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2016 Vol. 42, No. 11

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Volume 42 Issue112016
2016 Year 42 Volume 11 Issue E-journal
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Design and verification of vacuum environmental simulation device for lunar surface drilling
DING Xilun, LIU Shuting, ZHANG Tao
2016, 42(11): 2271-2278. doi: 10.13700/j.bh.1001-5965.2015.0669
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The third stage of China's lunar exploration project presented the task of drilling samples of lunar soil over 2 m deep, which motivates us to study the thermal characteristics during the drilling process. To support this research, a lunar surface vacuum environmental simulation device was designed. According to the requirements of the drilling test, a three-part and dismountable vacuum chamber was designed which was pumped from the bottom of the chamber. Considering the lunar soil simulant's size and rapid vacuum acquirement requirements, a cribriform lunar soil container with multi-layer filtrations was designed. Based on the demand of repeatable drilling tests in the same condition, the slewing mechanism with missing teeth gear was designed which allowed external operation. Finally, a three-stage diffusion pump set was selected according to the vacuum and dust tolerance requirements. Experimental results show that the vacuum of this simulation device reaches to 10-1 Pa without lunar soil inside, and reaches to 7 Pa with lunar soil inside.These performance indicators satisfy the vacuum requirements of the drilling test. The outgassing amount curve of simulated lunar soil is obtained by measuring the variation of vacuum with time during the pumpout process, which is valuable for the lunar soil vacuum system's application.
Numerical simulation and parameter optimization of seal property of bidirectional rotating cylinder gas film
MA Gang, YANG Weiru
2016, 42(11): 2279-2288. doi: 10.13700/j.bh.1001-5965.2015.0682
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Based on cognizing of advantages of cylinder gas film seal system, this paper proposes a new bidirectional rotating cylinder gas film seal system with inverted T interface structure and double-groove interface structure. It establishes mathematical model and numerical analysis model of the bidirectional rotating cylinder gas film with inverted T interface structure and double-groove interface structure based on finite element method. It develops calculation program about pressure distribution, steady and dynamic property of the gas film, and multidimensional parameter optimization of groove structure on the basis of finite element method on the VC platform. It realizes calculation and analysis of pressure distribution, property of the seal system and structural parameter optimization design. It builds physical models and finite element models of the inverted T cylinder gas film with different average thickness in Gambit. And then, this paper carries out numerical simulation of the gas film under different rotational speed through FLUENT. The simulation results of commercial software are consistent with numerical results of the self-developed program, verifying the correctness of the developed program. It calculates and compares steady and dynamic properties of two kinds of interface structures, and seal performance of inverted T type is better than double-groove type under the same design conditions, which provides reference for selection model of seal system. The calculation program of genetic algorithm-particle swarm optimization (GAPSO) has guiding significance for the design of groove parameters.
Control strategy of traction control system for four-wheel drive vehicle
JIANG Libiao, QIU Huachuan, WU Zhongwei, LIU Wei, CHENG Cheng
2016, 42(11): 2289-2298. doi: 10.13700/j.bh.1001-5965.2015.0689
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Aimed at the problem of the vehicle dynamics and lateral stability of four-wheel drive vehicle, the integrated traction control strategy based on a new method of target slip ratio calculation and correction was proposed. First a mathematical model describing the main components of vehicle system was established. In view of different conditions, the traction control system integrated control strategy, which is based on the engine throttle valve control, inter-axis torque distribution control and driving wheel braking-force active control, was built by using fuzzy PID control technology. In the aspect of selection in tire target slip ratio, a lookup method of the optimal longitudinal slip ratio was proposed, and real-time correction of target slip ratio was carried out according to the vehicle velocity and tire slip angle. Finally, research on off-line simulation for four-wheel drive vehicle traction control system in typical conditions was completed by using MATLAB/Simulink software. The results show that the proposed traction control strategy can effectively inhibits the driving wheel from over slipping, fully use the road adhesion conditions and improve the vehicle longitudinal driving stability.
Multiple reference consistency check algorithm for sea-based JPALS
FENG Tao, MAO Xia, SONG Cheng
2016, 42(11): 2299-2305. doi: 10.13700/j.bh.1001-5965.2015.0672
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According to the characteristics of mobile carrier reference station, a novel multiple reference consistency check (MRCC) algorithm for the sea-based joint precision approach and landing system (JPALS) is proposed. First, the original pseudorange and carrier phase measurement of each reference station are converted to the ship reference point by using the attitude information from the inertial navigation system on the ship and the ship size measurement data. Then, the wide lane ambiguity of each reference station is obtained by filtering the converted geometry-free combined observables. Finally, the B-values of these converted measurements for each reference station are calculated. Under no fault condition, the B-values of these measurements distribute in a certain range, but the B-value may exceed the threshold in the case of reference station fault, severe multipath or radio interference. Observation data were collected by simulation experiment and then the B-values and their threshold were computed. The results show that generally the B-values of these observables are very small, but when any abnormal from some measurement occurs, it can be detected that the B-value exceeds their threshold. The algorithm satisfies the MRCC integrity risk requirements of the sea-based JPALS.
