The hottest research on RFID data acquisition tech

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Research on RFID data acquisition technology based on MES

manufacturing execution system (MES) is a workshop oriented information management system proposed by American mesa in the 1990s. It is a link between the planning layer and the field control layer. It optimizes enterprise management by providing information about the whole manufacturing process from order to product completion, and helps enterprises establish an integrated and real-time management information system. Therefore, real-time data transmission and sharing is the key technology for MES to ensure the implementation of production, and radio frequency technology (RFID) is a non-contact data acquisition and automatic identification technology. At present, it is applied to product labels in retail industry, vehicle operation management in transportation, warehousing and logistics, etc. With the development of manufacturing informatization, RFID is a technology with great potential for the manufacturing industry. The integration with the existing MES not only provides real-time information for production with the economic recovery, but also provides a mobile database for product life cycle management (PLM) by installing the corresponding fixtures, which can obtain the strength and stiffness performance data of automotive transmission shafts, halfshafts, and other shaft parts

1 manufacturing execution system

1.1 MES meaning

the definition of MES by MESA (Manufacturing Execution System Association) is that the information provided by MES optimizes the whole production process from order input to product completion. MES uses timely and accurate information to guide, start, respond to and record plant operation, respond quickly to changes in conditions, reduce non value-added activities, and improve the efficiency of plant operation process. MES can not only improve the return on investment of equipment, but also contribute to timely delivery, accelerate inventory turnover, and improve the performance of revenue and cash flow. MES provides the necessary information of production activities in the form of two-way interaction between enterprises and supply chains

As a production information system, MES collects a large amount of real-time data in the production process, analyzes and processes real-time events in time, and maintains two-way communication with the planning layer and the production control layer. It receives the corresponding data from the upper and lower layers and feeds back the processing results and production instructions. To be exact, MES is the integration of a series of functions, connecting planning and control system, design concept and production execution, sales capacity and production mechanism, customers and supply and demand, etc. On the one hand, pay attention to the real-time production in the production process and grasp the output and quality of WIP in real time. On the other hand, collect and analyze data to grasp the equipment operation status and materials in real time, and record the production process, equipment, materials used and operators. The main functions include resource allocation and status management, process production planning and scheduling, document control, field data collection, human resource management, quality management, process management, maintenance management, product tracking and performance analysis

1.2 data acquisition

the data acquisition function in MES is responsible for collecting all necessary real-time updated data information in the production site, and providing data sources for the data management of other MES functions. Data types are divided into process resource data, human resource data, and product quality data according to management methods, as shown in Table 1. Table 1 MES data collection types

it can be seen from table 1 that most of the collected data are related to process resources, and various data are more or less related, such as whether the machine tool is running, ready, stopped or idle; During operation, program start time, program stop time, program name, current tool number, spindle speed, etc; In the preparation state, whether to debug, inspect, or prepare tooling, etc; In the shutdown state, it should be able to report whether the shutdown reason is equipment failure or equipment maintenance

according to different industries, data collection methods are different. The degree of production automation in discrete manufacturing industry is not very high. Bar codes or other sensors, or even manual input, are mainly used to collect production data. In the continuous manufacturing industry, the degree of production automation is relatively high. Data acquisition is mainly through the deployment of various field buses

2 RFID technology

2.1 RFID system

rfid (radio frequency identification) system is composed of three parts: a tag with unique electronic code composed of coupling elements and chips, a mobile/fixed reader that reads/writes tag information, and an antenna that transmits radio frequency signals between tags and readers. The electronic tag is attached to the surface of the object to be identified. Electronic data in the agreed format is stored in the electronic label. After the tag enters the magnetic field, it receives the RF signal sent by the reader, sends the product information (passivetag, passive tag) stored in the chip with the energy obtained by the induced current, or actively sends the signal of a certain frequency (activetag, active tag), pastes the chip recording a large amount of information from price to production process on the surface of the product, reads and updates the information through the reader, and decodes it, Send it to the computer information system for relevant data processing

rfid technology uses radio frequency to conduct non-contact two-way data transmission between readers and radio frequency cards to achieve the purpose of target identification and data exchange. Compared with the traditional bar code, RFID electronic tag has the advantages of non-contact, repeatable reading and writing, fast speed, large amount of information, free from environmental impact, long service life and so on. It can process multiple cards at the same time. These advantages make RFID technology more suitable for the manufacturing industry with uncertain working environment

