With the soaring of land price, the storage cost of manufacturing enterprises and express delivery industry is rising. How to use limited land effectively has become an increasingly concerned problem for enterprises, and the three-dimensional shelf can effectively solve the current problems. According to rough statistics, by the end of 2016, the number of automated stereoscopic shelves in China exceeded tens of thousands, almost all over the industry. Intelligent warehouse is based on three-dimensional warehouse technology, combined with automatic control, intelligent detection, information management and other technologies, seamless docking with automatic production workshop or intelligent workshop, with more intelligent and fast cargo storage function. With the government vigorously promoting "made in China 2025" to promote automation and intelligence, intelligent warehouse will usher in greater opportunities in manufacturing and use. This paper introduces the application and research of an intelligent storage system based on AGV and RFID technology.
1. Brief introduction of main technologies
1.1 stereoscopic warehouse
Automated warehouse, also known as elevated warehouse or elevated shelf, generally refers to the shelf with multi-layer, more than ten or even dozens of layers of shelf storage unit goods, with the corresponding transport equipment for goods warehousing and outbound operations. Automatic storage system (as / RS) is a revolutionary achievement of logistics technology. It is generally composed of three-dimensional shelves, hoists, conveyors, control systems and computer management systems. It can complete the automatic storage and retrieval of goods under the control of computer systems.
At present, the realization methods of three-dimensional warehouse are generally roadway stacker, roadway stacker + shuttle car. In recent years, with the progress of technology, technologies such as child parent shuttle car and four-way shuttle car have gradually appeared. What kind of way to realize a three-dimensional warehouse needs to be comprehensively determined according to its own storage products and warehouse conditions.
Automated guided vehicle (AGV) is a transport vehicle equipped with magnetic stripe, optical or visual automatic guidance device, which can drive along the prescribed guidance path, has safety protection devices and various load transfer functions, and can be driverless in industrial applications, with battery storage as its power source. AGV can replace the conveyor line to transport goods, with greater flexibility and site occupation advantages. At present, its navigation mode usually uses magnetic stripe navigation or laser guidance.
1.3 RFID Technology
Radio frequency identification (RFID) is the abbreviation of radio frequency identification, and it is one of the non-contact automatic identification technologies. It can exchange non-contact data through radio frequency, and use radio frequency to identify RFID The chip can read or write, so as to achieve the purpose of identification and data exchange. It has advantages in real-time data update, information storage, service life, work efficiency, security and so on. It has been widely used in many fields, including logistics, transportation, identification, anti-counterfeiting, asset management, information statistics and other industries. RFID electronic chip is divided into ultra-high frequency, low frequency and high frequency according to its working frequency. The working frequency of ultra-high frequency tag is between 860MHz and 960MHz, and the maximum reading distance is more than 10 meters. Due to the long reading distance and fast data transmission rate, it is widely used in bulk goods identification and automatic toll collection system, but the cost is relatively high Electronic tags generally use the principle of electromagnetic coupling, less application; high frequency typical working frequency is 13.56MHz, reading distance is generally less than 1m, widely used in electronic ID card, access card, anti-counterfeiting label and other data interaction scenarios, the application scheme of this paper is based on high-frequency RFID tag technology.
2. Composition and implementation of system architecture
The whole system includes: RFID information processing reading and writing system, AGV shipping, warehousing and conveying system (realizing the function of two-way out and in), whole stacker belt size detection, goods warehousing elevator, shelf system, address identification bar code, shuttle mother car, shuttle sub car, goods outbound elevator, mother car vertical conveyor, outbound conveying system, electrical control system, information management system (WMS) And WCS), monitoring and dispatching system.
The system has the functions of AGV automatic transfer, transportation, cargo lifting, cargo intelligent access, RFID data information integration, automatic generation and implementation of access scheme, positioning, equipment self-help, equipment fault alarm, system function increase and decrease, system function customization, etc. the flow chart of in and out warehouse is shown in Fig. 1 and Fig. 2.
