A Comparative Approach for Time‐Delay Fractional Optimal Control Problems: Discrete Versus Continuous Chebyshev Polynomials

This paper aims to demonstrate the superiority of the discrete Chebyshev polynomials over the classical Chebyshev polynomials for solving time‐delay fractional optimal control problems (TDFOCPs). The discrete Chebyshev polynomials have been introduced and their properties are investigated thoroughly. Then, the fractional derivative of the state function in the dynamic constraint of TDFOCPs is approximated by these polynomials with unknown coefficients. The operational matrix of fractional integration together with the dynamical constraints is used to approximate the control function directly as a function of the state function. Finally, these approximations were put in the performance index and necessary conditions for optimality transform the under consideration TDFOCPs into an algabric system. A comparison has been made between the required CPU time and accuracy of the discrete and continuous Chebyshev polynomials methods. The obtained numerical results reveal that utilizing discrete Chebyshev polynomials is more efficient and less time‐consuming in comparison to the continuous Chebyshev polynomials.     

Solution of linear two-point boundary-value problems via shifted Chebyshev series

In this paper, the shifted Chebyshev polynomial functions approximation is extended to solve the linear ordinary differential equation of the two-point boundary-value problem. The linear ordinary differential equation of boundary-value problems are reduced to the linear functional differential equation of the initial-value problem. A new time-domain approach to the derivation of a Chebyshev transformation matrix is presented. Using the derived Chebyshev transformation matrix together with the Chebyshev integration matrix, the solution of the linear functional ordinary differential equation of initial-value problem can be obtained via shifted Chebyshev series. Two examples are given and the satisfactory computational results are compared with those of the exact solution.     

Chebyshev polynomial Kalman filter

A novel Gaussian state estimator named Chebyshev polynomial Kalman filter is proposed that exploits the exact and closed-form calculation of posterior moments for polynomial nonlinearities. An arbitrary nonlinear system is at first approximated via a Chebyshev polynomial series. By exploiting special properties of the Chebyshev polynomials, exact expressions for mean and variance are then provided in computationally efficient vector-matrix notation for prediction and measurement update. Approximation and state estimation are performed in a black-box fashion without the need of manual operation or manual inspection. The superior performance of the Chebyshev polynomial Kalman filter compared to state-of-the-art Gaussian estimators is demonstrated by means of numerical simulations and a real-world application.     

Relativistic three-quark bound states in separable two-quark approximation

Baryons as relativistic bound states in 3-quark correlations are described by an effective Bethe-Salpeter equation when irreducible 3-quark interactions are neglected and separable 2-quark correlations are assumed. We present an efficient numerical method to calculate the nucleon mass and its covariant wave function in this quantum field theoretic quark-diquark model with quark-exchange interaction. Expanding the components of the spinorial wave function in terms of Chebyshev polynomials, the four-dimensional integral equations are in a first step reduced to a coupled set of one-dimensional ones. This set of linear and homogeneous equations defines a generalised eigenvalue problem. Representing the eigenvector corresponding to the largest eigenvalue, the Chebyshev moments are then obtained by iteration. The nucleon mass is implicitly determined by the eigenvalue, and its covariant wave function is reconstructed from the moments within the Chebyshev approximation.     

On a functional approximation for inversion of Laplace transforms via shifted Chebyshev series

A functional representation for inversion of the Laplace transform of a function is considered. The function is given as a shifted Chebyshev series expansion. Using special operational properties, each Laplace transform is converted into a set of simultaneous linear algebraic equations that are then easily solved to give the coefficients of the Chebyshev series. The method is simple and very suitable for computer programming. Applications to rational and irrational Laplace transforms are presented to demonstrate the satisfactory results that the method provides.     

