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  According to the automated warehouse in modern logistics system management, the basic principle of radio frequency identification technology and radio frequency identification technology with wireless transmission of information, information transmission capacity and convenient and accurate dissemination of information, combined with the work of the automated warehouse, the application of RFID technology to the automated warehouse, construct a based on automation warehouse of radio frequency identification technology. Through practice, the system can process information more than 10 times faster than traditional methods. At the same time, it can process data information in real time and meet the needs of modern logistics system.
  
  With the automated warehouse system equipment production technology mature gradually and the popularization, the traditional manual record the main management mode has been unable to meet the needs of business, and magnetic card, bar code technology because of their own shortcomings, need is not suitable for the development of the logistics industry in the future. These patterns have exposed many shortcomings in the process of the development of modern enterprises, and greatly affected the process of enterprise information automation.


  RFID technology is a new and advanced automatic identification technology, and its broad prospects for development in various industries have attracted the attention of all countries and enterprises all over the world. RFID technology with other identification technology have not waterproof, antimagnetic, high temperature resistance, long service life, long reading distance, convenient, read tag data can be encrypted and it has larger data storage capacity and storage information freely change shape diversification, etc.. The emergence of RFID technology solves the problem of automatic identification of data, makes the information more rapid and accurate, reduces manual intervention and avoids tedious manual input, thus reducing production costs. Therefore, this paper presents a method to design the application of RFID technology in the warehouse system, normal operation can not only high speed and precision of the automated warehouse 80 warehouse position, production management can adapt to the modern enterprise.


  1 Radio frequency identification (RFID) technology 


  1.1 Radio frequency identification technology


  RFID,Radio Frequency Identification is a technique that uses radio frequency signals to realize contactless information transmission through spatial coupling (alternating magnetic field or electromagnetic field) and to achieve the purpose of identification through the transmitted information. The basic RFID system is usually made up of electronic tags, antennas, readers, and so on.


  (1)Tag。It is composed of lotus element and chip. Each electronic tag has global identification number (ID), which can not be modified and copied, and provides security. The tag is attached to the object to mark the target object. Electronic labels usually contain electronic data in the agreed format, such as the type of object to be identified, the batch number, the number of production, and the library number of the shelf.


  (2)Antenna。The RF signals are transmitted between the tag and the reader, i.e., the data information of the tag and the command information sent by the reader.


  (3)Reader。An apparatus for reading or writing electronic tag information, including handheld and fixed type. A reader can read and recognize electronic data stored in an electronic tag without contact so as to realize the object of automatic identification. And connected to the computer, read the tag information processing. The composition of the RFID system is shown in figure 1.
Figure 1 RFID system composition


  Compared with the traditional identification technology, RFID has the following advantages: small volume, fast processing speed; shape diversification; strong anti pollution ability, durable; reusable; penetrating, can be realized without the barrier of reading; data memory capacity; high security.


  1.2 Principles of radio frequency identification technology


  The reader sends energy through the antenna in a certain area to form an electromagnetic field, depending on the power, the frequency of operation, and the size of the antenna. When the tag enters the area, the radio frequency pulse of the reader is received and charged by the bridge rectifier to be charged as a working voltage after being regulated. At the same time, some of the data from the received demodulated RF pulse can be obtained and sent to the command and data control logic and control logic to accept instructions to send out product information stored in the label (Passive Tag, passive tags or passive tags), or label initiative to send a certain frequency signal (Active Tag, active tag or active label). After receiving the returned data, the reader decodes and performs error checking to determine the validity of the data, and then sends it to the central information system for data processing.


  2 The overall design of automated warehouse for RFID Technology 


  2.1 The composition of an automated warehouse system


  The main body of automated warehouse system is automated warehouse, in order to realize the automatic storage and removal of materials, it also needs the corresponding management and monitoring system. Therefore, the composition of the system is shown in figure 2.
Fig. 2 composition of an automated stereoscopic warehouse system



  2.2 Automated warehouse system mainly composed of


  (1)Master controller. The main controller adopted by the design of a small PLC of SIEMENS company, it has ability of 40 digital I/O points, and has two channels of communication / programming port, can realize the network control function of multiple sites in the system.


  (2)Detection device. The detection system includes the actuator location detection, system state estimation, detection means used including non-contact position sensor, photoelectric sensor (OMRON CX-24), rotary encoder (OMRON E6A2-CW5C) etc.


  (3)Stacker. In the automated warehouse system, the main executing mechanism is the stacker, which is used to automatically access the goods from the shelves. Three axis motion mechanism for stacker design in this system is mainly composed of a step motor, the selection of the motor adopts HS series high torque square hybrid stepping motor, small volume, high precision, it is formed by stacking machine with PLC controller can meet the requirement of accurate locating.