Tensile behavior of scarf joints after impact in different locations
NIE Hengchang, XU Jifeng, GUAN Zhidong, LI Zengshan, JI Zhaojie, TAN Riming
2016, 42(11): 2306-2320. doi: 10.13700/j.bh.1001-5965.2015.0694
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The damage introduced by low-velocity impact is a threat to composite bonded joints. Scarf joints were impacted in three different locations of joint areas and then tensile test after impact was conducted. Finite element models of impact and tensile after impact of scarf joints were established respectively. The test results demonstrate that when impact occurs at the back face of tips, the indentation depth is the largest and the tensile strength after impact is the lowest. When impact occurs at the middle of joint area, the indentation depth is the smallest and the tensile strength after impact is the highest. When impact occurs at the front face of tips, the indentation depth and tensile strength are medium. The finite element analysis results show that the major cause of structural failure is the extensive expansion of adhesive damage and fiber cracks.
Application of singular spectrum analysis to failure time series analysis
WANG Xin, WU Ji, LIU Chao, NIU Wensheng, ZHANG Hua, ZHANG Kui
2016, 42(11): 2321-2331. doi: 10.13700/j.bh.1001-5965.2015.0712
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Due to significant industrial demands toward flight safety andairplane maintenance quality, improving airplane's reliability in usage stage has become an important activity and the research domain is rapidly evolving. In this paper, eighteen years' field data gathered from the maintenance phase of two Boeing 737 aircrafts are prepared as time-to-failure series. Then singular spectrum analysis (SSA) is usedto cope with this data for modeling and forecasting. Furthermore, a SSA parameter optimization algorithm is proposed by minimizing root mean square error (RMSE) of the prediction results. Based on this,a broader method of model combination is raised by utilizing different time series models to the components obtained from SSA decomposition, which represent trend, period, residuals, etc.The combination model and detailed algorithm are designed. The experimental results are compared with those of cubic exponential smoothing (Holt-Winters) and autoregressive integrated moving average (ARIMA), which verifies that the proposed models and algorithms have better fitting and prediction accuracyin failure time series analysis.
Stable cluster-based routing protocol for mobile Ad Hoc networks
HUANG Jinke, FAN Xiaoguang, WAN Ming, ZHUO Zhenfu, YANG Yongjian, CHEN Shaohua
2016, 42(11): 2332-2339. doi: 10.13700/j.bh.1001-5965.2015.0720
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The dynamic topology of a mobile Ad Hoc network poses a real challenge in the design of clustering routing protocol. And as an essential technique of clustering routing protocol, clustering of nodes provides an efficient method for establishing a clustering structure in mobile Ad Hoc networks. In this paper, we designed a stable clustering algorithm and a corresponding clustering routing protocol for large-scale mobile Ad Hoc networks. Each cluster is composed of a clusterhead, several cluster gateway nodes, several cluster guest nodes and other cluster members. The proposed routing protocol uses proactive protocol between nodes within individual clusters and reactive protocol between clusters. Simulation results show that the proposed clustering algorithm improves the stability by decreasing the clusters' number and nodes' switch times between clusters. And the clustering routing protocol provides low average end-to-end delay, normalized routing overhead and high packet acceptance ratio compared with some existing routing protocols.
Virtualized GPU computing platform in clustered system environment
YANG Jingwei, MA Kai, LONG Xiang
2016, 42(11): 2340-2348. doi: 10.13700/j.bh.1001-5965.2015.0731
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A virtualized GPU computing platform is proposed for clustered systems, which are often equipped with GPUs in some nodes. All GPUs in system are uniformly abstracted as virtualized ones in a commonly accessed resource pool. Legacy GPU programs can execute on the virtualized GPU computing platform without any modification and any free virtualized GPU in the common resource pool is available to it, which relieves the burden of MPI programming. The platform frees programs with the limit of GPUs in local node and makes it possible for them to access any available GPU in distributed nodes, leading to higher system utilization and throughput. Based on pipelined communication, the run-time overhead and inter-node transmitting latency in virtualized GPU computing platform are hidden by intra-node memory copying and GPU computing. Compared with the non-pipelined communication, the total transmission latency is decreased by approximately 50%-70%. It results in a comparable performance with intra-node local data transmission.
