Beidou B3I signal, a new generation of civil code, has a higher rate and narrower chip width compared with B1I signal. Currently,there are few studies on the retrieval of sea surface height from B3I signals by using the Beidou reflected signal (BDS-R) technology and no relevant experimental results and accuracy evaluation.This paper usesthe direct and reflected signal data of the B1I/B3I dual band received by the receiver in the sea area near Weihai, Shandong on September 7, 2020, and adopts the delay-Doppler-map (DDM) and carrier phase delay methods respectively to carry out shore-based sea surface height retrieval. The measured data was used to confirm the retrieval’s accuracy, and the performance of the B1I and B3I signals’ sea surface height retrieval was assessed in terms of both their signal characteristics and their height measuring technique.The results show that the mean absolute error/root mean square error of B1I and B3I are 1.18 m/1.48 m and 0.84 m/1.10 m using DDM. The mean absolute error/root mean square error are 0.12 m/0.15 m and 0.10 m/0.12 m respectively using carrier phase delay.Due to the difference in signal characteristics, the accuracy of DDM altimetry B3I is 28% higher than that of B1I, and the accuracy of carrier phase delay altimetry B3I is slightly better than that of B1I, with no obvious difference between the two.Both B1I and B3I reflected signals are demonstrated to be suitable for retrieving sea surface height in this experiment, which compares the differences in retrieval accuracy between B1I and B3I related to signal characteristics and altimetry method.

The gaseous pollutants get into the cabin by the engine bleeding air system when the plane is waiting for taking off on the apron. However, the cabin air conditioning wind speed is constant, and the removal efficiency of the bleeding gaseous pollutants is low. To solve this problem, the Boeing737 cabin simulation model was established and the accuracy of the cabin simulation model was verified by particle image velocimetry (PIV) experiment. The air conditioning used sinusoidal wind instead of the constant wind, and used NO₂ as bleeding air pollutant. Three work modes of air supply, the ceiling air supply, sidewall air supply and mixed air supply were simulated. The distribution results of NO₂ in passenger breathing areas and cabin were obtained by constant wind and sinusoidal wind. A method based on air age and draft rating index (DR) was proposed to evaluate the best air conditioning work mode, which is efficient in removing cabin gaseous pollutants. In 180 seconds, the average concentration of NO₂ decreased by 7.95% by sinusoidal wind ceiling air supply mode. The sinusoidal wind sidewall air supply mode decreased by 6.51%, and the sinusoidal wind mixed air supply mode decreased by 23.3%. The sinusoidal wind mixed air supply mode has the best effect on the removal of NO₂ and the minimum air age. The draft rating index meets the requirements of thermal comfort.

Large inertia, a high center of mass, and time-varying friction are aspects of the aircraft towing process that have a significant impact on the stability of the aircraft tug. In order to improve the stability of the electric aircraft tug, the variable speed and torque that affect the stability of aircraft traction are taken as the research objects, and the control effect of the designed strategy is analyzed. Using ADAMS and MATLAB/Simulink simulation software, the aircraft and tug dynamic model and motor model are constructed, and the second-order nonlinear auto disturbance rejection controller based on speed and torque is designed. The dynamic characteristics of the wheel speed of the aircraft tug based on active disturbance rejection control (ADRC) and PID control during the shifting process are compared and analyzed, and the prototype control test of the shifting process is carried out. The results show that the aircraft traction system based on the second-order nonlinear auto-disturbance rejection control algorithm has better gear shifting effects, and the wheel speed during gear shifting is better in terms of response speed, stability and anti-disturbance ability; the test results match the simulation results, and the coincidence proves the feasibility and correctness of the simulation model and simulation results, which lays the foundation for the research of highly stable aircraft tug.