  (4)Conveying system. The function is to transport the goods to the stacker or remove the goods from the stacker. The most common conveyors are chain conveyors, belt conveyors, etc.
 
  (5)RFID system. The system uses V600 series produced by Japan Omron Corporation as RFID system, the device is electromagnetic coupling mode, and the oscillation frequency is 530kHz. It mainly includes read-write head, ID controller and passive electronic tag.


  ①Read and write head, model V600.H11, which is the bridge between the electronic tag and the ID controller, belongs to the amplifier built-in type. Through reading and writing heads, the commands of the host can be sent to the electronic tag in a certain range through the ID controller, and the response information of the electronic tag is transmitted to the ID controller. The ID controller, model V600-CA5D02, is used to connect with the read-write head of the V600-H series, and execute the command of the host to read and write the electronic tag. Meanwhile, the response signal of the electronic tag is returned to the host. Electronic tag, model V600.D23P66N, is the battery free data carrier in the OMRON V600 series, belonging to the passive electronic tag.


  2.3 System process analysis


  According to the flow of goods, the main process of the system is divided into warehousing operation process and outbound operation flow, as shown in Figure 3 and figure 4.


  (1)Warehousing process


  ①Warehousing preparation. The system's storage preparation includes the initialization of the system status and data initialization. At this time, the stacker is in the initial state, and the ID controller is ready to check the goods. Warehousing order issued. The receipt issued can be sent to the main controller through the form of manual or electronic version, the main controller according to the receipt of information, to identify the types of goods, but also need to deal with the detection of the goods the read / write head feedback ID information, the two information for comparison, when the goods and information storage by single, automatic system assign a number to the warehouse storage of goods, by the read / write head writes to the electronic label to. Enter the warehouse. Storage entry means that the stacker is transferred from the storage port to the loading platform. According to the distribution of goods storehouse, assign a space coordinates to the stacker stacker, this time from the initial state to the storage and operation, goods from the loading platform on the stage to pick up transfer stacker, prepare for the next step on. Storage shelves. Storage, shelves, warehouse for storage of the last operation step, the stacker will pick up the goods on the table into the designated library. The stacker automatically searches for an optimal trajectory according to the space coordinate points allocated by the system, and stores the goods from the storage port to the stereoscopic warehouse. Storage end. When the goods are on shelves, the stacker returns to standby, and the system updates the library data and completes the corresponding records.

 

  (2)Outbound operation flow


  ①Outbound preparation. The system is ready for delivery and storage. Delivery order. Chukuchan issued can be sent to the main controller through the form of manual or electronic version, the main controller according to the storehouse of the information, to identify the types of goods, but also need to deal with the detection of the goods the read / write head feedback ID information, the two information for comparison, when the goods information and out by single, prepare system the library. Enter a warehouse. After confirming the library operation, the stacker will get a definite space coordinate point according to the location information determined by the delivery order. Under the operation of the master controller, the stacker will arrive at the specified location along the optimal path from the current position. Delivery shelf. In the reservoir area, the stacker takes down the cargo from the designated position, reads and writes the header at the same time, reads the cargo ID information and feedback it to the main controller. The main controller determines the delivered goods information and Chukuchan information is consistent, when the information is confirmed, execution of pick up the goods to the warehouse operation, at the same time, the electronic tag system will be written into the tag library information to update the stored data. End of library. The stacker returns to standby status, updates the system data, and completes the corresponding records.


  3 Program design 


  In the operation process of the whole system, the core control technology includes two aspects: one is the automatic tracking and positioning in automatic warehouse stacking machine; on the other hand is the RFID automatic detection system and update data.


  From the system flow chart (see Figure 3 and Figure 4), the RFID system is divided into two main functions in the application, namely read information operations and write information operations. For the read-write operation of electronic tag, there is corresponding fixed communication format in the corresponding system, and the user can complete the corresponding control according to the format of communication.


  By changing the command code in the communication format, commands such as read and write operations can be implemented. The following main controller to control the reader to complete the operation of reading as an example to illustrate the design of the program.


  In order to complete the PLC ID controller, PLC controller to send the correct commands to the ID controller, the controller of the free VI instruction XMT (send command data) and RCV (command receiving data) to complete the operation of the ID controller to.


  When the goods arrive at the loading port, the switch signal of the photoelectric sensor triggered, the PLC executive sends command port XMT port is automatically read command (AUTO READ), then PLC port to receive instruction RCV goods receiving information read by the system, judgment, when the storage of goods and storage information when, according to the process, issued storage instructions, storage subroutine start, completion of storage.


  4 Concluding remarks


  Practice has proved that the application of RFID system to achieve a highly efficient, fast, can replace the original production line of some sensors and other detection equipment, saving space and relevant controller I/O, reduces the complexity of programming, to speed up the material flow, improve the production efficiency, accuracy and safety device.

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