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2008 Vol. 34, No. 01

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Method of image quality assessment based on human visual system and structural similarity
Yang Wei, Zhao Yan, Xu Dong
2008, 34(01): 1-4.
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Through analyzing the influence of certain digital image factors (brightness, texture details, dimentional position, etc.) on human visual characteristic, a mathematic model which combines human visual characteristic and structural similarity of images was built, a new image-quality assessment method in accordance with human visual characteristic was put forward. By unoverlapped partitioning of images using equal-sized sliding windows, this method can calculate the following factors with influence on the partitions: influencing brightness, influencing texture details, and influencing dimentional position. The weighted value of each partition is generated after normalization, and the weighted structural similarity is used as the assessing index of image quality. Experiment shows that this method is in accordance with human visual characteristic, and consistent with the result of subjective assessment.
Wall model in LES based on coherent structures
Zhang Nan, Liu Kai, Lu Lipeng, Yuan Xiangjiang
2008, 34(01): 5-8.
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The evolvement of a group of coherent structures in a turbulent boundary layer was studied previously. An initial structure was formed by the resonant triad waves which developed periodically in the streamwise direction. The characteristics and evolvement processes of the coherent structures were obtained by direct numerical simulation. Based on the coherent structures, a new type of wall model for large-eddy simulation (LES) was established. The height at which to supply the wall model was determined. And different choices of boundary conditions were tested. The results of a channel flow LES indicate that: the wall model decreases grid number adjacent to the wall region; the wall model provides the core flow LES sufficient near-wall region information so that the simulation can gain exact results compared with that without wall models.
Numerical simulation on opposing jet in hypersonic flow
Tian Ting, Yan Chao
2008, 34(01): 9-12.
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The detailed influences of the free mach number, jet mach number, attack angle on the drag coefficient reduction were studied by high precise simulation of N-S(Navier-Stockes) equations. The Numerical results show good agreement with the experiments. It is indicated that the opposing jet is effective in reducing the aerodynamic heating and drag coefficient. Conclusions were got that the opposing jet enlarges the factors of affections by influencing the strength and the positions of the barrel shock, the mach disk and the recirculation region. It is believed that the drag coefficient turns out to be very sensitive to the flow field-s structure which is highly depended on the free mach number, jet mach number and attack angle due to the opposing jet.
Effects of truncation on thrust performance of aerospike nozzles
Wang Yibai, Qin Lizi, Liu Yu, Wang Changhui
2008, 34(01): 13-16.
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To discuss the performance effects of plug truncation ratios, cold-flow tests were performed for 80%, 40%, 30% and 20% truncated aerospike nozzles by employing cold air as propellant. The test system apparatus and thrust measurement were introduced. The experimental altitude characteristics curves of the thrust coefficient efficiency were obtained. The results show that the efficiency of aerospike nozzles with bigger truncation ratios is higher than with smaller ratios, and the distinction of different truncations was minished with the pressure ratio increasing. The influence degree of the truncation on the thrust coefficient efficiency falls down by increasing the ratio. The performance loss is more due to selecting too small value of the truncation ratio. With too big ratio value the length of plug is much long, and the weight of plug increases much, but the nozzle performance elevates a little. Generally the truncation ratios can be chosen from 30% to 40%.
Climbing technique of cleaning robot for spherical surface
Wang Wei, Zhang Houxiang
2008, 34(01): 17-21.
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Based on analyzing the characteristic of cleaning robot, a kind of auto-climbing robot for spherical surface was described, which could scramble on the top of National Grand Theatre by itself. The motion function was described in detail. As an automatic cleaning machine, which can move in all direction on the top of a sphere surface, this robot features in its holding and climbing motion. It is very important for the designer to take more attention to the safety analysis of the climbing motion of the robot. To acquire the detailed motion feature of the robot, the kinematics model of the climbing motion was concluded at first. Then the dynamics of the robot was analyzed by the application of the Lagrange equation. The security during the climbing was discussed in detail using simulation. The force distribution of the front brace and the back brace was computed, which could be used to determine the switch time of the front and back supporting force.
Grinding burn mechanism of Titanium alloys with SG wheels
Zhang Hongxia, Chen Wuyi, Chen Zhitong
2008, 34(01): 22-26.
