WO2022209210A1

WO2022209210A1 - Force sensor

Info

Publication number: WO2022209210A1
Application number: PCT/JP2022/002376
Authority: WO
Inventors: 嵩幸遠藤
Original assignee: 日本電産コパル電子株式会社
Priority date: 2021-03-31
Filing date: 2022-01-24
Publication date: 2022-10-06
Also published as: JP2022156888A

Abstract

Disclosed is a force sensor that can improve detection accuracy by sufficiently using the output voltages of a plurality of bridge circuits. A plurality of bridge circuits 51₁, 51₂, …51_m are provided between a first structure and a second structure and output, as a plurality of voltage values, changes in the resistance values of two strain gauge groups of at least three strain sensors. A computation unit 61 computes the output voltages of the plurality of bridge circuits. The computation unit computes three forces and three moments using a determinant. A specific coefficient, that corresponds to a force in an x-direction and a y-direction of a matrix of coefficients and a moment around the z-axis, is a non-zero value.

Description

force sensor

Embodiments of the present invention relate to force sensors used in, for example, robot arms.

A force sensor is used, for example, in a robot arm or the like, and detects forces (Fx, Fy, Fz) and moments (Mx, My, Mz) with respect to three orthogonal axes (x, y, z). Reference 1).

JP 2018-48915 A

The force sensor is equipped with a plurality of strain sensors that can be deformed in 6-axis directions, for example, 3-axis directions and directions around 3 axes. Each strain sensor includes a plurality of strain gauges, and the plurality of strain gauges constitute a plurality of bridge circuits. The output voltages of multiple bridge circuits are used to detect forces (Fx, Fy, Fz) and moments (Mx, My, Mz). However, the conventional force sensor does not fully utilize the output voltages of the multiple bridge circuits.

This embodiment provides a force sensor capable of improving detection accuracy by fully utilizing the output voltages of a plurality of bridge circuits.

The force sensor of this embodiment includes a first structure, a second structure, a plurality of third structures connecting the first structure and the second structure, and the plurality of third structures. at least three strain sensors each having two strain gauge groups provided between the first structure and the second structure at positions different from and the two strain gauge groups of the at least three strain sensors a plurality of bridge circuits for outputting a change in resistance value as a plurality of voltage values; and a computing unit for computing the output voltages of the plurality of bridge circuits. Calculating 3 forces and 3 moments,

here,
Fx is the force in the x direction, Fy is the force in the y direction, Fz is the force in the z direction, Mx is the moment about the x axis, My is the moment about the y axis, Mz is the moment about the z axis, C ⁺ is the coefficient of the matrices V1 to Vm are the output voltages of the m bridge circuits, the matrix C ⁺ of said coefficients is shown in equation (2),

here,
C ₁₁ -C _6m are the coefficients of the coefficient matrix C ⁺ F ₁₁ -F ₆₆ are the forces applied to the multiple strain gauge groups when Fx-Mz are applied;
V ₁₁ to V _m6 are the output voltages of the m bridge circuits when Fx to Mz are applied;
When the number m of said bridge circuits is 6, the coefficients C ₁₄ , C ₁₆ , C ₂₂ , C ₂₄ , C ₂₆ , C ₆₁ of the matrix of coefficients C ⁺ are non-zero.

1 is a perspective view showing a force sensor according to this embodiment; FIG. FIG. 2 is an exploded perspective view showing the force sensor shown in FIG. 1 ; FIG. 3 is a perspective view showing a state in which part of the force sensor shown in FIG. 2 is assembled; FIG. 3 is a perspective view showing a state in which a part of the force sensor shown in FIG. 2 is further assembled; FIG. 3 is a perspective view showing a further exploded part of the force sensor shown in FIG. 2 ; The top view which takes out and shows the elastic body which concerns on this embodiment. The figure which shows typically the strain sensor which concerns on this embodiment. FIG. 2 is a circuit diagram showing an example of a bridge circuit; FIG. 2 is a configuration diagram schematically showing the control system of the force sensor according to the embodiment; FIG. 4 is a plan view schematically showing three strain sensors 19-1, 19-2, 19-3; FIG. 4 is a diagram schematically showing tension or compression force when force or moment is applied to each strain gauge group; The top view which shows the modification of this embodiment roughly.

