Abstract:To dynamically model slender structures conveniently by Cosserat rod theory, the dynamic equations for pre-stressed curved Cosserat rods are established within the framework of this rod theory by defining variables to describe their initial configurations, their pre-stresses and their initial deformations, which move along with their cross sections. Based on their corresponding specific assumptions, the dynamic equations for a cable with initial sag and a circular arch beam, which have wide applications in bridge structures, are explored within the framework of pre-stressed curved Cosserat rods, respectively. The results are in agreement with their corresponding equations obtained by other methods in references. Since the Cosserat theory is geometrically exact, the dynamic equations for pre-stressed curved Cosserat rods derived here are not only retaining all geometric nonlinear characteristics but also of universality, which can be effectively and efficiently exploited to nonlinear dynamically model for slender structures in practical engineering situations.

Abstract:Combining analytical prediction and optimization of parameters, a rapid method for basic firing data of flight program of the ballistic missile launched on mobile platform is studied. First, the analytical expressions between the parameters about flight program and attack information are obtained by using polynomial function approximation, by which the initial value of the firing data can be calculated. Second, considering the parameters of flight program as variables and the least square of the placement's aberration as the performance index, the Levenberg-Marquardt (L-M) Method is used to obtain the optimal values. Finally, as an example, the proposed method is provided to attacking targets with the LMG-30G. The simulation results show that, because of the less computational effort, the proposed method is suitable for the rapid design of the Big Wide Intratheater Mobility for the missile. When the precision of the placement is not highly demanded, the solution of analytical expressions can be used directly as the value of flight parameters to attack the target.

Abstract:In this paper, the problem of reachable landing locations generation is transformed into trajectory optimization of maximum downrange, minimum downrange, maximum crossrange and maximum crossrange at specified downrange under entry constraints, and the sequential gradient-restoration algorithm is used to solve the trajectory optimization problem. Numerical simulations are performed, and the simulation results show that the technology of reachable landing locations generation for lift entry vehicle is reasonable and feasible, and the reachable landing locations generation of lift entry vehicle is left-right asymmetry fan-shaped region. 

Abstract:This paper studies the problem of orbit control for intercepting satellite based on state feedback control considering parametric uncertainties, finite time performance, control input constraint and poles assignment. The sufficient condition of controller is derived by Lyapunov approach, and then the controller design is transformed into a convex optimization problem in terms of linear matrix inequality. An illustrative example shows that the system is asymptotically stable with the designed controller and the optimal performance is obtained with control input and poles assignment constraints.

Abstract:On-orbit servicing spacecraft has become a hot research field at domestic and abroad in recent years, communication supporting spacecraft as a class of on-orbit servicing spacecraft can provide date forwarding service to the communication fault spacecraft, which can prolong the on-orbit life. In order to improve the communication supporting spacecraft antenna pointing accuracy, relative navigation algorithm of communication supporting spacecraft based-on particle filter is proposed, then more precise relative position and speed between two spacecrafts are obtained. This method takes radio equipment as the main measurement parts for its inherent characteristics, such as long measuring distance, high covering rate and all-weather work, and combines the advantage relative position and speed estimation of particle filter in nonlinear system filtering. Simulation results show that the new algorithm can effectively reduce the errors and improving relative position and speed estimation precision, ensure the space missions of communication support effectively.

Abstract:In order to investigate the efficiency of attitude determination system using particle filter. The system state equation and measure equation of a satellite with star-sensors and gyros were established. And particle filter was used to estimate the attitude of satellite. The simulation results showed that the system can convergent not only for the small initial estimation error, but also for the big initial estimation error. But EKF can convergent only for the small initial estimation error. Finally, the effectiveness of PF applied to the gyro-free mode was also verified.

Abstract:To decrease the free energy, ferromagnetic crystal would reduce the stress energy by changing its magnetic state. Under the influence of stress-induced magnetic anisotropy in the interactions of stress and geomagnetic field, the physical mechanism of magnetic memory effect is studied. Crack propagation tests are performed on plate specimens of 45 quenched and tempered steel and non-quenched and tempered steel specimen. By three-point bending fatigue experiment and measurement in situ of metallurgical microscope, the magnetic signals were scanned by TSC-1M-4. The magnetic memory signals of quenched and tempered steel specimen are significantly lower than that of the non-quenched and tempered steel specimen. After eliminating stress by quenching the specimen, the results show that different stress states have significant effect on the magnetic field characteristics of the specimen.

