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2007 Vol. 33, No. 02

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Spacecraft autonomous navigation based on SSUKF algorithm
Liu Yong, Xu Shijie
2007, 33(02): 127-131.
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An improved unscented Kalman filter (UKF) algorithm based on spherical simplex unscented transformation (SSUT) was presented to satisfy the stability, precision and real time requirements of spacecraft autonomous navigation. The S SUT reduces the sigma points for the unscented transformation. Compared with the traditional UKF, the computational efficiency of spherical simplex unscented Ka lman filter (SSUKF) was improved, without sacrificing the estimation precision. A ccording to the similar computation process of UKF and extended Kalman filter (E KF), the combined Kalman filter based on SSUKF and EKF was designed. This algori thm can switch adaptively between the SSUKF and EKF through a mode switching fun ction which is the criterion of estimation errors. It solves both the inefficien cy problem of UKF and the instability problem of EKF. Simulation results show th at the combined Kalman filter integrates the advantages of SSUKF and EKF, improv es the computational efficiency, insures the estimation precision and robustness , therefore it is more suitable for the spacecraft autonomous navigation system.
Curvature effects on the film cooling with the rotation
Tao Zhi, Young Xiaojun, Ding Shuiting, Xu Guoqiang
2007, 33(02): 132-135.
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A computational heat transfer analysis was carried out to comprehend t he mechanism of rotation and the curvature effect on the film cooling which is i mportant in understanding the mixing process between the film coolant and the ho t stream air over the high pressure turbine blades. The CFX code was used to inv estigate the mixing effects of the rotation and the curvature. Turbulence model is k-ω model which has received wide application in the case of rotation. It was found that both rotation and curvature could affect the distribution of the fil m cooling. Rotation could lead to the departure of the film flow from the wall. The cooling effect will be improved on the suction side as the curvature str ength decreases. But on the pressure side, the departure of the film flow could be found. With the coolant-to-mainstream momentum flux ratio increased under u ni ty, the film trajectory on the pressure side will bend towards the blade tip. Bu t on the suction side, there is no clear influence.
Continuous and discrete gust responses of elastic missiles
Wu Zhigang, Yang Chao
2007, 33(02): 136-140.
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Elastic missiles in atmosphere may have intense response due to gust e xcitation, which has great influence on structural safety, flight performance, a nd attack precision. Approaches of the calculations of aeroservoelastic response to the continuous and discrete gust for missiles were presented. The equations of motion considered the interaction of rigid-body modes and elastic vibration m odes, and the generalized aerodynamic forces were formulated in a way of quasi- s teady aerodynamics. The approach of the continuous gust response was based on the calculation of the power spectral density(PSD) using frequency-domain transfer functions. The approach of the discrete gust response was a time-domain integra l based on the state-space formulation of the aeroservoelastic system. An actual process of evaluating aeroservoelastic stability, calculating continuous and dis crete gust response, and modifying flight control system for a cruise missile wa s demonstrated. Numerical results indicate that adverse coupling between structu re and control system may deteriorate the stability and gust response of the sys tem. An appropriate structural notch filter in the control loop can effectively alleviate the adverse effects of elastic modes.
Method based on μ-analysis techniques for the clearance of flight control laws
Liu Lin, Chen Zongji, Tang Qiang, Che Jun
2007, 33(02): 141-144.
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The clearance of modern flight control laws to take into account the m any uncertainties has become a great challenge to engineers and researchers, and traditional grid-based methods have gradually been incompetent for this task. A method based on μ-analysis techniques was used to solve this very difficult problem. The aircraft model and flight control law used in the prese nt study is a twin-engine fighter with a robust inverse dynamics estimatio n(RIDE) controller. Our approach was applied to evaluate a linear stability margi n criterion currently widely used by the aerospace industry. Using the linear fr actio nal transformation based uncertainty model developed from the nonlinear aircraft model, and a fictitious multiplicative input uncertainty representation of the criterion, stability robustness analysis results were presented for the flight co ntrol law. Compared with traditional grid-based ones, the μ-analysis based met ho d has two obvious advantages which provide more rigorous and efficient in the pr esence of multiple sources of parametric uncertainty. One is the points between grids can be cleared, the other is there exists no "disaster of dimension" pro blems.
