The output frequency of the vibrating beam accelerometer needs to be measured continuously and accurately, but the existing frequency measurement method applied to the miniaturised circuit board has a principle error compared to the frequency meter. Aiming at the problem that low accuracy in frequency measurement method utilizing the isoperiodic method, an improved isoperiodic method is proposed to measure the frequency value of the accelerometer output. The experiment uses an Altera max10 FPGA chip to implement the frequency measurement, data processing and operation. In the experiment, a frequency measurement circuit and a standard frequency meter 53220A are used to measure the frequency output of the standard signal source and the vibration beam accelerometer respectively. The experiment results show that the output accuracy of the frequency measurement circuit is effectively improved, and the value is changed from 3.513μg to 1.078μg compared with the improved algorithm before and after when the input signal is a standard signal source. The output accuracy is changed from 22μg to 9.2464μg after exponential smoothing filtering when the input signal is the output of the vibrating beam accelerometer. By comparing the frequency measurement results of a frequency meter on the output of a vibrating beam accelerometer, the main influencing factors affecting the frequency measurement accuracy of the accelerometer are analyzed. The measured results show that the proposed frequency measurement circuit based on the improved algorithm can effectively improve the accuracy compared to the isoperiodic method, and has the characteristics of miniaturisation and high accuracy, which is of good value for future applications.

In the past three decades, MEMS inertial sensor technology has made great progress and has been widely used in human life, industry and high-end equipment. Firstly, the development history and main routes of MEMS inertial sensor in China are summarized. Then, taking vehicle assisted driving as an example, the rapid development and typical applications of MEMS inertial sensor technology at home and abroad are summarized, and the accelerating development of MEMS inertial sensor are analyzed in the direction of high reliability, integration, high fusion and intelligence.

With the development of unmanned aerial vehicle(UAV) technology, technologies about UAV swarm have become a key research direction in recent years. UAV swarm cooperative navigation technology could improve the positioning and navigation capabilities of UAVs in the GNSS-denied environment, and become a major hotspot in the research of swarm cooperative technology. In this paper, all kinds of navigation technologies and swarm cooperative technologies are sorted out, the cooperative navigation technologies in the GNSS-denied environment are divided into four directions: cooperative organizational structure, navigation and positioning mode, inter-aircraft relative positioning and cooperative positioning optimization. The development status of the corresponding directions is summarized, the collaborative navigation technology schemes in different scenarios are analyzed. Finally, the key directions of the future development of the cooperative navigation are elaborated.

In order to achieve the goal of decreasing the bias(K₀) of pendulous integrating gyroscope accelerometer(PIGA), a kind of S-shaped flex lead is proposed. The influence of structure and layout of the flex lead on both the bias of PIGA and disturbing torque imposed on float are also analyzed. The S-shaped flex lead is divided into different tangent arcs, by changing arc length, arc radius and horizontal angle(α), and then the deformation, stress-strain distribution and free end reaction force of the flex lead are obtained under the given constraints by ANSYS Workbench Mechanical modular. The disturbing torque imposed on float and the bias of PIGA are computed combining with dimension size. The results contributed to providing reference for optimizing the structure and layout of the flex lead. The simulation results show that the disturbing torque and bias show a tendency of first increasing and then decreasing with the value of total arc length, radius and horizontal angle increasing. However, both disturbing torque and bias increase rapidly with the arc bisection number increasing.

Inclinometer is an instrument for measuring the horizontal inclination angle of an object, and has a wide range of applications in surveying and mapping instruments, antenna positioning, platform control, offshore platform monitoring and other aspects. In this paper, based on a high-precision dynamic inclination sensor with MEMS gyroscope and accelerometer as the core sensors and STM32H743 as the core controller, a fusion filtering algorithm is designed for the problems that the accelerometer is unsuitable for tracking dynamic angular motion under the influence of linear acceleration and the gyroscope is affected by drift which is subject to the accumulation of error. An extended Kalman filtering model is established by zero-speed correction and attitude self-observation method, and the gyroscope and accelerometer output data are fused and filtered by feedback correction to remove the interference error of accelerometer and the accumulated drift error of gyroscope, so as to obtain the high-precision horizontal attitude information of carrier. Static and dynamic test verifications are conducted respectively by using marble plate and three-axis turntable. During the measurement process, the dynamic inclinometer transmits the raw information of instruments and the attitude solving information to the ground acquisition equipment through RS422 serial port and CAN bus to achieve continuous, real-time calculation and display of the carrier attitude. After the test verification, this algorithm can effectively improve the system inclination angle tracking accuracy, and the measurement accuracy is better than 0.008°(1σ).

