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2015 Vol. 41, No. 3

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Volume 41 Issue32015
2015 Year 41 Volume 3 Issue E-journal
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Approximate calculation method of buckling load on integral sub-stiffened panel
XU Yuanming, LI Songze
2015, 41(3): 369-374. doi: 10.13700/j.bh.1001-5965.2014.0240
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To calculate the integral sub-stiffened panel buckling load in the preliminary design stage quickly, a simplifying approximate calculation method based on some reasonable assumptions was proposed. The perfect rectangular sub-stiffened panel simply supported on four sizes was used as investigation object. This structure has 3 instability forms, and the corresponding buckling loads were obtained by using the traditional stiffened plate theory. The minimum buckling load of the 3 instability forms was regarded as the approximate buckling load of the integral sub-stiffened panel. The buckling linear perturbation step method of ABAQUS was used to calculate the two sets of finite element (FE) models respectively: one set was used to validate the accuracies of the theoretical formulas for failure modes, and the other set was integral sub-stiffened panel finite element models which were used to verify the applicability of proposed calculation method of sub-stiffened panel buckling load. Only two load cases were considered in the research above: the longitudinal compression load and the combination of compression and shear load. The results indicate that the theoretical approximate calculation method can calculate the buckling load of sub-stiffened panel, which count for engineering application to some extent.
FPGA hardware implementation of the LZMA compression algorithm
LI Bing, ZHANG Lin, LIU Yong
2015, 41(3): 375-382. doi: 10.13700/j.bh.1001-5965.2014.0169
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Software-based LZMA (Lempel Ziv Markov-chain algorithm) nondestructive compression algorithm is very slow and consumes too much CPU (central processing unit) resources during the data compression process, as a result it can not meet the requirements of real-time systems. On the basis of the improved algorithm, a hardware accelerator for LZMA was designed with FPGA (field programmable gate array) implementation. The hardware accelerator is composed of LZ77 compressor, range encoder and send out controller. Ping-pong operation, parallel matching method with high performance, pipeline processing structure and other acceleration techniques were used to speed up LZMA compression algorithm. While at the same time, data compressed by the circuit is still compatible with standard LZMA file format. The compression rate of the circuit is speeded up to 125 Mb/s, nearly 10 times faster than that of the software based LZMA. The processing relative data of each clock is speeded up nearly 200 times. Results from the experiments on ML605 basing on a Virtex-6 FPGA development kit, show the accelerator is correct and feasible.
Building areas extraction basing on MSER in unmanned aerial vehicle images
DING Wenrui, KANG Chuanbo, LI Hongguang, LIU Shuo
2015, 41(3): 383-390. doi: 10.13700/j.bh.1001-5965.2014.0177
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Automatic detection and extraction of the building area is an important aspect of unmanned aerial vehicle (UAV) image processing. Based on the detailed analysis of UAV imaging characteristics and the maximum stable extremal regions (MSER) algorithm, a building area extraction algorithm of UAV image is proposed. The algorithm consists of five steps: firstly, the pretreatment of UAV image; secondly, analysis and calculation of image stable regions using MSER; thirdly, screening the building area by calculating the density of stable regions; then, using adaptive K-means clustering algorithm to divide the building area; ultimately, boundaries of the building area were generated using Graham algorithm in order to achieve automatic extraction of building area. Using the UAV real flying image data to do the experiment statistics, the conclusion includes: Firstly, the extraction accuracy of this algorithm reaches 92.25%; secondly, when compared with other building area extraction algorithm which based on Gabor transform or SIFT, the extraction time of building area is shortened and meets the needs of UAV real-time applications.
Simulink model testing method based on program mutation
ZHOU Yibin, YIN Yongfeng, LI Xiaodan, WANG Mingwei
2015, 41(3): 391-397. doi: 10.13700/j.bh.1001-5965.2014.0211
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In order to solve the current problems (expensive testing cost and low efficiency of test case generation) in mutation test for Simulink models, a mutation testing process and an optimized set of mutation operators were proposed for Simulink models based on program mutation according to the current mutation operators for the Simulink models. Experiments show that this set of mutation operators can effectively reduce the generation number of mutation models without prejudice to the mutation score of testing case set, thus it will effectively save the testing cost. Then a search-based test case generation method for Simulink models mutation testing was described. The test case generation problem was transformed into the objective function minimization problem, and the test cases which can kill the mutation models were ultimately obtained through the optimization of objective function by algorithm of simulated annealing. Finally, the application of a typical case for the method verified the correctness and effectiveness.
