Multi-axis inertial sensor

Abstract

This invention provides a multi-axis inertial sensor capable of measuring angular velocity components and acceleration components in three directions with high precision. [Solution] The multi-axis inertial sensor disclosed herein comprises four subsensors, four blocks, and a base. The subsensors measure the angular velocity in the Zs axis direction and the acceleration in the Xs axis direction in a Cartesian XsYsZs coordinate system to which the subsensors are fixed. The four blocks are fixed to a reference plane of the base. Each block has an inclined surface that is inclined with respect to the reference plane. Each subsensor is mounted on each block, and the subsensors are mounted such that the Zs axis of the local Cartesian coordinate system coincides with the normal direction of the inclined surface and the Ys axis is parallel to the reference plane. Of the four blocks, two are arranged along a first direction parallel to the reference plane with their inclined surfaces facing each other, and the remaining two blocks are arranged along a second direction parallel to the reference plane and perpendicular to the first direction with their inclined surfaces facing each other.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a multi-axis inertial sensor that measures angular velocity components and acceleration components in three orthogonal directions.

Background Art

[0002] Patent Document 1 discloses a multi-axis inertial sensor. The multi-axis inertial sensor includes four blocks and a base. The four blocks are fixed to the plane of the base. Hereinafter, for convenience, the plane of the base is referred to as the reference plane. A gyro sensor and an acceleration sensor are arranged in each block. Each block has an inclined surface inclined with respect to the reference plane and an orthogonal surface orthogonal to the reference plane. A gyro is attached to the inclined surface, and an acceleration sensor is attached to the orthogonal surface. The gyro sensor measures the angular velocity in the normal direction of the inclined surface. The acceleration sensor measures the acceleration in two directions, namely, the direction parallel and perpendicular to the reference plane. Two blocks are arranged side by side along the first direction such that the inclined surfaces face each other, and the remaining two blocks are arranged side by side along the second direction orthogonal to the first direction such that the inclined surfaces face each other. Both the first direction and the second direction are parallel to the reference plane.

[0003] Note that the angular velocity in three-dimensional space is represented by a vector in the direction in which a right-handed screw advances with respect to the rotation direction. "Angular velocity about the X-axis (Y-axis / Z-axis)" is expressed as "angular velocity in the X-axis (Y-axis / Z-axis) direction". The expression "angular velocity in the normal direction of the inclined surface" means "angular velocity about the normal of the inclined surface".

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The multi-axis inertial sensor described in Patent Document 1 requires four gyro sensors and four accelerometers. The accelerometers are of a type capable of measuring acceleration in two orthogonal directions. In other words, conventional multi-axis inertial sensors require four angular velocity measurements and eight acceleration measurements. Furthermore, because the gyro sensors and accelerometers are mounted on different faces of the block, there is a risk that the axes of the gyro sensors and accelerometers may be misaligned. While multi-axis inertial sensors output angular velocity components and acceleration components in three directions in a single local coordinate system (a local coordinate system with a fixed base), misalignment of the axes of the gyro sensors and accelerometers reduces the measurement accuracy in the local coordinate system with a fixed base. This specification provides a multi-axis inertial sensor capable of measuring angular velocity components and acceleration components in three directions with a smaller number of measurements and higher accuracy than conventional sensors. [Means for solving the problem]

[0006] The multi-axis inertial sensor disclosed herein comprises four subsensors, four blocks, and a base. Each subsensor can measure the angular velocity in the Zs axis direction and the acceleration in the Xs axis direction of a local XsYsZs coordinate system fixed to it. One plane of the base is referred to as the reference plane. The four blocks are fixed to the reference plane. Each block has an inclined surface that is inclined with respect to the reference plane. One subsensor is mounted on one block, and the subsensor is mounted such that the Zs axis of the local XsYsZs coordinate system coincides with the normal direction of the inclined surface and the Ys axis is parallel to the reference plane. The four blocks are arranged to satisfy either condition (1) or (2) below: (1) Two blocks are arranged along a first direction parallel to the reference plane with their inclined surfaces facing each other, and the remaining two blocks are arranged along a second direction parallel to the reference plane and perpendicular to the first direction, with their inclined surfaces facing each other. (2) Two blocks are arranged along a first direction parallel to the reference plane so that their inclined surfaces are back to back, and the remaining two blocks are arranged along a second direction parallel to the reference plane and perpendicular to the first direction so that their inclined surfaces are back to back.

