Pressed position estimation system, pressed position estimation method, and pressed position estimation program

Abstract

To provide a technology that reduces restrictions on housing design.SOLUTION: A pressed position estimation system comprises: a piezoelectric film having output anisotropy; a plurality of detection electrodes for detecting charges generated on the piezoelectric film; a detection unit for detecting a voltage signal generated in the detection electrode; and a processing unit for processing the signal output by the detection unit. The processing unit is configured to: hold information on a region of interest on a first main surface of the piezoelectric film, the region of interest being defined based on a line forming a boundary along which the polarity of the voltage of the detection electrode changes depending on a pressed position; retain information on the detection electrodes selected among the detection electrodes and associated with the region of interest; maintain an ideal array storing values indicating characteristics of the polarity of the voltage of the detection electrode associated with the region of interest when a position within the region of interest is pressed; generate an array of interest storing values corresponding to the voltages of the detection electrodes associated with the region of interest; and calculate the zero-mean normalized cross-correlation between the array of interest and the ideal array so as to estimate the pressed position.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for detecting pressure. [Background technology]

[0002] Conventionally, in products equipped with a general pressure trackpad, the amount of displacement of the housing caused by the user's pressure operation is measured using a strain sensor, ultrasonic sensor, or capacitive touch panel (see, for example, Patent Document 1), thereby estimating the pressure applied to the operating surface and detecting the user's pressure operation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-78888 Summary of the Invention [Problem to be solved by the invention]

[0004] A typical pressure trackpad measures the displacement of the housing and estimates the pressure position using the absolute amount of displacement. Therefore, the displacement of the housing must be adjusted to a predetermined standard. Therefore, to implement a pressure trackpad in a product, it is necessary to consider a housing structure that equalizes the displacement of the housing and the placement of the sensor element that measures the displacement of the housing. This results in high housing design costs and significant constraints on the housing design.

[0005] Furthermore, due to the large restrictions on housing design, it becomes necessary to design each product individually, which places large restrictions on product cost and design.

[0006] An object of the present invention is to provide a technology that reduces the constraints on housing design when implementing a pressure position estimation system in a product. [Means for solving the problem]

[0007] a ground electrode disposed on the second main surface of the piezoelectric film; a detection unit that detects voltage signals generated in the detection electrodes from the charges detected by the detection electrodes; and a processing unit that processes the signals output by the detection unit. The processing unit stores information about a region of interest defined on the first main surface of the piezoelectric film based on a boundary line along which the polarity of the voltage of the detection electrodes changes depending on the pressure position; stores information about detection electrodes selected from the detection electrodes and associated with the region of interest; stores an ideal array that stores values ​​representing characteristics of the polarity of the voltage of the detection electrodes associated with the region of interest when a position within the region of interest is pressed; generates a region of interest that stores values ​​corresponding to the voltage of the detection electrodes associated with the region of interest; and calculates a zero-mean normalized cross-correlation between the region of interest and the ideal array to estimate the pressure position.

[0008] a ground electrode disposed on the second main surface of the piezoelectric film; a detection unit that detects voltage signals generated in the detection electrodes from the charges detected by the detection electrodes; and a processing unit that processes the signals output by the detection unit. In this pressure position estimation method, the processing unit stores information about a region of interest defined on the first main surface of the piezoelectric film based on boundary lines along which the polarity of the voltage of the detection electrodes changes depending on the pressure position; stores information about detection electrodes selected from the detection electrodes and associated with the region of interest; stores an ideal array that stores values ​​representing characteristics of the polarity of the voltage of the detection electrodes associated with the region of interest when a position within the region of interest is pressed; generates a region of interest that stores values ​​corresponding to the voltage of the detection electrodes associated with the region of interest; and calculates a zero-mean normalized cross-correlation between the array of interest and the ideal array to estimate the pressure position.

[0009] a ground electrode disposed on the second main surface of the piezoelectric film; a detection unit that detects voltage signals generated in the detection electrodes from the charges detected by the detection electrodes; and a processing unit that processes the signals output by the detection unit. The pressure position estimation program is installed in a pressure position estimation system including: a piezoelectric film having a first main surface and a second main surface opposite to the first main surface and having output anisotropy; a plurality of detection electrodes disposed on the first main surface of the piezoelectric film and detecting charges generated in the piezoelectric film; a ground electrode disposed on the second main surface of the piezoelectric film; a detection unit that detects voltage signals generated in the detection electrodes from the charges detected by the detection electrodes; and a processing unit that processes the signals output by the detection unit. The program causes the processing unit to: retain information about a region of interest defined on the first main surface of the piezoelectric film based on boundary lines along which the polarity of the voltage of the detection electrodes changes depending on the pressure position; retain information about detection electrodes selected from the detection electrodes and associated with the region of interest; retain an ideal array that stores values ​​representing characteristics of the polarity of the voltage of the detection electrodes associated with the region of interest when a position within the region of interest is pressed; generate an array of interest that stores values ​​corresponding to the voltage of the detection electrodes associated with the region of interest; and calculate a zero-mean normalized cross-correlation between the array of interest and the ideal array, thereby estimating the pressure position. [Effects of the Invention]