Autonomous mobile drilling mechanism with metamorphic function
WANG Min, WANG Xiemiao, CHEN Wenliang, DING Liping
2015, 41(3): 398-404. doi: 10.13700/j.bh.1001-5965.2014.0242
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According to the application requirements of aircraft automatic assembly and the principle of metamorphic mechanism, a double eccentric source metamorphic mechanism was presented. On the basis, a autonomous mobile drilling mechanism with metamorphic function was designed, and the switching of changing freedom between the two functional stages of walking and posture alignment drilling. The calculation method of inverse kinematics was provided, which could calculate the driven displacement of legs during the posture alignment process which changed from initial to desired normal direction by pitching and side roll. This could be used to the online control. The offset domain of inverse arithmetic of each leg in working conditions were plotted by Matlab, and the dimensional designing of double eccentric source metamorphic mechanism was achieved. The virtual prototype model was established, and the kinematics simulation was carried out by using examples. The results confirmed that the kinematics calculation method and the double eccentric source metamorphic mechanism were applicable for the mechanism. The prototype of mechanism was developed, and the posture alignment accuracy of the system was tested. The result shows that the mechanism can meet the drilling requirements of the aircraft automatic assembly.
Influence factors analysis on wear of hydraulic axial piston pump/slipper pair
MA Jiming, LI Qilin, REN Chunyu, CHEN Juan
2015, 41(3): 405-410. doi: 10.13700/j.bh.1001-5965.2014.0204
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Wear of swash plate-slipper moving pair (slipper pair) of hydraulic axial piston pump results in increasing leakage, declining efficiency, and finally shorting the lifetime. An accelerated lifetime test method was presented based on the elasto hydrodynamic lubrication (EHL) wear model. As the most important factor effecting on wear process, oil film thickness of slipper pair was primarily analyzed. Running parameters (temperature/rotation speed/pressure) were integrated and considered when analyzing the wear, and the intrinsic factors affecting the wear process of sliding pair were revealed. An axial piston pump is selected as the study case. Firstly, under two different running conditions, wear amounts of slipper pair were analyzed and the analysis results were compared with long term test results, which verify the accuracy of analysis results of wear amounts and the feasibility of the method and mode. Then, based on the proposed method and wear analysis model, the relative relationship between medium temperature (viscosity), output pressure, rotate speed and wear ratio of slipper pair were analyzed comparatively. Finally, discussions about the accelerated means of piston pump when executing an wear accelerated lifetime test and the effects of working condition on acceleration ratio were given. Research result can be utilized to create the load spectrum of accelerated wear test of piston pump, and is also useful to do optimization for reducing wear of piston pump.
Calibration method of robot base frame by quaternion form
WANG Wei, LIU Lidong, WANG Gang, YUN Chao
2015, 41(3): 411-417. doi: 10.13700/j.bh.1001-5965.2014.0239
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The accuracy pose of robot base frame with respect to the world frame needs to be calibrated under the task of multi-arm cooperation, identification of kinematics parameter and off-line program of robot. An accurately calibration method of robot base frame using quaternion form was proposed and applied. The kinematic model of robot was established by the product-of-exponential formula. 5 tool center points (TCPs), which were not coplanar, were measured with the external measuring device, and the corresponding robot joint configurations were also recorded. By considering the elements of rotational matrix corresponding to the base frame pose as the variables, a group of incompatible equations was set up, and the initial homogeneous matrix of the base frame pose was also obtained. However, due to the errors of measuring and truncation, the rotational matrix part of initial homogeneous matrix cannot satisfy the regulation of unit orthogonal matrix. Using the geometrical constraints of a quaternion, an objective equation by the form of penalty function was established, and the initial homogeneous matrix was orthogonalized. By a set of practical calibration experiments of robot, the validity of calibration method was verified, which improved the accuracy of the location of robot end.
