检索结果-内蒙古大学图书馆

Clothoids Composition Method for Smooth Path Generation of Car-Like Vehicle Navigation

JOURNAL OF INTELLIGENT & ROBOTIC SYSTEMS 2017年第1期88卷 129-146页

作者： Gim, Suhyeon Adouane, Lounis Lee, Sukhan Derutin, Jean-Pierre Sungkyunkwan Univ Seoburo 2066 Suwon 440746 South Korea Univ Clermont Auvergne Inst Pascal IMobS3 CNRS SIGMA F-63000 Clermont Ferrand France

This paper addresses a continuous curvature path generation problem for car-like vehicle navigation. The continuous curvature path is generated by multiple clothoids composition and parametric adjustment. According to the geometric conditions of the given initial and final configurations, the path generation problem is classified into two cases and then, each problem is solved by by appropriate proposed algorithm. The solution is obtained by iterative procedure subject to geometric constraint as well as solution constraints. For computational efficiency and fast convergence in the proposed algorithms, a minimax sharpness constraint is proposed as the solution constraint by minimizing the maximum sharpness of the feasible solutions. After the generation of the proposed path, the resultant curvature/sharpness diagram provides a useful information about its orientation and curvature continuity along the travel length. The proposed path planning strategy, permits us to obtain online, smooth and safe path between two defined configurations while ensuring high passengers comfort (continuous curvature and transition between the different composed clothoids). The algorithmic proposals have been applied to generate continuous curvature for two cases. The first correspond to local path planning for ensuring obstacle avoidance or lane change. The second application corresponds to global path smoothing. The resultant global path path is tested on the Lyapunov-based control scheme and showed improved performance on its steering work (reduction of 41.0% than the driving based on the raw data), which permits us therefore to validate the effectiveness of the obtained global path for car-like vehicles path following.

关键词： Continuous curvature path planning iterative algorithm Minimax sharpness constraint Nonholonomic car-like vehicle Curvature and sharpness diagram

来源：评论

学校读者我要写书评

暂无评论

Strong stabilisation by output feedback controller for linear systems with delayed input

引用

IET CONTROL THEORY AND APPLICATIONS 2012年第10期6卷 1329-1340页

作者： Du, B. Lam, J. Shu, Z. Nanjing Univ Sci & Technol Dept Automat Nanjing 210094 Jiangsu Peoples R China Univ Hong Kong Dept Mech Engn Hong Kong Hong Kong Peoples R China Univ Southampton Fac Engn & Environm Electromech Grp Southampton SO17 1BJ Hants England

This study addresses the strong stabilisation problem for continuous-time linear systems with an unknown input delay via dynamic output feedback controllers. A new criterion for dynamic output feedback stabilisability is proposed in terms of matrix inequalities with the separation of the controller gain with the Lyapunov matrix and the system matrices. Based on these new characterisations, an iterative algorithm is given to design the dynamic output feedback controllers with the initial values obtained by some proposed state feedback stabilisation methods. The effectiveness and merits of the proposed approach are shown through several examples.

关键词： dynamic output feedback controller dynamic output feedback stabilisability Lyapunov matrix continuous time linear system stability Stability in control theory state feedback Lyapunov matrix equations linear systems feedback Algebra system matrices state feedback stabilisation method continuous time systems linear matrix inequalities matrix inequalities iterative algorithm delayed input controller gain strong stabilisation problem

来源：评论

学校读者我要写书评

暂无评论

Integral equations via saddle point problems for time-harmonic Maxwell's equations

引用

JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2003年第1期150卷 157-192页

作者： Collino, F Despres, B State Atom Energy Commiss F-91680 Bruyeres Le Chatel France Univ Paris 06 Lab Jacques Louis Lions F-75013 Paris France CERFACS F-31057 Toulouse France INRIA F-78153 Le Chesnay France

We propose a new system of integral equations for the exterior time harmonic Maxwell's equation. This system is derived first from elementary manipulations of classical equations then by the minimization of a quadratic functional associated to incoming and outgoing electromagnetic waves. We analyze the inf-sup condition and various penalized problems related to this system. Then we prove that an iterative algorithm for the solution of the system of integral equations is convergent. Other numerical issues are also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词： Maxwell integral equation saddle point scattering impedance boundary conditions iterative algorithm

来源：评论

学校读者我要写书评

暂无评论

iterative dual energy material decomposition from spatial mismatched raw data sets

引用

JOURNAL OF X-RAY SCIENCE AND TECHNOLOGY 2014年第6期22卷 745-762页

作者： Zhao, Xing Hu, Jing-Jing Zhao, Yun-Song Zhang, Hui-Tao Zhang, Peng Capital Normal Univ Sch Math Sci CT Lab Beijing 100048 Peoples R China Beijing Inst Technol Sch Software Beijing 100081 Peoples R China Beijing Ctr Math & Informat Interdisciplinary Sci Beijing Peoples R China

