Piezoelectric Sensing Devices

Abstract

The object is to provide an electronic device for sensing and / or for providing a tactile effect. According to an embodiment, a device includes a touch surface; a piezoelectric transducer mechanically coupled to the touch surface; and a control circuit electrically coupled to the piezoelectric transducer, configured to: obtain at least one parameter describing a reference response of the piezoelectric transducer; form a reference voltage curve based on the at least one parameter; drive the piezoelectric transducer with a drive voltage; measure the voltage curve on the piezoelectric transducer; compare the reference voltage curve and the measured voltage curve; and detect a touch on the touch surface based on the comparison. A device, method and computer program product are provided.

Description

Technical Field

[0001] The present disclosure relates to a device, and more particularly to an electronic device for sensing and / or for providing haptic effects. Background Art

[0002] Piezoelectric transducers can be used to provide haptic effects to a user, sense touch, or both. However, using a single piezoelectric transducer to perform both functions can present various challenges. For example, if the piezoelectric transducer is driven with a drive voltage at the same time, it can be difficult to detect the signal generated by the user's touch. Summary of the invention

[0003] This Summary is provided to introduce some concepts in a simplified form that are further described below in the Detailed Description.This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0004] The object is to provide an electronic device for sensing and / or for providing tactile effects. The aforementioned and other objects are achieved by the features of the independent claims. Further implementation forms are evident from the dependent claims, the description and the drawings.

[0005] According to a first aspect, a device includes: a touch surface; a piezoelectric transducer mechanically coupled to the touch surface; and a control circuit electrically coupled to the piezoelectric transducer, configured to: obtain at least one parameter describing a reference response of the piezoelectric transducer; form a reference voltage curve based on the at least one parameter; drive the piezoelectric transducer with a drive voltage; measure the voltage curve on the piezoelectric transducer; compare the reference voltage curve and the measured voltage curve; and detect a touch on the touch surface based on the comparison. For example, the device can detect a touch on the touch surface even when the piezoelectric transducer is driven with the drive voltage.

[0006] In an implementation form of the first aspect, the control circuit is further configured to detect a time-varying characteristic of the touch on the touch surface based on the comparison.The device can for example detect whether the force exerted by the touch is increasing or decreasing.

[0007] In another implementation form of the first aspect, the at least one parameter comprises an RC time constant of the piezoelectric transducer.For example, the apparatus is capable of forming a reference voltage curve using a single parameter.

[0008] In another implementation form of the first aspect, the control circuit is further configured to compare the reference voltage curve with the measured voltage curve by calculating a difference between the reference voltage curve and the measured voltage curve. The device may, for example, be capable of effectively comparing the reference voltage curve with the measured voltage curve.

[0009] In another implementation form of the first aspect, the control circuit is further configured to compare the reference voltage curve and the measured voltage curve by: subtracting the reference voltage curve from the measured voltage curve to generate a difference voltage curve; and detecting the touch based on the difference voltage curve. For example, the device can detect the touch even when the piezoelectric transducer is driven.

[0010] In a further implementation form of the first aspect, the control circuit is further configured to: calculate an integral of the difference voltage curve; and detect the touch based on the integral of the difference voltage curve. The device may, for example, be capable of effectively detecting a touch.

[0011] In a further implementation form of the first aspect, the control circuit is further configured to: calculate an amplitude of the difference voltage curve; and detect the touch based on the amplitude of the difference voltage curve. The device may, for example, be capable of effectively detecting a touch using vibrations caused by an object.

[0012] In another implementation form of the first aspect, the control circuit is further configured to compare the reference voltage curve and the measured voltage curve by: detecting a saturation period of the reference voltage curve; detecting a saturation period of the measured voltage curve; and comparing the saturation period of the reference voltage curve and the measured voltage curve. For example, the device can effectively detect touch even when saturation limits the detection of the signal.

[0013] In a further implementation form of the first aspect, the control circuit is further configured to: drive the piezoelectric transducer using a test drive voltage; measure a response voltage curve caused by the test drive voltage on the piezoelectric transducer; and calculate at least one parameter based on the response voltage curve. The device can, for example, update the at least one parameter. Thus, if the electrical and / or mechanical characteristics of the piezoelectric transducer change, the device can take these changes into account.

[0014] It should be understood that the above-mentioned implementation forms of the first aspect can be used in combination with each other. Several implementation forms can be combined together to form further implementation forms.

[0015] According to a second aspect, a method includes: obtaining at least one parameter describing a reference response of a piezoelectric transducer; forming a reference voltage curve based on the at least one parameter; driving the piezoelectric transducer with a drive voltage; measuring the voltage curve on the piezoelectric transducer; comparing the reference voltage curve and the measured voltage curve; and detecting a touch on a touch surface based on the comparison.

[0016] In an implementation of the second aspect, detecting the touch on the touch surface based on the comparison includes: detecting a time-varying characteristic of the touch on the touch surface based on the comparison.

[0017] In another implementation form of the second aspect, comparing the reference voltage curve to the measured voltage curve includes subtracting the reference voltage curve from the measured voltage curve to produce a difference voltage curve; and detecting a touch on the touch surface based on the comparison includes detecting the touch based on the difference voltage curve.

