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2008 Vol. 34, No. 02

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Wing-s optimization design using serial and parallel computations based on N-S equations
Wen Jianhua, Zhu Ziqiang, Wu Zongcheng, Chen Zemin
2008, 34(02): 127-130.
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The serial and parallel flow field solution program was validated at two Mach numbers between 0.7 and 0.9 using both a high and a moderate aspect ratio wings. The result based on the Navier-Stokes(N-S) equations proved it right and the parallel efficiency as well as speed-up ratio was discussed. With the goal of maximizing lift-to-drag ratio, the optimization of three-dimensional wing-s section thickness and twist angle was discussed. N-S equations as flow field sovler and Powell method were used as design tools, and the wing-s aspect shape was fixed. The subcritical parallel computation case and supercritical serial computation case demonstrated that nonlinear distribution of thickness and negative twist angle could ameliorate the condition of flow field around the wing, which lead to a higher lift-to-drag ratio. The optimization method is effective.
Scheme analysis of pump-valve coordinated control electro-hydrostatic actuator
Qi Haitao, Fu Yongling, Wang Zhanlin
2008, 34(02): 131-134.
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Aiming at the problem of low response which existed in the typical electro-hydrostatic actuator (EHA) systems, control valve was introduced into EHA systems to find a trade-off between efficiency and response. Three schemes of pump-valve coordinated control EHA were put forward. First was EHA with electro-hydraulic servo valve, second was EHA with direct drive valve, and third was EHA with total pressure control valve. The system composition and operating principle of the three schemes were analyzed. Also each scheme was simulated and compared in AMESim. The simulation results show that pump-valve coordinated control EHA will greatly improve the system response and its efficiency is also higher. As three transitional schemes, they have practical guidance significance to the research and development of present airborne electro-hydrostatic actuation system.
Trajectory optimization design for surface-to-air missile using multilayer approach
Jiang Huan, Zhou Hao, Chen Wanchun, Yang Baokui
2008, 34(02): 135-139.
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A multilayer approach to the midcourse trajectory design for a surface-to-air missile to maximize the kill probability was presented. Three layers were discussed. The first layer represented the midcourse trajectory of the missile, the second layer represented the terminal homing phase, and the third layer was the warhead damaging process. The first-layer trajectory was optimized with a constraint on the value of pitch angle at the handover point to the terminal phase. The pitch angle was used as the global parameter to combine the first and second layer in generating a field of optimum first-layer midcourse trajectories. The second-layer was a Monte-Carlo terminal homing simulation to get the average and standard deviation of miss distance, which combined the second-layer and the third-layer. The third-layer calculated the missile-s kill probability by using the standard deviation of miss distance. The pitch angle and midcourse which maximizing the kill probability were the optimum results of the system. The multilayer approach demonstrates the connection between the midcourse trajectory design and the kill probability. It allows the kill probability be a measure in the midcourse trajectory optimization. Two cases that intercepting high-attitude-high-speed and low-attitude-low-speed cruising target are presented.
Optimization of multi-mode motion estimation algorithm in H.264
Zhang Jiayi, Luo Xiling, Huang Zhigang
2008, 34(02): 140-143.
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The multi-mode motion estimation algorithm of H.264 standard have the problems of complicated coding mode and much computing. Based on analysis of motion estimation algorithm from H.264-s reference model JM10, an original mode selecting algorithm using time or space relativity and an efficient matching rule linking with one-dimension sum of absolute difference (SAD) were designed. It optimized the former algorithm from mode selecting and coding speed by improving serial full searching motion estimation algorithm to parallel partial searching motion estimation algorithm and using one-dimension SAD matching rule combined with classical two-dimension SAD matching rule. The experiment results show that comparing with reference model JM10, the optimized algorithm makes coding rate increase 20%~30% but peak-value of signal to noise ratio (PSNR) just drop 0.03 dB and code speed just increase 1.5%. It means that this scheme increased coding speed with little quality fall of the reconstructed image.
Novel spaceborne SAR ambiguity echo simulation method
Song Xi, Zhou Yinqing, Chen Jie, Li Chunsheng
2008, 34(02): 144-147.
