Abstract : This paper analyzes the feasibility of a PLC-based automated warehouse control system, and discusses its characteristics and design selection. Through the design of the hardware and software of the control system, using an OMRON PLC as the controller, the fully automated control of inbound, outbound, inventory, and shipping functions of the automated warehouse is achieved. Keywords : Automated warehouse; OMRON programmable logic controller; configuration software Using OMRON PLC as the controller, the result of auto control in a tridimensional warehouse was realized by designing the hardware and software of the control system. The auto control includes input goods, output goods, goods check, and consignment, etc. Keywords: Tridimensional Depository; OMRON PLC; configuration software 1. Introduction Automated storage and retrieval systems (AS/RS) are an important component of modern logistics and warehousing systems. AS/RS integrates mechanical, electronic, control, and computer technologies, possessing advantages such as high technological content, high efficiency in goods storage and retrieval, and high degree of automation. PLCs are powerful, highly reliable, have strong anti-interference capabilities, are easy to maintain, and are easy to integrate with electromechanical systems. They fully meet the requirements of the AS/RS working environment and control system. 2. Overall Design of the AS/RS Control System The logistics system consists of three roller conveyor belts, three inbound and outbound stations, a four-degree-of-freedom robotic arm, a fully automatic stacker crane, and two rows of storage racks. By connecting the sensors, actuators, and programmable controllers in the system and programming accordingly, the programmable controllers can control the logistics processes. The automated storage and retrieval system (AS/RS) control system consists of three parts: roller conveyor control, robotic arm control, and stacker crane control. Two OMRON CJ1 series PLCs are used as the control devices for the AS/RS, as shown in Figure 1. PLC #1 primarily controls the roller conveyor and stacker crane sections, while PLC #2 primarily controls the four-degree-of-freedom robotic arm. OMRON's Control Link network at the control layer connects the two PLCs, enabling coordinated actions among the three controlled components through data exchange, achieving integrated control. A host computer is configured in the control system, connected to the PLCs via RS-232. The host computer is used for editing, downloading, and debugging the control programs for the two PLCs, and also for monitoring and managing the AS/RS system. Three frequency converters are used in this system to control the operation of the three roller conveyor belts. The roller conveyors can operate in both forward and reverse directions, allowing for flexible configuration based on the needs of inbound and outbound operations. Frequency converters offer high operational reliability and functional versatility, reduce motor operating noise, and provide comprehensive and robust protection functions for the motors. The OMRON 3G3MZ series frequency converter is used here. For the control of the four-degree-of-freedom robot, the actuators are four-phase eight-step stepper motors: four stepper motors for X-axis extension, Z-axis lifting, chassis rotation, and robot wrist rotation. Two stepper motors control the stacker crane's lifting and walking, while DC motors are used for fork control. Controlling these six stepper motors is essentially controlling their corresponding drivers. The SH-2H057 model stepper motor driver is used in this system to drive the stepper motors. [align=center] Figure 1 Overall Structure Diagram of the Automated Warehouse Control System[/align] 3. Hardware Design of the Automated Warehouse Control System The automated warehouse control system uses two OMRON CJ1 series PLCs. The configuration diagram of the PLC unit is shown in Figure 2. [align=center]Figure 2 Configuration Diagram of PLC Unit[/align] The number of modules required for the entire control system is as follows: 1) Number of digital input points: 44 points in total, using 16-point input unit CJ1W-ID211, 3 units required. 2) Number of digital output points: 21 points in total, using 16-point output unit CJ1W-OD211, 2 units required. 3) Number of analog output points: 3 analog outputs are required to control the speed of 3 roller conveyor belts respectively, requiring 1 four-channel analog output unit DA041 to output 0~10V voltage signals. 4) Pulse output: 6 stepper motors (X-axis movement control of the robot arm, Z-axis movement control of the robot arm, chassis rotation of the robot arm, wrist rotation control of the robot arm, lifting control of the stacker crane, and walking control of the stacker crane) need to be controlled. Each CJ1W-NC113 unit controls one stepper motor, so a total of 6 are required. 