A Modified Iterative Learning Control Approach for the Active Suppression of Rotor Vibration Induced by Coupled Unbalance and Misalignment

This paper proposes a modified iterative learning control(MILC)periodical feedback-feedforward algorithm to reduce the vibration of a rotor caused by coupled unbalance and parallel misalignment.The control of the vibration of the rotor is provided by an active magnetic actuator(AMA).The iterative gain of the MILC algorithm here presented has a self-adjustment based on the magnitude of the vibration.Notch filters are adopted to extract the synchronous(1×Ω)and twice rotational frequency(2×Ω)components of the rotor vibration.Both the notch frequency of the filter and the size of feedforward storage used during the experiment have a real-time adaptation to the rotational speed.The method proposed in this work can provide effective suppression of the vibration of the rotor in case of sudden changes or fluctuations of the rotor speed.Simulations and experiments using the MILC algorithm proposed here are carried out and give evidence to the feasibility and robustness of the technique proposed.

Integration of the Coupled Orbit-Attitude Dynamics Using Modified Chebyshev-Picard Iteration Methods

This paper presents Modified Chebyshev-Picard Iteration(MCPI)methods for long-term integration of the coupled orbit and attitude dynamics.Although most orbit predictions for operational satellites have assumed that the attitude dynamics is decoupled from the orbit dynamics,the fully coupled dynamics is required for the solutions of uncontrolled space debris and space objects with high area-to-mass ratio,for which cross sectional area is constantly changing leading to significant change on the solar radiation pressure and atmospheric drag.MCPI is a set of methods for solution of initial value problems and boundary value problems.The methods refine an orthogonal function approximation of long-time-interval segments of state trajectories iteratively by fusing Chebyshev polynomials with the classical Picard iteration and have been applied to multiple challenging aerospace problems.Through the studies on integrating a torque-free rigid body rotation and a long-term integration of the coupled orbit-attitude dynamics through the effect of solar radiation pressure,MCPI methods are shown to achieve several times speedup over the Runge-Kutta 7(8)methods with several orders of magnitudes of better accuracy.MCPI methods are further optimized by integrating the decoupled dynamics at the beginning of the iteration and coupling the full dynamics when the attitude solutions and orbit solutions are converging during the iteration.The approach of decoupling and then coupling during iterations provides a unique and promising perspective on the way to warm start the solution process for the longterm integration of the coupled orbit-attitude dynamics.Furthermore,an attractive feature of MCPI in maintaining the unity constraint for the integration of quaternions within machine accuracy is illustrated to be very appealing.

Modified variational iteration method for an El Nio Southern Oscillation delayed oscillator

This paper studies a delayed air-sea coupled oscillator describing the physical mechanism of El Nino Southern Oscillation. The approximate expansions of the delayed differential equation＇s solution are obtained successfully by the modified variational iteration method. The numerical results illustrate the effectiveness and correctness of the method by comparing with the exact solution of the reduced model.

Efficient Orbit Propagation of Orbital Elements Using Modified Chebyshev Picard Iteration Method

This paper focuses on propagating perturbed two-body motion using orbital elements combined with a novel integration technique.While previous studies show that Modified Chebyshev Picard Iteration(MCPI)is a powerful tool used to propagate position and velocity,the present results show that using orbital elements to propagate the state vector reduces the number of MCPI iterations and nodes required,which is especially useful for reducing the computation time when including computationally-intensive calculations such as Spherical Harmonic gravity,and it also converges for>5.5x as many revolutions using a single segment when compared with cartesian propagation.Results for the Classical Orbital Elements and the Modified Equinoctial Orbital Elements(the latter provides singularity-free solutions)show that state propagation using these variables is inherently well-suited to the propagation method chosen.Additional benefits are achieved using a segmentation scheme,while future expansion to the two-point boundary value problem is expected to increase the domain of convergence compared with the cartesian case.MCPI is an iterative numerical method used to solve linear and nonlinear,ordinary differential equations(ODEs).It is a fusion of orthogonal Chebyshev function approximation with Picard iteration that approximates a long-arc trajectory at every iteration.Previous studies have shown that it outperforms the state of the practice numerical integrators of ODEs in a serial computing environment;since MCPI is inherently massively parallelizable,this capability is expected to increase the computational efficiency of the method presented.

