A MEMS strapdown attitude and heading reference system

Abstract

The application relates to a MEMS strapdown attitude and heading reference system, which comprises a cover plate, a main board, a power supply board, a capacitor, a socket, an inertial measurement unit, a shell and a magnetic heading sensor component; the shell is sealed by the cover plate; the power supply board and a plurality of main boards are sequentially and parallelly arranged from bottom to top in the shell; the inertial measurement unit and the magnetic heading sensor component are arranged in the shell cavity; the full-damping information fusion technology in the application improves the attitude and heading precision of the strapdown attitude and heading reference system by fusing the data of the magnetic heading sensor, the atmospheric machine speed, the satellite position and the added specific force; the flexible circuit with the lightning protection function enhances the external interface and the power supply lightning environment adaptability, the circuit board folding precision installation technology is adopted to expand the interface, enrich the external interface, improve the system external interface redundancy and system integration; the IMU precision installation technology determines the reference datum of the product azimuth measurement and the horizontal attitude measurement, and is also important for the product accurate calibration.

Description

Technical Field

[0001] This invention belongs to the field of strapdown attitude measurement technology, and specifically relates to a MEMS strapdown attitude measurement system. Background Technology

[0002] MEMS strapdown attitude control systems are strapdown systems composed of MEMS inertial measurement units, and they have found some applications in both military and civilian fields. The original strapdown attitude control systems composed of MEMS inertial measurement units are characterized by their small size, light weight, and simple structure. However, their disadvantages include low functional integration, simple functions and interfaces, poor interface redundancy, a single data source, and due to their small size, simple circuit board construction, and virtually no lightning protection, resulting in poor adaptability to lightning environments.

[0003] Currently, MEMS strapdown attitude control systems are mainly used in UAVs, helicopters, and airships. These products require high functional integration and abundant redundant interfaces, including multiple RS422 and ARINC429 interfaces, which need to interconnect with various devices such as displays, integrated processors, flight controllers, magnetic heading sensors, and atmospheric sensors. Furthermore, all external interfaces and power interfaces must have a certain level of lightning protection to meet the requirements for lightning environment adaptability. Simultaneously, advanced IMU precision installation technology is required to provide a more accurate attitude measurement reference; and fully damped information fusion technology is needed to improve the product's heading and attitude performance.

[0004] However, current MEMS strapdown attitude control systems cannot meet the above requirements. Therefore, it is necessary to design a new type of MEMS strapdown attitude control system to overcome existing defects and shortcomings. Summary of the Invention

[0005] In response to the problems mentioned in the background art regarding the simple functions and interfaces of existing MEMS strapdown attitude control systems, the single data source integration, poor interface redundancy, low functional integration, and incomplete adaptability to lightning environments, this invention proposes a novel MEMS strapdown attitude control system.

[0006] A MEMS strapdown attitude control system includes a cover plate 1, a main board 2, a power board 3, a capacitor 4, a socket 5, an inertial measurement unit 10, a housing 11, and a magnetic heading sensor component 14.

[0007] The housing 11 is a hollow cavity, and the top is sealed by a cover plate 1; power boards 3 and several mainboards 2 are arranged in parallel from bottom to top inside the housing 11.

[0008] The inner cavity of the housing 11 is also equipped with an inertial measurement unit 10 and a magnetic heading sensor component 14, and the outer wall is provided with a socket 5 and a capacitor 4.

[0009] The inertial measurement unit 10 is equipped with three orthogonal MEMS gyroscopes and MEMS accelerometers for real-time measurement of the carrier's angular rate and acceleration.

[0010] Furthermore, the bottom of the housing 11 has three protrusions, and the side wall is provided with positioning blocks; the three protrusions and positioning blocks serve as reference surfaces for the bottom and side, respectively.

[0011] Furthermore, the three orthogonal MEMS gyroscopes and MEMS accelerometers together form an IMU, which is fixed on three protrusions, and the surfaces of the protrusions are subjected to sulfuric acid anodizing treatment.

