MEMS gyroscope based on dithering structure and method for suppressing zero bias thereof

Abstract

The application discloses a MEMS gyroscope based on a dithering structure and a zero-offset suppression method thereof. The application adopts periodic dithering modulation on a sensitive axis of the gyroscope, and obtains an angular velocity through secondary demodulation. The zero-offset of the gyroscope is modulated to a high frequency at the same time when the angular velocity is obtained through the secondary demodulation, and the zero-offset modulated to the high frequency is eliminated through low-pass filtering. The zero-offset error of the application is 0, and periodic calibration and compensation of the zero-offset are no longer needed, which will greatly save the economic and time cost of user maintenance in practical application. The application solves the problem of long-term storage and calibration-free of the gyroscope, and greatly expands the application of the MEMS gyroscope in the field of long-time and long-range pure inertial navigation.

Description

Technical Field

[0001] This invention belongs to the field of gyroscope technology, and relates to zero bias suppression of MEMS gyroscopes, and particularly to MEMS gyroscopes based on jitter structures and their zero bias suppression methods. Background Technology

[0002] Zero-rate bias or zero-point drift of a gyroscope, or simply zero bias, refers to the angular velocity output generated without any rotational input to the gyroscope's sensitive axis. It is a crucial indicator of gyroscope performance and significantly limits its application in navigation, guidance, and other fields. During manufacturing, each individual gyroscope has a relatively small zero bias after calibration. However, the zero bias is not fixed over time and drifts due to factors such as temperature changes and aging of the materials used in the sensor. Therefore, the sensor needs to be periodically recalibrated to zero. This periodic calibration and compensation significantly increases the economic and time costs for users.

[0003] MEMS gyroscopes are characterized by their small size, light weight, low power consumption, easy integration, strong overload capacity, and mass production capability. Currently, the performance of conventional MEMS gyroscopes can meet the needs of most applications. However, because zero bias is greatly affected by temperature, mechanical environment, packaging stress, and packaging atmosphere, there is still significant room for performance improvement in long-endurance, long-term storage, and high-precision applications. In particular, the issue of long-term storage remains problematic. In practice, zero bias still drifts over time, preventing long-term calibration-free operation of MEMS gyroscopes and becoming a bottleneck restricting their application. Summary of the Invention

[0004] The purpose of this invention is to address the prominent problems that restrict the application of MEMS gyroscopes, and to achieve zero bias suppression during gyroscope angular velocity measurement and calibration-free long-term storage during use, so as to avoid the impact of zero bias in the gyroscope on the accuracy of the inertial navigation system.

[0005] To achieve the above objectives, this invention provides a jitter-based MEMS gyroscope, comprising: a double-ended tuning fork, a tuning fork driving module, a detection module, a jitter structure, a jitter driving module, and an angular velocity calculation module; wherein,

[0006] The double-ended tuning fork includes a driving end and a detection end. The tuning fork driving module drives the driving end of the double-ended tuning fork to vibrate.

[0007] The vibrating structure is connected to the double-ended tuning fork, and the vibrating drive module is used to drive the vibrating structure to vibrate, thereby causing the sensitive shaft of the double-ended tuning fork to vibrate.

[0008] The detection module detects the jitter generated by the jittering structure to obtain a jitter modulation signal, detects the displacement of the driving end of the double-ended tuning fork to obtain a driving end displacement signal, and detects the electrical signal of the detection end of the double-ended tuning fork to obtain a detection end detection signal. The detection module sends the obtained jitter modulation signal, driving end displacement signal and detection end detection signal to the angular velocity calculation module.

[0009] The angular velocity calculation module receives the jitter modulation signal, the drive end displacement signal, and the detection end detection signal obtained from the detection module. Based on the drive displacement signal and the jitter drive signal, it demodulates and filters the detection end detection signal to obtain the angular velocity signal.

[0010] Furthermore, the angular velocity calculation module includes a first multiplier, a second multiplier, a low-pass filter, and a frequency-doubled notch filter;

[0011] The first multiplier is used to multiply the detection signal at the detection end with the jitter modulation signal to obtain the first demodulated signal;

[0012] The second multiplier is used to multiply the first demodulated signal and the driving displacement signal to obtain the second demodulated signal;

[0013] Low-pass filter and frequency doubling notch filter are used to filter the second demodulated signal, eliminate zero bias and power frequency interference, and obtain the angular velocity signal.

[0014] Furthermore, the jitter frequency of the jitter structure is equal to the difference between the detection frequency of the sensing end of the sensitive structure and the driving frequency of the driving end.

