A three-axis closed-loop acceleration sensor and its monitoring system and method

Abstract

The present invention discloses a three-axis closed-loop acceleration sensor and a monitoring system and method thereof. The three-axis closed-loop acceleration sensor comprises: a top structure, an acceleration-sensitive structure, and a bottom mirror structure, which are arranged in sequence from top to bottom in a vertical direction. The acceleration-sensitive structure and the top structure constitute a Fabry-Perot interferometer cavity. In the vertical direction, the height between the acceleration-sensitive structure and the top structure is the cavity length of the Fabry-Perot interferometer cavity. The top structure is used to receive infrared light. After passing through the top structure and the acceleration-sensitive structure in sequence, the infrared light is reflected multiple times in the Fabry-Perot interferometer cavity and finally penetrates the bottom mirror structure to form multi-beam interference. The acceleration-sensitive structure comprises a mass block, which can move in a vertical direction. The cavity length changes according to the movement distance of the mass block, thereby changing the intensity of the multi-beam interference light passing through the bottom mirror structure. Electrostatic force feedback modulation is formed by utilizing metal electrode layers on the top structure and the bottom mirror structure.

Description

Technical Field

[0001] The present invention relates to the technical field of acceleration sensors, and in particular to a three-axis closed-loop acceleration sensor and a monitoring system and method thereof. Background Art

[0002] A Fabry-Perot cavity is an optical cavity structure composed of two parallel mirrors. Upon incident light, it undergoes multiple reflections and transmissions within the cavity, leading to interference between the reflected and transmitted light. With the development of microelectromechanical systems (MEMS) technology, MEMS Fabry-Perot cavities have begun to attract widespread attention, with their current application primarily in high-precision interferometers.

[0003] When laser light enters a Fabry-Perot microcavity, the reflected and transmitted light interfere with each other. The intensity of the interference light varies periodically with the cavity length. This property can be exploited to create microcavity-based accelerometers. However, due to the conflict between resolution and range of such accelerometers, most existing reports have limited their range, only being able to measure accelerations within ±1g, making them unsuitable for use in high-intensity vibration environments. Summary of the Invention

[0004] The object of the present invention is to provide a three-axis closed-loop acceleration sensor and a monitoring system and method thereof, so as to achieve improved integration and extended range of the sensor.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] The present invention provides a three-axis closed-loop acceleration sensor, which includes: a top structure, an acceleration-sensitive structure, and a bottom mirror structure, which are arranged in sequence from top to bottom in a vertical direction. The acceleration-sensitive structure and the top structure constitute a Fabry-Perot interferometer cavity. Along the vertical direction, the height between the acceleration-sensitive structure and the top structure is the cavity length of the Fabry-Perot interferometer cavity. The top structure is used to receive infrared light. The infrared light sequentially passes through the top structure and the acceleration-sensitive structure and then enters the Fabry-Perot interferometer cavity. The infrared light is reflected multiple times in the Fabry-Perot interferometer cavity. The multiple beams of reflected light respectively pass through the bottom mirror structure to form multi-beam interference. The acceleration-sensitive structure includes a mass block, which is movable in the vertical direction. The cavity length changes according to the movement distance of the mass block. The Fabry-Perot interferometer cavity is used to change the intensity of the multi-beam interference according to the change in the cavity length. The bottom mirror structure is used to constitute the lower surface of the Fabry-Perot interferometer cavity and output multi-beam interference light.

[0007] Optionally, the top structure includes a mirror body and an electrode part, the electrode part includes a plurality of "L"-shaped electrodes, and a plurality of "L"-shaped electrode arrays are arranged on the mirror body, each of the "L"-shaped electrodes has a "1" part and a "one" part, the "1" part is arranged through the mirror body, and the "one" part is attached to the side of the mirror body close to the acceleration sensitive structure; the "1" part is constructed as a silicon through-hole electrode, and the "one" part is constructed as a metal electrode.

