Physical modelling and control of lateral web position for wallpaper making processes

This paper presents a modelling and control algorithm for the lateral movement of web using a pivoting guider, where an accurate lateral positioning is important for web conveyor systems so as to achieve a high productivity and improve the product quality. The process considered is the hot embosser for the polyvinyl chloride-based materials where a steering guide is used for the in-register embossing. A new theoretical model is developed by regarding a moving web as a beam with a very small, but finite thickness. This leads to a transfer function that has four complex poles and two zeros with a time delay. This model has been validated through real experiments. The design of a Smith predictive control scheme has been made that shows, from a number of real-time applications, a high potential in speeding up the response of the pivoting guider and reducing the lateral variations of the moving web.     

移动荷载作用下非线性基础梁内共振分析

研究了有限长弹性基础上梁在移动载荷作用下的内共振响应.建立了移动集中力激励的非线性粘弹性基础支承的有限长Euler-Bernoulli梁模型,并对非线性偏微分方程进行离散,在第三阶固有频率与第一阶固有频率成三倍关系时,采用多尺度方法导出了3:1内共振的可解性条件,研究了有无移动载荷时基础阻尼和非线性刚度对梁内共振条件下自由振动响应和受迫振动响应的影响规律.在此基础上,应用Lyapunov第一方法确定了系统的稳定性条件.     

A twin shear beam model for double chord RHS joints

A finite element elasto-plastic analysis of a twin shear beam model, developed to shed light on the behavior of separated double chord gap joints of rectangular hollow sections (RHS), is presented. The model treats a single beam member as composed of a plate simulating its inner web and a channel representing top and bottom flanges and the outer web. The twelve degrees of freedom (DOF) nonconforming plate bending element and the eight DOF plane stress elements are used to form a plate element for the inner web, while the channel consists of a grillage of beam elements. The analysis, extended beyond the elastic limit, accounts for strain hardening and material nonlinearity. A comparison of theoretical predictions with the experimental results of 24 specimens shows generally good agreement. The mean ratios of theoretical to experimental values are 0.97 and 0.87 for elastic stiffness and carrying capacity measured at a post elastic deformation limit.     

Multivariable Adaptive Control of the Rewinding Process of a Roll-to-roll System Governed by Hyperbolic Partial Differential Equations

In this paper, an active control scheme for the rewinding process of a roll-to-roll (R2R) system is investigated. The control objectives are to suppress the transverse vibration of the moving web, to track the desired velocity profile, and to keep the desired radius value of a rewind roller. The bearing coefficient in the rewind shaft is unknown and the rotating elements in the drive motor are various. The moving web is modeled as an axially moving beam system governed by hyperbolic partial differential equations (PDEs). The control scheme utilizes two control inputs: a control force exerted from a hydraulic actuator equipped with a damper, and a control torque applied to the rewind roller. Two adaptation laws are derived to estimate the unknown bearing coefficient and the bound of variations of the rotating elements. The Lyapunov method is employed to prove the robust stability of the rewind section, specifically the uniform and ultimate boundedness of all of the signals. The effectiveness of the proposed control schemes was verified by numerical simulations.     

Finite element analysis of air-sheet interactions and flutter suppression devices

A computational procedure is developed to analyze the vibration of an axially moving web, controlled through self-acting air bearings. The Galerkin finite element method is employed for the spatial discretization of both the moving web and thin air layers. The predictor-corrector method is also implemented along with the Newton-Raphson iteration for the time integration. It is shown that the pressurized air layers between the moving web and bearing surfaces can significantly reduce the transverse web deflection and provide a means of effective stabilizing. Some comparisons with results obtained using ADINA are presented. The computational algorithm introduced in this paper can be used to optimize both bearing-geometry designs and spatial locations.     

A mathematical model to predict surface roughness and pattern thickness in roll-to-roll gravure printed electronics

The roll-to-roll printing processes have recently been applied for the manufacturing of printed electronics due to their advantages, such as their high-throughput capabilities and low associated costs. In a roll-to-roll printing machine, a web or substrate is moved from an unwinding roll to a winding roll. During printing, the operating tension is important for correct substrate handling to prevent substrate defects, such as wrinkles, scratches and breaks. Accordingly, the operating conditions of the moving web can affect the quality of the printed pattern. In this study, a mathematical model has been developed to predict the thickness and surface roughness of printed patterns. Because the dynamics of roll-to-roll printing systems are complicated and non-linear, a statistical model is preferred. A full factorial method has been used with four independent variables: operating tension, print speed, ink viscosity and theoretical transfer volume. This model accurately predicted the surface roughness and thickness of the printed pattern.     

