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In the case of nonlinear systems with random bias, the Optimal Two-Stage Unscented Kalman Filter (OTSUKF) can obtain the optimal estimation of system state and bias. But it requires random bias to be accurately modeled, while it is always very difficult in actual situation because the aircraft is a typical nonlinear system. In this paper, the faults of the Inertial Measurement Unit (IMU) are treated as a random bias, and the random walk model is used to describe the fault. The accuracy of the random walk model depends on the degree of matching between the covariance of the random walk model and the actual situation. For the IMU fault diagnosis method based on OTSUKF, the covariance of the random walk model is assigned with a constant matrix, and the value of the matrix is initialized empirically. It is very difficult to select a matching matrix in practical applications. For this problem, in this paper, the covariance matrix of the random walk model is adaptively adjusted online based on the innovation covariance matching technique, and an adaptive Two-Stage Unscented Kalman Filter (ATSUKF) is proposed to solve the fault diagnosis problem of the IMU. The simulation experiment compares the IMU fault diagnosis performance of OTSUKF and ATSUKF, and verifies the effectiveness of the proposed adaptive method.

To intercept a higher-speed target in the terminal guidance phase, this paper proposes a generalized relative biased proportional navigation (BPN) law. In order to enlarge the capture domain of the classical proportional navigation (PN) law and make full use of the maneuverability of a missile, the paper designs time-varying navigation coefficients; thus the modified PN guidance law integrates the advantages of the PN guidance law with those of the retro-PN guidance law. In order to intercept high-speed targets with impact angle constraints, the relative BPN law is introduced, and the impact angle is achieved by controlling the relative flight-path angle. In order to improve the performance of the guidance law for intercepting higher-speed maneuvering targets, some compensation measures are designed for guidance commands. Extensive simulations are conducted to verify the design features of the proportional navigation law.

A quasi-zero-stiffness vibration isolation consists of a pair of oblique springs and a vertical spring, aiming at widening the vibration isolation region, is studied in this paper. The time delay linear displacement feedback control strategy is introduced to improve the performance of the isolator. The characteristics of dynamical response under harmonically forcing excitation is obtained by using averaging method. The force transmissibility of the control isolator is presented in this paper. The influence of the time delay linear displacement control on the force transmissibility is studied theoretically. The results show that the performance of the vibration isolation with time-delay control is better than the equivalent linear isolator in either low or high frequency region and the performance of controlled system is better than uncontrolled system.

The parameter identification of a non-cooperative target is a key problem of on-orbit servicing. Due to poor priori information about the motion and structure of non-cooperative targets, the traditional cooperative estimation architecture is inadequate. In addition, the existing method based on single observation spacecraft is difficult to ensure a good observation state for a long time. This paper proposes a method for observing and estimating attitude kinematic state of a non-cooperative space target based on multi-spacecrafts cooperative observation. The space target's 3D point cloud data is reconstructed based on the data with different viewpoints. The target's attitude change is calculated based on the 3D point cloud matching, and the kinematics information is estimated via EKF filtering. The simulation results demonstrate the efficiency of the proposed approach. As the proposed method does not require priori model, structural information or accurate motion information of the tumbling non-cooperative target, it can avoid the influence of occlusion or date missing in space observation, it is suitable for space on-orbit servicing with non-cooperative target in future.

Walker constellation is the most effective constellation for global coverage and is often used for earth observation, navigation and internet communication. A scenario that several faulted satellites in a Walker constellation lead to its performance degradation can be quickly repaired to a certain extent by reconstructing the on-orbit satellite configuration. Different from the classical strategies such as adjusting the phase of the adjacent satellites, uniform the on-satellites' phase and adjusting the plane of the adjacent satellites, this paper proposes a bionic reconstruction method which uses the elastic mechanics method of thin film plate to generate the satellite maneuver strategy in the constellation reconstruction process, minimizes the performance degradation between the repaired configuration and the previous configuration. Thus, the maneuver strategy of each satellite can be calculated in reversely. The simulation example shows that the maneuver strategy by the bionic reconstruction method is more harmonious and natural than the classical strategies.

Distributed electric propulsion technology brings new ideas to the design of unmanned aerial vehicle(UAV), such as improving aerodynamic efficiency and propulsive efficiency, and new concept of vertical/short takeoff and landing configurations. However, compared with conventional UAV, the propulsion system of distributed electric propulsion UAV is more complex, which brings difficulties and challenges to the design of distributed electric propulsion UAV. Based on its special aerodynamic/propulsive coupling characteristics, this paper studies the design method and process of primary parameters of distributed electric propulsion UAV. A short takeoff and landing UAV with distributed electric propulsion system is taken as an example for the conceptual design and primary parameter design, and the influence of design parameters on the takeoff mass and endurance is analyzed. Finally, the validity of the established design method is verified by the flight test of the prototype. Results indicate that the distributed electric propulsion system accounts for more than 20% of the takeoff mass; the electric ducted fan efficiency, mass specific power of the motor, mass specific power of the electronic speed controller and the resistivity of power wires are the most significant design parameters that affect the performance of the UAV; with the improvement of technologies, the takeoff mass is expected to be reduced by more than 20%, and the endurance is expected to be increased by more than three times.

