Load analysis device and load analysis method

Abstract

A load analysis device and a load analysis method are provided that can analyze the characteristics of an applied load on a two-dimensional surface using a small number of cantilevers. [Solution] The load analysis device includes a sensor element having a first strain gauge 3L and a second strain gauge 3R attached to a fixed end Cf of a cantilever C, an elastic body that covers the sensor element and to which a load is applied, and a control unit that acquires a first response value corresponding to a change in resistance of the first strain gauge 3L and a second response value corresponding to a change in resistance of the second strain gauge 3R. The control unit calculates a composite response value obtained by combining the first response value multiplied by a first coefficient and the second response value multiplied by a second coefficient using multiple patterns each with a different combination of the first coefficient and the second coefficient, thereby changing the characteristics of the composite response value on a two-dimensional plane set based on the position of the cantilever C.

Description

[Technical Field]

[0001] The present invention relates to a load analysis device and a load analysis method. [Background technology]

[0002] Tactile sensors with tiny cantilevers fabricated by a MEMS (Micro Electro Mechanical Systems) process are known. For example, Patent Document 1 describes a tactile sensor that includes a sensor element including two cantilevers aligned in one axial direction and an elastic body that covers the sensor element. Patent Document 1 also describes a technology for identifying a load application position in one axial direction based on output values ​​corresponding to each of the two cantilevers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7265767 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology described in Patent Document 1 requires at least two cantilevers per axis to identify the load application position, so at least four cantilevers are required to analyze the load in two dimensions. It would be meaningful if the number of cantilevers could be further reduced for load analysis.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a load analysis device and a load analysis method that can analyze the two-dimensional characteristics of an applied load using a small number of cantilevers. [Means for solving the problem]

[0006] (1) In order to achieve the above object, a load analysis device according to a first aspect of the present invention comprises: a sensor element having a cantilever, in which a first strain gauge and a second strain gauge are provided side by side in the width direction of the cantilever at a fixed end of the cantilever; an elastic body that covers the sensor element and to which a load is applied; a control unit that acquires a first response value corresponding to a resistance change of the first strain gauge and a second response value corresponding to a resistance change of the second strain gauge, The control unit The characteristics of the composite response value on a two-dimensional plane set based on the position of the cantilever are changed by calculating a composite response value obtained by combining the first response value multiplied by a first coefficient and the second response value multiplied by a second coefficient in multiple patterns each having a different combination of the first coefficient and the second coefficient.

[0007] (2) In the load analysis device described in (1), The control unit may estimate the direction of the load on the two-dimensional surface or the load application position, which is the position of the load on the two-dimensional surface, based on the combined response value calculated for the multiple patterns.

[0008] (3) The load analysis device described in (2) above is a storage unit configured to store in advance sensitivity distribution information indicating a sensitivity distribution generated in a plurality of patterns, the sensitivity distribution being generated by applying an arbitrary load to each position of the elastic body corresponding to a plurality of coordinates set in advance on the two-dimensional plane, and combining the first response value multiplied by the first coefficient and the second response value multiplied by the second coefficient for each of the plurality of coordinates, The control unit may estimate the load application position based on the combined response value calculated for the plurality of patterns and the sensitivity distribution information.

[0009] (4) In the load analysis device described in (2) above, the sensor element has two cantilevers, a first cantilever and a second cantilever, spaced apart from each other; The control unit Calculating a first composite response value, which is the composite response value obtained based on the first response value and the second response value of the first cantilever, for the multiple patterns; Calculating a second composite response value, which is the composite response value obtained based on the first response value and the second response value of the second cantilever, for the multiple patterns; calculating a composite response ratio, which is a ratio between the first composite response value and the second composite response value, for each pattern having the same combination of the first coefficient and the second coefficient among the plurality of patterns; The load application position may be estimated based on the calculated composite response ratio.

[0010] (5) The load analysis device described in (4) above is a storage unit configured to store in advance position characteristic information indicating a relationship between the first response value and a force of each of the first cantilever and the second cantilever, and a relationship between the second response value and a force of each of the first cantilever and the second cantilever, at a plurality of coordinates preset on the two-dimensional plane; The control unit may estimate the load application position based on the calculated combined response ratio and the position characteristic information.

[0011] (6) In the load analysis device described in (5), The control unit may determine the load applied at the estimated load application position based on the estimated load application position and the position characteristic information.

[0012] (7) In the load analysis device according to any one of (1) to (6), The multiple patterns include: a pattern in which one of the first coefficient and the second coefficient is 0; a pattern in which both the first coefficient and the second coefficient are positive values; a pattern in which both the first coefficient and the second coefficient are negative values; The pattern may include a pattern in which one of the first coefficient and the second coefficient is a positive value and the other is a negative value.

