Piezoelectric sensing device

Abstract

To provide an electronic device for sensing and / or for providing a haptic effect.SOLUTION: A device comprises: a touch surface; a piezoelectric transducer mechanically coupled to the touch surface; and a control circuitry 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 driving voltage; measure a voltage curve over the piezoelectric transducer after driving the piezoelectric transducer with the driving voltage; compare the reference voltage curve and the measured voltage curve; and detect a touch on the touch surface based on the comparison. A device, a method, and a computer program product are provided.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a device, and more specifically, to an electronic device for providing a sensing and / or tactile effect.

Background Art

[0002] Piezoelectric transducers can be used to provide a tactile effect to a user, to sense touch, or for both. However, using a single piezoelectric transducer to perform both functions can pose various problems. For example, when the piezoelectric transducer is driven simultaneously with one driving voltage, it may be difficult to detect a signal generated by the user's contact.

Summary of the Invention

[0003] The summary of the present invention is provided to introduce a selection of concepts in a simplified form that will be further described in the detailed description of the invention that follows. This summary is not intended to identify the 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] An object is to provide an electronic device for providing a sensing and / or tactile effect. The foregoing object and other objects are achieved by the features of the independent claims. Further embodiments are apparent from the dependent claims, the description, and the drawings.

Means for Solving the Problems

[0005] According to a first aspect, the present device is a device comprising a contact surface, a piezoelectric transducer mechanically coupled to the contact surface, and a control circuit electrically coupled to the piezoelectric transducer, the device being configured to obtain at least one parameter indicating 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 a voltage curve of the piezoelectric transducer after driving the piezoelectric transducer with the drive voltage, compare the reference voltage curve with the measured voltage curve, and detect contact on the contact surface based on the comparison. The present device can also detect contact on the contact surface even, for example, when driving the piezoelectric transducer with a drive voltage.

[0006] In an implementation form of the first aspect, the control circuit is further configured to detect a temporal change characteristic of the contact on the contact surface based on the comparison. The present device can also detect, for example, whether the force applied by the contact is increasing or decreasing.

[0007] In a further embodiment of the first aspect, the at least one parameter includes an RC time constant of the piezoelectric transducer. The present device can also form a reference voltage curve using, for example, a single parameter.

[0008] In a further embodiment 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 present device can also efficiently compare, for example, the reference voltage curve and the measured voltage curve.

[0009] In a further embodiment of the first aspect, the control circuit is further configured to compare the reference voltage curve with the measured voltage curve by subtracting the reference voltage curve from the measured voltage curve to generate a differential voltage curve and detecting the contact based on the differential voltage curve. The present device can also detect contact even, for example, when driving the piezoelectric transducer.

[0010] In a further embodiment of the first aspect, the control circuit is further configured to calculate an integral of the differential voltage curve and detect the contact based on the integral of the differential voltage curve. For example, the device can also efficiently detect the contact.

[0011] In a further embodiment of the first aspect, the control circuit is further configured to calculate an oscillation amplitude of the differential voltage curve and detect the contact based on the oscillation amplitude of the differential voltage curve. For example, the device can also efficiently detect the contact using vibrations induced by an object.

[0012] In a further embodiment of the first aspect, the control circuit is further configured to detect a saturation period of the reference voltage curve, detect a saturation period of the measured voltage curve, and compare the reference voltage curve and the measured voltage curve by comparing the saturation periods of the reference voltage curve and the measured voltage curve. For example, the device can efficiently detect the contact even when signal detection is limited by saturation.

[0013] In a further embodiment 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 in the piezoelectric transducer, and calculate the at least one parameter based on the response voltage curve. For example, the device can update at least one parameter. Thus, when 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 embodiments of the first aspect described above can be used in combination with each other. Some embodiments can be combined to form further embodiments.

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

[0016] In an implementation form of the second aspect, the step of detecting contact on the contact surface based on the comparison includes detecting a temporal change characteristic of the contact on the contact surface based on the comparison.

[0017] In a further embodiment of the second aspect, the step of comparing the reference voltage curve and the measured voltage curve includes generating a differential voltage curve by subtracting the reference voltage curve from the measured voltage curve, and the step of detecting contact on the contact surface based on the comparison includes detecting the contact based on the differential voltage curve.

[0018] In a further embodiment of the second aspect, the method further includes calculating an integral of the differential voltage curve, and the step of detecting contact on the contact surface based on the comparison includes detecting the contact based on the integral of the differential voltage curve.

