1、中文 3800 字 New Environment Parameters Monitoring And Control System For Greenhouse Based On Master-slave Distributed Abstract-According to the actual need of monitoring and control of greenhouse environment parameters in rural areas,a master-slave distributed measurement and control system is designe
2、d,in which PC is taken as the host. The system consists of PC ,soil moisture measurement and control module,temperature and humidity, and CO2 monitoring and control module. In the system,PC has large amount of data storage which is easy to make use of fuzzy control expert system,configuration softwa
3、re-KingView is used to develop software for PC,by which the development cycle is shorten and a friendly human-computer interaction is provided.Each monitoring and control module consists of STC12 series of microcontrollers,sensors,relays etc.Different modules are select based on the need if system t
4、o achieve control greenhouse in partition and block. I. INTRODUCTION To modern indoor agriculture, the automatic measurement and control of environment parameters is the key to achieve crop yield and quality of greenhouse.In recent years,facilities agriculture develops vigorously in our country,matc
5、hed with it,the monitoring and control instrument of greenhouse have also made certain development.After nearly 10 years of unremitting hard work,our research team of measurement and control system of agriculture environment parameters,designed an intelligent measurement and control system of distri
6、bution combined of greenhouse which can be popularized in the vast rural areas.This system is mainly control of temperature,humidity,CO2 concentration,soil moisture and illumination of greenhouse.OF SCM,as the data storage is small,display interface is single,amount of information is limited,but its
7、 capability price ratio is high,so it is used as a front unit of data acquisition and control；and of PC,it has a large amount of data storage,rich software,convenient human-computer interaction,and so on.If we use outdated and low-priced PC,taking the PC as the upper machine,taking the different fun
8、ction control modules composed of multiple microcomputers as the lower machines,then a master-slave distributed and intelligent control system bases on microcomputer is made up,by which both better monitoring and control,display and data collection or management are achieved,but also lower cost of s
9、ystem is get according to the actual need. II SYSTEM STRUCTURE AND PRINCIPLE The most marked feature of the distribution combined and intelligent control system greenhouse is that of incorporating with data acquisition, control and management as a whole,module combination, simple structure,convenien
10、t human-computer interaction,and using technology of intelligent expert fuzzy control,which can adapt to a variety of crop management control in greenhouse.The basic structure of the system is shown in Fig.1. The structure of the distributed system is composed of two layers:the upper and lower.In th
11、e top-price PC is taken as the host to make system management and experts fuzzy operation in intelligent,and to provide a friendly human-computer interface,and to realize the united monitoring and management of greenhouse； the lower is composed of a series of modules of different function,and in eac
12、h module,a single chip of AT89C is adopted as the lower machine,RS485 is used to communicate PC with all AT89C,and then the collection,processing and control of the greenhouse parameters is achieved.Each function module is completely isolated in electrical,any failure on the nodule does not produce
13、any effect on other modules.The system collects separately ways of environment information through each monitoring and control module,and sends it to host PC through the RS485 interface.And in the PC configuration control system,the acquired parameters are compared with the values of setting,then ac
14、cording to a variety of expert intelligent fuzzy control system of crops at different growth stages,the fuzzy control instructions on the environment temperature,humidity,CO2 concentration,soil water content and the corresponding operation instructions or alarm are given. The system is applied in ru
15、ral greenhouses in Qinhuangdao.Usually at 1/4 near East and West end in a greenhouse,and at the height of 1.5m from the ground in the middle in the northern half (near the wet curtain) and the southern half (near the fan ),a module of air temperature and humidity ,CO2 concentration and a module of s
16、oil moisture content are set；a module of soil moisture content will be added in the middle of the greenhouse according to the actual condition；at the height of 1.5m in the main entrance,a water tank is set,of which the solenoid of drip tube should be set based on the need and controlled by module of
17、 soil moisture content；and the PC is placed in the main entrance to the greenhouse. III . HARDWARE DESIGN A. The CP and communication system In the distributed system of data acquisition and control,as the micro control unit is limited in data storage and slow in calculating of complex functions,so
