Modal spectral element formulation for axially moving plates subjected to in-plane axial tension

The use of frequency-dependent spectral element matrix (or dynamic stiffness matrix) in structural dynamics is known to provide very accurate solutions, while reducing the number of degrees-of-freedom to resolve the computational and cost problems. Thus, in the present paper, the modal spectral element is formulated for thin plates moving with constant speed under a uniform in-plane axial tension. The concept of the Kantorovich method is used to formulate the modal spectral element matrix in the frequency-domain. The present modal spectral element is then evaluated by comparing its solutions with exact analytical solutions as well as with FEM solutions. The effects of the moving speed and the in-plane tension on the dynamic characteristics of a moving plate are investigated numerically.     

A real-time self-tuning web tension regulation scheme

A self-tuning control scheme is proposed for tension regulation in a web transport system. A computationally efficient self-tuning method is first described. The frequency domain model of the plant is then described. Simulations of the on-line tuning are presented. The paper closes with a discussion of cognizant real-time implementation issues.     

Adaptive vibration isolation for axially moving strings: theory and experiment

High-speed transport of continuous materials such as belts, webs, filaments, or bands can cause unwanted vibration. Vibration control for these systems often focuses on restricting the response resulting from external disturbances (e.g. support roller eccentricity or aerodynamic excitation) to areas not requiring high precision positioning. This paper introduces vibration controllers for an axially moving string system consisting of a controlled span coupled to a disturbed span via an actuator. The system model includes a partial differential equation for the two spans and an ordinary differential equation for the actuator. Exact model knowledge and adaptive isolation controllers, based on Lyapunov theory, regulate the controlled span from bounded disturbances in the adjacent, uncontrolled span. Assuming distributed damping in the uncontrolled span, the exact model knowledge and adaptive controllers exponentially and asymptotically drive the controlled span displacement to zero, respectively, while ensuring bounded uncontrolled span displacement and control force. Experiments demonstrate the effectiveness of the proposed controller in isolating the controlled span from disturbances and damping the controlled span displacement.     

Transverse vibration of pre-tensioned nonlocal nanobeams with precise internal axial loads

This paper investigates the transverse vibration of a simply supported nanobeam with an initial axial tension based on the nonlocal stress field theory with a nonlocal size parameter. Considering an axial elongation due to transverse vibration, the internal axial tension is not precisely equal to the external initial tension. A sixth-order nonlinear partial differential equation that governs the transverse vibration for such nonlocal nanobeam is derived. Using a perturbation method, the relation between nat...     

Robust boundary control of an axially moving string by using a PR transfer function

In this note, a scheme for the vibration suppression of a translating string using a positive real (PR) transfer function is investigated. The transverse vibration of the string is controlled by hydraulic touch-rolls located at the right end of the string. The mathematical model of the system, which consists of a hyperbolic partial differential equation (PDE) describing the dynamics of the moving string and an ordinary differential equation (ODE) for the actuator dynamics, is derived by using Hamilton's principle for translating continua. The transfer function of the proposed boundary controller is a nonproper but PR function. The asymptotic stability of the closed-loop system in the presence of output disturbance is proved.     

Modelling and control for a class of axially moving nonuniform system

In this paper, we deal with the active control problem for a class of axially moving system. The system is nonuniform due to the spatial-varying mass and spatiotemporally varying tension. The infinite dimensional model of the nonuniform system represented by the hybrid partial-ordinary differential equations is derived with consideration of the spatiotemporally varying distributed disturbance. To suppress the vibration of the nonuniform system, full state feedback boundary control is developed. For the case that the system states cannot be measured, output feedback boundary control is proposed by using the high-order observers for the estimation of the unmeasurable states. The disturbance observer is introduced to mitigate the effects of the boundary disturbance. With the proposed boundary control, the stability of the closed-loop nonuniform system is achieved through rigorous analysis and the uniform boundedness of the all closed-loop signals is guaranteed. Numerical simulations are performed to validate the performance of the control scheme proposed.     

