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2016 Vol. 42, No. 9

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2016 Year 42 Volume 9 Issue E-journal
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Micro-immune optimization algorithm for solving probabilistic optimization problems
ZHANG Zhuhong, ZHANG Renchong
2016, 42(9): 1785-1794. doi: 10.13700/j.bh.1001-5965.2015.0563
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This paper investigates a micro-immune optimization algorithm for the problem of nonlinear probabilistic optimization with unknown random variable distribution. In the design of algorithm, an implicit parallel optimization structure is developed based on the danger theory, while individuals can be identified through a proposed adaptive sampling method. Those danger regions and subpopulations can be decided dynamically through regulating danger radiuses, and meanwhile multiple kinds of mutation strategies are used to guide individuals to move towards multiple directions. Such algorithm has the merits of small population, few adjustable parameters, structural simplicity and so forth; the computational complexity depends on iteration number, variable dimension and population size. Based on the theoretical test examples and a bus scheduling problem, numerically comparative experiments show that the proposed algorithm possesses some advantages of search efficiency and optimized effect, and has potential for solving complex probabilistic optimization problems.
Detection of skin desoldering defect in Ti-alloy honeycomb structure using lock-in infrared thermography test
ZHOU Zhenggan, HE Pengfei, ZHAO Hanxue, FAN Jin
2016, 42(9): 1795-1802. doi: 10.13700/j.bh.1001-5965.2015.0569
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Skin desoldering is the most common defect of Ti-alloy honeycomb sandwich during manufacturing and serving period. Due to low thermal conductivity of Ti-alloy material, as the skin of Ti-alloy honeycomb sandwich becomes thicker, temperature signal difference of defect and non-defect becomes weaker, and thus it is more difficult to test the defect by infrared thermography. Given the problem, the range of modulation frequency in this structure with different skin thickness by lock-in infrared thermography was studied. The finite element simulation model was built to analyze the variation of surface temperature under the heat flow. The extracted phase differences of defect and non-defect area based on correlation algorithm are available to analyze the effect of modulation frequency and skin thickness on these phase differences. Experiments were performed on the specimen with prefabricated defects of this structure using lock-in infrared detection system. The relationship between the phase difference and the modulation frequency was given after extracting the phase of defect and non-defect area. The research results show that the 0.04-0.10 Hz modulation frequencies applied to detect this structure of skin thickness within 0.6-2.0 mm can get optimal results. Research results provide a technical guidance for the practical detection of Ti-alloy honeycomb sandwich structure.
Enhanced switched-inductor quasi-Z-source inverter
LI Zhengming, ZHANG Guosong, FANG Congcong
2016, 42(9): 1803-1811. doi: 10.13700/j.bh.1001-5965.2015.0579
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Switched-inductor quasi-Z-source inverter and its improved version in terms of boost ratio cannot meet the stringent demands of new energy field, limiting the utilization of Z-source inverter in photovoltaic inverter and micro-grid. This paper proposes an enhanced switched-inductor quasi-Z-source inverter topology with a high voltage gain by changing the traditional switched-inductor quasi-Z-source inverter. On the basis of one switched-inductor cell, a new switched-inductor cell is added in the new topology, which avoids that the hardware structure is too complex and shoot-through duty ratio range is too narrow, and allows the boost ratio to increase 5-40 times; the continuous input current can be ensured. Moreover, both the capacitor voltage stress and inductor current ripple are effectively reduced in LC network X-shape structure. In this paper, the enhanced topology is theoretically analyzed in detail. On this basis, some simulations and experiments are carried out to validate the feasibility and superiority of the proposed topology.