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The ambiguity-to-signal ratio (ASR) is an important performance requirement for spaceborne synthetic aperture radar (SAR) system. A novel ambiguity echo simulation method for spaceborne SAR was proposed to analysis the impact of the ambiguity on SAR image quality quantitatively. A novel spaceborne SAR ambiguity echo model was utilized in the method. The SAR echo from both the observation zone and the ambiguity zone can be generated with this method. The SAR image with ambiguity characteristic can be acquired by applying imaging processing to the echo data. The method is an effective tool for studying the relationship between the ASR and image quality. It can reflect the geometric character of the target in the ambiguity zone, which provides reference for SAR image interpreting. The computer simulation validates the proposed method.
Personalized interest modeling on portal based on latent interest semantic description
Wu Jing, Zeng Xiao, Chen Zhenyong, Xiong Zhang
2008, 34(02): 148-152.
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There is a great potential for interest modeling on description and extension as the personalization services enrich the portal. A novel personalization interest model based on latent interest semantic description(PIM-LISD) was proposed. As a finite mixture, it was represented with personalized interests elicited implicitly on portal and latent interest relating semantic descriptions. The initialization method was to fit the posterior probabilities along with the different reasonable prior predictions, so the interpretative and adaptive capacity of the model could be perfect. During the building procedure, an improved tempered expectation maximization (TEM) was used for variational expectation maximization estimation. The experiments indicate that the proposed modeling method can not only avoid the complication of potential expensive modeling-building stage effectively, but also increase the prediction precision, therefore proving its validity and feasibility.
Human perceive system of simulative aircraft based on PIDNN
Dong Weijie, Liu Changhua, Song Hua
2008, 34(02): 153-157.
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A control scheme based on proportional integral differential neural network (PIDNN) was proposed to control the highly nonlinear and vulnerable simulative aircraft and sensing system. Firstly, the models of the human perceive system for the simulative aircraft was analyzed and studied, the system formula was ratiocinated consequently, and its disturbance from outside environment was analyzed theoretically. Then its superior function of PIDNN controller for its on-line training, learning and regulating ability were used to control the system in simulation environment. Comprising the all-ready used traditional proportional integral differential (PID) controllers, PIDNN has simpler structure, stronger adaptability and faster tracing ability without singularity. The simulation experiment result shows that the PIDNN has properties of quick response and nice steady accuracy, and has a well static and dynamic and robust character, so it can meet the need of real-time control.
Numerical simulation on flow field and infrared characteristics of chevron nozzles
Huang Hongyan, Wang Qiang
2008, 34(02): 158-161.
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The QUICK and finite volume method, RNG k-ε turbulence model, wall functions, discrete ordinates method (DOM) and the weighted-sum-of-gray-gases model (WSGGM) were employed to solve N-S equation, thermal conduction equation in solid wall and radiation transfer equation. A converging nozzle with chevron trailing edge was simulated, and the computed results were validated with available experimental data. The internal and external flow field and infrared characteristics of a converging-diverging nozzle with or without chevron trailing edge were simulated. The result of this research shows that the chevrons induce streamwise vortices into the shear layer, which lead to increased mixing and is benefit to the reduction of infrared radiation of the plume especially near to the nozzle exit.
Triangle mesh optimization based on DSI interpolation
Liu Ruigang, Cheng Dan, Yang Qin, Long Xiang
2008, 34(02): 162-166.
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The algorithm of triangle mesh optimization was provided by optimizing situation of the triangle vertices. The situation optimization is based on the discrete smooth interpolation(DSI). The compensated triangles were added to the vertex adjacent to the boundary during interpolation iterative computation in order to improve the optimization effect. The control point constraints were implemented in the interpolation algorithm in order to maintain the geometry detail characteristic of the primitive triangle mesh model. The algorithm in this dissertation was compared with the additive weighting Laplace algorithm in effect and applicability. With the improved algorithm, the adjustment triangle mesh both maintained the primitive mesh partial detail characteristic and improve the triangle quality well.
Optimization of special elliptic orbit constellation for regional coverage
Meng Bo, Han Chao, Huang Weijun
2008, 34(02): 167-170.