The coherent population trapping(CPT) atomic magnetometer can measure magnetic field scalar with high-precision, but it is difficult to make high-precision measurements of the magnetic field vector. In order to achieve the measuring ability of geomagnetic field vector, a method based on CPT effect for measuring the magnetic field vector using dual linearly polarized light path is proposed in this paper. In this method, a VCSEL light source is modulated by a 3.4 GHz microwave module to produce two linearly polarized pump lights that satisfy the CPT effect. The two linearly polarized pump lights, which propagation directions are perpendicular to each other, are injected into ⁸⁷Rb atomic vapor cell through a light path structure. The polarization direction of the two linearly polarized pump lights is adjusted. The polarization direction corresponding to the extremum of the CPT signal peak is measured. The angular position of the magnetic field in the plane perpendicular to the light propagation direction is subsequently determined. The amplitude and direction of the magnetic field vector are obtained from measurements of the two lights. The experiment results show that angle error is about 1° under the condition of a total magnetic field of 2133 nT. The feasibility of the proposed method for measuring magnetic field vector is proved. This method has the advantages of not being affected by signal amplitude fluctuations, high theoretical measurement accuracy, and no need for tri-axis coil assistance, and it can simplify the magnetic field measurement system, which is of great significance in satellite magnetic measurement.

The integrated navigation system is a typical nonlinear system. The model nonlinearity and noise uncertainty will affect the estimation accuracy of the system. Aiming at the problem that the filtering accuracy of traditional unscented Kalman filter decreases in the case of non-Gaussian noise, an improved adaptive maximum correntropy unscented Kalman filter algorithm is proposed. This method estimates the measurement noise at the current moment according to the filtering innovation, and determines the change interval of the kernel width by using the change degree of the estimated noise relative to the historical noise. The kernel width is adaptively adjusted according to the iterative error change of the maximum correntropy algorithm, which improves the convergence speed of the algorithm and the processing ability of non-Gaussian noise. Based on the non-Gaussian noise environment, the SINS/GNSS integrated navigation simulation experiment is built and the actual car experiment is carried out. Compared with the traditional unscented Kalman filter, the results show that the east position error and north position error obtained by the proposed algorithm are 2.11 m and 1.85 m under the condition of non-Gaussian noise. The filtering performance is obviously better than the traditional UKF, which improves the accuracy of the integrated navigation solution.

The single-pixel camera is not yet mature in terms of integration and engineering, and most research only focuses on building and testing in laboratory environments. However, in engineering applications, the volume, weight, and testing environment of the prototype are all factors that affect the quality of single-pixel imaging. Therefore, under the constraints of volume, weight, and testing environment, a single pixel camera in the near infrared band is tested in complex environments such as natural light sources and infrared lights using an efficient encoding and decoding algorithm integrated with C++ language. The integrated single-pixel camera can achieve 2.5 frames per second @256×256 pixels with an angular resolution of 7.3 mrad at a 6.25% sampling rate. As the exposure time increases, the image signal-to-noise ratio significantly rises. After processing with a deep learning denoising network, the quality of single-frame imaging still has room for improvement. Additionally, the response characteristics of the integrated prototype to vibration are also simulated and studied, and the adaptability of the prototype in general transportation environments is discussed. This study has a promoting effect on improving the technological maturity of single-pixel cameras, and provides a solution for low-cost infrared imaging.

In the process of feature extraction and matching in aircraft visual navigation, the imaging methods of heterogeneous images are different, and the feature information varies greatly. Due to different standards, it is difficult to achieve accurate matching for various types of image information. Considering the above issues, a heterogeneous image matching algorithm based on feature fusion is proposed in this paper, which can achieve high-precision matching of heterogeneous images. Firstly, an encoding network based on residual networks is designed to enhance the ability to extract deep level features of images. Then, dense connections are introduced in the decoding network to preserve intermediate layer features, enabling the fusion results to take into account information at all levels of the image. Besides, a fusion strategy including attention mechanism is designed to optimize the information proportion of the source image in the fusion features and improve the quality of the fusion features. Finally, the fused features are applied to image matching. The experiment results show that the proposed algorithm exhibits advantages in feature fusion evaluation indicators compared to common methods. In the experiment of heterogeneous image matching, the matching accuracy of the proposed algorithm is 96.71% and the matching accuracy under rotation is 89.40%, which reflects high accuracy and strong robustness performance.

