一种基于ZigBee技术的温室监控系统无线解决方案外文翻译资料

Journal of Zhejiang University SCIENCE A

ISSN 1673-565X (Print); ISSN 1862-1775 (Online)

www.zju.edu.cn/jzus; www.springerlink.com E-mail: jzus@zju.edu.cn

A wireless solution for greenhouse monitoring and control system based on ZigBee technology^*

ZHANG Qian^dagger;, YANG Xiang-long^{dagger;Dagger;}, ZHOU Yi-ming, WANG Li-ren, GUO Xi-shan

(School of Biosystem Engineering and Food Science, Zhejiang University, Hangzhou 310029, China)

dagger;E-mail: z_qian1979@163.com; xlyang@zju.edu.cn Received Dec. 31, 2006; revision accepted July 23, 2007

Abstract: With the rapid development of wireless technologies, it is possible for Chinese greenhouses to be equipped with wireless sensor networks due to their low-cost, simplicity and mobility. In the current study, we compared the advantages of ZigBee with other two similar wireless networking protocols, Wi-Fi and Bluetooth, and proposed a wireless solution for green- house monitoring and control system based on ZigBee technology. As an explorative application of ZigBee technology in Chinese greenhouse, it may promote Chinese protected agriculture.

Key words: Greenhouse, Monitoring and control, Wireless, ZigBee, IEEE802.15.4, JN5121

doi:10.1631/jzus.2007.A1584 Document code: A CLC number: S625.5 1; TN92

INTRODUCTION

Wireless technologies have been rapidly devel- oped during recent years. Starting from military and industrial controls, it is now being widely applied in environmental monitoring and agriculture. Its ad- vantages include the liability, simplicity, and low cost in both installation and maintenance. In greenhouse control applications, Serodio et al.(1998; 2001) de- veloped and tested a similarly distributed data acqui- sition and control system for managing a set of greenhouses. Inside each greenhouse, a WLAN net- work with a radio frequency of 433.92 MHz was used to link a sensor network to a local controller. Morais et al.(1996) implemented a wireless data acquisition network to collect outdoor and indoor climate data of greenhouses in Portugal. Mizunuma et al.(2003) de- ployed a WLAN in a farm field and greenhouse to monitor plant growth and implemented remote con- trol for the production system. Mancuso and Bustaffa

Dagger; Corresponding author

• Project (No. 2005C22060) supported by the Science and Technology Department of Zhejiang Province, China

(2006) worked at a short-term deployment of a wire- less sensors network in a tomato greenhouse in the south of Italy.

In China, Liu and Ying (2003) reported a greenhouse monitoring and control system using the Bluetooth technology. The system collected envi- ronmental data from a sensor network in a greenhouse and transmitted them to a central control system. Qiao et al.(2005) introduced systematic frames of wireless sensor networks and expatiated their agricultural applications such as monitoring greenhouse, irriga- tion, precision farming and so on. Luo et al.(2006) designed wireless sensors for greenhouse monitoring. The wireless communication was based on nRF401 wireless module, working at 433 MHz ISM frequency. Wu et al.(2006) reported the design and implementa- tion of Greenhouse Wireless Data Acquisition System based on CC2420, as a low-cost transceiver designed specifically for low-power, low-voltage RF applica- tions at the 2.4 GHz unlicensed ISM band. Li et al.(2007) reviewed cable and wireless communica- tions used in agriculture, and compared their advan- tages and disadvantages.

Wireless sensor technology, however, is still at

its early development phase in China, and its appli- cations in Chinese greenhouses remain few. In the current study, we compare the advantages of ZigBee with two similar wireless communications, Wi-Fi and Bluetooth, and propose a wireless solution for greenhouse monitoring and control system based on ZigBee technology.

COMPARISON OF ZIGBEE, WI-FI, AND BLUE- TOOTH PROTOCOLS

Wi-Fi, Bluetooth and ZigBee work at similar RF frequencies, and their applications sometimes overlap (Seager, 2006). In the current study, we chose the following five main factors of greenhouse networks to compare: cost, data rate, number of nodes, current consumption and battery life.

• 1. Cost. ZigBee chip is US$ 1 or less, the lowest; Wi-Fi and Bluetooth chips are $ 4 and $ 3, respec- tively. The overall system cost can be significantly reduced by the employment of ZigBee chip.
  2. Data rate. ZigBee is 250 kbps, while Wi-Fi and Bluetooth are 54 Mbps and 1~2 Mbps, respec- tively. Despite the lowest data rate, ZigBee is suffi- cient for a greenhouse. Generally, data traffic in a greenhouse is low—usually small messages such as the change of temperature or a command from the controller to an actuator. And also, low data rate helps to prolong the battery life.
  3. Number of nodes. The capacity of network is determined by the number of nodes, and ZigBee has up to 254 nodes, the largest among the three. It meets the application demand of more and more sensors and actuators in a greenhouse.
  4. Current consumption. ZigBee has the lowest current consumption, 30 mA, while Wi-Fi, 350 mA, and Bluetooth, 65~170 mA. It also greatly helps to prolong the battery life.
  5. Battery life. ZigBee chip has the longest battery life, a few months or even years.

