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2015 Vol. 41, No. 9

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Volume 41 Issue92015
2015 Year 41 Volume 9 Issue E-journal
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Pointing and tracking control with linearization and state feedback for gimbal on floating platform
ZHAO Guowei, WANG Weimin, FANG Yizhong, WANG Haoyu
2015, 41(9): 1567-1573. doi: 10.13700/j.bh.1001-5965.2014.0687
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2-DOF (degree of freedom) gimbal mounted on floating space platform caused attitude disturbance to the platform while pointing and tracking a space object. Therefore the attitude of platform was affected then the pointing direction of the end of the gimbal changed and the pointing accuracy was reduced. So the gimbal and the platform were dynamically coupled. This problem could not be ignored especially when the inertia of the gimbal was not small enough compared to that of the platform or when the gimbal was rotating fast. In order to solve this problem, a coupling compensation method was put forward. In this method, attitude motion of platform caused by the rotation of gimbal was considered to revise the tracking target of the gimbal. Furthermore, feedback linearized state feedback was used as control method. At last a simulation was carried out to compare the pointing accuracy between traditional PD control method and the method put forward. It is verified that the pointing accuracy is efficiently improved by using linearization and state feedback as control method.
Space interception orbit optimization design based on hybrid optimal algorithm
GAO Xiaoguang, TANG Hong, DUAN Junhong
2015, 41(9): 1574-1581. doi: 10.13700/j.bh.1001-5965.2014.0673
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Based on a hybrid algorithm combining genetic algorithm (GA) with improved Gauss method (IGM), a design method of space interception orbit was proposed for solving time-fuel-optimal trajectory planning problem of interceptor. First, classical Gauss method was improved by applying Newton-Raphson iteration, solving the problem of the classical Gauss method of slow convergence speed and small transfer angle. Then, a theorem on the necessary and sufficient condition for the existence of unique solution was proved. When the initial orbital parameters were given, this condition could be used to judge whether elliptical orbit could be introduced as the interception orbit. After that, constraints of transfer time and maximum pulse rate were given, as well as the calculation steps of hybrid optimal algorithm, and way of coding was improved. Finally taking optimization problem of space interception orbit as an example, simulation was carried out. Simulation result shows that the hybrid algorithm has fewer generations and shorter consuming time compared with conventional optimal algorithm, indicating the algorithm is applicable in determining interception orbit in space.
Differential excitation eddy current sensor testing for aircraft engine blades defect
YU Xia, ZHANG Weimin, QIU Zhongchao, CHEN Guolong, QIN Feng
2015, 41(9): 1582-1588. doi: 10.13700/j.bh.1001-5965.2014.0639
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The micro-crack detection experiments of the certain model aircraft engine turbine blades were carried out. Based on eddy current testing technology, a small differential excitation probe with high sensitivity and difference from traditional probes was designed and developed. The simulation analysis of micro-crack on aircraft engine turbine blades was completed by finite element analysis software. In order to realize the automatic and efficient detection of engine blades, a computerized numerical control (CNC) scanner with multi-degree of freedom was designed and adopted to control the acquisition process. The detection signals were acquired via the signal conditioning circuit, A/D card and input into computers, where the signals storing, processing and output completed. By comparing the experimental and simulation results, it can be seen that the difference incentive eddy current sensor can effectively and accurately determine the micro-crack position on the blade surface and has practical significance and reference value for evaluating micro-defects of aircraft turbine blade parts during early diagnosis.
