1. Introduction
The TRACK tracking model is a crucial component of the L2 system. Its primary task is to track and process data on materials within the heating furnace and on the steel plates being rolled. When a steel plate is at a specific position on the mill, it performs appropriate actions, such as activating pass calculations or initiating position detection. The TRACK model also maintains the L2's foundational data and participates in all tracking-related operational inputs, such as canceling the tracking of a single steel plate. The accuracy of material tracking directly impacts the effective operation of the entire L2 system.
The TRACK model is built upon information received from L1 (Level 1 process automation), which is fundamental to material tracking. To provide a more comprehensive explanation of the material tracking model, the relevant terms are explained below:
(1) Frame: This refers to the horizontal frame, such as the roughing mill and the finishing mill.
(2) Steel billet/plate: The start time of material rolling refers to the beginning of the first pass. Therefore, the upstream process of the product includes steelmaking and heating furnace. When the first pass begins, the steel plate is rolled.
(3) Rolling sequence: This is the order in which rolling commands will be executed. This sequence list is stored in a database. At the start of rolling, if a given steel plate needs to be removed from the rolling sequence, the operator must perform the change maintenance.
(4) Passes: refers to the reciprocating motion of the steel plate in a horizontal frame. Passes that do not change the thickness of the steel plate are called empty passes.
(5) Cooling: During hot rolling, the steel plate must be cooled, including the cooling of the billet before rolling.
(6) Basic Data: Basic data is stored in the database, including billet size, temperature, chemical composition, and target data for finished steel plates, as well as other rolling data such as the number of turns and TM mode. These data are calculated from the number of passes.
(7) Steel Plate ID Number: This is the unique identifier of the steel plate in the L2 system, in the format X-XXXXX-XXX.
(8) Handover instruction: Assign an ID number to a steel plate in the tracking model and detect the data structure of the steel plate.
2. Introduction to the TRACK Model
TRACK is a standalone subprocess within the L2 system, driven by detection signals from L1, and its activity status can be viewed in the relevant HMI. L1 is the manager of the tracking model, and the TRACK model is updated using information provided by L1. For example, L1 does not use steel plate ID numbers; instead, it uses L1 ID numbers from 1 to 5 and establishes a connection between the L1 ID numbers and the steel plate ID numbers. The TRACK model can process data from 12 steel plates simultaneously, while L1 can only process data from 5 steel plates. The TRACK model can handle virtual steel plates within the heating furnace.
2.1 Mirror Image
The material tracking model is a mirror image of a tracked object on the rolling mill. The TRACK model establishes a usable rolling mill mirror image, including sensors, tracking areas, and measurement positions. Sensors themselves do not provide tracking information; they only generate on/off signals. Generally, sensor observers provide tracking information and can apply sensor signals to perform a tracking function. A sensor observer can observe one or more sensors and can execute one or two on/off signals. A sensor can be paired with multiple sensor observers, and a sensor observer can also be paired with multiple sensors.
The tracking model defines the following sensors: a hot metal detector (HMD) (from the exit roller conveyor to the leveler inlet), an infrared thermometer to detect the initial rolling temperature, a thickness gauge, the roughing mill stand, and the finishing mill stand. All sensors are controlled by L1 for on/off switching.
2.2 Tracking Area
The tracking area is a physical area of the rolling mill. It is a set of rollers, a stand, or a section of slides in the furnace. It marks the start and end points and maintains a list of occupancy of the steel plate in that area. The tracking area covers the entire rolling mill area, from the furnace to the straightener.
The tracking area is the sensor observer. It contains tracking information, can assign on/off signals to sensors on a specific steel plate, and execute appropriate actions. The detection element can be switched on/off at any position on the steel plate within this area, and measurement is automatically initiated when the steel plate reaches the detection element. Therefore, all measuring elements and tracking areas in the rolling mill production line, from the heating furnace to the straightening machine, can successfully detect the actual position of the steel plate and display the operating status on the HMI for operator identification and confirmation. The tracking areas are mainly divided into the following:
(1) Put into the furnace
The furnace feed area is a special tracking zone within the furnace. This feed area connects to a complete furnace runner. Unlike ordinary tracking zones that can connect to form a chain along the production line, all feed areas are located in the same position on a given furnace runner, but they are also connected to form the billet arrangement diagram of the runner. Each feed corrects one billet within the furnace runner. The furnace runner is set to be occupied or unoccupied during feed and discharge. There are no detection elements in the feed area.