Take-off and landing adaptability of A380-800 large aircraft on existing pavement
ZHANG Xianmin, LIU Xiaolan, DONG Qian
2016, 42(9): 1812-1818. doi: 10.13700/j.bh.1001-5965.2015.0566
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In order to explore whether the existing rigid pavement can meet the normal take-off and landing requirements of A380-800 aircraft, the elastic layered model of rigid pavement and the whole main landing gear model of A380-800 are established, and numerical calculation is used to analyze the effect between A380-800 and pavement on influencing depth, the maximum tensile stress on panel bottom and the maximum vertical displacement on panel surface. The results are as follows: although the maximum take-off weight of A380-800 is 41.09% heavier than that of B747-400, more main landing gear tire number and larger main landing gear spacing and wheel track are advantageous to stress diffusion enhancement and superposition effect reduction, so the influencing depth of A380-800 is 4.29% more than that of B747-400; the locations of the maximum tensile stresses on panel bottom of A380-800 and B747-400 are different because of the main landing gear arrangement, and the maximum tensile stress on panel bottom of A380-800 is 1.09% less than that of B747-400; the maximum vertical displacement on the surface of A380-800 appears in the center of the three-axis double shaft section, while that of B747-400 appears in the back axle of the medial two-axis double cross section, and the maximum vertical displacement on panel surface of A380-800 is 0.49% less than that of B747-400 within the loading area. Therefore, the pavement structure layer which takes B747-400 as a design model or adapts to B747-400 normal take-off and landing can adapt to the normal take-off and landing of A380-800 from the perspective of mechanical properties.
Comprehensive assessment method of mission reliability based on FFMECA
CHEN Weidong, RAN Chenlong, ZHENG Qihui, HUANG Wenjun, LI Jianglong, XU Jiangtao
2016, 42(9): 1819-1826. doi: 10.13700/j.bh.1001-5965.2015.0576
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Mission reliability assessment is an important part of the process of weapon equipment development and production, and the assessment of FMECA in the attack mission stage has been made mostly in the qualitative aspect without consideration of the quantitative index of the degree of failure mode effect. In this paper, based on the fuzzy mathematics, the probability of failure mode effect is defined and given in the FMECA, and FFMECA method is formed. Based on this, the failure modes that affect the success of the mission are distinguished in the form of quantification, and the mission reliability is assessed with consideration of the probability of failure mode effect. The scatterable landmine is analyzed qualitatively and quantitatively in the attack mission stage. The results show that the method closely combines the early work of reliability, plans weapon equipment reliability assessment process, and is significative to engineering application of reliability assessment method.
Aircraft fuel volume calculation technique in state of variable velocity and attitude
YUAN Mei, HE Yiqiang, NIU Ben, DONG Shaopeng
2016, 42(9): 1827-1835. doi: 10.13700/j.bh.1001-5965.2015.0553
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To accurately measure remaining fuel in irregular tank, the adaptive step size cutting method (ASCM) which is used to build fuel quantity database is presented based on traditional look-up table and interpolation method. With the help of equivalent sensor, the method has integrated outputs of multi-sensor under different attitude. The method adjusts step size depending on the change rate of cross-sectional area to minimize interpolation error in fuel volume calculation. With multi-sensor's outputs to fit fuel surface by least mean square(LMS) method. When valid output is less, equivalent surface attitude angles are taken to fit fuel surface. It eliminates influence on fuel surface caused by acceleration. Three-dimensional look-up table interpolation method is improved to minimize deviation caused by attitude angle. Fuel volume calculation software is programmed with UG development kits. A number of CAD simulations with actual tank model are done. The results suggest that the method has compressed database size, accelerated calculation speed, corrected deviation resulting from acceleration and attitude, and reduced interpolation error. Thus, fuel measurement accuracy is improved.