Mobile robots to localize themselves is a prerequisite for full ego-motion. Simultaneous localization and mapping (SLAM), a key localization technology, has gained a lot of attention. An inertial measurement unit (IMU) is widely used in SLAM systems for its advantage of not being affected by the external environment. The backend of SLAM uses nonlinear optimization methods to optimize IMU states. There are problems of poor real-time performance and high energy consumption. This paper designs an accelerator for IMU state optimization on the field programmable gate array (FPGA) platform. Firstly, by analyzing the data flow of the algorithm, the accelerator realizes circuits and data reuse. Secondly, by making use of the sparse characteristics, calculation simplification and storage compression are realized. Finally, the hardware employs a configurable design for the equation solving step, which requires the most computation. By changing the configuration, the accelerator can achieve a compromise between performance, power consumption, and resource utilization. The experimental results on the Xilinx ZC706 platform indicate that the accelerator designed for high-performance scenarios can achieve 26.7 times and 87 times performance improvement compared to Intel i5-8250U and Arm Cortex-A57 processors; the performance improvement of low-power scenario accelerator is 17.4 times and 53.7 times, respectively. Besides, different configurations can save more than 90% of energy.

The ballistic coefficient is an important source of error in the orbit prediction of non-cooperative targets. For a large number of non-cooperative targets, calculating quickly the ballistic coefficient with the limited measurement and control resources is an urgent need. In this paper, based on the semi-major axis attenuation information of the two line element (TLE), an improved ballistic coefficient calculation algorithm is studied. Through polynomial smooth detection and quadratic discrimination, three situations, ie. outliers, orbital maneuvers and geomagnetic storms are identified. The basis for constructing semi-major axis attenuation observations is analyzed, and the influence of different observation arc lengths on the calculation of ballistic coefficients is compared. The accuracy of the ballistic coefficients is evaluated using the data of Tiangong-1, and the ballistic coefficients are used in the prediction of Tiangong-1’s reentry. The results show that the ballistic coefficients calculated based on the TLE elements are stable and accurate, and are suitable for non-cooperative target orbit prediction.

Accurate flight delay prediction is one of the most important preventive measures for the increasingly frequent airport flight delays. The airport network is transformed from irregular topological structure to regular network structure by spectral convolution. The graph convolutional network (GCN) and gated linear unit (GLU) are used to capture spatio-temporal correlation in the network and form spatio-temporal convolutional blocks. A spatio-temporal graph convolutional neural network (STGCN) is proposed to predict the departure flight delay. 51 major airports in the United States are selected to construct the airport network, and the on-time departure rate is predicted to carry out the example verification. The results show that when the prediction window is 1 day, the mean absolute error (MAE) of STGCN decreased by 18.19%, 10.45% and 6.24%, respectively compared with the historical average (HA) method, long short-term memory (LSTM) and stacked autoencoders (SAEs). When the forecast window is 2 days, MAE decreased by 9.93%, 3.96% and 4.37%; When the forecast window is 3 days, MAE decreased by 7.02%, 2.47% and 9.20%. The example proves that STGCN can improve the accuracy of delay prediction and provide reference and guidance for airport delay decision.

The autonomous orbit determination method based on remote sensing image has the problems of image mismatch and slow matching speed. Based on ontology knowledge base theory, this paper proposes an intelligent reasoning method for improving the effectiveness of remote sensing image. Firstly, the remote sensing information is preprocessed to extract the feature. Secondly, the knowledge structure framework based on image orbit determination is analyzed, and the corresponding knowledge base system is constructed by ontology. Finally, the image template selection and error judgment rules are designed, and the inference engine is used to deduce the effectiveness of the observational data. This method is applied to autonomous satellite orbit determination simulation based on image feature points. The feasibility of the intelligent reasoning method is verified. The simulation results show that the computation speed is improved by 59.58%, and the navigation position precision and velocity precision are improved by 10.58% and 12.49% respectively. Therefore, the image matching template selection and image error judgment reasoning effectively improve the autonomous satellite orbit determination accuracy.

To solve the anisotropic problem of laser additive manufacturing components, the propagation characteristics of ultrasonic wave in the anisotropic material have been researched and the total focusing method using an ultrasonic array has been optimized based on group velocity of anisotropic material. Then, the CIVA software was used to carry out a simulation study on total focusing imaging of samples with horizontal through holes and flat-bottom holes. Next, a simulated investigation of complete focusing imaging of samples with horizontal through holes and flat-bottomed holes was conducted using the CIVA program. The simulation results show that the anisotropy of material has a significant impact on the imaging quality, defect location accuracy and defect distribution range of total focusing imaging using an ultrasonic array. The inspection experiments using the conventional and optimized total focusing imaging method were carried out. The findings demonstrate that the flat-bottomed holes with a diameter of 0.8 mm in the titanium alloy specimen produced by laser additive manufacturing can be detected with accuracy, and that the array performance indicator (API) value is decreased to 0.43 and the defect positioning error is decreased to 0.54 mm. Both the detection capability and defect location accuracy are improved significantly.

