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Complex Software for the Automated Control System of the Controlled Cooling Unit for Sheet Products

 

УДК 621. 771. 23: 621. 771. 06-71: 65. 011
 
Beygelzimer E.Y., Ostapenko A.L., Kuzmin A.V., Kozlenko D.A. (RPC «Donix»)
 
Magazine «Stal'» № 8, 2006

To obtain high mechanical properties of sheet products, hot rolling mills are equipped with controlled water cooling units (CCU). Such units usually include a large number (dozens) of sections, located above and under the stock in the direction of its movement. Laminar cooling units became especially popular on plate and strip mills. The main task of the CCU is to ensure the stock cooling at a specified speed down to the specified temperature without its buckling. Modern requirements to the temperature control accuracy and to its stability along the stock length can be satisfied only through automatic control over the CCU operation.

 

 

The authors of this publication offered a new conception of automatic control over the sheet products cooling and the basic mathematical software for it, which was implemented in 2001 during the upgrade of the laminar strip cooling system on the exit roller table of 1700 mill of OJSC «ISPAT-KARMET». At present this system is in permanent use and ensures the specified coiling temperature along 95% of the strip length with deviations within ± 10 ºС for the stock thickness under 4 mm and ± 15 ºС for the stock thickness over 4 mm. As a result, the mill yield whi is dependent on mechanical properties increased from 97,1 to 98,9 % and the stability of the finished stock properties improved in 2002-2003 in comparison with 2000 (period of the cooling system operation before the upgrade).

The present conception of automatic control over the controlled cooling unit consists in using a special table - the so-called «basic matrix» to choose the specified values (tasks) to control the cooling section valves during the stock movement. This table contains data on the valves setup for all the combinations of three process variables - temperature at the entry into the cooling unit, metal speed and deviation of the temperature at the exit from the cooling unit from the specified value - which are possible for the given lot of the rolled stock. The basic matrix is prepared before the cooling of the stock begins. So to cool each section along the stock length the controller has just to choose the necessary cell in this table. To setup the system before the cooling begins the cell which meets the specified variables (initial setting) is chosen in the matrix. When the cooling begins the cells which meet the actual values from the in-process measurement sensors are chosen in the matrix (correction). Thus, if the temperature at the entry into the CCU or the metal speed , or if the temperature at the exit from the CCU deviates from the specified value, the controller program «slides» over the matrix, changing from one of its cells to another. The basic matrix itself is calculated on a separate computer and transferred to the controller before the rolling of the lot begins.

With the present conception it is not necessary to calculate the corrective actions in the controller during the stock movement. Besides, it ensures the most rapid response of the control system to any disturbances and deviations of the process variables.

In 2005 RPC «DONIX» created a program package (basic software) for the automated control systems of the CCU for plate products based on the described conception. It includes five main software products: 

  1. program for the basic matrix calculation;
  2. visualization program;
  3. program for monitoring the stock movement under the CCU;
  4. program for the section valves control;
  5. program for the calculation model adaptation.

The program package can be integrated into the control system of any laminar CCU, existent or being constructed. To ensure the compatibility with a CCU of any configuration, the mathematical model of cooling was improved significantly in comparison with the version implemented on 1700 mill of OJSC «ISPAT-KARMET».

The programs for the basic matrix calculation and for the calculation model adaptation are realized in Delphi 7 environment. The visualization program was developed using the Wonderware® InTouch® program package, included into the general Wonderware FactorySuiteTM package.

To check and preset the developed software, as well as to demonstrate its possibilities, RPC «DONIX» developed a simulation model of the CCU automated control system. It simulates the stock cooling process on a certain plate mill on the computer monitor in real-time mode. The user («mill operator») specifies the rolling schedule for a certain period (i.e., for the next hour or the next shift) and observes the entire mill operation process on the monitor. The simulation model works on any IBM-compatible personal computer with the operational system Microsoft Windows XP.

The following data serve as basic input data for the simulation model:

  • Layout of the equipment and in-process measurement devices.
  • Rated variables of the CCU (permissible water consumption per section etc.).
  • Inertial characteristics of the cooling unit.
  • Actual state of the CCU (numbers of inoperative sections, inoperative water blowoff facilities).
  • Mill usage program for the calculation period with the indication of sheets quantity, nominal dimensions, steel grade for each lot.
  • Specified values (range) of the temperature at the entry into the cooling unit and the stock speed for different products.
  • Specified temperature at the exit from the cooling unit for the given lot.
  • Specified cooling strategy for the given lot (early, late or uniform).
  • Actual temperature at the entry into the cooling unit and the stock speed.
  • Cooling water temperature.
  • Actual volume of the water in the tanks.