Performance analysis and parameter setting for Tong detection algorithm
ZHU Yunlong, CHOU Wusheng, YANG Dongkai
2015, 41(3): 418-423. doi: 10.13700/j.bh.1001-5965.2014.0181
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Tong detection algorithm is a common used signal detection algorithm. But the overall conclusions about statistical performance and parameter setting of Tong detection algorithm are absent. Aiming at these problems, statistical and recursive analysis methods were used to carry on theoretical analysis about mean value and variance of dwell times in signal search unit in detail, the corresponding expressions were given, a maximum dwell times constraint method was offered according to the 3Sigma principle. The relationships between detection probability, average dwell times of noise search unit and signal search unit, initial value and maximum value of algorithm counter, pre-detection signal to noise ratio were analyzed. Analysis results indicate that the parameters of Tong detection algorithm should be set according to signal strength and search modes, and the influence of parameter setting on detection probability and average dwell times of noise search unit or signal search unit should be balanced.
Multi-user collaborative interface
YANG Qiang, LIU Jie, ZOU Yu, QIN Yongqiang, YU Chun, SHI Yuanchun
2015, 41(3): 424-430. doi: 10.13700/j.bh.1001-5965.2014.0465
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The multi-user characteristic is a key factor for interactive tabletops. Some emerging collaborative patterns emerge during the process of multiple users gathering around interactive table and collaborating face to face. The interface which shows the emerging collaborative pattern is a design paradigm of emerging interface, which is called “interactive interface”. 6 characteristics and 5 emerging interactive modes, including concurrent operation of interactive interface and so on, were analyzed. In the aspect of design, the design paradigm for collaborative interface was proposed, and typical collaborative patterns were formally descripted and designed with hierarchical state machines. In the aspect of implementation, a set of component libraries embodying the collaborative traits and collaborative modes above were developed, and two typical applications were embodied based on these component libraries. Finally, user experiments were conducted, and experiment data were analyzed by Likert Scale. The results show that collaborative interface design based on interactive tabletops can improve decision quality, the efficiency of collaborative situation sensemaking and the visualization effect increase by more than 60%, the effect is significant.
Design of visual simulation system of aircraft flight load spectrum measured data based on double-buffering technology
TIAN Zhaofeng, YAN Chuliang
2015, 41(3): 431-436. doi: 10.13700/j.bh.1001-5965.2014.0599
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Aircraft load spectrum measured data visual simulation is an important means to identify maneuver and to verify the validity of measured data in flight testing. A data storage method based on logical data channels was put forward to solve the structural differentiation problem of different data sources caused by different measured objects; for the performance problems caused by model complexity when large amount of measured data was used to simulate the whole flight course, physical channel and logical data channel analytical model were established; based on data double-buffering and drawing double-buffering mechanisms, flight model and visual simulation system environment of measured data were established, and the measured flight data of different testing aircrafts were analyzed and verified. The results show that the visual system meets the verification of flight measured data and the demand of maneuver recognition of GB level load spectrum of different types well, and can reproduce the entire course of the flight completely. It provides a visual platform to identify maneuver of flight course of aircraft, verify the data validity and post process of data.
Performance analysis of high accuracy multi-dimensional limiting process
SUN Di, YAN Chao, YU Jian, QU Feng, HUA Jun
2015, 41(3): 437-442. doi: 10.13700/j.bh.1001-5965.2014.0185
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The conventional limiting process is mostly based on one-dimensional structure, which cannot keep monotonic features of quantities under conditions of multi-dimensional discontinuities, leading to non-physical oscillations. In order to overcome the structure defects of the conventional methods, multi-dimensional limiting process (MLP) is a high accuracy limiter whose basic idea is that the vertex values interpolated at a grid point should be within the maximum and minimum cell-average values of neighboring cells through multi-dimensional correction. The major advantage of MLP is to avoid multi-dimensional oscillatory effectively and ensure solving accuracy. According to a set of test cases including one-dimensional shock tube, non-viscous vortex flow and shock boundary-layer interaction, the performance of MLP with high accuracy was analyzed, it is verified that third-order MLP can avoid multi-dimensional oscillatory effectively both in continuous and discontinuous area. Compared with higher-order WENO (weighted essentially non-oscillatory) schemes, the third-order MLP maintains several desirable characteristics, such as simple algorithm, simple implementation, improving the solving accuracy, monotonicity and convergence. For these properties, MLP can be applied to study complicated flow in engineering and scientific research, and is expected to have a bright application future.