[0015] Furthermore, the jitter structure includes a support column, an outer ring, folding beams, and electrodes. The support column is fixed in the MEMS gyroscope, the outer ring is coaxially arranged with the support column, and multiple folding beams are radially arranged between the support column and the outer ring and evenly distributed within a 360-degree circumferential range. Each folding beam includes multiple single beam segments and connecting parts that connect adjacent single beams. Each single beam segment has positive and negative electrodes on its side. The multiple single beam segments are connected by connecting parts to form a left-right symmetrical folding structure. The folding structure is used to increase the surface area of ​​the positive and negative electrodes.

[0016] Furthermore, the single beam of the folding beam is a cuboid. A single beam is set on the axis of symmetry of the folding beam, and n folding structures are set on both sides of the axis of symmetry. The folding beam is folded a total of 2n times, where n is a natural number.

[0017] Furthermore, the positive and negative electrodes of the single beam of the folded beam are arranged only on the left and right sides. The arrangement of electrodes on the left and right sides is the same, and the positive and negative electrodes are arranged alternately along the length direction. There is a gap between the electrodes on the same side and the electrodes on different sides. The electrode distribution pattern of single beams with adjacent angles is opposite, and the electrode distribution pattern of folded beams with adjacent angles is opposite.

[0018] Furthermore, the outer ring has a hollow structure.

[0019] This invention also provides a method for suppressing zero-bias error in MEMS gyroscopes based on jitter, which, based on the aforementioned MEMS gyroscope, includes the following steps:

[0020] The steps for starting the MEMS gyroscope include: in this step, the double-ended tuning fork begins to vibrate under the drive of the tuning fork drive module, and the jittering structure begins to jitter under the drive of the jittering drive module, which in turn causes the sensitive axis of the double-ended tuning fork to jitter.

[0021] The steps for detecting the displacement of the driving end and obtaining the driving end displacement signal when a double-ended tuning fork vibrates;

[0022] The steps for detecting the electrical signal at the detection end and obtaining the detection signal at the detection end when a double-ended tuning fork vibrates;

[0023] The steps for detecting jitter in a jittering structure and obtaining a jitter modulation signal when the jittering structure jitters.

[0024] The demodulation and filtering steps involve demodulating and filtering the detection signal at the detection end based on the driving displacement signal and the jitter driving signal to obtain the angular velocity signal.

[0025] Furthermore, the demodulation and filtering steps include:

[0026] The step of multiplying the detection signal at the detection end by the jitter modulation signal and then multiplying it by the displacement signal at the driving end to obtain the demodulated signal;

[0027] The steps to eliminate zero bias and power frequency interference by performing low-pass filtering and frequency doubling notch filtering on the demodulated signal;

[0028] Furthermore, the jitter frequency of the jitter structure is equal to the difference between the detection frequency of the sensing end of the sensitive structure and the driving frequency of the driving end.

[0029] Beneficial effects

[0030] The jitter-based MEMS gyroscope and its bias suppression method described in this invention have the following advantages compared with existing bias suppression methods:

[0031] First, the present invention obtains the angular velocity through secondary demodulation, modulates the gyroscope zero bias to a high frequency, and eliminates it through filtering, thereby achieving zero bias-free operation.

[0032] Secondly, as the maximum jitter angle θ0 increases, the signal-to-noise ratio increases, thus suppressing noise.

[0033] Third, the working principle of this invention determines that its zero bias error is 0, so there is no need to periodically calibrate and compensate its zero bias, which will greatly save users' economic and time costs in practical applications.

[0034] Fourth, this invention solves the problem of long-term storage and calibration-free operation of gyroscopes, greatly expanding the application of MEMS gyroscopes in the field of long-endurance and long-range pure inertial navigation. Attached Figure Description

[0035] Figure 1 This is a system block diagram of the MEMS gyroscope in an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the tuning fork, the vibrating structure, and their installation methods in an embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of the MEMS gyroscope jitter structure in an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram of the vibration principle of the MEMS gyroscope tuning fork in an embodiment of the present invention.

[0039] Figure 5 This is a block diagram of the angular velocity calculation module of the MEMS gyroscope in an embodiment of the present invention.

[0040] Figure 6 This is a simulation schematic diagram of the MEMS gyroscope zero bias suppression method in an embodiment of the present invention.

[0041] Figure 7 This is a schematic diagram of the jitter structure of a MEMS gyroscope in another embodiment of the present invention.

[0042] Figure 8 This is a schematic diagram of the jitter structure electrode arrangement of a MEMS gyroscope in another embodiment of the present invention.

[0043] Figure 9 This is a flowchart of the MEMS gyroscope error suppression method in an embodiment of the present invention. Detailed Implementation

[0044] To achieve a zero-bias calibration-free MEMES gyroscope, this invention employs periodic jitter modulation of the gyroscope's sensitive axis, and finally obtains the angular velocity through secondary demodulation. While obtaining the angular velocity through the second demodulation, the gyroscope's zero bias is modulated to a high frequency, and the zero bias modulated to the high frequency is eliminated through low-pass filtering. Solving the zero bias problem also solves the long-term calibration-free problem.

