Wyniki wyszukiwania - BazTech

1

Heading control system design for a micro-USV based on an adaptive expert S-PID algorithm

Miao R., Dong Z., Wan L., Zeng J.

Polish Maritime Research

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2018

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nr 2

6--13

EN

The process of heading control system design for a kind of micro-unmanned surface vessel (micro-USV) is addressed in this paper and a novel adaptive expert S-PID algorithm is proposed. First, a motion control system for the micro-USV is designed based on STM32-ARM and the PC monitoring system is developed based on Labwindows/CVI. Second, by combining the expert control technology, S plane and PID control algorithms, an adaptive expert S-PID control algorithm is proposed for heading control of the micro-USV. Third, based on SL micro-USV developed in this paper, a large number of pool experiments and lake experiments are carried out, to verify the effectiveness and reliability of the motion control system designed and the heading control algorithm proposed. A great amount of comparative experiment results shows the superiority of the proposed adaptive expert S-PID algorithm in terms of heading control of the SL micro-USV.

2

Error mitigation algorithm based on bidirectional fitting method for collision avoidance of Unmanned Surface Vehicle

Song L., Chen Z., Mao Y., Dong Z., Xiang Z.

Polish Maritime Research

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2018

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nr 4

13--20

EN

Radars and sensors are essential devices for an Unmanned Surface Vehicle (USV) to detect obstacles. Their precision has improved significantly in recent years with relatively accurate capability to locate obstacles. However, small detection errors in the estimation and prediction of trajectories of obstacles may cause serious problems in accuracy, thereby damaging the judgment of USV and affecting the effectiveness of collision avoidance. In this study, the effect of radar errors on the prediction accuracy of obstacle position is studied on the basis of the autoregressive prediction model. The cause of radar error is also analyzed. Subsequently, a bidirectional adaptive filtering algorithm based on polynomial fitting and particle swarm optimization is proposed to eliminate the observed errors in vertical and abscissa coordinates. Then, simulations of obstacle tracking and prediction are carried out, and the results show the validity of the algorithm. Finally, the method is used to simulate the collision avoidance of USV, and the results show the validity and reliability of the algorithm.

3

3-D Simulation of Double-Bar Plush Fabrics with Jacquard Patterns

Zhang A., Li X., Jiang G., Dong Z., Cong H.

Autex Research Journal

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2018

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Vol. 18, no. 3

243--250

EN

A realistic computerized simulation of double-bar plush fabrics can result in a time-saving development process with high quality. Based on basic analysis of jacquard principles, a fast 3-D simulation method of warp-knitted plush fabrics is proposed by using a geometry shader on GPU. Firstly, pile areas and non-pile areas are identified according to the jacquard design graphs and chain notations. According to the directions of observation and raised pile, two layered chips are formed in the geometry shader with an approach of multi-layered textures. To ensure that the simulated piles resemble the real ones, the directions of the piles are randomized with the Perlin noise method. One pile is generated along its length with numerous layers in the plush fabric model. Simulation results of piles on both the technical face and technical back are obtained via the model built above, which is confirmed with practicability and efficiency. This 3D simulation approach improves the visualization appearance of piles just as they are actually raised.

4

Path following control of the underactuated USV based on the improved line-of-sight guidance algorithm

Liu T., Dong Z., Du H., Song L., Mao Y.

Polish Maritime Research

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2017

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nr 1

3--11

EN

The path following control problem of the underactuated unmanned surface vessel (USV) is studied in this paper. An improved line-of-sight (LOS) guidance algorithm is proposed which can adjust adaptively based on the path following error. The global asymptotically stable path following controller is designed based on the nonlinear backstepping method and the Lyapunov stability theory. Firstly, the USV path following error model is established in the Serret-Frenet (SF) coordinate frame. The path following error in the inertial coordinate frame is transformed into the SF coordinate frame, which is used to define the path following control problem. Secondly, inspired by the traditional LOS guidance algorithm, the longitudinal path following error in the SF coordinate frame is introduced into the improved LOS guidance algorithm. This allows the algorithm to adjust adaptively to the desired path. Thirdly, in order to solve the underactuated problem of the USV path following control system, the tangential velocity of the desired path is designed as a virtual input. The underactuated problem is converted to a virtual fully actuated problem by designing the virtual control law for the tangential velocity. Finally, by combining backstepping design principles and the Lyapunov stability theory, the longitudinal thrust control law and the yaw torque control law are designed for the underactuated USV. Meanwhile, the global asymptotic stability of the path following error is proved. Simulation experiments demonstrate the effectiveness and reliability of the improved LOS guidance algorithm and the path following controller.

