Cross-direction Control Research Articles

Optimization Methods For Control Systems of The Headbox And The Cross Direction Control on Papermaking Machines

This paper briefly introduces the Headbox and the Cross Direction, and analyzes challenges in their control systems. The main challenges in these two control systems are nonlinearity and parameter coupling. To solve these problems, or at least reduce the influence of these problems on the control systems, a few optimization methods are proposed. In this paper, some practical optimization methods are introduced based on modified PID control, which is the most commonly used control system in process industries, such as the paper-making industry. Those methods optimizing the PID control system can be mainly divided into two classes: decoupling and PID tuning. Besides, some practical methods optimizing the Cross Direction control systems are introduced. Also, the introduced methods can be divided into two classes: CD tuning and cooperating with parameters of the headbox system to optimize. The effectiveness of these methods is demonstrated in simulations. However, since the nonlinearity of the system, there is no accurate and unique solution. In addition, with the development of demand and technology, there will be no such thing as an algorithm suitable for every control system, so that new algorithms will be proposed.

Distributed Cross-Direction Control System Based on CAN-Bus

A distributed cross-direction control system based on CAN-bus was designed to solve the large-scale cross-direction control problem for paper machine. Multiple Master-Slave CAN networks were constructed in parallel to coordinate and control multiple array actuators, and the Ethernet/CAN converter was used to connect the monitoring station with the field intelligent actuators. The monitoring station accesses measured data and field data via OPC technology. A CAN application layer protocol and corresponding underlying communication software were designed according to the characteristics of the cross-direction control processes. Finally, the feasibility and reliability of the system were verified with practical applications.

A cost-effective sparse communication strategy for networked linear control systems: an SVD-based approach

In networked control, there is often an incentive to communicate only what is absolutely necessary to achieve the desired performance goals. This is true to both the downlink (between a control base station and actuators) and the uplink (between the sensors and base station). Here, we present a strategy aimed at this problem based on a singular value decomposition of the Hessian of the quadratic performance index generally considered in Model Predictive Control. The singular vectors are employed to generate an orthonormal basis function expansion of the unconstrained solution to the finite horizon optimal control problem. These are preloaded into each actuator and each sensor. On the downlink, the actuators are informed, in real-time, about which basis functions they should use. On the uplink, after a ‘burn in period’, the sensors need only communicate when their response departs from that pre-calculated for the given basis functions. We show that this strategy facilitates communication in both the downlink and uplink in a cost-effective fashion. We also show that the strategy can be modified so that input constraints are satisfied. We illustrate the proposed results by applying them to a simulation of the cross direction control of a paper machine. Potential extensions and other applications of the proposed strategy are also discussed. Copyright © 2014 John Wiley & Sons, Ltd.

Ultiple Property Cross Direction Control of Paper Machines

Cross direction (CD) control in sheet-forming process forms a challenging problem with high dimensions. Accounting the interactions between dierent properties and actuators, the dimensionality increases further and also computational issues arise. We present a multiple property controller feasible to be used especially with imaging measurements that provide high sampling frequency and therefore enable short control interval. The simulation results state the benets of multiple property CD control over single property control and single property control using full feedforward compensation. The controller presented may also be tuned in automated manner and the results demonstrate the eect of tuning on input saturation.

Branch and bound method for multiobjective pairing selection

Most of the available methods for selection of input–output pairings for decentralized control require evaluation of all alternatives to find the optimal pairings. As the number of alternatives grows rapidly with process dimensions, pairing selection through an exhaustive search can be computationally forbidding for large-scale processes. Furthermore, the different criteria can be conflicting necessitating pairing selection in a multiobjective optimization framework. In this paper, an efficient branch and bound (BAB) method for multiobjective pairing selection is proposed. The proposed BAB method is illustrated through a biobjective pairing problem using selection criteria involving the relative gain array and the μ -interaction measure. The computational efficiency of the proposed method is demonstrated by using randomly generated matrices and the large-scale case study of cross-direction control.

Cross direction register modeling and control in a multi-layer gravure printing

For the adaptation of the roll-to-roll printing method to printed electronics, it is mandatory to increase the resolution of the register control. Therefore, it is desired to derive a mathematical model for the register and to develop a controller to reduce register error. The mathematical model of cross direction register was derived considering both a lateral motion of a moving web and a transverse position of a printing roll. The proposed mathematical model could be used to improve the performance of the cross direction (CD) register controller in a large area, roll-to-roll printing machine. The mathematical model was validated by numerical simulations and experimental verifications in various operating conditions using a multi-layer direct gravure printing machine. The results showed that the proposed model was effective in predicting the CD register in multi-layer printing.

