CN117929786A - Light interference type micro-integrated triaxial acceleration sensing structure and resolving method thereof - Google Patents

Abstract

The invention provides an optical interference type micro-integrated triaxial acceleration sensing structure and a resolving method thereof, wherein the optical interference type micro-integrated triaxial acceleration sensing structure comprises a triaxial acceleration synchronous sensitive structure, an array grating structure and a photoelectric detection array structure which are sequentially arranged from bottom to top; the triaxial acceleration synchronous sensitive structure comprises a fixed frame, a special sensitive elastic beam, a stepped mass block and a reflective film. Has the following advantages: (1) The design responds to and realizes 3 axial acceleration measurements simultaneously by a single sensitive structure, and compared with a conventional sensing system with an array integrated 3-direction acceleration sensing unit, the integration level is further improved. In addition, the measurement result of the invention is more accurate. (2) And an arrayed sensing structure for detecting multi-site displacement on the sensitive structure is constructed by adopting a grating interference type displacement measurement method and combining an array grating structure and a photoelectric detection array structure, so that the integration level of the whole triaxial acceleration sensing module is further improved.

Description

An optical interferometric micro-integrated three-axis acceleration sensor structure and its solution method

Technical Field

The present invention relates to an optical interference type three-axis acceleration sensor structure, and in particular to an optical interference type micro-integrated three-axis acceleration sensor structure and a solution method thereof.

Background technique

At present, the inertial navigation module with 3-axis acceleration sensor as an important component has a wide range of application needs in the fields of aviation, intelligent machinery, consumer electronics, etc. By measuring the 3-axis acceleration of the moving object, further combining other motion parameter measurements, integrating and solving important information such as the posture, speed and displacement of the moving object, and further completing tasks such as motion trajectory planning and stability control with motion information feedback, it plays an important role in realizing autonomous navigation and intelligent control of sports equipment.

The new acceleration sensing technology based on optical measurement methods has the advantages of high sensitivity, low noise, and non-contact response. In particular, the combination of high-sensitivity optical interference displacement measurement methods and elastic beam-mass acceleration sensitive structures has become an important direction for the development of high-sensitivity acceleration sensors. However, compared with the more mature micro-electromechanical system (MEMS) electrical acceleration sensors, the current optical interference acceleration sensors still have gaps in miniaturization and integrated applications. First, the conventional optical interference displacement measurement is based on the interference optical path and the optical elements that form the optical path in a certain space. It is not easy to integrate with the mainstream silicon-based micro-sensitive structure, so the integration of a single acceleration sensor element is limited. On the other hand, the optical interference displacement measurement principle currently used for optical interference micro-acceleration sensors is only sensitive to the out-of-plane displacement of the sensitive structure, which is convenient for the acceleration sensor to be applied to the acceleration detection in a single z-axis direction, that is, the normal direction of the mass block. There are also studies on the use of optical interference measurement methods for displacement measurement generated by acceleration in the response plane of sensitive structures, but the detection optical path must be aligned with the vertical side plane of the sensitive structure to also achieve the measurement of out-of-plane response displacement. This type of method still limits the integration of sensor elements. The integration level of acceleration sensor elements used in a single axis is limited, and it is even more difficult to realize a micro-integrated sensing system that can measure acceleration in three axes simultaneously.

Summary of the invention

In view of the defects in the prior art, the present invention provides an optical interference micro-integrated three-axis acceleration sensor structure and a solution method thereof, which can effectively solve the above problems.

The technical solution adopted by the present invention is as follows:

The present invention provides an optical interference type micro-integrated three-axis acceleration sensing structure, comprising a three-axis acceleration synchronous sensitive structure, an array grating structure and a photoelectric detection array structure arranged in sequence from bottom to top;

The three-axis acceleration synchronous sensitive structure comprises a fixed frame (1), a specific sensitive elastic beam (2), a stepped mass block (3) and a reflective film (4); wherein the specific sensitive elastic beam (2) is provided in four numbers, namely a first specific sensitive elastic beam, a second specific sensitive elastic beam, a third specific sensitive elastic beam and a fourth specific sensitive elastic beam; and the reflective film (4) is provided in four numbers, namely a first reflective film, a second reflective film, a third reflective film and a fourth reflective film;

The fixed frame (1) is internally suspended with the stepped mass block (3); the upper surface edge X positive position of the stepped mass block (3) is connected to the fixed frame (1) via the first specifically sensitive elastic beam; the upper surface edge X negative position of the stepped mass block (3) is connected to the fixed frame (1) via the second specifically sensitive elastic beam; the upper surface edge Y positive position of the stepped mass block (3) is connected to the fixed frame (1) via the third specifically sensitive elastic beam; the upper surface of the stepped mass block (3) is connected to the fixed frame (1) via the third specifically sensitive elastic beam. The edge Y negative point is connected to the fixed frame (1) through the fourth specific sensitive elastic beam; the four specific sensitive elastic beams (2) are distributed in orthogonal directions in the plane, and are symmetrical with respect to the center of the projection point of the center of gravity of the stepped mass block (3) on the upper surface; on the upper surface of the stepped mass block (3), a first reflective film covering the area around the X positive point, a second reflective film covering the area around the X negative point, a third reflective film covering the area around the Y positive point, and a fourth reflective film covering the area around the Y negative point are arranged;

The array grating structure comprises a grating substrate (5) and a grating (6); the number of gratings (6) is four, namely a first grating, a second grating, a third grating and a fourth grating; the grating substrate (5) is fixedly mounted above the three-axis acceleration synchronous sensitive structure, the first grating is arranged on the surface of the grating substrate (5) facing the three-axis acceleration synchronous sensitive structure and on the surface facing the first reflective film, the second grating is arranged on the surface facing the second reflective film, the third grating is arranged on the surface facing the third reflective film, and the fourth grating is arranged on the surface facing the fourth reflective film;