Abstract:To understand the generation of temperature nonuniformity and its influence on effective emissivity, a radiant characteristics calculation method based on Monte Carlo(MC) full ray tracing technique for V-grooved surface blackbody is proposed. The exactitude of this method is approved by comparison with precise Bedford method, then the reason and development of temperature nonuniformity are discussed, and finally the effects of temperature nonuniformity on effective emissivity are disclosured. The results demonstrate that the temperature uniformity is deteriorated when small grooved angle, high grooved length and big temperature difference between surface temperature and environment are adopted. Further more, the grooved angle and length can exert influences on effective emissivity. It is concluded that the grooved angle of 45° of 60° and the grooved depth less than 2 mm can give a satisfied effective emissivity and temperature uniformity to general application. Better performance can be achieved when heat pipe technique and guarded sleeve are applied.

Abstract:To improve the anti-interference performance of UWB communication system, a new UWB communication system based on parallel combinatory spread spectrum is proposed after analyzing the characteristics of UWB and PCSS. The application of M-ary bi-orthogonal keying (MBOK) modulation in the new system is also discussed. In this paper, qualitative analysis is made to analyze the relationship between the system performance and band efficiency, and conclusion is got that the performance of PCSS-UWB communication system is related with the number of the transmission data in PCSS technology. Simulation shows that E_b/N_o is improved 9 dB in the system with MBOK modulation than that in the system with PPM modulation when BER is 10-4.

Abstract:To verify whether the comprehensive test bench of cabinet-end relationship for high-speed train can meet the demand or not, the positioning precision, maximum motion range, forward kinematics, dynamic tracking performance and maximum output speed tests were carried out. The results indicate that the maximum positioning error of translational motion is 0.1 mm and the maximum positioning error of rotation motion is 0.1°, far superior to the actual demand. The forward kinematics of the Stewart parallel manipulator is precise enough and can be used for monitoring the real-time state of the system. In the dynamic tracking test, the maximum aptitude attenuation and the maximum phase lag occur in the Y direction, 0.755 dB and 25.92°, respectively, significantly better than the amplitude attenuation 3 dB and phase lag 90°. The maximum output speed of three translational motion can meet the 0.2 m/s requirement. The results show that cabinet-end relationship comprehensive test bench can fully meet the demand of the high-speed train cabinet-end relationship test and has space for further improving performance.

Abstract:To evaluate distributed fault-tolerance, an automated test platform is designed and realized based on distributed fault-tolerance for massive storage, which contains a system monitor, a workload injection module and two fault-injection tools based on server level and directory and file operation. This platform can inject different levels faults including server level, directory level and files level, and can finish the test work by the master node. Experimental results show that the platform can compare performance index of the target system with different fault tolerance.

Abstract:To solve the "I/O wall" problem in the case of real-time accessing about mass information processing and to improve performance of distributed mass storage systems, an access policy based on storage unit pass-through is proposed and the problem of traditional access models is analyzed. Then the mechanism of pass-through pattern is studied, and a multi-level and distributed model is built up. Next, the continuous mapping of physical address, cache address of storage space and logical space address of storage system are realized depend on the different levels and mapping strategies. The time consuming of pass-through storage path in pass-through pattern is analyzed. Last, the performance of the storage unit in the simulated environment is tested. The results show that the method can improve the performance of storage system effectively, and can meet the needs of real-time accessing about massive information processing.

Abstract:To improve the comfort and handling stability of aircraft tractor, a quarter body model of aircraft tractor is built, and a model reference adaptive control algorithm is applied to the active suspension of the vehicle. General skyhook control force is added to the car body, and the reference model is obtained by optimal control theory, which is better than passive suspension no matter in ride comfort and handling stability. Using Lyapunov stability theory to solve adaptive adjustment rules can make the dynamics of controlled model approach the dynamics of reference model. The simulation results show that model reference adaptive control can obviously improve the performance of the suspension system, and this algorithm has self-adaptability to the changes in the suspension parameters.