[0019] In a further embodiment of the second aspect, the method further includes driving the piezoelectric transducer using a test driving voltage, measuring a response voltage curve induced in the piezoelectric transducer by the test driving voltage, and calculating the at least one parameter based on the response voltage curve.

[0020] It should be understood that the above-described embodiments of the second aspect can be used in combination with each other. Some embodiments can be combined to form further embodiments.

[0021] According to a third aspect, there is provided a computer program product comprising program code configured to implement the method described in the second aspect above when the program code is executed on a computer.

[0022] Many of the attendant features will be more readily understood as they become better understood by reference to the following detailed description, which is to be considered in connection with the accompanying drawings.

Brief Description of the Drawings

[0023] Exemplary embodiments will be described in more detail below with reference to the accompanying drawings.

[0024]

Figure 1

[0025]

Figure 2

[0026]

Figure 3

[0027]

Figure 4

[0028]

Figure 5

[0029]

Figure 6

[0030]

Figure 7

[0031]

Figure 8

[0032]

Figure 9

[0033]

Figure 10

[0034] Hereinafter, the same reference numerals are used to designate the same parts in the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, a description will be given with reference to the accompanying drawings. The drawings form a part of the present disclosure, and specific embodiments in which the present disclosure can be arranged are shown as examples in the drawings. It is understood that other aspects can be utilized and structural or logical changes can be made without departing from the scope of the present disclosure. Therefore, the following detailed description should not be construed in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

[0036] For example, it is understood that the disclosures related to the described method may also apply to the corresponding devices or systems configured to execute the method, and vice versa. For example, when a specific method step is described, the corresponding device may include units for executing the described method step, even if such units are not explicitly described or illustrated in the figures. On the other hand, for example, when a specific device is described based on functional units, the corresponding method may include steps for executing the described functions, even if such steps are not explicitly described or illustrated in the figures. Furthermore, it is understood that the features of the various exemplary aspects described herein can be combined with each other unless otherwise specified.

[0037] FIG. 1 shows a schematic cross-sectional view of a device 100 according to an embodiment.

[0038] FIG. 1 is a cross-sectional view of a device 100 according to the present embodiment. The device 100 may include a contact surface 101.

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

[0040] The contact surface 101 may include a first side and a second side. The first side is unobstructed at least in part thereof. The user may touch the first side with an object 104 such as a finger.

[0041] The device 100 may further include a piezoelectric transducer 102. The piezoelectric transducer 102 may be mechanically coupled to the contact surface 101.

[0042] As used herein, two elements being mechanically coupled may indicate that there is 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 implemented via other elements. For example, the piezoelectric transducer 102 may be in contact with the contact surface 101, or one or more other elements may be present between the piezoelectric transducer 102 and the contact surface 101. Thus, when a force is applied to the contact surface 101 and the object 104 contacts the contact surface 101, the force may be transmitted to the 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 acquire at least one parameter indicative of a reference response of the piezoelectric transducer 102.

[0044] The reference response may also be referred to by a reference behavior or a similar name. The reference response can indicate how the piezoelectric transducer 102 responds when driven by a predetermined signal / voltage such as a predetermined reference signal / voltage. The reference response may correspond to the time-dependent voltage on the piezoelectric transducer 102 when the piezoelectric transducer 102 is driven by a predetermined signal / voltage such as a predetermined 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, the RC time constant of the piezoelectric transducer 102. Alternatively, or additionally, the at least one parameter may include any other parameter indicative of the reference response of the piezoelectric transducer 102. Alternatively or additionally, the at least one parameter may include other parameters that describe the reference response of the piezoelectric transducer 102, the resistance R of the piezoelectric transducer 102, the capacitance C of the piezoelectric transducer 102, etc., and / or at least one mechanical property of the piezoelectric transducer 102 and / or the stiffness of the contact surface 101 and / or the stiffness of the piezoelectric transducer 102, etc.

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

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

[0049] Alternatively, or further, 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 the at least one parameter.

[0051] As used herein, "voltage curve" may refer to a voltage that is a function of time. The voltage curve may be continuous or discrete. The voltage curve can be represented, for example, using a mathematical formula that is a function of time or using a plurality of discrete voltage samples.