The photoelectric detection array structure comprises a photoelectric substrate (7), a first laser, a first light detector, a second laser, a second light detector, a third laser, a third light detector, a fourth laser and a fourth light detector; the photoelectric substrate (7) is arranged above the grating substrate (5), and a parallel cavity is formed between the photoelectric substrate (7) and the grating substrate (5); the first laser is arranged on the surface of the photoelectric substrate (7) facing the grating substrate (5) and on the surface facing the first reflective film, the first light detector is arranged at the diffracted reflected light position of the first grating, the second laser is arranged on the surface facing the second reflective film, the second light detector is arranged at the diffracted reflected light position of the second grating, the third laser is arranged on the surface facing the third reflective film, the third light detector is arranged at the diffracted reflected light position of the third grating, the fourth laser is arranged on the surface facing the fourth reflective film, and the fourth light detector is arranged at the diffracted reflected light position of the fourth grating.

Preferably, one end of each of the specifically sensitive elastic beams (2) is connected and fixed to the fixed frame (1), and the other end of each of the specifically sensitive elastic beams (2) is connected and fixed to a corresponding position of the upper surface edge of the stepped mass block (3).

Preferably, the specifically sensitive elastic beam (2) is composed of folded elastic beams symmetrical on both sides, and the connection with the stepped mass block (3) is a separate part of the folded elastic beams on both sides, with two connection points, and the distance between the connection points is not greater than 1/10 of the size of the upper surface of the stepped mass block (3), and the vertical thickness of each straight beam section in the specifically sensitive elastic beam (2) is not greater than 1/10 of the width.

Preferably, the specifically sensitive elastic beam (2) has a direction from a connection with the fixed frame (1) to a connection with the stepped mass block (3) as an axial direction, and in a plane where the specifically sensitive elastic beam (2) is located, a direction perpendicular to the axial direction is a lateral direction; and a direction perpendicular to the plane where the specifically sensitive elastic beam (2) is located is a normal direction;

With respect to normal bending deformation, the folded elastic beams on both sides are connected in parallel, so that the specifically sensitive elastic beam (2) exhibits a certain bending stiffness;

With respect to transverse bending deformation, the folded elastic beams on both sides are insensitive to transverse bending, and the specifically sensitive elastic beams (2) formed can neglect transverse bending deformation under normal loads;

With respect to torsional deformation, the folded elastic beams on both sides are connected in series, and because the distance between the discrete connection points of each beam and the stepped mass block (3) is small, the torsional stiffness of the formed specific sensitive elastic beam (2) relative to the torsional angle is extremely small;

With respect to axial deformation, since the thickness of each straight beam section in the folded elastic beam is much smaller than the width, the normal bending stiffness thereof is much smaller than the transverse bending stiffness, and the axial deformation stiffness of the constructed specific sensitive elastic beam (2) is much greater than the normal bending stiffness.

Preferably, the stepped mass block (3) comprises, from top to bottom, a reflective surface reinforcement step (301), a connecting step (302) and a sinking step (303);

The upper surface of the reflective surface reinforcement step (301) is connected to the specific sensitive elastic beam (2) and has a certain thickness to ensure that the surface of the connection point area is flat when subjected to the force of the specific sensitive elastic beam (2);

The horizontal cross-sectional dimension of the connecting step (302) is smaller than that of the reflective surface reinforcing step (301) and the sinking step (303);

The horizontal cross-sectional dimension of the sunken step (303) is larger than that of the reflective surface reinforcing step (301).

Preferably, the planar shape of the stepped mass block (3) is an axisymmetric shape relative to the orthogonal directions of the four specific sensitive elastic beams (2).

Preferably, the fixed frame (1), the specific sensitive elastic beam (2) and the reflective surface reinforcement step (301) in the stepped mass block (3) are an integrated structure manufactured on the same substrate, and the material is an elastic material.

Preferably, the grating substrate (5) is a light-transmitting bottom plate, and the grating (6) is a one-dimensional grating; the grating stripes of the first grating, the second grating, the third grating and the fourth grating are staggered at a certain angle.

The present invention also provides a solution method based on the optical interference micro-integrated three-axis acceleration sensor structure, comprising the following steps:

Step 1, connecting the first laser, the first photodetector, the second laser, the second photodetector, the third laser, the third photodetector, the fourth laser and the fourth photodetector to a photoelectric detection circuit;

The first reflective film and the first grating just above it constitute a first grating interference cavity; the second reflective film and the second grating just above it constitute a second grating interference cavity; the third reflective film and the third grating just above it constitute a third grating interference cavity; the fourth reflective film and the fourth grating just above it constitute a fourth grating interference cavity;

Step 2, the optical interference micro-integrated three-axis acceleration sensor structure is powered on; each laser and photodetector works simultaneously, the first laser emits a coherent light source, reaches the first grating interference cavity and is reflected and diffracted and received by the first photodetector, the first photodetector measures an interference light signal, and outputs an X forward voltage signal Vx ₊ through a photoelectric detection circuit; wherein the interference light signal measured by the first photodetector represents the normal displacement of the X forward position of the upper surface edge of the stepped mass block (3);

At the same time, the second laser emits a coherent light source, which reaches the second grating interference cavity and is reflected and diffracted and received by the second light detector. The second light detector measures an interference light signal and outputs an X-negative voltage signal V _x- through a photoelectric detection circuit. The interference light signal measured by the second light detector represents the normal displacement of the X-negative position of the upper surface edge of the stepped mass block (3).

