Abstract:Changes in aircraft dynamic model caused by body damage or other unknown faults may cause pre-designed control laws unsuitable for maintaining steady flight and adaptive control methods are needed to ensure flight safety. For this study, based on the nonlinear NASA Generic Transport Model (NASA_GTM), retrospective cost adaptive control (RCAC) is applied to maintain steady flight with unknown faults, including icing and control surfaces faults. With knowledge of Markov parameters which are calculated from the linearized version of NASA_GTM, output feedback RCAC controller is designed. Retrospective cost function is further optimized to update adaptive gains of RCAC controller and the thrust and control surfaces are adaptively modified to compensate for the impacts of unknown faults. The results show that RCAC controller is able to adapt its gains in order to maintain the steady flight and follow control commands.

Abstract:In order to improve the accuracy of the attitude-orbit coupling control problem of spacecraft with flexible attachments, a study on dynamic modeling of flexible spacecraft is conducted. As a result, a high-precision dynamic model based on the floating centroid frame system(FCFS) which can describe the attitude movement of spacecraft as well as the coupling relationship between the attitude maneuvering and the orbit movement better than the old ones is proposed by using the method of Finite-element along with Newton mechanics.The simulation result demonstrates that the FCFS model fits the practical restraint well and thus is applicable. The dynamic influence on the spacecraft caused by the vibration of the flexible attachments during the attitude maneuvering procedure can be calculated accurately by using the FCFS model and so is the changing of dynamic factors, such as the the velocity and the displacement of the centroid.The research results can provide theoretical basis for attitude-orbit coupling control problem of flexible spacecraft and thus achieve the purpose of improving control accuracy.

Abstract:To get high precision global sphere harmonic coefficients, selection strategy of test points and the partition method of polyhedron model are summarized. Quantitative analysis shows the superiority of uniform distribution test points and the polyhedron division method with equal size facets. Then, the concept of local sphere harmonic coefficient is proposed. After choosing the test points located in the detector’s major operation area, a new performance index to measure the effectiveness of local coefficients is constructed. The proposed new concept is shown to be able to effectively improve the gravity field modeling accuracy for certain area and overcome the defect of traditional sphere harmonic function method that can not be used in brillouin ball, resulting enlarged application range. Finally, the global and local sphere harmonic coefficients of Eros433 are calculated, which validates the effectiveness and availability of the method presented in this paper.

Abstract:Fused silica glass is non-crystalline material, the traditional detection methods have complicated steps and low measurement accuracy, residual stresses are often unable to direct quantitative detection. A new residual stress calculation method for fused silica polishing surface was proposed based on brittle solid fracture mechanics, in which a series of nano-indentation experiments were conducted by a sharp indenter, and the sensitive parameters were extracted during indentation process, the experimental data were linear fit and the line slopes were determined, so residual stress was often calculated indirectly by measuring the other physical parameters change caused by residual stress. Comparative analysis showed that the calculation results had in good consistency with the test results obtained by stress birefringence analyzer, so the correctness of the residual stress calculation method was verified.

Abstract:The data dependences irrelevant to program slicing should be calculated in traditional static program slicing algorithms based on PDG and SDG. To deal with this problem, a new fast algorithm for interprocedural static slicing is proposed in this paper, in which the program is represented as idUCF 5-tuple structure according to TOKEN and the information about control-flow of compound statement, and the interprocedural static slicing is calculated without using of intermediate representation of program, such as PDG and SDG. Experimental results show that the proposed method takes the information about function call into full account, reduces time and space complexity and ensures the integrity of static slicing for program with multi-nested structure. The algorithm only calculates the data dependence, control dependence and function call relevant to slicing. Thus, it has a low computation complexity.

Abstract:To systematically reveal the state of art of testing effort (TE) related to software reliability growth model (SRGM) and to evaluate performances of testing effort function (TEFs), modelling of TE dependent SRGM and comparisons for models are studied in this paper. More specifically, firstly, research evolution of TE is summarized since the early 1978 s, and the relation between TE and test cost is analyzed. Then, current TEFs are reviewed and discussed, and modeling process of SRGM incorporating TE is illustrated. Performances of 8 TEFs are evaluated and compared by 4 failure data sets published. Finally, conclusions indicate that appropriate TEF can support decision for research of reliability based on SRGM and evaluating SRGM incorporating TE would be worthwhile in future.

