Low Wen Piaogui resonance accelerometer structureTechnical Field
The invention relates to the technical field of inertial navigation, in particular to a low Wen Piaogui resonant accelerometer structure.
Background
A silicon resonant accelerometer is a micromechanical inertial device that characterizes acceleration by measuring the change in resonant frequency based on the principle of resonance. Compared with the traditional capacitive accelerometer, the resonant accelerometer modulates the acceleration sensitive signal on the frequency of the resonator before the acceleration sensitive signal enters the circuit, so that the acceleration signal is not easily affected by amplitude errors, high zero bias stability and scale factor stability are more easily realized, and the silicon resonant accelerometer has the advantages of small volume, low price, easiness in integration, semi-digital output and the like, has the potential of developing to navigation level precision, and has wide application prospect in the fields of national defense and military.
The silicon resonant accelerometer is generally composed of a sensitive mass block, a lever amplifying structure, a resonator, a supporting mechanism, a driving mechanism and a detecting mechanism. The main principle of the resonant accelerometer is that a driving mechanism maintains resonance of a resonator, when acceleration is input from the outside, a sensitive mass block converts the acceleration into inertia force, and then the inertia force is amplified by an amplifying lever to act on the resonator, so that the resonator generates tension or compression change to change the resonance frequency, and the information of the acceleration can be obtained by detecting the change of the resonance frequency of the resonator based on the force-frequency characteristic of the resonator.
Silicon resonant accelerometers were originally derived from the united states drager experiment, and the silicon resonant accelerometers currently being studied are still in world leading position with zero month stability. In addition, the university of california, berkeley, in the united states, designs a silicon resonant accelerometer with a two-stage amplification lever mechanism, the scale factor can reach 160Hz/g, and related researches are also carried out in the countries of the university of Korean, milan, french space agency, and the like. Universities and research institutions such as Qinghai university, beijing aerospace control instrument research, nanjing university and the like actively develop the research of the silicon resonant accelerometer, and various silicon resonant accelerometer structures are provided. Although the silicon resonant accelerometer with multiple structural forms such as multiple axes, high sensitivity, wide range and the like has been developed at home and abroad, the environmental adaptability is always a key index for restricting the development of the silicon resonant accelerometer, and the extreme temperature change working condition limits the practical engineering application of the silicon resonant accelerometer. The change of the ambient temperature has an important influence on the performance of the silicon resonant accelerometer, mainly because the thermal stress is generated due to the fact that the thermal expansion of the supporting anchor point is not matched, the performance of the accelerometer is unstable, the measurement precision of the accelerometer is reduced, the performance is deteriorated, and the engineering application of the silicon resonant accelerometer to a high-precision system is limited.
Disclosure of Invention
The invention aims to reduce the influence of thermal stress caused by temperature change by optimizing the structural design of the silicon resonant accelerometer, thereby improving the stability and measurement accuracy of the silicon resonant accelerometer in an extreme temperature change environment.
The technical scheme of the invention is that a low Wen Piaogui resonance accelerometer structure is provided, which comprises an intermediate layer, an upper glass cover plate and a lower glass cover plate;
The middle layer comprises a mass block, an amplifying lever structure, a resonator center supporting beam, driving detection comb teeth, a center anchor point and an outer frame;
The upper glass cover plate and the lower glass cover plate are respectively covered on two sides of the outer frame of the middle layer and are bonded with the outer frame of the middle layer, so that the middle layer is vacuum-packaged, and in addition, a metal wire is arranged in the upper glass cover plate and is connected with the driving detection comb teeth of the middle layer;
When the accelerometer structure has acceleration, the mass block applies inertial force to the amplifying lever structure under the inertial action, the inertial force is amplified by the amplifying lever structure, then the resonant frequency of the driving detection comb teeth is changed based on the force frequency characteristic, the resonant frequency influenced by the inertial force is measured by the driving detection comb teeth, and frequency signals are led out to the outside through metal wires to characterize the acceleration.
In any one of the above technical solutions, further, the intermediate layer further comprises a double-ended fixed tuning fork resonator;
The two-end fixed tuning fork resonator is connected to the resonator central supporting beam, and the thin end of the resonator central supporting beam is fixed at one side of the central anchor point;
The two groups of amplifying lever structures are respectively arranged at two sides of the thick end of the central supporting beam of the resonator through the third beam, the second beam of the amplifying lever structure is connected with the double-end fixed tuning fork resonator, and the first beam of the amplifying lever structure is connected with the mass block.
