1. Introduction The small-to-medium-sized steel rolling production line was built and put into operation in 1997, mainly producing round steel, spring flat steel, channel steel, and rebar. A water-cooling system is used for bar temperature control. During the rolling process, bars must be received from the cooling bed in the grouping area, and magnetic handles are used to compactly group and transport them to the shearing roller conveyor (CCL). The PLC control system for this production line is provided by ABB, and its grouping system uses the ABB MasterPiece 200/1 PLC control system, which realizes the neat placement, fixed support, and transport control of bars during the rolling process. 2. System Composition The basic automation system uses ABB's RMC200 steel rolling control system, which is an open distributed control system consisting of one MP200/1 process station and one AS520 operator station. The process station consists of a CPU rack and an I/O rack. The CPU rack is equipped with a CPU module DSPC172, a memory module DSMB176, a 16-channel DSAI130, an 8-channel DSAO120, and a 32-channel DI/DO module. It is connected to the MasterBus300 bus through the communication module DSCS140 to communicate with other process stations. The I/O rack is expanded by the bus expansion module DSBC172. The operator station uses an HP-UNIX workstation and is connected to the redundant interface of the MasterBus300 through a real-time accelerator board. Through it, operators can directly monitor the field water-cooled equipment. The main functions are: (1) automatic/manual start and stop of the group system (2) bar count setting and real-time monitoring (3) display and printing of event and alarm lists, etc. The main screens of the group system are the start screen, setting screen, maintenance screen, event screen and alarm screen. [b]3. Software implementation[/b] Includes system software and application software. (1) System Software: The ABB Master Piece200 central unit is a high-performance 32-bit microprocessor. The system software is stored in the EPROM module and includes a real-time operating system and an ABB Master Piece language (AMPL) executor. (2) Application Software: The application software is stored in the RWM (Read/Write Memory) with a backup battery and is programmed using the ABB Master Piece language (AMPL), realizing structured programming. Industrial control programs often have many functions. According to the requirements of industrial control, the programming elements are designed as graphical function blocks, called PC elements. There are three types of structural elements in the PC element: PCPGM, CONTRM, and FUNCM. PCPGM is the highest level of the program structure, which is designed to complete a complete control function. A PCPGM allows one or several CONTRMs, and a CONTRM can contain one or several FUNCMs, so that the entire program structure is hierarchical and realizes structured design. In addition, there is a real-time database in the CPU, which is used to permanently store data and transfer data between programs. The elements in the database are called DB elements. These elements include the I/O templates and signals used by the process station and other data information generated in the program. 4. Control function 4.1 Process equipment grouping area mainly receives bars from the cooling bed, and arranges the bars compactly by magnetic hand, groups them and transports them to the shearing roller conveyor (CCL). The grouping area includes the following equipment: Destacking device (DPAS), Alignment roller conveyor (LIN): 100 grooved roller grouping equipment: (1) Magnetic grouping trolley (FT); (2) Grouping conveyor chain (FC); (3) Magnetic finger (MF); (4) Support flap (SFL) Extraction and transfer equipment: Grouping transfer trolley (ET1, ET2, ET3, MET) The process flow diagram of the grouping area is shown in the figure: [align=left]4.2 Alignment roller conveyor (LIN) The alignment roller conveyor is located on the exit side of the cooling bed and consists of 100 grooved rollers, with 10 in each group. There is a fixed buffer mechanical baffle at the tail end of the cooling bed to align the head of the steel. The roller conveyor section used is set by the operator or automatically according to the rolling schedule. Forward rotation is controlled by MCC (reverse rotation has been cancelled). The operation status is intermittent or continuous operation. Intermittent cycle allows roller conveyor start conditions: cooling bed start cycle signal delay, delayed stop (T2). 4.3 Grouping and Transfer Area 4.3.1 Overview In this area, bars from the cooling bed are received using the same equipment, and the bars are precisely arranged compactly, grouped and transferred to the roller conveyor by magnetic hands. This area includes the following equipment: Grouping equipment: (1) Magnetic grouping trolley (FT); (2) Grouping conveyor chain (FC); (3) Magnetic fingers (MF); (4) Support flap (SFL) Extraction and transfer equipment: Grouping transfer trolley (ET1...ET10,MET) 4.3.2 Functional description 4.3.2.1 Magnetic grouping trolley To ensure continuous grouping, two sets of identical trolleys (A and B) are provided. Two sets of trolleys work in turn. One set always stops in the collection area (upper position: receiving bars from the cooling bed), while the other set unloads steel onto the extraction trolley, or returns to the parking position or remains parked (lower position). Each unit is driven individually by a DC motor via a gearbox. It is equipped with the following sensors: two encoders (speed and position control), two proximity switches (for position encoder reset: DI5.4/FT_SG1_CHG_A, DI5.5/FT_SG2_CHG_B), two proximity switches for cooling bed unloading (DI5.6/FT_SG3_DISCHG_A, DI5.7/FT_SG4_DISCHG_B), and four limit switches (motor emergency stop: DI5.8/FT_SG5_CHG_MOV_A, DI5.9/FT_SG6_DISCHG_MOV_A, DI5.12/FT_SG9_CHG_MOV_B, DI5.13/FT_SG10_DISCHG_MOV_B). 