[0045] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0046] Example 1

[0047] This embodiment provides a detailed description of the specific implementation and effects of the jitter-based MEMS gyroscope of the present invention.

[0048] like Figure 1 As shown, the jitter-based MEMS gyroscope of this embodiment includes: a double-ended tuning fork 100, a jitter structure 200, a tuning fork driving module 3, a jitter driving module 4, a detection module 5, and an angular velocity calculation module 6; wherein, the double-ended tuning fork 100 includes a driving end 111 and a detection end 112, and the tuning fork driving module 3 drives the double-ended tuning fork driving end 111 to vibrate; the jitter structure 200 is connected to the double-ended tuning fork 100, and the jitter driving module 4 drives the jitter structure 200 to jitter, thereby causing the sensitive axis of the double-ended tuning fork 100 to jitter; the detection module 5 detects the jitter generated by the jitter structure 200 to obtain a jitter modulation signal S52. The displacement of the driving end 111 of the double-ended tuning fork is detected to obtain the driving end displacement signal S53, and the electrical signal of the detection end 112 of the double-ended tuning fork is detected to obtain the detection end detection signal S51. The detection module sends the obtained jitter modulation signal S52, driving end displacement signal S53 and detection end detection signal S51 to the angular velocity calculation module 6. The angular velocity calculation module 6 receives the jitter modulation signal S52, driving end displacement signal S53 and detection end detection signal S51 obtained by the detection module, and demodulates and filters the detection end detection signal S51 according to the jitter modulation signal S52 and driving end displacement signal S53 to obtain the angular velocity signal.

[0049] Specifically, in this embodiment, the double-ended tuning fork, the vibrating structure, and their installation methods are as follows: Figures 2-3 As shown.

[0050] The jitter structure 200 includes a support column 201, folded beams 202, an outer ring 203, and electrodes. Multiple folded beams 202 are radially arranged between the support column 201 and the outer ring 203, and are evenly distributed within a 360-degree circumferential range. Each folded beam 202 has a symmetrical folding structure. Positive and negative electrodes are arranged on the sides of the folded beams 202. A circular fixed constraint region 204 serves as the fixed axis of the jitter structure and is positioned on the support column 201. The main body of the support column 201 is polygonal and located at the center of the entire jitter micro / nano structure. It is fixed within the MEMS gyroscope and used for fixing the entire jitter micro / nano structure. The outer ring 203 has the same shape as the support column 201. The main body of the support column 201 and the outer ring 203 have the same shape to facilitate the arrangement of the folded beams 202. The polygon has at least 4 sides. Figure 3 In the illustrated embodiment, the polygonal main body is hexagonal, and the support column 201 can be constrained between the gyroscope substrate and the double-ended tuning fork by the circular fixed constraint area 204 at its center. The folding beam 202 has a symmetrical folding structure, which increases the surface area of ​​the electrodes, resulting in a lower driving voltage for the same vibration amplitude. In this embodiment, the folding beam 202 includes five parallel single beams 21 and connecting portions 22 connecting adjacent single beams 21. Preferably, the single beam 21 is a cuboid. To ensure uniform vibration of the outer ring 203, 4 to 20 folding beams 202 can be evenly arranged between the support shaft 201 and the outer ring 203. Figure 3 The example shown has 6.

[0051] The double-ended tuning fork 100 includes a vibrating end 111 and a sensing end 112. The double-ended tuning fork 100 is placed on a vibrating structure 200, and the shaft 113 of the double-ended tuning fork 100 is coaxially mounted and fixed to the shaft 204 of the vibrating structure 200, maintaining relative stillness. Figure 4 As shown, the sensitive axis of the double-ended tuning fork is the M-axis. The drive axis of the double-ended tuning fork is perpendicular to the sensitive axis, and the drive axis and the sensitive axis form the tuning fork plane. The static position of the double-ended tuning fork is the position of the sensitive axis N when the vibrating structure is not working, denoted as the Y-axis. The axis perpendicular to the Y-axis in the tuning fork plane is denoted as the X-axis. The vibrating structure 200 drives the sensitive axis 113 of the tuning fork to vibrate periodically, that is, to vibrate periodically along the Y-axis from the static position of the sensitive axis M, with a vibrating angle of θ.