Simple and efficient novel multi-way relay network coding scheme
WU Zhanji, GAO Xiang
2015, 41(9): 1589-1594. doi: 10.13700/j.bh.1001-5965.2014.0632
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A simple and efficient novel network coding scheme was proposed to improve the throughput and transmission reliability of multi-user multi-way relay network with full-data exchange. It was based on a multi-stage two-way network coding scheme. Two paired users transmitted their information symbols to the relay node simultaneously. Then, the relay node judged whether these two symbols have the same sign by hard decision for the received superimposed signal and broadcasted the decision result to all the users. If the two symbols had the same sign, the transmitted symbols could be known. Otherwise, anyone of the two users was selected to perform the network coding in the next round. Each pair of users performed in this manner sequentially until the transmitted symbols of all the users are obtained by each other. Both theoretical analysis and simulation results indicate that compared to the plain routing scheme and the binary-signaling network coding reference scheme, the throughput per source per channel use is increased remarkably. Besides, due to the simple nature of 3-plus amplitude modulation (3-PAM), the proposed scheme has much lower complexity and much higher reliability compared to the referenced scheme for large-scale multi-way relay channels. On the additive white Gaussian noise (AWGN)channel, low density parity check (LDPC) codes are utilized in this scheme to improve the reliability. The simulation results show that the signal-to-noise ratio (SNR) gains to reference scheme increase as the number of users increases, and the SNR gains of the LDPC-coding scheme are even bigger than the uncoding scheme.
Identifying method of load for sensorless industrial robot
CHEN Youdong, JI Xudong, GU Pingping, HU Guodong
2015, 41(9): 1595-1599. doi: 10.13700/j.bh.1001-5965.2014.0669
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When the load of the industrial robot end-effector is changed in practical use, mechanical vibration occurs, in order to get high motion performance of the industrial robot, the end-effector load should be identified to modify the control parameter. A method of identifying load by servo motor output torque was proposed, which did not need an additional sensor. According to the static model of the robot, the load calculation model was achieved by the output torque difference between the end-effector with and without load. In the industrial workspace of the EFFORT QH165 robot, we randomly selected 10 measurement points to read the servo motor torque and calculated the load respectively. The results show that load identified by this method is the same with the given load. Through the experiments on the robot, the effectiveness of the proposed method is confirmed.
Parametric product family progressive optimization design approach
WEI Wei, FENG Yixiong, CHENG Jin
2015, 41(9): 1600-1607. doi: 10.13700/j.bh.1001-5965.2015.0002
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Parametric product family progressive optimization design approach is proposed based on product platform technique. The progressive optimization design process was constructed, the optimization of product family was carried out progressively using multi-objective mix-evolution algorithm. The mix-evolution algorithm used two kinds of populations to avoid the data perturbation problem. The strength Pareto evolutionary algorithm 2+and non-dominated sorting genetic algorithm-II were used progressively in the product platform design and product instance optimization. In the product family progressive optimization, the product platform was identified firstly. The multi-objective optimization mathematics optimization model of parametric product family was constructed, the sensibility of design parameter was analyzed and the diversity factor was calculated. The product platform constants and variables were divided. As a result, the product platform was constructed. Then the performances of each individual instance product were optimized in the robust product platform to get the optimal design parameter. Finally, the design of electromotor product family was used as an example to certify the proposed method's effectiveness and applicability.
Aerodynamic design of high-aspect-ratio flying wing based on criteria
GAN Wenbiao, ZHOU Zhou, XU Xiaoping
2015, 41(9): 1608-1614. doi: 10.13700/j.bh.1001-5965.2014.0672
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To improve aerodynamic performance of flying wing from design reality, aerodynamic design and analysis of high-aspect-ratio flying wing unmanned aerial vehicle (UAV) were conducted. In design and analysis process, according to features of flying wing, aerodynamic design criteria have been proposed. Based on design criteria, a design optimization framework, using updated design strategies, was built which combined variable fidelity numerical simulation and surrogated model optimization method. Flying wing UAV was carried out with parametric expression, automatic mesh generation of transfinite interpolation (TFI), and multi-round optimization. And then recommended configuration was obtained and validated for detailed aerodynamic performance by γ-Reθt transition model method. The results show that design configuration of flying wing UAV agrees well with design criteria, cruise lift-to-drag ratio of UAV increases 14% compared to the original configuration, γ-Reθt transition model method can analyze the detailed aerodynamic characteristics of high-aspect-ratio flying wing UAV.
