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2014 Vol. 40, No. 2

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Indirect method for trajectory optimization of hypersonic vehicle with static parameters
Zhang Hongwen, Zhang Kenan, Chen Wanchun
2014, 40(2): 141-147.
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An indirect method for optimal control problems with static parameters was developed. Trajectory optimization with static parameters for hypersonic vehicle was solved using this method. Static parameters were divided into three kinds, final time, boundary state variables and design variables. The final time can be transferred to a design variable, and convert the free final time problem to a fixed final time problem. The boundary conditions of costates corresponding to the free boundary states can be derived using the maximum value principle. A design variable can be looked as a state variable whose derivative is zero. And new state dynamics, costate dynamics and boundary conditions can be obtained. After that, the optimal control problem with static parameters was converted to a standard two-point boundary value problem (TPBVP). In the end, the wave-rider was taken for example, its aero shape parameters were looked as static parameters. After the aero shape and trajectory integrated optimization, the optimal aero shape was obtained with the global maximum range.
Three-dimensional crack analysis and fatigue life prediction of aero heavy-load face gear
Wang Yanzhong, Tian Zhimin, Hou Liangwei, Lan Zhou
2014, 40(2): 148-153.
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Aiming at that life of face gear used in the aero heavy-load condition is difficult to predict, it's necessary to analyze the processes and lives of crack initiation and propagation. Using strain-life relationship and MSC.Fatigue, the simulation of crack initiation life was in progress to analyze the trend of different load torques, surface roughnesses and surface treatments; according to the theory of linear fracture mechanics, the process of crack propagation was simulated using Franc3D until meeting the fracture criterion and the crack propagation life was calculated on the basis of stress intensity factor. Finally, fatigue life curves of face gear at different surface roughnesses and surface treatments were obtained, which can be used to predict fatigue life of face gear.
Numerical simulation of liquidity and uniformity of gasoline engine intake manifold
Ji Fenzhu, Gu Keshuai
2014, 40(2): 154-159.
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The liquidity and uniformity of intake manifold have a major impact on engine performance. A four-cylinder gasoline engine model was created by GT-power and the gas flow rate of intake manifold was simulated. Gas pressure and velocity distribution were showed in different inlet angles though STAR-CD and the intake uniformity and inflatable coefficient were analyzed in each of the branched pipe. The results show that the gas liquidity and the gas flow quality in branched pipe were improved by changing the air inlet direction and regulator chamber volume and other geometric parameters, which made the gas flow tended to be uniform in each pipe. The calculation results provide a theoretical basis for designing the intake manifold modified.
Numerical simulation on the stealth characteristics of twin-vertical-tails for fighter
Yue Kuizhi, Sun Cong, Ji Jinzu
2014, 40(2): 160-165.
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In order to reduce the radar cross section (RCS) of fighter, the twin-vertical-tails effect on the RCS character of fighter was studied. The 3D digital fighter prototype was meshed. The RCS character effect of head, side and tail in three-surface fighter when twin-vertical-tails had a same deflection to two direction based on physical optics method was simulated. The electromagnetic testing on prototype fighter shrunk on a certain scale was made. The practicality of the physical optics method and the accuracy of numerical simulation were verified. The simulation results show that the side RCS of three-surface fighter reduced to 9.8% of what it had been, but the head and tail RCS had a little change when twin vertical fins deflected from 0° to 10°.
Edges interference errordetection and reflector gaps correction for large-scale compact range
Zhou Guofeng, Li Xiaoxing, Luan Jingdong, Cheng Deji
2014, 40(2): 166-171.
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In order to avoid the physical interference and reflecting surface deformation caused by a single reflector edge error, and ensure the final surface accuracy and electrical performance of large-scale compact range, an unified orthogonal distance regression model taking account of the typical forms of compact range(CR) reflection surface was proposed based on the evaluation of single reflector panel edge profile tolerance. And this model was employed to calculate the panels' nominal size, interference error and edge correction.Meanwhile this model also could be used to predict and mend the overall gaps interference high risk area. The single reflector's edges of a large compact range were measured by a laser tracker. After analyzing and correcting the high interference risk areas through the above approach, the CR gaps satisfied the design index of (0.4±0.2) mm.