Output data are:

  • numbers of operative cooling sections;
  • water consumption per section;
  • switching-on and switching-off moments for the sections .

The simulation model includes all the five abovementioned software products, as well as an additional program simulating the data which come from adjacent automated control systems, in-process measurement sensors, actuators etc. on a real unit. In the simulation model all these programs work and carry out the data ex on one computer. But structurally the simulation model is divided into three big units (Figure 1), corresponding to their physical layout in the real automated control system:

  •  calculating unit (operates as a system computer for the basic matrix calculation, the calculation model adaptation, data archiving etc.);
  • simulation programs unit (operates as a controller monitoring the stock position, controlling the section valves, as well as carrying out the data ex with other automated control systems, in-process measurement sensors etc.);
  • visualization unit (operates as the operator's workstation).

If we present the CCU automated control system as a two-level structure, the simulation program unit builds the lower level realizing the measurement, control, intermediate processing and direct control functions according to the tasks from the upper level or the CCU operator. The additional simulation program realizes the functions of adjacent automated control systems of the mill, not included into the CCU automated control system. The upper level consists of the calculation unit (which ensures the task calculation for the lower level and data storage) and the visualization program (data visualization for the staff).

Calculation Unit

The calculation unit is used to calculate the cooling modes, brought together into the basic matrix, and to calculate the adaptation corrections.

During normal operation the calculation of the basic matrix is initiated, when the last stock of the preceding lot passes the pyrometer at the exit from the rolling stands (by that moment data about the new lot are already available). Besides, the calculation is initiated automatically, if at least one of the variables (any of them) from the input data (received from the simulation or visualization program) s:

  • numbers of inoperative cooling valves;
  • numbers of inoperative water blowoff facilities;
  • cooling strategy;
  • inter-lot correction of the temperature at the entry into the cooling unit, specified by the operator;
  • numbers of the chosen sections,
  • operation mode of the chosen sections,
  • fraction of water consumption in the chosen sections;
  • fraction of water consumption in the upper sections;
  • ranges of water consumption in the sections;
  • temperature of the cooling water;
  • air temperature;
  • intra-lot adaptation correction of the temperature at the entry into the cooling unit, calculated in the adaptation unit.

The calculation may also be initiated by the operator (from the visualization program). The calculation results are transferred to the simulation program in the form of a basic matrix.

Simulation Program Unit

The simulation program realizes a number of functions:

  • operation of adjacent automated control systems which generate input data to calculate the cooling modes;
  • operation of the programmable controller (including the distributed input-output stations), which processes input signals, controls the actuators, carries out diagnostics and data ex with the elements of the CCU automated control system and adjacent automated control systems;
  • operation of the in-process sensors which serve as input or output signals for the model in general;
  • operation of the actuators (control of the specified water consumption for each section);
  • data ex with the visualization and calculation program.

 

All the functions are realized simultaneously. Data about the adjacent automated control systems (temperature at the entry into and exit from the cooling unit, stock speed at the exit from the rolling stands and on the cooling roller table, steel grades etc.) are generated cyclically from the first stock of the first lot up to the last stock of the last lot. If necessary, data generation can begin from any lot, specified in the program. Before the rolling of each new lot begins the data are automatically transferred to the calculation program. If the lot is not the first one, the data are transferred, after the last stock of the preceding lot passes the temperature sensor at the exit from the rolling stands. The data are used for visualization and serve as input data for the calculation of cooling modes for each stock. For each stock of each lot the program simulates some s in on-line data (actual values of speeds at the exit from the rolling stands and on the cooling roller table, data from the pyrometers and photocells, installed in the processing line etc.). Data from the sensors generated in the simulation program serve as input data both for the model of the controller and for other programs.

The simulation program interface consists of several windows. From the window (Fig. 2) one can control the operation of the program and call auxiliary windows. The main window contains several windows, which characterize the operation of the program. It also contains a graphic presentation of the CCU segment, including upper and lower sections, pyrometers at the exit from the rolling stands, at the entry into and exit from the cooling unit, stock position pyrometers.