Abstract:This paper presents a combination method based on fuzzy C-means clustering algorithm and Kalman filter, which effectively improves the GPS static point positioning accuracy. Firstly, the latitude and longitude data collected by GPS was filtered by Kalman filtering, which could eliminate large fluctuations in the data. Secondly, the fuzzy C-means clustering algorithm was used to find the clustering center as the final positioning coordinate. The experimental result shows that, this method can effectively promote the degree of accuracy of GPS static single point positioning with low cost, and the coordinates of the positioning is more close to the true geographical coordinates. 

Abstract:For landing on planet, a dual control strategy is developed to solve the problem of poor estimation performance which results from the lack of observability. The system uncertainty is incorporated into the quadratic performance index as a cost by extending state space, which takes advantage of the nonlinear coupling between observability and trajectory to overcome the lack of observability and to achieve better estimation performance. By stochastic optimizing the landing trajectory, the overall performance of GNC system for landing on planets is improved.

Abstract:To choose the suitable benchmark data for data-driven controller performance monitoring from data based on kinds of multiple mode in the history database,a new method based on multiple variables classification is proposed. First the method provides a combined similarity factor to measure the similarity between real-time acquisition data and data from some mode in the history database, and then it determines the mode that real-time data belongs to, finally it assesses the controller performance. Simulation study demonstrates the efficiency of the proposed approach.

Abstract:To solve the problem of storage and transmission of elemental image array in the integral imaging, the distributed prediction coding method is used to compress the elemental image array. First, the elemental image array is transformed to sub-image array according to the pixel relationship between the elemental images, then the hierarchical coding of the sub-image array is performed via the optimal displacement prediction combined with PRISM distributed coding structure in line with the regular changes of the sub-image arrays. The experiment results indicate that the method is obviously prior to the JPEG in the rate distortion property, and when the resolution of the elemental image array is fixed, the higher the display resolution of the integral imaging, the better the compression performance of the method, which will make it have better adaptability in the high display resolution integral imaging in the future.

Abstract:Each method of edge detection is regarded as an expert. To solve the problem of inconsistency of different expert responses and the difficulty of choosing right expert, a model of edge detection based on multi-expert and principal component analysis (PCA) is proposed. Firstly, a statistical model for expert response is established, and theoretical analysis shows that the edge detection model can effectively suppress noise coming from the expert. Then, the information of multiple detection results were combined to obtain the general detection result with the model based on multi-expert and PCA. The experimental results are very satisfactory.

Abstract:In order to improve the RFID system read efficiency, a reading mode named UID-Listed Reading Mode is proposed. With putting the UID of tags to be identified into the address list of a RFID reader, which was formed in advance, the address list would be tracked and searched until all of the tags were identified one by one, according to certain rules. To prove the strong points of the UID-Listed reading mode proposed, query times, transmission delay and system efficiency were simulated, and then contrasted with the Binary Search Algorithm, which had similar operation principle with proposed reading mode. The consequences of simulation indicate that the UID-Listed reading mode turns out to be better than the classical binary search algorithm.

Abstract:To manufacture face gear with high precise, computer numerical controlled (CNC) grinding method and grinding disk in face gear machining was investigated. The tooth surface equation of face gear machined by grinding disk was determined by coordinate transformation. The motion laws of CNC machine were established by the equivalence principle of position and movement of tool in different machining method, and then the laws were transformed into Taylor expansion for convenient programming. The deviation of CNC machining tooth surface from that of theoretical was calculated, in an illustrated example the maximal deviation was 0.0719 micrometers. The result shows that the grinding method of face gear is feasible, the CNC motion laws are correct and the desired precision is easy to meet.

Abstract:A novel approach to mixed H₂/H∞ control of spacecraft large angle attitude maneuvers is proposed based on sum of squares (SOS) optimization. By using modified Rodrigues parameters, the attitude dynamics of the spacecraft is represented in terms of linear parameter varying (LPV) systems. To reduce the designed conservativeness, a new mixed H₂/H∞ performance criterion is presented by introducing additional slack matrix variables, which eliminates the coupling terms between system matrices and Lyapunov matrix. Based on this, a sufficient condition for the existence of mixed H₂/H∞ controller is derived by using Lyapunov approach and SOS optimization. Finally, the H₂/H∞ controller design problem is converted into a parameter optimization problem with SOS constraints.

