1. Introduction With the continuous development of modern urban construction, infrastructure and real estate industries are booming, and the quality requirements for construction projects are becoming increasingly stringent. High-quality building materials are the guarantee of high-quality projects. The traditional method of producing concrete on-site is inevitably being replaced by automated concrete mixing plants due to its unreliable quality and high noise and dust pollution. Automated concrete mixing plants have the characteristics of excellent product quality, high production efficiency, and good environmental performance, and are becoming the mainstream of concrete production. This control system is stable and reliable. It can automatically and continuously control the metering, feeding, mixing, and discharging of materials according to the set formula. At the same time, this system also has a series of management functions such as browsing, querying, statistics, and printing of data. In addition, the system uses the division by n remainder oscillation curve method to automatically correct the drop, accurately controlling the accuracy issue. 2. System Structure 2.1 Hardware Structure The control system consists of a host computer and a slave computer. The system hardware structure is shown in Figure 1. Due to the system's requirements for operating speed, sensitivity, stability, dustproofing, shock resistance, and noise reduction, the host computer selected is the Advantech IPC-810P/FSC-1621VD industrial PC. It boasts superior I/O expansion capabilities compared to ordinary PCs, features 8MB of dedicated video memory supporting 3D graphics acceleration for intuitive on-site monitoring, and includes an ISA bus with high drive capability up to 64mA and 15000V electrostatic protection for the serial port. This industrial PC enables the design and development of configuration software, PLC programs, and the transmission of software to the PLC's CPU unit via serial port. The slave computer utilizes the powerful, reliable, easy-to-maintain, and interference-resistant OMRON CQM1H programmable controller to acquire and control the mixing plant parameters. The OMRON PLC is a high-speed, tightly integrated programmable controller composed of a power supply, a central processing unit, and I/O components. Due to the ever-increasing demand for more advanced functions and processing speeds in mechanical control, this system adopts the CQM1H, a compact PLC with comprehensive functions. It provides value-added machine control and has the ability to be upgraded through various advanced internal boards. It features large program capacity and storage units. The CPU unit also has an RS-232C interface, enabling real-time data acquisition, which is then processed by the host computer program. Since the system must have manual operation functions while meeting fully automated production requirements, a weight indicator and power control cabinet are required. The weight indicator uses the Tianheng Fuzhong WC-2000C weight display, a smart instrument controlled by a single-chip microcomputer, integrating weighing, setting, and control. The use of highly integrated integrated circuits makes the circuit simpler and more reliable. Unique anti-interference measures have been added to the circuitry, enabling the instrument to operate stably and reliably in harsh field environments. The instrument is simple to operate and accurate in measurement. Except for additives, which are accurate to 0.01kg, other instruments have an accuracy of 1kg. The power control section typically consists of circuit breakers (air switches), AC contactors, control transformers, intermediate relays, etc. The main circuit consisting of a circuit breaker and an AC contactor is shown in Figure 2. The circuit breaker has short-circuit and overload protection functions, while the contactor is simply a high-power switch that can directly drive motors and other electrical appliances. The control transformer provides various isolation power supplies required for the secondary circuit (control circuit), such as 220V and 24V. The intermediate relay is the control object of the low-voltage system (computer system) or the master control device. Its function is to provide electrical isolation between low-voltage and high-voltage systems, and to expand the control power and control signal. Schematic diagram: 2.2 Software Structure Industrial control configuration software is a software package that can collect data in real time from devices such as programmable controllers and various data acquisition cards, issue control commands, and monitor whether the system is operating normally. The configuration software can make full use of the powerful graphics editing function of Windows to display the operating status of the monitoring equipment in an animated manner, easily construct monitoring screens and realize control functions, and can generate reports, historical databases, etc., providing a convenient software development platform for industrial monitoring software development and improving the overall quality of industrial control software. CenturyStar 5.0, developed by Beijing Jinjialuo Company, is a configuration software running on Windows 98/NT. It consists of two parts: the project browser CSMaker and the screen execution system CSViewer. CSMaker is the core of the CenturyStar software and its management and development system. Its function is to create animation display windows. Its toolbox allows for easy creation of real-time graphs, historical trend charts, and alarm record displays. CSViewer is the runtime environment for displaying the graphical windows created in CSMaker. In the mixing plant control system, the structure of the control software is shown in Figure 3. The host computer uses the Omronhj.dll driver to communicate with the PLC, accessing the corresponding registers through the serial port to obtain the actual values ​​of parameters of various equipment at the mixing plant or to control the opening of on-site switch and analog quantities, such as the valve openings. In this system, DM0～DM100 of the PLC are set as read-write areas, meaning the host computer can read and write to this area on the slave computer; DM101～DM399 are set as read-only areas, meaning the host computer can only read the values ​​in this area on the slave computer and cannot change them. The configuration software of the upper computer of the batching plant control system basically meets the requirements for measurement and control of the batching plant. It concisely and vividly simulates the on-site process flow of the batching plant, allowing operators to understand the entire operating