2.1 RFID information processing read-write system
Before the empty pallet embedded with RFID chip enters the palletizer buffer area of the front-end automatic line to load products, the read-write system will first detect whether the RFID tag of the pallet is readable. If the RFID pallet tag is readable, the RFID chip data will be cleared and transported to the palletizer loading area. If the reading fails, the sound and light alarm will be given, and the workers will remove the damaged empty pallet. In the loading area, the RFID pallet information collection system receives the product information issued by ERP production system or manually set, and binds with the collected RFID pallet tag information. The binding information is transmitted to the stereoscopic warehouse management system through the wired network.
RFID reading and writing equipment is installed in the in and out conveyor line of stereoscopic warehouse, which is used to collect RFID of pallet The label information can check the pallet cargo information in the process of the warehouse in and out system to ensure the accuracy of reading the cargo information. The collected pallet label information is sent to the stereoscopic warehouse management system through the network. The warehouse management system controls the pallet in and out operation and updates the WMS data in real time to ensure the accuracy of the data.
2.2 AGV transfer
AGV automatically receives the full load signal of pallets from the front-end automatic palletizing loading area, and then takes the pallets from the loading area. The system controls the beat and transports the pallets to the storage and transportation system according to the preset path, and places the pallets at fixed points and directions. In the process of transportation, it can automatically identify the RFID tag of pallets, judge where the goods are put into storage, and display the current cargo transportation status in the control system in real time, so as to meet the demand of more flexible transportation.
2.3 in and out transportation system
In and out transportation system is composed of conveying roller table, chain machine, transfer machine, RFID identifier, etc. Through the central control system, these equipment can coordinate actions to complete the corresponding process data acquisition; in the position where the goods need to stop accurately, photoelectric switch and mechanical stop are used to make them reach the same position in any case.
The warehousing system realizes the online transportation of pallet goods from AGV to palletizing machine and warehousing elevator, and realizes palletized goods transportation and caching, automatic identification of pallet RFID tags, and judgment of the specific requirements of warehousing.
The outbound system realizes the online transportation of pallet goods from the outbound elevator to the loading buffer zone, realizes the transfer buffer of pallet goods, automatically identifies the RFID tag of pallets, and judges the number of transfer flat cars to the corresponding unloading location.
2.4 dimension inspection stacker
Identify and detect the overall dimensions of pallet goods, judge whether the warehousing goods need to be palletized, sort out the surface dimensions of pallets, make the overall dimensions meet the warehousing standards, and ensure that the warehousing goods meet the specific dimensional requirements of internal three-dimensional shelves.
The size detection device is set up in the whole stacker, which is used for the shape detection of the length, width and height of the goods. The automatic opening and closing of the whole stacking plate is set at the left and right corners of the longitudinal plane of the storage buffer conveying line. A guide plate is arranged at the left and right directions of the conveying line, a longitudinal stopper for positioning the front and rear positions of the tray is arranged on the front side of the conveying plane of the conveying line, and the clamping force of the baffle plate is controlled by the servo motor.
2.5 goods in and out of warehouse elevator
The warehouse in and out elevator realizes the palletized goods transportation up and down in the warehousing transportation system. The software sets the transmission path, speed and beat, and frequency conversion controls the running speed, and has safety protection measures to ensure the safety of personnel and goods. The goods in and out of warehouse elevator is compatible with the vertical hoist of the parent car. In case of serious failure and other maintenance failure of the sub trolley in the internal conveying roadway of the three-dimensional rack, it can be transported to the lower level of the three-dimensional shelf through the warehouse in and out elevator, which can meet the flexibility of maintenance or replacement, reduce the risk of high-altitude operation of maintenance personnel and the impact of the maintenance process on the working continuity of the whole three-dimensional shelf Ring.
2.6 shuttle bus
The shuttle mother car is composed of shuttle mother car and shuttle car. The shuttle mother car runs in each layer of sliding contact line track of the main rack body, and the sliding contact line supplies power, so as to realize the fast and straight-line transportation of pallet goods from the storage elevator to the designated location, from the designated location to the outbound elevator.
