In another embodiment, as an addition or alternative to the previously described embodiments, the use of the signal generated by the electrostatic charge sensor 6 can also be used to detect touch conditions that persist over time, such as when a user performs a touch while holding the touchscreen, with pressure lasting for a fraction of a second (e.g., 0.6 seconds). This event is referred to herein as a “long touch,” and it can be used to activate additional or different functionality with respect to functionality that can be activated by conventional, typically rapid touch events.

[0107] If signal S Q_var A long touch event is identified if the time remaining above the threshold Th_Q is longer than the minimum time, which is predefined during the design phase and can be configured as needed in any case. Clearly, the comparison threshold used for long touches can be a different threshold than Th_Q, for example, chosen to be equal to 10000 LSB. Figure 13 The diagram illustrates the signal S indicating a long touch. Q_var Examples.

[0108] also, Figure 10 This method can also be used to identify multiple touch events (e.g., two or three touches) to verify the existence of multiple consecutive touch events within a predefined (and possibly configurable) time period, similar to the reference. Figure 4 The method is described above.

[0109] Figure 14 An electronic device 100 including the aforementioned electronic system 1 is schematically illustrated according to any embodiment of the present disclosure.

[0110] For example, electronic device 100 includes a touch-sensitive surface 102 (detection surface), which is the surface on which a user performs a physical touch gesture. This surface is made of, for example, a plastic material with a thickness of approximately 1 mm. Electronic system 1 is placed below surface 102, for example, housed within its own package.

[0111] To optimize signal S Q and S acc The generation of the electronic system 1, preferably but not necessarily, requires that the relative arrangement between surface 102 and electronic system 1 satisfies one or more of the following parameters: Sensors used to detect acceleration and charge changes are arranged as close as possible to the area identified as the touch surface; and Sensors used to detect acceleration and charge changes are placed close to each other to optimize the correlation of the corresponding signals.

[0112] This disclosure can be effectively implemented in all those devices where impermeability, dust immunity, or mechanical strength requirements are necessary, or where mechanical contact cannot exist. Some examples include: smartphones, smartwatches, true wireless stereo (TWS) headphones, electrical appliances, industrial equipment, etc.

[0113] The advantages achieved through this disclosure are obvious from the foregoing description.

[0114] In particular, compared to solutions that provide "touchscreen" type panels for sensors, the use of accelerometers and, in corresponding embodiments, electrostatic charge sensors allow for a significant reduction in power consumption.

[0115] In addition, refer to Figure 4 The described solution (detecting stationarity before and / or after detecting the first and second peaks) allows for a significant reduction in false alarms. The solution using an electrostatic charge sensor further improves the performance in rejecting false alarms compared to solutions with only an accelerometer.

[0116] In addition, the use of electrostatic charge sensors expands the range of gestures (e.g., long touch) that users can use to give commands to the system 100.

[0117] Variations and modifications may be applied to this disclosure without departing from the scope defined by the claims.

[0118] For example, it can provide (e.g., using a low-pass or high-pass filter) a filter for signal S. acc and S Q The corresponding filtering operation is performed. Specifically, the filtering has a starting point from signal S. acc and S Q Remove noise or insignificant frequency interference components or low-frequency components (e.g., gravitational acceleration components or those attributed to S). acc The function of human movement (the movement of human activities).

[0119] Furthermore, the signal processing of the accelerometer 4 and the electrostatic charge sensor 6 can be implemented entirely in hardware, entirely in software, or in a hybrid hardware / software manner, as needed.

[0120] A system (1) for detecting a user's touch gesture on a detection surface (102) is provided, the system being generally summarized as including a processing unit (2); an accelerometer (4) operatively coupled to the processing unit (2), configured to detect vibrations at the detection surface (102) and generate a corresponding vibration signal (S). acc_raw ), wherein the processing unit (2) is configured to: acquire vibration signal (S acc_raw ), in vibration signal (S acc_raw S acc_filt ) detect signal characteristics (p1, p2) that can be related to the user's touch gesture, in the vibration signal (S acc_raw S acc_filt The system detects the stability conditions before and / or after the detected signal characteristic, and enables the user's touch gesture if both the signal characteristic and the stability conditions before and / or after the signal characteristic have been detected.

