The present article attempts a more comprehensive review of recent literature in the broader area of mechanically fastened polymer-matrix composite joints with protruding-head bolts. The article begins with a review of the mechanical configurations of composite joints. A study of the mechanical configurations of composite joints opens the topic. This is followed by a discussion of the failure progression of composite joints in tensile loading. The remaining sections are devoted to the influence of composite properties (fiber type, reinforcement structure, fiber and metal mixed laminates, ply angle and proportion, curing process, initial material defects), fastener performance (fastener stiffness, bolt head type, bolt diameter, thread seal, gap fit, interference fit, fastener missing), connection plate performance, lateral constraints (tightening moment,bearing area, compensation gasket, contact surface friction factors), geometric effects (composite plate size, plate thickness to hole diameter ratio, specimen width to hole diameter ratio, hole end distance to hole diameter ratio, hole shape, hole quality, hole position error) as well as loads (static load, dynamic load, fatigue load, creep, relaxation, warm and wet load) on joint strength and failure. Finally, comments are offered regarding the most important remaining problems in this area, along with recommendations for future work.

The leading edge slat is an important lift increasing device in the take-off and landing stages of large aircraft. But affected by its own body stiffness and support stiffness, the slat is prone to warpage and deformation under aerodynamic load, resulting in gaps with the wing box, which affects the aerodynamic efficiency of the wing. To eliminate the deformation of slat in cruise and improve the aerodynamic efficiency of the wing, the leading edge slat interference trailing edge structural design technology is proposed in this paper. Firstly, the main factors affecting the normal and chord deformation of slat structure are theoretically analyzed. Then, taking the leading edge slat of a large domestic aircraft as the research object, the influence of skin and other structural dimensions on the stiffness of slat body is discussed in detail from two aspects of weight and deformation. Finally, on the premise of maintaining the size and weight of the original slat structure, the leading edge slat interference trailing edge structure is designed. The results show that the proposed interference trailing edge structure can maintain the state of non separation from the wing under the aerodynamic load of cruise condition, improve the aerodynamic performance, and effectively avoid the increase of weight.

The temperature stability of optical system and detector of high precision stereo mapping camera affects the mapping accuracy of mapping camera. For transmission optical system, multi-stage external heat flow suppression technology is adopted to improve the temperature stability of the star camera lens by 6 times; for reflective optical system, thermal control technologies such as indirect radiation temperature control are adopted to make the temperature stability of the primary and secondary mirrors reach ±0.3 ℃; for high-power charge-coupled device (CCD), energy-saving temperature control technology based on loop heat pipe (LHP) is adopted to make the LHP driving power cycle average from 60 W to 33.8 W, while saving about 40% of the primary condenser area and mass; for CMOS, using two-stage temperature fluctuation suppression technology, the temperature stability is ±0.3 ℃. The method of ground thermal test was investigated, and the flight temperature data of key components of the mapping camera system under extreme space environment were reported, which fully verified the correctness of the thermal control design method.

To carry out airport safety risk early warning under the circumstance of non-suspend air construction, a risk early warning model is constructed by integrating dynamic weight and matter-element extension analysis (DW-MEE). Through the analysis of historical accidents, literature, rules and regulations, and expert interviews, airport safety risk early warning index system under the circumstance of non-suspend air construction was preliminarily constructed, and 33 indexes were selected by Delphi method. The comprehensive safety risk warning situation and single index warning situation of the airport under the circumstance of non-suspend air construction were divided into four grades: no alarm, light alarm, medium alarm and heavy alarm. The dynamic warning model based on dynamic weight and matter-element extension analysis was established. The study found that among 10 sample airports, 1 is in red heavy alarm state, 3 are in yellow light alarm state, and 6 airports are in green no alarm state. The three indexes of pilot’s situational awareness, pilot’s professional skill level and airport non-suspend air construction safety supervision ability are the most sensitive to the influence of alarm situation, while the three indexes of construction’s influence on ground service, the scientific nature of non-stop construction emergency plan and the maintenance of power supply equipment are the least sensitive to the influence of comprehensive warning situation.