Simulation and analysis of data frequency mixing errors in IMU based on FOG
PAN Xiong, HUANG Yuqiong, ZHANG Shaobo, WANG Xiaxiao, SONG Ningfang
2016, 42(9): 1836-1842. doi: 10.13700/j.bh.1001-5965.2015.0544
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The asynchronous resampling of fiber optic gyroscope (FOG) output data by navigation computer can cause frequency mixing errors. Based on the characteristics of FOG signal detection, a simulation model was established using the update rate of FOG closed-loop output and the resampling frequency of inertial measurement unit (IMU) as parameters, the sinusoidal noise frequency of vehicle as a variable, and the decrease of signal direct current (DC) amplitude error received by navigation computer as the target. The frequency mixing errors and delay characteristics of interpolation and decimation scheme and sliding filter scheme were analyzed. A variable sliding window length scheme was proposed and the sensitivity of error response spectrum to sliding window length was suppressed. The simulation results show that the maximum error of the variable sliding window length scheme is reduced from 0.056 85 to 0.009 737 compared with the sliding filter scheme with sliding window length's deviation from the optimal value of 4%. Besides, the proposed scheme can better accommodate the engineering requirement of timing pulse frequency dithering or switch.
Accelerated degradation modeling method based on Inverse Gaussian processes with random parameters
WANG Haowei, TENG Kenan, XI Wenjun
2016, 42(9): 1843-1850. doi: 10.13700/j.bh.1001-5965.2015.0542
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In order to apply degradation models with random parameters to accelerated degradation tests to improve the accuracy of reliability evaluation, an accelerated degradation modeling method based on degradation models with random parameters was studied with Inverse Gaussian processes taken as examples. First, acceleration coefficient constant principle was used to deduce the relationships that the parameters of Inverse Gaussian process should satisfy under different stresses. Then, the acceleration models of parameters were constructed and acceleration coefficients were computed. So accelerated degradation data was extrapolated from accelerated stress levels to normal stress level. The conjugate prior distributions of random parameters were used and maximization expectation algorithm was utilized to estimate hyper-parameters. Simulation tests validate the feasibility and effectiveness of the proposed method, and a case study demonstrates that the proposed method has good engineering application value.
Differential game guidance law for dual and bounded controlled missiles
HUA Wenhua, MENG Qingling, ZHANG Jinpeng, ZHANG Yongjun
2016, 42(9): 1851-1856. doi: 10.13700/j.bh.1001-5965.2015.0574
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Due to disadvantages of single canard fin control or tail fin control for bounded-control interception missiles, a novel dual and bounded controlled differential game guidance law is presented based on two-sided optimization differential game theory. This guidance law realizes fusion of these two fin controls and optimal distribution of control commands. The differential game space of this guidance law is analyzed and the existence conditions of saddle point solution are studied from the relationships between maneuvering performance ratio and time constant ratio of the two-sided control systems. With the consideration of imperfect information scenario, a filter for target accelerations and a performance index for target interception are presented. Based on Monte Carlo method, simulations are carried out and the results show that this dual and bounded controlled guidance law has higher single shot kill probability and lower maneuvering performance requirements compared with the single-controlled scenario.
Cooperative guidance law based on MPSC and CPN guidance method
LI Xinsan, WANG Lixin, WANG Mingjian, YAN Xunliang, LIU Guohui, DING Bangping
2016, 42(9): 1857-1863. doi: 10.13700/j.bh.1001-5965.2015.0592
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Cooperative guidance of multiple missiles satisfying terminal impact angle constraints is considered. A suboptimal guidance law is presented using the recently proposed model predictive spread control (MPSC) method and cooperative proportional navigation (CPN) guidance law. The basic principle of the MPSC method is given and the MPSC guidance law is designed on the assumption that the control is considered to be a function of quadratic formulation. The MPSC method requires a control history to begin the algorithmic sequence. Guess control history is computed using the CPN technique, subject to constraint on impact time. A stationary target is attacked by two missiles in the simulation. It is observed from the simulation that the impact time error and terminal impact angle error are within the specified convergence tolerance. The terminal impact angle constraint is well satisfied in salvo attack scenario.