Optimization for composite wing based on Pareto genetic algorithm
Cheng Wenyuan, Cui Degang
2007, 33(02): 145-148.
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To solve the aileron reversal problem in aircraft design, an aero-elastic tailo ring optimization model of composite wing for engineering requirement was establ i shed and the Pareto genetic algorithm (PGA) based on Pareto optimal set was developed. In order to obtain the Pareto optimal set, the Pareto filtering pool was constructed based on weight information in PGA. And the niche techn ology was utilized to keep the diversity of population. The computation of the t e st function indicates that PGA has good convergence. In the numerical example, s etting the lifting coefficient and the rolling moment coefficient as objective f unctions, the expected Pareto optimal set was obtained by using PGA. The re sults show that the Pareto optimal set satisfies the engineering requirement and can provide many feasible projects for the decision-maker to choose.
Design of innovative control surfaces of flying wing aircrafts with large ratio aspect
Ma Chao, Li Lin, Wang Lixin
2007, 33(02): 149-153.
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Because the flying wing aircraft with large aspect ratio cancels the t raditional stabilizers and control surfaces which are used in traditional configur ation, many disadvantages of dynamic characteristic arise. The aerodynamics char acteristic of the innovative control surfaces which are implemented on the flyin g wing aircraft with large aspect ratio were introduced, and elevon and split rud der were involved. And the control effects on three axis were analyzed basing on computetional fluid dynamics(CFD) method. The concept of control volume was imp orted to introduce parameters-based method of control surfaces design. The cont rol effect requirements of the control surfaces were also evaluated. The origina l design of certain aircraft′s control surfaces was modified. An practical suit of steps for control surfaces design which can be used in flying wing aircraft with large aspect ratio has been provided.
Acceleration corrosion factor analysis for fatigue critical components based on the Weibull distribution
He Xiaofan, Liu Wenting, Yang Hongyuan
2007, 33(02): 154-158.
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Accounting for the pre-corrosion influence on the fatigue life, the st atistical analysis of acceleration corrosion factor for accelerated aging test to service or natural exposure environment on fatigue critical components was performed. Ass uming the pre-corrosion fatigue life follows the two-parameter Weibull distrib ut ion, and the relationship between the characteristic life and the pre-corrosion time can be expressed as an exponential model, the equations for acceleration corrosion fa ctor were established. The acceleration corrosion factor was proved to be a constant regardl ess of reliability degree and pre-corrosion time. The approximate distribution o f the acceleration corrosion factor estimate was gained, so the confidence intervals of the acceleration corrosion factor for LY12CZ aluminum alloys specimen were obtained.
Vision-based autonomous landing integrated navigation scheme of unmanned combat aerial vehicles
Chen Lei, Chen Zongji
2007, 33(02): 159-163.
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A computer-vision-based integrated navigation scheme for autonomous la nding of an unmanned combat air vehicle (UCAV) was presented. Based on this sche me, vision information with measurements of other on-board sensors, including i n ertial navigation system (INS) and altimeter system, could be fused according to t he characteristics of these sensor systems. The scheme gave navigation informati on without the help of external navigation equipments with high measurement accu racy. Since computer vision played an important role in this navigation scheme, the vision algorisms were complicated processes and were discussed, so that the vision sensor measurement could be output with a delay in a low ban dwidth. A multi-rate extended Kalman filter was constructed to fuse multi-rate information and gave high bandwidth attitude and pose estimations based on the output bandwidth of INS. The navigation scheme could run properly on the real-t ime simulation system for autonomous landing of the UCAV.
Study of active periodical structure′s controlling the direction of reflector electromagnetic wave
Su Donglin, Zhou Yan
2007, 33(02): 164-168.