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The merit of elliptic orbit was analyzed, and the merit was that elliptic orbit could give a biasing of earth coverage towards a given latitudinal zone or a given region. The method of designing special elliptic orbit which was critical inclined, sun synchronous and repeating ground trace was expounded, and the calculation process of this method was summarized. The approach to design critical inclined, sun synchronous, repeating ground trace orbit constellation was proposed, and the time each satellite-s ground track passed the destination was taken as the key parameter to influence constellation performance. The mathematical models used in genetic algorithm(GA) for constellation optimization were introduced, and the parameters of constellation were optimized by GA. The statistic rule of optimization results was discussed, and the constellation which accorded with this rule was the constellation studied. The analysis result of constellation performance shows that this kind of constellation is fit for regional coverage.
High resolution finite element procedure for compressible flows simulation
Yang Zhongzhou, Lee Chun-Hian
2008, 34(02): 171-174.
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Spatial discretization of N-S equations was first deduced based on the classical Galerkin method. Taking the above semi-discretized formulation as the basic scheme, a diffusion and an associated anti-diffusion terms were then added, keeping the scheme to possess a local extremum diminishing (LED) property. After taking the time discretization of the above derived semi-discretized scheme, the resulting system of sparse linear algebraic equations was solved by utilizing generalized minimal residual(GMRES). In order to validate the developed scheme with associated code, numerical computations for the shock tube problems, as well as supersonic flows over a cylinder and a double ellipsoid were performed, which revealed that the developed scheme did provide high resolution results.
Method for static response interval of structures and engineering applications
Xia Yuying, Qiu Zhiping
2008, 34(02): 175-178.
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Aimed at physical and geometrical uncertainties broadly existed in practical engineering, an effective method for the supremum and infimum of the static response of structures with bounded uncertainties was presented. The linear interval equations were changed into two standard linear programming problems, and the mathematical proof was given. By the interface program with the finite element analysis(FEA) software ANSYS and the interval computation program, the method was extended to the practical engineering area. The static response intervals were estimated by taken example for a long-span steel framing building. The results show that this method can not only give the result as exact as the traditional Deif-s method, but also have the less calculation times. The interface program with the FEA software ANSYS and the interval computational program can be used for solving the problems of practical engineering structures, directly.
Heterogeneous data integration and coordination in national geology grid
Guo Haoming, Hao Guoshun
2008, 34(02): 179-182.
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In national geology grid(NGG) environment,applications are developed with distributed geologic data. To facilitate application, a uniform data integration framework should be provided. For geologic application-s characteristics, the data integration systems should focus on maintaining dynamic data resource information, searching among heterogeneous data and coordinating constrain relations in the distributed environment. For the needs, a service oriented architecture(SOA) based mechanism for data resource integration was proposed. In the mechanism, a layered data information structure that was consisted by virtualized local data resource information and global data view for searching was implemented. Uncertainty of dynamic data resource was hidden by the structure through which application accessed data uniformly. Constrain relations between data that were maintained in the global data view were checked through triggers of local data base(DB) system and web services. Coordination among heterogeneous data base management system(DBMs) was realized. Based on the mechanism, a middleware named NGG-DBMs has been constructed and serves for NGG.
Position of rover by UHF communication link on lunar surface
Li Xue, Xu Yong, Wang Ce, Zhang Qishan
2008, 34(02): 183-187.
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To position the rover on lunar precisely, a new approach for ranging and measureing angle at high accuracy was presented by utilzing the ultra high frequency(UHF) communication link between rover and lander. In the position system, direct-sequence spread spectrum(DSSS) and consultative committee for space data systems(CCSDS) proximity-1 protocol were introduced for full-duplex data communication, precisely ranging of non-coherent mode was realized by DSSS moduled asynchronous transfer frame, azimuth of lunar was determinated by means of short baseline formed by the dual-antenna on lander. The format of version-3 transfer frame for precisely ranging, the principle of dual one-way ranging(DOWR) and azimuth interfere measurement by carrier phase were discussed at details, then the landing reference on lunar surface was constructed, therefore the approach of lunar position was deduced finally. For the advantage of the method presented, such as intergrated communication & position, more precise position, more efficient utilization rate of channel resources, lower power consumption, simply device structure, it is suitable for the task requirement of lunar rover exploration.
Simulation of parachute-s opening process with multi-node model
Pan Xing, Cao Yihua
2008, 34(02): 188-192.
