Automated Position Control System for the Screw-Down Structure of Vertical Rolls of Slabbing Mill “1150”, ACS “APCS VRSDS 1150”
Purpose of the automated position control system for the screw-down structure of vertical rolls of the slabbing mill (ACS "APCS VRSDS") is to ensure automated control over the width of the rolled slabs to obtain minimal scrap edges during subsequent transit rolling of the obtained slabs on the hot wide-strip mill.
Fig. 1 shows outline flowchart of the system.
Fig. 1- Outline Flowchart of ACS «APCS VRSDS»
The system’s functions are:
- to collect data about the basic energy-power values of the main drives of slabbing mill «1150»;
- to collect data about the screw-down structures position on slabbing mill «1150»;
- to collect data about the condition of the VRSDS electric drive circuit;
- to collect data about the basic energy-power values of the VRSDS electric drive;
- to collect data from the existing systems in the roughing and sheet rolling shops through the server of APCS;
- to track metal travel relative to the slabbing mill stands based on the collected data;
- to calculate energy consumption for deformation;
- to store the drafting maps used by the operator and to reproduce them later;
- to select the drafting maps automatically based on the collected data, according to the technological instruction;
- to calculate the VRSDS position automatically with correction for certain rolling conditions taking into account required tolerances for consequent rolling on the hot thin-strip mill;
- to move vertical rolls to a specified position automatically by the operator’s command before the next pass;
- to stop the VRSDS electric drive automatically in case of emergency situation in the VRSDS electric drive or «APCS VRSDS 1150» system (System);
- to record emergency oscillograms automatically with 80% prehistory to analyze the causes of emergency situations in the VRSDS electric drive and in the System;
- to display symbolic diagrams, real-time oscillograms of the VRSDS electric drive and other data necessary for duty electricians of the computer room to control the VRSDS electric drive operation; all the above data are displayed on the System control cabinet monitor;
- to ensure convenient input of setup variables without shutting the System down;
- to protect setup variables against unauthorized access;
- to generate and view System messages in real-time mode, to view messages for any elapsed period (over 200 types of built-in System messages);
- to carry out System diagnostics using additional software;
- to display oscillograms of all the basic signals of the System in real-time mode with the possibility to change the colour, to invert, stop, record, playback, and measure the selected signals on the System control cabinet monitor;
- to record all the basic signals of the System simultaneously with further representation in MS Exell to analyze the System operation and rolling technology;
- to display process data (graphical representation) necessary to control the System process part operation on the System control cabinet monitor;
- to display required process data (graphical representation) on the monitor of the slabbing mill operator’s workstation (dials of screw-down structures, currents, speeds of the main electrical drives, condition of electrical drive circuits, control systems availability, process data, rolling tables etc.);
- to display required process data on the monitor of the duty electrician’s workstation in the control room; to display data about the VRSDS electric drive condition; to display real-time oscillograms of the VRSDS electric drive and main drives of the slabbing mill; to view and print System messages; to view, analyze and print System oscillograms; to prepare and correct rolling tables.
The System has six operation modes. Three operation modes ensure direct control over the VRSDS electric drive. There exist the following operation modes:
- «Manual» mode – standard manual operation mode of the VRSDS electric drive
- «Memory» mode - reproduction of the stored drafting schedules
- «Table» mode – automatic selection of drafting schedules according to the drafting schedules specified in the technological instruction and data about the steel grade, ingot type, required dimensions, ingots quantity, and number of orders in the melt, which are obtained through the information network.
- «After-Rolling» mode – auxiliary mode for temporary switching to manual control over the screw-down structure of vertical rolls before the new rolling cycle begins, in order to remove any defects of the ingot caused by nonuniform heating etc.
- «Setup» mode – system operation in observation mode without visualization of control actions concerning the VRSDS electric drive;
- «Emergency» mode – the mode is activated automatically in case of failures in the system or in the electric drive, which results in the system disconnection from the VRSDS electric drive and shutdown of protective switching equipment (if that is provided for by setup variables).
Hardware
The System consists of component parts from famous automation equipment producers: ADVANTECH, OCTAGON SYSTEMS, GRAYCHILL, HIRCHMANN, RITTAL, DATAFORTH, WAGO, BALLUFF, FASTWELL etc.
Fig. 2 Fig. 3 Fig. 4
Operator’s workstation System control cabinet Duty electrician’s workstation
Software
Operational system of the upper and lower level - QNX4.25
The software is written in Watcom C language, graphical applications are written in Photon 1.14 environment.
Fig. 5 – Main visualization windows
The System passed experimental-industrial tests and is being implemented in the roughing shop of Metallurgical Works «Zaporozhstal».
High accuracy of vertical rolls positioning on the slabbing mill (error makes at the most +/- 1 mm according to the position sensor) was obtained thanks to original engineering solutions for determination of the vertical rolls position and application of the algorithm of adaptive nonlinear position controller with correction of static current and voltage of the screw-down structure electric drive. To obtain such a high accuracy it was necessary to decide some problems which arise due to the following factors: variation (with time) of static load applied to the VRSDS electric drive; the drive’s circuit and mechanical features that don’t give the possibility of readjusting the drive to obtain the required parameters, provided for by the classical theory of the electric drive, without large investments. Variation of static load applied to the VRSDS electric drive results from design and operation features of the mechanical part of the VRSDS. Variation of VRSDS operation modes, ambient temperature, inter-repair maintenance, and accelerated wear of the mechanical part influence the static load variation.
Fig. 6 – Oscillogram of VRSDS electric drive operation controlled by the System
The System is unique, the same way as each roughing mill is unique.
Results obtained during creation of the present System can be used to create various systems of automated control over the screw-down structures of rolling mills.
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