Embodiments will be described below with reference to the drawings. In the drawings, the same parts are given the same reference numerals.

A configuration of a force sensor 10 according to the present embodiment will be described with reference to FIGS. 1 to 6. FIG.
The force sensor 10 is used, for example, in a robot arm or the like, and detects forces (Fx, Fy, Fz) along the X, Y, and Z axes and torques (moments: Mx, My, Mz) around the X, Y, and Z axes. to detect

As shown in FIGS. 1 and 2, the force sensor 10 includes a cylindrical main body 11 and a cylindrical cover 12 that covers the main body 11. A mounting plate 13 is provided inside the cover 12 as a movable body operable with respect to the main body 11 , and the mounting plate 13 is fixed to the cover 12 with a plurality of screws 14 . A cover 12 and a mounting plate 13 are operably provided with respect to the body 11 .

The body 11 is fixed to, for example, the body of a robot arm (not shown). The mounting plate 13 is fixed to, for example, a hand portion of the robot arm.

A ring-shaped sealing member 15 is provided between the main body 11 and the cover 12 . The sealing member 15 is made of an elastic material such as rubber or foam, seals the gap between the main body 11 and the cover 12 , and allows the cover 12 to move relative to the main body 11 .

An elastic body 16 is provided between the main body 11 and the mounting plate 13 . The elastic body 16 is made of metal, for example. and a plurality of third structures 16-3 and the like provided between the structures 16-2. A plurality of second structures 16-2 are arranged at regular intervals around the first structure 16-1.

In this embodiment, the elastic body 16 has, for example, three second structures 16-2. However, the number of second structures 16-2 is not limited to three, and may be three or more. Further, when this embodiment is applied to, for example, a torque sensor other than a force sensor, the number of second structures 16-2 may be two.

As shown in FIG. 3, the first structure 16-1 has six first elastic parts 16-4 around it. The first elastic portion 16-4 has a linear shape along the periphery of the first structure 16-1.

Each of the second structures 16-2 includes two substantially U-shaped second elastic portions 16-5 and two second elastic portions 16-5 between the two second elastic portions 16-5. It has a relay portion 16-6 on a straight line for connecting.

The third structure 16-3 has one end connected to the first elastic portion 16-4 and the other end connected to the relay portion 16-6. Two third structures 16-3 provided between the first structure 16-1 and one second structure 16-2 are arranged in parallel.

The second structure 16-2 is fixed to the main body 11 by a plurality of screws 17, and the first structure 16-1 is fixed to the mounting plate 13 by a plurality of screws 18, as shown in FIGS. be.

As shown in FIGS. 2 and 3, the strain sensor 19 is provided between the first structure 16-1 and the relay portion 16-6. Specifically, one end of the strain sensor 19 is fixed to the first structure between the two first elastic portions 16-4 by a fixing plate 20 and a screw 21 inserted into the back surface of the first elastic portion 16-4. Fixed at 16-1. The other end of the strain sensor 19 is fixed to the central portion of the relay portion 16-6 by a fixing plate 22 and a screw 23 inserted into the rear surface of the relay portion 16-6. As will be described later, the strain sensor 19 has a plurality of strain gauges arranged on the surface of a metal strain body.

When the mounting plate 13 and the cover 12 are moved with respect to the main body 11 by an external force, the third structure 16-3, the first elastic portion 16-4, the second elastic portion 16-5, and the relay portion 16-6 are deformed. do. As a result, the strain generating body of the strain sensor 19 is deformed, and an electric signal is output from the strain gauge.

Each strain gauge of each strain sensor 19 constitutes a bridge circuit as will be described later. are detected (moments: Mx, My, Mz).

As shown in FIG. 2, the main body 11 is provided with a plurality of stoppers 30 that protect the elastic body 16 from external force. Each stopper 30 is composed of a cylindrical stopper member 31 , a screw 32 as a fixing member, and a plurality of openings 13 a provided in the mounting plate 13 .

