Research On Some Key Technologies Of Container Tag System

Using the RFID (Radio Frequency Identification) technology to record the logistics information, we can trace the flow information of container in the transportation in real-time, and eliminate the latent accident, such as wrong container and missing container during the container transportation process. On the other hand, it can improve the customs-pass speed, the security and reliability of the transportation. Therefore, the application of RFID in container transportation can advance the whole efficiency and the service level of the container port. But its application environment is very complex, and its technology is difficult. The technical indices and functional demands in the container field are much higher than ones in the other fields. Some urgent pivotal problems of the electronic tag in container logistics were researched through the methods including theoretical analysis, modeling simulation and actual test.First, the main theories were analyed in the research and development process of the container RFID system. Beginning with the electromagnetic wave propagation theory, based on the antenna current element model, the distance-field condition and near-field condition were analyzed when using the electromagnetic wave communication. The energy transfer formula of the antenna distance-field radiation was also inferred, and the antenna noise characteristics and the traits of the RFID coupling communication modes were discussed.Second, the application environment of the container RFID system, the transmission modes and characteristics of the electric wave were analyzed. The ground reflection loss model was used to analyze electric wave propagation characteristics at warehouse and the container terminal, and an electric wave diffractive loss model of container RFID system was established. The testing results show the model can effectually forecast the electric wave path loss. Based on this model, the relationship among system max identification distance, sending power, polarization modes and read-write reliability was analyzed through the computer simulation. These made a theoretical basis for the design of the RFID system. The influence of the multi-path transmission and metal interference to the container RFID system were also analyzed. The theoretical basis to ignore the multi-path delay and Doppler Effect was given. The technical measures were presented to resist the metal interference in container RFID system.Third, CY (Container Yard) to CY and CFS (Container Freight Station) to CFS were analyzed, which were the container production technologic flows. It was indicated that the electronic tag's read-write process have discreteness, fixity and particularity during the container logistics process. The container electronic tag low power loss strategy and the optimized method were summarized. One kind of passive activating mechanism and the project to realize it were proposed. A technical scheme was presented to solve the near-path interference and the tag location by using the passive activating mechanism. And the electronic tag power loss and real-time performance under the timing and passive activating mechanisms respectively were analyzed, and a new communication mode based on the double activating mechanisms was proposed. The test result proved that the double activating mechanisms satisfied the container electronic tag system's performance requirements preferably.In succession, aimed at the conflict characteristic of the container electronic tag, the commonly used Slotted ALOHA algorithm was emphatically analyzed. The Markov chain to build model for its recognition process was introduced and the relationship between the system recognition success ratio, the number of time slots and tags' number was got. It was found that when the number of the tags was very large or unknown in Slotted ALOHA algorithm, the collision ratio would increase and the recognition success ratio would decrease sharply. So a new anti-collision algorithm which based on the subset-partition and the dynamic-match mechanism was presented. The simulation analysis indicated that this anti-collision recognition algorithm has the auto-adaptive merit as well as the high recognition efficiency and success ratio.Finally, based on the front research fruits, combining with the actual project application, the key technologies of the container fixed reader from both the hardware and the software design were researched and developed. The overall design scheme of the fixed reader was given. The design idea was also given as well as the realization method to the reader's several essential parts. The actual tests to verify the reader's operating performance were carried on.After resolved the key technologies above, the reliability of the container RFID system and the recognition speed of the electric tag can be improved. The tag's service life can be extended. The system application cost can be lowered.