[0121] The operation of detecting the signal characteristics (p1, p2) may include: filtering the vibration signal (S) via a high-pass filter. acc_raw ) is filtered, and the filtered vibration signal (S) is calculated. acc_filt ); Detect the filtered vibration signal (S) acc_filt The first peak value (p1) of the filtered vibration signal (S) exceeds the first threshold (-Th; +Th). acc_filtThe second peak (p2) of the first threshold (+Th; -Th) exceeds the second threshold (+Th; -Th), where the first threshold can be one of the positive threshold and the negative threshold, and the second threshold can be the other of the positive threshold and the negative threshold.

[0122] The processing unit (2) can also be configured to process vibration signals (S) acc_raw Sampling is performed, and digital filters can be used to calculate the filtered vibration signal (S). acc_filt The operation of detecting the first peak value may include: detecting the filtered vibration signal (S). acc_filt The first sample (p1) exceeding the first threshold is detected; the filtered vibration signal (S) immediately preceding the first sample (p1) and whose modulus value may be lower than that of the first sample (p1) is detected. acc_filt The second sample (p1') is detected; and the filtered vibration signal (S) immediately following the first sample (p1) and whose modulus value may be lower than that of the first sample (p1) is detected. acc_filt The third sample (p1) of the first peak corresponds to the first sample (p1).

[0123] The operation of detecting the second peak value (p2) may include: detecting the filtered vibration signal (S acc_filt The fourth sample (p2) exceeding the second threshold is detected; the filtered vibration signal (S) immediately preceding the fourth sample (p2) and whose modulus value may be lower than that of the fourth sample (p2) is detected. acc_filt The fifth sample (p2') is detected; and the filtered vibration signal (S) immediately preceding the fourth sample (p2) and whose modulus value may be lower than that of the fourth sample (p2) is detected. acc_filt The sixth sample (p2) of the second peak corresponds to the fourth sample (p2).

[0124] The operation of detecting the signal characteristics (p1, p2) may further include: verifying that the first peak (p1) and the second peak (p2) are at a mutual distance that may be lower than the maximum value of the number of samples included between the first peak (p1) and the second peak (p2).

[0125] In vibration signal (S) acc_raw S acc_filt The operation of detecting the stationarity condition before the signal characteristics (p1, p2) in the signal may include: after detecting the first peak (p1), verifying the filtered vibration signal (S) before the first peak (p1). acc_filt The value of the first plurality of samples (p_pre) can be included in the first range (±Th') of the reference value.

[0126] In vibration signal (S)acc_raw S acc_filt The operation of detecting the stationarity condition after the signal characteristics (p1, p2) in the signal may include: after detecting the second peak (p2), verifying the filtered vibration signal (S) after the second peak (p2). acc_filt The value of the second multiple sample (p_post) can be included in the second range (±Th") of the reference value.

[0127] In vibration signal (S) acc_raw S acc_filt The operation of detecting the stationarity condition after the signal characteristics (p1, p2) in the process may also include: discarding the filtered vibration signal (S acc_filt The third multiple sample (p_excl) immediately follows the second peak (p2) and can be included in the second peak (p2) and the filtered vibration signal (S). acc_filt Between the second plurality of samples.

[0128] The system may also include a static charge change sensor (6) operatively coupled to the processing unit (2), which is configured to detect static charge changes at the detection surface and thus generate a charge change signal (S). Q ).

[0129] The processing unit (2) can also be configured to calculate the charge change signal (S) Q The variance of ) is used to generate the variance signal (S) Q_var ).

[0130] The processing unit (2) can also be configured to: when the vibration signal (S) is detected, the processing unit (2) can be configured to: acc_raw S acc_filt When the signal characteristics that can be related to the user's touch gesture are detected in the signal, the variance signal (S) is detected. Q_var The maximum point (p) MAX ).

[0131] The processing unit (2) can also be configured to: verify the variance signal (S Q_var The maximum point (p) MAX Whether it can be in a predefined relationship with a third threshold, and in the case that both the signal characteristic and the stationarity condition before and / or after said signal characteristic have been detected, only if the variance signal (S) Q_var The maximum point (p) MAX The touch gesture is only enabled when the predefined relationship with the third threshold is satisfied.

