基于改进遗传算法的环形倒立摆PID参数整定

针对传统的环形倒立摆PID控制器参数整定方法主观性强,系统响应性能不佳等问题,提出来了一种基于改进遗传算法的环形倒立摆PID参数整定方法.采用仿真研究方法,比较了试凑法、遗传算法和改进遗传算法求取的PID控制器参数对环形倒立摆的控制效果.实验表明,相比于试凑法,遗传算法得到的PID控制器参数使系统的超调量减小、调节时间缩短;改进的遗传算法得到的PID控制器参数使系统的响应性能进一步优化.改进遗传算法求取PID控制器参数的方法对于环形倒立摆以外的控制系统也有借鉴作用.     

基于遗传算法的PID控制器参数优化研究

研究自动控制器参数优化问题,PID参数优化是自动控制领域研究的重要内容,系统参数选择决定控制的稳定性和快速性,也可保证系统的可靠性.传统的PID参数多采用试验加试凑的方式由人工进行优化,往往费时而且难以满足控制的实时要求.为了解决控制参数优化,改善系统性能,提出一种遗传算法的PID参数优化策略.通过建立遗传算法优化的PID控制器参数模型,在控制过程中将PID参数作为遗传算法中的个体,采用控制误差绝对值时间积分函数作为优化目标,动态调整PID的三个控制参数,进行PID控制参数的在线优化,将优化方案应用于农业温室温度控制系统进行了仿真.仿真表明,引入遗传算法的PID控制系统,提高了动态性能,增强系统稳定性和快速性,保证实现了控制效果.     

基于双种群遗传算法的四旋翼飞行器PID参数整定方法

针对四旋翼飞行器的PID控制器参数整定问题,提出使用双种群遗传算法对控制器参数进行寻优;四旋翼飞行器的PID参数调整困难,由于通道间的耦合关系使常规的参数调整方法失效,提出结合双种群遗传算法,寻找最优的PID参数组合,实现飞行器控制;结合动力学模型并加以适当简化,设计了PID控制器,使用双种群遗传算法整定参数,进行了数据仿真实验;结果表明,双种群遗传算法能够提高单种群遗传算法5%的性能,获得的参数控制效果更好。     

基于改进遗传算法的PID控制器设计

针对一般遗传算法存在的不足，提出一种改进的遗传算法，并将其应用于PID控制器参数设计。该方法采用实数编码，是为了操作方便、提高精度和收敛速度，且能克服传统PID参数整定的费时性。仿真结果表明，基于改进遗传算法设计的PID控制器获得了良好的控制效果，其控制性能优于常规的PID控制器。     

基于免疫遗传新算法的PID参数整定

为使PID参数整定工作更加快捷有效,在传统遗传算法的基础上,提出基于独特型免疫动力学网络模型的新型免疫算法,以激励水平作为抗体选择操作的量度,并构建精英抗体库,以便给精英抗体更多交叉变异的机会.将该算法用于PID控制器参数整定,仿真结果表明,新算法能更快地找到控制器PID参数最优组合,且经该算法优化后的系统控制性能优于传统遗传算法优化的PID控制器,故该算法用于PID参数优化是可行且有效的.     

PID 控制器参数优化中的仿真研究

研究 PID 控制器参数优化选择问题.传统的 PID 参数优化多采用试验加试凑的方式,费时且难找到最优参数,同时,常规 BP 神经网络 PID 参数优化训练收敛速度较慢,控制效果不理想.为了获得最优 PID 参数,提高系统的控制性能.提出一种遗传算法 BP 神经网络PID 参数优化方法.方法首先采用全局寻优的遗传算法对...     

智能PID控制器优化仿真研究

研究PID控制器优化问题,现代工业控制过程中,由于许多被控对象受到于扰因素影响,具有高度非线性和不确定性,常规PID控制精度低,提出一种遗传算法、粒子群算法和RBF神经网络相融合的PID控制器设计方法(GA-PSO-RBF).首先采用遗传算法选择PID控制参数初始值,然后采用粒子群算法优化RBF神经网络参数,采用优后的RBF神经网络辨识控制对象的输出对输入的变化灵敏度,最后采用单神经元对PID控制器进行在线性调整,得到理想的控制效果.仿真结果表明,GA-PSO-RBF神经网络PID控制器的超调量小,响应速度快,提高了系统的控制精度.     