[0008] Optionally, an insulating layer is further provided between the top structure and the acceleration sensitive structure, and the insulating layer is used to prevent electrical connection between the top structure and the acceleration sensitive structure.

[0009] Optionally, the acceleration sensitive structure further includes a spring beam support and a structural frame, the mass block is located at the geometric center of the structural frame, and the spring beam support connects the mass block and the structural frame to support the movement of the mass block in the vertical direction.

[0010] Optionally, the acceleration sensitive structure further includes a contact boss supported between the structural frame and the bottom mirror structure to provide a movable space for the mass block.

[0011] Optionally, the underlying mirror structure includes a bottom body, a contact electrode and an external electrode, and the side of the underlying mirror structure close to the acceleration sensitive structure is constructed as an electrode surface, and the contact electrode and the external electrode are both arranged on the electrode surface, and the contact electrode is simultaneously connected to the contact boss and the external electrode so as to penetrate the external electrode and the acceleration sensitive structure through the contact electrode.

[0012] Optionally, two U-shaped grooves are provided on a side of the bottom body close to the acceleration sensitive structure, the two U-shaped grooves are symmetrically arranged about the midline of the length of the bottom body, a second metal electrode is provided between the two U-shaped grooves, an ASIC circuit is provided in the U-shaped groove, and a group of contact electrodes and external electrodes are provided on the other side of each U-shaped groove.

[0013] Optionally, the contact electrode and the contact boss are connected to form a closed structure, the external electrode is located outside the closed structure, and there are a plurality of external electrodes, which are arranged at intervals.

[0014] The present invention also provides an acceleration monitoring system, which includes the above-mentioned three-axis closed-loop acceleration sensor based on semiconductor micro-optical cavity, and also includes: a coherent light source and a light intensity detection module, the coherent light source is used to emit infrared light, and the light intensity detection module is used to receive the transmitted light and the reflected light to generate a light intensity detection result, and provide negative feedback based on the light intensity detection result to ensure system stability.

[0015] The present invention also provides an acceleration monitoring method based on the above-mentioned acceleration monitoring system, the monitoring method comprising:

[0016] S1: Controls the coherent light source to emit infrared light;

[0017] S2: Use the Fabry-Perot interferometer cavity inside the accelerometer to modulate the infrared light to obtain multi-beam interference light;

[0018] S3: Control the light intensity detection module to receive the multi-beam interference light and generate a light intensity detection result;

[0019] S4: Obtaining a feedback variable using a PID closed-loop control algorithm according to the light intensity detection result;

[0020] S5: Feedback is performed on the cavity length according to the feedback variable to restore the cavity length to an initial state.

[0021] The present invention has the following beneficial effects:

[0022] The present invention adopts the combination of MEMS and ASIC to combine the sensing unit with the circuit unit, thereby improving the integration of the system; at the same time, it innovatively adopts a multi-layer bonding structure to achieve closed-loop adjustment of the mass block displacement in the vertical direction, thereby realizing the range expansion of the acceleration sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of the three-axis closed-loop acceleration sensor provided by the present invention;

[0024] Figure 2 This is a schematic structural diagram of the acceleration monitoring system provided by the present invention;

[0025] Figure 3 This is a schematic structural diagram of the acceleration sensitive structure provided by the present invention;

[0026] Figure 4 This is a schematic diagram of the working principle of the three-axis closed-loop acceleration sensor provided by the present invention;

[0027] Figure 5 This is a schematic diagram of the manufacturing process of the three-axis closed-loop acceleration sensor provided by the present invention.

