1. Introduction The weighing system under the blast furnace trough in Laiwu Steel's newly built No. 3 750 blast furnace adopts fieldbus technology. Through Schneider's intelligent weighing module and MB+ network hardware and software, a real-time data acquisition network is formed, realizing the digital transmission of measurement data. This improves the measurement accuracy of the blast furnace charge weight signal and the anti-interference capability of the measurement system. It effectively solves the problem of distortion and loss of signal acquired by the primary measuring device during transmission due to interference. 2. Overview of the Blast Furnace Charging Process The blast furnace charge includes large sintered ore, small sintered ore, coke, sintered pellets, and other auxiliary materials, transported from the raw material yard, vertical shaft furnace, and sintering machine, respectively, and conveyed to various silos via the trough. The type and weight of the charge are selected according to the charge list. When a silo is selected, the charge in the silo is conveyed to the weighing hopper via a vibrating screen for weighing. After weighing, it is conveyed by belt to the loading trolley and sent to the top charge hopper. Figure 1 shows a schematic diagram: [align=center] Figure 1 Schematic diagram of process flow[/align] 3. Topology of the intelligent weighing system The fieldbus of the intelligent weighing system is based on the MB+ network and 12 ISP momentum weighing modules, forming a token bus. It is connected to the control system through the NOM module of the PLC under the slot. The PLC controller is connected to the fiber optic backbone network (Ethernet) of the No. 3 750 blast furnace through the NOM Ethernet module. The server and workstation are both connected to the Ethernet, as shown in Figure 2. [align=center] Figure 2 Schematic diagram of the topology of the intelligent weighing system[/align] The 12 ISP momentum weighing modules hold tokens in the order of the logical ring. Whoever holds the token has the right to exchange information with the controller, including control commands, collected data, parity checks, module status, etc. Valid weight signals are forwarded by the controller to the server and shared by the controller and workstation. The controller uses these signals for real-time batching control, material empty/full material judgment, furnace charge moisture correction, furnace charge ratio control, etc., and displays them on the monitoring screen of the workstation. 4. Software Functions of the Intelligent Weighing System The software functions of this system include communication, weighing device setting and calibration, intelligent control, historical record and printing settings, etc. 4.1 Communication Functions To adapt to different application scenarios, the system reserves multiple communication methods and interfaces, including: mb+, mb, mbtcp/ip, and m1 for network communication; RS232/RJ11 as a field programming interface, which can be configured on-site or run independently as a single module; RS485/RJ11 as a field display port; and a 9-pin serial port as a field printing port. The system is based on fieldbus technology, uploading data to the server via the mb+ port, with other interfaces serving as emergency backups. The system is based on an mb+ network, with 12 intelligent modules forming a logical token ring. Each module sequentially obtains a token. When the i-th module obtains the token, it is authorized to exchange information with the controller, including control commands, collected data, parity checks, and module status. Valid weight signals are forwarded by the controller to the server. After completion, the module passes the token to another module, and so on. If a module fails, it will be automatically removed from the logic loop and reconnected to the logic loop after it recovers. The communication rate of the fieldbus is 1 Mbps. 4.2 Weighing device setting and verification 1) Weighing device setting Weighing interval: In order to adapt to different sizes of weighing hoppers and different materials, the weighing interval needs to be set. The interval level is from 0.01, 0.02, 0.05, 0.1... up to 50000 kg. The user should select the corresponding weighing scale according to the rated value of the scale; Weighing limit setting: The system provides three options: 2% mr, 5% mr, 9% mr (max range), which can be flexibly selected according to the status of the equipment. (2) Weighing device verification: The verification of the weighing device is divided into three modes and two stages. Three modes: · Standard mode: When the calibration load is ≥75%mr, calibration is performed in this mode; · Degradation mode: When the calibration load does not meet the requirements of the standard mode, this mode is executed; · Forced mode: When the previous calibration is considered to be problematic or invalid, this mode is executed to overwrite the previous calibration. This mode is further divided into load increase and load decrease. Two stages: · Zero point calibration: The weighing hopper is empty, and the zero point of the weighing is adjusted according to the self-weight of each weighing hopper; · Load calibration: The linearity of the weighing device is calibrated with an appropriate load. One of the above three modes can be selected according to the specific site conditions. The standard mode is usually used. 4.3 Intelligent control (1) Zero point migration and automatic tracking The migration range of the zero point is two: ±2%mr and ±5%mr. To achieve automatic zero-point tracking, the zero-point migration range must be selected as ±2% mr. The system automatically records the net load w1 loaded into the weighing hopper and the net load w2 unloaded each time, and then calculates the difference δw. Based on the magnitude and polarity of δw, the zero point of the weighing device is automatically corrected. δw＝w1-w2 (2) In the digital filtering weighing system, the material weight signal collected by the weighing sensor is initially an analog signal. During the acquisition and transmission process, it is inevitably subject to interference. To eliminate this interference, the system performs A/D conversion on the signal and then performs digital filtering. There are two types of digital filters: FIR filter and IIR filter. (3) Adaptive measurement stability To ensure the accuracy of the measurement data, the weight change within a certain time interval (t) must be within the allowable range (r). The system adaptively adjusts according to the rate of weight change. The selectable values ​​for t and r are: t: 0.4s, 0.5s, 0.7s, 1s; r: 2.25d, 3.25d, 4.25d, 6.25d, 8.25d (division). (4) Flow Calculation and Feeding Slip Control System: The system can calculate the instantaneous and cumulative flow values ​​of a weighing device or a type of furnace charge (in one or more bins). After the operator fills in the feeding slip on the monitoring screen, the set weight of each type of furnace charge is determined. The system calculates the cumulative value of each type of furnace charge. When it is equal to the set value, the feeding of that type of furnace charge ends. When all feeding slips are completed, the system waits for the next feeding slip. (5) Material Flow Control: In order to improve the accuracy of quantitative weighing and the working efficiency of the weighing system, and to control the load of the weighing hopper from exceeding its rated value, it is necessary to control the material flow entering the weighing hopper. Quantitative weighing here includes two stages: quantitative loading and quantitative unloading. The loading weighing process is as follows: At the beginning, the material is loaded with a larger flow rate, and the system outputs a q1 level to control the material flow; when the weight in the weighing hopper reaches the high flow cut-off point, the system outputs a q2 level to reduce the material flow; when the net weight in the weighing hopper reaches the set value, the material flow is shut off. The material flow curve is shown in Figure 3. The weighing process of unloading is similar to that of loading. [align=center] Figure 3 Schematic diagram of material flow control[/align] 4.4 Historical record and printing settings are convenient for production management. The system stores the material weight data within a specified time period in the database, which can be displayed on the workstation and provided for viewing and printing. 5 System debugging (1) Zero point calibration Zero point calibration requires confirming that there is no load in the weighing hopper, removing debris from the hopper, inputting the maximum measurement range of the measuring element, selecting the scale division value, and pressing the zero point calibration button to enter the calibration program. After the process ends, the data is automatically archived and recorded; (2) Load calibration After the zero point calibration is completed, load calibration is performed in the standard mode. The net load is added to 75% of the rated value. Press the load calibration button to enter the calibration program. After the calibration process ends, the data is automatically archived and recorded. After the measurement is completed, the load is reduced by 25% of the rated value until the load is completely removed. (3) Data transmission debugging: After the weighing system is calibrated, data transmission debugging is performed to ensure the accuracy and reliability of data transmission during production; (4) Logic loop debugging: If a node is artificially caused to fail, can the system automatically remove it? After restoring the node, can the system automatically add it back to the logic loop? (5) Transmission rate and bit error rate test: Data transmission and data reception tests are performed under medium load conditions on the network. 6. Conclusion: Since the system was put into operation, data transmission and measurement have been accurate. Due to the realization of digital data transmission, long-line interference in the traditional analog signal transmission process is avoided, greatly improving the anti-interference capability of the weighing system. Adaptive control is implemented in measurement scale division, zero-point calibration, and measurement stability, which improves the accuracy of quantitative weighing. User feedback has been positive, and it has high promotional value.