Attitude control method within finite time globally for hypersonic vehicles
LIU Haidong, BAO Weimin, LI Huifeng, GONG Chunye, LIAO Yuxin
2016, 42(9): 1864-1873. doi: 10.13700/j.bh.1001-5965.2015.0547
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Taking six degrees of freedom model of a generic hypersonic vehicle as the research object, this paper proposes a terminal sliding mode attitude control method which can converge to the equilibrium point within finite time globally. In the design of the controller, dynamic inversion is applied to deal with strong couplings among pitch angle, yaw angle and roll angle. In the case of considering the model uncertainties and external disturbances, the terminal sliding mode variable structure control method is used to guarantee the robustness of the system. In addition, by improving the traditional exponential approach law, the control command can be tracked within finite time globally. Based on the Lyapunov stability theory, it is proved that the finite time convergence in both reaching and sliding phases can be achieved. Finally, simulation results demonstrate that the proposed attitude control method is efficient.
FDTD parallel algorithm based on distributed platform
FENG Yuan, DAI Xiaoxia, TANG Xiaobin, GONG Xiaoyan
2016, 42(9): 1874-1883. doi: 10.13700/j.bh.1001-5965.2015.0593
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A new finite difference time domain (FDTD) parallel algorithm is developed based on distributed platform, which is based on VC++, CUDA5.0 development platform, calling Intel MPI 4.1.0 library for testing, developing software debugging on the platforms of high performance computing center graphics processing units (GPU) cluster in Shanghai Jiao Tong University, "Rubik's Cube" commercial super computer at Shanghai Supercomputer Center, and "Divinity Blue" domestic super computer at the National Supercomputing Center in Jinan. By pure CPU, GPU, and CPU and GPU hybrid test, thread scheduling level and kernel function processing speed improve significantly, while the proportion of the execution time of communication reduces, and the acceleration ratio and operation efficiency improve. Finally, the topology optimization of the model is verified by 2×2 micro-strip arrays. The results show that the algorithm is accurate and effective.
Model transformation method from AADL2ECPN and its application in IMA
LIU Chang, GU Tao, ZHOU Qing, WANG Shihai, LI Zelin
2016, 42(9): 1884-1891. doi: 10.13700/j.bh.1001-5965.2015.0562
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Resource allocation modeling and safety analysis of integrated modular avionics (IMA) are essential in the process of IMA application integration. According to model transformation method, a set of transformation rules from the architecture analysis and design language (AADL) to the extended colored Petri net (ECPN) is proposed. Using the model transformation rules, the AADL model is transformed into the ECPN for subsequent safety analysis, and any of critical resource elements will not be lost in the model transformation process. Finally, a simple example is employed to show how to apply the model transformation method. Through the experimental results, the feasibility of the proposed method in IMA safety analysis is confirmed.
Dynamic Web service recommendation based on tensor factorization
ZHANG Wancai, LIU Xudong, GUO Xiaohui
2016, 42(9): 1892-1902. doi: 10.13700/j.bh.1001-5965.2015.0582
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In the area of Web service computing, in order to select a suitable service for users in a large number of Web services and API with the identical function，the issue of Web service recommendation is becoming more and more critical. At present, in the quality of service (QoS) based service recommendation systems, the hypothesis of the system model is a two-dimensional static model which is composed of dyadic relationship between users and service interaction. However, in view of the practical application, the QoS value is affected by many factors, and a tensor model is proposed to describe the factors which affect the QoS. Then, we propose a method to discover the latent factors that govern the associations among these multi-type objects of QoS. A new recommendation approach based on tensor factorization is proposed to address the issue of Web service QoS value prediction with considering Web service invocation time. The experimental results show that compared with six related algorithms, the mean absolute error (MAE) of the proposed tensor factorization algorithm is reduced by 20%-50%, and our model can be used to describe more factors and to dynamically recommend Web service.
