A Z-axis sensitive MEMS coupled stiffness modulation accelerometer

Abstract

This invention provides a Z-axis sensitive MEMS coupled stiffness modulation accelerometer, comprising an upper structure and a lower structure. The upper structure is a silicon micromechanical sensor based on silicon material, and the lower structure is a silicon dioxide-based glass base. The silicon micromechanical sensor is connected to the glass base via anchor points, and signal electrodes are distributed on the glass base. The silicon micromechanical sensor includes an inertial mass, a first resonator, a second resonator, an elastic support beam system, and anchor points. This invention enhances the displacement response of the inertial mass in the Z-axis direction, enabling sensitive detection and signal amplification of Z-axis acceleration, thereby improving the overall performance and measurement accuracy of the accelerometer.

Description

Technical Field

[0001] This invention belongs to the field of microelectromechanical systems (MEMS), specifically relating to a Z-axis sensitive MEMS coupled stiffness modulation accelerometer. Background Technology

[0002] With the rapid development of microelectromechanical systems (MEMS) technology, accelerometers based on microstructure resonators have been widely used in aerospace, intelligent equipment, and precision navigation due to their advantages such as high sensitivity, easy integration, and low power consumption. MEMS accelerometers mainly adopt capacitive, piezoresistive, or resonant structures.

[0003] In recent years, weakly coupled resonant sensors with higher sensitivity have gradually become a more cutting-edge research direction. Existing weakly coupled resonant sensors typically change the mechanical characteristics of the system by altering the equivalent stiffness or equivalent mass of the resonant unit, thereby achieving sensitivity to external signals. This approach is affected by mode mixing effects and has a theoretical upper limit to sensitivity. In addition, existing research mainly focuses on in-plane (X / Y axis) acceleration detection, and high-sensitivity detection schemes for out-of-plane (Z axis) acceleration are still relatively lacking, especially in terms of high-resolution sensing capability for weak acceleration signals under complex working conditions. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a Z-axis sensitive MEMS coupled stiffness modulation accelerometer. Through electrostatic coupling and stiffness perturbation mechanism, the detection sensitivity and stability of Z-axis acceleration are effectively improved, overcoming the limitations of traditional structures in terms of sensitivity limit and environmental adaptability.

[0005] The accelerometer described in this invention includes an upper structure and a lower structure;

[0006] The upper structure is a silicon micromechanical sensor based on silicon material, and the lower structure is a glass base based on silicon dioxide.

[0007] The silicon micromechanical sensor is connected to a glass base via anchor points, and signal electrodes are arranged on the glass base.

[0008] The silicon micromechanical sensor includes an inertial mass block, a first resonator, a second resonator, an elastic support beam system, and anchor points.

[0009] The second resonator is disposed inside the inertial mass block and is directly connected to the upper inner side and the lower inner side of the inertial mass block;

[0010] The first resonator is disposed inside the second resonator and fixedly mounted on the glass base, and is not connected to the inertial mass block;

[0011] The elastic support beam system includes a first elastic support beam system, a second elastic support beam system, a third elastic support beam system, and a fourth elastic support beam system;

[0012] The first elastic support beam system, the second elastic support beam system, the third elastic support beam system, and the fourth elastic support beam system are located on the upper, left, right, and lower sides of the inertial mass block, respectively, and are all directly connected to the inertial mass block.

[0013] The anchor points are located on the outside of the first elastic support beam system, the second elastic support beam system, the third elastic support beam system, and the fourth elastic support beam system.

[0014] The first elastic support beam system includes a first inner elastic support beam, a first middle elastic support beam, and a first outer elastic support beam;

[0015] The second elastic support beam system includes a second inner elastic support beam, a second middle elastic support beam, and a second outer elastic support beam;

[0016] The third elastic support beam system includes a third inner elastic support beam, a third middle elastic support beam, and a third outer elastic support beam.

[0017] The fourth elastic support beam system includes a fourth inner elastic support beam, a fourth middle elastic support beam, and a fourth outer elastic support beam.

[0018] The first, second, third, and fourth middle-layer elastic support beams are symmetrically arranged on the upper left, lower left, upper right, and lower right sides of the inertial mass block, respectively.

[0019] The first outer elastic support beam and the first inner elastic support beam are located between the first middle elastic support beam and the third middle elastic support beam, and are located on the upper side of the inertial mass block.

[0020] The second outer elastic support beam and the second inner elastic support beam are located between the first middle elastic support beam and the second middle elastic support beam, and are located to the left of the inertial mass block;

[0021] The third outer elastic support beam and the third inner elastic support beam are located between the third middle elastic support beam and the fourth middle elastic support beam, and are located to the right of the inertial mass block.

[0022] The fourth outer elastic support beam and the fourth inner elastic support beam are located between the third middle elastic support beam and the fourth middle elastic support beam, and are located below the inertial mass block.

[0023] Anchor points are located on the upper side of the first outer elastic support beam, the left side of the second outer elastic support beam, the right side of the third outer elastic support beam, and the lower side of the fourth outer elastic support beam.

[0024] The lower side of the first inner elastic support beam, the right side of the second inner elastic support beam, the left side of the third inner elastic support beam, and the upper side of the fourth inner elastic support beam are all inertial mass blocks.

[0025] The first resonator is a fully constrained fixed resonant structure, which is symmetrical about the X-axis.