[0007] Note that since the inclined surfaces are inclined with respect to the reference plane, "so that the inclined surfaces face each other (back to back)" does not mean that the inclined surfaces are parallel to each other, but rather that, when viewed from the direction of the normal of the reference plane, the normals of each inclined surface point in opposite directions.

[0008] If the arrangement of the four sub-sensors satisfies either condition (1) or (2) above, the angular velocity and acceleration components in three orthogonal directions can be determined from the four angular velocity measurements and four acceleration measurements. The calculation formula will be described later. In conventional multi-axis inertial sensors, where the sensor that measures angular velocity and the sensor that measures acceleration are separate, the relative axial misalignment of these two sensors affects the final measurement. In the multi-axis inertial sensor disclosed herein, one sub-sensor measures both angular velocity and acceleration. Therefore, the measurement accuracy of the multi-axis inertial sensor is improved.

[0009] The sub-sensor is of the vibration type, which vibrates two weights. The two weights are excited in opposite phases (180-degree phase difference) along the Ys axis, and the angular velocity around the Zs axis and the acceleration along the Xs axis are measured according to the displacement of the weight along the Xs axis. Since this sub-sensor can obtain both angular velocity and acceleration from the displacement of the two weights, in principle, the direction of the measured angular velocity and the direction of the acceleration are precisely perpendicular. Therefore, the angular velocity components and acceleration components in three directions in a base-fixed coordinate system can be obtained with high accuracy.

[0010] The two weights are preferably aligned along the Ys axis and connected by an elastic member. Since the two weights can vibrate due to resonance, vibrations with opposite phases (a 180-degree phase difference) can be reliably achieved.

[0011] Details of the technology disclosed herein and further improvements are described in the following "Modes for Carrying Out the Invention". [Brief explanation of the drawing]

[0012] [Figure 1]This is a perspective view of the multi-axis inertial sensor of the embodiment. [Figure 2] This is a perspective view of a single block. [Figure 3] This is a plan view of a multi-axis inertial sensor. [Figure 4] This diagram illustrates the principle of measuring angular velocity components in three directions. [Figure 5] This diagram illustrates the measurement principle for acceleration components in three directions. [Figure 6] This is a plan view showing the internal structure of the subsensor. [Figure 7] This is the circuit diagram for the sub-sensor. [Figure 8] This is a perspective view of a modified multi-axis inertial sensor. [Modes for carrying out the invention]

[0013] The multi-axis inertial sensor 100 of the embodiment will be described with reference to the drawings. Hereinafter, for convenience of explanation, "multi-axis inertial sensor" may be abbreviated as "inertial sensor".

[0014] Figure 1 shows a perspective view of the inertial sensor 100. The inertial sensor 100 comprises four blocks 4a, 4b, 4c, and 4d, four subsensors 6a, 6b, 6c, and 6d, and a base 2. The base 2 is a plate, with one of its planes referred to as the reference plane 3. The four blocks 4a-4d are fixed to the base 2, and each of the four subsensors 6a-6d is attached to each of the four blocks 4a-4d.

[0015] The four blocks 4a-4d are all the same shape. The four subsensors 6a-6d are also all the same shape and have the same performance. In the following, when referring to any one of the four blocks 4a-4d without distinction, it will be written as block 4, and when referring to any one of the four subsensors 6a-6d without distinction, it will be written as subsensor 6.