[0012] Furthermore, the mainboards 2 are supported by support columns, and the mainboards 2 and the power board 3 are supported by support pillars.

[0013] Furthermore, the circuit board on the motherboard has a flexible length that is 4-6mm longer than the circuit board spacing, and the printed circuit board has a built-in process edge during production.

[0014] A control method for a MEMS strapdown attitude control system includes the following steps:

[0015] Step 1: System initialization. Collect three-axis acceleration and three-axis angular rate data through the motherboard, calculate geophysical parameters, gravitational acceleration, Earth angular rate, harmful acceleration, body angle increment, and geographic velocity increment parameters, and calculate attitude quaternions, attitude matrix, heading, and attitude angle based on body angle increment.

[0016] Step 2: Collect and calculate the magnetic heading data from the magnetic heading sensor using the mainboard to correct the system heading;

[0017] Step 3: Collect and process satellite data through the motherboard, determine the validity of satellite position data, and perform inertial data latching every 4.98 seconds to achieve 5-second synchronization between satellite position data and inertial position data;

[0018] Step 4: Collect atmospheric data through the motherboard, determine the validity of the atmospheric data, and perform inertial data latching every 1.5 seconds to achieve synchronization of atmospheric velocity data and inertial velocity data every 2 seconds;

[0019] Step 5: Based on the data source information, prioritize the combination and select the combination mode: First, determine whether the satellite data is valid. If valid, combine the inertial / satellite data; otherwise, further determine whether the atmospheric data is valid. If the atmospheric data is valid, combine the inertial / atmospheric data and then perform filtering correction; if both atmospheric and satellite data are invalid, determine whether the accelerator correction is enabled. If so, perform accelerator leveling correction; otherwise, display an error message.

[0020] Furthermore, in step 2, the correction process includes the following sub-steps:

[0021] Step 2.1: First, determine if the magnetic heading data is valid. If invalid, the process ends.

[0022] Step 2.2: If the magnetic heading data is valid, calculate the system heading change and magnetic heading change. If the heading change is less than 0.5°, the magnetic heading change is less than 0.8°, the attitude angle is within 20°, and the three-axis angular rate is within 0.5° / s, and all the above conditions are met, calculate the difference between the current heading and the magnetic heading. If the absolute value of the difference is less than 1°, subtract 0.2 times the difference from the original heading value to obtain the new heading value, thus achieving magnetic heading correction.

[0023] Step 2.3: Update the quaternion and attitude matrix using the corrected heading value.

[0024] Furthermore, step 5 specifically includes the following sub-steps for adding leveling and correction:

[0025] Step 5.1: Determine whether the change in heading is less than 0.5°, the triaxial angular rate is less than 0.5° / s, and the resultant acceleration of the triaxial fuselage is less than 0.05 m / s². 2 If all three conditions are met, it is determined that the carrier is in level flight or stationary state, and the leveling correction can be performed using the accelerator, and then the attitude angle can be calculated using the three-axis specific force value.

[0026] Step 5.2: Determine if the absolute value of the roll angle is within 30°. If it is, calculate the difference between the current roll angle and the previous roll angle. If the absolute value of the difference for each beat is greater than 0.001° and the roll angle difference is positive, then the positive count is accumulated; otherwise, the negative count is accumulated. Then, by judging the difference between the positive and negative counts, if it is greater than or equal to 10, then add 0.01° to the original roll angle and reset the accumulated count to zero; otherwise, if the difference between the negative and positive counts is greater than or equal to 10, then subtract 0.01° from the original roll angle and reset the accumulated count to zero. This achieves the added roll value correction and the added leveling effect.

