Abstract: This paper describes a method for quantitative control of lead anode plate casting using dynamic weight loss method. The principle of quantitative casting control is explained, and the hardware composition and software design method of the system are introduced. Keywords: Industrial control computer, quantitative casting, dynamic weight loss method, lead anode plate 1 Introduction For quantitative casting of lead anode plates, timed control or volumetric quantitative control are commonly used in China. Timed control achieves quantitative control by controlling the casting time, while volumetric quantitative control measures the metal volume according to a set value. However, due to the influence of many factors such as the flow rate and velocity of the molten lead, oxide slag, and slag buildup at the casting port or lead storage tank, the measurement error is large, resulting in a low product yield. We have technically modified the timed casting system of a smelter and developed a backflow-free dynamic weight loss method quantitative casting microcomputer control system, which solves the measurement accuracy problem. 2. Production Process Requirements and Performance Indicators Liquefied lead is injected from the lead pot into the lead storage tank via a lead pump. The frequency of the lead pump is controlled by a frequency converter, thus controlling the flow rate of the injected molten lead. The weighing and metering device in the lead storage tank, along with a solenoid valve, controls the weight of the molten lead poured from the storage tank into the lead anode plate mold. 1) The main performance indicators for lead anode plate weight control are: 120±4KG per casting. Casting time is less than 8 seconds, and the casting cycle is 18 seconds. It has two control modes: timed casting and dynamic weightlessness casting, which can be switched between. 2) Lead molten lead backflow control monitors the weight of the molten lead in the storage tank. The lead pump frequency is adjusted only once per casting cycle to ensure a constant flow rate of injected molten lead during the casting time and to prevent molten lead from flowing back into the lead pot. 3) Dynamic online display of production process data, lead storage tank weight, lead anode plate weight, shift output, etc., as well as online modification and display of operating parameters. 3. Casting Control Principle The timing diagram of dynamic weightlessness casting is shown in Figure 1. At time t0, the lead anode plate mold is in place, and the solenoid valve is opened for casting; at time t1, the casting weight reaches the control weight, and the solenoid valve is closed; at time t2, the lead pump frequency is adjusted; from time t3 to t0, the flow rate of molten lead injected into the lead storage tank is measured. 1) After the lead anode plate is cast without backflow control, at the same time t2 in each casting cycle, the frequency f of the lead pump is adjusted. Based on the control weight Wg of the metering tank and the material weight W1 of the metering tank, the weight error E is calculated, and the lead pump frequency is determined using PI control. Weight error: E(k) = Wg - W1 Lead pump frequency: f(k) = f(k-1) + Kp [E(k) - E(k-1)] + KI E(k) 2) Lead liquid flow detection Since lead liquid is continuously injected into the lead storage tank throughout the entire casting cycle, it is necessary to ensure that the lead liquid flow rate is constant before casting and to measure the flow rate. Therefore, the lead liquid flow rate Q is measured during the time from t3 to t0 after the lead liquid flow rate has stabilized. Lead liquid flow rate: Q = (W₀ - W₃) / (t₀ - t₃) 3) Lead anode plate weight control: The solenoid valve is opened when the lead anode plate mold is in place, and closed when the lead anode plate weight reaches the casting control weight W_control. Lead anode plate weight: W = W₀ - W₁ + Q (t₁ – t₀) + W_advance. W_advance is the weight deviation caused by the solenoid valve action to the casting port, which is small and relatively constant. Based on the error between the given weight and the actual weight of the lead anode plate, PI control is used to compensate for the error in the control weight W_control for the next cycle. 