船舶全局一致渐进路径跟踪变积分增益导航策略

本文利用一种新的导航策略和反馈控制器解决了欠驱动船舶受到外部扰动作用下的保持直线运动问题.与传统的视野线(line-of-sight,LOS)导航策略相比,改进的LOS导航策略具有变积分增益能够补偿外部环境扰动引起的侧滑效应并且能够避免积分饱和影响,其中积分增益是以垂直距离误差为函数引导船舶灵活快速地趋向期望的轨迹.本文所提出的积分导航策略和基于积分器反演控制策略组成一种串联结构的系统,并且证明了当所有控制目标实现时整个系统是全局一致渐进稳定的.仿真结果说明了所提出内容的有效性和性能.     

Weighted minimal hypersurface reconstruction

Many problems in computer vision can be formulated as a minimization problem for an energy functional. If this functional is given as an integral of a scalar-valued weight function over an unknown hypersurface, then the sought-after minimal surface can be determined as a solution of the functional's Euler-Lagrange equation. This paper deals with a general class of weight functions that may depend on surface point coordinates as well as surface orientation. We derive the Euler-Lagrange equation in arbitrary dimensional space without the need for any surface parameterization, generalizing existing proofs. Our work opens up the possibility of solving problems involving minimal hypersurfaces in a dimension higher than three, which were previously impossible to solve in practice. We also introduce two applications of our new framework: We show how to reconstruct temporally coherent geometry from multiple video streams, and we use the same framework for the volumetric reconstruction of refractive and transparent natural phenomena, bodies of flowing water.     

Microsoft C#.NET program and electromagnetic depth sounding for large loop source

A program, in the C# (C Sharp) language with Microsoft.NET Framework, is developed to compute the normalized vertical magnetic field of a horizontal rectangular loop source placed on the surface of an n-layered earth. The field can be calculated either inside or outside the loop. Five C# classes with member functions in each class are, designed to compute the kernel, Hankel transform integral, coefficients for cubic spline interpolation between computed values and the normalized vertical magnetic field. The program computes the vertical magnetic field in the frequency domain using the integral expressions evaluated by a combination of straightforward numerical integration and the digital filter technique. The code utilizes different object-oriented programming (OOP) features. It finally computes the amplitude and phase of the normalized vertical magnetic field. The computed results are presented for geometric and parametric soundings. The code is developed in Microsoft.NET visual studio 2003 and uses various system class libraries.     

Characterization of influence zones of simulated droughts and floods of water bodies in a floodplain

During flooding processes, randomly situated water bodies of varying sizes and shapes in a floodplain tend to self-organize. At high degrees of flooding intensity, water bodies contact together to form influence zones, which indicate the self-organized criticality of the flooding of water bodies. The characterization of water bodies and their influence zones provides useful insight into the geomorphic properties of floodplain terrains. In this paper, characterization of the influence zones of simulated droughts and floods of water bodies in a floodplain is performed. First, drought and flood simulations are implemented by performing morphological erosion and dilation, respectively, on water bodies using square kernels of increasing sizes. The level of droughting/flooding is indicated by the kernel size. The average areas of the influence zones of the generated simulated droughts and floods of water bodies are computed. It is observed that as the droughting level increases from 1 to 5, the average area of the influence zones of water bodies reduces due to the shrinking of water bodies. As the droughting level increases from 5 to 15, the average area of the influence zones of water bodies increases due the vanishing of small water bodies. Flooding causes an increase in the average area of the influence zones of water bodies due to the merging of adjacent water bodies. A power law relationship is observed between the average area of the influence zones of the simulated droughts/floods and the level of droughting/flooding. The scaling exponent of this power law, which is named as a fractal dimension, indicates the rate of change of average area of the influence zones of simulated droughts/floods of water bodies in a floodplain over varying levels of droughting/flooding.     

Control of a heavy-duty robotic excavator using time delay control with integral sliding surface

The control of a robotic excavator is difficult from the standpoint of the following problems: parameter variations in mechanical structures, various nonlinearities in hydraulic actuators and disturbance due to the contact with the ground. In addition, the more the size of robotic excavators increase, the more the length and mass of excavator's links; the more the parameters of a heavy-duty excavator vary. A time-delay control with switching action (TDCSA) using an integral sliding surface is proposed in this paper for the control of a 21-ton robotic excavator. Through analysis and experiments, we show that using an integral sliding surface for the switching action of TDCSA is better than using a PD-type sliding surface. The proposed controller is applied to straight-line motions of a 21-ton robotic excavator with a speed level at which skillful operators work. Experiments, which were designed for surfaces with various inclinations and over broad ranges of joint motions, show that the proposed controller exhibits good performance.     