With the development of modern war, it is of great significance to fight for the right to control low and ultra-low altitudes. Terrain-aided navigation is an effective means to achieve the navigation and positioning of low-altitude aircraft such as helicopters. Aiming at the problem that terrain matching in terrain-aided navigation under helicopter low altitude flight scene is greatly affected by measurement errors, which leads to matching errors and affects positioning accuracy, through analyzing the traditional matching correlation operation methods, the probability density of terrain elevation difference is introduced as the correlation calculation method, and a terrain matching method using the probability density features of terrain elevation difference is proposed. The terrain complexity and similarity are introduced to evaluate the confidence of terrain matching to reduce the impact of error matching on navigation error correction. The simulation results show that the proposed terrain matching method based on probability density features has higher adaptability to measurement errors and higher matching accuracy. Compared with traditional methods, the matching accuracy can be improved by 56.5% in the case of large measurement errors. By evaluating the confidence of terrain matching, the root mean square error of integrated navigation positioning error can be reduced to 3.54% of the traditional method in the scene with many mismatches, effectively improving the fault tolerance of terrain-aided navigation system.

Hemispherical resonator gyroscope is a new type of solid-state gyroscope with high precision, small mass and long life. It has a wide application prospect in navigation, aviation, aerospace and other fields. The mass non-uniformity leveling technology of hemispherical resonator gyroscope is the key technology to manufacture high-precision hemispherical resonator gyroscope. For this technology, the fourth harmonic defect identification method and its key performance indicators development status, which have the greatest impact on the performance of the harmonic oscillator, are firstly analyzed. Secondly, the identification methods for primary, secondary, and tertiary harmonic defects that affect the performance of the harmonic oscillator are sorted out. Then, the four types of leveling processes for harmonic oscillators—methods and characteristics of traditional machining, chemical etching, laser etching and ion beam etching, are summarized and analyzed. Finally, the problems to be solved and the future research focus of the harmonic oscillator leveling technology are prospected.

In aerospace, automotive and other fields, all kinds of complex workpieces have complex structure, weak textures and are stacked aliasing. In the intelligent manufacturing process, there are rapid and high-precision measurement and identification problems. For the above problems, a high-precision 3D disorderly grasping system for industrial robots is established. Based on the surface structured light 3D measurement technology, a 3D visual measurement equipment with a fixed base for large scenes is constructed to obtain 3D point cloud data of large and complex parts. A part point cloud template is established, the location of the grasping point is set, and the point cloud registration technology is used to identify the parts and estimate the current pose. A hand-eye calibration optimization strategy is proposed to realize the accurate guidance of industrial robot, complete the grasping of parts in any pose and assemble them at the required position. The experiment results show that the designed disordered grasping system has a translation error of 0.413mm and an angular error of 0.123°, which can quickly and effectively identify and locate the stacked parts with high accuracy and guide the industrial robot to accurately grasp and place them. This system can be demonstrated and applied on industrial production lines in fields such as aerospace and automotive.

Universal time(UT1) is a time measurement system based on the Earth’s rotation and plays an important role in the orbital coordinate transformation of spacecraft. In this paper, an overview of the demand for precise orbit determination of spacecraft for universal time(UT1) measurement precision is provided. An analysis is conducted on the current methods of measuring UT1 using space geodetic methods, large ring laser gyroscope(RLG), large fiber optic interferometer(FOI), and other methods. Elaborate on the key technologies that need to be addressed in the UT1 measurement based on high-precision FOI. The large-scale high-precision FOI and the UT1 measurement system implemented in this paper is experimentally verified. The continuous 15 day test data shows that after adopting the directional measurement error elimination method, the bias stability of the FOI reaches 9.7×10^-7(°)/h(1h, 1σ), the standard deviation of the measurement system for calculating UT1 is 1.5ms. After compared and verified with the IERS, the measurement error of the UT1 measurement system is less than 7ms. Finally, prospects are made for the measurement accuracy of UT1 and other Earth parameters based on high-precision FOI.

Vehicle-mounted visual navigation performs poorly in scenarios such as large angle rotation and high-speed motion. Due to the complementary error characteristics of vision and inertia, the visual inertial integrated navigation algorithm has a good application prospect. The large field of view camera obtains rich external information, but the low sampling frequency of the camera affects the visual data acquisition. Moreover, the calculation speed of the optimized integrated navigation algorithm is slow. Therefore, a vehicle-mounted visual inertial integrated navigation algorithm suitable for large field of view camera is proposed in this paper. The algorithm focuses on data preprocessing: a contrast limited adaptive histogram equalization based on gamma function is designed to reduce image noise, and feature extraction and optical flow tracking are completed by combining FAST corner points with optical flow method to further accelerate the calculation speed. The inertial data equivalent rotation vector two-sample algorithm is introduced to reduce the amount of data and calculation, and the pre-integration algorithm is used to reduce the amount of calculation for error optimization. The accuracy is improved by joint optimization of visual error, inertial error and marginalization error. Compared with other integrated navigation algorithms, this algorithm has higher accuracy and fastest calculation speed, and saves 19.7% more time than VINS-Mono.

