基于瞬时最优控制神经网络的建筑结构主动控制研究

改进一种基于瞬时最优控制的神经网络训练算法。本方法以瞬间最优控制价值函数最小化为训练目标,考虑了地震输入的能量,利用最速下降梯度法计算权值的改变量,并对敏感度矩阵进行近似处理,可解决神经网络控制中神经网络控制器难以获得的训练输入/输出样本对的难题。该方法适合多输入/多输出结构体系,整个推导过程都是针对此体系进行的。文中通过对一个三层框架结构体系进行有效的仿真计算,说明了算法的有效性。     

有限观测绝对加速度响应下剪切框架在未知地震作用下损伤诊断

针对框架结构的绝对加速度响应部分观测、地震作用未观测的情况,提出一种多层剪切框架结构诊断的方法。该方法先依次采用扩展卡尔曼估计和递推最小二乘对一层以上结构的扩展状态向量和未知作用力进行递推;然后利用结构频率特征方程,对第一层的结构参数进行估计;最后基于数值求解一阶微分方程,识别未观测的地震荷载。算例表明, 该方法能够很好识别出结构参数和地震输入,通过跟踪结构刚度参数的退化,对未知地震作用下结构损伤进行诊断。     

基于随机游走和输入估计方法的振动主动控制研究

摘要:为了研究未知外扰作用下动力学系统的振动主动控制问题,结合Kalman滤波和LQG(linear quadratic Gaussian)控制方法,提出了基于随机游走和输入估计的振动主动控制方法。为尽量获取未知外扰信息,首先采用随机游走模型构建求知外扰信号的离散递推形式,并将其作为辅助状态引进受控系统的状态方程。然后,借助具有信号识别和跟踪能力Kalman滤波原理,对含有辅助状态的系统进行状态估计,从而得到未知外扰的估计值．根据系统已知测量输出、未知状态及外扰的估计值构造系统目标函数,采用ＬＱＧ方法求解系统最优控制输入。最后针对sdof模型进行数值仿真。结果表明受控系统在非随机和随机外激励下都具有良好的控制效果,且控制精度优于传统ＬＱＧ方法     

Optimal control of vortex shedding using low‐order models. Part I—open‐loop model development

An approach to developing active control strategies for separated flows is presented. The methodology proposed is applied to the incompressible unsteady wake flow behind a circular cylinder at a Reynold's number of 100. Control action is achieved via cylinder rotation. Low‐order models which are amenable to control and which incorporate the full non‐linear dynamics are developed by applying the proper orthogonal decomposition technique to data provided by numerical simulation. This process involves extensions to the usual POD approach and the results are therefore assessed for two ‘open‐loop’ test cases. The predictions are found to be satisfactory for control purposes, assuming the model can be reset periodically. The use of these models for optimal control is discussed in a companion paper, Part II. Copyright © 1999 John Wiley & Sons, Ltd.     

Optimal shape control of functionally graded smart plates using genetic algorithms

This paper deals with optimal shape control of functionally graded smart plate containing patches of piezoelectric sensors and actuators. The genetic algorithm (GA) is designed to search for optimal actuator voltage and displacement control gains for the shape control of the functionally graded material (FGM) plates. The work extends the earlier finite element formulations of the two leading authors, so that it can be readily treated using genetic algorithms. Numerical results have been obtained to study the effect of the shape control of the FGM plates under a temperature gradient by optimising (i) the voltage distribution for the open loop control, and (ii) the displacement control gain values for the closed loop feedback control. The effect of the constituent volume fractions of zirconia, through varying the volume fraction exponent n, on the optimal voltages and gain values has also been examined.     

