Abstract:Attitude containment control is a kind of distributed cooperative control with multiple leaders, whose objective is to drive all the followers into the leaders formed convex hull. For the case of undirected angular information topology and directed angular velocity information topology, a containment control algorithm based on relative angular and relative angular velocity is proposed, and the constrained conditions for the angular velocity information topology to ensure containment objective are obtained by using algebraic graph theory. When the relative angular velocity is unavailable, a containment control algorithm with damping element on angular velocity is proposed, and its convergence is proved by Lyapunov method. Numerical simulations results validate the correctness of the algorithm. 

Abstract:To reduce the exchange time of dual-stage lithography, a modified fifth-order S-curve planning method and a minimum-time and minimum-jerk control method are proposed. The dual-driver and dual-bridge exchange method of the wafer stages is analyzed, and the wafer stages on the exposure position and pre-alignment position make five point-to-point movements to complete the exchange process. A minimum-jerk optimization index is added to fifth-order S-curve based on numerical integration method, and a modified fifth-order S-curve planning algorithm is proposed to ensure the acceleration curve is smooth. Aiming at a minimum-time and minimum-jerk criterion, an optimal control system is designed to reduce the exchange time and overcome the default of controlling the acceleration mutation only by the minimum-time Bang-Bang control. Simulation and experiment results show that the exchange process can be realized by trajectory planning and optimal control method. The acceleration curve of modified fifth-order S-curve is the most smooth, and minimum-time and minimum-jerk optimal control system can achieve a shorter exchange time.

Abstract:This paper investigates the robust admissibility analysis and static output feedback controller synthesis for a class of discrete-time piecewise affine singular systems. Based on the piecewise Lyapunov functions combined with Projection lemma and some basic lemmas,two novel approaches based on sufficient linear matrix inequality (LMI) conditions to the static output feedback controller synthesis are developed for the piecewise affine singular systems. It is shown that the controller gains can be obtained by solving a family of LMIs parameterized by scalar variables, which can not only ensure the stability of systems, but also guarantee the regularity and causality of systems. Finally, the applicability of the suggested methodologies is demonstrated via some simulation examples.

Abstract:A 2D axisymmetrical numerical model was established to investigate the drag coefficient during the natural deceleration of an underwater projectile with supercavity at a relative low cavitation number. Based on dynamic mesh technology, the variations of unsteady drag coefficient with time have been studied under several model slenderness ratios at a range of initial cavitation number. The simulation results show that the variations of the supercavity length lag behind that of the supercavity thickness during the same supercavitation movements. Whatever the model slenderness ratio is, the model drag coefficients are quasi-linear ascent over time. The cavitation number is ascent over the deceleration, when the cavitation number is low, the curve slope of the drag coefficients is small and the drag coefficient is almost unchanged and when the cavitation number is high, the curve of the drag coefficient is quick ascent. When the initial cavitation number is low enough, the changes of the drag coefficient with the initial cavitation number are very small and the variation of the effect of supercavitation drag reduction with the descent of the initial cavitation number is no longer obvious.

Abstract:To solve the problem of performance degradation due to nonhomogeneous clutter in adaptive radar processing, a new training data selector in non-homogeneous compound-Gaussian clutter based on polarization knowledge was proposed. The polarization scatting matrix of every training sample was estimated using maximum likelihood estimation (MLE) method, and then the error between the estimation and prior polarization knowledge was used to remove outliers from training data. The performance of the knowledge-based algorithm was analyzed on simulated radar data. The results show that the new data selector removes outliers effectively when outlier-clutter ratio is low and achieves a satisfactory performance level for the estimation of clutter covariance matrix.

Abstract:To achieve autonomous table tennis playing, this paper presents a table tennis robot system which consists of binocular vision camera, embedded central control processor, 6 DOF robot arm, visual processing computer and monitoring computer. Based on the modular design, the 6 DOF dexterous robot arm integrates joint torque sensor, joint position sensor, motor position sensor, drive current sensor, temperature sensor and so on. The multi-level electronic structure arm can realize the joint communication, BLDC motors control and data collection by a field programmable gate array (FPGA). The hitting strategy, positive and inverse kinematics and trajectory planning are functioned in the central control processor which employs the Intel Core II dual-core embedded CPU as the control core and the FPGA as the communication logic control chip. The system identification method, which can effectively reduce the accidental error and improve the prediction accuracy by collecting multiple points during the ball moving, is applied to the table tennis trajectory prediction. Based on the predicted trajectory equation of ball and the working space of robot arm, the position, posture and velocity of the robot arm on hitting the ball can be determined. In the motion planning, the arm motion is constrained by multiple points and multiple segments to improve the successful rate of hitting table tennis. Finally, the effectiveness of the robot system and the hitting strategy are validated by experiments.