[0026] The first resonator includes a first resonator anchor point, a first driving comb tooth, a first detection comb tooth, a first coupling capacitor plate, and a first resonant beam;

[0027] The first resonator anchor point is located at the top of the first resonator and is fixedly connected to the glass base;

[0028] The first driving comb teeth are provided in two sets, symmetrically arranged on both sides of the Y-axis direction of the first resonator anchor point;

[0029] The first resonant beam is located below the anchor point of the first resonator and is arranged symmetrically along the Y-axis;

[0030] The first detection comb teeth are disposed on the inner side of the first resonant beam and are symmetrically distributed along the Y-axis;

[0031] The first coupling capacitor plate is disposed on the outside of the first drive comb teeth and is symmetrically distributed along the Y-axis;

[0032] The first coupling capacitor plate and the second coupling capacitor plate on the second resonator are parallel to each other, forming an electrostatic stiffness coupling system.

[0033] The second resonator includes a second resonator connection, a second driving comb tooth, a second detection comb tooth, a second coupling capacitor plate, and a second resonant beam;

[0034] The second resonator connection is located at the top of the second resonator and is connected to the inertial mass block;

[0035] The second drive comb teeth are provided in two sets, symmetrically arranged on the outer side of the second resonator connection along the Y-axis direction;

[0036] The second resonant beam is located outside the second drive comb teeth and is arranged symmetrically along the Y-axis;

[0037] The second detection comb teeth are located on the outside of the second resonant beam and are symmetrically distributed along the Y-axis;

[0038] The second coupling capacitor plate is disposed inside the second drive comb teeth and is symmetrically distributed along the Y-axis;

[0039] The second resonator and the first resonator have a preset difference in elastic stiffness, forming an initial stiffness mismatch, so that the amplitude ratio of the resonant system composed of the second resonator and the first resonator is only affected by the coupling stiffness.

[0040] The first outer elastic support beam, the second outer elastic support beam, the third outer elastic support beam, the fourth outer elastic support beam, the first middle elastic support beam, the second middle elastic support beam, the third middle elastic support beam, the fourth middle elastic support beam, the first inner elastic support beam, the second inner elastic support beam, the third inner elastic support beam, and the fourth inner elastic support beam have the same irregular geometric structure and mechanical parameters;

[0041] The irregular geometric structure is designed such that the width of the first outer elastic support beam in the X and Y axes parallel to the glass base is significantly greater than (more than 100 times) the height of the first outer elastic support beam in the Z axis perpendicular to the glass base.

[0042] The irregular geometry gives the elastic support beam system high stiffness in the X and Y axes, effectively suppressing the displacement of the inertial mass in the X and Y axes; and relatively low stiffness in the Z axis, allowing the inertial mass to only produce Z-direction displacement under acceleration.

[0043] The anchor point is a closed frame-type square ring, and the thickness of the anchor point along the X, Y, and Z axes is significantly greater than (more than 100 times) that of the adjacent functional structure.

[0044] The bottom surface of the anchor point is fixed to the surface of the glass base, forming a fixed constraint on the X, Y, and Z axes;

[0045] The anchor points are used to limit the X, Y, and Z displacements of the elastic support beam system and the inertial mass block within the range of elastic deformation.

[0046] The closed-frame square ring structure can restrict the movement of the elastic support beam system in the X and Y axis directions, and further restrict the movement of the inertial mass block in the X and Y axis directions.

[0047] The signal electrodes include a common electrode, a common electrode lead-out electrode, a first driving signal application electrode, a second driving signal application electrode, a third driving signal application electrode, a fourth driving signal application electrode, a fifth driving signal application electrode, a sixth driving signal application electrode, a seventh driving signal application electrode, and an eighth driving signal application electrode; and a first detection signal electrode, a second detection signal electrode, a third detection signal electrode, a fourth detection signal electrode, a fifth detection signal electrode, a sixth detection signal electrode, a seventh detection signal electrode, and an eighth detection signal electrode.

[0048] First driving signal lead-out electrode, second driving signal lead-out electrode, third driving signal lead-out electrode, fourth driving signal lead-out electrode, fifth driving signal lead-out electrode, sixth driving signal lead-out electrode, seventh driving signal lead-out electrode, eighth driving signal lead-out electrode; first detection signal lead-out electrode, second detection signal lead-out electrode, third detection signal lead-out electrode, fourth detection signal lead-out electrode;

[0049] The common electrode is connected to the ground terminal of the external drive and detection circuit through the common electrode lead-out electrode, which is used to provide a reference potential for each drive and detection unit.

[0050] The first driving signal application electrode, the second driving signal application electrode, the third driving signal application electrode, the fourth driving signal application electrode, the fifth driving signal application electrode, the sixth driving signal application electrode, the seventh driving signal application electrode, and the eighth driving signal application electrode are respectively led out through the first driving signal lead-out electrode, the second driving signal lead-out electrode, the third driving signal lead-out electrode, the fourth driving signal lead-out electrode, the fifth driving signal lead-out electrode, the sixth driving signal lead-out electrode, the seventh driving signal lead-out electrode, and the eighth driving signal lead-out electrode, and are connected to an external driving power supply to provide alternating excitation signals to the first resonator and the second resonator;

[0051] The first, second, third, fourth, fifth, sixth, seventh, and eighth detection signal electrodes are led out through the first, second, third, and fourth detection signal leads-out electrodes, respectively, and are connected to an external signal detection and processing circuit to collect the differential capacitance signal generated during the resonator's vibration.