[0027] Step 5.3: Simultaneously determine whether the absolute value of the pitch angle is within 30°. If it is, calculate the difference between the current pitch angle and the previous pitch angle. If the absolute value of the difference for each beat is greater than 0.001°, and the pitch angle difference is positive, then the positive count is accumulated; otherwise, the negative count is accumulated. Then, by judging the difference between the positive and negative counts, if it is greater than or equal to 10, add 0.01° to the original pitch angle and reset the accumulated count to zero; otherwise, if the difference between the negative and positive counts is greater than or equal to 10, subtract 0.01° from the original pitch angle and reset the accumulated count to zero. This achieves the pitch value correction by adding the counter, thus achieving the leveling effect.

[0028] Furthermore, in step 5, when combining inertial / satellite data and inertial / atmospheric data, satellite data and atmospheric data are used as measurements respectively. After the satellite data and atmospheric data are synchronized with the inertial data and the measurements are updated, Kalman filtering technology is used to estimate the error, and the estimated parameters are used to correct the system data.

[0029] Invention Effects

[0030] The technical advantages of this invention are as follows: This invention discloses a novel MEMS strapdown attitude control system, which solves the problems of the original MEMS strapdown attitude control system, such as simple functions and interfaces, weak redundancy and small-scale integration, and poor adaptability to lightning environments. It realizes functions such as data acquisition by MEMS inertial measurement unit, full damping information fusion, attitude calculation, and real-time output of aircraft attitude information, and meets the requirements of high functional integration, rich interfaces and functions, and lightning protection performance of strapdown attitude control systems.

[0031] This invention specifically employs full-damping information fusion technology, flexible circuit design with lightning protection, and precise IMU installation technology. The full-damping information fusion technology integrates data from magnetic heading sensor, atmospheric velocity data, satellite position data, and accelerometer force data, primarily to improve the attitude accuracy of the strapdown induction mount system. The flexible circuit design with lightning protection enhances the adaptability of external interfaces and power supplies to lightning environments. Precise circuit board folding installation technology expands interfaces, enriching external interfaces, improving system redundancy, and enhancing system integration. The precise IMU installation technology is primarily used to determine the reference benchmarks for product orientation and horizontal attitude measurements, and is also crucial for accurate product calibration. Attached Figure Description

[0032] Figure 1 Product structure diagram

[0033] Figure 2 Product principle block diagram

[0034] Figure 3 Framework diagram of fully damped information fusion technology

[0035] Figure 4 Flowchart of Full Damping Information Fusion Technology

[0036] Figure 5 Flowchart of Kalman filtering technique

[0037] Figure 6 Flowchart of Leveling Technology

[0038] Figure 7 Flowchart of heading correction technology

[0039] Figure 8 TVS diode surge protection schematic diagram

[0040] Figure 9 Circuit board folding and mounting diagram

[0041] Figure 10 Precise installation diagram for IMU

[0042] Explanation of reference numerals in the attached drawings: 1-Cover plate; 2-Main board; 3-Power board; 4-Capacitor; 5-Socket; 6-Sealing gasket; 7-Second support column; 8-First support column; 9-Support column; 10-Inertial measurement unit; 11-Housing; 12-Nameplate; 13-Magnetic heading sign; 14-Magnetic heading sensor component Detailed Implementation

[0043] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] See Figures 1-10 This system consists of two main parts: a strapdown attitude control unit and a magnetic heading sensor unit. The structural composition is as follows: Figure 1 As shown. The strapdown attitude control unit consists of a cover plate, main board, power board, inertial instrument assembly, and housing. The magnetic heading sensor assembly consists of a JLD-P5.0 magnetic heading sensor.

[0045] The inertial instrumentation unit (MEMS) is an inertial measurement unit. The inertial measurement unit is equipped with three orthogonal MEMS gyroscopes and MEMS accelerometers, which are used to sense the angular rate and acceleration of the carrier in real time. After attitude calculation, the aircraft's heading angle, pitch angle, and roll angle are calculated in real time.