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Titanium alloys have been widely used in aerospace for their excellent heat-resistant, erosive-resistant and especially high strength-to-weight ratio. Grinding burn is apt to occur in the grinding process of titanium alloys. The grinding burn mechanism of titanium alloys was studied on the base of systematical analysis of variable characteristics of the grinding force, grinding temperature, surface roughness and topography of ground surface, hardness distribution of surface layer, as well as morphology of surface layer from a metallographic point of view. Some conclusions were given as follows. The grinding burn occurs at the temperature over 600℃. The surface topography deteriorates gradually with elevating grinding temperature. When severe burn appears, some microcracks perpendicular to the grinding direction on the surface of the test-piece are found. With the onset of grinding burn, α phase particles become coarsening, which deteriorate the mechanical properties of titanium alloys obviously. The results provide a theoretical and experimental basis for technical optimization in the grinding of titanium alloys with high efficiency and high quality.
Optimal research of distributed parallel genetic algorithm for reactive power optimization
Liu Keyan, Li Yunhua, Sheng Wanxing
2008, 34(01): 27-30.
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A distributed parallel genetic algorithm based on personal computer (PC) cluster was proposed to solve reactive power optimization, aiming at the disadvantage of traditional genetic algorithm, such as the bad searching quality and long computation time. It adopts the improved genetic simulated annealing algorithm and distributed parallel technique message passing interface (MPI), to implement the distributed computing on PC cluster. The algorithm uses the individual migration strategy to collaboratively optimize every process. The dynamic populations are adopted to balance the computing load. An IEEE 14 test system and a practical power system are tested. The results reveal that the algorithm has a good stable searching capacity and good parallel efficiency. The proposed method can be used to solve the reactive power optimization of large-scale power system.
Aadptive control with feedback linearization of hysteresis nonlinear aeroelasticity
Li Daochun, Xiang Jinwu
2008, 34(01): 31-34.
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The question of active flutter control of prototypical aeroelastic wing section in subsonic uncompressible flow is investigated. The dynamic equations of a two-dimensional airfoil with control surface are described in state space. Then based on Lie derivative, the partial input/output feedback linearization was obtained. Suppose that there is parametric uncertainty in the hysteresis nonlinear model, Lyapunov function was used to design an adaptive control law. The simulation results show that the unstable aeroelastic system exhibit limit circle oscillation while the closed loop system, including the adaptive control law, become stable. It should be emphasized that the control law can be used only when the internal dynamics is stable. Even if there is a hard constraint on the control input, satisfactory responses can be achieved.
Real-time visual system of night-flying across the sea
Yang Xinying, Gong Guanghong, Wang Xingren
2008, 34(01): 35-38.
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The natural scene simulation is a key technology in the field of virtual reality. Stars, the moon and their mirror images in water are all special natural scenes when pilots flying across the sea. In order to generate a high quality night flying virtual reality system, a particle system was adopted for star simulation, the dynamic twinkling phenomenon of stars was deduced to the concept of particle life, and a dominant algorithm appending random disturbance method was presented for simulating the night sky. An efficient texture blending method was introduced for simulating the moon and the mirror of night sky. The special texture was made up of three steps, such as texture-generating, scene-rendering and graph-blending. The blending gene parameters were confirmed according to light attenuation criterion of reflecting mirror and textures were blended with the background screen using the alpha method. Finally, a high quality virtual reality system of night flying over the sea was implemented.
Intrusion detection response model based on cost-analysis
Dong Hong, Qiu Wanhua, Lü Junjie
2008, 34(01): 39-42.
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Applying the methodologies of game theory and network security, considering the decision interdependence of the players, a game model of intrusion response based on cost analysis was presented. The study showed the optimal strategies for the players in the deployment of security technique-Intrusion Detection System(IDS), discussed the Nash equilibrium solutions, and verified the model rationality by cost-analysis from the theoretic and empirical aspects. Focusing on the problem of intrusion response without considering cost now, the model was introduced damage cost and response cost. With comparison with the two kinds of cost, the conditional cost of responding was analyzed, thus an adaptive intrusion response strategy to system administrator was made. This method can illustrate the response policy of system administrator in the actual decision further, improve security and avoid wasting unnecessary resource, then achieve the balance between information protection and resource.