ADAMANT: A surface and volume integral-equation solver for the analysis and design of helicon plasma sources

We present a full-wave numerical tool, dubbed ADAMANT (Advanced coDe for Anisotropic Media and ANTennas), devised for the analysis and design of radiofrequency antennas which drive the discharge in helicon plasma sources. ADAMANT relies on a set of coupled surface and volume integral equations in which the unknowns are the surface electric current density on the antenna conductors and the volume polarization current within the plasma. The latter can be inhomogeneous and anisotropic whereas the antenna can have arbitrary shape. The set of integral equations is solved numerically through the Method of Moments with sub-sectional surface and volume vector basis functions. This approach allows the accurate evaluation of the current distribution on the antenna and in the plasma as well as the antenna input impedance, a parameter crucial for the design of the feeding and matching network. We report several numerical examples which serve to validate ADAMANT against other well-established numerical approaches as well as experimental data. The numerical accuracy of the computed solution versus the number of basis functions in the plasma is also assessed. Finally, we employ ADAMANT to characterize the antenna of a real-life helicon plasma source.     

Computation of transfer function data from frequency response data with application to data-based root-locus

This paper describes the computation and use of transfer function data (TFD) computed from frequency response data of a system. TFD can be regarded as a sampled, data-based representation of the transfer function. TFD can be computed from frequency response data for stable, lightly damped systems using a Cauchy integral. Computational accuracy and complexity are extensively discussed. As a use-case of TFD it is shown that a root-locus can be computed in a data-based way, using only frequency response data of a system. Experiments on a benchmark motion system demonstrate the use of TFD in minimizing the settling time.     

Image-Space Decomposition Algorithms for Sort-First Parallel Volume Rendering of Unstructured Grids

Twelve adaptive image-space decomposition algorithms are presented for sort-first parallel direct volume rendering (DVR) of unstructured grids on distributed-memory architectures. The algorithms are presented under a novel taxonomy based on the dimension of the screen decomposition, the dimension of the workload arrays used in the decomposition, and the scheme used for workload-array creation and querying the workload of a region. For the 2D decomposition schemes using 2D workload arrays, a novel scheme is proposed to query the exact number of screen-space bounding boxes of the primitives in a screen region in constant time. A probe-based chains-on-chains partitioning algorithm is exploited for load balancing in optimal 1D decomposition and iterative 2D rectilinear decomposition (RD). A new probe-based optimal 2D jagged decomposition (OJD) is proposed which is much faster than the dynamic-programming based OJD scheme proposed in the literature. The summed-area table is successfully exploited to query the workload of a rectangular region in constant time in both OJD and RD schemes for the subdivision of general 2D workload arrays. Two orthogonal recursive bisection (ORB) variants are adapted to relax the straight-line division restriction in conventional ORB through using the medians-of-medians approach on regular mesh and quadtree superimposed on the screen. Two approaches based on the Hilbert space-filling curve and graph-partitioning are also proposed. An efficient primitive classification scheme is proposed for redistribution in 1D, and 2D rectilinear and jagged decompositions. The performance comparison of the decomposition algorithms is modeled by establishing appropriate quality measures for load-balancing, amount of primitive replication and parallel execution time. The experimental results on a Parsytec CC system using a set of benchmark volumetric datasets verify the validity of the proposed performance models. The performance evaluation of the decomposition algorithms is also carried out through the sort-first parallelization of an efficient DVR algorithm.     

纵向速度和艏向角受限的水面艇有限时间协同路径跟踪

研究多个欠驱动水面艇在纵向速度和艏向角受限情况下的协同有限时间直线路径跟踪问题.针对水面艇在位置和速度方向上受到的干扰,考虑欠驱动水面艇同时受到匹配和不匹配扰动的情况,通过在控制方案中引入积分视线制导律和有限时间观测器来估计并补偿两类扰动.设计非对称障碍Lyapunov函数来保证欠驱动水面艇在航行过程中不违反约束条件,...     

Parameter reduction and automata evaluation for grammar-compressed trees

Trees can be conveniently compressed with linear straight-line context-free tree grammars. Such grammars generalize straight-line context-free string grammars which are widely used in the development of algorithms that execute directly on compressed structures (without prior decompression). It is shown that every linear straight-line context-free tree grammar can be transformed in polynomial time into a monadic (and linear) one. A tree grammar is monadic if each nonterminal uses at most one context parameter. Based on this result, polynomial time algorithms are presented for testing whether a given (i) nondeterministic tree automaton or (ii) nondeterministic tree automaton with sibling-constraints or (iii) nondeterministic tree walking automaton, accepts a tree represented by a linear straight-line context-free tree grammar. It is also shown that if tree grammars are nondeterministic or non-linear, then reducing their numbers of parameters cannot be done without an exponential blow-up in grammar size.     