[0046] The principle block diagram of this system is as follows: Figure 2As shown, the inertial instrument component, namely the MEMS inertial measurement unit, in the strapdown attitude control system of the product senses the three-axis angular rate and three-axis acceleration of the aircraft; the magnetic heading sensor component measures the magnetic heading of the aircraft. This measured information is sent to the product's acquisition and calculation board to complete initial alignment, error compensation, and attitude calculation. After obtaining the aircraft's pitch angle, roll angle, and three-axis angular rate, it is sent to the flight display and integrated processor for display. At the same time, the product receives satellite position or atmospheric data from the flight display for data fusion and performs error correction on the system to improve the heading and attitude accuracy of the product.

[0047] To simultaneously meet the requirements of protecting against indirect lightning effects and miniaturizing the product at low cost, a flexible circuit design is used. For products not limited by size, lightning protection designs typically employ a motherboard-to-lightning protection board or a lightning protection filter connector to achieve protection against indirect lightning effects. However, this approach is not suitable for miniaturized MEMS strapdown attitude control systems. Furthermore, the motherboard-to-lightning protection board method has the disadvantage of occupying space and increasing costs due to the motherboard and adapter connectors. Lightning protection filter connectors require customization, are expensive, have long production cycles, and are relatively large compared to ordinary connectors.

[0048] This invention utilizes a flexible circuit design, integrating the surge protection circuit, host, and interface circuits onto a single circuit board. This satisfies surge protection requirements while saving significant space and cost. The design of the flexible zone length is related to various factors, including circuit board spacing, bending angle, signal quality, installation operability, and enclosure space. Considering the lifespan and safety of the flexible circuit board, to ensure its lifespan during bending installation, the bend should not be too close to the rigid-flex board connection area; the bend should maintain a certain curvature, and the flexible zone design should not be too short. From an installation operability perspective, a longer flexible zone length facilitates disassembly and assembly. However, a longer flexible zone makes the signal more susceptible to interference and attenuates; therefore, from a signal quality perspective, the flexible zone should be as short as possible. From an enclosure space perspective, the flexible zone circuit occupies space on the circuit board and enclosure sidewalls; an excessively long flexible zone can be squeezed by the circuit board and enclosure during installation. Considering these four points, and combining the characteristics of this product and its installation method, the designed flexible zone length is 4-6mm longer than the circuit board spacing.

[0049] The motherboard closest to the power supply board is defined as layer 1, followed by layers 2 and 3. The power supply board and layer 1 are supported by pillars, layer 1 and layer 2 are supported by a first support pillar, and layer 2 and layer 3 are supported by a second support pillar.

[0050] The spacing between the first and second layer circuit boards is 16mm. The flexible connection area faces the enclosure wall with external sockets, allowing ample space for flexible bending. The first layer circuit board is on the bottom of the enclosure; for ease of installation, the flexible connection area needs to be longer. Additionally, the traces in this flexible area are all differential signals output externally, requiring some anti-interference capability. Therefore, the flexible connection area length is designed to be 22mm, an increase of 6mm from the spacing between the first and second layer circuit boards. The spacing between the second and third layer circuit boards is 14mm. The flexible board can only bend within a narrow 1.5mm space between its side and the enclosure. To address the issue of pressure on the flexible board from the enclosure sidewall, the rigid board at the flexible-rigid connection point is reduced by 3.5mm, ensuring a basic bending space of 5mm for the flexible board and preventing excessive pressure. Since the traces in this flexible area contain important signals, their length should not be too long. Finally, the flexible connection area length is determined to be 18mm, an increase of 4mm from the spacing between the boards. The PCB design also considers manufacturability, incorporating a process edge. Each printed circuit board (PCB) is equipped with a process edge during production to prevent accidental damage during manufacturing, transportation, soldering, and debugging. This is especially important for flexible areas, as the number of bends affects their lifespan; the process edge prevents unnecessary bending of flexible areas before use. This protection reduces transportation difficulty, eliminating the need for special protection during transport. Furthermore, the process edge is designed with positioning points and clamping edges for machine soldering compatibility. For PCB folding and installation, see [link / details]. Figure 9 .