Today's clinical dual energy computed tomography (DECT) scanners generally measure different rays for different energy spectra and acquire spatial mismatched raw data sets. The deficits in clinical DECT technologies suggest that mainly image based material decomposition methods are in use nowadays. However, the image based material decomposition is an approximate technique, and beam hardening artifacts remain in decomposition results. A recently developed image based iterative method for material decomposition from inconsistent rays (MDIR) can achieve much better image quality than the conventional image based methods. Inspired by the MDIR method, this paper proposes an iterative method to indirectly perform raw data based DECT even with completely mismatched raw data sets. The iterative process is initialized by density images that were obtained from an image based material decomposition. Then the density images are iteratively corrected by comparing the estimated polychromatic projections and the measured polychromatic projections. Only three iterations of the method are sufficient to greatly improve the qualitative and quantitative information in material density images. Compared with the MDIR method, the proposed method needs not to perform additional water precorrection. The advantages of the method are verified with numerical experiments from inconsistent noise free and noisy raw data.

关键词： Dual energy computed tomography iterative algorithm basis material decomposition calibration

来源：评论

学校读者我要写书评

暂无评论

MULTIGRID ACCELERATION OF A RELAXATION PROCEDURE FOR THE REDUCED NAVIER-STOKES EQUATIONS

引用

AIAA JOURNAL 1988年第9期26卷 1044-1051页

作者： HIMANSU, A RUBIN, SG University of Cincinnati Cincinnati Ohio

The multigrid method is applied to obtain significant improvements in the convergence rate of an iterative relaxation procedure for the numerical solution of the reduced Navier-Stokes equations. The iterative algorithm uses “streamwise” marching sweeps, in a line-relaxation mode, to determine the pressure field. With the use of the multigrid procedure, considerable computational work multiplied by memory efficiency results for both inviscid transonic flow and laminar viscous flow with strong interaction. In addition to applying the standard Full Approximation Storage multigrid technique (full coarsening), a modified technique involving multigridding in only the streamwise direction (semicoarsening) is investigated. The latter is shown to be significantly better for flow behavior that is sensitive to grid stretching in the direction normal to the body surface. The problems considered in this study include trailing-edge flow (where the pressure gradient is singular), separated flow in a Carter-Wornom trough, and transonic inviscid flow over a parabolic-arc airfoil. © 1988 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Navier Stokes Calculations Incompressible Flow Trailing Edges iterative Solution Airfoil iterative algorithm Freestream Mach Number Pressure Coefficient Fluid Flow Boundary Value Problems

来源：评论

学校读者我要写书评

暂无评论

iterative criteria for identifying strong H-tensors

引用

JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2019年 352卷 93-109页

作者： Huang, Baohua Ma, Changfeng Fujian Normal Univ Coll Math & Informat Fuzhou 350117 Fujian Peoples R China Fujian Normal Univ FJKLMAA Fuzhou 350117 Fujian Peoples R China

Strong H-tensors play an important role in the theories and applications of numerical linear algebra. It is necessary to identify whether a given tensor is a strong H-tensor or not. In this paper, we establish some iterative criteria for identifying strong H-tensors. These criteria depend on the elements of the tensors: therefore, they are easy to be verified. The results obtained in this paper extend the corresponding conclusions for strictly generalized diagonally dominant matrices. As an application, some sufficient conditions for the positive definiteness of an even-order real symmetric tensor are presented. Some numerical experiments show the feasibility and efficiency of the results which are obtained in this paper. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Strong H-tensors Strictly generalized diagonally dominant iterative algorithm Positive definiteness Numerical experiments

来源：评论

学校读者我要写书评

暂无评论

Sampling and quasi-optimal approximation for signals in a reproducing kernel space of homogeneous type

引用

JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2017年 319卷 296-307页

作者： Jiang, Yingchun Wang, Suping Guilin Univ Elect Technol Sch Math & Computat Sci Guilin 541004 Peoples R China Tianjin Univ Sch Math Tianjin 300354 Peoples R China

This paper considers the reconstruction of signals in a reproducing kernel space of homoge neous type from finite samples. First, a pre-reconstruction operator based on finite samples and probability measure is proposed and its bounded property is studied. Secondly, the stability and an iterative algorithm with exponential convergence are established for sampling and recovering signals in a subspace of homogeneous reproducing kernel space. Then, we show that the proposed algorithm also provides a quasi-optimal approximation to signals in a reproducing kernel space of homogeneous type. Finally, some numerical simulations are given to reconstruct signals on an interval. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Average sampling Quasi-optimal approximation Homogeneous type Reproducing kernel space iterative algorithm