[0018] In another implementation form of the second aspect, the method further comprises: calculating an integral of the difference voltage curve; wherein detecting a touch on the touch surface based on the comparison comprises detecting the touch based on the integral of the difference voltage curve.

[0019] In another implementation form of the second aspect, the method further includes: driving the piezoelectric transducer using a test drive voltage; measuring a response voltage curve caused by the test drive voltage on the piezoelectric transducer; and calculating at least one parameter based on the response voltage curve.

[0020] It should be understood that the above-mentioned implementation forms of the second aspect can be used in combination with each other. Several implementation forms can be combined together to form further implementation forms.

[0021] According to a third aspect, there is provided a computer program product comprising program code configured to perform the method according to the second aspect when the computer program is executed on a computing device.

[0022] Many of the accompanying features will be more readily appreciated as the same become better understood by reference to the following detailed description considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Below, example embodiments are described in more detail with reference to the accompanying drawings and figures, in which:

[0024] Figure 1 shows a cross-sectional representation of a device according to an embodiment;

[0025] Figure 2 shows a schematic representation of a computing unit according to an embodiment;

[0026] Figure 3 shows a circuit diagram representation of a device according to an embodiment;

[0027] Figure 4 shows a schematic representation of a voltage pulse and a reference voltage curve for driving a piezoelectric transducer according to an embodiment;

[0028] Figure 5 shows a schematic representation of a measured voltage curve on a piezoelectric transducer according to an embodiment;

[0029] Figure 6shows a schematic representation of a differential voltage curve according to an embodiment;

[0030] Figure 7 shows a schematic representation of a measured voltage curve on a piezoelectric transducer according to an embodiment;

[0031] Figure 8 shows a schematic representation of a differential voltage curve according to an embodiment;

[0032] Fig. 9 A flowchart representation showing a method according to an embodiment is shown; and

[0033] Fig.10 A flow chart representation of voltages used by a control circuit according to an embodiment is shown.

[0034] Hereinafter, in the drawings, the same reference numerals are used to denote the same components. DETAILED DESCRIPTION

[0035] In the following description, reference is made to the accompanying drawings, which form a part of the present disclosure and in which specific aspects of the present disclosure may be placed are shown by way of illustration. It should be understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description should not be construed as limiting, as the scope of the present disclosure is defined by the appended claims.

[0036] For example, it should be understood that the disclosure related to the described method is also applicable to the corresponding device or system configured to perform the method, and vice versa. For example, if a specific method step is described, the corresponding device may include a unit for performing the described method step, even if such a unit is not explicitly described or illustrated in the accompanying drawings. On the other hand, for example, if a specific device is described based on a functional unit, the corresponding method may include steps for performing the described function, even if such steps are not explicitly described or illustrated in the accompanying drawings. In addition, it should be understood that the features of the various exemplary aspects described herein may be combined with each other unless otherwise specifically noted.

[0037] Figure 1 A schematic representation of a cross section of a device 100 according to an embodiment is shown.

[0038] Device 100 may include touch surface 101 .

[0039] The touch surface 101 may also be referred to as a layer, a surface layer, a touch interface surface or a touch interface layer. The touch surface 101 may be part of a touch user interface. The touch surface 101 may be part of a touch pad or a key / button of, for example, a laptop or a touch screen.

[0040] The touch surface 101 may include a first side and a second side. The first side may be at least partially unobstructed. A user may touch the first side with an object 104 such as a finger.

[0041] Device 100 may further include piezoelectric transducer 102. Piezoelectric transducer 102 may be mechanically coupled to touch surface 101.

[0042] Here, two elements that are mechanically coupled may refer to the presence of a mechanical connection between the two elements. The two elements may, for example, be in contact with each other, or the mechanical connection may be achieved via other elements. For example, piezoelectric transducer 102 may be in contact with touch surface 101, or one or more other elements may be present between piezoelectric transducer 102 and touch surface 101. Therefore, when a force is applied to touch surface 101 by object 104 touching touch surface 101, the force may be transferred to piezoelectric transducer 102.

[0043] The device 100 may further include a control circuit 103 electrically coupled to the piezoelectric transducer 102. The control circuit 103 may be configured to obtain at least one parameter describing a reference response of the piezoelectric transducer 102.

[0044] The reference response may also be referred to as reference behavior or similar terms. The reference response may describe how the piezoelectric transducer 102 responds when the piezoelectric transducer 102 is driven with a preconfigured signal / voltage, such as a preconfigured reference signal / voltage. The reference response may correspond to a time-dependent voltage across the piezoelectric transducer 102 when the piezoelectric transducer 102 is driven by a preconfigured signal / voltage, such as a preconfigured reference signal / voltage.

[0045] The at least one parameter may correspond to a reference response of the piezoelectric transducer 102 .

[0046] The at least one parameter may include, for example, an RC time constant of the piezoelectric transducer 102. Alternatively or additionally, the at least one parameter may include any other parameter describing a reference response of the piezoelectric transducer 102, such as a resistance R of the piezoelectric transducer 102, a capacitance C of the piezoelectric transducer 102, and / or at least one mechanical property of the piezoelectric transducer 102 and / or the touch surface 101, such as a stiffness of the touch surface 101 and / or a stiffness of the piezoelectric transducer 102.