Iterative technique for circular thin plates on Gibson elastic foundation using modified Vlasov model

In this paper, to investigate the influence of soil inhomogeneity on the bending of circular thinplates on elastic foundations, the static problem of circular thin plates on Gibson elasticfoundation is solved using an iterative method based on the modified Vlasov model. On the basisof the principle of minimum potential energy, the governing differential equations and boundaryconditions for circular thin plates on modified Vlasov foundation considering the characteristics ofGibson soil are derived. The equations for the attenuation parameter in bending problem are alsoobtained, and the issue of unknown parameters being difficult to determine is solved using theiterative method. Numerical examples are analyzed and the results are in good agreement withthose form other literatures. It proves that the method is practical and accurate. Theinhomogeneity of modified Vlasov foundations has some influence on the deformation andinternal force behavior of circular thin plates. The effects of various parameters on the bending ofcircular plates and characteristic parameters of the foundation are discussed. The modified modelfurther enriches and develops the elastic foundations. Relevant conclusions that are meaningful toengineering practice are drawn.

Modified iterative method for augmented system

The successive overrelaxation-like （SOR-like） method with the real param- eters ω is considered for solving the augmented system. The new method is called the modified SOR-like （MSOR-like） method. The functional equation between the parameters and the eigenvalues of the iteration matrix of the MSOR-like method is given. Therefore, the necessary and sufficient condition for the convergence of the MSOR-like method is derived. The optimal iteration parameter ω of the MSOR-like method is derived. Finally, the proof of theorem and numerical computation based on a particular linear system are given, which clearly show that the MSOR-like method outperforms the SOR-like （Li, C. J., Li, B. J., and Evans, D. J. Optimum accelerated parameter for the GSOR method. Neural, Parallel ＆ Scientific Computations, 7（4）, 453-462 （1999）） and the modified sym- metric SOR-like （MSSOR-like） methods （Wu, S. L., Huang, T. Z., and Zhao, X. L. A modified SSOR iterative method for augmented systems. Journal of Computational and Applied Mathematics, 228（4）, 424-433 （2009））.

求解鞍点问题的修正MSOR-like方法

针对一类非对称鞍点问题,分析了MSOR-like迭代存在的缺陷,构建了一种修正的迭代方法。其主要思想是引入新参数来提高迭代关联系数矩阵的灵敏度,合理给出参变量正定矩阵的选取方法。根据所建迭代格式的特点,运用矩阵特征值理论,证明了所给迭代的收敛性,并得到相关参数的取值范围。最后通过数值实验,证实了修正MSOR-like方法用于求解鞍点问题的有效性。

基于镜像修正FxLMS控制算法的船舶管路振动主动控制

针对船舶管路减振和抗冲击的需求,本文根据镜像修正自适应滤波算法,设计出了一种管路振动主动控制策略,能够有效地控制管路在低频下的振动,并且在次级通道发生突变时,控制系统可再次快速收敛,进行稳定控制。本文先对镜像修正自适应滤波算法进行理论研究,分析算法的迭代及控制过程;再通过仿真分别验证算法在不同参考信号输入下的收敛性及稳定性;最后搭建实验台架,通过试验验证算法的实际控制效果。试验结果表明:该控制策略在管路振动主动控制中能够降低15.37%的振动强度,比自适应滤波算法控制策略的控制效果好8.85%。所以镜像修正自适应滤波算法能够及时有效地进行管路振动控制。

方程求根迭代法的一类修正格式与收敛性分析

研究方程求根迭代法的一类修正格式及其收敛性.通过引入乘子函数λ和利用泰勒展开式,建立一般迭代法的修正格式,并对其进行收敛性分析,进而给出修正格式的全局收敛和局部收敛条件;通过误差补偿,建立修正格式的加速公式,以保证在较高精度的情况下降低一般迭代公式对初值选择的敏感度.

基于改进经验模态分解的直线电机伺服系统迭代学习控制

针对直线电机伺服系统迭代学习过程中因误差积累效应引起的收敛速度慢和跟踪精度差的问题,提出一种基于改进经验模态分解的控制策略。首先,设计一种具有自适应性调节特点的迭代学习位置控制器。然后,提出一种基于三角极值波延拓与互补集合经验模态分解的改进算法,该算法可将各次迭代的跟踪误差进行分解,筛选并剔除影响误差收敛的分量。通过仿真分析并与传统迭代学习控制进行比较,证明了本文方法具有更快的收敛速度,能够以较少的迭代次数实现直线电机的高精度跟踪控制。

轴旋转法标定中的机器人运动学建模方法研究

轴旋转法标定是通过依次旋转机器人关节轴获取测量点,利用测量点拟合机器人轴线方程。基于轴线方程,利用两种方法建立机器人运动学方程,第一种方法首先求取机器人各轴理论坐标系相对于基坐标系的变换矩阵,然后基于理论轴线与实际轴线间的微小误差,求取各轴实际坐标系相对于基坐标系的变换矩阵,最后求取六变量相邻变换矩阵。第二种方法是直接利用新MDH法求取实际机器人的相邻变换矩阵,即对于空间交叉轴,求其公垂线确定轴坐标系,对于平行轴,通过交叉轴的公垂线交点向另一轴作垂线,确定另一轴坐标系的x轴方向。比较两种方法发现,第一种方法无法求解各轴的零位偏差,而第二种方法可以解耦求取各轴零位偏差与几何参数。利用牛顿迭代法求解两种模型的逆运动学方程,并用实验和仿真计算比较两种方法的标定效果,其轨迹精度达到−0.83~+0.52 mm。

