Design of remote control system for automatic sprayer based on GPRS in greenhouse

Because of its huge economic and social benefits, horticulture production in China develops rapidly. However, problems still exist with this rapid development such as improper infrastructure, inadequate facilities, the low product quality and safety, and high labor cost. All those limit the sustainable development of horticulture industry, particularly agricultural production in controlled environment. For lowering intensive labor cost and relieving serious operator's health impact caused by conventional pesticide application in greenhouse, we developed an advanced remote control system for greenhouse sprayer based on GPRS communication technology and distributed control principle. The objective of this paper was to develop a mist sprayer remote control automatic spraying system to lower high labor cost, to improve safety for greenhouse production, and to increase pesticide utilization rate. The system developed was divided into the upper computer and the mist sprayer. The upper computer run the mist sprayer management system software designed in Qt platform. According to the requirements of the mist sprayer management system design for the main interface, we established the mist sprayer management interface and parameter setting interface of the software. Multithreading was used for managing sprayers working in different greenhouses and socket technology to get the intercommunication between host computer and the mist sprayer. GPRS network was used to transmit user's instruction to the mist sprayer. Three work modes were defined as the work condition variation of sprayer. On the sprayer side, we introduced the hardware design of the mist sprayer control system with STM32F103ZET6 for the main controller and SIM900A for GPRS module. The hardware circuit of the control system was designed according to these chips, which comprised of the periphery circuit of the main controller, the GPRS module circuit and the driving circuit of the motor. According to the characteristics of mist sprayer, we made arrangement of mist sprayer track and defined comprehensive mist sprayer orbit movement rules in three modes: standby mode, automatic operation mode, and remote control mode, from which we calculated control object motion parameters to the mist sprayer. The fuzzy-PID strategy was used for the output of PWM that was downloaded by the STM32 controller. The controller received the data from the host computer through SIM900A chip. The mist machine control system software included the main program, GPRS communication program, and working mode subroutine designed by the C programming language in the Keil uVision3 development tools. A series of experiments were designed in this paper to test the e-control system including communication trial, mist test and droplet deposition test. The contents of communication trial were to manufacture circuit board and to send the instructions to the board. If the instructions can be displayed on the LCD screen, we concluded that system can receive the instructions correctly. For the mist test, we used the test sprayer to spray the model plant, then to calculate the errors between theoretical value and actual value. In the droplet deposition test, we let the test sprayer walk along a line with a uniform speed and used the test strip to receive the droplets, then calculated coefficient of variation. The results showed that, the software could send commands correctly to the sprayer. In addition, the error between the actual value and the theoretical value of spray flow, spray volume were 3.9%, 5%, respectively. The system response time was about 2.25 s, while the coefficient of variation of droplet deposition was smallest when the sprayer speed was set at 18 cm/s. The results of this paper suggested that the sprayer designed by the method could effective decrease of the usage of pesticides. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.