Pressure sensor, pressing position estimation method, and pressing position estimation program

Abstract

This pressure sensor is provided with: a holding plate; a piezoelectric film that has a first main surface and a second main surface opposite to the first main surface, and that generates electric charge in response to torsional deformation of the holding plate; a plurality of detection electrodes that are disposed on the first main surface of the piezoelectric film to detect the electric charge generated in the piezoelectric film; a ground electrode disposed on the second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated at the detection electrode on the basis of the electric charge detected by the detection electrode; and a processing unit that processes the voltage signal detected by the detection unit. The processing unit estimates a pressing position on the holding plate by defining a determination target cell on the holding plate with respect to a position on the holding plate, and calculating, as a pressing feature quantity, a difference between: the sum of the voltage value of an upper-left detection electrode of the determination target cell and the voltage value of a lower-right detection electrode of the determination target cell; and the sum of the voltage value of a lower-left detection electrode of the determination target cell and the voltage value of an upper-right detection electrode of the determination target cell.

Description

Pressing force sensor, pressing position estimation method, and pressing position estimation program

[0001] The present invention relates to a technique for estimating a pressing position.

[0002] Patent Literature 1 discloses a user interface device that determines the position where a pressure is applied. This user interface device includes a contact position detection unit, a pressure detection unit, a pressure center position determination means, and a pressure position determination means. The contact position detection unit detects the contact position of a finger on the operation surface. The pressure detection unit detects the pressure applied by the finger in contact with the operation surface. The pressure center position determination means calculates one pressure center position where the pressure is estimated to have been applied based on multiple pressure values ​​output from the pressure detection unit. The pressure position determination means determines the contact position closest to the pressure center position among the contact positions detected by the contact position detection unit as the contact position where the pressure has been applied.

[0003] Patent No. 5833511

[0004] The user interface device disclosed in Patent Document 1 determines one pressing position from among multiple detected contact positions. That is, this user interface device is based on the premise that even when touch operations are performed simultaneously at multiple positions, pressing operations are performed at only one position.

[0005] However, there are cases where it is desired to perform an operation of pressing multiple positions simultaneously. In such a case, when multiple positions are pressed simultaneously, it is necessary to distinguish between the respective pressed positions.

[0006] An object of the present invention is to provide a technique that makes it possible to distinguish the pressed position.

[0007] The pressure sensor of the present invention comprises a holding plate, a piezoelectric film having a first main surface and a second main surface opposite the first main surface, the piezoelectric film generating an electric charge in response to torsional deformation of the holding plate, a plurality of detection electrodes arranged on the first main surface of the piezoelectric film and detecting the electric charges generated in the piezoelectric film, a ground electrode arranged on the second main surface of the piezoelectric film, a detection unit detecting a voltage signal generated in the detection electrodes from the electric charges detected by the detection electrodes, and a processing unit processing the voltage signal detected by the detection unit, wherein the processing unit determines a target cell on the holding plate with respect to a position on the holding plate, and estimates the target cell position on the holding plate by calculating the difference between the sum of the voltage value of the detection electrode at the top left of the target cell and the voltage value of the detection electrode at the bottom right of the target cell and the sum of the voltage value of the detection electrode at the bottom left of the target cell and the voltage value of the detection electrode at the top right of the target cell as a feature of the indentation.

[0008] The indentation position estimation method of the present invention provides a pressure sensor comprising: a holding plate; a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film generating an electric charge in response to torsional deformation of the holding plate; a plurality of detection electrodes arranged on the first main surface of the piezoelectric film to detect the electric charges generated in the piezoelectric film; a ground electrode arranged on the second main surface of the piezoelectric film; a detection unit detecting a voltage signal generated in the detection electrodes from the electric charges detected by the detection electrodes; and a processing unit processing the voltage signal detected by the detection unit. The processing unit determines a target cell on the holding plate with respect to a position on the holding plate, and estimates the indentation position on the holding plate by calculating the difference between the sum of the voltage value of the detection electrode at the top left of the target cell and the voltage value of the detection electrode at the bottom right of the target cell and the sum of the voltage value of the detection electrode at the bottom left of the target cell and the voltage value of the detection electrode at the top right of the target cell as a feature of the indentation.

[0009] The indentation position estimation program of the present invention is mounted on a pressure sensor including: a holding plate; a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film generating an electric charge in response to torsional deformation of the holding plate; a plurality of detection electrodes arranged on the first main surface of the piezoelectric film to detect the electric charges generated in the piezoelectric film; a ground electrode arranged on the second main surface of the piezoelectric film; a detection unit detecting a voltage signal generated in the detection electrodes from the electric charges detected by the detection electrodes; and a processing unit processing the voltage signal detected by the detection unit. The indentation position estimation program causes the processing unit to determine a target cell on the holding plate relative to a position on the holding plate, and to estimate the target cell on the holding plate by calculating the difference between the sum of the voltage value of the detection electrode at the top left of the target cell and the voltage value of the detection electrode at the bottom right of the target cell and the sum of the voltage value of the detection electrode at the bottom left of the target cell and the voltage value of the detection electrode at the top right of the target cell as a feature of the indentation.