As a whole, ZigBee technology offers long bat- tery life, small size, high reliability, automatic or semi-automatic installation, and, particularly, a low system cost. Therefore, it is a better choice for greenhouse monitoring and control than

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一种基于ZigBee技术的温室监控系统无线解决方案

张倩，杨向龙，周一明，王立人，郭锡山

(浙江大学生物系统工程与食品科学学院，杭州310029)

摘要:随着无线技术的飞速发展，我国大棚的安装成为可能无线传感器网络由于其低成本、简单和移动性。在目前的研究中，我们比较了ZigBee与另外两种类似的无线网络协议Wi-Fi和蓝牙，提出了一种基于ZigBee技术的温室监控系统无线解决方案。作为ZigBee技术在汉语中的探索性应用温室效应，可以促进中国保护性农业的发展。

关键字:温室，监控，无线，ZigBee, ieee802.15.4, JN5121

介绍

无线技术近年来发展迅速。它从军事和工业控制开始，现在广泛应用于环境监测和农业。它的优点包括安装和维护的可靠性、简单性和低成本。在温室控制应用方面，思瑞迪奥等(1998;2001)设计并测试了一个类似的分布式数据采集和控制系统，用于管理一组温室。在每个温室内，一个无线局域网网络-工作与无线电频率433.92兆赫用于连接传感器网络到一个本地控制器。Morais等(1996)在葡萄牙实施了一种无线数据采集网络，用于采集温室的室外和室内气候数据。Mizunuma等人(2003)在农田和温室中设计了无线局域网来监测植物生长，并对生产系统实施了远程控制。Mancuso和Bustaffa(2006)在意大利南部的一个番茄温室短期部署了一个无电线传感器网络。

在中国，Liu和Ying(2003)报道了一个使用蓝牙技术的温室监控系统。该系统从温室的传感器网络中采集环境信息，并将其传输到中央控制系统。乔等(2005)介绍了无线传感器网络的系统框架，阐述了无线传感器网络在温室监测、灌溉、精准农业等农业领域的应用。罗等(2006)设计了用于温室监测的无线传感器。无线通信采用nRF401无线模块，工作频率为433 MHz。Wu等人(2006)报道了基于CC2420的温室无线数据采集系统的设计与实现，该系统是一种低成本的收发器，专门用于2.4 GHz无授权ISM频段的低功耗、低压射频应用。Li等人(2007)综述了有线和无线通信在农业中的应用，并比较了它们的优缺点。

然而，无线传感器技术在中国还处于早期发展阶段，在中国温室中的应用还很少。本研究比较了ZigBee与Wi-Fi和蓝牙两种无线通信方式的优点，提出了一种基于ZigBee技术的温室监控系统无线解决方案。

ZIGBEE、WI-FI和蓝牙协议的比较

Wi-Fi，蓝牙和ZigBee工作在相似的射频频率，他们的应用有时重叠(Seager, 2006)。在目前的研究中，我们选择了温室网络的五个主要因素进行比较:成本、数据速率、节点数量、电流消耗和电池寿命。

(1)成本。ZigBee芯片为1美元以下，最低;Wi-Fi和蓝牙芯片分别为4美元和3美元。采用ZigBee芯片可以显著降低系统整体成本。

(2)数据速率。ZigBee为250kbps, Wi-Fi和蓝牙分别为54mbps和1~ 2mbps。尽管数据率最低，ZigBee对于温室来说已经足够了。一般来说，温室里的数据流量很低——通常是一些小消息，比如温度的变化或者从控制器到执行器的命令。此外，低数据速率有助于延长电池寿命。

(3)节点的数量。网络容量由节点数量决定，ZigBee拥有254个节点，是三个节点中最大的。它满足了温室中越来越多的传感器和执行器的应用要求。

(4)当前的消费。ZigBee的电流消耗最低，为30 mA, Wi-Fi为350 mA，蓝牙为65~170 mA。它也大大有助于延长电池寿命。

(5)电池寿命。ZigBee芯片的电池寿命最长，只有几个月甚至几年。

作为一个整体，ZigBee技术提供了长寿命、小尺寸、高可靠性、自动或半自动安装，特别是低系统成本。因此，它是一种较好的温室监测和控制方案。

我们的无线温室解决方案

解决方案概述

如图1所示，无线传感器，如温度传感器、湿度传感器、光传感器等(集成了PIC 16F877和ZigBee mod- ule)，收集环境信息并传输到手持控制器(HHC)(集成了ARM单片机和ZigBee模块)。在HHC中，数据被存储并显示在LCD上。通过控制算法处理数据后，HHC将控制命令发送给执行器(也与PIC 16F877和ZigBee模块相结合)。执行机构完成实际控制任务。所有的无线节点都基于ZigBee模块。