In order to improve the feature expression ability of the Siamese network without deepening the network, a Siamese network tracking algorithm was propose based on high-level semantic embedding. First, a semantic embedding module was designed with convolution and up-sampling operations, which effectively integrated deep features with shallow features, thus achieving the purpose of optimizing shallow features, and this module can be flexibly designed and deployed for any network. Then, under the Siamese network framework, two semantic embedding modules were added between different layers of the AlexNet backbone network. Cyclic optimization was carried out in the offline training stage to gradually transfer the deep semantic information to the shallow feature layer. In the tracking stage, the semantic embedding module was abandoned and the original network structure was adopted. The experimental results show that compared with SiamFC on the OTB2015 data set, the accuracy is improved by 0.102 and the success rate is increased by 0.054.

Blended wing-body (BWB) aircraft can meet the economic, environmentally friendlyand low-carbon operation needs and is one of the key development directions of future civil aviation. Aiming at the flight control system of BWB aircraft, its safety analysis and system design are studied. First, a description of the system-theoretic accident model, processes, and associated safety analysis procedure is provided. The complex logic relationship, unsafe control actions and hazard cause factors in the control system of BWB aircraft are analyzed emphatically. Then the switching system is designed. Analyzing the switching logic, the design process for both the high reliability backup system and the low reliability advanced system is presented. Finally, the simulation is carried out based on the design. The examination of the complicated logic relationships in the BWB flight control system can be understood using the applied safety analysis approach, and the designed flight control system has a certain level of safety and viability.

To improve the wet gas metering accuracy by using a vortex flowmeter, aiming at the problems of low prediction accuracy and narrow application scope of the traditional meter overreading correlations, a meter overreading model based on flow parameters of the entrained droplets (entrainment fraction and droplet size) was proposed. To conduct experimental studies on different entrained droplet conditions, the annular mist flow loop based on atomizing mixing was developed, and the optical imaging system was built to measure the droplet diameter and distribution. The dimensionless scaling parameters were discovered by combining the annular mist flow pattern with the vortex meter overreading mechanism and taking into account the droplet-liquid film mass transfer and the droplet-vortex coupling mechanism. The meter overreading model was developed with liquid mass loading, Weber number and Stokes number, taking the effects of the entrained droplet parameters and the carried gas parameters (density and velocity) into consideration, thus, its application scope is expanded. Finally, the performance of other overreading correlations was evaluated and analyzed by the differences of the entrained droplet parameters in their experimental conditions and the model assumptions. The results indicate that the proposed model provides a uniform prediction for the meter overreading, the relative deviations are within ±1.0% error band, both the predicted accuracy and the model extensibility are greatly improved compared with other overreading correlations.

This paper analyzes the power measurement deviations of the direct and reflected signals from BDS GEO satellites. Firstly, the expressions of direct and reflected BDS GEO signals received by actual antennas in ground-based scenario are presented. Then, the relative deviations of direct and reflected signal power measurement of BDS GEO satellite are discussed. Finally, simulations were carried out to analyze relative deviations in a specific observation scenario. Both theory and simulation show that the power measurement deviation of the direct and reflected BDS GEO signals are fixed under a specific scene and at a given time. The deviations are codetermined by the suppression performance of the antenna to the interference signals, antenna height and the dielectric constant of the reflector. The relative deviation decreases with the enhancement of the suppression performance of the antenna to the interference signal, fluctuates within a certain range with the change of the antenna height, and varies with the dielectric constant of the reflector.