[0010] According to the present invention, it is possible to distinguish the pressed position.

[0011] FIG. 1 is a functional block diagram of the pressure sensor 1. FIG. 2 is a cross-sectional view of the piezoelectric sensor 11. FIG. 3 is a plan view showing an example of the arrangement of the detection electrodes 17. FIG. 4 is a conceptual diagram showing a first cell. FIG. 5 is a conceptual diagram showing an example of the voltage values ​​of the detection electrodes. FIG. 6 is a conceptual diagram showing another example of the voltage values ​​of the detection electrodes. FIG. 7 is a conceptual diagram showing a cell to be determined. FIG. 8 is a conceptual diagram showing a modified example of the cell to be determined. FIG. 9 is a conceptual diagram showing a second cell. FIG. 10 is a conceptual diagram showing an example of the voltage values ​​of the detection electrodes and a cell to be determined. FIG. 11 is a conceptual diagram showing the feature amount of a press when the voltage values ​​shown in FIG. 10 are applied. FIG. 12 is a conceptual diagram showing another example of the voltage values ​​of the detection electrodes and a cell to be determined. FIG. 13 is a conceptual diagram showing the feature amount of a press when the voltage values ​​shown in FIG. 12 are applied. FIG. 14(A) is a diagram showing an example of the detection result of the voltage values ​​of the detection electrodes when the press position is one point. FIG. 14(B) is a diagram showing the calculation result of the feature amount of a press when the voltage values ​​shown in FIG. 14(A) are applied. FIG. 14C is a diagram showing an example of the detection results of the voltage values ​​of the detection electrodes when there are two press positions. FIG. 14D is a diagram showing the calculation results of the press feature when the voltage values ​​shown in FIG. 14C are given. FIG. 15 is a conceptual diagram showing an example of the press feature. FIG. 16 is a conceptual diagram showing positions where press feature values ​​are compared with each other. FIG. 17A is a conceptual diagram showing an example of the voltage values ​​of the detection electrodes while an object is pressing at press position p. FIG. 17B is a conceptual diagram showing an example of the voltage values ​​of the detection electrodes while the object is being released at press position p. FIG. 18A is a conceptual diagram showing the press feature when the voltage values ​​shown in FIG. 17A are given. FIG. 18B is a conceptual diagram showing the press feature when the voltage values ​​shown in FIG. 17B are given. FIG. 19 is a conceptual diagram for explaining the weighted average of the press feature. FIG. 20 is a diagram showing changes in the press feature and average feature when the position is changed in the lateral direction. Fig. 21 is a functional block diagram of the pressure sensor 1a. Fig. 22 is a cross-sectional view of the piezoelectric sensor 11 and the touch sensor 31. Fig. 23 is a flowchart of the touch and press confirmation process of the processing unit. Fig. 24 is a functional block diagram of the pressure sensor 1b.

[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 sensor 1. FIG. 2 is a cross-sectional view of a piezoelectric sensor 11. The pressure sensor 1 includes a piezoelectric sensor 11, a detection unit 12, and a processing unit 13. The piezoelectric sensor 11 includes a holding plate 15, a piezoelectric film 16, multiple detection electrodes 17, and a ground electrode 18. The holding plate 15 is formed of a flexible flat plate such as a glass plate. The piezoelectric film 16 has a first main surface 21 and a second main surface 22 opposite the first main surface 21. An electric charge is generated in response to torsional deformation of the holding plate 15. The piezoelectric film 16 is formed, for example, from uniaxially stretched poly-L-lactic acid (PLLA). The detection electrode 17 is disposed on the first main surface 21 of the piezoelectric film 16 and detects the electric charge generated in the piezoelectric film 16. The ground electrode 18 is disposed on the second main surface 22 of the piezoelectric film 16. The detection unit 12 detects a voltage signal generated in the detection electrode 17 from the electric charge detected by the detection electrode 17. The detection unit 12 has, for example, a charge amplifier circuit, an amplification circuit, and an A / D conversion circuit. The processing unit 13 processes the voltage signal detected by the detection unit 12. The processing unit 13 is composed of a CPU, memory, etc., and stores a program, and processes the voltage signal by executing the program.

[0014] As described below, the processing unit 13 determines the cell to be evaluated on the holding plate 15 relative to its position on the holding plate 15, and estimates the indentation position on the holding plate 15 by calculating the difference between the sum of the voltage value of the detection electrode 17 at the top left of the cell to be evaluated and the voltage value of the detection electrode 17 at the bottom right of the cell to be evaluated and the sum of the voltage value of the detection electrode 17 at the bottom left of the cell to be evaluated and the voltage value of the detection electrode 17 at the top right of the cell to be evaluated as a feature of the indentation.