Channel capacity of cooperative grouped satellites with array based transmission
XIAO Zhenyu, LI Yao, BAI Wenjie, BAI Lin
2015, 41(9): 1615-1623. doi: 10.13700/j.bh.1001-5965.2014.0681
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In order to improve the system capacity of cooperative grouped satellites, we considered the transmission mode of equipping the satellites with antenna arrays. Channel condition of downlink with maximum channel capacity was analyzed. Implementation approaches to the maximum channel capacity were put forward. Influences of system parameters to the channel capacity were researched. The results show that the channel capacity changes with the ground antenna distance periodically. The changing cycle of the channel capacity curve is in inverse proportion to the number of satellites (sat-number), to the cosine value of the angle between the ground array and an east-west line and to the angular distance between satellites (sat-angular-distance). The envelope of the channel capacity curve changes with the ground antenna distance periodically as well in a multi-satellites multi-antennas environment. An arrangement strategy of ground antennas in a multi-satellites multi-antennas environment was proposed to decrease the ground antenna distance and to lower the requirement of the ground array measurement accuracy as well, which was verified by the simulation results.
Rotor downwash interference calculation and helicopter trims with free-wake/panel method
LYU Shaojie, WEI Jingbiao, CAO Yihua
2015, 41(9): 1624-1630. doi: 10.13700/j.bh.1001-5965.2014.0680
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A coupled free-wake/panel method to predict the rotor downwash aerodynamic interaction and helicopter trims is presented. Based on lifting-surface theory, free-wake method was developed to analyze aerodynamics interference of rotor wake. A three dimensional panel model was applied to represent the fuselage, the vortex line mirror method was adopted to account for the induced and obstructed effects of the fuselage on the rotor wake. Based the coupled method, the rotor wake geometry and rotor downwash velocity on fuselage, horizontal stabilator and tail rotor of UH-60A helicopter were investigated including comparisons with the wind tunnel measured data. Combined with the helicopter flight dynamic model, the coupled method was embedded in the trim procedure and applied to trim. Comparisons among predictions, vortex particle model results and flight test results were for the control stick positions and attitude angles, coincidence of the results validated accuracy of the present methodology.
Constraint model and vibration response analysis of rotor rub-impact
ZHANG Li, MA Yanhong, LIANG Zhichao, HONG Jie
2015, 41(9): 1631-1637. doi: 10.13700/j.bh.1001-5965.2014.0647
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Considering the additional constraints induced by rub-impact, a mechanical model was proposed for typical mechanical characteristic of rub-impact. Based on the constraint model, some characteristics in response such as resonant interval extending, amplitude jumping and contact instability were analyzed. Impact of typical mechanical characteristic parameters on rotor response during rub-impact process was studied. It is found that additional constraint stiffness will cause the extension of the resonant range and instable contact region, while greater friction coefficient between rotor and stator causes the decrease of the vibration response and resonant range. A rub-impact analytical model with structure features of aero-engine was built, numerical simulation shows that in addition to the resonance range extension caused by additional constraints, characteristics of rotor response are closely related to rub location and mode shapes. System's response shows characteristics of quasi-periodic in soft rub-impact, while rotor movement tends unstable and closer to the mechanical model in heavy rub-impact.
Computing approach of uncut chip thickness in orthogonal turn-milling with inserted cutters
QIU Wenwang, LIU Qiang, YUAN Songmei
2015, 41(9): 1638-1644. doi: 10.13700/j.bh.1001-5965.2014.0700
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The computing of uncut chip thickness is the basis for further studying the cutting mechanism as well as simulating the cutting process. The research about orthogonal turn-milling operation with inserted cutters was focused on. By simplifying the trajectory of cutting edge, the uniform formulation to calculate uncut chip thickness for cutters with different shapes was derived and then compared with the numerical method through several examples. Upon the presented formulation of uncut chip thickness, the cutting force in orthogonal turn-milling operation was predicted and a validation experiment was carried out on a turn-milling machine tool. Both the comparison examples and the result of cutting force prediction show that the presented approach can provide a solution for the calculation of uncut chip thickness with good accuracy and high computation efficiency. Due to the uniform expression, the proposed approach is suitable for the development of general simulation software for orthogonal turn-milling process and thus has potential value in engineering practice.