[0047] The control circuit 103 may be further configured to form a reference voltage curve based on the at least one parameter.

[0048] For example, if the at least one parameter includes an RC time constant of the piezoelectric transducer, the control circuit 103 may form an RC voltage discharge curve of the piezoelectric transducer 102 .

[0049] Alternatively or additionally, the at least one parameter may include a plurality of parameters. In such a case, the control circuit 103 may be configured to form a more complex reference voltage curve.

[0050] The control circuit 103 may be configured to generate a reference voltage curve based on at least one parameter. The control circuit 103 may be configured to synthesize a reference voltage curve based on at least one parameter.

[0051] Here, a "voltage curve" may refer to a voltage as a function of time. A voltage curve may be continuous or discrete. A voltage curve may be represented using, for example, a mathematical expression that may be a function of time or using a plurality of discrete voltage samples.

[0052] The control circuit 103 may also be configured to drive the piezoelectric transducer using a driving voltage. The driving voltage may also be referred to as a driving voltage curve.

[0053] The drive voltage may be a function of time. The drive voltage may include, for example, a voltage pulse. The voltage pulse may be, for example, a substantially Gaussian voltage pulse.

[0054] The control circuit 103 may also be configured to measure a voltage curve across the piezoelectric transducer. This may generate a measured voltage curve.

[0055] The control circuit 103 may include at least one resistor electrically connected to the piezoelectric transducer 102. The at least one resistor may discharge the piezoelectric transducer 102. The control circuit 103 may be configured to measure a voltage curve across the piezoelectric transducer 102 when the piezoelectric transducer 102 is discharged via the at least one resistor.

[0056] The control circuit 103 may also be configured to compare the reference voltage curve with the measured voltage curve. This may produce a comparison result. The control circuit 103 may compare the reference voltage curve with the measured voltage curve by, for example, subtracting the reference voltage curve from the measured voltage curve, or vice versa.

[0057] The control circuit 103 may be further configured to detect a touch on the touch surface 101 based on the comparison.

[0058] The control circuit 103 may be configured to detect a touch on the touch surface 101 based on the comparison result.

[0059] The piezoelectric transducer 102 may be arranged on the second side of the surface 101. The device 100 may include a plurality of piezoelectric transducers 102. The disclosure herein may be applied to each piezoelectric transducer 102 of the plurality of piezoelectric transducers.

[0060] If device 100 includes multiple piezoelectric transducers 102, control circuit 103 may be configured to infer the position of object 104 on touch surface 101 based on the forces detected in each piezoelectric transducer 102. Control circuit 103 may perform this operation using, for example, a weighted average or similar process.

[0061] The piezoelectric transducer 102 may be adjacent to the second side, close to the second side, or located at a distance from the second side. Each of the plurality of piezoelectric transducers 102 may be configured to convert a mechanical stress in the piezoelectric transducer 102 caused by a force applied by the object 104 to the first side of the touch surface 101 into a voltage. The mechanical stress may also be referred to as a stress. The voltage may be referred to as a voltage, a stress-induced voltage, or a corresponding voltage. The voltage may be proportional to the mechanical stress.

[0062] Piezoelectric transducer 102 may be configured to convert mechanical stress into voltage via the piezoelectric effect, which is also referred to as the piezoelectric effect. Object 104 may be, for example, a user's finger, any other body part of a person, a stylus, or some other object held by a user. In the case where object 104 is a finger, the user may be wearing a glove, and only the fabric of the glove may be in direct contact with touch surface 101.

[0063] The voltage induced on the piezoelectric transducer 102 , and therefore the measured voltage curve, may be proportional to the rate of change of the force / pressure applied by the object 104 to the touch surface 101 .

[0064] The piezoelectric transducer 102 may also be configured to convert a voltage applied to the piezoelectric transducer into mechanical stress via the piezoelectric effect. Therefore, when a driving voltage is applied to the piezoelectric transducer 102 , a tactile effect may be sensed in the touch surface 101 .

[0065] Despite Figure 1 Only one object 104 is shown in the embodiment of the present invention, but there may be multiple objects 104 touching the touch surface 101 at the same time. Any embodiment of the device 100 described herein can be configured to locate the position of each of the multiple objects 104 on the touch surface 101. The location of each object 104 can be performed as described herein.

[0066] Figure 2 A schematic representation of a calculation unit 200 according to an embodiment is shown. The control circuit 103 may include the calculation unit 200 .

[0067] The computing unit 200 may include at least one processor 201. The at least one processor 201 may include, for example, one or more of various processing devices, such as a coprocessor, a microprocessor, a digital signal processor (DSP), a processing circuit with or without an accompanying DSP, or various other processing devices, including integrated circuits, such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microprocessor unit (MCU), a hardware accelerator, a dedicated computer chip, etc.

[0068] The computing unit 200 may also include a memory 202. The memory may be configured to store, for example, a computer program, etc. The memory may include one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination of one or more volatile memory devices and non-volatile memory devices. For example, the memory may be embodied as a magnetic storage device (e.g., a hard disk drive, a floppy disk, a magnetic tape, etc.), an optical magnetic storage device, and a semiconductor memory (e.g., a mask ROM, a PROM (programmable ROM), an EPROM (erasable PROM), a flash ROM, a RAM (random access memory), etc.).

