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2016 Vol. 42, No. 10

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Volume 42 Issue102016
2016 Year 42 Volume 10 Issue E-journal
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Application of synthetic aperture focusing technique to defect quantification for immersion ultrasonic testing
ZHOU Zhenggan, ZHOU Jianghua, ZHANG Kuanshuang, MA Liyin, SUN Guangkai
2016, 42(10): 2017-2023. doi: 10.13700/j.bh.1001-5965.2015.0601
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Among the common defect quantification methods for immersion ultrasonic testing, some are high cost while others have relatively large quantitative error. Given the problem, a new 6 dB drop defect quantification method based on frequency domain synthetic aperture focusing technique (FSAFT-DQM) was studied. The FSAFT imaging method for spherically focused transducer used by immersion ultrasonic testing was established. Experiments conducted on specimens containing either circular cylindrical cavities or flat bottom hole show that defect depth has little effect on FSAFT-DQM's accuracy; compared with 6 dB drop method, flat bottom hole's quantitative error of FSAFT-DQM drops from 71.9% to within 10.0% with step length below half-wavelength of transducer's center frequency and the error decreases from 17.2% to 5.6% by image interpolation algorithm with step length between half-wavelength and wavelength. The research results show that FSAFT-DQM improves the precision of defect quantification effectively.
Power dispatch of actuator of aircraft based on improved particle swarm optimization algorithm
SHI Shan, LIU Depeng, LI Chengmao
2016, 42(10): 2024-2030. doi: 10.13700/j.bh.1001-5965.2015.0708
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In view of the large amount of electric energy waste caused by the small system load of aircraft electromechanical actuator, an electromechanical actuator system is designed. In order to make the system work in the near optimal efficiency, according to the nonlinear relationship between motor efficiency and load factor, a mathematical power dispatch model is also established. An improved basic particle swarm optimization algorithm and an improved binary particle swarm optimization algorithm are proposed, which has better global optimization ability and faster convergence speed. The proposed method takes the improved binary particle swarm optimization for outer unit combination and improved basic particle swarm optimization algorithm for inner economic load dispatch．The minimum number of running system was used to deal with power balance constraints，which simplifies the operation; in order to solve the spare constraint, a priority table of the system was established, which effectively improves the capability of optimization．The results of simulation experiment show that the improved particle swarm optimization algorithm is effective for power dispatch of electromechanical actuator and it is conducive to the energy optimization of aircraft.
Influence of copper particle pollution on transformer oil kinematic viscosity
CHEN Bin, HAN Chao, LIU Ge
2016, 42(10): 2031-2037. doi: 10.13700/j.bh.1001-5965.2015.0628
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Copper particle pollution in the transformer oil is easy to affect the physical and chemical properties of the oil, and even leads to major accidents. On the basis of ISO4406：1999, 24 groups of samples of different pollution particles containing copper were made up, and the kinematic viscosity (40℃) of the samples was tested; the influence rules were achieved between copper particle pollution and oil kinematic viscosity. A simulation model was established between the different particle sizes, content copper particles in the sample and the kinematic viscosity of oil samples using partial least squares (PLS) method and support vector machine (SVM) method. The influence laws of the different particle sizes and content copper particle pollution on the oil kinematic viscosity were investigated. The results show that the oil kinematic viscosity decreases with the increase of copper particles' pollution degree. Copper particle pollution within the particle size range of 15-25 μm has obvious influence on the oil kinematic viscosity, and the oil kinematic viscosity increases with the increase of particle size. The correlation coefficient and root mean square error (RMSE) of the established SVM model are obtained to forecast the validation set, which are 0.962 6 and 4.597×10-5, respectively. This provides a new way to eliminate the experimental error, reduce the influence of artificial factors, and know the copper particle pollution impact on oil kinematic viscosity more accurately.
