China Mobile Smart Home Security Patrol Positioning System Design Scheme
RFID (RadioFrequencyIdentification) is a non-contact automatic identification technology. Its principle is to use radio frequency for non-contact two-way communication to realize automatic identification of objects. Due to its characteristics of high-speed moving object recognition, multi-target recognition and non-contact recognition, RFID technology strongly promotes the development of home automation, industrial automation, modern logistics and other fields; ZigBee is an emerging short-range wireless networking technology, which is A networking protocol for implementing wireless sensor networks. Using ZigBee technology to build a task-oriented distributed network composed of a large number of nodes, real-time monitoring of information targets through various micro-sensors, and transmission of information to remote users through wireless communication networks. In this paper, RFID wireless sensor network is established through the fusion of RFID and WSN, and it is applied to the home intelligent security system.
The traditional wired security system has the disadvantages of difficult wiring, high cost, and inconvenient arming and disarming, and it is difficult to meet people’s increasing security needs. The establishment of an intelligent security system based on RFID wireless sensor network can effectively solve the above problems. RFID mainly realizes the patrol and positioning of home security smart cars, and WSN completes the distributed intelligent monitoring of home environment parameters. The system not only inherits the characteristics of RFID technology to automatically identify the target, but also realizes the function of active sensing and communication of wireless sensor network. This system designs an adaptive star network with a mobile router, which not only ensures the real-time performance of the home security system, but also avoids the complex network topology, thereby improving the overall performance of the home security system.
1 The overall architecture of the system
The overall design framework of the system is based on the intelligent home gateway as the central coordinator to form a ZigBee star network. Install various security monitoring module nodes in the home environment. Once an abnormal situation is detected, the specific information of the police situation will be sent to the home intelligent gateway immediately, and the home intelligent gateway will carry out corresponding police situation processing according to the specific situation, such as wireless alarm, on-site alarm Or dispatch a patrol car to further detect the police situation; the intelligent patrol car is a mobile node in the network and acts as a mobile router. At the same time, according to the instructions of the home intelligent gateway, it can carry out more detailed information on the areas in the home environment that may have hidden dangers. and the objects with smart RFID tags are mainly used for patrol positioning of smart cars.
1.1 RFID wireless sensor network positioning principle
The primary concern of the home security system is, what happened in what location or area, and in practice, the positioning of the patrol car only needs to determine the following three questions, where am I? Where am I going? How to go? In this system, a patrol positioning method using RFID tags as road signs and WSN for navigation is adopted.
Put passive RFID tags on some fixed objects in the home (such as sofas, tables, chairs and bookcases, etc.) and some important positions, these are the location signs in the home environment. The family car with the RFID card reader is on patrol in the home environment. Once it detects an RFID tag around it, it stops immediately, reads the RFID tag, and sends the tag value to the home smart gateway through the wireless sensor network. The specific location of each RFID tag, the location information of its adjacent RFID tags, and the relative positional relationship between each RFID tag are pre-stored in the home smart gateway in the form of a location table, a neighbor table, and a navigation table. The patrol task, the current RFID tag value and the information of these three tables can be used to navigate the intelligent patrol car.
1.2 Home Smart Gateway
The smart home gateway is at the center of the smart home network and is the core of communication, decision-making and alarm. On the one hand, the home intelligent gateway uses the ZigBee network to collect and process environmental data for each security monitoring module node deployed in the home, and at the same time realizes the management and control of the internal network equipment of the home; remote communication. When the security monitoring module node detects the occurrence of an alarm situation, the home intelligent gateway sends an alarm text message or makes an alarm call to the remote user through the GSM module.
1.3 Security Monitoring Module Node
Various security monitoring module nodes are deployed in areas where security risks may occur in the home environment. According to the different monitoring environmental parameters, the principle is slightly different, but basically all security sensors (temperature, humidity, smoke, infrared and vibration) It is composed of CC2430 RF module.
1.4 Intelligent patrol car
The designed smart patrol car is based on a miniature racing car and is equipped with a CC2430 radio frequency module, an RFID card reader, a camera, and home security sensors such as temperature and smoke.
