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2016 Vol. 42, No. 4

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Volume 42 Issue42016
2016 Year 42 Volume 4 Issue E-journal
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Hardware-in-the-loop simulation method and influence analysis of missiles considering body elasticity
LIU Li, WANG Yansong, ZHOU Sida, ZHANG Wulong
2016, 42(4): 639-645. doi: 10.13700/j.bh.1001-5965.2015.0245
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With the increasing requirements of velocity and accuracy, the elasticity has been a non-ignorable factor in the dynamic analysis and design of missiles, which could evidently influence the flight performance and control accuracy. In this case, considering the elastic vibration of missiles would improve the precision while running a hardware-in-the-loop simulation of a flexible missile. A flight dynamic model considering the elasticity was developed, and the model of hardware-in-the-loop simulation system was established at the same time. The integrated simulation of math simulation model and hardware-in-the-loop simulation model was realized, based on which, the influences of the elastic vibration and the simulation equipment were analyzed. The results could provide a theoretical basis for the future hardware-in-the-loop simulation of missiles considering the elasticity.
Method of face gear grinding-honing machining based on aviation environment
WANG Yanzhong, ZHAO Hongpu, LAN Zhou, HOU Liangwei, ZHONG Yang
2016, 42(4): 646-653. doi: 10.13700/j.bh.1001-5965.2015.0260
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Face gear drives become the main direction of research for aeronautical drives because of their special advantages. The equation of face gear tooth surface was established based on the face gear transmission theory. For improving the precision machining technology of face gear, the method of face gear grinding-honing machining was put forward. The applied coordinate systems of face gear were set up and then the special grinding tool for face gear was developed based on special face gear numerical control grinding machine, influence of face gear grinding, slotted technique and the honing theory of traditional gear. In addition, flexible honing tool was designed. And then the tool used for grinding-honing parts machining was manufactured. The special tool was used to do face gear grinding-honing machining experiment, and then surface quality inspection on face gear was conducted, such as the detection of surface roughness, residual stress testing and observation of surface micro texture. The analysis of the surface quality detection results proves this method is reliable.
Dynamic pressure characteristic analysis for double-cavity model of air system
DING Shuiting, CHE Weiwei, LIU Chuankai
2016, 42(4): 654-661. doi: 10.13700/j.bh.1001-5965.2015.0256
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When the engine slam accelerates or suddenly fails, the pressure wave formed by cavity effect and pipe fluid inertia in a short time will have negative impact on some components of air system. On the basis of the simulation program of the modular transient air system, the pressure variation of cavity and different parts of pipe in the double-cavity model is analyzed. The influence law analysis of the size of the key components for pressure wave is mainly considered. Results show that the pressure wave produced in the transient state is closely related to the geometric structure size of the air system. The analysis method of this model can be used as a basis for fast transient research of air system of the integrated engine.
Kinematics modeling and simulation of seed implantation robot for prostate tumors
ZHANG Yongde, LIANG Yi, BI Jintao, XU Yong
2016, 42(4): 662-668. doi: 10.13700/j.bh.1001-5965.2015.0288
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We developed a 3-PCR parallel-chain type of seed implantation robot for prostate tumors, based on measurement workspace in the perineum of prostate and quantitative analysis of the surgery procedure. For this kind of symmetry less degrees of freedom of parallel-chain mechanisms as position adjustment device, the kinematics characteristics need further research. The forward and reverse kinematics equations of 3-PCR parallel-chain mechanisms were established by the closed vector method and Bezout elimination, and forward and reverse model was verified by numerical calculation to be correct. The kinematics simulation was performed under the helical cure in space with point p by MATLAB software, and simulation results provide evidence that this parallel-chain mechanism has better movement stability and is convenient for real-time control. The limit boundary searching method was used to solve the workspace of this mechanism under the posture with α=β=γ=0°, and workspace with YOZ section was 15 674 mm2 under x =0, which also meets the requirements of clinical surgery.