[0010] According to the present invention, it is possible to reduce the constraints on the housing design when implementing a pressure position estimation system in a product. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a functional block diagram of a pressure position estimation system according to an embodiment. [Figure 2] 2(A) and 2(B) are cross-sectional views of a piezoelectric sensor. [Figure 3] FIG. 3 is a cross-sectional view of a piezoelectric film sensor. [Figure 4] FIG. 4 is a plan view showing the arrangement of the detection electrodes. [Figure 5] 5(A) to 5(C) are conceptual diagrams for explaining the voltage generated in the detection electrode. [Figure 6]6A and 6B are conceptual diagrams for explaining the region of interest. [Figure 7] FIG. 7 is a conceptual diagram for explaining the sequence of interest. [Figure 8] FIG. 8 is a conceptual diagram for explaining an ideal arrangement. [Figure 9] FIG. 9 is a flowchart showing the calculation process of the press probability array by the processing unit. [Figure 10] FIG. 10 is a diagram showing an example of values ​​according to the voltage of the detection electrode. [Figure 11] FIG. 11 is a diagram showing a press probability array calculated when values ​​according to the voltages of the detection electrodes shown in FIG. 10 are given. [Figure 12] FIG. 12 is a plan view showing the arrangement of detection electrodes according to the first modified example. [Figure 13] FIG. 13 is a conceptual diagram for explaining a voltage generated in the detection electrode according to the first modified example. [Figure 14] 14(A) and 14(B) are conceptual diagrams for explaining the region of interest according to the first modified example. [Figure 15] FIG. 15 is a conceptual diagram for explaining the sequence of interest according to the first modified example. [Figure 16] FIG. 16 is a conceptual diagram for explaining an ideal arrangement according to the first modified example. [Figure 17] FIG. 17 is a plan view showing the arrangement of detection electrodes according to the second modified example. [Figure 18] FIG. 18 is a conceptual diagram for explaining the region of interest according to the second modified example. [Figure 19] FIG. 19 is a conceptual diagram for explaining the sequence of interest according to the second modified example. [Figure 20] FIG. 20 is a conceptual diagram for explaining an ideal arrangement according to the second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, several embodiments of the present invention will be described. In each embodiment, differences from the previous embodiments will be described. Similar effects due to similar configurations will not be mentioned for each embodiment.

[0013] [Embodiment] Fig. 1 is a functional block diagram of a pressure position estimation system according to an embodiment. Fig. 2(A) and Fig. 2(B) are cross-sectional views of a piezoelectric sensor. Fig. 3 is a cross-sectional view of a piezoelectric film sensor.

[0014] The pressure position estimation system 1 includes a piezoelectric sensor 11, a detection unit 12, and a processing unit 13. The piezoelectric sensor 11 includes a rigid bottom plate 15, a flat elastic member 16, and a piezoelectric film sensor 17. The piezoelectric film sensor 17 includes a piezoelectric film 21, adhesive materials 22 and 23, a plurality of detection electrodes 24, a ground electrode 25, and flexible substrates 26 and 27.

[0015] The pressure position estimation system 1 is configured to estimate the position of a pressure on the main surface 31 of the piezoelectric film sensor 17 .

[0016] As shown in FIG. 3 , the piezoelectric film 21 has a first main surface 33 and a second main surface 34 opposite the first main surface 33, and has output anisotropy. The piezoelectric film 21 is formed, for example, from uniaxially stretched polylactic acid (PLLA). The detection electrode 24 is disposed on the first main surface 33 of the piezoelectric film 21 and detects charges generated in the piezoelectric film 21. The detection electrode 24 is formed on a flexible substrate 26 and attached to the first main surface 33 of the piezoelectric film 21 with an adhesive material 22. The ground electrode 25 is disposed on the second main surface 34 of the piezoelectric film 21 and provides a reference potential. The ground electrode 25 is formed on a flexible substrate 27 and attached to the second main surface 34 of the piezoelectric film 21 with an adhesive material 23.

[0017] 1 and 3, the detection unit 12 detects a voltage signal generated in the detection electrode 24 from the charge detected by the detection electrode 24. The detection unit 12 has, for example, a charge amplifier circuit, an amplification circuit, and an A / D conversion circuit. The detection unit 12 then converts, for example, the charge generated in the detection electrode 24 into a voltage, amplifies the voltage obtained by the conversion, and outputs the amplified voltage after A / D conversion. The processing unit 13 processes the signal output by the detection unit 12. The processing unit 13 is composed of a CPU, memory, etc., and stores a program, and processes the signal by executing the program.

[0018] As will be described in detail below, the processing unit 13 holds information about a region of interest defined on the first principal surface 33 of the piezoelectric film 21 based on a boundary line along which the polarity of the voltage of the detection electrodes 24 changes depending on the pressing position. The processing unit 13 holds information about a detection electrode 24 selected from the detection electrodes 24 and associated with the region of interest. The processing unit 13 holds an ideal array that stores values ​​representing characteristics of the polarity of the voltage of the detection electrodes 24 associated with the region of interest when a position within the region of interest is pressed. The processing unit 13 generates a region of interest that stores values ​​corresponding to the voltage of the detection electrodes 24 associated with the region of interest. The processing unit 13 then estimates the pressing position by calculating the zero-mean normalized cross-correlation between the region of interest and the ideal array.

[0019] As shown in FIG. 2(A), the elastic member 16 is disposed between the bottom plate 15 and the piezoelectric film sensor 17. The elastic member 16 is attached to the piezoelectric film sensor 17 and the bottom plate 15, for example, with an adhesive or a pressure-sensitive adhesive. As shown in FIG. 2(B), when the elastic member 16 is pressed, the thickness of the elastic member 16 at the pressed position p changes. Therefore, when the main surface 31 of the piezoelectric film sensor 17 is pressed, the piezoelectric film sensor 17 locally recesses around the pressed position p. The elastic member 16 is made of a material such as rubber or sponge.

[0020] In this way, the piezoelectric sensor 11 is preferably configured so that the piezoelectric film 21 is locally recessed around the pressing position.

