Digital Integrated System of Control over the Main Drive of the Rolling Mill 1300 in the Blooming Shop of KRSIMMW "Krivirozhstal"

The system controls the roll motors of a reversing roughing mill. The principle of the system's configuration can be used for similar control systems on rolling mills of other types.

A fundamentally new approach was chosen to manage the problems of control over the rolling mill main drives, where the rolling process and the drive are considered as a united multivariable system (motors - rolls - ingot - rollers). The system allows to reduce dynamic equipment loads and to increase the mill performance. This is achieved by means of continuous determining the complex factor of the current rolling process stability. Besides, the system develops an optimal strategy for motor torque and speed control.

Dynamic control of stand drives speed-torque characteristics is carried out to ensure stability of the rolling process. Partial damping of rolling-induced oscillatory processes as well as of natural shafts vibrations by the motors also contributes to the reduction of dynamic loads on mechanical parts of the equipment, induced by impact loads

Functional structure of the control system:

The technique-adapted system of automated control over the top and bottom motor speeds and currents.
The first process control loop. It includes the following systems: system of control of the motor torques and speeds relationship; detection of unstable operation modes (including cobbles); determination of process load; speed schedules control with the function of determining the quality of metal biting. The control loop also includes dynamic torque and power settings control; the unit of ski-shape bending and front/end pressure generation during rolling; calculated motor torque sensors; process protection of static torques and preliminary protection of energy-power parameters of the motors, etc. Most systems are realized for the first time.
Units of energy-power parameter sensors, of digital motor speed sensors and stand machinery position sensors, sensors of the power-electrical equipment current state.
Information-analytic system (is being developed). The second process control loop. Its main tasks are to analyse the production process and to work out integrated control action according to the processing situation, and to display the received data for the attendants. The system will help to accumulate data about the rolling process (appoximately 500 parameters) with the possibility of further analysis.

The system consists of the main control cabinet, rolling control operator and control room operator terminals, the adjuster's workstation, connected through Ethernet. A PC-compatible open platform, based on Fastwel controllers with an extended operating temperature range (-40? : +70?), is used as the system's control module. The open platform allows to use QNX real-time operational system, which ensures flexible approach to the current tasks.

The system is equipped with an extended graphic interface, which provides visual monitoring of current energy-power parameters during rolling. During rolling the operator can carry out set-up for a certain rolling technique. During rolling the attendants can change approximately 300 parameters of the control system in the on-line mode, using an integrated real-time program oscillograph, to monitor the condition and carry out the measurement of more than 200 system variables.

The system allowed to increase the rolling process stability and the mill performance as a result of significant reduction of the durability and gravity of unstable rolling schedules or as a result of their complete elimination.

After the installation of new ("raw") rolls the mill performance falls due to an increased amount of dangerous unstable operation modes, which can lead to the equipment failure. After the rolls running-in the mill achieves its full performance. Inevitable "cobbles", mainly caused by the absence of a heat scheme, are detected and eliminated by the system with the accuracy of almost 100 %. The biting quality evaluation, early detection of unstable modes and overloads reduction allow the operator to work in a stable mode and to avoid the unnecessary rolling speed and drive load reduction. Finally that ensures increase of the mill performance. The results of the system's implementation are equal to the increase of the motors capacity by 15 : 25 %.

The period of the operator's training when changing for new technologies has been shortened. Besides, the dependence of mill performance on the operator's experience has been reduced. In fact, operators with a relatively short period of service provide the performance, similar to the one, provided by the experienced ones.