Pendulous integrating gyro accelerometer(PIGA) is widely used in high-precision inertial navigation and guidance systems for long-range rockets at home and abroad because of its high-precision, large range, anti-interference and automatic integration. By adopting air-flotation, liquid-floating, and magnetic levitation support technology, the tri-floated PIGA has become the most accurate accelerometer in current engineering applications. The current development status, technological advantages, key technologies such as tri-floated support, servo control and precision manufacturing of tri-floated gyroscope accelerometers are summarized. Finally, the development of the PIGA technology is prospected.

Because the inertial measurement unit is a high-precision sensor module greatly affected by external factors such as temperature, it needs to be tested and compensated in the production process to ensure the accuracy of the unit. In view of the shortcomings of the original inertial measurement unit test method, such as cumbersome program, long test cycle and low efficiency, an automatic test system of inertial measurement unit based on LabVIEW is designed in this paper. After experiment verification, the system can collect and store the output data while carrying out the static test and dynamic test of inertial measurement unit, provide data support for the subsequent compensation verification of inertial measurement unit, improve the test efficiency, and can achieve all-weather testing. It has the advantages of high automation and short test cycle.

As an important part of aerial photoelectric pod, photoelectric platform is widely used in UAV, seeker and other fields. In order to compensate friction, angular velocity disturbance and other unknown disturbances and improve the system stabilizing accuracy, a composite control method based on fuzzy tuning rules and improved disturbance observer(IDOB) is proposed. In this method, fuzzy rules are used to adjust PID parameters online, and an improved disturbance observer based on angular velocity is used to observe the external disturbance in the servo control system, which is equivalent to the control quantity for feedforward compensation. The prototype swing experiment results show that the RMS value of the proposed compound control method is 12.24% less than that of the fuzzy PID control under the condition of low frequency disturbance, which effectively improves the line of sight stabilizing accuracy and robustness under low frequency disturbance motion. The composite control method has better stability, and has reference significance for engineering practice.

In order to improve the navigation accuracy of hemispherical resonator gyroscope inertial navigation system effectively, and solve the problem that temperature has great influence on fast start-up and practical application precision of the product, the temperature characteristics of system-level calibration error parameters are analyzed in this paper, and the temperature error model is established. Finally, the temperature compensation experiment and the platform mode calibration experiment are designed to verify the compensation effect. The experiment results show that the established temperature error compensation model is accurate and effective, the stability of error parameters is improved, and the performance of hemispherical resonator gyroscope inertial navigation system is improved in the start-up phase. The calculation amount is small, and it has high engineering application value.

Fluorinated oil is fluorine-containing organic compound, which is formed after the hydrogen in alkane or ether molecules is completely or partially replaced by fluorine. It includes perfluorocarbon oil, fluorochlorine oil, and perfluoropolyether oil. Fluorinated oil has excellent chemical and thermal stability, viscosity temperature properties and lubrication properties, and is widely used in fields such as aerospace, electronics, chemical, mechanical and nuclear industries. In this article, in order to investigate the chemical and thermal stability of fluorinated oil, a simulated acceleration test method is proposed, which accelerates the micro degradation of fluorinated oil by adding oxygen, heating and pressurizing. Differential scanning calorimetry and nuclear magnetic resonance are used to detect the fluorinated oil samples, which are undergone accelerated testing. A highly sensitive ion chromatography method is developed to determine the fluorine ion concentrations in the samples to investigate the chemical and thermal stability of fluorinated oil. Under the simulated acceleration test conditions and test methods in this paper, when the concentration of fluorine ion is not more than 5mg/L, it can be preliminarily shown that the fluorinated oil has good stability.

MEMS gyroscope has been widely used in the civil field because of its small size and low price. However, due to the limitation of technology level, there are a lot of random errors in the measurement data of MEMS gyroscope. In order to reduce the random error of MEMS gyroscope measurement and improve the measurement accuracy, a random error filtering method based on progressive forgetting multi-innovation Kalman filtering is proposed. The AR model of MEMS gyroscope random error is established. In the classical Kalman filtering, the multi-innovation correction method is introduced, and the progressive forgetting factor is used to weaken the accumulated interference of historical data. Thus, the progressive forgetting multi-innovation Kalman filtering method with random error is given. At the same time, classical Kalman filtering and progressive forgetting multi-innovation Kalman filtering are used to process the output data of MEMS gyroscope, and Allan variance is used to analyze the noise content. It can be seen that the QN noise of the data after progressive forgetting multi-innovation Kalman filtering is reduced by 2 orders of magnitude compared with classical Kalman filtering, ARW noise is reduced by 1 order of magnitude, Bi noise is reduced by 2 orders of magnitude, RRW noise and RR noise is reduced by about 1/5 of the original. The experiment results verify the progressiveness of the progressive forgetting multi-innovation Kalman filtering in gyroscope random error filtering.