In any one of the above technical solutions, further, the double-ended fixed tuning fork resonator includes a first resonator beam, a second resonator beam, and two resonator side beams;
the first resonator beam and the second resonator beam are both fixed on a resonator center supporting beam, the first resonator beam is closer to a center anchor point, the two resonator side beams are connected to the end points of the first resonator beam and the second resonator beam to form a closed frame structure, and driving detection comb teeth are arranged at the center of the resonator side beams close to the outer sides.
In any of the above solutions, further, the portion of the resonator side beam close to the first resonator beam has a higher rigidity, and the side close to the second resonator beam has a lower rigidity.
In any one of the above technical schemes, further, the driving detection comb teeth comprise movable comb teeth, first fixed comb teeth, second fixed comb teeth and electrodes;
The movable comb teeth are fixed on the side beam of the resonator, electrodes are respectively connected to one ends of the first fixed comb teeth and one end of the second fixed comb teeth, the first fixed comb teeth and the second fixed comb teeth are respectively bonded with the upper glass cover plate through the electrodes connected with the electrodes, the movable comb teeth and the comb teeth of the first fixed comb teeth are mutually staggered to form a driving capacitor, and the first fixed comb teeth apply electrostatic force on the movable comb teeth to drive the movable comb teeth to move so as to enable the side beam of the resonator to resonate, meanwhile, the second fixed comb teeth and the movable comb teeth detect capacitance, and the second fixed comb teeth detect capacitance changes, so that the resonant frequency of the side beam of the resonator is measured, and the acceleration is represented.
In any of the above technical schemes, the middle layer further comprises a mass block supporting anchor point and a mass block supporting beam;
The mass block is connected with four mass block supporting anchor points through four mass block supporting beams, and the four mass block supporting anchor points are arranged in four frame corners of the outer frame and are bonded with the upper glass cover plate.
In any of the above technical solutions, further, the mass support beam has a U-shaped beam structure.
In any of the above solutions, further, after the resonator side beam is subjected to a compressive force or a tensile force, the resonant frequency of the resonator side beam is changed, and the resonant frequency of the resonator side beam may be expressed as:
Wherein FF is the resonance frequency of the resonator side beam after being stressed, E is the Young's modulus of monocrystalline silicon, w is the width of the resonator side beam, Lf is the length of the resonator side beam, h is the thickness of the middle layer, F is the pressure applied to a single resonator side beam, if the pressure is a pull force, the pressure is a negative value, ρ is the density of monocrystalline silicon, and m is the mass of movable comb teeth connected with the resonator side beam;
the above can be developed by taylor, and the higher order term is eliminated to obtain:
In the formula, fn is the resonance frequency of the side beam of the resonator when the stress is not applied, so that the resonance frequency of the side beam of the resonator is in linear relation with the applied stress, and further the side beam of the resonator can be used for representing the acceleration.
The beneficial effects of the invention are as follows:
according to the invention, the supporting points of the double-end fixed tuning fork resonator are concentrated at the geometric center of the accelerometer by designing the central supporting beam and the central anchor point, so that the influence of thermal expansion mismatch and thermal stress caused by temperature change is effectively reduced. The structural design enables the sensitive part (such as a resonator) to approach to a free thermal expansion state when the temperature changes, reduces measurement errors caused by the temperature changes, and remarkably reduces temperature drift (low temperature drift).
The invention obviously improves the zero offset stability and the scale factor stability of the accelerometer due to the inhibition of temperature change on thermal stress. The accelerometer can still keep highly stable performance under the extreme temperature change environment, and is suitable for high-precision navigation and inertial measurement systems.
By optimizing the layout of the supporting beams and the supporting anchor points, the accelerometer designed by the invention reduces unnecessary supporting points, so that the whole structure is simpler. After the structure is simplified, the processing technology requirement is reduced, so that common mode errors caused by inaccurate processing are reduced, and the stability and performance of the accelerometer are further improved.
Drawings
The advantages of the foregoing and additional aspects of the invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic diagram of an intermediate layer structure of a low Wen Piaogui resonant accelerometer structure according to one embodiment of the invention;
FIG. 2 is a schematic diagram of a lever amplification structure of a low Wen Piaogui resonant accelerometer structure according to one embodiment of the invention;
FIG. 3 is a schematic diagram of a dual-ended fixed tuning fork resonator structure of a low Wen Piaogui-resonant accelerometer structure according to one embodiment of the invention;
FIG. 4 is a schematic diagram of a resonator center beam support structure of a low Wen Piaogui-resonance accelerometer structure according to one embodiment of the invention;
FIG. 5 is a schematic diagram of a drive detection comb structure of a low Wen Piaogui resonance accelerometer structure according to one embodiment of the invention;
FIG. 6 is a schematic diagram of a mass support beam structure of a low Wen Piaogui resonant accelerometer structure according to one embodiment of the invention;
Fig. 7 is a graph of frequency versus acceleration simulation results for a silicon resonant accelerometer of a low Wen Piaogui resonant accelerometer structure according to one embodiment of the invention.
