Web Handling Research Articles

1200 柔軟連続媒体の搬送・巻き取り時におけるディフェクト予測とその防止(キーノートスピーチ,柔軟媒体ハンドリング/画像形成機器)

1200 柔軟連続媒体の搬送・巻き取り時におけるディフェクト予測とその防止(キーノートスピーチ,柔軟媒体ハンドリング/画像形成機器)

Traction force between rotating rolls and moving web considering the effect of air-entrainment

High-speed transportation of paper web sometimes leads the web handling system into unstable state because of increase in the air-entrainment into the gap between a rotating roll and moving web or the nip region of winding system. In this paper, the property of the traction change with increase in the air-entrainment into the gap between a paper roll and web or the nip region of winding system was investigated experimentally and theoretically. The critical speed to avoid slippage between a roll and web was found to be estimable by applying and extending the concept of “effective” frictional coefficient with the consideration of air-entrainment, which is proposed by Good et al. (Proceedings of the fourth international conference on web handling, 1997), Hashimoto (Proc JSME 1999(5):183–184, 1999a) and so on, to the estimation of the traction force defined as the frictional force on a paper roll or at the nip region. Consequently, the web handling stability at high-speed was found to be predictable.

Traction Force Between Rotating Rolls and Moving Web Considering the Effect of Air-entrainment

High-speed transportation of paper web sometimes leads the web handling system into unstable state because of increase in the air-entrainment into the gap between a rotating roll and moving web or the nip region of winding system. In this paper, the property of the traction change with increase in the air-entrainment into the gap between a paper roll and web or the nip region of winding system was investigated experimentally and theoretically. The critical speed to avoid slippage between a roll and web was found to be estimable by applying and extending the concept of “effective” frictional coefficient with the consideration of air-entrainment to the estimation of the traction force defined as the frictional force on a paper roll or at the nip region. Consequently, the web handling stability at high-speed was found to be predictable.

Visualizing the Motion of a Unicycle on a Sphere

The kinematics, dynamics, and control of a unicycle (with yaw and roll inputs) moving without slip on a planar surface has been studied extensively in the geometric mechanics and nonholonomic literature. This paper considers the kinematic extension to the case of a unicycle moving on a nonplanar surface: specifically, a spherical surface and the associated visualization, including use of computer-aided design (CAD) software packages (e.g., SolidWorks® & MATLAB®). Such a scenario allows one to move closer to an understanding of the motion of an actual multiwheeled vehicle traversing nonplanar surfaces that may be approximated as spherical surface patches as well the realistic portrayal of virtual vehicles in computer graphics environments, in addition to other applications, such as those that employ kinematic inversion (e.g., industrial web handling). Differential equations of motion are derived based on the nonholonomic no-slip constraint and spherical trigonometry from which the associated Lie algebra is revealed and a related example foliation formulation is illustrated that offers further generalization. For a fixed body yaw rate it is shown that a circular trajectory of a specific radius results — this can also form the basis of an instantaneous centre integration (ICI) algorithm. Numerical studies designed to exercise the equations of motion (using MATLAB® and SIMULINK®) were performed based on combinations of several different types of input trajectories: constant, non-infinitesimal Lie bracket manoeuvres, sinusoidal, and that induced by a prescribed contact point trajectory. Finally, the resulting interesting motions were plotted in 2D and 3D and provide a source of qualitative corroboration of the equations in addition to computer-generated artwork.

