Abstract:The wear of bearing parts of aviation engine is one of the main factors that cause engine failure and serious accidents. This paper analysis the mechanism of sudden severe wear caused by fatigue wear failure on aviation engine, describe the relationship between wear degree and particle size and quantity, systematically introduce on-line detection technology of lubrication oil wear particles in aviation engine, discuss various technical methods and its theoretical principle, features, typical parameters and application and the latest research results as well as the technical adaptability. On-line detection of lubrication oil wear particles can effectively detect the sudden abrupt wear on aviation engine and warning failure in time, to avoid serious accidents. It has important theoretical significance and engineering application value.

Abstract:The existing solar cell surface defect detection algorithms based on machine vision are all designed to use various types of mathematical models to carry out the algorithm design. In order to further improve the detection accuracy, inspired by human vision bionics, the human visual attention mechanism is firstly introduced in the solar cell surface defect detection, and a solar cell surface defect detection algorithm based on visual saliency is proposed in this paper. First of all, the acquired solar cell surface image is preprocessed to remove the noise and grids that influence the defect detection. Secondly, a visual saliency detection algorithm based on selflearning features is put forward to roughly locate the defect region. Then, an algorithm that combines the visual saliency and superpixel segmentation is proposed to precisely locate the defect region. At last, the final detection result is obtained using morphological postprocessing. The subjective and objective experiment evaluations on a test image database containing various types of defects demonstrate that the proposed algorithm has high detection accuracy.

Abstract:This paper proposes an online diagnosis method that adopts inductive coupling technique to realize noncontact cable fault diagnosis; the method solves the problems of large signal attenuation of capacitive coupling and poor diagnosis effect in existing noncontact detection approaches. Compared with contact diagnostic methods, noncontact diagnosis approaches avoid the electrical connection between diagnostic device and the cable under test, and is safer and more convenient. Firstly, based on the main factors (mutual inductance, broadband signal coupling ability) that affect inductive coupling method, the paper analyzes theoretically the materials and parameter characteristics of the coupler under ideal condition in which the diagnosis effects are the same for inductive coupling method and contact, direct injection method; the inductive coupler is analyzed and designed. Then, theoretical analysis and simulation verify that even if the inductive coupler suffers from the influence of actual parasitic parameters, the signal attenuation of inductive coupling is still less than that of capacitive coupling. At last, experiment results verify that the detection rate of inductive noncontact cable fault diagnosis reaches to above 93%, the positioning error is less than 0.42 meters. The proposed method has great actual application value.

Abstract:Ultrasonic phased array full focusing method is an imaging algorithm based on full matrix data. It exhibits advantages of high imaging accuracy and great defect characterization ability, while there are some disadvantages, such as large amount of data, long computation time and large nearsurface noise. At present it is mainly used in postprocessing imaging. A correction model based on the angular directivity function is established, and an accelerating algorithm based on triangular matrix data capture and data index technology is designed, combining with parallel computing device. It is tested on an aluminum block with artificial holes with a 16element phased array probe. The result shows that time consumption of each image is decreased to less than 135 ms with the accelerating algorithm, which can be deemed realtime. The correction model is helpful to decrease nearsurface noise, reduce false defects, and improve signal to noise ratio of the image.

Abstract:In this dissertation, taking the magnetic flux leakage (MFL) detection system for longdistance oil pipeline as study object, the online compression algorithm of magnetic flux leakage detection data is studied. Aiming at the problem that traditional data compression method is difficult to apply in the embedded online work environment, compressed sensing (CS) theory is introduced and an online CS compression method for MFL detection data is proposed. The wavelet base is determined as the best sparse representation base of the magnetic flux leakage signal, and the mathematical expression of the wavelet sparse base matrix is derived; A measurement matrix optimization algorithm based on Welch bound and PRP conjugate gradient algorithm is proposed; An important data segment screening method of the MFL detection data is proposed, which greatly reduces the data storage size. The simulation results show that the proposed online compression algorithm greatly reduces the computation complexity of compression encoding in online environment, has the advantages of simple and rapid operation, high compression ratio, high reconstruction precision and etc., and meets the actual requirements of MFL detection data online compression.