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The conception of active reflection was presented. Using th e periodical surface′s character of band gap and impedance transition of electr omagnetic crystal structure such as photonic band gap(PBG), frequency selection surface(FSS), high impedance surface(HIS) and so on, the varactor diode was p ut onto the approximate HIS′s surface to join each cell of metal on top layer t o realize the electronic control for periodical structure. The active periodical structure was eslablished. The propagation characteristic of incident electromagnetic wave was effected and controlling the refle cted phase and direction of reflector electromagnetic wave were realized. The si mulation test proves that this method and technology can control reflector w ave′s phase and direction of on working freque ncy band by using single or double layer active periodical structure effectively .
New method of ATI moving targets indication based on amplitude and phase thresholds
Yuan Hao, Zhou Yinqing, Li Jingwen
2007, 33(02): 169-175.
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The factors, which influence the distribution of the amplitude and pha se of the points in the phase interferogram of SAR-ATI moving targets indicatio n , including radar-noise, scatter energy, background uneven RCS and the side lob e of image pixels were analyzed. To resolve the problem of the high fal se alarm rate in SAR-ATI, an improved method was proposed based on the MTI of th e joint amplitude-phase threshold. Firstly, the points with polluted phase in th e image of every channel were pre-filtered. Secondly, after eliminating the point s with invalidated phase, the adaptive amplitude filtering was processed with the threshold set by the probability, according to the radar-noise and the phase in t erferogram. In the end, the detection with the phase threshold method was perform ed to reduce the false alarm rate effectively. An empiric al formula derived from the statistic fitted curves in the phase interferogram was presented to reduce the false alarm rate in the low CNR condition evidently. The computer simulation demonstrates this method.
Optimum design of erecting system
Li Zhongming, Jiao Zongxia, Wang Kejun
2007, 33(02): 176-179.
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Optimum design of erecting system was analyzed from the points of view of rapidity and acting force, and the objective function of optimization wa s established. Each objective function was nondimensionalized, and the multiobje ctive optimization function was solved by conventional weighting method. Sample point was appointed by uniform design. The polynomial response surface model was set up based on sample experimental data of collaborative simulation. Multidisc iplinary design optimization of the position of key pivots on some erecting syst em was carried out. The polynomial response surface method was compared with con ventional multiobjective optimization method through the evaluation function con structed. It shows that the polynomial response surface method is effective by a nalyzing the difference between the two methods. This method is a favorable tool for further development and design of erecting system.
Dynamic target assignment method based on multi-agent decentralized cooperative auction
Liao Mo, Chen Zongji
2007, 33(02): 180-183.
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The multi-UAV(uninhabited aerial vehicle) cooperative target assignment problem is to decide which UAV attack which target so as to improve efficiency and reduce cost. The mathem atic model for multi-UAV cooperative target assignment problem was built. Assigning targets in multi-UAVs, the model considered about effect of the battle field situation and differences in different UAVs and targets. A dynamic target assignment method based on multi-agent decentralized cooperative auction was pr es ented. The simulation result and the statistical data demonstrate that the meth od can present assign schemes with good optimal objective function and the metho d is a kind of dynamic method which gets schemes with expected optimal effect un der certain time or resource constraints.
Nonlinear filter algorithm for GPS/DR integrated positioning
Liu Xu, Zhang Qishan, Yang Dongkai
2007, 33(02): 184-187.
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A filter model and its algorithm based on UKF (unscented Kalman filter) for GPS/DR (global positioning system/dead reckoning) integrated positioning in land vehicle navigation system were established. Aiming at the system characteristic of linear state equation and nonlinear measurement equation, the algorithm which combines UKF with EKF (extended Kalman filter) was proposed. Compared with general UKF,the operation time used for the phase of time updating is less than that of general UKF. The error caused by the linearization of EKF is eliminated and the precision is improved contributing to processing the nonlinear problem with unscented transform. The simulation result demonstrates that the algorithm has better filtering precision than EKF, and reduces computing time, which is fit for integrated navigation system demanding for little resource and high precision.