At the same time, the third laser emits a coherent light source, which reaches the third grating interference cavity and is received by the third light detector after reflection and diffraction. The third light detector measures an interference light signal and outputs a Y forward voltage signal V _y+ through a photoelectric detection circuit. The interference light signal measured by the third light detector represents the normal displacement of the Y forward position of the upper surface edge of the stepped mass block (3).

At the same time, the fourth laser emits a coherent light source, which reaches the fourth grating interference cavity and is received by the fourth light detector after reflection and diffraction. The fourth light detector measures an interference light signal and outputs a Y negative voltage signal V _y- through a photoelectric detection circuit. The interference light signal measured by the fourth light detector represents the normal displacement of the Y negative position of the upper surface edge of the stepped mass block (3).

Step 3, respectively solving the X positive voltage signal Vx ₊ , the X negative voltage signal _Vx- , the Y positive voltage signal _Vy+ and the Y negative voltage signal _Vy- , to obtain the normal displacement measurement value Sx ₊ of the X positive point, the normal displacement measurement value Sx- of the X negative point, the normal displacement measurement value _Sy+ of the Y positive point and the normal displacement measurement value Sy- of the Y negative point on the upper surface edge of the stepped mass block ( _{3 )} ;

Step 4: Pre-calibrate and measure to obtain the mapping matrix K between the three-axis acceleration to be measured and the normal displacement of each directional site. According to the following formula, the normal displacement measurement value of each directional site is solved to obtain the three-axis acceleration measurement value, including: X-axis acceleration measurement value _Ax , Y-axis acceleration measurement value _Ay and Z-axis acceleration measurement value _Az :

in:

k _x+ is the proportional coefficient of the displacement S _x+ of the positive position on the surface of the step-type mass block produced by the X-axis acceleration measurement value A _x ; k _x- is the proportional coefficient of the displacement S _x- of the negative position on the surface of the step-type mass block produced by the X-axis acceleration measurement value A _x ; k _zx+ is the proportional coefficient of the displacement S x+ of the positive position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; k _zx- is the proportional coefficient of the displacement S _x- of the negative position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; _ky+ is the proportional coefficient of the displacement S _y + of the positive position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A _y ; _ky- is the proportional coefficient of the displacement S _y- of the negative position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A _y ; k _zy- is the proportional coefficient of the displacement S _y- of the negative position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; k _zy+ is the proportional coefficient of the displacement S _y + of the positive position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A y; The _z action produces a proportional coefficient of the Y positive position displacement _Sy+ on the upper surface of the stepped mass block.

The optical interference micro-integrated three-axis acceleration sensor structure and its solution method provided by the present invention have the following advantages:

(1) The acceleration sensitive structure composed of a specific sensitive elastic beam and a stepped mass block responds to three-axis accelerations simultaneously and converts them into normal displacements on the upper surface of the mass block. Then, the displacements of different points on the upper surface of the mass block are measured by combining a non-contact optical interference displacement measurement method that can measure point displacements. The multiple measurement data obtained at the same time are synchronously solved to obtain acceleration measurement values in three axes. This design uses a single sensitive structure to respond to and realize acceleration measurement in three axes at the same time, which further improves the integration level compared to the conventional array-integrated three-directional acceleration sensor unit sensing system. In addition, the measurement results of the present invention are more accurate.

(2) The grating interferometry displacement measurement method is adopted, and the array grating structure and the photoelectric detection array structure are combined to construct an array sensing structure for detecting multi-point displacement on the sensitive structure, thereby further improving the integration of the entire three-axis acceleration sensor module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a cross-sectional view of an optical interference micro-integrated three-axis acceleration sensor structure provided by the present invention;

FIG2 is a top view of a three-axis acceleration synchronous sensing structure provided by the present invention;

FIG3 is a cross-sectional view of a three-axis acceleration synchronous sensitive structure provided by the present invention;

FIG4 is a schematic diagram of deformation of a specific sensitive elastic beam provided by the present invention;

FIG5 is a schematic diagram of the principle of a three-axis acceleration synchronous sensing structure provided by the present invention;

FIG6 is a bottom view of the array grating structure provided by the present invention;

FIG7 is a schematic diagram of a three-axis acceleration calculation method provided by the present invention;

FIG8 is a schematic diagram of four displacement measurement sites in the three-axis acceleration solution method of the present invention.

In the figure: 1—fixed frame; 2—specific sensitive elastic beam; 3—stepped mass block; 301—reflective surface reinforcement step; 302—connecting step; 303—sunken step; 4—reflective film; 5—grating substrate; 6—grating; 7—photoelectric substrate; 8—laser; 9—photodetector.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

The present invention provides an optical interference micro-integrated three-axis acceleration sensing structure, as shown in FIG1 , comprising a three-axis acceleration synchronous sensitive structure, an array grating structure and a photoelectric detection array structure arranged sequentially from bottom to top.

In the present invention, as shown in FIG. 2 and FIG. 3, the three-axis acceleration synchronous sensitive structure includes a fixed frame 1, a specific sensitive elastic beam 2, a stepped mass block 3 and a reflective film 4; wherein the number of the specific sensitive elastic beams 2 is four, namely, a first specific sensitive elastic beam, a second specific sensitive elastic beam, a third specific sensitive elastic beam and a fourth specific sensitive elastic beam; the number of the reflective films 4 is four, namely, a first reflective film, a second reflective film, a third reflective film and a fourth reflective film;

The stepped mass block 3 is suspended inside the fixed frame 1, and the positive position X of the upper surface edge of the stepped mass block 3 is connected to the fixed frame 1 through the first specific sensitive elastic beam, the negative position X of the upper surface edge of the stepped mass block 3 is connected to the fixed frame 1 through the second specific sensitive elastic beam, the positive position Y of the upper surface edge of the stepped mass block 3 is connected to the fixed frame 1 through the third specific sensitive elastic beam, and the negative position Y of the upper surface edge of the stepped mass block 3 is connected to the fixed frame 1 through the fourth specific sensitive elastic beam; therefore, one end of each of the specific sensitive elastic beams 2 is connected and fixed to the fixed frame 1, and the other end of each of the specific sensitive elastic beams 2 is connected and fixed to the corresponding position of the upper surface edge of the stepped mass block 3.