Effect of surface roughness on flow transition and heat transfer of turbine blade
LI Hongyang, ZHENG Yun
2016, 42(10): 2038-2047. doi: 10.13700/j.bh.1001-5965.2015.0659
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For the purpose of researching the effect of surface roughness on flow transition and heat transfer of turbine blade, a roughness modification method for γ-Reθ transition model was proposed through self-developed CFD code. Verification was conducted referring to the experimental data of flat plate and turbine vane cases, and satisfactory results were obtained. Taking surface roughness effect into consideration, No. 5411 working condition of Mark Ⅱ turbine vane was simulated and the result was analyzed in detail. Main conclusions are as follows: surface roughness has little effect on heat transfer of laminar boundary layer, while it has considerable effect on turbulent boundary layer. Compared with smooth surface, 5 μm equivalent sand roughness increases the suction side wall temperature by about 5.7 K in turbulent boundary layer, while 100 μm roughness increases the temperature by about 28.4 K, reaching an increase of 5%. Under low roughness degree, effect of shock wave on boundary layer transition process of suction side plays a dominant role, while after reaching a critical degree, effect of surface roughness abruptly changes the transition position, and the critical degree is around 150 μm in the current case.
Dynamic modeling and key error sources analysis of magnetically suspended sensitive gyroscopes
XIN Chaojun, CAI Yuanwen, REN Yuan, MIAO Cunxiao, ZHANG Liyuan
2016, 42(10): 2048-2058. doi: 10.13700/j.bh.1001-5965.2015.0650
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The mathematical model of a new magnetically suspended sensitive gyroscope (MSSG) with rotor of double spherical envelope surfaces is established based on rotor dynamics, and the key error sources of the gyro in sensing angular rate are analyzed theoretically. First, structural features and sensing principles of the MSSG are described. Second, the theoretical models of electromagnetic forces and moments acting on the rotor are built respectively. The influencing mechanisms of rotor translation and titling on its mechanical state are analyzed. Simulation results by finite-element method software ANSYS are basically in agreement with the calculated results. Finally, two key error sources of rotor asphericity and Lorentz force magnetic bearing process errors are analyzed, and the analytical expression of the disturbing torques has been constructed. Calculation results show that the rotor aspheric factors and the inhomogeneous magnetic field in Lorentz force magnetic bearing are the major factors inducing disturbance torques. The model provides a valuable theoretical basis for further research on optimization design and analysis of the MSSG.
Numerical study on nonlinear characteristics of Rayleigh-Taylor instability
KANG Ning, LI Yikai, HE Xu
2016, 42(10): 2059-2068. doi: 10.13700/j.bh.1001-5965.2015.0667
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The research on the nonlinear dynamics of Rayleigh-Taylor (RT) before mainly focused on deducing and measuring the constant penetration velocity of the bubble and had little detailed analysis of the nonlinear dynamic characteristics in the liquid spike region. An accurate numerical simulation of the single-mode RT instability was carried out based on the coupled Level-Set and Volume-of-Fluid (CLSVOF) interface capturing method. The detailed information on the pressure fields and velocity fields was obtained. In addition, the steady-state dynamic characteristics in the nonlinear development stage were analyzed. Simulation results show that a local maximum pressure point which is caused by the horizontal impinging flow with the action of inertial force appears at the root of the spike. The dependence of the different characteristic parameters of the steady flow on the initial perturbation wavelength and the inertial acceleration is determined. This work may extend the relevant classical theories of the low speed jet to the RT instability inducing atomization field.
Performance analysis on structural dynamics of EIDI system
LI Guangchao, HE Jiang, LIN Guiping
2016, 42(10): 2069-2074. doi: 10.13700/j.bh.1001-5965.2015.0609
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As an electromechanical de-icing system, electro-impulse de-icing (EIDI) technology has broad application prospect. In the present paper, structural dynamics characteristics of a simplified EIDI system consisting of coil and metal plate were numerically and experimentally studied. A finite element simulation model of an EIDI system was constructed, and the structural dynamics was analyzed by FEM software MSC/NASTRAN. The inherent characteristics (modal and frequency) as well as the transient response of the model were analyzed. The simulation was then validated by the experimental measurement. The structure dynamics characteristics of an EIDI model were studied. The maximum strain and displacement of the skin surface characteristic locations were evaluated with different capacitance, voltage and clearance between the skin and the coils. It is found that under the electro-impulse, the maximum displacement of the metal plate presents a saddle-like distribution. Increasing the capacitance and voltage will increase the impulse peak value and the structural deformation, and meanwhile, the strain of fixed location will be decreased.
