Bias error suppression method for butterfly-wing MEMS resonant structure under random vibration

Abstract

The present invention discloses a method for suppressing bias errors of a butterfly-wing MEMS resonant structure under random vibration. By setting an error correction electrode on the electrode layer of the butterfly-wing MEMS resonant structure and applying a step-by-step DC voltage to the error correction electrode, the sensitive structure in the butterfly-wing MEMS resonant structure is subjected to vibration mode tuning until the bias error of the butterfly-wing MEMS resonant structure under the random vibration environment is completely suppressed. The present invention is applied to the field of MEMS sensors. After applying a DC voltage to the error correction electrode, the circumferential and normal orientations of the sensitive structure in the butterfly-wing MEMS resonant structure that moves in space under the working state can be adjusted to achieve the mode vibration mode tuning of the sensitive structure in the butterfly-wing MEMS resonant structure, overcome the bias change caused by the change in the motion state of the sensitive structure caused by the random vibration disturbance, and eliminate other errors that cause the bias change, effectively achieving the complete suppression of the bias error of the butterfly-wing MEMS resonant structure.

Description

Technical Field

[0001] The invention relates to the technical field of MEMS sensors, and in particular to a method for suppressing bias errors of a butterfly-wing MEMS resonant structure under random vibration. Background Art

[0002] Microelectromechanical system (hereinafter referred to as "MEMS") sensors have the advantages of low cost, small size, and easy batch manufacturing. They are currently widely used in military / civilian fields such as consumer electronics and guided munitions. As the application scenarios become more diverse, its working environment has also become more severe, for example, random vibration, a typical external environmental interference factor. Random vibration refers to vibration that has statistical characteristics but cannot be represented by a single deterministic function. It will change the distribution of stress in the resonant structure of the MEMS sensor and its motion state, resulting in a decrease in measurement accuracy. In severe cases, it may even cause the device to fail. These problems limit the engineering application of high-precision MEMS sensors.

[0003] To avoid the influence of random vibration on the operation of MEMS sensors, the traditional strategy is to add a vibration isolation device between the mounting base and the resonant structure, which has the advantages of good vibration isolation performance, simple and flexible design, etc., but the passive vibration isolation device will increase the system complexity and packaging space, while the active vibration isolation device will increase the power consumption of the device. From the perspective of structural design, the vibration resistance of the resonant structure itself can be improved. The main way is to add a vibration isolation frame to the sensitive structure and increase the resonant frequency of the sensitive structure. However, there are manufacturing errors and cost issues caused by high-precision processing requirements. Advanced algorithms for error compensation can be independent of the resonant structure design, and the output data of the resonant structure can be directly used to reduce the offset change caused by vibration. However, due to the different error mechanisms between different resonant structures, the bias repeatability is low, resulting in limitations in its compensation effect. The vibration immunity performance of the resonant structure bias error mechanism caused by random vibration is improved without changing the structure itself or the packaging form, and no output data post-processing is required. However, the current research results have not achieved complete error suppression, so there is an urgent need to propose a more perfect method to compensate for the bias error caused by random vibration and achieve better error suppression. Summary of the invention

[0004] In view of the deficiencies in the above-mentioned prior art, the present invention provides a method for suppressing the bias error of a butterfly-wing MEMS resonant structure under random vibration, which can effectively achieve complete suppression of the bias error of the resonant structure under random vibration environment without changing the resonant structure, packaging form and without the need for data post-processing.