[0052] The control circuit 103 may further be configured to drive the piezoelectric transducer with a drive voltage. The drive voltage may also be referred to as a drive 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 pulse.

[0054] The control circuit 103 may further be configured to measure the voltage curve on the piezoelectric transducer. Thereby, a measured voltage curve can be generated.

[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 the voltage curve of the piezoelectric transducer 102 while the piezoelectric transducer 102 discharges through the at least one resistor..

[0056] The control circuit 103 may further be configured to compare the reference voltage curve and the measured voltage curve. As a result, a comparison result may be generated. The control circuit 103 can compare the reference voltage curve and the measured voltage curve, for example, by subtracting the reference voltage curve from the measured voltage curve or vice versa.

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

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

[0059] The piezoelectric transducer 102 may be disposed on the second side surface of the contact surface 101. The device 100 may include a plurality of piezoelectric transducers 102. The disclosure of this specification may be applied to each piezoelectric transducer 102 in the plurality of piezoelectric transducers.

[0060] When the device 100 includes a plurality of piezoelectric transducers 102, the control circuit 103 may be configured to estimate the position of the object 104 on the contact surface 101 based on the forces detected by each piezoelectric transducer 102. The control circuit 103 can perform this, for example, using a weighted average or a similar procedure.

[0061] The piezoelectric transducer 102 may be arranged adjacent to, close to, or away from the second side surface of the second side surface. Each piezoelectric transducer 102 in the plurality of piezoelectric transducers may be configured to convert the mechanical stress of the piezoelectric transducer 102 induced by the force applied to the first side surface of the contact surface 101 by the object 104 into a voltage. The mechanical stress may also be called stress. The voltage may sometimes be called voltage, stress-induced voltage, or corresponding voltage. The voltage may be proportional to the mechanical stress.

[0062] The piezoelectric transducer 102 may be configured to convert mechanical stress into voltage through the piezoelectric effect, which is also called piezoelectricity. The object 104 may be, for example, a user's finger, any other body part of a human, a stylus pen, or any other object held by the user. When the object 104 is a finger, the user may wear gloves, and only the cloth of the gloves may come into direct contact with the contact surface 101.

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

[0064] The piezoelectric transducer 102 may also be configured to convert the voltage applied to the piezoelectric transducer into mechanical stress through the piezoelectric effect. Therefore, when a driving voltage is applied to the piezoelectric transducer 102, a tactile effect may be induced on the contact surface 101.

[0065] In the embodiment of FIG. 1, only one object 104 is shown, but there may be a plurality of objects 104 that are in contact with the contact surface 101 at the same time. Any embodiment of the device 100 described in this specification may be configured to identify the position of each object among the plurality of objects 104 on the contact surface 101. The positioning of each object 104 can be performed as described in this specification.

[0066] FIG. 2 shows a schematic diagram of a computing unit 200 according to an embodiment. The control circuit 103 may include the computing unit 200.

[0067] The computing unit 200 can include at least one processor 201. The at least one processor 201 can include, for example, a coprocessor, a microprocessor, a digital signal processor (DSP), a processing circuit with or without an accompanying DSP, or various other processing devices 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., including one or more of various processing devices.

[0068] The computing unit 200 may further include a memory 202. The memory can be configured to store, for example, a computer program, etc. The memory can 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, specific examples of the memory include magnetic storage devices (hard disk drives, floppy disks, magnetic tapes, etc.), magneto-optical storage devices, and semiconductor memories (mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

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

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

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

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

[0073] FIG. 3 shows a circuit diagram representation of the device 100 according to one embodiment.

[0074] Some components of the device 100 are shown as part of the control circuit 103, but this is not the only way the device 100 can be implemented, and it is not necessary to implement the control circuit 103 as a single unit. Rather, the control circuit 103 can include various components within the device 100 used to control the piezoelectric transducer 102.

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

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

[0077] 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 remove unwanted frequency components.

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

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

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

[0081] The first 307 and the second diode 308 can limit the voltage supplied to the ADC 309. The first diode 307 can be coupled between the first conductor 310 and the maximum voltage V max and. The second diode 308 can be coupled between the first conductor 310 and the minimum voltage -V max and. The first conductor 310 can be electrically coupled to the ADC 309. Thus, the voltage supplied to the ADC 309 via the first conductor 310 can be limited between -V max and +V max and. The dynamic range of the ADC 309 can be 2V max and.