Analysis on influence of rotor/empennage aerodynamic interaction on helicopter trim characteristic
TAN Jianfeng, WU Chao, WANG Haowen, LIN Changliang
2016, 42(11): 2349-2357. doi: 10.13700/j.bh.1001-5965.2015.0770
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Unsteady aerodynamic interaction of rotor and empennage is the core content of helicopter trim model and flight dynamic model. The rotor/empennage aerodynamic interaction effect was considered indirectly through rotor inflow or induced velocity of rotor wake in classical trim method. However, the nonlinear airload induced by the unsteady aerodynamic interaction was not fully taken into account, and it is then difficult to reflect the influence of the rotor/empennage aerodynamic interaction on the trim characteristic. Therefore, based on unsteady panel/viscous vortex particle method, a rotor/empennage unsteady aerodynamic interactional model is established by adding an unsteady pressure term into empennage panel which is induced by unsteady interaction of rotor and empennage wake, and the nonlinear airload on empennage is simulated. The helicopter trim characteristic analysis method under rotor/empennage aerodynamic interaction is then established by coupling with helicopter trim method based on GA/LM hybrid optimization. The control of rotor and attitude of fuselage of UH-60A are simulated and compared with the flight test data to validate the present method. Compared with the result of the classic helicopter trim method in which rotor/empennage aerodynamic interaction is indirectly accounted through induced velocity, it is shown that the increase of longitudinal control and fuselage attitude is not simulated by the classic helicopter trim method; however, the phenomenon is captured by the present method, and is consistent with the tested characteristics of OH-6A, EH-101, etc. The influence of empennage's type on helicopter trim characteristic is then analyzed, and it is shown that the increase of rotor longitudinal control is great with low-set empennage, forward-set empennage in low-speed forward flight, and high-set empennage in high-speed forward flight. Start-set empennage for right revel rotor is useful to decrease the increasement of longitudinal control and fuselage attitude in low-speed forward.
Safety requirements analysis method based on control characteristics of scenarios
ZHU Danjiang, YAO Shuzhen, TAN Huobin
2016, 42(11): 2358-2370. doi: 10.13700/j.bh.1001-5965.2015.0757
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Safety requirements are critical to ensure the system safety. With the increase of system complexity and coupling degree, it becomes more difficult to analyze and extract the safety requirements. We construct the variables effect graph which describes the relationships among system variables in the control process through control structure and process analysis modeling for the system scenario. Then we present a safety requirements analysis method. By using the method, the control process is analyzed with variables effect graph etc., and the hazardous control actions based on the systems-theoretic accident model and process (STAMP) are created, and thereby the system safety requirements are generated. The experimental results show that our method is effective on correctness and consistency.
Life analysis method for products based on failure behavior models
ZHA Guoqing, JING Hailong, CHEN Yunxia, KANG Rui
2016, 42(11): 2371-2377. doi: 10.13700/j.bh.1001-5965.2015.0739
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With the situation that traditional reliability engineering methods cannot meet the demand of design and analysis for the products with high reliability and long life index, this paper considers the uncertainty of inner and outside factors which cause the life dispersion, and on the basis of product functional models or digital prototype models, with the failure behavior model of products, a method is proposed to conduct the life analysis for products with long life index. The dispersion of inner and outside parameters can be expressed by the probability density function and obtained by analyzing the actual use and production conditions. Thus the life characteristics of products obtained with this method can remedy the disadvantage that the reliability prediction method based on physics of failure cannot reflect the actual normal use conditions of the products.
Research of sustainable feedstock for future alternative aviation fuels
ZHAO Jing, GUO Fang, A Lusi, YANG Xiaoyi
2016, 42(11): 2378-2385. doi: 10.13700/j.bh.1001-5965.2015.0676
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Based on the whole life-cycle analysis, the feedstock sustainability has been evaluated for alternative aviation fuels. Eight sources, including coal, natural gas, algae, jatropha, soybean, palm, rapeseed and camelina, have been compared with petroleum-based aviation fuel in energy consumption, fossil fuel consumption, water consumption, greenhouse gas (GHG) emissions, and PM10 and PM2.5 emissions. The whole life cycle concluded feedstock production, fuel refining and combustion application. In the first stage of feedstock production, energy and emissions comprise the influence of infrastructure construction. The fuel refining process considered the emissions caused by nested electricity utilization. This paper provides theoretical and data support to assess the sustainable feedstock for alternative aviation fuel. The results indicate that compared with petroleum-based one, the GHG emissions of biomass all decrease in feedstock production stage, and soybean conducts the minimum GHG emission. Jatropha-based fuel gives the highest PM10 and PM2.5 emissions as the result of high fertilizer input. During the fuel refining stage, coal-based Fischer-Tropsch aviation fuel performs the highest energy consumption and GHG emission. Among eight feedstocks, coal-based Fischer-Tropsch aviation fuel shows the highest GHG emission in the whole life cycle, while algae-based aviation fuel shows the lowest GHG emission and followed by soybean. Owing to non-arable land and non-competition with food, algae are very promising as the sustainable feedstock for alternative aviation fuel in the future.