基于改进遗传算法的非线性PID控制器

基于PID控制器各增益参数与偏差信号之间呈现非线性关系,该文提出了一种非线性PID控制器.同时,针对经典遗传算法收敛速度慢、易于早熟、局部寻优能力差等缺点,在前人研究成果的基础上,改进了传统的遗传算法,并将其应用于非线性PID控制器参数寻优.仿真结果表明,基于此遗传算法寻优设计的非线性PID控制器可以极大地提高寻优的速度,同时兼顾系统的动态和静态性能.     

基于在线自适应遗传算法的PID参数整定和优化

研究自动控制系统优化问题,控制系统响应特性取决于系统参数的调整.针对传统的PID控制算法参数较多,且难以整定,使得控制效果不理想等问题,提出了自适应遗传算法的PID参数整定.根据遗传算法具有在线性差的问题,对遗传算法作了改进.通过自适应遗传算法对PID参数进行整定与寻优,选择自适应度大的个体所对应的PID控制参数作为采样时间下的PID控制参数.改进后的算法有效提高了遗传算法的寻优能力,提高了算法的收敛的速度,在一定的范围可以求得最优全局解.在MATLAB上仿真结果表明,在PID参数的寻优过程中,自适应遗传算法具有更强的寻优能力,提高了控制系统的自适应性,为优化控制系统设计提供了依据.     

采用遗传优化自适应模糊PID控制球杆系统

为解决球杆系统动态、静态性能不高的问题,提出了遗传算法优化自适应模糊PID控制器的控制方法.该模型在拉格朗日方程建立球杆系统数学模型的基础上,采用遗传算法优化模糊控制规则、隶属函数和自适应PID参数.在GBB1004系统中建立了遗传算法优化后的自适应模糊PID控制器以及控制模型,并对该控制器进行实验验证.实验结果证明了遗传算法优化后的模糊控制器有效地减小了系统的超调量,缩短了系统的调节时间,能够较好地控制球杆系统.     

QCDgrid: A Grid Resource for Quantum Chromodynamics

Quantum Chromodynamics (QCD) is an application area that requires access to large supercomputing resources and generates large amounts of raw data. The UK's national lattice QCD collaboration UKQCD currently stores and requires access to around five Tbytes of data, a figure that is growing dramatically as the collaboration's purpose built supercomputing system, QCDOC [P.A. Boyle, D. Chen, N.H. Christ, M. Clark, S.D. Cohen, C. Cristian, Z. Dong, A. Gara, B. Joo, C. Jung, C. Kim, L. Levkova, X. Liao, G. Liu, R.D. Mawhinney, S. Ohta, K. Petrov, T. Wettig and A. Yamaguchi, “Hardware and software status of QCDOC, arXiv: hep-lat/0309096”, Nuclear Physics. B, Proceedings Supplement, Vol. 838, pp. 129–130, 2004. See: http://www.ph.ed.ac.uk/ukqcd/community/qcdoc/; P.A. Boyle, D. Chen, N.H. Christ, M.A. Clark, S.D. Cohen, C. Cristian, Z. Dong, A. Gara, B. Joo, C. Jung, C. Kim, L.A. Levkova, X. Liao, R.D. Mawhinney, S. Ohta, K. Petrov, T. Wettig and A. Yamaguchi, “Overview of the QCDSP and QCDOC computers”, IBM Journal of Research and Development, Vol. 49, No. 2/3, p. 351, 2005] came into full production service towards the end of 2004. This data is stored on QCDgrid, a data Grid currently composed of seven storage elements at five separate UK sites.     