[0069] When the computing unit 200 is configured to implement some functions, some components and / or multiple components of the computing unit 200, such as at least one processor and / or memory, may be configured to implement the functions. In addition, when at least one processor is configured to implement some functions, the functions may be implemented using, for example, a program code included in the memory.

[0070] The memory 202 may include at least one parameter 203 .

[0071] Computing unit 200 may further include, for example, a boost converter circuit, a microprocessor, and other components for interacting with piezoelectric transducer 102. The boost converter may provide a high voltage that may be needed to drive piezoelectric transducer 102 in the case of haptic feedback.

[0072] When the control circuit 103 is configured to perform a calculation operation, the calculation unit 200 can be configured to perform the calculation operation. Such a calculation operation can include, for example, obtaining at least one parameter, forming a reference voltage curve based on at least one parameter, comparing the reference voltage curve and the measured voltage curve, and / or detecting a touch on the touch surface based on the comparison.

[0073] Figure 3 A circuit diagram representation of a device 100 according to an embodiment is shown.

[0074] Although some components of device 100 are shown as part of control circuit 103, this is not the only way device 100 can be implemented, and control circuit 103 need not be implemented in a single unit. Instead, control circuit 103 may refer to various components in device 100 for controlling piezoelectric transducer 102.

[0075] The piezoelectric transducer 102 may be modeled as a capacitor. Other electrical / physical properties of the piezoelectric transducer 102, such as resistance, inductance, hysteresis, and LC resonance, may also be modeled by adding corresponding electrical components to the model of the piezoelectric transducer 102. For example, a resistor may be added to simulate resistive losses in the piezoelectric transducer 102. An inductor may be added to simulate the inductance of the piezoelectric transducer 102. In many cases, the capacitive behavior of the piezoelectric transducer 102 may be dominant, so modeling the piezoelectric transducer 102 as a single capacitor may be sufficient.

[0076] The device 100 may include a voltage divider 303 including a first resistor 301 and a second resistor 302 .

[0077] The device 100 may further include a low pass filter 306 including a third resistor 304 and a capacitor 305. The low pass filter 306 may be configured to filter out unwanted frequency components.

[0078] The cutoff frequency of the low pass filter 306 may be in the range of, for example, 50-300 Hertz (Hz), or any sub-range thereof, such as 50-200 Hz, 50-150 Hz, or 70-130 Hz.

[0079] The device 100 may further include a first diode 307 and a second diode 308 .

[0080] The device 100 may further comprise an analog-to-digital converter (ADC) 309. The control circuit 103 may comprise the ADC 309, for example.

[0081] The first diode 307 and the second diode 308 may limit the voltage fed into the ADC 309. The first diode 307 may be coupled between the first conductor 310 and the maximum voltage V max The second diode 308 can be coupled between the first conductor 310 and the minimum voltage -V max The first conductor 310 may be electrically coupled to the ADC 309. Therefore, the voltage fed into the ADC 309 via the first conductor 310 may be between -V max Between and V max The dynamic range of ADC 309 can be 2V max .

[0082] The control circuit 103 may further include a reference voltage circuit 330. The reference voltage circuit 330 may provide a reference voltage V ref .

[0083] ADC 309 can be electrically coupled to second conductor 311. Second conductor 311 can be at a reference voltage V ref The reference voltage may correspond to, for example, ground voltage, 1 / 2V dd , etc. V dd The ADC 309 may be configured to measure the voltage between the first conductor 310 and the second conductor 311 .

[0084] V ref Any practical voltage within the dynamic range of ADC 309 can be included, which allows readings above and below V ref The piezoelectric voltage V ref It is not required to be in the center of the dynamic range of ADC 309, nor is it required that the responses above / below it be linear, or that the responses above / below it have similar dynamics. However, for V ref It may be desirable to have the ability to measure differently in two directions.

[0085] or V ref However, ADC 309 may need to be able to read negative voltages as well, which may increase the manufacturing cost of device 100 .

[0086] The device 100 may further include other components not shown in the figure.

[0087] The device 100 may include a multiplexer. The plurality of piezoelectric transducers 102 may be coupled to the ADC 309 via the multiplexer.

[0088] The device 100 may further include a boost converter 320. The boost converter 320 may be configured to drive the piezoelectric transducer 102. When the control circuit 103 is configured to drive the piezoelectric transducer 102, the computing unit 200 may be electrically coupled to the boost converter 320, and the computing unit 200 may control the boost converter 320 so that the boost converter 320 provides a driving voltage / current for the piezoelectric transducer 102. The boost converter 320 may drive a plurality of piezoelectric transducers 102 via a multiplexer.

[0089] In device 100, boost converter 320 and sensing circuitry can always be connected to piezoelectric transducer 102 without switching between sensing and haptic driving. This can achieve high responsiveness and improved usability.

[0090] When the device 100 is idle, each terminal of the piezoelectric transducer 102 may be at a reference voltage. The reference voltage may be selected according to the upcoming sensing system. In the idle state, the voltage may remain substantially constant. Therefore, there may be no voltage across the first resistor 301 and / or the second resistor 302.