Application of graphene on improving atomic oxygen resistance of material
Zhang Wen, Yi Min, Shen Zhigang, Zhang Xiaojing
2014, 40(2): 172-176.
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The application of graphene on spacecrafts was proposed. Graphene was prepared by the ultrasonic cavitation method, then it was added into epoxy resin and nanocomposites were prepared by the mixing method. Results of thermogravimetric analysis show that the thermal stability of the nanocomposite is improved. The atomic oxygen effect experiments of pure epoxy resin and nanocomposites are conducted in a ground-based simulation facility. Results of mass loss, surface morphology and surface composition indicate that the atomic oxygen erosion resistance of nanocomposites is improved obviously.
Robust H∞ control for hypersonic vehicles under asynchronous switching
Wu Zhendong, Wang Qing, Dong Chaoyang
2014, 40(2): 177-182.
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A new robust H∞ control design method was presented for hypersonic vehicles under asynchronous switching between the controllers and subsystems. A Lyapunov function dependent on switching signal of controllers was constructed, which could effectively counteract the intractable problem of controller design under asynchronous switching. Moreover, employing the average dwell time technique and Lyapunov function method, the globally uniformly asymptotically stable with the H∞ performance index was investigated, and the robust H∞ controllers were designed. Simulation results show that the robust H∞ control system of hypersonic vehicles provides satisfactory command tracking and avoids the state jumping under asynchronous switching with a high containment procedure for the turbulence.
Wear status recognition of piston pump based on side frequency relative energy summation
He Zhaomin, Wang Shaoping
2014, 40(2): 183-187.
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Wear is a kind of progressive failure in piston pumps on aircrafts. As amount of wear is difficult to directly measure, vibration signal is often used to reflect it. However, characteristics of the vibration signal caused by wear are usually weak, and it is difficult to make an accurate recognition of the wear status. Considering these problems, a recognition method of wear status based on relative energy summation of side frequency was proposed, vibration signal of piston pump was addressed with Hilbert envelope demodulation to eliminate high frequency cycling interference, and clear harmonic components were acquired, the summation of the maximum energy to average energy ratio in the side band of each harmonic frequency was used as the indicator to reflect the wear status of piston pumps, the grid search method was used to optimize the range of the side frequency. Experimental results show that side frequency relative energy summation has higher distinction and is suitable for wear status recognition compared with the traditional frequency energy.
Analysis of effect of interior pressure to deformation of inflatable wing with fluid-structure interaction analysis method
Yang Yongqiang, Ma Yunpeng, Wu Zhe
2014, 40(2): 188-192.
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Fluid-structure interaction (FSI)analysis of inflatable wing was carried out based on the ABAQUS-FLUENT FSI software. Distance-weighted average interpolation function was used to transfer aerodynamic pressure distribution between coupling interfaces. Deformation data was transferred using constant volume tetrahedron transformation method. Relationship among interior pressure, stiffness and buckling behavior of inflatable wing was obtained. Analog loading system of inflatable wing was established to validate the feasible of the optimization scheme. The results show that FSI method is applicable to make the deformation analysis of inflatable wing. The results of the FSI analysis and the analog loading test coincide to each other well.
Statistical analysis for crosstalk of twisted-wire pairs with non-uniform pitch
Bao Guihao, Su Donglin, Dai Fei, Gao Wanfeng
2014, 40(2): 193-197.
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The pitch error of random twisted wire pair (TWP) could directly impact the immunity levels of TWP. The randomness of pitch error would cause the uncertainty of crosstalk prediction of TWP. According to the analysis of the TWP production principle, the probability density of the pitch error of TWP was accurately obtained by the production parameters. The crosstalk model of the TWP with non-uniform pitch was rapidly presented by the equal radian discrete method and concept of generalized multi-port network, likewise, the relationship between the inductive coupling and pitch error was obtained. The statistical properties of crosstalk in random TWP could be analyzed effectively based on the probability density function of pitch error. The simulation analysis further validates that the mean and variance of shafts' angular velocity are the key factors of affecting the inductive coupling of random TWP. For the TWP production, the mean and variance of shafts' angular velocity must be taken into account carefully to ensure the immunity levels of TWP.
DMU-based project monitoring technology of aircraft development
Chen Changyu, Yu Yong, Zhao Gang
2014, 40(2): 198-203.