Abstract:Because the manipulability index based on conventional Jacobian matrix of Gough-Stewart platform (GSP) is with no physical meaning and variant with the change of units, a new invariant manipulability index of GSP is established based on a dimensionless Jacobian matrix. A multimodal evolutionary algorithm, AEGA, is proposed to search the optimal solutions for the optimal design of GSP with only one objective function, and then many solutions are found as the candidates for the designer. To solve the problem with two or more objective functions needed to optimize simultaneously, one of the multi-objective evolutionary algorithms, Elitist Non-Dominated Sorting Genetic Algorithm version II (NSGA-II), is applied to the optimal design process of GSP, then many sets of trade-off solutions, namely, the Pareto optimal set parameters, are found. To illustrate the proposed methodology, a practical GSP as a motion simulator is optimized. The results validate the usefulness to solve the mentioned problems by using the applied optimal algorithms which could meet more engineering demands in practice than using the conventional optimal design method in single objective function.

Abstract:On the basis that taking flexibility and dynamic elastic coupling of each phase transmission mechanism of P-CVT into consideration, a new parallel work of multiple-phase transmission mechanism of P-CVT is proposed, and the judge principle of transmission mechanism working condition is given. Base on accurate KED method, Kineto-Elasto dynamics model of CVT parallel multiple-phase transmission mechanism is established. Taking the typical P-CVT as an example to analyze its output speed, pulse rate and working state, the result indicated that with the increase of rotational inertia of output shaft, the transit time increased and the pulse rate decreased. The phenomenon of single phase, multiple phases or zero phase working occurred. The number of mechanisms that functions in the parallel work and the duration both increased with the increase of transmission rate. In comparison with the traditional methods, the dynamics model given in this article reflected the real movement of transmission mechanism of P-CVT accurately.

Abstract:Based on the theoretical analysis of kinematics principles of the abrasive, dimensionless parameter K was defined to describe the impact effects. Smooth Particle Hydrodynamics (SPH) Finite Element Method was used to study the mechanisms of crack formation and extension in the interior of the material under the impact of the abrasive. The simulation results showed that, with the increasing of K, the inclination and the depth of the inclined crack decreased. The interaction mechanisms between the abrasive and the workpiece showed that the impact of the abrasive was the main reason for the crack formation and extension. In the cutting process, the cutting force increased rapidly, and then, due to the formation of the cracks, the vertical impact forces reduced dramatically, but the horizontal impact force changed little. As the local micro-impact phenomenon between the material and the abrasive, the cutting forces in both directions fluctuated within a relatively large range.

Abstract:To get the corrosion condition of tank bottom accurately, master the statistical rule of maximal corrosion depth of the tank bottom in long-term service, and evaluate the residual service life of storage tank more effectively, the generalized extreme value (GEV) distribution was adopted as statistical model for the corrosion depth of the tank bottom, and the statistical law of the corrosion depth was analyzed. L-moments method was used for calculating the values of the parameters. The method was used to three tank bottoms in one unite plants from Shengli Oilfield, and the results showed that the maximum corrosion depth accorded with the GEV distribution Ⅲ (Weibull distribution), which got though the Kolmogorov inspection. The GEV distribution Ⅲ can fit the statistical rule of maximum corrosion depth better than that of the GEV distributionⅠ.

Abstract:To provide a novel technique to prolong the service life of diamond cutting tools, a thermo-chemical erosion method by using nano-scale copper oxide under vacuum atmosphere was proposed to perform the post-treatment of natural diamond crystals, which had been pre-polished with mechanical lapping procedure. As indicated in the experiments, when the temperature under vacuum atmosphere was 100 ℃, the oxidation and deoxidation appeared between the damaged diamond carbon atoms on the topmost surface layer and the copper oxide powder. The surface roughness of natural diamond crystal declined slowly with the increment of erosion time, i.e. generating a weak planarization tendency. When the vacuum atmosphere temperature was 200 ℃, two hours erosion time was considered as the optimal configuration. At 30 nm indentation depth, the micro-hardness and elastic ratio of the eroded diamond crystal surface reached the maximal value. If the erosion time was larger than two hours, the micro-hardness and elastic ratio declined. 