Reality of virtual damage identification based on neural networks and vibration analysis of a damaged bridge under a moving vehicle

Presented here is a reality of virtual damage detection and vibration behaviour study of a discrete beam-like bridge with one or several non-propagating edge cracks subjected to a moving vehicle. In this model, the simply supported beam elements are replaced by a range of rigid bars, which are connected by transverse and rotational springs, while the mass and rotational moment of inertia may be lumped at various points along the beam. The adopted vehicle model here is a four degrees-of-freedom, two axes half-vehicle model with tires flexibility and linear suspensions. Damage can be modelled by altering the spring stiffness equation at the crack position according to predictions, which allows the inclusion of simple or complex damage. To simplify, damage is represented here by an open crack, and stiffness of a given element with damage is calculated by fracture mechanics. Both the discrete element and finite element methods are used to investigate vibration analysis of a discrete beam model subjected to a moving vehicle to confirm model feasibility in vibration analysis under a moving vehicle. Besides, some dynamic response laws are obtained. Considering an irregular road profile, the effects of the moving vehicle velocity, the moving vehicle mass, the crack location and the crack depth on dynamic response of a beam-like bridge are analysed by a numerical example, combining a vehicle–bridge coupled vibration MATLAB program with ANSYS. In addition, the neural network is used to identify the damage of the structure. Numerical results of the numerical model predictions, compared with those obtained from the continuous elements beam, support the accuracy of the discrete elements beam model in both cases of undamaged beam and damaged one. The evidence for condition assessment and damage identification of bridge is obtained from this simulation as obtaining the vibrational characteristics of the damaged beam structure subjected to a moving vehicle. And the inversion results show that the neural network method can identify the injury location and injury size of the structure accurately.

     

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.     

Dynamic response of double-FG porous beam system subjected to moving load

In this paper, the vibration response of the double-FG porous beam system (DFGPBS) acted by a moving load is investigated. The DFGPBS composed of two parallel FG porous beams with their material properties varying along both the axial and transverse directions, i.e., bi-directional FG material distribution, is taken into account. The porous imperfection is simulated by distributing the porosity along the beam thickness with even and uneven patterns. The governing equations of this bi-directional DFGPBS under a moving load are established with the aid of the Hamilton principle associated with the Timoshenko beam theory. The Ritz method is adopted to discrete the differential governing equations, which are solved by the Newmark-β approach. The validation of the present model is performed by comparing the numerical results with two previous works. Then, the parametric study is carried out to investigate the influences of bi-directional gradient indices, porosity volume fraction, boundary conditions, stiffness of elastic layer, and velocity of the moving load on the vibration response of bi-directional DFGPBSs excited by a moving load. It is demonstrated that the vibration response of the double-beam system subjected to moving loads can be governed by tailoring the distribution of the bi-directional FG materials. The present work can be used to guide the multi-functional design of a double-beam system under dynamic loadings.

     

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。     

Discrete element analysis of dynamic response of Timoshenko beams under moving mass

In this paper, dynamic response of Timoshenko beams under moving mass is analyzed using a numerical method called discrete element technique (DET). In DET, continuous flexible beam elements are replaced by a system of rigid bars and flexible joints. We present a DET model of Timoshenko beams under moving mass. The results of our DET model are compared with the solutions obtained by PAFEC (programs for automatic finite element calculations) for Euler–Bernoulli beams and finite difference method for Timoshenko beams. The effects of beam thickness and moving mass velocity on dynamic response of beams under moving mass are numerically studied.     

用微分求积法分析轴向移动粘弹性梁的非平面非线性振动

用微分求积法分析了轴向移动粘弹性梁非平面非线性振动的动力学行为.轴向移动粘弹性梁非平面非线性振动的数学模型是一非常复杂的非线性偏微分方程组.首先用微分求积法对其控制方程组进行空间离散,得到非线性常微分方程组,然后求解常微分方程组得到数值结果.在数值结果的基础上结合非线性动力学理论,利用分叉图、时间历程图、相图对其非线性动力学特性进行了分析.     

Identification of masses moving on multi-span beams based on a genetic algorithm

This paper describes a theoretical study on the identification of masses moving on a multi-span continuous beam using the acceleration measurements. In the study, the acceleration measurements are simulated from the solution to the forward problem of a continuous beam under moving masses, together with the addition of artificially generated measurement noise. In particular, the forward problem for the simulation is solved using the modified beam vibration functions. A simple dynamic force identification procedure using pseudo-inverse and singular value decomposition is first employed to arrive at rough approximations of the moving masses. A genetic algorithm is then used to find the best estimated values of the moving masses by minimizing the errors between the measured accelerations and the reconstructed accelerations from the moving masses in each generation. Five numerical examples are given to demonstrate the robustness of this method. Various possible sources of error including the effects of measurement noise and surface roughness are also discussed.     