[0005] To achieve the above-mentioned purpose, the present invention provides a method for suppressing bias errors of a butterfly-wing MEMS resonant structure under random vibration, wherein an error correction electrode is arranged on the electrode layer of the butterfly-wing MEMS resonant structure, and a stepped DC voltage is applied to the error correction electrode to adjust the stiffness matrix and the damping matrix in the modal parameters of the sensitive structure in the butterfly-wing MEMS resonant structure, thereby achieving vibration mode tuning of the sensitive structure in the butterfly-wing MEMS resonant structure, until the bias error of the butterfly-wing MEMS resonant structure under the random vibration environment is completely suppressed;

[0006] Stiffness matrix after applying DC voltage to the error correction electrode K' for:

[0007] ;

[0008] in, , When considering the stiffness coupling error, x, y Directional stiffness, for x Directions to y Stiffness coupling error in the direction, for y Directions to x Stiffness coupling error in the direction, , They are right x, y The influence of directional stiffness, for right x Direction and y Effect of stiffness coupling error between directions ， for right y Direction and x The influence of the stiffness coupling error between directions, is the stiffness generated by the electrostatic force after the error correction voltage is applied to the error correction electrode;

[0009] Damping matrix after applying DC voltage to the error correction electrode C' for:

[0010] ;

[0011] in, , When considering the damping coupling error, x, y Directional damping, for x Directions to y The damping coupling error in the direction, fory Directions to x The damping coupling error in the direction, , They are right x, y The influence of directional damping, for right x Direction and y The influence of damping coupling error between directions, for right y Direction and x The influence of damping coupling error between directions, It is the damping produced by the electrostatic force after the error correction voltage is applied to the error correction electrode.

[0012] In one embodiment, the error correction electrode is provided on the electrode layer of the butterfly-wing MEMS resonant structure, specifically:

[0013] Two groups of error correction electrodes distributed in an "X" shape are arranged on the electrode layer of the butterfly-wing MEMS resonant structure.

[0014] In one embodiment, applying a stepped DC voltage to the error correction electrode specifically comprises the following steps:

[0015] Step 1, installing a sensor consisting of a butterfly-wing MEMS resonant structure provided with an error correction electrode on a vibration table and then powering it on;

[0016] Step 2, randomly selecting a group of error correction electrodes as current error correction electrodes;

[0017] Step 3, under the premise that the input voltage on the current error correction electrode is U0, the vibration table is set to work in a random vibration mode, and the output signals of the sensor composed of the butterfly-wing MEMS resonant structure before, during and after the vibration are collected, thereby obtaining the first bias error data and its error amount, wherein the value of U0 is equal to the reference voltage value of the sensitive structure in the butterfly-wing MEMS resonant structure;

[0018] Step 4, let the voltage U=U0+δu, where δu is the step voltage value;

[0019] Step 5, under the premise that the input voltage on the current error correction electrode is U, the vibration table is set to work in a random vibration mode, and the output signals of the sensor composed of the butterfly-wing MEMS resonant structure before, during and after the vibration are collected, thereby obtaining the second bias error data and its error amount;

[0020] Step 6, determining whether the error amount of the second bias error data is greater than the error amount of the first bias error data:

[0021] If yes, select another set of error correction electrodes as the current error correction electrodes and return to step 3;

[0022] Otherwise, proceed to step 7;

[0023] Step 7, determining whether the error amount of the second bias error data is equal to 0:

[0024] If yes, the current voltage U is output as the input voltage on the current error correction electrode, so as to achieve complete suppression of the bias error of the butterfly-wing MEMS resonant structure under the random vibration environment;

[0025] Otherwise, set U = U + δu and return to step 5.

[0026] In one embodiment, in step 3, the process of obtaining the first bias error data and its error amount is:

[0027] Before the vibration table vibrates randomly, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure is collected in the first period and the average value is calculated. ;

[0028] During the random vibration of the vibration table, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the second period is collected and the average value is calculated. ;

[0029] After the vibration table stops random vibration, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the third period is collected and the average value is calculated. ;

[0030] The error amount of the first bias error data is calculated as .

[0031] In one embodiment, in step 4, the process of acquiring the second bias error data and the error amount thereof is:

[0032] Before the vibration table vibrates randomly, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the fourth period is collected and the average value is calculated. ;

[0033] During the random vibration of the vibration table, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the fifth period is collected and the average value is calculated. ;

[0034] After the vibration table stops random vibration, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the sixth period is collected and the average value is calculated. ;

[0035] The error amount of the second bias error data is calculated as .