Weaker convergence for Newton's method under Hölder differentiability

We use more precise majorizing sequences than in earlier studies such as [J. Appell, E. De Pascale, J.V. Lysenko, and P.P. Zabrejko, New results on Newton–Kantorovich approximations with applications to nonlinear integral equations, Numer. Funct. Anal. Optim. 18 (1997), pp. 1–17; I.K. Argyros, Concerning the ‘terra incognita’ between convergence regions of two Newton methods, Nonlinear Anal. 62 (2005), pp. 179–194; F. Cianciaruso, A further journey in the ‘terra incognita’ of the Newton–Kantorovich method, Nonlinear Funct. Anal. Appl. 15 (2010), pp. 173–183; F. Cianciaruso and E. De Pascale, Newton–Kantorovich approximations when the derivative is Hölderian: Old and new results, Numer. Funct. Anal. Optim. 24 (2003), pp. 713–723; F. Cianciaruso, E. De Pascale, and P.P. Zabrejko, Some remarks on the Newton–Kantorovich approximations, Atti Sem. Mat. Fis. Univ. Modena 48 (2000), pp. 207–215; E. De Pascale and P.P. Zabrejko, Convergence of the Newton–Kantorovich method under Vertgeim conditions: A new improvement, Z. Anal. Anwendvugen 17 (1998), pp. 271–280; J.A. Ezquerro and M.A. Hernández, On the R-order of convergence of Newton's method under mild differentiability conditions, J. Comput. Appl. Math. 197 (2006), pp. 53–61; J.V. Lysenko, Conditions for the convergence of the Newton–Kantorovich method for nonlinear equations with Hölder linearizations (in Russian), Dokl. Akad. Nauk BSSR 38 (1994), pp. 20–24; P.D. Proinov, New general convergence theory for iterative processes and its applications to Newton–Kantorovich type theorems, J. Complexity 26 (2010), pp. 3–42; J. Rokne, Newton's method under mild differentiability conditions with error analysis, Numer. Math. 18 (1971/72), pp. 401–412; B.A. Vertgeim, On conditions for the applicability of Newton's method, (in Russian), Dokl. Akad. N., SSSR 110 (1956), pp. 719–722; B.A. Vertgeim, On some methods for the approximate solution of nonlinear functional equations in Banach spaces, Uspekhi Mat. Nauk 12 (1957), pp. 166–169 (in Russian); English transl.: Amer. Math. Soc. Transl. 16 (1960), pp. 378–382; P.P. Zabrejko and D.F. Nguen, The majorant method in the theory of Newton–Kantorovich approximations and the Pták error estimates, Numer. Funct. Anal. Optim. 9 (1987), pp. 671–684; A.I. Zinc?enko, Some approximate methods of solving equations with non-differentiable operators (Ukrainian), Dopovidi Akad. Nauk Ukraïn. RSR (1963), pp. 156–161] to provide a semilocal convergence analysis for Newton's method under Hölder differentiability conditions. Our sufficient convergence conditions are also weaker even in the Lipschitz differentiability case. Moreover, the results are obtained under the same or less computational cost. Numerical examples are provided where earlier conditions do not hold but for which the new conditions are satisfied.     

Isogeometric variational multiscale modeling of wall-bounded turbulent flows with weakly enforced boundary conditions on unstretched meshes

In this work, we combine (i) NURBS-based isogeometric analysis, (ii) residual-driven turbulence modeling and iii) weak imposition of no-slip and no-penetration Dirichlet boundary conditions on unstretched meshes to compute wall-bounded turbulent flows. While the first two ingredients were shown to be successful for turbulence computations at medium-to-high Reynolds number [I. Akkerman, Y. Bazilevs, V. M. Calo, T. J. R. Hughes, S. Hulshoff, The role of continuity in residual-based variational multiscale modeling of turbulence, Comput. Mech. 41 (2008) 371–378; Y. Bazilevs, V.M. Calo, J.A. Cottrell, T.J.R. Hughes, A. Reali, G. Scovazzi, Variational multiscale residual-based turbulence modeling for large eddy simulation of incompressible flows, Comput. Methods Appl. Mech. Engrg., 197 (2007) 173–201], it is the weak imposition of no-slip boundary conditions on coarse uniform meshes that maintains the good performance of the proposed methodology at higher Reynolds number [Y. Bazilevs, T.J.R. Hughes. Weak imposition of Dirichlet boundary conditions in fluid mechanics, Comput. Fluids 36 (2007) 12–26; Y. Bazilevs, C. Michler, V.M. Calo, T.J.R. Hughes, Weak Dirichlet boundary conditions for wall-bounded turbulent flows. Comput. Methods Appl. Mech. Engrg. 196 (2007) 4853–4862]. These three ingredients form a basis of a possible practical strategy for computing engineering flows, somewhere between RANS and LES in complexity. We demonstrate this by solving two challenging incompressible turbulent benchmark problems: channel flow at friction-velocity Reynolds number 2003 and flow in a planar asymmetric diffuser. We observe good agreement between our calculations of mean flow quantities and both reference computations and experimental data. This lends some credence to the proposed approach, which we believe may become a viable engineering tool.     

Book reviews

CALCULUS AND THE COMPUTER (An Approach to problem solving) by T. V. Fossum and R. W. Gatterdam, 1980, pub. by Scott, Forrseman & Co., Glenview, Illinois, 217pp+Index. $6.95 (only U.S. Price available).

KNOWLEDGE BASED PROGRAM CONSTRUCTION, by David R. Barstow, The Computer Science Library, Programming Languages Series No. 6. North-Holland, 1979. $10.