[0051] The precise installation of the inertial measurement unit (IMU) directly affects the accuracy of the attitude control system. Through the mounting design of the housing positioning blocks and bottom bosses, the bottom surface and measurement reference plane of the IMU are determined during installation. These are used as measurement references to define the IMU's body coordinate system during application. This precise IMU installation technology ensures the installation accuracy of the IMU, provides a reference benchmark for measuring heading and attitude, guarantees the accuracy of product calibration, and improves the installation efficiency of the IMU.

[0052] Three mounting bosses are designed on the bottom of the product housing, and locating blocks are designed on the sides, serving as reference surfaces for the bottom and sides. These reference surfaces have high requirements for flatness and perpendicularity, ensuring a parallelism and perpendicularity of 0.01, forming a good installation reference. The IMU is fixed to the three mounting bosses with three M4 screws. The surfaces of the bosses undergo sulfuric acid anodizing treatment to improve their corrosion and oxidation resistance, ensuring the parallelism of the boss planes. The design of the locating blocks against the mounting surface improves the installation efficiency of the IMU while ensuring the overall installation accuracy. The side locating blocks and the three boss reference surfaces ensure the measurement reference for azimuth and attitude, determining the product's heading and attitude reference surfaces, ensuring the accuracy of product calibration. For detailed installation design, see [link to installation details]. Figure 10 .

[0053] Due to the low precision and poor stability of MEMS devices, the long-term attitude accuracy of a product cannot be guaranteed simply by improving the zero-bias repeatability of MEMS gyroscopes. Therefore, it is necessary to improve the attitude accuracy of the system through fully damped information fusion technology, and to select the combination priority order by data source selection.

[0054] The full-damping information fusion technology works as follows: When both position data and atmospheric data are valid, position combination technology and magnetic heading correction technology are used to correct heading and attitude. When position data is invalid but atmospheric data is valid, atmospheric combination technology and magnetic heading correction technology are used to correct heading and attitude. When both position data and atmospheric data are invalid, accelerometer leveling technology and magnetic heading correction technology are used to correct heading and attitude. The overall block diagram of the full-damping information fusion technology is shown below. Figure 3 .

[0055] For the detailed process of the fully damped information fusion technology, please refer to [link / reference]. Figure 4 The specific steps are as follows:

[0056] Step 1: First, perform system initialization. Collect three-axis acceleration and three-axis angular rate data through the motherboard, calculate geophysical parameters, gravitational acceleration, Earth angular rate, harmful acceleration, body angle increment, geographic velocity increment, etc., and calculate attitude quaternions, attitude matrix, heading and attitude angle based on body angle increment.

[0057] Step 2: Collect and calculate the magnetic heading data from the magnetic heading sensor using the mainboard to perform system heading correction. See the magnetic heading correction process below. Figure 7 ;

[0058] Magnetic heading correction technology: For MEMS inertial measurement units, a magnetic heading sensor is required for heading correction. When the carrier attitude angle, heading change, three-axis angular rate, and three-axis specific force data meet certain conditions, magnetic heading correction technology can be used to correct the heading. The specific steps are as follows:

[0059] Step 2.1: First, determine if the magnetic heading data is valid;

[0060] Step 2.2: If the magnetic heading data is valid, calculate the system heading change and magnetic heading change. If the heading change is less than 0.5°, the magnetic heading change is less than 0.8°, the attitude angle is within 20°, and the three-axis angular rate is within 0.5° / s, and all the above conditions are met, calculate the difference between the current heading and the magnetic heading. If the absolute value of the difference is less than 1°, subtract 0.2 times the difference from the original heading value to obtain the new heading value, thus achieving magnetic heading correction.

[0061] Step 2.3: Finally, update the quaternion and attitude matrix using the corrected heading value.