5

Texture Analysis Method Based on Fractional Fourier Entropy and Fitness-scaling Adaptive Genetic Algorithm for Detecting Left-sided and Right-sided Sensorineural Hearing Loss

Wang S., Yang M., Li J., Wu X., Wang H., Liu B., Dong Z., Zhang Y.

Fundamenta Informaticae

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2017

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Vol. 151, nr 1/4

505--521

EN

To detect the sensorineural hearing loss (SNHL) from healthy people accurately, we used magnetic resonance imaging (MRI) to obtain the imaging data, and then proposed a new computer-aided diagnosis (CAD) system, on the basis of texture analysis method. In the first, we extracted 12-element feature from each brain image via fractional Fourier entropy (FRFE). Afterwards, multilayer perceptron (MLP) was employed as the classifier, which was trained by a novel fitness-scaling adaptive genetic algorithm (FSAGA). The statistical analysis over 49 subjects showed the overall accuracy of our method yielded 95.51%. Experimental results performed better than four state-of-the-art weight optimization methods, and this CAD system give significantly better performance than manual interpretation.

6

Warp-knitted Fabric Defect Segmentation Based on the Shearlet Transform

Dong Z., Xia D., Ma P., Jiang G.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 5 (125)

87--94

EN

The Shearlet transform has been a burgeoning method applied in the area of image processing recently which, differing from the Wavelet transform, has excellent properties in processing singularities for multidimensional signals. Not only is it similar to the performance of the Curvelet transform, it also overcomes the disadvantage of the Curvelet transform with respect to discretization. In this paper, the Shearlet transform with segmented threshold de-nosing is proposed to segment a warp-knitted fabric defect. Firstly a warp-knitted fabric image of size 512*512 is filtered by the Laplacian Pyramid transform and decomposed into low frequency and high frequency coefficients. Secondly the high frequency coefficients are operated with a pseudo-polar grid and then convoluted by the window function. Thirdly the shearlet coefficients will be obtained through redefining the Cartesian coordinates from the pseudo-polar grid coordinates and de-noised by the segmented threshold method. Then the coefficients which have high energy are selected for reconstruction in an inverse way using the previous steps. Finally the iterative threshold method and object operation based on morphology are applied to segment out the defect profile. The experiment’s result states that the Shearlet transform shows excellent performance in segmenting a common warp-knitted fabric defect, indicating that the segment results can be applied for further defect automatic recognition.

PL

Transformacja Shearleta jest ostatnio dynamicznie rozwijającą się metodą stosowaną w dziedzinie przetwarzania obrazu, która różni się od transformaty Wavelet i ma doskonałe właściwości w przetwarzaniu sygnałów wielowymiarowych. Transformacja Shearleta ma prostszą implementację dyskretną, niż przekształcenie Curveleta w oparciu o rygorystyczne i proste ramy matematyczne. Może także dostarczyć bardziej elastycznego rozkładu na podstawie reprezentacji wieloskalowej i geometrycznej. Ostateczny wynik segmentacji uzyskano poprzez powtarzalną segmentację progową i operację morfologiczną. Wyniki wykazały, że segmentowy profil uszkodzeń jest dość wyraźny i porównywalny w porównaniu z pierwotnymi wadami dzianiny.

7

Natural Fibres From the Bark of Mulberry Branches for Textile Application

Dong Z., Ding Z., Zhang S., Zhang Y., Fan H., Yang Y.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 3 (123)

20--25

EN

Fibers with low gum content were extracted from the bark of mulberry branches by a combination of bacteria and peroxide treatments. The bark of mulberry branches, with 30% cellulose, is a copious and inexpensive source of natural fibers. However, fibers extracted by microwave, enzyme or alkali had a high gum content (15.5% for hemicellulose and 8.6% for lignin), which rendered them difficult to be made into high- value textiles. In this research, strains with high polygalacturonase activities and subsequent hydrogen peroxide decreased the hemicellulose content to 2.5% and lignin content to 2.4%. Mulberry fibers in our study could be spun into yarns with a fineness of 18.2 tex. Compared to flax yarns, mulberry fiber yarns had a tenacity 20% higher, an elongation 18% higher and an unevenness 30% lower. Cotton/mulberry fiber fabrics had softer and smoother hand than cotton/flax fabrics. Overall, the fibers in our study show better potential for industrial textile applications than those in previous studies.