[0028] Description of Reference Numerals

[0029] 1-top structure; 11-part "I"; 12-part "1"; 13-optical window; 2-acceleration sensitive structure; 21-spring beam support; 22-mass block; 23-contact boss; 24-structural frame; 3-bottom mirror structure; 31-second metal electrode; 32-contact electrode; 33-external electrode; 4-insulating layer; 41-coherent light source; 42-light intensity detection module. DETAILED DESCRIPTION

[0030] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0031] Example

[0032] The technical solution of the present invention to solve the above technical problems is as follows:

[0033] The present invention provides a three-axis closed-loop acceleration sensor, referring to Figure 1 As shown, the three-axis closed-loop acceleration sensor includes: a top structure 1, an acceleration sensitive structure 2, and a bottom mirror structure 3 arranged in sequence from top to bottom along the vertical direction. The acceleration sensitive structure 2 and the top structure 1 constitute a Fabry-Perot interferometer cavity. Along the vertical direction, the height between the acceleration sensitive structure 2 and the top structure 1 is the cavity length of the Fabry-Perot interferometer cavity. The top structure 1 is used to receive infrared light. The infrared light sequentially passes through the top structure 1 and the acceleration sensitive structure 2 and then enters the Fabry-Perot interferometer cavity. It is reflected multiple times in the Fabry-Perot interferometer cavity. The multiple beams of reflected light respectively pass through the bottom mirror structure 3, forming multi-beam interference after passing. The acceleration sensitive structure 2 includes a mass block 22. The mass block 22 is movable in the vertical direction. The cavity length changes according to the movement distance of the mass block 22. The Fabry-Perot interferometer cavity is used to change the intensity of the multi-beam interference according to the change in the cavity length. The bottom mirror structure 3 is used to constitute the lower surface of the Fabry-Perot interferometer cavity and output multi-beam interference light.

[0034] Alternatively, refer to Figure 1 As shown, the top structure 1 includes a mirror body and an electrode part, the electrode part includes a plurality of "L"-shaped electrodes, and a plurality of "L"-shaped electrode arrays are arranged on the mirror body, each of the "L"-shaped electrodes has a "1" part 12 and a "one" part 11, the "1" part 12 is arranged through the mirror body, and the "one" part 11 is attached to the side of the mirror body close to the acceleration sensitive structure 2; the "1" part 12 is constructed as a silicon through-hole electrode, and the "one" part 11 is constructed as a metal electrode.

[0035] In addition, reference Figure 2 As shown, there are four "L"-shaped electrodes, and therefore, the electrode-free portion between the four "I" parts 11 forms an optical window 13. The optical window 13 is used to transmit infrared rays, and therefore, no electrode is arranged under the optical window 13.

[0036] Optionally, an insulating layer 4 is further provided between the top structure 1 and the acceleration sensitive structure 2 , and the insulating layer 4 is used to prevent electrical connection between the top structure 1 and the acceleration sensitive structure 2 .

[0037] Of course, in the present invention, the top structure 1 and the acceleration sensitive structure 2 are connected by bonding technology.

[0038] Alternatively, refer to Figure 1 and Figure 3 As shown, the acceleration sensitive structure 2 further includes a spring beam support 21 and a structural frame 24. The mass block 22 is located at the geometric center of the structural frame 24. The spring beam support 21 connects the mass block 22 and the structural frame 24 to support the movement of the mass block 22 in the vertical direction.

[0039] Here, the spring beam support member 21 is a support beam structure with spring properties, and generally can adopt a straight beam, a folded beam, a serpentine beam and other structures, and the present invention does not make specific limitations.

[0040] refer to Figure 1 In order to prevent the acceleration sensitive structure 2 from contacting the underlying mirror structure 3 during movement, the acceleration sensitive structure 2 also includes a contact boss 23, which is supported between the structural frame 24 and the underlying mirror structure 3 to provide a movable space for the mass block 22.

[0041] In the present invention, the acceleration sensitive structure 2 is an integrated structure, and is formed by a combination of conventional MEMS manufacturing processes, including photolithography, etching, deposition, sputtering, and the like.

[0042] Alternatively, refer to Figure 1 and Figure 2 As shown, the underlying mirror structure 3 includes a bottom body, a contact electrode 32 and an external electrode 33. The side of the underlying mirror structure 3 close to the acceleration sensitive structure 2 is constructed as an electrode surface. The contact electrode 32 and the external electrode 33 are both arranged on the electrode surface, and the contact electrode 32 is simultaneously connected to the contact boss 23 and the external electrode 33, so that the external electrode 33 and the acceleration sensitive structure 2 are connected through the contact electrode 32.