[0062] Step 3: Collect and process satellite data through the motherboard, determine the validity of satellite position data, and perform inertial data latching every 4.98 seconds to achieve 5-second synchronization between satellite position data and inertial position data;

[0063] Step 4: Collect atmospheric data through the motherboard, determine the validity of the atmospheric data, and perform inertial data latching every 1.5 seconds to achieve synchronization of atmospheric velocity data and inertial velocity data every 2 seconds;

[0064] Step 5: Based on the data source information, prioritize the combination and select the combination mode. First, determine if the satellite data is valid. If valid, combine inertial / satellite data; otherwise, if the atmospheric data is valid, combine inertial / atmospheric data, and then perform filtering correction. If both atmospheric and satellite data are invalid, determine if accelerator correction is enabled and perform accelerator leveling correction. For the specific accelerator leveling correction process, see [link to accelerator leveling correction procedure]. Figure 6 .

[0065] The accelerator-based leveling technology determines whether the carrier is in level flight or stationary by analyzing its attitude angles, heading changes, three-axis angular rates, and three-axis specific forces. If the leveling requirements are met, the attitude angles are calculated using the accelerator's output specific force values. The specific steps are as follows:

[0066] Step 5.1: Based on the characteristics of MEMS strapdown attitude control products, first determine whether the change in heading is less than 0.5°, whether the three-axis angular rate is less than 0.5° / s, and whether the resultant acceleration of the three-axis body acceleration is less than 0.05m / s². 2 If all three conditions are met, it can be determined that the carrier is in level flight or stationary state, and the autopilot leveling technology can be used.

[0067] Step 5.2: Determine if the absolute value of the roll angle is within 30°. If it is, calculate the difference between the current roll angle and the previous roll angle. If the absolute value of the difference for each beat is greater than 0.001° and the roll angle difference is positive, then accumulate the positive count; otherwise, accumulate the negative count. Then, by judging the difference between the positive and negative counts, if it is greater than or equal to 10, add 0.01° to the original roll angle and reset the accumulation count to zero; conversely, if the difference between the negative and positive counts is greater than or equal to 10, subtract 0.01° from the original roll angle and reset the accumulation count to zero. This achieves the added roll value correction and leveling effect.

[0068] Step 5.3: Simultaneously determine whether the absolute value of the pitch angle is within 30°. If it is, calculate the difference between the current pitch angle and the previous pitch angle. If the absolute value of the difference for each beat is greater than 0.001°, and the pitch angle difference is positive, then the positive count is accumulated; otherwise, the negative count is accumulated. Then, by judging the difference between the positive and negative counts, if it is greater than or equal to 10, add 0.01° to the original pitch angle and reset the accumulated count to zero; otherwise, if the difference between the negative and positive counts is greater than or equal to 10, subtract 0.01° from the original pitch angle and reset the accumulated count to zero. This achieves the pitch value correction by adding the counter, thus achieving the leveling effect.

[0069] Position integration and atmospheric integration techniques use satellite and atmospheric data, respectively, as measurements. Once the external data is synchronized with the inertial data and the measurements are updated, Kalman filtering can be used for error estimation. The estimated parameters are then used to correct the system data. For a detailed description of the Kalman filtering process, please refer to [link to documentation]. Figure 5 .

[0070] The product communicates with the outside world via one power signal, five RS422 signal channels, and two ARINC429 receiver signals. The power and RS422 signals utilize transient voltage suppressor diodes (TVS diodes) to prevent damage to the internal circuitry from induced lightning strikes. See the schematic diagram below. Figure 8 The ARINC429 chip uses the HI-3584APQT-15 chip with surge protection. The circuit board layout is functionally divided into the host section, interface section, and surge protection section. Flexible circuit boards are used to interconnect signals between these sections. When impedance is controlled simultaneously in both rigid and flexible areas, the trace width changes from 0.5mm into the rigid area from the flexible area; traces requiring bends must remain at least 0.5mm away. Traces and copper pours in the flexible area must be at least 2mm away from the edge of the flexible area. The flexible area circuit board uses a double-layer design to reduce trace density.