[0132] The processing unit (2) can also be configured to: when both the signal characteristic and the stationarity condition before and / or after the signal characteristic have been detected, and if the variance signal (S) Q_var The maximum point (p) MAX If the variance signal (S) satisfies the predefined relationship with the third threshold, then the variance signal (S) is verified. Q_var Is it possible for a signal to be stationary, and only if the variance signal (S) is in a stationary state? Q_var The touch gesture will only take effect when the stability condition is met.

[0133] If the variance signal (S) Q_var If at least one current sample of a variance signal (S) has a value that is included within the range of the stationarity reference value, then the variance signal (S) Q_var The stationarity condition of can be satisfied.

[0134] The system may also include the following steps: if the variance signal (S) Q_var If the touch event remains above the fourth threshold for a period of time that may be longer than the predetermined touch time, then touch events that continue over time will be detected.

[0135] An electronic device (100) may be summarized as including a detection surface (102) for a user's touch gesture; and a system (1) for detecting touch gestures according to any one of claims 1-15.

[0136] A method for using a system (1) to detect a user's touch gesture on a detection surface (102), the system being generally summarized as including a processing unit (2); an accelerometer (4) operatively coupled to the processing unit (2), configured to detect vibrations at the detection surface (102) and generate a corresponding vibration signal (S). acc_raw The method includes the steps performed by the processing unit (2): acquiring a vibration signal (S) acc_raw ), in vibration signal (S acc_raw S acc_filt ) detect signal characteristics (p1, p2) that can be related to the user's touch gesture, in the vibration signal (S acc_raw S acc_filt The system detects the stability conditions before and / or after the detected signal characteristic, and enables the user's touch gesture if both the signal characteristic and the stability conditions before and / or after the signal characteristic have been detected.

[0137] The system (1) may further include a static charge change sensor (6) operatively coupled to the processing unit (2), and the method may further include the steps of: detecting a static charge change at the detection surface by means of the static charge change sensor (6), and thus generating a charge change signal (S) by means of the static charge change sensor (6). Q ).

[0138] The various embodiments described above can be combined to provide other embodiments. If needed, aspects of the embodiments can be modified to employ the concepts of various embodiments to provide other embodiments.

[0139] These and other changes can be made to the embodiments based on the above detailed description. Generally, the terminology used in the following claims should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted to include all possible embodiments and the full scope of the equivalents enjoyed by those claims. Therefore, the claims are not limited to this disclosure.

Claims

1. A system for detecting touch gestures on a detection surface, the system comprising: An accelerometer is configured to detect vibrations at the detection surface and generate a vibration signal corresponding to the vibrations; and The processing unit is operatively coupled to the accelerometer and is configured to: Acquire the vibration signal, Detecting signal characteristics in the vibration signal related to the touch gesture includes: calculating a filtered vibration signal by filtering the vibration signal via a high-pass filter, and detecting a first peak value of the filtered vibration signal exceeding a first threshold. Detecting a stationarity condition in the vibration signal that is adjacent to the detected signal characteristic in the time series includes: after detecting the first peak, verifying that the values ​​of a first plurality of samples of the filtered vibration signal before the first peak are within a first range of reference values, and The touch gesture is activated in response to the detection of both the signal characteristics and the stability condition.

2. The system according to claim 1, wherein detecting the signal characteristics comprises: Detect the second peak value of the filtered vibration signal that exceeds the second threshold. The first threshold is either a positive threshold or a negative threshold, and the second threshold is either the positive threshold or the negative threshold.

3. The system of claim 2, wherein the processing unit is further configured to sample the vibration signal and use a digital filter to perform calculations on the filtered vibration signal. The detection of the first peak value includes: The first sample of the filtered vibration signal that exceeds the first threshold is detected; The second sample of the filtered vibration signal is detected, the second sample is immediately before the first sample, and has a modulus value lower than that of the first sample; as well as The third sample of the filtered vibration signal is detected. The third sample is immediately after the first sample and has a lower modulus value than the first sample. The first peak corresponds to the first sample.

4. The system of claim 3, wherein detecting the second peak value comprises: Detect the fourth sample of the filtered vibration signal that exceeds the second threshold; The fifth sample of the filtered vibration signal is detected, the fifth sample being immediately before the fourth sample and having a lower modulus value than the fourth sample. as well as The sixth sample of the filtered vibration signal is detected. The sixth sample immediately follows the fourth sample and has a lower modulus value than the fourth sample. The second peak corresponds to the fourth sample.