4.3.2.2 Grouped Conveyor Chain The grouped conveyor chain consists of three groups, each driven by an AC motor via a gearbox. Each section is equipped with the following sensors: a pulse generator and a thermocouple mounted on the motor. The group conveyor chain and magnetic grouping trolleys are synchronized, allowing steel bars to be placed at the required distance. The detection elements for the group conveyor chain include: two proximity switches to detect the steel bars on the chain (DI5.14/FC_SG1_LAYERDET, DI5.15/FC_SG2_LAYERDET); a computer sends a speed setpoint to the frequency converter cabinet (AO1.1/FC1_IN_SPREF, AO1.2/FC2_IN_SPREF, AO1.3/FC3_IN_SPREF); and simultaneous monitoring of the encoder's operating voltage (AI1.2/FC1_TACHO_5V, AI1.3/FC2_TACHO_5V, AI1.4/FC3_TACHO_5V). During collection, the movement of the conveyor chain and the grouping trolleys is always synchronized. Once grouping is complete, the grouping trolleys and conveyor chain move to the extraction area within a short time, less than the cooling bed cycle time. The grouping trolleys operate in rotation. Each group of bars consists of N bars (set in the OS). After the grouping trolley rises from the stop position, it moves to the appropriate position to collect the first bar of the group. During each cooling bed cycle, the bar detected by the limit switch on the last tooth of the fixed crossbeam is loaded onto the grouping trolley, and the bar counter N1 increments by one. After the bar is loaded onto the trolley (at an appropriate time after the start of the cooling bed cycle), if N1 > 4.3.2.3, an electromagnetic hand is used. The electromagnetic hand is used to grasp the bars in the grouping area and correctly place them onto the grouping trolley. Two sets of fingers, "A" and "B," are provided to grip the steel when the trolley is positioned. When two bars are unloaded simultaneously (double-tooth cycle), both sets of fingers are used simultaneously; otherwise, only one set is used. The distance from the fingers to the cooling bed can be mechanically adjusted according to the product dimensions. 4.3.2.4 The supporting flaps and magnetic fingers have the same function and are used simultaneously. It is fixed to the cooling bed frame. Equipped with two sets of flaps (A, B), used to grip the bars during trolley positioning, they operate at the same cycle as the magnetic fingers. Detection elements include: two proximity switches (DI5.1/MF_SG1_FLAP1_DWN, DI5.2/MF_SG2_FLAP2_DWN) to detect the lower position of the two sets of flaps respectively, and operator control (CP3): flap lifting/lowering control. 4.3.2.5 Bar Group Transfer Equipment This equipment is divided into four parts: the first part includes an electromagnetic extraction trolley; the remaining parts are extraction trolleys. Extraction sequence and conveying on the roller conveyor: 1. The last group of trolleys steps forward and the extraction trolley is at the stop position (P1): The extraction trolley rises and is magnetized. 2. The trolley is at the collection position: The group trolley is demagnetized and descends. 3. The group trolley is at the lower position: The group trolley returns to the waiting position. A sensor (driven by a cam device mounted on the cooling bed fixed teeth) detects the return stroke. Simultaneously, the trolley rises to the highest position (*1). 4. The extraction trolley is at the upper position, and signals from the position transmitter and the first extraction trolley sensor are added with a delay Ts (*2): The extraction trolley moves forward towards the roller conveyor. 5. If the roller conveyor is running or/and material is detected on it, the extraction trolley stops at the middle position (P2) (*3). If the roller conveyor and pinch rollers stop and no material is detected on the roller conveyor: The extraction trolley advances to the unloading position P3, P3 is at the center position of the roller conveyor (*4). 6. The extraction trolley is at position P3 (*3): The extraction trolley descends. 7. The first group of extraction trolleys is demagnetized and lowered to the lowest position. All trolleys are lowered and all extraction trolleys return to the stop position (P1). The roller conveyor starts. ET1 has three position detections: upper, middle, and lower. ET2, including ET2 to ET5, only has lower position detection. ET3, including ET6 to ET10, only has lower position detection. In the horizontal direction, each group of trolleys has left and right over-limit detection and loading position detection switches. In the program, the ET action has the following seven steps, which are cyclical rectangular motion. ET_LIFTPOSPICKUP; (2) ET_LIFTPOSUNLOAD; (3) ET_POSWAIT; (4) ET_POSCRT; (5) ET_LIFTPOSCRTLVL; (6) ET_LIFTPOSDOWN; (7) ET_POSPARK. When moving in the horizontal direction, the horizontal position (0, 300, 1460) is assigned to ET_POSREF, and finally communicates to the transmission system of the four trolleys through the I4ORD1 and I4ORD2 terminals of the COM_CV01 element to control the action of the equipment. 4.4 Stacking and slow cooling system. This system is used for spring flat steel. For spring flat steel, only a 60m cooling bed is used, and the flat steel needs to be cooled slowly. Therefore, they are stacked and sent into the cooling bed. After entering the unloading area, the flat steel is unloaded one by one. The main equipment of the unstacking and slow cooling system is: (1) unstacking equipment; (2) lifting equipment; (3) tilting equipment; (4) lifting baffle. 5. Application effect Since the system was put into operation at the end of 1997, it has been reliable and stable, greatly improving its working efficiency and ensuring the production of rolled steel. References: [1] ABB Process Automation: Layer Forming Control. [2] ABB RMC.5 PC Program listing. [3] Liang Guowei. Measurement Technology and Instruments. Machinery Industry Press, 2002.