Several windows of the main window represent the operation of the program. The window «Data from SAPP» (SAPP - System of Automatic Production Planning) characterizes the operation of the simulation program in the adjacent automated control systems, the window «Intermediate Data» characterizes the operation of the main controller related to the stock movement monitoring, rolled stocks record, calculated cooling modes control. The windows «Transfer to the visualization program» and «Receive from the visualization program» characterize the data ex between the programs. The menu items («File», «SAPP», «Additional») and menu buttons of the simulation program («Start», «Stop», «Matrix», «DDE», «SAPP», «Sections») are situated in the upper part of the window. The corresponding buttons (or menu items) activate the windows which display

  • data about the heats of the stocks;
  • results of the mathematical model calculation;
  • data, participating in the ex between the programs;
  • data about the stock movement along the processing line.

The complete length of the stock is conventionally divided into discrete segments (for control purposes). All the segments, but for the last one, have equal length, divisible by the length of the cooling sections. The length of the last segment corresponds to the remaining rear end of the stock. The program controls the position of each segment on the roller table and collects all the in-process measurement data about it (temperature at the exit from the rolling stands, at the entry into the cooling unit, at the exit from the cooling unit, the stock speed). Based on the in-process measurement data the program calculates the keys for the basic matrix and chooses the cell which corresponds to these keys. The cell contains the following information: which valves are to be opened to cool the given segment of the stock and the water consumption for them. Switching-on and switching-off moments of the corresponding valves are determined depending on the current position of the given segment on the roller table and the specified persistence of the water feed system.

Thus, as the new stock segments enter the CCU the system moves from one cell of the basic matrix to another, depending on the actual temperature at the entry into the cooling unit and on the stock speed of the given segment. If the temperature at the exit from the cooling unit deviates from the specified value the water feed is corrected in the same way. If the actual values of the variables in the matrix deviate from the centre of their range in the basic matrix too much, the basic matrix is calculated again in the calculation program and the updated matrix is sent back to the simulation program. To estimate the said deviations the calculation program receives from the simulation program the actual values of the variables (temperature at the entry into the cooling unit and at the exit from the cooling unit, the stock speed in the spraying zone) for a certain stock segment, called «adaptation segment», which is situated at a certain distance from the stock front end. The distance is specified by the operator in the visualization program.

The initial setting is carried out according to the predicted values of the variables. The correction is carried out depending on the disturbances ( in the temperature at the entry into the cooling unit, in the stock speed) as well as on the deviation (deviation from the specified temperature at the exit from the cooling unit). In both cases the operation of the simulation program consists in moving from one cell of the basic matrix to another depending on the disturbance (deviation) value. The initial setting for the first, second and third stock of the lot is carried out according to the mean specified value of the temperature at the entry into the cooling unit, the cooling roller table speed and the temperature at the exit from the cooling unit. The initial setting for the fourth and further stocks is carried out according to the mean values of the temperature at the entry into the cooling unit, at the exit from the cooling unit and of the cooling roller table speed for the adaptation segments of the preceding three stocks of the given lot.

The correction of the temperature at the entry into the cooling unit is carried out, after the first signal comes from the corresponding sensor. From this moment the corresponding temperature value is assigned to each segment along the stock length. The movement of each segment through the cooling unit is monitored by the program. Thus, each segment is cooled by the sections which correspond to the cell of the basic matrix with the required temperature at the entry into the cooling unit. The correction of the stock speed in the CCU is carried out according to the actual speed of the cooling roller table, received from the corresponding sensor. The correction of the temperature at the exit from the cooling unit is carried out, when the temperature of the adaptation segment at the exit from the cooling unit is received. This temperature is used to choose the cell of the basic matrix. In the cell of the basic matrix this temperature is obtained by adding up the specified value and the adaptation correction which takes into account the deviation of the actual temperature at the exit from the cooling unit from the specified value.

Visualization unit

Visualization unit is used by the operator to control the CCU operation and carry out the following main functions:

  • visualize the cooling process (stock movement, switching-on and switching-off of the sections etc.);
  • display the data, characterizing the process (temperature variables, water consumption etc.);
  • input the necessary data (numbers of inoperative sections, lengths of the uncooled front and rear end etc.);
  • control the cooling process (operation mode, re-calculation of the cooling modes  etc.);
  • realize service and test functions (archive data review, operation in the test and manual mode etc.);
  • ex data with other programs.

The visualization program consists of eight main windows and of the menu window:

  • «MENU». Selection of active windows of the visualization program; display of general information about the operation of the CCU automated control system;
  • «F1 - Main». The window displays the processing line from the finishing stand up to the pyrometer at the exit from the cooling unit; the main data about the CCU automated control system;
  • «F2 - CCU». Detailed display of the operation of the cooling sections;
  • «F3 - Setup». Settings for the operation of the CCU automated control system;
  • «F4 - Control». s in the operation mode of the CCU automated control system and the settings for the semi-automatic and manual modes;
  • «F5 - Trends». Graphs of the temperature and water consumption measurement;
  • «F6 - Service». Results of the mathematical model calculation;
  • «F7 - Archive». Data about the stock cooling and the log of the CCU automated control system operation;
  • «F8 - Adjustment». Adjustment of the CCU automated control system (data ex with the modeling and calculation programs).