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

[0083] ADC309 can be electrically coupled to a second conductor 311. The second conductor 311 can be at a reference voltage V ref . The reference voltage can correspond to, for example, a ground voltage, 1 / 2V dd , or the like. V dd may be the supply voltage. ADC309 can be configured to measure the voltage between a first conductor 310 and a second conductor 311.

[0084] V ref can include any practical voltage within the dynamic range of ADC309, which enables reading of the piezoelectric voltages above and below V ref . V ref need not be at the center of the dynamic range of ADC309. Also, the upper and lower responses need not be linear, nor need they have the same dynamics above and below. However, in relation to V ref , a function to measure differentially in both directions may be required.

[0085] Alternatively, V ref may correspond to the ground voltage. However, in that case, ADC309 may need to be able to read negative voltages, which can increase the manufacturing cost of device 100.

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

[0087] Device 100 may include a multiplexer. A plurality of piezoelectric transducers 102 can be coupled to ADC309 via the multiplexer.

[0088] 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. The computing unit 200 can control the boost converter 320 such that the boost converter 320 provides a drive voltage / current to the piezoelectric transducer 102. The boost converter 320 can drive a plurality of piezoelectric transducers 102 via a multiplexer.

[0089] In device 100, the boost converter 320 and the sensing circuit can always be connected to the piezoelectric transducer 102 without the need to switch between sensing and haptics. This can enable high responsiveness and improved usability.

[0090] When device 100 is in an idle state, each terminal of the piezoelectric transducer 102 may be at a reference voltage V ref . The reference voltage can be selected according to the in-hand sensing system. In the idle state, this voltage may remain substantially constant. Thus, there should 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 the measurement terminal. The terminal of the piezoelectric transducer 102 connected to the second conductor 311 may be referred to as the reference terminal.

[0092] Whenever an object 104 contacts the contact surface 101 or a voltage pulse generates a potential on the piezoelectric transducer 102, the potential of the high-impedance measurement terminal of the piezoelectric transducer 102 increases compared to the more stable low-impedance reference terminal, thus introducing a voltage difference that the control circuit 103 can measure using the ADC 309 between the terminals.

[0093] The potential difference can introduce a current through the first resistor 301 and the second resistor 302, and the current discharges the charges in the piezoelectric transducer 102. This can be detected by the control circuit 103 as the voltage across the second resistor 302. The voltage includes an RC discharge curve resulting from the resistance of the piezoelectric transducer 102, the first resistor 301, and the second resistor 302, as well as the capacitance of the piezoelectric transducer 102.

[0094] The resistances of the first resistor 301 and the second resistor 302 can dominate the internal resistance of the piezoelectric transducer 102. The resistances of the first resistor 301 and the second resistor 302 can be selected to produce a reasonable attenuation rate of the voltage of the piezoelectric transducer 102 for the purpose of the human interface.

[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 acquire samples of the voltage measurement values via the ADC 309. The computing unit 200 can also control the boost converter 320. If the boost converter 320 is configured to perform some operation, the computing unit 200 may be configured to perform that operation by controlling the boost converter 320.

[0096] FIG. 4 shows a schematic diagram of a drive voltage 402 and a reference voltage curve 401 used to drive the piezoelectric transducer 102 according to an embodiment.

[0097] The scales of the drive voltage 402 and the reference voltage curve 401 may not be the same. For example, the amplitude of the drive voltage 402 can be in the range of 50 - 500 volts (V), or any sub-range thereof, such as 50 - 300V, 100 - 300V, or 150 - 250V. On the other hand, the maximum value of the reference voltage curve 401 can be limited by the saturation voltage level 403. The saturation voltage level 403 can be less than 10V, for example, 3.3V.

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

[0099] The reference voltage curve 401 may correspond to the drive voltage 402. When the piezoelectric transducer 102 is driven by the drive voltage 402, the reference voltage curve 401 may correspond to the voltage on the piezoelectric transducer 102 when the piezoelectric transducer 102 is not contacted by the object 104.

[0100] The control circuit 103 can form the reference voltage curve 401 based on at least one parameter 203. For example, when at least one parameter 203 includes the RC constant τ of the piezoelectric transducer 102, the temporal behavior of the reference voltage curve 401 may follow the following equation. [Number] Here, t is time, and V0 may be a certain maximum voltage at time t = 0 and τ = RC. Here, R is the resistance of the piezoelectric transducer 102, and C may be the capacitance of the piezoelectric transducer 102. R includes the resistance of the first resistor 301 and / or the second resistor 302.