[0071] In summary, the strapdown attitude control system of this invention employs fully damped information fusion technology, enabling the product to combine position data and atmospheric velocity data sent by external devices for combined filtering and calculation. Simultaneously, it utilizes the magnetic heading sensor component within the system to correct heading through magnetic heading correction technology, continuously correcting heading and attitude errors to improve heading and attitude accuracy. The flexible circuit design with lightning protection enhances the product's external interfaces and power supply's lightning protection capabilities, meeting the product's adaptability in lightning environments. Furthermore, flexible connection technology enriches the product's external interfaces, providing four RS422 interfaces and an ARINC429 interface, increasing the redundancy of the system's external interfaces and thus improving the reliability of external transmission. Finally, precise IMU installation technology ensures the provision of a high-precision calibration reference plane, thereby determining the product's heading and attitude reference planes.

Claims

1. A control method of a MEMS strapdown attitude and heading system, characterized in that, The MEMS strapdown attitude and heading reference system comprises a cover plate (1), a main board (2), a power supply board (3), a capacitor (4), a socket (5), an inertial measurement unit (10), a shell (11) and a magnetic heading sensor component (14); wherein a lightning protection circuit and a main machine and an interface circuit are integrated on one circuit board by using a flexible circuit design; The shell (11) is a cavity, and the top is closed and sealed by the cover plate (1); the power supply board (3) and a plurality of main boards (2) are distributed in parallel from bottom to top in the shell (11); The shell (11) also contains an inertial measurement unit (10) and a magnetic heading sensor component (14), and the outer wall is provided with a socket (5) and a capacitor (4); The inertial measurement unit (10) internally installs three orthogonal MEMS gyroscopes and MEMS accelerometers for real-time measurement of the motion angular velocity and acceleration of the carrier; The product has one power supply, five RS422 signals and two ARINC429 receiving signals for crosslinking signals with the outside world; The power supply signal and the RS422 signal adopt a transient voltage suppression diode TVS tube to prevent inductive lightning damage to the internal circuit of the product; the ARINC429 chip adopts a HI-3584APQT-15 chip with lightning protection function; the circuit board layout design is divided into a main machine part, an interface part and a lightning protection part according to functions; the flexible circuit board is used for crosslinking signals between the parts, and the impedance is controlled simultaneously in the rigid area and the flexible area; the line width changes at 0.5mm from the flexible area into the rigid area, and the wiring needs to be kept outside 0.5mm when it needs to be bent; the wiring and copper laying distance of the flexible area are more than 2mm from the edge of the flexible area; the flexible circuit board adopts a double-layer design to reduce the wiring density; The control method comprises the following steps: Step 1: system initialization, acquiring three-axis acceleration and three-axis angular velocity data through the main board, calculating geophysical parameters, gravitational acceleration, earth angular velocity, harmful acceleration, body angular increment, geographical velocity increment parameters, calculating attitude quaternion according to the body angular increment, calculating attitude matrix, calculating heading and attitude angle; Step 2: acquiring and solving the magnetic heading data of the magnetic heading sensor through the main board to correct the system heading; Step 3: acquiring and solving satellite data through the main board, judging the validity of the satellite position data, performing inertial data latching processing every 4.98 seconds, and realizing 5-second synchronization of satellite position data and inertial position data; Step 4: acquiring atmospheric data through the main board, judging the validity of the atmospheric data, performing inertial data latching processing every 1.5 seconds, and realizing 2-second synchronization of atmospheric velocity data and inertial velocity data; Step 5: combining and judging according to the data source information, selecting the combination mode: firstly judging whether the satellite data is valid, if valid, then performing inertial / satellite data combination, otherwise further judging whether the atmospheric data is valid, if valid, then performing inertial / atmospheric data combination, and then performing filtering correction; if neither the atmospheric data nor the satellite data is valid, then judging whether the correction is enabled, if yes, then performing correction, otherwise, prompting error information; The following sub-steps are included: Step 5.1: judge whether the heading change is less than 0.5°, the three-axis angular rate is less than 0.5° / s, and the combined acceleration of the three-axis body acceleration is less than 0.05 m / s2, if the three conditions are met at the same time, it is determined that the carrier is in a steady state, and the pitch angle can be calculated by using the three-axis specific force value; Step 5.2: judge whether the absolute value of the roll angle satisfies within 30°, if satisfied, calculate the difference value between the current roll angle and the last roll angle, if the absolute value of the difference value of each beat is greater than 0.001° and the roll angle difference value is positive, then the positive count is accumulated, otherwise the negative count is accumulated; then judge the difference value between the positive count and the negative count, if greater than or equal to 10, then increase the original roll angle by 0.01°, and clear the accumulated number respectively; otherwise, if the difference value between the negative count and the positive count is greater than or equal to 10, then reduce the original roll angle by 0.01°, and clear the accumulated number respectively, to realize the pitch correction and achieve the pitch leveling effect; Step 5.3: judge whether the absolute value of the pitch angle satisfies within 30° at the same time, if satisfied, calculate the difference value between the current pitch angle and the last pitch angle, if the absolute value of the difference value of each beat is greater than 0.001° and the pitch angle difference value is positive, then the positive count is accumulated, otherwise the negative count is accumulated; then judge the difference value between the positive count and the negative count, if greater than or equal to 10, then increase the original pitch angle by 0.01°, and clear the accumulated number respectively; otherwise, if the difference value between the negative count and the positive count is greater than or equal to 10, then reduce the original pitch angle by 0.01°, and clear the accumulated number respectively, to realize the pitch correction and achieve the pitch leveling effect.