THe button with the name of the window or functional keys F1-F8 are used to switch between the windows . Additional windows can be called from each main window.

The «MENU» window and «F1 - Main» window are shown at Fig. 3.

The «MENU» window displays

  • functional keys to choose the active windows;
  • conventional designation of the upper and lower sections of the CCU and the water blowoff facilities as well as their state;
  • data about the heat which is being processed in the CCU (number of the heat, steel grade, dimensions, number of ingots in the current lot and number of the stock which is being processed);
  • current operation mode of the CCU automated control system (automatic or other);
  • data about the current date, time;
  • data about the calculation of the basic matrix of cooling (time of the last calculation and indication of the current calculation);
  • buttons to start and stop the simulation and calculation program operation.

The window «F1 - Main» displays the segment of the processing line from the finishing stand up to the pyrometer measuring the temperature at the exit from the cooling unit, the stock position at the present moment, the operation of the cooling sections and other data, characterizing the operation of the CCU automated control system and the cooling process

  • width of cooling;
  • length of the uncooled front and rear ends;
  • correction of the temperature at the exit from the cooling unit, total (specified by the operator);
  • correction of the temperature at the exit from the cooling unit, within the given lot (calculated by the calculation program);
  • cooling strategy;
  • specified and actual temperatures at the entry into and at the exit from the cooling unit;
  • current and total water consumption for the stock at all the sections of the CCU;
  • air and cooling water temperature;
  • speed of the cooling roller table;
  • volume of the water in the tanks;
  • current temperatures at the exit from the rolling stands, at the entry into and exit from the cooling unit (if the stock is under the corresponding pyrometer).

The window «F2 - CCU» displays the processing line of the CCU from the pyrometer measuring the temperature at the entry into the cooling unit up to the pyrometer measuring the temperature at the exit from the cooling unit. This window displays the operation of the CCU sections. The window «F3-Setup» is used to enter the settings; here the operator enters the process variables for the operation of the CCU automated control system. The window is divided into two parts - with general and limited access (password). Without the password the operator can choose (specify):

  • operative/inoperative sections and blowoff facilities (the operative section is marked green);
  • chosen sections (the chosen section is marked blue);
  • cooling strategy (early, late, uniform, interrupted);
  • length of the uncooled front and rear ends;
  • operation mode of the chosen sections (to use/not to use);
  • correction of the temperature at the exit from the cooling unit, total.

Using the password the operator can

 

  • specify the size of the uncooled side segments;
  • specify the variables for pairwise switching-on of the sections (exceptional, top or low);
  • choose the strategy within the top or lower priority (earlier, later, uniform, max. consumption);
  • allow or forbid the calculation of the intra-lot adaptation correction of the temperature at the exit from the cooling unit;
  • specify the distance of the adaptation segment from the front end of the stock;
  • ecify the delays for switching-on and switching-off of the section (to take into account the stock monitoring by the simulation program);
  • specify the minimal and maximal ranges of water consumption in the sections for each segment of the CCU;
  • specify the fraction of water consumption in the chosen sections;
  • specify the fraction of water consumption in the upper sections.

The window «F4 - Control» is used by the operator to choose the operation mode («automatic», «semi-automatic», «manual», «without cooling», «test») and to specify the variables for it. The window «F5 - Trends» displays trends with the curves of s in temperatures at the entry into and exit from the cooing unit (specified and actual) as well as current and total water consumption for the stocks (total and for each segment). The window «F6 - Service» is used by advanced users to see the results of the mathematical model calculation. The window «F7-Archive» displays data about the cooling mode for each stock and the log of the CCU automated control system operation. The window «F8 - Adjustment» is used to adjust the simulation model of the CCU automated control system; the window displays all the data necessary for data ex between the programs.

Conclusion

RPC «Donix» developed a complex software package for the automated control systems of laminar controlled cooling units (CCU) for plate and strip hot rolling mills. The developed program package can serve as a base for the creation of automated control systems for almost any laminar cooling unit for sheet products. To check and preset the software RPC «Donix» developed a simulation model of the automated control system for a CCU for plate products. The model operates in real-time mode.

 

 

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