A set of new Chebyshev kernel functions for support vector machine pattern classification

In this study, we introduce a set of new kernel functions derived from the generalized Chebyshev polynomials. The proposed generalized Chebyshev polynomials allow us to derive different kernel functions. By using these polynomial functions, we generalize recently introduced Chebyshev kernel function for vector inputs and, as a result, we obtain a robust set of kernel functions for Support Vector Machine (SVM) classification. Thus in this study, besides clarifying how to apply the Chebyshev kernel functions on vector inputs, we also increase the generalization capability of the previously proposed Chebyshev kernels and show how to derive new kernel functions by using the generalized Chebyshev polynomials. The proposed set of kernel functions provides competitive performance when compared to all other common kernel functions on average for the simulation datasets. The results indicate that they can be used as a good alternative to other common kernel functions for SVM classification in order to obtain better accuracy. Moreover, test results show that the generalized Chebyshev kernel approaches to the minimum support vector number for classification in general.     

线性相位切比雪夫数字滤波器的时窗函数

切比雪夫滤波器是一种性能优良的滤波器，由于是在频域上定义其响应特性，从而限制了它的适用性。本文利用切比雪夫多项式，直接百坟域上定义线性相位切比雪夫数字滤波器的时窗函数，结合实例说明这种时窗函数显式具有一定的实用价值，并简要讨论了数据加权和补零这个基本问题。     

基于实数域扩散离散Chebyshev多项式的公钥加密算法

将Chebyshev多项式与模运算相结合,对其定义在实数域上进行了扩展,经过理论验证和数据分析,总结出实数域多项式应用于公钥密码的一些性质.利用RSA公钥算法和ElGamal公钥算法的算法结构,提出基于有限域离散Chebyshev多项式的公钥密码算法.该算法结构类似于RSA算法,其安全性基于大数因式分解的难度或者与El...     

Numerical solution of fourth-order integro-differential equations using Chebyshev cardinal functions

A numerical technique is presented for the solution of fourth-order integro-differential equations. This method uses the Chebyshev cardinal functions. The method consists of expanding the required approximate solution as the elements of Chebyshev cardinal functions. Using the operational matrix of derivative, we reduce the problem to a set of algebraic equations. Some numerical examples are included to demonstrate the validity and applicability of the technique. The method is easy to implement and produces very accurate results.     

Chebyshev Approximation by Exponential-Power Expression

The properties of the Chebyshev approximation by exponential-power expressions with four unknown parameters are investigated. The condition for the existence and uniqueness of such approximation with the smallest relative error is established. A method to determine the parameters of the Chebyshev approximation is proposed and justified. The error of the Chebyshev approximation by the exponential–power expression is estimated.     

Chebyshev series approximation for solving differential–algebraic equations (DAEs)

The numerical solution of differential–algebraic equations (DAEs) using the Chebyshev series approximation is considered in this article. Two different problems are solved using the Chebyshev series approximation and the solutions are compared with the exact solutions. First, we calculate the power series of a given equation system and then transform it into Chebyshev series form, which gives an arbitrary order for solving the DAE numerically.     

Chebyshev polynomial and heat conduction equation in cylindrical geometry

The solutions of the unsteady heat conduction equations in cylindrical geometry in one and two dimensions are obtained using the Chebyshev polynomial expansions in the spatial domain. Equations are discretized in the time domain using the trapezoidal rule. The resulting differential equations are reduced to backward recurrence relations for the coefficients occurring in the Chebyshev polynomial expansions, which are then solved using the Tau method. It is shown that the Chebyshev polynomial solutions produce results to the machine-precision accuracy in the spatial domain using only a modest number of terms, and are, therefore, excellent alternatives to the other techniques used.     

A chaotic coverage path planner for the mobile robot based on the Chebyshev map for special missions

We introduce a novel strategy of designing a chaotic coverage path planner for the mobile robot based on the Chebyshev map for achieving special missions. The designed chaotic path planner consists of a two-dimensional Chebyshev map which is constructed by two one-dimensional Chebyshev maps. The performance of the time sequences which are generated by the planner is improved by arcsine transformation to enhance the chaotic characteristics and uniform distribution. Then the coverage rate and randomness for achieving the special missions of the robot are enhanced. The chaotic Chebyshev system is mapped into the feasible region of the robot workplace by affine transformation. Then a universal algorithm of coverage path planning is designed for environments with obstacles. Simulation results show that the constructed chaotic path planner can avoid detection of the obstacles and the workplace boundaries, and runs safely in the feasible areas. The designed strategy is able to satisfy the requirements of randomness, coverage, and high efficiency for special missions.     