Chattering-free sliding mode guidance law with impact angle constraint
ZHOU Weidong, CHEN Yankui, XIONG Shaofeng
2016, 42(4): 669-676. doi: 10.13700/j.bh.1001-5965.2015.0290
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Taking into account both the autopilot dynamics and impact angle constraint,a novel chattering-free sliding mode control guidance law for homing missile to intercept a target performing evasive maneuvers was proposed. Firstly, we establish the guidance system state equation by differentiating the line-of-sight (LOS) angle three times. Secondly, a new sliding mode control system is put forward based on guidance system state equation, and we choose full-order TSM (terminal sliding mode)manifold to avoid the singularity of TSM, and introduce the sliding mode switching term compensating the unknown bounded disturbance in the derivative of controller to eliminate the chattering phenomenon. Finally, we apply the new sliding mode control in designing the guidance law, which enforces the LOS angle convergence to desired value in finite time. Compared with the existing finite time guidance laws, this guidance law can not only compensate for the effects of the autopilot lag but also eliminate chattering phenomenon of controller effectively. The numerical simulation verifies the effectiveness of the proposed method in the design of guidance law.
Carbon nanotubes thin film sensor and characterization of its strain sensing
NIE Peng, ZHANG Daguo, CHEN Yanhai, LU Shaowei, HAN Jiao
2016, 42(4): 677-684. doi: 10.13700/j.bh.1001-5965.2015.0271
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Due to the aviation accident caused by structure deformation occurring frequently, the health monitoring of aircraft's structure has become one of the effective means of prevention. Carbon nanotubes thin film can be used as strain sensor for health monitoring of structure damage. The dispersion techniques such as mechanical agitation, ultrasonic processing and centrifugal processing had been combined for realizing the monodispersion of carbon nanotubes in aqueous medium. Carbon nanotubes thin films was fabricated with monodispersion solution of muti-walled carbon nanotubes through vacuum filtration method for strain sensing. We designed a carbon nanotubes thin film sensor which was formed with matrix of structure for strain sensing. Bending strain sensing experiment shows that carbon nanotubes thin film sensors in different strain ranges and different cycling times and different temperature conditions has good strain sensing characteristic. The response and sensitivity to strain of carbon nanotubes thin film were investigated. The sensing mechanism of carbon nanotubes film shows that the resistance of the carbon nanotubes thin film increases with the increase of strain. The results indicate that carbon nanotubes thin film sensor has a very high strain sensitivity in the strain range of 0-22 500 με with gauge factor of 188.31 and has excellent reversible and repetition characteristics.
Integrated physiological model for mental workload assessment and prediction of aircraft flight deck display interface
LU Kun, WEI Zongmin, ZHUANG Damin, WANYAN Xiaoru
2016, 42(4): 685-693. doi: 10.13700/j.bh.1001-5965.2015.0254
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This paper focuses on the objective discrimination and prediction of mental workload of the aircraft flight deck display interface. By three physiological measurement methods of event-related potentials (ERP), electrocardiograph (ECG) and electro-oculogram (EOG), as well as subjective evaluation and performance evaluation, both experimental measurement and mathematical modeling of mental workload were carried out under the same flight simulation task conditions. The experimental results indicate that as the mental workload increased, the peak amplitude of the mismatch negativity (MMN) at Fz significantly increased, while the peak amplitude of P3a at Fz, the standard deviation of normal-to-normal RR intervals (SDNN) value, and the eye blink numbers significantly decreased. Based on the results of experimental measurement, the Bayesian discrimination analysis method was employed to construct the mental workload discrimination model of the aircraft flight deck display interface. The integrated physiological model showed a higher accuracy in the discrimination and prediction of mental workload compared with NASA_TLX. Thus, this model provides not only a new approach for the objective and real-time discrimination and prediction of mental workload of the aircraft cockpit display interface, but also a new compliance verification tool for the human factor airworthiness certification of flight deck display interface of the new generation fighter aircraft and large passenger aircraft.
Properties of pendulum motion of tether tugging system and its stable control
ZHAO Guowei, ZHANG Xingmin, TANG Bin, SUN Liang
2016, 42(4): 694-702. doi: 10.13700/j.bh.1001-5965.2015.0286
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Taking account of the attitude motion of tethered system, mission satellite and abandoned satellite, dynamics and control models of tethered system are established. According to the flight process under a constant thrust in the tangential direction, an attitude control of mission satellite is adopted on the basis of thrusters and momentum wheels; then, the characteristics of the oscillation of abandoned satellite, the pendulum motion of tethered system and the attitude motion of mission satellite are studied and effects among each other are analyzed. In order to ensure the flight safety of tethered system, the tether tension control which includes damp control law and position-keeping control law, and mission satellite attitude control are adopted. Numerical simulation results indicate that the regular oscillation of abandoned satellite at a specific angular frequency which caused by the offset of hanging position may arouse high order pendulum motion of tethered system during deorbiting under a constant thrust. Furthermore, the attitude motions of satellites are the main factors which bring disturbance torque to mission satellite. In addition, the oscillation of abandoned satellite is damped out and the distance between satellites is maintained by the adopted tension controller, which guarantees the flight safety and stability of tethered system combining with mission satellite attitude control and also reduces energy consuming of mission satellite.