[0101] In a typical usage scenario, τ is, for example, 5 - 10 milliseconds (ms).

[0102] Due to the limited dynamic range of the ADC 309, the reference voltage curve 401 may saturate as shown in the embodiment of FIG. 4. Thus, the reference voltage curve 401 can follow the above behavior only when the reference voltage curve 401 is not saturated.

[0103] It should be understood that components other than the piezoelectric transducer 102 may affect the reference voltage curve and / or at least one parameter. For example, some components may include capacitances that can affect the reference voltage curve 401 and / or at least one parameter 203. Accordingly, at least one parameter 203 may include the RC time constant of the circuit including the piezoelectric transducer 102.

[0104] FIG. 5 shows a schematic diagram of a measured voltage curve 501 on the piezoelectric transducer 102 according to an embodiment.

[0105] The measured voltage curve 501 presented in the embodiment of FIG. 5 may correspond to a situation where the object 104 in contact with the contact surface 101 is reducing the pressing force. This can be observed as the difference between the reference voltage curve 401 and the measured voltage curve 501. Due to the decreasing force, the value of the measured voltage curve 501 becomes greater than the value of the reference voltage curve 401 when the force is decreasing.

[0106] It should be understood that the description herein may assume that the piezoelectric transducer 102 is depolarized. If the piezoelectric transducer 102 is not depolarized, the situation presented in the embodiment of FIG. 5 may correspond to a situation where the pressing force is increasing.

[0107] The control circuit 103 may further be configured to compare the reference voltage curve 401 and the measured voltage curve 501 as follows. Detect the saturation period 502 of the reference voltage curve 402 and detect the saturation period 503 of the measured voltage curve 501. Then, compare the saturation periods of the reference voltage curve 401 and the measured voltage curve 501.

[0108] Here, the "saturation period" may refer to the length of the time interval during which the voltage curve in question is in a saturated state. If the value of the voltage curve is equal to or greater than the saturation voltage level 403, the voltage curve may be in a saturated state.

[0109] For example, the saturation period of the reference voltage curve 401 is the time interval t shown in the embodiment of FIG. 5 s、rIt is possible to indicate the length of 502. Similarly, the saturation period of the measured voltage curve 501 is the time interval t shown in the embodiment of FIG. 5 s、m It is possible to indicate the length of 503.

[0110] The control circuit 103 can, for example, calculate the time difference Δt between t s、r 502 and t s、m 503. [Number] If Δt is positive, the measured voltage curve 501 is in a saturated state for a longer time than the reference voltage curve 401. An example of such a situation is shown in the embodiment of FIG. 5. This may correspond to a situation where the object 104 in contact with the contact surface 101 is reducing the pressing force.

[0111] On the other hand, if Δt is negative, the measured voltage curve 501 is in a saturated state for a shorter time than the reference voltage curve 401. This may correspond to a situation where the object 104 in contact with the contact surface 101 is increasing the pressing force.

[0112] FIG. 6 shows a schematic diagram of a differential voltage curve 601 according to an embodiment.

[0113] The control circuit 103 can be further configured to compare the reference voltage curve 401 and the measured voltage curve 501 by calculating the difference between the reference voltage curve 401 and the measured voltage curve 501.

[0114] The control circuit 103 can be further configured to compare the reference voltage curve 401 and the measured voltage curve 501 by subtracting the reference voltage curve 401 from the measured voltage curve 501 that generates the differential voltage curve 601, and detect contact based on the differential voltage curve 601.

[0115] The differential voltage curve V diff (t) 601 can be obtained, for example, by subtracting the reference voltage curve V meas (t) from the measured voltage curve V ref (t). [Number]

[0116] For example, the differential voltage curve shown in FIG. 6 can be obtained by subtracting the reference voltage curve 401 from the measured voltage curve 501 shown in FIG. 5.

[0117] The control circuit 103 can be configured to detect the sign / polarity of the differential voltage curve V diff (t). For example, in the case of the differential voltage curve 601 presented in FIG. 6, the control circuit 103 can be configured to detect that the differential voltage curve 601 is mainly positive.