[0021] In this specification, a predetermined direction parallel to the first main surface 33 of the piezoelectric film 21 according to the polarization charge on the first main surface 33 of the piezoelectric film 21 is defined as the x-axis direction or horizontal direction. A direction parallel to the first main surface 33 of the piezoelectric film 21 and perpendicular to the x-axis direction is defined as the y-axis direction or vertical direction. A direction perpendicular to the first main surface 33 of the piezoelectric film 21 is defined as the z-axis direction. One side of the x-axis direction is defined as the right direction, and the other side of the x-axis direction is defined as the left direction. One side of the y-axis direction is defined as the up direction, and the other side of the y-axis direction is defined as the down direction.

[0022] 3 and 4, the detection electrodes 24 have a rectangular shape when the first main surface 33 of the piezoelectric film 21 is viewed in plan. The detection electrodes 24 are aligned with almost no gaps in the vertical and horizontal directions on the first main surface 33 of the piezoelectric film 21, and cover almost the entire first main surface 33 of the piezoelectric film 21.

[0023] Instead of a rectangle, the detection electrodes 24 may have a hexagon, a circle, a parallelogram, or various other shapes. Also, the detection electrodes 24 do not need to be packed tightly or aligned on the piezoelectric film 21 as long as the required resolution can be obtained.

[0024] 5(A) to 5(C) are conceptual diagrams for explaining the voltage generated in the detection electrodes. In FIG. 5(A) to FIG. 5(C), attention is focused on one detection electrode 24, and other detection electrodes 24 are not shown.

[0025] The difference in the voltage of the detection electrode 24 from the reference potential is proportional to the difference between the time differential of the normal strain in the x'-axis direction of the piezoelectric film and the time differential of the normal strain in the y'-axis direction of the piezoelectric film. The x'-axis direction corresponds to the direction that forms a 45° counterclockwise angle with the x-axis direction. The y'-axis direction corresponds to the direction perpendicular to the x'-axis direction.

[0026] As illustrated in FIG. 5A, when a pressing body presses a position p1 in the first region e1, the piezoelectric film stretches primarily in the y'-axis direction at the position of the detection electrode 24. The pressing body is an object that performs pressing, such as a finger. The first region e1 is composed of regions on and near the detection electrode 24 that are located to the upper left and lower right of the center of the detection electrode 24. As illustrated in FIG. 5B, when a pressing body presses a position p2 in the second region e2, the piezoelectric film stretches primarily in the x'-axis direction at the position of the detection electrode 24. The second region e2 is composed of regions on and near the detection electrode 24 that are located to the lower left and upper right of the center of the detection electrode 24. As illustrated in FIG. 5C, when a pressing body presses a position p3 on the boundary f between the first region e1 and the second region e2, the piezoelectric film stretches in the x-axis or y-axis direction at the position of the detection electrode 24, and therefore stretches evenly in the x'-axis and y'-axis directions.

[0027] Therefore, no matter which position in the first region e1 the pressing body presses, the voltage of the detection electrode 24 has the same polarity. The positive or negative polarity of the voltage of the detection electrode 24 means the positive or negative difference of the voltage of the detection electrode 24 with respect to the reference potential. No matter which position in the second region e2 the pressing body presses, the voltage of the detection electrode 24 has the same polarity. The voltage of the detection electrode 24 when the pressing body presses the first region e1 has the opposite polarity to the voltage of the detection electrode 24 when the pressing body presses the second region e2. When the pressing body presses the boundary f between the first region e1 and the second region e2, the detection electrode 24 is at the reference potential v G Furthermore, the voltage of detection electrode 24 when the pressing body presses into the piezoelectric film has the opposite polarity to the voltage of detection electrode 24 when the pressing body separates from the piezoelectric film. Boundary f between first region e1 and second region e2 forms the boundary where the polarity of the voltage of detection electrode 24 changes depending on the pressing position.

[0028] Such characteristics of the voltage generated in the detection electrode 24 are due to the output anisotropy of the piezoelectric film and appear regardless of the shape or arrangement of the electrodes.

[0029] In this embodiment, when the pressing body presses the first region e1, the voltage of the detection electrode 24 has a positive polarity.

[0030] However, in a modified example, when the pressing body presses the first region e1, the voltage of the detection electrode 24 may have a negative polarity.

[0031] 6(A) and 6(B) are conceptual diagrams for explaining the region of interest. In Fig. 6(A) and Fig. 6(B), the boundaries between adjacent detection electrodes 24 are depicted in a simplified manner.

[0032] Similarly, in the drawings described below, the boundaries between adjacent detection electrodes 24 may be depicted in a simplified manner.

[0033] As shown in Fig. 6(A), a region of interest r is defined on the first principal surface of the piezoelectric film. The region of interest r is defined by first straight lines g1 and g2 and second straight lines h1 and h2. The first straight lines g1 and g2 and the second straight lines h1 and h2 correspond to the boundary f (see Figs. 5(A) to 5(C)) between the first region e1 and the second region e2, and form the boundary where the polarity of the voltage of the detection electrode 24 changes depending on the pressing position. The first straight lines g1 and g2 are adjacent to each other. The second straight lines h1 and h2 are perpendicular to the first straight lines g1 and g2 and are adjacent to each other.

[0034] More specifically, the detection electrodes 24 include detection electrodes 41, 42, 43, and 44. The detection electrodes 42, 43, and 44 are adjacent to the detection electrode 41 and are located below, to the right of, and below and to the right of the detection electrode 41, respectively. A first line g1 defines a boundary along which the polarity of the voltage applied to the detection electrodes 41 and 43 changes depending on the pressing position, passes through the center of the detection electrodes 41 and 43, and extends horizontally. A first line g2 defines a boundary along which the polarity of the voltage applied to the detection electrodes 42 and 44 changes depending on the pressing position, passes through the center of the detection electrodes 42 and 44, and extends horizontally. A second line h1 defines a boundary along which the polarity of the voltage applied to the detection electrodes 41 and 42 changes depending on the pressing position, passes through the center of the detection electrodes 41 and 42, and extends vertically. The second straight line h2 forms a boundary along which the polarity of the voltage of the detection electrodes 43, 44 changes depending on the pressing position, passes through the center of the detection electrodes 43, 44, and extends in the vertical direction.