Abstract:Titanium bump in hydrogen maser and cesium clock require 3 000 and 3 500 V high working voltage to keep ultrahigh vacuum of storage bulb and cesium beam tube respectively, and needs to sense the output current of the high voltage power supplies to judge their working conditions. In this paper, buckcurrentfed pushpull topology and CockcroftWalton voltage doubling rectifying circuit are employed to develop the high voltage power supply for titanium bump. The snubber circuits of three buck current feed circuits, 50% duty cycle alternative driving circuit based on D flipflop and low output current sensing circuit are presented. The high voltage assembly adopts vacuum encapsulated process, singlesided surface mounted PCB design and the structure design of high voltage and low voltage cabins. This design decreases the voltage stress of the rectifier diodes. The high voltage power supply achieves 0.5% load regulation, 20～50 V wide input voltage range, 0～18 μA output current sensing, and passes vacuum discharging test, which satisfies the requirement of titanium bump in atomic clocks.

Abstract:Digital medical technology is inevitable trend in the future orthodontic treatment. The robotic technology is used to assist orthodontics archwire bending clincally, and the digital expression of orthodontic archwire is prerequisite of the robotic bending. Because of the individuation of human tooth arrangement and complexity of archwire shape design, it is difficult to realize the digital expression of individual archwire. This paper present a method of the interactive adjustment for individual orthodontic archwire. Based on reference points on bracket, it’s defined that orthodontic wire curve is composed of the straight line segment for bracket and the transitional curve segment. And the transitional curve segment is constructed by the mathematical model of 3th order Bezier curve. Refer to process of bending wire by hand, the mathematical model and model library about special function arch curve are established based on the discrete and combinatorial method. The method of interactive adjustment for individual orthodontics archwire is studied by adjusting position of the straight line segment for bracket, shape changes of the transitional curve segment, selecting the position and type of special function arch curve. The experiment is achieved in the interactive adjustment software designed on the Labview software platform. The result shows that the method is feasible and effective.

Abstract:Muscle fatigue is a complex physiological phenomenon. The real-time assessment of muscle fatigue by surface electromyography requires that fatigue indices are rapid, noise immunity, and reliable. Thus, the real-time assessment of muscle fatigue has been proposed based on the marginal spectrum entropy. First, deterministic periodic signals with different data lengths and Gauss white noise has been used to analyze the rapidity of marginal spectrum entropy and the robustness of data length. Then, the muscle fatigue signals of long extensor carpi when the 10 subjects grip under continuous static contraction state decreases from 100% maximal voluntary contraction to 50% maximal voluntary contraction, has been used to analyze the reliability of assessment method of muscle fatigue based on marginal spectrum entropy and the stability of the method applied to different individuals. Finally, the noise immunity of marginal spectral entropy has been investigated by adding Gauss white noise and electrocardiogram noise into the muscle fatigue signal of a subject. The experimental results show that compared with approximate entropy and median frequency, the calculation based on marginal spectrum entropy is more rapid and data length robustness is more obvious. Also, Goodness of fit based on marginal spectrum entropy is better(0.46±0.14) ,the marginal spectrum entropy can reliably assess muscle fatigue. Slope of the coefficient of variation is lower(30.30%),the marginal spectrum entropy is highly stable for different individuals. Rate of change of the goodness of fit of the marginal spectral entropy is lower after adding Gaussian white noise and electrocardiogram noise(additive Gaussian white noise and additive electrocardiogram noise are 34.39% and 3.78% respectively).Therefore, marginal spectrum entropy has the advantages of rapidity, noise immunity, reliability of assessing muscle fatigue. It can be concluded that the marginal spectrum entropy is suitable for real-time assessment of muscle fatigue, which supplies a new method for muscle fatigue assessment.