A coaxial-rigid-rotor helicopter flight dynamics model, which can be coupled with unsteady ship airwake, was developed to investigate flight characteristics of the rotorcraft during deck landing. In the numerical simulation of ship flowfield, the detached eddy simulation method was used to obtain high-precision data of the flowfield. In building the flight dynamic model, an interaction factor of coaxial twin rotor was introduced to develop the induced velocity model of the coaxial rigid rotor, and the concept of equivalent flapping was adopted to establish the flapping movement function of coaxial rigid rotor. Then, a strategy which can transmit computational fluid dynamics (CFD) data to the flight dynamics model was established based on the “one-way” coupling idea. The accuracies of the flight dynamics model and the data transfer strategy were verified by analyzing the XH-59A coaxial-rigid-rotor helicopter and the combination of UH-60A/SFS2, respectively. Next, the combination of SFS2 ship model and XH-59A coaxial-rigid-rotor helicopter was chosen to investigate the influences of the ship airwake on the helicopter in terms of control margins and unsteady loading level. The time-averaged results showed that due to the differences in disturbance between the upper and lower rotor, pilots had to reduce the differential collective pitch to maintain the direction of the helicopter nose, while increasing the collective pitch to maintain the altitude at the same time. Furthermore, the unsteady level results indicated that for coaxial configuration, the disturbances in its thrust and pitch moment are the primary causes of pilot workload.

This paper proposes a three-dimensional integrated design method for missile guidance and control with fixed-time convergence to address the issues of impact angle constraints, state constraints, and control constraints. A three-channel fully coupled design model of guidance and control system with impact angle constraints is constructed, and the unknown disturbances in the integrated design model are estimated and compensated by a fixed-time convergent sliding mode disturbance observer. Based on the fixed-time stability theory, terminal sliding mode control and backstepping control method, the integrated design of the guidance and control system is carried out, and the second-order instruction filter is used to restrict the system states and control instructions. The fixed-time convergence property of the integrated algorithm is proved, and the specific convergence time expression is given. The effectiveness and superiority of the integrated guidance and control law are verified by six degrees of freedom simulation of the missile.

The ellipse-based optical navigation technology has become a novel and precise autonomous navigation method. Therefore, how to fit the elliptic edge of the space object is the essential condition of the optical navigation method. We propose an ellipse detection algorithm for the spacecraft optical navigation in this paper. First, the elliptic curves are extracted by utilizing the polygonal curve to approximate the edge in edge map of the navigation image. Second, the elliptic curves are merged accurately by a model selection criterion derived from the maximal likelihood ratio hypothesis test. Finally, the ellipses in the navigation image are detected by fitting the merged elliptic curves. The experimental results demonstrate that the proposed algorithm can detect ellipses with higher accuracy and robustness than the traditional ellipse detection methods, and can be applied in the ellipse detection for the spacecraft optical navigation method to provide the precise curves as the inputs.

To solve the problem of accuracy maintenance of low-cost MEMS-INS/GPS integrated navigation under the condition of insufficient observable GPS satellites, a MEMS-INS/GPS pseudo loosely-integrated navigation method is proposed based on grey model and adaptive Kalman filter. In the framework of the proposed navigation mode, a state space model of integrated navigation system is established. Based on the MEMS-INS/GPS historical observation data, grey model is used to predict the difference between GPS and MEMS-INS, and this prediction is named system pseudo-observation. When the observable GPS satellites are sufficient, noise adaptive estimating Kalman filter is used for MEMS-INS/GPS integrated navigation; otherwise, this filter is used for MEMS-INS/GPS pseudo loosely-integrated navigation based on the system pseudo-observation. An example of low-cost MEMS-INS/GPS integrated vehicle navigation system is used in simulation and experimental verification. The results show that when the observable GPS satellites are insufficient, the traditional MEMS-INS/GPS loosely-integrated navigation decreases in accuracy rapidly and diverges, but the MEMS-INS/GPS pseudo loosely-integrated navigation is not significantly different from the normal GPS navigation in terms of accuracy, maintaining a high precision navigation state.