Qualitative analysis of a food chain model with alternative prey
LI Ya, HU Hanyan, LIN Junyi
2016, 42(10): 2075-2081. doi: 10.13700/j.bh.1001-5965.2015.0642
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Studies in ecology show that alternative prey has important effects on predator-prey system in the aspects of system stability, species persistence, etc. For species at the intermediate level of a food chain, they are prey of top predators, while predating the bottom prey at the same time. Therefore, the effect of changes in intermediate predators' population on the system cannot be ignored. We set up a three-dimensional food chain model composed of top predator, intermediate predator and prey, assuming that the intermediate predator had alternative choice of prey. The existence and stability of the equilibria were derived through dynamical study of the system. The existence of Hopf bifurcation was explored in depth. The numerical simulations used the prey choice parameter as the bifurcation variable to study the possible Hopf bifurcations. The effect of alternative prey on the stability of the food chain system was derived through the theoretical and numerical results.
Multiple maneuvering targets tracking with unknown clutter density using PHD
YUAN Changshun, WANG Jun, ZHANG Yaotian, BI Yanxian, XIANG Hong
2016, 42(10): 2082-2090. doi: 10.13700/j.bh.1001-5965.2015.0623
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The jump Markov system (JMS) based on the random finite set (RFS) is an effective approach for multiple maneuvering targets tracking. However, these approaches assume that the clutter density is known and priori. This is unrealistic for real applications, as it is often previously unknown and its value may be time-varying as the environment changes. To solve this problem, this paper proposes a novel algorithm for multiple maneuvering targets tracking with the linear Gaussian models in the case of unknown clutter density. The proposed method models the clutters and actual targets based on the Gaussian mixture probability hypothesis density filter with unknown clutter rate (λ-GMPHD), which removes the need of the prior clutter density, describes the maneuvering process by the linear Gaussian JMS and derives a closed-form solution to the GMPHD recursion for multiple maneuvering targets tracking under unknown clutter density. The simulation results indicate that the proposed algorithm can accurately estimate the target number and corresponding multi-target states as well as the clutter density.
Structure design and performance analysis of a new buffering leg
ZHANG Ziqiang, CHEN Diansheng, CHEN Kewei
2016, 42(10): 2091-2098. doi: 10.13700/j.bh.1001-5965.2015.0626
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The leg structure is an important component to achieve good buffering performance for bionic locust jumping robot, so the structure design and analysis of the leg has important significance. In order to achieve the better landing buffering performance, a new buffering leg is designed based on the physiological structure of the locust's leg and the structure of bionic series buffering leg. After the kinematic and mechanical property analysis for the buffering leg, the structure parameters are analyzed and optimized according to the buffering performance evaluation principle, and the buffering performance of the new buffering leg and bionic series buffering leg, which are in the optimal state, is compared and analyzed. Compared with the bionic series buffering leg, the amplitude of the force that the new buffering leg is subjected to from the ground reduces by 25.3%, and the energy storage capacity increases by 34.6%. It provides a basis for the development of robot and other landing mechanism.
Fault diagnosis of particle filter nonlinear systems based on adaptive threshold
JIANG Dongnian, LI Wei
2016, 42(10): 2099-2106. doi: 10.13700/j.bh.1001-5965.2015.0611
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In view of the problem of actual nonlinear system that the traditional method is difficult to obtain reliable fault diagnosis, this paper uses the particle filter method and applies the logarithm likelihood function as evaluation index to study the nonlinear non-Gaussian system fault detection and fault isolation with the aid of adaptive threshold design. The selection of threshold value is the criterion for accurately judging system failure. This paper analyzes the statistical properties of residual error, determines the residual error statistical property of normal distribution, and designs an adaptive threshold method based on particle filter fault diagnosis, which reduce the miss alarm and false alarm ratios of fault diagnosis. Through the simulation example of non-constant temperature continuous stirred tank reactor, the accuracy and feasibility of this method in fault diagnosis are verified.
Simulation and experiment of event-triggered control for inverted pendulum system
YU Hao, OUYANG Li, HAO Fei
2016, 42(10): 2107-2117. doi: 10.13700/j.bh.1001-5965.2015.0631
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This paper investigates the event-triggered control for single linear inverted pendulum system from theoretical, simulation and experimental points of view to illustrate the feasibility and practicability of event-triggered control. Firstly, the parameter in event condition was designed based on linear matrix inequality, and the estimation of lower bound of inter-event times was provided. Secondly, the feasibility of theoretical results without quantization is illustrated by Simulink simulations. Finally, the influence of quantization was studied by experiments, which is quite negative on the system with model-based controller. According to the experiment results, the mixed event condition and zero-order-hold controller are more suitable for practical inverted pendulum system. They can guarantee the stability with efficient reduction of communication frequency, which reflects the potential practical value of event-triggered control.