The four specifically sensitive elastic beams 2 are distributed in orthogonal directions in the plane, and are symmetrical with respect to the center of the projection point of the center of gravity of the stepped mass block 3 on the upper surface; on the upper surface of the stepped mass block 3, a first reflective film covering the area around the X positive direction site, a second reflective film covering the area around the X negative direction site, a third reflective film covering the area around the Y positive direction site, and a fourth reflective film covering the area around the Y negative direction site are provided; wherein the area around each direction site is the connection area between the stepped mass block 3 and each specifically sensitive elastic beam.

Specifically, the specifically sensitive elastic beam 2 is composed of folded elastic beams that are symmetrical on both sides, and the connection with the stepped mass block 3 is a discrete part of the folded elastic beams on both sides, with two connection points, and the distance between the connection points is not greater than 1/10 of the size of the upper surface of the stepped mass block 3, and the vertical thickness of each straight beam section in the specifically sensitive elastic beam 2 is not greater than 1/10 of the width.

The stiffness characteristics of the specific sensitive elastic beam 2 of the present invention in various directions are shown in FIG4 : the overall specific sensitive elastic beam 2 takes the direction from the connection with the fixed frame 1 to the connection with the stepped mass block 3 as the axial direction, and in the plane where the specific sensitive elastic beam 2 is located, the direction perpendicular to the axial direction is the lateral direction; the direction perpendicular to the plane where the specific sensitive elastic beam 2 is located is the normal direction;

For normal bending deformation, the folded elastic beams on both sides are connected in parallel, and the formed specific sensitive elastic beam 2 exhibits a certain bending stiffness; for lateral bending deformation, the folded elastic beams on both sides are insensitive to lateral bending, and the formed specific sensitive elastic beam 2 can ignore the lateral bending deformation under normal load; for torsional deformation, the folded elastic beams on both sides are connected in series, and since the distance between each discrete connection point with the stepped mass block 3 is very small, the formed specific sensitive elastic beam 2 has extremely small torsional stiffness relative to the torsion angle; for axial deformation, since the thickness of each straight beam section in the folded elastic beam is much smaller than the width, the normal bending stiffness itself is much smaller than the lateral bending stiffness, and the axial deformation stiffness of the formed specific sensitive elastic beam 2 is much greater than the normal bending stiffness.

In the present invention, the stepped mass block 3 includes, from top to bottom, a reflective surface reinforcement step 301, a connecting step 302 and a sinking step 303;

The upper surface of the reflective surface reinforcing step 301 is connected to the specific sensitive elastic beam 2 and has a certain thickness to ensure that the surface of the connection point area is flat when subjected to the force of the specific sensitive elastic beam 2;

The horizontal cross-sectional dimension of the connecting step 302 is smaller than that of the light-reflecting surface reinforcing step 301 and the sinking step 303; the horizontal cross-sectional dimension of the sinking step 303 is larger than that of the light-reflecting surface reinforcing step 301. Therefore, the connecting step 302 with a smaller horizontal cross-sectional dimension connects the light-reflecting surface reinforcing step 301 and the sinking step 303, and the sinking step 303 has a larger horizontal cross-sectional dimension and thickness to lower the center of gravity position of the stepped mass block 3.

The planar shape of the stepped mass block 3 is an axisymmetric shape relative to the orthogonal directions of the four specific sensitive elastic beams 2 , for example, it can be a square, a regular octagon, a circle, etc.

In the present invention, at least the fixed frame 1, the specific sensitive elastic beam 2 and the reflective surface reinforcement step 301 in the stepped mass block 3 in the three-axis acceleration synchronous sensitive structure are an integrated structure processed and manufactured on the same substrate, and the material can be high-quality elastic materials such as silicon and metal.

The principle of the three-axis acceleration synchronous sensitive structure of the present invention is shown in FIG5. When the z-axis acceleration in the vertical direction acts on the sensitive structure, the normal inertial force acts on the stepped mass block. To achieve balance, the four specific sensitive elastic beams are bent in the same direction, and the upper surface of the stepped mass block produces a normal translation. When the x-axis (y-axis) acceleration in the planar direction acts on the sensitive structure, the lateral inertial force acts on the lower center of gravity of the stepped mass block. To achieve balance, the two relative specific sensitive elastic beams in the x-axis (y-axis) direction are bent in the opposite direction, and a reverse force is applied at the two edge connections on the upper surface of the stepped mass block to form a moment balance with the lateral inertial force. At the same time, the two y-axis (x-axis) directions are bent in the opposite direction. The two relative specific sensitive elastic beams exert a force in the opposite direction to the lateral inertial force at the two edge connections with the upper surface of the step-type mass block. However, since the specific sensitive elastic beams are insensitive to the lateral force, the lateral bending deformation can be ignored. The upper surface of the step-type mass block rotates around the y-axis (x-axis). At this time, since the torsional stiffness of the two relative specific sensitive elastic beams in the y-axis (x-axis) direction is extremely low, the torsional moment of the two relative specific sensitive elastic beams in the y-axis (x-axis) direction generated by the rotation of the step-type mass block can be ignored. Finally, opposite normal displacements are generated at the connection between the upper surface of the step-type mass block and the two relative specific sensitive elastic beams in the x-axis (y-axis) direction.