The device comprises a 1-mass block, a 2-amplifying lever structure, a 3-double-end fixed tuning fork resonator, a 4-resonator center supporting beam, 5-driving detection comb teeth, a 6-center anchor point, a 7-mass block supporting anchor point, an 8-mass block supporting beam, a 9-outer frame, a 10-first beam, a 11-second beam, a 12-third beam, a 13-first resonator beam, a 14-second resonator beam, a 15-resonator side beam, a 16-thin end, a 17-thick end, 18-movable comb teeth, 19-first fixed comb teeth, 20-second fixed comb teeth and 21-electrodes.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description. It should be noted that, without conflict, embodiments of the present invention and features in the embodiments may be combined with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those described herein, and therefore the scope of the present invention is not limited to the specific embodiments disclosed below.
As shown in FIG. 1, the embodiment provides a low Wen Piaogui resonant accelerometer structure that includes an intermediate layer, an upper glass cover plate, and a lower glass cover plate.
The upper glass cover plate and the lower glass cover plate are respectively covered on two sides of the outer frame of the middle layer and are bonded with the outer frame of the middle layer, so that the middle layer is vacuum-packaged, and in addition, a metal wire is arranged in the upper glass cover plate and is connected with an electrode of the driving detection comb teeth 5 of the middle layer, so that a frequency signal is led out to the outside.
The middle layer specifically comprises a mass block 1, an amplifying lever structure 2, a double-end fixed tuning fork type resonator 3, a resonator center supporting beam 4, a driving detection comb tooth 5, a center anchor point 6, a mass block supporting anchor point 7, a mass block supporting beam 8 and an outer frame 9.
The mass block 1 is made of monocrystalline silicon and is manufactured by adopting a bulk silicon processing technology, the mass block 1 is connected with four mass block supporting anchor points 7 through four mass block supporting beams 8, and the four mass block supporting anchor points 7 are arranged in four frame corners of an outer frame 9 and are bonded with an upper glass cover plate.
The central anchor point 6 is arranged at the center of the middle layer and is bonded with the upper glass cover plate, the mechanical structure of the middle layer is symmetrically distributed to two sides by taking the central anchor point 6 as the center, only one side is distributed, and the other side is symmetrical and is not repeated.
As shown in fig. 2 to 4, the double-ended fixed tuning fork resonator 3 is attached to the resonator center support beam 4, and the thin end 16 of the resonator center support beam 4 is fixed to one side of the center anchor point 6.
Two groups of amplifying lever structures 2 are respectively arranged at two sides of the thick end 17 of the resonator center support beam 4 through a third beam 12, a second beam 11 of the amplifying lever structure 2 is connected with the double-end fixed tuning fork resonator 3, and a first beam 10 of the amplifying lever structure 2 is connected with the mass block 1.
Specifically, the double-ended fixed tuning fork resonator 3 comprises a first resonator beam 13, a second resonator beam 14 and two resonator side beams 15, wherein the first resonator beam 13 and the second resonator beam 14 are both fixed on a resonator center support beam 4, the first resonator beam 13 is closer to a center anchor point 6, the two resonator side beams 15 are connected to the end points of the first resonator beam 13 and the second resonator beam 14 to form a closed frame structure, and the center of the resonator side beam 15, which is close to the outer side, is provided with a driving detection comb tooth 5.
In particular, the portion of the resonator side beam 15 close to the first resonator cross beam 13 has a higher rigidity, ensuring the stability of the connection, and the side close to the second resonator cross beam 14 has a lower rigidity, facilitating an increase in the magnification factor when the magnification lever structure 2 transmits the pressure.
As shown in fig. 5, the drive detection comb teeth 5 include movable comb teeth 18, first fixed comb teeth 19, second fixed comb teeth 20, and electrodes 21.