Airborne pseudolite navigation systems depend on geometry configuration, however previous research on how to create the ideal geometry configuration with the least amount of energy was limited. To solve this problem, the path planning algorithm of airborne pseudolite installed on stratospheric airships was discussed in this paper. First, the effect of pseudolite geometry configuration on positioning precision was analyzed. Second, the stratospheric airship dynamic model, wind field model and stratospheric airship energy consumption model were studied. Thirdly, a grid-based strategy for planning space establishment and path representation was described. Furthermore, a novel cost function for stratospheric airship path planning comprising positioning precision index and energy consumption index was designed. Based on the classic A^* algorithm, a path planning algorithm for airborne pseudolite installed on a stratospheric airship was constructed. And finally, simulations were executed with various inputs to verify the proposed algorithm. The outcomes of the simulations demonstrated that the suggested approach may effectively increase geometric precision improvement while lowering stratospheric airship energy consumption.

A wind tunnel device simulating Herbst maneuver and the related motion/flow synchronous measurement technology are developed. By the device, the roll oscillation of the chined-body configuration undergoing the Herbst maneuver is studied. The device is used to study the roll oscillation of the chined-body configuration during the Herbst maneuver. The main stage form the rolling motion is revealed and the influence of motion parameters on the rolling motion is analyzed. Results show that the roll oscillation in the Herbst maneuver mainly comes from the pitch-up stage, and the conical motion stage has little effect on the rolling motion. In the pitch-up stage, the rolling motion can be divided into the quasi-static region, transition region and sine-like region. As the reduced pitch rate is 0.01, the curves of the rolling motions undergoing pitch up coincide each other before the pitch angle of 50°, and after that pitch angle the curves are dispersed. The reduced pitch rate can be used as a dimensionless parameter for the rolling motion of the chined-forebody configuration undergoing pitch up within a certain range of pitch angle. The rolling motion of the chined-forebody configuration undergoing pitch up within a specific range of pitch angle can be described by the reduced pitch rate, which can be employed as a dimensionless parameter.

Aiming at the difference of hydroplaning behavior characteristics of aircraft wheel group during different taxiing processes and under various accumulated water conditions, the additional resistance of accumulated water is studied in this paper. The critical judgment index of hydroplaning traditionally based on the vertical supporting force on the tire print is improved.The main landing gear of Airbus A320 model is studied as an example. A fluid-solid coupling model of two-wheel configuration running on the pavement surface with accumulated water is established for hydroplaning analysis. Regular analysis of influence factors related to additional resistance is then carried out. Results show that the additional resistance reaches its maximum value at the critical condition of tire hydroplaning. The difference of the hydroplaning speed between the numerical simulation and NASA’s equation calculation is less than 5%. As compared with the supporting force, the additional resistance of accumulated water is considered to be more suitable for hydroplaning analysis, which may continuously affect the taxing process of aircraft after the critical state. Instantaneous hydroplaning may occur when aircraft tires land on the pavement at a rather high speed. The water resistance during landing is smaller than that during take-off. The critical hydroplaning speed during landing is reduced by 8.3%~10.6% as compared with that during take-off. Therefore, the risk of aircraft hydroplaning during landing is increased, which is in good accordance with the rules of accidental statistics. The distribution of accumulated water is affected by rut deformation of the pavement surface, which may lead to temporal and spatial differences of hydroplaning development within the wheel group.The number of tires can be approximately taken as the wheel group coefficient of water resistance with an idealized water distribution. The median value of such a coefficient is smaller than 2.0 for wheel groups running on the rut pavement surface. Thus, the overall deceleration of landing aircraft can be postponed.