(2) Roller conveyor control and monitoring
Each set of roller conveyors uses a tracking area for correction, primarily relying on speed for judgment. Because tracking within the roller conveyor area is relatively simple and can perform very small tracking actions, numerous roller conveyors can achieve customized tracking behavior. The roller conveyor areas on the production line are divided into tasks, performing corresponding operations:
RE1: Roughing mill front roller table. Used to set the billet descaling time and activate the rolling table calculation. Updates the billet layout in the furnace and detects the current billet position and temperature.
FE4: Roll table where the finishing mill and roughing mill connect. The rolling schedule needs to be recalculated for the number of passes.
FE1: Pre-rolling conveyor rollers for the finishing mill. The detection element indicates that the steel plate has entered, and the pass calculation restarts.
FX1: Finishing mill rear roller table. The detection element indicates that the steel plate has left the finishing mill, and the pass calculation restarts.
FX2: Thickness gauge roller conveyor after finishing mill. Steel plate detected entering the thickness gauge area.
FX3 to the straightener roller conveyor: After the steel plate leaves the thickness gauge area, it enters the ACC cooling area and the straightener area.
(3) Rack area
The stand area refers to the rolling mill where rolling is currently taking place. It occupies only a position, not a length like other areas. The stand area is where the speed of the currently rolled steel plate begins and ends, and it also tracks whether the stand is under load or not. It is divided into roughing mill stands and finishing mill stands.
(Figure 1: Material tracking diagram)
3. Functional Analysis
Material tracking is one of the main tasks of the TRACK model in L1, but it must perform specific related tracking functions in the L2 system.
3.1 Handover Function
Handover refers to creating an entry in the steel plate tracking record structure. Only steel plates that have undergone handover in the L2 system and entered the material tracking can be rolled. Once a steel plate has been handed over through rolling and processed by the L2 system, it will remain in the tracking catalog until the steel plate leaves the tracking area, is removed, or the handover is canceled. L2 defines several forms of handover: automatic handover, manual handover, priority handover, in-furnace handover, and virtual handover. Specific functional descriptions are as follows:
3.1.1 Automatic handover
This is the commonly used mode. The next billet is automatically handed over in the rolling sequence, and the tracking graph in L1 indicates that a new billet is currently on the exit roller conveyor. On the HMI interface in L2, the operator can use the "Automatic Handover" button to perform the operation.
If the TRACK model doesn't know what the next billet is, it will mark the billet as "unrecognized," displayed as "I-don't-know" on the HMI. The operator should switch to manual handover mode, at which point automatic handover will be unavailable.
3.1.2 Priority handover
If a billet must be changed when automatic handover or automatic handover mode is unavailable, priority handover mode can be used. Before the billet leaves the furnace, its name (Bill ID) has already indicated that a handover operation has been performed, giving the operator ample time to complete the process. Priority handover mode is implemented manually by the operator using the handover dialog box on the HMI.
To indicate that the billet has been given priority handover, the steel plate's ID number is displayed with a high-brightness background on the HMI. Once the billet has been handed over, its ID has been transferred from priority handover to a new billet, and rolling continues uninterrupted.
3.1.3 Manual handover
Manual handover is required when automatic handover is unavailable, or when the rolling sequence is empty after a "cancel handover" process has been performed. Manual handover is similar to priority handover. It is also performed manually by the operator through a dialog box on the HMI. During manual handover, the ID number of the steel plate is assigned to an unknown billet during tracking, which is displayed as "I-don't-know" on the HMI.