[0013] (8) In order to achieve the above object, a load analysis method according to a second aspect of the present invention comprises: A load analysis method using a tactile sensor including a sensor element in which a first strain gauge and a second strain gauge are arranged side by side in the width direction of the cantilever at a fixed end of the cantilever, and an elastic body that covers the sensor element and to which a load is applied, acquiring a first response value corresponding to a resistance change of the first strain gauge and a second response value corresponding to a resistance change of the second strain gauge; and a step of calculating a composite response value obtained by combining the first response value multiplied by a first coefficient and the second response value multiplied by a second coefficient in a plurality of patterns each having a different combination of the first coefficient and the second coefficient, thereby changing the characteristics of the composite response value on a two-dimensional plane set based on the position of the cantilever. [Effects of the Invention]

[0014] According to the present invention, the characteristics of an applied load on a two-dimensional surface can be analyzed using a small number of cantilevers. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a configuration diagram of a load analysis device according to an embodiment of the present invention. [Figure 2] FIG. 3 is a schematic cross-sectional view of the elastic body and the vicinity of the cantilever of the sensor element according to the embodiment. [Figure 3] FIG. 2 is a plan view of the cantilever according to the embodiment. [Figure 4] FIG. 1 is a schematic diagram of an experimental system according to Example 1. [Figure 5] FIG. 2 is a diagram showing a two-dimensional plane set in the first embodiment. [Figure 6] 5A and 5B are diagrams according to Example 1, in which (a) shows the sensitivity distribution of a first strain gauge, and (b) shows the sensitivity distribution of a second strain gauge. [Figure 7] FIG. 3 is a diagram according to Example 1, showing a combined sensitivity distribution obtained by combining sensitivity distributions of a first strain gauge and a second strain gauge in a plurality of patterns. [Figure 8] FIG. 3 is a diagram showing estimated coordinates according to the first embodiment. [Figure 9] FIG. 10 is a diagram illustrating the first and second cantilevers according to the second embodiment. [Figure 10] FIG. 10 is a diagram for explaining a method for calculating a composite response ratio according to the second embodiment. [Figure 11] 10A and 10B are diagrams according to a second embodiment, in which FIG. 10A shows estimated coordinates, and FIG. 10B shows position characteristic information at the estimated coordinates. [Figure 12] 10A and 10B are diagrams according to a second embodiment, in which FIG. 10A shows estimated coordinates, and FIG. 10B shows position characteristic information at the estimated coordinates. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the present invention will be described with reference to the drawings.

[0017] As shown in FIG. 1, the load analysis device A includes a tactile sensor 100 and a control device 200.

[0018] (Tactile Sensor 100) The tactile sensor 100 includes a sensor element 10, an elastic body 20 that covers the sensor element 10 from above and to which a load is applied, and a circuit board 30.

[0019] The sensor element 10 is fabricated by a MEMS (Micro Electro Mechanical Systems) process and has a cantilever C (microcantilever) as shown in FIG. 2. As shown in FIG. 3, a pair of strain gauges consisting of a first strain gauge 3L and a second strain gauge 3R is provided at the fixed end Cf of the cantilever C. The first strain gauge 3L and the second strain gauge 3R are provided at a distance from each other in the width direction of the cantilever C. The fixed end Cf of the cantilever C may be a stress concentration portion of the cantilever C, and may be a certain range including the fixed end of the cantilever C (see the two-dot chain line in FIG. 2). In other words, the first strain gauge 3L and the second strain gauge 3R are provided side by side at the stress concentration portion of the cantilever C. The first strain gauge 3L and the second strain gauge 3R are formed by the strain gauge layer 3 shown in FIG. 2.

[0020] An example of a manufacturing method for the sensor element 10 will now be described with reference to FIG. 2. A wafer of SOI (Silicon on Insulator) 1 is used to manufacture the sensor element 10. The SOI 1 has a three-layer structure consisting of a support substrate 1a, a BOX layer 1b, and an active layer 1c. The support substrate 1a is made of Si. The BOX layer 1b is a buried oxide film between the support substrate 1a and the active layer 1c, and is made of SiO2. The active layer 1c is made of Si. As a preliminary step, the SOI 1 wafer is subjected to pre-film formation treatment, which involves ultrasonic cleaning with acetone and removing native oxide films using dilute hydrofluoric acid.

[0021] First, Si3N4 as the insulating layer 2 is deposited on an SOI wafer by LPCVD (Low-Pressure Chemical Vapor Deposition), NiCr as the strain gauge layer 3, and Au as the wiring layer 4 by sputtering, and then patterned by photolithography and etching. Next, Cr as the shape control layer 5 for tilting the cantilever C is deposited by electron beam evaporation and patterned by lift-off. Then, the cantilever C is formed using a method for creating a hollow structure by selective etching (hereinafter referred to as sacrificial layer etching), with the BOX layer 1b as a sacrificial layer. During the creation of this hollow structure, the cantilever C autonomously bends and tilts due to the tensile stress caused by the difference in the linear expansion coefficients of the shape control layer 5 and the active layer 1c. After sacrificial layer etching, the sensor element 10 is washed with pure water, and then ethanol substitution is performed to prevent the cantilever C from sticking to the support substrate 1a due to the surface normal force of the pure water. Thereafter, vacuum drying is performed to complete the sensor element 10 (sensor chip).

[0022] Here, the description has been given taking the portion of the sensor element 10 corresponding to one cantilever C as an example, but the manufacturing process of a sensor chip including multiple cantilevers C is similar. Furthermore, the manufacturing method and laminated structure of the sensor element 10 are not limited to the above example and are arbitrary as long as the first strain gauge 3L and the second strain gauge 3R can be created at the fixed end Cf of the cantilever C. For example, the shape control layer 5 may be formed on the active layer 1c in a region covering the entire outer shape of the cantilever C.