Efficient Linear Programming Formulations of Model Predictive Control for Cross-Directional Control of a Paper Machine

Efficient formulations of linear programming based model predictive control are considered for cross direction (CD) control of a dual headbox paper machine. A number of techniques including coincidence points, efficient mathematics, implementation strategies, and the solution of progressively more complicated optimization problems are considered for both their performance and efficiency.

Improved Threshold for the Local Approach in Detecting Faults

Fault detection and isolation (FDI) has become a critical issue for increasing availability, reliability, and production safety in industrial process monitoring. While model-based FDI methods rely on the mathematical model and input−output data of a process to perform detection, the local approach is a new model-based FDI method that aims to detect slight changes of parametric properties of a system. Robustness with respect to model uncertainties is an important issue for the local approach. To reduce false alarms caused by the estimation error of process parameters, a new algorithm is proposed to recalculate the threshold based on the original threshold and covariance matrix of the estimated parameters. A similar algorithm is also provided to recalculate the threshold to reduce false alarms due to regular parameter fluctuations. The effectiveness of the proposed algorithms is shown by simulation studies on a papermaking cross-direction control system.

Closed-loop identification with MPC for an industrial scale CD-control problem

An approach to implementing closed-loop identification in a model predictive-control framework for the cross-direction control of basis weight is proposed. The closed-loop-identification technique uses the concepts of Markov parameters to determine a step-response model that can then be used within a model predictive controller. The technique is applied to an industrial-scale paper-machine-simulation benchmark problem for cases of varying degrees of shrinkage. The performance of wet- and dry-end full-array sensors are compared. Also, the performance of the closed-loop identification is compared for a nominal case and two cases in which shrinkage occurs in the drying process.

最新の塗工量測定・制御技術について

Coated Paper needs have been wide and rich in variety in Japan. That is why the paper coating process and operation became more severe on quality and productivity.In B/M 9000 CS-our newest QCS products introduced in 1998-, we have provided solutions for it, which are three methods to measure Coat Weight and applications for quality control of cross direction and machine direction. Precise measurement of Coat Weight profile and cross direction control, for instance, can reduce product rejection and extend lifetime of coater blade. These technologies are major contributor to produce results in product needs of quality and throughput.

Customization strategies for the solution of linear programming problems arising from large scale model predictive control of a paper machine

Abstract This paper presents an application of a customized linear programming (LP) based model predictive control strategy to the paper machine cross direction (CD) control problem. The objective of CD control is to maintain flat profiles of variables of interest by minimizing worst case deviations from setpoints (defects). These control problems can have as many as 200 actuators (inputs) and 400 sensor measurements (outputs). This large size coupled with the stringent real-time requirement of computing a control move in a few seconds poses a very challenging control problem. Computational results that demonstrate the effectiveness of this strategy will be presented. For typical disturbances this algorithm can compute provably optimal control moves for a 400 input ×400 output control problem in approximately 5 s versus approximately 90 s for a generic LP algorithm on a HP 9000/770 workstation.

計装 プロファイル制御におけるニューラルネットワークを用いた自動チューニングツール

We have developed an automatic tuning tool that defines all tuning constants in profile control in paper and coater machines. The tuning tool is installed in Windows PCs and those PCs are connected to our measurement and control computer systems by Ethernet communication. This tool executes step response tests of cross direction actuators automatically by using neural network theory and it defines automatically all tuning constants for performing cross direction control by using wavelet analysis and neural network theory.

Closed-Loop Analysis and Tuning of Cross-Direction (CD) Control for Sheet-Forming Processes

Abstract This paper presents the closed-loop performance analysis of a cross-direction (CD) control system and explores the tuning criterion for CD control applications. The paper extends the closed-loop analysis from a linear time-invariant causal (or temporal) control system to a linear non-causal (or spatial) CD control system. Although the CD controllers are different from the temporal controllers, both controllers exhibit similar closed-loop behavior, particularly, their disturbance rejection responses. The disturbance rejection expressed in the spectral domain is key to the performance analysis of a CD closed-loop control system. The spectral amplitude ratio can be used for establishing a tuning criterion for CD control applications. Combining the spectral response of disturbance rejection and the power specuum of process disturbances, the potential reduction of process variations can be estimated.