[0035] The region of interest r is associated with detection electrodes 41, 42, 43, and 44 selected from the detection electrodes 24.

[0036] As shown in FIG. 6(B), the regions of interest r are arranged without gaps on the first main surface of the piezoelectric film and are defined so as to cover almost the entire first main surface of the piezoelectric film.

[0037] FIG. 7 is a conceptual diagram for explaining the array of interest. The array of interest is determined for each region of interest r. The array of interest stores values ​​according to the voltage of the detection electrodes 24 associated with the region of interest r. The value according to the voltage of the detection electrodes 24 corresponds to, for example, the value of data output from the detection unit according to the voltage of the detection electrodes 24, and corresponds to, for example, the voltage obtained by converting the charge generated in the detection electrodes 24 into a voltage, amplifying the voltage obtained by the conversion, and A / D converting the amplified voltage. The array of interest is a=(a1, a2, ..., a N ) where a i , i=1,...,N represents a value corresponding to the voltage of the ith detection electrode 24 associated with the region of interest r. N represents the number of detection electrodes 24 associated with the region of interest r. Specifically, a=(a1,a2,a3,a4)=(v1,v2,v3,v4). Here, v1, v2, v3, and v4 represent values ​​corresponding to the voltages of the detection electrodes 41, 42, 43, and 44, respectively.

[0038] FIG. 8 is a conceptual diagram for explaining the ideal array. The ideal array stores values ​​that represent the polarity characteristics of the voltage of the detection electrode 24 associated with the attention area r when a position within the attention area r is pressed. The ideal array is a set of values ​​t=(t1, t2, ..., t N ) where t i , i=1,...,N corresponds to the polarity of the voltage of the ith detection electrode 24 associated with the region of interest r and takes a value of 1 or -1. Specifically, when position p within the region of interest r is pressed, the voltages of the detection electrodes 41 and 44 have positive polarity and the voltages of the detection electrodes 42 and 43 have negative polarity. Therefore, the ideal arrangement is defined as t=(t1,t2,t3,t4)=(1,-1,-1,1), where t1, t2, t3, and t4 correspond to the polarity of the voltages of the detection electrodes 41, 42, 43, and 44, respectively.

[0039] In addition, as long as elements of the target array and the ideal array with the same numbers correspond to the same detection electrodes, the order of the elements of the target array and the ideal array may be changed arbitrarily. In addition, the ideal array is expressed as follows: α0 is an arbitrary real number, α1 is an arbitrary real number other than 0, and t i →α0+α1t i , i=1,...,N.

[0040] 9 is a flowchart showing the calculation process of the press probability array by the processing unit. As shown below, the press probability array stores the press probability for each attention area. The press probability indicates a value related to the probability that the corresponding attention area has been pressed.

[0041] The processing unit holds information on each region of interest, information on the detection electrodes associated with each region of interest, and an ideal arrangement, which are given in advance.

[0042] Then, first, the processing unit selects one of the regions of interest defined on the first principal surface of the piezoelectric film (s1). Next, the processing unit generates a sequence of interest for the selected region of interest (s2). Next, the processing unit calculates the covariance σ between the generated sequence of interest and the ideal sequence. at Calculate the covariance σ at is expressed as follows:

[0043]

number

[0044] Next, the processing unit calculates the standard deviation σ of the generated sequence of interest. a Calculate the standard deviation σ a is expressed as follows:

[0045]

number

[0046] Next, the processing unit calculates the standard deviation σ of the calculated sequence of interest. aand the standard deviation σ of the ideal array calculated in advance t Multiplying by and gives the standard deviation product ξ at =σ a σ t Calculate the standard deviation of the ideal array σ t is expressed as follows:

[0047]

number

[0048] Next, the processing unit calculates the covariance σ at The product of standard deviations ξ at Divide by and get the pressing probability ρ=σ at / ξ at The pressing probability ρ corresponds to the zero-mean normalized cross-correlation (ZNCC) between the target sequence and the ideal sequence (s6).

[0049] Next, the processing unit stores the calculated pressing probability in a pressing probability array (s7). If the processing unit has not finished calculating the pressing probability for all attention areas (s8: no), it selects the next attention area (s1). If the processing unit has calculated the pressing probabilities for all attention areas (s8: yes), it ends the calculation process of the pressing probability array.

[0050] The processing unit may execute step 3 after executing steps 4 and 5. The processing unit may also calculate the pressing probability using an equation obtained by modifying the equation expressing the pressing probability.

[0051] When a position within the region of interest is pressed, the value corresponding to the voltage of the detection electrode associated with that region of interest is approximately β0 + β1t i , i=1,...,N, specifically β0+β1, β0-β1, β0-β1, β0+β1. Here, β0 is equal to a value corresponding to the reference potential, and β1 is proportional to the speed at which the pressing body presses. Therefore, the pressing probability for that region of interest is equal to or close to 1 or -1. If a position within the region of interest is not pressed, the value corresponding to the voltage of the detection electrode 24 associated with that region of interest is β0+β1t i, i=1,...,N. Therefore, the pressing probability for that region of interest takes a value far from 1 and -1. Therefore, when the pressing probability is equal to or close to 1 or -1, there is a high probability that the position in the region of interest corresponding to that pressing probability has been pressed. Therefore, by comparing the pressing probability with 1 or -1, it is possible to determine whether the position in the region of interest corresponding to that pressing probability has been pressed.