[0043] Since the acceleration sensitive structure 2 is an integrated structure, the basic boss, structural frame, spring beam support 21 and mass block 22 in the acceleration sensitive structure 2 are all electrically connected to the contact electrode 32 , so that they can be connected to external electrical circuits through the external electrode 33 .

[0044] Alternatively, refer to Figure 1 As shown, two U-shaped grooves are provided on one side of the bottom body close to the acceleration sensitive structure 2. The two U-shaped grooves are symmetrically arranged about the midline of the length of the bottom body. A second metal electrode 31 is provided between the two U-shaped grooves. An ASIC circuit 34 is provided in the U-shaped groove. A group of contact electrodes 32 and external electrodes 33 are provided on the other side of each U-shaped groove.

[0045] Here, the length direction of the bottom body is Figure 2 In the direction parallel to the paper surface, the other side of each U-shaped groove is the opposite side between the two U-shaped grooves.

[0046] In addition, due to the presence of the metal electrode 11 and the second metal electrode 31, an electrostatic voltage V can be applied to the top structure 1 and the bottom mirror structure 3 respectively. 上 and V 下 , so the acceleration sensitive structure 2 always maintains zero potential. And due to the existence of the ASIC circuit 34, the electrostatic bias voltage V 上 and V 下 , thereby making the mass block 22 stable within a certain range of movement, thereby ensuring the stability of the performance of the acceleration sensor of the present invention.

[0047] Alternatively, refer to Figure 2 As shown, the contact electrode 32 and the contact boss 23 are connected to form a closed structure, and the external electrode 33 is located outside the closed structure. There are multiple external electrodes 33, and the multiple external electrodes 33 are arranged at intervals.

[0048] Therefore, those skilled in the art can think of that each external electrode 33 is connected to a corresponding contact electrode 32. Therefore, when making a specific design, multiple contact bosses 23, multiple contact electrodes 32 and multiple external electrodes 33 can be designed, and each contact boss 23, contact electrode 32 and external electrode 33 are arranged in a one-to-one correspondence.

[0049] The present invention also provides an acceleration monitoring system, referring to Figure 2As shown, the acceleration monitoring system includes the above-mentioned three-axis closed-loop acceleration sensor based on semiconductor micro-optical cavity, and also includes: a coherent light source 41 and a light intensity detection module 42, wherein the coherent light source 41 is used to emit infrared light, and the light intensity detection module 42 is used to receive the transmitted light and the reflected light to generate a light intensity detection result, and provide negative feedback based on the light intensity detection result to ensure system stability.

[0050] The present invention also provides an acceleration monitoring method based on the above-mentioned acceleration monitoring system, the monitoring method comprising:

[0051] S1: Control the coherent light source 41 to emit infrared light;

[0052] S2: Use the Fabry-Perot interferometer cavity inside the accelerometer to modulate the infrared light, refer to Figure 4 As shown, multiple beam interference light is obtained;

[0053] Here, the transmitted light and the reflected light each form interference, and the interference light intensity changes periodically as the cavity length changes.

[0054] S3: Control the light intensity detection module 42 to receive the multi-beam interference light and generate a light intensity detection result; therefore, after receiving the cavity length change, the transmitted light and the reflected light, the light intensity detection module 42 can derive the external acceleration based on the cavity length change, and the light intensity change of the transmitted light and the reflected light is the gravitational acceleration.

[0055] S4: Obtaining a feedback variable using a PID closed-loop control algorithm according to the light intensity detection result;

[0056] Here, the PID closed-loop control algorithm is a proportional-integral-differential control algorithm. Of course, those skilled in the art may also adopt other algorithms, and the present invention does not impose any specific limitation thereto.