Abstract:Wrinkling characteristics of inflated membrane arch are studied in this paper using numerical and experimental methods to obtain the rules of winkling formation and evolution. The influences of pressure, thickness, structural size and loading cases on the winkling characteristics of inflated membrane arch are analyzed in detail. The wrinkling forces, wrinkling locations, wrinkling evolutions and load-carrying ability of the inflated membrane arch subject to different loading cases are then predicted. The experimental tests verify the accuracy of the numerical results in the end. The results show that the structural size is the most important factor to winkling characteristic of inflated membrane arch, the inflated pressure is the second important factor, and the thickness is the less important factor. In five loading cases, Fx is the safest one, Fz is the most dangerous one, anther three loading cases are just between the two loading cases above.

Abstract:To improve the real time performance of simulation system based on HLA, and make it be taken on hardware-in-loop simulation system, a novel method based on HLA bridge was proposed. By using this strategy to interconnect federations, the federations execute in the form of parallel computing. After describing the structure of HLA bridge, the design and implementation of a HLA simulating system based on HLA bridge and parallel RTI are introduced in detail. Then the publish-subscribe function, update-reflect function and equal time step advance function of HLA bridge are realized. At last, simulation results show that the real-time performance of simulating system based on HLA bridge and parallel RTI is better than that of original system. This is an effective method in real time performance improvement.

Abstract:To improve the photocatalytic performance of TiO₂, we prepared TiO₂/graphene composite (TiO₂/RGO) with a one-step hydrothermal method. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectra (RS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), transmission electron microscopy (TEM). The photocatalytic activities of the composites prepared with different mass ratio were evaluated using the photocatalytic degradation of methyl orange under visible light. The results showed that TiO₂ particles with an average size of 10 nm were dispersed on the surface of graphene sheets uniformly in the TiO₂/RGO composite. Compared with TiO₂ obtained under the same conditions, the absorption of TiO₂/RGO composite in the visible region was significantly enhanced and the absorption edge was showed a red shift of 20 nm. The photocatalytic degradation efficiency of the composite prepared with 1∶0.005 of mass ratio was about 74.79% after 2 h irradiation. The visible light catalytic performance of TiO₂ to incorporate graphene into TiO₂ can be effectively improved.

Abstract:To solve the problems, such as poor ultraviolet resistance, easy to fall off, easy to change color or bleaching under UV irradiation and so on, of black coatings on aluminum surface by traditional anodic oxidation, the black oxidation ceramic coatings on the surface of LD10 aluminum alloy by micro-arc oxidation were obtained. Its morphology, phase composition, elemental component and solar absorptance were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and UV/VIS spectrophotometer. The results showed that micro-arc oxidation ceramic coatings were composed of α-Al₂O₃ and γ-Al₂O₃. The solar absorptance of ceramic coatings was increased at first then decreased with the increasing of FeSO₄ concentration. When the concentration of FeSO₄ was 5 g/L, the solar absorptance value of the ceramic coating could reach up to 0.91.

Abstract:The segmentation of triangular mesh model in CAD model reconstruction cannot embody significance. To solve this problem, the knowledge base composed by basic modeling features and machining features was constructed to provide prior knowledge for segmentation. Firstly, depending on the fitting error of quadric surface and curvature, every patch of the model corresponding to the surface was extracted successively and the significance of segmentation was reflected by the primitive design element of surface. Then, both features in the knowledge base and the surface set of preliminary segmentation were represented by the attributed adjacency graph (AAG). Finally, the AAG of the features were applied to match the parts of the model which had the isomorphic AAG. This embodied more meaning from the view of engineering semantics. The experimental results demonstrate that the proposed efficient algorithm can get meaningful segmentation.

