改进比例-积分-微分控制方法在无功补偿和混合滤波综合补偿系统中的应用

设计了一种兼有无功补偿和混合滤波功能的综合补偿系统。由于传统比例-积分-微分控制方法对上述系统的检测精度、计算延时和被控对象状态变化具有较强的依赖性,文中将增量递推预测模型预作用于上述系统以补偿延时带来的控制误差,提出了一种采用预测模型实现的多模比例-积分-微分控制方法,使得当电网状态变化时该补偿系统可自动在比例-积分和比例-微分模型间切换。仿真结果和实际运行情况表明该补偿系统具有控制精度高、鲁棒性强等特点,验证了该控制方法的正确性和有效性。

The Partition of Unity Method for High-Order Finite Volume Schemes Using Radial Basis Functions Reconstruction

This paper introduces the use of partition of unity method for the development of a high order finite volume discretization scheme on unstructured grids for solving diffusion models based on partial differential equations.The unknown function and its gradient can be accurately reconstructed using high order optimal recovery based on radial basis functions.The methodology proposed is applied to the noise removal problem in functional surfaces and images.Numerical results demonstrate the effectiveness of the new numerical approach and provide experimental order of convergence.

High Precision Motion Control of Hybrid Five-Bar Mechanism with an Intelligent Control

Hybrid mecihanism is a new type of planar controllable mechanism. Position control acouracy of system determines the output aconracy of the mechanism. In order to achieve the desired high acowacy, nonlinear factors as friction nmst be accurately compensated in the real-time servo control algoritinn. In this paper, the model of a hybrid five-bar mechanism is introduced. In terms of the characteristics of the hybrid mechanism, a hybrid intelligent control algorithm based on proportional-integral-derivative （PID） control and cerebellar model articulation control techniques was presented and used to perform control of hybrid five-bar mechanism for the lust time. The sinmulation results show that the hybrid control method can improve the control effect remarkably, compared with the traditional PID control strategy.

Numerical Minimum Time Control to a Class of Singular Integro-Differential Equations

This study presents a numerical method for determining the minimum time required for the states of one class of integro-differential equations of the first kind to reach its attainable region by assuming the forcing terms of the equations as controls. These equations consist of integro-differential parts containing weakly singular kernels. The feasibility of the numerical method is demonstrated by comparing the minimum time and corresponding possible time by using extreme controls to reach the attainable region under different initial conditions.

温室二氧化碳浓度测控系统

为解决设施园艺中二氧化碳(CO_2)浓度的检测与控制问题,研制了一种基于钠超离子导体(NASICON)固体电解质传感器的温室CO_2测控系统,该系统包括CO_2测量节点、无线通信网络和控制终端。采用STM32微处理器处理采集到的CO_2浓度信息,使用模糊比例-积分-微分(PID:Proportional Integration Differential)算法控制CO_2气体的释放,从而智能调节温室内CO_2气体的浓度,使其达到作物所需数值。在实验室条件下,对设计的CO_2传感器节点进行了标定和稳定性测试。对体积分数为400×10^(-6)和1 000×10^(-6)的CO_2气体样品分别进行了>8 h的长时间浓度测量,其相对波动小于2.5%。在国信集团现代农业基地温室对所研制的CO_2浓度测控系统进行实地测试的结果显示,当设定的CO_2浓度的期望值为800×10^(-6)时,调控后CO_2体积分数的波动范围约为±40×10^(-6)。现场应用试验表明,该系统具有较好的实用性,且成本低廉、集成度高,具有一定的推广价值。

基于StOMP算法的WSN压缩感知数据重构

分段正交匹配追踪算法(StOMP)运算速度快、计算量小,适用于无线传感器网络(WSN)压缩感知数据重构。为此,分析并研究StOMP算法的门限阈值选取对WSN压缩感知数据重构精度的影响,提出一种StOMP算法门限阈值的自适应调整方法。基于比例-积分-微分方法的思想,根据StOMP算法的当次重构误差计算门限阈值的调整值,并使用调整后的门限阈值重新进行数据重构,重复该过程以提高重构精度。实验结果表明,该方法能快速找到满足误差要求的门限阈值,与采用固定门限阈值的调整方法相比,重构精度更高。

A new method for integration of a Birkhoffian system

The idea of the gradient method for integrating the dynamical equations of a nonconservative system presented by Vujanovic is transplanted to a Birkhoffian system, which is a new method for the integration of Birkhoff＇s equations. First, the differential equations of motion of the Birkhoffian system are written out. Secondly, 2n Birkhoff＇s variables are divided into two parts, and assume that a part of the variables is the functions of the remaining part of the variables and time. Thereby, the basic quasi-linear partial differential equations are established. If a complete solution of the basic partial differential equations is sought out, the solution of the problem is given by a set of algebraic equations. Since one can choose n arbitrary Birkhoff＇s variables as the functions of n remains of variables and time in a specific problem, the method has flexibility. The major difficulty of this method lies in finding a complete solution of the basic partial differential equation. Once one finds the complete solution, the motion of the systems can be obtained without doing further integration. Finally, two examples are given to illustrate the application of the results.

Structural dynamic responses analysis applying differential quadrature method

Unconditionally stable higher-order accurate time step integration algorithms based on the differential quadrature method (DQM) for second-order initial value problems were applied and the quadrature rules of DQM, computing of the weighting coefficients and choices of sampling grid points were discussed. Some numerical examples dealing with the heat transfer problem, the second-order differential equation of imposed vibration of linear single-degree-of-freedom systems and double-degree-of-freedom systems, the nonlinear move differential equation and a beam forced by a changing load were computed, respectively. The results indicated that the algorithm can produce highly accurate solutions with minimal time consumption, and that the system total energy can remain conservative in the numerical computation.