PL

Kora gałęzi morwy jest bogatym i niedrogim źródłem włókien naturalnych. W pracy przedstawiono proces otrzymywania włókien z kory morwy z wykorzystaniem szczepów bakteryjnych oraz nadtlenku wodoru, co zmniejszyło zawartość hemicelulozy do 2,5% i zawartości ligniny do 2,4%. W porównaniu do przędz lnianych, przędze z włókien morwy wykazywały o 20% wyższą wytrzymałość, o 18% wyższe wydłużenie i o 30% niższą nierównomierność. Tkaniny bawełniane z dodatkiem morwy miały bardziej miękki i gładszy chwyt, niż tkaniny bawełniane z dodatkiem lnu. Stwierdzono, że metoda pozyskiwania włókien z kory morwy przy zastosowaniu bakterii i nadtlenku wodoru może być stosowana do wyodrębniania włókien morwowych w celu produkcji wyrobów o wysokiej wartości i szerokim spektrum możliwości zastosowań przemysłowych.

8

Flat Knitting Loop Deformation Simulation Based on Interlacing Point Model

Jiang G., Lu Z., Cong H., Zhang A., Dong Z., Jia D.

Autex Research Journal

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2017

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Vol. 17, no. 4

361--369

EN

In order to create realistic loop primitives suitable for the faster CAD of the flat-knitted fabric, we have performed research on the model of the loop as well as the variation of the loop surface. This paper proposes an interlacing point-based model for the loop center curve, and uses the cubic Bezier curve to fit the central curve of the regular loop, elongated loop, transfer loop, and irregular deformed loop. In this way, a general model for the central curve of the deformed loop is obtained. The obtained model is then utilized to perform texture mapping, texture interpolation, and brightness processing, simulating a clearly structured and lifelike deformed loop. The computer program LOOP is developed by using the algorithm. The deformed loop is simulated with different yarns, and the deformed loop is applied to design of a cable stitch, demonstrating feasibility of the proposed algorithm. This paper provides a loop primitive simulation method characterized by lifelikeness, yarn material variability, and deformation flexibility, and facilitates the loop-based fast computer-aided design (CAD) of the knitted fabric.

9

Analysis Of Factors Affecting Gravity-Induced Deflection For Large And Thin Wafers In Flatness Measurement Using Three-Point-Support Method

Liu H., Dong Z., Kang R., Zhou P., Gao S.

Metrology and Measurement Systems

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2015

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Vol. 22, nr 4

531--546

EN

Accurate flatness measurement of silicon wafers is affected greatly by the gravity-induced deflection (GID) of the wafers, especially for large and thin wafers. The three-point-support method is a preferred method for the measurement, in which the GID uniquely determined by the positions of the supports could be calculated and subtracted. The accurate calculation of GID is affected by the initial stress of the wafer and the positioning errors of the supports. In this paper, a finite element model (FEM) including the effect of initial stress was developed to calculate GID. The influence of the initial stress of the wafer on GID calculation was investigated and verified by experiment. A systematic study of the effects of positioning errors of the support ball and the wafer on GID calculation was conducted. The results showed that the effect of the initial stress could not be neglected for ground wafers. The wafer positioning error and the circumferential error of the support were the most influential factors while the effect of the vertical positioning error was negligible in GID calculation.

10

Model of line-of-sight ultraviolet propagation

Li B., Wang Hongbo, Mao Z., Dong Z., Zhang X.

Optica Applicata

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2014

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Vol. 44, nr 4

601--610

EN

The traditional line-of-sight ultraviolet model cannot serve better for link performance study for the reason that the scattering characteristic is often ignored in the modelling process. Therefore, a line-of-sight ultraviolet bipyramid model in combination with transceiver full beam angles and geometrical relationship of the transceiver field of view intersection is established. The theoretical rationality of the bipyramid model in comparison with a traditional line-of-sight model is demonstrated by the classically analytical model for line-of-sight scenario. Based on a bit error rate requirement of voice communication, the effects of transmitting power versus range for three line-of-sight ultraviolet communication modes are further analyzed.

11

Estimating the number of components in an OSL decay curve using the Bayesian Information Criterion

Peng J., Dong Z., Han F., Han Y., Dai X.

Geochronometria

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2014

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Vol. 41, no. 4

334--341

EN

The optically stimulated luminescence (OSL) decay curve is assumed to consist of a number of first-order exponential components. Improper estimation of the number of components leads to under-or over-fitting of the curve under consideration. Hence, correct estimation of the number of components is important to accurately analyze an OSL decay curve. In this study, we investigated the possibility of using the Bayesian Information Criterion to estimate the optimal number of components in an OSL decay curve. We tested the reliability of this method using several hundred measured decay curves and three simulation scenarios. Our results demonstrate that the quality of the identification can be influenced by several factors: the measurement time and the number of channels; the variability of the decay constants; and the signal-to-noise ratios of a decaying component. The results also suggest that the Bayesian Information Criterion has great potential to estimate the number of components in an OSL decay curve with a moderate to high signal-to-noise ratio.