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Multi-node model of canopy and parachute system under axisymmetrical hypothesis was set up according to their structural and mechanics characteristics. Dynamics equations of this model for simulating inflation process of flat circular parachute with no angle of attack have been constructed by considering the effect of stress, gravity and pressure. On the assumption that the evolvement of fluid field is quasi-steady, the pressure values on the canopy at selected moments were calculated out by solving RANS(Reynolds averaged navier-stokes) equations of RNG(renormalization group) k-ε turbulence model with simple algorithm. With the combination of dynamics equations code and CFD(computational fluid dynamics) program, the fluid-structure interaction study of a selected parachute was carried out, and the change of its shape and characteristics was simulated. The feasibility of multi-node model is confirmed by analyzing calculated results and comparing them with those from some other researches. A new method to study the fluid-structure interaction of parachute is established.
Optimized formation assignment for large-scale air fleet using fuzzy clustering and genetic algorithm
Xiong Wei, Ding Quanxin, Chen Zongji, Zhou Rui
2008, 34(02): 193-196.
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Aiming at the low efficiency, fallibility of formation assignment result and lack of intelligence in optimized formation assignment for large-scale air fleet, a new hybrid genetic fuzzy clustering algorithm (GFCA) was proposed for large-scale air fleet optimized formation assignment by incorporating the fuzzy clustering algorithm into the genetic algorithm (GA). The GFCA solved the uncertainty problem of formation assignment for air fleet by fuzzy clustering algorithm, avoided the local minima and was robust to initialization by using improved GA, with new genetic arithmetic operators, so as to obtain the global optima for formation assignment quickly. The results of two examples show that the GFCA has better generalization, effectiveness and intelligence, and it is applicable to optimized formation assignment for large-scale air fleet.
Effects of free stream local disturbance on delta wing aerodynamics
Zuo Linxuan, Wang Jinjun, Liu Yang
2008, 34(02): 197-201.
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The effects of free stream disturbance on micro air vehicle (MAV) aerodynamics was investigated using delta wings with disturbance introduced by an upstream cylinder in wind tunnel. The results indicate that the stall-delay happen when disturbance is introduced in the upstream of apex for both rigid and flexible delta wings, the stall-delay of rigid wing relates with wake flow of disturbing cylinder, the stall-delay for flexible wing not only relates with this but also with its vibration. Without disturbance or the disturbance introduced in the upstream of wing apex, the lift coefficient of flexible wing is larger than that of rigid one when attack angle is in the range of 4° to 18°, but the corresponding lift to drag ratio of flexible wing is smaller than that of rigid one. Because of the coupling among the vibrations of flexible wing, the flow structure and the aerodynamics, the dominant frequencies of flexible wing-s apex and tip vibration were changed regularly with the sweep angle increases. The dominant frequency of vibration for flexible wing tip is frequency of vortex shedding around stall angle.
Autonomous orbit determination algorithm for constellation from relative position measurements
Chen Pei, Han Chao
2008, 34(02): 202-205.
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The ability of autonomous navigation is one of the key features supporting autonomous operation of the new generation navigation constellations. Autonomous navigation based on relative position measurements among satellites can be described as a high order nonlinear estimation problem, solving such a problem will be a big challenge for onboard computers. A new solution was introduced to improve the computational efficiency of autonomous navigation: an autonomous navigation constellation made up with three satellites was designed to reduce the difficulties in algorithm implementation. The measurements are relative satellite positions in inertial space. Square root version unscented Kalman filter( SRUKF) was introduced to deal with the nonlinearity of the relative measurements and orbit dynamics model. A new autonomous navigation algorithm was designed so that all the three satellites- positions can be determined at the same time. Simulation results show that an accuracy requirement of 5m user range error(URE) within 100 days can be met.
Optimization of energy absorption in high speed fluid-driven mechanism
Chen Weiwei, Sun Lingyu, Zhang Guangyue, Li Fei
2008, 34(02): 206-209.
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For a high speed moving mechanism driven by fluid, abrupt stop resulted from barriers will lead to its large deformation, even fracture. To achieve optimum structural style and parametric matching of buffer members, nine test samples were selected out of twenty-seven design styles through orthogonal experiment method in advance. Their high-speed moving and impacting process were simulated by nonlinear finite element method(FEM) considering fluid structure interaction. On the basis of the above results, a modified error back-propagation(BP) network method was applied to train these samples, and obtained the nonlinear mapping relation between parameters of tubes for energy absorption and strain energy of crucial parts. The optimum structural parameters of buffer tube were determined, at the same time, the efficiency of schemes selection was improved obviously.