我们设计的节点基于Jennic公司(Jennic Ltd.， 2006a)生产的JN5121模块。JN5121是一系列低功耗、低成本的兼容IEEE802.15.4的无线微控制器中的第一款，它结合了32位芯片上的RISC(重新引导指令集计算)核心、一个完全兼容2.4 GHz IEEE802.15.4收发机、64 kBROM和96 kB RAM。高水平的集成有助于降低整个系统的成本。JN5121通过SPI(串行外围接口)或并行连接上位控制器和传感器/执行器。

图1提出的无线解决方案概述温室监控

网络的建立

Sinem Coleri Ergen(2004)总结了ZigBee的三种拓扑类型:星型拓扑、对等拓扑和集群树拓扑。在星型拓扑中，设备和称为PAN(个人区域网络)协调器的单个中央控制器之间建立通信。PAN协调器可能由电源供电，而设备很可能由电池供电。每个星型网络选择一个PAN标识符，该标识符目前不被射电领域内的任何其他网络使用。这使得每个星型网络可以独立运行。

在我们的项目中，我们根据星型拓扑结构建立了网络。如图2所示，当HHC (FFD，全功能设备)第一次被激活时，它会建立自己的网络，be- come为PAN协调器。然后初始化硬件、堆栈和应用程序变量，选择一个未使用的PAN标识符为零，并将信标帧广播给传感器和执行器(RFD, reduced Function Device)。接收信标帧的传感器和执行器可以请求加入网络工作。HHC将把它们作为子设备添加到它的邻居列表中，并返回一个响应。传感器和执行器将在其邻居列表中添加HHC作为其母节点，并返回一个确认。HHC实时监控所有网络节点，主要包括网络信息数据库PIB (PAN信息库)。

1: HHC向传感器/执行器广播信标帧;2:传感器/执行器请求加入网络;

3: HHC返回传感器/执行器的响应;4:传感器/交流控制器向HHC返回确认信息

图2网络建立

节点软件系统

软件系统的主要任务是无线节点之间的通信。它分为初始化过程和信息处理过程两部分。根据参考手册JN5121-EK000演示应用(Jennic Ltd.， 2006b)设计软件系统。在每个节点的代码中，中断被广泛地用于同步操作，这使得设备可以让CPU长时间休眠，而什么也不发生。

图3为通讯初始化过程。一旦协调器(HHC)创建了PAN，它就会发出常规信标。传感器/执行器节点成功接收并验证数据帧和MAC命令帧后，向协调器发送一个确认。传感器/执行器节点然后进入休眠模式。协调器使用传感器/执行器节点转换其主机-从角色。然后协调器在从属模式下工作，等待对连接请求的响应。此时，传感器/执行器节点在主机模式下工作，等待被请求唤醒并启动连接请求。初始化后，传感器/执行器节点在休眠模式下工作，拒绝任何连接请求。这种设计大大降低了传感器/执行器节点的功耗。此外，由于传感器/执行器节点是按需激活的，它有效地防止了其他传感器/执行器的非法连接请求，从而为协调器和传感器/执行器节点之间的通信提供了安全可靠的保证。

图3通信初始化

信息处理又分为两个子过程。图4a为协调器与传感器节点之间的信息处理过程。当传感器节点检测到监控参数的变化时，主要处理信息，发起连接请求，并将处理后的信息发送给协调器。图4b为协调器节点与执行器节点之间的信息处理过程。当执行器节点接收到来自coordi- nator的中断请求时，它们将被激活，并开始接收来自协调器的命令。在传输和接收完成后，传感器节点和执行器节点返回到它们的睡眠模式。已经证明在工程测试无线sen -法师/致动器节点睡眠模式下的99%,和功耗的数学期望可能低至30micro;A。

图4协调器与传感器之间的信息处理(a)协调器与执行器节点之间的信息处理(b)

结论

本研究探讨了基于ZigBee技术的温室监控系统无线解决方案，并设计了无线节点、网络搭建和软件系统。基于zigbee的监控系统具有自组织、自配置、自诊断和自修复等功能，为传感器的安装提供了近乎无限的灵活性，增强了网络的鲁棒性，大大降低了成本。该系统已在浙江省丽水农业科学院现代温室中顺利运行，证明了该系统的实用性和可靠性。因此，我们认为基于zigbee的温室监控系统可以很好地解决温室监控问题。

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