This embodiment shows a case where three stoppers 30 are provided. However, the number of stoppers 30 is not limited to three, and may be three or more. The three stoppers 30 are arranged respectively between the three second structures 16-2.

By arranging the stopper 30 between the second structures 16-2, it is possible to suppress an increase in the diameter and outer size of the elastic body 16 and the force sensor as a whole.

Three protrusions 11a are provided on the surface of the main body 11 at positions corresponding to the spaces between the three second structures 16-2.

As shown in FIG. 4, the stopper member 31 is inserted into the opening 13a of the mounting plate 13 and fixed to the projection 11a of the main body 11 by a screw 32. As shown in FIG. The outer diameter of the stopper member 31 is set slightly smaller than the inner diameter of the opening 13a, as will be described later. When the mounting plate 13 moves with respect to the main body 11 and the outer surface of the stopper member 31 contacts the inner surface of the opening 13a, the mounting plate 13 is prevented from moving, and the elastic body 16 and strain sensor 19 are destroyed. is prevented.

As shown in FIG. 5, a printed circuit board 41, a plurality of flexible printed circuit boards 42, a back cover 43, a lead wire assembly 44, and a hollow tube 45 are provided on the back surface of the main body 11. The printed circuit board 41 includes a processing circuit (not shown) for supplying power to the bridge circuit and processing the output signal of the bridge circuit.

One end of the plurality of flexible printed boards 42 is arranged on the upper surface side of the main body 11 and connected to each strain sensor 19, as shown in FIG. The other ends of the plurality of flexible printed boards 42 are connected to a processing circuit or the like on the back surface of the printed board 41 . A plurality of flexible printed circuit boards 42 supply power to the strain gauges and supply signals from the strain gauges to the processing circuitry.

The lead wire assembly 44 is connected to the printed circuit board 41 to supply power to the processing circuit and transmit signals from the processing circuit. The back cover 43 is fixed to the main body 11 with a plurality of screws and covers the printed circuit board 41 .

The main body 11, the cover 12, the mounting plate 13, the first structure 16-1 of the elastic body 16, the printed circuit board 41, and the back cover 43 are provided with openings communicating with each other at their central portions, and are hollow tubes. 45 is provided within this opening.

As shown in FIGS. 2 and 3, one end of the hollow tube 45 penetrates the back cover 43, the printed circuit board 41, and the first structure 16-1 and protrudes to the surface of the first structure 16-1. be. A ring-shaped sealing member 26 is provided at one end of the hollow tube 45 protruding from the surface of the first structure 16-1. The sealing member 26 is made of rubber or foam material, for example, and seals the gap between the opening of the mounting plate 13 and one end of the hollow tube 25 . This prevents dust from entering the mounting plate 13 from the outside of the cover 12 .

(Structure of elastic body)
FIG. 6 shows the elastic body 16 and strain sensor 19 . As described above, the elastic bodies 16 are provided in one first structure 16-1, three second structures 16-2, a plurality of third structures 16-3, and the first structure 16-1. six first elastic parts 16-4 provided, two second elastic parts 16-5 provided in each of the three second structures 16-2, and between the two second elastic parts 16-5 It has a provided relay section 16-6.

The second elastic portion 16-5 is substantially U-shaped and has lower bending or torsional rigidity than the second structure 16-2. The first elastic portion 16-4 has torsional rigidity equal to or lower than that of the second elastic portion 16-5.

The strain sensor 19 is provided between the first structural body 16-1 located between the two first elastic portions 16-4 and the central portion of the relay portion 16-6. Furthermore, the strain sensor 19 is positioned between the two third structures 16-3 and arranged parallel to the two third structures 16-3.

The thicknesses of the first elastic portion 16-4, the second elastic portion 16-5, and the relay portion 16-6 are the same as those of the first structure 16-1, the second structure 16-2, and the third structure 16-3. The width W of the first elastic portion 16-4, the second elastic portion 16-5, and the relay portion 16-6 is equal to the width of the third structure 16-3. The longer the lengths L1 and L2 of the U-shaped portion and the narrower the width W of the U-shaped portion, the softer the second elastic portion 16-5. -6 is also more flexible as the width is narrower.

