Sensorless tension control in paper machines

Abstract

Abstract-Proper operation of the dry end of a paper machine requires some type of sheet tension control. Present systems use either indirect-speed-control-based schemes, or sensor-based direct tension control utilizing load cells or swing rolls. The indirect schemes are inadequate for most newer machines, and both types of the commonly used sensor-based schemes are invasive, expensive, require either special, or extra rolls, and add complexity to the sheet runs. This paper proposes and evaluates sheet tension estimation using only conventional motor and control signals, present in all newer drive controllers, integrated into a process model observer. This observer-based approach eliminates the need for the invasive tension transducers, and may also be used to replace the inaccurate indirect speed control schemes.

Expert System for Integrated Control and Supervision of Dry-End Sections of Paper Machines

“…In [1] the authors presented a sensorless tension control for dry-end sections of a paper machine, which is capable of estimating and controlling the sheet tension in the upstream draws of the calender and reel sections. The tension estimation algorithm uses torque commands (or torque component of currents) of the drives and is robust to load changes and reduced, or null, differential tension in central sections.…”

“…The objective of the Sensorless Tension Control Supervision block of the proposed expert system is to help and assure the long-term stability of the sensorless tension control presented in [1]. This is done by monitoring the dry-end sections and: 1) using the event recognition ability of the system to keep track of the status in the dry-end sections; 2) refreshing the initial data used by the sensorless algorithms; 3) detecting any abnormal situation by cross-checking the computed values and comparing them with the historical records.…”

No-Tension Sensor Closed-Loop Control Method with Adaptive PI Parameters for Two-Motor Winding System

“…Valenzuela et al at the University of Concepcion, Chile, proposed a control scheme without tension sensor in papermaking system. Two new tension estimators are developed for a two-drum electric-brakinggenerator production winder that are based on unwinding and rewinding variables, respectively, with the essential dynamic, friction, and inertial variation effects considered in the scheme [8][9][10][11]. Lynch from the University of Alberta in Canada exploited linear time-varying error dynamics to design a reduced-order, nonlinear tension observer.…”

Expert system for integrated control and supervision of dry-end sections of paper machines

“…N a previous paper [1], the authors presented a novel sensorless tension control based on section torque commands, which is capable of properly estimating sheet tension even in the presence of section load variations and/or small or null differential tension. This control algorithm was evaluated in a three-section dry-end subsystem of a lightweight coated (LWC) paper machine.…”

“…Actions include messages to the operator of normal conditions, current status of process related sequences, warning messages of abnormal or potentially dangerous ongoing conditions, and tension control of the paper sheet using the sensorless control algorithms proposed in [1].…”