[0091] The terminal of the piezoelectric transducer 102 connected to the first resistor 301 may be referred to as a measurement terminal. The terminal of the piezoelectric transducer 102 connected to the second conductor 311 may be referred to as a reference terminal.

[0092] Whenever an object 104 touches the touch surface 101 or a voltage pulse generates a potential on the piezoelectric transducer 102, the potential of the higher impedance measurement terminal of the piezoelectric transducer 102 increases relative to the more stable, lower impedance reference terminal, thereby introducing a voltage difference between the terminals, which the control circuit 103 can measure using ADC309.

[0093] This potential difference may induce a current through the first resistor 301 and the second resistor 302, and the current discharges the charge in the piezoelectric transducer 102. This may be detected by the control circuit 103 as a voltage across the second resistor 302. Due to the resistance of the piezoelectric transducer 102 and the resistance of the first resistor 301 and the second resistor 302 and due to the capacitance of the piezoelectric transducer 102, the voltage may include an RC discharge curve.

[0094] The resistance of first resistor 301 and second resistor 302 may determine the internal resistance of piezoelectric transducer 102. The resistance of first resistor 301 and second resistor 302 may be selected such that they produce a reasonable attenuation rate of the voltage across piezoelectric transducer 102 for human-machine interface purposes.

[0095] The device 100 may include a computing unit 200. The control circuit 103 may include the computing unit 200. The computing unit 200 may be electrically coupled to the boost converter 320 and / or the ADC 309. The computing unit 200 may obtain voltage measurement samples via the ADC 309. The computing unit 200 may also control the boost converter 320. When the boost converter 320 is configured to perform a certain operation, the computing unit 200 may be configured to perform the operation by controlling the boost converter 320.

[0096] Figure 4 A schematic representation of a driving voltage 402 and a reference voltage curve 401 for driving a piezoelectric transducer 102 according to an embodiment is shown.

[0097] The ratio of the driving voltage 402 to the reference voltage curve 401 may be different. For example, the amplitude of the driving voltage 402 may be in the range of 50 to 500 volts (V), or in a sub-range thereof, such as 50 to 300 V, 100 to 300 V, or 150 to 250 V, while the maximum value of the reference voltage curve 401 may be limited to a saturation voltage level 403. The saturation voltage level 403 may be less than 10 V, such as 3.3 V.

[0098] The saturation voltage level 403 may be due to, for example, a limited dynamic range of the ADC 309 .

[0099] Reference voltage curve 401 may correspond to driving voltage 402. When piezoelectric transducer 102 is driven with driving voltage 402, reference voltage curve 401 may correspond to a voltage on piezoelectric transducer 102 when piezoelectric transducer 102 is not touched by object 104.

[0100] The control circuit 103 may form the reference voltage curve 401 based on the at least one parameter 203. For example, when the at least one parameter 203 includes the RC constant of the piezoelectric transducer 102, the time characteristic of the reference voltage curve 401 may follow:

[0101]

[0102] Wherein, t is time, V0 may be a certain maximum voltage at time t=0, τ=RC, and where R may be the resistance of the piezoelectric transducer 102, and C may be the capacitance of the piezoelectric transducer 102. The resistance may also include the resistance of the first resistor 301 and / or the second resistor 302.

[0103] In a typical usage scenario, τ may be, for example, 5-10 milliseconds (ms).

[0104] Due to the limited dynamic range of ADC 309, reference voltage curve 401 may be saturated, such as Figure 4 As shown in the embodiment, therefore, the reference voltage curve 401 follows the above behavior only when the reference voltage curve 401 is not saturated.

[0105] It should be understood that other components besides the piezoelectric transducer 102 may affect the reference voltage curve and / or the at least one parameter. For example, some components may include a capacitor that may affect the reference voltage curve 401 and / or the at least one parameter 203. Thus, the at least one parameter 203 may include an RC time constant of a circuit that includes the piezoelectric transducer 102.

[0106] Figure 5 Shown is a schematic representation of a measured voltage curve 501 on a piezoelectric transducer 102 according to an embodiment.

[0107] exist Figure 5 The measured voltage curve 501 presented in the embodiment of FIG. 4 may correspond to a situation when the object 104 touching the touch surface 101 is reducing the pressing force. This can be observed as a difference between the reference voltage curve 401 and the measured voltage curve 501. Due to the reduced force, the value of the measured voltage curve 501 is greater than the value of the reference voltage curve 401 when the force is reduced.

[0108] It should be understood that the discussion herein may assume that the piezoelectric transducer 102 is reverse polarized. If the piezoelectric transducer 102 is not reverse polarized, then Figure 5 The situation presented in the embodiment may correspond to a situation where the pressing force increases.

[0109] The control circuit 103 may also be configured to compare the reference voltage curve 401 and the measurement voltage curve 501 by: detecting a saturation period 502 of the reference voltage curve 402 , detecting a saturation period 503 of the measurement voltage curve 501 ; and comparing the saturation periods of the reference voltage curve 401 and the measurement voltage curve 501 .

[0110] Here, the “saturation period” may refer to the length of the time interval during which the voltage curve in question is in saturation. When the value of the voltage curve is greater than or equal to the saturation voltage level 403, the voltage curve is in saturation.