The strain body 19a constituting the strain sensor 19 has a thickness of a first structure 16-1, a second structure 16-2, a third structure 16-3, a first elastic portion 16-4, and a second elastic portion. 16-5 and the thickness of the relay portion 16-6, and the width of the strain generating body 19a is the third structure 16-3, the first elastic portion 16-4, the second elastic portion 16-5, and the relay portion. Wider than 16-6 wide. However, the thickness, width, and size relationship of the first elastic portion 16-4, the second elastic portion 16-5, the relay portion 16-6, and the third structure 16-3 can be changed as required.

The configuration of the second structural bodies 16-2 is not limited to this, and the three second structural bodies 16-2 may be integrally configured, for example, in a ring shape, as indicated by broken lines.

(Configuration of strain sensor)
FIG. 7 shows an example of the strain sensor 19. As shown in FIG. As described above, the strain sensor 19 is composed of a strain body 19a and a plurality of strain gauges R1 to R8 provided on the surface of the strain body 19a. The strain-generating body 19a is made of metal, and its thickness is smaller than its width. Therefore, the strain-generating body 19a is easily deformed in the thickness direction and is difficult to be deformed in the width direction.

One end of the strain generating body 19a is provided on the first structure 16-1, and the other end is provided on the relay portion 16-6 of the second structure 16-2.

Strain gauges R1, R2, R3, R4, R5, R6, R7 and R8 made of, for example, thin film resistors are provided on the surface of the strain generating body 19a. Strain gauges R1, R2, R3, and R4 for detecting Fx, Fy, and Mz are arranged obliquely with respect to the longitudinal direction of the strain generating body 19a. Specifically, the strain gauges R1, R2, R3, and R4 are arranged at the corners of the strain body 19a along the diagonal lines of the strain body 19a. On the other hand, strain gauges R5, R6, R7, and R8 for detecting Mx, My, and Fz are arranged parallel to the longitudinal direction of the strain-generating body 19a at the center of the strain-generating body 19a. Furthermore, the strain gauges R1, R3, R5 and R8 are arranged near one longitudinal end of the strain body 19a, and the strain gauges R2, R4, R6 and R7 are arranged at the other longitudinal end of the strain body 19a. placed in the vicinity.

FIG. 8 shows an example of a bridge circuit using the strain gauges R1 to R8. Strain gauges R1, R2, R3, and R4 constitute a first bridge circuit BC1, and strain gauges R5, R6, R7, and R8 constitute a second bridge circuit BC2.

In the first bridge circuit BC1, a series circuit of strain gauges R2 and R1 and a series circuit of strain gauges R4 and R3 are arranged between the power source V and the ground GND. An output voltage Vout+ is output from a connection node between the strain gauges R2 and R1, and an output voltage Vout- is output from a connection node between the strain gauges R4 and R3. The output voltage Vout+ and the output voltage Vout− are supplied to the operational amplifier OP1, and the output voltage Vout is output from the output terminal of the operational amplifier OP1.

In the second bridge circuit BC2, a series circuit of strain gauges R6 and R5 and a series circuit of strain gauges R8 and R7 are arranged between the power source V and the ground GND. An output voltage Vout+ is output from a connection node between the strain gauges R6 and R5, and an output voltage Vout- is output from a connection node between the strain gauges R8 and R7. The output voltage Vout+ and the output voltage Vout− are supplied to the operational amplifier OP2, and the output voltage Vout is output from the output terminal of the operational amplifier OP2.

Hereinafter, the first bridge circuit BC1 and the operational amplifier OP1, and the second bridge circuit BC2 and the operational amplifier OP2 are simply referred to as bridge circuits.

The force sensor 10 of this embodiment has three strain sensors 19, and each strain sensor 19 is provided with a pair of bridge circuits. Therefore, the force sensor 10 has a total of six bridge circuits.

FIG. 9 shows the configuration of the control system of the force sensor 10. As shown in FIG. _{Output voltages V 1} _, _V ₂ _, _. In this embodiment, m=6. The computing unit 61 is configured by, for example, a microcomputer, and the microcomputer includes a microprocessor, memory, and software or firmware. However, the calculation unit 61 is not limited to this. The calculation unit 61 calculates Fx, Fy, Mz, Mx, My, and Fz from the output voltages V ₁ , V ₂ , . . . V _m of the bridge circuits 51 ₁ , 51 ₂ to 51 _m .