Abstract:To overcome disadvantages of conventional Doppler estimation and compensation on UUV (Unmanned Underwater Vehicle) platform, a novel algorithm based on joint time-frequency searching is proposed to track and rapidly compensate the time-variant Doppler in underwater acoustic OFDM (Orthogonal Frequency Division Multiplexing) communication. The algorithm utilizes the comb pilots combined with frequency-domain resampling to calculate the channel impulse response with different Doppler factors. Then the correct Doppler factor is achieved and eliminated by seeking the sparest channel impulse response, which is accessed using matching pursuit method. Experiment results performed by Monte Carlo simulation and sea-trial data are provided, demonstrating that the proposed algorithm can effectively track and rapidly compensate the time-variant Doppler factor, thus ensuring the stable underwater acoustic OFDM mobile communication for UUV.

Abstract:The grey bootstrap evaluation model GBM (1, 1) for dynamic measurement results of atmospheric pressure is built through fusing the grey model GM (1, 1), bootstrap method and uncertainty evaluation theory. The parameters, such as the estimated true value, estimated interval and mean uncertainty are selected to describe the estimation results. The experiment results indicate that the GBM (1, 1) model combines the advantages of the GM (1, 1) grey model and bootstrap method, can accurately simulate the probability distribution of dynamic measurement data and track the variation trends of the measured quantity during dynamic measurement progress. The maximum value and mean value of the estimated errors are smaller than those of the measurement errors of original data, respectively. The interval estimation reliability of the GBM (1, 1) model exceeds 96%, and the estimated interval can fully envelop the dynamic fluctuation range of the measured quantity, which proves that the GBM (1, 1) model can improve the measurement accuracy of atmospheric pressure and evaluate the uncertainty of dynamic measurement results accurately.

Abstract:The position and pose reconstruction of spatial hole widely exists in industrial and architecture areas. This paper proposes a method for recognizing the position and pose of space hole, named the directrixgeneratrix method. The principle of the reconstruction method is as follows: fitting the hole directrix according to the marginal points on the cross section of the hole; through other points in hole cylindrical surface respectively, drawing the hole cylindrical surface generatrix in the direction given by the hole axis; LM (Levenberg Marquard) algorithm is adopted to perform the optimization, in which the algebraic sum of the distances from the crossover points of the generatrices and the hole cross section to the hole directrix is minimum. Then, the hole axis direction is obtained, and the center of hole directrix could be used as the hole location. The experiment result shows that the proposed method requires less sample data, and features very simple calculation process and high accuracy, which is also suitable to the position and pose reconstruction for axis and other cylindrical surfaces.

Abstract:In order to improve the success rate of adaptive reclosure and minimize the incomplete phase operative time, a method based on flatness characteristics of allphase FFT (apFFT) spectrum is presented to detect the arc extinction time for transient singlephase earth faults in transmission lines with shunt reactors. The apFFT spectrum of the terminal voltage of faulty phase is analyzed. It is found that, before the secondary arc extinguishes, the apFFT phase spectrum is not smooth, because of outstanding variation of highfrequency components caused by the highly nonlinear transition resistances. After the secondary arc extinguishes, the apFFT phase spectrum is flat, because the transition resistance disappears and highfrequency signals change smoothly. Utilizing the difference of the flatness characteristic in highorder harmonic apFFT phase spectrum before and after the secondary arc extinguishes, a reliable method is proposed to identify the arc extinction time accurately and effectively. Simulations using ATPEMTP verify the correctness and effectiveness of the proposed method. The proposed method is almost insusceptible to fault location, transition resistance and power angle. The validity of the method is verified by the analysis of the actual wave data.

Abstract:The signaltonoise ratio (SNR) of space coherent optical communication system is greatly influenced by the laser linewidth. This paper compares and analyzes the influence of laser linewidth on the SNR of the heterodyne detection output when the time difference τd that two beams arrive at the photosensitive surface of the balanced detector and the detector characteristic parameter are different. Theoretical analysis and experiment result show that the differential frequency signal bandwidth increasing caused by laser linewidth broadening is independent withτd. When the differential frequency signal bandwidth increases by 2.673 times, the output SNR decreases by 0.369 2 times, which is approximately equal to 1/2.673. Increasing the internal gain, response degree and response bandwidth of the detector can slow down the SNR decreasing speed as the laser linewidth increases; however, when the internal gain and response bandwidth are too large, corresponding noise signal is also stronger, which is not benefit to the improvement of the SNR.