一种严密的结构最优控制极值条件及算法实现

针对结构振动控制的特点,导出了可用于时域响应最优控制的极值条件。该组表达式对于采用线性二次型最优控制的强迫振动系统而言,是概念上严密的极值条件。对比了几种现有最优控制算法的思路,介绍了对结构控制算法建模思路进行改进的技术要点。利用伴随方程与状态方程形式上的相似性,用数值方法实现了一种新的结构最优控制算法。选用由作者承担设计过的三个实际隔震工程作为算例,对比了输入三种不同地震波时各种算法在模型表达和减震效果上的几个重要特点。     

Stochastic control of hysteretic structural systems

A method of stochastic optimal control of hysteretic structural systems under earthquake excitations is presented. Stochastic estimation and control problems are formulated in the form of Itô stochastic differential equations on the basis of the theory of continuous Markov processes. The conditional moment equations given observation data are derived for nonlinear filtering, and are closed by introducing appropriate analytical form of the conditional probability density functions of the state variables. Under the assumption that the admissible controls are expressed as functions of the conditional moment functions the Bellman equation is derived. If the spatial variables of the Bellman equation are defined by a part of the full set of conditional moment functions appearing in the closed moment equations, the resulting Bellman equation is coupled with conditional moment equations both for filtering and for prediction. The Gaussian and non-Gaussian stochastic linearization techniques combined with simple solution techniques to the Bellman equation are examined to solve the Bellman equation or extended Riccati equations without prediction procedures.     

高速铁路轮轨作用力的全息辨识模型

结合最优控制理论、卡尔曼滤波方法以及轮轨蠕滑理论,该文建立了轮轨作用力的全息辨识模型,并将模型的反演结果与动力学解答和实验测量结果作对比,验证了模型的适用性。首先,根据车辆系统的状态空间方程,设计一个最优化加速度状态跟踪器,将轮轨作用力辨识问题转换成为最优控制策略的设计问题;然后,利用SVD （singular value decomposition奇异值分解）分解技术对最优控制问题进行逆向求解,完成系统的动态载荷预测值的辨识;进一步结合卡尔曼滤波技术及加速度测试值,对辨识动载荷预测值进行正向修正,得到左、右轮轨垂向力及轮轴横向力;最后,结合轮轨蠕滑理论,将左、右轮轨横向力转换为到左、右轮轨垂向力及轮对横移量的函数,消减不适定性,从而能够分别辨识出轮轨左、右的横向力。辨识模型得到的结果与动力学解答的相关系数分别达到0.65、0.8以上,与实测载荷的相关系数分别达到0.51、0.69以上。     

Multi‐rate digital control for a cascaded system consisting of two subsystems with different input time delays

Abstract

This paper presents a multi‐rate state‐space control scheme for digital control of a cascaded continuous‐time system with fractional time delays. First, a discrete‐time state‐space representation of a continuous‐time system with a fractional input delay is established. Based on the time‐delay digital modelling, an ideal state reconstructor is also presented such that system states are exactly reconstructed via the measurement histories of inputs and outputs without a state observer. Next, a time‐delay subsystem (designated subsystem 1) with a fast sampling rate is designed to form the inner loop of the overall system, then the designed closed‐loop subsystem 1 is cascaded with a time‐delay open‐loop subsystem 2 with a slow sampling rate. A digital modelling of the time‐delay open‐loop subsystem 2, based on a fast‐rate sampling, is also formed for obtaining the digital modelling of the overall cascaded continuous‐time system by using the block‐pulse function approximation. Then, the fast‐rate overall system is converted into a slow‐rate model via the newly developed model conversion technique. Furthermore, subsystem 2 is separated from the slow‐rate overall system via a linear transformation for achieving a reduced‐order subsystem design. As a consequence, a digital control law is determined on some specific goals for the overall system. The proposed method is suitable for digital control of a multivariable, multi‐rate, time‐delay system in which state variables are not accessible.     

Exploring the Use of Design of Experiments in Industrial Processes Operating Under Closed‐Loop Control

Industrial manufacturing processes often operate under closed‐loop control, where automation aims to keep important process variables at their set‐points. In process industries such as pulp, paper, chemical and steel plants, it is often hard to find production processes operating in open loop. Instead, closed‐loop control systems will actively attempt to minimize the impact of process disturbances. However, we argue that an implicit assumption in most experimental investigations is that the studied system is open loop, allowing the experimental factors to freely affect the important system responses. This scenario is typically not found in process industries. The purpose of this article is therefore to explore issues of experimental design and analysis in processes operating under closed‐loop control and to illustrate how Design of Experiments can help in improving and optimizing such processes. The Tennessee Eastman challenge process simulator is used as a test‐bed to highlight two experimental scenarios. The first scenario explores the impact of experimental factors that may be considered as disturbances in the closed‐loop system. The second scenario exemplifies a screening design using the set‐points of controllers as experimental factors. We provide examples of how to analyze the two scenarios. © 2017 The Authors Quality and Reliability Engineering International Published by John Wiley & Sons Ltd     