Vibration and guiding of moving media with edge weave imperfections

This paper examines the steady-state-forced vibration of a moving medium that is guided by a partial elastic foundation, and where geometric imperfections on the medium's edge act as an excitation source. Such a system is of technical interest in the areas of web handling and magnetic tape transport where externally pressurized air bearing guides are sometimes used to control lateral position. The axially moving strip is modeled here as a string that is guided by elastic foundation segments, and that is subjected to traveling wave excitation as the edge's imperfection interacts with the foundation. The equation of motion for this “moving medium and moving load” system incorporates a skew-symmetric Coriolis acceleration component that arises from convection. The governing equation is cast in state-space form, with one symmetric and one skew-symmetric operator, as is characteristic of gyroscopic systems. Through modal analysis, the forced response of the system is obtained to the complex harmonic excitation associated with the interaction between the edge's weave pattern and the guides. Parameter studies are presented in the transport speed, foundation stiffness, guide placement, guide width, and imperfection wavelength. Of potential technological application, for a given wavelength of the edge's imperfection, it is possible to reduce the medium's vibration at a certain location by judiciously selecting the locations and spans of the foundation segments.

STATE FEEDBACK CONTROLLERS SYNTHESIS USING BMI OPTIMISATION FOR LARGE SCALE WEB HANDLING SYSTEMS

In web transport systems, the main concern is to control independently speed and tension in spite of perturbations such as radius variations and changes of set point. In this paper we present multivariable H2 controllers, with and without integrator, applied to winding systems. Different controller structures are considered: a centralized and a semi-decentralized controller with or without overlapping. The use of decentralized control leads to performance deterioration as compared to centralized control, but brings other advantages: on one hand, it allows for a local implementation close to each actuator, on the other, sensor or actuator failures create only local disturbances. Our approach consists in designing state feedback control, with bilinear matrix inequality (BMI) optimisation. Simulation results are given based on a nonlinear model for a web handling system, identified on an experimental bench.

AN IMPROVED FRICTION SLIDING MODEL FOR WEB HANDLING SYSTEMS. APPLICATION TO THE CONTROLLER PARAMETRIZATION

In web transport systems, the main concern is to independently control speed and tension in spite of perturbations such as radius variations and changes of setting points. So far, simulation models representing web handling systems have only dealt with continuously rolling web without considering friction between web and rollers. This article aims at introducing the modeling of friction as well as the risk for the web to slide on traction rollers. The influence of several physical factors on the occurrence of such sliding is studied. In this paper, we focused on analyzing the special case of an emergency shutdown.The authors observed and analyzed the consequences of several controllers on the occurrence or not of sliding. An approach for defining the optimal command to decrease the speed as fast as possible in the case of an emergency shutdown without occurrence of sliding is proposed.

2419 ウェブ搬送におけるウェブ損傷図(S80 柔軟媒体ハンドリングと画像形成システム)

In the web handling systems, before being converted to the final product, the web undergoes several processes, for example, transportation by the drag roller, press, printing, coating, drying, slittering, winding, and so on. Under such processes, the web is given the additional values to enhance the quality and function of product. However, when the web defect are generated in the handling processes, the defect immediately result in quality loss. Therefore, to predict and protect the defect is very important engineering problems cannot be seen in the literature. In this paper, the idea of web defect map for predicting the web defects such as wrinkling, slipping and lateral motion of web is presented.

Robust Decentralized Control Strategies for Large Scale Web Handling Systems

In web transport systems, the main concern is to control independently speed and tension in spite of perturbations such as radius variations and changes of setting point. Nevertheless, in these control techniques, tracking properties and perturbation rejection are interdependent and cannot be specified separately. In this paper we present multivariable decentralized H∞ controllers with one or two degrees of freedom (DOF), with and without explicit integrator, applied to winding systems. Different controller structures are considered: a centralized controller and semi-decentralized controllers with or without overlapping. The 2DOF approach improves significantly the disturbance rejection while reducing the coupling between tension and velocity. The use of decentralized control leads to performance deterioration as compared to centralized control. The off-diagonal elements of the plant are represented as uncertainties. This enables us to analyse the stability of a decentralized control structure. Finally, a design method for state feedback control, applied to web handling systems and using a bilinear matrix inequality (BMI) approach, is proposed and discussed. Simulation results are given based on a nonlinear model identified on an experimental bench.