Adaptive backstepping control method used in DGMSCMG gimbal servo system
LI Haitao, YAN Bin
2016, 42(4): 703-710. doi: 10.13700/j.bh.1001-5965.2015.0282
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To overcome the problem of the precision of gimbal angular speed control brought by the coupling torque between inner and outer gimbal of double gimbal magnetically suspended control moment gyroscope (DGMSCMG) and the nonlinear transmission characteristics of the transmission gear, a nonlinear robust controller based on adaptive backstepping control method is proposed. Firstly, the effects of the double gimbal coupling torque and the nonlinear transmission characteristics of the transmission gear on the stability of the system and the precision of gimbal angular speed are analyzed. Secondly, based on backstepping theory, the control law is recursively deduced by constructing the suitable Lyapunov function, which ensures convergence of parameter estimation and global stability of the adaptive system. Finally, simulation analysis and experiment with small DGMSCMG show that the disturbance restraint ability of double gimbal servo system and the precision of gimbal angular speed are significantly improved by the proposed method, compared with current feed-forward control.
Network selection algorithm based on cell attractor selection scheme
XIA Haiying, ZENG Cheng, CAI Fengtian, ZHOU Wei
2016, 42(4): 711-717. doi: 10.13700/j.bh.1001-5965.2015.0278
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With the development of mobile communication, there are many different kinds of wireless networks, such as the internet of things, vehicular networks, and body networks. These mobile networks need the reliable seamless roaming among a multitude of access network technologies. Any single communication technology cannot satisfy the requirement of multi-kinds of network services. How to choose a stable network in the moving environment has become a hot subject in the academic field and industry. A network selection algorithm based on the attractor selection is proposed in this paper. In order to demonstrate the strengths in bio-inspired mechanism and provide a deep insight into the difference between attractor selection based and utility function based solutions, a group decision making method for vehicular network selection is proposed in our work. In addition, simulation experiment is performed to verify as well as to highlight the potential of bio-inspired solution based on attractor selection.
Output-feedback sliding mode control for MIMO affine extremum seeking systems
ZUO Bin, ZHANG Lei, LI Jing
2016, 42(4): 718-727. doi: 10.13700/j.bh.1001-5965.2015.0297
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An output-feedback sliding mode control method is proposed for a class of multi-input multi-output (MIMO) affine nonlinear extremum seeking systems. Firstly, the original MIMO affine nonlinear extremum seeking system is decomposed into several single-input single-output (SISO) extremum seeking subsystems. Considering the subsystem's states are unmeasurable, the control method uses a simple ramp time function as the reference signal of the subsystem's output, constructs the sliding mode manifold by the output tracking error and the integral of the sign function of the tracking error, and designs the output-feedback extremum seeking control law with sliding mode. The stability analysis shows that the MIMO nonlinear seeking extremum system with the proposed control method is possible to achieve an arbitrarily small neighborhood of the desired optimal point under all initial conditions, and all the states in the closed-loop system remain uniformly bounded. Simulation results are presented to illustrate the effectiveness of the control method.
Alliance algorithm of converging feedback network on P2P real-time media streaming
SHEN Mengru, ZHANG Jinyu
2016, 42(4): 728-736. doi: 10.13700/j.bh.1001-5965.2015.0300
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Quality of service and the services providing ability of system are deeply influenced by unfairness of client contributions, a alliance algorithm based on distance-convergence was proposed by implementing the converging feedback network in dynamic traffic condition, and it can avoid the unreasonable traffic which cannot be eliminated by the random-alliance, content-likeness driven alliance and bandwidth-likeness driven alliance. A node mix distance algorithm was implemented, which combines IP static range algorithm and dynamic packet probe ranging method. The node mix distance algorithm can overcome the drawbacks that packet probing range is easily affected by the traffic fluctuation, the real-time feature cannot be ensured by the client perception range, and the IP-based range algorithm lacks precision. Moreover, a uniform flow cycle request collaborative mechanism based on Polling was introduced, which not only keeps the lower-offset merit of the pushing-pulling periodic requesting mechanism, but also provides enough resilience against transport ability decline and transport failure. The simulation results show that our mechanism can reduce the probabilities of unreasonable traffic and the vice behavior of non-contribution, and can provide better performance of delay, packet loss rate and packet arriving rate than other alliance mechanisms in larger scale.