The array grating structure of the present invention comprises a grating substrate 5 and a grating 6; as shown in FIG6 , the number of gratings 6 is four, namely, a first grating, a second grating, a third grating and a fourth grating; the grating stripes of the first grating, the second grating, the third grating and the fourth grating are staggered at a certain angle. The grating substrate 5 is fixedly mounted above the three-axis acceleration synchronous sensitive structure, and the first grating is arranged on the surface of the grating substrate 5 facing the three-axis acceleration synchronous sensitive structure and on the surface facing the first reflective film, the second grating is arranged on the surface facing the second reflective film, the third grating is arranged on the surface facing the third reflective film, and the fourth grating is arranged on the surface facing the fourth reflective film;

Specifically, the grating substrate 5 is a light-transmitting bottom plate, and the grating 6 is a semi-transparent and semi-reflective one-dimensional diffraction grating on the surface of the grating substrate facing the three-axis acceleration synchronous sensitive structure, and is divided into four areas corresponding to the four specific sensitive elastic beam connection areas on the upper surface of the step-type mass block in the three-axis acceleration synchronous sensitive structure. The grating stripes in each area are staggered by a certain angle, presenting a grating array that can stagger each diffraction plane, and a parallel cavity is formed between the lower surface of the array grating structure and the upper surface of the step-type mass block in the three-axis acceleration synchronous sensitive structure opposite thereto, with the grating substrate 5 or the fixed frame 1 providing a support structure at the edge to form a parallel cavity.

The photoelectric detection array structure of the present invention includes a photoelectric substrate 7, a first laser, a first photodetector, a second laser, a second photodetector, a third laser, a third photodetector, a fourth laser and a fourth photodetector;

The photoelectric substrate 7 is arranged above the grating substrate 5, and a parallel cavity is formed between the photoelectric substrate 7 and the grating substrate 5; the first laser is arranged on the surface of the photoelectric substrate 7 facing the grating substrate 5 and on the surface facing the first reflective film, the first light detector is arranged at the diffraction reflection light position of the first grating, the second laser is arranged on the surface facing the second reflective film, the second light detector is arranged at the diffraction reflection light position of the second grating, the third laser is arranged on the surface facing the third reflective film, the third light detector is arranged at the diffraction reflection light position of the third grating, the fourth laser is arranged on the surface facing the fourth reflective film, and the fourth light detector is arranged at the diffraction reflection light position of the fourth grating.

Specifically, each group of lasers 8 and photodetectors 9 is mounted on a photoelectric assembly plane of a photoelectric substrate 7 facing the array grating structure and electrically connected, and a parallel cavity is formed between the photoelectric assembly plane and the upper surface of the relative grating substrate by providing a supporting structure at the edge of the photoelectric substrate 7; a total of 4 groups of lasers 8 and photodetectors 9 constitute an array, and each laser 8 is perpendicular to the reflective film 4 in the connection area between the stepped mass block 3 and the specific sensitive elastic beam 2 in the three-axis acceleration synchronous sensitive structure, and each photodetector 9 is located at a position to receive the reflected light diffracted by the one-dimensional grating facing the area.

In the micro-integrated three-axis acceleration sensor structure of the present invention, the assembly of each layer structure can be achieved by using a microstructure bonding process, or by using a conventional bonding or other mechanical assembly process.

The overall sensing principle of the micro-integrated three-axis acceleration sensing structure of the present invention is as follows: combined with the principle of the above-mentioned three-axis acceleration synchronous sensitive structure, the accelerations of the three axes are converted by the sensitive structure into normal displacements of the connection points between the upper surface of the stepped mass block and the four specific sensitive elastic beams. The reflective films in the four connection areas and the one-dimensional grating directly above constitute a typical grating interference cavity, and then combined with the lasers and detectors corresponding to each area in the array to form a typical grating interference measurement structure. The coherent light emitted by the laser reaches the grating interference cavity and is reflected and diffracted and received by the corresponding light detector. The interference light intensity signal measured by the light detector is modulated by the cavity length of the grating interference cavity. Combined with the fixed grating plane, the interference light intensity signal measured by the light detectors in the four arrays can characterize the normal displacements of the four edge areas of the stepped mass block.

The synchronous calculation method of the three-axis acceleration based on the sensor signal of the micro-integrated three-axis acceleration sensor structure of the present invention is shown in FIG7 , and is specifically as follows:

Step 1, connect the first laser, the first light detector, the second laser, the second light detector, the third laser, the third light detector, the fourth laser and the fourth light detector to a photoelectric detection circuit; the photoelectric detection circuit is a conventional photoelectric detection circuit, including a laser driving circuit, a light detector signal conversion circuit, and necessary signal conditioning circuits and power supply voltage stabilization circuits.

The first reflective film and the first grating just above it constitute a first grating interference cavity; the second reflective film and the second grating just above it constitute a second grating interference cavity; the third reflective film and the third grating just above it constitute a third grating interference cavity; the fourth reflective film and the fourth grating just above it constitute a fourth grating interference cavity;

Step 2, the optical interference micro-integrated three-axis acceleration sensor structure is powered on; when the power is turned on, each laser emits a coherent light source, and the corresponding four detectors receive the returned interference light signal of the grating interference cavity length at each point, and output four voltage signals, Vx ₊ , _Vx- , Vy ₊ , and _Vy- , through the detection circuit.