[0052] When acceleration is applied to the acceleration time, the elastic support beam system has an inner, middle and outer three-layer structure, and a large thickness in the X and Y axis directions, exhibiting high elastic stiffness; at the same time, the anchor points fixed to the glass base have high stiffness in the X, Y and Z axis directions, which is used for the stable installation of the overall structure and further constrains the movement of the inertial mass block in the X and Y axis directions.

[0053] Under the joint guidance and constraint of the elastic support beam system and the anchor point, the inertial mass block is constrained to produce displacement only in the Z-axis direction, and the second resonator moves synchronously in the Z-direction with the inertial mass block through the second resonator connection point.

[0054] The first resonator is fixedly mounted on the glass base via a first resonator anchor point and remains stationary under acceleration, causing a relative displacement in the Z-axis direction between the first and second resonators. This relative displacement causes a change in the effective overlap area of ​​the first and second coupling capacitor plates located between the first and second resonators, thereby modulating the electrostatic coupling stiffness. The change in coupling stiffness causes a change in the system amplitude ratio, ultimately enabling the measurement of acceleration in the Z-axis direction and improving measurement sensitivity.

[0055] This invention is mainly used for high-sensitivity detection of out-of-plane acceleration.

[0056] The present invention has the following beneficial effects: (1) The first resonator and the second resonator adopt a spatial nested configuration, which reduces the area occupied by the sensor; the two achieve weak energy transfer through electrostatic coupling, avoiding mechanical connection loss; the two resonators have different preset stiffness parameters, ensuring that the amplitude ratio of the resonant system they form is only affected by the coupling stiffness; when the Z-axis acceleration is applied, the displacement of the first resonator causes the effective overlapping area of ​​the coupling capacitor plate to change, which expands the sensitivity range through the coupling stiffness disturbance mechanism and provides better response to micro-acceleration.

[0057] (2) The present invention effectively improves the constraint stiffness in the X and Y axis directions by increasing the thickness of the elastic support beam in the X / Y axis direction and the anchor point closed square layout structure, and suppresses the interference motion in the non-Z axis direction. At the same time, the structure can enhance the displacement response of the inertial mass block in the Z axis direction, realize sensitive detection and signal amplification of Z axis acceleration, and improve the overall performance and measurement accuracy of the accelerometer.

[0058] (3) This invention achieves performance optimization through a heterogeneous structure design of an elastic support beam system and an inertial mass block, using a differentiated thickness topology configuration. Specifically, the elastic support beam has a smaller thickness in the Z-axis direction, while the inertial mass block has a larger thickness in the Z-axis direction. This configuration achieves a significantly reduced support beam thickness ratio (beam thickness / inertial mass block thickness), effectively reducing the system's Z-axis support stiffness while significantly increasing the effective mass of the inertial mass block, making the inertial mass block's motion performance in the Z-axis direction more pronounced. This design breaks through the mutual constraints on stiffness and mass parameters of traditional homogeneous microstructures. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the overall mechanical structure of the present invention.

[0060] Figure 2 This is a schematic diagram of the silicon micromechanical structure of the present invention.

[0061] Figure 3 This is a schematic diagram of the first resonator structure of the present invention.

[0062] Figure 4 This is a schematic diagram of the second resonator structure of the present invention.

[0063] Figure 5 This is a schematic diagram of the elastic support beam system of the present invention.

[0064] Figure 6 This is a schematic diagram of the elastic support beam system and anchor point relationship of the present invention.

[0065] Figure 7 This is a schematic diagram of the differentiated design of the elastic beam of the present invention.

[0066] Figure 8 This is a schematic diagram of the signal leads of the present invention.

[0067] Explanation of reference numerals in the attached drawings: 1, inertial mass block; 2, first resonator; 3, second resonator; 4, elastic support beam system; 5, anchor point; 6, glass base; 2-1, anchor point of the first resonator; 2-2, first driving comb tooth; 2-3, first detection comb tooth; 2-4, first coupling capacitor plate; 2-5, first resonant beam; 3-1, connection point of the second resonator; 3-2, second driving comb tooth; 3-3, second detection comb tooth; 3-4, second coupling capacitor plate; 3-5, second resonant beam; 4-1, first elastic support beam system; 4-2, second elastic support beam system; 4-3, third elastic support beam system; 4-4, fourth elastic support beam system; 4-1-1, first inner elastic support beam; 4-1-2, first middle elastic support beam; 4-1-3, first outer elastic support beam;

[0068] 4-2-1, Second inner layer elastic support beam; 4-2-2, Second middle layer elastic support beam; 4-2-3, Second outer layer elastic support beam;

[0069] 4-3-1, Third inner layer elastic support beam; 4-3-2, Third middle layer elastic support beam; 4-3-3, Third outer layer elastic support beam;

[0070] 4-4-1, Fourth inner layer elastic support beam; 4-4-2, Fourth middle layer elastic support beam; 4-4-3, Fourth outer layer elastic support beam;

[0071] 7-9-1, Common electrode; 7-10-1, Common electrode lead-out electrode; 7-1-1, First drive signal application electrode; 7-1-2, Second drive signal application electrode; 7-2-1, Third drive signal application electrode; 7-2-2, Fourth drive signal application electrode; 7-2-3, Fifth drive signal application electrode; 7-2-4, Sixth drive signal application electrode; 7-3-1, Seventh drive signal application electrode; 7-3-2, Eighth drive signal application electrode;