[0016] Block 4 has an inclined surface 5 that is inclined with respect to the reference plane 3, and the sub-sensor 6 is attached to the inclined surface 5. In FIG. 1, only the inclined surfaces of blocks 4b and 4c are labeled with the symbol "5", and the symbol "5" is omitted for the inclined surfaces of blocks 4a and 4d.

[0017] FIG. 2 shows a perspective view of one block 4 fixed to the base 2 and the sub-sensor 6 fixed to the block 4. The coordinate system XsYsZs in the figure represents the local coordinate system (local XsYsZs coordinate system) fixed to the sub-sensor 6. Also, the coordinate system XdYdZd in the figure represents the local coordinate system (local XdYdZd coordinate system) fixed to the base 2. Hereinafter, the local coordinate system fixed to the sub-sensor 6 is referred to as the sub-sensor coordinate system, and the local coordinate system fixed to the base 2 is referred to as the base coordinate system. Both the sub-sensor coordinate system and the base coordinate system are orthogonal coordinate systems. The Zd axis of the base coordinate system coincides with the direction of the normal line of the reference plane 3, and the Xd axis and the Yd axis extend parallel to the reference plane. The inclined surface 5 of the block 4 is inclined with respect to the reference plane 3.

[0018] The sub-sensor 6 is fixed to the inclined surface 5 such that the Zs axis coincides with the normal direction of the inclined surface 5 and the Ys axis is parallel to the reference plane 3 of the base 2. At this time, the Xs axis is parallel to the inclined surface 5. Also, the plane including the Xs axis and the Zs axis is orthogonal to the inclined surface 5.

[0019] The sub-sensor 6 can measure the angular velocity in the Zs axis direction and the acceleration in the Xs axis direction of the sub-sensor coordinate system. As described above, the expression "angular velocity in the Zs axis direction" means "angular velocity around the Zs axis". The sub-sensor 6 has a function that combines a one-axis (Zs axis) angular velocity sensor and a one-axis (Xs axis) acceleration sensor. The internal structure of the sub-sensor 6 and the measurement principles of the angular velocity and the acceleration will be described later.

[0020] Fig. 3 shows a plan view of the inertial sensor 100. Fig. 3 is a view of the inertial sensor 100 seen along the Zd axis of the base coordinate system. The two blocks 4a and 4b are arranged along the first direction (the Xd axis direction of the base coordinate system) parallel to the reference plane 3 such that the inclined surfaces 5 face each other, and the remaining two blocks 4c and 4d are arranged along the second direction (the Yd axis direction) parallel to the reference plane 3 and perpendicular to the first direction such that the inclined surfaces 5 face each other. As described above, the inclined surface 5 is inclined with respect to the reference plane 3, and "such that the inclined surfaces 5 face each other" means that when viewed from the normal direction of the reference plane 3, the normals of the inclined surfaces 5 face in opposite directions to each other.

[0021] With the above-described arrangement of the four blocks 4 and the four sub-sensors 6, the inertial sensor 100 can measure the angular velocity components and acceleration components in three orthogonal directions (the directions of the Xd axis, Yd axis, and Zd axis of the base coordinate system). In other words, the inertial sensor 100 can measure the angular velocity vector and acceleration vector acting on itself in three-dimensional space for each component in three orthogonal directions.

[0022] Fig. 4 is a diagram for explaining the measurement principle of the angular velocity component. Fig. 4(a) is a schematic side view of the inertial sensor 100 seen from the direction along the Yd axis of the base coordinate system, and Fig. 4(b) is a schematic side view of the inertial sensor 100 seen from the direction along the Xd axis.