NUMERICAL ANALYSIS OF SEMICONDUCTOR DEVICES. Proceedings of the NASECODE 1 Conference held at Trinity College, Dublin, from 27th-29th June 1979, edited by B.T. Browne and J. J. H. Miller, pub. by Boole Press Ltd., P.O. Box No. 5, 51 Sandycove Road, Dunlaoghaire, Co. Dublin, Ireland, August 1979, XII + 303 pages, Cloth £20 (U.S. $42) ISBN 0-906783-003.     

New shape-based auroral oval segmentation driven by LLS-RHT

A new method that exploits shape to localize the auroral oval in satellite imagery is introduced. The core of the method is driven by the linear least-squares (LLS) randomized Hough transform (RHT). The LLS-RHT is a new fast variant of the RHT suitable when not all necessary conditions of the RHT can be satisfied. The method is also compared with the three existing methods for aurora localization, namely the histogram-based k-means [C.C. Hung, G. Germany, K-means and iterative selection algorithms in image segmentation, IEEE Southeastcon 2003 (Session 1: Software Development)], adaptive thresholding [X. Li, R. Ramachandran, M. He, S. Movva, J.A. Rushing, S.J. Graves, W. Lyatsky, A. Tan, G.A. Germany, Comparing different thresholding algorithms for segmenting auroras, in: Proceedings of the International Conference on Information Technology: Coding and Computing, vol. 6, 2004, pp. 594-601], and pulse-coupled neural network-based [G.A. Germany, G.K. Parks, H. Ranganath, R. Elsen, P.G. Richards, W. Swift, J.F. Spann, M. Brittnacher, Analysis of auroral morphology: substorm precursor and onset on January 10, 1997, Geophys. Res. Lett. 25 (15) (1998) 3042-3046] methods. The methodologies and their performance on real image data are both considered in the comparison. These images include complications such as random noise, low contrast, and moderate levels of key obscuring phenomena.     

A DAFT DL_POLY distributed memory adaptation of the Smoothed Particle Mesh Ewald method

The Smoothed Particle Mesh Ewald method [U. Essmann, L. Perera, M.L. Berkowtz, T. Darden, H. Lee, L.G. Pedersen, J. Chem. Phys. 103 (1995) 8577] for calculating long ranged forces in molecular simulation has been adapted for the parallel molecular dynamics code DL_POLY_3 [I.T. Todorov, W. Smith, Philos. Trans. Roy. Soc. London 362 (2004) 1835], making use of a novel 3D Fast Fourier Transform (DAFT) [I.J. Bush, The Daresbury Advanced Fourier transform, Daresbury Laboratory, 1999] that perfectly matches the Domain Decomposition (DD) parallelisation strategy [W. Smith, Comput. Phys. Comm. 62 (1991) 229; M.R.S. Pinches, D. Tildesley, W. Smith, Mol. Sim. 6 (1991) 51; D. Rapaport, Comput. Phys. Comm. 62 (1991) 217] of the DL_POLY_3 code. In this article we describe software adaptations undertaken to import this functionality and provide a review of its performance.     

Comparison of computational approaches for predicting the effects of missense mutations on p53 function

We applied our recently developed kinetic computational mutagenesis (KCM) approach [L.T. Chong, W.C. Swope, J.W. Pitera, V.S. Pande, Kinetic computational alanine scanning: application to p53 oligomerization, J. Mol. Biol. 357 (3) (2006) 1039–1049] along with the MM-GBSA approach [J. Srinivasan, T.E. Cheatham 3rd, P. Cieplak, P.A. Kollman, D.A. Case, Continuum solvent studies of the stability of DNA, RNA, and phosphoramidate-DNA helices, J. Am. Chem. Soc. 120 (37) (1998) 9401–9409; P.A. Kollman, I. Massova, C.M. Reyes, B. Kuhn, S. Huo, L.T. Chong, M. Lee, T. Lee, Y. Duan, W. Wang, O. Donini, P. Cieplak, J. Srinivasan, D.A. Case, T.E. Cheatham 3rd., Calculating structures and free energies of complex molecules: combining molecular mechanics and continuum models, Acc. Chem. Res. 33 (12) (2000) 889–897] to evaluate the effects of all possible missense mutations on dimerization of the oligomerization domain (residues 326–355) of tumor suppressor p53. The true positive and true negative rates for KCM are comparable (within 5%) to those of MM-GBSA, although MM-GBSA is much less computationally intensive when it is applied to a single energy-minimized configuration per mutant dimer. The potential advantage of KCM is that it can be used to directly examine the kinetic effects of mutations.     