Efficient probabilistic public-key encryption schemes with | n|+k bit plaintexts
Jiang Zhengtao, Liu Jianwei, Qin Bo, Wang Yumin
2008, 34(01): 43-46.
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Based on the intractable problems of n th residuosity and quadratic residuosity, by choosing proper parameters and without increasing the length of ciphertexts, the efficiency and the size of plaintexts of a probabilistic public-key encryption scheme proposed by Paillier and Pointcheval were improved. The improved encryption scheme can encrypt |n|+k bit messages with higher efficiency. Security and efficiency analysis of the improved encryption scheme were also provided, and the security of the improved scheme is equivalent to that of the original encryption scheme, the higher residuosity problem and quadratic residuosity problem modulo n . Compared to the original Paillier-Pointcheval encryption scheme, the improved encryption scheme has features of higher efficiency, lower traffic date and larger size of plaintexts.
Friction modeling and compensation of positioning stage driven by linear motors
Zhang Congpeng, Liu Qiang
2008, 34(01): 47-50.
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An H-type precise positioning table driven by dual linear motors was introduced. To decrease the velocity following error and positional error of the table, friction modeling and compensation of this precise positional system were studied. As the guide ways of the motion table have different friction characteristics at different positions, an improved friction modeling method was proposed, based on the classical Stribeck friction model and slide plate position to get better compensation effect. The improved Stribeck friction models of the guide ways were identified through experiments and parameters regression analysis. Based on the improved friction identification model, friction was compensated by feed forward technique. Friction compensation experiments results show that the friction compensation based on friction model enhances the control performance of the table and the improved friction model has better compensation effect than traditional Stribeck friction model. The improved friction model is suitable for friction compensation of the positional table with long travel distance.
Numerical study for film cooling characteristics on rotating model
Yang Bin, Xu Guoqiang, Ding Shuiting, Tao Zhi
2008, 34(01): 51-54.
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Computations were performed to simulate the two rows of 90° staggered holes film cooling characteristics over a rotating turbine blade model both on leading and trailing surfaces. The influences of the Reynolds number Re, rotation number Rt and the blowing ratio M on the film cooling effectiveness η and discharge coefficient Cd distributions were presented. Results show that the coolant is influenced by the centrifugal force and Coriolis force to deflect towards the high-radius locations, and this will lead to low values of η . The enhancement of Re can impair the film cooling effectiveness, and the high values of M are not suitable for the thermal protection near the exit of cooling holes. All the discharge coefficients increase with the augmentation of M , and decrease with the increase of Rt . Moreover, the Cd values beside trailing surface are much higher than that beside the leading surface under the same operating conditions.
Distributed power aware topology control algorithm for self-organizing networks
Wang Zijian, Zhang Jun, Luo Xiling
2008, 34(01): 55-58.
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To efficiently use the power in self-organizing networks, a distributed power aware topology control algorithm for self-organizing networks was proposed, which integrates the minimum connected dominating set and the computational geometry. First, a power aware minimum connected dominating set (PAMCDS) was constructed with nodes whose energy lives are above threshold energy life, which ensures that the dominator nodes have enough energy to relay messages for the network. Then, the localized Delaunay triangulation on top of the PAMCDS was applied to reduce transmission energy cost and ensure that the paths are energy-efficiency and the topology is planar. Alternative PAMCDS was reconstructed once the initial dominating set is invalidated, which dynamically balances the energy of the whole network. Simulation results show that the size of the dominating set is smaller and the lifetime of the network is prolonged.
Heading feedback in coaxal pilotless helicopter-s course flight
Li Hongwei, Zhang Xiaolin
2008, 34(01): 59-62.
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Soft simulation replicated the flight performence of coaxal pilotless helicopter controlled by classical navigation algorithm based on d(deviation distance) and its- variation ratio d · in various situations (undisturbed, constant gust disturbed). The heading bias, sideslip velocity and deviation distance were analyzed to explain the phenomenon of sideslip in the situation of constant gust disturbance during the course flight when using the classical algorithm. To solve this problem an amendatory algorithm was proposed and analyzed with simulation. Two approaches were compared to analysis the effect of introducing different feed-back (one was only using heading feed-back, the other was using heading feed back and integral of d). The results indicate that the algorithm based on heading feed-back and integral of d performs well in smooth turning and achieves better performance in avoiding sideslip on the premise of achieving satisfying navigation precision. As a result, the amendatory algorithm proposed improves the course flight efficiency of coaxal pilotless helicopter.