[0015] In this specification, a predetermined direction parallel to the main surface of the holding plate 15 according to the distribution of polarization charges in the piezoelectric film 16 is defined as the horizontal direction or x-axis direction. A direction parallel to the main surface of the holding plate 15 and perpendicular to the horizontal direction is defined as the vertical direction or y-axis direction. A direction perpendicular to the main surface of the holding plate 15 is defined as the z-axis direction. One side of the horizontal direction is defined as the right direction or +x-axis direction, and the other side of the horizontal direction is defined as the left direction or -x-axis direction. One side of the vertical direction is defined as the upward direction or +y-axis direction, and the other side of the vertical direction is defined as the downward direction or -y-axis direction.

[0016] 3 is a plan view showing an example of the arrangement of the detection electrodes 17. The detection electrodes 17 are arranged in the vertical and horizontal directions on the piezoelectric film 16.

[0017] 4 is a conceptual diagram showing a first cell. The first cell is defined on the main surface of the holding plate and corresponds to the area occupied by one detection electrode on the main surface of the holding plate when viewed from above. The voltage value of the detection electrode, i.e., the voltage value between the detection electrode and the ground electrode, is determined for each first cell.

[0018] The position of the first cell is represented as (i, j), where i = 1, ..., M, j = 1, ..., M. Here, i represents the horizontal position of the first cell, j represents the vertical position of the first cell, M represents the number of first cells arranged horizontally, and N represents the number of first cells arranged vertically. The first cell at position (i, j) is represented as c1(i, j). The voltage value of the detection electrode at position (i, j), i.e., the voltage value of the detection electrode of first cell c1(i, j), is represented as v(i, j). The first cell at position (i, j) corresponds to the i-th first cell counting from the left and the j-th first cell counting from the bottom.

[0019] Fig. 5 is a conceptual diagram showing an example of the voltage values ​​of each detection electrode. Fig. 6 is a conceptual diagram showing another example of the voltage values ​​of each detection electrode. In the diagrams showing the voltage values ​​of the detection electrodes such as Fig. 5 and Fig. 6, the symbol "+" indicates that the voltage value is a positive value. The symbol "-" indicates that the voltage value is a negative value. The symbol "0" indicates that the voltage value is 0.

[0020] As shown in Figure 5, when the pressing position p is at the intersection of the boundaries of the first cell, the voltage value in the upper left region of the pressing position p and the voltage value in the lower right region of the pressing position p have the same positive and negative signs. The voltage value in the lower left region of the pressing position p and the voltage value in the upper right region of the pressing position p have the same positive and negative signs. The voltage value in the upper left region of the pressing position p and the voltage value in the lower left region of the pressing position p have opposite positive and negative signs. In Figure 5, the voltage values ​​in the upper left and lower right regions of the pressing position p are negative, and the voltage values ​​in the lower left and upper right regions of the pressing position p are positive.

[0021] As shown in Figure 6, when the pressed position p is off the intersection of the boundary lines of the first cell, the voltage value of the first cell that overlaps with the line extending vertically and horizontally through the pressed position p is 0. The voltage values ​​in other areas are the same as when the pressed position is at the intersection of the cell boundary lines. In Figure 6, the pressed position p is at the center of the first cell, and the voltage values ​​of the first cells that are vertically and horizontally from the pressed position p are 0.

[0022] Such a distribution of voltage values ​​of the detection electrodes appears because the piezoelectric film generates electric charges in response to the torsional deformation of the holding plate.

[0023] FIG. 7 is a conceptual diagram showing a cell to be judged. The processing unit determines the cell to be judged on the holding plate. The cell to be judged is composed of 2 x 2 first cells, i.e., two vertical columns and two horizontal columns of first cells. As with the first cells, the position of the cell to be judged is expressed as (i, j). For the cell to be judged, i = 1, ..., M-1, j = 1, ..., N-1. Here, i represents the horizontal position of the cell to be judged, and j represents the vertical position of the cell to be judged. The cell to be judged at position (i, j) is expressed as e(i, j). The cell to be judged e(i, j) is composed of first cells c1(i, j), c1(i+1, j), c1(i, j+1), and c1(i+1, j+1).

[0024] The processor calculates the indentation feature for each target cell by subtracting the sum of the voltage values ​​of the lower left cell and the upper right cell from the sum of the voltage values ​​of the first upper left cell and the lower right cell. The processor calculates the indentation feature for each target cell as the value at the center position of the target cell.

[0025] In other words, for the target cell e(i, j), i = 1, ..., M-1, j = 1, ..., N-1, the processing unit calculates the indentation feature f(i, j) as the value of the center position q of the target cell e(i, j) using the following equation:

[0026]

[0027] In a modified example, the processor may calculate the pushing feature as the sum of the voltage value of the bottom left cell and the voltage value of the top right cell minus the sum of the voltage value of the first top left cell and the voltage value of the bottom right cell. Alternatively, the processor may calculate the pushing feature as a value at another position within the target cell.

