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RFID (Radio Frequency Identification) is a non-contact automatic identification technology that uses radio frequency signals through spatial coupling (alternating magnetic field or electromagnetic field) to achieve contactless information transmission and achieve the purpose of identification through the transmitted information, without identification work Manual intervention has the advantages of large data storage capacity, readable and writable, non-contact, long recognition distance, fast recognition speed, good confidentiality, strong penetration, long life, good environmental adaptability, and the ability to recognize multiple tags at the same time, etc. Can work in various harsh environments.
In discrete manufacturing, the production workshop is the center of product manufacturing, the starting point of finished product logistics and supply logistics. The manufacturing capacity of the workshop and its internal logistics capacity play a decisive role in the production capacity of the enterprise. The Manufacturing Execution System (MES) serves as the hub to undertake the ERP (Enterprise Resource System, Enterprise Resource Planning) system, coordinate the SCM (Supply Chain Management, Supply Chain Management) system, and dispatch the underlying production control system. In the workshop production process Played an important role. The fierce market competition puts forward further requirements for the modern manufacturing industry, which are manifested in the following aspects: a small number of various production modes, continuously shortening production cycles, and timely response to the changing needs of customers. All these require modern manufacturing to have a higher degree of automation and informatization. Research and application of RFID technology, exploring the reorganization of corporate information flow, maximizing the existing resource advantages of my country’s manufacturing industry, and promoting the technological progress of enterprises and the upgrading of traditional manufacturing industries have become a top priority. The integration of RFID technology into the MES system must be one of many ways to promote the development and upgrading of traditional manufacturing.
1 System requirement analysis
As a typical situation in discrete industrial production, automobile assembly production activities have the following characteristics: the production process is parallel and asynchronous, the equipment function is redundant, the control amount is independent of each other, the production resource management is complicated, and the parts in the production process are discrete. State, the production of vehicles is mainly realized through physical processing and assembly.
This article combines the specific situation of an automobile manufacturer in Anhui Province to study the application mode of RFID technology on the automobile assembly line.
Currently, the company mainly uses barcode technology on its automobile assembly production line. Work station employees manually scan body VIN codes and component barcodes for vehicle tracking and assembly information collection. The entire collection process is relatively time-consuming. When the bar code is damaged or stained and cannot be recognized, employees need to manually enter the vehicle VIN code or part code, which has a high error rate, time-consuming, and difficult to speed up the production cycle. The degree of visualization of the production site needs to be improved. It is necessary to provide workers with real-time and accurate assembly guidance to prevent the occurrence of missing and incorrect installations. The assembly of vehicles on the production line also needs to be monitored in real time. Material consumption information feedback is not timely, and it is difficult to realize the real-time pull of production materials, resulting in excessive inventory of production materials and affecting the flow of funds. The lack of associated management of employees and their assembled parts makes it difficult to assign responsibility to people when tracing quality problems caused by manual operations.
RFID technology is not just a simple replacement of bar code technology, its application in discrete manufacturing will change the production and operation of discrete manufacturing enterprises. Because RFID technology has the many advantages mentioned above, it can replace the bar code to identify and track vehicles on the automobile production line. There is no manual intervention in the whole process, which can greatly reduce the labor intensity and error rate of workers. Nowadays, RFID technology can be used to realize automatic, high-speed, and effective recording, reduce the labor intensity of operators, and increase the pass rate of products offline.
Applying RFID technology to the automobile manufacturing industry and integrating it into the MES system can improve the management and control level of the production process, and effectively track, manage and control the resources required for production, including materials, equipment, and human resources; combined with the upper management system , Can reasonably schedule and manage these resources, improve manufacturing competitiveness, improve production organization, shorten production cycle, reduce the number of products in progress, improve product quality and reduce human resource consumption. It has important theoretical significance for the development of discrete manufacturing manufacturing system models and application solutions, improving the visual monitoring of the manufacturing process and product quality tracking, promoting the formation of RFID technology application standards and specifications in the manufacturing industry, and driving the development of my country’s RFID technology industrialization. Value.
2 System goals
Based on the above demand analysis, the following overall system goals are proposed: make full use of the technical advantages of RFID, combined with the MES system of the assembly shop, to solve the problem Execution system) The information and management gap between the internal logistics level of the workshop and the production control level of the MES system, the vehicle quality traceability system and the original MES system, realizes the visualization and digital management of manufacturing and quality. It is specifically broken down into the following sub-goals:
(1) Combine RFID technology with the production line scheduling system, and realize intelligent production line scheduling on the basis of production line scheduling automation.
(2) Integrate RFID technology into the assembly station of the production workshop, use RFID tags to identify parts for data collection, keep track of the material consumption information of the production line, drive supply logistics without delay, and further meet the needs of the JIT supply model; Important components are installed and recorded to provide detailed and reliable data support for the quality traceability system.
(3) Combine the RFID technology with the on-site visualization system to provide real-time and accurate assembly guidance to the workers.
(4) Combining RFID technology with workshop personnel management system and quality traceability system, in addition to realizing the function of personnel management, assembly operations can also be recorded, so that assembly responsibilities can be assigned to people.
