When guaranteeing equipment and equipment, the records of training use, maintenance, installation and transformation are performed by traditional manual operations. The management personnel must register the name of the equipment, the type and quantity of the equipment, the manufacturer, the date of delivery, and many other attributes one by one. Low work efficiency and error-proneness have become a bottleneck restricting work progress. If equipment information management uses RFID tags instead of paper resumes, it records equipment from the factory, equipment, use, maintenance, storage, accidents, retrofits, retired and scrapped the entire life cycle of the history information, read the radio frequency tag with a handheld reader And the daily information of the information recording device can help the operator to grasp the equipment working status in time and provide information support for the maintenance support personnel.
But different from the ordinary logistics field, because the equipment information is more complicated, a single ordinary label is difficult to carry all the required information. Considering economy and practicability, the multi-tag method with different frequencies can better meet the requirements. Therefore, this article focuses on the analysis of the RFID data structure of equipment information, and studies the storage and management of the internal data of the embedded reader in detail to meet the needs of equipment support informatization.
1.1 RFID data characteristics
The RFID data model is the basis for managing RFID data. Generally speaking, RFID applications have common requirements and characteristics:
(1) Identification: The RFID tag uniquely identifies the object.
(2) Location: A location can be a geographic location or a special location with background meaning, such as a warehouse, shooting range, etc.
(3) Relationship: Another key concept of RFID applications is aggregation, that is, the relationship formed between objects. A common aggregation situation is the containment relationship, that is, during the movement of the object, the contained object has the same movement path and other characteristics as the outer packaging object. Another collective situation is collaboration, that is, there is a certain relationship between labeled objects [1]. If a certain type of missile shooting training is completed by the launch vehicle and the detection vehicle, there is a collaboration relationship between the launch vehicle and the detection vehicle.
1.2 Data model
This article focuses on the use of database technology to achieve hierarchical management of equipment data information. The data involved in the system mainly includes static data and dynamic data.
1.2.1 Static data
Static data is data about fixed information, business rules, and system settings, and it is not easily changed over time [2]. In this system, static data mainly includes:
(1)Objects: All use radio frequency tags to identify the system, including the name, model, manufacturer, year of production and other information of the system and its accessories.
(2) Organizations: Information about the assembly changes during the life cycle of the equipment (the time between leaving the factory and being decommissioned), including information about the assembly unit, assembly time, and battle sequence.
(3) Actions: Transaction processing type. Including records of major activities, technical inspections, maintenance, retrofitting and other information.
1.2.2 Dynamic data
Dynamic data reflects the transaction process in the operation of the system, and is closely related to time and space. Dynamic data mainly includes: Arrangement, used to describe the hierarchical relationship between equipment entities (Objects) and status; ObjectOrganizaTIon, used to describe the allocation and adjustment of equipment entities (Objects) within a certain period of time; ActIonItem, used to describe equipment processing conditions.
1.2.3 The establishment of the data model
If there is a static relationship, it can be mapped into a table according to the mapping relationship of the ER model [3]. For a state-based relationship between two entities, a time interval (sTIme, etime) is added between the primary keys of the two entity tables, where the time interval represents the life cycle of the relationship or state. The event-based dynamic relationship consists of the primary key mapped in the two tables plus the timestamp attribute timestamp. This timestamp represents the point in time when the time occurs.
2 Based on embedded RFID reader data management2.1 System design ideas
According to the above analysis, data sources are mainly divided into two categories: one is fixed equipment identification information, which generally does not change with time, and the amount of data is relatively small; the other is dynamic equipment life information, which is usually recorded daily The start time of the operation and the allocation and adjustment of equipment, the amount of data is slightly larger and requires repeated reading and writing.