[0052] Furthermore, for example, it is possible to determine whether a position within the region of interest has been pressed by calculating a time series of press probability and comparing that time series of press probability with a time series of typical press probability during pressing.

[0053] Even when a position on the boundary of the attention area is pressed, the press probability takes a significant value, so the press position can be estimated by calculating the press probability.

[0054] The voltages of the detection electrodes associated with the region of interest when the pressing body presses the region of interest have the opposite polarity to the voltages of the detection electrodes when the pressing body leaves the region of interest. Therefore, the pressing probability for the region of interest when the pressing body presses the region of interest has the opposite positive or negative sign to the pressing probability for the region of interest when the pressing body leaves the region of interest. Therefore, the processing unit may determine whether the pressing body is pressing the region of interest or leaving the region of interest based on the positive or negative sign of the pressing probability.

[0055] FIG. 10 is a diagram showing an example of values ​​corresponding to the voltage of a detection electrode. In FIG. 10, values ​​corresponding to the voltage of a detection electrode are shown at the position of the detection electrode. Also, in FIG. 10, 6 × 14 detection electrodes are arranged. The values ​​corresponding to the voltage of the detection electrodes that are in contact with the pressing position p and located to the upper left and lower right of the pressing position p are larger than the values ​​corresponding to the reference potential. The value corresponding to the reference potential is approximately 2000. The values ​​corresponding to the voltage of the detection electrodes that are in contact with the pressing position p and located to the lower left and upper right of the pressing position p are smaller than the values ​​corresponding to the reference potential. The values ​​corresponding to the voltage of the detection electrodes that are located away from the pressing position p are close to the values ​​corresponding to the reference potential.

[0056] FIG. 11 is a diagram showing a press probability array calculated when values ​​corresponding to the voltages of the detection electrodes shown in FIG. 10 are given. In FIG. 10, the press probabilities are shown at the positions of the attention areas corresponding to the press probabilities. In the attention areas that overlap with the press position p, the press probability is close to 1. In most attention areas that do not overlap with the press position p, the press probability is far from 1.

[0057] Furthermore, by removing noise from the data regarding the voltage of the detection electrodes before calculating the pressure probability array, it is possible to prevent the pressure probability for an unpressed area of ​​interest from becoming equal to or close to 1 or -1.

[0058] According to this embodiment, a zero-mean normalized cross-correlation between the target array and the ideal array is calculated to estimate the pressure position. To this end, the difference between the value corresponding to the voltage of the detection electrode associated with the target area and its mean value, i.e., the relative amount of the value corresponding to the voltage of the detection electrode, is used, and therefore the relative amount of the housing displacement is used. Furthermore, the relative amount of the value corresponding to the voltage of the detection electrode, and therefore the normalized relative amount of the housing displacement, is used. In this way, to estimate the pressure position, the tendency of the housing displacement is compared with a predetermined reference tendency. Therefore, it is not necessary to precisely match the housing displacement to the predetermined reference. As a result, the only constraint on the housing design when implementing the pressure position estimation system in a product is that the main surface of the piezoelectric film sensor be recessed at the pressure position. This reduces the constraints on the housing design when implementing the pressure position estimation system in a product. This also reduces product costs and increases the flexibility of product design.

[0059] Furthermore, as described above, in order to estimate the pressed position, the tendency of the displacement amount of the housing is compared with a predetermined reference tendency, so there is no need to calibrate the pressed position estimation system.

[0060] Furthermore, the polarity of the voltage of the detection electrodes associated with the region of interest is used to estimate the pressed position, so the detection electrodes do not need to have a specific shape or arrangement, allowing for greater freedom in designing the detection electrodes.

[0061] [First Modification] The pressed position estimation system according to the first modification differs from the pressed position estimation system according to the above embodiment in that the piezoelectric film sensor has regular hexagonal detection electrodes.

[0062] 12 is a plan view showing the arrangement of detection electrodes according to the first modified example. The detection electrodes 35 have a regular hexagonal shape when the first main surface 33 (see FIG. 3) of the piezoelectric film 21 is viewed in plan. The detection electrodes 35 are aligned with almost no gaps on the first main surface 33 of the piezoelectric film 21 to form a honeycomb structure, covering almost the entire surface of the first main surface 33 of the piezoelectric film 21.

[0063] Fig. 13 is a conceptual diagram for explaining the voltage generated in the detection electrode according to the first modification. Fig. 13 focuses on one detection electrode 35 and does not show the other detection electrodes 35. As in the above embodiment, the boundary f between the first region e1 and the second region e2 forms a boundary where the polarity of the voltage of the detection electrode 35 changes depending on the pressing position.

[0064] 14(A) and 14(B) are conceptual diagrams illustrating regions of interest according to a first modification. As shown in FIG. 14(A), region of interest r1 includes regions of interest r11, r12, r13, and r14. Regions of interest r12, r13, and r14 are adjacent to region of interest r11 and are located below, to the right, and below and to the right of region of interest r11, respectively. Region of interest r11 is defined by first lines g11 and g12 and second lines h11 and h12; region of interest r12 is defined by first lines g12 and g13 and second lines h11 and h12; region of interest r13 is defined by first lines g11 and g12 and second lines h12 and h13; and region of interest r4 is defined by first lines g12 and g13 and second lines h12 and h13. The first straight lines g11, g12, and g13 and the second straight lines h11, h12, and h13 form boundaries where the polarity of the voltage of the detection electrode 35 changes depending on the pressing position.