[0023] The symbols used in Fig. 4 will be explained. The symbol θ1 represents the angle (acute angle) formed by the inclined surface 5 of the block 4a and the reference plane 3. The same applies to θ2 - θ4. The symbols ωX, ωY, and ωZ represent the Xd axis component, Yd axis component, and Zd axis component of the angular velocity vector acting on the inertial sensor 100. The symbol S1 represents the magnitude of the angular velocity measured by the sub-sensor 6a, and the arrow of the symbol S1 represents the direction of the angular velocity measured by the sub-sensor 6a (the angular velocity around this arrow line). As described above, the sub-sensor 6a measures the angular velocity in the Zs axis direction of the sub-sensor coordinate system. That is, the arrow line of the symbol S1 is parallel to the Zs axis. The symbols S2 - S4 have the same meaning.

[0024] The inertial sensor 100 obtains angular velocity components S1, S2, S3, and S4 using four sub-sensors 6a-6d. From the geometric relationship in Figure 4, the following relationship (Equation 1) holds between the angular velocity components S1, S2, S3, and S4 measured by the four sub-sensors 6a-6d and the axial components ωX, ωY, and ωZ of the angular velocity vector acting on the inertial sensor 100.

[0025]

number

[0026] Equation (1) can be transformed into Equation (2) using matrix notation.

[0027]

number

[0028] According to (Equation 2), the inertial sensor 100 can obtain the orthogonal components (ωX, ωY, ωZ) of the angular velocity vector acting on the inertial sensor 100 from the measured values ​​[S1, S2, S3, S4] of the four sub-sensors 6a-6d.

[0029] Figure 5 illustrates the measurement principle of the acceleration component. Figure 5(a) is a schematic diagram of the inertial sensor 100 viewed from the direction along the Yd axis of the base coordinate system, and Figure 5(b) is a schematic diagram of the inertial sensor 100 viewed from the direction along the Xd axis.

[0030] The symbols used in Figure 5 are explained below. Symbols θ1-θ4 are the same as in Figure 4. Symbols GX, GY, and GZ represent the Xd, Yd, and Zd components of the acceleration vector acting on the inertial sensor 100. Symbol R1 represents the magnitude of the acceleration measured by the sub-sensor 6a, and the arrow of symbol R1 represents the direction of the acceleration measured by the sub-sensor 6a. As mentioned earlier, the sub-sensor 6a measures the acceleration in the Xs axis direction of the sub-sensor coordinate system. That is, the arrow line of symbol R1 is parallel to the Xs axis. Symbols R2-R4 have the same meaning.

[0031] The inertial sensor 100 obtains acceleration components R1, R2, R3, and R4 using four sub-sensors 6a-6d. From the geometric relationship in Figure 5, the following relationship (Equation 3) holds between the acceleration components R1, R2, R3, and R4 measured by the four sub-sensors 6a-6d and the axial components GX, GY, and GZ of the acceleration vector acting on the inertial sensor 100.

[0032]

number

[0033] Equation (3) can be transformed into the following Equation (4) using matrix notation.

[0034]

number

[0035] According to (Equation 4), the inertial sensor 100 can obtain the orthogonal components (GX, GY, GZ) of the acceleration vector acting on the inertial sensor 100 from the acceleration measurements [R1, R2, R3, R4] of the four sub-sensors 6a-6d.

[0036] As described above, the inertial sensor 100 can measure the components of the angular velocity vector and acceleration vector acting on it in the three orthogonal directions. In other words, the inertial sensor 100 can measure the angular velocity vector and acceleration vector acting on it.

[0037] The ability to obtain angular velocity and acceleration components in three orthogonal directions is due to setting the angular velocity direction and acceleration direction measured by the sub-sensor 6 (i.e., the Zs axis and Xs axis of the sub-sensor coordinate system) as shown in Figure 2.