Research on automatic tracking system for directional antenna of UAV
ZHA Changliu, DING Xilun, YU Yushu, WANG Xueqiang
2016, 42(4): 737-744. doi: 10.13700/j.bh.1001-5965.2015.0268
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In order to meet the requirements of communication of unmanned aerial vehicle (UAV) over a long distance, the ground directional antenna automatic tracking system has been developed with the UAV location information to guide. With the real-time acquisition directional antenna vehicle position, velocity, azimuth and elevation information, the directional antenna automatic tracking ability in motion is realized and it enhances the system mobility and concealment. The traditional methods to calculate the target angle using 2 points usually need the information of relative position of the 2 points. The relative position is difficult to be obtained in real time systems. Thus a novel method is presented in this paper. The proposed method does not need to consider the relative position of 2 points, which is more convenient in applications. When the directional antenna is moving with its loading vehicle, the GPS signal is easy to be disturbed, resulting in the loss of the target tracking. The tracking system has larger motor fluctuation and greater tracking error caused by the low update frequency of the UAV position. In order to overcome these shortcomings, UAV speed is adopted to predict the position in order to realize smooth angle tracking and solve the fluctuation, thus the tracking accuracy is improved. The hardware and software design of the control system is described in detail. Test results show that the developed directional antenna has motorized tracking capability and high tracking accuracy and it can meet the requirements of UAV control.
Dynamic strength valuation method of pipeline structures under preload
WANG Shuai, ZHANG Mingming, LIU Zhen, JIA Liang, RONG Kelin
2016, 42(4): 745-750. doi: 10.13700/j.bh.1001-5965.2015.0289
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For the problems of pipeline structures environment test in current aerospace, first of all, we researched the analytical method for dynamical strength characteristic of pipeline structures under preload and multiaxial random vibration experiments, and then made clear the difference and processing between differential stiffness and prestress caused by preload in structural vibration analysis and fatigue life calculation. We provided an analysis method to preestimate the fatigue damage of pipeline structure under random vibration in various actual experimental environments, and this method solves the following problems: how the conditions of actual experimental environment tests srepresent the preexperimental environments and how to estimate the effects of inconsistency between the actual experimental environments and the preexperimental environments on dynamic strength of pipeline structures with. Finally, by simulation calculation for pipeline structures, we analysized the weak points and residual strength coefficient of dynamic strength in pipeline structures, as well as the fatigue life. The simulation results verify the effectiveness of this method, thus this analysis method provides engineering guidance for analyzing the adaptability and reliability of pipeline structures in the actual environment.
Damage resistance property of stiffened composite panels under low-velocity impact
JI Zhaojie, GUAN Zhidong, LI Zengshan
2016, 42(4): 751-761. doi: 10.13700/j.bh.1001-5965.2015.0261
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In order to study the effect of impact energy and structural geometry on damage resistance of stiffened composite panels under low-velocity impact, 3 groups of I-section stringer-stiffened composite panels were experimentally and numerically investigated. Drop weight low-velocity impact tests were conducted to capture the damage characteristics such as impact force histories, indentation depths and delamination areas. Finite element (FE) models were established based on an anisotropic elato-plastic theory incorporating fiber failure. Indentation depths of the specimens were simulated by the FE models. The simulated results are coordinated with the tested results very well. The results indicate that there is a knee point for the curve of impact energy and dent depth of stiffened composite panels. Some fiber breakage at the impact location on the surface of specimens can be found after the knee point occurs. The maximum impact force increases with the increasing impact energy, while the delamination initiation load and delamination area do not. The impact energy and the maximum impact force of specimens containing 1.5 mm indentation increase with the increasing thickness of skin or stiffener while the delamination initiation load only increases with the increasing thickness of skin.