有约束复杂随动系统模型建立与控制研究

提出了一种有约束复杂随动系统--小碗摆球系统,并以小碗摆球系统为研究对象,针对有约束复杂随动系统的控制策略进行研究;利用拉格朗日动力学方法建立了小碗摆球系统的动力学模型。在讨论了系统能控和能观性的基础上分别采用鲁棒性双闭环PID控制和基于遗传算法的线性二次型最优控制进行了实际系统控制效果的实验对比,对比结果表明鲁棒性双闭环PID控制器具有更好的鲁棒性和瞬态特性,而遗传算法优化的线性二次型控制具有更好的动态特性。     

包装过程称量信号处理方法研究

目的 为提高包装过程定量称量精度,结合卡尔曼滤波算法和模糊控制原理设计一种称量信号处理方法。方法 定量称量控制系统一般由触摸屏、控制器、称量传感器、变频器等电气设备组成。以传感器信号处理为主要研究对象,提出一种改进卡尔曼滤波算法。采用卡尔曼滤波器实现称量信号中随机噪声的处理。利用模糊控制器来实时监测卡尔曼滤波每次更新后实际方差和理论方差的差值。最后,进行实验研究。结果 实验结果表明,改进卡尔曼滤波的实际性能比较理想,滤波处理前,称量误差最大可以达到2.5%;经滤波处理后,最大称量误差只有0.26%。结论 所述信号处理方法可以有效地降低称量信号噪声,提高称量精度。     

Design and implementation of FPGA-based phase modulation control for series resonant inverters

Owing to the tremendous advances in the digital technology, and improved reliability and performance of the digital control mechanisms, this paper focuses on design and implementation of digital controller using FPGA-based circuit design approach. The digital controller proposed is designed for series resonant inverter used in DC-DC converter applications. Phase modulation technique is proposed for the realization of digital controller on FPGA. The Series Resonant Converter (SRC) is considered in this paper as a preferred converter topology for high power, high voltage power supplies. This paper studies the implementation of phase shift modulation technique using FPGA. The inverter designed, is IGBT based, and Zero Voltage Switching (ZVS) technique is implemented due to reduced stresses on devices and increased efficiency. The phase modulated series resonant inverters (PM-SRC) promotes ZVS operation when its switching frequency is greater than resonant frequency. The designed PM controller is realized using FPGA on which control algorithm and other features of a controller are developed. The series resonant inverter is built and tested for full load under open loop and closed loop conditions at a switching frequency of 20 kHz. The results are presented under varying load conditions. The simulation and the experimental results were found to match closely.     

State‐space characterization of all solutions to a positive real control problem

Abstract

The purpose of this paper is to give a state‐space characterization of all internally stabilizing finite‐dimensional linear time‐invariant output feedback controllers for a given finite‐dimensional linear time‐invariant plant which ensure that the resulting closed‐loop transfer function is extended strictly positive real(ESPR). All such controllers are parameterized by a fixed linear fractional transformation with an ESPR, stable free parameter. The parameterized controllers have a state dimension not less than that of the open‐loop plant. The development uses only elementarily algebraic ideas beginning with a change of variables, an extended version of Kalman‐Yacubovich‐Popov positive real lemma, and Youla parameterization, thus the proofs given are simple and clear.     

Genetic algorithm based optimal design for vibration control of composite shell structures using piezoelectric sensors and actuators

The present article deals with the design of optimal vibration control of smart fiber reinforced polymer (FRP) composite shell structures using genetic algorithm (GA) based linear quadratic regulator (LQR) and layered shell coupled electro-mechanical finite element analysis. Open loop procedure has been used for optimal placement of actuators considering the control spillover of the higher modes to prevent closed loop instability. An improved real coded GA based LQR control scheme has been developed for designing an optimal controller in order to maximize the closed loop damping ratio while keeping actuators voltages within limit. Results show that increased closed loop-damping has been achieved with a large reduction of control effort considering control spillover.     