An LPV control scheme is proposed to design integrated flight control laws for unmanned helicopters. The LPV control law achieves explicit model following performance for an unmanned helicopter in velocity, sideslip angle, altitude, and yaw angle control channels, leading to desired flight path control performance. A nonlinear mathematical model is developed for an unmanned helicopter to take into consideration the coupling among rotor blade flapping and lead-lag dynamics, rotor inflow dynamics, and fuselage dynamics. Since helicopter dynamics is periodic, harmonic balance method is employed to conduct trim and model linearization, leading to an LPV model used to perform LPV control design in a velocity envelope. Parameters of the LPV control law are determined by solving a convex optimization problem. Numerical simulations are conducted to examine the performance of the LPV control law based on typical helicopter maneuvers under sensor noise. Results show that the proposed law has good performance and robustness in helicopter velocity envelope, satisfying performance standards of each maneuver of an unmanned helicopter.

Erosion is a common occurrence in the civic, industrial, military, and other sectors, and it frequently results in equipment being struck by particles and suffering varied degrees of damage. This paper selects Q345 steel to carry out the erosion experiment under the liquid-solid two-phase flow condition. Based on the weight loss method and surface analysis technology, the effect of particle size, particle concentration, erosion angle (15°-90°), erosion time and other factors on erosion were studied. And the morphological characteristics of the surface of the sample after the erosion were partitioned. The experimental results show that as the particle mass concentration increases, the rate of erosion weight loss gradually tends to be flat. 3D morphological observation found that after the concentration was higher than 0.01%, all of the material surface was eroded, and the maximum erosion depth was reduced. Q345 steel has the largest mass loss near the 30° attack angle, which is related to its strong toughness and plasticity. Based on the analysis of metallographic microscopy, the sample surface is divided into three zones after the 90° jet impact. The 2 zones near the outer edge of the nozzle have the largest number of pits and furrows and the most serious damage, which is related to the characteristics of the jet flow field and particle distribution.

In this paper, a deviation model dynamic surface control algorithm (DM-DSC) is designed for automatic wave-off control of carrier aircraft when the optimal wave-off trajectory is available. Firstly, the optimal wave-off trajectory is given based on Radau pseudospectral method. Furthermore, according to the optimal wave-off trajectory and the corresponding control scheme, the deviation control models and Backstepping controllers of the velocity subsystem and altitude subsystem are given respectively. Then the dynamic surface structure is introduced to obtain the differential signal of the virtual control variable, and at the same time, the “differential expansion” problem in Backstepping control is avoided. Then, in order to acquire the differential signal of the virtual control variable and simultaneously avoid the "differential expansion" problem in Backstepping control, the dynamic surface structure is introduced. Considering the uncertainty of aerodynamic parameters and the disturbance of carrier air wake, the linear extended state observer (LESO) is used to estimate and compensate for the disturbance in the control model, and the anti-saturation auxiliary structure is introduced to suppress the influence of control saturation on the controller performance. Finally, the boundedness of the closed-loop system is proved based on the Lyapunov method. The comparative simulation results demonstrate that the DM-DSC algorithm has good control performance.

In order to further improve the reliability and recognition accuracy of the solenoid valve fault diagnosis method based on current detection at the drive end, a research was conducted on the solenoid valve fault pattern recognition method. First, a method for extracting eigenvalues based on time-frequency analysis of current signals and time-domain parameters was proposed; then, through designing an acquisition experiment of the current signal at the solenoid valve drive end, the time domain signal of the solenoid valve drive end current and the multi-characteristic curve of the second-order rate of change were obtained. Meanwhile, the time-domain parameters and the frequency band energy corresponding to the second-order rate of change were extracted as the characteristic value, in order to construct the feature vector of multi-feature fusion. Finally, a multi-class support vector machine based on the radial basis kernel function was used to identify the electromagnetic directional valve pattern. The research results showed that compared with the support vector machine based on energy eigenvalues, the support vector machine based on multi-feature fusion can improve the recognition accuracy by 8.7% and the verification accuracy by 42.11%.