Specifically, each laser and photodetector works simultaneously, the first laser emits a coherent light source, reaches the first grating interference cavity and is reflected and diffracted and received by the first photodetector, the first photodetector measures an interference light signal, and outputs an X forward voltage signal V _x+ through a photoelectric detection circuit; wherein the interference light signal measured by the first photodetector represents the normal displacement of the X forward position of the upper surface edge of the stepped mass block 3;

At the same time, the second laser emits a coherent light source, which reaches the second grating interference cavity and is received by the second light detector after reflection and diffraction. The second light detector measures the interference light signal and outputs the X negative voltage signal V _x- through the photoelectric detection circuit. The interference light signal measured by the second light detector represents the normal displacement of the X negative position of the upper surface edge of the stepped mass block 3.

At the same time, the third laser emits a coherent light source, which reaches the third grating interference cavity and is received by the third light detector after reflection and diffraction. The third light detector measures the interference light signal and outputs the Y forward voltage signal V _y+ through the photoelectric detection circuit. The interference light signal measured by the third light detector represents the normal displacement of the Y forward position of the upper surface edge of the stepped mass block 3.

At the same time, the fourth laser emits a coherent light source, which reaches the fourth grating interference cavity and is received by the fourth light detector after reflection and diffraction. The fourth light detector measures an interference light signal, and outputs a Y negative voltage signal V _y- through a photoelectric detection circuit. The interference light signal measured by the fourth light detector represents the normal displacement of the Y negative position of the upper surface edge of the stepped mass block 3.

Step 3, respectively solving the X positive voltage signal V _x+ , the X negative voltage signal V _x- , the Y positive voltage signal V _y+ , and the Y negative voltage signal V _y- , to obtain the normal displacement measurement value S _{x+ of the X positive point, the normal displacement measurement value S x-} of the X negative point, the normal displacement measurement value S _{y +} of the Y positive point, and the normal displacement measurement value S _y- of the Y negative point on the upper surface edge of the stepped mass block 3;

As shown in Figure 8, since the four voltage signals Vx ₊ , _Vx- , Vy ₊ , and _Vy- are the normal displacement measurement signals corresponding to the four positions x+, x-, y+, and y- on the upper surface of the stepped mass block, respectively, the normal displacement measurement values Sx ₊ , _Sx- , _Sy+ , and _Sy- of the four positions are calculated by combining the four voltage signals Vx ₊ , _Vx- , Vy ₊ , and _Vy- with the previous calibration data of the sensor.

Specifically, the method for calculating the measured displacement by outputting the voltage signal adopts a conventional grating interferometric displacement sensor signal calculation method, which will not be described in detail here.

Step 4: Calculate the triaxial acceleration measurement values from the normal displacement measurements at the four locations:

The pre-calibration measurement obtains the mapping matrix K between the three-axis acceleration to be measured and the normal displacement of each position. Specifically, according to the sensitive theory of the three-axis acceleration synchronous sensitive structure and the experimental calibration method, the mapping matrix K between the three-axis acceleration to be measured and the normal displacement measurement values S _x+ , S _x- , Sy ₊ , _Sy- of the four positions is obtained:

Specifically, the mapping matrix K is based on the sensitive principle of the three-axis acceleration synchronous sensitive structure and the stiffness characteristics of the specific sensitive elastic beam therein. The accelerations in the three axes mainly cause the normal bending deformations of the specific sensitive elastic beams in four orthogonal directions through the step-type mass block, corresponding to the normal displacements of the connection points between each specific sensitive elastic beam and the edge of the step-type mass block. In addition, within the elastic deformation range of each specific sensitive elastic beam, the effects produced by the three axial accelerations are approximately in a linear superposition relationship, as shown in the following equation.

in:

k _x+ is the proportional coefficient of the displacement S _x+ of the positive position on the surface of the step-type mass block produced by the X-axis acceleration measurement value A _x ; k _x- is the proportional coefficient of the displacement S _x- of the negative position on the surface of the step-type mass block produced by the X-axis acceleration measurement value A _x ; k _zx+ is the proportional coefficient of the displacement S x+ of the positive position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; k _zx- is the proportional coefficient of the displacement S _x- of the negative position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; _ky+ is the proportional coefficient of the displacement S _y + of the positive position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A _y ; _ky- is the proportional coefficient of the displacement S _y- of the negative position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A _y ; k _zy- is the proportional coefficient of the displacement S _y- of the negative position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; k _zy+ is the proportional coefficient of the displacement S _y + of the positive position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A y; The _z action produces the proportional coefficient of the Y positive position displacement _Sy+ on the upper surface of the stepped mass block.

According to the above formula, the normal displacement measurement values of each directional point are solved to obtain the three-axis acceleration measurement values, including: X-axis acceleration measurement value A _x , Y-axis acceleration measurement value A _y and Z-axis acceleration measurement value A _z .

All calculation operations in the above steps (3) and (4) are performed in a computer, single-chip microcomputer or other device having the required digital signal processing operation function.

The optical interference type micro-integrated three-axis acceleration sensor structure and its solution method of the present invention have the following advantages:

(1) The acceleration sensitive structure composed of a specific sensitive elastic beam and a stepped mass block responds to three-axis accelerations simultaneously and converts them into normal displacements on the upper surface of the mass block. Then, the displacements of different points on the upper surface of the mass block are measured by combining a non-contact optical interference displacement measurement method that can measure point displacements. The multiple measurement data obtained at the same time are synchronously solved to obtain acceleration measurement values in three axes. This design uses a single sensitive structure to respond to and realize acceleration measurement in three axes at the same time, which further improves the integration level compared to the conventional array-integrated three-directional acceleration sensor unit sensing system. In addition, the measurement results of the present invention are more accurate.