4 System Hardware Design The hardware block diagram of the lead anode plate casting system, composed of an APCI5000 series industrial computer, PLC, etc., is shown in Figure 2. [align=center]Figure 2 Hardware Block Diagram of Lead Anode Plate Casting System[/align] 4.1 The APCI5000 series industrial computer system uses APCI5094 CPU board, APCI5458A/D board, and APCI5476 D/A board from Beijing Kangtuo Industrial Computer Co., Ltd. The APCI5094 CPU board is a highly integrated 486 single-board computer with all the functions of an industrial computer, including CPU, BIOS, super I/O core, L2 cache, RAM memory, enhanced IDE hard disk drive, floppy drive interface, multi-mode parallel port, two serial ports, keyboard/mouse connector, real-time clock/calendar, watchdog timer, flat VGA interface, Ethernet interface, DOC interface, and FLASH electronic disk interface. The APCI5458A/D board is an intelligent opto-isolated 32-channel 16-bit acquisition board that uses an 89C51 microcontroller as the intelligent component. It has a dual-port RAM chip, allowing it to independently complete A/D acquisition and data processing without occupying the main CPU time. The APCI5476 is an optically isolated multi-function interface board with 8 channels (12-bit D/A, 16 channels (DI), and 8 channels (DO). One D/A output current signal is sent to the frequency converter to control the lead pump frequency. A high-precision, small-signal, high-temperature resistant tensile sensor is used for the weighing sensor; a high-precision, low-drift operational amplifier forms the amplification circuit, amplifying the weight signal locally before remotely transmitting it to the industrial computer. The 4.2 PLC (Programmable Logic Controller) is an FBE-40MC model, which communicates with the APCI5000 series industrial computer serially. Switching input signals include: lead anode plate mold position, chain position, and plate retraction position, with position signals detected by LJKB-20/200 proximity switches. Field control signals include: weightlessness method/timing method, automatic/manual, stop casting, stop demolding, stop disc, and other control signals. Switching output signals include: control signals for the casting valve, demolding valve, plate valve, and offset valve, as well as start/stop control signals for the disc and chain. The actuator adopts a hydraulic valve system to ensure accurate and reliable operation. It features low impact, high force, and durability. 5 System Software Design This system uses the APCI5000 series industrial computer as its core. The industrial computer communicates with the PLC via serial communication. The software of the industrial computer is written in C language and adopts structured programming, resulting in a clear program structure. 5.1 Main Program Module This module mainly completes the initialization of the system and serial communication, and realizes various control functions. The software flowchart is shown in Figure 3. [align=center] Figure 3 Main Program Flowchart[/align] 5.2 Start-up Casting Module This module includes dynamic weightless casting and timed casting. 1) Dynamic Weightless Casting: When there is no backflow of lead liquid, the casting process is as follows: measure the lead liquid flow rate — measure the initial weight W[sub]0[/sub] when the lead mold is in place — open the casting valve and monitor the weight of the lead anode plate — close the casting valve — adjust the lead pump frequency. In cases of backflow during lead melting or on-site suspension of casting, a timed casting method is used. Once no backflow is detected, a dynamic weightlessness casting method is employed. 2) Timed casting process: Close casting valve — Lead mold in place — Open casting valve — Timed casting — Close casting valve — Adjust lead pump frequency. 5.3 Shutdown module stops the system from casting during operation. 5.4 Parameter modification module allows online or offline modification of parameters such as the given lead anode plate weight, advance weight, and timed casting time, whether the system is in shutdown or casting operation state. The industrial control computer saves the modified results to an electronic disk. 5.5 Data clearing module clears the number of ingots and the total casting weight per shift, whether the system is in shutdown state. The industrial control computer saves the modified results to an electronic disk. 5.6 Calibration module is effective when the system is in shutdown state. The calibration process is: Measure weight G0 — Hang weights — Measure weight G1 — Calculate calibration coefficient. When the system performs a certain function, the display shows the corresponding function or operation prompt. 6. Conclusion Compared with the original timed casting system, this system uses a dynamic weightlessness casting method, resulting in smaller casting errors and improved yield of finished lead anode plates. Due to the control of the lead pump frequency, there is no backflow of molten lead in the storage tank, reducing the generation of oxide slag and lowering energy consumption. References: 1. Ling Cheng (ed.). *The Essence of PC Bus Industrial Control Systems*. Tsinghua University Press, 1998. 2. Wang Tong (ed.). *Applications of PCs in Measurement and Control*. Harbin Institute of Technology Press, 1995.