To understand the cooling heat transfer problem in air-kerosene heat exchangers, numerical study on the heat transfer of supercritical RP-3 aviation kerosene in vertical helical tubes has been conducted. The heat transfer characteristics and mechanisms under different operating parameters and structural parameters were investigated, including the average heat transfer along the flow direction, and the local heat transfer along the circumferential direction. The temperature and secondary flow distributions in tube cross-sections were discussed. The effect mechanism of centrifugal force on heat transfer was analyzed through radial differences of velocity and turbulent kinetic energy. Based on the error analysis, an effective heat transfer correlation was obtained. The results show that the enhanced heat transfer appears in the downstream section, and the local deteriorated heat transfer is observed at low-pressure condition. The centrifugal force results in the abnormal lateral stratification of temperature in the fluid domain, the uneven thickness of boundary layer in the circumferential direction, and the secondary flow in tube cross-sections. The outer position has the large fluid velocity and turbulent kinetic energy. Hence, the heat transfer of the outer position. is significantly better than that the inner position. Increases the pressure, decreases the heat-mass radio, increases the helical diameter, and increases the pitch could suppress the effect of centrifugal force, leading to the weakened secondary flow intensity. The Merkel heat transfer formula can better realize the heat transfer prediction of aviation kerosene in vertical helical tubes.

The path planning in an unknown wind field is the main application challenge for stratospheric aerostats, which are a crucial platform for exploring the region of near space. The research object of this paper is stratospheric aerostat with certain horizontal actuation which are encountered with low dynamic, huge structural scale and the flight performance significantly affected by environmental wind field. An approach of two-dimensional global path planning based on the Markov decision process (MDP) in the wind field is presented, in which the problem of path planning is regarded as looking for the optimal path with the shortest time required for rapid deployment from the current location to the target. The actual wind vector field is not known exactly and may deviate significantly from the wind velocities estimated by the model. Since the exact wind vector field is unknown, it is possible that it will differ greatly from the model's predicted wind velocities. To address this issue, our technique explicitly incorporates wind uncertainty into the path planning algorithm, and designs the related parameters of approach in order to establish the determined wind field model and the uncertain wind field model . To solve this problem, we developed a method that explicitly accounts for wind uncertainty in the path planning algorithm and designs the relevant approach parameters to create both a determined wind field model and an uncertain wind field model. The reachability of aerostat with horizontal actuation in a given region relative to the target under different wind field models is compared, in addition, the shortest flight time path and the optimal action sequences are planned. The numerical simulations show that the optional path and actions sequence change with difference of the positions of start/target, the horizontal actuations and wind field models. The numerical simulations also show that the regional accessibility enlarges and the difference of the influence between two wind field models on the two-dimensional global path planning of the aerostat decreases with increase of the horizontal actuation of the aerostat.

The crisscross heat pipe network was designed to convert the point heat source into a surface heat source in order to meet the heat rejection of multiple heat sources, high power dissipation, and large power density of the satellite phased array antennas, consisting of external heat pipes and embedded heat pipes, Additionally, U-shaped heat pipes coupling +Z panel and ±Y panel were used to strengthen the heat transfer between honeycomb panels, the satellite heat flow was analyzed by finite element model and experimentally verified. The simulation results show that the U-shaped heat pipes conduct 32.9% of the satellite phased array antennas heat dissipation, of which 66.6% is conducted to the +Y panel in the shaded region and 33.4% to the −Y panel in the sunlight region. According to the experimental findings, phased array antennas' temperatures meet interface requirements and the temperature differential between the heat pipes was less than 1 °C during the satellite's long-term peak operating mode. The heat pipe network meets the heat rejection of the satellite long-time peak working mode, the crisscross heat pipe network has been verified, and the U-shaped heat pipes couple +Z panel and ±Y panels, which solves the problem of insufficient heat rejection of single honeycomb panel.