[0057] Specifically, by analyzing the change in light intensity, using the PID closed-loop control algorithm, enabling the voltage control circuit, changing the electrostatic bias voltage, generating a balancing force, and providing negative feedback for the system, thereby pulling the mass block 22 back to the initial equilibrium position.

[0058] Through fast PID control, the system can ensure that under varying acceleration conditions, the mass 22 always remains within a small range not far from the center position. The current acceleration value can be inferred from the magnitude of the electrostatic bias voltage.

[0059] Compared with the method of simply detecting acceleration by light intensity, the advantage of this test method is that it avoids problems such as device damage, electrode attraction, and over-range testing caused by excessive impact and vibration, and the system has greater stability.

[0060] S5: Feedback is performed on the cavity length according to the feedback variable to restore the cavity length to an initial state.

[0061] In addition, reference Figure 5 As shown, the manufacturing method of the three-axis closed-loop acceleration sensor of the present invention is as follows:

[0062] refer to Figure 5 (a) Using a high-temperature wet oxidation method to form an oxide film on the bottom of the original single-crystal silicon wafer to obtain a single-crystal silicon wafer;

[0063] refer to Figure 5 (b) performing preliminary processing on the single crystal silicon wafer to obtain a preliminarily processed single crystal silicon wafer, wherein the preliminary processing includes removing silicon oxide at a target location by photolithography and wet etching, and etching a large U-shaped groove at the target location;

[0064] refer to Figure 5 (c) sputtering a second metal electrode 31 on the single crystal silicon wafer after the preliminary treatment;

[0065] refer to Figure 5 (d) manufacturing a top structure 1, wherein the manufacturing of the top structure 1 includes forming an electrode portion using a through silicon via technique;

[0066] Obtain a single crystal silicon wafer; here, the single crystal silicon wafer is used to form the acceleration sensitive structure 2.

[0067] refer to Figure 5 (e), bonding single crystal silicon wafers and single crystal silicon wafers;

[0068] refer to Figure 5 (f) thinning the single crystal silicon wafer by grinding and polishing, and etching the contact boss 23 by potassium oxide to obtain a processed single crystal silicon wafer;

[0069] refer to Figure 5 (g) A single crystal silicon wafer after patterning to form a structural frame, spring beam support 21 and mass block 22;

[0070] Obtaining a first single crystal silicon wafer including two U-shaped grooves and an ASIC circuit 34;

[0071] refer to Figure 5 (h) Bonding the first single crystal silicon wafer and the single crystal silicon wafer.

[0072] The present invention has the following beneficial effects:

[0073] The present invention adopts the combination of MEMS and ASIC to combine the sensing unit with the circuit unit, thereby improving the integration of the system; at the same time, it innovatively adopts a multi-layer bonding structure to achieve closed-loop adjustment of the mass block displacement in the vertical direction, thereby realizing the range expansion of the acceleration sensor.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An acceleration monitoring system comprising a three-axis closed-loop acceleration sensor, characterized in that: The three-axis closed-loop acceleration sensor comprises: A top structure (1), an acceleration sensitive structure (2) and a bottom mirror structure (3) are arranged in sequence from top to bottom along a vertical direction; The acceleration sensitive structure (2) and the bottom mirror structure (3) form a Fabry-Perot interferometer cavity, and along the vertical direction, the height between the acceleration sensitive structure (2) and the bottom mirror structure (3) is the cavity length of the Fabry-Perot interferometer cavity; The top structure (1) is used to receive infrared light. The infrared light sequentially passes through the top structure (1) and the acceleration sensitive structure (2) and then enters the Fabry-Perot interferometer cavity, where it is reflected multiple times. The multiple beams of reflected light respectively pass through the bottom mirror structure (3), forming multi-beam interference after the transmission. The acceleration sensitive structure (2) includes a mass block (22), the mass block (22) is movable in a vertical direction, the cavity length changes according to the moving distance of the mass block (22), and the Fabry-Perot interference cavity is used to change the intensity of the multi-beam interference according to the change of the cavity length; The bottom mirror structure (3) is used to form the lower surface of the Fabry-Perot interferometer cavity and output multi-beam interference light; The top structure (1) includes a mirror body and an electrode part, the electrode part includes a plurality of "L"-shaped electrodes, and a plurality of "L"-shaped electrode arrays are arranged on the mirror body, each of the "L"-shaped electrodes has a "1" part (12) and a "one" part (11), the "1" part (12) is arranged through the mirror body, and the "one" part (11) is attached to the side of the mirror body close to the acceleration sensitive structure (2); the "1" part (12) is constructed as a silicon through-hole electrode, and the "one" part (11) is constructed as a metal electrode; The acceleration sensitive structure (2) further comprises a spring beam support member (21) and a structural frame (24), the mass block (22) is located at the geometric center of the structural frame (24), and the spring beam support member (21) connects the mass block (22) and the structural frame (24) to support the movement of the mass block (22) in the vertical direction; The acceleration sensitive structure (2) further includes a contact boss (23), wherein the contact boss (23) is supported between the structural frame (24) and the bottom mirror structure (3) to provide a movable space for the mass block (22); The bottom mirror structure (3) comprises a bottom body, a contact electrode (32) and an external electrode (33); a side of the bottom mirror structure (3) close to the acceleration sensitive structure (2) is configured as an electrode surface; the contact electrode (32) and the external electrode (33) are both arranged on the electrode surface; and the contact electrode (32) is simultaneously connected to the contact boss (23) and the external electrode (33), so that the external electrode (33) and the acceleration sensitive structure (2) are connected through the contact electrode (32); Two U-shaped grooves are provided on one side of the bottom body close to the acceleration sensitive structure (2), the two U-shaped grooves are symmetrically arranged about the midline of the length of the bottom body, a second metal electrode (31) is provided between the two U-shaped grooves, an ASIC circuit (34) is provided in the U-shaped groove, and a group of contact electrodes (32) and external electrodes (33) are respectively provided on the other side of each U-shaped groove.

2. The acceleration monitoring system comprising a three-axis closed-loop acceleration sensor according to claim 1, characterized in that: An insulating layer (4) is further provided between the top structure (1) and the acceleration sensitive structure (2), and the insulating layer (4) is used to prevent electrical connection between the top structure (1) and the acceleration sensitive structure (2).

3. The acceleration monitoring system comprising a three-axis closed-loop acceleration sensor according to claim 1, characterized in that: The contact electrode (32) and the contact boss (23) are connected to form a closed structure, the external electrode (33) is located outside the closed structure, and there are multiple external electrodes (33), and the multiple external electrodes (33) are arranged at intervals.

4. The acceleration monitoring system comprising a three-axis closed-loop acceleration sensor according to claim 1, characterized in that: The acceleration monitoring system further comprises: a coherent light source (41) and a light intensity detection module (42), wherein the coherent light source (41) is used to emit infrared light, and the light intensity detection module (42) is used to receive transmitted light and reflected light to generate a light intensity detection result, and provide negative feedback based on the light intensity detection result to ensure system stability.

5. An acceleration monitoring method of an acceleration monitoring system according to any one of claims 1 to 4, characterized in that: The monitoring method comprises: S1: controlling the coherent light source (41) to emit infrared light; S2: Use the Fabry-Perot interferometer cavity inside the accelerometer to modulate the infrared light to obtain multi-beam interference light; S3: controlling the light intensity detection module (42) to receive the multi-beam interference light and generate a light intensity detection result; S4: Obtaining a feedback variable using a PID closed-loop control algorithm according to the light intensity detection result; By analyzing the change in light intensity, using a PID closed-loop control algorithm, enabling a voltage control circuit, changing the electrostatic bias voltage, generating a balancing force, and providing negative feedback for the system, thereby pulling the mass block (22) back to its initial equilibrium position; The current acceleration value can be inferred from the magnitude of the electrostatic bias voltage; S5: Feedback is performed on the cavity length according to the feedback variable to restore the cavity length to an initial state.

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