LP methods in MPC of large‐scale systems: Application to paper‐machine CD control

AbstractAn application of a linear‐programming based model‐predictive control strategy to the paper‐machine cross‐direction (CD) control problem is presented. The objective of CD control is to maintain flat profiles of variables of interest by minimizing worst‐case deviations from setpoints (defects). These control problems can have as many as 200 actuatiors (inputs) and 400 sensor measurements (outputs). This large size coupled with the stringent real‐time requiremnt of computing a control move in a few seconds poses a very challenging control problem. The LP‐based strategy is particularly well suited for solving such classes of control problems. This strategy has demonstrated its ability to solve large‐scale control problems (over 100 inputs and 100 outputs) in real time and exhibits robustness to model uncertainty.

Adaptation of cross-direction basis-weight control in paper machines using fuzzy decision logic

An important quality characteristic in the production of paper webs is the range of fluctuations in the basis weight. This should be kept as small as possible. The basis-weight profile is a measure of these fluctuations. Deviations in the profile that arise during the papermaking process can be rectified by installing slice screws across the web and by suitable control functions. However, due to web shrinkage and displacement in the cross direction, the location on which a slice screw is acting in the profile is not known. This relationship, or mapping, is an essential precondition for cross-direction control. If it cannot be implemented accurately enough, the profile develops unevenness and, in the worst case, becomes unstable. This paper describes a method that identifies this relationship by means of statistical process and a fuzzy decision logic, and that appropriately adapts cross-direction control.

Adaptive cross-direction control of paper basis weight

The initial setting and maintaining of the desired paper basis weight (in machine direction and cross direction) is to be ensured adaptively for several given paper grades. Technical equipment includes: usual traversing gauge at the output of the paper machine, special traversing robot for shaping the headbox lip (sequential setting of screws), control computer. Adaptive multivariate LQG control with recursive identification generalized to distributed parameter system has been designed with the following features: integral (convolution type) model of the process respecting the continuous nature of all signals and kernels involved (by means of spline approximation), repetitive control synthesis (via Riccati equation with periodical solutions).

抄紙機の幅方向制御の実施状況

抄紙機の幅方向制御の実施状況

Adaptive Cross-Direction Control of Paper Basis Weight

Paper basis weight, temporal (machine direction - MD) and spatial (cross direction - CD), is controlled to achieve reliable production homogeneity. The initial setting and maintaining of desired quality is to be ensured adaptively for several given paper grades.Available technical equipment includes: usual traversing gauge at the output of the paper machine, special traversing robot for shaping the headbox lip (one screw at given time moment only), control computer.Adaptive multivariate (both in time and space) LQG control with recursive identification generalized to distributed parameter system has been designed with the following features: integral (convolution type) model of the process respecting the continuous nature of all signals and kernels involved (by means of spline approximation), repetitive control synthesis (via Riccati equation with periodical solutions).Problem formulation emphasizing the specific process and hardware limitations with the outline of underlying theory is given and graphically illustrated.

最近の計装技術 （Ｖ） 抄紙機・幅方向制御

This serial report describes current topics in pulp and paper making process instrumentation technology, and this paper is reviewed of paper machine cross direction control.

A Simulation Study of the Moisture Cross-direction Control Problem

This study aims at understanding the influence of some design factors on the performance of a moisture cross-direction(CD) control system in papermaking. Among the factors are: measurement and actuator widths, misalignment of actuator and sensor, measurement noise level, influence of machine-direction variations, and some examples of measurement/actuator mismatch. A simulation system, characterized by dual signal paths, has been designed. One path represents the signal flow in an industrial CD-control system. The purpose of the second path is to examine the true CD-profile and how it is affected by the control actions. The signals in this path represent process information that are generally not available in an industrial system. Sine waves of various frequencies (in cross-machine length-units) are used as the basic process variations to be controlled. Hence, conclusions can be made about the streak reduction capability of the system. Diagrams are presented showing the reduction of the profiles as functions of the design-factors. Another type of result deals with the difference between the measured and the actual CD-profile. The performance of an industrial control system is generally based on the reduction of the variations measured by an online system. The study points out situations where these measurements can lead to misleading conclusions.