[0111] For example, the saturation period of the reference voltage curve 401 may be Figure 5 The time interval t shown in the embodiment of s,r 502, similarly, the saturation period of the measured voltage curve 501 can be Figure 5 The time interval t shown in the embodiment of s, m Length of 503.

[0112] The control circuit 103 can calculate, for example, the time difference between 502 and 503:

[0113] Δt=t s,m -t s,r .

[0114] If Δt is positive, the measured voltage curve 501 is in saturation for a longer period of time than the reference voltage curve 401. An example of this is Figure 5 In the embodiment shown in FIG. 1 , this may correspond to a situation where the object 104 touching the touch surface 101 reduces the pressing force.

[0115] On the other hand, if Δt is negative, the measured voltage curve 501 is in saturation for a shorter period of time than the reference voltage curve 401. This may correspond to a situation where the object 104 touching the touch surface 101 increases the pressing force.

[0116] Figure 6 A schematic representation of a differential voltage curve 601 according to an embodiment is shown.

[0117] The control circuit 103 may be further configured to compare the reference voltage curve 401 and the measured voltage curve 501 by calculating a difference between the reference voltage curve 401 and the measured voltage curve 501 .

[0118] The control circuit 103 may be further configured to compare the reference voltage curve 401 and the measurement voltage curve 501 by generating a difference voltage curve 601 by subtracting the reference voltage curve 401 from the measurement voltage curve 501 ; and detect a touch based on the difference voltage curve 601 .

[0119] For example, by measuring the voltage curve V meas (t) minus the reference voltage curve V ref (t) to obtain the differential voltage curve V diff (t)601:

[0120] V diff (t) = V meas (t)-V ref (t).

[0121] For example, Figure 6 The differential voltage curve shown in Figure 5 It is obtained by subtracting the reference voltage curve 401 from the measured voltage curve 501 presented in FIG.

[0122] The control circuit 103 may be configured to detect the sign / polarity of the differential voltage curve. Figure 6 In case of the difference voltage curve 601 presented in , the control circuit 103 may be configured to detect that the difference voltage curve 601 is mainly positive.

[0123] The control circuit 103 may be configured to detect the time-varying nature of the touch based on the sign / polarity of the differential voltage curve. Figure 6 In the case of the differential voltage curve 601 presented in FIG. 6 , the control circuit 103 may be configured to detect that the force applied by the touch is decreasing.

[0124] Control circuit 103 may be further configured to detect a time-varying characteristic of the touch on touch surface 101 based on the comparison.

[0125] The time-varying characteristics of a touch on touch surface 101 may refer to any characteristics of a touch that change over time. For example, control circuit 103 may be configured to detect whether the force / pressure applied by the touch increases, decreases, or remains constant.

[0126] The control circuit 103 may be further configured to calculate an integral of the differential voltage curve and detect a touch based on the integral of the differential voltage curve.

[0127] The control circuit 103 may be configured to calculate, for example, the following integral:

[0128]

[0129] t1 may be the time when the device 100 starts driving the piezoelectric transducer with the driving voltage. t2 may be a preconfigured time after t1.

[0130] Based on the result of the integration, the control circuit 103 can infer whether an object is touching the surface 101. Figure 6 Therefore, the result of the integration is positive, and the control circuit 103 can infer that the object may be touching the surface 101 with decreasing force.

[0131] The control circuit 103 can diff The integral presented above is approximated by a sample sum of :

[0132]

[0133] Where V diff [i] can refer to V diff The ith sample, N may refer to the total number of samples, and T may be the length of the time period over which the sample is acquired, eg, T=t2-t1.

[0134] Alternatively, the control circuit 103 may use other methods to evaluate the integrated value I.

[0135] The control circuit 103 may be configured to detect a touch on the touch surface 101 in response to the integral I reaching a preconfigured threshold.

[0136] The time resolution T / N may be, for example, less than 1 ms.

[0137] T and / or N may include preconfigured values. Alternatively or additionally, the control circuit 103 may be configured to sample the differential voltage curve until a certain preconfigured threshold is reached. In response to reaching the preconfigured value, the control circuit 103 may detect a touch on the touch surface 101.

[0138] According to an embodiment, the control circuit 103 is further configured to calculate the amplitude of the difference voltage curve, and detect the touch based on the amplitude of the difference voltage curve.

[0139] When object 104 touches surface 101 , object 104 may induce vibrations into touch surface 101 . The vibrations may be detected via piezoelectric transducer 102 .

[0140] The control circuit 103 can calculate the average difference voltage V using, for example, the following formula: diff,ave :

[0141]

[0142] Where N is the number of samples used to calculate the mean.

[0143] For each sample V diff [i], the computing device 200 can use, for example, the following formula to calculate the amplitude A i :

[0144] A i =|V diff [i]-V diff,ave |.

[0145] The control circuit 103 can calculate the average amplitude A using, for example, the following formula: ave :

[0146]

[0147] or

[0148]

[0149] Average amplitude A ave The amount of vibration in the piezoelectric transducer 102 can be quantified. The amplitude of the differential voltage can include an average amplitude A ave .