张力控制在纸机传动控制系统中的研究

介绍了张力控制在造纸机变频传动控制系统中的程序设计与应用。配合速度控制，张力控制更有效的解决成品纸生产的质量状况。更好的提高了系统的精确性和稳定性。     

A structured light vision system for out-of-plane vibration frequencies location of a moving web

In this paper, we address the problem of the detection of out-of-plane web vibrations by means of a single camera and a laser dots pattern device. We have been motivated by the important economical impact of web vibrations phenomena which occur in winding/unwinding systems. Among many sources of disturbances, out-of-plane vibrations of an elastic moving web are well-known to be one of the most limiting factors for the velocity in the web transport industry.The new technique we proposed for the contact-less estimation of out-of-plane web vibration properties and during the winding process is the main contribution of this work. As far as we know, this is the first time a technique is proposed to evaluate the vibrations of a moving web with a camera. Vibration frequencies are estimated from distance variations of a web cross-section with respect to the camera.Experiments have been performed on a winding plant for elastic fabric with a web width of 10 cm. Distances from the web surface to the camera have been estimated all along an image sequence and the most significant frequencies have been extracted from the variations of this signal (forced and free vibrations) and compared to those provided with strain gauges and also with a simple elastic string model, in motion.     

Modeling of web conveyance systems for multivariable control

A distributed parameter model of the lateral dynamic behavior of a moving web in an n-roller system is proposed. A span of web moving longitudinally and under tension is modeled as a beam with shear flexibility (Timoshenko beam). A quasistatic simplification of the model is made on the basis of spectral separation. Boundary conditions at the web-roller interface are considered. Actuator dynamics are introduced through the formulation of the boundary conditions. Closed-loop simulations using a state-space version of the simplified model are in agreement with experimental results     

移动质量激励悬臂梁振动主动控制系统

利用压电材料的正逆压电效应,实现了移动质量激励悬臂梁振动主动控制;建立了压电元传感方程和作动方程,进一步将其转化为状态空间模型中的状态方程和输出方程;设计了基于线性二次型最优控制(LQR)策略的振动主动控制器,以TMS320VC33 DSP芯片为核心组建了相应的硬件电路。实验结果表明:采用压电自感作动器可很好地抑制移动质量激励引起的悬臂梁振动。     

基于PC的张力控制系统

张力控制是造纸、塑料、纺织工业等卷绕自动化生产线中的关键技术。本文从墙纸生产过程的实际出发，研制了一套基于PC张力控制系统。经过实际生产运行证明，该系统张力控制稳定，实时性好，运行可靠。实现了墙纸生产过程的最优控制。     

Boundary control of container cranes from the perspective of controlling an axially moving string system

The control objectives in this paper are to move the load of a container crane to its target position and to suppress the transverse vibration of the load. Owing to the fact that the load is hoisted up and down, the crane is modeled as an axially moving string system. The dynamics of the moving string are derived using Hamilton’s principle for systems with changing mass. The Lyapunov function method is used in deriving a boundary control law, where the Lyapunov function candidate takes the form of the total mechanical energy of the system. The boundary control law utilizes the hoisting speed as well as the sway angle of the rope at the gantry side. Through experiment, the effectiveness of the proposed control law is demonstrated particularly in the lift-up process of the load. Recommended by Editorial Board member Dong Hwan Kim under the direction of Editor Hyun Seok Yang. A preliminary version of this work (with Hahn Park) has been presented at the 16th IFAC World Congress, Prague, 2005. This work was supported by Korea Research Foundation Grant No. KRF-2007-314-D00011. Chang-Sei Kim received the B.S. degree in Control and Mechanical Engineering from Pusan National University in 1998, the M.S. degree in Mechanical Design and Production Engineering from Seoul National University in 2000. Since 2000, he has been with Robot Research and Development Team in DSME (Daewoo Shipbuilding and Marine Engineering, Korea, as a researcher. In DSME, he has worked on the development of welding robots, painting robots and factory automation. His current research interests include nonlinear robust control, robotic system, hydraulic systems, and control system applications. Keum-Shik Hong received the B.S. degree in Mechanical Design and Production Engineering from Seoul National University in 1979, the M.S. degree in ME from Columbia University in 1987, and both the M.S. degree in Applied Mathematics and the Ph.D. degree in ME from the University of Illinois at Urbana-Champaign in 1991. He served as an Associate Editor for Automatica (2000–2006) and as an Editor for the International Journal of Control, Automation, and Systems (2003–2005). Dr. Hong received Fumio Harashima Mechatronics Award in 2003 and the Korean Government Presidential Award in 2007. Dr. Hong’s research interests include nonlinear systems theory, adaptive control, distributed parameter system control, robotics, and vehicle controls.     

Web应用系统中权限控制的研究与实现

分析并比较了当前权限系统设计过程中主要的权限控制模型,指出了各自的特点和应用局限性.针对当前Web应用系统中存在的用户变化较多而角色相对变化较少的情况,提出并实现了一种扩展了的基于角色的访问控制方法,能够根据登录用户权限的不同生成不同的用户界面,并给出了该方法在项目开发中的实际应用.项目开发的实践结果表明,该方法可有效地用于Web应用系统的权限控制管理中.     