To this end, taking a certain type of vehicle equipment as an example, a 13.56 MHz passive tag is used to store equipment identity information, and an active tag with a frequency of 2.4 GHz is used to store dynamic life information. This design uses Windows CE as the operating system, reads the required data through the RFID radio frequency transceiver module, analyzes, extracts, and stores the data, and builds an embedded SQLite database to realize the management of the data. The most convenient way for users to query and modify stored data is to implement them in a Web page. Therefore, a Web server needs to be built so that users can control the completion of these tasks and achieve operational access to data through the Web page.
Device management provides a unified reader interface program, which can control the work of multiple types of readers; data management completes the filtering and storage of data, and uses the embedded Web server to query and modify the data; embedded The embedded Web server is the product of the combination of embedded technology and network technology. The Web server in the Internet is tailored to a certain extent and embedded in the device, so that the embedded Web server can be used to operate and manage the device. This article intends to use GoAhead WebServer, which is an embedded Web server with free source code that can run on multiple platforms, and supports ASP, embedded JavaScript and standard CGI execution, which can better meet the needs.
2.2 Data analysis and filtering
The reader reads a large amount of unprocessed data from the tag. Generally speaking, the data read is not completely useful tag data. It needs to be extracted and parsed to obtain useful information. Data will inevitably be interfered by the outside world during the transmission process and errors will occur. Therefore, the data must be filtered, and the filtered data will be stored [4].
Tag data is generally binary coded. After reading, the binary coded data needs to be converted into unicode data.
In the label reading process, the conversion of the binary bit code of the label to the unicode code is realized. In the label data processing link, the label is filtered according to the label unicode code obtained by the conversion and the filtering conditions, and meaningful label information is provided for the information application layer.
The filtering rules can be set through the Web page, and the setting information is stored in the filtering rule configuration file. When filtering, the filter reads the configuration file and applies it to the filtering rules.
3 Realization of data storage and management3.1 Build an embedded database
SQLite3 is a lightweight, free and open source embedded database that supports most of the standard SQL92 statements, works fast, and can meet the real-time requirements of middleware data processing. Therefore, the choice of SQLite3 database is an ideal compromise in terms of size and functionality.
The SQLite3 embedded database provides source code, which can be transplanted by cross-compiling the source code on the hardware platform. After compilation, the sqlite3 executable file with a size of 93 KB and the sqlite3 dynamic link library libsqlite3.so with a size of 991 KB are generated.
3.2 The realization of the data model in the database
The embedded database stores data in the form of a single library file, and the database file can be used under different operating system platforms without conversion. The database file is organized in two storage structures: table data pages and index data pages. User-defined temporary tables and temporary tables in the system (used for operations such as sorting and grouping) are managed in the form of temporary database files.
On the development board, use the sqlite3 executable file generated in the previous step to generate the database tables required by the system. The Sqlite3 database is similar to the Access database and uses a single file mode. For this reason, a database file named rfid is generated, and the necessary data tables are planned according to the needs of the project.
Type "sqlite3 rfid;" directly on the command line to generate the rfid database, and get the prompt "sqlite3>". You can create the required table by entering the SQL statement:
create table rfid(Number integer primary key, Objects varchar(),Organizations varchar(),Actions varchar(),ActionItem varchar(),ObjectOrganization varchar(),Arrangement varchar());
.quit;
Only the basic attributes are considered here, and additional attributes can be implemented as an extended table for the data table.
With reference to the grammar of SQL DML, the main elements of the logical structure of the model are described as follows:
(1) Objects: Objects (EPC Primary Key, name, deseription), recording system and accompanying information.
(2) Organizations: Organizations (organizationID Primary Key, organization), which identifies the assembly unit and organization sequence of the equipment during the life cycle.
(3) Actions: Actions (actionID Primary Key, actType), which identifies the transaction type in the business process. Among them, actionID is the transaction type identification code; actType represents the name of the transaction type.