[0038] Next, the structure of the sub-sensor 6 and the measurement principles of angular velocity and acceleration will be explained. Figure 6 shows a plan view of the internal structure of the sub-sensor 6. The coordinate system in the figure is the sub-sensor coordinate system XsYsZs. As mentioned earlier, the sub-sensor 6 can measure angular velocity in the Zs axis direction (angular velocity around the Zs axis) and acceleration in the Xs axis direction. In the figure, the angular velocity in the Zs axis direction is represented by the symbol Ω, and the acceleration in the Xs axis direction is represented by the symbol G.

[0039] The subsensor 6 is manufactured using MEMS (Micro Electro Mechanical Systems) technology. The structure shown in Figure 6 is mounted on a substrate in a package similar to that of a semiconductor device.

[0040] The subsensor 6 comprises a first weight 31 supported by four support beams 32 and a second weight 41 supported by four support beams 42. The hatching in the figure represents the part of the subsensor 6 that is fixed to the substrate (not shown) inside the package. One end of the support beams 32 (42) is fixed to the substrate, and the other end is connected to the first weight 31 (second weight 41). The support beams 32 (42) are flexible, and the first weight 31 (second weight 41) is displaced in accordance with the acceleration and angular velocity applied to the subsensor 6.

[0041] The first weight 31 can move within the Xs-Ys plane of the subsensor coordinate system, but is constrained in the Zs axis direction. Drive electrodes 33 (33p, 33n) are positioned on both sides of the first weight 31 in the Ys axis direction. The subscript "p" indicates the positive electrode, and the subscript "n" indicates the negative electrode. The positive drive electrode 33p is positioned on one side of the first weight 31 in the Ys axis direction, and the negative drive electrode 33n is positioned on the other side.

[0042] The first weight 31 is provided with weight electrodes (not shown) on its side so as to face each of the drive electrodes 33 (33p, 33n). When a voltage of a predetermined frequency is applied between the positive drive electrode 33p and the negative drive electrode 33n, an electrostatic attraction is generated between the drive electrode 33 and the weight electrodes, causing the first weight 31 to vibrate in the Ys axis direction at a predetermined frequency.

[0043] The same applies to the second mass 41; when a voltage of a predetermined frequency is applied between the positive drive electrode 43p and the negative drive power electrode 43n, the second mass 41 also vibrates in the Ys axis direction at a predetermined frequency. When the same frequency voltage is applied to the drive electrodes 33 (33p and 33n) and 43 (43p and 43n), the first mass 31 and the second mass 41 vibrate in opposite phases (with a phase difference of 180 degrees) in the Ys axis direction. The first mass 31 and the second mass 41 have the same shape and mass, and are aligned in the Ys axis direction of the subsensor coordinate system and connected by an elastic member 35. The elastic member 35 expands and contracts in the Ys axis direction. The first mass 31 and the second mass 41 connected by the elastic member 35 form a resonant system with a natural frequency. When a voltage that changes with the aforementioned natural frequency is applied to the drive electrode 33 and the drive electrode 43, the first weight 31 and the second weight 41 generate out-of-phase tuning fork vibrations that move in opposite directions to each other.

[0044] Detection electrodes 34 (positive electrode 34p and negative electrode 34n) are positioned on both sides of the first weight 31 in the Xs-axis direction, and weight electrodes (not shown) are provided on the sides of the first weight 31 in the Xs-axis direction, facing each of the detection electrodes 34 (34p, 34n). A capacitance exists between the detection electrodes 34 and the weight electrodes, and the capacitance changes depending on the distance between the detection electrodes 34 and the weight electrodes. When the first weight 31 is at rest, the distance D1P between the detection electrode positive electrode 34p and the first weight 31 is d0, and the distance D1N between the detection electrode negative electrode 34n and the first weight 31 is also d0.

[0045] Similarly, detection electrodes 44 (positive electrode 44p and negative electrode 44n) are positioned on both sides of the second weight 41 in the Xs-axis direction, and weight electrodes (not shown) are provided on the side of the second weight 41 in the Xs-axis direction, facing each of the detection electrodes 44 (44p, 44n). When the second weight 41 is at rest, the distance D2P between the detection electrode positive electrode 44p and the second weight 41 is d0, and the distance D2N between the detection electrode negative electrode 44n and the second weight 41 is also d0.