[0052] When a MEMS gyroscope is working normally, a drive signal is applied to the drive end, causing the double-ended tuning fork to vibrate in the plane of the tuning fork under the action of strain forces of equal magnitude and opposite direction along the drive axis. This vibration is also called the reference vibration. At the same time, the jittering structure is driven by the drive voltage to generate jitter, which in turn causes the double-ended tuning fork to jitter.

[0053] The angular velocity calculation module demodulates the second modulated signal, including first demodulation and second demodulation; the jitter modulation signal S52 performs a first demodulation on the detection signal S51 at the detection end to obtain the first demodulated signal; the displacement signal S53 at the drive end performs a second demodulation on the first demodulated signal to obtain the second demodulated signal; the second demodulated signal is then subjected to low-pass filtering and frequency doubling notch filtering to obtain the frequency doubling notch filtered signal. In this embodiment, as... Figure 5 As shown, the angular velocity calculation module 6 includes a first multiplier 61, a second multiplier 62, a low-pass filter 63, and a frequency-doubled notch filter 64. The first multiplier is used to multiply the drive-end detection signal S51 and the jitter modulation signal S52 to obtain a first demodulated signal. The second multiplier is used to multiply the first demodulated signal and the drive-end displacement signal S53 to obtain a second demodulated signal. The low-pass filter and the frequency-doubled notch filter are used to filter the second demodulated signal to eliminate zero bias and power frequency interference.

[0054] The working principle of this embodiment is as follows: Figure 6 As shown, when the MEMS gyroscope is working, at the driving end of the tuning fork, the driving end velocity signal and the jitter modulation signal perform secondary modulation (equivalent to double multiplication) on the angular velocity sensed by the tuning fork sensitive axis; the frequency of the jitter modulation signal is equal to the frequency difference between the detection frequency at the detection end and the driving frequency at the driving end, and the frequency of the signal after secondary modulation is located at the detection frequency. The detection frequency is the resonant frequency of the detection end. The detection signal obtained by detecting the electrical signal at the detection end of the double-ended tuning fork includes the secondary modulated signal and the zero bias Ω. B and noise Ω n The detected signal is first demodulated twice using the displacement signal and jitter modulation signal obtained from the drive end. The zero bias of the gyroscope is modulated to a high frequency and then eliminated by filtering. Finally, the angular velocity is obtained and zero bias is achieved.

[0055] The Coriolis effect-induced vibration is detected by measuring the change in capacitance of the gyroscope. This capacitance change is extracted, amplified, and processed by the detection circuit to characterize the angular velocity. A metric is needed to evaluate the output signal's ability to sense the Coriolis effect; this metric is called sensitivity, defined as the rate of change between the voltage output signal and the input angular velocity. Sensitivity is a crucial metric for gyroscopes; high sensitivity significantly improves the zero-bias performance. Therefore, this invention sets the frequency of the MEMS gyroscope's driving mode to be close to or equal to the frequency of the detection mode, making the frequency of the jitter modulation signal close to or equal to the frequency difference between the detection and driving frequencies. Specifically, the jitter frequency of the jitter structure is set to be equal to or close to the difference between the detection frequency at the detection end and the driving frequency at the driving end of the double-ended tuning fork. The resonance amplification of the tuning fork is used to enhance sensitivity, maximizing the gyroscope's sensitivity.

[0056] Example 2

[0057] This embodiment provides a detailed description of the jitter structure of the jitter-based MEMES gyroscope in Embodiment 1.

[0058] Figure 7 This is a schematic diagram of the MEMS gyroscope jitter structure 200' in another embodiment of the present invention, wherein 201 is a support column, 202 is a folded beam, 203 is an outer ring, and the circular fixed constraint area 204 is the fixed axis of the jitter structure, which is set on the support column 201.

[0059] like Figure 7 As shown, the micro / nano structure of the MEMS gyroscope in this embodiment includes a support post 201, a folded beam 202, an outer ring 203, and electrodes. The support post 201 and the outer ring 203 are coaxially arranged. Multiple folded beams 203 are radially arranged between the support post 201 and the outer ring 203 and are evenly distributed in a 360-degree range in the circumferential direction. Each folded beam 202 has a left-right symmetrical folding structure. Positive and negative electrodes are arranged on the side of the folded beam 202.

[0060] The support column 201, with a polygonal main body, is located at the center of the entire shaking micro / nano structure and is fixed in the MEMS gyroscope for securing the entire structure. The polygonal shape of the support column 201 facilitates manufacturing and allows for easy connection to the folding beam. The polygon has at least four sides. Figure 7 In the embodiment shown, the polygonal body is set as a hexagon. Figure 7 The four corners shown are optional and are used to adjust the overall structural balance. The support column 201 can be constrained between the gyroscope base plate and the double-ended tuning fork by the circular fixed constraint area 204 at its center.