Abstract:This paper investigates parametric stabilization of port-controlled Hamiltonian systems with dissipation (PCHD). A controller is designed to make the PCHD system parametric stable as the parameters drift based on its passivity. The form of the controller is related to PCHD system. Thus, the closed-loop system maintains dissipative form and the energy function achieves its minimal value at the equilibrium point determined by the unknown parameter. An excitation system is taken as an example, and the effect of equilibrium point of the system is analyzed as the parameter varies. A controller is designed to make the excitation system parametric stable. Simulation results are given to show the effectiveness of the proposed method.

Abstract:Aimed at the problem that the existed spatial join algorithms can not solve the spatial join query within the constrained range, the constrained spatial join query is proposed which finds all the pairs of objects satisfying some spatial predicate within the given range. The directed solving methods and algorithms based on R-tree are given. Based on good property of QR-tree, a constrained spatial join algorithm is proposed which avoids larger storage cost of quadtree and overcomes the drawbacks of R-tree node overlapping. Thus the algorithm implements the constrained spatial join query on many small R-tree and the problem of expensive spatial join overhead is solved. The cost analysis for the proposed algorithms is given. Experiments show the algorithm has high efficiency.

Abstract:The UFastSLAM algorithm's resampling process will bring “sample reproverishment” problem. To improve the algorithm performance and increase the estimate accuracy, and based on the thought of auxiliary particle filtering algorithm, a solution named “Auxiliary UFastSLAM” is presented for SLAM problem. In view of the specialty of UFastSLAM algorithm, the recent observation information in its suggestion distribution function's seeking process to enhance stability of particle sampling, and one time weighting and second time weighting in its resampling process to alleviate particle degeneration are introduced. The experimental results indicate that the Auxiliary UFastSLAM algorithm does well on both estimate accuracy and consistency.

Abstract:To eliminate time delay and uncertainty that cause some undesired effects in the actual system, using robust control system design techniques, a feedback gain controller is designed which allows the system to meet design requirements within the allowable range of uncertainty, and reduces the sensitivity of the system. A class of stability control problem for uncertain time-varying delay systems with state delay is investigated. By materializing uncertain structural information and constructing a new appropriate Lyapunov-Krasovskii functional based on LMIS, the controller design method is derived. 

Abstract:To accurately know heat transfer and flow processes of AP1000 passive residual heat removal heat exchanger(PRHR HX), and provide a reference for the safe operation of our new AP1000 advanced pressurized water reactor nuclear power plant, FLUENT software is used. By comparative analysis of the distribution of temperature-field and flow-field in different locations at the same time, and the change of temperature-field and flow-field in the same location at different times, we can know the heat transfer and flow characteristics which are changed with time more intuitive, and analyze the effect of straight tubes and elbow tubes on the natural circulation. The results show that the temperature difference, vortex, flow around make the interaction of temperature field and flow field. Due to the influence of elbow tubes structure, the fluid natural convection in the IRWST is more complex.

Abstract:In order to quickly obtain the 3D digital surface of the dental wax, an original design and achievement of a novel digital laser dental scanning system is introduced based on three-axis platform. 3D surface and design of Dental model are implemented by the presented system which integrates optical, mechanical, electronic technologies, data processing technology and so on. The system consists of laser probe, three-axis platform, electronic control system, master computer and system software. 3D point cloud of Dental wax without any blind point can be scanned through controlling line structured light vision sensor and three-axis platform in phase. Experiment demonstrates that the scanning precision of the system is 0.182mm, scanning speed is 8 000 pts/s. Therefore, the system works fast with high accuracy, its operation is simple and flexible, so it can meet requirements of collecting 3D surface of the dental wax.

Abstract:To achieve the attitude control of air-breathing hypersonic vehicle, it′s necessary to analyze its complex aerodynamic characteristics, and complete the control system design. Aerodynamic characteristic of air-breathing hypersonic vehicle, namely, the variations of lift coefficient, lift-drag ratio and pitch-moment coefficient with that of attack angle at different Mach numbers, is explored by the data from wind tunnel test. The longitudinal dynamic coefficients are calculated to analyze its stability. Two different control strategies are designed based on aerodynamic analysis, one is attack angle feedback control and the other is normal overload control, and their time domain and frequency domain characteristics are calculated respectively. Experiment result shows that air-breathing hypersonic vehicle not only satisfies longitudinal dynamic stability, but also demonstrates good flight control performance.