The intelligent patrol car mainly has the following functions in the home security system:
①The intelligent patrol car acts as a mobile routing node of the home security sensor network. ZigBee star network simplifies the system design, but each node can only communicate with the home intelligent gateway. In the actual home environment, the signal transmitted by the security node in the bedroom is affected by the interior wall and indoor obstacles, so the signal received by the home intelligent gateway in the living room is very weak, and adding multiple routing nodes will increase the network. Complexity, this system solves this problem by adding a mobile routing node in the network. If no reply signal is received within a certain period of time, the home smart gateway orders the patrol car to go to a specific location (identified by an RFID tag) to collect node data with weak signals, and then forward it to the home smart gateway.
②The intelligent patrol car is equipped with various security sensors. When performing patrol tasks, it will conduct a more careful monitoring of each area with potential safety hazards, such as a comprehensive gas leak detection in the area near the gas pipeline.
③ When a security monitoring module node detects an alarm situation, the home smart gateway navigates the smart car to the site for a detailed patrol to determine whether a false alarm is caused by environmental interference signals. Once it is determined that an alarm situation occurs, turn on the camera to take pictures on the spot .
2 Hardware Design of Main Function Modules
2.1 CC2430 RF Module Design
The combination of CC2430 and CC2591 power amplifier used in the design of RF module, CC2430 continues the architecture of previous CC2420 chip, the chip integrates ZigBee radio frequency (RF) front-end, memory and microcontroller on a single chip; CC2591 integrates power amplifier, low noise Amplifiers, baluns, switches, inductors and RF matching networks, etc., the maximum output power can reach 22dbm, and the sensitivity can be increased by 6dbm. According to the characteristics of the RF matching network already included in the CC2591, there is no need to add an additional matching network in the RF input/output part, thereby simplifying the circuit design.
2.2 RFID reader module design
The RFID card reader module is extended on the CC2430 radio frequency module, and the RFID main chip is CLRC632.
The connection mode of the radio frequency chip RC632 and CC2430 selects the independent read/write strobe mode. The connection mode of CLRC632 in this mode. The card reader IC utilizes advanced modulation and demodulation concepts and fully integrates all types of passive contactless communication methods and protocols under 13156MHz. The RFID communication protocol used in this design is the IEC15693 protocol.
CC2430 is connected to the data bus of CLRC632 through port P0, which can realize the transfer of commands and data with the wireless radio frequency chip RC632. The pin P210 and pin P211 of CC2430 are connected with the NWR pin and NRD pin of CLRC632 respectively, and control the writing and reading of the data of RC632 respectively. At the same time, take P112 of CC2430 as the input end of the chip select signal of RC632, and this port is active at low level. The RSTPD pin is a reset and power-down pin. When it is high, it stops the input and disconnects it from the outside. The falling edge of the pin signal triggers the chip reset, which is controlled by pin P116.
3 System Test Analysis
The system designs and implements the CC2430 radio frequency module and the RFID card reader module. In order to expand the design of the home intelligent gateway based on the CC2430 radio frequency module, the front is the CC2430 module and the back is the TC35iGSM module; Patrol car.
The system performance was tested in a laboratory environment simulating a home environment. The following are some analysis conclusions of the test results:
① The effective communication distance of CC2430 RF module is within 50m when there are no obstacles indoors, and the signal attenuation is serious when encountering physical obstacles.
②The effective reading distance of the RFID card reader is within 15cm, and the card reading rate is 5card/s.
③ The intelligent patrol car can identify RFID tags when moving at a low speed of 015m/s, and can complete the positioning from one RFID tag to another RFID tag.
④Send GSM short message to realize remote wireless control and alarm.
Wireless sensor network and RFID technology are both hot research topics today. The combination of the two to form RFID wireless sensor network can be applied to logistics and supply chain management, manufacturing and assembly, telemetry, emergency rescue, security and other fields at a lower cost. . Aiming at the problems existing in the current home security system, this paper designs a smart home security system based on RFID wireless sensor network, and the design also has certain reference value for other similar extended applications.