Abstract:In order to effectively recognize and measure individual credit risk and avoid the negative impact which financial crisis has on the commercial banks, and thus keep the normal operation of the credit and financial markets in China, this paper summarizes the main model of personal credit scoring and its development, and also clarifies the validity and integrity of the credit samples, the rationality of the index system and the selection, applicability of the model in the study of personal credit rating. In view of this, based on correlation analysis, early warning of abnormal samples can be achieved, and the samples are complemented through the Monte Carlo Algorithm. Combined with the statistical model and artificial intelligence model, the index system is optimized and given respective significant weight through traversal algorithm. With accuracy, robustness, first misjudgment rate, second misjudgment rate and difference as the selection index, the selection and output of the scoring model can be realized. Through the above optimization algorithm, the problem in personal credit scoring is solved, and the risk control ability of commercial banks is improved as well.

Abstract:The mechanical model of the spacecraft equipped with the hoop truss deployable antenna was developed and its characteristic of dynamic responses in the stage of attitude adjustments are solved numerically. Firstly the FE model composed of the central platform, solar panels and deployable antenna was established and its natural frequencies and mode shapes in the unconstrained condition were calculated. By the union simulation of FEM and Adams the zero-order rigid-flexible coupling dynamic model of the spacecraft was set up, and then the model's translation and rotation angle as well as dynamic responses of solar panels and the deployable antenna in the process of attitude adjustments were given. Results show that the lower order mode shapes of the model are mainly from the antenna′s connecting link and solar panels′ deformation while the antenna′s shape is fixed. In the procedure of attitude adjustments, the spacecraft′s flexible attachments can deform elastically along with rigid motions and the vibration is rather serious.The antenna′s geometry central point keeps vibrating around the equilibrium position even though attitude adjustments are finished.

Abstract:For the study of distributed dual-polarized MIMO land mobile satellite (MIMO-LMS) system, a statistical model for the channels is proposed after the analysis of the channel characteristics. The second order statistics are calculated and channel capacity of different type of MIMO-LMS system is estimated. Considering the Doppler spread in the small scale fading and selecting the proper form of MIMO model, the channel model can keep the statistic characteristics as well as the correlation of the sub-channels unchanged. The simulation result shows that the channel capacity can be increased by applying MIMO to LMS communication and enhances with the increasing number of the antennas.

Abstract:The identification of misalignment and redesign of pinion surface were proposed to get favorable contact pattern and operating performance in actual conditions for spiral bevel gears. The relationship among different groups of misalignment which would lead to the same contact pattern was studied. The digital features of contact pattern were extracted, and the equivalent misalignment was obtained by an optimal method according to the minimum sum of contact path deviation. Machine settings of pinion were redesigned by local synthesis with consideration of misalignment. A numerical example is presented to illustrate this method, of which the effectiveness is verified by comparing the deviation between pinion surfaces redesigned according to actual misalignment and equivalent misalignment.

Abstract:An approach based on CNC grinding machine of plunge shaving cutter for diagonal modified helical gear was proposed to reduce grinding errors and improve meshing performance. Firstly, the corresponding plunge shaving cutter surfaces for the diagonal modified helical pinion was established based on gear theory. Secondly, a free-form flank topographic correction method based on Y7432 grinding machine, with flat wheel translated along normal sections of invented rack-cutter, was established according to principle of rack-cutter generating involute pinion. Thirdly, an error correction model based on a sensitivity analysis was determined, each axis of the machine was formulated as a six-degree polynomial and a disturbed polynomial coefficient on the topographic flank errors was developed by estimating whether the wheel contacted with the pinion. Finally, using minimum squared error as the objective function to get the smallest grind errors, the PSO optimization algorithm was introduced to solve equations of the corrections, and the polynomial coefficients were ascertained. The result shows that the methods can effectively reduce the grinding error, and the topologically modified tooth for plunge cutter can be represented by sum of longitudinal and diagonal deviations surface. The slight variations in pressure angle and generating angle and helix angle can attain some specific diagonal modified tooth respectively, besides, the diagonal modified helical gear with big size and helix angle can then be efficiently ground by slightly adjusting three-axis movement with a smaller translating flat wheel.