4. Supervisory Computer Monitoring System Design The supervisory computer monitoring system is responsible for the centralized monitoring and coordination of the roller conveyor, robotic arm, and stacker crane sections in the automated warehouse. It can display the real-time operating status of each piece of equipment and the transportation and storage of goods, playing a crucial role in connecting the upper and lower levels and coordinating the overall operation. The supervisory computer in this system is connected to PLC #1 via COM1 port, and PLC #1 then transmits data to PLC #2 via Control Link network to jointly complete equipment monitoring. 4.1 Design of the Supervisory Computer Monitoring Program using "KingSCADA" 6.03 Software "KingSCADA" is a configuration software based on a real-time database. The real-time database contains rich data types, and the database used by the system for data refresh, trend display, alarm judgment, historical data recording, and reporting is all taken from the real-time database. KingSCADA 6.03 transmits data to the PLC via RS-232, including issuing various control commands such as inbound and outbound instructions to the PLCs controlling the robotic arm and stacker crane. The PLCs then drive the actuators to complete the assigned tasks. Each device also returns its operational status and results to the host computer via the PLC. A VB-written program receives various information and simultaneously operates the ACCESS database for database-driven automated warehouse management. The software structure diagram of the automated warehouse control system is shown in Figure 3. In this system, the control system can be divided into automatic control, manual control, and remote control. In automatic control mode, goods will be operated according to the pre-programmed automatic control program within a specified time, without operator intervention. In manual mode, operators use various operation buttons on the control panel to transport goods. Remote control allows operators to directly control the operation of various electrical devices on the test platform via communication between the host computer and the PLC. [align=center]Figure 3 Software Structure Diagram of the Automated Warehouse Control System[/align] 4.2 Implementation of the Automated Warehouse Management System In an automated warehouse management system, establishing a complete and powerful database is essential. Querying different cargo parameters in the database allows operators to have a clear understanding of the inventory situation, facilitating their control over cargo entry, exit, and other operations. I established two management systems: an inbound/outbound management system and an inventory management system. VB programming and an ACCESS database were used to implement the warehouse system management. The main functions of the management system are: VB uses DDE to complete dynamic data exchange with "KingSCADA," transmitting various parameters of different cargoes to the VB program; VB connects to the database using ADO technology, writing data into the ACCESS database; VB serves as the database display interface, displaying the database content on the VB interface through data binding controls; and VB programming and SQL language are used to implement database query, add, delete, and print functions. 5. Conclusion Automated three-dimensional warehouses involve technical fields such as logistics monitoring technology, computer application technology, communication technology, and warehouse location optimization management. Its characteristics are marked by high-rise three-dimensional warehouses, based on a complete set of advanced handling equipment, and using advanced computer control technology as the main means to efficiently utilize warehouse space and save time and manpower for various operations. It generates huge social and economic benefits and has a broad market prospect. References [1] Zhang Wanzhong, Sun Jin. Introduction to Programmable Controllers and Application Examples [M]. Beijing: China Electric Power Press, 2005. [2] Deng Zeming, Qi Suifang. Electrical Appliances and Programmable Controller Application Technology [M]. Beijing: Machinery Industry Press, 1997. [3] Xu Zhangyi, Ma Shihua. Value Realization Forms of Reverse Supply Chain - Logistics Technology [M]. Machinery Industry Press, 2004. [4] Kang Bo Studio, Visual Basic 5.0 Creation Examples and Techniques [M]. Beijing: China Water Resources and Hydropower Press. First author Wang Leiyong, male, born in 1981, is currently a postgraduate student at the School of Vehicle and Transportation Engineering, Qingdao University of Technology; his research interests include the design of computer control and detection systems. Second author Zhang Tiankai (1953-), male, from Qingdao, Shandong, is a professor currently working at the School of Automation Engineering, Qingdao University of Technology; his research interests include the design of computer control and detection systems. Contact information: P.O. Box 282, Qingdao University of Technology; Mailing address: School of Automation Engineering, Qingdao University of Technology, No. 11 Fushun Road, Qingdao, 266033, China; Tel: 0532-85071298, 13276396045; Email: [email protected]