3.1.4 Handover inside the furnace
When a steel billet reaches the front of the furnace runner, the in-furnace handover is automatically initialized. The purpose of this handover is to perform a pre-calculation of a pass schedule, so the operator can see the pass rolling schedule. It also alerts the operator to avoid generating an invalid rolling schedule for this billet. Once the billet is handed over to the tracking record, it may require the operator to enter steel plate process data, which can affect the calculation of the rolling schedule.
3.1.5 Virtual handover
Sometimes, a steel billet that has already undergone pass calculations is remelted, in which case a virtual handover will be performed. The operator needs to select the virtual dialog box on the HMI to perform the operation, and the pass calculation for this steel billet will be executed. Subsequent virtual handovers will overwrite the previous virtual handovers.
3.2 Cancellation of handover (reprocessing operation)
Sometimes, incorrect automatic billet handovers occur. This could be due to an incorrect rolling sequence or tapping the wrong pass in the furnace. The operator can manually correct this by selecting the billet's ID number in the "Cancel Handover" dialog box and changing it to "I-don't-know" on the HMI interface. When the cancellation request is set as a priority handover, the billet is removed from the tracking catalog.
3.3 Tracking graph update
The tracking map update function is a virtual material tracking mechanism. The L1 system sends an updated tracking map and status information every 192ms. The TRACK model uses this function to update its own tracking map and sensor detection status information and measurement values to generate on/off signals. These signals drive the entire L2 automatic control system. Clearly, this periodic information from L1 is central to the entire L2 system.
3.3.1 Update the furnace internal status and layout diagram
Each time the RE1 roller sensor is activated, it means a new steel billet has passed through the descaling machine. At this time, the TRACK model sends an L2_F2_RequestStatusTrackMap message to FU_L2_StatusTrackMap, updating the furnace diagram in L2. All basic data for new steel billets is read from the DS database and stored in the local database. This process is repeated after each loading or unloading operation.
The TRACK model updates the billet layout in the furnace by reading basic data from the DS database and storing it in its local database. The TRACK model moves the billet to the first position at the start of the rolling sequence, and after confirming that the automatic handover has read the correct billet information, it sends a notification to the L1 system.
3.3.2 Tracking and Correction
If the HMD thermal detector or other tracking sensors malfunction, the position of the steel plate in the tracking map will not match its actual position. Using the "Tracking Correction" dialog box on the HMI, the operator can correct the position of the steel plate and the number of passes. The TRACK model transmits this correction to L1 to update the tracking map.
3.4 Clear Tracking
In rare cases, it may be necessary to completely reset the tracking catalog, which is achieved by applying the Clear Tracking procedure. All plate IDs in the tracking catalog table will be cleared. The Clear Tracking procedure is initialized in the Tracking Correction dialog box on the HMI; because this is crucial, the operator must confirm this action.
3.5 Calculation process
A model closely related to the TRACK model is the PSC pass calculation model. The activation of the PSC model is generally triggered by the following instructions or events: (1) after the handover instruction; (2) after billet descaling; (3) when the FE4 roller is handed over to the finishing mill; (4) before billet centering/before the steel plate arrives at the finishing mill; (5) after each pass of the finishing mill; (6) after feedback from the thickness gauge; (7) operator activation; (8) request for L1 setting, etc.
Based on the steel plate position determined by the TRACK model, process calculations for four passes are activated: (1) PSC1 before exiting the furnace; (2) PSC2 before the first pass of the finishing mill; (3) PSC3 during finishing mill rolling; and (4) PSC4 after finishing mill rolling. After the pass calculations are completed, a message is sent to the TRACK model. If an error occurs, an error code and error text are sent to the operator interface (HMI).
(Figure 2: Flowchart of the course calculation steps)
4. Summary
The TRACK tracking model plays a crucial role in the control of the L2 system. It places high demands on the setting of the roller conveyor speed, the sensitivity of the detection elements, and the communication connection with the L1 primary automatic control system. Understanding its main functions and components allows for better maintenance and optimization of the secondary system, ensuring the effective operation of the model.
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