[0023] The elastic body 20 is made of an elastomer such as PDMS (Poly-dimethyl-siloxane). The elastic body 20 covers the sensor element 10 from above and seals the cantilever C. In a plan view, the elastic body 20 has a larger area than the sensor element 10. The upper surface of the elastic body 20 functions as an applied surface 21 to which a load is applied. The applied surface 21 is set, for example, parallel to the upper surface of the circuit board 30. When an object comes into contact with the applied surface 21, a load is applied to the tactile sensor 100, causing the cantilever C to bend. The tactile sensor 100 detects this bending of the cantilever C as a change in resistance (change in electrical resistance) of the first strain gauge 3L and the second strain gauge 3R.

[0024] The circuit board 30 is a PCB (Printed Circuit Board) on which a bridge circuit that converts the change in resistance of the cantilever C into an analog voltage and an output circuit that supplies a digital signal output value to the control device 200 are mounted. This output circuit includes, for example, an amplifier that amplifies the output voltage of the bridge circuit and an ADC (Analog to Digital Converter) that converts the output voltage of the amplifier into a digital signal output value. The circuit board 30 is electrically connected to each of the first strain gauge 3L and the second strain gauge 3R via the wiring layer 4. The circuit board 30 supplies to the control device 200 a first response value (hereinafter sometimes represented by the symbol L) corresponding to the change in electrical resistance of the first strain gauge 3L and a second response value (hereinafter sometimes represented by the symbol R) corresponding to the change in electrical resistance of the second strain gauge 3R.

[0025] The sensor element 10 manufactured as described above is adhered to the circuit board 30 using an epoxy adhesive, and the wiring layer 4 is electrically connected to the wiring formed on the circuit board 30. Then, PDMS is applied to the sensor element 10 using a spin coater to form the elastic body 20. In this manner, the tactile sensor 100 is manufactured. Note that the elastic body 20 is not limited to PDMS and may be made of any material, such as acrylic resin, epoxy resin, or silicone resin.

[0026] (Control device 200) The control device 200 analyzes the load applied to the tactile sensor 100 based on the first response value and the second response value acquired from the circuit board 30. The control device 200 is configured as a computer and has a memory unit 210 and a control unit 220. The memory unit 210 is configured from a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The ROM of the memory unit 210 stores an operating program for analyzing the load, and data such as sensitivity distribution information and position characteristic information, which will be described later. The control unit 220 is configured from a CPU (Central Processing Unit), etc., and executes the operating program stored in the memory unit 210 to analyze the load.

[0027] In the tactile sensor 100, when deformation occurs in the direction in which the cantilever C extends (the longitudinal direction in the example of FIG. 3 ), the resistances of the first strain gauge 3L and the second strain gauge 3R change in the same way (i.e., the first response value and the second response value change in the same way). On the other hand, when torsional deformation occurs in the cantilever C in the width direction of the cantilever C, the resistances of the first strain gauge 3L and the second strain gauge 3R change in opposite directions (i.e., the first response value and the second response value change in opposite directions). Using this phenomenon, the control device 200 analyzes the load applied to the tactile sensor 100 based on the first response value and the second response value acquired from the tactile sensor 100. Below, we will explain how the tactile sensor 100 and the control device 200 should be specifically configured, in conjunction with Examples 1 and 2, which are experiments conducted by the inventors of the present application.

[0028] Example 1 (Experiment to measure the spatial distribution characteristics of sensitivity) In this experiment, a tactile sensor 100 was used, which was fabricated by mounting a 5 mm x 5 mm square sensor element 10 on a circuit board 30 and then sealing the sensor element 10 with an elastic body 20 having an area larger than the sensor element 10. The length from the fixed end to the free end of the cantilever C in the sensor element 10 was 360 μm, and the width of the cantilever C was 260 μm.

[0029] Figure 4 shows a schematic diagram of the experimental system. In this experiment, a force (load) was applied to the tactile sensor 100 by vertically contacting an acrylic fixture with a 1 mm x 1 mm square contact surface with the applied surface 21 of the tactile sensor 100, which was fixed to a 3-axis motorized stage. The force applied to the tactile sensor 100 was measured as a reference using a 6-axis force sensor. The resistance change rate of the tactile sensor 100 was also measured using a digital multi-meter.

[0030] Figure 5 shows a two-dimensional plane set based on the position of cantilever C. As a two-dimensional plane, an XY plane (XY coordinate system) was set with the center of cantilever C as the origin, the Y axis pointing in the longitudinal direction of cantilever C, and the X axis pointing in the width direction of cantilever C. The unit of the coordinate system is μm, and the distance between adjacent coordinates in the X or Y direction is 500 μm.

