Modeling and computer simulation of zero speed splice unwinds

A computer program for conducting model simulations for zero speed splice unwinds is described in this paper. A typical unwind system consisting of the unwinding material roll, festoon, dancer, and pull rolls is considered. The developed computer model is general enough to be applicable to a variety of unwinds containing these components. The paper also provides a procedure for determining zero speed splicing parameters when the characteristics of the festoon and the splicer, such as number of carriage rollers, festoon capacity, clamp and dwell time, etc., are given; this method can be employed for the selection of splicing parameters, such as acceleration and deceleration profiles, splice diameter, spindle speed profiles, etc. The computer model can predict the transport behavior of webs through the unwinds; this was verified by comparing data from model simulations and experiments on a production unwind. The computer program can be used to evaluate different scenarios of unwind operation prior to actual implementation on production unwinds. Thus, providing a significant benefit in terms of operational efficiency as well as improved process capability

Comparison of control strategies for roll-to-roll printing presses

Flexible printed electronics is touted to be a significant part of the future of the roll-to-roll (R2R) printing industry. Electronic devices, such as RFID tags, low-cost displays and lighting devices, polymer solar cells, sensors, etc., can be manufactured on a flexible substrate using roll-to-roll machines. In recent years there has been a significant focus towards printing electronics on a flexible substrate using R2R printing methods. These studies have primarily dealt with the feasibility of printing electronic components such as thin metal lines, electrodes, capacitors, thin film transistors, etc., on the flexible substrate. In order to realize the goal of low cost printing of electronics on a flexible substrate using R2R techniques, the web handling aspects related to R2R printing have to be addressed adequately. This paper focuses on the web handling aspects related to R2R printing by analyzing the print registration process using mathematical models and by studying control schemes to improve print registration.Mechanical and Aerospace Engineerin

Roll speed and web tension regulation using two degree of freedom control systems

In this paper, we first consider the problem of load speed regulation in a two inertia system consisting of a motor shaft connected to the load shaft via a mechanical transmission. The problem is reminiscent of a material roll (load) connected to the motor shaft through a belt-pulley and gear transmission system. In typical industrial speed control systems, the motor shaft speed is controlled under the assumption that the load shaft speed is indirectly controlled at its desired value scaled by the transmission ratio. In the presence of the transmission dynamics introduced by compliance and backlash, regulation of motor shaft speed does not translate to regulation of roll speed. The problem is further exacerbated when there are disturbances on the roll. One must consider the transmission dynamics in developing a control system that can provide the desired performance for the roll speed. We propose a two degree of freedom control system that utilizes measurement of motor shaft and roll shaft angular velocities in developing a control action necessary to regulate the roll speed. The control system consists of both feedback and model-based feedforward actions. The model-based feedforward action is generated by utilizing the model and adaptively estimating the disturbances on the roll. Experimental results conducted on a web machine indicate improved roll speed regulation in the presence of disturbances, which will be presented and discussed. Utilizing the improved roll speed regulation scheme a tension control strategy is also proposed and experiments were conducted with web transport. Experimental results indicate improved tension regulation with such a strategy.Mechanical and Aerospace Engineerin

Application of dimensional analysis to roll-to-roll manufacturing systems

In this paper, we investigate the application of dimensional analysis for R2R systems. First, dimensional form of governing equations for web tension and speed are transformed to non-dimensional form using dimensional analysis, and discussions are provided to highlight their usefulness in further analysis and design of R2R systems. Second, two specific cases are considered to show application of dimensional analysis to R2R systems: analysis of an accumulator and redesign for capacity scaling and scaling of process and controller parameters of an example R2R system for a change in the web material. In the first case, we provide results from model computer simulations to evaluate the method, and in the second case, results from experiments conducted on a large R2R platform are presented and discussed. Further, frequency response experiments are conducted for a subsystem of web spans and rollers for different materials to also evaluate the results of applying dimensional analysis to R2R systems.Mechanical and Aerospace Engineerin

IMECE2002-DSC-33421 ON THE ADAPTIVE CONTROL OF MECHANICAL SYSTEMS WITH TIME-VARYING PARAMETERS AND DISTURBANCES

ABSTRACT In this paper, we propose and investigate a new adaptive control algorithm for mechanical systems with time-varying parameters and/or time-varying disturbances. The proposed method does not assume any structure to the time-varying parameter or disturbance. The idea is based on the expansion of the timevarying parameter/disturbance using the Taylor series expansion; this facilitates expanding a time-varying function as a finite length polynomial and a bounded residue; the coefficients of the finite length polynomial are estimated in a time interval small enough so that they can be assumed to be constant within that interval. A novel experiment is designed using a two-link mechanical manipulator to investigate the proposed algorithm experimentally. Simulation and experimental results validate the proposed new adaptive control algorithm; we discuss these results and also give some future research directions

Design of tension control systems to minimize interaction and disturbance propagation in web process lines

In roll-to-roll systems (R2R), a local controller is designed for each section or tension zone based on measurement of web tension and speed from that section; this is typically referred to as decentralized control. This is particularly suitable for R2R systems because of ease of implementation and their structure. Since the material is transported from the unwind to the rewind through the process sections, the entire machine can be divided into several sections and decentralized controllers may be utilized for each section. It is important to understand the dynamics of web transport from one section to other downstream sections, that is, interaction between different sections, and how disturbances are propagated. Tension control system designs that minimize disturbance propagation will aid in improving process performance.In this paper, we will first investigate minimization of interaction between subsystems of R2R systems when decentralized feedback and feedforward controllers are employed. In particular, we will consider a new interaction metric for dynamical systems which will quantify the amount of interaction; and show how model-based feedforward action can be gainfully employed to minimize disturbance propagation. We will also discuss control strategies that will minimize disturbance propagation. To evaluate the proposed designs and recommendations, we will show results from experiments conducted on a large experimental web platform.Mechanical and Aerospace Engineerin

Modeling of the transport behavior of low modulus webs

We consider three key issues in this study for low modulus webs. First, transport in the high strain region is considered when the materials exhibit nonlinear and viscoelastic behavior. Second, in-plane biaxial strain is considered in the development of the governing equation for web strain in the transport direction. Governing equations for web strain and tension are developed and evaluated using parameter sensitivity analysis and both time and frequency domain computer simulations under typical scenarios of transport and machine and environment induced disturbing forces. Third, the effect of moisture and heat diffusion in fibrous and porous non-woven webs on longitudinal web strain is considered. Moisture and heat diffusion is studied using known non-Fickian models which better represent the diffusion behavior in porous, fibrous materials.Mechanical and Aerospace Engineerin

IMECHE2005-81501 MODELING OF WEB SLIP ON A ROLLER AND ITS EFFECT ON WEB TENSION DYNAMICS

ABSTRAC

Spatially dependent transfer functions for web lateral dynamics

In this paper we derive spatially dependent transfer functions for web span lateral dynamics which provide web lateral position and slope as outputs at any location in the span; the inputs are guide roller displacement, web lateral position disturbances from upstream spans, and disturbances due to misaligned rollers. This is in sharp contrast to the existing approach where only web lateral position response is available on the rollers. We describe the inherent drawbacks of the existing approach and how the new approach overcomes them. The new approach relies on taking the 1D Laplace transform with respect to the temporal variable of both the web governing equation and the boundary conditions. One can also obtain the web slope at any location within the web span with the proposed approach. A general span lateral transfer function, which is an explicit function of the spatial position along the span, is obtained first followed by its application to different intermediate guide configurations