[0072] 7-1-3, First detection signal electrode; 7-1-4, Second detection signal electrode; 7-3-3, Third detection signal electrode; 7-3-4, Fourth detection signal electrode; 7-4-1, Fifth detection signal electrode; 7-4-2, Sixth detection signal electrode; 7-4-3, Seventh detection signal electrode; 7-4-4, Eighth detection signal electrode; 7-5-2, First drive signal lead-out electrode; 7-5-3, Second drive signal lead-out electrode; 7-6-1, Third drive signal lead-out electrode; 7-6-2, Fourth drive signal lead-out electrode; 7-6-3, Fifth drive signal lead-out electrode; 7-6-4, Sixth drive signal lead-out electrode; 7-7-1, Seventh drive signal lead-out electrode; 7-7-2, Eighth drive signal lead-out electrode; 7-5-1, First detection signal lead-out electrode; 7-7-3, Second detection signal lead-out electrode; 7-8-1, Third detection signal lead-out electrode; 7-8-2, Fourth detection signal lead-out electrode. Detailed Implementation

[0073] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0074] like Figure 1 As shown, this embodiment of the invention provides a Z-axis sensitive MEMS coupled stiffness modulation accelerometer. The accelerometer adopts a heterogeneous integrated structure with upper and lower layers. The upper layer is a silicon micromechanical sensor based on silicon material, and the lower layer is a glass base 6 based on silicon dioxide. The two are fixed together by anchor points 5. A signal electrode array is integrated on the surface of the glass base 6 for electrical signal transmission.

[0075] like Figure 2 As shown, the silicon-based micromechanical sensor includes an inertial mass block 1, nested first resonator 2 and second resonator 3, a first elastic support beam system 4-1, a second elastic support beam system 4-2, a third elastic support beam system 4-3, a fourth elastic support beam system 4-4, and an anchor point 5. The first elastic support beam system 4-1, the second elastic support beam system 4-2, the third elastic support beam system 4-3, and the fourth elastic support beam system 4-4 constitute the elastic support beam system 4.

[0076] The second resonator 3 is in the shape of a hollow frame, including a second resonator connection 3-1, a second driving comb tooth 3-2, a second detection comb tooth 3-3, a second coupling capacitor plate 3-4, and a second resonant beam 3-5; the second resonator 3 is rigidly connected to the inner side of the inertial mass block 1 through the second resonator connection 3-1.

[0077] The first resonator 2 is located in the cavity inside the second resonator 3 and is directly fixed to the glass base 6 through the first resonator anchor point 2-1, without any mechanical connection to the second resonator 3.

[0078] like Figure 3 As shown, the first resonator 2 is a fixed reference structure, including a first resonator anchor point 2-1, a first driving comb tooth 2-2, a first detection comb tooth 2-3, a first coupling capacitor plate 2-4, and a first resonant beam 2-5; the first resonator anchor point 2-1 locks the first resonator to the glass base 6; the first driving comb tooth 2-2 and the fixed comb tooth of the base constitute an electrostatic force excitation source; the first detection comb tooth 2-3 forms a differential capacitance sensing interface on both sides of the first resonant beam 2-5; the first coupling capacitor plate 2-4 extends to the end of the beam and is parallel to and opposite to the second coupling capacitor plate 3-4.

[0079] like Figure 4 As shown, the second resonator 3 is a movable structure, and the connection 3-1 of the second resonator achieves displacement synchronization with the inertial mass block 1; the second driving comb 3-2 and the second detection comb 3-3 constitute the excitation and sensing unit; the second coupling capacitor plate 3-4 and the first coupling capacitor plate 2-4 form an electrostatic stiffness coupling interface. The resonant beam stiffness of the two resonators is differentiated to form an initial stiffness mismatch, ensuring that the amplitude ratio of the resonant system they form is only affected by the coupling stiffness.

[0080] like Figure 5 , Figure 6 As shown, the first elastic support beam system 4-1 includes a first inner elastic support beam 4-1-1, a first middle elastic support beam 4-1-2, and a first outer elastic support beam 4-1-3;

[0081] The second elastic support beam system 4-2 includes a second inner elastic support beam 4-2-1, a second middle elastic support beam 4-2-2, and a second outer elastic support beam 4-2-3;

[0082] The third elastic support beam system 4-3 includes a third inner elastic support beam 4-3-1, a third middle elastic support beam 4-3-2, and a third outer elastic support beam 4-3-3;

[0083] The fourth elastic support beam system 4-4 includes a fourth inner elastic support beam 4-4-1, a fourth middle elastic support beam 4-4-2, and a fourth outer elastic support beam 4-4-3;

[0084] The first middle layer elastic support beam 4-1-2, the second middle layer elastic support beam 4-2-2, the third middle layer elastic support beam 4-3-2, and the fourth middle layer elastic support beam 4-4-2 are symmetrically arranged on the upper left, lower left, upper right, and lower right sides of the inertial mass block 1, respectively.

[0085] The first outer elastic support beam 4-1-3 and the first inner elastic support beam 4-1-1 are located between the first middle elastic support beam 4-1-2 and the third middle elastic support beam 4-3-2, and are located on the upper side of the inertial mass block 1.

[0086] The second outer elastic support beam 4-2-3 and the second inner elastic support beam 4-2-1 are located between the first middle elastic support beam 4-1-2 and the second middle elastic support beam 4-2-2, and are located to the left of the inertial mass block 1.

[0087] The third outer elastic support beam 4-3-3 and the third inner elastic support beam 4-3-1 are located between the third middle elastic support beam 4-1-2 and the fourth middle elastic support beam 4-2-2, and are located to the right of the inertial mass block 1.