[0031] In this experiment, we focused on the independent sensitivities of the first strain gauge 3L and the second strain gauge 3R and evaluated the spatial distribution characteristics of their sensitivities. Specifically, we evaluated the two-dimensional spatial distribution of sensitivity by applying a 1 N force to the tactile sensor 100 while moving the fixture in the X and Y directions in the range of -4000 to +4000 at 500 μm intervals. Figure 6(a) shows the two-dimensional spatial distribution of the first response value (L) corresponding to the first strain gauge 3L (hereinafter referred to as the sensitivity distribution of the first strain gauge 3L), and Figure 6(b) shows the two-dimensional spatial distribution of the second response value (R) corresponding to the second strain gauge 3R (hereinafter referred to as the sensitivity distribution of the second strain gauge 3R). It can be seen that the positive and negative sensitivities of the first strain gauge 3L and the second strain gauge 3R are diagonally inverted around the cantilever C. Moreover, the first strain gauge 3L and the second strain gauge 3R exhibit sensitivity distributions that are symmetrical like mirror images.

[0032] FIG. 7 shows a composite sensitivity distribution obtained by combining the sensitivity distribution of the first strain gauge 3L and the sensitivity distribution of the second strain gauge 3R using different coefficients at the same coordinates. The eight composite sensitivity distributions shown in FIG. 7 were obtained by calculating composite response values ​​obtained by combining the first response value multiplied by the first coefficient and the second response value multiplied by the second coefficient in multiple patterns (eight patterns in FIG. 7) each with a different combination of the first and second coefficients. Note that the eight composite sensitivity distributions shown in FIG. 7 have been normalized by the maximum composite response value in each distribution and scaled. Specifically, for the composite response value at each coordinate expressed as S = aL + bR, where a is the first coefficient, b is the second coefficient, and S is the composite response value, the eight combinations of the first and second coefficients and the composite response value are as follows:

[0033] Pattern 1: (a,b)=(1,1), S=L+R Pattern 2: (a,b)=(0.5,1), S=0.5L+R Pattern 3: (a,b)=(0,1), S=R Pattern 4: (a,b)=(-0.5,1), S=-0.5L+R Pattern 5: (a,b)=(-1,1), S=-L+R Pattern 6: (a, b) = (-1, 0.5), S = -L + 0.5R Pattern 7: (a,b)=(-1,0), S=-L Pattern 8: (a, b) = (-1, -0.5), S = -L-0.5R

[0034] In the eight patterns of composite sensitivity distribution shown in Fig. 7, solid circles are placed near the coordinates where the composite response value is maximum, and dashed circles are placed near the coordinates where the composite response value is minimum. Fig. 7 shows that it is possible to rotate the distribution by combining the sensitivity distribution of the first strain gauge 3L and the sensitivity distribution of the second strain gauge 3R with different coefficients.

[0035] (Experiment to estimate the load application position) (Experimental Method) Referring to Figure 7, it can be seen that the sensitivity distribution of the tactile sensor 100 can be controlled by combining the sensitivity distributions of the first strain gauge 3L and the second strain gauge 3R with different coefficients. Based on this, an experiment was conducted to predict a position from the sensor response when a load force was applied to an arbitrary position. The experimental procedure is as follows.

[0036] Step 1: In the experimental system shown in Figure 4, a force of 1 N is applied to a randomly selected position (hereinafter referred to as the applied coordinate), and the resistance changes of the first strain gauge 3L and the second strain gauge 3R are measured as the first response value and the second response value, respectively. Step 2: The composite response value obtained by combining the first response value multiplied by the first coefficient and the second response value multiplied by the second coefficient is calculated for multiple patterns (the aforementioned eight patterns) each with a different combination of the first and second coefficients. This changes the characteristics of the composite response value on a two-dimensional plane (XY plane) set based on the position of the cantilever C. Step 3: Eight patterns of composite sensitivity distributions shown in FIG. 7 are prepared in advance. Step 4: Within an error range of ±5%, the coordinates at which the eight patterns of composite response values ​​calculated in Step 2 match are obtained in the eight patterns of composite sensitivity distribution prepared in Step 3. Step 5: Among the coordinates obtained from the eight patterns in Step 4, the most frequently occurring coordinate is taken as the estimated coordinate. If the position derived is closest to the actual applied coordinate, it is evaluated as correct; otherwise, it is considered incorrect.

[0037] (Experimental results) When a force was applied to a randomly selected application coordinate (X, Y) = (-2360, +450) [μm], the first and second response values ​​were measured as (L, R) = (101.6, -121.9) [ppm]. The estimated coordinates derived in step 5 are shown in Figure 8. The estimated coordinates were (X, Y) = (-2500, +500), which were closest to the actual application coordinates within a 500 μm interval. A similar experiment was conducted on 50 randomly selected application coordinates. Many correct answers were obtained at distances of 1000 to 2500 μm from the origin, while the number of correct answers was relatively low near the origin or at a distance of approximately 3000 μm from the origin. These results suggest that, due to the high sensitivity and irregularity near the origin, it is preferable to use plots finer than 500 μm (e.g., 100 μm intervals). In the data of Fig. 8, due to the convenience of the measurement system, the direction of the X-axis arrow shown in Fig. 5 (right in Fig. 5) was taken as the negative direction, and the opposite direction (left in Fig. 5) was taken as the positive direction. This concludes the description of Example 1.

[0038] Based on the first embodiment, the load analysis device A is configured to have the following features.