Integrating design of performance and reliability for flight control systems
Chen Yunxia, Zeng Shengkui, Jin Yanzun
2008, 34(02): 210-214.
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By analyzing and summarizing the achievements and shortages of related research works about integrating design of performance and reliability (IDPaR), the research thought of IDPaR was put forward. From considering the internal and external factors related to product failure, a generic modeling method of comprehensive model for IDPaR was given, and definition of performance-reliability and calculation formulas were presented. According to flight control system, the detailed modeling methods of all kinds of influencing factors were described, and the algorithm flow and analyzing methods of IDPaR were summarized and proposed. Finally, taking X-missile-s flight control system as a typical case, the correctness of the model and algorithm were verified by simulation result.
Comprehensive biomechanical analysis of microcosmic trabecular structure of cancellous bone
Pei Baoqing, Wang Tianmiao, Wang Junqiang
2008, 34(02): 215-218.
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Femoral cancellous bone has microcosmic trabecular structure and its element characteristics effect the gross mechanical property of the femur. Finding proper cell configuration and its distribution will be of great importance for more effective biomechanical analysis of cancellous bone. A lot of microcosmic trabecular models with different structures were used to study the biomechanical performance of the elements. The biomechanical analysis of the femur model with different trabecular structures and distributions were carried out with the combination of the finite element method and the mechanics experiment of sample part fabricated by rapid prototyping processes. The relation between the trabecular structure and its biomechanical characteristics was obtained. Also, the comparison between the finite element results and the mechanics experiment was worked out. Based on analysis, better microcosmic trabecular structure and its distribution were found and utilized in building an analytic model of the femoral cancellous bone. The optimized microcosmic element structure can be applied to the manufacture of the biological materials effectively.
Behavior of silica sol during the anodizing process of magnesium alloy
Li Yihong, Zhu Liqun, Liu Huicong, Chen Yichi
2008, 34(02): 219-223.
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Anodic films were prepared on AZ91D magnesium alloy and Mg-Li alloy separately in 150 g/L NaOH and 1.0 mol/L Na2SiO3 with varied silica sol addition. The conductivity of the solution and the surface morphologies of the anodic films were characterized by conductivity instrument (DDS-307) and scanning electron microscopy (SEM). The solution-s conductivity would become small with the silica sol addition. The energy dispersion spectrometry (EDS),the thickness and the X-ray diffraction (XRD) of the films were also investigated. Results show that the thickness of the anodic film increases linearly with the addition of silica sol in both solutions and mainly depends on the anodizing break voltage which is affected by the solution-s conductivity and the resistance of the magnesium/solution interface. The sol particles take part in the anodizing reaction process. The silica sol reacts with MgO and the product is Mg2SiO4.
Design and control of air bearing precision positioning stage driven by linear motors
Zhang Congpeng, Liu Qiang
2008, 34(02): 224-228.
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In order to master the design and control techniques of the workpiece table in photoetching machine, an H-type air bearing precise positioning stage driven by dual linear motors was established. Some key techniques, including design method of air bearing slider and synchronic-motion control of dual linear motors, were studied. Three air bearing sliders were analyzed and designed by finite element method. Preload technologies were adopted to improve air bearing-s static performance. The experiment results show that the air-bearing sliders have high load capability and stiffness. The static stiffness of X -slider in the vertical direction is 276.9N/μm and that of Y -slider is 333.3N/μm. The dual linear motors of H-type stage require high-precision synchro-control. Traditional tandem and parallel synchronous control can-t fulfill the demand. An improved parallel structure synchronous controller based on velocity synchro-error was proposed, which adaptively tuned the PID parameters by fuzzy controllers. The experiment results show that the synchronous velocity precision is improved more than three times by using the improved synchronous controller, which is suitable for multi-motor synchronization control with strong mechanical coupling. H-type air bearing positioning stage driven by linear motors has high load capability (40kg) and high accuracy (<2μm) and suits to be used in precision engineering.
Underactuated control of micro-satellite using thrusters based on (w,z) parametrization
Liu Haiying, Wang Huinan, Chen Zhiming
2008, 34(02): 229-233.