Highly robust position control of BLDDSM using an improved integral variable structure systems

A highly robust position controller for brushless direct drive servo motors (BLDDSM) is presented using a new improved variable structure system with an integral-augmented sliding surface. With the proposed technique, the reaching phase is completely removed by the integral sliding surface. The dynamics of its ideal sliding mode is analytically obtained from a given initial condition to the origin without any reaching phase. In order to choose a suitable integral sliding surface, the optimal regulator theory is effectively applied. Moreover, the suggested control technique can exhibit the output response identical to that previously designed in the integral sliding surface for all the load variations and parameter uncertainties. The usefulness of the proposed algorithm is illustrated through the comparative experiment studies on the position controls of BLDDSM under load variations.     

Fast marching subjected to a vector field–path planning method for mars rovers

Path planning is an essential tool for the robots that explore the surface of Mars or other celestial bodies such as dwarf planets, asteroids, or moons. These vehicles require expert and intelligent systems to adopt the best decisions in order to survive in a hostile environment. The planning module has to take into account multiple factors such as the obstacles, the slope of the terrain, the surface roughness, the type of ground (presence of sand), or the information uncertainty. This paper presents a path planning system for rovers based on an improved version of the Fast Marching (FM) method. Scalar and vectorial properties are considered when computing the potential field which is the basis of the proposed technique. Each position in the map of the environment has a cost value (potential) that is used to include different types of variables. The scalar properties can be introduced in a component of the cost function that can represent characteristics such as difficulty, slowness, viscosity, refraction index, or incertitude. The cost value can be computed in different ways depending on the information extracted from the surface and the sensor data of the rover. In this paper, the surface roughness, the slope of the terrain, and the changes in height have been chosen according to the available information. When the robot is navigating sandy terrain with a certain slope, there is a landslide that has to be considered and corrected in the path calculation. This landslide is similar to a lateral current or vector field in the direction of the negative gradient of the surface. Our technique is able to compensate this vector field by introducing the influence of this variable in the cost function. Because of this modification, the new method has been called Fast Marching (subjected to a) vector field (FMVF). Different experiments have been carried out in simulated and real maps to test the method performance. The proposed approach has been validated for multiple combinations of the cost function parameters.     

Synoptic mapping of internal-wave motions and surface currents near the Lombok Strait using the Along-Track Stereo Sun Glitter technique

A multi-component satellite remote sensing program is required to track the response of the world's oceans, lakes and rivers to climate change. Central to this endeavor is the ability to detect the motions of internal waves, swell waves and currents and hence follow energy transport and exchange. However, the present methods of monitoring the motions of water bodies from space, such as those based on altimetry or gravity measurements, are geared mostly toward applications on large spatial scales, whereas the capacity to map the fine details of hydrospheric flows is limited. This paper describes a satellite-based method of detecting wave motion and surface currents at high (in principle metric) resolution that can be applied under specific circumstances in the confined environs of narrow sea straits, lakes and rivers and that compliments the use of other high-spatial resolution techniques such as those based on Synthetic Aperture Radar (SAR). The Along-Track Stereo Sun Glitter (ATSSG) technique makes use of images of water bodies that are separated in time by roughly 1 min and are gathered in the forward-, nadir- and backward-looking directions by space-borne optical sensors performing along-track observations. When sensor viewing geometries lead to the presence of Sun glitter in these images, surface slicks, internal waves, swell waves and other phenomena become highlighted through the surface roughness changes they induce, since these in turn modulate the reflected glitter radiance. Measurement of the differential displacements between congruent sections of the surface roughness signatures present within image pairs of the stereoscopic sequence then enables internal wave or swell wave motions to be determined, while surface currents can be deduced if “passive” tracers of the flow in the form of surface roughness structures (such as slicks) are present. The application of the ATSSG technique described herein makes use of data acquired at a spatial resolution of 2.5 m by the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) to provide the first along-track fine-scale synoptic mapping of the surface motions of individual components within a large group of internal waves and to generate supporting surface-current measurements. The PRISM data we employ were acquired to the south of the Lombok Strait (Indonesia), where highly energetic internal-wave growth takes place and where through-flow surface-current data, of the type derived by the ATSSG technique, can be of value in climate studies.     