Research for ground-based astrodynamical experiment for spacecraft relative motion
QI Yu, SUN Jun, SHI Peng, ZHAO Yushan
2016, 42(10): 2118-2129. doi: 10.13700/j.bh.1001-5965.2015.0637
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This paper proposes a method to build the spacecraft relative motion's ground-based astrodynamical experiment and figures out an approach to prove the reliability of ground-based experimental results. First, the spacecraft relative motion's ground-based astrodynamical experiment is carried out with the help of similarity theory, then the compensation method for making up the dynamical difference between space environment and experimental environment, after that the dynamical model of experimental disturbances is given for further counteract. Second, an experimental control method similar to space control system is designed for controlling the relative motion and compensating the inertia forces, and both the numerical simulation and experimental results show the effectiveness of control system. Finally, a similarity function used for measuring the similarity degree of experimental result will be helpful in proving the reliability of spacecraft relative motion's ground-based astrodynamical experiment. According to the results of simulation, the experimental scheme is available and reliable. This method is helpful for the development of ground-based astrodynamical experiment.
Cooperative path planning with reconnaissance duration time constraints
ZHU Qian, ZHOU Rui
2016, 42(10): 2130-2138. doi: 10.13700/j.bh.1001-5965.2015.0613
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When performing reconnaissance tasks, unmanned aerial vehicles (UAVs) keep reconnoitering the targets during different reconnaissance time for acquiring effective target information. It is assumed that UAVs fly in a straight line, which is suitable for better reconnaissance results during reconnaissance missions. A new simultaneous reconnaissance scheme was proposed by geometrical analysis for less than or equal to three reconnaissance mission overlapping. For the purpose of minimizing cooperative reconnaissance path length, modified hybrid particle swarm optimization algorithm with elitism mechanism was used to optimize the reconnaissance sequence, and the path planning was implemented between consecutive reconnaissance missions by Dubins path, with consideration of reconnaissance missions overlapping and reconnaissance duration time constraints. Simulation results demonstrate the effectiveness of the proposed method.
Production plan and integrated dispatch optimization of aircraft digital assembly
ZHAO Limin
2016, 42(10): 2139-2145. doi: 10.13700/j.bh.1001-5965.2015.0632
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The aircraft assembly is a long-time complex procedure with multiple steps. In consideration of quality and efficiency demands of aircrafts, it is necessary to reasonably plan the steps and schedule resources, such as devices and workers, in assembly process. Production planning and resource scheduling in aircraft assembly were analyzed in order to change the current inefficient assembly management state. A production planning method was proposed considering the characteristics of aircraft assembly and factors affecting assembly efficiency. As resource scheduling is relatively complex due to the existence of dynamic condition in assembly procedure, an integrated dispatch optimization method, based on ant colony algorithm, was developed for resource scheduling. Mapping relationships between structure chart and assembly cycle are defined to abstract the issue and give path reference for artificial ants, and the basic steps of assembly cycle mapping were also given. By optimizing the move path of artificial ants, resource scheduling could be optimized.
Tracking approach based on online multiple instance learning with weight distribution and multiple feature representation
YANG Honghong, QU Shiru, MI Xiuxiu
2016, 42(10): 2146-2154. doi: 10.13700/j.bh.1001-5965.2015.0644
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When most existing tracking algorithms are used, target drift problem is easy to occur under a complex environment such as occlusion, pose and illumination change. This paper proposes an online visual target tracking algorithm based on the framework of multiple instance learning (MIL) tracking. The MIL tracking algorithm cannot describe the target appearance accurately because it only uses single haar-like feature, adopts the same weight during the process of learning sample packages which contain positive samples and negative samples, and ignores the characteristic of different positive samples and negative samples having different importance to the sample bags. Therefore, this paper combines the multiple features to represent the target, constructs the classifiers, integrates the complementary characteristic of multiple features to the MIL online learning process, exploits the characteristics of complementary properties to establish more accurate target appearance model, and overcomes the problem of MIL tracking algorithm that it is insufficient to describe the target appearance. Simultaneously, the weights are assigned based on the importance of different positive samples and negative samples to the sample bags, and the tracking precision is improved. The experimental results show that the proposed algorithm can effectively handle video scene occlusions, illumination changes and scale changes with high accuracy and strong robustness. Compared with incremental learning of visual tracing (IVT), MIL and online AdaBoost (OAB) tracking algorithms, through the different challenging video sequences, the average center position error of the proposed algorithm in 5 groups of test videos is far smaller than the other three algorithms, which is only 10.14 pixel, while those of IVT, MIL and OAB algorithms are 17.99, 20.29 and 33.64 pixel, respectively.
