On-Line Parametric Identification of MDOF Nonlinear Hysteretic Systems

A method based on adaptive estimation approaches is presented for the on-line identification of hysteretic systems under arbitrary dynamic environments. The availability of such an identification approach is crucial for the on-line control and monitoring of time-varying structural systems. Previous work by the writers is extended to handle the general case when no information is available on the system parameters, even the mass distribution. A robust, least-squares-based adaptive identification algorithm, incorporating a Bouc-Wen hysteresis element model with additional polynomial-type nonlinear terms, is used to investigate the effects of persistence of excitation and of under- and overparameterization: challenging problems in realistic applications. In spite of the challenges encountered in the identification of the hereditary nature of the restoring force of such nonlinear systems, it is shown through the use of simulation studies of single-degree-of-freedom and certain multi-degree-of-freedom systems that the proposed approach can yield reliable estimates of the hysteretic restoring force and the hysteretic element model parameters.     

Integrated Genetic Algorithm for Optimization of Space Structures

Gradient‐based mathematical‐optimization algorithms usually seek a solution in the neighborhood of the starting point. If more than one local optimum exists, the solution will depend on the choice of the starting point, and the global optimum cannot be found. This paper presents the optimization of space structures by integrating a genetic algorithm with the penalty‐function method. Genetic algorithms are inspired by the basic mechanism of natural evolution, and are efficient for global‐searches. The technique employs the Darwinian survival‐of‐the‐fittest theory to yield the best or better characters among the old population, and performs a random information exchange to create superior offspring. Different types of crossover operations are used in this paper, and their relative merit is investigated. The integrated genetic algorithm has been implemented in C language and is applied to optimization of three space truss structures. In each case, an optimum solution was obtained after a limited number of iterations.     

Material Identification Procedure for Elastoplastic Drucker–Prager Model

A procedure to identify the material parameters of an elastoplastic model is presented. It aims to predict uniaxial stress–strain curves in tension or compression. The Drucker–Prager model is chosen because of its simplicity. The procedure takes into account the hardening/softening regime by varying two physical parameters related to the model: the cohesion and the friction angle.     

Modified Cross-Correlation Method for the Blind Identification of Structures

Recently, blind source separation (BSS) methods have gained significant attention in the area of signal processing. Independent component analysis (ICA) and second-order blind identification (SOBI) are two popular BSS methods that have been applied to modal identification of mechanical and structural systems. Published results by several researchers have shown that ICA performs satisfactorily for systems with very low levels of structural damping, for example, for damping ratios of the order of 1% critical. For practical structural applications with higher levels of damping, methods based on SOBI have shown significant improvement over ICA methods. However, traditional SOBI methods suffer when nonstationary sources are present, such as those that occur during earthquakes and other transient excitations. In this paper, a new technique based on SOBI, called the modified cross-correlation method, is proposed to address these shortcomings. The conditions in which the problem of structural system identification can be posed as a BSS problem is also discussed. The results of simulation described in terms of identified natural frequencies, mode shapes, and damping ratios are presented for the cases of synthetic wind and recorded earthquake excitations. The results of identification show that the proposed method achieves better performance over traditional ICA and SOBI methods. Both experimental and large-scale structural simulation results are included to demonstrate the applicability of the newly proposed method to structural identification problems.     

重大危险源的辩识与控制

根据重大危险源的定义和分级标准,确定包钢板稀土钢板材公司重大危险源辨识范围,通过理论计算和分析危险化学品、锅炉、容器、管道的实际存储量及工作压力,明确了现有的重大危险源数量和等级。同时制定重大危险源控制措施,降低事故风险,保障实现持续安全生产发展目标。     

Parameter Identification Procedure for Heterogeneous Viscoelastic Composites Using Iterative Functions