Fiber reinforced resin matrix composites have advantages such as high specific strength/specific modulus, strong designability, and fatigue resistance, and have been widely used in aerospace field. However, they also face production costs and efficiency issues. Aiming at the problem of high cost and high consumption for autoclave process, a comprehensive analysis is conducted on the advantages and disadvantages of autoclave process and vacuum assisted resin infusion(VARI) process. After integrating the advantages of the two molding processes, a new low-cost non-autoclave molding process is designed based on VARI process, and the performance of the molded parts using this process is evaluated. The results show that, compared with VARI process, the fiber volume fraction, tensile modulus, tensile strength and interlaminar shear strength of glass fiber laminates formed by non-autoclave process increase by 6%, 2.24GPa, 61MPa and 2.96MPa, respectively. This design significantly improves the mechanical properties of VARI process parts, and it has a certain application prospect.

Aiming at the miniaturization demands of current navigation systems, a navigation microsystem circuit based on SiP technology is designed. The microsystem circuit can achieve RF baseband integration, and is internally integrated with low noise signal amplifier, GNSS RF baseband chip, channel selector, overcurrent locking protection chip and passive components. High thermal conductivity alumina ceramic shell is used to achieve great heat dissipation, the size of SiP is effectively reduced by using the double cavity structure, the size is only 26mm×26mm, and its area is reduced to 26% of the original board card. The module is simulated to meet the design requirements. The test results show that the circuit can achieve GPS and BD dual-mode navigation, positioning accuracy reaches 10m, speed measurement accuracy reaches 0.2m/s, it can meet the requirements of system miniaturization.

With the development of marine science construction, the application of submersibles is developing towards deep-sea, multi-functional, long-range, and ultra-high speed directions. Integrated navigation systems are widely used in deep-sea navigation due to their high reliability and good real-time performance. With the increasing scale of submersibles and the complexity of mission environments, the failure rate of navigation systems is also increasing. Once a failure occurs, it will lead to system failure or even mission interruption. Therefore, it is necessary to establish a comprehensive fault detection scheme, timely detect faults and make corrections to improve the reliability of complex tasks. Traditional fault detection methods rely on prior knowledge or models and have been widely applied. However, when dealing with complex systems, multi-source and high-dimensional data, fault detection techniques based on intelligent algorithms are showing their advantages. Firstly, based on the characteristics of deep-sea environment and the navigation scheme of underwater vehicles, the traditional methods and the detection methods based on intelligent algorithms are introduced. Then, the characteristics of different detection methods and their applications in underwater environments are analyzed based on case studies, and the research progress of fault detection methods is summarized. Finally, the research direction of fault detection methods for future deep-sea submersible integrated navigation systems is discussed.

Inductive displacement sensors are commonly used in precision measurement fields such as high-speed and high-precision beam positioning devices. In order to improve the performance of inductive displacement sensors, it is necessary to study the factors that affect the sensitivity, linearity, resolution and bandwidth of inductive sensors. A transformer model based on eddy current effect is established to investigate the relationship between the sensitivity of inductors with different conductivities. The results show that the higher conductivity of the armature, the lower its sensitivity. The selection principle of excitation frequency is analyzed, and the calculation method for separate measurement of inductance and resistance is derived. In order to determine the relationship between displacement resolution and bandwidth based on digital phase-locked amplifier demodulation, a measurement error model based on digital phase-locked amplifier demodulation is established. A displacement detection system using a differential inductive sensor has been designed. According to the experiment results, the sensitivity is 6.888V/mm after three cycles of forward and reverse travel measurements at a bandwidth of 1kHz and a total range of 1mm. The repeatability reaches 0.275%, and the displacement resolution reaches 26.40nm. After cubic spline smoothing and nonlinear compensation, the linearity can reach 99.93%. Within the same range and bandwidth, the resolution and linearity are superior to some sensors with better performance both domestically and internationally.