Formation control-based adaptive update algorithm of HELLO message
HUANG Shaocheng, MA Linhua, RU Le, CAI Zhao, ZHANG Song, HU Xing
2016, 42(10): 2155-2161. doi: 10.13700/j.bh.1001-5965.2015.0645
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In the unmanned aerial vehicles (UAVs) formation ad hoc network, in order to solve the instability of formation control problem and reduce the large control overhead, both of which are caused by unreasonable update cycle of the position information, a formation control-based adaptive update algorithm of HELLO message is proposed. The algorithm employs the maximum tolerable delay which is deduced by the formation control stability theory for formation control, and combines with the formation stability theory to set an adaptive HELLO update cycle. The simulation results demonstrate that, compared with the fixed HELLO update algorithm, the proposed algorithm not only ensures the stability in the formation forming stage, but also maintains the link availability in the formation stability stage and effectively reduces the unnecessary control overhead.
Predicting filling mass of nitrogen in fire agent bottle based on Peng-Robinson equation of state with Wong-Sandler mixing rule
CHEN Mengdong, XIE Yongqi, GUO Xiangxiang, YU Jianzu, MA Wei
2016, 42(10): 2162-2168. doi: 10.13700/j.bh.1001-5965.2015.0661
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Nitrogen supplies driving force for the rapid discharge of fire agent in the fire extinguisher of the helicopter. Calculating the filling nitrogen and its mole fraction is one of the key issues to be solved in the design of fire extinguishing system of the engine nacelle in helicopter. Based on Peng-Robinson (PR) equation of state and Wong-Sandler (W-S) mixing rule, a prediction method to calculate the filling mass of nitrogen is proposed. To different filling cases of Halon1301 and HFC-227ea, the mass of filling nitrogen is obtained after three layers iteration relation and compared with the experimental and literature data. Also the change of pressure and mole fraction of nitrogen with temperature in the fire agent bottle is analyzed. The results show that, for the one-half and two-thirds filling conditions of Halon1301, the calculation errors of nitrogen are about 4.7% for one-half condition and 1.1% for two-thirds condition, and the calculation results are better than those of the PROFISSY and HFLOW software. For the one-half and two-thirds filling conditions of HFC-227ea, the calculation errors of nitrogen are about 4.3% and 2.3%, respectively. This method can be used in the design of aircraft fire extinguishing system.
Effects of debond size on compressional behavior of single-stiffened composite panels
JI Zhaojie, GUAN Zhidong, LI Zengshan, XUE Bin
2016, 42(10): 2169-2179. doi: 10.13700/j.bh.1001-5965.2015.0603
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In order to research the effects of debond size on buckling and post-buckling behavior of single-stiffened composite panel under axial compression, four types of I-section stringer-stiffened composite panels containing different debond defects were investigated by test and numerical simulation. Strain measurement and ultrasonic scan were conducted to monitor the deformation and defect propagation in the process of buckling and post-buckling. Finite element analysis(FEA) models were established based on ABAQUS. LaRC03 criteria were introduced for the judgment of intralaminar damage and cohesive elements were used to simulate the damage of the interface between stringer and panel. Buckling wave was introduced by initial geometric imperfection. Processes of buckling and post-buckling of specimens were simulated by the FEA models. The simulated results are coordinated with the test results very well. Failure process and mechanism of debond propagation were analysis and discussed based on the tested and simulated results. The results indicate that debond size has significant effects on the buckling and post-buckling behavior of the specimens instead of the final failure mode. Loading capacity decreases rapidly with the increasing debond size, which needs to be focused on in the damage tolerance design of stiffened composite structures.