Abstract:Aiming at the surface defect detection of the thickwalled pipe, a PZT based the flexible comb Rayleigh wave transducer was proposed. Firstly, the finite element simulation was carried out to optimize the parameters of element interval, element width, element number and element length. The influence of the element number and the element length on the directivity of the transducer was studied. The tailing of the Rayleigh wave signal was suppressed by optimizing the backing materials and the backing thickness. Secondly, a new type of flexible comb Rayleigh wave transducer was developed according to simulation results. The characteristic of the transducer was tested, and experimental results agreed well with the simulation. According to the simulation and optimization, the tailing of the Rayleigh wave were shrinked and the exciration energy was concentrated, with the element interval of λR (λR equals the Rayleigh wavelength), the element width of λR/2, and the number of elements of 5. The experimental result showed that the comb Rayleigh wave transducers possessed good directivity and capability of examination of the surface defects of thick walled pipes.

Abstract:The measurement accuracy of tilt angle directly detemines the effect of the state control system. On the basis of studying single sensor tilt angle mensurement, this paper discusses the method using sensor data fusion technology in tilt angle measuresment. Firstly, the tilt angle measurement principle based on accelerometer and gyroscope is analyzed, and the frequency characteristics of accelerometer and gyroscope measurement results are studied. Secondly, the complementary filter is selected as the data fusion method according to the frequency characteristics of accelerometer and gyroscope measurement results. Finally, the quantumbehaved particle swarm optimization (QPSO) algorithm is introduced as the parameter optimization method of the complementary filter, and the parameter optimization effects of QPSO and particle swarm optimization (PSO) algorithms are conpared in this paper. The experiment results show that the complementary filter can accurately measure the tilt angle in a wide frequency range, and QPSO algorithm has better parameter optimization effect than PSO algorithm.

Abstract:A multi parameter measurement sensor for hydraulic oil pollutants is proposed. Based on the planar microfluidic inductance sensor, a single layer inductance coil is added in the sensor. Two singlelayer coils are arranged on both sides of the straight microchannel. On the basis of inductance parameter detection, the two singlelayer inductor coils are equivalent to a pair of ring shaped capacitor plates, the capacitance parameter detection is introduced, and the multiparameter sensor achieves the detection of four pollutants (ferromagnetic metal particles, nonferromagnetic metal particles, water droplets and air bubbles) in the hydraulic oil. The design of multiparameter sensor was carried out, and the detection position was optimized through simulation and experiments. The capacitance parameter detection experiment realizes the differential detection of 180 μm water droplets and 240 μm air bubbles; and the inductance parameter detection experiment realizes the differential detection of 80 μm iron particles and 150 μm copper particles in hydraulic oil, respectively. The study provides a new approach for the differential detection of multipollutants in hydraulic oil.

Abstract:In order to meet the requirements of thermal damage assessment of large equivalent warhead, improve the impact and ablation resistance of the traditional thin-skin calorimeter, a new type of heat sink cooling heat flux sensor is designed by adding heat sink to the rear surface of heat sensitive element. The incident heat flux can be indirectly obtained by measuring the rear surface temperature of heat sensitive element. In this paper, the model of sensor is established, the response time expression is derived, and the response characteristics of the sensor are simulated by numerical simulation. Simulation results show that: The response time of sensor is only related to the size and material of heat sensitive element, and not related to the heat sink. The response time of sensor which designed with the copper heat sensitive element is about 1.1ms; Greater the endothermic coefficient of heat sink is, smaller the temperature rise of heat sensitive element becomes. At the same time, the temperature rise rate decreases gradually with the increase of time. Validation experiment shows that the addition of heat sink can effectively reduce the temperature rise of heat sensitive element, and the sensor can correctly reflect the change of incident heat flux.