[0036] In one embodiment, the first time period is equal to the fourth time period in length, the second time period is equal to the fifth time period in length, and the third time period is equal to the sixth time period in length.

[0037] Compared with the prior art, the present invention has the following beneficial technical effects:

[0038] 1. The present invention sets an error correction electrode on the butterfly-wing MEMS resonant structure. After applying a DC voltage to the error correction electrode, the circumferential and normal orientations of the sensitive structure in the butterfly-wing MEMS resonant structure that moves in space under the working state can be adjusted, thereby realizing the modal vibration type tuning of the sensitive structure in the butterfly-wing MEMS resonant structure, overcoming the bias change caused by the change of the motion state of the sensitive structure caused by random vibration disturbance, and eliminating other errors causing bias changes, such as stiffness coupling error, damping coupling error and force coupling error, thereby effectively realizing the complete suppression of the bias error of the butterfly-wing MEMS resonant structure.

[0039] 2. The present invention can neither change the MEMS resonant structure form and processing difficulty, nor require a large amount of prior data and complex algorithm support, and can quickly and effectively improve the vibration immunity of the sensor from the perspective of error mechanism analysis and suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0041] Figure 1 Schematic diagram of a butterfly-wing MEMS resonant structure in an embodiment of the present invention;

[0042] Figure 2 FIG. 1 is a schematic diagram of the sensitive structure and electrodes of the butterfly-wing MEMS resonant structure in an embodiment of the present invention, wherein Figure 2 (a) is a schematic diagram of the sensitive structure. Figure 2 (b) is a schematic diagram of electrodes;

[0043] Figure 3 : is a simulation diagram of the sensitive structure mode of the butterfly-wing MEMS resonant structure in an embodiment of the present invention, wherein Figure 3 (a) is the schematic diagram of the second-order mode. Figure 3 (b) is the schematic diagram of the third-order mode;

[0044] Figure 4 It is a simulation diagram of the spatial displacement change of the mass block of the sensitive structure in the butterfly-wing MEMS resonant structure in the embodiment of the present invention under different working conditions;

[0045] Figure 5 Schematic diagram of a multi-error coupling single-point mass model of a butterfly-wing MEMS resonant structure in an embodiment of the present invention;

[0046] Figure 6 The butterfly-wing MEMS resonant structure under different stiffness coupling errors and damping coupling errors in the embodiment of the present invention is shown in FIG. y Schematic diagram of directional displacement output changes;

[0047] Figure 7 is a design diagram of an error correction electrode for realizing vibration mode tuning in an embodiment of the present invention;

[0048] Figure 8 It is a flow chart of a method for suppressing bias errors under random vibration of a butterfly-wing MEMS resonant structure in an embodiment of the present invention;

[0049] Fig. 9 is a structural block diagram of the vibration mode tuning control in an embodiment of the present invention;

[0050] Fig.10 Schematic diagram of the suppression effect of the error correction voltage on the bias error under different axial random vibrations in an embodiment of the present invention.

[0051] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0054] The present embodiment discloses a method for suppressing bias errors of a butterfly-wing MEMS resonant structure under random vibration. An error correction electrode is provided on an electrode layer of the butterfly-wing MEMS resonant structure, and a stepped DC voltage is applied to the error correction electrode to adjust the stiffness matrix and the damping matrix in the modal parameters of the sensitive structure in the butterfly-wing MEMS resonant structure. Vibration mode tuning of the sensitive structure in the butterfly-wing MEMS resonant structure is achieved, until the bias error of the butterfly-wing MEMS resonant structure under a random vibration environment is completely suppressed without changing the sensitive structure and packaging form of the resonant structure and without performing data post-processing.

[0055] During the specific implementation process, two groups of error correction electrodes distributed in the "×" direction are designed on the electrode layer of the butterfly-wing MEMS resonant structure. After a DC voltage is applied to the error correction electrodes, the circumferential and normal orientations of the sensitive structure in the butterfly-wing MEMS resonant structure moving in space under the working state can be adjusted, thereby realizing the modal vibration tuning of the sensitive structure in the butterfly-wing MEMS resonant structure.