基于人工鱼群算法的随机结构AMD控制系统LQR权矩阵优化

针对随机结构在平稳随机激励下线性二次最优控制的权参数选取问题,提出了基于人工鱼群算法的随机结构AMD控制系统权矩阵优化设计方法。该方法以结构随机响应和控制力均方值的加权组合为目标函数,考虑了结构和外激励的随机性对于控制效果的影响。其优化结果不仅保证了控制器的控制效果,而且降低了控制效果对于随机参数的敏感性,增强了控制器的鲁棒性。最后结合数值算例,验证了所述方法的有效性和正确性。     

A simple practical analytic design method for multiloop‐controlled PWM switching regulators

Abstract

In this paper, a simple practical analytic method is proposed for designing multiloop‐controlled pulse width modulation (PWM) switching regulators. First, an equivalent single loop gain is presented and an approximate optimal set of closed‐loop poles is suggested according to the given specification such that the familiar design concept of a single‐loop second order system can be applied directly. In particular, closed form expressions of the feedback gains and the unknown parameters of the standard implemented circuit are derived. This renders the implementation problem surprisingly simple. Finally, some experimental results are also presented to demonstrate the effectiveness of the proposed method.     

Closed loop control-based real-time dispatching heuristic on parallel batch machines with incompatible job families and dynamic arrivals

In this paper, a real-time closed loop control dispatching heuristic (RCLC) algorithm is proposed to address the scheduling problem of parallel batch machines with incompatible job families, limited waiting time constraints, re-entrant flow and dynamic arrivals in the diffusion and oxidation areas of a semiconductor wafer fabrication system (SWFS), which is known to be strongly NP-hard. The basis of this algorithm is the information of lots in the buffer when the parallel batch machines are idle and available. In RCLC, if the number of any family lots is less than the maximum batch size, the dispatching heuristic can be seen as a pull–pull–push–push (P⁴) strategy; otherwise, a genetic algorithm (GA). A look-itself strategy, P⁴ strategy and GA can build a closed loop control system. The experiments are implemented on the Petri nets-based real-time scheduling simulation platform of SWFS, and demonstrate the effectiveness of our proposed method.     

基于离散小波变换和Kalman滤波的直升机主减智能状态预测

主减速器（简称“主减”）是直升机传动系统的关键部件,它常处于高转速高负荷的恶劣环境下,对其运行状态进行预测,于直升机的安全性来说至关重要。鉴于此,提出了一种离散小波变换（DWT）、Kalman滤波以及Elman神经网络相结合的直升机主减智能状态预测系统：DWT使用“db44”母小波对振动信号进行分解提取特征向量,Kalman滤波对未来各时刻的特征向量进行预测,Elman神经网络对预测值进行故障辨识和分类。在Kalman滤波算法中,提出了一种新的预测算法,并用实验对该算法组成的系统进行验证,结果表明：该 Kalman滤波算法预测效果好,更适用于对主减的特征向量进行预测;离散小波变换（DWT）、Kalman滤波以及Elman神经网络相结合组成的智能状态预测系统是可行的,它能很好地对主减的未来状态进行预测。     

Optimal design and optimal control of structures undergoing finite rotations and elastic deformations

In this work, we deal with the optimal design and optimal control of structures undergoing large rotations and large elastic deformations. In other words, we show how to find the corresponding initial configuration through optimal design or the corresponding set of multiple load parameters through optimal control, in order to recover a desired deformed configuration or some desirable features of the deformed configuration as specified more precisely by the objective or cost function. The model problem chosen to illustrate the proposed optimal design and optimal control methodologies is the one of geometrically exact beam. First, we present a non‐standard formulation of the optimal design and optimal control problems, relying on the method of Lagrange multipliers in order to make the mechanics state variables independent from either design or control variables and thus provide the most general basis for developing the best possible solution procedure. Two different solution procedures are then explored, one based on the diffuse approximation of response function and gradient method and the other one based on genetic algorithm. A number of numerical examples are given in order to illustrate both the advantages and potential drawbacks of each of the presented procedures. Copyright © 2004 John Wiley & Sons, Ltd.