Abstract:The bias magnetic field is related to the coupling efficiency of magnetostrictive effect and its inverse effect sensors. In order to meet the need for longitudinal mode magnetostrictive guided wave inspection, a method was proposed to evaluate the bias magnetic field produced by permanent magnets. Firstly, from the point of energy conversion in magnetostrictive guided wave defection process, the connection between the bias magnetic field and amplitude of guided wave signal is obtained. Secondly, a method was proposed to estimate bias magnetic field considering the uneven distribution of the magnetic field and the principle of magnetostrictive effect and its inverse effect. Thirdly, a finite element model is built and experiments are carried out to confirm the feasibility of the characterization of bias magnetic field. At last, a verification experiment was conducted to confirm the effectiveness of method. This method takes advantages of the values of magnetic field intensity along the circumferential direction on the pipe outer surface to characterize the bias magnetic field, using the relationship lines between signal amplitude and bias magnetic field. As a consequence, this method can be used to estimate the bias magnetic field for improving the efficiency of magnetostrictive longitudinal guided wave testing and provide a basis for the future study of intelligent instrument.

Abstract:A parallel permanent magnetic suspension system is proposed, which is composes of a servo motor, a radial magnetized disk permanent magnet, an F shape magnetizer and suspending objects. In the system, the parallel suspending objects are two iron balls with different weights placed right under the magnetizer, the disk permanent magnet is driven by a servo motor and rotates. By changing the effective magnetic flux flowing through the suspended objects, the suspension force is controlled and the stable suspension of the two iron balls is realized. The system model is simplified based on the system structure and the parallel permanent magnetic suspension principle of the controllable flux path, and the mathematic model of the system is built, the stable suspension feasibility of the system is analyzed and the feedback gain range of the PD controller that makes the system stable suspending is analyzed. The experiment results indicate that when the PD control parameters meet the calculated range, the system can response to a small step disturbance quickly with realtime control and reach to new stable suspension state in a short response tine; the same disturbance causes the displacement responses of two iron balls in different directions, the displacement direction of the left ball is the same as that of the disturbance and the right one is inverse to that of the disturbance.

Abstract:A nonlinear model of electromechanical governed system with multiple uncertain parameters and disturbances is established, and a backstepping nonlinear adaptive L2gain speed control (L2NASC) method with additional control variables and selfmodified parameters is proposed. By adopting KClass functions and additional control variables, the stable speed of the electromechanical governed system can be improved, and the γdissipation inequality can be disregarded in virtual function design. Comparing with the traditional speed control method, the backstepping L2NASC simulation results show that the response speed of the operating components, i.e., as control sleeve, etc., can be increased, the overshoot of the control output can be decreased and the stability of the speed control system can be enhanced.

Abstract:The flow filed in the jet pipe and receivers is very complicated, especially in the dynamic situation, back flow and vortex etc. exist . Based on the model of a certain jet pipe servo valve, the movement equation of valve is obtained by combining force equilibrium of spool. Applying Reynolds averaged NavierStokes equations and the standard two equation model (liquid phase), a visual simulation model of the jet pipe to receivers of jet pipe servo valve is established through fluid dynamic software FLUENT. The fluid field and transient response of the prestage are simulated and analyzed which is from jet pipe to receivers. Simulation results demonstrate that the intensity of vorticity has effects on step response of jet pipe sevo valve. The greater vorticity intensity results in the greater oscillation and the slower step response. The 45 degree is the best design of the angle between two receivers by comparing different angles between two receivers. This work has important reference value for improving dynamic response of jet pipe servo valve.

Abstract:Nowadays still widely used manual filling control approach to the small-doses and high-speed liquid medicine filling system with high filling accuracy requirement is difficult to reduce filling errors due to dynamic behavior time-varying of the high-speed filling system (HSFS). In order to improve the filling control accuracy of the HSFS, this paper designs an intelligent filling controller (IC) based on the model of the HSFS. On the basis of the IC, for solving the problem caused by filling behavior nonlinearity, this paper proposes an adaptive intelligent filling control method, in which a locally linear model of the HSFS is built online by the least squares method (LSM), the sensitivity of the filling system is analyzed online based on the model, and an adaptive controller is designed to overcome the influence of dynamics time-varying and nonlinearity of the HSFS. Real-time filling control experiments are carried out using manual control, the intelligent control and the adaptive control methods, respectively. The results show that the adaptive control performance is the best compared to other two control approaches, both the intelligent controller and adaptive controller can cope with the behavior time-varying of the HSFS very well, and the adaptive controller has the ability to overcome the influence of nonlinearity of the HSFS.