Buzz-saw noise generated by fan/compressor blade tips is one of the main noise sources in high bypass ratio Turbofan engine. To reduce the noise, the detached shock-wave system at the blade leading edge of a relative supersonic and subsonic axial two-dimensional cascade is studied. First, based on the geometric hermit interpolation (GHI) method, a three-segment Bezier curve was proposed to construct a continuous-curvature leading edge, which has higher degree of freedom in modification design. Next, by changing the position of the transition points between the three Bezier curves on the leading edge, the effects of local curvature optimization, overall curvature optimization, and optimization with extra thickness upon the strength of the shock-wave and noise level at the leading edge were explored. A comparison of numerical results showed that the continuous curvature design could decrease the size of the over expanded zone at the leading edge of the blade, thus reducing the reverse pressure gradient. Through local curvature optimization and overall curvature optimization, noise level at one chord length upstream from the leading edge could be lowered by 1.6 dB and 4.6 dB.

Using Terahertz communication technology to achieve centimeter level inter-board/chip interconnection in avionics can reduce pins and connectors, electronic equipment volume, and maintenance costs. For the short-range Terahertz communication network with omni-directional antenna transceiver and on-off keying (OOK) modulation, the calculation results of Terahertz channel capacity are given by analyzing the point-to-point communication link considering the molecular absorption noise and loss. Combined with the timed token multi-access protocol between nodes, and according to the channel capacity, the service curve model is used to analyze the total flow analysis (TFA) and separate flow analysis (SFA) in the worst case. The real-time performance analysis method of time limited token Terahertz interconnection is obtained by fully considering the burst degree of application layer communication task with probability guarantee. The case study shows that, compared with time division multiple access (TDMA), the collision free multiple access mechanism based on time limited token protocol can adapt to the random changes of physical layer capacity and application layer load, ensure less delay, and is conducive to the realization of Terahertz Interconnection Networking and real-time communication between avionics chips and boards.

The part of an aero engine with the highest temperature is the turbine blade. The film material is prepared on the surface of the object to be measured to form a thermocouple sensor, which can timely and effectively measure the temperature of the turbine blade. The diffusion failure of the thermal oxidation interface between multilayer films of thin film thermocoupleis one of the main reasons for the low reliability of thin film thermocouples. One of the main causes of the low reliability of thin film thermocouples is the diffusion failure of the thermal oxidation interface between multilayer layers. Based on Fick's second law, this paper proposes a diffusion reliability model of multilayer film to quantitatively describe the diffusion failure mechanism of thin film thermocouples. Through simulation calculation and particle swarm optimization, the optimal structure of each layer is obtained with the goal of maximizing the lifetime of thin-film, It provides a certain method reference for improving the lifetime of thin film thermocouple in structure and technology.

To characterize the dynamic combustion behavior of metal fuel in solid propellants, a simultaneous measurement method for the burning particle size and velocity based on light field imaging is proposed in this paper. A light field imaging system is established and the burning metal particles are imaged by the light field imaging system. The refocusing images of the burning particles are further obtained through refocusing algorithm. The calibrations of the light field system are carried out and the relationship curve between the depth and the optimal refocusing parameter is determined. The image segmentation algorithm is used to identify and locate the particles in the refocused image and then the particle sizes of the burning particles are calculated. Following the identification and localization of the particles in the refocused image using the image segmentation technique, the burning particle sizes are determined. The trajectories and velocities of particles are reconstructed through 3D particle tracking technology. Experimental results illustrated that the light field imaging technology is capable of making 3D measurements of the size and velocity of the burning particles of metal fuel, and characterizing the combustion process of metal particles. The results of the experiments showed that the light field imaging technique is able to characterize the combustion process of metal particles and make 3D measurements of the size and velocity of the burning metal fuel particles.