[0046] When an acceleration G in the +Xs direction is applied to the sub-sensor 6, the first weight 31 is displaced in the -Xs direction. If the displacement of the first weight 31 due to the acceleration G is represented by the symbol dG, then the distance D1P between the positive electrode 34p and the first weight 31 is d0-dG, and the distance D1N between the negative electrode 34n and the first weight 31 is d0+dG. The same applies to the second weight 41; the distance D2P between the positive electrode 44p and the second weight 41 is d0-dG, and the distance D2N between the negative electrode 44n and the second weight 41 is d0+dG.

[0047] When an angular velocity Ω around the Zs axis is applied to the subsensor 6, a Coriolis force is generated on the first mass 31, which is vibrating in the Ys axis direction at a predetermined frequency, and at a certain moment, the first mass 31 is displaced in the Xs axis direction. If the displacement of the first mass 31 due to the Coriolis force of angular velocity Ω is represented by the symbol dΩ, then the distance D1P between the positive electrode 34p and the first mass 31 is d0-dΩ, and the distance D1N between the negative electrode 34n and the first mass 31 is d0+dΩ. Since the second mass 41 vibrates in the opposite phase to the first mass 31, a Coriolis force acts on the second mass 41 in the opposite direction to the Coriolis force on the first mass 31. The distance D2P between the positive electrode 44p and the second mass 41 is d0+dΩ, and the distance D2N between the negative electrode 44n and the second mass 41 is d0-dΩ. Ultimately, the distances D1P, D1N, D2P, and D2N are given by the acceleration G in the Xs-axis direction and the angular velocity Ω in the Zs-axis direction as follows: D1P = d0 - dG - dΩ, D1N = d0 + dG + dΩ, D2P = d0 - dG + dΩ, and D2N = d0 + dG - dΩ, respectively (see Figure 6).

[0048] Even if angular velocity in the Xs-axis direction or Ys-axis direction acts on sub-sensor 6, it does not affect the distances D1P, D1N, D2P, and D2N. Similarly, even if acceleration in the Zs-axis direction or Ys-axis direction acts on sub-sensor 6, it does not affect the distances D1P, D1N, D2P, and D2N.

[0049] The circuit 50 of the sub-sensor 6 calculates the displacement dG due to acceleration G and the displacement dΩ due to angular velocity Ω from the above-mentioned D1P, D1N, D2P, and D2N. The circuit diagram of circuit 50 is shown in Figure 7. The distance between the detection electrode and the weight electrode (D1P, D1N, D2P, D2N) is measured as the voltage between the detection electrode and the weight electrode, and the voltage corresponding to each distance is input to circuit 50. However, here, for the sake of understanding, the operation of circuit 50 will be explained using the dimensions of distance (D1P, D1N, D2P, D2N). In addition, although circuit 50 is implemented in the package of the sub-sensor 6, the illustration of circuit 50 is omitted in Figure 1-6.

[0050] Circuit 50 has differencers 51, 52, and 53, and an adder 54. Differencer 51 receives distances D1P and D1N as inputs and outputs the difference between them (ΔD1 = D1N - D1P). Differencer 52 receives distances D2P and D2N as inputs and outputs the difference between them (ΔD2 = D2P - D2N). Differencer 53 receives the outputs of differencers 51 and 52, i.e., ΔD1 and ΔD2, and outputs their difference (ΔD1 - ΔD2 = 4dG). Adder 54 also receives the outputs of differencers 51 and 52, i.e., ΔD1 and ΔD2, and outputs their sum (ΔD2 + ΔD1 = 4dΩ). Although not shown in the diagram, circuit 50 is equipped with a multiplier that multiplies the output of differencer 53 by 0.25 and a multiplier that multiplies the output of adder 54 by 0.25. As a result, circuit 50 obtains the displacement dG caused by the acceleration G in the Xs axis direction and the displacement dΩ caused by the angular velocity in the Zs axis direction. A unique relationship exists between the acceleration G and the displacement dG, and a unique relationship also exists between the angular velocity Ω and the displacement dΩ. Although not shown in the diagram, circuit 50 uses these relationships to ultimately output the value of the acceleration G in the Xs axis direction and the value of the angular velocity Ω in the Zs axis direction.