A new combustion diagnosis and measurement technology should be developed in order to realize the collaborative reconstruction of multiple physical parameter fields, such as the three-dimensional temperature field, the radiation physical property field, and the component concentration field of the gas-solid combustion products of the high-temperature soot flame. In order to overcome the problem of low efficiency and low accuracy in the coordinated reconstruction of flame temperature and radiation property caused by unknown radiation characteristics in practical engineering applications, a new method of collaborative reconstruction of multi-physical parameter fields of high temperature soot flame based on active and passive tomography fusion is proposed by combining active laser tomography absorption spectroscopy and passive radiation imaging technology. Based on the radiation transmission mechanism of the flame dispersion medium, a multi-parameter collaborative reconstruction model of active and passive tomography is established by combining the transmission measurement signal of laser tomography and spontaneous emission light field measurement signal of flame in the multi-spectral range. According to the numerical simulation flame and the combustion experiment data of Yale University, the cooperative reconstruction of three dimensional radiation physical property, temperature and the gas-solid two-phase combustion product component concentration field of the high-temperature soot flame was simulated and studied, and the error transfer analysis is carried out on the measurement noise of various signals. The results show that when the laser signal-to-noise ratio is greater than 25, the correlation coefficient of the reconstructed extinction coefficient field of the simulated flame is close to 1, and the reconstruction results of temperature field is in good agreement with the true value; When the laser signal-to-noise ratio is greater than 30, the correlation coefficient of reconstructed soot concentration field of the experimental flame is close to 1, and the correlation coefficient of the reconstructed temperature field is about 0.83; The influence of light-field signal measurement noise on temperature reconstruction accuracy is more significant than that of laser measurement noise, and the calibration accuracy of laser and light-field measurement system should be ensured in the measurement process to improve the accuracy of parameter reconstruction.

In order to avoid discretizing the whole structure and reduce the error between the geometric model and the discrete model, a shape optimization method based on the flower pollination algorithm and isogeometric boundary element method is proposed. The boundary element method only needs to discretize the structure boundary, and this simplifies the discretization process. The boundary element method only needs to discretize the structure boundary, and this simplifies the discretization process. Furthermore, the isogeometric analysis is exploited to improve the accuracy. Firstly, the objective function is to minimize the displacement or stress, and the constraint condition is that the structural area is equal to the specified area; secondly, the constrained optimization model is transformed into an unconstrained optimization model by using the augmented lagrange multiplier method; Then, the bearing condition of the structure is analyzed by the isogeometric boundary elementmethod (IGABEM); finally, the elite opposite-based learning strategy and large scale estimation of distribution algorithms (LSEDA) are used to improve the flower pollination algorithm, and the coordinates of control points are optimized by the improved flower pollination algorithm. After that, the boundary of structure is constructed by the non-uniform rational B-splines (NURBS) basis function, and the optimal structure shape is drawn. According to the test findings for the Ackley function, the enhanced flower pollination algorithm converges in 14 steps as opposed to 136 steps for the original flower pollination algorithm, and its minimum value is 8.881 8×10⁻¹⁶ less than 0.0014, demonstrating that it is more capable of optimization. The computational results of shape optimization show that the proposed algorithm can effectively solve two-dimensional shape optimization problem based on isogeometric boundary element method.

In order to investigate the joint influence of the fan and the core on the aerodynamic characteristics of the cruise, this paper takes a 350-seat blended-wing-body aircraft as the object of study, using the method of first changing the spanwise position of the core and, on this basis, later changing the chordwise and spanwise positions of the power system. The study results show that: Under cruise conditions, the core position has little influence on the pressure distribution on the fairing surface and the aerodynamic characteristics of the aircraft; under cruise conditions, the lift-to-drag ratio can reach 22.39 when the power system swept back angle is −12° and the chord position is 0.8; under the condition that the power system area and flow rate remain unchanged, reducing its spread width will lead to a reduction in lift, drag, lift-to-drag ratio and an increase in the lifting moment. The aircraft reaches a maximum lift-to-drag ratio of 22.39 at a cruise angle of attack of 3.2° and a lift coefficient of 1.0541 at a take-off angle of attack of 10°, which meets the take-off lift coefficient requirement.