Dexterous workspace analysis of surgical robot
Liu Da, Wang Tianmiao
2007, 33(02): 188-191.
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Although it is difficult for surgical robot to have full dexterous workspace, surgical robot must have high dexterity orienting to minimally invas ive surgery. Firstly, according to the practical requirement of surgery, quadran t segmentation principle was proposed. The surgical workspace was divided into 8 quadrants, so the dexterous workspace occupied only eighth workspace. And then, the analysis relation was derived between dexterous workspace and workspace of surgical robot. The workspace area of surgical robot could be obtained from the analysis relation, and then the kinematics parameters of surgical robot could be confirmed. Finally, kinematics parameters of the self-defined surgical robot w e re optimized. Therefore, this principle decreases the demand on dexterity of sur gical robot and resolves the conflict between structure and dexterity of robot.
Complex engineering system synthesis design optimization framework
Wang Zhenhua, Deng Jiati, Sui Pengfei, Wang Yongpo
2007, 33(02): 192-196.
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Synthesis design optimization environment was built for system integration, proc ess unification, parameter optimization and collaborative design. The high exten sible and multi-tiered architecture of this environment was built on the analysis of characteristic of complex engineering system. Four key modules were discussed: project organization and management module guarantees project schedul e and quality; process modeling and running module applies design task structure for representing design processes, workflow reference model for running, and pr ovides the ability of task transition across organization; design task unit base d on component technology integrates people, data and tool over network, and pro vides a coherent task model for system design; product data model uses PDM(prod uct data management) as information infrastructure, and provides a single repre sentation of product. The implementation of the environment and running mechanis m were presented. The prototype of this environment has been successfully tested by the design and optimization experimentations in fields of pneumatics, struct ure, control and system design.
Core process skeleton based process planning during the early stage of product development
Wei Li, Zheng Lianyu
2007, 33(02): 197-200.
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The early stage of product development has a crucial effect on capabil ity, cost and quality of products. Research on theory and approach of early proc ess planning was based on feature information, and could not utilize rough-gra n ularity incomplete product information. Therefore, core process skeleton based p rocess planning approach was proposed on the basis of key characteristics which have been proposed to express rough-granularity incomplete product information. Core process planning is a kind of abstract of process plans which satisfy key characteristics requirement, and it expresses core process of various variation of product/part family. Process plans can be configured rapidly according to e mbranchment and existence rules. The procedure of process planning on the basis of core process skeleton includes four steps: determining product/part family, s earching core process skeleton, configuring core process and process route plann ing. Validity rule, principle rule and customized rule were employed to assure v eracity of process planning. Finally, machining process of the girder of the win g was used to validate feasibility of this approach.
Optimization of loading trajectory in skin stretch forming process
Zhang Yanmin, Zhou Xianbin
2007, 33(02): 201-205.
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The influence of loading trajectory was discussed to solve the precisi on forming problem of double curve skin in stretch forming. The method of combin g finite element analysis and optimization algorithms was proposed to acquire th e reasonable loading trajectory. Characteristic and insufficiency of common load ing trajectories were analyzed which used in double curve skin forming. Optimiza tion mathematics model was set up in order to reduce springback and improve the fittability. Approximate model and variables range were set up with orthogonal d esign. The reasonable loading trajectory was found through the numerical simulat ion and sequential quadratic programming optimization algorithm under the restri ctive of maximal thickness strain. The optimization results show that the fittab ility, strain distributing and thickness uniformity were improved greatly.
Influence of Bauschinger effect on springback in sheet metal stretch bending
Du Song
2007, 33(02): 206-209.
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To theoretically investigate the influence of Bauschinger effect on sp ringback in sheet metal stretch bending, the constitution relation of a kinemati c hardening was used to determine the stress distributions of stretch bending b y numerical calculation, so that the springback was calculated. They were compar ed with the results calculated according to the constitution relation of an isot ropic hardening. The function of Bauschinger effect on springback during stretch bending was analyzed in accordance with the distinguishing feature of those dis tributions. The results of investigation show that in bending after stretch Bauschinger effect is beneficial to decreasing the springback and its influence is little, for small is either pre-stretching or the zone which loads in the oppo s ite direction are acting on; and that in stretching after bend it is detrimental to reducing the springback, but its influence is not evident, for alteration to the inner bending moment and the curvature radius of strain neutral surface is r estricted mutually.