5. The system according to claim 2, wherein detecting the signal characteristics comprises: Regarding the number of samples between the first peak and the second peak, it is verified that the first peak and the second peak are at a distance from each other that is less than the maximum number of samples.

6. The system of claim 2, wherein the operation of detecting a stationarity condition in the vibration signal adjacent to the signal characteristic comprises: After detecting the second peak, verify that the values ​​of the second plurality of samples of the filtered vibration signal after the second peak are within the second range of the reference value.

7. The system of claim 6, wherein detecting the stationarity condition adjacent to the signal characteristic in the vibration signal further includes: A third plurality of samples of the filtered vibration signal are discarded. The third plurality of samples immediately following the second peak and located between the second peak and the second plurality of samples of the filtered vibration signal.

8. The system of claim 1 further includes a static charge change sensor operatively coupled to the processing unit, the static charge change sensor being configured to detect static charge change at the detection surface and generate a charge change signal based on the static charge change.

9. The system of claim 8, wherein the processing unit is further configured to calculate a variance value based on the charge change signal.

10. The system of claim 9, wherein the processing unit is further configured to detect the maximum point of the variance value in response to the detection of the signal characteristics associated with the user's touch gesture in the vibration signal.

11. The system of claim 10, wherein the processing unit is further configured to: Verify whether the maximum point of the variance signal satisfies the relationship with the third threshold, and The touch gesture is activated only when both the signal characteristic and the stationarity condition adjacent to the signal characteristic have been detected, and the maximum value of the variance signal satisfies the relationship with the third threshold.

12. The system of claim 10, wherein the processing unit is further configured to: If both the signal characteristic and the stationarity condition before and / or after the signal characteristic have been detected, and if the maximum point of the variance signal satisfies a predefined relationship with a third threshold, then the variance signal is verified to be in a stationarity condition, and the touch gesture is enabled only if the variance signal satisfies the stationarity condition.

13. The system of claim 12, wherein at least one current sample of the variance signal has a value within a stationarity reference range, and the stationarity condition of the variance signal is satisfied.

14. The system according to claim 9, further comprising: Touch events that persist over time are detected in response to the variance signal remaining above a fourth threshold for a period longer than a predefined touch time.

15. The system according to claim 1, comprising: The detection surface is configured to receive touch gestures from the user.

16. A method for detecting a user's touch gesture on a detection surface, the method comprising: Vibration at the detection surface is detected by an accelerometer; The accelerometer generates a vibration signal corresponding to the detected vibration; The vibration signal is acquired by a processing unit, which is communicatively coupled to the accelerometer. The processing unit detects signal characteristics in the vibration signal related to the user's touch gesture, including: calculating a filtered vibration signal by filtering the vibration signal via a high-pass filter, and detecting a first peak value of the filtered vibration signal that exceeds a first threshold. The processing unit detects a stationarity condition in the vibration signal that is adjacent to the detected signal characteristic in the time series, including: after detecting the first peak, verifying that the values ​​of a first plurality of samples of the filtered vibration signal before the first peak are within a first range of reference values; and In response to the detection of both the signal characteristics and the stability condition, the processing unit activates the touch gesture.

17. The method of claim 16, further comprising: The change in static charge at the detection surface is detected by a static charge change sensor, which is operatively coupled to the processing unit; as well as As a result of detecting the change in static charge, the static charge change sensor generates a charge change signal.

18. A system for detecting touch gestures on a detection surface, the system comprising: An accelerometer is configured to detect vibrations at a detection surface and generate a vibration signal based on the vibrations; A static charge change sensor is configured to detect static charge changes at the detection surface and generate a charge change signal based on the static charge changes; and The processing unit is communicatively coupled to the accelerometer and the electrostatic charge change sensor, and is configured to: Acquire the vibration signal, Detect the signal characteristics in the vibration signal that are related to the touch gesture. The stationarity condition in the vibration signal that is adjacent to the detected signal characteristic in the time series is detected. The variance value is calculated based on the charge change signal, and The touch gesture is activated in response to the detection of both the signal characteristics and the stationarity condition, and based on the variance value.

19. The system of claim 18, wherein enabling the touch gesture based on the variance value comprises: Verify whether the maximum value of the variance meets the threshold.

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