The simplest multi-position analytic alignment for SINS
TAN Caiming, WANG Yu, SU Yan, ZHU Xinhua
2015, 41(9): 1645-1650. doi: 10.13700/j.bh.1001-5965.2015.0033
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The strapdown inertial navigation system (SINS) need to be installed on a servo platform and rotated through 90 ° or 180 ° about the up axis for traditional multi-position analytic alignment method. Thus it will bring inconvenience, and the precision of the servo platform will directly affect the precision of the multi-position analytic alignment method. To address the issue, a simplest multi-position analytic alignment method was proposed. The multi-position analytic alignment can be done by any two positions, or to say, the constant biases of the inertial measurement unit (IMU) can be ordinarily obtained through the information in any two positions. The computation procedure of this method was given and simulations proved the validity of this method. The simplest multi-position analytic alignment with any two positions can be used as a simple initial alignment method or a field calibration method. Moreover, it is proposed that the constant bias of the accelerometer or the constant drift of the gyroscope in a certain axis can be well estimated when the IMU stays in some particular attitudes. The conclusion can be used for further improvement of the multi-position alignment method.
Application of multiple linear regression to fault diagnosis of bleed air system
LIANG Kun, ZUO Hongfu, SUN Jianzhong, WANG Ronghui
2015, 41(9): 1651-1658. doi: 10.13700/j.bh.1001-5965.2014.0633
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To solve the fault diagnosis problem of civil aircraft systems by utilizing quick access record(QAR) data, with the civil aircraft bleed air system as the research object, we proposed a fault detection method of multiple linear regression model for multi-flight cycle data characteristics. Firstly, the multi-linear regression model of bleed air system performance was established for multi-flight cycles data and the fault detection method of flight cycles and flight cycle's interior was designed. Then the model parameters were estimated by maximum posteriori method. Finally, the maximum posteriori estimation algorithm of the model parameters was designed for multi-flight cycle data. With simulated data and actual flight data collected by airlines, the method was validated. The results show the method's feasibility and application value in engineering practice.
Parametric finite element meshing and adjustment for delta wing
XU Menghui, QIU Zhiping
2015, 41(9): 1659-1665. doi: 10.13700/j.bh.1001-5965.2014.0641
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To reduce the time of finite element (FE) modeling for a delta wing as well as improve the efficiency of structural analysis, design and optimization, a method, with the only input of its geometry profile meeting the pre-defined aerodynamic performance, for parametric modeling based on the self-defined geometrical matrix was established. Number rules for nodes and elements were firstly defined. And preliminary identification of the inner skeleton configuration with respect to arbitrary input parameters was subsequently accomplished by the criteria for rib-end locations. Nodes and elements were then generated by user-input parameters for the finite element size. Secondly the FE meshing was refined by the opening setting, amendment of rib-end locations and stringers modeling, based on which modifications of rib assignment with small amplitude for both the inside and outside ailerons as well as those of the rotation angle for control surfaces were made for ease in use of structural analysis under different flying conditions. At last, a parametric modeling module was simultaneously programmed using Patran command language (PCL) language and examples illustrate the effectiveness and reliability of the proposed method.