[0088] The fourth outer elastic support beam 4-4-3 and the fourth inner elastic support beam 4-4-1 are located between the third middle elastic support beam 4-3-2 and the fourth middle elastic support beam 4-4-2, and are located below the inertial mass block 1.

[0089] Anchor points 5 are located on the upper side of the first outer elastic support beam 4-1-3, the left side of the second outer elastic support beam 4-2-3, the right side of the third outer elastic support beam 4-3-3, and the lower side of the fourth outer elastic support beam 4-4-3.

[0090] The lower side of the first inner elastic support beam 4-1-1, the right side of the second inner elastic support beam 4-2-1, the left side of the third inner elastic support beam 4-3-1, and the upper side of the fourth inner elastic support beam 4-4-1 are all inertial mass blocks 1.

[0091] like Figure 7 As shown, the elastically supported beam system has special geometric characteristics: all beams are parallel to the base in the X and Y axes (e.g., ...). Figure 2 As shown in the X and Y planes, the width in the X and Y directions is significantly greater than (more than 100 times) the thickness in the Z direction. This irregular design makes the system exhibit high stiffness in the X and Y directions, which can effectively suppress the in-plane displacement of the inertial mass block; while maintaining low stiffness in the Z direction, allowing the inertial mass block to respond to out-of-plane acceleration.

[0092] The glass base and signal leads of the present invention are as follows: Figure 8As shown, the signal electrodes include a common electrode 7-9-1, a common electrode lead-out electrode 7-10-1, a first driving signal application electrode 7-1-1, a second driving signal application electrode 7-1-2, a third driving signal application electrode 7-2-1, a fourth driving signal application electrode 7-2-2, a fifth driving signal application electrode 7-2-3, a sixth driving signal application electrode 7-2-4, a seventh driving signal application electrode 7-3-1, an eighth driving signal application electrode 7-3-2, a first detection signal electrode 7-1-3, a second detection signal electrode 7-1-4, a third detection signal electrode 7-3-3, a fourth detection signal electrode 7-3-4, a fifth detection signal electrode 7-4-1, a sixth detection signal electrode 7-4-2, a seventh detection signal electrode 7-4-3, and an eighth detection signal electrode 7-4-4.

[0093] The first driving signal lead-out electrode 7-5-2, the second driving signal lead-out electrode 7-5-3, the third driving signal lead-out electrode 7-6-1, the fourth driving signal lead-out electrode 7-6-2, the fifth driving signal lead-out electrode 7-6-3, the sixth driving signal lead-out electrode 7-6-4, the seventh driving signal lead-out electrode 7-7-1, and the eighth driving signal lead-out electrode 7-7-2;

[0094] The first detection signal lead-out electrode is 7-5-1, the second detection signal lead-out electrode is 7-7-3, the third detection signal lead-out electrode is 7-8-1, and the fourth detection signal lead-out electrode is 7-8-2.

[0095] The common electrode 7-9-1 is connected to the ground terminal of the external drive and detection circuit through the common electrode lead-out electrode 7-10-1, which is used to provide a reference potential for each drive and detection unit.

[0096] The first driving signal application electrode 7-1-1, the second driving signal application electrode 7-1-2, the third driving signal application electrode 7-2-1, the fourth driving signal application electrode 7-2-2, the fifth driving signal application electrode 7-2-3, the sixth driving signal application electrode 7-2-4, the seventh driving signal application electrode 7-3-1, and the eighth driving signal application electrode 7-3-2 are respectively led out through the first driving signal lead-out electrode 7-5-2, the second driving signal lead-out electrode 7-5-3, the third driving signal lead-out electrode 7-6-1, the fourth driving signal lead-out electrode 7-6-2, the fifth driving signal lead-out electrode 7-6-3, the sixth driving signal lead-out electrode 7-6-4, the seventh driving signal lead-out electrode 7-7-1, and the eighth driving signal lead-out electrode 7-7-2, and connected to an external driving power supply, for providing alternating excitation signals to the first resonator 2 and the second resonator 3.

[0097] The first detection signal electrode 7-1-3 and the second detection signal electrode 7-1-4 are led out through the first detection signal lead-out electrode 7-5-1; the third detection signal electrode 7-3-3 and the fourth detection signal electrode 7-3-4 are led out through the second detection signal lead-out electrode 7-7-3; the fifth detection signal electrode 7-4-1 and the sixth detection signal electrode 7-4-2 are led out through the third detection signal lead-out electrode 7-8-1; and the seventh detection signal electrode 7-4-3 and the eighth detection signal electrode 7-4-4 are led out through the fourth detection signal lead-out electrode 7-8-2. They are connected to an external signal detection and processing circuit to collect the differential capacitance signal generated during the resonator's vibration.

[0098] When the accelerometer is subjected to acceleration, the inertial mass block 1 moves only in the Z-axis direction, driving the second resonator 3. This relative displacement changes the effective overlap area between the first coupling capacitor plate 2-4 on the first resonator 2 and the second coupling capacitor plate 3-4 on the second resonator 3. Based on the electrostatic negative stiffness effect, the change in the overlap area of ​​the coupling capacitor plates modulates the electrostatic coupling stiffness between the two resonators. This coupling stiffness disturbance causes a change in the system amplitude ratio, enabling highly sensitive measurement of external Z-axis acceleration.