Modeling and semi-physical simulation of in-flight alignment for MIMU under large heading error
Cao Juanjuan, Fang Jiancheng, Sheng Wei
2008, 34(01): 63-66.
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The micro inertial measurement unit (MIMU) in micro unpiloted aerial vehicles initial alignment time is short, so in-flight alignment for MIMU is worked under large heading error with the global positioning system (GPS) assistant. Aimed at the requirement of high estimation precision and real time,a linear model with large heading error is introduced by regarding nonlinear vector as state vector, and adaptive Kalman filter (AKF) base on this linear model is used for MIMU in-flight alignment. The semi-physical simulation results show that this method has better precision than extended Kalman filter (EKF) with nonlinear model, and the heading error descends very quickly from 60° to around 2°. Furthermore, AKF need less computation time than EKF, only 67% of EKF.
Computer generate force modeling and simulation framework
Ma Yaofei, Gong Guanghong
2008, 34(01): 67-70.
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The computer generate force(CGF) modeling and simulation framework tends to provide a development platform for CGF simulations. Reusability and composability are the foundation to achieve the goal of rapid development. The key technologies are identified by analyzing the development process by a top-down approach, and a layered components view is proposed to guide the framework implementation. To access and represent the models in an uniform way, a model specification is designed to provide the model template, which helps to develop the simulation concept model, and reduce the concrete work by code generation. The specification also gives a higher-level description for behavior models, which always need to deal with logic process when compose. The description is drawn from the base object model(BOM), which describes the interaction by sequence diagram and finite state machine.
Getting parameters of absorbing structure based on genetic evolutional algorithm
Su Donglin, Qi Wanquan, Zhang Wei, Lu Zhanyong
2008, 34(01): 71-74.
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Electromagnetic parameters of unknown layer in absorbing structure were gotten. Model of calculated reflection coefficients was founded by the relation of material parameters and reflection coefficients based on transmission line theory. Reflection coefficients of different incident-angle was measured with platform based on free space method. Electromagnetic parameters of unknown layer in absorbing structure were gotten with new genetic evolutional algorithm. In the process of evolution, Gauss-s random number was used instead of uniform random number. Used this method, the problems of multi-value and thickness resonance are solved and it is avoided to get into local best value during calculation. Compared with traditional transmission/reflection method, it is proved that the method is reliably. This method can be used for both high and low loss materials.
Analysis of landing response of virtual prototype landing gear
Liao Lijuan, Jia Yuhong
2008, 34(01): 75-78.
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The landing dynamics equations were educed with the establishment of two-mass equivalent model and the supplementary equations under the sideslip landing. An aircraft model with flexible fuselage using virtual prototype was applied basing on the mathematical models of landing gear in landing and ADAMS/Aircraft version. A simulation of dynamic response under sideslip landing has been analyzed. Simulation results show that the flexible fuselage leads to the increase of returning roll torque and the decrease of the tires- sideslip. It leads to symmetrical landing fast. The flexible fuselage can absorb and dissipate the landing shock energy. The comfort of airplane can be improved and the weight of landing gear can be decreased. Then the foundation to ameliorate landing gear has been laid.
Strategy of state transition in UML based on Petri net
Yao Shuzhen, Jin Maozhong
2008, 34(01): 79-83.
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The related semantics of UML(unified modeling language) state machine view was analyzed, and basic features of Petri net and its capabilities of modeling concurrency, synchronization and conflict were discussed. In order to get unambiguous, executable and verifiable models, based on the CPN(colored Petri net) and hierarchical Petri net, HCPN(hierarchical colored Petri net) for UML state machine view was constructed. In an HCPN, CPNs in different levels are related to each other by place-subnets or transition-subnets. Taking an HCPN as an example, the process was demonstrated to get its marked Petri net by merging CPNs from its all levels for analysis purpose. The marked Petri net can be used to guide the event-driven simulation, whereas the basic Petri net transformed from the marked Petri net can be used for the analysis, evaluation and improvement of models based on Petri net theory.