[0028] In yet another modification, the target cell may be composed of a plurality of first cells instead of the 2x2 first cells. Preferably, the target cell is formed into a substantially square or rectangular shape by combining the plurality of first cells. The target cell may be preset or changed in real time depending on the shape or dimensions of the object being pressed.

[0029] 8 is a conceptual diagram showing a modified example of the target cell. In this modified example, the processing unit determines a target cell consisting of 3 × 3 first cells, and calculates the indentation feature f(i, j) for the target cell e(i, j) using the following equation:

[0030]

[0031] As described in the previous paragraph, the indentation feature is calculated based on the voltage values ​​of the four first cells, regardless of the number of first cells included in the target cell. More specifically, if the target cell has a square or rectangular shape, the four first cells are the rightmost and topmost first cell, the rightmost and bottommost first cell, the leftmost and topmost first cell, and the leftmost and bottommost first cell among the multiple first cells included in the target cell. Intuitively, the four first cells can be said to correspond to the first cells located at the four corners of the target cell. Note that if the indentation position is at the intersection of the boundaries of the first cells, when the indentation position is inside the target cell, the voltage values ​​of the rightmost and topmost first cell and the leftmost and bottommost first cell have the same positive or negative sign.

[0032] 9 is a conceptual diagram showing a second cell. The second cell is defined on the main surface of the holding plate, has its center at the center position q of the target cell, and has the same dimensions as the first cell. The indentation feature is determined for each second cell.

[0033] As with the first cell, the position of the second cell is also represented as (i, j). For the second cell, i = 1, ..., M-1, j = 1, ..., N-1. Here, i represents the horizontal position of the second cell, and j represents the vertical position of the second cell. The second cell at position (i, j) is represented as c2(i, j). The feature at position (i, j), i.e., the feature of the second cell c2(i, j), i.e., the feature of the center position q of the second cell c2(i, j), corresponds to f(i, j).

[0034] Fig. 10 is a conceptual diagram showing an example of voltage values ​​of each detection electrode and a target cell. Fig. 11 is a conceptual diagram showing a feature amount of indentation when the voltage values ​​shown in Fig. 10 are applied. Fig. 12 is a conceptual diagram showing another example of voltage values ​​of each detection electrode and a target cell. Fig. 13 is a conceptual diagram showing a feature amount of indentation when the voltage values ​​shown in Fig. 12 are applied.

[0035] In the diagrams showing the indentation feature quantities such as those in FIGS. 11 and 13, the symbol "+" indicates that the indentation feature quantity is a positive value, the symbol "-" indicates that the indentation feature quantity is a negative value, and the symbol "≈0" indicates that the indentation feature quantity is approximately 0.

[0036] The feature quantities of the second cells c21, c22, and c23 shown in Fig. 11 correspond to the feature quantities calculated for the target cells e1, e2, and e3 shown in Fig. 10. The feature quantities of the second cells c21, c22, and c23 shown in Fig. 13 correspond to the feature quantities calculated for the target cells e1, e2, and e3 shown in Fig. 12.

[0037] When the push position is outside the target cell, as in the positional relationship between the push position p and the target cells e1 and e2 shown in Figures 10 and 12, the feature quantity calculated for the target cell is approximately 0, as in the feature quantities of the second cells c21 and c22 shown in Figures 11 and 13. On the other hand, when the push position is inside the target cell, as in the positional relationship between the push position p and the target cell e3 shown in Figures 10 and 12, the feature quantity calculated for the target cell is a significant value, as in the feature quantity of the second cell c23 shown in Figures 11 and 13. Furthermore, when the push position is on the boundary between the inside and outside of the target cell, the feature quantity calculated for the target cell is approximately 0.

[0038] Fig. 14(A) is a diagram showing an example of the detection result of the voltage value of the detection electrode when there is one press-in position. Fig. 14(B) is a diagram showing the calculation result of the press-in feature amount when the voltage value shown in Fig. 14(A) is given. Fig. 14(C) is a diagram showing an example of the detection result of the voltage value of the detection electrode when there are two press-in positions. Fig. 14(D) is a diagram showing the calculation result of the press-in feature amount when the voltage value shown in Fig. 14(C) is given. The voltage value of the detection electrode varies over a wide range around the press-in position p, but the press-in feature amount changes significantly only near the press-in position p.

[0039] FIG. 15 is a conceptual diagram showing an example of a feature of a depression. In FIG. 15, the symbol "--" represents a negative value with a larger absolute value than the symbol "-". The processing unit estimates the depression position from the feature of the depression, for example, as follows: First, connected regions having absolute values ​​of the feature equal to or greater than a predetermined threshold are found. Next, the center position of the second cell having the largest absolute value of the feature within each of the found regions is estimated to be the depression position. In the example shown in FIG. 15, the center position q1 of the second cell within region a1 and the center position q2 of the second cell within region a2 are estimated to be the depression positions.