[0056] like Figure 1 FIG. 1 is a schematic diagram of the structure of the butterfly-wing MEMS resonant structure in this embodiment, which is mainly composed of a sensitive structure, an electrode and a cap. Figure 2 (a), the sensitive structure includes a mass block, a vibration beam, an anchor point and a stress release frame. The mass blocks are coupled through the vibration beam, and the anchor point is used to support and fix the sensitive structure to ensure the stability of the structure. The vibration beam is an irregular polygon to increase the vibration amplitude of the butterfly-wing MEMS resonant structure to improve the sensitivity. In addition, a stress release structure is designed on the sensitive structure to reduce the stress effect. Figure 2 (b) The electrode layer of the butterfly-wing MEMS resonant structure is designed with multiple functional electrodes, including driving electrodes, detection electrodes, error correction electrodes, common electrodes and frequency modulation electrodes, which can meet different measurement and control requirements.

[0057] The typical working mode of butterfly-wing MEMS resonant structure is "in-plane driving and out-of-plane detection", which corresponds to the second-order mode and the third-order mode respectively. Figure 3 As shown in the figure, the resonant frequencies are 5929.9 Hz and 6258.8 Hz respectively. When the second-order mode is excited, due to the anti-phase spatial motion between the mass blocks, under the Coriolis effect, the two mass blocks will perform opposite torsional swing motion, and its vibration mode is consistent with the third-order mode. At the same time, full differential detection can be achieved by connecting the diagonal detection electrodes under the mass blocks, which not only significantly improves the mechanical sensitivity of the butterfly-wing MEMS resonant structure, but also effectively eliminates the common-mode error caused by external environmental disturbances.

[0058] Based on COMSOL simulation, the changes in the motion state of the butterfly-wing MEMS resonant structure under different conditions are analyzed, and the displacement of the sensitive structure under different motion states is calculated according to Figure 2 The marks of the measurement points in (a) are counted, such as Figure 4 As shown. In the case of only driving moment input and no Gorbachev effect, the two mass blocks will perform anti-phase spatial tangential motion. On the other hand, when typical random vibration conditions (for example, the effective value of equivalent acceleration is 6.06g) are applied to the sensitive structure from different directions as external disturbance forces, when the external random vibration is transmitted to the sensitive structure through the anchor point, the motion form of the butterfly-wing MEMS resonant structure changes, and the spatial displacement changes significantly. Due to the delay in system control, it will directly change the vibration mode of the sensitive structure.

[0059] refer to Figure 5 , which is a multi-error coupling model of butterfly-wing MEMS resonant structure caused by random vibration. The model mainly includes the external disturbance error caused by the equivalent acceleration of random vibration, and the deviation of excitation parameters and inherent parameters caused by the existence of design coupling and processing errors, resulting in stiffness coupling error and damping coupling error, as well as driving force deviation error. Figure 5 middle, x and y The axes represent the second-order mode direction and the third-order mode motion direction, ω 1 and ω 2 represents the angular frequency of the main stiffness axis, is the stiffness axis deviation x Azimuth of the axis; and represents the decay time constant corresponding to the damping axis, To damp the axis deviation x Azimuth of the axis; is the magnitude of the driving force, and its angle of deviation from the coordinate system is α ; Indicates the random vibration equivalent acceleration x The load force generated by the shaft; Indicates the random vibration equivalent acceleration y The load force generated by the shaft.

[0060] Butterfly-wing MEMS resonant structure x Direction and y The displacement outputs in the directions can be expressed as:

[0061] (1)

[0062] (2)

[0063] In the formula, for x Directional mechanical thermal noise; for y Directional mechanical thermal noise; Indicates that when the damping coupling error is considered x Directional damping; Indicates that when the damping coupling error is considered y Directional damping; express x Directions to y Damping coupling error in direction; express y Directions to x Damping coupling error in direction; Indicates that when considering the stiffness coupling error x Directional stiffness; Indicates that when considering the stiffness coupling error y Directional stiffness; express x Directions to y Stiffness coupling error in direction; express y Directions to x The stiffness coupling error in the direction; and , .