2.2 application of RFID data acquisition in MES

modern manufacturing MES is an accurate execution process relying on information management, which inevitably requires accurate comparison between plan and execution, and accurate recording of data. This requires more automatic identification of data acquisition in the process, so as to ensure the consistency between plan and execution, and timely take measures to adjust non-compliance. Therefore, RFID technology, as a means of data acquisition and management, is entering the core of the manufacturing process from the supply chain. Through automatic temperature control, automatic timing and automatic alarm, RFID technology is gradually adopted at the factory floor, which can seamlessly and continuously integrate the information captured from RFID and link it to the existing control system infrastructure (such as PROFIBUS), and coordinate with the supply chain configured with RFID functions, Accurate and reliable real-time information flow can be sent to the existing manufacturing execution system, so as to create added value, improve productivity and significantly save investment

① in terms of quality management, RFID can provide constantly updated real-time data flow, which can be used to ensure the correct use of labor, machines, tools and components, so as to achieve paperless production and reduce downtime, so as to ensure reliability and high quality; Collect information such as product identifier, physical attributes, order number, etc., and automatically establish quality tracking and work history documents required to support the quality assurance system, so as to realize complex batch tracking. Especially in the production of hybrid assembly line, the assembly parts can be delivered to the designated area accurately, thus reducing the error rate

② in terms of product tracking, it can realize comprehensive tracking from raw materials to final products. As long as the parts enter the production line or arrive at the completion area, the process, equipment and operator number and processing time will be automatically recorded, avoiding inaccurate data or errors caused by later manual data input, barcode scanning and other operations

③ in terms of planning and scheduling, RFID on processing equipment such as machine tools provides running time, availability status, performance characteristics, and includes technical parameters, tool usage, and production activities that have been carried out, so that real-time planning and scheduling in the workshop can be carried out according to the utilization rate of existing equipment in combination with the product process specification

④ in terms of equipment management, operators can check the equipment and its location by reading the information on the tag, maintain or repair the equipment, and then write the latest data to update the RFID tag, which helps to improve the value of the equipment, optimize the performance of the equipment and maximize the utilization of the equipment

3 RFID and MES integration technology

3.1 RFID Middleware

middleware technology is produced to solve the problem of heterogeneous distribution of various hardware system platforms and various system software. It is a general service between different operating system platforms and specific applications. These services have standard program interfaces and protocols. RFID middleware is a message oriented middleware. Information is transmitted between programs in the form of messages. Its function is not only to transmit information, but also to include services such as interpreting data, security, data broadcasting, error recovery, locating network resources, prioritization of messages and requirements, and extended debugging tools

therefore, as a bridge connecting RFID hardware equipment and background business application system, RFID middleware is an integrated technology to realize data acquisition and management between RFID and background application software (such as MES software)

3.2 integration method of RFID and MES

rfid middleware is composed of data acquisition and background database network application system. After three stages (as shown in Figure 1), RFID data acquisition completes the collection, filtering and merging of RFID data from RFID hardware devices; RFID data management completes the storage, maintenance, access and aggregation of RFID data. The initial RFID middleware is designed to integrate and connect RFID readers and writers in series with application programming. It is suitable for the situation that there are few collection points and readers and writers of the same specification, but it has low efficiency and high maintenance cost; As the complexity of enterprise application system increases, the database software changes or the types of readers and writers increase, enterprises cannot load to write adapters for each application software. At the same time, there are problems such as object-oriented standardization, so RFID architecture middleware is produced; The third middleware stage is that each manufacturer puts forward specific solutions for different industry fields, such as Sun Java System RFID software of sun closed company, including solutions for specific industry applications such as warehouse management, asset tracking, drug identification, etc

Figure 1 development process of integration method

for the current RFID architecture middleware integration method, from the application level, it includes the edge layer, enterprise layer and application layer; From the physical structure, it can be divided into five layers: hardware layer, data collection layer, workflow management layer, service layer and legacy system layer. From the functional level, the core modules include RFID edge server and RFID enterprise server. The edge server is directly connected with various terminal devices to control RFID reading and writing devices to work in a predetermined way, ensure that different devices can cooperate and coordinate well, and filter data according to certain rules, screen out most of the redundant data, and transmit the really effective data to the background information system; The enterprise server centrally manages all edge servers, handles various RFID events and information exchange, real-time workflow management, and integrates well with various existing application systems. Users can carry out business process innovation and new applications around these data (as shown in Figure 2)

Figure 2 RFID architecture middleware structure

3.3 RFID and MES integrated data flow

rfid tag built-in code is the carrier of data. EPCglobal divides tag categories into categories according to whether they can be read and written, the number of times they can be read and written, etc. for example, level 0 tag code is composed of 4 segments of 96 bits, representing the composition of information, manufacturer, product category and product name respectively. These codes stored in RFID are polled and read by readers and writers 120 and 400 times per second, and are connected to the fieldbus through rs422/rs232 interface. The label URI (unified resource identification) data is removed from redundant data by ale (application layer event management), and the filtered label data is counted by ons (object name resolution service)

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