2. The control method of a MEMS SINS according to claim 1, wherein, The shell (11) is provided with three bosses at the bottom and positioning blocks on the side wall; the three bosses and the positioning blocks are used as reference surfaces of the bottom and the side wall respectively.

3. The control method of a MEMS SINS according to claim 1, wherein, The three orthogonal MEMS gyroscopes and the MEMS accelerometer together constitute an IMU, the IMU is fixed on the three bosses, and the surfaces of the bosses are respectively subjected to sulfuric acid anodic oxidation treatment.

4. The control method of a MEMS SINS according to claim 1, wherein, The main boards (2) are supported by support columns, and the main boards (2) and the power supply board (3) are supported by support columns.

5. The control method of a MEMS SINS according to claim 1, wherein, The flexible length of the circuit board on the main board is increased by 4-6 mm on the basis of the spacing of the circuit board, and the printed board has a process edge during production.

6. The control method of a MEMS SINS according to claim 1, wherein, In step 2, the correction process includes the following substeps: Step 2.1: first judge whether the magnetic heading data is valid, if not, the process is ended; Step 2.2: if the magnetic heading data is valid, calculate the system heading change and the magnetic heading change, if the heading change is less than 0.5°, the magnetic heading change is less than 0.8°, the attitude angle is within 20°, and the three-axis angular rate is within 0.5° / s, and the above conditions are met at the same time, then calculate the difference value between the current heading and the magnetic heading, if the absolute value of the difference value is less than 1°, then the new heading value is obtained by subtracting 0.2 times the difference value from the original heading value, to realize the magnetic heading correction; Step 2.3: update the quaternion and the attitude matrix by using the corrected heading value.

7. The control method of a MEMS SINS as claimed in claim 1, wherein, In step 5, the satellite data and the atmospheric data are used as measurements in the inertial / satellite data combination and the inertial / atmospheric data combination, respectively, and after the measurements are updated by synchronizing the inertial data with the satellite data and the atmospheric data, the Kalman filtering technique is used to estimate the errors, and the estimated parameters are used to correct the system data.

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