In the dynamic modeling of wireless power transfer system based on the first harmonic approximation, it is generally assumed that the input voltage and current of the rectifier bridge are in the same phase, which, however, may reduce the model accuracy. To solve this problem, a novel method is proposed to enhance the dynamic modeling accuracy of wireless power transfer system. This approach incorporates the phase angle and gain of the rectifier bridge as hyperparameters into traditional dynamic models, estimating the optimal rectifier bridge parameters by minimizing the quadratic loss function between model and measured outputs. Experiment results show that dynamic models of wireless power transfer system obtained by this method has an output curve that is closer to the actual output curve, and can better describe the dynamic characteristics of the system.

The full process flight tracking and monitoring of civil aviation aircraft in global regional has always been a focus of aviation aircraft research and development work. Due to lack of ADS-B and ACARS signal coverage in remote area, such as Tibet and Xinjiang, the civil aircraft can not be tracked in time. The Beidou communication technique based on RDSS short message can fill the gap in civil aircraft monitoring. Based on the Beidou short message data link, tracking and positioning of transportation aircraft can be achieved, and real-time monitoring of aircraft flight conditions can be carried out. In order to improve the communication successful rate in the complex air channel environment, the anti-jamming antenna design is optimized and the signal reception quality is improved based on the analysis of the air signal quality. Functions including aircraft trajectory tracking display, aircraft data alarm and data analysis based on Beidou are implemented. According to the verification result in trial environment, the average data reception success rate has increased by 3.53%, the function and performance indicators of system design have reached the design goals, which can effectively supplement the existing aircraft monitoring signal gap.

In irradiation environment, the spectral width, mean-wavelength stability and optical power stability of erbium-doped fiber source(EDFS) are directly related to the accuracy of fiber-optic gyroscopes(FOGs). In order to study high-performance radiation-resistant EDFS, the radiation-induced active band attenuation(RIABA) characteristic of EDFS is firstly researched. Then, by using the intrinsic luminescence spectrum of Er³⁺ as original output spectrum, combined with “multiple photo-bleaching” and “980nm pump power closed-loop feedback control technology”, a high-performance radiation-resistant Er-doped photonic crystal fiber source(EDPCF) design scheme is proposed. The results show that it demonstrates a mean-wavelength stability of 5.4×10^-7/krad and the output power attenuation of less than 0.1dB with 3dB bandwidth more than 40nm under 50krad irradiation dose. The broadband source proposed demonstrates excellently performances in radiation environment, which is quite feasible for strategic grade high-precision interferometric fiber-optic gyroscopes.

Laser strapdown inertial navigation system(SINS) is used in weapons, aircraft, and other fields because of its good short-term accuracy and stability. Aiming at the problem of reduced navigation accuracy caused by the mechanical dithered RLG sensitive axis bending in a continuous-rotation environment, a model for bending error of the mechanical dithered RLG sensitive axis is established, and the finite element simulation results are used to perfect the model. A calibration method is proposed, which fully excites 6 bending error parameters of the sensitive axis through a new calibration layout scheme. Then, all error parameters can be estimated using Kalman filtering method. The simulation tests show that this method can accurately calibrate bending error parameters of the sensitive axis. The calibration and compensation experiments of SINS are conducted to verify the correctness of calibration, which shows that the velocity error is decreased by 80% in a dynamic environment after compensating for the bending errors. This calibration and compensation method can improve the dynamic navigation accuracy of SINS and has certain engineering value.

In the process of wireless power transfer, the position misalignment of the transmitter and receiver for aerospace instruments is inevitable, which decreases the power and efficiency sharply. To solve this problem, a misalignment tolerant hybrid topology WPT system consisting of LCC-LCC and S-S topologies parallel is proposed based on the misalignment insensitive double-cross coil. Firstly, COMSOL finite element simulation is used to analyze the magnetic field distribution characteristics of the mechanism. Then, the circuit characteristics of LCC-LCC and S-S compensated parallel hybrid topology and the characteristics of vibration misalignment are analyzed. Finally, the reliability and effectiveness of misalignment tolerance using the double cross coil and detuned hybrid topology WPT system are verified by simulation and experiment. The experiment results show that the output power and the transmission efficiency of the system under the position misalignment of the receiver coil basically remain unchanged.

According to experience, the PID parameters determined artificially in the process of turntable adjustment are not only inefficient, but also low-precision. It is difficult to achieve satisfactory results. To solve this problem, a PID parameter optimization method based on beetle swarm optimization algorithm is proposed. Firstly, the mathematical model of turntable is established. Secondly, the algorithm flow, objective function and optimization process of the beetle swarm optimization algorithm are introduced. Finally, the IAE criterion is used to optimize the parameters by the algorithm to obtain a set of optimal solutions. Compared with the PID parameters determined by experience, the PID parameters obtained by the beetle swarm optimization algorithm are more reliable, and the step response settling time of the turntable control system is 1.1s, and the overshoot is 7.4 %.