Aiming at the problem of turbulence model selection for unsteady flow simulation in a long and narrow enclosed cabin, this study uses an aircraft cabin as a typical environment and uses the heat shrinkage ratio method based on similar criteria to build a simplified experimental platform. The experimental results are compared and analyzed with the numerical simulation results obtained by the three turbulence models of RNG k-ε, DES and LES, and the appropriate turbulence model in the study of unsteady flow characteristics in the long and narrow enclosed cabin is evaluated. The results demonstrate that the RNG k-ε and DES models are capable of qualitatively describing the flow trend, but the LES model is more accurate in capturing the unpredictability and instability of the flow field, and its flow field structure is more in line with the experimental findings. Therefore, the LES model can more truly reflect the unsteady flow of the long and narrow enclosed cabin.

For lack of research on degradation test (DT) for molecular sieve oxygen concentrator (MSOC) and clear account of the factors causing degradation failure of molecular sieve bed (MSB), a DT design method of MSOC based on orthogonal test was proposed. Based on the working principle of MSOC, the main factors causing degradation failure of MSB were determined, and a DT system of the MSOC was built. The optimal test height for the DT was 9 km, as was determined and verified by several controlled tests. A DT scheme of MSOC was designed based on the orthogonal test idea. The influence of various factors could be obtained through 9 typical tests, which reduced the test times and costs, and improved the efficiency of coupling tests. The test design can simulate the real working environment, and can effectively reduce the impact of test factors on the initial value of the test results.

In view of the deficiency of the power supply mode for the electric slip ring of the stratospheric airship anemometer, a contactless power supply system of the airship anemometer based on DSP control is designed. Based on the principle of electromagnetic induction, the composition of contactless power supply system is defined; by establishing the equivalent circuit model of the system, the factors affecting the transmission efficiency and power of the system are analyzed; combined with the structure and application background of the boat borne anemometer, the nested loosely coupled coil is designed with the help of ANSYS Maxwell electromagnetic simulation software. Finally, the main circuit of the system is simulated, and the primary and secondary circuits based on DSP are built to verify the working characteristics of the system. Simulation and experimental results show that the designed contactless power supply system can accomplish good wireless energy transmission, and can supply power for stratospheric shipboard anemometer after depressurization.

To solve the problems of lack of prior information and incomplete reliability of monitoring data in structural safety assessment of large liquid tanks (LLT), a structural safety assessment model of large liquid tanks considering environmental disturbance is proposed based on the belief rule base (BRB) and finite element method (FEM). First, the FEM estimates the basic parameters of the proposed model using industry standards and subject-matter knowledge. Secondly, the index credibility is calculated based on the information consistency method to reflect the influence of disturbance factors on the monitoring data in actual engineering. Then, a new fusion method can be used to integrate the index credibility into the model reasoning process to complete the construction of the proposed model. Finally, a 100,000 m3 oil storage tank is selected as the research object to verify the effectiveness of the proposed model. The results show that the proposed model can not only effectively deal with the problem of unreliable monitoring data, but also take into account the internal structure mechanism of large liquid tanks, thereby minimizing the negative effects of a lack of prior knowledge on the accuracy of the assessment.

For the problem of inadequate terrain adaptability caused by the fixed structure of traditional helicopter landing gears, a new landing gear integrated for buffering actuation and walking with two stage buffering system was designed. The buffering function under multiple conditions was realized, the magnetorheological damper works to realize function in the conventional landing; the magnetorheological buffer and the oil-gas buffer work together to realize crashworthiness under the dangerous condition. A drop simulation model was established in the multibody dynamics software LMS Virtual.Lab Motion. The adaptive landing gear can adjust attitudes by two hydraulic actuating cylinders. The drop simulation analysis of the normal condition and the crash-resistant condition was carried out, and the buffer parameters were designed according to simulation data., the drop test was carried out under various conditions. Compared with the test and simulation results, the results show that the system’s buffering efficiency reached 85% and 75% respectively at two landing speeds. The adaptive landing gear can adjust to different attitudes actively, and it has good buffering performance at each attitude and a crashworthiness ability. The fact that the simulation and test findings were in agreement shows how well the multi-body dynamic model of the landing gear simulates the drop process.