A full-resolution motion compensation method used for real-time digital image stabilization
ZHAI Bo, ZHENG Jin, WANG Yue
2016, 42(4): 762-771. doi: 10.13700/j.bh.1001-5965.2015.0293
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With the foundation of inter-frame translation motion of the videos captured in outdoor video monitoring, a real-time video stabilization method was presented with equilibrium position modification and adaptive update of storage frames, which can realize the full-resolution video stabilization. Firstly, the Kalman filter was used to estimate the intentional motion of the camera, in which the equilibrium position of the currently stabilized frame was obtained. Secondly, the reference frames and subsequent frames were stored. Based on the spatial coverage of the storage frames, the equilibrium position was modified to reach the full-resolution in-painting of the compensated current frame. Finally, taking the modified equilibrium position as the standard, and guaranteeing the coexistence of the storage frames with deviation in upper left, upper right, lower left, and lower right directions, we substituted the newest captured frames online for the earliest and redundant reference frames, so the storage frames can achieve the greatest coverage and temporal-spatial correlation with limited storage resource. The presented video stabilization algorithm achieves the full-resolution stabilization and real-time processing, which can be applied to the integrated and embedded video surveillance systems.
Performance characteristics of single rotor compound helicopter
CAO Fei, CHEN Ming
2016, 42(4): 772-779. doi: 10.13700/j.bh.1001-5965.2015.0267
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In order to analysis the performance of the compound helicopter, a performance calculation model consisting of all the aerodynamics mathematical model parts is established. Based on the calculation model, using various flight conditions, we constructed the compound helicopter transition flight border, studied the characteristic variation of flight power from hover flight mode to high-speed flight mode by selecting different routes, and investigated the effects of multiple factors including rotor speed, forward speed, rotor and wing loading distribution in high-speed mode. The results indicated that the reduction of flight power could be achieved by increasing the offload lift from the rotor to the wing; moreover, it was more effective to reduce the rotor speed than reduce the rotor collective pitch, during the compound helicopter transits from hover mode to high-speed mode. The rotor could not operate at very low speed, which might increase the power consumption during high-speed flight mode. Furthermore, the low rotor speed could also influence the trim of the aircraft model, and made its calculation iteratively divergent.
Intelligent target following strategy design for UAV against multi-threats
QI Xiaoming, WEI Ruixuan, ZHOU Kai
2016, 42(4): 780-788. doi: 10.13700/j.bh.1001-5965.2015.0296
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With the development of integrative combat, the task will be converted into target following mode when unmanned aerial vehicle (UAV) finishes searching ground moving target. Complex combat environment is considered, and the problem of UAV following moving target in the condition of multi-threats source are studied. An intelligent target following strategy based on decision trees is proposed in order to ensure the security of UAV and the precision of target following. Firstly, threat probability map (TPM) model was established. Secondly, the problem how to solve the minimum of TPM was researched. Then, the different rules were generated on the basis of the different priorities for object tasks by geometric method; the complete decision trees were established; the heading and speed commands of UAV were generated for different rules. Finally, simulation results demonstrate the validity of the proposed method.
Motion parameters estimation method of single walking human
SUN Zhongsheng, WANG Jun, SUN Jinping, ZHANG Yaotian, YUAN Changshun, XIANG Hong
2016, 42(4): 789-795. doi: 10.13700/j.bh.1001-5965.2015.0305
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Radar micro-Doppler of human motion can provide signatures for target recognition. It is very difficult to extract motion parameters from radar echo of walking human because of its complexity. An estimation method of single walking human's bulk velocity, gait cycle and cycle length is proposed to realize accurate target recognition. First, the micro-Doppler spectrum of radar echo is obtained using generalized S transform (GST). Then, the micro-Doppler component of torso is extracted, and it is converted into one-dimensional time frequency sequence. Finally, the bulk velocity and gait cycle of walking are estimated directly from this time frequency sequence, and the cycle length is estimated from aforementioned estimations indirectly. The simulation results show that the proposed method has good performance of anti-noise and high estimation precision when signal-to-noise ratio is higher than 4 dB.