Abstract:When measuring the surface residual stresses generated by turning Ti6Al4V tube parts, considering the accuracy, convenience of the measurements and material saving, an appropriate length of the tube was chosen based on the FEM result. When the ratio of the length to the external diameter reaches λ≥50/45 =1.11, the edge effect to the accuracy of the measurements can be neglected. In order to compensate the changes of the residual stresses caused by layer removal, the FEM correction method was used to correct the stress values got by XRD method, and the results revealed that the surface residual stresses generated by turning in both cutting and normal directions were compressive, the magnitude of the residual stress in the cutting direction was larger than that in the normal direction, at the depth of 60 μm, the residual stresses in both directions reduced nearly to 0. The measuring process has revealed that the computation is simple, as proven by FEM, the accuracy of the FEM correction method is much higher than that of the traditional correction method, so it can be applied in practice.

Abstract:The output force model of elongation type pneumatic compliance actuator has been improved and the mathematical model of static stiffness and dynamic stiffness has been developed for the variable stiffness control. The dynamic stiffness is the sum of static stiffness and pressure stiffness. The result based on the experiment and simulation has shown that the air supply pressure is a major factor affecting the static stiffness and dynamic stiffness of elongation type pneumatic compliance actuator. The static stiffness and dynamic stiffness increase with the increasing of supply pressure linearly.

Abstract:To improve the reliability of integrated navigation, a tightly coupling nonlinear model based on pseudo range and rate is proposed for reducing the estimation error of tradi-tional algorithm using linear measurement model in this work. For the application of particle filtering to SINS/GPS tightly integrated navigation system, the dimension of the state variables has been a major constraint for the Real-time system. In this new arithmetic, a linear KF deduction and nonlinear GPF method have been employed for the linear part and the non-linear part to improve the precision and real time performance, respectively. Results from the simulation show that the hybrid algorithm can effectively improve the performance of the integrated navigation system, and the precision increases one time.

Abstract:To investigate the characteristics of flow field on the flight deck for the frigate ship, and obtain the high accuracy data for the piloted flight simulation, isolated simplified frigate ship was calculated using FLUENT in this paper. Specifically, through reasonable mesh generation and validated solving method ,the impact on the calculation results with different grid forms as well as the Reynolds number was discussed, and the simulation applicability of different turbulence models for ship flow field was also analyzed. The spectral characteristics of votex shedding on the flight deck were captured accurately and calculation data accuracy for ship airwake was improved significantly. The results show that ILES model is more appropriate for the ship flow field simulation with higher accuracy requirements, and the numerical simulation method for ship flowfield also provides an important reference for engineering applications.

Abstract:For the task sets in the fault tolerant real time systems, the disadvantages of the local optimal checkpoint interval are under a single fault assumption and also not the global optimal checkpoint interval. To solve these, the multi-objective optimization model for the checkpoint interval global optimization was given first, and then the checkpoint interval global optimization algorithm based on the mixed particle swarm optimization algorithm was proposed. This algorithm avoids the shortcoming of falling into local optimum and enhances the ability of searching the global approximate optimal checkpoint interval by the crossover and mutation operations of the mixed particle swarm optimization algorithm, and further reduces the task worst case response time. The simulation results show that the algorithm can further improve the system fault resilience over the other checkpoint interval optimization algorithms. At the same time, the checkpoint interval global optimization can search the checkpoint intervals of the task set globally when the faults occur many times, by which the number of checkpoint and the number of fault detection can be reduced and the preemption time by the high priority tasks and the fault recovery time can also be decreased, and also the system schedulability can be improved.