[0118] The control circuit 103 can be configured to detect the time-varying characteristics of the contact based on the sign / polarity of the differential voltage curve V diff (t). For example, in the case of the differential voltage curve 601 presented in FIG. 6, the control circuit 103 can be configured to detect that the force applied by the contact is decreasing.

[0119] The control circuit 103 can further be configured to detect the time-varying characteristics of the contact on the contact surface 101 based on a comparison.

[0120] The time-varying characteristics of the contact on the contact surface 101 can refer to any characteristic of the contact that changes over time. For example, the control circuit 103 can be configured to detect whether the force / pressure applied by the contact is increasing, decreasing, or remaining constant.

[0121] The control circuit 103 can further be configured to calculate the integral of the differential voltage curve and detect the contact based on the integral of the differential voltage curve.

[0122] The control circuit 103 can be configured to calculate, for example, the following integral. [Number] t1 can be the moment when device 100 starts driving the piezoelectric transducer with a driving voltage. t2 can be a preset time after t1.

[0123] Based on the result of integral I, control circuit 103 can infer whether an object is in contact with contact surface 101. For example, in the case of the embodiment of FIG. 6, V diff (t) is positive in most cases. Therefore, the result of the integral is positive, and control circuit 103 can infer that the object may be in contact with contact surface 101 with a decreasing force.

[0124] Control circuit 103 can approximate the above-mentioned integral by summing the samples of the differential voltage curve V diff . [Number] Here, V diff [i] refers to the i-th sample of V diff , N refers to the total number of samples, and T refers to the length of the period during which the samples are acquired. For example: T = t2 - t1.

[0125] Alternatively, control circuit 103 can use other methods to evaluate the value of integral I.

[0126] Control circuit 103 can be configured to detect contact on contact surface 101 in response to integral I reaching a preset threshold.

[0127] The time resolution T / N can be less than 1 millisecond, for example.

[0128] T and / or N can include preset values. Alternatively or additionally, control circuit 103 can be configured to sample the differential voltage curve until a certain preconfigured threshold is reached. In response to reaching the preconfigured value, control circuit 103 can detect contact on contact surface 101.

[0129] According to one embodiment, the control circuit 103 is further configured to calculate the oscillation amplitude of the differential voltage curve and detect contact based on the oscillation amplitude of the differential voltage curve.

[0130] When the object 104 contacts the contact surface 101, the object 104 can introduce vibration to the contact surface 101. This vibration can be detected via the piezoelectric transducer 102.

[0131] The control circuit 103 can calculate, for example, the average differential voltage V diff、ave using the following.

Equation

[0132] For each sample V diff [i], the calculation unit 200 can calculate the oscillation amplitude A i using the following, for example.

Equation

Equation

Equation

[0133] Since the amount of vibration of the element 102 may be inversely proportional to the distance between the piezoelectric transducer 102 and the object 104, the calculation unit 200 can calculate / estimate the position of the object 104 on the contact surface 101 using the vibration component of each piezoelectric transducer 102.

[0134] The control circuit 103 can compare, for example, the oscillation amplitude of the differential voltage with a preset threshold value. When the oscillation amplitude of the differential voltage is greater than the preset threshold value, the control circuit 103 can estimate that the object 104 is in contact with the contact surface 101.

[0135] FIG. 7 shows a schematic diagram of a voltage curve 701 measured on the piezoelectric transducer 102 according to an embodiment.

[0136] The measured voltage curve 701 shown in the embodiment of FIG. 7 may correspond to a situation where the object 104 in contact with the contact surface 101 is increasing the pressing force. This can be observed as the difference between the reference voltage curve 401 and the measured voltage curve 701. Since the force increases, the value of the measured voltage curve 701 is smaller than the value of the reference voltage curve 401.

[0137] FIG. 8 shows a schematic diagram of a differential voltage curve 801 according to an embodiment.

[0138] The differential voltage curve 801 shown in FIG. 8 can be obtained by subtracting the reference voltage curve 401 from the measured voltage curve 701 shown in FIG. 7.

[0139] The control circuit 103 may be configured to detect the sign / polarity of the differential voltage curve V diff (t). For example, in the case of the differential voltage curve 801 presented in FIG. 8, the control circuit 103 may be configured to detect that the differential voltage curve 801 is mainly negative.

[0140] The control circuit 103 may be configured to detect the temporal change characteristics of the contact based on the sign / polarity of the differential voltage curve V diff (t). For example, 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 contact is increasing.