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Aimed at the attitude stabilization of micro-satellite under actuator failure, a control scheme based on the (w,z) parametrization was proposed. The (w,z) parametrization is a new attitude describing method, which describes the attitude of satellite using two perpendicular rotations thus complements the Euler angles and quaternion. Using (w,z) parametrization method the kinematics and dynamics model were established, and three controllers named spin-axis stabilization, angular velocities stabilization and attitude stabilization were designed, which applied on three aspect of non-symmetry satellite under actuator failure. Numerical examples of underactuated control by micro-thrusters which is based on pulse width modulation(PWM) technology demonstrated the effectiveness of the derived method.
Design real-time traffic information by cell transmission model
Shang Huayan, Huang Haijun, Gao Ziyou
2008, 34(02): 234-238.
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The variable message signs (VMS) have been widely used in guiding and managing the dynamic traffic with development of intelligent transportation technologies.Such traffic dynamics as shock waves and jam can be well reproduced by cell transmission model (CTM). A new method to estimate the route travel times based on the CTM was presented and the LOGIT rule to govern the route choice was adopted. The impacts of VMS on recurrent and non-recurrent congestion were numerically investigated using the formulae proposed. The real-life traffic conditions could well be reproduced as simulation results shown. Travelers- decision making could be positively influenced by the VMS so as to alleviate the grave degree of recurrent congestion. In the case of non-recurrent congestion, the VMS induced similar effects no matter high and low the traffic demand was. However, the resultant flow pattern was sensitive within a small range of the model parameter when the demand was high.
Key techniques in simulation of machining distortion for aeronautical monolithic component
Zhang Hongwei, Zhang Yidu, Zhao Xiaoci, Wu Qiong
2008, 34(02): 239-243.
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Key techniques in the process of simulating machining distortion in milling due to residual stresses were researched. The calculation program was developed to generate residual stresses file and the finite element model containing original residual stresses was established. The thin-walled structure was obtained after milling machining. In order to improve simulation accuracy, a new method was carried out to model the finite element model by combining solid-shell element with solid element. Considering the contact action by unilateral constraint between workpiece and baseplate when the workpiece was located by press clamps, contact method was put forward to simulate the effect of the compression only supported by thinking of workpiece as elastic body while workbase as rigid body. The modal analysis results of representative component based on finite element simulation were compared with experiment results. The validity and reliability were verified. The material removal was realized using element birth-death. The finite element simulation of machining distortion for aerospace structures was realized by using these techniques.
Force distribution of plane 2-DOF overactuated parallel manipulator with fault tolerance
Yan Caixia, He Guangping, Lu Zhen
2008, 34(02): 244-248.
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In order to ensure the fault tolerant capacity of manipulator under scenario the failed actuators are no more than system redundancy, the driving force distribution before and after failure was researched. Based on the D-Alembert principle and the equivalent force theory, a plane 2-DOF(degree of freedom) overactuated parallel manipulator dynamics model was built. Then, dynamics equation of manipulator with partial failure was analyzed. And fault tolerant driving force redistributing method was further deduced. To reduce the impact of active force abrupt change to end effectors before and after failure, a driving force distributing method was brought forward. It took the minimum quadratic sum of driving force difference between overactuated and faulting system as optimization objective. With data analysis, the force change ranges of traditional method and minimum difference oriented fault tolerant method were compared. The result indicates this optimized force distribute method can obviously improve fault tolerant performance.
Parametric design and analysis of front independent suspension of 6×6 off-road vehicle with ADAMS/View
Jiang Libiao, Ni Qiang
2008, 34(02): 249-252.
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Methods of parametric modeling and analysis supplied by ADAMS/View were used to design and analyze front independent suspension of 6×6 off-road vehicle, and better results were received. The whole process is that firstly dimension parameters of suspension were designed according to design conditions, and then virtual prototype model was built in ADAMS/View, design study and design of experiments.DOE(Desidgn of Expeximents) on suspension model were done at last. It can be obtained by analysis that sideways displacement of wheel has a dereasing tendency when length of lower sway arm is growing and assembly angle of lower sway arm is decreasing. So the length and assembly angle of lower sway arm were chosen to be design variables, and sideway displacement is taken as design objective, parametric optimization was done in ADAMS/Insight. The final test results meet demands of design. This method can improve advances design speed and quality of suspension, and can supply reference for designing high performance suspension in the future.

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