Hybrid-and-forward cooperative system based on joint layered decoding of QC-LDPC codes
ZHANG Song, MA Linhua, TANG Hong, ZHANG Haiwei, HU Xing, TIAN Yu
2015, 41(9): 1666-1672. doi: 10.13700/j.bh.1001-5965.2014.0645
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A hybrid-and-forward cooperative system based on the joint layered decoding of quasi-cycle low-density parity-check (QC-LDPC) codes was designed to improve the overall performance of the relay cooperative system. The construction method of the QC-LDPC systematic codes used between source node and relay node was presented and a new joint layered decoding algorithm for the cooperative system was proposed. According to the characteristics of traditional decode-and-forward and coded cooperation, a relay hybrid-and-forward cooperative strategy was adopted. Regardless of the decoding results of the relay, the relay node sent some redundant information to the destination node, so as to improve the coding gain and diversity gain of the cooperative system. Simulation results show that the designed hybrid-and-forward cooperative system can sufficiently play the advantages of diversity and coding brought by relay. Compared to non-cooperative system, the proposed hybrid-and-forward cooperative system can improve the decoding performance of the relay cooperative system.
Design of lightning protection test generator for airborne equipment
LIU Shuai, YANG Lanjun, ZHUANG Weichun, WANG Wei, HUANG Dong, HUANG Yizhi
2015, 41(9): 1673-1677. doi: 10.13700/j.bh.1001-5965.2014.0651
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The waveform of lightning protection pin injection test for airborne equipment is a combination wave in which the open circuit voltage waveform is the same as short circuit current waveform. For such class of combination wave, a novel combination wave generator circuit was proposed based on the linear RLC circuit of impulse current. The relationship between the time of peak value, the peak current, the time of half peak value and damping coefficient parameter of the circuit was studied. A design method was proposed for combination wave circuit which the time of peak value and half peak value serve as target parameters. The circuit parameters of lightning protection pin injection test generator for airborne electronic equipment were obtained by calculation and simulation, taking account of the influence of the stray parameters. Simulation results show that the output waveform of the generator designed can meet RTCA/DO-160G standard requirements, and the generator could be used in lightning protection pin injection test for airborne equipment.
Fatigue life prediction for 7050-T7451 aluminum alloy plate with scratch defect
ZHAN Zhixin, HU Weiping, ZHANG Miao, MENG Qingchun
2015, 41(9): 1678-1685. doi: 10.13700/j.bh.1001-5965.2014.0656
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Fatigue damage of 7050-T7451 aluminum alloy plate with scratch was studied, and the fatigue life of aluminum alloy plate after scratching was predicted considering the common effects of the residual stress, plastic damage and fatigue load. The nonlinear dynamic finite element (FE) analysis was conducted to simulate scratch generation, and the residual stress field and plastic strain field near scratch were obtained. According to the equation of plastic damage, the initial damage field near scratch caused by plastic deformation in the scratching process was calculated. Based on the multiaxial fatigue damage model, the finite element numerical method was established to analyze fatigue damage, and the calibration of material parameters in the damage evolution equation was conducted. This method was used to predict the fatigue life of scratched aluminum alloy plates with synthetically considering the residual stress field, the initial plastic damage and fatigue damage. The predicted results were compared with results from the fatigue test of specimens, and the theoretical prediction was in accordance with the test results of fatigue life. A new method and a practical means for fatigue life prediction of metal component with scratch defect were provided.
Wave propagation in cracked elastic media based on EMT using FEM
LIU Ning, LI Min, CHEN Weimin
2015, 41(9): 1686-1692. doi: 10.13700/j.bh.1001-5965.2014.0663
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Understanding mechanism of wave propagation in elastic media with cracks is the key scientific issue in exploration and extraction of shale and other unconventional oil and gas resources. Based on the advantages of the numerical simulation, the excitation and propagation of elastic wave in the cracked media were simulated by Nastran, a commercial solver for finite element analysis. Then the dependence of dynamic characteristics of propagation in that kind of media was further analyzed based on the microstructure (crack density, aspect ratio). Some conclusions were obtained as follows. Finite element method (FEM) would be effectively used to study the issue. Hudson's effective medium theory (EMT) could not be applied into materials with Poisson's ratio of nearly 0.5. Increasing crack density and aspect ratio would reduce the primary wave (P wave) velocity, with decaying the displacement amplitude of the P wave in time-domain. Crack density of the medium exposes greater effect on the anisotropy than the aspect ratio.