(calculation operation)
First, the principle will be explained.
FIG. 10 schematically shows three strain sensors 19 (19-1, 19-2, 19-3). Here, the strain gauges R1, R2, R3, and R4 at the corners of the strain sensor 19-1 are shown as a strain gauge group (1), and the strain gauges R5, R6, R7, and R8 at the central portion are shown as a strain gauge group (2). indicated by . The strain gauges R1, R2, R3, and R4 at the corners of the strain sensor 19-2 are shown as a strain gauge group (3), and the strain gauges R5, R6, R7, and R8 at the central portion are shown as a strain gauge group (4). The strain gauges R1, R2, R3, and R4 at the corners of the strain sensor 19-3 are shown as a strain gauge group (5), and the strain gauges R5, R6, R7, and R8 at the central portion are shown as a strain gauge group (6).

FIG. 11 shows strain gauge groups (1), (2), (3), and (4) when Fx, Fy, Mz, Mx, My, and Fz are applied to the strain sensors 19-1, 19-2, and 19-3. (5) It schematically shows the magnitude of tension or compression applied to (6). Here, "T" indicates high tension and "t" indicates low tension. A "C" indicates a high compressive force and a "c" indicates a low compressive force. A "-" indicates that no tension or compression force is applied.

For example, when Fx is applied, a large tension is applied to the strain gauge group (1) arranged at the corners of the strain sensor 19-1, and the strain gauge group (1) arranged at the corners of the strain sensors 19-2 and 19-3. A small compressive force is applied to the strain gauge groups (3) and (5).

　Fx and Fy cannot be detected using only strain gauge groups (1) (3) (5). Specifically, tension or compression forces (T, c, c) applied to strain gauge groups (1), (3), and (5) in the case of Fx, and strain gauge groups (1), (3) in the case of My ) (5) and the tension or compression forces (t, c, c) applied to the strain gauge group (1) differ only in the magnitude of the tension applied to the strain gauge group (1). ) (5) are equal in compression force. For this reason, it is impossible to determine whether Fx or My. can be determined.

In the case of Fy, the tensile or compressive forces (-, C, T) and -Mx (-) applied to the strain gauge groups (1), (3), and (5) indicate that the directions of the moments are opposite. ), the tension or compression force (-, c, t) applied to the strain gauge group (1) (3) (5) is compared to is not applied and only the magnitudes of the compressive and tension forces applied to the strain gauge groups (3) and (5) are different. Therefore, it is not possible to determine whether Fy or -Mx. can determine if there is

Next, calculations of Fx, Fy, _Fz , Mx, My, and _Mz _{using the output voltages V 1} _{, V 2} _, _.

Fx, Fy, _Fz , Mx, My, and _Mz _apply the coefficient matrix C ⁺ to the _{output voltages V 1 , V 2} _, _. calculated by multiplying

The matrix C ⁺ of coefficients is the force F applied to the six strain gauge groups when only Fx is applied to the three strain sensors, the six output voltages output from the six bridge circuits, and the three strain sensors Fy alone. The force F applied to the 6 strain gauge groups when applied to the sensors and the 6 output voltages output from the 6 bridge circuits, and . . . the 6 strain gauge groups when only Mz is applied to the 3 strain sensors is obtained by solving simultaneous equations for the force F applied to and the six output voltages output from the six bridge circuits. Specifically, the matrix of coefficients C ⁺ is shown in equation (2).

Equation (2) is a matrix of forces F ₁₁ to F ₆₆ applied to the six strain gauge groups when Fx to Mz are applied, and voltages output from the six bridge circuits when Fx to Mz are applied. The coefficient matrix C ⁺ is obtained by multiplying the inverse matrices of V ₁₁ to V _m6 .