A Lagrange–Eulerian formulation of an axially moving beam based on the absolute nodal coordinate formulation

In the scope of this paper, a finite-element formulation for an axially moving beam is presented. The beam element is based on the absolute nodal coordinate formulation, where position and slope vectors are used as degrees of freedom instead of rotational parameters. The equations of motion for an axially moving beam are derived from generalized Lagrange equations in a Lagrange–Eulerian sense. This procedure yields equations which can be implemented as a straightforward augmentation to the standard equations of motion for a Bernoulli–Euler beam. Moreover, a contact model for frictional contact between an axially moving strip and rotating rolls is presented. To show the efficiency of the method, simulations of a belt drive are presented.     

轴向运动功能梯度粘弹性梁横向振动的稳定性分析

基于Euler梁理论研究了轴向运动功能梯度粘弹性梁横向振动的稳定性问题.基于问题的数学模型和控制方程,利用微分求积法求得了轴向匀速运动功能梯度粘弹性梁亚临界区域内横向振动的复频率,分析其随着轴向运动速度、材料梯度指数等参数的变化情况,探讨上述参数对超临界区域失稳形式的影响.然后应用多尺度法结合边界条件分析了轴向速度带有周期扰动成分的变速运动功能梯度粘弹性梁的失稳问题,重点讨论了当速度扰动频率为固有频率二倍或者为两固有频率之和/差时所发生的次谐波共振及组合共振所导致的失稳.数值算例表明,随着梯度指数的增大,匀速运动功能梯度粘弹性梁的临界发散速度、耦合速度以及变速运动功能梯度粘弹性梁的稳定区域减小,且粘弹性系数的影响逐渐变弱,同等条件下,轴向运动功能梯度粘弹性固支梁比简支梁更为稳定.     

An investigation of the effect of counterweight configuration on main bearing load and crankshaft bending stress

In this study, effects of counterweight mass and position on main bearing load and crankshaft bending stress of an in-line six-cylinder diesel engine is investigated using Multibody System Simulation Program, ADAMS. In the analysis, rigid, beam and 3D solid crankshaft models are used. Main bearing load results of rigid, beam and 3D solid models are compared and beam model is used in counterweight configuration analyses. Twelve-counterweight configurations with a zero degree counterweight angle and eight-counterweight configurations with 30° counterweight angle, each for 0%, 50% and 100% counterweight balancing rates, are considered. It is found that maximum main bearing load and web bending stress increase with increasing balancing rate, and average main bearing load decreases with increasing balancing rate. Both configurations show the same trend. The load from gas pressure rather than inertia forces is the parameter with the most important influence on design of the crankshaft. Results of bearing loads and web bending stresses are tabulated.     

基于抑制光线强度变化影响的运动目标检测

在运动目标检测过程中,若两帧图像拍摄条件下光线强度不同,则运动目标检测的结果将会受到影响。据此,该文提出了抑制光线强度变化影响的运动目标检测方法。首先,对两帧图像通过自适应高斯核平滑滤波器处理,以降低图像的随机噪声对处理结果的影响;然后,根据两帧图像对应像素的灰度变化量信息,判断该两帧图像的光强变化程度;最后,根据本文所研究的抑制光线强度变化影响的方法,将运动目标从背景中检测出来。实验证明,取得了良好的效果。     

造桥机结构的有限元仿真分析

为了研究造桥机的静力学性能,利用ANSYS 有限元软件对造桥机进行有 限元分析,并对造桥机进行静力学试验。首先介绍了造桥机的整体结构和工作原理,然后 建立造桥机的有限元模型,接下来对造桥机的移机就位、制梁前、制梁和调移下导梁等具 有代表性的工况进行静力学性能仿真分析,并对分析结果进行详细的论述。最后,对造桥 机进行一系列静力学性能试验,结果表明：利用ANSYS 对造桥机进行的静力学性能分析结 果与试验结果较为吻合,对造桥机的设计和生产具有积极的指导意义。     

Robust stability—degree assignment and its applications to the control of flexible structures

A new method of robust controller synthesis is introduced which is an extension of robust stabilization to robust stability-degree assignment. This method guarantees a lower bound of stability degree for all uncertainties within a prescribed magnitude band. The method is applied to the control of four types of flexible structures, namely, colocated beam, non-colocated beam, beam with moving base and large scale satellite model. Excellent performances have been obtained experimentally with respect to the response speed and the robustness.     

Research on resource allocation for multi-tier web applications in a virtualization environment

Resource allocation for multi-tier web applications in virtualization environments is one of the most important problems in autonomous computing. On one hand, the more resources that are provisioned to a multitier web application, the easier it is to meet service level objectives (SLO). On the other hand, the virtual machine which hosts the multi-tier web application needs to be consolidated as much as possible in order to maintain high resource utilization. This paper presents an adaptive resource controller which consists of a feedback utilization controller and an auto-regressive and moving average model (ARMA)-based model estimator. It can meet application-level quality of service (QoS) goals while achieving high resource utilization. To evaluate the proposed controllers, simulations are performed on a testbed simulating a virtual data center using Xen virtual machines. Experimental results indicate that the controllers can improve CPU utilization and make the best tradeoff between resource utilization and performance for multi-tier web applications.