The movable comb teeth 18 are fixed on the resonator side beam 15, the electrodes 21 are respectively connected to one ends of the first fixed comb teeth 19 and the second fixed comb teeth 20, the first fixed comb teeth 19 and the second fixed comb teeth 20 are bonded with the upper glass cover plate through the electrodes 20 respectively connected with the movable comb teeth 18 and the first fixed comb teeth 19, comb teeth of the movable comb teeth 18 and the first fixed comb teeth 19 are mutually staggered to form a driving capacitor, the first fixed comb teeth 19 apply electrostatic force on the movable comb teeth 18 to drive the movable comb teeth to move, and therefore the resonator side beam 15 resonates, meanwhile, the second fixed comb teeth 19 and the movable comb teeth 18 form a detection capacitor, capacitance changes are detected through the second fixed comb teeth 20, and therefore the resonant frequency of the resonator side beam 15 is measured, and the electrodes 21 lead out frequency signals to the outside through metal conductors of the upper glass cover plate connected with the electrodes, and the capacitor is used for representing the acceleration.
As shown in fig. 6, in order to eliminate the thermal stress of the mass support anchor point 7 along the X-sensitive axis direction, the mass support beam 8 is designed into a U-shaped beam structure, so as to reduce the rigidity along the X-direction, and simultaneously ensure the rigidity along the Y-direction, and avoid the occurrence of the quadrature coupling error.
When the accelerometer senses acceleration in the external X direction, the mass block supporting beam 8 plays a role in supporting and buffering the mass block, the mass block 1 applies inertial force to the first beam 10 of the amplifying lever structure 2 under the effect of inertia, the inertial force is sequentially transmitted to the resonator side beam 15 through the amplifying lever structure 2 and the double-end fixed tuning fork resonator 3, and the driving detection comb teeth 5 arranged on the resonator side beam 15 detect vibration change conditions of the resonator side beam 15 to calculate the acceleration suffered by the low Wen Piaogui resonance accelerometer structure.
Specifically, the resonance frequency of the resonator side member 15 changes when the resonator side member 15 is subjected to a compressive or tensile force, and the resonance frequency of the single resonator side member 15 can be expressed as:
Where FF is the resonant frequency of the stressed resonator side beam 15, E is the young's modulus of single crystal silicon, w is the width of the resonator side beam 15, Lf is the length of the resonator side beam 15, h is the thickness of the middle layer, F is the pressure applied to the single resonator side beam 15, if the tensile force is negative, ρ is the density of single crystal silicon, and m is the mass of the movable comb teeth 18 connected with the resonator side beam 15.
The above can be developed by taylor, and the higher order term is eliminated to obtain:
Where fn is the resonant frequency of the resonator side member 15 when not under tension or compression. The resonant frequency of the resonator side beam 15 is thus linearly dependent on the applied force and can thus be used to characterize the acceleration. As shown in FIG. 7, the result of the structural simulation by using COMSOL software shows that the input acceleration is in a linear relation with the resonance frequency of a single resonance beam, and the simulation result also shows that the thermal stress of the resonator side beam 15 is very small and only 0.02MPa at maximum, and the influence on the resonance frequency of the resonator side beam 15 is basically negligible.
In summary, the invention provides a low Wen Piaogui resonant accelerometer structure, which comprises an intermediate layer, an upper glass cover plate and a lower glass cover plate.
The middle layer comprises a mass block 1, an amplifying lever structure 2, a resonator center support beam 4, driving and detecting comb teeth 5, a center anchor point 6 and an outer frame 9.
The upper glass cover plate and the lower glass cover plate are respectively covered on two sides of the outer frame of the middle layer and are bonded with the outer frame of the middle layer, so that the middle layer is vacuum-packaged, and in addition, a metal wire is arranged in the upper glass cover plate and is connected with the driving detection comb teeth 5 of the middle layer.
When the accelerometer structure has acceleration, the mass block 1 applies inertial force to the amplifying lever structure 2 under the action of inertia, the inertial force is amplified by the amplifying lever structure 2, then the resonance frequency of the driving detection comb teeth 5 is changed based on the force frequency characteristic, the driving detection comb teeth 5 are driven to measure the resonance frequency influenced by the inertial force, and frequency signals are led out to the outside through metal wires to represent the acceleration.
In the present invention, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and the terms "connected" may be, for example, a fixed connection, a removable connection, or an integral connection, and the terms "connected" may be directly or indirectly connected through an intermediary. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
The shapes of the various components in the drawings are illustrative, and do not exclude certain differences from the actual shapes thereof, and the drawings are merely illustrative of the principles of the present invention and are not intended to limit the present invention.
Although the invention has been disclosed in detail with reference to the accompanying drawings, it is to be understood that such description is merely illustrative and is not intended to limit the application of the invention. The scope of the invention is defined by the appended claims and may include various modifications, alterations and equivalents of the invention without departing from the scope and spirit of the invention.