Abstract:Aiming at the smoothness and responding speed of total brake force of electric and mechanical brake system, the closed loop control strategy of brake force based on the feedforward-feedback structure is proposed to meet the demand of driver request brake force and recover the brake energy efficiently. The strategy can harmonize the static distribution and dynamic control of electric and mechanical brake force, and recuperate the dynamic responding speed of mechanical brake force by the rapid responding speed of motor brake force. The feedforward part of strategy calculates the desired characteristic of the brake force, and the feedback part of strategy adjusts the dynamic characteristic of the total and mechanical brake forces by the closed loop algorithm for enhancing the smoothness and responding speed of total brake force. The simulation results indicate that the desired control characteristic of closed loop strategy is validated and the complex control problem of electric and mechanical brake with multi control objective and multi closed loop can be solved well by the feedforward-feedback control structure.

Abstract:To identify the false QoS information and the complicity fraud between Web services, the paper adopts a QoS trust evaluation approach based on D-S evidence theory. This approach quantifies QoS information from both the public and private trust perspectives, which can determine the trustiness of Web services and identify the complicity fraud between the Web services. Preliminary simulation experiments show that, when the interactions between Web services increase, the approach can increase the success rate of trusted Web services, which is higher than the normal approach used before (which cannot identify false QoS information). The result supports the feasibility and effectiveness of the approach, prepares for the next large-scale empirical study.

Abstract:1/3 continues phase chirp keying（1/3-CPCK）is proposed as a new narrow-band digital modulation scheme. 1/3-CPCK employs sectional type chirp signal as modulated signal waveform samples, of which the phase is continuous, the frequency is smooth and the energy is highly concentrated. This technique can be used in narrower band for high-speed data communication. The mathematical model of 1/3-CPCK is set up in this paper, the similarity of modulated signal waveform samples is analyzed, and the BER performance under AWGN based on coherent demodulation is presented. Theoretical derivation and simulation indicates that the waveform of 1/3-CPCK modulated signal is smooth and it has high energy concentration. When transmission bandwidth is absolutely limited, bandwidth efficiency is 1 bps/Hz and E_b/N₀ is 13.5 dB, BER of 1/3-CPCK Communication system can reach 10-4 by setting proper modulation factor.

Abstract:To improve the practicality and effectiveness of irregular flights recovery, a slot secondary assignment problem for airline in collaborative decision making mechanism was studied. This paper presented an unbalanced slot assignment model for autonomous flight cancellation under flight bank operations. By proving theorems, the characteristics of the model were analyzed and a kind of two-phase alternating solution process was developed. First the un-balanced model was converted to the balanced one and the optimized solution was obtained; and then the depth-first algorithm was used to obtain the optimized unbalanced solution via heuristic flight cancellation. The analysis results show that this method can not only reduce passenger delay time and save time slot resources, but enhance the efficiency of performance, which satisfies the requirements for quick decision and cost-effectiveness during irregular flights recovery.

Abstract:A granule-viewed segmentation method is established based on morphological jump connected operator and spectral graph clustering to solve the problem of content-driven color image segmentation. In the framework of granular computing, basic granules in image segmentation are constructed by color jump connected operator. Based on evaluation of the size of basic granules, regularization of basic granules is conducted by orthogonal polynomial surface fitting. Then spectral graph clustering is used to fuse basic granules and segmentation of a color image is achieved. The validity of the proposed method is demonstrated by experiments. The granule-viewed technique exceeds to regular-blocking-based and pixel-based methods in both elimination of edge-blocking effect and reduction of computational complexity.

Abstract:The acquisition block in the Global Navigation Satellite System (GNSS) receiver is used to provide initial pseudorandom code bias and carrier Doppler estimates of the received signal for the tracking loop. The demand of more accurate tracking loop requires higher resolution on the acquisition block. A variant of classical FFT-based fast acquisition algorithm is proposed, of which the idea is to compress the sequence of sampled signal to shorter sequences. The correlations of the compressed sequences with local replica are processed in parallel. Then the precise code bias is given according to the correlation results. Both analytical results and simulation results indicate that the proposed algorithm can dramatically reduce the computational payload of acquisition while suffering very limited loss in detection probability.

Abstract:Aiming at the shortage of Zigbee network stratification, the annular stratification is introduced. The improved flood routing which is combined with the mechanism of updating stratification and the mechanism of frame transmit is adopted to achieve the target. The wastes of resources and data implosion are avoided by using the improved flood routing. And the process of establishing annular stratification structure is also optimized. The simulation result shows that the improved flood routing is suitable for uniform network and non-uniform network. At last, the improved flood routing is carried out on the CC2430, and the real results match the expected results.