Experiment of cavity and trajectory characteristics of oblique water entry of revolution bodies
SONG Wuchao, WANG Cong, WEI Yingjie, XU Hao
2016, 42(11): 2386-2394. doi: 10.13700/j.bh.1001-5965.2015.0690
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Studies of the oblique water entry of revolution bodies are conducted. By the experiment of revolution body velocity water entry with different velocities and angles, cavity evolution on revolution bodies is discussed, including formation, development and pinch-off of oblique entry. The influence of water entry velocity and angle on the cavities, revolution body velocity, pitching angle and drag coefficients was experimentally obtained. The experiments show that at the moment when the cavity is pinched off, the length and largest diameters of the cavity, and the depth of the closure point are larger as the velocity of revolution bodies increases. The cavity closure time increases slightly with the increase of revolution body velocity. When the velocity of revolution bodies is larger, the pitching angle and angle velocity are smaller. With the increase of water-entry angle of revolution bodies, the diameter of the cavity and the velocity of revolution bodies gradually become smaller, but the drag coefficients become larger.
Design of array with multiple interleaved subarrays based on subarray excitation energy-matching
LI Longjun, WANG Buhong, XIA Chunhe, LIU Xinbo, CAO Shuai
2016, 42(11): 2395-2402. doi: 10.13700/j.bh.1001-5965.2015.0680
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The shared aperture array antennas with multiple interleaved subarrays is an effective solution of the design of multi-functional array antennas. A new method for interleaving multiple subarrays based on excitation energy-matching is proposed in this paper. In light of the Fourier transform mapping between the element excitations and array factor of uniform linear array, the spectrum of the array factor is first obtained by fast Fourier transform (FFT) and its excitation energy distributions are analyzed thoroughly. The element positions are then selected carefully in a staggered way which ensures that the uniform distribution of the excitation energy of the array antenna elements and the similar patterns can be obtained. Then the peak sidelobe levels (PSL) of the subarrays are reduced with the iterative FFT algorithm. Futhermore, the design of shared aperture antenna array with low sidelobe levels and same performance is achieved. Some numerical simulations and experiments demonstrate that the interleaved subarrays generated from the proposed method possess many favorable characteristics, such as, reduced computational burden, high aperture efficiency, lower PSL than the random thinned array, and perfect matched patterns. By controlling the mainbeam direction, the multi-functional array antenna can be easily designed with multiple beam lobes.
Flow field structure and fluid dynamic characteristics of semi-closed cylinder water-entry
LU Zhonglei, WEI Yingjie, WANG Cong, SUN Tiezhi
2016, 42(11): 2403-2412. doi: 10.13700/j.bh.1001-5965.2015.0711
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Numerical simulation for the vertical water-entry process of an end-closed cylinder shell was performed based on reynolds-averaged Navier-Stokes equations. The results of pressure and velocity contours, features of cavity wave and closure, rule of mass flow rate into the cavum, and hydrodynamic change rule were achieved. The influence of air compression-expansion on flow field structure and fluid dynamics was analyzed. The results show that water flow passing the open end in and out of cavum is synchronized with air movement; fluctuant pressure source appears at the open end of shell, leading to periodic pressure and velocity distribution; the expansion diameters of different axisymmetrical cavity sections are inversely proportional to speed of water into cavum; an air vortex generates in cavity, periodically enters and discharges from cavity, and prevents cavity closing; fluid dynamics present fluctuation characteristics whose frequency is equal to that of air, and the amplitude is in proportional relationship with that of air compression-expansion. The air compression-expansion motion in the progress of water-entry by the open cavum structure produces periodic perturbation of flow field and fluid dynamics, reduces impact of water-entry, and enhances the stability of cavity and motion of the an end-closed cylinder shell.
Design of major time frame for ARINC 653 partitioned real-time systems
TAN Longhua, DU Chenglie
2016, 42(11): 2413-2422. doi: 10.13700/j.bh.1001-5965.2015.0726
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The ARINC 653 standard for integrated modular avionics defines that the system adopts intra-partition scheduling and inter-partition scheduling. As specified by the standard, local scheduling is specified by partition application designers and partitions are scheduled statically by the major time frame. How to design the major time frame to schedule partitions is a problem in the phase of partition integrating. The bounded delay parameters of a partition are derived based on schedulability analysis and converted to parameters which can be used for partition scheduling afterwards. An algorithm referred to as the minimum number of windows fit-best fit (MFBF) is proposed to reduce the number of partition switches when partitions are scheduled to generate the major time frame. The proposed process from partition parameters deriving to inter-partition scheduling completes the design of the major time frame from several partition applications. Experimental results show that the MFBF algorithm reduces the number of partition switches effectively.