Carrier airwake simulation methods based on improved multi-objective genetic algorithm
TAO Yang, HAN Wei
2015, 41(3): 443-448. doi: 10.13700/j.bh.1001-5965.2014.0198
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A new numerical turbulence simulation method to enhance the credibility of simulation of carrier airwake free-air turbulence components has been presented. At first, the turbulence sequence of each direction was presented as the Euler forward different format with correction factors. Meanwhile, associated with the thought of intelligence algorithm, the mean squared error and correlation function error in turbulence correlation test were regarded as the optimized objective functions. And the selection of correction factors was treated as a multi-objective optimization problem. The correction factors were determined by improving multi-objective genetic algorithm. At last, the validity and rationality of this method were verified by simulation cases. The calculation results show that the required turbulence sequences can be generated flexibly with different sampling steps. Especially in case of some small sampling step, the simulated turbulence sequences fit the theoretical values very well, and the method can meet the requirement of virtual flight test.
Printed circuit board model updating based on response surface method
XU Fei, LI Chuanri, JIANG Tongmin
2015, 41(3): 449-455. doi: 10.13700/j.bh.1001-5965.2014.0219
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Optimization analysis based on response surface is used in finite element (FE) model updating in recent years. Printed circuit board (PCB) model updating process based on response surface was presented. First six modal frequencies of PCB were calculated using ANSYS and correlated with modal test results. Three objective functions were formed using the first three orders of FE analytical and measured modal frequencies. The fourth objective function was formed by the square of residuals between first six resonant frequencies. Each resonant frequency was given the same weight. A multi-objective genetic algorithm (MOGA) was used in optimized analysis to minimize the four objective functions. A case was presented to illustrate the proposed updating procedure. The results show that the model updating technique based on response surface can be used to improve the accuracy of PCB FE model, and can be analyzed directly by using commercial FE softwares now available, which is conducive to engineering application.
Simultaneous topology and shape optimization method in conceptual design of disk
FAN Jun, YIN Zeyong, WANG Jianjun, MI Dong, YAN Cheng
2015, 41(3): 456-465. doi: 10.13700/j.bh.1001-5965.2014.0232
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To minimize the effects of artificially chosen variables on optimization results, simultaneous topology and shape optimization (STSO) method was proposed for structural optimization of aero-engine disk at the conceptual design phase. This method was based on solid isotropic material with penalization (SIMP) method, by analyzing the sensitivities of the optimized object and constraints, sequential quadratic programming (SQP) optimized method was used to solve the problem. Then, taking shell structure for instant, the results of STSO method and multi-step optimization method were comparatively analyzed, which confirmed the advantage of STSO method. At last, the STSO method was utilized to design a conceptual disk structure. Results of disk structural optimization of STSO method were compared to that of the sole topology optimization method. Influence of frequency constraints of different vibration modes on optimization results was discussed. The results show that the structural forms of optimization results of frequency constraints of different vibration modes vary a lot. Convergence rate of STSO method is faster than that of solo topology optimization, and the consequences of STSO method are more accurate. Meanwhile, the results of STSO method may be invalid for excessive mesh distortion caused by the wrong choice of the value range of shape optimization variables.
Real-time drawing technique for textured surface based on multi-projector system
CHEN Feng, LIU Yue, WANG Yongtian
2015, 41(3): 466-471. doi: 10.13700/j.bh.1001-5965.2014.0466
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With the development of the hardware performance of projectors and techniques on computer graphics, projections are used on more common surfaces so as to provide vivid and shocking visual effects. A new method that employed multi-projector system and interactive flat devices to modify the appearance of textured surface in real-time was introduced. On the basis of analyzing the color modeling of the system, an algorithm which recovered radiometric parameters and distributed the projection energy properly was presented. Efficient interactive-rendering pipelines were developed to insure that newly designed patterns could be projected on surface of objects without geometry and radiometric distortions. Experimental results show that the proposed method could improve the system accuracy of compensation while enlarging the system intensity range. Interaction, drawing and rendering modules of the system work synchronously to compensate the target appearances in real-time.
Numerical simulation of adsorption characteristics of magnetic take-up roll for amorphous ribbon
SONG Yanming, YANG Yang
2015, 41(3): 472-478. doi: 10.13700/j.bh.1001-5965.2014.0180
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Take-up roll (TUR) is a key component in amorphous ribbon automatic production line. Take-up rate of TUR determines the ribbon quality and production rate. Because the line speed of amorphous ribbon in the ribbon process is fast and the amorphous ribbon suffers from different resistance, TUR should generate enough adsorption force to overcome the different resistance conditions. According to the requirements of ribbon production process, the structure of magnetic TUR with NdFeB permanent magnet was proposed. The finite element method was used to analyze magnetic adsorption characteristics in different ribbon steps. The magnetic adsorption force contour and magnetic field distribution were obtained along different axes under different air gaps. The calculation results show that the magnetic TUR can supply enough adsorption force to take up the ribbon when air gap is smaller than 30 mm in specification range. Finally, the maximum magnetic adsorption force under different air gaps were measured by spot tests. It is verified that the test result is consistent with the simulation result.