[0065] More specifically, the detection electrodes 35 include detection electrodes 51, 52, 53, and 54. The detection electrodes 51, 52, and 54 are adjacent to the detection electrode 53 and are located to the lower left, lower right, and lower of the detection electrode 53, respectively. A first line g11 forms a boundary along which the polarity of the voltage applied to the detection electrode 53 changes depending on the pressing position, passes through the center of the detection electrode 53, and extends horizontally. A first line g12 forms a boundary along which the polarity of the voltage applied to the detection electrodes 51 and 52 changes depending on the pressing position, passes through the centers of the detection electrodes 51 and 52, and extends horizontally. A first line g13 forms a boundary along which the polarity of the voltage applied to the detection electrode 54 changes depending on the pressing position, passes through the center of the detection electrode 54, and extends horizontally. A second line h11 forms a boundary along which the polarity of the voltage applied to the detection electrode 51 changes depending on the pressing position, passes through the center of the detection electrode 51, and extends vertically. The second line h12 forms a boundary along which the polarity of the voltage applied to the detection electrodes 53 and 54 changes depending on the pressing position, passes through the center of the detection electrodes 53 and 54, and extends in the vertical direction. The second line h13 forms a boundary along which the polarity of the voltage applied to the detection electrode 52 changes depending on the pressing position, passes through the center of the detection electrode 52, and extends in the vertical direction.

[0066] The regions of interest r11 and r12 are associated with detection electrodes 51, 53, and 54 selected from the detection electrodes 35. The regions of interest r13 and r14 are associated with detection electrodes 52, 53, and 54.

[0067] As shown in FIG. 14(B), the set of regions of interest r11, r12, r13, and r14 are arranged without gaps on the first main surface of the piezoelectric film and are defined so as to cover almost the entire first main surface of the piezoelectric film.

[0068] 15 is a conceptual diagram for explaining an array of interest according to a first modified example. For regions of interest r11 and r12, the array of interest is determined as a = (a1, a2, a3) = (v11, v13, v14). For regions of interest r13 and r14, the array of interest is determined as a = (a1, a2, a3) = (v12, v13, v14). Here, v11, v12, v13, and v14 represent values ​​corresponding to the voltages of detection electrodes 51, 52, 53, and 54, respectively.

[0069] 16 is a conceptual diagram illustrating an ideal arrangement according to a first modification. When position p in the region of interest r11 is pressed, the voltages of the detection electrodes 51 and 53 have negative polarity, and the voltage of the detection electrode 54 has positive polarity. Therefore, for the region of interest r11, the ideal arrangement is defined as t = (t1, t2, t3) = (-1, -1, 1). Similarly, for the region of interest r12, the ideal arrangement is defined as t = (t1, t2, t3) = (1, -1, 1) so as to correspond to the polarities of the voltages of the detection electrodes 51, 53, and 54 when a position in the region of interest r12 is pressed. For the regions of interest r11 and r12, t1, t2, and t3 correspond to the polarities of the voltages of the detection electrodes 51, 53, and 54, respectively.

[0070] For region of interest r13, the ideal arrangement is defined as t = (t1, t2, t3) = (1, 1, -1) so that the polarities of the voltages on detection electrodes 52, 53, and 54 correspond to the polarities of the voltages on detection electrodes 52, 53, and 54 when a position within region of interest r13 is pressed. For region of interest r14, the ideal arrangement is defined as t = (t1, t2, t3) = (-1, 1, -1) so that the polarities of the voltages on detection electrodes 52, 53, and 54 correspond to the polarities of the voltages on detection electrodes 52, 53, and 54 when a position within region of interest r14 is pressed. For regions of interest r13 and r14, t1, t2, and t3 correspond to the polarities of the voltages on detection electrodes 52, 53, and 54, respectively.

[0071] The processing unit calculates a press probability array by executing the same processes as steps s1 to s8 shown in FIG. 9, thereby estimating the press position.

[0072] According to the first modification, it is possible to obtain the same effects as those of the above embodiment.

[0073] [Second Modification] The pressed position estimation system according to the second modification differs from the pressed position estimation system according to the above embodiment in that the piezoelectric film sensor has four triangular detection electrodes.

[0074] 17 is a plan view showing the arrangement of detection electrodes according to the second modified example. The detection electrode 36 has a triangular shape when the first main surface 33 (see FIG. 3) of the piezoelectric film 21 is viewed in plan. The detection electrode 36 includes detection electrodes 61, 62, 63, 64, and 65. The detection electrode 61 is located on the upper left side of the first main surface 33 of the piezoelectric film 21, the detection electrode 62 is located on the upper right side of the first main surface 33 of the piezoelectric film 21, the detection electrode 63 is located on the lower left side of the first main surface 33 of the piezoelectric film 21, and the detection electrode 64 is located on the lower right side of the first main surface 33 of the piezoelectric film 21.

[0075] 18 is a conceptual diagram illustrating regions of interest according to the second modification. Region of interest r2 includes regions of interest r21, r22, r23, r24, and r25. Region of interest r21 is located in the center of the first main surface of the piezoelectric film, region of interest r22 is located to the right of the first main surface of the piezoelectric film, region of interest r23 is located below the first main surface of the piezoelectric film, region of interest r24 is located to the left of the first main surface of the piezoelectric film, and region of interest r25 is located above the first main surface of the piezoelectric film.

[0076] The region of interest r21 is defined by first lines g21 and g22 and second lines h21 and h22. The region of interest r22 is defined within the region bounded by the first lines g21 and g22, the second line h22, and the edge of the piezoelectric film. The region of interest r23 is defined within the region bounded by the first line g22, the second lines h21 and h22, and the edge of the piezoelectric film. The region of interest r24 is defined within the region bounded by the first lines g21 and g22, the second line h21, and the edge of the piezoelectric film. The region of interest r25 is defined within the region bounded by the first line g21, the second lines h21 and h22, and the edge of the piezoelectric film.

