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2006 Vol. 32, No. 06

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Operational effectiveness analyses of air-to-ground strike for two-plane formation
Sun Kangwen, Huang Jun, Wu Zhe
2006, 32(06): 625-629.
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Two-plane formation is a main organization of the battle mode in the rivalry of air defense, which can fight the enemy’s strategic target more effectively. By using Markov random processes, a method of probability, which usually can be used in the evaluation of system’s effectiveness, the prediction of battle field and the mathematics model under the condition of two-plane formation which attacked the enemy strategic target in a threat environment were built. The operational effectiveness measures of the two-plane formation, including the probability of mission success, the probability that the target was killed and the probability that the aircraft was killed for an air-to-ground target attacking operation were deduced. Finally, by introducing viability enhanced quotient in an instance, the superiority of two-plane formation in attacking the enemy strategic surface target in a dangerous environment was validated by means of the comparison between two-plane interindependence and two-plane formation in their relative effectiveness measures.
Improved semi-analytical correlation approach for the flowfield downstream of swirl cups
Huang Yong, Guo Zhihui
2006, 32(06): 630-634.
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An improved semi-analytical correlation was proposed for the prediction of the flowfields downstream a typical swirl cup on the basis of previous correlations proposed by Rizk & Mongia. The improved correlation has clear physical definition and is adequate for its constants determination by large amount of experimental data. The comparison between the selected experimental data and the predictions by the correlation is quite well, especially about the characteristic data such as the peak velocity, the radial location of the peak velocity, the decay of the velocity, the size of the recirculation zone, and the development of the recirculation zone. Meanwhile, the influences of the constants in the correlation are shown quantitatively, and the possible reason has been analyzed briefly. The analysis showed that all the empirical constants were independent with each other, thus the semi-analytical correlation could be used easily as further validation for different data.
Experimental analysis on oscillations of vortex breakdown location over delta wing
Zhang Minglu, Zhu Liguo
2006, 32(06): 635-638.
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Experiments of flow visualization and dynamic pressure measurement were carried out in a water channel and a wind tunnel respectively to research oscillations of the vortex breakdown location over delta wings. Based on statistics and spectral analysis location of vortex breakdown on video picture of flow visualization , result shows that there are two nondimensional primary frequencies. One of them is equal to 0.07 which is a transition frequency of spiral-bubble-spiral form of vortex breakdown, the other primary frequency is at 0.2~0.4 which is the oscillation frequency of spiral breakdown location with smaller amplitude. By correlation analysis of statistical breakdown location data it indicates that there is a negative correlation between signals of left and right vortex breakdown location after low pass filter. Based on dynamic pressure measurement of different station along wing surface under the identical vortex, it is found that there is a strong positive correlation between oscillation signals of pressure by low pass filter.
Theoretical and experimental determination of DFR-corrosion-influence-factors
Bao Rui, Zhang Jianyu, Zheng Xiaoling, Fei Binjun
2006, 32(06): 639-644.
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The relationship of detail fatigue rating(DFR)-corrosion-influence-factors and aggressive environments was studied, which makes the DFR method under erosion environments for civil aircraft structures’ fatigue analysis more applicable to different structure details and different service environments. The way wasestablished to decompose DFR-corrosion-influence-factor into ground-corrosion- influence-factor and air-corrosion-fatigue-influence-factor. The relationship between ground-corrosion-influence-factor and corrosion time as well as the relationship of perplexing environment corrosion-fatigue-influence-factor and mono-medium corrosion-fatigue-influence-factors were studied. Experiments for typical influence factors testing were conducted and reported. The results show that DFR-corrosion-influence-factors are decreasing as the increasing of ground-corrosion-time and the aggravating of environments causticity. The influence of corrosion fatigue is much serious than that of ground-corrosion. The example of structure fatigue analysis with DFR method under corrosive environment shows the detail steps and data requirements. The analysis indicates that DFR of a given structure is reduced significantly by corrosion, and the influence must be taken into account properly in fatigue analysis.
Influence of empennage on flow over upswept after-body
Huang Tao, Wang Yankui, Deng Xueying, Zhan Huiling
2006, 32(06): 645-648.