基于改进贪心算法的电力通信网故障诊断方法

现行方法在电力通信网故障诊断中的效果不佳,灵敏度和查准率均较低,为解决现行方法存在的缺陷与不足,提出基于改进贪心算法的电力通信网故障诊断方法。利用数据采集卡采集通信网物理层、链路层、网络层和传输层状态数据信息,建立通信网故障诊断问题模型,通过对贪心算法迭代周期的优化,实现对贪心算法的改进,利用改进贪心算法求解问题模型,实现电力通信网故障诊断决策。实验证明,该设计方法灵敏度在95%以上,查全率在90%以上,在电力通信网故障诊断领域具有良好的应用前景。

ITERATIVE APPROXIMATION OF FIXED POINTS OF (ASYMPTOTICALLY) NONEXPANSIVE MAPPINGS

Let E be a uniformly convex Banach space which satisfies Opial's condition or has a Frechet differentiable norm,and C be a bounded closed convex subset of E. If T∶C→C is (asymptotically)nonexpansive,then the modified Ishikawa iteration process defined byx n+1 =t nT ns nT nx n+1-s nx n+(1-t n)x n,converges weakly to a fixed point of T ,where {t n} and {s n} are sequences in [0,1] with some restrictions.

ON THE ITERATIVE APPROXIMATION PROBLEM OF FIXED OINTS FOR ASYMPTOTICALLY NON-EXPANSIVE TYPE MAPPINGS IN BANACH SPACES

Some iterative approximation theorems of fixed points for asymptotically nonexpansive type mappings in Banach spaces are obtained.

CONVERGENT PROBLEM OF ITERATIVE SEQUENCES FOR NONLINEAR MAPPINGS WITH ERROR MEMBERS IN BANACH SPACES

In this paper,the approximation problems of Ishikawa iteration with errors of fixed points for asymptotically nonexpansive mappings and asymptotically pseudocontractive mappings in arbitrary real Banach spaces are investigated.Some necessary condition and sufficient condition for the convergence of iterative sequences are given respectively.The results thus extend and improve some recent corresponding results.

Operator Equation and Application of Variation Iterative Method

In this paper, we study some semi-closed 1-set-contractive operators A and investigate the boundary conditions under which the topological degrees of 1-set contractive fields, deg (I-A, Ω, p) are equal to 1. Correspondingly, we can obtain some new fixed point theorems for 1-set-contractive operators which extend and improve many famous theorems such as the Leray-Schauder theorem, and operator equation, etc. Lemma 2.1 generalizes the famous theorem. The calculation of topological degrees and index are important things, which combine the existence of solution of for integration and differential equation and or approximation by iteration technique. So, we apply the effective modification of He’s variation iteration method to solve some nonlinear and linear equations are proceed to examine some a class of integral-differential equations, to illustrate the effectiveness and convenience of this method.

风电场双回送出线路时域故障测距新方法

由于故障时新能源电源输出的短路电流呈现出频率偏移、谐波含量占比高、幅值受限、正负序阻抗不相等等特征,从而导致基于工频相量的故障定位方法存在失效的风险。为此,提出适用于风电场双回送出线路故障测距方法。采用时域有限差分法离散以偏微分方程形式表示的传输线方程,再利用改进变分迭代法求解传输线方程,得到线长的函数,并将线路两端的相电压、相电流作为边界条件;最后,构造故障测距函数以实现故障定位。通过PSCAD/EMTDC和硬件在环测试实验平台进行分析,验证了所提算法能准确地定位故障位置。

ITERATIVE APPROXIMATION OF FIXED POINTS OF NON-LIPSCHITZIAN ASYMPTOTICALLY PSEUDOCONTRACTIVE MAPPINGS

The purpose of this paper is to investigate the problem of approximatingfixed points of non- Lipschitizian asymptotically pseudocontractive mappings in an ar-bitrary real Banach space by the modified Ishikawa iterative sequences with errors.

Modified Ishikawa Iterative Process with Errors in Normed Linear Spaces

Ishikawa iterative sequences with errors different from the iterative sequences introduced by Liu and Xu are given. Moreover, the problem of approximating the fixed points of （ψ）-hemicontractive mapping in normed linear spaces by the modified Ishikawa iterative sequences with errors is investigated. The results presented in this paper improve and extend the results of the others.