[0150] Since the amount of vibration in element 102 may be inversely proportional to the distance between piezoelectric transducer 102 and object 104 , computing unit 200 may calculate / estimate the position of object 104 on surface 101 using the vibration component of each piezoelectric transducer 102 .

[0151] The control circuit 103 may, for example, compare the amplitude of the difference voltage with a preconfigured threshold value. If the amplitude of the difference voltage is greater than the preconfigured threshold value, the control circuit 103 may infer that an object 104 is touching the touch surface 101 .

[0152] Figure 7 A schematic representation of a measured voltage curve 701 across a piezoelectric transducer 102 according to an embodiment is shown.

[0153] exist Figure 7The measured voltage curve 701 presented in the embodiment of FIG. 4 may correspond to a situation where the object 104 touching the touch surface 101 is increasing the pressing force. This can be observed as a difference between the reference voltage curve 401 and the measured voltage curve 701. Due to the increasing force, the value of the measured voltage curve 701 is less than the value of the reference voltage curve 401 when the force increases.

[0154] Figure 8 A schematic representation of a differential voltage curve 801 according to an embodiment is shown.

[0155] Figure 8 The differential voltage curve 801 shown in FIG. Figure 7 It is obtained by subtracting the reference voltage curve 401 from the measured voltage curve 701 presented in FIG.

[0156] The control circuit 103 may be configured to detect the sign / polarity of the differential voltage curve. Figure 8 In the case of the difference voltage curve 801 presented in , the control circuit 103 may be configured to detect that the difference voltage curve 801 is mainly negative.

[0157] The control circuit 103 may be configured to diff (t) to detect the time-varying nature of the touch. Figure 8 In the case of the differential voltage curve 801 presented in FIG. 8 , the control circuit 103 may be configured to detect that the force / pressure applied by the touch is increasing.

[0158] Fig. 9 A flow chart representation of a method according to an embodiment is shown.

[0159] According to one embodiment, method 900 includes obtaining 901 at least one parameter describing a reference response of a piezoelectric transducer.

[0160] The method 900 may further include forming 902 a reference voltage curve based on at least one parameter.

[0161] The method 900 may further include driving 903 the piezoelectric transducer using a driving voltage.

[0162] Method 900 may also include measuring 904 a voltage curve across the piezoelectric transducer.

[0163] The method 900 may further include comparing 905 the reference voltage curve and the measured voltage curve.

[0164] Method 900 may also include detecting 906 a touch on the touch surface based on the comparison.

[0165] Fig.10A flow chart representation of voltages used by control circuit 103 is shown in accordance with an embodiment.

[0166] The control circuit 103 may also be configured to drive the piezoelectric transducer 102 using the test drive voltage 1001 .

[0167] Test drive voltage 1001 may be similar to drive voltage 402. Test drive voltage 1001 may include any preconfigured voltage profile suitable for testing electrical and / or mechanical characteristics of piezoelectric transducer 102, for example.

[0168] The control circuit 103 may be configured to drive the piezoelectric transducer 102 with the test drive voltage 1001 when there is no external force applied to the touch surface 101 by the object 104 .

[0169] The control circuit 103 may also be configured to measure a response voltage curve 1002 caused by the test drive voltage 1001 on the piezoelectric transducer 102 .

[0170] Since the control circuit 103 can be configured to drive the piezoelectric transducer 102 using the test drive voltage 1001 when there is no external force applied to the touch surface 101 by the object 104, the response voltage curve 1002 can correspond to the reference voltage curve 402. Therefore, the control circuit 103 can obtain the reference voltage 402 curve by measuring the response voltage curve 1002.

[0171] The control circuit 103 may be further configured to calculate 1003 at least one parameter 203 based on the response voltage curve 1002 .

[0172] The control circuit 103 may further be configured to store at least one parameter 203. The control circuit 103 may store the at least one parameter 203 into the memory 202, for example.

[0173] The control circuit 103 may estimate the RC time constant of the piezoelectric transducer 102, for example, based on the response voltage curve 1002. The control circuit 103 may obtain the at least one parameter 203 from the response voltage curve 1002 using, for example, curve fitting and / or other computational procedures.

[0174] The control circuit 103 may, for example, periodically perform the aforementioned operations for calculating the at least one parameter 203. Since the electrical and / or mechanical characteristics of the piezoelectric transducer 102 may change over time, the control circuit 103 may update the at least one parameter 203 in this manner to correspond to the current characteristics of the piezoelectric transducer 102. Therefore, the reference voltage curve 401 formed based on the at least one parameter 203 may more accurately describe the reference behavior of the piezoelectric transducer 102.

[0175] The control circuit 103 can then obtain at least one parameter 203, form a reference voltage curve 401 based on the at least one parameter 203, drive the piezoelectric transducer using a drive voltage 402, measure a voltage curve 501 on the piezoelectric transducer 102, compare the reference voltage curve 401 and the measured voltage curve 501, and detect a touch on the touch surface 101 based on the comparison as described herein.

[0176] Any range or device value given herein may be expanded or changed without losing the effect sought. Moreover, any embodiment may be combined with another embodiment unless explicitly not permitted.

[0177] Although the subject matter has been described in language specific to structural features and / or acts, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features and acts described above are disclosed as examples of implementing the claims, and other equivalent features and acts are intended to fall within the scope of the claims.