The shuttle passing sub vehicle walks in the lane where the goods are placed, and the battery of the sub vehicle is powered by the parent car, so as to realize the on-line rapid transportation of pallet goods from the parent car to the designated cargo location and from the designated cargo location to the parent vehicle. The sub vehicle carries the palletized goods and the parent vehicle carries the sub car on the main track. The integrated RFID reader of the sub car has the functions of inventory and database checking. The data exchange with WCS / WMS is realized through WLAN, and the working status and the status of the transported goods are updated and displayed in real time. In the process of transportation in the roadway, three kinds of ranging and positioning methods, namely wheel line ranging, address bar code and infrared ranging, can be realized.
2.7 electrical control system
The main functions of the electrical control system are manual automatic control mode switching, information inquiry, power failure protection, emergency alarm and other functions. The on-site distributed touch screen is set with password protection, and the important operation can only enter the operation interface after the password is input and confirmed, which can realize the authority change. The main control modes include manual mode, automatic mode, online mode and emergency stop mode .
Main control box (master station): the bus cable is connected from the Ethernet interface of CPU module to the interface module of the control box of the next slave station, the power cable and signal cable are connected to the terminal in the cabinet, and connected to the components in the cabinet through the corresponding column head of the terminal. PLC module and communication module are installed in the cabinet. Field control box (slave station): each group of equipment is equipped with a field control box, which is installed at a suitable position at the lower part of the conveyor. The controller in the box controls the motor of the controlled equipment; the I / O module collects the signal of the detection element on the controlled equipment and controls the executive device.
2.8 information management system (WMS and WCS)
It mainly includes computer management system, computer scheduling, monitoring system, handheld terminal system, interface management system. Realize the unified management and scheduling of automated stereoscopic storage, realize the information integration with operation execution layer, realize the unified scheduling of logistics equipment and system, and the unified management and use of inventory materials, and realize the functions of operation plan management and material management, as shown in Figure 3.
The basic information includes the definition of material code, logical definition of storage area, definition of material storage security (including upper and lower limit of reserves and storage period), material allocation rule definition, material transfer definition and customer code definition. Basic information management is composed of material basic information management, storage area logical division definition, material storage security management, customer information management, etc. The basic information can be connected and synchronized with the basic data of the upper ERP management system, and the material status of the upper ERP can be updated in real time to avoid data error and repeated entry.
Based on RFID The technical shuttle car can make inventory checking more convenient. At a specific time, it can delimit the scope of inventory or review the whole warehouse. The shuttle vehicle will visit all cargo pallets, collect the storage information of each pallet in turn, review the type and location of goods, and get the detailed inventory information such as the overall inventory, the number of goods types, the distribution of goods and the free shelves, Compared with the data in the current WMS database, the WMS data information is updated after multiple inventory. When necessary, the internal warehouse can be automatically transferred according to the distribution of goods, which is convenient for centralized management of inventory goods and optimization of shelf storage efficiency .
2.10 monitoring and dispatching system
The monitoring and dispatching system is connected with the upper logistics layer management, receives the relevant instructions and plans from the logistics management level, decomposes and issues them to each executive equipment layer, and feeds back the completion status of the lower level equipment, and supports the addition and management of a variety of equipment. Real time monitoring of the operation of all parts of the whole stereoscopic warehouse, dynamic display of the operation position of the sub trolley and the transmission equipment in and out of the warehouse as well as the goods, display the current operation status of all tasks and error alarm, and can directly and independently control the operation of all equipment in the warehouse .
This paper mainly introduces a set of intelligent warehouse management system based on AGV and RFID technology, which makes use of AGV transfer convenience and RFID The technology's non-contact data security reading and writing function can realize intelligent information reading and input, data review and inventory, and in and out of warehouse transportation, improve the accuracy, safety and convenience of goods storage information, meet the real-time visibility and accuracy of goods transportation, optimize the warehousing operation process, effectively reduce the temporary storage cost of products, reduce the labor cost and enhance automation Production level, in order to effectively improve the storage efficiency, has a certain application value.
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