[0061] The folded beam 202 has a symmetrical folding structure, which increases the surface area of ​​the electrodes, resulting in a lower driving voltage for the same jitter amplitude. Similar to Embodiment 1, the folded beam 202 in this embodiment includes multiple parallel single beams 21 and connecting portions 22 that connect adjacent single beams 21. Preferably, the single beam 21 is a cuboid. Figure 7 As shown, a single beam 21 is arranged on the axis of symmetry, and four single beams 21 are symmetrically arranged on both sides of the axis of symmetry, forming a structure that is folded twice on one side. More generally, according to the pattern shown in the figure, in other embodiments of the present invention, the folding beam 2 can be folded 2n times, where n is a natural number, as long as the space and process constraints are met. To ensure uniform vibration of the outer ring, 4 to 20 folding beams 022 can be evenly arranged between the support shaft 201 and the outer ring 203. Figure 7The illustrated embodiment has six folding beams. The above description of the symmetrical structure of the folding beams of this invention does not imply that the invention can only be configured according to the above folding pattern. Those skilled in the art, based on common knowledge and the inventive concept of this invention, can design other folding beams with bilateral symmetry to achieve the purpose of increasing the surface area of ​​the electrodes through folding.

[0062] Figure 8 This diagram shows the distribution of positive and negative electrodes in the MEMS gyroscope jitter structure of this embodiment. The solid line area represents the positive electrode 205, and the dashed line area represents the negative electrode 206. In this embodiment, electrodes are arranged only on the left and right sides of the single beam 21. The electrode distribution pattern is the same on both sides, and each side uses two electrodes, one positive and one negative, arranged alternately along the length direction, with a gap between the electrodes. In the same folded beam 202, the electrode distribution patterns of two angularly adjacent single beams 21 are opposite, and the electrode distribution patterns of adjacent folded beams 202 are opposite. Specifically, the positive electrode 205 is set on the part of the left and right sides near the support column 201, and the negative electrode 206 is set on the part near the support column 201, or the negative electrode 206 is set on the part of the left and right sides near the support column 201, and the positive electrode 205 is set on the part near the support column 201. In the five single beams 21, the electrode distribution patterns of two angularly adjacent single beams 21 in the folded beams 202 are opposite, and the electrode distribution patterns of angularly adjacent folded beams 202 are opposite.

[0063] The folded beam of this invention increases the surface area, allowing for the flexible arrangement of more positive and negative electrodes, thus increasing the surface area of ​​the electrodes and resulting in a lower driving voltage for the same vibration amplitude. Therefore, more generally, in other embodiments of this invention, the same single beam 21 can have M electrodes, with adjacent electrodes having opposite polarities, where M is an integer greater than or equal to 2. For ease of manufacturing, the electrodes are generally rectangular.

[0064] In this embodiment, when the jitter structure is used in a MEMS tuning fork gyroscope, the support column is constrained between the substrate and the tuning fork; six folded beams are distributed in a ring at equal angular intervals and connected to the support column; the outer ring is connected to the support column through the six folded beams and is arranged coaxially with the support column; electrodes are arranged on the sides of the six folded beams, and the outer ring connected to one end of the electrode is grounded; to make the folded beams jitter, a periodically varying driving voltage is applied to the positive electrode, and the negative electrode is grounded. In this embodiment, the positive electrodes are all connected together by gold wires, and then a sinusoidal driving voltage with constant frequency and amplitude is applied; the negative electrodes are all connected together by gold wires and then grounded. In this embodiment, for ease of manufacturing and reliable grounding, the negative electrodes are all connected together by gold wires and then connected to the outer ring, which is grounded through the outer ring. At this time, due to the inverse piezoelectric effect, the six folded beams will produce periodic deformation in the same direction; the deformation of the folded beams is transmitted to the outer ring, causing the outer ring to produce periodic vibration; the periodic vibration of the outer ring causes the tuning fork mounted on it to produce periodic vibration; the vibration micro-nano structure of the MEMS gyroscope of the present invention is used to periodically modulate the sensitive axis of the gyroscope, and the frequency of the vibration is modulated by zero bias.

[0065] Furthermore, to improve driving efficiency, the outer ring 203 of the jitter structure 200' in this embodiment adopts a hollow structure, which reduces weight and results in a larger jitter amplitude under the same voltage drive. The hollow structure of the outer ring improves the overall strength of the structure, enabling higher jitter frequency, larger jitter amplitude, shorter start-up time, and faster response speed.