Dimensional optimization method for manipulator based on orientation manipulability
JIA Shiyuan, JIA Yinghong, XU Shijie
2015, 41(9): 1693-1700. doi: 10.13700/j.bh.1001-5965.2014.0665
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To solve the dimensional optimization design problem of manipulator, the numerical index of dexterity was presented by pose probability coefficient, which was defined as the ratio between possibly sampled orientations and sampled orientations of the working point. According to the pose probability coefficient, the concept of orientation manipulability was proposed, which represented the operability of manipulator. On the basis of orientation manipulability, an algorithm of dimensional optimization to manipulator was proposed. Based on the original structure design, this algorithm takes the reciprocal of the orientation manipulability as fitness function. Under the condition of self-collision, dimensional parameters of manipulator were optimized to maximize the operability by using genetic algorithm. Optimization algorithm was applied to a six-degree of freedom (DOF) manipulator. Results show that the orientation manipulability increases by 40.33% after optimization. Finally, validity of the algorithm was further verified by dexterous workspace and the effect of the pose probability coefficient to the optimal results was also discussed.
Helly-theorem-based time-optimal consensus for multi-agent systems
HU Chunhe, CHEN Zongji
2015, 41(9): 1701-1707. doi: 10.13700/j.bh.1001-5965.2014.0676
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The final convergence state of multi-agent under ordinary consensus control is restricted by communication topology structure and edge weight. Different convergence states further influence the convergence speed of multi-agent. To attain identical convergence state under different communication topologies, and achieve time-optimal consensus, we designed a time-optimal distributed consensus control strategy for linear multi-agent system with input constraint. Firstly, we proved that the time-optimal consensus state and convergence time uniquely existed based on Helly theorem. More specifically, for the multi-agent system with n agents with input constraint in the d(n >d) dimension state space, the time-optimal state can be determined by d+1 agents at most. When the d+1 crucial agents were obtained, so was the consensus state. According to this theorem, we designed a new distributed coordination algorithm for multi-agent to achieve common knowledge on those critical agents together with the time-optimal consensus state and convergence time, and after that, each of the agents designed its own local optimal control law with terminal-time and terminal-state constraints, which guaranteed the time-optimal consensus of multi-agent. To demonstrate the correctness and efficiency of the algorithm, we applied our algorithm to the second-order dynamic multi-agent systems. Simulation result verifies the feasibility of the distributed algorithm. When the coordinating state dimension is much smaller than the number of agents, the algorithm significantly reduces the amount of computations and increases computation speed.
Design of experimental setup for elastic scattering and breakup reaction of 17F+58Ni
ZHENG Lei, LIN Chengjian, ZHANG Gaolong, JIA Huiming, ZHANG Huanqiao
2015, 41(9): 1708-1713. doi: 10.13700/j.bh.1001-5965.2014.0644
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At energies around Coulomb barrier the study of the dynamic effect of weakly bound nuclei is one of presently hot subjects. However, due to the experimental studies about this field are scarce, especially on the medium-mass target nuclei. It has no systematic conclusion. Therefore, this study needs to be done in the future from the experiment. The experimental setup was designed on basis of elastic scattering and breakup reaction of proton drip-line nucleus 17F on medium-mass 58Ni target. According to the kinematics, the distributions of scattered 17F as well as breakup 16O and proton were simulated by Monte Carlo simulation. The parameters of the experimental setup including geometry efficiency, covered solid angle, energy deposit and geometry relation of production 17F, 16O and proton etc., which were designed on basis of the simulation results. The coincident efficiency of 16O and proton is 4.7%±0.1%. It gives a basis for future experiment. Using this equipment a series of experiments will be developed in the internationally large facilities for science.