[0099] The specific principle can be illustrated as follows:

[0100] First resonator support stiffness High, second resonator support stiffness The initial stiffness mismatch is relatively low due to the difference in support stiffness between the two components. Represented as:

[0101] (1),

[0102] Coupling stiffness variation: When the inertial mass moves, the coupling stiffness... The relationship between coupling stiffness and inertial mass acceleration will change and can be expressed as follows:

[0103] (2),

[0104] Where l is the length of the first coupling capacitor plate and the second coupling capacitor plate, and h is the initial overlap height of the first coupling capacitor plate and the second coupling capacitor plate. Polarization voltage, Let be the vacuum dielectric constant, and d be the distance between the first and second coupling capacitor plates. This represents the micro-displacement of the second coupling capacitor plate caused by acceleration.

[0105] Micro-displacement of the second coupling capacitor plate caused by acceleration The expression is:

[0106] (3),

[0107] in, The gain represents the conversion gain between micro-displacement and acceleration, which is negatively correlated with the stiffness of the elastic beam in the elastically supported structure and positively correlated with the equivalent stiffness of the inertial mass block. The acceleration is the input.

[0108] When acceleration is applied to the accelerometer, the inertial mass block 1, guided by the low Z-axis stiffness elastic support beam system, only produces Z-axis displacement, which drives the second resonator 3 to move synchronously. The first resonator 2, fixed to the base, remains stationary, resulting in a relative displacement between the first resonator 2 and the second resonator 3. This displacement causes a change in the effective facing area between the first coupling capacitor plate 2-4 and the second coupling capacitor plate 3-4. According to the electrostatic negative stiffness effect, the coupling stiffness between the first resonator 2 and the second resonator 3 changes accordingly. This stiffness disturbance is amplified by the weakly coupled resonant system and ultimately manifests as a change in the amplitude ratio. The expression for the ratio of the vibration amplitudes of the nested resonators is:

[0109] (4),

[0110] in, This refers to the mechanical stiffness disturbance of the inner and outer tuning fork resonator beams. The coupling stiffness is used. Ultimately, the improvement in Z-axis acceleration detection and sensitivity is achieved based on the calculation of the amplitude ratio change.

[0111] In this embodiment, the key structural parameters of the core nested resonator are set as follows:

[0112] 1. The first resonant beam has a length of 1875 μm and a width of 10 μm, with an equivalent support stiffness of [missing value]. = 107.75 N / m;

[0113] 2. The second resonant beam has a length of 1877 μm and a width of 10 μm, with an equivalent support stiffness of [missing value]. = 105.7 N / m;

[0114] 3. The length of the first and second electrostatic coupling parallel plates is 1750 μm, the initial height is 60 μm, the distance between the two plates is 2 μm, and the initial overlap area is A = 105,000 μm².

[0115] 4. The difference in bias voltage applied between the electrostatic coupling parallel plates =80V;

[0116] 5. Micro-displacement-acceleration conversion gain =0.42g / μm;

[0117] Based on the above structural parameters and according to the principle described in this invention, when the acceleration is 1g, the inertial mass block produces a displacement of approximately 2.38μm in the Z direction. The resulting change in the overlapping area of ​​the first and second coupling capacitor plates is approximately 4.17 × [missing value]. m², corresponding to a capacitance change of approximately 1.84 × F. Considering the initial stiffness mismatch of the two resonators Δk = 2.05 N / m, if the initial coupling stiffness is set... =0.1 N / m, then the sensitivity coefficient γ of the coupling stiffness to the capacitor is approximately 2.15 × 10⁻⁶ N / m, obtained by the following formula. N / m / F:

[0118] γ= (5),

[0119] in This is the initial capacitance.

[0120] Substitute into the sensitivity calculation formula:

[0121] (6),

[0122] The amplitude ratio change sensitivity of the device at an input of 1g is approximately 1.94× / g. This result shows that, compared with traditional accelerometers, the accelerometer of the present invention can detect only Z-axis acceleration and achieve higher output sensitivity.