This paper presents a new numerical procedure for the determination of the viscoelastic compliance properties of a matrix phase from a simple three-point bending test on a composite beam. The composite is modeled as elastic inclusions randomly dispersed throughout a viscoelastic matrix. It is also assumed that the spatial distribution of the inclusions in the composite is known or can be determined. Zevin’s method of iterative functions is proposed for the determination of the matrix properties. Following a detailed explanation of the proposed scheme, a numerical verification is performed using three-dimensional finite-element (FE) analysis simulations. The proposed scheme was applied to the experimentally obtained creep compliance of the asphalt concrete beam. The obtained viscoelastic properties of the asphalt binder matrix phase were used as input into the FE model to simulate the behavior of the composite beam. An excellent comparison between the experimental data and the predicted beam deflections was observed. This shows that the proposed method is robust and it can be implemented to solve identification problems for viscoelastic composite materials.     

Time-Delayed Positive Velocity Feedback Control Design for Active Control of Structures

In this paper we present and propose a design methodology that uses intentional time delays for the active control of structures. We use here positive velocity-feedback, time-delayed control and show that its performance is, in general, superior to the previously developed methodology of using time delayed, negative velocity-feedback control. A detailed study carried out in this paper of the nonsystem poles and their interaction with the system poles reveals the reasons for this. Analytical results related to performance and stability of the new method are presented. We apply the time delayed positive velocity feedback active control methodology to a multidegree-of-freedom system subjected to the S00E component of ground acceleration recorded during the El Centro 1940 earthquake. The excellent behavior in terms of stability, performance, and control efficiency that is demonstrated by our time-delayed control design as well as its facile implementation makes it attractive for earthquake hazard mitigation in a practical sense.     

Least-Squares Estimation with Unknown Excitations for Damage Identification of Structures

System identification and damage detection for structural health monitoring of civil infrastructures have received considerable attention recently. Time domain analysis methodologies based on measured vibration data, such as the least-squares estimation and the extended Kalman filter, have been studied and shown to be useful. The traditional least-squares estimation method requires that all the external excitation data (input data) be available, which may not be the case for many structures. In this paper, a recursive least-squares estimation with unknown inputs (RLSE-UI) approach is proposed to identify the structural parameters, such as the stiffness, damping, and other nonlinear parameters, as well as the unmeasured excitations. Analytical recursive solutions for the proposed RLSE-UI are derived and presented. This analytical recursive solution for RLSE-UI is not available in the previous literature. An adaptive tracking technique recently developed is also implemented in the proposed approach to track the variations of structural parameters due to damages. Simulation results demonstrate that the proposed approach is capable of identifying the structural parameters, their variations due to damages, and unknown excitations.     

面向可持续发展的半导体制造的集成产品和过程控制

Semiconductor fabrication is a manufacturing sequence with hundreds of sophisticated unit operations and it is always challenged by strategy development for ensuring the yield of defect-free products. In this paper, an advanced control strategy through integrating product and process control is established. The proposed multiscale scheme contains three layers for coordinated equipment control, process control and product quality control. In the upper layer, online control performance assessment is applied to reduce the quality variation and maximize the overall product performance (OPP). It serves as supervisory control to update the recipe of the process controller in the middle layer. The process controller is designed as an exponentially weighted moving average (EWMA) run-to-run controller to reject disturbances, such as process shift, drift and tool worn out, that are exerted to the operation. The equipment in the process is individually controlled to maintain its optimal operational status and maximize the overall equipment effectiveness (OEE), based on the set point given by the process controller. The efficacy of the proposed integrated control scheme is demonstrated through case studies, where both the OPP (for product) and the OEE (for equipment) are enhanced.     

Motion Control of Space Structures

A new area of civil engineering is emerging as we begin to establish a permanent presence in space. The new area of civil engineering is the motion control of space structures. This paper describes why the motion control of space structures is fundamentally a civil engineering problem.     