Curing method and temperature distribution of composites based on flexible electric heating film
LI Jinliang, GU Yizhuo, LI Min, WANG Shaokai, JIN Chao, ZHANG Zuoguang
2015, 41(9): 1714-1721. doi: 10.13700/j.bh.1001-5965.2014.0683
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Low-cost curing is a challenging task for composite manufacturing, especially for large-scale part. Vacuum assisted resin infusion (VARI) molding process was employed to fabricate carbon fiber/epoxy composite laminate. A curing method using flexible electric heating film (FEHF) was developed. The effects of lay-up type of FEHF and temperature cycle on the uniformity of temperature and curing degree of composite were studied. The results show that splicing overlaying FEHF has the most uniform temperature distribution with 11℃ maximum temperature difference at constant temperature stage. The temperature uniformity is improved by 26.7% and 38.9% compared to the cases using overlapping overlaying and interval overlaying FEHF, respectively. In addition, adding isothermal temperature platform is useful to reduce temperature difference during heating process, but the final temperature difference and distribution are the same as the case without adding isothermal temperature platform. By means of splicing overlaying FEHF, large antenna carbon fiber/epoxy composite reflector skin was fabricated, and the glass transition temperature of the reflector skin is over 80℃, and the reflector tolerance is 0.7 mm (r.m.s.). It demonstrates that FEHF is a feasible way for curing large composite part.
Identification of time-varying systems using multi-scale radial basis function
LIU Qing, LI Yang
2015, 41(9): 1722-1728. doi: 10.13700/j.bh.1001-5965.2014.0693
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A time-varying autoregressive model with time-varying coefficients was investigated to identify linear system parameters from nonstationary time series. The basis function of multi-scale radial basis function (MRBF) was employed, and the identification of nonstationary modeling problem was then simplified to a linear time-invariant modeling problem. Particle swarm optimization (PSO) algorithm was applied to search the optimal RBF scales for the estimation of time-varying system parameters. The basis functions of RBF can better estimate time-varying parameters with a variety of dynamic process because optimal different RBF scales with good local properties can be effectively adjusted by the PSO algorithm. One simulation example of second-order time-varying autoregressive model with time-varying parameters involved different waveform was presented to show the effectiveness of the proposed method. Compared with classical approaches of time-varying parametric estimations such as recursive least square algorithms and the expansion approach of Legendre polynomial basis function, the identification results of time-varying parameters can be more accurately estimated which validates the effectiveness of the proposed time-varying modeling method.
Design of actuator rate for flying wing aircraft
HE Qianlin, WANG Lixin
2015, 41(9): 1729-1735. doi: 10.13700/j.bh.1001-5965.2014.0631
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The actuator rate is one of the important constraints in designing flight control system. When the actuator rate is saturated, the disturbed aircraft or the aircraft under control may go into pilot induced oscillation (PIO) resulting in lowering the flying quality. The design method of limiting the actuator rate value for flying wing was built. The design examples of actuator rate for the triaxial main control surface of high-aspect-ratio flying wing aircraft were introduced. The effects of actuator rate limit on dynamic response characteristics of the aircraft and a combined parameter composed of aerodynamic derivative of aircraft, moment of inertia, and aspect-ratio were analyzed. The result indicates that for aircraft with high-aspect-ratio the requested actuator rate of roll control surface is the highest, later is in the pitch control and that of the directional control surface is the lowest. The research method and results can be used to guide the preliminary design of actuator and flight control system for flying wing aircraft.