Specifically, in order to clarify the force applied to the force sensor, force is applied for each single axis (F ₁₁ =Fx, F ₂₂ =Fy, F ₃₃ =Fz, F ₄₄ =Mx, F ₅₅ = My, _F66 = Mz). That is, only one of Fx, Fy, Fz, Mx, My, and Mz is applied to the force sensor, and the output voltages V ₁ to V ₆ of the six bridge circuits are measured. This measurement is performed for each of Fx, Fy, Fz, Mx, My and Mz. As a result, six determinants shown in Equation (1) are obtained. The coefficients C ₁₁ to C _m6 are calculated by solving the simultaneous equations shown in Equation (2) from these six determinants. This gives the matrix C ⁺ of coefficients.

In this embodiment, the matrix C ⁺ of coefficients is shown in equation (3).

By obtaining the matrix C ^{1 +} of the above coefficients in advance and using this matrix C ^{1 +} of coefficients, Fx to Mz applied to the force sensor can be detected. In the matrix C ⁺ of coefficients, the coefficients C11, C13, C15, C21, C23, C25, C32, C34, C36, C42, C44, C46, C54, C56, C63, C65 are non-zero.

Moreover, in the coefficient matrix C ⁺ , among the coefficients corresponding to the x-direction force Fx, the y-direction force Fy, and the moment Mz about the z-axis, specific coefficients C14, C16, C22, C24, C26, C61 The value is a value other than 0. Therefore, it is possible to detect the values of Fx, Fy, Mx, and My with high accuracy using the output voltages of the bridge circuits corresponding to these coefficients.

That is, the coefficients C14, C16, C22, C24, C26, and C61 are coefficients that take into consideration the outputs corresponding to the moments Mx and My when the moments Mx and My are applied. If this coefficient is, for example, 0, for example, although only the moment My is applied, it is calculated as if the force Fx was applied simultaneously with the moment My. In order to avoid this, conventionally, a plurality of strain gauges had to be arranged at positions where the outputs corresponding to Fx, Fy, Fz, Mx, My and Mz do not mechanically interfere with each other. In this case, the values of the coefficients C14, C16, C22, C24, C26, and C61 can be set to zero, but the shape of the elastic body is enlarged.

The present embodiment uses C14, C16, C22, C24, C26, and C61 in consideration of the outputs corresponding to the moments Mx and My to prevent the shape of the elastic body 16 from increasing in size, thereby preventing Fx, Fy, and Mx , My can be improved.

Equation (4) shows an example of each numerical value of the coefficient matrix C ⁺ . The numerical value of each coefficient can be changed.

(Effect of Embodiment)
According to the above embodiment, the three strain sensors 19 provided between the first structure 16-1 and the three second structures 16-2, and the two strain sensors 19 provided in each of the three strain sensors 19. The output signals of the set of strain gauge groups are detected by six bridge circuits, and the output voltages V ₁ to V ₆ of the six bridge circuits are multiplied by the coefficient matrix C ⁺ to obtain Fx, Fy, Fz, Mx, My, Looking for Mz. Moreover, in the coefficient matrix C ⁺ , among the coefficients corresponding to Fx, Fy, Mx, and My, coefficients C14, C16, C22, C24, C26, and C61 are values other than zero. Therefore, by using the output voltage of the bridge circuit corresponding to these coefficients, it is possible to prevent the elastic body from increasing in size and detect the values of Fx, Fy, Mx, and My with high precision.

(Modification)
FIG. 12 shows a modification of this embodiment.
The above embodiment used three strain sensors 19 . In a variant, four strain sensors 19 are used. The concentrically arranged first structure 16-1 and second structure 16-2 are connected by a plurality of third structures 16-3. The four strain sensors 19 are provided between the first structure 16-1 and the second structure 16-2 at positions different from the plurality of third structures 16-3. The structure of each strain sensor 19 is the same as that shown in FIG. 7, and each strain sensor 19 constitutes two bridge circuits. Therefore, this modification includes eight bridge circuits.

In this modification, eight output voltages V ₁ to V ₈ are output from the eight bridge circuits, and these output voltages V ₁ to V ₈ are used to apply Fx, Fy, Fz, Mx to the force sensor 10. , My, Mz are detected.