Abstract:For light-weight unmanned surface vessel(USV), the observability of course is low when sailing at low speed(7 knots). In terrible ocean environment and strong surge, It is difficult to meet the measuring accuracy requirement because the compass is not stable. In order to realize the smoothing filtering of course angle of the USV, the article estimate the process noise of course angle effectively according to the system control frequency and the boat body movement performance. We use an α-β filter to smoothing the course of USV based on the estimated process noise. In order to eliminating the boundary dis-continuous of course angle which will cause singular value when using α-β filter, we proposed a boundary filtering strategy to realize the full range smooth filtering for the course angle. Real-time data playback verified the effectiveness of the method on the navigation control for the USV.

Abstract:In order to improve the efficiency of obstacle avoidance of unmanned surface vehicles(USV), this paper presents a avoidance algorithm for unmanned surface vehicles USV to navigate safely in dynamic, cluttered environments. In the existing path planning algorithms, most of them take avoidance measures by making circular modelings to obstacles. Based on the actual collision problem of USV in the marine environment, this paper proposed elliptical clustering method of dynamic vessels to improve the obstacle avoidance efficiency. Furthermore, our algorithm also applies the International Regulations for Preventing Collisions at Sea (known as COLREGS, for collision regulations), and USV return the specified routes after the obstacle avoidance. Finally, we shown simulation analysis and experimental testing of avoidance algorithm.

Abstract:Space-Time Image Velocimetry (STIV) is a time-averaged velocity measurement method. It takes a testing line as the Interrogation Area (IA), and detects the texture orientation of a generated Space-Time Image to estimate the 1D velocity. STIV has great potential in real-time monitoring of river flow owe to its high spatial resolution and low time complexity. However, its practicality is still limited by the deficiencies of sensitivity analysis and uncertainty evaluation due to the complexity of field conditions and the variability of river flow. To handle this problem, a rolling painting device is designed to simulate the movement of river surface flow, and the quantitative evaluation of a DFT-STIV method is comprehensively conducted. Compared to the evaluations based on numerical simulation and field measuring, it provides relatively real measuring environment and stable motion parameters. Experiment results show that the length of testing line and the tracing condition are main sensitive factors of velocity measurement. With reasonable parameter settings, the uncertainty of STIV can be controlled within ±1%, which meets the accuracy requirement of hydrometry.

Abstract:The traditional random walks based image segmentation algorithm requires setting seed points interactively to obtain the desired segmentation results. Based on visual attention, the paper proposes a new random walks based image segmentation algorithm with the seed points determined automatically. Firstly, the probability boundary map (PBM) is generated and the image is divided into super pixels. Then, the key segmentation region is searched by shifting visual attention focus with Itti model. In order to determine the seed points of the key segmentation region, the probabilistic boundary map is transformed into polar coordinates map taking the current focus of attention as the pole. The energy function about the boundary of the focal region is established on the obtained polar coordinate probabilistic boundary map. The energy function can be minimized by the maxflow mincut algorithm, and the super pixels within the boundary of focal region are the seed points of segmentation region. Finally, super pixels of images are used as nodes to construct a graph, random walks algorithm is conducted on the graph to complete the image segmentation. The experiments on Berkeley Segmentation Data Set show that the proposed method is effective to complex images’ segmentation.