(2) The grating interferometry displacement measurement method is adopted, and the array grating structure and the photoelectric detection array structure are combined to construct an array sensing structure for detecting multi-point displacement on the sensitive structure, thereby further improving the integration of the entire three-axis acceleration sensor module.

The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention.

Claims (9)

1. An optical interference micro-integrated three-axis acceleration sensing structure, characterized in that it includes a three-axis acceleration synchronous sensitive structure, an array grating structure and a photoelectric detection array structure arranged in sequence from bottom to top; The three-axis acceleration synchronous sensitive structure comprises a fixed frame (1), a specific sensitive elastic beam (2), a stepped mass block (3) and a reflective film (4); wherein the specific sensitive elastic beam (2) is provided in four numbers, namely a first specific sensitive elastic beam, a second specific sensitive elastic beam, a third specific sensitive elastic beam and a fourth specific sensitive elastic beam; and the reflective film (4) is provided in four numbers, namely a first reflective film, a second reflective film, a third reflective film and a fourth reflective film; The fixed frame (1) is internally suspended with the stepped mass block (3); the upper surface edge X positive position of the stepped mass block (3) is connected to the fixed frame (1) via the first specifically sensitive elastic beam; the upper surface edge X negative position of the stepped mass block (3) is connected to the fixed frame (1) via the second specifically sensitive elastic beam; the upper surface edge Y positive position of the stepped mass block (3) is connected to the fixed frame (1) via the third specifically sensitive elastic beam; the upper surface of the stepped mass block (3) is connected to the fixed frame (1) via the third specifically sensitive elastic beam. The edge Y negative point is connected to the fixed frame (1) through the fourth specific sensitive elastic beam; the four specific sensitive elastic beams (2) are distributed in orthogonal directions in the plane, and are symmetrical with respect to the center of the projection point of the center of gravity of the stepped mass block (3) on the upper surface; on the upper surface of the stepped mass block (3), a first reflective film covering the area around the X positive point, a second reflective film covering the area around the X negative point, a third reflective film covering the area around the Y positive point, and a fourth reflective film covering the area around the Y negative point are arranged; The array grating structure comprises a grating substrate (5) and a grating (6); the number of gratings (6) is four, namely a first grating, a second grating, a third grating and a fourth grating; the grating substrate (5) is fixedly mounted above the three-axis acceleration synchronous sensitive structure, the first grating is arranged on the surface of the grating substrate (5) facing the three-axis acceleration synchronous sensitive structure and on the surface facing the first reflective film, the second grating is arranged on the surface facing the second reflective film, the third grating is arranged on the surface facing the third reflective film, and the fourth grating is arranged on the surface facing the fourth reflective film; The photoelectric detection array structure comprises a photoelectric substrate (7), a first laser, a first light detector, a second laser, a second light detector, a third laser, a third light detector, a fourth laser and a fourth light detector; the photoelectric substrate (7) is arranged above the grating substrate (5), and a parallel cavity is formed between the photoelectric substrate (7) and the grating substrate (5); the first laser is arranged on the surface of the photoelectric substrate (7) facing the grating substrate (5) and on the surface facing the first reflective film, the first light detector is arranged at the diffracted reflected light position of the first grating, the second laser is arranged on the surface facing the second reflective film, the second light detector is arranged at the diffracted reflected light position of the second grating, the third laser is arranged on the surface facing the third reflective film, the third light detector is arranged at the diffracted reflected light position of the third grating, the fourth laser is arranged on the surface facing the fourth reflective film, and the fourth light detector is arranged at the diffracted reflected light position of the fourth grating. 2. According to claim 1, an optical interference micro-integrated three-axis acceleration sensor structure is characterized in that one end of each of the specific sensitive elastic beams (2) is connected and fixed to the fixed frame (1), and the other end of each of the specific sensitive elastic beams (2) is connected and fixed to a corresponding position of the upper surface edge of the stepped mass block (3). 3. According to claim 1, an optical interference micro-integrated three-axis acceleration sensor structure is characterized in that the specific sensitive elastic beam (2) is composed of a folded elastic beam symmetrical on both sides, and the connection with the stepped mass block (3) is a discrete part of the folded elastic beam on both sides, with two connection points, and the distance between the connection points is not more than 1/10 of the size of the upper surface of the stepped mass block (3), and the vertical thickness of each straight beam section in the specific sensitive elastic beam (2) is not more than 1/10 of the width. 4. According to claim 3, an optical interference micro-integrated three-axis acceleration sensor structure is characterized in that the direction from the connection with the fixed frame (1) to the connection with the stepped mass block (3) of the specific sensitive elastic beam (2) is the axial direction, and in the plane where the specific sensitive elastic beam (2) is located, the direction perpendicular to the axial direction is the lateral direction; the direction perpendicular to the plane where the specific sensitive elastic beam (2) is located is the normal direction; With respect to normal bending deformation, the folded elastic beams on both sides are connected in parallel, so that the specifically sensitive elastic beam (2) exhibits a certain bending stiffness; With respect to transverse bending deformation, the folded elastic beams on both sides are insensitive to transverse bending, and the specifically sensitive elastic beams (2) formed can neglect transverse bending deformation under normal loads; With respect to torsional deformation, the folded elastic beams on both sides are connected in series, and because the distance between the discrete connection points of each beam and the stepped mass block (3) is small, the torsional stiffness of the formed specific sensitive elastic beam (2) relative to the torsional angle is extremely small; With respect to axial deformation, since the thickness of each straight beam section in the folded elastic beam is much smaller than the width, the normal bending stiffness thereof is much smaller than the transverse bending stiffness, and the axial deformation stiffness of the constructed specific sensitive elastic beam (2) is much greater than the normal bending stiffness. 