Effect of forebody strake control technology on static directional stability
WEN Jing, WANG Yankui, DENG Xueying
2016, 42(10): 2180-2188. doi: 10.13700/j.bh.1001-5965.2015.0746
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When static directional stability of an aircraft is unstable, the typical effectiveness of the vertical tail and rudder to the yawing moment falls off because the vertical tail gradually becomes enveloped in the wake of wing and fuselage. Meanwhile, the forebody remains in the undisturbed flow field, and therefore the static directional stability can be enhanced though addition of forebody strake at the forebody. From the results of a series of experiments on forebody strake, it was found that the angle of attack for static directional stability from stable to unstable was increased by about 8° when chord of the forebody strake being 3% of the length of the fuselage was used. Moreover, as the sideslip angle became smaller, the more angle of attack for static directional stability from stable to unstable rose. The positive effects of forebody strake on static directional stability is due to the vortices of the forebody strake, which could affect the front part of fuselage and thus result in the reduction of negative pressure value on leeward side of forebody. Hence, the unstable yawing moment of cross sections of forebody also decreases, and the static directional stability increases.
Joint optimization of maintenance time and carrying spare parts for k-out-of-N system
ZHANG Yongqiang, XU Zongchang, HU Kaikai, HU Chunyang
2016, 42(10): 2189-2197. doi: 10.13700/j.bh.1001-5965.2015.0622
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Maintenance support of repairable warship k-out-of-N system during a task was researched. A method of how to trade off maintenance frequency, carrying spare parts and repair capacity was given. Taking the three parameters as decision variables and combined with the using and maintenance processes of k-out-of-N system, a joint optimization model of maintenance and carrying spare parts was established, in which operational availability was taken as a constraint condition and minimal maintenance costs as objective function, and repair initial condition, numbers of carrying spare parts and numbers of repair men were taken as decision variables. A modified marginal analysis algorithm was applied to solve the model through improving some drawbacks of the traditional one, and the drawbacks and corresponding improvements were also listed. Three tests were done: firstly, in order to verify the proposed model, a simulation for k-out-of-N system was implemented, and the results show that the absolute error of the proposed model is very small; second, using the optimal solution of enumeration as benchmark, performances of traditional marginal analysis algorithm and its modified algorithm were compared, and the results show that the modified algorithm has lower error and can enhance optimizing probability; third, the contribution of each modified item to marginal analysis algorithm was respectively tested.
Differential planetary gears based underactuated arm for capturing moving target
WANG Qingchuan, QUAN Qiquan, DENG Zongquan, HOU Xuyan
2016, 42(10): 2198-2205. doi: 10.13700/j.bh.1001-5965.2015.0660
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A novel underactuated robotic arm was proposed for moving target capturing, which has the capability of collision energy absorption. The proposed underactuated three-degree-of-freedom robotic arm has base joint, median joint and distal joint, and three joints are driven by two actuators. The base joint is driven by a single motor. The median joint and the distal joint employ a set of one-input-dual-output planetary gears to distribute power. Upon the occurrence of a collision in the process of capturing a moving target, part of the collision energy can be transmitted to the distal joint through the planetary gears as kinetic energy. Even though the time delay exists in the control system, the underactuated joints can also move cooperatively with the collided target through the mechanical passive response. Moreover, the impedance-based control algorithm of the underactuated robotic arm is presented for capturing the target after the collision. Capture experiment for moving target was carried out to confirm desirable characteristics of the proposed arm and feasibility of the control strategy.
Dynamic meshing characteristics analysis of spur gears based on LS-DYNA
LIU Yanxue, WANG Jianjun, ZHANG Tao
2016, 42(10): 2206-2213. doi: 10.13700/j.bh.1001-5965.2015.0607
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Based on contact finite element analysis theory and explicit calculation method, the dynamic meshing process of gears could been simulated with high-fidelity by using LS-DYNA software. The precise finite element analysis model of a meshed gear in one experiment is built, its dynamic meshing process in experiment is simulated by using the above methods, and the dynamic vibration characteristics of gears are obtained through studying the numerical results. The results of numerical simulation through LS-DYNA software have good consistency with experiment results. The gear with thin rim and thin web has more chances to produce structural vibrations and its rim vibration is more obvious. The gear meshing load shared by rim and web would increase when the thickness of rim and web are reduced. When the web is not located at the center of face width, the axial force will appear in spur meshing process. Besides, the conditions of gear resonance and the method for determining gear resonance state are summarized.