Environmental factors and the detection of open surface water areas with X-band radar imagery

The ability to map open surface water is integral to many hydrologic and agricultural models, wildlife management programmes, and recreational and natural resource studies. Open surface water is generally regarded as easily detected on radar imagery. However, this view is an oversimplification. This study used X-band HH polarized airborne Synthetic Aperture Radar ( SAR) imagery to examine the potential of SAR data to map open fresh water areas extant on 1:100000 USGS topographic maps. Seven study sites in the U.S.A. with a combined area of over 68000km²were analysed. Detection accuracies and minimum size for detection varied among the seven locations. Size and shape of water bodies and radar shadow all affected detection. However, environmental modulation factors including vegetation and forest cover, moisture, and landscape composition and morphology had the greatest influence and exhibited the most complex role in explaining variability     

The optimal control problem on SO(4) and its applications toquantum control

We consider the problem of steering control via an input electro-magnetic field for a system of two interacting spin 1/2 particles. This model is of interest in applications because it is used to perform logic operations in quantum computing that involve two quantum bits. The describing model is a bilinear system whose state varies on the Lie group of special unitary matrices of dimension 4, SU(4). By using decompositions of the latter Lie group, the problem can be decomposed into a number of subproblems for a system whose state varies on the (smaller) Lie group of 4×4 proper orthogonal matrices, SO(4). We tackle the time optimal control problem for this system and show that the extremals can be computed explicitly and they are the superposition of a constant field and a sinusoidal one     

Improved solution for potential flow about arbitrary axisymmetric bodies by the use of a higher-order surface source method

In recent years the surface-source method of calculating potential flow about arbitrary bodies has been developed extensively and has proved to be a useful tool in a wide variety of low-speed design applications ranging from simple shapes to complicated inlets with centerbodies, multi-element airfoils, and wing-fuselage-pylon-nacelle combinations. Two-dimensional, axisymmetric, and three-dimensional methods have been developed. While the method is generally quite satisfactory, it is desirable to increase computational speed and accuracy for certain applications, particularly interior flows and exterior flows about complicated multiple-body combinations. Such improvements can be realized by refining the formulation. In the basic method the profile curve of a two-dimensional or axisymmetric body is approximated by a large number of straight-line elements over each of which the source density is constant. The so-called higher-order refinement consists of using curved surface elements and a source density that varies over an element. This paper describes the analysis for the axisymmetric case and presents a number of test cases to show the large increases of speed and accuracy that can be obtained with the higher-order formulation.     

Design of the PID Controller for Hydro-turbines Based on Optimization Algorithms

In this study, multiple objective particle swarm optimization (MOPSO), genetic algorithm, bees, and reinforcement learning (RL) are used to calculate the rise time (tr), integral square-error, integral of time-multiplied-squared-error, integral absolute error, and integral of time multiplied by absolute error of the system transfer function and then we use a fuzzy algorithm on MOPSO, GA, bees, and RL based on the frequency sensitivity margin of a water turbine governor to optimize the proportional gain (kp) and integral gain (ki) and calculate the relative collapsing frequency response values. The MOPSO algorithm returned the optimal result. The radial basis function (RBF) neural network curve is obtained from the MOPSO algorithm with three variables (i.e., kp, ki, kd = 0.6 and grid frequency deviations values), and finally we identify and predict three variable values near the RBF neural network curve through deep learning. The result of the grid frequency deviation is close to 0, and the gain response time is better for damping the frequency oscillations in different operating conditions.

     

Multispectral landuse classification using neural networks and support vector machines: one or the other,or both?

Land use classification is an important part of many remote sensing applications. A lot of research has gone into the application of statistical and neural network classifiers to remote‐sensing images. This research involves the study and implementation of a new pattern recognition technique introduced within the framework of statistical learning theory called Support Vector Machines (SVMs), and its application to remote‐sensing image classification. Standard classifiers such as Artificial Neural Network (ANN) need a number of training samples that exponentially increase with the dimension of the input feature space. With a limited number of training samples, the classification rate thus decreases as the dimensionality increases. SVMs are independent of the dimensionality of feature space as the main idea behind this classification technique is to separate the classes with a surface that maximizes the margin between them, using boundary pixels to create the decision surface. Results from SVMs are compared with traditional Maximum Likelihood Classification (MLC) and an ANN classifier. The findings suggest that the ANN and SVM classifiers perform better than the traditional MLC. The SVM and the ANN show comparable results. However, accuracy is dependent on factors such as the number of hidden nodes (in the case of ANN) and kernel parameters (in the case of SVM). The training time taken by the SVM is several magnitudes less.     

Input impedance of microstrip-slot-coupled dielectric resonator antennas mounted on thin dielectric layers

An efficient numerical technique based upon a surface integral equation formulation for the coupling of bodies of revolution (BORs) to non-BOR geometries for the design of practical microstrip-slot-aperture-coupled dielectric resonator antennas is presented. The moment method matrix fill time and memory requirements are significantly reduced by utilizing Fourier mode basis functions on the BOR together with the spectral domain Green's function for the printed circuit board. Two practical antennas are designed and fabricated. Antenna input impedances predicted by this technique are in good agreement with those of the actual devices. © 1996 John Wiley & Sons, Inc.