Performance analysis of circuit fault self-repair strategy based on EHW and RBT
ZHANG Junbin, CAI Jinyan, MENG Yafeng
2016, 42(11): 2423-2435. doi: 10.13700/j.bh.1001-5965.2015.0742
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The method of improving the reliability of the electronic systems based on redundant fault-tolerant technology is limited in aerospace, deep sea and some specific fields. Then the fault self-repair strategy based on evolvable hardware (EHW) begins to be researched. However, there are some kinds of disadvantages, such as large evolvable circuit scales, slow evolvable speed, finite ability of fault self-repair and so on, for which a novel fault self-repair strategy based on EHW and reparation balance technology (RBT) had been proposed in previous research. The contrast analysis is carried out in three aspects, which are the ability of fault self-repair, the speed of fault self-repair and the consumption of hardware resource. Compared to the conventional fault self-repair strategy based on EHW, the fault self-repair strategy based on EHW and RBT, which has flexible methods of troubleshooting, repairs many fault types, reduces the scales of evolvable circuit, decreases the evolvable time, and increases the speed of evolvable circuit. The consumption of hardware resource can be controlled. Its feasibility and validity have been demonstrated. The proposed fault self-repair strategy has important engineering application significance.
Range extension design on superfluid gyroscope based on overlap factor optimization
ZHAO Yulong, REN Yuan, SHEN Huairong
2016, 42(11): 2436-2444. doi: 10.13700/j.bh.1001-5965.2015.0747
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Aimed at the limited range caused by single value interval of amplitude-angular velocity of heat driven double weak link superfluid gyroscope whose working curve is periodic, a superfluid gyroscope range extension method based on overlap factor optimization is proposed. First, on the basis of range limiting mechanism of gyroscope, the amplitude-locking range extension scheme is designed. Second, considering the relationship between hot phase and heating delay, with the concept of overlap factor, a genetic optimization method based on overlap factor is proposed to optimize the gyroscope amplitude-locking control parameter. Through indirect coding the left width of triangle membership function, the fuzzy linear membership function is optimized to find the best parameters of amplitude-locking system under the premise of avoiding adjacent membership function with no overlap or too much overlap. Finally, comparison results between this method and traditional P method show that the film amplitude of superfluid gyroscope can be locked to the expectations quickly and stably by this method, which extend the range of the superfluid gyroscope with measurement accuracy guaranteed.
Efficient ground noise prediction method based on secondary noise radiation model
WANG Fei, SHI Yongjie, XU Guohua
2016, 42(11): 2445-2453. doi: 10.13700/j.bh.1001-5965.2015.0756
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An efficient ground noise prediction method for the analysis of helicopter noise in flight based on the secondary noise radiation is developed. The method to predict the aerodynamic force and aeroacoustic characteristics based on the free-wake/FW-H, the noise propagation model that can take the effects of atmosphere absorption, ground absorption and reflection on noise radiation characteristics into account, as well as ground noise computation model are included in this method. In order to improve computational efficiency, the secondary sound radiation model built on the hypothesis of compact source is introduced between the noise source computation and noise radiation. To achieve the real time simulation of ground noise, the noise radiation model database is built according to the idea of parametric modeling. The efficiency and effectiveness are illustrated through the comparison of computed results and compute time with the direct computing method for AH-1 rotor. Furthermore, the effects of atmosphere and ground on noise radiation as well as ground noise characteristics are analyzed with this method.
Influence of pitch manipulation modes on controllability and stability of autogyro
LIN Qing, CAI Zhihao, YAN Kun, WANG Yingxun
2016, 42(11): 2454-2465. doi: 10.13700/j.bh.1001-5965.2015.0776
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To study the influence of two manipulation modes on flight dynamics characteristics of autogyro, an example autogyro UAV was chosen and modeled based on closed-form blade element method. Then the differences of the two modes in trim results, stability and handling characteristics were analyzed in the whole speed envelope. The results indicate that each manipulation mode has its advantages and disadvantages:for the rotor manipulation mode, the trim pitch angle has little change and the phugoid mode is stable, but the spiral mode is unstable in the whole envelope. For the elevator manipulation mode, the spiral mode is stable at relatively high speed and the attainable pitch moment is larger, but the trim angle of attack is negative at high speed and the speed static stability is negative. Then two prototype autogyro UAVs were assembled and flight-tested for the two manipulation modes respectively. The autorotation of the main rotor during the whole flight were analyzed. Attitude control laws were designed and flight-tested for the two prototype UAVs, which both achieve attitude tracking relatively well. Finally, the model of the autogyro UAV was validated with the flight test data.