New approach for dynamics modeling of dual-arm cooperating manipulators
LIU Jia, LIU Rong
2016, 42(9): 1903-1910. doi: 10.13700/j.bh.1001-5965.2015.0555
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High nonlinearity and coupling were shown from the dynamic characteristics of dual-arm cooperating manipulators because of the constrained relationship brought by desired task. Therefore, it was difficult to establish dynamical equation with traditional Lagrange equation. Aimed at the dynamics modeling of dual-arm cooperating planar manipulators, a generalized dynamical equation of multi-link planar manipulators was established and proved with traditional Lagrange equation. Then the additional torque and dynamical equation of dual-arm cooperating planar manipulators subject to some desired trajectory were acquired based on the famous Udwadia-Kalaba equation in analytical mechanics field and the above-mentioned generalized dynamical equation of multi-link planar manipulators. The new approach overcomes the disadvantage of obtaining dynamical equation from traditional Lagrange equation by Lagrange multiplier. The stimulation results of the varying law of the joint angles and the motion path of the bar prove that the dynamical equation established by this method conforms to the matter of fact.
Approach of credibility evaluation for testing system with small samples
WU Yunjie, WANG Jianmin, YANG Wenguang
2016, 42(9): 1911-1917. doi: 10.13700/j.bh.1001-5965.2015.0559
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Aimed at the problem that the small sample test data are lack of information and it is difficult to use probability statistic method for interval estimation, a novel approach of credibility evaluation for small sample testing system is proposed by integrating the repeated sampling method and the small sample interval estimation method. Many similar small samples with the same sample size are obtained using the theory of repeated sampling. According to the grey system theory, an improved definition and calculation method for grey confidence level and grey confidence interval is proposed. On this basis, the common area of the grey confidence intervals of many small samples is calculated, which is the grey confidence interval for the original small sample data. Under the same confidence level, the above confidence interval has narrower interval width and higher precision. The rationality and validity of the above method is verified through example simulation, which provides certain method guidance for small sample data system evaluation in engineering test.
Improved schedulability analysis for multiprocessor mixed-criticality systems
CHEN Yao, LI Qiao, LU Jun, XIONG Huagang
2016, 42(9): 1918-1926. doi: 10.13700/j.bh.1001-5965.2015.0551
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For mixed-criticality systems implemented upon multiprocessor platforms and scheduled by the popular global scheduling algorithm named fixed-priority and earliest deadline first by virtual deadline (fpEDF-VD), the issue how to determine their schedulability is studied, addressing the concern of multiple certification requirements. According to fpEDF-VD, the task's priority is determined by the combination of task utilization and virtual deadline, and the schedulability of the system depends on the existence of valid scaling factor for virtual deadline tuning. Considering that current approaches only verify finite scaling factor candidates, an improved schedulability analysis is proposed, which is capable of determining the feasible region of the scaling factor accurately. This approach investigates schedulability requirements at different criticality levels by exploiting the function graph of the schedulability condition derived for the regular (non mixed-criticality) fpEDF algorithm, and on this basis provides the accurate range of the parameter for tuning virtual deadlines. An illustrative example is presented to demonstrate its validity and efficiency. In accordance with theoretical analysis, extensive simulation experiments with randomly-generated task sets show the dominance of the proposed schedulability analysis over the existing ones in terms of acceptance ratio.
Life prediction of helicopter planetary carrier plate fatigue crack propagation
FAN Lei, WANG Shaoping, ZHANG Chao, KONG Dehe, MAO Yang
2016, 42(9): 1927-1935. doi: 10.13700/j.bh.1001-5965.2015.0586
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Planetary carrier plate (referred to as the carrier) is one of the most important components of a helicopter transmission system, and its reliability is critical for the helicopter flight safety. Subjected to a variety of factors, the development of the carrier fatigue crack fault is difficult to be diagnosed or prognosed. In order to predict the fatigue crack life of the carrier, crack fault mechanism is studied and a log-linear method is developed in this paper. The crack propagation process is discretized by combining the Paris law with Miner rule, then the fatigue crack damage is accumulated. And the value of the cracked carrier remaining service life corresponding to different crack length is obtained. Calculated numerical results are compared with simulation data using the commercial finite element software ANSYS Workbench fatigue life calculation module, which validates good accuracy and effectiveness of the developed method in predicting the remaining life of a cracked carrier.