[0077] The first line g21 forms a boundary along which the polarity of the voltage applied to the detection electrodes 61 and 62 changes depending on the pressing position, passes through the center of the detection electrodes 61 and 62, and extends horizontally. The first line g22 forms a boundary along which the polarity of the voltage applied to the detection electrodes 63 and 64 changes depending on the pressing position, passes through the center of the detection electrodes 63 and 64, and extends horizontally. The second line h21 forms a boundary along which the polarity of the voltage applied to the detection electrodes 61 and 63 changes depending on the pressing position, passes through the center of the detection electrodes 61 and 63, and extends vertically. The second line h22 forms a boundary along which the polarity of the voltage applied to the detection electrodes 62 and 64 changes depending on the pressing position, passes through the center of the detection electrodes 62 and 64, and extends vertically.

[0078] Detection electrodes 61, 62, 63, and 64 are associated with the regions of interest r11, r12, r13, r14, and r15.

[0079] 19 is a conceptual diagram for explaining the arrangement of interest according to the second modification. For each region of interest r2, the arrangement of interest is determined as a = (a1, a2, a3, a4) = (v21, v22, v23, v24). Here, v21, v22, v23, and v24 represent values ​​corresponding to the voltages of the detection electrodes 61, 62, 63, and 64, respectively.

[0080] FIG. 20 is a conceptual diagram illustrating an ideal arrangement according to a second modification. When position p in the region of interest r21 is pressed, the voltages of the detection electrodes 61 and 64 have positive polarity, and the voltages of the detection electrodes 62 and 63 have negative polarity. Therefore, for the region of interest r21, the ideal arrangement is defined as t = (t1, t2, t3, t4) = (1, -1, -1, 1). Similarly, for another region of interest r2, the ideal arrangement is defined to correspond to the polarity of the voltages of the detection electrodes 36 when a position in that region of interest r2 is pressed. Specifically, for the region of interest r22, the ideal arrangement is defined as t = (t1, t2, t3, t4) = (1, 1, -1, -1). For the region of interest r23, the ideal arrangement is defined as t = (t1, t2, t3, t4) = (1, -1, 1, -1). For region of interest r24, the ideal arrangement is defined as t = (t1, t2, t3, t4) = (-1, -1, 1, 1). For region of interest r25, the ideal arrangement is defined as t = (t1, t2, t3, t4) = (-1, 1, -1, 1), where t1, t2, t3, and t4 correspond to the polarities of the voltages on detection electrodes 61, 62, 63, and 64, respectively.

[0081] The processing unit executes the same processes as steps s1 to s8 shown in FIG. 9 to calculate the press probability array.

[0082] As described above, the processing unit may compare the pressing probability with 1 or −1 to determine whether the position in the region of interest corresponding to the pressing probability has been pressed.

[0083] Alternatively, the processing unit may determine that a position within the region of interest corresponding to a pressing probability has been pressed if the absolute value of the pressing probability is greater than a threshold value and is the largest among the pressing probabilities stored in the pressing probability array.

[0084] According to the second modification, it is possible to obtain the same effects as the above embodiment, and also to increase the number of attention areas more than the number of detection electrodes.

[0085] The configurations shown in the above embodiments may be replaced or combined as appropriate.

[0086] The above description of the embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications that are equivalent to the scope of the claims and fall within the scope thereof.

[0087] The present invention has the following configuration.

[0088] (1) a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film having output anisotropy; a plurality of detection electrodes disposed on a first main surface of the piezoelectric film to detect charges generated in the piezoelectric film; a ground electrode disposed on a second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated in the detection electrode from the charge detected by the detection electrode; a processing unit that processes the signal output by the detection unit, The processing unit On the first main surface of the piezoelectric film, information on a region of interest is held, the region of interest being determined based on a line forming a boundary along which the polarity of the voltage of the detection electrode changes depending on a pressing position; storing information of a detection electrode selected from the detection electrodes and associated with the region of interest; maintaining an ideal array storing values ​​characteristic of the polarity of the voltage of a detection electrode associated with the region of interest when a position within the region of interest is pressed; generating a target array storing values ​​corresponding to voltages of detection electrodes associated with the target region; A pressure position estimation system that estimates a pressure position by calculating a zero-mean normalized cross-correlation between the target array and the ideal array.

[0089] (2) The pressure position estimation system described in (1), wherein the attention area is defined by two first lines that form the boundary and are adjacent to each other, and two second lines that form the boundary, are perpendicular to the first lines, and are adjacent to each other.

[0090] (3) The pressure position estimation system described in (1) or (2), wherein the detection electrodes have a rectangular or regular hexagonal shape when viewed in a plane on the first main surface of the piezoelectric film, and are aligned on the first main surface of the piezoelectric film.

[0091] (4) The pressure position estimation system according to any one of (1) to (3), wherein the region of interest is defined within an area surrounded by the boundary line and the edge of the piezoelectric film.

[0092] (5) The bottom plate and a flat elastic member; the elastic member is disposed between the bottom plate and the piezoelectric film; The pressure position estimation system according to any one of (1) to (4), wherein when the elastic member is pressed, the thickness of the elastic member at the pressed position changes.