[0040] The processing unit may estimate the pressing position from the pressing feature amount using another method, as will be exemplified in a modified example described later.

[0041] According to this embodiment, the processing unit calculates the characteristic amount of the press from the voltage value of the detection electrode. The characteristic amount of the press reacts strongly only to the press position near the press position. This makes it possible to identify the press position, which was difficult when using the voltage data output from the piezoelectric sensor as is.

[0042] [Variation 1] The pressure sensor of this variation differs from pressure sensor 1 in the following respect: If the absolute value of the feature amount of the press at the first position is greater than the absolute value of the feature amount of the press at a second position surrounding the first position, the processing unit determines whether the object is being pressed at the first position or the object is being removed from the first position, depending on the positive or negative sign of the feature amount of the press at the first position.

[0043] 16 is a conceptual diagram showing positions at which the feature quantities of the pressing are compared. If the feature quantity of the center position q1 of the second cell is a positive value and the absolute value of the feature quantity of the center position q1 is greater than the absolute value of the feature quantity of the center position q2 of the second cell located above, below, to the left, to the right, or diagonally from the center position q1, the processing unit determines that the object is being pressed at the center position q1. On the other hand, if the feature quantity of the center position q1 is a negative value and the absolute value of the feature quantity of the center position q1 is greater than the absolute values ​​of the feature quantities of the center positions q2 located above, below, to the left, to the right, or diagonally from the center position q1, the processing unit determines that the object is being removed from the center position q1.

[0044] In other words, when f(i,j)>0, |f(i,j)|>|f(i+k,j+l)| for the position (i,j), the processing unit determines that the object is being pushed into the center position q1 of the second cell c(i,j). On the other hand, when f(i,j)<0, |f(i,j)|>|f(i+k,j+l)| for the position (i,j), the processing unit determines that the object is being removed from the center position q1 of the second cell c(i,j). Here, k=-1, 0, 1, and when k=-1, 1, l=-1, 0, 1, and when k=0, l=-1, 1.

[0045] In a modified example, the range of the second positions compared with the first position may be wider than the range consisting of positions adjacent to the first position. Also, the processing unit may calculate the indentation feature as a value of another position within the target cell, and set the first position and the second position to the other position.

[0046] In yet another variation, the pressure sensor may be designed so that the detection unit detects a voltage value whose positive and negative values ​​are opposite to each other with respect to pressing. In this case, the processing unit may determine that pressing is in progress when the feature value of the pressing position is a negative value, and that releasing is in progress when the feature value of the pressing position is a positive value.

[0047] The processing unit may execute the method described with reference to Fig. 16 for the pressed position estimated by the method described with reference to Fig. 15. Alternatively, the processing unit may execute the method described with reference to Fig. 16 for the center position of each second cell without executing the method described with reference to Fig. 15.

[0048] Fig. 17(A) is a conceptual diagram showing an example of voltage values ​​of the detection electrodes while an object is being pressed at a pressing position p. Fig. 17(B) is a conceptual diagram showing an example of voltage values ​​of the detection electrodes while the object is being released at a pressing position p. Fig. 18(A) is a conceptual diagram showing a feature amount of a pressing when the voltage value shown in Fig. 17(A) is applied. Fig. 18(B) is a conceptual diagram showing a feature amount of a pressing when the voltage value shown in Fig. 17(B) is applied.

[0049] In the examples shown in Figures 17(A) and 18(A), the feature amount of the press reaches a positive peak at the press position p. Therefore, the processing unit determines that the object is being pressed at the press position p. In the examples shown in Figures 17(B) and 18(B), the feature amount of the press reaches a negative peak at the position p. Therefore, the processing unit determines that the object is being released from the press position p.

[0050] According to this modification, it is possible to determine whether the button is pressed and released, in addition to distinguishing the pressed position.

[0051] [Variation 2] The pressure sensor of this variation differs from pressure sensor 1 in the following respect: If the absolute value of the press feature amount at the first position is greater than the absolute value of the press feature amount at a second position surrounding the first position, the processing unit calculates a weighted average of the press feature amounts in a range including the first position.

[0052] More specifically, if the absolute value of the feature quantity at the first center position of the second cell is greater than the absolute value of the feature quantities at the second center positions of the second cells located above, below, to the left, right, or diagonally from the first center position, the processing unit calculates a weighted average of the feature quantities within a predetermined range centered on the first center position as an average feature quantity. The average feature quantity is determined for successive positions on the main surface of the holding plate and has a significant value at the indentation position. The weight is experimentally determined so that the peak position of the average feature quantity approaches the indentation position. The processing unit estimates the peak position of the average feature quantity as the indentation position.