Critical CTOA measurement based on quasi-static tensile test
LU Longkun, WANG Shengnan, WANG Zhao, SONG Enpeng
2016, 42(9): 1936-1943. doi: 10.13700/j.bh.1001-5965.2015.0557
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In order to find a more simple and accurate measurement critical crack tip opening angle (CTOAc) method and promote CTOA criterion's application, measurement methods of material CTOAc were studied. The relationship between two different crack tip opening displacement (CTOD) definitions has been derived from CTOA's properties and CTOAc estimation method proposed by Göteborgs Kungliga Segel Sällskap (GKSS). Upon the relationship, a CTOAc measurement method based on quasi-static tensile test was proposed, which is equivalent to but simpler than GKSS estimation method. In order to verify the validity of the proposed method, static tensile tests on 7B04 M(T) specimens were performed, and the 7B04's CTOAc values were estimated by the two methods above. The results show that only 1% discrepancies have been observed between the two CTOAc values. In addition, plane strain core model and plane stress model on specimens were generated in elastic plastic finite element, and the simulation results have coincided with test results.
Composite control for electric dynamic loading system based on fractional order iterative learning
LYU Shuaishuai, LIN Hui
2016, 42(9): 1944-1951. doi: 10.13700/j.bh.1001-5965.2015.0543
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To solve the problem of surplus torque, a composite torque controller is proposed for electric dynamic loading system where the position and torque closed-loops are applied for feedback control and the iterative learning control is applied for feedforward compensation. To improve the dynamic response and reduce the complexity of the system model, direct torque control is used for the permanent magnet synchronous motors. The mathematical model of the electric dynamic loading system is established in frequency domain. The traditional PID and iterative learning control are replaced by fractional order PIλDμ for position and torque closed-loops. Fractional order iterative learning control is used for feedforward compensation. The dynamic response and robustness of the controller are enhanced owing to the information memory characteristics of fractional order calculus. The convergence conditions of the fractional order PD-type iterative learning control are presented through theoretical analysis. Experiments on the loading torque with sinusoidal and trapezoidal wave torque and testing of the surplus torque suppression were performed. The experimental results prove that the controllers are effective in achieving a better torque tracking and restraining the surplus torque for the electric dynamic loading system.
Bio-inspired navigation method based on constraint strategy under geomagnetic abnormal disturbance
LIU Kun, LIU Mingyong, YANG Panpan, LI Hong, PENG Xingguang
2016, 42(9): 1952-1957. doi: 10.13700/j.bh.1001-5965.2015.0568
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The abnormity of geomagnetic field will form an extreme value region in the navigation space and disturb the magnetotaxis behavior. Such abnormity will cause the searching based bio-inspired geomagnetic navigation to fall into local minimum, and make the vehicle lose its navigation direction and fail to get out of the abnormal region, which leads to the failure of navigation behavior. In this paper, a navigation method based on behavior constraint strategy is proposed by expanding the exploration scope of vehicle under the constrained searching behavior, and the vehicle is then forced to get rid of the disturbance of abnormal region and get into the normal geomagnetic field. The statistic characteristics of magnetotaxis and convergence state of multi-objective functions are utilized to construct the trigger and termination conditions of behavioral constraints, and better historical data of magnetotaxis are taken as the constraint behavior. The evolution population is updated with the movement of vehicle and finally leads the vehicle to get to the target position. Simulation results show that this method can effectively overcome the abnormal disturbance to the bio-inspired geomagnetic navigation and enhance the success rate of autonomous long range navigation.