[0064] By adjusting the driving force deflection angle, driving displacement, driving amplitude, driving reference phase, damping coupling error and stiffness coupling error and other variables, the error caused by random vibration equivalent acceleration can be effectively eliminated. However, since the butterfly-wing MEMS resonant structure cannot achieve circumferential excitation, the driving force deflection angle is not adjustable. In order to improve the detection accuracy and ensure the maximum vibration amplitude, the driving force should be kept at the lowest level at this time to achieve performance optimization. The adjustment rules of the above parameters are certain. Stiffness coupling error and damping coupling error are non-ideal factors that affect the performance of the system and need to be eliminated, so they can be used as adjustment quantities for system parameters.

[0065] Figure 6 For only existence x Different stiffness coupling errors and damping coupling errors have an impact on the equivalent acceleration of random vibration in different directions. y It can be seen that by changing the values ​​of stiffness coupling error and damping coupling error, even under the influence of random vibration equivalent acceleration, the y The modulation of the directional displacement output is the adjustment of the bias of the butterfly-wing MEMS resonant structure. During the adjustment process, not only the stiffness coupling error and the damping coupling error can be suppressed, but also the random vibration equivalent acceleration can be y The effect of directional displacement output can also be offset.

[0066] The relationship between the stiffness coupling error and the damping coupling error and the stiffness and damping of the sensitive structure in the butterfly-wing MEMS resonant structure can be expressed as:

[0067] (3)

[0068] (4)

[0069] In the formula, ω express ω 1 and ω The sum of 2, express ω 1 and ω The difference of 2, express and of and, express and difference.

[0070] From equations (3) and (4), it can be seen that the vibration mode will change with the change of the stiffness coupling error and the damping coupling error. Since the bias error comes from the change of the motion state of the sensitive structure in the butterfly-wing MEMS resonant structure caused by the equivalent acceleration of random vibration, this embodiment adjusts the vibration mode of the sensitive structure by regulating the stiffness coupling error and the damping coupling error, so that it is not affected by the random vibration disturbance, thereby suppressing the bias error. Specifically, the relationship between the stiffness and damping of the sensitive structure can be expressed as:

[0071] (5)

[0072] in, c is the damping of the system, k is the stiffness of the system, Q is the equivalent quality factor of the system, ω n is the resonant frequency;

[0073] The resonant frequency links the stiffness and damping of the system together. The negative electrostatic stiffness effect is a method to change the resonant frequency. Applying a DC voltage to the error correction electrode changes the potential difference between the electrode and the sensitive structure, thereby adjusting the electrostatic force. At the same time, the stiffness distribution of the system changes, causing the resonant frequency to change, and the damping distribution also changes accordingly. At this time, the change in the modal parameters of the system will be reflected in the vibration mode, achieving the effect of vibration mode tuning.

[0074] In this embodiment, for a butterfly-wing MEMS resonant structure in which a mass block is coupled through a vibration beam and a non-planar translation vibration occurs, an error correction electrode is arranged just below the top corner of the mass block, and four electrodes are arranged on the electrode layer below a single mass block, which are distributed in two groups along the diagonal direction of the mass block, so that spatial adjustment of vibration modes in different directions can be achieved, such as Figure 7 As shown, then, the stiffness matrix after the error correction voltage is added to the error correction electrode is K' It can be expressed as:

[0075] (6)

[0076] in, K t is the stiffness generated by the electrostatic force after the error correction voltage is applied to the error correction electrode, K txx express K t right x Effect of Directional Stiffness 、K txy express K t right x Direction and y Effect of stiffness coupling error between directions 、K tyx express K t right y Direction and x Effect of stiffness coupling error between directions 、K tyy express K t right y The influence of directional stiffness.