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Due to characteristics of the long cycle, complex data and concurrent events, aircraft development project demands efficient management environment. To satisfy this demand, a method of project monitoring technology based on digital mockup (DMU) was proposed, and then an integrated model of project management (PM) and product data management (PDM) was developed. The DMU model was proposed to be bound with task information to realize multi-perspective project monitoring environment. Double-layer loading strategy was adopted to reduce system display burden when visualizing the DMU model. Based on the visualization and interaction of the DMU model, this solution provides project managers with a project monitoring interface which is able to display multi-perspective information and thus enriches the interaction between the users and enterprise information.
Numerical simulation of high-speed water-entry cavity of cone cylinder
Ma Qingpeng, Wei Yingjie, Wang Cong, Cao Wei
2014, 40(2): 204-209.
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Numerical simulation for modeling the cavity formation induced by the high-speed water-entry of a cylinder body with a cone head was performed. Volume of fluid (VOF) model and dynamic mesh were introduced for the multiphase flow and the movement of the body. The velocity attenuation and induced cavity shape were obtained with an initial velocity of 500 m/s. Good agreements were obtained compared with the theoretical results. During the early period of the water entry, the penetrating velocity decreased rapidly because of the high impact load affected on the cone which can be thousand times atmospheric pressure. The maximum cavity diameters of the water-entry cavity get larger when the initial velocity is higher. As the rigid body moves deeper, there is more vapor than air; the multiphase affects the stability of the cavity markedly.
Pressure oscillation analysis of aircraft hydraulic braking system considering pipeline
Huang Cheng, Jiao Zongxia, Shang Yaoxing
2014, 40(2): 210-215.
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Pressure servo-valve is usually used for aircraft hydraulic braking system, and the brake pipeline between the valve and the actuator is usually long. The long pipeline brings under damping frequency characteristic into the system, which will couple with the local close-loop pressure control structure of pressure servo-valve, and make pressure control oscillate easily. Based on a model considered pipeline for the hydraulic braking system, the reason of pressure servo-valve and pipeline coupling was analyzed. The influence of the changes in pipeline and oil parameters on pressure control was given. Simulations of the pressure control of aircraft hydraulic braking system were conducted to verify the frequency analysis. And three solutions for avoiding pressure oscillation, including matching design of pipeline, increasing the system damping and reducing the gain were also analyzed. Theoretical reference for the design and optimization of the aircraft hydraulic braking system was provided.
General calculation study method of thermodynamic functions for substances
Liu Lie, Liang Guozhu
2014, 40(2): 216-221.
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The substance's thermodynamic functions (heat capacity, entropy, enthalpy) were commonly used in the rocket engine's thermal property analysis. According to the thermodynamic relation, the three functions above can be expressed as polynomial on temperature with the same seven factors. Due to the technological progress, newer and more precious data at different temperatures were demanded. The function data were divided into different intervals based on temperatures, to ensure the calculated data were equal at adjacent intervals, with the least square method and program calculating, 135 kinds of substances' temperature coefficients were redefined. And the above substances' calculated thermodynamic functions from 300 K to 5 000 K were determined. Furthermore, to get more precise values, the heat capacities of 26 substances such as nitrogen atom, liquid lead, crystalline silicon, which had larger relative errors were corrected by using the least square method and the precision of heat capacities is 100 times higher than before. Compared with the standard data, the calculated data have small error and high precision and can be applied to many disciplines.
Reliability analysis of structures with fuzzy and non-probabilistic hybrid variables
Xu Menghui, Qiu Zhiping
2014, 40(2): 222-228.
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For the reliability analysis of structures in the case of coexistence of fuzzy and non-probabilistic uncertainties, the hybrid analysis model was transformed into non-probabilistic analysis models at different membership values distributed in the interval [0,1] continuously based on the decomposition principle of fuzzy mathematics theories. An algorithm for determining the minimum/maximum of the structural performance function was presented to overcome the complexity in calculating the non-probabilistic reliability based on the optimization strategy dimension by dimension, by which the determination of the extreme values was converted to that of the extreme point vectors of the performance function. The quantification of the fuzziness in structural reliability was accomplished with the membership function of the structural reliability obtained by traversing the membership value in the interval[0,1]. The reasonability of the presented method was proved by two engineering applications and the merits of high accuracy and efficiency suggest a feasible way for the reliability analysis and optimization of complicated engineering structures.