Specifically, in the above equations (1) and (2), the number m of bridge circuits is calculated as eight. In this modification, the matrix C ⁺ of the coefficients of equation (2) is given by equation (5).

In this modification, the values of the coefficients C12, C16, C24, C28 of the coefficient matrix C ⁺ are values other than zero.

In this modification, when a moment Mx is applied, the strain sensors 19 positioned at 90° and 270° are bent, whereas the strain sensors 19 positioned at 0° and 180° are twisted. Therefore, by measuring the moment Mx with strain gauge groups (1), (3), (5), and (7) and obtaining the coefficients C12, C16, C24, and C28, the detection accuracy of Fx, Fy, Mx, and My can be improved.

According to this modification, Fx to Mz can be detected by using the coefficient matrix C ⁺ . Moreover, since the coefficients C12, C16, C24 and C28 of the matrix C ⁺ are non-zero values, the output voltages of the bridge circuit corresponding to these coefficients can be fully utilized. Therefore, it is possible to detect the values of Fx, Fy, Mx, and My with high accuracy while suppressing an increase in the size of the elastic body.

In addition, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the gist of the present invention at the implementation stage. Also, various inventions can be formed by appropriate combinations of the plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all components shown in the embodiments. Furthermore, components across different embodiments may be combined as appropriate.

Claims

a first structure;
a second structure;
a plurality of third structures connecting the first structure and the second structure;
at least three strain sensors each having two strain gauge groups provided between the first structure and the second structure at positions different from the plurality of third structures;
a plurality of bridge circuits that output changes in resistance values of the two strain gauge groups of the at least three strain sensors as a plurality of voltage values;
a computing unit that computes the output voltages of the plurality of bridge circuits;
and
The calculation unit calculates three forces and three moments using the following equations,

here,
Fx is the force in the x direction, Fy is the force in the y direction, Fz is the force in the z direction, Mx is the moment about the x axis, My is the moment about the y axis, Mz is the moment about the z axis, C + is the coefficient of The matrices V1 to Vm are the output voltages of the m bridge circuits, the matrix C + of said coefficients is given by

here,
C 11 -C 6m are the coefficients of the coefficient matrix C + F 11 -F 66 are the forces applied to the multiple strain gauge groups when Fx-Mz are applied;
V 11 to V m6 are the output voltages of the m bridge circuits when Fx to Mz are applied;
The haptic sensation characterized in that when the number m of the bridge circuits is 6, the coefficients C 14 , C 16 , C 22 , C 24 , C 26 , and C 61 of the coefficient matrix C + are values other than 0. sensor.
a first structure;
a second structure;
a plurality of third structures connecting the first structure and the second structure;
at least three strain sensors each having two strain gauge groups provided between the first structure and the second structure at positions different from the plurality of third structures;
a plurality of bridge circuits that output changes in resistance values of the two strain gauge groups of the at least three strain sensors as a plurality of voltage values;
a computing unit that computes the output voltages of the plurality of bridge circuits;
and
The calculation unit calculates three forces and three moments using the following equations,

here,
Fx is the force in the x direction, Fy is the force in the y direction, Fz is the force in the z direction, Mx is the moment about the x axis, My is the moment about the y axis, Mz is the moment about the z axis, C + is the coefficient of The matrices V1 to Vm are the output voltages of the m bridge circuits, the matrix C + of said coefficients is given by

here,
C 11 -C 6m are the coefficients of the coefficient matrix C + F 11 -F 66 are the forces applied to the multiple strain gauge groups when Fx-Mz are applied;
V 11 to V m6 are the output voltages of the m bridge circuits when Fx to Mz are applied;
The force sensor, wherein when the number m of the bridge circuits is 8, coefficients C 12 , C 16 , C 24 , and C 28 of the coefficient matrix C + are values other than zero.
Each of the strain sensors includes a strain body made of a metal plate thinner than the first structure, the second structure, and the third structure, and the plurality of strain gauges extend along the length of the strain body. A plurality of first strain gauge groups arranged obliquely with respect to a direction, and a plurality of second strain gauge groups arranged parallel to the longitudinal direction of the strain-generating body. Or the force sensor according to 2.