Abstract:To improve the accuracy of heart rate (HR) in daily behaviors, multi-sensor fusion method was used in this paper to fuse ECG and pulse wave (PW)whichis closely related to biological electrophysiology and biomechanics, respectively. And a wearable heart rate monitoring system with high reliability based on Android platform was achieved. The proposed system and ST-1212 ECG workstation were used for 18 cases simultaneousexperiment of different motion intensity in daily behaviors. Signal quality indices (SQI) that reflect the level of signal quality were calculated by analyzing the signal characteristics in time domain, and then Kalman-Filter (KF) was adaptively regulated to make the optimal estimation of the HR derivedfrom the dual-channel signal according to SQI, and finally KF residuals were used to adjust the weights to get the fused HR.The results indicate that the fused HR can improve the accuracy more than 46% than those derived from ECG or PW directly. The system can effectively reduce the artifact on HR estimationby using multi-sensor fusion method, thus it can be used for continuous monitoring of HR with low physiological and mental burden for a relatively long time.

Abstract:An online anomaly detection algorithm based on incremental projective non-negative matrix factorization is proposed to detect the network anomaly real-timely and efficiently. Firstly, an incremental projective non-negative matrix factorization is given, which has the same expression with PCA, and is able to construct normal and abnormal subspace to detect network-wide anomalies online by Shewhart control chart. Theoretic analysis indicates that, the proposed algorithm computation is far smaller than NMF-NAD. In addition, traffic matrix datasets analyzing for internet and simulation results show that the network anomalies detection algorithms based on NMF(such as NMF-NAD and ODA-IPNMF) performs better than that based on PCA, and the proposed ODA-IPNMF has comparable network anomaly detection by NMF-NAD, which the ability to detect the network anomaly online.

Abstract:To reduce the de-mapping complexity of cross-constellation QAM in G.HN standard, we first introduce a novel concept of contribution weight to evaluate the contribution of given constellation to the log-likelihood ratio. With its help, a low complexity de-mapping algorithm within shrunk search range is proposed. And then, some boundary conditions are analyzed and solved. Furthermore, an adaptive configuration of search range is also presented with the assistance of channel estimation. The simulation result validates that the proposed algorithm downsizes the search range without any sacrifice of performance. 2 048-QAM and 512-QAM shrink their average of searching constellations to 1.9％ and 5.7％ respectively of the whole constellations. Therefore, the proposed algorithm makes good tradeoffs between performance and complexity, and is expected to have important engineering value and widely application foreground.

Abstract:In order to provide the technical support for the safety of ship structure design, this paper focuses on the response of stiffened plate structure under in-plane compression by utilizing the nonlinear structural analysis code ABAQUS, once ultimate strength of the stiffened plate is reached, the load-displacement relationships, i.e. the post-ultimate strength behaviour can be obtained. Parametric dependencies of the post-ultimate strength behaviour of stiffened plates,such as geometric dimensions of plate, material parameters, initial imperfection and boundary conditions which influence the load carrying capacity are explored. Conclusions can be drawn: The increase of number of stiffeners is advantageous for enhancing the load carrying capacity of the structure when the deflection is assumed, and increasing of thickness of plate cannot effectively improve the load carrying capacity of the damaged structure.

Abstract:In order to research the influence of doping lanthanon on Ti-Al series ductility in room temperature, based on first-principles full potential linearized augmented plan wave method, we use generalized gradient approximation (GGA) and local density approximation (LDA) to build a unit cell model, and use Castep to calculate and analyze TiAl structure doped with Sm, La, structure and mechanical property of intrinsic TiAl and doped TiAl. The data show that as TiAl has been doped with Sm, covalency of TiAl is enhanced, bonding directivity and hardness are improved; ionicity is declined and ductility is reduced. As TiAl has been doped with La, covalency of TiAl is declined, bonding directivity and hardness are reduced; ionicity is enhanced and ductility is improved. Therefore, doping intermetallic compounds with lanthanon may improve mechanical property, it is a promising research direction.