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To provide a foundation of upswept after fuselage drag reduction, the flow patterns and aerodynamic characteristics over two upswept rear fuselages with and without empennages were investigated in a 1.5 by 1.5 meters low speed wind tunnel by the methods of oil flow, smoke wire/laser and force measurement. The results were obtained at 40 m/s and Reynolds number of 1.191×105 at angles of attack ranging from -10° to 20°. With the attack angle increasing from negative to positive, the flow over rear fuselage, which is developed from the end of body to forward, goes through three kinds of open separation mode, namely up-separation, non-separation and down-separation. The drag difference between the after-bodies with and without empennages is due to the friction drag on empennages for non-separation mode and is due to separation on the empennages at higher attack angle. The drag reduction caused by separation weakening on vertical tail results in drag increasing slowly with the increase of the positive attack angle.
Dynamic design method of elastic ring squeeze film damper
Hong Jie, Deng Yin, Zhang Dayi
2006, 32(06): 649-653.
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A high efficient oil film damper which is known as elastic ring squeeze film damper (ERSFD) has special dynamical characteristics based on the conventional squeeze film damper (SFD). The characteristics of a gas turbine engine with ERSFD including the supporting stiffness of the elastic ring, the distribution of pressure field and oil film damping were investigated by taking advantage of the elastic deformation of the elastic ring. For ERSFD, finite element method not only has the advantages of simple modeling and small computation work, but also can be used in appropriate boundary conditions, for various damper sealing configurations. It was indicated that the calculative methods and results were put forward contributing to the preliminary design modification of the current body structure. Compared with SFD, the oil film clearance of ERSFD is divided into several parts. It can automatically adjust the oil film clearance by taking advantage of the elastic deformation of the elastic ring, which controls the oil film clearance in a suitable range. ERSFD has optimal effect on reducing nonlinear vibration markedly.
Effect of ice accretion on aircraft flight performance
Zhang Qiang, Cao Yihua, Pan Xing, Jiang Chongwen
2006, 32(06): 654-657.
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An engineering method was presented to deal with the problems of aircraft flight performance affected by ice accretion. Based on the calculation method placing linear varying strength vortex panels on airfoil contour, ice accretion shapes on the leading edges of airfoils were predicted. While computing aircraft flight performance affected by ice accretion, the numerical simulation method was used to solve RANS(Reynolds averaged Navier-Stokes) equations of RNG (renormalization group) k-ε turbulence model and calculate the flow field characteristics of the whole aircraft. Flight performance, including lift and drag characteristics, was obtained according to the simulation results. The lift and drag penalties showed that ice accretion can worsen aircraft flight performance severely. The agreement of this conclusion with some experimental results indicates that this method could be applied into engineering field to estimate aircraft flight performance which is affected by ice accretion quickly and effectively, and to provide references for developing de-icing technologies and improvement of the aircraft flight performance.
Effect of temperature ratio on the film cooling with the rotation
Yang Xiaojun, Tao Zhi, Ding Shuiting, Xu Guoqi
2006, 32(06): 658-661.
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A computional heat transfer(CHT) analysis was carried out to comprehend the mechanism of rotation and the temperature ratio of the film and the main flow on the film cooling which is important in understanding the mixing process between the film coolant and the hot stream air over the high pressure turbine blades. It was found that both parameters could affect the distribution of the film cooling, which was clearly shown with the film cooling effectiveness distribution graph. On the suction side rotation leads to that the effective film trace bends centrifugally and on the pressure side it inclines centripetally, which is consistent with the direction of the Coriolis force. With the increase of the coolant-to-mainstream temperature ratio, the effective film trace bends centrifugally, which is determined by the increase of the centrifugal buoyancy force. Rotation could lead to the decrease of the film cooling effectiveness. Contrast to this, temperature ratio has little effect on the film cooling effectiveness.
Preparation of magnesium hydroxide flame retardant via MgCl2-NH3·H2O synthesis and hydrothermal modification treatment methods
Li Zhiqiang
2006, 32(06): 662-666.
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In order to solve the problem that the Mg(OH)2 is incompatible with the polymer, the two steps reaction of high dispersive Mg(OH)2 preparation, synthetic reaction and hydrothermal modification treatment, was studied. The effect of the synthetic reaction temperature, hydrothermal modification temperature and time was investigated for preparation of Mg(OH)2 flame retardant with large crystalline structure and small specific surface area. The experimental results indicate that the growth direction of Mg(OH)2 crystal is changed and the regular hexagonal plates of Mg(OH)2 with uniform particle size and high dispersion characteristic are formed after the hydrothermal modification treatment. With the increasing MgCl2 concentration and/or feeding excessive NH3·H2O, percent conversion rates of raw materials are discussed. The results show some new technologies should be studied for increasing percent conversion of raw materials when synthetic reaction is equivalent.
