| The production of crops includes planting, fertilization, cultivation management and the prevention of diseases, pests and weeds and many other production processes. The prevention of diseases, pests and weeds is one of the most important part. In recent years, our country's pesticide production capacity has grown by leaps and bounds.Our country plays an important role in preventing diseases, pests and weeds effectively.However, the spraying method which is widely used at present, under the assumption that farmland plant disease has the same situation, use the same spraying process.This kind of method that neglects the differences of farmland plant disease, will inevitably lead to enlarge pesticide investment, increase production cost,the crops have the chemical damage and have many problems such as pollution of the environment. In addition, along with the development of agricultural mechanization, the growing area of operation, the disadvantage of such spraying way has become serious day by day. To overcome the above-mentioned drawbacks of traditional spraying method,the only way is to implement"the variable spraying".This paper is a sub-project of Research and Application on Corn Variables Fertilizer,Variable Spraying and Intelligence Measurement of Production Technology in the State 863 modern agriculture domain ,mainly carries on the research of variable spraying, aims at designing a set of automatic variable spraying control system based on Linux. The working principle of this system is as follows:The information, which involves the location and speed of the spraying machine, is received by the GPS receiver, then it is transferred to the control center through UART. The location information is processed, and then extract the spraying information from the prescription chart which is made by the agriculture experts beforehand.Combined with the Feedback information of pressure sensor and flow sensor, control center sent the reasonable signals to implementation device such as the solenoid valve and electric valve. Make sure that the practical spaying quantity is agree with that of Prescription chart. Solenoid valve is installed at the entrance of nozzle.By controlling the state of solenoid valve, nozzle will start spraying or stop spraying. The spraying quantity of each nozzle is controlled through controlling the length of solenoid valve opened time.Moreover,we may change the pressure of pipeline by adjusting the electric valve, realizes the change of droplet size along with weather conditions.Achieves optimum spraying effect.The main tasks of this paper are as follows:At the aspect of overall design: Systems control plan choice, By comparing the three spraying control modes widely used currently, we select pulse electrically controlled variable spraying control mode as Spraying control method;Hardware plan choice, The system includes control center, storage device, power, human interface, the sensory equipment, implementation equipment, GPS positioning device and so on.Then we give Functional block diagram;Software plan choice: Mainly includes whether to use the embedded system and use what kind of embedded operating system and so on.At the aspect of hardware:This system takes low-power,high-performance embedded processor S3C2410 as the core control device, outside expands 64M SDRAM and 64M Flash,LCD and 4*4 keyboard as the human interface,solenoid valve,electric valve,liquid pump as the implementation devices,U disk as the prescription storage device, and also takes the turbine flow sensor and resistor strain gauge sensor as the flow sensor and pressure sensor respectively.The position and speed of Spraying machine is sended by DGPS, the power to the system is using the 12V vehicle power from the spraying machine.The circuits of core and external modules were designed and described.At the aspect of software:We have established the embedded Linux development environment, thorough analyzed the embedded Linux transplant process. Then complete the transplant work of embedded Linux to the hardware platform of system.Design embedded Linux drivers, focusing on the design of PWM timer driver. Design application of system in detail, mainly include three modules, reading and processing the information, the mechanism control and the human interface.We analyzed the reading method of GPS localization, Prescription chart, pressure and current information, the mechanism control strategy, the process to control electric valve, the designing of human interface. The detailed software flows of above function modules are designed.The central innovations in this paper are as follows:First,the use of low-power, high-performance 32bit ARM embedded processor as core of control system, compared with the single chip, greatly enhanced operational capability, improved efficiency of data processing. Moreover, the port of ARM processor is rich, may expand many kinds of device.Second,first introduced Embedded Linux operating system as a system software platform, enhanced the stability of the system and make it easier for transplant of driver and applications, it was advantageous in realization of complex algorithm. Make full use of a powerful device management features of embedded Linux kernel, manage many devices such as PWM, LCD, USB,UART and so on,make them parallel running. Reduce the workload of system design.Third,the use of U disk as the prescription storage device,greatly facilitated agricultural experts to create and modify prescription chart. The spraying operation staff only need to insert U disk to the USB port of hardware platform before Spraying operation,then he will operate the spraying machine easily.This method has solved the problem that the previous prescription chat was storaged in EEPROM, before each operation agricultural experts all need to re-configure the prescription information.The automatic variable spraying control system designed in this paper, through the laboratory confirmation, has realized basically to the spraying quantity accuracy control. Certainly, the system also has the trifle deficiency need to consummate, system's field work stable situation must further experimental verification. |
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