Technology on evaluating damage and reliability of aircraft structure fatigue critical parts
Wang Lei, Liu Wenting
2008, 34(01): 84-87.
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Analysis was started with character of fatigue failure and damage evolution of structure. The structure reliability analysis model which expressed in fatigue damage of critical parts was given. The damage and reliability evaluation technique and corresponding parameter index of fatigue critical parts of in service aircraft were presented by basing on above model. The method based on integrated data of full-scale fatigue test on aircraft structure at room environment and flight parameters of every aircraft recorded in service. The method can carry out timely calculating structure damage state and reliability using flight parameters of every aircraft, and can satisfy with requirement of fatigue damage monitoring technique of aircraft in service. Finally the engineering demonstration based on usage of certain type aircraft was given. The method can be applied to timely evaluating structure damage and reliability of certain type aircraft, as also can provide important service information of every aircraft structure in service for the user. Then it is possible to allocating and using every aircraft in service reasonable with the precondition of ensuring aircraft structure safely.
On-the-fly ambiguity resolution by restricting coordinates predicted by Doppler
Chai Yanju, Ou Jikun, Yuan Yunbin, Liu Genyou
2008, 34(01): 88-91.
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The main difficulty of kinematic positioning using carrier phase observations is the ill-posed problem of normal matrix. The float ambiguity and its covariance matrix are inaccurate, so impact the success rate of ambiguity resolution. A new method was put forward for resolving the ill-posed problem in kinematic positioning by restricting the coordinates predicted by Doppler observations. The float ambiguity and its covariance matrix were improved because the coordinates predicted by Doppler were more accurate than that determined by pseudo-range observations, so the success rate of ambiguity searching was advanced. The results indicate that the effect of the new method for on-the-fly ambiguity resolution of the short baseline is clear.
Near-filed imaging method of two-dimension interferometric synthetic aperture radiometer
Hu Anyong, Liu Chongkan, Miao Jungang, Wan Guolong
2008, 34(01): 92-95.
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A near-field imaging method of two-dimension interferometric synthetic aperture radiometer was presented. Based on the principle of the two-dimension interferometric synthetic aperture radiometer and the near-field condition, the shortcomings of FFT(fast Fourier transform) imaging method were analyzed, and a near-filed numerical imaging method by phase compensating was proposed. The imaging simulation of single point-target by FFT reverse algorithm and the near-filed reverse algorithm were carried out respectively. The simulation results show that the near-filed reverse algorithm has better resolution than FFT reverse algorithm. The imaging experiment of two separate man-made points with these two methods was accomplished, and the experiment results prove that the near-field imaging method is valid.
Experimental and numerical investigation of controls for closed cavity flow
Li Jun, Zhang Qunfeng, Zeng Honggang, Li Tian
2008, 34(01): 96-99.
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The effects of control rod on the characteristic of the closed cavity flow and the sound pressure level (SPL) along the cavity bottom wall were investigated by means of the numerical simulation and wind tunnel test. Closed cavity flow was simulated by solving the 3D Favre-averaged Navier-Stokes equations using AUSM+ schemes and Wilcox k-ω turbulence model. The experiments were conducted in the supersonic wind tunnel with cross section of 0.6m×0.6m. The model was instrumented with 40 static pressure orifices and 15 dynamic pressure orifices. It was obtained that the closed cavity flow produces a strong adverse static pressure gradient over the cavity flow in supersonic flow, and there are not obvious peaks on the spectrum of the SPL. When the control rod is introduced, the longitudinal static pressure gradient becomes weaker along the bottom wall, and the spectrum of SPL near the front separation region of the cavity is increased and the spectrum of SPL near the rear separation region of the cavity is reduced.
Design of blinding analysis tool for satellite optical sensors
He Heng, Deng Jiati, Hu Lingyun
2008, 34(01): 100-103.
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In satellite configuration design, blinding analysis should be made to determine whether the optical sensor will fail due to being blinded by components of the satellite. A blinding analysis tool for satellite optical sensors was developed to replace the inefficient way of manual analysis. The design rationale and functions of the tool were presented. It was based on the 3D CAD software, SolidWorks, and embedded in it by means of DLL (dynamic link library). It was a plug-in customized with the SolidWorks API and Visual Basic, and with knowledge of computer graphics. It can treat with satellite assembly in SolidWorks to carry on the following blinding analysis functions: setting attributes for sensor optical cone, painting blinding chart, and computing blinding ratio.