Multi-variable variable gain controller design and simulation based on aero engine
LI Jia, LI Huacong, XU Xuan, WANG Shuhong
2016, 42(9): 1958-1968. doi: 10.13700/j.bh.1001-5965.2015.0583
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Aimed at multi-variable variable gain controller design of aero engine in full envelope work, an improved KQ algorithm and its simulation applications are presented. First, we clarified the control theory and optimization algorithm of multi-variable KQ algorithms, and designed KQ controller via closed-loop desired function selection, controller structure selection and controller parameter optimization. Then we gave the stability proof and singular value analysis based on the designed KQ controller. Analysis shows that the designed KQ controller can make the system closed-loop stability, and has satisfactory low frequency instruction track, interference suppression, sensor noise suppression, high frequency unmodeled dynamic robust stability and non-sensitive low frequency engine modeling error, which can meet the control requirements of engine. Then, we designed a turbofan engine multi-variable KQ gain scheduling controller through scheduling variable selection, designed-point's KQ controller design and undersigned-points' KQ controller design by interpolation, and carried out a simulation to verify it. The results show that at the designed point, the controlled parameters have a fast response, the rise time is less than 1 s, and the coupling effect is less than 6% when the turbine temperatures and pressure ratios are step reference input signals. The KQ variable gain controller by interpolation method has better performance at the undersigned-points, and can achieve the turbofan engine full envelope control performance requirements.
Fillet modeling method in analysis of structural dynamic characteristics
DENG Hao, CHENG Wei
2016, 42(9): 1969-1976. doi: 10.13700/j.bh.1001-5965.2015.0536
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In view of the large number of rounded corners in thin-walled structures, the equivalent modeling method is presented based on the combination of beam element and shell element. Through the analysis of the contribution of the fillet to the stiffness of the thin-walled structure, the contribution was divided into in-plane stiffness contribution and out-of-plane stiffness contribution. The contribution effect of the fillet to the out-of-plane stiffness is equivalent to the beam. The section parameters of the equivalent beam element were derived by using the theory of torsion. For the in-plane effects of the fillet, the equivalent model was established by using shell element. The three-dimensional structure was simplified to a two-dimensional structure by using the plane strain state assumption. In plane, the equivalent thickness and elastic modulus of shell element were calculated by the equivalent stiffness principle. The correctness and accuracy of the modeling method are verified by two examples.
Structure design of piezoelectric fans and research on influence of parameters
KONG Yue, LI Min, XIN Qingli
2016, 42(9): 1977-1985. doi: 10.13700/j.bh.1001-5965.2015.0567
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A piezoelectric fan mainly consists of vibrating plate and actuator made by piezoelectric material. Vibrating plates are driven by actuators to cause fluid motion, which is a new kind of device for removal of heat. The purpose of this research is to investigate the influence of several parameters on the performance of piezoelectric fans and give advice to the design of piezoelectric fans. The method of computational fluid dynamics is used in this research to simulate the development of piezoelectric fan's flow field. Three parameters are studied including flexural modes of vibrating plates, double-plate orientation and phase difference between two plates. The results are as follows: the frequency of actuator should be equal to the fundamental resonance frequency of vibrating plate; for the models with two vibrating plates, the best phase difference is π (plates oriented in vertical direction) and 0.8π (plates oriented in horizontal direction). The cause of parameter influence is presented through analyzing the development of the flow field.
Quantitative method of dynamic fault tree analysis for imperfect coverage system
LI Peichang, YUAN Hongjie, CAO Zhenya, ZHANG Hailong
2016, 42(9): 1986-1991. doi: 10.13700/j.bh.1001-5965.2015.0590
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In order to efficiently perform reliability analysis for imperfect coverage system which contains standby units that make the dynamic fault tree analysis very complicated, a quantitative reliability analysis method applied to warm spare gate is proposed. The step function and impulse function are introduced to describe the dynamic failure characteristics of standby units. Then, considering the dynamic system with imperfect coverage, the paper deduces the formulas for calculating the reliability of warm spare gate. Finally, an airborne electronic device as an example illustrates the feasibility of the method by establishing system dynamic fault tree. Compared to the existing method without consideration of imperfect coverage, combined with system sensitivity analysis, the computational result of the proposed method is more rational and provides a novel foundation for further research on reliability quantitative analysis.