The liquid floated gyroscope has the advantages of high accuracy, high reliability and strong adaptability to the environment. However, due to its complex structure and uneven internal temperature distribution, the floating liquid flows, this interference moment generated by the floating liquid is a crucial factor that affects the accuracy of the gyroscope. At the same time, the liquid floated gyroscope has a closed cavity, and there are solid, liquid and gas states, which makes it difficult to directly measure the temperature distribution of the instrument through the experiment. According to the actual working conditions and working principle of the liquid floated gyroscope, the fluid solid thermal multi physical field calculation model of the gyroscope is established by using multi physical field finite element simulation software. The temperature distribution of the liquid floated gyroscope and the flow and temperature fields of the internal floating oil and gas are obtained through calculation. Compared with the temperature of the experimental test point, the temperature error of the test point calculated by the model is 0.36%. The precision of the temperature gradient in critical areas could achieve a resolution of 0.01K. After the grid is refined by 20%, the temperature gradient of the instrument changed by 0.05%. The research in this paper will provide an important basis for the temperature control and accuracy improvement of the subsequent liquid floated gyroscope.

In addressing the non-uniform deformation issue caused by tightening the threaded connections in instruments, uniformity assembly offers a more economical and versatile approach to enhancing the precision and stability of instruments. In this paper, a method for evaluating the deformation uniformity is introduced, which characterizes the degree of uniformity through the characteristic parameter of a coexistence matrix. Combining with the critical structure of the instrument, namely the motor rotor structure, a refined simulation analysis model is established. Numerical simulation methods are employed to investigate the influence of preload process parameters on the deformation uniformity in the motor rotor cover connected by threaded joints. The results indicate that the dispersion of preload is not significantly correlated with the deformation uniformity of rotor cover, while the uniform distribution of preload contributes to improving the precision of instrument assembly. The findings of this study provide a theoretical basis for precision product threaded connections design and process design.

The stable operation of auto-tracking accelerometer current digital conversion circuit requires the optimisation of system controller proportional integral derivative(PID) parameters, but the adjustment of parameters is mostly done by trial and error and empirical judgement, which has the problems of long adjustment time and low control accuracy. To address this problem, the root trajectory-based method is proposed to solve PID parameters of the control system. This method firstly constructs a mathematical model of the continuous control system, and then uses the root trajectory method to solve the corrected controller parameters of the control system, the corrected dynamic performance index of the control system is close to the desired value, and the -3dB bandwidth reaches 6.2kHz. Then, this method uses the continuous domain-discrete design method to discretize the continuous domain controller. Finally, Simulink is used to construct the simulation models of the closed-loop control system in the continuous domain and the discrete domain respectively. The simulation results show that the step response curves of the two systems are basically the same. In the discrete domain, when inputting a unit step signal, the system is stable and the output steady-state error is 0. The simulation results can be used to optimise the control parameters of the current digital conversion circuit.

Suspended oil is an important part of liquid floated gyroscope. The uneven temperature distribution of the working environment causes the local changes of the suspended oil density, resulting in the generation of disturbance torque. The finite element method can simulate the temperature field and analyze the disturbance torque of the liquid floated gyroscope, but it’s lack of research on the physicochemical properties and changes of the suspended oil. The molecular chains and density calculation models of perfluoropolyethers are established and optimized by molecular dynamics simulation, and the effects of molecular weight and temperature on density are calculated. The results show that the density of perfluoropolyethers increases with the increase of molecular weight, and the simulated values are consistent with the measured values. The density of perfluoropolyethers decreases with the increase of temperature. There is a linear correlation between density and temperature, the lower the molecular weight, the faster the density decreases. After fitting and correcting the temperature-density equations, the quantitative analysis of perfluoropolyethers properties is realized, which provides the basic parameters for finite element simulation and the design of liquid floated gyroscope.

Alternating temperature load can affect the threaded connection status, thus affecting the accuracy and stability of precision inertial instrument. Electromechanical impedance technology is widely used in the field of threaded connection detection because of its fast response and sensitivity to minor damage. However, the existing electromechanical impedance detection methods ignore the influence of temperature. In this paper, the influence of temperature change on electromechanical impedance is analyzed theoretically. Taking the structure of dynamic pressure air bearing for precision inertial instrument as the research object, the feasibility of identifying the threaded connection status for precision instrument by electromechanical impedance technology is explored. A simulation model is established to study the influence of temperature on PZT signal attached to the structure, and the sensitivity of PZT signal to temperature is verified experimentally to be affected by the frequency band. It is shown that an increase in temperature shifts the peak frequency of the impedance signal to the left, and the wave amplitude decreases with increasing temperature. At the same time, the lower the excitation frequency, the smaller the peak frequency offset, and the more significant change in wave amplitude. The study verifies the feasibility of electromechanical impedance technology to identify the threaded connection status of precision instruments, provides technical support for the application of electromechanical impedance detection technology, and provides a theoretical basis for the health detection of complex precision inertial instruments.