Precision analysis of long distance navigation of rendezvous
Zhang Liyan, Qi Faren, Li Yili
2006, 32(06): 667-670.
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To get performance of attainable end point accuracy of long range navigation, error factors influencing precision were analyzed, and a precision analyzing method using simplified dynamical model together with quasi-mean element and covariance method was put forward, mathematical models of error propagating and analyzing were deduced, simulation was carried out based on mathematical models presented. The results show that end point accuracy of long range navigation is mainly affected by error propagation, and that position and velocity errorscan be controlled below 5 km and 3 m/s respectively under certain initial circumstances when propagating time is less than 6 h. Along-track error and radial error are main error factors in error propagating and along-track error becomes larger as propagating time becomes longer, therefore improving end point accuracy along-track error and radial error must be mainly restrained. Accuracy analyzing method introduced above considers comprehensively various error factors and is convenient and quick. It is suitable for engineering utilizing in scheme design phase.
Transient analytical method of vane forcing response under stator-rotor wake influence
Meng Yue, Li Lin, Li Qihan
2006, 32(06): 671-674.
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Rotor blade forcing response problems due to the wake of front vane row was analyzed. A transient analytical method was presented for blade forcing response. Then displacement and stress could be predicted. The analysis of three-dimension unsteady flow field was performed with NUMECA to provide the wake influence force and the pressure was introduced into calculating structure dynamics(CSD). Structure analysis was performed by finite element package ANSYS using transient analysis type. Force boundary condition was written with ANSYS parametric design language(APDL), a scripting language for ANSYS. The displacement and stress under different rotate speed were calculated. Then compared them with Compbell method. For transient analytical method, whether flow field or structure analysis were both presented with well-rounded software, so it’s easy for using in engineering field.
Hopfield network based approach to aircraft design
Zhou Shengqiang, Xiang Jinwu
2006, 32(06): 675-679.
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Combining augmented lagrange multiplier(ALM) method to Hopfield neural network(HNN), was proposed to solve nonlinear constrained optimization. HNNis taken as a dynamic approach for minimization subproblem in ALM method, only needing the first derivative of the Lagrange function. The random neural network was extended by adding Gaussian noise gradually reducing with the temperature, whose ablity escapeing from the attraction of the localminimum points was limitedby the initial temperature. Combined with the simulated annealing, an improved algorithm for Euler method was presented for numerical implementation of the network. The approach was applied to jet trainer aircraft preliminary optimization. The results show that the computing process is stable and the optimal result is enough precise. The trade-off of design requirements was studied through the Lagrange multipliers. An aerodynamic/structural design optimization for the wing of a trunkeliner was studied.
Computation method improvement of military training plane effectiveness
Li Hanghang, Song Bifeng, Gao Hongjian
2006, 32(06): 680-683.
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The training effectiveness of military training plane is important to pilot cadets to master airmanship and to raise tactical level. Moreover, the quantitative evaluation of training effectiveness of training plane is the prerequisite to optimization of training system and evaluation of training syllabus. The typical computation model of training effectiveness of training plane has limitation in selection of flight parameters as well as insufficient attention to avionics and control system. Improved evaluation model of training effectiveness of training plane based on analytic hierarchy process covers the above-mentionedshortages, at the same time, provides new selection method for the weighting of flight subjects. Improved model can well satisfy the needs of training effectiveness evaluation of the third generation pilots, and lay the foundation for modern flight training syllabus and evaluation of flight training system. Simulation proves better feasibility and rationality of improved model.
Temperature compensation of pressure sensor based on the interpolation of splines
Fan Shangchun, Zhang Qiuli, Qin Jie
2006, 32(06): 684-686.
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The temperature compensation method based on the interpolation of cubic splines was presented. This method was applied for the temperature compensation of the experimental results of calibration of high precision resonant cylinder pressure sensors. The measuring range of the pressure sensor is 0.013 3×105~3.198 9×105 Pa and the applied temperature range is -55~+80℃. To make the calibrating process of pressure sensor fast, the principle of reducing the number of calibrating points was presented. The results indicate that the integrated error of the presented method of temperature compensation is 0.007 9%, when the number of calibrating points reduces about 2/3. The integrated error is approximately half of the method of temperature compensation based on the radial basis function(RBF)neural network. Thereby the presented method reduces the cost and workload of calibration effectually. The proposed method can provide a valuable theoretical reference for the temperature compensation of the high precision pressure sensors.