[0053] 19 is a conceptual diagram for explaining the weighted average of the indentation feature amount. More specifically, the processing unit calculates the average feature amount g(x, y) of the position (x, y) at each position (x, y) within a predetermined range a whose center position is the center position q of the second cell where the feature amount reaches its peak, using the following equation:

[0054]

[0055] Here, x represents the horizontal position on the holding plate and is a real value. y represents the vertical position on the holding plate and is a real value. The weight ω(x, y, i, j) is, for example, a function that decreases as the distance d(x, y, i, j) between the position (x, y) and the center position of the second cell c2(i, j) increases. The weight ω(x, y, i, j) is, for example, a Gaussian function of the distance d(x, y, i, j).

[0056] In a modified example, the range of the second positions compared with the first position may be wider than the range consisting of positions adjacent to the first position. Also, the processing unit may calculate the indentation feature as a value of another position within the target cell, and set the first position and the second position to the other position.

[0057] In yet another modification, the center position of the range in which the average feature amount is calculated may be shifted from the position where the feature amount peaks.

[0058] The processing unit checks whether the feature amount reaches a peak at the center position of each second cell, and if so, calculates the average feature amount.

[0059] Fig. 20 shows the changes in the indentation feature amount and average feature amount when the position is changed in the lateral direction. As shown in Fig. 20, the indentation feature amount is determined for discrete positions on the main surface of the holding plate. On the other hand, the average indentation feature amount is determined for continuous positions on the main surface of the holding plate.

[0060] According to this modification, the processing unit calculates an average indentation feature value from the indentation feature values. The average indentation feature value is determined for successive positions on the main surface of the holding plate and responds strongly to indentations at the indentation positions. This improves the resolution of the indentation position, enabling the indentation position to be estimated with higher accuracy.

[0061] [Modification 3] Fig. 21 is a functional block diagram of a pressure sensor 1a. Fig. 22 is a cross-sectional view of a piezoelectric sensor 11 and a touch sensor 31. The pressure sensor 1a differs from the pressure sensor 1 in the following respects. That is, the pressure sensor 1a includes a holding plate 15 that is configured as a touch sensor 31.

[0062] The pressure sensor 1 a detects not only a pressure on the main surface of the holding plate 15 but also a touch on the main surface of the holding plate 15 .

[0063] The detection unit 12 detects signals from the piezoelectric sensor 11 and the touch sensor 31. The processing unit 13 estimates the pressing position from the data of the piezoelectric sensor 11, and estimates the touch position from the data of the touch sensor 31. If the estimated touch position is near the estimated pressing position, the processing unit 13 determines that the estimated touch position and pressing position are valid. On the other hand, if the estimated touch position is not near the estimated pressing position, the processing unit 13 determines that neither a touch nor a pressing has occurred.

[0064] 23 is a flowchart of the touch and press confirmation process performed by the processor. First, the processor acquires data from the touch sensor to estimate the touch position (s1). Next, it acquires data from the piezoelectric sensor, i.e., the voltage signal of the detection electrode, to estimate the press position (s2).

[0065] In a variant, the processing unit may perform step s2 before step s1.

[0066] If the estimated touch position is near the estimated pressing position, for example, if the distance between the estimated touch position and the estimated pressing position is less than a predetermined threshold (s3: Yes), it is determined that the touch and pressing are valid, and a predetermined process is performed (s4). If the estimated touch position is not near the estimated pressing position, for example, if the distance between the estimated touch position and the estimated pressing position is equal to or greater than a predetermined threshold (s3: No), it is determined that neither a touch nor a pressing has occurred, and a predetermined process is performed or no process is performed (s5). The processing unit repeats steps s1 to s5 at regular intervals.

[0067] If the processing unit cannot detect the touch position, it determines that neither a touch nor a press has occurred. If the processing unit detects the touch position but cannot detect the press position, it determines that a touch has occurred but no press has occurred.

[0068] If the processing unit determines that the pressing is valid, it ultimately estimates the estimated touch position, which is in the vicinity of the pressing position estimated from the data of the piezoelectric sensor, as the pressing position.

[0069] According to this modification, if the touch position estimated from the touch sensor data is not near the pressing position estimated from the piezoelectric sensor data, the processing unit determines that neither a touch nor a pressing has occurred. This reduces false detection of a pressing. Furthermore, this reduces malfunctions in electronic devices that include a pressure sensor and use pressure sensor data, such as when the electronic device responds even when there is no pressing.

[0070] In general, the accuracy of estimating a touch position from touch sensor data is higher than the accuracy of estimating a pressing position from piezoelectric sensor data. According to this modification, the processing unit ultimately estimates an estimated touch position near the pressing position estimated from the piezoelectric sensor data as the pressing position. That is, the processing unit corrects the estimated pressing position with a touch position corresponding to the pressing position. This improves the accuracy of estimating the pressing position.