Uncertain Method for Optimal Control Problems With Uncertainties Using Chebyshev Inclusion Functions

In this paper, a new uncertain analysis method is developed for optimal control problems, including interval variables (uncertainties) based on truncated Chebyshev polynomials. The interval arithmetic in this research is employed for analyzing the uncertainties in optimal control problems comprising uncertain‐but‐bounded parameters with only lower and upper bounds of uncertain parameters. In this research, the Chebyshev method is utilized because it generates sharper bounds for meaningful solutions of interval functions, rather than the Taylor inclusion function, which is efficient in handling the overestimation derived from the wrapping effect due to interval computations. For utilizing the proposed interval method on the optimal control problems with uncertainties, the Lagrange multiplier method is first applied to achieve the necessary conditions and then, by using some algebraic manipulations, they are converted into the ordinary differential equation. Afterwards, the Chebyshev inclusion method is employed to achieve the solution of the system. The final results of the Chebyshev inclusion method are compared with the interval Taylor method. The results show that the proposed Chebyshev inclusion function based method better handle the wrapping effect than the interval Taylor method.     

A boundary value problem for the KdV equation: Comparison of finite-difference and Chebyshev methods

Solutions of a boundary value problem for the Korteweg–de Vries equation are approximated numerically using a finite-difference method, and a collocation method based on Chebyshev polynomials. The performance of the two methods is compared using exact solutions that are exponentially small at the boundaries. The Chebyshev method is found to be more efficient.     

基于Chebyshev小波的分布参数系统辨识

工程实际和社会系统中广泛存在着分布参数系统,因而研究分布参数系统的辨识与控制具有重要意义.但由于其复杂性,对分布参数系统的辨识研究十分困难.借助于Chebyshev多项式的逼近性质,以及小波的时频特性,构造了Chebyshev小波,并利用其积分运算矩阵,运用于分布参数系统的辨识,从而将一类分布参数系统的辨识问题转化为一般代数问题.并且考虑了初始条件和边界条件对辨识结果的影响,因此具有较好的适用性,仿真结果证实了该方法的有效性.     

Polynomial solutions of certain differential equations

In this paper, the Chebyshev matrix method is applied generalisations of the Hermite, Laguerre, Legendre and Chebyshev differential equations which have polynomial solution. The method is based on taking the truncated Chebyshev series expansions of the functions in equation, and then substituting their matrix forms into the result equation. Thereby the given equation reduces to a matrix equation, which corresponds to a system of linear algebraic equations with unknown Chebyshev coefficients.     

基于模拟电路的Chebyshev神经网络电路设计

以Ｃｈｅｂｙｓｈｅｖ神经网络为基础,给出了３个非线性函数的仿真实例,并提出了用模拟电路实现Ｃｈｅｂｙｓｈｅｖ神经网络的方法。     

Perturbed Chebyshev rational approximation

In this work, we give a perturbed Chebyshev rational approximation for a function f (x) which has a Chebyshev expansion. This approximation contains a perturbation parameter ~ which is calculated so that the perturbed Chebyshev rational approximation agrees with the Chebyshev expansion to a certain number of terms. Also, we introduce a perturbed Chebyshev rational approximation for the definite integral of a function f (x) having Chebyshev expansion and show that this method can be used iteratively to approximate the multiple integral of the considered function. The method has been applied to approximate some functions and their definite integrals.     

Chebyshev expansions for wave functions

Chebyshev series expansion of solutions of linear differential equations which occur in atomic scattering problems is discussed. We apply this technique to obtain both the regular and the irregular radial Coulomb wave functions. The Chebyshev expansion technique is extended to evaluate linearly independent solutions for the modified Coulomb potential. It is further shown that relativistic Coulomb wave functions may also be evaluated using Chebyshev expansion techniques.An advantage of this technique is that wave functions and their derivatives can be represented to a very high accuracy in terms of only a small number of Chebyshev expansion coefficients over a wide range of values of the independent variable. Moreover, in certain cases it is possible to evaluate matrix elements involving functions so represented by using properties of Chebyshev polynomials and thus avoiding numerical integration altogether.