[0039] (1) The control unit 220 provided in the load analysis device A calculates a composite response value obtained by combining the first response value multiplied by the first coefficient and the second response value multiplied by the second coefficient in multiple patterns, each with a different combination of the first coefficient and the second coefficient, thereby changing the characteristics of the composite response value on a two-dimensional plane set based on the position of the cantilever C. The above feature (1) corresponds to the above steps 1 and 2. This feature makes it possible to change the characteristics of the composite response value on a two-dimensional plane with a single cantilever C, so that the characteristics of the applied load on a two-dimensional plane can be analyzed with a small number of cantilevers.

[0040] (2) Furthermore, the control unit 220 estimates the direction of the load on the two-dimensional surface or the load application position, which is the position of the load on the two-dimensional surface, based on the combined response value calculated for the multiple patterns. The above feature (2) corresponds to the above step 5, and the load application position corresponds to the above estimated coordinates. Note that the control unit 220 may estimate the load direction on the two-dimensional surface based on the combination of the first coefficient and the second coefficient that calculates the highest combined response value among the combined response values ​​calculated using multiple patterns, without relying on a prepared combined sensitivity distribution. The load direction on the two-dimensional surface may be, for example, the direction of the load application position relative to an arbitrary position (e.g., the origin) set based on the cantilever C.

[0041] (3) The load analysis device A further includes a memory unit 210 that stores in advance sensitivity distribution information indicating a sensitivity distribution generated in multiple patterns, the sensitivity distribution being generated by applying an arbitrary load to each position of the elastic body 20 corresponding to multiple coordinates set in advance on a two-dimensional plane and synthesizing a first response value multiplied by a first coefficient and a second response value multiplied by a second coefficient for each of the multiple coordinates, and the control unit 220 estimates the load application position based on the synthesized response value calculated in the multiple patterns and the sensitivity distribution information. Here, the sensitivity distribution information stored in advance in the storage unit 210 may be, for example, data indicating a composite sensitivity distribution of a plurality of patterns (eight patterns in this example) prepared in advance in step 3 above.

[0042] In the method using a single cantilever C as in Example 1 above, if the magnitude of the applied load is unknown, it is not possible to determine whether the magnitude of the response is due to the distance from the detection element or the magnitude of the load. Example 2, which will be described next, is an experiment that proves that it is possible to estimate the load application position and the magnitude of the applied load using two cantilevers C.

[0043] Example 2 In Example 2, it was assumed that the sensor element 10 had two cantilevers C. Specifically, the two cantilevers C were a first cantilever C1 and a second cantilever C2 that were spaced apart from each other, as shown in Fig. 9. The first cantilever C1 and the second cantilever C2 had the same shape and size, and were spaced apart from each other by 500 µm in the length direction (Y direction).

[0044] In the following, a first response value corresponding to the resistance change of the first strain gauge 3L of the first cantilever C1 will be referred to as L1, and a second response value corresponding to the resistance change of the second strain gauge 3R of the first cantilever C1 will be referred to as R1. Furthermore, a first response value corresponding to the resistance change of the first strain gauge 3L of the second cantilever C2 will be referred to as L2, and a second response value corresponding to the resistance change of the second strain gauge 3R of the second cantilever C2 will be referred to as R2. That is, in the configuration of Example 2, the control unit 220 can acquire each of (L1, R1) and (L2, R2) from the tactile sensor 100.

[0045] In Example 2, eight patterns of composite sensitivity distributions were prepared for each of the first cantilever C1 and the second cantilever C2, as in step 3 of Example 1. Hereinafter, the composite sensitivity distribution corresponding to the first cantilever C1 will be referred to as the first composite sensitivity distribution, and the composite sensitivity distribution corresponding to the second cantilever C2 will be referred to as the second composite sensitivity distribution.

[0046] In the second example, the first composite sensitivity distribution was generated in the same manner as in step 3, and the second composite sensitivity distribution was obtained by shifting the generated first composite sensitivity distribution by 500 μm in the Y direction (i.e., by one coordinate in the Y direction). That is, the second example is a simulation of the case where two cantilevers C are provided apart from each other. In addition, in the second example, for convenience of the measurement system, the origin was set not at the center of the cantilever C but at the center of the sensor element 10 (a position shifted by 500 μm in the Y direction from the center of the cantilever C). Furthermore, based on the experimental result of the first example that the sensor response may become irregular near the origin, in the second example, the load was measured for coordinates (X, Y) between (-500, +500) and (+500, -1500) set at 100 μm intervals (i.e., the distance between adjacent coordinates in the X or Y direction was 100 μm).