Auto-adapted fitting algorithm of B-spline surface objects
Chen Guozhen, Liu Jinghua
2007, 33(02): 210-213.
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In view of the reappearance of complex curved surface object in virtua l environment, the control apexes of the surface were fast calculated based on th e known points taken from the curved surface. The control apexes and pitch-poin t vector determined a B-spline curved surface, named the real object′s fitting c urved surface. Because the data points have noise and swings, the fitting curved surface may deviate to the known curved surface at some points. The points wher e the deviation happened could be found by the estimating error condition and the more real control apexes could be calculated according to the deviating points, th e deviation direction and the offset distance, which aimed at automatically repair ing the fitting curved surface. In practice, such as CAD(computer aided design), CAM(computer aided manufacture) and VR(virtual reality), the algorithm can meet the different requests of precision for the three-dimensional body modeling.
Design technique based on CDD function for industrial CT system
Wei Dongbo, Fu Jian, Li Bing, Zhang Lei
2007, 33(02): 214-218.
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Industrial computed tomography(ICT) is an advanced, non-contact and non-destructive testing method. It is complicated, non-universal and expe ns ive. It is necessary to make the custom development to reduce the risk and the c ost. A kind of design technique frame based on the contrast-detail-dose(CDD) fu nction was proposed for the development of ICT system. According to this frame, t he design method for fan-beam 3rd generation two dimensional ICT(2D-ICT) was d ed uced and the corresponding software platform was implemented which is consisted of three parts. They are the computer aided design(CAD) part based on the CDD func tion, the simulation part and the performance evaluation part. The initial desig n parameters firstly entered the CAD part. They secondly entered the simulation part if they passed the CAD check. The simulation results were finally evaluated by the evaluation part. The validity of the proposed method was proved by the computer simulation and the example of the engineering development.
Fast selective algorithm of Intra prediction for H.264/AVC
Meng Qinglei, Yao Chunlian, Song Jianbin, Li Wei
2007, 33(02): 219-223.
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The newest video coding standard H.264/AVC provides several predic ting modes and directions for Intra prediction in the spatial region, and the op timal mode was selected by rate-distortion optimization(RDO) with high coding c omplexity. In order to solve this problem, the fast selection algorithm was prop osed from different aspects: Firstly, for luminance mode selection, the method w as proposed that utilizes the image entropy value to predict the mode of the mac roblock, and updates the threshold adaptively by a sliding window. Secondly, int ermediate computing results were reused to reduce the predicting directions. Fin ally, in the RDO performance, the arithmetic structure of Intra prediction was c hanged with calculating the best chromance mode separately. Experimental results s how that with similar distortion performance, the algorithm that adopt the above three strategy can efficiently reduce the computational complexity up to 76% wi th 2.6% increase of bits rate averagely.
Design and realization of BHU facial expression database
Xue Yuli, Mao Xia, Zhang Fan
2007, 33(02): 224-228.
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A comprehensive facial expression database was provided, which incl udes three kinds of facial expressions: pure facial expressions, mixed facial ex pressions and complex facial expressions. The database contains some unique emot ional facial expressions not appeared in other facial databases, and is benefit to the world facial expression databases. Questionnaire investigation for some v ideos of pure facial expressions was done to give the evaluation of every v ideo. The evaluation of each pure facial expression data was obtained throug h statistical manner. Facial expression recognition experiment on nine pure faci al expressions demonstrated the feasibility of recognizing multiple facial expre ssions. The database is helpful to the development of facial expression recognit ion technologies and emotional human-machine interaction systems.
Image fusion algorithm based on multiscale edges
Li Xiaojuan, Zhao Wei
2007, 33(02): 229-232.