An efficient method for estimating various variance-based sensitivity indices
YUN Wanying, LYU Zhenzhou, MU Shanshan
2016, 42(4): 796-805. doi: 10.13700/j.bh.1001-5965.2015.0309
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In order to simultaneously estimate various variance-based sensitivity indices, a method is proposed by combining space-partition idea and unscented transformation (UT) method, which can estimate variance-based global sensitivity index (Sobol index), variance-based regional sensitivity index and variance-based W index by repeatedly using a set of UT samples. Besides, a modified variance-based W index is proposed, which can analyze the sensitivity of the model input variables comprehensively and reasonably. What's more, the modified variance-based W index includes both the original one and the variability of effect on the variance of model output when the model input variable is fixed in different intervals. Thus, the modified one more reasonably reflects the average impact on the variance of the model output when model input variable is fixed in different intervals. The results of numerical and engineering examples illustrate the accuracy and efficiency of the proposed method and the reasonability of the modified variance-based W index.
Adaptive simple WENO limiter-discontinuous Galerkin method for Euler equations
WU Zeyan, WANG Lifeng, WU Zhe
2016, 42(4): 806-814. doi: 10.13700/j.bh.1001-5965.2015.0237
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To achieve high precision and high resolution numerical result of Euler equations, the basic principle of discontinuous Galerkin method, the simple WENO limiter on triangular meshes and shock capturing method based on adaptive mesh refinement were introduced. The simple WENO limiter-discontinuous Galerkin method was applied to the curved quadrilateral element, and the adjacent elements of every element with the same coordinates of the Gauss integral points on the boundaries were found. The adaptive computation based on “trouble element” refinement was accomplished. Several benchmark test cases were computed. The numerical results show that the simple WENO limiter is appropriate for the curvilinear boundary quadrilateral element and for the shock capturing based on unstructured grids with hanging nodes.
Reliability robust design of tracked vehicle torque axis with multiple failure modes
LIU Zhe, TAO Fenghe, JIA Changzhi
2016, 42(4): 815-820. doi: 10.13700/j.bh.1001-5965.2015.0253
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Several potential failure modes may occur when tracked vehicle torque axis fail, and therefore it is necessary to take each failure mode into account as reliability sensitivity estimation is performed. A reliability sensitivity analysis method for mechanical components with multiple failure modes is proposed. Concerning the unknown distributions of random variables, the random perturbation technique and the fourth moments method are employed to respectively calculate the first four moments and the reliability index of each performance function of the failure mode. According to the characteristic that the overall fails when a failure mode occurs in mechanical parts, the mechanical parts reliability calculation method with correlation between different failure modes is determined. The calculating formulas of reliability sensitivity with respect to the mean and variance of random variables are derived with the gradient method. According to the result of reliability sensitivity analysis, we put forward the model multi-objective optimization design of mechanical parts with multiple failure modes. The numerical example illustrates that the proposed method could quickly and effectively estimate the reliability sensitivity of the mechanical components with multiple failure modes, and could optimize the mechanical robust design.
Added mass of trans-media moving object
ZHANG Xiaoqiang, FENG Jinfu, LIN Ke, HU Junhua
2016, 42(4): 821-828. doi: 10.13700/j.bh.1001-5965.2015.0478
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Trans-media moving object was equipped with outstanding advantages in multiple fluid media environment. However, its moving characteristics were hard to predict because of the free surface problem and complex stress. Added mass method was common to solve fluid-structure coupling problems in engineering, but the existing conclusions could not be extended to trans-media process with free surface. A new method was proposed aiming to solve the time-varying added mass problems in trans-media process. Changing laws of added mass of some cylinder were studied, which lied in different depths in both separation step and entry step of the trans-media process. It is shown that the two steps have same changing trend and similar depth-varying curve with the depth varying; in the same depth, normal added mass of separation step is near to that of the entry step and both depth-varying curves have linear characteristics; as for axial added mass, added inertia moment, and added static moment, the results of two steps in the same depth are different obviously, so the two steps are irreversible. The proposed method is helpful for design of trans-media structure, and can be extended to other situations of added mass computing with free surface.
Gap filling method for space environment data based on singular spectrum analysis
LIU Shuai, LI Zhi, GONG Jiancun, LIN Ruilin, MA Zhihao
2016, 42(4): 829-836. doi: 10.13700/j.bh.1001-5965.2015.0554
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The space environment data is known to be nonlinear and non-stationary and often contains missing values, which brings great challenge to the model-building procedures, predictions and posterior analysis. To fill the data gaps, a new gap filling method based on the iterative singular spectrum analysis (SSA) algorithm was put forward. The new method considered the distribution of missing values by extracting a distribution array first and used the array to generate the test data set. The discrete particle swarm optimization algorithm was adapted to obtain the two key parameters of SSA, i.e. the embedded window size and the number of principal components. Taking the solar wind parameters and geomagnetic indices of different solar activity years as examples, the test results demonstrate that the filling method is effective.