Guidance and control optimization method for fighter with threat avoidance
Yu Lei, Fu Zhaowang, Li Zhanwu, Li Fei
2014, 40(2): 229-234.
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Guidance method with threat avoidance was researched based on optimal control theory. Guidance model was established based on situation parameter of air combat, and fighter guidance problem was constructed as an optimal control problem with nonlinear state restriction and path restriction. Weapon effective envelope was adopted for threat description. In order to assure the safety for fighter, threat avoidance restriction was converted into state restriction based on fire threat model for target, receding horizon control (RHC) strategy was introduced for real-time requirement in guide control, and Gauss pseudospectral method (GPM) was adopted in numerical calculation for precision requirement. Simulation was given based on typical operational scenario. Result shows the guidance method can reach the optimal guidance under safety condition.
Application of BP-AdaBoost model in temperature compensation for fiber optic gyroscope bias
Liu Yuanyuan, Yang Gongliu, Li Siyi
2014, 40(2): 235-239.
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Aimed at the complex non-linearity in bias temperature error model of fiber optic gyroscope(FOG), based on back propagation (BP) neural network and adaptive boosting(AdaBoost) learning algorithm, a new BP-AdaBoost temperature compensation method was proposed to effectively enhance the FOG bias stability. The effects of model parameters on the prediction precision were also investigated. A program for determining the number of hidden layer neurons in BP neural network and the number of iterations in AdaBoost model was given. The prediction error by this BP-AdaBoost algorithm is smaller than that by single BP neural network. By large amount of experiments and calculations from FOG, the compensation results show that, the proposed approach has better performance compared with those traditional linear regression model, mixed linear regression model, and single BP neural network. Through the analysis and simulation, this approach improved is validated and has a great value of engineering reference.
Transformation control for the formation of multiple cruise missiles
Du Yang, Wu Sentang
2014, 40(2): 240-245.
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For the satisfaction and requirement of the cooperative engagement capability for multiple cruise missiles, a formation transformation control scheme was proposed to solve the intermediate collision within the whole flight formation system during the formation change. The limitation of missiles maneuver was considered and the avoidance of the intermediate collision was achieved by two works: one was the designing of the model predictive control law based on local kinetic model which evolved all the neighboring individuals; the other was the approach that deconstructed the formation transformation into a series of sub-formations with easier implementations. A contrastive simulation where a team of seven missiles changed their formation from a regular hexagon into a straight line shows that the proposed scheme can make the transformation smooth and reliable.
Optimal trajectory planning for small-scale unmanned helicopter obstacle avoidance
Meng Shaohua, Xiang Jinwu, Luo Zhangping, Ren Yiru
2014, 40(2): 246-251.
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Obstacle avoidance for unmanned helicopter safely flying in complex-low environments was investigated. A solving strategy based on nonlinear optimal control theory was developed. The computation of optimal obstacle avoiding maneuvers was viewed as an optimal control problem, where the solution minimized the maneuvering duration subjected to the 6-freedom nonlinear dynamics equations and limitations of helicopter flight performance, in which the obstacles in 3D space were formulated as inequality constraints by using 1-norms. Gauss pseudospectral method (GPM) was employed to transform the trajectory planning problem to non-linear programming(NLP) problem, which can be solved using a sequential quadratic programming algorithm. Moreover the influence of obstacles sizes to the planned trajectory was investigated. Simulation results show that the proposed method can generate feasible trajectories with high accuracy, and the optimal maneuver depends on the ratio of obstacle height and weight.
Path planning of UAV in dynamic environment
Liu Yang, Zhang Weiguo, Li Guangwen, Shi Jingping
2014, 40(2): 252-256.
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In order to solve the problem of path planning in dynamic environment, a new method which introduced the time axis was given. Based on the configuration space (C space), the time axis was introduced to expand the C space to the configuration-time space (CT space), and the position of moving obstacles at all times could be expressed in the CT space. In the path generation stage, an improved ant colony algorithm was proposed. The heading information was introduced as heuristic information to the ant colony algorithm, and at the beginning of the algorithm ants could be guided to search the road map more efficiently. The simulation results show that the moving obstacles can be expressed well in the CT space. The improved ant colony algorithm is more efficient and it can converge to the best solution more quickly.