Interfacial stability of regenerated moulds against molten ZTC4 alloy
CHAI Lianjing, CHENG Xu, WU Guoqing, WANG Hong, NAN Hai
2016, 42(11): 2466-2471. doi: 10.13700/j.bh.1001-5965.2015.0683
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Aimed at the effect rules of several typical metal ions from reclaimed shells on contaminating casting surface, with the method of adding metallic elements such as Al, Nb and Mn to shell materials used to actually cast ZTC4 alloy (Ti-6Al-4V), this study analyzed the influence of different residual metals in casting process on casting surface quality, ceramic/titanium alloy interaction compositions, microstructure morphology and micro-hardness, and discussed the impact of residual casting metal in recycled mould materials on the interface stability between ceramic mould and new titanium alloy cast. The results show that the cast surface of ZTC4 alloy using moulds containing Al, Nb or Mn ions looks smooth with no obvious casting defects; compared with none metal containing mould, the roughness of ZTC4 cast using shells with residual metal increases markedly; Al vestigital had little effect on the interface inertness of ceramic against molten titanium alloy, while Nb and Mn can obviously reduce the interface inertness, and to some degree, casting surface roughness can reflect the interface stability; when the mould contains Al, Ti5Si3 phase is found at ceramic/metal interface.
Precise height control for UAV based on LADRC
QI Pengyuan, WANG Yong, ZHANG Daibing
2016, 42(11): 2472-2480. doi: 10.13700/j.bh.1001-5965.2015.0725
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Aimed at solving the impact of sophisticated wind disturbance, research on the control strategy, control structure and parameter optimization design is developed in this paper to realize height control with high precision performance in the longitudinal channel of unmanned aerial vehicle (UAV). First, based on the features of linear active disturbance rejection control (LADRC), the whole control structure is determined, and the probable disturbance from both inside and outside of the system can be estimated using the extended state observer (ESO). As a result, influence of disturbance on the output of the system can be eliminated by introducing this estimated value into the control law. Second, the power spectrum density of the wind turbulence and discrete gust are also analyzed, and a comprehensive fitness function considering impact of wind disturbance on height, characteristics of time domain response and stability margin is constructed, so that controller parameters with high precision and high disturbance-rejection performance can be produced through the particle swarm optimization algorithm to reduce the conservatism of controller parameter design. Finally, the outstanding performance of linear active disturbance rejection controller in the longitude channel of UAV is illustrated through being compared with the regular proportinal-integral-derivative (PID) height controller.
Work-conserving-based packet scheduling algorithm for CICQ switches
ZHANG Yuanhao, XIONG Qingxu
2016, 42(11): 2481-2487. doi: 10.13700/j.bh.1001-5965.2015.0688
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Although packet scheduling for combined input-crosspoint-queued (CICQ) switches has been extensively investigated, the performance in terms of throughput and average delay of packets is not satisfied, especially compared to the results obtained by employing output queued architecture. The key reason is that output queneing(OQ) switch can operate in work-conserving state. Different from the popular approaches appeared in the literatures, our work focuses on scheduling packet so that the switch works approximately in work-conserving state to the largest extent. First, the sufficient and necessary conditions for the switch with CICQ architecture to work in work-conserving state are investigated and proved. Then, a new CICQ input scheduling algorithm called crossbuffer queue balance (CQB) is put forward, which is combined with the classical longest queue first (LQF) scheduling used for output arbiter to obtain CQB-LQF algorithm. Simulation results show that the performance in terms of throughput and average packet delay obtained by CQB-LQF is much better than the classical and popular algorithms.
Microstructure and properties of ceramic/stainless steel joint with Ni foam interlayer
ZHANG Yu, ZHU Ying, GUO Wei, QI Dan, QI Zewu
2016, 42(11): 2488-2494. doi: 10.13700/j.bh.1001-5965.2015.0760
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Al2O3 ceramic and 1Cr18Ni9Ti stainless steel were brazed with or without Ni foam interlayer at the temperature of 850℃ for 60 min at vacuum. The microstructure of the joint was investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), besides shearing tests were used to test the mechanical properties of the joints. The experimental results show that the average shear strength of the joint without Ni foam interlayer is 7.7 MPa, and the fracture occurs in the ceramic. While Ni foam interlayer is used, the average shear strength of the joint is up to 101.7 MPa, and the fracture is located at the interface of ceramic and Ni foam interlayer. Without Ni foam, Ti is mainly distributed at the interface of ceramic and Ag-Cu-Ti and the interface of steel and Ag-Cu-Ti. With Ni foam, element Ti is distributed at the interlayer zone where TiNi3 is formed during the brazing process, besides, the distribution of Ag, Cu, Ti element is more uniform.