Abstract:In order to address the issues that the performance of instrument identification system in intelligent patrol robot is affected by the varying illumination, and has the low identification accuracy, instrument identification system with high accuracy is built according to the characteristics of pointer instrument image from high voltage electronic field. In view of the outdoor work environment of patrol robot, iterative Otsu algorithm is proposed in the paper, which can achieve the extraction of pointer area in instrument image under all kinds of illuminations. After the analysis of pointer rotation mechanism and image characteristic, pointer angle recognition algorithm based on Hough transform is proposed in the paper, the function between pointer angle and reading is deduced. Compared with the traditional pointer angle extraction algorithm based on Hough transform, the constraint condition of pointer center line through the center is added in the algorithm, which can increase the accuracy of angle extraction, and reduce the amount of search data and time. The proposed instrument identification system in the paper can achieve more than 95% of the correct recognition rate under all kinds of outdoor illumination. Experiments show that the system proposed in the paper is robust to illumination condition, pointer width, dial interference, imaging angle without the shadow of pointer. However, when the shadow of pointer is generated due to imaging angle, the extraction of central line and the calculation of angle are biased, then the accuracy of reading recognition is reduced.

Abstract:In order to improve the adaptive ability and segmentation accuracy of video object segmentation algorithm in various complex scenes, an object segmentation algorithm based on motion saliency map and optical flow vector analysis is proposed in this paper. Firstly, the proposed algorithm extracts the rough target region based on motion saliency map. Then, the motion boundaries of the motion object and background region are determined based on the optical flow vector between pairs of subsequent frames. The above information is combined to acquire the accurate pixels inside the moving objects with the pointinpolygon principle from the computational geometry. Finally, to refine the spatial accuracy of object segmentation in the previous step, per frame superpixels are acquired with oversegmenting method. And these superpixels are labeled as foreground or background based on confidence level and statistical model. The proposed algorithm was compared with typical algorithms in different scenes, and the results indicate that the proposed algorithm can effectively deal with the moving object segmentation on a variety of challenging scenes, and has higher segmentation accuracy than other existing algorithms.

Abstract:In the cyberphysical environment, the loss of packet with clock information will have an impact on clock synchronization performance during clock synchronization bidirectional information exchange process. This paper discusses the output feedback model predictive control based on tubes (TubesMPC) clock synchronization method based on the state space model of modern control theory. Based on the principle of separation, the localized state estimator and controller are designed. And the exponential stability of the output feedback TubesMPC clock synchronization is realized. Based on the observation model under incomplete measurement, the upper bound and lower bound of the variance of synchronization error in statistical meaning are analyzed quantitatively, and using the SetTheoryinControl method in MPC, the interference error set under complete measurement is intersected with the set of additional estimation errors introduced by packet loss. The optimization model of model prediction under set constraints is established. The constructed output feedback TubesMPC clock synchronization systematic method in a unified framework comprehensively considers the application feasibility of control theory online computational complexity and network control perspective, has robustness to the unreliability, network size and convergence performance of wireless network, and can be easily extended to the network level absolute clock state space model.

Abstract:Clock difference prediction is a key technology of time keeping work. Kalman algorithm as a kind of optimal prediction algorithm, has the characteristics of real-time, widely used in time keeping work. The classical Kalman algorithm needs to accurately know the random error of the model and measurement error, otherwise, the state estimate will bring error, which is characterized by atomic clocks noise and clock difference measure noise in the atomic time algorithm. Noise parameters of atomic clock is usually estimated through Allan variance, if estimate is not accurate, Kalman filter prediction error will appear. In this paper, the adaptive Kalman filtering prediction algorithm based on window of Sage was researched, the state model error was corrected real-time. The model error was reduced by adjusting the state prediction covariance matrix using adaptive factor, which improved the prediction accuracy. Finally, the effectiveness of the algorithm was verified by the measured data of two hydrogen atomic clocks and two cesium atomic clocks.

Abstract:In order to weaken the strength of turbulence and also reduce its effect on accuracy of the ultrasonic transducer signal acquisition,factors influencing the flow field of the transducer array are analyzed in this paper and design a new transducers array.This new array consist of six transceiver integrated ultrasonic transducers and three independent paths .According to the different flow direction, wind speed calculation model was established, combining the working characteristics of transducer chip so as to optimize the design of wind array and reduce the effect of shadows.Several typical arrays are selected to compare and analyze the flow field distribution features in the array by changing Reynolds number, wind speed and direction through the FLUENT software.With the analysis of the contour maps and speed curves,the datum of wind measuring paths in this new array meet the requirements of precision.