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An image fusion algorithm just using multiscale edges of original imag es was proposed. There are three steps in this algorithm. Firstly, multiscale ed g es of the original images were detected. Secondly, these multiscale edges were fus ed to get the fusion image′s multiscale edges according to the fusion rule, max i mizing edge correlation between the fusion image and original images. At last, t he fusion image was reconstructed from its multiscale edges. The algorithm using only multiscale edges reduced the computation complexity in the fusion process. The fusion rule enabled the fusion image to hold as much as edge in formation of original images. Furthermore, the algorithm could compress data even without using any compression coding method, which reduced memory cost and decre ased data transfer bandwidth. The experimental results demonstrate that fusion i mages generated by this algorithm contain the information of original images eff ectively.
Design and implementation of global content management system
Wu Guoshi, He Suoju
2007, 33(02): 233-237.
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The algorithms of "change detection for database content" and "change detecti on for file" were put forward for detecting the change of client con tent data based on the actuality of multilingual contents in the enterprises. An effectively centralized multilingual content management system was designe d and implemented by using the XML, CORBA(common object request broker architecture) and workflow technologies. Based on th e features of the multilingual contents, the system framework, workflow processe s, content change detection algorithms and system implementation were designed in detail. The feasibility of the algorithms and system design was verified by impl ementing the system.
Wide area oriented network active publish/subscribe system design framework
Gao Qingyi, Lu Peng, Lin Xuelian, Wang Bin
2007, 33(02): 238-242.
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Event space partition technology changes the traditional basic interaction model of the content-based publish/subscribe system and its related implementation strategies, and enables a class of system which is named active publish/subscribe system. In order to establish the integrity of active publish/subscribe system solutions, based on the analysis of active publish/subscribe system basic interaction model, an active publish/subscribe system design framework ACTPS (active publish/subscribe system)was proposed. ACTPS comprised six design models which were event model, subscription model, partition model, component model, routing model and matching model. Detailed description of key features and the core of implementation strategy of these models, and the linkages among the various models were presented. ACTPS provides the general reference model for designing and realization of active publish/subscribe system. It is also a theory foundation for further in-depth research and analysis of publish/subscribe system.
Method of enterprise knowledge integration based on semantic web
Gu Wendong, Xia Guoping, You Weijia
2007, 33(02): 243-247.
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In most of today′s enterprises, organization knowledge is located in separate operation systems, therefore the knowledge management is not well realized. Based on enterprise′s legacy systems, an application framework which supports the EKI(enterprise knowledge integration) by applying semantic web technology was proposed. The architecture of the framework was divided into four layers from bottom to top: data layer, operation application layer, knowledge integration layer and knowledge service layer. Each layer was introduced in detail. Four key techniques for the architecture, i.e. data semantic transformation, unified knowledge representation by RDF(resource description framework)/RDFS(RDF schema), constructing knowledge chain and knowledge query were further studied. An approach with eight definite steps to develop the framework was also proposed for referenced. Finally, application of the proposed framework in a famous Chinese large scale hydropower corporation was further provided to illustrate the effectiveness of the framework.
Formal models of UML statechart diagrams based on Petri nets
Guo Feng, Yao Shuzhen
2007, 33(02): 248-252.
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A formal model named SC_Net which can precisely describe the dynamic features of UML statechart diagrams was presented. Firstly a formal syntactic of UML statechart diagrams was given and a series of auxiliary functions to describe the structure features of UML statechart diagrams were presented in which target determinator and source restriction were used to describe the inter-level transitions and open events and close events were used to describe the communication among UML statechart diagrams. Then, based on C_Net an extended Petri net model named SC_Net was defined which can be used for the semantic models of UML statechart diagrams. Besides the control parts, SC_Net also included the data process parts which was lacked in the research area of formal semantics of UML statechart diagrams. The translation process from UML statechart diagrams to SC_Net was defined. At last, an example in flexible manufacture systems was given. Results show that SC_Net can be used to verify the properties of the UML statecharts.

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