5. The optical interference micro-integrated three-axis acceleration sensor structure according to claim 1, characterized in that the stepped mass block (3) comprises, from top to bottom, a reflective surface reinforcement step (301), a connecting step (302) and a sinking step (303); The upper surface of the reflective surface reinforcement step (301) is connected to the specific sensitive elastic beam (2) and has a certain thickness to ensure that the surface of the connection point area is flat when subjected to the force of the specific sensitive elastic beam (2); The horizontal cross-sectional dimension of the connecting step (302) is smaller than that of the reflective surface reinforcing step (301) and the sinking step (303); The horizontal cross-sectional dimension of the sunken step (303) is larger than that of the reflective surface reinforcing step (301). 6. An optical interference micro-integrated three-axis acceleration sensor structure according to claim 5, characterized in that the planar shape of the stepped mass block (3) is an axisymmetric shape relative to the orthogonal directions of the four specific sensitive elastic beams (2). 7. According to claim 5, an optical interference micro-integrated three-axis acceleration sensor structure is characterized in that the fixed frame (1), the specific sensitive elastic beam (2) and the reflective surface reinforcement step (301) in the stepped mass block (3) are an integrated structure processed and manufactured on the same substrate, and the material is an elastic material. 8. An optical interference micro-integrated three-axis acceleration sensor structure according to claim 1, characterized in that the grating substrate (5) is a light-transmitting bottom plate, and the grating (6) is a one-dimensional grating; the grating stripes of the first grating, the second grating, the third grating and the fourth grating are staggered at a certain angle. 9. A method for solving a light interference micro-integrated three-axis acceleration sensor structure according to any one of claims 1 to 8, characterized in that it comprises the following steps: Step 1, connecting the first laser, the first photodetector, the second laser, the second photodetector, the third laser, the third photodetector, the fourth laser and the fourth photodetector to a photoelectric detection circuit; The first reflective film and the first grating just above it constitute a first grating interference cavity; the second reflective film and the second grating just above it constitute a second grating interference cavity; the third reflective film and the third grating just above it constitute a third grating interference cavity; the fourth reflective film and the fourth grating just above it constitute a fourth grating interference cavity; Step 2, the optical interference micro-integrated three-axis acceleration sensor structure is powered on; each laser and photodetector works simultaneously, the first laser emits a coherent light source, reaches the first grating interference cavity and is reflected and diffracted and received by the first photodetector, the first photodetector measures an interference light signal, and outputs an X forward voltage signal Vx ₊ through a photoelectric detection circuit; wherein the interference light signal measured by the first photodetector represents the normal displacement of the X forward position of the upper surface edge of the stepped mass block (3); At the same time, the second laser emits a coherent light source, which reaches the second grating interference cavity and is reflected and diffracted and received by the second light detector. The second light detector measures an interference light signal and outputs an X-negative voltage signal V _x- through a photoelectric detection circuit. The interference light signal measured by the second light detector represents the normal displacement of the X-negative position of the upper surface edge of the stepped mass block (3). At the same time, the third laser emits a coherent light source, which reaches the third grating interference cavity and is received by the third light detector after reflection and diffraction. The third light detector measures an interference light signal and outputs a Y forward voltage signal V _y+ through a photoelectric detection circuit. The interference light signal measured by the third light detector represents the normal displacement of the Y forward position of the upper surface edge of the stepped mass block (3). At the same time, the fourth laser emits a coherent light source, which reaches the fourth grating interference cavity and is received by the fourth light detector after reflection and diffraction. The fourth light detector measures an interference light signal and outputs a Y negative voltage signal V _y- through a photoelectric detection circuit. The interference light signal measured by the fourth light detector represents the normal displacement of the Y negative position of the upper surface edge of the stepped mass block (3). Step 3, respectively solving the X positive voltage signal Vx ₊ , the X negative voltage signal _Vx- , the Y positive voltage signal _Vy+ and the Y negative voltage signal _Vy- , to obtain the normal displacement measurement value Sx ₊ of the X positive point, the normal displacement measurement value Sx- of the X negative point, the normal displacement measurement value _Sy+ of the Y positive point and the normal displacement measurement value Sy- of the Y negative point on the upper surface edge of the stepped mass block ( _{3 )} ; Step 4: Pre-calibrate and measure to obtain the mapping matrix K between the three-axis acceleration to be measured and the normal displacement of each directional point. According to the following formula, the normal displacement measurement value of each directional point is solved to obtain the three-axis acceleration measurement value, including: X-axis acceleration measurement value _Ax , Y-axis acceleration measurement value _Ay and Z-axis acceleration measurement value _Az : in: k _x+ is the proportional coefficient of the displacement S _x+ of the positive position on the surface of the step-type mass block produced by the X-axis acceleration measurement value A _x ; k _x- is the proportional coefficient of the displacement S _x- of the negative position on the surface of the step-type mass block produced by the X-axis acceleration measurement value A _x ; k _zx+ is the proportional coefficient of the displacement S x+ of the positive position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; k _zx- is the proportional coefficient of the displacement S _x- of the negative position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; _ky+ is the proportional coefficient of the displacement S _y + of the positive position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A _y ; _ky- is the proportional coefficient of the displacement S _y- of the negative position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A _y ; k _zy- is the proportional coefficient of the displacement S _y- of the negative position on the surface of the step-type mass block produced by the Z-axis acceleration measurement value A _z ; k _zy+ is the proportional coefficient of the displacement S _y + of the positive position on the surface of the step-type mass block produced by the Y-axis acceleration measurement value A y; The _z action produces a proportional coefficient of the Y positive position displacement _Sy+ on the upper surface of the stepped mass block.