3D solutions for static/vibration of FGPM plate/pipe in Hamiltonian system
Dai Haitao, Cheng Wei, Li Mingzhi
2008, 34(01): 104-107.
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The 3-dimensional couple equations of piezoelectric-mechanic were derived into Hamilton system by the principle of Hamilton theorem. The problem of single sort of variables was converted to double sorts of variables, and the Hamilton canonical equations were established. The dynamic characteristics of the simply supported functionally graded piezoelectric material (FGPM) plate and pipe are investigated in different coordinate systems. Finally, the problem was solved by the symplectic algorithm. The results show that the complex electromechanical problems of FGPM structures can be solved in the Hamiltonian system. The general displacement and stress of the medium are divided into so-called out-of-plane variables and in-plane variables. The former is continuous while the latter is discontinuous along the depth.
Time-domain low order equivalent system base on hybrid optimization algorithm
Zhang Xuemin, Fei Yuhua, Gao Jinyuan
2008, 34(01): 108-111.
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The order of modern highly augmented aircraft is very high. It should be reduced to it-s low order equivalent system (LOES) for evaluating the handling quality of aircraft and the design of flight control system. The time-domain equivalent matching can acquire on-line data of input and output, considering the influence of nonlinearities in the system, and the on-line estimation of equivalent parameters is given, it has more practical value than the frequency-domain method. A hybrid optimization algorithm is introduced for the time-domain equivalent matching, namely direct search-simulated annealing method. This method improves the local and global optimization with the limitations to the range of parameters in the process of optimization and can converge the globally optimal solution quickly. The result is not influenced by the initial value and is significant for the on-line evaluation of aircraft handling qualities.
Development of PCI-based multi-axis controller
Wu Xingming, Chen Weihai, Yu Shouqian, Li Xiang
2008, 34(01): 112-116.
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The characteristics of a PCI(peripheral component interconnect)-based multi-axis real-time control system for realizing high-accuracy motion control were introduced. To reduce the workload from host computer and utilize the intelligence of DSP(digital signal processor) efficiently for a complex task, the developed controller was designed with master-slave structure. The controller can also use serial communication control instead of PCI bus to satisfy users- requirements to some applications. The hardware development was focused on multi-axis controller, PCI local bus control logic, and PCI bus design; these parts are key technologies for a PCI-based controller design. Through a test in which a 3-DOF manipulator was used to follow a spatial screw trajectory, it was proved that the developed multi-axis controller can realize a near-real-time high-accuracy coordinated motion control.
Faster generation of LALR(1) parsers
Li Hu, Yang Xiaojin, Liu Chao
2008, 34(01): 117-121.
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Deremer & Pennello-s formula for computing LALR(1) lookaheads was studied in practice, by introducing a forward searching method for the computation of lookback and includes relations which were defined in the formula. Efficient algorithms for implementing of the two relations were designed. Several experiments were conducted to show that the computation of LR(0) items closure and searching for a sate in LR(0) state machine are the main bottlenecks of parser generation. Effective and efficient data structures and algorithms for the optimization of these two computations were also proposed. Experimental results show that the speed of LALR(1) parser generation implemented by improved algorithm is even faster than the speed of Bison, a well-known defacto industrial standard of LALR(1) parser generator.
Software architecture description technique based on template
Gao Hui, Zhang Li, Fan Zhiqiang
2008, 34(01): 122-126.
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The modeling elements of software architecture can be classified, and the classification is in fact a higher level of abstraction. In order to represent these abstraction levels, both of the software architecture template layer and the software template instance layer were defined by the template mechanism, and the basic conceptions in the two layers were explained. Then, the template-based software architecture description language (TADL) was defined using UML profile mechanism, which was extended from UML2.0. Many UML2.0 modeling elements and mechanism were reused by the <> in TADL. The design requirement, definition technology and profile of TADL were explained. Further more, the modeling basic principles and guidelines of TADL were proposed to model software architecture patterns and software architecture, and a modeling example of ATM(automatic taller machine) was given to explain these.

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