Acquisition for BOC (1,1) signal in GALILEO receiver
Xing Zhaodong, Zhang Qishan, Yang Dongkai
2006, 32(06): 687-690.
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The zero values in BOC(1,1)(binary-offset-carrier) signal correlation function could make the receiver judge that the signal was not acquired. From the sub-carrier phase and code phase viewpoint, an acquisition method with three parallel tags was proposed to acquire the BOC(1,1) completely. The BOC(1,1) and its spread code correlation function figure were drawn by digital simulation, and the correlation function peaks were compared. The analytic formula for BOC(1,1) autocorrelation function was deduced, the position for peak values and zero values were shown. The correlation function values and acquisition were compared between BOC(1,1) and its spread code. The phase in one tag served as benchmark, the other two tags phases were respectively earlier or later than the benchmark in three local BOC(1,1) signals. The generation method for three local BOC(1,1) signals and the acquisition method figure were shown. When the difference of code phase between the received and the local BOC(1,1) signal lies in the half code chip, the signal acquisition rate increases from 33.3% to 100%,and the code phase range increases from 1/6 to 1/2 chip width by simulation. The method can provide phase information to the track loop and adapt to acquisition for BOC(n,n) signal.
MOEMS accelerometer based on double Fabry-Perot interferometers and closed loop
Feng Lishuang, Liu Huilan, Lin Heng, Zhang Chunxi
2006, 32(06): 691-694.
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A micro-opto-electro-mechanical accelerometer based on differential double Fabry-Perot interferometers(DFPI) and closed loop was designed. The principle and the structure of the accelerometer were introduced. Inertial sensitive module was used to translate carrier’s acceleration measurement to its displacement measurement. The displacement was measured by Fabry-Perot interferometers composedof the mass and the end surface of fiber self-focusing lens. The structure of differential DFPI was designed to improve the sensitivity and restrain the influence of environment factors such as temperature. The closed loop accelerometer using electrostatic servo technology was put forward to improve the output linearity and dynamic range. The mathematic model of the accelerometer was founded, and particular calculation and analysis was made for important parameters, such as sensitivity, carrying capacity of the sensitivity head, natural frequency, etc. The parameters were designed under the requirement of some background. The results show that the system precision can be better than 5×10-6g.
Segmental training scheme for embedded hidden markov model
Xue Bindang, Xue Wenfang, Jiang Zhiguo
2006, 32(06): 695-699.
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A segmental scheme to retrain E-HMM(embedded hidden Markov models) for face recognition was presented. The current samples were assumed to be a subset of the whole training samples, after the training process, the E-HMM parameters and the necessary temporary parameters in the parameter re-estimating process were saved for the use of next step. When new training samples were added, the trained E-HMM parameters were chosen as the initial parameters, the E-HMM was retrained based on the new samples and the new temporary parameters were obtained. These temporary parameters were combined with the saved temporary parameters to form the final E-HMM parameters so that one person face was presented. Experiments on face database showed that the segmental training method was effective.
Novel vision system for large field inspection based on phase matching
Zhao Huijie, Ji Xiang
2006, 32(06): 700-703.
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To solve the problem of large scale three-dimensional (3D) measurement with high accuracy, a new binocular stereo vision inspection system was presented. By projecting variable period fringes, the surface with different curvature was coded with phase. The stereo matching points were determined using phase matching technique, so that dense 3D coordinate points could be calculated by the intrinsic and extrinsic parameters of the calibrated cameras. In order to solve the problem of small measurement field of sensor unit, the vision sensor scanned the whole surface of a large object under a step motor’s control, then quaternion was used to realize 3D registration. The sensor’s standard deviation in length measurement is 36 μm, and the relative error of angular measurement is 0.2% compared with the CMM(coordinate measuring machine). The 3D integration of a large object (360 mm×360 mm) is given correctly.The vision system is of great engineering value in large 3D non-contact online measurement with high accuracy.
End-user specification for diagrammatic model languages
Xu Hongxia, Zhang Li
2006, 32(06): 704-708.
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Formal specification of diagrammatic languages is not applicable to end users because of the requisition of computer theory. In order to satisfy the requirement of end users to define their own domain-specific modeling language, a language named EUVDL(end-user visual definition language),was proposed, which could be used to specify the 2-dimensional syntactic structure of diagrammatic model in software engineering. The specification technique of EUVDL combined the object-oriented methods and the rule-based approaches rather than formal specification. The support to end users was provided from following aspects: paradigm, abstract syntax, and concrete syntax. In order to make EUVDL available, the practical strategies for end users were presented and a framework for diagrammatic modeling environment generator was designed. Through comparison to other specification methods and demonstration of an example of visual process model, the conclusion can be drawn out that the specification method has the feature of simple structure, expressive power and reusable ability, and is adapted to end-users.