[0077] Damping Matrix C' It can be expressed as:

[0078] (7)

[0079] in, C t is the damping generated by the electrostatic force after the error correction voltage is applied to the error correction electrode, C txx express C t right x Effect of directional damping 、C txy express C t right x Direction and y Effect of damping coupling error between directions 、C tyx express C t right y Direction and x Effect of damping coupling error between directions 、C tyy express C t right y The influence of directional damping.

[0080] From the calculation process of the stiffness matrix and damping matrix of the butterfly-wing MEMS resonant structure, it can be seen that adding a DC voltage to the error correction electrode of the butterfly-wing MEMS resonant structure can adjust the stiffness matrix and damping matrix in the modal parameters of the sensitive structure and realize modal vibration tuning. Figure 8 The bias error suppression method of the butterfly-wing MEMS resonant structure under random vibration in this embodiment specifically includes the following steps:

[0081] Step 1, installing a sensor consisting of a butterfly-wing MEMS resonant structure provided with an error correction electrode on a vibration table and then powering it on;

[0082] Step 2, randomly selecting a group of error correction electrodes as current error correction electrodes;

[0083] Step 3, under the premise that the input voltage on the current error correction electrode is U0, the vibration table is set to work in a random vibration mode, and the output signals of the sensor composed of the butterfly-wing MEMS resonant structure before, during and after the vibration are collected, thereby obtaining the first bias error data and its error amount, wherein the value of U0 is equal to the reference voltage value of the sensitive structure in the butterfly-wing MEMS resonant structure;

[0084] Step 4, let the voltage U=U0+δu, where δu is the step voltage value;

[0085] Step 5, under the premise that the input voltage on the current error correction electrode is U, the vibration table is set to work in a random vibration mode, and the output signals of the sensor composed of the butterfly-wing MEMS resonant structure before, during and after the vibration are collected, thereby obtaining the second bias error data and its error amount;

[0086] Step 6, determining whether the error amount of the second bias error data is greater than the error amount of the first bias error data:

[0087] If yes, select another set of error correction electrodes as the current error correction electrodes and return to step 3;

[0088] Otherwise, proceed to step 7;

[0089] Step 7, determining whether the error amount of the second bias error data is equal to 0:

[0090] If yes, the current voltage U is output as the input voltage on the current error correction electrode, so as to achieve complete suppression of the bias error of the butterfly-wing MEMS resonant structure under the random vibration environment;

[0091] Otherwise, set U = U + δu and return to step 5.

[0092] It is worth noting that, although two groups of error correction electrodes are arranged on the butterfly-wing MEMS resonant structure electrode in this embodiment, and the two groups of error correction electrodes are arranged in an X shape on the butterfly-wing MEMS resonant structure electrode, in specific applications, the number of error correction electrodes is not limited to two, nor is it limited to an X shape arrangement. For example, three groups of error correction electrodes may be arranged in a rice shape, or the number or position of the corresponding error correction electrodes may be set according to actual needs.

[0093] In this embodiment, the process of obtaining the first bias error data and its error amount is as follows:

[0094] First, before the vibration table vibrates randomly, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the first period is collected and the average value is calculated. ;

[0095] Secondly, during the random vibration of the vibration table, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the second period is collected and the average value is calculated. ;

[0096] Then, after the vibration table stops random vibration, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the third period is collected and the average value is calculated. ;

[0097] Finally, the error amount of the first bias error data is calculated as .

[0098] In this embodiment, the process of obtaining the second bias error data is as follows:

[0099] First, before the vibration table vibrates randomly, the output signal of the sensor composed of butterfly-wing MEMS in the fourth period is collected and the average is calculated. ;

[0100] Secondly, during the random vibration of the vibration table, the output signal of the sensor composed of butterfly-wing MEMS in the fifth period is collected and the average value is calculated. ;

[0101] Then, after the vibration table stops random vibration, the output signal of the sensor composed of butterfly wing MEMS in the sixth period is collected and the average value is calculated. ;

[0102] Finally, the error amount of the second bias error data is calculated as .