[0141] FIG. 9 shows an expression in the form of a flowchart of a method according to an embodiment.

[0142] According to one embodiment, method 900 includes step 901 of obtaining at least one parameter indicating a reference response of a piezoelectric transducer.

[0143] Method 900 may further include step 902 of forming a reference voltage curve based on the at least one parameter.

[0144] Method 900 may further include step 903 of driving the piezoelectric transducer with a drive voltage.

[0145] Method 900 may further include step 904 of measuring a voltage curve on the piezoelectric transducer.

[0146] Method 900 may further include step 905 of comparing the reference voltage curve and the measured voltage curve.

[0147] Method 900 may further include step 906 of detecting contact on the contact surface based on the comparison.

[0148] FIG. 10 shows a flowchart representation of the voltages used by control circuit 103 according to one embodiment.

[0149] Control circuit 103 may further be configured to drive piezoelectric transducer 102 using test drive voltage 1001.

[0150] Test drive voltage 1001 may be similar to drive voltage 402. Test drive voltage 1001 may include, for example, any preconfigured voltage curve suitable for testing the electrical and / or mechanical characteristics of piezoelectric transducer 102.

[0151] Control circuit 103 may be configured to drive piezoelectric transducer 102 with test drive voltage 1001 when there is no external force applied to contact surface 101 by object 104.

[0152] Control circuit 103 may further be configured to measure response voltage curve 1002 caused by test drive voltage 1001 on piezoelectric transducer 102.

[0153] The control circuit 103 can be configured to drive the piezoelectric transducer 102 with the test drive voltage 1001 when no external force is applied to the contact surface 101 by the object 104. Therefore, the response voltage curve 1002 can correspond to the reference voltage curve 402. Thus, the control circuit 103 can obtain the reference voltage 402 curve by measuring the response voltage curve 1002.

[0154] The control circuit 103 can further be configured to calculate at least one parameter 203 based on the response voltage curve 1002.

[0155] The control circuit 103 can further be configured to store at least one parameter 203. The control circuit 103 can store at least one parameter 203 in, for example, the memory 202.

[0156] The control circuit 103 can, for example, estimate the RC time constant of the piezoelectric transducer 102 based on the response voltage curve 1002. The control circuit 103 can obtain at least one parameter 203 from the response voltage curve 1002 using, for example, curve fitting and / or other calculation procedures.

[0157] The control circuit 103 can, for example, periodically perform the aforementioned operations for calculating at least one parameter 203. Since the electrical and / or mechanical characteristics of the piezoelectric transducer 102 can change over time, the control circuit 103 can thus update at least one parameter 203 to correspond to the current characteristics of the piezoelectric transducer 102. Therefore, the reference voltage curve 401 formed based on at least one parameter 203 can more accurately indicate the reference behavior of the piezoelectric transducer 102.

[0158] Next, the control circuit 103 acquires at least one parameter 203, forms a reference voltage curve 401 based on the at least one parameter 203, drives the piezoelectric transducer with a drive voltage 402, measures a voltage curve 501 on the piezoelectric transducer 102, compares the reference voltage curve 401 with the measured voltage curve 501, and detects contact on the contact surface 101 based on the comparison described herein.

[0159] The ranges or device values described herein can be extended or changed without losing the desired effect. Also, any embodiments can be combined with other embodiments unless explicitly prohibited.

[0160] The subject matter has been described in language specific to structural features and / or acts, but 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. Rather, the specific features and acts described above are disclosed as examples for implementing the claims, and other equivalent features and acts are intended to be within the scope of the claims.

[0161] It will be understood that the above benefits and advantages may relate to one embodiment or to several embodiments. Embodiments are not limited to those that solve any or all of the described problems or have any or all of the described benefits and advantages. Further, reference to "one" item may refer to one or more of that item.

[0162] The steps of the methods described herein can be performed in any suitable order or simultaneously if necessary. Further, individual blocks can be deleted from any method without departing from the spirit and scope of the subject matter described herein. Any aspect of any of the above embodiments can be combined with any aspect of any of the other described embodiments to form further embodiments without losing the desired effect.

[0163] The term "comprising" as used herein is used to mean including the identified method, block, or element, but such block or element does not include an exclusive list and the method or apparatus may include additional blocks or elements.