Self-adaptive laser marking technology for marking code on tool
XU Lang, HE Weiping, WAN Min, LI Weidong, LEI Lei
2015, 41(3): 479-484. doi: 10.13700/j.bh.1001-5965.2014.0206
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In view of the recent situation that several defects of traditional laser marking code on tool appear such as marking inefficiency, marking quality instability and the harm to workers, a self-adaptive laser marking technology was put forward. The conveyor and V-block of specific structure were designed with photoelectric switch detection function to realize self-adaptive tool delivery. Besides, a kind of gripper was developed that made the different tool axes stand in the same position after grasping, which ensured that all of the different tool ends could quickly locate to laser marking area. Moreover, using the rapid moving of gripper, a photoelectric switch was adopted auxiliary focus to improve the speed and precision of focusing. Under the support of the three key technologies above, the whole design of project was completed. The test results of prototype prove that the self-adaptive laser marking technology increases the marking efficiency of more than four times compared with that of the traditional way and ensures the marking quality reliably. This technology achieves the goal of unmanned marking.
Resonance suppression method based on digital filter for servo system
WANG Jianmin, WU Yunjie, LIU Youmin, ZHANG Wulong
2015, 41(3): 485-491. doi: 10.13700/j.bh.1001-5965.2014.0218
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According to mechanical resonance problem in flight simulation servo system (turntable system), the principles of resonance suppression about traditional notch filter and second-order low-pass filter were analyzed. Afterwards the two-second resonance suppression digital filter was proposed. The two-second digital filter combines the characteristics of traditional notch filter and second-order low-pass filter, and it can suppress the resonance point and the anti-resonance point at the same time. Through theoretical analysis and simulation combination, the principle of the two-second digital filter restraining the resonance point and the anti-resonance point simultaneously was explained. The experiments were also conducted, in which above all filters were joined into the turntable system respectively. Experimental results show that, the proposed filter ensures high tracking precision meanwhile effectively widens the bandwidth of the servo system.
Improved back-projection imaging algorithm for approximate forward looking missile-borne SAR
YE Xiaoming, ZHANG Guofeng, HU Xiaoguang, CHEN Ruiguo, SUN Yanhe
2015, 41(3): 492-501. doi: 10.13700/j.bh.1001-5965.2014.0223
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In order to solve the problems that the existing high squint missile-borne synthetic aperture radar (SAR) algorithm can not deal with too high squint angle, and that the calculated amount of traditional back-projection (BP) imaging algorithm is too large, as well as that the current fast BP algorithm can not process the echo data in parallel, an improved approximate forward looking missile-borne SAR back-projection imaging algorithm which can process echo data in parallel was proposed. According to geometrical relationship of approximate forward looking missile-borne SAR, an echo signal model was established. And the imaging area was divided to equidistance strip in range along the distance direction. The image was split when merging sub aperture, and the splitting and merging did not stop until the accuracy of image met the requirements. Next the raw echo data was back projected to each strip for coherent integration, and then the missile-borne SAR image was obtained. If these strips were processed for imaging in parallel, the imaging speed would be further improved. Finally, results of simulation echo data and real echo data validate that the improved algorithm can deal with approximate forward looking scene with 86° squint angle, and it can greatly improve the computation speed compared with that of traditional BP algorithm. Moreover, the computation speed is faster than that of other improved BP algorithms by processing those strips in parallel.
Regulation strategies on the public transit system with information provision
LIU Dalong, TIAN Qiong
2015, 41(3): 502-508. doi: 10.13700/j.bh.1001-5965.2014.0227
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The effects of various regulation strategies on the transit fare and frequency in public transit system with information provisionwas studied. Besides two extreme strategies, namely monopoly optimum and social optimum, the rate-of-return strategy and quantity control strategy were also investigated as two more realistic regulation policies. The model assumes that the arriving passengers follow passion process and the percentages of passengers who plan their trips are endogenous and depend on the frequency of service and on the quality of information provided. There is a certain relationship between monopoly optimal and social optimal under the above model. In addition, the problem of profit maximization by public transport company under transit regulations was also analyzed. The results of the study found that the information provided undersocial optimum is better than monopoly optimal, and the number of passengers under social optimumis two times than monopoly optimal, other exogenous variables also have a significant effect of the four kinds of regulation strategies.