During the blisk side milling, the blade is thin and the tool suspension length is large, which is easy to occur milling system chatter. The wavy surface left by chatter has great effect on the surface roughness and service performance of the aero-engine blisk. To accurately predict the stability of the blisk side milling, the influence of random variables on the machining stability was considered. In this paper, the chatter reliability model of the blisk side milling system was established using the first-order second-moment method. The model takes structural parameters and spindle speed as random variables and chatter frequency as intermediate variables. The chatter reliability model was used to draw the reliability lobe diagram, which can be used to divide the machining reliability area. The effectiveness of this method was verified by experiments and compared with Monte Carlo method. The validation results showed that the reliability lobe diagram can be used to determine the stability probability prediction of blisk side milling and can replace the traditional stability lobe diagram.

Aircraft lug joint is the key part of load transfer. In order to improve the safety of lug joint, on the premise of meeting the design requirements of static strength and fatigue, the composite connection lug structure design technology of different metal materials is proposed in this paper. Firstly, the damage safety design and life reliability analysis of the lug structure are studied theoretically. Secondly, based on the concept of damage safety design and the design principle of deformation coordination, the design method of composite connection lug with deformation coordination is proposed, and the thickness ratio of single ear is 0.8:1:0.8. Finally, the reliability of the composite lug is analyzed. The results show that the structural design scheme of aluminum-titanium composite ear piece can meet the requirements of static strength and damage tolerance, and compared with the conventional ear structure, the failure probability of structure mission life is greatly reduced when the weight of the composite connection lug is only increased by 4.9%. The proposed method can effectively guide the structural design of composite ear piece.

Under the modern high-tech condition, the demand of air combat has been stricter on the combat performance and the integration of fighter, which impels the application of integrated vehicle management technology and makes it become the core technology of the advanced fighter about the mission management and vehicle management. From an overview of tactical flight management system's technical background and the state of development, this paper systematically introduces the issues, including the development process & history, architecture framework of the integrated vehicle management system (IVMS) which divided into perception layers, decision layer and execution layer, and function system architecture and software system architecture. Through a comprehensive analysis for the functions of each level, comprehensively expounds the basic function and key technology of IVMS which included situation awareness and assessment, mission path planning, integrated navigation, automatic attack guidance, health management and prognostic and intelligent pilot-vehicle interface, and the future development directions are also discussed.

In this paper, a practical improved dynamic inverse control method is proposed to solve the large control error and control hysteresis of post stall maneuver under unsteady aerodynamics. Firstly, depending on the wind tunnel experimental data of the advanced fighter aircraft model under biaxial coupled large oscillation, an accurate unsteady aerodynamic model is established by using the improved extreme learning machine (ELM) method. Secondly, in terms of the time scale separation, the control error caused by unsteady aerodynamic is reduced by adding integral in the fast loop, and the control delay caused by unsteady aerodynamic is eliminated by applying the lag correction link in the slower loop. The deflections of conventional aerodynamic surface and thrust vector are allocated by the daisy chain method. Finally, the formula of the reduced frequency, which is the key factor in the unsteady aerodynamic modelling process, is derived by analyzing the wind tunnel data. The effectiveness of the present method for the scaled model is verified by herbst post stall maneuver. The present work provides a practical and reliable way for the flight test of post stall maneuver.

Pressure pipes have broad applications in aviation, space flight, mechanical engineering, industrial and civil architecture etc. Instability destruction is their main failure mode. Firstly, in this paper, a complex fluid-solid coupling problem was simplified as a buckling problem of a pipe under two stresses which were along the pipe wall. The two stresses consisted of a compressive stress which was perpendicular to the pipe wall and a tangential stress which was parallel to the pipe wall. Secondly, the buckling performs of the pressured pipe were discussed by finite element analysis method under a working state and an off-working state, respectively. Some obtained conclusions were drawn as follows by the analysis in this paper.1). Provided the tangential stress is unchanged, by increasing compressive stress eigenvalue buckling critical load increases and nonlinear buckling critical load decreases.2). Provided the compressive stress is unchanged, when the direction of the tangential stress is same as that of the axial pressure, by increasing the absolute value of tangential stress the buckling critical load decreases; provided the compressive stress is unchanged, when the direction of the tangential stress is in the opposite direction of the axial pressure, by increasing the absolute value of tangential stress the buckling critical load increases.

Rapid evaluation of aerodynamic forces is a key technology in conceptual and preliminary performance assessment and design optimization for supersonic/hypersonic vehicles, which is expected to achieve a balance between accuracy and time. In this paper, the preliminary evaluation platform of aerodynamic forces is built based on the physical theories and engineering methods. This platform computes the local velocity vector by using the streamline tracing technology, and extracts the pressure and friction coefficients by calling methods in method database. Furthermore, an example based on HL-20 is brought out. A good agreement is obtained by comparing the calculated results via CFD with the experimental. Also, a good angle of attack compatibility of streamline tracing technology is concluded. This platform has a computation time less than that via CFD and an flight range greater than that via wind tunnel. Finally, the simple flight dynamics simulation is taken out and the synergetic process is verified.