Aiming at the problems of slow diagnostic speed and difficulty in pardmeter selection in artifical intelligence algorithms currently used in fault diagnosis of aviation generator rotating rectifiers, an extreme learning machine (SSA-ELM) and complementary ensemble empirical mode decomposition (CEEMD) based fault diagnosis approach is investigated. In the finite element software Maxwell and Simplorer, the three-stage motor model is built, the excitation current signal is collected, the excitation current signal is decomposed into a series of modal components by CEEMD, and the fault characteristic parameters are constructed. Then the training parameters and parameters of the extreme learning machine are optimized by the SSA algorithm, and the fault is diagnosed. Finally, it is verified by the experimental platform. The results show the effectiveness of the three-stage synchronous motor finite element model.Compared with the existing methods, the rotating rectifier diode fault diagnosis method based on CEEMD and SSA-ELM has higher fault diagnosis accuracy and classification speed.

To achieve accurate and continuous pedestrian positioning in complex indoor environments, we propose a multi-source fusion positioning algorithm based on hierarchical optimization is proposed. First, the geomagnetic matching range is constrained with the Wi-Fi positioning result. Afterwards, particle swarm optimization (PSO) is adopted to optimize the BP-AdaBoost ensemble learning algorithm. The optimized BP-AdaBoost-PSO is employed to fuse the Wi-Fi and the constrained geomagnetic positioning results. Particle filter (PF) is then applied to fuse the above fusion result and the pedestrian dead reckoning (PDR) result. Simulation results indicate that the proposed algorithm has sufficient robustness and can effectively improve the continuous positioning accuracy in a pedestrian motion state.

In order to evaluate the mental workload of pilots in flight task, a quantitative evaluation model of mental workload based on task demand load (TDL) and staff workload capacity (SWC) was established. Based on this, the evaluation methods of surplus mental workload (SMWL) and occupancy rate of mwl (ORMWL) were proposed. The information entropy method was used to quantify the amount of information on the information display and control interface, based on the flight situation experiment designed by the MATB task platform, in order to verify the validity of the model, the mental workload of 15 subjects at different task levels was evaluated. Based on the flight situation experiment designed by the MATB task platform, the information entropy method was used to quantify the amount of information on the information display and control interface. In order to verify the validity of the model, the mental workload of 15 subjects at different task levels was evaluated. The results show that the SMWL value of the SMWL model method was correlated with the NASA subjective scale value. And, the increase of task level had a significant U-shaped impact on the mental workload of the staff. Meanwhile, the increase of task level had a significant U-shaped impact on the mental workload of the staff. Therefore, the model established in this paper and based on the concepts of SMWL and ORMWL can be used to conduct a real-time and quantitative evaluation of the mental workload of pilots during flight tasks, providing a new idea for the quantification of mental workload.

Mixed polarity Reed-Muller (MPRM) circuit area optimization has become a research hotspot in the field of integrated circuit design. It is a combinatorial optimization, aiming at finding the MPRM expression with the least number of terms among many MPRM expressions. A explosion strategy and restart strategy based whale optimization algorithm (ERWOA) is proposed. In addition, a multi-output MPRM circuit area optimization method is proposed, which uses the improved whale algorithm and the improved polarity conversion algorithm to search for the MPRM circuit with the least number of AND terms. Results on the MCNC Benchmark circuits show that the proposed algorithm increases the conversion efficiency by 99.93% and 99.96% at most, compared with the mixed polarity and inter-polarity conversion algorithms based on the list technology, respectively. Compared with the genetic algorithm and the artificial bee colony algorithm, the improved whale optimization algorithm saves the circuit area up to 18.32% with an average of 5.54%, and 14.41% with an average of 5.00%, respectively.

This paper addresses the problem of the fast time-varying mismatch disturbance and measurement noise that inevitably exist in actual control systems, proposing a backstepping disturbance rejection control method based on the bi-bandwidth extended state observer (BESO). The BESO adjusts the bandwidth of the observer through a direction switching operator and a bi-bandwidth scaling factor. Therefore, it can accurately estimate the fast time-varying disturbance while avoiding the amplification of measurement noise. Then the backstepping control is combined with the BESO to form a step-by-step compensation control scheme, and the corresponding control law is given through the Lyapunov approach to ensure the asymptotic stability of the system for the mismatch disturbance. Suggestions for the parameter tuning process are given for engineering practice. In the end, the proposed approach is applied to the height control of a quadrotor micro-UAV. The results verify its effectiveness in the mismatch disturbance compensation and measurement noise suppression.