[0051] In equations (1) and (2), [S1, S2, S3, S4] correspond to the angular velocity output Ω of the four sub-sensors 6a-6d. In equations (3) and (4), [R1, R2, R3, R4] correspond to the acceleration output G of the four sub-sensors 6a-6d. As mentioned earlier, the inertial sensor 100 can obtain the orthogonal components of the angular velocity vector and acceleration vector acting on the inertial sensor 100 from the outputs [S1, S2, S3, S4] and [R1, R2, R3, R4] of the four sub-sensors 6a-6d.

[0052] The sub-sensor 6 can simultaneously obtain acceleration G in the Xs axis direction and angular velocity Ω in the Zs axis direction from the displacement of two weights (first weight 31 and second weight 41). Therefore, theoretically, the direction of acceleration G strictly coincides with the Xs axis, and the direction of angular velocity Ω strictly coincides with the Zs axis. For this reason, the inertial sensor 100 has higher measurement accuracy compared to conventional inertial sensors that have acceleration sensors and angular velocity sensors separately. (If acceleration sensors and angular velocity sensors are provided separately, there is a risk that the measurement direction of acceleration G and the measurement direction of angular velocity Ω will not be strictly orthogonal. The inertial sensor ultimately outputs three components of the acceleration vector and angular velocity vector in a single coordinate system (base coordinate system) fixed to the base 2. If the measurement direction of the acceleration and the measurement direction of the angular velocity deviate from orthogonal, errors will occur when the acceleration and angular velocity are converted to values ​​in a single base coordinate system.)

[0053] The inertial sensor 100 employs a sub-sensor 6 that can simultaneously measure acceleration in the Xs axis direction and angular velocity in the Zs axis direction. In other words, the sub-sensor 6 has a sensitivity axis in the Xs axis direction for acceleration and a sensitivity axis in the Zs axis direction for angular velocity. Compared to inertial sensors that have separate acceleration and angular velocity sensors, the inertial sensor 100 can reduce manufacturing costs. Furthermore, the sub-sensor 6 can simultaneously measure acceleration and angular velocity by utilizing the opposite-phase resonance of two weights, and the measurement directions of acceleration and angular velocity are theoretically strictly orthogonal. Therefore, by employing such a sub-sensor 6, the measurement accuracy of the inertial sensor 100 is improved. The inertial sensor 100 is lower cost and more accurate than conventional sensors.

[0054] (Modified Version) Figure 8 shows a perspective view of a modified inertial sensor 200. The inertial sensor 200 comprises four blocks 4a-4d and four subsensors 6a-6d. Each block 4 and each subsensor 6 is the same as in the inertial sensor 100 of the embodiment. In the inertial sensor 200, the arrangement of the four blocks 4a-4d differs from that of the inertial sensor 100. In the inertial sensor 100, two blocks 4a and 4b are arranged along a first direction (Xd axis direction) parallel to the reference plane 3 so that their respective inclined surfaces 5 face each other, and the remaining two blocks 4c and 4d are arranged along a second direction (Yd axis direction) parallel to the reference plane 3 and perpendicular to the first direction (Xd axis direction), so that their respective inclined surfaces 5 face each other.