Multi-federation system based on tree-topology
Lin Xin, Wang Xingren
2006, 32(06): 709-712.
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The system logic structure has innumerous effect to the development, execution, and scalability of multi-federation system. A multi-federation system based on tree-topology structure was provided. Federations in the system were connected through proxies. Each federation was connected only with federations directly upper and lower. Thus multi-channels and loops in data transmission were avoided. A strategy was also presented to synchronize time advancement in real time multi-federation systems using RTI (run-time infrastructure) time management. Time-regulation federates and time-constraint federates in multi-federation systems were settled specially to ensure that synchronization signals created in root federation could be transmitted to leaf federations through tree-topology. The synchronization of time advancement of the whole system was realized. The time delay of synchronization signals in system was also analyzed as a result a time-delay formula was given. This formula reveals that more levels in system structure would lead to more delay.
Experiment on influence of machining on transmission properties of frequency selective surfaces
, Wang Huanqing, Wu Zhe
2006, 32(06): 713-715.
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The machining technics affect the resonant frequency and transmission ratio of FSS (frequency selective surface). Effects on the transmission properties of FSS were explored by experiments to the machining method, surface conductivity and additional conductive coating under the same condition respectively, based on planar FSS of finite extent and PNA 8363B test system. The experimental results show that the resonant frequency of planar FSS is moved by the machining method, the edge burr of FSS cell may effect the property, and may also effect the transmission ratio for different incidence angles. FSS surface conductivity also effects transmission ratio of planar FSS, transmission ratio reduces with the increase of sheet resistance value. The transmission properties are hardly changed by the additional conductive coating.
Finite volume method in thermal analysis of avionics
Fu Guicui, Wang Xiangfen, Jiang Tongmin
2006, 32(06): 716-720.
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The influence of heat to the system reliability was introduced. The merits and drawback of numerical methods in solving temperature distribution were compared. In order to solve the problem of avionics of high reliability which requires highly precise result and rapidly computational velocity in thermal analysis, a computed approach of the finite volume method (FVM) to solve the temperature distribution was devoloped. The mathematical model of temperature distribution was built based on typical avionics and its boundary condition was given. Then the control equation was discretized by means of the FVM. The mesh division, the process of discretization and the disposal of boundary were included. The temperature distribution was calculated with an example. The comparison between the result of calculation and the result of measurement demonstrates a high precision of thermal analysis. The validity of this method was verified. The reason of calculated error was indicated and a reasonable proposal about further thermal design based on the result was offered in the end.
Software encryption and just-in-time decryption for software protection
Liu Zhicheng, Zhou Bosheng
2006, 32(06): 721-724.
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Software protection via encryption is an effective way to prevent software pirate from understanding the program by means of reverse engineering. Traditional software protection method via encryption has obvious runtime overhead and start up delay because of its one-time decryption prior to execution. Moreover, fully decrypted code can easily be obtained from memory. A novel approach, called just-in-time(JIT) decryption, was proposed. JIT decryption differs from traditional decryption method in that it decrypts only one function in a time and reveal the secret of the software step by step. The runtime JIT decipherator only decrypts called functions in a certain run of the program. The uncalled functions remain a secret for an attacker, where self-checking code can be hidden. So it is hard for an attacker to understand the entire program and thus hard to remove all the protecting code. Because decryption is scattered, the start up delay no longer exists. One-time pad based cipher further reduce the runtime overhead as compared with symmetric algorithms. JIT decryption makes encryption based software protection more applicable in practice and harder to attack.
Harden correction based on original projection sinogram for X-CT
Fu Jian, Lu Hongnian, Ren Huayou, Jin Hu
2006, 32(06): 725-728.
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The polychromatic spectrum leads to cup or streak beam hardening artifacts and reduces the image quality in X-CT (X-ray computed tomography). A correction method for beam hardening, involving simple operations of the original polychromatic projection sinogram, was presented based on the analysis of three physics properties implied by beam hardening. Its correction principle was deduced mathematically. A noise reduction method was proposed to suppress the noise enlarged by the harden correction by processing the high-frequency and the low-frequency components in the projection sinogram respectively. The validity of this method was proved by correction results from computer simulations and CT scan experiments of two typical objects. A prior CT scan and complex operations, which were need for the conventional beam hardening correction method with the polynomial fit technique to create the correction models, were not necessary for this correction method. So it is much simpler and quicker, with better signal-noise-ratio, and not affected by scan conditions.