[0047] Then, between the first composite sensitivity distribution generated from a plurality of patterns (the above-mentioned eight patterns) each having a different combination of the first coefficient and the second coefficient, and the second composite sensitivity distribution generated from the same plurality of patterns, a composite response ratio, which is the ratio between the first composite response value and the second composite response value, was calculated for each pattern having the same combination of the first coefficient and the second coefficient at all of the set coordinates, as schematically shown in Fig. 10. In other words, the eight-pattern composite response ratio calculated at each of the set coordinates is expressed as follows:

[0048] Pattern 1: (L1+R1) / (L2+R2) Pattern 2: (0.5L1+R1) / (0.5L2+R2) Pattern 3: (R1) / (R2) Pattern 4: (-0.5L1+R1) / (-0.5L2+R2) Pattern 5: (-L1+R1) / (-L2+R2) Pattern 6: (-L1 + 0.5R1) / (-L2 + 0.5R2) Pattern 7: (-L1) / (-L2) Pattern 8: (-L1-0.5R1) / (-L2-0.5R2)

[0049] Here, we explain the reason for calculating the composite response ratio as described above. The composite response value S [ppm] depends on the position (X, Y) on a two-dimensional plane and the force (load) F [N]. That is, it can be expressed as S = f(X, Y, F). If we consider the dependency of the composite response value on position and its dependency on force to be independent, we can approximate it as S = f(X, Y) · f(F). Furthermore, since the relationship between force and response value (first response value or second response value) at a certain coordinate is roughly linear, as shown in Figures 11(b) and 12(b), the relationship between force and composite response value can also be considered linear. This allows us to express f(F) = kF (k is a proportionality constant), and therefore S = kF · f(X, Y).

[0050] If the first resultant response value based on the first cantilever C1 is S1 and the second resultant response value based on the second cantilever C2 is S2, then these can be expressed as S1 = kF·f1(X,Y) and S2 = kF·f2(X,Y). The resultant response ratio, which is the ratio of these values, is S1 / S2 = f1(X,Y) / f2(X,Y), and depends only on the position (X,Y) on the two-dimensional surface.

[0051] As described above, if position characteristic information, which is information obtained by measuring f1(X,Y) and f2(X,Y) in advance through experiments or simulations and digitizing it, is stored in advance in the memory unit 210, the control unit 220 can identify the load application position on a two-dimensional surface based on this position characteristic information and (L1,R1) and (L2,R2) obtained from the tactile sensor 100. The data indicating f1(X, Y) only needs to be capable of calculating S1 / kF at each of all coordinates set on a two-dimensional plane, and should include at least data on the relationship (L1, F) between the first response value and the force (see FIG. 11(b)) and data on the relationship (R1, F) between the second response value and the force (see FIG. 12(b)), corresponding to the first cantilever C1. This is because the control unit 220 can calculate the data on the relationship (S1, F) between the first composite response value and the force from these data. Similarly, the data indicating f2(X, Y) only needs to be capable of calculating S2 / kF at each of all coordinates set on a two-dimensional plane, and should include at least data on the relationship between the first response value and the force (L2, F) and data on the relationship between the second response value and the force (R2, F) corresponding to the second cantilever C2. This is because the control unit 220 can calculate the data on the relationship between the second composite response value and the force (S2, F) from these data.

[0052] The storage unit 210 may further store first response ratio data indicating the relationship between a first composite response ratio and a position (P1,X,Y) in a plurality of patterns, and second response ratio data indicating the relationship between a second composite response ratio and a position (P2,X,Y) in a plurality of patterns. Note that the first response ratio data and second response ratio data may be calculated and generated by the control unit 220 from position characteristic information including data indicating f1(X,Y) and f2(X,Y).

[0053] The control unit 220 identifies (estimates) the load application position (X, Y) where the vertical load is applied on the two-dimensional plane, based on the position characteristic information stored in the storage unit 210, the first and second response values ​​(L1, R1) based on the first cantilever C1, and the first and second response values ​​(L2, R2) based on the second cantilever C2. Furthermore, if the load application position can be estimated, f1(X, Y) and f2(X, Y) are known from the position characteristic information, and therefore the control unit 220 can obtain (estimate) the load (force) at the identified load application position from F=S1 / {kf1(x)} or F=S2 / {kf2(x)}.

[0054] 11 and 12 show the experimental results of a load analysis based on the above method.

[0055] Figure 11(a) shows the estimated load application position, i.e., the estimated coordinates, when a load of F = 0.5 N is applied to a randomly selected application coordinate (X, Y) = (-325, -882) [μm] using the experimental system of Figure 4, and the response based on the first cantilever C1 is (L1, R1) = (-24.0, 111.1) [ppm], and the response based on the second cantilever C2 is (L2, R2) = (-98.0, 37.1) [ppm]. The estimated coordinates are (X, Y) = (-300, -900) [μm], which shows that the application coordinates can be estimated with good accuracy within the set coordinate range.

[0056] Figure 11(b) shows the data on the relationship (L1, F) between the first response value and force corresponding to the first cantilever C1 at the estimated coordinates (X, Y) = (-300, -900) [μm] shown in Figure 11(a), and the magnitude of the load (force) estimated based on this data and the obtained first response value (L1 = -24.0 ppm), which is 0.47 N. The load actually applied to the applied coordinates is F = 0.5 N, so it can be seen that the load was determined with good accuracy. Note that -50.9 ppm / N shown in Figure 11(b) is the slope when the (L1, F) relationship is considered as a linear function.