Multicriteria Optimization for Design of Structures with Active Control

This paper describes a method to design a structure and control system simultaneously using a multiobjective optimization approach based on global criteria. The control system was based on a modified linear quadratic regulator (LQR) with bounds placed on the control forces to simulate limitations of real actuators. In the design of the control system, the state space equations were integrated using a Runge-Kutta method for a specified initial boundary condition. The structural weight, the weight of the actuators, the time required to suppress an initial disturbance, and the performance index were considered as different objective functions to be optimized. The design variables were the bounds on the maximum values of the control force, the cross-sectional areas of the structural elements, and elements of the weighting matrices in the control design. As an example to illustrate the application of the approach, a box beam idealized by rod elements was used. The actuators and sensors were collocated and assumed to be embedded in structural elements. The results are presented for optimum designs obtained by changing different parameters in the definition of the global criteria.     

1号高炉过程检测与控制技术进步

介绍1号高炉炉内摄像系统、炉顶十字测温装置、风口小套检漏系统、风口成像系统等仪表、过程检测和控制系统的特点和应用效果。     

过程控制抗干扰技术的探讨

干扰是过程控制中经常遇到的不利因素，为了使自动控制系统安全可靠地运行，必须提高自动控制系统的抗干扰能力，探讨了抗干扰的各种措施与技术。     

全燃气工业蒸汽锅炉的自动化控制过程实现

结合天津钢铁公司14t/h锅炉计算机控制系统,论述了蒸汽锅炉计算机控制系统的工作原理,锅炉控制中的几个重要的控制回路,及各个环节控制的实现方法。     

Optimal Control Method for Seismically Excited Building Structures with Time-delay in Control

Optimal control method for seismic-excited linear structures with time delay in control is investigated in this paper. Using zero-order holder, the continuous time differential equation with time delay can be transformed into a standard discrete time form that contains no time delay in terms of two cases that the time delay is integer and noninteger times of sampling period, respectively. The continuous time performance index is used in the design of the optimal controller and it is also transformed into discrete form. Then, the optimal controller can be designed according to the classical discrete LQR method. The controller obtained contains not only current step of state feedback but also a linear combination of some former steps of control. Because the optimal controller is obtained directly from the time-delay differential equation, it is prone to guarantee the stability of the controlled structures. Furthermore, this control method is available for case of large time delay. The performance of the control method proposed and system stability are both demonstrated by numerical simulation results. Simulation results demonstrate that the control method proposed in this paper is a viable and attractive control strategy for application to seismically excited linear structures.     

Adaptive Dynamic Surface Control for Integrated Missile Guidance and Autopilot

Integrated guidance and control for homing missiles utilizing adaptive dynamic surface control approach is considered based on the three channels independence design idea.A time-varying integrated guidance and control model with unmatched uncertainties is first formulated for the pitch channel, and an adaptive dynamic surface control algorithm is further developed to deal with these unmatched uncertainties.It is proved that the proposed feedback controller can ensure not only the accuracy of target interception,but also the stability of the missile dynamics.Then, the same control approach is further applied to the control design of the yaw and roll channels.The 6-degree-of-freedom (6-DOF) nonlinear missile simulation results demonstrate the feasibility and advantage of the proposed integrated guidance and control design scheme.     

Parallel Algorithms for Integrated Structural/Control Optimization

Optimization of combined structural and control systems is a complex problem requiring an inordinate amount of computer‐processing time, especially the solution of the eigenvalue problem of a general unsymmetric square real matrix with complex eigenvalues and eigenvectors, which is frequently used in such problem. The few algorithms presented in the literature thus far have been applied to small structures with a few members and controllers only. Parallel processing on new‐generation multiprocessor computers provides an opportunity to solve large‐scale problems. In this paper, the integrated structural and control optimization problem is formulated by including constraints on displacements, stresses, and closed‐loop eigenvalues and the corresponding damping factors. Then, parallel algorithms are presented for integrated optimization of structures on shared‐memory multiprocessors such as the Cray YMP 8/864 supercomputer. In particular, parallel algorithms are presented for the solution of complex eigenvalue problems encountered in structural control problems using the method of matrix iteration for dominant eigenvalue(s). The solution is divided into two parts. The first part is the iteration for dominant eigenvalue(s) and the corresponding eigenvector(s) and the second part is the reduction of the matrix to obtain the smaller eigenvalue(s) and the corresponding eigenvector(s).