Accurate identification of pedestrian motion modals can aid gait detection. For the problem of inaccurate gait detection under pedestrian continuous motion modals, a multi-conditional constraint gait detection algorithm based on modal identification is proposed in this paper. Firstly, based on the motion characteristics of pedestrians and the pose characteristics of handheld terminals, finite state machine idea is introduced to construct lightweight classifiers to identify three motion states of pedestrians(stationary, walking and running) and three usage modes of terminals(flat end, telephone and swing arm), in order to improve the adaptability of gait detection. Then, the gait detection accuracy is improved by extreme value constraint, periodicity constraint and peak/valley matching mechanism. Finally, the pseudo-peaks/valleys are eliminated by the adjacent peak/valley substitution mechanism to achieve more accurate gait detection. The experiment results show that the algorithm has a minimum gait detection accuracy of 98.89% in a single-motion modal and an overall detection accuracy of 100% in continuous complex modals, which has strong accuracy and robustness.

In inertial navigation system, the current signal output by the accelerometer needs to be converted into the output pulse through the analog-to-digital conversion circuit. Aiming at the problem for nonlinear distortion due to the unsatisfactory device in output of I/F analog-to-digital conversion circuit in inertial navigation system, a two-stage compensation algorithm is proposed in this paper. In this algorithm, temperature compensation model and linearity compensation model are established to compensate the linearity of the circuit, the error caused by temperature change is compensated, and the problem that the hardware only compensates the first-order error is solved, which makes the analog-to-digital conversion circuit maintain high-precision in large range environment even if the device parameters are unsatisfactory. The algorithm is applied to the practical circuits, and the experiment results show that this algorithm can reduce the nonlinear index of I/F analog-to-digital conversion circuit from 7.20×10^-4 to 4.93×10^-6, and effectively decrease the nonlinear distortion caused by the unsatisfactory device.

With the increasing demands for assembly accuracy and automation of large cabin products such as aircraft and rocket in the aerospace field, the assembly modes of large cabin are moving from the original manual operation mode of “visual shouting and manual pushing” to the direction of automation, digitalization and intelligence. In this paper, to address this issue, an automatic docking system based on machine vision is designed, and a method for measuring the relative pose of large cabin based on two sets of monocular vision is proposed. The system uses two sets of monocular vision to independently measure the position and attitude of the target on the surface of the module, and combines the pre-calibrated position relationship between the target and the module, and integrates the two sets of monocular vision measurement results to calculate the final docking attitude of the module. The experiment results show that the measurement accuracy of the system is better than 0.04 mm, and the docking accuracy is better than 0.3 mm, which has strong application value.

Aiming at the problem of difficult description of the complex structure and the movement position of the internal frames of the inertial platform system during testing, the visualization of the digital model of the inertial platform and a method of the model driven are proposed. A three-dimensional visualization system of inertial platform for online testing and offline teaching is developed by using Qt/OpenGL. The inertial platform is modeled by a CAD modeling software, and the interface between OpenGL and the CAD software, as well as the interface between digital prototype and actual platform, are determined. The verification based on online/offline platform tests shows that the developed system realizes the real-time tracking of the digital prototype to the actual movement of the platform frames. The structure and positions of the frames during online/offline testing are displayed clearly. The developed system effectively improves the onsite communication during testing and the training among platform testing.

A new operation and maintenance technology based on digital twin for strapdown inertial navigation system has been proposed to address the complex data analysis, inaccurate fault localization, and difficulty in managing the lifecycle of the production process. By combining digital twin technology with strapdown inertial navigation system, it offers innovative solutions for the intricate design, production, and lifecycle maintenance of strapdown inertial navigation system. By designing a digital twin system based on the full element visualization of the strapdown inertial navigation system, the equipment is managed for lifecycle data. Results from production show that this technology can replicate physical entities in a virtual space and achieve real-time interaction between physical and digital spaces throughout the lifecycle of strapdown inertial navigation system by using historical data, real-time data, technical knowledge, processing algorithms, functional models, thus establish a fault database and enable digital health management.