[0057] Figure 12(a) shows the estimated load application position, i.e., the estimated coordinates, when a load of F = 0.8 N is applied to a randomly selected application coordinate (X, Y) = (-21, -1148) [μm] using the experimental system of Figure 4. The response based on the first cantilever C1 is (L1, R1) = (164.9, 72.1) [ppm], and the response based on the second cantilever C2 is (L2, R2) = (92.0, -51.6) [ppm]. The estimated coordinate is (X, Y) = (0, -1100) [μm], which shows that the application coordinate can be estimated with good accuracy within the set coordinate range.

[0058] Figure 12(b) shows the data on the relationship (L1, F) between the first response value and force corresponding to the first cantilever C1 at the estimated coordinates (X, Y) = (0, -1100) [μm] shown in Figure 12(a), and the magnitude of the load (force) estimated based on this data and the obtained first response value (L1 = 164.9 ppm), which is 0.77 N. The load actually applied to the applied coordinates is F = 0.8 N, so it can be seen that the load was determined with good accuracy. Note that 213.6 ppm / N shown in Figure 12(b) is the slope when the (L1, F) relationship is considered as a linear function.

[0059] In the above, the magnitude of the load is calculated from the data on the relationship (L1, F) between the first response value and the force corresponding to the first cantilever C1. However, the magnitude of the load may also be calculated from the data on the relationship (R1, F) between the second response value and the force corresponding to the first cantilever C1. Also, the magnitude of the load may be calculated from the data on the relationship (L2, F) between the first response value and the force corresponding to the second cantilever C2, or the data on the relationship (R2, F) between the second response value and the force corresponding to the second cantilever C2. Furthermore, the composite response ratio is not limited to S1 / S2=f1(X,Y) / f2(X,Y), but may be its reciprocal, S2 / S1=f2(X,Y) / f1(X,Y).

[0060] Based on the second embodiment, the load analysis device A is configured to have the following features.

[0061] (4) In the load analysis device A, the sensor element 10 has two cantilevers, a first cantilever C1 and a second cantilever C2, which are provided apart from each other. The control unit 220 calculates, for a plurality of patterns, a first composite response value that is a composite response value obtained based on the first response value and the second response value of the first cantilever C1, and calculates, for a plurality of patterns, a second composite response value that is a composite response value obtained based on the first response value and the second response value of the second cantilever C2, and calculates a composite response ratio that is the ratio between the first composite response value and the second composite response value for each pattern that has the same combination of the first coefficient and the second coefficient among the plurality of patterns, and estimates the load application position based on the calculated composite response ratio. The feature (4) above makes it possible to estimate the load application position on a two-dimensional surface using only two cantilevers.

[0062] (5) Specifically, the load analysis device A further includes a storage unit 210 that stores in advance position characteristic information indicating the relationship between the first response value and the force of each of the first cantilever and the second cantilever, and the relationship between the second response value and the force, at a plurality of coordinates that are preset on a two-dimensional plane. The control unit 220 then estimates the load application position based on the calculated composite response ratio and the position characteristic information.

[0063] (6) Furthermore, the control unit 220 determines the load applied at the estimated load application position based on the estimated load application position and the position characteristic information. Due to the feature (6) above, it is possible to obtain the applied load (force) at the load application position estimated on a two-dimensional plane using only two cantilevers.

[0064] (7) In the load analysis device A described in the first and second embodiments, it is preferable that the multiple patterns of different combinations of the first and second coefficients include a pattern in which one of the first and second coefficients is 0, a pattern in which both the first and second coefficients are positive values, a pattern in which both the first and second coefficients are negative values, and a pattern in which one of the first and second coefficients is positive and the other is negative.

[0065] (8) Furthermore, the load analysis method using the tactile sensor 100 includes the steps of acquiring a first response value corresponding to a change in resistance of the first strain gauge 3L and a second response value corresponding to a change in resistance of the second strain gauge 3R, and calculating a composite response value obtained by combining the first response value multiplied by the first coefficient and the second response value multiplied by the second coefficient in multiple patterns each having a different combination of the first coefficient and the second coefficient, thereby changing the characteristics of the composite response value on a two-dimensional plane set based on the position of the cantilever C. The feature (8) above allows the characteristics of the composite response value in a two-dimensional plane to be changed with a single cantilever, making it possible to analyze the characteristics of the applied load in a two-dimensional plane with a small number of cantilevers.

[0066] The tactile sensor 100 described above is used, for example, as a sensor for detecting the mechanical relationship between a robot hand and a target object. However, the tactile sensor 100 is not limited to use in robot hands and can be used for any purpose, such as being attached to a tool or implement to detect contact with a human part (e.g., a hand or a foot).

[0067] The present invention is not limited to the above-described embodiments and drawings, and modifications (including the deletion of components) can be made as appropriate within the scope of the present invention.

[0068] The number of patterns with different combinations of the first and second coefficients is not limited to eight, and may be any number as long as it allows analysis of the load on a two-dimensional surface.

[0069] The load-receiving surface 21 of the elastic body 20 is not limited to a flat surface and can be any surface, and as long as the load can be analyzed using the above method, the load-receiving surface 21 may include a curved surface or a raised portion.

[0070] The circuit board 30 is not limited to a rigid board and may be made of a flexible board. At least a part of the various circuits (bridge circuits, amplifiers, and output circuits including ADCs) formed on the circuit board 30 may be provided outside the circuit board 30.