[0071] [Variation 4] Fig. 24 is a functional block diagram of pressure sensor 1b. Pressure sensor 1b differs from pressure sensor 1a in the following respects. That is, pressure sensor 1b further includes a determination unit 32. The determination unit 32 determines whether touch sensor 31 is operating using known technology. If the determination unit 32 determines that touch sensor 31 is operating, it outputs a signal from touch sensor 31 to detection unit 12. On the other hand, if the determination unit 32 determines that touch sensor 31 is not operating, it outputs a signal indicating that touch sensor 31 is not operating to detection unit 12.

[0072] When the touch sensor 31 is operating, the processing unit 13 performs the same touch and press estimation process as in the case of the pressure sensor 1a. On the other hand, when the touch sensor 31 is not operating, the processing unit 13 estimates the touch position and press position using data from the piezoelectric sensor 11. The processing unit 13 may determine whether a touch or a press has occurred based on, for example, the absolute value of the press feature amount.

[0073] For example, capacitive touch sensors do not work well when used with gloved fingers, underwater, or at construction sites where moisture, dust, or other foreign matter is attached to the input surface.

[0074] According to this modification, when the touch sensor is not operating, the processing unit estimates the touch position using data from the piezoelectric sensor. Therefore, touch detection is possible even in an environment where the touch sensor is not operating. Furthermore, therefore, in an electronic device that includes a pressure sensor and uses data from the pressure sensor, the electronic device can be used even in an environment where the touch sensor is not operating.

[0075] [Other Embodiments] The pressure sensor may be used in electronic devices that detect multiple input positions and provide feedback to a user, such as smartphones, software keyboards, wearable devices, and medical devices. Such medical devices may take the form of shoe insoles or be attached directly to the soles of a user's feet to detect the user's gait, i.e., weight shift while walking. Such medical devices may also be attached directly to bending parts of the human body, such as the knee, elbow, or wrist, to detect human body movement.

[0076] The pressure sensor can deform according to the shape of the object to be attached, which allows the electronic device to be independent of the shape of the object to be attached, and such an electronic device may be attached to a cylinder, a human body, or an object of other shapes.

[0077] The configurations shown in the above embodiments may be replaced or combined as appropriate.

[0078] 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.

[0079] The present invention has the following configuration.

[0080] a ground electrode disposed on the second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated in the detection electrodes from the charge detected by the detection electrodes; and a processing unit that processes the voltage signal detected by the detection unit, wherein the processing unit determines a target cell on the holding plate with respect to a position on the holding plate, and estimates the target position on the holding plate by calculating, as a feature of the indentation, the difference between the sum of the voltage value of the detection electrode at the top left of the target cell and the voltage value of the detection electrode at the bottom right of the target cell and the voltage value of the detection electrode at the bottom left of the target cell and the voltage value of the detection electrode at the top right of the target cell.

[0081] (2) The pressure sensor according to (1), wherein, when an absolute value of a feature of a press at a first position is greater than an absolute value of a feature of a press at a second position surrounding the first position, the processing unit determines whether an object is being pressed at the first position or an object is being removed from the first position, depending on a positive or negative sign of the feature of the press at the first position.

[0082] (3) The pressure sensor according to (1) or (2), wherein the processing unit calculates a weighted average of the indentation feature amounts in a range including the first position when an absolute value of the indentation feature amount at a first position is greater than an absolute value of the indentation feature amount at a second position around the first position.

[0083] (4) A pressure sensor according to any one of (1) to (3), wherein the holding plate is composed of a touch sensor, the processing unit estimates a touch position from data of the touch sensor, the processing unit determines that the estimated touch position and pressing position are valid if the estimated touch position is in the vicinity of the estimated pressing position, and the processing unit determines that neither a touch nor a pressing has occurred if the estimated touch position is not in the vicinity of the estimated pressing position.

[0084] (5) The pressure sensor according to (4), further comprising a determination unit that determines whether the touch sensor is operating.

[0085] (6) A method for estimating a pressing position comprising: a holding plate; a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film generating an electric charge in response to torsional deformation of the holding plate; a plurality of detection electrodes disposed on the first main surface of the piezoelectric film and detecting the electric charges generated in the piezoelectric film; a ground electrode disposed on the second main surface of the piezoelectric film; a detection unit that detects a voltage signal generated in the detection electrodes from the electric charges detected by the detection electrodes; and a processing unit that processes the voltage signal detected by the detection unit, wherein the processing unit determines a target cell on the holding plate with respect to a position on the holding plate, and estimates the pressing position on the holding plate by calculating, as a feature of pressing, the difference between the sum of the voltage value of the detection electrode at the top left of the target cell and the voltage value of the detection electrode at the bottom right of the target cell and the sum of the voltage value of the detection electrode at the bottom left of the target cell and the voltage value of the detection electrode at the top right of the target cell.