3 Application scheme of RFID technology in automobile assembly line
The application scheme involves two different types of RFID tags of high frequency (13.56MHz) and ultra high frequency (915MHz). The selected RFID tag specifications are shown in Table 1 and Table 2.
Among them, the staff is equipped with high-frequency RFID tags, which store the employee ID and basic information; each part bin is placed with a high-frequency RFID tag, and the part number is stored in the tag; each vehicle is placed with a UHF RFID Label, the unique identification code (VIN code) of the vehicle is stored in the label. The vehicle label is packaged with glue-magnetic, which is convenient to be adsorbed on the surface of the vehicle body.
Before the vehicle goes online, the staff installs the initialized label on the upper surface of the front hood of the vehicle body.
The employees of the production line need to swipe their cards on the high-frequency card readers on the workstations to complete the on-the-job certification, and the system records the current job status information of the employees.
Before the vehicle goes online, the staff scans the body VIN barcode, the UHF reader writes the VIN code information into the vehicle RFID tag within the field strength of its antenna, and the subsequent stations complete the production line vehicle monitoring and control by reading and writing the body RFID tag. Data collection and other tasks.
In the assembly station, after the UHF reader reads the vehicle tag, it prompts the installation information of the parts at the corresponding station. The staff installs the corresponding parts, and brushes the high-frequency RFID tags in the corresponding parts bin on the high-frequency reader. The system obtains the component installation information and staff information of the corresponding vehicle for later quality tracking, and the system returns the material consumption information to the LES system, and refreshes the station parts installation information prompt until all the components to be installed at the station are installed. In the supply link to the production line station, after the production logistics department delivers the parts to the station, the system updates the number of parts information.
In the offline station, the UHF reader reads the vehicle tag, the system checks the assembly information, and the staff removes the RFID tag for recycling.
4 Car assembly manufacturing execution system based on RFID technology
4.1 System Function Module
The functional modules of the automobile assembly manufacturing execution system based on RFID technology are mainly divided into four functional modules: workshop production management, production line visualization, RFID tag management, and workshop personnel management. The specific functional structure is shown in Figure 1:
Workshop personnel management: manage basic information of workshop personnel, configure employee job information, and provide relevant basic data for functions such as personnel work records and vehicle parts data acquisition.
General assembly workshop production management: At the planning level, the coarse-grained production plan is obtained from the ERP system and decomposed into daily production plans to guide workshop production. In the vehicle production process, guide and monitor each assembly step of the vehicle to standardize the entire production process, including providing assembly instructions to assembly workers, automating vehicle assembly and material consumption data collection, and providing accurate parts information , The assembly records of the assembly personnel information and the supplier information, and the real-time feedback of the consumption data of the station materials to the MES system.
Production line visualization: Provide real-time feedback on the production line and vehicle status information, which is helpful for managers to grasp the production situation in real time.
RFID tag management: Responsible for the issuance and management of personnel tags, issuance and recovery of tags in the recycling of vehicle tags, and asset management for vehicle tags.
4.2 System Architecture
This system uses the RFID software middleware deployed in the workshop server to uniformly manage the workshop reader network, which is beneficial to shield the difference of RFID equipment, improve the stability and efficiency of the RFID reader network, and RFID equipment does not rely on workstations. Terminal, no special configuration of the station terminal is required, which is convenient for deployment. The structure of the automobile assembly manufacturing execution system based on RFID technology is shown in Figure 2:
4.3 System software architecture
This system adopts B/S architecture, under the J2EE development environment, combined with mainstream open source frameworks such as Struts2, Hibernate, Spring, DWR, etc., it has good cross-platform compatibility. The software architecture of the automobile assembly management system based on RFID technology is shown in Figure 3:
The Struts framework is a framework based on the MVC (Model-View-Controller) pattern, which is mainly implemented using JSP and Servlet technologies. The system uses the Struts framework to integrate Servlet, JSP, custom tags and information resources to complete the system’s response to the front page operations.
The system uses Hibernate as the Java persistence layer solution to establish object/relational mapping and realize the conversion from relational data to object data.
As a web framework that implements Ajax interactive capabilities, DWR can expose any Java object on the server side as a remote object that can be accessed through JavaScript in the browser. This system uses the DWR framework to implement forward and reverse Ajax functions, push the data acquired by the RFID processing module to the response business module in real time, reduce browser redundant requests, reduce server pressure, and improve system operating efficiency.
Spring framework is a lightweight J2EE framework implemented on the basis of J2EE. This system uses it to provide Bean configuration, AOP support, and abstract transaction support for the program, organize the business service layer and data access layer objects in the system, and realize the loose coupling between the creation and use of component objects.
5 concluding remarks
According to the actual operation of the system on the assembly line of an automobile manufacturer in Anhui, the automobile assembly manufacturing execution system based on RFID technology enables the company to timely and accurately grasp the status of the production line and improve production efficiency, which is indeed beneficial to the MES system and the LES system. Work collaboratively between them to provide accurate data guarantee for product quality tracking.
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