来源：评论

学校读者我要写书评

暂无评论

Implicit space mapping with adaptive selection of preassigned parameters

引用

IET MICROWAVES ANTENNAS & PROPAGATION 2010年第3期4卷 361-373页

作者： Koziel, S. Cheng, Q. S. Bandler, J. W. Reykjavik Univ Sch Sci & Engn Engn Optimizat & Modeling Ctr IS-103 Reykjavik Iceland McMaster Univ Dept Elect & Comp Engn Simulat Optimizat Syst Res Lab Hamilton ON L8S 4K1 Canada Bandler Corp Dundas ON L9H 5E7 Canada

Implicit space mapping is one of the latest developments in space mapping (SM) technology. Its advantage is that the variables (the so-called preassigned parameters) used to adjust the surrogate model to have it match the fine model are typically separate from the design variables. Also, implicit space mapping offers greater flexibility in creating and enhancing surrogate models. Still, choosing the proper model as well as the right set of preassigned parameters - both being critical for the performance of the space mapping algorithm - is an open problem. Here, the authors apply suitable assessment techniques that help in automatically making the right selection of the model and, consequently, its associated parameters. The assessment is embedded into the SM algorithm so that the choice of the most suitable model is performed before each iteration of the algorithm. Our approach is verified using several microwave design optimisation problems. The authors also present a modified version of the adaptive SM to improve performance. Our examples are repeated using the modified adaptive SM and compared with the basic adaptive SM.

关键词： implicit space mapping technology iterative methods Interpolation and function approximation (numerical analysis) iterative algorithm Filters and other networks optimisation microwave design optimisation problems microstrip filters adaptive SM algorithm Optimisation techniques preassigned parameters Waveguide and microwave transmission line components surrogate model

来源：评论

学校读者我要写书评

暂无评论

Robust beamforming and power allocation in cognitive radio relay networks with imperfect channel state information

引用

IET COMMUNICATIONS 2014年第9期8卷 1560-1569页

作者： Mohammadkhani, Saeideh Kahaei, Mohammad Hossein Razavizadeh, Seyed Mohammad Iran Univ Sci & Technol Sch Elect Engn Tehran Iran

The authors study robust beamforming and power allocation in cognitive relay networks using several relays in the secondary link. The channel state information is imperfect modelled by Gaussian random variables. First, minimisation of the total transmit power of relays and the secondary transmitter is considered with a constraint on the interference in the primary receiver. Also, a constraint is assumed on the received signal-to-interference plus noise ratio (SINR) in the secondary receiver. In the other scenario, maximisation of the SINR in the secondary receiver is investigated with a limit on the maximum transmit power of relays and the secondary transmitter. For each non-convex optimisation problem, an iterative and robust algorithm is derived. It is proved that the first proposed algorithm converges to the global optimum. Simulation results similarly show the convergence of both algorithms with a few number of iterations. The outperformance of the robust algorithms is shown compared with a non-robust design.

关键词： cognitive radio relay networks (telecommunication) array signal processing channel allocation radio links Gaussian processes random processes radio receivers radio transmitters interference suppression minimax techniques concave programming iterative methods convergence robust beamforming algorithm power allocation cognitive radio relay network imperfect channel state information radio link convergence iterative algorithm nonconvex optimisation problem secondary transmitter SINR maximisation secondary receiver SINR signal-to-interference plus noise ratio primary receiver transmit power minimisation Gaussian random variables

来源：评论

学校读者我要写书评

暂无评论

Design of Earth-Moon Free-Return Trajectories

引用

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2013年第1期36卷 263-271页

作者： Luo, Qinqin Yin, Jianfeng Han, Chao Beihang Univ Beijing 100191 Peoples R China

A new algorithm for designing free-return lunar flyby trajectories between the Earth and the moon is developed. The pseudostate theory is adopted to get the initial solution of the free-return trajectory. Using this initial solution, an improved differential-correction method is employed to find the final solution with a more complicated dynamic model. Compared with the original differential-correction method, the improved one can extend the convergence domain and have a fast convergence speed. A large number of numerical examples are carried out to test the reliability and efficiency of the algorithm, and also study the global features of free-return lunar flyby trajectories. The features are mainly affected by the geometric relationship between the Earth and the moon, the altitude of perilune, and the transfer time from perigee to perilune.

关键词： Free Return Trajectory Earth Moon Perigee Lambert's Problem Keplerian Orbit Lunar Transfer iterative algorithm Orbit Determination Search algorithm

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：