Analysis on vibration transmission characteristics of box-like power structure
GAO Weijin, WANG Liang, LIU Yongguang
2015, 41(3): 509-516. doi: 10.13700/j.bh.1001-5965.2014.0245
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Box-like dynamic structures are proceeding at the direction of maximization and flexibility. Vibration transmission characteristics of geared shaft-bearing-housing were studied by finite element method under different excitation conditions for two-stage reducer. Gearbox was used as a flexible substructure reduced to the center of bearing hole by Craig-Bampton dynamic reduction technique. When mesh transmission error and torque fluctuations of input shaft served as excitation source respectively, meanwhile nonlinear factors such as time-varying meshing stiffness, meshing misalignment, gear tooth backlash, axial contact ratio, and the gravity effect of shafts and gears were taken into consideration, dynamic acceleration response at gearbox reduction nodes and bearing inner ring were analyzed based on the thought of shaft section node. Finally, the natural frequencies of gearbox were extracted based on Block Lanzos method. Numerical analysis results show that the bearings of output shaft do not play an attenuation effect in the process of dynamic response transmission, and should be replaced to prevent the influence on the performance of whole system. Gearbox is conservatively designed that needs to be optimized according to the dynamic response of gearbox reduction nodes.
Perigee altitude control using aerodynamic force during aerobraking
JI Yingliang, ZHU Hongyu, YANG Bo
2015, 41(3): 517-522. doi: 10.13700/j.bh.1001-5965.2014.0197
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An approach of perigee altitude control using aerodynamic force was provided to deal with the decline of perigee during the orbital transfer process of aerobraking. The atmospheric flight control law considering the bank angle as control variable was investigated, and the computer simulation which referred to the relevant interplanetary exploration mission was performed for demonstration. The perigee altitude was controlled by changing the bank angle to adjust the aerodynamic force component along altitude direction. And the feedback gains were automatically adjusted according to the currently actual altitude and the desired altitude of perigee. The present control law effectively limited the decline of perigee altitude and reduced the quantity of decline finally during whole aerobraking without fuel consumption. Meanwhile, the max dynamic pressure and the max heat flux were decreased gradually, which ensure the security of spacecraft.
Post-buckling damage analysis and fatigue life prediction of thin plate
XIAO Hao, HU Weiping, ZHANG Miao, MENG Qingchun
2015, 41(3): 523-529. doi: 10.13700/j.bh.1001-5965.2014.0174
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Post-buckling damage of thin plate under compressive load in plan was studied, and the fatigue life of plate was predicted by taking the coupling effect of buckling and fatigue damage into account. Firstly, the finite element model was established, and the critical buckling load and buckling mode were obtained by linear buckling analysis, then the large deflection theory was adopted, first order buckling mode was applied as the initial displacement perturbation, and the corresponding critical buckling load was determined by nonlinear bucking analysis of thin plate. Secondly, damage evolution equation of thin plate material under monotonic loading was established based on damage mechanics theory and method, and parameters of damage evolution were obtained by the parameter identification based on the material fatigue test results. Post-bucking damage was analyzed base on nonlinear bucking analysis results and damage evolution equations. Finally, the effect of fatigue load was took into consideration, finite element numerical method was used to solve the problem based on damage mechanics theory, considering the coupling effect of the damage caused by load each time and post-bucking stress strain fields analyze, the fatigue life of the structure was achieved by repeating iterative computations. The research provides a new method and a practical means for the analysis of post-buckling damage and fatigue life considering post-buckling damage of engineering structures.
New adaptive PID control method based on IFA-ELM for aero-engine
JIAO Yang, LI Qiuhong, LI Yebo
2015, 41(3): 530-537. doi: 10.13700/j.bh.1001-5965.2014.0182
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For the strong nonlinear and variable parameters properties of high bypass ratio turbofan engine, an adaptive PID control method based on optimized extreme learning machine (ELM) was proposed to predict the engine's parameters. To improve the prediction accuracy and the real-time property of ELM, an improved Firefly algorithm (IFA) for multi-peak optimization was adopted to optimize the network parameters of the ELM, and formed an optimized ELM training method IFA-ELM. Under the premise of ensuring prediction accuracy, the algorithm effectively simplified the network scale and improved its generalization capability. The engine fan speed prediction model was built by this algorithm, and gradient descent method was adopted to adjust the PID parameters online based on the model to improve the dynamic performance of engine. Digital simulation results show that compared with conventional PID control, IFA-ELM based adaptive PID method shortens the settling time by 0.2~1.4s, and reduces the overshoot by 0.2%~1.5%, which demonstrates the effectiveness of the proposed control method.