Data communication protocol based on dual CAN bus for digital servo drive
Liu Yanqiang, Huan Ji
2006, 32(06): 729-733.
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The communication performance of advanced field bus protocols used in NC systems was analysed, and a new data communication protocol was defined based on dual CAN(controller area network) for position control system in NC—CANsmc(CAN for synchronous motion control). CANsmc, defined as a master/slave topology, consisted of one master and at most 61 slaves with two communication channels. Its communication control was polling with synchronous telegram. The protocol was based on CAN chip, and CANsmc telegram head was defined with CAN telegram descriptor. Three types of telegram were transmited in CANsmc: MST(master synchronous telegram), MDT(master data telegram) and DT(drive telegram). Master transmited MST and MDT to slaves through the master channel, and slaves fed DT back to the master through the slave channel when they received their own MDT. Finally, a CANsmc prototype was built, and protocol was implemented by using software. The master was based on PC ISA interface and the slave was a position control unit with position control, speed control and zero return functions. The prototype system proves that CANsmc could meet the satisfiction of industrial robot and CNC machine control.
Construction of case-based knowledge base for aircraft sheet metal forming
Chen Qingxin, Li Xinjun, Wan Min
2006, 32(06): 734-737.
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To promote further technological innovation for aeronautic industry and improve the conventional aircraft sheet metal forming process with information technology, a system of case-based knowledge base for aircraft sheet metal forming was developed by using Oracle database management system and Visual C+ +.NET. It is based upon a great deal of data and information from the aircraft manufacturing, pre-research, sheet metal forming manual and process tests in aeronautic industry. This system establishes a uniform information model of process cases as elementary cells of information. It includes a lot of data and information about forming processes and dies, and has functions such as the knowledge maintenance, the knowledge matching, the knowledge revise and so on. The general structure, key techniques and solution methods of this system were also analyzed.
Cleaning robot design for cone high-rise glass-curtain wall
Wang Wei, Tang Boyan
2006, 32(06): 738-741.
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To fulfill the demand for the lightness, high reliability and safety, three structure design principles were proposed for a cone high-rise glass-curtain wall cleaning robot. The whole cleaning robot structure was designed based on the principles which were described as the motion driver dispersed configuration, the main and secondary motion integrative drive and the soft drive structure for the main motion. The methods adopted by the robot to go through, attach and clean the glass-curtain wall were detailed consequently. The architecture dimension error’s infection to the robot was analyzed to testify the feasibility of the soft drive structure and the adaptability of the robot to the error. The cleaning robot for an airport control tower was developed according to the principles discussed. The practicability and reliability of the robot were testified by the fieldwork. The cleaning robot system proposed is now used for the airport control tower’s daily cleaning service.
Numerical method for Lyapunov exponents of multibody systems with constraints
Fu Shihui, Wang Qi
2006, 32(06): 742-746.
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Dynamic equations of multibody systems with constraints induced by the first kind of Lagrange’s equations are nonlinear differential-algebraic equations. To be solved numerically, nonlinear differential-algebraic equations were transformed into ordinary differential equations with the augmentation approach. Ordinary differential equations and their Jacobian matrix were given in the matrix form to improve computational efficiency. A numerical method of Lyapunov exponents of nonlinear dynamics of multibody systems was demonstrated. An example was given to analysis dynamical behavior of two multibody systems with topological tree and non-tree configuration, such as bifurcation and chaos by calculating Lyapunov exponents along with Poincare maps and phase graphs.
Clustering algorithm based on kernel methods and its application
Ji Qiuying, Lin Jian
2006, 32(06): 747-750.
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Based on the analysis of the core concepts of the kernel methods, a clustering algorithm based on kernel methods was put forward. In general, traditional clustering algorithms are suitable to implement clustering only if the feature differences of data are large. If the feature differences are small and even cross in the original space, it is difficult for traditional algorithms to cluster correctly. By using kernel functions, the data in the original space was mapped into a high-dimensional feature space, in which more features of the data were exposed so that clustering could be performed efficiently. Compared with the traditional clustering methods, this clustering method had superiorities in dealing with the nonlinear data, which made its clustering result more objective and valid. This method was applied to the classification of 16 groups of data, and results show the feasibility and effectiveness of the kernel clustering algorithm.

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