[0071] The two-dimensional surface set based on the position of the cantilever C is not limited to a flat surface, but may be a curved surface having coordinates that correspond one-to-one with the coordinates set on the plane.

[0072] Although the above describes an example in which the cantilever C is long in the Y direction (length direction), the cantilever C may have a shape in which the width is greater than the length. Furthermore, the first cantilever C1 and the second cantilever C2 are not limited to being spaced apart from each other in the Y direction, as long as they are spaced apart from each other. Furthermore, the orientation of the free end of the first cantilever C1 and the orientation of the free end of the second cantilever C2 do not have to be the same, and may be opposite to each other or may be oblique to each other.

[0073] In the above description, in order to facilitate understanding of the present invention, descriptions of well-known technical matters have been omitted as appropriate.

[0074] This invention allows various embodiments and modifications without departing from the broad spirit and scope of this invention. Furthermore, the above-described embodiments are intended to explain this invention and do not limit the scope of this invention. That is, the scope of this invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of the invention equivalent thereto are considered to be within the scope of this invention. [Explanation of symbols]

[0075] A...Load analysis device 100...Tactile sensor 10...Sensor element C: cantilever, Cf: fixed end C1...first cantilever, C2...second cantilever 3L...1st strain gauge, 3R...2nd strain gauge 20...elastic body, 21...attached surface 30...Circuit board 200...control device, 210...storage unit, 220...control unit 1...SOI, 1a...support substrate, 1b...BOX layer, 1c...active layer 2...insulation layer, 3...strain gauge layer, 4...wiring layer, 5...shape control layer

Claims

1. a sensor element having a cantilever, in which a first strain gauge and a second strain gauge are provided side by side in the width direction of the cantilever at a fixed end of the cantilever; an elastic body that covers the sensor element and to which a load is applied; a control unit that acquires a first response value corresponding to a resistance change of the first strain gauge and a second response value corresponding to a resistance change of the second strain gauge, The control unit a composite response value obtained by combining the first response value multiplied by a first coefficient and the second response value multiplied by a second coefficient is calculated using a plurality of patterns in which the combinations of the first coefficient and the second coefficient are different, thereby changing the characteristics of the composite response value on a two-dimensional plane set based on the position of the cantilever; Load analysis device.

2. the control unit estimates a direction of the load on the two-dimensional plane or a load application position, which is a position of the load on the two-dimensional plane, based on the combined response value calculated for the plurality of patterns. The load analysis device according to claim 1 .

3. a storage unit configured to store in advance sensitivity distribution information indicating sensitivity distributions generated in a plurality of patterns, the sensitivity distributions being generated by applying an arbitrary load to each position of the elastic body corresponding to a plurality of coordinates set in advance on the two-dimensional plane, and combining the first response value multiplied by the first coefficient and the second response value multiplied by the second coefficient for each of the plurality of coordinates, the control unit estimates the load application position based on the combined response value calculated for the plurality of patterns and the sensitivity distribution information. The load analysis device according to claim 2 .

4. The sensor element has two cantilevers, a first cantilever and a second cantilever, which are spaced apart from each other; The control unit calculating a first composite response value, which is the composite response value obtained based on the first response value and the second response value of the first cantilever, for the plurality of patterns; calculating a second composite response value, which is the composite response value obtained based on the first response value and the second response value of the second cantilever, for the plurality of patterns; calculating a composite response ratio, which is a ratio between the first composite response value and the second composite response value, for each pattern having the same combination of the first coefficient and the second coefficient among the plurality of patterns; estimating the load application position based on the calculated composite response ratio; The load analysis device according to claim 2 .

5. a storage unit configured to store in advance position characteristic information indicating a relationship between the first response value and a force of each of the first cantilever and the second cantilever, and a relationship between the second response value and a force of each of the first cantilever and the second cantilever, at a plurality of coordinates preset on the two-dimensional plane; the control unit estimates the load application position based on the calculated combined response ratio and the position characteristic information. The load analysis device according to claim 4 .

6. the control unit determines a load applied at the estimated load application position based on the estimated load application position and the position characteristic information. The load analysis device according to claim 5 .

7. The multiple patterns include: a pattern in which one of the first coefficient and the second coefficient is 0; a pattern in which both the first coefficient and the second coefficient are positive values; a pattern in which both the first coefficient and the second coefficient are negative values; a pattern in which one of the first coefficient and the second coefficient is a positive value and the other is a negative value, The load analysis device according to any one of claims 1 to 6.

8. A load analysis method using a tactile sensor including a sensor element in which a first strain gauge and a second strain gauge are provided side by side in a width direction of the cantilever at a fixed end of the cantilever, and an elastic body that covers the sensor element and to which a load is applied, acquiring a first response value corresponding to a resistance change of the first strain gauge and a second response value corresponding to a resistance change of the second strain gauge; and calculating a composite response value obtained by combining the first response value multiplied by a first coefficient and the second response value multiplied by a second coefficient in a plurality of patterns each having a different combination of the first coefficient and the second coefficient, thereby changing the characteristics of the composite response value on a two-dimensional plane set based on the position of the cantilever. Load analysis method.

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