A pedestrian flow model at primary school gate after school
SHAO Yixiao, TANG Tieqiao, CHEN Liang
2016, 42(9): 1992-1998. doi: 10.13700/j.bh.1001-5965.2015.0549
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Based on the pedestrian flow patterns of primary students, this paper investigates the features of pedestrian flow under the rules of the certain scenario. During the primary students' evacuation process after school, various pedestrian behavior takes place, including pedestrian uneven distribution, pedestrian's input and output according to certain rules, paired phenomena and congestion phenomena. This paper uses the cellular automaton model and the static floor field to propose a pedestrian flow model and design an algorithm to calculate distance earnings of next move. This method is applied to simulate the evacuation behavior of pedestrians at the gate of Affiliated Primary School to Beihang University after school. The simulation results indicate that the input rate and the number of pedestrians at the initial stage have significant impacts on the evacuation efficiency and that there is a negative correlation between the average evacuation time and the initial number of pedestrians.
Surface cracking and melting behavior of tungsten-vanadium alloys under thermal shock
DING Dan, ZHANG Ying, YUAN Yue, LYU Guanghong, LIU Xiang, ZHOU Zhangjian
2016, 42(9): 1999-2007. doi: 10.13700/j.bh.1001-5965.2015.0597
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Surface cracking and melting behavior of tungsten-vanadium (W-V) alloys prepared by mechanical alloying + hot pressing (HP) sintering under thermal shock has been investigated in this paper. Mass fraction of V in the alloy is taken as a variable to explore the effect of mass fraction of V (1%-10%) on thermal shock resistance of W-V alloys. A variety of test methods such as optical microscope, scanning electron microscope, energy disperse spectrometer, and nano indentation are used to analyze the structure characteristics of W-V alloys produced by HP sintering, and the characteristics of surface cracking and melting behavior of W-V alloys under thermal shock. Results show that under the conditions of 1 800℃ and 20 MPa，and with heat preservation for 2 h, W-V alloys with high density and high alloying degree can be produced. Moreover, with the increase of vanadium content, the density of W-V alloys increases. In the alloys, the hardness of tungsten matrix is bigger than vanadium rich phase, and therefore, tungsten matrix's ability of preventing the crack growth is obviously greater than vanadium rich phase, when exposed to thermal shock in international thermonuclear experimental reactor (ITER) edge localized modes (ELMs) which are simulated by high energy electron beam; with the increase of vanadium content, the cracking threshold and melting threshold both decrease. The underlying mechanism is discussed detailed in this paper.
Wind tunnel test of rolling maneuver load alleviation
QIN Hangyuan, WU Zhigang, YANG Chao, DAI Yuting, MA Chengji
2016, 42(9): 2008-2016. doi: 10.13700/j.bh.1001-5965.2016.0142
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Abstract:
It has been documented that maneuver load alleviation possesses a strong potency for reducing structure weight which would improve flight performance in the field of aircraft design. In view of this situation, a wind tunnel test was designed and conducted in this study to evaluate the control method of rolling maneuver load alleviation (RMLA) with multiple control surfaces. According to the demands for test, a series of models and procedures were designed, including the test aircraft model with a normal layout and a small aspect ratio, rolling and limiting device, measurement and control system based on test model, zero-degree keeping circuit, and RMLA control systems. The test was conducted using two control laws with different combinations of control surfaces to evaluate the effects on load alleviation. It was found that, compared with baseline control law, the additional maneuver load generated during the process of rolling maneuver was effectively alleviated using the method of simultaneously deflecting multiple control surfaces. The control law 1 with the simultaneous deflection of wing and trailing-edge outboard (TEO) control surface alleviated the bending and torsion moments of wing by 30.1% and 38.0%, respectively, and the bending and torsion moments of empennage by 57.9% and 12.5%, respectively. The control law 2 with the simultaneous deflection of wing, TEO, and trailing-edge inboard (TEI) control surfaces alleviated the bending and torsion moments of wing by 33.0% and 35.5%, respectively, and the bending and torsion moments of empennage by 45.7% and 54.8%, respectively.

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