Servomechanism controller design of web handling systems

In traditional web handling processes, web tension and speed are typically controlled assuming that the web system consists of a number of single-input-single-output systems. This assumption often results in large interactions occurring in the closed-loop system between the control loops and, hence, results in high-quality control being difficult to achieve. In this paper, the control of the web handling processes is treated as a multivariable servomechanism problem. Two types of controller design, the "perfect control servomechanism controller" and the "tuning regulator", are studied and implemented on an industrial web machine. The experimental results obtained show that these controllers provide excellent tension and speed response compared with conventional controllers used in web systems. In particular, it is shown that the "tuning regulator" approach is only marginally worse than the "perfect control servomechanism controller" approach, despite the fact that it does not require a mathematical model of the web process, and is simpler to implement.

A Numerical Algorithm for Determining the Traction Between a Web and a Circumferentially Grooved Roller

Air entrainment can become a significant problem in a web handling process line. The development of an air film between a roller and web can cause a reduction in traction. This can cause a velocity difference between the web and roller and may also cause guiding problems. Roller grooving is a common method to reduce the effects of the air entrainment to improve traction. A traction simulation model for circumferentially grooved rollers has been devised. The model is based on classical plate and shell theory, the Reynolds’ equation, and asperity contact theory. The governing equations are solved in an iterative scheme using a finite difference method with a variable mesh. Theoretical results are experimentally verified. [S0742-4787(00)02203-7]

QMotor 2.0-a real-time PC based control environment

This paper describes QMotor 2.0, a QNX based single-processor software environment that allows the implementation of real-time control programs on standard Intel processor based personal computers (PCs). The control program, as well as the development tools and graphical user interface, can all execute simultaneously on the PC due to the deterministic response of the operating system. This architecture replaces the traditional multiprocessor Host/DSP board architecture used in control applications. Advantages of a single-processor system include reduced cost and complexity, as well as increased flexibility and upgradability. Since its development, QMotor 2.0 has been used successfully in all of the control experiments, including motor and robot control, active magnetic bearing experiments, web handling, and vibration control in flexible structures.

Edge Buckling of Imperfectly Guided Webs

Web handling is germane to a diverse set of industries, including paper, polymer, textile, and sheet metal processing. Angular misalignment of the guides used to position a web in its transport system generates non-uniform in-plane forces that can result in transverse buckling of the web, even for misalignments as small as a fraction of a degree. In this paper, the state of stress, the associated in-plane deformation, out-of-plane vibration, and stability of webs with misaligned guides are investigated experimentally and theoretically. The onset of edge buckling, in which transverse corrugations are present along an entire free edge or are localized near a guide, is governed by the stability of a relatively high mode of the nominally aligned web. Two models of common web transport components—termed “free sliding” and “edge guided” —are developed and discussed in the light of laboratory measurements for predicting and bounding critical buckling angles.

Viscoelastic Effects in Modeling Web Handling Systems: Unsteady-State Analysis

A model to predict the tension in open spans of web handling systems during transient operations has been developed. Governing equations were developed by using the White-Metzner equation to describe the material response in conjunction with mass and force balances. The governing equations were nondimensionalized and solved via the MacCormack predictor/corrector technique. Two dimensionless parameters emerged from the analysis, the Deborah number, De, and the ratio of the viscous stress to the steady state stress, N. The resulting model is the companion to a previously reported model for steady-state operations (Guan et al, 1995). The model was used to predict the behavior of a web handling system during start-up, transition between steady states, and a periodic disturbance. During start-up and transition, systems responded more rapidly at low De. The system response during a periodic disturbance was correlated to De, the frequency, and the magnitude of the disturbance.

Modeling a multiple-zone air impingement dryer

A complete model for the simulation of the drying process of a binary system in a modular air impingement dryer is presented. The underlying equations and the numerical scheme were chosen such that large-scale parameter studies could be performed efficiently with an ordinary PC. The influence of the operating parameters on the drying progress and the energy efficiency was investigated, considering a wide range of technically important constraints such as proper web handling, the risk of explosion or the generation of bubbles in the coating.