[0103] As a preferred implementation mode, in the process of obtaining the first bias error data and the second bias error data, the data collection time under different working conditions is equal, that is, the time lengths of the first time period and the fourth time period are equal, the time lengths of the second time period and the fifth time period are equal, and the time lengths of the third time period and the sixth time period are equal. Further preferably, the first time period, the second time period, the third time period, the fourth time period, the fifth time period, and the sixth time period can all be set to be equal.

[0104] The bias error suppression method of the butterfly-wing MEMS resonant structure under random vibration in this embodiment is further described below with reference to specific examples.

[0105] Fig. 9 The structure block diagram of the bias error suppression of the butterfly-wing MEMS resonant structure under random vibration in this embodiment is shown, including a butterfly-wing MEMS resonant structure module, a signal conversion and separation module, a drive control module and a detection output module. When the butterfly-wing MEMS resonant structure module is in working state, the capacitance output of the second-order mode after the input excitation on the driving electrode is converted into a voltage signal by the signal C / V conversion module with weak capacitance detection capability, and then enters the drive control module through the first high-frequency carrier multiplication demodulation. The signal is demodulated by orthogonal multiplication through the second-order modal resonant frequency in the drive control module and then amplitude and phase discrimination are performed. The output amplitude is controlled by PID to ensure the amplitude stability, and the output phase is controlled by PLL to ensure that the sensitive structure in the butterfly-wing MEMS resonant structure is in a resonant state. The output of PID and PLL is used as the second-order modal control signal of the sensitive structure, and is modulated by the second-order modal resonant frequency and the first high-frequency carrier as a control signal and returned to the drive control module to input the driving electrode. On the other hand, the capacitance output between the detection electrode and the sensitive structure corresponding to the third-order mode modulated by the second high-frequency carrier is converted into a voltage signal by a signal conversion module with weak capacitance detection capability, and then enters the detection module through the second high-frequency carrier multiplication demodulation. The signal is orthogonally multiplied and demodulated by the second-order mode resonance frequency in the detection output module and is low-pass filtered to form a bias output signal orthogonal to the phase of the driving amplitude signal and an orthogonal error output signal with the same phase as the driving amplitude signal. After applying the error correction voltage to the error correction electrode, the output signal of the detection output module can be used to determine whether the error correction direction is correct and the bias error suppression effect.

[0106] according to Fig.10It can be seen that when the correct error correction direction is selected, the error correction voltage is increased on the error correction electrode, and the bias error of the butterfly-wing MEMS resonant structure under random vibration disturbances in different axes will decrease with the increase of voltage. In this embodiment, the voltage at which the bias error is suppressed to 0 is about 9.72V, thereby verifying the effectiveness of the error suppression method proposed in this embodiment, but when the error correction voltage continues to increase, the bias error under random vibration disturbance will increase in the opposite direction, indicating that the ideal vibration mode is a balanced state. In summary, this method has the ability to suppress the bias error caused by random vibrations in different axes or between different devices to 0, but due to temperature changes, measurement and instrument errors, and the existence of bias drift of the resonant structure itself, the voltage at which the bias error is completely suppressed will be different, which does not affect the effectiveness of this method.

[0107] The above description is only a preferred embodiment of the present invention, and does not limit the protection scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the protection scope of the present invention.