[0123] This invention provides a Z-axis sensitive MEMS coupled stiffness modulation accelerometer. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A Z-axis sensitive MEMS coupled stiffness modulation accelerometer, characterized in that, Includes upper structure and lower structure; The upper structure is a silicon micromechanical sensor based on silicon material, and the lower structure is a glass base based on silicon dioxide (6). The silicon micromechanical sensor is connected to the glass base (6) via an anchor point (5), and the glass base (6) is provided with signal electrodes. The silicon micromechanical sensor includes an inertial mass block (1), a first resonator (2), a second resonator (3), an elastic support beam system (4), and an anchor point (5). The second resonator (3) is disposed inside the inertial mass block (1) and is directly connected to the upper inner side and the lower inner side of the inertial mass block (1); The first resonator (2) is located inside the second resonator (3) and is fixedly installed on the glass base (6), and is not connected to the inertial mass block (1); The elastic support beam system (4) includes a first elastic support beam system (4-1), a second elastic support beam system (4-2), a third elastic support beam system (4-3), and a fourth elastic support beam system (4-4). The first elastic support beam system (4-1), the second elastic support beam system (4-2), the third elastic support beam system (4-3) and the fourth elastic support beam system (4-4) are located on the upper side, left side, right side and lower side of the inertial mass block (1) respectively, and are all directly connected to the inertial mass block (1); The anchor point (5) is located on the outside of the first elastic support beam system (4-1), the second elastic support beam system (4-2), the third elastic support beam system (4-3), and the fourth elastic support beam system (4-4); The second resonator (3) and the first resonator (2) have a preset difference in elastic stiffness, forming an initial stiffness mismatch, so that the amplitude ratio of the resonant system composed of the second resonator (3) and the first resonator (2) is only affected by the coupling stiffness. The first outer elastic support beam (4-1-3), second outer elastic support beam (4-2-3), third outer elastic support beam (4-3-3), fourth outer elastic support beam (4-4-3), first middle elastic support beam (4-1-2), second middle elastic support beam (4-2-2), third middle elastic support beam (4-3-2), fourth middle elastic support beam (4-4-2), first inner elastic support beam (4-1-1), second inner elastic support beam (4-2-1), third inner elastic support beam (4-3-1), and fourth inner elastic support beam (4-4-1) of the first elastic support beam system (4-1), second elastic support beam (4-2-1), third inner elastic support beam (4-3-1), and fourth inner elastic support beam (4-4-1) have the same irregular geometric structure and mechanical parameters. The irregular geometric structure is designed such that the width of the first outer elastic support beam (4-1-3) in the X and Y axis directions parallel to the glass base (6) is greater than the height of the first outer elastic support beam (4-1-3) in the Z axis direction perpendicular to the glass base (6); The irregular geometric structure gives the elastic support beam system (4) high stiffness in the X and Y axis directions, which can suppress the displacement of the inertial mass block (1) in the X and Y axis directions; and low stiffness in the Z axis direction, which allows the inertial mass block (1) to only produce Z-direction displacement under acceleration. The anchor point (5) is a closed frame square ring, and the thickness of the anchor point (5) along the X, Y, and Z axes is greater than that of the adjacent functional structure. The bottom surface of the anchor point (5) is fixed to the surface of the glass base (6) to form fixed constraints on the X, Y, and Z axes; The anchor point (5) is used to limit the X, Y, and Z displacements of the elastic support beam system (4) and the inertial mass block (1) within the range of elastic deformation; The structure of the closed frame square ring can restrict the movement of the elastic support beam system (4) in the X and Y axis directions, and further restrict the movement of the inertial mass block (1) in the X and Y axis directions.

2. The Z-axis sensitive MEMS coupled stiffness modulation accelerometer according to claim 1, characterized in that, The first elastic support beam system (4-1) includes a first inner elastic support beam (4-1-1), a first middle elastic support beam (4-1-2), and a first outer elastic support beam (4-1-3). The second elastic support beam system (4-2) includes a second inner elastic support beam (4-2-1), a second middle elastic support beam (4-2-2), and a second outer elastic support beam (4-2-3). The third elastic support beam system (4-3) includes a third inner elastic support beam (4-3-1), a third middle elastic support beam (4-3-2), and a third outer elastic support beam (4-3-3). The fourth elastic support beam system (4-4) includes a fourth inner elastic support beam (4-4-1), a fourth middle elastic support beam (4-4-2), and a fourth outer elastic support beam (4-4-3). The first middle layer elastic support beam (4-1-2), the second middle layer elastic support beam (4-2-2), the third middle layer elastic support beam (4-3-2), and the fourth middle layer elastic support beam (4-4-2) are symmetrically arranged on the upper left, lower left, upper right, and lower right sides of the inertial mass block (1), respectively. The first outer elastic support beam (4-1-3) and the first inner elastic support beam (4-1-1) are located between the first middle elastic support beam (4-1-2) and the third middle elastic support beam (4-3-2), and are located on the upper side of the inertial mass block (1); The second outer elastic support beam (4-2-3) and the second inner elastic support beam (4-2-1) are located between the first middle elastic support beam (4-1-2) and the second middle elastic support beam (4-2-2), and are located to the left of the inertial mass block (1); The third outer elastic support beam (4-3-3) and the third inner elastic support beam (4-3-1) are located between the third middle elastic support beam (4-3-2) and the fourth middle elastic support beam (4-4-2), and are located to the right of the inertial mass block (1); The fourth outer elastic support beam (4-4-3) and the fourth inner elastic support beam (4-4-1) are located between the third middle elastic support beam (4-3-2) and the fourth middle elastic support beam (4-4-2), and are located below the inertial mass block (1); Anchor points (5) are located on the upper side of the first outer elastic support beam (4-1-3), the left side of the second outer elastic support beam (4-2-3), the right side of the third outer elastic support beam (4-3-3), and the lower side of the fourth outer elastic support beam (4-4-3). The lower side of the first inner elastic support beam (4-1-1), the right side of the second inner elastic support beam (4-2-1), the left side of the third inner elastic support beam (4-3-1), and the upper side of the fourth inner elastic support beam (4-4-1) are all inertial mass blocks (1).

3. The Z-axis sensitive MEMS coupled stiffness modulation accelerometer according to claim 2, characterized in that, The first resonator (2) is a fully constrained fixed resonant structure, and the whole is symmetrical about the X-axis; The first resonator (2) includes a first resonator anchor point (2-1), a first driving comb tooth (2-2), a first detection comb tooth (2-3), a first coupling capacitor plate (2-4), and a first resonant beam (2-5); The first resonator anchor point (2-1) is located on the top of the first resonator (2) and is fixedly connected to the glass base (6). The first driving comb teeth (2-2) are provided in two sets, symmetrically arranged on both sides of the first resonator anchor point (2-1) in the Y-axis direction; The first resonant beam (2-5) is located below the first resonator anchor point (2-1) and is arranged symmetrically along the Y-axis; The first detection comb teeth (2-3) are disposed on the inner side of the first resonant beam (2-5) and are symmetrically distributed along the Y-axis; The first coupling capacitor plate (2-4) is disposed on the outside of the first driving comb tooth (2-2) and is symmetrically distributed along the Y-axis; The first coupling capacitor plate (2-4) and the second coupling capacitor plate (3-4) on the second resonator (3) are parallel to each other, forming an electrostatic stiffness coupling system.