Damage identification method for functionally graded Timoshenko beams
DENG Hao, CHENG Wei
2016, 42(10): 2214-2221. doi: 10.13700/j.bh.1001-5965.2015.0618
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To acquire high precision damage identification method for functionally graded materials, based on the state space variable replacement, the transfer matrix of the functionally graded Timoshenko beam along the axial exponential distribution is obtained. By analyzing the influence of crack on the local flexibility of structure, the contribution of the crack to the local stiffness of the structure is simulated by the torsion spring. The surface crack transfer matrix of functionally graded Timoshenko beams is established. And the theoretical model of multi-span beam under complex boundary conditions is derived. In this paper, the nonlinear equations are transformed into a single objective function optimization problem. The generalized Lagrange algorithm and differential evolution algorithm are combined to identify the damage of the structure. Computational examples show that the proposed algorithm has the characteristics of high precision and fast convergence and is suitable for damage identification of multi-damage model under complex boundary conditions.
Mathematical simulation and assessment of airworthiness compliance of climb gradient during takeoff of civil aircraft
MENG Xiangguang, WANG Lixin, LIU Hailiang
2016, 42(10): 2222-2230. doi: 10.13700/j.bh.1001-5965.2015.0617
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The climb gradient along the takeoff path reflects the civil aircraft's ability of flying over the ground obstacles to reach the safe height. According to the requirements of airworthiness regulations for takeoff procedure and climb performance, an airworthiness compliance assessment method of climb gradient with one engine inoperative was proposed based on the pilot-in-loop flight simulation and calculation. A nonlinear aircraft model, a landing gear model and pilot control models were established and assessment criteria were set up. A simulation task of takeoff with one engine inoperative as well as the control procedure of the pilot was designed. The climb gradient of various states was assessed based on the closed-loop digital flight simulation. This method can be applied to the preliminary design phase of civil aircrafts to provide support for the configuration design and the determination of takeoff weight limit, and offer theoretical references for flight tests of climb performance with one engine inoperative.
Solution of output feedback μ controller based on LMI
LI Zhe, GAO Yuanlou, LI Peilin
2016, 42(10): 2231-2237. doi: 10.13700/j.bh.1001-5965.2015.0556
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D-K iteration is the main implementation method of structured singular value (μ), which has problems of strict solution conditions and poor system suitability. Aimed at overcoming limitation shortage of D-K iteration application, the linear matrix inequality (LMI) was proposed to improve D-K iteration, which uses Schur's lemma and bounded real lemma to get LMI criterion of upper boundary of structured singular value, and elimination method was developed to obtain H∞ controller in output feedback system. Based on improvements related to LMI, D-K iteration was adopted to solve μ controller in output feedback system, which avoids solution limitation of Riccati equation and influence by selection quality of some uncertain parameters, enhances its applicability in general system, and improves the solution efficiency of controller in output feedback system. Numerical results show that this method gets not only robust stability but also robust performance superior to the traditional D-K iteration of output feedback system.
Phenomenological study of double-beta decay half-lives
XIAO Yang, GENG Lisheng
2016, 42(10): 2238-2242. doi: 10.13700/j.bh.1001-5965.2015.0604
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In order to study the physical interpretation of a phenomenological formula which can well describe the available experimental data and connects double-beta decay half-lives and decay energy, a convincible explanation for the source of the inverse relationship between the logarithm of the double-beta decay half-life and the decay energy in the phenomenological formula is proposed based on the analyses of double-beta decay phasespace factor. In addition, based on shell model theory, a slight modification to the phenomenological formula is proposed, which can further improve the description of the experimental data. The results indicate that double-beta decay phasespace factor is the source of the inverse relationship between the logarithm of the double-beta decay half-life and the decay energy in the phenomenological formula. By using the new formula, the average deviation between theoretical and experimental values of the logarithms of the double-beta decay half-lives reduces from 0.486 to 0.408.