Optimization method of thermal sensor placement for microprocessor with noise
LI Xin, YANG Jinxiao, CHENG Yuanle
2016, 42(11): 2495-2500. doi: 10.13700/j.bh.1001-5965.2016.0204
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High-performance processors employ dynamic thermal management (DTM) techniques,which use a set of on-chip thermal sensors to continuously monitor temperatures during the runtime. However, on-chip sensors are inevitably accompanied by a range of noise sources due to fabrication randomness and fluctuations, which greatly affects the reliability of DTM. Therefore, in order to improve the accuracy of thermal monitoring, this paper utilizes principal component analysis (PCA) to approximately reduce dimensionality of the original sample matrix of the thermal image, and combines it with matrix perturbation analysis to propose the optimization method of thermal sensor placement which is based on simulated annealing algorithm. Experimental results indicate that the proposed method significantly outperforms the existing greedy algorithm in the aspects of thermal reconstruction error, Signal to noise ratio (SNR) and false alarm, which can be better applied in dynamic thermal management techniques to achieve accurate thermal monitoring.
Degrees of freedom of networks with coexistence of 2×2 X channel and point-to-point channel
GUO Qianqian, LIU Feng, ZENG Liansun, QIN Wenming
2016, 42(11): 2501-2506. doi: 10.13700/j.bh.1001-5965.2015.0696
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Degrees of freedom (DOF) is a spatial multiplexing conception, which was introduced in multiple antenna systems. And it characterizes the utilization efficiency of spatial resource for wireless channels. In the area of cognitive radio, since the primary and secondary networks interfere with each other, the DOF will be reduced. This paper mainly studies the DOF of the network on 2×2 X channel (XC) and point-to-point (PTP) channel which coexist. The result of this paper is also applied to the scenario when the XC has priority over PTP channel. If channel state information (CSI) is available at all transmitters, we propose the signal processing scheme using asymptotic interference alignment approach based on symbol extension model. It is shown that the lower bound of DOF tends to 5/3 when n tends to infinity. A propagation delay model is used to show its achievability. In addition, we analyze the upper bound on the DOF.
Evaluation method of airflow field plan in warship based on improved ELECTRE method
ZHANG Xiuyuan, CHANG Xin, LI Xiang, YANG Fangqing
2016, 42(11): 2507-2515. doi: 10.13700/j.bh.1001-5965.2015.0703
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Based on the influence of airflow field on deck-landing aeroplane operations, an evaluation index system for airflow field of warship is constructed. In view of the defect of consistency check by analytic hierarchy process (AHP), a weighting method which is combined with group eigenvalue method (GEM) and the theory of decision entropy is formed; the method can obtain outcomes, whose reliability is quantifiable. Combining the concepts of fuzzy theory, the classical elimination et choice translating reality (ELECTRE) method is extended for fuzzy multiattribute group decision making; all attribute values in sorting are expressed in triangular fuzzy numbers; when airflow field plans of warship are sorted with improved fuzzy ELECTRE, the use of fuzzy number ensures the complete processing of fuzzy data which is from the experts. Evaluation-computing is run for three airflow field plans, which verifies the feasibility of this improved evaluation method that can be a new method for general airflow field plan evaluation.
Vibration amplitude characteristics of tubular electrode in EDM drilling
YU Zhiqiang, TONG Hao, LI Yong, CHAI Yongsheng, WANG Zhiqiang, LI Chaojiang
2016, 42(11): 2516-2523. doi: 10.13700/j.bh.1001-5965.2015.0736
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In the drilling of electric discharge machining (EDM) by use of a tubular electrode with high-pressure dielectric fluid, the random electrode vibration causes short circuit and second discharge which have a bad effect on machining accuracy and efficiency. In this paper, the microscopic amplitude characteristics of the electrode vibration are researched by adopting methods of simulations, experiments and comparative analysis. Based on ANSYS simulation platform of finite-element software, a finite element model was established to simulate the vibration characteristics of the tubular electrode, and then the effects of multiple factors including hydraulic pressure of dielectric fluid, electrode-guide gap, drilling depth, discharge gap, spindle speed and electrode overhanging length on the electrode vibration amplitude were analyzed. In addition, the significant level of every factor was analyzed by numerical simulation under the condition of coupling these factors. The EDM drilling experiments were carried out to verify the simulation results. Our research shows that the guide gap, drilling depth and hydraulic pressure have positive correlation with the electrode vibration amplitude, and reducing the guide gap from 10 μm to 1 μm can effectively reduce 20 μm of the error of the aperture. By analyzing these coupling factors, the order of significance affecting the electrode vibration is drilling depth, hydraulic pressure of dielectric fluid, discharge gap, spindle speed and electrode overhanging length. This research provides a basis for optimizing machining process and spindle design of EDM drilling using a tubular electrode.