[0055] In the inertial sensor 200, two blocks 4a and 4b are arranged along a first direction (Xd axis direction) parallel to the reference plane 3, with their respective inclined surfaces 5 facing back to back. The remaining two blocks 4c and 4d are arranged along a second direction (Yd axis) parallel to the reference plane 3 and perpendicular to the first direction (Xd axis direction), with their respective inclined surfaces 5 facing back to back. Even with this arrangement, equations (1)-(4) hold true. Therefore, the inertial sensor 200 has the same effect as the inertial sensor 100.

[0056] The following points should be noted regarding the technology described in the examples. As can be understood from (Equation 1)-(Equation 4), the angles θ1, θ2, θ3, and θ4 may be the same value or may be different values.

[0057] The subsensor 6 is a vibration type that vibrates two weights (first weight 31 and second weight 41). The subsensor 6 excites the two weights (first weight 31 and second weight 41) in opposite phases in the Ys axis direction and measures the angular velocity in the Z axis direction and the acceleration in the Xs axis direction according to the displacement of each weight in the Xs axis direction. The two weights (first weight 31 and second weight 41) are aligned in the Ys axis direction and connected by an elastic member 35. The elastic member 35 expands and contracts in the Ys axis direction of the subsensor coordinate system. By connecting the two weights (first weight 31 and second weight 41) with the elastic member 35, the two weights (first weight 31 and second weight 41) resonate in exact opposite phases. By applying a voltage that changes at the resonant natural frequency of the two weights (first weight 31 and second weight 41) to the drive electrodes 33 and 43, the two weights resonate.

[0058] In the embodiment, the inertial sensors 100 and 200 are configured with the sub-sensor 6 arranged as shown in Figure 2 and the four blocks 4 arranged as shown in Figure 1 or Figure 8, enabling high-precision measurement of the orthogonal three-directional components of acceleration and angular velocity in three-dimensional space.

[0059] The circuit shown in Figure 7 is just one example; any circuit 50 that can derive dG and dΩ from four distances D1P, D1N, D2P, and D2N is acceptable.

[0060] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0061] 2: Base 3: Reference plane 4, 4a-4d: Block 5: Inclined surface 6, 6a-6d: Sub-sensor 31, 41: Weight 32, 42: Support beam 33, 43: Drive electrode 34, 44: Detection electrode 35: Elastic member 50: Circuit 51, 52, 53: Differencer 54: Adder 100, 200: Multi-axis inertial sensor

Claims

1. This is a multi-axis inertial sensor that measures angular velocity and acceleration components in three orthogonal directions. Four sub-sensors, which are fixed to the sub-sensors, measure the angular velocity in the Zs axis direction and the acceleration in the Xs axis direction of the local XsYsZs coordinate system, A base having a reference plane, Four blocks fixed to the aforementioned reference plane and having inclined surfaces that are inclined with respect to the aforementioned reference plane, It is equipped with, The subsensors are mounted on the inclined surface of each of the blocks such that the Zs axis coincides with the normal direction of the inclined surface and the Ys axis is parallel to the reference plane. (1) Two of the blocks are arranged along a first direction parallel to the reference plane such that their inclined surfaces face each other, and the remaining two blocks are arranged along a second direction parallel to the reference plane and perpendicular to the first direction such that their inclined surfaces face each other. or (2) Two of the blocks are arranged along a first direction parallel to the reference plane such that their inclined surfaces are back to back, and the remaining two blocks are arranged along a second direction parallel to the reference plane and perpendicular to the first direction such that their inclined surfaces are back to back. Multi-axis inertial sensor.

2. The multi-axis inertial sensor according to claim 1, wherein the subsensor is of the vibration type that vibrates two weights, and the two weights are excited in opposite phases in the Ys axis direction, and the angular velocity in the Z axis direction and the acceleration in the Xs axis direction are measured according to the displacement of the weights in the Xs axis direction of the local XsYsZs coordinate system.

3. The multi-axis inertial sensor according to claim 2, wherein the two weights are aligned in the Ys axis direction and connected by an elastic member.

Images