Effect of chloride ion and temperature on corrosion of aluminum alloy in coolant
CHEN Xin, TIAN Wenming, LI Songmei, GAO Shulun, LIU Jianhua
2016, 42(10): 2243-2249. doi: 10.13700/j.bh.1001-5965.2015.0627
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Abstract:
The effect of chloride concentration and temperature on the corrosion of aluminum alloy in the stimulated coolant was studied by potentiodynamic polarization and electrochemical impedance spectra. The surface characterization of aluminum alloy after polarization was featured by metallurgical microscope and scanning electron microscope. The results show that chloride ions would be involved in the film formation, and decrease the stability of the film. Under a certain temperature (30℃), when the concentration of chloride ion is higher than 0.01 mol/L, the adsorption of intermediate was significant. Inductive loop emerged in the low frequency part of Nyquist diagram, and pits initiate. With the increase of chloride ion concentration (more than 0.01mol/L), the corrosion resistance of aluminum alloy decreased. With the increase of temperature, as the resistance of anodic and cathodic reaction decreased, the rate of anodic and cathodic reaction increased, and corrosion rate increased. When the temperature rose, the dominant effect of diffusion in corrosion process was weakened due to the content of oxygen decreased，the adsorption effect of intermediate was enhanced and inductive loop emerged in the low frequency part. Temperature affects the size of single pit and facilitates the growth of pits.
Feature extraction of precession targets based on wideband and narrowband micro-Doppler information
ZHAO Shuang, LU Weihong, FENG Cunqian, HE Sisan, LI Jingqing
2016, 42(10): 2250-2257. doi: 10.13700/j.bh.1001-5965.2015.0649
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Micro-motion feature is one of the crucial features used for ballistic target recognition. Aimed at the model of cone-shaped target, a novel algorithm based on hybrid-scheme radar network combining wideband radar with narrowband radar is proposed to extract the micro-motion parameters. First, on the basis of analyzing the micro-Doppler change rule of the equivalent scattering centers on the precession cone-shaped target in detail, each scattering center in different system radar echoes is matched and identified by utilizing the micro-Doppler sum-difference ratio. Second, the associated systems of equations of micro-Doppler information are established, and parameters including the precession angle, radius of undersurface and height of cone-shaped target are extracted jointly. Furthermore, comparative study on the relationship between parameter estimation accuracy and error change of curve parameter extraction is made. Finally, the simulation results show that even though errors occur in curve parameter extraction, the parameter estimation accuracy of target is still enough.
Short-frame prior scheduling with weighted round robin transmission strategy in AFDX terminal system
YANG Jingzhong, GE Hongjuan, WU Shuang, XU Yuanyuan
2016, 42(10): 2258-2264. doi: 10.13700/j.bh.1001-5965.2015.0664
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A new scheduling strategy of terminal system virtual link (VL) is put forward, which is based on the short-frame prior scheduling and integrated with weighted round robin (WRR).The new approach ensures the priority of the important short-frame and balances the delay upper bound of other different priority signals. Based on the theory of network calculus, the paper derives the delay upper bound of different virtual links through the new combinatorial scheduling strategy and researches the relation among the maximum delay upper bound, weight ratio and frame length. The Avionics Full Duplex Switched Ethernet (AFDX) network model based on OPNET is established, and the terminal system data transmission delay under the three scheduling strategies is simulated and compared. The results show that the new scheduling strategy can reduce the maximum delay time of short-frame virtual link, and improve the processing bandwidth of relatively important task in long-frame data transmission. It is feasible and applicable to airborne system network with more short-frame and different priority data flow.
Precise measurement of PN code phase by accumulative least square method
ZHANG Bo, GUO Ying, QI Zisen, ZHANG Dongwei, ZHANG Kunfeng
2016, 42(10): 2265-2270. doi: 10.13700/j.bh.1001-5965.2015.0620
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Abstract:
As least square (LS) method, which is applied to precise measurement of PN sequence phase in high-accuracy, is limited in narrow range condition of coarse synchronization, it is difficult to satisfy the needs of practical project. A novel realized structure of accumulative LS method for PN sequence phase measurement is presented. According to the characteristic of phase discrimination curve, the accumulative maximal value and minimal value of the phase discrimination curve are viewed as the characteristic reference position, and the samples between the maximal value and the minimal value are fitted by LS method. A high-accuracy measurement of the PN sequence phase can be achieved in half-width of the chips under the condition of coarse synchronization. It is proved that the characteristic of phase discrimination is linear in theory, and can use accumulative LS method suitably. The simulation results indicate that the proposed method has wider range of coarse synchronization and higher measurement precision.

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