The Design Of Monitoring And Controlling System For Greenhouse Environment Based On ZigBee And ARM

The practical experience of greenhouse planting shows that, improving the automatic control and management level of greenhouse can significantly improve the quality and yield of crops and can reduce the energy consumption.The development of greenhouse monitoring and controlling technology has large influence on greenhouse industry and modernization of agriculture in China. With the rapid development of embedded system, wireless communication technology and automatic control technology, greenhouse monitoring and controlling technology also develop towards the direction of digital, networked and intelligent. At present,the developing trends of greenhouse monitoring and controlling system is the mass using of ZigBee technology which is convenient, and the using of embedded microcontroller for intelligent control.This paper used embedded technology, computer control technology, wireless communication technology of ZigBee and the GPC, designed a monitor and control system for greenhouse environment based on ZigBee and ARM. The upper computer is PC and the lower computer is Devkit8000, the ARM development board based on processor OMAP3530based on TI.The environment monitoring part included several CC2430, a ZigBee module and DHT21, a temperature and humidity sensor, which made up the wireless sensor network. Temperature and humidity data were obtained by wireless means, which gathered in ARM embedded system, then sent to upper computer in monitoring center for displaying and saving simultaneously by WL4432, the wireless communication module.The controlling part took the way of serial relay connecting AC contactor of motor, the close and open of relay were controlled by control signal sent by ARM, so the start and stop of the corresponding motor can be controlled. Remote inching control and auto control can be achieved by the aid of WL4432. Embedded linux was chosen as the operation system for lower computer, and Qt, a development tool for man-machine interactive contact surface has been transplanted, so current greenhouse environment condition can be shown on LCD screen in lower computer. C#was used for upper computer software, which achieves the sending of control signal, displaying of the greenhouse environment and the action information of actuator in real time, database was also used for data saving.In order to solve the problem of executing agency acting frequently near the temperature setpoint, this paper used the GPC, simulated the approximated linear cooling model by fully open a actuator in several cycles. This method predicted the opening percent needed in independent cycle within setting range, completed action by the method of fully open in many times. It was known by the experiment of comparing with the traditional method of fully open the executing agency in setpoint, the using of the GPC can ensure a smooth change of greenhouse temperature while outside temperature has the rapid rise, and eliminate temperature vibration which can cause energy wasting.After running for a long time, it showed software and hardware fit together very well. The system also has high reliability and strong expansibility. Greenhouse environment information can be fully understood by using the monitor method of muti wireless spot, and avoid the heavy and tedious for arranging the wire. The control method is simple and practical, which provides a smooth change of greenhouse temperature. It also has great economic and social benefit.