Calculation of brake disk life based on unsteady discontinuous brake
ZHOU Bin, LI Shulin, CHANG Fei, SHI Xiaopeng, YIN Junjie
2015, 41(3): 538-544. doi: 10.13700/j.bh.1001-5965.2014.0184
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Focus on the problem that the actual service life of brake disks is always shorter than the calculated data underground test, made use of the friction coefficient curves and took the actual statistic using boundary of carbon brake disk to fit a friction coefficient curve of unsteady discontinuous brake. The wear distance of one and several brakes to stop is calculated by using dynamic theory, and the wear rate of the two different braking is 1:1.899 7-1:2.036 3 using the formula of abrasive wear, which is exact compared with the statistic result 1:1.88-1:2.09 in the airfield. The wear condition becoming worse in unsteady discontinuous brake is the main reason leading to the wear speeding up of carbon brake disks fitting on the airplane. The important role of friction layer to reduce wear is proven and a calculation method is established to improve brake disks life test and estimate actual service lives of different-material brake disks by this study.
Forecasting for aero-engine failure risk based on Monte Carlo simulation
ZHAO Hongli, LIU Yuwen
2015, 41(3): 545-550. doi: 10.13700/j.bh.1001-5965.2014.0190
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In view of the fact that aero-engines have complicated structure and multiple failure modes, traditional methods are difficult to meet the requirements. A forecasting method for aero-engine failure risk based on Monte Carlo simulation is presented, which is used to evaluate the possibility of failure for each component of engine in the future. According to the characteristics of aero-engine failure data, the failure probability model is based on the Weibull distribution whose parameters are estimated by the method of rank regression. Combining multiplicative congruent generator with the inverse transform method, the random numbers are produced to satisfy Weibull distribution. The method used to forecast failure risk for engines with multi-failure modes is based on the one with single failure mode. The simulation procedures and algorithm, by comparing the simulation results with the forecasting datum from the engine manufacture are presented, it proves that the algorithm and Monte Carlo simulation are effective in aero-engine failure risk forecast.
Calculation and analysis of the scatter of load spectrum damage based on Fokker F27 airplanes
LI Tang, HE Xiaofan, LIU Wenting
2015, 41(3): 551-558. doi: 10.13700/j.bh.1001-5965.2014.0195
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To assess the reliability life of a fleet, the scatter of the load spectrum must be considered. In this paper, 56 individual load spectra are compiled based on the acceleration-exceedance curves corresponding to a fleet of Fokker F27. With the application of the SWT formula and linear accumulative damage rule, the flight damage and the ground-air-ground (GAG) damage, as well as the total damage per flight have been analyzed. Next, the probabilistic coordinate regression is conducted to examine the distribution parameters of the three types of the damage of load spectra respectively. The goodness fit shows that the flight damage follows the Weibull distribution whilst the GAG damage follows the lognormal distribution, and the total damage comprehensively including flight damage and GAG damage follows a lognormal distribution. In addition, the lognormal standard deviation of the total damage is 0.073 7.
Object tracking based on the joint model using L2-norm minimization
WANG Meng, WU Yi, DENG Jiankang, LIU Qingshan
2015, 41(3): 559-566. doi: 10.13700/j.bh.1001-5965.2014.0455
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Abstract:
The computational cost of the tracking algorithm based on the sparse representation is so much large, at the same time, the target apparence changes on account of a variety of reasons,which makes the object tracking process complicated and time consuming. A joint model is reasonably proposed by combining the global template based on the discriminant model and the generation model based on the local descriptor, properly solved by the L2-norm minimization solution in a bayesian inference framework, which is proved to be effective and efficient. In the process of the object tracking process, the plus template and the minus template of the discriminant model and the coefficient vector of the generative model are timely updated so as to have a strong adaptability and robust discrimination. The experimental results finally show that compared with other typical algorithms, the proposed algorithm has stronger robustness in the case of illumination, scale changes, shelter, rotation and so on.

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