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1. Application Introduction
In 2003, after Walmart and the U.S. Department of Defense (DOD) respectively announced the large-scale adoption of RFID technology for its merchandise logistics and supply chain tracking, people’s understanding and research on this technology
Set off an unprecedented boom. Because RFID technology has the characteristics of non-visual reading, data readable and writable, strong environmental adaptability, and high-speed simultaneous reading of multiple tags, in many applications of RFID,
The field of logistics and supply chain is generally considered to be the largest application field of RFID in the future. In addition, RFID has also been widely used in the areas of national life such as vehicle management and luggage tracking.
People often try to use RFID technology to finely manage goods in the warehouse management link of the logistics field. In fact, it is quite complicated to apply RFID data collection technology to multiple links of logistics. So far, the application of RFID in the logistics field has not made breakthrough application progress, which is mainly due to the influence of the following factors:
Complexity of characteristics of logistics operation objects
The characteristics of logistics objects are very complex. These characteristics including material, shape, size, packaging environment, moving speed, etc. will affect the implementation effect of RFID system to varying degrees. It can be said that there is no RFID system in the world today. The automatic identification of all logistics objects was successfully completed.
The complexity of the logistics operating environment
The working environment of logistics and supply chain often has metal brackets, shelves, columns, etc., and there are also complex environments such as wires, cables, network lines, etc. that may or generate electromagnetic clutter. The objective existence of these environmental factors will affect to a certain extent To the performance of the RFID system.
The complexity of the social links of logistics
In logistics, especially supply chain management, the flow of goods is very social. In the process of flow, the sharing and distribution of information puts forward requirements for data and application specifications for the RFID system. Therefore, in the open-loop logistics In management, the RFID application system becomes very complicated.
However, like other supporters of RFID, we do not hesitate to believe that with the development of RFID technology and the lowering of the application threshold, RFID technology will become an important technical means of modern logistics management.
2. System selection
As the RFID system used in the logistics field to automatically identify logistics objects, the physical characteristics, shape, size, moving speed, number of tags recognized at the same time, installation environment, application level, tag shape and size of the identified object must be considered. Installation method, label cost, etc.
1. Physical characteristics of logistics objects
The so-called physical characteristics of logistics objects refer to the shape (solid, liquid, gas), conductivity (conductive and non-conductive), metallic properties (metal and non-metal), density, etc. of the identified object. Generally speaking, conductive liquid substances will have a strong absorption effect on electromagnetic waves, while metal objects or high-density non-metallic materials will have a reflection effect on electromagnetic waves. However, in logistics applications, especially in daily necessities, luggage sorting, etc., the content of logistics objects is often uncertain, that is, the nature of logistics objects is very complex, with solid and possible Conductive liquid, metal objects may also be present.
Therefore, in this situation, it is difficult to use a certain single-frequency RFID system to identify all identified objects. In this sense, RFID is suitable for the situation where the logistics object is a single species. As for the different characteristics of such a single type of logistics object, it is also necessary to use RFID systems of different frequencies for identification. Generally speaking, for products containing conductive liquid media, low-frequency (LF) or high-frequency (HF) products can be used for identification; for non-metallic and non-conductive media, ultra-high frequency can be used for identification. (UHF) system; and for the identification of metal materials, currently, a layer of ferrite material is added between the metal and the identified object and the label to solve the problem.
2. The shape of the recognized object
The shape of the recognized object involves the installation of the label. For regular-shaped objects, the label is easier to install, or stick or hang. The recognized object itself will not block the label, because even if it is Metal materials will also have a certain attenuation effect on electromagnetic waves, thereby affecting the recognition effect of RFID. In addition, label reading may also have a certain directionality. For example, linear polarization RFID systems have stricter label directionality requirements. Irregular shapes of objects, especially flexible packaging bags, will change the reading direction of the label, which will also lead to a reduction in the reading rate.
3. The size of the recognized object
The size of the recognized object is directly related to the reading distance of the system, and affects the installation method of the reader system. Of course, if the tag is fixedly installed on one side of the reader antenna, the reading effect can be guaranteed to be ideal.
4. The moving speed of the recognized object
The moving speed of the identified object is related to the time the tag stays in the electromagnetic field, that is, the time for the tag to obtain energy. The longer this time is, the more the internal capacitance of the tag will be charged, the longer the continuous discharge time, and the more stable and reliable the work will be. Therefore, too high speed will affect the accuracy of reading results.
5. Number of tags recognized at the same time
This is one of the inherent good characteristics of the RFID system. However, the same, the more tags that are recognized at the same time, the more unreliable the system is to read. In addition, for systems with different frequencies, the anti-collision performance of the system will vary. The impact resistance of UHF is the best, and the low frequency is the worst.
6. Installation environment
Since the basic principle of the RFID system is the coupling and propagation of electromagnetic waves, the performance of the system is very sensitive to the electromagnetic influence of the installation environment. In actual applications, a wire, network cable, etc. in the installation environment may have a greater impact on the reading performance of the system.
7. Application level
The so-called application level of the RFID system refers to the level to which the RFID tag is applied, whether it is at the item level, small package level, large package level, pallet level or container level, and so on. Taking cigarettes as an example, the application can be each pack of cigarettes, one piece, or one box, and for warehouse management, it can also be a tray. Different levels of applications will change the size of the identification object, the number of identification objects simultaneously identified, etc., and therefore will also affect the quality of the identification effect.
8. Label shape and size
The shape and size of the label are related to the installation method. The smaller the label, the worse the reading effect, and the more difficult it is to encapsulate the label. The label has a variety of shapes, including strip, card, cylindrical, and all kinds of special-shaped labels. The size and shape of the label need to be determined according to the needs of the specific application system.
9. Installation method
The label can be installed on the identified object by pasting, hanging, embedding, wearing, etc. For larger labels used on trucks, containers, etc., riveting can also be used. The choice of installation method and installation location is also very important for the system.
10. The cost of labels
For RFID systems, tags are consumables. The other investment in the system is one-time, while the investment in the label is recurring. Even if it is a recyclable system, it is necessary to frequently replenish damaged or missing labels. At present, the cost of tags is relatively high. Therefore, the choice of RFID system must be comprehensively considered based on the value of the identified item itself and the added value that can be created. At present, the cost of RFID tags is generally less than 3 yuan for low frequency, less than 15 yuan for high frequency, and more than 30 yuan for UHF tags. For active systems, the cost of tags is more expensive, mostly above 100 yuan.
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