[0066] like Figure 7 As shown, in this embodiment, the outer ring 203 includes an outer ring body 230, inner spokes 231, and outer spokes 232. The inner spokes 231 are optional and used for positioning. One end of the inner spokes 231 is connected to the inner ring of the outer ring body 230, and the other end is suspended. The inner spokes 231 are evenly distributed between two angularly adjacent folding beams 202. One end of the outer spokes 232 is connected to the outer ring of the outer ring body 230 and is evenly distributed on the circumference. Mass blocks 233 are set on one or more circumferences outside the outer ring body 230 and between the outer spokes 232. The two ends of the mass blocks 233 are connected to adjacent outer spokes 232 through connecting beams 234, thereby forming a hollow structure of the outer ring 203. The entire hollow structure is centrally symmetrical, and the center of gravity is located at the center of the outer ring 203. The shape of the mass blocks includes, but is not limited to, rectangles, trapezoids, rounded rectangles, circles, squares, ellipses, etc. The number of rings for the mass block distribution can also be set as needed, generally ranging from 1 to 5. The number of mass blocks per ring can also be changed, but the quantity must ensure a symmetrical distribution. Figure 7 The spoke settings shown are selected as multiples of 12. Generally, for ease of mass block setup, the depth-to-width ratio of the slot between the two outer spokes in the hollow structure is greater than 1 / 3.

[0067] Example 3

[0068] This embodiment provides a detailed description of the jitter-based MEMS gyroscope zero-bias suppression method of the present invention.

[0069] like Figure 9 As shown, the jitter-based MEMS gyroscope zero-bias suppression method includes the following steps:

[0070] S1: The step of starting the MEMS gyroscope. In this step, the double-ended tuning fork starts to vibrate under the drive of the tuning fork drive module, and the jittering structure starts to jitter under the drive of the jittering drive module, which in turn causes the sensitive axis of the double-ended tuning fork to jitter.

[0071] S2: The steps for detecting the displacement of the driving end and obtaining the displacement signal of the driving end when the double-ended tuning fork vibrates;

[0072] S3: The steps of detecting the electrical signal at the detection end and obtaining the detection signal at the detection end when the double-ended tuning fork vibrates;

[0073] S4: The steps for detecting jitter in the jitter structure and obtaining the jitter modulation signal when the jitter structure jitters;

[0074] S5: Demodulation and filtering steps. In this step, the detection signal at the detection end is demodulated and filtered based on the driving displacement signal and the jitter driving signal to obtain the angular velocity signal.

[0075] Furthermore, the demodulation and filtering steps include:

[0076] The step of multiplying the electrical signal at the detection end by the jitter modulation signal and then multiplying it by the displacement signal at the driving end to obtain the demodulated signal;

[0077] The steps to eliminate zero bias and power frequency interference by performing low-pass filtering and frequency doubling notch filtering on the demodulated signal;

[0078] In some embodiments of the present invention, the jitter frequency of the jitter structure is set to be equal to or close to the difference between the detection frequency of the detection end of the sensitive structure and the driving frequency of the driving end.

[0079] Example 4

[0080] This embodiment provides a detailed explanation of the principle of the jitter-based MEMS gyroscope zero-bias suppression method of the present invention based on simulation.

[0081] This embodiment uses Simulink to simulate the method of the present invention, based on... Figures 1-6 A simulation model of the apparatus and method was established. The specific steps of implementing the method of the present invention using the simulation model are as follows:

[0082] S1. The step of starting the MEMS gyroscope: In this step, the double-ended tuning fork starts to vibrate under the drive of the tuning fork drive module, and the jittering structure starts to jitter under the drive of the jittering drive module, which in turn drives the sensitive axis of the double-ended tuning fork to jitter. Specifically, the tuning fork drive module drive circuit generates a drive signal and keeps the frequency and amplitude of the drive signal stable; the jittering drive module controls the jittering structure to drive the tuning fork to jitter, thereby realizing the periodic jittering of the sensitive axis M of the tuning fork.

[0083] The angular velocity is modulated once by vibration and a second time by jitter. Figure 6 The driving signals include driving displacement signals and driving speed signals, where ωq is the angular frequency of the driving signals. Specific parameter settings are shown in Table 1.

[0084]

[0085] Drive speed signal modulated with angular velocity to obtain and :

[0086] ,

[0087] (1)

[0088] The The X-axis component of the angular velocity. The y-axis component of the angular velocity; Y-axis angular velocity component The signal after the first modulation, X-axis angular velocity component The signal after the first modulation;

[0089] The signal after the first modulation is then modulated a second time to obtain a second modulated signal. This second modulation projects the first modulated signal onto the sensitive axis M, and the resulting second modulated signal is denoted as... and :

[0090]

[0091] in, Projection onto the sensitive axis M, Projection onto the sensitive axis M, The angle between the gyroscope's sensing axis M and the Y-axis, and ; It is a jitter-modulated signal; The maximum angle of the vibration. The specific parameters for the jitter angular frequency are shown in Table 2:

[0092]

[0093] jitter modulation signal The vibration is obtained from the vibration generated by the vibration measurement structure;

[0094] S2: The steps for detecting the displacement of the driving end and obtaining the displacement signal of the driving end when the double-ended tuning fork vibrates;

[0095] S3: The step of detecting the electrical signal at the detection end and obtaining the detection signal at the detection end when the double-ended tuning fork vibrates; the detection signal at the detection end includes the signal after the second modulation and the zero bias signal. and noise The detection end receives the signal as follows: The expression is:

[0096] ;

[0097] S4: The steps for detecting jitter in the jitter structure and obtaining the jitter modulation signal when the jitter structure jitters;

[0098] S5: Demodulation and filtering step. In this step, the detection signal from the detection end is demodulated and filtered based on the driving displacement signal and the jitter driving signal to obtain the angular velocity signal. The detection signal from the detection end is multiplied by the jitter modulation signal for the first demodulation, and the zero bias detected by the detection end is obtained. and Multiplication results in zero bias. Modulated to Then, it is multiplied with the displacement signal at the drive end for a second demodulation. The second demodulation combines the signal after the first demodulation with the drive speed signal. Multiplication makes the first demodulation modulated to zero bias at the point It is further modulated to At the specified frequency, the demodulated signal is obtained; zero bias. Modulated to At this frequency, the zero bias after modulation is called high-frequency zero bias.

[0099] The demodulated signal is low-pass filtered using a cutoff frequency lower than [the specified frequency]. A low-pass filter is used to filter the demodulated signal, removing high-frequency zero-bias and other high-frequency terms, resulting in a zero-bias-free signal. Then, a frequency-doubling notch filter is applied to eliminate power frequency interference. Other high-frequency terms are those with frequencies higher than […]. Items.

[0100] The signal after zero bias cancellation is: ;

[0101] S6. Perform a proportional transformation on the signal after zero bias cancellation to obtain the demodulated angular velocity; the demodulated angular velocity is:

[0102] The scaling factor is used to transform the zero-bias-eliminated signal into a scaling factor. Multiply;

[0103] Thus, from S1 to S6, the method for zero bias suppression of MEMS gyroscopes based on jitter structure was completed.

[0104] The jitter-based MEMS gyroscope and its bias suppression method described in this invention have the following advantages compared with existing bias suppression methods:

[0105] First, the present invention obtains the angular velocity through secondary demodulation, modulates the gyroscope zero bias to a high frequency, and eliminates it through filtering, thereby achieving zero bias-free operation.

[0106] Second, the present invention varies with the maximum angle of the vibration. Increasing the signal-to-noise ratio helps suppress noise.

[0107] Third, the working principle of this invention determines that its zero bias error is 0, so there is no need to periodically calibrate and compensate its zero bias, which will greatly save users' economic and time costs in practical applications.

[0108] Fourth, this invention solves the problem of long-term storage and calibration-free operation of gyroscopes, greatly expanding the application of MEMS gyroscopes in the field of long-endurance and long-range pure inertial navigation.