Claims

1. A method for suppressing bias error of a butterfly-wing MEMS resonant structure under random vibration, characterized in that: An error correction electrode is arranged on the electrode layer of the butterfly-wing MEMS resonant structure, and a stepped DC voltage is applied to the error correction electrode to adjust the stiffness matrix and the damping matrix in the modal parameters of the sensitive structure in the butterfly-wing MEMS resonant structure, so as to achieve vibration mode tuning of the sensitive structure in the butterfly-wing MEMS resonant structure until the bias error of the butterfly-wing MEMS resonant structure in a random vibration environment is completely suppressed, wherein the number of the error correction electrodes is two groups; Stiffness matrix after applying DC voltage to the error correction electrode for: ; in, , When considering the stiffness coupling error, x, y Directional stiffness, for x Directions to y Stiffness coupling error in the direction, for y Directions to x Stiffness coupling error in the direction, , They are right x, y The influence of directional stiffness, for right x Direction and y Effect of stiffness coupling error between directions ， for right y Direction and x The influence of the stiffness coupling error between directions, The stiffness generated by the electrostatic force after applying a DC voltage to the error correction electrode; Damping matrix after applying DC voltage to the error correction electrode for: ; in, , When considering the damping coupling error, x, y Directional damping, for x Directions to y The damping coupling error in the direction, for y Directions to x The damping coupling error in the direction, , They are right x, y The influence of directional damping, for right x Direction and y The influence of damping coupling error between directions, for right y Direction and x The influence of damping coupling error between directions, The damping caused by the electrostatic force after applying a DC voltage to the error correction electrode; The step of applying a stepped DC voltage to the error correction electrode specifically comprises the following steps: Step 1, installing a sensor consisting of a butterfly-wing MEMS resonant structure provided with an error correction electrode on a vibration table and then powering it on; Step 2, randomly selecting a group of error correction electrodes as current error correction electrodes; Step 3, the input voltage on the current error correction electrode is Under the premise of setting the vibration table to work in random vibration mode, and collecting the output signals of the sensor composed of the butterfly-wing MEMS resonant structure before, during and after vibration, and then obtaining the first bias error data and its error amount, wherein, The value is equal to the reference voltage value of the sensitive structure in the butterfly-wing MEMS resonant structure. The acquisition process of the first bias error data and its error amount is: Before the vibration table vibrates randomly, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure is collected in the first period and the average value is calculated. ; During the random vibration of the vibration table, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the second period is collected and the average value is calculated. ; After the vibration table stops random vibration, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the third period is collected and the average value is calculated. ; The error amount of the first bias error data is calculated as follows: ; Step 4: Set the voltage ,in, is the step voltage value; Step 5: Under the premise that the input voltage on the current error correction electrode is U, the vibration table is set to work in a random vibration mode, and the output signals of the sensor composed of the butterfly-wing MEMS resonant structure before, during and after vibration are collected to obtain the second bias error data and the error amount thereof. The process of obtaining the second bias error data and the error amount thereof is as follows: Before the vibration table vibrates randomly, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the fourth period is collected and the average value is calculated. ; During the random vibration of the vibration table, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the fifth period is collected and the average value is calculated. ; After the vibration table stops random vibration, the output signal of the sensor composed of the butterfly-wing MEMS resonant structure in the sixth period is collected and the average value is calculated. ; The error amount of the second bias error data is calculated as ; Step 6, determining whether the error amount of the second bias error data is greater than the error amount of the first bias error data: If yes, select another set of error correction electrodes as the current error correction electrodes and return to step 3; Otherwise, proceed to step 7; Step 7, determining whether the error amount of the second bias error data is equal to 0: If yes, the current voltage U is output as the input voltage on the current error correction electrode, so as to achieve complete suppression of the bias error of the butterfly-wing MEMS resonant structure under the random vibration environment; Otherwise, let Then return to step 5.

2. The method for suppressing bias error of a butterfly-wing MEMS resonant structure under random vibration according to claim 1, characterized in that: The error correction electrode is provided on the electrode layer of the butterfly-wing MEMS resonant structure, specifically: Two groups of error correction electrodes distributed in an "X" shape are arranged on the electrode layer of the butterfly-wing MEMS resonant structure.

3. The method for suppressing bias error of a butterfly-wing MEMS resonant structure under random vibration according to claim 1, characterized in that: The first time period is equal to the fourth time period in length, the second time period is equal to the fifth time period in length, and the third time period is equal to the sixth time period in length.

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