Introduction
With the 2009 climate change conference in Copenhagen, the world is promoting a more energy-efficient and environmentally friendly lifestyle.
One of the important measures to curb carbon emissions and cope with climate change is to develop indoor lighting control systems to improve lighting efficiency.
In recent years, a lot of research has been carried out on indoor lighting control systems at home and abroad. ZigBee wireless sensor network and fuzzy control technology have been introduced into the research of indoor lighting control respectively, which provides a good idea for further research of indoor lighting control, but the indoor lighting control system constructed by combining the two is still rare.
This paper combines ZigBee wireless sensor network and fuzzy control technology to design a new indoor lighting control system. Since natural light can provide some or all of the indoor lighting needs, the system makes full use of natural light. By controlling the rotation angle of the blinds, natural light is introduced as a light source, supplemented by artificial lighting, so that indoor lighting can meet people's needs for lighting, and Energy saving can be achieved.
1 overall system design
The whole system consists of ZigBee wireless sensor network, base station and remote monitoring center. The overall structure is shown in Figure 1. Each room is equipped with sensors that detect environmental information, natural light controllers, and artificial lighting controllers. Various environmental information such as the illumination of the room and the position of the person are collected by the sensor and transmitted to the base station PC via the Zig2Bee wireless sensor network. The base station PC automatically analyzes and processes related information, calculates the amount of natural light and supplemented artificial illumination required by the room, determines the illumination mode, and outputs the result through the ZigBee wireless sensor network to control the artificial lighting Controller and the natural Light Controller. Work to achieve automatic control of indoor lighting. The base station PC can also display relevant information of each device in real time, and transmit the information to the user (remote monitoring center) through wireless communication.
Figure 1 Overall structure of the system
In this system, the ZigBee wireless sensor network adopts a star network topology, and the nodes are divided into four categories: sensor nodes, controller nodes, routing nodes, and coordinator nodes. The sensor node embeds a variety of sensors for reading and transmitting the relevant environmental information required for lighting control. The controller node is embedded in the natural light control panel and the artificial lighting control panel to control the amount of natural light introduced and the amount of artificial illumination added; in addition, the controller node has an interrupt response function that can handle the user's control commands. The routing node receives the relevant information collected by the room sensor node and transmits it to the coordinator node, and then transmits the control command of the coordinator node to the sensor node and the controller node. The coordinator node is connected to the base station PC through the RS2232 serial port for address assignment and management of all network nodes, and can monitor the transmission and reception of various information.
The base station is responsible for controlling the entire network, and needs to complete the collection of the wireless sensor network node information, and complete the analysis processing and control output of the collected information to complete the fuzzy control of the indoor lighting and achieve the purpose of energy saving. Through the PC software user interface, display the topology map of the entire system network and the working status of each node and the collected real-time data information; query the history and real-time data of each room; with remote setting function, the user can set a certain remote monitoring center The lighting modes of some rooms, such as full-on/full-off, etc.; also have the functions of device management and user management. The software can update the device and wireless sensor network node information in real time, with the adaptive ability of device update, and through user management. The security of the system is guaranteed.
2 Z igBee network node design
ZigBee network node design is the core of hardware design. The system node adopts modular design. Four kinds of nodes adopt common core modules, and different types of nodes are equipped with different expansion modules.
The network node is based on Freescale's MC13192 chip and Philip's LPC2138 chip. The MC13192 features an optimized digital core that helps reduce MCU processing power and reduces its execution cycle.
In addition to the three operating states of receive, transmit and idle, the chip has three low-power modes of operation: power-down mode, sleep mode, and sleep mode. The operating frequency is 2. 405~2. 480 GHz, and 16 channels are divided in the frequency band, each channel occupies 5 MHz bandwidth, and the direct sequence spread spectrum communication technology is adopted, and the data transmission rate is 250 kb / s. With programmable power output mode, the transmit power is 0~4 dBm, the receive sensitivity can reach 92 dBm, and the transmission distance is 30~70 m. The LPC2138 chip is a 32-bit ARM 7 microcontroller that supports real-time emulation and embedded tracking. It features 512 KB of embedded high-speed F ray memory and 32 KB of on-chip static RAM and multiple serial interfaces, two 8-channel 10-bit A/D converters, one D/A converter and 47 GP IOs. And up to 9 edge or level triggered external interrupts.
The LPC2138 has two low power modes: Idle mode and Power Down mode. Due to its small package and low power consumption, the LPC2138 can ideally be combined with the MC13192 as a wireless sensor network node based on ZigBee technology. The LPC2138 and MC13192 are connected via the SP I bus. The LPC2138 reads and writes to the internal registers of the MC13192 through the 4-wire SP I interface, thus completing the control and data communication of the MC13192. The analog signal output by the sensor is input to the L PC2138 after 8 channels of 10 bit A/D conversion. The LPC2138 processes the signal collected by the sensor and transmits it from the antenna.
The control signal of the sensor can be received from the antenna, demodulated and despread to obtain the original data, and then transmitted to the LPC2138 through the SPI. After being judged by the LPC2138, it is transmitted to the sensor through the GPIO port to realize the control of the sensor.
The core board is connected with various sensors to form a sensor node, and is connected with the natural light control board and the artificial lighting control board to form a controller node. After the serial communication interface is extended, the coordinator node is configured to communicate with the base station PC, and the extended power supply interface is connected to the power module. . The node hardware framework is shown in Figure 2.
Figure 2 Z igBee network node hardware framework diagram
According to the node type, the transmit power and energy consumption required by the node, the power module is divided into three types: mains, solar energy and Battery . The coordinator node has a large transmitting power and is powered by the mains; the controller node is connected to the control board to drive the corresponding circuit for natural light and artificial lighting control. Therefore, the controller node can be powered by the mains as the control board; the outdoor sensor node is used. Solar powered; other nodes are battery powered [ ] .
3 lighting control design
Lighting control design needs to avoid glare, use natural light as a light source as much as possible, supplemented by artificial lighting to meet the lighting needs of indoor personnel. In order to avoid glare and protect your vision, you need to determine the maximum angle of rotation of the blinds. In order to meet the needs of indoors for lighting, it is necessary to determine the ideal angle of rotation of the blinds. By comparing the two, the angle of rotation of the louver can be determined. When the ideal rotation angle is the maximum rotation angle, the louver is kept at the maximum rotation angle, and the insufficient illumination is supplemented by artificial illumination. The overall idea flow chart is shown in Figure 3.
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