(4) Arrangement: Arrangement (ID Primary Key, EPC, parentEPC, QtyOfChild, organizationID, stime, etime), Arran-
The gement relationship is the key to this data model, reflecting the physical hierarchical relationship of items. Among them, parentEPC identifies the EPC code of the previous level of the EPC; QtyOfChild records the number of items at the next level identified by the EPC; stime and etime respectively identify the occurrence and end time of the hierarchical relationship.
(5) ActionItem: ActionItem (ID Primary Key, actionID, EPC references Objects, timestamp): ID identifies each transaction that occurs; timestamp is the time when the transaction occurred.
(6) ObjectOrganization (ID Primary Key, EPC refferenees Objects, organizationID, timestamp): ID identifies the allocation and adjustment of equipment and changes in the preparation of battle sequences.
SQLite database provides a wealth of C language API interface functions, which makes the operation of the database very convenient. This system only needs the following 3 core functions to connect to the database, process queries and other operations:
int sqlite3_open(const char*db,int mode,char* *errmsg);
int sqlite3_close(sqlite*db);
int sqlite3_exec(sqlite*db,char*sql,int(*callback) (void*,
int,char**,char**),void*parg,char**errmsg);
Among them, the first two functions are used to open and close the database, the third function sqlite3_exec() is used to process SQL queries, the second parameter of this function is used to process one or more SQL statements, if it is a SELECT statement , Each record of the query result must call the Callback function of the third parameter, and the fourth parameter is the pointer of the first parameter of the Callback function; if it is not a query statement, the third and fourth parameters are NULL. After all SQL is executed, it returns 0, otherwise it returns an error code. You can view the detailed error information through the fifth parameter value.
Use the sqlite3_mprintf function to add the value of the data segment to the SQL statement, and then execute the SQL statement through the sqlite3_exec function to insert the label data into the database.
3.3 Data access operations
GoAhead WebServer is a web server for embedded systems, as a data forwarding and module bearing platform in the system. Migrating to the Wince system is relatively simple. Open the workspace webs.dsw in the CE subdirectory in Visual C++ 6.0, and import the generated webs.exe and required Web pages into the corresponding location in the WinCE system. It should be noted that the computer system environment variable Path should be set to include include and lib, and to ensure that the characteristic values ​​including CE, UEMF, webs and UNICODE are defined.
Before using GoAhead WebServer, you need to configure GoAhead WebServer:
(1) When entering the address in the browser, the server returns to a certain page, which is set by the initWebs function in the main.c file. The setting statement is:
websRedirec(wp,T("index.htm"));
(2) When the browser visits a directory under a certain address, the server will return to the default page under the directory, which is set through the websHomePageHandler function in the main.c file. The setting statement is:
websSetDefaultPage(T("default.asp"));
After the user configures the filtering rules on the page, the CGI program writes the configuration results into the configuration file filter.conf. When performing data filtering, the filter will read this configuration file to obtain the corresponding filtering rules to filter the data.
First, use the C language API to call sqlite3_open() to open the database, then call the sqlite3_exec() function to execute SQL statements to complete operations such as reading, writing and updating the database, and finally execute sqlite3_close() to close the database.
Usually, the CGI application outputs the execution result to the standard output (stdout), and the WebServer reads information from the standard output in the CGI application and returns the information to the client [5]. Therefore, if you want to output the SQL query results to the customer in the program. CGI applications can use the prinf() function to output the query results to standard output in the form of HTML, and then the Web server returns a dynamic page to the client, thus realizing the interaction between the user, WebServer and SQLite3 embedded data.
Through compilation, webs.ere will finally run as a sub-process of the operating system, which can communicate and transmit data with other processes in the operating system, so as to realize the interaction between the internal programs of the operating system.
This paper studies the RFID data structure model for equipment information, uses the SQLite database to store and filter tag data, and designs a simple and easy-to-use Web interface. You can complete the filtering rules with simple operations through the browser. Settings and interaction with data and other functions. The future work is to carry out more page optimization designs, which will make it more valuable in practical applications.
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