Computation of one—dimensional consolidation of double layered ground using differential quadrature method

The authors give the solution to the problem of one-dimensional conso l idation of double-layered ground with the use of the differential quadrature me t hod. Case studies showed that the computational results for pore-water pressure in soil layer agreed with those of analytical solution; and that in the computat ional results for the interface of soil layer also agreed with those of the anal ytical solution except for the small discrepancies during shortly after the star t of computation. The advantages of the solution presented in this paper are tha t compared with the analytical solution, it avoids the cumbersome work in solvin g the transcendental equation for eigenvalues, and in the case of the Laplace transform s olution, it can resolve the precision problem in the numerical solution of long time inverse Laplace transform. Because of the matrix form of the solution in th is paper, it is convenient for formulating computational program for engineering practice. The formulas for calculating double-layered ground consolidation may be easily extended to the case of multi-layered soils.

Application of the Generalized Differential Quadrature Method in Solving Burgers' Equations

The aim of this paper is to obtain numerical solutions of the one-dimensional,two-dimensional and coupled Burgers' equations through the generalized differential quadrature method(GDQM).The polynomial-based differential quadrature(PDQ) method is employed and the obtained system of ordinary differential equations is solved via the total variation diminishing Runge-Kutta(TVD-RK) method.The numerical solutions are satisfactorily coincident with the exact solutions.The method can compete against the methods applied in the literature.

Numerical Solutions of a New Type of Fractional Coupled Nonlinear Equations

In this paper, we investigate a new type of fractional coupled nonlinear equations. By introducing the fractional derivative that satisfies the Caputo＇s definition, we directly extend the applications of the Adomian decomposition method to the new system. As a result, with the aid of Maple, the realistic and convergent rapidly series solutions are obtained with easily computable components. Two famous fractional coupled examples： KdV and mKdV equations, are used to illustrate the efficiency and accuracy of the proposed method.

Application of pH control to a tubular flow reactor

Tubular flow reactors are mainly used in chemical industry and waste water discharged units. Control of output variables is very difficult because of the existence of high dead-time in these types of reactors. In the present work, sodium hydroxide and acetic acid solutions were sent to the tubular flow reactor. The aim was to control p H at 7 in the nonlinear region. The p H control of a tubular flow reactor with high time delay and a highly nonlinear behavior in p H neutralization reaction was investigated experimentally in the face of the various load and set point changes. Firstly, efficiency of conventional Proportional-Integral-Derivative(PID) algorithm in the experiments was tested. Then self-tuning PID(STPID) control system was applied by using the ARMAX model. The model parameters were calculated from input–output data by using PRBS signal as disturbance and Bierman algorithm. Lastly, the experimental fuzzy control of p H based on fuzzy model was achieved to compare the success of fuzzy approach with the performance of other control cases studied.

A NOTE ON STABILITY OF THE SPLIT-STEP BACKWARD EULER METHOD FOR LINEAR STOCHASTIC DELAY INTEGRO-DIFFERENTIAL EQUATIONS

In the literature （Tan and Wang, 2010）, Tan and Wang investigated the convergence of the split-step backward Euler （SSBE） method for linear stochastic delay integro-differential equations （SDIDEs） and proved the mean-square stability of SSBE method under some condition. Unfortu- nately, the main result of stability derived by the condition is somewhat restrictive to be applied for practical application. This paper improves the corresponding results. The authors not only prove the mean-square stability of the numerical method but also prove the general mean-square stability of the numerical method. Furthermore, an example is given to illustrate the theory.

An h-p Petrov-Galerkin finite element method for linear Volterra integro-differential equations

We analyze an h-p version Petrov-Galerkin finite element method for linear Volterra integrodifferential equations. We prove optimal a priori error bounds in the L2- and H1-norm that are explicit in the time steps,the approximation orders and in the regularity of the exact solution. Numerical experiments confirm the theoretical results. Moreover,we observe that the numerical scheme superconverges at the nodal points of the time partition.

Method of characteristics and first integrals for systems of quasi-linear partial differential equations of first order

Given a set of independent vector fields on a smooth manifold, we discuss how to find a function whose zero-level set is invariant under the flows of the vector fields. As an application, we study the solvability of overdetermined partial differential equations: Given a system of quasi-linear PDEs of first order for one unknown function we find a necessary and sufficient condition for the existence of solutions in terms of the second jet of the coefficients. This generalizes to certain quasi-linear systems of first order for several unknown functions.

高速公路大区段交通事故预测模型研究

针对交通事故记录位置精度较低和路段划分过短可能引起的分析结论偏差问题,探讨了大区段划分条件下高速公路交通事故预测模型的构建方法。结合辽宁省5条高速公路的交通事故数据和道路交通条件数据,提出了基于高速公路天然节点(互通式立交和服务区)的大区段划分方法。构建了处理大区段内指标异质性的模型变量,应用积分-微分方法确定了变量模块,进而利用负二项回归方法建立了高速公路交通事故预测模型。研究表明:在大区段条件下,年平均日交通量、累积纵坡和标志密度等变量的事故预测模块为Hoerl函数,累积曲率为幂函数,而挖方段比例为指数函数;路段长度、年平均日交通量、累积纵坡和标志密度等因素对大区段上的交通事故发生具有显著影响,且考虑这些变量的模块式模型具有较高的预测精度。