Response to the comments on "Fundamental limits of reconstruction-based superresolution algorithms under local translation"

Wang and Feng (IEEE Trans. Pattern Analysis and Machine Intelligence, vol. 28, no. 5, p 846, May 2006) pointed out that the deduction in (Z. Lin and H. Y. Shum, IEEE Trans. Pattern Analysis and Machine Intelligence, vol. 26, no. 1, pp. 83-97, Jan. 2004) overlooked the validity of the perturbation theorem used in (Z. Lin and H. Y. Shum, IEEE Trans. Pattern Analysis and Machine Intelligence, vol. 26, no. 1, pp. 83-97, Jan. 2004). In this paper, we show that, when the perturbation theorem is invalid, the probability of successful superresolution is very low. Therefore, we only have to derive the limits under the condition that validates the perturbation theorem, as done in (Z. Lin and H. Y. Shum, IEEE Trans. Pattern Analysis and Machine Intelligence, vol. 26, no. 1, pp. 83-97, Jan. 2004).     

A counterexample of a theorem by Tsolas et al. and an independentresult by Zaborszky et al. [with reply]

Recent results on the composition of the stability boundary by N.A. Tsolas et al. (IEEE Trans. Circuits Syst., vol.CAS-32, no.10, pp.1041-9, Oct. 1985) and J. Zaborszky et al. (Proc. IFAC Symp. Power Syst. Power Plant. Contr., Beijing, China, Aug. 1986, pp.597-603) claimed that it consisted of the stable manifolds of index-one unstable equilibria and their closures. A counterexample shows the potential existence of additional structures within the boundary. This finding invalidates numerous theorems published in the literature. The author concedes that the counterexample to the theorem in the paper by N.A. Tsolas et al. is unassailable and identifies the error in his proof     

On the estimation of the general parameter

In this paper, we first discuss the origin, developments and various thoughts by several researchers on the generalized linear regression estimator (GREG) due to Deville and Särndal [Deville, J.C., Särndal, C.E., 1992. Calibration estimators in survey sampling. J. Amer. Statist. Assoc. 87, 376-382]. Then, the problem of estimation of the general parameter of interest considered by Rao [Rao, J.N.K., 1994. Estimating totals and distribution functions using auxiliary information at the estimation stage. J. Official Statist. 10 (2), 153-165], and Singh [Singh, S., 2001. Generalized calibration approach for estimating the variance in survey sampling. Ann. Inst. Statist. Math. 53 (2), 404-417; Singh, S., 2004. Golden and Silver Jubilee Year-2003 of the linear regression estimators. In: Proceedings of the Joint Statistical Meeting, Toronto (Available on the CD), 4382-4380; Singh, S., 2006. Survey statisticians celebrate Golden Jubilee Year-2003 of the linear regression estimator. Metrika 1-18] is further investigated. In addition to that it is shown that the Farrell and Singh [Farrell, P.J., Singh, S., 2005. Model-assisted higher order calibration of estimators of variance. Australian & New Zealand J. Statist. 47 (3), 375-383] estimators are also a special case of the proposed methodology. Interestingly, it has been noted that the single model assisted calibration constraint studied by Farrell and Singh [Farrell, P.J., Singh, S., 2002. Re-calibration of higher order calibration weights. Presented at Statistical Society of Canada conference, Hamilton (Available on CD); Farrell, P.J., Singh, S., 2005. Model-assisted higher order calibration of estimators of variance. Australian & New Zealand J. Statist. 47 (3), 375-383] and Wu [Wu, C., 2003. Optimal calibration estimators in survey sampling. Biometrika 90, 937-951] is not helpful for calibrating the Sen [Sen, A.R., 1953. On the estimate of the variance in sampling with varying probabilities. J. Indian Soc. Agril. Statist. 5, 119-127] and Yates and Grundy [Yates, F., Grundy, P.M., 1953. Selection without replacement from within strata with probability proportional to size. J. Roy. Statist. Soc. Ser. 15, 253-261] estimator of the variance of the linear regression estimator under the optimal designs of Godambe and Joshi [Godambe, V.P., Joshi, V.M., 1965. Admissibility and Bayes estimation in sampling finite populations—I. Ann. Math. Statist. 36, 1707-1722]. Three new estimators of the variance of the proposed linear regression type estimator of the general parameters of interest are introduced and compared with each other. The newly proposed two-dimensional linear regression models are found to be useful, unlike a simulation based on a couple of thousands of random samples, in comparing the estimators of variance. The use of knowledge of the model parameters in assisting the estimators of variance has been found to be beneficial. The most attractive feature is that it has been shown theoretically that the proposed method of calibration always remains more efficient than the GREG estimator.