Mission-oriented flying qualities criteria for high angle of attack aircraft
HOU Tianjun, GUO Youguang, WANG Lixin
2015, 41(9): 1736-1741. doi: 10.13700/j.bh.1001-5965.2014.0682
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The flying qualities evaluation of high angle of modern attack aircraft lacks of quantitative evaluation criteria. Based on the conventional flying qualities criteria, with mission-oriented flying qualities evaluation method, various flying by wire systems with different transfer function parameters were tested, by subjective evaluation method and objective evaluation method. Thus, quantitative longitudinal and lateral flying qualities criteria for high angle of attack aircraft were developed. The result of comparison between the conventional flying qualities evaluation criteria and the quantitative evaluation criteria for high angle of attack aircraft shows that with higher short period damping ratio and control anticipate parameter in longitudinal and higher roll mode time constant in lateral, the flying qualities for high angle of attack aircraft get better. Therefore, the developed criteria is more adaptable in evaluation the flying qualities for the high angle of attack aircraft. This new criteria could be used as a guideline when designing modern air fighters.
Preparation methods of PVDF film with electroactive phase by solution method
SUN Meiling, DENG Yuan, WANG Yao
2015, 41(9): 1742-1748. doi: 10.13700/j.bh.1001-5965.2014.0685
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Poly (vinylidene fluoride) (PVDF) films with electroactive phases were prepared by simple feasible solution crystallization method. The influences of various precursor solution concentrations, different stirring times and hot pressing process on the formation of electroactive crystal phase structures in PVDF were studied. The X-ray diffraction(XRD)and Fourier transform infrared spectroscopy (FTIR) were used to determine the crystal structure and analyze the formation mechanism of the electroactive phases in PVDF. The results indicate that the different precursor solution concentrations and different processing times have a great influence on the formation of electroactive phases in PVDF. It is easier to form β phase when the solution concentrations range from 7% to 10% and processing times between 2 hours and 3 hours. By using FTIR techniques, a maximum content of 81.3% for β phase is calculated in the situation that solution concentration is 7% and processing time is 2 hours. Hot pressing process plays an important role in the change of crystal structure, and this γ phase in PVDF films will transform into more dense β phase after hot-press process.
Standard trajectory guidance for CAV reentry based on fuzzy sliding mode control
HUANG Kangqiang, ZHAO Hui, REN Yang, CAI Yawei
2015, 41(9): 1749-1757. doi: 10.13700/j.bh.1001-5965.2014.0742
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Abstract:
For the question that the standard trajectory guidance was too sensitive to initial value of state and robustness was worse, a new standard trajectory guidance method based on the fuzzy sliding mode control was proposed. The robustness of sliding mode control was used to improve the adaptive capacity of guidance method, in order to definitely estimate the uncertain factors, the universal approximation property of fuzzy system was used to approach uncertain factors. Through analyzing the determinate principle of membership function combined with the characteristics of reentry process, the longitudinal guidance law was established, the simulation results validate that the master control law combined fuzzy approximation with state feedback is effective. And the lateral guidance law was designed based on the scheme mentioned before. Numerical simulation results show that this method can not only ensure a high precision but also improve the robustness of standard trajectory guidance law, and simplify the calculation process greatly.
MHD control of weakly ionized plasma jet flows
LUO Weidong, LI Feng, SUN Baigang, ZHAO Kai, XIONG Yiwei, WANG Changsheng
2015, 41(9): 1758-1764. doi: 10.13700/j.bh.1001-5965.2014.0668
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Abstract:
In order to study the feasibility of the thrust vectoring using magnetohydrodynamic(MHD) control weakly ionized plasmas at low temperature, the experimental method based on the MHD control plasma flow theory was put forward. We established a MHD flow control experiment platform of seeds (alkali metal salts) induced gas ionization to research jet deflection vector angle under the condition of different temperature and different magnetic direction, and explored the feasibility of the numerical study MHD control by user defined function (UDF)loading the MHD model to solve the three-dimensional Navier-Stokes equations. It is demonstrated that injecting low ionization energy seed into the combustor can induce gas ionization, forming magnetic liquid and achieving thrust vector control under magnetic field; the numerical simulation results and experimental results of plasma flow deflection are consistent, meaning numerical simulation MHD flow control has a certain credibility.

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