Secure routing protocol based on optimized trust evaluation in Ad Hoc network
CHEN Shaohua, FAN Xiaoguang, ZHUO Zhenfu, HUANG Jinke, SUN Xianming
2016, 42(11): 2524-2531. doi: 10.13700/j.bh.1001-5965.2016.0184
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Aimed at the attack of selfish nodes in mobile Ad Hoc networks, this paper proposes a secure routing protocol TEAR, which is based on trust evaluation. In order to realize the accuracy and timeliness of trust values, the proposed protocol, which is based on the trust evaluation scheme of node behavior, uses the link trust and path trust to represent the reliability of a node and a path respectively, and introduces the indirect trust evaluation scheme with public neighbors' trust values and variable time window. The trust value table of each node and the new structure of RREQ and RREP provide the quick selection of secure routing. Finally, TEAR protocol was verified by NS2 simulation and compared with AODV and TA-AODV which is based on fixed time window trust evaluation. The simulation results show that the improved trust evaluation scheme has a superior performance, and TEAR can not only detect the selfish nodes correctly but also select secure path, which improves the function of Ad Hoc networks.
Subtle intrapulse feature extraction based on CEEMDAN for radar signals
WANG Wenzhe, WU Hua, WANG Jingshang, ZHANG Qiang
2016, 42(11): 2532-2539. doi: 10.13700/j.bh.1001-5965.2016.0410
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Effective signal feature extraction builds the foundation of highly accurate radar emitter identification, a key function of the electronic warfare. Conventional features used in practice such as the pulse description words cannot fulfill the task in complex electromagnetic environments. An effective subtle intrapulse radar feature extraction method based on the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) was proposed. Radar signals were reconstructed by components provided by the CEEMDAN decomposition process, which was highly effective for non-stationary and nonlinear signals; the de-noising effect of the reconstruction on radar signals was validated through 1 000 Monte Carlo experiments, and an intrapulse feature space based on the reconstruction was designed. The identification accuracy of the proposed feature space was compared to that of the mainstream methods in the area, on 3 000 noise-contaminated signal samples supposed to be generated by 6 radar emitters, with different intrapulse modulation. Experimental results show that the samples are totally distinguishable in the proposed feature space, and the proposed method is more accurate in the comparison, especially in highly noisy environment, with accuracy above 90% at 0 dB signal to noise ratio (SNR).
Energy suboptimal flight strategy of bank-to-turn maneuver for lifting vehicle
YANG Ding, LIU Ming, YANG Lingxiao, YANG Ming, GE Yajie
2016, 42(11): 2540-2547. doi: 10.13700/j.bh.1001-5965.2016.0613
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When lifting vehicle is returning into earth's atmosphere, some path constraints including heating rate, dynamic pressure and overload should be enforced strictly. In order to reduce the energy losing during the performance of bank-to-turn maneuver, it is necessary to develop a suboptimal flight strategy. The main research contents of this paper are as follows. The trajectory characteristic of bank-to-turn maneuver is analyzed via studying the entry dynamics. The analytical solution to terminal velocity at the special terminal heading angle is derived. Furthermore, a suboptimal flight strategy, which considers the path constraints, is proposed based on this analytical solution. In order to verify the optimality of this flight strategy, a trajectory optimization problem is formulated so as to provide optimal energy trajectory. Then, Gauss pseudospectral method is used to solve this problem. The results show that both trajectories are highly consistent, and the flight strategy is more efficient and has greater engineering applicable values.
Observability analysis for transfer alignment of inertial navigation system on moving base
HUANG Shuai, CAI Hong, DING Zhijian
2016, 42(11): 2548-2554. doi: 10.13700/j.bh.1001-5965.2015.0765
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A novel approach that starts from the basic observability definition is used to investigate the observability of the transfer alignment system on moving base. The original nonlinear state equations are analyzed directly to eliminate errors of the model. Sufficient conditions to make alignment fully observable are analytically derived. And maneuver scheme of vehicle is designed according to it. The results show that translatory motions with varying acceleration can enhance the observability of sensor bias, fix error angle and attitude, whereas angular motions are in favor of the observability of the lever arm. Different from traditional linearization-based observability studies, this kind of analysis approach is straightforward and comprehensive, with no need of nonanalytical support from numerical simulations. Besides, it has explicit physical meanings, revealing the inherent connecting link between the observability of transfer alignment system and vehicle maneuvers, and providing new insights into the analysis and design of nonlinear systems. Finally, covariance simulations with an extended Kalman filter (EKF) are carried out to estimate the states, and the numerical results accord with the theoretical analysis.

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