Aiming at the characteristics of high power density, complex working conditions, high integration of components and the wide variety of faults of electro hydrostatic actuator (EHA), a fault diagnosis and fault-tolerant controller of electro-hydro actuator based on an adaptive neural network robust observer is designed. A robust observer is proposed to observe the internal state of the model. The uncertain parameters, such as elastic modulus of hydraulic system is estimated by adaptive law; and the nonlinear, such as friction disturbance is approximated by radial basis function (RBF) neural network. The feedforward compensation method is used to compensate the fault and parameter uncertainty, and the robust term is designed to overcome other disturbances. By using Lyapunov stability theorem, it is proved that the proposed controller can realize the bounded stability of the system in the presence of faults. The co-simulation results show that the proposed controller has higher control accuracy and robustness than the traditional proportional, integral and differential controller (PID) and adaptive robust controller (ARC).

Abstract: Aiming at the flight control problem of proximity spacecraft formation near the artificial L1point of the sun-earth system, a hybrid propulsion control method combining solar sail propulsion and Coulomb force formation technology is proposed. By controlling the relative attitude angles of the follower’s sail, the solar radiation pressure difference between two spacecraft can be adjusted, and matched with Coulomb force, not only the underactuated problem of solar sail control alone is solved, but the controllability of Coulomb formation is also improved. Firstly, based on the solar sail circular restricted three-body problem (SSCRTBP) model, the calculation method of the position of the collinear artificial libration point is given and the orbit of the main craft is constructed. The relative motion equation of the hybrid propulsion configuration is then determined by the introduction of the Coulomb force between spacecraft. Finally, the fixed-time sliding mode control strategy is designed to control the formation configuration by taking the two attitude angles of the follower’s sail and the charge product between the two crafts as the control parameters. Then the sliding mode control strategy is compared with the LQR control strategy in order to reflect its high performance. The simulation results show that the fixed-time sliding mode control strategy is superior to the LQR control strategy in terms of control accuracy, required time and energy consumption. During a 3-year mission, the formation can be deployed in only 23 days. The baseline relative error is less than 1%, whereas the error on the other two axes is on the scale of centimeters. For long-term deep space exploration trips in the future, the fact that no fuel is used throughout the entire process is extremely important.

The classic anti-jamming algorithm will null mismatch in the high-dynamic scene where the jamming source moves quickly in relation to the anti-jamming antenna, resulting in the failure of anti-jamming performance. Therefore, this paper proposed a polarization space-time multi-dimensional domain joint covariance matrix taper (CMT) algorithm. Specifically, a taper matrix was constructed based on Laplace distribution to simulate the disturbance motion state. Then, it reconstructed a new covariance matrix through the taper matrix and the original covariance matrix to achieve null broadening. In this way, the array weight vector was solved by combining the minimum variance distortionless response (MVDR) criterion. According to the simulation results, the robustness of the algorithm in the case of rapidly changing jamming position can be confirmed from three aspects, including the beam pattern, output performance and satellite acquisition results. The jamming signal can still be efficiently suppressed even if the navigation signal and jamming signal are in the same azimuth and frequency band.

The performance degradation of bolted joints is a problem which should be considered for the safety of aero-engine. The concept of preload mistuning of bolted joints can characterize the performance degradation, and the preload mistuning amplitude and the preload mistuning ratio are used to illustrate the state of the preload mistuning. The influence of mistuning bolted joints on the dynamic characteristics of thin-walled cylinder was studied based on the combination of preload mistuning with the improved thin-layer element method of bolted joints. First of all, the deterministic analysis of the influence of preload mistuning on the thin-walled cylinder was proposed, including the influence of the natural frequency and steady-state response. Moreover, the influence of preload mistuning on the probabilistic response characteristics of thin-walled cylinder was researched considering the randomness of bolt preload. The results indicate that the separation degree of the same-order natural frequency of thin-walled cylinder increases with the decrease of preload mistuning amplitude, and presents a “double peak” characteristic with the increase of preload mistuning ratio. The preload mistuning makes the frequency corresponding to the response peak of thin-walled cylinder reduce but the amplitude increase. The random preload mistuning makes the frequency band of the response peak point wider, and when the input parameter is exponential distribution, the output parameter is Weibull distribution.