[0164] The foregoing description has been presented by way of example only and it will be understood that various modifications may be made by those skilled in the art. The foregoing specifications, examples, and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a degree of particularity or with reference to one or more individual embodiments, those skilled in the art can make numerous changes to the disclosed embodiments without departing from the spirit or scope of this specification.

Claims

1. A contact surface (101), a piezoelectric transducer (102) mechanically coupled to the contact surface (101), and a control circuit (103) electrically coupled to the piezoelectric transducer (102), wherein the device (100) comprises: obtaining at least one parameter (203) indicating 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) with a driving voltage (402); measuring a voltage curve of the piezoelectric transducer (102) after driving the piezoelectric transducer (102) with the driving voltage (402); comparing the reference voltage curve (401) with a measured voltage curve (501, 701) obtained by measuring the voltage curve; and detecting contact on the contact surface (101) based on the comparison, characterized in that the device (100) is configured to detect contact on the contact surface (101).

2. The device (100) according to claim 1, wherein the control circuit (103) is further configured to detect a temporal change characteristic of the contact on the contact surface (101) 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 any one of claims 1 to 3, wherein the control circuit (103) is further configured to compare the reference voltage curve (401) with the measured voltage curve (501, 701) by calculating a difference between the reference voltage curve (401) and the measured voltage curve (501, 701).

5. The device (100) according to any one of claims 1 to 4, wherein the control circuit (103) is further configured to generate a differential voltage curve (601, 801) by subtracting the reference voltage curve (401) from the measured voltage curve (501, 701), and detect the contact based on the differential voltage curve (601, 801), thereby comparing the reference voltage curve and the measured voltage curve.

6. The device (100) according to claim 5, wherein the control circuit (103) is further configured to calculate an integral of the differential voltage curve (601, 801) and detect the contact based on the integral of the differential voltage curve.

7. The control circuit (103) is further configured to calculate an oscillation amplitude of the differential voltage curve (601, 801) and detect the contact based on the oscillation amplitude of the differential voltage curve. The device (100) according to claim 5 is characterized in that.

8. The control circuit (103) is further configured to detect a saturation period (502) of the reference voltage curve (401), detect a saturation period (503) of the measured voltage curve (501, 701), and compare the reference voltage curve with the measured voltage curve by comparing the saturation periods of the reference voltage curve and the measured voltage curve. The device (100) according to any one of claims 1 to 7 is characterized in that.

9. The control circuit (103) further uses a test drive voltage (1001) to drive the piezoelectric converter (102), measures a response voltage curve (1002) caused in the piezoelectric converter (102) by the test drive voltage (1001), and calculates the at least one parameter (203) based on the response voltage curve (1002). The device (100) according to any one of claims 1 to 8 is characterized in that.

10. A step (901) of obtaining at least one parameter indicating a reference response of the piezoelectric converter, A step (902) of forming a reference voltage curve based on the at least one parameter, A step (903) of driving the piezoelectric converter with a drive voltage, A step (904) of measuring a voltage curve of the piezoelectric converter after driving the piezoelectric converter with the drive voltage, A step (905) of comparing the reference voltage curve with a measured voltage curve obtained by measuring the voltage curve, A step (906) of detecting a contact on the contact surface based on the comparison, A method (900) characterized by including.

11. Based on the comparison, the step of detecting a contact on the contact surface includes a step of detecting a temporal change characteristic of the contact on the contact surface based on the comparison. The method (900) according to claim 10 is characterized in that.

12. The step (905) of comparing the reference voltage curve and the measured voltage curve includes a step of subtracting the reference voltage curve from the measured voltage curve to generate a differential voltage curve, and the step (906) of detecting contact on the contact surface based on the comparison includes a step of detecting the contact based on the differential voltage curve. The method (900) according to claim 10 or 11, characterized in that it is included.

13. Furthermore, it includes a step of calculating the integral of the differential voltage curve, and the step (906) of detecting contact on the contact surface based on the comparison includes a step of detecting the contact based on the integral of the differential voltage curve. The method (900) according to claim 12, characterized in that it is included.

14. A step of driving the piezoelectric transducer using a test drive voltage, A step of measuring a response voltage curve caused in the piezoelectric transducer by the test drive voltage, A step of calculating the at least one parameter based on the response voltage curve, The method (900) according to any one of claims 10 to 13, further characterized in that it is included.

15. A computer program product provided with program code, the computer program product being configured to implement the method according to any one of claims 10 to 14 when the program code is executed on a computer.

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