[0093] (6) a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film having output anisotropy; a plurality of detection electrodes disposed on a first main surface of the piezoelectric film to detect charges generated in the piezoelectric film; a ground electrode disposed on a second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated in the detection electrode from the charge detected by the detection electrode; a processing unit that processes a signal output by the detection unit, The processing unit On the first main surface of the piezoelectric film, information on a region of interest is held, the region of interest being determined based on a line forming a boundary along which the polarity of the voltage of the detection electrode changes depending on a pressing position; storing information of a detection electrode selected from the detection electrodes and associated with the region of interest; maintaining an ideal array storing values ​​characteristic of the polarity of the voltage of a detection electrode associated with the region of interest when a position within the region of interest is pressed; generating a target array storing values ​​corresponding to voltages of detection electrodes associated with the target region; A pressure position estimation method for estimating a pressure position by calculating a zero-mean normalized cross-correlation between the target array and the ideal array.

[0094] (7) a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film having output anisotropy; a plurality of detection electrodes disposed on a first main surface of the piezoelectric film to detect charges generated in the piezoelectric film; a ground electrode disposed on a second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated in the detection electrode from the charge detected by the detection electrode; a processing unit that processes the signal output by the detection unit, The processing unit On the first main surface of the piezoelectric film, information on a region of interest is held, the region of interest being determined based on a line forming a boundary along which the polarity of the voltage of the detection electrode changes depending on a pressing position; storing information of a detection electrode selected from the detection electrodes and associated with the region of interest; maintaining an ideal array storing values ​​characteristic of the polarity of the voltage of a detection electrode associated with the region of interest when a position within the region of interest is pressed; generating a target array storing values ​​corresponding to voltages of detection electrodes associated with the target region; a pressure position estimation program that causes estimation of a pressure position by calculating a zero-mean normalized cross-correlation between the target sequence and the ideal sequence; [Explanation of symbols]

[0095] 1: Pressure position estimation system 11: Piezoelectric sensor 12: Detection unit 13: Processing section 15: Bottom plate 16: Elastic member 17: Piezoelectric film sensor 21: Piezoelectric film 22,23:Adhesive material 24, 35, 36, 41-44, 51-54, 61-65: Detection electrodes 25: Ground electrode 26, 27: Flexible substrate 31: Main surface 33: First main surface 34: Second main surface

Claims

1. a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film having output anisotropy; a plurality of detection electrodes disposed on a first main surface of the piezoelectric film to detect charges generated in the piezoelectric film; a ground electrode disposed on a second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated in the detection electrode from the charge detected by the detection electrode; a processing unit that processes the signal output by the detection unit, The processing unit On the first main surface of the piezoelectric film, information of a region of interest is held, the region of interest being determined based on a line forming a boundary along which the polarity of the voltage of the detection electrode changes depending on a pressing position; storing information of a detection electrode selected from the detection electrodes and associated with the region of interest; maintaining an ideal array storing values ​​characteristic of the polarity of the voltage of a detection electrode associated with the region of interest when a position within the region of interest is pressed; generating a target array storing values ​​corresponding to voltages of detection electrodes associated with the target region; A pressure position estimation system that estimates a pressure position by calculating a zero-mean normalized cross-correlation between the target array and the ideal array.

2. 2. The pressure position estimation system according to claim 1, wherein the region of interest is defined by two first lines that form the boundary and are adjacent to each other, and two second lines that form the boundary, are perpendicular to the first lines, and are adjacent to each other.

3. The pressure position estimation system according to claim 1 , wherein the detection electrodes have a rectangular or regular hexagonal shape in a plan view of the first main surface of the piezoelectric film, and are aligned on the first main surface of the piezoelectric film.

4. The pressure position estimation system according to claim 1 or 2, wherein the region of interest is defined within an area surrounded by the boundary line and an edge of the piezoelectric film.

5. The bottom plate and a flat elastic member; the elastic member is disposed between the bottom plate and the piezoelectric film; The pressure position estimation system according to claim 1 , wherein when the elastic member is pressed, a thickness of the elastic member at the pressed position changes.

6. a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film having output anisotropy; a plurality of detection electrodes disposed on a first main surface of the piezoelectric film to detect charges generated in the piezoelectric film; a ground electrode disposed on a second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated in the detection electrode from the charge detected by the detection electrode; a processing unit that processes a signal output by the detection unit, The processing unit On the first main surface of the piezoelectric film, information of a region of interest is held, the region of interest being determined based on a line forming a boundary along which the polarity of the voltage of the detection electrode changes depending on a pressing position; storing information of a detection electrode selected from the detection electrodes and associated with the region of interest; maintaining an ideal array storing values ​​characteristic of the polarity of the voltage of a detection electrode associated with the region of interest when a position within the region of interest is pressed; generating a target array storing values ​​corresponding to voltages of detection electrodes associated with the target region; A pressure position estimation method for estimating a pressure position by calculating a zero-mean normalized cross-correlation between the target array and the ideal array.

7. a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film having output anisotropy; a plurality of detection electrodes disposed on a first main surface of the piezoelectric film to detect charges generated in the piezoelectric film; a ground electrode disposed on a second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated in the detection electrode from the charge detected by the detection electrode; a processing unit that processes the signal output by the detection unit, The processing unit On the first main surface of the piezoelectric film, information of a region of interest is held, the region of interest being determined based on a line forming a boundary along which the polarity of the voltage of the detection electrode changes depending on a pressing position; storing information of a detection electrode selected from the detection electrodes and associated with the region of interest; maintaining an ideal array storing values ​​characteristic of the polarity of the voltage of a detection electrode associated with the region of interest when a position within the region of interest is pressed; generating a target array storing values ​​corresponding to voltages of detection electrodes associated with the target region; a pressure position estimation program that causes estimation of a pressure position by calculating a zero-mean normalized cross-correlation between the target sequence and the ideal sequence;

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