Model-based feedforward register control of roll-to-roll web printing systems

Roll-to-roll (R2R) printing press provides a continuous printing process to print the multi-color patterns onto a web. To correctly print patterns on webs without the register error, it is necessary to regulate the web tension and transport velocity. In this paper, a mathematical model is built for R2R web printing system, and a model-based feedforward PD (MFPD) control method is proposed to reduce the effects of interaction in adjacent print units whose print cylinders are driven by electrical line shafts and is compared with other control methods. The proposed control method is applied to an industrial 7-color gravure printing register system. The register error can be controlled in the range of ±0.1 mm at a steady high speed, which meets the requirement of modern industrial application.     

Stabilization analysis of a generalized nonlinear axially moving string by boundary velocity feedback

This paper addresses vibration suppression of an axially moving nonlinear string subject to boundary control at either the downstream or the upstream end. The equation of motion and the boundary conditions are derived from Hamilton's Principle, using the exact expression of the strain to describe the geometrical nonlinearity due to the finite transverse deformation. We can approximate this model by various simpler models found in the literature. We show that the oscillations of the moving string can be stabilized exponentially via linear negative velocity feedback acting at one end of the string. Our proofs rely on Lyapunov's direct method, using a carefully constructed energy functional.     

Reliable regulation in centralized control systems

This paper addresses the design of a reliable control system for a linear, asymptotically stable plant. Specifically, the considered problem consists in finding a regulator which guarantees asymptotic stability, signal tracking and disturbance rejection when all the instrumentation is operational, and ensures that these properties are preserved, to the maximum possible extent, when an arbitrary number of sensors and/or actuators faults occur, that is, some of the feedback loops open. With reference to a centralized control structure and exogenous signals with multiple poles on the imaginary axis, the paper supplies a necessary and sufficient condition for the problem to admit a solution, and a possible least order regulator.     

Reliable regulation in decentralised control systems

This article addresses the design of decentralised regulators which supply the control systems with signal tracking and disturbance rejection. This property has to be attained, to the maximum possible extent, even when instrumentation faults occur, thus causing the opening of some feedback loops. The problem is tackled for LTI asymptotically stable plants, subject to perturbations, under the assumption that the Laplace transforms of the exogenous signals have multiple poles on the imaginary axis. The proposed regulator is composed of an LTI nominal controller supervised by a reconfiguration block. Once the actions of the reconfiguration block have been settled, the synthesis of the nominal controller is reformulated as a suitable regulation problem. A constructive sufficient condition for its solvability is established. This condition turns out to be also necessary if the exogenous signals are polynomial in time.     

Adaptive nonstationary positioning control of vibration systems by means of solutions of time-varying Riccati equations

The author’s previous study proposed an efficient design method of time-varying gain type controller using the solutions of time-varying Riccati equations (TVREs) and its application to positioning control of time-invariant vibration systems. The responses of this method become similar to the responses of conventional nonstationary optimal regulators (NORs) which are effective controllers for positioning of vibration systems. This method generates the solutions of a TVRE and the responses of a controlled object simultaneously. The time-varying gains are obtained by real-time computations in actual implementations. This feature is convenient for the realization of some adaptive control. However, such a control method has not been fully addressed yet. This study proposes an adaptive nonstationary control (ANSC) method based on the feature of the previous study. We choose a cart with a time-varying vibration system whose natural frequency is time-varying as a controlled object example. The positioning and residual vibration reduction of the object are discussed in this paper. The effectiveness of the ANSC method is verified by simulations and experiments.     

Self-1 through self-learning: Overload control for distributed web systems

Overload control is a challenging problem for web-based applications, which are often prone to unexpected surges of traffic. Existing solutions are still far from guaranteeing the necessary responsiveness under rapidly changing operative conditions. We contribute an original self-1 overload control (SOC) algorithm that self-configures a dynamic constraint on the rate of incoming new sessions in order to guarantee the fulfillment of the quality requirements specified in a service level agreement (SLA). Our algorithm is based on a measurement activity that makes the system capable of self-learning and self-configuring even in the case of rapidly changing traffic scenarios, dynamic resource provisioning or server faults. Unlike other approaches, our proposal does not require any prior information about the incoming traffic, or any manual configuration of key parameters.We ran extensive simulations under a wide range of operating conditions. The experiments show how the proposed system self-protects from overload, meeting SLA requirements even under intense workload variations. Moreover, it rapidly adapts to unexpected changes in available capacity, as in the case of faults or voluntary architectural adjustments. Performance comparisons with other previously proposed approaches show that our algorithm has better performance and more stable behavior.