18、PC is used and the master-slave module is adopted in the system,that is a system of,taking PC as the host and taking the SCM systems located in the scene as slave. In this distributed system,communication is the key to it.Generally,the serial port of PC is standard RS232,of which transmission distan
19、ce is shorter.But in agriculture control system.its communication distance is of tens of meters or several kilometers, so RS232/RS485 converter is used to achieve communication between the PC and SCM.To reduce investment,both considering the user convenience and friendly human-computer interaction,l
20、ow-price PC of above 486 and below PIV is adopted；and considering the operation of configuration software,it is required that memory is 64M or above and hard disk is 10Gb or above. B. The control modules of temperature and humidity,illuminance and CO2 concentration Each control unit consists of SCM,
21、sensors,signal processing circuit,RS485 interface and output circuit.The hardware structure of module of temperature and humidity,CO2 concentration is shown in Fig.2. CO2 concentration is measured by sensor based on NDIR technology,measurement is of 02 103mol.Through the sensor,control system,by sof
22、tware of digital filter,linear interpolation and temperature compensation,the CO2 concentration is output as digital adhered to UART protocol,and then is input directly to the SCM. The new intelligent sensor of SHT11 based on CMOSens technology is chosen in the measurement of temperature and humidit
23、y.In SHT11,the temperature and humidity sensors,signal amplification,A/D,I2C bus are all integrated in a chip；it has full-scale calibration,second-line digital output,and humidity measuring range of 0100% RH,temperature measurement range of -40 +123.8 ,humidity measurement accuracy of 3.0% RH,temper
24、ature measurement accuracy of 0.4 ,the response time of 4s. The illuminance sensor of JY1-TBQ-6 of silicon photovoltaic detection is used Light measuring.Its measurement range is 0200,000 Lux；spectral range is 400700(nm) visible light；measurement error is less than 2%； output is 420mA or 020mV；outpu
25、t signal can be directly send to the A/D of the SCM after being amplified to 04V. Modules accept the instructions form the the Upper,and output via the output circuit .The output circuit consists of optical isolation,the signal driver and the output relays. C. The measurement and control modules of
26、soil moisture Water is a polar medium, the dielectric constant of the soil containing water is mainly determined by the water,when water content is different,the wave impedance is different.The soil moisture is measured by standing wave radio method in this system. Based on the theory of Engineering
27、 Electromagnetic Field,for lossy medium,the electromagnetic wave impedance as follows: Z0= / (1+j /( ) Where is medium permeability,and of soil is 0 is the vacuum permeability； is medium dielectric constant； is medium conductivity； is electromagnetic wave frequency. In the very low audio(2000Hz),the
28、 loss tangent of dry soil dielectric is / 0.07,if you choose the frequency of the signal source at above 20MHz.then, ,the imaginary part of the soil wave impedance is neglect,only the real part,which amounts to a pure resistance. Soil moisture sensor consists of 100MHz signal source,a coaxial transm
29、ission line and a 4-pin stainless probe.The electromagnetic waves of signal transmit to the probe along the lines.As the probe impedance and line impedance are different,the superimposition of incident waves and reflected waves forms a standing waves. Taking the coaxial transmission line as a lossle
30、ss uniform line,wave impedance is Z0,Zl is the load impedance. Then the reflected coefficient of voltage wave at the probe is: = （ ZL-Z0） /(ZL+Z0) Choosing the length of transmission line is l= /4,the maximum and minimum of both ends of the line are Umax and Umin,Then the standing wave radio in the
31、line can be expressed as: S=Umax /Umin =(1-| |)/(1+| |) In the way,the soil moisture radio can be measured by measuring the standing wave rate of transmission line. As shown in Fig.3.,soil moisture module consists of sensors and controllers,the sensors are subordinated to controllers,controllers can
32、 be omitted without the need of irrigation in greenhouse. To simplify the control,irrigation technology of node-type in partition is adopted in the control soil moisture in this system.To a certain extent,the parameters of upper and lower the ground can be decoupled by adopting this technology. IV C
33、ONTROL SYSTEM PROGRAMMING The software of PC is developed by KingView 6.51 of Beijing-controlled Asia.This configuration software has high reliability,shorter development cycle,perfect capability of graphical interface generation,and friendly human-computer interaction；and can create dynamic images and charts in accordance with the layout of equipment in the scene；can visually display the changes of parameters,control status,and can give an alarm when over-limited；and can achieve fuzzy control of greenhouse parameters by using the history curve of environment parameters