Effects of Foil Bending Rigidity on Spacing Height Characteristics of Hydrostatic Porous Foil Bearings for Web Handling Processes

In this paper, the effects of foil bending rigidity on the spacing height characteristics of hydrostatic foil bearings with a hollow porous shaft for web handling processes are analyzed by the finite width bearing theory. In the analysis, in order to save computation time and to improve the convergence of solutions, the two-dimensional modified Reynolds equation considering the added flow through porous shaft is reduced to an ordinary differential equation based on the weighted residual method. The reduced Reynolds equation and elastic equation for the foil are discretized by the finite difference method and solved numerically by the iterative technique. The numerical solutions for the pressure and film thickness distributions between foil and shaft are obtained for a wide range of bearing width-to-diameter ratio under various combinations of foil bending rigidity and foil wrap angle, and the spacing height characteristics of the foil bearings are examined theoretically.

Wide web coating of complex materials

For over 25 years, the thermal evaporation of aluminium onto thin polymeric webs, such as polyester (PET) and polypropylene (PP), has generated large volumes of barrier packaging films, decorative films, capacitor films and some window films. During the 1980s, the experience of wide web handling was combined with deposition technologies, such as electron-beam evaporation, magnetron sputtering and plasma-enhanced chemical vapour deposition (PECVD), to create a large number of new, exciting, coating materials, including oxides and nitrides of most elements. More particularly, combinations of these coating layers into a complex coating stack led to new products, such as low emissivity, solar heat reflecting, architectural glazing films, electrochromic devices and high performance optical reflectors. With these technologies, unique coating characteristics can be realized, e.g. transparent electrodes, transparent, flexible glassy barriers for moisture and gases and amorphous soft magnetics for security devices. Having their beginnings in exclusive markets, these new, exciting products are now finding their way into larger consumer markets.

Wide web coating of complex materials

For over 25 years, the thermal evaporation of aluminium onto thin polymeric webs, such as polyester (PET) and polypropylene (PP), has generated large volumes of barrier packaging films, decorative films, capacitor films and some window films. During the 1980s, the experience of wide web handling was combined with deposition technologies, such as electron-beam evaporation, magnetron sputtering and plasma-enhanced chemical vapour deposition (PECVD), to create a large number of new, exciting, coating materials, including oxides and nitrides of most elements. More particularly, combinations of these coating layers into a complex coating stack led to new products, such as low emissivity, solar heat reflecting, architectural glazing films, electrochromic devices and high performance optical reflectors. With these technologies, unique coating characteristics can be realized, e.g. transparent electrodes, transparent, flexible glassy barriers for moisture and gases and amorphous soft magnetics for security devices. Having their beginnings in exclusive markets, these new, exciting products are now finding their way into larger consumer markets.

Viscoelastic Effects in Modeling Web Handling Systems: Steady-State Analysis

The effect of viscoelasticity in web handling systems is examined by introducing a viscoelastic equation of state into a model for tension control. Case studies and generalized results for a single open-span system and a double open-span system are presented to compare the results of the viscoelastic model to a model based on a purely elastic equation of state. The results show only small differences in the tension behavior for the single-span system. However, large differences in the magnitude and reversal of the sign of the tension in the second span of a two-span system are seen for even small degrees of viscoelasticity in the web material. The results clearly demonstrate that viscoelasticity must be considered in modeling multispan web handling systems.

The Importance of Traction in Web Handling

An experimental study shows that the traction coefficient of friction (μT) is a function of the predicted air film height, the roller and film surface roughness, and the static coefficient of friction between the web and roller. The traction coefficient shows a noticeable decrease as the air film height becomes greater than the equivalent root mean square roughness of the web and roller and also becomes less dependent on the static coefficient of friction.