Carrier phase difference estimation method based on DDMR-assistance for GNSS-R altimetry
Wang Yiran, Hong Xuebao, Zhang Bo, Zhang Yanzhong
2014, 40(2): 257-261.
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A carrier phase difference estimation method based on the delay-Doppler map receiver (DDMR)-assistance for (GNSS-R) coastal altimetry was proposed. The system structure and the signal processing method were given. The proposed method, which can avoid the complicated search for the GNSS spreading codes, uses the code phase difference observed from DDMR as the estimated time-delay between the spreading codes of the direct signal and the reflected signal, and then delays the tracked codes of the direct signal to achieve the open-loop tracking of the reflected signal. Field experiments with real coastal receivers demonstrate the effectiveness of this method, which can steadily track the weak reflected signal and accurately extract the difference of the carrier phase. The experiment results show that the altimetry accuracy is about 2.5 cm without data average or 0.6 cm with 0.5 s average.
Reliability analysis based on algebraic model for flight control computers
Zhang Jingkai, Zhang Weiguo, Liu Xiaoxiong, Wang Xiaoguang
2014, 40(2): 262-267.
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According to the architecture of modern airliners' flight control computers, a method dynamic fault tree analysis was used to assess the system reliability. Algebraic models with temporal operators which can handle dynamic logics were built for warm spare gates included in the system. Based on the expressions of logical symbols such as structure functions, the quantitative formulation was deduced to analyze a warm spare gate with dissimilar redundancy. The algebraic models proposed are applicable in any distribution type of lifetime. Compared to the classical Markov method, the application using algebraic models for a case of a typical flight control computer system shows the efficiency and convenience in practice.
Cooperative active collision avoidance algorithm based on sliding mode control
Wang Pangwei, Yu Guizhen, Wang Yunpeng, Wang Di
2014, 40(2): 268-273.
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The traditional active collision avoidance algorithm of vehicles is mainly realized by applying brake of the following vehicle. But collisions can't be avoided if two vehicles are too close. Also, the emergency braking will cause sickness to drivers and passengers. To solve the problem, a new cooperative active collision avoidance(CACA) algorithm was presented, in which the desired deceleration of the following vehicle was calculated by the sliding mode control equation, and collisions could be avoided by distributing acceleration to the leading vehicle. The new algorithm ensures a safe and comfortable driving environment much better than the traditional active collision avoidance algorithm. The feasibility of the new CACA algorithm was verified by simulation of CarSim and Matlab/Simulink.
Algorithm of trajectory prediction in free phase based on range adjusting
Liu Yonglan, He Zhenghong, Li Zhenxing, Yang Haoyun
2014, 40(2): 274-279.
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Radar has the characteristic that range accuracy is higher than angle accuracy. With taking full use of the asymmetrical measurement, a method of trajectory prediction in free phase based on the range adjusting was put forward. On the basis of ballistic missile movement data in free phase measured by radar, the method dealed with the data with the sliding window midpoint smoothing means, reused the range information to dynamically differential correct the orbital elements, improving the utilization of measured data and the accuracy of trajectory prediction. Simulation results show that the method is evidently better than the basic elliptical trajectory, and greatly enhances the accuracy of trajectory prediction.
Design and analysis of flexible fixture for aircraft side panels
Ma Zhengwei, Li Weidong, Wan Min, Gao Hong
2014, 40(2): 280-284.
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Based on the analysis of two kinds of aircraft side panels and requirements in digital assembly, a novel type of flexible fixture suitable for aircraft side panels assembly was proposed. The fixture based on four accurate 3-coordinate manipulators can be equivalent to a 6-DOF parallel mechanism. Manipulators were aligned in two rows and side panel was supported by 4 protruding arms. By analyzing the mechanism kinematics, reverse solution algorithm was developed. Joints displacement can be calculated from the given initial and final postures of the side panel. Computer simulation model was used to verify the reverse solution. The simulation result shows the accuracy of the algorithm, which provides the technological basis of accurate control for posture alignment of the large side panels.

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