status of the batching plant, including various alarms, on the computer screen in the control room. Authorized operators can modify formula parameters and moisture content in the control room, and all switching between automatic and semi-automatic modes is seamless. Each control button and each automatic/semi-automatic switch button has further confirmation or cancellation options to prevent accidental operation. The lower computer of the batching plant control system is a PLC controller. The system adopts a modular design, consisting of program modules such as A/D data processing, control parameter processing, input/output control, batching process control, feeding process control, mixing operation control, and upper computer jogging control. The program is directly written using ladder diagrams. Within the scope allowed by the program framework, the types of ingredients can be added arbitrarily, or the feeding sequence can be set. For example, aggregates can be fed into the middle hopper first, and then powder and water can be added to the mixer in sequence to start mixing. This system also makes the feeding sequence a window, allowing users to modify it in real time. The communication parameters between the host computer and the slave computer are shown in Table 1. 3. Database Structure Since the host computer software is based on the Windows 98/NT platform, features a fully Chinese browsing interface, and employs event-driven technology, the database program design can utilize the open program interface configured to record data via API (Dynamic Link Library). Data can also be stored in Access, containing customer information, project names, contract numbers, etc., for browsing and querying. A VB program can be used to process the recorded data, thus enabling statistical data management. Specific functions are as follows: Recipe Management: Up to one thousand recipes can be set and managed, with passwords to prevent accidental modification and deletion. Project Management: Projects can be managed by proportion number, contract number, project name, and construction unit, or statistically analyzed by vehicle number and work number. Report Printing: Reports can be printed or not, and the printing method can be selected according to actual needs. [b]4. Main Functions of the Control System[/b] 1) Display Function: Display of process flow, measured values, equipment operating status, operation mode, alarms, etc., and screen recall functions; 2) Alarm Handling and Report Generation Function: Timely alarm function when a fault occurs; the system output reports can be selected by time, proportion number, project name, construction unit, etc.; 3) Database Storage and Access: Automatic creation and second-level recording of the Access historical database during each system run, and storage of field data; 4) Screen System: Modification and storage of control parameters and system calibration; Seamless switching between automatic/semi-automatic/manual operation modes of the monitoring system; 5) Management Authority: Implementation of different levels of system management authority; system operators can input and modify formulas; authorized engineers can modify the control software and lower-level software according to actual conditions. 5. Other Technical Measures 5.1 Measures to Enhance Reliability To improve the reliability of the system, the following measures were taken in the design: The PLC uses a separate power supply and a separate grounding wire. The industrial control computer and low-voltage components are powered by an online 500W UPS, which purifies the power supply to the low-voltage components and ensures that the industrial control computer will not lose data due to sudden power outages. The grounding resistance of the entire system must be less than 1Ω. All control outputs and alarm inputs in the industrial control computer and weighing instruments use opto-isolation technology to effectively prevent external interference signals from entering. All AC contactors are equipped with RC snubbers. All intermediate relay coils are equipped with diode snubber circuits. All low-voltage transmission cables are shielded, and the shielding layer is grounded at one end. 5.2 Measures to improve accuracy and production efficiency: The oscillation curve method (dividing by n and taking the remainder) is used for drop tracking adjustment, which can automatically correct during production or be set to a fixed drop. This ensures that the aggregate error is within ±2%, and other powder materials within ±1%. Pre-processing of data allows for pre-weighing in continuous production to improve efficiency. Other methods include: using variable-speed feeding for cement and fly ash to reduce the impact of impulse. During weighing, high-speed feeding is used initially, and after reaching approximately 90% of the set value, the feeding speed automatically switches to low-speed batching for precise weighing. For aggregates (stone and sand), a dual-bin, successive approximation method is employed for precise weighing. During coarse weighing, both bins are fully open, and the discharge gate is closed after quickly reaching the closing value (formula value - drop). Once stable, the pulse replenishment time is automatically calculated based on the difference from the formula value. Then, only the fine discharge gate is opened, and precise batching is generally completed after 1-2 replenishments. A coarse and fine pipe water supply scheme is used for water, achieving precise flow rate weighing. Through these technical measures, weighing accuracy is improved, and production efficiency is guaranteed. 6. Conclusion The mixing plant control system based on PLC and configuration software studied in this paper utilizes the strong anti-interference capability and suitability for industrial sites of PLC, and leverages the powerful data processing and graphical representation capabilities of configuration software. It integrates advanced automation technology, computer technology, communication technology, fault diagnosis technology, and software technology, featuring high reliability, simple operation, and easy maintenance. Currently, the system has been successfully installed in more than 30 batching plants in major cities such as Beijing, Shanghai, Hangzhou, Chongqing, Sanya in Hainan, and Hami in Xinjiang. To date, it has produced more than 2 million cubic meters of commercial concrete with good results. It is of great significance to the operation efficiency of batching plants and the development of concrete in the entire construction industry. At the same time, it has greatly improved the level of automation and reduced the labor intensity of workers.