[0109] The above are merely preferred embodiments of the invention and are not intended to limit the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A MEMS gyroscope based on dithering, comprising a double-ended tuning fork, a tuning fork driving module, a detection module, a dithering structure, a dithering driving module, and an angular velocity calculation module; the double-ended tuning fork comprises a driving end and a detection end, the tuning fork driving module drives the double-ended tuning fork to vibrate at the driving end; the dithering structure is connected to the double-ended tuning fork, and the dithering driving module is used to drive the dithering structure to dither, thereby driving the sensitive axis of the double-ended tuning fork to dither; characterized in that, The detection module detects the jitter generated by the jittering structure to obtain a jitter modulation signal, detects the displacement of the driving end of the double-ended tuning fork to obtain a driving end displacement signal, and detects the electrical signal of the detection end of the double-ended tuning fork to obtain a detection end detection signal. The detection module sends the obtained jitter modulation signal, driving end displacement signal and detection end detection signal to the angular velocity calculation module. The angular velocity calculation module receives the jitter modulation signal, the drive end displacement signal, and the detection end detection signal from the detection module. Based on the drive end displacement signal and the jitter drive signal, the detection end detection signal is demodulated and filtered to obtain the angular velocity signal. The jitter structure includes a support column, an outer ring, folding beams, and electrodes. The support column is fixed in the MEMS gyroscope. The outer ring is connected to the support column through the folding beams and is coaxially arranged with the support column. The support column is constrained between the substrate and the tuning fork. The electrodes are arranged on the side of the folding beams and the outer ring connected to one end of the electrodes is grounded. Multiple folding beams are arranged radially between the support column and the outer ring and are evenly distributed within a 360-degree circumferential range. Each folding beam includes multiple single beam segments and connecting parts connecting adjacent single beams. Positive and negative electrodes are provided on the side of each single beam segment. Multiple single beam segments are connected through the connecting parts to form a left-right symmetrical folding structure. The folding structure is used to increase the surface area of ​​the positive and negative electrodes. The single beam of the folded beam has positive and negative electrodes arranged only on the left and right sides. The arrangement of electrodes on the left and right sides is the same, and the positive and negative electrodes are arranged alternately along the length direction. There is a gap between the electrodes on the same side and the electrodes on different sides. The electrode distribution pattern of single beams with adjacent angles is opposite, and the electrode distribution pattern of folded beams with adjacent angles is opposite. The folding beam is a cuboid. A section of the single beam is set on the axis of symmetry of the folding beam. The two sides of the axis of symmetry are respectively set with n folding structures. The folding beam is folded a total of 2n times, where n is a natural number. The outer ring includes an outer ring body, inner spokes and outer spokes. The inner spokes are optional and are used for limiting. One end of the inner spoke is connected to the inner ring of the outer ring body, and the other end is suspended. The inner spokes are evenly distributed between two folding beams with adjacent angles. One end of the outer spokes is connected to the outer ring of the outer ring body and is evenly distributed on the circumference. Mass blocks are set on one or more circumferences outside the outer ring body and between the outer spokes. The two ends of the mass blocks are connected to the adjacent outer spokes through connecting beams, thus forming the hollow structure of the outer ring. The entire hollow structure is centrally symmetrical, and the center of gravity is located at the center of the outer ring. The number of rings of mass blocks ranges from 1 to 5, and their number is symmetrically distributed. The depth-to-width ratio of the slot between two outer spokes in the hollow structure is greater than 1 / 3. The jitter frequency of the jitter structure is equal to the difference between the detection frequency of the sensing end of the sensitive structure and the driving frequency of the driving end.

2. The MEMS gyroscope of claim 1, wherein, All the positive electrodes are connected together, and then a sinusoidal driving voltage with constant frequency and amplitude is applied; all the negative electrodes are connected together and connected to the outer ring, which is grounded through the outer ring; at this time, due to the inverse piezoelectric effect, the folded beam will produce periodic deformation in the same direction; the deformation of the folded beam is transmitted to the outer ring, causing the outer ring to produce periodic vibration; the periodic vibration of the outer ring causes the tuning fork mounted on it to produce periodic vibration, which periodically modulates the sensitive shaft.

3. The MEMS gyroscope of claim 1, wherein, The angular velocity calculation module includes a first multiplier, a second multiplier, a low-pass filter, and a frequency-doubled notch filter; The first multiplier is used to multiply the detection signal at the detection end with the jitter modulation signal to obtain the first demodulated signal; The second multiplier is used to multiply the first demodulated signal and the drive end displacement signal to obtain the second demodulated signal; Low-pass filter and frequency doubling notch filter are used to filter the second demodulated signal, eliminate zero bias and power frequency interference, and obtain the angular velocity signal.

4. The MEMS gyroscope of claim 3, wherein, The positive electrode and the negative electrode are all connected together by gold wires.

5. The MEMS gyroscope of claim 1, wherein, The outer ring has a hollow structure, and the shape of the mass block includes rectangle, trapezoid, rounded rectangle, circle, square or ellipse.

6. A method for suppressing zero-bias error in a MEMS gyroscope based on jitter, based on the MEMS gyroscope as described in any one of claims 1-5, comprising the steps of: The steps for starting the MEMS gyroscope include: the double-ended tuning fork starts to vibrate under the drive of the tuning fork drive module, and the jittering structure starts to jitter under the drive of the jittering drive module, which in turn causes the sensitive axis of the double-ended tuning fork to jitter. The steps for detecting the displacement of the driving end and obtaining the driving end displacement signal when a double-ended tuning fork vibrates; The steps for detecting the electrical signal at the detection end and obtaining the detection signal at the detection end when a double-ended tuning fork vibrates; The steps for detecting jitter in a jittering structure and obtaining a jitter modulation signal when the jittering structure jitters. The demodulation and filtering steps involve demodulating and filtering the detection signal at the detection end based on the displacement signal at the driving end and the jitter driving signal to obtain the angular velocity signal.

7. The dither-based MEMS gyroscope zero bias error suppression method of claim 6, wherein, The demodulation and filtering steps include: The step of multiplying the detection signal at the detection end by the jitter modulation signal and then multiplying it by the displacement signal at the driving end to obtain the demodulated signal; The steps involve low-pass filtering and frequency doubling notch filtering of the demodulated signal to eliminate zero bias and power frequency interference.

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