Frequency measurement of wing-tip vortex instability by flow visualization
XUE Dong, PAN Chong, LI Guangchao
2016, 42(4): 837-843. doi: 10.13700/j.bh.1001-5965.2015.0594
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The accurate measurement of the dominant frequency of wing-tip vortex core oscillation is essential for controlling the wing-tip vortex. In the present study, the instability of wing-tip vortex, which is generated from an elliptical wing, was investigated under low Reynolds number via flow visualization technique. Point-wise spectrum method and dynamic mode decomposition were applied to extract the dominant frequency of the short-wave instability of the wing-tip vortex core from the flow visualization image sequence, and the maximum relative error of these two methods is less than 5%. The results show that short-and long-wave instability modes are developed simultaneously among the vortex pair; the high-frequency vortex core oscillation is coupled with the slow side-to-side movement of vortex tube, and the former is the main energy mode; the non-dimensional frequency of the short-wave instability increases with the increase of Reynolds number, and decreases with the angle of attack increasing.
Diagnostic strategy building method based on MDP
LIANG Yajun, XIAO Mingqing, SONG Haifang, YANG Zhao, LIANG Peng
2016, 42(4): 844-850. doi: 10.13700/j.bh.1001-5965.2015.0277
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Aiming at the problem that by the traditional method, it is difficult to get the global optimal diagnostic strategy of the complicated test system in fault detection for ignoring the uncertainty factors in the test execution and lacking of the long cycle optimization mechanism, a new diagnostic strategy building method based on Markov decision processes (MDP) is proposed. The process of fault detection and isolation is expressed as a Markov process; the unlimited discount model of the utility integrated criterion function is structured through the discount factor and objective weights; the global optimal diagnostic strategy is obtained with the policy iteration algorithm. The example shows that the test uncertainty factors are well considered, stable optimal strategy of overall situation can be achieved by this method, and the fast fault detection and isolation in the engineering practice can be guided effectively as well.
Optimization on stealth aircraft RCS models using Bayesian-MCMC estimation
DAI Xiaoxia, CAO Chen, FENG Yuan
2016, 42(4): 851-857. doi: 10.13700/j.bh.1001-5965.2015.0248
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When statistically modeling a stealth aircraft, conventional methods estimate characteristic parameters via calculating the statistics of radar cross section (RCS) directly, which may lead to relatively large fitting errors. Therefore,we introduce the Bayesian-Markov chain Monte Carlo (Bayesian-MCMC) method to improve the parameter accuracy so as to reduce the fitting errors. The posterior parameter estimators of the Chi-square and lognormal models are derived in the Bayesian framework. Then the MCMC sampling algorithm is adopted to calculate the parameter estimates by constructing Markov chains. Numerical results show that the estimation errors of the proposed method are 1-2 orders of magnitude lower than the error convergence threshold. Besides, the proposed method is suitable for both target fluctuation models and improves the curve fitting accuracy by more than 50%.
Estimation of space manipulator random vibration signals with poor information based on grey bootstrap method
WANG Qiyue, WANG Zhongyu, WANG Yanqing, YAO Zhenjian
2016, 42(4): 858-864. doi: 10.13700/j.bh.1001-5965.2015.0270
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Abstract:
The classic statistical methods based on statistical theory can not solve the estimation of poor information data. A novel method based on grey bootstrap model for space manipulator random vibration signals with poor information was presented. The random vibration measurement data was processed by the bootstrap sampling．The bootstrap sequence was derived from the bootstrap distribution, and then the system theory was used to establish a bootstrap model. The true value and the interval of the space manipulator random vibration signals with poor information were estimated．grey bootstrap method is compared with grey method and bootstrap method. Experimental results show that grey bootstrap method has high accuracy. The validity of the proposed method is examined．The mean value of estimated relative errors are less than 5%, meanwhile, the estimated interval accuracy calculated with different confidence levels are more than 97%.

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