[0086] (7) A press position estimation program mounted on a pressure sensor including: a holding plate; a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film generating electric charges in response to torsional deformation of the holding plate; a plurality of detection electrodes disposed on the first main surface of the piezoelectric film and detecting electric charges generated on 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 electric charges detected by the detection electrodes; and a processing unit that processes the voltage signals detected by the detection unit, the program causing the processing unit to determine a target cell on the holding plate with respect to a position on the holding plate, and to estimate a press position on the holding plate by calculating, as a feature of press position, the difference between the sum of a voltage value of the detection electrode at the top left of the target cell and the voltage value of the detection electrode at the bottom right of the target cell and the sum of the voltage value of the detection electrode at the bottom left of the target cell and the voltage value of the detection electrode at the top right of the target cell.

[0087] 1, 1a, 1b: pressure sensor 11: piezoelectric sensor 12: detection unit 13: processing unit 15: holding plate 16: piezoelectric film 17: detection electrode 18: ground electrode 21: first main surface 22: second main surface 31: touch sensor 32: determination unit

Claims

1. A pressing sensor comprising: a holding plate; a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film generating an electric charge in response to torsional deformation of the holding plate; a plurality of detection electrodes disposed on the first main surface of the piezoelectric film for detecting the electric charge generated in the piezoelectric film; a ground electrode disposed on the second main surface of the piezoelectric film; a detection unit for detecting a voltage signal generated in the detection electrodes from the electric charge detected by the detection electrodes; and a processing unit for processing the voltage signal detected by the detection unit, wherein the processing unit determines a cell to be determined on the holding plate with respect to a position on the holding plate, and calculates, as a feature amount of pressing, a difference between the sum of the voltage value of the detection electrode at the upper left of the cell to be determined and the voltage value of the detection electrode at the lower right of the cell to be determined and the sum of the voltage value of the detection electrode at the lower left of the cell to be determined and the voltage value of the detection electrode at the upper right of the cell to be determined, thereby estimating the pressing position on the holding plate.

2. The pressing sensor according to claim 1, wherein when the absolute value of the feature amount of pressing at the first position is greater than the absolute value of the feature amount of pressing at a second position around the first position, the processing unit determines, according to the positive or negative sign of the feature amount of pressing at the first position, whether the object is being pressed at the first position or the object is being released from the first position.

3. The pressing sensor according to claim 1 or 2, wherein when the absolute value of the feature amount of pressing at the first position is greater than the absolute value of the feature amount of pressing at a second position around the first position, the processing unit calculates a weighted average of the feature amounts of pressing in a range including the first position.

4. The holding plate is constituted by a touch sensor, the processing unit estimates a touch position from the data of the touch sensor, the processing unit determines that the estimated touch position and the pressing position are valid when the estimated touch position is in the vicinity of the estimated pressing position, and the processing unit determines that neither a touch nor a pressing is being performed when the estimated touch position is not in the vicinity of the estimated pressing position. The pressing sensor according to any one of claims 1 to 3.

5. The pressing sensor according to claim 4, further comprising a determination unit for determining whether the touch sensor is operating.

6. A pressing position estimation method for a pressing sensor including a holding plate, a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film generating electric charges in response to torsional deformation of the holding plate, a plurality of detection electrodes disposed on the first main surface of the piezoelectric film for detecting the electric charges generated in the piezoelectric film, a ground electrode disposed on the second main surface of the piezoelectric film, a detection unit for detecting a voltage signal generated in the detection electrodes from the electric charges detected by the detection electrodes, and a processing unit for processing the voltage signal detected by the detection unit. The processing unit determines a determination target cell on the holding plate with respect to a position on the holding plate, and calculates, as a feature amount of pushing, a difference between the sum of the voltage value of the detection electrode at the upper left of the determination target cell and the voltage value of the detection electrode at the lower right of the determination target cell and the sum of the voltage value of the detection electrode at the lower left of the determination target cell and the voltage value of the detection electrode at the upper right of the determination target cell, thereby estimating the pushing position on the holding plate.

7. A pushing position estimation program for causing a processing unit of a pressing sensor including a holding plate, a piezoelectric film having a first main surface and a second main surface opposite to the first main surface, the piezoelectric film generating electric charges in response to torsional deformation of the holding plate, a plurality of detection electrodes disposed on the first main surface of the piezoelectric film for detecting the electric charges generated in the piezoelectric film, a ground electrode disposed on the second main surface of the piezoelectric film, a detection unit for detecting a voltage signal generated in the detection electrodes from the electric charges detected by the detection electrodes, and a processing unit for processing the voltage signal detected by the detection unit, to execute, with respect to a position on the holding plate, determining a determination target cell on the holding plate, and calculating, as a feature amount of pushing, a difference between the sum of the voltage value of the detection electrode at the upper left of the determination target cell and the voltage value of the detection electrode at the lower right of the determination target cell and the sum of the voltage value of the detection electrode at the lower left of the determination target cell and the voltage value of the detection electrode at the upper right of the determination target cell, thereby estimating the pushing position on the holding plate.

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