[0178] It should be understood that the above benefits and advantages may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those embodiments that solve any or all of the problems described, or those embodiments that have any or all of the benefits and advantages described. It will also be understood that reference to "an" item may refer to one or more of these items.

[0179] The steps of the methods described herein may be performed in any suitable order, or simultaneously where appropriate. In addition, individual blocks may be deleted from any method without departing from the spirit and scope of the subject matter described herein. Aspects of any of the above embodiments may be combined with aspects of any other embodiment described to form additional embodiments without losing the effects sought.

[0180] The term "comprising" is used herein to mean including the identified methods, blocks or elements, but such blocks or elements do not include an exclusive list and the method or apparatus may contain additional blocks or elements.

[0181] It should be understood that the above description is given as an example only, and various modifications may be made by those skilled in the art. The above description, examples and data provide a complete description of the structure and use of the exemplary embodiments. Although various embodiments are described above with a certain degree of particularity or with reference to one or more separate embodiments, those skilled in the art may make many changes to the disclosed embodiments without departing from the spirit or scope of this specification.

Claims

1. A device (100), comprising: Touch surface (101); a piezoelectric transducer (102) mechanically coupled to the touch surface (101); as well as A control circuit (103), electrically coupled to the piezoelectric transducer (102), is configured to: Obtaining at least one parameter (203) describing a reference response of the piezoelectric transducer (102); forming a reference voltage curve (401) based on the at least one parameter (203); driving the piezoelectric transducer (102) using a driving voltage (402); After driving the piezoelectric transducer (102) using the driving voltage (402), measuring a voltage curve (501, 701) on the piezoelectric transducer (102); comparing the reference voltage curve (401) with the measured voltage curve (501, 701); as well as detecting a touch on the touch surface (101) based on the comparison, The control circuit (103) is further configured to: Using a test drive voltage (1001) to drive the piezoelectric transducer (102); measuring a response voltage curve (1002) caused by the test drive voltage (1001) on the piezoelectric transducer (102); and The at least one parameter (203) is calculated based on the response voltage curve (1002).

2. The device (100) according to claim 1, wherein The control circuit (103) is further configured to: A time-varying characteristic of the touch on the touch surface (101) is detected based on the comparison.

3. The device (100) according to claim 1 or claim 2, wherein: The at least one parameter (203) includes an RC time constant of the piezoelectric transducer (102).

4. The device (100) according to claim 1 or claim 2, wherein: The control circuit (103) is further configured to compare the reference voltage curve (401) with the measurement voltage curve (501, 701) by calculating a difference between the reference voltage curve (401) and the measurement voltage curve (501, 701).

5. The device (100) according to claim 1, wherein The control circuit (103) is further configured to compare the reference voltage curve and the measured voltage curve by: subtracting the reference voltage curve (401) from the measured voltage curve (501, 701) to produce a difference voltage curve (601, 801); and The touch is detected based on the difference voltage curve (601, 801).

6. The device (100) according to claim 5, wherein: The control circuit (103) is further configured to: calculating the integral of the differential voltage curve (601, 801); and The touch is detected based on the integration of the differential voltage curve.

7. The device (100) according to claim 5, wherein The control circuit (103) is further configured to: calculating the amplitude of the differential voltage curve (601, 801); and The touch is detected based on the amplitude of the differential voltage curve.

8. The device (100) according to claim 1 or claim 2, wherein: The control circuit (103) is further configured to compare the reference voltage curve and the measured voltage curve by: Detecting a saturation period (502) of the reference voltage curve (401); detecting a saturation period (503) of the measured voltage curve (501, 701); and A saturation period of the reference voltage curve and a saturation period of the measurement voltage curve are compared.

9. A method (900), comprising: Obtaining (901) at least one parameter describing a reference response of a piezoelectric transducer; forming (902) a reference voltage curve based on the at least one parameter; driving (903) the piezoelectric transducer using a driving voltage; After driving the piezoelectric transducer with the driving voltage, measuring (904) a voltage curve on the piezoelectric transducer; comparing (905) the reference voltage curve and the measured voltage curve; detecting (906) a touch on the touch surface based on the comparison; driving the piezoelectric transducer using a test drive voltage; measuring a response voltage curve caused by the test drive voltage on the piezoelectric transducer; as well as The at least one parameter is calculated based on the response voltage curve.

10. The method (900) of claim 9, wherein: Detecting a touch on the touch surface based on the comparing includes: A time-varying characteristic of the touch on the touch surface is detected based on the comparison.

11. The method (900) of claim 9, wherein said comparing (905) said reference voltage curve and said measured voltage curve comprises subtracting said reference voltage curve from said measured voltage curve, thereby producing a difference voltage curve; and Detecting (906) a touch on the touch surface based on the comparison includes detecting the touch based on the differential voltage curve.

12. The method (900) of claim 11, further comprising: calculating an integral of the differential voltage curve; Wherein detecting (906) a touch on the touch surface based on the comparing includes detecting the touch based on an integration of the differential voltage curve.

13. A computer program product comprising a program code, the program code being configured to perform the method according to any one of claims 9 to 12 when the program code is executed on a computer.

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