4. The Z-axis sensitive MEMS coupled stiffness modulation accelerometer according to claim 3, characterized in that, The second resonator (3) includes a second resonator connection (3-1), a second drive comb (3-2), a second detection comb (3-3), a second coupling capacitor plate (3-4), and a second resonant beam (3-5); The second resonator connection (3-1) is located on the top of the second resonator (3) and is connected to the inertial mass block (1); The second drive comb (3-2) has two sets, which are symmetrically arranged on the outer side of the second resonator connection (3-1) along the Y-axis direction; The second resonant beam (3-5) is located outside the second drive comb tooth (3-2) and is arranged symmetrically along the Y-axis; The second detection comb teeth (3-3) are located on the outside of the second resonant beam (3-5) and are symmetrically distributed along the Y-axis; The second coupling capacitor plate (3-4) is disposed inside the second drive comb (3-2) and is symmetrically distributed along the Y-axis.

5. The Z-axis sensitive MEMS coupled stiffness modulation accelerometer according to claim 4, characterized in that, The signal electrodes include a common electrode (7-9-1), a common electrode lead-out electrode (7-10-1), a first driving signal application electrode (7-1-1), a second driving signal application electrode (7-1-2), a third driving signal application electrode (7-2-1), a fourth driving signal application electrode (7-2-2), a fifth driving signal application electrode (7-2-3), a sixth driving signal application electrode (7-2-4), a seventh driving signal application electrode (7-3-1), and an eighth driving signal application electrode (7-3-2); a first detection signal electrode (7-1-3), a second detection signal electrode (7-1-4), a third detection signal electrode (7-3-3), a fourth detection signal electrode (7-3-4), a fifth detection signal electrode (7-4-1), a sixth detection signal electrode (7-4-2), a seventh detection signal electrode (7-4-3), and an eighth detection signal electrode (7-4-4). First driving signal lead-out electrode (7-5-2), second driving signal lead-out electrode (7-5-3), third driving signal lead-out electrode (7-6-1), fourth driving signal lead-out electrode (7-6-2), fifth driving signal lead-out electrode (7-6-3), sixth driving signal lead-out electrode (7-6-4), seventh driving signal lead-out electrode (7-7-1), eighth driving signal lead-out electrode (7-7-2); first detection signal lead-out electrode (7-5-1), second detection signal lead-out electrode (7-7-3), third detection signal lead-out electrode (7-8-1), fourth detection signal lead-out electrode (7-8-2); The common electrode (7-9-1) is connected to the ground terminal of the external driving and detection circuit through the common electrode lead-out electrode (7-10-1) to provide a reference potential for each driving and detection unit; The first driving signal application electrode (7-1-1), the second driving signal application electrode (7-1-2), the third driving signal application electrode (7-2-1), the fourth driving signal application electrode (7-2-2), the fifth driving signal application electrode (7-2-3), the sixth driving signal application electrode (7-2-4), the seventh driving signal application electrode (7-3-1), and the eighth driving signal application electrode (7-3-2) are respectively led out through the first driving signal lead-out electrode (7-5-2), the second driving signal lead-out electrode (7-5-3), the third driving signal lead-out electrode (7-6-1), the fourth driving signal lead-out electrode (7-6-2), the fifth driving signal lead-out electrode (7-6-3), the sixth driving signal lead-out electrode (7-6-4), the seventh driving signal lead-out electrode (7-7-1), and the eighth driving signal lead-out electrode (7-7-2), and connected to an external driving power supply, for providing alternating excitation signals to the first resonator (2) and the second resonator (3); The first detection signal electrode (7-1-3), the second detection signal electrode (7-1-4), the third detection signal electrode (7-3-3), the fourth detection signal electrode (7-3-4), the fifth detection signal electrode (7-4-1), the sixth detection signal electrode (7-4-2), the seventh detection signal electrode (7-4-3), and the eighth detection signal electrode (7-4-4) are respectively led out through the first detection signal lead-out electrode (7-5-1), the second detection signal lead-out electrode (7-7-3), the third detection signal lead-out electrode (7-8-1), and the fourth detection signal lead-out electrode (7-8-2), and are connected to an external signal detection and processing circuit to collect the differential capacitance signal generated during the vibration of the resonator.

6. The Z-axis sensitive MEMS coupled stiffness modulation accelerometer according to claim 5, characterized in that, When acceleration is applied to the acceleration time, the inertial mass block (1) is constrained to only produce displacement in the Z-axis direction under the joint guidance and restriction of the elastic support beam system (4) and the anchor point (5). The second resonator (3) generates Z-direction motion synchronously with the inertial mass block (1) through the second resonator connection (3-1). The first resonator (2) is fixedly installed on the glass base (6) through the first resonator anchor point (2-1) and remains stationary under the action of acceleration, so that the first resonator (2) and the second resonator (3) undergo relative displacement in the Z-axis direction; The relative displacement causes a change in the effective overlap area of ​​the first coupling capacitor plate (2-4) and the second coupling capacitor plate (3-4) located between the first resonator (2) and the second resonator (3), thereby modulating the electrostatic coupling stiffness; the change in coupling stiffness causes a change in the system amplitude ratio, and finally realizes the measurement of acceleration in the Z-axis direction.

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